Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention is a third divisional from Canadian Patent
Application S.N. 498587 filed December 24, 1985.
The field of the present invention relates to static
hydraulic pressure type continuously variable transmissions, and
more particularly to such transmissions in which a hydraulic closed
circuit is formed between a swashplate type hydraulic pump and a
swashplate type hydraulic motor.
A static hydraulic pressure type continuously variable
transmission of the type herein referred to is disclosed, for
example, in Japanese Patent Application Laid~Open No. 70,968/82
Specification and Japanese Patent Publication No. 38,467/84
Specification.
In conventional static hydraulic pressure type continuously
variable transmissions, a motor cylinder and a motor swashplate of a
hydraulic motor are independently supported on a casing. This can
result in a great thrust load, applied to the motor swashplate from
a group of motor plungers in sliding contact with the motor cylinder
being borne by the casing during operation. Accordingly, such a
casing is preferably formed with a highly rigid wall thickness,
which can be heavy.
In addition, a pump cylinder of such a hydraulic pump and
a motor cylinder of such a hydraulic motor are concentrically
arranged with the former disposed internally of the latter. In such
an arrangement the extexnal large-diameter motor cylinder is heavy.
Furthermore, in a conventional static hydraulic pressure
type continuously variable transmission, a pump cylinder of the
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hydraulic pump is pressed in sliding contact aga1nst a distribution
board fixedly mounted on the motor cylinder of the hydraulic motor
so that working fluiZs of the hydraulic pump and hydraulic motor
are transferred through an oil path extending through the rotary
sliding surfaces. Because of this, pressurized oil tends to leak
from between the opposed rotary sliding surfaces of the distribu-
tion board and the pump cylinder, leading to deterioration of
transmission efficiency due to such leakage.
In addition, in a conventional apparatus provided with
a variable capacity swashplate type hydraulic motor, a hydraulic
servo is connected to a motor swashplate to lightly adjust an
angle of inclination of the motor swashplate, as is well known.
However, the hydraulic servo~motor has a complicated construction
and is expensive.
More~ver, in a conventional construction, a clutch valve
and its operating system, which control communication between the
discharge and intake sides of the hydraulic pump for regulating
power transmission from the hydraulic pump to the hydraulic motor,
project axially from the end of the hydraulic motor increasing
the overall length of he transmission. This is particularly txue
where the hydraulic pump and the hydraulic motor are disposed on
one and the same axis.
SUMMARY OF THE INVENTION
It is the primary object of the present invention to
inexpensively provide a static hydraulic pressuxe type continuously
variable transmission which is free from the disadvantages noted
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70488-4F
above, and which is light-weight and small, and has excellent
transmission e~ficiency.
The invention herein claimed is a static hydraulic
pressure type continuously variable transmission comprising: a
hydraulic pump having a pump cylinder; a hydraulic motor having a
motor cyllnder; and a hydraulic closed circuit between the
hydraulic pump and motor, the hydraulic closed circuit having a
high pressure oil passage and a low pressure oil passage which are
defined in the pump and motor cylinders in a manner distanced from
each other; wherein a number of cylinder bores are arranged in the
pump cylinder and in the motor cylinder to slidably receive
therein a number of plungers, respectively; and wherein a number
o~ distribution valves ar~ disposed in at least one of the pump
cylinder and the motor cylinder, said number of distribution
valves being rotatahle in response to rotation of said at least
one cylinder and alternately communlcating the cylinder bores of
said at least one cylinder with the hlgh pre~sure oil passage and
low pressure oil passage, respectively, while being drlven
externally of the cylinder to perform a reciprocating movement by
a distributor valve driving means which is located outside of said
one cylinder.
