JPH0689717B2 - Exhaust gas recirculation device diagnostic equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention 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.

BACKGROUND ART An exhaust gas recirculation device incorporated in an internal combustion engine used in a vehicle such as an automobile generally has an exhaust gas recirculation control valve for exhaust gas recirculation flow rate control and a negative pressure control valve for back pressure control,
If a failure occurs in these components, including the temperature sensitive valve, etc., the exhaust gas recirculation will not be performed normally and the internal combustion engine will be operated in the state where the low range of Nox in the exhaust gas is not made. There is fear. Even if exhaust gas recirculation is not performed due to a failure, the internal combustion engine will operate without failure, and the driver may be aware of this for a long period of time. The problem arises. Further, if the exhaust gas recirculation is not normally performed in the predetermined operation range, the fuel economy may be deteriorated due to the pump loss due to the intake air of the internal combustion engine itself.

In view of the above-mentioned problems, when the exhaust gas recirculation device fails to perform normal exhaust gas recirculation, a failure alarm device configured to inform the driver of this and to motivate the repair has already been proposed. This is disclosed in, for example, Japanese Utility Model Publication No. 52-9471 and Japanese Utility Model Publication No. 50-67220, and in Japanese Patent Application No. 60-163288 by the same applicant as the applicant of the present application. Even suggested.

Problems to be Solved by the Invention The failure diagnosis of the exhaust gas recirculation device is based 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. When the temperature of the exhaust gas recirculation passage is equal to or lower than a predetermined value, it may be determined that the exhaust gas recirculation device is out of order because the exhaust gas does not flow through the exhaust gas recirculation passage. However, the exhaust gas recirculation passage temperature does not rise steeply immediately after the exhaust gas recirculation is started, and the lower the outside air temperature is, the more it is absorbed by the conduit that guides the recirculated exhaust gas or radiated into the atmosphere. Due to the high heat quantity, the rate of increase in the temperature of the exhaust gas recirculation passage becomes small and the temperature rise is delayed, so the time required to rise to a certain temperature becomes longer. Therefore, when the exhaust gas recirculation is to be performed, it is necessary to simply determine whether the exhaust gas recirculation passage temperature is equal to or higher than a predetermined value. Although it is normal, it is apt to be erroneously diagnosed as a failure, and conversely, when the outside air temperature is high, it is easily erroneously diagnosed as normal although the exhaust gas recirculation device is abnormal.

Further, in order to prevent such erroneous diagnosis, it is possible to lower the predetermined value as the determination reference value as the outside air temperature is lower,
As described above, the increase rate of the exhaust gas recirculation passage temperature is smaller as the outside air temperature is lower, and the difference between the temperature before the start of exhaust gas recirculation and the temperature immediately after the start of exhaust gas recirculation is very small.
It is very difficult to set the predetermined value that can judge the failure of the exhaust gas recirculation device including the failure that the flow rate of the recirculated exhaust gas is not the original flow rate. Even if it is judged whether the temperature of the exhaust gas recirculation passage is below a predetermined value when a certain short time has elapsed from the time when it was detected, it is possible to accurately determine whether the exhaust gas recirculation device is normal or not. I can't judge.

The present invention, as long as the exhaust gas recirculation is normally continued, the exhaust gas recirculation passage temperature always rises to a certain temperature which is sufficiently higher than the temperature before the start of exhaust gas recirculation regardless of the outside air temperature, Focusing on the fact that the time to reach that temperature is longer as the outside air temperature is lower and shorter as the outside air temperature is higher, and by setting the determination time according to the outside air temperature, an improved exhaust gas that solves the above-mentioned problems An object is to provide a diagnosis device for a gas recirculation device.

According to the present invention, there is provided an exhaust gas recirculation operating area detecting means for detecting whether or not an operating area for exhaust gas recirculation, and an exhaust gas recirculating means. Exhaust gas recirculation passage temperature detecting means for detecting the temperature of the passage, outside air temperature detecting means for detecting the outside air temperature, and the outside air temperature is longer as the outside air temperature is lower according to the outside air temperature detected by the outside air temperature detecting means. The determination time setting means for setting the determination time so as to be shorter as it is higher, and the state detected by the exhaust gas recirculation operation area detection means as the operation area for performing exhaust gas recirculation are set by the judgment time setting means. When the temperature detected by the exhaust gas recirculation passage temperature detecting means is equal to or less than a predetermined value when the exhaust gas recirculation passage temperature detection means continues for a predetermined determination time, the exhaust gas recirculation device is determined to be defective. And a diagnosis device of the exhaust gas recirculation system having

According to the above-mentioned configuration, the determination time is set by the determination time setting means such that the lower the outside air temperature detected by the outside air temperature detecting means is, the longer the outside air temperature is, and the shorter the outside air temperature is,
The temperature detected by the exhaust gas recirculation passage temperature detection means is a predetermined value when the state detected by the exhaust gas recirculation operation area detection means as the operation area in which exhaust gas recirculation is performed continues for the judgment time. If the exhaust gas recirculation device is determined to be a failure by the determination means in the case of the following, it is determined that the wrong exhaust gas recirculation device is defective due to the low outside air temperature, The exhaust gas recirculation device is mistakenly determined to be normal due to the high outside air temperature, or the exhaust gas recirculation gas flow rate is not the expected flow rate when the outside air temperature is low. It is possible to reliably prevent the recirculation device from being erroneously determined to be normal, and it is possible to perform reliable and accurate failure diagnosis regardless of the outside air temperature.

Example 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.
10 and exhaust gas injection port 11 are conduits for exhaust gas recirculation
12 and the exhaust gas recirculation control valve 20 and the conduit 13 are connected to each other.

The exhaust gas recirculation control valve 20 has an inlet port 21 and an outlet port 22.
And the inlet port 21 is communicatively connected to the exhaust gas intake port 10 by a conduit 12 and the outlet port 22 is a conduit 13
Is connected in communication with the exhaust gas injection port 11.
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. The valve element 24 is connected to the diaphragm 26 of the diaphragm device 25, and is pushed down by the spring force of the compression coil spring 28 when a negative pressure larger than a predetermined value, for example, −70 mmHg, is not introduced into the diaphragm chamber 27, so that the valve port is closed.
23 is closed, and when a negative pressure larger than a predetermined value is applied to the diaphragm chamber 27, the compression coil spring 28 is responsive to the negative pressure.
It rises against the spring force of the valve and opens the valve port 23.

The diaphragm chamber 27 of the exhaust gas recirculation control valve 20 is connected to the conduit 2
9, negative pressure control valve for back pressure control 30, conduit 31, temperature sensing valve 32, conduit 3
Intake pipe negative pressure extraction port 34 provided in the intake pipe 5 via 3
Connected to. As shown in the drawing, the intake pipe negative pressure extraction port 34 is located upstream of the throttle valve 4 in the fully closed position, and is opened when the throttle valve 4 is opened by a relatively small predetermined opening or more. 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, and the diaphragm 37 is an atmosphere release chamber opened to the atmosphere on the upper side in the figure. 38 and a diaphragm chamber 39 on the lower side. Further, the diaphragm is located at a position where the valve element 36 is separated from the valve port 35 by the action of the compression coil spring 40 to open the valve port when the pressure (positive pressure) of the predetermined value or more is not introduced into the diaphragm chamber 39, On the other hand, when a pressure equal to or higher than a predetermined value is introduced into the diaphragm chamber 39, it is displaced upward in the drawing against the action of the compression coil spring 40 to bring the valve element 36 into contact with the valve port 35 and Is located in the closed position.

The diaphragm chamber 39 of the negative pressure control valve 30 has a pressure between the valve port 23 of the exhaust gas recirculation control valve 20 and the orifice 42 provided on the upstream side in the exhaust gas flow direction by the conduit 41. The chamber 43 is connected to communicate with the chamber 43, and 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 well-known back pressure control mechanism, and in the exhaust gas recirculation operation range 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 opening degree of the valve port 23 is adjusted, As a result, the ratio of the exhaust gas recirculation flow rate to the intake air flow rate, that is, the EGR rate is constantly kept almost 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 cooling water temperature is equal to or higher than the predetermined value, the communication between the conduits 31 and 33 is established.

According to the configuration as described above, the exhaust gas recirculation control valve 20 acts on the conduit 29 with a negative pressure larger than a predetermined value, for example, a negative pressure larger than -70 mmHg, and the temperature of the cooling water of the internal combustion engine 1 reaches a predetermined value, for example 60. When the temperature-sensitive valve 32 is opened at a temperature equal to or higher than 0 ° C., the valve is opened, and exhaust gas recirculation is performed at a flow rate according to the valve opening amount.

