U.S. patent application number 12/400368 was filed with the patent office on 2009-09-10 for tandem pump.
This patent application is currently assigned to HITACHI, LTD.. Invention is credited to Keigo Kajiyama, Toshihiro Koizumi, Norihiro Saita.
Application Number | 20090226298 12/400368 |
Document ID | / |
Family ID | 41053777 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090226298 |
Kind Code |
A1 |
Kajiyama; Keigo ; et
al. |
September 10, 2009 |
TANDEM PUMP
Abstract
An apparatus comprising a tandem pump which includes first and
second pump sections driven by a rotation shaft, and a housing
defining a pump receiving portion including a first pump chamber
receiving the first pump section and a second pump chamber
receiving the second pump section. The first and second pump
chambers are separated by a partition. The partition is positioned
by the housing at least in the axial direction of the rotation
shaft.
Inventors: |
Kajiyama; Keigo; (Tokyo,
JP) ; Koizumi; Toshihiro; (Atsugi-shi, JP) ;
Saita; Norihiro; (Atsugi-shi, JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
HITACHI, LTD.
|
Family ID: |
41053777 |
Appl. No.: |
12/400368 |
Filed: |
March 9, 2009 |
Current U.S.
Class: |
415/65 |
Current CPC
Class: |
F04C 2/18 20130101; B60T
8/4031 20130101; F04C 14/02 20130101; F04C 11/001 20130101; B60T
8/4872 20130101 |
Class at
Publication: |
415/65 |
International
Class: |
F01D 1/24 20060101
F01D001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2008 |
JP |
2008058970 |
Claims
1. An apparatus comprising a tandem pump which comprises: a
rotation shaft extending in an axial direction; first and second
pump sections driven by the rotation shaft; a housing defining a
pump receiving portion including a first pump chamber receiving the
first pump section and a second pump chamber receiving the second
pump section; and a partition separating the first and second pump
chambers from each other, the partition being positioned in the
axial direction by the housing.
2. The apparatus as claimed in claim 1, wherein the housing is
arranged to regulate rotation of the partition.
3. The apparatus as claimed in claim 2, wherein the housing
includes a main housing member including the pump receiving portion
and a cover member closing the pump receiving portion.
4. The apparatus as claimed in claim 3, wherein the partition
includes a plate member which is separate from the housing and
which includes an outer circumferential portion clamped between the
housing main member and the cover member so that the position of
the partition is fixed by being clamped.
5. The apparatus as claimed in claim 4, wherein the main housing
member includes a surrounding wall surrounding the pump receiving
portion including a first portion having a smaller sectional size,
a second portion having a larger sectional size greater than the
smaller sectional size, and a step which is formed between the
first and second portions of the pump receiving portion and which
is arranged to abut against the plate member of the partition so
that the plate member is clamped between the step and the cover
member.
6. The apparatus as claimed in claim 3, wherein the housing
includes an internally threaded portion formed inside the pump
receiving portion, and the partition is a plate member which is
separate from the housing, the plate member including an externally
threaded portion which is formed on an outer circumference of the
plate member and which is screwed in the internally threaded
portion of the housing so that the position of the plate member is
fixed.
7. The apparatus as claimed in claim 6, wherein the main housing
member includes a surrounding wall which surrounds the pump
receiving portion including a first portion having a smaller
sectional size, a second portion which has a larger sectional size
greater than the smaller sectional size, and which includes the
internally threaded portion formed in the second portion.
8. The apparatus as claimed in claim 5, wherein the plate member of
the partition includes a first plate member, a second plate member,
and a seal groove which is formed between the first and second
plate member and which receives a seal member surrounding the
rotation shaft.
9. The apparatus as claimed in claim 3, wherein the partition is
formed as an integral part of the housing.
10. The apparatus as claimed in claim 9, wherein the housing is
made of an aluminum alloy, the first and second pump sections are
made of a ferrous material, and a slide member is provided between
the partition and each of the first and second pump sections.
11. The apparatus as claimed in claim 5, wherein each of the first
and second pump sections includes a driving gear drivingly
connected with the rotation shaft and a driven gear engaged with
the driving gear, the first pump section is interposed between a
first side plate and a first side portion of the partition, the
second pump section is interposed between a second side plate and a
second side portion of the partition, and the first and second side
portions are integral parts of the partition.
12. The apparatus as claimed in claim 3, wherein the apparatus is
further comprises: a wheel cylinder set including a first subset
including a first wheel cylinder provided for braking a first wheel
of a vehicle and a second subset including a second wheel cylinder
provided for braking a second wheel of the vehicle; and a hydraulic
system including a first subsystem including a first control valve
and connecting the first pump section with the first wheel cylinder
to increase a fluid pressure of the first wheel cylinder, and a
second subsystem including a second control valve and connecting
the second pump section with the second wheel cylinder to increase
a fluid pressure of the second wheel cylinder.
13. The apparatus as claimed in claim 1, wherein the partition is
arranged to separate the first and second pump chambers from each
other in a liquid-tight manner to enable control of fluid pressures
in the first and second pump chambers at different pressure levels,
and the housing is arranged to fix the position of the partition in
the axial direction and in a radial direction of the rotation
axis.
14. An apparatus comprising a tandem pump which comprises: a
rotation shaft extending in an axial direction; first and second
pump sections driven by the rotation shaft; a housing defining a
pump receiving portion including a first pump chamber receiving the
first pump section and a second pump chamber receiving the second
pump section; a partition located axially between the first and
second pump chambers, and volume change preventing means for
preventing volume change of the first and second pump chambers by
preventing the partition from being moved in the axial direction
relative to the housing.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a tandem pump capable of
increasing a first fluid pressure in a first hydraulic circuit and
a second fluid pressure in a second hydraulic circuit by using one
driving source (such as a motor).
[0002] A published Japanese patent Application Publication No.
2007-177687 shows a tandem pump including first and second driving
gears of first and second pumps, a drive gear driving the driving
gears and a center plate separating the first and second driving
gears axially.
SUMMARY OF THE INVENTION
[0003] In the tandem pump of the above-mentioned patent document,
the center plate is not positioned in the axial direction.
Accordingly, a pressure difference, if produced between the first
and second pumps, tends to shift the center plate from the higher
pressure side toward the lower pressure side. This shift of the
center plate causes interference between the center plate and the
driving gear on the lower pressure side and thereby increases the
friction therebetween. On the higher pressure side, the center
plate moves away from the driving gear, and increases the
leakage.
[0004] Therefore, it is an object of the present invention to
provide a tandem pump adapted to restrain the friction and the
leak.
[0005] According to one aspect of the invention, an apparatus
includes at least a tandem pump. The tandem pump comprises: a
rotation shaft extending in an axial direction; first and second
pump sections (or gear sections) driven by the rotation shaft; a
housing defining a pump receiving portion including a first pump
chamber receiving the first pump section and a second pump chamber
receiving the second pump section; and a partition separating the
first and second pump chambers from each other. The partition is so
arranged that the position of the partition is determined, at least
in the axial direction, by the housing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a hydraulic circuit diagram showing a hydraulic
system including a tandem pump P according to a first embodiment of
the present invention.
[0007] FIG. 2 is a front view showing a z positive side of the
tandem pump P.
[0008] FIG. 3 is a sectional view taken across a line I-I shown in
FIG. 4.
[0009] FIG. 4 is a z axis direction sectional view of FIG. 2
showing a longitudinal or axial section of the tandem pump P.
[0010] FIG. 5 is a perspective view of a center plate (400) shown
in FIG. 4.
[0011] FIG. 6 is a perspective view of a (first) side plate (150)
shown in FIG. 4.
[0012] FIG. 7 is a perspective view of a leaf spring (300) shown in
FIG. 2.
[0013] FIG. 8 is a z axis direction sectional view of a tandem pump
P according to a second embodiment of the present invention.
[0014] FIG. 9 is a z axis direction sectional view of a tandem pump
P according to a third embodiment.
[0015] FIG. 10 is a perspective view showing a first center plate
(400P) shown in FIG. 9.
[0016] FIG. 11 is a perspective view showing a second center plate
(400S) shown in FIG. 9.
[0017] FIG. 12 is a z axis direction sectional view of a tandem
pump P according to a fourth embodiment.
[0018] FIG. 13 is a z axis direction sectional view of a tandem
pump P according to a fifth embodiment.
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
[Hydraulic Circuit]
[0019] A tandem pump P is applied to a hydraulic unit H/U as shown
in a circuit diagram of FIG. 1, according to a first embodiment of
the present invention (and subsequent embodiments). Hydraulic unit
H/U is connected between a master cylinder M/C and wheel cylinders
W/C. Tandem pump P is a combination of a first pump P1 and a second
pump P2, which are driven by a single common drive shaft (110), and
so arranged that first and second pumps P1 and P2 are equal in the
discharge quantity per unit time and the discharge pressure.
