U.S. patent application number 15/683826 was filed with the patent office on 2018-03-01 for variable displacement hydraulic pump with electromechanical actuator and method thereof.
This patent application is currently assigned to Schaeffler Technologies AG &. The applicant listed for this patent is Schaeffler Technologies AG & Co. KG. Invention is credited to Joseph Johnson, Jonathan Richards.
Application Number | 20180058449 15/683826 |
Document ID | / |
Family ID | 61242027 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180058449 |
Kind Code |
A1 |
Johnson; Joseph ; et
al. |
March 1, 2018 |
VARIABLE DISPLACEMENT HYDRAULIC PUMP WITH ELECTROMECHANICAL
ACTUATOR AND METHOD THEREOF
Abstract
A pump, including: inlet port and outlet ports; a cylinder block
including a piston disposed in a through-bore; a swash plate
engaged with the piston; a drive shaft non-rotatably connected to
the drive shaft, arranged to rotate the cylinder block to draw
fluid through the inlet port into the through-bore and to expel the
fluid from the through-bore and through the outlet port and
including an axis of rotation; an axis transverse to the axis of
rotation; and an actuator including a roller screw; a nut disposed
about the roller screw and in threaded contact with the roller
screw; an actuator pin; and an electric motor arranged to rotate
the roller screw or the nut to axially displace the actuator pin to
pivot the swash plate or the cylinder block about the axis and
control an amount of the fluid expelled from the through-bore.
Inventors: |
Johnson; Joseph;
(Mooresville, NC) ; Richards; Jonathan; (Waxhaw,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schaeffler Technologies AG & Co. KG |
Herzogenaurach |
|
DE |
|
|
Assignee: |
; Schaeffler Technologies AG
&
Herzogenaurach
DE
|
Family ID: |
61242027 |
Appl. No.: |
15/683826 |
Filed: |
August 23, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62380769 |
Aug 29, 2016 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 49/12 20130101;
F04C 14/185 20130101; F04B 1/324 20130101 |
International
Class: |
F04C 14/18 20060101
F04C014/18 |
Claims
1. A variable displacement hydraulic pump, comprising: an inlet
port; an outlet port; a cylinder block including a first piston
disposed in a first through-bore; a swash plate engaged with the
first piston; a drive shaft: non-rotatably connected to the
cylinder block; arranged to rotate the cylinder block to draw fluid
through the inlet port into the first through-bore and to expel the
fluid from the first through-bore and through the outlet port; and,
including an axis of rotation; an axis transverse to the axis of
rotation; and, an actuator including: a roller screw; a nut
disposed about the roller screw and in threaded contact with the
roller screw; an actuator pin engaged with the roller screw; and,
an electric motor arranged to rotate the roller screw or the nut to
axially displace the actuator pin to: pivot the swash plate about
the axis and control an amount of the fluid expelled from the first
through-bore; or, pivot the cylinder block about the axis and
control an amount of the fluid expelled from the first
through-bore.
2. The variable displacement hydraulic pump of claim 1, wherein the
actuator includes a resilient element urging the roller screw in a
first axial direction.
3. The variable displacement hydraulic pump of claim 1, wherein:
the electric motor is arranged to rotate the roller screw or the
nut to axially displace the actuator pin to pivot the swash plate
about the axis; the cylinder block includes: a second through-bore;
and, a second piston disposed in the second through-bore and
engaged with the swash plate; and, rotation of the cylinder block
is arranged to: displace the first piston within the first
through-bore; displace the second piston within the second
through-bore; draw the fluid through the inlet port into the second
through-bore; and, expel the fluid from the second through-bore and
through the outlet port.
4. The variable displacement hydraulic pump of claim 1, wherein:
the electric motor is arranged to rotate the roller screw or the
nut to pivot the cylinder block about the axis; the cylinder block
includes: a second through-bore; and, a second piston disposed in
the second through-bore and engaged with the swash plate; and,
rotation of the cylinder block is arranged to: displace the first
piston within the first through-bore; displace the second piston
within the second through-bore; draw the fluid through the inlet
port into the second through-bore; and, expel the fluid from the
second through-bore and through the outlet port.
5. The variable displacement hydraulic pump of claim 1, wherein:
the electric motor is arranged to rotate the roller screw to
axially displace the actuator pin to pivot the swash plate about
the axis; the electric motor is arranged to rotate the roller screw
in a first circumferential direction about the axis of rotation to
displace the actuator pin in a first axial direction; the actuator
pin is arranged to pivot the swash plate about the axis in a second
circumferential direction to increase the amount of fluid expelled
from the first through-bore; the electric motor is arranged to
rotate the roller screw in a third circumferential direction,
opposite the first circumferential direction, about the axis of
rotation to displace the actuator pin in a second axial direction,
opposite the first axial direction; and, the actuator pin is
arranged to pivot the swash plate about the axis in a fourth
circumferential direction, opposite the second circumferential
direction to decrease the amount of fluid expelled from the first
through-bore.
