Electrically Actuated Booster

• US 20090115242A1
• Filed: 09/26/2006
• Published: 05/07/2009
• Est. Priority Date: 09/26/2005
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: Ohtani, Yukio, Nagai, Kazuhiro, Ikeda, Junichi
• Granted Patent: US 8,500,213 B2
• Time in Patent Office: Days
• US Class Current: 303/3
• CPC Class Codes: B60T 13/02 with mechanical assistance or drive combined with fluid pressure B60T13/588
• CPC Class Codes: B60T 13/745 acting on a hydraulic system, e.g. a master cylinder
• CPC Class Codes: B60T 2220/04 Pedal travel sensor, stroke sensor; Sensing brake request
• CPC Class Codes: B60T 2270/604 Merging friction therewith; Adjusting their repartition
• CPC Class Codes: B60T 7/042 by electrical means, e.g. using travel or force sensors
• CPC Class Codes: B60T 8/3275 Systems with a braking assistant function, i.e. automatic full braking initiation in dependence of brake pedal velocity
• CPC Class Codes: F15B 15/20 Other details , e.g. assembly with regulating devices

Abstract

An electrically actuated booster capable of obtaining various desired brake characteristics and improving brake feeling performs displacement control such that the relative displacement relationship between an input member and an assist member is variable according to the absolute displacement of the input member.

A target displacement that makes variable the relative displacement relationship between an input piston and a booster piston is set according to a detection signal from a potentiometer (86) (input absolute displacement detecting means), and displacement control is performed so that the relative displacement between the two pistons becomes equal to the target displacement on the basis of a signal from a relative displacement sensor (100) that detects the relative displacement between the two pistons.

Claims

1-12. -12. (canceled)

13. An electrically actuated booster having an input member that moves forward and backward in response to an operation of a brake pedal, an assist member arranged to be movable relative to said input member, and a electrically-operated actuator that causes said assist member to move forward and backward, wherein a boosted brake fluid pressure is generated in a master cylinder by an assist thrust applied to said assist member according to movement of said input member caused by said brake pedal, said electrically actuated booster comprising:

input absolute displacement detecting means that detects an absolute displacement of said input member;

either one of relative displacement detecting means that detects a relative displacement between said input member and said assist member and assist absolute displacement detecting means that detects an absolute displacement of said assist member; and

control means that sets a target displacement that makes variable relative displacement relationship between said input member and said assist member according to a detection signal from said input absolute displacement detecting means and that controls said electrically-operated actuator so that the relative displacement relationship between said input member and said assist member becomes equal to said target displacement on a basis of a signal from said relative displacement detecting means or said assist absolute displacement detecting means.

14. The electrically actuated booster of claim 13, wherein a brake fluid pressure is generated in the master cylinder by an input thrust applied to said input member from said brake pedal and an assist thrust applied to said assist member from said electrically-operated actuator, and even when said input member and said assist member are displaced relative to each other, a part of a reaction caused by said brake fluid pressure is transmitted to said input member, and another part of said reaction is transmitted to said assist member.

15. The electrically actuated booster of claim 13, wherein urging means is provided between said input member and said assist member to urge said input member relative to said assist member toward a neutral position of relative displacement therebetween.

16. The electrically actuated booster of claim 14, wherein urging means is provided between said input member and said assist member to urge said input member relative to said assist member toward a neutral position of relative displacement therebetween.

17. The electrically actuated booster of claim 13, wherein said control means controls said electrically-operated actuator so that, as said input member moves in a direction for increasing the brake fluid pressure, the absolute displacement of said assist member becomes larger or smaller than the absolute displacement of said input member.

18. The electrically actuated booster of claim 16, wherein said control means controls said electrically-operated actuator so that, as said input member moves in a direction for increasing the brake fluid pressure, the absolute displacement of said assist member becomes larger or smaller than the absolute displacement of said input member.

19. The electrically actuated booster of claim 13, wherein said control means controls said electrically-operated actuator on a basis of the signal from said input absolute displacement detecting means such that when the absolute displacement of said input member is detected to have moved from an initial position by a predetermined amount, said assist member is started to be displaced so that the absolute displacement of said assist member becomes equal to or larger than the absolute displacement of said input member.

