Equivelocity universal joint and axial piston pump. motor device using the joint

Abstract: The present invention relates to an equivelocity universal joint suitable for coupling shafts, and for an axial piston pump. One ends of the driving pins (5) of the equivelocity universal joint rotate along a predetermined locus on a concentric circle while rotating and sliding by themselves in the cylinder bores (6, 8) of the driving (1) or driven (2) shaft. Spherical head portions (7) of the other ends perform rotating motion in cylinder bores or ball receiving bores of the driving or driven shaft. Accordingly, the respective driving pins continue linear sliding motion in response to the rotation of the driving or driven shaft and thereby the spherical head portions of the other ends are held at the concentric circle on the driving or driven shaft so as to keep the driving center in floating state. As a result, the respective pistons are driven on a concentric circle, thereby an equivelocity universal joint is realized and the mechanical vibration thereof is substantially eliminated.

Description: Background of the Invention The present invention relates to an equivelocity universal joint suitable for coupling rotating shafts according to the preamble portion of claim 1 and to an axial piston pump motor device using the joint according to claim 10. Such a joint is known from US-A-1 707 530. In a conventional universal joint, as disclosed in JP-A-63-308220 (1988), which corresponds to US-A 4,894,045, a pair of driving pins are disposed between facing driving shafts while interposing a guide pin therebetween and one ends of the driving pins are constituted to be slidable into the axial direction and the other ends thereof are shaped into spherical heads and are permitted free rotation and movement into radial direction. Further, in a device applying a universal joint, as disclosed in JP-A-63-309785 torque transmission between a cylinder block and a piston support disposed concentrically on the axis line of a driving shaft is effected by a pair of driving pins embedded along diagonal lines on the end face of the cylinder block and by a spherical bearing supported within a driving groove provided on the piston support, adapted to be freely movable on the driving pins and further freely movable into radial direction within the driving groove. The first and second conventional arts indicated above were constituted to cancel out the difference of pitch diameters of the driving pins which vary in response to variations of inclination angle of the driving shaft (joint shaft), however the rotating velocity thereof changes twice for every one rotation so that there arose a problem that rotation could not necessarily be transmitted with equivelocity. JP-A-63-13921, filed by the same assignee of the present application and laid open on January 21, 1988, discloses a universal joint including driving pins and a center guide pin. However, there are such problems that its inclined turn angle is limited and some mechanical loss is caused because of torque transmission via the wall face of the driving pin insertion bores. US-A-891,736 discloses a flexible joint for driving shafts in which a compression spring is disposed between the pair of driving shafts, however the center of the joint cannot be fixed so that when the inclination between the driving shafts is increased, the joint cannot operate as an equivelocity joint because of its off-centering. US-A-1,322,474 also discloses a floating tool chuck, a kind of joint, in which no substantial sliding movement of the links is permitted so that no inclination between the shank member and drill members can be obtained. CH-A-276 816, on which the preamble of claim 10 is based, describes a piston pump device with an inclined plate. This device comprises on one side guide pins in respective cylinders which are pushed out by springs and are thus pressed against the inclined plate on the other side of the device. The spherical head of such a guide pin is accomodated on the inclined plate side by a fixed spherical shell which is, with other spherical shells, located on a concentric circle. Due to the spherical shape of their head the pins are pivotable and tiltable around it. US-A-1 707 530, on which the preamble of claim 1 is based, describes a universal coupling with a telescopic driving pin, which consists of rod and sheave. Rod as well as sheave have a spherical head which is accomodated by a spherical shell on the driving shaft side and the driven shaft side, respectively. The length of a telescopic driving pin is adapted to the inclination angle of the two shafts by means of a compression spring between sheave and rod. Summary of the Invention An object of the present invention is to provide an equivelocity universal joint with a simple structure which enables to transmit rotation with equivelocity even if the inclination angle of the driving shafts changes, and to provide an axial piston pump motor device which enables to drive a cylinder barrel or a driving shaft with equivelocity even if the inclination angle of a piston support changes in response to rotation of the driving shaft. The object of the present invention is achieved by a universal joint according to claim 1 and an axial piston pump motor device according to claim 10. The one ends of the driving pins of this equivelocity universal joint rotate along a predetermined locus on the concentric circle while each rotating