JPH0868367A - Fuel pump control device - Google Patents

Abstract

PURPOSE: To reduce an amount of vaporizing fuel discharged to the atmosphere when abnormality occurs to an evaporative emission control system. CONSTITUTION: When leakage through a fuel tank 11 and a canister 10 and abnormality of an evaporative emission control system, such as the close stick of a purge control valve 15 are detected by a control circuit 20, the drive circuit 80 of a fuel pump 70 is switched and the drive current of a fuel pump is reduced. Since an amount of high temperature surplus fuel returning to a fuel tank without being consumed is reduced, a fuel oil temperature in the fuel tank is reduced and vaporization of fuel oil is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the amount of evaporative fuel released from a fuel tank to the atmosphere when an abnormality occurs in an evaporative emission control device (EVAPORATIVE EMISSION CONTROL SYSTEM, hereinafter abbreviated as "evaporation device"). The present invention relates to a fuel pump control device that can be reduced.

[0002]

2. Description of the Related Art In order to prevent evaporative fuel from a fuel tank from being released to the atmosphere, the evaporative fuel from the tank is guided to a canister and adsorbed by an adsorbent in the canister, and under a predetermined operating condition of the engine. The purge air is passed through the canister to release the absorbed evaporated fuel from the adsorbent, and the mixture of purge air and evaporated fuel (purge gas)
There is known an evaporation device that supplies the air to an engine intake passage and burns it in the engine.

In the above evaporation device, if an abnormality occurs in the device, the evaporated fuel is not supplied to the engine and is released into the atmosphere, which may cause air pollution. For example, if the airtightness of the canister or fuel tank is destroyed and leaks occur, or if the vapor piping connecting the fuel tank and the canister leaks, evaporated fuel is released from these parts to the atmosphere. It will be. Also, if the purge control valve that controls the supply of purge gas from the canister to the engine is stuck and does not open, in the case of drunkenness, the adsorbent in the canister is not purged normally and the adsorbent evaporates. Since the fuel is saturated with the fuel, the evaporated fuel may be released into the atmosphere without being adsorbed by the canister.

Further, even if such an abnormality of the evaporation device occurs, there is no problem in the operation of the engine, so the driver may continue to operate the engine as it is without noticing the occurrence of the abnormality. In order to solve the above-mentioned problems, various abnormality detection devices have been devised which detect the occurrence of an abnormality in the evaporation device and notify the driver of the occurrence of the abnormality.

An example of this type of apparatus is disclosed in Japanese Patent Application Laid-Open No. 6-26408. The device of the publication is provided with an internal pressure control valve for maintaining a constant tank internal pressure in a vapor pipe connecting a canister and a fuel tank, and a pressure sensor for detecting the pressure in the tank. The presence or absence of an abnormality such as a decrease in airtightness of the fuel tank or a leak of vapor piping is detected from the change, and when an abnormality occurs, an alarm device is activated to notify the driver of the abnormality.

[0006]

SUMMARY OF THE INVENTION However, as in the above-mentioned Japanese Patent Application Laid-Open No. 6-26408, an abnormality detection device that detects the occurrence of an abnormality in the evaporative device and warns the driver is to drive the abnormality of the device. Although it is possible to notify the person to repair the device, it is not possible to prevent the evaporative fuel from being released into the atmosphere due to the abnormality of the evaporation device, and the evaporated fuel is released into the atmosphere when the abnormality occurs.

Further, even if an abnormality occurs in the evaporation device, the operation of the engine is performed without any trouble. Therefore, when the driver ignores the abnormality alarm and continues the operation of the engine, the evaporated fuel is released to the atmosphere. There is a problem that is done for a long time. In view of the above problems, the present invention is a fuel pump control capable of reducing the amount of evaporated fuel generated from a fuel tank when an abnormality occurs in the evaporation device, and reducing the amount of evaporated fuel itself released to the atmosphere. The purpose is to provide a device.

