U.S. patent application number 15/326094 was filed with the patent office on 2017-07-27 for variable capacity piston pump.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. Invention is credited to Tsutomu MATSUO, Yuki UEDA, Takashi UNO, Naoya YOKOMACHI.
Application Number | 20170211556 15/326094 |
Document ID | / |
Family ID | 55078345 |
Filed Date | 2017-07-27 |
United States Patent
Application |
20170211556 |
Kind Code |
A1 |
UEDA; Yuki ; et al. |
July 27, 2017 |
VARIABLE CAPACITY PISTON PUMP
Abstract
A variable capacity piston pump including a control piston
pressing a pressed portion of a swashplate from a cylinder block
side to adjust an inclination of the swashplate between a maximum
inclination and a minimum inclination, and a swashplate return
spring biasing the pressed portion of the swashplate toward the
cylinder block side of the sliding contact surface, wherein there
is a positional relationship in which a vertical reference line
passes between a first seat surface center position of the
swashplate return spring when the swashplate is at the maximum
inclination and a second seat surface center position of the
swashplate return spring when the swashplate is at the minimum
inclination.
Inventors: |
UEDA; Yuki; (Kariya-shi,
JP) ; YOKOMACHI; Naoya; (Kariya-shi, JP) ;
MATSUO; Tsutomu; (Kariya-shi, JP) ; UNO; Takashi;
(Kariya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA JIDOSHOKKI |
Kariya-shi, Aichi |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOYOTA
JIDOSHOKKI
Kariya-shi, Aichi
JP
|
Family ID: |
55078345 |
Appl. No.: |
15/326094 |
Filed: |
July 2, 2015 |
PCT Filed: |
July 2, 2015 |
PCT NO: |
PCT/JP2015/069137 |
371 Date: |
January 13, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 1/2078 20130101;
F04B 1/2007 20130101; F04B 1/32 20130101; F04B 1/324 20130101 |
International
Class: |
F04B 1/32 20060101
F04B001/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2014 |
JP |
2014-145923 |
Claims
1. A variable capacity piston pump performing suction and discharge
of a hydraulic fluid by reciprocation of a piston in a cylinder
block rotating integrally with a rotating shaft, the stroke of the
reciprocation of the piston depending on an inclination of a
swashplate, wherein the swashplate includes a sliding contact
surface contacting slidably with one end portion of the piston via
a shoe, the swashplate being disposed to enable to turn about a
turning center to change the inclination that defines the stroke of
the piston, the variable capacity piston pump comprising: a
pressing portion disposed on one side with respect to the sliding
contact surface of the swashplate, the pressing portion pressing a
pressed portion of the swashplate to adjust the inclination of the
swashplate between a maximum inclination and a minimum inclination,
wherein a discharge capacity of the hydraulic fluid is maximized at
the maximum inclination and the discharge capacity of the hydraulic
fluid is minimized at the minimum inclination, and a swashplate
return spring disposed on the other side with respect to the
sliding contact surface of the swashplate, the swashplate return
spring extending along one direction and biasing the pressed
portion of the swashplate toward the one side of the sliding
contact surface, wherein the swashplate return spring is capable of
taking a first seat surface center position and a second seat
surface center position, wherein the first seat surface center
position is a position of a seat surface center on the swashplate
side when the inclination of the swashplate is the maximum
inclination and the second seat surface center position is a
position of the seat surface center on the swashplate side when the
inclination of the swashplate is the minimum inclination, and
wherein there is a positional relationship in which a vertical
reference line passes between the first seat surface center
position and the second seat surface center position, the vertical
reference line being a straight line perpendicular to a parallel
reference line and passing through the turning center of the
swashplate, the parallel reference line being a straight line
parallel to an axial direction of the swashplate return spring and
passing through the turning center of the swashplate.
2. The variable capacity piston pump according to claim 1, wherein
there is a positional relationship in which the vertical reference
line passes through a midpoint between the first seat surface
center position and the second seat surface center position.
3. The variable capacity piston pump according to claim 1, wherein
the swashplate return spring is disposed so that the axial
direction thereof is parallel to the rotating shaft.
Description
TECHNICAL FIELD
[0001] The present invention relates to a variable capacity piston
pump.
BACKGROUND ART
[0002] As a variable capacity piston pump in the related art, for
example, as described in Patent Literature 1 (Japanese Unexamined
Patent Publication No. 2006-348911), a variable capacity piston
pump which is used as a hydraulic pressure generation source of a
hydraulic circuit and changes a discharge capacity by adjusting the
inclination of a swashplate is known.
[0003] The variable capacity piston pump described in Patent
Literature 1 includes a control piston which presses the swashplate
and a swashplate return spring which biases the swashplate from a
side opposite to the control piston. As the control pressure of the
control piston is changed, the magnitude of a pressing force
exerted on the swashplate is changed. By controlling the magnitude
of the pressing force, the inclination of the swashplate is
adjusted. Specifically, when the pressing force of the control
piston is decreased, the inclination of the swashplate is increased
by the biasing force of the swashplate return spring. When the
pressing force of the control piston is increased, the inclination
of the swashplate is decreased.
