Image forming apparatus and program thereof

1. Field of the Invention

The disclosures herein generally relate to an image forming apparatus and a program thereof.

2. Description of the Related Art

Conventionally, some image forming apparatuses are provided with sensors for detecting passage of recording media. In the above-described image forming apparatuses, a method of estimating a failure location in the sensor by comparing a number of recording media detected by the sensor and a number of recording media that passed the sensor has been known (See, for example, Japanese Published Patent Application No. 2012-71916).

Furthermore, Japanese Patent No. 3604056 discloses a sheet feeding apparatus includes a main body power source for selectively supplying power to sections of the apparatus and a sheet containing section for containing plural sheets, and a manual sheet feeding entrance for feeding a sheet by manual operation.

However, in the method disclosed in Japanese Published Patent Application No. 2012-071916, since a substitute signal is not used, the image forming apparatus may halt its operation or a status of the image forming apparatus cannot be recognized in a case of the sensor failure or the like.

It is a general object of at least one embodiment of the present invention to provide an image forming apparatus and a program thereof that substantially obviate one or more problems caused by the limitations and disadvantages of the related art.

In one embodiment, an image forming apparatus includes a first detection unit configured to output a first detection signal upon detecting a recording medium; a second detection unit configured to output a second detection signal upon detecting the recording medium, which is conveyed from the first detection unit; a signal generation unit configured to generate a substitute signal for the first detection signal in a case where the first detection unit does not output the first detection signal; and a state determination unit configured to determine a state of the image forming apparatus based on the first detection signal and the second detection signal. The state determination unit determines that the first detection unit is in a failure state upon receiving the second detection signal and the substitute signal, which is input instead of the first detection signal.

In another embodiment, a non-transitory computer-readable storage medium stores a program for causing an image forming apparatus including a first detection unit and a second detection unit to perform a process of forming an image on a recording medium. The process includes a first detection step of the first detection unit outputting a first detection signal upon detecting the recording medium; a signal generation step of generating a substitute signal for the first detection signal in a case where the first detection signal is not output; a second detection step of the second detection unit outputting second detection signal upon detecting the recording medium, which is conveyed from the first detection unit; and a state determination step of determining a state of the image forming apparatus based on the first detection signal and the second detection signal. In the state determination step, the first detection unit is determined to be in a failure state in a case where the second detection signal and the substitute signal, which is input instead of the first detection signal, are received.

According to the present invention, reliability of the image forming apparatus is improved and the state of the image forming apparatus can be recognized easily in the case of the sensor failure or the like.

Other objects and further features of embodiments will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating an example of an entire configuration of an image forming apparatus according to a first embodiment;

FIG. 2 is a block diagram for explaining an example of a hardware configuration of the image forming apparatus according to the first embodiment;

FIG. 3 is a block diagram for explaining an example of a functional configuration of the image forming apparatus according to the first embodiment;

FIG. 4 is a timing chart for explaining an example of determination based on a signal according to the first embodiment;

FIG. 5 is a flowchart for explaining an example of entire processing for an image formation according to the first embodiment;

FIG. 6 is a timing chart for explaining an example of determination for a detection mechanism based on an amount of delay according to a second embodiment;

FIG. 7 is a timing chart for explaining an example of determination for a conveyance mechanism based on the amount of delay according to the second embodiment; and

FIG. 8 is a table for explaining an example of determination based on a detection signal according to the first and second embodiments.

In the following, embodiments of the present invention will be described with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a diagram illustrating an example of an entire configuration of an image forming apparatus according to a first embodiment.

The image forming apparatus 1 according to a first embodiment illustrates an example of the image forming apparatus of the present invention. The image forming apparatus 1 , for example, an electrophotographic image forming apparatus provided with a secondary transfer mechanism called a tandem system in forming color images. In the following, the image forming apparatus illustrated in FIG. 1 will be explained.

The image forming apparatus includes developing units for the respective colors 1 H 1 A, 1 H 1 B, 1 H 1 C and 1 H 1 D, toner containers for the respective colors 1 H 2 A, 1 H 2 B, 1 H 2 C and 1 H 2 D, and a transfer belt 3 . Furthermore, the image forming apparatus 1 includes a transfer belt drive roller 1 H 4 and a transfer belt tension roller 1 H 5 .

The developing units for the respective colors 1 H 1 A, 1 H 1 B, 1 H 1 C and 1 H 1 D, and the toner containers for the respective colors 1 H 2 A, 1 H 2 B, 1 H 2 C and 1 H 2 D are arranged, for example, along the transfer belt 3 .

The developing units 1 H 1 A, 1 H 1 B, 1 H 1 C and 1 H 1 D and the toner containers 1 H 2 A, 1 H 2 B, 1 H 2 C and 1 H 2 D correspond to the colors, respectively. The colors include, for example, yellow (Y), cyan (C), magenta (M), black (K) or the like. In the following, the colors may be indicated appropriately by symbols shown in the parentheses.

The transfer belt 3 is held by the transfer belt drive roller 1 H 4 and the transfer belt tension roller 1 H 5 , and is driven by a rotation of the transfer belt drive roller 1 H 4 .

The developing unit 1 H 1 A includes a photoconductor 1 H 6 A, a charging device 1 H 7 A, an exposure device 1 H 8 A, a developing device 1 H 9 A and a cleaner blade 1 H 10 A.

The charging device 1 H 7 A, the exposure device 1 H 8 A, the developing device 1 H 9 A and the cleaner blade 1 H 10 A are arranged on the periphery of the photoconductor 1 H 6 A.

Since the developing units 1 H 1 B, 1 H 1 C and 1 H 1 D have the same configuration as that of the developing unit 1 H 1 A, explanations will be omitted.

The exposure device 1 H 8 emits laser lights corresponding to the respective colors 1 H 11 A, 1 H 11 B, 1 H 11 C and 1 H 11 D.

The image forming apparatus 1 further includes a paper feeding tray 1 H 13 , a paper feeding roller 1 H 14 , a registration roller 1 H 15 , a paper ejection roller 1 H 16 , a double-side roller 1 H 17 and a secondary transfer roller 1 H 18 . Furthermore, the image forming apparatus 1 includes a fixing device 1 H 19 , a waste toner box 1 H 21 and primary transfer rollers for the respective colors 1 H 22 A, 1 H 22 B, 1 H 22 C and 1 H 22 D.

The image forming apparatus 1 further includes, for example, a paper ejection sensor 1 H 20 , a registration sensor 1 H 23 , a paper feeding sensor 1 H 24 and a fixing sensor 1 H 25 . Details of the above-described sensors will be described later.

The paper feeding tray 1 H 13 accommodates recording media 1 H 12 . The recording media 1 H 12 include, for example, papers, high-quality papers, plastic sheets, metallic sheets or the like. In the following, the case where the recording media are papers will be illustrated.

The paper feeding roller 1 H 14 is a mechanism for conveying a recording medium 1 H 12 from the paper feeding tray 1 H 13 .

The registration roller 1 H 15 is a mechanism for conveying the recording medium 1 H 12 conveyed by the paper feeding roller 1 H 14 to the secondary transfer roller 1 H 18 .

Details of the paper feeding roller 1 H 14 and the registration roller 1 H 15 will be described later.

The paper ejection roller 1 H 16 is a mechanism for ejecting the recording medium 1 H 12 from the image forming apparatus 1 .

