U.S. patent application number 11/574827 was filed with the patent office on 2008-05-08 for tandem pump no-load operation device.
This patent application is currently assigned to TBK. CO., LTD.. Invention is credited to Takeshi Hoji.
Application Number | 20080107545 11/574827 |
Document ID | / |
Family ID | 36089971 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080107545 |
Kind Code |
A1 |
Hoji; Takeshi |
May 8, 2008 |
Tandem Pump No-Load Operation Device
Abstract
When the pressure in the main oil supply channel is lower than
the no-load operation start pressure, the pressurized oil within
the secondary oil supply channel passes through the internal flow
channel of the spool and flows into the main oil supply channel. At
this time oil output from both the main and secondary oil pumps is
merged and supplied to the oil supply destination. When the
pressure within the main oil supply channel rises and reaches the
no-load operation start pressure, the spool moves in opposite
direction to the direction of the force of the spring, the
pressurized oil within the secondary oil supply channel is drained,
the poppet contacts the spool and blocks the internal flow channel
of the spool. At this time, the secondary oil pump enters the
no-load operation state, and oil output from the main oil pump only
is transmitted to the oil supply destination.
Inventors: |
Hoji; Takeshi; (Kanagawa,
JP) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
TBK. CO., LTD.
Tokyo
JP
|
Family ID: |
36089971 |
Appl. No.: |
11/574827 |
Filed: |
August 3, 2005 |
PCT Filed: |
August 3, 2005 |
PCT NO: |
PCT/JP05/14610 |
371 Date: |
March 7, 2007 |
Current U.S.
Class: |
417/307 |
Current CPC
Class: |
F04C 14/26 20130101;
F04B 23/04 20130101; F04C 14/065 20130101; F04C 2270/56
20130101 |
Class at
Publication: |
417/307 |
International
Class: |
F04C 14/06 20060101
F04C014/06; F04B 23/04 20060101 F04B023/04; F04C 14/02 20060101
F04C014/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 22, 2004 |
JP |
2004-274855 |
Claims
1. A tandem pump no-load operation device, comprising: a tandem
pump comprising a main fluid pump and a secondary fluid pump that
are simultaneously driven by a drive source; a main fluid supply
channel that extends from an outlet of the main fluid pump to a
fluid supply destination; a secondary fluid supply channel that
extends from an outlet of the secondary fluid pump and is connected
to the middle of the main fluid supply channel; a valve bore that
forms a part of the secondary fluid supply channel; a spool,
disposed by fitting and insertion within the valve bore so that the
spool can freely move, having an internal flow channel that extends
in an axial direction; an urging member that urges the spool within
the valve bore toward connection with the main fluid supply
channel; and a poppet disposed within the valve bore so as to be
able to freely move, that is closer to the connection with the main
fluid supply channel than the spool within the valve bore, and that
can move to a closed position in which an end portion of the poppet
contacts and closes an end of the internal flow channel of the
spool, and move to an open position in which the poppet is
separated from the end of the internal flow channel, wherein a
drain flow channel is provided that is connected to the valve bore,
and when the spool is acted on by the pressure within the main
fluid supply channel the spool can move against the force of the
urging member; when the pressure within the main fluid supply
channel is smaller than a no-load operation start pressure, the
spool is moved by the force of the urging member towards the
connection with the main fluid supply channel, the link with the
drain channel is closed, and the secondary fluid supply channel and
the main fluid supply channel are linked by the internal flow
channel; and when the pressure within the main fluid supply channel
rises higher than the no-load operation start pressure, the spool
moves against the force of the urging member, and the secondary
fluid supply channel is connected to the drain flow channel, and
the poppet is moved into the closed position against the spool by a
difference in pressure between the secondary fluid supply channel
and the main fluid supply channel resulting from pressurized oil
within the secondary fluid supply channel being drained.
2. The tandem pump no-load operation device according to claim 1,
wherein the tandem pump comprises gear pumps comprising a drive
gear driven by the drive source and a first driven gear and a
second driven gear that circumscribes and meshes with the drive
gear.
3. The tandem pump no-load operation device according to claim 1,
wherein the spool comprises: an intermediate portion having the
internal flow channel; and an urging member housing portion, at one
end of the intermediate portion, that is acted on by the force of
the urging member, wherein the external periphery of the
intermediate portion is provided, in the center in the axial
direction, with a small diameter spool rod portion, and spool land
portions are provided to the left and right of the spool rod
portion, the left and right spool land portions mate with the valve
bore, and the spool is inserted and installed within the valve bore
so as to be able to move freely.
