JPS62248864A - Exhaust gas recirculation controller for diesel engine - Google Patents

Abstract

PURPOSE:To correctly control the exhaust recirculation quantity in accordance with all the operation states by varying the cooling water temperature correction value for the recirculation quantity of exhaust gas in accordance with the operation state of a Diesel engine which is judged from the number of revolution and load. CONSTITUTION:An electronic control unit 64 receives each detection value of a revolution speed sensor 28, load sensor 60, and a water temperature sensor 62, and controls the EGR valve 16 of a Diesel engine through a negative pressure adjusting actuator 65. The electronic control unit 64 judges if the engine operation is in the A or B region where EGR is executed or the region where EGR is not executed on the basis of the revolution speed and load. The electronic control unit 64 further obtains the correction quantity corresponding to the engine water temperature according to the A or B region, and controls the opening degree of the EGR valve 16.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an exhaust gas recirculation control device for a diesel engine, and more particularly to an improvement in an exhaust gas recirculation control device for a diesel engine suitable for use in exhaust gas 1 recirculation of an electronically controlled diesel engine for an automobile.

[Prior Art 1] In diesel engines, particularly diesel engines for automobiles, exhaust gas recirculation (hereinafter referred to as EGR) is performed in order to reduce NOx in exhaust gas. Generally, in an engine that performs EGR, cylinder bores, pistons, rings, etc. may wear significantly, and this tendency is particularly noticeable when the cooling water temperature is low. Therefore, it is necessary to perform EGR after cooling water reaches a predetermined temperature, and various techniques have been put into practice or proposed to perform EGR at a predetermined humidity. That is, an example of an EGR device for a diesel engine employing such technology is an EGR device mounted on a diesel engine 10 as shown in FIG. 5, for example. This EGR device is equipped with an EGR valve 16 for introducing exhaust gas in the exhaust system 12 of the diesel engine 10 into the air supply system 14, and this EGR valve 16 is controlled by the temperature of the engine 10 (water temperature, intake temperature, etc.). A temperature sensing negative pressure switching valve (hereinafter referred to as BVSv) 18 operated by an electronically controlled negative pressure regulating valve (EVRV) 20 and a negative pressure R extension valve (V
TV) 21, negative pressure control valve (VCV122) is used for control.In this case, the EV
The RV 20 includes a lever opening sensor 2'6 that detects the opening of the adjusting lever of the idle up switch 24.
Based on the output signal Accp of the engine speed sensor 28 and the output signal NE of the engine speed sensor 28, the EGR injection timing altitude compensation device (AC
It is controlled by a controller 30 of TA). Furthermore, this A
CTA advances the injection timing at high altitudes to prevent the emission of white smoke. Also, in the figure, 32 is the AICTA diaphragm, 34 is the ACTA negative pressure switching valve (VSV), and 36
is ACTA negative pressure control valve (VCV), 38 is constant pressure valve (CP
V), 40 is a 'z-lar compressor, 41 is a vacuum pump, 42 is an idle up VSV, 43 is an overheat water temperature switch that detects overheating of the engine 10 from the water temperature, and 44 is an air conditioner idle up switch 24 that switches the air conditioner idle up switch 24 at the time of overheating. Air conditioner cut relay that cuts via idle up VSV42, 46 is altitude compensation switch (BAC8), 48 is supercharging pressure switch, 50 is water cooling turbo, 52 is gas filter, 5
3 is a three-way throttle valve. In the EGR device as described above, the BVSV is turned on and off based on a constant exhaustion mark regardless of the EGR range. As such a device, for example, Japanese Patent Application Laid-Open No. 55-72641
Then, EGR is blocked during the period when the engine is in the first cold state where the engine temperature is very low, and a small amount of EGR is performed until the engine temperature rises and warm-up is completed, and then a large amount of EGR is performed when warm-up is completed. An exhaust gas recirculation device for an engine has been proposed. Furthermore, in Japanese Patent Application Laid-open No. 55-40247, the applicant has already made it possible to perform EGR at a reflux rate corresponding to warm-up II operation of the engine, thereby reducing the NOx concentration in exhaust gas while ensuring the necessary engine operability. We are proposing an EGR device that effectively reduces the Also, EG RI using vSv instead of BVSV
A Q III device is also considered, and a technique has also been proposed in which the EGRfit is controlled according to the cooling water temperature level only during idle, and known control is performed during load operation. Problem 1 to be Solved by the Invention However, as mentioned above, when EGR is performed, the wear of the cylinder bore, piston, rings, etc. may become significant, and this is especially noticeable when the cooling water temperature is low. Therefore, it is desirable that the set temperature at which EGR is turned on is higher;
The higher the set temperature is, the more NOx in the exhaust gas during the engine 111 process increases. Therefore,
EGR that responds not only to cooling water but also to engine operating conditions
Control is required. However, conventionally, BVSV was put into a negative pressure circuit,
Because EGR was turned on and off by the water temperature switch,
It is necessary to control the EGR temperature at the same set temperature throughout the entire EGR range, and as mentioned above, EGR is controlled according to the engine operating condition.
There was a problem that IIJ6tl could not be used. [Object of the Invention] 41 The present invention has been made in view of the above-mentioned conventional problems, and is capable of controlling the amount of exhaust gas recirculation taking into consideration not only the engine temperature but also the engine operating condition. The present invention aims to provide an exhaust gas recirculation control device for a diesel engine.