SUMMARY OF INVENTION
Technical Problem
[0004] However, in the variable capacity piston pump described
above, due to the displacement of the inclination of the
swashplate, the position of a seat surface center in the swashplate
return spring on the swashplate side deviates from the axial line
of the swashplate return spring. That is, there is a possibility
that, the end portion of the swashplate return spring on the
swashplate side may be locally bent and buckled or may be damaged
due to local stress, resulting in functional deterioration. In
addition, as a result of the bending, there is a possibility that
the swashplate return spring may come into contact with other
components and may be damaged, resulting in functional
deterioration.
[0005] Therefore, in the variable capacity piston pump described in
Patent Literature 1, a member having a spherical surface on the
swashplate side is disposed at the end portion of the swashplate
return spring on the swashplate side. However, in the case where
the member having a spherical surface on the swashplate side is
disposed at the end portion of the swashplate return spring on the
swashplate side, there is a problem of an increase in the number of
components or an increase in costs due to a complex assembly
process.
[0006] An object of various aspects of the present invention is to
provide a variable capacity piston pump capable of suppressing
functional deterioration in a swashplate return spring.
Solution to Problem
[0007] According to an aspect of the present invention, there is
provided a variable capacity piston pump performing suction and
discharge of a hydraulic fluid by reciprocation of a piston in a
cylinder block rotating integrally with a rotating shaft, the
stroke of the reciprocation of the piston depending on an
inclination of a swashplate, wherein the swashplate includes a
sliding contact surface contacting slidably with one end portion of
the piston via a shoe, the swashplate being disposed to enable to
turn about a turning center to change the inclination that defines
the stroke of the piston, the variable capacity piston pump
comprising: a pressing portion disposed on one side with respect to
the sliding contact surface of the swashplate, the pressing portion
pressing a pressed portion of the swashplate to adjust the
inclination of the swashplate between a maximum inclination and a
minimum inclination, wherein a discharge capacity of the hydraulic
fluid is maximized at the maximum inclination and the discharge
capacity of the hydraulic fluid is minimized at the minimum
inclination, and a swashplate return spring disposed on the other
side with respect to the sliding contact surface of the swashplate,
the swashplate return spring extending along one direction and
biasing the pressed portion of the swashplate toward the one side
of the sliding contact surface, wherein the swashplate return
spring is capable of taking a first seat surface center position
and a second seat surface center position, wherein the first seat
surface center position is a position of a seat surface center on
the swashplate side when the inclination of the swashplate is the
maximum inclination and the second seat surface center position is
a position of the seat surface center on the swashplate side when
the inclination of the swashplate is the minimum inclination, and
wherein there is a positional relationship in which a vertical
reference line passes between the first seat surface center
position and the second seat surface center position, the vertical
reference line being a straight line perpendicular to a parallel
reference line and passing through the turning center of the
swashplate, the parallel reference line being a straight line
parallel to an axial direction of the swashplate return spring and
passing through the turning center of the swashplate.
[0008] In the variable capacity piston pump, there is a positional
relationship in which the vertical reference line passes between
the first seat surface center position which is the position of the
seat surface center on the swashplate side when the inclination of
the swashplate is the maximum inclination and the second seat
surface center position which is the position of the seat surface
center on the swashplate side when the inclination of the
swashplate is the minimum inclination. When the position of the
seat surface center on the swashplate side is on the vertical
reference line or near the vertical reference line, there is a
small variation of the seat surface center positions in the
directions of the vertical reference line. In the variable capacity
piston pump according to the present invention, since the first
seat surface center position and the second seat surface center
position are positioned with the vertical reference line interposed
therebetween, the position of the seat surface center on the
swashplate side is on the vertical reference line or near the
vertical reference line. Therefore, variation of the position of
the seat surface center on the swashplate side in the directions of
the vertical reference line can be reduced. Therefore, the
swashplate return spring can be provided such that the deviation
amount that the position of the seat surface center of the
swashplate return spring deviates from the axial line of the
swashplate return spring is decreased regardless of the inclination
of the swashplate. Therefore, in a range from the maximum
inclination to the minimum inclination of the swashplate, local
bending of the end portion of the swashplate return spring on the
swashplate side can be suppressed. Accordingly, functional
deterioration in the swashplate return spring can be
suppressed.