4. The tandem pump no-load operation device according to claim 3,
wherein linking holes that penetrate the external peripheral
surface and link to the internal flow channel are provided in the
left spool land portion, so that within the range of movement of
the spool the linking holes are always connected to the outlet side
of the secondary fluid pump in the secondary fluid supply
channel.
5. The tandem pump no-load operation device according to claim 3,
wherein when the pressure within the main fluid supply channel
exceeds the no-load operation start pressure and the spool is moved
against the force of the urging member, the secondary fluid supply
channel is connected to the drain flow channel via the spool rod
portion.
6. The tandem pump no-load operation device according to claim 1,
wherein a flow channel serving also as a drain that opens to both
the main fluid supply channel and the external peripheral surface
of the poppet is provided within the poppet, and when the pressure
within the main fluid supply channel exceeds the no-load operation
start pressure and reaches a relief setting pressure that is still
higher than the no-load operation start pressure, the spool is
acted on by the force of the relief setting pressure and is moved
to a position where the flow channel serving also as a drain and
the drain flow channel are connected, and the pressurized fluid
within the main fluid supply channel is drained from the drain flow
channel.
7. The tandem pump no-load operation device according to claim 6,
wherein the spool comprises: an intermediate portion having the
internal flow channel; and an urging member housing portion at one
end of the intermediate portion of which is acted on by the force
of the urging member, wherein the external periphery of the
intermediate portion is provided with, in the center in the axial
direction, a small diameter spool rod portion, and spool land
portions are provided to the left and right of the spool rod
portion, the left and right spool land portions mate with the valve
bore, and the spool is inserted and installed within the valve bore
so as to be able to move freely.
8. The tandem pump no-load operation device according to claim 7,
wherein drain apertures are provided in the right spool land
portion that penetrate the external peripheral surface, and that
links with a part closer to the main fluid supply channel than a
part blocked by the poppet in the internal flow channel, and when
the pressure in the main fluid supply channel reaches the relief
setting pressure, the spool is acted on by the relief setting
pressure and moves to a position where the drain apertures link
with the drain flow channel, and the flow channel serving also as a
drain is connected to the drain flow channel.
9. The tandem pump no-load operation device according to claim 4,
wherein when the pressure within the main fluid supply channel
exceeds the no-load operation start pressure and the spool is moved
against the force of the urging member, the secondary fluid supply
channel is connected to the drain flow channel via the spool rod
portion.
Description
TECHNICAL FIELD
[0001] The present invention relates to a tandem pump which
comprises two fluid pumps that are driven simultaneously by a
single drive source, and in which the pressurized oil output from
both fluid pumps is merged and supplied to the fluid supply
destination. In more detail, the present invention relates to a
tandem pump no-load operation device in which when the fluid supply
flow rate increases and the pressure within the fluid supply
channel reaches the no-load operation start pressure, one of the
fluid pumps is operated under no-load to reduce the power from the
drive source.
BACKGROUND ART
[0002] A tandem pump includes two fluid pumps that are driven
simultaneously by a single drive source, and the pressurized oil
output from the respective outlets of the two fluid pumps can be at
the same or different pressures. Two separate actuators can be
connected to the two outlets of this type of tandem pump and the
actuators can be separately operated, but by merging the
pressurized oil output from the two pumps and supplying a fluid
supply destination, it is possible to obtain a flow rate
corresponding to two fluid pumps. An example of the use of the
latter tandem pump is an oil pump provided in an automobile engine,
for example, that supplies oil (engine oil) to an oil gallery
provided in the engine block to lubricate and cool each part of the
engine. This is configured so that the drive shaft of the tandem
pump is driven by a gear installed on the engine crankshaft. When
the engine rotation speed is low, and the flow rate of the oil
output from both pumps is small, the oil output from both oil pumps
is merged in the oil supply channel, and when the engine rotation
speed is large and the flow rate of the oil output from both oil
pumps is large, the oil output from one of the two oil pumps is
drained and the oil pump is operated under no load, and the oil
output from the other oil pump only is supplied to the oil supply
channel. In this type of configuration, when the rotation speed of
the engine is low, sufficient supply flow rate of lubricating oil
can be ensured, so when the vehicle is traveling at low speed it is
possible to provide sufficient lubrication to each part of the
engine. This type of tandem pump is disclosed in for example
Japanese Patent Application Laid-open No. H10-131751 and Japanese
Patent Application Laid-open No. 2001-132624.
