Image-forming apparatus configured to control rotation of developing roller to prevent toner leakage

This application claims priority from Japanese Patent Application No. 2017-148629 filed Jul. 31, 2017. The entire content of the priority application is incorporated herein by reference.

The present disclosure relates to an image-forming apparatus.

Japanese Patent Application Publication No. 2008-039905 discloses a conventional image-forming apparatus that includes a photosensitive drum, a developing roller, a collecting roller, a belt, and a cleaning member. The developing roller is configured to supply toner to the photosensitive drum. The collecting roller is configured to collect residual toner on the photosensitive drum. The belt is in contact with the photosensitive drum. The cleaning member is configured to collect the toner on the belt to clean the belt.

In this image-forming apparatus, the residual toner collected by the collecting roller is configured to move from the collecting roller to the belt through the photosensitive drum. The cleaning member is then configured to collect the residual toner moved onto the belt.

In the above-described image-forming apparatus, toner deposited on a peripheral surface of the developing roller may accumulate to form a lump of toner thereon. Such lump of toner may cause toner leakage from around the developing roller.

For example, assume that the image-forming apparatus is further provided with a thickness regulating blade for regulating a thickness of the toner carried on the developing roller. In this case, toner may accumulate between the thickness regulating blade and the developing roller to become harder therebetween. As the lump of toner grows larger, a gap is likely to be formed between the thickness regulating blade and the developing roller. As a result, toner leakage may occur through the gap between the thickness regulating blade and the developing roller.

In view of the foregoing, it is an object of the present disclosure to provide an image-forming apparatus capable of suppressing toner leakage around a developing roller.

In order to attain the above and other objects, the present disclosure provides an image-forming apparatus including: a photosensitive drum; a developing roller rotatable to supply toner to the photosensitive drum; a collecting roller; a belt in contact with the photosensitive drum; a cleaner in contact with the belt; and a controller. The developing roller is movable between a contact position in contact with the photosensitive drum and a separation position spaced away from the photosensitive drum. The collecting roller is rotatable to collect residual toner on the photosensitive drum. The cleaner is capable of collecting the residual toner on the belt. The controller is configured to perform a process in response to receiving a prescribed signal. The process starts with a first process and ends with a second process. In the first process, the controller causes the developing roller to rotate at a first speed in a first direction while maintaining the developing roller at the contact position, the first process being executed in response to receiving the prescribed signal. In the second process, the controller causes the collecting roller to move the residual toner thereon to the photosensitive drum and then to the belt to allow the cleaner to collect the residual toner on the belt while maintaining the developing roller at the separation position. The process further includes: (a) causing the developing roller to halt rotating while maintaining the developing roller at the contact position; and (b) causing the developing roller having stopped rotating in the (a) causing to start rotating at a second speed lower than the first speed in the first direction while maintaining the developing roller at the contact position. The (a) causing is executed after the first process, and the (b) causing is executed after the (a) causing and prior to the second process.

In the drawings:

FIG. 1 is a central cross-sectional view schematically illustrating an image-forming apparatus according to a first embodiment, wherein each developing roller is at its contact position;

FIG. 2 is a block diagram illustrating configurations of a controller, a first motor and a second motor for controlling operations of photosensitive drums and developing rollers according to the first embodiment;

FIG. 3 is a flowchart illustrating steps in a process executed by the controller to control operations of the image-forming apparatus according to the first embodiment;

FIG. 4 is a timing chart illustrating operations of the first motor, second motor, developing rollers, and collecting rollers in the process of FIG. 3 ;

FIG. 5A is an explanatory view illustrating a state of toner accumulated between a thickness regulating blade and its corresponding developing roller during a normal-speed rotation process executed in the process of FIG. 3 ;

FIG. 5B is an explanatory view illustrating a state of toner accumulated between the thickness regulating blade and its corresponding developing roller during a halting process executed in the process of FIG. 3 ;

FIG. 6 is an explanatory view illustrating a state of toner accumulated between the thickness regulating blade and its corresponding developing roller during a low-speed rotation process executed in the process of FIG. 3 ;

FIG. 7A is a flowchart illustrating steps executed by a main controller of the controller during the halt process and the lower-speed rotation process executed in the process of FIG. 3 ;

FIG. 7B is a flowchart illustrating steps executed by a sub controller of the controller during the halt process and the lower-speed rotation process executed in the process of FIG. 3 ;

FIG. 8 is a central cross-sectional view schematically illustrating the image-forming apparatus according to the first embodiment, wherein each developing roller is at its separation position;

FIG. 9 is a flowchart illustrating steps in a process executed by a controller to control operations of an image-forming apparatus according to a second embodiment;

FIG. 10 is a block diagram illustrating configurations of a controller, a first motor and a second motor according to a third embodiment;

FIG. 11A is a flowchart illustrating steps in a process executed by the controller to control operations of an image-forming apparatus according to the third embodiment;

FIG. 11B is a flowchart illustrating steps in a process executed by a controller to control operations of an image-forming apparatus according to a variation of the third embodiment;

FIG. 12 is a flowchart illustrating steps in a process executed by a controller to control operations of an image-forming apparatus according to a fourth embodiment;

FIGS. 13A through 13C are explanatory views illustrating a state of toner accumulated between a thickness regulating blade and its corresponding developing roller according to the fourth embodiment;

FIG. 14 is a block diagram illustrating configurations of a controller, a first motor and a second motor according to a modification to the first embodiment;

FIG. 15 is a block diagram illustrating configurations of a controller and a first motor according to another modification to the first embodiment; and

FIGS. 16A through 16G depict various modifications to a thickness regulation blade of the first embodiment.

First Embodiment

An image-forming apparatus 1 according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 through 8 .

As illustrated in FIG. 1 , an image-forming apparatus 1 includes a main casing 2 , a plurality of (four) drum cartridges 3 Y, 3 M, 3 C, and 3 K, a plurality of (four) developing cartridges 4 Y, 4 M, 4 C, and 4 K, a plurality of (four) exposure devices 5 Y, 5 M, 5 C, and 5 K, a belt unit 6 , a cleaner 7 , a fixing device 8 , a sheet feeder 9 , and a sheet tray 10 .

1. Overall Structure of the Image-Forming Apparatus 1

<Main Casing 2 >

The main casing 2 constitutes an exterior of the image-forming apparatus 1 . The main casing 2 accommodates therein the drum cartridges 3 Y, 3 M, 3 C and 3 K, the developing cartridges 4 Y, 4 M, 4 C and 4 K, the exposure devices 5 Y, 5 M, 5 C and 5 K, the belt unit 6 , the cleaner 7 , the fixing device 8 , the sheet feeder 9 , and the sheet tray 10 .

