Note: Descriptions are shown in the official language in which they were submitted.
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1 ROTARY HYDRAULIC MACHINE AND CONTROLS
2
3 BACKGROUND OF THE INVENTION
4
FIELD OF THE INVENTION
6 [0001] The present invention relates to hydraulic machines.
7
8 DESCRIPTION OF THE PRIOR ART
9 [0002] There are many different types of hydraulic machines that
can be used to convert
mechanical energy into fluid energy and vice versa. Such machines may be used
as a pump in
11 which mechanical energy is converted into a flow of fluid or as a motor
in which the energy
12 contained in a flow of fluid is converted into mechanical energy. Some
of the more sophisticated
13 hydraulic machines are variable capacity machines, particularly those
that utilize an inclined
14 plate to convert rotation into an axial displacement of pistons or vice
versa.
[0003] Such machines are commonly referred to as swashplate pumps or motors
and have
16 the attribute that they can, handle fluid under relatively high pressure
and over significant range
17 of flows. A particular advantage of such machines is the ability to
adjust the capacity of the
18 machine to compensate for different conditions imposed upon it.
19 [0004] The swashplate machines are, however, relatively complex
mechanically with
rotating and reciprocating components that must be manufactured to withstand
large hydraulic
21 and mechanical forces. These constraints lead to a reduction in the
efficiency due to mechanical
22 and hydraulic losses, a reduced control resolution due to the mechanical
inefficiencies and the
23 required size and mass of the components and a relatively expensive
machine due to the
24 manufacturing complexity.
[0005] In use as a variable capacity machine the swashplate is modulated to
achieve a
26 desired movement of component of a machine, either a position, rate of
movement or applied
27 force.
28 [0006] The movement of the swashplate is usually controlled by a
valve supplying fluid to an
29 actuator that acts through a compression spring on the swashplate.
Control signals for the valve
are generated from a set controller and a feedback, typically provided by a
sensed parameter. In
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its simplest form the feedback may be provided by the operator who simply
opens and closes the
valve to achieve the desired movement or positionino, of the component. More
sophisticated
controls however sense preselected parameters and provide feedback signals to
a valve
controller. The valve controller may be mechanical. hydraulic but more usually
electronic to
offer greater versatility in the control functions to be performed.
100071 The control of the swashplate is determined to a large extent by the
response of the
system to changes of the sensed parameter. In order for effective response to
be obtained, the
valve must be able to supply the actuators controlling the swashplate with
.fluid under pressure at
all times. At the same time, however, the pressure of fluid delivered by or to
the machine may
vary and accordingly a source of pressure at optimum conditions may not be
available. The
common technique to provide pressurized fluid is to use a separate charge pump
but this is
expensive and inefficient.
100081 The response of the machine is also dependent on the mechanical and
hydraulic
losses present in the machine during its operation. A mechanically inefficient
machine will not
respond consistently as loads on the machine vary and the dynamics and static
operating
characteristics may differ significantly leading to a less predictable
response.
100091 It is therefore an object to the present invention to obviate or
mitigate the above
disadvantages.
SUMMARY OF THE INVENTION
100101 In accordance to one aspect to the present invention, there is
provided a rotary
hydraulic machine having a housing, and a rotating group located within the
housing. The
rotating group includes a plurality of variable capacity chambers defined
between pistons
slidcable within respective cylinders. The pistons are displaceable relative
to the cylinders upon
rotation of the barrel to vary the volume of the chambers and thereby induce a
flow of fluid
through the chambers from an inlet port to an outlet port as the rotating
group rotates. An
adjustment assembly includes an actuator operable upon the rotating group to
adjust the stroke of
the pistons in the cylinder and thereby adjust the capacity of the machine. A
fluid supply is
provided for the actuator and a control valve is interposed between the fluid
supply and the
actuator to control flow to the actuator. The fluid supply includes a conduit
to convey pressurised
fl uid from one of the ports to a load. There is also a hydraulic accumulator
connected to the
2
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conduit to store pressurised fluid from the conduit and supply stored fluid to
the control valve. A
check valve is located between the accumulator and the conduit to inhibit flow
from the
accumulator to the conduit upon reduction of pressure in the conduit below
that of the
accumulator whilst maintaining the application of stored fluid to the control
valve.
[00111 Preferably the control valve is a closed centre valve and is
moveable from a centred
position in which flow to and from the actuator is inhibited to a first
position in which flow to the
actuator from the accumulator is permitted and to a second position in which
flow from the
actuator to a drain is permitted.
BRIEF DESCRIPTION OF THE DRAWINGS
[00121 Embodiments of the invention will now be described by way of example
only with
reference to the accompanying drawings in which:
100131 Figure 1 is a side elevation of a hydraulic machine.
100141 Figure 2 is a top view of the hydraulic machine of Figure 1.
100151 Figure 3 is a view on the line III-111 of Figure 2.
100161 Figure 4 is a view on the line IV-1V of Figure 1.
100171 Figure 5 is a perspective view of the rotating components of the
machine shown in
I igures 3 and 4.
100181 Figure 6 is an exploded perspective view of the component shown in
Figure 5.
100191 Figure 7 is a front perspective view, partly in section of the
assembly shown in
Figure 3.
100201 Figure 8 is a perspective view of a portion of the machine in the
direction of arrow
VIII-VIII of Figure 3.
