U.S. patent application number 12/520749 was filed with the patent office on 2009-11-26 for hydrostatic axial piston machine.
This patent application is currently assigned to ROBERT BOSCH GMBH. Invention is credited to Josef Beck, Martin Zug.
Application Number | 20090288552 12/520749 |
Document ID | / |
Family ID | 39259629 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090288552 |
Kind Code |
A1 |
Beck; Josef ; et
al. |
November 26, 2009 |
HYDROSTATIC AXIAL PISTON MACHINE
Abstract
The invention relates to a hydrostatic axial piston engine with
a cylinder drum (106) which is mounted rotatably in a housing
(103). Longitudinally displaceable working pistons (111) are
disposed in cylinder boreholes (110) in the cylinder drum (106).
The working pistons (111) are connected movably to sliding blocks
(149) and are supported on a face (116) of an inclined disk (115).
Furthermore, the hydrostatic axial piston engine (101) has a
control piston (126) which interacts with the inclined disk (115)
for adjusting an angle of inclination of the face (116) with
respect to an axis of rotation (144) in the cylinder drum (106).
The control piston (126) is supported over a control piston sliding
block (149') on the face (116) of the inclined disk (115) in order
to exert a regulating force on the inclined disk (115).
Inventors: |
Beck; Josef;
(Villingen-Schwenningen, DE) ; Zug; Martin;
(Hirrlingen, DE) |
Correspondence
Address: |
SCULLY SCOTT MURPHY & PRESSER, PC
400 GARDEN CITY PLAZA, SUITE 300
GARDEN CITY
NY
11530
US
|
Assignee: |
ROBERT BOSCH GMBH
Stuttgart
DE
|
Family ID: |
39259629 |
Appl. No.: |
12/520749 |
Filed: |
December 20, 2007 |
PCT Filed: |
December 20, 2007 |
PCT NO: |
PCT/EP07/11303 |
371 Date: |
August 4, 2009 |
Current U.S.
Class: |
91/505 |
Current CPC
Class: |
F04B 1/324 20130101 |
Class at
Publication: |
91/505 |
International
Class: |
F01B 3/00 20060101
F01B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2006 |
DE |
10 2006 061 145.4 |
Claims
1. Hydrostatic axial piston machine having a cylinder drum, which
is mounted rotatably in a housing and in which working pistons are
disposed in a longitudinally displaceable manner in cylinder bores,
wherein the working pistons are movably connected to sliding shoes
and the working pistons are supported via the sliding shoes against
a contact surface of a swash plate, and having a positioning
piston, which interacts with the swash plate in order to adjust an
angle of inclination of the contact surface relative to an axis of
rotation of the cylinder drum, wherein the positioning piston is
connected to a positioning-piston sliding shoe and via the
positioning-piston sliding shoe the contact surface of the swash
plate is loaded with a positioning force.
2. Hydrostatic axial piston machine according to claim 1, wherein
the positioning piston and the positioning-piston sliding shoe are
connected to one another by a ball joint.
3. Hydrostatic axial piston machine according to claim 1, wherein
the positioning piston and the working pistons have an identical
geometry.
4. Hydrostatic axial piston machine according to claim 1, wherein
the positioning-piston sliding shoe and the sliding shoes of the
working pistons have an identical geometry.
5. Hydrostatic axial piston machine according to claim 1, wherein
the positioning piston is disposed in a positioning device housing
in a longitudinally displaceable manner along a longitudinal axis
of the positioning device housing and the longitudinal axis of the
positioning device housing extends at least approximately parallel
to the axis of rotation of the cylinder drum.
6. Hydrostatic axial piston machine according to claim 5, wherein
the positioning piston is disposed in a stepped recess of the
positioning device housing and a valve piston is arranged offset in
axial direction relative to the positioning piston in the stepped
recess.
7. Hydrostatic axial piston machine according to claim 5, wherein
for feedback of positional information of the positioning piston a
feedback spring is provided, which is supported on the one hand
against the positioning piston and on the other hand against a
valve piston.
8. Hydrostatic axial piston machine according to claim 7, wherein
the feedback spring is identical with press-on springs inserted in
the cylinder recesses.
9. Hydrostatic axial piston machine according to claim 1, wherein
the positioning device housing is fastened in a port plate of the
axial piston machine.
Description
[0001] The invention relates to a hydrostatic axial piston machine
having the features of the preamble of claim 1.