[0009] According to another aspect of the present invention, in the
variable capacity piston pump, there may be a positional
relationship in which the vertical reference line passes through a
midpoint between the first seat surface center position and the
second seat surface center position. In this case, the deviation
amount of the position of the seat surface center on the swashplate
side deviating from the axial line of the swashplate return spring
when the inclination of the swashplate is the maximum inclination
and the deviation amount of the position of the seat surface center
on the swashplate side deviating from the axial line of the
swashplate return spring when the inclination of the swashplate is
the minimum inclination can be equal to each other. That is, the
deviation amount of the position of the seat surface center on the
swashplate side deviating from the axial line of the swashplate
return spring does not excessively increase in any of cases where
the inclination of the swashplate is the maximum inclination or the
minimum inclination. Therefore, the deviation amount of the
position of the seat surface center of the swashplate return spring
deviating from the axial line of the swashplate return spring due
to the displacement of the inclination of the swashplate can be
minimized. Accordingly, local bending of the end portion of the
swashplate return spring on the swashplate side due to the
displacement of the inclination of the swashplate can be further
suppressed.
[0010] According to another aspect of the present invention, in the
variable capacity piston pump, the swashplate return spring may be
disposed so that its axial direction thereof is parallel to the
rotating shaft. In this case, assembly of the swashplate return
spring in the variable capacity piston pump is facilitated.
Advantageous Effects of Invention
[0011] According to the various aspects of the present invention, a
variable capacity piston pump capable of suppressing local bending
of a swashplate return spring is provided.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a schematic sectional view illustrating a variable
capacity piston pump according to an embodiment of the present
invention.
[0013] FIG. 2 is a perspective view of a swashplate illustrated in
FIG. 1.
[0014] FIG. 3 is a side view of the swashplate illustrated in FIG.
1 viewed from a side of a sliding contact surface.
[0015] FIG. 4 is a side view of the swashplate illustrated in FIG.
1 viewed on a side opposite to the sliding contact surface.
[0016] FIG. 5 is a view schematically illustrating the positional
relationship between the sliding contact surface of the swashplate
and a turning center of the swashplate.
[0017] FIG. 6 is a schematic view illustrating variation in the
position of a seat surface center of a swashplate return
spring.
[0018] FIG. 7 is a schematic view illustrating the position of a
seat surface center of a swashplate return spring at a position
different from that of FIG. 6.
[0019] FIG. 8 is a perspective view illustrating a swashplate
according to a modification example.
DESCRIPTION OF EMBODIMENTS
[0020] Hereinafter, an embodiment of the present invention will be
described in detail with reference to the accompanying drawings. In
the description, like elements which are the same or having the
same function are denoted by like reference numerals, and
overlapping description thereof will be omitted.
[0021] First, a variable capacity piston pump (hereinafter, "a
pump") according to the embodiment will be described with reference
to FIG. 1. A pump 1 includes a pump housing 10, a rotating shaft
20, and a cylinder block 14.
[0022] The pump housing 10 is configured by bonding a front housing
10a, a center housing 10b, and a rear housing 10c together, and has
a crank chamber 12 therein.
[0023] Most of the rotating shaft 20 is accommodated in the crank
chamber 12 of the pump housing 10, and only one end portion thereof
protrudes from the pump housing 10. The rotating shaft 20 is
rotatably held in the crank chamber 12 by a bearing. The end
portion of the rotating shaft 20 protruding from the pump housing
10 is connected to a power take-off (not illustrated) such that the
entirety of the rotating shaft 20 is driven to rotate by an
engine.
[0024] The cylinder block 14 is also accommodated in the crank
chamber 12 of the pump housing 10. The cylinder block 14 is
spline-fitted to the rotating shaft 20 so as to rotate integrally
with the rotating shaft 20. In the cylinder block 14, a plurality
of cylinder bores 14a, each including an opening on a side of the
protruding end portion of the rotating shaft 20, are provided, and
the plurality of cylinder bores 14a are disposed with intervals
therebetween at a predetermined angle around the rotating shaft 20
in the cylinder block 14. In addition, in each of the plurality of
cylinder bores 14a, a piston 16a having a head protruding toward
the side of the protruding end portion of the rotating shaft 20 is
accommodated.
[0025] A swashplate 30 is further accommodated in the crank chamber
12 of the pump housing 10. Hereinafter, the configuration of the
swashplate 30 will be described with reference to FIGS. 2 to 4.
FIG. 2 is a perspective view of the swashplate 30 illustrated in
FIG. 1. FIG. 3 is a side view of the swashplate illustrated in FIG.
1 viewed from a side of a sliding contact surface. FIG. 4 is a side
view of the swashplate illustrated in FIG. 1 viewed on a side
opposite to the sliding contact surface.
[0026] As illustrated in FIGS. 2 to 4, the swashplate 30 includes a
body portion 31, a pair of sliding portions 32, and a pressed
portion 33.
[0027] The body portion 31 has a substantially plate shape, and the
center portion thereof is provided with a through-hole 31a through
which the above-described rotating shaft 20 is inserted. The pair
of sliding portions 32 are provided at positions with the body
portion 31 interposed therebetween to be integrated with the body
portion 31.
