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 brake system, in particular for a vehicle brake system.

BACKGROUND ART

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

[0003] Patent Document 1 discloses a hydraulic actuator for a brake system, comprising a brake master cylinder, an electric motor, and a transmission device that couples the electric motor to the brake master cylinder to convert the motion of the electric motor into actuation of the brake master cylinder. Here, the transmission device is received in a housing, and in this case the brake master cylinder is positioned in an opening of the housing.

[0004] The advantage of this type of electrohydraulic actuator lies in particular in that the actuator can trigger highly dynamic pressure changes in the brake system via the transmission device by means of a rapid axial displacement of the brake master cylinder. However, since pressure equalization inside the housing is frequently prevented by the components of the transmission device, considerable pressure differences can temporarily arise between different regions of the housing inside the normally fluid-tightly sealed housing relative to the surroundings, due to the high-speed movement of the components inside the housing.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0005] [Patent Document 1] German Patent No. 102013213888 Specification [Overview of the Initiative]

[0006] Against this backdrop, the present invention provides an electrohydraulic actuator that has the constituent elements of claim 1.

[0007] An electrohydraulic actuator for a brake system according to the present invention includes a housing that defines an internal space having a first opening and a second opening; a brake master cylinder positioned within the first opening and mounted in the housing such that the first opening is fluid-tightly sealed; an electric motor disposed in the housing; and a transmission device received within the internal space of the housing and kinematically coupled to the brake master cylinder, wherein the transmission device has a transmission device intermediate member that is movable along a longitudinal axis, thereby dividing the housing into a first housing region in which the brake master cylinder is housed and a second housing region on the side of the second opening, with respect to the longitudinal axis. Furthermore, the actuator includes a compensating diaphragm that is elastically deformable to close the second opening fluid-tightly, particularly liquid-tightly and preferably airtightly, and to reduce the pressure difference between the first housing region and the second housing region when the transmission device intermediate member is displaced axially.

[0008] The underlying concept of this invention is to reduce the pressure difference within the housing resulting from the high-speed motion of at least one component of the transmission within the housing by placing an elastically deformable diaphragm at the opening of the housing. The diaphragm changes its deformation state in response to the pressure changes within the housing, thereby increasing or decreasing the effective volume of each housing region.

[0009] The brake master cylinder is operable by an electric motor via a transmission. In particular, the transmission has a component that is displaceable along the longitudinal axis, and the transmission operates the brake master cylinder, for example, by the axial displacement of the piston of the brake master cylinder. The transmission generally has a transmission intermediate member that divides the housing into a first region and a second region with respect to the longitudinal axis. The first region and the second region are coupled to each other in a fluid-guiding manner, for example, by a slit between the housing and the transmission intermediate member. These penetrations between the first housing region and the second housing region, determined between the transmission intermediate member and the housing, create considerable fluid resistance when the transmission intermediate member moves at high speed, resulting in a pressure difference between the first region and the second region. This pressure difference can be advantageously reduced using a diaphragm according to the present invention.

[0010] The advantage of the present invention lies in the fact that the compensating diaphragm reduces the pressure difference inside the housing. This facilitates the dynamic operation of the actuator. Furthermore, by reducing the pressure difference between the first and second housing regions, the power cost for operating the brake master cylinder can also be reduced, which has a positive effect in terms of the energy consumption and dynamic behavior of the actuator. In addition, the compensating diaphragm provides a cost-friendly possibility by liquid-tightly closing the housing while still facilitating pressure compensation between housing regions.

[0011] Advantageous configurations and further configurations will become apparent from the description with reference to further dependent claims and multiple drawings.

[0012] In many embodiments, the compensating diaphragm may have a flange portion that abuts the housing in the region of the second opening and an arched portion that protrudes from the housing. The flange portion may, for example, abut at least partially the inner circumferential surface of the second opening. The second opening may generally be formed in a circular shape. The arched portion may be formed in a conical or truncated cone shape, but is not limited thereto. For example, a spherical arch or something similar may be provided. Since the arched portion protrudes from the outer surface of the housing, it advantageously avoids spatial collisions with components in the internal space of the housing. Furthermore, the possible volume changes of the second housing region are increased in this way.

[0013] In many examples, the compensating diaphragm may be formed from a synthetic material, and in particular from a rubber material such as ethylene propylene diene rubber (EPDM).

