Injector drive device and injector drive system

This application is based on and incorporates herein by reference Japanese Patent Applications No. 2006-164969 filed on Jun. 14, 2006 and No. 2007-52943 filed on Mar. 2, 2007.

The present invention relates to an injector drive device and a injector drive system that drive an injector for injecting fuel and, in particular, to an injector drive device and an injector drive system that are applicable to a vehicle using an internal combustion engine such as a diesel engine as a driving source or an engine-motor hybrid vehicle that is driven by a combination of an internal combustion engine and an electric motor.

A conventional injector drive device (for example JP-2005-16431A) includes a power supply unit such as a DC-DC converter, and a drive switch unit (injector drive unit) that is supplied with power from the power supply unit and drives an injector and the like. In the power supply unit, a voltage (12V or 24V) supplied from a battery is raised or boosted to a high voltage of tens to hundreds of volt and is supplied to the injector drive unit.

In recent years, it is required to finely control fuel injection to reduce noxious substances contained in emission gas. To cope with this, it is required to increase the number of times of fuel injection by injector operation. If the number of times of injector operation is increased, energy for driving an injector is correspondingly increased. Therefore, it is required to increase the power output capacity of the power supply unit, and this increases the amount of heat produced in the power supply unit.

The power supply unit is usually housed in a housing of the drive switch unit. Heat produced in the power supply unit or an injector drive unit is radiated to the atmosphere through the housing. When the amount of heat produced in the power supply unit is increased, it is required to increase the size of the housing in correspondence to increase in the amount of produced heat, thereby ensuring a required heat radiation capability. Therefore, when the capacity of the power supply unit is increased to increase the number of times of injector operation, the housing, that is, the drive switch unit, need be sufficiently large.

It is an object of the present invention to reduce an increase in the size of a drive switch unit even when the number of times of injector operation is increased.

According to one aspect, an injector drive device for driving a fuel injector of an engine has a power supply unit and a drive switch unit. The power supply unit is supplied with power from a battery and generates a voltage higher than the voltage of the battery. The drive switch unit has a drive unit that is supplied with power from the power supply unit and drives the injector. The drive unit is housed in a housing. The power supply unit is placed externally to the housing of the drive switch unit.

According to another aspect, an injector drive device for driving an injector for supplying fuel into an internal combustion engine of an engine-motor hybrid vehicle has a drive switch unit and an input terminal. The drive switch unit has a drive unit that is supplied with power from a high-voltage battery, which also supplies power to the electric motor, and drives an injector. The drive unit is housed in a housing. The input terminal is provided on the housing through which power from the battery is inputted. The drive unit is directly connected to the input terminal.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is an electric circuit diagram showing an injector drive system according to in a first embodiment of the present invention;

FIG. 2 is a time diagram showing the operation of the injector drive system in the first embodiment;

FIG. 3 is an electric circuit diagram showing an injector drive system according to a second embodiment of the present invention;

FIG. 4 is an electric circuit diagram showing an injector drive system according to a third embodiment of the present invention;

FIG. 5 is a time diagram showing the operation of the injector drive system in the third embodiment; and

FIG. 6 is an electric circuit diagram showing an injector drive system according to a fourth embodiment of the present invention.

First Embodiment

An injector drive system 1 is mounted in a vehicle that has a diesel engine (not shown) as a vehicle driving source. This injector drive system 1 includes a fuel injector 10 for injecting fuel into the diesel engine, and an injector drive device 20 for driving the injector 10 . The injector drive device 20 includes a power supply unit (first power supply unit) 30 that is supplied with power from a battery 50 mounted in the vehicle and generates a voltage higher than the voltage of the battery 50 , and an electronic drive unit (EDU) 40 .

In this embodiment, the battery 50 generates a voltage of 12V, and the power supply unit 30 generates a high voltage of tens to hundreds of volt. The power supply unit 30 , EDU 40 and battery 50 are placed in an engine compartment in which the diesel engine is housed. The power supply unit 30 is placed externally to the EDU 40 , that is, externally to the EDU 40 .

