Electrohydraulic actuator for brake system

Abstract

An electro-hydraulic actuator for a brake system, comprising: a housing (1) defining an inner space (10), the housing having a first opening (11) and a second opening (12); a master brake cylinder (2) positioned in the first opening, said master brake cylinder being attached at the housing so as to seal the first opening in a fluid-tight manner; an electric motor (4) arranged at the housing; the invention relates to a brake device (1) comprising a housing (2), a master brake cylinder (3) accommodated in the interior of the housing, and a transmission (3) which is movably coupled to the master brake cylinder, the transmission having a transmission intermediate part which can be moved along a longitudinal axis (L1) and which divides the housing relative to the longitudinal axis into a first housing region (13) and a second housing region (14), a master brake cylinder is arranged in the first housing region, and the second housing region faces the second opening. The actuator further comprises an equalization diaphragm which closes the second opening in a fluid-tight manner, said equalization diaphragm being elastically deformable in order to reduce a pressure difference between the first housing region and the second housing region upon axial displacement of the transmission intermediate part.

Description

Technical Field

[0001] The invention relates to an electrohydraulic actuator for a brake system, in particular a brake system of a vehicle. Background Art

[0002] Electrohydraulic brake boosters are generally used to boost the actuation force generated at the manual brake pedal by operating the master brake cylinder with the aid of an electric motor. Electrohydraulic brake boosters are also used as actuators in so-called "brake-by-wire" systems, where a control signal is generated by operating the brake pedal or otherwise, and an electrohydraulic actuator is operated based on the control signal to generate brake pressure.

[0003] DE 10 2013 213 888 B3 discloses a hydraulic actuator for a brake system having a master brake cylinder, an electric motor and a transmission mechanism, wherein the transmission mechanism couples the electric motor to the master brake cylinder in order to convert a movement of the motor into an actuation of the master brake cylinder. Here, the transmission mechanism is accommodated in a housing, wherein the master brake cylinder is positioned in an opening of the housing.

[0004] The advantages of such electrohydraulic actuators are, in particular, that they can bring about highly dynamic pressure changes in the brake system by means of rapid axial adjustment of the master brake cylinder via the transmission. However, in a housing which is usually sealed in a fluid-tight manner relative to the environment, rapid movements of components within the housing can sometimes lead to significant pressure differences between different areas of the housing, since pressure equalization within the housing is usually impeded by transmission components. Summary of the invention

[0005] Against this background, according to the invention an electrohydraulic actuator is provided having the features of claim 1 .

[0006] The electronic hydraulic actuator for a brake system according to the present invention comprises: a housing defining an inner space, the housing having a first opening and a second opening; a master brake cylinder positioned in the first opening, the master brake cylinder being attached to the housing so as to seal the first opening in a fluid-tight manner; an electric motor arranged at the housing; a transmission mechanism accommodated in the inner space of the housing, the transmission mechanism being movably coupled to the master brake cylinder, wherein the transmission mechanism has a transmission mechanism intermediate component movable along the longitudinal axis, the transmission mechanism intermediate component dividing the housing into a first housing area and a second housing area relative to the longitudinal axis, the master brake cylinder being arranged in the first housing area and the second housing area facing the second opening. The actuator further comprises a balancing diaphragm closing the second opening in a fluid-tight manner, in particular liquid-tight or preferably also air-tight manner, the balancing diaphragm being elastically deformable so as to reduce the pressure difference between the first housing area and the second housing area when the transmission mechanism intermediate component is axially displaced.

[0007] The invention is based on the idea of ​​reducing the pressure difference in the housing caused by the rapid movement of at least a part of the transmission mechanism in the housing by arranging an elastically deformable membrane in the opening of the housing. Due to the pressure changes in the housing, the membrane changes its deformation state and in this way increases or reduces the effective volume of the corresponding housing area.

[0008] The master brake cylinder can be operated by an electric motor via a transmission mechanism. In particular, the transmission mechanism has a component that can be displaced along the longitudinal axis, which operates the master brake cylinder in the following manner, for example, by axially displacing the master brake cylinder. The transmission mechanism usually has a transmission mechanism intermediate component, which divides the housing into a first area and a second area relative to the longitudinal axis. The first area and the second area are connected to each other in a fluid-conducting manner, for example, via a gap between the housing and the transmission mechanism intermediate component. In the case of rapid movement of the transmission mechanism intermediate component, the passage defined between the transmission mechanism intermediate component and the housing and between the first and second housing areas forms a significant flow resistance, so that a pressure difference is established between the first area and the second area. According to the invention, this pressure difference is advantageously reduced by means of a diaphragm.