[Means to solve the problem]

The present invention provides an exhaust gas recirculation control device for a diesel engine, which has means for detecting engine speed, engine load, and cooling water temperature, and corrects the amount of exhaust gas recirculation based on the detected cooling water temperature. The above object is achieved by comprising means for changing the cooling water temperature correction value of the exhaust gas recirculation amount according to the engine operating state determined by the detected engine speed and engine load. be.

[Effect]

In the present invention, in the exhaust gas recirculation control device for a diesel engine, a correction value for the amount of exhaust gas recirculation is changed in accordance with the engine operating state determined by the detected engine speed and engine load. Therefore, the amount of exhaust gas recirculation can be corrected by taking into account not only the cooling water temperature but also the engine operating state determined by the engine speed and engine load. It becomes possible to correct and control the amount of exhaust gas recirculation, which was previously absent, by adjusting the engine speed and load.

【Example】

Embodiments of the exhaust gas recirculation control device for a diesel engine according to the present invention will be described in detail below. This embodiment is an EGR device installed in a diesel engine 10 as shown in FIG. 5 above, for example, and as shown in FIG. Water temperature sensor 62 and each sensor 2
A digitally controlled electronic control unit (hereinafter referred to as EGRffi) that changes EGRffi based on the output signal from 8.60.62.
CU) 64, and a negative pressure adjustment actuator 65 for adjusting and supplying the negative pressure generated by the EGR valve 16 and the vacuum pump 41 based on the output signal of the ECU 64. In addition, 66 in the figure is exhaust gas from the exhaust pipe of the engine.
68 is a valve body of the EGR valve 16. The effects of the embodiment will be explained below. The EGR device shown in FIG. 1 controls the EGR valve 16 as follows based on the control flowchart shown in FIG.
Control the introduction into 4. In the flowchart, first, step 100
At step 110, the engine speed is read from the engine speed sensor 28, and at step 110, the engine load is read from the load sensor 60. In step 120 and subsequent steps, the engine operating state specified based on the engine speed and load belongs to which region of the EGR regions divided as shown in FIG. 3, that is, region A, region B, or other regions. to judge. If the determination result in step 120 is positive, that is, the read engine speed and engine load belong to the A region shown in FIG. Basic EQ
Calculate the Rbase command value. Then step 14
At step 0, the engine water temperature detected by the engine water temperature sensor 62 is read, and at step 150, the calculated EG Rbase command value is corrected based on the water temperature read. This correction is performed based on the relationship between the corrections to the engine water temperature as shown in FIG. 4, and in the case of region A, the correction is performed based on the relationship indicated by the broken line indicated by the symbol A in the figure. Next, in step 160, the corrected EGR command value is output to control the negative pressure adjustment actuator 65 to change EGRffl. On the other hand, if the determination result in the previous step 120 is negative, the process proceeds to step 170, where it is determined whether or not the read engine speed and load are in region B shown in FIG. If the determination result is positive, the process advances to step 180. In steps 180 and 190. E G Rbas as in previous steps 130 and 140
eCalculate the command value and read the water temperature. Then step 2
00, correct the calculated E G Rbase command value based on the relationship indicated by the solid line indicated by the symbol B in
Find the GR command value. Next, in step 210, the obtained EGR command value is output and EGRlm is controlled in the same manner as in the previous step 160. On the other hand, if the determination result in the previous step 170 is negative, that is, the read engine speed and load are A as shown in FIG.
If the engine does not belong to either the region or the B region, the process proceeds to step 220 and the EGR valve 16 is turned off. If EGRffl is controlled as described above, conventionally
The set temperature for turning on EGR was the same across the entire GR range, but by using the engine water temperature sensor 62 and digitally controlled ECU 64, the EGR range is divided into separate parts as shown in Figure 3. It becomes possible to provide a water temperature correction amount or a water temperature correction coefficient. In addition, conventionally, EGR could only be controlled on/off, but as shown in FIG.
~ θ2), thereby gradually increasing the EG
It becomes possible to change Rfi. With such fine-grained control, for example, as in this embodiment, relatively N
In the light load range (A range in the example), including idling, where the amount of Ox emissions is low and the usage time is long, the EGR ON temperature setting is relatively high; ), it is possible to make the EGR ON setting In relatively low, thereby improving the reliability of the engine body and reducing NOx in the exhaust gas. In the embodiment, in order to correct the EGR command value,
The relationship between EGR areas A and B is shown in Figure 3.
It was divided into two regions, and the EGR command value was corrected separately based on the relationship shown in FIG. 4 for each region. This allows the configuration to be simplified by using existing sensors, and since it is only divided into two areas, the ECU6
As mentioned above, it was possible to achieve both engine reliability and NOx reduction without consuming much memory in the engine. However, the relationship for dividing the EGR region for correcting the exhaust gas recirculation m according to the present invention is not limited to the two regions shown in FIG. The correction value of the exhaust gas recirculation m can be varied from a relationship different from that shown in FIG. Furthermore, in the embodiment described above, the present invention was applied to an exhaust gas recirculation control device having the configuration shown in FIG. It is clear that the present invention is not limited to this, and can be applied to exhaust gas recirculation control devices having other configurations.

