Brake actuator for a friction brake, friction brake and vehicle

Abstract

The present invention relates to a brake actuator (100) for a friction brake, the brake actuator (100) having a piston (106) and a rotary-translatory gear (104) for converting a rotational movement of a drive into a linear movement of the piston (106), and an angular compensation element (116) being arranged between a translational component (114) of the gear (104) and the piston (106) for decoupling the translational component (114) from lateral forces on the piston (106).

Description

Field of the invention

[0001] The invention relates to a brake actuator for a friction brake, a friction brake with such a brake actuator and a vehicle with at least one such friction brake. State of the art

[0002] A brake actuator of a friction brake can generate the required contact force to create friction between the brake pads and a rotor of the friction brake. The brake actuator can be electromechanical, for example. An electric motor generates a rotary motion, which is converted into a linear motion via a rotary-translator gear. The linear motion is then transmitted to at least one brake pad.

[0003] Since the brake pad mounts require some play to allow for the brake pad's linear movement, the brake pad moves in one direction of rotation of the rotor during braking until it is held by the mounts. This movement occurs perpendicular to the linear movement and is also transmitted to the rotary-translator gear. Disclosure of the invention

[0004] Against this background, the approach presented here presents a brake actuator for a friction brake, a friction brake with such a brake actuator, and a vehicle with at least one such friction brake according to the independent claims. Advantageous further developments and improvements of the approach presented here emerge from the description and are described in the dependent claims. Advantages of the invention

[0005] In the approach presented here, a rotary-translatory gear of a brake actuator, for example a ball screw or a screw drive, is decoupled from the effects of lateral forces by an additional decoupling element.

[0006] Here, angular mobility between the transmission and a piston acting on a brake pad is ensured by an angle compensation element. This allows the piston to tilt slightly laterally in response to lateral forces without this tilting movement being transmitted to the transmission. However, a direct coupling is still maintained in an axial direction of the transmission.

[0007] The approach presented here allows the gearbox to be dimensioned for only axial loads, as the angle compensation element prevents any lateral loads from being introduced into the gearbox. This allows the gearbox to be manufactured cost-effectively, as oversizing is not required.

[0008] A brake actuator for a friction brake is presented, wherein the brake actuator has a piston and a rotary-translatory gear for converting a rotary movement of a drive into a linear movement of the piston, wherein an angle compensation element for decoupling the translational component from transverse forces on the piston is arranged between a translational component of the gear and the piston.

[0009] Furthermore, a friction brake for a vehicle is presented, wherein the friction brake has a rotor, a brake caliper and a brake actuator according to the approach presented here, wherein a movable brake pad of the friction brake is arranged between the brake actuator and one side of the rotor and a fixed brake pad of the friction brake is arranged between the brake caliper and an opposite side of the rotor, wherein the angle compensation element arranged between the translational component of the transmission and the piston is configured to decouple the translational component from transverse forces on the piston.

[0010] Furthermore, a vehicle with at least one friction brake according to the approach presented here is presented.

[0011] Ideas for embodiments of the present invention can be considered, among other things, to be based on the thoughts and findings described below.

[0012] A brake actuator can be an electromechanical brake actuator, abbreviated as EMB. The brake actuator can be mounted on a brake caliper or a brake calliper of a disc brake. The brake actuator has an electric drive motor, a rotary-translator gear, and a piston mounted in the brake caliper. Similar to a hydraulic brake, the piston presses against the back of a brake pad of the disc brake. The brake pad is movably mounted in the brake caliper by a guide. A counterforce to the contact force of the piston is supported on the brake caliper via the rotary-translator gear and transmitted to an opposite brake pad of the disc brake. This clamps the brake disc between the brake pads, and the brake pads are pressed against the opposing friction surfaces of the brake disc with approximately the same force to generate friction.

[0013] When friction generates a braking force, a counterforce to the braking force is absorbed by the brake pad guides. Until the counterforce is fully absorbed, the brake pads move perpendicular to the contact force. This exerts a lateral force on the piston during braking.

[0014] The lateral force causes a slight tilt of the piston in the brake caliper. In the approach presented here, the angle compensation element decouples the rotational-translational transmission from this tilt.

