JPS591091Y2 - Engine evaporative fuel treatment device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an evaporative fuel processing device for an engine, in which evaporative fuel generated in a fuel tank is introduced into the intake system of the engine and combusted within the engine.

Several evaporative fuel processing devices for this type of engine have been proposed in the past.

By the way, the amount of evaporated fuel generated tends to increase during idling operation due to the large amount of high-temperature fuel returning near the engine and the fact that the fuel tank is warmed by radiant heat from the exhaust system, but it remains constant. When running under load, the amount of fuel returned decreases,
Since the fuel tank is cooled by the wind while driving, there is a tendency for the amount of evaporation to decrease.

Therefore, as mentioned above, when introducing and processing evaporated fuel into the intake system, a large amount of evaporated fuel is introduced especially during idling, resulting in an overrich air-fuel ratio, resulting in an engine stop due to overrich, and a reduction in purification performance. decline,
There is a problem of heat damage caused by the high temperature of the purification equipment.

Therefore, a system has been proposed that opens the air bypass passage to correct the air-fuel ratio when the pressure in the evaporated fuel passage rises above a set value (see Japanese Utility Model Publication No. 18665/1983). Since the release of evaporated fuel and the opening timing of the bypass air passage do not coincide, there is a problem that the air-fuel ratio becomes overrich when the bypass air passage is in a closed state.

Therefore, this invention solves the above problem by introducing air at the same time when the amount of evaporated fuel increases and introduces it into the intake system, thereby preventing as much as possible the fluctuation of the air-fuel ratio due to the introduction of the evaporated fuel. The basic purpose is to eliminate

At the same time, this invention maintains the evaporated fuel in a compressed state in the fuel tank until the evaporated fuel rises above a certain pressure, especially when the evaporated fuel increases and the pressure rises while the engine is stopped. The second purpose is to store evaporated fuel in a canister or inside the engine to prevent evaporated fuel from escaping into the atmosphere.

Therefore, in the evaporated fuel processing device for an engine according to the present invention, the first on-off valve is provided in the evaporated fuel passage that communicates the upper space of the fuel tank with the intake passage downstream of the carburetor throttle valve, while the carburetor throttle valve is closed. An air bypass passage is provided to connect the upstream and downstream sides of the air bypass passage, and a second on-off valve is provided, and when the pressure in the upper space of the fuel tank rises above a certain value, the first and second on-off valves are connected to the The basic feature is that the devices open simultaneously.

Hereinafter, the present invention will be specifically explained with reference to the illustrated embodiments.

In FIG. 1, 1 is a fuel tank, 2 is an evaporated fuel passage 6 that communicates a condensation tank 1b provided above an upper space 1a of the fuel tank 1 with a downstream side of a throttle valve 5 of a carburetor 4 in an intake passage 3; 9 is an evaporated fuel passage that communicates between the crankcase of the engine E and a canister 8 attached to the upper center of the air cleaner 7 and adsorbs evaporated fuel accumulated in the crankcase into the canister 8; 9 is a passage between the inside of the air cleaner 7 and the intake passage 3; This is an air bypass passage that communicates with the downstream side of the carburetor throttle valve 5 and supplies air to the intake passage 3, bypassing the carburetor 4.

The fuel vapor passage 2 that communicates the upper space 1a of the fuel tank 1 with the carburetor throttle valve 5 of the intake passage 3 includes a fuel tank 1.
A safety valve 10, a first opening/closing valve 11, and a first throttle 12 are provided in order from the side, and a branch passage 13 branched downstream of the first throttle 12 communicates with the crankcase, while a passage connecting to the intake passage 3 communicates with the crankcase. opens with negative intake pressure,
A ventilation valve 14 is provided which closes when the engine is stopped.

Although not specifically shown, the safety valve 10 is a one-way valve that normally communicates with the evaporated fuel passage 2 and introduces the atmosphere when the pressure of the fuel tank 1 abnormally decreases, and a one-way valve that introduces the atmosphere when the pressure of the fuel tank 1 abnormally increases. It is equipped with a one-way valve that releases high pressure to the atmosphere.