The double-sided roller 1 H 17 is a mechanism for conveying the recording medium 1 H 12 , upon performing the image formation on both sides of the recording medium 1 H 12 , so that after the image formation is performed on one side of the recording medium 1 H 12 the image formation is performed on the other side of the recording medium 1 H 12 .

The secondary transfer roller 1 H 18 is a mechanism for performing a so-called “secondary transfer”, i.e. transferring n image formed on the transfer belt 1 H 3 onto the recording medium 1 H 12 .

The fixing device 1 H 19 is a device for fixing toners transferred on the recording medium 1 H 12 by the secondary transfer.

The paper ejection sensor 1 H 20 is a sensor for detecting the recording medium 1 H 12 to be ejected by the paper ejection roller 1 H 16 .

The waste toner box 1 H 12 is a container for collecting a pattern formed on the transfer belt 1 H 3 or toners remaining on the transfer belt 1 H 13 which were not transferred onto the recording medium 1 H 12 .

<Outline of Operation of Image Forming Apparatus>

The image forming apparatus, upon performing an image formation, charges the photoconductors of the respective colors 1 H 6 A, 1 H 6 B, 1 H 6 C and 1 H 6 D by the charging units 1 H 7 A, 1 H 7 B, 1 H 7 C and 1 H 7 D, respectively.

The exposure unit 1 H 8 emits laser lights 1 H 11 A, 1 H 11 B, 1 H 11 C and 1 H 11 D on the charged photoconductors 1 H 6 A, 1 H 6 B, 1 H 6 C and 1 H 6 D, performs exposure and forms electrostatic latant images, respectively.

The developing devices 1 H 9 A, 1 H 9 B, 1 H 9 C and 1 H 9 D stick toners to the electrostatic latent images formed on the photoconductors 1 H 6 A, 1 H 6 B, 1 H 6 C and 1 H 6 D, performs developing and forms toner images, respectively.

Next, a so-called “primary transfer” is performed for the toner images by the photoconductors 1 H 6 A, 1 H 6 B, 1 H 6 C and 1 H 6 D contacting with the transfer belt 1 H 3 . The primary transfer is performed by the primary transfer rollers of the respective colors 1 H 22 A, 1 H 22 B, 1 H 22 C and 1 H 22 D. The toner images are formed on the transfer belt 1 H 3 by the primary transfer.

After the primary transfer ends, toners remaining on the photoconductors 1 H 6 A, 1 H 6 B, 1 H 6 C and 1 H 6 D are removed by the cleaner blades 1 H 10 A, 1 H 10 B, 1 H 10 C and 1 H 10 D, respectively.

A toner image formed in the developing unit 1 H 1 A is conveyed to the next developing unit 1 H 1 B by the transfer belt 3 . Similarly, the developing unit 1 H 1 B, 1 H 1 C and 1 H 1 D perform transfers so that toner images of the respective colors are superimposed each other. By the developing units 1 H 1 A, 1 H 1 B, 1 H 1 C and 1 H 1 D a full-color toner image is formed.

The full-color toner image formed on the transfer belt 3 is conveyed to the secondary transfer roller 1 H 18 , which performs a secondary transfer, by the transfer belt 3 .

The recording medium 1 H 12 is conveyed from the paper feeding tray 1 H 13 to the registration roller 1 H 15 by the paper feeding roller 1 H 14 . The conveyed recording medium 1 H 12 is further conveyed to the secondary transfer roller 1 H 18 , which performs the secondary transfer, by the registration roller 1 H 15 .

The conveyance of the recording medium 1 H 12 by the registration roller 1 H 15 and the conveyance of the toner image by the transfer belt 1 H 3 are performed at a timing that the toner image is transferred onto the recording medium 1 H 12 at a predetermined position. That is, at the timing that the recording medium 1 H 12 and the toner image overlap each other at a position of the secondary transfer roller 1 H 18 that performs the secondary transfer, the registration roller 1 H 15 and the transfer belt driving roller 1 H 4 start driving.

The secondary transfer roller 1 H 18 performs the secondary transfer for the toner image on the transfer belt 1 H 3 onto the recording medium 1 H 12 conveyed by the registration roller 1 H 15 . The fixing device performs a fixing process, such as heating or pressurizing for the recording medium 1 H 12 on which the secondary transfer was performed.

The recording medium 1 H 12 on which the fixing process is performed is ejected to the outside of the image forming apparatus 1 by the paper ejection roller 1 H 16 .

In the case of so-called “double sided printing”, the recording medium 1 H 12 on which the fixing process is performed is conveyed to the registration roller 1 H 15 by the double-sided roller 1 H 17 . The recording medium 1 H 12 conveyed to the registration roller 1 H 15 is conveyed by the registration roller 1 H 15 again. For the recording medium 1 H 12 conveyed by the registration roller 1 H 15 again the secondary transfer and the fixing process are performed on the side where the image formation has not been performed. Then, the recording medium 1 H 12 is ejected to the outside of the image forming apparatus 1 by the paper ejection roller 1 H 16 .

The developing units of the respective colors 1 H 1 A, 1 H 1 B, 1 H 1 C and 1 H 1 D are provided with toner amount sensors (not shown) for detecting amounts of toners. The toner amount sensor determines whether the amount of toner in the developing unit is less than or equal to a predetermined amount. In the case where it is determined that the amounts of toners in the developing units are less than or equal to the predetermined amount, toners are supplied from the toner containers of the respective colors 1 H 2 A, 1 H 2 B, 1 H 2 C and 1 H 2 D.

<Detection of Recording Medium>

The detection unit includes, for example, the paper ejection sensor 1 H 20 , the registration sensor 1 H 23 , the paper feeding sensor 1 H 24 and the fixing sensor 1 H 25 . In the following, the paper ejection sensor 1 H 20 , the registration sensor 1 H 23 , the paper feeding sensor 1 H 24 and the fixing sensor 1 H 25 are explained as examples.

The sensor is placed, for example, between the paper feeding tray 1 H 13 and the paper ejection roller 1 H 16 , i.e. on a conveyance path on which the recording medium 1 H 12 is conveyed from the paper feeding to the paper ejection. Each sensor detects a recording medium 1 H 12 passing through the position where the sensor is located. For example, the paper feeding sensor 1 H 24 detects a recording medium 1 H 12 fed by the paper feeding roller 1 H 14 . The registration sensor 1 H 23 detects a recording medium 1 H 12 fed by the paper feeding roller 1 H 14 and conveyed to the registration roller 1 H 15 . The fixing sensor 1 H 25 detects a recording medium 1 H 12 conveyed to the fixing device 1 H 19 . The paper ejection sensor 1 H 20 detects a recording medium 1 H 12 conveyed to the paper ejection sensor 1 H 16 .

From the paper feeding to the paper ejection for a recording medium 1 H 12 in the image forming apparatus 1 , the recording medium 1 H 12 is detected by the paper feeding sensor 1 H 24 , the registration sensor 1 H 23 , the fixing sensor 1 H 25 , the paper ejection sensor 1 H 20 and the like. In the following, it will be explained as an example the case where the respective sensors detect a recording medium 1 H 12 , in the order of the detection by the paper feeding sensor 1 H 24 , the detection by the registration sensor 1 H 23 , the detection by the fixing sensor 1 H 25 and the detection by the paper ejection sensor 1 H 20 , when processes from the paper feeding to the paper ejection are performed.

Meanwhile, positions where the detection units are placed, a number of the detection unit which are placed and an order of the placed detection units are not limited to those illustrated in FIG. 1 . For example, the detection unit may be placed at a position other than that shown in FIG. 1 .

<Hardware Configuration>

FIG. 2 is a block diagram for explaining an example of a hardware configuration of the image forming apparatus according to the first embodiment.

The image forming apparatus 1 includes, for example, an electronic circuit substrate (not shown), and includes hardware on the electronic circuit substrate which is configured as shown in FIG. 2 .

The image forming apparatus 1 includes a CPU (Central Processing Unit) 1 D 1 , a storage device 1 D 2 and a control device 1 D 3 . The image forming apparatus 1 further includes an ASIC (Application Specific Integrated Circuit) 1 D 4 and a sensor 1 D 5 . The respective elements included in the image forming apparatus 1 are connected via a bus 1 D 6 , and data, signals or the like are sent to or received from each other.

Meanwhile, connection to the bus 1 D 6 may be a configuration of a connection via a bridge circuit (not shown). Moreover, the configuration of the image forming apparatus 1 is not limited to the connection configuration shown in FIG. 2 . For example, the image forming apparatus may be configured so that plural buses are provided and a configuration element, which performs a process according to a fast transmission, such as an input to/output from the CPU 1 D 1 and a configuration element, which performs a process according to a slow transmission, such as an input interface device (not shown) are connected to different buses, respectively.

The CPU 1 D 1 performs various processes that the image forming apparatus 1 performs. For example, the CPU 1 D 1 acquires data or a program stored in the storage device 1 D 2 , which will be described later, via the bus 1 D 7 . Moreover, the CPU 1 D 1 outputs an instruction, a parameter or the like to the control device 1 D 3 and the ASIC 1 D 4 , which will be described later, via the bus 1 D 6 , thereby controls the entire image forming apparatus 1 .

The CPU 1 D 1 performs various determinations based on a signal input from the sensor 1 D 5 , which will be described later, by the sensing control device 1 D 31 , which will be described later. The CPU 1 D 1 includes a sensor register 1 D 11 . The sensor register 1 D 11 is a port for inputting information of a signal to the CPU 1 D 1 , wherein the sensor register 1 D 11 being provided for each signal correspondingly.

The CPU 1 D 1 controls the devices included in the image formation apparatus 1 , such as the fixing device 1 H 19 in FIG. 1 , a motor (not shown) for the paper feeding roller 1 H 14 in FIG. 1 and the like, for example, through a control device for respective devices 1 D 32 , which will be described later.

Meanwhile, the CPU 1 D 1 may be configured by plural devices or plural cores so as to speed up processes by a parallel processing. Moreover, the processes by the CPU 1 D 1 may be performed by a distributed processing or the parallel processing wherein a separated hardware resource (not shown) is provided inside or outside the image forming apparatus 1 and assists the CPU 1 D 1 .

The storage device 1 D 2 is a so-called “main storage unit”, an auxiliary storage unit or the like, such as a memory, a register, a hard disk (HD) or the like, which is provided with a storage area and a control device. The storage device 1 D 2 stores, for example, information such as various data including intermediate results of processes based on the control by the CPU 1 D 1 , parameters or programs.

The control device 1 D 3 performs control for various devices included in the image forming apparatus 1 . The control device 1 D 3 includes, for example, the sensing control device 1 D 31 and the control device for respective devices 1 D 32 .

The sensing control device 1 D 31 controls the sensor 1 D 5 . The control device for respective devices 1 D 32 controls devices included in the image forming apparatus 1 .

The sensor 1 D 5 includes, for example, the paper ejection sensor 1 H 20 , the registration sensor 1 H 23 , the paper feeding sensor 1 H 24 and the fixing sensor 1 H 25 . Each of the sensors detects presence or absence of a recording medium 1 H 12 and outputs a signal. For example, the registration sensor 1 H 23 detects whether a recording medium 1 H 12 is conveyed to the registration roller in FIG. 1 . In the case where the recording medium 1 H 12 is conveyed to the registration roller in FIG. 1 , the registration sensor 1 H 23 output a signal of a predetermined potential. The sensing control device 1 D 31 performs a process such as A/D conversion and detects whether the recording medium 1 H 12 is conveyed to the registration roller in FIG. 1 based on the signal output from the registration sensor 1 H 23 .

The control device for respective devices 1 D 32 controls the respective devices, for example, by transmitting a control signal or supplying electric power to the respective devices based on an instruction from the CPU 1 D 1 .

The ASIC 1 D 4 is a processing circuit for performing specific processing, such as image processing, for example. Based on the instruction from the CPU 1 D 1 , for example, the ASIC 1 D 4 performs processing for generating image data for an image formed on the recording medium 1 H 12 .

Meanwhile, the ASIC 1 D 4 is not limited to an ASIC. The ASIC 1 D 4 may be realized by, instead of an ASIC, an FPGA (Field-Programmable Gate Array), a CPLD (Complex Programmable Logic Device) or the like.

Meanwhile, the hardware configuration is not limited to the configuration illustrated in FIG. 2 . For example, the configuration may include other device.

<Functional Configuration>

FIG. 3 is a block diagram for explaining an example of a functional configuration of the image forming apparatus according to the first embodiment.

The image forming apparatus 1 includes an input/output unit 1 F 1 , a control unit 1 F 2 , a detection unit 1 F 3 and a processing unit 1 F 4 .

The input/output unit 1 F 1 inputs/outputs information such as data or an operation by a user to/from the image forming apparatus 1 . The input/output unit 1 F 1 is realized, for example, by the CPU 1 D 1 in FIG. 2 , the control device for respective devices 1 D 32 and the like. For example, the CPU 1 D 1 in FIG. 2 and the control device for respective devices 1 D 32 realize a process for inputting/outputting information such as image data by controlling an input device (not shown) and an output device (not shown) included in the image forming apparatus 1 .

The control unit 1 F 2 controls the respective devices included in the image forming apparatus 1 . The control unit 1 F 2 is realized by the CPU 1 D 1 in FIG. 2 , the control device 1 D 3 and the like. The control device 1 F 2 realizes, for example, the respective processes performed upon the image formation such as the conveyance, the transfer, the fixing and the like, by controlling the respective devices.

The detection unit 1 F 3 detects a recording medium 1 H 12 at a predetermined location and outputs a detection signal. Details of the detection signal will be described later. The detection unit 1 F 3 includes a paper feeding roller location detection unit 1 F 31 , a registration roller location detection unit 1 F 32 , a fixing device location detection unit 1 F 33 and a paper ejection roller location detection unit 1 F 34 .

The paper feeding roller location detection unit 1 F 31 is realized by the paper feeding sensor 1 H 24 in FIG. 1 , which is a sensor in FIG. 2 , and the sensing control device 1 D 31 in FIG. 2 . When a recording medium 1 H 12 is conveyed at the location of the paper feeding roller 1 H 14 in FIG. 1 , the paper feeding roller location detection unit 1 F 31 outputs a first detection signal SIG 1 , which is a detection signal.

The registration roller location detection unit 1 F 32 is realized by the registration sensor 1 H 23 in FIG. 1 , which is a sensor in FIG. 2 , and the sensing control device 1 D 31 in FIG. 2 . When a recording medium 1 H 12 is conveyed at the location of the registration roller 1 H 15 in FIG. 1 , the registration roller location detection unit 1 F 32 outputs a second detection signal SIG 2 , which is a detection signal.

The fixing device location detection unit 1 F 33 is realized by the fixing sensor 1 H 25 in FIG. 1 , which is a sensor in FIG. 2 , and the sensing control device 1 D 31 in FIG. 2 . When a recording medium 1 H 12 is conveyed at the location of the fixing device 1 H 19 in FIG. 1 , the fixing device location detection unit 1 F 33 outputs a third detection signal SIG 3 , which is a detection signal.

