Parking control circuit

• US 6,802,573 B2
• Filed: 11/05/2002
• Issued: 10/12/2004
• Est. Priority Date: 08/19/1999
• Status: Expired due to Term

• Current Assignee: Bendix Commercial Vehicle Systems LLC (Estate of Heinz Hermann Thiele)
• Original Assignee: Bendix Commercial Vehicle Systems LLC (Estate of Heinz Hermann Thiele)
• Inventors: Eberling, Charles E., Knight, David J.
• Primary Examiner(s): Graham, Matthew C.
• Assistant Examiner(s): NGUYEN, XUAN LAN T
• Application Number:
  US10/288,150
• Publication Number:
  US 20030057766A1
• Time in Patent Office: 707 Days
• Field of Search: 303/3, 303/15, 303/20, 303/191, 180/271
• US Class Current: 303/15
• CPC Class Codes: B60T 13/66 Electrical control in fluid-pressure brake systems
• CPC Class Codes: B60T 13/683 in pneumatic systems or parts thereof in vacuum systems B60T13/72
• CPC Class Codes: B60T 7/12 for automatic initiation; for initiation not subject to will of driver or passenger limiting speed of vehicles other than rail vehicles B60K31/00

Abstract

A parking brake control circuit engages the parking brake of a vehicle when the transmission of the vehicle is in the “park” position and the engine of the vehicle is turned off, without requiring the constant application of electrical power. The parking brake control circuit utilizes latching solenoid technology that eliminates the need for a constant voltage source. A time-delay relay is used to change the state of the latching solenoid. The time-delay relay is preferably activated through a circuit containing an engine oil pressure switch, a transmission park switch and a vehicle speed switch. Activation of the relay latches the solenoid in a position that allows the parking brake to be applied, without requiring the application of a constant voltage to the solenoid. Accordingly, the possibility of inadvertent brake application due to electrical failure is avoided.

Claims

1. A parking brake control circuit for a vehicle, comprising:

a first switch set as a function of an engine oil pressure of the vehicle;

a second switch set as a function of a status of a transmission of the vehicle;

means for applying and enabling release of a parking brake without continuous application of a signal; and

relay means for applying the signal for a limited time to the means for applying and enabling release of the parking brake as a function of the settings of the first and second switches.

2. The parking brake control circuit as set forth in claim 1, wherein the relay means applies the signal for enabling release of the parking brake when:

the engine oil pressure is above a predetermined level; and

the status of the transmission is “

park.”

3. The parking brake control circuit as set forth in claim 2, wherein the relay means applies the signal for applying the parking brake when:

the engine oil pressure is below a predetermined level; and

the status of the transmission is “

park.”

4. The parking brake control circuit as set forth in claim 3, wherein:

the engine oil pressure indicates an operating status of the vehicle.

5. The parking brake control circuit as set forth in claim 4, wherein:

the operating status of the vehicle is “

off”

when the engine oil pressure is below the predetermined level; and

the operating status of the vehicle is “

on”

when the engine oil pressure is one of above and equal to the predetermined level.

6. The parking brake control circuit as set forth in claim 1, wherein the second switch detects the status of the transmission.

7. The parking brake control circuit as set forth in claim 1, wherein the means for applying and enabling release of the parking brake includes:

a solenoid which, upon application of the signal, latches in one of a plurality of positions as a function of the first and second switches.

8. The parking brake control circuit as set forth in claim 7, wherein the relay means applies the signal to the solenoid for a predetermined time.

9. The parking brake control circuit as set forth in claim 7, wherein the means for applying and enabling release of the parking brake further includes:

a park control valve which applies the parking brake and enables release of the parking brake as a function of the latched position of the solenoid.

10. The parking brake control circuit as set forth in claim 7, wherein the signal is a pulse.

11. A parking brake control circuit for a vehicle, comprising:

an engine oil pressure switch which detects an operating status of the vehicle;

a transmission park switch which detects a transmission status of the vehicle;

a control valve which controls application of a parking brake;

a control switch, set as a function of the engine oil pressure switch and the transmission park switch, which supplies control signals to the valve, the control switch drawing power for a limited time after the valve receives one of the control signals for applying and enabling release of the parking brake;

a solenoid; and

a first relay for communicating one of the control signals, for applying the parking brake, to the solenoid for the limited time if the operating status of the vehicle is “

off” and

the transmission status of the vehicle is “

park.”

12. The parking brake control circuit as set forth in claim 11, wherein the control switch further includes:

a vehicle speed switch which prevents the control signal for applying the parking brake from being communicated to the solenoid if the vehicle is moving greater than a predetermined speed.

13. The parking brake control circuit as set forth in claim 11, wherein the control switch further includes:

a second relay for communicating the control signal for enabling release of the parking brake to the solenoid for the limited time if at least one of the operating status of the vehicle is “

on” and

the transmission status of the vehicle is “

park.”

14. The parking brake control circuit as set forth in claim 13, wherein:

the first relay communicates the signal for applying the parking brake from a power source to the solenoid via the engine oil pressure switch and the transmission park switch; and

the second relay communicates the signal for enabling release of the parking brake from the power source to the solenoid via an ignition circuit, the engine oil pressure switch, and the transmission park switch.

15. The parking brake control circuit as set forth in claim 13, further including:

an override switch for communicating an override signal for enabling release of the parking brake after the signal for applying the parking brake has been communicated from the control switch to the valve even if the operating status of the vehicle is “

off” and

the transmission status of the vehicle is “

park.”

16. The parking brake control circuit as set forth in claim 15, wherein:

the override signal is communicated from the power source to the solenoid via the ignition circuit and the override switch.

17. A parking control circuit for a vehicle, comprising:

an engine detector for detecting an operating state of an engine of the vehicle;

transmission detector for detecting an operating state of a transmission of the vehicle; and

control means, including a time-delay relay and a switch, for selectively enabling release of a parking brake of the vehicle in response to the engine operating state and the transmission operating state, the time-delay relay communicating electrical power to the switch, during a limited time period when the engine operating state is “

on” and

the transmission operating state is “

park,”

for causing the parking brake to be selectively enabled for release both while the electrical power is communicated to the switch and after the electrical power is no longer communicated to the switch.

18. The parking control circuit for a vehicle as set forth in claim 17, wherein the control means selectively engages the parking brake in response to the engine operating state and the transmission operating state, the control means engaging the parking brake when the engine operating state is “

off” and

the transmission operating state is “

park,” and

maintaining the engagement of the parking brake without the use of electrical power, the parking control circuit further comprising;

vehicle speed detection means for detecting a speed of the vehicle, the control means engaging the parking brake when the vehicle speed detection means detects that the speed of the vehicle is below a predetermined level.

19. The parking control circuit for a vehicle as set forth in claim 18, further comprising:

override means for providing an override signal to the control means, wherein the control means enables disengagement of the parking brake in response to the override signal.

20. The parking control circuit for a vehicle as set forth in claim 17, wherein the engine detection means detects an oil pressure of the engine.

21. The parking control circuit for a vehicle as set forth in claim 17, wherein the switch is a solenoid.

22. A method for selectively applying and enabling release of a parking brake of a vehicle, the method comprising:

detecting an operating state of an engine;

detecting an operating state of a transmission;

supplying electrical power to a switch for a limited time period, via a time-delay relay means, for selectively applying and enabling release of the parking brake as a function of the engine operating state and the transmission operating state; and

maintaining the parking brake as one of applied and enabled for release after the limited time period when the electrical power is no longer being applied to the switch.

23. The method for selectively applying and enabling release of a parking brake of a vehicle as set forth in claim 22, wherein the step of supplying includes:

if the operating state of the engine is “

off” and

the operating state of the transmission is “

park,”

closing for the limited period of time;

while the time-delay relay means is closed, transmitting a signal for latching the switch in a position causing the engagement of the parking brake.

24. The method for selectively applying and enabling release of a parking brake of a vehicle as set forth in claim 23, wherein the step of maintaining includes, after the limited period of time:

opening the time-delay relay means; and

maintaining the switch in the latched position without using electrical power.

25. The method for selectively applying and enabling release of a parking brake of a vehicle as set forth in claim 22, further including:

detecting a speed of the vehicle;

wherein the step of supplying electrical power to a switch for a limited time period, supplies the electrical power for engaging the parking brake when the engine operating state is “

off,”

the transmission operating state is “

park,” and

the speed of the vehicle is less than a predetermined level.

26. The method for selectively applying and enabling release of a parking brake of a vehicle as set forth in claim 22, further including:

enabling release of the parking brake in response to an override signal.