Further, in the middle of the evaporated fuel passage 6 which communicates the crankcase and the canister 8, one end thereof is connected to a communication passage 17 which communicates with the air vent pipe 15 of the carburetor 4 via a switching valve 16.

This switching valve 16 communicates the air vent pipe 15 with the float chamber 4a of the carburetor 4 when the engine E is in operation to allow the air vent pipe 115 to perform its original function, and when the engine E is stopped, communicates the air vent pipe 15 with the float chamber 4a of the carburetor 4. Passage 17
The evaporated fuel in the float chamber a is led out to the evaporated fuel passage 17.

On the other hand, a second on-off valve 18 is provided in the middle of the air bypass passage 9, and a second throttle 19 is provided downstream thereof.

Above 1. In this embodiment, the second on-off valves 11 and 18 are solenoid valves, and the first on-off valves 11 and 18 are solenoid valves. Second on-off valve 11, 18
On/off is controlled by a pressure detection valve 20 provided between the safety valve 10 and the first on-off valve 11 of the evaporated fuel passage 2.

This pressure detection valve 20 is composed of a kind of diaphragm device, and one chamber 20b partitioned by a diaphragm 20a communicates with the evaporated fuel passage 2, while the other chamber 20b is partitioned by a diaphragm 20a.
0C has a structure in which a spring 20d is compressed as an atmospheric chamber, and a microswitch 20e is installed which is turned on and off by the deflection of a diaphragm 20a.

This diaphragm pressure detection valve 20 turns on a microswitch 20e by the bias of a diaphragm 20a when the pressure on the fuel tank 1 side reaches a set pressure that is higher than the set load of a spring 20d. 1゜Second on-off valve 1
1.18 is connected to the battery 21, and the 1st and 2nd on-off valves 1
1.18 is excited to open the fuel passage 2 and air bypass passage 9.

Next, the operation of the above structure will be explained.

When the engine is stopped for a long time, the evaporated fuel that accumulates in the upper space 1a of the fuel tank 1 is liquefied in the condensation tank 1b and returned to the fuel tank 1.
The stationary cycle is repeated.

Therefore, the pressure in the evaporated fuel passage 2 does not increase and is maintained in a closed state by the first on-off valve 11.

By the way, immediately after the car is stopped, even if the engine E is stopped, the vaporizer 4 and fuel tank 1 are heated by heat radiation from the engine body and the exhaust system, so the pressure of the evaporated fuel is lower than the set pressure of the pressure detection valve 20. may rise above.

Therefore, in this case, the operation of the pressure detection valve 20 causes the first. The second on-off valve 11, 1B is connected to the battery 21,
The evaporated fuel passage 2 and the air bypass passage 9 are each opened.

As a result, the high-pressure evaporated fuel flows down the evaporated fuel passage 2, but when the engine is stopped, the ventilation valve 1
4 is completely closed, and the high-pressure evaporated fuel flowing down is guided into the crankcase of the engine E through the branch passage 13, and a part of it is adsorbed into the canister 8 through another evaporated fuel passage 6.

At this stage, the switching valve 16 is switched to the carburetor float chamber 4a.
and the communication path 17, and the vaporizer float chamber 4a
The evaporated fuel is also led to the evaporated fuel passage 6, a part of which is accommodated in the crankcase, and a part of which is adsorbed into the canister 8.

Therefore, when the engine E is stopped, the entire amount of vaporized fuel generated is confined within the system and is not released to the outside.
Even if the valve is opened, no air is introduced because no negative intake pressure is applied.

The above state ends as the pressure of the evaporated fuel decreases as the engine body E and the exhaust system cool down.
The first on-off valve 11 is closed again.

On the other hand, when the engine E is started, a negative intake pressure is generated in the intake passage 3, and the ventilation valve 14 is opened by this intake negative pressure.

However, immediately after startup, the pressure of the evaporated fuel is not so high that the pressure detection valve 20 does not operate.
The second on-off valves 11 and 1B are closed.

