Electrohydraulic actuator for braking systems

Abstract

The electrohydraulic actuator (100) for a braking system comprises a housing (1) defining an interior space (10) with a first opening (11) and a second opening (12), a brake master cylinder (2) positioned in the first opening and mounted in the housing such that the first opening is sealed fluid-tight, an electric motor (4) arranged in the housing, and a transmission (3) received in the interior space of the housing and kinematically connected to the brake master cylinder, the transmission having a transmission intermediate member movable along a longitudinal axis (L1) such that the housing is divided, with respect to the longitudinal axis, into a first housing area (13) in which the brake master cylinder is arranged and a second housing area (14) on the side of the second opening. The actuator further includes an elastically deformable compensating diaphragm (5) for fluid-tightly closing the second opening and reducing the pressure difference between the first housing area and the second housing area when the transmission intermediate member is axially displaced.

Description

[Technical field]

[0001] The present invention relates to an electrohydraulic actuator for a braking system, in particular for a vehicle braking system. [Background technology]

[0002] An electrohydraulic brake booster is usually used to amplify the brake pedal operation force applied manually by operating a brake master cylinder with an electric motor. In a so-called "Brake-by-Wire" system in which an operating signal is generated by operating the brake pedal or by other means, and an electrohydraulic actuator is operated based on this operating signal to generate brake pressure, the electrohydraulic brake booster is also used as an actuator.

[0003] US Patent No. 5,399,633 discloses a hydraulic actuator for a braking system including a brake master cylinder, an electric motor, and a transmission that connects the electric motor with the brake master cylinder to convert the motion of the electric motor into the operation of the brake master cylinder, where the transmission is received in a housing, with the brake master cylinder being positioned in an opening in the housing.

[0004] The advantage of electrohydraulic actuators of this kind is, inter alia, that they can induce highly dynamic pressure changes in the brake system via the transmission by means of fast axial displacements of the brake master cylinder. However, because components of the transmission frequently prevent pressure equilibrium within the housing, within the housing which is usually sealed fluid-tight against the environment, the fast movements of components within the housing can temporarily result in considerable pressure differences between different areas of the housing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent No. 102013213888 Summary of the Invention

[0006] Against this background, according to the invention an electrohydraulic actuator is provided which comprises the features of claim 1.

[0007] The electrohydraulic actuator for a braking system according to the invention comprises a housing defining an interior space with a first opening and a second opening, a brake master cylinder positioned in the first opening and mounted in the housing such that the first opening is sealed in a fluid-tight manner, an electric motor arranged in the housing, and a transmission received in the interior space of the housing and kinematically connected to the brake master cylinder, the transmission having a transmission intermediate member movable along a longitudinal axis and dividing the housing, relative to the longitudinal axis, into a first housing area in which the brake master cylinder is arranged and a second housing area on the side of the second opening. Furthermore, the actuator comprises an elastically deformable compensation diaphragm for closing the second opening in a fluid-tight, in particular liquid-tight and preferably also gas-tight manner, and for reducing the pressure difference between the first housing area and the second housing area when the transmission intermediate member is displaced in the axial direction.

[0008] The idea behind the invention is to reduce the pressure difference inside the housing resulting from the high speed movement of at least one part of the transmission inside the housing by arranging an elastically deformable diaphragm in the opening of the housing, the diaphragm changing its deformation state due to the pressure change inside the housing and thus increasing or decreasing the effective volume of the respective housing area.

[0009] The brake master cylinder can be actuated by an electric motor via a transmission. In particular, the transmission has a part displaceable along a longitudinal axis, by means of which the brake master cylinder is actuated, for example by axial displacement of a piston of the brake master cylinder. The transmission generally has a transmission intermediate part dividing the housing into a first area and a second area with respect to the longitudinal axis. The first area and the second area are connected to one another in a fluid-conducting manner, for example by a slot between the housing and the transmission intermediate part. These penetrations between the first and second housing areas, which are determined between the transmission intermediate part and the housing, form a considerable flow resistance during high-speed movements of the transmission intermediate part, so that a pressure difference occurs between the first and second areas. According to the invention, this pressure difference is advantageously reduced by means of a diaphragm.