<Drum Cartridges 3 Y, 3 M, 3 C, and 3 K>

Each of the four drum cartridges 3 Y, 3 M, 3 C and 3 K is mountable in and removable from the main casing 2 . When mounted in the main casing 2 , the four drum cartridges 3 Y, 3 M, 3 C and 3 K are aligned with one another in a predetermined direction (hereinafter, to be referred to as “alignment direction”).

Since the drum cartridges 3 Y, 3 M, 3 C, and 3 K have the same structures as one another, the drum cartridge 3 K will be described in detail, while descriptions on the drum cartridges 3 Y, 3 M, and 3 C will be omitted.

The drum cartridge 3 K includes a photosensitive drum 11 K, a charger 12 K, and a collecting roller 13 K. In other words, the image-forming apparatus 1 includes the photosensitive drum 11 K and the collecting roller 13 K.

The photosensitive drum 11 K is rotatable about an axis extending in an axial direction crossing the alignment direction. In the present embodiment, the axial direction and the alignment direction are orthogonal to each other. The photosensitive drum 11 K is configured to rotate in a clockwise direction in FIG. 1 (indicated by an arrow in FIG. 1 ).

The charger 12 K is arranged to face a peripheral surface of the photosensitive drum 11 K to charge the peripheral surface of the photosensitive drum 11 K. In a state where the drum cartridge 3 K is mounted in the main casing 2 , the charger 12 K is positioned between the collecting roller 13 K and the exposure device 5 K in a rotation direction of the photosensitive drum 11 K (i.e., the clockwise direction in FIG. 1 ). Specifically, the charger 12 K is positioned upstream of the collecting roller 13 K, and downstream of the exposure device 5 K in the rotation direction of the photosensitive drum 11 K. In the present embodiment, the charger 12 K is a scorotron-type charger.

The collecting roller 13 K is configured to collect residual toner on the peripheral surface of the photosensitive drum 11 K. The collecting roller 13 K is in contact with the peripheral surface of the photosensitive drum 11 K. In the state where the drum cartridge 3 K is mounted in the main casing 2 , the collecting roller 13 K is positioned between a transfer roller 17 K (described later) of the belt unit 6 and the charger 12 K in the rotation direction of the photosensitive drum 11 K.

<Developing Cartridges 4 Y, 4 M, 4 C, and 4 K>

Since the developing cartridges 4 Y, 4 M, 4 C, and 4 K have the same structures as one another, the developing cartridge 4 K will be described in detail, while descriptions on the developing cartridges 4 Y, 4 M, and 4 C will be omitted.

The developing cartridge 4 K is detachably attachable to the drum cartridge 3 K. The developing cartridge 4 K attached to the drum cartridge 3 K is mountable in and removable from the main casing 2 . The developing cartridge 4 K stores toner therein. The developing cartridge 4 K includes a developing roller 14 K and a thickness regulating blade 15 K. In other words, the image-forming apparatus 1 includes the developing roller 14 K.

The developing roller 14 K is configured to supply toner to the photosensitive drum 11 K. In the present embodiment, the developing roller 14 K is a rubber roller having electrical conductivity. The developing roller 14 K has a columnar shape and extends in the axis direction. Specifically, in the present embodiment, the developing roller 14 K has a diameter of 13 mm. In a state where the drum cartridge 3 K and the developing cartridge 4 K are mounted in the main casing 2 , the developing roller 14 K is positioned between the exposure device 5 K and the transfer roller 17 K in the rotation direction of the photosensitive drum 11 K.

The developing roller 14 K is movable between a contact position (depicted in FIG. 1 ) and a separation position (depicted in FIG. 8 ). At the contact position, the developing roller 14 K is in contact with the photosensitive drum 11 K to allow toner supply to the photosensitive drum 11 K. At the separation position, the developing roller 14 K is separated from the photosensitive drum 11 K so that the developing roller 14 K cannot supply toner to the photosensitive drum 11 K. In order to allow the developing roller 14 K to move between the contact position and the separation position, a well-known separation member can be applied. For example, a separation member described in Japanese Patent Application Publication No. 2013-054058 may be employed.

The thickness regulating blade 15 K is configured to regulate a thickness of the toner carried on a peripheral surface of the developing roller 14 K to a constant thickness. The thickness regulating blade 15 K has a plate shape and extends in the axis direction. The thickness regulating blade 15 K includes a blade body 20 A and a contact portion 20 B, as illustrated in FIG. 5A .

Specifically, referring to FIGS. 5A to 6 , the blade body 20 A has a plate shape extends in the axial direction. The blade body 20 A has an end E 1 and another end E 2 . The end E 1 of the blade body 20 A is supported by a housing of the developing cartridge 4 K. The other end E 2 is positioned away from the end E 1 .

The contact portion 20 B is provided on the blade body 20 A at a position between the end E 1 and the other end E 2 . The contact portion 20 B extends in the axis direction. The contact portion 20 B is in contact with a peripheral surface of the developing roller 14 K. The contact portion 20 B has a semicircular shape in cross-section. The contact portion 20 B is made of a silicone rubber, for example. The thickness regulating blade 15 K can regulate the thickness of the toner borne on the peripheral surface of the developing roller 14 K into the constant thickness in accordance with rotation of the developing roller 14 K with the contact portion 20 B in contact with the peripheral surface of the developing roller 14 K. In a normal-speed rotation process (described later), a rotation direction of the developing roller 14 K at a point of contact between the developing roller 14 K and the contact portion 20 B (i.e., a first direction R 1 depicted in FIGS. 5A to 6 ) is opposite to a direction from the end E 1 toward the other end E 2 of the blade body 20 A of the thickness regulating blade 15 K. The rotation direction of the developing roller 14 K is referred to as a first direction R 1 . The normal-speed rotation process will be described later.

<Exposure Devices 5 Y, 5 M, 5 C, and 5 K>

Since the exposure devices 5 Y, 5 M, 5 C, and 5 K have the same structures as one another, the exposure device 5 K will be described in detail, while descriptions on the d exposure devices 5 Y, 5 M, 5 C will be omitted.

