JPH07101019B2 - Exhaust gas recirculation control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exhaust gas recirculation (EGR) control device, and relates to improvement of EGR control accuracy.

[Conventional technology]

Exhaust gas recirculation is a method of extracting a part of exhaust gas from the exhaust system, recirculating it to the intake system by controlling an appropriate temperature, timing, or flow rate, and is effective in reducing NOx.

In such an apparatus, conventionally, for example, JP-A-59-21
As shown in Japanese Patent No. 5952, etc., an accelerator opening sensor detects an engine load equivalent, and the EGR control map is used to detect E according to the engine speed and the output from the sensor.
GR command value is set and controlled. Since this EGR control map is used to calculate the control amount using at least two signals as parameters, it is of course necessary to form at least a two-dimensional map, which requires a large memory capacity.

[Problems to be solved by the invention]

However, for example, the pump injection amount at a constant accelerator opening decreases according to a so-called governor pattern indicating the injection amount characteristic, as the engine speed becomes higher, the fuel is cut off at a predetermined speed or higher. Therefore, in the above device, the map for EGR control is as shown in FIG. 4, and there is a fuel cut region (II) where EGR control is unnecessary. Therefore, the number of EGR command value map points in the EGR control area (I) where the EGR control should be performed is restricted by the existence of the fuel cut area (II), and the EGR control accuracy will be improved. In that case, it was necessary to increase the number of memories in the computer in order to increase the number of map points. In FIG. 4, the boundary line A between the EGR control region (I) and the fuel cut region (II) is a line representing the relationship between the accelerator opening and the engine speed when the injection amount in the governor pattern is zero.

Therefore, the present invention has been made in view of the above points, and saves the memory number by eliminating the mapping in the unnecessary area of the EGR control area, and as a result, the EGR control area without increasing the overall memory number. The purpose is to provide an exhaust gas recirculation control device that can improve the EGR control accuracy by increasing the number of map points in the execution area.

[Means for solving problems]

In order to achieve the above object, the means of the present invention is an exhaust gas recirculation passage connecting an exhaust pipe and an intake pipe of an engine, and an exhaust gas arranged in the exhaust gas recirculation passage to control an opening area of the passage. A recirculation valve body, detection means for detecting a value corresponding to at least the engine speed and engine load, and an exhaust gas recirculation map for predetermining a desired exhaust gas recirculation control amount using the engine speed and engine load as parameters are stored. In the exhaust gas recirculation control device, the control signal corresponding to the signal from the detection device is created according to the map and is output to the exhaust gas recirculation valve body. Has an offset calculation means for offsetting the actual value of the above parameter by a predetermined offset value in the region where the exhaust gas recirculation control amount becomes zero. The control map is stored as a map for determining a desired exhaust gas recirculation control amount with respect to the values of the parameters excluding the offset value.

[Action]

According to the present invention, as in the conventional case, the desired exhaust gas recirculation amount is determined in the exhaust gas recirculation map using the engine speed and the engine load as parameters.
In the region where exhaust gas recirculation is not performed, the actual value of the parameter is offset by a predetermined offset value, and the exhaust gas recirculation map determines the exhaust gas recirculation amount using the engine speed and engine load excluding this offset value as parameters. Since it is mapped so as to reduce the number of memories by reducing the mapping in the area where exhaust gas recirculation is unnecessary, if the same number of memory for the exhaust gas recirculation map is secured as in the conventional case, It is possible to increase the number of grid points in the map and improve the control accuracy of exhaust gas recirculation.

〔Example〕

 The present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 2 shows an exhaust gas recirculation type (hereinafter referred to as EGR) to which this embodiment is applied.
(Referred to as a formula) shows a schematic configuration of a diesel engine and its surroundings.

Here, 21 is a diesel engine, 22 is a cylinder, 23 is an exhaust manifold connected to an exhaust port 25 of a cylinder head 24, and 26 is an intake manifold connected to an intake port 27 of the cylinder head 24.

Exhaust gas recirculation pipe that is an exhaust flow path from the exhaust manifold 23
28 is arranged in the intake manifold 26. A diaphragm type exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 29 is provided in the middle of the exhaust gas recirculation pipe 28, and its opening area is changed according to the change in the negative pressure of the air supplied from the pipe 30. The amount of exhaust gas recirculated from the exhaust manifold 23 to the intake manifold 26 is adjusted.

