Electro-hydraulic power steering systems having improved efficiency

• US 6,122,912 A
• Filed: 10/15/1998
• Issued: 09/26/2000
• Est. Priority Date: 10/16/1997
• Status: Expired due to Fees

• Current Assignee: Techco Corp.
• Original Assignee: Techco Corp.
• Inventors: Phillips, Edward H.
• Primary Examiner(s): NGUYEN, HOANG M
• Application Number:
  US09/172,835
• Time in Patent Office: 712 Days
• Field of Search: 60/413, 60/431, 60/384, 91/375 R, 91/375 A
• US Class Current: 60/413
• CPC Class Codes: B62D 5/065 characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist

Abstract

A regenerative power steering system 10 for a vehicle, alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an energy regeneration mode which recovers energy while the vehicle exits a turn. The system comprises a motor pump 24 connected to a fluid delivery line 20 and a reservoir structure 76, in turn connected to a closed-center control valve assembly 38 for actuating a power cylinder 18 connected to the vehicle wheels. The pump 24 is connected to the delivery line 20 and the reservoir structure 76 by a four-way cross-over valve 30.

Claims

1. A regenerative power steering system (10) for a vehicle, alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an energy regeneration mode which recovers energy while the vehicle exits a turn;

wherein the system (10) employs a fluid, and wherein the system (10) comprises;

a power cylinder (18);

a valve assembly (38) fluidly connected to and controlling actuation of the power cylinder (18);

a fluid delivery line (20) fluidly connected to the valve assembly (38);

a reservoir structure (76) fluidly connected to the valve assembly (38);

a motor pump (24) having an outlet port (78) and an inlet port (80);

means (28) for switching the system (10) between the straight steering, powered assist and energy regeneration modes, comprising a four-way cross-over valve (30) operable between;

(a) a first position associated with the powered assist mode of the system (10), in which the four-way cross-over valve (30) fluidly connects the motor pump outlet port (78) to the fluid delivery line (20) and fluidly connects the motor pump inlet port (80) to the reservoir structure (76); and

(b) a second position associated with the energy regeneration mode of the system (10), in which the four-way cross-over valve (30) fluidly connects the motor pump outlet port (78) to the reservoir structure (76) and fluidly connects the motor pump inlet port (80) to the fluid delivery line (20); and

a motor generator (26) operatively connected to the motor pump (24), the motor generator (26) driving the motor pump (24) so as to provide a flow of pressurized fluid to the valve assembly (38) and the power cylinder (18) during the powered assist mode of the system (10), and the motor generator (26) generating energy recovered through the motor pump (24) during the power regeneration mode of the system (10).

2. The power steering system (10) according to claim 1, further comprising a means (82) for storing and delivering electrical energy, and an electronic control means (32) for coordinating (a) movement of the four-way cross-over valve (30) between its first and second positions and (b) connection of the motor generator (26) to the electrical energy storing and delivering means (82), in a manner so that electrical energy is delivered from the electrical energy means (82) to the motor generator (26) during the powered assist mode of the system (10), and is stored to the electrical energy means (82) by the motor generator (26) during the energy regeneration mode of the system (10).

3. The power steering system (10) according to claim 1, wherein the switching means (28) further comprises a solenoid (34) operatively connected to the four-way cross-over valve (30).

4. The power steering system (10) according to claim 3, wherein the solenoid (34) is a centering, push-pull, double actuated solenoid.

5. The power steering system (10) according to claim 1, wherein the system (10) generates signals representative of the torque applied by the motor generator (26) to the motor pump (24) and the fluid pressure in the fluid delivery line (20), and wherein the system (10) further comprises an electronic control means (32) for actuating the switching means (28) in response to the polarity of the difference between the signals representative of the torque applied by the motor generator (26) to the motor pump (24) and the fluid pressure in the fluid delivery line (20).

6. The power steering system (10) according to claim 1, wherein the reservoir structure (76) comprises a fluid reservoir (50) and a fluid return line (22) fluidly connecting the valve assembly (38) to the fluid reservoir (50);

and wherein the system (10) further comprises a check valve (36) fluidly connected to the fluid delivery line (20) and the fluid return line (22) and disposed in parallel with the valve assembly (38), the check valve (36) being closed when the pressure of the fluid in the fluid delivery line (20) is greater than the pressure of the fluid in the fluid return line (22) and being open when the pressure of the fluid in the fluid return line (22) is greater than the pressure of the fluid in the fluid delivery line (20), thereby preventing cavitation in the fluid delivery line (20) upon abrupt actuation of the valve assembly (38) controlling actuation of the power cylinder (18).

7. The power steering system (10) according to claim 1, wherein the reservoir structure (76) comprises a fluid reservoir (50), a suction line (48) fluidly connecting the four-way cross-over valve (30) to the fluid reservoir (50) and a check valve (52) disposed in parallel with the suction line (48), oriented so as to prevent cavitation of the motor pump (24) during the powered assist mode.

