U.S. patent application number 11/887796 was filed with the patent office on 2009-02-19 for eccentric radial piston pump and eccentric radial piston motor.
This patent application is currently assigned to Komatsu Ltd.. Invention is credited to Hideshi Iitani, Kenji Morino, Tadashi Nakagawa.
Application Number | 20090047146 11/887796 |
Document ID | / |
Family ID | 37086789 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090047146 |
Kind Code |
A1 |
Morino; Kenji ; et
al. |
February 19, 2009 |
Eccentric Radial Piston Pump and Eccentric Radial Piston Motor
Abstract
In an eccentric radial piston pump, a rib 12 protruded in a
radial direction is formed on an inner peripheral surface of an end
portion on a discharge side of an eccentric cam ring 3 over a
prescribed range. In an eccentric radial piston motor, a rib 12
protruded in a radial direction is formed on an inner peripheral
surface of an end portion on a high pressure side of an eccentric
cam ring 3 over a prescribed range. By the rib 12 formed in the
radial direction, a rigidity of the eccentric cam ring 3 can be
improved, and the eccentric cam ring can be prevented from being
deformed by a thrust from the piston. Thus, the rigidity of the
eccentric cam ring can be increased without increasing the
thickness of the eccentric cam ring, and further the eccentric
radial piston pump and the eccentric radial piston motor in which
outside dimensions in the radial direction are reduced can be
provided.
Inventors: |
Morino; Kenji; (Tochigi,
JP) ; Nakagawa; Tadashi; (Tochigi, JP) ;
Iitani; Hideshi; (Fukushima, JP) |
Correspondence
Address: |
EVEREST INTELLECTUAL PROPERTY LAW GROUP
P. O. BOX 708
NORTHBROOK
IL
60065
US
|
Assignee: |
Komatsu Ltd.
Tokyo
JP
|
Family ID: |
37086789 |
Appl. No.: |
11/887796 |
Filed: |
March 24, 2006 |
PCT Filed: |
March 24, 2006 |
PCT NO: |
PCT/JP2006/305912 |
371 Date: |
October 3, 2007 |
Current U.S.
Class: |
417/273 |
Current CPC
Class: |
F04B 1/07 20130101; F04B
49/125 20130101; F04B 9/045 20130101; F04B 1/0413 20130101; F04B
9/042 20130101 |
Class at
Publication: |
417/273 |
International
Class: |
F04B 1/04 20060101
F04B001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2005 |
JP |
2005-112440 |
Claims
1. An eccentric radial piston pump in which a displacement volume
of pressure oil is changed in accordance with an eccentric amount
of an eccentric cam ring, wherein the eccentric cam ring is
slidably disposed between a pair of guiding surfaces which are
opposingly disposed inside a casing of the eccentric radial piston
pump, and a rib protruded in a radial direction is disposed on an
inner peripheral surface of an end portion on a discharge side of
the eccentric cam ring over a prescribed range.
2. The eccentric radial piston pump according to claim 1, wherein
the rib is disposed covering an entire inner periphery of the inner
peripheral surface of the end portion.
3. The eccentric radial piston pump according to claim 1 or 2,
wherein a thickness of the eccentric cam ring is approximately
equal to that of the rib.
4. The eccentric radial piston pump according to claim 1 or 2,
wherein a rotation stop engaging member being used when the
eccentric cam ring is made eccentric and/or an engaging member
engaging an operative mechanism which imparts the eccentric amount
to the eccentric cam ring is/are provided on an outer side surface
of the rib which is parallel to an eccentric direction of the
eccentric cam ring.
5. The eccentric radial piston pump according to claim 3, wherein a
rotation stop engaging member being used when the eccentric cam
ring is made eccentric and/or an engaging member engaging an
operative mechanism which imparts the eccentric amount to the
eccentric cam ring is/are provided on an outer side surface of the
rib which is parallel to an eccentric direction of the eccentric
cam ring.
6. An eccentric radial piston motor in which a displacement volume
of pressure oil is changed in accordance with an eccentric amount
of an eccentric cam ring, wherein the eccentric cam ring is
slidably disposed between a pair of guiding surfaces which are
opposingly disposed inside a casing of the eccentric radial piston
motor, and a rib protruded in a radial direction is provided on an
inner peripheral surface of an end portion on a high-pressure side
of the eccentric cam ring over a prescribed range.
7. The eccentric radial piston motor according to claim 6, wherein
the rib is disposed covering an entire inner periphery of the inner
peripheral surface of the end portion.
8. The eccentric radial piston motor according to claim 6 or 7,
wherein a thickness of the eccentric cam ring is approximately
equal to that of the rib.
9. The eccentric radial piston motor according to claim 6 or 7,
wherein a rotation stop engaging member being used when the
eccentric cam ring is made eccentric and/or an engaging member
engaging an operative mechanism which imparts the eccentric amount
to the eccentric cam ring is/are provided on an outer side surface
of the rib which is parallel to an eccentric direction of the
eccentric cam ring.
10. The eccentric radial piston motor according to claim 8, wherein
a rotation stop engaging member being used when the eccentric cam
ring is made eccentric and/or an engaging member engaging an
operative mechanism which imparts the eccentric amount to the
eccentric cam ring is/are provided on an outer side surface of the
rib which is parallel to an eccentric direction of the eccentric
cam ring.