[0020] First pump P1 is connected with a P subsystem, and second
pump P2 is connected with an S subsystem. First and second pumps P1
and P2 are arranged to supply the respective discharge pressures to
the P and S subsystems independently. Tandem pump P and other
components (such as valves GV-IN, GV-OUT, IN-V, and OUT-V) in the
hydraulic circuit are controlled by a control unit CU.
[0021] This hydraulic brake system includes two independent brake
subsystems, the P subsystem including a P route hydraulic circuit
10P and the S subsystem including an S route hydraulic circuit 20S.
In this example, these two circuits 10P and 20S are arranged in a
so-called X piping arrangement. The P route circuit 10P is
connected to wheel cylinder W/C(FL) for a front left wheel of the
vehicle, and wheel cylinder W/C(RR) for a rear right wheel. The S
route circuit 20S is connected to wheel cylinder W/C(FR) for a
front right wheel, and wheel cylinder W/C(RL) for a rear left
wheel. It is optional to employ, for the brake circuit,
arrangements other than the X piping arrangement. In this example,
a wheel cylinder set including the four wheel cylinders is divided
into a first subset including two of the fourth wheel cylinders and
a second subset including the other two of the fourth wheel
cylinders.
[0022] A brake pedal BP is arranged to transmit a driver's brake
pedal operation through a brake booster BS and an input rod IR, to
a master cylinder M/C. This master cylinder M/C is a tandem master
cylinder including two pistons arranged in tandem to define two
fluid pressure chambers in the cylinder. These two pressure
chambers are arranged to receive the supply of a brake fluid from a
reservoir tank RES. The first pressure chamber is connected with
the first brake circuit 10P, and the second pressure chamber is
connected with the second brake circuit 20S.
[0023] When brake pedal BP is depressed, the master cylinder M/C
produces fluid pressures (master cylinder pressures Pmc) in the two
pressure chambers in accordance with the brake pedal depression
quantity, and supplies the produced master cylinder pressures Pmc,
respectively, to first and second brake circuits 10P and 20S. A
cup-shaped seal member (of known type) is provided on the outer
circumference of each master cylinder piston, and arranged to shut
off the connection between reservoir tank RES and the corresponding
pressure chamber to enable a pressure increase in the corresponding
pressure chamber at the time of piston stroke. In this case, the
brake fluid is not supplied from reservoir tank RES to brake
circuits 10P and 20S. The brake fluid is supplied only from the
pressure chambers of master cylinder M/C to brake circuits 10P and
20S.
[0024] When brake pedal BP is returned, the master cylinder pistons
are returned by respective return springs (provided in the pressure
chambers). In this case, the cup-shaped seal members make the fluid
connection between reservoir tank RES with the pressure chambers
again, and thereby enable the supply of the brake fluid from
reservoir tank RES to the pressure chambers, again. The following
explanation is directed mainly to first brake circuit 10P.
[0025] Brake circuit 10P includes a gate-out valve GV-OUT(P)
connected between an upstream second passage 10n leading to master
cylinder M/C, and a downstream second passage 10k extending toward
wheel cylinders W/C. Gate-out valve GV-OUT(P) is a normally-open
proportional solenoid valve. A check valve 10p is disposed in a
passage 10j connected in parallel to gate-out valve GV-OUT(P), and
arranged to prevent the fluid flow in the direction from the
downstream side (near the wheel cylinders W/C) to the upstream side
(toward master cylinder M/C).
[0026] Downstream passage 10k bifurcates into a first branch
circuit 10a extending to a first outlet point connected with one of
the wheel cylinders W/C(FL, RR) and a second branch circuit 10b
extending to a second outlet point connected to the other of the
wheel cylinders W/C(FL, RR) of the P subsystem. First and second
flow-in valves IN/V(FL, RR) are provided, respectively, in the
first and second branch circuits 10a and 10b. The flow-in valves
IN/V are normally-open proportional solenoid valves.
[0027] A check valve 10q is disposed in a passage 10l connected in
parallel to the first flow-in valve IN/V(FL), and arranged to
prevent the fluid flow from the upstream side to the downstream
side. Similarly, a check valve 10r is disposed in a passage 10m
connected in parallel to the in the second flow-in valve IN/V(RR),
and arranged to prevent the fluid flow from the upstream side to
the downstream side.
[0028] A first flow-out valve OUT/V(FL) is disposed in a first
return passage 10c extending from the first outlet point (connected
with wheel cylinder W/C(FL)) to a confluent return passage 10e. A
second flow-out valve OUT/V(RR) is disposed in a second return
passage 10d extending from the second outlet point (connected with
wheel cylinder W/C(RR)) to the confluent return passage 10e. First
and second flow-out valves OUT/V are normally-closed on-off
solenoid valves. The confluent return passage 10e extends to a
reservoir 16 provided in hydraulic unit H/U.
[0029] A gate-in valve GV-IN(P) is provided in a first passage log
which is connected with the upstream second passage 10n on the
upstream side of gate-out valve GV-OUT(P). Gate-in valve GV-IN(P)
is a normally-closed on-off solenoid valve arranged to open or
close the first passage 10g. First passage 10g joins with a return
passage 10f extending from reservoir 16, and forms a suction (or
inlet) passage 10h.
[0030] The pump P is provided as a secondary pressure source in
addition to master cylinder M/C. Pump P of this example is a tandem
type gear pump including the first pump P1 (for the P side) and
second pump P2 (for the S side) both driven by an electric motor M.
The suction (inlet) side of first pump P1 is connected with the
suction circuit 10h. The discharge (outlet) side of first pump P1
is connected with a discharge (outlet) circuit 10i, and further
connected, through the discharge circuit 10i, with the downstream
side second circuit 10k.
[0031] A check valve 10s is provided in return circuit 10f, and
arranged to prevent the fluid flow from first circuit 10g (gate-in
valve GV-IN(P)) to reservoir 16. A check valve 10u is provided in
discharge circuit 10i and arranged to prevent the fluid flow from
downstream second passage 10k (gate-out valve GV-OUT(P)) or from
branch circuits 10a and 10b (wheel cylinders W/C), to first pump P1
(discharge side). The brake circuit 20S is constructed in the same
manner as the brake circuit 10P, as shown in FIG. 1 (in which the
brake circuits 10P and 20S are arranged in a manner of bilateral
symmetry).
[Brake Control]
[0032] In a normal brake operation, hydraulic unit H/U enables a
boosting control (or pressure increasing control)(as mentioned
below), an automatic brake control such as ACC (adaptive cruise
control: control for controlling a distance between vehicles) and
VDC (vehicle dynamics control or vehicle behavior control), and
anti-skid brake control. In the automatic brake control such as the
vehicle behavior control, the control unit CU closes the gate-out
valve GV-OUT(P), and opens the gate-in valve GV-IN(P)(in the case
of the brake circuit 10P, as an example). At the same time, by
driving the pump P, the hydraulic unit HU supplies the brake fluid
from master cylinder M/C, through passages 10g and 10h and
discharge circuit 10i, toward the branch circuits 10a and 10b.
[0033] Furthermore, the control unit CU controls the gate-out valve
GV-OUT(P) or the flow-in valves IN/V(FL, RR) to produce a desired
wheel cylinder fluid pressure Pwc* corresponding to a braking force
required for stabilizing the vehicle behavior. The brake circuit
20S is controlled in the same manner.
[0034] At the time of anti-skid brake control, the control unit CU
opens the flow-out valve OUT/V(FL), and closes the flow-in valve
IN/V(FL) in the case of wheel FL, as an example. By so doing, the
control unit CU decreases the wheel cylinder pressure by
discharging the brake fluid from wheel cylinder W/C(FL) to
reservoir 16. When wheel FL recovers from a locking tendency, the
control unit CU holds the wheel cylinder pressure by closing the
flow-out valve OUT/V(FL). Moreover, control unit CU increases the
wheel cylinder pressure appropriately by driving the pump P and
opening the flow-in valve IN/V(FL). Pump P functions to return the
brake fluid drained to reservoir 16 at the time of pressure
decreasing operation, to the second passage 10k.
