PISTON HYDRAULIC DEVICE

Abstract

 A piston hydraulic device is disclosed. The device comprises a cylinder block having a plurality of cylinder assemblies. The cylinder block being rotatable about a first rotation axis wherein each cylinder assembly comprises a cylinder and a piston. A first conduit provides passage of a fluid at a first pressure. A second conduit provides passage of a fluid at a second pressure wherein the first pressure is different from the second pressure. The piston hydraulic device further comprises a plurality of directional control valves fluidly connected to the first and second conduits and the respective cylinders wherein each directional control valve connects the respective cylinder to the first conduit in a first position and to the second conduit in a second position. A controller is operatively associated with the directional control valves for switching between the first and the second positions.

Description

Technical Field

[0001] This disclosure relates to the field of piston hydraulic devices such as pumps or motors, particularly to variable displacement piston hydraulic devices, and more particularly to the control of the fluid displacement and of management of early/late connection with the high/low pressure line in the piston hydraulic devices.

Background

[0002] Piston hydraulic devices may be axial piston machines or radial piston. The piston hydraulic devices may be operated as pumps or motors.

[0003] Variable axial piston hydraulic devices may be swash plate type devices or bent axis type devices. Swash plate type axial piston devices have a tiltable swash plate that controls the stroke of the piston within a rotating cylinder block. With bent axis type axial piston devices, the pistons are at an angle to the drive/ driven shaft.

[0004] In both the "swash plate" and the "bent axis" types, the devices comprise a cylinder block carrying the pistons. The cylinder block rotates about a first axis. The devices also comprise a transmission shaft that rotates around a second axis of rotation, also called the transmission axis. Through this shaft mechanical work that is carried out for the compression of fluid (in the case of the pumps) or mechanical work (in the case of the motors) is determined by the pressure of the operating fluid.

[0005] In the swash plate type device, the first and second axes coincide. The swash plate has a variable inclination to vary the stroke of the pistons between the dead points and, accordingly, the displacement of the machine. For varying displacement in the swash plate type device, the inclination of the plate is varied to change the stroke of the pistons.

[0006] In bent-axis type device, the first and the second axis are incident. The relative inclination of these axes is varied to vary the stroke of the pistons between the dead points and, accordingly, the displacement of the machine. For varying displacement in the bent-axis type device, the inclination of the cylinder block is varied.

[0007] In both the "swash plate" and the "bent axis" types, the device comprises a port plate having a first port and a second port for the connection of the chamber of each piston, alternately, to the high and low pressure line. The first and second ports are angularly spaced relative to the first rotation axis. The geometry of the first and second ports is fixed and defines the timing for the connection of the chamber of each piston to the high or the low pressure line relative to the dead points of piston travel.

[0008] The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of the prior art system.

Brief Summary of the Invention

[0009] In a first aspect, the present disclosure describes a piston hydraulic device comprising a cylinder block having a plurality of cylinder assemblies, the cylinder block being rotatable about a first rotation axis wherein each cylinder assembly comprises a cylinder and a piston; a first conduit for the passage of a fluid at a first pressure; a second conduit for the passage of a fluid at a second pressure wherein the first pressure is different from the second pressure; characterized in that, the piston hydraulic device further comprises a plurality of directional control valves fluidly connected to the first and second conduits and the respective cylinders wherein each directional control valve connects the respective cylinder to the first conduit in a first position and to the second conduit in a second position; and a controller operatively associated with the directional control valves for switching between the first and the second positions.

[0010] In a second aspect, the present disclosure describes a method for controlling a piston hydraulic device. The method comprises the steps of providing a cylinder block having a plurality of cylinder assemblies, the cylinder block being rotatable about a first rotation axis wherein each cylinder assembly comprises a cylinder and a piston; supplying or receiving a fluid at a first pressure through a first conduit; supplying or receiving a fluid at a second pressure through a second conduit wherein the first pressure is different from the second pressure; and actuating independently a plurality of directional control valves between a first and a second positions, the plurality of directional control valves being fluidly connected to the first and second conduits and the respective cylinders wherein each directional control valve connects the respective cylinder to the first conduit in the first position and to the second conduit in the second position.

