Electromechanically actuatable brake actuator

Abstract

The invention relates to an electromechanically actuatable brake actuator. The brake actuator includes: a caliper housing having a cylindrical recess; the invention relates to a brake device for a motor vehicle, comprising a drive spindle having a first spindle end and a second spindle end, the first spindle end having a drive geometry for transmitting a torque to the drive spindle, and a brake piston device having a spindle nut, the first spindle end having a drive geometry for transmitting a torque to the drive spindle, the driving shaft is operatively connected to the driving main shaft in the driving aspect; a sliding guide by means of which the brake piston device is guided in the cylindrical recess; and a brake piston for actuating the at least one brake pad arrangement, the brake piston arrangement having an open side, a circumferential wall and a closed base opposite the open side, such that the brake piston arrangement has an interior, the second spindle end protruding through the open side into the interior, an axial bearing is arranged between the second spindle end and the closed base.

Description

Technical Field

[0001] This invention relates to an electromechanically actuated brake actuator for a disc brake in a motor vehicle, the brake actuator having a spindle drive mechanism including a drive spindle and a brake piston assembly that can be linearly guided. The invention also relates to a disc brake in a motor vehicle having such a brake actuator. Furthermore, the invention relates to a method for determining the position of a corresponding brake piston assembly and positioning the corresponding brake piston assembly. The invention also relates to a spindle drive mechanism. Background Technology

[0002] In electromechanically actuated brake actuators used in automotive disc brakes, a brake piston assembly is typically mounted in a cylindrical recess of the brake caliper to allow axial displacement but is fixed to prevent rotation. The brake piston assembly can be moved axially by means of a drive spindle, which can be rotated via a drive geometry at the end of a first spindle. By means of the brake piston assembly, one or more brake pads can be pressed against or released from the brake disc in this manner. The drive spindle typically has external threads and the brake piston assembly has internal threads, so that these two components work together as a spindle drive mechanism.

[0003] The brake piston assembly can move into the cylindrical recess in the brake caliper, i.e., into the "retracted" position. For example, the retracted position exists when one or more associated brake pads are separated from the brake disc. The brake piston assembly can also move slightly further out of the cylindrical recess in the brake caliper, i.e., into the "extended" position. For example, the extended position exists when one or more associated brake pads are applied to the brake disc. Depending on the pad thickness or wear condition of the brake pads, the brake piston assembly can occupy various positions when extended.

[0004] Typically, a brake piston assembly has an open side, a circumferential wall, and a closed base opposite the open side. Due to the thickness of the circumferential wall, the brake piston assembly has a circumferential surface that defines the assembly in the axial direction, and the assembly extends into a cylindrical recess through this surface. In this prior art solution, the problem arises that as the brake piston assembly moves in, the cylindrical surface moves until it is blocked by the corresponding housing base. Depending on the speed at which they move together, this can lead to damage to the axial fixing mechanism of the drive spindle. Although the brake piston assembly stops immediately upon contact with the housing, the drive spindle can still move a little further in the axial direction. If the drive spindle is fixed relative to the housing to maintain its axial position, for example by means of a retaining ring, excessive force may act on the retaining ring due to the movement of the brake piston assembly and the housing together, potentially damaging the retaining ring. Damage to other components is also possible.

[0005] Another problem with existing solutions is that the reference position of the brake piston device can only be determined insufficiently or is too complex. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide an electromechanically actuated brake actuator whose brake piston assembly can be moved to any retracted position without any interference, damage, or jamming, and to provide a disc brake for a motor vehicle having such a brake actuator. Another object of the present invention is to provide a method that allows for precise and low-cost determination of the reference position of the brake piston assembly. Furthermore, the object of the present invention is to provide a spindle drive in which axial jamming between the spindle and the spindle nut is avoided.

[0007] According to the present invention, this objective is achieved by the following electromechanically actuated brake actuator, the following motor vehicle disc brake, the following method, and the following spindle drive device.

[0008] An electromechanically actuated brake actuator for a disc brake of a motor vehicle according to the present invention comprises: a brake caliper housing having a cylindrical recess; and a spindle drive including a drive spindle and a brake piston assembly linearly movably guided. The drive spindle has a first spindle end and a second spindle end, the first spindle end having drive geometry for transmitting torque to the drive spindle. The brake piston assembly has a spindle nut, a sliding guide, and a brake piston, the spindle nut being operatively connected to the drive spindle in drive, the brake piston assembly being guided in the cylindrical recess by means of the sliding guide, and the brake piston assembly for actuating at least one brake pad assembly. The brake piston assembly has an open side, a circumferential wall, and a closed base opposite the open side, such that an internal space is correspondingly formed within the brake piston assembly. The second spindle end extends through the open side into the internal space. According to the present invention, an axial bearing is arranged between the second spindle end and the closed base.