[0009] The invention has the advantage that the equalizing diaphragm reduces the pressure difference in the housing. This simplifies the dynamic operation of the actuator. Furthermore, by reducing the pressure difference between the first housing area and the second housing area, the force expenditure for actuating the master brake cylinder can also be reduced, which has a positive effect on the energy consumption and dynamic behavior of the actuator. Furthermore, the equalizing diaphragm offers a cost-effective option for closing the housing in a fluid-tight manner and still simplifying the pressure equalization between the housing areas.

[0010] Advantageous embodiments and developments emerge from the further dependent claims and from the description with reference to the drawings.

[0011] According to some embodiments, the balancing diaphragm can have a flange section and a curved section, the flange section abutting the housing in the region of the second opening, the curved section protruding from the housing. The flange section can, for example, at least partially abut the inner circumferential surface of the second opening. The second opening can usually be particularly conical or truncated cone-shaped, but is not limited thereto. For example, a spherical camber or the like can also be provided. Since the curved section protrudes from the outside of the housing, structural space conflicts with components located in the interior space of the housing are advantageously avoided. In addition, the possible volume changes in the second housing region are increased in this way.

[0012] According to some embodiments, it can be provided that the balancing diaphragm is made of a plastic material, in particular a rubber material, for example, ethylene propylene diene monomer rubber, EPDM for short.

[0013] According to some embodiments, it can be provided that the balancing diaphragm is designed as a closed body. Therefore, the balancing diaphragm alone or only closes the second opening. In particular, the balancing diaphragm can be designed without a through opening that connects the interior space of the housing to the environment. Therefore, the balancing diaphragm has only the following purpose: to increase or reduce the volume of the second housing area by its elastic deformation caused by pressure changes, so as to reduce the pressure difference between the housing areas.

[0014] According to some embodiments, it can be provided that the transmission has an operating part movable along the longitudinal axis and a guide part, the operating part being movably coupled to the master brake cylinder, and the guide part being coupled to the operating part and guided along the longitudinal axis, wherein the guide part forms a transmission intermediate part.

[0015] According to some embodiments, it can be provided that the operating part is designed as a threaded spindle, wherein the transmission mechanism has a spindle nut and an input shaft, the spindle nut is engaged with the threaded spindle, and the input shaft can be driven by an electric motor and is engaged with the spindle nut to rotate the input shaft around the longitudinal axis. In this way, a space-saving structure of the transmission mechanism is achieved.

[0016] According to some embodiments, it can be provided that the guide element is coupled to the threaded spindle in a rotationally fixed manner. Thus, the guide element prevents the spindle from rotating together with the spindle nut due to its guidance along the longitudinal axis.

[0017] According to some embodiments, it can be provided that the threaded mandrel can be moved to at least one axial position in which the threaded mandrel protrudes through the second opening. The first opening and the second opening can be arranged coaxially with each other, for example, along the longitudinal axis. The threaded mandrel can be displaced along the longitudinal axis, for example, it can move forward and backward in order to move the piston of the master brake cylinder. Here, the mandrel can also be moved to a position in which the mandrel protrudes through the second opening. In this case, it is particularly advantageous if the balancing diaphragm has a flange section and a bent section as described above, because the mandrel can thus extend into the space delimited by the bent section. Therefore, the balancing diaphragm can additionally contribute to achieving a more compact structure of the housing relative to the longitudinal axis.

[0018] According to some embodiments, it can be provided that the guide component is designed as a disk, which has at least one first guide element, in particular a projection, at its outer circumference, which engages with a second guide element, in particular a guide groove of the housing, extending parallel to the longitudinal axis. The second guide element, for example in the form of a groove, can be formed in particular in the housing.

