JP2012184686A - Engine control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a driver failure by fuel injection when a driver drive voltage is decreased in an engine control unit that drives the fuel injection device of an internal combustion engine.SOLUTION: The engine control unit includes: a high-side driver which controls a current value by a boost voltage higher than a battery voltage; the high-side driver and a low-side driver downstream the high-side driver, which control a current value by a battery voltage; a control means which drives to open and close a fuel injection value and controls energization to a coil; and monitoring means which monitors the battery voltage or the driver drive voltage, in the fuel injection device of an internal combustion engine. The control means stops the energization to the coil in accordance with a value monitored by the monitoring means. Thereby, the engine control unit can protect the driver by stopping its driving when the driver drive voltage decreases, which may cause failure in the driver.

Description

  The present invention relates to an engine control unit that drives a fuel injection device of an internal combustion engine.

  Japanese Patent Application Laid-Open No. 2003-8415 discloses a high-side driver that switches driving of a boosted voltage and battery voltage, and a low-side driver that monitors current as a system for driving a fuel injection device. .

JP 2003-8415 A

  The gate voltage of the low side driver is generated by the battery voltage supplied to the driver IC, but this voltage varies. When the gate voltage of the low-side driver decreases due to a battery voltage drop that is not guaranteed, the low-side driver has a characteristic that the resistance value increases. In the configuration of Patent Document 1, when a large current flows with respect to the lowered gate voltage, heat generation of the low-side driver increases, which may cause destruction. Therefore, it is necessary to prevent this, and for this reason, it is necessary to stop the driving of the fuel injection device when a low battery voltage outside the guarantee is input.

  Therefore, an object of the present invention is to monitor the battery voltage or the driver drive voltage, stop the injection when the voltage is low, and prevent a failure of the low side driver.

  In order to solve the above problems, a fuel injection device for an internal combustion engine having a drive circuit that opens and closes a fuel injection valve and controls energization to a coil, and has a function of monitoring a battery voltage or a driver drive voltage. Control to stop energizing the coil according to the monitor value.

According to the present invention, it is possible to prevent the driver from being damaged even when the driver drive voltage is lowered, and to realize a highly reliable engine control unit.

1 is an outline of a fuel injection device according to the present invention. Control unit block diagram. Coil load drive waveform. The control unit block diagram used as the Example of this invention. Example 1 (flow chart) of the present invention. Example 2 (flow chart) of the present invention.

  Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings.

  First, the configuration of an internal combustion engine system equipped with the fuel injection control apparatus according to the present embodiment will be described with reference to FIG. The engine 1 is provided with a piston 2, an intake valve 3, and an exhaust valve 4. The intake air passes through the air flow meter (AFM) 20 and enters the throttle valve 19, and is supplied to the combustion chamber 21 of the engine 1 through the intake pipe 10 and the intake valve 3 from the collector 15 which is a branching portion. The fuel is supplied from the fuel tank 23 to the internal combustion engine by the low-pressure fuel pump 24, and further increased to a pressure required for fuel injection by the high-pressure fuel pump 25. The fuel boosted by the high-pressure fuel pump 25 is injected and supplied from the fuel injection valve 5 to the combustion chamber 21 of the engine 1 and ignited by the ignition coil 7 and the spark plug 6. The fuel pressure is measured by the fuel pressure sensor 26.

  The exhaust gas after combustion is discharged to the exhaust pipe 11 via the exhaust valve 4. The exhaust pipe 11 is provided with a three-way catalyst 12 for purifying exhaust gas. A fuel injection control device 27 is built in the ECU (engine control unit) 9, and the signal of the crank angle sensor 16 of the engine 1, the air amount signal of the AFM 20, the signal of the oxygen sensor 13 for detecting the oxygen concentration in the exhaust gas, Signals such as the accelerator opening of the accelerator opening sensor 22 and the fuel pressure sensor 26 are input. The ECU 9 calculates the required torque to the engine from the signal of the accelerator opening sensor 22 and determines the idle state. The ECU 9 is provided with a rotational speed detection means for calculating the engine rotational speed from the signal of the crank angle sensor 16.

  Further, the ECU 9 calculates an intake air amount necessary for the engine 1 and outputs an opening signal corresponding to the intake air amount to the throttle valve 19. Further, the fuel injection control device 27 of the ECU 9 calculates a fuel amount corresponding to the intake air amount, outputs a current for the fuel injection valve 5 to perform fuel injection, and outputs an ignition signal to the spark plug 6.

  The exhaust pipe 11 and the collector 15 are connected by an EGR passage 18. An EGR valve 14 is provided in the middle of the EGR passage 18. The opening degree of the EGR valve 14 is controlled by the ECU 9, and the exhaust gas in the exhaust pipe 11 is recirculated to the intake pipe 10 as necessary.