6. The variable displacement hydraulic pump of claim 1, wherein:
the electric motor is arranged to rotate the nut to axially
displace the actuator pin to pivot the swash plate about the axis;
the electric motor is arranged to rotate the nut in a first
circumferential direction about the axis of rotation to displace
the actuator pin in a first axial direction; the actuator pin is
arranged to pivot the swash plate about the axis in a second
circumferential direction to increase the amount of fluid expelled
from the first through-bore; the electric motor is arranged to
rotate the nut in a third circumferential direction, opposite the
first circumferential direction, about the axis of rotation to
displace the actuator pin in a second axial direction, opposite the
first axial direction; and, the actuator pin is arranged to pivot
the swash plate about the axis in a fourth circumferential
direction, opposite the second circumferential direction to
decrease the amount of fluid expelled from the first
through-bore.
7. The variable displacement hydraulic pump of claim 1, wherein:
the electric motor is arranged to rotate the roller screw to
axially displace the actuator pin to pivot the cylinder block about
the axis; the electric motor is arranged to rotate the roller screw
in a first circumferential direction about the axis of rotation to
displace the actuator pin in a first axial direction; the actuator
pin is arranged to pivot the cylinder block about the axis in a
second circumferential direction to increase the amount of fluid
expelled from the first through-bore; the electric motor is
arranged to rotate the roller screw in a third circumferential
direction, opposite the first circumferential direction, about the
axis of rotation to displace the actuator pin in a second axial
direction, opposite the first axial direction; and, the actuator
pin is arranged to pivot the swash plate about the axis in a fourth
circumferential direction, opposite the second circumferential
direction to decrease the amount of fluid expelled from the first
through-bore.
8. The variable displacement hydraulic pump of claim 1, wherein:
the electric motor is arranged to rotate the nut to axially
displace the actuator pin to pivot the cylinder block about the
axis; the electric motor is arranged to rotate the nut in a first
circumferential direction about the axis of rotation to displace
the actuator pin in a first axial direction; the actuator pin is
arranged to pivot the cylinder block about the axis in a second
circumferential direction to increase the amount of fluid expelled
from the first through-bore; the electric motor is arranged to
rotate the nut in a third circumferential direction, opposite the
first circumferential direction, about the axis of rotation to
displace the actuator pin in a second axial direction, opposite the
first axial direction; and, the actuator pin is arranged to pivot
the cylinder block about the axis in a fourth circumferential
direction, opposite the second circumferential direction to
decrease the amount of fluid expelled from the first
through-bore.
9. The variable displacement hydraulic pump of claim 1, wherein:
the actuator pin is arranged to pivot the swash plate about the
axis; and, the actuator pin is arranged to pivot the swash plate
about the axis to control an extent of displacement of the first
piston within the first through-bore.
10. The variable displacement hydraulic pump of claim 1, wherein:
the actuator pin is arranged to pivot the cylinder block about the
axis; and, the actuator pin is arranged to pivot the cylinder block
about the axis to control an extent of displacement of the first
piston within the first through-bore.
11. A variable displacement hydraulic pump, comprising: an inlet
port; an outlet port; a cylinder block including: a through-bore;
and, a piston at least partially disposed in the through-bore; a
drive shaft: non-rotatably connected to the cylinder block;
arranged to rotate the cylinder block to displace the piston to
draw fluid through the inlet port into the through-bore and expel
the fluid from the through-bore and through the outlet port; and,
including an axis of rotation; an axis transverse to the axis of
rotation; an actuator including: a roller screw; a nut disposed
about and in contact with the roller screw; an actuator pin engaged
with the roller screw and the swash plate; and, an electric motor
arranged to rotate the roller screw to axially displace the
actuator pin to: pivot the swash plate about the axis and control
an amount of the fluid expelled from the through-bore; or, pivot
the cylinder block about the axis and control an amount of the
fluid expelled from the through-bore.
12. A variable displacement hydraulic pump, comprising: an inlet
port; an outlet port; a cylinder block including: a through-bore;
and, a piston at least partially disposed in the through-bore; a
drive shaft: non-rotatably connected to the drive shaft; arranged
to rotate the cylinder block to displace the piston to draw fluid
through the inlet port into the through-bore and expel the fluid
from the through-bore and through the outlet port; and, including
an axis of rotation; an axis transverse to the axis of rotation; an
actuator including: a roller screw; a nut disposed about and in
contact with the roller screw; an actuator pin engaged with the
roller screw and the swash plate; and, an electric motor arranged
to rotate the nut to axially displace the actuator pin to: pivot
the swash plate about the axis and control an amount of the fluid
expelled from the through-bore; or, pivot the cylinder block about
the axis and control an amount of the fluid expelled from the
through-bore.
