U.S. patent application number 13/641043 was filed with the patent office on 2013-08-15 for axial piston machine having a retraction plate, and method for the production thereof.
This patent application is currently assigned to Robert Bosch GmbH. The applicant listed for this patent is Josef Beck, Ulrich Gordon Mohn, Martin Zug. Invention is credited to Josef Beck, Ulrich Gordon Mohn, Martin Zug.
Application Number | 20130205989 13/641043 |
Document ID | / |
Family ID | 44023070 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130205989 |
Kind Code |
A1 |
Zug; Martin ; et
al. |
August 15, 2013 |
Axial Piston Machine having a Retraction Plate, and Method for the
Production Thereof
Abstract
An axial piston machine comprises a cylinder drum in which a
multiplicity of pistons are arranged in a longitudinally
displaceable manner. The pistons are supported, via sliding blocks,
on a running surface which is inclined relative to the cylinder
drum axis. The sliding blocks are held, at that side thereof which
faces away from the running surface, by means of a retraction
plate. The retraction plate is produced from processed sheet metal
in a non-cutting punching and stamping process.
Inventors: |
Zug; Martin; (Hirrlingen,
DE) ; Beck; Josef; (Villingen-Schwenningen, DE)
; Mohn; Ulrich Gordon; (Horb, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zug; Martin
Beck; Josef
Mohn; Ulrich Gordon |
Hirrlingen
Villingen-Schwenningen
Horb |
|
DE
DE
DE |
|
|
Assignee: |
Robert Bosch GmbH
Stuttgart
DE
|
Family ID: |
44023070 |
Appl. No.: |
13/641043 |
Filed: |
February 22, 2011 |
PCT Filed: |
February 22, 2011 |
PCT NO: |
PCT/EP2011/000845 |
371 Date: |
December 24, 2012 |
Current U.S.
Class: |
92/51 ;
29/888 |
Current CPC
Class: |
F04B 1/126 20130101;
F04B 1/20 20130101; F01B 3/00 20130101; Y10T 29/49229 20150115 |
Class at
Publication: |
92/51 ;
29/888 |
International
Class: |
F01B 3/00 20060101
F01B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2010 |
DE |
102010015073.8 |
Claims
1. An axial piston machine comprising: a cylinder drum; a plurality
of pistons arranged longitudinally displaceably in the cylinder
drum; and a retraction plate produced from a refined metal sheet,
without cutting, in a stamping/embossing operation, wherein the
plurality of pistons are supported via sliding shoes on a running
surface inclined with respect to a drum axis of the cylinder drum,
and wherein the sliding shoes are held, so as to bear against the
running surface by means of the retraction plate on a retention
surface facing away from their sliding surface bearing against the
running surface.
2. The axial piston machine as claimed in claim 1, wherein the
retraction plate has a region in the form of an envelope of a cone
frustum which is shaped such that, in a nonloaded state, a distance
of the retraction plate at its outer circumference from the running
surface is shorter than in a region of a retraction plate
bearing.
3. The axial piston machine as claimed in claim 1, wherein a
circumferential edge runs in each case partially parallel to an
outer region of a sliding shoe reception orifice in each case.
4. The axial piston machine as claimed in claim 1, wherein the
retraction plate bearing includes a spherical cap in the retraction
plate.
5. The axial piston machine as claimed in claim 4, wherein a
diameter of the spherical cap and a diameter of the sliding shoe
reception orifices are equal.
6. A method for the production of a retraction plate for an axial
piston machine, comprising: generating a refined metal sheet with a
bearing surface finish-machined so as to bear against the sliding
shoes; stamping sliding shoe orifices into the refined metal sheet;
and forming a retraction plate bearing in the refined metal
sheet.
7. The method as claimed in claim 6, wherein the metal sheet is
formed such that, in a cross section through the retraction plate,
the bearing surface forms an angle of less than 180.degree..
8. The method as claimed in claim 7, wherein an outer region is
removed by stamping, so that a circumferential edge of the
retraction plate runs in each case partially parallel to an outer
region of a sliding shoe reception orifice in each case.
9. The method as claimed in claim 6, wherein the retraction plate
bearing is introduced in the form of a spherical cap into the metal
sheet by means of an embossing operation.
10. The method as claimed in claim 6, further comprising: forming a
molding from a planar metal sheet (i) by embossing the retraction
plate bearing in the form of a spherical cap, and (ii) by
generating a region in the form of an envelope of a cone frustum
outside the retraction plate bearing.
Description
[0001] The invention relates to an axial piston machine having a
retraction plate and to a method for the production of the
retraction plate.
[0002] In an axial piston machine, pistons are arranged
longitudinally displaceably in the axial direction in a rotatable
cylinder drum. These are supported on a running surface inclined in
relation to the cylinder drum axis. Where a hydraulic pump is
concerned, pressure conditions in this case prevail during the
suction stroke which relieve the sliding shoe completely of load
and would therefore cause it to lift off from the running surface.