Therefore, the evaporated fuel on the fuel tank 1 side is transferred to the first on-off valve 1.
1, but the first on-off valve 11
The subsequent evaporated fuel in the evaporated fuel system is drawn to the intake negative pressure and led out to the intake passage 3.

Additionally, the evaporated fuel adsorbed in the canister 8 is also drawn into the intake passage 3 as fresh air is introduced.

If the engine E continues to operate idle or at low load for a long time after starting, the amount of heated fuel returned from the carburetor 4 is large, and the fuel tank 1 is also heated by the exhaust heat. The vaporized fuel pressure on the fuel tank 1 side gradually increases.

When this evaporated fuel pressure exceeds the set pressure of the pressure detection valve 20, the pressure detection valve 20 is activated to cause the first. Second on-off valve 11.
18 will be held at the same time.

As a result, the evaporated fuel passes through the evaporated fuel passage 2 and is discharged from the ventilation valve 14 to the intake passage 3, and at the same time, fresh air bypasses the carburetor 4 and flows from the air bypass passage 9 to the carburetor throttle valve. 5 downstream.

In this case, the amount of vaporized fuel introduced and the amount of bypass air are:
1st each. The diameter of the second throttle 12.19 determines the diameter of the first throttle so that the bypass air amount A exceeds the evaporated fuel introduction amount B at a predetermined ratio, as shown in FIG.
The second throttle aperture is set and adjusted so that the air-fuel ratio does not change much before and after the start of introduction of vaporized fuel.

Note that when shifting to steady operation such as constant speed driving, the pressure of the evaporated fuel gradually decreases due to the driving wind, etc., and the pressure detection valve 2
As a result, the first and second on-off valves 1 are stabilized below the set pressure of 0.
1.1B is closed.

Next, the embodiment shown in FIG. 2 will be described.

In this embodiment, in place of the electromagnetic first and second on-off valves 11.1B shown in FIG. It is characterized in that second on-off valves 22 and 23 are integrally provided.

As shown, the base housing 24 includes a top and side portion.
It has a diaphragm support seat 25, 26 and an upper support seat 25.
The upper casing 28 is fixed with the first diaphragm 27 held therebetween to form the first diaphragm device 29, while the side casing 32 is fixed on the side support seat 26 with the second diaphragm 31 held thereon. As a result, a first diaphragm device 33 is formed.

The upper side of the base housing 24 has a first diaphragm 27 having a ring-shaped protrusion supported at the center of the lower surface of the first diaphragm 27.
The first on-off valve 22 is formed by partitioning the valve body 34 and the cylindrical valve seat 35 provided at the center of the upper part of the base housing 24 into an outer peripheral part 36 and an inner peripheral part 37. , communicates with a communication port 30 that communicates with the fuel tank 1 side.

Further, the negative pressure chamber 38, which has both bottoms formed by the first diaphragm 27 and the upper casing 28, is located upstream of the carburetor throttle valve 5 when it is fully closed, and located downstream of it when the opening is more than the set opening degree. It communicates via a throttle 41 with a negative pressure outlet passage 40 having a negative outlet 39 set as shown in FIG.

42 is a spring compressed within the negative pressure chamber 38.

On the other hand, the lower space of the base housing 24 is located at the inner peripheral portion 3.
The engine E is divided into a chamber 43 serving as a communication passage communicating with the engine E and a communication passage 44 communicating with the crankcase of the engine E, both of which are communicated by a small diameter communication hole 45.

The second diaphragm 31 that partitions the chamber 43 and the atmospheric chamber 47 opened to the atmosphere through the atmospheric opening 46 supports a rod 48 passing through the side casing 32 and supports a conical valve body 49 at its tip. and a valve seat 5 formed between the outer casing 50 and the outer casing 50 fixed to the outside of the side casing 32.
A second on-off valve 23 is formed to open and close the air bypass passage 9', thereby communicating or blocking the air bypass passage 9'.

