WO2013165737A2

WO2013165737A2 - Steering circuit with bypass valve

Info

Publication number: WO2013165737A2
Application number: PCT/US2013/037688
Authority: WO
Inventors: Akshay Avinash DURGE
Original assignee: Eaton Corporation
Priority date: 2012-04-30
Filing date: 2013-04-23
Publication date: 2013-11-07
Also published as: WO2013165737A3; IN2014DN09111A

Abstract

A steering circuit includes a fluid pump having an inlet in communication with a reservoir and an outlet. An actuator is in selective communication with the fluid pump. A steering unit defines a fluid inlet port in fluid communication with the fluid pump, a fluid outlet port in fluid communication with the fluid pump, and first and second control ports in fluid communication with the actuator. The steering unit includes a valve assembly having an open-center neutral position that provides fluid communication between the fluid inlet port and the fluid outlet port and a fluid meter. A pressure relieving valve provides fluid communication between the outlet of the fluid pump and the reservoir when fluid pressure exceeds a threshold value. A bypass valve provides selective fluid communication between the outlet of the fluid pump and the reservoir. The bypass valve is disposed in parallel to the pressure relieving valve.

Description

STEERING CIRCUIT WITH BYPASS VALVE

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is being filed on 23 April 2013, as a PCT International

Patent application and claims priority to U.S. Patent Application Serial No. 61/640,215 filed on 30 April 2012, the disclosure of which is hereby incorporated herein by reference.

BACKGROUND

[0002] In many "off -highway" vehicles, such as tractors, combines, loaders, line painting vehicles, sweepers, pavers, marine vehicles, etc., hydraulic steering circuits are utilized to control an actuator that steers the vehicle. In these hydraulic steering circuits, hydraulic steering control units are used to assist the driver in steering the vehicle by providing additional force to the steered wheels.

SUMMARY

[0003] An aspect of the disclosure relates to a steering circuit. The steering circuit includes a reservoir. A fluid pump includes an inlet that is in fluid communication with the reservoir and an outlet. An actuator is in selective fluid communication with the fluid pump. A steering control unit defines a fluid inlet port that is in fluid communication with the outlet of the fluid pump, a fluid outlet port that is in fluid communication with the outlet of the fluid pump, and first and second control ports in fluid communication with the actuator. The steering control unit includes a proportional valve assembly that has an open-center neutral position. The open-center neutral position provides fluid

communication between the fluid inlet port and the fluid outlet port. The steering control unit further includes a fluid meter in fluid communication with the proportional valve assembly. A pressure relieving valve provides fluid communication between the outlet of the fluid pump and the reservoir when a pressure of the fluid at the outlet of the fluid pump exceeds a threshold value. A bypass valve provides selective fluid communication between the outlet of the fluid pump and the reservoir. The bypass valve is disposed in parallel to the pressure relieving valve.

[0004] Another aspect of the present disclosure relates to a steering circuit. The steering circuit includes a reservoir, a fluid pump having an inlet in fluid communication with the reservoir and an outlet, an actuator in selective fluid communication with the fluid pump and a steering control unit. The steering control unit defines a fluid inlet port that is in fluid communication with the outlet of the fluid pump, a fluid outlet pump that is in fluid communication with the reservoir, and first and second control ports in fluid communication with the actuator. The steering control unit includes a proportional valve assembly and a fluid meter. The proportional valve assembly has an open-center neutral position that provides fluid communication between the fluid inlet port and the fluid outlet port. The fluid meter is in fluid communication with the proportional valve assembly. A pressure relieving valve provides fluid communication between the outlet of the fluid pump and the reservoir when a pressure of the fluid at the outlet of the fluid pump exceeds a threshold value. The steering circuit further includes a flow path disposed in parallel to the pressure relieving valve. The flow path provides selective fluid communication between the outlet of the fluid pump and the reservoir.