13. A method of operating the variable displacement hydraulic pump
of claim 1, comprising: rotating, with the drive shaft, the
cylinder block; drawing the fluid through the inlet port and into
the first through-bore; expelling the fluid from the first
through-bore and through the outlet port; rotating, with the
electric motor, the roller screw or the nut; axially displacing the
actuator pin; and, pivoting, with the actuator pin: the swash plate
about the axis and controlling an amount of the fluid expelled from
the first through-bore; or, the cylinder block about the axis and
controlling an amount of the fluid expelled from the first
through-bore.
14. The method of claim 13, further comprising: blocking, with a
resilient element in the actuator, axial displacement of the
actuating pin.
15. The method of claim 13, further comprising: pivoting, with the
actuator pin, the swash plate about the axis; rotating, with the
electric motor, the roller screw in a first circumferential
direction about the axis of rotation; displacing, with the roller
screw, the actuator pin in a first axial direction; pivoting, with
the actuator pin, the swash plate about the axis in a second
circumferential direction; increasing the amount of fluid expelled
from the first through-bore; rotating, with the electric motor, the
roller screw in a third circumferential direction, opposite the
first circumferential direction, about the axis of rotation;
displacing, with the roller screw, the actuator pin in a second
axial direction, opposite the first axial direction; pivoting, with
the actuator pin, the swash plate about the axis in a fourth
circumferential direction, opposite the second circumferential
direction; and, decreasing the amount of fluid expelled from the
first through-bore.
16. The method of claim 13, further comprising: pivoting, with the
actuator pin, the cylinder block about the axis; rotating, with the
electric motor, the roller screw in a first circumferential
direction about the axis of rotation; displacing, with the roller
screw, the actuator pin in a first axial direction; pivoting, with
the actuator pin, the cylinder block about the axis in a second
circumferential direction; increasing the amount of fluid expelled
from the first through-bore; rotating, with the electric motor, the
roller screw in a third circumferential direction, opposite the
first circumferential direction, about the axis of rotation;
displacing, with the roller screw, the actuator pin in a second
axial direction, opposite the first axial direction; pivoting, with
the actuator pin, the cylinder block about the axis in a fourth
circumferential direction, opposite the second circumferential
direction; and, decreasing the amount of fluid expelled from the
first through-bore.
17. The method of claim 13, further comprising: pivoting, with the
actuator pin, the swash plate about the axis; rotating, with the
electric motor, the nut in a first circumferential direction about
the axis of rotation; displacing, with the roller screw, the
actuator pin in a first axial direction; pivoting, with the
actuator pin, the swash plate about the axis in a second
circumferential direction; increasing the amount of fluid expelled
from the first through-bore; rotating, with the electric motor, the
nut in a third circumferential direction, opposite the first
circumferential direction, about the axis of rotation; displacing,
with the roller screw, the actuator pin in a second axial
direction, opposite the first axial direction; pivoting, with the
actuator pin, the swash plate about the axis in a fourth
circumferential direction, opposite the second circumferential
direction; and, decreasing the amount of fluid expelled from the
first through-bore.
18. The method of claim 13, further comprising: pivoting, with the
actuator pin, the cylinder block about the axis; rotating, with the
electric motor, the nut in a first circumferential direction about
the axis of rotation; displacing, with the roller screw, the
actuator pin in a first axial direction; pivoting, with the
actuator pin, the cylinder block about the axis in a second
circumferential direction; increasing the amount of fluid expelled
from the first through-bore; rotating, with the electric motor, the
nut in a third circumferential direction, opposite the first
circumferential direction, about the axis of rotation; displacing,
with the roller screw, the actuator pin in a second axial
direction, opposite the first axial direction; pivoting, with the
actuator pin, the cylinder block about the axis in a fourth
circumferential direction, opposite the second circumferential
direction; and, decreasing the amount of fluid expelled from the
first through-bore.
19. The method of claim 13, further comprising: pivoting, with the
actuator pin, the swash plate about the axis; and, controlling,
with the swash plate, an extent of displacement of the first piston
within the first through-bore.
20. The method of claim 12, further comprising: pivoting, with the
actuator pin, the cylinder block about the axis; and, controlling,
with the swash plate, an extent of displacement of the first piston
within the first through-bore.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Application No. 62/380,769, filed
Aug. 29, 2016, which application is incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to a variable displacement
hydraulic pump with torque sensing and a method thereof, in
particular, a variable displacement hydraulic pump using torque
sensing to attain or maintain a desired flow rate correlated to a
known torque level on a drive shaft for the pump.
BACKGROUND
[0003] Known variable flow hydraulic pumps use an auxiliary
hydraulic control piston or an electromechanical controller to
control the flow rate for the pump. Feedback for control of the
piston is typically provided by down-stream (of the pump outlet)
measurements of pressure or flow. However, pressure in the control
piston is affected by the overall pressure in the hydraulic system,
for example to due to activation of various hydraulic components.