The paper ejection roller location detection unit 1 F 34 is realized by the paper ejection sensor 1 H 20 in FIG. 1 , which is a sensor in FIG. 2 , and the sensing control device 1 D 31 in FIG. 2 . When a recording medium 1 H 12 is conveyed at the location of the paper ejection sensor 1 H 20 in FIG. 1 , the paper ejection roller location detection unit 1 F 34 outputs a fourth detection signal SIG 4 , which is a detection signal.

The processing unit 1 F 4 performs the respective processes. The processing unit 1 F 4 is realized by the CPU 1 D 1 in FIG. 2 and the like. The processing unit 1 F 4 includes a first reception unit 1 F 41 , a second reception unit 1 F 42 , a third reception unit 1 F 43 , a fourth reception unit 1 F 44 , a signal generation unit 1 F 45 , a sensor state determination unit 1 F 46 and an apparatus state determination unit 1 F 47 .

When the paper feeding roller location detection unit 1 F 31 detects a recording medium 1 H 12 , the first detection signal SIG 1 is input to the first reception unit 1 F 41 .

When the registration roller location detection unit 1 F 32 detects a recording medium 1 H 12 , the second detection signal SIG 2 is input to the second reception unit 1 F 42 .

When the fixing device location detection unit 1 F 33 detects a recording medium 1 H 12 , the third detection signal SIG 3 is input to the third reception unit 1 F 43 .

When the paper ejection roller location detection unit 1 F 34 detects a recording medium 1 H 12 , the fourth detection signal SIG 4 is input to the fourth reception unit 1 F 44 .

The signal generation unit 1 F 45 generates a substitute signal SIG 5 as a substitute for the first, second, third and fourth detection signals (SIG 1 , SIG 2 , SIG 3 and SIG 4 ) in a predetermined case.

The apparatus state determination unit 1 F 47 determines a state of a failure or the like including a paper jam in the image forming apparatus 1 (hereinafter, referred to as “jam”) and states of the sensors. The sensor state determination unit 1 F 46 determines a state of failure or the like in each of the sensors. Details of the determination will be described later.

<Determination According to Signal>

FIG. 4 is a timing chart for explaining an example of determination based on a signal according to the first embodiment.

In FIG. 4 , a case where each signal is a so-called “high active signal” will be explained as an example. A high potential is 5 volts for example, and a low potential is 0 volts for example. In the case where each of the sensors detect a recording medium 1 H 12 , the sensor outputs a signal of the high potential.

The apparatus state determination unit 1 F 47 in FIG. 3 compares timings of a comparison signal SIG 6 , for example, and of each of the detected signals, and performs determination. The comparison signal SIG 6 is a signal for setting a timing being a criterion of comparison for each of the detected signals. In the following, it will be explained with reference to FIG. 4 as an example.

Assume that in FIG. 4 , in the case where an active signal of the first detection signal SIG 1 is asserted between a timing T 1 and a timing T 2 , the paper feeding roller location detection unit 1 F 31 in FIG. 3 detects a recording medium 1 H 12 . That is, in the case where the first detection signal SIG 1 is asserted between the timing T 1 and the timing T 2 , the apparatus state determination unit 1 F 47 determines that the image forming apparatus 1 is a “normal” state to the paper feeding sensor 1 H 24 without a jam or the like. In FIG. 4 , since the first detection signal SIG 1 has a rising edge at the timing T 9 , it is the asserted state.

Similarly, timings T 3 and T 4 are set in the comparison signal SIG 6 for the second detection signal SIG 2 . Similarly, timings T 5 and T 6 are set in the comparison signal SIG 6 for the third detection signal SIG 3 . Similarly, timings T 7 and T 8 are set in the comparison signal SIG 6 for the fourth detection signal SIG 4 .

In an upper part (A) of FIG. 4 , the apparatus state determination unit 1 F 47 determines that a recording medium 1 H 12 is conveyed to the locations of the paper feeding sensor 1 H 24 , the registration sensor 1 H 23 , the fixing sensor 1 H 25 and the paper ejection sensor 1 H 20 in order and that the image forming apparatus 1 is in the “normal” state.

In the following, a case where distances among the paper feeding sensor 1 H 24 , the registration sensor 1 H 23 , the fixing sensor 1 H 25 and the paper ejection sensor 1 H 20 are 100 millimeters, the conveyance speed of the recording medium 1 H 12 is 200 millimeters per second and the timing T 9 is 1.0 second will be explained as an example.

Since the first detection signal SIG 1 transits from low to high at the timing T 9 , in the comparison signal SIG 6 a criterion for detecting the timing T 9 , which is the rising edge of the first detection signal SIG 1 , is set. The criterion is set with a margin taking account of an error or the like. For example, in the case where the margin is 0.1 seconds, the criterion of detecting the timing T 9 is set as 0.9 seconds to 1.1 seconds. That is, in the case where the rising edge of the first detection signal occurs between 0.9 seconds to 1.1 seconds, the apparatus state determination unit 1 F 47 determines that it is the state where the recording medium 1 H 12 is conveyed to the location of the paper feeding sensor 1 H 24 . When it is determined that it is the state where the recording medium 1 H 12 is conveyed to the location of the paper feeding sensor 1 H 24 , the apparatus state determination unit 1 F 47 determines that it is “normal” to the location of the paper feeding sensor 1 H 24 .

In the case where it is “normal” to the location of the paper feeding sensor 1 H 24 , the recording medium is conveyed to the registration sensor 1 H 23 . Time taken from the paper feeding sensor 1 H 24 to the registration sensor 1 H 23 is 0.5 seconds. Therefore, in the case where the timing T 9 is 1.0 second, the timing T 10 of a rising edge of the second detection signal SIG 2 is 1.5 seconds. In the same way as the criterion of detecting the timing T 9 , in the comparison signal SIG 6 the criterion of detecting the timing T 10 , which is the rising edge of the second detection signal SIG 2 , is set as 1.4 seconds to 1.6 seconds. In the case where the timing T 9 is 1.1 seconds, the criterion is set as 1.5 seconds to 1.7 seconds. In the same way as the case of the paper feeding sensor 1 H 24 , when the rising edge of the second detection signal SIG 2 occurs within the criterion, the apparatus state determination unit 1 F 47 determines that it is “normal” from the paper feeding sensor 1 H 24 to the registration sensor 1 H 23 . In the case where it is “normal” from the paper feeding sensor 1 H 24 to the registration sensor 1 H 23 , the recording medium 1 H 12 is conveyed to the location of the fixing sensor 1 H 25 .

Similarly, the apparatus state determination unit 1 F 47 performs determination to the locations of the registration sensor 1 H 23 and the fixing sensor 1 H 25 based on the third detection signal SIG 3 . In the case of “normal”, the recording medium 1 H 12 is conveyed to the location of the paper ejection sensor 1 H 20 .

Furthermore, the apparatus state determination unit 1 F 47 performs determination to the locations of the fixing sensor 1 H 25 and the paper ejection sensor 1 H 20 based on the fourth detection signal SIG 4 . In the case of “normal”, the recording medium 1 H 12 is conveyed by the paper ejection roller 1 H 16 and ejected.