The valve opening condition in this case is set by the pressure acting on the chamber 43, the spring force of the spring 52 compressed in the chamber 43, and the spring force of the spring 58 compressed in the casing 50 side.

Further, the communication passage 44 has the other end narrowed to a small diameter, and has a rubber-like valve body 54 on the inclined wall surface 53 of the base nozzle 24 that forms the open end, so as to reduce the intake negative pressure. A ventilation valve 55 is provided, which opens under action, and the downstream side of the ventilation valve 55 is connected to the carburetor throttle valve 5 of the intake passage 3 together with the air bypass passage 9' by a passage 57 via a restriction 56 provided in the valve 55. It is connected downstream.

The operation of the embodiment shown in FIG. 2 is basically the same as the operation of the embodiment shown in FIG. 1 except for mechanical and electrical differences, and a description thereof will be omitted for the sake of brevity.

However, in this embodiment, when the carburetor throttle valve 5 is opened to a preset opening degree or higher and the load is medium or higher, the intake negative pressure acting on the negative pressure outlet 39 causes the first diaphragm 27 to
is lifted up against the spring 42, and as a result, the outer circumferential portion 36 and the inner circumferential portion 37 communicate with each other, and the evaporated fuel on the fuel tank 1 side flows from the outer circumferential portion 36 to the inner circumferential portion 31 even if the pressure is low. One chamber 43 is introduced into the intake passage 3 through a path of a continuous communication hole 45, a ventilation valve 55, and a passage 57.

In this case, the pressure in the chamber 43 is low and the second diaphragm 31 is not biased, so air bypass is not performed, but the amount of evaporated fuel introduced is small and the amount of air mixture is large. The effect on the air-fuel ratio can be ignored.

It is preferable that the diameter of the communication hole 45 is smaller than the diameter of the throttle 56 of the ventilation valve 55 so that blow-by gas accumulated in the crankcase is not brought into the chamber 43.

As is clear from the above detailed explanation, the present invention provides a first opening/closing valve in the vaporized fuel passage that communicates the upper space of the fuel tank with the downstream side of the carburetor throttle valve in the intake passage; A second on-off valve is provided in the air bypass passage that communicates the upstream and downstream sides of the first valve, and when the evaporated fuel pressure on the fuel tank side reaches a set value or more, the diaphragm device closes the first valve.
To provide an evaporative fuel processing device for an engine, characterized in that a second opening/closing valve is simultaneously opened to simultaneously supply evaporated fuel and bypass air downstream of a carburetor throttle valve, thereby preventing changes in the air-fuel ratio. It is something.

According to the present invention, therefore, bypass air can be introduced in response to the introduction of evaporated fuel during idling or low-load operation when the evaporated fuel pressure increases, and as the air-fuel ratio becomes overrich. It is possible to prevent engine stall, deterioration of purification performance, and heat damage to the purification device.

[Brief explanation of drawings]

Fig. 1 is a processing system diagram showing one embodiment of an engine evaporative fuel processing device according to the present invention, Fig. 2 is an enlarged explanatory diagram of main parts showing another embodiment, and Fig. 3 is a evaporative fuel processing system according to the present invention. and a graph showing a bypass air supply method. 1... Fuel tank, 2... Vaporized fuel passage, 3... Intake passage, 5... Carburetor throttle valve, 9... Airbinosu aisle, 11...
...First on-off valve, 18...Second on-off valve, 20.
...Diaphragm device, 22.23...
1st. Second on-off valve.

Claims (1)

[Scope of utility model registration request] An evaporated fuel passage that communicates the upper space of the fuel tank with an intake passage downstream of the carburetor throttle valve, a first on-off valve interposed in the evaporated fuel passage, and an air bypass passage that communicates the upstream and downstream sides of the carburetor throttle valve. , when the pressure between the second on-off valve interposed in the air bypass passage, the upper space of the tank, and the first on-off valve rises above a set value, the first on-off valve and the second on-off valve are opened. An evaporative fuel processing device for an engine, characterized in that it is configured with a diaphragm device that