Braking system for a hydraulic motor

Abstract

The present disclosure is directed towards a hydraulic motor. The hydraulic motor may include a housing having a fluid inlet and a fluid outlet. The hydraulic motor may further include a shaft rotatably disposed within the housing, a rotating element coupled to the shaft configured to rotate with the shaft, and a plurality of pumping elements coupled to the rotating element in fluid communication with the fluid inlet and fluid outlet. The hydraulic motor may also include a brake rotor coupled to the shaft and a braking mechanism selectively coupled to the brake rotor.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from U.S. Provisional Application No. 61/193,771 to Nelson filed on Dec. 22, 2008.

TECHNICAL FIELD

The present disclosure relates generally to a hydraulic motor and, more particularly, to a hydraulic motor with a braking system.

BACKGROUND

Machines such as excavators, dozers, loaders, motor graders, or any other earth moving machine generally include an engine-driven hydraulic pump fluidly connected to one or more hydraulic drive motors for powering one or more propulsion devices to propel the machine. The hydraulic drive motors include an integrated braking mechanism to exert a braking force when the supply of driving fluid is suspended. The braking mechanism typically includes a piston that selectively engages a plurality of friction disks associated with a barrel plate of the hydraulic drive motor. When engaged, the piston is pressed against the friction disks, thereby exerting a significant frictional force on the barrel plate, which substantially prevents rotation and, therefore, operation of the hydraulic drive motor.

An alternative configuration is disclosed in U.S. Pat. No. 4,464,979 (“the '979 patent”) issued to Forster on Aug. 14, 1984. The '979 patent discloses an axial piston machine having a drive-flange shaft supported by two radial bearings and a gear wheel located on the drive-flange shaft between the radial bearings. The axial piston machine further includes a first and second brake disk associated with the gear wheel. Pressurized fluid directs an actuator piston against the first disk which in turn presses against the second disk. In this manner, the actuator piston generates friction against both the first and second disks, thereby slowing rotation of the drive-flange shaft of the axial piston machine.

Although the axial piston machine arrangement of the '979 patent may be adequate for some situations, other problems persist. In order to service, inspect, and/or repair the brake disks of the axial piston machine disclosed in the '979 patent, a portion of the axial piston machine housing needs to be removed to gain sufficient access to the brake disks. Gaining access to the brake disks by moving at least a portion of the axial piston machine's housing may be labor intensive and time consuming.

The following structure and system is directed to one or more improvements in the existing technology.

SUMMARY

In one aspect, the present disclosure is directed towards a hydraulic motor. The hydraulic motor may include a housing having a fluid inlet and a fluid outlet. The hydraulic device may further include a shaft rotatably disposed within the housing, a rotating element coupled to the shaft configured to rotate with the shaft, and a plurality of pumping elements coupled to the rotating element in fluid communication with the fluid inlet and fluid outlet. The hydraulic device may also include a brake rotor coupled to the shaft and a braking mechanism selectively coupled to the brake rotor.

In another aspect, the present disclosure is directed towards a method of operating a hydraulic motor with a braking system. The hydraulic motor may include a housing having a first port and a second port, a shaft rotatably disposed within the housing, and a brake rotor coupled to the shaft. The method may include adjusting a supply of pressurized fluid delivered to one of the first port and the second port; and selectively engaging the brake rotor to restrain rotation of the shaft

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary disclosed machine;

FIG. 2 is a cross-sectional illustration of an exemplary hydraulic motor of the machine of FIG. 1 having a braking system.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 10. Machine 10 may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, or any other industry known in the art. For example, machine 10 may be an earth moving machine, such as an excavator, a wheel loader, a backhoe, or any other suitable earth moving machine known in the art. Machine 10 may include, among other things, one or more traction devices 12, a power source 14, and a transmission 16 including a hydraulic motor 20 having a braking system 43 (FIG. 2).

Referring back to FIG. 1, traction devices 12 may include one or more tracks located on each side of machine 10 (only one side shown). Alternatively, traction devices 12 may include belts, wheels, or other traction devices known in the art. Any of traction devices 12 may be driven and/or steerable.