[0009] The drive spindle can be positioned in rotation by means of a drive geometry, preferably a form-fitting or force-fitting pin. Drive is preferably provided by an electric motor or an electric motor and an intermediate gear mechanism. Due to the axial bearing between the second axial end and the closed base, the drive spindle and the brake piston assembly can move together without jamming. When the brake piston assembly is moved to its maximum retracted position, the drive spindle and the brake piston assembly move together to stop. This means that, in this case, there is no longer any clearance in the series circuit or arrangement of the spindle end, the axial bearing, and the closed base of the brake piston assembly. However, due to the characteristics of the axial bearing, the components do not jam. The axial bearing transmits force in the axial direction, and when moving together, the axial bearing no longer allows any axial movement. However, the axial bearing provides rotational freedom about the longitudinal axis or rotational axis of the drive spindle, allowing the brake piston assembly to easily move out of the retracted position again.

[0010] Preferably, in the first retracted position of the brake piston assembly, the axial bearing is in contact with both the second spindle end and the closed base. Preferably, in the first retracted position, the axial force is transmitted between the second spindle end and the closed base. As explained above, the closed base and the second spindle end move together in this case, so that there is no longer any axial clearance between these components. However, the axial bearing that transmits the axial force is arranged between the closed base and the second spindle end; releasing the components that have moved together is easily achieved. The fact that the second axial end is in contact with the closed base causes the movement of both the brake piston assembly and the drive spindle to stop simultaneously in this maximum retracted position. After reaching this position of the brake piston assembly, the drive spindle cannot continue to rotate and thus move axially as in the prior art. Therefore, damage to components (especially the drive spindle bearing and the axial fixing device of the drive spindle) is avoided.

[0011] Preferably, the second spindle end has a first contact surface oriented laterally relative to the longitudinal axis of the drive spindle. In this case, "laterally" means that the contact surface can also be tapered. However, the first contact surface is preferably orthogonal to the longitudinal axis of the drive spindle. The first contact surface is preferably an end face of the second spindle end. Preferably, the enclosed base has a second contact surface oriented laterally to, and preferably orthogonally to, the longitudinal axis of the drive spindle within its internal space. The second contact surface is preferably a base surface of the enclosed base. In the first retracted position, the first contact surface preferably contacts the first bearing side of the axial bearing, and the second contact surface contacts the second bearing side of the axial bearing opposite to the first bearing side.

[0012] In a preferred embodiment of the brake actuator, an axial bearing is fixed to the end of the second spindle. In this way, the axial bearing can be installed securely and easily. Preferably, the axial bearing is inserted into a recess in the end face of the second spindle end.

[0013] Particularly preferably, the axial bearing is designed as a rolling contact bearing. In a rolling contact bearing, due to the rolling friction between the bearing surface and the rolling element, the components can be easily separated even under high axial forces that may occur when the drive spindle and brake piston assembly move together. Alternatively, a flat bearing (preferably a sliding disc) can also be used as the axial bearing.

[0014] Preferably, the spindle drive is configured as a ball screw drive (also known as a recirculating ball spindle drive). Ball screw drives are highly efficient and not self-locking. This is generally important for the efficient sizing of the brake actuator and the corresponding disc brake. However, it also benefits from the fact that the brake piston can easily retract from the cylindrical recess after moving to its blocked state (i.e., at the maximum retracted position of the brake piston). Preferably, the drive spindle has external threads for guiding the balls, and the spindle nut of the brake piston or brake piston assembly has internal threads for guiding the balls, wherein the drive spindle, balls, and spindle nut together form the ball screw drive. Preferably, the balls are guided back within the drive spindle.

[0015] In a preferred improvement of the brake actuator, the spindle nut, sliding guide, and brake piston are formed as a single piece. This means that the brake piston assembly combines three functional units into a single component. In this case, the brake piston assembly is a brake piston whose circumferential wall forms the sliding guide, and has an internal thread on the inner side of the circumferential wall, which is operatively connected to the external thread of the drive spindle in terms of actuation.

