US20090007773A1

US20090007773A1 - Axial plunger pump or motor

Info

Publication number: US20090007773A1
Application number: US12/231,783
Authority: US
Inventors: Raphael Zhu
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-14
Filing date: 2008-09-05
Publication date: 2009-01-08
Also published as: WO2007104257A1; CN101415944A; KR20090020549A; JP2009529619A; CN101415944B; EP2012010A1

Abstract

An axial plunger pump or motor comprises a casing (1), a main shaft (2), a rotor cylinder (14), a rotary swash plate (9) and a plurality of plunger assemblies (10), wherein a constant velocity universal coupling (11) transmits torque between the rotary swash plate and the main shaft, such that the main shaft (14) and the rotary swash plate (9) rotate about the main shaft axis (41) and the swash plate axis (91) forming an angle therebetween, respectively, so as to realize transition between hydraulic energy and rotary mechanical energy.

Description

This application claims priority from and is a continuation of and hereby expressly incorporates by reference in its entirety, PCT application PCT/CN/2007/000807 having publication number WO 2007/104257 for AN AXIAL PLUNGER PUMP OR MOTOR which was published Sep. 20, 2007 which in turn claims priority from Chinese application for the same AN AXIAL PLUNGER PUMP OR MOTOR application filed Mar. 14, 2006 having Chinese application number 200620007920.7 both by same inventor ZHU, Raphael, the disclosure of which is incorporated herein by reference in its entirety.

FIELD

The present invention relates to a hydraulic pump or motor device in hydraulic mechanisms, particularly to an axial plunger pump or motor.

BACKGROUND

In hydraulic mechanisms, a hydraulic pump or motor is the heart of the hydraulic device. Theoretically, a hydraulic pump and a motor are switchable, except for some partial differences. Therefore, the description of the invention will only focus on the design of the pump, and the structure of a motor will be omitted in that it is similar to that of the pump. Plunger pumps or so named piston pump have been increasingly widely employed in engineering mechanisms due to their high efficiency, adaptation to high pressure and aptness to carry out variable displacement adjustment.
The plunger pump can be classified into two categories according to the stroke direction of the plunger, that is, an axial plunger pump and a radial plunger pump. In the axial plunger pump, according to the mechanism of motion transition, it may be classified into a swash plate plunger pump and a bent axis plunger pump, the structural characteristics of which are referred to FIGS. 1 through 3, respectively.
An axial plunger pump of a swash plate type is a variable displacement pump of high pressure, high speed, high impact resistance and high integration degree. As shown in FIGS. 1 and 2, a rotor is driven to rotate by the main shaft through involute splines. A plurality of plungers, which are uniformly distributed in the rotor, press the sliding shoes of the plunger assemblies against the plane of the frictional plate of the swash plate through a ball joint and a return press plate. Since there is an angle between the swash plate plane and the rotation axis, the plunger body not only rotates with the rotor, but also reciprocates along the plunger hole of the rotor. In this way, the plunger pump carries out oil intaking and oil outleting. The stroke of the plunger can be changed through adjusting the inclination angle of the swash plate plane, so as to perform variable displacement adjustments. Changing the inclination direction of the swash plate leads to variations of the flow direction of the pressurized oil, or the rotation direction of the rotor in case of serving as a hydraulic motor.
In such an axial plunger pump of a swash plate type, it is easy to perform variable displacement adjustments, and convenient to change the direction of the pressurized oil and the rotation direction of the rotor and to switch between the pump state and the motor state. It has a low cost, with relatively simple structure and small volume. However, an axial plunger pump of a swash plate type has three main friction pairs, i.e., a pair between rotor and oil-distributing disk, a pair between plunger and plunger hole, and a pair between the sliding shoe of the plunger and swash plate. In the friction pair between plunger and plunger hole, the plunger is not only subject to an axis force, but also to a tangential force and a moment due to a normal force acted upon the sliding shoe of the plunger by the swash plate. The force and moment are balanced by the pressure applied on the plunger by the plunger hole of the rotor. The sliding friction caused by such force and moment leads to a reduced mechanical efficiency and component wearing. Therefore, the rotor needs to be balanced through a center axis supporting or an additional bearing since it is also acted upon by a rollover moment. Thus, such a pump has three disadvantages: (i) the overall efficiency is relatively low, wherein the volume efficiency of the oil pump is between 0.92 and 0.98 and the mechanical efficiency is between 0.90 and 0.95, and the overall efficiency is not higher than 0.95; (ii) it is susceptible to staining from oil, thus resulting in a short pump service life; (iii) the allowable rotation speed is not high.
As shown in FIG. 3, the working principle of a bent axis plunger pump is fairly similar to that of a swash plate pump. However, they have large differences in structure, and they also have different force profiles. In a bent axis plunger pump, the method of articulating the ball head of the plunger is substituted for the approach of employing the sliding shoes and the swash plate in the swash plate pump, such that the structural strength and the impact resistance are improved. When the pump is operating, since the angle between the axis of the linking rod and the axis of the plunger is not large, the lateral pressure between the plunger and the cylinder wall is much smaller than that in the case of a swash plate pump. Therefore, wearing during operation is small, and the inclination angle β may also be increased to 25 through 30 degrees (less than 20 degrees in case of a swash plate pump), such that the variation range of flow flux is enlarged. Furthermore, the drive shaft of a bent axis plunger pump is small in dimension, or it does not penetrate through the oil-distributing disk, such that the rotor diameter of the cylinder is correspondingly reduced. Thus, leakage and friction loss are decreased, resulting in a higher overall efficiency than that of the swash plate pump, e.g., higher by 2-3% under the same technical level. The pump performance in oil-intaking is thus improved since the circumferential speed of the oil cylinder is decreased, and the rotation speed limit of the pump can therefore be increased. Furthermore, the requirement on the accuracy of oil-filtering in a bent axial pump is low, e.g., generally 25 m, in comparison with 10 to 15 m in a swash plate pump.
Due to above advantages, such bent axis plunger pumps have been increasingly employed in the hydraulic mechanisms. However, such a pump carries out variable displacement through cylinder swinging, and the profile dimension is large. The inclination between the rotor and the power shaft makes the profile form a corner shape, which is not desirable in situations of narrow space or in case where coaxial assembly is required. In addition, structure and technical requirements are relatively complicated, thus leading to a high cost.

SUMMARY

The object of the invention is to provide an axial plunger pump or motor, which enables to increase the efficiency of the plunger pump or motor, has a simplified structure, a decreased volume, a lower cost, and a wider application range, and particularly is applicable to situations where special installation requirements should be meet, such as in transmissions of motor vehicles.
The above mentioned object of the invention may be achieved by the following technical solutions, i.e., an axial plunger pump or motor, comprising:
a casing;
a main shaft rotatably supported on the casing;
a rotor cylinder with a plurality of plunger holes, which is coupled to the main shaft and is driven to rotate about a main shaft axis by the main shaft and which has an oil-distributing end surface;
an oil-distributing disk in cooperation with the oil-distributing end surface of the rotor cylinder;
a rotary swash plate, whose end surface is disposed in a manner axially opposing the plurality of plunger holes of the rotor cylinder and which can rotate about a swash plate axis forming an angle with respect to the main shaft axis;
a plurality of plunger assemblies, an end of each being articulated to the end surface of the rotary swash plate and another end of each being slidably disposed in the plunger holes of the rotor cylinder;
a constant velocity universal coupling, which is provided between the rotary swash plate and the main shaft and transmits torque therebetween, so that the main shaft and the rotary swash plate rotate about the main shaft axis and the rotary swash plate axis with an angle therebetween, respectively.
In the invention, said constant velocity universal coupling may be a Rzeppa constant velocity universal coupling, a half angular Rzeppa constant velocity universal coupling, a ball joint constant velocity universal coupling or a Weiss constant velocity university coupling and etc.
The Rzeppa constant velocity universal coupling in the invention comprises an inner race ring with an outer raceway, an even number of steel balls, a holder and an outer race ring with an inner raceway, wherein said steel balls are arranged on the holder and are located in the inner raceway and the outer raceway, said inner race ring is coupled to the main shaft, said outer race ring is coupled to the rotary swash plate, such that the main shaft and the rotary swash plate are respectively rotated about the main shaft axis and the swash plate axis via the Rzeppa constant velocity universal coupling.
In the invention, as a particular example, said outer race ring may be integrally formed on the rotary swash plate.
In the invention, as an alternative example, said rotary swash plate may be supported on the casing via a swash plate bearing.
In the invention, as another alternative example, said rotary swash plate is supported on a pendulous disk via a swash plate bearing, the pendulous disk is supported on said casing via a pendulous disk bearing, and a rotation axis of the pendulous disk bearing is perpendicular to the main shaft axis and passes through the center of the constant velocity universal coupling.
In the above example, said pendulous disk may be connected with a variable displacement adjustment mechanism for adjusting the deflection angle of the pendulous disk, such that an angle between the swash plate axis of the rotary swash plate supported thereon and the main shaft axis is adjusted through changing the deflection angle of the pendulous disk, and therefore the strokes of the plunger assemblies are changed so as to carry out variable displacement adjustment.
As an alternative example, said variable displacement adjustment mechanism in the invention is a variable displacement oil cylinder, the piston of which is connected to the pendulous disk so as to drive the pendulous disk to deflect through extending and retracting of the piston.
As another alternative example, the variable displacement adjustment mechanism is a variable displacement adjustment mechanism of a trunnion type, which includes a trunnion connected to the pendulous disk and a driving mechanism for driving the trunnion to rotate, a rotation axis of the trunnion is coincident with the rotation axis of the pendulous disk so as to drive the pendulous disk to deflect through rotation of the trunnion.
In the invention, said rotor cylinder is in a taper shape, a diameter thereof at the end closer to the rotary swash plate is larger than that at the other end.
In the above-mentioned example, the plurality of plunger holes on said rotor cylinder are also distributed in a taper form, wherein the diameter of the circle in which the plunger hole center is located at the end in corporation with the plunger assemblies is larger than that at the other end.
In the invention, said plunger assembly may particularly be a plunger assembly of a ball joint type, which comprises a plunger and a ball-headed rod with a ball head at each of both ends thereof, in an end surface of said rotary swash plate there is provided with a socket, a ball head at an end of the ball-headed rod is located in the socket to form a ball-joint connection with the rotary swash plate, and a ball head at the other end thereof is located in the plunger to form a ball-joint connection with the plunger, and the plunger is slidably provided in the plunger hole. In the middle portion of the ball-headed rod and the plunger there is provided with an oil hole in communication with the plunger holes so as to introduce pressurized oil to lubricate the ball head at the both ends.
In the invention, articulation centers of said plurality of plunger assemblies on the rotary swash plate are located in a same plane, and an intersection point of the plane with the main shaft axis is coincident with the center of the constant velocity universal coupling.
In the invention, said rotor cylinder is provided with an oil-distribution disk at the rear end thereof, the rotor cylinder is axially positioned along the main shaft through a pressure spring and a pressure spring stop collar, at an end of the main shaft there is provided with an oil hole and a radial oil path, such that the pressure between the rotor cylinder and the oil-distribution disk is adjusted through introducing pressurized oil into the radial oil path.
In the invention, as an alternative embodiment, the oil-distribution end surface of said rotor cylinder may be a spherical surface, said oil-distribution disk forms a spherical surface fit with the oil-distribution end surface.
In the invention, said swash plate bearing may be a combination bearing of a needle bearing and a cylindrical or taper roller thrust bearing. The pendulous disk bearing in the invention is a needle bearing in a crescent form.