[0002] In axial piston machines a cylinder drum is disposed in a
rotatable manner. The cylinder drum is connected in a rotationally
fixed manner to a driving shaft. A plurality of cylinder bores are
arranged distributed along a circumferential circle in the cylinder
drum. In each of the cylinder bores a working piston is disposed in
a longitudinally displaceable manner. In order during a rotation of
the cylinder drum to achieve a stroke of the working pistons
disposed in the cylinder bores, the working pistons are supported
on a contact surface of a swash plate. The contact surface is
disposed obliquely relative to the axis of rotation of the cylinder
drum.
[0003] In adjustable axial piston machines the inclination of this
contact surface is adjustable. For this purpose, the contact
surface is disposed on a swash plate that frequently takes the form
of a swiveling cradle. Such an axial piston machine is known from
DE 199 49 169 A1. In order to be able to adjust the angle of
inclination of the contact surface relative to the axis of rotation
of the axial piston machine, an adjusting device is disposed there,
in a housing opening. The adjusting device comprises a positioning
piston, which for adjusting the inclination of the swash plate
interacts with the swash plate. For this purpose, there is formed
on the positioning piston a spherical head that engages into a
spherical recess of the swash plate. The articulated connection
thus formed between the positioning piston and the swash plate
enables an inclination of the two elements relative to one another,
such as arises automatically during an adjustment of the angle of
the swash plate. The location opening that is provided for
receiving the adjusting device in the housing of the axial piston
machine is disposed obliquely relative to the axis of rotation of
the cylinder drum.
[0004] In the axial piston machine known from DE 199 49 169 A1 it
is disadvantageous that a special articulated connection of the
swash plate to the positioning piston of the adjusting device is
formed. The fixed distance of the working point of the positioning
piston on the swash plate moreover necessitates a lateral motion
compensation, in the event of a change of inclination of the swash
plate. This increases the complexity of manufacture of the axial
piston machine considerably. What is more, the oblique arrangement
of the adjusting device in a recess of the housing is a drawback
because the arising forces that are necessary for adjustment of the
swash plate are considerable. The load removal therefore has to be
effected via the housing, thereby entailing the use of a
high-quality housing material. This increases the cost of the whole
axial piston machine.
[0005] The object of the present invention is therefore to provide
an axial piston machine that allows an improved adjustment of the
angle of inclination of the swash plate and is simple and
economical to manufacture.
[0006] The object is achieved by the axial piston machine according
to the invention having the features of claim 1.
[0007] The axial piston machine according to the invention has a
housing, in which a cylinder drum is rotatably mounted. Disposed in
the cylinder drum is a plurality of cylinder recesses, in each of
which a working piston is disposed in a longitudinally displaceable
manner. The working pistons are supported in each case by means of
a sliding shoe against a contact surface of a swash plate. The
connection between the working piston and the sliding shoes is of a
movable design. A positioning piston is further provided, which
interacts with the swash plate in order to adjust an angle of
inclination of the contact surface relative to the axis of rotation
of the cylinder drum. According to the invention, the positioning
piston is connected to a positioning-piston sliding shoe, which is
supported on the contact surface of the swash plate in order in
this way to generate a positioning force upon the swash plate. The
design according to the invention has the advantage that, as far as
the swash plate is concerned, only a contact surface need be
formed. This contact surface generally takes the form of a simple
flat surface. Thus, by means of the sliding shoe a thrust force may
easily be exerted by the positioning piston on the contact surface
of the swash plate. At the same time, during a positioning movement
the support point of the positioning-piston sliding shoe may
automatically adapt in radial direction on the contact surface. A
special construction of an articulated connection between the swash
plate and the positioning piston is not necessary.
[0008] Advantageous developments of the axial piston machine
according to the invention are outlined in the sub-claims.
[0009] Preferably, a ball joint is disposed between the positioning
piston and the positioning-piston sliding shoe. The effect achieved
by connecting the positioning piston to the positioning-piston
sliding shoe by a ball joint is that the assembly position of the
positioning piston and/or of the positioning-piston sliding shoe
with regard to a twisting of the positioning piston or of the
positioning-piston sliding shoe is insignificant. In this case, it
is particularly advantageous if the positioning piston and the
working pistons have an identical geometry. A separate manufacture
of the positioning piston therefore no longer applies. As a result
of the increased number of identical parts inside the axial piston
machine it is therefore possible to achieve a considerable cost
saving. It is in particular also advantageous for the
positioning-piston sliding shoe to be designed identically with the
sliding shoes of the working pistons. It is particularly preferred
if both the positioning piston is identical with the working
pistons and the positioning-piston sliding shoe has an identical
geometry to the sliding shoes of the working pistons.