and sliding by themselves in the cylinder bore of the driving or driven member. The spherical head portions of the other ends perform rotating motion in the cylinder bores or ball receiving bores of the driving or driven member. Accordingly, the respective driving pins continue linear sliding motion in response to the rotation of the driving or driven member and thereby the spherical head portions of the other ends are held at the concentric circle on the driving or driven member so as to keep the driving center in floating state. As a result, the respective pistons are driven on a concentric circle, thereby an equivelocity universal joint is realized and the mechanical vibration thereof is substantially eliminated. Brief Description of the Drawings. Fig. 1 is a sectional view of one embodiment showing a major part of an equivelocity universal joint according to the present invention ; Fig. 2 is a cross sectional view taken along the line II - II in Fig. 1 ; Fig. 3 is a partial vertical sectional view of an inclined shaft type piston pump · motor device ; Fig. 4 is a cross sectional view taken along the lined IV - IV in Fig. 3 ; Fig. 5 is a partial vertical sectional view of a swash type piston pump · motor device ; Fig. 6 is a cross sectional view taken along the line VI - VI in Fg. 5 ; Fig. 7 through Fig. 10 are respectively sectional views of other embodiments showing major parts of equivelocity universal joints according to the present invention ; Fig. 11 is a partial vertical sectional view of still another embodiment of an equivelocity universal joint according to the present invention ; Fig. 12 is a side view of the driving pin in Fig. 11 ; and Fig. 13 is the driven pin in Fig. 11. Description of the Preferred Embodiments Hereinbelow, the first embodiment of the present invention is explained with reference to Fig. 1 and Fig. 2. Both an input shaft ( driving member ) 1, to which separately installed driving means is mechanically coupled, and an output shaft ( driven member ) 2, are produced via such as cold forging processing and cutting work, the input shaft 1 is provided with four cylinder bores 3 opened at their one ends, extending parallel to the axis and formed at a concentric circle thereon with a uniform distance via such as milling. The output shaft 2 is configurated in the same manner, in that cylinder bores 4 are formed at the corresponding positions to the cylinder bores 3 on the opposing face. One ends of driving pins 5 are respectively inserted and disposed in the cylinder bores 3 via compression springs 6, and in the same manner the other ends of spherical head portions 7 are respectively disposed in the open ends of the cylinder bores 4 in the output shaft 2 via compression springs 8. Herein, the compression forces of the compression springs 6 and 8 are selected to be substantially the same ( compression springs having somewhat weaker compression force may be used for those at the output shaft side ), and are balanced so as to always maintain the driving pins 5 at the center portion in floating state. Further, spring seats 9 with a ring shape are disposed in such a manner that the compression springs 8 are not forced into the spaces between the spherical head portions 7 of the driving pins and the circumferential face of the cylinder bores to prevent the movement of the spherical head portions. However, when the shape of the spring or the relationship with the spherical head portions permits, the spring seats 9 can be omitted. In the above construction, the four driving pins 5 are preferably arranged at a common concentric circle with a uniform distance as shown in Fig. 2, however, at least three driving pins are also satisfactory, and when even number of the driving pins are selected and each pair of driving pins are arranged in opposing relation with respect to the center of the common circle, thereby the balance thereof is satisfactorily achieved. Further, the size of the spherical head portions 7 is determined depending upon the required mechanical strength, and further depending upon necessity, hardening processing and surface treatment processing such as titanium coating may be applied thereto and another material appropriate thereto may be used. The input shaft 1 and the output shaft 2 are arranged with a predetermined inclined turn angle ϑ as shown in Fig. 1. When the input shaft 1 is rotated, the driving pins successively displace the compression springs 6 and 8 within the range from the maximum compression to the minimum compression thereof in response to the inclined turn positions and transmit a rotating driving force to the output shaft 2. At this instance, since the compression forces of the compression springs 6 and 8 are adjusted so as to always balance each other, the driving pins 5 move into their axial directions so as to always locate thereof at the driving center in floating state and the spherical head portions 7 always move along the locus on the concentric circle without fail, thereby a genunine equivelocity universal joint is realized. Further, in this embodiment, the joint including compression springs is explained, however, when the inclined turn angle is more than 5°, the compression springs on the side of the spherical head portions are not necessarily needed because the cylindrical bores limit the axial movement of the spherical head portions. In the above embodiment, four driving pins 5 are arranged along the concentric circle as shown, however