Description
TECHNICAL FIELD
[0001] The present invention relates to an eccentric radial piston
pump and an eccentric radial piston motor.
BACKGROUND ART
[0002] In an eccentric radial piston pump or an eccentric radial
piston motor, the center of an eccentric cam ring and the rotation
center of the casing in a radial piston pump or an eccentric radial
piston motor are made eccentric, and by changing this eccentric
amount, the stroke amount of the piston in a cylinder block is
changed. By changing the stroke amount of the piston, displacement
volume of pressure oil by the piston is changed so that the volume
of the eccentric radial piston pump or the eccentric radial piston
motor can be variably controlled.
[0003] An eccentric radial piston pump having a structure as
disclosed in Patent Document 1 has been employed conventionally. In
the eccentric radial piston pump disclosed in Patent Document 1,
the arrangement relationship of a control piston for driving an
eccentric cam ring and a servo control valve is specified, so that
the occupancy space in the radial direction is attempted to be
reduced.
[0004] A cross-sectional shape of the eccentric radial piston pump
described in Patent Document 1 is shown in FIG. 13 as a prior art
example in the present invention. Respective pistons 41 are
disposed in respective cylinder bores of a cylinder block 40.
Respective connecting rods 42 having respective piston shoes 42a
are rotatably coupled with the respective pistons 41. The piston
shoe 42a slides along the inner peripheral surface of an eccentric
cam ring 43 disposed in the outer periphery side of the cylinder
block 40.
[0005] A pintle 44 having an intake port and a discharge port is
disposed at the center of the cylinder block 40, and the center of
the pintle 44 and the center of the eccentric cam ring 43 can be
disposed such that they are eccentric. The eccentric cam ring 43
can eccentrically move while maintaining a parallel condition with
respect to the center axis line of the cylinder block 40.
[0006] The eccentric amount of the eccentric cam ring 43 is
controlled by control pistons 46, 47. The respective ends of the
control pistons 46, 47 make contact with the eccentric cam ring 43
and press the eccentric cam ring 43 from the both sides by the
urging force of springs 48, 49. The eccentric cam ring 43 can be
eccentric with respect to the center axis of the pintle 44 by
pressure oil that acts on the control piston 46.
[0007] Pressure oil supplied to the control piston 46 is controlled
by a servo control valve 50 disposed to be tilted in a
circumferential direction of a casing 45.
Patent Document 1: Japanese Patent Laid-open Publication No.
2004-68796
DISCLOSURE OF THE INVENTION
Problem to Be Solved by the Invention
[0008] In the eccentric radial piston pump or the eccentric radial
piston motor, the eccentric amount of the center of the eccentric
cam ring and the rotation center of the casing in the radial piston
pump or the eccentric radial piston motor is controlled by the
movement amount of the eccentric cam ring. Thrust force generated
by the piston is supported by the inner peripheral surface of the
eccentric cam ring. Thus, the entire thrust force from the piston
is supported in such a way that a concentrated load is supported on
the lower surface of the eccentric cam ring.
[0009] Accordingly, when rigidity of the eccentric cam ring is
small, and for example, when the thickness of the eccentric cam
ring is thin, the eccentric cam ring is deformed to be a triangular
shape by a thrust force from the piston. That is, as shown in FIG.
14, the eccentric cam ring which is circular in an unloaded
condition receives a thrust force (indicated by arrows in FIG. 15)
from the pistons whose cylinder bores' insides are at high
pressure, so that the eccentric cam ring receives a deformation
stress from the inside thereof to be deformed. Thus, the eccentric
cam ring, while being circular in an unloaded condition as shown in
FIG. 14, is deformed to be a triangular shape by receiving the
deforming stress as shown in FIG. 15.
[0010] In the case where deformation occurs in the eccentric cam
ring, the cylindrical surface of the piston shoe sliding along the
inner peripheral surface of the eccentric cam ring is not in
complete contact with the inner peripheral surface of the deformed
eccentric cam ring along their whole surfaces, so that a gap is
generated. Due to this gap, the contact of the piston shoe against
the inner peripheral surface of the eccentric cam ring becomes
nonuniform.
[0011] For example, while the piston shoe is sliding along the
inner peripheral surface of the eccentric cam ring, when it reaches
a place where the outer diameter on the cylindrical surface of the
piston shoe is larger than the inner diameter of the eccentric cam
ring, only both end edge sides in the circumferential direction of
the piston shoe slide on the inner diameter of the eccentric cam
ring, so that a large surface pressure is applied to the both end
edge sides. By the large surface pressure applied to the both end
edge sides in the circumferential direction of the piston shoe,
bending stress is generated in the piston shoe. Further, when it
reaches a place where the outer diameter on the cylindrical surface
of the piston shoe is smaller than the inner diameter of the
eccentric cam ring, the contact of the piston shoe becomes less, so
that it is likely to float.
[0012] With respect to Patent Document 1, as shown in FIG. 13, in
the conventional eccentric radial piston pump or the eccentric
radial piston motor, the thickness of the eccentric cam ring is
configured to be thick in order to prevent the eccentric cam ring
from being deformed.
[0013] However, in the case where the thickness of the eccentric
cam ring is configured to be thick, a problem arises in that the
outside dimension in the radial direction in the eccentric radial
piston pump or the eccentric radial piston motor becomes large.
Specifically, in the eccentric radial piston pump or the eccentric
radial piston motor, while the outside dimension in the radial
direction is required to be constructed as small as possible,
making the outside dimension in the radial direction large runs
counter to the requirement.
[0014] An object of the present invention is to solve the problems
in the prior art and to provide an eccentric radial piston pump and
an eccentric radial piston motor by which the rigidity of an
eccentric cam ring can be increased even when the thickness of the
eccentric cam ring is not configured to be thick, and the outside
dimension in the radial direction can be configured to be
small.
Means to Solve the Problems
[0015] Objects of the present invention can be achieved by
respective inventions described in claims 1 to 10.
[0016] That is, in the first present invention, an eccentric radial
piston pump in which a displacement volume of pressure oil is
changed in accordance with an eccentric amount of an eccentric cam
ring is most mainly characterized in that a rib protruded in a
radial direction is provided on an inner peripheral surface of an
end portion on a discharge side of the eccentric cam ring over a
prescribed range.
[0017] In the second present invention, the shape of the rib is
defined, and that is the main characteristic.
[0018] Further, in the third present invention, the relationship of
the thickness of the eccentric cam ring and that of the rib is
defined, and that is the main characteristic.
[0019] Moreover, in the fourth and fifth present inventions, the
structure in a side end surface of the rib is defined, and that is
the main characteristic.
[0020] In the sixth present invention, an eccentric radial piston
motor in which a displacement volume of pressure oil is changed in
accordance with an eccentric amount of an eccentric cam ring is
most mainly characterized in that a rib protruded in a radial
direction is provided on an inner peripheral surface of an end
portion on a high-pressure side of the eccentric cam ring over a
prescribed range.
[0021] In the seventh present invention, the shape of the rib is
defined, and that is the main characteristic.
[0022] Further, in the eighth present invention, the relationship
of the thickness of the eccentric cam ring and that of the rib is
defined, and that is the main characteristic.
[0023] Moreover, in the ninth and tenth present inventions, the
structure in a side end surface of the rib is defined, and that is
the main characteristic.
EFFECT OF THE INVENTION
[0024] In the present invention, in an eccentric radial piston pump
and an eccentric radial piston motor, by forming a rib in the
radial direction on the inner peripheral surface of the eccentric
cam ring without increasing the thickness of the eccentric cam
ring, the rigidity of the eccentric cam ring can be increased.
[0025] Furthermore, by forming the rib on the inner peripheral
surface of the end portion on the discharge side of the eccentric
cam ring in the eccentric radial piston pump, and by forming the
rib on the inner peripheral surface of the end portion on the high
pressure side of the eccentric cam ring in the eccentric radial
piston motor, the eccentric cam ring can be prevented from being
deformed by a thrust from the piston.
[0026] In the present invention, the rib can also be disposed
covering the entire inner periphery of an inner peripheral surface
of the end portion of the eccentric cam ring. By disposing the rib
covering the entire inner periphery of the inner peripheral surface
of the end portion, deformation prevention of the eccentric cam
ring can be further rigidly achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic vertical cross-sectional view of an
eccentric radial piston pump (First Embodiment).
[0028] FIG. 2 is a vertical cross-sectional view of an eccentric
cam ring (First Embodiment).
[0029] FIG. 3 is a vertical cross-sectional view of another
eccentric cam ring (First Embodiment).
[0030] FIG. 4 is a vertical cross-sectional view of yet another
eccentric cam ring (First Embodiment).
[0031] FIG. 5 is a perspective view of an eccentric cam ring (First
Embodiment).
[0032] FIG. 6 is another perspective view of an eccentric cam ring
(First Embodiment).
[0033] FIG. 7 is yet another perspective view of an eccentric cam
ring (First Embodiment).
[0034] FIG. 8 is a model view for analyzing the rigidity of an
eccentric cam ring (First Embodiment).
[0035] FIG. 9 is a view showing stress distribution of the
analytical model (First Embodiment).
[0036] FIG. 10 is a table showing analysis results (First
Embodiment).
[0037] FIG. 11 is a schematic vertical cross-sectional view of an
eccentric radial piston pump (Second Embodiment).
[0038] FIG. 12 is a schematic vertical cross-sectional view of an
eccentric radial piston motor (Third Embodiment).
[0039] FIG. 13 is a schematic vertical cross-sectional view of an
eccentric radial piston pump (Conventional example).
[0040] FIG. 14 is a configuration view of an eccentric cam ring in
an unloaded condition (Explanatory example).
[0041] FIG. 15 is a deformed view of the eccentric cam ring when a
load is applied (Explanatory example).