[0028] The rear surface side of the body portion 31 and the sliding
portions 32 become a flat surface 30a as illustrated in FIG. 3, and
this surface is the sliding contact surface, which will be
described later. On the other hand, the front surface side of the
body portion 31 and the sliding portions 32 has a shape in which
the sliding portions 32 protrude from the body portion 31 as
illustrated in FIGS. 2 and 4. The section of the sliding portion 32
has a half-moon shape (D shape), and has a sliding surface 32a
which is curved at a predetermined curvature so as to be convex
toward the front surface side.
[0029] In addition, in the body portion 31, the pressed portion 33
which extends upward from the body portion 31 is provided. On the
rear surface side in the pressed portion 33, an accommodation hole
33a is formed, and a cylindrical member 33b, which will be
described later, is disposed in the accommodation hole 33a. In
addition, the cylindrical member 33b may be disposed in a fixed
state so as not to be turned, or may be disposed so as to be
turned. In addition, on the front surface side in the pressed
portion 33, at a position biased by the tip end portion of a
swashplate return spring 60, a protruding portion 33c and a planar
portion 33d with which the tip end portion of the swashplate return
spring 60 is engaged are formed.
[0030] Returning to FIG. 1, the position of the swashplate 30 is
held by a swashplate receiving member 34 disposed on the front
surface side thereof. The swashplate receiving member 34 has a
support surface 34a having substantially the same curvature as that
of the sliding surface 32a of the sliding portion 32 of the
swashplate 30 described above. The swashplate 30 is disposed so as
to cause the sliding surface 32a of the sliding portion 32 to come
into contact with the support surface 34a of the swashplate
receiving member 34 and is thus supported by the swashplate
receiving member 34 to be oscillated along the curvature. More
specifically, the swashplate 30 is capable of turning (regarded as
tilting or regarded as rotating) about the center X of curvature of
the support surface 34a of the swashplate receiving member 34 as
the origin. The center X of curvature is also the center of
curvature of the sliding surface 32a of the sliding portion 32 of
the swashplate 30. In addition, the center X of curvature can be
defined as a point at a constant distance (shortest distance) from
the sliding contact surface 30a regardless of the turning position
of the swashplate 30. In the following description, the center of
curvature is referred to as a turning center X. In addition, in
FIG. 1, the turning center X is denoted by a dot. However, the line
of the turning center X extends in an inward direction (a direction
perpendicular to the figure).
[0031] The swashplate 30 is disposed so as to turn about the
turning center X and change the inclination that defines the stroke
of the piston 16. For example, the inclination can be defined as an
angle with respect to a straight line perpendicular to the axial
line of the rotating shaft 20. In the embodiment, the inclination
is defined as an angle of the sliding contact surface 30a with
respect to the straight line perpendicular to the axial line of the
rotating shaft 20.
[0032] The sliding contact surface 30a on the rear surface side of
the swashplate 30 faces the cylinder block 14 side. The head (one
end portion) of each piston 16 protruding from the cylinder block
14 comes into sliding contact with the sliding contact surface 30a
via a shoe 36. The shoe 36 to which the head of the piston 16
attached is held in a disk-shaped retainer 35 having a hole into
which the shoe 36 is inserted. When the cylinder block 14 is
rotated along with the rotating shaft 20, each piston 16 rotates
about the rotating shaft 20 while sliding on the sliding contact
surface 30a via the shoe 36.
[0033] As the swashplate 30 is turned and inclined about the
turning center X, the end portion of the head side (the left end
portion in FIG. 1) of each piston 16 accommodated in the cylinder
block 14 comes in pressing contact via the shoe 36, and the
cylinder block 14 comes into pressing contact with a valve plate 40
fixed to the inner end wall surface of the rear housing 10c.
[0034] In addition, as the cylinder block 14 and the rotating shaft
20 rotate integrally with each other, the stroke of each piston 16
defined by the inclination of the swashplate 30 is reciprocated,
and the cylinder bore 14a alternately communicates with a suction
port 40a and a discharge port 40b forming an arc shape, which are
provided to penetrate through the valve plate 40. Accordingly,
hydraulic oil is suctioned into the cylinder bore 14a from the
suction port 40a, and the hydraulic oil in the cylinder bore 14a is
discharged from the discharge port 40b due to a pump action. In
addition, a suction passage 10d and a discharge passage 10e are
formed in the rear housing 10c to respectively communicate with the
suction port 40a and the discharge port 40b.
[0035] The pump 1 is further provided with a control piston 50
provided on the rear surface side of the swashplate 30, that is, on
the cylinder block 14 side. The control piston 50 is provided at a
side portion of the center housing 10b of the pump housing 10, and
includes a housing 52 that communicates with the crank chamber 12
and a piston portion 58 that reciprocates in the housing 52. The
housing 52 has a substantially cylindrical shape extending in a
direction inclined with respect to the rotating shaft 20 so as to
cause the piston portion 58 to face the pressed portion 33 of the
swashplate 30.
[0036] One opening of the openings of the housing 52 distant from
the swashplate 30 is blocked by a screw 54. Accordingly, a piston
accommodation chamber 56 is defined in the housing 52, and the
piston portion 58 is accommodated in the piston accommodation
chamber 56.