The power supply unit 30 includes a filter 32 constructed of a coil L 1 and a capacitor C 1 , a DC-DC capacitor C 2 , and a housing 34 for housing the filter 32 and the DC-DC capacitor C 2 . The housing 34 is formed of aluminum, resin, or the like. One end of the coil L 1 of the filter 32 is connected to the positive terminal of the battery 50 through a terminal T 1 provided on the housing 34 . The other end is connected to the EDU 40 through a terminal T 2 provided on the housing 34 . One end of the capacitor C 1 of the filter 32 is connected to the point of junction between the coil L 1 and the EDU 40 . The other end of the capacitor C 1 is grounded and further connected to the EDU 40 through a terminal T 3 . The negative pole of the DC-DC capacitor C 2 is connected to the point of junction between the capacitor C 1 and the EDU 40 . Its positive pole is connected to the EDU 40 through a terminal T 4 provided on the housing 34 .

The EDU 40 includes a drive unit 42 that is supplied with power from the power supply unit 30 and drives the injector 10 , a control IC 43 that controls turn-on/off of a charge switch SW 1 and a discharge switch SW 2 , and a housing 44 for housing the drive unit 42 . The housing 44 of the EDU 40 is provided with terminals T 5 to T 7 connected to the power supply unit 30 , terminals T 8 , T 9 connected to the injector 10 , and a terminal T 10 connected to an electronic control unit (ECU) 52 that controls the engine of the vehicle. The housing 44 is formed of aluminum, resin, or the like. The drive unit 42 of the EDU 40 is connected directly to the terminal T 6 without any circuit element such as a resistor. This drive unit 42 includes a charge switch SW 1 , a discharge switch SW 2 , a charging/discharging coil L 2 , and diodes D 1 to D 4 .

The control IC 43 controls turn-on/off of the charge switch SW 1 and the discharge switch SW 2 in response to an injection signal inputted from the ECU 52 through the terminal T 10 . It thereby causes the drive unit 42 to drive the injector 10 . One end of the charge switch SW 1 is connected to the positive pole of the DC-DC capacitor C 2 through the terminal T 6 and the terminal T 4 . The other end is connected to one end of the charging/discharging coil L 2 . One end of the discharge switch SW 2 is connected to the point of junction between the charge switch SW 1 and the charging/discharging coil L 2 , and the other end is grounded.

The diode D 1 is provided in parallel with the charge switch SW 1 . The anode of the diode D 1 is connected to the charge switch SW 1 on the charging/discharging coil L 2 side, and its cathode is connected to the charge switch SW 1 on the power supply unit 30 side. The diode D 2 is provided in parallel with the discharge switch SW 2 . The anode of the diode D 2 is connected to the discharge switch SW 2 on the ground side, and its cathode is connected to the discharge switch SW 2 on the charge switch SW 1 side. The anode of the diode D 3 is connected to the coil L 1 and capacitor C 1 of the filter 32 through the terminal T 5 and the terminal T 2 , and its cathode is connected to the cathode of the diode D 4 . The anode of the diode D 4 is connected to the negative pole of the DC-DC capacitor C 2 and the capacitor C 1 of the filter 32 through the terminal T 7 and the terminal T 3 . It is also connected to the injector 10 through the terminal T 9 . The point of junction between the cathode of the diode D 3 and the cathode of the diode D 4 is connected to the injector 10 through the terminal T 8 . Further, it is connected to the other end of the charging/discharging coil L 2 (the end on the opposite side to the charge switch SW 1 ).

The injector 10 is a piezoelectric injector includes a piezoelectric element P, connectors T 11 , T 12 connected to the terminals T 8 , T 9 of the EDU 40 , and a connector case (not shown) for protecting the connectors. One end of the piezoelectric element P is connected to the anode of the diode D 4 through the connector T 12 and the terminal T 9 of the EDU 40 . Further, it is connected to the negative pole of the DC-DC capacitor C 2 and the capacitor C 1 of the filter 32 through the connector T 12 , the terminals T 9 , T 7 of the EDU 40 , and the terminal T 3 of the power supply unit 30 . The other end of the piezoelectric element P is connected to the other end of the charging/discharging coil L 2 (the end on the opposite side to the charge switch SW 1 ) through the connector T 11 and the terminal T 8 of the EDU 40 .

Although only one injector 10 and only one EDU 40 are shown in FIG. 1 , the injector 10 and the EDU 40 are provided for each of the (four) cylinders of the engine, and the injectors 10 and EDUs 40 are connected in parallel.

