JPH07116996B2 - Diagnostic device for exhaust gas recirculation system of internal combustion engine - 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,
The temperature sensor, etc. are included, and if a failure occurs in these components, exhaust gas recirculation will not be performed and NO
There is a risk that the internal combustion engine will be operated in the state where 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 problems, and the driver may not notice this and operate for a long period of time. Occurs. If exhaust gas recirculation is not performed within a predetermined operating range, knocking may occur, and fuel consumption may deteriorate due to pump loss due to intake of the internal combustion engine itself.

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. 52-9471 and Japanese Utility Model Publication No. 50-67220.
It is also proposed in −163288.

Problems to be Solved by the Invention In the failure diagnosis of the exhaust gas recirculation device, when the operating state of the internal combustion engine is in a state where exhaust gas recirculation should be performed, the temperature of the exhaust gas recirculation passage rises above a predetermined value. May be performed depending on whether or not In an internal combustion engine, the operating state in which exhaust gas recirculation is performed is usually after the internal combustion engine has reached a predetermined warm-up state, and the exhaust gas recirculation impairs the smooth rotation of the internal combustion engine. The low load operating region and the high load operating region in which the output performance of the engine is impaired by the exhaust gas recirculation are the medium load operating regions. Whether or not the operating state of the internal combustion engine is within the lower load side, that is, the lower limit side of the exhaust gas recirculation operation region is detected by whether or not the intake air flow rate of the internal combustion engine is equal to or higher than a predetermined lower limit value. Well, whether or not the operating condition of the internal combustion engine is within the limit of the high load side, that is, the upper limit side of the exhaust gas recirculation operating range is that the intake air flow rate per revolution of the internal combustion engine is less than or equal to a predetermined upper limit value. It may be detected depending on whether or not.

Therefore, especially in the lower limit region of the exhaust gas recirculation operation range, the failure diagnosis of the exhaust gas recirculation device detects whether the internal combustion engine has reached a predetermined warm-up state, and determines the intake air flow rate of the internal combustion engine. Detects whether or not is above a predetermined lower limit,
The temperature of the exhaust gas recirculation system, which should be raised by the exhaust gas recirculation, is set to a predetermined value even though the internal combustion engine has reached the warm-up state and the intake air flow rate of the internal combustion engine is equal to or higher than the predetermined lower limit value. When it is less than or equal to the lower limit value of, it can be diagnosed that a failure has occurred in the exhaust gas recirculation device.

However, in the vicinity of the lower limit of the exhaust gas recirculation operation range, the gas flow rate of exhaust gas recirculation is set to a small flow rate corresponding to the small intake air flow rate, so the exhaust gas recirculation exhaust gas recirculates the exhaust gas recirculation. The amount of heat introduced into the circulation system is extremely small, while heat is dissipated from the exhaust gas recirculation system to the surroundings due to heat conduction, convection, or radiation. Even if there is no failure in the recirculation system, the temperature of the exhaust gas recirculation system may momentarily drop below a predetermined lower limit value due to temporary fluctuations in the operating state of the internal combustion engine. Therefore, the diagnosis device of the exhaust gas recirculation device simply detects whether the cooling water temperature of the internal combustion engine is equal to or higher than a predetermined value or whether the intake air amount is equal to or higher than a predetermined lower limit value, and the cooling water is detected. An alarm lamp that indicates a failure of the exhaust gas recirculation device when the temperature of the exhaust gas recirculation system falls below a specified lower limit value, even though the temperature is above the specified value and the intake air flow rate is above the specified value. When the exhaust gas recirculation system is turned on, the exhaust gas recirculation system does not actually fail, and even when the temperature of the exhaust gas recirculation system temporarily falls below the specified lower limit value. The alarm lamp lights up, giving the driver anxiety,
It may interfere with safe and comfortable driving.

The present invention, in a diagnostic device for an exhaust gas recirculation system for an internal combustion engine as described above, avoids unwanted and unnecessary lighting of an alarm lamp that may occur particularly in the lower limit region of the exhaust gas recirculation operating range. It is an object of the present invention to provide a diagnostic device that can be used.