【Effect of the invention】

As explained above, according to the present invention, exhaust gas recirculation, which conventionally could only be controlled on and off based on the set water temperature, can be controlled by changing the set temperature for turning on, for example, depending on the EGR region, or gradually controlling it depending on the water temperature. It becomes possible to change both parts sm. Therefore, the amount of exhaust gas recirculation can be accurately corrected in accordance with the engine operating state determined not only by the cooling water temperature but also by the engine speed and engine load. In addition, this allows the amount of exhaust gas recirculation to be changed between light load and high engine load even at the same water temperature, improving the reliability of the engine itself and reducing emissions in the exhaust gas, such as NOx. It has excellent effects such as being able to reduce the amount of water used.

[Brief explanation of drawings]

FIG. 1 is a block diagram including a partial view showing the configuration of an embodiment of the exhaust gas recirculation control device for a diesel engine according to the present invention, and FIG. 2 shows the control performed in the embodiment. A flowchart showing the procedure, FIG. 3 is a diagram showing examples of each region for determining the exhaust gas recirculation region used in the above embodiment, and FIG. 4 is a diagram showing the correction for engine water temperature in each of the above regions. A diagram illustrating an example of the relationship between quantities, Figure 5, is
1 is a piping diagram including a partial partial view showing the overall configuration of an exhaust gas recirculation control device installed in a conventional diesel engine. DESCRIPTION OF SYMBOLS 10... Diesel engine, 12... Exhaust system, 14... Air supply system, 16... EGR pulp, 28... Engine rotation speed sensor, 60... Load sensor, 62... Engine water temperature sensor, 64... electronic control unit (ECU), 65... negative pressure adjustment actuator, 66... introduction pipe, 68... valve body.

Claims (1)

[Claims] (1) In an exhaust gas recirculation control device for a diesel engine, which has means for detecting engine speed, engine load, and cooling water temperature, and is adapted to correct the amount of exhaust gas recirculation based on the detected cooling water temperature, Exhaust gas recirculation for a diesel engine, comprising means for changing the cooling water temperature correction value of the exhaust gas recirculation amount according to the engine operating state determined by the detected engine speed and engine load. Control device.