Brief Description of the Drawings

[0011] The foregoing and other features and advantages of the present disclosure will be more fully understood from the following description of various embodiments, when read together with the accompanying drawings, in which:

Fig. 1 is a schematic illustration of the piston hydraulic device according to the present disclosure;

Fig. 2 is a cross sectional view of a portion of a swash plate type axial piston hydraulic device according to the present disclosure; and

Fig. 3 is a cross sectional view of a portion of a bent axis type axial piston hydraulic device according to the present disclosure.

Detailed Description

[0012] This disclosure generally relates to a piston hydraulic device. The device is configured to have continuous variation of fluid displacement and an efficient management of the timing for the connection of a cylinder assembly to the high or the low pressure line relative to the dead points of a piston stroke.

[0013] Fig. 1 schematically illustrates the piston hydraulic device 10 (hereinafter referred to as "device"). In an embodiment the device 10 is an axial piston hydraulic device. In an alternative embodiment, the device 10 may be a radial piston hydraulic device. The device 10 comprises a cylinder block 12, a first conduit 14, a second conduit 16, a plurality of directional control valves 56 and a controller 58.

[0014] The cylinder block 12 comprises a plurality of cylinder assemblies 24. The cylinder block 12 is rotatable about a first rotation axis A (not shown). The cylinder block 12 is rotatably supported in the device 10. Cylinder block 12 is rotatably supported in a housing (not shown) of the device 10. The cylinder assemblies 24 are radially positioned in the cylinder block 12 relative to the first rotation axis A. The cylinder assemblies 24 are mutually angularly spaced. The cylinder block 12 has first block surface 30 and a second block surface 32. First and second block faces 30, 32 are formed on opposite sides of the cylinder block 12. First and second block faces 30, 32 are parallel.

[0015] Each cylinder assembly 24 comprises a cylinder 26 and a piston 28. The cylinders 26 have respective openings 34 on the first block surface 30. Pistons 28 extend and retract in the cylinders 26. Pistons 28 extend from the openings 34. Cylinders 26 have a base 36. A cylinder conduit 48 extends from the base 36 to the second block face 32. Cylinder conduit communicates with the cylinder 26. Fluid enters and exits the cylinder 26 through the cylinder conduit 48. Pistons 28 have a piston head 42 and a piston base 44. Piston head 42 is positioned external to the cylinder 26. Piston base 44 travels in the cylinder 26 during a stroke of the piston 28. Piston base 44 may move towards the base 36 of the cylinder 26 at the end of the return stroke. Each piston 28 moves along the respective cylinder 26 in parallel to the first rotation axis A.

[0016] Piston 28 defines a chamber 46 in the cylinder 26. The chamber 46 varies in volume as the piston 28 extends and retracts in the cylinder 26. Change in the fluid in the chamber 46 acts on the piston base 44. The chamber 46 varies in volume from a maximum volume which is reached when the piston 28 is at the top dead centre of an extraction stroke to a minimum volume which is reached when the piston 28 is at the bottom dead centre of a return stroke.

[0017] The first conduit 14 provides a passage of a fluid at a first pressure. The second conduit 16 provides a passage of a fluid at a second pressure. The first pressure is different from the second pressure. In an embodiment, the first pressure is higher than the second pressure. In a further embodiment, a high pressure fluid flows along the first conduit 14 and a low pressure fluid flows along the second conduit 16. In an alternate embodiment the first pressure is lower than the second pressure. In a further embodiment, a low pressure fluid flows along the first conduit 14 and a high pressure fluid flows along the second conduit 16.

[0018] The plurality of directional control valves 56 are fluidly connected to the first conduit 14. Each directional control valve 56 is independently fluidly connected to the first conduit 14. The first conduit 14 supplies/receives fluid at the first pressure to/from the plurality of directional control valves 56.

[0019] The plurality of directional control valves 56 are fluidly connected to the second conduit 16. Each directional control valve 56 is independently fluidly connected to the second conduit 16. The second conduit 16 supplies/receives fluid at the second pressure to/from the plurality of directional control valves 56.