[0016] Preferably, the brake actuator is configured such that the brake piston assembly can be moved to a defined second retracted position by means of an electronic controller, wherein, in the second retracted position of the brake piston assembly, the axial bearing is not in contact with the closed base or no axial force is transmitted between the end of the second spindle and the closed base. Using the brake actuator according to the invention, starting from the first retracted position of the brake piston assembly (in the first retracted position, the closed base is in clearance contact with the end of the second spindle via the axial bearing), the brake piston assembly can thus be moved to a defined second retracted position by means of an electronic controller. This could be, for example, a position that establishes a desired clearance between the brake pad and the brake disc. Therefore, the first retracted position can be used as a reference position from which the electronic controller can move the brake piston assembly to another defined axial position of the brake piston assembly by actuating an associated electric motor.

[0017] The disc brake for motor vehicles according to the invention has an electromechanically actuated brake actuator as described above or below. The features, technical effects, and advantages described with respect to the brake actuator according to the invention also similarly apply to disc brakes for motor vehicles.

[0018] The method for determining the position of the brake piston device of the brake actuator according to the present invention comprises the following steps:

[0019] Move the brake piston assembly to the first retracted position;

[0020] The position value of the brake piston device in the first retracted position is stored by means of an electronic controller;

[0021] By means of an electronic controller, values ​​for variables used to activate the drive spindle are calculated, enabling the brake piston assembly to be moved to a determinable position different from the first retracted position. Preferably, the position different from the first retracted position corresponds to the second retracted position already explained in the preceding description. This method, combined with the brake piston assembly according to the invention, represents an accurate and inexpensive solution for determining the reference position of the brake piston assembly.

[0022] The spindle drive according to the invention includes a spindle, preferably a drive spindle, having a first contact surface, preferably an end face, oriented laterally, preferably orthogonally, relative to the longitudinal axis of the spindle. The spindle drive also includes a spindle nut operatively connected to the spindle in a driving manner, the spindle nut having a second contact surface oriented laterally, preferably orthogonally, relative to the longitudinal axis of the spindle. An axial bearing, preferably a rolling contact bearing or a sliding disc, is arranged between the first and second contact surfaces.

[0023] In a preferred improvement of the spindle drive, at a first axial position of the spindle nut relative to the spindle, the axial bearing is in contact with both the first and second contact surfaces. Alternatively or additionally, at the first axial position of the spindle nut relative to the spindle, the axial bearing transmits axial force between the first and second contact surfaces. In this improvement of the spindle drive, at at least one additional axial position of the spindle nut relative to the spindle, the axial bearing does not transmit axial force between the first and second contact surfaces. Alternatively or additionally, the axial bearing is in contact with only one of the first and second contact surfaces, or not in contact with either the first or second contact surface.

[0024] The technical effects and advantages of the brake actuator according to the invention, and especially its spindle drive, are also similarly applicable to the aforementioned embodiments of the spindle drive according to the invention. Attached Figure Description

[0025] Other features, advantages, and possible applications of the invention are described and illustrated in the following exemplary embodiments. Figure 1 This is derived from [the text]. Figure 1 In this context, the same reference numerals may also denote the same or similar objects.

[0026] Figure 1 Exemplary embodiments of a brake actuator according to the invention, details of a disc brake for a motor vehicle according to the invention, and exemplary embodiments of a spindle drive according to the invention are shown. Detailed Implementation

[0027] A cylindrical recess 6 is introduced into the brake caliper housing 5 of the brake actuator 1 of the disc brake 100 of a motor vehicle. This recess opens toward the brake disc groove 8 and is defined by the housing base 7 in its deepest region in the axial direction. The brake piston assembly 40 is arranged in the cylindrical recess 6 so that it can be axially displaced and is fixed to prevent rotation.

[0028] In an exemplary embodiment of the present invention, the brake piston assembly 40 integrates the brake piston 48, the spindle nut 42, and the sliding guide 44 into a single component. Therefore, although the aforementioned components are designed as a single unit in the present case, each component (at least these components are different sections or regions), namely the brake piston 48, the spindle nut 42, and the sliding guide 44, is provided with reference numerals. The brake piston assembly 40 is canister-shaped and has a closed base 55 protruding from a cylindrical recess 6, a circumferential wall 54, and an open side 51. As a result, the brake piston assembly 40 has an internal space 59 in which the drive spindle 20 is placed. The circumferential wall 54 has a sliding guide 44 on its outer side, through which the brake piston assembly 40 is slidably guided within the cylindrical recess 6 of the brake caliper housing 5. The brake piston assembly 40 is fixed to prevent rotation relative to the brake caliper housing 5 by means of an anti-rotation fixing device 63 guided in the recess. The brake piston assembly 40 has an internal thread 60 on the inner side of the circumferential wall 54.