In this embodiment, as shown in FIG. 2 , the EDU 40 drives the injector 10 when an injection signal is inputted from the ECU 52 to the EDU 40 . The control IC 43 of the EDU 40 monitors the voltage of the power supply unit 30 . When the EDU 40 is not driving the injector 10 , the voltage of the power supply unit 30 is increased. The discharge switch SW 2 operates as a boost switch for increasing (boosting) the voltage of the power supply unit 30 . Further, the charging/discharging coil L 2 operates as a boost coil for boosting the voltage of the power supply unit 30 (voltage of the DC-DC capacitor C 2 ). When the EDU 40 repeatedly turns on and off the discharge switch SW 2 , energy is thereby accumulated in the charging/discharging coil L 2 and the accumulated energy is supplied to the DC-DC capacitor C 2 . Thus, electric charges are accumulated in the DC-DC capacitor C 2 and the voltage of the power supply unit 30 is increased.

The EDU 40 performs the operation of increasing the voltage of the power supply unit 30 (operation of turning on and off the discharge switch SW 2 ). As shown in FIG. 2 , this operation is carried out during the period from time t 1 , when the EDU 40 starts the voltage boosting operation, to time t 2 , when a time TA has passed and the voltage of the power supply unit 30 reaches a predetermined voltage V 1 . When the voltage of the power supply unit 30 drops below a predetermined voltage V 2 due to driving of the injector 10 , spontaneous discharge, or the like (time t 6 in FIG. 2 ), the voltage boosting operation is started. The predetermined voltage V 2 is set to a value lower than the predetermined voltage V 1 . Thus, in the injector drive system 1 , substantially constant high-voltage power can be continuously supplied by the power supply unit 30 .

In this embodiment, when the injection signal from the ECU 52 is inputted to the EDU 40 at time t 3 in FIG. 2 , the EDU 40 repeatedly turns on and off the charge switch SW 1 with the discharge switch SW 2 kept off. Thus, when the charge switch SW 1 is turned on, a current flows from the DC-DC capacitor C 2 to the piezoelectric element P and energy is accumulated in the charging/discharging coil L 2 . When the charge switch SW 1 is turned off, a current is caused to flow to the piezoelectric element P by the energy accumulated in the charging/discharging coil L 2 . Therefore, the piezoelectric element P is charged with electric charges, and the piezoelectric element P is expanded to inject fuel.

When the injection signal is not inputted to the EDU 40 any more at time t 4 when a time TB has passed after time t 3 , the EDU 40 repeatedly turns on and off the discharge switch SW 2 with the charge switch SW 1 kept off. Thus, when the discharge switch SW 2 is turned on, a current flows from the positive pole of the piezoelectric element P, that is, from the charging/discharging coil L 2 side, and further energy is accumulated in the charging/discharging coil L 2 . When the discharge switch SW 2 is turned off, a regenerative current is caused to flow to the DC-DC capacitor C 2 by the energy accumulated in the charging/discharging coil L 2 . Therefore, the electric charges accumulated in the piezoelectric element P are discharged, and the piezoelectric element P is contracted to terminate fuel injection. The control IC 43 monitors the voltage on the positive pole side of the piezoelectric element P When the control IC 43 detects that the voltage on the positive pole side of the piezoelectric element P has dropped to a predetermined voltage V 3 or below (time t 5 in FIG. 2 ), it stops the operation of turning on and off the discharge switch SW 2 .

In this embodiment, the power supply unit 30 is placed separately from and externally to the EDU 40 , that is, externally to the housing 44 . Therefore, it is unnecessary to radiate heat produced by the power supply unit 30 to the atmosphere through the housing 44 of the EDU 40 . Therefore, even when the capacity of the power supply unit 30 is increased to increase the number of times of operation of the injector 10 and the amount of heat produced in the power supply unit 30 is increased, it is unnecessary to increase the size of the housing 44 of the EDU 40 . The EDU 40 and the power supply unit 30 are constructed separately from each other. Therefore, the EDU 40 can be standardized, and the number of times of injector operation can be increased or decreased just by replacing the power supply unit 30 according to the specifications of the vehicle.