In order to keep the sliding shoes in sliding bearing contact
against the running surface in every operating state and thereby
supplement the suction intake of pressure medium, a retraction
plate is consequently provided. The retraction plate is arranged
parallel to the running surface and engages with a plurality of
recesses in each case around a sliding shoe. Such an arrangement
and such a retraction plate are known from EP 1 561 031 B1. In
order to keep the costs for manufacturing the retraction plate low,
it is already proposed there to produce the retraction plate in a
stamping/embossing operation. By means of the stamping/embossing
operation, on the one hand, the passage orifices are stamped out of
the basic body designed as a planar circular disk and then surround
the sliding shoe. On the other hand, at the same time, a bearing
surface for supporting the retraction plate is formed. After this
forming step, a planar surface which subsequently transmits the
retention force to the sliding shoe is provided. This subsequent
reworking is carried out by cutting and may include additional heat
treatment, thus signifying a considerable additional outlay in
manufacturing terms.
[0003] The object on which the invention is based is to provide an
axial piston machine having a retraction plate and also a method
for the production of the retraction plate, said method being
simplified as compared with the known retraction plates.
[0004] The axial piston machine according to the invention has a
cylinder drum in which are arranged longitudinally displaceably a
plurality of pistons. The pistons are supported via sliding shoes
on a running surface inclined with respect to the cylinder drum
axis, the sliding shoes being held, so as to bear against the
running surface, by means of a retraction plate on a retention
surface facing away from their sliding surface bearing against the
running surface. According to the invention, the retraction plate
is produced from refined sheet metal, without cutting, in a
stamping/embossing operation. In the method according to the
invention, when the retraction plate is produced, first a refined
metal sheet with a surface finish-machined so as to bear against
the sliding shoes is generated. This refined metal sheet is
subsequently subjected to a stamping/embossing operation, with the
aid of which the sliding shoe reception orifices are introduced.
The method according to the invention and the axial piston machine
according to the invention are, in particular, more cost-effective
than the known methods, and also weight can be saved on the
retraction plate. Using or generating a refined metal sheet before
a forming process takes place has the advantage that remachining by
cutting and/or thermal treatment may be dispensed with. The sliding
properties are already determined by the refined metal sheet
itself.
[0005] The sub claims relate to advantageous developments of the
axial piston machine according to the invention and of the method
according to the invention.
[0006] In particular, it is advantageous to form on the retraction
plate a region which is in the form of the envelope of a cone
frustum. This region is shaped such that, in the nonloaded state,
the distance of the retraction plate at its outer circumference
from the running surface is shorter than in the region of the
retraction plate bearing. Higher forces upon the sliding shoe are
thus generated in the region facing radially away from the cylinder
drum axis. The tendency of the sliding shoe to lift off under the
action of centrifugal forces on the outside is consequently
counteracted. Such prestress is advantageous especially when the
refined metal sheet has spring-elastic properties, so that, after
mounting, tension is generated in the retraction plate, since the
latter is supported, on the one hand, in the region of the
retraction plate bearing and, on the other hand, in the outer
region on the sliding shoes.
[0007] Furthermore, it is advantageous, in order to save weight,
that an outer circumferential edge of the retraction plate runs in
each case partially parallel to an outer region of a sliding shoe
reception orifice in each case. Consequently, the retraction plate
has no circular outer geometry and the material present between the
individual sliding shoe reception orifices at the outer
circumferential margin can be removed. The use of material can thus
be diminished and therefore the weight of the retraction plate can
also be reduced. The outer geometry shaped in this way is in this
case preferably generated simultaneously with the forming operation
in a stamping/embossing process without cutting.
[0008] The retraction plate bearing of the retraction plate is
preferably designed in the form of a spherical cap and without any
passage orifice. In particular, in this case, that side of the
metal sheet which faces away from the side co-operating with the
sliding shoes is also refined such that low frictional forces occur
between the retraction plate bearing configured in the form of a
spherical cap and the counterpiece of the axial piston machine.
Such a retraction plate bearing in the form of a spherical cap has
especially the advantage that automatic centering of the retraction
plate takes place even when the angle of inclination of the running
surface changes. Furthermore, advantageously, a corresponding
depression may be arranged in the running surface itself, so that
the retraction plate comes to bear there permanently and therefore
a constant distance is ensured. Moreover, the supporting force
generated on the retraction plate by means of the retraction plate
bearing may be used at the same time for keeping the pivoting
cradle, on which the running surface is formed, in position and, in
particular, in its pivoting cradle bearing.
[0009] The diameter of the retraction plate bearing in the form of
a spherical cap is in this case preferably selected such that this
diameter is equal to the diameter of the sliding shoe reception
orifices.
