U.S. patent number RE46,294 [Application Number 15/085,797] was granted by the patent office on 2017-01-31 for variable displacement pump.
This patent grant is currently assigned to HITACHI AUTOMOTIVE SYSTEMS, LTD.. The grantee listed for this patent is HITACHI AUTOMOTIVE SYSTEMS, LTD.. Invention is credited to Atsushi Naganuma, Hideaki Ohnishi, Yasushi Watanabe.
United States Patent |
RE46,294 |
Watanabe , et al. |
January 31, 2017 |
Variable displacement pump
Abstract
A variable displacement oil pump for an automotive engine. The
oil pump includes a cam ring accommodating thereinside a pump
element having a rotor. The cam ring is swingingly movably
accommodated in a housing and biased in a direction to increase an
eccentricity amount of the cam ring relative to the axis of the
rotor by a biasing member. First and second pressure chambers are
defined inside the housing by the outer peripheral section of the
cam ring. The first pressure chamber is supplied with a discharge
pressure to be applied to the cam ring to oppose to a biasing force
of the biasing member. The second pressure chamber is supplied with
the discharge pressure to be applied to the cam ring to assist the
biasing force of the biasing member. Additionally, a control device
is provided for controlling supply of the discharge pressure to the
second pressure chamber.
Inventors: |
Watanabe; Yasushi (Kanagawa,
JP), Ohnishi; Hideaki (Atsugi, JP),
Naganuma; Atsushi (Atsugi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI AUTOMOTIVE SYSTEMS, LTD. |
Hitachinaka-shi, Ibaraki |
N/A |
JP |
|
|
Assignee: |
HITACHI AUTOMOTIVE SYSTEMS,
LTD. (Hitachinaka-Shi, JP)
|
Family
ID: |
1000002110560 |
Appl.
No.: |
15/085,797 |
Filed: |
March 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
12719147 |
Mar 8, 2010 |
8684702 |
Apr 1, 2014 |
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Foreign Application Priority Data
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Mar 9, 2009 [JP] |
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2009-054366 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C
14/223 (20130101); F04C 14/226 (20130101); F04C
14/226 (20130101); F04C 14/223 (20130101); F04C
2/3442 (20130101); F04C 2/3442 (20130101); F04C
2210/14 (20130101); F04C 2210/14 (20130101) |
Current International
Class: |
F04B
49/00 (20060101); F04C 14/22 (20060101); F04C
2/344 (20060101) |
Field of
Search: |
;417/220 ;418/26,27 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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53-137403 |
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Nov 1978 |
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JP |
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S53-137403 |
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Nov 1978 |
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JP |
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3-119589 |
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Dec 1991 |
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JP |
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03-119589 |
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Dec 1991 |
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JP |
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2005-520096 |
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Jul 2005 |
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JP |
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2008-524500 |
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Jul 2008 |
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JP |
|
Other References
Final Office Action in U.S. Appl. No. 12/719,147 dated Mar. 15,
2013. cited by applicant .
Final Office Action issued in U.S. Appl. No. 14/186,464 DTD Dec.
31, 2014. cited by applicant .
Non-Final Office Action in U.S. Appl. No. 12/719,147 dated Oct. 24,
2012. cited by applicant .
Non-Final Office Action in U.S. Appl. No. 14/186,464 dated Aug. 12,
2014. cited by applicant .
Notice of Allowance dated Nov. 19, 2013 in U.S. Appl. No.
12/719,147. cited by applicant .
Notice of Allowance issued in U.S. Appl. No. 14/186,464 DTD May 8,
2015. cited by applicant .
Office Action issued in corresponding Japanese application No.
2009-0524366 issued Aug. 30, 2012. cited by applicant .
Translation of JP 03-119589, published Dec. 10, 1991. cited by
applicant .
JP Office Action for Japanese application No. 2009-054366, issued
on Aug. 30, 2012. cited by applicant.
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Primary Examiner: Doerrler; William
Attorney, Agent or Firm: Foley & Lardner LLP
Claims
What is claimed is:
1. A variable displacement oil pump for supplying oil at least to
sliding sections of an internal combustion engine, comprising: a
pump element including a rotor configured to be rotationally driven
by the internal combustion engine, and a plurality of vanes
disposed at an outer peripheral section of the rotor; a cam ring
having an inner peripheral section for accommodating the pump
element thereinside, and an outer peripheral section having a
swinging movement fulcrum, the cam ring being swingingly movable
around the swinging movement fulcrum to change an eccentricity
amount of the cam ring relative to an axis of the rotor; a housing
for accommodating the cam ring thereinside and including side walls
disposed respectively on axially opposite sides of the cam ring to
define a plurality of hydraulic fluid chambers each of which is
defined by the rotor and adjacent ones of the vanes, the housing
further including: a discharge section in which volumes of the
hydraulic fluid chambers decrease along the discharge section in a
rotational direction of the rotor to realize pumped oil, a first
pressure chamber bounded by the outer peripheral section of the cam
ring and an inner surface of the housing, a discharge hole opened
through at least one of the side walls to discharge the pumped oil
from the variable displacement oil pump, with the first pressure
chamber opening to the discharge hole, and a suction hole opened
through at least one of the side walls to supply oil to a suction
section in which volumes of the hydraulic chambers increase along
the rotational direction of the rotor; a biasing member for biasing
the cam ring in a direction to increase the eccentricity amount of
the cam ring relative to the axis of the rotor; the first pressure
chamber having a first pressure receiving surface on the outer
peripheral section of the cam ring, and directly connected to the
discharge section via an open valve-less path, to constantly
receive a discharge pressure of the pumped oil fed into the first
pressure chamber from the discharge section, to allow the discharge
pressure to be applied through the first pressure receiving surface
to the cam ring to oppose to a biasing force of the biasing member
so as to provide the cam ring with a swinging force in a direction
to decrease the eccentricity amount of the cam ring; a second
pressure chamber defined by the outer peripheral section of the cam
ring and the housing, and having a second pressure receiving
surface on the outer peripheral section of the cam ring, where
introduction of the same discharge pressure that is introduced into
the first pressure chamber causes the discharge pressure to be
applied through the second pressure receiving surface to the cam
ring to assist the biasing force of the biasing member so as to
provide the cam ring with a swinging force in a direction to
increase the eccentricity amount of the cam ring, the second
pressure receiving surface being set smaller in pressure receiving
area than the first pressure receiving surface; and a hydraulic
switch for changeover controlling supply of the discharge pressure
to the second pressure chamber, based on an energizing current.
2. A variable displacement oil pump as claimed in claim 1, where
the hydraulic switch is selectable between a first state where the
second pressure chamber is connected via a first hydraulic path to
receive the discharge pressure, and a second state where the second
pressure chamber is connected via a second hydraulic path to
release pressurization to achieve a pressure lower than the
discharge pressure.
3. A variable displacement oil pump as claimed in claim 2, wherein
the hydraulic switch has a configuration to establish the first
state in a current supply condition, and to establish the second
state in a non-current supply condition.
4. A variable displacement oil pump as claimed in claim 2, wherein
the hydraulic switch has a configuration to establish the second
state in a current supply condition, and to establish the first
state in a non-current supply condition.
5. A variable displacement oil pump as claimed in claim 3, wherein
the hydraulic switch is a solenoid valve.
6. A variable displacement oil pump as claimed in claim 1, further
comprising a control device configured to control the hydraulic
switch in accordance with an engine speed of the engine.
7. A variable displacement oil pump as claimed in claim 1, further
comprising a control device configured to control the hydraulic
switch in accordance with an engine load of the engine.
8. A variable displacement oil pump as claimed in claim 1, further
comprising a control device configured to control the hydraulic
switch in accordance with an oil temperature of the engine.
9. A variable displacement oil pump as claimed in claim 1, wherein
each of the first and second pressure chamber is defined by an
outer peripheral surface of the cam ring, an inner peripheral
surface of the housing and the swinging movement fulcrum of the cam
ring.
10. A variable displacement oil pump as claimed in claim 9, wherein
a region within the housing and outside the cam ring, except for
the first and second pressure chambers, is set at atmospheric
pressure or a suction pressure.
11. A variable displacement oil pump as claimed in claim 10,
wherein the biasing member is disposed at a site where the
atmospheric pressure or the suction pressure is set, in the region
outside the cam ring.
12. A variable displacement oil pump for supplying oil at least to
sliding sections of an internal combustion engine, comprising: a
pump element including a rotor configured to be rotationally driven
by the internal combustion engine, and a plurality of vanes
disposed at an outer peripheral section of the rotor; a cam ring
having an inner peripheral section for accommodating the pump
element thereinside, and an outer peripheral section having a
swinging movement fulcrum, the cam ring being swingingly movable
around the swinging movement fulcrum to change an eccentricity
amount of the cam ring relative to an axis of the rotor; a housing
for accommodating the cam ring thereinside and including side walls
disposed respectively on axially opposite sides of the cam ring to
define a plurality of hydraulic fluid chambers each of which is
defined by the rotor and adjacent ones of the vanes, the housing
further including: a discharge section in which volumes of the
hydraulic fluid chambers decrease along the discharge section in a
rotational direction of the rotor to realize pumped oil, a first
pressure chamber bounded by the outer peripheral section of the cam
ring and an inner surface of the housing, a discharge hole opened
through at least one of the side walls to discharge the pumped oil
from the variable displacement oil pump, with the first pressure
chamber opening to the discharge hole, and a suction hole opened
through at least one of the side walls to supply oil to a suction
section in which volumes of the hydraulic chambers increase along
the rotational direction of the rotor; a biasing member for biasing
the cam ring in a direction to increase the eccentricity amount of
the cam ring relative to the axis of the rotor; the first pressure
chamber having a first pressure receiving surface on the outer
peripheral section of the cam ring, and directly connected to the
discharge section via an open valve-less path, to constantly
receive a discharge pressure of the pumped oil fed into the first
pressure chamber from the discharge section, before the pumped oil
is discharged out of the discharge hole of the oil pump, to allow
the discharge pressure to be applied through the first pressure
receiving surface to the cam ring to oppose to a biasing force of
the biasing member, so as to provide the cam ring with a swinging
force in a direction to decrease the eccentricity amount of the cam
ring; a second pressure chamber defined by the outer peripheral
section of the cam ring and the housing, and having a second
pressure receiving surface on the outer peripheral section of the
cam ring, where introduction of the same discharge pressure that is
introduced into the first pressure chamber, causes the discharge
pressure to be applied through the second pressure receiving
surface to the cam ring to assist the biasing force of the biasing
member so as to provide the cam ring with a swinging force in a
direction to increase the eccentricity amount of the cam ring, the
second pressure receiving surface being set smaller in pressure
receiving area than the first pressure receiving surface; and a
hydraulic switch for changeover controlling supply of the discharge
pressure to the second pressure chamber, based on an energizing
current; wherein a part of the first pressure chamber is disposed
overlapping with the discharge section in a radial direction of the
rotor.
