JPH0438907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an engine in which evaporated fuel in a fuel tank is supplied to an intake system, in which the air-fuel ratio of the air-fuel mixture is prevented from changing due to the evaporated fuel. The present invention relates to an air-fuel ratio control device.

Car fuel tanks are generally used to store fuel to be supplied to the engine, but the upper space of the fuel tank is filled with evaporated volatile fuel, and the pressure is high. If this happens, there is a risk that the tank will explode, so it is necessary to release the evaporated fuel outside the tank. in this case,
One possible method is to release the evaporated fuel directly into the atmosphere, but this method has the drawbacks of fuel loss and air pollution.

Therefore, as one of the conventional fuel tanks, the evaporated fuel in the tank is temporarily accumulated in a canister installed outside the tank, and then it is supplied to the engine intake system via the evaporator passage by the engine's intake negative pressure. There is a system that prevents tank damage by releasing evaporated fuel outside the tank, and also prevents fuel loss and air pollution problems (Tokuko Showa).
(See Publication No. 47-21842).

Incidentally, the amount of evaporation of fuel in the fuel tank of an automobile changes depending on the driving conditions of the automobile and the outside temperature. For example, while driving, the wind blows against the fuel tank, so the tank does not get too hot, and the fuel in the tank does not evaporate in large amounts. When the vehicle is parked, the fuel tank becomes hot and a large amount of fuel evaporates. If a large amount of fuel evaporates like this, in a conventional fuel tank, most of the evaporated fuel will accumulate in the canister, and when the engine is started in this condition,
A large amount of evaporated fuel will be supplied to the engine's intake system. As a result, the air-fuel mixture is relatively small,
That is, the fuel became rich, causing misfires, and the exhaust gas contained a large amount of unburned gases such as HC and CO.

This invention was made in view of the above-mentioned conventional problems, and includes an on-off valve provided in the evaporator passage upstream of the canister, and when the pressure upstream of the on-off valve reaches a predetermined value or higher, the on-off valve opens and The longer this is based on the valve opening time, that is, the greater the amount of vaporized fuel supplied to the intake system, the more the air-fuel ratio is adjusted by the air-fuel ratio adjustment device to increase the air-fuel ratio. It is an object of the present invention to provide an air-fuel ratio control device that can reduce the content of unburned gas in exhaust gas by maintaining it at an appropriate value.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an air-fuel ratio control device according to an embodiment of the present invention. In the figure, 1 is the intake passage of the engine, and the upstream end of the intake passage 1 is connected to the air cleaner 2.
A throttle valve 3 which is opened in conjunction with an accelerator pedal (not shown) is disposed in the middle of the intake passage 1, and a ventilator portion 4 is formed upstream of the throttle valve 3. One end of a fuel supply passage 5 is open and provided in this ventilate portion 4, and the other end of the passage 5 is connected to a float chamber of a carburetor (not shown). 7 is now being delivered.

In addition, one end of the evaporator passage (evaporated fuel passage) 8 is located on the upper surface of the fuel tank 6.
The other end of the passage 8 is connected to the downstream side of the throttle valve 3 of the intake passage 1,
The evaporator passage 8 guides evaporated fuel in the fuel tank 6 to the intake passage 1. A canister (accumulation member) 9 for temporarily accumulating evaporated fuel is interposed in the middle of this evaporator passage 8.
An atmosphere introduction passage 10 whose one end is open to the atmosphere is connected to the bottom surface of the canister 9.

An air passage 12 is formed in the intake passage 1 by a partition wall 11, bypassing the ventilary part 4 and the throttle valve 3, and an air-fuel ratio adjustment valve (air-fuel ratio adjustment valve) for opening and closing the air passage 12 is provided in the middle of the air passage 12. device) 13 is installed. On the other hand, a solenoid valve (opening/closing valve) 14 is disposed upstream of the canister 9 in the evaporator passage 8 to open and close it.
Further upstream thereof is a pressure sensor 15 that detects the pressure inside the evaporator passage 8 upstream of the solenoid valve 14.
A detection signal a from the pressure sensor 15 is applied to an arithmetic circuit 16. This arithmetic circuit 16
applies a valve opening signal b to the solenoid valve 14 when the pressure upstream of the solenoid valve 14 exceeds a predetermined value, and a signal d applied when the ignition switch or starter switch is turned on.
A control signal c is sent to the air-fuel ratio adjustment valve 13 by
is now being added.