By employing the above-mentioned structure of the invention, while the main shaft is driving the rotary cylinder to rotate, the axial plunger pump or motor according to the invention may drive, via the constant velocity universal coupling, the rotary swash plate to rotate about the swash plate axis forming an angle with respect to the main shaft axis. In this way, the plunger assemblies reciprocate in the plunger holes of the rotor cylinder, causing volume variations in the cylinder, and communicate with the inlet port and the outlet port sequentially via the cooperation with the oil-distributing disk at the rear end of the rotor cylinder. In this way, oil-intaking and oil-extruding are carried out, or in other words, transition between rotation mechanical energy and hydraulic energy is achieved. Wherein, since the constant velocity universal coupling transfers the rotating motion and the moment of the main shaft to the rotary swash plate which is rotating relative to the main shaft about a inclined axis, the inclination angle of the rotary swash plate may be changed through driving the pendulous disk to swing by the variable displacement mechanism, so as to conveniently perform variable displacement adjustments.
As compared to a prior art axial plunger pump or motor of a swash plate type or a prior art axial plunger pump or motor of a inclined axial type, the axial plunger pump or motor according to the present invention has the following effects:
(A) When compared with a variable displacement swash plate pump, the method of articulating the plunger assembly and the rotary swash plate is substituted for the sliding shoe and the swash plate in a swash plate pump, therefore structures corresponding to the three main friction pairs of the swash plate pump are changed to a large extent: (i) Sliding friction between the sliding shoe of the plunger and the swash plate is changed to rolling friction, thus friction and leakage are decreased, and the surface area of the ball head which forms a ball joint is larger than the discal area of a sliding shoe of the same diameter, thereby the radial dimension of the swash plate is decreased; (ii) As for the friction pair between the plunger and the rotor cylinder, the friction force is accordingly decreased since the lateral pressure is much less than in the case of the swash plate pump, the requirement on the accuracy of oil-filtering is largely relaxed, and the wearing is suppressed. (iii) As for the friction pair between the rotor cylinder and the oil-distribution disk, since the main shaft is free of the bending moment and only serves to support at the rotor end, the dimension of the friction pair can be reduced, thereby the diameter of the oil-distributing port of the rotor cylinder may decreased, such that the circumference of the oil port and the linear velocity of the relative motion is decreased and the power loss due to friction and leakage is suppressed. In addition, since the inclination angle β of the rotary swash plate of the pump may be increased to 25 through 30 degrees (not larger than 20 degrees in case of a swash plate pump), the variation range of flow flux is enlarged, the dimension of the pump is decreased and the pump performance in oil-intaking is thus improved since the circumferential speed of the oil cylinder is decreased; at the same time, the hydraulic thrusting acted upon the plunger is directly transferred to the casing through the ball head, the rotary swash plate, the bearing and the pendulous disk support, such that movement components, such as the main shaft and the rotor cylinder, etc., are free of other additional forces and moments. In this way, the force profile of the movement components is improved, and friction and leakage are suppressed. The above factors have the following effects:
(1) a higher overall efficiency than that of a swash plate pump, (2) an increased structural strength, a higher impact resistance, an increased resistance to staining from oil, a decreased wearing and an extended service life, (3) an increased rotation speed limit of such a pump or motor, (4) a further decreased dimension of such a pump or motor.
(B) When compared with a variable displacement bent axis axial plunger pump, although in structural point of view, a synchronous constant velocity universal coupling is added, leading to a certain power loss (generally, 1-3%), four benefits can be obtained, that is:
(1) a decreased volume and a decreased weight. The means of deflecting and adjusting the pendulous disk is substituted for swinging the rotor body, so the radial dimension required by the same deflection angle is decreased. Because of the change of the force profile, the power shaft is subject to a large bending moment while being acted upon by a torque, thus a certain axial length is necessary for the purpose of balancing, leading to a longer power shaft; in addition, the oil-distributing disk, the pendulous disk and the variable displacement adjustment mechanism located at the afterbody may occupy large space. With the same parameters, the axial length and the radial dimension of the inventive variable displacement plunger pump is decreased by more than ⅓ as compared to the conventional bent axis axial plunger pump.
(2) coaxial transmission or transmission by a common shaft is achieved. It is suitable for applications of limited installation space which needs coaxial transmission or transmission by a common shaft, such as the case in which a plurality of pumps are required to be connected in serials. This may simplify or optimize the mechanical systems in some application.
(3) an easy adjustment and switch. The output flow flux may be adjusted only by varying the inclination angle of the pendulous disk, and the flow direction and the switch between pump and motor may be changed simply by changing the direction of inclination angle. However, in prior art inclined axial plunger pump, a large stroke space and drive power are necessary to perform the same implementation.
(4) a further increased efficiency. Although the additional constant velocity universal coupling leads to a somewhat decrease in the efficiency, the prior art structure, which needs three heavy-duty bearings to bear the radial force, the axial force and the bending moment of the main shaft, is significantly simplified, i.e., only one heavy-duty bearing is needed. Thus the power loss due to friction is lowered, this is because the power shaft is free of bending moment and the end surface bearing functions to positioning only. The inventive structure dispenses with a sliding fit surface between the oil-distributing disk and the velocity adjusting disk as compared with the prior art mechanism which carries out velocity adjustment through swinging the rotor, thus corresponding leakage is suppressed and the volume efficiency is increased. In this way, the overall efficiency is higher than a conventional variable displacement bent axis axial plunger pump.