[0015] The angle compensation element can be designed as a type of ball joint. At least a partial area of ​​a spherical socket can be formed on one part of the angle compensation element. Another part of the angle compensation element can be supported in the spherical socket for angular movement. Alternatively or additionally, at least a partial area of ​​a spherical surface can be formed on one part of the angle compensation element. The spherical surface can be supported in an angular movement on another part of the angle compensation element. A spherical socket can be concave. A spherical surface can be convex. A spherical socket and / or spherical surface is particularly well suited to transmitting high compressive forces at variable angles. If the spherical socket and the spherical surface fit together, a low surface pressure results despite a high contact force.Rolling elements can be arranged between the spherical shell and the spherical surface, resting against the spherical shell or spherical surface. The rolling elements can be balls or rollers, for example. Balls can have point contact with the spherical shell or spherical surface. Rollers can have line contact with the spherical shell or spherical surface. In this case, the angle compensation element can be designed as a low-friction rolling bearing.

[0016] The part of the angle compensation element with the spherical surface can be connected to the translational component of the gear. A spherical surface can be formed on the translational component particularly easily, for example, by turning. The spherical surface can be integrally connected to the translational component via a stem.

[0017] The spherical surface can be at least a hemisphere. The spherical surface can also be, for example, a three-quarter sphere. The spherical surface can rest laterally against the other part of the angle compensation element and be laterally guided on the other part. The spherical surface can have at least linear contact with the other part. Alternatively, the spherical surface can have a circumferential groove. A spring washer can be arranged in the groove and held under tension by the other part. The spring washer can lock the spherical surface into the other part.

[0018] The part with the spherical surface can be pressed into the other part. By pressing the spherical surface into an undersized recess, i.e., a press fit, the angle compensation element can transmit tensile forces and actively retract the piston.

[0019] The angle compensation element can also be designed to compensate for lateral positioning errors. For example, a spring washer can be arranged in a deep circumferential groove. The spring washer can have lateral play in the groove. By moving the spring washer relative to the sphere's surface, positioning errors can be compensated in addition to angular errors.

[0020] The angle compensation element can have a sliding piece. The sliding piece can be supported on a radial sliding surface of the piston. The sliding piece can, in particular, form the spherical socket. The sliding piece can slide laterally on the sliding surface to compensate for positioning errors.

[0021] At least one sliding ring can be arranged between the piston and a cylinder wall of the brake actuator. Since the brake actuator functions without hydraulic fluid, piston seals are not required. In a hydraulic brake, the piston seals not only seal the piston but also axially guide the piston. A sliding ring can be made of a more abrasion-resistant material than a seal and is less expensive. The sliding ring can be made of a plastic material, for example. The sliding ring can be arranged at the level of one end of the rotary component, for example. The piston can then tilt in the sliding ring, thus deflecting lateral loads from the translational component.

[0022] A position compensation element can be arranged between the piston and the brake pad of the friction brake to decouple the piston from transverse forces on the brake pad. A position compensation element can enable lateral displacement between the brake pad and the piston within a predefined displacement range. In a simple design, the position compensation element can be a plain bearing. The position compensation element can at least substantially prevent the transmission of the lateral displacement of the brake pad to the piston during braking. The lateral freedom of movement of the brake pad reduces the tilting of the piston. The piston can then essentially only be tilted due to one-sided wear of the brake pad and / or tilting of the brake pad.

[0023] The position compensation element can be designed as an axial bearing with lateral tolerance. The position compensation element can be designed primarily to transmit axial forces. Lateral forces and / or axial torques, in particular, cannot be transmitted.

[0024] The position compensation element can be designed as a rolling bearing. The position compensation element can have rolling elements arranged between two running surfaces. The rolling elements can have point contact or line contact with at least one of the running surfaces. The rolling element can be a bearing for rotary motion and have circularly arranged rolling elements. Alternatively, the rolling element can also be a linear bearing and have rolling elements arranged in rows. The rows can be aligned with an expected direction of movement of the brake pad.

[0025] The rolling bearing can be designed as a needle bearing or a roller bearing. Needles or rollers can have a larger contact area with the raceways via line contact. The large contact area allows for low surface pressure on the raceways and rolling elements. The large contact area allows the rolling bearing to tolerate tilting, i.e., asymmetrical loading, without damaging the needles or rollers. The rolling elements on one side of the bearing can be subjected to greater loads than those on the opposite side.

[0026] The rolling bearing can be designed as a self-aligning bearing. The rolling bearing can have spherical or curved running surfaces, at least in some areas. As a self-aligning bearing, the rolling bearing can compensate for angular tolerances while ensuring that the rolling elements of the bearing are evenly loaded.

