JPH03115767A - Failure diagnosis device for exhaust gas recirculation device for engine - Google Patents

Abstract

PURPOSE:To prevent wrong judgment by providing a partition wall in an intake passage in such a way as to face the intake passage side opening part of an EGR passage, and disposing a temperature sensor between the partition wall and the opening part formed side wall of the intake passage, thereby judging the failure of an EGR device on the basis of the output of the temperature sensor. CONSTITUTION:An EGR device 4 is provided with an EGR passage 41 with one end thereof connected to an opening part 41a formed at the intermediate wall of an intake passage 2 on the downstream side of a throttle valve 23 and the other end connected to an exhaust passage, and an EGR valve 42 is provided at the intermediate part of the EGR passage 41. The EGR valve 42 is provided with a valve body 42a operated by a negative pressure type actuator 42b. In this case, a partition wall 5 is provided in the intake passage 2 in such a way as to face the EGR passage opening part 41a, thereby forming a small passage 51 with open ends between the partition wall 5 and the intake passage wall. A temperature sensor 6 is disposed on the downstream side of the opening part 41a of the small passage 51, and on the basis of its output, the failure of the EGR device 4 is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a failure diagnosis device for diagnosing whether or not an exhaust gas recirculation device of an engine is operating normally.

[Conventional technology]

2. Description of the Related Art Conventionally, engines have been known that are equipped with an exhaust gas recirculation device (EGR device) in order to reduce NOx in exhaust gas.

As is generally well known, this exhaust gas recirculation device includes an exhaust gas recirculation passage that communicates an intake passage and an exhaust passage, and an exhaust gas recirculation valve that controls the amount of recirculation of exhaust gas flowing through this exhaust gas recirculation passage. In cooperation with By supplying the fuel to the combustion chamber again, combustion is suppressed, the combustion temperature is lowered, and NOx is reduced.

In the above exhaust gas recirculation device, if the exhaust gas recirculation valve malfunctions or the exhaust gas recirculation passage becomes clogged due to accumulation of carbon, etc. in the exhaust gas, the exhaust gas may not be allowed to flow through the exhaust gas recirculation passage, or the exhaust gas may not flow at all. Failures such as flow stopping may occur. However, even in such a state, the engine itself continues to operate, so there is a risk that the driver may continue to operate the engine without noticing that the exhaust gas recirculation device has failed.

Therefore, in order to detect and notify the driver when the exhaust gas recirculation system malfunctions, for example, Japanese Patent Laid-Open No. 63-269
A failure diagnosis device disclosed in Japanese Patent No. 263 and the like has already been proposed.

The conventional failure diagnosis device described above includes a temperature sensor provided in the exhaust gas recirculation passage, and determines whether or not there is a failure in the exhaust gas recirculation device based on the temperature detected by the temperature sensor. In other words, in the exhaust gas recirculation system, if a failure occurs in which high-temperature exhaust gas is allowed to flow through the exhaust gas recirculation passage, the temperature inside the exhaust gas recirculation passage will become abnormally high, and the exhaust gas will no longer flow at all. When this failure occurs, the temperature in the exhaust gas recirculation passage becomes abnormally low even when the engine is operating in a state where exhaust gas is recirculated. Therefore, conventional failure diagnosis devices detect exhaust gas when an abnormally high temperature is detected by the temperature sensor, or when the temperature detected by the temperature sensor does not become old even though the engine is operating to recirculate exhaust gas. It is determined that the reflux device is malfunctioning.

[Problem to be solved by the invention]

However, in the past, since the temperature sensor was provided in the exhaust gas recirculation passage, there was a problem that the temperature sensor was affected by the temperature of the exhaust gas remaining in the exhaust gas recirculation passage. Therefore, even if a malfunction occurs in which the exhaust gas is not flowing through the exhaust gas remote flow passage (but the temperature detected by the temperature sensor does not drop and the exhaust gas no longer flows through the exhaust gas recirculation passage), the exhaust gas There was a problem in that it was determined that the reflux device was not malfunctioning, causing an erroneous determination.

In view of the above circumstances, it is an object of the present invention to provide a failure diagnosis device for an engine exhaust gas recirculation device that can accurately determine failure.

[Means to solve the problem]

A failure diagnosis device for an exhaust gas recirculation device for an engine according to the present invention includes an exhaust gas recirculation passage that communicates an intake passage and an exhaust passage of an engine, and an exhaust gas recirculation passage that measures the amount of recirculation of exhaust gas flowing through this exhaust gas recirculation passage. In an exhaust gas recirculation device for an engine including a gas recirculation valve, a partition is provided in the intake passage so as to face an opening on the intake passage side of the exhaust gas far flow passage, and the partition and the opening of the intake passage are formed. A temperature sensor is provided between the exhaust gas recirculation device and the side wall, and a failure determination means is provided for determining failure of the exhaust gas recirculation device based on the output of the temperature sensor.

