JPH0477143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas recirculation control method for a diesel engine used in a vehicle such as an automobile, and more specifically relates to an exhaust gas recirculation control method for a diesel engine in which the amount of fuel injection is electronically controlled. Relates to gas recirculation control method.

For diesel engines used in vehicles such as automobiles, depending on the operating state of the diesel engine detected by various sensors, for example, the accelerator pedal depression amount detected by an accelerator sensor and the engine rotation speed detected by an engine rotation speed sensor. An electronically controlled diesel engine equipped with an electronically controlled fuel supply device that determines the fuel injection amount by calculation or by reading data from a storage device, and controls the fuel injection amount of the fuel injection pump based on the fuel injection amount. It has been known.

In order to reduce NOx in the exhaust gas even in electronically controlled diesel engines such as those mentioned above, exhaust gas recirculation can be performed at a flow rate that corresponds to the operating status of the diesel engine, just as in general diesel engines. Conceivable.

In electronically controlled diesel engines such as those mentioned above, it is possible to prevent the fuel injection amount of the fuel injection pump from becoming uncontrollable due to abnormal operation or failure of the microcomputer, various sensors, and electric actuators of the electronically controlled fuel supply system. In order to do this, the operating status of the microcomputer, various sensors, and electric actuators is electrically monitored by diagnosis using various methods, and the operating status of the microcomputer, various sensors, and electric actuators is monitored electrically to detect abnormalities in the operation of the microcomputer, various sensors, or electric actuators. When a failure occurs, the fuel injection amount is forcibly reduced to zero to stop the diesel engine, or a pseudo signal is used to prevent the fuel injection amount from exceeding a predetermined value, and the diesel engine is operated only at low speeds. Built-in fail-safe features. In addition, in electronically controlled diesel engines equipped with an intake throttle device, if the electronically controlled fuel supply device malfunctions or breaks down, the fuel injection amount is controlled as described above, and the intake throttle is In this way, the amount of intake air is limited and the output of the diesel engine is controlled.

However, even if intake throttling is performed in the event of abnormal operation or failure of the electronically controlled fuel supply system, if exhaust gas is injected into the intake passage downstream of the intake throttling section for exhaust gas recirculation, of oxygen is supplied into the engine combustion chamber, and when the intake pressure is quite low, air flows through the exhaust passage along with the recirculated exhaust gas into the engine fuel chamber, increasing the amount of intake air and recirculating the exhaust gas. The fuel that was incompletely combusted when it was not being used will now be completely combusted, and there is a risk that the output of the diesel engine will not be adequately controlled. Furthermore, the relatively high temperature exhaust gas flowing into the combustion chamber of the engine increases the temperature of the combustion chamber, which also makes the fuel more likely to burn, and the output of the diesel engine may not be suppressed.

In addition, when the exhaust gas recirculation flow rate is determined according to the operating status of the diesel engine detected by various sensors of the electronically controlled fuel supply system, abnormal operation of the sensor can be detected depending on the operating status of the diesel engine. If exhaust gas recirculation is performed based on information from this sensor, the exhaust gas recirculation flow rate will not be controlled to an appropriate flow rate depending on the operating status of the diesel engine, and the diesel engine will Engine operability may be significantly impaired and a large amount of black or white smoke may be generated.

In view of the above problems, the present invention forcibly stops exhaust gas recirculation when the electronically controlled fuel supply system of an electronically controlled diesel engine is operating abnormally, and exhaust gas recirculation is performed at this time. The purpose of the present invention is to provide an exhaust gas recirculation control method that prevents harmful effects caused by this, especially runaway of a diesel engine.

According to the present invention, this purpose is to provide an electronically controlled system that determines the fuel injection amount according to the operating state of the diesel engine detected by various sensors, and controls the fuel injection amount of the fuel injection pump based on the fuel injection amount. In an exhaust gas recirculation control method for a diesel engine equipped with a fuel supply device, the operating state of the electronically controlled fuel supply device is electrically monitored, and when the electronically controlled fuel supply device is operating normally, This is achieved by an electronically controlled fuel supply system control method that performs exhaust gas recirculation depending on the operating state of the diesel engine, and stops exhaust gas recirculation when the electronically controlled fuel supply system is operating abnormally. Ru.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

The attached figure shows one embodiment of a diesel engine equipped with an exhaust gas recirculation control device implementing the exhaust gas recirculation control method according to the invention. In the figure, 1 indicates a diesel engine, which has a cylinder bore 2, a piston 3 is slidably received in the cylinder bore, and a combustion chamber 4 is defined above the piston 3. There is. The diesel engine 1 has a swirl chamber 6 communicating with a combustion chamber 4 through a nozzle 5, and liquid fuel for the diesel engine is injected into the swirl chamber from a fuel injection nozzle 7.

