ROTARY FLUID ENERGY CONVERTER

Abstract: A rotary fluid energy converter which can be used either as a hydraulic pump or as a motor and which can recover energy with high efficiency. The converter has a spring (52) for urging a pintle (14), which supports a torque ring (2), in one direction, and a hydraulic actuator (66) for moving the pintle (14) in the opposite direction against the action of the spring (52). High pressure fluid used in the converter is introduced into the actuator (66) via a pressure compensation valve (93) to maintain the pressure of this fluid at the pressure continuously set by the valve.

Description: The present invention relates to a rotary fluid energy converter that is used as a hydraulic pump or motor of the variable displacement type. A rotary energy converter of this type, or hydrostatic rotary fluid pump/motor, has two members which are rotatable relative to each other for increasing or decreasing the volume of a chamber for sucking or discharging fluid. Such a converter can be used either as a pump or as a motor. A support member supporting one of the two members is reciprocated at right angles to an axis of rotation to adjust the distance between the centers of the two members so as to change the displacement of the converter. This structure is customarily called variable displacement type. Recently, hydraulically driven systems of the power recovery type have been required to maintain a constant pressure regardless of the discharge or suck of liquid. To conform to this requirement, the energy converter of the variable displacement type is equiped with a pressure compensation mechanism, and the displacement can be varied in such a way that when the load pressure reaches a certain preset value, the discharge of the pump is adjusted according to the discharge pressure. Such an energy converter performing a control over the pressure is now described in more detail by referring to Fig. 4. When the pump operates at a certain flow rate a, if the discharge pressure increases up to a preset pressure, then the pressure compensation valve opens, gradually reducing the flow rate discharged as indicated by b. Thus, the displacement automatically changes to a non-discharging condition. Consequently, the present situation is that any energy converter of this kind cannot be switched between pump and motor at will, nor can recover energy efficiently. In view of the foregoing difficulties, it is an object of the present invention to provide a rotaty fluid energy converter capable of recovering energy with a very high efficiency, which conventional energy converters equiped with the pressure compensation mechanism fail to do. In one embodiment of the invention, the rotary fluid energy converter comprises a spring element for resiliently urging the support member toward one side of the axis of rotation of the other fixed member ; a hydraulic actuator for moving said support member in direction of the opposite side of said fixed axis of rotation, and possibly across said axis, against the urging action of the spring element ; and a pressure compensation valve through which a high pressure fluid is introduced into the actuator in such a way that the pressure of this fluid is maintained at the compensated pressure set by the valve when the converter acts as a motor as well as when it acts as a pump. In another embodiment of the invention, the fluid energy converter further comprises in addition to the above-mentioned components of the first embodiment, a balance piston introducing said high pressure fluid into the converter so as to provide a pressure cancelling the unbalanced force acting on the support member. In the structure constructed according to the above-mentioned embodiments, when the converter is used as a pump, the spring element urging the support member holds said support member at a position set off in one direction with respect to the axis of rotation whereby the pump is providing a given displacement when the high pressure fluid used in the pump exceeds a preset value, the hydraulic actuator being operated to move the support member in the opposite direction against the action of the spring element. At this time, the converter acts as a motor. In this case, power is taken from the rotating shaft of the motor that rotates in the same direction as said pump. When the converter functions as such a motor, if the pressure of the high pressure fluid drops below the preset value, then the converter returns to its original state. Accordingly, it then acts as a pump. The pressure of the high pressure fluid is kept at the pressure set for the pressure compensation value, whether the converter acts as a pump or as a motor. Especially in the structure constructed according to the above mentioned second embodiment, the support member is supported by the balance piston utilizing the pressure of the high pressure fluid in the converter, in such a way that