[0019] According to some embodiments, it can be provided that the actuator can have an electrical interface for signal connection to the electric motor, the electrical interface being used to connect the electric motor to a voltage source and / or for receiving control signals for operating the electric motor, wherein the actuator can be operated solely via the signals received at the interface, in particular without mechanically replacing the control interface. Thus, the actuator can be designed for exclusive "wire control" operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is explained below with reference to the accompanying drawings, wherein:

[0021] Figure 1 A perspective cross-sectional view showing an electronic hydraulic actuator according to an embodiment of the present invention;

[0022] Figure 2 Show Figure 1 A side view of a cross-sectional view of the actuator shown in ;

[0023] Figure 3 Show Figure 1 A top view of a first opening of the actuator shown in , wherein the master brake cylinder is omitted;

[0024] Figure 4 Show Figure 1 A perspective view of the balanced diaphragm of the actuator shown in FIG.

[0025] In the figures, unless otherwise indicated, the same reference signs denote identical or functionally identical components. DETAILED DESCRIPTION

[0026] Figure 1 By way of example, an electrohydraulic actuator 100 is shown for a brake system, for example for a brake system of a motor vehicle. Figure 2 Show Figure 1 Side view of the actuator in FIG. Figure 1 and Figure 2 As shown in FIG. 1 , the actuator 100 includes a housing 1 , a master brake cylinder 2 , a transmission mechanism 3 , an electric motor 4 and a compensating diaphragm 5 .

[0027] The housing 1 generally defines an interior space 10. For example, the housing 1 may have a plurality of walls 1A which delimit the interior space 10. The housing 1 has in particular a first opening 11 and a second opening 12. The openings 11, 12 form a connection of the interior space 10 to the surroundings. The openings 11, 12 may, for example, have a circular circumference, as in Figure 3 For example, this can be seen for the first opening 11. However, in principle, other circumferential shapes of the openings 11, 12 are also conceivable. Figure 1 and Figure 2By way of example, the first opening 11 and the second opening 12 can be arranged opposite to each other. In particular, the first opening 11 and the second opening 12 can be arranged coaxially with each other. For example, the first opening 11 and the second opening 12 can be arranged coaxially with the longitudinal axis L1. The housing 1 can be a cast housing, for example, made of a metal material or a plastic material.

[0028] The master brake cylinder 2 is designed to convey hydraulic fluid to hydraulic consumers, such as wheel brake cylinders, and away from them in order to build up and reduce hydraulic pressure. For this purpose, the master brake cylinder 2 can in particular have a cylinder 20 in which at least one piston 21 is supported in an axially displaceable manner. Figure 1 and Figure 2 , a tandem master brake cylinder 2 with a directly actuatable first piston 21A and a floating piston 21B is shown purely by way of example.

[0029] like Figure 1 and Figure 2 It is also shown that the master brake cylinder 2 is positioned in the first opening 11 of the housing 1. In particular, the master brake cylinder 2 projects through the first opening 11 into the interior 10 of the housing 1. The master brake cylinder 2, in particular one or more pistons 21, is preferably positioned coaxially with respect to the longitudinal axis L1. The cylinder 20 of the master brake cylinder 2 is arranged in a fixed position on the housing 1, in particular fixed to the housing 1, for example screwed to the housing. For example, a flange 22 can be formed on the cylinder 20, which is centered in the first opening 11 and completely covers the first opening, as in Figure 1 and 2 A sealing element (not shown) may provide additional sealing of the first opening 11. Typically, the master brake cylinder 2 is attached to the housing 1 in such a way that the first opening 11 is sealed in a fluid-tight manner.

[0030] Electric motor 4 Figure 1 and Figure 2 The electric motor 4 is only shown in simplified form and can be arranged, for example, on the outside of the housing 1 and fastened to the housing 1. In this case, the electric motor 4 can be oriented in particular such that the axis of rotation A4, about which the drive shaft of the motor 4 rotates, extends transversely or perpendicularly to the longitudinal axis L1.

[0031] The transmission mechanism 3 movably couples the master brake cylinder 2 to the electric motor 4, in particular, such that a rotation of the motor 4 causes a piston 21 or a plurality of pistons 21A, 21B of the master brake cylinder 2 to move along the longitudinal axis L1. Figure 1 and Figure 2 As shown, the transmission mechanism 3 is accommodated in the inner space 10 of the housing 1. Figure 1 and Figure 2: The transmission mechanism 3 may include an operating member 30 and a guide member 31. Generally, the operating member 30 is movably coupled to the piston 21, in particular the piston 21A of the master brake cylinder 21, for example, via a connecting rod 35, and may be moved along the longitudinal axis L1 by the electric motor 4. The guide member 31 is connected to or coupled to the operating member 30 and guided along the longitudinal axis L1, for example, guided at the housing 1.

