Brake actuator for a friction brake, friction brake and vehicle

Abstract

The present invention relates to a brake actuator (100) for a friction brake, wherein the brake actuator (100) has at least one piston (106) acting on a brake pad (108) of the friction brake, wherein a position compensation element (114) for decoupling the piston (106) from transverse forces on the brake pad (108) is arranged between the piston (106) and the brake pad (108).

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 provides 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, the mobility of a brake pad relative to a piston acting on it is ensured by a position compensation element. This largely prevents the effect of lateral forces on the piston. Without the lateral forces, the piston is not moved transversely to a designated axial direction, and the rotational-translational gear is not subjected to asymmetric loads.

[0007] The approach presented here allows the gearbox to be dimensioned for only axial loads, as the position 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 at least one piston acting on a brake pad of the friction brake, wherein a position compensation element for decoupling the piston from transverse forces on the brake pad is arranged between the piston and the brake pad.

[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 position compensation element of the brake actuator arranged between the piston of the brake actuator and the movable brake pad is configured to decouple the piston from transverse forces on the brake pad.

[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 would exert a lateral force on the piston during braking.

[0014] In the approach presented here, the position compensation element decouples the piston from this lateral movement and thus from lateral force.

[0015] The 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 movement of the brake pad to the piston during braking. The lateral freedom of movement of the brake pad also reduces piston tilting. The piston can then essentially only be tilted due to one-sided wear of the brake pad and / or tilting of the brake pad.

[0016] 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.

[0017] At least a portion of a spherical socket can be formed on at least one part of the position compensation element. Another part of the position compensation element can be supported in the spherical socket for angular movement. This angular movement can prevent the transmission of a tilting movement of the brake pad to the piston. This allows the piston to be subjected to only a purely axial load. This also applies a purely axial load to the rotary-translatoric transmission.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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 preventing lateral loads from being applied to the translational component.

[0023] An angle compensation element can be arranged between the piston and a translational component of a rotary-translational gear of the brake actuator to decouple the translational component from transverse forces on the piston. 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 for transmitting high compressive forces at variable angles.When the ball socket and the ball surface fit together, low surface pressure results despite high contact force. Rolling elements can be arranged between the ball socket and the ball surface, which rest against the ball socket or ball surface. The rolling elements can be balls or rollers, for example.

[0024] Balls can have point contact with the ball shell or ball surface. Rollers can have line contact with the ball shell or ball surface. In this case, the angle compensation element can be designed as a low-friction rolling bearing.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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

[0031] 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.

[0032] The figure is merely schematic and not to scale. Like reference numerals denote like or equivalent features. Embodiments of the invention

[0033] 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.

[0034] Here, a position compensation element 114 is arranged between the intermediate plate 112 and the piston 106. The position compensation element 114 enables a lateral relative movement between the piston 106 and the brake pad 108. As a result, the piston 106 is no longer depressed laterally during braking and moves purely axially along a rotational axis 116 of the rotary-translator gear 104.

[0035] In one embodiment, the position compensation element 114 is designed as an axial bearing with lateral position tolerance. The axial bearing is aligned with the rotational axis 116. A part 118 of the position compensation element 114 coupled to the brake pad 108 or the intermediate plate 112 can be displaced by the position tolerance relative to a part 120 of the position compensation element 114 coupled to the piston 106.

[0036] The position compensation element 114 also has an angular tolerance. Even if the brake pad 108 is tilted relative to the rotation axis 116, the position compensation element 114 has sufficient contact surface to prevent plastic deformation.

[0037] In one embodiment, the position compensation element 114 is designed as a rolling bearing. Here, rolling elements 122 are arranged between the two parts 118, 120 of the position compensation element 114. The rolling elements 122 rest against the running surfaces of the parts 118, 120. The running surfaces are wider than the rolling elements 122. This provides the rolling bearing with the position tolerance.

[0038] In one embodiment, the rolling elements 122 are needle-shaped. The rolling bearing is thus an axial needle bearing.

[0039] In one embodiment, the rolling bearing is sealed. Parts 118, 120 are designed as bearing shells and have labyrinth seals 124. Tensile forces are transmitted between the bearing shells via nesting of the labyrinth seals 124. Compressive forces are transmitted via the rolling elements 122.