[0005] Another aspect of the present disclosure is related to a method of operating a bypass valve in a steering circuit. The method includes providing a reservoir, a fluid pump having an inlet in fluid communication with the reservoir and an outlet, an actuator, a steering control unit in selective fluid communication with the actuator, wherein the steering control unit includes a proportional valve assembly, having an open-center neutral position that provides fluid communication through the proportional valve assembly between the fluid pump and the reservoir when the proportional valve assembly is in the neutral position, and a fluid meter in fluid communication with the proportional valve assembly, a bypass valve, which is disposed in parallel to the proportional valve of the steering unit, providing selective fluid communication between the outlet of the fluid pump and the reservoir. The method further includes receiving a first signal that indicates that the actuator is at a travel limit. The bypass valve is actuated to an open position so that fluid is communicated from the outlet of the pump to the reservoir through the bypass valve. A second signal is received that indicates the actuator is being moved in a direction away from the travel limit. The bypass valve is actuated to the closed position.

DRAWINGS

[0006] FIG. 1 is a schematic representation of a steering circuit having exemplary features of aspects in accordance with the principles of the present disclosure.

[0007] FIG. 2 is a cross-sectional view of an exemplary steering control unit suitable for use with the steering circuit of FIG. 1.

[0008] FIG. 3 is an alternate embodiment of a steering circuit having exemplary features of aspects in accordance with the principles of the present disclosure.

[0009] FIG. 4 is a representation of exemplary modes of operation of the steering circuit of FIG. 1.

[0010] FIG. 5 is a representation of a power steering mode of operation.

DETAILED DESCRIPTION

[0011] Reference will now be made in detail to the exemplary aspects of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like structure.

[0012] Referring now to FIG. 1, a steering circuit 10 of a vehicle is shown. The steering circuit 10 could be utilized on a variety of off -highway type vehicles including tractors, skid steers, backhoes, etc. The steering circuit 10 includes a fluid pump 12, an actuator 14 and a steering control unit 16.

[0013] The fluid pump 12 includes an inlet 18 and an outlet 20. In the depicted embodiment, the fluid pump 12 is a fixed displacement pump. In one embodiment, the fluid pump 12 is a gear pump. The inlet 18 of the fluid pump 12 is in fluid

communication with a reservoir 22. The outlet 20 of the fluid pump 12 is in selective fluid communication with the actuator 14 via the steering control unit 16. [0014] In the depicted embodiment, the actuator 14 is a cylinder. The actuator 14 includes a piston rod 24 that is slidably disposed in a piston bore 26. The actuator 14 includes a first port 28 and a second port 30. The piston rod 24 extends or retracts in response to fluid supplied to the first and second ports 28, 30.

[0015] Referring now to FIGS. 1 and 2, the steering control unit 16 includes a proportional valve assembly 32. The steering control unit 16 defines a fluid inlet port 34, a fluid outlet port 36, a first control port 38 and a second control port 40. The fluid inlet port 34 is in fluid communication with the outlet 20 of the fluid pump 12 via a first flow path 42. The fluid outlet port 36 of the steering control unit 16 is in fluid communication with the reservoir 22 via a second flow path 44. The first and second control ports 38, 40 are in fluid communication with the first and second ports 28, 30 of the actuator 14 via third and fourth flow paths 46, 48, respectively. The proportional valve assembly 32 is disposed between the fluid inlet port 34 and the first and second control ports 38, 40.

[0016] In the subject embodiment, the proportional valve assembly 32 includes a rotary valve (e.g., a spool) 50 and a follow-up valve member (e.g., a sleeve) 52. The rotary valve 50 rotates within a bore 54 of the follow-up valve member 52 as a result of actuation of a steering actuation member 56 (e.g., a steering wheel, ajoystick, etc.). In one embodiment, the actuation of the steering actuation member 56 is manual. The proportional valve assembly 32 is movable from a neutral position N to a right turn position R or a left turn position L through the actuation of the steering actuation member 56.

[0017] In the right turn position R, fluid from the fluid inlet port 34 is communicated to the first control port 38 through a fluid meter 58 of the steering control unit 16 while fluid from the second control port 40 is communicated to the fluid outlet port 36 through the fluid meter 58. In the left turn position L, fluid from the fluid inlet port 34 is communicated to the second control port 40 through the fluid meter 58 while fluid from the first control port 38 is communicated to the fluid outlet port 36 through the fluid meter 58.