[0008]

According to the present invention, a canister for adsorbing evaporated fuel from an internal combustion engine fuel tank,
An evaporated fuel discharge suppressing device having a purging device for purging the fuel adsorbed in the canister into an engine intake passage under a predetermined operating condition of the engine, and an abnormality detection for detecting an abnormality in the evaporated fuel discharge suppressing device Means, and discharge amount reducing means for reducing the discharge flow rate of a fuel pump that supplies fuel from the fuel tank to the engine when the abnormality detecting means detects an abnormality in the fuel vapor emission suppression device. A fuel pump controller is provided.

[0009]

When the abnormality detecting means detects an abnormality in the evaporated fuel emission suppressing device and it is expected that the evaporated fuel is released to the atmosphere, the discharge amount reducing means reduces the discharge amount of the fuel pump. Normally, the discharge flow rate of the fuel pump is set to an amount obtained by adding a predetermined amount of margin to the maximum fuel consumption amount of the engine. Therefore, most of the fuel discharged from the fuel pump during engine operation is returned to the fuel tank without being consumed by the engine. Since the reflux fuel has passed through a high temperature portion in the engine room, the temperature thereof has risen, and the temperature of the entire fuel oil in the tank rises due to the reflux of the high temperature fuel during engine operation.

According to the present invention, the discharge amount reducing means reduces the discharge amount of the fuel pump when an abnormality occurs in the evaporation device within a range that does not hinder the operation of the engine. Therefore, the high temperature fuel that is returned to the fuel tank without being consumed by the engine is reduced. The amount of Therefore, the temperature of the fuel oil in the fuel tank is lowered, and the evaporation of the fuel in the tank is suppressed.

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of an embodiment of an internal combustion engine for a vehicle to which the present invention is applied. In FIG. 1, 1
Is an internal combustion engine body, 2 is an intake passage of the engine 1, and 3 is an air cleaner arranged in the intake passage. The intake passage 2 is provided with a throttle valve 6 that opens according to the operation of an accelerator pedal (not shown) by the driver. Further, the intake passage 2 is provided with a fuel injection valve 7 for injecting pressurized fuel supplied from a fuel pump 70 described later into each cylinder fuel port of the engine 1.

Reference numeral 11 in FIG. 1 denotes a fuel tank of the engine 1. The fuel oil in the tank 11 is boosted by the fuel pump 70, and is fed through the feed pipe 71 to the fuel injection valve 7
Pumped to. Further, reference numeral 72 in FIG. 1 is a pressure regulator for controlling the pressure of the fuel oil supplied to the fuel injection valve 7 to be constant. In this embodiment, the fuel pump 7
An electric diaphragm pump is used as 0,
The rated discharge flow rate Q of the pump 70 is an amount obtained by adding a margin Q ₂ to the maximum fuel consumption amount Q ₁ of the engine 1 (Q = Q ₁
+ Q ₂ ). For this reason, when the engine is operating, a considerably larger amount of fuel than the fuel injected from the fuel injection valve 7 is pump 70.
Is supplied to the fuel injection valve 7 from the feed pipe.
This excess fuel is returned from the regulator 72 to the fuel tank 11 via the return pipe 73.

Reference numeral 20 in FIG. 1 is a control circuit of the engine 1. The control circuit 20 includes a ROM (read only memory) 22, a RAM (random access memory) 23, and a C
PU (microprocessor) 24 and input / output port 2
5, 26 is composed of a digital computer of a known structure in which a bidirectional bus 21 is connected to each other, and performs basic control such as fuel injection control of the engine 1. In this embodiment, the opening control of a purge control valve 15 described later is performed. The abnormality detection of the evaporation device and the discharge amount control of the fuel pump 70 at the time of abnormality detection are performed.

For the above control, the output port 26 of the control circuit 20 is connected to the fuel injection valve 7 of the engine 1 via a drive circuit (not shown) and the valve opening time of the fuel injection valve 7 (fuel injection amount).
The purge control valve 15 is connected to an actuator 15a of the purge control valve 15 to control the operation of the control valve 15.
Further, the output port 26 is connected to the drive circuit 80 of the fuel pump 70.

