EP1030057B1 - Hydraulic pump or motor - Google Patents
Hydraulic pump or motor Download PDFInfo
- Publication number
- EP1030057B1 EP1030057B1 EP98947948A EP98947948A EP1030057B1 EP 1030057 B1 EP1030057 B1 EP 1030057B1 EP 98947948 A EP98947948 A EP 98947948A EP 98947948 A EP98947948 A EP 98947948A EP 1030057 B1 EP1030057 B1 EP 1030057B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pistons
- shoes
- piston
- cylinder block
- hydraulic pump
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B53/00—Component parts, details or accessories not provided for in, or of interest apart from, groups F04B1/00 - F04B23/00 or F04B39/00 - F04B47/00
- F04B53/18—Lubricating
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
- F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
- F04B1/122—Details or component parts, e.g. valves, sealings or lubrication means
- F04B1/124—Pistons
- F04B1/126—Piston shoe retaining means
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
- F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
- F04B1/20—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis having rotary cylinder block
- F04B1/22—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis having rotary cylinder block having two or more sets of cylinders or pistons
- F04B1/24—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis having rotary cylinder block having two or more sets of cylinders or pistons inclined to the main shaft axis
Definitions
- the invention relates to a hydraulic axial piston pump or motor, and more particularly, to an improvement in a mount construction of a piston and a shoe.
- pistons In hydraulic axial piston pumps, pistons suffer lateral forces in a direction perpendicular to the axes of the pistons in accordance with inclination of a swash plate. As a result, great frictional forces are generated on sliding surfaces of the pistons and cylinder bores.
- Japanese Utility Model Laid-Open Nos. 48-55229 , 48-68204 , 48-57702 , and 48-68203 or Japanese Patent Laid-Open No. 8-151975 have proposed, as a measure for reducing lateral forces acting on pistons, a construction in which pistons and shoes are in contact with each other in planes perpendicular to axes of the pistons.
- the device comprises a plurality of pistons mounted to be received reciprocatably on a concentrical circle of a rotary axis of a cylinder block, whereby a ring member is tilted to a rotary axial center of the cylinder block to come into contact with a point end of the piston, whereby the rotary shaft member rotates synchronously with the cylinder block and the shoe is brought into spherical surface contact with a ring member.
- a hydraulic pump or motor comprises a rotating disk rotatably supported in a housing, a cylinder block rotatably supported in an inner space of the housing, the cylinder block having an axis of rotation inclined relative to an axis of rotation of the rotating disk.
- a plurality of cylinder bores are arranged on a circle a center of which coincides with the axis of rotation of the cylinder block, and pistons reciprocate in the respective cylinder bores.
- Semi-spherical shoes having spherical surfaces held on the rotating disk and flat smooth surfaces on the opposite side, are provided. The flat surfaces are adapted to contact with the pistons.
- a valve plate is fixed to the housing.
- the valve plate has a sliding contact with a bottom surface of the cylinder block, and allows successive inflow and outflow of a working fluid to and from the respective cylinder bores as the cylinder block rotates.
- a joint is provided to connect the rotating disk and the cylinder block to each other to cause the synchronous rotation thereof, and a drive shaft is connected to the rotating disk or the cylinder block.
- a connecting mechanism is provided for connecting the shoes and corresponding pistons respectively. The connecting mechanism allows the shoes and the corresponding pistons to slide on each other along contact surfaces thereof while preventing relative movements in a direction away from each other.
- a biasing mechanism is further provided for bringing the contact surfaces of the shoes and the corresponding pistons into close contact with each other.
- the connecting mechanism preferably comprises a connecting rods which connect the shoes and the corresponding pistons to each other.
- the connecting rods are inserted into through holes provided in the pistons such that flanges formed at tip ends of the connecting rods are latched on interiors of the pistons.
- Base ends of the connecting rods are fixed to the shoes such that minute gaps are provided between the pistons and the shoes, and predetermined gaps are provided between inner peripheries of the through holes and outer peripheries of the connecting rods.
- the biasing mechanism preferably comprises spring members or ring-shaped elastic members interposed between flanges formed at tip ends of the connecting rods and inner surfaces of the pistons.
- the connecting mechanism may alternatively comprise spaces formed in the shoes and large diameter portions provided on the pistons.
- the large diameter portions are accommodated in the storage spaces such that predetermined gaps are provided between inner peripheries of the storage spaces and outer peripheries of the large diameter portions.
- the biasing mechanism preferably comprises spring members or ring-shaped elastic members interposed between the shoes and the large diameter portions in the spaces.
- the connecting mechanism may alternatively comprise rods projecting from the shoes and inserted into through holes formed in the pistons, threaded portions provided at tip ends of the rods, and nuts screwed onto the threaded portions such that predetermined gaps are provided between inner peripheries of the through holes and outer peripheries of the rods.
- the biasing mechanism preferably comprises spring members interposed between the nuts and the pistons.
- the shoes are connected to the pistons through the connecting mechanism, and the connection is ensured even when the pistons are performing the suction stroke, where forces exerted on the shoes from the pistons become small.
- the shoes will not separated from the pistons, the contact surfaces between the shoes and the pistons will not be abraded, and noises due to collision will not be generated when the discharge stroke begins.
- a pump housing 11 comprises a cylindrical casing 11C gripped by a side block 11A and a port block 11B, as shown in Fig. 1.
- a pump drive shaft 12 extending through the side block 11A is rotatably supported by a bearing 13.
- a cylinder block 14 is arranged in the inner space of the pump housing 11.
- a rotation shaft 15 inserted in the center of the cylinder block 14 supports the cylinder block 14 via a bearing 16, thereby allowing the cylinder block 14 to rotate about the rotation shaft 15.
- Axes of the pump drive shaft 12 and the rotation shaft 15 intersect each other, such that the cylinder block 14 is inclined at an angle relative to the drive shaft 12.
- the drive shaft 12 connects to the cylinder block 14 through a joint 17, so that rotation of the drive shaft 12 is transmitted to the cylinder block 14.
- the joint 17 has spline heads 17C on both ends. On of the spline heads 17C is spline jointed to a spline hole 17A formed at an end of the drive shaft 12, and the other spline head 17C is spline jointed to a spline hole 17B formed at the center of an end surface of the cylinder block 14. Outer peripheries of the spline heads 17C are formed so as to have spherical surfaces such that favorable spline engagement with the spline holes can be constantly maintained, even when axes of the spline hole 17A and the spline hole 17B intersect each other, and rotation can be transmitted from the drive shaft 12 to the cylinder block 14.
- the cylinder block 14 has a plurality of cylinder bores 18, which are disposed at a regular interval on a circle about the rotation shaft 15 as center such that each bore axes are in parallel to the rotation shaft 15. Pistons 20 are accommodated slidably in the cylinder bores 18, respectively.
- the pistons 20 are pushed in the direction of extension by coil springs 21 disposed in the cylinder bores 18.
- a spring support 22 is inserted so as to prevent the spring 21 from bending.
- the spring support 22 is disposed inside the hollow piston 20 and an end of the spring support 22 is fixed to the piston 20. With this construction, the spring 21 is prevented from buckling and from contacting with an inner periphery of the piston 20.
- the spring supports 22 are formed from a material having low friction characteristics.
- a tubular-shaped piston cover 23 formed of a synthetic resin (an engineering plastic) is fixed to an outer periphery of the piston 20 by means of an adhesive, etc., thereby reducing the friction between the sliding surfaces of the cover 23 and the cylinder bore 18.