EXPLANATION OF REFERENCE NUMERALS
[0042] 1 eccentric radial piston pump [0043] 3 eccentric cam ring
[0044] 4 cylinder block [0045] 5 piston [0046] 8 pintle [0047] 10
intake port [0048] 11 discharge port [0049] 12 rib [0050] 15a, 15b
piston [0051] 22, 23 operative mechanism [0052] 25a, 25b piston
[0053] 28a, 28b pressing member [0054] 30, 31 engaging member
[0055] 32 eccentric radial piston motor [0056] 33 pintle [0057] 34,
35 port [0058] 40 cylinder block [0059] 41 piston [0060] 43
eccentric cam ring [0061] 44 pintle [0062] 46, 47 control piston
[0063] 50 servo control valve
BEST MODE FOR CARRYING OUT THE INVENTION
[0064] A suitable embodiment of the present invention will be
described specifically below with reference to the accompanying
drawings. As the structures of an eccentric radial piston pump and
an eccentric radial piston motor of the present invention,
configurations and arrangement structures through which the
problems of the present invention can be solved can also be
adopted, other than configurations and arrangement structures
described below. Thus, the present invention is not limited to
embodiments described below, and various modifications are
possible.
[0065] An eccentric radial piston pump or an eccentric radial
piston motor according to the present invention also includes an
eccentric radial piston pump/motor which can employ both pump
operation and motor operation.
FIRST EMBODIMENT
[0066] FIG. 1 illustrates a schematic vertical cross-sectional view
of an eccentric radial piston pump 1 according to an embodiment of
the present invention. FIG. 2 illustrates a vertical
cross-sectional view of an eccentric cam ring 3. As shown in FIG.
1, the eccentric cam ring 3 is disposed in a casing 2, and a
cylinder block 4 is rotatably disposed inside the eccentric cam
ring 3. In the cylinder block 4, a plurality of cylinder bores 7
are formed in the radial direction thereof, and respective pistons
5 are slidably disposed in the respective cylinder bores 7.
[0067] A piston shoe 6 is swingably supported in the piston 5. The
piston shoe 6 slides on a cam surface 3A of the eccentric cam ring
3 and slides on the cam surface 3A in accordance with the rotation
of the cylinder block 4. Sliding of the piston shoe 6 on the cam
surface 3A can impart reciprocating motion to the piston 5.
[0068] A pintle 8 disposed in the casing 2 is fitted into a pintle
inserting portion 9 of the cylinder block 4 to rotatably support
the cylinder block 4. In the pintle 8, an intake port 10 and a
discharge port 11 are formed. By the rotation of the cylinder block
4, the piston 5 repeats an intake process and a discharge
process.
[0069] In the intake process, the piston 5 slides in a direction in
which the piston 5 protrudes from the cylinder bore 7 from the top
dead center to the bottom dead center to suck pressure oil from the
intake port 10 to the inside of the cylinder bore 7. In the
discharge process, the piston 5 slides from the bottom dead center
to the top dead center to compress the pressure oil in the cylinder
bore 7. The pressure oil which became high pressure by the
compression is discharged from the discharge port 11.
[0070] As shown in FIG. 2, a ring-shaped rib 12 is formed along the
inner peripheral surface of the eccentric cam ring 3. In FIG. 1,
the ring-shaped rib 12 formed along the inner peripheral surface of
the eccentric cam ring 3 is illustrated as a shape in which it
extends from the cam surface 3A to the center side of the eccentric
cam ring 3.
[0071] In the left and right sides of the casing 2, cylinder
chambers 14a, 14b are formed, and in the respective cylinder
chambers 14a, 14b, pistons 15a, 15b making contact with the outer
peripheral surface of the eccentric cam ring 3 are slidably
disposed respectively. The respective pistons 15a, 15b are urged by
springs 16a, 16b, respectively, and top end portions of the
respective pistons 15a, 15b make contact with the outer peripheral
surface of the eccentric cam ring 3, while pressing it
constantly.
[0072] By a switching operation of a switching valve 18, pressure
oil from a hydraulic pump 19 is supplied to one side cylinder
chamber 14a or the cylinder chamber 14b, and pressure oil in the
other side cylinder chamber 14b or the cylinder chamber 14a can be
discharged to a tank 20.
[0073] The outer peripheral surface of the eccentric cam ring 3
slides on guiding surfaces 13 formed on upper and bottom portions
of the casing 2. By activating the pistons 15a, 15b in accordance
with the switching operation of the switching valve 18, the
eccentric cam ring 3 can be moved along the guiding surfaces 13,
and the eccentric amount with respect to the rotational center of
the cylinder block 4 can be adjusted.
[0074] As shown in FIG. 2, the rib 12 is formed on the inner
peripheral surface of the end portion of the eccentric cam ring 3,
circularly toward the inside in the radial direction, so that the
rigidity of the eccentric cam ring 3 is increased by the rib
12.
[0075] Since the rigidity of the eccentric cam ring 3 is increased
by forming the rib 12 so that its deformation can be prevented, the
cam surface 3A of the eccentric cam ring 3 can constantly maintain
a certain shape. Thus, a sliding condition of the piston shoe 6 and
the cam surface 3A can be maintained in an excellent condition
constantly, and the piston shoe 6 can be prevented from floating
from the cam surface 3A.
