U.S. patent application number 09/749209 was filed with the patent office on 2001-05-31 for hydraulic control unit for a motor vehicle braking system.
Invention is credited to Mohr, Kurt, Oliveri, Salvatore, Wagner, Thomas.
Application Number | 20010002236 09/749209 |
Document ID | / |
Family ID | 7875226 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002236 |
Kind Code |
A1 |
Mohr, Kurt ; et al. |
May 31, 2001 |
Hydraulic control unit for a motor vehicle braking system
Abstract
A hydraulic control unit for a motor-vehicle braking system
comprises a pump (32) delivering hydraulic fluid under pressure,
said pump being capable of being controlled by an electronic
control unit (ECU) and supplying the hydraulic fluid for at least
one braking device (22) which is coupled to a wheel of the vehicle,
and also a first reservoir (34) for pressureless hydraulic fluid,
which is assigned to the pump (32) on the input side, and a second
reservoir (36) for hydraulic fluid under pressure, which is
assigned to the pump (32) on the output side. In order to design
the control unit in such a way that it is not unshapely and
problems [sic] as regards installation space arise in not
uncritical manner, the pump (32), the first reservoir (34) and the
second reservoir (36) are arranged in a common casing (60),
integrated as an electrohydraulic modular unit.
Inventors: |
Mohr, Kurt; (Halsenbach,
DE) ; Oliveri, Salvatore; (Filsen, DE) ;
Wagner, Thomas; (Vallendar, DE) |
Correspondence
Address: |
MACMILLAN SOBANSKI & TODD, LLC
ONE MARITIME PLAZA FOURTH FLOOR
720 WATER STREET
TOLEDO
OH
43604-1619
US
|
Family ID: |
7875226 |
Appl. No.: |
09/749209 |
Filed: |
December 27, 2000 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09749209 |
Dec 27, 2000 |
|
|
|
PCT/EP99/05249 |
Jul 22, 1999 |
|
|
|
Current U.S.
Class: |
417/118 ;
417/138; 417/410.1; 417/472 |
Current CPC
Class: |
B60T 8/368 20130101;
B60T 17/02 20130101; F15B 1/02 20130101; B60T 13/686 20130101; B60T
17/06 20130101; B60T 8/4081 20130101; F15B 1/26 20130101 |
Class at
Publication: |
417/118 ;
417/138; 417/410.1; 417/472 |
International
Class: |
F04B 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 1998 |
DE |
19833410.9 |
Claims
1. A hydraulic control unit for a motor-vehicle braking system,
with a pump (32) delivering hydraulic fluid under pressure, said
pump being capable of being controlled by an electronic control
unit (ECU) and supplying the hydraulic fluid for at least one
braking device (22) which is coupled to a wheel of the vehicle, a
first reservoir (34) for pressureless hydraulic fluid, which is
assigned to the pump (32) on the input side, a second reservoir
(36) for hydraulic fluid under pressure, which is assigned to the
pump (32) on the output side, characterised in that the pump (32),
the first reservoir (34) and the second reservoir (36) are arranged
in a common casing (60), integrated as an electrohydraulic modular
unit.
2. Hydraulic control unit according to claim 1, characterised in
that the second reservoir (36) is a hydraulic pressure accumulator,
into which the hydraulic fluid is capable of being conveyed by the
pump (32) contrary to the force of a spring arrangement (72),
whereby at least a first part of the spring arrangement (72) is
formed by a corrugated bellows, preferably made of metal.
3. Hydraulic control unit according to claim 1 or 2, characterised
in that one wall of the hydraulic pressure accumulator (36)
constituting the second reservoir (36) is formed at least partially
by a recess (62) in the casing (60).
4. Hydraulic control unit according to one of claims 1 to 3,
characterised in that the corrugated bellows (72) is connected at a
first end to a cover (64), which seals the recess (62) in the
casing (60), and is connected at a second end to a base (78).
5. Hydraulic control unit according to one of claims 1 to 4,
characterised in that the corrugated bellows (72) divides the
recess (62) in the casing (60) into two regions, of which a first,
inner or outer region (124) is filled with gas and a second, outer
or inner region forms the second reservoir (36) for hydraulic fluid
under pressure.