[0027] The rolling bearing can have a two-part shell. Tensile forces can be transmitted via the shell. A shell can consist of nested sealing shells. The sealing shells can form a labyrinth seal. Due to the nesting, the resulting tensile forces can be transmitted from the piston to the brake pad when the brake pad is retracted.

[0028] It should be noted that some of the possible features and advantages of the invention are described herein with reference to different embodiments. One skilled in the art will recognize that the features may be appropriately combined, adapted, or interchanged to achieve further embodiments of the invention. Short description of the drawing

[0029] Embodiments of the invention are described below with reference to the accompanying drawings, wherein neither the drawings nor the description are to be interpreted as limiting the invention. Fig. 1 shows a detailed sectional view of a brake actuator according to an embodiment.

[0030] The figure is merely schematic and not to scale. Like reference numerals denote like or equivalent features. Embodiments of the invention

[0031] Fig.1 shows a detailed sectional view of a brake actuator 100 according to one exemplary embodiment. The brake actuator 100 is integrated into a brake caliper 102 of a disc brake. The brake actuator 100 has a drive, a rotary-translator gear 104, and a piston 106. The piston acts on a brake pad 108 of the disc brake. For example, the piston 106 presses on a back plate 110 of the brake pad 108, with an intermediate plate 112 arranged between the back plate 110 and the piston 106.

[0032] Here, an angle compensation element 116 is arranged between a translational component 114 of the transmission 104 and the piston 106. The angle compensation element 116 enables angular mobility between the piston 106 and the translational component 114. As a result, a tilting of the piston 106 from a rotational axis 118 of a rotary component 120 of the transmission 104 is not transmitted to the translational component 114 when transverse forces act on the piston 106 during braking.

[0033] In one embodiment, the angle compensation element 116 is designed as a type of ball joint. At least one side of the angle compensation element 116 has a positive or negative spherical shape, at least in some areas. Here, a ball 122 is formed on the translational component 114 and is arranged in a receptacle 124 of the piston 106.

[0034] In one embodiment, the ball 122 is pressed into the receptacle 124. The receptacle 124 is therefore undersized compared to the ball 122. As a result, the ball 122 does not jump out of the receptacle 120 even when slight tensile forces are transmitted, such as when the brake pad 108 is retracted from the brake disc 126.

[0035] In one embodiment, the receptacle 124 also has a spherical shape in a partial area. The spherical shape is arranged in particular in the area of ​​a point of intersection of the rotational axis 118. This results in an enlarged contact surface between the ball 122 and the receptacle 124. The enlarged contact surface results in reduced surface pressure on the ball 122 and the receptacle 124 during braking.

[0036] In one embodiment, the ball 122 has a circumferential line contact with the receptacle 124. Due to the line contact, the ball 122 is guided laterally in all directions perpendicular to the rotation axis 118.

[0037] In one embodiment, at least one sliding ring 130 is arranged between the piston 106 and a base body 128 of the brake caliper 102. The sliding ring 130 is arranged in a groove in a cylindrical surface of a piston bore of the base body 128 and protrudes slightly beyond the cylindrical surface. As a result, a small gap exists between the cylindrical surface and a circumferential surface of the piston 106, and the piston 106 does not touch the base body 128.

[0038] In one embodiment, the sliding ring 130 is arranged in the region of the angle compensation element 116. This allows the piston 106 to tilt in the sliding ring 130 without laterally deflecting the translational component 114.

[0039] In one embodiment, the sliding ring 130 is made of a plastic material. This provides the sliding ring 130 with good sliding properties on its outer surface. The plastic material is particularly harder than the sealing material of sealing rings, such as those used in hydraulic brakes.

[0040] In the following, possible embodiments of the invention are summarized again or presented with slightly different wording.

[0041] A mechanism for generating axial force for electromechanical brakes is presented.

[0042] In an electro-hydraulic brake, the rotation of a motor can be translated into the translational movement of a piston to generate hydraulic pressure with the help of a planetary gear and a ball screw. The piston can be guided in a piston guide of a valve housing. Seals can also help guide and center the piston in the valve housing. The ball screw can be rigidly coupled to the piston, which is guided in the valve housing without any angular freedom. This means that the accuracy of the ball screw in linear movement must be so good that the piston within its guide in the valve housing does not experience excessive wear over its service life. This can require an expensive coating of the valve housing (partial anodizing).