the urging force of the spring element is augmented. Therefore, the load applied to the spring element is reduced, which thus effectively eliminates the corresponding design requirements. Fig. 1 is a cross-sectional view of a rotary fluid energy converter according to the invention ; Fig. 2 is a cross-sectional view taken along line II-II of fig. 1 ; Fig. 3 is a cross-sectional view taken along line III-III of fig. 1 ; Fig. 4 is a graph for illustrating the operational characteristics of an energy converter equipped with a conventional pressure compensation function ; and Fig. 5 is a graph for illustrating the operational characteristics of the converter according to the invention. Referring to Figs. 1-3, there is shown a rotary fluid energy converter according to the invention. This energy converter comprises a housing 1 and a torque ring 2 respectively constituting said first and second members rotating relatively to each other. The ring 2 is rotatably and closely held against the inner surface of the housing 1 via first static pressure bearings 3. The housing 1 is shaped as a cone with a bottom po­ rtion and is provided at one end with an opening 1a. A surface 4 that tapers off toward the opening 1a is formed in the portion of the inner surface of the housing 1 on which ring 2 bears. the ring 2 is shaped like a cup, and has a peripheral wall 2a presenting the same apical angle as the tapering surface 4. A rotating shaft 6 protrudes away from one end of the axially central portion of the ring 2. The front end of the shaft 6 extends outwardly from the housing 1 through the opening 1a. The first static pressure bearings 3 have shoes 5 rigidly secured to the outer periphery of the ring 2 at required positions. The shoes 5 are attached to the tapering surface 4 of the housing 1. Each shoe 5 is provided with three pressure pockets 7a, 7b, 7c axially adjacent to one another. Pressure fluid is introduced into these pockets 7a, 7b, 7c. An odd number of pressure bearings 3 are circumferentially regularly spaced from one another. Flat surfaces 2c are formed in the inner surface of the ring 2 and at locations corresponding to the first bearings 3. Pistons 8 are disposed at locations corresponding to the flat surfaces 2c of the inner surface of the ring 2. The front ends 8a of the pistons 8 are connected to their respective inner surfaces 2c via second static pressure bearings 9, whose active surfaces are made flat so that the front ends 8a of the pistons 8 are in intimate contact with the inner surfaces 2c. Pressure pockets 11 are formed in the front ends 8a, and fed with pressure fluid. The bottom ends of the pistons 8 are held by a piston holder 12. Chambers 13 are formed between the piston holder 12 and each piston 8 so that the fluid may be introduced into them. More specifically, the piston holder 12 consists of a pintle 14 and an annular cylinder barrel 15 fitted over the outer periphery of the pintle 14. The axis n of the pintle 14 is parallel to the axis of both the housing 1 and the ring 2, i.e., the axis of rotation m. In the illustrated embodiment, when the converter is used as a pump, the axis of the pintle is located at +n, and when it is used as a motor, the axis is located at -n. The pintle 14 comprises a sliding portion 14a carried on the housing 1. The barrel 15 is provided with cylinders 16 which are circumferentially regularly spaced from one another. The axes of the cylinders are substantially perpendicular to the outer periphery of the pintle 14. The pistons 8 are fitted in the respective cylinders 16 so as to be slidable. The bottom end surfaces 8b of the pistons 8 cooperate with the inner surfaces of the cylinders 16 to form the chambers 13. The cylinder barrel 15 is connected to the torque ring 2 via an Oldham coupling 20 or similar and rotates at the same angular velocity as ring 2. The contour of pintle 14 takes the form of a truncated cone making substantially the same apical angle as the peripheral wall 2a of the ring 2. The pistons 8 are held in such a way that they can move perpendicularly to said peripheral wall 2a of the ring 2. The sliding portion 14a of the pintle 14 is shaped into a vertically elongated block of trapezoidal cross section. The housing 1 is formed with a trapezoidal groove 19 in which the sliding portion 14a is fitted so as to be slidable. In other words, the pintle 14 is so held as to be slidable in a direction perpendicular to the axis m of the housing 1. This makes it possible to adjust the distance ± D between the axis ± n of the pintle 14 and the axis m of the housing 1 to any desired value, including zero. As shown in Fig. 2, the inside of the housing 1 is divided into a first region A and a second region B by an imaginary line P drawn along the direction in which the pintle 14 slides. Any chamber 13 moving across the first region A communicates with a first fluid communication passage 21. Any chamber 13 passing across the