[0010] The advantage of the present invention is that the compensating diaphragm reduces the pressure difference inside the housing, which facilitates dynamic operation of the actuator. Furthermore, due to the reduced pressure difference between the first and second housing regions, the power costs for operating the brake master cylinder can also be reduced, which has a positive effect in terms of energy consumption and dynamic behavior of the actuator. Furthermore, the compensating diaphragm offers a cost-effective possibility to close the housing fluid-tight and still facilitate pressure compensation between the housing regions.

[0011] Advantageous and further configurations are evident from the further dependent claims and the description with reference to several figures of the drawing.

[0012] According to various embodiments, it may be provided that the compensating diaphragm has a flange portion abutting against the housing in the region of the second opening and an arched portion protruding from the housing. The flange portion may, for example, at least partially abut against the inner circumferential surface of the second opening. The second opening may generally be formed, in particular circular. The arched portion may, in particular, be formed conically or truncated conically, but without being limited thereto. For example, a spherical arch or the like may be provided. The arched portion protrudes from the outer surface of the housing, so that construction space collisions with components located in the inner space of the housing are advantageously avoided. Furthermore, the possible volumetric changes of the second housing region are thus enlarged.

[0013] According to various embodiments, it may be provided that the compensating diaphragm is made of a synthetic material, in particular a rubber material, such as ethylene propylene diene rubber (abbreviated EPDM).

[0014] In many embodiments, it may be provided that the compensating diaphragm is formed as a closing body. Therefore, only the compensating diaphragm closes the second opening. In particular, the compensating diaphragm may be formed without a through hole that communicates the inner space of the housing with the surroundings. The compensating diaphragm therefore has the sole purpose of reducing the pressure difference between the housing regions by increasing or decreasing the volume of the second housing region by its elastic deformation due to pressure changes.

[0015] In many embodiments, it may be considered that the transmission has an operating member that is movable along a longitudinal axis and kinematically connected to the brake master cylinder, and a guide member that is connected to the operating member and guided along the longitudinal axis, in which case the guide member forms a transmission intermediate member.

[0016] In many embodiments, it may be provided that the operating member is formed as a threaded spindle, in which case the transmission has a spindle nut engaged with the threaded spindle and an input shaft that can be driven by an electric motor and is engaged with the spindle nut in order to rotate the spindle nut about its longitudinal axis. In this way, a space-saving design of the transmission is achieved.

[0017] According to various embodiments, it can be provided that the guide element is connected to the threaded spindle in a non-rotatable manner, and thus prevents the spindle from rotating together with the spindle nut due to its guidance along the longitudinal axis.

[0018] According to many embodiments, it may be provided that the threaded spindle is movable to at least one axial position, in which the threaded spindle projects through the second opening. The first opening and the second opening may, for example, be arranged coaxially with one another along the longitudinal axis. The threaded spindle is displaceable along the longitudinal axis, for example, forward and backward, in order to move the piston of the brake master cylinder. In this case, the spindle can also travel to a position in which it projects through the second opening. In this case, it is particularly advantageous if the compensating diaphragm, as described above, has a flange portion and an arched portion, since this allows the spindle to project into the space defined by the arched portion. In this way, the compensating diaphragm can also contribute to realizing a more compact construction of the housing with respect to the longitudinal axis.

[0019] According to various embodiments, it may be provided that the guide element is formed as a disk, which has at least one first guide element, in particular a projection, on its outer periphery, which engages with a second guide element running parallel to the longitudinal axis, in particular a guide groove in the housing. The second guide element, for example in the form of a groove, may in particular be formed in the housing.

[0020] According to many embodiments, the actuator has an electrical interface in signal communication with the electric motor for connecting the electric motor to a voltage source and / or for receiving control signals for operating the electric motor, in which case it may be considered that the actuator can be operated exclusively via signals received at the interface, in particular without a mechanical alternative operating interface, and thus the actuator may be designed exclusively for "by wire" operation.