In a lower part (B) of FIG. 4 , a substitute signal SIG 5 is used. A case where it is determined that the output of the detection unit is not normal is illustrated in the lower part (B) of FIG. 4 . In the following, it will be explained with reference to the lower part (B) of FIG. 4 as an example. In this case, the third detection signal SIG 3 is not asserted between the timings T 5 and T 6 . Then, the signal generation unit 1 F 45 in FIG. 3 generates a substitute signal SIG 5 which is a signal as a substitute for the third detection signal SIG 3 . The apparatus state determination unit 1 F 47 performs determination based on the substitute signal SIG 5 instead of the third detection signal SIG 3 .

If the substitute signal SIG 5 is not used instead of the third detection signal SIG 3 , the apparatus stated determination unit 1 F 47 determines that a jam occurs in the image forming apparatus 1 , and stops the conveyance of recording medium 1 H 12 in the image forming apparatus 1 . By using the substitute signal SIG 5 , the apparatus state determination unit 1 F 47 can receive the fourth detection signal SIG 4 .

The signal generation unit 1 F 45 generates the substitute signal SIG 5 as a substitute for the third detection signal SIG 3 based on the first detection signal SIG 1 and the second detection signal SIG 2 . The signal generation unit 1 F 45 inputs the generated substitute signal SIG 5 in the apparatus state determination unit 1 F 47 . When the substitute signal is input to the apparatus state determination unit 1 F 47 , the apparatus state determination unit 1 F 47 , in the same way as the third detection signal SIG 3 , compares the substitute signal SIG 5 with the comparison signal SIG 6 , and determines that the recording medium 1 H 12 is conveyed to the location of the fixing sensor 1 H 25 . By inputting the substitute signal SIG 5 , the image forming apparatus 1 can release the state where the conveyance of recording medium 1 H 12 is stopped based on the determination by the apparatus state determination unit 1 F 47 .

In the case where the substitute signal SIG 5 is input, by conveying the recording medium 1 H 12 , the recording medium 1 H 12 is conveyed to the location of the paper ejection sensor 1 H 20 and further.

In the case where the substitute signal SIG 5 is input instead of the third detection signal SIG 3 and the fourth detection signal SIG 4 is not detected, it is determined that there is some defect on a conveyance path, for example. The defect includes a state where the conveyance of the recording medium 1 H 12 is obstructed due to, for example, abrasion accompanying aging deterioration of a conveyance member or an occurrence of warpage by a rise in temperature or the like. Accordingly, the apparatus state determination unit 1 F 47 can perform determination of the jam or the like at the fixing sensor 1 H 25 and on the conveyance path of a recording medium 1 H 12 by inputting the substitute signal SIG 5 . Details of the determination of the jam will be described later.

In the case where when the substitute signal SIG 5 is input and the recording medium 1 H 12 is conveyed, the fourth detection signal SIG 4 is asserted between the timings T 7 and T 8 , the sensor state determination unit 1 F 46 determines that the fixing sensor 1 H 25 is in a state of “failure”.

In the case where the fixing sensor 1 H 25 is determined to be in the state of “failure”, the apparatus state determination unit 1 F 47 determines that a jam does not occur but the fixing sensor 1 H 25 is in the state of “failure”, and identifies the state of the image forming apparatus 1 . Accordingly, the apparatus state determination unit 1 F 47 is made easy to identify the state of the image forming apparatus 1 by using the substitute signal SIG 5 .

Meanwhile, the present embodiment is not limited to using a so-called “high active signal”. Moreover, the present embodiment is not limited to using the rising edge. For example, a falling edge or both edges may be used.

Furthermore, the present embodiment is not limited to using an edge. For example, so-called “detection for level”, using a high active signal or a low active signal, which is longer than or equal to a predetermined length, may be used.

Moreover, in the present embodiment, in the case of conveyance of plural recording media, the substitute signal may be generated from the detection signal sequentially from behind depending on a size of the recording medium, the location of the sensor or the like.

<Entire Processing>

FIG. 5 is a flowchart for explaining an example of the entire process of the image formation according to the first embodiment.

First, the image forming apparatus 1 inputs image formation data, an image formation condition and the like by the input/output unit 1 F 1 in FIG. 3 (step S 0501 ).

The image forming apparatus 1 performs setting for detecting the first detection signal by the apparatus state determination unit 1 F 47 (step S 0502 ) in FIG. 3 . Processing for setting for detecting the first detection signal includes, for example, calculating a time for the timing of the rising edge of the first detection signal SIG 1 in FIG. 4 , setting a criterion for detection in the comparison signal SIG 6 , and the like. In the calculation, for example, a start time is set at a timing when a clutch (not shown) of the paper feeding roller 1 H 14 in FIG. 1 turns to ON, and the criterion of detecting the rising edge of the first detection signal SIG 1 is calculated from a distance to the paper feeding sensor 1 H 24 .

The image forming apparatus 1 determines whether the first detection signal is detected by the apparatus state determination unit 1 F 47 in FIG. 3 (step S 0503 ). In the case where the first detection signal is detected (step S 0503 : YES), the process of the image forming apparatus 1 proceeds to step S 0505 . When the first detection signal is not detected (step S 0503 : NO), the process of the image forming apparatus 1 proceeds to step S 0504 . At step S 0503 , the image forming apparatus 1 performs determination according to whether the first detection signal SIG 1 is asserted based on the criterion set at step S 0502 .

At step S 0504 , the image forming apparatus 1 generates a substitute signal for the first detection signal by the signal generation unit 1 F 45 in FIG. 3 . The image forming apparatus 1 generates the substitute signal SIG 5 as a substitute for the first detection signal SIG 1 by the signal generation unit 1 F 45 in FIG. 3 .

At step S 0505 , the image forming apparatus 1 conveys a recording medium 1 H 12 to the location of the registration sensor 1 H 23 by the control unit 1 F 2 in FIG. 3 . At step S 0505 , the image forming apparatus 1 controls a motor (not shown) for the paper feeding roller 1 H 14 or the like to convey the recording medium 1 H 12 to the registration sensor 1 H 23 .

Next, the image forming apparatus 1 performs setting for detecting the second detection signal by the apparatus state determination unit 1 F 47 (step S 0506 ) in FIG. 3 . Processing for setting for detecting the second detection signal includes, for example, calculating a time for the timing of the rising edge of the second detection signal SIG 2 in FIG. 4 , setting a criterion for detection in the comparison signal SIG 6 , and the like. In the calculation, for example, the criterion of detecting the rising edge of the second detection signal SIG 2 is calculated based on the time for the timing detected at step S 0503 and a distance from the paper feeding sensor 1 H 24 to the registration sensor 1 H 23 .

The image forming apparatus 1 determines whether the second detection signal is detected by the apparatus state determination unit 1 F 47 in FIG. 3 (step S 0507 ). In the case where the second detection signal is detected (step S 0507 : YES), the process of the image forming apparatus 1 proceeds to step S 0510 . When the second detection signal is not detected (step S 0507 : NO), the process of the image forming apparatus 1 proceeds to step S 0508 . At step S 0507 , the image forming apparatus 1 performs determination according to whether the second detection signal SIG 2 is asserted based on the criterion set at step S 0506 .

At step S 0508 , the image forming apparatus 1 determines whether a substitute signal for the first detection signal is generated by the apparatus state determination unit 1 F 47 in FIG. 3 . That is, at step S 0508 , the image forming apparatus 1 determines whether the process at step S 0504 is performed by the apparatus state determination unit 1 F 47 in FIG. 3 . In the case where the substitute signal for the first detection signal is generated (step S 0508 : YES), the process of the image forming apparatus 1 proceeds to step S 0522 . When the substitute signal for the first detection signal is not generated (step S 0508 : NO), the process of the image forming apparatus 1 proceeds to step S 0509 .