three of the driving pins are satisfactory and in case of odd number arrangement, an arrangement with a uniform pitch is preferable because of their desirable stress balancing. Fig. 7 shows another embodiment of the present invention, spherical head portions 7 are inserted into cylinder bores 4 via slippers 10, and the slippers 10 receive compression springs 8. Further, when slippers 10 with C-shape or half ring shape are used, the slippers 10 are assembled with the spherical head portions, thereafter the assemblies are inserted into the respective cylinder bores. Thus constituing, sliding property of the spherical head portions is improved, and the slippers further serve as the spring seats to thereby smooth the movement. Fig. 8 and Fig. 9 show another modification, wherein hydraulic pressure is used in place of the above indicated compression springs 6, the bottoms of cylinder bores 3 are connected by crossing passages 11 and liquid ( oil ) 12 is filled into the cylinder bores. In this instance, the piston units are provided with O rings 13 so as to prevent leakage of the liquid. Thereby, an equivelocity universal joint having a desirable compression balance and facilitating elimination of mechanical vibration to thereby reduce noise is obtained. Fig. 10 shows another type of universal joint according to the present invention with compression springs 6 wherein bearing metals 14 are forced into the cylinder bores 3 for smoothing the slide of pistons 5, the pistons 5 are supported via the bearing metals 14. As a result desirable slide of the pistons is obtained to thereby reduce mechanical loss therein and as well to reduce noise. Now, an embodiment using the above explained equivelocity universal joint is explained with reference to Fig. 3 through Fig. 6. Intially, Fig. 4 shows an inclined axis type piston pump device, in the drawings, a casing 20 is constituted by a side cover 22 including a suction port 22a and a delivery port 22b and cup shaped housing 23 sealingly connected to the side cover 22. A cylinder pin 24 is embedded perpendicularly at the center of the side cover 22 extending toward its inner space. A cylinder barrel 26 is rotatably mounted to the cylinder pin 24 via a valve plate 25. The cylinder barrel 26 is formed of a columnar body and is provided with an odd number ( nine ) of cylinder bores 26a formed along a common circle with a uniform distance which communicates with the suction ports 22a or delivery ports 22b via the valve plate 25. A plurality ( four ) of cylinder insertion bores 26b are formed along a concentric circle with respect to the central cylinder pin 24 with a uniform distance. A driving shaft 27 formed integrally together with a piston support 27a is held on an inclined turn plate 30 via needle bearings while permitting free rotation thereof, and the inclined turn plate 30 is contacted via its half spherical surface 31 to the half spherical surface 32 of the housing 23. 33 are pistons which are inserted into the cylinder bores 26a, and rotatably disposed therein via seal rings 34, spherical head portions 33a at the other ends are rotatably disposed on the piston support 27a and are held by a pulling-off preventing plate 36. 37 are driving pins disposed along an inner concentric circle from that for the pistons 33, and the piston portions thereof are inserted into driving pin insertion bores 39 via compression springs 38, and spherical head portions 37a thereof are inserted and disposed in ball receiving bores 27b formed on the end face of the piston support 27a via compression springs 39a. Further, the driving pin insertion bores 39 and the ball receiving bores 27b are provided with oil passages 40 and 41 at their respective bottoms to thereby improve their lubricating ability. In the above constitution, when the driving shaft 27 is rotated, the rotating effort is transmitted to the cylinder barrel 26 via the piston support 27a and the driving pins 37, and rotated in synchronism therewith. On the other hand, the driving pins 37 and the pistons 33 begin to slide in their axial directions in association with their rotational movement due to the inclination of the piston support 27a, and the pistons 33 perform the auction-delivery operation via the valve plate 25. In the above operation, the difference between the pitch circle of the cylinder bores 26a and the pitch circle of the spherical heads 33a, which is caused when the inclined turn angle ϑ is changed, is canceled out by free movement of the pistons 33. On the other hand, the corresponding difference is also canceled out by the sliding movement of the driving pins 37 in their axial directions, and thereby the driving force is smoothly transmitted from the driving shaft 27 to the cylinder barrel 26. The pump unit of the present embodiment is so called variable capacity type, so that the piston stroke thereof can be optionally changed by shifting the driving shaft 27 into right and left to vary the delivery capacity. In Fig. 3, stopper 21a is provided at the portion of the maximum inclined turn angle 22° where one end of the inclined turn plate 30 is adapted to be stopped. According to the present embodiment, although the driving pins 37 effect an elliptical motion, the spherical head portions move into their axial directions thereby no undesirable force is caused in the joint so that a smooth rotation thereof is achieved and mechanical vibration thereof is reduced. Further, the driving pins are separated from the