[0021] The invention will now be described with reference to the several figures of the drawing. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional perspective view of an electrohydraulic actuator according to one embodiment of the present invention. [Diagram 2] 2 is a side cross-sectional view of the actuator shown in FIG. 1. [Diagram 3] 2 is a plan view of a first opening of the actuator shown in FIG. 1, with the brake master cylinder omitted. [Figure 4] FIG. 2 is a perspective view of a compensating diaphragm of the actuator shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the drawings, unless otherwise stated, like reference numbers indicate identical or functionally similar elements.

[0024] Fig. 1 illustrates an electrohydraulic actuator 100 for a braking system, for example for an automotive braking system. Fig. 2 shows a side view of the actuator of Fig. 1. As shown in Figs. 1 and 2, the actuator 100 includes a housing 1, a brake master cylinder 2, a transmission 3, an electric motor 4, and a compensation diaphragm 5.

[0025] The housing 1 generally defines an interior space 10. For example, the housing 1 may have a number of walls 1A that define the interior space 10. The housing 1 in particular has a first opening 11 and a second opening 12. The openings 11, 12 form the connection of the interior space 10 to the surroundings. The openings 11, 12 may have, for example, a circular periphery, as can be seen for the first opening 11 in FIG. 3. Basically, however, other periphery shapes for the openings 11, 12 are also conceivable. As illustrated in FIGS. 1 and 2, the first and second openings 11, 12 may be arranged opposite one another. In particular, the first and second openings 11, 12 may be arranged coaxially to one another. For example, the first and second openings 11, 12 may be arranged coaxially to a longitudinal axis L1. The housing 1 may in particular be a cast housing made of a metallic or synthetic material.

[0026] The brake master cylinder 2 is designed to transfer hydraulic fluid to and from hydraulic consumers, such as wheel brake cylinders, thereby boosting and reducing the hydraulic pressure. For this purpose, the brake master cylinder 2 may in particular have a cylinder 20, in which at least one piston 21 is supported so as to be axially displaceable. In Figures 1 and 2, a tandem brake master cylinder 2 with a directly actuable first piston 21A and a floating piston 21B is shown purely by way of example.

[0027] As further shown in Fig. 1 and Fig. 2, the brake master cylinder 2 is positioned in a first opening 11 of the housing 1. In particular, the brake master cylinder 2 projects through the first opening 11 into the interior space 10 of the housing 1. In this case, the brake master cylinder 2, in particular the piston 21, is preferably positioned coaxially with respect to a longitudinal axis L1. A cylinder 20 of the brake master cylinder 2 is fixedly arranged in the housing 1, in particular fixed thereto, for example screwed thereto. For example, the cylinder 20 may be formed with a flange 22, which is centered and completely covers the first opening 11, as illustrated in Fig. 1 and Fig. 2. A sealing element (not shown) may serve for additional sealing of the first opening 11. In general, the brake master cylinder 2 is mounted in the housing 1 in such a way that it seals the first opening 11 fluid-tight.

[0028] 1 and 2, the electric motor 4 can be arranged, for example, on the outside of the housing 1 and fixed thereto. The electric motor 4 can in particular be oriented in such a way that the axis of rotation A4, about which the drive shaft of the electric motor 4 rotates, extends transversely or perpendicularly to the longitudinal axis L1.

[0029] The transmission 3 kinematically connects the brake master cylinder 2 to the electric motor 4, in particular in such a way that the rotation of the electric motor 4 causes the movement of the piston 21 or the pistons 21A, 21B of the brake master cylinder 2 along a longitudinal axis L1. As shown in FIGS. 1 and 2, the transmission 3 is accommodated in the interior space 10 of the housing 1. As illustrated in FIGS. 1 and 2, the transmission 3 may have an operating member 30 and a guide member 31. In general, the operating member 30 is kinematically connected to the piston 21 of the brake master cylinder 21, in particular to the piston 21A, for example via a connecting rod 35 and is movable along the longitudinal axis L1 by the electric motor 4. The guide member 31 is connected to or coupled with the operating member 30 and is guided, for example in the housing 1, along the longitudinal axis L1.

