Electromechanical vehicle brake

Abstract

Electromechanical vehicle brake (10) with at least one brake caliper (12) in which a space (14) for receiving a brake rotor (16) is provided, a first linearly guided brake piston (20), a first brake pad (18) associated with the first brake piston (20) and to be moved by it, a second linearly guided brake piston (22) and a second brake pad (19) associated with the second brake piston (22) and to be moved by it, wherein the brake pads (18, 19) are associated with a common brake rotor (16) and can be applied to the brake rotor (16) by their associated brake piston (20, 22), and a drive assembly (24) for moving the two brake pistons (20, 22) between a retracted position and an extended position, wherein the drive assembly (24) comprises a differential gear (32).

Description

[0001] The invention relates to an electromechanical vehicle brake.

[0002] Electromechanical vehicle brakes are used, for example, as service brakes in vehicles. Vehicle brakes are typically designed with a desired brake clamping force in mind. The higher the clamping force required, the larger the vehicle brake components must be. In particular, the size of the brake piston increases with increasing clamping force requirements.

[0003] Instead of a single brake piston, two smaller brake pistons can be used to achieve the same clamping force. This is advantageous in terms of radial space requirements, as the two brake pistons have a smaller diameter than a single brake piston designed for the same clamping force. However, the disadvantage is that each of the two brake pistons requires a separate drive, which increases costs.

[0004] It is therefore an object of the invention to provide an optimized electromechanical vehicle brake for high clamping force requirements, which is optimized with regard to size and costs.

[0005] This object is achieved according to the invention by an electromechanical vehicle brake having at least one brake caliper in which there is an intermediate space for receiving a brake rotor, a first linearly guided brake piston, a first brake pad assigned to the first brake piston and moved by it, a second linearly guided brake piston, and a second brake pad assigned to the second brake piston and moved by it. The brake pads are assigned to a common brake rotor and can be applied to the brake rotor by their assigned brake piston. The electromechanical vehicle brake also comprises a drive assembly for moving the two brake pistons between a retracted position and an extended position, wherein the drive assembly comprises a differential gear.

[0006] Using a differential gear, both brake pistons can be driven by a common drive. This allows for a cost-effective and compact vehicle brake design. The drive control is also simplified, as only a single drive needs to be controlled.

[0007] The use of a differential gear can also compensate for an imbalance in the clamping force between the two brake pistons. Such an imbalance arises, for example, when the brake pads are applied to the brake rotor with different clamping forces due to a wedge effect. The differential gear also ensures even wear on the brake pads. Conversely, the differential gear can compensate for uneven wear on the brake pads, as differences in clamping force due to premature application of one brake pad compared to the other are compensated by the differential gear.

[0008] The two brake pistons can be guided in a common, one-piece brake caliper or each in its own separate brake caliper.

[0009] The drive assembly includes, for example, an electric motor configured to drive the first brake piston and the second brake piston simultaneously via the differential gear. The required clamping force of the vehicle brake can thus be achieved by appropriately controlling the electric motor.

[0010] The drive assembly can be designed such that the first brake piston and the second brake piston move at the same speed. In this case, the design of the drive assembly is particularly simple. The contact pressure of the brake pistons can thus be controlled solely by a corresponding rotation of the electric motor.

[0011] In an alternative embodiment, the drive assembly can be designed such that the first brake piston and the second brake piston are moved at different speeds. In this case, one of the two brake pistons is leading, so that the brake pad assigned to the leading brake piston is applied to the brake rotor before the other brake pad. This can influence the distribution of the clamping force. Furthermore, with such a vehicle brake, it is also conceivable that in a low force range, i.e. when the clamping force is low or at low vehicle speeds, only one of the two brake pads is applied to the brake rotor. When the clamping force is higher, both brake pistons can be extended far enough by continuously driving the differential gear, in particular by the electric motor, that both brake pads are applied to the brake rotor.In this case, the differential gear compensates for the different clamping forces of both brake pistons, thereby counteracting an undesirable wedge effect.

[0012] Furthermore, it is conceivable that the leading brake piston or the associated brake pad serves as a brake rotor wiper without causing any noticeable braking force.

[0013] The drive assembly is preferably designed such that the rear brake piston, viewed in the direction of rotation of the brake rotor, leads the other brake piston. This means that the brake piston at which the brake rotor terminates is the leading piston. When viewed in the vehicle, this is the front brake piston. This allows the so-called wedge brake principle to be simulated. According to this principle, when only a single brake piston is present, the brake piston is deliberately positioned slightly at an angle to the brake rotor to compensate for deformation of the brake caliper. This ensures that, in an active braking state, the brake pads are in contact with the brake rotor over as much of their entire surface as possible, particularly under high clamping forces.

[0014] According to one embodiment, the differential gear comprises a housing rotatable about an axis, wherein the axis is defined by opposing output shafts extending outward through the housing. Each output shaft is assigned to only one of the brake pistons. The output shafts are coupled inside the housing to one of two opposing output bevel gears, both of which mesh with an input bevel gear projecting into the interior of the housing and freely rotatably mounted on the housing. The output bevel gears can thus rotate together with the housing about the housing's axis of rotation and about themselves.