- the piston cover 23 has a length at least of an effective stroke range of the piston 20, and a flange 23a formed inward from an end of the cover 23 engages with a bottom end of the hollow piston 20.
- the piston cover 23 is formed of a polymer material having a small frictional coefficient.
- a reinforcement material such as carbon fiber may be added to the polymer material.
- a valve plate 25 adapted to contact with a bottom surface of the cylinder block 14 is fixed to the port block 11B.
- the valve plate 25 is provided with a pair of kidney ports (not shown), one for suction and the other one for discharge. These ports are made to successively connect to ports 18A which are formed through the cylinder block 14 from the bottoms of the respective cylinder bores 18.
- a top end of the piston 20 is provided with a flat surface 20A perpendicular to the piston axis, and a pad 27 made of a synthetic resin with a small friction coefficient is fitted to the piston 20 to cover the flat surface 20A.
- the pad 27 has a projection 27A on its back, which is fitted into a hole of the piston 20.
- a through hole 27B is formed at the center of the projection 27A, and is communicated with the inside of the piston 20.
- the pad 27 has a flat support surface 27C with a pocket 27D, to which a pressure in the cylinder bore is introduced through an interior of the piston 20.
- Semi-spherical shoes 29 are provided to contact with the pads 27.
- the shoes 29 are respectively supported on a side of the side block 11A by sockets 32 fitted to a torque plate 31, which is a rotating member arranged around the pump drive shaft 12.
- the sockets 32 are formed of a synthetic resin with a small coefficient of friction, and are respectively fitted into recesses 31A, formed in the torque plate 31.
- Each of the socket 32 is provided with a semi-spherical recess 32A, in which a spherical surface 29B of the shoe 29 is rotatably fitted.
- the shoe 29 is provided with a smooth surface 29A which has a diameter slightly greater than or substantially the same as that of the flat support surface 27C of the pad 27. These smooth surface 29A and the support surface 27C are brought into surface contact with each other. As described above, the pressure in the cylinder bore is introduced into the pocket 27D, thereby forming a fluid hydrostatic bearing between the shoe 29 and the pad 27. Due to the pressure in the pocket 27D, the surfaces 29A and 27C are subject to a hydrostatic pressure which makes the abrasion therebetween as small as possible.
- a through hole 29C is formed between the smooth surface 29A and the spherical surface 29B of the shoe 29, and a fluid from the pocket 27D of the pad 27 is introduced into a pocket 29D, which is formed on the spherical surface 29B of the shoe 29, to promote a fluid bearing which reduces friction between the contact surfaces of the shoe 29 and socket 32.
- the piston 20 and the shoe 29 is connected by a connecting rod 40.
- the connecting rod 40 couple the piston 20 and the shoe 29 so as to allow a relative movement in a direction along the contact surfaces of the pistons 20 and the shoes 29 within a small range while preventing a relative movement of the pistons 20 and the shoes 29 in a direction away from each other.
- the connecting rod 40 is inserted into the through hole 29C of the shoe 29 as well as the through holes 27B of the pads 27, which is fitted into the through hole 20B of the piston 20.
- a flange 41 is formed at an end of the connecting rod 40 so as to contact a spring seat 42 inside the piston 20.
- a male screw portion 43 is formed at another end of the connecting rod 40 so as to engage with a female screw portion formed on an inner periphery of the through hole 29C of the shoe 29.
- the spring seat 42 is a part of the spring support 22.
- a step 45 is formed midway along the connecting rod 40.
- a predetermined gap is provided between an outer periphery of the connecting rod 40 and an inner periphery of the through hole 27B of the pad 27, whereby the shoe 29 and the piston 20 are displaceable in a direction along the contact surfaces thereof while limiting their relative movement in the axial direction of the piston within a quite limited range.
- a fluid passage 46 is formed through the connecting rod 40 along its center axis, and branch passages 47 extending radially from the fluid passage 46 are formed midway along the fluid passage 46.
- the working fluid from the hollow piston is introduced to the contact surfaces of the shoe 29 and pad 27 as well as to the contact surfaces of the shoe 29 and semi-spherical recess 32A of the socket 32, so as to lubricate the contact surfaces.
- the working fluid introduced between these contact surfaces also form the hydrostatic bearings.
- a quantity of the fluid supplied to the shoe 29 and the pocket 27D can be suitably controlled.
- the torque plate 31 has a central spline hole 31B engaged with a spline portion 12A provided on an outer periphery of the pump drive shaft 12. Due to this engagement, the torque plate 31 rotates together with the pump drive shaft 12, and, as a result, rotates in synchronism with the cylinder block 14 in the same direction. Therefore, the shoe 29 supported in the socket 32 on the torque plate 31, and the piston 20 contacting it through the pad 27, rotate along a circle around the pump drive shaft 12, while always maintaining the same positional relationship therebetween.
- the torque plate 31 is fitted in a circular recess 33 formed in the side block 11A about the pump drive shaft 12 as center, and its bottom surface is in contact with a disk-shaped thrust plate 35.
- the thrust plate 35 is formed of a synthetic resin with a small coefficient of friction and is fixed to the side block 11A.
- the torque plate 31 is provided with pockets 31C on a sliding surface thereof facing the thrust plate 35, and the fluid pressure is introduced to each of the pockets 31C.
- the fluid pressure is led into each of the pocket 31C from a part corresponding to the fluid bearing of the shoe 29, via a through hole 32C formed through the socket 32 and a through hole 31D formed through the torque plate 31. Due to this fluid pressure in the pockets 31C, the contact surfaces between the torque plate 31 and the thrust plate 35 are supported by the hydrostatic bearings, so the friction there between is reduced.
- a bush 36 formed of a synthetic resin with a small coefficient of friction is provided facing an outer periphery of the torque plate 31, and the fluid pressure is conducted to sliding surfaces between the outer periphery of the torque plate 31 and an inner periphery of the bush 36, so as to reduce the friction therebetween by forming a hydrostatic bearing.
- a pressure introduction passage 37 communicated with the pump discharge passage is formed in the side block 11 A, and pockets 36A which communicate with the pressure introduction passage 37 are provided facing the sliding surfaces of the bush 36 and the torque plate 31.
- a force in the axial direction is exerted on the piston 20 corresponding to the fluid pressure in the cylinder bore 18.
- This force is supported by the torque plate 31 via the shoes 29.
- a reaction force from the shoe 29 posses a component force in a direction perpendicular to the axis of the piston 20.
- the piston 20 and the shoe 29 are always brought into contact with each other by planes perpendicular to the center axis, i.e., the support plate 27C of the pad 27 fitted to the piston 20 is in contact with the flat smooth face 29A of the shoe 29. Accordingly, almost no force in the direction perpendicular to the center axis of the piston 20 which is parallel to these contact faces is exerted on the piston 20 by the shoe 29.
- the pistons 20 are free from the lateral forces acting in the direction perpendicular to the axes thereof, so a frictional force acting on the sliding surfaces of the cylinder bores 18 is very small.
- Rotational torque of the pump drive shaft 12 is transmitted to the cylinder block 14 via the joint 17, as well as to the torque plate 31 via the spline portion 12A. Accordingly, the cylinder block 14 rotates together with the torque plate 31 and the pistons 20 and the shoes 29 rotate around the pump drive shaft 12 while maintaining substantially the same positional relationship therebetween. Therefore, no relative torque acts between the pistons 20 and the shoes 29 at any rotation angle and also thereby, large lateral force is not exerted on the piston 20.
