GB2240971A

GB2240971A - Device for capturing and collecting fuel vapours in fuel systems

Info

Publication number: GB2240971A
Application number: GB9102877A
Authority: GB
Inventors: Manfred Schafer; Otto Hartmann
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG
Priority date: 1990-02-14
Filing date: 1991-02-12
Publication date: 1991-08-21
Also published as: ITRM910054A1; FR2658249A1; ITRM910054A0; DE4004500C2; GB9102877D0; DE4004500A1; JPH04219455A; IT1247757B

Abstract

In a device for capturing and collecting fuel vapours in an internal-combustion engine via a gas draw-off line 6, 7 from which the fuel is fed to the fuel circuit, a condensation system reconverts the vapour to the liquid phase. Preferably the condensation system comprises a compressor 5 and a pressure chamber 9 in which the compressed vapours condense. As a result of the fuel-vapour condensation, the use of an activated-charcoal filter in the gas draw-off line is avoided. <IMAGE>

Description

j i? el 0 -3 -7 1 1 Device for ca-PturinQ and collecting fuel vaDours in

fuel svstems The invention relates to a device for a fuel system for an internal combustion engine, in which there is a device for capturing and collecting fuel vapours via a gas draw-off line from which the fuel is fed to the fuel circuit.

German Offenlegungsschrift 3,602,155 makes known a device of the relevant type for the capture and intermediate storage of fuel vapours by means of an activated-charcoal filter in a gas draw-off line of a fuel system for an internalcombustion engine and for the return of the fuel to the fuel circuit.

A disadvantaae of this version is that the activatedcharcoal filter can absorb fuel vapours to a limited extent only. Furthermore, the filter has to be regenerated again from time to time, thus requiring an additional device and involving energy consumption. Moreover, the constantly changing quantity of fuel vapour flushed out of the activated- charco a 1 filter with air has an adverse effect on the mixture composiLion for the internal-combustion engine, and this leads to uneven combustion, with the emission of larger amounts of harmful substances, and can be corrected only incompletely by the closed control circuit for the mixture former.

The present invention seeks, therefore, to provide a device which captures and collects the evaporated fuel independently of its quantity and which feeds it to the fuel circuit without impairing the composition of the fuel mixture for the internal-combustion engine.

According to the present invention there is provided a device for capturing and collecting fuel vapours via a gas draw-off line in a fuel system for an internal-combustion engine, from which draw-off line the fuel is fed to the engine fuel circuit, wherein the device consists of a condensation system which reconverts the vapour to the liquid phase.

By the use of a compressor and of a following pressure chamber, the fuel vapours are extracted from the tank space and compressed isothermally in the pressure chamber by the 2 compressor located between the chamber and tank, so that condensation of the vapours occurs. Since, after being reconverted to the liquid phase, the f uel is in its original state, it can now easily be returned to the tank or fed to a fuel pump.

With the method of phase transition of f uel vapours, an absorber device with an activated-charcoal filter becomes unnecessary and the difficulties associated with the device no longer exist.

An exemplary embodiment of the invention will now be explained in more detail with reference to the following drawing, which shows diagrammatically a tank with a pressure sensor connected to a compressor which is driven by an electric motor and which is connected to a pressure chamber containing a filling-level meter and equipped with a solenoid valve.

Incorporated in the ceiling 1 of a fuel-filled tank 2 of a fuel system, described only in so far as it relates to the invention and arranged, for example, in a motor vehicle, is a pressure sensor 3 which detects the vapour pressure of the fuel. If the pressure exceeds a predetermined value, the signal-processing electronics (not shown) connected to the sensor 3 activates an electric motor 4 which drives a compressor 5. When the vehicle is in operation, its internalcombustion engine, not shown here, performs the function of the electric motor 4. This is connected to the tank ceiling 1 via a gas draw-off line 6. The compressor 5 sucks off the fuel vapours until the pressure falls below a second predetermined value. During the working phase, the compressor 5 compresses isothermally the vapours sucked-in which pass, during this operation, via a gas drawoff line 7 through the ceiling 8 of a pressure chamber 9, having the form of a capsule and mounted vertically, and into the latter. The compression brings about a condensation of the fuel vapours which collect as fluid at the bottom 10 of the chamber 9. Clamped vertically in the ceiling 8 of the chamber 9 is one end 11 of a f illing level meter 12 consisting of a bar 13, the f ree end 14 of which is inserted in an annular f loat 15 movable along the bar 13. Furthermore, a pressure sensor 16 is arranged in the chamber i 1 3 ceiling 8.

When the filling level or pressure in the chamber 9 reaches a preset maximum value, the electronics connected to the filling-level meter 12 and to the pressure sensor 16 and not described in any more detail here switch off the electric motor 4 of the compressor 5. At the same time, a so lenoid valve 17 located in a return line 18 at the chamber bottom 10 is opened. When the filling level or pressure reaches a minimum value, the solenoid valve 17 closes. Finally, with the valve 17 open, the fuel can be fed to the fuel circuit, that is to say either to the tank 2 or to a suction or delivery line of a fuel pump not shown here.

4

Claims

1. A device for capturing and collecting fuel vapours via a gas draw-off line in a fuel system for an internal-combustion engine, from which drawoff line the fuel is fed to the engine fuel circuit, wherein the device consists of a condensation system which reconverts the vapour to the liquid phase.

2. A device according to Claim 1, wherein the condensation system consists of a compressor and of a pressure chamber.

3. A device according to Claim 1 or 2, wherein the compressor is located between the fuel tank and the pressure chamber and is connected to each of these by means of a gas draw-off line.

4. A device according to any one of Claims 1 to 3, wherein the compressor is operable by an electric motor.

5. A device according to any one of Claims 1 to 4, wherein the pressure chamber contains a filling-level meter and a pressure sensor.

6. A device according to any one of Claims 1 to 5, wherein the fillinglevel meter and the pressure sensor are equipped with signal processing.

7. A device according to any one of Claims 1 to 6, wherein a return line leads into the bottom of the chamber, and this return line is opened or closed by means of a solenoid valve.

8. A device according to any one of Claims 1 to 7, wherein mounted in the tank ceiling is a pressure sensor which is equipped with signal processing.

j i 1 1

9. A device for capturing and collecting fuel vapours via a gas draw-off line in a fuel system for an internal -combustion engine, substantially as described herein, with reference to, and as illustrated in, the accompanying drawings.

Published 1991 at Ile Patent Office. State House. 66171 High Holbom, London WC1R4TP, Further copies may be obtained from Sales Branch, Unit 6. Nine Mile Point Cwmfchnfach. Cross Keys, Newport. NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent,