JPS59173549A - Device for preventing fuel vapor from scattering - Google Patents

Abstract

PURPOSE:To prevent fuel vapor from scattering into the atmosphere, and as well to enhance the power performance of an engine, by disposing a gas separating membrane parting between a fuel vapor introducing space into which fuel vapor from a fuel tank is introduced and an atmospheric space so that condensed fuel is returned into the tank. CONSTITUTION:During rest of an engine fuel vapor generated in fuel tank 1 is introduced into a fuel vapor introduction space 14 in a fuel vapor separating container 3 from a inlet port 4 by way of a vapor passage 2. Then air permeates a gas separating membrane 26 in a gas separating part 12 and enters into an atmospheric space, accompanied with increase in the pressure of the above-mentioned space 14. At this time fuel vapor is inhibited from permeating the gas separating membrane 26, and therefore, is pooled in this space 14. Fuel vapor in the space 14 is finally condensed, and is pooled in a fuel pooling section 18. When the engine is operated so that gas pressure within a gas space in the tank 1 lowers resulting in that a pressure differential across a check valve 8 reaches a predetermined value, the check valve 8 opens so that fuel in a fuel pooling section 18 is returned to the tank 1 through a return passage 5 due to negative pressure of the tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel vapor emission prevention device that prevents fuel vapor generated in a fuel tank of an automobile from escaping into the atmosphere while the engine is stopped.

In the well-known fuel vapor emission prevention device, activated carbon adsorbs fuel vapor generated in the fuel tank while the engine is stopped.
During the next engine operation, fuel vapor is desorbed from the activated carbon, released into the intake passage, and burned in the combustion chamber. In this case, since the fuel components are returned to the intake system, the air-fuel ratio fluctuates and the air-fuel mixture becomes overrich, resulting in deterioration of air-fuel ratio control accuracy, increase in the amount of harmful components in the exhaust, and reduction in power performance due to misfire. This may cause other problems.

An object of the present invention is to provide a fuel vapor diffusion prevention device that can prevent problems caused by the release of fuel vapor into an intake passage.

To achieve this objective, the fuel and vapor diffusion prevention device of the present invention includes a fuel vapor introduction space into which fuel vapor from a fuel tank is introduced, a gas partition membrane that partitions between the atmospheric space and the fuel vapor introduction space, and A return passage is provided for returning condensed fuel that accumulates at the bottom of the fuel vapor introduction space to the fuel tank.

The fuel vapor is thus prevented from passing through the gas separation membrane (sometimes referred to as an oxygen enrichment membrane) and remains in the fuel vapor space, where it eventually condenses and is recovered into the fuel tank via the return passage. Therefore, the air-fuel ratio of the air-fuel mixture is prevented from being disturbed by the release of fuel vapor, and it is possible to prevent deterioration of air-fuel ratio control accuracy, increase in the amount of harmful components in the exhaust gas, and deterioration of power performance.

In the present invention, the adsorbent can be omitted.

The present invention will be described in detail with reference to the drawings.

In FIG. 1, the upper part of the fuel tank 1 is connected through a vapor passage 2 to an inlet 4 at the upper part of the fuel vapor separation vessel 3, and through a return passage 5 to an outlet 6 at the lower part of the fuel vapor separation vessel 3. The vapor passage 2 and the return passage 5 each have
Check valves 7 and 8 are provided in a forward direction from the fuel tank l to the fuel vapor separation container 3 and from the fuel vapor separation container 3 to the fuel tank 1. The fuel vapor separation vessel 3 has an atmosphere port 9 at the bottom.

FIG. 2 shows the inside of the fuel vapor separation vessel 3. The gas separation membrane section 12 extends annularly and partitions a radially outer fuel vapor introduction space 14 from a radially inner central space 16 . The inlet 4 is connected to a fuel vapor introduction space 14,
The central space 16 is connected as an atmospheric space to the outside of the fuel vapor separation vessel 3 via the atmospheric port 9. The fuel reservoir 18 is provided at the lower part of the fuel vapor introduction space 14 and is connected to the outlet 6. The capacity of the fuel vapor separation vessel 3 is suitably 41 when the capacity of the fuel tank 1 is, for example, 60A.

FIG. 3 is a vertical sectional view of the gas separation membrane section 12.

Gas separation membranes 26 made of cellulose filter paper and Teflon material are alternately stacked in the radial direction.

The operation of this device will be explained.

This occurs in the fuel tank 1 while the engine is stopped. The check valve 7 opens when the pressure difference reaches, for example, 300 Aq. As the pressure in the fuel vapor introduction space 14 increases, air passes through the gas separation membrane 26 of the gas separation membrane section 12 and reaches the atmospheric space, but the fuel vapor is blocked from passing through the gas separation membrane 26 and the fuel vapor is not introduced. It stays in the space 14. Thus, the fuel vapor eventually condenses and accumulates in the fuel reservoir 18.

While the engine is operating, the gas pressure in the gas space of the fuel tank 1 decreases as fuel is sent from the fuel tank 1 to the intake system. In this way, the pressure difference at the check valve 18 is 200 mmA.
4 or more, the check valve 8 opens and the fuel in the fuel reservoir 18 is recovered to the fuel tank 1 via the return passage 5 due to the negative pressure in the fuel tank 1.

FIG. 4 shows another embodiment of the fuel vapor separation vessel 3. In FIG. Filter papers 28 and 30 are provided above and below the fuel vapor introduction space 14, respectively, and the fuel vapor introduction space 14 is filled with activated carbon 32 as an adsorbent. In this embodiment, the heavy components of the fuel vapor are adsorbed by the activated carbon 32, the light components are separated from the air by the gas separation membrane section 12, and the condensed fuel and desorbed fuel vapor are removed by negative pressure during the next engine operation. It is sucked in and returned to the fuel tank 1 via the return passage 5. Since fuel vapor components that tend to escape adsorption by the activated carbon 32 are prevented from being released into the atmosphere by the gas separation membrane section 12, it is possible to reliably prevent fuel vapor from dispersing into the atmosphere.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is an internal structural diagram of a fuel vapor separation vessel, FIG. 3 is a diagram showing the configuration of a gas separation membrane section in a fuel vapor separation vessel, and FIG. FIG. 4 is a diagram showing another example of the structure of the fuel vapor separation vessel. DESCRIPTION OF SYMBOLS 1... Fuel tank, 5... Return passage, 14... Fuel vapor introduction space, 26... Gas separation membrane. Figure 1 Figure 2 Figure 4 Figure 4

Claims (1)

[Claims] A fuel vapor introduction space into which fuel vapor from the fuel vapor tank is introduced, a gas membrane that partitions the atmospheric space and the fuel vapor introduction space, and a return for returning condensed fuel that accumulates at the bottom of the fuel vapor introduction space to the fuel tank. A fuel vapor diffusion prevention device characterized by comprising a passage.