JPH051387B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an evaporated fuel control device for an internal combustion engine.

(Background and prior art) In general, in internal combustion engines for automobiles, as part of exhaust gas countermeasures, the evaporative gases generated in the fuel tank, etc. (mainly harmful HC components) are prevented from being released into the atmosphere. It is equipped with an evaporative fuel control device that allows the fuel to flow back into the engine for combustion processing.

Conventionally, as this type of evaporative fuel control device, although it is an engine equipped with an electronically controlled fuel injection device, for example,
There is one as shown in the figure (see Japanese Patent Laid-Open No. 143155/1983).

Air sucked from an air cleaner 1 first passes through an air flow meter 2, the flow rate is measured, and then passes through a throttle chamber 4 equipped with a throttle valve 3, and then from an intake manifold 5 to the engine body 6 for each combustion chamber. supplied to the chamber.

The air chamber 8 of the fuel tank 7, which is the fuel evaporation source of the engine, and the storage chamber 10 filled with an adsorbent such as activated carbon of the canister 9 are connected by a passage 12 having a separator 11 in the middle. Evaporated fuel generated in the fuel tank 7 after engine operation is stopped is sent to the canister 9, where it is temporarily adsorbed and stored.

Further, the storage chamber 10 of the canister 9 and the intake passage (intake manifold) 5 downstream of the throttle valve 3 are connected by an evaporated fuel supply passage 13, and the supply passage 13 is connected to the intake passage 5 downstream of the throttle valve 3. The conduction is controlled by a diaphragm type purge control valve 14 which opens during partial load operation when the negative pressure of the purge becomes strong.

That is, the purge control valve 14 responds to the negative pressure (VC negative pressure) near the throttle valve 3 introduced into the pressure chamber 15 via the pressure signal passage 16, and the pressure chamber 15 responds to the negative pressure (VC negative pressure) introduced into the pressure chamber 15 through the pressure signal passage 16. When the negative pressure inside increases, the diaphragm 17 moves upward in the figure,
As a result, the valve body 18 integrated with the diaphragm 17
opens the valve port 19 of the vaporized fuel supply passage 13 mentioned above.

Therefore, when the throttle valve 3 is controlled to close in the low and medium load range of the engine and the pressure near the throttle valve 3 in the intake passage 5 becomes high negative pressure, the purge control valve 14 is opened as described above. evaporated fuel supply passage 13
is conductive.

As a result, suction negative pressure downstream of the throttle valve 3 acts on the storage chamber 10 of the canister 9 through the supply passage 13, and this suction negative pressure causes the adsorbed fuel in the storage chamber 10 to pass through the filter material 20 of the canister 9. The air is introduced into the intake passage 5 through the supply passage 13 along with the atmospheric air, and is thereby supplied to each combustion chamber of the engine body 6 for combustion processing.

In this way, the evaporated fuel is burned as appropriate depending on the operating state of the engine, so that problems such as air pollution caused by the evaporated fuel being released into the atmosphere do not occur.

In the figure, reference numeral 21 denotes an electromagnetic fuel injection valve that is driven and controlled by a control circuit 22, which will be described later, to inject the fuel required by the engine.

That is, the control circuit 22 calculates the basic fuel injection amount (pulse width) based on the intake air amount signal input from the air flow meter 2 and the engine rotation speed signal input from the ignition coil (not shown).
Furthermore, this is connected to a temperature sensor 23 that detects the intake air temperature.
After correcting the position of the throttle valve 3 according to the operating state of the engine based on the signal from the throttle valve switch 24, etc., which detects the position of the throttle valve 3, a pulse signal (drive signal) is output to the fuel injection valve 21 in synchronization with the engine rotation. do. As a result, the amount of fuel required by the engine is injected from the fuel injection valve 21, and a mixture having a predetermined air-fuel ratio is supplied to the engine body 6.

However, in such a conventional evaporative fuel control device, the purge control valve 14 controls the purge (removal) of evaporative fuel in the canister 9 using the VC negative pressure of the throttle chamber 3. Since the system was designed to introduce evaporated fuel from the canister 9 to the intake manifold 5 in the low and medium load range of the engine, the throttle valve 3 could be suddenly operated under conditions where a large amount of evaporated fuel was stored in the canister 9 due to flame heating. When this is done, a large amount of evaporated fuel is instantaneously supplied to the engine body 6, causing the problem that the air-fuel ratio becomes overrich and the engine stalls.