[0010] It is further preferred if the positioning piston is
disposed in a positioning-device housing and is displaceable there
along a longitudinal axis of the positioning-device housing. The
longitudinal axis of the positioning-device housing extends at
least approximately parallel to an axis of rotation of the cylinder
drum. Such an approximately parallel arrangement reduces the
required installation space in lateral direction relative to the
axis of rotation of the cylinder drum. In the positioning-device
housing a stepped recess is preferably disposed. Disposed in axial
succession in the stepped recess are the positioning piston as well
as a valve piston of a valve for activating a positioning pressure
that acts upon the positioning piston. In the positioning-device
housing it is therefore possible to provide a single multi-stepped
bore, in which all of the components needed to generate a
positioning movement of the swash plate and hence a working volume
of the axial piston machine are disposed. In particular, there may
also be provided inside the positioning-device housing a feedback
spring, with the aid of which the position of the positioning
piston is fed back to the valve piston. Such feedback enables an
adjustment of the displacement volume of the hydrostatic piston
machine that corresponds to, for example is proportional, to a
control signal.
[0011] In this case, it is particularly preferred if the feedback
spring is identical with press-on springs inserted in the cylinder
bores of the cylinder drum. The use of the, in any case necessary,
press-on springs also in the adjusting device means that the number
of identical parts inside the axial piston machine is again
increased and so a cost reduction is achieved.
[0012] It is further preferred if the positioning-device housing is
fastened in a port plate of the axial piston machine. Disposed in
the port plate are the pressure lines for supplying and removing
the pressure medium delivered for example by means of a hydraulic
pump. If therefore the positioning device housing is disposed in
the port plate, then the valve piston disposed in the positioning
device housing may be loaded with the pressures required for
adjustment via shorter lines and/or channels. It is possible to
dispense with external lines because all of the channels may be
provided inside the port plate and/or inside the positioning device
housing. In particular, assembly is also facilitated because the
port plate may be preassembled jointly with the adjusting device as
an assembly group and then inserted, after insertion of the driving
gear, into the housing of the axial piston machine.
[0013] An embodiment according to the invention of an axial piston
machine is represented in the drawings and explained in detail in
the following description. The drawings show:
[0014] FIG. 1 a diagrammatic representation of a hydrostatic axial
piston machine with a known adjusting device;
[0015] FIG. 2 a hydraulic circuit diagram for explaining the mode
of operation of the adjusting device; and
[0016] FIG. 3 an enlarged representation of an axial piston machine
according to the invention.
[0017] First, before an axial piston machine according to the
invention is described in detail with reference to FIG. 3, the
basic layout and the function of a hydrostatic axial piston machine
will be described with reference to FIG. 1.
[0018] In FIG. 1 a hydrostatic axial piston machine 1 is
represented. The known hydrostatic axial piston machine 1 comprises
a driving gear 2, which is disposed in a housing 3. For inserting
the driving gear 2 into the housing 3, the housing 3 is open at one
end. After assembly of the driving gear 2 in the housing 3, the
open end is closed by means of a port plate 4. On the port plate 4
the line connections are provided in a manner that is not
represented.
[0019] The driving gear 2 comprises a driving shaft 5 and a
cylinder drum 6 connected thereto in a rotationally fixed manner.
The driving shaft 5 is disposed so as to be rotatable jointly with
the cylinder drum 6 in the housing 3.
[0020] For this purpose, the driving shaft 5 at one end of the
housing 3 is mounted rotatably in a first bearing 7. At the
opposite end of the driving shaft 5 a second bearing 8 is provided,
which in the illustrated embodiment is disposed in the port plate
4. The driving shaft 5 with one end 9 penetrates the first bearing
7 as well as the end face of the housing 3 of the hydrostatic axial
piston machine 1.
[0021] For the following description it is assumed that the
hydrostatic axial piston machine 1 is a variable displacement
hydraulic pump 1. The end 9 of the driving shaft 5 is therefore
connected to a drive motor for driving the hydraulic pump.