[0020] Each directional control valve 56 is fluidly connected to the respective cylinder assembly 24. In a preferred embodiment, each directional control valve 56 is fluidly connected to the respective cylinder 26. In yet a preferred embodiment, each directional control valve 56 is fluidly connected to the respective cylinder 26 through the cylinder conduit 48. Each cylinder assembly 24 is fluidly connected to the respective directional control valve 56. In a preferred embodiment, each cylinder 26 is fluidly connected to the respective directional control valve 56. In yet a preferred embodiment, each cylinder 26 is fluidly connected to the respective directional control valve 56 through the cylinder conduit 48. The plurality of directional control valves 56 are each actuatable independently.

[0021] Fluid at a first pressure from the first conduit 14 is supplied to/sent out from the cylinder 26 through the respective directional control valve 56. Fluid at a second pressure from the second conduit 16 is supplied to/sent out from the cylinder 26 through the respective directional control valve 56. Each cylinder 26 receives/sends out either the fluid at the first pressure or the fluid at the second pressure from the respective directional control valve 56.

[0022] The at least one directional valve 56 is actuatable between a first position 57 and a second position 59. The at least one directional valve 56 is actuatable between a first position 57 and a second position 59 through mechanical means. The mechanical means is electronically controlled. In an embodiment, the mechanical means is an actuation member 60. Actuation member 60 may be comprised in the at least one directional valve 56.

[0023] In a further embodiment, the actuation member 60 may operate in conjunction with a return spring 62. The activation of the actuation member 60 may actuate the at least one directional valve 56 from the first position 57 to the second position 59. The deactivation of the actuation member 60 permits the return spring 62 to return the at least one direction valve 56 from the second position 59 to the first position 57. In an embodiment, the directional control valve 56 is a three way two position valve.

[0024] Each directional control valve 56 connects the respective cylinder 26 to the first conduit 14 in the first position 57. The piston 28 extends or retracts corresponding to the first fluid pressure relative to the fluid pressure in chamber 46. The piston 28 extends or retracts correspondingly in regards to the pressure differential between the chamber 46 and the first pressure in the first conduit 14.

[0025] Each directional control valve 56 connects the respective cylinder 26 to the second conduit 16 in the second position 59. The piston 28 extends or retracts corresponding to the second fluid pressure relative to the fluid pressure in chamber 46. The piston 28 extends or retracts correspondingly in regards to the pressure differential between the chamber 46 and the second pressure in the second conduit 16.

[0026] The controller 58 is operatively associated with the plurality of directional control valves 56 for switching between the first and the second positions 57, 59. Controller 58 electronically sends signals to the actuation member 60 for actuation of the at least one directional control valve 56 between the first and the second positions 57, 59. In embodiment, controller 58 electronically sends signals to the actuation member 60 for actuation of the at least one directional control valve 56 from the first position 57 to the second position 59. Controller 58 comprises a programmable memory module. The memory module is programmable for the actuation of the at least one directional control valve 56. The timing and operation of the actuation may be performed in accordance to the programmable memory.

[0027] In an embodiment, a controller 58 is connected to the plurality of directional control valves 56. In yet a further embodiment, a plurality of controllers 58 are connected to each directional control valve 56.

[0028] The device 10 may further comprises a positioning sensor 80. In an embodiment, the positioning sensor 80 senses the angular position of the cylinder block 12. In alternative embodiment, the positioning sensor 80 senses the angular position of a shaft [not shown]. The positioning sensor 80 is connected to the controller 58. The positioning sensor 80 provides information of the angular position to the controller 58. The information in relation to the angular position may be used to compute the timing of the connection of the respective cylinders 26 to the first or second conduit 14, 16.

[0029] The device 10 further comprises a plurality of connecting conduits 64. The plurality of connecting conduits 64 are interposed between the plurality of directional control valves 56 and the respective cylinders 26.

