EP1055067A1

EP1055067A1 - A hydraulic rotating axial piston engine

Info

Publication number: EP1055067A1
Application number: EP99906661A
Authority: EP
Inventors: Filip Alm
Original assignee: Parker Hannifin AB
Current assignee: Parker Hannifin AB
Priority date: 1998-02-13
Filing date: 1999-02-12
Publication date: 2000-11-29
Also published as: WO1999041499A1; SE9800411L; KR20010040962A; SE9800411D0

Abstract

A hydraulic rotating axial piston engine (1), having a housing (2), enclosing a rotatable cylinder barrel (11), having a number of axial cylinders (13a, 13b) with a number of reciprocating pistons (12). Said pistons being reciprocating between two defined end positions and cooperated with an angled plate (21) in order to obtain said reciprocating movement. The cylinders (13a, 13b) have ports (16) alternatingly acting as inlet and outlet ports and the housing has at least one inlet and outlet channel (5, 6), each having a kidney shaped port, facing towards said inlet and outlet ports of the cylinder barrel, communicating with a number of the ports at the barrel. The cylinder barrel (11) is rotatable relative to a first axis (10), which is inclined relative to a second axis (9) of an input/output shaft (8), the angled plate being rotatable together with the input/output shaft around the second axis. The rotation of the cylinder barrel and the input/output shaft are synchronized by means of synchronizing means. The combination of the cylinders and pistons being an even number and the synchronizing means has a synchronizing torque which during the whole rotation of the cylinder barrel is directed in substantially one single direction.

Description

TITLE :

^A hydraulic rotating axial piston engine.

TECHNICAL FIELD:

The present invention relates to a hydraulic rotating axial piston engine, having a housing, enclosing a rotatable cylinder barrel, having a number of axial cylinders with a number of reciprocating pistons, said pistons reciprocating between two defined end positions, said pistons cooperating by means of piston rods with spherical recesses in an angled plate in order to obtain said reciprocating move_¬ ment, said pistons being inclined relative to the longitudinal axis of the cylinders, said cylinders having ports alternatingly acting as inlet and outlet ports, said housing having at least one inlet and outlet channel, each having a kidney shaped port, facing towards said inlet and outlet ports of said cylinder barrel, communicating with a number of said ports at said barrel, said cylinder barrel beⁱng rotatable relative to a first axis, which is inclined relative to a second axis of an input/output shaft, said angled plate being rotatable together with said input/out_¬ put shaft around said second axis, said cooperation between saⁱd piston rods and said recesses in the angled plate creating a ^driving torque in the angled plate, said rotatⁱon of said cylinder barrel and said angled plate beⁱng synchronized by means of synchronizing means, said synchronizing means including synchronizing torque transferring surfaces having backlash.

PRIOR ART:

From EP-A1-0 567 805 a hydraulic piston engine _{is prior} known, which has a number of axial cylinders, which are crrcumferentially arranged in a rotatable cylinder barrel

CONFIRMATION COPY Each of said cylinders is provided with a channel, which alternatingly communicates with an inlet port or an outlet port in a housing. From said reference it is apparent that the engine is provided with synchronizing means of the type of tooth gear transmission. This type of synchronizing means has backlash which in connection with prior art engines may cause noise, vibrations and power losses. From the reference it is apparent that the drawings show a longitudinal cross sectional view showing that the pistons and cylinders in the cylinder barrel are not positioned diametrically opposite to each other. Prior known hydraulic rotating axial piston engines, having synchronizing means having backlash, are namely provided with an uneven number of pistons and cylinders.

From US-A-4 920 860 a hydraulic piston engine is prior known having synchronizing means of the type universal joint of tripoid synchronization. From the cross sectional view of the drawing it is apparent that the pistons and cylinders in the cylinder barrel are not arranged in diametrically opposite positions. From the description it is apparent that the number of cylinders is nine, i.e. an uneven number of cylinders. Also this type of synchronization has backlash, which in combination with the present type of engine causes noise and vibrations.

It has been discovered that the common reason behind the above described disadvantages with prior known axial hydraulic piston engines is that the synchronizing torque changes direction.

THE PRESENT INVENTION:

The object of the present invention is to provide a hydraulic rotating axial piston engine of the above discussed typ having reduced noise level and reduced vibrations .

