U.S. patent application number 10/484520 was filed with the patent office on 2005-08-11 for crash-protected vacuum brake booster for motor vehicles.
Invention is credited to Graichen, Kai-Michael, Saalbach, Kurt, Wagner, Wilfried.
Application Number | 20050172801 10/484520 |
Document ID | / |
Family ID | 7694388 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050172801 |
Kind Code |
A1 |
Saalbach, Kurt ; et
al. |
August 11, 2005 |
Crash-protected vacuum brake booster for motor vehicles
Abstract
In order to improve the deformation behavior of a vacuum brake
booster provided with force transmission pins that are used to
transmit forces onto a body splashboard of a motor vehicle, the
invention discloses that the force transmission pins are made up of
two sections having different strength. To achieve a sufficiently
low strength when a fastening screw is used for a first section,
the first section is embodied as a hollow body, and the fastening
screw extends only over the length of a second section of the pin.
Because the first section is configured as a hollow body, the screw
arranged in the second section can be actuated through the first
section.
Inventors: |
Saalbach, Kurt;
(Morfelden-Wladorf, DE) ; Wagner, Wilfried;
(Huttenberg, DE) ; Graichen, Kai-Michael;
(Egelsbach, DE) |
Correspondence
Address: |
RATNERPRESTIA
P O BOX 980
VALLEY FORGE
PA
19482-0980
US
|
Family ID: |
7694388 |
Appl. No.: |
10/484520 |
Filed: |
January 16, 2004 |
PCT Filed: |
August 7, 2002 |
PCT NO: |
PCT/EP02/08831 |
Current U.S.
Class: |
92/169.1 |
Current CPC
Class: |
B60T 13/5675
20130101 |
Class at
Publication: |
092/169.1 |
International
Class: |
F01B 011/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2001 |
DE |
101 38 301.0 |
Claims
1-7. (canceled)
8. Vacuum brake booster for motor vehicles with a booster housing
including two opposed housing shells, with at least one movable
wall subdividing the interior of the booster housing into two
chambers, as well as with at least one force transmission pin that
extends in parallel to the longitudinal axis of the vacuum brake
booster from a first housing shell to the second housing shell
arranged on the opposite side of the movable wall and is sealed in
relation to the movable wall, and at the end of which force
transmission pin fastening elements for a vehicle body wall or a
master brake cylinder connected downstream of the vacuum brake
booster are designed, with the force transmission pin including at
least one first section and one second section, wherein the
material cross-section of the first section is chosen to be small
compared to the material cross-section of the second section to
such an extent that it decreases its length extending in the
longitudinal direction of the pin when a predetermined force is
exceeded.
9. Vacuum brake booster as claimed in claim 8, wherein the first
section is configured as a hollow cylinder, whose wall thickness is
chosen so be so thin that the first section will reduce its length
extending in the longitudinal direction of the pin when a
predetermined force is exceeded.
10. Vacuum brake booster as claimed in claim 9, wherein the pin
comprises a second section designed as a hollow cylinder, and in
that a fastening screw extends through the second section and is
supported with its screw head at least indirectly on the end
surface of the section that forms the second cylinder and, with its
threaded other end projects through the second housing shell close
to the body wall.
11. Vacuum brake booster as claimed in claim 10, wherein the first
and the second section are integrally formed or non-detachably
interconnected.
12. Vacuum brake booster as claimed in claim 11, wherein the first
section is provided with a projection made by deformation, with
pressure forces that act on the first housing shell being supported
on said projection.
13. Vacuum brake booster for motor vehicles with a booster housing
including two opposed housing shells, with at least one movable
wall subdividing the interior of the booster housing into two
chambers, as well as with at least one force transmission pin that
extends in parallel to the longitudinal axis of the vacuum brake
booster from a first housing shell to the second housing shell
arranged on the opposite side of the movable wall and is sealed in
relation to the movable wall, and at the end of which force
transmission pin fastening elements for a vehicle body wall or a
master brake cylinder connected downstream of the vacuum brake
booster are designed, with the force transmission pin including at
least one first section and one second section, wherein the first
section and the second section are formed of hollow cylinders, that
the first and the second section are fixed in position to each
other in the longitudinal direction of the pin by a holding
connection, that the holding connection is disengaged when a
predefined force that acts in the longitudinal direction of the pin
is exceeded and the two sections are telescopically displaced into
each other, and that a fastening screw projects through the second
section and is supported with its screw head on the end face of the
cylinder that forms the second section and with its threaded, other
end projects through the second housing shell close to the body
wall.