[0018] In the subject embodiment, the fluid meter 58 is a gerotor gear set. The gerotor gear set includes a star 60 eccentrically disposed in a ring 62. The fluid meter 58 functions as a metering device that measures the proper amount of fluid to be fed to the appropriate control port 38, 40 of the steering control unit 16 in response to rotation of the steering actuation member 56. The fluid meter 58 also functions as a follow-up device that provides follow-up movement to the follow-up valve member 52 of the proportional valve assembly 32. For example, pressurized fluid flowing through the proportional valve assembly 32 in response to rotation of the rotary valve 50 flows through the fluid meter 58 causing orbital and rotational movement of the star 60 within the ring 62. Such movement by the star 60 causes follow-up movement of the follow-up valve member 52 of the proportional valve assembly 32 by means of a drive shaft 64. The drive shaft 64 has a first end 66 that is engaged with the star 60 and an oppositely disposed second end 68 that is engaged with the follow-up valve member 52 via a pin.

[0019] The proportional valve assembly 32 of the steering control unit 16 has an open-center configuration. The open-center configuration provides fluid communication through the proportional valve assembly 32 between the fluid inlet port 34 and the fluid outlet port 36 of the steering control unit 16 when the proportional valve assembly 32 is in the neutral position N.

[0020] The steering circuit 10 includes a conventional pressure relieving valve 70 disposed upstream of the proportional valve assembly 32. The pressure relieving valve 70 is downstream of the outlet 20 of the fluid pump 12 and upstream of the fluid inlet port 34 of the steering control unit 16. In the subject embodiment, the pressure relieving valve 70 is adapted to communicate fluid from first flow path 42 to the second flow path 44 when the pressure of the fluid at the outlet 20 of the fluid pump 12 exceeds a threshold value (e.g., a pressure setting, etc.) of the pressure relieving valve 70. In the subject embodiment, the pressure relieving valve 70 is adapted to communicate fluid from outlet 20 of the fluid pump 12 to the reservoir 22 when the pressure of the fluid at the outlet 20 of the fluid pump 12 exceeds the threshold value of the pressure relieving valve 70.

[0021] The steering circuit 10 further includes a bypass valve 72 (e.g., directional valve, check valve, flow regulator valve, sequencing valve, etc.). The bypass valve 72 is adapted to provide fluid communication between the outlet 20 of the fluid pump 12 and the reservoir 22 when certain conditions are met regardless of the fluid pressure at the outlet 20 of the fluid pump 12 so that fluid from the fluid pump 12 can bypass the steering control unit 16. The bypass valve 72 is disposed in a parallel with the pressure relieving valve 70 of the steering control unit 16.

[0022] The bypass valve 72 includes a fluid inlet 74 and a fluid outlet 76. The fluid inlet 74 is in fluid communication with the first flow path 42 at a location between the outlet 20 of the fluid pump 12 and the fluid inlet port 34 of the steering control unit 16. The fluid outlet 76 of the bypass valve 72 is in fluid communication with the reservoir 22. In the depicted embodiment, the fluid outlet 76 of the bypass valve 72 is in fluid communication with the second flow path 44 at a location between the fluid outlet port 36 of the steering control unit 16 and the reservoir 22.

[0023] In one embodiment, the bypass valve 72 is a proportional valve. In a first position (shown in FIG. 1), fluid communication between the fluid inlet 74 and the fluid outlet 76 of the bypass valve 72 is blocked. In the second position, fluid communication between the fluid inlet 74 and the fluid outlet 76 is open and unrestricted. In the depicted embodiment, the bypass valve 72 is biased to the first (i.e., closed) position.

[0024] In the subject embodiment of FIG. 1 , the bypass valve 72 is an electro- hydraulic valve. The bypass valve 72 includes a solenoid 78. The solenoid 78 is adapted to receive a signal 80 from a controller 82. In response to the signal 80, the solenoid 78 actuates the bypass valve 72 to the second (i.e., open) position.