[0035] Thus, as shown in FIG. 1, the hydraulic brake system
includes at least: a wheel cylinder set including a first subset
including at least a first wheel cylinder (W/C) provided for
braking a first wheel of a vehicle and a second subset including at
least a second wheel cylinder (W/C) provided for braking a second
wheel of the vehicle; and a hydraulic (valve) system including a
first subsystem including at least a first control valve (IN-V,
OUT-V) and connecting the first pump section with the first wheel
cylinder to increase the fluid pressure of the first wheel
cylinder, and a second subsystem including at least a second
control valve (IN-V, OUT-V) and connecting the second pump section
with the second wheel cylinder (W/C) to increase the fluid pressure
of the second wheel cylinder.
[Tandem Pump]
[0036] FIG. 2 shows a z positive side of the tandem pump P. FIG. 3
shows tandem pump P in a section taken across a line I-I shown in
FIG. 4. FIG. 4 is a z axis (axial) sectional view of tandem pump P.
In FIG. 3, a leaf spring 300 is omitted. FIG. 5 shows a center
plate (partition) 400 in perspective. FIG. 6 shows a first side
plate 150 in perspective. FIG. 7 shows the leaf spring 300 in
perspective. First and second side plates 150 and 160 are
substantially identical in shape, so that only the first side plate
150 is shown in FIG. 6.
[0037] In the following explanation, an x positive direction in
which an x axis extends is a direction from a driven shaft 120 to a
driving shaft 110 in a pump assembly 100, a y positive direction in
which a y axis extends is a direction which is perpendicular to the
x positive direction and which extends toward the position of seal
blocks 200, and a z positive direction of a z axis is an axial
direction which is parallel to the axis (Op) of driving shaft 110,
and which extends toward a first end of driving shaft 110 adapted
to be connected with motor M.
[0038] Tandem pump P is a pump of a type driving first and second
pumps P1 and P2 simultaneously with the single common driving shaft
110. First and second pumps P1 and P2 are substantially identical
in construction. First and second pumps P1 and P2 produce discharge
pressures for the P and S circuits, respectively or independently.
Center plate 400 (serving as a partition) is interposed (axially)
between first and second pumps P1 and P2, and arranged to seal
first and second pumps P1 and P2 from each other.
[Housing]
[0039] Housing 1 of tandem pump P is composed of a main housing
member 10 (first housing member) and a cover member 20 (second
housing member), which are made of metallic material which is
aluminum alloy in this example. Main housing member 10 includes an
end wall (first end wall) formed with a driving shaft support hole
11 and a surrounding (or circumferential) wall defining a pump
receiving portion 12 which, in this example is an inside cavity in
the form of a stepped cylinder. Pump assembly 100 is inserted into
pump receiving portion 12 from a z negative side (from the left
side as viewed in FIG. 4). Driving shaft 110 is supported rotatably
through bushing by the drive shaft support hole 11.
[0040] The surrounding wall of main housing member 10 includes a
step 13 formed in pump receiving portion 12. Pump receiving portion
12 is composed of a first (smaller cylindrical) portion 14 (serving
as a first side receiving portion) and a second (larger
cylindrical) portion 15 which is greater in cross sectional size or
in diameter than first portion 14 (and which can serve as a middle
receiving portion located axially between the first side receiving
portion 14 and a second side receiving portion on the z negative
side). Step 13 is formed between first and second portions 14 and
15. Step 13 includes an annular shoulder surface facing in the z
negative direction (second axial direction) to abut against the
center plate 400 of pump assembly 100 and thereby to limit the
movement of pump assembly 100 in the z positive direction (first
axial direction). The surrounding wall of main housing member 10
includes a first wall portion surrounding and defining the first
(smaller) portion 14, and a second wall portion surrounding and
defining the second (larger) portion 15 located on the z negative
side of the first (smaller) portion 14.
[0041] As shown in FIGS. 2 and 3, the cylindrical pump receiving
portion 12 is defined by an inside circumferential (or cylindrical)
surface including a first region 12a used as a positioning abutment
surface and a second region 12b. The first region 12a is adapted to
abut on the seal block 200 shown in FIGS. 2 and 3, and thereby to
position the pump assembly 100. Therefore, first region 12a is
formed more accurately than the second region 12b. Main housing
member 10 is formed with discharge circuits 10h and 20h connecting
the pump receiving portion 12 fluidly with the outside. Discharge
circuits 10i and 20i are located on the x positive side.
[0042] Cover member 20 is fixed to main housing member 10 by bolts
B. Cover member 20 is located on the z negative side of main
housing member 10. Pump assembly 100 is enclosed liquid-tightly in
the pump receiving portion 12 by cover member 20 and main housing
member 10. Cover member 20 is a cup-shaped member having a bottom.
Cover member 20 includes a base portion (forming a second end wall
axially confronting the first end wall formed with the drive shaft
support hole 11) and a (cylindrical) projecting portion 21
projecting in the z positive direction from the base portion and
receiving second pump P2. The (cylindrical) projecting portion 21
is provided with a seal ring 33 fit in an annular groove formed in
the outside circumferential surface of projecting portion 21, and
inserted liquid-tightly in the pump receiving portion 12 of main
housing member 10. The projecting portion 21 of cover member 20
includes a surrounding wall defining a second side receiving
portion which is similar to the first portion 14 (defining the
first side receiving portion) and which receives the second pump P2
and second side plate 160 like the first portion 14 of pump
receiving portion 12.
[Details of Pump Assembly]
[0043] Pump assembly 100 includes first and second seal blocks 200,
drive shaft 110, driven shaft 120, first and second driving gears
130 and first and second driven gears 140, first and second side
plates 150 and 160 (a pair of side plates) and center plate
400.
[0044] Pump assembly 100 is temporarily united by C-shaped leaf
springs 300. Seal blocks 400 are shorter in the width in the x
direction than the first and second side plates 150 and 160. Center
plate 400 liquid-tightly defines first and second discharge regions
(pump chambers) Dout1 and Dout2 formed, respectively, on the radial
outer side of first and second side plates 150 and 160.
[0045] First driving gear 130P and first driven gear 140P for the P
route circuit are provided on the z positive side of center plate
400. Second driving gear 130S and second driven gear 140S for the S
route circuit are provided on the z negative side of center plate
400. As shown in FIG. 4, the first driving and driven gears 130P
and 140P are located axially (along the z axis) between the center
plate 400 on the z negative side and the first side plate 150 on
the z positive side. The second driving and driven gears 130S and
140S are located axially between the center plate 400 on the z
positive side and the second side plate 160 on the z negative side.
Center plate 400 is located axially between the first driving and
driven gears 130P and 140P on the z positive side, and the second
driving and driven gears 130S and 140S on the z negative side.
[0046] A P route discharge circuit 10i is formed in the region
which is located on the z positive side of center plate 400 and on
the x positive side of first side plate 150. An S route discharge
circuit 20h is formed in the region which is located on the z
negative side of center plate 400 and on the x positive side of
second side plate 160. S route discharge circuit 20i is formed by
drilling center plate 400.
[0047] Two of the seal blocks 200 are disposed, respectively, on
the y positive side of first and second side plates 150 and 160. As
shown in FIG. 4, along the z axis, the center plate 400 is located
between the first pump P1 for the P route on the z positive side
(the right side as viewed in FIG. 4) and the second pump P2 for the
S route on the z negative side (the left side in FIG. 4). However,
it is optional to reverse the positions of the first and second
pumps of the P route and S route so that first pump P1 for the P
route is located on the z negative side and second pump P2 for the
S route is located on the z positive side.
[0048] The center plate 400, first and second side plates 150 and
160 and first and second seal blocks 200 are bilaterally
symmetrical with respect to an imaginary straight line II-II
(representing an imaginary flat median plane) in a radial plane or
cross sectional plane (x-y plane) as shown in FIG. 2. This II-II
line is located at the middle between driving shaft 110 and driven
shaft 120. Moreover, the leaf spring 300 shown in FIG. 2 is
bilaterally symmetrical with respect to the II-II line, and leaf
spring 300 is arranged to produce resilient forces symmetrical with
respect to the II-II line. The II-II line extends along the y axis
between the driving and driven shafts 110 and 120 both extending
along the z axis.
[0049] In the x-y plane, as shown in FIG. 2, pump assembly 100 and
leaf spring 300 are set in point contact with each other at three
contact points A, B and C. The first contact point A is located on
the y positive side of the seal block 200 shown in FIG. 2. The
second and third contact points B and C are located at two x end
portions 152 (162 in the case of second side plate 160) in a y
negative side 151 (161) of the side plates 150 (160), respectively,
as shown in FIG. 2.
[0050] First contact point A is located on the II-II line (the
median plane) which extends through the middle point M between the
axes Op and Os of driving shaft 110 and driven shaft 120, in
parallel to the y axis. Second and third contact points B and C are
located on the y negative side of an imaginary III-III straight
line passing through the axes Op and Os (and representing an
imaginary transverse plane), one on the x positive side of the
II-II line and the other on the x negative side.