capacitive delivery pistons thereby a high output piston with low cost is obtained without unduly increasing the size of the device. Next, one embodiment of a swash plate type piston pump for gas use is explained with reference to Fig. 5 and Fig. 6. The one end of a driving shaft 50 is supported on a side cover 51 via a bearing 52 and the other end thereof on a housing 53 via a bearing 54. On the one end portion of the driving shaft 50 is disposed and secured a cylinder barrel 55 via a valve plate 56 in the same manner as shown in Fig. 3. A plurality of pistons 57 are inserted into cylinder bores 55a and the spherical head portions thereof are coupled and held on a piston support 58 concentrically supported at the center of the driving shaft 50. Further, the holding structure of the present embodiment is similar to that in the previous embodiment, the explanation thereof is omitted. 59 are driving pins disposed on an inner concentric circle from that for the pistons 57 as shown in Fig. 6, the piston portions thereof are inserted into driving pin insertion bores 55b and spherical head portions 59a of the other ends are inserted and disposed in ball receiving bores 58b formed on the end face of the piston support 58. An inclined turn plate 62 placed on the back face of the piston support 58 is a cylindrical body having a tapered face and is fixed to the housing with such as pins ( not shown ) after the hollow portion 60 thereof is fitted onto a stepped face 53a of the housing 53 and is positioned by means of a positioning pin 61. In this kind of pump device, when the driving shaft 50 is driven, the cylinder barrel 55 rotates in synchronism therewith, and the pistons are driven to rotate. Thereby, through the rotation the pistons perform a reciprocating motion to produce delivery pressure. In this instance, when the cylinder barrel 55 is rotated, the driving pins 59 transmit rotating driving force to the piston support 58, and the driving pins 59 slide in response to the rotation angle and thereby the spherical head portions transmit the driving force along the concentric circle. Thereby, the present device achieves a synchronous rotation without applying any external force to the piston units which substantially determine the performance thereof. Further, it is preferable to prepare several kinds of inclined turn plates 62 having different inclination angles and to select one of them optionally depending upon required delivery capacity. According to the present embodiment, a small sized gas pressure pump with low noise and low cost is easily provided. All of the above embodiments are effective for an equivelocity universal joint wherein the distance between the driving shaft and the driven shaft is kept unchanged, however the embodiment shown in Fig. 11 through Fig. 13 is useful for an equivelocity universal joint wherein the load is applied in such a manner to reduce the distance between the driving shaft and the driven shaft. Like the previous embodiments, a pair of driving shaft 101 and driven shaft 102 are provided with cylinder bores 103 and 104, and driving pins 105 inserted and disposed in the cylinder bores 103 and 104 via compression springs 106 and 108 and seats 109. A significant difference from the previous embodiments is that the driven shaft 102 is provided with a half spherical shaped protrusion 110 at the center portion thereof and the driving shaft 101 is provided with a stopper pin 112 at the center thereof opposing to the protrusion 110 via compression spring 111. In the above construction, the protrusion may be formed integrally with the driven shaft or may be formed separately and thereafter connected to the driven shaft. Further, when the driving shaft 101 is formed of a synthetic resin, the stopper pin 112 is preferably made of metal and embedded into the driving shaft 101, and when the driving shaft is made of metal, it is advantageous to form the stopper in integral with the driving shaft, in this instance the compression spring is omitted. In the present embodiment, the stopper is provided at the center of both the driving shaft and driven shaft so as to limit their axial movement, thereby the inclined turn angle of this equivelocity universal joint is increased. The stopper is preferably shaped into a half spherical such that load applied to the shafts into the axial direction is concentrated to the center thereof thereby to keep the balance satisfactory. According to the present embodiment, an equivelocity universal joint is easily and surely obtained. Generally, the casing including that of the first embodiment is formed of metal such as aluminum, however for the purpose of light weight, plastic may be used while achieving the objects of the present invention. Further, it is needless to say that in the above embodiments even when the driving side is interchanged with the driven side the objects of the present invention is also achieved. According to the present invention, the distortion stress due the rotation with nonuniform velocity of the driving pins is canceled out by the back and forth movement of the driving pins, thereby an advantage that the rotation is transmitted with equivelocity even when the inclination angle of the driving shaft changes. Further, the rotating force is surely transmitted in synchronism so that loose gaps between the constituents are eliminated so that a product having such advantages as low vibration, low noise and simple strucure is realized.