8. The power steering system (10) according to claim 1, wherein the four-way cross-over valve (30) is an underlapped, closed-center valve.

9. The power steering system (10) according to claim 8, wherein the four-way cross-over valve (30) is further operable in a neutral position between its first and second positions, associated with the straight steering mode of the system (10), in which the four-way cross-over valve (30) fluidly connects all of the motor pump outlet port (78), the motor pump inlet port (80), the fluid delivery line (20) and the reservoir structure (76) to one another.

10. The power steering system (10) according to claim 1, wherein the power cylinder (18) comprises a pair of ports (56 and 58) fluidly connectable to the valve assembly (38) for actuation of the power cylinder (18), and wherein the valve assembly (38) is an underlapped, closed-center, four-way valve, operable in a neutral position associated with the straight steering mode of the system (10), in which the valve assembly (38) fluidly connects all of the fluid delivery line (20), the reservoir structure (76) and the ports (56 and 58) of the power cylinder (18) to one another.

11. The power steering system (10) according to claim 1, wherein the motor pump (24) rotates in the same direction during substantial portions of both the powered assist and energy regeneration modes of the system (10).

12. The power steering system (10) according to claim 1, wherein the motor pump (24) and the motor generator (26) do not rotate during the straight steering mode of the system (10).

13. A regenerative power steering system (10) for a vehicle, alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an energy regeneration mode which recovers energy while the vehicle exits a turn;

wherein the system (10) employs a fluid, and wherein the system (10) comprises;

a power cylinder (18);

an underlapped, closed-centered, four-way valve assembly (38) fluidly connected to and controlling actuation of the power cylinder (18);

a fluid delivery line (20) fluidly connected to the valve assembly (38);

a reservoir structure (76) fluidly connected to the valve assembly (38);

a motor pump (24) having an outlet port (78) and an inlet port (80);

means (28) for switching the system (10) between the straight steering, powered assist and energy regeneration modes, comprising a four-way cross-over valve (30) and a centering, push-pull, double actuated solenoid operatively connected to the four-way cross-over valve (30), such that the four-way cross-over valve (30) is operable between;

(a) a first position associated with the powered assist mode of the system (10), in which the four-way cross-over valve (30) fluidly connects the motor pump outlet port (78) to the fluid delivery line (20) and fluidly connects the motor pump inlet port (80) to the reservoir structure (76); and

(b) a second position associated with the energy regeneration mode of the system (10), in which the four-way cross-over valve (30) fluidly connects the motor pump outlet port (78) to the reservoir structure (76) and fluidly connects the motor pump inlet port (80) to the fluid delivery line (20);

a motor generator (26) operatively connected to the motor pump (24), the motor generator (26) driving the motor pump (24) so as to provide a flow of pressurized fluid to the valve assembly (38) and the power cylinder (18) during the powered assist mode of the system (10), and the motor generator (26) generating energy recovered through the motor pump (24) during the power regeneration mode of the system (10), the system (10) generating signals representative of the torque applied by the motor generator (26) to the motor pump (24) and of the fluid pressure in the fluid delivery line (20);

a means (82) for storing and delivering electrical energy; and

an electronic control means (32) for;

(i) coordinating both (a) movement of the four-way cross-over valve (30) between its first and second positions, and (b) connection of the motor generator (26) to the electrical energy storing and delivering means (82), in a manner so that electrical energy is delivered from the electrical energy means (82) to the motor generator (26) during the powered assist mode of the system (10), and is stored to the electrical energy means (82) by the motor generator (26) during the energy regeneration mode of the system (10); and

(ii) for actuating the solenoid (34) in response to the polarity of the difference between the signals representative of the torque applied by the motor generator (26) to the motor pump (24) and the fluid pressure in the fluid delivery line (20);

wherein the motor pump (24) rotates in the same direction during substantial portions of both the powered assist and energy regeneration modes of the system (10), and wherein the motor pump (24) and the motor generator (26) do not rotate during the straight steering mode of the system (10);

wherein the reservoir structure (76) comprises a fluid reservoir (50), a fluid return line (22) fluidly connecting the valve assembly (38) to the fluid reservoir (50), a suction line (48) fluidly connecting the four-way cross-over valve (30) to the fluid reservoir (50) and a check valve (52) disposed in parallel with the suction line (48), oriented so as to prevent cavitation of the motor pump (24) during the powered assist mode; and

wherein the system (10) further comprises a check valve (36) fluidly connected to the fluid delivery line (20) and the fluid return line (22) and disposed in parallel with the valve assembly (38), the check valve (36) being closed when the pressure of the fluid in the fluid delivery line (20) is greater than the pressure of the fluid in the fluid return line (22) and being open when the pressure of the fluid in the fluid return line (22) is greater than the pressure of the fluid in the fluid delivery line (20), thereby preventing cavitation in the fluid delivery line (20) upon abrupt actuation of the valve assembly (38) controlling actuation of the power cylinder (18);

wherein the four-way cross-over valve (30) is further operable in a neutral position between its first and second positions, associated with the straight steering mode of the system (10), in which the four-way cross-over valve (30) fluidly connects all of the motor pump outlet port (78), the motor pump inlet port (80), the fluid delivery line (20) and the reservoir structure (76) to one another; and

wherein the power cylinder (18) comprises a pair of ports (56 and

     58) fluidly connectable to the valve assembly (38) for actuation of the power cylinder (18), and wherein the valve assembly (38) is further operable in a neutral position associated with the straight steering mode of the system (10), in which the valve assembly (38) fluidly connects all of the fluid delivery line (20), the reservoir structure (76) and the ports (56 and

     58) of the power cylinder (18) to one another.

14. A method of controlling and regenerating energy in a power steering system (10) for a vehicle, the system (10) being alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an energy regeneration mode which recovers energy while the vehicle exits a turn, and the system (10) employing a fluid;

wherein the system (10) comprises a power cylinder (18), a fluid delivery line (20) switchably fluidly connected to the power cylinder (18), a motor pump (24) supplying a flow of pressurized fluid through the delivery line (20) and to the power cylinder (18) during the powered assist mode of the system (10), and a motor generator (26) operatively connected to the motor pump (24) so as to generate energy recovered from the motor pump (24) during the energy regeneration mode of the system (10); and

wherein the method comprises the steps of;

generating normalized signals representative of the torque applied by the motor generator (26) to the motor pump (24), and of the fluid pressure in the fluid delivery line (20);

switching operation of the system (10) to the energy regeneration mode when the polarity of the respective difference between the signals is negative; and

switching operation of the system (10) to the powered assist mode when the polarity of the respective difference between the signals is positive.

15. A power steering system (240) for a vehicle, alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an returned energy dissipation mode which dissipates returning stored energy while the vehicle exits a turn;

wherein the system (240) employs a fluid, and wherein the system (240) comprises;

a power cylinder (18);

a valve assembly (38) fluidly connected to and controlling actuation of the power cylinder (18);

a motor pump (24) having an outlet port (78) and an inlet port (80);

a fluid delivery line (20) fluidly connecting the outlet port (78) to the valve assembly (38);

a reservoir (50);

a suction line (21) fluidly connecting the reservoir (50) to the inlet port (80);

a fluid return line (22) fluidly connecting the valve assembly (38) to the reservoir (50);

dynamic braking means (244) for dissipating stored energy recovered from the power cylinder (18) during the returned energy dissipation mode, comprising a pressure balanced bypass valve assembly (246) operable between;

(a) a closed position associated with the powered assist mode of the system (240); and

(b) a modulated partially open position associated with the returned energy dissipation mode of the system (240), in which the pressure balanced bypass valve assembly (246) fluidly connects the fluid delivery line (20) to the fluid return line (22) in a selectably restricted manner; and

a motor generator (26) operatively connected to the motor pump (24), the motor generator (26) driving the motor pump (24) so as to provide a flow of pressurized fluid to the valve assembly (38) and the power cylinder (18) during the powered assist-node of the system (240).

16. The power steering system (240) according to claim 15, further comprising a means (82) for storing and delivering electrical energy, and

an electronic control means (242) for coordinating (a) movement of the pressure balanced bypass valve assembly (246) between its closed and modulated partially open positions and (b) connection of the motor generator (26) to the electrical energy storing and delivering means (82), in a manner so that electrical energy is delivered from the electrical energy means (82) to the motor generator (26) during the powered assist mode of the system (240), and is dissipated via the restricted passage of pressurized fluid through the pressure balanced bypass valve assembly (246) during the returned energy dissipation mode of the system (240).

17. The power steering system (240) according to claim 16, wherein the system (240) generates signals representative of the torque applied by the motor generator (26) to the motor pump (24) and of the fluid pressure in the fluid delivery line (20), and wherein the electronic control means (242) coordinates the movement of the pressure balanced bypass valve assembly (246) and the connection of the motor generator (26) to the electrical energy storing and delivering means (82) in response to the signals representative of the torque applied by the motor generator (26) to the motor pump (24) and of the fluid pressure in the fluid delivery line (20).

18. The power steering system (240) according to claim 17, wherein the electronic control means (242) causes the pressure balanced bypass valve assembly (246) to selectively permit the restricted passage of pressurized fluid through the pressure balanced bypass valve assembly (246) in response to the signal representative of the fluid pressure in the fluid delivery line (20) exceeding the signal representative of the torque applied by the motor generator (26) to the motor pump (24).