[0015] In this way, the differential gear can compensate for differences in the rotational speed of the output shafts, which are coupled to the brake pistons, as soon as one of the two brake pistons encounters resistance.

[0016] On the output side of the differential gear, a separate intermediate gear is preferably provided for each brake piston, with different gear ratios. The different gear ratios easily achieve different travel speeds for the brake pistons.

[0017] A planetary gear can be interposed between the electric motor and the differential gear. This allows the electric motor to be positioned radially offset from the differential gear, while simultaneously achieving a flat design for the vehicle brake.

[0018] To further increase the radial offset between the electric motor and the differential gear without increasing the size of the planetary gear itself, a spur gear can be inserted between the electric motor and the planetary gear. This allows the distance between the electric motor and the differential gear to be adjusted as easily as possible to the available space.

[0019] Further advantages and features of the invention will become apparent from the following description and from the accompanying single drawing, to which reference is made. This drawing shows, partly schematically, an electromechanical vehicle brake according to the invention.

[0020] In Fig. 1 shows an electromechanical vehicle brake 10.

[0021] The vehicle brake 10 represents a service brake of a vehicle. This means that the vehicle brake is actuated in the normal service braking case and not only in the parking brake case or exceptionally as an emergency brake.

[0022] The vehicle brake 10 comprises a brake caliper 12.

[0023] A space 14 is provided in the brake caliper 12 to accommodate a brake rotor 16.

[0024] Brake pads 18, 19 are arranged in the intermediate space and can be applied to the brake rotor 16. The brake rotor 16 represents, in particular, a common brake rotor for the brake pads 18, 19.

[0025] The vehicle brake 10 further comprises a first linearly guided brake piston 20 and a second linearly guided brake piston 22. Each brake piston 20, 22 is movable by axial displacement between a retracted position and an extended position.

[0026] Each brake piston 20, 22 is assigned one of the brake pads 18, 19, which are to be moved by the associated brake piston 20, 22. The brake pads 18, 19 can thus be applied to the brake rotor 16 by their associated brake piston 20, 22.

[0027] A drive assembly 24 is provided for moving the brake pistons 20, 22.

[0028] The drive assembly 24 comprises an electric motor 26, a spur gear 28, a planetary gear 30, a differential gear 32, two intermediate gears 34, 36, and a first and a second spindle drive 38, 40, each of which is implemented as a ball screw drive in the exemplary embodiment. The individual intermediate stages are arranged in the sequence mentioned in the operative flow between the electric motor 26 and the spindle drives 38, 40.

[0029] The spindle drives 38, 40 each have a rotatably mounted, electric motor-driven spindle 42, 44.

[0030] One of the brake pistons 20, 22 is seated on each of the spindles 42, 44. The brake pistons 20, 22 represent in particular a spindle nut of the respective spindle drive 38, 40.

[0031] A rotation of the spindles 42, 44 consequently causes an axial movement of the associated brake piston 20, 22.

[0032] The electric motor 26 is coupled to the spindles 42, 44 via the aforementioned gears in order to move the brake pistons 20, 22 between the retracted and extended positions.

[0033] The spur gear 28 is arranged between the electric motor 26 and the planetary gear 30. In the exemplary embodiment, the spur gear 28 comprises three spur gears 45, 46, 47. Alternatively, however, the spur gear 28 can also have a different number of spur gears.

[0034] The spur gear 47, which forms the output gear of the spur gear 28, drives a sun gear 48 of the planetary gear 30. A planet gear carrier 50 of the planetary gear 30 forms the output of the planetary gear 30 and is coupled to the differential gear 32 via an intermediate gear 52.

[0035] The planetary gear 30 is therefore arranged between the electric motor 26 and the differential gear 32.

[0036] The differential gear 32 comprises a housing 54 rotatable about a fictitious axis X.

[0037] The housing walls of the housing 54 may be at least partially open, so that the housing 54 represents a cage.

[0038] The axis X is defined by opposite output shafts 56, 58 extending outward through the housing 54.

[0039] Each output shaft 56, 58 is assigned to only one of the two brake pistons 20, 22.

[0040] The output shafts 56, 58 are coupled inside the housing 54 to one of two opposite output bevel gears 60, 62, both of which come with an input bevel gear 64 projecting into the interior of the housing 54 and freely rotatably mounted on the housing 54.

[0041] The output shafts 56, 58 each drive a drive wheel 65, 66 of the intermediate gears 34, 36.

[0042] An output gear 67, 68 of the intermediate gears 34, 36 is coupled to a spindle 42, 44 of the spindle drives 38, 40 in order to rotate them.

[0043] In the exemplary embodiment, the intermediate gears 34, 36 have two gears, but it is also conceivable that the intermediate gears 34, 36 have more than two gears.

[0044] In the exemplary embodiment, the drive assembly 24 is designed such that the first brake piston 20 and the second brake piston 22 are moved at different speeds.

