U.S. patent application number 10/904415 was filed with the patent office on 2006-05-11 for internal leakage control and venting for abs unit.
This patent application is currently assigned to ROBERT BOSCH CORPORATION. Invention is credited to Omar Bravo, Bernhard Gnamm, Stephen Kramp, Brian Shull.
Application Number | 20060099090 10/904415 |
Document ID | / |
Family ID | 36316512 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060099090 |
Kind Code |
A1 |
Kramp; Stephen ; et
al. |
May 11, 2006 |
Internal Leakage Control and Venting for ABS Unit
Abstract
A housing block for a hydraulic unit of a vehicle brake system
that retaining a piston pump and an eccentric element that rotates
the piston. A motor drives the eccentric element within an
eccentric chamber. The block has a cylindrical cavity within a
hydraulic leakage reservoir and a fluid leakage path that begins
near a lower most portion of the eccentric element chamber and
extends to a cylindrical cavity by way of a passage defined by an
intersection of the eccentric chamber and cylindrical cavity. A
pressure equalization path extends from the eccentric chamber
upwardly to a point intermediate the housing block and motor
enclosure and into the motor enclosure to a location that is
substantially above the eccentric chamber. A seal intermediate the
motor enclosure and housing block is formed as a closed curve of
mastic material encircling the motor shaft, eccentric chamber,
hydraulic leakage reservoir hydraulic fluid leakage path, and
pressure equalization path.
Inventors: |
Kramp; Stephen;
(Summerville, SC) ; Shull; Brian; (Charleston,
SC) ; Bravo; Omar; (Mt. Pleasant, SC) ; Gnamm;
Bernhard; (Summerville, SC) |
Correspondence
Address: |
LEO H MCCORMICK
2112 MISHAWAKA AVE
P O BOX 4721
SOUTH BEND
IN
46634
US
|
Assignee: |
ROBERT BOSCH CORPORATION
2800 South 25th Avenue
Broadview
IL
|
Family ID: |
36316512 |
Appl. No.: |
10/904415 |
Filed: |
November 9, 2004 |
Current U.S.
Class: |
417/415 ;
417/410.1 |
Current CPC
Class: |
F04B 53/04 20130101;
F04B 1/0443 20130101; B60T 8/368 20130101 |
Class at
Publication: |
417/415 ;
417/410.1 |
International
Class: |
F04B 35/04 20060101
F04B035/04; F04B 17/00 20060101 F04B017/00 |
Claims
1. In the manufacture of a braking system hydraulic pump having a
pump housing with a generally planar face, at least one pump piston
reciprocably disposed within the housing, a pump actuating motor
having a face joinable to the housing face and having a motor shaft
with an eccentric near a free end thereof for drivingly coupling
the motor shaft and at least one piston, and an eccentric cavity in
the housing for receiving said eccentric, an improved process of
providing a hydraulic fluid leakage reservoir in the housing,
comprising: creating a blind hole in said housing extending
generally orthogonally from said housing face into the housing and
intersecting the eccentric cavity within the housing; and sealing
the open bore end along the housing face byjoining the motor and
housing faces.
2. The process of claim 1, including the additional steps of
forming a pressure differential vent in the motor face, and sealing
the vent from the external environment.
3. The process of claim 2, wherein the steps of sealing the open
bore and sealing the vent are performed simultaneously by applying
a mastic material to one of the motor face and housing face, and
juxtaposing the housing and motor faces.
4. The process of claim 1, wherein the step of sealing the open
bore includes applying a viscous sealant material to one of the
motor face and housing face, and juxtaposing the housing and motor
faces.
5. The process of claim 1 wherein the eccentric cavity comprises a
blind generally cylindrical bore extending inwardly from the
housing face and an undercut region along a portion of the bore
cylinder intermediate the ends thereof, the step of boring the
blind hole in the housing including intersecting the eccentric
cavity only in the undercut region.
6. The process of claim 1, further including the steps of; creating
an additional blind hole in the housing extending generally
orthogonally from said housing face into the housing and
intersecting the eccentric cavity within the housing; and sealing
the open bore end and additional bore end along the housing face by
applying a mastic material to one of the motor face and housing
face, and joining the motor and housing faces.
7. A hydraulic pump for a braking system, comprising: a pump
housing having a cavity for receiving a driving shaft and
eccentric, and a pair of opposed pump piston cylinders spanning the
cavity; a pump driving motor and motor enclosure having a shaft
rotatable about an axis with an eccentric member extending
therefrom, the housing and motor enclosure being sealinglyjoinable
along a common generally planar surface with the shaft axis
extending generally orthogonal to the planar surface; the pair of
pump cylinders adapted to receive respective pistons reciprocable
therein along a common axis generally orthogonal to the shaft axis
in response to eccentric motion; and a leakage fluid reservoir
including a reservoir cylinder in fluid communication with the
eccentric cavity for receiving leakage hydraulic fluid therefrom,
the reservoir cylinder having an axis extending generally parallel
to the shaft axis.
8. The hydraulic pump of claim 7, wherein the eccentric cavity
comprises a blind generally cylindrical bore extending inwardly
from the planar surface, and an undercut region along a portion of
the bore cylinder intermediate the ends thereof, the leakage fluid
reservoir cylinder being in fluid communication with the eccentric
cavity solely in the undercut region.
9. The hydraulic pump of claim 7, wherein the housing and motor
enclosure are sealingly joined along the common surface, and
further including a pressure differential compensating vent
providing an air path between the housing interior and the motor
interior.
10. The hydraulic pump of claim 7, wherein the leakage fluid
reservoir includes a lowermost portion of the eccentric cavity and
a second reservoir cylinder in fluid communication with the
eccentric cavity for receiving leakage hydraulic fluid therefrom,
the second reservoir cylinder having an axis extending generally
parallel to the shaft axis.
11. A hydraulic pump for a braking system, comprising: a pump
housing having a cavity for receiving a driving shaft and
eccentric, and a pair of opposed pump piston cylinders spanning the
cavity; a pump driving motor and motor enclosure having a shaft
rotatable about an axis with an eccentric member extending
therefrom, the housing and motor enclosure being sealingly joinable
along a common surface with the shaft axis extending generally in a
horizontal direction into the eccentric cavity; the pair of pump
cylinders adapted to receive respective pistons reciprocable
therein along a common axis generally orthogonal to the shaft axis
in response to eccentric motion; a leakage fluid reservoir
including a reservoir cylinder in fluid communication with the
eccentric cavity for receiving leakage hydraulic fluid therefrom;
and a pressure differential compensating vent positioned above the
eccentric cavity for providing an air path between the housing
interior and the motor enclosure interior.
12. The hydraulic pump of claim 11, wherein the reservoir cylinder
has an axis extending generally parallel to the shaft axis.
13. The hydraulic pump of claim 11, wherein the eccentric cavity
comprises a blind generally cylindrical bore extending inwardly
from the common surface, and an undercut region along a portion of
the bore cylinder intermediate the ends thereof, the leakage fluid
reservoir cylinder being in fluid communication with the eccentric
cavity solely in the undercut region.
14. The hydraulic pump of claim 13, wherein the undercut region
comprises a portion of a cylinder of diameter and axial extents
both less than the respective diameter and axial extents of the
bore cylinder.
15. The hydraulic pump of claim 13, wherein the leakage fluid
reservoir includes the undercut region of the eccentric cavity and
a second reservoir cylinder in fluid communication with the
eccentric cavity undercut region for receiving leakage hydraulic
fluid therefrom, the second reservoir cylinder having an axis
extending generally parallel to the shaft axis.
16. A hydraulic unit of a vehicle brake system, comprising a
housing block, at least one piston pump retained inside the housing
block having a piston with an eccentric element that displaces the
piston, an eccentric element chamber within the housing block in
which said eccentric element is rotatable, a motor for driving said
eccentric element, a motor enclosure, a hydraulic leakage reservoir
comprising at least one generally cylindrical cavity in said
housing block, a hydraulic fluid leakage path that begins near a
lower most portion of the eccentric element chamber and extends to
the at least one generally cylindrical cavity through a passage
comprising an intersection of the eccentric element chamber and
cylindrical cavity, and a pressure equalization path extending from
the eccentric element chamber upwardly intermediate the housing
block and motor enclosure and into the motor enclosure at a
location substantially above the eccentric chamber.
17. A hydraulic unit in accordance with claim 16, further
comprising a seal intermediate the motor enclosure and housing
block formed as a closed curve of mastic material encircling the
motor shaft, eccentric chamber, hydraulic leakage reservoir,
hydraulic fluid leakage path, and pressure equalization path.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates, in general, to an
electronically controlled brake system for automobiles and, more
particularly, to an electronically controlled brake system provided
with an internal fluid reservoir for receiving leakage brake fluid
as well as an internal pressure differential compensating
feature.
[0003] 2. Description of the Related Art
[0004] It is desirable to isolate any brake fluid leaking from a
braking system pump from the electric motor which powers that pump.
This may be facilitated by internal storage of fluid which has
leaked as well as avoidance of pressure differentials which might
otherwise cause leakage fluid to enter the motor chamber.