[0025] In the subject embodiment, the steering circuit 10 includes an actuator position sensor 84 and a steering actuator sensor 86. In the depicted embodiment, the actuator position sensor 84 is adapted to provide the position of the actuator 14. In one embodiment, actuator position sensor 84 detects when the actuator reaches an end or stop position. In another embodiment, the actuator position sensor 84 is a King Pin angle sensor.

[0026] The steering actuator sensor 86 is adapted to provide information related to the actuation of the steering actuation member 56. In one embodiment, the steering actuator sensor 86 is adapted to provide information regarding the position of the steering actuation member 56 and/or the rotation direction of the steering actuation member 56 and/or the RPM of the steering actuation member 56. [0027] In another embodiment, the steering circuit 10 may include a sensor that senses the amount of flow being communicated to the actuator 14. In another embodiment, the steering circuit 10 may include a sensor that senses the pressure of the fluid being communicated to the actuator 14.

[0028] In the subject embodiment, the controller 82 receives inputs from the sensors 84, 86. In response to the inputs from the sensors 84, 86, the controller outputs the signal 80 to the solenoid 78.

[0029] Referring now to FIG. 3, an alternate embodiment of a steering circuit 210 is shown. In FIG. 3, the components and features of the steering circuit 210 that are the same as those in the steering circuit 10 will have the same reference numerals and will not be further described. New components and features will have a reference number greater than 200.

[0030] The steering circuit 210 includes the fluid pump 12, the actuator 14 and the steering control unit 16. The steering circuit 210 further includes a bypass valve 272 that is in selective fluid communication with the outlet 20 of the fluid pump 12 and the reservoir 22. The bypass valve 272 is disposed in parallel with the pressure relieving valve 70. The bypass valve 272 functions similarly to the bypass valve 72. In the depicted embodiment, however, the bypass valve 272 is actuated manually. The bypass valve 272 includes an actuation member (e.g., button, lever, etc.) 273. By actuating the actuation member 273, the bypass valve 272 can be actuated between the first position and the second position.

[0031] Referring now to FIGS. 1 and 4, the steering circuit 10 has a plurality of modes of operation 100. In the depicted embodiment, the steering circuit 10 includes a power steering mode 102, a neutral mode 104 and an assist mode 106. In one

embodiment, the mode of operation would be selectable by the operator.

[0032] Referring now to FIGS. 1 , 4 and 5, an exemplary embodiment of the power steering mode 102 will be described. The power steering mode 102 would likely be selected by an operator when the steering actuation member 56 is going to be actuated.

[0033] In step 107 of the power steering mode 102, the controller 82 evaluates whether the actuator 14 is at a travel limit (e.g., fully extended, fully retracted, abutting a mechanical stop, etc.). In step 107, the controller 82 evaluates the signal from the actuator position sensor 84 to determine if the actuator 14 is at a travel limit. If the actuator 14 is not at a travel limit, the bypass valve 72 is actuated to the first position (i.e., the closed position) in step 108 so that fluid communication between the fluid inlet 74 and the fluid outlet 76 of the bypass valve 72 is blocked. In this position, the fluid from the outlet 20 of the fluid pump 12 is communicated to the proportional valve assembly 32 of the steering control unit 16.

[0034] If the actuator 14 is at a travel limit, the bypass valve 72 is actuated to the second position (i.e., the open position) in step 110 so that fluid communication between the fluid inlet 74 and the fluid outlet 76 of the bypass valve is open. With the bypass valve 72 in the second position, fluid from the outlet 20 of the fluid pump 12 is communicated to the reservoir 22 through the bypass valve 72.

[0035] In a conventional steering circuit, the pressure of the fluid from the pump outlet would increase when the steering actuator (e.g., cylinder) reached the travel limit. The pressure would increase until it exceeded the setting of a pressure relief valve at which point the pressure relief valve would open allowing fluid to be communicated to the reservoir. As the pressure of the fluid in the conventional steering circuit would be at the pressure relief valve setting, the pump would require more energy to operate. In addition, the temperature of the fluid in the conventional steering circuit would increase as it flowed over the pressure relief valve. In the steering circuit 10 described herein, the pressure of the fluid at the outlet 20 of the fluid pump 12 is below the setting of the pressure relieving valve 70 when the actuator 14 is at a travel limit due to the open flow path to the reservoir 22 through the bypass valve 72. As a result, the power consumed by the pump is low. In addition, since the fluid does not pass through the pressure relieving valve 70 when the actuator 14 is at the travel limit, less heat is generated as compared to the conventional steering circuit.

