JPS60192870A - Exhaust-gas recirculation control in diesel engine - Google Patents

Abstract

PURPOSE:To suppress the generation of smoke in exhaust gas during acceleration operation and reduce the concentration of NOX in exhaust gas by reducing the exhaust- gas recirculation flow-rate according to the flow rate corresponding to the acceleration speed in acceleration operation, in comparison with the case in ordinary operation. CONSTITUTION:When the temperature of cooling water which is detected by a water- temperature sensor 28 is over a prescribed value, in other words, after the completion of warming, the fundamental exhaust-gas recirculation flow rate Qb corresponding to the fuel injection amount and the number of revolution is read from a ROM53. Further, the increasing speed of the engine load is calculated from the increase rate with the passage of time of the fuel injection amount, and the amount reduction coefficient A in acceleration is determined. Then, the fundamental exhaust-gas recirculation flow rate Qb is multiplied by the inverse number of the amount reduction coefficient A in acceleration, and the optimum exhaust-gas recirculation flow rate Qr is determined. The pulse signal having the duty ratio corresponding to Qr is output into a driving circuit 57. In other words, as the acceleration speed is larger, exhaust recirculation is carried-out with the flow rate largely reduced from the fundamental exhaust-gas recirculation amount at that time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for controlling exhaust gas recirculation of a diesel engine used in a vehicle such as an automobile, and more particularly relates to a method for controlling exhaust gas recirculation of a diesel engine used in a vehicle such as an automobile. The present invention relates to an exhaust gas recirculation control method for reducing and correcting the exhaust gas recirculation flow rate during operation.

BACKGROUND OF THE INVENTION Exhaust gas recirculation of a deep-pill engine, which is performed to reduce the Noxtll degree in the exhaust gas, converts a portion of the excess intake air drawn into the engine combustion chamber into the exhaust gas.
1. It is only necessary to carry out the change depending on the engine load, that is, the amount of fuel supplied to the combustion chamber or the amount of depression of the accelerator pedal and the engine speed. Exhaust gas recirculation control methods for controlling the exhaust gas recirculation flow rate in accordance with (Unexamined Japanese Patent Publication No. 57-2625
3), Japanese Patent Application No. 1983-40807 (Japanese Patent Application No. 1983-
15704) and Japanese Patent Application No. 58-2594.

In general, in a diesel engine, during acceleration operation when the amount of fuel supplied into the engine combustion chamber increases, especially when accelerating from a low load to a high load, the amount of smoke increases compared to during steady operation when the amount of fuel does not change much. Therefore, if exhaust gas recirculation is performed at the same flow rate during acceleration operation as during steady operation, smoke is more likely to occur in some areas.

In view of the above-mentioned problems, it is proposed in Japanese Patent Application No. 56-40810 (Japanese Unexamined Patent Publication No. 57-15) to reduce or eliminate the exhaust gas recirculation flow rate during acceleration operation, that is, to stop exhaust gas recirculation.
7048), Japanese Patent Application No. 134511 (Sho 56-134511)
No. 8-35255).

However, the previously proposed methods reduce the exhaust gas recirculation flow rate at a constant flow rate or completely stop exhaust gas recirculation during acceleration operation exceeding a predetermined acceleration speed. Therefore, depending on the acceleration speed, the amount of reduction in the exhaust gas recirculation flow rate may be insufficient or, on the contrary, may be excessive, and the reduction in the degree of Noxal or smoke in the exhaust gas may not be achieved sufficiently.

Purpose of the Invention The present invention avoids the generation of smoke in the exhaust gas during acceleration operation by reducing the exhaust gas recirculation flow rate at a flow rate corresponding to the acceleration speed during acceleration operation compared to during steady operation. The present invention aims to provide an exhaust gas recirculation control method for a diesel engine that reduces NOxl* in exhaust gas as much as possible.

According to the present invention, an exhaust gas recirculation flow rate is determined according to the load of a diesel engine, the rate of increase in the load, and the rotational speed, and the flow rate is determined according to the rate of increase in the load. This is achieved by a diesel engine exhaust gas recirculation control method that controls the exhaust gas recirculation flow (6) so as to reduce the exhaust gas recirculation flow rate when the increase rate is large.