- Friction on the sliding surfaces of the pistons 20 and of the cylinder bores 18 mainly corresponds to lateral forces exerted on the pistons 20, so that the weaker the lateral forces, the less sliding frictional forces can be reduced.
- the cover 23 formed of a resin material is fitted to the outer periphery of the piston 20 so as to reduce sliding resistance of the piston 20 with respect to the cylinder bore 18.
- the pad 27 made of a synthetic resin having a small friction coefficient are interposed between the piston 20 and the shoe 29, so as to prevent metal contact between the piston 20 and the shoe 29. Further, the pocket 27D is formed in the pad 27, inner pressure of the cylinder bore 18 is conducted to the pocket 27D via the interior of piston 20, and a hydrostatic bearing is constituted between the contact faces of the pad 27 and shoe 29. As a result, the contact pressure therebetween is reduced by the hydraulic pressure, and the wear of the contacting faces is reduced.
- the contact pressures between the pad 27 and the shoe 29 is high during the discharge stroke of the piston 20, and is conversely low during the suction stroke thereof. Accordingly, the pressure required for the hydrostatic bearing becomes high during the discharge stroke, and low during the suction stroke. Since the inner pressure of the cylinder bore 18 is conducted to the pocket 27D via the piston 20, the characteristics of the pressure provided to the pocket 27D coincides with those required for the hydrostatic bearing. The pocket 27D, therefore, functions as an excellent hydraulic bearing.
- the sockets 32 formed of a synthetic resin are provided between the shoes 29 and the torque plate 31 so as to eliminate direct contact between the shoes 29 and the torque plate 31, thus preventing metallic contact therebetween. Further, the fluid pressure is conducted to spherical-shaped contact surfaces between the socket 32 and the shoe 29 via the pocket 29D, so as to constitute a hydrostatic bearing between the contact surfaces of the socket and the shoe. Accordingly, metallic contact occurs less often between these contact surfaces, thus enabling a reduction of abrasion.
- the torque plate 31 rotating together with the pump drive shaft 12 suffers a reaction force of the pistons 20 in the discharge stroke, and is pushed towards the recess portion of the side block 11A in the thrust direction and the radial direction in accordance with the inclination of the pistons 20.
- the torque plate 31 is supported by the thrust plate 35 in the direction of the rotational axis thereof against the thrust force and is supported by the bush 36 in the lateral direction against the radial force. Accordingly, the metallic contact of the sliding surfaces is prevented under the action of these forces. Further, fluid pressures are introduced so as to constitute a hydrostatic bearing between the contact surfaces of the thrust plate 35 and the bush 36, thus reducing mechanical contact forces. Accordingly, mechanical contact of these members is avoided, wear of the torque plate 31 is reduced, and the durability is enhanced.
- the piston 20 and the shoe 29 is connected to each other by the connecting rods 40 so as to allow little movements in the axial direction. Therefore, even when pushing force between the shoe 29 and the piston 20 is weak during the suction stroke, the shoe 29 will not separate from the piston 20, so neither uneven contact between the shoe 29 and the piston 20 nor abnormal noise due to their collision will occur.
- Fig. 3 shows a second embodiment of this invention.
- the gap between the flange 41 of the connecting rod 40 and the spring seat 42 is made larger, so as to allow a belleville spring 51 to be interposed between the flange 41 and the spring seat 42.
- the spring seat 42 is formed with an annular-shaped step 42A, into which the belleville spring 51 is fitted.
- the piston 20 and the shoe 29 are closely pressed against each other by the resilient force of the belleville spring 51, whereby the shoe 29 can be prevented from separating from the piston 20 in the suction stroke, and noises due to collision can be certainly reduced.
- spring supports 22 and the pads 27 made of a synthetic resin in the first embodiment are omitted in this embodiment and in the embodiments to be described hereafter.
- Fig. 4 shows a third embodiment of this invention.
- a ring-shaped elastic member 52 is interposed between the flange 41 of the connecting rod 40 and the spring seat 42 of the piston 20.
- rubber, resin material or the like is used for the elastic member 52.
- Fig. 5 shows a fourth embodiment of this invention.
- a coil spring 53 is interposed between the flange 41 and a bearing seat 20D formed on an inner wall of the piston 20.
- Fig. 6 shows a fifth embodiment of this invention.
- This embodiment employs another connecting means in place of using the connecting rod 40 in the first - fourth embodiments described above.
- This connecting means comprises a cylindrical portion 54 extending axially from the outer periphery of the shoe 29.
- the cylindrical portion 54 is inwardly bent at its end at right angles to form a flange 54A, thereby defining a cylindrical space 55 in the shoe 29.
- the space 55 accommodates a large diameter portion 20C formed at an end of the piston 20.
- a predetermined gap is provided between an outer periphery of the large diameter portion 20C of the piston 20 and an inner periphery of the space 55.
- a predetermined minute gap is provided between the large diameter portion 20C of the piston 20 and the inner periphery of the space 55 in the direction of the center axis of the piston 20 based on the difference of the thickness of the large diameter portion 20C and the axial height of the storage space 55.
- the large diameter portion 20C of the piston 20 is accommodated in the cylindrical space 55, and is prevented by the flange 54A from falling out, so that the shoe 29 will not separate from the piston 20 and is allowed to move slightly in a direction along contact surfaces of the two members.
- Fig. 7 shows a sixth embodiment of this invention.
- a belleville spring 56 is interposed between the large diameter portion 20C of the piston 20 and the flange 54A, so as to bring the piston 20 and the shoe 29 into close contact with each other.
- annular-shaped elastic member 57 is interposed between the large diameter portion 20C and the flange 54A, so as to bring the piston 20 and the shoe 29 into close contact with each other.
- any elastic means such as a waver washer or the like can be employed instead of the belleville spring or annular-shaped elastic member.
- Fig. 9 shows an eighth embodiment of this invention.
- a shoe 29 is integrally provided centrally with a rod 58, of which a tip end is formed with a threaded portion 58A.
- the rod 58 penetrates a through hole 20B of the piston 20 and a nut 60 is screwed onto the tip end of the rod 58 via a washer 59 therebetween.
- a predetermined gap is provided between an inner periphery of the through hole 20B and an outer periphery of the rod 58, and the washer 59 is made to abut against a step portion 58B of the rod 58, so as to ensure a minute gap between the washer 59 and a spring seat 42 of the piston 20.
- the shoe 29 can slide relative to the piston 20 at contact surfaces thereof, but is separated only a minute amount therefrom in an axial direction. Therefore, it is possible to prevent occurrence of uneven contact and noises due to collision, while ensuring a smooth lateral movement between the piston 20 and the shoe 29.
- the arrangement is made simple and the manufacturing cost can be reduced as compared with the case where the connecting rod is provided.
- Fig. 10 shows a ninth embodiment of this invention.
- two nuts 60A, 60B are employed so as to form a double nut locking mechanism in order to position a washer 59, thereby precisely setting a minute gap between the washer 59 and a spring seat 42.
- Fig. 11 shows a tenth embodiment of this invention.
- an elastic member 62 is interposed between the washer 59 and the spring seat 42, and the elasticity of the elastic member 62 is used to prevent separation of the shoe 29 and the piston 20 from each other.
- the elastic member 62 it is possible to use an elastic material such as rubber, resin or the like and a spring material such as coil springs, wave washers, belleville springs or the like.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Reciprocating Pumps (AREA)
- Hydraulic Motors (AREA)
Description
- The invention relates to a hydraulic axial piston pump or motor, and more particularly, to an improvement in a mount construction of a piston and a shoe.