[0051] The point contact in the x-y plane means a line contact in
the x-y-z space on a straight line extending along the z axis. Leaf
spring 300 shown in FIG. 2 contacts with the seal block 200 along a
straight line passing through contact point A and extending along
the z axis, and further contacts with the (first) side plate 150
(160) along straight lines passing through contact points B and C,
respectively, and extending along the z axis.
[0052] Accordingly, pump assembly 100 is held at the first contact
point A from the y positive side, and urged toward the y positive
side at the second and third points B and C by leaf spring 300.
With this three-point support structure at the points A, B and C,
the leaf spring 300 can press the seal block 200 from the y-axis
positive side against the first side plate 150 (160), and thereby
unite or bind the pump assembly 100 provisionally. The second side
plate 160 and second seal block 200 are bound and united in the
same manner as shown in FIG. 2.
[0053] Seal blocks 200 are narrower in the width measured along the
x axis than first and second side plates 150 and 160. Therefore,
each of seal blocks 200 is urged stably toward the y negative side
with leaf spring 300 including a one-point support portion
supporting the y positive side of seal block 200 at point A, and a
two-point support portion supporting the y negative side of the
first or second side plate 150 or 160 at points B and C.
[Drive Shaft and Driven Shaft]
[0054] Drive shaft 110 is connected with first and second driving
gears 130P and 130S made of a ferrous material so that they rotates
as a unit. Driven shaft 120 is connected with first and second
driven gears 140P and 140S made of the ferrous material so that
they rotates as a unit. As shown in FIG. 4, driving shaft 110
extends, along the z axis, from a second (left) end to a first
(right) end (z positive end) which is adapted to be connected with
the motor not shown in FIG. 4. The gears 130P, 130S, 140P and 140S
are spur gears. On each of the first and second sides for the P and
S circuits, driving gear 130 (130P, 130S) and driven gear 140
(140P, 140S) are engaged with each other in the form of a spur gear
set as shown in FIG. 3, so that driven shaft 120 is driven by
driving shaft 110.
[0055] [Center Plate]
[0056] Center plate 400 is a circular disc-shaped member including
a step as best shown in FIG. 5. Center plate 400 is an integral
member formed by a forming process of uniting a plate (third side
plate) 150' (FIG. 4) adapted to be in sliding contact with driving
and driven gears 130P and 140P, and another plate 160' (FIG. 4)
adapted to be in sliding contact with driving and driven gears 130S
and 140S.
[0057] Center plate 400 includes a step 410, a smaller section 420
having a smaller diameter and lying on the z positive side of step
410, and a larger section 430 having a larger diameter larger than
the diameter of smaller section 420, and lying on the z negative
side of step 410. Center plate 400 further includes a drive shaft
hole 401 receiving drive shaft 110 rotatably, and a driven shaft
hole 402 receiving driven shaft 120 rotatably.
[0058] Seal members 34 and 35 are received, respectively, in
annular grooves 401a and 402a formed in drive shaft 110 and driven
shaft 120 (as shown in FIG. 4). Seal members 34 and 35 seal the
clearances around the drive shaft 110 and driven shaft 120,
respectively, and thereby seal off the first and second pumps P1
and P2 from each other.
[0059] The smaller section 420 of center plate 400 includes a z
positive side 421 including a sliding surface 421a adapted to be in
sliding contact with the driving and driven gears 130P and 140P (as
shown in FIG. 4 and FIG. 5), and an abutting surface 421b formed on
the y positive side of the sliding surface 421a (as shown in FIG.
5) and adapted to be abut on the first seal block 200
liquid-tightly.
[0060] Similarly, the larger section 430 of center plate 400
includes a z negative side 431 including a sliding surface 431a
adapted to be in sliding contact with the drive and driven gears
130S and 140S (as shown in FIG. 4), and an abutting surface 431b
formed on the y positive side of the sliding surface 431a and
adapted to be abut on the second seal block 200 liquid-tightly.
[0061] The sliding surfaces 421a and 431a are formed around the
drive shaft hole 401 and driven shaft hole 402 in inner regions of
z positive and negative sides 421 and 431 of center plate 400,
respectively. FIG. 5 shows only the z positive side 421 of the
smaller section 420, and explanation on the sliding surface 431a
and abutting surface 431b of the larger section 430 is omitted
since the sliding surfaces 421a and 431a, and the abutting surfaces
421b and 431b are substantially identical in shape and
position.
[0062] Sliding surface 421a is an 8-shaped region including a first
annular portion surrounding the drive shaft hole 401, and a second
annular portion surrounding the driven shaft hole 402. Gears 130P
and 140P can slide liquid-tightly on the sliding surface 421a.
Between the gear sliding surface 421a and the seal block abutting
surface 421b, there are formed sliding surfaces 158 and seal block
sliding surfaces 210 and 220, as shown in FIG. 5.
[0063] Seal block abutting surface 421b is a C-shaped region
surrounding a suction passage Din. Suction passage Din is defined
liquid-tightly by the C-shaped abutting surface 421b and an inlet
side recessed portion 421c which is formed in the 8-shaped sliding
surface 421a on the y positive side toward the abutting surface
421b, at the middle of the 8-shaped sliding surface 421a in the x
direction.
[0064] An outlet side recessed portion 421d is formed on the
opposite side (y negative side) of the sliding surface 421a. The
8-shaped sliding surface 421a includes a connecting portion which
is formed, along the x axis, between the first annular portion
surrounding the drive shaft hole 401 and the second annular portion
surrounding the driven shaft hole 402, and which is located between
the inlet side recessed portion 421c and outlet side recessed
portion 421d, along the y axis. Outlet side recessed portion 421d
is located on the outlet or discharge side of the driving and
driven gears 130P and 140P, and arranged to cause the outlet
pressure to flow smoothly to the discharge region Dout1 formed on
the outer side of the sliding surface 421a.
[0065] A (smaller) seal ring 31 is fit in an annular groove 422a
formed in the (cylindrical) circumference 422 of smaller section
420. Similarly, a (larger) seal ring 32 is fit in an annular groove
432a formed in the (cylindrical) circumference 432 of larger
section 430. There are further provided, respectively, in drive and
driven shafts 110 and 120, seal rings 34 and 35 for sealing off the
first and second pumps P1 and P2 from each other.
[0066] The circumference 432 of larger section 430 is formed with
at least one opening of inlet circuit 20h for supplying an inlet
pressure to second pump P2 for the S circuit. The supply of the
inlet pressure to first pump P1 for the P circuit is achieved by
inlet circuit 10h formed in main housing member 10 on the z
positive side of first plate 150 (as shown in FIG. 3).
[0067] The (external) annular step 410 of center plate 400 includes
an annular step surface which faces in the z positive direction
(first axial direction) and which abuts on the annular shoulder
surface of the (internal) step 13 of main housing member 10 so that
the axial movement of center plate 400 in the z positive direction
is limited by the shoulder surface of step 13. Cover member 20
includes cylindrical projecting portion 21 projecting in the z
positive direction and terminating at an annular forward end 22,
which abuts on an outer circumference portion 433 of the second
side (z negative side) 431 of the larger section 430. Therefore,
center plate 400 is clamped axially between the shoulder surface of
step 13 of main housing member 10 and the forward end 22 of cover
member 20 so that center plate 400 is unable to move in the axial
direction along the z axis.
[Side Plates]
[0068] First and second side plates 150 and 160 are members having
the same 8-shaped form as shown in FIG. 6. Each of side plates 150
and 160 is formed with a drive shaft hole 153 or 163 and a driven
shaft hole 154 or 164. FIG. 6 shows only the first side plate 150
and the following explanation is directed mainly to first side
plate 150 since first and second side plates 150 and 160 are
substantially identical and arranged substantially symmetrical with
respect to an imaginary center radial plane (x-y plane) at the
middle axially between the first and second side plates 150 and
160.
[0069] Discharge region Dout1 (or Dout2) is formed around side
plate 150 (or 160), as shown in FIG. 2 and FIG. 4. Side plate 150
(160) includes a first annular section surrounding drive shaft hole
153 (163) and a second annular section surrounding driven shaft
hole 154 (164). Side plate 150 (160) further includes a middle
recessed portion 150b (160b) recessed in the y negative direction,
from a y positive side 150a (160a), between the first annular
section on the x positive side and the second annular section on
the x negative side.