13. A variable displacement oil pump as claimed in claim 12,
wherein whole of each of the first and second pressure chambers is
disposed overlapping with a range of the discharge section, in the
radial direction of the rotor.
14. A variable displacement oil pump as claimed in claim 12,
wherein a whole of each of the first and second pressure chambers
is disposed overlapping with a peripheral direction range in which
the discharge section is formed.
15. A variable displacement oil pump for supplying oil at least to
sliding sections of an internal combustion engine, comprising: a
pump element including a rotor configured to be rotationally driven
by the internal combustion engine, and a plurality of vanes
disposed at an outer peripheral section of the rotor; a cam ring
having an inner peripheral section for accommodating the pump
element thereinside, and an outer peripheral section having a
swinging movement fulcrum, the cam ring being swingingly movable
around the swinging movement fulcrum to change an eccentricity
amount of the cam ring relative to an axis of the rotor; a housing
for accommodating the cam ring thereinside and including side walls
disposed respectively on axially opposite sides of the cam ring to
define a plurality of hydraulic fluid chambers each of which is
defined by the rotor and adjacent ones of the vanes, the housing
further including: a discharge section in which volumes of the
hydraulic fluid chambers decrease along the discharge section in a
rotational direction of the rotor to realize pumped oil, a first
pressure chamber bounded by the outer peripheral section of the cam
ring and an inner surface of the housing, a discharge hole opened
through at least one of the side walls to discharge the pumped oil
from the variable displacement oil pump, with the first pressure
chamber opening to the discharge hole of the oil pump, and a
suction hole opened through at least one of the side walls to
supply oil to a suction section in which volumes of the hydraulic
chambers increase along the rotational direction of the rotor; a
biasing member for biasing the cam ring in a direction to increase
the eccentricity amount of the cam ring relative to the axis of the
rotor; the first pressure chamber having a first pressure receiving
surface on the outer peripheral section of the cam ring, and
directly connected to the discharge section via an open valve-less
path, to constantly receive a discharge pressure of the oil pump
fed into the first pressure chamber from the discharge section,
before the pumped oil is discharged out of the discharge hole of
the oil pump, to allow the discharge pressure to be applied through
the first pressure receiving surface to the cam ring to oppose to a
biasing force of the biasing member so as to provide the cam ring
with a swinging force in a direction to decrease the eccentricity
amount of the cam ring; and a second pressure chamber defined by
the outer peripheral section of the cam ring and the housing, and
having a second pressure receiving surface on the outer peripheral
section of the cam ring, where introduction of the same discharge
pressure that is introduced into the first pressure chamber causes
the discharge pressure to be applied through the second pressure
receiving surface to the cam ring to assist the biasing force of
the biasing member so as to provide the cam ring with a swinging
force in a direction to increase the eccentricity amount of the cam
ring, the second pressure receiving surface being set smaller in
pressure receiving area than the first pressure receiving surface;
a hydraulic switch for changeover controlling supply of the
discharge pressure to the second pressure chamber, based on an
energizing current; wherein the first and second pressure chambers
are disposed nearer to the swinging movement fulcrum than to the
axis of the rotor.
16. A variable displacement oil pump as claimed in claim 15,
wherein the singing movement fulcrum is a pivot formed integral
with the outer peripheral section of the cam ring.
17. A variable displacement oil pump as claimed in claim 16,
wherein each of the first and second pressure chambers is defined
by an outer peripheral surface of the cam ring, and an inner
peripheral surface of the housing, and are separated from each
other by the fulcrum.
18. A variable displacement oil pump as claimed in claim 16,
wherein the pivot is swingably movably disposed supported in a
depression formed in the inner peripheral section of the
housing.
19. A variable displacement oil pump as claimed in claim 15,
wherein a region outside the cam ring, except for the first and
second pressure chambers, is set at atmospheric pressure or a
suction pressure.
.Iadd.20. A variable displacement oil pump for supplying oil at
least to sliding sections of an internal combustion engine,
comprising: a pump element including a rotor configured to be
rotationally driven by the internal combustion engine, and a
plurality of vanes disposed at an outer peripheral section of the
rotor; a ring having an inner peripheral section for accommodating
the pump element thereinside, and an outer peripheral section, the
ring being movable to change a position of the ring relative to an
axis of the rotor; a housing for accommodating the ring thereinside
and including side walls disposed respectively on axially opposite
sides of the ring to define a plurality of hydraulic fluid chambers
each of which is defined by the rotor and adjacent ones of the
vanes, the housing further including: a discharge section in which
volumes of the hydraulic fluid chambers decrease along a rotational
direction of the rotor to realize pumped oil, a first pressure
chamber bounded by the outer peripheral section of the ring and an
inner surface of the housing, a discharge hole opened through at
least one of the side walls to discharge the pumped oil from the
variable displacement oil pump, and a suction hole opened through
at least one of the side walls to supply oil to a suction section
in which volumes of the hydraulic chambers increase along the
rotational direction of the rotor; a biasing member for biasing the
ring in a direction to increase differentiation in volume of the
hydraulic fluid chambers; the first pressure chamber having a first
pressure receiving surface on the outer peripheral section of the
ring, and the first pressure chamber being connected to the
discharge section via an open valve-less path, to receive a
discharge pressure of the pumped oil fed into the first pressure
chamber from the discharge section, to allow the discharge pressure
to be applied through the first pressure receiving surface to the
ring to provide the ring with a force against the biasing force of
the biasing member in a direction to decrease differentiation in
volume of the hydraulic fluid chambers; a second pressure chamber
defined by the outer peripheral section of the ring and the
housing, and having a second pressure receiving surface on the
outer peripheral section of the ring, where introduction of the
pumped oil from the same discharge section that is introduced into
the first pressure chamber causes a discharge pressure to be
applied through the second pressure receiving surface to the ring
to assist the biasing force of the biasing member so as to provide
the ring with a force in a direction to increase a moving amount of
the ring, the second pressure receiving surface being set different
in pressure receiving area from the first pressure receiving
surface; and a controller configured to be electrically driven for
changeover controlling supply of the hydraulic fluid to the second
pressure chamber, based on an energizing current, and allowing the
second pressure chamber to be opened to an atmospheric
environment..Iaddend.
.Iadd.21. A variable displacement oil pump as claimed in claim 20,
wherein the ring comprises a cam ring, and the outer peripheral
section of the ring has a swinging movement fulcrum..Iaddend.
.Iadd.22. A variable displacement oil pump as claimed in claim 20,
wherein the first pressure chamber is directly connected to the
discharge section..Iaddend.
.Iadd.23. A variable displacement pump, comprising: a housing; a
pump element movably contained in the housing to suck and discharge
hydraulic fluid, volumes of the hydraulic fluid discharged by the
pump element being changed according to the position of the pump
element; a biasing element that biases the pump element in a
direction for increasing the discharged volumes of the hydraulic
fluid; a first control fluid chamber defined between the pump
element and the housing, the hydraulic fluid discharged from the
pump element being introduced into the first chamber, the pump
element being moved in a direction for decreasing the discharged
volumes of the hydraulic fluid by the hydraulic fluid being
introduced into the first chamber; a second control fluid chamber
defined between the pump element and the housing, the second
chamber being separately formed from the first chamber, the
hydraulic fluid discharged from the pump element being introduced
into the second chamber, the pump element being moved in a
direction for increasing the discharged volumes of the hydraulic
fluid by the hydraulic fluid being introduced into the second
chamber; and an electrically controlled valve that is provided in a
fluid passage that guides the hydraulic fluid discharged from the
pump element to the second chamber, the valve including a first
condition for allowing the hydraulic fluid discharged from the pump
element to be therethrough introduced into the second chamber and a
second condition for allowing the second chamber to be opened to
atmospheric environment, the valve being maintained in the second
condition when the valve is deenergized..Iaddend.
.Iadd.24. A variable displacement pump as claimed in claim 23,
wherein the valve comprises: a body, a valve member that moves
between the first condition and the second condition, an elastic
member that biases the valve in a direction such that the valve
member is placed in the second condition, and an actuator that is
electrically driven to bias the valve member in a direction such
that the valve member is placed in the first
condition..Iaddend.
.Iadd.25. A variable displacement pump as claimed in claim 24,
wherein the valve member is controlled between the first condition
and the second condition..Iaddend.
.Iadd.26. A variable displacement pump as claimed in claim 23,
wherein the valve includes an inlet port connected to a discharged
port of the pump element, an outlet port connected to the second
chamber, and a drain port connected to the atmosphere..Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates to a variable displacement pump which is
applied, for example, to a hydraulic pressure source for supplying
hydraulic oil to various sliding sections and the like of an
automotive internal combustion engine, and more particularly to the
variable displacement pump whose discharge amount (discharge
pressure) is variable in accordance with engine operating
conditions.
As a conventional variable displacement pump to be used for an oil
pump of an automotive vehicle, there is proposed one disclosed in
International Application Publication (Tokuhyou) No. 2008-524500.
In summary, this variable displacement pump is of a so-called vane
type and arranged such that a discharge pressure is selectively
supplied to two pressure chambers defined between a housing and a
cam ring so as to control the eccentricity amount of the cam ring
which is always biased in a direction to be eccentric relative to
the center axis of a rotor, thereby rendering the discharge amount
(discharge pressure) variable.
