U.S. patent application number 11/535162 was filed with the patent office on 2007-06-21 for axial piston machine having an adjustable bent axis valve segment and a variable unit for the electrically proportional adjustment of the displacement.
This patent application is currently assigned to SAUER-DANFOSS INC.. Invention is credited to Wilhelm GOLLNER, Markus REIMER.
Application Number | 20070137475 11/535162 |
Document ID | / |
Family ID | 38109102 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070137475 |
Kind Code |
A1 |
REIMER; Markus ; et
al. |
June 21, 2007 |
AXIAL PISTON MACHINE HAVING AN ADJUSTABLE BENT AXIS VALVE SEGMENT
AND A VARIABLE UNIT FOR THE ELECTRICALLY PROPORTIONAL ADJUSTMENT OF
THE DISPLACEMENT
Abstract
The invention relates to an axial piston machine having an bent
axis segment which is adjustable by means of an actuating piston,
and a variable unit for the electrically proportional adjustment of
the displacement. The variable unit has a control piston for
controlling the oil pressure which displaces the actuating piston,
an electrically controllable proportional solenoid which acts on
the control piston, a feedback spring on the control piston for
retracting the instantaneous Bent axis valve segment and a
adjustment mechanism for setting the start current. To set the
start current, the adjustment mechanism has a setting spring which
acts on the armature of the proportional solenoid with an
adjustable force.
Inventors: |
REIMER; Markus; (Klein
Nordende, DE) ; GOLLNER; Wilhelm; (Neumunster,
DE) |
Correspondence
Address: |
ZARLEY LAW FIRM P.L.C.
CAPITAL SQUARE, 400 LOCUST, SUITE 200
DES MOINES
IA
50309-2350
US
|
Assignee: |
SAUER-DANFOSS INC.
Ames
IA
|
Family ID: |
38109102 |
Appl. No.: |
11/535162 |
Filed: |
September 26, 2006 |
Current U.S.
Class: |
91/505 |
Current CPC
Class: |
F01B 3/0002
20130101 |
Class at
Publication: |
91/505 |
International
Class: |
F01B 3/00 20060101
F01B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2005 |
DE |
10 2005 060 960.0 |
Claims
1. Axial piston machine having a Bent axis valve segment which is
adjustable by means of an actuating piston, and a variable unit (2)
for the electrically proportional adjustment of the displacement,
which has a control spool (7) for controlling the oil pressure
which displaces the actuating piston (10), an electrically
controllable proportional solenoid (3) which acts on the control
spool (7), a feedback spring (9) on the control spool (7) for
retracting the instantaneous Bent axis valve segment and a
adjustment mechanism (16) for setting the start current, the
adjustment mechanism (16) having a setting spring (4) which acts on
the armature (5) of the proportional solenoid (3) with an
adjustable force.
2. Axial piston machine according to claim 1, in which the force of
the setting spring (4) is directed counterto the force of the
feedback spring (9)
3. Axial piston machine according to claim 1, in which the setting
spring (4) is integrated into the proportional solenoid (3).
4. Axial piston machine according to claim 1, in which the setting
spring (4) and the armature (5) of the proportional solenoid (3)
and also the control valve are arranged along a common axis.
5. Axial piston machine according to claim 1, in which the setting
spring (4), the armature (5), the control spool (7), the feedback
spring (9) and the actuating piston (10) are arranged along a
common axis.
6. Axial piston machine according to claim 1, in which the feedback
spring (9) is held at one side by a bore of the actuating piston
(10) and rests at the other side on the control spool (7) via a
spring seat (8)
7. Axial piston machine according to claim 1, in which the setting
spring (4) force which acts on the armature (5) is adjustable by
means of a adjustment screw (17) which is arranged in the
longitudinal direction of the Bent axis.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to an axial piston machine having an
adjustable Bent axis valve segment and a variable unit f or the
electrically proportional adjustment of the displacement according
to the features of claim 1.
[0002] To set the displacement, axial piston machines of this type
which are embodied as variable displacement motors have a Bent axis
valve segment, the position of which can be adjusted by means of an
actuating piston. The actuating piston is controlled by a control
spool which, when displaced along its longitudinal axis, connects
or disconnects ducts in such a way that oil which is at a certain
pressure is made available to displace the actuating piston. Axial
piston machines are often equipped with electrically proportional
adjustment means. The input signal in a variable unit of this type
is an electric current which controls a proportional solenoid which
displaces and acts on the control piston. The output signal is the
hydraulic pressure which acts on the actuating piston.
[0003] In order to adjust the axial piston machine to the
displacement set by the adjustment device, a feedback spring is
provided which closes the control loop. The instantaneous swivel
angle of the valve segment is fed back to the control piston by the
feedback spring in such a way that when the set value is reached,
said control piston is returned to its initial position by the
force of the feedback spring which opposes the setting force of the
proportional solenoid.
[0004] When starting up using hydrostatic drives, the variable
displacement pump which supplies the motor is generally initially
set to the maximum feed volume, before the variable displacement
motor, which is normally initially at the maximum angle when
starting up occurs, is to begin swiveling. The electrically
controlled, servo-adjusted hydrostatic variable displacement motors
are intended to depart from the initial swivel angle, and thus vary
the displacement per revolution, at a defined current, the start
current. Normally, a fixed current value is provided by the
electronics for this purpose.
[0005] However, the elements used for adjustment and closed-loop
position control such as a proportional solenoid, piston, feedback
springs etc. have unavoidable tolerances which leads to
considerable fluctuations in the forces which occur. The deviations
in the force ratios are normally so large that, without
compensation for the tolerances, the variable displacement motors
would actually depart from the initial swivel angle at very
different start currents, and the driving behaviour would
correspondingly vary from vehicle to vehicle.