Claims: An equivelocity universal joint between a driving member (1) and a driven member (2) coupled by a plurality of driving pins, the ends (5, 7) of the driving pins being slidably disposed in respective cylindrical axial bores (3, 4) on a concentric circle in the driving member (1) and the driven member (2), and being positioned by respective compression means (6, 8) characterized in that the driving pins are formed of one piece with one end (5) having a columnar shape permitting a free axial movement and the other end (7) having a spherical shape permitting the free axial movement as well as a pivotal movement, and the cylindrical axial bores (3, 4) are formed free of portions of reduced diameter so as to permit the free axial movement of the driving pin. An equivelocity universal joint according to claim 1, characterized in that said compression means is liquid filled into the cylindrical bores and said adjacent cylindrical bores (3, 4) are connected to each other via communicating passages (11). An equivelocity universal joint according to claim 1, characterized in that the columnar bodies of the driving pins (5) are disposed in the cylindrical bores (3) via bearings (14). An equivelocity universal joint according to claim 1, characterized in that said compression means is a compression spring. An equivelocity universal joint according to claim 4, characterized in that said compression springs face the spherical head portions via slippers or spring seats. An equivelocity universal joint according to claim 1, characterized in that the driving pins are arranged at a concentric circle on the facing surfaces of the members and that there are further provided stopper means (110) at the center of the members so as to limit the axial movement thereof. An equivelocity universal joint according to claim 6, wherein said stopper means (110) comprises a stopper of a half spherical shape, located on either one of said driving and driven members and a stopper pin (112) facing to the stopper and located on the other opposing member while permitting rotating movement thereof. An equivelocity universal joint according to claim 7, wherein the stopper pin (112) is disposed in the other opposing member via a compression spring (111) while permitting sliding movement thereof. An equivelocity universal joint according to claim 7 wherein the stopper pin (112) contacts to the stopper (110) via a spherical surface. An axial piston pump motor device including a cylinder barrel (26, 55) rotated in synchronism with the rotation of a drive shaft (27, 50), a piston support (27a, 58) inclined with respect to the opposing face of the cylinder barrel (26, 55), a plurality of piston units (33, 57) disposed between the piston support (27a, 58) and the cylinder barrel (26, 55) and performing reciprocating motion and a plurality of driving pins (37, 59) disposed between the piston support (27a, 58) and the cylinder barrel (26, 55) on an inner concentric circle from that for the piston units (33, 57) and mechanically coupling both, the one ends of pistons in said piston unit being held at a common circle in the cylinder barrel while permitting thereto free rotation and axial movement and the other ends thereof having spherical head portions (33a, 57a) being held on the end face of the piston support (27a, 58) while permitting free rotation, and the driving pins (37, 59) being formed of one piece, the one ends of the driving pins (37, 59) being columnar bodies and being held in cylindrical axial bores (39, 55a) formed in the cylinder barrel (26, 55) via a compression spring (38, 60) while permitting thereto free rotation and axial movement and the other ends thereof having spherical head portions being held in the piston support (27a, 58) while permitting free rotation, characterized in that said spherical head portions are held in cylindrical axial bores (27b, 58b) formed in the piston support, the cylindrical axial bores being formed free of portions of reduced diameter so as to permit the free axial movement of the driving pins (37, 59) thereby to constitute an equivelocity universal joint between the cylinder barrel (26, 55), piston support (27a, 58) and the driving shaft (27, 50). An axial piston pump motor device according to claim 10, characterized in that the driving shaft (27) is disposed in an inside face of a housing via an inclined turn plate (30).

Inventors: KANAMARU HISANOBU, KANAMARU, HISANOBU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1991
Main classification: F04B1
IPC codes: F04B1, F16D3