- In hydraulic axial piston pumps, pistons suffer lateral forces in a direction perpendicular to the axes of the pistons in accordance with inclination of a swash plate. As a result, great frictional forces are generated on sliding surfaces of the pistons and cylinder bores.
-
Japanese Utility Model Laid-Open Nos. 48-55229 48-68204 48-57702 48-68203 Japanese Patent Laid-Open No. 8-151975 - Of
JP 8-151975 - With this construction, the shoes exert no component forces on the pistons in a direction perpendicular to the axes of the pistons, so the lateral forces acting on the pistons become very small. It is therefore possible to reduce friction between the pistons and cylinder bores.
- In this case, however, since the shoes which are made to be in contact with the pistons can not be fixed to the swash plate, the pistons are pushed by springs in a direction of extension so as to maintain the contact with the shoes at any time, thereby preventing the shoes from dropping from the swash plate, even when the pump is not operated.
- When the shoes are held by such relatively small spring forces, however, the following problems may arise.
- For example, when there is a failure of lubrication and a grinding of foreign matter between the shoes and a rotating disk which supports the shoes, the forces pressing the pistons against the shoes become weak, especially when the pistons are performing a suction stroke and the pressures in associated cylinders are low. Therefore, some of the shoes may not be pressed against the rotation disk sufficiently, then these shoes may partially separated from the rotating disk, and, as a result, uneven contact between a piston and a shoe may occur. Such an uneven contact damages the contact face of the shoe.
- On the other hand, when the pistons are brought into a discharge stroke, the pressures in the associated cylinders rise, and the shoes are intensely pushed by the pistons, so that the shoes are returned to a full surface contact condition from the condition of uneven contact, at which noises due to collision may be generated.
- It is therefore an object of this invention to prevent the separation of shoes and pistons while allowing slight sliding movement of contact surfaces of the shoes and the pistons.
- A hydraulic pump or motor according to the invention comprises a rotating disk rotatably supported in a housing, a cylinder block rotatably supported in an inner space of the housing, the cylinder block having an axis of rotation inclined relative to an axis of rotation of the rotating disk. A plurality of cylinder bores are arranged on a circle a center of which coincides with the axis of rotation of the cylinder block, and pistons reciprocate in the respective cylinder bores. Semi-spherical shoes having spherical surfaces held on the rotating disk and flat smooth surfaces on the opposite side, are provided. The flat surfaces are adapted to contact with the pistons. A valve plate is fixed to the housing. The valve plate has a sliding contact with a bottom surface of the cylinder block, and allows successive inflow and outflow of a working fluid to and from the respective cylinder bores as the cylinder block rotates. A joint is provided to connect the rotating disk and the cylinder block to each other to cause the synchronous rotation thereof, and a drive shaft is connected to the rotating disk or the cylinder block. Further, a connecting mechanism is provided for connecting the shoes and corresponding pistons respectively. The connecting mechanism allows the shoes and the corresponding pistons to slide on each other along contact surfaces thereof while preventing relative movements in a direction away from each other.
- Preferably, a biasing mechanism is further provided for bringing the contact surfaces of the shoes and the corresponding pistons into close contact with each other.
- The connecting mechanism preferably comprises a connecting rods which connect the shoes and the corresponding pistons to each other. The connecting rods are inserted into through holes provided in the pistons such that flanges formed at tip ends of the connecting rods are latched on interiors of the pistons. Base ends of the connecting rods are fixed to the shoes such that minute gaps are provided between the pistons and the shoes, and predetermined gaps are provided between inner peripheries of the through holes and outer peripheries of the connecting rods.
- The biasing mechanism preferably comprises spring members or ring-shaped elastic members interposed between flanges formed at tip ends of the connecting rods and inner surfaces of the pistons.
- The connecting mechanism may alternatively comprise spaces formed in the shoes and large diameter portions provided on the pistons. The large diameter portions are accommodated in the storage spaces such that predetermined gaps are provided between inner peripheries of the storage spaces and outer peripheries of the large diameter portions.
- In this case, the biasing mechanism preferably comprises spring members or ring-shaped elastic members interposed between the shoes and the large diameter portions in the spaces.
- The connecting mechanism may alternatively comprise rods projecting from the shoes and inserted into through holes formed in the pistons, threaded portions provided at tip ends of the rods, and nuts screwed onto the threaded portions such that predetermined gaps are provided between inner peripheries of the through holes and outer peripheries of the rods.
- In this case, the biasing mechanism preferably comprises spring members interposed between the nuts and the pistons.
- Forces are acting on the pistons in axial directions, as reaction forces from the shoes, in accordance with the inclination of the rotating disk with respect to the cylinder block and with pressures in the cylinder bores. Since the shoes are in contact with the pistons at smooth surfaces perpendicular to the axes of the pistons, no forces parallel to the contact surfaces are generated, and the pistons suffer almost no lateral forces. Therefore, friction between the pistons and the cylinder bores becomes extremely small, thus making it possible to reduce abrasion on the sliding surfaces of the pistons. Since the rotational axis of the cylinder block is inclined relative to the rotational axis of the rotating disk, a circular path which the pistons take is slightly offset from a circular path which the shoes take. However, the pistons and the shoes can slide slightly relative to each other in directions along the contact surfaces thereof, so that smooth operation can be maintained.
- Further, the shoes are connected to the pistons through the connecting mechanism, and the connection is ensured even when the pistons are performing the suction stroke, where forces exerted on the shoes from the pistons become small. Thus the shoes will not separated from the pistons, the contact surfaces between the shoes and the pistons will not be abraded, and noises due to collision will not be generated when the discharge stroke begins.
-
- Fig. 1 is a cross-sectional view of an axial piston pump showing a first embodiment of this invention.
- Fig. 2 is an enlarged cross-sectional view of an essential part of Fig. 1.
- Fig. 3 is a cross-sectional view of a part of a piston according to a second embodiment of this invention.
- Fig. 4 is a cross-sectional view of a part of a piston according to a third embodiment of this invention.
- Fig. 5 is a cross-sectional view of a part of a piston according to a fourth embodiment of this invention.
- Fig. 6 is a cross-sectional view of a part of a piston according to a fifth embodiment of this invention.
- Fig. 7 is a cross-sectional view of a part of a piston according to a sixth embodiment of this invention.
- Fig. 8 is a cross-sectional view of a part of a piston according to a seventh embodiment of this invention.
- Fig. 9 is a cross-sectional view of a part of a piston according to an eighth embodiment of this invention.
- Fig. 10 is a cross-sectional view of a part of a piston according to a ninth embodiment of this invention.
- Fig. 11 is a cross sectional view of a part of a piston according to a tenth embodiment of this invention.