[0040] In one embodiment, at least one of the parts 118, 120 is crowned or hollow. As a result, the position compensation element 114 also has an angular tolerance. For example, due to wear or forces acting during braking, the brake pad 108 can be slightly inclined to the rotation axis 116 without resulting in one-sided loading of the position compensation element 114. For example, the brake pads 108 can be worn more severely on the side where the brake disc 126 enters between the brake pads 108 than on the side where the brake disc exits between the brake pads 108.

[0041] In one embodiment, the rolling bearing is designed as a self-aligning bearing. The running surfaces approximately represent spherical surfaces, at least in some areas. Due to the self-aligning bearing, the position compensation element 114 also has an angular tolerance.

[0042] 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.

[0043] 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.

[0044] In the following, possible embodiments of the invention are summarized again or presented with slightly different wording.

[0045] A needle bearing mechanism for generating axial force for electromechanical brakes is presented.

[0046] 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).

[0047] 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. The mechanism incorporates the same ball screw drive technology as an electrohydraulic brake, with the same rigid locking mechanism for the ball screw on the piston.

[0048] In the proposed approach, the piston is connected to the intermediate disk via a needle bearing, which centers the outer ring of the needle bearing. The axial force generated by the ball screw is transmitted via the inner ring centered on the piston to the rollers on the outer ring centered in the intermediate disk.

[0049] The needle bearing ensures radial tolerance compensation of the ball screw relative to the intermediate disk and additionally compensates for the lateral forces resulting from the braking force generated by the brake pad.

[0050] In this way, the accuracy of the ball screw for linear motion can be reduced compared to current designs. This results in a cost-effective ball screw design with inexpensive parts. Grinding of parts can be avoided.

[0051] The piston is also 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.

[0052] Summary of axial force flow: The piston presses via the needle bearing onto the intermediate disc on the back plate with the brake pad onto the brake disc.

[0053] The proposed design offers a robust and cost-effective solution, as partial anodizing of the piston housing is avoided by using a plastic ring. Furthermore, the design allows for the use of cost-effective (non-ground) ball screw components through the radial force compensation provided by the needle bearing.

[0054] 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 at least one piston (106) acting on a brake pad (108) of the friction brake, wherein a position compensation element (114) for decoupling the piston (106) from transverse forces on the brake pad (108) is arranged between the piston (106) and the brake pad (108). [2] Brake actuator (100) according to claim 1, wherein the position compensation element (114) is designed as an axial bearing with lateral tolerance. [3] Brake actuator (100) according to one of the preceding claims, wherein the position compensation element (114) is designed as a rolling bearing. [4] Brake actuator (100) according to claim 3, wherein the rolling bearing is designed as a needle bearing or roller bearing. [5] Brake actuator (100) according to one of the preceding claims, in which at least a partial region of a spherical shell is formed on at least one part (118) of the position compensation element (114), wherein another part (120) of the position compensation element (114) is supported in the spherical shell in an angularly movable manner. [6] Brake actuator (100) according to one of claims 3 to 4 and claim 5, wherein the rolling bearing is designed as a self-aligning bearing. [7] Brake actuator (100) according to one of claims 3 to 6, wherein the rolling bearing has a two-part shell, wherein tensile forces are transmitted via the shell. [8] 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). [9] Brake actuator (100) according to one of the preceding claims, in which an angle compensation element for decoupling the translational component from transverse forces on the piston (100) is arranged between the piston (106) and a translational component of a rotary-translational gear (104) of the brake actuator (100). [10] Brake actuator (100) according to claim 9, wherein the angle compensation element is designed as a type of ball joint, wherein at least a partial region of a spherical shell is formed on one part of the angle compensation element and another part of the angle compensation element is supported in the spherical shell in an angularly movable manner. [11] Friction brake for a vehicle, the friction brake comprising a rotor, a brake caliper (102) and a brake actuator (100) according to one of claims 1 to 10, 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 position compensation element (114) of the brake actuator (100) arranged between the piston (106) of the brake actuator (100) and the movable brake pad (108) is configured to decouple the piston (106) from transverse forces on the brake pad (108). [12] Vehicle with at least one friction brake according to claim 11.

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