Axial piston machine utilizing a bent-axis construction

Abstract

A hydrostatic axial piston machine (1) has a cylinder barrel (7) with a plurality of piston bores having pistons (10) fastened in an articulated manner to a drive flange (3). For articulated fastening of the pistons (10) to the drive flange (3), ball joints (20) are provided that are formed by a spherical cap-shaped receptacle socket (3a) in an end surface (3b) of the drive flange (3) and a ball head (10a) that is operatively connected with the piston (10). The receptacle sockets (3a) are each in the form of hemispheres that extend to the ball equator, and on one end surface (3b) of the drive flange (3), in the vicinity of the receptacle sockets (3a), there is a retaining web (30) that extends beyond the ball equator of the hemisphere to grip the ball head (10a) at an angle of greater than 180°.

Claims

1. A hydrostatic axial piston machine with a bent-axis construction, comprising: a drive shaft located inside a housing and rotatable around a first axis of rotation (R.sub.t), a drive flange located inside the housing and rotatable around the first axis of rotation (R.sub.t), a cylinder barrel located inside the housing and rotatable around a second axis of rotation (R.sub.z), wherein the cylinder barrel includes a plurality of piston bores, a longitudinally displaceable piston located in each piston bore, wherein the pistons are fastened in an articulated manner to the drive flange; and ball joints for articulated fastening of the pistons to the drive flange, wherein the ball joints include a spherical cap-shaped receptacle socket in an end surface of the drive flange and a ball head operatively connected with the piston, wherein the receptacle sockets comprise hemispheres that extend to a ball equator, and wherein on an end surface of the drive flange, in a vicinity of the receptacle sockets, there is a retaining web that extends beyond the ball equator of the hemisphere to grip the ball head at an angle of greater than 180°, and wherein the retaining web on each receptacle socket forms two retaining segments that are located opposite each other on the receptacle socket, and extend beyond the hemisphere.

2. The hydrostatic axial piston machine as recited in claim 1, wherein the retaining web comprises a circular ring-shaped elevation on the end surface of the drive flange.

3. The hydrostatic axial piston machine as recited in claim 1, wherein a center of the retaining web is located on the first axis of rotation (R.sub.t) of the drive flange.

4. The hydrostatic axial piston machine as recited in claim 1, wherein the retaining web is located in a vicinity of a reference circle, on which centers of the hemispheres are located.

5. The hydrostatic axial piston machine as recited in claim 1, wherein the retaining web is one piece with the end surface of the drive flange.

6. The hydrostatic axial piston machine as recited in claim 1, wherein the ball head includes two grooves located opposite each other, wherein a distance between groove bases of the two grooves is less than an aperture width of the two retaining segments on the respective receptacle socket.

7. The hydrostatic axial piston machine as recited in claim 6, wherein a groove width of the grooves is greater than a width of the retaining web.

8. The hydrostatic axial piston machine as recited in claim 6, wherein the grooves are located on the ball head at an inclination with respect to a longitudinal axis of the piston.

9. The hydrostatic axial piston machine as recited in claim 8, wherein the angle of inclination of the grooves is such that the angle of inclination is different from tilting angles of the pistons that occur during operation of the axial piston machine.

10. The hydrostatic axial piston machine as recited in claim 1, wherein a recess for a piston rod of the piston is located on the drive flange on each receptacle socket.

11. The hydrostatic axial piston machine as recited in claim 1, wherein a spherical guide for guidance of the cylinder barrel is located between the drive flange and the cylinder barrel.

12. The hydrostatic axial piston machine as recited in claim 10, wherein the recess is formed in a radially outer area of the receptacle socket in the end surface of the drive flange.

13. The hydrostatic axial piston machine as recited in claim 10, wherein the drive flange includes a bevel on an outer edge of an end surface, wherein the bevel forms the recess for the piston rod of the piston.

14. The hydrostatic axial piston machine as recited in claim 6, wherein the grooves are aligned in a straight-line path.

15. The hydrostatic axial piston machine as recited in claim 6, wherein the grooves are aligned in a bent path.

16. The hydrostatic axial piston machine as recited in claim 15, wherein the grooves have a first segment that is inclined with respect to a longitudinal axis of the piston, and a second segment that is bent with respect to the first segment and is oriented perpendicular to the longitudinal axis of the piston.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional advantages and details of the invention are described in greater detail below on the basis of the exemplary embodiments illustrated in the accompanying schematic figures, in which like reference numbers identify like parts throughout.

(2) FIG. 1 illustrates an axial piston machine of the invention employing a bent-axis construction in a longitudinal section;

(3) FIG. 2 is an enlarged detail from FIG. 1;

(4) FIG. 3 is a plan view of the end surface of the drive flange;

(5) FIG. 4 is a section along line B-B in FIG. 3;

(6) FIG. 5 is a section along line A-A in FIG. 4;

(7) FIGS. 6a-6d are illustrations illustrating the installation of the pistons;

(8) FIGS. 7a-7d are views in perspective illustrating the installation of the pistons;

(9) FIGS. 8a-8d are additional views in perspective illustrating the installation of the pistons;

(10) FIGS. 9a-9c are multiple views along a line C-C in FIG. 3 at different angles of inclination of the pistons;

(11) FIGS. 10a-10c are multiple views in perspective of a piston installed in the receptacle socket;

(12) FIG. 11a shows a first embodiment of a piston; and

(13) FIG. 11b shows a second embodiment of the piston.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(14) A hydrostatic axial piston machine 1 of the invention in the form of a bent-axis machine is illustrated in FIG. 1. The axial piston machine 1 has a housing 2 that includes a housing assembly 2a and a housing cover 2b that is fastened to the housing assembly 2a. Located in the housing are a drive flange 3 and a drive shaft 4 that can rotate around an axis of rotation R.sub.t that corresponds to a longitudinal axis L of the axial piston machine 1. In the illustrated exemplary embodiment, the drive shaft 4 is mounted by bearing devices 5a, 5b so that it can rotate around the axis of rotation R.sub.t. In the illustrated exemplary embodiment, the drive flange 3 is formed in one piece with the drive shaft 4.

(15) A cylinder barrel 7 is located in the housing 2 axially next to the drive flange 3. The cylinder barrel 7 rotates around an axis of rotation R.sub.Z and is provided with a plurality of piston bores 8 which, in the illustrated exemplary embodiment, are located concentric to the axis of rotation R.sub.Z of the cylinder barrel 7. A piston 10 is located so that it can move longitudinally in each piston bore 8.

(16) The axis of rotation R.sub.t of the drive shaft 4 intersects the axis of rotation R.sub.Z of the cylinder barrel 7 at the intersection point SP.

(17) The drive shaft 4 is equipped on the drive flange end with torque transmission means 12, such as splines, for the introduction of a drive torque or the tapping of an output torque.

(18) For control of the feed and discharge of hydraulic fluid in the displacement chambers V formed by the piston bores 8 and the pistons 10 the cylinder barrel 7 is in contact with a control surface 15, which is provided with kidney-shaped control bores (not illustrated in any detail) which form an inlet connection 16 and an outlet connection of the axial piston machine 1. For connection of the displacement chambers V formed by the piston bores 8 and the pistons 10 with the control bores, the cylinder barrel 7 is provided with a control opening 18 at each piston bore 8.

(19) The axial piston machine illustrated in FIG. 1 is a variable displacement machine with a variable displacement volume. On the variable displacement machine, the angle of inclination α, and thus the pivoting angle of the axis of rotation R.sub.Z of the cylinder barrel 7, is variable with reference to the axis of rotation R.sub.t of the drive shaft 4 to vary the displacement volume. The control surface 15 with which the cylinder barrel is in contact is located on a cradle body 19 located in the housing 2 so that it can rotate around a pivoting axis that lies at the intersection point SP of the axis of rotation R.sub.t of the drive shaft 4 and the axis of rotation R.sub.Z of the cylinder barrel 7 and is oriented perpendicularly to the axes of rotation R.sub.t and R.sub.Z.

(20) Depending on the position of the cradle body 19, the angle of inclination α of the axis of rotation R.sub.Z of the cylinder barrel 7 varies relative to the axis of rotation R.sub.t of the drive shaft 4. The cylinder barrel 7 can be pivoted into a null position where the pivoting angle is 0°, in which the axis of rotation R.sub.Z of the cylinder barrel 7 is coaxial with the axis of rotation R.sub.t of the drive shaft 4. Starting from this null position, the cylinder barrel 7 can be pivoted to one or both sides, so that the axial piston machine illustrated in FIG. 1 can be a unilaterally or bilaterally pivotable variable displacement machine. A device for pivoting the cradle body 19, and thus the cylinder barrel 7, is not illustrated in detail in FIG. 1.

