JPH0650088B2 - Exhaust gas recirculation equipment diagnostic equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a diagnostic device for diagnosing whether an exhaust gas recirculation device for an internal combustion engine used in a vehicle such as an automobile is operating normally. .

[Prior Art] An exhaust gas recirculation device incorporated in an internal combustion engine used in a vehicle such as an automobile generally includes an exhaust gas recirculation control valve for exhaust gas recirculation flow rate control and a negative pressure control valve for back pressure control. ,
If the components such as the temperature sensitive valve are broken down, exhaust gas recirculation will not be performed and N
There is a possibility that the internal combustion engine may be operated in a state where the O _x is not reduced. Even if exhaust gas recirculation is not performed due to a failure, the internal combustion engine can be operated without any problem, and therefore the driver may not notice this and operate for a long period of time, which causes a problem of air pollution.

In view of the above-mentioned problems, there has already been proposed a failure alarm device configured to inform the user of this when exhaust gas recirculation is stopped due to a failure of the exhaust gas recirculation device and to motivate the repair. This is disclosed, for example, in Japanese Utility Model Publication No. 50-67220, Japanese Utility Model Publication No. 52-9471, Japanese Patent Application Laid-Open No. 61-182450, and Japanese Utility Model Publication No. 62-71363.

The failure diagnosis of the exhaust gas recirculation device may be performed depending on whether or not the temperature of the exhaust gas recirculation passage is equal to or higher than a predetermined value under the condition that the exhaust gas recirculation should originally be performed. Is less than a predetermined value, it may be determined that the exhaust gas recirculation device is out of order because the exhaust gas is not flowing through the exhaust gas recirculation passage, but the actual temperature of the exhaust gas recirculation passage is the exhaust gas. It changes depending on whether the recirculation is repeatedly performed or stopped. Therefore, it is difficult to accurately detect whether the exhaust gas is flowing through the exhaust gas recirculation passage only from the temperature rise and fall, and the exhaust gas recirculation is simply detected. If a failure diagnosis of the exhaust gas recirculation device, that is, diagnosis is performed by determining the temperature of the exhaust gas recirculation passage under the condition where the circulation is performed, this may not be correctly performed.

In view of this, the operating range in which exhaust gas recirculation is performed, that is, the exhaust gas recirculation operating range is detected from the operating state of the internal combustion engine, and when the operating range of the internal combustion engine is the exhaust gas recirculating operating range, it is counted up. When the count value of this up-count is equal to or more than a predetermined value, if the exhaust gas recirculation is normally performed, it is assumed that the exhaust gas recirculation passage temperature is always equal to or more than the predetermined value When the exhaust gas recirculation passage temperature is equal to or lower than a predetermined value (fault determination temperature), it is already considered that the exhaust gas recirculation device is determined to be faulty. This type of diagnostic device is disclosed, for example, in Japanese Utility Model Laid-Open No. 62-7136.
Japanese Patent Application No. 61-235263 and Japanese Patent Application No. 62-2 by the same applicant as the applicant of the present application.
It has already been proposed in No. 4179.

[Problems to be Solved by the Invention] In the diagnosis device as described above, if the failure determination temperature is low, it is determined to be normal even when the exhaust gas recirculation passage temperature rises due to heat received from the internal combustion engine. If the failure determination temperature is high, on the other hand, the exhaust gas recirculation passage temperature does not reach the failure determination temperature and the failure occurs even though the exhaust gas recirculation is normally performed. The possibility of misjudgment increases.

The amount of difference in exhaust gas recirculation passage temperature between when exhaust gas recirculation is being performed and when exhaust gas recirculation is not being performed increases with the passage of time during which exhaust gas recirculation is being performed. Therefore, in the diagnosis device that makes a failure determination from this difference amount, the failure determination temperature should be variably set according to the exhaust gas recirculation time, which reduces the possibility of erroneous determination as described above. Conceivable.

An object of the present invention is to provide an improved exhaust gas recirculation device diagnostic device in view of the above viewpoint.

[Means for Solving the Problems] According to the present invention, the above-described object is to detect whether the operating range of the internal combustion engine is an operating range in which exhaust gas recirculation is performed,
When it is in the exhaust gas recirculation operating range, the count value of the counter is counted up, and when the count value is equal to or more than the predetermined value, the exhaust gas recirculation passage temperature is not higher than the failure judgment temperature, the exhaust gas recirculation device is malfunctioning. An exhaust gas recirculation device diagnostic device that determines that there is an exhaust gas recirculation device that has failure determination temperature setting means for increasing the failure determination temperature in accordance with the increase in the count value. Achieved by the diagnostic device of the circulator.

[Operation and Effect of the Invention] According to the above-described configuration, the failure determination temperature is set to a temperature corresponding to the change over time of the exhaust gas recirculation temperature under the state where the exhaust gas recirculation is normally performed. From this, the diagnosis of the exhaust gas recirculation device due to the exhaust gas recirculation passage temperature can be accurately performed without causing an erroneous judgment, and the failure judgment start time can be set early. Become.

[Examples] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows one embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the present invention.
In the figure, 1 indicates an internal combustion engine, which is
Air is sucked into a combustion chamber 7 through an air cleaner 2, an air flow meter 3, an intake pipe 5 having a throttle valve 4, and an intake manifold 6, and fuel is injected and supplied from a fuel injector 8 to burn burned gas, that is, exhaust gas. Is discharged to the exhaust manifold 9.

The exhaust manifold 9 is provided with an exhaust gas intake port 10 for exhaust gas recirculation, and the intake manifold 6 is provided with an exhaust gas injection port 11, respectively, and the exhaust gas intake port 10 and the exhaust gas injection port 11 are provided. Are connected to each other by an exhaust gas recirculation conduit 12, an exhaust gas recirculation control valve 20, and a conduit 13.

The exhaust gas recirculation control valve 20 has an inlet port 21 and an outlet port 22, the inlet port 21 is communicatively connected to the exhaust gas intake port 10 by a conduit 12, and the outlet port 22 is injected by the conduit 13 with exhaust gas. It is connected to the port 11 for communication. The exhaust gas recirculation control valve 20 has a valve port 23 and a valve element 24, and the valve port 23 is opened and closed by the valve element 24 and its opening degree is controlled to control the exhaust gas recirculation flow rate. ing. Valve element 24
Is connected to the diaphragm 26 of the diaphragm device 25, and the diaphragm chamber 27 has a predetermined value, for example, -70 mmHg.
When a larger negative pressure is not introduced, it is pushed down by the spring force of the compression coil spring 28 to close the valve port 23, and when a negative pressure larger than a predetermined value is introduced into the diaphragm chamber 27, compression is performed according to the negative pressure. Coil spring 28
The valve port 23 is opened by opening against the spring force of the valve.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 has an intake pipe negative pressure extraction provided in the intake pipe 5 via a conduit 29, a back pressure control negative pressure control valve 30, a conduit 31, a pipe temperature valve 32, and a conduit 33. It is communicatively connected to the port 34. As shown in the drawing, the intake pipe negative pressure extraction port 34 is located upstream of the throttle valve 4 when it is in the fully closed position, and when the throttle valve 4 is opened by a relatively small predetermined opening or more, those ports are opened. It is provided to be located on the downstream side.

The negative pressure control valve 30 has a valve element 36 for opening and closing the valve port 35 and a diaphragm 37 carrying the valve element. The diaphragm 37 is open to the atmosphere open to the atmosphere on the upper side in the figure. A chamber 38 and a diaphragm chamber 39 on the lower side are respectively defined, and the diaphragm is operated by a compression coil spring 40 when a pressure (positive pressure) below a predetermined value is not introduced into the diaphragm chamber 39. The element 36 is located at a position where the valve port 35 is separated from the valve port 35 and the valve port is opened. On the other hand, when a pressure equal to or higher than a predetermined value is introduced into the diaphragm chamber 39, the element is moved upward against the action of the compression coil spring 40. To move the valve element 36 to the valve port 3
5 is brought into contact with the valve 5 to close the valve port.

The diaphragm chamber 39 of the negative pressure control valve 30 has a pressure difference 4 between the valve port 23 of the exhaust gas recirculation control valve 20 and the orifice 42 provided downstream of the valve chamber 23 due to the conduit 41.
3, the exhaust gas pressure in the pressure chamber is introduced.

The structure including the negative pressure control valve 30 and the orifice 42 as described above is a known back pressure control mechanism, and in the exhaust gas recirculation operation region where the intake pipe negative pressure is applied to the exhaust gas recirculation control valve 20, The negative pressure supplied to the diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is adjusted so that the exhaust gas pressure in the pressure chamber 43 is always kept substantially constant, in other words, the valve port 2
The degree of opening of No. 3 is adjusted so that the ratio of the exhaust gas recirculation flow rate to the intake air flow rate, that is, the EGR rate is always kept substantially constant.

The temperature sensitive valve 32 is sensitive to the temperature of the cooling water of the internal combustion engine 1, and is closed during the warm-up process in which the temperature of the cooling water is a predetermined value, for example, 60 ° C. or less, to cut off the communication between the conduits 31 and 33. On the other hand, when the temperature of the cooling water is equal to or higher than the predetermined value, the communication between the conduits 31 and 33 is established.

According to the above configuration, the exhaust gas recirculation control valve 20 causes the conduit 29 to have a negative pressure larger than a predetermined value, for example, -70 mmHg.
When a large negative pressure acts and the temperature of the cooling water of the internal combustion engine 1 reaches a predetermined value, for example, 60 ° C. or more and the temperature sensitive valve 32 is heard, the valve is opened, and the exhaust gas is regenerated at a flow rate according to the valve opening amount. Circulation takes place.

In the figure, reference numeral 50 denotes a microcomputer for controlling the fuel injection amount and for diagnosing the exhaust gas recirculation device. The microcomputer 50 has a general structure, has a central processing unit (CPU) 51, a memory 52, an input port 53, and an output port 54, and is provided in a distributor 55 of the internal combustion engine 1 to rotate. The number sensor 56 provides information about the number of revolutions of the internal combustion engine 1, the water temperature sensor 57 provides information about the temperature of the cooling water of the internal combustion engine 1, the air flow meter 3 provides information about the intake air flow rate, and the exhaust gas recirculation conduit 13 is in the middle. Information about the temperature of the conduit 10 is given from a temperature sensor 59 provided in the exhaust gas recirculation system, and whether the exhaust gas recirculation device is operating normally or not according to the flow chart shown in FIG. When the diagnosis is performed and it is determined that the exhaust gas recirculation device is not operating normally, the indicator lamp 58 is turned on. It has become.

Next, the operation of the diagnosis apparatus according to the present invention will be described with reference to the flow chart shown in FIG.
The routine shown in FIG. 2 is an exhaust gas recirculation operation area determination routine, and this routine is performed every predetermined time, for example, 2
It is executed as a repeating interrupt routine every 40 msec.

First, in step 10, it is determined whether or not the rotation speed of the internal combustion engine 1 detected by the rotation speed sensor 56 is equal to or higher than a predetermined first predetermined value Neset ₁ . If Ne ≧ Neset ₁ , the process proceeds to step 20, and if not, the process proceeds to step 70.

In step 20, it is determined whether the rotation speed of the internal combustion engine 1 detected by the rotation speed sensor 56 is equal to or smaller than a second predetermined value Neset ₂ which is larger than the predetermined first predetermined value Neset ₁ or not. Judgment is made. If Ne ≤ Neset ₂ , the process proceeds to step 30, otherwise, the process proceeds to step 70.

In step 40, the intake air Q / Ne corresponding to one engine stroke calculated from the intake air flow rate Q detected by the air flow meter 3 and the engine speed Ne detected by the rotation speed sensor 56 is predetermined. First predetermined value Q / N
It is determined whether it is greater than eset1. Q / Ne ≧
If Q / Neset ₁ , go to step 40, otherwise go to step 70.

In step 40, the intake air flow rate Q / equivalent to one stroke of the engine calculated in the same manner as in step 30
A determination is made as to whether Ne is smaller than a second predetermined value Q / Neset _{2 which is} larger than a predetermined first predetermined value Q / Neset ₁ . It is determined whether or not it is smaller than a second predetermined value Q / Neset ₂ larger than Q / Ne ≦ Q / Neset ₁ . When Q / Ne ≦ Q / Neset ₂ , the process proceeds to step 50, and when not, the process proceeds to step 70.

In step 50, it is determined whether or not the cooling water temperature Tw of the internal combustion engine 1 detected by the water temperature sensor 57 is higher than a predetermined value Twset. Tw ≧ Tws
If it is et, the process proceeds to step 60, and if not, the process proceeds to step 70.

Step 60 is executed in the exhaust gas recirculation operation range based on the determination results of Step 10 to Step 50,
In step 60, the count value C of the counter is counted up.

Step 70 is executed when it is not in the exhaust gas recirculation operation range, and in this step 70, the count value C of the counter is down-counted.

Exhaust gas recirculation operation area discrimination routine is step 60 or 7
0 ends by being executed.

FIG. 3 shows a failure determination routine, which is also executed as a repetitive interrupt routine at predetermined time intervals.

In step 100, it is determined whether the count value C of the counter is larger than a predetermined value Cset. When C ≧ Cset, the internal combustion engine 1 has been operated in the exhaust gas recirculation operation region for a predetermined time or longer. At this time, the routine proceeds to step 120. Otherwise, the failure determination routine may be immediately terminated. Done.

