WO2017187228A1

WO2017187228A1 - Hydraulic pump with isolated commutator

Info

Publication number: WO2017187228A1
Application number: PCT/IB2016/052374
Authority: WO
Inventors: David Thomas SHANNON
Original assignee: Canada Metal (Pacific) Ltd.
Priority date: 2016-04-27
Filing date: 2016-04-27
Publication date: 2017-11-02

Abstract

A hydraulic pump assembly includes a stationery pump body with a back panel, at least one compression chamber in the pump body, a piston slidably disposed in the compression chamber, an input shaft, an actuator means for reciprocating the piston according to a rotary input to the input shaft, and a commutator rotatably disposed in a central bore of the pump body to rotate according to the rotary input. The commutator defines a first inlet port for receiving hydraulic fluid from the compression chamber, a first outlet port for transmitting hydraulic fluid to the compression chamber, a second inlet port for receiving hydraulic fluid from the back panel, a second outlet port for transmitting hydraulic fluid to the back panel. The back panel includes an inlet fluid path in fluid communication with the second inlet port and an outlet fluid path in fluid communication with the second outlet port.

Description

HYDRAULIC PUMP WITH ISOLATED COMMUTATOR

The invention relates to a hydraulic pump. More particularly, this invention relates to an axial piston pump having a rotating commutator that is structurally isolated from adverse input loads generated during normal operation. Background

Axial piston pumps have a wide range of application in hydraulics. One such application is in the steering systems of marine vessels. In marine vessels, an axial piston pump is used to move the rudder to steer the vessel. These pumps are also called helm pumps or steering pumps. The axial piston pump used in such applications is connected to a steering wheel. The rotation of the steering wheel imparts rotation in the pump shaft either directly or through some intermittent gear mechanisms. The steering may also be electronically operated by use of electric motors, switches or joysticks.

A common problem with such helm pumps is wear and tear, and leakage resulting from such wear and tear. An axial piston pump has various moving parts, and in order to operate with endurance and reliability these parts need to be properly lubricated to reduce overall friction. Wear and tear can also be reduced by designing the pump to keep the number and mass of moving parts in the pump to a minimum. Also, the pump can be designed to ensure that adverse operational loads are not carried by moving parts that have close tolerance fits, which further enhances the performance of the pump. US Patent number 5,081,908 to James B. McBeth et al discloses a pump assembly with a floating spigot valve to reduce wear and tear. However, the drawback of the assembly provided by McBeth et al. is that the cylinder block rotates inside the pump body. Cylinder block being a heavy and bigger component, its movement in the pump body leads to high wear and tear in the parts of the pump. Summary of the Invention

Present disclosure provides for a hydraulic pump with stationary cylinder block and with a structurally isolated rotating commutator. The hydraulic pump assembly comprises of a stationary pump body with a back panel. At least one compression chamber is disposed in the pump body. A piston is slidably disposed in the compression chamber. An actuator means is mounted on an input shaft for reciprocating the piston in the compression chamber in response to a rotary input to the input shaft. A commutator is rotatably disposed in a central bore of the pump body and non-rigidly coupled to the input shaft. The commutator is configured for rotation in response to rotary input to the input shaft. The commutator defines a first inlet port for receiving hydraulic fluid from the compression chamber, a first outlet port for transmitting hydraulic fluid to the compression chamber, a second inlet port for receiving hydraulic fluid from the back panel and a second outlet port for transmitting hydraulic fluid to back panel. The back panel has an inlet fluid path in fluid communication with the second inlet port and an outlet fluid path in fluid communication with the second outlet port to convey hydraulic fluid to and from the pump body via the commutator. Brief Description of Drawings

FIG. 1 illustrates a perspective view of hydraulic pump 10 in accordance with an embodiment.

FIG. 2 illustrates a rear view of hydraulic pump 10 in accordance with an embodiment. FIG. 3 illustrates a bottom view of hydraulic pump 10 in accordance with an embodiment.

FIG. 4 illustrates a cross section view of hydraulic pump 10 along the line 4-4 indicated in FIG. 3 in accordance with an embodiment.

FIG. 5 illustrates a perspective view of commutator 500 in accordance with an embodiment.