Piezoelectric injectors are superior to solenoid injectors in response speed and make it possible to increase the pressure of injected fuel. However, they require more power in operation than solenoid injectors do. Therefore, this embodiment is especially effective.

Second Embodiment

In the first embodiments power of the battery 50 is supplied directly to the power supply unit 30 . In the second embodiment, power of the battery 50 is supplied by the power supply unit 30 through the EDU 40 . As shown in FIG. 3 , an injector drive system 2 is different from the injector drive system 1 in that the filter 32 is provided in the EDU 40 , not in the power supply unit 30 .

One end of the capacitor C 1 of the filter 32 is connected to one end of the coil L 1 of the filter 32 . The other end is connected to the negative pole of the DC-DC capacitor C 2 , the anode of the diode D 4 , the end of the piezoelectric element P on the opposite side to the charging/discharging coil L 2 , and the negative terminal of the battery 50 . The other end of the coil L 1 of the filter 32 is connected to the positive terminal of the battery 50 through the terminal T 5 of the EDU 40 . Thus, in the injector drive system 2 , power of the battery 50 is supplied by the power supply unit 30 through the injector 10 and the EDU 40 .

In this embodiment, even when the capacity of the power supply unit 30 is increased to increase the number of times of injector operation and the amount of heat produced at the power supply unit 30 is increased, it is unnecessary to increase the size of the housing 44 of the EDU 40 .

Since the coil L 1 and capacitor C 1 of the filter 32 are constructed integrally with the EDU 40 , a current caused by turning on and off the discharge switch SW 2 to increase the voltage of the power supply unit 30 and a current flowing from the coil L 1 to the discharge switch SW 2 by way of the diode D 3 and the charging/discharging coil L 2 do not flow outside the EDU 40 . Therefore, noise produced by turning on and off the discharge switch SW 2 can be reduced.

Third Embodiment

In the first and second embodiments, the EDU 40 is provided for each injector 10 . In this third embodiment, one EDU 70 drives multiple (for example, four) injectors 90 . As shown in FIG. 4 , an injector drive system 3 in this embodiment includes an injector drive device 80 having a power supply unit 60 and an EDU 70 for the injectors 90 .

The power supply unit 60 is placed externally to the EDU 70 , that is, externally to its housing 76 . The power supply unit 60 includes the filter 32 , the DC-DC capacitor C 2 , a boost coil L 3 , a diode D 5 , a boost switch SW 3 , and a housing 62 . In the housing 62 of the power supply unit 60 , there are housed the filter 32 , DC-DC capacitor C 2 , boost coil L 3 , diode D 5 , and boost switch SW 3 .

One end of the coil L 1 of the filter 32 is connected to the positive terminal of the battery 50 through a terminal T 13 provided on the housing 62 , and the other end is connected to one end of the boost coil L 3 . The other end of the boost coil L 3 is connected to the other end of the boost switch SW 3 one end of which is grounded, and the point of junction between the boost coil L 3 and the boost switch SW 3 is connected to the anode of the diode D 5 . The cathode of the diode D 5 is connected to the EDU 70 through a terminal T 14 provided on the housing 62 . One end of the capacitor C 1 of the filter 32 is connected to the point of junction between the coil L 1 and the boost coil L 3 , and the other end is grounded. The positive pole of the DC-DC capacitor C 2 is connected to the point of junction between the diode D 5 and the EDU 70 , and its negative pole is grounded.

The EDU 70 includes a power supply unit 72 , a drive unit 74 , and cylinder select switches SWA to SWD. In the housing 76 of the EDU 70 , there are housed the power supply unit 72 , drive unit 74 , and the cylinder select switches SWA to SWD.

The power supply unit 72 of the EDU 70 is supplied with power from the battery 50 and generates a voltage higher than the voltage of the battery 50 . The power supply unit 72 includes a filter 78 constructed of a coil L 4 and a capacitor C 3 , a DC-DC capacitor C 4 , a boost coil L 5 , a diode D 6 , and a boost switch SW 4 . One end of the coil L 4 of the filter 78 is connected to the positive terminal of the battery 50 through a terminal T 15 provided on the housing 76 , and the other end is connected to one end of the boost coil L 5 . The other end of the boost coil L 5 is connected to the other end of the boost switch SW 4 , one end of which is grounded. The point of junction between the boost coil L 5 and the boost switch SW 4 is connected to the anode of the diode D 6 . The cathode of the diode D 6 is connected to one end of the charge switch SW 1 . The point of junction between the diode D 6 and the charge switch SW 1 is connected to the positive pole of the DC-DC capacitor C 4 whose negative pole is grounded. At the same time, it is connected to the positive pole of the DC-DC capacitor C 2 and the cathode of the diode D 5 through a terminal T 16 provided on the housing 76 and the terminal T 14 .