At step S 0509 , a substitute signal for the second detection signal is generated by the signal generation unit 1 F 45 in FIG. 3 . The image forming apparatus 1 generates the substitute signal SIG 5 as a substitute for the second detection signal SIG 2 by the signal generation unit 1 F 45 in FIG. 3 .

At step S 0510 , the image forming apparatus 1 conveys the recording medium 1 H 12 to the location of the fixing sensor 1 H 25 by the control unit 1 F 2 in FIG. 3 . At step S 0510 , the image forming apparatus 1 controls a motor (not shown) for the registration roller 1 H 15 or the like to convey the recording medium 1 H 12 to the fixing sensor 1 H 25 . That is, at step S 0510 , the image forming apparatus 1 conveys the recording medium 1 H 12 to the fixing device 1 H 19 .

Next, the image forming apparatus 1 performs setting for detecting the third detection signal by the apparatus state determination unit 1 F 47 (step S 0511 ) in FIG. 3 . Processing for setting for detecting the third detection signal includes, for example, calculating a time for the timing of the rising edge of the third detection signal SIG 3 in FIG. 4 , setting a criterion for detection in the comparison signal SIG 6 , and the like. In the calculation, for example, the criterion of detecting the rising edge of the third detection signal SIG 3 is calculated based on the time for the timing detected at step S 0507 and a distance from the registration sensor 1 H 23 to the fixing sensor 1 H 25 .

The image forming apparatus 1 determines whether the third detection signal is detected by the apparatus state determination unit 1 F 47 in FIG. 3 (step S 0512 ). In the case where the third detection signal is detected (step S 0512 : YES), the process of the image forming apparatus 1 proceeds to step S 0515 . When the third detection signal is not detected (step S 0512 : NO), the process of the image forming apparatus 1 proceeds to step S 0513 . At step S 0512 , the image forming apparatus 1 performs determination according to whether the third detection signal SIG 3 is asserted based on the criterion set at step S 0511 .

At step S 0513 , the image forming apparatus 1 determines whether a substitute signal for the first detection signal or the second detection signal is generated by the apparatus state determination unit 1 F 47 in FIG. 3 . That is, at step S 0513 , the image forming apparatus 1 determines whether the process at step S 0504 or the process at step S 0509 is performed by the apparatus state determination unit 1 F 47 in FIG. 3 . In the case where the substitute signal for at least one of the first detection signal and the second detection signal is generated (step S 0513 : YES), the process of the image forming apparatus 1 proceeds to step S 0522 . When neither the substitute signal for the first detection signal nor the substitute signal for the second detection signal is generated (step S 0513 : NO), the process of the image forming apparatus 1 proceeds to step S 0514 .

At step S 0514 , a substitute signal for the third detection signal is generated by the signal generation unit 1 F 45 in FIG. 3 . The image forming apparatus 1 generates the substitute signal SIG 5 as a substitute for the third detection signal SIG 3 by the signal generation unit 1 F 45 in FIG. 3 .

At step S 0515 , the image forming apparatus 1 conveys the recording medium 1 H 12 to the location of the paper ejection sensor 1 H 20 by the control unit 1 F 2 in FIG. 3 . At step S 0515 , the image forming apparatus 1 controls a motor (not shown) for the fixing device 1 H 19 or the like to convey the recording medium 1 H 12 to the paper ejection sensor 1 H 20 .

Next, the image forming apparatus 1 performs setting for detecting the fourth detection signal by the apparatus state determination unit 1 F 47 (step S 0516 ). Processing for setting for detecting the fourth detection signal includes, for example, calculating a time for the timing of the rising edge of the fourth detection signal SIG 4 in FIG. 4 , setting a criterion for detection in the comparison signal SIG 6 , and the like. In the calculation, for example, the criterion of detecting the rising edge of the third detection signal SIG 3 is calculated based on the time for the timing detected at step S 0512 and a distance from the fixing sensor 1 H 25 to the paper ejection sensor 1 H 20 .

The image forming apparatus 1 determines whether the fourth detection signal is detected by the apparatus state determination unit 1 F 47 in FIG. 3 (step S 0517 ). In the case where the fourth detection signal is detected (step S 0517 : YES), the process of the image forming apparatus 1 proceeds to step S 0520 . When the fourth detection signal is not detected (step S 0517 : NO), the process of the image forming apparatus 1 proceeds to step S 0518 . At step S 0517 , the image forming apparatus 1 performs determination according to whether the fourth detection signal SIG 4 is asserted based on the criterion set at step S 0516 .

At step S 0518 , the image forming apparatus 1 determines whether a substitute signal for at least any one of the first to third detection signals is generated by the apparatus state determination unit 1 F 47 in FIG. 3 . That is, at step S 0518 , the image forming apparatus 1 determines whether at least any one of the processes at step S 0504 , S 0509 and S 0514 is performed by the apparatus state determination unit 1 F 47 in FIG. 3 . In the case where the substitute signal for at least any one of the first to third detection signals is generated (step S 0518 : YES), the process of the image forming apparatus 1 proceeds to step S 0522 . When none of the substitute signals for the first to third detection signals are generated (step S 0518 : NO), the process of the image forming apparatus 1 proceeds to step S 0519 .

At step S 0519 , a substitute signal for the fourth detection signal is generated by the signal generation unit 1 F 45 in FIG. 3 . The image forming apparatus 1 generates the substitute signal SIG 5 as a substitute for the fourth detection signal SIG 4 by the signal generation unit 1 F 45 in FIG. 3 .

At step S 0520 , the image forming apparatus 1 ejects the recording medium 1 H 12 by the control unit 1 F 2 in FIG. 3 . At step S 0520 , the image forming apparatus 1 controls a motor (not shown) for the paper ejection roller 1 H 16 or the like to eject the recording medium 1 H 12 from the image forming apparatus 1 .

Next, the image forming apparatus 1 determines whether the recording medium 1 H 12 is ejected by the control unit 1 F 2 in FIG. 3 (step S 0521 ). At step S 0521 , the image forming apparatus 1 determines whether the recording medium 1 H 12 is ejected according to the process at step S 0520 . The ejection of the recording medium 1 H 12 is detected by a sensor (not shown) for detecting the paper ejection, for example. When the paper ejection is detected (step S 0521 : YES), the process of the image forming apparatus 1 proceeds to step S 0525 . When the paper ejection is not detected (step S 0521 : NO), the process of the image forming apparatus 1 proceeds to step S 0522 .

At step S 0522 , the image forming apparatus 1 determines that the image forming apparatus 1 is in a state of a jam by the apparatus state determination unit 1 F 47 in FIG. 3 . At step S 0522 , the image forming apparatus 1 is, for example, in a state where the substitute signal SIG 5 for the first detection signal is generated at step S 0504 and the second detection signal is not detected at step S 0507 . The case where the second detection signal is not detected will be explained later in detail. In the image forming apparatus 1 of this state, some failures such as a jam occurs from the paper feeding tray 1 H 13 to the paper feeding sensor 1 H 24 .

At step S 0523 , the image forming apparatus 1 restricts the conveyance of a recording medium 1 H 12 by the control unit 1 F 2 in FIG. 3 . At step S 0523 , the image forming apparatus 1 is in a state where the sensor is not in the state of failure, but the image forming apparatus 1 is determined to be in the state of a jam. Accordingly, the image forming apparatus 1 performs restriction for the conveyance of the recording medium 1 H 12 , such as stopping the conveyance of the recording medium.

