JPS63195386A - Rotating fluid pressure device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to rotary fluid pressure devices, and more particularly to gerotor fluid evacuation systems that utilize low speed diversion valve actuation.

(Prior Art/Problem to be Solved by the Invention) A conventional gator-type motor that utilizes a low-speed diversion valve (i.e., the rotary valve element is not controlled by the rotation speed of the gerotor wheel, but by the rotation of the gerotor wheel). (rotating at speed), valve actuation is accomplished by a rotating valve member and a stationary valve member, each separate valve member from the gerotor's fluid evacuation mechanism. One of the drawbacks of conventional gerotor type motor valve mechanisms is that "typing" errors occur, especially in motor designs where the rotary valve element is driven by a motor output shaft or a dogbone type shaft. When torque winding is carried out in the dogbone type shaft, the relative position of the gerotor star and the rotary valve deviates from the theoretical position, resulting in an error in the valve "timing", i.e. the volume when the volume chamber expands and contracts. An error occurs in the communication between the chamber and the fluid. Another disadvantage of having the stationary and rotary valve elements separate from the gerotor mechanism is that it simply requires an extra number of parts and is therefore more expensive.

It has been recognized for many years as a solution to the types of problems described above to provide gerotor-type motors with a rotating valve member within part of the gerotor star itself (a "valve-in-star"). It has been recognized that the valve-in-star design substantially eliminates valve typing errors due to the constant relationship between the star and the rotary valve ports. Moreover, the small number of elements surrounded by the leakage gap and the small number of elements that require some pressure balancing result in a motor that is able to achieve high volumetric efficiency and high mechanical efficiency. A very early construction of a valve-in-star design is shown in U.S. Pat. No. 3,825,576.

However, each rotation port associated with a gerotor star opens directly into the volume chamber and thus follows a star profile, which has long been recognized as undesirable.

A recent arrangement that provides a gerotor-type motor with a satisfactory star-in-star valve is shown in U.S. Pat. While occurring between the end caps, diversion valve actuation occurs at the axially opposite end face of the star at the interface between the star and the adjacent valve plate. This type of configuration effectively requires valve operation to require a "fixed gap" condition as opposed to a pressure equilibrium or pressure imbalance condition. Furthermore, the arrangement in US Pat. No. 4,411,606 requires a plurality of axial holes extending through the star to communicate the ends of the star. If the hole has a small diameter, a large surface dynamic resistance will result, and if the hole has a large diameter, a pressure drop will occur in the motor, thereby reducing the mechanical efficiency of the motor.

On the other hand, if this hole is made large enough to avoid excessive flow resistance, the star will be weakened.

Accordingly, it is an object of the present invention to provide an improved low speed, high torque gerotor motor that utilizes a valve-in-star design that substantially overcomes the problems of prior art devices.

Another object of this invention is to provide an apparatus in which both manifold valve actuation and diversion valve actuation occur at the interface of the gerotor star and an end cap located adjacent the star.

The low-speed, high-torque gerotor motor that this invention is wrong with is
The relief valve is approximately 245 kf/ai (4500p
si) and the motor is approximately 210kv.
/aj (4QQOpsi). In recent years, there has been a demand in the market for motors that can operate at relatively high pressures, at least intermittently, in systems where the relief valves are set up to 315 kf/d (4,500 psi) or 350 kf/di (5,000 psi). It is increasing.

In the star-in-valve type motor shown in the aforementioned U.S. Pat. would be inappropriate for high pressure applications.

The aforementioned U.S. Patent No. 4. The motor shown in aN, 606 is a "fixed gap" type valve in which the valve actuation occurs between the end faces of the star and an adjacent member fixed to the end face of the gerotor ring. Due to its operation, it is also not suitable for high pressure applications. As is well known, when fixed gap valves are subjected to relatively high pressures, excessive "cross port" leakage occurs, thereby reducing volumetric efficiency.

Accordingly, another important object of this invention is to provide an improved low speed, high torque gerotor motor that utilizes a valve-in-star design that allows the motor to be utilized in relatively high pressure applications. be.

It is also an object in the art to provide a simple but efficient two-speed gerotor motor. The term "two-speed" as used herein means that for any given fluid flow rate into the motor, there is a full selection of two different motor output speeds; high speed (low torque) and normal low speed (high torque). There is. US Patent No. 477a198 discloses the basic concept for achieving two speed operation of a gerotor type motor. The motor shown therein is of the spool valve type, with a fixed radial clearance between the rotating spool valve and the adjacent cylindrical housing surface, which limits the motor to relatively low pressures and torques. Ru.

No. 448, recently assigned to the assignee of this invention.
No. Q971 discloses a two-speed gerotor motor of the disc valve type and thus suitable for applications requiring relatively high pressures and torques. Although the apparatus shown in U.S. Pat. No. 448Q971 is believed to provide a commercially successful two-speed gerotor motor, the design disclosed therein is somewhat larger and more complex, and the design disclosed therein is somewhat larger and more complex than the disc-valve gerotor motor. subject to inherent pressure and torque limitations.

It is therefore still another object of the present invention to provide an improved low speed high torque gerotor motor that utilizes a valve-in-star design configuration in which the motor may be operated in a low speed high torque mode or a high speed low torque mode. It is to be.

(Means for Solving the Problems) The above and other objects of the present invention are achieved by the above-mentioned U.S. Pat.
This is achieved by providing an improved rotary fluid pressure device having an overall configuration as shown in the '606 patent. a gerotor associated therewith and including an internally toothed ring member and an externally toothed star member eccentrically disposed within the ring member;・Gear set: The ring member or the star member performs a pivoting movement relative to the other of these members, and the star member performs a rotational movement relative to the ring member end and the housing device: the internal teeth of the ring member and A device comprising: a shaft device; and external teeth of a star member interdigitate to form a plurality of N+1 expansion and contraction fluid chambers during relative pivoting and rotational motion, the device comprising: a shaft device; a first fluid pressure chamber in continuous communication with the inlet or outlet port, and a second fluid pressure chamber in continuous communication with the other port; and the star member is defined as;
a first fluid pressure chamber in continuous fluid communication with the first fluid pressure chamber;
forming a manifold region and a second manifold region in continuous fluid communication with the second fluid pressure chamber;
The star member includes an end surface disposed toward the end cap member defining first and second sets of fluid ports, the first set of fluid ports being adjacent to the first end cap member. This is achieved by providing an apparatus in continuous fluid communication with a manifold region and having a second set of fluid ports in continuous fluid communication with said second manifold region.

The improved device has the following features: <a+ the end surface of the star member is in sliding sealing engagement with the adjacent surface of the end cap member; (b) the end cap member is in the fifth (C) the star member defines a third manifold region in continuous fluid communication with the third fluid pressure chamber; (C) the star member defines a third manifold region in continuous fluid communication with the third fluid pressure chamber; (d) the end face of the star member defines a fifth set of fluid ports in continuous fluid communication with the fifth manifold region; (e) the adjacent face of the end cap member defines a plurality of N+1 fluid ports; defining valve passages, each valve passage being in continuous fluid communication with one of the inflation and deflation fluid volume chambers; (f) the first, second and fifth sets of fluid ports are connected to the star member; and (g) the valve arrangement is in diversion fluid communication with a plurality of N+1 valve passages formed by the end cap members in response to the relative rotational movement; and a second state communicating the control fluid passageway to the second fluid pressure chamber.

(Function) The present invention provides a ring member (19) and a star member (23).
It is a rotary fluid pressure device of the type that includes a gerotor gear set, and the double edges of the manifold valve actuation and diversion valve actuation are connected to the end face (42) of the star (23) and the end cap member (17). ) is achieved at the boundary with the end surface (41). The end cap (17) has three coaxial core pressure chambers (43), (51) and (47).
), and each star forms a pressure chamber (A5
)l(5 in continuous communication with ri and (47)
Manifold regions (63), (67) and (65)i forming two coaxial centers are defined, and this manifold region (6
3), (67); and (65) each communicate with fluid ports (69), (77) and (73), respectively, defined by the end face (42) of the star (23).

A valve spool (97) communicates manifold regions (63) and (67) to provide low speed high torque (LSRT)
) mode operation is achieved, and the manifold area (
67) and (65) to communicate with each other to generate high-speed, low-torque (H
8LT) mode operation can be selectively operated between the second state and the second state that achieves mode operation.

(Example) In the drawings, which are not intended to limit the invention, FIG. 1 shows a low speed, high torque type gerotor motor. The hydraulic motor shown in FIG.
It is made up of multiple sexy tubes that are fixed to each other. The motor body includes a shaft housing portion 13, a gerotor fluid evacuation mechanism 15, and an end cap member 17.

