JP2001234793A - Solenoid driving circuit for fuel injection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solenoid driving circuit for fuel injection capable, of controlling a valve opening electric current of an injector at a specified value regardless of an inherent characteristic and reducing electric power consumption by reducing a burden of a DC-DC converter. SOLUTION: This solenoid driving circuit for fuel injection is constituted by furnishing a DC-DC converter 30, a gate forming circuit 10, an FET 100 for high voltage application connected to one of injectors 200 and to apply high voltage 30c from an output capacitor 37 to the injector 200, a diode 150 of carry an electric current when an electric potential is lower than an earth electric potential, an FET 130 for VB application, a diode 140 for back-flow prevention, an FET 110 for electric current control connected to the other of the injectors 200 to carry an electric current, an electric current detection resistor 120 and a diode 160 connected to the other of the injectors 200 and the output capacitor 37 and to carry an electric current 160a when the electric potential is higher than voltage of the output capacitor 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection solenoid driving circuit used for a fuel injection device for an automobile, and more particularly to a fuel injection solenoid driving circuit for driving a fuel injector (injector) by applying a high voltage. About.

[0002]

2. Description of the Related Art In-cylinder fuel injection engines for directly injecting fuel into cylinders of engines have been put into practical use. In this in-cylinder fuel injection engine, there is a problem in particular of reducing exhaust gas and fuel consumption due to lean combustion. From such a background, it is required to drive the injector in such a way that the response time of the injector to the injection signal is made faster and the injector is controlled proportionally from a range in which the time width of the injection signal is small.
As a means for this, a method of applying a high voltage to the injector at the time of the rising of the injection signal to flow a large current, shortening the valve opening time, and thereafter controlling a holding current for holding the valve opening is common. .

In order to generate a high voltage, a step-up DC
-A DC converter is required. As an example of the performance of this DC-DC converter, the DC-DC converter boosts the battery voltage (14 V) to about 70 to 100 V and supplies a peak current of about 10 A. Further, when the maximum rotation speed is 6600 rpm in a six-cylinder engine, for example, the injector is driven every 3 ms. Therefore, after driving the injector once, the high voltage becomes a predetermined value within 3 ms. It is required that the battery be restored and the battery voltage can be guaranteed up to 10V. like this,
The step-up DC-DC converter consumes a large amount of power, and in a thermally severe environment, heat dissipation becomes a serious problem.

As methods proposed to solve this problem, there are, for example, those described in Japanese Patent Publication No. 7-78374 and Japanese Patent Application Laid-Open No. H10-153141. In the devices described in these publications, energy stored by flowing a current through a solenoid (equivalent to an injector) is stored in a capacitor by interrupting the current to obtain a high voltage.

[0005]

However, such a device according to the prior art is disclosed in Japanese Patent Publication No. 7-7837.
In the device described in Japanese Patent Application Publication No. 4 (1999) -1994, a DC-
The energy stored in the solenoid is partially stored in the output capacitor of the DC converter.
That is, energy is stored in the output capacitor only twice when the valve opening current flowing at a high voltage is reduced to the holding current and when the injection signal ends and the holding current is reduced to zero. In this method, the effect on the boosting operation of the DC-DC converter that generates a high voltage is not sufficient. Also, Japanese Patent Application Laid-Open
No. 0-153141, the DC-DC
The circuit as a converter is eliminated, and the energy stored in the solenoid is stored in a capacitor.
The power consumption in the C-DC converter is set to zero.

[0006] The operation of accumulating in the capacitor is such that the free-wheeled current is connected to the capacitor via a diode such that every time the current flowing through the solenoid is cut off, all the accumulated energy is accumulated in the capacitor. From this circuit configuration, the energy stored in the capacitor is determined by the time of the current flowing through the solenoid, that is, the time width of the injection signal. In this method, there is an effect that the heat dissipation can be satisfactorily solved by a combination of the value of the capacitor to be stored and the solid state characteristics of the solenoid. However, the following problems occur in the drive in which an unspecified number of condensers and injectors are combined for the purpose of lean combustion.