(0021) Figure 9 is an enlarged view of the portion of the machine shown in
Figure 4 within
the circle A.
100221 Figure 10 is a schematic representation of the assembly of a set of
components used
in the machine of Figures 4 and 5.
100231 Figure 11 is a view on the line XI-XI of Figure 1.
100241 Figure 12 is a top view on the line X11-XII of Figure 1.
100251 Figure 13 is a view similar to Figure 12 showing alternate positions
of the
components of the machine shown in Figures 4 and 5.
3
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1 [0026] Figure 14 is a view on the line XIV-XIV of Figure 1.
2 [0027] Figure 15 is a section on line XV-XV of Figure 3.
3 [0028] Figure 16 is a view on the line XVI-XVI of Figure 15.
4 [0029] Figure 17 is a schematic hydraulic circuit showing the
operation of the components
shown in figure 1 to 16.
6 [0030] Figure 18 is a section through a tool used to assemble the
components shown
7 schematically in Figure 10.
8 [0031] Figure 19 is a detailed view of a portion of the tool shown
in Figure 18.
9 [0032] Figure 20 is a plan view of a further tool used to assemble
the components shown in
Figure 10.
11 [0033] Figure 21 is a view similar to Figure 4 of an alternative
embodiment of machine.
12 [0034] Figure 22 is a front view of a port plate used in the
embodiment of Figure 4.
13 [0035] Figure 23 is a side view of the port plate of Figure 22.
14 [0036] Figure 24 is a rear view of the port plate of Figure 23.
[0037] Figure 25 is a section on the line XXV ¨ XXV of Figure 22.
16 [0038] Figure 26 illustrates the sequential movement of a cylinder
across a port plate of
17 Figure 22
18 [0039] Figure 27 is an exploded perspective view of a further
embodiment of port plate;
19 [0040] Figure 28 is a rear perspective view of the port plate of
Figure 27;
[0041] Figure 29 is a front view of the port plate of Figure 27;
21 [0042] Figure 30 is a section on the line XXX-XXX of Figure 29;
22 [0043] Figure 31 is a section on the line XXXI-XXXI of Figure 29;
23 [0044] Figure 32 is a section on the line XXXII-XXXII of Figure
29;
24 [0045] Figure 33 is an end view of an alternative embodiment of
swashplate
26 DESCRIPTION OF THE PREFERRED EMBODIMENTS
27 [0046] Referring therefore to Figures 1 through 4, a hydraulic
machine 10 includes a housing
28 12 formed from a casing 14, an end plate 16 and a control housing 18.
The casing 14 has an
29 opening 15 on its upper side with a planar sealing surface 17 around the
opening 15. The control
housing 18 has a lower surface 19 that extends across the opening 15 and is
secured to the casing
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1 14. The control housing 18, end plates 16 and casing 14 define an
internal cavity 20 in which the
2 rotating group 22 of the machine 10 is located.
3 [0047] As can be seen in Figures 3,4, 5 and 6, the rotating group
22 includes a drive shaft 24
4 that is rotatably supported in the casing 14 on a roller bearing assembly
26 and sealed with a seal
assembly 28. One end of the drive shaft 24 projects from the casing and
includes a drive
6 coupling in the form of a key 30 for connection to a drive or driven
component (not shown) e.g.
7 an engine, electric motor or wheel assembly. The opposite end 32 of the
drive shaft 24 is
8 supported in a roller bearing 34 located in a bore 36 of the end plate
16. The shaft 24 is thus free
9 to rotate along a longitudinal axis A-A of the housing 12.
[0048] A barrel 40 is secured to the shaft 24 by a key 42 located in a key
way 44 formed in
11 the shaft 24. The barrel 40 similarly has a key way 46 that allows the
barrel 40 to slide axially
12 onto the shaft 24 and abut against a shoulder 48 formed on a drive shaft
24. The barrel 40 is
13 provided with a set of axial bores 50 uniformly spaced about the axis of
the shaft 24 and
14 extending between oppositely directed end faces 52,54. As can be seen in
greater detail in
Figure 9, each of the bores 50 is lined with a bronze sleeve 56 to provide a
sliding bearing for a
16 piston assembly 58, described in greater detail below.
17 [0049] A toothed ring 60 is secured on the outer surface of the
barrel 40 adjacent the end
18 face 52. The toothed ring 60 has a set of uniformly spaced teeth 62 each
with a square section
19 and is a shrink fit on the barrel 40. The barrel 40 is formed from
aluminium and the toothed ring
60 from a magnetic material. The barrel 40 has reduced diameter adjacent to
the ring 60 so that
21 the teeth 62 project radially from the surrounding surface of the barrel
40.
22 [0050] A port plate 64 is located adjacent to the end face 54 and
has a series of ports 66 at
23 locations corresponding to the bores 50 in the barrel 40. The port plate
64 is located between the
24 barrel 40 and the end plate 16 and is biased into engagement with the
end plate 16 by coil springs
68 and a conical washer 70. The coil springs 68 are positioned at the radially
outer portion of the
26 barrel 40 and between adjacent bores 50 to bias the radially outer
portion of the plate 64 into
27 engagement with the end plate 16. As seen more clearly in Figure 9, the
conical washer 70 is
28 located at the radially inner portion of the barrel 40 and its radially
outer edge received in a
29 recess 72 formed in the port plate 64 to urge the inner portion against
the end plate 16. The port
plate 64 is thus free to float axially relative to the barrel 40.