[0037] The piston portion 58 has a columnar external shape. The
diameter of the piston portion 58 is designed such that there is no
gap from the inner wall surface of the piston accommodation chamber
56 and the piston portion 58 slides in the piston accommodation
chamber 56. The end surface of the piston portion 58 on the
swashplate 30 is a planar shape and can move to a position that
comes into contact with the cylindrical member 33b in the pressed
portion 33 of the swashplate 30. As illustrated in FIG. 1, the end
surface of the piston portion 58 on the swashplate 30 side, which
is a pressing portion, comes into contact with the cylindrical
member 33b of the pressed portion 33 of the swashplate 30 to always
press the cylindrical member 33b with a predetermined pressing
force.
[0038] A space between the piston portion 58 and the screw 54 in
the piston accommodation chamber 56 functions as a control chamber
56a into which the hydraulic oil flows. The pressure in the control
chamber 56a (hereinafter, referred to as control pressure) is
changed due to the inflow of the hydraulic oil. The control piston
50 causes the piston portion 58 to slide due to a change in the
control pressure and press the swashplate 30 from the cylinder
block 14 side. Accordingly, the control piston 50 adjusts the
inclination of the swashplate 30 between the maximum inclination,
at which the discharge capacity of the hydraulic oil is maximized,
and the minimum inclination, at which the discharge capacity of the
hydraulic oil is minimized.
[0039] The pump 1 further includes the swashplate return spring 60
which is a cylindrical spiral shape (coil spring) extending in one
direction on the front surface side of the swashplate 30. That is,
the swashplate return spring 60 is disposed on the side opposite to
the control piston 50 with respect to the sliding contact surface
30a of the swashplate 30. Specifically, the base end portion of the
swashplate return spring 60 is accommodated in a spring chamber 70
formed in the front housing 10a of the pump housing 10.
[0040] In the embodiment, the spring chamber 70 is formed in
parallel to the rotating shaft 20, and the swashplate return spring
60 extends toward the swashplate 30 from the spring chamber 70. As
a result, the swashplate return spring 60 is disposed so that the
axial direction thereof is parallel to the rotating shaft 20. The
tip end portion of the swashplate return spring 60 abuts the front
surface of the pressed portion 33 of the swashplate 30 described
above and is engaged with the protruding portion 33c and the planar
portion 33d formed on the front surface. The swashplate return
spring 60 is not fixed to the spring chamber 70 and the swashplate
30 and the position and posture thereof are held in a state of
being interposed between the spring chamber 70 and the pressed
portion 33.
[0041] In other words, regarding the seat surfaces (spring end
surfaces) of the swashplate return spring 60, a seat surface 60a of
the base end portion abuts the bottom wall of the spring chamber
70, and a seat surface 60b of the tip end portion abuts the pressed
portion 33 of the swashplate 30. Accordingly, the swashplate return
spring 60 is compressed such that the swashplate 30 is biased
toward the cylinder block side with respect to the sliding contact
surface 30a. In addition, the swashplate return spring 60 is a wire
spring formed by processing a metallic wire rod such as SWP-B.
[0042] Next, with reference to FIGS. 5 and 6, the position of a
seat surface center of the swashplate return spring 60 on the
swashplate 30 side will be described in detail. Here, the seat
surface center of the swashplate return spring 60 on the swashplate
30 side is the center in the seat surface 60b of the swashplate
return spring 60 on the swashplate 30 side (tip end side), and for
example, refers to a position at an equivalent distance from all
the points on the outer circumference of the seat surface 60b. In
the embodiment, since the swashplate return spring 60 has a
cylindrical spiral shape, the shape of the seat surface 60b (that
is, the sectional shape of the tip end portion of the swashplate
return spring 60) is a circular shape, and the center of the circle
may be defined as the seat surface center. Hereinafter, the center
in the seat surface 60b of the swashplate return spring 60 on the
swashplate 30 side is referred to as the seat surface center of the
swashplate return spring 60.
[0043] First, references such as the turning center X, the vertical
reference line and the parallel reference line for the position of
the seat surface center of the swashplate return spring 60 will be
described. FIG. 5 is a view schematically illustrating the
positional relationship between the sliding contact surface 30a of
the swashplate 30 and the turning center X of the swashplate 30. In
addition, in FIG. 5, the turning center X is denoted by a dot.
However, the line of the turning center X extends in an inward
direction (a direction perpendicular to the figure).
[0044] As illustrated in FIG. 5, a distance d from the sliding
contact surface 30a of the swashplate 30 to the turning center X at
the maximum inclination indicated by "Max" and a distance d from
the sliding contact surface 30a of the swashplate 30 to the turning
center X at the minimum inclination indicated by "Min" are the
same. That is, the distance of the turning center X from the
sliding contact surface 30a is constant regardless of the
inclination of the swashplate 30. In addition, in a section, an
imaginary circle E that touches both the sliding contact surface
30a of the swashplate 30 at the maximum inclination and the sliding
contact surface 30a of the swashplate 30 at the minimum inclination
is drawn as a circle having the turning center X as its center.