  FIG. 2 shows a circuit block diagram of the fuel injection device drive circuit. The fuel injection device is generally built in the ECU 9 shown in FIG. The voltage of the battery 41 is supplied to the ECU 9, and this voltage is supplied to the power supply IC 43, the driver IC 47, the fuel injection device driving booster circuit 51, the high side driver 52, and the like. Further, the power supply IC 43 supplies a voltage to the microcomputer 44, the driver IC 47, and the like.

  The driver IC 47 includes a communication unit 49 with the microcomputer 44, a booster circuit driving unit 50, and a driver driving unit 48. A switching signal is sent from the booster circuit drive unit 50 to the booster circuit 51, and the voltage boosted by the booster circuit is supplied to the high side driver 52. The voltage boosted by the booster circuit 51 is fed back to the booster circuit driver 50, and the driver IC 47 determines whether or not to send a switching signal again.

  The voltage boosted by the booster circuit 51 can also be fed back to the A / D converter 45 of the microcomputer 44, and the driver IC 47 is supplied from the communication unit 46 in the microcomputer 44 based on the A / D value. Can be signaled. The A / D converter included in the microcomputer 44 can input and monitor signals from a fuel pressure sensor, a temperature sensor, etc. in addition to the boosted voltage. In addition, the microcomputer 44 has an input / output port 42 that drives an external load and monitors an external signal. The high side driver 52 can obtain a power source for the booster circuit 51 and the battery 41 system, and includes a driver 52a driven by the boosted voltage and a driver 52b driven by the battery voltage. The drive signal (A, B) of the driver drive unit 48 has a role of flowing current to the coil load 54 having a coil.

  The low-side driver 53 has a role of causing a current from the coil load 54 having a coil to flow to the ground potential by a drive signal (C) from the driver drive unit 48. In addition, either or both of the high-side driver 52 and the low-side driver 53 have a current detection function using a shunt resistor and a terminal voltage detection function, and detect the current value flowing through the driver and the coil load 54. The driver is driven by feeding back the current value. Moreover, it is possible to detect an overcurrent to the driver, a terminal power supply fault, and a ground fault by these functions.

  Here, the booster circuit 51, the high side driver 52, and the low side driver 53 may be provided inside or outside the driver IC 47, and the driver IC 47 may be used as a driver or a pre-driver.

  FIG. 3 is a diagram showing the relationship between the drive waveform output from the driver drive unit 48 and the current flowing to the coil load 54. The microcomputer 44 outputs a Pi pulse that determines the valve opening time and a Ti pulse that determines the injection time. The times Pi and Ti are set according to the characteristics of the coil load, and are usually constant values.

  The driver IC 47 to which the Pi pulse and Ti pulse are input transmits A, B, and C signals to each driver according to this waveform, and drives the driver. Immediately after receiving the Pi pulse and Ti pulse signals, the signals A, B, and C are turned on to start driving (state 61). Here, since the boosted voltage is higher than the battery voltage, the signal B may or may not be driven. By continuing this state until the set peak current value Ipeak (valve opening current 1) is reached, the current is increased (state 62). Immediately after reaching Ipeak, signal A is turned off and signal B is duty-driven (state 63). ).

  Thereafter, the signal B is driven to hold the set Ihold1 (valve opening current 2) (state 64). At this time, duty driving using the signal A instead of the signal B may be performed. This state is maintained until the time reaches Pi, and immediately after the time Pi is reached, the duty ratio of the signal B is changed so as to maintain the set Ihold2 (holding current) (state 65). Here, the duty drive by the signal A instead of the signal B may be performed.

  This state is maintained until the time reaches Ti (state 66). Immediately after the time reaches Ti, the signal that was turned on is turned off and the driving is ended (state 67). The figure shows voltage waveforms of the boost voltage (Vboost) and the battery voltage (VB). When the signal A is turned on and the boosted voltage is used, the boosted voltage drops (state 62). Since the boosted voltage can be monitored by the booster circuit driving unit 50, when the signal A is turned off after the current reaches Ipeak (state 63), the boosted voltage rises until it returns to the set value, After reaching this value, the set value is retained.

  If driving at Ihold1 and Ihold2 is performed at the boosted voltage, the boosted voltage is used even in this state, and the voltage drops. Regarding the battery voltage, since the current capacity of the battery is large, the voltage drop is small, and the recovery time after the drop is negligibly short.

  Here, the signal C in FIGS. 2 and 3 is often supplied from the battery voltage, and therefore the voltage level of the signal C varies depending on the battery voltage. The low-side driver 53 often uses a field effect transistor, and has a characteristic that when the voltage level of the signal C decreases, the resistance value of the driver itself increases. When a low battery voltage that is out of warranty is input and a large current flows as in state 62 in FIG. 3, heat generation of the low-side driver 53 increases, and the driver may be destroyed. Therefore, a monitor circuit using FIG. 4 as an example is required.