Changes in the overall pressure cause deviations in the position of
the piston, which in turn affects the flow rate of the pump. The
control piston can be made more precise by using an
electromechanical actuator, but the control loop still has errors
and lag induced by the down-stream measurement of pressure or flow.
Thus, it is difficult to quickly and accurately attain or maintain
a desired flow rate for known variable flow hydraulic pumps.
SUMMARY
[0004] According to aspects illustrated herein, there is provided a
variable displacement axial pump, including: an inlet port; an
outlet port; a cylinder block including a first piston disposed in
a first through-bore; a swash plate engaged with the first piston;
a drive shaft non-rotatably connected to the drive shaft, arranged
to rotate the cylinder block to draw fluid through the inlet port
into the first through-bore and to expel the fluid from the first
through-bore and through the outlet port, and including an axis of
rotation; an axis transverse to the axis of rotation; and an
actuator including a roller screw, a nut disposed about the roller
screw and in threaded contact with the roller screw, an actuator
pin engaged with the roller screw, and an electric motor arranged
to rotate the roller screw or the nut to axially displace the
actuator pin to pivot the swash plate about the axis and control an
amount of the fluid expelled from the first through-bore or pivot
the cylinder block about the axis and control an amount of the
fluid expelled from the first through-bore.
[0005] According to aspects illustrated herein, there is provided a
variable displacement hydraulic pump, including: an inlet port; an
outlet port; a cylinder block including a through-bore and a piston
at least partially disposed in the through-bore; a drive shaft
non-rotatably connected to the drive shaft, arranged to rotate the
cylinder block to displace the piston to draw fluid through the
inlet port into the through-bore and expel the fluid from the
through-bore and through the outlet port, and including an axis of
rotation; an axis transverse to the axis of rotation; an actuator
including a roller screw, a nut disposed about and in contact with
the roller screw, an actuator pin engaged with the roller screw and
the swash plate and an electric motor arranged to rotate the roller
screw to axially displace the actuator pin to pivot the swash plate
about the axis and control an amount of the fluid expelled from the
through-bore or pivot the cylinder block about the axis and control
an amount of the fluid expelled from the through-bore.
[0006] According to aspects illustrated herein, there is provided a
variable displacement hydraulic pump, including: an inlet port; an
outlet port; a cylinder block including a through-bore and a piston
at least partially disposed in the through-bore; a drive shaft
non-rotatably connected to the drive shaft, arranged to rotate the
cylinder block to displace the piston to draw fluid through the
inlet port into the through-bore and expel the fluid from the
through-bore and through the outlet port, and including an axis of
rotation; an axis transverse to the axis of rotation; an actuator
including a roller screw, a nut disposed about and in contact with
the roller screw, an actuator pin engaged with the roller screw and
the swash plate and an electric motor arranged to rotate the nut to
axially displace the actuator pin to pivot the swash plate about
the axis and control an amount of the fluid expelled from the
through-bore or pivot the cylinder block about the axis and control
an amount of the fluid expelled from the through-bore.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Various embodiments are disclosed, by way of example only,
with reference to the accompanying schematic drawings in which
corresponding reference symbols indicate corresponding parts, in
which:
[0008] FIG. 1 is a cross-sectional view of an electromechanical
actuator for a variable displacement pump with a driven nut;
[0009] FIG. 2 is a cross-sectional view of an electromechanical
actuator for a variable displacement pump with a roller screw;
[0010] FIG. 3 is a schematic representation of a variable
displacement pump with a pivotable swash plate and including the
actuator of FIG. 1 or the actuator of FIG. 2;
[0011] FIG. 4 is a schematic representation of the variable
displacement pump of FIG. 3 with the swash plate pivoted;
[0012] FIG. 5 is a schematic representation of a variable
displacement bent-axis pump including the actuator of FIG. 1 or the
actuator of FIG. 2; and,
[0013] FIG. 6 is a schematic representation of the variable
displacement bent-axis pump of FIG. 5 with a cylinder block
pivoted.
DETAILED DESCRIPTION
[0014] At the outset, it should be appreciated that like drawing
numbers on different drawing views identify identical, or
functionally similar, structural elements of the disclosure. It is
to be understood that the disclosure as claimed is not limited to
the disclosed aspects.
[0015] Furthermore, it is understood that this disclosure is not
limited to the particular methodology, materials and modifications
described and as such may, of course, vary. It is also understood
that the terminology used herein is for the purpose of describing
particular aspects only, and is not intended to limit the scope of
the present disclosure.
[0016] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood to one of
ordinary skill in the art to which this disclosure belongs. It
should be understood that any methods, devices or materials similar
or equivalent to those described herein can be used in the practice
or testing of the disclosure.
[0017] FIG. 1 is a cross-sectional view of electromechanical
actuator 100 for a variable displacement pump, with a driven nut.