[0076] The rib 12 may be constructed integrally with the eccentric
cam ring 3 or may be constructed as a distinct body form the
eccentric cam ring 3. In the case where the rib 12 is constructed
as a distinct body, the rib 12 may be fixedly fitted into the inner
peripheral surface of the eccentric cam ring 3 by using pressure or
the like, or may be fixedly secured to the eccentric cam ring 3 by
employing a fixing means such as welding or the like.
[0077] The rib 12 needs to be constructed in such a way that the
protrusion amount of the rib 12 in the radial direction is set to
an amount by which the rib 12 can have an enough rigidity to
prevent the eccentric cam ring from being deformed by a thrust from
the piston 5. Further, in the relationship between the material and
thickness of the rib 12, the protrusion amount in the radial
direction can be adjusted.
[0078] As shown in FIG. 3, as the ribs 12 respectively disposed on
both end portions of the eccentric cam ring 3, one rib may be
constructed integrally with the eccentric cam ring 3, and the other
rib 12 may be constructed as a distinct body from the eccentric cam
ring 3. The rib 12 constructed as the distinct body may be
structured in such a way that it has a flange portion projecting
toward the inner peripheral surface side of the eccentric cam ring
3 as shown in FIG. 3, or the rib 12 may be constructed in such a
way that it has flange portions projecting toward the inner
peripheral surface side and the outer circumferential surface side
of the eccentric cam ring 3, respectively, as shown in FIG. 4. The
rib 12 constructed as the distinct body can be fixed to the
eccentric cam ring 3, by employing a fitting fixing method by using
pressure or the like, or a fixing method such as welding or the
like.
[0079] The structure of the rib 12 may have shapes shown by
perspective views of the eccentric cam ring 3 illustrated in
respective FIGS. 5 to 7 other than the circular rib shape. The
shapes of the rib 12 shown in FIGS. 5 to 7 are examples, and the
present invention is not limited to those shapes. These shapes can
be employed as the rib of the present invention as far as it is a
rib shape by which rigidity of the eccentric cam ring 3 can be
increased, and the rib shape at that time is included in the
present invention.
[0080] As shown in FIG. 5, the rib 12 can be disposed on a portion
of the inner peripheral surface of one end portion of the eccentric
cam ring 3. In this case, the same rib 12 can be disposed on a
portion to which a thrust from the piston 5 disposed on the
cylinder block 4 is largely applied. That is, the rib 12 can be
disposed on the inner peripheral surface of the end portion on a
discharge side of the eccentric cam ring 3.
[0081] The structure in which the rib 12 is disposed on the inner
peripheral surface of the end portion may include both structures
in which the rib 12 is disposed inside the inner peripheral surface
of the eccentric cam ring 3 and in which a side surface of the rib
12 and an end portion surface of the eccentric cam ring 3 are in
firmly contact with each other.
[0082] As shown in FIG. 6, the ribs 12 may also be disposed on both
end portions of the eccentric cam ring 3 to which a thrust from the
piston 5 is largely applied respectively. Further, as shown in FIG.
7, the ribs 12 may be disposed on the inner peripheral surface of
the end portion on both port sides of the eccentric cam ring
respectively.
[0083] Thus, the rib 12 can be formed in an area of the inner
peripheral surface of the end portion of the eccentric cam ring 3
which receives a large deformation load. By constructing it in this
way, the eccentric cam ring can be efficiently prevented from being
deformed by the rib 12 which is disposed over a required minimum
range.
[0084] As is apparent from the foregoing, the rib 12 disposed on
the inner peripheral surface of the end portion of the eccentric
cam ring 3 may be formed covering the entire circle of the inner
peripheral surface of the end portion of the eccentric cam ring 3,
or may also be formed in an area of the inner peripheral surface of
the end portion of the eccentric cam ring 3 which receives a large
deformation load as a thrust from the piston 5 since pressure oil
inside the cylinder bore 7 is at a high pressure.
[0085] In the case where the rib 12 is disposed on a part of the
inner peripheral surface of the end portion of the eccentric cam
ring 3, it is necessary that the rib 12 is constructed in such a
way that concentrated load is not applied to the boundary between
the portion where the rib 12 is disposed and the portion where it
is not disposed, that is, the boundary between the rib 12 and one
end portion surface of the eccentric cam ring 3.
[0086] In the case where the ribs 12 is disposed on inner
peripheral surfaces of both end portions the eccentric cam ring 3
respectively, the rib 12 disposed at least one end side may have a
divided shape and may be constructed as a distinct body from the
eccentric cam ring 3. Or, as shown in FIG. 6, the rib 12 may be
constructed in such a way that the protrusion amount in the radial
direction of the rib 12 disposed on one end side is smaller than
that in the radial direction of the rib 12 disposed on the other
end portion side.
[0087] By constructing in such a way, at the time of assembling the
eccentric radial piston pump 1, rib pieces formed as distinct
bodies by dividing the rib 12 into several pieces may be assembled
sequentially in accordance with insertion and assembly of the
piston into the cylinder block.
[0088] Alternatively, the outer circumferential diameter including
the piston shoes 6 of when the respective pistons 5 are inserted
into the respective cylinder bores 7 of the cylinder block 4 until
the top dead center may be set to be an outer circumferential
diameter which enables to be inserted through the opening, which is
formed by the upper end of the rib 12 on the side where the
protrusion amount in the radial direction of the rib 12 is lowered
and by the inner peripheral surface of the eccentric cam ring
3.
[0089] Thus, the ribs can be disposed on both ends of the eccentric
cam ring, and assembly work in which the pistons 5 are attached to
the cylinder block 4 disposed inside the eccentric cam ring 3 can
be done easily.
[0090] The thickness of the rib 12 is desired to be approximately
equal to the thickness of the eccentric cam ring 3. FIG. 8 shows an
analyzing model view showing the relationship between the thickness
t1 of the eccentric cam ring 3 and the thickness t2 of the rib 12,
and shows the cross-sectional shape of an adjacent region of the
eccentric cam ring 3.
[0091] Respective models of the eccentric cam ring 3 in which the
ratio of the thickness t1 of the eccentric cam ring 3 and the
thickness t2 of the rib 12 is changed were made under conditions in
which the inner diameter, flange inner diameter, and cam width of
the eccentric cam ring 3 are fixed sizes, employing the eccentric
cam ring 3 shown in FIG. 8, and analysis by finite element method
was done with respect to cam stresses in the respective models.
While the analysis by the finite element method was done, the ratio
of the thickness t1 and the thickness t2 was changed under the
condition in which the mass of the eccentric cam ring 3 is
approximately constant.
[0092] Stress distribution of the cam stress calculated by
employing the finite element method became the stress distribution
as shown in FIG. 9. FIG. 9 is a principal part perspective view in
which a portion where the eccentric cam ring 3 makes contact with
the guiding surface 13 of the casing 2 is the center thereof. As is
apparent from FIG. 9, maximum stress .sigma..sub.1 is generated at
a portion where the eccentric cam ring 3 on the discharge side
makes contact with the guiding surface 13 of the casing 2. Further,
it is apparent that the stress becomes smaller from .sigma..sub.2
to .sigma..sub.3, and .sigma..sub.4 in accordance with the distance
from the portion where it makes contact with the guiding surface 13
becoming larger.
[0093] Further, as is apparent from FIG. 9, in the portion where at
least maximum stress .sigma..sub.1 is generated, or in a portion
where stress which is larger than a desired stress (for example,
stress larger than .sigma..sub.3) is generated, by forming another
rib on one end portion of the eccentric cam ring 3, stress
generated can be suppressed small. That is, in FIG. 9, although an
example in which the rib 12 is formed on one side of the eccentric
cam ring 3 is shown, for example, the rib 12 may be formed on both
end sides of the eccentric cam ring 3 as shown in FIG. 6, so that
the eccentric cam ring 3 can have a structure which is further hard
to be deformed.
[0094] FIG. 9 is a table showing analysis results of the cam stress
calculated through the finite element method under the
above-mentioned conditions in the above-mentioned respective
models. As is apparent from FIG. 9, when the ratio of the thickness
t1 of the eccentric cam ring 3 and the thickness t2 of the rib 12
is 1:1, the cam stress is minimum. Moreover, maximum cam stress
generated at that time can be in an allowable range. Further, when
the ratio of the thickness t1 and the thickness t2 is 1:1, the
outside dimension of the eccentric cam ring 3 can be minimum.
[0095] Thus, when the ratio of the thickness t1 and the thickness
t2 is 1:1, the dimension of the eccentric radial piston pump 1 in
the radial direction can be configured to be small. Further, the
rigidity of the eccentric cam ring 3 can be strong enough to
prevent the eccentric cam ring 3 from being deformed.
[0096] In this way, by the structure in which the thickness t1 of
the eccentric cam ring 3 is approximately equal to the thickness t2
of the rib 12, the eccentric cam ring 3 can be provided with a
rigidity by which deformation due to a thrust from the piston can
be prevented, and further the dimension of the eccentric cam ring 3
can be minimum.
[0097] Moreover, sliding stability of the piston shoe 6 can be
obtained, and the eccentric radial piston pump 1 can be stably
driven. Furthermore, the rigidity of the eccentric cam ring 3 can
be increased without increasing the thickness t1 of the eccentric
cam ring 3. Thus, the outside dimension of the eccentric radial
piston pump 1 in the radial direction thereof can be configured to
be small, and further, volume efficiency can be improved.
[0098] Even when an operative mechanism or the like of the
eccentric cam ring 3 is disposed inside the eccentric radial piston
pump 1, the outside dimension of the eccentric radial piston pump 1
in the radial direction thereof can be reduced.
[0099] When the operative mechanism or the like which imparts the
eccentric amount to the eccentric cam ring 3 is disposed outside
the eccentric cam ring 3 in the axial direction thereof, the length
of the eccentric radial piston pump 1 in the axial direction
thereof is long. However, since the outside dimension of eccentric
radial piston pump 1 in the radial direction thereof can be
reduced, as a result, the maximum dimension including the vertical
and horizontal lengths and the height of the eccentric radial
piston pump 1 can be configured to be small.
[0100] Further, since the outside dimension of the eccentric radial
piston pump 1 in the radial direction thereof is reduced, the area
on which the eccentric radial piston pump 1 is disposed can be
reduced, so that it can be disposed effectively even on a compact
hydraulic machine or the like.