As described above, the energy stored in the capacitor, that is, the value of the high voltage, changes according to the time width of the injection signal. Therefore, when the injection signal time is short, a sufficient valve opening current of the injector cannot be supplied. is there. Further, when the value of the high voltage changes, when the holding current is set to 0, the fall time of the current changes and the fuel injection amount varies.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to obtain a high voltage of a predetermined value and reduce the valve opening current of the injector to a predetermined value regardless of the specific characteristics of the injector. And can be controlled by DC
An object of the present invention is to provide a fuel injection solenoid drive circuit that can reduce the load on a DC converter and reduce power consumption.

[0009]

In order to achieve the above object,
The fuel injection solenoid drive circuit of the present invention basically includes a DC-DC converter that feeds back an injector, a high-voltage charging capacitor, and a voltage of the high-voltage charging capacitor to control the voltage of the capacitor to a predetermined value. A converter, a first switch connected to one of the injectors for applying a high voltage from a high-voltage charging capacitor to the injector in response to an injection signal, and connected between a ground and the potential lower than the ground potential; A second switch means connected to the other of the injectors for supplying current when the current flows, and a second switch means for supplying current with the high voltage and a voltage different from the high voltage, and a second switch means connected between the second switch means and ground. Current detection means, connected to the other of the injectors and the high voltage charging capacitor, if the potential is higher than the capacitor voltage The first switch means is turned on simultaneously with the injection signal, is turned off at a first level of a first level detector connected to the current detection means, and the second switch means The switch means is turned on at the same time as the injection signal, is turned off at a second level lower than the first level of the first level detector connected to the current detection means, and is turned on at a second level connected to the current detection means. It is characterized in that it turns on at a second level of the level detector and turns off at a first level higher than the second level of the second level detector.

In a specific embodiment of the fuel injection solenoid drive circuit according to the present invention, the injector, the high-voltage charging capacitor, and the voltage of the high-voltage charging capacitor are fed back to set the voltage of the capacitor to a predetermined value. DC-DC to control
A converter, a first switch connected to one of the injectors for applying a high voltage from a high-voltage charging capacitor to the injector in response to an injection signal, and connected between a ground and the potential lower than the ground potential; A diode for supplying an hour current, a third switch for applying a voltage different from the high voltage to the injector in accordance with an injection signal, and a third switch for connecting in series with the third switch;
A diode for preventing backflow to a voltage different from the high voltage;
A second switch connected to the other of the injectors and supplying a current together with the high voltage and a voltage different from the high voltage; a current detection unit connected between the second switch and a ground; A diode connected to the other of the injectors and the high-voltage charging capacitor, and for supplying a current when a potential is higher than the capacitor voltage;
The third switch means continues to be turned on during the period of the injection signal, and the first switch means is turned on at the same time as the injection signal, and the first level of the first level detector connected to the current detection means And the second switch means is turned on at the same time as the injection signal, is turned off at a second level lower than a first level of the first level detector connected to the current detection means, and The second level detector connected to the means is turned on at a second level and is turned off at a first level higher than the second level of the second level detector.

The DC-to-DC generator for generating a high voltage by the fuel injection solenoid driving circuit of the present invention having the above-described structure.
The power consumption of the DC converter can be reduced, and it is easy to cope in a thermally severe environment. Further, another specific aspect of the present invention is characterized in that the first switch means is a MOSFET.

In a specific embodiment of the fuel injection solenoid drive circuit according to the present invention, the fuel injection solenoid drive circuit further includes a voltage limiting means for limiting a voltage level higher than a predetermined value of the capacitor voltage in parallel with the high voltage charging capacitor. It is characterized by. Further, another specific aspect of the present invention is characterized in that the voltage limiting means is a constant voltage diode connected in parallel with the high voltage charging capacitor.

