JP2013174200A - Drive device for fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such the problem that the withstand voltage of a boosting capacitor in a booster circuit is required to be equal to or higher than a feed voltage to a solenoid coil for driving a fuel injection valve, thus causing the upsizing of a drive circuit, and a diode for preventing a backward flow which prevents the backward flow of current from high voltage to a battery side or a diode for preventing the damage of a switching element by counter electromotive force of the solenoid coil for driving the fuel injection valve is required, thus causing the physical upsizing of the drive circuit.SOLUTION: A fuel injection solenoid valve is driven by supplying the voltage of a battery of a fuel injection device to the high voltage side of the solenoid coil for driving the fuel injection valve and supplying negative voltage generated in a step-down circuit to the low voltage side of the solenoid coil for driving the fuel injection valve to secure high voltage. As a result, the withstand voltage of a step-down capacitor in the step-down circuit is lowered by the amount of a battery voltage.

Description

  The present invention relates to a drive device for a fuel injection valve that supplies fuel to an internal combustion engine, and more particularly to a drive device for a fuel injection valve that injects fuel directly into a cylinder of the internal combustion engine.

  As represented by automobiles, an internal combustion engine (gasoline engine or diesel engine) that uses gasoline, light oil, or the like as fuel is used as a power generation source.

  In this internal combustion engine, a fuel injection valve that directly injects fuel into the cylinder is used for the purpose of improving fuel efficiency and output. A fuel injection valve that directly injects fuel into such a cylinder uses fuel that has been pressurized to a higher pressure than the conventional method (method in which a fuel injection valve is provided in the intake pipe that supplies air to the cylinder). It is characterized by.

  Therefore, a large amount of electrical energy is required to open the fuel injection valve against the compression pressure in the cylinder and the pressure of high-pressure fuel. Further, in order to cope with improvement in control performance (responsiveness) of the fuel injection valve and high rotation (high speed control), it is necessary to supply this electric energy to the fuel injection valve in a short time.

  In general, a driving apparatus for driving such a fuel injection valve is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-169762 (Patent Document 1), and generates a voltage higher than a battery voltage using a booster circuit. The switching element connected to is turned on / off, and the fuel injection valve is driven by passing a current through the electromagnetic coil of the fuel injection valve using the boosted voltage obtained thereby to pass a large current in a short time. The fuel is directly injected into the cylinder.

JP 2008-169762 A

  First, before explaining the present invention, the configuration and problems of a conventional fuel injection valve driving device using a booster circuit will be described with reference to FIGS.

  FIG. 7 shows a drive device (drive circuit) for driving a fuel injection valve of a typical conventional fuel injection control device.

  An electronic control unit (ECU) 70 combusts according to the operation status of the internal combustion engine from the operation information of the internal combustion engine such as the amount of air taken into the internal combustion engine, the rotational speed of the internal combustion engine, the water temperature, and the air-fuel ratio. A function of calculating an appropriate fuel injection amount to be injected into the chamber is provided. An appropriate fuel amount calculated by the electronic control unit 70 is input to the control circuit 60 as a pulse signal, for example, and the energization control to the fuel injection valve is performed by controlling the ON / OFF state of each switching element described below. .

  Here, as described above, in an internal combustion engine that directly injects fuel into a cylinder of the internal combustion engine, high-pressure fuel is injected into the cylinder and high response is required. The valve element is opened by applying a high voltage to the coil to flow a large current.

  For this reason, the drive device for the fuel injection valve has a booster circuit 30 (so-called DC-DC converter) that generates a high voltage from the battery power supply 1 (14V power supply here). The booster circuit 30 includes a booster coil 33, a booster switching element 31, a rectifier diode 32, and a booster capacitor 34 for storing high voltage energy.

  When the boosting circuit 30 performs a boosting operation, the boosting switching element 31 is turned on and off, whereby the high voltage energy stored in the boosting coil 33 is stored in the boosting capacitor 34 by the diode 32 to generate the high voltage VH. To do. For example, here, the boosted voltage at this time is “65V”.