Reference numeral 31 denotes a fuel injection valve attached to the cylinder head 24, which supplies the fuel supplied from the fuel injection pump 32 through the high-pressure fuel injection pipe 32a to the sub chamber 33 of the diesel engine 21.
To inject. This sub chamber 33 corresponds to a pre-combustion chamber type, a swirl chamber type or an air chamber type. A water temperature sensor 34 is attached to the cylinder 22 and detects a cooling water temperature of the engine and outputs a signal corresponding to the water temperature. Reference numeral 35 denotes a rotation speed sensor that works in conjunction with a crankshaft (not shown) of the diesel engine 21 to detect the engine rotation speed and output a signal corresponding to the rotation speed.

Reference numeral 42 denotes an accelerator pedal, and by rotating an accelerator lever 32b of a fuel injection pump 32 which is interlocked with the accelerator pedal, a high-pressure injection pipe 32a for pressure-feeding an injection amount of fuel corresponding to the rotation amount thereof is rotated.
The fuel is injected to the fuel injection valve 31 via the. Reference numeral 42a represents an accelerator opening sensor which is interlocked with the accelerator pedal 42 and outputs the depression amount as an analog electric signal.

Reference numeral 61 is an electromagnetic negative pressure control valve, which introduces a negative pressure from a vacuum pump 62 through a pipe 63 and a negative pressure port 64, while a control signal
The negative pressure is adjusted by introducing the atmosphere from the air intake port 66 based on 65, and the controlled negative pressure is supplied from the negative pressure control port 67 to the EGR valve 29 via the pipe 30.

70 is an electronic control circuit, based on the signals output from the rotation speed sensor 35 and the accelerator opening sensor 42a, performs a calculation according to a program, and outputs a control signal 65 to the electromagnetic pressure control valve 61, etc. Execute the process.

Next, FIG. 3 shows a block diagram of an example of the electronic control circuit 70 and its related parts.

71 is a central processing unit (hereinafter simply referred to as CPU) that performs processing for inputting and calculating data output from each sensor according to a control program, and controlling various devices, and 72 is a control program and initial data. Read-only memory (hereinafter simply RO
M), 73 is a random access memory (hereinafter simply referred to as RAM) in which data input to the electronic control circuit 70 and data necessary for arithmetic control are temporarily read and written, and 74 is even if the key switch is turned off. Backup random access memory (hereinafter simply referred to as backup RAM) as a non-volatile memory backed up by a battery so as to retain data necessary for subsequent engine operation, 75 and 76 are buffers of output signals of each sensor, and 79 is Multiplexer that selectively outputs the output signal of each sensor to the CPU 71, 8
0 is an A / D converter that converts analog signals into digital signals,
Reference numeral 81 is a buffer, multiplexer 79 and A / D converter 80
Represents the input / output port for outputting the control signals of the multiplexer 79 and the A / D converter 80 from.

Reference numeral 84 represents a shaping circuit that shapes the waveform of the output signal of the rotation speed sensor 35, and each sensor signal is sent from the shaping circuit 84 directly to the CPU 71 via the input port 87.

Further, 90 represents a drive circuit for driving the electromagnetic negative pressure control valve 61 by a signal from the CPU 71 via the output port 93. 94 is a bus line that serves as a passage for signals and data,
Reference numeral 95 denotes a clock circuit that sends a clock signal as control timing at predetermined intervals to the CPU 71, ROM 72, RAM 73 and the like.

Next, the control program in the electronic control circuit 70, which is the main part of this embodiment, will be described with reference to the flowchart shown in FIG.

When this control is started, first, in step 1, the engine speed N _E is detected by a signal from the speed sensor 35, and then the accelerator opening α as a value according to the engine load of the present invention is set to the accelerator opening α. It is detected by the signal from the sensor 42a. Next, at step 2, the offset value Δα of the accelerator opening α is obtained from the one-dimensional offset map shown in FIG. 5 according to the engine speed N _E. Note that FIG. 5 is a map of the accelerator opening α corresponding to the boundary line A between the EGR control region (I) and the fuel cut region (II) in FIG. 4 described above with respect to the engine speed N _E. Is. Next, at step 3, the offset accelerator opening α'is calculated from the offset value Δα. Here, the offset accelerator opening α ′ is a value obtained by subtracting (offset) the offset value Δα from the accelerator opening α. Then step 4
At, the desired EGR amount is detected from the map shown in FIG. 6 based on the engine speed N _E and the offset accelerator opening α ′. Then, in step 5, the EGR amount is set and the EGR amount is set.
The duty ratio of the signal for controlling the electromagnetic negative pressure control valve 61 is calculated according to the amount, and EGR control is performed.