Then, the image forming apparatus 1 gives notice of the jam by the control unit 1 F 2 in FIG. 3 (step S 0524 ). At step S 0524 , the image forming apparatus 1 gives notice of a result of determination at step S 0522 , for example, to a user, a serviceman or the like.

At step S 0525 , the image forming apparatus 1 determines states of the sensors by the sensor state determination unit 1 F 46 in FIG. 3 . At step S 0525 , a substitute signal is generated for any one of the first, second, third and fourth detection signals SIG 1 , SIG 2 , SIG 3 and SIG 4 , or none of the substitute signals for the first to fourth detection signals are generated. In the case where none of the substitute signals for the first to fourth detection signals are generated, the sensors are in the so-called “normal” state where the paper feeding sensor 1 H 24 , the registration sensor 1 H 23 , the fixing sensor 1 H 25 and the paper ejection sensor 1 H 20 detect the conveyed recording medium 1 H 12 .

In the case where the substitute signal for the first detection signal SIG 1 is generated at step S 0504 and the second detection signal SIG 2 is detected at step S 0507 , the sensor state determination unit 1 F 46 determines that the paper feeding sensor 1 H 24 that outputs the first detection signal is in a state of “failure”.

In the case where the substitute signal for the second detection signal SIG 2 is generated at step S 0509 and the third detection signal SIG 3 is detected at step S 0512 , the sensor state determination unit 1 F 46 determines that the registration sensor 1 H 23 that outputs the second detection signal is in a state of “failure”.

In the case where the substitute signal for the third detection signal SIG 3 is generated at step S 0514 and the fourth detection signal SIG 4 is detected at step S 0517 , the sensor state determination unit 1 F 46 determines that the fixing sensor 1 H 25 that outputs the third detection signal is in a state of “failure”.

In the case where the substitute signal for the fourth detection signal SIG 4 is generated at step S 0519 and the paper ejection is detected at step S 0521 , the sensor state determination unit 1 F 46 determines that the paper ejection sensor 1 H 20 that outputs the fourth detection signal is in a state of “failure”.

<Image Formation Using Substitute Signal>

The lower part (B) of FIG. 4 illustrates the case where the fixing sensor 1 H 25 is determined to be in the state of “failure”. In the case where any one of the detection units is determined to be in the state of “failure”, the signal generation unit 1 F 45 generates a substitute signal SIG 5 instead of the third detection signal SIG 3 , and inputs the substitute signal SIG 5 . Since the substitute signal SIG 5 is input, the image forming apparatus 1 can convey the recording medium 1 H 12 . Since the recording medium 1 H 12 is conveyed, the image forming apparatus 1 can perform the image formation.

If the substitute signal SIG 5 is not input, since the fixing sensor 1 H 25 is in the state of “failure”, the third detection signal SIG 3 is not output. In the case where the substitute signal SIG 5 and the third detection signal SIG 3 are not input, the apparatus state determination unit 1 F 47 determines that the image forming apparatus 1 is in a state where a jam or the like occurs. When the apparatus state determination unit 1 F 47 determines that it is in the state where the jam or the like occurs, the image forming apparatus 1 stops the conveyance of the recording medium 1 H 12 and the image formation.

That is, by inputting the substitute signal SIG 5 , the image forming apparatus 1 can perform the image formation. In the image forming apparatus 1 according to the present embodiment, even if the third detection signal is not output, the image formation may be performed. According to this feature, the mean time between failures (MTBF) of the image forming apparatus 1 can be made longer. By making the MTBF longer, the reliability can be enhanced.

Moreover, in the case illustrated in the lower part (B) of FIG. 4 , when the fixing sensor 1 H 25 is determined to be in the state of “failure”, the image forming apparatus 1 gives notice of the result of the determination to a service man or the like who will repair the image forming apparatus 1 . The service man or the like easily recognizes that the fixing sensor 1 H 25 is in the state of failure. Since the state of the image forming apparatus 1 can be recognized in detail, such as the fixing sensor 1 H 25 being in the state of failure, repair time can be shortened. Accordingly, by determining the state of the image forming apparatus 1 based on the substitute signal SIG 5 , the mean time to repair (MTTR) can be made shorter. By making the MTTR shorter, the reliability can be enhanced.

Second Embodiment

In a second embodiment, the image forming apparatus 1 shown in FIG. 1 is used as in the first embodiment. Therefore, an explanation for the entire configuration will be omitted.

In the same as in the first embodiment, the case where in the image forming apparatus 1 , which performs processes of the paper feeding to the paper ejection for a recording medium, the recording medium is detected by the paper feeding sensor 1 H 24 , the registration sensor 1 H 23 , the fixing sensor 1 H 25 and the paper ejection sensor 1 H 20 , in this order, will be explained as an example.

In the second embodiment, as in the first embodiment, the apparatus state determination unit 1 F 47 in FIG. 3 compares timings of a comparison signal SIG 6 , for example, and of the detected signals and performs determination. In the second embodiment, upon comparing the timings of the comparison signal SIG 6 and of each of the detected signals, a delay time (hereinafter, referred to as “delay amount”) of each of the detected signals with respect to the comparison signal SIG 6 is measured.

The measurement of the delay amount is performed, for example, on the detection at step S 0503 , S 0507 , S 0512 or S 0517 .

FIG. 6 is a timing chart for explaining an example of determination for the detection mechanism based on the delay amount according to the second embodiment.

With reference to FIG. 6 , an example for the third detection signal SIG 3 will be explained. FIG. 6 exemplifies a case where a criterion is set by the comparison signal SIG 6 that there is a timing of a rising edge T 13 of the third detection signal SIG 3 between the timings T 11 and T 12 . Similarly, FIG. 6 also exemplifies a case where a criterion is set by the comparison signal SIG 6 that there is a timing of a rising edge T 16 of the fourth detection signal SIG 4 between the timings T 14 and T 15 .

As shown in FIG. 6 , there is not the timing T 13 in the criterion, i.e. between the timings T 11 and T 12 , but the timing T 13 is delayed from the criterion. The apparatus state determination unit 1 F 47 in FIG. 3 , for example, measures a delay amount from the timing T 11 to the timing T 13 .

The signal generation unit 1 F 45 in FIG. 3 generates a substitute signal SIG 5 for the third detection signal SIG 3 which is delayed. As explained in the first embodiment, by using the substitute signal SIG 5 , the image forming apparatus 1 can convey the recording medium 1 H 12 also to the location of the paper ejection sensor 1 H 20 and further.

In the second embodiment, in the case of using the substitute signal SIG 5 , the apparatus state determination unit 1 F 47 in FIG. 3 measures the timing T 16 of the rising edge of the fourth detection signal SIG 4 .

In FIG. 6 , since the timing T 16 is detected between the timings T 14 and T 15 , it is determined to be in a state where there is not a delay, i.e. a “normal” state.

In the case shown by FIG. 6 , the timing T 13 is delayed but the timing T 16 is not delayed (a “normal” state). FIG. 6 exemplifies the case where it is determined that an output abnormality occurs in the third detection signal.

In the case where the timing T 13 is delayed, a member of a mechanism at the location where the fixing sensor 1 H 25 is placed, i.e. a detection mechanism for the fixing device 1 H 19 , may be abraded. The detection mechanism for the fixing device 1 H 19 is, for example, a so-called “filler mechanism”. In the following, the filler mechanism will be explained.