[0005] A conventional brake system for vehicles consists of a
booster and a master cylinder, which form braking fluid pressure in
response to a motion of a brake pedal and feeds the fluid pressure
to wheel brakes, thus reducing the traveling speed of a vehicle or
maintaining a stopped state of the vehicle. However, the vehicles
with such conventional brake systems may slip over a road in
accordance with road surface conditions or variations in fluid
pressure during a braking operation. In an effort to overcome such
problems, a variety of electronically controlled brake systems,
such as an anti-lock brake system (ABS), a traction control system
(TCS) and similar brake control systems have been proposed and
widely used. The ABS electronically controls the fluid pressure fed
to wheel brakes and prevents slippage of wheels during a braking
operation. The TCS is designed to prevent excessive slippage of
drive wheels during quick drive or sudden acceleration.
[0006] Electronically controlled brake systems frequently employ an
electrically powered pump unit including an electric motor, one or
more piston pumps, one or more pressure fluid accumulators and
other related components. These units are typically sealed against
the ingress of external moisture, thus, any fluid which leaks from
the piston pumps is not readily removable from the unit. Attempts
to form such units as two mutually isolated sub-units (motor and
pump) have not proven successful. One problem is that internal
heating which occurs during unit operation may create pressure
differentials within the unit causing fluid to flow between the
sub-units.
[0007] A radial piston pump is known, having an electric motor
which drives a piston pump arrangement. To keep any leaking
hydraulic fluid away from the electric motor, in the housing of the
piston pump arrangement collecting chambers and channels are
formed, into which leaking hydraulic fluid passes under the action
of gravitational and/or centrifugal force in order to be stored
there. Disposed between the electric motor and the piston pump
arrangement is an open rolling-contact bearing and disposed at the
side of the rolling-contact bearing facing the electric motor is a
slinger, which is driven by the electric motor. Leaking hydraulic
fluid, after it has passed through the open rolling-contact
bearing, is kept away from the electric motor by means of the
slinger. The radial piston pump may be installed only with a
horizontal orientation (with the electric motor next to the piston
pump arrangement) or with a vertical orientation such that the
electric motor is disposed above the piston pump arrangement, for,
if the radial piston pump were to be installed with the electric
motor below the piston pump arrangement, the hydraulic fluid under
the action of gravitational force alone would flow out of the
collecting chambers and the channels into the electric motor,
particularly when the electric motor was stopped and the slinger
was not driven.
[0008] With such pumping sets there is also the problem that
because of temperature variations between the interior of the
electric motor and the space, in which the eccentric pump
arrangement is situated, a (short-term) differential pressure may
arise. As a result, excess hydraulic fluid is sucked out of the
space, in which the leakage of the eccentric pump arrangement is
situated, through the ball bearing or needle bearing for the output
shaft and into the interior of the electric motor. Particularly in
the event of extended operating times of the pumping set, a
significant quantity of hydraulic fluid may escape and be drawn
into the electric motor by a vacuum, which arises in the electric
motor as a result of short-term cooling in the interior of the
electric motor. Conventional scaling methods (sealing rings, sealed
bearings etc.) are too expensive and also do not prevent the
hydraulic fluid from being dispersed into the environment.
SUMMARY OF THE INVENTION
[0009] The present invention provides an internal leakage reservoir
in a pump housing designed for sealed ABS hydraulic units where
internal hydraulic fluid seepage must be stored inside the unit
over the product life
[0010] The invention comprises, in one form thereof, a hydraulic
pump for a braking system including a pump housing with a cavity
for receiving a driving shaft and eccentric and a pair of opposed
pump piston cylinders spanning the cavity. There is a pump driving
motor having a shaft rotatable about an axis with an eccentric
member extending therefrom. The housing and motor have generally
planar faces which are sealingly joined along a common surface with
the shaft axis extending generally in a horizontal direction
orthogonal to the motor and housing surfaces and into the eccentric
cavity. A pair of pump pistons are disposed in respective cylinders
to be reciprocable therein along a common axis generally orthogonal
to the shaft axis in response to eccentric motion. At least one
generally cylindrical leakage fluid reservoir is in fluid
communication with the eccentric cavity near a lower extremity
thereof for receiving leakage hydraulic fluid therefrom and a
pressure differential compensating vent is positioned above the
eccentric cavity for providing an air path between the housing
interior and the motor interior.
[0011] Also in general, and in one form of the invention, a
hydraulic fluid leakage reservoir or sump is provided in a
hydraulic pump housing by creating a blind hole in the housing
extending generally orthogonally from a generally planar housing
face into the housing and intersecting an eccentric cavity within
the housing, and subsequently sealing the open bore end along the
housing face byjoining motor and housing faces. A pressure
differential vent may be formed in the motor face and, thereafter,
the vent sealed from the external environment. Sealing the open
bore and sealing the vent may be accomplished simultaneously by
applying a viscous sealant or mastic material to one or both of the
motor face and housing face, and juxtaposing the housing and motor
faces. The eccentric cavity may comprise a blind generally
cylindrical bore extending inwardly from the housing face and an
undercut region along a portion of the bore cylinder intermediate
the ends thereof in which case, the step of creating the blind hole
in the housing typically includes intersecting the eccentric cavity
only in the undercut region.
[0012] An advantage of the present invention is that the location
of the reservoir of the present invention prevents hydraulic fluid
from entering the electric motor portion of the unit.
[0013] Another advantage is the simple arrangement and machining of
the cavity with existing tooling. No reservoir cap or other extra
parts are necessary.
[0014] A further advantage of the present invention is its
applicability to a variety of existing hydraulic pump designs by
minimal modification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a simplified cross-sectional side view of a sealed
hydraulic unit according to the invention in one form;
[0016] FIG. 2 is a perspective view of the pump housing of FIG.
1;
[0017] FIG. 3 is a cross-sectional view of the pump housing along
the lines 3-3 of FIG. 2;
[0018] FIG. 4 is a simplified perspective view of the pump housing
of FIG. 1;
[0019] FIG. 4a is a simplified perspective view of a reservoir
portion of the pump housing of FIG. 4;
[0020] FIG. 5 is a side elevation view of a prior art pump housing
showing a technique for sealing the junction between the pump
housing and motor portion; and
[0021] FIG. 6 is a side elevation view of a pump housing similar to
FIG. 5, but showing a technique for sealing the junction between
the pump housing and motor portion according to the present
invention.
[0022] Corresponding reference characters indicate corresponding
parts throughout the several drawing views.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Referring now to the drawings and particularly to FIG. 1,
there is shown a hydraulic unit 11 which includes a pump housing
block 13 and, mounted against the housing block 13, a pump driving
motor 15, having motor shaft 27 rotatable about axis 83. The motor
is positioned within a motor enclosure or covering hood 17. The
pump housing 13 has a generally planar securing face 19 for
receiving the motor 15 shown in FIGS. 2, 4 and 6. Extending from
this securing face 19 in the housing block 13 is a bore 21
communicating with an undercut region 23, which together define an
eccentric chamber. An eccentric member 25 is fixed to the driving
shaft 27 which shaft passes through a ball bearing 29 that is
supported by the stepped bore 21. The eccentric member alternately
actuates a pair of pump pistons (not shown) in cylinders 31 and 33.
The eccentric member or element 25 may be a cam element, known
swash plate, conventional crank shaft and connecting rod
configuration, or other cam-like curves or surfaces may be
employed.
[0024] In FIG. 3, the pump cylinders 31 and 33 extend along a
common axis 85 generally orthogonal to motor shaft axis 81 and are
combined with outlet valves generally at 35 and 37 forming two
piston pumps that are operative independently of one another.
Cylindrical bores 39 and 41 are drilled vertically from below into
the housing block 13. In the bores 39 and 41, spring loaded storage
pistons (not shown) are located to provide fluid accumulators.
Connecting conduits 43 and 45 extend upward from the cylindrical
bores 39 and 41 and connect the storage chambers to the inlets of
the two piston pumps. Further details of the hydraulic pump unit as
thus far described may be gleaned from U.S. Pat. No. 6,142,751.
[0025] An internal leakage reservoir is formed by the region 23 in
conjunction with a symmetrically disposed pair of blind holes 51
and 53 drilled along axes 59 and 89 parallel to motor shaft axis 83
and orthogonally to the housing block face 19 (FIGS. 2 and 4) which
holes intersect the undercut region 23 as best seen in FIG. 4a. The
pump pistons in cylinders 31 and 33 provide pressurized hydraulic
fluid to the braking system and some leakage past the pistons into
the bore 21 may occur. A hydraulic fluid leakage path extends from
the piston cylinders 31 and 33 into bore 21, downwardly into the
undercut region 23 and into the bores 51 and 53. This reservoir
provides an enlarged interior region into which leakage fluid may
drain under the influence of gravity functioning as a sump and
allowing storage of hydraulic fluid that seeps from the piston
pumps. The fluid is kept away from the electric motor bearing 29
and motor shaft 27, where it could enter the motor and cause
premature motor failures. The hydraulic unit of the present
invention is designed for deployment with the axis of the motor
shaft 27 disposed horizontally with the reservoir cavity located
below the piston pump bores 31 and 33 in the pump housing 13, in
order to collect and hold the pump seepage by gravity. The
reservoir bores 51 and 53 are uniquely arranged to restrict
hydraulic fluid from splashing back onto motor shaft 27 during
rough road operation of the vehicle. The openings formed where the
bores 51 and 53 intersect the undercut region 23 are kept at a
maximum to allow the hydraulic fluid to enter the cavity freely.