- According to a first embodiment in which this invention is applied to an axial piston pump, a
pump housing 11 comprises acylindrical casing 11C gripped by a side block 11A and aport block 11B, as shown in Fig. 1. - A
pump drive shaft 12 extending through the side block 11A is rotatably supported by abearing 13. Acylinder block 14 is arranged in the inner space of thepump housing 11. Arotation shaft 15 inserted in the center of thecylinder block 14 supports thecylinder block 14 via abearing 16, thereby allowing thecylinder block 14 to rotate about therotation shaft 15. - Axes of the
pump drive shaft 12 and therotation shaft 15 intersect each other, such that thecylinder block 14 is inclined at an angle relative to thedrive shaft 12. Thedrive shaft 12 connects to thecylinder block 14 through a joint 17, so that rotation of thedrive shaft 12 is transmitted to thecylinder block 14. - The joint 17 has
spline heads 17C on both ends. On of thespline heads 17C is spline jointed to aspline hole 17A formed at an end of thedrive shaft 12, and theother spline head 17C is spline jointed to aspline hole 17B formed at the center of an end surface of thecylinder block 14. Outer peripheries of the spline heads 17C are formed so as to have spherical surfaces such that favorable spline engagement with the spline holes can be constantly maintained, even when axes of thespline hole 17A and thespline hole 17B intersect each other, and rotation can be transmitted from thedrive shaft 12 to thecylinder block 14. - The
cylinder block 14 has a plurality of cylinder bores 18, which are disposed at a regular interval on a circle about therotation shaft 15 as center such that each bore axes are in parallel to therotation shaft 15.Pistons 20 are accommodated slidably in the cylinder bores 18, respectively. - The
pistons 20 are pushed in the direction of extension bycoil springs 21 disposed in the cylinder bores 18. In each of the coil springs 21, aspring support 22 is inserted so as to prevent thespring 21 from bending. Thespring support 22 is disposed inside thehollow piston 20 and an end of thespring support 22 is fixed to thepiston 20. With this construction, thespring 21 is prevented from buckling and from contacting with an inner periphery of thepiston 20. The spring supports 22 are formed from a material having low friction characteristics. - A tubular-shaped
piston cover 23 formed of a synthetic resin (an engineering plastic) is fixed to an outer periphery of thepiston 20 by means of an adhesive, etc., thereby reducing the friction between the sliding surfaces of thecover 23 and the cylinder bore 18. Thepiston cover 23 has a length at least of an effective stroke range of thepiston 20, and a flange 23a formed inward from an end of thecover 23 engages with a bottom end of thehollow piston 20. Thepiston cover 23 is formed of a polymer material having a small frictional coefficient. A reinforcement material such as carbon fiber may be added to the polymer material. - A
valve plate 25 adapted to contact with a bottom surface of thecylinder block 14 is fixed to theport block 11B. Thevalve plate 25 is provided with a pair of kidney ports (not shown), one for suction and the other one for discharge. These ports are made to successively connect toports 18A which are formed through thecylinder block 14 from the bottoms of the respective cylinder bores 18. When thepistons 20 contract the cylinder bores 18, a working fluid is discharged therefrom, and when thepistons 20 expands the cylinder bores 18, the working fluid is sucked into the cylinder bores 18. - A discharge passage and a suction passage, not shown, which are made to connect to the kidney ports, are formed in the
port block 11B. - As shown in Fig. 2, a top end of the
piston 20 is provided with aflat surface 20A perpendicular to the piston axis, and apad 27 made of a synthetic resin with a small friction coefficient is fitted to thepiston 20 to cover theflat surface 20A. Thepad 27 has aprojection 27A on its back, which is fitted into a hole of thepiston 20. A throughhole 27B is formed at the center of theprojection 27A, and is communicated with the inside of thepiston 20. Also, thepad 27 has aflat support surface 27C with apocket 27D, to which a pressure in the cylinder bore is introduced through an interior of thepiston 20. -
Semi-spherical shoes 29 are provided to contact with thepads 27. Theshoes 29 are respectively supported on a side of the side block 11A bysockets 32 fitted to atorque plate 31, which is a rotating member arranged around thepump drive shaft 12. - The
sockets 32 are formed of a synthetic resin with a small coefficient of friction, and are respectively fitted into recesses 31A, formed in thetorque plate 31. Each of thesocket 32 is provided with asemi-spherical recess 32A, in which aspherical surface 29B of theshoe 29 is rotatably fitted. - The
shoe 29 is provided with asmooth surface 29A which has a diameter slightly greater than or substantially the same as that of theflat support surface 27C of thepad 27. Thesesmooth surface 29A and thesupport surface 27C are brought into surface contact with each other. As described above, the pressure in the cylinder bore is introduced into thepocket 27D, thereby forming a fluid hydrostatic bearing between theshoe 29 and thepad 27. Due to the pressure in thepocket 27D, thesurfaces - Further, a through
hole 29C is formed between thesmooth surface 29A and thespherical surface 29B of theshoe 29, and a fluid from thepocket 27D of thepad 27 is introduced into apocket 29D, which is formed on thespherical surface 29B of theshoe 29, to promote a fluid bearing which reduces friction between the contact surfaces of theshoe 29 andsocket 32. - The
piston 20 and theshoe 29 is connected by a connectingrod 40. The connectingrod 40 couple thepiston 20 and theshoe 29 so as to allow a relative movement in a direction along the contact surfaces of thepistons 20 and theshoes 29 within a small range while preventing a relative movement of thepistons 20 and theshoes 29 in a direction away from each other. The connectingrod 40 is inserted into the throughhole 29C of theshoe 29 as well as the throughholes 27B of thepads 27, which is fitted into the throughhole 20B of thepiston 20. - A
flange 41 is formed at an end of the connectingrod 40 so as to contact aspring seat 42 inside thepiston 20. Amale screw portion 43 is formed at another end of the connectingrod 40 so as to engage with a female screw portion formed on an inner periphery of the throughhole 29C of theshoe 29. It should be noted that thespring seat 42 is a part of thespring support 22. - A
step 45 is formed midway along the connectingrod 40. By screwing the connectingrod 40 into theshoe 29 until thestep 45 interferes with theshoe 29, the connecting rod is precisely positioned, and a minute gap is defined between theflange 41 and thespring seat 42. - A predetermined gap is provided between an outer periphery of the connecting
rod 40 and an inner periphery of the throughhole 27B of thepad 27, whereby theshoe 29 and thepiston 20 are displaceable in a direction along the contact surfaces thereof while limiting their relative movement in the axial direction of the piston within a quite limited range. - A fluid passage 46 is formed through the connecting
rod 40 along its center axis, andbranch passages 47 extending radially from the fluid passage 46 are formed midway along the fluid passage 46. - Via the fluid passage 46, the working fluid from the hollow piston is introduced to the contact surfaces of the
shoe 29 andpad 27 as well as to the contact surfaces of theshoe 29 andsemi-spherical recess 32A of thesocket 32, so as to lubricate the contact surfaces. The working fluid introduced between these contact surfaces also form the hydrostatic bearings. - If an orifice, a choke or the like is provided in the fluid passage 46, a quantity of the fluid supplied to the
shoe 29 and thepocket 27D can be suitably controlled. - The
torque plate 31 has acentral spline hole 31B engaged with aspline portion 12A provided on an outer periphery of thepump drive shaft 12. Due to this engagement, thetorque plate 31 rotates together with thepump drive shaft 12, and, as a result, rotates in synchronism with thecylinder block 14 in the same direction. Therefore, theshoe 29 supported in thesocket 32 on thetorque plate 31, and thepiston 20 contacting it through thepad 27, rotate along a circle around thepump drive shaft 12, while always maintaining the same positional relationship therebetween. - The