(Object of the Invention) The present invention has been made in view of such conventional problems, and an object of the present invention is to effectively avoid engine stalling caused by evaporated fuel under flaming heat.

(Structure and operation of the invention) In order to achieve the above object, the present invention provides an evaporative fuel control device as described above, which includes a solenoid valve that controls the opening/closing of the pressure signal passage or the evaporative fuel supply passage of the purge control valve, and A temperature sensor to detect the intake air flow rate and a flow rate sensor to detect the intake air flow rate are provided, and when the intake air temperature is above the set value and the intake air flow is below the set value based on the signals from the above two sensors, the electromagnetic valve is closed. A control circuit that outputs a signal is provided, and the purge control valve is forcibly closed or the evaporated fuel supply passage is cut off in an operating region where the amount of intake air is small under flaming heat.

(Example) Next, an example of the present invention will be described using FIG. 2, but the same members as in FIG.

In this embodiment, first, a solenoid valve 25 is provided in the middle of a pressure signal passage 16 that connects the pressure chamber 15 of the purge control valve 14 and the vicinity of the throttle valve 3 of the throttle chamber 4 to control the opening and closing of the passage 16. .

Similarly to the fuel injection valve 21, the solenoid valve 25 is driven and controlled by a signal from the control circuit 22.

In other words, the control circuit 22 controls the fuel injection valve 21
When an engine operating state in which the intake air temperature is above the set value and the intake air flow is below the set value is detected based on the signals from the temperature sensor 23 and air flow meter 2 that have been input in advance for driving, the solenoid valve 25 is energized, etc. It is designed to close this using a lever.

Due to this configuration, in an operating region where the amount of intake air is small under flaming heat (for example, when the intake air temperature is 33° C. or higher), the solenoid valve 25 is closed by the signal from the control circuit 22 as described above, so that the pressure signal Passage 16 is blocked.

This causes the purge control valve 14 to close its pressure chamber 1.
Since no VC negative pressure acts on 5, the valve is closed and the vaporized fuel supply passage 13 is cut off.

As a result, vaporized fuel is not purged from the canister 9 into the operating range, preventing the air-fuel ratio from becoming overrich due to the vaporized fuel being purged into the operating range, thereby preventing engine stalling.

On the other hand, when the intake air amount increases and exceeds the set value from the above-mentioned state, or when the intake air temperature decreases and falls below the set value, the solenoid valve 25 is opened with a certain time delay, and the pressure Signal path 16 is rendered conductive.

As a result, the purge control valve 14 opens and closes according to the VC negative pressure, and as before, it opens in the low and medium load range where the VC negative pressure increases, and purges the evaporated fuel from the canister 9 into the intake manifold 5. The combustion process is then carried out in the engine body 6. Of course, the same effect is performed even if the above-mentioned conditions are present from the beginning.

In this embodiment, the pressure signal passage 16 is opened and closed by the electromagnetic valve 25 described above, but it goes without saying that the evaporative fuel supply passage 13 may also be controlled to open and close. Further, according to this embodiment, since the general control circuit 22 can be modified and used, there is an advantage that the cost can be reduced.

(Effects of the Invention) As explained above, according to the present invention, in an operating region where the amount of intake air is small under flaming heat, the purge control valve is forcibly closed or the evaporative fuel supply passage is cut off, and the canister Since the purge of evaporated fuel to the intake system is stopped in the above-mentioned operation range, over-richness of the air-fuel ratio can be prevented, and engine stalling can be effectively avoided.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional example, and FIG. 2 is a schematic diagram of an embodiment of the present invention. 7... Fuel tank, 9... Canister, 3... Throttle valve, 5... Intake manifold, 13... Evaporated fuel supply passage, 14... Purge control valve, 16... Pressure signal passage, 25... Solenoid valve, 23... Temperature sensor, 2... Air flow meter, 22...control circuit.

Claims (1)

[Claims] 1. A canister that stores evaporated fuel generated in a fuel tank, etc., an evaporated fuel supply passage that connects this canister and the intake passage downstream of the throttle valve, and a evaporated fuel supply passage that responds to the negative pressure in the intake passage near the throttle valve. An evaporative fuel control device for an internal combustion engine, comprising: a purge control valve that controls opening and closing of the purge control valve; and a flow rate sensor that detects the intake flow rate, and a control circuit that outputs a close signal to the solenoid valve when the intake air temperature is above a set value and the intake flow rate is below the set value based on signals from both of the above sensors. An evaporated fuel control device for an internal combustion engine, characterized in that it is provided with: