U.S. patent application number 15/326061 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 | 20170211555 15/326061 |
Document ID | / |
Family ID | 55078344 |
Filed Date | 2017-07-27 |
United States Patent
Application |
20170211555 |
Kind Code |
A1 |
UEDA; Yuki ; et al. |
July 27, 2017 |
VARIABLE CAPACITY PISTON PUMP
Abstract
A variable capacity piston pump including a piston portion of
the control piston causing a pressing force to act along one
direction by 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 action position
which is an action position of the pressing force when the
inclination of the swashplate is the maximum inclination and a
second action position which is an action position of the pressing
force when the inclination of the swashplate is 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: |
55078344 |
Appl. No.: |
15/326061 |
Filed: |
July 2, 2015 |
PCT Filed: |
July 2, 2015 |
PCT NO: |
PCT/JP2015/069135 |
371 Date: |
January 13, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 1/2078 20130101;
F04B 1/295 20130101; F04B 1/32 20130101; F04B 1/324 20130101 |
International
Class: |
F04B 1/29 20060101
F04B001/29; F04B 1/14 20060101 F04B001/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2014 |
JP |
2014-145926 |
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 causing a
pressing force to act along one direction by 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 biasing the pressed portion of the swashplate toward the one
side of the sliding contact surface, wherein the pressed portion is
capable of taking a first action position and a second action
position, wherein the first action position is a position at which
the pressing force of the pressing portion acts when the
inclination of the swashplate is the maximum inclination and the
second action position is a position at which the pressing force of
the pressing portion acts 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 action position and the second action 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 a direction in which the pressing force of the pressing
portion acts 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 action position
and the second action position.
3. The variable capacity piston pump according to claim 1, wherein
the pressing portion is disposed in 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. When the inclination is changed,
the swashplate turns about a certain turning center.
SUMMARY OF INVENTION
Technical Problem
[0004] The inventors found that when the inclination of the
swashplate is changed, the distance between the pressing force of
the control piston and the turning center (that is, the length of a
moment arm of the pressing force of the control piston about the
turning center) is changed, resulting in deterioration in
controllability over the inclination of the swashplate.
[0005] For example, when the control piston presses the swashplate
to decrease the inclination of the swashplate, in a case where the
length of the moment arm is shortened as the inclination of the
swashplate is decreased, the moment of the pressing force of the
control piston about the turning center is decreased, and it
becomes difficult for the swashplate to rotate. In this case, the
responsiveness of the inclination of the swashplate to the pressing
force of the control piston deteriorates (for example, the response
speed becomes slow), and inappropriate control over the inclination
of the swashplate may be incurred.
[0006] In contrast, when the control piston presses the swashplate
to decrease the inclination of the swashplate, in a case where the
length of the moment arm is lengthened as the inclination of the
swashplate is decreased, the moment of the pressing force of the
control piston about the turning center is increased, and the
swashplate more easily rotates. In this case, the response of the
inclination of the swashplate to the pressing force of the control
piston becomes excessively sensitive (for example, the response
speed becomes excessively fast), and inappropriate control over the
inclination of the swashplate may be incurred.
[0007] An object of various aspects of the present invention is to
provide a variable capacity piston pump which achieves an
improvement in controllability over the inclination of a
swashplate.
Solution to Problem
[0008] 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
causing a pressing force to act along one direction by 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 biasing the pressed portion of the swashplate toward the one
side of the sliding contact surface, wherein the pressed portion is
capable of taking a first action position and a second action
position, wherein the first action position is a position at which
the pressing force of the pressing portion acts when the
inclination of the swashplate is the maximum inclination and the
second action position is a position at which the pressing force of
the pressing portion acts 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 action position and the second action 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 a direction in which the pressing force of the pressing
portion acts and passing through the turning center of the
swashplate.
[0009] In the variable capacity piston pump described above, there
is a positional relationship in which the vertical reference line
passes between the first action position which is the position at
which the pressing force of the pressing portion acts on the
pressed portion when the inclination of the swashplate is the
maximum inclination and the second action position which is the
position at which the pressing force of the pressing portion acts
on the pressed portion when the inclination of the swashplate is
the minimum inclination. When the position at which the pressing
force of the pressing portion acts on the pressed portion is on the
vertical reference line or near the vertical reference line, the
length of a moment arm of the pressing force due to the pressing
portion barely changes. In the variable capacity piston pump
described above, since the first action position and the second
action position are positioned with the vertical reference line
interposed therebetween, the position at which the pressing force
of the pressing portion acts on the pressed portion is on the
vertical reference line or near the vertical reference line.