In the figure, reference numeral 50 designates a microcomputer for performing diagnosis of 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 a distributor of the internal combustion engine 1.
For the exhaust gas recirculation, information on the number of revolutions of the internal combustion engine 1 is provided by the rotational speed sensor 56 provided at 55, information about the temperature of the cooling water of the internal combustion engine 1 is provided by the water temperature sensor 57, and information about the intake air flow rate is given by the aerometer 3. Information about the temperature inside the conduit 13, that is, the exhaust gas recirculation passage temperature Tegr is given from the temperature sensor 59 provided in the middle of the conduit 13, and information about the outside air temperature is given from the temperature sensor 60 attached to the intake pipe 5, Based on this information, the exhaust gas recirculation device is diagnosed as to whether it is operating normally according to the flowchart shown in FIG. 2, and it is determined that the exhaust gas recirculation device is not operating normally. When it does, the indicator lamp 58 is turned on.

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 EGR diagnosis routine shown in FIG. 2 is executed as an interrupt routine at predetermined time intervals, and in the first step 10, it is determined whether or not the indicator lamp 58 is in the on state, that is, whether or not it is already lit. Be seen. When the indicator lamp 58 is in the on state, it is already judged that the exhaust gas recirculation device is abnormal and is reset at this time, while when the indicator lamp 58 is not in the on state, the routine proceeds to step 12.

In step 12, it is judged whether or not it is in the exhaust gas recirculation operation region. Whether or not it is in the exhaust gas recirculation operation range is determined by the intake air flow rate detected by the air flow meter 3, the rotation speed of the internal combustion engine 1 detected by the rotation speed sensor 56, and the internal combustion engine 1 detected by the water temperature sensor 57. Is carried out in accordance with the cooling water temperature of No. 1, and if it is in the exhaust gas recirculation operation region, the routine proceeds to step 14, otherwise it is reset.

In step 14, the exhaust gas recirculation passage temperature Tegr detected by the temperature sensor 59 is taken in. After step 14, the process proceeds to step 16.

In step 16, it is determined whether or not the exhaust gas recirculation passage temperature Tegr is equal to or lower than a predetermined value Tset. If Tegr <Tset, proceed to step 18, otherwise reset.

In step 18, the outside air temperature Tair detected by the temperature sensor 60 is taken in. After step 18, the process proceeds to step 20.

In step 20, the determination time Cj is determined according to the characteristics as shown in FIG. 3 according to the outside air temperature Tair. The determination time Cj is set shorter as the outside air temperature Tair is higher, and conversely is set longer as the outside air temperature Tair is lower. After step 20, the process proceeds to step 22.

In step 22, the continuous time after the exhaust gas recirculation operation range is determined in step 12, that is, the EGR continuation time Cegr is calculated from the counter value or the like.
After step 22, the process proceeds to step 24.

At step 24, it is judged if the EGR continuation time Cegr is longer than the judgment time Cj. When Cegr> Cj, it is judged that the exhaust gas recirculation device is out of order and the step
Go to 26, otherwise reset.

In step 26, the indicator lamp 58 is turned on, that is, turned on.

When the exhaust gas recirculation device is diagnosed according to the flow chart as described above, it is determined that the exhaust gas recirculation device is malfunctioning due to the low outside air temperature or the outside air temperature is high. It is incorrectly determined that the exhaust gas recirculation system is normal, or the exhaust gas recirculation system is normal when the recirculated exhaust gas flow rate is not what it should be when the outside air temperature is low. It can be reliably prevented from being erroneously determined to be present, so that the failure diagnosis of the exhaust gas recirculation device can be accurately performed regardless of the outside air temperature.

[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,
FIG. 2 is a flowchart showing the operation of the diagnosis device according to the present invention, and FIG. 3 is a graph showing an example of the relationship between the outside air temperature Tair and the determination time Cj. 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, 24 …… 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 open 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 …… Revolution sensor, 57 …… Water temperature sensor, 58 …… Indicator lamp, 59, 60 …… Temperature sensor

Claims (1)

[Claims] 1. Exhaust gas recirculation operating region detecting means for detecting whether or not the operating region is for exhaust gas recirculation, and exhaust gas recirculating passage temperature detecting means for detecting the temperature of the exhaust gas recirculating passage. An outside air temperature detecting means for detecting the outside air temperature, and a determination time setting means for setting a determination time such that the outside air temperature is lower and the outside air temperature is higher and the outside air temperature is shorter according to the outside air temperature detected by the outside air temperature detecting means. The exhaust gas recirculation when the state detected by the exhaust gas recirculation operation region detection means as an operation region in which exhaust gas recirculation is performed continues for the judgment time set by the judgment time setting means. A diagnosis of an exhaust gas recirculation device, which has a judgment device for judging that the exhaust gas recirculation device is out of order when the temperature detected by the passage temperature detection device is below a predetermined value. Apparatus.