JPS5941320Y2 - Fuel evaporation prevention device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a valve in a fuel evaporation prevention device.

In general, when a fuel tank is stopped during driving, high-speed driving, or when left at high temperatures, the fuel in the tank expands and evaporates rapidly due to the influence of heat from the engine, various parts of the car body, and the road surface, resulting in abnormal pressure. It may happen.

For this reason, in the conventional fuel evaporation prevention device, as shown in FIG. The adsorbent in the canister 3 separates the fuel and air, and only the air is released into the atmosphere.The fuel is removed from the adsorbent during the next operation and sent through the passage 5 to the air intake system such as the cleaner, intake port, and intake pipe. 6.

In that case, the canister 3 prevents backflow from the intake system 6 and operates according to the negative pressure in the intake system 6 depending on the opening degree of the throttle valve T and the engine speed, and the pressure inside the tank 1. Tank 1 only when is above a certain level.
It is necessary to introduce evaporated fuel from the tank 1 and to supply air from the atmospheric communication part A of the canister 3 to the tank 1 when the pressure in the tank 1 decreases, and usually each check of the structure satisfies these requirements. Pulp 7', 7#, 71
11 (for example, see Japanese Utility Model Publication No. 52-9454).

And these check pulps 7', 7',? The opening pressure of "' is designed to be a very low value due to the operating characteristics.

In addition, these check pulps have 7' in the middle of the passage 5,
Even if 7'' and 7'# are provided in parallel in the middle of the passage 4, the same configuration can be achieved.

When the amount of fuel in the tank 1 becomes full beyond a certain amount, the amount of fuel filling the upper air chamber 2 increases, and expansion and evaporation due to the above-mentioned heat effects become more intense, leading to the fuel flowing from the passage 4 to the canister 3. Vaporized fuel, or in extreme cases, a large amount of fuel may flow and overflow from the canister and be released into the atmosphere, or if the engine is running, it may be sucked into the intake system and affect the air-fuel ratio. There is.

This causes rich stalling, rough idling, and even an inability to start.

For this reason, the inlet pipe 9 of the fuel tank 1 is generally provided with a pipe 8 for regulating the amount so as not to exceed a design value.

In the figure, 10 is a gas-liquid separation device disposed in the middle of the passage 4, and 11 is an air cleaner.

However, with such conventional fuel evaporation prevention devices, the check pulp 71, 777, 711 may not be completely seated due to impurities impregnated in the fuel or vibrations of the vehicle body, and it is difficult to confirm this. From the check valve 1" during which the air in the air chamber 2 passes through 4 including into the canister during fuel injection.

7"' to the atmosphere through the diameter of the canister 3, and fuel was sometimes injected in an amount exceeding the designed value.

Therefore, during injection, running or stopping, a large amount of evaporated fuel and, in severe cases, a large amount of fuel flow from the air chamber 2 through the passage 4 to the canister 3, and are further sucked into the intake system, affecting the air-fuel ratio. was giving.

In other words, this causes rich stalling, rough idling, and starting difficulty.

In view of the above-mentioned drawbacks of the conventional art, the present invention has been developed to improve and eliminate these drawbacks.

The configuration of the present invention will be explained below according to the embodiments shown in the drawings.

It should be noted that the same reference numerals as in the prior art represent the same members.

As shown in FIG. 2, the present invention has a tank 1 and a canister 3.
(as much as possible in the middle of the passage 4 connecting the check valve 71)
, 711 side is preferable) is provided with a valve 13 equipped with a variable orifice 12 whose opening area changes with a predetermined pressure as a boundary.

This valve 13 is made by cutting out an elastic body 14 made of rubber or plastic into a predetermined shape such as a single letter, a cross, or a U-shape, as shown in FIGS. 3a, b, c and 4. It is constructed by drilling a small hole 15 in the hole.

In this case, the elasticity of the elastic body is selected so that the opening area of the variable orifice 12 does not change, for example, at about the pressure inside the tank when the amount of fuel at the time of fuel injection reaches a designed value.

In such a configuration, the check valve 1 of the canister 3 is now damaged due to impurities contained in the fuel, vibrations of the vehicle body, etc.
', 7'', 7', particularly 71, 711, has a seating failure, and it is assumed that fuel is being injected in this condition.

In the case where the fuel reaches the design value, the air and fuel in the tank 1 are replaced through the design value setting pipe 8 and the inlet vibe 9.

After reaching the design value, the air and evaporated fuel in the air chamber 2 begin to flow out from the passage 4 through the canister 3 to the atmosphere.

However, in the present invention, the flow rates of these air and vaporized fuel components are controlled by the valve 13.

In this case, the valve 13 has a very small opening area /J4L1
5 is open, and the flow rate is insignificant.

Therefore, the fuel cannot be injected by the injection gun after the design value is reached, and the design value can be maintained accurately.

Furthermore, for expansion and evaporation due to normal thermal effects during operation, after high-speed operation, and when stopped due to high-temperature storage, the nominal opening area is sufficient for gas flow.

If the small hole is occluded by a foreign object, the pressure difference will cause the notch in the elastic body to open and allow circulation.

Furthermore, if the fuel expands and evaporates rapidly and the pressure inside the tank 1 becomes abnormal, the notch in the elastic body 14 opens in response to the pressure difference between the air chamber 2 and the canister 3 (equal to atmospheric pressure) side. , the opening area changes in the direction of increasing (third
(see figure).

Therefore, the air and evaporated fuel in the air chamber 2 flow into the canister 3 in an amount corresponding to the pressure difference and are processed.

That is, overflow in the canister 3 can be prevented.1. Normal effects can be obtained.

In addition, when the internal pressure of the tank decreases and the pressure difference becomes large, the atmosphere from the atmosphere communication part A flows into the tank via the check valve 7 or T and valve 13 in the passage between the tank and the canister. Of course, it is necessary to maintain normal pressure inside the tank.

As explained above, the present invention provides a fuel evaporation prevention device that communicates a fuel tank and an intake system via a canister, in which a check valve is provided midway between the fuel tank and the canister to prevent the flow of fuel toward the fuel tank. Since a variable orifice valve made of an elastic body whose opening area changes depending on the local pressure is installed between the check valve and the fuel tank, if fuel is being injected while the check valve is not seated properly, After the fuel injection amount reaches the design value, the air in the upper part of the fuel tank and even the fuel flowing out to the canister can be suppressed by the throttling effect of the variable orifice, and the fuel will not be injected beyond the design value. In addition, it is possible to prevent the problem of filling the canister with liquid fuel.

In addition, since it is a variable orifice, there is no abnormal increase in the pressure inside the fuel tank due to clogging, and when the pressure inside the fuel tank exceeds a predetermined pressure, the opening area of the variable orifice increases, allowing the fuel to escape to the outside through the canister. There is.

[Brief explanation of the drawings] Fig. 1 is a schematic diagram showing the entire conventional fuel evaporation prevention device;
Fig. 2 is a schematic diagram showing the entire fuel evaporation prevention device according to the present invention, and Fig. 3 a, b, and c are examples of the configuration of the elastic body of the valve in the above device of the present invention, and its normal state and predetermined pressure difference. FIG. 4, which shows the above state, is a sectional view of the valve. 13... Valve, 12... Variable orifice, 14... Elastic body.

Claims (1)

[Scope of utility model registration request] In a fuel evaporation prevention device that communicates a fuel tank and an intake system via a canister, a check pulp is provided between the fuel tank and the canister to prevent the flow toward the fuel tank, and a check pulp is provided between the check pulp and the fuel tank. A fuel evaporation prevention device comprising a variable orifice valve made of an elastic body whose opening area changes at a predetermined pressure.