Actuator 100 includes housing 102, electric motor 104, roller screw
106, nut 108 and actuator pin 110. Pin 110 is engaged with screw
106, for example is axially fixed to screw 106 such that pin 110
axially displaces with screw 106. In an example embodiment, motor
104 includes stator 112 and rotor 114. Nut 108 is disposed about
screw 106 and is in threaded engagement with screw 106. For
example, nut 108 includes threads 116 in contact with threads 118
of screw 106. In an example embodiment, screw 106 is a differential
roller screw.
[0018] Electric motor 104 rotates nut 108 about axis of rotation
AR1 for nut 108 in opposite circumferential directions CD1 and CD2.
In the example of FIG. 1, nut 108 is axially fixed and rotating nut
108 about axis of rotation AR1 in opposite circumferential
directions CD1 and CD2 displaces screw 106 and pin 110 in opposite
axial directions AD1 and AD2, respectively. In an example
embodiment, rotating nut 108 about axis of rotation AR1 in opposite
circumferential directions CD1 and CD2 displaces screw 106 and pin
110 in axial directions AD2 and AD1, respectively. The discussion
that follows is directed to rotation of nut 108 about axis of
rotation AR1 in circumferential directions CD1 and CD2 displacing
screw 106 and pin 110 in axial directions AD1 and AD2,
respectively. However, it should be understood that the discuss
that follows is applicable to rotation of nut 108 about axis of
rotation AR1 in circumferential directions CD1 and CD2 displacing
screw 106 and pin 110 in axial directions AD2 and AD1,
respectively.
[0019] In an example embodiment, pump 100 includes resilient
element 120. Element 120 reacts against housing 102 to urge screw
106 in direction AD2 to prevent back-driving of screw 106 in
direction AD2. Thus, pump 100 is self-locking. For example, when
motor 104 is de-energized, element 120 frictionally engages threads
116 and 118 to prevent screw 106 from rotating in direction CD2 and
displacing in direction AD2. Element 120 can be any resilient
element known in the art, including but not limited to a wrap
spring (shown in FIG. 1) or a spring-pressurized friction pad. In
an example embodiment (not shown), pump 100 includes an
electromechanical brake to prevent back-driving of screw 106.
[0020] FIG. 2 is a cross-sectional view of electromechanical
actuator 200 for a variable displacement pump, with a driven nut.
Actuator 200 includes housing 202, electric motor 204, roller screw
206, nut 208 and actuator pin 210. Pin 210 is engaged with screw
206, for example is axially fixed to screw 206 such that pin 210
axially displaces with screw 206. In the example of FIG. 2, screw
206 is an actuating pin as further described below. In an example
embodiment, motor 204 includes stator 212 and rotor 214. Nut 208 is
disposed about screw 206 and is in threaded engagement with screw
206. For example, nut 208 includes threads 216 in contact with
threads 218 of screw 206. In an example embodiment, screw 206 is a
differential roller screw.
[0021] Electric motor 204 rotates screw 206 about axis of rotation
AR2 for screw 206 in opposite circumferential directions CD1 and
CD2. In the example of FIG. 2, nut 208 is rotationally fixed and
rotating screw 206 about axis of rotation AR2 in opposite
circumferential directions CD1 and CD2 displaces screw 206 and pin
210 in opposite axial directions AD1 and AD2, respectively. In an
example embodiment, nut 208 is rotationally fixed and rotating
screw 206 about axis of rotation AR1 in opposite circumferential
directions CD1 and CD2 displaces screw 206 and pin 210 in axial
directions AD2 and AD1, respectively. The discussion that follows
is directed to rotation of screw 206 about axis of rotation AR1 in
circumferential directions CD1 and CD2 displacing screw 206 and pin
210 in axial directions AD1 and AD2, respectively. However, it
should be understood that the discuss that follows is applicable to
rotation of screw 206 about axis of rotation AR2 in circumferential
directions CD1 and CD2 displacing screw 206 and pin 210 in axial
directions AD2 and AD1, respectively.
[0022] FIG. 3 is a schematic representation of variable
displacement pump 300 with a pivotable swash plate and including
actuator 100 of FIG. 1 or actuator 200 of FIG. 2. Pump 300 includes
housing 302, inlet port 304, outlet port 306, drive shaft 308,
cylinder block 310 non-rotatably connected to shaft 308, swash
plate 312, actuator 100 or actuator 200, axis of rotation AR3 for
shaft 308, and axis of rotation AR4 for block 310. Cylinder block
310 includes through-bores 318 and 320 and pistons 322 and 324 at
least partially disposed in through-bores 318 and 320,
respectively. The discussion that follows assumes actuator 100 is
included in pump 300; however, it should be understood that the
discussion for actuator 100 in pump 300 is applicable to actuator
200 in pump 300.
[0023] By "non-rotatably connected" elements, we mean that: the
elements are connected so that whenever one of the elements
rotates, all the elements rotate; and relative rotation between the
elements is not possible. Radial and/or axial movement of
non-rotatably connected elements with respect to each other is
possible, but not required.