[0070] The middle recessed portion 150b (160b) of side plate 150
(160) is connected with the inlet or suction circuit 10i (20i) and
arranged to supply the operating fluid therethrough. The y positive
side 150a (160a) of side plate 150 (160) includes a driving side
sealing curved surface 158a (168a) on the x positive side of the
middle recessed portion 150b (160), and a driven side sealing
curved surface 158b (168b) on the x negative side of the middle
recessed portion 150b (160b). The sealing curved surfaces are used
for sealing with the corresponding seal block 200.
[0071] First side plate 150 includes a (8-shaped) z negative side
surface 159 adapted to be in sliding contact with the first driving
and driven gears 130P and 140P liquid-tightly. Similarly, second
side plate 160 includes a (8-shaped) z positive side surface 169
adapted to be in sliding contact with the second driving and driven
gears 130S and 140S liquid-tightly.
[0072] First side plate 150 includes a z positive side surface 155
in which a first seal ring 170 is provided , as shown in FIG. 4.
Second side plate 160 includes a z negative side surface 165 in
which a second seal ring 180 is provided. Each of first and second
seal rings 170 and 180 surrounds the drive shaft 110 and driven
shaft 120 (as shown in FIG. 2). First seal ring 170 abuts on main
housing member 10. Second seal ring 180 abuts on cover member
20.
[0073] Thus, each of the seal rings 170 and 180 surrounds the
sliding surfaces between the drive and driven shafts 110 and 120
and the first or second side plate 150 or 160, and thereby defines
the suction region Din (first fluid chamber) sealed off
liquid-tightly from the discharge region Dout (second fluid
chamber) formed on the outer side of the seal ring 170 or 180.
[0074] The side plate 150 (160) includes two grooves 156 (166)
recessed radially inwards (along the x axis toward the center M, as
shown in FIG. 2), respectively, from the x-axis positive and
negative end surfaces 157 (167), at the middle of the width in the
z-axis direction (as shown in FIG. 6) (by cutting, for
example).
[0075] Therefore, in the x-y plane, on each of the x-axis positive
side and negative side of side plate 150 (160), the bottom of the
groove 156 (166) and the x-axis end surface 157 (167) are curved,
so as to form a rounded end like a circular arc, with unequal
curvatures. The z-axis width of each of the grooves 156 (166) as
measured along the z axis, is greater than the z-axis width of each
of metal bands 301 and 302 of the leaf spring 300.
[0076] Thus, the grooves 156 and the z positive side surface 151 of
first side plate 150 are formed so as to have different curvature,
and the grooves 166 and the z negative side surface 161 of second
side plate 160 are formed so as to have different curvature.
Moreover, the grooves 156 and 166 have the z-axis width greater
than the z-axis width of the metal bands 301 and 302. Thus, the
grooves 156 (166) of side plate 150 (160) are formed so as to
prevent abutment between the leaf spring 300 and the grooves 156
(166) when leaf spring 300 is fit over pump assembly 100.
[0077] Therefore, the leaf spring 300 touches the side plates 150
(160) only at the contact points B and C with the inner sides of
both end portions 321 and 322, and thereby forms the three-point
support structure together with the contact point A of abutment
between leaf spring 300 and seal block 200. The grooves 156 (166)
prevent interference of legs 320 of leaf spring 300 with the x-axis
ends 157 (167) of side plates 150 (160), and ensure the three-point
support structure.
[Seal Blocks]
[0078] The following explanation is directed mainly to the first
seal block 200 shown in FIG. 2 and the first side plate 150. The
second seal block 200 and second side plate 160 are substantially
identical to the first seal block 200 and first side plate 160, and
arranged substantially symmetrical with respect to the imaginary
center radial plane (x-y plane) at the middle axially between the
first and second side plates 150 and 160. The seal block 200 shown
in FIG. 2 is placed between the abutting surface 12a of housing 1
on the y positive side and the side plate 150 (160) on the y
negative side, and designed to achieve sealing. Seal block 200
includes an arched y positive side surface 240 facing in the y
positive direction in the form of a convex surface curved like a
circular arc and abutting on the abutting surface 12a of housing
main member 10 for positioning, and a y negative side surface
abutting on the side plate 150 (160). The y negative side surface
of seal block 200 includes a driving side arched (concave) sealing
surface 210 (shown in FIGS. 2 and 3) and a driven side arched
(concave) sealing surface 220 (shown in FIGS. 2 and 3) which are
curved like a circular arc for abutting liquid-tightly,
respectively, on the driving side arched (convex) sealing surface
158a (shown in FIG. 6)(168a and the driven side arched (convex)
sealing surface 158b (shown in FIG. 6)(168b) of the 8-shaped side
plate 150 (160). The mating (concave and convex) arched surfaces of
the seal block 200 and the side plate 150 (160) are cylindrical
surfaces having the same curvature.
[0079] In the pump driving state, the tops (131) of teeth of the
driving gear 130 rotate on the radial outer side of the
corresponding sealing surface 158a (168a) of the side plate 150
(160), and the tops (141) of teeth of the driven gear 140 rotate on
the radial outer side of the corresponding sealing surface 158b
(168b) of side plate 150 (160).
[0080] Therefore, these sealing surfaces of seal blocks 200 are
ground by the tops of the gear teeth so as to form tooth contact
surfaces (211, 221). The thus-formed structure can ensure the
sealing by reducing the clearance almost to zero while avoiding
contact between the sealing surfaces and the gear teeth.
[0081] Seal block 200 further includes a middle recessed portion
230 which extends, between the sealing surfaces 210 and 220 (as
shown in FIG. 2), over the entire axial width along the z axis, and
which is recessed in the y positive direction. Together with the
middle recessed portion 150b (160b) of the side plate 150 (160),
this middle recessed portion 230 of seal block 200 defines an inlet
region Din for introducing the operating fluid (oil) from the
suction circuit 10i (20i) to the engaging portions of the driving
and driven gears 130 and 140.
[0082] The y positive side surface 240 of seal block 200 is curved
like a circular arc, as shown in FIG. 2. Seal block 200 includes z
positive and negative sides 201 (FIG. 2) and 202 formed with (third
and fourth) step portions 251 (FIG. 2) and 252, respectively. Each
of the step portions 251 and 252 has a convex shape bulging in the
y positive direction up to a y positive side end (peak) 253 or 254
which is located on the median plane represented by the II-II
straight line, and which abuts on the leaf spring 300 and thereby
defines the first contact point A.
[0083] Seal block 200 further includes a projecting portion 250
projecting in the y positive direction between the step portions
251 and 252. The metal bands 301 and 302 of leaf spring 300 abut
against the seal block 200 at the contact point A. Thus, leaf
spring 300 is fit over the projecting portion 250 of seal block 20
and thereby positioned. Moreover, leaf spring 300 abuts against the
steps portions 251 and 252 of seal block 200, and thereby limits
the movement of seal block 200 in the y positive direction.
[0084] The distance between the z positive side surface 155 of
first side plate 150 and the z negative side surface 165 of second
side plate 160 is set equal to the distance between the seal blocks
200 along the z axis. Therefore, the seal rings 170 and 180
provided in the first and second side plates 150 and 160 abut
axially on the seal blocks 200 along the z axis, respectively.
Thus, the driving side and driven side sealing surfaces 158a (168a)
and 158b (168b) of the side plate 150 (160) and the sealing
surfaces of the seal block 200 are sealed by the seal ring 170
(180) on the z positive or negative side end surface.
[0085] [Liquid Pressure Difference]
[0086] By the operation of the driving and driven gears 130 and 140
in the pump drive state, the operating fluid is sucked from the z
negative side of the inlet passage Din, and discharged to from the
z positive side. Therefore, the pressure difference is produced in
the y negative direction by the pump operation between the higher
pressure discharge side formed on the outer side around the pump
assembly 100 and the seal block 200 (excepting the abutting
surface) and the lower pressure suction side of the abutting
surface of the seal block 200. By this pressure difference, pump
assembly 100 is urged in the y positive direction, and seal block
200 is urged in the y negative direction and pressed against pump
assembly 100. Therefore, the pressure difference acts to improve
the sealing performance in the abutting surfaces between pump
assembly 100 and seal block 200.
[Leaf Spring]
[0087] Leaf spring 300 shown in FIG. 7 is a resilient member for
provisionary uniting or binding the pump assembly 100. Leaf spring
300 is bilaterally symmetrical, in the shape and elastic force,
with respect to a median plane passing through a middle point A'
located at the middle in the dimension in the x direction. By the
use of leaf spring 300, it is possible to avoid influence of
elastic force decrease due to time degradation unlike a coil
spring.
[0088] Leaf spring 300 includes the first and second metal bands
301 and 302 extending side by side (in parallel to each other) so
as to describe the letter C from a first end 321 to a second end
322, and connecting portions 303.about.306 connecting the first and
second metal bands 301 and 302 like rungs of a ladder. Connecting
portions 305 and 306 extend in the z direction, respectively, at
the first and second ends 321 and 322 of leaf spring 300.
