JPH0344226B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to a fuel vapor removal device for improving restartability of an internal combustion engine at high temperatures.

B. Prior Art An internal combustion engine operates normally by being supplied with an air-fuel mixture of an appropriate air-fuel ratio according to the operating state of the engine from an intake passage.

Considering the state after the engine is stopped, the engine remains in a high temperature state for a while after stopping due to residual heat from the exhaust pipe, catalyst, etc. Therefore, the evaporation of the fuel remaining in the float chamber, fuel passage, etc. of the carburetor is promoted, and a portion of it flows from the float chamber through the air vent or flows out from the main nozzle, acceleration nozzle, etc. into the intake passage. As a result, the air-fuel mixture in the intake passage has an excess fuel component. If the engine is restarted at this point, a rich mixture will be sucked into the combustion chamber, resulting in poor restartability.

In order to solve this problem, the invention disclosed in Japanese Utility Model Application Publication No. 57-126558 has been proposed. This system communicates the intake passage with the canister (evaporative fuel collection device) when the engine is stopped, allowing excess fuel components in the intake passage to be absorbed by the canister, making the air-fuel mixture appropriate, and improving restartability. There is.

Furthermore, in the fuel evaporation control device disclosed in Japanese Utility Model Application Publication No. 57-3858, a solenoid valve is provided in the vent passage that communicates the upper space of the carburetor float chamber with the canister, and the solenoid valve is operated only during a predetermined period of time after the engine is stopped. Equipped with a valve control device that opens the valve.

In these conventional techniques, in order to adsorb excess evaporated fuel onto the canister, the evaporated fuel is moved toward the canister due to its diffusion and the difference in specific gravity with air. Therefore, it was necessary to promote the movement of evaporated fuel by lowering the mounting position of the canister.

C. Problems to be Solved by the Invention The above-mentioned conventional technology has a limitation in that the canister must be installed at a low position, and has the disadvantage that there is no flexibility in the arrangement of equipment in the engine room of the automobile. Furthermore, in recent years, the number of front-wheel drive cars, cab-over cars, turbo cars, etc. has been increasing, but the temperature in the engine compartment of these cars is much higher, so the amount of fuel that flows into the intake passage after the engine stops has increased significantly. are doing. In order to respond to such recent trends in automobiles, the conventional techniques described above lack the ability to discharge evaporated fuel and cannot meet the emission capacity required by these automobiles.

The purpose of this invention is to propose a fuel vapor removal device that can solve these problems.

D. Structure of the Invention The fuel vapor removal device of the present invention includes a canister 1
0, one end is the canister 10 and the other end is the intake passage 3
, which has a purge pipe 13 communicating with the vicinity of the throttle valve 8 and an atmospheric opening 14 connected to the canister 10, in which one end opens to the intake passage 3 of the internal combustion engine and the other end communicates with the canister 10. A passage 9, a pump 11 provided in the evaporated fuel passage 9 and discharging evaporated fuel in the intake passage to the canister 10, a check valve 12 that prevents the flow of evaporated fuel in the direction of the intake passage, and a check valve 12 that detects the temperature in the engine room. Temperature switch 17 that operates only when the temperature is high
When the engine is stopped while the temperature switch 17 is operating, the pump 1 is stopped for a certain period of time.
1 and a control circuit section 15 for driving the control circuit 1.

E. Function: When the engine stops at a high temperature, the control circuit drives the pump for a certain period of time to forcibly discharge the evaporated fuel in the intake passage, and the canister absorbs it. The check valve prevents excess air from being drawn into the intake passage from the evaporated fuel passage during engine operation.

The supply of the vaporized fuel adsorbed to the canister to the engine is controlled according to the opening and closing of the throttle valve at the time of restart.

F. Example In FIG. 1, 1 is an engine, 2 is a carburetor attached to the engine via an intake passage 3, and 4 is a carburetor attached to the engine via an intake passage 3.
is an air cleaner. 5 is a float chamber, 6 is an air vent, 7 is a main nozzle, and 8 is a throttle valve. 9 is an evaporative fuel passage whose one end (left end) opens into the intake passage 2, and the other end opens into the canister 10.
A pump 11 and a check valve 12 are provided in series in the middle. 13 has one end connected to the canister 10,
The other end of the purge pipe communicates with the intake passage near the throttle valve, and 14 is an atmospheric opening connected to the canister 10. 15 is a control circuit connected to the pump 11 by an electric wire 16, and 17 is a temperature switch which detects the temperature in the engine room and closes only when the temperature is high.

The control circuit section 15 is composed of the electric circuit shown in FIG. 18 is battery, 19 and 20 are resistance,
21 is Keith Chitsuchi, 22 is NOR gate, 23
is a trigger circuit, 24 is a timer circuit, 25 is a
The AND gate 26 is a transistor and is connected as shown in the figure to form a control circuit.
Note that the location indicated by the arrow +V in the figure is connected to a constant positive voltage. This positive voltage is obtained from the positive terminal of the battery 18 or from a stabilized power supply circuit (not shown).

