GB2185075A - A fluid pump/motor - Google Patents

Abstract

A fluid pump/motor includes a shaft 10 carrying a crank pin. A piston member 15 is mounted on the crank pin and is reciprocable in a cylinder member 21. The cylinder member 21 defines a cylinder 19 for a piston 18 and is rockably mounted in a housing for pivoting about an axis parallel to the shaft axis. The cylinder 19 has an opening 22 in the cylinder head which communicates successively with ports 28 and 29 during rotation of the shaft. The pump/motor may be incorporated in a drive system which includes a pump driving a motor of similar construction; the combination may be used in a clutchless, gearless transmission for vehicles (Figures 3, 4, not shown). <IMAGE>

Description

SPECIFICATION Fluid pump/motor This invention relates to a fluid pump/motor and to drive systems incorporating the fluid pump/motor, usually, but not exclusively, systems in which a fluid pump supplies operating fluid to a similar unit acting asafluid motor.

According to the invention a fluid pump/motor comprises a drive or driven shaft carrying a crank pin, at least one piston member rotatably carried on the crank pin, at least one cylinder member defining a cylinder for receiving a piston ofthe piston member, bearing means for the cylinder member whereby the cylinder member is pivotable about an axis lying parallel to the shaft axis and spaced outwardly from the shaft axis, and an opening in the cylinder above the piston and communicating with inlet and outlet means for passing fluid to and from the cylinder, the piston being reciprocal in the cylinder during rotation of the shaft, fluid entering and leaving the cylinderto drive or be driven by the shaft.

Preferably the pump/motor includes three cylinder members each associated with a piston member, the piston members being equiangularly spaced around the crank pin or pins.

The piston member is conveniently formed as a rigid unit including a connecting rod portion rotatably carried at one end on the crank pin and supporting the piston at the other end.

In the case in which morethan one piston member is included the piston members are mounted on a common crank pin in side by side relationship. Moreoverthe piston members and the associated cylinder members are arranged to lie in a common plane at a right angle to the shaft axis.

Preferably the cylinder member is of generally disc shape having a cylinder extending diametrically of the disc from one side towards the other. At said other side the opening from the cylinder head is arrangedto communicatewith the inletand outlet means.

The inlet and outlet means conveniently includes circumferentially-spaced openings or ports communicating successively with the cylinder opening during rotation of the shaft. The spacing of the inlet and outletopenings isarrangedto enabletimed communication between the cylinder and the inlet and outlet openings during pivoting of the cylinder member and during exhaust and charging strokes of the piston in the cylinder. In this way movement of the cylinder member between positions in which the cylinder opening communicates with one and the other ofthe inlet and outlet openings occurswhen the piston is at or near its top or bottom dead centre positions.

The fluid pump/motorofthe invention can be used in a wide variety oftransmission systems, usually systems in which a driven pump supplies fluid to a corresponding motor. For example a combination driven pump and motor can be used to replace a conventional clutch and gearbox in a drive system for vehicles, machine tools, hoists etc. Alternatively the motor or motors can be used to directly drive a vehicle wheel orwheels in such a combination.

Fluid flow control means are usually provided whereby flow offluid from thefluid pump may be reversed through the motor, by-pass the motor, or is otherwise controlled to give gearless drive to the motor.

Further features ofthe invention will appear from the following description of an embodiment of the invention given by way of example only and with re ferencetothedrawings, in which Figure lisa diagrammatictransverse crosssection through a fluid pump/motor, Figure2 is a diagrammatic longitudinal cross sectionthroughthe pump/motorof Figure 1, Figure3shows an application of a pump and a motor in combination, and Figure4shows a further application of a pump and various motors in a vehicle drive system.

Referring to the drawings and firstly to Figures 1 and 2, a pump/motor is shown which, for the sake of convenience, will be described as a pump. However it will be understood thatthe unit can equally well be used as a motor when fluid power is put into the unit instead of being derived from the unit.

