Tandem power transmission unit and brake systems using same

Patent metadata

Field	Value
Publication number	US-12570262-B2
Application number	US-202217708070-A
Country	US
Kind code	B2
Filing date	Mar 30, 2022
Priority date	Mar 30, 2022
Publication date	Mar 10, 2026
Grant date	Mar 10, 2026

Abstract

A tandem power transmission unit includes a ball screw and a ball nut selectively driven by the ball screw for longitudinal motion relative thereto. A primary piston is operatively coupled to the ball nut. A secondary piston is operatively coupled to the primary piston. A primary chamber is configured to contain hydraulic fluid and is selectively pressurized by reciprocal motion of the primary piston. A secondary chamber is configured to contain hydraulic fluid and is selectively pressurized by reciprocal motion of the secondary piston driven indirectly by longitudinal motion of the ball nut. A first output channel selectively places the primary chamber in fluid communication with at least one component of a brake system for provision of pressurized hydraulic fluid thereto. A second output channel selectively places the secondary chamber in fluid communication with at least one component of a brake system for provision of pressurized hydraulic fluid thereto.

First claim

I claim:

1 . A tandem power transmission unit, comprising:
a ball screw; a ball nut having an opening into which the ball screw extends, the ball nut being selectively driven by the ball screw for longitudinal motion relative thereto; a primary piston operatively coupled to the ball nut; a secondary piston operatively coupled to the primary piston; a block housing at least partially enclosing the primary piston, the secondary piston, and the ball screw; a primary chamber at least partially defined by the block housing and a face of the primary piston, the primary chamber being configured to contain hydraulic fluid and selectively pressurized by reciprocal motion of the primary piston with respect to the block housing driven directly by longitudinal motion of the ball nut relative to the block housing; a secondary chamber at least partially defined by the block housing and a face of the secondary piston, a backside of the secondary piston at least partially defining the primary chamber, the secondary chamber being configured to contain hydraulic fluid and selectively pressurized by reciprocal motion of the secondary piston with respect to the block housing driven indirectly by longitudinal motion of the ball nut relative to the block housing; a first output channel selectively placing the primary chamber in fluid communication with at least one component of a brake system for provision of pressurized hydraulic fluid thereto; a second output channel selectively placing the secondary chamber in fluid communication with at least one component of a brake system for provision of pressurized hydraulic fluid thereto; an electric motor for selectively driving the ball screw to move the ball nut longitudinally relative to the block housing and responsively reciprocate at least one of the primary and secondary pistons within a corresponding primary or secondary chamber; and a motor housing at least partially enclosing the ball nut and the electric motor.

2 . The tandem power transmission unit of claim 1 , including a bearing for rotatably supporting a supported end of the ball screw spaced apart from the primary chamber, wherein the motor housing includes a bearing retainer to maintain the bearing in relation to the motor housing.

3 . The tandem power transmission unit of claim 2 , including at least one disc spring longitudinally interposed between the ball nut and the bearing, the at least one disc spring selectively compressing under longitudinal force directed from the ball nut toward the bearing.

4 . The tandem power transmission unit of claim 1 , including a primary spring interposed longitudinally between the primary and secondary pistons, the primary spring selectively resisting longitudinally directed compressive force therebetween.

5 . The tandem power transmission unit of claim 4 , including a secondary spring interposed longitudinally between the secondary spring piston and an end portion of the block housing, the secondary spring selectively resisting longitudinally directed compressive force therebetween, and the primary spring having a greater resistance to compression than does the secondary spring.

6 . The tandem power transmission unit of claim 1 , including a secondary spring interposed longitudinally between the secondary piston and an end portion of the block housing, the secondary spring selectively resisting longitudinally directed compressive force therebetween.

7 . The tandem power transmission unit of claim 1 , wherein the secondary chamber is at least partially defined by an end cap located on the block housing longitudinally opposite the electric motor.

8 . The tandem power transmission unit of claim 7 , wherein the end cap is retained on the block housing via at least two fastening structures.

9 . The tandem power transmission unit of claim 1 , wherein the electric motor includes a motor rotor operatively coupled to the ball screw and a motor stator mounted on the motor housing wherein torque developed by the motor stator is resisted by at least a portion of the motor housing.

10 . The tandem power transmission unit of claim 9 , including a bearing for rotatably supporting a supported end of the ball screw spaced apart from the primary chamber, wherein the motor rotor is interposed longitudinally between the ball nut and the bearing.

11 . The tandem power transmission unit of claim 1 , wherein at least one of the primary and secondary pistons includes a concave cup portion having an interior surface at least partially defined by a respective face of the piston, the concave cup portion at least partially defining a respective primary or secondary chamber.

12 . The tandem power transmission unit of claim 11 , wherein at least one of the primary and secondary pistons includes a cage structure carried by the face of the piston and extending from the face into a respective primary or secondary chamber, the cage structure and cup portion collectively defining an annular cavity therebetween, wherein the annular cavity is substantially coaxial with the respective primary or secondary chamber.

13 . The tandem power transmission unit of claim 12 , including at least one of a primary and secondary spring at least partially contained within the annular cavity, the at least one of a primary and secondary spring being operative to selectively resist longitudinally compressive force developed in the respective primary or secondary chamber.

14 . The tandem power transmission unit of claim 11 , wherein the primary piston includes the cage structure, the cage structure includes a central cage aperture at a cage end face spaced longitudinally apart from the face of the primary piston, the secondary piston carries a longitudinally extending pin protruding from the backside of the secondary piston, and the longitudinally extending pin penetrates slidingly through the central cage aperture for selectively limiting longitudinal travel of the secondary piston relative to the primary piston.

15 . The tandem power transmission unit of claim 1 , wherein the first and second output channels are arranged relative to the block housing such that rotation of the ball screw drives the primary and secondary pistons longitudinally to block the respective first and second output channels substantially simultaneously during operation of the tandem power transmission unit.

16 . The tandem power transmission unit of claim 1 , including an electronic control unit housing selectively connected to a portion of the block housing spaced longitudinally apart from the primary and secondary chambers, the electronic control unit housing enclosing an electronic control unit therein for operative connection to the electric motor.

17 . The tandem power transmission unit of claim 16 , including a bearing for rotatably supporting a supported end of the ball screw spaced apart from the primary chamber, wherein the motor housing includes a bearing retainer to maintain the bearing in relation to the motor housing, and wherein the bearing retainer is interposed longitudinally between the electronic control unit and the electric motor for preventing fluid communication therebetween.

18 . The tandem power transmission unit of claim 1 , wherein each of the primary and secondary chambers includes at least one annular sealing groove configured to contain an annular seal for resisting egress of hydraulic fluid from the respective primary or secondary chamber.

19 . The tandem power transmission unit of claim 1 , including a primary reservoir channel

Assignees

• Zf Active Safety Us Inc

Inventors

• Ganzel Blaise J

Classifications

• F15B1/26

  Supply reservoir or sump assemblies · CPC title

• B60T2270/203

  hydraulic system components · CPC title

• B60T2270/402

  Back-up · CPC title

• F15B13/02

  Fluid distribution or supply devices characterised by their adaptation to the control of servomotors · CPC title

• B60T2270/403

  Brake circuit failure · CPC title