[0043] In an electromechanical brake (EMB), a large lateral force acts on the piston via the brake pads, and the hydraulic pressure that helps center the piston in its guide is missing. Therefore, a robust rotation-translation mechanism for an EMB is presented here. The piston is connected to the ball screw via a radially flexible spherical connection. This allows the accuracy of the ball screw for linear motion to be reduced compared to current designs. This results in a cost-effective ball screw design with low component costs. Grinding of parts can be avoided.

[0044] The piston is additionally guided by a plastic ring mounted in the piston housing. This eliminates the need for complex coating of the piston housing (e.g., anodizing) to prevent excessive wear over its service life.

[0045] The flexible connection is achieved by the spherical design of the inner part of the ball screw, which is attached to the piston with a press fit, allowing radial angular compensation between the movement of the piston and the movement of the ball screw. This design eliminates any play along the piston axis for the linear movement of the piston. Instead, it can compensate for a deviation from the axial movement of the ball screw and its fixation in the piston housing, which does not follow the piston movement in its guide via the plastic ring in the piston housing.

[0046] In this way, the interference fit, together with the ball design, can compensate for axial misalignments between the piston movement and the ball screw movement. However, the axial connection of the ball screw to the piston, especially during the piston's backward movement, is ensured by the detailed design of the interference fit with the line contact of the ball to the press-fit geometry of the piston.

[0047] Summary of axial force flow: The piston presses onto the brake disc via the intermediate disc on the back plate with the brake pad.

[0048] The proposed design offers a robust and cost-effective solution, as the plastic ring avoids the partial anodizing of the piston housing and the use of the low-cost (non-ground) components of the ball screw drive.

[0049] Finally, it should be noted that terms such as "comprising," "having," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Reference signs in the claims are not to be considered limiting.

Claims

[1] Brake actuator (100) for a friction brake, wherein the brake actuator (100) has a piston (106) and a rotary-translator gear (104) for converting a rotary movement of a drive into a linear movement of the piston (106), wherein an angle compensation element (116) for decoupling the translatory component (114) from transverse forces on the piston (106) is arranged between a translatory component (114) of the gear (104) and the piston (106). [2] Brake actuator (100) according to claim 1, wherein the angle compensation element (116) is designed as a type of ball joint, wherein at least a partial region of a spherical shell is formed on one part (124) of the angle compensation element (116) and another part (120) of the angle compensation element (116) is supported in the spherical shell in an angularly movable manner. [3] Brake actuator (100) according to one of the preceding claims, in which the angle compensation element (116) is designed as a type of ball joint, wherein at least a partial area of ​​a spherical surface is formed on one part (122) of the angle compensation element (116) and the spherical surface is supported in an angularly movable manner on another part (124) of the angle compensation element (122). [4] Brake actuator (100) according to claim 3, wherein the part (122) with the spherical surface is connected to the translational component (114). [5] Brake actuator (100) according to one of claims 3 to 4, wherein the spherical surface is at least a hemisphere, wherein the spherical surface bears laterally against the other part (124) and is guided laterally on the other part (124). [6] Brake actuator (100) according to claim 5, wherein the part (122) with the spherical surface is pressed into the other part (124). [7] Brake actuator (100) according to one of the preceding claims, wherein the angle compensation element (116) is further designed to compensate for lateral position errors. [8] Brake actuator (100) according to claim 7, wherein the angle compensation element (116) has a sliding piece which is supported on a radial sliding surface of the piston (106). [9] Brake actuator (100) according to one of the preceding claims, wherein at least one sliding ring (130) is arranged between the piston (106) and a cylinder wall of the brake actuator (100). [10] Brake actuator (100) according to one of the preceding claims, in which a position compensation element for decoupling the piston (106) from transverse forces on the brake pad (108) is arranged between the piston (106) and a brake pad (108) of the friction brake. [11] Brake actuator according to claim 10, wherein the position compensation element is designed as an axial bearing with lateral tolerance. [12] Brake actuator according to one of claims 10 to 11, wherein the position compensation element is designed as a rolling bearing. [13] Friction brake for a vehicle, wherein the friction brake comprises a rotor, a brake caliper (102) and a brake actuator (100) according to one of claims 1 to 12, wherein a movable brake pad (108) of the friction brake is arranged between the brake actuator (100) and one side of the rotor and a fixed brake pad of the friction brake is arranged between the brake caliper (102) and an opposite side of the rotor, wherein the angle compensation element (116) arranged between the translational component (114) of the gear (104) and the piston (106) is configured to decouple the translational component (114) from transverse forces on the piston (106). [14] Vehicle with at least one friction brake according to claim 13.

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