[0030] Fig. 2 illustrates the device 10 as a swash plate type axial piston hydraulic device. Device 10 comprises a housing 72. A shaft 76 is coupled to the cylinder block 12. In an embodiment, shaft 76 may be a drive shaft. In an alternative embodiment, shaft 76 may be a driven shaft. In a further embodiment, shaft 76 may be coupled to a drive shaft. In an alternative further embodiment, shaft 76 may be coupled to a driven shaft. The shaft 76 is rotatably supported by the housing 72 around the rotation axis A.

[0031] A swash plate 74 is coupled to the housing 72. The shaft 76 is inserted passing through the swash plate 74. The swash plate 74 has ring conformation. The plurality of directional control valves 56 are coupled to the housing 72. The directional control valves 56 are separately connected to the first and the second conduits 14, 16. The cylinder block 12 is rotatably supported in the housing 72. Pistons 28 are movably positioned in the respective cylinders 26. Pistons 28 are coupled to the swash plate 74. The positioning sensor 80 is coupled to the housing 72. The positioning sensor 80 is located to sense the angular position of the shaft 76.

[0032] A plurality of annular grooves 78 are interposed between the connecting conduits 64 and cylinder conduits 48. The annular grooves 78 are defined in the housing 72. Each annular groove 78 is fluidly connected to a respective directional control valve 56. Sealing gaskets (not shown) are interposed between the annular grooves 78, the housing 72 and the cylinder block 12.

[0033] Fig. 3 illustrates the device 10, as a bent axis type axial piston hydraulic device. Device 10 comprises a housing 72. A shaft 76 is coupled to the cylinder block 12. In an embodiment, shaft 76 may be a drive shaft. In an alternative embodiment, shaft 76 may be a driven shaft. In a further embodiment, shaft 76 may be coupled to a drive shaft. In an alternative further embodiment, shaft 76 may be coupled to a driven shaft. The shaft 76 is rotatably supported by the housing 72 around the rotation axis A. The shaft 76 is rotatably supported by the housing 72 around a second rotation axis B inclined in respect of the first rotation axis A.

[0034] The plurality of directional control valves 56 are coupled to the housing 72. The directional control valves 56 are separately connected to the first and the second conduits 14, 16.The cylinder block 12 is rotatably supported in the housing 72. Pistons 28 are movably positioned in the respective cylinders 26. Pistons 28 are coupled to the shaft 76. The positioning sensor 80 is coupled to the housing 72. The positioning sensor 80 is located to sense the angular position of the shaft 76.

[0035] A plurality of annular grooves 78 are interposed between the connecting conduits 64 and cylinder conduits 48. The annular grooves 78 are defined in the housing 72. Each annular groove 78 is fluidly connected to a respective directional control valve 56. Sealing gaskets (not shown) are interposed between the annular grooves 78, the housing 72 and the cylinder block 12.

[0036] In operation, the device 10 controls the displacement through the plurality of directional control valves 56. The switching between the first and second conduit 14, 16 by the directional control valves 56 controls the level of fluid displacement and the timing of the fluid connection of the cylinders 26 to the first or the second conduit 14, 16 during the rotation about the first rotation axis A. The actuation of the directional control valves 56 are in turn controlled by the controller 58.

[0037] Controller 58 controls the actuation of each directional control valve 56 for switching between the first and the second position 57, 59. Controller 58 controls the time in the first or second position 57, 59 as a function of the rotation speed. This enables the management of an early or late connection of the cylinders 46 with either the first or second conduit 14, 16 with respect to the travel of the piston 28 between the top or bottom dead points.

[0038] Continuous control of displacement of the axial piston hydraulic device 10 is effected over a complete rotation of the cylinder block 12. The fluid displacement of a cylinder assembly 24 is control through the actuation of the directional control valve 56 over a rotation of 360 degrees of the cylinder block 12 relative to said cylinder assembly 24.

[0039] In an embodiment, the device 10 is configured to operate as a hydraulic motor. In an alternate embodiment, the device 10 is configured to operate as a pump.