[0029] The drive spindle 20 has a first spindle end 22 that extends through the housing base 7 of the brake caliper housing 5 and has a drive geometry 23. The drive spindle 20 can be driven to rotate by an electric motor via this drive geometry 23. The drive geometry can be formed, for example, as a grooved or splined shaft profile. In the region of the first spindle end 22, the drive spindle 20 is mounted and supported relative to the housing base 7 by means of a spindle bearing 12 and by means of bearing elements, and is axially fixed by an axial fixing device 13. The axial fixing device includes a retaining ring 4.

[0030] The drive spindle 20 extends along its longitudinal axis 21 into the internal space 59 and is axially bounded there by the second spindle end 25, which is also its axis of rotation. The drive spindle 20 has an external thread 29 in the spindle region that extends into the internal space 59. The drive spindle 20 and the brake piston assembly 40 together form the spindle drive 10. The internal thread 60 and the external thread 29 are operatively connected in terms of actuation. Since this spindle drive 10 is constructed as a ball screw drive, the balls 16 are arranged in the threads of the drive spindle 20 and the brake piston assembly 40 or the spindle nut 42 and are movably guided, such that the balls 16 are also part of the spindle drive 10 in this exemplary embodiment. The balls return within the drive spindle 20. The drive spindle 20 has a larger spindle diameter in the region where the external thread 29 is arranged than in the region at the first spindle end. In addition, the drive spindle 20 has a blind hole 26 in the region of the second spindle end 25, which is introduced into the drive spindle 20 from the first contact surface 27.

[0031] Due to the construction of the spindle drive 10, the brake piston assembly 40, which is axially movable but not rotatably arranged, can be axially moved by the rotation of the drive spindle 20, which is rotatably mounted but axially fixed. As a result of actuating the brake actuator 1, the brake piston assembly 40 can move into or out of the cylindrical recess 6 (retracted position) to press the associated brake pad against the associated brake disc or release the brake pad from the brake disc.

[0032] On the second spindle end 25, the drive spindle 20 has an axial bearing 70, which is designed as a rolling contact bearing. The rolling element may be, for example, a rolling contact needle or a cylindrical roller, whose axis of rotation extends orthogonally to the longitudinal axis 21 of the drive spindle 20. The second spindle end 25 has a first contact surface 27 on which the rolling element is supported or rolls. This means that the axial bearing 70 has a first bearing side 72 there. This contacts the first contact surface 27. The first contact surface 27 is slightly recessed into the second spindle end 25, such that the axial bearing 70 has a corresponding bearing seat.

[0033] The enclosed base 55 has a second contact surface 57 on its inner side, i.e., in the internal space 59. This extends parallel to the first contact surface 27. If the brake actuator 1 is actuated to move the brake piston assembly 40 to its maximum possible retracted position, the second contact surface 57 contacts the second bearing side 74 of the axial bearing 70, which is opposite to the first bearing side 72. This prevents the brake piston assembly 40 from moving against the brake caliper housing 5 to another point. Once the brake piston assembly 40 is in such a way (i.e., via the axial bearing 70) with the drive spindle 20 without clearance, both spindle drive components are simultaneously stationary, and the drive spindle 20 does not subsequently undergo undesirable axial movement. As a result, damage to components (especially the axial fixing device 13) is avoided. If the brake piston assembly 40 and the drive spindle 20 move in such a way that they block each other, this situation also represents a reliable and reproducible reference position for the brake piston assembly 40, and can be used to position the brake piston assembly 40 at other determinable positions by means of an electronic controller.

