U.S. patent number 3,834,281 [Application Number 05/325,889] was granted by the patent office on 1974-09-10 for control system for axial-piston machines and the like.
This patent grant is currently assigned to Linde Aktiengesellschaft. Invention is credited to Karl-Heinz Bergmann, Walter Heyl, Hermann Kern.
United States Patent |
3,834,281 |
Heyl , et al. |
September 10, 1974 |
CONTROL SYSTEM FOR AXIAL-PISTON MACHINES AND THE LIKE
Abstract
A motion-transmitting system for converting linear actuating
movement into a pivotal movement of a controlled member, especially
for the control of an axial-piston machine having a tiltable
controlled member by a working piston capable of linear movement,
comprises a cylindrical guide body rotating in a cylindrical bore
of a working piston and connected to the control member by a
cylindrical pin received in a transverse bore of the cylindrical
guide body. The pin is preferably threaded directly to the
controlled member of the axial piston machine.
Inventors: |
Heyl; Walter (Oberafferbach,
DT), Bergmann; Karl-Heinz (Feldkahl, DT),
Kern; Hermann (Grosskrozenburg, DT) |
Assignee: |
Linde Aktiengesellschaft
(Wiesbaden, DT)
|
Family
ID: |
5834571 |
Appl.
No.: |
05/325,889 |
Filed: |
January 22, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Jan 31, 1972 [DT] |
|
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2204466 |
|
Current U.S.
Class: |
91/506;
417/222.1 |
Current CPC
Class: |
F04B
1/122 (20130101); F04B 1/324 (20130101) |
Current International
Class: |
F04B
1/32 (20060101); F04B 1/12 (20060101); F01b
003/00 () |
Field of
Search: |
;91/377,378,422,466,506
;417/222 ;92/131 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Attorney, Agent or Firm: Ross; Karl F. Dubno; Herbert
Claims
We claim:
1. A motion-transmitting mechanism for an axial piston machine
comprising:
a linearly shiftable working piston formed with a first cylindrical
bore;
a cylindrical guide body rotatably received in said cylindrical
bore and snugly surrounded by said piston, said body being provided
with a second cylindrical bore having an axis transverse to the
axis of said first cylindrical bore and said body;
a cylindrical pin rotatably received in said second cylindrical
bore and shiftable therein while being snugly surrounded by said
body, said pin having an end projecting from said body along the
axis of said second cylindrical bore;
a swingable controlled member having a swing axis and connected to
said end for pivoting motion about said swing axis upon axial
displacement of said piston, said axial-piston machine comprising a
cylindrical drum rotatable about an axis perpendicular to said
swing axis and provided with a plurality of axially reciprocable
pump pistons, and a control disk acting upon ends of said pump
pistons, one of said drum and said control disks constituting said
controlled member, said pin threadedly engaging said control
member;
a cylinder receiving said working piston; and
a pilot piston controllable to feed fluid selectively to opposite
sides of said working piston for driving same in opposite
direction, said first bore lying between said opposite sides, said
working piston being formed with a passage leading from said pilot
piston to one side of said working piston, said passage
communicating with said first bore, said guide body being formed
with a recess at least along an arc of its circumference and
communicating with said passage.
2. The mechanism defined in claim 1 wherein said swing axis lies in
a plane at least substantially perpendicular to the axis of said
working piston and the axis of said first bore is at least
approximately parallel to said swing axis.
3. The mechanism defined in claim 1 wherein said swing axis is at
least approximately parallel to the axis of said working piston and
the axis of said first bore is at least approximately perpendicular
to a plane of said swing axis parallel to the axis of said working
piston.
4. The mechanism defined in claim 1 wherein said controlled member
is said disk.
5. The mechanism defined in claim 4 wherein said axial-piston
machine comprises a housing receiving said drum and said disk, said
mechanism further comprising means forming a cylinder for said
piston in said housing substantially parallel to the axis of said
drum and laterally offset therefrom, said piston being received in
said cylinder and defining at opposite ends of said piston working
chambers pressurizable to shift said working piston in opposite
directions, said working piston being formed with an axially
extending bore communicating with a source of control fluid and a
pilot piston received within said axially extending bore of said
working piston from controlling fluid flow to said chambers; and a
control pin extending laterally into said working piston and
engaging said pilot piston for shifting the latter and thereby
inducing said working piston to follow the motion of said pilot
piston.
