Combined hydraulic and regenerative braking system

• US 4,270,806 A
• Filed: 08/09/1979
• Issued: 06/02/1981
• Est. Priority Date: 08/09/1979
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Department Of Energy
• Original Assignee: United States Department of Energy (Government of the United States of America)
• Inventors: Mericle, Gerald E., Venkataperumal, Rama R.
• Primary Examiner(s): Reger, Duane A.
• Application Number:
  US06/065,033
• Time in Patent Office: 663 Days
• Field of Search: 188/159, 188/160, 192/2, 303/3, 303/15, 303/16, 303/20
• US Class Current: 303/3
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/545 Temperature
• CPC Class Codes: B60L 2250/26 by pedal actuation
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 3/0076 relating to braking
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 7/12 for vehicles propelled by dc motors
• CPC Class Codes: B60L 7/26 Controlling the braking effect
• CPC Class Codes: B60T 13/586 the retarders being of the electric type
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A combined hydraulic and regenerative braking system and method for an electric vehicle, with the braking system being responsive to the applied hydraulic pressure in a brake line to control the braking of the vehicle to be completely hydraulic up to a first level of brake line pressure, to be partially hydraulic at a constant braking force and partially regenerative at a linearly increasing braking force from the first level of applied brake line pressure to a higher second level of brake line pressure, to be partially hydraulic at a linearly increasing braking force and partially regenerative at a linearly decreasing braking force from the second level of applied line pressure to a third and higher level of applied line pressure, and to be completely hydraulic at a linearly increasing braking force from the third level to all higher applied levels of line pressure.

Claims

1. A combined hydraulic and regenerative braking system, comprising:

a first wheel;

a brake assembly for said wheel;

a hydraulic brake line connected to said assembly;

means for creating increased pressure in said brake line for application to said brake assembly for actuating said brake assembly to brake said wheel;

a motor generator rotatably connected to said wheel; and

means responsive to a predetermined level of said created pressure for controlling the degree of hydraulic braking and for controlling said motor generator to be driven as a generator by said wheel,

said responsive means being responsive to hydraulic pressure in said brake line to control braking of said wheel to be completely hydraulic up to a first level of said created pressure, to control braking to be partially hydraulic at a constant hydraulic braking force and partially regenerative at a linearly increasing regenerative braking force from the first level of created pressure to a higher second level of said created pressure, to control braking to be partially hydraulic at a linearly increasing hydraulic braking force and partially regenerative at a linearly decreasing regenerative braking force from the second level of said created pressure to a third and still higher level of said created pressure, and to control braking to be completely hydraulic at a linearly increasing hydraulic braking force from the third level to all higher levels of said created pressure.

5. The braking system of claim 1, further including:

a second wheel;

a second brake assembly for said second wheel, said second assembly being connected directly to said brake line for direct and full application of all levels of pressure from said pressure creating means to said second assembly to brake said second wheel completely hydraulically with the same degree of braking effort as the combined hydraulic and regenerative braking effort applied to said first wheel.

2. A combined hydraulic and regenerative braking system, comprising:

a first wheel;

a brake assembly for said wheel;

a hydraulic brake line connected to said assembly;

means for creating increased pressure in said brake line for application to said brake assembly for actuating said brake assembly to brake said wheel;

a motor generator rotatably connected to said wheel; and

means responsive to a predetermined level of said created pressure for controlling the degree of hydraulic braking and for controlling said motor generator to be driven as a generator by said wheel, said responsive means including;

hydraulic metering means having an input and an output; and

switching means for hydraulically interposing said metering means in said brake line between said pressure creating means at said metering means input and said brake assembly at said metering means output;

said metering means being operable upon being interposed to establish a pressure differential between said input and output; and

transducing means for generating an electrical signal corresponding to said pressure differential.

3. The braking system of claim 2, wherein said switching means is a solenoid operated valve having a normally open passage connected in said brake line to bypass said input and output of said metering means, said braking system being completely hydraulically operated when said passage is open, and wherein said responsive means includes means for energizing said solenoid to close said passage and thereby interpose said metering means in said brake line.

4. The braking system of claim 2, wherein said metering means is a metering valve having said input connected to said pressure creating means and said output connected to said brake assembly and said transducing means is hydraulically connected across said metering valve input and output.

6. A method for combining hydraulic and regenerative braking for braking a first wheel by application of hydraulic pressure from a pressure creating means through a brake line to a brake assembly associatd with said wheel and by selectively controlling a motor generator to be driven as a generator by said wheel, including the steps of:

creating increased pressure in said brake line for application to said brake assembly for actuating said assembly to brake said wheel;

selectively maintaining a differential pressure between said created applied pressure and said brake assembly to diminish the hydraulic braking in a predetermined amount; and

transducing said differential pressure to an electrical signal that is proportional thereto for controlling said motor generator to be driven as a generator by said wheel to a degree that is proportional to said signal to thereby apply regenerative braking effort to said wheel in an amount equal to said diminished hydraulic braking effort,

said differential pressure being maintained at a level to control braking of said wheel to be completely hydraulic up to a first level of said created applied pressure, to control braking to be partially hydraulic at a constant hydraulic braking force and partially regenerative at a linearly increasing regenerative braking force from the first level of said applied pressure to a higher second level of created applied pressure, to control braking to be partially hydraulic at a linearly increasing hydraulic braking force and partially regenerative at a linearly decreasing regenerative braking force from the second level of created applied pressure to a third and still higher level of said created applied pressure, and to control braking to be completely hydraulic at a linearly increasing hydraulic braking force from the third level to all higher levels of said created applied pressure.

7. The method of claim 6, wherein said differential pressure is selectively maintained by metering the pressure between said created applied pressure and said brake assembly.