[Effect]

According to the above configuration, the exhaust gas passing through the exhaust gas recirculation passage is reliably guided to the temperature sensor by the partition wall provided in the intake passage and the wall on the opening side of the intake passage. Furthermore, by providing the temperature sensor in the intake passage between the partition wall and the wall on the side where the opening of the intake passage is formed, the area around the temperature sensor is scavenged by the intake air flowing in the intake passage.

〔Example〕

1 and 2 show a failure diagnosis device for an engine exhaust gas recirculation device according to the present invention. In these figures, 1 is an engine, and a cylinder block 1
1, a cylinder head 12, and a piston 13. The combustion chamber 14 formed by the cylinder block 11, the cylinder head 12, and the piston 13 is connected to an intake passage 2 and an exhaust passage 3, respectively. An intake valve 15 and an exhaust valve 16 are provided at the openings, respectively.

In the intake passage 2, in order from the upstream side, an air cleaner 21, an air flow meter 22 for detecting the amount of intake air, and a throttle valve 2 are installed.
3. A surge tank 24 and a fuel injection valve 25 are provided. The intake passage 2 is also equipped with an intake pressure sensor 26 for detecting intake pressure and an intake temperature sensor 27 for detecting intake temperature.

4 is an exhaust gas recirculation device, which includes an exhaust gas recirculation passage 41
and an exhaust gas recirculation valve 42 interposed in the middle of this passage 41.
It is equipped with The exhaust gas recirculation passage 41 has one end connected to an opening 41a formed in a wall in the middle of the intake passage 2 (for example, the surge tank 24 portion), and the other end connected to an opening formed in a wall in the middle of the exhaust passage 3. 41b.

As a result, the intake passage 2 and the exhaust passage 3 are communicated with each other through the exhaust gas recirculation passage 41.
A part of the exhaust gas can be returned to the intake passage 2 through the intake passage 2.

The exhaust gas recirculation valve 42 has a valve body 42a and a diaphragm type actuator 42b.

The actuator 42b is operated by negative pressure introduced from the duty solenoid valve 43 to drive the valve body 42a. Duty solenoid valve 43
is equipped with a negative pressure boat 438 that introduces negative pressure from the intake passage 2 and an atmospheric pressure boat 43b that introduces atmospheric pressure. By selectively introducing the negative pressure introduced into the actuator 42b, the negative pressure introduced into the actuator 42b is controlled. That is, the engine control unit 7 outputs a control signal according to the engine operating state, and the duty solenoid valve 43 is controlled according to the control signal to introduce a negative It is designed to control pressure. Then, when the negative pressure introduced into the actuator 42b is controlled, the actuator 42b opens and closes the valve body 42a according to the negative pressure, thereby controlling the recirculation port of the exhaust gas passing through the exhaust gas recirculation passage 41. It looks like this.

A partition wall 5 is provided in the surge tank 24 of the intake passage 2 so as to face the opening 41a of the exhaust gas recirculation passage 41 on the intake passage 2 side. As a result, a small passage 51 is formed between the partition wall 5 and the opposite wall of the intake passage 2 on the side where the opening 41a is formed, with both ends open to allow intake air to flow. A temperature sensor 6 is disposed in the small passage 51 at a position downstream from the opening 41a.

The temperature sensor 6 outputs a temperature detection signal corresponding to the temperature inside the small passage 51, and this detection signal is input to the engine control unit 7. The engine control unit 7 includes the aerometer 2.
2. Detection signals are also input from the intake pressure sensor 26 and the intake temperature sensor 27, respectively, and the crankshaft 1
A detection signal is also input from an engine rotation speed sensor 18 that is installed in the engine 7 and detects the engine rotation speed.

The engine control unit 7 is a failure determining means for determining whether or not the exhaust gas recirculation device 4 is malfunctioning based on various detection signals such as a temperature detection signal from the temperature sensor 6 and a detection signal from the intake temperature sensor 27. It is equipped with 71. When the failure determining means 71 determines that the exhaust gas recirculation device 4 is malfunctioning, it outputs a lighting command signal to the lamp 8 to turn on the lamp 8.

The engine control unit 7 also determines the operating state of the engine based on various detection signals, and outputs a control signal to the duty solenoid valve 43 in accordance with the determination result.

FIG. 3 shows a specific example of control by the engine control unit 7. In this flowchart, when started, first, in step S1, engine rotation speed Ne1, intake port Q1, intake pressure P , intake temperature THA
and various signals such as the temperature inside the small passageway TA.