Effects of the Invention According to the exhaust gas recirculation control method according to the present invention, the exhaust gas recirculation is performed in accordance with the increasing rate of engine load, that is, the acceleration rate, so that when the acceleration rate is large, the exhaust gas recirculation flow rate is reduced. By controlling the flow rate, the amount of reduction in the exhaust gas recirculation flow rate during acceleration operation can be set appropriately according to the acceleration speed, and the NOx in the exhaust gas can be reduced by 1 degree while avoiding smoke generation during acceleration operation. It will be possible to reduce it as much as possible.

DESCRIPTION OF EMBODIMENTS The present invention will now be described in detail with reference to embodiments with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a diesel engine equipped with an exhaust gas recirculation device implementing the exhaust gas recirculation control method according to the present invention. In the figure, 1 indicates a diesel engine body, 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. are doing.

The diesel engine main body 1 has a swirl chamber 6 communicating with the combustion chamber 4 through a nozzle 5, and liquid fuel for the diesel engine is injected and supplied to the swirl chamber from a fuel injection nozzle 7. .

The fuel injection nozzle 7 is connected to an electromagnetically controlled fuel injection pump 45 through a fuel conduit 46, and liquid fuel is pumped through the fuel injection pump. The fuel injection pump 45 is of a distribution type that injects fuel 101 according to the position of a spill ring (not shown) built into the pump, and the spill ring is driven by the linear solenoid 24. The -C spill position is controlled according to the applied current, and the fuel injection amount is controlled.

The diesel engine main body 1 takes air into a combustion chamber 4 from an intake boat (not shown) via an intake manifold 8, and exhausts exhaust gas from the combustion chamber 4 via an exhaust boat 10 to an exhaust manifold 11. There is. The intake boat and the exhaust boat 10 are each opened and closed by poppet valves, and only the exhaust poppet valve 12 is shown in the figure.

The exhaust manifold 11 includes an exhaust gas intake boat 31.
Each intake manifold 8 is provided with an exhaust gas injection boat 32, and the exhaust gas intake boat 31 is connected to a conduit 33.
, an exhaust gas recirculation control valve 34, and a vI pipe 35 to communicate with the exhaust gas injection port 32.

The exhaust gas recirculation control valve 34 includes a valve element 37 that opens and closes a valve boat 36 and is in drive communication with a diaphragm device 39 by a valve rod 38 and a diaphragm 40
When a negative pressure greater than a predetermined value is not introduced into the diaphragm chamber 41 provided on one side of the When a larger negative pressure is introduced, 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 device 41 from a negative pressure regulating valve 43. The negative pressure regulating valve 43 is supplied with negative pressure from a negative pressure supply device 23 such as a negative pressure pump, 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. It is supposed to be done. The relationship between the current value given to the negative pressure regulating valve 43 and the output negative pressure of the negative pressure regulating valve 43 is shown in FIG. 2, and the output negative pressure of the negative pressure regulating valve 43 is almost proportional to the increase in the current value. and increase.

Next, the m control device 25 will be explained with reference to FIG.

The control device 25 includes a microcomputer 50, and the microcomputer 50 has an input port 51.
, a random access memory (RAM) 52, a read-only memory (ROM) 53, and a central processing unit (C
PU) 54 and an output port device 55, information regarding the engine speed is sent from the rotation speed sensor 4J26, information about the engine cooling water temperature is sent from the water temperature sensor 28, and information about the engine cooling water temperature is sent from the accelerator sensor 29 to the accelerator pedal. Information regarding the amount of depression of each of the 17 is given to the input port device 51, this information is taken into the RAM 52 and the CPU 54, and based on the program and data stored in the ROM 53, the output port device 55 adjusts the negative pressure with the linear solenoid 24. Control signals are output to drive circuits 56 and 57 of each of the valves 43.

The microcomputer 50 uses the CPU 54 to determine the basic fuel injection amount by screening or reading from the data memory of the ROM 53 according to the accelerator pedal depression amount detected by the accelerator sensor 29 and the engine rotation speed detected by the rotation speed sensor 26. Then, the water temperature sensor 28
The calculation is corrected according to the engine cooling water humidity detected by
A port device 5 outputs a fuel injection amount signal that is revealed based on this calculation result.
5 to the drive circuit 56.