14. Vacuum brake booster as claimed in claim 13, wherein the first
section is provided with a projection that is formed by deformation
and on which pressure forces that act on the first housing shell
are supported.
Description
TECHNICAL FIELD
[0001] The present invention relates to a vacuum brake booster for
motor vehicles with a booster housing including two opposed housing
shells, with at least one movable wall subdividing the interior of
the booster housing, as well as with at least one force
transmission pin that extends in parallel to the longitudinal axis
of the vacuum brake booster from one housing shell to the housing
shell arranged on the opposite side of the movable wall and is
sealed in relation to the movable wall, and at the ends of which
force transmission pin fastening elements for a vehicle body wall
or a master brake cylinder connected downstream of the vacuum brake
booster are designed.
BACKGROUND OF THE INVENTION
[0002] A vacuum brake booster of this type is disclosed in German
patent DE 28 45 794. A disadvantage of this prior art vacuum brake
booster is its unfavorable deformation behavior in accidents,
causing deformations of the front part of the motor vehicle. The
cause for this are the force transmission pins that increase the
rigidity of the booster housing, have a comparatively large
diameter and, in an accident, exert an excessive resistance against
deformation of the booster. Consequently, the splashboard of the
vehicle is deformed, whereby the position of the bearing for the
pedal will change so that the pedal can injure the driver in an
accident. Details on this feature are described in DE 19524492.
[0003] DE 19523021 A1 discloses a vacuum brake booster for motor
vehicles with a force transmission pin, said force transmission pin
changing its length when a predetermined longitudinal force is
exceeded.
BRIEF SUMMARY OF THE INVENTION
[0004] In view of the above, an object of the present invention is
to disclose novel measures for a vacuum brake booster for motor
vehicles with a booster housing including two opposed housing
shells, with at least one movable wall subdividing the interior of
the booster housing into two chambers, as well as with at least one
force transmission pin that extends in parallel to the longitudinal
axis of the vacuum brake booster from a first housing shell to the
second housing shell arranged on the opposite side of the movable
wall and is sealed in relation to the movable wall, and at the end
of which force transmission pin preferably fastening elements for a
vehicle body wall or a master brake cylinder connected downstream
of the vacuum brake booster are designed, with the force
transmission pin including at least one first section and one
second section enabling further improvement of the booster's
deformation behavior in accidents.
[0005] A first solution of this object involves that the force
transmission pin includes at least one first section and one second
section, and that the material cross-section of the first section
is chosen to be small compared to the material cross-section of the
second section to such an extent that it decreases its length
extending in the longitudinal direction of the pin when a
predetermined force is exceeded. A very simple construction is
achieved thereby, and the separate provision of special
predetermined breaking points is avoided. The first section is
shortened alone by its reduced strength or its strength reduced
compared to the second section. On the other hand, the position of
the shortened length that results from bulging or buckling is fixed
by the position of the first section.
[0006] In a preferred aspect of the invention, it is advisable that
the first section is configured as a hollow cylinder, whose wall
thickness is chosen so be so thin that the first section will
reduce its length extending in the longitudinal direction of the
pin when a predetermined force is exceeded. This provides an option
in particular for the case that it is desired to screw the booster
from the tandem master cylinder to the splashboard by means of a
screw that projects through the booster. In this case, the screw
can be introduced through the hollow cylinder of the first section,
the outside peripheral surface of which is sealed in relation to
the interior of the housing.
[0007] It is preferred according to a favorable aspect of the
invention that the pin comprises a second section designed as a
hollow cylinder, and in that a fastening screw extends through the
second section and is supported with its screw head at least
indirectly on the end surface of the section that forms the second
cylinder and, with its threaded other end projects through the
second housing shell close to the body wall. Thus, a sealed passage
is achieved through which the screw can extend for attachment. The
difficulty is that the screw shall be rigid enough to anchor the
booster at the splashboard. On the other hand, a screw disposed in
the first section would considerably reinforce the section's
strength. Buckling or bulging of the first section when subjected
to a sufficient amount of longitudinal force would therefore be no
longer ensured. Further features of claim 3 provide a remedy in
this respect. More specifically, the screw is lowered so deeply
into the hollow cylinder of the first section that the screw can no
longer contribute to reinforcement of the first section.