[0003] FIG. 7 shows an example of a conventional tandem pump
no-load operation device. In FIG. 7, a main oil pump P1 and a
secondary oil pump P2 are driven simultaneously by a single drive
source (an engine M). A main oil supply channel L1 is connected to
an oil supply destination (for example, an oil gallery provided
within the engine block) OB from the outlet of the main oil pump P1
via a line filter that is not shown in the drawings. Also, a
secondary oil supply channel L2 that extends from the outlet of the
secondary oil pump P2 is connected to the middle portion of the
main oil supply channel L1. A check valve CV is installed in the
secondary oil supply channel L2 to prevent the inflow of hydraulic
oil from the main oil supply channel L1 towards the secondary oil
pump P2 side, and an unload valve AV is installed on the secondary
oil supply channel L2 between the check valve CV and the secondary
oil pump P2.
[0004] Here, when the rotation speed of the engine is low, and the
pressure within the main oil supply channel L1 is low, the unload
valve AV is closed, and the oil output from the secondary oil pump
P2 passes through the check valve CV and flows into the main oil
supply channel L1, so the oil output from both main and secondary
oil pumps P1, P2 is merged and transmitted to the oil supply
destination OB from the main oil supply channel L1. On the other
hand, when the rotation speed of the engine is high, the flow rate
of oil output from both oil pumps increases, and when the pressure
within the main oil supply channel L1 is equal to or greater than
the no-load operation start pressure, the pressurized oil within
the main oil supply channel L1 presses a spool in the unload valve
AV which opens the unload valve AV, so the hydraulic oil within the
secondary oil supply channel L2 is released to the drain side, and
the secondary oil pump P2 enters the no-load operation state. At
this time, the pressure in the secondary oil supply channel L2
reduces, and the check valve CV closes the secondary oil supply
path L2, so only oil output from the main oil pump P1 is supplied
to the oil supply destination OB. Also, a relief valve (pressure
regulator valve) LV is provided on the main oil supply channel L1,
so that the pressure in the main oil supply channel L1 does not
rise above the relief setting pressure.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0005] In the conventional tandem valve as described above there
was the problem that the check valve CV and the unload valve AV are
provided on the secondary oil supply channel L2 and the relief
valve (pressure regulator valve) LV is provided on the main oil
supply channel L1 as separate valves, so the freedom of layout is
limited in circuit design, and it is difficult to make the entire
device compact.
[0006] With the foregoing problems in view, it is an object of the
present invention to provide a tandem pump no-load operation device
having the same performance as a conventional device, but which can
be made more compact.
Means to Solve the Problems
[0007] The tandem pump no-load operation device according to the
present invention comprises: a tandem pump comprising a main fluid
pump (for example, the main oil pump 7 in the embodiments) and a
secondary fluid pump (for example, the secondary oil pump 8 in the
embodiments) that are driven simultaneously by a drive source; a
main fluid supply channel (for example, the main oil supply channel
9 in the embodiments) that extends from an outlet of the main fluid
pump to a fluid supply destination (for example, the oil supply
destination OB in the embodiments); a secondary fluid supply
channel (for example, the secondary oil supply channel 10 in the
embodiments) that extends from an outlet of the secondary fluid
pump and is connected to the middle of the main fluid supply
channel; a valve bore that forms a part of the secondary fluid
supply channel; a spool disposed by fitting and insertion within
the valve bore so that the spool can freely move, having an
internal flow channel that extends in an axial direction; an urging
member (for example, the spring 30 in the embodiments) that urges
the spool within the valve bore toward connection with the main
fluid supply channel; and a poppet disposed within the valve bore
so as to be able to move freely, that is closer to the connection
with the main fluid supply channel than the spool within the valve
bore, and that can move to a position in which an end portion of
the poppet contacts and closes an end of the internal flow channel
of the spool, and to a position in which the poppet is separated
from the end of the internal flow channel to open the internal flow
channel. Furthermore, a drain channel is provided that is connected
to the valve bore, and when the spool is acted on by the pressure
within the main fluid supply channel the spool can move against the
force of the urging member; when the pressure within the main fluid
supply channel is lower than a no-load operation start pressure,
the spool is moved by the force of the urging member towards the
connection with the main fluid supply channel, the link with the
drain channel is closed, and the secondary fluid supply channel and
the main fluid supply channel are linked by the internal flow
channel; and furthermore when the pressure within the main fluid
supply channel rises higher than the no-load operation start
pressure, the spool moves against the force of the urging member,
and the secondary fluid supply channel is connected to the drain
flow channel, and the poppet is moved into a position to contact
and close the end of the internal flow channel of the spool by the
difference in pressure between the secondary fluid supply channel
and the main fluid supply channel resulting from pressurized oil
within the secondary fluid supply channel being drained.