FIG. 6 illustrates a bottom view of commutator 500 in accordance with an embodiment.

FIG. 7 illustrates a cross section view of commutator 500 along the line 7-7 as indicated in FIG. 6 in accordance with an embodiment. FIG. 8 illustrates a cross section of commutator 500 along a line 8-8 as indicated in

FIG. 6 in accordance with an embodiment.

FIG. 9 illustrates a cross section of hydraulic pump 10 along a line 9-9 as indicated in FIG. 2 in accordance with an embodiment.

FIG. 10 illustrates a commutator 500' in accordance with an embodiment. FIG. 11 illustrates a cross sectional view of the commutator 500' as illustrated in FIG.

10.

Detailed Description

With respect to FIG. 1, 2 and 3 a hydraulic pump 10 in accordance with an embodiment is illustrated. The hydraulic pump 10 may be an axial piston pump with a wobbling swash plate. The pump 10 has a pump body 100, a back panel 200, an input shaft 300 and a lock valve assembly 400. Various parts in the hydraulic pump may be fastened via fasteners 602 wherever necessary. Set screws 604 may be used to attach the pump to a dashboard. O-ring seals 606 (shown in FIG. 4) are used to prevent hydraulic fluid leakage wherever necessary. Grooves may be defined on the pump 10 to receive the O-ring seals 606.

The lock valve assembly 400 is attached to the back panel 200 of the hydraulic pump 10. The lock valve assembly 400 has an inlet 410 and an outlet 420 to supply and dispense hydraulic fluid from the hydraulic pump 10. A transfer plate 450 is disposed between the back panel 200 and the lock valve assembly 400. A first end 310 of the input shaft 300 is disposed outside the pump body 100. A filling port plug 120 is disposed on the top of the pump body 100 to fill or drain out fluid from the hydraulic pump 10. The lock valve assembly 400 may be provided with a pressure relief mechanism 570 with return oil directed to the pump chamber 110.

Referring to FIG. 4, the pump body 100 and the back panel 200 define a pump chamber 110. The pump chamber 110 acts as a reservoir for hydraulic fluid for lubrication, oil make-up, etc. A cylinder block 250 is disposed in the pump chamber 110 and is fixed to the back panel 200. Alternatively, the cylinder block 250 may be formed integral to the back panel 200. The cylinder block 250 along with the back panel 200 defines a central bore 230. The central bore 230 is made up of a cylinder block bore 232 and a back panel bore 234. The central bore 230 is configured to receive a second end 320 of the input shaft 300 and a commutator 500.

The input shaft 300 has the first end 310 disposed outside the pump body 100 and the second end 320 disposed inside the central bore 230 proximal to the cylinder block 250. First end 310 is configured to be attached to a rotary input mechanism. The rotary input mechanism for the shaft 300 may be either manual through a steering wheel (not shown) directly attached to the input shaft 300 at the first end 310. Alternatively, the first end 310 may be coupled to some steering mechanism via gears or belts, to be controlled either manually or electronically.

The first end 310 is mounted in the pump body 100 using a first needle roller bearing 132. A seal 134 is used to prevent leakage. A clamp cover 136 is fastened to the pump body over the seal 134 using the fasteners 602. The second end 320 of the input shaft 300 is supported by second needle roller bearing 252 inside the central bore 230 of the cylinder block 250. The input shaft 300 is non-rigidly coupled to a commutator 500 using a slot and key arrangement. In the embodiment as illustrated, slots 514 (better shown in FIG. 5) are formed on the commutator 500 and keys 322 are used. The keys 322 may be formed on the input shaft 300.