[0032] exist Figure 1 and Figure 2 The transmission mechanism 3 is shown by way of example in the figure, wherein the operating part 30 is designed as a threaded spindle 30A having an external thread 30B, and the guide part 31 is designed as a disk 31A guided on the housing 1. Figure 1 and Figure 2 The transmission mechanism 3 shown in the example has a spindle nut 32 with an internal thread 32B, which engages with an external thread 30B of a threaded spindle 30A, and an input shaft 33. The spindle nut 32 is rotatably supported in the housing 1 around the longitudinal axis L1, for example, by a roller bearing 34, as shown in Figure 1 and Figure 2 In addition, the input shaft 33 can be designed as a worm shaft, for example, which engages with an external toothed portion (not shown) of the spindle nut 32. The input shaft 33 can be directly connected to a drive shaft (not shown) of the electric motor 4, for example.

[0033] Here, the guide element 31 or the disk 31A is coupled to the threaded spindle 30A in a rotationally fixed manner, thereby forming an anti-twist device for the threaded spindle 30A. Figure 3 As shown in FIG. 1 , the disk 31A may have at least one first guide element 31B at its outer circumference. Figure 3 The first guide element is designed as a projection, for example, and engages with a second guide element 1B extending parallel to the longitudinal axis L1. Figure 3 It is shown here by way of example that the second guide element 1B can be designed as a guide groove of the housing 1 which extends parallel to the longitudinal axis L1 .

[0034] Thus, by turning the spindle nut 32 by means of the input shaft 33 driven by the electric motor 4, the threaded spindle 30A together with the disk 31A is displaced along the longitudinal axis L1, so that the threaded spindle 30A moves the piston 21A, which in turn causes the displacement of the floating piston 21B by the squeezing of the hydraulic fluid. Figure 1 and Figure 2 , the following position of the threaded spindle 30A is shown by way of example, in which the threaded spindle is in the maximum retracted position. This means that the pistons 21A, 21B of the master brake cylinder 21 are in the starting position and can move along the longitudinal axis L1 to build up pressure. Figure 1 and Figure 2, the threaded spindle 30A can, for example, protrude through the second opening 12 of the housing 1 in this position. Generally, the threaded spindle 30A can be moved to at least one axial position in which the threaded spindle 30A protrudes through the second opening 12.

[0035] In general, the master brake cylinder 2 can be operated by moving the operating part 30 along the longitudinal axis L1 by means of the electric motor 4. In this case, the guide member 31 moves accordingly. In this case, the guide member 31 forms a transmission intermediate part, which divides the housing 1 relative to the longitudinal axis L1 into a first housing area 13 and a second housing area 14, in which the master brake cylinder 2 is arranged, and the second housing area faces the second opening 12. Figure 1 and Figure 2 In the actuator 100 exemplarily shown in FIG. 1 , in particular the spindle nut 32 and the bearing 34 as well as the spindle 30A are arranged in the second housing region 14 .

[0036] like Figure 1 As symbolically indicated by a rectangle in the figure, the actuator 100 can have an electrical interface 6 which is connected to the electric motor 4 signal. The interface 6 can be designed to electrically connect the electric motor 4 to a voltage source and / or to receive control signals for operating the electric motor 4. For example, the interface 6 can be designed as a socket with connecting contacts. Optionally, it can be provided that the electric motor 4 and thus the actuator 100 can be operated only via the signals received at the interface 6. Figure 1 and Figure 2 As shown, a mechanical coupling between the transmission mechanism 3 and a pedal or the like can be omitted. Therefore, the actuator 100 can generally be designed for dedicated "wire control" operation.

[0037] exist Figure 4 The balancing diaphragm 5 is shown in a stereoscopic diagram as an example. Generally, the balancing diaphragm 5 is formed of an elastically deformable but airtight material, in particular a plastic material. For example, the balancing diaphragm 5 can be formed of a plastic material, in particular a rubber material, such as ethylene propylene diene monomer rubber, referred to as EPDM. Generally, the balancing diaphragm 5 is designed as a planar body. Figure 4 As shown in the figure by way of example, the balancing membrane 5 can have, for example, a flange section 51 and a bent section 52. The flange section 51 is designed for attachment in and / or at the second opening 12 of the housing 1.