Further, another specific aspect of the present invention is characterized in that the second switch means includes voltage limiting means for limiting a voltage level higher than a predetermined value of the capacitor voltage. Further, in another specific aspect of the present invention, the second switch means is a MOSFET,
The voltage limiting means is a constant voltage diode connected between a drain and a gate of the MOSFET. By providing the voltage limiting means in this manner, it is possible to limit the voltage so that the voltage does not increase without limit by the energy stored in the output capacitor.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a fuel injection solenoid drive circuit according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to the first embodiment. FIG. 1 shows a circuit for one cylinder in an injector drive circuit of a multi-cylinder engine.

In FIG. 1, reference numeral 1 denotes a battery, 200 denotes an injector, 2 denotes a fuel injection solenoid drive circuit for driving the injector 200, and the fuel injection solenoid drive circuit 2 includes an output capacitor 37 (high voltage charging capacitor). The DC-DC converter 30 that feeds back the voltage to control the voltage of the output capacitor 37 to a predetermined value, and each FE based on the supplied injection signal 10a and current detection signal.
Injection signals (gate signals) 100a, 110 applied to T
and a high voltage application FET 100 connected to one of the injectors 200 for generating a high voltage 30c from the output capacitor 37 in response to the injection signal 100a. ) And a diode 150 connected between the ground and conducting current when the potential is lower than the ground potential.
And a VB application FET 1 for applying a voltage different from the high voltage 30c to the injector 200 according to the injection signal 130a.
30 (third switch means) and VB applying FET 13
0 and a reverse current blocking diode 140 connected to the other side of the injector 200, and a current control FET 110 connected to the other of the injector 200 and conducting current together with the high voltage 30c and a voltage different from the high voltage 30c. (Second switch means) and a current detection resistor 120 (current detection means) connected between the current control FET 110 and the ground.
A diode 160 that is connected to the other end of the injector 200 and the output capacitor 37 and that conducts a current 160a when the potential is higher than the voltage of the output capacitor 37;
The B application FET 130 keeps on during the injection signal 130a, and the high voltage application FET 100
0a, and turns off at the first level Ip1 of the peak current detector 20 (first level detector) connected to the current detection resistor 120. The current control FET 110 turns on at the same time as the injection signal 110a. It turns off at the second level Ip2 lower than the first level of the peak current detector 20 connected to the current detection resistor 120, and turns off the second of the holding current detector 21 (second level detector) connected to the current detection resistor 120. 2
It is configured to turn on at the level Ih2 and turn off at the first level Ih1 higher than the second level Ih2 of the holding current detector 21.

DC-DC converter 3 for generating high voltage
0 denotes a gate control circuit 31 for controlling a switching time by comparing an output voltage with a reference voltage, a coil 32 as an inductor, and a DC-DC for turning on / off a current 32a of the coil 32 from the + (plus) side of the battery 1. Converter FET3
3. It comprises a diode 34 for supplying a current to the coil 32 when the FET 33 is turned off, resistors 35 and 36, and an output capacitor 37 for charging a current supplied to the diode 37. The voltage 30c of the output capacitor 37 is equal to the resistance 3
The voltage is divided by 5, 36 and the gate control circuit 31 of the FET 33
And the gate control circuit 31 outputs the output capacitor 3
7 is controlled so that the voltage 30c becomes a predetermined high voltage.

The + side of the battery 1 is connected to the injector 200+ side through the high voltage application FET 100 via the output side of the output capacitor 37 of the DC-DC converter circuit 30. The VB application FET 130 and the backflow prevention diode 14 are connected to the injector 200+ side from the + side of the battery 1 (hereinafter referred to as battery 1+).
0 is connected.

The injector 200- (minus) side is a current control FE for controlling the injector current 200a to a predetermined value.
It is connected to the negative side of battery 1 by T110 and current detection resistor 120. A diode 150 that freewheels the energy of the injector 200 when the FET 100 and the FET 130 are turned off is connected from the negative side of the battery 1 (hereinafter referred to as battery 1-) to the injector 200+ side.

Further, DC is applied from the injector 200- side.
-The output capacitor 37 of the DC converter circuit 30 includes:
When the current control FET 110 is turned off, the injector 2
The diode 160 is connected as a path for charging the current of 00 to the output capacitor 37.