DRAWINGS

FIG. 1 is a schematic view of the structure of a prior art swash plate pump;

FIG. 2 is a sectional view taken along line A-A in FIG. 1;

FIG. 3 is a schematic view of the structure of a prior art bent axis axial plunger pump;

FIG. 4 is a view showing the principles of the structure of the invention;

FIG. 5 is a schematic view showing the structure of the embodiment 1 of the invention in a front view;

FIG. 6 is a sectional view taken along line A-A in FIG. 5;

FIG. 7 is a sectional view taken along line B-B in FIG. 6;

FIG. 8 is a schematic view showing the structure of the embodiment 2 of the invention in a front view;

FIG. 9 is a schematic view showing the assembly structure of a Rzeppa constant velocity universal coupling; and

FIG. 10 is a perspective view showing the exploded structure of the Rzeppa constant velocity universal coupling.

DESCRIPTION OF REFERENCE NUMBERS

- 1—casing, 2—pendulous disk bearing, 3—

DETAILED DESCRIPTION OF EMBODIMENTS

As shown in FIG. 4, an axial plunger pump or a motor according to the invention mainly includes a casing 1, a main shaft 4 rotatably supported on the casing 1, a rotor cylinder 14 with a plurality of plunger holes which is coupled to the main shaft 4 and is driven to rotate about the main shaft axis 41 by the main shaft 4 and which has an oil-distributing end surface, an oil-distributing disk 15 in cooperation with the oil-distributing end surface of the rotor cylinder 14, a rotary swash plate 9 whose end surface is disposed in a manner axially opposing the plurality of plunger holes of the rotor cylinder 14 and which may rotate about the swash plate axis 91 forming an angle with respect to the main shaft axis 41, a plurality of plunger assemblies 10, an end of each articulated to an end surface of the rotary swash plate 9 and another end of each slidably disposed in the plunger holes of the rotor cylinder 14, a constant velocity universal coupling 11 which is provided between the rotary swash plate 9 and the main shaft 4 and transmits torque therebetween, and which rotates the main shaft 4 and the rotary swash plate 9 about the main shaft axis 41 and the swash plate axis 91 forming an angle therebetween, respectively. In this way, when the invention is employed as an axial plunger pump, the main shaft 4 is driven to rotate about the main shaft axis 41, and the rotary swash plate 9 is driven, by constant velocity universal coupling 11, to rotate about the swash plate axis 91 forming an angle with respect to the main shaft axis 41. Thus the plunger assemblies 10 axially reciprocate in the plunger holes of the rotor cylinder 14, causing volume variations in the rotor cylinder 14 to carry out oil-intaking and oil-extruding, or in other words, transition between rotation mechanical energy and hydraulic energy is achieved. When the invention is employed as an axial plunger motor, the rotary swash plate 9 rotates about the swash plate axis 91 by the hydraulic oil in the plunger holes so as to drive the main shaft 4 to rotate about the main shaft axis 41 via the constant velocity universal coupling 11 and to drive the rotor cylinder 14 coupled with the main shaft 4 to rotate simultaneously. In this way, the plunger assemblies 10 reciprocate in the plunger holes, such that hydraulic energy is transited to rotary mechanical energy of the main shaft. In view of similarity in basic structures whether the inventive axial plunger pump or motor is employed as a pump or as a hydraulic motor, the present invention will mainly describe in detail the situation where the inventive axial plunger pump or motor is employed as a pump.
In the present invention, as one particular example, the casing 1 and a rear end cap 18 are connected to each other via screws so as to form a closed box, and the main shaft 9 is supported in the box via a front bearing 6 and a rear bearing 16, as shown in FIGS. 4 to 7. An inlet slot and an outlet slot in the oil-distributing disk 15 are communicated with an inlet port 13 and an outlet port 20, respectively. The main shaft 9 penetrates through the oil-distributing disk 15, the rotor cylinder 14, a pressure spring 19, the constant velocity universal coupling 11 and the rotary swash plate 9 in order, and projects through an end seal cap 5 from an end of the box. The rotor cylinder 14 is circumferentially fixed to the main shaft 4 via a spline, and is pressed against the oil-distributing disk 15 by the pressure spring 19 surrounding the main shaft 4 so as to achieve an initial seal between the rotor cylinder 14 and the oil-distributing disk 15. The rotating main shaft 4 drives rotary swash plate 9 to rotate about the swash plate axis 91 via the constant velocity universal coupling 11, while driving the rotor cylinder 14 to rotate via the spline. In this way, the plunger assemblies 10 are driven to reciprocate in the plunger holes in the rotor cylinder 14, causing volume variations in the plunger holes. These plunger holes communicates with the inlet port 13 and the outlet port 20 sequentially via the cooperation with the oil-distributing disk 15. In this way, oil-intaking and oil-extruding are conducted, i.e., transition between rotation mechanical energy and hydraulic energy is achieved.
In the invention, the constant velocity universal coupling 11 may be a Rzeppa constant velocity universal coupling, a half angular Rzeppa constant velocity universal coupling, a ball joint constant velocity universal coupling or a Weiss constant velocity university coupling, etc. The invention mainly takes a Rzeppa constant velocity universal coupling as an example and gives a detailed explanation thereof. Other types of constant velocity universal coupling, such as a half angular Rzeppa constant velocity universal coupling, a ball joint constant velocity universal coupling, a Weiss constant velocity university coupling, and the like, are also applicable if it is permitted by space dimension, even though their structures are relatively complicated as compared with the structure of a Rzeppa constant velocity universal coupling. Therefore detailed explanations thereof are omitted. As shown in FIGS. 5 through 10, in an example where the constant velocity universal coupling 11 is a Rzeppa constant velocity universal coupling, it comprises an inner race ring 111 with an outer raceway, an even number of steel balls 112, a holder 113 and an outer race ring 114 with an inner raceway, wherein the outer race ring 114 is coupled to the rotary swash plate 9 and the inner race ring 111 is coupled to the main shaft 4, such that the main shaft 4 can drive the rotary swash plate 9 which is coupled to the outer race ring 114 to rotate about the swash plate axis 91 forming an angle with respect to the main shaft axis 41 (i.e., the rotation axis about which the outer race ring 114 rotates) while driving the inner race ring 111 to rotate about the main shaft axis 41. As a particular example, the inner holes of the outer race ring and the rotary swash plate 9 may be combined so as to integrate the outer race ring 114 with the rotary swash plate 9, thus space effectiveness in the radial direction is ensured. Even though the inner race ring 111 and the main shaft 4 may also be combined such that the inner race ring 111 is integrated with the main shaft 4, in this embodiment, they are provided separately in consideration of manufacture process and installation feasibility, the inner race ring 111 is circumferentially fixedly coupled to the main shaft 4 via a spline and is restrained in the axial direction by a stop collar 21 on the shaft. As shown in FIG. 9, according the principles of a Rzeppa constant velocity universal coupling, the sphere centers of both the inner race ring and the outer race ring should be arranged on the main shaft axis 41 and be located on each side of the center point of the constant velocity universal coupling 11 with equal distances thereto. The holder 113 confines the even number of steel balls 112 in a same plane which also passes through the center point of the coupling.
As an alternative example, the plurality of plunger assemblies 10 in the invention may be plunger assembles of a ball joint type, which comprises a plunger and a ball-headed rod with a ball head at both ends thereof and which is provided with an oil hole for introducing pressurized oil to lubricate the ball head at the both ends. The structure of the plunger assemblies 10 is the same as the structure of the plunger assemblies of the bent axis axial plunger pump. Uniformly distributed on the right end of the rotary swash plate 9 are a plurality of sockets with their center points located in a same plane. The ends of ball heads of the plunger assemblies 10 are imbedded into the sockets of the rotary swash plate 9 and restrained therein by a retainer plate 23, and the plunger ends of the plunger assemblies 10 projects into the plunger holes of the rotor cylinder 14. The number of the plunger assemblies 10 is equal to the number of the sockets in the rotary swash plate 9 and the number of plunger holes in the rotor. The center point of the constant velocity universal coupling 11 is coincident with the intersection point of the central plane of the plurality of sockets in the rotary swash plate 9 with the main shaft axis.
In the invention, as shown in FIG. 4 through 8, the middle case of casing 1 and the front end cap may be an integral structure cast from cast iron or die-cast from aluminum alloy, while the rear end cap 18 is connected to the middle case via screws. Certainly, other structural forms may be employed, e.g., the middle case and the front end cap are separated and they are coupled with each other via screws. The integral structure has a higher strength, but it is more difficult to process, contrary to the latter case.
As shown in FIGS. 4 through 7, as an alternative example of the invention, in embodiment 1, the axial plunger pump or motor according to the invention may carry out variable displacement adjustment. The rotary swash plate 9 may be embedded into a pendulous disk 7 via a swash plate bearing 8 which can resist a radial force, an axial force and a bending moment at the same time. The pendulous disk 7 is supported to the casing 1 via a pendulous disk bearing 2. The rotation axis of this pendulous disk bearing 2 is perpendicular to the main shaft axis 41 and passes through the center of the constant velocity universal coupling 11. In other words, the pendulous disk 7 can only swing about the center of the constant velocity universal coupling 11 in a plane parallel to the main shaft axis 41. In this way, the inclination angle of the rotary swash plate 9 (i.e., the inclination angle of the swash plate axis 91 with respect to the main shaft axis 41) may be adjusted through deflecting the pendulous disk 7 so as to carry out variable displacement adjustment. In embodiment 1, as shown in FIGS. 4 through 7, the pendulous disk 7 may be connected with a variable displacement adjustment mechanism for adjusting the deflection angle of the pendulous disk 7. The constant velocity universal coupling 11 transfers the rotation motion of the main shaft 4 and thus the moment to the rotary swash plate 9 rotating about the swash plate axis 91, therefore it is very convenient to carry out variable displacement adjustment of a pump or motor through driving, via the variable displacement adjustment mechanism, the pendulous disk 7 to swing so as to change the inclination angle of the rotary swash plate 9.