In step 120, the failure determination temperature Teset is determined according to the count value C of the counter according to the characteristics shown in FIG. Failure judgment temperature Tes
et indicates the minimum value when the count value C is a predetermined value Cset, and from this, the count value C increases according to the increase of the count value C until it reaches a certain value Ca.
The increase in the failure judgment temperature Teset is caused by the count value C and a certain value Ca.
As shown in FIG. 5, the temperature of the exhaust gas recirculation passage does not increase indefinitely even if exhaust gas recirculation is performed for a long time in a normal state as shown in FIG. This is because the temperature is always kept higher than the exhaust gas temperature.

After step 120, the routine proceeds to step 130, where it is judged whether or not the exhaust gas recirculation passage temperature Te detected by the temperature sensor 59 is higher than the failure judgment temperature Teset determined at step 120. Is done. When Te ≧ Teset, it means that the exhaust gas recirculation is normally performed, and the routine proceeds to step 140 for normality judgment. On the other hand, when Te ≧ Teset, the exhaust gas recirculation is normally performed. If not, the process proceeds to step 150 for failure determination.

FIG. 5 shows changes in the exhaust gas passage temperature with time.
When the exhaust gas recirculation is normally performed, the exhaust gas recirculation passage temperature rises relatively rapidly after the start of the exhaust gas recirculation. On the other hand, when exhaust gas recirculation is not performed due to a failure, the exhaust gas recirculation passage does not receive heat directly from the exhaust gas, so the temperature of the exhaust gas recirculation passage gradually rises due to the ambient temperature in the engine room. However, this causes a temperature difference between when exhaust gas recirculation is normally performed and when it is not. Therefore, when a failure determination is made based on this temperature difference, the temperature difference increases as the time elapses from the start of exhaust gas recirculation,
The failure determination based on the temperature difference is better as the time elapses from the time when exhaust gas recirculation is started, but this does not result in early failure determination, and the failure determination temperature is when exhaust gas recirculation is not performed. It is sufficient to set the temperature higher than the maximum temperature, but in this case as well, the failure determination waiting time becomes long.

On the other hand, in the diagnosis apparatus according to the present invention, the failure determination temperature Teset is variably set as described above, and this failure determination temperature corresponds to the change over time of the exhaust gas recirculation passage temperature during normal operation. Because it may be
Accurate failure determination can be performed early after the operating range of the internal combustion engine enters the exhaust gas recirculation operating range. Since the exhaust gas recirculation passage temperature when exhaust gas recirculation is not performed increases as the duration of low vehicle speed travel with less traveling wind increases, the failure determination temperature Teset is set when the duration is long. May be incrementally compensated.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the present invention,
2 and 3 are flowcharts showing the operation of the diagnosis device according to the present invention, FIG. 4 is a graph showing a failure judgment temperature characteristic, and FIG. 5 is a graph showing a change with time of the exhaust gas recirculation passage temperature. is there. 1 ... Internal combustion engine, 2 ... Air cleaner, 3 ... Air flow meter, 4 ... Throttle valve, 5 ... Intake pipe, 6
Intake manifold, 7 Combustion chamber, 8 Fuel injector, 9 Exhaust manifold, 10 Exhaust gas intake port, 11 Exhaust gas injection port, 12, 13
...... Conduit, 20 ...... Exhaust gas recirculation control valve, 21 …… Inlet port, 22 …… Outlet port, 23 …… Valve port, 2
4 ... Valve element, 25 ... Diaphragm device, 26 ... Diaphragm, 27 ... Diaphragm chamber, 28 ... Compression coil spring, 29 ... Conduit, 30 ... Negative pressure control valve, 31 ...
… Conduit, 32 …… Temperature sensitive valve, 33 …… Conduit, 34 …… Intake pipe negative pressure extraction port, 35 …… Valve port, 36 …… Valve element, 37 …… Diaphragm, 38 …… Atmosphere opening chamber, 39
... Diaphragm chamber, 40 ... Compression coil spring, 41 ...
... Conduit, 42 ... Orifice, 43 ... Pressure chamber, 50 ...
… Microcomputer, 51… Central processing unit,
52 ... Memory, 53 ... Input port, 54 ... Output port, 55 ... Distributor, 56 ... Rotation speed sensor, 57 ... Water temperature sensor, 58 ... Indicator lamp, 59 ... Temperature sensor

Claims (1)

[Claims] 1. A method for detecting whether or not an operating range of an internal combustion engine is an operating range in which exhaust gas recirculation is performed, and when the operating range is an exhaust gas recirculation operating range, a count value of a counter is up-counted,
In the diagnosis device of the exhaust gas recirculation device, which determines that the exhaust gas recirculation device is in failure unless the exhaust gas recirculation passage temperature is equal to or higher than the failure determination temperature when the count value is a predetermined value or more, A diagnostic device for an exhaust gas recirculation device, comprising a failure determination temperature setting means for increasing the failure determination temperature according to an increase in a count value.