Reference numeral 10 in FIG. 1 is a canister for adsorbing the evaporated fuel in the fuel tank. The canister 10
A vapor pipe 12 is connected to a space above the fuel oil surface of the fuel tank 11, and a purge pipe 14 is connected to a portion of the intake passage 2 on the downstream side of the throttle valve 6. FIG.
Reference numeral 15 denotes a purge control valve 15 that opens and closes the purge passage 14. The purge control valve 15 is opened under a predetermined operating condition of the engine by a signal from a control circuit 20 described later,
The canister 10 communicates with a portion of the intake passage 2 on the downstream side of the throttle valve 6. As a result, the canister 10 is purged. Reference numeral 15a in FIG. 1 denotes an actuator of an appropriate type such as a solenoid for driving the purge control valve 15 or a negative pressure actuator.

FIG. 2 shows the structure of the canister 10 of this embodiment. The canister 10 includes a housing 10a and an evaporative fuel adsorbent 13 such as activated carbon filled in the housing. The housing 10a is provided with an internal pressure control valve 16 and an atmosphere valve 18, and controls adsorption of vaporized fuel from the tank 11 to the adsorbent 13 and release from the adsorbent, as described later.

An internal pressure control valve 16 is provided inside the housing 10a.
A partition plate 10b is provided at a position between the air valve 18 and the atmosphere valve 18, and the adsorbent 13 in the housing is divided into two compartments, a compartment 13a on the internal pressure control valve 16 side and a compartment 13b on the atmosphere valve 18 side. . Further, the internal pressure control valve 1 is attached to the partition plate 10b.
6 and the atmosphere valve 18 are provided with communication holes on the side far from each other, and the two compartments 13a and 13b of the adsorbent are communicated with each other.

The internal pressure control valve 16 has a port 16a communicating with the inside of the housing 10 and a diaphragm 1 biased by a spring 16c in a direction to close the port 16a.
6b, and the pressure chamber 16d formed on the spring 16c side of the diaphragm 16b communicates with the atmosphere via the port 16e. A pressure chamber 16f formed on the side of the diaphragm 16b opposite to the spring 16c is connected to an upper space in the fuel tank 11 via a vapor pipe 12.

The pressure chamber 16f has a check ball 17
It communicates with the housing 10a of the canister through a pressure equalizing valve 17 composed of a and a spring 17b. On the other hand, the atmospheric valve 18 is also configured to be substantially similar to the internal pressure control valve 16, and has a port 18a and a diaphragm 18 communicating with the inside of the housing.
b, and a spring 18c. But atmosphere valve 1
8, the pressure chamber 18d formed on the spring 18c side of the diaphragm 18b is connected to the compartment 13a on the internal pressure control valve 16 side of the housing 10a via the pipe 18g, and the pressure chamber 18f is connected to the air cleaner 3 via the pipe 18e. Has been done.

The compartment on the atmosphere valve 18 side in the canister housing 10a communicates with the atmosphere via an atmosphere release valve 19 composed of a check ball 19a and a spring 19b. Further, the above-mentioned purge pipe 14 is connected to a section of the housing 10a on the internal pressure control valve 16 side.