The operation of the above embodiment will be explained with reference to FIGS. 1 to 3. Since the key switch 21 is closed during engine operation, the output point A of the NOR gate 22 is at a low potential. Also, if the engine temperature is high at this time, the temperature switch 17 is closed. When the key switch 21 is opened to stop the engine in this state, both inputs of the NOR gate become low potential, so the voltage at the output point A rises, and the trigger circuit 23 detects this voltage rise and sends a trigger signal. is applied to the timer circuit 24. The timer circuit 24 is, for example, a circuit such as a monostable multivibrator, and upon application of the trigger signal, it sends out an output for a certain period of time. Therefore, the voltage at the output point B of the AND gate 25 is at a high potential for the predetermined period of time, making the transistor 26 conductive and driving the pump 11. Therefore, the mixture of evaporated fuel and air in the intake passage 3 is sent to the canister 10 by the pump 11, only the fuel component is adsorbed by the canister, and only the air is released into the atmosphere from the atmosphere opening 14. Timer circuit 24 serves to prevent battery 18 from being consumed.

In winter, when the temperature is low, the temperature in the engine room does not rise to a high temperature, so the fuel in each part of the carburetor does not reach a high temperature, and there is little vaporization. Therefore, there is no need to operate the pump 11. Since the temperature switch 17 detects the temperature and opens in such a case, the output point A of the NOR gate 22 becomes a low potential and the pump 11 is not driven.

Next, when the engine is restarted, the air-fuel mixture in the intake passage 3 is drawn into the engine 1, but due to the action of the pump 11 after the engine has stopped, there is no rich mixture in the intake passage, so the air-fuel mixture in the intake passage 3 is sucked into the engine 1. Crab explosion occurred,
Good restart. In this way, when the engine is restarted, the intake passage 3 becomes negative pressure, and this negative pressure acts on the evaporated fuel passage 9 and the purging pipe 13. The check valve 12 is closed by this negative pressure, thereby closing the evaporated fuel passage. Since the negative pressure acting on the purging pipe 13 is transmitted to the canister 10, outside air is sucked in from the atmospheric opening 14, passes through the canister 10 and the purging pipe 13, and flows into the intake passage 3. Due to this air flow, excess fuel adsorbed on the canister 10 is released, and the canister 10
returns to the state before adsorption.

At this time, the amount of fuel released from the canister is
Controlled according to the opening and closing of the throttle valve.

FIG. 4 shows another embodiment of the control circuit section 15.

27 is a buffer amplifier, and 28 and 29 are resistors. 30 is a thermoelectric generating element attached to an exhaust pipe, a catalyst, a muffler, etc. Note that other elements having the same symbols as in FIG. 2 are the same elements.

Each element is connected as shown.

In the control circuit shown in this figure, a timer circuit for operating the pump 11 for a certain period of time after the engine is stopped is not provided, and the thermoelectric generating element 30 performs the function of determining the certain period of time.

When the key switch 21 is closed and the engine is running and the temperature in the engine compartment is high, the temperature switch 17
is closed, and the voltage at the output point A of the NOR gate 22 is at a low potential. Now open the key switch 21 and stop the engine, as shown in Figure 5.
Since the voltage at the output point A of the NOR gate 22 becomes a high potential, the transistor 26 (shown in FIG. 4) becomes conductive.
Pump 11 is driven. The evaporated fuel in the intake passage is then discharged. At this time, the power to drive the pump 11 is provided by the thermoelectric generating element 30. This is advantageous because there is no need to consume battery to drive the pump 11. Further, after the engine is stopped, the exhaust pipe, catalyst, muffler, etc. cool down, the electromotive force of the thermoelectric generator stops, and the operation of discharging evaporated fuel from the intake passage automatically stops.

G. Effects of the Invention Figure 6 shows temporal changes in intake pipe negative pressure during restart. During cranking, the engine speed is low, so the negative pressure in the intake pipe is small, about -150mmHg. When the engine fully explodes and starts, the engine speed increases to the idle speed, and the intake pipe negative pressure rises to about -500mmHg. In the invention of
The time it takes for the intake pipe negative pressure to reach around -500 mmHg has been reduced by more than 3 seconds compared to the conventional device.

As described above, according to the present invention, after the engine is stopped at a high temperature, air is automatically and forcibly scavenged in the intake passage for a certain period of time, and evaporated fuel is adsorbed to the canister. This has the effect of reliably improving restartability even in vehicles where the engine compartment is particularly hot.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram explaining an embodiment of this invention, Fig. 2 is an electric circuit diagram used in Fig. 1, and Fig. 3 is an electric circuit diagram used in Fig. 2.
Figure 4 is a diagram explaining the operation of the circuit in Figure 4, Figure 4 is a diagram explaining the operation of the electric circuit in Figure 4, Figure 6 is a diagram explaining the operation of the electric circuit in Figure 4, and Figure 6 is a diagram explaining the intake pipe negative pressure when restarting the engine. FIG. DESCRIPTION OF SYMBOLS 1... Engine, 2... Carburetor, 3... Intake passage, 9... Evaporated fuel passage, 10... Canister, 11... Pump, 12... Check valve, 15...
Control circuit section, 17...Temperature switch.

Claims (1)

[Claims] 1. A device having a canister 10, a purge pipe 13 having one end communicating with the canister 10 and the other end communicating with the intake passage 3 near the throttle valve 8, and an atmospheric opening 14 connected to the canister 10,
A fuel vapor passage 9 having one end open to the intake passage 3 of the internal combustion engine and the other end communicating with the canister 10, a pump 11 provided in the fuel vapor passage 9 and discharging the vapor fuel in the intake passage to the canister 10, and the intake passage. There is a check valve 12 that prevents the flow from flowing in that direction, a temperature switch 17 that detects the temperature in the engine room and operates only when the temperature is high, and a temperature switch 17 that detects the temperature in the engine room and operates only when the temperature is high. and a control circuit 15 for driving the pump 11 during the fuel vapor removal system of an internal combustion engine.