20. The electrically actuated booster of claim 16, wherein said control means controls said electrically-operated actuator on a basis of the signal from said input absolute displacement detecting means such that when the absolute displacement of said input member is detected to have moved from an initial position by a predetermined amount, said assist member is started to be displaced so that the absolute displacement of said assist member becomes equal to or larger than the absolute displacement of said input member.

21. The electrically actuated booster of claim 13, wherein when the absolute displacement of said input member detected by said input absolute displacement detecting means has become a predetermined amount, said control means controls said electrically-operated actuator so that the absolute displacement of said assist member becomes larger than the absolute displacement of said input member.

22. The electrically actuated booster of claim 16, wherein when the absolute displacement of said input member detected by said input absolute displacement detecting means has become a predetermined amount, said control means controls said electrically-operated actuator so that the absolute displacement of said assist member becomes larger than the absolute displacement of said input member.

23. The electrically actuated booster of claim 13, wherein when said control means judges from the absolute displacement of said input member detected by said input absolute displacement detecting means that a speed of movement of said input member has reached a predetermined speed, said control means controls said electrically-operated actuator so that the absolute displacement of said assist member becomes larger than the absolute displacement of said input member.

24. The electrically actuated booster of claim 16, wherein when said control means judges from the absolute displacement of said input member detected by said input absolute displacement detecting means that a speed of movement of said input member has reached a predetermined speed, said control means controls said electrically-operated actuator so that the absolute displacement of said assist member becomes larger than the absolute displacement of said input member.

25. The electrically actuated booster of claim 13, wherein when said control means judges from the absolute displacement of said input member detected by said input absolute displacement detecting means that movement of said input member in a direction for increasing the brake fluid pressure has stopped, said control means sets a target displacement so that said assist member is displaced relative to said input member by a predetermined amount in the direction for increasing the brake fluid pressure, and controls said electrically-operated actuator on a basis of said target displacement.

26. The electrically actuated booster of claim 16, wherein when said control means judges from the absolute displacement of said input member detected by said input absolute displacement detecting means that movement of said input member in a direction for increasing the brake fluid pressure has stopped, said control means sets a target displacement so that said assist member is displaced relative to said input member by a predetermined amount in the direction for increasing the brake fluid pressure, and controls said electrically-operated actuator on a basis of said target displacement.

27. The electrically actuated booster of claim 13, wherein said control means is connected to an acceleration sensor that detects an operation of an accelerator pedal or connected to a throttle sensor that detects opening and closing of an engine throttle, and when said acceleration sensor detects cancellation of the operation of said accelerator pedal or when said throttle sensor detects that said engine throttle has been closed, said control means controls said electrically-operated actuator so that said assist member is displaced relative to said input member in a direction for increasing the brake fluid pressure to reduce an ineffective stroke of said master cylinder.

28. The electrically actuated booster of claim 16, wherein said control means is connected to an acceleration sensor that detects an operation of an accelerator pedal or connected to a throttle sensor that detects opening and closing of an engine throttle, and when said acceleration sensor detects cancellation of the operation of said accelerator pedal or when said throttle sensor detects that said engine throttle has been closed, said control means controls said electrically-operated actuator so that said assist member is displaced relative to said input member in a direction for increasing the brake fluid pressure to reduce an ineffective stroke of said master cylinder.

29. The electrically actuated booster of claim 13, wherein when a braking operation by a regenerative braking system is performed, said control means controls said electrically-operated actuator so that said assist member is displaced relative to said input member in a direction for reducing the brake fluid pressure.

30. The electrically actuated booster of claim 16, wherein when a braking operation by a regenerative braking system is performed, said control means controls said electrically-operated actuator so that said assist member is displaced relative to said input member in a direction for reducing the brake fluid pressure.

31. The electrically actuated booster of claim 13, wherein said input absolute displacement detecting means is a displacement sensor that detects an absolute displacement of said input member relative to a fixed part.

32. The electrically actuated booster of claim 13, wherein said input absolute displacement detecting means detects an absolute displacement of said input member by computing a detection signal from any one of a brake pedal depressing force sensor that detects a depressing force applied to said brake pedal, an electric current sensor that detects an amount of electric current supplied to an electric motor constituting said electrically-operated actuator, and a fluid pressure sensor that detects a fluid pressure generated by a piston in said master cylinder.