6. A mechanism defined in claim 5 wherein said working piston is
provided with a passage extending through said first bore and
formed at least in part by a sectoral recess in said guide body for
communicating between one of said chambers and said pilot
piston.
7. The mechanism defined in claim 6 further comprising oppositely
effective spring means on either side of said working piston for
yieldably biasing same against displacement.
8. The mechanism defined in claim 7 wherein the axis of said first
bore is perpendicular to the axis of said working piston, the axis
of the pin received in said second bore is perpendicular to the
axis of said first bore and said swing axis is parallel to a plane
defined by the axis of said piston and the axis of said first bore.
Description
FIELD OF THE INVENTION
The present invention relates to a motion-transfer mechanism and
more particularly to a mechanism for converting linear displacement
of a control member into angular displacement of a controlled
member; the invention especially relates to axial-piston machines
using such mechanisms, e.g. for the pivotal operation of a flow
control member by a working piston.
BACKGROUND OF THE INVENTION
The term "axial-piston machine" is used generally in the art of
fluid mechanics to indicate broadly a hydraulic pump or hydraulic
motor having a plurality of pistons parallel to an axis of rotation
of a cylinder block or drum and angularly equispaced therearound,
the drum being rotated by an applied force in the case of a pump or
driving a shaft in the case of a motor.
Usually an axial-piston machine can operate either as a pump or as
a motor, depending upon whether an external force is applied to the
shaft or the shaft is to be driven by the supply of fluid from an
external source. Hence the expression axial-piston machine is
intended to identify machines of the general configuration
described below and which can either be a pump or a motor or which
can operate both as a pump or as a motor.
Axial-piston machines of this general type comprise a
fluid-distribution surface, generally lying in a plane
perpendicular to the axis of the drum or cylinder block and
provided directly, or thorugh the intermediary of a valve or
distribution plate, with arcuate or kidney-shaped fluid
distribution ports. The cylinder drum, barrel or block may be
rotable with a shaft extending perpendicular to this surface and
can be urged against the surface while being provided with a
plurality of bores extending axially within the cylinder drum and
angularly equispaced therearound, the cylinder bores communicating
by axially extending passages with the kidney-shaped ports. These
passages open at a face of the drum which bears against the fluid
distribution or fluid collection surface. The pistons, which are
reciprocable within these cylinder bores, extend from the cylinder
drum into engagement with an inclined plate or control plate which
may lie generally transverse to the axis of the drum at an angle
other than 90.degree. therewith so that, with rotation of the drum,
pistons in the region of closest approach of the plate to the drum
are urged inwardly and pistons as they approach the region of
greatest distance from the drum move outwardly, thereby alternately
contracting and expanding the chambers within each of the
cylinders. When the machine is operated as a pump, fluid is forced
under pressure from the cylinder bores as the compartments contract
and is drawn into the cylinder bores as the compartments expand.
When fluid under pressure is forced into a contracted compartment
of a machine operated as a motor, the piston is driven outwardly
and the system rotates to expand the compartments.
In hydrostatic or axial-piston transmissions, for example, the
output of an axial-piston pump may be connected to the inlet of an
axial-piston motor while the outlet of the motor is connected to
the input of the pump, thereby creating a relatively close
fluid-transmitting system between the two. As the pump displaces
fluid, the motor operates. Axial-piston machines of the type with
which the invention is concerned, are generally of the
variable-displacement type, the displacement being a function of
the angle at which the control plate intersects the drum axis. By
varying this angle it is possible to reduce the displacement to
zero, increase the displacement or reverse the direction to flow
substantially continuously and thus a transmission of this type is
generally a continuously variable torque-transmission system.