The exposure device 5 K is configured to expose the peripheral surface of the corresponding photosensitive drum 11 K to light. In the state where the drum cartridge 3 K and the developing cartridge 4 K are mounted in the main casing 2 , the exposure device 5 K is positioned downstream of the charger 12 K and upstream of the developing roller 14 K in the rotation direction of the photosensitive drum 11 K. Specifically, in the present embodiment, the exposure device 5 K is an LED array.

<Belt Unit 6 >

The belt unit 6 includes a belt 16 , and a plurality (four) of the transfer rollers 17 Y, 17 M, 17 C, and 17 K. In other words, the image-forming apparatus 1 includes the belt 16 .

The belt 16 is in contact with each of the four photosensitive drums 11 Y, 11 M, 11 C, and 11 K. In the present embodiment, the belt 16 is an endless belt. The belt 16 is mounted over two rollers 18 and 19 and supported by the two rollers 18 and 19 . The rollers 18 and 19 are arranged to be spaced away from each other in the alignment direction.

The belt 16 has a first portion 16 A and a second portion 16 B. The first portion 16 A is positioned between the roller 18 and the roller 19 in the alignment direction. The first portion 16 A extends in the alignment direction. The first portion 16 A is in contact with each of the four photosensitive drums 11 Y, 11 M, 11 C, and 11 K. The second portion 16 B and the photosensitive drums 11 Y, 11 M, 11 C, and 11 K are positioned opposite to each other with respect to the first portion 16 A. The second portion 16 B is positioned between the roller 18 and the roller 19 in the alignment direction. The second portion 16 B extends in the alignment direction. The second portion 16 B is in contact with the cleaner 7 .

The belt 16 is circularly movable over the two rollers 18 and 19 . As the belt 16 circulates, the first portion 16 A moves toward the fixing device 8 in the alignment direction. In accordance with circulation of the belt 16 , a sheet of paper supplied onto the first portion 16 A sequentially comes into contact with the photosensitive drums 11 Y, 11 M, 11 C, and 11 K. The sheet nipped between the first portion 16 A and the respective photosensitive drums 11 Y, 11 M, 11 C, and 11 K is thus conveyed toward the fixing device 8 as the belt 16 circulates.

The four transfer rollers 17 Y, 17 M, 17 C, and 17 K are positioned between the roller 18 and the roller 19 in the alignment direction. The transfer rollers 17 Y, 17 M, 17 C, and 17 K are aligned with one another in the alignment direction.

Since the transfer rollers 17 Y, 17 M, 17 C, 17 K have the same structures as one another, the transfer roller 17 K will be described in detail, while descriptions on the d exposure devices 5 Y, 5 M, 5 C will be omitted.

The transfer roller 17 K is configured to allow a toner image on the photosensitive drum 11 K to transfer onto the sheet conveyed by the belt 16 . The transfer roller 17 K is positioned opposite to the photosensitive drum 11 K with respect to the first portion 16 A of the belt 16 .

<Cleaner 7 >

The cleaner 7 is configured to clean the belt 16 . In the present embodiment, the cleaner 7 is a cleaning roller. The cleaner 7 is in contact with the second portion 16 B of the belt 16 from below.

<Fixing Device 8 >

The fixing device 8 is configured to heat and press the sheet on which the toner image has been transferred, thereby fixing the toner image to the sheet. The sheet having passed through the fixing device 8 is configured to be discharged onto an upper face of the main casing 2 .

<Sheet Feeder 9 >

The sheet feeder 9 is configured to feed sheets stacked in the sheet tray 10 into a space between the first portion 16 A of the belt 16 and the photosensitive drum 11 Y.

<Sheet Tray 10 >

The sheet tray 10 is configured to accommodate therein the sheets to be supplied to the belt unit 6 via the fixing device 8 .

2. Controller of the Image-Forming Apparatus 1

As illustrated in FIG. 2 , the image-forming apparatus 1 also includes a first motor 21 , a second motor 22 , and a controller 23 .

The first motor 21 is disposed inside the main casing 2 (see FIG. 1 ). The first motor 21 is configured to generate a driving force to be transmitted to the developing roller 14 K. In other words, the developing roller 14 K is rotatable by the driving force of the first motor 21 .

The second motor 22 is also disposed inside the main casing 2 . The second motor 22 is configured to generate a driving force to be transmitted to each of the photosensitive drums 11 Y, 11 M, 11 C, and 11 K, and the developing rollers 14 Y, 14 M, and 14 C. In other words, the photosensitive drums 11 Y, 11 M, 11 C, and 11 K and the developing rollers 14 Y, 14 M, and 14 C are rotatable by the driving force of the second motor 22 .

The controller 23 is provided inside the main casing 2 . The controller 23 is configured to control operations of the image-forming apparatus 1 . The controller 23 includes a circuit substrate, a main controller 23 A and a sub controller 23 B. The main controller 23 A and the sub controller 23 B are mounted on the circuit substrate. The controller 23 may also include a memory for storing various data necessary for executing processes described later.

Specifically, the main controller 23 A is an application specific integrated circuit (ASIC) in the present embodiment. The main controller 23 A includes a circuit for controlling operations of the first motor 21 . The main controller 23 A is electrically connected to the first motor 21 . The main controller 23 A further includes: a circuit for controlling movements of the developing rollers 14 Y, 14 M, 14 C, and 14 K between the contact position and the separation position; a circuit for controlling biases (bias voltages) to be applied to the respective collecting rollers 13 K, 13 Y, 13 M, and 13 C (see FIG. 1 ); a circuit for controlling biases (bias voltages) to be applied to the transfer rollers 17 Y, 17 M, 17 C, and 17 K (see FIG. 1 ); and a circuit for controlling a bias (a bias voltage) to be applied to the cleaner 7 (see FIG. 1 ).

The sub controller 23 B is an application specific integrated circuit (ASIC) in the present embodiment. The sub controller 23 B includes a circuit for controlling operations of the second motor 22 . The sub controller 23 B is electrically connected to the second motor 22 . The sub controller 23 B is also electrically connected to the main controller 23 A. The sub controller 23 B communicates with the main controller 23 A through synchronization signals. The sub controller 23 B is thus synchronized with the main controller 23 A.

3. Operations of the Image-Forming Apparatus 1

As illustrated in FIGS. 3 and 4 , the controller 23 is configured to execute the normal-speed rotation process (S 1 ), a halting process (S 2 ), a low-speed rotation process (S 3 ), and a cleaning process (S 4 ), sequentially. Note that the halting process (S 2 ), the low-speed rotation process (S 3 ), and the cleaning process (S 4 ) are configured to be executed sequentially in the recited order once the normal-speed rotation process (S 1 ) is initiated. In other words, the execution of the normal-speed rotation process (S 1 ) triggers sequential execution of the halting process (S 2 ), the low-speed rotation process (S 3 ), and the cleaning process (S 4 ).