Next, the adsorption and purging action of the evaporated fuel of the canister 10 will be described. In FIG. 2, when the fuel oil temperature rises with the purge control valve 15 of the purge pipe 14 closed, the pressure inside the tank 11 rises due to evaporation of the fuel oil. The pressure in the tank 11 is introduced into the pressure chamber 16f of the internal pressure control valve 16 through the vapor pipe 12, and the atmospheric pressure is introduced into the pressure chamber 16d through the port 16e. Therefore, when the internal pressure of the tank 11 becomes higher than the atmospheric pressure by a predetermined value or more, the diaphragm 16b is pressed by the pressure in the pressure chamber 16f and opens the port 16a against the biasing force of the spring 16c. As a result, the evaporated fuel in the tank 11 is transferred from the port 16a to the canister housing 10a.
Flows into. When the pressure in the canister housing 10a rises due to the opening of the port 16a, the check ball 19a of the atmosphere release valve 19 provided in the compartment 13b moves against the biasing force of the spring 19b due to the internal pressure of the housing 10a, so that the compartment 13b is exposed to the atmosphere. Communicate with. As a result, the air containing the evaporated fuel in the tank 11 can be transferred to the port 16
a into the canister housing 10a, flows through the adsorbents 13a and 13b, and the vaporized fuel is adsorbed by the adsorbent 13a.
Only air is adsorbed by and released from the atmosphere release valve 19. As described above, due to the action of the internal pressure control valve 16, the pressure in the fuel tank 11 is higher than the atmospheric pressure by a predetermined value or more (for example, 25
When it becomes higher than 0 mmAq), the port 16 is opened and the evaporated fuel flows into the canister 10, so that the fuel tank 11
The internal pressure of is always maintained below the predetermined value.

On the other hand, when a predetermined operating condition is reached during engine operation, the purge control valve 15 is opened and the canister housing 1
The partition 13a of 0a is connected to the intake passage 2 via the purge pipe 14.
The throttle valve 62 communicates with the downstream side. Therefore, the intake negative pressure on the downstream side of the throttle valve 6 acts in the housing 10a. The pressure chamber 18d of the atmosphere valve 18 is connected to the compartment 13a of the housing 10a via a pipe 18g,
As a result, the pressure in the pressure chamber 18d becomes lower than the atmospheric pressure. Further, since the atmospheric pressure in the air cleaner 3 is introduced into the pressure chamber 18f of the atmosphere valve 18 through the pipe 18e, the diaphragm 18b of the atmosphere valve 18 is the spring 18
It moves against the urging force of c and opens the port 18a.
Therefore, the clean air from the air cleaner 3 is supplied to the pipe 18
e, compartment 13 of housing 10a through port 18a
flow into b. This air flows in the adsorbent 13 from the sections 13b to 13a, releases the evaporated fuel adsorbed from the adsorbent 13, becomes purge gas containing the evaporated fuel, and flows into the intake passage 2 from the purge pipe 14. This allows
Saturation of the adsorbent 13 due to fuel adsorption is prevented, and the fuel released from the adsorbent is burned in the engine, so that evaporative fuel is prevented from being released into the atmosphere.

The tank 11 is cooled by cooling after the engine is stopped.
When the internal pressure decreases and becomes lower than the internal pressure of the canister housing 10a, the pressure equalizing valve 17 opens and the housing 10a is connected to the tank via the vapor pipe 12. Further, when the internal pressure of the tank 11 becomes lower than atmospheric pressure, the internal pressure of the canister housing 10a also becomes lower than atmospheric pressure and the atmospheric valve 18 opens, so that the air from the air cleaner 3 passes through the adsorbent 13 and the pressure equalizing valve 19 and the vapor. It flows from the pipe 12 into the tank 11. As a result, excessive pressure drop in the tank 11 is prevented.

As described above, the canister 10 and the pipe 1
If the evaporation device including the purge control valves 15, 14, etc. is operating normally, the adsorbent in the canister 10 adsorbs and purges the evaporated fuel in the fuel tank 11 according to the opening / closing of the purge control valve 15. Since the above is repeated, the release of evaporated fuel to the atmosphere is prevented. However, if an abnormality occurs in the evaporation device, the evaporated fuel may be released to the atmosphere.

For example, when the airtightness of the fuel tank 11 or the canister housing 10a is broken and leakage occurs, the fuel in the tank or canister may leak to the atmosphere. Further, when the purge control valve 15 is stuck and does not open (close stick of the purge control valve), the adsorbent 13 in the canister is no longer purged, and the adsorbent is saturated with the evaporated fuel. The vaporized fuel flowing from the vapor pipe 12 into the canister is adsorbent 1
3 is not adsorbed on the air but is directly released from the atmosphere release valve 19 to the atmosphere.