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

The microcomputer 500ROM 53 stores in advance the basic exhaust gas recirculation flow rate according to the fuel injection amount and the engine speed as a two-dimensional map with the fuel injection amount and the engine speed as variables, and the CPU 54 stores the basic exhaust gas recirculation flow rate according to the fuel injection amount and the engine speed. When the temperature of the cooling water detected by the CPU is equal to or higher than a predetermined value, that is, after warm-up is completed, the fuel injection amount determined by the CPU and the engine rotation speed detected by the rotation speed sensor 26 are different from each other. The data values of the basic exhaust gas recirculation flow rate corresponding to the two control variables are successively output from the ROM 53, and the data values are changed according to the rate of increase in the engine load found from the rate of increase over time of the fuel injection amount. 'r-When the increase rate is reached, the calculation is corrected at a large reduction rate, and a pulse signal with a duty ratio corresponding to the data value based on the calculation result is output from the output port device 55 to the drive circuit 57. On the other hand, during the warm-up process when the temperature of the cooling water detected by the water temperature sensor 28 is not higher than a predetermined value, an off signal is output from the output port device 55 to the drive circuit 57.

As shown in FIG. 4, the drive circuit 57 is a D/A
converter 60, amplifier 61, oscillator 62, comparator 6
3 and a transistor 64, which converts the pulse signal of the duty ratio given by the microcomputer 50 into a direct current with a current value proportional to the duty ratio, and converts the direct current into a direct current with a current value proportional to the duty ratio. It is designed to supply an electromagnetic coil that is not shown.

Next, with reference to the flowchart shown in FIG. 5, the implementation procedure of the exhaust gas recirculation control method according to the present invention will be explained.

In the first step 1, information is input from various sensors. Step 10 Next, proceed to step 2.

In step 2, it is determined whether the temperature of the cooling water detected by the water temperature sensor 28 is equal to or higher than a predetermined value. When the cooling water temperature is above the predetermined value, the process proceeds to step 3, whereas when the coolant temperature is not above the predetermined value, the process proceeds to step 7.

In step 3, the R
The data value of the basic exhaust gas recirculation flow rate is read from the OM 53, and the basic exhaust gas recirculation flow ff1Qb can be determined. Step 30 Next, proceed to step 4.

In step 4, the rate of increase in engine load is calculated from the rate of increase over time of the fuel injection tJJfi), and the acceleration reduction coefficient A is determined based on the calculation result. The acceleration weight loss coefficient A is predetermined according to the rate of increase in engine load, an example of which is shown in Fig. 6. The reduction (a) coefficient A is 1 when the rate of increase in the engine load is less than or equal to the predetermined value v1, and the increase is between the rate of increase in the engine load between the predetermined value 1 and the predetermined value V2, which is greater than the predetermined value V2. It increases in proportion to the increase in speed, reaches the maximum value A max at a predetermined value v2, and is maintained at the maximum value A max when the rate of increase in the engine load is equal to or higher than the predetermined value 1aVe.Step 4
Next, proceed to step 5.

In step 5, an acceleration weight loss calculation is performed in which the basic exhaust gas recirculation flow IQb determined in step 3 is multiplied by the reciprocal 1/A of the acceleration weight loss coefficient determined in step 4. The optimum exhaust gas recirculation flow ff1Qr is determined. After step 5, proceed to step 6.

In step 6, a valve switch a@ having a duty ratio corresponding to the optimum exhaust gas recirculation flow rate Qr determined in step 5 is output.

In step 7, a pulse signal with a duty ratio of O,
That is, an off signal is output.