[0030] 1 and 2 show, purely by way of example, a transmission 3 in which the operating member 30 is embodied as a threaded spindle 30A with an external thread 30B and the guide member 31 is embodied as a disk 31A guided in the housing 1. Furthermore, the transmission 3 illustrated in FIGS. 1 and 2 has a spindle nut 32 with an internal thread 32B which engages with the external thread 30B of the threaded spindle 30A, and an input shaft 33. The spindle nut 32 is supported in the housing 1 so as to be rotatable about a longitudinal axis L1, for example by means of a rolling bearing 34, as illustrated in FIGS. 1 and 2. Furthermore, the input shaft 33 can be configured, for example, as a worm shaft which engages with an external toothing (not shown) of the spindle nut 32. The input shaft 33 can be directly connected, for example, to a drive shaft (not shown) of the electric motor 4.

[0031] In this case, the guide element 31 or the disk 31A is connected to the threaded spindle 30A in a non-rotatable manner and thus forms a torsion protection for the threaded spindle 30A. As illustrated in Fig. 3, the disk 31A can have at least one first guide element 31B on its outer periphery, which is embodied as a projection which engages with a second guide element 1B, which, as shown purely by way of example in Fig. 3, runs parallel to the longitudinal axis L1. Fig. 3 shows, purely by way of example, that the second guide element 1B can be formed as a guide groove in the housing 1 running parallel to the longitudinal axis L1.

[0032] In this way, by rotating 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 displaces the piston 21A, which causes the displacement of the floating piston 21B by the discharge of the working fluid on its side. In Figs. 1 and 2, the position of the threaded spindle 30A is illustrated by way of example, in which the threaded spindle is in the maximum retraction position. That is to say, the pistons 21A, 21B of the brake master cylinder 21 are in the starting position and can travel along the longitudinal axis L1 for boosting pressure. As illustrated by way of example in Figs. 1 and 2, the threaded spindle 30A can for example protrude through the second opening 12 of the housing 1 in this position. In general, the threaded spindle 30A can be displaced to at least one axial position protruding through the second opening 12.

[0033] In general, the brake master cylinder 2 can be operated by moving the operating member 30 along the longitudinal axis L1 by means of the electric motor 4. In this case, the guide member 31 also moves together. In this case, the guide member 31 forms a transmission intermediate part, which divides the housing 1 with respect to the longitudinal axis L1 into a first housing area 13 in which the brake master cylinder 2 is arranged and a second housing area 14 on the side of the second opening 12. In the case of the actuator 100 illustrated in Figures 1 and 2, in particular the spindle nut 32, the bearing 34 and the spindle 30A are located in the second housing area 14.

[0034] As symbolically suggested by a rectangle in FIG. 1, the actuator 100 may have an electrical interface 6 for signal connection with the electric motor 4. This interface 6 may be formed for electrically connecting the electric motor 4 to a voltage source and / or for receiving control signals for operating the electric motor 4. For example, the interface 6 may be embodied as a female connector with connecting contacts. Optionally, it may be considered that the electric motor 4, and thus the actuator 100, can be operated exclusively via signals received at the interface 6. As illustrated in FIGS. 1 and 2, in particular a mechanical connection between the gearing 3 and pedals or the like can be omitted. In general, the actuator 100 may therefore be formed exclusively for "by-wire" operation.

[0035] The compensating diaphragm 5 is illustrated in a perspective view in FIG. 4. In general, the compensating diaphragm 5 is made of an elastically deformable but gas-impermeable material, in particular a synthetic material. For example, the compensating diaphragm 5 may be made of a synthetic material, in particular a rubber material, such as ethylene propylene diene rubber, EPDM for short. In general, the compensating diaphragm 5 is formed as a flat body. As shown purely by way of example in FIG. 4, the compensating diaphragm 5 may have, for example, a flange portion 51 and an arched portion 52. The flange portion 51 is formed for attachment to the inside and / or the side of the second opening 12 of the housing 1.