[0014] In many embodiments, it may be considered that the compensating diaphragm is formed as a closure. Therefore, only the compensating diaphragm closes the second opening. In particular, the compensating diaphragm may be formed without through holes that connect the internal space of the housing to the surroundings. Therefore, the sole purpose of the compensating diaphragm is to reduce the pressure difference between the housing regions by increasing or decreasing the volume of the second housing region through its elastic deformation due to pressure changes.

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

[0016] In many embodiments, the operating member is formed as a screw spindle, in which case the transmission device may be considered to have a spindle nut engaged with the screw spindle and an input shaft that is driveable by an electric motor and engaged with the spindle nut in order to rotate the spindle nut around a vertical axis. In this way, a space-saving configuration of the transmission device is realized.

[0017] In many embodiments, it may be considered that the guide member is connected to the screw spindle in a way that prevents relative rotation. Thus, the guide member prevents the spindle from rotating together with the spindle nut based on its guidance along the longitudinal axis.

[0018] In many embodiments, it may be considered that the screw spindle is movable to at least one axial position, and in this at least one axial position, the screw spindle protrudes through a second opening. The first and second openings may be arranged, for example, coaxially along the longitudinal axis. The screw spindle is displaceable along the longitudinal axis to move the piston of the brake master cylinder, for example, it can move forward and backward. In this case, the spindle can also travel to a position where it protrudes through the second opening. In this example, as described above, it is particularly advantageous if the compensating diaphragm has a flange portion and an arched portion, because this allows the spindle to protrude into the space defined by the arched portion. Thus, the compensating diaphragm can also contribute to achieving a more compact housing configuration with respect to the longitudinal axis.

[0019] In many embodiments, the guide member is formed as a disc, and the disc may have at least one first guide element on its outer circumference, particularly having a projection, and the first guide element may engage with a second guide element extending parallel to the longitudinal axis, particularly with a guide groove in the housing. For example, the second guide element, which is groove-shaped, may be formed in particular within the housing.

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

[0021] The present invention will now be described with reference to several figures of the drawings. Brief Description of the Drawings

[0022] [Figure 1] It is a cross-sectional perspective view of an electrohydraulic actuator according to one embodiment of the present invention. [Figure 2] It is a side cross-sectional view of the actuator shown in Figure 1. [Figure 3] It is a plan view of the first opening of the actuator shown in Figure 1, with the brake master cylinder omitted from illustration. [Figure 4] It is a perspective view of the compensation diaphragm of the actuator shown in Figure 1. Modes for Carrying Out the Invention

[0023] In the figures, identical reference numerals denote identical or functionally identical components unless otherwise specified.

[0024] Figure 1 illustrates an electrohydraulic actuator 100 for a brake system, for example for a motor vehicle brake system. Figure 2 shows the actuator of Figure 1 in a side view. As shown in Figures 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 determines the internal space 10. For example, the housing 1 may have a plurality of walls 1A that define the internal space 10. The housing 1 particularly has a first opening 11 and a second opening 12. The openings 11 and 12 form the connection of the internal space 10 to the surroundings. The openings 11 and 12 may have, for example, a circular periphery, as seen with respect to the first opening 11 in Figure 3. However, basically, other periphery shapes of the openings 11 and 12 are also possible. As illustrated in Figures 1 and 2, the first and second openings 11 and 12 may be arranged opposite each other. In particular, the first and second openings 11 and 12 may be arranged coaxially with respect to each other. For example, the first and second openings 11 and 12 may be arranged coaxially with respect to a vertical axis L1. The housing 1 may particularly be a cast housing made of a metallic or composite material.

[0026] The brake master cylinder 2 is designed to increase and decrease hydraulic pressure by supplying or transferring the working fluid to or from a hydraulic consumption device, such as a wheel brake cylinder. For this reason, the brake master cylinder 2 may have a cylinder 20 in particular, within which at least one piston 21 is supported so as to be axially displaceable. Figures 1 and 2 show a tandem brake master cylinder 2 with a directly operable first piston 21A and a floating piston 21B purely as an example.