Therefore, even when the inclination of the swashplate changes from
the maximum inclination to the minimum inclination, the length of
the moment arm of the pressing force barely changes. Accordingly,
the amount of variation in the moment of the pressing force can be
suppressed regardless of the inclination of the swashplate. As a
result, controllability over the inclination of the swashplate can
be improved.
[0010] 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 action position and the second action
position. In this case, the length of the moment arm when the
inclination of the swashplate is the maximum inclination and the
length of the moment arm when the inclination of the swashplate is
the minimum inclination can be equal to each other. Therefore, the
amount of a change in the length of the moment arm of the pressing
force while the inclination of the swashplate displaces from the
maximum inclination to the minimum inclination can be minimized.
Accordingly, the amount of variation of the moment of the pressing
force due to the displacement of the inclination of the swashplate
can be suppressed to the maximum degree. As a result,
controllability over the inclination of the swashplate can be
further improved.
[0011] According to another aspect of the present invention, in the
variable capacity piston pump, the pressing portion may be disposed
in parallel to the rotating shaft. In this case, design of the
variable capacity piston pump can be facilitated.
Advantageous Effects of Invention
[0012] According to the various aspects of the present invention, a
variable capacity piston pump which achieves an improvement in
controllability over the inclination of a swashplate is
provided.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 is a schematic sectional view illustrating a variable
capacity piston pump according to an embodiment of the present
invention.
[0014] FIG. 2 is a perspective view of a swashplate illustrated in
FIG. 1.
[0015] FIG. 3 is a side view of the swashplate illustrated in FIG.
1 viewed from a side of a sliding contact surface.
[0016] FIG. 4 is a side view of the swashplate illustrated in FIG.
1 viewed on a side opposite to the sliding contact surface.
[0017] 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.
[0018] FIG. 6 is a schematic view illustrating variation in an
action position of a pressing force of a piston portion.
[0019] FIG. 7 is a schematic view illustrating variation in the
action position of the pressing force of the piston portion as a
comparative example of the embodiment in addition to the case of
FIG. 6.
[0020] FIG. 8 is a schematic view illustrating variation in the
action position of the pressing force of the piston portion at a
position different from that of FIG. 6.
[0021] FIG. 9 is a perspective view illustrating a swashplate
according to a modification example.
[0022] FIG. 10 is a schematic sectional view illustrating main
parts of a variable capacity piston pump according to a
modification example.
DESCRIPTION OF EMBODIMENTS
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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, in
practice, the line of the turning center X extends in an inward
direction (a direction perpendicular to the figure).
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] Next, with reference to FIGS. 5 to 7, an action position
which is a position at which the pressing force of the piston
portion 58 which is the pressing portion acts on the pressed
portion 33 will be described in detail. Here, the position at which
the pressing force of the piston portion 58 acts on the pressed
portion 33 is, for example, a position at which the end surface of
the piston portion 58 on the swashplate 30 side comes into contact
with the cylindrical member 33b of the pressed portion 33 of the
swashplate 30 and presses the cylindrical member 33b with a
predetermined pressing force. Hereinafter, the position at which
the end surface of the piston portion 58 on the swashplate 30 side
comes into contact with the cylindrical member 33b of the pressed
portion 33 of the swashplate 30 and presses the cylindrical member
33b with a predetermined pressing force is referred to as an action
position of the pressing force of the piston portion 58.
[0046] First, references such as the turning center X, the vertical
reference line and the parallel reference line for the action
position of the pressing force of the piston portion 58 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).
[0047] 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 is the 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.
[0048] The parallel reference line Y is a straight line which is
parallel to a direction in which the pressing force of the piston
portion 58 acts and passes through the turning center X. 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.
[0049] FIG. 6 is a schematic view illustrating variation in the
action position of the pressing force of the piston portion 58 of
the control piston 50. 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 pressing force of the
piston portion 58 is indicated by a pressing force F, a line of
action of the pressing force F when the inclination of the
swashplate 30 is the maximum inclination is indicated by a line of
action S1, and a line of action when the inclination of the
swashplate 30 is the minimum inclination is indicated by a line of
action S2. In addition, a direction in which the pressing force F
acts is a direction parallel to the parallel reference line Y.
[0050] In FIG. 6, variation in the action position of the pressing
force of the piston portion 58 in the pump 1 according to the
embodiment is indicated by a double-headed arrow A. The
double-headed arrow A represents that the action position of the
pressing force F varies between a position of the pressing force F
when the inclination of the swashplate 30 is the maximum
inclination (hereinafter, referred to as a first action position)
A1, and a position of the pressing force F when the inclination of
the swashplate 30 is the minimum inclination (hereinafter, referred
to as a second action position) A2. The angular difference between
the maximum inclination and the minimum inclination of the
swashplate 30 is indicated by .theta.. As illustrated in FIG. 6,
the action position of the pressing force F moves between the first
action position A1 and the second action position A2 along an arc
of the imaginary circle having the turning center X as its center.
This is because the distance between the cylindrical member 33b on
which the pressing force F acts and the turning center X is always
constant regardless of the inclination.
[0051] 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 action position A1 when the inclination of the
swashplate 30 is the maximum inclination and the second action
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 action position A1 when the
inclination of the swashplate 30 is the maximum inclination and the
second action position A2 when the inclination of the swashplate 30
is the minimum inclination.
[0052] In a case where the first action position A1, the second
action position A2, and the vertical reference line Z have this
positional relationship, as illustrated in FIG. 6, the action
position of the pressing force F moves just beside the action
position 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 action position of the pressing force F moves from
the first action position A1 to the second action position A2,
there is substantially no displacement in the directions of the
vertical reference line Z (a change in the height position of each
of the lines of action S1 and S2 with respect to the parallel
reference line Y).
[0053] As described above, while the inclination of the swashplate
30 moves from the maximum inclination to the minimum inclination,
the action position of the pressing force F barely displaces in the
directions of the vertical reference line Z. Therefore, the
distance between the pressing force F and the turning center X when
the inclination of the swashplate 30 is the maximum inclination
(that is, the length of a moment arm of the pressing force F about
the turning center X) La.sub.1 and the distance between the
pressing force F and the turning center X when the inclination of
the swashplate 30 is the minimum inclination La.sub.2 barely
change. That is, even when the inclination of the swashplate 30
moves from the maximum inclination to the minimum inclination, the
length of the moment arm of the pressing force F about the turning
center X barely changes. Therefore, the amount of variation in the
moment of the pressing force F about the turning center X due to a
change in the inclination of the swashplate 30 can be
suppressed.
[0054] FIG. 7 is a schematic view illustrating variation in the
action position of the pressing force F of the piston portion 58 as
a comparative example of the embodiment in addition to the case of
FIG. 6. In FIG. 7, while the case where the vertical reference line
Z passes between the first action position A1 and the second action
position A2 is indicated by the double-headed arrow A as in FIG. 6,
cases where the vertical reference line Z does not pass between a
first action position and a second action position 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 is the same as the
difference .theta. of the double-headed arrow A described
above.
[0055] The double-headed arrow B indicates variation in the action
position of the pressing force F in a case where both a first
action position B1 and a second action position B2 are positioned
on the swashplate return spring 60 side in relation to the vertical
reference line Z. As illustrated in FIG. 7, when the inclination of
the swashplate 30 changes from the maximum inclination to the
minimum inclination and accordingly the action position of the
pressing force F moves from the first action position B1 to the
second action position B2, the action position of the pressing
force F gradually moves in a downward direction and significantly
displaces in the directions of the vertical reference line Z.
Therefore, regarding the case of the double-headed arrow B, the
length Lb.sub.2 of the moment arm of the pressing force F when the
inclination of the swashplate 30 is the minimum inclination becomes
shorter than the length Lb.sub.1 of the moment arm of the pressing
force F when the inclination of the swashplate 30 is the maximum
inclination.
[0056] As described above, when the length of the moment arm of the
pressing force F is shortened as the inclination of the swashplate
30 is decreased, the moment of the pressing force F is decreased,
and it is difficult for the swashplate 30 to rotate. Therefore, the
responsiveness of the inclination of the swashplate 30 to the
pressing force F of the piston portion 58 deteriorates (for
example, the response speed becomes slow), and the inclination of
the swashplate 30 is not appropriately controlled.
[0057] The double-headed arrow C indicates variation in the action
position of the pressing force F in a case where both a first
action position C1 and a second action position C2 are positioned
on the control piston 50 side in relation to the vertical reference
line Z. As illustrated in FIG. 7, when the inclination of the
swashplate 30 changes from the maximum inclination to the minimum
inclination and accordingly the action position of the pressing
force F moves from the first action position C1 to the second
action position C2, the action position of the pressing force F
gradually moves in an upward direction and significantly displaces
in the directions of the vertical reference line Z. Therefore,
regarding the case of the double-headed arrow C, the length
Lc.sub.2 of the moment arm of the pressing force F when the
inclination of the swashplate 30 is the minimum inclination becomes
longer than the length LC.sub.1 of the moment arm of the pressing
force F when the inclination of the swashplate 30 is the maximum
inclination.