The pump includesa driveshaft 10which maybe driven by any suitable power source, for example, an internal combustion engine. The shaft 10 is carried in bearings 11 (Figure 2) in a pump housing 12.

Theshaft 10 carries a crank 13 and crankpin 14 which, in the illustrated arrangement, is common to three piston members 15 which are rotatably mounted side by side on the pin 14. Alternatively a three throw crank pin arrangement may be employed to drive the three piston members 15, or, if other than three piston members are provided, a corresponding number of crank pins are included.

The piston members 15 are each of rigid construction having an apertured bearing portion 16 atone end, an intermediate connecting rod portion 17 and a piston portion 18 at the other end.

The piston portion 18 locates in a cylinder 19 def- ined by a cylinder member 21 for each piston member 15. The cylinder members 21 are each of generally disc-like shape, the cylinder 19 extending diametrically across the member 21 and having a fluid opening 22 at its cylinder head end opposite the openingforthepiston 18.

The cylinder member 21 has a circular periphery 23 defining a bearing surface whereby the member 21 is rotatable or rockable about its central axis which lies parallel to the axis of the shaft 10. The member 21 is located in a shaped portion of the housing 12 and between the housing 12 and a plate 24 bolted thereto by bolts 25.

The piston members 15 and the cylinder members 21 are equally spaced from one another around the axis ofthe shaft 10 so that in the illustrated arrangement, employing three sets of members 15 and 21, the spacing is at 1 with respect to one another about the shaft axis.

The housing 12 and the plate 24 are located in face to face contact and over the cooperating faces are formed circular rows of grooveswhichtogetherde- fine inlet and outlet passageways 26 and 27 located to one side and outwardly of the cylinders 19. The passageways 26 and 27 are connected to the cylinders 19 by a port 28 or a port 29, formed in the housing 12. The cylinders 19 connect with the passageways 26 and 27 successively through the ports 28 and 29 during rotation ofthe shaft depending on whetherthe piston 18 is effecting a movement in the discharge orinlet direction. As shown in Figure 1 one ofthe pistons, piston 18A, is moving in a direction to admitfluid into the cylinderthrough port 22 from the inlet passageway 28.

Another piston, piston 18B, is, as shown, atthe bottom dead centre position at which the opening 22 in the cylinder 19 is moving between alignmentwith the port 28 to alignment with the discharge port 29 and discharge passageway 27.

The third piston is moving in a discharge direction discharging fluid into the outlet passageway 27. As described the shaft is assumed to be rotating in an anticlockwise direction, as shown in Figure 1.

Itwill be appreciated thatthere are theoretical dead positions ofthe cylinder member 21 when the opening 22 is connected neithertothe inlet port 28 nor the outlet port 29. However these positions are reached when the piston is at its top or bottom dead centre positions, the cylinder member 21 pivoting or rocking between alignmentwith one port or the other port 28 or 29 during location of the piston at said dead centre positions. Preferably the ports 28 and 29 are spaced circumferentiallyfrom one another a distance slightly greaterthan the circumferential extent of the cylinder opening 22 so that direct access between the ports 28 and 29 is impossible.

The passageways 26 and 27 communicate with further ports 31 and 32 whereby the fluid is supplied to and from the passageways to a motor or other user ofthe fluid from the pump.

In the arrangement shown in Figures 1 and 2 the pistons and cylinders all lie in a common plane art a right angle to the shaft 10 and to achieve this the connecting rod portions 17 of the piston members are cranked for accommodation on the common crank pin 14.

The pump of Figures 1 and 2 can be used as a pump, as described, or as a motor supplied by a similar unit acting as a pump. Figure 3 shows an arrangement in which a pump 35, according to the invention, acts as a drive unitfor a motor 36, according to the invention, acting as a driven unit in a drivetrans- mission arrangement. In such an arrangementthe pump 35 and motor36 may be arranged backtoback with a plate 24 which is common to both units. In the fluid connection between the pump and the motor are a series of control valves (not shown) contained in a housing 37.Such valves enable the following functions: a) direct passage offluidfrom the pumptothe motor in both directions fordirect forward andre- verse drive ofthe motor, b) by-passing pumped fluid from the motor so that no drive between pump and motortakes place, to give an idling condition, c) passingonlya proportion ofthepumpedfluidto the motor so that the motor does not rotate atthe same speed as the pump, d) preventing rotation of the motortherebyto act to brake the transmission.