Connecting portions 303 and 304 extend in the z direction so that
the seal blocks 200 are placed between the connecting portions 303
and 304 in the x direction.
[0089] An engagement hole 311 is formed by connecting portions 303
and 304 on the y positive side and the first and second metal bands
301 and 302. The projecting portion 250 of seal block 200 is fit in
the engagement hole 311. Engagement hole 311 facilitates the
positioning operation at the time of assemblage.
[0090] Leaf spring 300 is curved so as to bulge in the y positive
direction like a mountain, and to have a vertex at the middle A' in
the x dimension. The vertex point (or points) A' is located on the
II-II straight line as shown in FIG. 2, and the leaf spring 300 is
designed to deform in the symmetrical manner with respect to the
median plane (II-II). A middle portion 310 of leaf spring 300
straddles the seal block 200 and abuts against the seal block 200
so that the point A' of leaf spring 300 is in point contact with
the point A of seal block 200. In the assembled state, the points A
and A' coincide with each other.
[0091] On the both sides of the middle portion 310 in the dimension
in the x direction, leg portions 320 extend in the y negative
direction, respectively, to the first and second ends 321 and 322,
and fit over the side plate 150 (160). The first and second ends
321 and 322 of leaf spring 300 abut on the side plate 150 (16) so
that contact points B' and C' on the inner sides of first and
second ends 321 and 322 are in point contact with the contact
points B and C of the (first and second) side plate 150 (160),
respectively.
[0092] The shapes of first and second side plates 150 and 160 are
not limited to the illustrated example. Side plates 150 and 160 and
leaf springs 300 may be shaped in other forms to produce the urging
forces having components in the y positive direction and to prevent
interference between the legs 320 and the end surfaces 157 and
167.
[Reduction of Friction and Leak]
[0093] Driving and driven gears 130 and 140 are identical in
construction, between first and second pump P1 and P2 for the P and
S circuits, and both pumps are driven by one and the same drive
shaft 110. Moreover, the pump chambers Dout1 and Dout2 of first and
second pumps P1 and P2 are formed by the first and second side
plates 150 and 160 having the same shape and the first and second
seal blocks 200 having the same shape. Therefore, in the normal
state, the discharge flow rates and the discharge pressures are
equal between the first and second pumps P1 and P2, so that center
plate 400 receives forces by the equal discharge pressures on both
sides along the z axis, and the forces acting on center plate 400
are balanced.
[0094] However, when either of the P and S circuits fails or when
the pressures of the P and S circuits are controlled at different
levels, the pressure on one side of center plate 400 becomes higher
than the pressure on the other side, and the balance is lost among
the force acting in the z direction on center plate 400, so that
center plate 400 is pushed in the z positive direction or the z
negative direction.
[0095] When, for example, center plate 400 is moved in z positive
direction, the center plate 400 pushes the gears 130P and 140P
axially, and increases the friction. On the other hand, the center
plate 400 increases the clearance between center plate 400 and the
gears 130S and 140S on the z negative side by being moved in the z
positive direction away from the gears 130S and 240S, and thereby
increases the leakage. When center plate 400 is moved in the z
negative direction, the same problem arises in the reverse
manner.
[0096] According to the first embodiment, an outer encasing or
housing wall structure (10, 20) encases first and second pump
sections (P1, P2) each including at least one rotating element
(130, 140), and includes a surrounding (or circumferential) wall
(formed by housing main body 10) surrounding the first and second
pump sections disposed in a central region, a first end wall
(formed by housing main member 10) and a second end wall (formed by
cover member 20). There is further provided a partition or
partition wall (formed by center plate 400) separating the first
and second pump sections liquid-tightly (together with a seal
member such as seal members 31, 32, 34 and 35). The partition
includes a first abutting surface (or step surface formed by step
410) facing in a first axial direction (z positive direction)
toward the first end wall, and a second abutting surface (end
surface 433) facing toward the second end wall (20) in a second
axial direction (z negative direction) opposite to the first axial
direction. The first abutting (step) surface (410) and the second
abutting (end) surface (433) surround a central region in which
rotating elements (130, 140) of the first and second pump sections
are disposed, and the first and second abutting surfaces (410, 433)
may be both annular. The surrounding wall (formed by housing main
member 10) includes a shoulder surface (formed by step 13) which
faces in the second axial direction (z negative direction) and
which may be annular, and the second end wall (formed by cover
member 20) includes a projecting end surface (22) which faces in
the first axial direction (z positive direction) and which may be
annular. In the assembled state, the (annular) shoulder surface
(13) of the surrounding wall (10) abuts axially on the (annular)
first abutting (step) surface (410) of the partition (400), and
thereby limits the movement of the partition (400) in the first
axial direction. On the other hand, the (annular) projecting end
surface (22) of the second end wall (20) abuts axially on the
(annular) second abutting surface (433) of the partition (400) and
thereby limits the movement of the partition (400) in the second
axial direction. This partition structure holds the position of
partition (400) fixed at the predetermined position without regard
to the pressure states of the first and second pumps (for the P and
S systems), and thereby prevent undesired increase in the friction
and leak.
[0097] The second end wall (20) is fastened to the surrounding wall
(10) by fastening devices (such as bolts B) extending axially
(along the z axis), so that the second end wall (20) pushes the
partition (400) in the first axial direction (z positive
direction). This axial pushing force is applied, through the first
abutting surface (410) of the partition (400), to the shoulder
surface (13) of the surrounding wall (10), and the partition (400)
is pushed in the first axial (z positive) direction against the
surrounding wall (10). Furthermore, this pushing force acts to
produce a friction force between the first abutting surface (410)
of the partition (400) and the shoulder surface (13) of the
surrounding wall (10), and this frictional force acts to restrain
rotational movement of the partition (400) with respect to the
surrounding wall (10).
[0098] The surrounding wall (10) receives the pushing force through
the first abutting surface (410) and the shoulder surface (13).
Therefore, this abutment structure can prevent the pushing force
from being applied from the second end wall (20), to the rotating
elements (130P, 140P, 130S and 140S) of the first and second pump
sections, and thereby eliminates the need for controlling the
tightening torque of the fastening devices (B) severely.
Effects of First Embodiment
[0099] (1) A tandem pump apparatus including at least a tandem pump
which includes a first pump section (P1) including a first rotating
element (130P, 140P) for producing a first fluid pressure, a second
pump section (P2) including a second rotating element (130S, 140S)
for producing a second fluid pressure, a rotating shaft (110)
driving the first and second rotating elements, a housing including
a housing wall structure (10, 20). The housing wall structure
includes a surrounding wall (10) surrounding and defining a pump
receiving portion or inside cavity (12) which includes a first
discharge region (Dout1) receiving the first rotating element
(130P, 140P) and a second discharge region (Dout2) receiving the
second rotating element (130S, 140S), and a partition (400)
extending in the pump receiving portion (12) and separating the
first and second discharge regions liquid-tightly from each other.
The partition (400) is engaged with the surrounding wall (10) so
that the position of the partition (400) is determined by the
surrounding wall (10) at least in an axial direction along the axis
of the rotating shaft (110). This tandem pump apparatus can fix the
axial position of the partition (400), and reduce the friction and
the leak of the operating fluid.
[0100] (2) The housing wall structure (10, 20) is arranged to
prevent rotational movement of the partition (400) about the axis
of rotating shaft 110. Therefore, the tandem pump apparatus can fix
the partition (400) securely.
[0101] (3) The housing wall structure (10, 20) includes a first
housing member (10) including the surrounding wall (and the first
end wall) and a second housing member (20) including the second end
wall. Therefore, this structure makes it easier to install a pump
assembly (100) including the first and second pump sections in the
housing wall structure.
[0102] (4) The partition of the first embodiment is in the form of
a plate member (400) which is separate from the first housing
member (10), and which is positioned by being interposed or
clamped, at the outer circumferential (or annular) portion (433),
between the first housing member (10) and the second housing member
(20). Therefore, this tandem pump apparatus can position the plate
member (400) at a position avoiding interference with the rotating
elements (130, 140) of the pump sections.