The drive circuit 57 generates a larger current as the duty ratio of the input pulse signal becomes larger, and supplies this to the negative pressure regulating valve 43.
The negative pressure regulating valve 43 generates a larger output negative pressure as the energized current value increases, and the exhaust gas recirculation control valve 34 increases the valve opening m when the gal from the negative pressure regulating valve 43 is large. to increase the exhaust gas recirculation flow rate. Therefore, by controlling the control signal to the negative pressure regulating valve 43 by the W control device 25 as described above, no exhaust gas recirculation is performed during the warm-up process when the cooling water temperature is below a predetermined value, and the cooling After warm-up is completed when the water temperature is above the predetermined value, during steady operation or deceleration operation when the rate of increase in engine load is below the predetermined value V+, basic exhaust gas regeneration is performed according to the gJII3g load and engine speed at that time. Exhaust gas recirculation is performed in the circulation flow ■, and when the engine load is increasing at a predetermined rate of 1fi V H or more during acceleration operation, the rate of increase in the engine load at that time, in other words, when the acceleration rate is large according to the acceleration speed. Exhaust gas recirculation is performed at a flow rate that is significantly reduced from the basic exhaust gas recirculation flow rate at that time.

By controlling the exhaust gas recirculation flow rate as described above, exhaust gas recirculation is performed at the maximum flow rate that does not generate smoke during acceleration operation, and the exhaust gas is recirculated while avoiding the generation of smoke. Noxill degree is reduced as much as possible.

In the above-mentioned embodiment, the basic exhaust gas recirculation flow rate, which is predetermined according to the fuel injection amount and engine speed, is modified as a two-dimensional map according to the acceleration reduction coefficient. Although the optimum exhaust gas recirculation flow rate was determined by the above method, the present invention is not limited to this, but the present invention is based on a two-dimensional exhaust gas recirculation flow rate map for deceleration and steady operation. Using a two-dimensional map of multiple exhaust gas recirculation flow rates during acceleration operation depending on the degree and acceleration speed of slow, medium, and sudden acceleration, One exhaust gas recirculation flow rate two-dimensional map is selected from the two-dimensional circulation flow rate map, and the exhaust gas is recirculated at the exhaust gas recirculation flow rate according to the fuel injection amount and engine speed stored in this two-dimensional map. may be configured so that

FIG. 7 shows a flowchart of an embodiment of this two-dimensional map selection method.

Incidentally, in the embodiment described above, the microcomputer 5
The acceleration speed of the diesel engine was detected based on the rate of increase in the fuel injection amount calculated by Alternatively, the change rate may be determined by the rate of change in the amount of depression of the accelerator pedal.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these, and it is understood that various embodiments can be made 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 control device that implements the exhaust gas recirculation control method according to the present invention, and Fig. 2 shows the current value of the negative pressure regulating valve and the Figure 3 shows the control circuit diagram of the diesel engine shown in Figure 1 without showing the relationship with the output negative pressure. Figure 4 shows the drive circuit of the exhaust gas recirculation control system. Figure 5 is a block diagram showing one implementation of the exhaust gas recirculation control method according to the present invention, Figure 6 is a block diagram showing the relationship between the weight loss coefficient during acceleration and the rate of increase in engine load. FIG. 7 is a flowchart showing another embodiment of the exhaust gas recirculation control method according to the present invention. 1... Diesel engine body, 2... Cylinder bore. 3... Piston, 4... Combustion chamber, 5... Nozzle, 6
... Vortex chamber, 7... Fuel injection nozzle, 8... Intake manifold. 10...Exhaust port, 11...Exhaust manifold,
12... Poppet valve, 23... Negative pressure supply device, 24
...Linear solenoid, 25...Control @W1.26
...Rotation speed sensor, 28...Water temperature sensor, 29...
・Accelerator 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, 4
4... Spill position sensor, 45... Fuel injection pump, 46... Conduit, 50... Microcomputer,
51... Input boat device, 52... Random access memory. 53... Read only memory, 54... Central processing unit, 55... Output boat device, 56.57...
Drive circuit, 60... D/A converter, 61... Amplifier, 62... Oscillator, 63... Comparator, 64... Transistor patent applicant Toyota Motor Corporation Representative Patent attorney Akashi Shoki No. 1 Figure 4

Claims (1)

[Claims] Determine the exhaust gas recirculation flow rate according to the load of the diesel engine, the speed of increase in the load, and the rotational speed, and reduce the exhaust gas recirculation flow rate when the speed of increase is large according to the speed of increase in the load. An exhaust gas recirculation control method for a diesel engine, which controls the exhaust gas recirculation flow rate so as to increase the exhaust gas recirculation flow rate.