That is, the turning center X can be defined as a central axial
line of a column having, as its section, the imaginary circle E
that touches the sliding contact surface 30a of the swashplate 30
regardless of the inclination of the swashplate 30.
[0045] The parallel reference line Y is a straight line which is
parallel to the axial direction of the swashplate return spring 60
and passes through the turning center X. In the embodiment, since
the axial line of the swashplate return spring 60 is parallel to
the rotating shaft 20, the parallel reference line Y is a line
parallel to the rotating shaft 20. A straight line that is
perpendicular to the parallel reference line Y and passes through
the turning center X is defined as the vertical reference line
Z.
[0046] FIG. 6 is a schematic view illustrating variation in the
position of the seat surface center of the swashplate return spring
60 due to the displacement of the inclination of the swashplate 30
in the pump 1. In FIG. 6, the parallel reference line Y, the
vertical reference line Z, and the turning center X shown in FIG. 5
are shown. In FIG. 6, furthermore, the axial line of the swashplate
return spring 60 is indicated by axial line S.
[0047] In FIG. 6, variation in the position of the seat surface
center of the swashplate return spring 60 in the pump 1 according
to the embodiment is indicated by a double-headed arrow A. The
double-headed arrow A represents that the position of the seat
surface center of the swashplate return spring 60 varies between a
position of the seat surface center of the swashplate return spring
60 when the inclination of the swashplate 30 is the maximum
inclination (hereinafter, referred to as a first seat surface
center position) A1, and a position of the seat surface center of
the swashplate return spring 60 when the inclination of the
swashplate 30 is the minimum inclination (hereinafter, referred to
as a second seat surface center position) A2. The angular
difference between the maximum inclination and the minimum
inclination of the swashplate 30 is indicated by 8. As illustrated
in FIG. 6, the position of the seat surface center of the
swashplate return spring 60 moves between the first seat surface
center position A1 and the second seat surface center position A2
along an arc of the imaginary circle having the turning center X as
its center. This is because the distance between the pressed
portion 33 of the swashplate 30 at which the seat surface center of
the swashplate return spring 60 is positioned and the turning
center X is always constant regardless of the inclination.
[0048] As indicated by the double-headed arrow A of FIG. 6, in the
pump 1 according to the embodiment, for example, when viewed in a
direction perpendicular to a plane parallel to the parallel
reference line Y and the vertical reference line Z (a direction
perpendicular to the figure), the vertical reference line Z passes
between the first seat surface center position A1 when the
inclination of the swashplate 30 is the maximum inclination and the
second seat surface center position A2 when the inclination of the
swashplate 30 is the minimum inclination. That is, the vertical
reference line Z is interposed between the first seat surface
center position A1 when the inclination of the swashplate 30 is the
maximum inclination and the second seat surface center position A2
when the inclination of the swashplate 30 is the minimum
inclination.
[0049] In a case where the first seat surface center position A1,
the second seat surface center position A2, and the vertical
reference line Z have this positional relationship, as illustrated
in FIG. 6, the position of the seat surface center of the
swashplate return spring 60 moves just beside the position of the
seat surface center in the range of the double-headed arrow A, and
there is substantially no displacement in upward and downward
directions (that is, directions of the vertical reference line Z)
of FIG. 6. Therefore, even when the inclination of the swashplate
30 moves from the maximum inclination to the minimum inclination
and accordingly the position of the seat surface center of the
swashplate return spring 60 moves from the first seat surface
center position A1 to the second seat surface center position A2,
the position of the seat surface center of the swashplate return
spring 60 barely changes in the directions of the vertical
reference line Z.
[0050] Therefore, by disposing the swashplate return spring 60 so
as to cause the axial line S to approach the first seat surface
center position A1 and the second seat surface center position A2,
the deviation amount of the position of the seat surface center of
the swashplate return spring 60 deviating from the axial line S at
the position of the maximum inclination (A1), at the position of
the minimum inclination (A2), and the position of an arbitrary
inclination therebetween is suppressed.
[0051] In FIG. 6, for comparison, cases where the vertical
reference line Z does not pass between the first seat surface
center position and the second seat surface center position of the
swashplate return spring 60 are indicated by double-headed arrows B
and C. In addition, in any case of the double-headed arrows B and
C, the difference .theta. between the maximum inclination and the
minimum inclination of the swashplate 30 is the same as the
difference .theta. of the double-headed arrow A described
above.