The drive unit 74 is supplied with power from the power supply unit 60 and the power supply unit 72 , and drives the injectors 90 . The drive unit 74 includes the charge switch SW 1 , discharge switch SW 2 , charging/discharging coil L 2 , control IC (not shown) that controls turn-on/off of the charge switch SW 1 and the discharge switch SW 2 , and diodes D 1 , D 2 , D 7 .

One end of the charge switch SW 1 is connected to the cathode of the diode D 6 , the positive pole of the DC-DC capacitor C 4 , the positive pole of the DC-DC capacitor C 2 , and the anode of the diode D 5 . The other end is connected to one end of the charging/discharging coil L 2 . The other end of the charging/discharging coil L 2 is connected to the injectors 90 provided for the respective cylinders through a terminal T 17 provided on the housing 76 . The point of junction between the charging/discharging coil L 2 and the injectors 90 is connected with the cathode of the diode D 7 whose anode is grounded. One end of the discharge switch SW 2 is connected to the point of junction between the charge switch SW 1 and the charging/discharging coil L 2 , and the other end is grounded.

The diode D 1 is provided in parallel with the charge switch SW 1 . The anode of the diode D 1 is connected to the charge switch SW 1 on the charging/discharging coil L 2 side, and its cathode is connected to the charge switch SW 1 on the power supply unit 72 side. The diode D 2 is provided in parallel with the discharge switch SW 2 . The anode of the diode D 2 is connected to the discharge switch SW 2 on the ground side, and its cathode is connected to the discharge switch SW 2 on the charging/discharging coil L 2 side.

The cylinder select switches SWA to SWD are for selecting an injector 90 to be driven from among the injectors 90 provided for the respective cylinders of the engine. The select switches in the number equal to the number (four) of cylinders of the engine are provided. One end of each of the cylinder select switches SWA to SWD is grounded, and the other end is connected to the injector 90 corresponding to that cylinder select switch SWA to SWD through one of terminals T 18 to T 21 provided on the housing 76 .

The injector 90 is a piezoelectric injector that is operated by the piezoelectric element P being expanded and contracted. There are provided the injectors 90 in the number equal to the number (four) of cylinders of the engine. One end of each injector 90 is connected to the charging/discharging coil L 2 and the cathode of the diode D 7 through the terminal T 17 of the EDU 70 , that is, the housing 76 . The other end of each injector 90 is connected to the cylinder select switch SWA to SWD corresponding to that injector 90 through one of the terminals T 18 to T 21 .

According to this injector drive system 3 , the four injectors 90 are driven sequentially by the one EDU 70 . Unlike the first and second embodiments, therefore, the injector drive system 3 turns on the cylinder select switch SWA to SWD corresponding to that injector 90 is turned on, fuel is injected from an injector 90 , that is, when a piezoelectric element P is charged.

An injection signal for specifying an injector 90 from which fuel should be injected among the four injectors 90 is inputted to the EDU 70 . When this injection signal is inputted to the EDU 80 , the EDU turns on the cylinder select switch SWA to SWD corresponding to the injector 90 specified by that injection signal. Thereafter, the EDU 70 repeatedly turns on and off the charge switch SW 1 with the discharge switch SW 2 kept off as in the first and second embodiments. The piezoelectric element P of the injector 90 specified by the injection signal is thereby expanded to inject fuel.

Discharge of the electric charges accumulated in the piezoelectric element P is the same as in the first and second embodiments.

When one EDU 70 drives multiple (four) injectors 90 , the power required for the EDU 70 to drive the injectors 90 is increased as compared with in the first and second embodiments. If power for driving the injectors 90 is supplied by only the power supply unit 72 of the EDU 70 , for this reason, it is required to increase the capacity of the power supply unit 72 and the size of the EDU 70 . However, in this embodiment, the power supply unit 60 is placed externally to the EDU 40 , and the drive unit 74 is supplied with power at least from the power supply unit 60 .