[0027] As further shown in Figures 1 and 2, the brake master cylinder 2 is positioned within the first opening 11 of the housing 1. In particular, the brake master cylinder 2 protrudes into the internal space 10 of the housing 1 through the first opening 11. In this configuration, the brake master cylinder 2, and especially the piston 21, is preferably positioned coaxially with respect to the longitudinal axis L1. The cylinder 20 of the brake master cylinder 2 is fixedly positioned in the housing 1, and in particular, fixed thereto, for example, by being screwed thereto. For example, a flange 22 may be formed on the cylinder 20, which is centered on the first opening 11 and completely covers it, as illustrated in Figures 1 and 2. A sealing element (not shown) may serve to provide an additional seal over the first opening 11. Generally, the brake master cylinder 2 is mounted in the housing 1 to fluidly seal the first opening 11.

[0028] Although the electric motor 4 is only simply illustrated in Figures 1 and 2, it may be, for example, positioned on the outer surface of the housing 1 and fixed to the housing 1. In this case, the electric motor 4 may be oriented such that its rotation axis A4 (around which the drive shaft of the electric motor 4 rotates) extends laterally or perpendicularly with respect to the vertical axis L1.

[0029] The transmission device 3 kinematically connects the brake master cylinder 2 to the electric motor 4, specifically in the following manner: namely, the rotation of the electric motor 4 causes the movement of the piston 21 or pistons 21A, 21B of the brake master cylinder 2 along the vertical axis L1. As shown in Figures 1 and 2, the transmission device 3 is housed within the internal space 10 of the housing 1. As illustrated in Figures 1 and 2, the transmission device 3 may have an operating member 30 and a guide member 31. Generally, the operating member 30 is kinematically connected to the piston 21 of the brake master cylinder 21, particularly piston 21A, for example via a connecting rod 35, and is movable along the vertical axis L1 by the electric motor 4. The guide member 31 is coupled to or connected to the operating member 30 and is guided along the vertical axis L1, for example, within the housing 1.

[0030] Figures 1 and 2 illustrate a transmission device 3 purely as an example, in which the operating member 30 is implemented as a screw spindle 30A with a male thread 30B, and the guide member 31 is implemented as a disc 31A guided in the housing 1. Furthermore, the transmission device 3 illustrated in Figures 1 and 2 includes a spindle nut 32 with a female thread 32B that engages with the male thread 30B of the screw spindle 30A, and an input shaft 33. The spindle nut 32 is supported in the housing 1 by a rolling bearing 34 so as to be rotatable around a longitudinal axis L1, for example, as illustrated in Figures 1 and 2. Furthermore, the input shaft 33 may be formed as a worm shaft that engages with the external teeth (not shown) of the spindle nut 32, for example. The input shaft 33 may be directly coupled to the drive shaft (not shown) of an electric motor 4, for example.

[0031] In this case, the guide member 31 or disc 31A is connected to the screw spindle 30A in a manner that prevents relative rotation, and thus forms a torsion prevention portion of the screw spindle 30A. As illustrated in Figure 3, the disc 31A may have at least one first guide element 31B on its outer circumference, which is implemented as a projection that engages with a second guide element 1B extending parallel to the longitudinal axis L1, as purely illustrated in Figure 3. Figure 3 purely illustrates that the second guide element 1B may be formed as a guide groove in the housing 1 extending parallel to the longitudinal axis L1.

[0032] In this way, by rotating the spindle nut 32 using the input shaft 33 driven by the electric motor 4, the screw spindle 30A is displaced along the vertical axis L1 together with the disc 31A, resulting in the screw spindle 30A moving the piston 21A, which in turn causes the piston to displace the floating piston 21B by the discharge of the working fluid. Figures 1 and 2 illustrate the position of the screw spindle 30A as an example, in which the screw spindle is in its maximum retracted position. That is, the pistons 21A and 21B of the brake master cylinder 21 are in their starting position and can travel along the vertical axis L1 to increase pressure. As illustrated in Figures 1 and 2, the screw spindle 30A can protrude through the second opening 12 of the housing 1, for example, in this position. In general, the screw spindle 30A may be movable to at least one axial position in which it protrudes through the second opening 12.

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

[0034] As symbolically indicated by the rectangle in Figure 1, the actuator 100 may have an electrical interface 6 that is signal-connected to the electric motor 4. This interface 6 may be formed 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 may be implemented as a female connector with connection contacts. Optionally, it may be considered that the electric motor 4, and therefore the actuator 100, can be operated solely via signals received at the interface 6. As illustrated in Figures 1 and 2, in particular, the mechanical connection between the transmission 3 and the pedal, etc., can be omitted. Therefore, generally, the actuator 100 may be formed solely for "by-wire" operation.