SUMMARY OF THE INVENTION
However, the above-mentioned conventional variable displacement
pump takes such a structure that the biasing force of the spring is
balanced with a hydraulic pressure force based on the internal
pressures (discharge pressures) of the above two pressure chambers.
Accordingly, it is required to increase the biasing force of the
spring, thereby raising a problem of unavoidably making the pump
large-sized.
An object of the present invention is to provide an improved
variable displacement oil pump which can overcome drawbacks
encountered in conventional variable displacement pumps.
Another object of the present invention is to provide an improved
variable displacement oil pump which is small-sized as compared
with the conventional variable displacement oil pumps.
A further object of the present invention is to provide an improved
variable displacement oil pump of a so-called vane type, provided
with first and second pressure chambers defined outside a cam ring
and supplied therein with a discharge pressure, in which the first
pressure chamber has a first pressure receiving surface for causing
the discharge pressure to act on the cam ring in a direction to
decrease the eccentricity amount of the cam ring, and the second
pressure chamber has a second pressure receiving surface for
causing the discharge pressure to act on the cam ring in a
direction to increase the eccentricity amount of the cam ring.
Thus, the variable displacement oil pump according to the present
invention is arranged such that the eccentricity amount of the cam
ring is controlled by balancing the internal pressures of the first
and second pressure chambers. Consequently, a biasing member such a
spring for biasing the cam ring is not necessarily required, or the
biasing force of the biasing member is not required to be large
even if the biasing member is used, thus effectively making the oil
pump small-sized.
A first aspect of the present invention resides in a variable
displacement oil pump comprising a pump element including a rotor
rotationally driven by an internal combustion engine, and a
plurality of vanes disposed at an outer peripheral section of the
rotor to be projectable from and retractable in the outer
peripheral section. A cam ring is provided having an outer
peripheral section for accommodating the pump element thereinside,
and an outer peripheral section having a swinging movement fulcrum,
the cam ring being swingingly movable around the swinging movement
fulcrum to change an eccentricity amount of the cam ring relative
to an axis of the rotor. Side walls are disposed respectively on
axially opposite sides of the cam ring to define a plurality of
hydraulic fluid chambers each of which is defined by the rotor and
the adjacent vanes. A housing is provided for accommodating the cam
ring thereinside and including a discharge section opened through
at least one of the side walls to a discharge region in which
volumes of the hydraulic fluid chambers decrease along a rotational
direction of the rotor, and a suction section opened through at
least one of the side walls to a suction region in which volumes of
the hydraulic chambers increase along the rotational direction of
the rotor. A biasing member is provided for biasing the cam ring in
a direction to increase the eccentricity amount of the cam ring
relative to the axis of the rotor. A first pressure chamber defined
is by the outer peripheral section of the cam ring having a first
pressure receiving surface, a discharge pressure being introduced
into the first pressure chamber to allow the discharge pressure to
be applied through the first pressure receiving surface to the cam
ring to oppose to a biasing force of the biasing member so as to
provide the cam ring with a swinging force in a direction to
decrease the eccentricity amount of the cam ring. A second pressure
chamber defined is by the outer peripheral section of the cam ring
having a second pressure receiving surface, the discharge pressure
being introduced into the first pressure chamber to allow the
discharge pressure to be applied through the second pressure
receiving surface to the cam ring to assist the biasing force of
the biasing member so as to provide the cam ring with a swinging
force in a direction to increase the eccentricity amount of the cam
ring. Additionally, a control device is provided for controlling
supply of the discharge pressure to the second pressure
chamber.
A second aspect of the present invention resides in a variable
displacement oil pump comprising a pump element including a rotor
rotationally driven by an internal combustion engine, and a
plurality of vanes disposed at an outer peripheral section of the
rotor to be projectable from and retractable in the outer
peripheral section. A cam ring is provided having an outer
peripheral section for accommodating the pump element thereinside,
and an outer peripheral section having a swinging movement fulcrum,
the cam ring being swingingly movable around the swinging movement
fulcrum to change an eccentricity amount of the cam ring relative
to an axis of the rotor. Side walls are disposed respectively on
axially opposite sides of the cam ring to define a plurality of
hydraulic fluid chambers each of which is defined by the rotor and
the adjacent vanes. A housing is provided for accommodating the cam
ring thereinside and including a discharge section opened through
at least one of the side walls to a discharge region in which
volumes of the hydraulic fluid chambers decrease along a rotational
direction of the rotor, and a suction section opened through at
least one of the side walls to a suction region in which volumes of
the hydraulic chambers increase along the rotational direction of
the rotor. A biasing member is provided for biasing the cam ring in
a direction to increase the eccentricity amount of the cam ring
relative to the axis of the rotor. A first pressure chamber defined
is by the outer peripheral section of the cam ring having a first
pressure receiving surface, a discharge pressure being introduced
into the first pressure chamber to allow the discharge pressure to
be applied through the first pressure receiving surface to the cam
ring to oppose to a biasing force of the biasing member so as to
provide the cam ring with a swinging force in a direction to
decrease the eccentricity amount of the cam ring. A second pressure
chamber defined is by the outer peripheral section of the cam ring
having a second pressure receiving surface, the discharge pressure
being introduced into the first pressure chamber to allow the
discharge pressure to be applied through the second pressure
receiving surface to the cam ring to assist the biasing force of
the biasing member so as to provide the cam ring with a swinging
force in a direction to increase the eccentricity amount of the cam
ring. Additionally, a control device is provided for controlling
supply of the discharge pressure to the second pressure chamber. In
the above oil pump, a part of each of the first and second pressure
chambers is disposed overlapping with the discharge region in a
radial direction of the rotor.
A third aspect of the present invention resides in a variable
displacement oil pump comprising a pump element including a rotor
rotationally driven by an internal combustion engine, and a
plurality of vanes disposed at an outer peripheral section of the
rotor to be projectable from and retractable in the outer
peripheral section. A cam ring is provided having an outer
peripheral section for accommodating the pump element thereinside,
and an outer peripheral section having a swinging movement fulcrum,
the cam ring being swingingly movable around the swinging movement
fulcrum to change an eccentricity amount of the cam ring relative
to an axis of the rotor. Side walls are disposed respectively on
axially opposite sides of the cam ring to define a plurality of
hydraulic fluid chambers each of which is defined by the rotor and
the adjacent vanes. A housing is provided for accommodating the cam
ring thereinside and including a discharge section opened through
at least one of the side walls to a discharge region in which
volumes of the hydraulic fluid chambers decrease along a rotational
direction of the rotor, and a suction section opened through at
least one of the side walls to a suction region in which volumes of
the hydraulic chambers increase along the rotational direction of
the rotor. A biasing member is provided for biasing the cam ring in
a direction to increase the eccentricity amount of the cam ring
relative to the axis of the rotor. A first pressure chamber defined
is by the outer peripheral section of the cam ring having a first
pressure receiving surface, a discharge pressure being introduced
into the first pressure chamber to allow the discharge pressure to
be applied through the first pressure receiving surface to the cam
ring to oppose to a biasing force of the biasing member so as to
provide the cam ring with a swinging force in a direction to
decrease the eccentricity amount of the cam ring. A second pressure
chamber defined is by the outer peripheral section of the cam ring
having a second pressure receiving surface, the discharge pressure
being introduced into the first pressure chamber to allow the
discharge pressure to be applied through the second pressure
receiving surface to the cam ring to assist the biasing force of
the biasing member so as to provide the cam ring with a swinging
force in a direction to increase the eccentricity amount of the cam
ring. Additionally, a control device is provided for controlling
supply of the discharge pressure to the second pressure chamber. In
the above oil pump, the first and second pressure chambers are
disposed nearer to the swinging movement fulcrum than to the axis
of the cam ring.
A fourth aspect of the present invention resides in a variable
displacement oil pump comprising a pump element including a rotor
rotationally driven by an internal combustion engine, and a
plurality of vanes disposed at an outer peripheral section of the
rotor to be projectable from and retractable in the outer
peripheral section. A cam ring is provided having an outer
peripheral section for accommodating the pump element thereinside,
and an outer peripheral section having a swinging movement fulcrum,
the cam ring being swingingly movable around the swinging movement
fulcrum to change an eccentricity amount of the cam ring relative
to an axis of the rotor. Side walls are disposed respectively on
axially opposite sides of the cam ring to define a plurality of
hydraulic fluid chambers each of which is defined by the rotor and
the adjacent vanes. A housing is provided for accommodating the cam
ring thereinside and including a discharge section opened through
at least one of the side walls to a discharge region in which
volumes of the hydraulic fluid chambers decrease along a rotational
direction of the rotor, and a suction section opened through at
least one of the side walls to a suction region in which volumes of
the hydraulic chambers increase along the rotational direction of
the rotor. A first pressure chamber defined is by the outer
peripheral section of the cam ring having a first pressure
receiving surface, a discharge pressure being introduced into the
first pressure chamber to allow the discharge pressure to be
applied through the first pressure receiving surface to the cam
ring to oppose to a biasing force of the biasing member so as to
provide the cam ring with a swinging force in a direction to
decrease the eccentricity amount of the cam ring. A second pressure
chamber defined is by the outer peripheral section of the cam ring
having a second pressure receiving surface, the discharge pressure
being introduced into the first pressure chamber to allow the
discharge pressure to be applied through the second pressure
receiving surface to the cam ring to assist the biasing force of
the biasing member so as to provide the cam ring with a swinging
force in a direction to increase the eccentricity amount of the cam
ring. Additionally, a control device is provided for controlling
supply of the discharge pressure to the second pressure chamber. In
the above oil pump, the first pressure receiving surface is set
larger in area than the second pressure receiving surface.