Therefore, according to the present embodiment, since the map for determining the desired EGR amount is used as the one obtained by subtracting the offset value Δα from the accelerator opening α, it is necessary to increase the map score by the offset value Δα. Can, EG
R control accuracy can be improved.

The present invention is not limited to the above-described embodiments, and various modifications can be made, for example, as shown below, without departing from the spirit of the present invention.

(1) The offset value referred to in the present invention may be the accelerator opening corresponding to the injection amount level in the no-load state, or may be less than that value. In such a case, there is a region where the EGR control is not performed even though there is a fuel injection amount.
It may be necessary to consider such as outputting a command to fully open the GR valve.

(2) Although the diesel engine has been described in the above embodiment, the present invention is also applicable to a gasoline engine and the like.

〔The invention's effect〕

As described above, according to the present invention, the number of memories for the exhaust gas recirculation map in the region where the exhaust gas recirculation is unnecessary can be reduced. Therefore, the number of map points can be increased correspondingly to improve the accuracy of the exhaust gas recirculation control. There is an effect that you can.

[Brief description of drawings]

FIG. 1 is a flow chart showing a control program in one embodiment of the present invention, FIG. 2 is a schematic configuration diagram of an EGR type diesel engine to which the embodiment in FIG. 1 is applied and its periphery, and FIG. 3 is FIG. FIG. 4 is a block diagram of an example of an electronic control circuit in FIG. 4 and its related parts, FIG. 4 is a diagram showing a conventional EGR control map, FIG. 5 is a diagram showing an offset map of the embodiment in FIG. 1, and FIG. It is a figure which shows the EGR control map of the Example in FIG. 21 …… Diesel engine, 23 …… Exhaust manifold, 26
...... Intake manifold, 28 ...... Exhaust gas recirculation pipe, 29 ...... Exhaust gas recirculation control valve, 32 ...... Fuel injection pump, 35 ...... Rotation sensor, 61 ...... Electromagnetic negative pressure control valve, 70 ...... Electronic control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshimi Matsumura 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor Hiroshi Nakamura, 1-town Toyota town, Toyota city, Aichi prefecture Toyota Automobile Co., Ltd. (72) Inventor Takanobu Noda 1 Toyota Town, Toyota City, Aichi Toyota Motor Co., Ltd. (56) References JP-A-60-224961 (JP, A) JP-A-58-85353 (JP, A) Special Kai 57-168032 (JP, A)

Claims (3)

[Claims] 1. An exhaust gas recirculation passage connecting an exhaust pipe and an intake pipe of an engine, an exhaust gas recirculation valve body arranged in the exhaust gas recirculation passage for controlling an opening area of the passage, and at least an engine rotation. A detection means for detecting a value according to the number and the engine load, and an exhaust gas recirculation map for determining a desired exhaust gas recirculation control amount by using the engine speed and the engine load as parameters are stored in advance, and the detection is performed according to the map. An exhaust gas recirculation control device comprising: an electric control device that creates a control signal corresponding to a signal from the device and outputs the control signal to the exhaust gas recirculation valve body. In the area where is, the offset calculation means for offsetting the actual value of the parameter by a predetermined offset value is provided, and the exhaust gas recirculation control map is set to the offset value. An exhaust gas recirculation control device, wherein the exhaust gas recirculation control device stores the exhaust gas recirculation control amount for determining a desired exhaust gas recirculation control amount with respect to the values of the above parameters. 2. The offset calculating means comprises a one-dimensional map for determining an offset amount of an engine load with respect to an engine speed.
The exhaust gas recirculation control device according to the paragraph. 3. The exhaust gas recirculation control according to claim 1 or 2, wherein the offset value corresponds to an accelerator opening degree according to the engine speed in a non-injection state. apparatus.