torque plate 31 is fitted in acircular recess 33 formed in the side block 11A about thepump drive shaft 12 as center, and its bottom surface is in contact with a disk-shapedthrust plate 35. Thethrust plate 35 is formed of a synthetic resin with a small coefficient of friction and is fixed to the side block 11A. Thetorque plate 31 is provided withpockets 31C on a sliding surface thereof facing thethrust plate 35, and the fluid pressure is introduced to each of thepockets 31C. The fluid pressure is led into each of thepocket 31C from a part corresponding to the fluid bearing of theshoe 29, via a throughhole 32C formed through thesocket 32 and a throughhole 31D formed through thetorque plate 31. Due to this fluid pressure in thepockets 31C, the contact surfaces between thetorque plate 31 and thethrust plate 35 are supported by the hydrostatic bearings, so the friction there between is reduced. - Also, a
bush 36 formed of a synthetic resin with a small coefficient of friction is provided facing an outer periphery of thetorque plate 31, and the fluid pressure is conducted to sliding surfaces between the outer periphery of thetorque plate 31 and an inner periphery of thebush 36, so as to reduce the friction therebetween by forming a hydrostatic bearing. In order to supply fluid pressure for this purpose, apressure introduction passage 37 communicated with the pump discharge passage is formed in the side block 11 A, and pockets 36A which communicate with thepressure introduction passage 37 are provided facing the sliding surfaces of thebush 36 and thetorque plate 31. - When the
pump drive shaft 12 is rotated by a prime mover (not shown), thetorque plate 31 rotates therewith, and simultaneously thecylinder block 14 is rotated through the joint 17. - Since the
cylinder block 14 is inclined relative to thetorque plate 31, the distance between thecylinder block 14 and thetorque plate 31 facing each other changes as they rotates. - In a rotation position range where the distance between the
cylinder block 14 and thetorque plate 31 increases after the position at which the distance therebetween has taken the smallest value, thepiston 20 expands the cylinder bore while maintaining contact between thepiston 20 and theshoe 29 by being pushed by thespring 21 and the working fluid is sucked to the cylinder bore 18 via theport 18A. On the other hand, in another rotation position range where the distance between thecylinder block 14 and thetorque plate 31 decreases after the position at which the distance therebetween has taken the largest value, thepiston 20 is pushed by theshoe 29 and the fluid in the cylinder bore 18 is discharged from theport 18A. The fluid is sucked via the suction passage and discharged via the discharge passage by operation of thevalve plate 25. - In this way, by rotating the
cylinder block 14, thepistons 20 reciprocate while maintaining the contact with theshoes 29 held by thetorque plate 31, and suction and discharge of the working fluid from and to the cylinder bore 18 is repeated to thereby function as the axial piston pump. - Hereupon, a force in the axial direction is exerted on the
piston 20 corresponding to the fluid pressure in the cylinder bore 18. This force is supported by thetorque plate 31 via theshoes 29. In this case, since thetorque plate 31 is not perpendicular to the center axis of thepiston 20, but is inclined instead at a certain angle relative thereto, a reaction force from theshoe 29 posses a component force in a direction perpendicular to the axis of thepiston 20. - However, the
piston 20 and theshoe 29 are always brought into contact with each other by planes perpendicular to the center axis, i.e., thesupport plate 27C of thepad 27 fitted to thepiston 20 is in contact with the flatsmooth face 29A of theshoe 29. Accordingly, almost no force in the direction perpendicular to the center axis of thepiston 20 which is parallel to these contact faces is exerted on thepiston 20 by theshoe 29. - Therefore, the
pistons 20 are free from the lateral forces acting in the direction perpendicular to the axes thereof, so a frictional force acting on the sliding surfaces of the cylinder bores 18 is very small. - Rotational torque of the
pump drive shaft 12 is transmitted to thecylinder block 14 via the joint 17, as well as to thetorque plate 31 via thespline portion 12A. Accordingly, thecylinder block 14 rotates together with thetorque plate 31 and thepistons 20 and theshoes 29 rotate around thepump drive shaft 12 while maintaining substantially the same positional relationship therebetween. Therefore, no relative torque acts between thepistons 20 and theshoes 29 at any rotation angle and also thereby, large lateral force is not exerted on thepiston 20. - Friction on the sliding surfaces of the
pistons 20 and of the cylinder bores 18 mainly corresponds to lateral forces exerted on thepistons 20, so that the weaker the lateral forces, the less sliding frictional forces can be reduced. Also, thecover 23 formed of a resin material is fitted to the outer periphery of thepiston 20 so as to reduce sliding resistance of thepiston 20 with respect to the cylinder bore 18. - As a result, the frictional force of the sliding surface of the
piston 20 on the cylinder bore 18 is reduced. Therefore, even when water is used as the working fluid, wear of the sliding face is reduced and high durability is achieved. - Also, the
pad 27 made of a synthetic resin having a small friction coefficient are interposed between thepiston 20 and theshoe 29, so as to prevent metal contact between thepiston 20 and theshoe 29. Further, thepocket 27D is formed in thepad 27, inner pressure of the cylinder bore 18 is conducted to thepocket 27D via the interior ofpiston 20, and a hydrostatic bearing is constituted between the contact faces of thepad 27 andshoe 29. As a result, the contact pressure therebetween is reduced by the hydraulic pressure, and the wear of the contacting faces is reduced. - The contact pressures between the
pad 27 and theshoe 29 is high during the discharge stroke of thepiston 20, and is conversely low during the suction stroke thereof. Accordingly, the pressure required for the hydrostatic bearing becomes high during the discharge stroke, and low during the suction stroke. Since the inner pressure of the cylinder bore 18 is conducted to thepocket 27D via thepiston 20, the characteristics of the pressure provided to thepocket 27D coincides with those required for the hydrostatic bearing. Thepocket 27D, therefore, functions as an excellent hydraulic bearing. - Also, the
sockets 32 formed of a synthetic resin are provided between theshoes 29 and thetorque plate 31 so as to eliminate direct contact between theshoes 29 and thetorque plate 31, thus preventing metallic contact therebetween. Further, the fluid pressure is conducted to spherical-shaped contact surfaces between thesocket 32 and theshoe 29 via thepocket 29D, so as to constitute a hydrostatic bearing between the contact surfaces of the socket and the shoe. Accordingly, metallic contact occurs less often between these contact surfaces, thus enabling a reduction of abrasion. - The
torque plate 31 rotating together with thepump drive shaft 12 suffers a reaction force of thepistons 20 in the discharge stroke, and is pushed towards the recess portion of the side block 11A in the thrust direction and the radial direction in accordance with the inclination of thepistons 20. Thetorque plate 31 is supported by thethrust plate 35 in the direction of the rotational axis thereof against the thrust force and is supported by thebush 36 in the lateral direction against the radial force. Accordingly, the metallic contact of the sliding surfaces is prevented under the action of these forces. Further, fluid pressures are introduced so as to constitute a hydrostatic bearing between the contact surfaces of thethrust plate 35 and thebush 36, thus reducing mechanical contact forces. Accordingly, mechanical contact of these members is avoided, wear of thetorque plate 31 is reduced, and the durability is enhanced. - Since the axis of the
cylinder block 14 is inclined relative to the axis of thetorque plate 31, thepistons 20 arranged in thecylinder block 14 draw an elliptical path slightly offset from a circular path, which theshoes 29 rotating together with thetorque plate 31 draw. Accordingly, the contact surfaces of thepiston 20 and of theshoe 29 slides relative to each other. Such sliding is allowed by a gap existent between the connectingrod 40 and the throughhole 27B, whereby a smooth operation is maintained. - On the other hand, the
piston 20 and theshoe 29 is connected to each other by the connectingrods 40 so as to allow little movements in the axial direction. Therefore, even when pushing force between theshoe 29 and thepiston 20 is weak during the suction stroke, theshoe 29 will not separate from thepiston 20, so neither uneven contact between theshoe 29 and thepiston 20 nor abnormal noise due to their collision will occur. - Fig. 3 shows a second embodiment of this invention.