[0036] As illustrated in Fig. 4, the flange portion 51 may have, for example, a base or frame portion 51A that fits the inner circumference of the second opening 12, which in Fig. 4 is formed in the shape of a ring corresponding to the circular embodiment of the second opening 12. Alternatively or additionally, the flange portion 51 may have a collar 51B that is formed for abutting the area of ​​the housing 1 surrounding the second opening 12. For example, the collar 51B may project radially from the base portion 51A as illustrated in Fig. 4.

[0037] Arcuate portion 52 extends from flange portion 51 to define an open interior or receiving space 53. As illustrated in Figure 4, arcuate portion 52 may have, for example, a frusto-conical shape, however, the invention is not so limited and other arcuate shapes are contemplated, such as, for example, a spherical shape.

[0038] As shown in Fig. 1 and Fig. 2, the compensating diaphragm 5 seals the second opening 12 of the housing 1, more precisely in a fluid-tight manner. As shown in particular in Fig. 2, the compensating diaphragm 5 can be partially inserted into the second opening 12. In particular, the base part 51A can rest against the inner circumferential surface 12 of the second opening 12, while the flange 51B rests against the area of ​​the housing 1 surrounding the second opening 12. The flange part 51 thus rests against the housing 1 in the area of ​​the second opening 12, and the arched part 52 projects from the housing 1. As illustrated in Fig. 1 and Fig. 2, the operating member 30 (here the threaded spindle 30A) can, for example, project into a receiving space 53 determined by the arched part 52 of the diaphragm 5. The compensating diaphragm 5 can, for example, be connected to the housing 1 in a material-bonding manner, for example by being glued thereto. Alternatively, mechanical fixing of the compensation diaphragm 5 to the housing 1 may also be contemplated, for example via a clamp ring (not shown) that clamps and fixes the flange 51B of the flange portion 51 between itself and the housing 1.

[0039] 1, 3 and 4, the compensating diaphragm 5 can be configured as a closure, in particular without through holes, for example in the arched portion 52. The compensating diaphragm 5 is thus preferably used to vary the effective internal volume of the housing 10, as will be described in more detail below, in that several components are guided through it and the compensating diaphragm is not provided to act as a kind of sleeve.

[0040] The compensating diaphragm 5 closes the second opening 12 of the housing 1 in a fluid-tight manner. Similarly, the first opening 11 of the housing 1 is closed in a fluid-tight manner by the brake master cylinder 2. The inner space 10 of the housing 1 is therefore essentially closed in a fluid-tight manner, so that the actuator 100, in particular its housing 1, can be considered not to be submerged in fluid. The transmission intermediate part, i.e. for example in Figs. 1 and 2 the guide member 31 or the disk 31A, divides the inner space 10 of the housing 10 into the first housing area 13 and the second housing area 14, as described above. When the operating member 30 or the spindle 30A moves at high speed along the longitudinal axis L1, for example to obtain a dynamic pressure boost or pressure reduction by the brake master cylinder 2, the transmission intermediate part expels the air in the inner space 10 of the housing 1 in front of it in the direction of movement. Between the transmission intermediate part and the inner surface of the housing 1 there is only a narrow slit S, through which air exchange can take place between the first housing region 13 and the second housing region 14. In the embodiment of figures 1 and 2, the bearing 34 and the spindle nut 32 provide additional protection against gas exchange. A possible flow path F between the first housing region 13 and the second housing region 14 is symbolically shown in figure 2.

[0041] A fast displacement of the transmission intermediate part along the longitudinal axis L1 therefore leads to an unsteady pressure increase in one of the housing regions 13, 14 and an unsteady pressure decrease in the other housing region 13, 14, respectively. This results in a pressure difference between the housing regions 13, 14 which only slowly decreases, for example via the flow path F. The compensating diaphragm 5 advantageously reduces the increasing pressure difference by means of its elastic deformation capability. If the transmission intermediate part, i.e. here the disk 31A, moves together with the spindle 30A, for example in the direction of the second opening 12, this leads to an increase in pressure in the first housing region 13 and a decrease in pressure in the second housing region 14. The decrease in pressure in the second housing region 14 leads to a deformation of the compensating diaphragm 5 such that it reduces the effective volume of the interior space 10 or alternatively the effective volume of the second housing region 14 remains substantially constant. Figuratively speaking, the deformation of the diaphragm 5 follows the movement of the transmission intermediate part, thus reducing the pressure difference between the first housing area 13 and the second housing area 14 when the transmission intermediate part is displaced axially.

