Motor vehicle parking brake control device

• US 20020092720A1
• Filed: 10/04/2001
• Published: 07/18/2002
• Est. Priority Date: 10/19/2000
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Poehlman, Michael, Schafer, Helmut, Hoess, Bruno
• Granted Patent: US 6,698,555 B2
• Time in Patent Office: Days
• US Class Current: 188/158
• CPC Class Codes: B60T 1/005 by locking of wheel or transmission rotation
• CPC Class Codes: B60T 13/22 Brakes applied by springs or weights and released hydraulically
• CPC Class Codes: B60T 13/686 in hydraulic systems or parts thereof
• CPC Class Codes: F16H 63/3483 with hydraulic actuating means
• CPC Class Codes: F16H 63/3491 Emergency release or engagement of parking locks or brakes
• CPC Class Codes: F16H 63/483 Circuits for controlling engagement of parking locks or brakes

Abstract

A control device for the parking brake of a motor vehicle has a hydraulic cylinder with a piston chamber that can be pressurized by means of a valve arrangement, and has a hydraulic piston connected mechanically to engagement elements of the parking brake. The parking brake is forced into an engaged or disengaged position depending on the hydraulic pressure in the piston chamber. The piston chamber connects to a pressure sensor providing pressure signals that represent the state of the parking brake and that are evaluated by an electrical control unit. The control unit defines a first predetermined pressure threshold corresponding to the engaged state of the parking brake, and a second predetermined pressure threshold corresponding to the disengaged state of the parking brake.

Claims

1. A motor vehicle parking brake control device having a hydraulic cylinder with a piston chamber that can be charged with hydraulic pressure by means of a valve arrangement, the control device having a hydraulic piston connected mechanically to engagement elements of a parking brake, the parking brake being forced into an engaged or disengaged position depending on the hydraulic pressure, the piston chamber being connected to a pressure sensor providing pressure signals which represent the state of the parking brake and which are evaluated by an electrical control unit, wherein:

the control unit defines a first predetermined pressure threshold which corresponds to the engaged state of the parking brake, and defines a second, predetermined pressure threshold which corresponds to the disengaged state of the parking brake.

2. The parking brake control device according to claim 1, wherein:

the hydraulic piston is coupled to an activating mechanism for the parking brake by a connection which transmits only pressure forces.

3. The parking brake control device of claim 2, wherein:

a compression spring forces the hydraulic piston into its unpressurized position independent of the activating mechanism.

4. The parking brake control device of claim 2, wherein:

a main spring is attached to the activating mechanism of the parking brake, the main spring forcing the activating mechanism into a locked position and indirectly forcing the hydraulic piston into an unpressurized position.

5. The parking brake control device of claim 1, wherein:

the hydraulic piston is forced by a spring into an unpressurized stop position, in which a spring force acting on the hydraulic piston is greater than zero; and

the first pressure threshold corresponds to a value which is between zero and a piston pressure corresponding to said spring force.

6. The parking brake control device of claim 5, wherein:

the first pressure threshold corresponds to a value which is between 40% and 80% of the pressure threshold corresponding to said spring force.

7. The parking brake control device of claim 1, wherein:

the hydraulic piston is forced by a spring towards an unpressurized stop position; and

the second pressure threshold corresponds to a value that is between a piston pressure which corresponds to a maximum spring force in a disengaged position of the hydraulic piston and the hydraulic system pressure provided by the valve arrangement.

8. The parking brake control device of claim 7, wherein:

the second pressure threshold corresponds to a value between 60% and 90% of the system pressure.

9. The parking brake control device of claim 1, wherein:

the pressure sensor is an analog sensor.

10. The parking brake control device of claim 1, wherein:

the pressure sensor supplies a pressure sensor signal that is greater than zero for an unpressurized piston chamber.