Variation of the output of the machine can be accomplished by
pivoting the control plate or disk or by pivoting the barrel or
cylinder drum about a swing axis perpendicular to but coplanar with
the drum axis and the shaft axis. In a position of the control
plate in which it is perpendicular to the drum axis and to the
shaft axis, there is zero displacement. An axial-piston hydraulic
machine of this type is disclosed in the commonly owned U.S. Pat.
No. 3,678,804.
Various means have been proposed for swinging the control plate and
the cylinder drum and, unless otherwise stated herein, any
description with respect to swinging movement of a control plate
can be considered as equally applicable to the swinging of the
cylinder barrel when the control plate is held stationary. Of
interest to the present application, however, are servo-type
control systems for the swingable control plate of an axial machine
and which employ a working piston connected to this control member.
In prior-art control mechanisms, which must convert the
substantially linear movement of the working piston into a pivotal
movement or angular movement of the controlled member, e.g., the
control plate, a pin or the like was threaded into a bore of the
control plate and was received in a sliding block, slot or other
camming system of the piston. This has the disadvantage that the
camming arrangement must be manufactured at high cost with low or
no tolerances to eliminate play. Furthermore, the forces applied to
the system were invariably of the type which could cause excessive
wear or even jamming of the device. Finally, it should be mentioned
that many of these prior art systems allowed only point or line
contact between the bearing surfaces, thereby increasing wear and
creating the possibility of excessive play.
OBJECTS OF THE INVENTION
It is the principal object of the present invention to provide an
improved motion-transmitting mechanism, especially for axial-piston
machines, which can be produced at low cost, has improved force
transmitting properties and low wear, is free from play, and is of
simple, reliable, adjustable and replaceable construction.
It is another object of the invention to provide an axial-piston
machine embodying an improved motion-transmitting mechanism having
the attributes set forth immediately above.
Another object of the invention is to provide an improved
controlled system for an axial-piston machine whereby the
disadvantages of the earlier systems set forth above can be
eliminated.
It is also an object of the invention to provide a
motion-transmitting mechanism which, at low cost, is substantially
free from locking or jamming and is capable of transmitting force
by surface-to-surface contact rather than the line contact or point
contact characterizing earlier systems.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are
attained, in accordance with the present invention with a
motion-transmitting mechanism between a linear actuator and a
swingable controlled member, the linear actuator having a working
piston provided with a transverse bore of cylindrical
configuration. Within this bore there is received a cylindrical
guide body, snugly fitting within and at least rotatable in this
bore in substantially all-around contact with the wall thereof.
According to an essential feature of the invention, this guide body
is provided with a cylindrical guide bore transversely to the axis
of the cylindrical body and intersecting same or somewhat offset
therefrom. Preferably, the axis of the guide bore is perpendicular
to the axis of the cylindrical body and receives a cylindrical pin
fixed to the swinging member.
Upon swinging movement of the latter member with axial displacement
of the working piston, this pin slides axially within the guide
bore and/or rotates about its axis while the cylindrical guide body
rotates about its axis and forces transmit between the piston and
the angularly adjustable member by surface-to-surface contact
without the danger of jamming.
When the axis of the bore in the piston (receiving the cylindrical
guide body) is not parallel to the axis about which the controlled
member swings (hereinafter referred to as the swinging axis), the
pin will rotate in the guide body.
The position of the piston axis with respect to the swing axis is
not of significance since the relatively movable force transmitting
elements, namely, the cylindrical guide body and the cylindrical
pin, can shift relatively to compensate for any relative position
of the two axes.
An important advantage of the system described above is found in
the fact that all relative movement between the piston and the
swingable control member can be compensated by relative
displacement of the pin and the cylindrical guide body so that the
piston need not be rotated in its bore. It will be understood that
such pistons frequently are provided with bores co-operating with
bores in the cylinder wall or with seats which are detrimentally
affected by relative rotation of the working piston and its
cylinder. In addition, the nonrotatability of the working piston
allows the latter to accommodate a pilot piston or valve which can
be actuated by a pin extending laterally into the working piston.
The pin, which can be connected to a lever or other control
mechanism, thus serves to limit rotation of the working piston but,
because of the cylindrical force transmitting elements described
above, does not need to withstand stress. Moreover, the use of
cylindrical force-transmitting elements permits the system to be
manufactured easily, inexpensively and with small manufacturing
tolerances.