[0058] As described above, when the length of the moment arm of the
pressing force F is lengthened as the inclination of the swashplate
30 is decreased, the moment of the pressing force F is increased,
and the swashplate 30 more easily rotate. Therefore, the response
of the inclination of the swashplate 30 to the pressing force F of
the piston portion 58 becomes excessively sensitive (for example,
the response speed becomes excessively fast), and the inclination
of the swashplate 30 is also not appropriately controlled.
[0059] As described above, in the pump 1 according to the
embodiment, since the first action position A1 and the second
action position A2 are positioned with the vertical reference line
Z interposed therebetween, the position at which the pressing force
F of the piston portion 58 of the control piston 50 acts on the
cylindrical member 33b of the pressed portion 33 is on the vertical
reference line Z or near the vertical reference line Z. Therefore,
even when the inclination of the swashplate 30 displaces from the
maximum inclination to the minimum inclination, the length of the
moment arm of the pressing force F barely changes, and the amount
of variation in the moment of the pressing force F due to the
displacement of the inclination of the swashplate 30 can be
suppressed. As a result, controllability over the inclination of
the swashplate 30 can be improved.
[0060] In addition, the positional relationship in which the
vertical reference line Z passes between the first action position
A1 and the second action position A2, that is, the positional
relationship in which the vertical reference line Z is interposed
between the first action position A1 and the second action position
A2 includes a positional relationship in which the vertical
reference line Z overlaps the first action position A1 or the
second action position A2.
[0061] In addition, as indicated by the double-headed arrow A of
FIG. 8, the positional relationship between the first action
position A1, the second action 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 action
position A1 and the second action position A2. In this case, the
vertical reference line is coincident with the perpendicular
bisector of the straight line that connects the first action
position A1 and the second action position A2.
[0062] At this time, the length La.sub.1 of the moment arm when the
inclination of the swashplate 30 is the maximum inclination and the
length La.sub.2 of the moment arm when the inclination of the
swashplate 30 is the minimum inclination can be equal to each
other. That is, the length of the moment arm does not excessively
increases in any of cases where the inclination of the swashplate
30 is the maximum inclination or the minimum inclination.
Therefore, the amount of variation of the moment due to the
displacement of the inclination of the swashplate 30 can be
minimized. Accordingly, controllability over the inclination of the
swashplate 30 can be further improved.
[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. 9 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
oscillates about the turning center X by cooperation between the
sliding portions 32 and the swashplate receiving member 34.
However, the swashplate 130 can oscillate 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.
[0066] In addition, FIG. 10 is a schematic sectional view
illustrating main parts of a variable capacity piston pump
according to a modification example. In FIG. 10, the vicinity of
the control piston 50 in the variable capacity piston pump
according to the modification example is enlarged to be
illustrated.
[0067] As illustrated in FIG. 10, in the variable capacity piston
pump according to the modification example, the piston portion 58
of the control piston 50 is disposed in parallel to the rotating
shaft 20. The pump 1 is generally designed on the basis of the
axial line of the rotating shaft 20. Therefore, when the piston
portion 58 of the control piston 50 is disposed in parallel to the
rotating shaft 20, design of the control piston 50 or the pump
housing 10 (particularly the center housing 10b in which the
control piston 50 is provided) is facilitated.
[0068] In addition, in the case where the control piston 50 is
disposed obliquely with respect to the rotating shaft 20 as in the
above-described embodiment, the dimensions (diameter dimension) of
the center housing 10b are greater than those of the front housing
10a or the rear housing 10c. In the case where the piston portion
58 of the control piston 50 is disposed in parallel to the rotating
shaft 20, an increase in the dimensions is suppressed. As a result,
miniaturization of the variable capacity piston pump can be
realized.
REFERENCE SIGNS LIST
[0069] 1 variable capacity piston pump [0070] 14 cylinder block
[0071] 16 piston [0072] 20 rotating shaft [0073] 30, 130 swashplate
[0074] 30a sliding contact surface [0075] 33, 133 pressed portion
[0076] 58 piston portion (pressing portion) [0077] 60 swashplate
return spring [0078] X turning center [0079] Y parallel reference
line [0080] Z vertical reference line [0081] A1 first action
position [0082] A2 second action position
* * * * *