  A high voltage side switching element 42 for supplying the high voltage VH generated by the boosting capacitor 34 to the high voltage side of the driving electromagnetic coil 50 of the fuel injection valve, and a battery voltage for supplying the holding current The holding current driving switching element 41 to be connected is connected via a backflow preventing diode 45 for preventing current from flowing to the battery side when a high voltage is applied. A diode 46 is also connected to allow a free wheel current of the driving electromagnetic coil 50 of the fuel injection valve to flow when the switching elements 41 and 42 are turned off.

  A switching element 43 for operating the fuel injection valve for supplying a current to the low voltage side of the driving electromagnetic coil 50 and a diode 44 for supplying a freewheel current on the low voltage side of the driving electromagnetic coil 50 for the fuel injection valve. Is connected.

  An operation when the drive electromagnetic coil 50 is energized in such a fuel injection valve drive device will be described. FIG. 8 shows an operation timing chart of the drive circuit of the conventional fuel injection valve shown in FIG. 7, and the high voltage boosted from the drive stop state of the fuel injection valve for the time indicated by “period A2”. Then, the application of the high voltage is stopped for the time indicated by “period B2”, and then the battery power is switched to supply the battery voltage to the fuel injection valve for the time indicated by “period C2”. It represents the period until the “stop period” that is the end of valve opening.

  The operation of the drive circuit will be described with reference to the timing chart shown in FIG. 8. In FIG. 9, the operation state of the drive circuit in “period A2” is shown. When the fuel injection valve is opened, the high-voltage side supply switching element 42 and the fuel injection valve operation switching element 43 are turned on, and the holding current drive switching element 41 is turned off to inject a high voltage of "65 V". Applied to the high voltage side of the solenoid coil 50 for driving the valve. At this time, since the operation switching element 43 is on, the low pressure side of the driving electromagnetic coil 50 of the fuel injection valve is “0 V”. Therefore, it is necessary to determine the withstand voltage of the boosting capacitor 34 corresponding to the voltage difference “65 V” between the high voltage side and the low voltage side of the driving electromagnetic coil 50. One of the problems is to reduce the withstand voltage of the capacitor.

  At this time, the current is supplied from the boosting capacitor 34 via the high-voltage side supply switching element 42 to the driving electromagnetic coil 50 of the fuel injection valve and rises, and thereafter, the current is supplied from the driving electromagnetic coil 50 of the fuel injection valve to the fuel injection valve. The current flows to GND through the operation switching element 43. Further, the diodes 45 and 46 are configured so that no current flows outside this path.

  In particular, when the diode 45 is not provided, the battery voltage VB and the high voltage VH of the battery 1 are dead-shorted via the protective diode in the holding current driving switching element 41. For this reason, the diode 45 is an indispensable electronic component. Also, eliminating the diode 45 is one of the problems.

  Next, FIG. 10 illustrates an operation state of the driving circuit in “period B2”. When the current flowing through the driving electromagnetic coil 50 of the fuel injection valve reaches the valve opening current (Ipeak) and the high voltage side supply switching element 42 is turned off, the driving electromagnetic coil 50 of the fuel injection valve causes a current to flow due to the counter electromotive force. In an attempt to continue, the current flows from the diode 46 to the driving electromagnetic coil 50 of the fuel injection valve and the switching element 43 for operating the fuel injection valve, and falls.

  Next, FIG. 11 illustrates an operation state of the driving circuit in “period C2”. Each time the current flowing through the driving electromagnetic coil 50 of the fuel injection valve reaches the holding current 1 (Ihold1) and the holding current 2 (Ihold2), the holding current driving switching element 41 is turned on to drive the fuel injection valve driving electromagnetic coil. 50 is supplied with current. At this time, in order to make the holding current constant, the holding current driving switching element 41 is switched and the rising state and the falling state are repeated, so that the holding current is controlled to be almost constant on average.

  Finally, FIG. 12 shows the operating state of the drive circuit during the “stop period”. The supply of current to the fuel injection valve is stopped by turning off all the switching elements. The current generated by the back electromotive force of the driving electromagnetic coil 50 of the fuel injection valve is regenerated to the boosting capacitor 34 via the diodes 46 and 44, and finally the current does not flow and the operation of the fuel injection valve is stopped.

  The above is the circuit configuration of the fuel injection valve driving apparatus that has been proposed so far and injects the fuel directly into the cylinder.

  As described above, the fuel injection valve drive device is required to open the valve body of the fuel injection valve by applying a high voltage to the injection electromagnetic valve to flow a large current. For this reason, a booster circuit 30 that generates a high voltage from the battery voltage is required, but the high voltage generated by the booster circuit 30 is stored in a charge storage element such as the boost capacitor 34. Since the high voltage applied to the fuel injection valve is stored in this charge storage element, a withstand voltage higher than the stored voltage is required.

  Generally, the withstand voltage of the boosting capacitor 34 of the boosting circuit 30 needs to be equal to or higher than the supply voltage to the driving electromagnetic coil 50 of the fuel injection valve, which has caused a physical enlargement of the driving device, particularly the driving circuit. Further, the backflow prevention diode 45 for preventing the backflow of the current from the boosted high voltage to the battery 1 side and the back electromotive force of the electromagnetic coil 50 for driving the fuel injection valve when each of the switching elements 41, 42, 43 is turned off. The diodes 44 and 46 for preventing the destruction of each switching element are required, which also causes a physical enlargement of the drive circuit.

  SUMMARY OF THE INVENTION The main object of the present invention is to provide a fuel injection valve drive device that can reduce the size of charge storage element components such as capacitors used in a booster circuit that supplies a high voltage to a drive electromagnetic coil of the fuel injection valve. There is to do.

  Another object of the present invention is to provide a fuel injection valve drive device that can reduce the number of electronic components such as a backflow prevention diode and reduce the size of the drive circuit.

  A feature of the present invention is that a battery voltage source is connected to the high voltage side of the driving electromagnetic coil of the fuel injection valve, and a negative voltage power source generated by a step-down circuit is connected to the low voltage side of the driving electromagnetic coil. A desired voltage is supplied to the driving electromagnetic coil.

  According to the present invention, by connecting the battery voltage source and the negative voltage source of the step-down circuit to both ends of the driving electromagnetic coil of the fuel injection valve, the withstand voltage corresponding to the battery voltage can be lowered in the charge storage element. Become. Therefore, it can be expected to reduce the size of charge storage element components such as capacitors.

It is a circuit diagram which shows the structure of the drive circuit which is a drive device of the fuel injection valve which becomes one Example of this invention. FIG. 2 is an operation timing chart showing the operation timing of the drive circuit shown in FIG. 1. FIG. 3 is an operation explanatory diagram illustrating an operation state of the drive circuit in “period A1” at the operation timing illustrated in FIG. 2. FIG. 3 is an operation explanatory diagram illustrating an operation state of the drive circuit in “period B1” at the operation timing illustrated in FIG. 2. FIG. 3 is an operation explanatory diagram for explaining the operation state of the drive circuit in “period C1” at the operation timing shown in FIG. FIG. 3 is an operation explanatory diagram for explaining the operation state of the drive circuit in the “stop period” at the operation timing shown in FIG. 2. It is a circuit diagram which shows the structure of the drive circuit which is the drive device of the conventional fuel injection valve. FIG. 8 is an operation timing chart showing the operation timing of the circuit shown in FIG. 7. FIG. 9 is an operation explanatory diagram illustrating an operation state of the drive circuit in “period A2” at the operation timing illustrated in FIG. 8. FIG. 9 is an operation explanatory diagram illustrating an operation state of the drive circuit in “period B2” at the operation timing illustrated in FIG. 8. FIG. 9 is an operation explanatory diagram illustrating an operation state of the drive circuit in “period C2” at the operation timing illustrated in FIG. FIG. 9 is an operation explanatory diagram for explaining the operation state of the drive circuit in the “stop period” at the operation timing shown in FIG. 8.