For this reason, when the power supply unit 72 is housed in the housing 76 of the EDU 7 , and one EDU 70 drives multiple injectors 90 and the number of times of injector 90 operation is increased, as in this embodiment, the following measure only has to be taken, by increasing capacity of the power supply unit 60 is increased.

In this embodiment, the power supply unit 60 and the power supply unit 72 have the same functions. In this embodiment, the same voltage boosting operation as in the injector drive system 1 in the first embodiment is performed.

In the power supply unit 60 in this embodiment, the boost switch SW 3 is repeatedly turned on and off and energy is thereby accumulated in the boost coil L 3 , and the accumulated energy is supplied to the DC-DC capacitor C 2 . This accumulates electric charges in the DC-DC capacitor C 2 and increases the voltage of the power supply unit 60 .

Also, in the power supply unit 72 , the boost switch SW 4 is repeatedly turned on and off and energy is thereby accumulated in the boost coil L 5 , and the accumulated energy is supplied to the DC-DC capacitor C 4 . This accumulates electric charges in the DC-DC capacitor C 4 and increases the voltage of the power supply unit 72 .

The power supply unit 60 and the power supply unit 72 start voltage boosting operation with the identical timing. Similarly in the first embodiment mentioned above (Refer to FIG. 2 ), this voltage boosting operation is started at time t 7 in FIG. 5 and is performed until the voltages of the power supply unit 60 and the power supply unit 72 reach a predetermined voltage V 1 at time t 8 when a time TC has passed.

When the voltage of the power supply units 60 , 72 drop below a predetermined voltage V 2 due to driving of an injector 90 , spontaneous discharge, or the like (Refer to time t 9 in FIG. 5 ), the above voltage boosting operation is started. The predetermined voltage V 2 is set to a value lower than the predetermined voltage V 1 . Thus, in the injector drive system 3 , substantially constant high-voltage power can be constantly supplied by the power supply units 60 and 72 .

The power supply unit 60 and the power supply unit 72 operate independently of each other. Therefore, the capacitor C 2 and the capacitor C 4 are brought to a common voltage, and when this common voltage drops, they substantially simultaneously operate. With this construction, increase in the size of the power supply unit 72 , that is, increase in the size of the EDU 70 can be suppressed and the number of times of operation of injector 90 can be increased.

Also, in this embodiment, the same advantage as in the first and second embodiments mentioned above is brought. That is, even when the capacity of the power supply unit 60 is increased to increase a number of times of injector 90 operation and the amount of heat produced at the power supply unit 60 is increased, the following is implemented: it is unnecessary to increase the size of the housing 76 of the EDU 70 , and thus increase in the size of the EDU 70 can be suppressed.

In this embodiment, the power supply unit 60 is a first power supply unit and the power supply unit 72 is a second power supply unit.

Fourth Embodiment

In the first to third embodiments, the injector drive system 1 to 3 is mounted in a vehicle using a diesel engine as a driving source. In this fourth embodiment, an injector drive system 4 is for a hybrid vehicle that runs by a combination of a diesel engine and an electric motor.

As shown in FIG. 6 , the injector drive system 4 includes an injector 100 for injecting fuel into the diesel engine of the hybrid vehicle and an injector drive device 110 that drives the injector 100 .

The injector drive device 110 includes a drive unit 122 that is supplied with power from the battery 55 for supplying power to the electric drive motor mounted in the hybrid vehicle and drives the injector 100 , and an EDU 120 having a housing 124 for housing the drive unit 122 . Since the battery 55 is for supplying power to the electric drive motor mounted in the hybrid vehicle, the battery 55 generates a high voltage of tens to hundreds of volt.

The housing 124 of the EDU 120 is provided with a terminal T 22 connected to the positive terminal of the battery 55 , a terminal T 23 connected to the negative terminal of the battery 55 , terminals T 24 to T 26 connected to an injector 100 , and a terminal T 27 connected to the ECU 52 . The drive unit 122 is connected directly to the terminal T 27 without a circuit element placed between it and the terminal T 27 . The drive unit 122 includes the charge switch SW 1 , the discharge switch SW 2 , and diodes D 1 , D 2 , D 8 .