The invention fur her provides a swashplate type
hydraulic system comprising: a cylinder block having a number of
cylinder bores annularly arranged therein; a number of plungers
each slidably received in one of the cylinders bores; a ~washplate
engaging those ends of said plungers which protrude from the
cylinder bores; and a high pressure oil passage and a low pressure
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70488-4F
oil passage which are defined in the cylinder block in a manner
distanced from each other; wherein a working oil is transferred
between these high and low oil pressura passages and the cylinder
bores durin~ relative rotation between the cylinder block and the
swashplate; wherein a plurality of distribution valves are
disposed in the cylinder block to alternately communicate the
cylinder bores with said high pressure oil passage and low
: pressure oil passage, respectively, while being urged to perform a
reciprocating movement by a distribution valve drivlng means; and
wherein said distribution valve driving means is disposed outside
of the cylinder block and is adapted to drive the distribution
valves at positions outside of the cylinder block in response to
the relative rotation between the cylinder block and the
swashplate.
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BRIEF DESCRIPTION OF THE DRAWINGS
The drawings show one embodiment of the present
invention.
Figure 1 is a longitudinal plan view of a static
hydraulic pressure type continuously variable transmission
incorporated in a power transmission system of a motor-cycle;
Figures 2 and 3 are sectional views taken on line II~II
and line III-III, respectively, of Figure l; and
Figure 4 is an exploded perspective view of major
components of Figure i.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present application will now be described in the
environment of the parent application.
Referring now to the drawings and more particularly to
Figure 1, power of a motor-cycle engine is transmitted from a
crank shaft 1 to an unshown rear wheel via a chain type primary
reduction gear 2, a static hydraulic pressure type continuously
variable
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transmission T and a chain type secondary reduction gear 3.
The continuously variable transmission T comprises a
swashplate type hydraulic pump P of a constant capacity type and
a swashplate type hydraulic motor M of a variable capacity type,
which are accommodated within a crank case 4 as a casing which
carries a crank shaft 1.
The hydraulic pump P comprises a cup-like input member
5 integrally provided with an output sprocket 2a of the primary
reduction gear 2. A pump cylinder 7 is relatively rotatably fitted
in the inner peripheral wall of the input memher 5 through a needle
bearing 6. Pump plungers 9, 9 ... are slidably fitted in a plural-
ity and odd-number of annularly disposed cylinder bores 8, 8
provided in the pump cylinder 7 so as to surround the rotary center
thereof, and a pump swashplate 10 is in contact with the outer
ends of the pump plungers 9, 9 ...
The back surface of the pump swashplate 10 is rotatably
supported on the inner end wall of the input member 5 in an atti-
tude inclined by a predetermined angle with respect to the axis
of the pump cylinder 7 through a thrust roller bearing 11. When
input member 5 ~s rotated, the pump plungers 9, 9 .... are recipro-
cated to repeatedly effect suction and exhaust strokes.
The back surface of the input member 5 is supported on
a support sleeve 13 through a thrust roller bearing 12.
~: On the other hand, the hydraulic motor ~ comprises
a motor cylinder 17 coaxially and closely coupled to the pump
cylinder 7. A support shaft 24 and an output shaft 25 are
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integrally formed to central parts of both inner and outer ends of
the motor cylinder 17 and extending in an axial direction. Motor
plungers 19, 19 ... are respectively slidably fitted in a plurality
and odd-number of annu~arly disposed cylinder~bores 18, 18 ...
provided in the motor cylinder 17 so as to surround the rotary
center thereof. A motor swashplate 20 is in contact with outer
ends of the motor plungers 19, 19 .... A swashplate holder 22 for
supporting the back surface of the motor swashplate 20 through
a thrust roller bearing 21 is positioned in a swashplate anchor
23 for suppoxting the back surface of the swashplate holder 22.
The motor swashplate 20 is tiltingly movable between an
upright position at right angles to the axis of the motor cylinder
17 and a position inclined at a certain angle. At the inclined
position, the motor plungers 19, 19 ... are reciprocated upon
rotation of the motor cylinder 17 to repeatedly effect expansion
and contraction strokes.
The aforesaid support shaft 24 extends through the cen-
tral portion of the pump cylinder 7. A nut 26 is threadedly en-
gaged with the support shaft 24 to retain the pump cylinder 7 and
the motor cylinder 17 integrally connected to each other. The
support shaft 24 further extends through the input member 5 and
rotatably supports the input member 5 through a needle bearing 27.