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1 [0051] To provide fluid transfer between the bores 50 and the
ports 66, an annular sleeve 74
2 is located within each of the bores 50 and sealed by an 0-ring 76. The
opposite end of the sleeve
3 74 is received in the circular recess 67 of the port 66, as best seen in
Figure 9, and is located
4 axially by a shoulder 68 provided on the sleeve 74. A fluid tight seal is
thus provided between
the barrel 40 and the port plate 64. The ports 66 smoothly transform from a
circular cross-
6 section facing the bore 50 to an arcuate slot for co-operation with
conduits 78, 79 formed in the
7 end plate 16.
8 [0052] As most readily seen in Figure 8, the end plate 16 has a
pair of kidney ports 80,82
9 disposed about the bore 36. The kidney ports 80, 82 connect pressure and
suction conduits 78,
79 respectively to fluid entering and leaving the bores 50. The end plate 16
has a circular
11 bearing face 84 that is upstanding from the end plate 16 and has a set
of radial grooves 86
12 formed in a concentric band about the axis of the shaft 24. The grooves
86 provide a hydro-
13 dynamic bearing between the port plate 64 and the bearing face 84 in
order to maintain a seal
14 whilst facilitating relative rotation between the port plate 64 and face
84.
[0053] Referring again to Figure 4 and 9, each of the piston assemblies 58
is axially slideable
16 within a respective sleeve 56 and comprises a tubular piston 90 and a
slipper 92 interconnected
17 by a ball joint 94. The piston 90 is formed from a tube that is heat
treated and ground to
18 diameter to be a smooth sliding fit within the sleeves 56. As can be
seen in greater detail in
19 Figure 10, the outer surface of one end 96 of the piston 90 is reduced
as indicated at 98 and a part
spherical cavity 100 formed on the inner walls of the end 96. The cavity 100
is dimensioned to
21 receive a ball 102 with a through bore 104. The cavity 100 has an axial
depth greater than the
22 radius of the ball 102 so that the inner walls extend beyond the equator
of the ball 102. The bore
23 104 in ball 102 is stepped as indicated at 106 to provide an increased
diameter at its inner end.
24 [0054] During the first step of forming of the piston assembly 58,
indicated at 109, the ball
102 is inserted in the cavity 100 with the bore 104 aligned generally with the
axis of the piston
26 90. To retain the ball 102 in the cavity 100, the reduced section 98 of
the piston 90 at the end 96
27 is swaged about the ball 100 indicated in Figure 10 (b).
28 [0055] Slipper 92 that has a stem 110 and a base 112 is inserted
into the bore 104 (step (c)).
29 A passageway 114 is formed through the stem 110 to communicate between
the interior of the
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1 piston 90 and a recess 116 formed in the base 112. The slipper 92 is
secured to the ball 102 by
2 swaging, the end of the stem 110 so it is secured by the step 106, as
shown in step (d).
3
[0056] After securing the slipper to the ball, a radial force is applied to
the equator of the ball
4 as indicated by the arrows F in Figure 10e that has the effect of
displacing the material on the
equator to provide a small clearance between the ball 102 and cavity 100. This
clearance enables
6 the ball joint 94 to rotate smoothly within the cavity 100 whilst
maintaining an effective seal
7 from the interior of the piston.
8
[0057] The process shown in Figure 10 may conveniently be performed using
the tool set
9 shown in Figures 18, 19 and 20. A tool set 120 has a fixed die 122 and a
moveable die 124. The
fixed die 122 is secured to a base plate 126 and has a central pin 128 on
which the piston 90 is
11 located. A supporting sleeve 130 supports the upper end of the piston 90
adjacent to the
12 reduction 98. The pin 128 also aligns the ball 102 by extending into the
bore 104 of the ball 102.
13
[0058] The moveable die 124 is formed with a part spherical recess 132
dimensioned to
14 engage the end 96 and form it about the ball 102. The moveable die may
be advanced into
engagement with the ball 102 through the action of a press in which the tool
set 120 is mounted.
16
[0059] After forming, the piston assembly 58 is inserted into a 3 disk die
134 shown in
17 Figure 20. The 3 disk die has a pair of driven rollers 135 and an idler
roller 136 that are disposed
18 around the circumference of the end 96 of the piston assembly 58 to form
point contact with the
19 outer surface 98. The idler roller 136 is moveable along a radial path
by means of a hydraulic
cylinder 137 that applies a constant force to the roller 136. The advance of
the roller is
21 controlled by a flow control valve 138 until the material surrounding
the equator of the ball 102
22 is sufficiently displaced to provide free movement of the ball within
the cavity.
23
[0060] Referring again to Figures 4, 5 and 6 of the base 112 of the slipper
92 engages a
24 swashplate assembly 140 supported within the housing 14. The swashplate
assembly 140
includes a semi cylindrical swashplate 142 having a generally planar front
face 144 and an
26 arcuate rear face 146. The planar front face 144 has a recess 148 to
receive a lapped plate 150
27 against which the slippers 92 bear. The slippers 92 are held against the
plate 150 by a retainer
28
152 that has holes 154 through which the piston assemblies 58 project. The
holes 154 are
29 dimensioned to engage the outer periphery of the base 112 of the slipper
92 and inhibit axial
movement relative to the plate 150. The retainer 152 is located axially by a
pair of C-shaped
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1 clamps 156 that are secured to the front face 144 of the swashplate 142.
