JPS63117154A - Self-diagnosis device for exhaust gas recirculation system - Google Patents

Abstract

PURPOSE:To decide the abnormality of an exhaust gas recirculation system accurately, by outputting an abnormality signal if the temperature in the exhaust gas recirculation system does not reach to a predetermined level within predetermined time after provision of an exhaust gas recirculation instruction. CONSTITUTION:A control unit 60 is inputted with detection values such as intake air quantity, intake tube negative pressure, vehicle speed, rotation, accelerator opening or cooling water temperature and provides an EGR valve drive signal A to an EGR valve 12 based on said information. If a value detected by a temperature sensor 16 arranged in an exhaust recirculation path does not reach to a predetermined level within a predetermined time after provision of the drive signal A, it is decided that the exhaust gas recirculation system is abnormal and an alarm lamp 26 is lighted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a self-diagnosis device for an exhaust gas recirculation system that can automatically determine the presence or absence of a failure in the exhaust gas recirculation system, and particularly relates to a self-diagnosis device for an exhaust gas recirculation system that can automatically determine whether or not there is a failure in the exhaust gas recirculation system. This invention relates to an improvement in the operation detection means of the I-flow system.

[Prior Art] In general, in internal combustion engines, whether it is a gasoline engine or a diesel engine, continuous exhaust gas flow (hereinafter simply referred to as EGR) is used to lower combustion temperature as a measure to reduce NOx (nitrogen oxides). Many systems are beginning to be adopted.

FIG. 3 shows the structure of a conventional EGR system, in which exhaust gas is returned from an exhaust manifold 1 to an intake manifold 3 via an exhaust gas recirculation passage 2.

This distance am is determined under the control of the exhaust gas recirculation valve 4 in accordance with the operating state of the engine, for example, the cold section water temperature detected by the temperature-sensitive vacuum valve 5.

In addition, 6 is a negative pressure transducer, 7 is an auxiliary EGR negative pressure signal path, 8 is an exhaust recirculation negative pressure signal path, 9 is a carburetor, 1
0 is the orifice.

By the way, when this EGR system is operating normally, NOx is reduced as described above, but when it fails, the following situation occurs.

■ Excessive EGR failure The combustion of the engine becomes unstable and the power performance decreases, making it easier for the driver to notice, but on the other hand, the generation of NOx is reduced, so
Even if discovery and success are delayed, there will be little damage to the environment.

■ Insufficient EGR or EGR failure In general, engine combustion tends to be better and power performance is improving, so drivers do not feel dissatisfied and problems tend to be overlooked. There is a problem in which increased NOx continues to be released into the environment until it is discovered.

Therefore, in order to reduce the loss when the EGR system fails as described above, it is necessary to include an EGR system in the control system of the internal combustion engine.
It is considered desirable to provide an appropriate self-diagnosis device 1A that warns of the presence or absence of a failure in the GR system based on the determination result.

[Problems to be Solved by the Invention] However, since there has been no effective means for detecting the operation of the EGR system, it has not been possible to obtain a self-diagnosis device for the EGR system at a practical level.

That is, as an example of a method for detecting the operation of the EGR system, a valve that controls EGRffi (referred to as an EGR valve)
There has also been a proposal to directly detect the movement of the needle valve by attaching a potentiometer or ○N/○FF switch to the extremely restricted location of the needle valve.

However, according to this, even if malfunction of the needle valve itself can be detected, the r!
Problems such as A blockage or leakage due to a defective needle valve seat cannot be detected. In addition, it is difficult to obtain a sensor at a low cost that can withstand the high heat of EGR gas and the inevitable large photographic acceleration that is applied because it is located at the tip of the needle valve without interfering with the smooth operation of the needle valve of the EGR valve. there were.

Furthermore, sensors such as potentiometers and switches, especially if they are contact type, can affect the operation of the EGR pulp needle valve,
There is also the problem that hysteresis is increased in the MAVF control performance of the EGR valve, which impedes smooth EGR control. It would seem that this problem could be easily solved by creating a structure with low contact resistance or a non-contact type that does not interfere with the smooth operation of the EGR valve needle valve, but in reality, such a structure It was technically difficult to establish this.