[0038] like Figure 4 As shown in the example, the flange section 51 may have, for example, a base or frame section 51A adapted to the inner circumference of the second opening 12, the base or frame section being Figure 4In the embodiment of the present invention, the flange section 51 is annularly configured according to the circular implementation of the second opening 12. Alternatively or additionally, the flange section 51 has a bead 51B, which is designed to abut against the area of ​​the housing 1 around the second opening 12. For example, the bead 51B can protrude radially from the base section 51A, such as Figure 4 It is shown as an example in FIG.

[0039] The bent section 52 extends from the flange section 51 and defines an open inner space or receiving space 53. Figure 4 As shown in the example, the curved section 52 may have a truncated cone shape, for example. However, the present invention is not limited thereto, and other curved shapes, such as a spherical shape, etc., are also conceivable.

[0040] like Figure 1 and Figure 2 As shown, the equalizing diaphragm 5 closes the second opening 12 of the housing 1, more precisely in a fluid-tight manner. Figure 2 As shown, the balancing diaphragm 5 can be partially introduced into the second opening 12. In particular, the base section 51A can be pressed against the inner circumferential surface 12 of the second opening 12, and the bead 51B is pressed against the area of ​​the housing 1 around the second opening 12. Therefore, the flange section 51 is pressed against the housing 1 in the area of ​​the second opening 12, and the bent section 52 protrudes from the housing 1. Figure 1 and Figure 2 , the operating part 30 (here, for example, the threaded mandrel 30A) can, for example, extend into the receiving space 53 defined by the bent section 52 of the diaphragm 5. The balancing diaphragm 5 can, for example, be connected to the housing 1 in a materially bonded manner, for example, by gluing it thereto. Alternatively, the balancing diaphragm 5 can also be mechanically fastened to the housing 1, for example, via a clamping ring (not shown), which clamps the flange 51B of the flange section 51 between itself and the housing 1.

[0041] like Figure 1 , Figure 3 and Figure 4 As shown in , the equalizing membrane 5 can be designed as a closed body, in particular without through-openings, such as in the curved section 52. Therefore, the equalizing membrane 5 is preferably not provided for passing components through it and acts as a kind of cuff, but is used to change the effective internal volume of the housing 10, as will be explained in detail below.

[0042] The equalizing diaphragm 5 closes the second opening 12 of the housing 1 in a fluid-tight manner. In the same way, the first opening 11 of the housing 1 is closed in a fluid-tight manner by the master brake cylinder 2. The interior 10 of the housing 1 is therefore essentially sealed in a fluid-tight manner, and the actuator 100, in particular its housing 1, can thus be regarded as immersion-tight. Figure 1 and2 The guide part 31 or the disk 31A in the example divides the interior space 10 of the housing 10 into a first housing area 13 and a second housing area 14, as described above. If the operating part 30 or the spindle 30A is moved rapidly along the longitudinal axis L1, for example in order to achieve a dynamic pressure increase or pressure reduction with the aid of the master brake cylinder 2, the transmission intermediate part expels the air in the interior space 10 of the housing 1 that is located in front of the transmission intermediate part with respect to the movement direction. There is only a narrow gap S between the transmission intermediate part and the inner surface of the housing 1, through which air exchange can take place between the first housing area 13 and the second housing area 14. Figure 1 and Figure 2 In the example of FIG. 3 , the bearing 34 and the spindle nut 32 additionally inhibit the gas exchange. Figure 2 A possible flow path F between the first housing region 13 and the second housing region 14 is shown symbolically in FIG.