As shown in FIG. 4 through 6, in the embodiment 1, the pendulous disk 7 comprises an upper partial cylinder and a lower partial cylinder, and is supported to the casing 1 via the pendulous disk bearing 2, with its right end provided with an inner cylinder surface of a stepped shape for the swash plate bearing 8 to be embedded. As shown in FIG. 6 and FIG. 7, as one example of a variable displacement adjustment mechanism, the variable displacement adjustment mechanism may be an variable displacement adjustment mechanism of a trunnion type which conducts adjustment from outside. It includes a trunnion 24 connected to the pendulous disk 7 and a driving mechanism for driving the trunnion 24 to rotate. The rotation axis of the variable displacement trunnion 24 is coincident with the swing axis of the pendulous disk 7. In this way, the variable displacement adjustment is achieved through the peripherally provided driving mechanism driving the trunnion 24 to rotate. In this example, at one side of the pendulous disk 7 there may be provided with a seat 26 for the variable displacement trunnion via a threaded member 27. The variable displacement trunnion 24 is circumferentially fixedly connected to the trunnion seat 26 via a spline or a flat key so as to install the variable displacement trunnion 24 to the pendulous disk 7. Thus, the structure is simple and straightforward in that the pendulous disk 7 can be driven to swing only through rotating the trunnion 24. As another example of a variable displacement adjustment mechanism, the variable displacement adjustment mechanism may also be a variable displacement oil cylinder 28, the piston of which is connected to the pendulous disk 7 so as to drive the pendulous disk 7 to deflect through extending and retracting the piston, thereby carry out variable displacement adjustment. The variable displacement adjustment mechanism may certainly assume other forms, for example, they may take use of variable displacement mechanism of various swash plate pumps, only if the deflection angle of the pendulous disk 7 can be changed by means of the variable displacement adjustment mechanisms. Herein explanations thereof are omitted.
As shown in FIG. 5 and FIG. 6, the swash plate bearing 2 in the embodiment 1 may be two needle bearings in a crescent form which are up and down symmetric. The rotation axis of the bearing 2 is perpendicular to the axis of the main shaft 4 and passes through the center of the constant velocity universal coupling 11. The outer race ring of the bearing is fixed to the bearing seat of the casing 1, and the inner race ring thereof is fixed to the cylindrical surface of the pendulous disk 7 on the left side or is integral with the cylindrical surface. The function of the bearing is to transfer the thrust force acted upon the pendulous disk 7 to the casing 1 and to suppress the swinging resistance to the pendulous disk 7. The bearing may be other types of bearing, such as a sliding bearing.
In the embodiment 1, the rotary swash plate 9 may be provided with a flare-shaped inner hole at its left end through which the main shaft 4 passes, and does not interfere with the main shaft 4 when swinging with the pendulous disk 7. The rotary swash plate 9 is also provided with an outer cylinder surface at its left end so as to install the swash plate bearing 8. The rotary swash plate 9 has a plurality of sockets on its right end surface, the center points of which sockets are located in a same plane. Generally, the number of the sockets is odd, such as 5 to 11. At the central portion of its right end, the rotary swash plate 9 is provided with a spherical hole, and there is engraved an inner raceway along the direction of the main shaft 4, serving as the out race ring of the Rzeppa constant velocity universal coupling 11.
As shown in FIG. 8, in the embodiment 2 which is another embodiment of the invention, the axial plunger pump or motor of the invention may be applicable to a constant displacement pump. Since no variable displacement adjustment is needed, the pendulous disk 7, the pendulous disk bearing 2 and the variable displacement mechanism in embodiment 1 can be dispensed with and the rotary swash plate 7 can be directly supported at the oblique surface of the casing 1 by the swash plate bearing 8, such that the whole structure is very simple and compact.
The important friction surface in the invention may be subject to plating or coating, for example, molybdenum disulfide plating so as to decrease friction loss and improve efficiency and service life.