[0022] In the cylinder drum 6 a plurality of cylinder bores 10 are
introduced into the cylinder drum 6 and arranged distributed along
a circumferential circle. Disposed in each cylinder bore 6 is a
working piston 11. The working piston 11 may be displaced in
longitudinal direction along the centre line of the cylinder bore
10. The working piston 11 is connected by a ball joint connection
13 movably to a sliding shoe 12. The sliding shoes 12 of the
working pistons 11 are supported by a sliding face on a awash plate
15. The swash plate 15 in the illustrated embodiment takes the form
of a swiveling cradle that is disposed rotatably in a spherical
bearing. On the side of the swash plate 15 facing the cylinder drum
6 is a contact surface 16 in the form of a flat surface.
[0023] Whereas in FIG. 1 the contact surface 16 and/or the swash
plate 15 is represented in its neutral position, which corresponds
to a zero delivery volume of the hydraulic pump, the working
pistons 11 are shown in a position that would correspond to a
swivel angle .alpha. of the swash plate 15.
[0024] During a rotation of the driving shaft 5 the cylinder drum
6, because of the rotationally fixed connection, also rotates. In
this case, the sliding shoes 12 are supported against the contact
surface 16 of the swash plate 15 and constrain the working pistons
11 into a reciprocating movement. In order during an intake stroke
to prevent the sliding shoes 12 from lifting off the contact
surface 16 of the swash plate 15, a retraction plate 14 is
provided. The retraction plate 14 follows the angle of inclination
of the swash plate 15 and is mounted on a spherical bearing 17.
[0025] For temporarily connecting the cylinder bores 10 to the
lines of a hydrostatic circuit a control plate 18 is provided.
Formed in the control plate 18 are control openings 19, 20, with
which during a revolution of the cylinder drum 6 the cylinder bores
10 alternately communicate. In order to hold the cylinder drum 6 at
the mouth side of the cylinder bores 10 in sealing abutment with
the control plate 18, a spring 21 is provided in the interior of
the cylinder drum 6. The spring 21 is supported on the one hand
against the cylinder drum 6, in which for this purpose for example
a Seeger circlip ring is disposed as a first spring bearing. A
second spring bearing is formed at the opposite end of the spring
21 on the driving shaft 5.
[0026] For adjusting the working volume of the axial piston machine
1 an adjusting device 22 is provided. The adjusting device 22 is
actuated by means of a proportional magnet 23. The proportional
magnet 23 acts in a non-illustrated manner upon a valve piston of
the adjusting device 22 that adjusts a positioning pressure, which
acts upon a positioning piston 26.
[0027] Formed on the positioning piston 26 is a spherical
connection element 24. This spherical connection element 24 engages
into a spherical recess 25 disposed in the swash plate 15. The
longitudinal axis of the adjusting device 22 with the axis of
rotation of the cylinder drum 6 includes an angle differing from
0.
[0028] FIG. 2 shows a hydraulic circuit that is provided for
adjusting an axial piston machine 1. The hydrostatic axial piston
machine 1, which in the case of a hydraulic pump is driven via the
driving shaft 5, takes in pressure medium through a suction line 27
from a tank volume 28. In the illustrated embodiment, an
arrangement in an open circuit is shown. The axial piston machine
may however also be arranged in a closed circuit. The pressure
medium taken in by the hydrostatic axial piston machine 1 is
delivered in accordance with the adjusted delivery volume into a
working line 29. For adjusting the delivery volume of the hydraulic
pump the adjusting device 22 is provided. The adjusting device 22
comprises, besides the positioning piston 26, a
positioning-pressure regulating valve 32. The positioning-pressure
regulating valve 32 adjusts a positioning pressure that acts upon
the positioning piston 26. The positioning pressure acting upon the
positioning piston 26 is removed from the working line 29 through a
removal line 31. The positioning piston 26 is loaded in one
direction with a spring force by means of a restoring spring 33. In
a positioning pressure chamber 35 a feedback spring 34 is disposed,
which transmits to a valve piston of the positioning-pressure
regulating valve 32 a force that is dependent upon the position of
the positioning piston 26. The positioning-pressure regulating
valve 32 in its position represented in FIG. 2 is situated in the
normal position of the positioning device 22. In this position the
removal line 31 is connected to a positioning pressure line 36. As
a result, the pressure prevailing in the working line 29 arises in
the positioning pressure chamber 35. This pressure acts upon the
positioning piston 26 with its piston area oriented towards the
positioning pressure chamber pressure space 35. The positioning
piston 26 is consequently deflected in FIG. 2 to the left. The
positioning piston 26 owing to the positioning movement compresses
the restoring spring 33. Upon a positioning movement of the
positioning piston 26 counter to the action of the restoring spring
33, the hydrostatic axial piston machine 1 is adjusted in the
direction of its minimum delivery volume.