Claims

1. An electromechanically actuated brake actuator (1) for a disc brake (100) of a motor vehicle, the brake actuator (1) comprising: Brake caliper housing (5), the brake caliper housing (5) having a cylindrical recess (6); and A spindle drive (10) includes a drive spindle (20) and a brake piston device (40) that can be linearly guided. The drive spindle (20) has a first spindle end (22) and a second spindle end (25), wherein the first spindle end (22) has a drive geometry (23) for transmitting torque to the drive spindle (20). The brake piston device (40) includes a spindle nut (42), a sliding guide (44), and a brake piston (48). The spindle nut (42) is operatively connected to the drive spindle (20) in terms of actuation. The brake piston device (40) is guided in the cylindrical recess (6) by means of the sliding guide (44). The brake piston device (40) is used to actuate at least one brake pad device. The brake piston device (40) has an open side (51), a circumferential wall (54), and a closed base (55) opposite to the open side (51), such that the brake piston device (40) has an internal space (59). The second spindle end (25) extends through the open side (51) into the internal space (59). The feature is that an axial bearing (70) is arranged between the end of the second spindle (25) and the closed base (55).

2. The brake actuator (1) according to claim 1, wherein, In the first retracted position of the brake piston device (40), the axial bearing (70) is in contact with both the second spindle end (25) and the closed base (55) and / or transmits axial force between the second spindle end (25) and the closed base (55).

3. The brake actuator (1) according to any one of the preceding claims, wherein, The second spindle end (25) has a first contact surface (27), particularly an end face, which is laterally and particularly orthogonally oriented relative to the longitudinal axis (21) of the drive spindle (20). The closed base (55) has a second contact surface (57), particularly a base surface, in the internal space (59). The second contact surface (57) is laterally and particularly orthogonally oriented relative to the longitudinal axis (21) of the drive spindle (20). In the first retracted position, the first contact surface (27) contacts the first bearing side (72) of the axial bearing (70), and the second contact surface (57) contacts the second bearing side (74) of the axial bearing (70) opposite to the first bearing side (72).

4. The brake actuator (1) according to any one of the preceding claims, wherein, The axial bearing (70) is fastened to the end of the second spindle (25).

5. The brake actuator (1) according to any one of the preceding claims, wherein, The axial bearing (70) is a rolling contact bearing or a planar bearing, particularly a sliding disc.

6. The brake actuator (1) according to any one of the preceding claims, wherein, The main shaft transmission device (10) is a ball screw transmission device.

7. The brake actuator (1) according to any one of the preceding claims, wherein, The spindle nut (42), the sliding guide (44), and the brake piston (48) are formed as a single piece.

8. The brake actuator (1) according to any one of claims 2 to 7, wherein, The brake actuator (1) is configured such that the brake piston assembly (40) can be moved by means of an electronic controller to a defined second retracted position, wherein, in the second retracted position of the brake piston assembly (40), the axial bearing (70) does not contact the closed base (55) and / or does not transmit axial force between the second spindle end (25) and the closed base (55).

9. A disc brake (100) for a motor vehicle, the disc brake (100) having an electromechanically actuated brake actuator (1) according to any one of claims 1 to 8.

10. A method for determining the position of a brake piston device (40) of a brake actuator (1) according to claim 8, the method comprising the steps of: Move the brake piston device (40) to the first retracted position; The position value of the brake piston device (40) in the first retracted position is stored by means of an electronic controller; The electronic controller calculates the values ​​of the variables used to activate the drive spindle (20) so that the brake piston device (40) can be moved to a determinable position different from the first retracted position, in particular to the second retracted position.

11. A spindle drive device (10), the spindle drive device (10) comprising: The spindle (20), particularly the drive spindle, has a first contact surface (27), particularly the end face, which is laterally and particularly orthogonally oriented relative to the longitudinal axis (21) of the spindle (20). and A spindle nut (42), operatively connected to the spindle (20) in terms of drive, the spindle nut (42) having a second contact surface (57) oriented laterally, and particularly orthogonally, relative to the longitudinal axis (21) of the spindle (20), The feature is that an axial bearing (70), particularly a rolling contact bearing or a sliding disc, is arranged between the first contact surface (27) and the second contact surface (57). In a first axial position of the spindle nut (42) relative to the spindle (20), the axial bearing (70) is in contact with both the first contact surface (27) and the second contact surface (57) and / or transmits axial force between the first contact surface (27) and the second contact surface (57). Wherein, at at least one additional axial position of the spindle nut (42) relative to the spindle (20), the axial bearing (70) does not transmit axial force between the first contact surface (27) and the second contact surface (57), and / or wherein the axial bearing (70) contacts only one of the first contact surface (27) and the second contact surface (57) or does not contact either of the first contact surface (27) and the second contact surface (57).

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