The swash plate bearing 8 of the invention need resist an axial force, a radial force and a rollover moment from the swash plate. Therefore, the combination of a needle/cylinder (tape) roller thrust bearing may be employed, and other types of bearings or combination bearings are also applicable if only they can perform the same functions.
In the present invention, as shown in FIGS. 4 through 6 and FIG. 8, the main shaft 4 is provided with a spline or a flat key at its front end so as to be connected to other motive machines or working machines. On the middle of main shaft 4 there is provided with splines to be circumferentially fixedly connected to the constant velocity universal coupling 11 and rotor cylinder 14, respectively, so as to drive the rotary swash plate 9 and the rotor cylinder 14 to rotate and to transfer torque. At the middle of the main shaft 4 there is supported a disk pressure spring 19 with a pressure spring stop collar 21 and a pressure spring seat. The pressure spring 19 may also be a cylinder-shaped coil spring. Generally, a residual pressure method is employed to calculate the pre-compression force of the spring, with the principle being to ensure reliable seal between the rotor cylinder 14 and the oil-distributing disk 15. The right end of the main shaft 4 is provided with an oil hole and a radial oil path, such that the pressurized oil introduced from the outside of the pump acts upon the right end surface of the rotor cylinder 14. Thus, the pressure between the rotor cylinder 14 and the oil-distributing disk 15 may be adjusted through adjusting the pressure of the pressurized oil from outside. In this way, the pressure between the rotor cylinder 14 and the oil-distributing disk 15 can be conveniently adjusted to ensure a higher overall efficiency of the pump under various working conditions.
As shown in FIGS. 4 through 6 and FIG. 8, the rotor cylinder 14 in the invention may be a cylinder with a plurality of plunger holes arranged uniformly in the circumferential direction. These plunger holes are in a close movable fit with the plungers of the plunger assemblies 10. As shown in FIG. 5 and FIG. 8, the oil-distribution end surface of the rotor cylinder 14 is a spheric surface, which is in a close fit with the spheric oil-distributing disk 15, thus generating a spheric surface fit therebetween and presenting a good self-centering characteristics. The rotor cylinder 14 may be made of such materials as copper, spheroidal graphite cast iron, cast steel, forged steel, etc. The inner surface of the plunger holes and the spheric oil-distribution surface are subject to the treatment (such as embedding and plating) to decrease friction and enhance wear resistance. Since the constant velocity universal coupling 11 should be installed at the center of the rotary swash plate 9, the radial dimension thereof will consequentially be increased in case of the pump of small displacement. In this case, the rotor cylinder 14 may be formed in a taper shape, that is, its diameter on the left end is larger than its diameter on the right end. The plurality of plunger holes are shaped in a taper form, wherein, the diameter of the circle in which the plunger hole center is located at the end (in the left end of the drawing) in corporation with the plunger assemblies 10 is larger than that at the other end (in the right of end the drawing). In this way, it is not necessary to increase the diameter of the rotor cylinder 14 on the whole, and it is possible to decrease the diameter of the oil-distribution hole. As shown in FIG. 4, the oil-distribution end surface of the rotor cylinder 14 may be in a planar form, such that the process is easy.
Next, the characteristics of the structure dimensions of the invention will be set forth in combination with calculation of particular parameters of the variable displacement pump as described in the embodiment 1 according to the invention, which has a displacement of 16 l/r and a rating pressure of 35 Mpa.
Assuming the number of the plungers of this pump is 7, thus each plunger has an effective volume of 2.3 ml. The maximal stroke of the piston is 1.8 cm to 2.0 cm, and the diameter of the plunger is 12 mm to 13 mm. The diameter of the circle in which the plunger center is located is dependent on the swinging angle of the pendulous disk 7. The swinging angle is chosen to be 20 degrees according to experience, such that the diameter of said circle should be 56 mm. The outer diameter of the rotor cylinder 14 is 75 mm×40 mm. The rating output torque of the pump is 89 Nm, therefore, the diameter of the power shaft (main shaft 4) which employs simple steel is only between 15 mm and 20 mm. In consideration of the constrains on strength, dimension and angle of the constant velocity universal coupling 11 itself, and the strength and stiffness of the power shaft, the rotor cylinder 14 is formed in a taper shape, the rotor diameter at the larger end being 82 mm and that at the smaller end being 72 mm. The rotary swash plate 9 has a diameter of 85 mm, and the pendulous disk 7 has a diameter of 100 mm. Thus the dimension of the whole pump is 120 mm×150 mm (the extension length of the shaft end not included). Obviously, the dimension and the weight of the pump are smaller than those of the swash plate pump with the same displacement, and are even much smaller than those of the bent axis axial plunger pump.