Based on the injection signal 10a and the detection results of the peak current detector 20 and the holding current detector 21, the gate generation circuit 10 controls each gate of the high voltage application FET 100, the current control FET 110, and the VB application FET 130. Generate signals 100a, 110a, and 130a. Hereinafter, the operation of the fuel injection solenoid drive circuit configured as described above will be described.

FIG. 2 is an operation waveform diagram showing a change in voltage and current of each circuit portion of the fuel injection solenoid drive circuit. The numbers in FIG. 2 correspond to the corresponding signals in FIG. First, the operation at the time of opening the valve is as follows. When the injection signal 10a is input to the gate generation circuit 10, the gate generation circuit 10
0a, 110a, 130a, and VB application FET
In addition to outputting the gate signal 130a of 130, the gate signal 100a of the high voltage application FET 100 and the gate signal 110a of the current control FET 110 are output. Thereby, the high voltage application FET 100 and the current control FET
110, the VB application FET 130 is turned on, and the injector 200 has the output capacitor 3 of the DC-DC converter.
7, the charged high voltage 30c is applied, and the injector current 200a starts to flow (see FIG. 2).

The injector current 200a causes a voltage drop in the current detection resistor 120. Current detection resistor 1
20 is detected by the peak current detector 20, and when the peak current detector 20 detects the first level Ip1, the gate generation circuit 10 receiving this detection result outputs the gate signal 100a of the high voltage application FET 100. Is set to 0, the high voltage application FET 100 is turned off, and the application of the high voltage ends.

When the high voltage application FET 100 is turned off,
The injector current 200a is freewheeled through the path of the injector 200 → the current control FET 110 → the current detection resistor 120 → the diode 150 → the injector 200. Then, the peak current detector 20 detects the level Ip2
Is detected, the gate generation circuit 1 receiving this detection result
0 sets the gate signal 110a of the current control FET 110 to 0 to turn off the current control FET 110. This is the first falling of the gate signal 110a in FIG. 2, and the operation at the time of opening the valve is completed, and the process shifts to the holding current control.

Next, the transition to the holding current control and the control will be described. When the current control FET 110 is turned off, the injector current 200a changes from the injector 200 → the diode 160 → the output capacitor 37 → the diode 150
→ The output capacitor 37 is charged through the path of the injector 200 and contributes to the return of the high voltage 30c.

When the injector current 200a decreases and the holding current detector 21 detects the second level Ih2, the gate generation circuit 10, which has received the detection result, sets the current control F
The gate voltage 110a of the ET 110 is output to turn on the current control FET 110. This is the gate signal 1 in FIG.
This is shown at the second rise of 10a. Further, the VB application FET 130 continues to be turned on during the injection signal 130a. When the current control FET 110 is turned on, the battery 1 + → the VB application FET 130 → the diode 140 →
Injector 200 → current control FET 110 → current detection resistor 120 → battery 1 → battery voltage VB
Is applied, and the injector current 200a increases.

When the holding current detector 21 detects the first level Ih1, the gate generation circuit 10 receiving the detection result outputs the gate voltage 11 of the current control FET 110.
By setting 0a to 0, the current control FET 110 is turned off. This is indicated by the second falling of the gate signal 110a in FIG. When the current control FET 110 is turned off, the injector current 200a decreases in the path of the injector 200 → the diode 160 → the output capacitor 37 → the diode 150 → the injector 200, and this current is charged in the output capacitor 37 to return the high voltage 30c. Complicate.

When the holding current detector 21 detects the second level Ih2 again, the gate voltage 110a of the current control FET 110 is output and the current control FET 110
Is turned on, the battery 1 + → VB application FET 130 → diode 140 → injector 200 → current control FE
The battery voltage VB is applied in the path of T110 → current detection resistor 120 → battery 1 →
0a increases. This operation of the holding current control is repeated until the injection signal 10a becomes 0.

When the injection signal 10a is output and the high voltage application FET 100 is turned on, the high voltage application F
While the ET 100 is ON, the injector current 200 is supplied from the output capacitor 37 of the DC-DC converter 30.
a, the high voltage 30c decreases as shown in FIG. 2 and becomes smaller than the high voltage set value 30c1 to reduce the DC-D
The C converter 30 starts operating. Gate control circuit 3
The operation of the DC-DC converter 30 according to No. 1 is as follows.