The base 112 thus bears
2 against the lapped face of the plate 150 as the barrel is rotated by the
drive shaft 24.
3 [0061] The rear face 146 of the swashplate 142 is supported on a
complimentary curved
4 surface 158 of the casing 14 opposite the end plate 16. The rear face 146
is coated with a
polymer to reduce friction between the face 146 and surface 158. A suitable
polymer coating is a
6 nylon coating formulated from type 11 polyamide resins, such as that
available from Rohm &
7 Haas under the trade name CORVEL. A 70 000 series has been found suitable
although other
8 grades may be utilized depending on operating circumstances. After
deposition on the face 146,
9 the coating is ground to a uniform thickness of approximately 0.040
inches. Alternatively, it has
been found satisfactory to harden the face 146 and apply a TEFLON TM coating.
11 [0062] As seen in Figure 7, a pair of grooves 160, 162
respectively are formed in the rear
12 face 146 and terminate prior to the linear edges of the face 146 to
provide a pair of closed
13 cavities. The grooves 160, 162 are generally aligned with the kidney
ports 80, 82 formed in the
14 end plate 16 and it will be noted that the width of the groove 160 which
is aligned with the
pressure conduit is greater than the width of the groove 162 aligned with the
suction conduit.
16 Fluid is supplied to the grooves 160, 162 through internal passageways
164, 166 respectively
17 formed in the casing 14. Flow through the passageways is controlled by a
pair of pressure
18 compensated flow control valves 168 that supply a constant flow of fluid
to the grooves 160,
19 162. The grooves 160, 162 thus provide a fluid bearing for the rear face
146 against the surface
158 to facilitate rotational movement of the swashplate 142.
21 [0063] Adjustment of the swashplate 142 about its axis of rotation
is controlled by a pair of
22 actuators 170, 172 respectively located in the casing 14. As shown most
clearly in Figures 5 and
23 11, each of the actuators 170, 172 includes a cylinder 174 in which a
piston 176 slides. Each of
24 the cylinders 174 is received within a bore 178 formed in the casing 14
and extending from the
end plate 16 into the cavity 20. The cylinders 174 have an external thread 180
which engages
26 with an internal thread on the bore 178 to secure the cylinder in the
casing 14. The end plate 16
27 (Figure 8) has a pair of recesses 192 that fit over the end of the
pistons 176. The self contained
28 actuator, 170, 172 located in the casing 14 ensures that axial load
generated by the actuators 170
29 are imposed on the casing 14 rather than across the joint between the
end plate 16 and casing 14
to maintain integrity of the housing 12. To avoid distortion of the cylinders
174 during
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1 assembly, it has been found preferable to form the cylinder 174 as two
components, namely a
2 body 174a which is located in the bore 178 by a shoulder and an end cap
174b carrying the
3 threads 180. The cap 174b bears against the end of the body 174a to hold
it in the bore 178.
4 [0064] The cylinder 174 is provided with cross drillings 182 to
permit fluid supplied through
internal passageways 183 (Fig. 12) in the housing 14 to flow to and from the
interior of the
6 cylinder 174. A spring 184 acts between the cylinder 174 and piston 176
to bias it outwardly
7 into engagement with the swashplate assembly 140. Preferably one of the
springs 184 has a
8 greater axial force than the other so that the swashplate is biased to a
maximum strike position in
9 the absence of fluid in the actuators 170, 172.
[0065] The actuators 170, 172 bear against a horseshoe extension 186 of the
swashplate 142
11 that projects outwardly above the barrel 40. The extension 186 has a
pair of part cylindrical
12 cavities 188 at opposite ends into which a cylindrical pin 190 is
located. The cavities 188 are
13 positioned such that the outer surface of the pin 190 is tangential to a
line passing through the
14 axis of rotation of the swashplate. The end face of piston 176 engages
the outer surface of the pin
190 to control the position of the swashplate.
16 [0066] As illustrated in Figure 13, extension of the piston 176 of
one of the actuators 170,
17 172 will induce rotation of the swashplate assembly 140 in the casing 14
and cause a
18 corresponding retraction of the other of the actuators 170, 172. The
assembly 140 slides over the
19 curved surface 158 and as the assembly 140 rotates, the pins 190
maintain contact with the end
face of the pistons 170. The position of the pins 190 on a common diameter of
the swashplate
21 assembly ensures that a rolling motion, rather than sliding, is provided
across the end face of the
22 pistons 176 to reduce friction during the adjustment. As can be seen in
Figure 13, the actuators
23 170, 172 are disposed to provide a full range of rotation on both sides
of a neutral or no stroke
24 position with rolling contact being made over this range of motion.
[0067] Flow to the actuators 170, 172 is controlled by a control valve 200,
Figure 14, located
26 in the control housing 18. The control valve 200 is a solenoid operated,
spool valve having a
27 centred position in which no flow is permitted through the valve. The
spool may be moved to
28 either side of the centred position to apply pressure to one of the
actuators and connect the other
29 actuator to drain. The control housing 18 is shown in greater detail in
Figures 3, 15 and 16 has a
peripheral skirt 191 extending from a base 192. A pair of bores 193, 194
extend through the base
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1 192 to receive control valve 200 and an accumulator 220 respectively.