Gerotor fluid evacuation mechanisms 15 (best shown in FIG. 3) are well known in the art and are assigned to the assignee of this invention and are included herein by reference and for ease of reference. No. 4.34 described in U.S. Pat.
600 and described in detail.

B Particularly, the fluid discharge mechanism 15 is made of Ge H-7 (Geroler).
) an internally toothed ring member 19f which is a gear set and defines a plurality of generally semi-cylindrical apertures;
It fulfills the function of 9 internal teeth. Eccentrically disposed within ring 19 is an externally toothed star 25, which star 23 typically has an external tooth slightly smaller than the internal teeth 21, so that star 23 pivots relative to ring member 19. and rotate. The relative pivoting and rotational movement between ring 19 and star 23 creates a plurality of inflation fluid volumes 25 and a plurality of deflation fluid volumes 27, as is well known in the art.

In FIG. 1, star 23 defines a plurality of linear internal splines 29 that engage a set of external layer top splines 31 formed at one end of main drive shaft 33. . Main drive shaft 33
At the other end there is another set of external layer top splines 35, which splines 35 are connected to another set of linear internal top splines defined by a shaped rotary output, such as a shaft or wheel hub. It is adapted to engage a spline. As is well known in the art, gerotor type motors of the type to which the present invention relates include:
It includes a rotating output shaft supported in suitable bearings, which shaft is disclosed in U.S. Pat.
The invention is not limited to output shafts of any particular profile, although they may be of the type shown in the above specification. It is essential that this device includes a shaft arrangement of a predetermined shape capable of transmitting the rotational movement of the star 230.

In the main embodiment, the ring member 19 has nine internal teeth 21.
and since star 23 includes eight external teeth, eight revolutions of star 23 will cause star 23 to make one complete revolution, as is well known in the art. , the output end of the main drive shaft 33 makes one complete revolution.

Referring to FIG. 2 in conjunction with FIG. 1, end cap member 17 includes fluid inlet port 37 and fluid outlet port 5.
It includes 9. The end cap member 17 includes an end surface 41 that is connected to an end surface 42 (first
(see figure) and is positioned adjacent to the gerotor gearset 15. End surface 41 defines a fluid pressure chamber 43 which is in fluid communication with fluid inlet port 37 via fluid passageway 36 by tubular member 45 and which is in fluid communication with fluid inlet port 37 via fluid passageway 36 by tubular member 45. 17 is press-fitted into a circular opening defined by 17. The end face 41 preferably further includes a fluid pressure chamber 4
3 defines an annular fluid pressure chamber 47 which is coaxially arranged. The pressure chamber 47 is connected to the fluid outlet port 3 by a passage 49.
9.

An annular pressure chamber 5 radially between fluid pressure chambers 43 and 47
1 is disposed, and the annular fluid pressure chamber 51 is in fluid communication with the core passageway 53 defined by the end cap member 17 by a generally tube-shaped member 55 . Tubular member 55 is press fit into the circular opening of end cap member 17 and functions to separate annular fluid pressure chambers 47 and 51.

The end surface 41 of the end cap member 17 is flat.

A plurality of stationary valve passages 57 are defined and the passages 5
7 is also called a "timing slot". In the main embodiment, each valve passage 57 is typically radially oriented and slotted, and each valve passage 57 is disposed in constant continuous fluid communication with an adjacent one of the volume chambers 25 or 27, respectively. ing. Valve passages 57 are preferably arranged in a generally annular pattern coaxial with annular fluid pressure chamber 43, as shown in FIG.

The externally toothed star 23 will be explained in detail with reference to FIG. 1 and FIG. 4. Although not an essential feature of the invention, it is preferred that the star 23 is constructed from two separate pieces. In the main embodiment, the star 23 consists of two separate powder metal pieces and includes a main part 59 containing external teeth and an insert or plug 61.

Main portion 59 and insert 61 cooperate to define various fluid regions, passageways, and ports described below.

