JPH0689715B2 - 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.

2. Description of the Related Art In an internal combustion engine used in a vehicle such as an automobile, it has been conventionally performed in various ways to incorporate an exhaust gas recirculation device for performing exhaust gas recirculation to reduce NOx in exhaust gas. ing. Exhaust gas recirculation devices of this type are disclosed, for example, in Japanese Utility Model Publication No. 54-121116, JP-A-58-88450, and JP-B-60-243.
It is shown in each gazette such as No. 03.

The exhaust gas recirculation device generally includes an exhaust gas recirculation control valve for controlling the exhaust gas recirculation flow rate, a negative pressure control valve for controlling the back pressure, a temperature sensitive valve, etc., and a failure occurs in these components. Then, there is a possibility that the internal combustion engine is operated in a state where exhaust gas recirculation is not performed and NOx in the exhaust gas 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. 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. 49-64623.

Problems to be Solved by the Invention The failure diagnosis of the exhaust gas recirculation device is performed by checking whether the temperature of the exhaust gas recirculation passage is higher than a predetermined value under the condition that the exhaust gas recirculation should be performed originally. When the temperature is equal to or lower than the predetermined value, it may be determined that the exhaust gas recirculation device is out of order because exhaust gas does not flow through the exhaust gas recirculation passage. However, the actual temperature of the exhaust gas recirculation passage changes due to the repeated execution and stop of exhaust gas recirculation, and whether the exhaust gas is flowing through the exhaust gas recirculation passage can be accurately determined from only this high or low temperature. Difficult to detect. Further, generally, the temperature of the exhaust gas recirculation passage is affected by the outside air temperature and varies depending on the outside air temperature. Therefore, under the condition that the exhaust gas recirculation is performed, it is only necessary to determine whether the temperature of the exhaust gas recirculation passage is equal to or higher than a certain reference value. There is a risk that gnosis will not be performed properly.

Therefore, it is conceivable to detect the temperature of the exhaust gas recirculation passage under the condition that the exhaust gas recirculation should be performed and diagnose the failure based on the amount of increase of the temperature in the predetermined time. When diagnosing with the amount of increase in temperature, that is, the rate of temperature increase, the temperature of the exhaust gas recirculation passage is more
It is strongly affected by other temperature factors, such as the outside air temperature or the ambient temperature, and although the exhaust gas recirculation device is operating normally, the desired temperature rise cannot be obtained and a failure is diagnosed, or exhaust gas is exhausted. There is a risk that the gas recirculation device may be diagnosed as normal even though the gas recirculation device is not operating normally, and it is necessary to detect the temperature at an optimum time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved exhaust gas recirculation device diagnosis system which solves the above problems.

Means for Solving the Problems According to the present invention, the above-described object is to detect exhaust gas recirculation operating area by detecting whether the engine operating state is an operating area where exhaust gas recirculation is performed. An engine state detecting means for detecting a predetermined engine state in which the temperature of the exhaust gas recirculation passage is hardly affected by a temperature other than the recirculation exhaust gas, and a temperature detecting means for detecting the temperature of the exhaust gas recirculation passage, The exhaust gas recirculation operating area detecting means detects that the exhaust gas recirculation is in an operating area, and the engine state detecting means detects that the engine is in a predetermined engine state. An exhaust gas recirculation device diagnostic device having a judgment device for judging that the exhaust gas recirculation device is out of order when the amount of increase in temperature detected by the temperature detection device is not more than a predetermined value. Will be achieved.

The exhaust gas recirculation operation range detection means performs exhaust gas recirculation by design based on the intake air flow rate, the intake pipe pressure or a combination of these with the engine speed, and further with a combination of these and the engine cooling water temperature. The operating range, in other words, the operating range in which the exhaust gas recirculation is always performed if the exhaust gas recirculation device is operating normally, may be detected. The temperature of the exhaust gas recirculation passage is not affected by the temperature of the exhaust gas recirculation exhaust gas. It suffices to detect engine states other than the engine state where the expected amount of temperature rise due to circulating exhaust gas cannot be expected, and the detection items of these detection means are determined according to the exhaust gas recirculation control characteristics. It is sufficient that.