Fluid is supplied to the
2 bores 193, 194 by an internal supply gallery 195 and a drain gallery 196
is connected between
3 the bore 193 and the cavity 20 of the casing 12. Internal galleries 197,
198 also communicate
4 between the bore 193 and the internal passageways 183 connected to
actuators 170, 172. The
valve 200 controls the flow from the internal supply gallery 196 to the
actuators and drain as will
6 be described below.
7 [0068] The fluid flow controlled by the control valve 200 is
obtained from the pressure
8 conduit 78 and supplied through an accumulator 220 located in the bore
194 of control housing
9 18 adjacent to the control valve 200. The accumulator, shown in Figure
14, includes a piston
222 slideable within a cylinder 224 and biased by a spring 226 to a minimum
volume. The
11 piston 222 has a seal 223 and carries a stop 228 that limits
displacement of the piston 222 within
12 the cylinder 224. The piston 222 may be formed in two pieces to
facilitate insertion of the seal
13 223. The stop 228 in combination with the spring 226 effectively
establishes a maximum stored
14 pressure for the accumulator 220. The supply gallery 195 extends through
a branch conduit 227
to the interior of cylinder 224 and is connected with the pressure conduit 78
through a check
16 valve 230 located in an internal bore 232 in the housing 14. The check
valve 230 ensures that
17 the pressure fluid in the accumulator 220 is maintained as the pressure
supplied to conduit 78
18 fluctuates and that control fluid is available to the valve 200. The
supply gallery 195 is also
19 connected to the pressure compensated flow control valves 168 to ensure
a constant flow of fluid
to the bearings 160, 162.
21 [0069] To provide control signals to the valve 200, a block 202 is
secured to the swashplate
22 142 within the horseshoe extension 186 and presents a planar surface
204. A position sensor 206
23 engages the planar surface 204 eccentrically to the axis of rotation of
the swashplate assembly
24 140 to provide a signal indicative of the disposition of the swashplate
assembly 140. The
position sensor 206 includes a pin 208 slideable within a sensing block 210
that extends
26 downwardly from the control housing 18. The pin 208 is formed from a
stainless steel so as to
27 be non-magnetic and has a magnet 212 inserted at its inner end. The
sensing block 210
28 accommodates a Hall effect sensor 214 in a vertical bore 215 where it is
sealed to prevent
29 migration of oil from the cavity 20 to the control housing 18. The
sensor 214 provides a varying
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1 signal as the pin 208 moves axially within the block 210. The Hall effect
sensor thus provides a
2 position signal that varies as the swashplate is rotated by the actuators
170, 172.
3 [0070] The sensing block 210 also carries a further Hall effect
sensor 216 located in a bore
4 217 extending through the block 210 to a nose 219 positioned adjacent to
the toothed ring 60.
The sensor 216 is sealed in the bore 217 and provides a fluctuating signal as
the teeth 62 pass it
6 so that the frequency of the signal is an indication of rotational speed
of the barrel 22. The
7 control signals obtained from the Hall effect sensors 214 and 216 are
supplied to a control circuit
8 board 218 located within the control housing 18. Further input signals,
such as a set signal from
9 a manual control, a temperature signal indicating the temperature of
fluid in the machine, and a
pressure signal indicating the pressure of fluid in the pressure conduit 78,
are obtained from
11 transducers located in or adjacent to the conduits 78, 80. The input
signals are, also fed to the
12 control circuit board 218 which implements a control algorithm using one
or more of the set,
13 pressure, temperature and flow signals fed to it. The output from the
control circuit board 216 is
14 provided to the control valve 200 which is operable to control the flow
to or from the actuators
171, 172 in response to the control signal received.
16 [0071] The operation of the machine 10 will now be described. For
the purpose of the
17 description it will be assumed that the machine is functioning as a pump
with the shaft 24 driven
18 by a prime mover such as an electric motor or internal combustion
engine. Initially, the bias of
19 the springs has moved the swashplate 140 to a position of maximum stroke
and fluid in the
accumulator 220 has discharged through the flow control valves 168. Rotation
of the shaft 24
21 and barrel 40 causes full stroke reciprocation of the pistons 58 as the
slippers 92 move across the
22 lapped plate 150 to discharge fluid into the pressure port 78. The fluid
is delivered through the
23 check valve 230 to the supply gallery 195 to provide fluid to the
control valve 200 and charge the
24 accumulator 220.
[0072] In its initial condition, the control is set to move, the swashplate
assembly 140 to a
26 neutral or no-flow position. Accordingly, as fluid is supplied to the
control valve 200, it is
27 directed to the actuator 170 to move the swashplate 140 to the neutral
position. As the
28 swashplate moves toward the neutral position, the pin 208 of position
sensor 206 follows the
29 movement and adjusts the position signal provided to the board 218. Upon
attainment of the
neutral position, the flow to the actuator 170 is terminated by the valve 200.
In this position, the
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1 barrel 22 is rotating but the piston assembly 58 is not reciprocating
within the barrel. The
2 accumulator 220 is charged to maintain supply to the flow control valves
168 through the gallery
3 195, and to the control valve 200.