[0008] Also, in the above tandem pump no-load operation device, it
is desirable that a flow channel serving also as a drain opens to
both the main fluid supply channel and the external peripheral
surface of the poppet is provided within the poppet, and when the
pressure within the main fluid supply channel exceeds the no-load
operation start pressure and reaches a relief setting pressure that
is still higher, the spool is acted on by the force of the relief
setting pressure and is moved to a position where the flow channel
serving also as a drain and the drain flow channel are connected,
and the pressurized fluid within the main fluid supply channel is
drained from the drain flow channel.
Advantageous Effects of the Invention
[0009] In the tandem pump no-load operation device according to the
present invention, when the pressure within the main fluid supply
channel is lower than the no-load operation start pressure, the
pressurized fluid within the secondary fluid supply channel passes
through the internal flow channel of the spool and flows into the
main fluid supply channel. At this time the fluid output from the
main and secondary fluid pumps is merged and transmitted to the
fluid supply destination. When the pressure within the main fluid
supply channel rises and reaches the no-load operation start
pressure, the spool moves in the direction opposite to the
direction of the force of the urging member, the pressurized fluid
within the secondary fluid supply channel is drained, the poppet
contacts the spool, and the internal flow channel of the spool is
closed. At this time, the secondary fluid pump enters the no-load
operation state, and oil output from the main fluid pump only is
transmitted to the fluid supply destination. In this way, the
tandem pump no-load operation device according to the present
invention has a configuration in which the necessary components,
which are the spool, the urging member, and the poppet, are
provided within a single valve bore, while maintaining the same
function as the conventional art, namely when the pressure in the
secondary fluid supply channel rises and reaches the no-load
operation start pressure, the secondary fluid pump enters the
no-load operation state which reduces the power from the drive
source (and furthermore when the pressure within the main fluid
supply channel reaches the relief setting pressure, the pressurized
oil within the main fluid supply channel is relieved), therefore
the degree of freedom during circuit design is increased, and it is
possible to make the overall device more compact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a section view showing the configuration of the
tandem pump no-load operation device according to an embodiment of
the present invention;
[0011] FIG. 2 is a partially exploded section view of the no-load
operation device;
[0012] FIG. 3 is an exploded isometric view of the components
within the valve body;
[0013] FIG. 4 is a view showing an example of the operation
position of the spool and poppet when the oil discharged from both
the main and secondary oil pumps merge and is transmitted to the
supply destination;
[0014] FIG. 5 is a view showing an example of the operation
position of the spool and poppet when the secondary oil pump is in
the no-load operation state and oil discharged from the main oil
pump only is transmitted to the supply destination;
[0015] FIG. 6 is a view showing an example of the operation
position of the spool and poppet when the outlet pressure in the
outlet channel reaches the relief setting pressure and a part of
the discharged oil of the main oil pump is drained; and
[0016] FIG. 7 is a hydraulic circuit diagram showing an example of
the configuration of a conventional tandem pump no-load operation
device.
BEST MODE FOR CARRYING OUT THE INVENTION
[0017] The following is an explanation of the preferred embodiments
of the present invention with reference to the drawings. FIG. 1
shows a tandem pump no-load operation device according to an
embodiment of the present invention. The no-load operation device
is provided in an automobile engine to transmit under pressure oil
(engine oil) that lubricates and cools all parts of the engine to
an oil supply destination (for example, an oil gallery provided
within the engine block, that is not shown in the drawings) OB, and
is assembled into a pump body 1 formed in a part of the crank case
of the engine. A pump chamber 2 is formed in the pump body 1,
within which a tandem pump 3 is disposed. The tandem pump 3
includes a drive gear 4, and two driven gears (a first driven gear
5 and a second driven gear 6) on either side of and meshing with
the drive gear 4, the drive gear 4, the first driven gear 5, and
the second driven gear 6 are rotatably supported by a drive shaft
4a, and driven shafts 5a, 6a respectively. The drive shaft 4a of
the drive gear 4 is driven by the crankshaft of an engine (not
shown in the drawings) to rotate in the direction of the arrow
shown in FIG. 1 (counterclockwise). The first driven gear 5 and the
second driven gear 6 rotate in the direction of the arrows shown in
FIG. 1 (clockwise) in accordance with the rotation of the drive
gear 4.