second region B communicates with a second communication passage 22. The first fluid communication passage 21 comprises cylinder ports 23, a port 24 extending through pintle 14, and a fluid inlet/outlet port 25 formed in the housing 1. The ports 23 permit the chambers 13 to communicate with the inner surface of the cylinder barrel 15. One end of the port 24 extends to the outer periphery of the pintle 14 in the first region A, while the other end extends to an inclined surface 14b of the sliding portion 14a of the pintle 14 in the second region B. The port 25 extends the other end of port 24. Formed at said one end of the port 24 is a pressure pocket 27 that is used to form a third static pressure bearing 26 between the outer periphery of the pintle 14 and the inner surface of the cylinder barrel 15. Formed at the other end of the port 24 is a pressure pocket 29 that is employed to form a fourth static pressure bearing 28 between the inclined surface 14b of the pintle 14 and the inner surface of the housing 1. The pocket 27 is elongated circumferentially, and acts to place all the chambers 13 present in the first region A in communication with the port 24 extending through the pintle. The pocket 29 is elongated in the direction in which the pintle 14 slides, and acts to prevent the inlet/outlet port 25 from being disconnected from the port 24 when the pintle 14 is sliding. The second fluid communication passage 22 comprises the cylinder ports 23, a port 34 extending through the pintle 14, and a fluid inlet/outlet port 35 formed in the housing 1. One end of the port 34 extends to the outer periphery of pintle 14 in the second region B, while the other end extends to an inclined surface 14c of the sliding portion 14a of the pintle in the first region A. The inlet/outlet port 35 extends the other end of port 34. A pressure pocket 37 is formed at said one end of the port 34 to form a third static pressure bearing 36 between the pintle 14 and the cylinder barrel 15. Formed at the other end of port 34 is a pressure pocket 39 that is employed to form a fourth static pressure bearing 38 between the inclined surface 14c of the pintle 14 and the inner surface of the housing 1. These pressure pockets 37 and 39 are similar in structure to pressure pockets 27 and 29. In the system constructed as described above, the pressure fluid in the chambers 13 corresponding to the pistons 8 is introduced into the pressure pockets 11 of the corresponding second static pressure bearing 9 via a pressure inlet passage 41 formed along the axis of the piston 8. Then, the pressure fluid inside the pockets 11 is introduced into the pressure pockets 7a, 7b, 7c of the corresponding first static pressure bearing 3 via fluid passages 42a, 42b, 42c formed in the torque ring 2. The directions and area of the bearings 3 and 9 are so set that the force acting on the ring 2 due to the static pressure of the fluid introduced into the first bearings 3 is equal in magnitude but opposite in sense to the force acting on the ring 2 due to the static pressure of the fluid introduced into the second bearings 9. The area of the second bearings 9 is set to such a value that the force acting on the pistons 8 due to the static pressure of the fluid introduced into the second bearings 9 is cancelled by the force acting on the pistons 8 due to the static pressure of the fluid inside the chambers 13. Also, the area of the third static pressure bearings 26 and 36 is set to such a value that the force acting on the cylinder barrel 15 due to the static pressure introduced into the bearings 26 and 36 is cancelled by the force acting on the barrel 15 due to the static pressure of the fluid within the chambers 13 present in the respective regions A and B. Further, the angle at which the surfaces 14b and 14c having the fourth bearings 28 and 38 are inclined is set to such a value that the force acting on the pintle 14 due to the static pressure of the fluid introduced into the fourth bearings 28 and 38 is cancelled by the force acting on the static pressure of the fluid introduced into the third bearings 26 and 36 existing in the respective regions A and B corresponding to the inclined surfaces 14b and 14c. Also shown are seal members 43 and bearings 44 for auxiliary holding the rotating shaft. The cylinder barrel 15 is tightly fixed to the pintle 14 with a fixing element 45. A permanent magnet 46 pulls pintle 14 toward the inner surface of a rear cover 1b being a portion of the housing 1. The hydrostatic fluid energy converter constructed as described above is further equipped with the following means for displacing the pintle 14 that supports the torque ring (second member), at right angle to the axis of rotation. The pintle 14 has its sliding portion 14a taking the form of a block at its bottom end, and this sliding portion 14a is fitted in the groove 19 in the housing 1. The sliding portion 14a is provided with a recess 51 extending