[0010] The stamping/embossing operation preferably takes place in a
plurality of successive steps. In this case, in one step, after the
refined metal sheet has been generated, first a molding
corresponding to a circular disk is shaped so as to form the region
which is in the form of a cone envelope. In this case, in cross
section, the surface ultimately forming the bearing surface forms
an angle of less than 180.degree..
[0011] The introduction of the retraction plate bearing in the form
of a spherical cap is preferably carried out by means of an
embossing operation and, in particular, may be carried out
simultaneously with the generation of the geometry in the form of
the envelope of a cone frustum. The center point of the geometry in
the form of a spherical cap and the apex of the cone frustum lie in
this case in the same side of the retraction plate.
[0012] The axial piston machine according to the invention and the
corresponding method for the production of the retraction plate are
explained in more detail by means of the following explanations and
the accompanying drawings in which:
[0013] FIG. 1 shows a part section through an axial piston machine
according to the invention to explain the co-operation of the
individual parts of an axial piston machine;
[0014] FIG. 2 shows a section through a molding as an intermediate
product in the generation of the retraction plate;
[0015] FIG. 3 shows a perspective illustration of a finished
retraction plate; and
[0016] FIG. 4 shows a simplified illustration of the method to
explain the method for the production of the retraction plate.
[0017] The axial piston machine 1 according to the invention is
illustrated in a part section in FIG. 1. It has a housing 2 in
which a cylinder drum 3 is arranged so as to be rotatably mounted.
A plurality of cylinder bores 4, only one of which is illustrated
for the sake of simplification, are introduced into the cylinder
drum 3. The cylinder bores 4 are connected, via orifices 5 which
issue on an end face of the cylinder drum 3, alternately to a
high-pressure connection and a low-pressure connection of a working
circuit when the cylinder drum 3 is rotated. For this purpose, the
cylinder drum 3 is rotatable about its cylinder drum axis 6. The
plurality of cylinder bores 4 are arranged, distributed uniformly,
on a circumferential circle around the cylinder drum axis 6. On the
side facing away from the orifice 5, the cylinder bores 4 are open
toward the second end face of the cylinder drum 3. In each case a
piston 7 is arranged longitudinally displaceably in the cylinder
bores 4.
[0018] Each of the pistons 7 is connected to a sliding shoe 8 in an
articulated manner. For this purpose, the sliding shoe 8 has a
spherical head which engages into a corresponding recess of the
piston 7. The recess or the piston 7 in this case surrounds the
head to an extent such that tensile and compressive forces can be
transmitted between the sliding shoe 8 and the piston 7. The
sliding shoes 8 bear slidably, in each case with a sliding surface
9 formed on a foot region of the sliding shoe 8, against a running
surface 10. The running surface 10 is formed on a pivoting cradle
11. The inclination of the pivoting cradle 11 in relation to the
cylinder drum axis 6 can be adjusted by means of an actuating
device 12. The adjustability of the inclination of the pivoting
cradle 11 and therefore of the running surface 10 in relation to
the cylinder drum axis 6 is already known per se. A detailed
illustration is therefore dispensed with at this juncture. To
absorb the compressive forces, the pivoting cradle 11 is supported
in a pivoting cradle bearing 13. The pivoting cradle 11 is mounted
rotatably in the latter.
[0019] During one revolution of the cylinder drum 3, the pistons 7
execute a lifting movement in their respective cylinder bore 4.
Where a pump is concerned, in this case the cylinder drum 3 is
driven and, during the delivery stroke, the volume enclosed in the
cylinder bore 4 by the piston 7 is reduced and therefore a volume
flow through the orifice 5 into the working circuit is generated.
During further rotation of the cylinder drum 3, the volume enclosed
by the cylinder bore 4 and the piston 7 has to be increased again.
In order to hold the sliding shoe 8 with its sliding surface 9
against the running surface 10 during this suction stroke, a
retraction plate 14 is provided. The retraction plate 14 has a
number of sliding shoe reception orifices 15 which corresponds to
the number of sliding shoes 8. The sliding shoe reception orifices
15 are in this case selected in terms of their diameter such that
they can be placed over the head of the sliding shoe 8 onto the
foot of the sliding shoe. The reflection plate 14 bears there with
a bearing surface against a retention surface 16, formed at the
foot, of the sliding shoe 8.
[0020] To generate the necessary retention force, the retraction
plate 14 is supported by means of a retraction plate bearing 17 on
a bearing bolt 18. The bearing bolt 18 is loaded by a helical
spring 19 which acts upon the bearing bolt 18 in the direction of
the pivoting cradle 11. The helical spring 19 and the bearing bolt
18 are inserted into a recess 20 which is formed as a blind bore in
the cylinder drum 3. The recess 20 in this case extends in the
direction of the cylinder drum axis 6.