The cylinder block 250 defines plurality of compression chambers 260 disposed inside the pump chamber 110 equidistantly and orbitally around the central bore 230. The compression chambers 260 have their axis substantially parallel to the axis of rotation of the input shaft 300. There may be any number of compression chambers 260 in the hydraulic pump. Each compression chamber 260 has a piston 270 slidably disposed inside the compression chamber 260. The piston 270 seals the compression chamber from one side. The ingress and egress of the hydraulic fluid inside the compression chamber 260 is allowed via a connecting channel 262, discussed later. The piston 270 is configured to reciprocate telescopically in the compression chamber 260. Hydraulic pump 10 further includes an actuator means for actuating pistons 270 of the hydraulic pump 10 in the compression chambers 260. In the embodiment illustrated, the actuator means is a swash plate 350 disposed on the input shaft 300. A swash carrier 352 is mounted on the input shaft 300. The swash carrier 352 has a swash plate axial thrust ball bearing 354. A needle thrust bearing assembly 138 is mounted on the input shaft 300 between the swash carrier 352 and the pump body 100. The swash plate axial thrust ball bearing 354 is disposed angularly, at a non-perpendicular plane, with respect to the axis of rotation of the input shaft 300. The swash carrier 352 and the swash plate axial thrust ball bearing 354 are coupled to the input shaft 300 concentrically so as to rotate along with the rotation of the input shaft 300. A piston return spring 272 is disposed inside the piston 270 and the compression chamber 260 as shown in FIG. 4. The piston return spring 272 creates biasing force which pushes the piston 270 out of the compression chamber 260 towards the swash plate axial thrust ball bearing 354. The piston 270 is supported by the swash plate ball bearing 354, as shown in FIG. 4. On rotation of the input shaft 300, angularly disposed swash plate 350 imparts reciprocatory motion to the piston 270.

A piston bleed tube 274 is also disposed inside the compression chamber 260 to release trapped air in the hydraulic fluid. For more detailed description of the bleed tube 274 and its operation, reference may be made to US Patent No. 4,898,077 to McBeth.

Each compression chamber 260 has a connecting channel 262 which fluidly connects the compression chamber 260 to the central bore 230. Reciprocating motion of the piston 270 in the compression chamber creates an expansion stroke and a compression stroke to draw in and pump out fluid from compression chamber 260, respectively. Hydraulic fluid enters and exits the compression chamber 260 via the connecting channel 262 when the piston 270 reciprocates inside the compression chamber 260.

With respect to FIG. 4-8, a commutator 500 is disposed inside the central bore 230. The commutator 500 is partly disposed in the cylinder block bore 232 and partly in the back panel bore 234. The commutator 500 has various ports to convey fluid between the cylinder block 250 and the back panel 200. Commutator 500 also serves as a timing valve, that aligns different hydraulic ports in the hydraulic pump 10 to effect the pump operation.

In the embodiment shown, the commutator 500 has a cylindrical shape with dimension to fit into the central bore 230 with very minimal clearance (not shown) with the abutting parts of the hydraulic pump 10. The minimal clearance allows formation of a film of hydraulic fluid around the commutator 500. This minimal clearance provides for radial movement between the commutator 500 inside the central bore 230 while blocking any significant oil flow along central bore 230 inside the hydraulic pump 10 when the hydraulic pump 10 is in operation. Blocking of the fluid flow is needed as the major oil flow should only take place in the defined fluid paths in the pump 10, and not through the clearance allowed in the assembly of different parts in the pump body. Certain clearances are necessary for allowing the commutator 500 to freely rotate inside the central bore 230. However, the amount of clearance should not be so high such that it affects the fluid flow during the operation of the pump 10. Hydraulic fluid is allowed to enter these clearances such that the hydraulic fluid forms a thin film for adequate lubrication between the moving parts, for e.g. the commutator 500. This hydraulic film substantially reduces wear and tear in the commutator 500 and its abutting parts. As the cylinder block 250 is stationary, overall wear and tear reduces to a great extent. Further, it may be understood that excess clearance may result in undesirable increased hydraulic slip which is detrimental to the operation of the pump. Therefore, the clearances may be designed to prevent hydraulic slip.

At a first end 510, the commutator 500 is coupled to the second end 320 of the input shaft using a structurally isolated slot and key arrangement transmitting only torsion. In the illustrated embodiment, the commutator 500 has the key-slots 514 (shown in FIG. 5) and the input shaft 300 has keys 322 to fit into the key-slots 514. An alternate embodiment may have keys on the commutator 500 and corresponding key slots on the input shaft.

A second end 520 of the commutator 500 abuts a transfer plate 450 of the lock valve assembly 400. The transfer plate 450 has different ports to allow fluid communication between the ports in the back panel 200 and the lock valve assembly 400.