Nevertheless, it is still possible to fasten the booster, coming
from the master cylinder, by means of a screw that extends through
the housing.
[0008] In an improvement of the invention, the first and the second
section are integrally formed or non-detachably interconnected. The
non-detachable connection may e.g. be made by means of welding,
soldering, cementing, form-lock or similar connection methods.
[0009] A simple possibility of supporting forces that act on the
second section can be achieved because the first section is
provided with a projection preferably made by deformation, with
pressure forces that act on the first housing shell or, as the case
may be, tension forces being supported on said projection.
[0010] A second solution of the object underlying the invention
involves that the force transmission pin includes at least one
first section and one second section, that the first section and
the second section are configured as hollow cylinders, that the
first and the second section are fixed in relation to each other by
a holding connection in the longitudinal direction of the pin, that
the holding connection is disengaged and the two sections are
telescoped into each other when a predetermined force that acts in
the longitudinal direction of the pin is exceeded, and that a
fastening screw extends through the second section and is supported
with its screw head on the end face of the cylinder forming the
second section and with its other, threaded end projects through
the second housing shell close to the body wall. This obviates the
need for different strength or material thickness of the two
sections. The second section is rather reinforced by the screw that
extends only through it, yet does not contribute to reinforcing the
first section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 for better comprehension of the state of the art, is
a view of a vacuum brake booster including a pin disclosed in DE
19523021 of the species of a brake booster to be taken from the
preamble of claim 1.
[0012] FIG. 2 is a first embodiment of the invention.
[0013] FIG. 3 is a second embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The vacuum brake booster 1 shown in FIG. 1 shows a booster
housing 2 formed of two interconnected housing shells 20, 21, of
which especially housing shell 20 illustrated on the left in FIGS.
1 and 2 carries a master brake cylinder (not shown), while the
housing shell 21 illustrated on the right is attached to a motor
vehicle body wall (likewise not shown). In a cylindrically designed
extension (not shown) of the right housing shell 21, a control
housing 8 is slidably guided in a sliding sealing ring 3 and houses
a control valve 9 that is operable by means of an input member 4
coupled to a brake pedal (not shown). At its end remote from the
input member 4, the control housing 8 carries a movable wall 5
formed of a diaphragm plate 22 and a rolling diaphragm 23 abutting
thereon, said movable wall subdividing the interior of the brake
booster housing 2 into a vacuum chamber 6 that can be evacuated and
a working chamber 7, with control valve 9 permitting a connection
between the working chamber 7 and the vacuum chamber 6 or the
atmosphere. The control valve 9 is preferably formed by two
coaxially arranged annular sealing seats 10, 11 which cooperate
with a rotationally symmetrical elastic valve member 12, e.g. a
poppet valve, or abut thereon in the release position of the vacuum
brake booster 1. The first sealing seat 10, opening of which allows
a connection between the two chambers 6, 7, is designed in the
control housing 8. The second sealing seat 11, opening of which
allows ventilation of the working chamber 7, is designed on a valve
piston 15 that is guided in the control housing 8 and is in a
force-transmitting connection with input member 4. The valve piston
15 is in a force-transmitting connection with a rubber-elastic
reaction plate 13 arranged in a cylindrical recess 16 of the
control housing 8, said reaction plate permitting a transmission of
both the actuating force introduced at the input member 4 and the
boosting force generated by the movable wall 5 onto an output
member 14 that cooperates with a master brake cylinder piston (not
shown).
[0015] Preferably two rod-shaped force transmission pins are
provided within the booster housing 2, arranged in parallel to the
longitudinal axis of the brake booster, with one of them designated
by reference numeral 17 being shown. The control housing 8 carrying
the movable wall 5 is displaceably guided on this connecting pin 17
and, therefore, is able to move uninhibited in an axial direction
during operation. The sealing of the force transmission pins 17 in
apertures 19 designed in the control housing 8 is preferably done
by sliding seals integral with the rolling diaphragm 23, with the
sliding seal associated with the force transmission pin 17 being
shown and designated by reference numeral 24.
