Driver circuit for fuel vapor leak detection system

• US 6,301,955 B1
• Filed: 01/27/1999
• Issued: 10/16/2001
• Est. Priority Date: 01/27/1999
• Status: Expired due to Term

• Current Assignee: Siemens Canada Limited (Siemens AG)
• Original Assignee: Siemens Canada Limited (Siemens AG)
• Inventors: Boucher, William J., Cook, John E., Rasokas, Raymond
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/238,192
• Time in Patent Office: 993 Days
• Field of Search: 73/39, 73/40, 73/46, 73/47, 73/497, 731/172, 731/173, 731/181
• US Class Current: 73/49.7
• CPC Class Codes: F02M 2025/0845 Electromagnetic valves
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F02M 25/0836 Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold

Abstract

An on-board evaporative emission leak detection system has a module (22) for detecting leakage from an evaporative emission space of a fuel system of an automotive vehicle. Interior space (103) of the module'"'"'s enclosure (102) is communicated to atmosphere. A pump (50) is disposed within space (103) and has an inlet (56) communicated to the interior space and a flow passage (70, 72) at its outlet (58) to allow the pump to create pressure in the evaporative emission space suitable for performance of a leak test. A vent valve (52) is disposed within space (103) and is selectively operable to vent and not vent the flow passage to space (103). An electromagnet actuator (104) has a single electric coil (116) that operates both the pump and the vent valve. A driver circuit (1000) to the coil provides a first current component for operating the pump and a second current component for operating the vent valve.

Claims

1. An evaporative emission leak detection system for detecting leakage from an evaporative emission space of a fuel system of an automotive vehicle comprising:

a pump comprising a reciprocal pumping mechanism for pumping gaseous fluid with respect to an evaporative emission space;

a vent valve that is selectively operable to a first state that vents the evaporative emission space to atmosphere and to a second state that does not vent the evaporative emission space to atmosphere; and

an electromechanical actuator for operating both the pump and the vent valve comprising, an electric device comprising an electromagnetic coil for receiving an electric control signal for controlling operation both of the pump and of the vent valve, a first electromechanical coupling operatively coupling the device with the pump such that the pump operation is controlled by the electric control signal, and a second electromechanical coupling operatively coupling the device with the vent valve such that the vent valve operation is also controlled by the electric control signal;

including an electric circuit providing the electric control signal to the coil wherein the electric circuit comprises a first current path to the coil comprising a controlled conduction device that is connected in series circuit relationship with the coil and is cycled alternately between different states of conductivity to reciprocate the reciprocal pumping mechanism of the pump, and a second current path to the coil comprising an electric circuit component for maintaining a threshold electric current in the coil.

2. A system as set forth in claim 1 in which the electric circuit component for maintaining a threshold electric current in the coil comprises a resistor for maintaining threshold electric current in the coil when no current flows through the first path.

3. A system as set forth in claim 2 in which the controlled conduction device comprises a semiconductor.

4. A system as set forth in claim 3 in which the semiconductor comprises a field effect transistor, and the circuit further comprises a zener diode connected between drain and source terminals of the field effect transistor for limiting the magnitude of reverse voltage across the drain and source terminals of the field effect transistor.

5. A system as set forth in claim 1 in which the electric circuit component comprises a resistor, and the controlled conduction device comprises a semiconductor switch.

6. A system as set forth in claim 1 including a sensing circuit for providing a sensed signal representative of pressure in the evaporative emission space and controlling operation of the controlled conduction device in accordance with the sensed signal.

7. A system as set forth in claim 6 in which the sensed signal controls the application of a pulse waveform signal to the controlled conduction device.

8. A system as set forth in claim 7 in which the pulse waveform causes the pumping mechanism to execute a pumping stroke during a pulse of the waveform and to execute a charging stroke between pulses.