<Normal-Speed Rotation Process>

The controller 23 is configured to launch the normal-speed rotation process in response to receiving a prescribed signal. The prescribed signal may be a command to initiate a print operation, or may be a command to start preparation for a print operation. Specifically, in the present embodiment, the normal-speed rotation process is configured to be initiated: when the image-forming apparatus 1 forms a monochrome image; or when the image-forming apparatus 1 forms a color image; or for a certain period of time after the image-forming apparatus 1 is powered; or for a certain period of time after the image-forming apparatus 1 returns from a sleep state.

Referring to FIGS. 3 and 4 , in the normal-speed rotation process in S 1 , the controller 23 drives the first motor 21 while the developing roller 14 K is at the contact position, in order to rotate the developing roller 14 K in the first direction R 1 (see FIG. 5A ) at a first speed. Specifically, in the present embodiment, the first speed is 200 rpm or faster. More preferably, the first speed be 270 rpm.

During rotation of the developing roller 14 K at the first speed, a surface speed (circumferential speed) of the developing roller 14 K is 135 m/s or faster. Preferably, the surface speed be 180 m/s.

Incidentally, during the normal-speed rotation process in S 1 , the controller 23 may also drive the second motor 22 to rotate the developing rollers 14 Y, 14 M, and 14 C at the first speed, as needed. For example, the controller 23 causes the developing rollers 14 Y, 14 M, and 14 C to rotate at the first speed in order to perform color printing at the image-forming apparatus 1 .

While the normal-speed rotation process (S 1 ) is being executed, some toner may not pass through between the contact portion 20 B and the peripheral surface of the developing roller 14 K. Conceivably, such toner on the peripheral surface of the developing roller 14 K may be accumulated between the contact portion 20 B and the peripheral surface of the developing roller 14 K to form a lump of toner (“toner lump 100 ”), as illustrated in FIG. 5A .

<Halting Process>

The controller 23 is configured to execute the halting process in S 2 after the normal-speed rotation process in S 1 and before the cleaning process in S 4 . In the present embodiment, the execution of the normal-speed rotation process (S 1 ) triggers the execution of the halting process (S 2 ).

Specifically, referring to FIG. 4 , the halting process is configured to be initiated at a point of time t 1 when the normal-speed rotation process ends (hereinafter, referred to as “timing t 1 ”). In the halting process, the controller 23 stops driving the first motor 21 while the developing roller 14 K is at the contact position. The developing roller 14 K is thus caused to stop rotating at the timing t 1 .

Note that, in case that the developing rollers 14 Y, 14 M, and 14 C are also rotated in the normal-speed rotation process in S 1 , the controller 23 also stops the second motor 22 while the developing rollers 14 Y, 14 M, and 14 C are at the contact position (see FIG. 4 ). The developing rollers 14 Y, 14 M, and 14 C are thus caused to stop rotating at the timing t 1 .

Specifically, in the halting process, the main controller 23 A stops driving the first motor 21 to stop rotation of the developing roller 14 K (see S 21 of FIG. 7A ). Likewise, in case that the developing rollers 14 Y, 14 M, and 14 C are also rotated in the normal-speed rotation process in S 1 , the sub controller 23 B also stops driving the second motor 22 to stop rotation of the developing rollers 14 Y, 14 M, and 14 C (see S 22 in FIG. 7B ).

Referring to FIG. 4 , the halting process is configured to be executed for a period of time from when the main controller 23 A stops the first motor 21 until when the main controller 23 A starts driving the first motor 21 again. That is, the halting process is configured to be executed during a period of time from the timing t 1 until a point of time t 2 (hereinafter, referred to as “timing t 2 ”).

Note that the halting process to stop rotation of the developing rollers 14 Y, 14 M, and 14 C may also be executed for the period of time from the timing t 1 to the timing t 2 , as illustrated in FIG. 4 . Note that the sub controller 23 B stops the second motor 22 at the same timing t 1 as the main controller 23 A stops the first motor 21 .

In the present embodiment, the halting process is configured to be executed for a period of 200 milliseconds. This is longer than such a period of time that: rotation of the first motor 21 comes to a halt after the first motor 21 receives a signal to stop the first motor 21 (OFF signal) from the main controller 23 A; and rotation of the developing roller 14 K actually stops subsequently. This configuration can prevent the first motor 21 from start driving again before the developing roller 14 K stops rotating after the first motor 21 stops upon receipt of the OFF signal from the main controller 23 A. Hence, rotation of the developing roller 14 K can be reliably halted in the halting process.

As a result of execution of the halting process, as depicted in FIG. 5B , a state of contact between the thickness regulating blade 15 K and the developing roller 14 K is allowed to change from the state of contact during the normal-speed rotation process depicted in FIG. 5A .

More specifically, referring to FIG. 5A , while the developing roller 14 K is rotating, the contact portion 20 B of the thickness regulating blade 15 K is pulled by the rotating developing roller 14 K, due to friction with the developing roller 14 K. The contact portion 20 B therefore makes contact with the developing roller 14 K with a relatively strong force. On the other hand, while the rotation of the developing roller 14 K is halted, the contact portion 20 B is not pulled by the developing roller 14 K as the developing roller 14 K remains stationary. Hence, the contact portion 20 B can make contact with the developing roller 14 K with a smaller force, compared to the force while the developing roller 14 K is rotating. Therefore, while the halting process is being executed, a force applied to the toner lump 100 accumulated between the contact portion 20 B and the developing roller 14 K can be made smaller, compared with that applied to the toner lump 100 while the normal-speed rotation process is being executed.

With this configuration, the toner lump 100 accumulated between the contact portion 20 B and the developing roller 14 K is easier to break during the halting process, compared with the toner lump 100 during the normal-speed rotation process. Therefore, the toner lump 100 accumulated between the contact portion 20 B and the developing roller 14 K can easily collapse and pass through between the thickness regulating blade 15 K and the developing roller 14 K during the low-speed rotation process which is to be executed after the halting process (see S 3 in FIGS. 3 and 4 ).

<Low-Speed Rotation Process>

As illustrated in FIGS. 3 and 4 , the low-speed rotation process (S 3 ) is configured to be executed after the normal-speed rotation process (S 1 ) and prior to the cleaning process (S 4 ). Particularly, the low-speed rotation process (S 3 ) is configured to be executed after the halting process (S 2 ) and before the cleaning process (S 4 ). In the present embodiment, the execution of the halting process (S 2 ) triggers the execution of the low-speed rotation process (S 3 ).