[0029] From the indicated normal position of the
positioning-pressure regulating valve 32 the positioning-pressure
regulating valve 32 may be loaded with a force in the direction of
a second end position. This force is generated for example by a
proportional magnet 23. The force of the proportional magnet 23
acts counter to the action of the feedback spring 34. If the
proportional magnet 33 then receives a control signal, the valve
piston of the control-pressure regulating valve 33 experiences a
force in the direction of its second end position. In this second
end position the positioning pressure line 36 is connected to a
connection line 37. The positioning-pressure regulating valve 32 is
infinitely adjustable between these two end positions. During
normal operation the connection line 37 is connected by a safety
valve 39 to the tank line 30. In the second end position of the
positioning-pressure regulating valve 32, therefore, the
positioning pressure chamber 35 is connected by the connection line
37 to the tank line 30 and the positioning pressure chamber 35 is
relieved into the tank volume 28. As a result of this, the force
upon the piston area of the positioning piston 26 reduces and the
restoring spring 33 moves the positioning piston 26 in such a way
that the hydrostatic axial piston machine 1 is adjusted in the
direction of an increasing delivery volume.
[0030] In order to be able to adjust a proportional positioning
movement and/or a proportional delivery volume of the hydrostatic
axial piston machine 1, the force of the feedback spring 34 acts in
the opposite direction to the force of the proportional magnet 23
upon the valve piston of the positioning-pressure regulating valve
32. Thus, there is exerted on the valve piston of the
positioning-pressure regulating valve 32 a force that is dependent
upon the respective position of the positioning piston 26.
[0031] The positioning pressure line 36 is further connected by a
bypass line 36' to the connection line 37. In the bypass line 36' a
throttle point 38 is disposed. Via the throttle point 38 a flow of
pressure medium out of the positioning pressure chamber 35
therefore becomes possible if for example the positioning-pressure
regulating valve 32 is adjusted from its first end position
slightly in the direction of its second end position as a result of
the proportional magnet 23 receiving a lower control signal.
[0032] The safety valve 39 in its normal position connects the
connection line 27 in the previously described manner to the tank
line 30. This normal position is defined by means of a safety valve
spring 40. In the opposite position of the safety valve 39,
however, a further connection line 41 is connected to the
connection line 37. The further connection line 41 branches off
from the removal line 31. In the opposite position of the safety
valve 39, therefore, the pressure of the working line 29 is
supplied to the connection line 37. The pressure prevailing in the
further connection line 41 is further supplied via a first
measuring line 42 to a measuring area formed on the safety valve
39. The hydraulic force effective at the measuring area acts
counter to the action of the safety valve spring 40. Conversely,
the pressure in the tank line 30 acts via a second measuring line
43 in the same direction as the safety valve spring 40 upon the
safety valve 39.
[0033] By means of the safety valve spring 40, which is designed as
an adjustable spring, the opening differential pressure of the
safety valve 39 may be adjusted. If this opening pressure is
exceeded by the pressure difference between the pressures supplied
via the first measuring line 42 and the second measuring line 43,
then the safety valve 39 is adjusted in the direction of its second
end position. With increasing adjustment in the direction of the
second end position, the pressure in the positioning pressure
chamber 35 rises, even if the positioning-pressure regulating valve
32 is situated in its second end position. Consequently, the
positioning piston 26 is adjusted in FIG. 2 to the left, thereby
leading to a reduction of the delivery volume.
[0034] FIG. 3 shows an enlarged representation of a detail of an
axial piston machine 101 according to the invention. For the sake
of greater clarity, the as such known elements of the axial piston
machine 101 are not represented. Instead, the axial piston machine
101 in the region of the adjusting device 122 is represented to an
enlarged scale. Elements and features that are identical to FIG. 1
are provided with reference characters increased by 100.
[0035] As already explained with reference to FIG. 1, in the
cylinder drum 126, in cylinder bores 110 provided there, working
pistons 111 are disposed in a longitudinally displaceable manner.