The fuel injection nozzle 7 is supplied with liquid fuel by an electromagnetically controlled fuel injection pump 45 at a flow rate measured according to the engine load. Electromagnetic control fuel injection pump 8
The pump is of a distribution type that measures the amount of fuel to be injected according to the position of a built-in spill ring (not shown).The spill ring is driven by a linear solenoid 24, and the current applied to the linear solenoid is The spill position, that is, the fuel injection amount is controlled accordingly. Power supply control to the linear solenoid 24 is performed by a control device 25, which will be described later.
This is done by

The diesel engine 1 takes air into the combustion chamber 4 through an intake throttle device 8 and an intake manifold 9 through an intake port (not shown), and exhausts exhaust gas from the combustion chamber 4 through an exhaust port 10 to an exhaust manifold 11. . Intake port and exhaust port 10
are opened and closed by poppet valves, and only the poppet valve 12 for exhaust is shown in the figure.

The intake throttle device 8 includes a main intake throttle valve 14 that opens and closes the main intake passage 13, and a sub-intake throttle valve 16 that opens and closes a sub-intake passage 15 provided to bypass the main intake passage 13. The main intake throttle valve 14 is drivingly connected to the accelerator pedal 17, and is located in the fully closed position as shown in the figure when the accelerator pedal 17 is released, and opens as the accelerator pedal 17 is depressed. I'm starting to do that. The auxiliary intake throttle valve 16 is drivingly connected to a double diaphragm device 18, and the diaphragm chamber 1
When atmospheric pressure is introduced into both 9 and 20, it is in the fully open position as shown in the figure, and when atmospheric pressure is introduced into the diaphragm chamber 19 and negative pressure is introduced into the diaphragm chamber 20, it is in the half open position. When negative pressure is introduced into both diaphragm chambers 19 and 20, the diaphragm chambers 19 and 20 are in a fully closed position.

Negative pressure and atmospheric pressure are selectively introduced into the diaphragm chambers 19 and 20 from negative pressure control valves 21 and 22, respectively. The negative pressure control valves 21 and 22 are
Both are electromagnetic negative pressure control valves, and when energized, the negative pressure in the negative pressure tank 23 is transferred to the diaphragm chamber 19 or 2.
0, and atmospheric pressure is introduced into the diaphragm chamber 19 or 20 when the current is not energized.
The negative pressure control valves 21 and 22 are energized and controlled by a control device 25, which will be described later.

The exhaust manifold 11 is provided with an exhaust gas intake port 31, and the intake manifold 9 is provided with an exhaust gas injection port 32. The exhaust gas intake port 31 is provided with a conduit 33, an exhaust gas recirculation control valve 3,
4. It is connected to the exhaust gas injection port 32 via a conduit 35.

The exhaust gas recirculation control valve 34 includes a valve element 37 that opens and closes a valve port 36, the valve element being connected to a diaphragm device 39 by a valve rod 38;
When negative pressure is not introduced into the diaphragm chamber 41 provided on one side of the diaphragm 40, the spring force of the compression coil spring 42 pushes down and closes the valve port 36, and in contrast, negative pressure is introduced into the diaphragm chamber 41. When it is pressed, it is lifted against the spring force of the compression coil spring 42, and the valve port 36 is opened according to the magnitude of the negative pressure.

Negative pressure is supplied to the diaphragm chamber 41 from a negative pressure regulating valve 43. Negative pressure regulating valve 43
is supplied with negative pressure from the negative pressure pump 23, adjusts the negative pressure according to a current signal given to the negative pressure regulating valve 43, and supplies this to the diaphragm chamber 41.

Next, the control device 25 will be explained with reference to FIG. The control device 25 is a microcomputer 5
Contains 0. The microcomputer 50 is
Input port device 51, random access memory (RAM) 52, and read only memory (ROM)
53, a central processing unit (CPU) 54, and an output port device 55. It receives information about the engine speed from the rotation speed sensor 26, information about opening and closing of these from the engine switch 27, and information about the water temperature. The sensor 28 provides information regarding the engine cooling water temperature, the accelerator sensor 29 provides information regarding the amount of depression of the accelerator pedal 17, and the intake pressure sensor 30 provides information regarding the intake air flow in the intake passage downstream of the intake throttle device 8. , information regarding whether or not the main intake throttle valve 14 is in the fully closed position is provided from the fully closed switch 46 to the input port device 51, and this information is stored in the RAM 52.
Based on the program and data taken into the CPU 54 and stored in the ROM 53, the output port device 55 outputs the linear solenoid 24 and the negative pressure control valve 2.
1, 22, and each drive circuit 56 of the negative pressure regulating valve 43
The control signal is output to the terminals 59 to 59.