Figure 2 shows the pressure sensor 15 and the calculation circuit 16.
In the pressure sensor 15, 17 is a diaphragm device;
The pressure on the upstream side of the canister 9 in the evaporator passage 8 is introduced into the first chamber 17a by a pressure introduction passage 18. A spring member 17d is disposed in the second chamber 17b of the diaphragm device 17 to urge the diaphragm 17c upward in the figure, and a contact 17e is fixed to the surface of the diaphragm 17c on the second chamber 17b side, and the contact 17e is connected to the ground. Lead wire 1 between
A battery 20 is connected by 9. Further, a contact 17f is fixed on the inner surface of the second chamber 17b opposite to the contact 17e, and a lead wire 21 is connected to the contact 17f. Therefore, the diaphragm 17c is pushed downward by the pressure inside the evaporator passage 8 against the spring force of the spring member 17d, and both the contacts 17e and 17f come into contact with each other, and the current in the battery 20 is transferred to the lead wires 19 and 17f. Contact 17e,
17f and the lead wire 21, the pressure sensor 15 outputs a detection signal a.

Further, in the arithmetic circuit 16, 22 is an oscillator that oscillates at a constant frequency, 23 is a first AND circuit having two inputs: the detection signal a of the pressure sensor 15 and the output of the oscillator 22, and 24 is the output of the oscillator 22, which will be described later. A second circuit whose two inputs are the output of the drive circuit 27
The AND circuit 25 is an up-down counter that counts up the output of the first AND circuit 23 and counts down the output of the second AND circuit 24. Further, 26 is a relay operated by a signal d from an ignition switch or a starter switch, 26a is its relay coil, 26b
is the relay contact. 27 is the relay contact 2
6b is a drive circuit connected to the output of the up-down counter 25, and when the arithmetic circuit 16 receives the detection signal a of the pressure sensor 15, it applies it to the solenoid valve 14 as a valve opening signal b, and the circuit 16 The output of the drive circuit 27 is applied to the air-fuel ratio adjusting valve 13 as a control signal c.

Next, the operation will be explained.

When the engine is stopped, fuel evaporates and fills inside the fuel tank 6 due to the influence of outside air temperature, etc., and when the pressure exceeds a predetermined value, the diaphragm 17c in the pressure sensor 15 resists the spring force of the spring member 17d. The contacts 17e, 1 are pushed downward.
7f makes contact, so the pressure sensor 15 generates a detection signal a. The arithmetic circuit 16 receives this detection signal a.
In response, a valve opening signal b is generated, and the solenoid valve 14
is open while receiving the valve opening signal b. The evaporated fuel in the fuel tank 6 is then led to the canister 9 via the evaporator passage 8 and accumulated there.
At the same time, in the arithmetic circuit 16, the first
The AND circuit 23 outputs the output pulse of the oscillator 22 as is while the detection signal a of the pressure sensor 15 is applied, and the counter 25 counts up the number of pulses to measure the opening time of the solenoid valve 14. . At this time, since the signal d is not applied to the relay 26, the relay contact 26
b is open, the output of the counter 25 is not applied to the drive circuit 27, and the output of the second AND circuit 24 remains constantly at "0".

In this way, the evaporated fuel is transferred to the fuel tank 6.
When the pressure drops to a predetermined value or less, the diaphragm 17 in the pressure sensor 15
c is deformed and moved upward by the spring force of the spring member 17d, causing the contacts 17e and 17f to separate, and the pressure sensor 15 stops outputting the detection signal a, which causes the arithmetic circuit 16 to output the valve opening signal b. , the solenoid valve 14 is closed, and since the output of the first AND circuit 23 in the arithmetic circuit 16 becomes "0", the counter 25 stops its counting operation.

In this way, when the engine is stopped, whenever the pressure inside the fuel tank 6 exceeds a predetermined value, the solenoid valve 14 opens, and the evaporated fuel is discharged from the tank 6 and accumulated in the canister 9.
measures the opening time of the solenoid valve 14.

When the engine is started in such a state, air from the air cleaner 2 is sucked into the intake passage 1 in an amount corresponding to the opening degree of the throttle valve 3 by the action of the engine's intake negative pressure. The intake air is mixed with fuel from the fuel supply passage 5 in the ventilate section 4, and is taken into the engine. At that time, a large amount of evaporated fuel accumulated in the canister 9 is also drawn into the intake passage 1 by the effect of the intake negative pressure, so the air-fuel ratio of the mixture becomes smaller than the appropriate value, that is, becomes rich. There is a risk. However, in this case, in this device, the arithmetic circuit 16
, the relay 26 is actuated by the signal d from the ignition switch or the starter switch, and its relay contact 26b is closed, and the drive circuit 27 is activated.
receives the output of the counter 25 and generates a signal according to the magnitude of the output, the second AND circuit 24 outputs the output pulse of the oscillator 22 as is while there is an output of the drive circuit 27, and the counter 25 In order to count down the number of pulses, the arithmetic circuit 16 outputs a control signal c according to the output of the counter 25 until the output of the counter 25 becomes "0". Then, the air-fuel ratio adjustment valve 13 receives this control signal c and opens to an opening degree according to the signal c, and air from the air cleaner 2 flows into the downstream side of the throttle valve 3 of the intake passage 1 for the opening time of the solenoid valve 14. That is, since only a flow rate corresponding to the amount of evaporated fuel accumulated in the canister 9 is taken in through the air passage 12, the air-fuel ratio of the air-fuel mixture does not decrease and is maintained at an appropriate value.