Yet another advantage of the system, especially important for the
large-scale production of axial-piston means, is the fact that the
force-transmitting elements allow various orientations of the
piston- and -cylinder arrangement with respect to the axis of the
machine and the swing axis. For example, the axis of the pin may
intersect the swing axis or may be substantially parallel thereto.
In the latter case, during the swinging movement, the guide body
also may shift axially in the working piston because the axis of
the pin describes a circular arc-segmental path about the swinging
axis.
The system of the present invention permits one and the same
working piston, with its associated working cylinder, to be
positioned in various configurations with appropriate modification
of position of the guide body. This is especially significant when
the motion-transmitting mechanism is used as the control device for
different axial-piston pumps.
For example, the same control mechanism can be used with
axial-piston pumps with adjustable control disks since the axis of
the cylindrical bore is at least approximately parallel to the axis
of the shaft and to the cylinder drum.
The pin can lie precisely in the plane of the axis of the shaft and
the axis of the piston, when the latter axes are parallel, or can
be offset from this plane when tis arrangement is more desirable
for space considerations. With the lateral offset of the pin from
the shaft axis large enough, we may provide an arrangement such
that the axis of the pin may be parallel to the swing axis. Of
course, the axis of the pin may be swung through 90.degree. so that
the axis of the pin lies parallel to the swing axis but the
guide-body axis is swung through 90.degree. as well. The axis of
the piston can thus be parallel to the axis of the motor shaft or
the right angles thereto so that the axis of the piston lies in a
plane to which the axis of the shaft is perpendicular. This latter
arrabgement has been found to be most desirable for swinging-drum
axial-piston machines. Furthermore, the bore in which the pin is
threaded, e.g., on a pivoting control plate, may be tilted in one
way or another during manufacture, the force-transmitting assembly
compensating for it.
It has also been found to be advantageous to provide the guide body
with an arc-segmental recess through which fluid is fed to one of
the compartments of a double-acting piston for the purposes
described. This arrangement has also been found to be advantageous
in reducing oil-and pressure-leakage or rendering the same
ineffective in limiting efficient operation of the system. Also,
the assembly and adjustment of the device are simple, economical
and designed to facilitate mass production of the parts.
DESCRIPTION OF THE DRAWING
The above and other objects, features and advantages of the present
invention will become more readily apparent from the following
description, reference being made to the accompanying drawing in
which:
FIG. 1 is an axial cross-sectional view taken generally along the
line I--I of FIG. 2, showing an axial-piston machine provided with
a motion-transmitting mechanism according to the invention;
FIG. 2 is a cross-sectional view taken along line II--II of FIG.
1;
FIG. 3 is an enlarged perspective view of the guide body of the
mechanism shown in FIG. 2;
FIG. 4 is a cross-sectional view through a guide body according to
another embodiment of the invention; and
FIG. 5 is a view similar to FIG. 2 of a fragment of another
embodiment of the invention.
SPECIFIC DESCRIPTION
In FIGS. 1 through 3 of the drawing, we show an axial-piston
machine, e.g., an axial-piston pump, which may form part of a power
transmission in accordance with conventional principles discussed
above.
This pump comprises a housing 1 closed at one end by a cover plate
2 and provided with a shaft 3 journaled in self-aligning roller
bearing 4 and 5. The shaft 3 may be coupled at its threaded end 3a
to an electric, internal combustion or other motor or engine, has a
cylindrical portion 3b receiving the inner race of roller bearings
4 and a shoulder 3c abutting this inner race to form a
thrust-resisting member therewith. At the opposite end of the shaft
3, a cylindrical portion 3d receives the inner race of roller
bearings 5 and a shaft has a shoulder 3e which axially abuts this
inner race. A central portion 3f is splined to rotatably entrain a
cylindrical drum 6 in which pistons 11 are reciprocable, the
pistons being angularly equispaced about the axis A of the
drum.