[0052] The double-headed arrow B indicates the amount of variation
in the position of the seat surface center of the swashplate return
spring 60 in a case where both a first seat surface center position
B and a second seat surface center position B2 of the swashplate
return spring 60 are positioned on the swashplate return spring 60
side in relation to the vertical reference line Z. As illustrated
in FIG. 6, when the inclination of the swashplate 30 changes from
the maximum inclination to the minimum inclination and accordingly
the position of the seat surface center of the swashplate return
spring 60 moves from the first seat surface center position B1 to
the second seat surface center position B2, the position of the
seat surface center of the swashplate return spring 60 gradually
moves in a downward direction and significantly displaces in the
directions of the vertical reference line Z. That is, in the case
where both the first seat surface center position B1 and the second
seat surface center position B2 are positioned on the swashplate
return spring 60 side in relation to the vertical reference line Z,
compared to the case where the vertical reference line Z passes
between the first seat surface center position A1 and the second
seat surface center position A2, displacement of the position of
the seat surface center of the swashplate return spring 60 in the
directions of the vertical reference line Z is increased.
[0053] Therefore, regard the case of the double-headed arrow B,
even when the swashplate return spring 60 is disposed so as to
cause the axial line S to be set closely to any of the position of
the maximum inclination (B1) and the position of the minimum
inclination (B2), the position of the seat surface center of the
swashplate return spring 60 significantly deviates from the axial
line S during the operation.
[0054] The double-headed arrow C indicates the amount of variation
in the position of the seat surface center of the swashplate return
spring 60 in a case where both a first seat surface center position
C1 and a second seat surface center position C2 are positioned on
the control piston 50 side in relation to the vertical reference
line Z. As illustrated in FIG. 6, when the inclination of the
swashplate 30 changes from the maximum inclination to the minimum
inclination and accordingly the position of the seat surface center
of the swashplate return spring 60 moves from the first seat
surface center position C1 to the second seat surface center
position C2, the position of the seat surface center of the
swashplate return spring 60 gradually moves in an upward direction
and significantly displaces in the directions of the vertical
reference line Z. That is, even in the case where both the first
seat surface center position C1 and the second seat surface center
position C2 are positioned on the control piston side in relation
to the vertical reference line Z, compared to the case where the
vertical reference line Z passes between the first seat surface
center position A1 and the second seat surface center position A2,
displacement of the position of the seat surface center of the
swashplate return spring 60 in the directions of the vertical
reference line Z is increased.
[0055] Therefore, regard the case of the double-headed arrow C,
similarly to the case of the double-headed arrow B, even when the
swashplate return spring 60 is disposed so as to cause the axial
line S to be set closely to any of the position of the maximum
inclination (C1) and the position of the minimum inclination (C2),
the position of the seat surface center of the swashplate return
spring 60 also significantly deviates from the axial line S during
the operation.
[0056] As described above, in the pump 1 according to the
embodiment, there is a positional relationship in which the
vertical reference line Z passes between the first seat surface
center position A1 of the swashplate return spring 60 and the
second seat surface center position A2 of the swashplate return
spring 60. When the position of the seat surface center of the
swashplate return spring 60 on the swashplate 30 side is on the
vertical reference line Z or near the vertical reference line Z,
there is a small variation in the directions of the vertical
reference line Z. In the pump 1 described above, since the first
seat surface center position A1 and the second seat surface center
position A2 are positioned with the vertical reference line Z
interposed therebetween, the position of the seat surface center on
the swashplate 30 side is on the vertical reference line Z or near
the vertical reference line Z. Therefore, variation of the position
of the seat surface center on the swashplate 30 side in the
directions of the vertical reference line Z can be reduced.
Therefore, the swashplate return spring 60 can be provided such
that the amount of the position of the seat surface center of the
swashplate return spring 60 deviating from the axial line S of the
swashplate return spring 60 is decreased regardless of the
inclination of the swashplate 30. Accordingly, functional
deterioration in the swashplate return spring 60 can be
suppressed.
[0057] In addition, the positional relationship in which the
vertical reference line Z passes between the first seat surface
center position A1 of the swashplate return spring 60 and the
second seat surface center position A2 of the swashplate return
spring 60, that is, the positional relationship in which the
vertical reference line Z is interposed between the first seat
surface center position A1 and the second seat surface center
position A2 includes a positional relationship in which the
vertical reference line Z overlaps the first seat surface center
position A1 or the second seat surface center position A2.
[0058] In the pump 1 according to the embodiment, the swashplate
return spring 60 is disposed so that the axial line thereof is
parallel to the rotating shaft 20. The swashplate return spring 60
is assembled between the front housing 10a and the center housing
10b which are arranged in the direction of the rotating shaft 20.
When the front housing 10a and the center housing 10b are joined to
each other, a pressing force along the axial line of the rotating
shaft 20 is exerted. Therefore, when the direction of the force is
the same as the axial direction of the swashplate return spring 60,
assembly of the swashplate return spring 60 is facilitated.
Furthermore, the pump 1 is generally designed on the basis of the
axial line of the rotating shaft 20. Therefore, when the spring
chamber 70 provided in the front housing 10a or the swashplate
return spring 60 extending from the spring chamber 70 are disposed
in parallel to the rotating shaft 20, design is facilitated.