The other objects and features of this invention will become
understood from the following description with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, like reference numerals designate like parts and
elements throughout all figures, in which:
FIG. 1 is a perspective exploded view of a first embodiment of a
variable displacement oil pump according to the present
invention;
FIG. 2 is a front view of the variable displacement oil pump of
FIG. 1 in a state where a cover member is removed, showing a
condition where the eccentricity amount of a cam ring is the
maximum;
FIG. 3 is a front view similar to FIG. 2 but showing a condition
where the eccentricity amount of the cam ring is the minimum;
FIG. 4 is a cross-sectional view taken substantially along the line
A-A of FIG. 2;
FIG. 5 is a front view of a housing of the variable displacement
oil pump of FIG. 1, showing the inside of the housing;
FIG. 6 is a vertical sectional view of a solenoid valve used in the
variable displacement oil pump of FIG. 1, showing a state where no
current is supplied to the solenoid valve;
FIG. 7 is a vertical sectional view similar to FIG. 6 but showing a
state where current is supplied to the solenoid valve;
FIG. 8 is a diagram of a hydraulic circuit including the variable
displacement oil pump of FIG. 1;
FIG. 9 is a graph showing the relationship between engine oil
pressure and engine speed of an internal combustion engine on which
the variable displacement oil pump of FIG. 1 is mounted;
FIG. 10 is a vertical sectional view of a solenoid valve forming
part of a modified example of the first embodiment of the variable
displacement oil pump of FIG. 1, showing a state where no current
is supplied to the solenoid valve;
FIG. 11 is a vertical sectional view similar to FIG. 1, showing a
state where current is supplied to the solenoid valve;
FIG. 12 is a perspective exploded view of a second embodiment of
the variable displacement oil pump according to the present
invention;
FIG. 13 is a front view of the variable displacement oil pump of
FIG. 12 in a state where a cover member is removed, showing a
condition where the eccentricity amount of a cam ring is the
maximum;
FIG. 14 is a front view similar to FIG. 13 but showing a condition
where the eccentricity amount of the cam ring is the minimum;
FIG. 15 is a front view of a cover member of a third embodiment of
the variable displacement oil pump according to the present
invention;
FIG. 16 is a back-side view of the cover member of FIG. 15;
FIG. 17 is a front view of a fourth embodiment of the variable
displacement oil pump according to the present invention, showing a
state where a cover member is removed and showing a condition where
the eccentricity amount of a cam ring is the maximum;
FIG. 18 is a front view similar to FIG. 17 but showing a condition
where the eccentricity amount of the cam ring is the minimum;
FIG. 19 is a cross-sectional view of an oil pressure direction
changeover valve of a fifth embodiment of the variable displacement
oil pump according to the present invention, showing an inoperative
condition of the oil pressure direction changeover valve;
FIG. 20 is a cross-sectional view similar to FIG. 19 but showing an
operative condition of the oil pressure direction changeover
valve;
FIG. 21 is a diagram of a hydraulic circuit including a variable
displacement oil pump according to the present invention; and
FIG. 22 is a graph showing the relationship between engine oil
pressure and engine speed of an internal combustion engine on which
the variable displacement oil pump of FIG. 21 is mounted.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGS. 1 to 9 of the drawings, a first embodiment
of a variable displacement oil pump according to the present
invention is illustrated by the reference numeral 10. As shown in
FIGS. 1 to 3, oil pump 10 is disposed at a front end section or the
like of a cylinder block of an automotive internal combustion
engine and includes a housing (no numeral) which has
container-shaped pump body 11 which is formed to be opened at its
one end and formed thereinside with pump accommodating chamber 13
as a cylindrical space. Cover member 12 closes the opening at the
one end of pump body 11. Drive shaft 14 is rotatably supported by
the housing and passes through an about central portion of pump
accommodating chamber 13 so as to be rotationally driven by a
crankshaft of the engine. Pump element (no numeral) includes rotor
15 which is rotatably disposed inside pump accommodating chamber 13
and has a central section connected to drive shaft 14. Vanes 16 are
respectively disposed projectable from and retractable in slits 15a
which are formed as cutouts at an outer peripheral section of rotor
15 in a manner to extend radially outwardly. Cam ring 17 is
disposed at an outer peripheral side of the pump element to be
capable of being eccentric relative to a center or rotational axis
of rotor 15 and defines pump chambers 20 as hydraulic fluid
chambers upon cooperation with rotor 15 and adjacent vanes 16, 16.
In other words, the pump element is disposed inside an inner
peripheral section of cam ring 17. Spring 18 as a biasing member is
accommodated within pump body 11 and normally biases cam ring 17 in
a direction to increase an eccentricity amount of cam ring 17
relative to the center axis of rotor 15. Two ring members 19, 19
are slidably disposed respectively at the opposite side sections of
rotor 15 and located radially inside of the outer peripheries of
rotor 15, each ring member having an outer diameter smaller than
rotor 15.
Pump body 11 is formed of aluminum alloy as a single body and has a
bearing hole 11a which is formed at the about central portion of
bottom wall 13a of the pump accommodating chamber 13 so as to
pierce bottom wall 13a in order to rotatably support one end
section of drive shaft 14 as shown in FIGS. 4 and 5. Support groove
11b is semicylindrical and is formed as a cutout at a certain
position of the inner peripheral wall of pump accommodating chamber
13 or of pump body 11 in order to swingably support cam ring 17 as
shown in FIG. 5. Additionally, first and second seal sliding
surfaces 11c, 11d are formed on the opposite sides of flat plane M
(referred hereinafter to as "cam ring standard plane") connecting
the center axis of the bearing hole 11a and the center axis A of
support groove 11b as shown in FIGS. 3 and 5. The center axis A
lies on a plane including an inner peripheral surface S of the pump
body 11 as shown in FIGS. 3 and 4. Seal members 30, 30 discussed
after are respectively in slidable contact with first and second
seal sliding surfaces 11c, 11d. Each of these seal sliding surfaces
11c, 11d is formed arcuate in cross-section to form part of a
cylinder which has center axis A and has a certain radius R1, R2 on
a cross-sectional plane perpendicular to the center axis of the
bearing hole 11a as shown in FIG. 5. Each of sealing-sliding
surfaces 11c, 11d is set to have such a peripheral length that each
seal member 30 is always in slidable contact with the seal sliding
surface 11c within an eccentrically swingable range of cam ring 17.
By this, when cam ring 17 makes its eccentrically swinging
movement, the cam ring is slidably guided along respective seal
sliding surfaces 11c, 11d so as to accomplish a smooth operation
(eccentrically swinging movement) of cam ring 17.
Additionally, as shown in FIGS. 2 and 5, bottom wall 13a of pump
accommodating chamber 13 is formed with suction port 21 serving as
a suction section and with discharge port 22 serving as a discharge
section, the suction and the discharge ports being located radially
outside of the periphery of bearing hole 11a and located on
opposite sides of the axis of bearing hole 11a. The suction port 21
is formed as a generally arcuate groove upon being cut out and
opened to a suction region in which the internal volume of each
pump chamber 20 increases with the pumping action of the
above-mentioned pump element. The discharge port 22 is formed as a
generally arcuate groove upon being cut out and opened to a
discharge region in which the internal volume of each pump chamber
20 decreases with the pumping action of the above-mentioned pump
element.
Suction port 21 is connected at its central position to
introduction passage 24 formed extending to the side of spring
accommodating chamber 28. Suction hole 21a is located in the
introduction passage 24 and formed passing through the bottom wall
of pump body 11 and opened to the outside. By this, as shown in
FIG. 8, lubricating oil stored in oil pan 52 of the engine is
sucked into each pump chamber 20 within the above-mentioned suction
region through suction hole 21a and suction port 21 under a suction
developed by the pumping action of the above-mentioned pump
element. Suction hole 21a is configured together with suction
passage 24 to abut on a region outside the outer peripheral surface
of cam ring 17 at a pump suction side, thereby introducing a
suction pressure into the outer peripheral surface outside region
of the cam ring. By this, since the outer peripheral surface
outside region of cam ring 17 at the pump suction side adjacent
each pump chamber 20 in suction region takes a suction pressure or
atmospheric pressure, leak of lubricating oil from each pump
chamber 20 to the outer peripheral surface outside region of the
cam ring at the pump suction side can be suppressed. Here, the
"pump suction side" means a left-side region of a flat plane N
(referred hereafter to as "cam ring eccentrically movable direction
plane") which is perpendicular to plane M as shown in FIG. 2.
Discharge port 22 is connected at its one or lower end portion to
introduction passage 25 extending to abut on first pressure chamber
31 (discussed after) which is defined outside the outer peripheral
surface of cam ring 17. The other or upper end portion of discharge
port 22 is formed with discharge hole 22a which pierces the bottom
wall of the pump body 11 and opened to the outside of the pump body
11. This discharge hole 22a is communicated with various sliding
sections within the engine and with a valve timing control system
though not shown. With such an arrangement, lubricating oil
discharged from each pump chamber 20 upon being pressurized under
the pumping action of the above-mentioned pump element is supplied
to the various sliding sections within the engine and to the valve
timing control system through the discharge port 22 and the
discharge hole 22a. Discharge hole 22a is configured together with
introduction passage 25 to abut on a region outside the outer
peripheral surface of cam ring 17 at a pump discharge side, so that
a discharge pressure is introduced to the outer peripheral surface
outside region of cam ring 17 at the pump discharge side. Here, the
above-mentioned "pump discharge side" means a right-side region of
the cam ring eccentrically movable direction plane N in FIG. 2.
Further, communication groove 23 is formed as a cutout near the
lower end portion of discharge port 22 to allow discharge port 22
to be communicated with the bearing hole 11a, so that lubricating
oil is supplied through the communication groove 23 to bearing hole
11a and additionally to side sections of rotor 15 and banes 16
thereby securing a lubrication to various sliding sections.
Communication groove 23 is formed extending in a direction which
does not agree to a direction in which each vane 16 is projectable
from and retractable in the slit, so that the vane can be prevented
from getting off from its position to the communication groove when
the vane makes its projection from and retraction in the slit.
Cover member 12 is generally plate-shaped and formed slightly
thicker at its portion corresponding to bearing hole 11a of pump
body 11 which portion is located at its outer side surface, than
other portions thereof. Bearing hole 12a is formed piercing the
thicker portion in order to rotatably support the other end section
of drive shaft 14. While the inner side surface of cover member 12
has been shown and described as being formed flat in this
embodiment, it will be understood that suction and discharge ports
21, 22 may be formed at the inner side surface of the cover member
similarly to at the bottom surface of pump body 11. Additionally,
it will be understood that a groove for introducing lubricating oil
to bearing hole 12a may be formed at the inner side surface of
cover member like communication groove 23. This cover member 12 is
installed to the surface of the open end of pump body 11 with a
plurality of bolts 26.
