JPS6128735A - Control device for fuel injection - Google Patents

Abstract

PURPOSE:To prevent overrun of an engine, by providing a trouble detecting means which detects a trouble on the system of a spill valve by means of signals from a detecting means for a signal for the number of revolutions of an engine and an electromagnetic valve driving signal detecting means. CONSTITUTION:The fuel injection pump of a Diesel engine is controlled by an electromagnetic spill valve to control injection of fuel. A driving signal detecting circuit detects function of an electromagnetic valve. By means of signals from the driving signal detecting circuit and a detecting circuit for a signal for the number of revolutions, a trouble detecting circuit detects the presence of a trouble. Based on a signal from the trouble detecting circuit, a fuel cut valve is driven to shut off the fuel when a trouble occurs. This enables prevention of overrun of an engine even during failure in operation of the spill electromagnetic valve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to fail-safe control of electrical control of a fuel injection pump of a diesel engine.

[Prior art]

Conventionally, there has been a device that controls the fuel injection pump of a diesel engine using a spill solenoid valve. For example, JP-A-58-1
Publication No. 83826. In these devices, if the solenoid valve was disconnected or short-circuited, or if the control circuit failed, the solenoid valve would stop operating, and there was a slight risk that the engine would overrun.

[Purpose of the invention]

Therefore, the present invention prevents diesel engine overflow by cutting fuel when there is an abnormality in the spill solenoid valve system.
The purpose is to prevent runs. [Structure of the Invention] The present invention includes a drive signal detection circuit, a rotation speed signal detection circuit, an abnormality detection circuit, and a fuel cut valve as shown in FIG. 1, and as shown in FIG. 2. The system is characterized in that when the engine is rotating and no spill valve drive signal is detected, it is regarded as an abnormality in the spill valve system, and fuel is cut accordingly.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

First, a fuel injection system to which the present invention is applied will be explained.

Figure 3 shows a diesel engine in which the present invention is implemented;
1 shows a diesel engine body, to which a fuel injection pump 2, an operating state detector 3, and a rotation speed detector 5 are attached. The fuel injection pump 2 is a distribution type injection pump whose details are shown in FIG. This includes a reference position detector 6, a fuel cant valve 7, and a spill valve 8, which will be described later, as shown.

As shown in FIG. 4, this pump 2 is connected to a suction port 6 by a plunger 62 which is rotated and reciprocated by a face cam 63.
The fuel sucked from 9 is transferred to a pump chamber 65 as a pressurizing chamber.
It is of a type in which the air is pressurized at the cylinder, and is fed under pressure to the nozzle through a suction valve 64 from a distribution port 66 to each cylinder.

In the present invention, in addition to the above configuration, a solenoid valve 8 is disposed at one end of an overflow port (overflow passage) 67 that is constantly connected to the pressure of the pump chamber 65. When this solenoid valve is opened, the high pressure fuel in the pump chamber 65 overflows into the low pressure housing 70 via the passages 67a and 70a.

Next, the operating state detector 3 includes an accelerator position detector 4, an intake pressure detector, a cooling water temperature detector, a battery voltage detector, and the like.

The accelerator position detector 4 uses a known potentiometer or the like.

The rotational speed detector 5 utilizes a known electromagnetic pickup, and as shown in FIG. 5, is mounted opposite to a gear that stops and rotates with the rotation of the engine or injection pump.

This outputs a signal as shown in FIG. 6 (al), and becomes a pulse signal as shown in FIG. 6 (bl) by the waveform type circuit 11.

The reference position detector 6 detects the rotational reference position of the pump. For example, in the case of a distribution type injection pump for a four-cylinder engine, four protrusions are provided on the face cam or plunger shaft, and a Hall element and a magnetic The reference position is detected by installing a resistive element, a photodetector, etc.

The fuel cut valve (FCV) 7 is a solenoid valve that cuts off the fuel supply to the injection pump.It is installed in the position shown in Figure 4, and when the internal solenoid is energized, the normal fuel supply is stopped. When no current is flowing, an internal spring closes the valve and cuts fuel.

As mentioned above regarding the fuel injection pump, the spill valve (SPV) 8 is used to open this valve and cause high-pressure fuel to overflow into the low-pressure chamber, thereby ending fuel injection and adjusting the fuel injection amount. There are two possible types of valves: a type that opens by passing an electric current and a type that closes. In this embodiment, a type of valve that closes by passing an electric current is used.

Next, a control circuit (ECU) 20 that receives signals from each of the sensors and controls the spill valve will be described.

Reference numeral 9 denotes an A/D converter which converts signals from various operating state detectors into digital signals and inputs them to the microcomputer 12.

10 is a waveform shaping circuit which shapes the signal from the reference position detector 6 into a waveform and converts it into a pulse, and then passes the signal to the microcomputer 1.
2. Manpower.

11 is a waveform shaping circuit which shapes the big amplifier signal as shown in FIG. It calculates the valve timing and valve closing timing, determines the valve opening time and valve closing time based on the reference position signal, and outputs the 0N-OFF signal to the spill valve drive circuit 13 at that time. Consists of run timer, timer interrupt device, etc.

Reference numeral 13 denotes a spill valve drive circuit, for example, a circuit as shown in FIG. 7, which includes a power transistor 71 for driving the spill valve 8, and a surge power transistor 71.
It consists of a Zener diode 72 for preventing damage to the power transistor 71, a resistor 73 for constantly outputting an "L" level to the drive signal detection circuit 14 in the event of damage to the power transistor 71 due to disconnection of the harness A, etc.

14 is a drive signal detection circuit, as shown in FIG.
Consisting of a V converter 74, a comparison voltage generator 75, and a comparator 76, for example, when the frequency of Vl is 111z or more, v2 is "H"
Set the comparison voltage REFI so that the 1
Reference numeral 5 denotes a rotational speed signal detection circuit, which has the same configuration as the drive signal detection circuit as shown in Fig. 9. For example, when the frequency of ″ level is output.

16 is an abnormality detection circuit, which is shown on the left side of FIG.
Vs-“’H” only when 2=“L” and ■4-“’H”
”, which is a logic circuit that detects an abnormality. 17 is a fuel cut valve drive circuit, which is shown on the right side of Figure 10.
5 - This is a circuit that cants 0FFL fuel from FCV7 when it is "L".

Next, let's start with Figures 1I to 121m regarding normal operation.
This will be explained according to the flowcharts (A) to (D).

When the program starts, first step 9 in Figure 11
Initialize with 02. Next, in step 903, it is determined whether the engine has been instructed. For example, the determination can be made based on whether the starter is turned on. If starting is confirmed, the process proceeds to step 904 and the rotational speed is calculated. This means that every time the waveform-shaped signal of the rotation speed signal mentioned above is input to the microcomputer 12,
The signal interval T of the input rectangular wave is generated by generating the rotation speed interrupt shown in
N is the current and previous timer counter values TNi, TNi-
It is calculated by calculating from 1, taking its reciprocal, and multiplying by a constant. Next, in step 905, the accelerator position is detected. The accelerator position signal is taken into the microcomputer through the A/D converter 9.

Next, in step 906, other operating conditions are calculated. This allows the signal from other operating state detection B3 to be sent to A/
It is input through the D converter 9 and calculated from there.

Next, in step 907, the target injection amount Q is calculated from the information calculated in steps 904 to 906 using a memory map or a calculation formula. At 908, the target valve opening timing TO is calculated from the engine speed and the target injection amount. Next, in step 909, a target valve closing timing Tc is calculated. The target valve opening timing TO and the target valve closing timing Tc are calculated using the corresponding crank angle positions as the time from the reference signal.

The program then returns to step 904, and so on.

In this way, while the routine shown in FIG. 11 is being repeatedly calculated, the reference position signal is
is man-powered. Then, an interrupt occurs and the program jumps to the routine shown in FIG. 12(B). The timer counter value Ts at that time is read into the computer. Next, the value of To calculated in step 908 is
s and writes the result to the timer interrupt # register. Next, the value of TC calculated in step 909 is added to the Ts, and the result is written to the timer interrupt #2 register. The program then returns to the routine of FIG.

After that, when the timer interrupt # register value and the timer counter value match, timer interrupt #1 occurs and the program starts
2. Jump to the routine shown in Figure 2 (C). Then, the spill valve is opened to terminate fuel injection. Further, when the value of the timer interrupt #2 register and the timer counter value match, timer interrupt #2 is generated, and the spill valve is closed to prepare for the next fuel injection. The waveforms of each part at this time are shown in FIG.

As explained above, the spill valve (SPV) drive waveform is a pulse with the same frequency as the reference position signal under normal conditions, so the SP■ drive signal is It should be an AC signal.

Next, an abnormality occurs in the SPV system, and the engine is rotating (rotation speed signal detection circuit output 'l/a = "H") and s
When the pv drive signal is not an AC signal (output v2 of the drive signal detection circuit = “L”), the output v5 of the abnormality detection circuit 16
= "H" and closes the fuel cant valve to prevent engine overrun.

Although the method of executing fail-safe by turning off the FCV has been described above, fail-safe can also be executed even if the FCV, which is the fail-safe means in the first embodiment, is replaced with an intake shutter. Further, the present invention is not limited to the FDV or the intake shutter, but any other means may be used as long as it is a means for stopping the engine or a means for preventing overrun.

〔Effect of the invention〕

As described above, the present invention shuts off the fuel passage and stops the fuel supply when the spill solenoid valve fails, so it has the excellent effect of preventing engine overrun even when the spill solenoid valve fails.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a state diagram for determining normality and abnormality, Fig. 3 is a diesel engine system to which the embodiment of the present invention is applied, and Fig. 4 is a fuel fuel of the embodiment of the present invention. A sectional view of the main parts of the injection pump, Fig. 5 is a schematic diagram of the rotation speed detector and waveform shaping circuit, Fig. 6 is a waveform diagram of the part numbered in Fig. 5, Fig. 7
The figure is a spill valve drive circuit diagram, Figure 8 is a block diagram of the drive signal detection circuit, Figure 9 is a block diagram of the rotational speed signal detection circuit, and Figure 10 is a circuit diagram of the abnormality detection circuit and fuel power/nod valve drive circuit. , FIG. 11 is a schematic flowchart of the main routine of control, FIGS. 12A to 12D are schematic flowcharts of each interrupt routine, and FIG. 13 is a timing chart of control. 1...Diesel engine, 2...Fuel injection pump, 3
... Operating status detector, 4... Accelerator position detector,
5... Rotation speed detector, 7... Fuel cut valve, 8
... Spill valve, 14 ... Drive signal detection circuit, 1
5... Rotation speed signal detection circuit, 16... Abnormality detection circuit, 17... Fuel cant valve drive circuit.

Claims (1)

[Claims] A device for controlling fuel injection by controlling a fuel injection pump of a diesel engine with an electromagnetic spill valve, comprising: drive signal detection means for detecting whether the electromagnetic valve is operating; and drive signal detection means for detecting whether the diesel engine is rotating. a rotational speed signal detection means for detecting; an abnormality detection means for detecting the presence or absence of an abnormality in the spill valve system based on signals from the drive signal detection means and the rotational speed signal detection means; and a signal of the abnormality detection means. A fuel injection control device comprising: means for driving the fuel cut valve based on the above to cut off fuel in the event of an abnormality.