Each of the pump pistons 11 is received within a cylinder bore 6a
extending axially in the cylinder drum or block 6 and vented at 6b
to the chamber 1a surrounding the cylinder drum. Each piston 11 is
also provided with a generally spherical head 11a which is received
with two degrees of freedom in the generally spherical socket 10a
of a shoe 10 whose surface 10b slidingly engages the annular face
9a of a swingable control disk 9. A retaining ring 9b which rests
upon a hub 9c of spherical outer configuration, centered upon the
axis of swing B of the disk 9, retains the shoes 10 axially against
the surface 9a. The hub 9c is seated upon a boss 6c of the cylinder
drum so that the latter is urged to the right by the spring disk
9b.
The shoes 10 are provided with passages 10c connecting the socket
interfaces with the surface interfaces 9a, 10b to insure
lubrication of the sliding parts.
At their ends, remote from the control disk 9, the cylinders 6a
communicate via axial passages 6d with registering passages formed
in a valve plate 40 whose apertures 41 and 42 may have the
kidney-shaped configuration customarily used to distribute fluid to
or receive fluid from the cylindrical drum of an axial piston
machine.
Apertures 41 and 42, in turn, communicate with passages 43 and 44
of the cover 2 and these passages terminate in ports 7 and 8 for
the entry of fluid 2 and its discharge from the pump.
The control disk 9 (FIG. 2) has a pair of hubs 9d and 9e
diametrically opposite locations along its pivot axis B and journal
in roller bearings 37 and 38 of the housing. A threaded boss 9f is
also provided for connection to the control piston as will be
apparent hereinafter. It will be evident that, when the disk 9 lies
in a plane perpendicular to axis A, there is no axial displacement
of the pistons 11 and rotation of the drum by a motor does not
displace fluid. When the disk 9 is canted or tilted about its swing
axis B in one sense from this perpendicular position, rotation of
the drum will cause certain pistons 11 to be drawn axially out of
the cylinder and certain pistons to be placed further into the
respective cylinders as the drum rotates, thereby alternately
drawing fluid into each cylinder and discharging fluid therefrom,
effecting a pumping action.
Along the upper side of housing 1, there is provided a means for
actuating the control disk 9, in the form of a fluid-responsive
servomechanism. The servomechanism comprises a cylinder housing 12
which is mounted on the top of the housing 1 and which slidably
receives a working piston 13 whose axis C is here shown to lie
parallel to the axis A of the cylinder drum and in the section
plane of FIG. 1. The piston 13 is formed with a transverse
cylindrical bore 13' in which a cylindrical guide body 14 is
rotatably received, this guide body having an axis D which is
generally parallel to the axis B and is perpendicular to the axis
C. On opposite sides of the cylindrical bore 13', there are
provided recesses or openings 15 in the piston 12, into which the
opposite ends of a pin 16 projects. The pin 16 is axially shiftable
and rotatable in a bore 14a of the cylindrical guide body 14, the
axis E of pin 16 lying perpendicular to the axis C (in one position
as illustrated of the pin 16) and perpendicular to the axis D.
Thus, the axis of pin 16 is perpendicular (in the latter position)
to the plane defined by the axes C and D of the working piston 13
and the cylindrical guide body 14, respectively.
At its lower end, the pin 16 is provided with a thread 17 screwed
into the boss 9f of the complementarily threaded control disk 9,
while the other end of the pin 16 is provided with an internal
hexagonal socket 18 adapted to receive an Allen wrench. The Allen
wrench may be inserted in a threaded bore in cylinder 12, in axial
alignment with the pin 16, which is closed by a plug 19. This
enables the pin to be screwed into the disk or to be removed
therefrom.
Cylinder 12 is closed at its right-hand end by a cylindrical
housing 20 forming a seat for a pair of springs 21 of the coil
compression type, the springs being seated against a plate 22.
The working piston 13 is provided with a threaded axially extending
bore receiving a pair of counterlocking screws 24 and 25 having
Allen-wrench hexagonal sockets and adapted to be rotated counter to
one another to lock an adjustment of the working piston into the
system. The screw 25 rests against the spring seat 22 when the
working piston 13 is in the position shown in FIG. 1 and the
swinging control disk 9 is perpendicular to the shaft 3.