Drive shaft 14 is configured to rotate rotor 15 clockwise in FIG. 2
under the rotational force transmitted from the crankshaft. The
left half side of cam ring eccentrically movable direction plane N
perpendicular to flat plane M at the center axis of drive shaft 14
is the above-mentioned pump suction side, while the right half side
of cam ring eccentrically movable direction plane is the
above-mentioned pump discharge side.
As shown in FIGS. 1 and 2, rotor 15 is formed with slits 15a as
cutouts which slits radially outward extend from its radially inner
central side to its radially outer peripheral side. Each slit 15a
is formed at its base end or radially inward portion with a back
pressure chamber 15b which is generally circular in cross-section
and supplied with lubricating oil discharged to discharge port 22.
By this, each vane 16 is pushed radially outward under the
centrifugal force with rotation of rotor 15 and the oil pressure
within back pressure chamber 15b.
Each vane 16 is slidably contacted at its tip end surface with the
inner peripheral surface of cam ring 17 and has the base end or
radially inward portion whose side surfaces are respectively
slidably contacted with the sliding surfaces of ring members 19,
19. By this, even when the engine speed of the engine is low so
that the above-mentioned centrifugal force and the oil pressure
within back pressure chamber 15b are low, pump chamber 20 can be
defined to maintain a secure liquid sealing with the outer
peripheral surface of rotor 15, the respective inside surfaces of
adjacent vanes 16, 16, the inner surface of cam ring 17, bottom
surface 13a of pump accommodating chamber 13 of pump body 11
serving as a side wall, and the inside surface of cover member 12
serving as another side wall.
Cam ring 17 is formed of a so-called sintered metal and formed
generally cylindrical as a single piece. Cam ring 17 is provided
with a pivot section or swinging movement fulcrum 17a which is
formed at a certain position in its outer peripheral section and
projects radially outwardly from the outer peripheral surface
thereof. Pivot section 17a is generally semicylindrical and axially
extends so as to be fitted in support groove 11b of pump body 11
constituting a support point for eccentric movement of the cam
ring. Arm section 17b is formed projecting from a position of the
cam ring 17 which position is located generally on an opposite side
of the center axis of cam ring 17 with respect to pivot section 17a
so as to be in cooperation with spring 18.
Here, pump body 11 is formed thereinside with a spring
accommodating chamber 28 which is located on an opposite side of
the center axis of the pump body with respect to support groove 11b
and communicated with pump accommodating chamber 13 through
communication section 27 having a certain width L. Spring 18 is
accommodated within this spring accommodating chamber 28. This
spring 18 is springingly maintained between the tip end section of
arm section 17b extending through communication section 27 to
spring accommodating chamber 28 and the bottom surface of the
spring accommodating chamber 28 with a certain set load W. Arm
section 17b is provided at the bottom surface of its tip end
section with support projection 17i which is formed generally
semispherical and engaged with the inner peripheral side of spring
18, so that one end of spring 18 is supported by support projection
17i.
With this arrangement, spring 18 is configured to always bias cam
ring 17 through arm section 17b in a direction (clockwise in FIG.
2) to increase the eccentricity amount of the cam ring under the
biasing force based on the above-mentioned set load W. By this, in
an inoperative condition of cam ring 17 as shown in FIG. 2, cam
ring 17 is in a state where the upper surface of the arm section
17a is brought into contact with stopper portion 28a projected from
the upper wall of spring accommodating chamber 28 with the biasing
force of spring 18, so that cam ring 17 is put into a position at
which the eccentricity amount is the maximum. As discussed, arm
section 17b is formed extending on the opposite side to pivot
section 17a thereby configuring such that the tip end portion of
arm section 17 is biased by spring 18, so that the maximum toque is
applied to cam ring 17. This achieves making spring 18 small-sized,
thereby small-sizing the pump itself.
Cam ring 17 are provided at its outer peripheral section with first
and second seal constituting sections 17c, 17d which are generally
triangular in cross-section and project radially outward. First and
second seal constituting sections 17c, 17d are respectively formed
with first and second seal surfaces 17g, 17h which are respectively
coaxial with and face first and second seal sliding surfaces 11c,
11d. Each surface 17c, 17d, 17g, 17h forms part of a cylindrical
surface which is arcuate in cross-section. Seal constituting
sections 17c, 17d are respectively formed at their seal surfaces
17g, 17h with first and second seal supporting grooves 17e, 17f
which are formed axially extending as cutouts, each seal supporting
groove having a generally rectangular cross-section. Seal members
30, 30 are respectively maintained in seal supporting grooves 17e,
17f so as to come into contact with seal sliding surfaces 11c, 11d
when cam ring 17 makes its eccentrically swingable movement.
Here, seal surfaces 17g, 17h respectively form parts of cylinders
which respectively have certain radiuses R3, R4 which are
respectively slightly smaller than radiuses R1, R2 with which the
corresponding seal sliding surfaces 11c, 11d are respectively
configured as shown in FIGS. 3 and 5, in which each radius R3, R4
is from the center axis of pivot section 17a which center axis
corresponds to the center axis A of the support groove 11b. Small
clearance C is formed between each seal surface 17g, 17h and each
seal sliding surface 11c, 11d as shown in FIG. 2.
Each seal member 30, 30 is formed, for example, of a fluororesin or
fluorine-containing resin having a low friction characteristics and
linearly extends in an axial direction of cam ring 17. Seal members
30, 30 are respectively configured to be biased against seal
sliding surfaces 11c, 11d under the elastic force of elastic
members 29, 29 formed of rubber or elastomeric material which
elastic members are respectively disposed in the bottom sections of
seal supporting grooves 17e, 17f. This always maintains a good
fluid-tight sealing for pressure chambers 31, 32 as discussed
below.
In the inoperative condition of cam ring 17, first pressure chamber
31 and second pressure chamber 32 are formed outside the outer
peripheral surface of cam ring 17 and located within a side (or the
pump discharge side) including pivot section 17a relative to the
cam ring eccentrically movable direction plane N. First and second
pressure chambers 31, 32 are respectively located on opposite sides
of pivot section 17a, in which each pressure chamber 31, 32 is
defined between the outer peripheral surface of cam ring 17 and the
inner peripheral surface of pump body 11, and more specifically
defined with the outer peripheral surface of cam ring 17, pivot
section 17a, each seal member 30 and the inner peripheral surface
of pump body 11. While whole first and second pressure chambers 31,
32 are shown and described as being located within the
above-mentioned pump discharge side in the region outside the outer
peripheral surface of cam ring 17 in this embodiment, it will be
understood that first and second pressure chambers 31, 32 are
preferably located within a region overlapping with the
above-mentioned discharge region which serves as a pressurizing
region in a radial direction of the pump, i.e., within a region on
an opposite side of the cylindrical wall of cam ring 17 with
respect to pump chamber 20 which is always at a positive
pressure.
A discharge pressure fed to discharge port 22 is always introduced
through introduction passage 25 to first pressure chamber 31, so
that the discharge pressure acts on first pressure receiving
surface 33 which is constituted by a part of the outer peripheral
surface of cam ring 17 which surface abuts on first pressure
chamber 31, the first pressure receiving surface being configured
to receive a force against the bias of spring 18. By this, cam ring
17 is supplied with a swinging force (moving force) in a direction
(or counterclockwise in FIG. 2) to decrease the eccentricity amount
of the cam ring. In other words, a pressure in first pressure
chamber 31 always biases cam ring 17 in such a direction that the
center axis of cam ring 17 approaches the center axis of rotor 15,
i.e., in a direction toward a coaxial relationship with rotor 15,
thus accomplishing a control for the moving amount of cam ring 17
in a direction toward the coaxial relationship with rotor 15.
The discharge pressure is suitably introduced into second pressure
chamber 32 through introduction hole 35 formed piercing the bottom
wall of pump body 11, the introduction hole is connected to
discharge hole 22a through solenoid valve 40 which will be
discussed below and is controlled in accordance with engine
operating conditions. The discharge pressure introduced into second
pressure chamber 32 acts on second pressure receiving surface 34
which is constituted by a part of the outer peripheral surface of
cam ring 17 which surface abuts on second pressure chamber 32, the
second pressure receiving surface being configured to receive a
force for assisting the biasing force of spring 18. By this, cam
ring 17 is supplied with a swinging force (moving force) in a
direction (or clockwise in FIG. 2) to increase the eccentricity
amount of the cam ring.
Here, as shown in FIG. 2, a pressure receiving area S2 of second
pressure receiving surface 34 is set smaller than a pressure
receiving area S1 of first pressure receiving surface 33, so that
the biasing force in an eccentrically movable direction of cam ring
17 based on the internal pressure in second pressure chamber 32 and
the biasing force of spring 18 can be balanced under a certain
force relationship. In other words, in second pressure chamber 32,
the discharge pressure supplied through solenoid valve 40 when
required acts on second pressure receiving surface 34 thereby
assisting the biasing force of spring 18, thus accomplishing a
control for the moving amount of cam ring 17 in the eccentrically
movable direction.
As shown in FIG. 8, oil pump 10 is separately provided with
solenoid valve 40 which is operated in accordance with engine
operating conditions of the engine under the action of energizing
current from an ECU 51 mounted on a vehicle equipped with the
engine. Discharge hole 22a and introduction hole 35 are connected
to each other through this solenoid valve 40, so that first
pressure chamber 31 and second pressure chamber 32 are brought into
communication with each other when solenoid valve 40 is opened.
As shown in FIGS. 6 and 7, solenoid valve 40 includes valve body 41
which is opened at its one end and closed at the other end. Valve
member 42 is axially slidably disposed inside valve body 40 and
provided at its opposite end portions with first and second land
portions 42a, 42b which are in slidable contact with the inner
peripheral surface of valve body 41. Back pressure chamber 45 is
defined at the side of the closed end of valve body 41 by second
land portion 42b of valve member 42. Spring 43 is disposed in back
pressure chamber 45 to bias valve member 42 toward the open end of
valve body 41. Electromagnetic unit 44 is installed to the open end
of valve body 41 and arranged to cause rod 44b to project upon
supplying electric current or energizing current, thereby axially
moving valve member 42 toward the closed end of valve body 41
against the biasing force of spring 34.