[0042] Although the invention has been described above by way of example on the basis of several embodiments, the invention is not limited thereto and may be modified in many ways, in particular combinations of several of the above-described embodiments. [Explanation of symbols]

[0043] 1. Housing 1B Second guide element provided on housing 2 Brake master cylinder 3 Transmission 4 Electric motor 5 Compensating diaphragm 6 Electrical Interface 10. Housing internal space 11 First opening of housing 12 Second opening of housing 13 First housing area 14 Second housing area 30 Transmission device operating member 30A screw spindle 31 Transmission device guide member 31A Disc 31B First guide element on disc 32 Transmission spindle nut 33 Transmission input shaft 51 Flange part of compensating diaphragm 52 Arched portion of compensating diaphragm 100 Actuator L1 Vertical axis

Claims

1. An electrohydraulic actuator (100) for a braking system, comprising: a housing (1) defining an interior space (10) with a first opening (11) and a second opening (12); a brake master cylinder (2) positioned within the first opening (11) and mounted to the housing (1) such that the first opening (11) is fluid-tight sealed; an electric motor (4) arranged in the housing (1); a transmission (3) received in the internal space (10) of the housing (1) and kinematically connected to the brake master cylinder (2), the transmission (3) having a transmission intermediate member movable along a longitudinal axis (L1) and dividing the housing (1) with respect to the longitudinal axis (L1) into a first housing area (13) in which the brake master cylinder (2) is arranged and a second housing area (14) on the side of the second opening (12); a compensating diaphragm (5) elastically deformable for closing the second opening (12) in a fluid-tight manner and for reducing the pressure difference between the first housing area (13) and the second housing area (14) when the transmission intermediate member is displaced axially; An actuator (100) having

2. 2. The actuator (100) according to claim 1, wherein the compensation diaphragm (5) has a flange portion (51) abutting the housing (1) in the area of ​​the second opening (12) and an arched portion (52) protruding from the housing (1).

3. 3. An actuator (100) according to claim 1 or 2, wherein the compensation diaphragm (5) is made from a synthetic material, in particular from a rubber material, such as for example ethylene propylene diene rubber.

4. 4. The actuator (100) according to claim 1, wherein the compensation diaphragm (5) is formed as a closed body, in particular without a through hole connecting the interior space (10) of the housing (1) with the surroundings.

5. 5. The actuator (100) according to claim 1, wherein the transmission (3) comprises an operating member (30) movable along the longitudinal axis (L1) and kinematically connected to the brake master cylinder (2), and a guide member (31) connected to the operating member (30) and guided along the longitudinal axis (L1), the guide member (31) forming the transmission intermediate member.

6. 6. The actuator (100) according to claim 5, wherein the operating member (30) is formed as a threaded spindle (30A), and the transmission (3) comprises a spindle nut (32) engaged with the threaded spindle (30A), and an input shaft (33) drivable by the electric motor (4) and engaged with the spindle nut (32) to rotate the spindle nut (32) around the longitudinal axis (L1).

7. 7. The actuator (100) of claim 6, wherein the guide member (31) is non-rotatably connected to the threaded spindle (30A).

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

9. 9. The actuator (100) according to any one of claims 5 to 8, wherein the guide member (31) is formed as a disk (31A) which has at its outer periphery at least one first guide element (31B), in particular a protrusion, which first guide element engages with a second guide element (1B) extending parallel to the longitudinal axis (L1), in particular a guide groove of the housing (1).

10. In addition, it has the following:

10. The actuator (100) according to any one of claims 1 to 9, comprising an electrical interface (6) in signal connection with the electric motor (4) for connecting the electric motor (4) to a voltage source and / or for receiving control signals for operating the electric motor (4), the actuator (100) being operable exclusively via signals received at the interface (6), in particular without a mechanical alternative operating interface.

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