The commutator 500 has a contact structure 524 protruding from the surface 522 of the second end 520, as shown in FIG. 5. Further, as shown in FIG. 4, contact structure 524 abuts the transfer plate and creates a small sump 526 inside the back panel bore 234, between the transfer plate 450 and surface 522 of the commutator 500. Also, as contact structure 524 prevents the surface 522 from abutting the transfer plate 450, this minimizes friction between commutator 500 and transfer plate 250.

The commutator 500 defines a plurality of fluid channels connecting its ports. The commutator 500 has a first inlet port 552, a first outlet port 554, a second inlet port 556 and a second outlet port 558. In the embodiment illustrated, the first inlet port 552 and the first outlet port 554 are formed as arcuate grooves on the outer surface of the commutator 500. As illustrated in FIG. 8, the ports 552, 554 are disposed opposite to each other on the same plane that lies perpendicular to the commutator's axis of rotation. Commutator 500 may further have decompression slots 553 defined on distal ends of the arcuate grooves 552, 554. When the commutator 500 rotates along with the input shaft 300 in a clockwise or anti-clockwise direction, these ports 552, 554 alternatively connect with the connecting channel 262 of the compression chamber 260.

The second inlet port 556 and the second outlet port 558 are in form of annular grooves defined on the outer surface of the commutator 500. Second inlet port 556 is configured to receive hydraulic fluid from the back panel 200, and the second outlet port 558 is configured to transmit fluid to the back panel 200. The commutator 500 has a first fluid channel 562 that connects the first inlet port 552 to the second outlet port 558, and a second fluid channel 564 that connects first outlet port 554 to the second inlet port 556.

Referring to FIG. 9, back panel 200 has an inlet fluid path 210 and an outlet fluid path 220. The inlet 410 (shown in FIG. 3) of lock valve assembly 400 is configured to receive hydraulic fluid and supply it to inlet fluid path 210. The outlet 420 (shown in FIG. 3) is configured to receive the hydraulic fluid from the outlet fluid path 220 and dispense the fluid out of the pump 10.

The inlet fluid path 210 has a first end 212 configured to receive hydraulic fluid from the inlet 410 in the lock valve assembly 400 and a second end 214 configured to supply the hydraulic fluid to the second inlet port 556 of the commutator 500. Similarly, the outlet fluid path 220 has a first end 222 to receive hydraulic fluid from the second outlet port 558 of the commutator 500 and a second end 224 to supply the hydraulic fluid to the outlet 420 in the lock valve assembly 400. The lock valve assembly may define an inlet path (not shown) that connects the inlet 410 to the inlet fluid path 210 and an outlet path (not shown) that connects outlet 420 to the outlet fluid path 220.

When the commutator 500 rotates, the second inlet port 556 remains in fluid communication with the inlet fluid path 210 of the back panel 200, and the second outlet port 558 remains in fluid communication with the outlet fluid path 220 of the back panel 200 via the annular grooves defined on the commutator 500. Further, referring to FIG. 7, the commutator 500 may also have an oil make up mechanism. Two oil make up check valves 592, 594 are installed on the surface 512 of the first end 510 of the commutator 500. When the pressure inside the fluid channels 562, 564 is lower than a certain threshold, check valves 592, 594 allow fluid to enter the fluid channels 562, 564 to make up for the shortfall of the fluid created by the low pressure. During operation of the pump 10, among the plurality of compression chamber 260 some of the compression chambers 260 are in a fluid receiving state and some of the compression chambers 260 are in a fluid delivering state. The oil make up check valves 592, 594 are activated by negative pressure which develops when volume of oil received by the compression chambers 260 that are in oil receiving state is less than the volume of oil being delivered by the compression chambers 260 that are in oil delivering state. This imbalance can be caused by hydraulic line expansion under pressure or by activating a compression chamber 260 that has unbalanced volumes either side of the piston. The pump 10 may be provided with a pressure relief mechanism 570. The pressure relief mechanism 570 may be provided in the commutator 500. FIG. 10 and FIG. 11 illustrate, a commutator 500' with the pressure relief mechanism 570. The pressure relief mechanism 570 may include two spring loaded pressure relief check ball and seats 572 and 574. The check ball and seats 572, 574 may be provided on the second end 520 of the commutator 500' in the first fluid channel 562 and the second fluid channel 564. When the fluid pressure inside the channels 562, 564 crosses a certain threshold, check ball and seats 572 and 574 allow fluid to escape toward the sump 526 and into the pump chamber 110 of pump 10 via return line 580 of the commutator 500. In an alternate embodiment, the pressure relief mechanism 570 may be placed inside the lock valve assembly 400. Referring to FIG. 4, the lock valve assembly 400 may have pressure relief valves placed in the inlet path and the outlet path that direct the fluid towards a pressure relief line 460 when the fluid pressure inside the inlet path and the outlet path surges above a threshold. In an embodiment, the pressure relief valves may be a spring loaded ball and seat that allows passage of pressurized fluid from the outlet path to the pressure relief line 460 which is in communication with the pump chamber 110 of the pump 10 via a return line 580 of the commutator 500 when the pressure in the outlet path surges above a threshold pressure.