In this embodiment, a pressure sensor 30 (see FIG. 1) is provided to detect the abnormality of the evaporation device. The pressure sensor 30 outputs a voltage signal proportional to the differential pressure between the detected pressure and the atmospheric pressure.
Is supplied to the input port 25 of the control circuit 20 through an A / D converter (not shown). Further, the pressure detecting portion of the pressure sensor 30 is connected to the vapor pipe 12 and a portion of the purge pipe 14 between the canister 10 and the purge control valve 15 via the three-way valve 31, and by switching the three-way valve 31. Both the pressure of the vapor pipe 12 (internal pressure of the fuel tank 11) and the pressure of the purge pipe 14 (internal pressure of the canister housing 10a) can be detected. Reference numeral 31a in FIG. 1 is an actuator of the three-way valve 31 of an appropriate type such as a solenoid or a negative pressure actuator. The actuator 31a is connected to the output port 26 of the control circuit 20 via a drive circuit (not shown), switches the three-way valve 31 in response to a signal from the control circuit 20, and connects the detection end of the pressure sensor 30 to the vapor pipe 12 or. Connect to the purge pipe 14.

A method for detecting an abnormality in the evaporation device using the pressure sensor 30 of this embodiment will be described later. By the way, in the present embodiment, the abnormality of the evaporation device is detected and the alarm lamp is turned on to notify the driver of the abnormality of the device as described later, but the abnormality is not repaired only by notifying the abnormality. Evaporative fuel will continue to be released into the atmosphere until the repair of the device is completed. Therefore, in this embodiment, the amount of the evaporated fuel generated in the fuel tank 11 is reduced to reduce the evaporated fuel released to the atmosphere.

As described above, during operation of the engine, the fuel is
Of the fuel supplied from the pump 70 to the fuel injection valve 7,
Excess fuel that was not actually injected from the fuel injection valve
It is recirculated to the fuel tank 11 from the fuel pipe 73. This
Surplus fuel passes through hot parts in the engine room
It is heated to a high temperature. Also, the fuel pump 7
The rated discharge flow rate Q of 0 is the maximum fuel consumption Q of the engine.₁Against
And a big margin Q ₂Is set to the amount added.
On the other hand, in normal driving, the fuel consumption Q of the engine_CIs the maximum value Q
₁Much less than the fuel tank during normal driving
11 for the above Q ₁And Q_CThe margin Q₂Amount added
Will be recirculated. Therefore, during engine operation
A large amount of heat flows into the tank 11 and fuel in the tank
The oil temperature rises.

When the temperature of the fuel oil rises, the amount of the fuel that evaporates also increases. Therefore, when the evaporation device is abnormal, the higher the fuel oil temperature, the larger amount of the evaporated fuel will be released to the atmosphere. Therefore, if the temperature of the fuel oil in the fuel tank can be lowered when the evaporation device is abnormal, the amount of evaporated fuel released to the atmosphere can be reduced. For this purpose, it is conceivable to provide a cooling device in the fuel tank to cool the fuel oil, but this is not practical from the viewpoint of complication of the device and cost increase.

Therefore, in this embodiment, when the evaporation device is abnormal, the temperature of the fuel oil in the tank is lowered by reducing the amount of high temperature surplus fuel flowing back to the fuel tank.
The fuel oil temperature in the tank is determined by the balance between the amount of heat that flows in due to the recirculating excess fuel and the amount of heat that is released from the tank due to heat dissipation to the atmosphere. By reducing the amount of heat, the fuel oil temperature becomes balanced on the low temperature side, and the fuel oil temperature in the tank drops.