The present object is obtained by means of an engine according to the present invention which is characterized in the combination that said cylinders and pistons being an even number and are positioned pairwise diametrically opposite to each other and that said synchronizing means having a synchronizing torque which during the whole rotation of the cylinder barrel is directed in substantially one single direction, and in that the ports of said housing and said cylinder barrel ports are arranged to substantially simultaneously discharge and pressurize the pistons in diametrically opposite cylinders.

BRIEF DESCRIPTION OF DRAWINGS:

The invention will now be described in more detail with reference to a preferred embodiment shown in the drawings, in which

Fig. 1 shows an axial section of a pump according to the present invention, Fig. 2 is a plan view of a connecting part of the pump as seen separately from the inside,

Fig. 3 is a cross sectional view of the pump along the lines III-III in Fig. 1, Fig. 4 corresponds to Fig. 2, having cylinder barrel ports indicated with dotted and dashed lines, Fig. 5 shows a diagram over the synchronizing torque in an engine according to prior art, Fig. 6 shows a diagram over the synchronizing torque in the engine according to the present invention. 4 DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT:

The hydraulic rotating piston engine according to the present invention is shown in a preferred embodiment in Fig. 1 which shows the general parts of a pump. The pump is an axial piston pump 1 having a housing 2 which is comprised by at least two parts, in the shown example three parts, namely a housing part 3 and a connecting part 4, having connecting openings, namely an inlet opening 5 and an outlet opening 6 for connecting input and output conduits for hydraulic fluid to the pump. A third part 7 of the housing is a support part of the input shaft 8 which is provided to be connected with a drive motor, not shown. The pump is of a so called bent axis type, having a first rotational axis 9, forming a rotational axis for the input shaft 8 and a second rotational axis 10 inclined relative to the first axis by an angle of for example 40°. The second rotational axis is an axis for a cylinder barrel 11 which is rotatably journalled in the housing. The cylinder barrel 11 has a number of axially extending pistons 12, movable axially, i.e. substantially in parallel with the axis 10 in a reciprocating movement in a corresponding number of cylinders 13, also extending axially with the axis 10, and circumferentially equally spaced along a circle line 14, see Fig. 3. Each cylinder 13 has a fluid passage 15 with a port 16 in the planar end surface 17 of the cylinder barrel 11. Each opening 16 has preferably its largest length along the peripheral circle line 14 and are preferably kidney-shaped. From Fig. 1 it is further apparent that each piston 12 has a piston rod 18 having spherical heads 19, supported in spherical bearing surfaces, forming recesses 20 in a swash plate 21 or angled plate which forms an integral part of the input shaft 8. The spherical recesses 20 are rotatably arranged around a radial plane which is angled relative to the radial plane of the cylinder barrel 11 which results in the reciproca- ting movement of the pistons 12 and the pumping action according to a prior known principle, in order to create vacuum i.e. suction in the inlet opening 5 and pressure in the outlet opening 6, see for example US patent No. 5,176,066. The cooperation between the pistons 12 and the recesses 20 creates a driving torque in the swash plate 21, which is tranferred to the input shaft 8. Synchronizing means are arranged in order to synchronize the rotational movements of the cylinder barrel with the rotation of the swash plate 21 so that the piston rods 18 will maintain their correct directions. In the shown example the synchronizing means are made in the form of tooth gear formed by a tooth wheel rim 22 on the cylinder barrel cooperating with a tooth wheel 23 of the input shaft 8. A support pin 24 supports the cylinder barrel 11 along the axis 10 cooperating with a shaft 25 which forms the rotational axis 10 and projects through a bore 26 of the cylinder barrel and supported in a bore 26' of the connecting piece 4 of the housing.

As mentioned above the cylinders 13 extend with their longitudinal axis 13' axially, i.e. in parallel with the rotational axis 10 of the cylinder barrel 11. However, it is apparent from Fig. 1 that the longitudinal axis 18' of each piston rod 18 will deviate from the longitudinal axis 13' of the cylinder in which the piston rod performs a reciprocating movement. The longitudinal axis 18' is also the symmetrical axis of each piston which together with its rod will be inclined in each cylinder 13. This inclination depends on the fact that the bearing surfaces 20 are arranged along a circle line in the swash plate 21. As the cylinder barrel 11 and the cylinders 13 are inclined relative to the swash plate 21 the spherical heads 19 perform an elliptic movement as seen along the rotational axis 10. This results in conical movements of the piston rods. This results in turn in a contribution to the total synchronization torque. This contribution is the largest contribution to a bidirectional synchronizing torque, which according to the present invention is neutralized in a large extent.