First, the DC-DC converter FET 33 is turned on to supply a current 32 a to the coil 32.
Turn 3 off. The current flowing through the coil 32 flows through the diode 34 to the output capacitor 37 to charge the output capacitor 37. High voltage 30c is high voltage set value 30
This operation is repeated until the voltage exceeds c1, and the operation stops when the high voltage 30c becomes 30c2.

During the injection signal 10a, the output capacitor 3
7 includes a diode 1 of the injector current 200a.
The current 160a passing through 60 (see the hatched portion 200a in FIG. 2) and the current 30b of the coil current 30a flowing through the coil 32 (see the hatched portion 30a in FIG. 2)
And the high voltage 30c increases to the high voltage set value 30c1. Therefore, since the voltage 30c of the output capacitor 37 can quickly return to the predetermined value 30c1, the operation time of the DC-DC converter 30 is shortened. Here, when the injection signal 10a is small, DC-
The output capacitor 37 of the DC converter 30 is no longer charged by the injector current 200a, and is charged only by the coil current 30a.

When the engine speed increases under these conditions, the injection interval between adjacent cylinders in a multi-cylinder engine is, for example, 3 ms at 6600 rpm for a six-cylinder engine. It is important that the time required to return to the voltage set value 30c1 be 3 ms or less. However, the engine speed is 6600r
Since the state in which the injection signal 10a is small at pm is not continuous, it is not practical to consider heat generation when the state is continuous under this condition.

According to the present embodiment, only the operation of the DC-DC converter 30, that is, three of the coil currents 30 a, is required for the high voltage 30 c to return to the high voltage set value 30 c 1.
The speed can be increased as compared with the case where the output capacitor 37 is charged only with 0b. This means that the operation time of the DC-DC converter 30 is shortened, so that the power consumption of the DC-DC converter 30 is small and the heat generation can be reduced.

Further, in this embodiment, when a surge voltage is applied, for example, +300 V is applied to the injector 2.
When the voltage is applied to the + terminal 200+ of the high voltage application FET 100, it is absorbed by the output capacitor 37 through the internal parasitic diode 101 (see FIG. 1) of the high voltage application FET 100, and this surge voltage is applied to the-terminal 200-of the injector 200. In this case, the voltage is absorbed by the output capacitor 37 through the diode 160. From this, the current control FE
T110, backflow blocking diode 140 and diode 1
The withstand voltage capacity of 50 is higher than that of surge voltage 30
There is an effect that can be set with c.

As described in detail above, the solenoid driving circuit 2 for fuel injection according to this embodiment includes the output capacitor 3
DC-DC converter 30 for controlling the voltage at 7 to a predetermined value
And injection signals 100a, 110a,
The gate generating circuit 10 for generating the voltage 130a and one of the injectors 200 are connected between the high voltage application FET 100 for applying the high voltage 30c from the output capacitor 37 to the injector 200 and the ground. Diode 150 that conducts current when lower
A VB application FET 130 for applying a voltage different from the high voltage 30c to the injector 200, and a VB application FET
130 is connected in series with the diode 130 for backflow prevention to a voltage different from the high voltage 30c;
And a current control FET 110 connected to the other of the first and second terminals for supplying a current together with the high voltage 30c and a voltage different from the high voltage 30c.
, A current detection resistor 120 connected between the current control FET 110 and the ground, the other end of the injector 200 and the output capacitor 37, and the potential is set to the output capacitor 37.
It comprises a diode 160 that conducts the current 160a when the voltage is higher than the voltage. And the injector 200
, The FET 100 and the FET 110 are turned on, the valve opening current for applying the high voltage 30c of the output capacitor 37, and FE
At T130, the battery voltage VB is applied, and the holding current for controlling the current to a predetermined value is caused to flow by the FET 110. When the valve-opening current flows, the high voltage 37a of the output capacitor 37 decreases, and the DC-DC converter 30 operates to return the high voltage 37a to the predetermined value 30c1. On the other hand, when the injector current 200a reaches the predetermined values Ip2 and Ih1, the FET 110 is turned off to charge the output capacitor 37 with the current 160a through the diode 160.