4 [0073] After initialization, the circuit board 218 receives a
signal indicating a movement of
the swashplate assembly 140 to a position in which fluid is supplied to the
pressure port 78. The
6 signal may be generated from the set signal, such as a manual operator,
or from a pressure
7 sensing signal and results in a control signal supplied to the valve 200.
The valve 200 is moved
8 to a position in which it supplies fluid to the actuator 170 and allows
fluid from the actuator 172
9 to flow to a sump. The supply fluid to the actuator 170 causes the piston
176 to extend and bear
against the pin 190. The internal pressure applied to the piston 176 causes
rotation of the
11 swashplate assembly 140 with the surface 146 sliding across the surface
158. Until such time as
12 pressure is delivered to the pressure port 78, the pressurized fluid is
supplied from the
13 accumulator 220 through the control valve and into the interior of the
actuator 170 to induce the
14 rotation. As the swashplate assembly is rotated about its axis, the
slippers 92 are retained against
the lapped plate 150 and the stroke of the pistons 90 is increased. Fluid is
thus drawn through
16 the suction port 69 past the kidney port 82 and into the pistons as they
move outwardly from the
17 barrel. Continued rotation moves the pistons into alignment with the
pressure port 78 and expels
18 fluid from the cylinders as the pistons 90 move into barrel. The
pressure supplied to the port 78
19 is also delivered to the internal supply galleries 195 to replenish the
accumulator 220.
[0074] As the swashplate rotates, the pin 208 follows the movement of the
planar surface
21 204 and provides a feedback signal indicative of the capacity of the
barrel assembly 22. The
22 signal from the toothed ring 60 also provides a feedback signal
indicative of rotation so that the
23 combination of the signal from the pin 208 and the signal from the ring
60 may be used to
24 compute the flow rate from the pump. If the set signal is a flow control
signal then the
combination of the speed and position are used to offset the set signal and
return the valve 200 to
26 a neutral position once the required flow is attained. Similarly, if the
set signal indicates a
27 pressure signal, then the pressure in the port 78 is monitored and the
valve returned to neutral
28 upon the set pressure being obtained.
29 [0075] As the swashplate 142 is adjusted, the flow of fluid into the
grooves 160, 162 on the
rear face 146 of the swashplate is controlled by the flow of the control
valves 168 so that a
12
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1 constant support for the swashplate is maintained. Similarly, the port
plate 64 is maintained
2 against the end face by the action of the spring 68, 70 to maintain a
fluid tight seal for the
3 passage of fluid into and out of the barrel assembly 40.
4 [0076] Movement of the swashplate to a position in which
pressurized fluid is delivered to
the port 78 recharges the accumulator 220 as well as supplying flow to the
actuators 170 and 172
6 and the grooves 160, 162. If the swashplate assembly 140 is returned to a
neutral position, the
7 pressurized fluid in the accumulator 220 is sufficient to provide the
control function and maintain
8 the balance of the swashplate 142.
9 [0077] During adjustment of the swashplate 142, the rolling action
of the pins 190 across the
end faces of the pistons 176 further minimizes the frictional forces applied
to the swashplate 140
11 and thereby reduces the control forces that must be applied.
12 [0078] It will also be appreciated that by providing the ball
joint 94 as part of the slipper, the
13 forces imposed on the slipper are minimized and the angle of adjustment
available increased to
14 enhance the range of follow rates that are available.
[0079] All movement of the swashplate 140 is followed by the pin 208 and
variations in the
16 rotational speed are sensed by the pickup 216 to permit the control
board 218 to provide
17 adjustment of the control parameters. It will also be noted that the
control function is located in
18 the housing 18 separate from the rotating component so that the control
board 218 and associated
19 electric circuit is not subject to the hydraulic fluid that might
adversely affect their operation.
[0080] The provision of the key 42 on the shaft 24 inhibits relative
rotation between the shaft
21 and barrel and thus reduces the oscillation and fretting that otherwise
occurs with a typical
22 splined connection. Any misalignment between the barrel and port plate
64 is accommodated by
23 the spring biasing applied to the port plate 64 by the springs 68, 70 so
that the keyed connection
24 to the shaft is possible.
[0081] The accumulator provides a supply of pressure fluid to the control
valve 200 to
26 enhance the response to variations in the control signal when the
pressure in the discharge
27 system falls below the accumulator setting.
28 [0082] If the machine 10 is to be utilized as a motor, it will be
appreciated that the pin 208 is
29 operable to follow movement of the swashplate to either side of a
neutral condition and therefore
provide reversibility of the output shaft 24 that is used to drive a load.
During such operation,
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1 the line 78 will be at a low pressure but the accumulator 220 supplies
fluid to the control valve
2 200 to maintain control of the swashplate.
3 [0083] In the above embodiment, the port plate is biased against
the end plate and floats
4 relative to the barrel 40. An alternative embodiment is shown in Figures
21 to 26 in which like
components are denoted with like reference numerals with a suffix 'a' added
for clarity.
6 [0084] In the arrangement shown in Figures 21 to 26, the port
plate 64a is arranged to float
7 relative to the end plate 16a and for relative rotation to occur between
the barrel 40a and the port
8 plate 64a. The port plate 64a is biased into sealing engagement with the
barrel 40a by springs
9 68a received in a counterbore 68a. In this way, minor misalignment
between the barrel and end
plate is accommodated. The counterbore 68a is sealed to the end plate 16a by
sleeves 74a that
11 accommodate axial movement and maintain a seal with 0-rings 76a.