Advantageous Effects of the Invention According to the above-described configuration, in a predetermined engine state where the temperature of the exhaust gas recirculation passage is not easily influenced by the temperature other than the recirculation exhaust gas in the operating range where the exhaust gas recirculation is performed. Since the exhaust gas recirculation device is diagnosed based on the temporal change in the temperature of the exhaust gas recirculation passage at a predetermined time in the If the temperature fluctuates drastically or if the temperature of the exhaust gas recirculation passage is strongly affected by the outside air temperature, etc., failure diagnosis will not be performed. The accurate diagnosis can be performed without erroneous determination due to fluctuations in the exhaust gas and the temperature of the exhaust gas recirculation passage affected by 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 system incorporating a diagnosis system according to the present invention.
In the figure, 1 indicates an internal combustion engine, which is
The mixture is sucked into the combustion chamber 5 through an air cleaner (not shown), the carburetor 2, and the intake manifold 3, and burnt gas, that is, exhaust gas is discharged to the exhaust manifold 6.

The exhaust manifold 6 is provided with an exhaust gas intake port 7 for exhaust gas recirculation, and the intake manifold 3 is provided with an exhaust gas injection port 8 respectively.
The exhaust gas injection port 8 and the exhaust gas recirculation conduit 9
The exhaust gas recirculation control valve 20 and the conduit 10 are connected to communicate with 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 7 by a conduit 9 and the outlet port 22 is a conduit 10
Is connected in communication with the exhaust gas injection port 8.
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.
When 23 is closed and a negative pressure larger than a predetermined value is being introduced into the diaphragm chamber 27, a compression coil spring is generated according to the negative pressure.
It rises against the spring force of 28 to open 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 carburetor 2 via 3
Connected to. As shown, 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. 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. Diaphragm chambers 39 are defined on the lower side and the diaphragm chamber 39, respectively. 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 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. By this, the ratio of the exhaust gas recirculation flow rate to the intake air flow rate, that is, the EGR rate is always 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.

FIG. 2 shows one embodiment of the diagnosis device according to the present invention. In FIG. 2, reference numeral 50 designates a microcomputer for performing diagnosis of the exhaust gas recirculation device. The microcomputer 50 has a general structure and includes a central processing unit (CPU) 51 and a memory (R).
OM) 52 and an input / output port 53, and a rotation speed sensor 54 provided in the distributor of the internal combustion engine 1 provides information on the rotation speed of the internal combustion engine 1 and a water temperature sensor 55 indicates the temperature of the cooling water of the internal combustion engine 1. Information on negative pressure switch 56
More information on the intake pipe negative pressure of the internal combustion engine 1, information on the throttle opening of the internal combustion engine 1 from the throttle switch 57, and an on-off signal based on the comparison result from the comparator 58 are given respectively. According to the flow chart as shown in FIG. 3, whether or not the exhaust gas recirculation device is operating normally is diagnosed, and when it is determined that the exhaust gas recirculation device is not operating normally, the transistor 61 is turned on. The indicator lamp 62 is turned on by energizing.

Negative pressure switch 56, as shown in FIG.
Intake pipe negative pressure extraction port provided in the carburetor 2 by
When the negative pressure larger than a predetermined value, for example, −100 mmHg is introduced from the intake pipe negative pressure extraction port 64, the contact point is closed and an ON signal is output.

The comparator 58 has a general structure composed of an OP amplifier, and one of its input terminals receives a comparison voltage that changes depending on whether or not the transistor 60 is in the ON state. When the transistor 60 is off, the comparison voltage becomes E (R ₂ + R ₃ ) / (R ₁ + R ₂ + R ₃ ), and the transistor 60
When is on, the comparison voltage is ER ₂ / (R ₁ + R ₂ ). A voltage signal according to the sensed temperature is applied from the temperature sensor 59 to the other input terminal of the comparator 58.

As shown in FIG. 1, the temperature sensor 59 is attached to the exhaust gas recirculation conduit 10 and is constituted by, for example, a thermistor, and detects the temperature in the exhaust gas recirculation conduit, that is, the exhaust gas recirculation passage temperature. It is like this.