[0024] Pump 300 is located in device D (for example, a bulldozer,
tractor, or construction equipment). Shaft 308 is rotated by engine
E of device D. Actuator 100 is arranged to receive, from processor
P, control signal 328. Actuator 100 is arranged to: pivot swash
plate 312 about axis A1, transverse to axis of rotation AR3,
according control signal 328; or maintain a circumferential
position of swash plate 312, about axis AR3, according to control
signal 328.
[0025] Pistons 322 and 324 are engaged with plate 312. Pistons 322
and 324 remain engaged to plate 312 as is known in the art. In an
example embodiment, each of pistons 322 and 324 is connected to
swash plate 312 via a respective retention assembly 330, as is
known in the art. In an example embodiment (not shown) fluids at
ports 304 and 306 are pressurized to force pistons 322 and 324 into
contact with plate 312 during rotation of block 310 about axis
AR3/AR4. For example, assemblies 330 are not used to maintain
connection between the pistons and plate 312.
[0026] As cylinder block 310 rotates about axis AR3 and AR4: when
piston 322 or 324 is aligned with port 304, plate 312 has displaced
piston 322 or 324 in direction AD1, within through-bores 318 or
320, respectively, to create suction and draw fluid F into
through-bore 318 or 320 through port 304; and when piston 322 or
324 is aligned with port 306, plate 312 has displaced piston 322 or
324 in direction AD2, within through-bores 318 or 320,
respectively, to expel fluid F from through-bore 318 or 320 into
port 306 at a flow rate. In FIG. 3, the flow rate is flow rate
332.
[0027] A flow rate at which fluid F is drawn into and expelled from
pump 300 is dependent upon the speed of rotation of block 310 and
the displacement of pistons 322 and 324, by plate 312, within
through-bores 318 and 320, respectively. The speed of rotation of
block 310 is a function of engine E, which is determined by
operations other than those for pump 300. That is, the speed of
rotation is not controllable by pump 300. For a given position of
plate 312 about axis A1, increasing and decreasing the speed of
rotation of block 310 increases and decreases rate 332,
respectively.
[0028] A flow rate for pump 300 is also governed by the
circumferential position of plate 312 with respect to axis A1. The
circumferential position of plate 312 determines the distance that
pistons 322 and 324 are displaced by plate 312 within through-bores
318 and 320, respectively. In the example of FIG. 3, pistons 322
and 324 are displaced distance 334 by plate 312 within
through-bores 318 and 320, respectively. Thus, pistons 322 and 324
displace distance 334 to draw fluid F into through-bores 318 and
320, respectively, and pistons 322 and 324 displace distance 334 to
expel fluid F from through-bores 318 and 320, respectively.
[0029] As discussed below, changing the extent of the axial
displacement of pistons 322 and 324 (for example, distance 334)
changes the amount of fluid F drawn into and expelled by block 310
and hence changes flow rate 332.
[0030] FIG. 4 shows variable displacement axial pump 300 of FIG. 3
with swash plate 312 pivoted. In the example of FIG. 4, swash plate
312 has been rotated in direction CD3 about axis A1 from the
position shown in FIG. 3. The alignment of through-bores 318 and
320 with ports 304 and 306 remains the same. The rotation and
subsequent tilting of swash plate 312 in FIG. 4 changes the axial
displacement of pistons 322 and 322. As a result: pistons 322 and
324 are displaced distance 336 by plate 312. In the example of
FIGS. 3 and 4: distance 336 is less than distance 334.
[0031] Assuming a constant speed of rotation of shaft 308 in FIGS.
3 and 4, and since distance 336 is less than distance 334, the
amount of fluid F drawn into and expelled from through-bores 318
and 320 in FIG. 4 decreases in comparison to the amount of fluid F
drawn into through-bores 318 and 320 in FIG. 3. Thus flow rate 338
in FIG. 4 is less than rate 332 in FIG. 3.
[0032] The following discussion is directed to a transition from
FIG. 4 to FIG. 3. To transition from FIG. 4 to FIG. 3, swash plate
312 is pivoted by actuator 100 about axis A1 in direction CD4.
Assuming a constant speed of rotation of shaft 308 in FIGS. 3 and
4, and since distance 336 is less than distance 334, the amount of
fluid F drawn into and expelled from through-bores 318 and 320 in
FIG. 3 increases in comparison to the amount of fluid F drawn into
through-bores 318 and 320 in FIG. 4. Thus rate 332 in FIG. 3 is
greater than rate 338 in FIG. 4.
[0033] FIG. 5 is a schematic representation of variable
displacement bent-axis pump 400 including actuator 100 of FIG. 1 or
actuator 200 of FIG. 2. Pump 400 includes: housing 402; inlet port
404, outlet port 406; shaft 408 with axis of rotation AR3; cylinder
block 410 with axis of rotation AR4; universal joint 411 connecting
block 410 to shaft 408; swash plate 412 non-rotatably connected to
shaft 408; and electromechanical actuator 100. The discussion that
follows assumes actuator 100 is included in pump 400; however, it
should be understood that the discussion for actuator 100 in pump
400 is applicable to actuator 200 in pump 400.