The filler mechanism is a mechanism for detecting a recording medium such as a conveyed paper.

The filler mechanism includes a sensor. The filler mechanism is placed at a position where the filler mechanism contacts with the conveyed recording medium. When the recording medium is conveyed, the filler mechanism rotates according to a contact with the recording medium. A sensor of the filler mechanism detects a rotation of the filler mechanism. The filler mechanism generates various detection signals based on the detection of the rotation of the filler mechanism, and outputs them.

For example, in the case where the filler mechanism is worn out due to an aging deterioration or the like, even when the conveyed recording medium contacts with the filler mechanism, the filler mechanism may not rotate or the rotation is delayed due to the deterioration. That is, according to the delayed rotation of the filler mechanism due to the deterioration, a delay may occur with the detection.

Accordingly, by measuring delay amounts of the third detection signal SIG 3 and of the fourth detection signal SIG 4 , a state of the mechanism for the fixing device 1 H 19 can be determined.

FIG. 7 is a timing chart for explaining an example of determination for the conveyance mechanism based on the delay amount according to the second embodiment.

In the case of measuring delay amounts, as in FIG. 6 , when a delay for the timing T 13 of the third detection signal is found, the image forming apparatus 1 uses the substitute signal SIG 5 . Furthermore, when the fourth detection signal SIG 4 is determined to be delayed in measuring the timing T 16 , the apparatus state determination unit 1 F 47 in FIG. 3 determines that there is a “failure” for the conveyance mechanism between the registration sensor 1 H 23 and the fixing sensor 1 H 25 . The “failure” for the conveyance mechanism occurs due to, for example, an aging deterioration, an abrasion or the like of the motor used for conveyance. For example, when a pressure for retaining a recording medium decreases due to the abrasion of rollers or the like, the conveyed recording medium may slip and a delay may occur.

Accordingly, by measuring the delay amounts of the third detection signal SIG 3 and the fourth detection signal SIG 4 , a state of the conveyance mechanism of the image forming apparatus 1 can be determined.

In the case where there is a “failure” in the conveyance mechanism, the mechanism, in which a delay occurs, can convey a recording medium without delay by advancing the start time for conveyance by the measured delay amount. For example, the conveyance of the recording medium without delay can be performed by the signal generation unit 1 F 45 in FIG. 3 generating a substitute signal which is advanced by the measured delay amount.

FIG. 8 is a table for explaining an example of a result of determination according to the first and second embodiments.

The determination result table 2 illustrates an example of results of determination based on the respective detection signals and delays of the respective detection signals.

In the case where it is determined that detection signals for any of the first to fourth detection signals SIG 1 to SIG 4 can be detected and none of the detection signals are delayed, the apparatus state determination unit 1 F 47 in FIG. 3 determines that the image forming apparatus 1 is in the “normal” state. The “normal” state is a state where, for example, the respective sensors detect a recording medium and mechanisms for conveyance operate or the like to convey the recording medium without slippage or the like.

In the case where it is determined that any one of the first to fourth detection signals SIG 1 to SIG 4 is delayed, the signal generation unit 1 F 45 in FIG. 3 generates a substitute signal for the detection signal which is determined to be delayed. The apparatus state determination unit 1 F 47 in FIG. 3 measures a delay amount for a detection signal which is detected in the downstream side of the detection signal for which the substitute signal is generated. In the example illustrated in FIG. 8 , in the case where it is determined that the third detection signal is delayed, the signal generation unit 1 F 45 in FIG. 3 generates a substitute signal for the third detection signal SIG 3 , and the apparatus state determination unit 1 F 47 in FIG. 3 measures a delay amount for the fourth detection signal SIG 4 .

When it is determined that the fourth detection signal SIG 4 is not delayed (the fourth detection signal is asserted within a predetermined time interval defined by the timings T 14 and T 15 ), the apparatus state determination unit 1 F 47 in FIG. 3 determines that the apparatus is in a state where an aging deterioration or the like occurs in the detection mechanism.

When it is determined that the fourth detection signal SIG 4 is delayed (the fourth detection signal is asserted after the predetermined time interval, but the delay amount is less than a predetermined time length), the apparatus state determination unit 1 F 47 in FIG. 3 determines that the apparatus is in a state where an aging deterioration or the like occurs in the conveyance mechanism.

When it is determined that the third detection signal SIG 3 and the fourth detection signal SIG 4 are not detected (“not detected” in FIG. 8 ), i.e. the third detection signal is not asserted before the delay amount reaches the predetermined time length and the fourth detection signal is not asserted before the delay amount reaches the predetermined time length, the apparatus state determination unit 1 F 47 in FIG. 3 determines that a jam, a warpage due to a change in temperature or the like occurs in the conveyance path. In the case of the warpage due to a change in temperature, when the temperature becomes a predetermined temperature, the apparatus state determination unit 1 F 47 in FIG. 3 may determine that the apparatus is in the “normal” state. Meanwhile, the detection signal may not be detected in the case where the detection unit is in the failure state. However, a probability that both the third detection unit and the fourth detection unit are in the failure state is considered to be extremely low.

<Image Formation Restriction Processing>

The image forming apparatus 1 may perform processing for restricting image formation (hereinafter, referred to as image formation restriction processing) in the case of using a substitute signal.

The image formation restriction processing is processing for restricting processing for image formation, e.g. stopping operations of the devices for the respective processes of transferring, fixing, image processing and the like.

The image forming apparatus 1 uses a substitute signal in the case of conveying a recording medium in order to perform determination of “failure” for the respective sensors. That is, since in the determination of “failure” an image is not formed on the recording medium, the image forming apparatus 1 stops the operations of the devices for the respective processes according to the image formation restriction process, and conveys the recording medium. Since the image forming apparatus 1 does not use electricity of high voltage by stopping the device, the apparatus can be in a safe state. Since the image forming apparatus 1 does not use a consumable supply such as toner by stopping the device, consumption of the consumable supply becomes lower. Since the image forming apparatus 1 can reduce power consumption for the devices by stopping the devices, the power consumption for the apparatus can be reduced. The device to be stopped includes, for example, the developing device 1 H 19 for stopping the fixing process, the ASIC 1 D 4 for stopping the image formation process of generating image data or the like, or the motor (not shown) of the transfer belt drive roller 1 H 4 for stopping the image formation process of the primary transfer or the like. The device to be stopped is preferably a device that greatly reduces power consumption by stopping the device, such as the device for fixing or for forming images. Moreover, the device to be stopped is preferably a device, which reduces a risk of fire, a burn or the like due to heating by stopping the device, such as the device for fixing or for forming images.

Since the image forming apparatus 1 according to the present invention can convey a recording medium by generating a substitute signal even if the sensor is in a state of “failure” and perform image formation, the reliability of the image forming apparatus 1 is enhanced. Moreover, when the sensor is in the state of “failure”, the image forming apparatus 1 can identify a location of the sensor which is in the state of “failure”, by generating the substitute signal. Furthermore, when a jam or the like occurs in the image forming apparatus 1 , the image forming apparatus 1 can be identified to be in the jam state by generating the substitute signal. Accordingly, by generating the substitute signal, the state of the image forming apparatus 1 can be easily identified.

Meanwhile, in the above-described embodiments, a program for performing the respective processes may be installed in the image forming apparatus and cause the image forming apparatus to perform the respective processes.

Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.

The present application is based on and claims the benefit of priority of Japanese Priority Application No. 2014-035908 filed on Feb. 26, 2014, the entire contents of which are hereby incorporated by reference.