(21) The pistons 10 are each fastened to the drive flange 3 in an articulated manner.

(22) Between the respective piston 10 and the drive flange 3, there is a ball joint connection 20 in the form of a spherical joint 20. The ball joint 20 (illustrated in greater detail in FIG. 2) is formed by a ball head 10a of the piston 10 and a spherical cap-shaped (hollow spherical shaped) receptacle socket 3a which is formed in the end surface 3b of the drive flange facing the cylinder barrel 7, in which the piston 10 with the ball head 10a is fastened.

(23) The pistons 10 can also each have a longitudinal bore 13 that runs through the piston 10, is in communication with the displacement chamber V, and extends through the ball head 10a, to hydrostatically relieve the ball joint 20.

(24) The pistons 10 each have a collar section 10b, with which the piston 10 is positioned in the piston bore 8. A piston rod 10c of the piston 10 connects the collar segments 10b with the ball head 10a.

(25) To make possible an equalization movement of the pistons 10 in the event of a rotation of the cylinder barrel 7, the collar segment 10b of the piston 10 is located in the piston bore 8 with some play. The collar segment 10b of the piston 10 can be spherical. To create a seal between the pistons 10 and the piston bores 8, sealing means 21, such as a piston ring, are located on the collar segment 10b of the piston 10.

(26) For mounting and centering of the cylinder barrel 7, a spherical guide 25 is located between the cylinder barrel 7 and the drive flange 3 or the drive shaft 4, respectively. The spherical guide 25 is formed by a spherical segment 26 of the drive flange 3 or of the drive shaft 4 on which the cylinder barrel 7 is located and has a hollow spherical segment 27. The center of segments 26, 27 lies at the intersection point SP of the axis of rotation R.sub.t of the drive shaft 4 and the axis of rotation R.sub.Z of the cylinder barrel 7. In the illustrated exemplary embodiment, the hollow spherical segment 26 is located on the end surface of a sleeve-like bushing 50, which is located and fastened in a central longitudinal bore 11 of the cylinder barrel 7 and, therefore, in the interior of the cylinder barrel 7.

(27) To drive the cylinder barrel 7 during operation of the axial piston machine 1, a drive device (not illustrated in detail) couples the drive shaft 4 and the cylinder barrel 7 in the direction of rotation. The drive device can be, for example, a drive linkage, such as a constant velocity joint.

(28) On the axial piston machine 1 employing the bent-axis construction (as illustrated in greater detail in FIGS. 3 to 5) the spherical cap-shaped receptacle sockets 3a are each in the shape of hemispheres that extend only to the equator of the ball. The centers M of the spherical shell-shaped receptacle sockets 3a (hemispheres) therefore lie in the plane generated by the end surface 3b of the drive flange 3. The spherical cap-shaped receptacle sockets 3a in the form of hemispheres wrap around the ball head 10a by 180°. FIG. 3 shows a plan view of the end surface 3b of the drive flange 3 in the vicinity of a receptacle socket 3a (the corresponding piston 10 is not shown).

(29) To positively secure the ball heads 10a of the pistons 10 in the hollow spherical shaped receptacle sockets 3a (hemispheres), a retaining web 30 is formed on the end surface 3b of the drive flange 3 in the vicinity of the receptacle sockets 3a and, as illustrated in FIG. 5, extends beyond the ball equator of the hemisphere to wrap around and grasp the ball head 10a over an angle of greater than 180°. The retaining web 30 is provided on the inner contour with a ball contour 31 that continues the spherical contour of the spherical cap-shaped receptacle sockets 3a.

(30) The retaining web 30 forms two retaining segments 30a, 30b on each receptacle socket 3a which, as illustrated in FIGS. 3 and 5, are located opposite each other on the receptacle socket 3a and are each provided with the ball contour 31.

(31) The retaining web 30 is formed by a circular ring-shaped encircling elevation 32 on the end surface 3b of the drive flange 3. The circular ring-shaped elevation 32, and thus the retaining web 30, are concentric to the axis of rotation R.sub.t of the drive flange 3, so that the center of the circular ring-shaped elevation 32 that forms the retaining web 30 is located on the axis of rotation R.sub.t of the drive flange 3.

(32) The circular ring-shaped elevation 32 is located on the end surface 3b of the drive flange 3 in the vicinity of a reference circle diameter T.sub.k on which the centers M of the hemispheric shaped receptacle sockets 3a are located.