6. Hydraulic control unit according to one of claims 1 to 4,
characterised in that the corrugated bellows (72) divides the
recess (62) in the casing (60) into two regions, of which a first,
inner or outer region forms the first reservoir for pressureless
hydraulic fluid and a second, outer or inner region forms the
second reservoir (36) for hydraulic fluid under pressure.
7. Hydraulic control unit according to one of the preceding claims,
characterised in that a first aperture (80) extending into the
first reservoir (34) is arranged in the cover (64), said first
aperture connecting said first reservoir to an overflow vessel
(82).
8. Hydraulic control unit according to one of the preceding claims,
characterised in that a second aperture (90) extending into the
first reservoir (34) is arranged in the cover (64), said second
aperture connecting said first reservoir to the input side (32a) of
the pump (32).
9. Hydraulic control unit according to one of the preceding claims,
characterised in that a third aperture (92) extending into the
second reservoir (36) is arranged in the wall of the recess (62),
said third aperture connecting said second reservoir to the output
side (32b) of the pump (32).
10. Hydraulic control unit according to one of the preceding
claims, characterised in that a controllable valve arrangement (42)
is arranged between the third aperture (92) extending into the
second reservoir (36) and the output side (32b) of the pump
(32).
11. Hydraulic control unit according to one of the preceding
claims, characterised in that a hydraulic-fluid line (102) is
arranged between the pressureless reservoir (34) and the reservoir
(36) under pressure, preferably in the base (78), in which a
pressure-relief valve (38) is located which at a predetermined
first pressure level in the reservoir (36) under pressure
establishes a fluid-conducting connection from the reservoir (36)
under pressure to the pressureless reservoir (34) and at a
predetermined second pressure level in the reservoir (36) under
pressure interrupts the fluid-conducting connection from the
reservoir (36) under pressure to the pressureless reservoir
(34).
12. Hydraulic control unit according to one of the preceding
claims, characterised in that parallel to the first part of the
spring arrangement (72) a second part of the spring arrangement
(120, 124) is arranged which assists the action of the first part
of the spring arrangement (72).
13. Hydraulic control unit according to the preceding claim,
characterised in that the second part of the spring arrangement is
a helical spring (120) taking the form of a compression spring
which is arranged between the base (78) and the cover (64).
14. Hydraulic control unit according to claim 12, characterised in
that the second part of the spring arrangement (72) is a helical
spring taking the form of a tension spring which is arranged
between the base (78) and the wall (76) of the recess (62).
15. Hydraulic control unit according to one of the preceding
claims, characterised in that the maximal expansion of the
reservoir (36) for hydraulic fluid under pressure is limited by a
stop member (122).
16. Hydraulic control unit according to one of the preceding
claims, characterised in that the pump (32) is coupled by a
transmission to an electric motor which is controlled by the
electronic control unit (ECU).
17. An assembly for a hydraulic modular unit, with a cover (64), a
preferably metallic corrugated bellows (72), one end of which is
firmly connected to the cover, and a base (78), to which the other
end of the corrugated bellows (72) is firmly connected, whereby the
assembly is capable of being introduced into a pot-shaped recess so
that the cover tightly seals said recess.
Description
[0001] The present invention relates to a hydraulic control unit
for a motor-vehicle braking system, in particular for a
motor-vehicle braking system with a pump delivering a hydraulic
fluid under pressure, said pump being capable of being controlled
by an electronic control unit and supplying the hydraulic fluid for
at least one braking device which is coupled to a wheel of the
vehicle, and with a first reservoir for pressureless hydraulic
fluid, which is assigned to the pump on the input side.
[0002] In the state of the art, pressure accumulators by way of
developments of a second reservoir are known which are designed as
gas-piston accumulators, as gas-diaphragm accumulators or as
multilayer gas-diaphragm accumulators, or as spring-piston
accumulators. In this connection the physical size of the
respective pressure accumulators varies considerably for the same
useful volume. Furthermore, for pressure accumulators with gas
filling there are problems with respect to the temperature
dependence and the imperviousness in long-term behaviour. Further
disadvantages in the case of multilayer gas-diaphragm accumulators
are the considerable weight and the high costs. In the case of
spring-piston accumulators there is the problem of wear and tear of
the seal between the cylinder and the moving piston. All these
problems limit the operating life of the pressure accumulators.