The CPU 54 calculates the accelerator pedal depression amount detected by the accelerator sensor 29 and the rotation speed sensor 2.
The basic fuel injection amount is calculated or read from the data memory of the ROM 53 and determined according to the engine rotational speed detected by the engine speed sensor 6, and the basic fuel injection amount is calculated based on the engine cooling water temperature detected by the water temperature sensor 28 and the intake pressure sensor. Calculation correction is performed in accordance with the intake pressure detected by 30, and a fuel injection amount signal based on the calculation result is outputted from an output port 55 to a drive circuit 56.

The drive circuit 56 includes a servo amplifier circuit, and the fuel injection pump 4 is controlled by the spill position sensor 44.
5 is input, the fuel injection amount signal from the microcomputer 50, in other words, the control target spill position signal is compared with the spill position signal from the spill position sensor 44, and based on this comparison result, A control command signal is output to the linear solenoid 24 so that the actual spill ring position becomes the control target position. As a result, the spill ring of the fuel injection pump 45 is driven by the linear solenoid 24 and its position is feedback-controlled, and the fuel injection pump 45 pumps liquid fuel at a flow rate corresponding to the fuel injection amount to the fuel injection nozzle 7. .

When the engine switch 27 is closed and the engine cooling water temperature detected by the water temperature sensor 28 is below a predetermined value, for example 60°C, the CPU 54 outputs an off signal to both drive circuits 57 and 58, and is greater than a predetermined value, an ON signal is output only to the drive circuit 58, and when the engine switch 27 is opened and the engine is stopped, an ON signal is output to both drive circuits 57 and 58 until a predetermined time has elapsed from the time the engine switch 27 was closed. It is designed to output an on signal.

As described above, by outputting the control signals to the drive circuits 57 and 58, the auxiliary intake throttle valve 16 is brought to the fully open position when the engine is warmed up, and is brought to the half open position after the warm-up is completed, and the engine is stopped. Sometimes brought to the fully closed position.

The ROM 53 stores the optimal amount of exhaust gas recirculation according to the fuel injection amount and engine speed as a two-dimensional map with the fuel injection amount and engine speed as variables, and the CPU 54 stores the optimum exhaust gas recirculation amount according to the fuel injection amount and engine speed. Based on the engine speed detected by the sensor 26, the optimum exhaust gas recirculation flow rate corresponding to the two control variables is read out from the ROM 53, and the optimum exhaust gas recirculation flow rate determined according to this data value or by interpolation calculation from the data value is read out from the ROM 53. A pulse signal having a Duether ratio corresponding to the exhaust gas recirculation flow rate is outputted from the output port 55 to the drive circuit 59.

As clearly shown in FIG. 3, the drive circuit 59 includes a D/A exchanger 60, an amplifier 61, an oscillator 62, a comparator 63, and a transistor 64. A given pulse signal with a predetermined duty ratio is converted into a current signal according to the duty ratio, and the current signal is supplied to the negative pressure regulating valve 43.

The PCU 54 outputs a pulse signal of a predetermined frequency to the fail-safe circuit 65 from the output port 55 when it is operating normally, and does not output the pulse signal when it is operating abnormally. As shown in FIG. 3, the failsafe 65 includes a rectifier circuit 66, an inverter 67, and a transistor 68, and when a pulse signal is applied, the base voltage of the transistor 68 is set to a low level to turn it off. In contrast, when no pulse signal is applied, the base voltage of the transistor 68 is set to a high level to turn it on. transistor 6
The emitter terminal 8 is connected to the output circuit of the D/A converter 60, and the collector terminal is grounded.

Therefore, when a pulse signal is applied to the fail-safe circuit 65, that is, when the CPU 54 is operating normally, the output signal of the D/A converter 60 is applied to the amplifier 60, and the negative pressure is adjusted accordingly. The valve 43 operates and exhaust gas recirculation is performed, but when the fail-safe circuit 65 is not given a pulse signal, that is, when the CPU 54 is not operating normally, the output signal of the D/A converter 60 is transferred to the transistor 68. Since the input level of the amplifier 61 becomes zero, the driving current of the negative pressure regulating valve 43 becomes zero, and the exhaust gas recirculation control valve 34 is fully closed and the exhaust gas recirculation is stopped. will be stopped.