(33) The circular ring-shaped elevation 32 is located facing the cylinder barrel 7 on the end surface 3b of the drive flange 3.

(34) The retaining web 30 has a width B in the radial direction that is significantly less than the diameter of the hemisphere, for example, a maximum of ⅓ of the diameter of the hemisphere and, thus, of the diameter of the ball head 10a. The radially outside peripheral surface 30d of the retaining web 30 is at a radially inward distance from the radially outside peripheral surface 3d of the drive flange 3.

(35) In the illustrated exemplary embodiment, the retaining web 30 is formed in one piece on the end surface 3b of the drive flange 3. The contour of the drive flange 4 is therefore provided with the retaining web 30 and thus the ring-shaped elevation 32 that projects out of the end surface 3b. Preferably, the retaining web 30 is formed as early as on a blank of the drive flange 3 with a certain amount of excess material so that the contour of the retaining web 30 can be economically produced in a lathe turning operation of the drive flange 3.

(36) In the axial piston machine 1, the retention of the piston heads 10a in the hemispheric shaped receptacle sockets 3a is limited to the area of the retaining web 30. Because the encircling retaining web 30 is at some distance radially inwardly from the radially outer peripheral surface 3d of the drive flange 3, an open space is created that makes it possible to bring the cylinder barrel 7 with the end surface 7a containing the piston outlet openings close to the end surface 3a of the drive flange 3, so that it becomes possible for the axial piston machine 1 to have compact dimensions in the axial direction of the longitudinal axis L. FIG. 2 illustrates one possible small distance s between the cylinder barrel 7 containing the end surface 7a containing the piston outlet openings and the centers M of the hemispheric receptacle sockets 3a which are located on the end surface 3b of the drive flange. To achieve the smallest possible distance s, the end surface of the retaining web 30 facing the cylinder barrel 7 is provided in the radially outer area with a bevel 33 that is inclined toward the end surface 3b of the drive flange 3.

(37) To be able to introduce the pistons 10 with the piston heads 10a into the receptacle sockets 3a, each ball head 10a (as illustrated in FIG. 5) is provided with two grooves 40a, 40b located opposite each other. The grooves 40a, 40b are places where material has been removed from the ball surface in the vicinity of the equator area of the ball heads 10a. The distance D between the cylindrical groove bases of the two grooves 40a, 40b oriented parallel to one another is less than the opening width E between the two retaining segments 30a, 30b of the retaining web 30 on the respective receptacle socket 3a.

(38) The groove widths F of the grooves 40a, 40b (as illustrated in FIG. 4) are each greater than the width B of the retaining web 30.

(39) The grooves 40a, 40b are inclined on the ball head 10a with a longitudinal axis L.sub.N with respect to the longitudinal axis L.sub.K of the piston 10. In the illustrated exemplary embodiment, the longitudinal axis L.sub.N of the grooves 40a, 40b is inclined with respect to the longitudinal axis L.sub.K of the piston 10 by an angle of inclination β.sub.M that forms an installation angle β.sub.M. The installation angle β.sub.M is less than 90°.

(40) In FIGS. 1 to 11a, the grooves 40a, 40b run in a straight line.

(41) The angle of inclination β.sub.M of the grooves 40a, 40b is such that the angle of inclination β.sub.M for the installation of the pistons 10 is different from the maximum tilting angles 131 of the pistons 10 that occur during operation of the axial piston machine 1.

(42) For installation of the pistons 10 into the receptacle sockets 3a, on the drive flange 3 on each receptacle socket 3a there is a recess 45 for the piston rod 10c of the piston 10. In the illustrated exemplary embodiment, the recesses 45 are located on the radially outer portion of the receptacle sockets 3a in the end surface 3b of the drive flange 3 and extend from the receptacle socket 3a radially outwardly toward the radially outer peripheral surface 3d of the drive flange 3. The recesses 45, viewed looking inwardly in the radial direction, have a depth that increases starting from the radially outer peripheral surface 3d toward the receptacle socket 3a.

(43) On the outer edge between the radially outer peripheral surface 3d and the end surface 3b, the drive flange 3 is also provided with a bevel 46. The recesses 45 extend into the area of the bevel 46.

(44) The process of installing the pistons 10 into the receptacle sockets is illustrated in greater detail in FIGS. 6a to 8d. The indices “a” to “d” in FIGS. 6a to 8d correspond to the same installation positions.