[0103] (5) The pump receiving portion (12) includes a first
(smaller) portion (14) and a second (larger) portion (15) which is
greater in the cross sectional size than the first portion, and the
surrounding wall (10) of the first housing member (10) includes a
first wall portion surrounding and defining the first (smaller)
portion (14), a second wall portion surrounding and defining the
second (larger) portion, and a step (13) which is formed between
the first and second wall portions and which includes the shoulder
surface in the pump receiving portion (12). The plate member (400)
of the partition is positioned by being clamped between the step
(13) of the first housing member (10) and the second housing member
(20). Therefore, tandem pump apparatus can determine the position
of the partition (400) relative to the surrounding wall (10)
reliably. In the illustrated example, the pump receiving portion
(12) is substantially circular in the cross section, and the plate
member (400) is clamped between the first and second housing
members (10, 20), in an outer annular zone surrounding a center
zone in which the first and second pump sections are disposed, so
that the plate member (400) is positioned securely.
[0104] (6) Each of the first and second pump sections includes a
driving gear (130) drivingly connected with the rotation shaft
(110) and a driven gear (140) engaged with the driving gear, the
first pump section (130P, 140P) is interposed (axially) between a
first side plate (150) and a first side portion (150') of the
partition (400), the second pump section (130S, 140S) is interposed
(axially) between a second side plate (160) and a second side
portion (160') of the partition (400), and the first and second
side portions (150', 160') are integral parts of the partition.
[0105] (7) The apparatus comprises the tandem pump (1); a wheel
cylinder set including a first subset including at least a first
wheel cylinder (W/C) provided for a first wheel of a vehicle and a
second subset including at least a second wheel cylinder (W/C)
provided for a second wheel of the vehicle; a hydraulic system (HU)
including a first subsystem which includes at least a first control
valve (IN-V, OUT-V)( and which connects the first pump section (P1)
with the first wheel cylinder to increase a first fluid pressure of
the first wheel cylinder, and a second subsystem which includes at
least a second control valve (IN-V, OUT-V) and which connects the
second pump section (P2) with the second wheel cylinder to increase
a second fluid pressure of the second wheel cylinder. The apparatus
may further comprises a control unit (CU) to control the first
fluid pressure to the first wheel cylinder and the second fluid
pressure to the second wheel cylinder, respectively, by controlling
the first and second pump sections and the first and second control
valves. Therefore, the hydraulic brake apparatus can fix the
position of the partition (400) reliably and prevent undesired
increase of the friction and leak even if one of the first and
second systems becomes abnormal or if the first and second systems
require different target pressure levels.
[0106] (8) A tandem pump comprises volume change preventing means,
provided in the pump receiving portion (12), for preventing volume
change of the first and second pump chambers (Dout1, Dout2), by
being positioned by the housing. This tandem pump can prevent the
volume changes in the first and second pump chambers, and thereby
reduce the friction and the leak of the operating fluid. The volume
change preventing means may include a partition (400) separating
the first and second pump chambers. Alternatively, the volume
change preventing means may include a means for preventing the
partition (400) from being moved (at least in the axial
direction)(by fluid pressures in the first and second pump
chambers).
[0107] (9) The fluid pressures of the first and second pump
chambers (Dout1, Dout2) are controlled at different pressure
levels, and the partition (400) is held immovable in the axial
direction and in the rotational direction. Therefore, this tandem
pump can prevent volume changes in the first and second pump
chambers, and thereby reduce the friction and the leak of the
operating fluid.
Embodiment 2
[0108] The second embodiment is substantially identical, in the
basic construction and arrangement in the hydraulic circuit, to the
first embodiment shown in FIGS. 1.about.7. The second embodiment is
different from the first embodiment in that, instead of the
fastening devices (bolts B) for fastening cover member 20 to main
housing member 10, the cover member 20 according to the second
embodiment is formed with a threaded portion (23) and screwed into
a mating threaded portion (16) of main housing member 10.
[0109] FIG. 8 shows a tandem pump P according to the second
embodiment in an axial section (in place of FIG. 4 of the first
embodiment). Cover member 20 of FIG. 8 includes a threaded portion
23 formed externally in the outer circumference of the cylindrical
projecting portion 21. On the other hand, main housing member 10
includes a threaded portion 16 formed internally in the inside
cylindrical surface defining the larger portion 15 of the pump
receiving portion 12. In this example, the externally threaded
portion 23 includes a male screw thread while the internally
threaded portion 16 includes a corresponding female screw
thread.
[0110] Cover member 20 is fixed to main housing member by screwing
the externally threaded portion 23 into the internally threaded
portion 16 formed in the surrounding wall formed by main housing
member 10. Cover member 20 abuts on center plate 400 axially with
the forward end 22 of cylindrical projecting portion 21, and
thereby determines the position of center plate 400 in the same
manner as in the first embodiment, so that the same effects can be
obtained.
Embodiment 3
[0111] The third embodiment is substantially identical, in the
basic construction and arrangement in the hydraulic circuit, to the
first embodiment. The third embodiment is different from the first
embodiment in that the center plate 400 is divided into two plates
(400P, 400S).
[0112] FIG. 9 is a sectional view similar to FIG. 4, but showing
the tandem pump of the third embodiment. FIGS. 10 and 11 are
perspective views showing, respectively, a first center plate 400p
on the z positive side, and a second center plate 400S located on
the z negative side of first center plate 400P.
[0113] Although seal members 34 and 35 are provided in the outer
circumferences of drive and driven shafts 110 and 120 in the first
embodiment, the seal members 34 and 35 according to the second
embodiment are fit, respectively, in (annular) seal grooves 401a
and 402a formed in the inner circumferences of drive shaft through
hole 401S and driven shaft through hole 402S of second center plate
400S.
[0114] Second center plate 400S includes a larger disc portion
having an annular z positive surface (K), and a center projecting
portion projecting in the z positive direction from a central
region of the larger disc portion, and having an z positive end
surface (K, N). First center plate 400P includes a smaller disc
portion forming the smaller section 420, an outside flange 410'
forming the step 410, and a center recess which is recessed from
the z negative side of first center plate 400P in the z positive
direction and which is adapted to receive the center projecting
portion of second center plate 400S fittingly. Therefore, the
center plate 400 is divided into first and second center plates
400P and 400S in a parting plane K (shown by a solid line in FIG.
9) composed of an outer annular flat region in which a flat annular
z negative surface of the flange 410' of first center plate 400P
abuts on a flat annular z positive surface of the larger disc
portion of second center plate 400S, and a central flat region
which extends in an imaginary flat plane N parallel to the x-y
plane whereas the outer annular flat region of the parting plane K
is located on the z negative side of the flat plane N. In the
center flat region of the parting plane K, the flat z positive side
surface of the center projecting portion of second center plate
400S abuts on or confronts the (flat) bottom of the center recess
of first center plate 400P. The center flat region of parting plane
K extends around the drive shaft 110 and driven shaft 120. Thus,
parting plane K includes a step K1 between the outer annular region
and the center region. The first and second grooves 401a and 402a
are opened in the center region of parting plane K at 401b and
402b, respective, to the z positive side. The imaginary plane N is
located on the z positive side of the step 13 of main housing
member 10, and the center projecting portion of second center plate
400S extends beyond the axial position of step 31, to the z
positive side. The outer annular flat region of parting plane K is
located on the z negative side of the axial position of step 13
whereas the central flat region of parting plane K is located on
the z positive side of the axial position of step 13 of main
housing member 10.
[0115] The z positive side surface of flange 410' of first center
plate 400P abuts on the step 13 of main housing member 10, and
thereby positions first center plate 400P securely. Therefore, even
if first center plate 400P is pushed in the z positive direction
because of leak from the S route discharge circuit 20h located on
the z negative side of step 410 (410'), the first center plate 400P
is held immovable at the correct position without increasing the
friction with the first driving and driven gears 130P and 140P.
[0116] The parting plane K includes regions forming z positive side
401a of 402b of seal grooves 401a and 402a. Thus, the seal grooves
401a and 402a are open in the parting plane K, toward the z
positive side, and the seal members 34 and 35 are bared in the z
positive side surface of second center plate 400S. Therefore, seal
members 34 and 35 can be fit readily in the respective grooves at
the time of the assembly.
[0117] The (annular) forward end 22 of cover member 20 abuts on the
outer annular region 433 of the larger disc portion of second
center plate 400S as in the first embodiment. The flange 410' of
first center plate 400P and the larger disc portion of second
center plate 400S form the larger section of the center plate
clamped between the step 13 of main housing member 10 and the
cylindrical projecting portion 21 of cover member 20, as in the
first embodiment. Thus, first and second center plates 400P and
400S are positioned and fixed immovable as a single unit in the z
direction.
[0118] In the tandem pump according to the first embodiment, the S
route discharge circuit 20h is formed by drilling in center plate
400. In the illustrated example of the third embodiment, the S
route discharge circuit 20h is formed partly by one or more cutout
portion 411 formed in the flange 410' of first center plate
400P.