Operation of the pump is described as follows.

Referring to FIG. 4, when the input shaft 300 rotates in one direction, the swash plate

350 on the input shaft 300 imparts a reciprocatory motion in the piston 270. Piston 270 is pushed inside the compression chamber 260 by the swash plate 350, and is pushed out by the piston return spring 272. Sliding of the piston 270 in and out the compression chamber 260 creates a compression stroke and an expansion stroke, respectively. When the expansion stroke begins, it creates a low pressure in the compression chamber 260. Hence, hydraulic fluid is sucked or drawn into the compression chamber 260 via connecting channel 262. As the expansion stroke starts, the first outlet port 554 comes in fluid communication with the connecting channel 262. The first outlet port 554 remains in communication with the connecting channel 262 till the expansion stroke is substantially completed. During the expansion stroke hydraulic fluid enters the pump from the inlet 410 in the lock valve assembly 400. The fluid then passes through the inlet fluid path 210 to the second inlet port 556 and is supplied via second fluid channel 564 and the first outlet port 554 to the connecting channel 262. When the expansion stroke completes, and the input shaft 300 rotates further, the first outlet port 554 of the commutator 500 disconnects from the connecting channel 262.

On further rotation of the input shaft 300, the compression stroke starts and now the pressure inside the compression chamber increases and the first inlet port 552 establishes fluid communication with the connecting channel 262. The hydraulic fluid is pushed out of the compression chamber 260 via connecting channel 262 to the first inlet port 552. The fluid then passes through the first fluid channel 562 and exits from the second outlet port 558 to enter the outlet fluid path 220 in the back panel 200. The outlet fluid path 220 further delivers the hydraulic fluid to the lock valve assembly 400 to be dispensed out from the outlet 420.

Fluid flow takes place as explained above when the input shaft 300 is rotated in one direction. If the input shaft 300 is rotated in opposite direction, the fluid flow also reverses. Thus, on rotating the input shaft in opposite direction, during expansion stroke the first inlet port 552 will supply fluid to the compression chamber 260, and in compression stroke first outlet port 554 will receive fluid from the compression chamber 260.

Industrial Applicability

The present disclosure provides for a hydraulic pump 10 with an isolated commutator 500. During operation of the hydraulic pump 10 in accordance with the present disclosure, the cylinder block 250 remains stationary with the input shaft 300 and the commutator 500 rotates for effecting the pump operation.

The present disclosure provides for reduction in mass of moving parts in the hydraulic pump and thus provides for reduction in overall wear and tear in the hydraulic pump. The hydraulic pump in accordance with the present disclosure may provide for a pump with increased life.

