JPS60222551A - Egr controlling device for diesel engine - Google Patents

Abstract

PURPOSE:To increase the controlling accuracy of an EGR control by controlling the opening of an exhaust throttle valve in accordance with deviation between an actual back pressure and a target back pressure determined in accordance with load and engine speed at the time of an EGR control area. CONSTITUTION:A control circuit 19 judges the operating condition of an engine 1 by means of various detected outputs from a water temp. sensor 13, a load sensor 14, an engine speed sensor 15, etc. And, when the condition is judged an EGR control area in which an EGR valve 5 is opened, an exhaust throttle valve 12 is controlled to a defined opening through a negative pressure control valve 16 and an exhaust throttle valve device 7, in accordance with deviation between an actual back pressure in an exhaust system passage 3 which is detected by a pressure sensor 200, and a target back pressure which is determined in accordance with previously stored engine load and engine speed, to make the actual back pressure agree with the target back pressure. Thereby, dispersion in controlled opening due to the tolerance, etc. of the exhaust throttle valve can be reduced, improving the controlling accuracy of the EGR control.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to an exhaust gas recirculation (EGJ controlled The present invention relates to an apparatus, and specifically relates to opening degree control of an exhaust throttle valve.

[Background of the invention]

'In a diesel engine, the differential pressure between intake and exhaust is generally small, so conventional devices of this type increase the back pressure by adjusting the effective area of the exhaust throttle valve installed in the exhaust system passage. , to ensure the amount of EGR required by the engine.

Generally, the opening degree of the exhaust throttle valve is controlled by driving the exhaust throttle valve so that the throttle valve opening degree is set based on the engine load and engine speed. Due to the variation in the control opening of the exhaust throttle valve due to the tolerance of
Problems such as reduced engine durability were occurring.

[Purpose of the invention]

An object of the present invention is to reduce variations in the control opening degree of an exhaust throttle valve, and to improve the control accuracy of EGI (control).

[Summary of the invention]

The present invention provides an EGRG passage that communicates an exhaust system passage and an intake system passage of a diesel engine, an EGR and a valve provided in the EGRG passage that adjusts the amount of EGR, and a downstream side of an EGRG outlet in the exhaust system passage. It takes in the detection outputs of an exhaust throttle valve provided to adjust the exhaust system passage area and various sensors indicating the operating state of the engine, and outputs a control signal for driving the EGR valve and the exhaust throttle valve based on the detection outputs. In the EGRG control device, which has at least a control circuit for By controlling the opening degree of the exhaust throttle valve so that the actual back pressure becomes the target back pressure according to the deviation from the target back pressure determined by the The purpose is to reduce variations in the control opening degree and ultimately improve the control accuracy of the EGRG control.

[Embodiments of the invention]

Embodiments of the present invention will be described based on the drawings. FIG. 1 shows the configuration of an embodiment of an EGRG control device according to the present invention, in which an EGR valve 5 is connected between an intake system passage 2 and an exhaust system passage 3 of a diesel engine 1. TeEG
A communication passage 4 is formed so as to communicate with the passage 2.3.

The BGR valve 5 includes a valve body 9 that increases or decreases the passage area of the BGRG passage 4, a tire diaphragm 23 to which the rear end of a rod 21 integrally formed with the valve body 9 is fixed, and the diaphragm 2.
3 is connected via a passage 330 to a compression spring 22 that urges it downward, and a negative pressure control valve 201 that controls the negative pressure generated by the vacuum pump 17 to a more appropriate negative pressure required by the engine. A diaphragm chamber 8 is introduced into the diaphragm chamber 8 through the passage 330, and is introduced from the exhaust system passage 3 through the BGRG passage 4 in response to the controlled negative pressure formed by the negative pressure control valve 201. It is configured to control the recirculation amount (EGR amount) of exhaust gas that is recirculated to the intake system passage 2.