[0036] In step 112, the controller 82 receives a signal from the steering actuator sensor 86. If the direction of actuation of the steering actuation member 56 is in a direction away from the travel limit, the bypass valve 72 is actuated to the first position (i.e., the closed position) in step 114. [0037] Referring now to FIGS. 1 and 4, the neutral mode 104 will be described.

The neutral mode 104 would be selected by an operator when the steering function is not required. In one embodiment, the neutral mode might be selected if the vehicle is stationary and auxiliary functions of the vehicle are being used.

[0038] In the neutral mode 104, the bypass valve 72 is actuated to the first position (i.e., the open position) in step 116. In the first position, fluid communication between the fluid inlet 74 and the fluid outlet 76 of the bypass valve 72 is open.

[0039] Since the fluid pump 12 is in open fluid communication with the reservoir

22 in the neutral mode 104, movement of the rotary valve 50 will not result in movement of the actuator 14 until a rotational limit of the rotary valve 50 has been reached. In one embodiment, the rotational limit is 15 degrees. At this rotational limit, the rotary valve 50 gets mechanically coupled to the fluid meter 58, which operates as a pump. With the fluid meter 58 operating as a pump, actuation of the steering actuation member 56 causes fluid to be communicated to the control ports 38, 40 of the steering control unit 16 through a check valve 90 and through the proportional valve assembly 32. This type of steering is referred to hereafter as manual steering. The actuation force exerted on the steering actuation member 56 in order to get movement from the actuator 14 during manual steering is greater than the actuation force exerted on the steering actuation member 56 in order to get movement from the actuator 14 during power steering.

[0040] Referring still to FIGS. 1 and 4, the assist mode 106 will be described.

The assist mode 106 would be selected by an operator when the operation of the vehicle does not require frequent actuation of the steering actuation member 56. In one embodiment, the assist mode 106 would be selected when the vehicle is operating in a field (e.g., harvesting, planting, etc.).

[0041] In step 118 of the assist mode 106, the bypass valve 72 is actuated to a third position between the first and second positions. The third position is an

intermediate position that allows restricted fluid communication between the fluid inlet 74 and the fluid outlet 76 of the bypass valve 72. With the bypass valve 72 in the third position, fluid flows from the fluid inlet 74 to the fluid outlet 76 but the restriction in the pathway between the fluid inlet 74 and the fluid outlet 76 causes the pressure of the fluid in the first flow path 42 to be higher than the pressure of the fluid in the first flow path 42 when the bypass valve 72 is in the second position (i.e., the open position).

[0042] In the assist mode 106, the steering control unit 16 can be actuated using manual steering. Since the pressure of the fluid in the first flow path 42 in the assist mode 106 is higher than the pressure of the fluid in the first flow path 42 in the neutral mode 102, the actuation force exerted on the steering actuation member 56 in order to get movement from the actuator 14 during manual steering in the assist mode 106 is less than the actuation force exerted on the steering actuation member 56 in order to get movement from the actuator 14 during manual steering in the neutral mode 104.

[0043] Various modifications and alterations of this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood that the scope of this disclosure is not to be unduly limited to the illustrative embodiments set forth herein.

Claims

What is claimed is:

1. A steering circuit comprising:

a reservoir;

a fluid pump having an inlet in fluid communication with the reservoir and an outlet;

an actuator in selective fluid communication with the fluid pump;

a steering control unit defining a fluid inlet port that is in fluid communication with the outlet of the fluid pump, a fluid outlet port that is in fluid communication with the reservoir, and first and second control ports in fluid communication with the actuator, the steering control unit including:

a proportional valve assembly having an open-center neutral position, wherein the open-center neutral position provides fluid

communication between the fluid inlet port and the fluid outlet port;

a fluid meter in fluid communication with the proportional valve assembly; a pressure relieving valve providing fluid communication between the outlet of the fluid pump and the reservoir when a pressure of the fluid at the outlet of the fluid pump exceeds a threshold value; and

a bypass valve providing selective fluid communication between the outlet of the fluid pump and the reservoir, the bypass valve being disposed in parallel to the pressure relieving valve.