On the outer periphery of the support shaft 24, the
support sleeve 13 is splined-fitted and secured by means of a nut
30. The support shaft 24 is rotatably supported in the cran~ case
4 through the support tube 13 and a roller bearing 31.
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The aforesaid output shaft 25 extends through the
central portion of the motor swashplate 20, the swashpla~e holder
22 and the swashplate anchor 23. A support sleeve 33 for support-
ing the back surface of the swashplate anchor 23 through a thrust
roller bearing 32 is splined-fitted to the end of the shaft 25
and is secured by means of a nut 34 with an input sprocket 3a of
the secondary reduction gear 3. The output shaft 25 is rotatably
supported on the crank case 4 through the support sleeve 33 and a
roller bearing 35.
Secured to the support shaft 24 is a spherical spline
member 36 in spline engagement with the lnner peripheral surface
of the pump swashplate 10 in a manner relatively tiltable in all
directions, and secured to the output shaft 25 is a spherical
spline member 37 in spline engagement with the inner peripheral
surface of the motor swashplate 20 relatively tiltably in all
directions. The couplings of the spiral spline members 36 and 37
with the swashplates 10 and 20 suppresses to a minimal extent
frictional contact between the group of pump plungers 9, 9 ... and
the pump swashplate 10 and between the motor plungers 19, 19
and the motor swashplate 20.
Between the hydraulic pump P and the hydraulic motor M
is formed a hydraulic closed circuit as described hereinafter.
In the motor cylinder 17, an annular high pressure oil
passage 40 and an annular low pressure oil passage 41 to encircle
the oil passage 40 are provided between the group of cylinder bores
8, 8 ... of the pump cylinder 7 and the group of cylinder bores
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_9_ 70488-~
18, 18 ... of the motor cylinder 17. The high pressure oil pas-
sage 40 communicates ~ith the cylinder bores 8, 8 ... of the pump
cylinder 7 through discharge valves 42, 42 .... The low pressure
oil passage 41 also communicates with the cylinder bores 8, 8 ...
through intake valves 43, 43 ... Accordingly, the discharge valves
42 and the intake valves 43 are respectively provided in the same
number as that of the pump plungers 9, 9 ....
These high and low pressure oil passages 40, 41 are
both communicated with the cylind~er bores 18, 18 ... of the motor
cylinder 17 through respective distribution valves 44, 44
Accordingly, the distribution valves 44 are provided in the same
number as that of the motor plungers 19, 19 .O..
The distribution valves 44, 44 ..., which are of a spool
type, are slidably fitted into valve holes 45, 45 ... radlally
provided in the motor cylinder 17 between the group of cylinder
bores 18, 18 ... and the high and low pressure oil passages 40, 41.
When the valve 44 occupies the radial inward position in the valve
hole 45, there is provided a communication between the corresponding
cylinder bore 18 and high pressure oil passage 40 whilst the
cylinder bore 18 is shut off from the low pressure oil passage 41,
and when the valve 44 occupies the radial outward position in the
valve hole 45, there is provided a communication between the cor-
responding cylinder bore 18 and low pressure oil passage 41 whilst
the bore is cut o~f its communication with the high pressure oil
passage 40.
Valve springs 46, 46 ... for biasing the distribution
valves 44, 44 ... radially and outwardly are accommodated within
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the valve holes 45, 45 ... to control the distribution valves
44, 44 ..., and the inner peripheral surface of an eccentric ring
47 is engaged with the outer end of each distribution valve 44.
The eccentric ring 47 is formed of an inner race of a
ball bearing 48 snapped in and secured to the crank case 4, and as
shown in Figure 2. The ring 47 is installed at such a position
that the center thereof is to be eccentric a 2redetermined distance
~ from the center of the motor cylinder 17 in a direction of the
tilting axis 0 of the motor swashplate 20. Accordingly, when the
motor cylinder rotates, each of the distribution valves 44 takes
the stroke of 2 , which is twice of the eccentric amount Ç of the
eccentric ring 47, within the valve hole 45 and reciprocates be-
tween the aforesaid outward position and inward position.
The distribution valve 44 also functions to bring a
replenishing oil passage 49 into communication with the low pres-
sure oil passage 41 when the valve assumes the inward position in
the valve hole 45. The replenishing oil passage 49 is provi~ed in
the central portion of the support shaft 24 and connected to the
discharge port of a replenishing pump 50.
The pump 50 is driven by the crank shaft 1 to supply
oil stored in an oil reservoir 51 at the bottom of the crank case
4 to the oil passage 49 under relatively low pressure.
Referrlng to Figures 1, 3 and 4, an outer peripheral
surface 20a of the moior swashplate 20 is formed into a spherical
surface having its center at the tilting axis 0. A spherical
recess 52 is formed in the front surface of the swashplate hoIder
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22 so as to receive the motor swashplate 20 along with the thrust
roller bearing 21. A back surface 22a of the swashplate holder 22
is formed in a circular surface about the tilting axis 0 of the
motor swashplate 20, and a semi-cylindrical recess 53 is formed
in the front surface of the swashplate anchor 23 so as to support
the swashplate holder 22 rotatably about the tilting axis O. This
swashplate anchor 23 is connected to the crank case 4 through
locating pins 54 so that the anchor may not be rotated about the
output shaft 25.
A pair of trunnion shafts SS, 55' aligned on the tilting
axis O are integrally projected on both ends of the swashplate
holder 22, the trunnion shafts 55, 55' being rotatably supported
on the swashplate anchor 23 throùgh needle bearings 56. In other
words, the tilting axis 0 is defined by the trunnion shafts 55,
55'.
An operating lever 57 is fixedly mounted on the outer
end of one trunnion shaft 55.
When the trunnion sha~t 55 is rotated by the operating
lever 57, the swashplate holder 22 integral therewith also
rotates and the latter can be tilted even during the rotation of
:~ the motor swashplate 20.
With the arrangement as described above, when the input
member 5 of the hydraulic pump P is rotated from the primary
reduction gear 2, suction and exhaust strokes are alternately im-
parted by the pump swashplate 10 to the pump plungers 9, 9
Then, each pump plunger 9, in suction stroke~ intakes worklng fluid
~L29~)62
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from the low pressure oil passage 41, and in exhaust stroke, feeds
high press~re working fluid to the high pressure oil passage 40.
The high pressure working fluid fed to the high pres-
sure oil passage 40 is supplied to a cylinder bore 18 through the
distribution valve 44 at the inward position to force a motor
plunger 19 in an expansion stroke. The working fluid within a
cylinder bore 18 being moved by a motor plunger 19 in a contrac-
tion stroke is discharged into the low pressure oil passage 41
through the distribution valve 44 at the outward position.
During this operation, the p~np cylinder 7 and motor
cylinder 17 are rotated by the sum of reaction torque received by
the pump cylinder 7 from the pump swashplate 10 through the pump
plungers 9 in an exhaust stroke and reaction torque received by
the motor cylinder 17 from the motor swashplate 20 through the motor
plunger 19 in an expansion stroke. This rotary torque is trans-
mitted from the output shaft 25 to the secondary reduction gear 3.
In this case, the speed change ratio of the output shaft
25 with respect to the input member 5 is given by the following
equation:
Speed change - Capacity of hydraulic motor M
speed ratio 1 Capacity of hydraulic pump P
Thus~ if the capacity of the hydraulic motor M is
changed from zero to a certain value, the speed change ratio can
changed from 1 to a required value.
Incidentally, since the capacity of the hydraulic motor
M is determined by the stroke of the motor plunger 19, the motor
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swashplate 20 can be tilted from an upright position to an inclined
position to thereby steplessly control the ratio from 1 to a cer-
tain value.
During the operation of the hydraulic pump P and hydrau-
lic motor M as described above, the pump swashplate 10 and motor
swashplate 20 receive the opposite thrust load from the group of
pump plungers 9, 9 ... and the group of motor plungers 19, 19, ...
respectively. The thrust load applied to the pump swashplate 10
is carried by the support shaft 24 through the thrust roller
bearing 11, input member 5, thrust roller bearing 12, support
sleeve 13 and nut 30. The thrust load applied to the motor swash-
plate 20 is carried by the output shaft 25 through the thrust
roller bearing 21, swashplate holder 22j swashplate anchor 23,
thrust roller bearing 32, support sleeve 33, sprocket 3a and nut
34. Since the support shaft 24 and output shaft 25 are integrally
connected together through the motor cylinder 17, the aforesaid
thrust load merely gives rise to tensile stress caused in the motor
cylinder 17 system and exerts no action on the crank case 4 which
supports the support shaft 24 and the output shaft ~5~
If worklng fluid~leaks from the hydraulic closed circuit
between the hydraulic pump P and the hydraulic motor M during the
aforementioned operation, when the distribution valve 44 assumes
the inward position in the valve hole 45, working fluid in the
leaked amount is replenished from the replenishing oil passage 49
to the low pressure oil passage 41 through that distribution valve
45.
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Turning again to Figure 1, a speed change control device
60 is connected to the operating lever 57 of the trunnion shaft
55 for the tilting operation of the motor swashplate 20.
The speed change control device 60 comprises a cylinder
61 secured to the swashplate anchor 23, and a pair of first and
second pistons 621, 622 which are slidably fitted in the cylinder
61 and are oppo-sed to each other so as to hold a tip end of the
operating lever 57 therebetween in their rotary direction. The
pistons 621, 622 are arranged so as to enable rotation of the
operating lever 57 by their sliding movement.
The first and second pistons 621, 622 define first and
second oil chambers 631~ 632 against respective opposed end walls
of the cylinder 61. There chambers 631, 632 accommodate therein
springs 641, 642 for urging the corresponding pistons 621, 622 to-
- ward the operating lever 57.
The first and second oil chambers 631r 632 communicate
with each other through a hyaraulic conduit 66 incorporating there-
in a speed change control valve 65. The conduit is fi}led
working fluid.
The speed change control valve 65 comprises a fixed
valve casing 67 and a rotary valve 69 rotatably fitted in a valve
port 68 of the valve casing 67. The rotary valve 69 is operated
for rotation between a hold position A, a speed reduction position
B and a speed increasing position C on hoth sides of the position
A by means of a speed change lever 70 secured to the outer end of
the rotary valve 69.
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The rotary valve 69 is provided with a communication
port 72 incorporating a check valve 71. The valve casing 67 in-
cludes a irst forked port 731 connected to the first oil chamber
631 and opening to one side of the valve port 68, and a second
forked port 732 connected to the second oil chamber 632 and open-
ing to the other side of the valve port 68. The communication
port 72 is designed such that in`the hold position A of the rotary
valve 69, the communication port 72 does not communicate with
either forked ports 731~ 732; in the speed reduction position B,
the port 72 communicates with both the forked ports 731~ 732 to
allow a flow of oil only in one direction from the former 731 to
the latter 732; and in the speed increasing position C, the port
72 communicates with both forked ports 731~ 732 50 as to allow oil
flow only in the direction from the latter 732 to the former 731.
Since the:number of the motor plungers 19, 19 ... is
odd, the thrust load applied by the group of motor plungers 19,
19 ... to the motor swashplate 20 during the rotation of the motor
cylinder 17 alternately varies in intensity between one side and
the other with the-tilting axis of the motor swashplate 20 as a
border. Vibratory tilting ~orque acts on the motor swashplate 20.
This vibratory tilting torque alternately acts as a pressing force
on the first and second pistons 621, 622 through the operating
lever 57.
With this, when the speed change lever 70 is shifted to
the reduction position B as shown, the flow of oil from the first
oil chamber 631 to the second oil chamber 632 is permitted by
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the check valve 71 but the opposite flow is inhibited. Thus,
when the pressing ~orce acts on the first piston 621 from the
operating lever 57, the oil flows from the first oil chamber 631 to
the second oil chamber 632. As a consequence of this, both the
pistons 621, 622 are moved toward the first oil chamber 631 to turn
the operating lever 57 in the direction of increasing the inclina-
tion of the motor swashplate 20.
When the lever 70 is shifted to the increasing position
C, the flow of oil from the second oil chamber 632 to the first
oil chamber 631 is permitted by the check valve 71 but the opposite
flow is inhibited. Thus, when the pressing force acts on the
second piston 622 from the operating lever 57, the oil flows from
: the second oil chamber 632 to the first oil chamber 531~ As a
consequence of this, both the pistons 621, 622 are moved toward
the second oil chamber 632 to turn the operating lever 57 toward
the upright position of the motor swashplate 20.
When the speed change lever 70 is returned to the hold
position A, communication between both the oil chambers 631, 632
is completely cut off and the flow of oil therebetween is inhibited.
Therefore, both the pistons~621, 622 become unable to move. The
operating lever 57 is held at its position to lock the motor swash-
plate 20 at the upright position or incl~ned position.
Between the high and low pressure oil passages 40, 4I,
there is provided one or more piston type clutch valves 80. This
; clutch valve 80 is slidably fitted in a radial valve port ~1 which
extends from the high pressure oil passage 40 to the low pressure
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~L299062
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oil passage 40 and opens to the outer peripheral surface of the
motor cylinder 17. When the valve occupies the radial inward
position (clutch ON position) in the valve port 81, both the oil
passages 40, 41 are interrupted. When the valve occupies the radial
outward position (clutch OFF position), both the oil passages 40,
41 are brought into communication with each other.
In order that the clutch valve 80 is urged toward the
clutch OFF position, the inner end thereof receives oil pressure
from the high pressure oil passage 40. A common clutch control
ring 82 is slidably provided around the outer periphery of the
pump cylinder 7 and is engaged with the outer end of valve a.
The clutch control ring 82 includes a cylindrical inner
peripheral surface 82a for defining the clutch ON position of the
clutch valve 80 and a tapered surface 82b joined to one end o said
inner peripheral surface to define the clutch OFF position of the
clutch valve 80. The ring is urged by means of a spring 83 toward
- the side wherein the clutch valve 80 is held in the clutch ON posi-
tion. This spring 83 is compressed between~the clutch control ring
82 and a retainer 84 engaged on the outer periphery of the pump
cylinder 7.
The clutch control ring 82 is connected to a not-shown
clutch operating lever through a shift fork 85, an intermediate
lever 86 and a clutch wire 87. The shift fork 85 engages an outer
peripheral groove 88 of the clutch control ring 82, and an operat-
ing rod 89 secured to the base of the shift fork 85 extends through
the crank case 4 and is operatively connected to the intermediate
1291~62
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lever 86.
With this, when the clutch control ring 82 is moved to
the right as viewed in the figure against the force of the spring
83 through the shift fork 85 by pulling the clutch wire 87, the
tapered surface 82b of the clutch control ring 82 assumes a posi-
tion opposed to the clutch valve 80. Therefore the clutch valve
80 is moved by the pressure of the high pressure oil passage 40
to the outward position, namel~, to the clutch OFF position. As
the result, the high pressure oil passage 40 and low pressure oil
passage 41 are short-circuited through the valve port 81, and so
the pressure of the high pressure oil passage 40 is lowered to dis-
able the feed of pressure oil to the hydraulic motor M to make the
hydraulic motor M inoperative. In this case, if a plurality of
clutch valves 80 are arranged in the circumferential direction of
the high and low pressure oil passag*s 40, 41, the shor~-circuiting
resistance of both the oil passages 40, 41 is decreased.
When the clutch control ring 82 is moved to left to
operate the clutch valve 80 toward the clutch ON position, the
workiny fluid is circulated between the hydraulic pump P and the
hydraulic motor M through the high and low pressure oil passages
40, 41 in a manner as previously mentioned, and the hydraulic motor
M is returned to its operating condition.
In an intermediate position between the a~oresaid right-
ward position and leftward position of the clutch control ring 82,
a communication opening between both the oil passages 40, 41 is
moderately adjusted and the working fluid may be cirzulated aceord-
ing to the degree of opening thereof to place the hydraulic motor
M in a half-clutch state.
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