Incidentally, as a related technique, there is Japanese Unexamined Patent Publication No. 138250/1983.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems by detecting the operation of the EGR system using the EGR gas temperature, eliminate restrictions on the mounting location of the detection means, and eliminate interference with the EGR system operation. EG that can automatically and easily diagnose system operation
An object of the present invention is to provide a self-diagnosis device for the R system.

[Means for Solving the Problems] The present invention in accordance with the above object includes installing a detection means for outputting a detection signal in response to the temperature of the exhaust gas recirculation in the exhaust gas recirculation system,
A ft1llW device is provided which outputs an abnormal signal when the detection output of the detection means does not reach a predetermined value after a predetermined period of time has elapsed since the exhaust gas recirculation drive signal as an exhaust gas recirculation operation command was issued.

[Function] When the EGR system operates, high-temperature exhaust gas is
The gas flows through the gas passage, and the temperature of the EGR system rises due to heat conduction.

The present invention takes advantage of this fact and detects the operation of the EGR system by representing the EGR gas temperature, and detects when the temperature still does not rise sufficiently after the EGR activation command or when the EGR activation command is issued. In cases such as when the temperature is rising, the controller determines that the EGR system is malfunctioning, and activates alarms 1 and 1 based on the determination result.

However, the EGR gas temperature changes significantly depending on the engine operating conditions, the outside temperature, etc. at that time. This is exhaust gas and EG
This is because a lot of heat enters and exits from the wall surface of the R gas passage, so the EGR gas temperature is greatly affected by the engine cooling water temperature and the outside air temperature. In addition, if a part of the EGR gas passage is installed in an f1!1 member that generates a large amount of heat, such as a cylinder head or intake pipe, it takes a long time to reach thermal equilibrium, and therefore, even during normal operation, the EGR Gas flow rate and operation I! Depending on the correlation of duration, various temperatures can be taken.

Therefore, when determining the operation of the EGR system using a temperature switch that operates at a fixed set temperature, the opportunity for determination is only when extremely limited conditions are met, which may lead to omissions in the determination or There are some months in the same month that make it difficult to set the judgment start conditions.

Therefore, in the present invention, an EGR system that generates a changing temperature signal
The EGR system is determined by focusing on how the EGR gas temperature changes using a gas temperature sensor.

[Example] An example of the present invention will be described below based on FIGS. 1 and 2.

FIG. 1 shows an embodiment of a self-diagnosis device for an EGR system according to the present invention.

11 is an EGR gas passage, and EGR flowing through this passage
The EGR valve 12 that controls the gas amount is driven by an EGR valve drive negative pressure signal A as an EGR operation command. This EGR valve drive negative pressure signal A is the water temperature sensing valve 1.
3, which is a negative pressure signal of the carburetor 14 that is turned on by 3, and is led to the EGR valve 12 via the negative pressure circuit 15.

A temperature sensor 16 serving as a detection means for outputting a detection signal in response to the EGR gas temperature is attached to a wall surface of an EGR gas passage 11 constituting a part of the EGR system. The temperature sensor 16 detects the EGR gas temperature and outputs the temperature sensor output TEG.
Output R. That is, the temperature sensor 16 detects the operation of the EGR system by representing the temperature of the EGR gas. The EGR system refers to a system in which high-temperature EGR gas flows through the gas passage 11 and is heated by heat conduction. Therefore temperature sensor 1
6 is not limited to the wall surface of the gas passage, but can be attached to other members constituting the EGR gas passage 11, the EGR gas passage 11, etc.
It may be inside the R gas passage, a member in contact with a member constituting the EGR gas passage, or an intake pipe close to the EGR gas inlet.

On the other hand, the engine is equipped with an electronic control unit 6o, and it is appropriate that the electronic control unit is also used, for example, as a unit for fuel injection or a feedback carburetor.