The working pistons 111 are connected by means of a ball joint
connection 113 to sliding shoes 112. For this purpose, a spherical
head 147 is formed on an end of the working pistons 111 that
projects from the cylinder bores 110 of the cylinder drum 106. This
spherical head 147 engages into a spherical recess 148 of the
sliding shoe 149. Introduced from the opposite side into the
working pistons 111 is a recess 146. The recess 146 preferably
takes the form of a bore, and is so dimensioned that a press-on
spring 145 may be disposed therein. A lubricating oil bore 150
connects the recess 146 to the head end of the working piston 111.
The press-on spring 145 in the non-tensioned state is longer than
the maximum distance between the head end of the bore 146 and the
opposite end of the cylinder bore 110. The press-on spring 145
therefore exerts a force both on the cylinder drum 106 and on the
working piston 111. The cylinder drum 106 is therefore held in
abutment with the control plate 118. The working piston 111 on the
other hand is held jointly with the sliding shoe 149 in abutment
with the contact surface 116 of the swash plate 115.
[0036] A sliding face 152 is formed on the sliding shoe 149. The
sliding face 152 preferably has at least one lubricating oil groove
151. The lubricating oil groove is connected by a connection bore
to the region in the spherical recess 148. The pressurized pressure
medium situated in the cylinder bore 110 is therefore conveyed
through the lubricating oil bore 150 and the connection bore in the
sliding shoe 149 to the lubricating oil groove 150, where it
effects a hydrostatic relief of the sliding shoe 149. The contact
area between the spherical recess 148 and the spherical head 147 is
further supplied with pressure medium for lubrication purposes.
Because of the ball-joint-like connection between the sliding shoe
149 and the spherical head 147 of the working piston 111 the
inclination of the sliding face 147 relative to the longitudinal
axis of the working piston 111 may be varied. It is thereby ensured
that the sliding face 152 may be adapted in every possible angular
position of the contact surface 147 relative to the axis of
rotation 144 of the cylinder drum 106. The spherical recess 148
encompasses the spherical head 147 to such an extent that tensile
forces may also be transmitted between the working piston 111 and
the sliding shoe 149.
[0037] For adjusting the angle of the contact surface 116 relative
to the axis of rotation 144 of the cylinder drum 106 the
positioning device 122 is provided.
[0038] For generating a positioning movement the positioning device
122 comprises a positioning piston 126. The positioning piston 126
is of an identical design to the working piston 111. A repeat
description of the individual components with regard to the
positioning piston 126 is therefore dispensed with. The positioning
piston 126 is connected by a joint connection 113' to a
positioning-piston sliding shoe 149'. The positioning-piston
sliding shoe 149' corresponds in its construction to the sliding
shoe 149 already described in connection with the working piston
111.
[0039] The positioning-piston sliding shoe 149' therefore also has
a sliding face 152' that is situated in abutment with the contact
surface 116. A positioning force that is exerted by the positioning
piston in FIG. 3 to the left may therefore be transmitted to the
contact surface 116 of the swash plate 115. In the recess 146 of
the positioning piston 126 a spring is likewise disposed. This
spring takes the form of a feedback spring 145'. The feedback
spring 1451 is supported on the one hand against the head end of
the recess 146' in the positioning piston 126. The opposite end of
the feedback spring 145' is supported against a spring bearing 147.
The spring bearing 147 in turn abuts a first end of a valve piston
158. There is therefore exerted on the valve piston 158 a force
that depends both upon the position of the valve piston 158 and
upon the position of the positioning piston 126. Thus, a
backward-driving force is exerted as positional information on the
positioning piston 158, as already described with reference to the
hydraulic circuit diagram of FIG. 2. This force is dependent upon
the position of the swash plate 115 and hence upon the adjusted
delivery volume.
[0040] The positioning device 122 comprises a positioning device
housing 153. The positioning device housing 153 is inserted,
preferably screwed, into a recess in the port plate 104. The port
plate 104 closes the housing 103 of the hydrostatic axial piston
machine 101.
[0041] The positioning device housing 153 has a stepped recess 154.
The stepped recess 154 takes the form of a bore and penetrates the
positioning device housing 153 along a longitudinal axis 162 of the
positioning device housing 153. The longitudinal axis 162 of the
positioning device housing 163 is preferably oriented parallel to
the axis of rotation 144 of the cylinder drum 106. However,
depending on the precise structural design of the port plate 104 a
slight deviation of a few degrees from parallel may also arise.