Next, in step S2, it is determined whether or not the engine is in the EGR zone, that is, whether the engine is in an operating state in which the exhaust gas recirculation device 4 is activated to recirculate exhaust gas.

This is determined by whether or not the engine rotational speed Ne and the load (intake air amount Q per rotation) are within the range shown by the solid line in FIG.

If it is determined in step S2 that the area is in the EGR zone,
In step S3, it is determined whether or not the load has changed suddenly.

If the load has not suddenly changed, it is determined in step s4 whether or not it is in the fail determination zone. The fail judgment zone is indicated by the two-dot chain line in Fig. 4.
It is determined whether the zone is a fail determination zone or not based on whether or not the engine rotation speed Ne and the load are within the range set narrower than the zone and surrounded by the two-dot chain line. If it is in the fail determination zone, a failure determination is made in step S5 as to whether or not a failure in which the exhaust gas recirculation is insufficient has occurred.

On the other hand, if the load is suddenly changing, or if it is in the EGR zone but not in the fail determination zone, the process returns to step S1 without making the failure determination in step S5.

That is, when the load changes suddenly, the engine is no longer in a steady operating state due to acceleration and deceleration, so the flow of intake air is not constant, and the temperature sensor 6 may be cooled down suddenly. This may lead to erroneous determination. Further, if the zone is not in the fail determination zone, the amount of exhaust gas recirculated is small even if it is in the EGR zone, so there is a risk of erroneous determination. Therefore, if the load is changing suddenly or if it is not in the fail judgment zone, the failure judgment in step S5 is not performed, and if the load is not changing suddenly, and
Failure determination is performed in step S5 only when the failure determination zone is present, thereby increasing the reliability of the failure determination result.

In step S5, the lagoon degree TA in the small passage detected by the temperature sensor 6 and the intake air temperature THA detected by the intake air temperature sensor 27 are determined.
It is determined whether or not the temperature difference between 6 and 6 is smaller than the lower limit set value T1. If it is determined that the If difference ΔT is smaller than the lower limit set value T1, it is determined in step Sa that a failure in which the amount of exhaust gas recirculation is insufficient has occurred, and step S7
Turn on the lamp. On the other hand, the temperature difference ΔT is the lower limit set value T
If it is determined that it is greater than 1, it is determined that there is no failure and the process returns to step S1.

That is, if it is determined in step S2 that the vehicle is in the EGR zone, unless the exhaust gas recirculation device f4 is malfunctioning, a large amount of exhaust gas is being recirculated, so the temperature TA in the vehicle passage becomes high. T increases with temperature difference. However, if a failure occurs in which the amount of exhaust gas recirculation is insufficient, such as when the exhaust gas recirculation passage 41 is clogged or the exhaust gas recirculation valve 42 does not open, almost no exhaust gas is recirculated, and the temperature TA in the vehicle passageway decreases. The temperature difference ΔT becomes smaller. Therefore, if it is determined in step S5 whether the temperature difference is smaller than the preset lower limit value T1, it is possible to detect the failure when the exhaust gas recirculation amount is insufficient as described above. I can do it.

If it is determined in step S2 that it is not in the EGR zone, in order to increase the reliability of the failure determination result in step S9, it is determined in step S8 whether or not the load has suddenly changed, and if the load has not suddenly changed, In step S9, a failure determination is made as to whether the exhaust gas recirculation valve 42 has failed and gas leakage has occurred, and if the load has suddenly changed, the process proceeds to step S1 without performing the failure determination in step S9. return.

In step S9, it is determined whether the temperature difference between the passageway temperature TA and the intake air temperature THA is larger than the upper limit setting value T2. If it is determined that the temperature difference ΔT is larger than the upper limit set value T2, then in step S10 the exhaust gas recirculation valve 4
2 is malfunctioning and causing a gas leak, and the lamp is turned on in step S11. On the other hand, if it is determined that the temperature difference ΔT is smaller than the upper limit set value T2, it is determined that there is no failure and the process returns to step S1.

That is, when it is determined in step S2 that the zone is not in the EGR zone, unless the exhaust gas recirculation device 4 is malfunctioning, the exhaust gas is not recirculated, so the temperature TA in the vehicle passage becomes low, and the temperature difference ΔT is becomes smaller. However, if a failure occurs such as the exhaust gas recirculation valve 42 not closing, the exhaust gas is constantly recirculated, so the temperature TA in the vehicle passage increases and the temperature difference ΔT increases. Therefore, if it is determined in step S9 whether the temperature difference ΔT is larger than the preset upper limit value T2, if a gas leakage failure occurs in the exhaust gas recirculation valve 42 as described above, the failure can be detected. I can do it.