[0003] In the case of the electrohydraulic braking systems that are
known in the state of the art, use is made of standard commercial
gas accumulators or diaphragm accumulators which are screwed to an
outer side of the hydraulic unit. As a result, the hydraulic unit
becomes unshapely, so that problems as regards installation space
arise in not uncritical manner.
[0004] A control device for brake fluid with a pump delivering
hydraulic fluid under pressure is known from JP-09086362 A. The
pump is capable of being driven by a motor, and a first reservoir
for pressureless hydraulic fluid is assigned to said pump on the
input side. A second reservoir for hydraulic fluid under pressure
is assigned to the pump on the output side. In a drawing pertaining
to JP-09086362 A the pump and the first and second reservoirs and,
in particular, also the motor are combined so as to form an
operating block. There is no indication in JP-09086362 A that the
aforementioned operating block is to be equated to a casing. In
known motor-vehicle braking systems the motor driving the pump has
its own motor casing which, for the most part, is produced from
synthetic material. This motor casing is attached to a pump casing
which, as a rule, is manufactured from a metal alloy. Since the
motor and the pump already have two individual casings, for a
person skilled in the art of motor-vehicle braking technology it is
eccentric to equate the operating block to a casing.
[0005] From the printed publication by Leichner, K. H.:
"Fahrzeuggerechte Speichersysteme und ihre Einsatzbedingungen", in
O+P lhydraulik und Pneumatik, Vol. 36, 1992, No. 8, pp 498-501 a
metal-bellows accumulator subject to gas preloading is described
[sic] which is capable of being employed in the motor-vehicle
industry. In this printed publication the practical implementation
of such a metal-bellows accumulator is assessed quite severely in
comparison with diaphragm accumulators as they exist at the present
time.
[0006] From U.S. Pat. No. 4,858,898 a pressure accumulator for a
vehicle is known which is provided, in particular, as a spring
device. With this pressure accumulator, hydraulic fluid is conveyed
to a spring-loaded bellows made of metal which encloses a gas
chamber. In the process the gas enclosed within the gas chamber is
compressed and constitutes a counterforce for the hydraulic
fluid.
[0007] The object underlying the invention is to develop further
the hydraulic control unit mentioned in the introduction in such a
way that these disadvantages are avoided.
[0008] In order to achieve this object, the pump, the first
reservoir and the second reservoir are arranged in a common
casing.
[0009] In this way, on the one hand a considerable saving of weight
is obtained, since a separate outer wall of the pressure
accumulator becomes unnecessary. On the other hand, the integration
of two functions (storage of potential energy and enclosure of the
fluid) in one structural part enables a considerable simplification
of the overall arrangement. Furthermore, moving seals, which can
wear out by reason of friction, are avoided. Since conduction paths
are dispensed with or are considerably shortened, a reduction in
weight and a reduction of installation effort are also
achieved.
[0010] By virtue of the integration of the first reservoir and the
associated omission of the return and suction line, there is the
advantage furthermore that the induction path leading to the pump
can be designed not only to be considerably shorter but also, above
all, to have a considerably larger induction cross-section,
resulting in an improved suction behaviour of the pump,
particularly at low temperatures, which contributes to enhancing
the performance of the electrohydraulic braking system.
[0011] The second reservoir is preferably a hydraulic pressure
accumulator, into which the hydraulic fluid is capable of being
conveyed by the pump contrary to the force of a spring arrangement,
whereby at least a first part of the spring arrangement is formed
by a corrugated bellows, preferably made of metal.
[0012] Astonishingly, by virtue of the configuration according to
the invention it is possible to obtain a space requirement that is
barely greater than or even less than the space requirement of a
traditional gas-pressure accumulator.
[0013] Nevertheless, the pressure accumulator according to the
invention is not temperature-dependent or is barely
temperature-dependent and, by reason of the absence of moving
seals, has no wear problems.
[0014] According to the invention, one wall of the hydraulic
pressure accumulator is formed at least partially by a recess in
the casing. In this connection a considerable amount of material
and weight is eliminated in comparison with the state of the
art.
[0015] In this case the corrugated bellows is connected at a first
end to a cover, which seals the recess in the casing and is [sic]
connected at a second end to a base.
[0016] Hence the corrugated bellows divides the recess in the
casing into two regions, of which a first (inner or outer) region
can be filled with gas and a second (outer or inner) region forms
the second reservoir for hydraulic fluid under pressure. The
included gas assists the spring action of the spring
arrangement.