(45) For installation of the piston 10 in the receptacle socket 3a, the piston 10 is introduced into the receptacle socket 3a at the installation angle β.sub.M illustrated in FIGS. 6a, 7a, and 8a. Because when the pistons 10 are tilted at the installation angle β.sub.M the longitudinal axis L.sub.N of the grooves 40a, 40b is oriented parallel to the retaining web 30, the piston 10 with the two grooves 40a, 40b can be inserted into the receptacle socket 3a between the two retaining segments 30a, 30b of the retaining web 30, as illustrated in FIGS. 6b, 7b, 8b, and 6c, 7c, 8c. When the piston 10 is inserted all the way into the receptacle socket 3a at the installation angle β.sub.M, the piston rod 10b comes into contact with the recess 45. If the ball head 10a has been introduced all the way into the receptacle socket 3a, the piston can be tilted back starting from the installation angle β.sub.M to the angle of inclination β.sub.1 (as illustrated in FIG. 6c by the arrow 60 and in FIGS. 6d, 7d, and 8d) so that the ball head 10a is positively secured in the receptacle socket 3a by the retaining web 30.

(46) During operation of the axial piston machine 1, the maximum tilting angles β1 occur on the pistons 10 (as illustrated in FIGS. 6d and 9a to 9c) so that the piston head 10a is reliably secured in the receptacle socket 3a during operation of the axial piston machine 1.

(47) FIGS. 10a to 10c are views in perspective of the pistons 10 secured in the receptacle socket 3a.

(48) FIG. 11b illustrates a second embodiment of a piston 10 in which the grooves 40a, 40b in the piston head 10a follow a bent path. The grooves 40a, 40b have a first segment oriented with a longitudinal axis L.sub.N at the angle of inclination β.sub.M at an inclination with respect to the longitudinal axis L.sub.K of the piston 10. A second segment of the grooves 40a, 40b is also bent with respect to the first segment and in the illustrated exemplary embodiment is oriented with a longitudinal axis L.sub.N2 perpendicular to the longitudinal axis L.sub.K of the piston 10. Because of the bent second segment of the grooves 40a, 40b, the ball end of the ball head 10a that is opposite the piston shaft 10c has a dimension t2 from the outer edge of the grooves 40a, 40b that is greater than the dimension t1 of a straight path of the grooves 40a, 40b (FIG. 11a), so that the load-bearing ball half that is opposite the piston rod 10c and transmits the piston forces in the receptacle socket 3a has an enlarged surface area.

(49) The invention has a series of advantages.

(50) The locking of the pistons 10 of the invention in the receptacle sockets 3a, on account of the hemispheric shaped receptacle sockets 3a and the retaining web 30 on the end surface 3b of the drive flange 3, which projects out of the end surface 3b of the drive flange 3, requires little extra manufacturing effort or expense. In addition, a compact axial dimension of the axial piston machine of the invention can be achieved with the locking of the piston 10 in the drive flange 3 of the invention. As a result of the presence of the two inclined grooves 40a, 40b, the locking of the pistons 10 is appropriate for use on variable displacement machines with a variable displacement volume and makes pivoting angles of 0° possible. The two grooves 40a, 40b on the piston heads 10a, compared to flattened areas on the piston heads 10a to manufacture cylindrical surfaces, on account of the small groove width F of the grooves 40a, 40b, results in a slight reduction of the ball surface area on the load-bearing ball half that is opposite the piston rod 10c.

(51) The invention is not limited to the illustrated exemplary embodiments. The axial piston machine 1, instead of being constructed as a variable displacement machine, can alternatively be constructed as a constant displacement machine. In a constant displacement machine, the angle of inclination α of the axis of rotation R.sub.Z of the cylinder barrel 7 is constant and fixed with respect to the axis of rotation R.sub.t of the drive shaft 4. The control surface 15 with which the cylinder barrel 7 is in contact can be formed on the housing 2.

(52) It goes without saying that the bushing 50 can be constructed in one piece with the cylinder barrel 7.

(53) The drive flange 3 can be in the form of a component that is separate from the drive shaft 4 and is connected with the drive shaft 4 in a torque-tight manner.

(54) The bevel 46 on the drive flange 3 can be enlarged so that the additional recesses 45 for the installation of the pistons 10 can be eliminated.

(55) It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breath of the appended claims and any and all equivalents thereof.