[0059] In addition, typically, in preparation of local bending of
the tip end portion of the swashplate return spring, a region where
movement of the bent end portion is expected is excessively
secured. In this case, miniaturization of the pump is hindered, or
an increase in the dimensions of the pump is incurred. Contrary to
this, according to the pump 1 according to the embodiment, local
bending of the swashplate return spring 60 can be suppressed.
Therefore, there is no need to secure a large region, and
miniaturization of the pump housing 10 can be realized.
[0060] In addition, as indicated by the double-headed arrow A of
FIG. 7, the positional relationship between the first seat surface
center position A1, the second seat surface center position A2, and
the vertical reference line Z may be an embodiment in which the
vertical reference line Z passes through a midpoint P which is the
point that bisects a straight line that connects the first seat
surface center position A1 and the second seat surface center
position A2. In this case, the vertical reference line is
coincident with the perpendicular bisector of the straight line
that connects the first seat surface center position A1 and the
second seat surface center position A2.
[0061] At this time, when the swashplate return spring 60 is
disposed so as to cause the axial line S thereof to pass through
the first seat surface center position A1, the axial line S also
passes through the second seat surface center position A2 and the
midpoint P. That is, the first seat surface center position A1, the
second seat surface center position A2, and the midpoint P are
arranged along the direction of the axial line S, and there is no
positional offset in the directions of the vertical reference line
Z.
[0062] Here, regarding the case of the double-headed arrow A of
FIG. 6, when the radius of an imaginary circle on which the
position of the seat surface center of the swashplate return spring
60 moves is referred to as r and the inclination of the straight
line that connects the second seat surface center position A2 and
the turning center X is referred to as .theta.', the amount of the
position of the seat surface center of the swashplate return spring
60 between the first seat surface center position A1 and the second
seat surface center position A2 deviating from the axial line S
becomes r(1-cos .theta.'). Contrary to this, regarding the
double-headed arrow A of FIG. 7, the difference .theta. of the
double-headed arrow A is bisected into the swashplate return spring
60 side and the control piston 50 side. Therefore, both the
inclination of the straight line that connects the first seat
surface center position A1 and the turning center X with respect to
the vertical reference line Z and the inclination of the straight
line that connects the second seat surface center position A2 and
the turning center X become .theta./2, which is smaller than
.theta.'. Therefore, the deviation amount of the seat surface
center of the swashplate return spring 60 between the first seat
surface center position A1 and the second seat surface center
position A2 deviating from the axial line S is represented by
r(1-cos(.theta./2)). As described above, in the case where the
vertical reference line Z passes through the midpoint P, the amount
of the position of the position of the seat surface center of the
swashplate return spring 60 deviating from the axial line S of the
swashplate return spring 60 due to the displacement of the
inclination of the swashplate 30 can be minimized. Accordingly,
local bending of the end portion of the swashplate return spring 60
on the swashplate 30 side due to the displacement of the
inclination of the swashplate 30 can be further suppressed.
[0063] While various embodiments of the present invention have been
described, the present invention is not limited to the embodiments,
and includes modifications without departing from the gist
described in the appended claims and applications to other
forms.
[0064] The swashplate 30 is not limited to that in the embodiment.
For example, instead of the swashplate 30, a swashplate 130 having
a shape illustrated in FIG. 8 may be employed.
[0065] The swashplate 130 includes a pair of rotating shaft
portions 132 instead of the pair of sliding portions 32 of the
swashplate 30. The above-described swashplate 30 has a form that
rotates about the turning center X by cooperation between the
sliding portions 32 and the swashplate receiving member 34.
However, the swashplate 130 can rotate about the turning center X
since the pair of rotating shaft portions 132 having a columnar
shape extending along the turning center X are rotatably held in
the crank chamber 12. The swashplate 130 also includes a
disk-shaped body portion 131 having the same function as that of
the body portion 31 of the swashplate 30 described above. The body
portion 131 includes a sliding contact surface 130a, which is the
same as the sliding contact surface 30a, on the rear surface side
thereof and further includes a pressed portion 133 which is the
same as the pressed portion 33 at the upper portion thereof. The
swashplate 130 illustrated in FIG. 8 has functions which are the
same as or equivalent to those of the swashplate 30 described
above. Moreover, since the swashplate 130 includes the pair of
rotating shaft portions 132, the swashplate receiving member 34
described above becomes unnecessary, and simplification of the
configuration of the pump 1 can be achieved.
REFERENCE SIGNS LIST
[0066] 1 variable capacity piston pump [0067] 14 cylinder block
[0068] 16 piston [0069] 20 rotating shaft [0070] 30, 130 swashplate
[0071] 30a sliding contact surface [0072] 33, 133 pressed portion
[0073] 58 piston portion (pressing portion) [0074] 60 swashplate
return spring [0075] X turning center [0076] Y parallel reference
line [0077] Z vertical reference line [0078] A1 first seat surface
center position [0079] A2 second seat surface center position
* * * * *