[0018] The drive gear 4 and the first driven gear 5, and the drive
gear 4 and the second driven gear 6 constitute conventional gear
pumps. In other words, when the drive gear 4 rotates, the first
driven gear 5 (or the second driven gear 6) is driven, and
hydraulic oil flows in from low pressure portion, and hydraulic oil
is expelled from the high pressure portion created by the rotation.
In the present embodiment, the part above the portion where the
drive gear 4 meshes with the first driven gear 5 is an inlet 7a,
and the part below the meshing portion is an outlet 7b. Also, the
part below the portion where the drive gear 4 meshes with the
second driven gear 6 is an inlet 8a, and the part above the meshing
portion is an outlet 8b. Here, the oil pump that includes the drive
gear 4 and the first driven gear 5 is referred to as the main oil
pump 7, and the oil pump that includes the drive gear 4 and the
second driven gear 6 is referred to as the secondary oil pump 8,
the inlet 7a is referred to as the main oil pump 7 inlet, the
outlet 7b is referred to as the main oil pump 7 outlet, the inlet
8a is referred to as the secondary oil pump 8 inlet, the outlet 8b
is referred to as the secondary oil pump 8 outlet.
[0019] As described above, the tandem pump 3 includes the main oil
pump 7 and the secondary oil pump 8 that are driven simultaneously
by a single drive source (the engine). Also, a main oil supply
channel 9 extends from the outlet 7b of the main oil pump 7 to
which the main oil supply channel 9 is connected, and a secondary
oil supply channel 10 (10a, 10b, 10c) extends from the outlet 8b of
the secondary oil pump 8 to which the secondary oil supply channel
10 is connected. The main oil supply channel 9 is connected to an
oil supply destination OB which is not shown in the drawings, and
as shown in FIG. 1, the secondary oil supply channel 10 (10a, 10b,
10c) is connected to the middle of the main oil supply channel 9.
Also, a first oil inlet channel 11 that is connected to the inlet
7a of the main oil pump 7 is connected to an oil pan T, and a
second oil inlet channel 12 that is connected to the inlet 8a of
the secondary oil pump 8 is connected to the middle of the first
oil inlet channel 11.
[0020] A valve bore 13 is extended in the secondary oil supply
channel 10 forming a part of the secondary oil supply channel 10,
and a spool 20 whose overall shape is cylindrical is inserted into
the valve bore 13 (see also FIGS. 2 and 3). As shown in FIG. 1, the
spool 20 includes an intermediate portion 22 having an internal
flow channel 21 that extends in the axial direction, and a spring
housing portion 23 provided to the left side of the intermediate
portion 22 (the left side in FIG. 1), that has a cylindrical shape
with a bottom and that is open to the left side, and that is
disposed within the valve bore 13 so that the spool 20 can move
freely in the direction of extension of the secondary oil supply
channel 10. The right end of a spring 30 disposed within a spring
housing space 14 formed in the pump body 1 is housed within the
spring housing portion 23, and the spool 20 is always forced by the
spring 30 to the right (towards the main oil supply channel 9
side). A hollow cylindrical shaped spool stopper 51 and a disk
shaped force adjustment fitting 52 are housed within the spring
housing space 14, and the spring housing space 14 is closed by an
end plate 53 installed in a plate installation groove 15 provided
within the pump body 1. The force of the spring 30 can be adjusted
as appropriate by changing and using force adjustment fittings 52
of different thicknesses.
[0021] At the right end of the valve bore 13 a spool contact
surface 13a is formed in a step shape, and to the right of the
spool contact surface 13a a poppet housing bore 13d is formed. As
discussed later, the poppet housing bore 13d and an aperture 13e on
the right end thereof form part of the secondary oil supply channel
10.
[0022] The spool 20 is acted on by the force of the spring 30 and
moves to the right within the valve bore 13, and can move until an
end 28 (see FIG. 2) of the spool 20 on the main oil supply channel
9 side (in FIG. 1 the right side of the plane of the paper)
contacts the spool contact surface 13a (see FIG. 2) formed in the
valve bore 13, the position of the spool 20 at this time is
referred to below as the "initial position". Also, the spool 20 is
positioned in the leftmost position within the valve bore 13 when
an end portion 23a of the spring housing portion 23 contacts an end
portion 51a of the spool stopper 51 (see FIG. 1 and FIG. 2) from
the right side, and this is referred to as the "leftmost
position".