[0034] Block 410 includes: through-bores 418 and 420; and pistons
422 and 424 engaged with swash plate 412 and at least partly
disposed in through-bores 418 and 420, respectively. Cylinder block
410 rotates with shaft 408 and about axis AR4 due to the action of
joint 411. Axis AR4 is displaceable in directions CD3 and CD4 with
respect to axis AR3.
[0035] Swash plate 412 is arranged to displace pistons 422 and 424
within through-bores 418 and 420, respectively, to draw fluid F
through port 404 into through-bores 418 and 420 and to expel fluid
F from through-bores 418 and 420 into port 406.
[0036] Swash plate 412 rotates about axis AR3 with shaft 408.
Pistons 422 and 424 remain engaged to plate 412 as is known in the
art. Block 410 rotates about axis AR4 with shaft 408 and plate 412.
As cylinder block 410 rotates about axis AR4: when piston 422 or
424 is aligned with port 404, plate 412 displaces piston 422 or 424
in direction AD3, within through-bores 418 or 420, respectively, to
draw fluid F into through-bore 418 or 420 through port 404 (the
displacement creates suction at port 404); and when piston 422 or
424 is aligned with port 406, plate 412 displaces piston 422 or 424
in direction AD4, within through-bores 418 or 420, respectively, to
expel fluid F from through-bore 418 or 420 into port 406 at a flow
rate. In FIG. 5, the flow rate is flow rate 432.
[0037] Pump 400 is located in device D (for example, a bulldozer,
tractor, or construction equipment). Shaft 408 is rotated by engine
E of device D. Actuator 100 is arranged to receive, from processor
P, control signal 428. Actuator 100 is arranged to: pivot cylinder
block 410 about axis A2, transverse to axis of rotation AR3 and AR4
according control signal 428; or maintain a circumferential
position of cylinder block 410, about axis A2, according to control
signal 428.
[0038] A flow rate at which fluid is drawn into and expelled from
pump 400 is dependent upon the speed of rotation of shaft 408 and
the displacement of pistons 422 and 424, by plate 412, within
through-bores 418 and 420, respectively. The speed of rotation of
block 410 is a function of engine E, which is determined by
operations other than those for pump 400. That is, the speed of
rotation is not controllable by pump 400. For a given position of
block 410 about axis A2, increasing or decreasing the speed of
rotation of block 410 increases or decreases flow rate 432,
respectively.
[0039] A flow rate for pump 400 is also governed by the
circumferential position of block 410 with respect to axis A2. The
circumferential position of block 410 determines the distance that
pistons 422 and 424 are displaced by plate 412 within through-bores
418 and 420, respectively. In the example of FIG. 5, pistons 422
and 424 are displaced distance 434 by plate 412 within
through-bores 418 and 420, respectively. Thus, pistons 422 and 424
displace distance 434 to draw fluid F into through-bores 418 and
420, respectively, and pistons 422 and 424 displace distance 434 to
expel fluid F from through-bores 418 and 420, respectively.
[0040] As discussed below, changing the extent of the axial
displacement of pistons 422 and 424 (for example, distance 434)
changes the amount of fluid F drawn into and expelled by block 410
and hence changes flow rate 432.
[0041] FIG. 6 shows variable displacement bent-axis pump 400 of
FIG. 5 with block 410 pivoted. In the example of FIG. 6, block 410
has been rotated in direction CD4 about axis A2 from the position
shown in FIG. 5. The alignment of through-bores 418 and 420 with
ports 404 and 406 remains the same. The rotation and subsequent
tilting of swash plate 412 in FIG. 6 changes the axial displacement
of pistons 422 and 422 by plate 412. As a result: pistons 422 and
424 are displaced distance 436 by plate 412. In the example of
FIGS. 5 and 6: distance 436 is less than distance 434.
[0042] Assuming a constant speed of rotation of shaft 408 in FIGS.
5 and 6, and since distance 436 is less than distance 434, the
amount of fluid F drawn into and expelled from through-bores 418
and 120 in FIG. 6 decreases in comparison to the amount of fluid F
drawn into through-bores 418 and 420 in FIG. 5. Thus flow rate 438
in FIG. 6 is less than rate 432 in FIG. 5.
[0043] The following discussion is directed to a transition from
FIG. 6 to FIG. 5. To transition from FIG. 6 to FIG. 5, block 410 is
pivoted about axis A2 in direction CD3. Assuming the constant speed
of rotation of shaft 408 in FIGS. 5 and 6, and since distance 436
is less than distance 434, the amount of fluid F drawn into and
expelled from through-bores 418 and 420 in FIG. 5 increases in
comparison to the amount of fluid F drawn into through-bores 418
and 420 in FIG. 6. Thus rate 432 in FIG. 5 is greater than rate 438
in FIG. 6.