In FIGS. 4 and 5, star 23 includes a central manifold region 63 that is in continuous fluid communication with pressure chamber 43. In FIGS. A further external manifold region 65 is provided coaxially with the manifold region 63 and includes an annular pressure chamber 47.
is in continuous fluid communication with. Disposed radially between and coaxially with manifold regions 63 and 65 is an intermediate manifold region 67 in continuous fluid communication with annular pressure chamber 51 . As shown in FIG. 4, with respect to manifold regions 65, 65 and 67 the term "
Utilizing the term ``region'' refers to a single opening (e.g., in the case of manifold region 63), or a plurality of separate circumferentially spaced openings (e.g., in the case of manifold regions 65 and 67) and includes It will be understood that

The end face 42 of the star 23 defines a set of fluid ports 69, each fluid port 69 being connected to a fluid passageway 71 (a fifth
(See Figure A) in fluid communication with the central manifold region 63. In the main embodiment, four ports 69 and fluid passages 71 are provided.

End face 42 of star 23 further defines a set of fluid ports 75t- each port being in fluid communication with one of the openings in outer manifold region 65 by fluid passageway 75. In the main embodiment, eight fluid ports 73 and fluid passages 25 are provided.

End face 42 of star 23 also defines a set of fluid ports 77, each in continuous fluid communication with one of the openings in intermediate manifold region 67 by fluid passageway 79. In the main embodiment, four fluid ports 77
and a fluid passage 79 are provided.

As is well known, since there are nine internal teeth 21, nine valve passages 57 are provided. Star 2
3 pivots and rotates relative to the ring member 19,
A set of eight fluid ports 69 and 73 engage valve passage 57 in low speed diversion valve operation. As a result, communication is provided only between the fluid ports 69 and 73 and the valve passage 57, which is in momentary fluid communication with one of the expansion volume chambers 25! ! It is in 4. At the same time, low-pressure exhaust fluid communicates from the deflated volume chamber 27 via a valve passage 57 that momentarily comes into communication with it, and the exhaust fluid communicates with the particular valve passage 57 containing the exhaust fluid.
The fluid flows into the fluid port 77 which is momentarily in communication with the fluid.

Referring again to FIG. 1, shaft housing portion 13 defines a recess 81 in which a pressure equalization plate 83 is seated. Balance plate 83 defines a plurality of apertures 85, each aperture 85 being in communication with one of volume chambers 25-i or 27. Each opening 85 communicates with a pressure equalization recess 87, which is located on the side of plate B5 opposite gerotor gearset 15. Members 81-87 are mentioned here for the sake of completeness, as pressure equalization is generally well known in the art of gerotor-type motors and does not form an essential part of this invention. , the size or shape of the pressure equalization plate 83 or the recess 87 will not be described in detail. The pressure balance plate 85 is connected to the star 2S'f
l: Used to "balance" the star 23 in the axial direction, i.e. to make the fluid pressures acting in opposite directions on the star 23 approximately the same, or a pressure equalization plate 83 is used to "balance" the star 23t with one end cap. It will be appreciated that it may be utilized for "unbalancing" the end face 41 of member 17 for a tight sealing engagement.

Reference is now made to FIG. 6, which is shown partially in section (line 6--6 of FIG. 1) and partially schematically. End cap member 17 defines a spool aperture 91 which intersects fluid passageways 56, 49 and 55 at axially spaced locations as shown in FIG. Both ends of the spool hole 910 are closed by a pair of screw fittings 93 and 95, and a Kti valve spool 97 is disposed within the mater spool hole 91.

The valve spool 97 is pushed to the left in FIG. 6 by the spring member 99, and the pressure M2O
3 to the right and biased to the position shown in FIG. 6th valve spool 97
The fluid pressure necessary to bias it into the position shown is communicated to pressure chamber 101 by any method well known and not forming part of this invention.

Assuming that the valve spool 97 is biased and pressed to the position shown in FIG. 6 and is in good condition, and the inflow port 37 is in communication with a high-pressure fluid supply source, the fluid passages 36 and 53 and the pressure chambers 43 and 51 are under high pressure. become. As a result, when star 23 pivots and rotates, high pressure is communicated from pressure chamber 43 to central manifold region 63 and from pressure fi 51 to intermediate manifold region 67. High pressure fluid is therefore present in all fluid ports 69 and 77, from where high pressure communicates via each fluid passageway 57'' to the expansion volume chamber 25 (shaded areas indicate high pressure fluid).
While the star 23 is rotated clockwise (fc) in FIG. Ru. Exhaust fluid from port 73 is routed via external manifold region 65 to pressure chamber 47 and thence via fluid passageway 49 to outlet port 39.
will be communicated to. Therefore, the valve spool 97
In the position shown, high pressure fluid is communicated to all four expansion volume chambers 25, while exhaust fluid is communicated to all four expansion volume chambers 25.
In communication with the two contraction volume chambers 27, the gerotor type motor is operated in a conventional low speed high torque (LSIT) mode.