from one longitudinal end of the sliding portion perpendicularly to the axis of rotation. A spring element 51 is mounted between the inner bottom surface 51a of the recess 51 and the inner surface of the housing. The pintle 14 is displaced into the eccentric position + n described above by the urging force of spring element 52. A hydraulic means 53 is also provided which produces a force cooperating with the urging force of the spring element 52. This hydraulic means 53 is composed of a cylindrical member 55 and a balance piston 56 slidably fitted in the cylindrical member 55. The cylindrical member 55 has an entry portion 54 through which working fluid enters. The cylindrical member 55 is fitted in a mounting aperture 57 with a seal 58, said aperture 57 being formed in the housing 1 in communication with the recess 51. The outer surface of the cylindrical member 55 bears on a sealing member 59, and the member 55 is rigidly fixed to the housing 1. The front surface 56a of the piston 56 abuts against the inner bottom surface 51a of the recess 51. The spring element 52 is sandwiched between the rear surface of the front surface 56a of the piston of the hydraulic means 53 and the bottom surface of the cylindrical member 55. The pintle 14 is urged by the spring element 52 via the balance piston 56. The hydraulic means 53 continuously introduces the high pressure fluid that is forced out of or into the converter into its suction portion 54, and is able to provide a supporting force that adds to the urging force to the pintle 14. More specifically, the illustrated energy converter is equipped with a hydraulic circuit that has the port 24 extending through the pintle, a fluid passage 61 branching off from the port 24 and extending to the inner bottom surface 51a of the recess, and another fluid passage 62 extending axially through the piston 56. The port 24 communicates with the fluid inlet/outlet port 25 which is set in such a way that the high pressure fluid is forced into and out of the converter through the port 25. The front end surface 56a of the balance piston is in intimate contact with the inner bottom surface 51a. One end of the passage 62 is connected to the open end of the passage 61, while the other end is connected to the suction portion 54. Accordingly, high pressure fluid is continuously transmitted to the suction portion 54. In other words, the hydraulic means 53 invariably supports the pintle 14 with a force that is the cross-sectional area of the cylinder multiplied by the pressure of the high pressure fluid introduced. On the front end surface 56a of the balance piston, the passages 61 and 62 are connected together via a seal 63 to prevent the working fluid from leaking on the contact surface. A threaded rod 64 is screwed to the inner bottom end of the cylindrical member 55. When the piston 56 is retracted into the cylindrical member, i.e., when the pintle 14 is urged toward the other end against the urging force of the spring element 52, the piston bears against the lower end of the piston 56, whereby the pintle 14 cannot move further. Since the rod 64 is screwed to the cylindrical member 55, the position of the rod can be adjusted forward or rearward. In other words, the threaded rod 64 acts to limit the displacement of the pintle 14 to a certain amount. In this specific embodiment, the pintle 14 is brought to a standstill at the eccentric position -n which is at a distance -D from the axis m of the housing 1. The energy converter is further equipped with a hydraulic actuator 66 that operates by utilizing a pressure compensation mechanism incorporated in the converter, in order to urge the pintle 14 in the opposite direction against the action of the spring element 52 and the hydraulic means 53. More specifically, the block 14a of the pintle is provided with a recess 67 extending at right angle to the axis of rotation in opposed relation to the recess 51, the block 14a being fitted in the groove 19 in the housing 1. A cylindrical member 69 is fitted in the recess 67 so as to be slidable on the inner surface of the recess 67. The cylindrical member 69 incorporates an introduction portion 68 for working fluid. A spring element 71 is mounted between a retaining step 69b formed on the inner bottom end of the cylindrical member 69 and the inner bottom surface 67a of the recess 67. When the cylindrical member 69 is sliding the bottom end surface is maintained in intimate contact with the inner surface of the housing 1. The top end surface 69a of the cylindrical member bears on the inner surface of the housing 1 via a seal 72 to prevent working fluid from leaking on the contact surface. A pintle abutment rod 74 extends from outside the housing 1 through the hollow inside of the cylindrical member 69 across a mounting hole 73 in the housing 1, the member 69 being fitted in the recess 67 in the pintle 14. The front end surface 74a of the rod 74 bears on the inner