That is, in the present embodiment, the control circuit 20 switches the drive circuit 80 of the fuel pump 70 to reduce the pump drive voltage to a predetermined voltage when an abnormality is detected in the evaporation device. As a result, the pump discharge flow rate decreases, and the amount of surplus fuel that flows back from the fuel injection valve 7 to the tank decreases. In this embodiment, the discharge flow rate of the fuel pump 70 is reduced within a range that does not hinder the operation of the engine when the evaporation device is abnormal. For example, in order to enable operation at the maximum engine output, even when the evaporation device is abnormal, the fuel injection valve 7 is supplied with an amount of fuel equal to the maximum engine fuel consumption.
Can be supplied to Therefore, in this embodiment, when the evaporation device is abnormal, the discharge flow rate Q of the fuel pump 70
Is reduced to an amount equal to the maximum engine fuel consumption Q ₁ . That is, when the evaporation device is abnormal, the fuel pump 7 is provided by the above-mentioned margin Q _{2 as} compared with the normal time.
The discharge amount of 0 is reduced.

FIG. 3 shows a drive circuit 80 for the fuel pump 70.
3 is a circuit diagram showing the configuration of FIG. In the figure, 81 is a switching relay for switching the pump drive voltage. The relay 81 has contacts a and b that can be switched depending on whether the exciting coil 81c is energized or not. The contact a is directly connected to the drive motor of the fuel pump 70, and the contact b is a resistor 82.
It is connected to the drive motor of the fuel pump 70 via.

The input terminal B of the relay 81 is connected to the battery via the main switch of the engine (not shown). Reference numeral 83 in the figure denotes a switching transistor. The collector of the transistor 83 is connected to the exciting coil of the relay 81, and the emitter is grounded. The base of the transistor 83 is connected to the output port 26 of the control circuit 20.

When no abnormality is detected in the evaporation device, the control circuit 20 outputs the transistor 83 from the output port 26.
The low level signal is output to the base of the transistor, the transistor 83 is not conductive, and no current flows through the exciting coil 81c.
Therefore, when the engine main switch is turned on, the contact a is closed, and the current from the battery flows directly to the fuel pump 70 drive motor without passing through the resistor 82. As a result, the battery voltage is directly applied to the drive motor of the fuel pump 70, and the fuel pump 70 discharges the fuel at the rated flow rate.

On the other hand, when an abnormality is detected in the evaporation device, the control circuit 20 outputs a high level signal from the output port 26 to the base of the transistor 83. As a result, the transistor 83 becomes conductive, and a current flows through the exciting coil 81c to make contact b
, The current from the battery flows through resistor 82 and the drive voltage of the fuel pump 70 drive motor is lower than the battery voltage. Therefore, the fuel pump 70
The discharge flow rate of is lower than the rated flow rate. The resistance value of the resistor 82 is set to a value necessary to reduce the discharge amount of the fuel pump 70 to an amount equal to the engine maximum fuel consumption amount Q ₁ .

Next, the abnormality detection of the evaporation device using the pressure sensor 30 of this embodiment will be described. In this embodiment, three evaporative device abnormalities are detected: tank leak, canister leak, and purge control valve close stick. It should be noted that the abnormality of the evaporation device to be detected is not limited to the above three, and other abnormality may be detected as long as there is a possibility that vaporized fuel may be released into the atmosphere.

Hereinafter, a method for detecting the above-mentioned three evaporation device abnormalities of the present embodiment will be briefly described. Detection of Tank Leakage In this embodiment, the presence / absence of tank leak abnormality is detected by the same method as in the above-mentioned JP-A-6-26408.

In this embodiment, the internal pressure control valve 16 of the canister 10 keeps the internal pressure of the fuel tank 11 below a predetermined pressure (for example, atmospheric pressure plus 250 mmAq). Therefore, when the temperature of the fuel oil in the fuel tank 11 rises after the engine is started, the internal pressure of the tank rises due to the evaporated fuel and the fuel pressure is maintained near the above predetermined pressure. On the other hand, when the engine is cold-started, the temperature inside the fuel tank 11 is lowered, and the pressure inside the tank 11 becomes lower than atmospheric pressure due to the decrease in fuel oil vapor pressure. In this case, when the internal pressure of the tank 11 decreases, the atmospheric air is introduced into the tank via the atmospheric valve 18 and the pressure equalizing valve 17 of the canister 10, but the internal pressure of the tank 11 is atmospheric pressure according to the operating pressure set values of these valves. Maintained near negative pressure. Further, after the engine is started, the level of the fuel oil in the tank is lowered by the operation of the fuel pump 70. Therefore, when the engine is started in the cold state, the tank internal pressure temporarily becomes a negative pressure.