The leakage reservoir must be sufficient in capacity to store the
internal leakage over the lifetime of the product.
[0026] In FIG. 1, air may surround the motor 15 in region 69 within
the motor enclosure 17 as well as occupying the regions 71, 73 and
23 within the pump housing 13. Operation induced temperature
variations and the resulting air pressure differentials could cause
air to migrate between the pump housing 13 and motor enclosure 17
along the motor shaft 27 and bearing 29. If leakage fluid is
present, particularly in cavity 73, that fluid could also move from
the pump housing into the motor enclosure. Such leakage fluid
migration is minimized by providing an air equalization path
identified generally by the arrows 77, 79 and 81 which passes
between the housing 13 and enclosure 17 byway of vent 55.
[0027] The leakage fluid capacity for one preferred embodiment was
approximately 2.6 ml., of which 1 ml. was provided by the undercut
region 23. The reservoir cavity was machined in the pump housing as
an undercut and two bores, however, depending on the pump housing
design, the reservoir could be of a different shape and size. As
best seen in FIG. 4a, the passages or apertures connecting the
eccentric cavity and additional seepage reservoirs each had a depth
along edge 57 parallel to the bore axis 59 equal to the depth of
the undercut. The chord or separation between the edges 57 and 61
was established by the location and diameter of bore 51 with the
arcuate length of the opening edges 63 and 65 being somewhat
greater. In that preferred embodiment, the motor was vented by a
hole 55 in the motor housing face to guarantee equal pressure and
free air exchange between the pump housing and motor. This pressure
differential vent 55 in the motor face is located above the motor
shaft and well above the sump to minimize the likelihood of fluid
entering the motor chamber by way of the vent. The technique by
which the electric motor is sealed off against the pump housing by
the special sealing contour around the cavity to prevent hydraulic
fluid from entering along the motor electrical connector 47 is best
understood by comparing FIGS. 5 and 6.
[0028] In FIG. 5, an illustrative face of a pump housing has an
outer bead of sealant, e.g., a silicone or other mastic material,
91 disposed about a closed generally circular path to providing
sealing of a pump-motor unit from external dust, moisture and other
environmental contaminants. An inner sealant bead 93 provides
sealing isolation between the central motor shaft and bearing
region 95, and the bore 97 through which electronic control unit
power cables such as 47 (FIG. 1) may pass. The sealing technique of
FIG. 5 undesirably depends on a motor shaft and bearing seal to
prevent leakage fluid ingress into the motor chamber.
[0029] FIG. 6, the seal 67 includes an outer sealant bead 99 which
provides the same sealing protection as bead 91 in FIG. 5. A second
bead of mastic material 101 isolates the electronic control unit
power cable opening 103 (along which contamination might enter)
from the motor shaft and bearing while leaving the housing facial
region 105 unsealed to function as part of the pressure
equalization path. An inner seal similar to 93 would block the air
pressure equalization path.
[0030] The process of providing the hydraulic fluid leakage
reservoir in the housing should now be clear. A first blind hole 51
is created in the housing 13 extending generally orthogonally from
the housing face into the housing and intersecting the eccentric
cavity portion 23 within the housing. The eccentric cavity
comprises a blind generally cylindrical bore 21 which extends
inwardly from the housing face 19 and the undercut region 23 along
a portion of the bore cylinder intermediate the ends thereof and
the step of creating the blind hole in the housing includes
intersecting the eccentric cavity only in the undercut region. A
pressure differential vent 55 is drilled in the motor face, and the
vent sealed from the external environment as the open bore end is
sealed along the housing face byjoining the motor and housing
faces. The steps of sealing the open bore and sealing the vent are
performed simultaneously by applying a mastic material to one of
the motor face and housing face as illustrated in FIG. 6 before
juxtaposing the housing and motor faces. Forming a second
cylindrical reservoir portion adds the step of creating an
additional blind hole in the housing extending generally
orthogonally from the housing face into the housing and
intersecting the eccentric cavity within the housing. The open bore
end and additional bore end are simultaneously sealed along the
housing face by applying a mastic material to one of the motor face
and housing face, and joining the motor and housing faces.
* * * * *