Thus, the output capacitor 37 is connected to DC
Current 3 flowing through coil 32 of DC converter 30
0b and the current 160a flowing through the injector 200. That is, the DC-DC converter 3
In addition to the boost operation of 0 itself, the stored energy due to the current flowing through the injector 200 is stored in the output capacitor 37. As a result, since the voltage 30c of the output capacitor 37 can quickly return to the predetermined value 30c1, the operation time of the DC-DC converter 30 is shortened, and the power consumption can be reduced by shortening the operation time of the DC-DC converter 30, There is an effect that it is possible to easily cope with a thermally severe environment. Next, a second embodiment of the present invention will be described.

FIG. 3 is a circuit diagram showing the configuration of a fuel injection solenoid drive circuit according to the second embodiment. In the description of the present embodiment, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted. In FIG. 3, 38
Is a constant voltage diode (voltage limiting means) for limiting a voltage level higher than a predetermined value of the voltage of the output capacitor 37, and the constant voltage diode 38 is a DC-DC converter 3
0 is provided in parallel with the output capacitor 37. Hereinafter, the operation of the fuel injection solenoid drive circuit configured as described above will be described. Since the overall operation is the same as that of the first embodiment, the description of the operation of this portion will be omitted, and different operations will be described.

FIG. 4 is an operation waveform diagram showing changes in voltage and current of each circuit portion of the fuel injection solenoid drive circuit, and corresponds to the waveform diagram of FIG. FIG.
Is longer in the injection signal 10a than in FIG. If the time of the injection signal 10a is long, the period of the above-described holding current control becomes long, and the current 160a of the injector current 200a passing through the diode 160 becomes the output capacitor 37 of the DC-DC converter 30 during the period of the holding current control. And the high voltage 30a increases beyond the high voltage set value 30c1. High voltage 30a
Becomes large, the injector current 200 during the valve opening operation is increased.
There are problems such as that a varies depending on the value of the high voltage 30a, and the withstand voltage of the parts used increases.

Therefore, a constant voltage diode 38 was connected in parallel with the output capacitor 37 of the DC-DC converter 30, and the voltage level of the constant voltage diode 38 was set to a level 30c3 higher than the high voltage set value 30c1. The difference between the high voltage set value 30c1 and the level 30c3 is
There is no difference in the valve opening operation of 00.

Thus, the output capacitor 37 has D
The charging of the output capacitor 37 by the C-DC converter 30 is up to the high voltage set value 30c1, and the current 160 of the injector current 200a passing through the diode 160
The charging by a is up to the level 30c3. And for more than that, the current 160a is
8 of current 38a. Current 3 of constant voltage diode 38
8a will cause power consumption, but will have little effect on the overall heat seen by the system for the following reasons.

As an example, the high voltage set value 30c1 is set to 72
V, and the injection signal 10a is 5 m at the maximum in a normal operation state.
When s is set, the high voltage value 30c becomes 75V. Level 3
If 0c3 is set to 77 V, the current 38a does not flow through the constant voltage diode 38 in most operating states, and thus no power is consumed. However, there is a control to lengthen the injection signal 10a under a small condition such as when starting at a low temperature, and a state where the injection signal 10a exceeds the level 30c3 occurs transiently, so that a voltage limitation is necessary as protection of the element.

According to the present embodiment, the high voltage 30a can be in the range of the high voltage set value 30c1 and the level 30c3, so that the injector current 200a at the time of the valve opening operation can be made constant and the withstand voltage of the used parts can be maintained. To level 30
There is an effect near c3. Next, a third embodiment of the present invention will be described.

FIG. 5 is a circuit diagram showing the configuration of a fuel injection solenoid drive circuit according to the third embodiment. In the description of the present embodiment, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted. In FIG. 5, a diode 1 is connected between the drain and the gate of the current control FET 110.
70 and a constant voltage diode 180 (voltage limiting means).