That is, when the engine is cold-started, the tank internal pressure is a negative pressure near the atmospheric pressure when the engine is started, and is temporarily negative after the engine is started. As the oil temperature rises, the tank internal pressure rises to near the set value of the internal pressure control valve 16. If the temperature of fuel oil in the tank is high at the time of starting when the engine is restarted in a short time after the engine is stopped, the tank internal pressure is higher than the atmospheric pressure after the engine is started. The set pressure of the control valve is reached.

However, when the tank 11 is leaking, the inside of the tank 11 is directly communicated with the atmosphere through the leaking portion, so that the internal pressure of the tank 11 is maintained near the atmospheric pressure regardless of the fuel oil temperature. . In this embodiment, the presence or absence of tank leakage is detected from the change in the internal pressure of the fuel tank 11 after the engine is started by the following method.

After starting the engine, the control circuit 20 switches the three-way valve 31 to connect the detection end of the pressure sensor 30 to the vapor pipe 12. Since the internal pressure of the vapor pipe 12 is equal to the internal pressure of the fuel tank 11, the pressure sensor 30 thereby detects the internal pressure of the tank 11. Next, the control circuit 20 monitors the tank 11 internal pressure P detected by the pressure sensor 30 until a predetermined time (for example, about 5 minutes to 20 minutes) elapses from the engine start time, and the tank 11 internal pressure is monitored during this predetermined time. Is equal to or more than the first predetermined value P ₁ or less than or equal to the second predetermined value P ₂ is determined.

Here, the first predetermined value P ₁ is the canister 1
The positive pressure is slightly lower than the set value (250 mmAq) of the internal pressure control valve 16 of 0, and the second predetermined value P ₂ is a negative pressure slightly lower than the atmospheric pressure. The control circuit 20 determines that the tank 11 is leaking when the tank internal pressure P never becomes higher than the first predetermined value P ₁ or lower than the second predetermined value P ₂ within the predetermined time. judge.

As described above, when the tank 11 is not leaked, the internal pressure of the tank becomes a negative pressure once during the cold start and then rises to the vicinity of the set value of the internal pressure control valve 16, and In the case of a high temperature start, the internal pressure control valve 16 rises to near the set value in a short time after the start. Therefore, if the tank internal pressure is never higher than P ₁ or lower than P ₂ even after a lapse of a predetermined time after the engine is started, it is considered that the tank is leaking.

Further, by performing the above detection, it is possible to detect not only the tank 11 but also the presence or absence of leakage of the vapor pipe connecting the tank 11 and the canister 10 at the same time. Detection of Canister Leakage Canister leak is detected by a change in the pressure inside the canister before and after the purge control valve 15 is opened.

When the purge control valve 15 is closed, the internal pressure of the canister housing 10a is higher than the set pressure of the atmospheric valve 18,
Moreover, the pressure is kept within a range not higher than the set pressure of the atmosphere release valve 19. However, when the purge control valve 15 is opened during the engine operation to perform the purge, the canister housing 10a
Since the intake negative pressure on the downstream side of the throttle valve 6 acts on the inside through the purge passage 14, the inside of the housing 10a becomes a negative pressure.

In the present embodiment, the control circuit 20 detects the pressure change in the canister housing before and after the opening of the purge control valve 15 when the purge execution condition is first satisfied and the purge control valve 15 is opened after the engine is started. When the pressure change is less than a predetermined amount, it is determined that the canister is leaking. That is, the control circuit 20 switches the three-way valve 31 after the engine is started and connects the detection end of the pressure sensor 30 to the purge pipe 14. Since the pressure in the purge pipe 14 is equal to the pressure in the canister housing 10a, the pressure in the canister housing 10a is detected by this.