  As described above, the withstand voltage of the boosting capacitor of the boosting circuit needs to be equal to or higher than the supply voltage to the driving electromagnetic coil of the fuel injection valve, resulting in a physical enlargement of the driving device, particularly the driving circuit. . Also, in order to prevent the destruction of each switching element due to the back electromotive force of the backflow prevention diode or the electromagnetic coil for driving the fuel injection valve when each switching element is turned off when the switching element is turned off. These diodes are required, and this also leads to physical enlargement of the drive circuit.

  The present invention proposes a technique for solving the problem of such a fuel injection valve drive device. Specifically, the present invention provides a drive electromagnetic coil for a fuel injection valve using a step-down circuit instead of a step-up circuit. The required drive voltage is ensured. Hereinafter, a fuel injection valve driving apparatus according to an embodiment of the present invention will be described in detail.

  FIG. 1 shows a specific circuit configuration of a fuel injection valve driving apparatus according to an embodiment of the present invention. The ECU 70 and the control circuit 60 are substantially the same as those shown in FIG. 7. The ECU 70 calculates the amount of injected fuel according to the operating state of the internal combustion engine, and opens and closes each switching element via the control circuit 60 according to the calculation result. I have control.

  In FIG. 1, a step-down circuit 10 for generating a negative voltage by stepping down from a battery voltage source 1 (here, 14 V power supply) includes a step-down switching element 11 connected in series to the positive electrode of the battery voltage source 1. The step-down diode 12, the step-down coil 13 connected between them and connected to the negative electrode of the battery voltage source 1, and the energy of the negative voltage connected to the negative electrode of the battery voltage source 1 connected to the step-down diode 12 Is constituted by a step-down capacitor 14 for accumulating.

  That is, the step-down circuit 10 includes at least the diode 12 and the step-down switching element 11 connected in series between the switching element 22 for supplying the negative voltage side of the driving electromagnetic coil 50 and the positive electrode of the battery voltage source 1, Between the step-down switching element 11 and the step-down coil 13 connected to the negative side of the battery voltage source 1, between the diode 12 and the switching element 22 for supplying the negative voltage side of the driving electromagnetic coil 50, and between the battery voltage source 1 The step-down capacitor 14 is connected to the negative electrode side. The step-down switching element 11 is controlled by a switching signal from the control circuit 60, and the step-down circuit 10 generates a step-down voltage (negative voltage). For example, the stepped down voltage at this time is “−51 V”.

  The high voltage side of the driving electromagnetic coil 50 of the fuel injection valve is connected to the positive electrode of the battery voltage source 1 via the battery voltage side supply switching element 21 for connection to the battery voltage source 1. The battery voltage side supply switching element 21 and the high voltage side of the driving electromagnetic coil 50 are connected to the diode 12 and the step-down capacitor 4 of the step-down circuit 10 through a diode 24.

  Furthermore, the diode 24 is connected to the low voltage side of the driving coil 50 of the fuel injection valve via the negative voltage side supply switching element 22. This diode 24 is a diode for allowing a free wheel current to flow in the driving electromagnetic coil 50 of the fuel injection valve when the battery voltage side supply switching element 21 and the negative voltage side supply switching element 22 are turned off.

  The low voltage side of the driving electromagnetic coil 50 of the fuel injection valve is connected to the connection point of the diode 12 and the step-down capacitor 4 of the step-down circuit 10 so that it can be used as a negative voltage supply source for the battery voltage source 1. It is configured.

  Between the connection point of the negative voltage supply switching element 22 for supplying the negative voltage VL on the low voltage side of the drive electromagnetic coil 50 and the GND, a holding current drive switching element 23 for flowing a holding current is provided. The negative voltage is connected via a diode 25 for preventing backflow so as not to flow into GND.