Power source 14 may provide power for the operation of machine 10. Power source 14 may embody a combustion engine, such as a diesel engine, a gasoline engine, a gaseous fuel powered engine (e.g., a natural gas engine), or any other type of combustion engine known in the art. Power source 14 may alternatively embody a non-combustion source of power such as a power storage device or any other suitable source of power.

Transmission 16 may include components that cooperate to efficiently transmit energy from power source 14 to traction devices 12. Transmission 16 may include a torque converter (not shown) for adjusting output torque from power source 14, a transmission controller (not shown) for controlling the operation of transmission 16, or any other such device for transmitting energy to traction devices 12. Although transmission 16 is illustrated as a hydrostatic transmission, it is contemplated that transmission 16 may include a hydro-mechanical transmission or any other means for transmitting power from power source 14.

Hydraulic pump 18 of transmission 16 may be operatively coupled to power source 14 and may be configured to convert at least a portion of a power output of power source 14 into a flow of pressurized fluid for driving hydraulic motor 20 associated with machine 10. Hydraulic pump 18 may be drivably connected to power source 14 via, for example, an input shaft 19. Alternatively, hydraulic pump 18 may be operably coupled to power source 14 via a torque converter (not shown), a clutch (not shown), a gear box (not shown), or in any other manner known in the art. Hydraulic pump 18 may be variable displacement, variable delivery, fixed displacement, or any other configuration known in the art. Hydraulic pump 18 may include an axial piston pump, a gear pump, a radial piston pump, or any other rotary driven device for pressurizing a flow of fluid.

Hydraulic motor 20 of transmission 16 may be fluidly connected to hydraulic pump 18 and may be configured to receive a flow of pressurized fluid from hydraulic pump 18. The flow of pressurized fluid through hydraulic motor 20 may cause an output shaft 22 of hydraulic motor 20 connected to traction devices 12 to rotate, thereby propelling and/or steering machine 10. Output shaft 22 of hydraulic motor 20 may be connected to traction devices 12 by, for example, a final drive 23. Final drive 23 may include a reduction gear arrangement, such as, for example, a bevel gear assembly, spur gear assembly, planetary gear assembly, and/or any other assembly known to those having skill in the art that provides a speed reduction. Although hydraulic motor 20 is illustrated as a drive for traction devices 12 it is contemplated that hydraulic motor 20 may be used in any application of machine 10 that may require mechanical energy to operate.

As illustrated in the embodiment of FIG. 2, hydraulic motor 20 may be an assembly of multiple components that interact to produce an output torque. In particular, hydraulic motor 20 may include a housing 28, a rotor 32, and output shaft 22. As described above, output shaft 22 may be coupled to traction devices 12 in a manner such that the rotational speed of output shaft 22 is directly proportional to the rotational speed of traction devices 12. Rotor 32 may be integral with output shaft 22 or, alternatively, joined to output shaft 22 through welding, sintering, or other known metal joining processes so that rotor 32 and output shaft 22 may rotate together. Output shaft 22 may extend through an opening in one end of housing and may be rotationally supported by housing 28 via bearings 31.

A plurality of piston members 34 may be fixedly connected to rotor 32. Each piston member 34 may be received in a respective piston sleeve 36. Specifically, each piston sleeve 36 may be coupled in a sealing manner around a spherical seal (not shown) of piston member 34. The plurality of piston sleeves 36 may be connected to barrel plate components 38 disposed in, for example, a first end 24 and a second end 26 of a central bore 27 of housing 28. Barrel plate components 38 disposed in first end 24 and second end 26 of central bore 27 may be connected to rotate with output shaft 22. Specifically, barrel plate components 38 may be fitted around output shaft 22 by a ball hinge and coupled to the output shaft 22 by, for example, a key connection. The ball hinge allows the barrel plate components 38 to wobble or tilt during rotation of output shaft 22 as barrel plate components 38 ride against an axial cam formed by face plates 40 disposed at first end 24 and second end 26 of housing 28. As output shaft 22, rotor 32, and barrel plate components 38 rotate, each piston sleeve 36 may move toward and away from a respective piston member 34 as barrel plate components 38 wobble or tilt. This reciprocation of piston sleeves 36 with respect to the piston members 34 causes an expansion and contraction of a chamber located in piston sleeves 36. While hydraulic motor 20 illustrated in the exemplary embodiment of FIG. 2 is described as a motor, it is understood that hydraulic motor 20 may function as both a pump and a motor depending on the tilt angle of the barrel components 38.