[0017] An advantageous further development provides that the
corrugated bellows divides the recess in the casing into two
regions, of which a first (inner or outer) region forms the first
reservoir for pressureless hydraulic fluid and a second (outer or
inner) region forms the second reservoir for hydraulic fluid under
pressure. This measure achieves an especially high utilisation of
space.
[0018] In a preferred embodiment of the invention a first aperture
extending into the first region is provided which connects said
first region to an overflow vessel.
[0019] In addition, a second aperture extending into the first
region is arranged in the cover, which connects said first region
to the input side of the pump.
[0020] Finally, a third aperture extending into the second region
is arranged in the wall of the recess, which connects said second
region to the output side of the pump.
[0021] A controllable valve arrangement is preferably arranged
between the third aperture extending into the second region and the
output side of the pump. Furthermore, yet other valve arrangements
may also be integrated into the control unit.
[0022] In addition, a hydraulic-fluid line is arranged between the
pressureless region and the region under pressure, preferably in
the base, in which a pressure-relief valve is located which at a
predetermined first pressure level in the region under pressure
establishes a fluid-conducting connection from the region under
pressure to the pressureless region and at a predetermined second
pressure level in the region under pressure interrupts the
fluid-conducting connection from the region under pressure to the
pressureless region. Hence the pump delivers in the event of
excessive pressure in the circuit.
[0023] With a view to increasing the achievable pressure level, a
second part of the spring arrangement is arranged preferably
parallel to the first part of the spring arrangement, which assists
the action of the first part of the spring arrangement.
[0024] In a first embodiment of the invention the second part of
the spring arrangement is a helical spring taking the form of a
compression spring which is arranged between the base and the
cover.
[0025] As an alternative to this, the second part of the spring
arrangement may be a helical spring taking the form of a tension
spring which is arranged between the base and the wall of the
recess.
[0026] It is to be understood that the arrangement of the helical
spring inside or outside the corrugated bellows as well as its
design as a tension spring or compression spring may also be
permuted with respect to the alternatives described above.
[0027] In both cases the maximal expansion of the reservoir for
hydraulic fluid under pressure is limited by a stop member.
[0028] The pump is coupled by a transmission to an electric motor
which is controlled by the electronic control unit (ECU).
[0029] Although the hydraulic control unit described above has been
described for a motor-vehicle braking system, to a person skilled
in the art it is also readily apparent that the hydraulic control
unit according to the invention can also be employed for other
purposes. For instance, a subassembly consisting of the cover, the
base, the spring-loaded corrugated bellows and/or the helical
spring can be inserted into an appropriately shaped recess or bore
in a casing, into which yet other components (e.g. valves or such
like) may also be integrated but do not have to be. In this case
the casing may be formed as a moulding made of metal or synthetic
material.
[0030] In this connection the space that is formed by the cover,
the corrugated bellows and the base may be either the reservoir for
the pressurised hydraulic fluid or the space for the pressureless
hydraulic fluid. This is dependent on the cabling and on the
incoming and outgoing lines.
[0031] Further modifications to, additions to and configurations of
the present invention will be elucidated on the basis of the
following description of the Figures.
[0032] FIG. 1 shows schematically the hydraulic circuit diagram of
the relevant part of a motor-vehicle braking system, in which the
hydraulic control unit according to the invention is employed.
[0033] FIG. 2 shows a first configuration of the hydraulic control
unit according to the invention in a schematic sectional view.
[0034] FIG. 3 shows a second configuration of a hydraulic control
unit according to the invention in a schematic sectional view.
[0035] FIG. 4 shows a third configuration of a hydraulic control
unit according to the invention in a schematic sectional view.
[0036] FIG. 5 shows a fourth configuration of a hydraulic control
unit according to the invention in a schematic sectional view.
[0037] FIG. 1 shows schematically an electronically controlled
hydraulic vehicle braking system. This vehicle braking system
comprises a brake pedal 10 which is coupled to a brake master
cylinder via an actuating rod 14. The brake master cylinder 12 is
connected to a pressureless reservoir 16 for hydraulic fluid. Two
electronically controlled valve arrangements 18 and 20 are
connected to the output of the brake master cylinder 12. The one
valve arrangement 20 establishes in its unactuated initial position
a connection to a braking device 22 pertaining to a wheel of the
vehicle. In its electronically controlled actuated position this
valve arrangement 20 blocks the connection between the brake master
cylinder 12 and the braking device 22.