bottom surface 67a of the recess 67. A suitable member 75 is mounted between the inner surface of the head 74b of the rod 74 and the outer surface of the housing 1, the head 74b protruding away from housing 1. A support cap 76 is firmly fixed to the housing 1, and the head 74b is fitted in this cap. A locking bolt 77 is fitted in the top of the cap. The distance between the cylindrical member 69 and the front end surface 74a protruding away from the member 69 can be adjusted by tightening or loosening the bolt 77. The pintle abutment rod 74 acts to limit the displacement of the pintle 14 caused by the action of the spring element 52, etc. In this specific embodiment, the pintle 14 is brought to a stanstill at the eccentric position +n that is of a distance D from the axis of rotation m of the housing 1. The hydraulic actuator 66 for shifting the pintle in this way is equipped with a hydraulic pressure circuit for forcing the high pressure fluid in the energy converter into the introduction portion 68 in the cylindrical member 69 via a pressure-compensation valve. This hydraulic pressure circuit comprises the port 24 extending through the pintle, a fluid passage 81 schematically shown in Fig. 1 as indicated by the dot-and-dash line, and other fluid passages 83, 84, 85. The port 24 communicates with the fluid inlet/outlet port 25 which is set in such a way that the high pressure fluid in the converter is forced into and out of the port 25 as mentioned already. The passage 81 branches off from the port 24, and acts to introduce working fluid into a port 82 formed in the rear cover 1b of the housing 1. The passage 83 is in communication with a fluid passage 92 formed in a block 91 incorporating a pressure compensation mechanism. The block 91 bears on the rear cover 1b of the housing 1. Working fluid is introduced from the passage 92 in the block into the housing 1 via a pressure compensation valve 93 and also via the passage 84. One end of the passage 85 is connected to the passage 84, while the other end is connected to the suction portion 68 in the cylindrical member 69 and also to the mounting hole 73 formed in one side wall of the housing 1, the rod 74 extending through said hole 73. The pressure compensation valve 93 incorporated in the block 91 is designed for enabling inserting a spool 94 in the fluid passage 92, said spool being held or moved according to a preset operating pressure. More specifically, the spool 94 has a land being in sliding contact with the wall of said fluid passage. This land is so located in the passage 92 as to fully bridge the opening of the passage 84. The moving front end of the spool 94 faces a larger support hole 95 connected to the passage 94. A spring element 98 is mounted between a retaining plate 96 fitted on the front end of the spool 94 and the inner surface of a locking bolt 97 being fitted in said support hole 95 on the opposite side. The urging force of the spring element 98 can be controlled by the stroke that can be adjusted by tightening or loosening the bolt 97. When the pressure of the high pressure fluid transmitted in the converter through the fluid passage 83 overcomes the urging force of the spring member 98, i.e., the pressure set by the pressure compensation valve 93, the spool 94 slightly slides toward the front end whereupon the spool 94 brings the fluid passage 84 into communication with the fluid passage 92. This permits the high pressure fluid to be forced into the hydraulic actuator 66 urging the pintle. Of course, when the pressure of the high pressure fluid drops below said preset value, the spool 94 returns to its original state, cutting off the supply of high pressure fluid into the actuator 66. After returning from the actuator 66, working fluid is caused to flow via fluid passages 86, 87, 88 into a case drain facing the inner surface of the housing. A stopper 99 is used to maintain the spool 94 in return condition. When working fluid is introduced into the hydraulic actuator 66 from the high pressure portion of the converter via the pressure compensation valve 93, the pintle 14 is moved to the other side in opposition to both the urging force of the spring element 52 and the force exerted by the balance piston 56. The force exerted upon the pintle 14 by the actuator 66 is equal to the area of the inner bottom surface 67a of the recess 67 multiplied by the pressure of the high pressure fluid introduced, said recess 67 forming the suction portion for the working fluid. The force displaces the pintle 14 into the eccentric position -n. Therefore, the output power of the actuator 66 is much larger than the force exerted by the balance piston 56 which overcomes the opposing urging force. For these purposes, the characteristics of the spring element 52 are determined based on the force exerted by the actuator 66 and also by the balance piston 56 in such a way that when the pressure of the high pressure fluid in