SECOND EMBODIMENT
[0101] FIG. 11 shows a schematic vertical cross-sectional view of
another eccentric radial piston pump 1 according to an embodiment
of the present invention. In the first embodiment, as a structure
for making the eccentric cam ring 3 eccentric, by operation of
pistons 15a, 15b provided on left and right sides of the casing 2,
the eccentric cam ring 3 can be eccentric.
[0102] On the other hand, in the second embodiment, engaging
members 30, 31 are formed on a side surface of the rib 12 disposed
on the eccentric cam ring 3, and operative mechanisms 22, 23
imparting an eccentric amount is allowed to affect the engaging
members 30, 31, so that the eccentric cam ring 3 is allowed to be
eccentric.
[0103] The second embodiment has this structure which is different
from the structure of the first embodiment. Other structures are
similar to those of the first embodiment. Thus, like reference
numerals designating corresponding structures in the second
embodiment, and explanation thereof will be omitted.
[0104] The engaging members 30, 31 formed on a side surface of the
rib 12 may be disposed on it as members which are fitted into a
hole 12a shown in FIG. 2, or they may be formed integrally with the
rib 12. The operative mechanism 22 is provided with a pair of
pistons 25a, 25b which receive pressure oil from the hydraulic pump
19 to press the engaging member 30 and springs 26a, 26b pressing
the pair of pistons 25a, 25b toward the engaging member 30 side
respectively. The operative mechanism 23 is provided with a pair of
pressing members 28a, 28b pressing from both ends of the engaging
member 31 and springs 29a, 29b urging pressing force to the pair of
pressing members 28a, 28b.
[0105] The pair of pistons 25a, 25b and the springs 26a, 26b in the
operative mechanism 22 are disposed inside cylinder chambers 24a,
24b, respectively. By switching of the switching valve 18, pressure
oil from the hydraulic pump 19 is supplied to the cylinder chamber
24b, and when pressure oil inside the cylinder chamber 24a is
discharged to the tank 20, the piston 25b slides toward the left
direction in FIG. 11, and the eccentric cam ring 3 also moves
toward the left direction in FIG. 11. When this switching valve 18
is switched from the switching position thereof to the opposite
switching position, the eccentric cam ring 3 can be moved toward
the right direction in FIG. 11.
[0106] The pair of pressing members 28a, 28b in the operative
mechanism 23 are urged toward a direction in which they come close
to each other by the urging force of the springs 29a, 29b disposed
inside spring chambers 27a, 27b, respectively. A rotation stop
mechanism of the eccentric cam ring 3 is formed by the pair of
pressing members 28a, 28b.
[0107] When the eccentric cam ring 3 moves by the operation of the
pair of pistons 25a, 25b in the operative mechanism 22, the springs
29a, 29b are deformed, respectively, and the eccentric cam ring 3
can be moved in parallel.
[0108] The disposed position of the cylinder chamber 24b and the
disposed position of the spring chamber 27a provided with the
pressing member 28a may be reversed to construct the operative
mechanism 22 and the operative mechanism 23. At this time, the
operative mechanism 22 is composed of the cylinder chamber 24a
provided with the piston 25a and the spring chamber 27a provided
with the pressing member 28a disposed in place of the cylinder
chamber 24b, and the operative mechanism 23 is composed of the
cylinder chamber 24b provided with the piston 25b disposed in place
of the spring chamber 27a and the spring chamber 27b provided with
the pressing member 28b.
[0109] Further, similarly, the disposed position of the cylinder
chamber 24b and the disposed position of the spring chamber 27b
provided with the pressing member 28b may be reversed to construct
the operative mechanism 22 and the operative mechanism 23.
[0110] Even when such a structure is made, pressure oil discharged
from the switching valve 18 is selectively supplied to the cylinder
chamber 24a and the cylinder chamber 24b, so that movement of the
eccentric cam ring 3 can be controlled.
[0111] In the structure of the second embodiment, pairs of pistons
making contact with both sides of the engaging members 30, 31 shown
in FIG. 11, respectively, may be disposed at both sides of the
engaging members 30, 31, respectively.
[0112] As shown in FIG. 11, since the operative mechanisms 22, 23
can be disposed on the outside of the eccentric cam ring 3 in the
axial direction thereof and even on the inner diameter side of the
eccentric cam ring 3, the outer shape of the eccentric radial
piston pump 1 in the radial direction thereof can be configured to
be small.
[0113] In this case, since the operative mechanisms 22, 23
imparting the eccentric amount to the eccentric cam ring 3 are
disposed on the outside of the eccentric cam ring 3 in the axial
direction thereof, the length of the eccentric radial piston pump 1
in the axial direction thereof becomes longer.
[0114] However, since the outside dimension of the eccentric radial
piston pump 1 in the radial direction thereof can be made small, as
a result, the maximum dimension including the vertical and
horizontal lengths and the height of the eccentric radial piston
pump 1 can be configured to be small.
[0115] Instead of the structure in which the hole 12a shown in FIG.