Valve body 41 is formed with IN port 41a connected to discharge
hole 22a and OUT port 41b connected to introduction hole 35, the
ports being formed piercing the peripheral wall of valve body 41.
Drain port 41c is formed piercing the peripheral wall of valve body
41 to connect the inside of the valve body to suction port 21 or
the outside of the valve body. Additionally, back pressure port 41d
is formed piercing the wall of the closed end of valve body 41 to
be always opened to back pressure chamber 45 and to be connected to
suction port 21 or the outside of the valve body.
Valve member 42 has an intermediate section which is reduced in
diameter thereby defining an annular space 46 between two land
portions 42a, 42b and by the inner peripheral surface of valve body
41, so that OUT port 41b is communicable with IN port 41b or with
drain port 41c through this annular space 46.
Electromagnetic unit 44 is configured as being known and includes a
coil unit 44a in which a bobbin is wound with a coil and fitted
inside a yoke though not shown. An armature (not shown) formed of a
magnetic material is axially projectably and retractably disposed
inside coil unit 44a. The armature is connected to rod 44b, so that
the rod is axially movable to project or retract with movement of
the armature in accordance with current supply conditions to coil
unit 44a.
Here, solenoid valve 40 is of a so-called normally opened type as
shown in FIG. 6 and therefore IN port 41a and OUT port 41b are
communicated with each other through annular space 56 in a
non-current supply condition where no current is supplied to coil
unit 44a, so that the discharge pressure is introduced into second
pressure chamber 32 (a first condition according to the present
invention). At this time, drain port 41c is kept in a state to be
opened to back pressure chamber 45.
In contrast, when the energizing current is supplied to coil unit
44a as shown in FIG. 7, valve member 42 is pushed back toward the
closed end of valve body 41 against the biasing force of spring 43
under the pushing force of rod 44b. By this, IN port 41a is closed
with first land portion 42a of valve body 42 while OUT port 41b is
communicated with drain port 41c through annular space 46, so that
second pressure chamber 32 is released to be supplied with the
suction pressure or atmospheric pressure (a second condition
according to the present invention).
With the above arrangement, in oil pump 10, the eccentricity amount
of cam ring 17 is controlled by regulating a force relationship
applied to cam ring 17, i.e., the force relationship between the
internal pressure of first pressure chamber 31 and the sum of the
biasing force of spring 18 and the internal pressure of second
pressure chamber 32 regulated by solenoid valve 40. This
eccentricity amount control regulates a variation in internal
volume of each pump chamber 20 during operation of the oil pump 10,
thereby controlling a discharge pressure characteristics of the oil
pump 10.
Hereinafter, featured operations of oil pump 10 according to the
present invention, i.e., the discharge pressure control of the pump
based on the eccentricity amount control of cam ring 17 will be
discussed with reference to FIGS. 2, 3 and 9.
First, the discharge pressure of oil pump 10 is decided by a
required oil pressure in various sliding sections of the engine and
the valve timing control system. Since the required oil pressure in
the engine varies according to the engine operating conditions of
the engine, there are a variety of required pressure whose typical
one is shown in a map of FIG. 9. Specifically, in case that the
valve timing control system is used, for example, for the purpose
of improving fuel economy and the like, the required oil pressure
takes a value P1. Additionally, the required oil pressure for the
internal combustion engine is decided mainly by an oil pressure
required in a bearing section of a crankshaft, in which this
required oil pressure varies in accordance with engine speed,
engine load (throttle valve opening degree), oil temperature and
the like. For example, during a low load and low engine oil
temperature engine operation, the required oil pressure takes a
value P2 in FIG. 9, whereas during a high load and high engine oil
temperature engine operation, the required oil pressure takes a
value P4 in FIG. 9. Further, during a high load engine operation,
it is required to use oil jet for cooling pistons, and therefore an
oil pressure P3 is required at a certain engine speed n in FIG. 9
during a medium engine speed engine operation.
Accordingly, oil pump 10 is set to take a low pressure
characteristics X (first discharge pressure characteristics)
meeting the required oil pressure represented by either one of P1
and P2 or the required oil pressures represented by both P1 and P2
in FIG. 9 during a low load or low engine oil temperature engine
operation, and to take a high pressure characteristics Y (second
discharge pressure characteristics) meeting the required oil
pressure represented by either one of P3 and P4 or the required oil
pressures represented by both P3 and P4. By changing over ON and
OFF of solenoid valve 40, the operational characteristics of cam
ring 17, i.e., first and second operational oil pressures Px, Py
(in FIG. 9) which are discharge pressures required for operation of
cam ring 17 are changed so as to select the optimum one of both oil
pressure characteristics X, Y thereby meeting the various required
oil pressures in the engine.
In this embodiment, as illustrated in FIG. 9, the low pressure
characteristics X is set at an oil pressure characteristics
indicated by a broken line connecting the required oil pressure P1
for a variable valve timing control system and the required oil
pressure P2 during a high engine speed engine operation under a low
load or low engine oil temperature condition, whereas the high
pressure characteristics Y is set at an oil pressure
characteristics indicated by a solid line connecting the required
oil pressure P3 during an intermediate engine speed engine
operation under a high load or high engine oil temperature
condition and the required oil pressure P4 during a high engine
speed engine operation under the same condition.
More specifically, in oil pump 10, the set load W of spring 18 is
set at a value corresponding to first operational oil pressure Px.
Accordingly, during the low load and low engine oil temperature
engine operation, the energizing current is supplied from ECU 51 to
solenoid valve 40, and therefore IN port 41a is closed so that the
discharge pressure is introduced only into first pressure chamber
31. By this, cam ring 17 is maintained in a state having the
maximum eccentricity amount until the internal pressure of first
pressure chamber 31 reaches first operational oil pressure Px as
shown in FIG. 2, so that the discharge pressure abruptly rises with
an increase in engine speed of the engine. Then, when the internal
pressure of first pressure chamber 31 reaches first operational oil
pressure Px under the rise of the discharge pressure, cam ring 17
makes its swingable movement around pivot section 17a serving as
the fulcrum, in a direction to decrease the eccentricity amount of
cam ring 17, i.e., downward along the cam ring eccentrically
movable plane N, as shown in FIG. 3. By this, a volume variation of
each pump chamber 20 is decreased during operation of the pump. As
a result, a rise in discharge pressure with rise in engine speed
becomes gentle, so that low pressure characteristics X as shown in
FIG. 9 can be obtained.
When the engine operation is shifted from the low load or low
engine oil temperature condition to the high load or high engine
oil temperature condition, supply of the energizing current to
solenoid valve 40 from ECU 51 is interrupted so that IN port 41a
and OUT port 41b are brought into communication with each other,
thereby introducing the discharge pressure not only into first
pressure chamber 31 but also in second pressure chamber 32. Then, a
pressure acting on second pressure receiving surface 34 of second
pressure chamber 32 works to assist the biasing force of spring 18.
Consequently, cam ring 17 cannot be operated even when the internal
pressure of first pressure chamber 31 reaches first operational oil
pressure Px in FIG. 9, so that cam ring 17 is kept in the state
having the maximum eccentricity amount until the difference between
the hydraulic pressure applied to first pressure receiving surface
33 with the internal pressure of first pressure chamber 31 and the
hydraulic pressure applied to second pressure receiving surface 34
with the internal pressure of second pressure chamber 32 reaches
the biasing force of spring 18, as shown in FIG. 2. More
specifically, during the high load or high engine oil temperature
engine operation, as shown in FIG. 9, until the discharge pressure
reaches second operational oil pressure Py at which the difference
between the hydraulic pressure applied to first pressure receiving
surface 33 with the internal pressure of first pressure chamber 31
and the hydraulic pressure applied to second pressure receiving
surface 34 with the internal pressure of second pressure chamber 32
becomes equal to the biasing force of spring 18, cam ring 17 is
kept at the state having the maximum eccentricity amount, so that
the discharge pressure largely rises with an increase in engine
speed of the engine. Then, when the internal pressure of first
pressure chamber reaches second operational oil pressure Py, cam
ring 17 makes its swingable movement in a direction to decrease the
eccentricity amount of cam ring 17 as shown in FIG. 3. By this, the
volume variation in each pump chamber 20 during operation of the
pump is decreased so that a rise of the discharge pressure with an
increase in engine speed becomes gentle, thereby obtaining high
pressure characteristics Y as shown in FIG. 9.
Thus, in oil pump 10, the pump discharge characteristics is
basically shifted to high pressure characteristics Y when ECU 51
makes its decision to require a high pressure in accordance with
engine speed, engine load, engine oil temperature and the like.
Normally, shifting to high pressure characteristics Y is made when
the engine load, engine oil temperature and the like are high, and
therefore high pressure characteristics Y has been shown and
described as being exhibited in a condition where the engine load
and the engine oil temperature are high, as an example. However,
for example, there is a case requiring an oil pressure higher than
the above required oil pressure P1 even in the valve timing control
system. In such a case, the charge-over action of solenoid valve 40
is made in accordance with operational signals of the valve timing
control system, so that the pump discharge pressure characteristics
is shifted to high pressure characteristics Y even in a condition
where the engine load, the engine oil temperature and the like are
low. In other words, while required oil pressure P1 has been shown
and described as being set at a normal required oil pressure for
the valve timing control system, it will be understood that
required oil pressure P1 may be set as the lowest required oil
pressure for the valve timing control system, according to the
specifications of a vehicle on which the engine including oil pump
10 is mounted.
When shifting is again made from the high load or high oil
temperature condition to the low load or low engine oil temperature
condition, the energizing current is again supplied from ECU 51 to
solenoid valve 40 so that the solenoid valve is put into its
energized state as shown in FIG. 7 in which second pressure chamber
32 is released to be supplied with the atmospheric pressure or
suction pressure. By this, operation of cam ring 17 depends on the
force relationship between the internal pressure of first pressure
chamber 31 and the biasing force of spring 18, so that the
discharge pressure characteristics of the pump is shifted to low
pressure characteristics X. As a result, the discharge pressure is
lowered by an amount corresponding to a discharge pressure which
becomes unnecessary upon shifting to the low engine load or low
engine oil temperature condition, thereby suppressing a power loss
of the engine.