[0044] The following should be viewed in light of FIGS. 1 through
6. The following describes a method of operating variable
displacement hydraulic pump 300 or 400. Although the method is
presented as a sequence of steps for clarity, no order should be
inferred from the sequence unless explicitly stated. It should be
understood that the method is applicable to pump 300 or pump 400
including actuator 100 or 200 unless indicated otherwise. This
conflation of applicability is shown by designating respective
elements included in the method with the nomenclature "3xx/4xx."
For example, the first step cites drive shaft 308/408. A first step
rotates, with drive shaft 308/408, cylinder block 310/410. A second
step draws fluid F through inlet port 304/404 and into through-bore
318/418. A third step expels fluid F from through-bore 318/418 and
through outlet port 306/406 at flow rate 332/432. A fourth step
rotates, with electric motor 104/204, roller screw 106 or nut 208.
A fifth step axially displaces actuator pin 110/210. A sixth step:
pivots, with actuator pin 110/210, swash plate 312/412 about axis
A1/A2 and controls an amount of fluid expelled from through-bore
318/418. In an example embodiment, a seventh step blocks, with
resilient element 120 in actuator 100, axial displacement of
actuating pin 110.
[0045] In an example embodiment, the fourth step rotates roller
screw 106 and an eighth step: rotates, with electric motor 104,
roller screw 106 in circumferential direction CD1; displaces, with
roller screw 106, actuator pin 110 in axial direction AD1; pivots,
with actuator pin 110, swash plate 312/412 about axis A1/A2 in
circumferential direction CD3; generates flow rate 338/438;
rotates, with electric motor 104, roller screw 106 in
circumferential direction CD2; displaces, with roller screw 106,
actuator pin 110 in axial direction AD2; pivots, with actuator pin
110, swash plate 312/412 about axis A1 in circumferential direction
CD4; and generates flow rate 332/432.
[0046] In an example embodiment, the fourth step rotates nut 208
and an eighth step: rotates, with electric motor 204, nut 208 in
circumferential direction CD1; displaces, with roller screw 206,
actuator pin 210 in axial direction AD1; pivots, with actuator pin
210, swash plate 312/412 about axis A1/A2 in circumferential
direction CD3; generates flow rate 338/438; rotates, with electric
motor 104, nut 208 in circumferential direction CD2; displaces,
with roller screw 206, actuator pin 210 in axial direction AD2;
pivots, with actuator pin 210, swash plate 312/412 about axis A1 in
circumferential direction CD4; and generates flow rate 332/432.
[0047] It will be appreciated that various of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Various presently unforeseen or unanticipated
alternatives, modifications, variations, or improvements therein
may be subsequently made by those skilled in the art which are also
intended to be encompassed by the following claims.
LIST OF REFERENCE CHARACTERS
[0048] A1 axis transverse to axis AR1 and AR2 [0049] A2 axis
transverse to axis AR1 and AR2 [0050] AD1 axial direction [0051]
AD2 axial direction [0052] AR1 axis of rotation for nut 108 [0053]
AR2 axis of rotation for roller screw 206 [0054] AR3 axis of
rotation for shafts 308 and 408 [0055] AR4 axis of rotation for
cylinder blocks 310 and 410 [0056] CD1 circumferential direction
about axis AR1 [0057] CD2 circumferential direction about axis AR1
[0058] CD3 circumferential direction about axis A1 and A2 [0059]
CD4 circumferential direction about axis A1 and A2 [0060] 100 axial
pump [0061] 102 housing [0062] 104 electric motor [0063] 106 roller
screw [0064] 108 nut [0065] 110 actuator pin [0066] 112 stator
[0067] 114 rotor [0068] 116 threads [0069] 118 threads [0070] 120
resilient element [0071] 200 axial pump [0072] 202 housing [0073]
204 electric motor [0074] 206 roller screw [0075] 208 nut [0076]
210 actuator pin [0077] 212 stator [0078] 214 rotor [0079] 216
threads [0080] 218 threads [0081] 220 resilient element [0082] 300
axial pump [0083] 302 housing [0084] 304 port [0085] 306 port
[0086] 308 shaft [0087] 310 cylinder block [0088] 312 swash plate
[0089] 318 through-bore [0090] 320 through-bore [0091] 322 piston
[0092] 324 piston [0093] 330 retention assembly [0094] 332 flow
rate [0095] 334 axial displacement distance [0096] 336 axial
displacement distance [0097] 338 flow rate [0098] 400 axial pump
[0099] 402 housing [0100] 404 port [0101] 406 port [0102] 408 shaft
[0103] 410 cylinder block [0104] 412 swash plate [0105] 418
through-bore [0106] 420 through-bore [0107] 422 piston [0108] 424
piston [0109] 430 retention assembly [0110] 432 flow rate [0111]
434 axial displacement distance [0112] 436 axial displacement
distance [0113] 438 flow rate
* * * * *