the converter increases from the pressure set by the pressure compensation valve 93, pintle 14 is smoothly displaced. The characteristics of the spring element 52 are also set in such a way that when the pressure of the high pressure fluid in the converter reaches the pressure set for the valve 93 and is about to actuate the actuator 66, the addition of the force of the spring element 52 and the force of the piston 56 is still somewhat larger than the force acting on the actuator. Immediatly after said preset pressure is overreached, pintle 14 is quickly shifted to the opposite side. As already mentioned, when pintle 14 is displaced in this way, the threaded rod 64 in the hydraulic means 53 limits the displacement of said pintle. The operation of the illustrated converter is now described. When the axis of the pintle 14 is set at the position +n and the torque ring 2 is rotated by an external force in the direction indicated by the arrow R, high pressure fluid is discharged from the first fluid communication line 21. Thus, the converter acts as a pump. When the axis of the pintle 14 is set at the position -n and high pressure fluid is supplied into the chambers 13 present in the first region via the first line 21, a couple is produced which rotates the ring 2 in the direction indicated by the arrow S. Hence, the converter acts as a motor. When the converter is used either as a pump or as a motor at the corresponding position of the axis of rotation, the shaft 6 of the converter is rotated in a certain direction. The way in which the converter is operated while varying its capacity is now described. It is first assumed that the converter is used as a source of hydraulic pressure and that this pressure is supplied to a hydraulically driven engine. When the converter is run as a pump under the condition that the axis of the pintle 14 is located at the eccentric position +n, the pump discharges fluid from the first fluid communication line 21 that is placed on the high pressure side, at a flow rate determined by the eccentricity. When the high load pressure (discharge pressure), reaches a certain preset value, the pressure compensation valve 93 opens, said valve 93 being mounted in the hydraulic pressure circuit through which the high pressure fluid flows. Then, the hydraulic actuator 66 allows the pressure to be admitted to its suction portion 68. If the pressure shows a tendency to increase at all, then the actuator 66 displaces the pintle 14 to transiently reset the discharge of the pump for the discharge pressure. If the pressure increases further, the actuator 66 overcomes the action of both the spring member 52 and the balance piston 56 to move the axis of the pintle 14 from the eccentric position -n determined by the aforementioned limiting means, i.e., the axis of rotation, to the opposite side. When the pintle 14 is fully displaced, the converter functions as a pump that discharges fluid from the first fluid line 21 at a negative flow rate. That is, the converter is automatically switched to a motor that rotates in the same direction by permitting the high pressure fluid to flow into it. For such a displacement of the converter, the relation of the flow rate of said converter to the load pressure is shown in Fig. 5. In a pump equipped with the prior art pressure compensation function the discharge is controlled merely according to the discharge pressure as indicated by a and b. In contrast, in the novel pump, when the preset value is exceeded, the pressure corresponding to the pressure set for the pressure compensation valve is maintained substantially constant as indicated by c, and the amount of fluid introduced from the high pressure side is simultaneously gradually increased until its capacity is reached. Then, the converter is driven as a motor by the hydraulic energy of the high pressure fluid. As an alternative embodiment, if a dynamo that rotates in one direction is connected to the rotating shaft 6 of the converter, and is used as a motor under conditions indicated by c and d, then the fluid energy can be recovered. Because of this function of energy recovery, the converter can be run while economizing on energy. In the embodiment described thus far, the pintle 14 is held and displaced by the urging force of the spring element 52 and also by the force exerted by the balance piston 56. The use of the piston 56 is not basically essential to the invention. For example, it is possible to displace and hold the pintle 14 only by the urging force of the spring element 52 and to balance this by the force exerted by the hydraulic actuator 66 that displaces the pintle. In practice, it is advantageous to install the balance piston 56 as in the embodiment above for the following reasons. In the hydrostatic converter as described above, when the axis of the pintle is brought into the eccentric position +n and the converter is employed as a pump, the forces acting on the