12 [0085] As can be seen from Figure 22, the port plate 64a has a
pair of kidney shaped ports
13 300, 302. The port 300 extends through the plate 64a with a central web
304 recessed from the
14 front face 306 of the plate 64a. The rear face 308 as shown in Figure
24, is undercut as indicated
at 310 to provide a clearance between the plate 64a and the end wall 16a.
16 [0086] The port 302 extends partially through the plate 64a and is
intersected by three
17 pressure ports 312 that extend from the rear face 308. Each of the ports
312 is configured to
18 receive a sleeve 74a which engages in complimentary recesses in the end
face 16a to provide a
19 sealed communication between the plate 64a and the end face 16a.
[0087] A restricted orifice 314 is formed at the inner end of the
counterbore 68a so as to
21 extend through to the front face 306. The orifice provides a restricted
access to the chamber
22 formed by the sleeve 74a within the counterbore 68a and is positioned
between the kidney ports
23 300, 302. A V-shaped notch 316 is formed in the front face 306 and
progressively increases in
24 breadth and depth toward the leading edge of the kidney port 302.
[0088] In operation, the front face 306 of plate 64a is forced against the
end face of the barrel
26 40a. The bores 50a are located at the same radius as the kidney ports
300, 302 and therefore pass
27 successively over the port plate as the barrel 40 rotates. As the bores
50a traverse the port 300
28 fluid is induced into the cylinders. Similarly, as the bores 50a
traverse the port 302, fluid is
29 expelled from the cylinders and directed through the sleeves 74a to the
pressure conduit 78a.
14
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1 During this rotation, the face 306 is maintained by the springs 68a
against the barrel 40a to
2 maintain an effective seal.
3 [0089] It will be noted that the adjacent ends of the ports 300,
302 are spaced apart by a
4 distance greater than the diameter of the bores 50a. This is shown is
Figure 26A where the
disposition of the bores at a particular position of the barrel 40a is shown.
The bore 50a shown
6 in chain dot line is associated with a piston that has just passed bottom-
dead center, ie. the
7 maximum volume of the cylinder and is starting to move axially to expel
fluid. However, the
8 rate of movement of the piston is relatively small by virtue of the
sinusoidal nature of the
9 induced movement. In the position shown in Figure 26A, the cylinder has
just passed the
terminal portion of the inlet port 300 but the small land created between the
end of the bore and
11 the terminal edge of the port 302 is such that there is a small leakage
from the piston into the low
12 pressure port 300. It will also be observed from Figure 26A that the
orifice 314 is positioned
13 within the cylinder.
14 [0090] As the barrel continues to rotate as shown in Figure 26B,
the bore is centered over the
orifice 314 and the limited movement of the piston is accommodated by
compression of the fluid
16 and components within the chamber 68a. Again, because of the sinusoidal
nature of the motion,
17 the axial displacement is minimized during this portion of the rotation.
Further rotation of the
18 barrel 40a brings the bore 50a to a position shown in Figure 26C in
which it overlaps the notch
19 316 and therefore fluid in the cylinder may be expelled into the high
pressure kidney port 302.
The tapered dimensions of the notch 316 allows the oil to progressively enter
the port 302 to
21 avoid an abrupt transition and thereby reduce potential noise. At this
time the cylinder is still in
22 communication with the bore 68a and high pressure fluid within that bore
can be expelled
23 through the orifice 314 and into the pressure port 302.
24 [0091] Continued rotation, as shown in Figure 26D moves the bore
50a so it begins to
overlap the kidney part 302 and has unrestricted access to the pressure
conduit 78a.
26 [0092] Similarly, as the bore 50a moves from the inlet port 300 to
the pressure port 302, a
27 circumferentially spaced bore indicated at 50a' on Figure 26A moves from
the high pressure
28 kidney port 302 to the suction port. As can be seen from Figure 26A, as
the piston approaches
29 top-dead center, the communication with the high pressure port is
progressively reduced until, as
it moves to the position shown in Figure 26C, it is in communication with the
orifice 314.
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1 Again, the piston is at its minimum rate of axial movement as it passes
the top-dead center and
2 the continued displacement of fluid can be accommodated within the
chamber 68a. At the
3 position shown in Figure 26D, the piston has gone past top-dead center
and is being moved
4 towards bottom-dead center. In this position however, it is not in
communication with the low
pressure kidney port 300 and the residual pressure within the chamber 68a
replenishes the fluid
6 within the cylinder to avoid cavitation. As the barrel continues to
rotate, the cylinder is put into
7 communication with the low pressure port and the fluid is drawn into the
cylinder.
8 [0093] It will be seen therefore that as the barrel 40a rotates,
the pistons are alternatively
9 connected to pressure and section ports 302, 300 and that the spacing of
the ports is such as to
inhibit leakage between the high pressure and low pressure chambers. The
provision of the
11 restricted orifice 314 together with the balancing chamber 68a
accommodates the small change
12 in volume as the pistons go over bottom-dead center or top-dead center
as well as providing a
13 balancing force to maintain the port plate against the end of the barrel
40a. The undercut 310
14 provides a relatively unrestricted ingress of fluid into the cylinders
to enhance the efficiency of
the machine and inhibit cavitation.