Further, an exhaust throttle valve device 7 is provided downstream of the RGRG outlet 6 of the exhaust system passage 3. The exhaust throttle valve device 7 is
A diaphragm 42 that defines a diaphragm chamber 40, a compression spring 44 that urges the diaphragm 42 upward in the figure, and a rod 11 whose one end is fixed to the diaphragm 42.
The exhaust throttle valve 12 is fixed to one end of the rod 30 and the other end is swingably attached to the rod 11. Negative pressure generated by the vacuum pump 17 flows into the diaphragm chamber 40 through a passage 45. The negative pressure control valve 161 is introduced through the passage 46, and the exhaust throttle valve 12 is controlled to a predetermined opening degree.

Further, a back pressure sensor 200 is provided upstream of the installation position of the exhaust throttle valve 12 in the exhaust system passage 3, and the back pressure sensor 200 detects the back pressure, converts it into an electrical signal, and sends it to the control circuit. Furthermore, 19 is a control circuit, and the control circuit 19 includes a water temperature sensor 13 that detects the engine cooling water temperature, a load sensor 14 that detects the engine load condition, a rotation speed sensor 15 that detects the engine rotation speed, and an exhaust Each detection output of the back pressure sensor 200 that detects the back pressure on the upstream side of the exhaust throttle valve 12 in the system passage 3 is taken in, and the EG
A control signal for controlling the flow rate of BGRG gas introduced into the intake system passage 2 via the RG passage 4 is sent to the negative pressure control valve 16.20.
Output each to 1.

Next, a specific configuration of the control circuit 19 is shown in FIG.

In the same figure, 50A, 50B, and 50C are water temperature sensor 1+13, which detects engine cooling water temperature, and engine 1, respectively.
It is a buffer amplifier that amplifies the detection outputs of the load sensor 14, which detects the load state of , 60 is a multiplexer (MX) for selectively taking in each output of these buffer amplifiers 50A, 50B, and 50C.

Further, 62 is an A/D converter for converting the analog signal selected by the multiplexer 60 into a digital signal, 64 and 66 are input/output ports, and 70 is a random access memory (RAM and ¥2 is a read-only memory (hereinafter referred to as ROM) for storing fixed data and programs, etc., and 74 is a ROM.
Various calculation processes are performed based on the programs stored in the 72, and the negative pressure control valve 16°2 is
This is a CPU that outputs control signals to each of the CPUs 01 and 01.

Furthermore, 28 is a rotation speed sensor 15 that detects the engine rotation speed.
56 is a clock pulse oscillator that outputs a clock pulse for synchronizing each part.

Next, FIG. 3 shows the contents of the program executed by the control circuit 19. In the figure, when the program is started, the detection output TW of the water temperature sensor 13 is taken in at step 300, and the engine cooling water temperature T is taken in at the next step 302.
It is determined whether W is TW≧Ko, and if it is determined that the engine cooling water temperature TW is equal to or higher than the set value Ko (for example, 50° C.), the process moves to step 304. In step 304, the engine rotation speed R is detected by the rotation speed sensor 15.
H is taken in, and furthermore, in step 306, the detection output of the load sensor 14 is taken in. Then, in step 308, the BG is transferred from the vacuum pump 17 via the negative pressure control valve 201 based on the control negative pressure map of the BGR valve 5 stored in advance in the ROM 72 as shown in FIG.
A predetermined negative pressure is supplied to the diaphragm chamber 8 of the R valve 5, and the B
The EGR′i· sent from the exhaust system passage 3 to the intake system passage 2 via the GR passage 4 is controlled to an appropriate value. Here, the controlled negative pressure map of the EGR valve 5 shown in FIG. 4 shows the controlled negative pressure value of the BGR valve 5 determined by the engine load and the engine rotational speed FLE. In this example,
For example, in the above map, the EGR valve 5 is -15Q mm
It starts to open at Hg and becomes fully open at -300mmHg.

Furthermore, in step 310, the ROM 72 as shown in FIG.
The target back pressure P is calculated based on the back pressure map stored in advance in
An interpolation calculation of M is performed. Then, in the next step 312, the detection output P of the pressure sensor 200 is captured,
In step 314, it is determined whether PM≧P, and if it is determined that PM≧P, step 316
The exhaust throttle valve 12 is adjusted so that the back pressure P approaches the target back pressure PM.
A control signal for throttling is output from the control circuit 19 to the negative pressure control valve 16 , and a higher negative pressure is applied to the diaphragm chamber 40 in the exhaust throttle valve device 7 from the vacuum pump 17 to the passage 45 . Negative pressure control valve 16 is supplied via passage 46.