2 is employed as a hole for attaching the engaging members 30, 31
engaging the operative mechanisms 22, 23, the hole 12a may be
employed as a rotation stop member for stopping the rotation of the
eccentric cam ring 3. Further, instead of the structure in which
the hole 12a is formed on a side surface of the rib 12, a rotation
stop member may be constructed integrally with the eccentric cam
ring.
THIRD EMBODIMENT
[0116] FIG. 12 shows a schematic vertical cross-sectional view of
an eccentric radial piston motor 32 according to an embodiment of
the present invention. The third embodiment has a structure similar
to that of the eccentric radial piston pump 1 in the first
embodiment except that it shows the structure of the eccentric
radial piston motor 32. Thus, as to the similar structures to the
eccentric radial piston pump 1, the explanation of the reference
numerals will be omitted below by employing the reference numerals
used in FIG. 1.
[0117] The eccentric radial piston motor 32 has a structure in
which the cylinder block 4 and a pintle 33 rotate integrally. Thus,
passages of pressure oil formed in the pintle 33, which are
communicated with ports 34, 35, respectively, are formed to have
the same diameter.
[0118] In this connection, the eccentric radial piston pump 1 is
constructed in such a way that the pintle 8 does not rotate while
the cylinder block 4 rotates. Thus, with respect to the passages of
pressure oil formed in the pintle 33, the diameter of the passage
communicated with the intake port 10 is larger than that of the
passage communicated with the discharge port 11.
[0119] The eccentric radial piston pump 1 may be constructed in
such a way that the diameter of the passage communicated with the
intake port 10 is the same as that of the passage communicated with
the discharge port 11. Specifically, in the eccentric radial piston
pump/motor, it is necessary that the diameter of the passage
communicated with the intake port 10 is the same as that of the
passage communicated with the discharge port 11.
[0120] Although FIG. 1 shows a structural example in which the
intake port 10 is arranged in a lower side in the drawing and in
which the discharge port 11 is arranged in an upper side in the
drawing, arrangement positions of the intake port 10 and the
discharge port 11 may be reversed with respect to the arrangement
positions of FIG. 1.
[0121] In the eccentric radial piston motor 32 shown in FIG. 12,
for example, the port 34 located in a lower side in FIG. 12 is
communicated with pressure oil of a high pressure side, and the
port 35 located in an upper side is communicated with pressure oil
of a low pressure side. When the port 35 communicated with the low
pressure side in the upper side goes in a lower side by the
rotation of the cylinder block 4 and the pintle 33, it is
communicated with pressure oil of the high pressure side this
time.
[0122] At the same time, the port 34 communicated with the high
pressure side in the lower side is communicated with pressure oil
of the low pressure side. That is, the ports 34, 35 are
communicated with pressure oil of the high pressure side and
pressure oil of the low pressure side, alternately, respectively,
in accordance with the rotation of the cylinder block 4 and the
pintle 33.
[0123] High pressure oil is supplied from the port 34 or the port
35 which is communicated with pressure oil of the high pressure
side into the cylinder bore 7. By High pressure oil supplied into
the cylinder bore 7, the piston 5 inside the cylinder bore 7 is
pressed to rotate the cylinder block 4.
[0124] Similarly to the description of the case of the eccentric
radial piston pump 1 in the first embodiment, the rib 12 may be
constructed in such a way that it protrudes in the radial direction
over a predetermined area of the inner peripheral surface of the
end portion on at least the high pressure side of the eccentric cam
ring 3. By constructing the rib 12, the rigidity of the eccentric
cam ring 3 can be increased so that the eccentric cam ring 3 is not
deformed.
[0125] The rib 12 may be constructed similarly to those shown in
FIGS. 2 to 7. As described in the description of the first
embodiment, as far as the rib shape can increase the rigidity of
the eccentric cam ring 3, those shapes can be employed as a rib of
the present invention.
[0126] By providing the rib 12 on the eccentric cam ring 3, working
effects similar to those of the case of the first embodiment in
which the eccentric cam ring 3 having the rib 12 is employed in the
eccentric radial piston pump 1 can be produced. The results of the
analysis models described employing FIGS. 8 to 10 can be applied to
the case of the eccentric radial piston motor 32 without any
changes.
[0127] The structure of the eccentric radial piston motor 32 may be
similar to the eccentric radial piston pump 1 shown in FIG. 11
other than the structure shown in FIG. 12. At this time, it is
desired that the diameters of the passages formed on the pintle
communicated with the intake port 10 and the discharge port 11,
respectively, have the same diameters.
[0128] Similarly to the description in the second embodiment, a
rotation stop engaging member being used when the eccentric cam
ring is made eccentric or an engaging member with respect to an
operative mechanism imparting an eccentric amount to the eccentric
cam ring can be provided on a side surface of the rib 12 disposed
on the eccentric cam ring 3.
[0129] Although the structure of the eccentric radial piston pump 1
and the structure of the eccentric radial piston motor 32 are
described in the embodiments described above, the structure of the
eccentric radial piston pump or the eccentric radial piston motor
described in the embodiments includes the structure of an eccentric
radial piston pump/motor.
INDUSTRIAL USABILITY
[0130] In the present invention, technical idea of the present
invention can be applied to a device or the like to which the
technical idea of the present invention can be applied.
* * * * *