Next, the operation of the diagnosis apparatus according to the present invention will be described with reference to the flow chart shown in FIG.

When the ignition switch of the internal combustion engine 1 is in the ON state, the indicator lamp 62 is first turned off in step 10, the flag F is set to 0 in step 20, and the count value of the counter is changed. Resetting C ₁ and C ₂ to 0 is performed. Steps 10 and 20 described above are executed only when the ignition switch is turned on due to the off state, that is, only when the engine is started, and the error is not made until the internal combustion engine is restarted.

From step 100, the diagnosis routine of the exhaust gas recirculation device is started. This routine is executed every predetermined time
For example, it may be executed as an interrupt routine that is repeated every 0.5 seconds.

In step 100, information is input from various sensors, switches and comparators. After step 100, the process proceeds to step 110.

At step 110, it is judged if the warm-up of the internal combustion engine 1 is completed. When the warm-up is completed, the routine proceeds to step 120, while when the warm-up is not completed, the routine proceeds to step 130.

In step 120, it is determined whether or not it is in the EGR on operation range. This is a determination as to whether or not the operating conditions under which exhaust gas recirculation is performed are performed. In this embodiment, the rotational speed of the internal combustion engine 1 detected by the rotational speed sensor 54 and the water temperature sensor 55 are used. The determination is made according to the detected coolant temperature of the internal combustion engine 1, the intake pipe negative pressure detected by the negative pressure switch 56, and the throttle opening detected by the throttle switch 57. When it is in the EGR on operation range, the routine proceeds to step 140, while when it is not in the EGR on operation region, the routine proceeds to step 130.

In step 130, the flag F is set to 0, and the count values C ₁ and C ₂ of the counter are both reset to 0.

In step 140, it is determined whether the flag F is 1. The flag F is a flag indicating that the exhaust gas recirculation passage temperature has reached the first predetermined value and a predetermined time has elapsed. If the flag F is not 1, step 15
On the other hand, when the flag F = 1, the process proceeds to step 160.

In step 150, the energization of transistor 60 is stopped. Step 150 is followed by Step 1
Proceed to 70.

In step 160, the transistor 60 is energized. After step 160, the process proceeds to step 170.

In step 170, it is determined whether the output signal of the comparator 58 is an ON signal or an OFF signal. Comparator 58
The comparison voltage is E when the transistor 60 is off.
(R ₂ + R ₃ ) / (R ₁ + R ₂ + R ₃ ), the ON signal is output when the exhaust gas recirculation passage temperature detected by the temperature sensor 59 is equal to or higher than the first predetermined value, On the other hand, when the transistor 60 is in the ON state, the comparison voltage is ER ₂ / (R ₁ + R ₂ )
When the exhaust gas recirculation passage temperature detected by the above is equal to or higher than a second predetermined value which is higher than the first predetermined value by a predetermined value, an ON signal is output. When the output signal of the comparator 58 is the ON signal, the routine proceeds to step 180, where the comparator 5
When the output signal of 8 is not on, the routine proceeds to step 220.

In step 180, the count value C _{2 of the} counter is reset to 0. After step 180, the process proceeds to step 190.

In step 190, it is determined whether the flag F is 1. When the flag F = 1, the diagnosis routine is ended, while when the flag F = 1 is not satisfied, the routine proceeds to step 200.

In step 200, it is judged whether or not the count value C ₁ of the counter of the counter which has started counting up in synchronization with the output of the ON signal by the comparator 58 is larger than a predetermined value C set _1. Is done. By this determination, it is determined whether or not a predetermined time has elapsed since the exhaust gas recirculation passage temperature reached the first predetermined value, and C ₁ > Cset
_If it is ₁ , proceed to step 210.

In step 210, the flag F is set to 1.

Step 220 is executed when the output signal of the comparator 58 is an off signal, and in this step 220, it is judged whether or not the flag F is 1. When the flag F = 1, the exhaust gas recirculation passage temperature does not exceed the _second predetermined value even if a predetermined time determined by the set value Cset ₁ of the counter elapses after the exhaust gas recirculation passage temperature reaches the first predetermined value. When the exhaust gas recirculation device is not operating normally, the routine proceeds to step 230. On the other hand, when the flag F = 1 is not satisfied, the exhaust gas recirculation passage temperature has not yet reached the first predetermined value. At this time, the routine proceeds to step 240.