[0042] In the end of the positioning device housing 153 facing the
swash plate 115 a liner 155 is inserted. The liner 155 is of a
substantially pot-shaped design, wherein in the base of the liner
155 a through-opening is provided. The through-opening of the liner
155 is disposed approximately in the region of the first end of the
valve piston 158 and so dimensioned that the spring bearing 157 may
pass through.
[0043] The liner 145 is retained by means of a Seeger circlip ring
160 in the swash-plate end of the adjusting device housing 122. The
positioning piston 126 and the valve piston 158 are arranged
axially offset relative to one another in the positioning device
housing 153. The positioning piston 126 is workingly connected by
the feedback spring 145' to the valve piston 158. On the valve
piston 158 annular grooves 159, 160 are formed. By means of the
annular grooves 159, 160 a connection between a removal channel 131
and the positioning pressure chamber 135 may be established in
dependence upon the position of the valve piston 158 relative to
the positioning device housing 153. In dependence upon the position
of the valve piston 158 the annular groove 160 connects the removal
channel 131 to the port 161 covered in FIG. 3 by the valve piston
158. The port 161 is connected by a likewise non-illustrated
channel to the positioning pressure chamber 135. Upon loading of
the valve piston 158 with an axial force by the proportional magnet
123, however, the second annular groove 159 is brought into a
position, in which the port 161 is connected to the connection
channel 137 in a manner allowing throughflow. The connection
channel 137 is formed in the port plate 104.
[0044] The axial force that is generated by a proportional magnet
123 is transmitted by means of a tappet 159 to the end of the valve
piston 158 remote from the spring bearing 157. In the region of the
end of the valve piston 158 remote from the spring bearing 157 a
normal position spring 161 is disposed. The normal position spring
161 is supported on the one hand against the adjusting device
housing 163 and on the other hand against a collar 165.
[0045] By virtue of designing the adjusting device 122 using parts
that may be used both as working piston 111 and as sliding shoe
149, a considerable simplification of the hydrostatic axial piston
machine 101 is achieved. In particular, manufacture is made more
economical as a separate parts manufacture for the positioning
piston may be avoided. In particular, manufacture of the swash
plate 115 is also extremely simplified. In contrast to the axial
piston machine of prior art, all that is required is to produce a
uniformly flat contact surface 116 that extends over the entire
circumference of the swash plate 115. Not only is the plurality of
working pistons 111 supported via their sliding shoes 149 on this
contact surface 116 but a positioning force may also be transmitted
from the positioning piston 126 by means of the positioning-piston
sliding shoe 149' to the contact surface 116. To enable a resetting
of the swash plate 115, a restoring spring 133 is disposed at the
side of the swash plate 115 remote from the contact surface 116.
The restoring spring 133 loads the swash plate 115 with a restoring
force counter to the positioning force of the positioning piston
126.
[0046] If the pressure chamber 135 of the positioning device 122,
given a corresponding position of the valve piston 128, is
therefore relieved into the tank volume 28, then because of the
force of the restoring spring 133 the swash plate 115 is brought
back into its neutral position. In this neutral position the
hydrostatic axial piston machine 101 is adjusted to its maximum
delivery volume. Thus, given an unpressurized system because of the
neutral position of the hydrostatic axial piston machine 101 first
a pressure build-up in the working line 29 may occur. This built-up
pressure is then supplied, because of the normal position of the
valve piston 158, also to the pressure chamber 135. As a result of
this, an equilibrium of forces arises at the valve piston 158. The
equilibrium of forces exists between the force of the feedback
spring 145 acting upon the valve piston 158 and the equidirectional
force of the normal position spring 163 as well as the oppositely
directed force of the proportional magnet 123, which acts via the
tappet 159 upon the valve piston 158.
[0047] The supplying of the sliding face 152' of the
positioning-piston sliding shoe 159' is effected likewise in a
comparable manner to the previously described lubrication of the
sliding face 152 of the sliding shoe 149. For this purpose, the
sliding face 152' is connected by a connection bore as well as a
lubricating oil bore in the positioning piston 126 to the
positioning pressure chamber 135. Thus, from the pressure acting in
the positioning pressure chamber 135 a lubricating film is
generated both between the spherical head of the positioning piston
126 and at the sliding face 152'. An exact swiveling angle
adjustment is achieved as a result of the reduction of
friction.
[0048] The invention is not limited to the represented embodiment.
The axial piston machine may therefore also take the form of a
hydraulic motor and in particular individual features of the
invention may also be combined with one another.
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