[0035] The compensating diaphragm 5 is illustrated in a perspective view in Figure 4. Generally, the compensating diaphragm 5 is formed from an elastically deformable but gas-impermeable material, particularly from a synthetic material. For example, the compensating diaphragm 5 may be formed from a synthetic material, particularly a rubber material such as ethylene-propylene-diene rubber, abbreviated as EPDM. Generally, the compensating diaphragm 5 is formed as a flattened body. As purely illustrated in Figure 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 mounting inside and / or to the side of the second opening 12 of the housing 1.

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

[0037] The arched portion 52 extends from the flange portion 51 and determines the open internal space or receiving space 53. As illustrated in Figure 4, the arched portion 52 may have, for example, a truncated cone shape. However, the present invention is not limited thereto, and other arch shapes, such as a spherical shape, are also conceivable.

[0038] As shown in Figures 1 and 2, the compensating diaphragm 5 seals, more precisely, the second opening 12 of the housing 1, providing a fluid-tight seal. Particularly as shown in Figure 2, a portion of the compensating diaphragm 5 may be inserted into the second opening 12. Specifically, the base portion 51A may abut against the inner circumferential surface 12 of the second opening 12, while the flange 51B abuts against the region of the housing 1 surrounding the second opening 12. Thus, the flange portion 51 abuts against the housing 1 in the region of the second opening 12, and the arched portion 52 protrudes from the housing 1. As illustrated in Figures 1 and 2, the operating member 30 (here, a screw spindle 30A) may protrude into a receiving space 53 determined, for example, by the arched portion 52 of the diaphragm 5. The compensating diaphragm 5 may be coupled to the housing 1, for example, by a material bond, or it may be bonded to it. Alternatively, mechanical fixing of the compensating diaphragm 5 to the housing 1 may also be considered. For example, the flange portion 51 may be mechanically fixed via a clamping ring (not shown) that tightens and fixes the flange 51B between itself and the housing 1.

[0039] As shown in Figures 1, 3, and 4, the compensating diaphragm 5 may be formed as a closed body, and in particular, for example, in the arched portion 52, it may be formed as a closed body without through holes. Therefore, the compensating diaphragm 5 is preferably used to change the effective internal volume of the housing 10, as will be described in more detail below, rather than being provided so that multiple components are guided through the compensating diaphragm and the compensating diaphragm acts as some kind of sleeve.

[0040] The compensating diaphragm 5 fluid-tightly closes the second opening 12 of the housing 1. Similarly, the first opening 11 of the housing 1 is fluid-tightly closed by the brake master cylinder 2. Thus, the internal space 10 of the housing 1 is substantially fluid-tightly closed, and therefore the actuator 100, and in particular its housing 1, can be considered not to be submerged in fluid. The transmission intermediate members, i.e., the guide member 31 or disc 31A in Figures 1 and 2, divide the internal space 10 of the housing 10 into a first housing region 13 and a second housing region 14, as described above. When the operating member 30 or spindle 30A moves at high speed along the longitudinal axis L1, for example to obtain a dynamic pressure increase or decrease by the brake master cylinder 2, the transmission intermediate members expel air from the internal space 10 of the housing 1 in front of them with respect to the direction of motion. Only a narrow slit S exists between the intermediate member of the transmission device and the inner surface of the housing 1, and air exchange can occur between the first housing region 13 and the second housing region 14 through this slit. In the embodiments of Figures 1 and 2, the bearing 34 and spindle nut 32 auxiliaryly block gas exchange. Possible flow paths F between the first housing region 13 and the second housing region 14 are symbolically illustrated in Figure 2.

[0041] Therefore, when the intermediate member of the transmission device is displaced at high speed along the vertical axis L1, an unsteady pressure increase occurs in one of the housing regions 13 and 14, and an unsteady pressure decrease occurs in the other of the housing regions 13 and 14, respectively. As a result, a pressure difference is created between the housing regions 13 and 14 that decreases only slowly, for example, through the flow path F. The compensating diaphragm 5 is advantageous because its elastic deformability reduces the increasing pressure difference. When the intermediate member of the transmission device, in this case the disc 31A, moves together with the spindle 30A, for example, in the direction of the second opening 12, this results in 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 causes the compensating diaphragm 5 to deform in such a way that it reduces the effective volume of the internal space 10, or it causes the compensating diaphragm 5 to deform in such a way that the effective volume of the second housing region 14 remains substantially constant. Figuratively speaking, the deformation of the diaphragm 5 follows the motion of the intermediate member of the transmission device. In this way, the pressure difference between the first housing region 13 and the second housing region 14 is reduced when the intermediate member of the transmission device is displaced in the axial direction.