That is, in FIG.
The diode 170 and the constant voltage diode 180 are connected between the drain and the gate of the current control FET 110 to make the current control FET 110 have a voltage limiting action. .

In this embodiment, the constant voltage diode 180
To the level 30c3 of the high voltage 30a, so that the drain voltage of the current control FET 110 becomes the level 30c3.
Is exceeded, a gate voltage is applied so that the high voltage 30a does not become higher than the level 30c3. According to the present embodiment, in addition to obtaining the same effect as the second embodiment, there is an effect that the constant voltage diode 180 can be downsized. Next, a fourth embodiment of the present invention will be described.

FIG. 6 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to a fourth embodiment. In the description of the present embodiment, the same components as those in FIG. 5 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted. In this embodiment, the VB application FET 130 (third switch means) connected in series with the backflow prevention diode 140 is omitted on the + side of the battery 1 in FIG.
40 only. In addition, similarly to FIG.
A diode 170 and a constant voltage diode 180 are connected between the drain and the gate of T110.

The VB application FET 130 is provided for the purpose of diagnosing when the terminal 200+ of the injector 200 is short-circuited to the ground and turning off the FET 130 to protect the FET 130. Therefore, if the system has no abnormality in the terminal 200+ of the injector 200, the FET 130 can be eliminated.

According to the present embodiment, the same effects as those of the third embodiment can be obtained, and the cost of parts can be reduced.

Next, a fifth embodiment of the present invention will be described.

FIG. 7 is a circuit diagram showing the configuration of a fuel injection solenoid drive circuit according to a fifth embodiment. In the description of the present embodiment, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description of the overlapping portions will be omitted. In FIG. 7, a diode 190 is connected in series with the high voltage application FET 100 so that a voltage can be applied to the injector 200.

When a short-circuit failure of the output capacitor 37 or a short-circuit failure of the diode 34 occurs in the DC-DC converter 30, the high voltage 30 c cannot be applied, and at the same time, a current due to the battery voltage also flows through the internal parasitic diode 101 of the FET 100. Converter 3
0, and the current 200a stops flowing through the injector 200.

The DC-DC converter 30 has only one circuit even in the case of a multi-cylinder engine, thereby reducing the circuit scale. Therefore, when the above-described failure occurs, the injectors 200 of all cylinders are operated. Can not do.
In the present embodiment, the high voltage 30c
Even if there is no battery voltage, the battery voltage can be applied. Therefore, when a failure is detected, the injection signal 10a is made long enough to allow the injector 200 to operate, and there is an effect that the vehicle can be driven as a fail-safe.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and the present invention is not limited to the above-described embodiments. Various changes can be made. For example, various types of design changes are possible for the type and number of capacitors and switch means that constitute the DC-DC converter 30, and for the gate signal generation method in the gate generation circuit 10. Similarly, MOSFE is used as each switch means.
Although T is used, the type and combination are merely examples, and the rising, falling, and active states of the signal can be changed as appropriate. In addition, it is also possible to use appropriate members as appropriate for the types of the voltage limiting means, the current detecting means, and the like, and to configure an equivalent circuit.

[0053]

As can be understood from the above description, the solenoid drive circuit for fuel injection according to the present invention is a DC-DC generator that generates a high voltage in a drive circuit that applies a high voltage to the injector to speed up the response. There is an effect that the power consumption of the converter can be reduced, and it is easy to cope in a severe thermal environment.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram showing changes in voltage and current of each circuit section of the fuel injection solenoid drive circuit of the embodiment.

FIG. 3 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to a second embodiment of the present invention.

FIG. 4 is an operation waveform diagram showing changes in voltage and current of each circuit section of the fuel injection solenoid drive circuit of the embodiment.