One end of the charge switch SW 1 is connected to the positive terminal of the battery 55 through the terminal T 22 , and the other end is connected to the injector 100 through the terminal T 24 . One end of the discharge switch SW 2 is connected to the point of junction between the charge switch SW 1 and the injector 100 , and the other end is grounded.

The diode D 1 is provided in parallel with the charge switch SW 1 . The cathode of the diode D 1 is connected to the charge switch SW 1 on the battery 55 side, and its another is connected to the charge switch SW 1 on the injector 100 side. The diode D 2 is provided in parallel with the discharge switch SW 2 . The anode of the diode D 2 is connected to the discharge switch SW 2 on the ground side, and its cathode is connected to the discharge switch SW 2 on the charge switch SW 1 side.

The anode of the diode D 8 is connected to the negative terminal of the battery 55 through the terminal T 23 , and further connected to one end of the piezoelectric element P of the injector 100 through the terminal T 26 . The cathode of the diode D 8 is connected to the other end of the piezoelectric element P of the injector 100 through the terminal T 25 .

As in the first embodiment, the injector 100 includes the piezoelectric element P, connector terminals T 28 to T 30 connected to the terminals T 24 to T 26 of the EDU 120 , and a connector case (not shown). One end of the piezoelectric element P is connected to the anode of the diode D 8 through the terminals T 26 and T 30 , and further connected to the negative terminal of the battery 55 through the terminal T 23 . The other end is connected to one end of the charging/discharging coil L 2 through the terminals T 24 and T 28 . The other end of the charging/discharging coil L 2 is connected to the point of junction between the charge switch SW 1 and the discharge switch SW 2 .

The point of junction between the piezoelectric element P and the charging/discharging coil L 2 is connected to the cathode of the diode D 8 through the terminals T 25 and T 29 . In this embodiment, the battery 55 can output a high voltage of tens to hundreds of volt. Therefore, it is unnecessary to separately provide a power supply unit that generates high voltage. For this reason, an injector drive system for hybrid vehicles can also be used as an injector system for ordinary vehicles that run only on an internal combustion engine.

When the injector drive system 4 is applied to an ordinary vehicle, the power supply unit 30 only has to be separately provided externally to the EDU 40 as in the first embodiment. When the injector drive system 4 is applied to a hybrid vehicle, the positive terminal of the battery 55 only has to be connected to the terminal T 22 without providing a power supply unit in the injector drive device 110 as in this embodiment.

In this embodiment, therefore, increase in the size of the EDU 120 can be suppressed, and further the injector drive system for a hybrid vehicle can also be used as an injector drive system for ordinary vehicles and increase in the number of times of operation of injector 100 can be coped with.

Other Embodiments

In the third embodiment, the power supply units 60 , 72 are provided internally and externally to the EDU 70 . In this case, the EDU 70 only has to be supplied with power at least from the power supply unit 60 of the two power supply units 60 , 72 when driving the injector 90 . The power supply unit 72 need not be used. The EDU 70 may be integrated with the ECU 52 .

In the fourth embodiment, the invention is applied to the hybrid vehicle that runs on a combination of the diesel engine and the electric motor. The invention can be applied to any kind of hybrid vehicle as long as it runs on a combination of the internal combustion engine and the electric motor. For example, it is applicable to the hybrid vehicle that runs on a combination of a gasoline engine and the electric motor.

When a battery that generates a high voltage of tens to hundreds of volt is mounted in a vehicle, the injector drive system in the fourth embodiment may be adopted as the injector drive system for the vehicle.

Although the drive unit 42 of the EDU 40 is directly connected to the terminal T 6 , a circuit element such as a resistor that has no influence on the operation of the drive unit 42 may be placed between the terminal T 6 and the drive unit 42 .

In the above embodiments, the operation of turning on and off the discharge switch SW 2 is stopped when the voltage of the positive pole of the piezoelectric element P drops to the predetermined voltage V 3 or below. However, this on/off operation may be stopped when a predetermined time has passed after the operation of turning on and off the discharge switch SW 2 was started. It is advisable to set this predetermined time to a time longer than the time until discharge of electric charges by the piezoelectric element P is terminated.