Specifically, referring to FIG. 4 , the low-speed rotation process is configured to be stated at a timing when the halting process ends. More specifically, the low-speed rotation process is configured to be executed at the timing t 2 .

The second speed is equal to or below two-thirds of the first speed. Preferably, the second speed be equal to or below one-third of the first speed. Specifically, in the present embodiment, the second speed is 90 rpm or slower. The developing roller 14 K rotating at the second speed provides a surface speed equal to 60 m/s or faster.

In the low-speed rotation process in S 3 , the controller 23 drives the first motor 21 while maintaining the developing roller 14 K at the contact position. Specifically, the main controller 23 A executes the process illustrated in FIG. 7A . The developing roller 14 K, which stops rotating during the halting process, is caused to start rotating in the first direction R 1 at a second speed slower than the first speed.

In the case where the developing rollers 14 Y, 14 M, and 14 C are also rotated in the normal-speed rotation process in S 1 , the controller 23 also drives the second motor 22 in the low-speed rotation process. Specifically, the sub controller 23 B executes the process illustrated in FIG. 7B to cause the developing rollers 14 Y, 14 M, and 14 C to start rotating at the second speed in the first direction R 1 .

Specifically, as illustrated in FIG. 7A , after stopping the first motor 21 in S 21 , the main controller 23 A determines in S 30 whether the period for the halting process (i.e., the time span from the timing t 1 to the timing t 2 in FIG. 4 ) has elapsed. The main controller 23 A repeats the routine in S 30 until the period for the halting process is determined to have elapsed (S 30 : NO). When the period for the halting process has elapsed (S 30 : YES), the main controller 23 A drives the first motor 21 in S 31 to initiate the low-speed rotation process for the developing roller 14 K.

On the other hand, referring to FIG. 7B , after stopping the second motor 22 in S 22 to end the normal-speed rotation process, the sub controller 23 B determines in S 32 whether the period for the halting process (i.e., the time span from the timing t 1 until the timing t 2 ) has elapsed. The sub controller 23 B repeats the routine in S 32 until the period for the halting process is determined to have elapsed (S 32 : NO). Once the period for the halting process is determined to have elapsed (S 32 : YES), the sub controller 23 B then determines in S 33 whether a prescribed first period of time T 1 (“first period T 1 ”) has elapsed. When the first period T 1 is determined to have elapsed (S 33 : YES), the sub controller 23 B starts driving the second motor 22 in S 34 to initiate the low-speed rotation process for the developing rollers 14 Y, 14 M and 14 C.

In this way, as illustrated in FIG. 4 , the sub controller 23 B starts driving the second motor 22 after the prescribed first period T 1 has elapsed since when the first motor 21 is driven again by the main controller 23 A for the low-speed rotation process. The low-speed rotation process is executed for the developing rollers 14 Y, 14 M, and 14 C when the first period T 1 has elapsed from the timing t 2 .

The first period T 1 is set so that a timing at which the first motor 21 starts driving does not overlap with a timing at which the second motor 22 starts driving in order to suppress excessive increase in electrical load to be applied to the image-forming apparatus 1 . Specifically, in the present embodiment, the first period T 1 is 200 milliseconds.

Referring back to FIG. 7A , after the first motor 21 is driven in S 31 , the main controller 23 A determines in S 35 whether a prescribed second period of time T 2 (“second period T 2 ”) has elapsed. The main controller 23 A continues driving the first motor 21 at the second speed until the second period T 2 is determined to have elapsed (S 35 : NO). Once the second period T 2 is determined to have passed (S 35 : YES), the main controller 23 A stops driving the first motor 21 in S 36 .

The second period T 2 is set such that a portion on the peripheral surface of the photosensitive drum 11 K does not come into contact with the developing roller 14 K, the portion having not yet been charged by the charger 12 K. Specifically, the second period T 2 ranges from 0.15 seconds to 3.15 seconds inclusive. The second period T 2 may be set beforehand so that a user cannot change the second period T 2 . Alternatively, the second period T 2 may be set so that the second period T 2 can be changed later by a user as desired.

On the other hand, in case that the as illustrated in FIG. 7B , after the second motor 22 is driven in S 34 , the sub controller 23 B determines in S 37 whether the prescribed second period T 2 has elapsed. The sub controller 23 B continues driving the second motor 22 at the second speed until the second period T 2 is determined to have elapsed (S 37 : NO). Once the second period T 2 is determined to have passed (S 37 : YES), the sub controller 23 B stops driving the second motor 22 in S 38 .

As illustrated in FIG. 4 , the low-speed rotation process is configured to be executed during a period of time from when the main controller 23 A starts driving the first motor 21 (at the timing t 2 ) until when the sub controller 23 B stops driving the second motor 22 (at a point of time t 3 , or “timing t 3 ”, hereinafter). In other words, the low-speed rotation process is configured to be executed during a time span between the timing t 2 and the timing t 3 .

During the low-speed rotation process, the rotation speed of the developing roller 14 K becomes slower, compared with the rotation speed during the normal-speed rotation process. A frictional force acting between the contact portion 20 B of the thickness regulating blade 15 K and the developing roller 14 K thus becomes smaller during the low-speed rotation process. Therefore, the contact portion 20 B contacts the peripheral surface of the developing roller 14 K in a weaker manner (not strongly) during the low-speed rotation process (depicted in FIG. 6 ) than during the normal-speed rotation process (depicted in FIG. 5A ).

With this configuration, while the low-speed rotation process is being executed, the toner lump 100 is easier to pass through between the thickness regulating blade 15 K and the peripheral surface of the developing roller 14 K than while the normal-speed rotation process is being executed (see FIG. 5A ). As a result, as depicted in FIG. 6 , the toner lump 100 accumulated between the contact portion 20 B and the developing roller 14 K can pass through between the thickness regulating blade 15 K and the developing roller 14 K while the low-speed rotation process is being executed. The toner lump 100 passed through between the thickness regulating blade 15 K and the developing roller 14 K is collected into the developing cartridge 4 K (see FIG. 1 ) as the developing roller 14 K rotates.

<Cleaning Process>

As illustrated in FIG. 3 , the cleaning process is configured to be executed in S 4 after the low-speed rotation process is executed in S 3 . In the present embodiment, the execution of the low-speed rotation process (S 3 ) triggers the execution of the cleaning process (S 4 ). In other words, in the present embodiment, the execution of the normal-speed rotation process (S 1 ) necessitates the execution of the cleaning process (S 4 ).

Specifically, referring to FIG. 4 , the cleaning process is configured to be started when the low-speed rotation process ends, i.e., at the timing t 3 .

In the cleaning process, referring to FIG. 8 , while each of the developing rollers 14 Y, 14 M, 14 C, and 14 K is at the separation position, residual toner collected by the collecting rollers 13 Y, 13 M, 13 C, and 13 K is moved therefrom onto the photosensitive drums 11 Y, 11 M, 11 C, and 11 K, respectively. The residual toner moved to each of the photosensitive drums 11 Y, 11 M, 11 C, and 11 K is then moved onto the first portion 16 A of the belt 16 . The residual toner moved to the belt 16 is then collected by the cleaner 7 .

Specifically, as illustrated in FIG. 4 , the controller 23 first causes each of the developing rollers 14 Y, 14 M, 14 C, and 14 K to move into the separation position.

Next, the controller 23 applies a bias (bias voltage) having a positive polarity (+) to each of the collecting rollers 13 K, 13 Y, 13 M, and 13 C. The polarity (+) is the same as a polarity (+) with which the residual toner is charged. A repulsive force thus occurs between each of the collecting rollers 13 K, 13 Y, 13 M, and 13 C and the residual toner collected by each of the collecting rollers 13 K, 13 Y, 13 M, and 13 C.

Accordingly, the residual toner collected by the collecting roller 13 K is moved onto the photosensitive drum 11 K. The residual toner collected by the collecting roller 13 Y is moved onto the photosensitive drum 11 Y. The residual toner collected by the collecting roller 13 M is moved onto the photosensitive drum 11 M. The residual toner collected by the collecting roller 13 C is moved onto the photosensitive drum 11 C.

Note that, in the normal-speed rotation process, the halting process, and the low-speed rotation process, the controller 23 applies a bias (bias voltage) having a negative polarity (−) to each of the collecting rollers 13 K, 13 Y, 13 M, and 13 C. The polarity (−) is opposite to the polarity (+) with which the residual toner is charged. An attracting force thus occurs between each of the collecting rollers 13 K, 13 Y, 13 M, and 13 C and the residual toner thereon.

The residual toner having moved to the photosensitive drum 11 K is then moved onto the belt 16 by the transfer roller 17 K. Likewise, the residual toner having moved to the photosensitive drum 11 Y is then moved onto the belt 16 by the transfer roller 17 Y. The residual toner having moved to the photosensitive drum 11 M is then moved onto the belt 16 by the transfer roller 17 M. The residual toner having moved to the photosensitive drum 11 C is then moved onto the belt 16 by the transfer roller 17 C. As the belt 16 circulates, the residual toner having moved to the belt 16 arrives at the cleaner 7 and is collected by the cleaner 7 , thereby cleaning the belt 16 .

The cleaning process is thus terminated.

4. Operational and Technical Advantages of the First Embodiment

In the image-forming apparatus 1 according to the first embodiment, as illustrated in FIG. 4 , the developing roller 14 K is configured to stop rotating once in the halting process after the normal-speed rotation process. The developing roller 14 K is subsequently caused to rotate again in the low-speed rotation process at the second speed slower than the first speed for the normal-speed rotation process.

With this configuration, as illustrated in FIG. 5A through 6 , even if the toner accumulates over the developing roller 14 K during the normal-speed rotation process, the accumulated toner becomes easier to break during the halting process and low-speed rotation process executed after the normal-speed rotation process.

As a result, a lump of the toner is less likely to be formed on the peripheral surface of developing roller 14 K. Toner is thus less likely to leak from around the developing roller 14 K.

Similar advantages can be obtained for the developing rollers 14 Y, 14 M, and 14 C.

Second Embodiment

A second embodiment will be hereinafter described with reference to FIG. 9 . Like parts and components are designated by the same reference numerals as those of the first embodiment in order to avoid duplicating description.

In the second embodiment, the halting process (S 2 ) is configured to be performed if a number of continuous rotations N of the photosensitive drum 11 K during the normal-speed rotation process (S 1 ) is determined to be equal to or larger than a predetermined number of continuous rotations N 1 (“continuous-rotation number N 1 ”).

Specifically, in the second embodiment, a process depicted in FIG. 9 is configured to be executed instead of the process depicted in FIG. 3 of the first embodiment. For example, the process of FIG. 9 may be executed for a case where the photosensitive drum 11 K rotates successively to perform image formation on a plurality of sheets of paper.

More specifically, referring to FIG. 9 , in the second embodiment, the controller 23 is further configured to count how many times the photosensitive drum 11 K rotates continuously while executing the normal-speed rotation process in S 1 .

The controller 23 then determines in S 41 whether the number of continuous rotations N of the photosensitive drum 11 K during the normal-speed rotation process is equal to or larger than the predetermined continuous-rotation number N 1 . The controller 23 repeats the routine of S 41 as long as the number of continuous rotations N of the photosensitive drum 11 K is smaller than the predetermined continuous-rotation number N 1 (S 41 : NO).

On the other hand, once the number of continuous rotations N reaches the predetermined continuous-rotation number N 1 or larger (S 41 : YES), the controller 23 then executes the halting process (S 2 ).

The predetermined continuous-rotation number N 1 may be set to such a number that how many times the photosensitive drum 11 K is required to rotate in order to feed 60 sheets of paper of A4 size, for example. Specifically, if a diameter of the photosensitive drum 11 K ranges from 20 mm to 50 mm inclusive, the continuous-rotation number N 1 may range from 100 rotations to 400 rotations (100 times to 400 times) inclusive, for example.

More specifically, in a case where the diameter of the photosensitive drum 11 K is 30 mm, the predetermined continuous-rotation number N 1 may range from 200 rotations to 240 rotations inclusive. Alternatively, in a case where the diameter of the photosensitive drum 11 K is 20 mm, the predetermined continuous-rotation number N 1 may range from 300 rotations to 350 rotations inclusive.

With this configuration, the halting process (S 2 ), the low-speed rotation process (S 3 ), and the cleaning process (S 4 ) can be executed at such a timing that the toner is predicted to be accumulated on the developing roller 14 K.

In case of color image formation, the processing depicted in FIG. 9 may also be executed for the photosensitive drums 11 Y, 11 M and 11 C and the developing rollers 14 Y, 14 M, and 14 C.