[0043] Therefore, a rapid displacement of the transmission intermediate part along the longitudinal axis L1 causes an unstable pressure increase in one of the housing regions 13, 14 and an unstable pressure reduction in the respective other of the housing regions 13, 14. As a result, a pressure difference is generated between the housing regions 13, 14, which is reduced only slowly, for example, via the flow path F. The equalizing diaphragm 5 advantageously reduces the increased pressure difference due to its elastic deformability. If the transmission intermediate part (here, therefore, the disk 31A) is moved together with the spindle 30A, for example, in the direction of the second opening 12, this causes an increase in pressure in the first housing region 13 and a decrease in pressure in the second housing region 14. The reduced pressure in the second housing region 14 causes the equalizing diaphragm 5 to deform, so that the deformation reduces the effective volume of the interior space 10 or so that the effective volume of the second housing region 14 remains essentially unchanged. Figuratively speaking, the deformation of the diaphragm 5 follows the displacement of the transmission intermediate part. In this way, the pressure difference between the first housing region 13 and the second housing region 14 is reduced during the axial displacement of the transmission intermediate part.

[0044] Although the present invention has been exemplarily explained above based on the embodiments, the present invention is not limited thereto but can be modified in various ways. In particular, combinations of the above embodiments are also conceivable.

Claims

1. An electronic hydraulic actuator (100) for a brake system, the actuator comprising: A housing (1) defining an interior space (10), the housing having a first opening (11) and a second opening (12); a master brake cylinder (2) positioned in the first opening (11), the master brake cylinder being attached to the housing (1) in such a way that the first opening (11) is sealed in a fluid-tight manner; an electric motor (4) arranged at the housing (1); a transmission mechanism (3) accommodated in the interior space (10) of the housing (1), the transmission mechanism being movably coupled to the master brake cylinder (2), wherein the transmission mechanism (3) has a transmission mechanism intermediate component that can be moved along the longitudinal axis (L1), the transmission mechanism intermediate component dividing the housing (1) relative to the longitudinal axis (L1) into a first housing area (13) and a second housing area (14), the master brake cylinder (2) being arranged in the first housing area, the second housing area facing the second opening (12); and A compensating diaphragm (5) closes the second opening (12) in a fluid-tight manner and is elastically deformable in order to reduce the pressure difference between the first housing area (13) and the second housing area (14) during axial displacement of the transmission intermediate component.

2. An actuator (100) according to claim 1, wherein the balancing diaphragm (5) has a flange section (51) and a bent section (52), wherein the flange section abuts against the housing (1) in the area of ​​the second opening (12) and the bent section protrudes from the housing (1).

3. The actuator (100) according to claim 1 or 2, wherein the balancing diaphragm (5) is made of a plastic material, in particular a rubber material, such as EPDM rubber.

4. The actuator (100) according to any of the preceding claims, wherein the equalizing diaphragm (5) is designed as a closed body, in particular without a through opening connecting the interior space (10) of the housing (1) to the environment.

5. An actuator (100) according to any one of the preceding claims, wherein the transmission mechanism (3) has an operating part (30) and a guide part (31) that can be moved along the longitudinal axis (L1), the operating part is movably coupled to the master brake cylinder (2), the guide part is coupled to the operating part (30) and guided along the longitudinal axis (L1), wherein the guide part (31) forms an intermediate part of the transmission mechanism.

6. An actuator (100) according to claim 5, wherein the operating part (30) is designed as a threaded spindle (30A), wherein the transmission mechanism (3) has a spindle nut (32) and an input shaft (33), the spindle nut is engaged with the threaded spindle (30A), and the input shaft can be driven by an electric motor (4) and engaged with the spindle nut (32) so as to rotate the input shaft around the longitudinal axis (L1).

7. The actuator (100) according to claim 6, wherein the guide member (31) is coupled to the threaded spindle (30A) in a rotationally fixed manner.

8. The actuator (100) according to claim 6 or 7, wherein the threaded spindle (30A) is movable to at least one axial position in which the threaded spindle protrudes through the second opening (12).

9. An actuator (100) according to any one of claims 5 to 8, wherein the guide component (31) is designed as a disk (31A), which has at least one first guide element (31B), in particular a protrusion, on its outer circumference, and the first guide element is engaged with a second guide element (1B) extending parallel to the longitudinal axis (L1), in particular a guide groove of the housing (1).

10. The actuator (100) according to any one of the preceding claims, additionally comprising: An electrical interface (6) connected to the electric motor (4) signal, the electrical interface being used to connect the electric motor (4) to a voltage source and / or to receive control signals for operating the electric motor (4), wherein the actuator (100) is operable solely via the signals received at the interface (6), in particular without a mechanically replaced operating interface.

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