[0023] A poppet 40 having a cylindrical shape with a bottom, that
is open to the side of the main oil supply channel 9, is disposed
within the poppet housing bore 13d, the poppet 40 can move freely
along the direction of the axis of the spool 20 within the poppet
housing bore 13d. The poppet 40 has a large diameter trunk portion
41 and a seat portion 42 whose outer diameter is smaller than the
outer diameter of the trunk portion 41 and that is located to the
left side (the spool 20 side) of the trunk portion 41, and a
plurality of linking holes 43b are formed in the seat portion 42 in
the diametral direction.
[0024] The seat portion 42 can enter a right side open portion 21a
of the spool 20 from the right (from the side of the main oil
supply channel 9). When the seat portion 42 of the poppet 40 is
inside the right side open portion 21a but separated from a valve
seat portion 24 formed within the internal flow channel 21 of the
spool 20, the internal flow channel 21 of the spool 20 is linked to
an internal space 43a of the poppet 40 via the linking holes 43b,
and furthermore links with the main oil supply channel 9 through
the secondary oil supply channel 10c (in this state, the poppet 40
is said to be in the open position). On the other hand, when the
seat portion 42 contacts the valve seat 24, the internal flow
channel 21 of the spool 20 is closed at this part by the poppet 40
(in this state the poppet 40 is said to be in the closed position).
The channel formed by the internal space 43a of the poppet 40 and
the plurality of linking holes 43b provided in the outer peripheral
surface of the seat portion 42 of the poppet 40 is referred to as a
drain multi-use linking channel 43. Therefore, when the seat
portion 42 of the poppet 40 is separated from the valve seat 24 of
the spool 20, as shown in FIG. 1, the internal flow channel 21 of
the spool 20 is linked to the main oil supply channel 9 via the
drain multi-use linking channel 43 of the poppet 40 and the
secondary oil supply channel 10c.
[0025] A spool rod 25 whose outer diameter is smaller than the
outer diameter on both sides is provided in the central portion of
the intermediate portion 22 of the spool 20. To the left and right
of the spool rod 25 a left and right spool land 26a, 26b is formed,
and the left and right spool lands 26a, 26b are inserted into and
mate with the valve bore 13 (13b, 13c). A plurality of linking
holes 27 is provided along the outer peripheral surface of the left
spool land 26a, and the linking holes 27 connect to the internal
flow channel 21. Also, a plurality of drain apertures 29 that
penetrates in the diametral direction is formed in the right spool
land 26b to the right of the spool rod 25, and the drain apertures
29 are also connected to the internal flow channel 21.
[0026] The secondary oil supply channel 10 is explained as being
divided into the part within the valve bore 13 (the channel lob),
the part from the outlet 8b of the secondary oil pump 8 to the
valve bore 13 (the flow channel 10a), and the part from the valve
bore 13 to the main oil supply channel 9 (the flow channel 10c),
but the linking holes 27 are positioned so that they are always
connected to the flow channel 10a even if the spool 20 moves from
the "initial position" to the "leftmost position".
[0027] A hydraulic oil channel 16 is formed between the outer
peripheral surface of the spool rod 25 and a seat bore 13b of the
valve bore 13 and the hydraulic oil channel 16 is connected to a
drain channel 17 that that leads to the oil pan T via the second
oil inlet channel 12. When the spool 20 is in the initial position,
or has moved a small amount to the left from the initial position,
the passage between the flow channel 10a and the hydraulic oil
channel 16 is obstructed by the spool land 26a mating with the seat
bore 13b, but when the spool 20 moves further to the left, the flow
channel 10a and the hydraulic oil channel 16 are linked.
[0028] As shown in FIG. 2, to assemble the no-load operation
device, the poppet 40, the spool 20, the spring 30, the spool
stopper 51, and the force adjustment fitting 52 are inserted into
the valve bore 13 (including the poppet bore 13d) of the pump body
1, then the force adjustment fitting 52 is pressed with a finger to
compress the spring 30, and then the end plate 53 is inserted into
the plate installation groove 15 of the pump body 1.
[0029] In the tandem pump 3 no-load operation device configured in
this way, when the drive gear 4 is driven to rotate, the first
driven gear 5 and the second driven gear 6 that are meshed with the
drive gear 4 also rotate, and the main oil pump 7 and the secondary
oil pump 8 operate as pumps. Specifically, the main oil pump 7
draws in oil in the oil pan T through the inlet 7a, and expels the
oil from the outlet 7b. Also, the secondary oil pump 8 draws in oil
in the oil pan T through the inlet 8a, and expels the oil from the
outlet 8b.