Housing 28 may include a plurality of ports in flow communication with the chamber located in piston sleeves 36. In one embodiment, housing 28 may include a first port 64 and a second port 66. First port 64 and second port 66 may be configured to provide flow communication between hydraulic pump 18 and the chamber in piston sleeves 36. More particularly, either one of first port 64 and second port 66 may act as a fluid inlet and deliver pressurized fluid from hydraulic pump 18 to piston sleeves 36 via distribution passageways 60 in housing 28 to drive output shaft 22. The other of first port 64 and second port 66 may act as a fluid outlet and return low pressure fluid to hydraulic pump 18.

Hydraulic motor 20 may include braking system 43 to exert a braking force when the supply of pressurized fluid to hydraulic motor 20 is suspended. Braking system 43 may include a brake rotor 44, and a braking mechanism 46 including one or more components configured to resist the rotation of brake rotor 44. Braking mechanism 46 may include brake springs 50, an actuator piston 52, and one or more brake disks 48.

Brake rotor 44 may be disposed in housing 28 and embody a plate-like member fixedly connected to an end of output shaft 22 such that a rotation of output shaft 22 results in a direct rotation of brake rotor 44. Brake rotor 44 may be integral to output shaft 22 or, alternatively, joined to output shaft 22 through welding, sintering, or other known metal joining processes. Brake rotor 44 may be held in place by way of a snap ring 54. It is contemplated that brake rotor 44 may be held in place by a fastener other than a snap ring, if desired, such as, for example a nut, pin, or any other fastener known to one skilled in the art.

Actuator piston 52 may disposed in housing 28 coaxially with brake rotor 44 on one side of brake rotor 44. Actuator piston 52 may receive a plurality of brake springs 50 in a plurality of bores formed in actuator piston 52. In one embodiment, the brake springs 50 may be received in a plurality of bores located on the periphery of actuator piston 52. The plurality of brake springs 50 may be configured to bias actuator piston 52 against brake disks 48. An end plate 45 may be provided to seal housing 28 and retain the plurality of brake springs 50 and actuator piston 52 in housing 28.

Brake disks 48 may be connected by way of a splined engagement to brake rotor 44 and configured to rotate together with brake rotor 44. Brake disks 48 may include alternating steel disks and friction disks such that, when actuator piston 52 is acted on by brake springs 50, brake disks 48 may be sandwiched between actuator piston 52 and housing 28 creating friction that resists the rotation of brake rotor 44. It will be understood that the number of brake disks 48 may vary, depending, for example, on the machine braking capacity. For example, while two steel disks and one friction disk are illustrated in the exemplary embodiment of FIG. 2, three or more steel disks and two or more friction disks may be used. While the exemplary embodiment of FIG. 2 may depict a gap between actuator piston 52 and brake disks 48, it is understood that the actuator piston and brake disks may be in frictional contact.

A pressure modulation chamber 56 may be formed between housing 28 and actuator piston 52. Pressure modulation chamber 56 may be configured to receive pressurized fluid from one of first port 64 and second port 66. More particularly, pressure modulation chamber 56 may be fluidly connected to first port 64 and second port 66 via distribution passages 60. In one embodiment, a resolver 62 may be disposed in a portion of distribution passageway 60, and may be configured to resolve the pressure of pressurized fluid contained within first and second ports 64, 66 and fluidly connect the respective ports thereof having higher pressure with pressure modulation chamber 56. For example, when the fluid at second port 66 has a pressure less than the pressure of fluid contained within pressure modulation chamber 56, resolver 62 may fluidly connect pressure modulation chamber 56 with first port 64. In this manner, pressurized fluid may be communicated to pressure modulation chamber 56 to act on a portion of actuator piston 52 and urge actuator piston 52 in a direction opposite of brake disks 48. It is contemplated that a valve such as, for example, a hydraulic valve, a pneumatic valve, or an electronic valve may be used in place of resolver 62. In yet another embodiment, a proportional valve may be placed in distribution passageway 60 to selectively communicate pressurized fluid to pressure modulation chamber 56 and control the braking force applied to brake rotor 44.