Furthermore, while the car is running, the fuel tank 6 is hit by the driving wind, so the temperature of the tank 6 does not rise much.
Vaporized fuel is also not generated in large quantities. In this case, in this device, when the pressure in the fuel tank 6 changes from below a predetermined value to above a predetermined value, the arithmetic circuit 16 receives the detection signal a from the pressure sensor 15 in the same manner as described above, and outputs the valve opening signal b. output and open the solenoid valve 14, and the evaporated fuel flows into the intake passage 1.
Due to the effect of the negative pressure inside, the air is immediately drawn into the intake passage 1 via the evaporator passage 8 and the canister 9. At that time, in the arithmetic circuit 16, the first
The AND circuit 23 outputs a pulse while the detection signal a is present, the counter 25 counts up the pulse, and the drive circuit 27 outputs a control signal c corresponding to the count value of the counter 25.
The AND circuit 24 outputs a pulse while the drive circuit 27 has an output, and the counter 25 counts down the pulse, so the count value of the counter 25 does not become so large after all, and the output of the drive circuit 27 also The value will not be that large. The air-fuel ratio adjustment valve 13 opens slightly in response to the small control signal c, and a small amount of air is sucked into the intake passage 1 via the air passage 12, thereby maintaining the air-fuel ratio of the air-fuel mixture at an appropriate value. When the pressure inside the fuel tank 6 drops below a predetermined value, the pressure sensor 15 stops outputting the signal a, and the arithmetic circuit 16
closes the solenoid valve 14, and in the arithmetic circuit 16, the output of the first AND circuit 23 is “0”.
Therefore, the counter 25 also counts down the output of the second AND circuit 24 and immediately becomes "0".
As a result, the arithmetic circuit 16
will be closed immediately.

In the device of this embodiment as described above, the opening time of the solenoid valve provided in the evaporator passage is measured,
Based on this valve opening time, the longer it is, the more the air-fuel ratio adjustment valve is opened, and the amount of air sucked into the intake passage is adjusted to increase the air-fuel ratio of the air-fuel mixture. Therefore, it is possible to prevent the air-fuel ratio from changing, thereby reducing the occurrence of misfires and greatly reducing the content of unburned gases such as HC and CO in the exhaust gas.

Furthermore, when detecting the flow rate of evaporated fuel, if you attempt to directly detect the flow rate using an air flow sensor, the evaporated fuel will adhere to the air flow sensor, reducing the detection accuracy and durability of the sensor.
While there are problems with the durability and reliability of the device, this device measures the opening time of the solenoid valve and indirectly detects the amount of evaporated fuel, which reduces the durability of the device. performance and reliability are very favorable.

In the above embodiment, an air-fuel ratio adjustment valve that adjusts the amount of intake air is used as the air-fuel ratio adjustment device, but this air-fuel ratio adjustment device may also be used to increase or decrease the amount of fuel supplied to the ventilate section. good.

As described above, according to the air-fuel ratio control device of the present invention, an on-off valve is provided in the evaporator passage upstream of the canister, and when the pressure upstream of the on-off valve becomes equal to or higher than a predetermined value, the on-off valve is opened and the on-off valve is opened. The longer this is based on the valve opening time, that is, the greater the amount of vaporized fuel supplied to the intake system, the more the air-fuel ratio is adjusted by the air-fuel ratio adjustment device. The air-fuel ratio can be maintained at an appropriate value, the amount of unburned gas in the exhaust gas can be greatly reduced, and the durability and reliability of the device can also be improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an air-fuel ratio control device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a pressure sensor and an arithmetic circuit of the device. 1... Intake passage, 6... Fuel tank, 8... Evaporator passage (evaporated fuel passage), 9... Canister, 13... Air-fuel ratio adjustment valve (air-fuel ratio adjustment device), 14... Solenoid valve (on/off valve) ), 15...
Pressure sensor, 16... calculation circuit.

Claims (1)

[Scope of Claims] 1. A fuel vapor passage having one end opened to a fuel tank and the other end opening to an intake passage of an engine, and guiding vaporized fuel in the fuel tank to the intake passage; and the fuel vapor passage. a storage member that is interposed in the storage member and temporarily stores the fuel vapor; an on-off valve that is provided in the fuel vapor passage upstream of the storage member and opens and closes the passage; and a pressure sensor that detects the pressure in the fuel vapor passage upstream of the valve. an air-fuel ratio adjustment device that adjusts the air-fuel ratio of the air-fuel mixture supplied to the engine; and an air-fuel ratio adjustment device that receives the output of the pressure sensor and opens the on-off valve when the pressure in the vaporized fuel passage upstream of the on-off valve is higher than a predetermined pressure. An air-fuel ratio control device comprising: an arithmetic circuit that controls the air-fuel ratio adjusting device to increase the air-fuel ratio as the time period increases, based on the time period during which the on-off valve is open.