On the other hand, if it is determined in step 314 that PM (P) is reached, then in step 318 the exhaust throttle valve 12 is adjusted to the target back pressure PM.
A control signal is outputted from the control circuit 19 to the negative pressure control valve 16 in order to open it so as to approach the diaphragm chamber 40, and the negative pressure supplied to the diaphragm chamber 40 by the control valve 16 decreases.

Furthermore, if it is determined in step 302 that the engine cooling water temperature is TW (KQ), that is, the engine operating state is E.
GR, step 3 if it is determined that the control area is blown.
20, and in step 320, the control circuit 19 connects the vacuum pump 17 to the negative pressure control valve 16 and exhaust throttle valve device f.
A control signal for cutting off the supply of negative pressure to the diaphragm chamber 40 at step 7 is output, and as a result, the exhaust throttle valve 12 becomes fully open, and the execution of this program ends.

As explained above, in this embodiment, the gGR passage that communicates the exhaust system passage and the intake system passage of the diesel engine,
The EGR is provided in the passage and adjusts the BGR, [E
The detection outputs of the GR valve, the exhaust throttle valve that adjusts the area of the exhaust system passage provided on the downstream side of the EGR extraction part in the exhaust system passage, and various sensors indicating the engine operating state are taken in, and based on the detection output. In an EGR control device having at least a control circuit that outputs a control signal for driving the EGR valve and the exhaust throttle valve, when the engine operating state is in the BGR control region, the actual back pressure in the exhaust system passage and Controlling the opening degree of the exhaust throttle valve so that the actual back pressure becomes the target back pressure according to a deviation between a pre-stored target back pressure determined according to the engine load and the engine rotation speed. As a result, it is possible to reduce variations in the control opening degree due to tolerances of the exhaust throttle valve, etc., and ultimately improve the control accuracy of EGR control.

〔Effect of the invention〕

According to the present invention, the control precision of EGB and control can be improved.

[Brief explanation of the drawing]

FIG. 1 is an instruction manual showing the configuration of an embodiment of the EGR control device according to the present invention, FIG. 2 is a block diagram showing the specific configuration of the control circuit 19, and FIG. 3 is a program executed by the control circuit 19. Flowchart showing the contents of RO
A diagram showing a control negative pressure map of the EGR valve 5 stored in M72, and FIG. 5 is a diagram showing a back pressure map similarly stored in ROM72. 1... Engine, 2... Intake system passage, 3... Exhaust system passage, 4... BGR passage, 5... EGFL valve, 1
3...Water temperature sensor, 14...Load sensor, 15...
- Rotation speed sensor, 16... Negative pressure control valve, 19... Control circuit, 200... Pressure sensor, 201... Negative pressure control valve. Agent Tatsuyuki Unuma (and 1 other person)

Claims (1)

[Claims] A BGR passage that communicates an exhaust system passage and an intake system passage of a diesel engine, an EGR valve provided in the EGR passage to adjust the amount of EGR, and an EGR between the exhaust system passage and the exhaust system passage.
The detection outputs of various sensors indicating the operating status of the engine and the exhaust throttle valve that is provided downstream from the extraction part and adjusts the exhaust system passage area are taken in, and the EG is adjusted based on the detection outputs.
It has at least a control circuit that outputs a control signal for driving the R valve and the exhaust throttle valve, and the various sensors include pressure sensors that detect back pressure upstream of the installation position of the exhaust throttle valve in the exhaust system passage. and the control circuit is configured to control the engine according to the actual back pressure in the exhaust system passage detected by the pressure sensor, the engine load and the engine rotation speed, which are stored in advance, when the engine operating state is in the BGR control region. The diesel engine is characterized by outputting a control signal for controlling the opening degree of the exhaust throttle valve so that the actual back pressure becomes the target back pressure according to the deviation from the target back pressure determined by the EGR control device