In FIG.
LT) mode of operation. I(
In order to select the SLT mode, it is necessary to reduce the pressure in the pressure chamber 101 sufficiently so that the spring member 99 biases the valve spool 97 to the position shown in FIG. , fluid passages 49 and 53 are in relatively unrestricted communication and both are isolated from fluid communication with fluid passage 36. In this mode of operation, when high pressure is communicated to inlet port 37, high pressure is present only in pressure chamber 43, and both pressure chambers 51 and 47 are in communication with low pressure fluid through fluid passages 53 and 49, respectively.

In H8LT mode, high pressure fluid is communicated from pressure chamber 43 through central manifold region 63 to fluid port 69 . As shown in factor 7, the result is that high pressure fluid is communicated only to the two expansion volume chambers 25. At the same time, exhaust fluid from the deflation volume chamber 27 is communicated to the pressure chamber 47 via the associated fluid port 73, external manifold region 65, as described in FIG. However, because fluid passages 49 and 53 are in open communication, a portion of the low pressure exhaust fluid from deflation volume chamber 27 is routed through fluid passage 53 to pressure chamber 51 and from there to intermediate manifold region 67 and then into fluid flow. It communicates with the other two expansion volume chambers 25 via port 77 . In other words, if the same volume of high pressure fluid is communicated to the inlet port 37 as in the LSHT mode, it will be communicated to only half of the expansion volume chamber 25 in the H5LT mode, and therefore the star 23 is twice as fast, but
Performing pivoting and rotational movements at half the torque is K.

In this invention, star 23 is 2 in H5LT software.
Although described in connection with embodiments of rotation at double speed but half torque, it will be clear that the invention is not so limited. ports and passageways;
etc. can be varied from those shown to achieve speed ratios other than 2:1.

[Brief explanation of the drawing]

FIG. 1 is an axial cross-sectional view of a conventional low-speed, high-torque gerotor motor according to the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1 showing the surface of the end cap member, and FIG. is a cross-sectional view taken along line 3-3 of FIG. 1 showing the end face of the gerotor gear set adjacent to the end cap, and FIG. 4 is an enlarged plan view similar to FIG. 3 showing an embodiment of the gerotor star in the present invention. Figures 5a, 5b and 5c are game a of Figure 4.
- each schematic simplified cross-sectional view, Figures 6 and 7, in three different positions of the Taster, partially schematically along line 6-6 of Figure 1, showing the operating state of the hydraulic circuit relevant to the invention; FIG. DESCRIPTION OF SYMBOLS 15... Housing device, 15... Gerotor gear set, 17... End cap member, 19... Internal tooth ring member, 21... Internal tooth, 23... External tooth star member, 25... Expansion fluid volume chamber, 27... Contraction fluid volume chamber, 29.51... Rotary motion transmission device, 33...
Shaft device, 41... end cap member adjacent surface, 4
2... Star member end surface, 43... First fluid pressure chamber,
47... Second fluid pressure chamber, 51... Fifth fluid pressure chamber, 53... Control fluid passage, 57... Valve passage, 6
5... First manifold region, 65... Second manifold region, 67... Third manifold region, 69... First set of fluid ports, 73... Second set of fluid ports, 77 ...Fifth set of fluid ports, 97...
Valve device. (2 others) FIG, 2 FIG, 3 FIG, 4 LSHT FIG, 6

Claims (1)

