JPS6341653A - Failure diagnosis device for exhaust gas recirculation apparatus - Google Patents

Abstract

PURPOSE:To aim at enlarging the range of diagnosis in a low level land and at preventing an erroneous diagnosis, by setting a predetermined failure diagnosis range to be set in an exhaust gas recirculation range with the use of three factors, engine rotational speed, fuel injection pulse width and intake-air vacuum. CONSTITUTION:A fuel injection pulse width computing means 13 disposed in a control circuit 12 computes a basic pulse width in accordance with an intake- air amount detected by an air-flow meter 9 which is disposed in an intake-air passage 2 in an engine 1 and an engine rotational speed detected by a crank angle sensor 11, and determines a drive pulse width for a fuel injection valve 8 by adding several increment factors to thus computed basic pulse width. Further, a drive range discriminating means 14 discriminates whether the operating condition of the engine is within a predetermined diagnosis range or not. Further, when the operating condition is in the predetermined diagnosis range, a failure diagnosis means 15 diagnoses an exhaust gas recirculation apparatus for failures in accordance with a detection signal from a temperature sensor 7 disposed in an exhaust recirculation passage 4, and energizes a suitable warning means 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a failure diagnosis device C2 for diagnosing whether or not an exhaust gas recirculation device in an automobile engine or the like is operating normally based on the temperature of an exhaust gas recirculation passage.

Conventional technology If the exhaust gas recirculation system of an automobile engine is malfunctioning, it goes without saying that normal exhaust purification cannot be performed, but malfunctions of this system are generally difficult for drivers to notice, and the malfunction remains for a long period of time. There is a risk that you may continue driving.

Therefore, as seen in Japanese Patent Application Laid-Open No. 51-94025, a temperature sensor such as a thermistor is installed in the exhaust gas recirculation passage equipped with an exhaust gas recirculation valve, and the temperature rises with the number of exhaust gases. Various devices have been proposed for diagnosing failures in exhaust gas recirculation devices based on the presence or absence of . In other words, in the operating range where exhaust gas should be recirculating, it is determined based on the temperature whether or not exhaust is actually recirculating, and if exhaust recirculation is not detected, it is diagnosed as a malfunction and the driver is informed. It gives some kind of warning.

Here, in electronically controlled fuel injection engines, the diagnostic range for performing the above diagnosis is set using the fuel injection pulse width, especially the basic pulse width Tp (determined from the intake air amount and engine speed) and the engine speed. Ru. Specifically, since the exhaust recirculation area appears as shown in Figure 3 a, the diagnosis @
A range (2) is set using the basic pulse width Tp and the engine rotational speed so as to include this exhaust recirculation area (2).・↓I), taking into account response delays, etc., the diagnosis is made when the driving problem remains within the diagnosis area for a predetermined period of time (1).

Problems to be Solved by the Invention By the way, an exhaust gas recirculation device is a general f-exhaust recirculation passage (an exhaust recirculation valve consisting of a diaphragm-type negative pressure valve that fully lifts at about 70 mmHg at the knee). 1. The negative pressure is changed to negative pressure η9 through various types of negative pressure control such as Tokoura VVT valve. The tenth exhaustion! 'tfrL Since the configuration is to control the opening and closing of the square, if the air density of the ground floor decreases, the exhaust gas recirculation valve will decrease as a result of the #shotonin suction negative pressure decreasing for the same basic pulse width T. An area that cannot be lifted occurs 1. ,,The exhaust Eura area becomes narrower that much. A2 in FIG. 4 shows the exhaust gas recirculation area at high altitudes, etc., and as is clear from the comparison with FIG. .

Therefore, if the 1-limit T, limit 1, and value of the diagnostic area are set along the exhaust gas recirculation area a in a lowland, then the suction Q pressure will be For example, -70
There is an iyJ capability that is smaller than mmHg, and it includes the non-operating range of the exhaust gas recirculation valve. In addition, (middle) in Fig. 7 is the tenth limit T, and (b) is the low limit 1゛1. This shows the case where the rotation speed is constant and the rotation speed is constant. As a result, while driving at high altitudes, the Wandering'A far-flow device 1q was misdiagnosed as a "failure" even though the IE was normal. There is a 7-year-old man.