2. The steering circuit of claim 1 , wherein the bypass valve is a proportional valve having a fluid inlet and a fluid outlet, the bypass valve includes a first position in which fluid communication between the fluid inlet and the fluid outlet is blocked and a second position in which fluid communication between the fluid inlet and the fluid outlet is open.

3. The steering circuit of claim 1 , wherein the bypass valve having a fluid inlet and a fluid outlet, the bypass valve includes a first position that provides no fluid communication between the fluid inlet and the fluid outlet, a second position that provides open fluid communication between the fluid inlet and the fluid outlet, and a third position that provides restricted fluid communication between the fluid inlet and the fluid outlet.

4. The steering circuit of claim 2, wherein the bypass valve is a directional valve.

5. The steering circuit of claim 2, wherein the bypass valve is configured for manual actuation.

6. The steering circuit of claim 2, wherein the bypass valve is biased to the first position.

7. The steering circuit of claim 2, wherein the bypass valve is an electro-hydraulic valve.

8. The steering circuit of claim 7, further comprising:

a sensor;

a controller in communication with the sensor and the bypass valve, wherein the controller actuates the bypass valve in response to a signal from the sensor.

9. The steering circuit of claim 8, wherein the sensor detects when the actuator reaches an end position.

10. The steering circuit of claim 8, wherein the sensor monitors actuation of the proportional valve assembly of the steering control unit.

11. A steering circuit comprising:

a reservoir;

an actuator in selective fluid communication with the fluid pump; a steering control unit defining a fluid inlet port that is in fluid communication with the outlet of the fluid pump, a fluid outlet port that is in fluid communication with the reservoir, and first and second control ports in fluid communication with the actuator, the steering control unit including:

communication between the fluid inlet port and the fluid outlet port;

a flow path disposed in parallel to the pressure relieving valve, the flow path providing selective fluid communication between the outlet of the fluid pump and the reservoir.

12. The steering circuit of claim 11, wherein the flow path provides restrictive fluid communication between the outlet of the fluid pump and the reservoir.

13. The steering circuit of claim 12, wherein the flow path includes a bypass valve that actuates between a first position and a second position.

14. The steering circuit of claim 13, wherein the bypass valve includes a third position disposed between the first and second positions.

15. The steering circuit of claim 14, wherein the bypass valve is a proportional valve.

16. The steering circuit of claim 11, wherein the flow path includes a bypass valve that is selected from the group consisting of an electrohydraulic valve, a proportional valve, a directional valve, a check valve, a flow regulator valve, and a sequencing valve.

17. A method for operating a bypass valve in a steering circuit, the method comprising:

providing a reservoir, a fluid pump having an inlet in fluid communication with the reservoir and an outlet, an actuator, a steering control unit in selective fluid communication with the actuator, wherein the steering control unit includes a proportional valve assembly, having an open-center neutral position that provides fluid communication through the proportional valve assembly between the fluid pump and the reservoir when the proportional valve assembly is in the neutral position, and a fluid meter in fluid communication with the proportional valve assembly, a bypass valve providing selective fluid communication between the outlet of the fluid pump and the reservoir, the bypass valve being disposed in parallel to the proportional valve of the steering unit;

receiving a first signal that indicates that the actuator is at a travel limit;

actuating the bypass valve to an open position so that fluid is communicated from the outlet of the fluid pump to the reservoir through the bypass valve;

receiving a second signal that indicates the actuator is being moved in a direction away from the travel limit; and

actuating the bypass valve to a closed position.

18. The method of claim 17, wherein an actuator position sensor that provides the position of the actuator provides the first signal.

19. The method of claim 18, wherein a steering actuator sensor that provides information related to actuation of a steering actuation member provides the second signal.

20. The method of claim 17, wherein the bypass valve is selected from the group consisting of an electrohydraulic valve, a proportional valve, a directional valve, a check valve, a flow regulator valve, and a sequencing valve.