The same or similar advantages as the first embodiment can also be obtained in the second embodiment.

Third Embodiment

A third embodiment will be hereinafter described with reference to FIGS. 10 and 11A . In the third embodiment, identical reference numerals are used to denote identical or substantially identical members in the second embodiment. Descriptions of such members are thus omitted.

As illustrated in FIG. 10 , the image-forming apparatus 1 may further include a built-in temperature sensor 31 . The built-in temperature sensor 31 is configured to measure a temperature H inside the image-forming apparatus 1 . The built-in temperature sensor 31 is electrically connected to the main controller 23 A. The main controller 23 A is configured to measure the temperature H inside the image-forming apparatus 1 based on electric signals outputted from the built-in temperature sensor 31 .

In the third embodiment, the halting process (S 2 ) and low-speed rotation process (S 3 ) are configured to be performed: if the number of continuous rotations N of the photosensitive drum 11 K in the normal-speed rotation process (S 1 ) becomes larger than the predetermined continuous-rotation number N 1 ; and if the temperature H inside the image-forming apparatus 1 exceeds a predetermined temperature H 1 .

Specifically, referring to FIG. 11A , the controller 23 determines in S 51 whether a print job is completed after starting the normal-speed rotation process in S 1 .

When the print job is not completed yet (S 51 : NO), the controller 23 then determines in S 52 whether the temperature H inside the image-forming apparatus 1 exceeds the predetermined temperature H 1 .

If the temperature H is still below the predetermined temperature (S 52 : NO), the routine goes back to S 51 to repeat the determination in S 51 . On the other hand, if the temperature H is determined to exceed the predetermined temperature H 1 (S 52 : YES), the controller 23 starts counting for the number of continuous rotations N of the photosensitive drum 11 K in S 53 .

The controller 23 keeps counting for the number of continuous rotations N of the photosensitive drum 11 K as long as the number of continuous rotations N of the photosensitive drum 11 K is determined to be smaller than the predetermined continuous-rotation number N 1 (S 54 : NO).

Upon determining that the number of continuous rotations N of the photosensitive drum 11 K has reached the predetermined continuous-rotation number N 1 (S 54 : YES), the controller 23 terminates the normal-speed rotation process started in S 1 . The controller 23 then executes the halting process (S 2 ), the low-speed rotation process (S 3 ), and the cleaning process (S 4 ), as in the first embodiment.

After executing the cleaning process in S 4 , the controller 23 resets the number of continuous rotations N of the photosensitive drum 11 K in S 55 . In other words, the controller 23 sets the number of continuous rotations N of the photosensitive drum 11 K to zero.

The routine then goes back to the routine of S 51 to determine whether the print job is completed. If the printing job is determined to be completed (S 51 : YES), the controller 23 terminates the normal-speed rotation process in S 56 and then ends the process of FIG. 11A .

Alternatively, the controller 23 may be configured to execute the halting process (S 2 ), low-speed rotation process (S 3 ) and cleaning process (S 4 ) after the normal-speed rotation process is ended in S 56 .

Incidentally, in a case where the routine goes back to S 51 after S 54 and the print job is determined not to be completed yet (S 51 : NO), the controller 23 tends to determine in S 52 that the temperature H inside the image-forming apparatus 1 exceeds the predetermined temperature H 1 again (S 52 : YES), since the temperature H is unlikely to drop suddenly at this moment.

As the temperature H inside the image-forming apparatus 1 rises, the toner accumulated over the developing roller 14 K becomes easier to adhere to each other. The toner thus tends to become harder easily.

Hence, in the third embodiment, the predetermined temperature H 1 is set to such a temperature that the toner is presumed to become harder based on a melting point of the toner, for example.

With this configuration, in the third embodiment, the halting process (S 2 ), the low-speed rotation process (S 3 ), and the cleaning process (S 4 ) can be executed in the case where the temperature H inside the image-forming apparatus 1 exceeds the predetermined temperature H 1 at which the toner is presumed to harden.

In the third embodiment, the same or similar advantages as the second embodiment can also be obtained.

Note that, the built-in temperature sensor 31 of the third embodiment may not be provided. In this case, instead of detecting the temperature H inside the image-forming apparatus 1 using the built-in temperature sensor 31 , the controller 23 may determine that the temperature H inside the image-forming apparatus 1 has exceeded the predetermined temperature H 1 if the number of continuous rotations N of the photosensitive drum 11 K during the normal-speed rotation process (S 1 ) reaches a predetermined number of continuous rotations N 2 (“continuous-rotation number N 2 ”) or larger. The halting process (S 2 ) and the low-speed rotation process (S 3 ) may then be executed.

More specifically, referring to FIG. 11B , the controller 23 does not execute the determination of S 52 of the third embodiment; the controller 23 is configured to start counting the number of continuous rotations N of the photosensitive drum 11 K in S 53 immediately after the determination in S 51 .

Here, the predetermined continuous-rotation number N 2 is a value different from a value of the predetermined continuous-rotation number N 1 . For example, the predetermined continuous-rotation number N 2 may be a number of rotations required for the photosensitive drum 11 K to feed 540 sheets of paper of A4 size.

After starting the counting in S 53 , the controller 23 then determines in S 61 whether the number of continuous rotations N of the photosensitive drum 11 K during the normal-speed rotation process (S 1 ) is equal to or larger than the predetermined continuous-rotation number N 2 . The controller 23 repeats the determination in S 61 until the number of continuous rotations N of the photosensitive drum 11 K has reached the predetermined continuous-rotation number N 2 or larger (S 61 : NO). Once the number of continuous rotations N of the photosensitive drum 11 K is determined to exceed the predetermined continuous-rotation number N 2 (S 61 : YES), the controller 23 executes the halting process (S 2 ) and the low-speed rotation process (S 3 ) as in the third embodiment.

In case of color image formation, the controller 23 may execute the processing depicted in FIGS. 11A and 11B for the photosensitive drums 11 Y, 11 M and 11 C and the developing rollers 14 Y, 14 M, and 14 C.

Fourth Embodiment

A fourth embodiment will be hereinafter described with reference to FIGS. 12 to 13C . In the fourth embodiment, identical reference numerals are used to denote identical or substantially identical members in the first embodiment. Descriptions of such members are thus omitted.

Referring to FIG. 12 , in the fourth embodiment, the controller 23 is configured to further execute a reverse rotation process (S 71 ) between the halting process (S 2 ) and the low-speed rotation process (S 3 ).