The fail-safe circuit 65 is designed to reduce the output current of the drive circuit 56 to zero when the CPU 54 is operating abnormally. When the output current of the drive circuit 56 becomes zero, the linear solenoid 24 returns to its initial position, and the fuel injection amount of the fuel injection pump 45 becomes substantially zero.

Furthermore, the fail-safe circuit 65 is configured to prevent the drive circuits 57 and 58 from operating abnormally when the CPU 54 is operating abnormally.
The output signal of the switch is forcibly switched to the on signal. As a result, when the CPU 54 operates abnormally, the auxiliary intake throttle valve 16 is brought to the fully closed position.

Further, the microcomputer 50 is designed to repeatedly execute fail-safe routines as shown in FIGS. 4 and 5 as interrupt routines. The fail-safe routine shown in FIG. 4 includes a step for determining abnormal operation of various sensors, a step for determining abnormal operation of a linear solenoid, and a step for determining abnormal operation of the CPU. When it is determined that there is no abnormality in the engine, normal control continues, and exhaust gas recirculation is performed at a flow rate that corresponds to the operating status of the diesel engine while the operation of the diesel engine is normally controlled. It is done. However, if any one of the sensor, linear solenoid, or CPU is operating abnormally, fail-safe control is performed to prevent the fuel injection amount of the fuel injection pump from becoming zero or exceeding a predetermined value, and the intake throttle is and exhaust gas recirculation is stopped.

Detection of abnormal operation of the CPU 54 in the fail-safe routine shown in FIG.
2 counter may be incremented and the process may be performed from this value.

The fail-safe routine shown in Figure 5 performs fail-safe against radio wave interference and abnormal operation of the fuel injection pump. When the engine speed is above a predetermined value even though it is below the specified value, fail-safe control is performed.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited thereto, and various embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a diesel engine equipped with an exhaust gas recirculation device that implements the exhaust gas recirculation control method according to the present invention, and FIG. 2 is a diagram of the diesel engine shown in FIG. 1. FIG. 3 is a block diagram showing the drive circuit and fail-safe circuit of the exhaust gas recirculation control device, and FIGS. 4 and 5 are flowcharts showing the fail-safe routine, respectively. . 1... Diesel engine, 2... Cylinder bore,
3... Piston, 4... Combustion chamber, 5... Nozzle, 6
... Vortex chamber, 7 ... Fuel injection nozzle, 8 ... Intake throttle device, 9 ... Intake manifold, 10 ... Exhaust port, 11 ... Exhaust manifold, 12 ...
Poppet valve, 13...Main intake passage, 14...Main intake throttle valve, 15...Sub-intake passage, 16...Sub-intake throttle valve, 17...Accelerator pedal, 18...Duffle diaphragm device, 19, 20... ... diaphragm chamber, 21, 22 ... negative pressure control valve, 23 ... negative pressure tank, 24 ... linear solenoid, 25 ... control device, 26 ... rotation speed sensor, 27 ... engine switch, 28 ... water temperature Switch, 29... Accelerator sensor, 30... Intake pressure sensor, 31... Exhaust gas intake port, 32... Exhaust gas injection port, 33... Conduit, 34... Exhaust gas recirculation control valve, 35... Conduit, 36... Valve port, 37...
Valve element, 38... Valve rod, 39... Diaphragm device, 40... Diaphragm, 41... Diaphragm chamber, 42... Compression coil spring, 43... Negative pressure regulating valve, 44... Spill position sensor, 45... …
Fuel injection pump, 46... Fully closed switch, 50...
...Microcomputer, 51...Input port,
52...Random access memory, 53...Read only memory, 54...Central processing unit, 5
5... Output port, 56-59... Drive circuit, 6
0...D/A converter, 61...Amplifier, 62...
Oscillator, 63... Comparator, 64... Transistor, 65... Fail-safe circuit, 66... Rectifier circuit, 67... Inverter, 68... Transistor.

Claims (1)

[Claims] 1 A diesel engine equipped with an electronically controlled fuel supply device that determines the fuel injection amount according to the operating state of the diesel engine detected by various sensors and controls the fuel injection amount of the fuel injection pump based on the fuel injection amount. In the method for controlling exhaust gas recirculation, the operating state of the electronically controlled fuel supply system is electrically monitored, and when the electronically controlled fuel supply system is operating normally, the operating state of the diesel engine is monitored. A method for controlling exhaust gas recirculation for a diesel engine, comprising performing exhaust gas recirculation and stopping the exhaust gas recirculation when the electronically controlled fuel supply device is operating abnormally.