FIG. 5 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a fuel injection solenoid drive circuit according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Battery 2 ... Fuel injection solenoid drive circuit 10 ... Gate generation circuit 20 ... Peak current detector (first level detector) 21 ... Holding current detector (second level detector) 30 ... DC-DC converter 37: output capacitor (high-voltage charging capacitor) 38, 180: constant-voltage diode (voltage limiting unit) 100: FET for applying high voltage (first switch unit) 110: FET for current control (second switch unit) 120 ... Current detection resistor (current detection means) 130 ... VB application FET (third switch means) 140 ... Backflow prevention diode 150,160,170 ... Diode 200 ... Injector

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Fumiaki Nasu 2520 Oita Takaba, Hitachinaka-shi, Ibaraki F-term in the Automotive Equipment Group of Hitachi, Ltd. (Reference) 3G066 AA02 AA04 AB02 AD12 BA17 CC06U CD25 CD26 CE22 CE29 3G301 JA02 JB08 LB01 LC01 LC10 MA11 NA08 NE17 PB03Z PG02Z

Claims (7)

[Claims] An injector, a high-voltage charging capacitor, a DC-DC converter that feeds back the voltage of the high-voltage charging capacitor to control the voltage of the capacitor to a predetermined value, and is connected to one of the injectors; First switch means for applying a high voltage from a high-voltage charging capacitor to the injector in response to an injection signal; a diode connected between the grounds and conducting a current when the potential is lower than the ground potential; A second switch connected to the other and supplying a current together with the high voltage and a voltage different from the high voltage; a current detector connected between the second switch and a ground; and the other of the injectors And a diode connected to the high-voltage charging capacitor and conducting a current when a potential is higher than the capacitor voltage. It said first switching means is turned on at the same time as the injection signal,
Turning off at a first level of a first level detector connected to the current detecting means, the second switch means turning on at the same time as the injection signal,
Turning off at a second level lower than the first level of the first level detector connected to the current detecting means, turning on at a second level of the second level detector connected to the current detecting means, A solenoid drive circuit for fuel injection, which is turned off at a first level higher than a second level of the second level detector. 2. An injector, a high-voltage charging capacitor, a DC-DC converter that feeds back the voltage of the high-voltage charging capacitor to control the voltage of the capacitor to a predetermined value, and is connected to one of the injectors. First switch means for applying a high voltage from a high-voltage charging capacitor to the injector in response to an injection signal; a diode connected between the grounds and supplying a current when the potential is lower than the ground potential; Third switch means for applying a voltage different from the high voltage to the injector in response thereto; a diode for preventing backflow to a voltage different from the high voltage, connected in series with the third switch means; A second switch means connected to the other and for supplying a current together with the high voltage and a voltage different from the high voltage; Current detecting means connected between the switch means and the ground; and a diode connected to the other one of the injectors and the high-voltage charging capacitor and for supplying a current when a potential is higher than the capacitor voltage, the third switch The means continues to be on for the duration of the injection signal; the first switch means is turned on simultaneously with the injection signal;
Turning off at a first level of a first level detector connected to the current detecting means, the second switch means turning on at the same time as the injection signal,
Turning off at a second level lower than the first level of the first level detector connected to the current detecting means, turning on at a second level of the second level detector connected to the current detecting means, A solenoid drive circuit for fuel injection, which is turned off at a first level higher than a second level of the second level detector. 3. The device according to claim 1, wherein said first switch means is a MOSFE.
3. The fuel injection solenoid drive circuit according to claim 1, wherein T is T. 4. The apparatus according to claim 1, further comprising a voltage limiting unit configured to limit a voltage level higher than a predetermined value of the capacitor voltage in parallel with the high-voltage charging capacitor. Fuel injection solenoid drive circuit. 5. The solenoid driving circuit for fuel injection according to claim 4, wherein said voltage limiting means is a constant voltage diode connected in parallel with said high voltage charging capacitor. 6. The fuel according to claim 1, wherein the second switching means includes a voltage limiting means for limiting a voltage level higher than a predetermined value of the capacitor voltage. Injection solenoid drive circuit. 7. The device according to claim 7, wherein said second switch means is a MOSFE.
7. The fuel injection solenoid driving circuit according to claim 6, wherein T is a constant voltage diode connected between a drain and a gate of the MOSFET.