In the reverse rotation process in S 71 , the developing roller 14 K is caused to rotate in a second direction R 2 opposite to the first direction R 1 . At this time, the developing roller 14 K may be rotatable at the first speed or at the second speed. The developing roller 14 K is then caused to rotate in the first direction R 1 at the second speed in the low-speed rotation process in S 3 .

That is, as illustrated in FIGS. 13A to 13C , the toner on the developing roller 14 K can be moved in the first direction R 1 (in the low-speed rotation process of S 3 ) after being moved once in the second direction R 2 (in the reverse rotation process of S 71 ) in the fourth embodiment. The toner on the developing roller 14 K is allowed to reliably collapse on the peripheral surface of the developing roller 14 K.

In the fourth embodiment, the same or similar advantages as the first embodiment can also be obtained.

In case of color image formation, the controller 23 may execute the processing depicted in FIG. 12 for the photosensitive drums 11 Y, 11 M and 11 C and the developing rollers 14 Y, 14 M, and 14 C.

Variations and Modifications

Hereinafter, various modifications to the depicted embodiments will be described. In the following description, like parts and components are designated by the same reference numerals as those in the above-described embodiments.

1. Transmission of Driving Forces

How to transmit the driving forces from the first motor 21 and the second motor 22 to each of the photosensitive drums 11 Y, 11 M, 11 C, and 11 K and each of the developing rollers 14 Y, 14 M, 14 C, and 14 K is not particularly limited to that disclosed in the above-depicted embodiments.

For example, as illustrated in FIG. 14 , the driving force of the first motor 21 may be transmitted to each of the photosensitive drums 11 Y, 11 M, 11 C, and 11 K, while the driving force of the second motor 22 may be transmitted to each of the developing rollers 14 Y, 14 M, 14 C, and 14 K.

Alternatively, as illustrated in FIG. 15 , the driving force of the first motor 21 may be transmitted to all of the photosensitive drums 11 Y, 11 M, 11 C, and 11 K and the developing rollers 14 Y, 14 M, 14 C, and 14 K. That is, the second motor 22 may be dispensed with. Hence, a controller 123 of this variation may not include the sub controller 23 B for controlling the second motor 22 .

2. Variations of the Thickness Regulating Blade 15 K

The configuration of the thickness regulating blade 15 K is not particularly limited to that of the first embodiment.

For example, FIG. 16A depicts a thickness regulating blade 215 K that does not include the contact portion 20 B of the first embodiment.

Alternatively, FIG. 16B illustrates a thickness regulating blade 315 K including a contact portion 320 B. Unlike the contact portion 20 B of the first embodiment, the contact portion 320 B is formed by bending a tip end portion of the blade body 20 A.

Still alternatively, FIG. 16C illustrates a thickness regulating blade 415 K including a contact portion 420 B having a generally rectangular-shaped cross-section. The contact portion 420 B may be made of a rubber material, for example.

Still alternatively, as illustrated in FIGS. 16D to 16G , the thickness regulating blade 15 K of FIGS. 16A to 16C may be arranged such that a direction from the end E 1 to the other end E 2 coincides with the first direction R 1 during the normal-speed rotation process.

Specifically, FIG. 16D depicts a thickness regulating blade 215 K′ without the contact portion 20 B of the embodiment, as a variation of the thickness regulating blade 215 K of FIG. 16A .

FIG. 16E depicts a thickness regulating blade 315 K′ including the contact portion 320 B, as a variation of the thickness regulating blade 315 K of FIG. 16A .

FIG. 16F depicts a thickness regulating blade 415 K′ as a variation of the thickness regulating blade 415 K of FIG. 16C . The thickness regulating blade 415 K′ includes a blade body 420 A and a contact portion 420 B′ having a rectangular-shaped cross-section.

Incidentally, the contact portion 420 B′ may not contact the peripheral surface of the developing roller 14 K with a lower surface of the contact portion 420 B′ as illustrated in FIG. 16F . For example, as shown in FIG. 16G , the thickness regulating blade 415 K′ may be arranged such that a corner portion of the contact portion 420 B′ may make contact with the peripheral surface of the developing roller 14 K.

Similar to the thickness regulating blade 15 K, the configurations of thickness regulating blades 15 Y, 15 M, and 15 C are not limited to those depicted in the first embodiment. For example, the thickness regulating blades 15 Y, 15 M, and 15 C may be configured as the thickness regulating blades 215 K, 315 K, 415 K, 215 K′, 315 K′ and 415 K′ illustrated in FIGS. 16A through 16G .

3. Other Variations

The image-forming apparatus 1 may be a machine dedicated solely for forming monochrome images. Alternatively, the image-forming apparatus 1 may be an intermediate transfer type image-forming apparatus.

Further, although the cleaner 7 of the depicted embodiments is configured as a cleaning roller, the cleaner 7 may be configured as cleaning blade.

Note that the depicted embodiments and modifications thereto described above may be appropriately combined with one another, as long as no contradiction is involved.

It would be apparent to those skilled in the art that the embodiment and foregoing modifications described above are merely an illustrative example of the present disclosure and that various modifications may be made therein without departing from the scope of the disclosure.

[Remarks]

The image-forming apparatus 1 is an example of an image-forming apparatus. The photosensitive drums 11 K, 11 Y, 11 C and 11 M are an example of a photosensitive drum. The developing rollers 14 K, 14 Y, 14 C and 14 M are an example of a developing roller. The collecting rollers 13 K, 13 Y, 13 C and 13 M are an example of a collecting roller. The belt 16 is an example of a belt. The cleaner 7 is an example of a cleaner. The controllers 23 , 123 are an example of a controller. The normal-speed rotation process executed in S 1 of the processing of FIGS. 3, 9, 11A, 11B and 12 is an example of a first process. The halting process executed in S 2 of the processing of FIGS. 3, 9, 11A, 11B and 12 is an example of (a) causing. The low-speed rotation process executed in S 3 of the processing of FIGS. 3, 9, 11A, 11B and 12 is an example of (b) causing. The cleaning process executed in S 4 of the processing of FIGS. 3, 9, 11A, 11B and 12 is an example of a second process. The determination executed in S 54 of the processing of FIG. 11A is an example of (c) determining. The determination executed in S 52 of the processing of FIG. 11A is an example of (d) determining. The determination executed in S 41 of the processing of FIG. 9 and the determination executed in S 61 of the processing of FIG. 11B is an example of (e) determining. The reverse rotation process executed in S 71 of the processing of FIG. 12 is an example of (f) causing.