Claims

We Claim:

1. A hydraulic pump assembly comprising:

a stationary pump body (100) with a back panel (200);

at least one compression chamber (260) disposed in the pump body (100); a piston (270) slidably disposed in the compression chamber (260);

an input shaft (300);

an actuator means (350) for reciprocating the piston (270) in the compression chamber (260) in response to a rotary input to the input shaft (300);

a commutator (500) rotatably disposed in a central bore (230) of the pump body (100) and non-rigidly coupled to the input shaft (300) and configured for rotation in response to the rotary input to the input shaft (300), the commutator (500) defining:

a first inlet port (552) for receiving hydraulic fluid from the compression chamber;

a first outlet port (554) for transmitting hydraulic fluid to the compression chamber;

a second inlet port (556) for receiving hydraulic fluid from the back panel;

a second outlet port (558) for transmitting hydraulic fluid to back panel (200); and

the back panel (200) having an inlet fluid path (210) in fluid communication with the second inlet port (556) and an outlet fluid path (220) in fluid communication with the second outlet port (558) to convey hydraulic fluid to and from the pump body (100) via the commutator (500).

2. A hydraulic pump assembly (10) as claimed in claim 1, wherein the central bore (230) defines a clearance to allow the commutator (500) to rotate in the central bore (230).

3. A hydraulic pump assembly (10) as claimed in claim 2, wherein the commutator (500) restricts fluid flow along the central bore 230.

4. A hydraulic pump assembly as claimed in claim 1, wherein the first inlet port (552) and the first outlet port (554) are arcuate grooves.

5. A hydraulic pump assembly (10) as claimed in claim 1, wherein the first inlet port (552) and the first outlet port (554) have decompression slots (553) at distal ends of the arcuate grooves.

6. A hydraulic pump assembly (10) as claimed in claim 1, wherein the second inlet port (556) and the second outlet port (558) are annular grooves.

7. A hydraulic pump assembly (10) as claimed in claim 1, wherein the compression chamber (260) is disposed in a cylinder block (250).

8. A hydraulic pump assembly (10) as claimed in claim 6, wherein cylinder block (250) and the back panel (200) are integral.

9. A hydraulic pump assembly 10 as claimed in claim 1, wherein the actuator means (350) is a swash plate coupled to the input shaft.

10. A hydraulic pump assembly as claimed in claim 1, wherein the commutator (500) has a first fluid channel (562) connecting the first inlet port (552) and the second outlet port (558) and a second fluid channel (562) connecting the first outlet port (554) and the second inlet port (556).

11. A hydraulic pump assembly (10) as claimed in claim 1, wherein the commutator further comprises a pressure relief mechanism.

12. A hydraulic pump assembly as claimed in claim 1, wherein the commutator further comprises an oil make up mechanism.

13. A hydraulic pump assembly (10) as claimed in claim 1, further comprising a lock valve assembly (400) to receive and transmit fluid from the back panel (200).

14. A commutator for a hydraulic pump assembly having a compression chamber (260) and a back panel (200), the commutator comprising:

a first inlet port (552) for receiving hydraulic fluid from the compression chamber (260); a first outlet (554) port for transmitting hydraulic fluid to the compression chamber (260);

a second inlet (556) port for receiving hydraulic fluid from the back panel

(200);

a second outlet port (558) for transmitting hydraulic fluid to back panel (200); a first fluid channel (562) connecting the first inlet port (552) and the second outlet port (558); and

a second fluid channel (564) connecting the first outlet port (554) and the second inlet port (556).

15. A commutator as claimed in claim 14, wherein the first inlet port (552) and the first outlet port (554) are arcuate grooves.

16. A commutator as claimed in claim 14, wherein the second inlet port (556) and the second outlet port (558) are annular grooves.

17. A commutator as claimed in claim 14, wherein the commutator defines a first end (510) configured to engage an input shaft and a second end (520) configured for positioning proximate to the back panel (200).

18. A commutator as claimed in claim 17, wherein the second inlet port (556) and the second outlet port (558) are positioned proximate to the second end (520) of the commutator (500).

19. A commutator as claimed in claim 17, wherein the first inlet port (552) and the first outlet port (554) are positioned proximate to the first end (510) of the commutator (500).

20. A commutator as claimed in claim 15, wherein the first inlet port (552) and the first outlet port (554) have decompression slots (553) at distal ends of the arcuate grooves.

21. A commutator as claimed in claim 14, wherein the commutator has a contact structure (524) at a second end surface (522) of the commutator. A commutator as claimed in claim 17, wherein the commutator further comprises a return line 580 to convey fluid to and from the first end 510 of the commutator 500 to the second end 520 of the commutator 500.