Claims

1. A axial plunger pump or motor, comprising:

a casing;

a main shaft rotatably supported on the casing;

a rotor cylinder with a plurality of plunger holes, which is coupled to the main shaft and is driven to rotate about a main shaft axis by the main shaft and which has an oil-distributing end surface;

an oil-distributing disk in cooperation with an oil-distributing end surface of the rotor cylinder;

a rotary swash plate whose end surface is disposed in a manner axially opposing the plurality of plunger holes of the rotor cylinder and which can rotate about a swash plate axis forming an angle with respect to the main shaft axis;

a plurality of plunger assemblies, an end of each being articulated to an end surface of the rotary swash plate and another end of each being slidably disposed in the plunger holes of the rotor cylinder;

a constant velocity universal coupling which is provided between the rotary swash plate and the main shaft and transmits torque therebetween, so that the main shaft and the rotary swash plate rotate about the main shaft axis and the swash plate axis forming an angle therebetween, respectively.

2. The axial plunger pump or motor according to claim 1, characterized in that, said constant velocity universal coupling is a Rzeppa constant velocity universal coupling, a half angular Rzeppa constant velocity universal coupling, a ball joint constant velocity universal coupling or a Weiss constant velocity university coupling.

3. The axial plunger pump or motor according to claim 2, characterized in that, said Rzeppa constant velocity universal coupling comprises an inner race ring with an outer raceway, a plurality of steel balls, a holder and an outer race ring with an inner raceway, wherein said steel balls are arranged on the holder and are located in the inner raceway and the outer raceway, said inner race ring is coupled to the main shaft, said outer race ring is coupled to the rotary swash plate, such that the main shaft and the rotary swash plate are respectively rotated about the main shaft axis and the swash plate axis via the Rzeppa constant velocity universal coupling, the cross point of the said two axis locate at the center point of the said Rzeppa constant velocity universal coupling.

4. The axial plunger pump or motor according to claim 1, characterized in that, said rotary swash plate is supported on the casing via a swash plate bearing, so as to form a constant-capacity axial plunger pump or motor, or

said rotary swash plate is supported on a pendulous disk via a swash plate bearing, the pendulous disk is supported on said casing via a pendulous disk bearing, said swash plate bearing is a combination bearing of a needle bearing and a cylinder or taper roller thrust bearing, said pendulous disk bearing is a needle bearing or sliding bearing in a crescent form, and the rotation axis of the pendulous disk is perpendicular to the main shaft axis and passes through the center of the constant velocity universal coupling, said pendulous disk is connected with a variable displacement adjustment mechanism for adjusting the deflection angle of the pendulous disk, such that an angle between the swash plate axis of the rotary swash plate supported thereon and the main shaft is adjusted through changing the deflection angle of the pendulous disk, so as to form a variable-capacity axial plunger pump or motor.

5. The axial plunger pump or motor according to claim 4, characterized in that, said variable displacement adjustment mechanism is a variable displacement oil cylinder, the piston of which is connected to the pendulous disk so as to drive the pendulous disk to deflect through extending and retracting of the piston.

6. The axial plunger pump or motor according to claim 4, characterized in that, the variable displacement adjustment mechanism is a variable displacement adjustment mechanism of a trunnion type, which includes a trunnion connected to the pendulous disk and a driving mechanism for driving the trunnion to rotate, a rotation axis of the trunnion is coincident with the rotation axis of the pendulous disk so as to drive the pendulous disk to deflect through rotation of the trunnion.

7. The axial plunger pump or motor according to claim 1, characterized in that, said rotor cylinder is in a taper shape, a diameter thereof at the end closer to the rotary swash plate is larger than that at the other end;

the plurality of plunger holes on said rotor cylinder are fairly distributed in a taper form accordingly.

8. The axial plunger pump or motor according to claim 1, characterized in that, said plunger assembly is a plunger assembly of a ball joint type, which comprises a plunger and a ball-headed rod with a ball head at each of both ends thereof, said rotary swash plate is provided with a socket, a ball head at an end of the ball-headed rod is located in the socket to form a ball-joint connection with the rotary swash plate, and a ball head at the other end is located in the plunger to form a ball-joint connection with the plunger, and the plunger is slidably provided in the plunger hole.

9. The axial plunger pump or motor according to claim 8, characterized in that, in the middle portion of the ball-headed rod and the plunger there is provided with a oil hole in communication with the plunger holes to introduce pressurized oil to lubricate the ball head at the both ends.

10. The axial plunger pump or motor according to claim 1, characterized in that, articulation centers of said plurality of plunger assemblies on the rotary swash plate are located in a same plane, and an intersection point of the plane with the main shaft axis is coincident with the center of the constant velocity universal coupling.

11. The axial plunger pump or motor according to claim 1, characterized in that, the rotor cylinder is axially positioned along the main shaft through a pressure spring and a pressure spring stop collar, an end of the main shaft is provided with an oil hole and a radial oil path, such that the pressure between the rotor cylinder and the oil-distribution disk is adjusted through introducing pressurized oil into the radial oil path.

12. The axial plunger pump or motor according to claim 1, characterized in that, the oil-distribution end surface of said rotor cylinder is a spheric surface, said oil-distribution disk forms a spherical surface fit with the oil-distribution end surface.