[0119] The cutout portion 411 is connected with an oil passage
(424) of second center plate 400S. This oil passage (424) is opened
by drilling like oil passage 20h of the first embodiment, and
connected with the suction region Din2 of second pump P2. Thus,
this oil passage (424) and cutout portion 411 form the S route
discharge circuit 20h.
[0120] It is possible to form one or more cutout portion 411 in
first center plate 400P readily (without the need for adding a
special manufacturing step) by forming the shape of the cutout
portion in a mold for forming first center plate 400P at the time
of forming the mold (by sintering, for example).
[0121] In the example of FIGS. 9-11, the step 410 and smaller
section 420 are formed in first center plate 400P, and the larger
section 430 is formed in second center plate 400S. Like center
plate 400 of the first embodiment, the smaller section 420 of first
center plate 400P includes the z positive side which includes the
sliding surface 421a and the seal block abutting surface 421b. The
larger section 430 of second center plate 400S includes the z
negative side 431 including the sliding surface 431a and the seal
block abutting surface 431b.
[0122] In the example of FIGS. 9.about.11 according to the third
embodiment, the plate member (400) of the partition includes a
first plate member (400P) formed with a through hole (401P) for
receiving the rotation shaft (110), a second plate member (400S)
formed with a through hole (401S) for receiving the rotation shaft,
and a seal groove (401a) which is formed (axially) between the
first and second plate members and which receives a seal member
(34) surrounding the rotation shaft (110). Therefore, the third
embodiment can provide the same effects as the first embodiment.
Furthermore, it becomes easier to form the center plate (400) with
smaller molds for the first and second plate members (400P, 400S).
The seal member (34) is bared in a parting plane (K) between the
first and second plate members, so that it is easier to fit the
seal member in the seal groove (401a). Seal member 35 can be fit
easily in the seal groove 402a in the same manner.
Embodiment 4
[0123] According to a fourth embodiment, the center plate 400 and
main housing member 10 are formed as a single integral member. As
in the first, second and third embodiments, the main housing member
10 is made of softer metallic material (aluminum alloy) and the
rotating elements of the pump (130, 140) are made of harder
metallic material (Fe based material).
[0124] FIG. 12 shows the tandem pump P according to the fourth
embodiment in the form of an axial section. The main housing member
10 shown in FIG. 12 includes a center partition wall serving as
center plate 400. The center wall is formed with the drive shaft
through hole 401 and the driven shaft through hole 402. The main
housing member 10 includes a z positive (first) side surface formed
with a first recessed portion 12d recessed in the z negative
direction from the z positive side surface facing in the z positive
direction, and a z negative (second) side surface formed with a
second recessed portion 12c recessed in the z positive direction
from the z negative side surface of the main housing member 10. The
first side plate 150 is disposed in the first recessed portion 12d,
and the second side plate 160 is disposed in the second recessed
portion 12c.
[0125] The center plate 400 is integral with the main housing
member 10, so that the partition formed by the center plate 400 is
stationary relative to main housing member 10. Therefore, cover
member 20 is not required to abut against the center plate 400
unlike the preceding embodiments. In the example of FIG. 12, the
forward end 22 of the cylindrical projecting portion 21 of cover
member 20 is spaced from center plate 400. Accordingly, it is not
necessary to increase the rigidity of the forward end 22 of cover
member 20, and it is possible to reduce the wall thickness of cover
member 20.
[0126] Since center plate 400 is integral with main housing member
10, it is not possible to insert the pump assembly 100 from the z
negative side into main housing member 10. Instead, the first and
second side plates 150 and 160 are inserted, respectively, from the
z positive side and the z negative side. Therefore, there is
provided an additional cover member 30 on the z positive side, in
addition to the cover member 20 on the z negative side. The
additional cover member 30 covers the first recessed portion 12d
and thereby defines the first discharge region Dout1
liquid-tightly. Seal members 34 and 35 for sealing the first and
second pumps P1 and P2 from each other are provided around drive
shaft 110 and driven shaft 120 as in the first embodiment. In the
fourth embodiment, main housing member 10 includes the surrounding
wall and partition, the cover member 20 include the second end wall
and the additional cover member 30 includes the first end wall. The
projecting portion 21 of cover member 20 is inserted in the second
recessed portion 12c which is larger in sectional size or diameter
than the first recessed portion 12d in the example of FIG. 12.
[0127] A first slide member 440 is provided between the partition
400 and the first driving and driven gears 130P and 140P in the
first recessed portion 12d. A second slide member 440 is provided
between the partition 400 and the second driving and driven gears
130S and 140S in the second recessed portion 12c. Since it is
troublesome to form sliding surfaces in the partition 400 of FIG.
12, the slide members 440 are used to reduce the friction and
improve the sliding contact characteristic without the need for an
accurate finishing operation for forming sliding surfaces in center
plate 400.
[0128] According to the fourth embodiment, the partition (400) is
integral with the housing (1). Therefore, the fourth embodiment can
determine the position of the partition securely, and provide the
same effects as in the first embodiment. Moreover, the use of the
partition integral with the housing reduces the number of component
parts. The fourth embodiment eliminates or reduce the need for
increasing the rigidity of the cover member (20) which is not
required to press the partition. In the fourth embodiment, it is
possible to eliminate the seal members 31 and 32 to be provided
around the center plate 400 (shown in FIG. 4). With the slide
members (440), it is possible to reduce the friction without the
need for forming a precisely finished sliding surface in the center
plate.
Embodiment 5
[0129] In the illustrated examples of the preceding embodiments,
the tandem pump P is a combination of external gear pumps.
According to a fifth embodiment, by contrast, the tandem pump P is
a combination of internal gear pumps.
[0130] FIG. 13 shows the tandem pump P according to the fifth
embodiment in axial section. This tandem pump P includes a first
internal gear pump P1 including first inner rotor 510P and a first
outer rotor 520P, and a second internal gear pump P2 including a
second inner rotor 510S and a second outer rotor 520S.
[0131] The first and second inner rotors 510P and 510S are
connected with and driven by the single common drive shaft 110.
First and second inner rotors 510P and 510S are engaged,
respectively, with first and second outer rotors 520P and 520S, and
arranged to produce the respective discharge fluid pressures
independently. Unlike the examples of the external gear pumps, the
tandem pump P of FIG. 13 does not include the driven gear
(120).
[0132] The main housing member 10 of FIG. 13 includes the pump
receiving portion 12 shaped like a hollow cylinder having a bottom
as in the illustrated example of the first embodiment. The pump
assembly 10 including first pump P1, center plate 400 and second
pump P2 is inserted into this pump receiving portion from the z
negative side, and the pump receiving portion 12 is closed by the
cover member 20 as in the illustrated example of the first
embodiment.
[0133] The center plate 400 is substantially cylindrical, and
includes an externally threaded portion 15a in the outer
circumference. On the other hand, the surrounding wall of main
housing member 10 includes an internally threaded portion 12e in
the inside wall of pump receiving portion 12. Center plate 400 is
positioned and fastened in main housing member 10 by screwing the
externally threaded portion 15a of center plate 400 into the
internally threaded portion 12e of main housing member 10. In this
example, the step 410 is made smaller.
[0134] The surrounding wall of main housing member 10 includes a
first wall portion surrounding and defining the first (smaller)
portion 14 of pump receiving portion 12, and a second wall portion
surrounding and defining the second (larger) portion 15(which is
greater in the cross sectional size than the first portion 14). In
the example of FIG. 13, the internally threaded portion 12e formed
in the second (larger) portion 15, so that main housing member 10
can position the center plate 400 securely.
[0135] In the example of FIG. 13, the surrounding wall of main
housing member 10 includes a third wall portion surrounding and
defining a third portion which is greater in the cross sectional
size than the second portion 15. Correspondingly, the center plate
400 of FIG. 13 includes a first portion, a second portion which is
greater in cross sectional size than the first portion and which is
formed with the externally threaded portion 15a, and a third
portion which is greater in cross sectional size than the second
portion. The second portion formed with the externally threaded
portion 15a is located axially between the first portion provided
with a seal ring (31) and the third portion provided with a seal
ring (32).
[0136] It is possible to employ the internal gear pumps in the
first, second, third and fourth embodiments, instead of the
external gear pumps. The fixing structure using the externally
threaded portion 15a and the internally threaded portion 12e can be
applied to the first through fourth embodiments.
[0137] This application is based on a prior Japanese Patent
Application No. 2008-058970 filed on Mar. 10, 2008. The entire
contents of this Japanese Patent Application are hereby
incorporated by reference.
[0138] Although the invention has been described above by reference
to certain embodiments of the invention, the invention is not
limited to the embodiments described above. Modifications and
variations of the embodiments 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.
* * * * *