In step 240, it is determined whether the count value C _{2 of the} counter started in synchronization with the operation range of the internal combustion engine 1 becoming the EGR on operation range is equal to or greater than a predetermined value Cset ₂ set in advance. Judgment is made. When C ₂ > Cset ₂ , the set value Cse is set after the operating range of the internal combustion engine 1 becomes the EGR on operating range.
When the temperature of the exhaust gas recirculation passage still does not reach the first predetermined value even after the predetermined time determined by t ₂ has elapsed, at which time it is determined that the exhaust gas recirculation device is not operating normally and step Proceed to 230.

In step 230, the transistor 61 is turned on and the indicator lamp 62 is turned on. The lighting of the indicator lamp 62 allows the user to know that a failure has occurred in the exhaust gas recirculation device.

Due to the diagnosis of the exhaust gas recirculation device according to the flowchart as described above, it is caused by a complicated temperature change in the exhaust gas recirculation conduit and a change in the outside air temperature accompanying the turning on and off of the exhaust gas recirculation. Accurate diagnosis is performed based on the temperature change state in the exhaust gas recirculation conduit without causing an erroneous determination.

In this embodiment, the determination in step 120 of FIG. 3 is
In the exhaust gas recirculation operation range detecting means of the present invention, the determination in step 170 after the power supply to the transistor 60 is stopped in step 150 of FIG. 3 is determined by the predetermined engine state detecting means of the present invention. The determinations in steps 170 and 220 after the transistor 60 is energized in step 160 of FIG. 1 correspond to the determination means of the present invention, and the temperature sensor 59 of FIG. 1 corresponds to the temperature detection means of the present invention. To do.

[Brief description of drawings]

FIG. 1 is a schematic view showing one embodiment of an exhaust gas recirculation device incorporating a diagnosis device according to the present invention,
FIG. 2 is a block diagram showing one embodiment of the diagnosis apparatus according to the present invention, and FIG. 3 is a flow chart showing the operation of the diagnosis apparatus according to the present invention. 1 ... Internal combustion engine, 2 ... Vaporizer, 3 ... Intake manifold, 4
...... Throttle valve, 5 ...... Combustion chamber, 6 ...... Exhaust manifold, 7 ...... Exhaust gas intake port, 8 ...... Exhaust gas injection port, 9, 10 ...... Conduit, 20 ...... Exhaust gas recirculation control valve ,twenty one……
Inlet port, 22 …… Outlet port, 23 …… Valve port, 24 ……
Valve element, 25 …… diaphragm device, 26 …… diaphragm, 2
7 …… Diaphragm chamber, 28 …… Compression coil spring, 29 …… Conduit, 30 …… Negative pressure control valve, 31 …… Conduit, 32 …… Temperature sensing 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 / output port, 54 ...... Revolution speed sensor, 55 …… Water temperature sensor, 56 …… Negative pressure switch, 59 …… Temperature sensor, 60, 61 ……
Transistor, 62 …… Indicator lamp, 63 …… Conduit, 6
4 ... Intake pipe negative pressure extraction port

Claims (1)

[Claims] 1. Exhaust gas recirculation operating region detection means for detecting an engine operating state and detecting whether or not the operating region is for exhaust gas recirculation, and the temperature of the exhaust gas recirculation passage is other than recirculation exhaust gas. Engine temperature detection means for detecting a predetermined engine state that is not easily affected by the temperature of the exhaust gas, temperature detection means for detecting the temperature of the exhaust gas recirculation passage, and exhaust gas recirculation by the exhaust gas recirculation operation area detection means. The amount of increase in the temperature detected by the temperature detecting means at a predetermined time under a state in which it is detected that it is the operating range to be performed and the engine state detecting means detects the predetermined engine state is a predetermined value. A diagnostic device for an exhaust gas recirculation device, which has a determining means for determining that the exhaust gas recirculation device is in failure when the above is not the case.