In addition, in the above control, the temperature difference ΔT, which is the failure determination level, is determined based on the intake mTH as shown in FIGS. 5 and 6.
A and the intake pressure P, so that the intake pressure I
The higher the THA or the lower the intake pressure P, the lower the failure determination level.

Furthermore, the lamps lit in step S7 and step S11 may be the same lamp or different lamps.

According to the above configuration, when the engine operating state is in the operating state where exhaust gas recirculation is performed, that is, in the EGR zone,
The exhaust gas recirculation valve 42 opens to recirculate the exhaust gas, and the exhaust gas is discharged into the intake passage 2 from the opening 41a of the exhaust gas recirculation passage 41 on the intake passage 2 side. The discharged exhaust gas is reliably guided to the temperature sensor 6 in the small passage 51 by the partition wall 5 and the opposing wall of the intake passage 2 on the side where the opening 41a is formed. Therefore, if you look at the temperature detected by the temperature sensor 6,
It is possible to determine whether or not exhaust gas is being recirculated, and a failure of the exhaust gas recirculation device 4 can be detected. That is, if the temperature detected by the temperature sensor 6 does not rise, it can be determined that a gas shortage failure has occurred, and the failure can be detected.

On the other hand, when the EGR zone is exhausted, the exhaust gas recirculation valve 42 closes and the exhaust gas is no longer recirculated, so that the exhaust gas is no longer guided to the temperature sensor 6. Therefore, when looking at the temperature detected by the temperature sensor 6, if the temperature is rising,
It can be determined that a gas leakage failure has occurred, and the failure can be detected.

Moreover, since the temperature sensor 6 is provided in the small passage 51 in the intake passage 2 instead of in the exhaust gas far-flow passage 41, it is not affected by the residual gas temperature in the exhaust gas recirculation passage 41, and the small passage 51 Since the intake air is always passed through, the area around the temperature sensor 6 is scavenged with the intake air. Therefore, if the exhaust gas is not flowing through the exhaust gas recirculation passage 41, the temperature sensor 6 will be cooled by the intake air, and even if the exhaust gas is not flowing through the exhaust gas recirculation passage 41, the temperature sensor 6 will be cooled down. This prevents the situation where the value does not decrease, and it becomes possible to prevent misjudgments.

Furthermore, in this embodiment, the vehicle passageway temperature TA and the intake air temperature T
Since the failure determination is made based on the temperature difference with the HA, the failure determination can be made taking into account the influence of the intake air ITHA, and the failure determination can be made more accurately.

(Effects of the Invention) The failure diagnosis device for the exhaust gas recirculation device of an engine according to the present invention includes a partition provided in the intake passage so as to face the intake passage side opening of the exhaust gas recirculation passage, and a partition between the partition and the intake passage. A temperature sensor is provided between the exhaust gas recirculation device and the wall on the side where the opening is formed, and a failure determination means is provided for determining failure of the exhaust gas recirculation device based on the output of the temperature sensor. Therefore, it is not affected by the humidity of the residual gas in the exhaust gas recirculation passage, and the area around the temperature sensor is scavenged by the intake air passing through the intake passage.
Misjudgments will be prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a main part of an embodiment of a failure diagnosis device for an engine exhaust gas recirculation device according to the present invention;
The figure is a schematic diagram of the overall configuration, Figure 3 is a flowchart showing a specific example of control, Figure 4 is a graph showing the times of the EGR zone and fail judgment zone, and Figure 5 is the relationship between intake air temperature and temperature difference. FIG. 6 is a graph showing the relationship between intake pressure and temperature difference. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Exhaust passage, 4... Exhaust gas recirculation device, 5... Partition wall, 6...
・Temperature sensor, 41...Exhaust gas recirculation passage, 41a・
・・Opening of exhaust gas recirculation passage on the intake passage side, 42 ・・
Exhaust gas recirculation valve, 71...Failure determination means.

Claims (1)

[Claims] 1. An exhaust gas recirculation device for an engine that includes an exhaust gas recirculation passage that communicates an intake passage and an exhaust passage of the engine, and an exhaust gas recirculation valve that controls the amount of recirculation of exhaust gas flowing through the exhaust gas recirculation passage, A partition is provided in the intake passage so as to face the opening on the intake passage side of the exhaust gas recirculation passage, and a temperature sensor is provided between the partition and the wall on the side where the opening is formed of the intake passage. A failure diagnosis device for an exhaust gas recirculation system for an engine, characterized in that a failure determining means for determining a failure of the exhaust gas recirculation system based on the output of the temperature sensor is provided.