  In FIG. 1, it goes without saying that each electrical or electronic component component is connected by an electrical path (for example, electrical wiring) indicated by a solid line.

  An operation when the drive electromagnetic coil 50 is energized in such a fuel injection valve drive device will be described. FIG. 2 shows an operation timing chart of the drive circuit for the fuel injection valve according to one embodiment of the present invention shown in FIG. 1, and the battery voltage source is set for the time indicated by “period A1” from the drive stop state of the fuel injection valve. 1 is connected to the high-voltage side of the drive electromagnetic coil 50 and supplied to the fuel injection valve. Thereafter, the application of the voltage is stopped for the time indicated by “period B1”, and further switched to the battery power source for the time indicated by “period C1”. Only the battery voltage is supplied to the fuel injection valve, and then the “stop period” that is the end of the fuel injection valve opening is shown.

  The operation of the drive circuit according to an embodiment of the present invention will be described with reference to the timing chart shown in FIG. 2. In FIG. 3, the operation state of the drive circuit in “period A1” is shown.

  In the “period A1”, the battery voltage side supply switching element 21 and the negative voltage side supply switching element 22 are turned on, and the voltage is supplied to the fuel injection solenoid valve driving coil 50 for the time when both AND conditions are satisfied. Here, the voltages at both ends of the driving electromagnetic coil 50 of the fuel injection valve are the battery voltage VB (14 V) and the negative voltage VL (−51 V), and the voltage VD = VB−VL = 65 V applied to the driving electromagnetic coil 50. . That is, the voltage applied to the drive electromagnetic coil 50 is “65 V” as in the conventional case.

  However, since the voltage of the negative voltage VL is VD−battery voltage VB = 65V−14V = 51V necessary for driving the fuel injection valve, the withstand voltage of the step-down capacitor 14 is boosted by the booster circuit constituting the conventional drive circuit. The battery voltage VB (14 V) is less than the “65 V” required for the capacitor.

  In this way, by turning on the battery voltage side supply switching element 21 and the negative voltage supply switching element 22, the applied voltage VD is supplied to the drive electromagnetic coil 50 of the fuel injection valve only during both AND conditions. Therefore, the current is supplied from the battery voltage side supply switching element 21 to the driving electromagnetic coil 50 and rises, and flows to the step-down capacitor 14 via the negative voltage side supply switching element 22. The diode 25 prevents a current from flowing from the GND to the driving electromagnetic coil 50 of the fuel injection valve.

  Next, FIG. 4 illustrates an operation state of the driving circuit in “period B1”. When the current flowing through the driving electromagnetic coil 50 of the fuel injection valve reaches the valve opening current (Ipeak) and the battery voltage side supply switching element 21 is turned off, the driving electromagnetic coil 50 of the fuel injection valve causes a current to flow due to the counter electromotive force. In an attempt to continue, the current flows from the diode 24 to the electromagnetic coil 50 for driving the fuel injection valve and the switching element 22 for supplying the negative voltage to fall.

  Next, FIG. 5 illustrates an operation state of the driving circuit in “period C1”. Each time the current flowing through the driving electromagnetic coil 50 of the fuel injection valve reaches the holding current 1 (Ihold1) and the holding current 2 (Ihold2), the battery voltage side supply switching element 21 and the holding current driving switching element 23 are turned on. Then, a current is supplied to the electromagnetic coil 50 for driving the fuel injection valve. At this time, the holding current is controlled by switching the battery voltage side supply switching element 21 and the holding current driving switching element 23 and repeating the rising state and the falling state in order to keep the holding current substantially constant. Yes.

  Finally, FIG. 6 shows the operating state of the drive circuit during the “stop period”. The holding current drive switching element 23 is turned on, and the battery voltage side supply switching element 21 and the negative voltage supply switching element 22 are turned off to stop the supply of the fuel injection valve to the drive electromagnetic coil 50.