[0006] The tolerances are normally compensated for by means of the
feedback spring system, the force action of which is directed
counter to the actuating force of the magnet, with the result that
the return force which forces the system into the initial position
is set. A complex adjustment mechanism and at least one further
spring, the force action of which is adjustable and is likewise
directed counter to the proportional solenoid, are necessary for
this purpose.
SUMMARY OF THE INVENTION
[0007] With the present invention, it is intended to produce an
axial piston machine having an improved setting capability to
compensate for deviations from the desired start current.
[0008] According to the invention, this goal is achieved with an
axial piston machine having an adjustable Bent axis valve segment
which is adjustable by means of an actuating piston, and a variable
unit for the electrically proportional adjustment of the
displacement, which machine has a control piston for controlling
the oil pressure which moves the actuating piston, an electrically
controllable proportional solenoid which acts on the control
piston, a feedback spring on the control piston for retracting the
instantaneous Bent axis valve segment and a adjustment mechanism
for setting the start current, the adjustment mechanism having a
setting spring which acts on the armature of the proportional
solenoid with an adjustable force.
[0009] One particular advantage of the setting spring according to
the invention is the fact that the force of said setting spring is
directed counter to the force of the feedback spring, resulting in
a particularly favourable setting capability for the force ratio
between the proportional solenoids and the feedback spring.
[0010] The setting spring is preferably integrated into the
proportional solenoid. The adjustment mechanism forms, together
with the magnet, one structural unit, which considerably reduces
the number of individual elements for assembly.
[0011] A further advantage of the arrangement according to the
invention is that the setting spring and the armature of the
proportional solenoid and also the control valve can be arranged
along a common axis, along which the feedback spring and the
actuating piston can also be arranged, resulting in an inline
return system, which requires no additional attachments to the end
housing, along the Bent axis.
[0012] The feedback spring is preferably held at one side by a bore
of the actuating piston, while resting at the other side on the
control spool via a spring seat. The setting spring force which
acts on the armature is adjustable by means of a adjustment screw
which is arranged in the longitudinal direction of the Bent axis,
as a result of which it is possible to adjust the preload with
which the spring acts on the armature, and thus the force ratio
between the actuating force of the magnet and the spring force of
the feedback spring, and also, as a result, a defined start
current.
[0013] Further features and advantages are disclosed in the
following description of the exemplary embodiment presented with
reference to FIG. 1.
BRIEF DESCRIPTION OF THE DRAWING
[0014] FIG. 1 is a sectional view of an axial piston machine.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The figure shows an axial piston machine 1 of bent axis
design having a valve segment 14, the swivel angle of which is
adjustable by means of the swivel mechanism 13. The swivel
mechanism 13 is actuated by the actuating piston 10, the
displacement of the motor being set in accordance with the swivel
angle of the valve segment 14. 011 pressure is applied to the
actuating piston 10 via ducts formed in the valve block 11 and in
the end housing 12 and during this time, it executes a linear
movement along the Bent axis 15.
[0016] For the adjustment of the actuating piston, the variable
unit 2 has a control valve and a proportional solenoid 3 which are
arranged one behind the other along the common Bent axis 15. When
displaced along this axis 15, the control spool 7 opens or closes
the ducts in the valve block 11 which lead to the actuating piston,
and is operatively connected to the ram or the armature 5 of the
proportional solenoid 3.
[0017] An adjustment mechanism 16 is integrated into the
proportional solenoid 3, which adjustment mechanism 16 serves to
compensate for tolerances and comprises a setting spring 4 and a
adjustment screw 17 which are both arranged in the direction of the
Bent axis 15. The adjustable force of the setting spring 4 acts
here on the armature 5, which is situated within the winding 6, of
the proportional solenoid 3 with a force which opposes that of the
feedback spring 9. The opening through which the adjustment screw
17 leads out is sealed off by means of a sealing element 18.
[0018] The feedback spring 9 is clamped between the spring seat 8
of the control spool 7 and the actuating piston 10. It rests at one
side on the spring seat 8 of the control spool 7 and at the other
side on the actuating piston 10 where it is partially held by a
bore in the actuating piston 10.
[0019] The arrangement operates as follows:
[0020] If a certain current is applied to the proportional solenoid
3, its armature 5 is displaced, and with it moves the control spool
7 which thus moves out of its initial position until the actuating
force of the magnet 3 is in equilibrium with the opposing force of
the feedback spring 9. At the same time, oil pressure is applied to
the actuating piston 10 via the unblocked ducts. Said actuating
piston 10 likewise moves out of its neutral position and, by means
of the swivel mechanism 13, adjusts the swivel angle of the valve
segment 14 and thus the displacement of the axial piston
machine.
[0021] As the actuating piston 10 is displaced out of its initial
position, the force of the feedback spring 9 increases and from
then on overcomes the actuating force of the magnet 3, and it
retracts the control spool 7 again until, when the set swivel angle
is reached, said control spool 7 reaches its initial position again
in which the ducts leading to the actuating piston 10 are closed.
The adjustment mechanism 16 which is integrated into the
proportional solenoid 3 is provided to compensate for tolerance
deviations. The preload of the setting spring is increased or
decreased by turning the adjustment screw 17. Its spring force
acts, via the armature 5 of the proportional solenoid 3, on the
control spool 7 and changes the force equilibrium of the
proportional solenoid 3 and of the feedback spring 9 which is
connected to the control spool 7 by means of the spring seat 8. The
force of the setting spring 4 is directed here in the direction of
the actuating force of the magnet counter to the force of the
feedback spring 9.
[0022] A simple adjustment mechanism for setting the start current
is produced by means of this arrangement, the complex and costly
apparatuses which are otherwise provided for this purpose being
dispensed with.
* * * * *