[0040] A method for controlling of a piston hydraulic device 10 comprising the following steps:
providing a cylinder block 12 having a plurality of cylinder assemblies 24, the cylinder block 12 being rotatable about a first rotation axis A wherein each cylinder assembly 24 comprises a cylinder 26 and a piston 28; supplying/receiving a fluid at a first pressure through a first conduit 14; receiving/supplying a fluid at a second pressure through a second conduit 16 wherein the first pressure is different from the second pressure; and actuating independently a plurality of directional control valves 56 between a first and a second positions 57, 59, the plurality of directional control valves 56 being fluidly connected to the first and second conduits 14, 16 and the respective cylinders 26 wherein each directional control valve 56 connects the respective cylinder 26 to thefirst conduit 14 in the first position 57 and to the second conduit 16 in the second position 59.

[0041] The direction of rotation of the cylinder block 12 relative to the housing 72 is determined by relative pressures of the respective fluids flowing through the first and the second conduit 14, 16. The cylinder block 12 may rotate in a first direction with a low pressure fluid flowing through the first conduit 14 and a high pressure fluid flowing through the second conduit 16. The cylinder block 12 may rotate in a second direction with a high pressure fluid flowing through the first conduit 14 and a low pressure fluid flowing through the second conduit 16

[0042] In a first operational configuration, the directional control valve 56 is actuated to the first position 57 for a rotation of 180 degrees of the respective cylinder assembly 24 about the rotational axis A. The directional control valve 56 is actuated to the second position 59 for the following rotation of 180 degrees of the respective cylinder assembly 24 about the rotational axis A. The first conduit 14 supplying/ receiving a high pressure fluid and the second conduit 16 supplying/ receiving a low pressure fluid or vice versa. The cylinder assembly 24 operates normally and contributes 100 percent to fluid displacement over a complete rotation of the cylinder block 12 relative to the cylinder assembly 24. The cylinder assembly 24 operates normally and contributes 100 percent to fluid displacement over a complete rotation of the cylinder block 12about the rotational axis A. The cylinder assembly 24 contributes to determining the fluid displacement for an amount equal to the difference between the maximum volume and the minimum volume of the corresponding chamber 46.

[0043] In a second operational configuration, the directional control valve 56 is actuated to the first position 57 for a rotation of less than 180 degrees of the respective cylinder assembly 24 about the rotational axis A. The directional control valve 56 is actuated to the second position 59 for the rotation of an angle for completion of the rotation of the respective cylinder assembly 24 about the rotational axis A. The first conduit 14 supplying/ receiving a high pressure fluid and the second conduit 16 supplying/ receiving a low pressure fluid or vice versa. The cylinder assembly 24 operates normally and contributes partially to fluid displacement over a complete rotation of the cylinder block 12 relative to the cylinder assembly 24. The cylinder assembly 24 operates normally and contributes partially to fluid displacement over a complete rotation of the cylinder block 12 about the rotational axis A. The cylinder assembly 24 contributes to determining the displacement only for a partial amount of the difference between the maximum volume and the minimum volume of the corresponding chamber 46.

[0044] In a third operational configuration, the directional control valve 56 is actuated to either the first or the second position 57, 59 for a rotation of 360 degrees of the respective cylinder assembly 24 about the rotational axis A. The cylinder assembly 24 is non-operational and does not contribute to fluid displacement over a complete rotation of the cylinder block 12 relative to the cylinder assembly 24. The cylinder assembly 24 is non-operational and does not contribute to fluid displacement over a complete rotation of the cylinder block 12 about the rotational axis A.

[0045] The skilled person would appreciate that foregoing embodiments may be modified or combined to obtain the piston hydraulic device 10 of the present disclosure.

Industrial Applicability

[0046] This disclosure describes a piston hydraulic device 10 that has individually variable pistons. The piston hydraulic device 10 provides for the continuous variation in fluid displacement. The continuous variation of displacement is enabled without modifying the geometric configuration piston hydraulic device 10. The relative inclination of the various structures such as the swash plate or the housing, are not varied to obtain the same objectives.

[0047] The device 10 manages efficiently the timing for the connection of a cylinder 26 to the high or the low pressure line (as determined by the fluid flowing in the first or second conduit 14, 16 relative to the dead points of piston 28 travel during the rotation about the rotational axis A.