  FIG. 4 shows a circuit to which a driver drive voltage monitor circuit is added according to an embodiment of the present invention. The first example is the addition of the low side driver 53 drive voltage monitor circuit 55. In this example, the battery voltage is monitored and formed using a circuit such as a comparator. The drive voltage monitor circuit 55 is installed inside or outside the driver IC 47.

  The second example is a method in which the driver drive voltage is monitored by the A / D converter 45 of the microcomputer 44, and includes a fuel injection device drive determination unit 56 that determines whether the monitored voltage is equal to or lower than a low voltage determination threshold value. . As a derivation of the second example, the driver drive voltage may be monitored by high / low determination using the input / output port 42 instead of the A / D converter 45.

  FIG. 5 is a flowchart showing an embodiment of the present invention according to the first example (drive voltage monitor circuit 55) of FIG. A driver drive voltage (battery voltage in the example of FIG. 4) is input to the drive voltage monitor circuit 55, and this voltage Vc is measured (61). When the voltage value Vc recognized by the drive voltage monitor circuit 55 is equal to or higher than the threshold value V0, the normal operation is performed (63). When the voltage value Vc is equal to or lower than the threshold value V0, the signal to the low-side driver drive signal C is stopped (64). ). At this time, the signals A and B may be stopped.

  FIG. 6 is a flowchart showing an embodiment of the present invention according to the second example of FIG. 4 (fuel injection device drive determination unit 56 in the microcomputer). A driver drive voltage (battery voltage in the example of FIG. 4) is input to the A / D converter 45 of the microcomputer 44, and this voltage Vc is measured (71). Based on the monitored voltage value Vc, the fuel injection device drive determination unit 56 in the microcomputer determines whether it is greater than or equal to a threshold value V0 (72). When the determination result is equal to or higher than the threshold value V0, the normal operation is performed (74). When the determination result is equal to or lower than the threshold value V0, a stop signal is output from the communication unit 46 inside the microcomputer to the driver IC 47 (75). The signal to the driver drive signal C is stopped (76). At this time, the signals A and B may be stopped in the same manner.

  Further, as shown in the description of FIG. 4, the driver drive voltage may be monitored by high / low determination using the input / output port 42 instead of the A / D converter 45.

1 Engine 2 Piston 3 Intake Valve 4 Exhaust Valve 5 Fuel Injection Valve 6 Spark Plug 7 Ignition Coil 8 Water Temperature Sensor 9 ECU (Engine Control Unit)
10 Intake pipe 11 Exhaust pipe 12 Three-way catalyst 13 Oxygen sensor 14 EGR valve 15 Collector 16 Crank angle sensor 18 EGR passage 19 Throttle valve 20 AFM
21 Combustion chamber 22 Accelerator opening sensor 23 Fuel tank 24 Low pressure fuel pump 25 High pressure fuel pump 26 Fuel pressure sensor 27 Fuel injection control device 41 Battery 42 Microcomputer input / output port 43 Power supply IC
44 Microcomputer 45 A / D converter 46 Communication section 47 in the microcomputer 47 Driver IC (or pre-driver)
48 Driver Driver 49 Communication Unit 50 Inside Driver IC Booster Circuit Driver 51 Booster Circuit 52 High Side Driver 53 Low Side Driver 54 Coil Load (Fuel Injection Device)
55 Drive Voltage Monitor Circuit 56 Fuel Injection Device Drive Determination Unit

Claims (5)

In a fuel injection device for an internal combustion engine,
A high-side driver that controls the current value of the boost voltage higher than the battery voltage
A high-side driver that controls the current value according to the battery voltage and a low-side driver downstream thereof;
Control means for driving the fuel injection valve to open and close, and for controlling energization to the coil;
Having monitor means for monitoring battery voltage or driver drive voltage;
The control means is an engine control unit that stops energization of the coil according to the value monitored by the monitoring means. In the engine control unit according to claim 1,
An engine control unit that monitors the battery voltage or driver drive voltage using a voltage monitoring circuit installed inside or outside the driver. In the engine control unit according to claim 1,
An engine control unit that uses an A / D converter to monitor battery voltage or driver drive voltage by the monitoring means. In the engine control unit according to claim 1,
An engine control unit for monitoring battery voltage or driver drive voltage by the monitoring means using high / low determination by an input / output port of a microcomputer. In a fuel injection device for an internal combustion engine having a drive circuit for opening and closing a fuel injection valve and controlling energization to a coil,
An engine control unit that has a function of monitoring battery voltage or driver drive voltage, and according to the monitored value, energization to the coil is stopped and damage to the driver can be prevented.

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