A spring 26 whose spring force is only about half the spring force
of springs 21 bears upon the working piston 13 from the left, i.e.,
in the direction opposite the applied force of springs 21. Spring
26 thus biases the working piston 13 to the right so that its screw
24 rests against the spring seat 22 as long as neither the right
nor the left hand effective faces of the piston 13 are under fluid
pressure.
The piston 13 is also provided with a throughgoing axially
extending control bore 27 in which a control piston 28 is
longitudinally shiftable. The piston 28, constituting a valve
member, is, in turn, selectively shiftable by a control pin 30
which extends into a lost-motion slot 28a of this valve member and
is controlled by mechanical means not illustrated in the drawing,
e.g., by a transmission-ratio or reversing lever. The piston 13 is
provided with a bore 29 communicating with an annular chamber 27a
surrounding the valve portion 28b of this valve member which is
also formed with an axially extending bore 28c for servo-operation
of the main piston 13. Hydraulic fluid can be admitted to the
cylinder 12 through a port not structurally illustrated in the
drawing to supply the actuating fluid for the control piston.
Consequently, when the pin 30 shifts the control piston 28 to the
left (FIG. 1), hydraulic fluid is permitted to flow through the
chamber 27a past the valve member 28b and through the passage 29 to
the right-hand side of the piston 13 and into the cylinder housing
20, thereby shifting the piston 13 to the left. Conversely, if the
piston 28 is shifted by pin 30 to the right, the valve is unblocked
to permit fluid to flow through the bore of piston 28 and a bore 31
therein to the left-hand side of piston 13, thereby shifting it to
the right to follow the movement of valve member 28. Member 28 thus
constitutes a pilot piston for the working piston 13. The left-hand
side of bore 12 is closed by a plate 32 to constitute one of the
working chambers, effective in the direction opposite that of the
working chamber formed by cylinder housing 20.
The connecting bore or passage 31 terminates at the transverse bore
13' receiving the guide body 14 and to permit the control fluid to
pass this body, it is formed with a sectoralrecess or groove 32
which communicates with bore 31 and the axial bore 27. Thus, the
control fluid from pilot valve 28 can flow through the recess 32
and passage 31 into the working chamber closed by plate 32.
A threaded plate 33 in cylinder housing 20 can be removed, when
necessary, to provide an axial aperture through which the second
screws 24 and 25 can be adjusted with Allen wrenches, thereby
adjusting the position of the working piston 13 in the neutral
position of the system as illustrated.
When the working piston 13 is shifted in cylinder 12, the control
disk 9 is swung about its axis B by the cylindrical pin which is
rotatable and axially shiftable within the cylindrical guide body
14. The pin 16 thus describes a circular arc about the common axis
of the bearings 37 and 38 at its end 17 threaded into the control
disk 9. During this movement, the pin 16 and the cylindrical guide
body 14 swing about the axis D, the pin being slightly canted from
its position as illustrated in FIG. 1. Should the thread 17 in the
boss 9f be slightly inclined as a result of a manufacturing error,
this will mean that the pin 16 will be slightly inclined to the
section plane II--II illustrated in FIG. 1 and the guide body 14
slightly rotated angularly about its axis D. The compensation may
be effected by adjusting the position of the piston 13 as
previously described. Should the thread 17 of the boss 9f be
manufactured with a slight deviation out of the plane of the
drawing in FIG. 1, a slight rotation of the piston 13 is all that
is required to compensate.
In FIG. 4 we show an arrangement in which the cylindrical guide
body 14 receives the pin 116 with an off-set between the axis D' of
guide body 114 and E' of the axis of pin 116. Of course, the pin 16
can be rotated through 90.degree. from its position as illustrated
with a corresponding rotation of the guide body 14. This has been
shown in FIG. 5 in which the cylindrical body 14 received the pin
16 which engages a lug 9f of the control disk 9'. A similar
modification can provide an arrangement in which the swinging axis
of the control disk 9 is approximately parallel to the axis of the
working piston and the axis of the bore-receiving pin 16 is
approximately perpendicular to the plane of the swing axis and
parallel to the axis of the working piston.
* * * * *