As discussed above, in oil pump 10, the operational characteristics
of cam ring 17 can be changed by changing over the operation of
solenoid valve 40 in accordance with various engine operating
information such as the engine speed, engine load, the engine oil
temperature and the like by ECU 51, thereby selecting the discharge
pressure characteristics of the pump, suitable for the engine
speed, the engine oil temperature and the like. This makes it
possible to suppress a power loss of the engine at the minimum
value.
Additionally, oil pump 10 does not require a complicated control
such as a duty cycle control or the like for the operational
control of cam ring 17, because it accomplishes the operational
control of cam ring 17 by a simple control or ON-OFF control of
solenoid valve 40. Further, such an operational control of cam ring
17 can be accomplished without requiring a high-precision machining
for the ports and the like of solenoid valve 40 and a tuning of
valve opening characteristics, and accordingly can be easily
accomplished by using a usual solenoid valve having a simple
structure. This achieves a production cost reduction for the oil
pump.
Further, in oil pump 10, the internal pressure of each pump chamber
20 in the discharge region acts on the inner peripheral surface of
cam ring 17 around pivot section 17a as indicated by fat dark
arrows in FIG. 3, so that cam ring 17 is pushed to the right side
along the cam ring standard plane M, i.e., toward the side of
support groove 11b thereby pushing pivot section 17a into support
groove 11b. However, in case of oil pump 10 of this embodiment, the
internal pressures of both pressure chambers 31, 32 act to push
back cam ring 17 in an opposite direction as indicated by fat
dotted arrows in FIG. 3 because both pressure chambers 31, 33 are
located at the region outside the outer peripheral surface of cam
ring 17 in the pump discharge side, i.e., on an opposite side of
the peripheral or cylindrical wall of cam ring 17 with respect to
each pump chamber 20. As a result, a pressure of pivot section 17a
to support groove 11b can be lightened thereby reducing a friction
between pivot section 17a and support groove 11b during the
eccentric movement of cam ring 17. This makes it possible to
suppress a wear of pivot section 17b and support groove 11b,
particularly of support groove 11b of pump body 11 which is formed
of a material low in hardness as compared with the material of cam
ring 17, thereby improving a durability of the oil pump.
Under such an operation, forces acting on the inside and outside of
cam ring 17 at the pump discharge side nearly offset each other;
however, the atmospheric pressure or suction pressure acts on a
region outside the outer peripheral surface of cam ring 17 which
region is located on an opposite side of cam ring eccentrically
movable direction plane N with respect to support groove 11b, so
that pivot section 17a is slightly pushed into support groove 11b
under the atmospheric pressure or suction pressure. As a result,
there is no fear of pivot section 17a being separated from the
inner surface of support groove 11b, thus obtaining a suitable
operation of cam ring 17 under a suitable sliding contact between
pivot section 17a and support groove 11b.
Furthermore, as discussed above, in the above-mentioned pump
discharge side, both pressure chambers 31, 32 are located opposite
to pump chambers 20 relating to the discharge region, and therefore
a pressure acting on an inner peripheral side of cam ring 17 and a
pressure acting on an outer peripheral side of cam ring 17 becomes
the discharge pressure and nearly equal to each other. Accordingly,
the pressure difference between the inner and outer peripheral
sides of cam ring 17 can be suppressed at the minimum value in the
discharge region. By this, it is made possible to suppress at the
minimum value leak of lubricating oil through a small clearance
between one side surface of cam ring 17 and bottom wall 13a of pump
accommodating chamber 13 and through a small clearance between the
other side surface of cam ring 17 and inner side surface of cover
member 12. As a result, a loss of work of oil pump 10 can be
sufficiently reduced, thereby obtaining a high efficiency of oil
pump 10.
Thus, according to oil pump 10 of the present invention, first and
second pressure chambers 31, 32 are located on the opposite sides
of pivot section 17a, and therefore the internal pressure of second
pressure chamber 32 acts to assist the biasing force of spring 18,
thereby making it possible to set the biasing force of spring 18 as
small as possible. More specifically, with such a location of
second pressure chamber 32, spring 18 is sufficient to have a
biasing force for securing low pressure characteristics X, i.e., a
biasing force balanced with first operational oil pressure Px, so
that a low load spring lower in spring constant than a conventional
spring can be used as spring 18. By this, a space required for
spring 18 can be small-sized in pump body 11, thereby achieving
making oil pump 10 small-sized and lightened in weight. As a
result, a mounting ability of oil pump on the engine can be
improved.
Additionally, second pressure receiving surface 34 is set to be
smaller in pressure receiving area than first pressure receiving
surface 33, and therefore the operational oil pressure for cam ring
17 can be set at two stages under the action of second pressure
chamber 32. By this, freedom of the discharge pressure
characteristics of the oil pump can be improved.
Further, a variety of conventional pumps have been heretofore
provided as a pump configured such that a cam ring is swingably
movably controlled under the pressure difference between two
pressure chambers, such as a variable displacement pump for a power
steering system or the like. Any of these conventional pumps has a
structure in which a pressure difference is developed based on a
pressure loss under the action of an orifice or the like, in which
this pressure loss lowers a pump efficiency. In contrast, in oil
pump 10 of the present invention, the discharge pressure is
introduced into first and second pressure chambers 31, 32 without a
pressure loss, in which an operational torque for cam ring 17 is
developed by the difference in pressure receiving area between
pressure chambers 31, 32, i.e., the difference in area between
first and second pressure receiving surfaces 33, 34. Accordingly,
oil pump 10 of the present invention has no fear of causing a pump
efficiency to be lowered like the above-mentioned conventional
pumps. By this, oil pump 10 of the present invention can be
improved in pump efficiency by an amount corresponding to the
pressure loss being not developed, as compared with the
above-mentioned conventional variable displacement pumps.
Further, oil pump 10 of this embodiment is set to take the high
pressure characteristics when solenoid valve 40 is not supplied
with the energizing current, and therefore a required discharge
pressure can be secured even when solenoid valve 40 is failed, thus
being providing with a function as a fail-safe.
FIGS. 10 and 11 illustrate a modified example of the first
embodiment of oil pump 10 according to the present invention, which
is similar to the first embodiment except for the structure of
solenoid valve 40. Solenoid valve 40 of this modified example is
configured to be of a so-called normally closed type.
Specifically, solenoid valve 40 of this modified example is
configured to be of the so-called normally closed type having a
reversed characteristics relative to that of the first embodiment.
As shown in FIG. 10, in this oil solenoid valve 40, IN port 51a is
closed while OUT port 51b is communicated with drain port 51c when
no energizing current is supplied to the solenoid valve as shown in
FIG. 10, whereas IN port 51a is communicated with OUT port 51b when
the energizing current is supplied to the solenoid valve as shown
in FIG. 11. By this, oil pump 10 takes low pressure characteristics
X when no energizing current is supplied to solenoid valve 40 and
high pressure characteristics Y when the energizing current is
supplied to solenoid valve 40.
With such an arrangement, in case that a frequency for taking high
pressure characteristics Y is lower than that for taking low
pressure characteristics X regarding the discharge pressure
characteristics of oil pump 10 required by the engine, it is
possible to shorten a current supply time for solenoid valve 40,
thereby suppressing the deterioration of solenoid valve upon time
lapse.
FIGS. 12 to 16 illustrate a second embodiment of oil pump 10
according to the present invention, which is similar to the first
embodiment with the exception that positions of seal members 30, 30
are changed while solenoid valve 40 is formed integral with the
housing.
Specifically, in this embodiment, seal supporting grooves 17e, 17f
formed in respective seal constituting sections 17c, 17d of cam
ring 17 in the first embodiment are omitted, and seal supporting
grooves 11e, 11f similar to seal supporting grooves 17e, 17f are
respectively formed at positions in seal sliding surfaces 11c, 11d
which positions are opposite to the omitted seal supporting grooves
17e, 17f, in place of the omitted seal supporting grooves 17e, 17f.
Seal members 30, 30 are respectively accommodated and located
together with the elastic members 29, 29 in seal supporting grooves
11e, 11f.
Additionally, in this embodiment, as shown in FIGS. 15 and 16,
valve body 41 of solenoid valve 40 is formed integral with cover
member 12 and located at the outside surface of the cover member
and extends parallel with cum ring eccentrically movable plane N,
so that solenoid valve 40 is incorporated with the housing to form
a single unit. The structure of solenoid valve 40 of this embedment
is similar to that in the first embodiment, so that valve member 42
is slidably movably disposed inside valve body 41 formed integral
with cover member 12 while electromagnetic unit 44 is installed to
the open end of valve body 41 which open end is shown as an upper
end in FIG. 5.
With such changes in arrangement, as shown in FIG. 16, cover member
12 is formed at its inside surface 12c with suction port 21,
discharge port 22, communication groove 23 for communicating
discharge port 22 and bearing hole 12a, and introduction passage 25
extending from discharge port 22, similarly to pump body 11.
Further, in this cover member 12, IN port 41a is formed piercing
the wall of the cover member and located at a certain position in
introduction passage 25 while OUT port 41b serving also as
introduction hole 35 is formed piercing the wall of the cover
member and located at a certain position which is generally
symmetric with the position of IN port 41a with respect to cam ring
standard plane M. Additionally, drain port 41c and back pressure
port 41d are respectively formed piercing and located at certain
positions of the peripheral wall and the bottom wall of valve body
11 which is formed integral with cover member 12.
Accordingly, with this embodiment, when cam ring 17 makes its
eccentric movement, each seal member 30, 30 is brought into
slidable contact with each seal surface 17g, 17h of cam ring 17
formed of a ferrous sintered material which is higher in hardness
than pump body 11 formed of an aluminum alloy material, and
therefore wear of an opposite member or pump body can be suppressed
by each seal member 30, 30. By this, oil pump 10 of this embodiment
can be improved in durability as compared with that of the first
embodiment.