[0038] Via the other valve arrangement 18, in the electronically
actuated position thereof, the brake master cylinder 12 is
connected to a cylinder/piston arrangement 24 for simulating the
behaviour of the brake pedal. In the unactuated initial position of
the valve arrangement 18 the connection between the brake master
cylinder 12 and the cylinder/piston arrangement 24 for simulating
the behaviour of the brake pedal is blocked. The actuating and
simulating unit 26 described above serves, in particular, for
so-called brake-by-wire vehicle braking systems such as are known
from DE 43 43 386 A1, for example. However, this arrangement has
the disadvantage that the feel of the brake pedal that is offered
to the driver and the behaviour of the brake pedal that can be
experienced by the driver only correspond inadequately to those
known from traditional vehicles. But since for the present
invention it is not primarily the actuating and simulating unit 26
that matters, the description of a characteristic-modelling device
has been dispensed with in the following.
[0039] The hydraulic control unit according to the invention
pertaining to the motor-vehicle braking system is the part in FIG.
1 bordered by a dot-and-dash line and provided with the reference
symbol 30.
[0040] The hydraulic control unit 30 contains a pump 32 delivering
hydraulic fluid under pressure, said pump being capable of being
controlled by an electronic control unit (not shown) and supplying,
in the brake-by-wire operating mode of the motor-vehicle system,
hydraulic fluid under pressure for the braking device 22. A first
reservoir 34 for pressureless hydraulic fluid is assigned to the
pump 32 on its input side 32a, and a second reservoir 36 for
hydraulic fluid under pressure is assigned to the pump 32 on its
output side 32b. The pump 32, the first and the second reservoirs
34, 36 are arranged in a common casing and form an integrated
electrohydraulic modular unit, as will be elucidated in detail
further below.
[0041] Between the pressureless reservoir 34 and the reservoir 36
for hydraulic fluid under pressure a pressure-controlled
pressure-relief valve 38 is arranged in parallel with the pump 32,
which at a predetermined first pressure level in the reservoir 36
under pressure establishes a fluid-conducting connection from the
reservoir 36 under pressure to the pressureless reservoir 34 and at
a predetermined second pressure level in the reservoir 36 under
pressure interrupts the fluid-conducting connection from the
reservoir 36 under pressure to the pressureless reservoir 34. A
check valve 40 is arranged on the output side 32b of the pump 32.
On the outlet side of the check valve 40 a valve arrangement 42
which is capable of being actuated electromagnetically is arranged
in the connecting line leading to the pressure-relief valve 38 and
to the second reservoir 36 for hydraulic fluid under pressure, said
valve arrangement being blocked in its unactuated initial position
and establishing in its actuated position the connection from the
pump 32 to the second reservoir 36.
[0042] From the output side of the check valve 40 a connecting line
leads to a 3-position control valve 50 with three connections which
is likewise capable of being actuated by the electronic control
unit (not shown). Depending on the position of the control valve
50, a so-called separating cylinder 52 which is connected in series
on the output side of said control valve is pressurised with
hydraulic fluid under pressure, or the hydraulic pressure contained
in the separating cylinder 52 is maintained or is vented into the
pressureless reservoir 34 via a separate line 54. By virtue of the
separating cylinder 52 a hydraulic decoupling is obtained between
the hydraulic pressure stemming from the hydraulic control unit 30
and the hydraulic pressure of the actuating and simulating unit
26.
[0043] For further details on the function of the vehicle braking
system that is shown in FIG. 1, reference is made to DE 196 16 538
A1.