In addition a pressure release valve is provided in the pump outlet, and the pump is connected to afluid reservoirto maintain the level offluid in the system.

In the Figu re 3 arrangement the motor36isarran- ged to drive a shaft 38, a differential 39 and the rear wheels 40 of a vehicle to provide a gearless, clutch- less drive system for the vehicle.

In Figure4 is shown a drive systemfora vehicle in which all four wheels are driven by a motor 41 associated with each wheel. The motors 41 are supplied with fluid from a common pump 42 driven bya prime mover 43 such as an internal combustion engine.

The drive system is controlled by valves which include a by-pass valve 44 preventing fluid flowfrom the pump to the motors. A reversing valve 45 reverses the flow offluid to the motor and regulates flow offluid to control the speed of the motors 41.

Valves 46 are connected to the vehicle brake pedal 47 to interruptfluid flow to orfrom the motor and thereby brake the vehicle. Afurthervalve 48 is connected to a handbrake 49. A pressure releasevalve (not shown) is also provided in the pump circuit.

The system provides slow running at full power and positive drive at all speeds. It is applicable to all wheel drive for vehicles and incorporatesfade-less braking on all driven wheels. The system is also selflubricating and no reduction gears are necessary.

For applications in driving machine tools the system can include an instant emergency stop facility.

In each case the prime mover can be protected against overloading.

Claims (10)

1. A fluid pu mp/motor comprises a drive or driven shaft carrying a crank pin, at least one piston member rotatably carried on the crank pin, at least one cylinder member defining a cylinder for receiving a piston of the piston member, bearing means for the cylinder memberwherebythe cylinder member is pivotable about an axis lying parallel to the shaft axis and spaced outwardly from the shaft axis, and an opening inthecylinderabovethe piston andcom- municating with inlet and outlet means for passing fluid to and from the cylinder, the piston being reciprocal in the cylinder during rotation of the shaft, fluid entering and leaving the cylinderto drive or be driven by the shaft.

2. Afluid pump/motor according to Claim 1 which includes three cylinder members each associated with a piston member, the piston members being equiangularlyspaced around the crank pin or pins.

3. Afluidpump/motoraccordingtoClaim 1 or2 wherein the piston member is formed as a rigid unit including a connecting rod portion rotatably carried at one end on the crank pin and supporting the piston at the other end.

4. Afluidpump/motoraccordingtoClaim 1,2or 3wherein the piston members are mounted a common crank pin in side by side relationship.

5. Afluidpump/motoraccordingtoanyoneof the preceding claims wherein the piston members and the associated cylinder members are arranged to lie in a common plane at a right angle to the shaft axis.

6. Afluid pump/motor according to any one of the preceding Claims wherein the cylinder member is of generally disc shape having the cylinderextending diametrically of the disc from one side towards the other.

7. Afluid pump/motor according to Claim 6 wherein at said other side the opening from the cylinder head is arranged to communicate with the inlet and outlet means.

8. Afluid pump/motor according to any one of the preceding claims wherein the inlet and outlet means include circumferentially-spaced openings or ports communicating successively with the cylinder opening during rotation of the shaft.

9. Afluid pump and fluid motor combination in which the fluid pump and fluid motor are as claimed in any one of Claims 1-8, the fluid pump being driven buy a prime mover and the fluid pump supplying fluid powertothefluid motor,the combination also in cludingcontrol means for controlling the flow of fluid from the motor including a noflowcondition in which nofluidpowerissuppliedtothe motor, afull flow condition to the motor, and a partial flow condition to the motor.

10. Afluid pump/motor substantially as descri- bed with reference to Figures 1 and 2.