INDUSTRIAL APPLICABILITY

The braking system of the present disclosure may find application in any type of machine including a hydraulic motor. For example, the present disclosure may be applicable to any machine including a hydraulic motor for powering one or more propulsion devices to propel the machine. In one embodiment, hydraulic motor may be a floating-cup motor have a plurality of piston members that interact with a plurality of cup-like piston sleeves hydrostatically supported by a barrel plate component. Operation of the disclosed braking system is explained below.

In operation, according to the exemplary embodiment of FIG. 1, power source 14 may drive hydraulic pump, via input shaft 19, to produced pressurized fluid. The pressurized fluid generated by hydraulic pump 18 may then be supplied to hydraulic motor 20 via one of first and second ports 64, 66 (FIG. 2). The flow of pressurized fluid may be distributed to the pumping chambers formed by piston members 34 and piston sleeves 36 via distribution passageways 60 in housing 28. The other of first port 64 and second port 66 may discharge low pressure fluid from hydraulic motor 20.

When pressurized fluid is supplied to one of first port and second ports 64, 66, a portion of the flow of pressurized fluid may be communicated to pressure modulation chamber 56. More particularly, resolver 62 may be configured to resolve the pressure of pressurized fluid contained within first and second ports 64, 66 and fluidly connect the respective ports thereof having higher pressure with pressure modulation chamber 56. For example, when the fluid at second port 66 has a pressure less than the pressure of fluid contained within pressure modulation chamber 56 (i.e., when first port 64 receives high pressure fluid from hydraulic pump 18), resolver 62 may fluidly connect pressure modulation chamber 56 with first port 64.

As pressure modulation chamber 56 is filled with pressurized fluid, the fluid may act on a portion of actuator piston 52. At high fluid pressures, the pressure force may be greater than the spring force of brake springs 50 to drive actuator piston 52 in a direction opposite of brake disks 48 connected to brake rotor 44. Accordingly, as a portion of the chambers formed by piston member 34 and piston sleeve 36 are filled with pressurized fluid and a second portion of chambers formed by piston members 34 and piston sleeves 36 are drained of fluid, rotor 32 may be urged to rotate. As rotor 32 rotates, output shaft 22 may be free to rotate therewith to propelling machine 10.

When the supply of pressurized fluid to hydraulic motor 20 is suspended, a pressure differential may form across the distribution passages 60 between pressure modulation chamber 56 and each of first port 64 and second port 66. Resolver 62 may fluidly connect pressure modulation chamber 56 with the one of first port 64 and second port 66 discharging fluid from hydraulic motor 20 so that pressurized fluid may drain from pressure modulation chamber 56. For example, when the fluid at first port 64 has a pressure less than the pressure of fluid contained within pressure modulation chamber 56 (i.e., when first port 64 no longer receives high pressure fluid), resolver 62 may fluidly connect pressure modulation chamber 56 with second port 66. As fluid drains from pressure modulation chamber 56, brake springs 50 may return to it's biased position. In this manner, brake springs 50 may urge actuator piston 52 into frictional contact with brake disks 48 to exert a significant frictional force on brake rotor 44, which may substantially prevent rotation of output shaft 22.

The disclosed braking system 43 may provide an alternative configuration for braking a hydraulic motor 20 in a drive application. Because braking system 43 may be located near at one end of output shaft 22, closest to end plate 45, the disclosed braking system 43 may be convenient to inspect/service during the lifetime of the machine.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed braking system and hydraulic motor without departing from the scope of the disclosure. For example, although a single brake rotor 44 is illustrated, multiple brake rotors located on either end of output shaft 22 may be contemplated. In yet another example, brake rotor 44 may be omitted and braking mechanism 46 may alternatively be associated with rotor 32 of hydraulic motor 20. It is to be understood that hydraulic motor 20 is not be limited to the embodiment illustrated in FIG. 2. Hydraulic motor 20 may include an inline motor, a bent-axis motor, or any other rotary driven device configured to receive a flow of pressurized energy and produce an output torque. It is further understood that the application of the disclosed braking system may be readily modified for use with, for example, any electric motor known in the art.

Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A hydraulic motor, comprising:

a housing having a fluid inlet and a fluid outlet;

a shaft rotatably disposed within the housing;

a rotating element coupled to the shaft and configured to rotate with the shaft;

a plurality of piston elements coupled to the rotating element in fluid communication with the fluid inlet and the fluid outlet;

a brake rotor coupled to the shaft; and

a braking mechanism selectively coupled to the brake rotor.

2. The hydraulic motor of claim 1, wherein the braking mechanism includes a plurality of brake disks coupled to the brake rotor and an actuator piston for exerting a pressing force to the plurality brake disks to frictionally engage the plurality of brake disks.

3. The hydraulic motor of claim 2, further including at least one brake spring configured to bias the actuator piston against the plurality of brake disks.

4. The hydraulic motor of claim 3, further including a pressure modulation chamber for introducing pressurized fluid to the actuator piston to direct the actuator piston in a direction opposite of the plurality brake disks.

5. The hydraulic motor of claim 4, wherein the pressure modulation chamber is connected to receive pressurized fluid from the fluid inlet.

6. The hydraulic motor of claim 1, wherein the brake rotor is disposed within the housing proximate to an end plate attached to the housing.

7. A method of operating a hydraulic motor with a braking system, the hydraulic motor including a housing having a first port and a second port, a shaft rotatably disposed within the housing, and a brake rotor coupled to the shaft, the method comprising:

selectively engaging the brake rotor to restrain rotation of the shaft as a function of a supply of pressurized fluid delivered to one of the first port and the second port.

8. The method of claim 7, wherein selectively engaging the brake rotor includes selectively engaging at least one brake disk coupled to the brake rotor.

9. The method of claim 7, further including controlling an actuator piston to act on the at least one brake disk coupled to the brake rotor, engaging the at least one brake disk against the housing.

10. The method of claim 9, further including directing pressurized fluid to a pressure modulation chamber to reduce the frictional engagement between the at least one brake disk and the housing.

11. The method of claim 10, wherein directing pressurized fluid to the pressure modulation chamber includes directing a portion of pressurized fluid to the pressure modulation chamber and the remaining portion to a plurality of chambers coupled to the rotating element.

12. The method of claim 11, further including resolving the pressure of pressurized fluid contained within the first port and the second port and fluidly connecting the respective port having a higher pressure with the pressure modulation chamber.

13. A floating-cup motor, comprising:

a housing having a fluid inlet and a fluid outlet;

a shaft rotatably disposed within the housing;

a rotor coupled to the shaft and configured to rotate with the shaft;

a plurality of piston members extending from the rotor;

a plurality of piston sleeves receiving the plurality of piston members, the plurality of piston sleeves in communication with the fluid inlet and the fluid outlet;

a brake rotor coupled to the shaft; and

an actuator piston for exerting a pressing force to a plurality of brake disks fixedly connected to the brake rotor.

14. The hydraulic motor of claim 13, further including a plurality of brake springs to bias the actuator piston against the plurality of brake disks.

15. The hydraulic motor of claim 14, wherein the plurality of brake springs are disposed in a plurality of bores located on the periphery of the actuator piston.

16. The hydraulic motor of claim 13, further including a pressure modulation chamber disposed between the actuator piston and the housing.

17. The hydraulic motor of claim 16, wherein pressurized fluid is introduced to the pressure modulation chamber to reduce the frictional contact between a plurality of brake disks and the housing.

18. The hydraulic motor of claim 16, wherein the pressure modulation chamber is connected to receive pressurized fluid from the fluid inlet.

19. The hydraulic motor of claim 13, wherein the brake rotor is disposed within the housing proximate to an end plate attached to the housing.

20. The hydraulic motor of claim 19, wherein the brake rotor is disposed between a cavity in the housing and the end plate.