[0044] FIG. 2 shows a first embodiment of the hydraulic control
unit according to the invention, in which the pump 32, the first
and the second reservoirs 34, 36 are integrated within a common
casing as an electrohydraulic modular unit. Visibly formed in a
metallic casing block 60 is a recess 62 in the form of a circular
cylinder which is sealed in fluid-tight manner by a cover 64. For
this purpose the cover 64 exhibits a flange 68 which engages the
recess 62 positively. In addition, the cover 64 is screwed to the
casing 60 with several screws 66. In addition, several O-ring seals
70a, 70b and 70c are arranged into [sic] appropriate grooves in the
cover. Welded to the side of the cover facing the recess 62 is a
corrugated bellows 72 made of steel which has a smaller diameter
than the recess 62, so that between the outside of the corrugated
bellows 72 and the cylindrical wall 76 of the recess 62 an outer
region is formed which, in the embodiment according to FIG. 2,
forms the second reservoir 36 for hydraulic fluid under pressure. A
base 78 is welded to the end of the corrugated bellows 72 that is
located opposite the cover 64, so that the inner region formed by
the cover 64, the corrugated bellows 72 and the base 78 forms the
first reservoir 34 for pressureless hydraulic fluid. For this
purpose a centrally arranged axial aperture 80 is provided in the
cover 64, which extends outwards from the region constituting the
first reservoir 34 and therefore connects the first reservoir 34 to
an overflow vessel 82 which is moulded onto the outside of the
cover. The overflow vessel 82 is formed by an annular ridge 82
which is integrally moulded onto the cover 64 and which is sealed
by a cowl 84 in which an aperture 86 leading to the atmosphere is
formed.
[0045] In the flange 68 of the cover 64 there is arranged a
radially extending second aperture 90 extending into the first
region constituting the pressureless reservoir 34, which connects
the pressureless reservoir 34 to the input side 32a of the pump 32.
In the region of the bottom of the recess 62 a third aperture 92
opens extending into the second reservoir 36 containing the
hydraulic fluid under pressure, which connects the second reservoir
36 to the output side 32b of the pump 32. Between the third
aperture 92 and the output side 32b of the pump 32 there are
arranged, in conformity with the hydraulic circuit diagram of FIG.
1, the reversing valve or the valve arrangement 42 and the check
valve 40. Said valve arrangement 42 is preferably also integrated
into the casing 60 in such a way that, for example, a valve member
which is controlled by an electromagnet 42b is capable of being
moved back and forth in a bore in the metal block constituting the
casing 60.
[0046] On the connecting line between the valve arrangement 42 and
the check valve 40 there is arranged a branch to the 3/3-way
control valve 50 (see also FIG. 1). This control valve 50 is also
integrated into the casing 60 so as to form a modular unit in the
same way as the valve arrangement 42.
[0047] In the base 78 a hydraulic-fluid line 102 is arranged
centrally between the pressureless reservoir 34 and the reservoir
36 under pressure. Located in the hydraulic-fluid line 102 is a
pressure-relief valve 38 constituted by a helical spring 106 which
is supported on an annular flange 108 and presses a spherical valve
element 110 against a valve seat 112. In this connection the
pressure-relief valve 38 is orientated in such a way that at a
predetermined first pressure level in the reservoir 36 under
pressure a fluid-conducting connection from the region 36 to the
pressureless reservoir 34 is established or is interrupted if this
pressure level is exceeded. Acting in parallel with the first part
of the spring arrangement in the form of the corrugated bellows 72,
a second part of the spring arrangement is provided in the form of
a helical spring 120 which assists the action of the corrugated
bellows 72. In the embodiment according to FIG. 2 the second part
of the spring arrangement is a helical spring 120 taking the form
of a compression spring which is clamped between the base 78 and
the cover 64.
[0048] By virtue of a rod-shaped stop member 122 which is arranged
inside the pressureless reservoir 34, coaxial with the helical
spring 120 and the corrugated bellows 72, the maximal expansion of
the reservoir 36 for hydraulic fluid under pressure is limited. If
the stop member 122 strikes the extension of the cover [sic] 78 in
which the pressure-relief valve 38 is located, the maximal
expansion of the reservoir 36 under pressure has been reached. When
the reservoir 36 is filled or pressurised with hydraulic fluid, the
corrugated bellows is compressed, so that the base 78 moves towards
the stop member 122. As a result, the distance by which the
corrugated bellows is compressed is proportional to the pressure
that has been supplied in the pressure chamber (reservoir 36). By
virtue of the proportionality of the pressure prevailing in the
pressure chamber to the distance of the base 78, this property can
be utilised for the purpose of recording the pressure in the
pressure chamber in simple and cost-effective manner by means of a
distance sensor, so that a costly pressure sensor which is used
conventionally can be eliminated.