[0021] As can be seen clearly in the exemplary embodiment
illustrated, the retraction plate 14 is designed there in the form
of a spherical cap in order to form the retraction plate bearing
17. The centerpoint of the spherical cap shape lies in this case on
that side of the retraction plate 14 which faces away from the
pivoting cradle 11. The bearing bolt 18 is configured spherically
on its side facing away from the helical spring 19 and engages on
the concave side of the retraction plate bearing 17 into the
geometry which is in the form of a spherical cap.
[0022] As is also explained in detail below, the retraction plate
14 is manufactured without cutting from a refined metal sheet and
therefore has an essentially constant material thickness. Changes
in the material thickness arise merely as a result of manufacturing
tolerances and due to the stretch of the material on account of the
forming operation. In the region of the retraction plate bearing 17
in the form of a spherical cap, a convex side, directed toward the
pivoting cradle 11, of the retraction plate bearing 17 is obtained.
This convex side engages into a depression 21 of the pivoting
cradle 11, so that the distance of the retraction plate 14 from the
pivoting cradle 11 is always constant. By means of the retraction
plate 14, therefore, the pivoting cradle 11 is also acted upon with
a force in the direction of the pivoting cradle bearing 13 by the
bearing bolt 18.
[0023] Details of the geometry of the retraction plate 14 are
explained below with reference to FIG. 2 and FIG. 3. FIG. 2
illustrates first a cross section through a molding of a retraction
plate 14, such molding being generated during production. The
retraction plate bearing 17 in the form of a spherical cap can be
seen in the middle of the retraction plate 14. A region A designed
in the form of the envelope of a cone frustum adjoins radially
toward the outer circumferential edge. This region A ensures that
the distance of the bearing surface 22 from the running surface 10
decreases from the retraction plate bearing 17 in the form of a
spherical cap toward the outer circumference of the retraction
plate 14. Thus, with an increasing distance from the cylinder drum
axis 6, the pressure force exerted upon the sliding shoes 8 by the
retraction plate 14 via the bearing surface 22 becomes greater. The
tendency of the sliding shoes 8 to lift off on their side further
away from the cylinder drum axis 6 is consequently
counteracted.
[0024] As can likewise be seen in FIG. 2, the centerpoint of the
retraction plate bearing 17 in the form of a spherical cap and the
apex of the cone frustum are formed on the same side of the
retraction plate 14.
[0025] A perspective illustration of a finish-machined retraction
plate 14 is shown in FIG. 3. In the production of the retraction
plate 14, first, the geometry illustrated in FIG. 2 is generated
from a basic shape which is initially in the form of a circular
disk. This basic shape in the form of a circular disk is a refined
metal sheet of constant material thickness t. The refinement in
this case takes place particularly with a view to the surface
quality of the bearing surface 22. That side of the metal sheet
which faces away from this plays a minor part in terms of its
quality. However, the region which is intended to produce the
retraction plate bearing 17 in the form of a spherical cap may also
be refined correspondingly. Refinement in this case takes case
particularly with a view to the sliding properties.
[0026] After first forming by embossing to generate the retraction
plate bearing 17 in the form of a spherical cap and the geometry of
the region A which is in the form of the envelope of a cone frustum
has been carried out, the plurality of sliding shoe reception
orifices 15 are introduced in a subsequent stamping step. The
sliding shoe reception orifices 15 are of circular design and are
distributed uniformly over the circumference of the retraction
plate 14. The diameter of the sliding shoe reception orifices 15
and the diameter of the retraction plate bearing 17 in the form of
a spherical cap are preferably identical. The forming and stamping
of the sliding shoe reception orifices 15 are carried out, starting
from a basic body with a diameter D. In order to save material, in
this case material can be removed in the marginal region by
stamping. The remaining webs around the sliding shoe reception
orifices 15 are in this case partially a constant width B. To make
clear the partially constant width B of the webs, a segment 20 is
illustrated. Over the largest part of this segment 20, the outer
circumferential edge 19 of the retraction plate 14 is parallel to
the outer region of the sliding shoe reception recess 15. Only
toward the boundary of the segment 20 does the web width increase
so as to reduce the notch effect at the transition to the adjacent
segment.
[0027] A greatly simplified method sequence is illustrated once
again in FIG. 4. First, in step S1, a basic body is produced from a
refined metal sheet. This basic body, which is preferably a
circular disk, is subsequently formed in a first forming step S2
into a molding such that a retraction plate bearing 17 in the form
of a spherical cap and the region A in the form of the envelope of
a cone frustum are generated. In step S3, the plurality of sliding
shoe reception orifices are introduced into this molding by
stamping. At the same time or in a subsequent step S4, the marginal
region is adapted so that the partially parallel circumferential
edge 19 is obtained.
* * * * *