Means for Solving the Problems According to the present invention, the above object is to provide a first detecting means for detecting whether or not the internal combustion engine has reached a predetermined warm-up state, and an intake air flow rate of the internal combustion engine. Is a predetermined lower limit value or more, and a second detecting means for detecting whether or not the temperature of the exhaust gas recirculation system of the internal combustion engine is a predetermined lower limit value or more. And the first detection means detects that the internal combustion engine has reached a predetermined warm-up state, and the second detection means detects that the intake air flow rate of the internal combustion engine is equal to or greater than a predetermined lower limit value. The exhaust gas recirculation system is operating in the exhaust gas recirculation operating region, the exhaust gas is detected when the third detecting means detects that the temperature of the exhaust gas recirculation system is equal to or lower than a predetermined lower limit value. Low load operation of an internal combustion engine that determines that there is a failure in the gas recirculation system In the diagnosis system of the exhaust gas recirculation device in the region, the first and second detecting means detects that the internal combustion engine is operating in the exhaust gas recirculation operation region. Until the exhaust gas recirculation system temperature is lower than a predetermined lower limit value by the third detecting means until the exhaust gas recirculation system continues for a predetermined time, an indication that the exhaust gas recirculation device has a failure is displayed. Achieved by a diagnostic device characterized by having no temporal alarm suppression means.

Actions and Effects of the Invention Even when the internal combustion engine is operating in the exhaust gas recirculation operation range in which the internal combustion engine reaches the predetermined warm-up state and the intake air flow rate of the internal combustion engine is equal to or more than the predetermined lower limit value as described above. Regardless of when the diagnosis device is made to judge that the exhaust gas recirculation system has a failure when the temperature of the exhaust gas recirculation system is equal to or lower than the predetermined lower limit value, the failure judgment of the exhaust gas recirculation device is made. By not issuing an alarm regardless of the temperature of the exhaust gas recirculation system until the state to be performed continues for a predetermined time, the exhaust gas is recirculated by the recirculation exhaust gas, especially in the low load operation range of the engine. The amount of heat supplied to the recirculation system is extremely small, and the difference between this heat input amount and the amount of heat released to the surroundings by heat conduction, convection, or radiation is smaller than that of the exhaust gas recirculation system, and temporary operation of the internal combustion engine To change the state When the temperature of the exhaust gas recirculation system tends to temporarily fall below a predetermined lower limit value despite no failure of the exhaust gas recirculation device, such a temporary exhaust gas It is possible to avoid displaying a failure of the exhaust gas recirculation device each time the temperature of the recirculation system drops and giving an unnecessary and unwanted warning to the driver. In this case, the warm-up state of the engine becomes lower than the predetermined warm-up state for performing diagnosis before the above-mentioned predetermined duration time expires,
When the intake air flow rate of the engine falls below the predetermined lower limit value for performing diagnosis, useless alarm generation is avoided. Even if the occurrence of an alarm within a predetermined time is suppressed by such a temporal alarm suppression means, when an actual failure occurs in the exhaust gas recirculation device, the failure state continues for a long time, so an alarm is always issued after the predetermined time has elapsed. Is issued and the alarm in case of failure is surely given.

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 the opening degree is controlled so that the exhaust gas recirculation flow rate is controlled. Has become. 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 the negative pressure larger than a predetermined value, for example, −70 mmHg, is not introduced into the diaphragm chamber 27, and the valve port 23 is opened. When the diaphragm chamber 27 is closed and a negative pressure larger than a predetermined value is introduced into the diaphragm chamber 27, the valve port 23 is opened in response to the negative pressure so as to rise against the spring force of the compression coil spring 28.

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 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) higher than 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 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. Is displaced to bring the valve element 36 into contact with the valve port 35 so that the valve port is in a closed position.

The diaphragm chamber 39 of the negative pressure control valve 30 is connected by a conduit 41 to a pressure chamber 43 between the valve port 23 of the exhaust gas recirculation control valve 20 and an orifice 42 provided downstream thereof, and the pressure of the pressure chamber 43 is reduced. The exhaust gas pressure in the 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 operating region where the intake pipe negative pressure is given 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 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 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.
The rotation speed sensor 56 provided at 55 provides information about the rotation speed 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, Information about the temperature of the conduit 13 is given from a temperature sensor 59 provided in the middle of the circulation conduit 13, and the exhaust gas recirculation device operates normally according to the flow chart shown in FIG. 2 based on this information. If it is determined that the exhaust gas recirculation device is not operating normally, the indicator lamp 58 is turned on.

The rotation speed sensor 56, the water temperature sensor 57, and the air flow meter 3 may be for fuel supply control.