Fig. 2 shows the connecting part 4 of the housing separately and from the inside. The connecting part 4 has on its inside a substantially planar, circular surface 27 which in the mounted position is faced to the planar surface 17 of the cylinder barrel 11. The two planar surfaces 17, 27 are arranged to contact each other with a sealing fit. On its inside the connecting part 4 is provided with one inlet port 28 and one outlet port 29, which are kidney-shaped. Between said two surfaces friction arises, which creates a torque, which the synchronizing torque is supposed to compensate for. The inlet port 28 communicates through a channel with the inlet opening 5 and the inner outlet opening 29 communicates through a separate channel with the outlet opening 6 on the outside of the connecting part 4. The inlet and outlet port 28, 29 extend along a peripheral circle line 30 which has a corresponding radius as the circle line 14 of the openings 16 of the cylinder barrel 11. The inlet and outlet opening 28, 29 extend on each half of said circle line 30, separated by a main plane 31 extending through the connecting part 4. The inlet and outlet ports 28, 29 are further divided by a second main plane 32 extending 90° relative to the first main plane 31. One of these main planes can be a symmetrical plane for the connecting part 4. The inlet and outlet port 28, 29 further extend along the circle line 30 along a predetermined peripheral angle which in the shown example is somewhat larger for the inlet opening 5 than for the outlet opening 6 and are arranged so that simultaneously more than one cylinder port 16 communicate with the inlet port 28 and the outlet port 29 respectively. The inlet and outlet ports 28, 29, one of them or both, can be provided with slit extensions 6', the ends of which determine the total angular extension of the inlet and outlet ports. According to the preferred embodiment the inlet and the outlet ports 28, 29 have the same angular extension. Preferably the inlet and outlet ports are symmetrically positioned relative to each other. However, the angular extension can differ between the ports. They may also be positioned without symmetry. The connecting part 4 is provided with connecting means for connecting the connecting part in a chosen position with the housing part 3. This is accomplished by means of screws 33, see Fig. 1, extending through holes 34 in the connecting part, see Fig.

2, and screwed into threaded holes 35 in the housing part

3, see Fig. 3. By means of this connection the angular position of the connecting part with respect to its main planes 31, 32 is determined relative to the main planes 37, 38 of the housing part.

From the sections according to Figs. 3 the arrangement of the cylinders 13 in the cylinder barrel 11 is shown. The cylinders are according to the present invention an even number, for example six cylinders which are pairwise diametrically positioned opposite to each other, arranged symmetrically relative to a diameter 38 extending through the cylinder barrel. In Fig. 4 the connecting part 4 according to Fig. 2 is shown and also it is indicated by means of dotted and dashed lines the arrangement of the ports 16 in the end surface 17 of the cylinder barrel 11. The ports 16 are circumeferencially equally spaced along a circle line which may be the same circle line 14 as for the cylinders 13. The cylinder ports 16 are pairwise diametrically arranged opposite to each other i.e. symmetrically arranged relative to a diameter, for example the diameter line 38. The number of cylinder ports 16 is an even number, in the shown example six ports. By means of this arrangement and based upon a chosen angular extension 8 of the kidney shaped inlet and outlet ports 28, 29 in the connecting part 4, the following will occur: Upon rotation of the input shaft 8 and the swash plate 21 by means of the motor the pistons are given their reciprocal movements in combination with the rotation of the cylinder barrel. By means of the pistons the hydraulic fluid will be sucked through the inlet port 28, which represents the low pressure side, and pressed out through the outlet port 29 which represents the high pressure side. This continuous rotation of the barrel and the reciprocal movements of the pistons create the pumping action. The pistons move between their lower dead point LDP and upper dead point UPD which occurs for each piston in a predetermined angular position relative to the angular positions of the inlet and outlet ports 28, 29. Said angular positions are chosen so that the ports of said housing, i.e. of the connecting part 4, and the cylinder barrel ports 16, 16' are arranged to substantially simultaneously discharge and pressurize the hydraulic fluid acting on pistons 12 in diametrically opposite cylinders 13a, 13b. This results in the fact that the synchronizing torque i.e. the torque, transferred to the cylinder barrel by means of the synchronizing means, will during the whole rotation of the cylinder barrel be directed in substantially one single direction. This characteristic is especially advantageous due to the fact that the synchronizing means as shown has backlash. Other examples of synchronizing means having backlash is universal joint of tripoid synchronization and a conical pistons synchronizing means which can be utilized as alternatives to the tooth gear transmission as shown. In an engine having conical piston synchronizing means, the piston or their rods have conical surfaces contacting the cylindrical surfaces of the cylinders. During the rotation of the engine the conical surface will maintain a linear roll contact. Different pistons will maintain contact in different directions in their respective cylinders, which is utilized to synchronize the cylinder barrel with the swash plate. An example of this type of synchronization is described in CH 592 812.