[0030] The oil supply destination OB for the expelled oil is the
oil gallery within the engine block, and as the flow rate of the
supplied oil increases the supply pressure increases. Therefore,
when the rotation speed of the engine is low, the flow rate of the
oil output by both the main and secondary oil pumps 7, 8 is also
small, so the pressure within the oil supply channels 9, 10 is also
low. Here, the output pressure from the secondary oil pump 8 acts
on the internal flow channel 21, and acts to force the spool 20 to
the left. Therefore, the spool 20 moves to the left from the
initial position resisted by the force of the spring 30, but the
output pressure is low so the amount of movement is small, and as
shown in FIG. 4 the passage between the secondary oil supply
channel 10a and the hydraulic oil channel 16 is obstructed by the
spool land 26 mating with the seat bore 13b. During this time, the
total amount of oil output into the flow channel 10a flows into the
internal flow channel 21 of the spool 20.
[0031] In this way, the oil output from the secondary oil pump 8
that has flowed into the internal flow channel 21 pushes the poppet
40 towards the main oil supply channel 9 side (the seat portion 42
of the poppet 40 is separated from the valve seat 24 of the spool
20) and flows into the main oil supply channel 9 (see the flow of
oil indicated by the arrows in FIG. 4). Therefore, the oil output
from the main oil pump 7 and the oil output from the secondary oil
pump 8 is merged, and transmitted to the oil supply destination OB
by the main oil supply channel 9. At this time, the flow rate of
oil output from both the main and secondary oil pumps 7, 8 is
small, but the two flows are combined and transmitted to the oil
supply destination OB, so overall a sufficient supply flow rate of
lubricating oil can be ensured.
[0032] Next, when the engine rotation speed increases, the flow
rate of oil output from both the main and secondary oil pumps 7, 8
also increases, so the pressure within the oil supply channels 9,
10 also increases. As a result the spool 20 moves further to the
left. Then when the pressure within the oil supply channels 9, 10
reaches the no-load operation start pressure, and as shown in FIG.
5 when the right end of the spool land 26a becomes positioned
within the flow channel 10a, the flow channel 10a and the hydraulic
oil channel 16 are linked, so a part of the oil output from the
secondary oil pump 8 is returned from the flow channel 10a to the
oil pan T via the hydraulic oil channel 16 and the drain channel
17. In other words, the spool 20 moves to the left resisted by the
force of the spring 30, and by connecting the secondary oil supply
channel 10 to the drain channel 17, the pressurized oil within the
secondary oil supply channel 10a is drained.
[0033] Hence, the pressure within the secondary oil supply channel
10a and the internal flow channel 21 of the spool 20 drops. As a
result, a pressure difference between the pressure within the main
oil supply channel 9 and the secondary oil supply channel 10a is
generated, so the poppet 40 moves to the left and is pressed
against the valve seat 24 of the spool 20. In this way the link
between the main oil supply channel 9 and the secondary oil supply
channel 10a is blocked by the poppet 40, moreover the poppet 40 is
pushed by the pressure within the main oil supply channel 9 and
forces the spool 20 to the left, so the spool 20 moves further to
the left, so the flow rate of pressurized oil returned from the
flow channel 10a to the oil pan T via the hydraulic oil channel 16
and the drain channel 17 increases, and all the oil output from the
secondary oil pump 8 is returned to the oil pan T.
[0034] In this way, the secondary oil pump 8 enters the no-load
operation state, and the power from the drive source (the engine)
to drive the tandem pump 3 is reduced. At this time, only the oil
output from the main oil pump 7 is transmitted to the oil supply
destination OB through the main oil supply channel 9, but the flow
rate of the oil output from the main oil pump 7 has already reached
a sufficient magnitude, so it is possible to ensure the necessary
supply flow rate of lubricating oil to the oil supply destination
OB.
[0035] Thereafter if the rotation speed of the engine further
increases the output pressure within the main oil supply channel 9
corresponding to the increase in the flow rate of the oil output
from the main oil pump 7 also increases, and this output pressure
acts on the poppet 40. Therefore, the pressure within the main oil
supply channel 9 (and the flow channel 10c) acts on the poppet 40
which moves while pushing the spool 20 to the left. Then when the
output pressure from the main oil pump 7 reaches the relief setting
pressure, the drain apertures 29 provided on the right spool land
26b of the spool 20 open into the drain channel 17, and a part of
the pressurized oil within the main oil supply channel 9 flows into
the drain multi-use flow channel 43 of the poppet 40 from the flow
channel 10c and into the drain flow channel 17 through the drain
apertures 29 provided on the spool 20, and is returned to the oil
pan T (see FIG. 6). In other words, if the pressure within the main
oil supply channel 9 is equal to or greater than the relief setting
pressure, the drain multi-use flow channel 43 is connected to the
drain flow channel 17 via the drain apertures 29, and the
pressurized oil within the main oil supply channel 9 is
drained.
