JPS63215863A - Exhaust gas reflux device for engine - Google Patents

Abstract

PURPOSE:To prevent the generation of error decision regardless of the variation of the atmospheric pressure by converting the trouble deciding condition responding to the variation of the atmospheric pressure, in the system in which the trouble of the exhaust gas reflux control system is decided by comparing the detected operational amount of an EGR valve and the trouble deciding level. CONSTITUTION:In an EGR valve 5 arranged at an EGR passage 4, its opening is controlled by using the suction negative pressure produced in a suction passage 3 as a valve operating source. And in a trouble deciding device 10 to input the output signals of an operational amount detecting device 8 to detect the actual operational amount of the EGR valve 5 and of a setting device 9 to set the trouble deciding level in a specific operational condition, the detected operational amount and the trouble deciding level are compared, when the operational condition is decided to be in a trouble deciding zone by a zone deciding device 11, to decide the trouble of the EGR control system. In this case, the trouble deciding condition by the trouble deciding device 10 is made to convert by a converting device 13 responding to the variation of the atmospheric pressure detected by an atmospheric pressure deciding device 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation device for an engine that is equipped with a failure determination function.

(Prior art) Conventionally, to control the exhaust gas distal flow rate of an engine, intake negative pressure is used as the operating source of a recirculation control valve that adjusts the exhaust gas recirculation amount, and the magnitude of the intake negative pressure is adjusted. It is common practice to control the amount of exhaust gas recirculation by using the following methods (see, for example, Japanese Patent Publication No. 35372/1983).

Also, check whether the above-mentioned reflux control valve is operating normally.
One idea is to compare the actually measured operation Φ of the recirculation control valve with a set value under normal conditions in a specific operating range of the engine, and to determine a failure based on the difference between the two.

(Problem to be solved by the invention) In the above-mentioned exhaust gas recirculation, the operation amount of the recirculation control valve changes depending on atmospheric pressure fluctuations, so if a failure is determined when atmospheric pressure changes such as at high altitudes, it may be normal. There is a risk that it may be incorrectly determined that the device is in a faulty state even if it is in a faulty state. That is,
The recirculation control valve adjusts its operating amount according to the differential pressure between the intake negative pressure and the atmospheric pressure, and when the atmospheric pressure decreases, the differential pressure with the intake negative pressure becomes smaller, causing the actual recirculation control valve to become smaller. The operating amount decreases, and when this operating amount becomes less than the failure judgment level, it is determined that the recirculation control system is in a failure state even if there is no failure, and accordingly, exhaust gas recirculation is stopped and the ignition timing is adjusted. , there is a problem of unnecessary change control such as air-fuel ratio setting.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide an exhaust gas recirculation device for an engine that prevents the occurrence of erroneous determinations when atmospheric pressure fluctuates in failure determination of an exhaust gas recirculation control system. be.

- (Means for solving the problem) The exhaust gas recirculation device of the present invention is provided with an exhaust gas recirculation control valve whose operating source is the intake negative pressure of the engine, and the actual operating amount of the recirculation control valve is used to determine a failure. A failure determination means is provided to determine the failure of the exhaust gas recirculation control system by comparing the level with the
Furthermore, it is provided with an atmospheric pressure determining means for detecting a change in atmospheric pressure, and a changing means for receiving the output of the cough atmospheric pressure determining means and changing the failure determination condition of the failure determining means in accordance with the change in atmospheric pressure. This is a characteristic feature.

FIG. 1 is an overall configuration diagram for clearly showing the tf4 configuration of the present invention.

An exhaust gas recirculation passage 4 is connected between the exhaust passage 2 and the intake passage 3 of the engine 1 . The exhaust gas recirculation passage 4 recirculates part of the exhaust gas flowing through the exhaust passage 2 to the intake passage 3 .

The amount of exhaust gas recirculated by the exhaust gas recirculation passage 4 is adjusted by adjusting the operation vJfJ1 of the recirculation control valve 5 interposed in the exhaust gas recirculation passage 4.

The recirculation control valve 5 uses the intake negative pressure as an operating source, and the intake passage 3
The intake negative pressure generated in the above is introduced by the negative pressure passage 6, and the intake fA pressure to the recirculation control valve 5 changes depending on the operating condition, and the exhaust gas is reduced according to the magnitude of the negative pressure.
It is something that flows. Alternatively, the intake negative pressure with respect to the recirculation control valve 5 is adjusted by an adjusting means according to the operating state, and the amount of exhaust gas recirculation is controlled.

On the other hand, an operation for detecting the actual operating amount of the reflux control valve 5
A J amount detection means 8 and a setting means 9 for setting a failure judgment level in a specific operating state are provided, and the failure judgment means 10 receives signals from both, and determines that the operating state is in the failure judgment zone as determined by the zone judgment means 11. When it becomes, it is a detection work! A failure of the exhaust gas recirculation control system is determined by comparing lJm with a failure determination level.

Further, an atmospheric pressure determining means 12 for detecting changes in atmospheric pressure is provided, and a changing means 13 receiving the output of the atmospheric pressure determining means 12 adjusts the failure determination condition of the failure determining means 10 according to the change in atmospheric pressure. It is subject to change.

The failure determination conditions of the failure determination means 10 may be changed by changing the failure determination zone in which failure determination is made in response to changes in atmospheric pressure, or by modifying the failure determination level in response to changes in atmospheric pressure. This is done by, for example, stopping execution of failure determination in response to changes in atmospheric pressure.

(Function) In the above-mentioned exhaust gas recirculation system, when a region is likely to cause erroneous failure judgments in response to changes in atmospheric pressure such as when atmospheric pressure drops, this condition is judged by the atmospheric pressure judgment means and the atmospheric pressure is The failure determination conditions in failure determination means 6 are changed by the change means in response to changes in the failure determination means, so that erroneous determination does not occur even if the atmospheric pressure fluctuates.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic configuration diagram of an exhaust gas recirculation device for an engine according to a specific example.

The engine 1 includes an intake passage 3 and an exhaust passage 2, and an exhaust gas recirculation passage 4 that recirculates a part of exhaust gas from the exhaust passage 2 to the intake passage 3 has an upstream end located at the upstream side of the exhaust passage 2. Their downstream ends are connected to the downstream portion of the throttle valve 15, respectively. A recirculation control valve 5 for adjusting the amount of exhaust gas recirculation is interposed in the middle of the exhaust gas recirculation passage 4, and the recirculation control valve 5 uses the intake negative pressure as its operating source.

In the recirculation control valve 5, a valve element 5a for opening and closing the exhaust gas recirculation passage 4 is supported by a diaphragm 5b, and is divided into an atmospheric chamber 5C and a negative pressure chamber 5d by the diaphragm 5b. A spring 5e that urges the valve 5a in the valve closing direction is compressed, and a negative pressure passage 6 that introduces the negative intake pressure generated in the intake passage 3 is connected. The upstream end of the negative pressure passage 6 is connected to the throttle valve 15 of the intake passage 3.
It opens immediately upstream of the throttle valve 15, and when the throttle valve 15 is opened to a predetermined opening degree, intake negative pressure downstream of the throttle valve 15 is introduced into the negative pressure chamber 5d. And this negative pressure passage 6
The larger the intake negative pressure introduced by the recirculation control valve 5
The opening degree is large, and the amount of exhaust gas recirculation increases.

Further, a modulator valve 16 is installed in the negative pressure passage 6 to adjust the intake negative pressure introduced into the recirculation control valve 5 according to the exhaust pressure of the exhaust gas recirculation passage 4. This modulator pulp 16 is provided with a leak port 16a communicating downstream of the orifice 6a of the negative pressure passage 6.
A pressure passage 17 is connected to the exhaust pressure chamber 16c at the back of the diaphragm 16b, and a pressure passage 17 is connected to the exhaust gas recirculation passage 4 upstream from the reflux control valve 5 and downstream from the orifice 4a. Exhaust pressure is introduced, and the leak hole 16d where the leak port 16a opens is opened to the atmosphere and the spring 16e is compressed. The larger the exhaust pressure in the exhaust gas remote flow passage 4 is, the more the leak port 16a is closed, the less the intake negative pressure in the negative pressure passage 6 leaks into the atmosphere, and the amount of exhaust gas recirculated increases.