[0045] Specifically, the drive assembly 24 is designed such that the rear brake piston 20, viewed in the direction of rotation of the brake rotor 16, is ahead of the other brake piston 22.

[0046] This is achieved in the exemplary embodiment by the fact that the gear ratios of the intermediate gears 34, 36 are different.

[0047] The intermediate gear 34, which is assigned to the first brake piston 20, has in particular a larger gear ratio than the intermediate gear 36, which is assigned to the second brake piston 22.

[0048] At the Fig. 1 illustrates the vehicle brake 10. During forward travel, the brake rotor 16 rotates from right to left, i.e., counterclockwise. Specifically, the brake rotor 16 engages the right brake piston 22 and disengages the left brake piston 20.

[0049] In an alternative embodiment, not shown for simplicity, the intermediate gears 34, 36 have the same gear ratio. In this case, the first brake piston 20 and the second brake piston 22 move at the same speed.

[0050] The operation of the vehicle brake 10 is described below.

[0051] If the electric motor 26 is controlled, for example by a control unit 70, the electric motor 26 drives the spindles 42, 44 of the spindle drives 38, 40 to move the brake pistons 20, 22 from their retracted position toward the extended position. In particular, the electric motor 26 drives the spindles 42, 44 via the spur gear 28, the planetary gear 30, the differential gear 32, and the intermediate gears 34, 36.

[0052] Due to the different gear ratios of the intermediate gears 34, 36, the brake pistons 20, 22 are moved at different speeds.

[0053] The leading brake piston 20 therefore first encounters resistance when the associated brake pad 18 is applied to the brake rotor 16.

[0054] Until this point, the output shafts 56, 58 rotate at the same speed. The output bevel gears 60, 62, arranged in the housing 54 and coupled to the output shafts 56, 58, rotate together with the housing 54 until this point, but not about their own axes.

[0055] As soon as the brake pad 18 assigned to the leading brake piston 20 hits the brake rotor 16, the leading brake piston 20 can no longer be extended or can only be extended slightly further.

[0056] However, since the lagging brake piston 22 has not yet been fully extended, the differential gear 32 causes the output shafts 56, 58 to rotate at different rotational speeds until the brake pad 19 associated with the lagging brake piston 22 also rests against the brake rotor 16 and the desired clamping force has been reached.

[0057] The output bevel gears 60, 62 rotate both with the housing 54 and around their own axis.

Claims

[1] Electromechanical vehicle brake (10) with at least one brake calliper (12) in which there is an intermediate space (14) for receiving a brake rotor (16), a first linearly guided brake piston (20), a first brake pad (18) associated with the first brake piston (20) and to be moved by it, a second linearly guided brake piston (22) and a second brake pad (19) associated with the second brake piston (22) and to be moved by it, wherein the brake pads (18, 19) are associated with a common brake rotor (16) and can be applied to the brake rotor (16) by their associated brake piston (20, 22), and a drive assembly (24) for moving the two brake pistons (20, 22) between a retracted position and an extended position, wherein the drive assembly (24) comprises a differential gear (32). [2] Electromechanical vehicle brake (10) according to claim 1, characterized bythat the drive assembly (24) comprises an electric motor (26) which is designed to drive the first brake piston (20) and the second brake piston (22) simultaneously via the differential gear (32). [3] Electromechanical vehicle brake (10) according to one of the preceding claims, characterized by that the drive assembly (24) is designed such that the first brake piston (20) and the second brake piston (22) are moved at the same speed. [4] Electromechanical vehicle brake (10) according to claim 1 or 2, characterized by that the drive assembly (24) is designed such that the first brake piston (20) and the second brake piston (22) are moved at different speeds. [5] Electromechanical vehicle brake (10) according to claim 4, characterized bythat the drive assembly (24) is designed such that the rear brake piston (20) viewed in the direction of rotation of the brake rotor (16) is in advance of the further brake piston (22). [6] Electromechanical vehicle brake (10) according to one of the preceding claims, characterized by in that the differential gear (32) comprises a housing (54) rotatable about an axis (X), the axis (X) being defined by opposite output shafts (56, 58) extending outwards through the housing (54), each output shaft (56, 58) being assigned to only one of the brake pistons (20, 22), and the output shafts (56, 58) being coupled inside the housing (54) to one of two opposite output bevel gears (60, 62), both of which mesh with an input bevel gear (64) projecting into the interior of the housing (54) and freely rotatably mounted on the housing (54). [7] Electromechanical vehicle brake (10) according to one of the preceding claims, characterized bythat on the output side of the differential gear (32) a separate intermediate gear (34, 36) is provided for each brake piston (20, 22), the transmission ratios of the intermediate gears (34, 36) differing. [8] Electromechanical vehicle brake (10) according to one of the preceding claims and additionally according to claim 2, characterized by that a planetary gear (30) is interposed between the electric motor (26) and the differential gear (32). [9] Electromechanical vehicle brake (10) according to claim 8, characterized by that a spur gear (28) is interposed between the electric motor (26) and the planetary gear (30).

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