Fig. 5 shows a diagram over the synchronizing torque of the synchronizing means of the type discussed above but utilized in a prior known engine having an uneven number of cylinders, namely five cylinders. From the diagram it is apparent that the torque is bidirectional, causing noise, vibrations and power losses. As mentioned above one large contribution to bidirectional torque is the torque caused by the fact that the piston rods are inclined in their cylinders.

Fig. 6 shows a diagram over the synchronizing torque in the engine according to the present invention having an even number of cylinders, for example six cylinders. From this diagram it is apparent that the torque is unidirectional, being directed in substantially one single direction. The lowered noise level and vibration level and reduction of power losses is surprisingly large in the engine according to the present invention.

The invention is not restricted to the above described and in the drawings shown embodiments . For example a different number of cylinders and synchronization can be utilized. For example eight or ten cylinders can be utilized. The same principle can also be utilized for a hydaulic motor in which the inlet port of the housing is connected to a pressurized hydraulic source and the shaft 8 is an output shaft transmitting power torque to a machine to be driven by the hydraulic motor.

Claims

10CLAIMS :

1. A hydraulic rotating axial piston engine ( 1 ) , having a housing (2), enclosing a rotatable cylinder barrel (11), having a number of axial cylinders (13) with a number of reciprocating pistons (12), said pistons reciprocating between two defined end positions, said pistons cooperating by means of piston rods with spherical recesses (20) in an angled plate (21) in order to obtain said reciprocating movement, said pistons being inclined relative to the longitudinal axis (13') of the cylinders, said cylinders having ports alternatingly acting as inlet and outlet ports (15), said housing having at least one inlet and outlet channel (5, 6), each having a kidney shaped port (28, 29), facing towards said inlet and outlet ports of said cylinder barrel, communicating with a number of said ports at said barrel, said cylinder barrel being rotatable relative to a first axis (10), which is inclined relative to a second axis (9) of an input/output shaft (8), said angled plate being rotatable together with said input/output shaft around said second axis, said cooperation between said piston rods and said recesses in the angled plate creating a driving torque in the angled plate, said rotation of said cylinder barrel and said angled plate being synchronized by means of synchronizing means 22, 23), said synchronizing means (22, 23) including synchronizing torque transferring surfaces having backlash, c h a r a c t e r i z e d i n the combination that said cylinders (13) and pistons (12) being an even number and are positioned pairwise diametrically opposite to each other and that said synchronizing means (22, 23) having a synchronizing torque which during the whole rotation of the cylinder barrel (11) is directed in substantially one single direction, and in that the ports (28, 29) of said housing and said cylinder barrel ports (15) are arranged to substantially 11 simultaneously discharge and pressurize the pistons (12) in diametrically opposite cylinders (13).

2. A hydraulic rotating axial piston engine according to claim 1, c h a r a c t e r i z e d i n that said kidney shaped ports (28, 29) of the inlet and outlet channels (5, 6) have substantially the same angular extension and are substantially symmetrically positioned relative to each other.

3. A hydraulic rotating axial piston engine according to claim 1, c h a r a c t e r i z e d i n that said syn- cronizing means (22, 23) is a tooth gear transmission.

4. A hydraulic rotating axial piston engine according to claim 1, c h a r a c t e r i z e d i n that said syn- cronizing means is a universal joint of tripoid synchronization.

5. A hydraulic rotating axial piston engine according to claim 1, c h a r a c t e r i z e d i n that said syn- cronizing means is a conical piston synchronizing means, including contact between conical surfaces of the piston rods of the pistons and surfaces of the cylinders.

6. A hydraulic rotating axial piston engine according to claim 1 or 3, c h a r a c t e r i z e d i n that said engine ( 1 ) is a pump and that said shaft ( 8 ) is an input shaft to be driven by a rotating motor.