[0036] This type of drain operation (relief operation) of the
pressurized oil within the main oil supply channel 9 by the spool
20 and the poppet 40 is an operation as a relief valve (pressure
regulator valve), and the pressure within the main oil supply
channel 9 is prevented from exceeding a predetermined maximum
pressure (relief setting pressure) by this type of relief
operation, so safety of the circuit is ensured.
[0037] When the rotation speed of the engine is reduced from the
state in which the pressurized oil within the main oil supply
channel 9 is relieved as described above, the force with which the
poppet 40 pushes the spool 20 to the left weakens, and the spool 20
moves to the right due to the force of the spring 30. Then, when
the drain apertures 29 formed in the spool 20 are closed by the
seat bore 13c of the valve bore 13, the flow of pressurized oil
from the main oil supply channel 9 to the drain flow channel 17 is
stopped, and the above relief operation is terminated (see FIG. 5).
Also, when the rotation speed of the engine further reduces, the
spool 20 is moved further to the right by the force of the spring
30. Also, when the spool land 26a of the spool 20 comes into
opposition with the seat bore 13b of the pump body 1, the flow of
pressurized oil from the within the secondary oil supply channel 10
(within the flow channel 10a) to the drain flow channel 17 stops,
and the no-load operation state of the secondary oil pump 8
terminates (see FIG. 4).
[0038] The "no-load operation start pressure" at which the no-load
operation of the secondary oil pump 8 starts and the "relief
setting pressure" at which pressurized oil within the main oil
supply channel 9 is relieved as described above can be arbitrarily
set by the spring characteristics of the spring 30 and the initial
displacement (the displacement of the spring 30 when the spool 20
is in the initial position). Therefore, to change the no-load
operation start pressure or the relief setting pressure the spring
30 may be changed for a spring with different spring
characteristics, or the force adjustment fitting 52 may be changed
for a fitting with a different thickness.
[0039] In the tandem pump no-load operation device disclosed in the
present embodiment, when the pressure in the secondary oil supply
channel 10 reaches the no-load operation start pressure, the
secondary oil pump 8 enters the no-load operation state and the
drive power from the drive source is reduces, furthermore, when the
pressure in the main oil supply channel 9 reaches the relief
setting pressure, the pressurized oil within the main oil supply
channel 9 is relieved, so the same function as the conventional art
is maintained, and the necessary components which are the spool 20,
the spring 30, and the poppet 40 are provided within a single valve
bore 13, so the degree of freedom of layout during circuit design
is high, and it is possible to make the overall device more
compact.
[0040] In the above embodiment, the drain multi-use flow channel 43
that is open to both the main oil supply channel 9 and the outer
peripheral surface of the poppet 40 is provided within the poppet
40, and the drain apertures 29 are provided in the valve spool 20,
and when the pressure within the main oil supply channel 9 reaches
the relief setting pressure, the drain multi-use flow channel 43 is
connected to the drain apertures 29, and the pressurized oil within
the main oil supply channel 9 is drained, and the spool 20, the
poppet 40, and the spring 30 have been configured to function as a
relief valve, but the drain multi-use flow channel 43 and the drain
apertures 29 may be omitted, and a separate relief valve provided
in the main oil supply channel 9. In this configuration, although a
separate relief valve is required, the components that perform the
function of the check valve and the unload valve in the
conventional configuration, namely the spool, the poppet, and the
spring, are housed within a single valve bore, so the effect that
the configuration can be simplified compared with conventional art
can be sufficiently obtained.
[0041] So far the preferred embodiments of the present invention
have been explained, but the scope of the present invention is not
limited to the embodiments described above. For example, in the
embodiments described above, an example in which the present
invention is provided in an automobile engine to transmit oil under
pressure to an oil supply destination OB such as an oil gallery or
the like to lubricate and cool each part of the engine was
disclosed, but this is an example, and there is no particular
limitation on the oil supply destination. Therefore, the oil supply
destination of the present invention may be a fluid actuator, and
the device may be used to control the operation speed of the
actuator in accordance with the load. Also, in the embodiments
described above, the fluid output from and supplied by the tandem
pump was oil, but the fluid is not limited to oil, and water or air
may be used. Also, the two fluid pumps comprising the tandem pump
were gear pumps, but provided two fluid pumps are driven
simultaneously by a single drive source, other forms of pump may be
used (for example, vane pumps, piston pumps, and so on).
* * * * *