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. In the first step 10, it is determined whether the indicator lamp 58 is in the on state, that is, whether it is already lit or not. 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 determined whether or not the cooling water temperature Tw detected by the water temperature sensor 57 is a predetermined value Twset, for example, 60 ° C. or higher. When Tw> Twset, the routine proceeds to step 14, and when not, it is reset when exhaust gas recirculation is not performed.

At step 14, it is judged if the intake air flow rate Q detected by the air flow meter 3 is equal to or higher than the lower limit value Qmin. If Q> Qmin, go to step 16,
If not, it is reset.

In step 16, the intake air flow rate Q detected by the air flow meter 3 and the rotation speed N of the internal combustion engine 1 detected by the rotation speed sensor 56 are used to calculate an intake air quantity Q / N corresponding to one engine stroke. , Equivalent intake air quantity Q per engine stroke
It is determined whether or not / N is less than or equal to the upper limit value Q / Nmax.
When (Q / N) <(Q / Nmax), it is determined that it is in the exhaust gas recirculation operation range. At this time, step 18
Go to, otherwise reset.

In step 18, it is determined whether or not the exhaust gas recirculation passage temperature Tegr detected by the temperature sensor 59 is equal to or lower than a predetermined Tset. If Tegr <Tset, proceed to step 20, otherwise reset.

In step 20, after the determination in step 16 is YES, that is, after the exhaust gas recirculation operation range is determined, the temperature of the exhaust gas recirculation passage is nevertheless increased.
The continuous time of the state where Tegr is determined to be lower than the predetermined value Tset, that is, the EGR time Cegr is calculated from the count value and the like. After step 20, the process proceeds to step 22.

In step 22, it is judged if the EGR time Cegr is longer than a predetermined judgment time Cset. Cegr>
If it is Cset, it is determined that the exhaust gas recirculation device is out of order and the process proceeds to step 24.
As long as the process returns to step 12 and steps 12 to 18 are all proceeded to the YES side, that is, the condition corresponding to the failure of the exhaust gas recirculation device continues, the duration time is measured. If any of the judgment results in steps 12 to 18 become NO before the judgment result in step 22 becomes YES, the diagnosis device is reset, and thereafter the diagnosis is restarted newly. To be done.

In step 24, the indicator lamp 58 is turned on, that is, turned on.

By performing the diagnosis of the exhaust gas recirculation device according to the above-described flowchart, the judgment region of the exhaust gas recirculation operation becomes the shaded region in the graph of FIG. 3, and all of this region In the diagnosis region, the diagnosis of the exhaust gas recirculation device can be reliably performed without making an erroneous determination.

[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 flow chart showing the operation of the diagnosis apparatus according to the present invention, and FIG. 3 is a graph showing the diagnosis area in the diagnosis apparatus according to the present invention. 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 ... Rotation speed sensor, 57 ... Water temperature sensor, 58 ... Indicator lamp, 59 ... Temperature sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A 63-41653 (JP, A) JP-A 61-182450 (JP, A) JP-A 60-192869 (JP, A) Actual development Sho-63- 134159 (JP, U)

Claims (1)

[Claims] 1. A first detecting means for detecting whether or not an internal combustion engine has reached a predetermined warm-up state, and a first detecting means for detecting whether or not an intake air flow rate of the internal combustion engine is equal to or more than a predetermined lower limit value. Two detection means, and a third detection means for detecting whether the temperature of the exhaust gas recirculation system of the internal combustion engine is equal to or higher than a predetermined lower limit value, the internal combustion engine by the first detection means The internal combustion engine is operated in the exhaust gas recirculation operating range in which the predetermined warm-up state is reached and the intake air flow rate of the internal combustion engine is detected to be equal to or higher than the predetermined lower limit value by the second detecting means. Despite this, if the third detecting means detects that the temperature of the exhaust gas recirculation system is equal to or lower than a predetermined lower limit value, it is determined that the exhaust gas recirculation system has a failure. Diagnostic equipment of exhaust gas recirculation system in the load operating range The third detection means is continued until the state in which the internal combustion engine is detected to be operating in the exhaust gas recirculation operation range by the first and second detection means continues for a predetermined time. It is characterized by having a temporal alarm suppression means that does not display that the exhaust gas recirculation device has a failure even if it is detected that the temperature of the exhaust gas recirculation system is below a predetermined lower limit value. Diagnostic device.