[0042] Although the present invention has been described above with reference to several embodiments, it is not limited thereto and can be modified in various ways. In particular, combinations of the above embodiments are also conceivable. [Explanation of Symbols]

[0043] 1 Housing 1B Second guidance element installed in the housing 2. Brake Master Cylinder 3. Transmission device 4 Electric motor 5. Compensation diaphragm 6. Electrical Interface 10. Interior space of the housing 11 First opening of the housing 12. Second opening of the housing 13. First Housing Area 14. Second Housing Area 30 Operating member of the power transmission device 30A Screw Spindle 31 Guide member of transmission device 31A Disk 31B First guide element provided on the disk 32 Spindle nut of the power transmission device 33 Input shaft of the power transmission device 51 Flange portion of the compensating diaphragm 52 Arch-shaped portion of the compensating diaphragm 100 actuators L1 Vertical axis

Claims

1. In an electrohydraulic actuator (100) for a brake system, A housing (1) that defines an internal space (10) having a first opening (11) and a second opening (12), A brake master cylinder (2) is positioned within the first opening (11) and mounted in the housing (1) such that the first opening (11) is fluidly sealed, The electric motor (4) is located in the housing (1), A transmission device (3) is received within the internal space (10) of the housing (1) and kinematically connected to the brake master cylinder (2), wherein the transmission device (3) has a transmission device intermediate member that is movable along a vertical axis (L1), and the transmission device (3) has a transmission device intermediate member that divides the housing (1) with respect to the vertical axis (L1) into a first housing region (13) in which the brake master cylinder (2) is housed and a second housing region (14) on the side of the second opening (12), A fluid-tightly closed second opening (12) and an elastically deformable compensating diaphragm (5) to reduce the pressure difference between the first housing region (13) and the second housing region (14) when the intermediate member of the transmission device is displaced in the axial direction, An actuator (100) having the following characteristics.

2. The actuator (100) according to claim 1, wherein the compensating diaphragm (5) has a flange portion (51) that abuts against the housing (1) in the region of the second opening (12) and an arch-shaped portion (52) that protrudes from the housing (1).

3. The actuator (100) according to claim 1 or 2, wherein the compensating diaphragm (5) is formed from a synthetic material, and the synthetic material is ethylene propylene diene rubber.

4. The actuator (100) according to claim 1 or 2, wherein the compensating diaphragm (5) is formed as a closed body without any through holes that allow the internal space (10) of the housing (1) to communicate with the surroundings.

5. The actuator (100) according to claim 1 or 2, wherein the transmission device (3) has an operating member (30) that is movable along the vertical axis (L1) and kinematically connected to the brake master cylinder (2), and a guide member (31) that is connected to the operating member (30) and guided along the vertical axis (L1), and the guide member (31) forms an intermediate member of the transmission device.

6. The actuator (100) according to claim 5, wherein the operating member (30) is formed as a screw spindle (30A), and the transmission device (3) has a spindle nut (32) engaged with the screw spindle (30A), and an input shaft (33) that is driveable by the electric motor (4) and engaged with the spindle nut (32) in order to rotate the spindle nut (32) around the vertical axis (L1).

7. The actuator (100) according to claim 6, wherein the guide member (31) is connected to the screw spindle (30A) in a manner that prevents relative rotation.

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

9. The actuator (100) according to claim 5, wherein the guide member (31) is formed as a disc (31A), and the disc has at least one first guide element (31B) on its outer circumference, particularly having a protruding portion, and the first guide element engages with a second guide element (1B) extending parallel to the vertical axis (L1), particularly with a guide groove of the housing (1).

10. In addition, it has the following, namely The actuator (100) according to claim 1 or 2, having an electrical interface (6) that is signal-connected to the motor (4) for connecting the motor (4) to a voltage source and / or for receiving control signals to operate the motor (4), wherein the actuator (100) is operable exclusively via signals received at the interface (6) and in particular operable without a mechanical alternative operating interface.

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