[0048] Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein.

[0049] Where technical features mentioned in any claim are followed by reference signs, the reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, neither the reference signs nor their absence have any limiting effect on the technical features as described above or on the scope of any claim elements.

[0050] One skilled in the art will realise the disclosure may be embodied in other specific forms without departing from the disclosure or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the disclosure described herein. Scope of the invention is thus indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.

Claims

1. A piston hydraulic device (10) comprising:

a cylinder block (12) having a plurality of cylinder assemblies (24), the cylinder block (12) being rotatable about a first rotation axis (A) wherein each cylinder assembly (24) comprises a cylinder (26) and a piston (28);

a first conduit (14) for the passage of a fluid at a first pressure;

a second conduit (16) for the passage of a fluid at a second pressure wherein the first pressure is different from the second pressure;

characterized in that, the piston hydraulic device (10) further comprises
a plurality of directional control valves (56) fluidly connected to the first and second conduits (16, 14) and the respective cylinders (26) wherein each directional control valve (56) connects the respective cylinder (26) to the first conduit (14) in a first position (57) and to the second conduit (16) in a second position (59); and
a controller (58) operatively associated with the directional control valves (56) for switching between the first and the second positions (57, 59).

2. The piston hydraulic device (10) of claim 1 wherein a plurality of connecting conduits (64) are interposed between the plurality of directional control valves (56) and the respective cylinders (26).

3. The piston hydraulic device (10) of claim 1 or 2 wherein the plurality of directional control valves (56) are coupled to a housing (72).

4. The piston hydraulic device (10) of any one of preceding claims 1 to 3 wherein the device (10) is a bent axis hydraulic device.

5. The piston hydraulic device (10) of any one of preceding claims 1 to 4 wherein the device (10) is a swash plate type hydraulic device.

6. The piston hydraulic device (10) of any one of preceding claims further comprising a positioning sensor (80).

7. The piston hydraulic device (10) of claim 6 wherein the positioning sensor (80) senses the angular position of the cylinder block (12).

8. The piston hydraulic device (10) of claim 6 wherein the positioning sensor (80) senses the angular position of a shaft (76).

9. The piston hydraulic device (10) of claim 8 wherein the shaft is a drive shaft (76) or a driven shaft (76).

10. The piston hydraulic device (10) of any one of preceding claims wherein the device is axial piston hydraulic device.

11. A method for controlling a piston hydraulic device (10) comprising the steps of:

providing a cylinder block (12) having a plurality of cylinder assemblies (24), the cylinder block (12) being rotatable about a first rotation axis (A) wherein each cylinder assembly (24) comprises a cylinder (26) and a piston (28);

supplying or receiving a fluid at a first pressure through a first conduit (14);

supplying or receiving a fluid at a second pressure through a second conduit (16) wherein the first pressure is different from the second pressure; and

actuating independently a plurality of directional control valves (56) between a first and a second positions (57, 59), the plurality of directional control valves (56) being fluidly connected to the first and second conduits (16, 14) and the respective cylinders (26) wherein each directional control valve (56) connects the respective cylinder (26) to the first conduit (14) in the first position (57) and to the second conduit (16) in the second position (59).

12. The method of claim 11 comprising actuating at least one directional control valve (56) to the first position (57) for a rotation of 180 degrees of the respective cylinder assembly (24) about the rotational axis (A) and subsequently to the second position (59) for the following rotation of 180 degrees of the respective cylinder assembly (24) about the rotational axis (A).

13. The method of claim 11 comprising actuating at least one directional control valve (56) to the first position (57) for a rotation of less than 180 degrees of the respective cylinder assembly (24) about the rotational axis (A) and subsequently to the second position (59) for a rotation of an angle for the completion of rotation of the respective cylinder assembly (24) about the rotational axis (A).

14. The method of claim 11 comprising actuating at least one directional control valve (56) to either the first position (57) or the second position (59) during at least a complete rotation of the respective cylinder assembly (24) about the rotational axis (A).

Drawing