pintle 14 having the role of a support member theoretically cancel out and thus no displacing force is developed. In practice, however, the compressibility of the working fluid delays pressure variations inside the chamber 13, and the force which is slow in being cancelled urges the pintle 14 toward its neutral position. Therefore, if the pintle 14 is supported only by the spring element 52, this element is required to exert a considerably large urging force. Consequently, since a long stroke is needed for the displacement as mentioned previously, it is very difficult to appropriately design the spring element 52. For instance, if the design limits were inappropriate, the maximum allowable shear stress for a coiled spring may be exceeded. If the number of turns were increased, the spring would easily buckle. Hence, it would be difficult or dangerous to assemble or disassemble it. In cases where the pintle 14 is supported by the balance piston 56, such difficulties do not arise. Therefore, ideal characteristics can be imparted to the spring element 52. This enables the converter to have a mechanism for stably varying the capacity. Of course, the structure of the body of the inventive converter acting either as a pump or as a motor is not limited to the structure of the illustrated embodiment. For example, it may be an ordinary pump or piston of the radial piston type. It is also to be noted that the balance piston includes balance pistons shaped like plungers. Since the novel converter is constructed as described thus far, it is automatically switched between two modes of operation in which it acts as a pump and as a motor, respectively, according to the high pressure while maintaining the direction of rotation of the rotating shaft constant. Consequently, it can recover energy with high efficiency, which cannot be accomplished by an energy converter equipped with the conventional pressure compensation function.

Claims: 1. A rotary fluid energy converter characterized in that it comprises : at least one chamber (13) for suction and discharge of fluid ; first (1) and second (2) members which are rotatable relatively to each other about parallel axis of rotation (m,n) with possibility of increasing or decreasing the volume of the chambers (13) ; a support member (14) supporting one (2) of said first and second members, said support member (14) being slidable perpendicularly to the axis (m,n) so as to adjust the distance between said axis (m,n) of the first (1) and second (2) members, for varying the capacity of the converter and let it act either as a pump or as a motor ; a spring element (52) for urging the support member (14) toward one side of the axis of rotation (m) of said other (1) fixed member ; a hydraulic actuator (66) for displacing the support member (14) in direction of the other side of said fixed axis of rotation (m) against the urging action of the spring element (52) ; and a pressure compensation valve (93) through which a high pressure fluid used in the converter is introduced into the actuator (66), whereby the pressure of said high pressure fluid is maintained at the pressure set by the pressure compensation valve (93) when the converter acts as a motor, as well as when it acts as a pump. 2. A rotary fluid energy converter characterized in that it comprises : at least one chamber (13) for suction and discharge of fluid ; first (1) and second (2) members which are rotatable relatively to each other about parallel axis of rotation (m,n) with possibility of increasing or decreasing the volume of said chamber (13) ; a support member (14) supporting one (2) of said first and second members, said support member (14) being slidable perpendicularly to the axis of rotation (m,n) so as to adjust the distance between said axis (m,n) of the first (1) and second (2) members, for varying the capacity of the converter and let it act either as a pump or as a motor ; a spring element (52) for urging the support member (14) toward one side of the axis of rotation (m) of said other fixed member (1) ; a balance piston (56) for producing a force that acts to cancel the unbalanced force in the direction in which the support member (14) is displaced ; a hydraulic actuator (66) for displacing the support member (14) in direction of the other side of said fixed axis of rotation (m) against the urging action of the spring element (52) ; and a hydraulic circuit which introduces a high pressure fluid used in the converter to act on one end surface of the balance piston (56) via a pressure compensation valve (93) to cause the balance piston (56) to produce said force, whereby the pressure of the high pressure fluid is maintained at the pressure set by the pressure compensation valve (93) when the converter acts as a motor, as well as when it acts as a pump.

Inventors: KITA, YASUO
Applicants: SHIMADZU CORPORATION
Application year: 1986
Main classification: F04B49
IPC codes: F04B49