Tank-venting arrangement and method of operating the same

• US 5,197,442 A
• Filed: 12/20/1991
• Issued: 03/30/1993
• Est. Priority Date: 12/20/1990
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Steinbrenner, Ulrich, Wild, Ernst, Denz, Helmut, Blumenstock, Andreas
• Primary Examiner(s): MILLER, CARL STUART
• Application Number:
  US07/811,294
• Time in Patent Office: 466 Days
• Field of Search: 123/516, 123/518, 123/519, 123/520, 123/521, 123/198 D
• US Class Current: 123/520
• CPC Class Codes: B60K 15/03504 adapted to avoid loss of fuel or fuel vapour, e.g. with vapour recovery systems
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space

Abstract

A tank-venting arrangement includes: a tank having a tank closure; an electrically drivable check valve; an adsorption filter; connecting lines for interconnecting the above components; a difference pressure sensor which measures the pressure difference between the pressure in the tank and the ambient pressure and supplies a pressure difference signal; a comparator which, at least for a running engine, compares the pressure difference signal to upper and lower threshold values and supplies an opening signal to the check valve to open the latter when the pressure difference signal is greater than the upper threshold value and a closure signal for closing the check valve when the pressure difference signal drops below the lower threshold value; and, a detector unit which supplies an opening signal to the check valve for opening the check valve when the sensor determines a possible opening of the tank and a closure signal for closing the check valve when the sensor determines a possible closure of the tank. With the aid of the check valve and the difference pressure sensor which measures the pressure difference between the pressure in the tank and the ambient pressure, the tank-venting arrangement can be so operated that at least for a running engine, a desired maximum overpressure in the tank can be obtained relative to the ambient pressure independently of the extent of the underpressure in that part of the arrangement forward of the check valve.

Claims

1. A method for operating a tank-venting arrangement on a motor vehicle having an engine, the tank-venting arrangement including a tank having a tank closure, an adsorption filter and check valve interconnecting the tank and the adsorption filter, the method comprising the steps of:

measuring the pressure difference between the pressure in the tank and the ambient pressure at least when the engine is running;

keeping the check valve closed to maintain an overpressure in the tank in a predetermined interval during running of the internal combustion engine when no indication is present that the tank may be opened;

opening the check valve when one of the following occurs;

the pressure difference increases beyond an upper thereshold valve and an indication is present that the tank may be opened; and

,

closing the check valve when one of the following occurs;

the pressure difference drops below a lower threshold value and an indication is present that the tank may be closed.

2. The method of claim 1, further comprising:

checking whether the tank closure is being opened or is being closed to obtain an indication as to an opening/closure operation; and

, then performing one of the following steps;

controlling the check valve to open when the check shows that the tank closure is being opened;

or,

controlling the check valve to close when the check shows that the tank closure is closed.

4. The method of claim 1, wherein the level of the threshold values for the pressure difference is dependent upon values of operating parameters and the level of said threshold values is reduced with such values of the operating parameters which point to an opening of the tank closure which may occur soon.

3. A method for operating a tank-venting arrangement on a motor vehicle having an engine, the tank-venting arrangement including a tank having a tank closure, an adsorption filter and a check valve interconnecting the tank and the adsorption filter, the method comprising the steps of:

measuring the pressure difference between the pressure in the tank and the ambient pressure at least when the engine is running;

opening the check valve when one of the following occurs;

the pressure difference increases beyond an upper threshold value and an indication is present that the tank may be opened; and

,

closing the check valve when one of the following occurs;

the pressure difference drops below a lower threshold value and an indication is present that the tank may be closed;

the operation of the engine being used as an indication for the opening/closing operation of the tank and the method including the further steps of;

opening the check valve when the engine is switched off; and

,

after a pregiven time span has elapsed after the opening of the check valve, again closing the check valve.

5. A method for operating a tank-venting arrangement on a motor vehicle having an engine, the tank-venting arrangement including a tank having a tank closure, an adsorption filter and a check valve interconnecting the tank and the adsorption filter, the method comprising the steps of:

measuring the pressure difference between the pressure in the tank and the ambient pressure at least when the engine is running;

opening the check valve when one of the following occurs;

the pressure difference increases beyond an upper threshold value and an indication is present that the tank may be opened; and

,

closing the check valve when one of the following occurs;

the pressure difference drops below a lower threshold value and an indication is present that the tank may be closed;

checking as to whether said tank-venting arrangement is tight; and

, controlling the check valve to open if a leak is determined.

6. A tank-venting arrangement comprising:

a tank having a tank closure;

an adsorption filter;

an electrically drivable check valve interconnecting said tank and said adsorption filter;

a difference pressure sensor for measuring the pressure difference between the pressure in said tank and the ambient and emitting a pressure difference signal indicative of said pressure difference;

comparator means for comparing said pressure difference signal to an upper and a lower threshold value and for supplying an opening signal to said check valve for opening said check valve when said pressure difference signal is greater than said upper threshold value and for supplying a closing signal to said check valve for closing said check valve when said pressure difference signal drops below said lower threshold value thereby maintaining a predetermined overpressure relative to atmospheric pressure in said tank independently of the pressure in said adsorption filter during operation of the vehicle and while no opening of said tank closure is expected; and

,

detector means for making a determination of a possible opening of the tank and supplying an opening signal to said check valve when said determination is made and for making a determination of a possible closing of the tank and supplying a closure signal to said check valve when said determination of possible closing is made.

7. The tank-venting arrangement of claim 6, further comprising a tank closure sensor for emitting a tank opening signal when the tank closure is opened;

and, a switching unit for opening said check valve in response to said opening signal.

8. The tank-venting arrangement of claim 6, said check valve being a valve which is closed in the non-driven condition.