The temperature sensor output TεGFL is guided to the control unit 60 along with the intake air amount, intake pipe negative pressure, vehicle speed, vehicle acceleration, engine rotation speed, intake air temperature, engine cooling water temperature, accelerator opening, etc. The control unit 60 gives the EGR valve drive signal A to the EGR valve 12 based on this information, and sends this to the I! I do it. Note that 26 is a warning lamp.

As shown in Figure 2, the tj1 function first determines that the cooling water temperature is above a predetermined value, and then determines whether the accelerator opening is greater than the idle opening or the intake pipe negative pressure is at the idle setting value. The EGR system is activated for the first time when it is smaller than , and is stopped at other times.

Next, after the EGR is activated, the process proceeds to two erroneous determination prevention steps. In the first step, it is determined whether the EGR malfunction determination start conditions are satisfied. This condition is satisfied when the engine speed is lower than a predetermined value and the intake air amount is within a predetermined range, the accelerator opening is within a predetermined range, or the intake pipe negative pressure is within a predetermined range, and the next prevention step is performed. Proceed to. Here, it is determined whether a predetermined period of time has elapsed after the EGR malfunction determination start condition was satisfied. This is to allow for a delay in the response of the sensor and a delay in the rise in temperature of the gas passage wall surface, etc.

Then, after a predetermined period of time has elapsed, the temperature sensor signal output T E
It is determined whether IJR is below a predetermined value, and in the following cases,
It is assumed that the εGR system has failed, and a malfunction alarm flag is set in the nonvolatile memory within the unit 60. This flag is stored as a code number, taken out from the outside as necessary, and the alarm lamp 26 is turned on. This warning lamp may also be used as a malfunction warning lamp for other components. The power source of the nonvolatile memory is also backed up directly from the battery B+, and the alarm flag is maintained unless it is manually reset. In addition, TE (iR
The predetermined value to be compared with is not always a fixed value (a table according to the engine operating situation, for example, a table with the vehicle speed and the duration of that vehicle speed as orthogonal axes, or a table with the engine speed and load as the orthogonal axes). Either the value searched from a table combining arbitrary parameters that are sufficient to predict the EGR gas temperature, or the value of TFQR before the EGR drive signal is generated < = the value of TFQR (named Tacra') that should be generated by EGR operation. , the change in R times ∆TEQ&), that is, s TEck + ∆TECtR
Refers to either or.

By changing the flow shown in FIG. 2, it is also possible to detect EGR other than when necessary, that is, excessive EGR due to a defective EGR pulp sheet or the like.

As described above, the above embodiment can be easily applied to an engine equipped with an electronic control unit, and since malfunction information can be stored for each code, the content of the malfunction can be identified and its handling becomes easy. . In addition, since it is possible to use both existing parts, the structure does not become complicated.

[Effects of the Invention] In summary, according to the present invention, the operation of the exhaust gas recirculation system is detected based on the temperature of the exhaust gas recirculation.
Since it is not necessary to attach the detection means to the needle valve of the exhaust gas recirculation valve, the detection means does not interfere with the operation of the EGR system, and this provides an excellent effect of effectively diagnosing the failure of the EGR system.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a self-diagnosis device for an exhaust gas recirculation system according to an embodiment of the present invention, Fig. 2 is a flowchart explaining the performance of the device shown in Fig. 1, and Fig. 3 is a diagram of a conventional EGR system. It is an overall configuration diagram. In the figure, 11 is an exhaust recirculation gas passage as an exhaust recirculation system;
2 is an exhaust gas recirculation valve, 16 is a temperature sensor as a detection means, and 60 is an electronic control unit as a υj sensor.

Claims (1)

[Claims] The exhaust recirculation system is equipped with a detection means that outputs a detection signal in response to the temperature of the exhaust recirculation gas, and an abnormality signal is generated when the detection output of the detection means does not reach a predetermined value after a predetermined time has elapsed since the exhaust recirculation activation command was issued. A self-diagnosis device for the exhaust recirculation system equipped with a controller that outputs output.