16 [0094] A further embodiment of port plate similar to that shown in
Figures 21 to 26 is
17 illustrated in Figures 27 through 32 in which like reference numerals
will be utilised to identify
18 like components with a suffix b added for clarity.
19 [0095] In the arrangement of Figures 27 through 32, the port plate
64b is arranged to float
relative to the end plate 16b and for relative rotation to occur between the
barrel 40b and the port
21 plate 64b as described above with respect to Figures 21 to 26. The port
plate 64b has a pair of
22 kidney shaped ports 300b, 302b. The port 300b extends through the plate
64b with a central web
23 304b recessed from the front face 306b of the plate 64b. A hydro dynamic
bearing 320 is formed
24 on the periphery of the front face 306b to mate with the end face of the
barrel 40b. The port
302b extends partially through the plate 64b from the front face 306b and is
intersected by
26 pressure ports 312b that extend from a rear face 308b best seen in
Figure 28.
27 [0096] The rear face 308b has a pair of upstanding walls 322, 324
that extend around the
28 periphery of the ports 300b, 302b respectively. A groove 326, 328 is
provided in each of the
29 walls 322, 324 to receive respective sealing rings 330, 332. A radial
shoulder 334 is formed at
the rear face 308b and is a snug fit within a bore 336 provided in the front
face of the end plate
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1 16b. A circlip 338 co-operates with a grove formed in the bore 336 to
retain the port plate 64a
2 within the bore 336.
3 [00971 Kidney shape inlet and outlet ducts 340, 342 respectively
are provided at the base of
4 the bore 336 and are of complimentary shape to the walls 322, 324
respectively to permit the
walls 340, 342 to rest within the ducts. The ducts 340, 342 communicate with
the inlet conduit
6 and outlet conduit (not shown) to supply fluid to the rotating group and
convey fluid away from
7 the rotating group as is conventional. The sealing rings 330, 332 ensure
a fluid tight fit between
8 the walls 322, 324 and their respective ducts 340, 342 whilst
accommodating limited axial
9 movement.
[0098] The port plate 64b is biased away from the end plate 16b by springs
68b. The springs
11 68b are accommodated within the ducts 340, 342 and act against the end
face 308 to provide the
12 necessary bias against the force generated by the pressure of fluid in
the barrel. A balancing
13 chamber is formed at diametrically opposed locations on the plate 64b by
sleeve 74b. As best
14 seen in Figure 31, the sleeves 74b are accommodated within counter bores
344 in the plate 64b.
A restricted orifice 314b connects the counter bore 344 with the front face
306b. The sleeve 74b
16 are axially moveable within the counter bores 344 and are sealed by o-
rings on the periphery of
17 the sleeve 74b. The balancing chamber are located at the cross over
between the pressure and
18 suction ports to accommodate the transition.
19 [0099] The operation is similar to that described above with
respect to Figures 21 through
26. To maintain an effective seal between the port plate 64b and barrel, the
area of the recesses
21 342 is selected to have a slightly greater effective area than the port
302b, typically in the range
22 of 2 to 5% greater, with 3% preferred. A positive bias from the
pressurized fluid is thus provided
23 to supplement the action of the spring 68b and maintain a seal between
the port plate and the
24 barrel. It is found that if the machine is maintained under pressure but
with no rotation, there is a
tendency for the pressure fluid to creep between the port plate and barrel and
separate the sealing
26 surfaces. The provision of the enlarged area for the port provides a
positive bias even without
27 rotation of the barrel relative to the port plate to maintain the
ceiling effect. If a perfect seal in
28 assumed between the face of the barrel and the port plate, a
differential in area of 25% is found
29 to be suitable. In practice, such an area differential when combined
with the inevitable pressure
17
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1 gradient at the edge of the port produces an effective differential in
the order of 3% to maintain
2 effective sealing.
3 [00100] An alternative embodiment of swasplate is shown in Figure 33 in
which like
4 components will be denoted with like reference numerals and a suffix 'a'
added for clarity. In
the embodiment described in Figure 7 above, the grooves 160, 162 are aligned
with the kidney
6 ports 80, 82 so as to provide increased load carrying capacity for the
high pressure loading of the
7 pistons.
8 [00101] In the embodiment of Figure 33, the grooves 160a, 162a extend in
a direction to
9 bridge the kidney ports 80, 82 and have a varying area to accommodate the
loads imposed. As
can be seen in Figure 27, each of the grooves 160a, 162a is generally an
inverted L-shape with an
11 enlarged head 350 and an elongate tail 352. Flow to the grooves 160a,
162a is controlled by
12 respective flow control valves 168a. A land 352 is provided in the head
350 to adjust the bearing
13 area.
14 [00102] The head 350 is generally aligned with the line of action of the
actuators 170, 172 to
provide an enlarged bearing area whilst the tails 352 provide a bearing area
for balance of the
16 forces. In this manner, the grooves 160a, 162a are located to provide a
fluid bearing in which the
17 higher forces are distributed between the two grooves and the shape of
the groove used to
18 compensate for difference loading. It will be noted that the tail 352 is
of varying width to
19 provide an increased area in opposition to the high pressure loads with
a reduced area to oppose
the low pressure loads. It will be appreciated that the grooves 160a, 162a may
be contoured to
21 suit the loading characteristics of the particular machine and provide
uniform support for the
22 swashplate.
23
18