[0049] FIG. 3 shows an alternative embodiment to FIG. 2, in which
the pressureless reservoir 34 is located outside the corrugated
bellows 72 and the reservoir 36 containing hydraulic fluid under
pressure is located inside the corrugated bellows 72. As a result,
when the second reservoir 36 is filled or pressurised, the
corrugated bellows 72 and the helical spring 120 are not compressed
in the longitudinal direction as in FIG. 2 but are expanded.
Therefore the pressure-limiting stop 122, the helical spring 120,
which may also serve for the purpose of setting the preloading
force, as well as the flow direction of the pressure-limiting valve
38 are also changed in comparison with FIG. 2. In other respects
the embodiments according to FIG. 2 and FIG. 3 are functionally
identical.
[0050] In a configuration of the hydraulic control unit such that
the actuating and simulating device 26 is also structurally
integrated within the same casing block, the reservoir 16 of the
actuating and simulating unit 26 may be identical with the
reservoir 34 of the hydraulic control unit 30. This brings about an
additional saving of space and weight.
[0051] The separately manageable assembly constituted by the cover
64, the corrugated bellows 72 and the base 78 (with the
pressure-relief valve 38), to which the helical spring 120 may also
be assigned in appropriate circumstances, is also suitable for the
structure of a hydraulic-accumulator battery in which one or more
recesses 62 are provided in a metal block, into which the assembly
described above is inserted. A decisive advantage in this case is
the minimal space requirement which results by virtue of the fact
that the pressureless region situated inside or outside the
corrugated bellows, depending on the embodiment, serves as a
reservoir for hydraulic fluid. For special applications it may not
even be necessary to provide, directly by the two reservoirs 34,
36, the pump 32 in the casing block in which the recesses 62 is
[sic] formed.
[0052] FIG. 4 shows an alternative embodiment to FIG. 2, in which
the pump 32, the first and the second reservoirs 34, 36 are again
integrated within a common casing as an electrohydraulic modular
unit.
[0053] In the metallic casing block 60 the recess 62 is formed
which is sealed in fluid-tight manner by the cover 64. For this
purpose the cover 64 exhibits the flange 68, in which two O-ring
seals 70a and 70b are arranged in appropriate grooves. Welded to
the flange 68 is the corrugated bellows 72 subdividing the recess
62 into the outer region, which forms the second reservoir 36, and
an inner region 124, which is filled with a gas. The base 78 is
welded to the end of the corrugated bellows 72 located opposite the
cover 64.
[0054] In the region of the bottom of the recess 62 the aperture 92
opens which extends into the second reservoir 36 and connects the
latter to the output side 32b of the pump 32. The valve arrangement
42 and the check valve 40 are arranged between the aperture 92 and
the output side 32b of the pump 32. The branch to the 3/3-way
control valve 50 is arranged on the connecting line between the
valve arrangement 42 and the check valve 40 (see also FIG. 2).
[0055] The first reservoir 34 is formed in the casing block 60 by
means of an overflow vessel. The pressureless reservoir 34 is
connected to the input side 32a of the pump 32.
[0056] In the hydraulic line 102 between the reservoir 36 or the
aperture 92 and the reservoir 34 the pressure-relief valve 38 is
arranged at a separate point in the casing block 62 [sic].
[0057] The gas in the region 124 acts, in the same way as the
helical spring 120 in FIG. 2, in parallel with the corrugated
bellows 72 and assists the action thereof. The maximal expansion of
the reservoir 36 is limited by the rod-shaped stop member 122
inside the region 124.
[0058] When the reservoir 36 is filled or pressurised with
hydraulic fluid, the corrugated bellows 72 and the gas included
within the region 124 are compressed, the distance by which the
corrugated bellows 72 is compressed being proportional to the
pressure that has been supplied in the reservoir 36.
[0059] FIG. 5 shows an alternative embodiment to FIG. 3, in which
the gas-filled region 124 is located outside the corrugated bellows
72 and the reservoir 36 is located inside the corrugated bellows
72. In this case the pressure-limiting stop 122 is changed in a
manner analogous to FIG. 3 and the pressure-limiting valve 38 is
changed in a manner analogous to FIG. 4. In other respects the
embodiments according to FIG. 4 and FIG. 5 are functionally
identical, whereby partial solutions of the embodiments--such as,
for example, the arrangement of the reservoir 34 in the region
124--are capable of being combined with one another.
* * * * *