- In this embodiment, the gap between the
flange 41 of the connectingrod 40 and thespring seat 42 is made larger, so as to allow a belleville spring 51 to be interposed between theflange 41 and thespring seat 42. In this embodiment, thespring seat 42 is formed with an annular-shaped step 42A, into which the belleville spring 51 is fitted. - With such an arrangement, the
piston 20 and theshoe 29 are closely pressed against each other by the resilient force of the belleville spring 51, whereby theshoe 29 can be prevented from separating from thepiston 20 in the suction stroke, and noises due to collision can be certainly reduced. - It should be noted that the spring supports 22 and the
pads 27 made of a synthetic resin in the first embodiment are omitted in this embodiment and in the embodiments to be described hereafter. - Fig. 4 shows a third embodiment of this invention.
- In this embodiment, in place of the belleville spring 51, a ring-shaped
elastic member 52 is interposed between theflange 41 of the connectingrod 40 and thespring seat 42 of thepiston 20. For example, rubber, resin material or the like is used for theelastic member 52. - Fig. 5 shows a fourth embodiment of this invention.
- In this embodiment, in place of the belleville spring 51 in the second embodiment, a
coil spring 53 is interposed between theflange 41 and a bearing seat 20D formed on an inner wall of thepiston 20. With such an arrangement, theshoe 29 is biased to closely contact with thepiston 20, and is surely prevented from separating from the piston. - Fig. 6 shows a fifth embodiment of this invention.
- This embodiment employs another connecting means in place of using the connecting
rod 40 in the first - fourth embodiments described above. - This connecting means comprises a
cylindrical portion 54 extending axially from the outer periphery of theshoe 29. - The
cylindrical portion 54 is inwardly bent at its end at right angles to form a flange 54A, thereby defining acylindrical space 55 in theshoe 29. Thespace 55 accommodates a large diameter portion 20C formed at an end of thepiston 20. A predetermined gap is provided between an outer periphery of the large diameter portion 20C of thepiston 20 and an inner periphery of thespace 55. A predetermined minute gap is provided between the large diameter portion 20C of thepiston 20 and the inner periphery of thespace 55 in the direction of the center axis of thepiston 20 based on the difference of the thickness of the large diameter portion 20C and the axial height of thestorage space 55. - The large diameter portion 20C of the
piston 20 is accommodated in thecylindrical space 55, and is prevented by the flange 54A from falling out, so that theshoe 29 will not separate from thepiston 20 and is allowed to move slightly in a direction along contact surfaces of the two members. - Fig. 7 shows a sixth embodiment of this invention.
- In this embodiment, a belleville spring 56 is interposed between the large diameter portion 20C of the
piston 20 and the flange 54A, so as to bring thepiston 20 and theshoe 29 into close contact with each other. - In a seventh embodiment shown in Fig. 8, in place of the above belleville spring 56, an annular-shaped
elastic member 57 is interposed between the large diameter portion 20C and the flange 54A, so as to bring thepiston 20 and theshoe 29 into close contact with each other. - It needless to say that any elastic means such a waver washer or the like can be employed instead of the belleville spring or annular-shaped elastic member.
- Fig. 9 shows an eighth embodiment of this invention.
- In this embodiment, a
shoe 29 is integrally provided centrally with arod 58, of which a tip end is formed with a threaded portion 58A. Therod 58 penetrates a throughhole 20B of thepiston 20 and anut 60 is screwed onto the tip end of therod 58 via awasher 59 therebetween. - A predetermined gap is provided between an inner periphery of the through
hole 20B and an outer periphery of therod 58, and thewasher 59 is made to abut against a step portion 58B of therod 58, so as to ensure a minute gap between thewasher 59 and aspring seat 42 of thepiston 20. - With this construction, the
shoe 29 can slide relative to thepiston 20 at contact surfaces thereof, but is separated only a minute amount therefrom in an axial direction. Therefore, it is possible to prevent occurrence of uneven contact and noises due to collision, while ensuring a smooth lateral movement between thepiston 20 and theshoe 29. In this case, the arrangement is made simple and the manufacturing cost can be reduced as compared with the case where the connecting rod is provided. - Fig. 10 shows a ninth embodiment of this invention.
- In this embodiment, two nuts 60A, 60B are employed so as to form a double nut locking mechanism in order to position a
washer 59, thereby precisely setting a minute gap between thewasher 59 and aspring seat 42. - Fig. 11 shows a tenth embodiment of this invention.
- In this embodiment, an
elastic member 62 is interposed between thewasher 59 and thespring seat 42, and the elasticity of theelastic member 62 is used to prevent separation of theshoe 29 and thepiston 20 from each other. For theelastic member 62, it is possible to use an elastic material such as rubber, resin or the like and a spring material such as coil springs, wave washers, belleville springs or the like. - While the respective embodiments described above are application of this invention to an axial piston pump, it goes without saying that they are also applicable to an axial piston motor.
Claims (7)
- A hydraulic pump or motor comprising:a rotating disk (31) rotatably supported in a housing (11);a cylinder block (14) rotatably supported in an inner space of the housing (11), the cylinder block (14) having an axis of rotation inclined relative to an axis of rotation of the rotating disk;a plurality of cylinder bores (18) arranged on a circle a center of which coincides with the axis of rotation of the cylinder block (14);pistons (20) reciprocating in the respective cylinder bores (18);semi-spherical shoes (29) having spherical surfaces held on the rotating disk, and flat smooth surfaces on the opposite side, the flat surfaces being adapted to contact with the pistons (20);a valve plate (25) fixed to the housing, the valve plate (25) having a sliding contact with a bottom surface of the cylinder block (14), and allowing successive inflow and outflow of a working fluid to and from the respective cylinder bores (18) as the cylinder block (14) rotates;a joint (17) connecting the rotating disk and the cylinder block (14) to each other to cause the synchronous rotation thereof;a drive shaft (12) connected to the rotating disk or the cylinder block (14); andconnecting means for connecting the shoes and corresponding pistons (20) respectively, the connecting means allowing the shoes (29) and the corresponding pistons (20) to slide on each other along contact surfaces thereof while preventing relative movements in a direction away from each other, characterized in that the hydraulic pump or motor further comprises biasing means (21) for bringing the contact surfaces of the shoes (29) and the corresponding pistons (20) into close contact with each other.
- The hydraulic pump or motor as defined in Claim 1, wherein the connecting means comprises a connecting rods (40) which connect the shoes (29) and the corresponding pistons to each other, the connecting rods (40) being inserted into through holes provided in the pistons (20) such that flanges formed at tip ends of the connecting rods are latched on interiors of the pistons, base ends of the connecting rods being fixed to the shoes such that minute gaps are provided between the pistons and the shoes (29), and predetermined gaps are provided between inner peripheries of the through holes and outer peripheries of the connecting rods (40).
- The hydraulic pump or motor as defined by Claim 1 or 2, wherein the biasing means (21) comprises spring members or ring-shaped elastic members interposed between flanges formed at tip ends of the connecting rods (40) and inner surfaces of the pistons (20).
- The hydraulic pump or motor as defined in one of the foregoing claims, wherein the connecting means comprises spaces formed in the shoes (29) and large diameter portions provided on the pistons (20), the large diameter portions being accommodated in the storage spaces such that predetermined gaps are provided between inner peripheries of the storage spaces and outer peripheries of the large diameter portions.
- The hydraulic pump or motor as defined in one of the foregoing claims, wherein the biasing means comprises spring members or ring-shaped elastic members interposed between the shoes (29) and the large diameter portions in the spaces.
