Expansible chamber devices – Displacement control of plural cylinders arranged in... – Adjustable abutment positioned within working chamber
Reexamination Certificate
2000-06-22
2002-11-19
Look, Edward K. (Department: 3745)
Expansible chamber devices
Displacement control of plural cylinders arranged in...
Adjustable abutment positioned within working chamber
C092S013800
Reexamination Certificate
active
06481333
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a positioning device, and more particularly to a positioning device for various types of equipment including control of the capacity of a variable displacement piston motor/pump. And, the invention also relates to a speed changing device of a rotating body using a hydraulic motor.
Today's machines and equipment have been improved in performance such as speedup and labor saving on the basis of the employment of a hydraulic pressure. Especially, the piston motor/pump has high performance and efficiency and is important. This piston motor/pump is extensively used for construction work machines and many other fields.
The hydraulic motor includes a variable displacement motor whose capacity can be changed and a fixed displacement motor whose capacity cannot be changed.
The variable displacement motor will be described with reference to
FIG. 8
to FIG.
10
.
FIG. 8
shows a sectional diagram of the hydraulic motor disclosed in Japanese Patent Publication No. 4-42550. This piston motor is changed its capacity between two levels.
Specifically, first seat face
58
a
of swash plate
58
housed in casing
55
is contacted to inside wall surface
55
a
of the casing to position the capacity at a maximum capacity position. The capacity is positioned at a minimum capacity position when second seat face
58
b
of the swash plate
58
is contacted to the inside wall surface
55
a
of the casing. The positioning accuracy of the maximum capacity position and the minimum capacity position is determined depending on the accuracy of various parts such as the swash plate
58
and the casing
55
.
FIG. 9
shows a sectional diagram of a hydraulic motor different from the one shown in FIG.
8
. This motor is an inclined shaft type piston motor. This piston motor changes the capacity position to two levels by pivoting valve plate
46
. The valve plate
46
is accommodated in casing
52
. The capacity position is variable according to the pivoting of the valve plate
46
. Main shaft
51
is an output shaft of the hydraulic motor. The stop position of the valve plate
46
is restricted by minimum capacity adjusting mechanism
54
and maximum capacity adjusting mechanism
53
. The minimum capacity adjusting mechanism
54
comprises adjusting screw
54
b
mounted on the casing
52
and nut
54
a
for fixing the adjusting screw
54
b
to the casing
52
. One end of the adjusting screw
54
b
protrudes from the inside surface of the casing
52
, and the other end protrudes from the outside surface of the casing
52
. The maximum capacity adjusting mechanism
53
is also formed in the same way.
The motor has the minimum capacity when the valve plate
46
comes in contact with the leading end of the adjusting screw
54
b
protruded from the inside surface of the casing
52
. Similarly, the motor has the maximum capacity when the valve plate
46
comes in contact with the leading end of the adjusting screw
53
b
protruded from the inside surface of the casing
52
.
The minimum capacity position is adjusted by the minimum capacity adjusting mechanism
54
.
Specifically, the fixed state of the adjusting screw
54
b
by the nut
54
a
is released to adjust the screw-in amount of the adjusting screw
54
b
, and the adjusting screw
54
b
is fixed again to the casing
52
by the nut
54
a
. Thus, the minimum capacity position is adjusted. The maximum capacity position is also adjusted in the same way.
FIG. 10
is a sectional diagram of a conventional three-speed motor. In
FIG. 10
, like reference numerals are used to indicate the like components of
FIG. 9
, and their descriptions are omitted.
As shown in
FIG. 10
, first piston
110
and second piston
120
are disposed in body
44
. The first piston
110
is connected to the valve plate
46
. In first pressure-receiving chamber
130
, the second piston
120
applies a pressure to the first piston
110
. Second pressure-receiving chamber
140
applies a pressure in a direction to separate the first piston
110
and the second piston
120
from each other. Third pressure-receiving chamber
150
applies a pressure to the first piston
110
in a direction of the second piston
120
.
The second piston
120
has second piston large-diameter section
120
a
having a large outside diameter.
Second piston restricting part is configured by the second piston large-diameter section
120
a
and body inside wall surface
44
a
with which the second piston large-diameter section
120
a
is contacted. Specifically, the large-diameter section
120
a
of the second piston
120
moves toward the first piston
110
to contact the large-diameter section
120
a
with the body inside wall surface
44
a
. Thus, the second piston
120
is stopped. The first piston
110
comes in contact with the second piston
120
whose movement is restricted, and the valve plate
46
is positioned at a middle position.
Servo valve
60
is a control valve for controlling the supply of pressure oil to the second pressure-receiving chamber
140
and the third pressure-receiving chamber
150
. The pressure oil discharged from an unillustrated hydraulic pump is supplied to the servo valve
60
. And, the pressure oil discharged from an unshown hydraulic pump through an unshown 2-position selector valve is supplied to the first pressure-receiving chamber
130
. Switching of the valve position of the 2-position selector valve is controlled so to control the supply and stop of the pressure oil to the first pressure-receiving chamber
130
. Thus, the supply of the pressure oil to the first pressure-receiving chamber
130
, the second pressure-receiving chamber
140
and the third pressure-receiving chamber
150
is controlled so to switch the position of the first piston
110
, namely the position of the valve plate
46
, among three positions. Therefore, the capacity position of the motor is changed among three levels of minimum, middle and maximum capacity positions. But, the hydraulic motor shown in
FIG. 10
is different from the one shown in FIG.
9
and does not have an adjusting mechanism for adjusting the minimum and maximum capacity positions.
The aforesaid capacity change of the variable displacement motor is used to change the speed of HST (hydrostatic transmission) vehicle.
The HST vehicle such as a bulldozer has its left and right running bodies (wheels or caterpillars) independently driven by left and right hydraulic motors respectively. In other words, the left running body of the vehicle is independently driven and changed its speed by a drive mechanism exclusively disposed for the left side Similarly, the right running body of the vehicle is independently driven and changed its speed by a drive mechanism exclusively disposed for the right side. Each drive mechanism comprises a hydraulic pump and a hydraulic motor.
When the HST vehicle is instructed to run at the same number of left and right rotations, namely to run straight, it causes a deviation from the course if the left and right motor capacities are different.
Therefore, the HST vehicle whose left and right running bodies are independently driven is demanded to have improved accuracy for the capacity control of the left and right variable displacement piston motors so to run without causing a deviation from the course when straight-ahead running is instructed.
And, it is also demanded to simplify a device for controlling the capacity of the variable displacement piston motor.
Besides, it is also said generally that the installing space for the hydraulic equipment mounted to the HST vehicle is limited. Therefore, it is demanded to decrease a mounting area of the hydraulic equipment.
But, there is not any conventional variable displacement piston motor which satisfies the aforesaid demands. Descriptions will be made as follows.
The piston motor of the aforesaid publication shown in
FIG. 8
is mainly applied to a vehicle such as a hydraulic excavator requiring two speeds of high and low. The hydraulic excavator adjusts the pump capacity only and does
Akasaka Toshiyuki
Miyata Takahiro
Nunotani Sadao
Komatsu Ltd.
Lazo Thomas E.
Varndell & Varndell PLLC
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