[0016] To attach the above-mentioned master brake cylinder to the
housing shell 20 shown on the left in FIG. 1 or the vacuum brake
booster 1 to the body splashboard, fastening elements 25, 26
provided on the ends of the force transmission pins 17 are
associated with the two housing shells 20, 21. To ensure that a
defined deformation of the booster housing 2 occurs in an accident
that has deformations of the vehicle front part as a result, the
force transmission pins 17 include three radial grooves or notches
18, 27, 28. While the grooves or notches 18 and 28 are designed in
the area of the fastening elements 25, 26, the third groove or
notch 27 is disposed in the area of the apertures 19 through which
the force transmission pin 17 extends and receives the
above-mentioned sliding seal 24. The grooves or notches 18, 27, 28,
the influence of which in the transmission of forces is well known
to the one skilled in the art, may preferably have a triangular,
square or semicircular design in cross-section. However, other
cross-sectional shapes are of course feasible as well. Favorably,
the force transmission pins 17 may also be seal-tightly coated with
a plastic layer 56 that has gliding qualities.
[0017] It is particularly disadvantageous in the prior art solution
that the booster cannot be screwed to the splashboard directly by a
screw projecting through the housing without minimizing the
collision protection of the booster. Figure z shows how this is
possible with the invention nevertheless. Only those components
that differ from FIG. 1 are described.
[0018] FIG. 2 shows a pin 101 for force transmission, which is
formed of a first section 102 and a second section 103. A fastening
screw 112 extends through the housing wall 120 of a first housing
shell 121. The fastening screw 112 has a bore 122. Bore 122
receives the end of the first section 102 being thus sealedly held
in housing 121. A circumferential edge 123 takes up the tensile
forces that act on the first section 102. The first section 102 is
sealed by means of a seal 114. Externally acting longitudinal
forces at the first section 102 are conducted by way of a
circumferential projection 105 at the first section 102 to the
housing 121 by way of a spacer 106. The second section 103 is
sealed and connected to the first section 102. In the area of the
connection, a step 108 is provided through which longitudinal
forces can be transmitted to the right in FIG. 2 by way of a screw
117. The setup of the connection between the first section 102 and
the second section 103 as shown in FIG. 2 is not imperative for the
invention. The two sections can also be integrally connected to
each other. It is only significant that there is a projection
allowing a screw 117 to make catch at pin 101 with its two sections
so that the screw in FIG. 2 can apply longitudinal forces to the
right, by which the booster can be drawn against the splashboard.
The section 103 is sealingly applied to a wall (not shown) of the
second housing shell in such a fashion that the screw 117 is able
to exert longitudinal forces beyond its edge 110 on the second
housing shell (not shown). To this end, there is an opening (not
shown in the drawing) in the second housing shell through which the
end of the screw extends through the second housing shell and can
be connected to the splashboard. The function of the illustrated
notch of screw 117 has already been described with regard to FIG.
1, it is, however, not absolutely necessary in the present
embodiment. Screw 117 may include a hexagon socket 118 by way of
which it can be tightened from the outside by means of a tool
reaching through the first section 102.
[0019] It is especially important for the invention that the
rigidity of the first section 102 vis--vis longitudinal forces,
especially pressure forces, is significantly lower than that of the
second section 103 having not only a larger wall thickness but, in
addition, being also reinforced vis--vis lateral forces by the
screw 117. Thus, screw 117 has two functions: it is not only used
to fasten the booster to the splashboard but additionally
reinforces the strength of the second section 103. Also, it is this
way possible to define the place of the deformation of the pin in a
crash more precisely.
[0020] The following features are important for dimensioning pin
101. The pin must be apt to take up the longitudinal forces and
pressure forces necessary for the mode of operation of the booster
without becoming deformed. On the other hand, the pin shall be
shortened compared to the normal distance of its two ends for the
case that the pressure forces that act on it exceed a defined
value. The second section 103 of the pin now as before must be able
to take up the additional longitudinal forces required to hold the
booster on the splashboard. Another requirement is that the first
section now as before makes catch at the second housing section 121
by a simple measure, which is satisfied by the circumferential
projection 105 in the present case.
[0021] The solution of FIG. 3 differs from the solution of FIG. 2
as follows. On the one hand, the wall thickness of the first
section 102 is as strong as the wall thickness of the second
section 103. The connection 119 between the first section 102 and
the second section 103 is chosen such that it can be disrupted by a
sufficient amount of force in the longitudinal direction of pin
101. The force necessary for disrupting the connection is higher
than the forces that normally develop in the mode of operation of
the booster. This force occurs in a crash. When the connection is
disengaged in a crash, longitudinal forces can no longer be
transmitted by way of pin 101, and the first section 102 is
displaced telescopically over the second section 103, thereby
reducing the length of the pin 101.
* * * * *