On the other hand, the recirculation control valve 5 is provided with a position sensor 18 that measures the opening degree of the valve body 5a, that is, the lift suspension, and a detection signal of the position sensor 18 is output to the control unit 19.

The control unit 19 is for determining failure of the control system including the reflux control valve 5, and the position sensor 18
In addition to the detection signal A from the atmospheric pressure sensor 20 that detects atmospheric pressure, the negative pressure sensor 21 that detects intake negative pressure.
A rotational speed signal Ne from a rotation sensor 22 is input to detect the engine rotational speed.

When the control unit 19 reaches a failure determination zone that is basically determined by the intake negative pressure (load) and the engine rotation speed, the control unit 19 determines the actual lift of the recirculation control valve 5 based on the output of the position sensor 18 and a preset failure. It compares with the judgment level and determines a failure when the measured lift amount is less than the judgment level, and the atmospheric pressure sensor 2
Based on the zero signal, when the atmospheric pressure is low, that is, at high altitudes, the failure determination zone is controlled to be in a region shifted to the high load side.

The operation of the control unit 19 will be explained based on the flowchart shown in FIG. After the start, step 8
1 to S3, engine rotation speed Nθ, position sensor 18
The measured lift amount P1 from the negative pressure sensor 21 and the intake negative pressure B from the negative pressure sensor 21 are respectively read. Further, in step S4, the atmospheric pressure A from the atmospheric pressure sensor 20 is read, and in step S5, it is determined whether or not this atmospheric pressure is at a high altitude below a predetermined value.

If this determination is NO and the system is at a low altitude, in step S6, the upper and lower limit values Ss, 82 of the intake negative pressure B in the failure determination zone are set to the set value Bns*Bn2 for low altitudes, whereas when the above determination is YES and the system is at a high altitude, In step S7, the upper and lower limits of negative pressure in the failure determination zone B1. Set B2 to high altitude setting value 3h.
1 # Set to Bhz. This high altitude setting value B h
l 1 B hz is the setting value ant for lowlands, 8nz
The intake negative pressure is set to a value on the atmospheric pressure side, that is, on the high load side.

In step S8, it is determined from the output of the negative pressure sensor 21 whether the intake negative pressure B is within the range of the upper and lower limit values Bs and Bz, and in step S9, the engine speed Ne is determined to be within the range of the failure determination zone. It is determined whether or not the rotational speed is within the range of Ns to N2. If the determinations in both steps 88 and 89 are YES, this means that it is within the failure determination zone, and in this case, failure determination is performed in step 810. This failure determination is to determine whether or not the measured lift lift P is less than a preset failure determination level pt, and this failure determination level Pt corresponds to the minimum lift lift in the operating state in the failure determination zone. A state in which the actually measured lift ff1P reaches a value below this failure determination level pt, which does not normally exist, is determined to be a failure occurrence.

When a failure occurs and the determination in step 810 is YES, a failure indication is output in step 811, and various backup controls such as ignition timing correction are performed in step 812.

Further, if the determination in step S10 is NO and no failure has occurred, and if the determination in step S8 or $9 is NO and it is not in the failure determination zone, step S1
The sensor input is performed by returning to the .

In this embodiment, even if the failure judgment level is the same, the failure judgment zone is corrected and the relative The same correction was made as the failure judgment level was revised to a small value in order to prevent false judgments from occurring at high altitudes.

FIG. 4 shows a flowchart of another embodiment, which is the same as the flowchart in FIG. 3 except for the part surrounded by a chain line in which the failure judgment conditions are changed according to the atmospheric pressure, and the same steps are given the same reference numerals. are doing.

In this example, the failure determination level itself is modified according to the atmospheric pressure.

That is, in step S4, the atmospheric pressure sensor 2
Atmospheric pressure A from 0 is read, and in step S5 it is determined whether or not it is a highland based on this atmospheric pressure A. If this determination is NO and lowland, then in step 86' the failure determination level pt is set to a set value for lowland p tn+ = setting, but the above judgment is YE
When S is a high altitude, the failure determination level pt is set to a high altitude setting value pth in step 87'. This setting value ptn for highlands is set to a smaller value than the setting value ptn for lowlands. After setting the failure determination level pt as described above, the failure determination zone is determined in steps 88 and 89, and the failure determination is performed in step 810 based on the failure determination level Pt set according to the atmospheric pressure. It is.

In this example as well, the failure determination level is corrected according to the atmospheric pressure to prevent the occurrence of erroneous determinations due to a reduction in lift amount when atmospheric pressure drops, that is, at high altitudes.

Note that on each side of Figures 3 and 4, the failure judgment zone and failure judgment level are modified and set in two stages according to the magnitude of atmospheric pressure; Depending on the situation, the settings may be made in more steps or continuously.

At this time, a sensor that continuously detects atmospheric pressure is required as the atmospheric pressure sensor 20, but the two-stage modification described above uses an atmospheric pressure switch that turns on and off according to changes in atmospheric pressure. It is possible.

Next, FIG. 5 shows a flowchart of still another embodiment, which is the same as the flowchart of FIG. 3 except for the part surrounded by a chain line in which the failure judgment conditions are changed according to the atmospheric pressure.
Identical steps are given the same reference numerals. In this example, failure determination is not performed at high altitudes where atmospheric pressure has decreased.

That is, in step S4, the atmospheric pressure sensor 2
The atmospheric pressure A from 0 is read, and in step S5 it is determined whether or not the area is at a high altitude based on this atmospheric pressure A. If this determination is NO and the area is at a low altitude, the process directly proceeds to step S8 to determine the failure determination zone. If YES is determined at high altitude, the process returns to step S1 and no failure determination is performed.

In this example as well, at high altitudes, the failure determination conditions, that is, whether or not to perform a failure determination are changed to prevent the occurrence of erroneous determination.

(Effects of the Invention) According to the present invention as described above, there is provided an atmospheric pressure determining means for detecting a change in atmospheric pressure, and an output of the atmospheric pressure determining means is received, and the failure determining means is determined according to the change in atmospheric pressure. By providing a means to change the failure judgment conditions, it is possible to prevent false judgments from occurring even when atmospheric pressure fluctuates, ensuring accurate failure judgment and optimal exhaust gas recirculation. It is something.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an engine exhaust gas recirculation device to clearly demonstrate the configuration of the present invention, Fig. 2 is a schematic diagram of a concrete example engine, and Fig. 3 is a diagram illustrating the operation of the control unit. FIG. 4 is a flowchart for explaining the operation of the control unit in another example, and FIG. 5 is a flowchart for explaining the operation of the control unit in still another example. 1...Engine, 2...Exhaust passage, 3
...Intake passage, 4...Exhaust gas remote flow passage, 5...Fast flow control valve, 6...Negative pressure passage, 8... ...Saku IIJ hanging detection means, 9...
・Setting means, 10... Failure determination means, 11...
... Zone determination means, 12 ... Atmospheric pressure judgment means, 13 ... Change means, 18 ... Position sensor, 19 ... Control unit, 20...Atmospheric pressure sensor. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] (1) An exhaust gas recirculation control valve whose operation source is the intake negative pressure of the engine is provided, an operation amount detection means for detecting the actual operation amount of the recirculation control valve, and a setting means for setting a failure determination level; In an exhaust gas recirculation system for an engine, the engine exhaust gas recirculation device includes a failure determination means that receives signals from the operation amount detection means and the setting means and compares the detected operation amount with a failure determination level to determine a failure of the exhaust gas recirculation control system. , comprising an atmospheric pressure determining means for detecting a change in atmospheric pressure, and a changing means for receiving the output of the atmospheric pressure determining means and changing the failure determination condition of the failure determining means in accordance with the change in atmospheric pressure. Engine exhaust gas recirculation device.