[Claims] 1. Fluid inflow port (37) and fluid outflow port (3
a housing device (13) comprising an end cap member (17) forming an end cap member (17); a gerotor gearset (15) comprising a member (23); one of said ring member and said star member performs a pivoting movement relative to the other of these members, and said star member engages said ring member and said housing performing a rotational movement relative to the device; the internal teeth (21) of said ring member and the external teeth of said star member mesh with each other, resulting in a plurality of N+1 expansions (25) and contractions (25) during said relative pivoting and rotational movement; 27)
forming a fluid volume chamber; a shaft device (33) and a device (29, 31) for transmitting the rotational movement of the star member to the shaft device; and a first fluid pressure chamber (43) in continuous fluid communication with the one of the fluid outlet ports, and a second fluid pressure chamber (43) in continuous fluid communication with the other of the fluid inlet port and the fluid outlet port. a first manifold region (63) in continuous fluid communication with the first fluid pressure chamber; and a first manifold region (63) in continuous fluid communication with the second fluid pressure chamber; a second manifold region (65) in fluid communication;
forming a first (69) and a second (
73) defining a set of fluid ports, wherein the first set of fluid ports is in continuous fluid communication with the first manifold region and the second set of fluid ports is in continuous fluid communication with the second manifold region; in continuous fluid communication, wherein: (a) the end surface of the star member is in sliding sealing engagement with an adjacent surface (41) of the end cap member; (b) the end cap member is a third fluid pressure chamber (51);
and a control fluid passage (53) in continuous fluid communication with the third fluid pressure chamber; (c) the star member is in continuous fluid communication with the third fluid pressure chamber; (d) said end face of said star member forming a fifth set of fluid ports (77) in continuous fluid communication with said third manifold region; (e) the adjacent surface of the end cap member has a plurality of N+1 pulp passages (57);
and each said valve passageway being in continuous fluid communication with one of said inflation and deflation fluid volume chambers; (f) said first, second and third sets of fluid ports; in response to the relative rotational movement of the star member, the valve arrangement (97) is in diversion fluid communication with the plurality of N+1 valve passageways formed by the end cap member; selectively between a first state (FIG. 6) in which the passage communicates with the first fluid pressure chamber and a second state (FIG. 7) in which the control fluid passage communicates with the second fluid pressure chamber; A rotary fluid pressure device characterized in that it is actuated. 2. The second fluid pressure chamber surrounds the first fluid pressure chamber, and the third fluid pressure chamber is disposed radially between the first and second fluid pressure chambers. A rotary fluid pressure device according to claim 1. 3. The rotary fluid pressure device of claim 2, wherein the third manifold region is radially disposed between the first and second manifold regions. 4. The first, second, and third fluid pressure chambers are annular, the third fluid pressure chamber surrounds the third fluid pressure chamber, and the second fluid pressure chamber has an annular shape, and the second fluid pressure chamber has an annular shape. Rotary fluid pressure device according to claim 1, characterized in that it encloses a chamber. 5. The first, second and third manifold regions are annular, the third manifold region surrounding the first manifold region, and the second manifold region surrounding the third manifold region. characterized by having
A rotary fluid pressure device according to claim 4. 6. The first, second and third sets of fluid ports include:
The rotary fluid pressure device according to claim 1, characterized in that it is formed only by the end surface of the star member. 7, the first (69), second (73) and third (77)
) sets of fluid ports are the first (71) and second (71), respectively.
75) and third (79) fluid passage devices in fluid communication with said first (63), second (6S) and fifth (67) manifold regions, respectively;
A rotary fluid pressure device according to claim 1. 8. The rotary fluid pressure device of claim 7, wherein said first and third fluid passage devices are disposed entirely within said star member. 9. The rotary fluid pressure device of claim 8, wherein said second fluid passageway device is disposed entirely within said star member. 10. The plurality of N+1 valve passages defined by the adjacent surfaces of the end cap are arranged in an annular pattern substantially coaxial with respect to the second fluid pressure chamber. The rotary fluid pressure device according to item 1. 11. The first and third sets of fluid ports defined by the end face of the star member include a plurality of N fluid ports.
The rotary fluid pressure device described in . 12. The first and third sets of fluid ports and the second set of fluid ports both include a plurality of 2N fluid ports.
The rotary fluid pressure device according to item 1. 13. The star member includes an axially opposite second end surface, and the housing device (13) and the second end surface cooperate to balance pressure in the axial direction of the star member. Rotary fluid pressure device according to claim 1, characterized in that it forms a pressure equalization device (81-87) that provides a pressure equalization device. 14. The pressure equalization device is capable of applying a pressure that brings the star member into an unbalanced state toward the end cap member in the axial direction.
A rotary fluid pressure device according to claim 13. 15. The first state of the valve device corresponds to a low speed, high torque mode of operation of the device, and the second state of the valve device corresponds to a high speed, low torque mode of operation of the device. A rotary fluid pressure device according to claim 1, characterized in that: