U.S. patent application number 10/520971 was filed with the patent office on 2005-08-11 for hydraulic device.
Invention is credited to Yogo, Teruaki.
Application Number | 20050175467 10/520971 |
Document ID | / |
Family ID | 32958691 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050175467 |
Kind Code |
A1 |
Yogo, Teruaki |
August 11, 2005 |
Hydraulic device
Abstract
A fluid pressure apparatus is obtained whose installation
position is not restricted. The fluid pressure apparatus is
provided with a fluid pressure pump (1) driven by an electric motor
(6) and rotatable in both directions. Both ports of the fluid
pressure cylinder are respectively connected to both ports of a
fluid pressure pump (1) through a pair of pipe lines. A sliding
cavity (38) is formed between an outer cylinder (32) and the inner
cylinder (34), and is divided into a preload chamber (50) and a
tank chamber (18) by the piston (44) slidably inserted in the
sliding cavity (38). The tank chamber (18) and the pair of pipe
lines are connected through check valves respectively provided in
directions so as to allow discharge from the tank chamber (18). The
tank chamber (18) is preloaded with air pressure introduced into
the preload chamber (60). In addition, a fluid pressure pump (1) is
disposed in the inner cylinder (34). The fluid pressure pump (1) is
a swash plate piston pump. The outer cylinder (32) and the inner
cylinder (34) are arranged coaxially with the rotating shaft 42 of
the electric motor (6). The outer cylinder (32) and the inner
cylinder (34) are mounted on the electric motor (6).
Inventors: |
Yogo, Teruaki; (Aichi,
JP) |
Correspondence
Address: |
DAVIS & BUJOLD, P.L.L.C.
FOURTH FLOOR
500 N. COMMERCIAL STREET
MANCHESTER
NH
03101-1151
US
|
Family ID: |
32958691 |
Appl. No.: |
10/520971 |
Filed: |
January 11, 2005 |
PCT Filed: |
March 3, 2004 |
PCT NO: |
PCT/JP04/02660 |
Current U.S.
Class: |
417/217 |
Current CPC
Class: |
F04B 23/021 20130101;
F04B 23/026 20130101; F15B 7/10 20130101; F15B 15/18 20130101 |
Class at
Publication: |
417/217 |
International
Class: |
F04B 049/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2003 |
JP |
2003056258 |
Claims
1-5. (canceled)
6. A fluid pressure apparatus provided with a fluid pressure pump
driven by an electric motor and rotatable in two directions, both
ports of a fluid pressure actuator and both ports of the fluid
pressure pump being respectively connected through a pair of pipe
lines; wherein a sliding cavity is formed between an outer cylinder
and an inner cylinder, and the sliding cavity is divided into a
preload chamber and a tank chamber by a piston slidably inserted in
the sliding cavity. the tank chamber and the pair of pipe lines are
connected through check valves respectively provided in directions
so as to allow discharge from the tank chamber, and the tank
chamber is preloaded with the air pressure introduced into the
preload chamber; and the fluid pressure pump is disposed in the
inner cylinder.
7. The fluid pressure apparatus according to claim 6, wherein the
fluid pressure pump is a swash plate piston pump.
8. The fluid pressure apparatus according to claim 6, wherein the
outer cylinder and the inner cylinder are arranged coaxially with a
rotating shaft of the electric motor, and the outer cylinder and
the inner cylinder are mounted on the electric motor.
9. The fluid pressure apparatus according to claim 6, wherein the
tank chamber communicates with the inside of the inner
cylinder.
10. The fluid pressure apparatus according to claim 6, wherein a
top end of the rotating shaft of the electric motor is rotatably
supported by a lid member closing one end of the outer cylinder and
one end of the inner cylinder.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fluid pressure apparatus
in which both ports of a fluid pressure pump, driven by an electric
motor and rotatable in both directions, are respectively connected
to both ports of a fluid pressure actuator through a pair of pipe
lines.
BACKGROUND ART
[0002] There are known conventional fluid pressure apparatus, such
as one shown in Publication of Unexamined Japanese Patent
Application No. 10-26101 (page 2, FIG. 2), in which both ports of a
fluid pressure pump driven, by an electric motor and rotatable in
both directions, are respectively connected to both ports of a
fluid pressure actuator through a pair of pipe lines. In this fluid
pressure apparatus, a fluid pressure tank and a pair of pipe lines
are connected through check valves oriented in respective
directions to allow the flow from the fluid pressure tank. The
sealed fluid pressure tank is preloaded by introducing air
pressure.
[0003] According to such a conventional fluid pressure apparatus,
however, a supply pipe connected to an air pressure source is
connected to the sealed fluid pressure tank, and air pressure is
introduced directly to the sealed fluid pressure tank. This leads
to a problem that in the installation of the fluid pressure tank,
it is necessary for an air layer formed in the fluid pressure tank
to be located in an upper position. In other words, the
installation position of the fluid pressure tank is restricted.
[0004] An object of the present invention is to provide a fluid
pressure apparatus whose installation position is not
restricted.
DISCLOSURE OF INVENTION
[0005] To achieve the above mentioned object, the present invention
has taken the following measures: there is provided a fluid
pressure apparatus provided with a fluid pressure pump driven by an
electric motor and rotatable in both directions, both ports of a
fluid pressure actuator and both ports of the fluid pressure pump
being respectively connected through a pair of pipe lines, wherein
a sliding cavity is formed between an outer cylinder and an inner
cylinder. The sliding cavity is divided into a preload chamber and
a tank chamber by a piston slidably inserted in the sliding cavity.
The tank chamber and the pair of pipe lines are connected through
check valves respectively provided in directions so as to allow
discharge from the tank chamber. The tank chamber is preloaded with
the air pressure introduced into the preload chamber, and the fluid
pressure pump is disposed in the inner cylinder.
[0006] The fluid pressure pump may be a swash plate pump. Also, it
may be possible to arrange the outer cylinder and the inner
cylinder coaxially with a rotating shaft of the electric motor, and
mount the outer cylinder and the inner cylinder on the electric
motor. Furthermore, the tank chamber may communicate with the
inside of the inner cylinder. Alternatively, a top end of the
rotating shaft of the electric motor may be rotatably supported by
a lid member closing one end of the outer cylinder and one end of
the inner cylinder.
BRIEF DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a cross-sectional view of a fluid pressure
apparatus as an embodiment of the present invention; and
[0008] FIG. 2 is a hydraulic circuit diagram of the fluid pressure
apparatus according to the present embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0009] An embodiment of the present invention will be described
below in detail based on the drawings.
[0010] As shown in FIG. 2, a fluid pressure pump 1 is a swash plate
piston pump that can be rotated in both directions. During a
rotation in a forward direction, an operating fluid is drawn in
from the side of a first port 2 and discharged from the side of a
second port 4. During a rotation in a reverse direction, the
operating fluid is drawn in from the side of the second port 4 and
discharged from the side of the first port 2. The fluid pressure
pump 1 is connected so as to be rotationally driven by an electric
motor 6, such as a servomotor.
[0011] A head side pipe line 8 and a rod side pipe line 10 are
respectively connected to the first port 2 and the second port 4.
The head side pipe line 8 is connected to a head side port 14 of a
fluid pressure cylinder 12 of a single-rod type, while the rod side
pipe line 10 is connected to a rod side port 16 of the fluid
pressure cylinder 12. Other than the fluid pressure cylinder 12 of
a single-rod type, any fluid actuator may be employed, such as a
fluid pressure cylinder of a double-rod type and a fluid pressure
motor
[0012] An after-mentioned tank chamber 18 is connected to the head
side pipe line 8 through a pilot check valve 20. The pilot check
valve 20 is oriented in a direction to allow the flow from the tank
chamber 18 toward the head side pipe line 8. The pilot check valve
20 is connected so as to introduce the fluid pressure in the rod
side pipe line 10 as a pilot pressure, and be opened to make the
head side pipe line 8 communicate with the tank chamber 18 when the
fluid pressure in the rod side pipe line 10 is increased.
[0013] Also, the rod side pipe line 10 is connected to the tank
chamber 18 through a pilot check valve 22. The pilot valve 22 is
oriented in a direction to allow the flow from the tank chamber 18
toward the rod side pipe line 10. The pilot check valve 22 is
connected so as to introduce the fluid pressure in the head side
pipe line 8 as a pilot pressure, and be opened to make the rod side
pipe line 10 communicate with the tank chamber 18 when the fluid
pressure in the head side pipe line 8 is increased. In the present
embodiment, the head side pipe line 8 and the rod side pipe line 10
are connected to the tank chamber 18 through relief valves 24, 26,
respectively. The relief valves 24, 26 may be provided when
necessary.
[0014] As shown in FIG. 1, there is provided a tank body 36
including a tubular outer cylinder 32 and a tubular inner cylinder
34 having a smaller diameter than the outer cylinder 32 and being
formed within the outer cylinder 32. The outer diameter of the
outer cylinder 32 is designed to be approximately the same as the
outer diameter of the electric motor 6. The outer cylinder 32 and
the inner cylinder 34 are arranged coaxially with each other.
[0015] A ring-shaped sliding cavity 38 is formed between the outer
cylinder 32 and the inner cylinder 34, one end of the ring-shaped
sliding cavity 38 being closed by a wall 40.
[0016] The wall 40 is mounted on one end of the electric motor 6,
and thereby the tank body 36 is fixed to the electric motor 6. A
rotating shaft 42 of the electric motor 6 is provided so as to be
positioned coaxially with the outer cylinder 32 and the inner
cylinder 34.
[0017] A ring-shaped piston 44 sealed by O-rings 46, 48 is slidably
inserted in the sliding cavity 38. The sliding cavity 38 is divided
into a preload chamber 50, on the side of the wall 40, and the tank
chamber 18 by the piston 44. A lid member 52 is mounted to the
other end of the sliding cavity 38 defined by the outer cylinder 32
and the inner cylinder 34, thereby closing the tank chamber 18. The
lid member 52 is also inserted inside the inner circumference of
the inner cylinder 34 so as to rotatably support a top end of the
rotating shaft 42, through a bearing 54.
[0018] A pump chamber 56 is formed by being enclosed by the inner
cylinder 34, the wall 40, and the lid member 52. The rotating shaft
42, sealed by a seal 57, penetrates the pump chamber 56. A cylinder
block 58, engagingly attached to and integrally rotatable with the
rotating shaft 42, is disposed within the pump chamber 56. The
cylinder block 58 is provided with a plurality of cylinder holes 60
bored in the axial direction. Through holes 62 are respectively
bored adjacent to the cylinder holes 60, and pistons 64 are
slidably inserted into the respective cylinder holes 60, so that
cylinder chambers 66 are formed by the cylinder holes 60 and the
pistons 64.
[0019] A valve plate 68 is provided between the cylinder block 58
and the lid member 52, such that the through holes 62 may
communicate with the first port 2 and the second port 4 through a
not-shown pair of port holes formed in the valve plate 68 in
accordance with the rotation of the cylinder block 58
[0020] On the other hand, a shoe 70, provided to be spherically
connected to one end of each of the pistons 64, is designed to
slide on an anti-friction member 74 attached to a swash plate 72.
The swash plate 72 is firmly attached to the wall 40 of the tank
body 36 so as to be restricted from rotation.
[0021] A coil spring 76, housed in the preload chamber 50, biases
the piston 44 toward the tank chamber 18. The preload chamber 50,
which is connected to a connection port 78, is connected to an air
pressure source 80 through the connection port 78. The tank chamber
18, communicating with the pump chamber 56 through a communication
path 82, is connected to the above-mentioned pilot check valves 20
and 22, and relief valves 24 and 26, through a connecting duct
84.
[0022] Next, the operation of the above described fluid apparatus
in the present embodiment will be described.
[0023] When the electric motor 6 is rotated in a forward direction,
the rotating shaft 42 rotates together with the cylinder block 58.
This causes each shoe 70 to slide on the anti-friction member 74
and each piston 64 to slide within the sliding hole 60 in
accordance with the inclination of the swash plate 72, thereby
changing the volume of the cylinder chamber 66. So that, an
operating fluid is drawn through the first port 2 and a pressure
fluid is discharged through the second port 4.
[0024] Accordingly, the operating fluid is drawn from the head side
port 14 of the fluid pressure cylinder 12 through the head side
pipe line 8 into the first port 2 of the fluid pressure pump 1.
Also, the pressure fluid is supplied from the second port 4,
through the rod side pipe line 10, and the rod side port 16 to the
fluid pressure cylinder 12.
[0025] Then, a cylinder rod 86 is driven in a pulling direction. In
this case, the amount of the operating fluid discharged from the
head side port 14 is different from the amount of the pressure
fluid flowing in from the rod side port 16 by the volume of the
cylinder rod 86. The excess amount of the operating fluid is
discharged through the head side pipe line 8 to the tank chamber
18, since the pilot check valve 20 is opened by the operation of
the pilot pressure from the rod side pipe line 10. In this regard,
the operation speed and the moving amount of the fluid pressure
cylinder 12 can be controlled by controlling the electric motor
6.
[0026] When the electric motor 6 is rotated in a reverse direction,
the operating fluid is drawn from the second port 4 of the fluid
pressure pump 1 through the rod side port 16 of the fluid pressure
cylinder 12, and the rod side pipe line 10, while the pressure
fluid is supplied to the fluid pressure cylinder 12 through the
first port 2, the head side pipe line 8, and the head side port 14.
Accordingly, the cylinder rod 86 is driven in a pushing
direction.
[0027] In this case, the amount of the operating fluid discharged
from the rod side port 16 is different from the amount of the
pressure fluid flowing in from the head side port 14 by the volume
of the cylinder rod 86 in the same manner as described above. The
deficient amount of the operating fluid is supplied from the tank
chamber 18 to the rod side pipe line 10 through the pilot check
valve 22, since the pressure in the rod side pipe line 10 is
decreased, and thereby the pilot check valve 22 is opened.
Specifically, the operating fluid is supplied to the rod side pipe
line 10 through the pilot check valve 22 due to the preload applied
to the tank chamber 18, which prevents the occurrence of cavitation
on the drawing side of the fluid pressure pump 1.
[0028] In contrast, when the rotation of the electric motor 6 is
stopped, the pressure fluid is not discharged from the fluid
pressure pump 1. Accordingly, both pilot check valves 20 and 20 are
opened by the operating fluid pressure in the tank chamber 18 due
to the preload of the compressed air from the air pressure source
80. Thereby, the pressure in the tank chamber 18 is introduced into
the head side pipe line 8 and the rod side pipe line 10.
[0029] As a result, the fluid pressure is introduced through both
ports 14 and 16 of the fluid pressure cylinder 12, and the cylinder
rod 86 is made difficult to move by a small external force even if
the external force is applied to the cylinder rod 86 and,
therefore, is prevented from deflecting. Also, since the tank
chamber 18 is preloaded by the piston 44 regardless of the
installation position of the tank body 36, there is no restriction
on the installation position of the fluid pressure apparatus. In
addition, since the circular tank chamber 18 is provided outside
the fluid pressure pump 1, a sufficient volume of the tank chamber
18 can be secured and downsizing of the fluid pressure apparatus
can be achieved.
[0030] The present invention is not limited to the above described
embodiment, but may be practiced in various forms within the scope
and not depart from the gist of the present invention.
[0031] As described in detail above, the fluid pressure apparatus
of the present invention presents an advantage that an appropriate
preload pressure can be applied regardless of its installation
position as well as an advantage that downsizing can be
achieved.
INDUSTRIAL APPLICABILITY
[0032] According to the present invention, there is provided a
fluid pressure apparatus capable of applying an appropriate preload
pressure regardless of its installation position and capable of
being downsized.
* * * * *