Furthermore, in this embodiment, solenoid valve 40 is formed
integral with cover member 12, i.e., incorporated with the housing
to form the single unit, so that a hydraulic circuit for oil pump
10 can be completed within this oil pump 10, thereby making
small-sized an oil pressure supply system including oil pump
10.
FIGS. 17 and 18 illustrate a third embodiment of oil pump 10
according to the present invention, which is similar to the first
embodiment. Accordingly, this oil pump 10 has basically the same
structure as the oil pump of the first embodiment, omitting seal
supporting grooves 17e, 17f formed respectively in seal
constituting sections 17c, 17d of cam ring 17 in the first
embodiment, and omitting elastic members 29, 29 and seal members
30, 30 accommodated in seal supporting grooves 17e, 17f in the
first embodiment.
More specifically, in this embodiment, in place of the omitted seal
members 30, 30 and the like, an inclined surface 17j of seal
constituting section 17c of cam ring 17 is formed flat while seal
constituting section 11h is formed at an inner peripheral section
of pump body 11 which section is near bolt insertion section 11g
into which bolt 26 is inserted. Seal constituting section 11h is
formed facing inclined surface 17j of first seal constituting
section 17c so as to be brought into contact with inclined surface
17j of the first seal constituting section 17c of cam ring 17 when
cam ring 17 makes its maximum eccentric movement to form seal
section SL.
This seal constituting section 11h is formed to be brought into
tight contact with inclined surface 17j of first seal constituting
section 17c of cam ring 17 when cam ring 17 makes its maximum
eccentric movement, so that the inside of first pressure chamber 31
is fluid-tightly maintained by seal section SL constituted with
seal constituting section 11h. With the above change in
arrangement, in this embodiment, the above-mentioned support
projection 17i formed at the inner peripheral surface of pump body
11 in the first embodiment for the purpose of restricting the
maximum eccentric position of cam ring 17 is omitted.
With such an arrangement, when cam ring 17 is not operated (taking
its maximum eccentric position), i.e., at a stage for raising the
discharge pressure, the inside of first pressure chamber 31 can be
fluid-tightly sealed with a similar degree to the first embodiment
under the action of seal section SL. By this, the discharge
pressure can be raised to first operational oil pressure Px set as
a minimally required oil pressure during a low engine speed engine
operation, with a suitable time (response). This can securely
provide a required oil pressure during the low engine speed engine
operation, such as required oil pressure P1 or the like for the
valve timing control system.
When cam ring 17 is operated (making its swingable movement), i.e.,
at a stage for suppressing a rise in discharge pressure, each
pressure chamber 31, 32 is sealed with small clearance C formed
between each seal sliding surface 11c, 11d and each seal surface
17g, 17h. In this case, while a slight leak occurs through small
clearance C, the discharge pressure exceeds first operational oil
pressure Px so as to be put into a state to be suppressed in its
rise at this stage, thereby permitting the above-mentioned
leak.
The above-mentioned clearance C is set similar to the clearance in
an axial direction between rotor 15 or cam ring 17 and the inner
side surface 12c of cover member 12 or bottom wall 13a of pump
accommodating chamber 13, or a clearance in a radial direction
between the outer peripheral surface of a rotor and the inner
peripheral surface of a housing in a known trochoid pump, so that
clearance C is set basically to put leak within an allowable
range.
Accordingly, according to this embodiment, by omitting seal members
30, 30 and the like, number of the component parts of oil pump 10
such as seal members 30, 30 and elastic members 29, 29 annexed to
the seal members can be reduced. This achieves reduction in number
of steps in assembling oil pump 10, thereby lowering a production
cost of oil pump 10.
In addition, reduction of the number of the component parts of oil
pump 10 can suppress occurrence of defects annexed to assembling,
such as assembling failure, thereby stabilizing and improving the
quality of oil pump 10.
FIGS. 19 to 22 illustrate a fourth embodiment of oil pump according
to the present invention, which is similar to the first embodiment.
Accordingly, this oil pump 10 has basically the same structure as
the oil pump of the first embodiment, and is provided with oil
pressure direction changeover valve 50 which is operated by the
discharge pressure to change a discharge pressure characteristics,
in place of solenoid valve 40 of the first embodiment.
Specifically, in this embodiment, in place of the above-mentioned
solenoid valve 40, oil pressure direction changeover valve 50 of
the known spool type is used. As shown in FIGS. 19 to 21, direction
changeover valve 50 includes a cylindrical valve body 51 whose one
end is opened while the other end is closed. Plug 52 closes the
open end of valve body 51. Valve member 53 is axially slidably
disposed in valve body 51 and is provided at its opposite end
portions with first and second land portions 53a, 53b which define
pressure chamber 55 and back pressure chamber 56 inside valve body
51. Spring 54 is accommodated within back pressure chamber 56 to
bias valve member 53 toward the side of pressure chamber 55.
Setting is made as follows: When the internal pressure of back
pressure chamber 54 exceeds certain set pressure Pz higher than the
above-mentioned required oil pressure P1 and lower than the
above-mentioned required oil pressure P2, valve member 53 moves
toward the side of back pressure chamber 56 against the biasing
force of spring 54, as shown in FIG. 20.
Valve body 51 is formed at its peripheral wall with IN port 51a
connected to discharge hole 22a, OUT port 51b connected to
introduction hole 35 and drain port 51c connected to suction port
21 or the outside, each port being located at axial certain
position of and formed piercing the peripheral wall of valve body
51. Additionally, back pressure port 51d is formed piercing the
side wall defining back pressure chamber 56 in order to allow back
pressure chamber 45 to be always released to be supplied with the
suction pressure or the atmospheric pressure upon being connected
to intake port 21 or the outside.
Plug 52 is screwed in a female screw section formed at the inner
peripheral surface of an end portion of valve body 51 containing
the open end. Introduction port 52a is formed piercing plug 52 and
extends along the center axis of the plug, so that the discharge
pressure is always introduced through introduction port 52a into
pressure chamber 55.
The axially intermediate section of valve member 53 is formed
smaller in diameter than other sections so that an annular space 57
is defined between land portions 53a, 53b, in which OUT port 51b
can be communicated with IN port 51a or with drain port 51c through
annular space 57. Specifically, when valve member 53 is in its
inoperative state, IN port 51a is closed with first land portion
53a while OUT port 51b and drain port 51c are communicated with
each other through annular space 57. When valve member 53 is
operated, drain port 51c is closed with second land portion 53b
while IN port 51a and OUT port 51b are communicated with each other
through annular space 57.
With the above-discussed arrangement, according to oil pump 10 of
this embodiment, in a condition where the engine speed of the
engine is low, IN port 51a of oil pressure direction changeover
valve 50 is closed so that the discharge pressure acts only on
first pressure chamber 31. Consequently, as shown in FIG. 22, when
the discharge pressure reaches first operational oil pressure Px,
cam ring 17 makes its eccentric movement in a direction to decrease
its eccentricity amount, thereby exhibiting the above-mentioned low
pressure characteristics X for which the rise of the discharge
pressure becomes gentle (corresponding to a zone T1 in FIG. 22).
Then, when the discharge pressure rises so that the internal
pressure of pressure chamber 55 reaches the above-mentioned set
pressure Pz, valve member 53 begins to make its axial movement
toward the side of back pressure chamber 55 against the biasing
force of spring 53 under the action of the internal pressure of
pressure chamber 55. With the axial movement of this valve member
52, the drain port 51c is closed with second land portion 53b while
IN port 51a is opened to annular space 57. By this, IN port 51a and
OUT port 51b are gradually brought into communication with each
other through annular groove 57, so that the discharge pressure is
introduced into second pressure chamber 32. As a result, the
internal pressure of second pressure chamber 32 rises, by which cam
ring 17 makes its eccentric movement in a direction to increase the
eccentricity amount of cam ring 17, so that the discharge pressure
is further increased thus exhibiting the above-mentioned high
pressure characteristics Y (corresponding to a zone T2 in FIG.
22).
Thus, according to this embodiment, while oil pressure direction
changeover valve 50 cannot accomplish a free changeover for the
discharge pressure in accordance with engine operating conditions,
like solenoid valve 40 in the first embodiment, it will be
appreciated that this embodiment can provide an oil pump provided
with a discharge pressure characteristics in relation to engine
speed, with a low production cost.
It will be understood that the present invention is not limited to
the arrangements of the above-mentioned embodiments, so that, for
example, the above-mentioned required oil pressures P1 to P5, the
above-mentioned first and second operational oil pressures Px, Py
and the above-mentioned set pressure Pz may be freely changed in
accordance with the specification of the internal combustion engine
of a vehicle on which oil pump 10 is mounted.
Further, while the side walls of oil pump 10 of the present
invention have been shown and described as being respectively the
bottom wall of pump body 11 and cover member 12 as examples in the
above embodiments, it will be understood that the side walls may be
respectively separate members which are, for example, located on
opposite sides of the pump element and respectively axially inside
the bottom wall of pump body 11 and cover member 12 so that the
side walls are separate and independent from the housing of oil
pump 10.
Furthermore, although the operation of cam ring 17 has been shown
and described as being controlled by balancing the internal
pressure of first pressure chamber 31 and the sum of the biasing
force of spring 18 and the internal pressure of second pressure
chamber 32 in the above embodiments, it will be appreciated that
the operation of cam ring 17 may be controlled only with the
internal pressure (pressure difference) of both pressure chambers
31, 32 omitting spring 18 by setting the pressure receiving area of
first pressure receiving surface 33 larger than the pressure
receiving area of second pressure receiving surface 34, according
to the specification of the oil pump.
Moreover, while the pressure receiving area of second pressure
receiving surface 33 has been shown and described as being smaller
than the pressure receiving area of first pressure receiving
surface 33, it will be understood that the pressure receiving
surfaces of first and second pressure receiving surfaces 33, 34 may
be set equal to each other.
The entire contents of Japanese Patent Application No. 2009-54366,
filed Mar. 9, 2009, are incorporated herein by reference.
Although the invention has been described above by reference to
certain embodiments and examples of the invention, the invention is
not limited to the embodiments and examples described above.
Modifications and variations of the embodiments and examples
described above will occur to those skilled in the art, in light of
the above teachings. The scope of the invention is defined with
reference to the following claims.
* * * * *