After the engine is started, the control circuit 20 drives the actuator 15a of the purge control valve 15 to open the purge control valve 15 when the engine reaches a predetermined operating condition and the purge execution condition is satisfied. Here, the purging execution conditions are, for example, that the engine cooling water temperature is equal to or higher than a predetermined value (engine warming up is completed), the engine air-fuel ratio is feedback-controlled to the target air-fuel ratio (engine by purging). The air-fuel ratio is not disturbed), the engine intake air amount is equal to or more than a predetermined value, the fuel cut is not being executed, and so on.

When the purge execution condition is first satisfied after the engine is started and the purge control valve 15 is opened, the control circuit 20 causes the pressure sensor 30 to set the pressure P _{3 in} the canister before the purge control valve 15 is opened. The canister internal pressure P ₄ after opening the valve is detected, and if P ₄ −P ₃ is smaller than a predetermined value, it is determined that the canister leakage has occurred. By performing the above detection, not only the leak of the canister housing 10a but also the leak of the purge pipe 14 can be detected.

Detection of Close Stick of Purge Control Valve Whether or not the purge control valve has a close stick is determined by forcibly opening and closing the purge control valve 15 during execution of the purge and detecting the pressure change in the purge pipe 14 during opening and closing. to decide. That is, the control circuit 20 performs an operation of forcibly closing the purge control valve 15 during execution of the purge (during the purge control valve opening), and then opening the valve. At this time, the control circuit 20 switches the three-way valve 31 to connect the detection end of the pressure sensor 30 to the purge pipe 14.

If the purge control valve 15 is normally opened and closed according to the signal from the control circuit 20, the purge control valve 15
As the throttle valve 6 opens and closes, the purge pipe 1
4, the intake pipe negative pressure acting on 4 is intermittent, so the pressure sensor 30
The pressure of the purge pipe 14 detected in step fluctuates. Control circuit 2
0 monitors the purge pipe pressure during the forced opening / closing operation of the purge control valve 15 and determines that the purge control valve 15 has stuck when the magnitude of the change in the purge pipe pressure is less than or equal to a predetermined value.

The control circuit 20 performs the above abnormality detection after the engine is started. If any one of the above is detected, the alarm is turned on to notify the driver of the abnormality and the fuel is also detected. A high level signal is output to the base of the transistor 83 of the drive circuit 80 of the pump 70 to reduce the discharge flow rate of the fuel pump. If the evaporation device abnormality from the above occurs, the evaporated fuel may be directly discharged to the atmosphere in any case. However, since the fuel oil temperature in the fuel tank decreases as described above by reducing the fuel pump discharge flow rate when the above abnormality occurs, the amount of evaporated fuel generated in the tank decreases and is released to the atmosphere. The amount of evaporated fuel is reduced.

[0052]

As described above, the fuel pump control apparatus of the present invention reduces the discharge flow rate of the fuel pump when the abnormality of the fuel vapor emission restraining apparatus is detected. This has an excellent effect of being able to reduce the amount of evaporated fuel released to the atmosphere at the time of abnormality.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of a vehicle internal combustion engine to which the present invention is applied.

FIG. 2 is a diagram illustrating the structure of the canister of FIG.

FIG. 3 is a circuit diagram showing a configuration of a drive circuit of a fuel pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 2 ... Intake passage 6 ... Throttle valve 10 ... Canister 11 ... Fuel tank 12 ... Vapor piping 14 ... Purge piping 15 ... Purge control valve 20 ... Control circuit 31 ... Three-way valve 70 ... Fuel pump 80 ... Fuel pump drive circuit

Claims (1)

[Claims] 1. An evaporative emission control device having a canister for adsorbing fuel vapor from an internal combustion engine fuel tank and a purge device for purging fuel adsorbed by the canister into an engine intake passage under predetermined engine operating conditions. An abnormality detecting means for detecting an abnormality in the evaporated fuel emission suppressing device; and a fuel from the fuel tank to the engine when the abnormality detecting device detects an abnormality in the evaporated fuel emission suppressing device. A fuel pump control device comprising: a discharge amount reducing means for reducing a discharge flow rate of a supplied fuel pump.