  The current generated by the back electromotive force of the fuel injection solenoid valve driving coil 50 is regenerated to the step-down capacitor 14 via the holding current driving switching element 23 and the diodes 25 and 24 so that the current does not flow and stops. Become.

  Thus, according to one embodiment of the present invention, the withstand voltage of the step-down capacitor 14 can be lowered from that of the conventional booster circuit, specifically, the battery voltage VB can be lowered, and the negative voltage can be set. Thus, the number of diodes, specifically, the diode 45 shown in FIG. 7 can be reduced by one. As a result, an increase in the size of the drive circuit and an increase in the number of components of the drive circuit can be suppressed.

  As described above, according to the present invention, since the step-down circuit is used instead of the step-up circuit, the withstand voltage of the capacitor can be lowered at least by the voltage of the battery voltage source, and the drive circuit is physically large. There is an effect that can be suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Battery, 10 ... Step-down circuit, 11 ... Step-down switching element, 12 ... Step-down diode, 13 ... High voltage coil, 14 ... High voltage capacitor, 21 ... Battery voltage side supply switching element, 22 ... Negative voltage side supply Switching element, 23... Holding current driving switching element, 24. Diode, 25. Diode, 60. Control circuit, 70 ECU.

Claims (6)

A fuel injection amount corresponding to the operating state of the internal combustion engine is calculated by the control means, and a current corresponding to the fuel injection amount is selectively supplied to a driving electromagnetic coil of a fuel injection valve for injecting fuel from a battery power source to the internal combustion engine. In the fuel injection valve drive device for driving the fuel injection valve,
The high-voltage side of the driving electromagnetic coil of the fuel injection valve is connected to a battery power source, the low-voltage side of the driving electromagnetic coil of the fuel injection valve is connected to a step-down circuit that reduces the voltage of the battery power source, A battery voltage side voltage supply switching element is provided between the high voltage side and the battery power supply to pass a current from the battery power supply to the drive electromagnetic coil, and the drive is provided between the low voltage side of the drive electromagnetic coil and the step-down circuit. A fuel injection valve drive apparatus comprising: a negative voltage side supply switching element for supplying a current from an electromagnetic coil to the step-down circuit, and driving control of each of the switching elements by the control means. The fuel injection valve drive device according to claim 1,
The step-down circuit includes at least a step-down diode and a step-down switching element connected in series between the negative voltage side supply switching element and the positive electrode of the battery power source, and between the step-down diode and the step-down switching element. And a step-down coil connected to the negative side of the battery power source, a step-down capacitor connected between the step-down diode and the negative voltage side supply switching element and the negative side of the battery power source. A drive device for a fuel injection valve. In the fuel injection valve drive device according to claim 2,
The step-down circuit has a function of dropping the battery power source to a negative voltage state, and the step-down circuit steps down the voltage of the battery power source when the drive electromagnetic coil of the fuel injection valve is energized and the negative voltage of the step-down circuit. A fuel injection valve drive device characterized in that the withstand voltage of the capacitor is determined. In the fuel injection valve drive device according to claim 2,
There is a free wheel current in an electrical path connecting the step-down capacitor and the negative voltage side supply switching element of the step-down circuit to the drive electromagnetic coil and the battery voltage side voltage supply switching element. A fuel injection valve drive device, characterized in that a diode for flowing the fuel is provided. In the fuel injection valve drive device according to claim 2,
A holding current driving switching element for holding the fuel injection valve in an open state is connected to a low pressure side of the driving electromagnetic coil of the fuel injection valve, and the holding current driving switching element is for supplying the battery voltage side Applying the voltage of the battery power source and the negative voltage of the step-down circuit to the driving electromagnetic coil by the switching element and the negative voltage side supply switching element, and then applying the voltage of the battery power source to the driving electromagnetic coil A fuel injection valve drive device. The fuel injection valve drive device according to claim 5,
A drive device for a fuel injection valve, characterized in that a backflow prevention diode is interposed between the low pressure side of the drive electromagnetic coil of the fuel injection valve and the holding current drive switching element.

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