On the other hand, as shown in (c) in Figure 7, it is possible to set the value as low as 1-1 so as not to include any non-operating areas at high altitudes, but in this case, , Figures 3 and 4, the diagnosis area is only the area between s and e in Figures 3 and 4, so diagnosis can only be performed in a part of the exhaust gas recirculation area a in lowlands (-. Therefore, as mentioned above, Considering the fact that the sensor must remain in the diagnostic range for a predetermined period of time, such as the response delay of the temperature sensor type, the opportunity for diagnosis will be significantly reduced by 1, which is not preferable.

Means for Solving the Problems Therefore, in the present invention, the high load side of the diagnostic area is divided by the throttle opening/stop or suction negative pressure (2), instead of the high load side of the diagnostic area. , is set using the engine speed, fuel injection pulse width, and throttle opening, or the engine speed, fuel injection pulse width, and suction negative pressure. .

If the high position I side of the action diagnosis area is set by suction negative pressure,
Areas where the exhaust gas recirculation valve is inoperative due to low suction negative pressure at high altitudes, etc. are always excluded from the diagnostic area. In other words, when the air density changes, the diagnostic area can change depending on the actual exhaust gas recirculation area C. Furthermore, since there is a unique relationship between each throttle stroke and the suction negative pressure regardless of variations in air density (there are two), the same result can be achieved even if this is used to set the high load side of the diagnostic region.

Embodiment FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention, in which 1 is an engine body, 2 is an intake passage, 3 is an exhaust passage, and 4
indicates an exhaust gas recirculation passageway that guides a portion of the exhaust gas from the exhaust passageway 3 to the suction passageway 2, and 5 represents an exhaust gas recirculation valve that is a diaphragm type negative pressure valve interposed in the exhaust gas recirculation passageway 4. The exhaust gas recirculation valve 5 uses suction negative pressure downstream of the throttle valve 6 as a negative pressure source, and when the negative pressure acts through a control mechanism (not shown), the f-passage 4ζ2 uses, for example, a thermistor as a temperature detection means. The temperature sensor T used is attached.

A fuel injection valve 8 is disposed in the intake passage 2, and f
2. For example, a hot wire air flow meter 9 is provided to detect the amount of intake air. A throttle opening sensor 1o, for example a potentiometer, is provided for detecting the opening of the diaphragm 96. In the present invention, it is only necessary to determine whether the throttle opening is equal to or greater than a predetermined opening, so a switch that operates at a predetermined opening may be used instead. Further, reference numeral 11 denotes a crank angle sensor that is provided to detect the engine speed and generates a pulse signal at every predetermined crank angle.

The control circuit 12 uses a so-called microcomputer system, and includes a fuel injection pulse width calculation means 1.
3, an operating range determining means 14, and a failure diagnosing means 15. The fuel injection pulse width calculation means 13 calculates a basic pulse width T from the intake air amount detected by the air flow meter 9 and the engine rotation speed detected by the crank angle sensor 11.
The driving pulse width of the fuel injection valve 8 is determined by calculating p and adding various correction increases to this value.

The driving region determining means 14 determines whether or not the driving conditions are within a preset diagnostic region C2, and if it is determined that the driving conditions have been maintained within the diagnostic region C2 for a certain period of time, 1. A fault diagnosis means 15 performs a fault diagnosis based on the detection signal of the temperature sensor 7. This is done based on, for example, whether the temperature detected by the temperature sensor 7 is higher than a predetermined temperature, or whether there is a change from a low temperature to a high temperature. If the exhaust gas flow is not detected, it is determined as a "failure". Alarm means such as an alarm lamp 16 is activated.

Next, FIG. 2 is a flowchart showing the processing of the operating range determining means 14. In step 1, it is determined whether the engine rotation speed is equal to or higher than a predetermined set rotation speed.

As shown by dl in FIG. 3, this set rotational speed is set to an extent C2 that slightly exceeds the lower limit rotational speed of the exhaust gas recirculation area a1. Further, in step 2, it is determined whether the basic pulse width Tp mentioned above is equal to or greater than the set value T. This setting T, value is
As shown in FIG. 3, C2 and C2 are set to slightly exceed the low-load limit of the exhaust gas recirculation area a1. In step 3, it is determined whether the throttle opening detected by the throttle opening sensor 10 is equal to or less than the set opening. This set opening degree is set so as not to match the non-operating range of the exhaust recirculation valve 5 at high altitudes.
It is designed to ensure sufficient suction negative pressure even at high altitudes. Furthermore, the relationship between suction negative pressure and throttle opening is as follows:
Since there are some variations due to sensor errors, etc., it is desirable to set C2 on the safe side, that is, to a low value so as not to cause false detection.

As mentioned above, depending on the engine speed, T, value, and throttle opening, the diagnostic area is the area surrounded by dl, bl, C1, and f2 in FIG. 3. This Fig. 3 shows the diagnosis area at low altitudes, but on the other hand, at high altitudes, as shown in Fig. 4, the throttle opening to obtain the same Tp value varies, so the high load side The limits of the diagnostic area are shown in C2. In other words,
The exhaust gas recirculation area a2 is reduced (accordingly, the diagnostic area is also reduced to bl and 02)
It is possible to reliably eliminate areas that cause misdiagnosis by reducing the size of the area between [2]. On the other hand, if we compare the diagnosis area on the high load side to the value of T as shown in Figure 3. It is.

Next, FIGS. 5 and 6 show an embodiment in which a negative pressure sensor 17 is disposed downstream of the throttle valve 6 in the intake passage 2, and the high load side of the diagnosis area is set according to the intake negative pressure. . In this case, as shown in fl in FIG. 3, the diagnosis area can be further expanded to a range that extends slightly below the exhaust gas recirculation area a1.

At high altitudes, the range falls within the range shown by f2+- in FIG. Note that a negative pressure switch that operates at a predetermined negative pressure may be used instead of the negative pressure sensor 17.

Effects of the Invention As is clear from the above explanation, the fault diagnosis device for the exhaust gas recirculation system according to the present invention (f.2) can secure a diagnosis area over a sufficiently wide range in lowlands, etc., and can be used as a temperature sensor with a relatively large response delay. Even in cases where a vehicle is used, a sufficient opportunity for diagnosis can be obtained within a very short period of time. Furthermore, in highlands and the like, the diagnosis area is also reduced as the exhaust gas recirculation area is reduced, and erroneous diagnosis does not occur.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 2 is a flowchart showing the flow of operation region determination, and FIG. 3 is a configuration explanatory diagram showing an embodiment in which the exhaust recirculation region and the diagnostic region in lowland are different. FIG. 6 is a flowchart showing the swelling of the operating range discrimination on the actual flow side, and FIG. 7 is a characteristic diagram showing the relationship between altitude and suction negative pressure when the Tp value is constant. 4... Exhaust recirculation passage, 7... Temperature sensor, 9...
Air flow meter, 10... Throttle opening sensor,
11... Crank angle sensor, 12... Suppression circuit, 1
7...Negative pressure sensor. 9M Afu %-7z Fig. 4 Enren rotation speed (rpm) Rido 9-area diagnosis lower limit setting Tp Hakuchinshoko f Name name setting mouth/entre opening i Now before Shimotatsuho σε rotation Mu Same Gincho Lord Lower Floor Disdain Tp Rent (Rental) Chin vLr Clothes ■Mutsu Line Immense Power E Slander! Seed area diagnosis T': Limit setting Tp Negative diagnosis 驎 r limit drum s 0 small l I chicken degree detection lower limit setting rotation song chin F 1 t U 1 limit adjustment Tp value (hammer chestnut) gingin f kuma rochu fixed inhalation chastity pressure Figure 6

Claims (1)

[Claims] (1) In a failure diagnosis device for an exhaust gas recirculation system, which includes a temperature detection means in an exhaust gas recirculation passage equipped with an exhaust gas recirculation valve that operates under negative pressure, and performs diagnosis based on the detected temperature in a predetermined diagnosis area set within the exhaust gas recirculation area. A failure diagnosis device for an exhaust gas recirculation system, characterized in that the diagnosis area is set using three factors: engine speed, fuel injection pulse width, throttle opening, or suction negative pressure.