- The hydraulic pump or motor as defined in one of the foregoing claims, wherein the connecting means comprises rods projecting from the shoes (29) and inserted into through holes formed in the pistons (20), threaded portions provided at tip ends of the rods, and nuts screwed onto the threaded portions such that predetermined gaps are provided between inner peripheries of the through holes and outer peripheries of the rods.
- The hydraulic pump or motor as defined in one of the foregoing claims, wherein the biasing means comprises spring members interposed between the nuts and the pistons (20).
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP28696497 | 1997-10-20 | ||
JP28696497A JP3894463B2 (en) | 1997-10-20 | 1997-10-20 | Axial piston pump or motor |
PCT/JP1998/004732 WO1999020899A1 (en) | 1997-10-20 | 1998-10-20 | Hydraulic pump or motor |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1030057A1 EP1030057A1 (en) | 2000-08-23 |
EP1030057A4 EP1030057A4 (en) | 2004-06-30 |
EP1030057B1 true EP1030057B1 (en) | 2007-08-15 |
Family
ID=17711242
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98947948A Expired - Lifetime EP1030057B1 (en) | 1997-10-20 | 1998-10-20 | Hydraulic pump or motor |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1030057B1 (en) |
JP (1) | JP3894463B2 (en) |
DE (1) | DE69838260T2 (en) |
DK (1) | DK1030057T3 (en) |
WO (1) | WO1999020899A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8316995B2 (en) | 2009-12-22 | 2012-11-27 | Parker-Hannifin Corporation | Hydraulic machine with oil dams |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102007001794A1 (en) | 2007-01-05 | 2008-07-10 | Robert Bosch Gmbh | Hydraulic piston machine |
DE102012016061A1 (en) * | 2012-08-14 | 2014-02-20 | Robert Bosch Gmbh | Housing unit for hydrostatic machine, particularly axial piston machine, comprises flange, which is arranged on body for flanging housing unit to another housing unit of hydrostatic machine and has recess configured to receive seal |
CN103075316B (en) * | 2012-12-24 | 2015-08-05 | 北京工业大学 | Cylinder inner bearing supports semi-shaft type Water Hydraulic Axial Piston Pump |
DE102017200244A1 (en) * | 2017-01-10 | 2018-07-12 | Robert Bosch Gmbh | Hydrostatic axial piston motor in bent axis design |
FR3063325B1 (en) * | 2017-02-27 | 2019-03-29 | Vianney Rabhi | ARTICULATED HITCH FOR PISTON SEALING DEVICE |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS4855229U (en) * | 1971-10-30 | 1973-07-16 | ||
JPS4868204U (en) * | 1971-11-30 | 1973-08-30 | ||
JP3710174B2 (en) * | 1994-09-30 | 2005-10-26 | カヤバ工業株式会社 | Axial piston pump / motor |
-
1997
- 1997-10-20 JP JP28696497A patent/JP3894463B2/en not_active Expired - Fee Related
-
1998
- 1998-10-20 WO PCT/JP1998/004732 patent/WO1999020899A1/en active IP Right Grant
- 1998-10-20 DE DE69838260T patent/DE69838260T2/en not_active Expired - Lifetime
- 1998-10-20 EP EP98947948A patent/EP1030057B1/en not_active Expired - Lifetime
- 1998-10-20 DK DK98947948T patent/DK1030057T3/en active
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8316995B2 (en) | 2009-12-22 | 2012-11-27 | Parker-Hannifin Corporation | Hydraulic machine with oil dams |
Also Published As
Publication number | Publication date |
---|---|
DK1030057T3 (en) | 2007-12-03 |
JPH11117856A (en) | 1999-04-27 |
DE69838260D1 (en) | 2007-09-27 |
DE69838260T2 (en) | 2007-12-20 |
EP1030057A4 (en) | 2004-06-30 |
JP3894463B2 (en) | 2007-03-22 |
WO1999020899A1 (en) | 1999-04-29 |
EP1030057A1 (en) | 2000-08-23 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6092457A (en) | Hydraulic pump or motor | |
KR100226537B1 (en) | Variable displacement piston type compressor | |
US4920859A (en) | Radial piston pump and motor | |
KR20020022681A (en) | Power transmission mechanism | |
US5469776A (en) | Hydraulic pumping device | |
CN112796968A (en) | Embedded return stroke structure of sloping cam plate and have plunger pump of this structure | |
JP4202832B2 (en) | Axial piston pump or motor | |
CN116194669A (en) | Piston-cylinder assembly for radial piston compressor and radial piston compressor | |
US4734014A (en) | Shoe-and socket joint between swash plate and pistons of swash plate type compressor | |
EP1030057B1 (en) | Hydraulic pump or motor | |
WO2008026501A1 (en) | Hydraulic rotation machine | |
US6368072B1 (en) | Hydraulic pump | |
US6612813B2 (en) | Power transmission mechanism | |
US6547531B1 (en) | Variable-displacement axial piston pump | |
US8137078B2 (en) | Axial piston machine | |
US3455585A (en) | Piston shoe construction | |
US6393964B1 (en) | Compressor having piston rotation restricting structure with lubricating inclined guide surface | |
US4927338A (en) | Radial piston pump | |
US6293761B1 (en) | Variable displacement swash plate type compressor having pivot pin | |
USRE32373E (en) | Fluid device having means for aligning a cylinder barrel | |
CA2391544A1 (en) | Axial piston pump with rocker cam counterbalance feed | |
KR100375167B1 (en) | Swash Plate Type Piston Motor | |
US6257120B1 (en) | Swash plate type compressor in which a piston joint uses a rotational elliptical surface and a spherical surface opposite thereto | |
WO2019176724A1 (en) | Swash plate-type compressor | |
JP3509907B2 (en) | Cylinder block engaging device for swash plate type piston pump motor |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 20000519 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE DK FI FR GB SE |
|
A4 | Supplementary search report drawn up and despatched |
Effective date: 20040518 |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: 7F 04B 1/12 B Ipc: 7F 04B 53/18 B Ipc: 7F 04B 1/24 A |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
GRAS | Grant fee paid |
Free format text: ORIGINAL CODE: EPIDOSNIGR3 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE DK FI FR GB SE |
|
REG | Reference to a national code |
Ref country code: GB Ref legal event code: FG4D |
|
REF | Corresponds to: |
Ref document number: 69838260 Country of ref document: DE Date of ref document: 20070927 Kind code of ref document: P |
|
REG | Reference to a national code |
Ref country code: SE Ref legal event code: TRGR |
|
REG | Reference to a national code |
Ref country code: DK Ref legal event code: T3 |
|
ET | Fr: translation filed | ||
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: SE Payment date: 20071017 Year of fee payment: 10 |
|
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed |
Effective date: 20080516 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20071031 |
|
EUG | Se: european patent has lapsed | ||
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST Effective date: 20090630 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20081021 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DK Payment date: 20141010 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FI Payment date: 20141009 Year of fee payment: 17 Ref country code: GB Payment date: 20141015 Year of fee payment: 17 Ref country code: DE Payment date: 20141014 Year of fee payment: 17 |
|
REG | Reference to a national code |
Ref country code: DE Ref legal event code: R119 Ref document number: 69838260 Country of ref document: DE |
|
REG | Reference to a national code |
Ref country code: DK Ref legal event code: EBP Effective date: 20151031 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20151020 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20160503 Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20151020 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: DK Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20151031 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FI Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20151020 |