Electromechanical vehicle brake

Abstract

Title: Electromechanical vehicle brake Electromechanical brake (10) for a motor vehicle comprising an electric motor (14) mounted on a brake caliper housing (18), a transmission unit (30) coupled to a spindle (34) of a spindle drive unit (38) is driven by the electric motor (14) such that the brake actuator (42) is axially displaced to generate the brake force. A spindle nut (50) of the spindle drive unit (38) and the spindle (34) are rotatably mounted relative to each other by a first ball screw mechanism (66); a second ball screw mechanism (74) is provided between the spindle nut (50) and the brake caliper housing (18); the spindle nut (50) is rotatably mounted by this ball mechanism relative to the brake caliper housing (18). Figure 1

Description

Title of the invention: Electromechanical vehicle brake FIELD OF THE INVENTION

[0001] The present invention relates to an electromechanical brake for a motor vehicle comprising an electric motor mounted on a brake caliper housing, a transmission unit coupled to a spindle of a spindle drive unit is driven by the electric motor to axially move the brake adjustment member to generate the brake force. STATE OF THE ART

[0002] Usually the service brake is a brake in which the brake fluid pushes a brake piston with its lining against the brake disc to brake the vehicle. In contrast, the parking brake is an electromechanical brake. Due to the development of the electrification of vehicle equipment, the service brake must also be implemented as an electromechanical brake to avoid brake fluid and the corresponding complex structures of valves and pipes. Such an electromechanical brake allows for a considerable reduction in maintenance.

[0003] Document EP 0 944 781 B1 describes an electromechanically controlled brake for braking by pressing its brake lining against the brake disc. The brake comprises a spindle drive unit with a spindle and its nut; the spindle is connected to the brake lining. The spindle nut is integral with the sleeve surrounding it. The sleeve is rotatably mounted by a bearing in the brake caliper. The sleeve comprises permanent magnets forming the rotor of an electric motor. The sleeve is surrounded by a stator to drive the rotor. Rotation of the spindle nut axially moves the brake lining to exert a braking force.

[0004] Document EP 3 421 773 B1 describes a telescopic roller spindle actuator intended for aviation.

[0005] Document EP 0 448 711 B1 describes a spindle adjustment member with a rotating ball screw.

[0006] Document WO 2022 / 210677 A1 describes a ball circulation spindle.

[0007] PURPOSE OF THE INVENTION

[0008] The aim of the present invention is to develop an electromechanical vehicle brake which makes it possible to apply a significant braking force and which, nevertheless, is compact and economical to manufacture.

[0009] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0010] For this purpose, the invention relates to an electromechanical vehicle brake. This electromechanical brake comprises an electric motor mounted in a caliper housing brake and a transmission unit coupled to a spindle of a spindle drive unit driven by the electric motor to axially move the brake actuator either to generate the braking force.

[0011] This brake is characterized by a spindle nut of the spindle drive unit and the spindle are rotatably mounted relative to each other by a first ball screw mechanism, a second ball screw mechanism being provided between the spindle nut and the brake caliper housing, the spindle nut being rotatably mounted by this ball mechanism relative to the brake caliper housing.

[0012] A brake actuator is a component that axially drives the spindle nut to apply a force to the brake lining or brake disc. A ball screw mechanism is formed by a set of balls circulating in ball races made in two parts installed opposite each other. According to the invention, the spindle nut does not cooperate with the brake caliper housing by a rotational lock but is connected via a second ball screw mechanism, rotating relative to the brake caliper housing. This saves the rotational lock of the screw nut.

[0013] The two ball screw mechanisms allow the braking force to be received by a larger number of balls. This, in turn, allows a higher braking force to be applied for the electromechanical brake without extending the axial length of the spindle drive unit to install a larger number of balls. This allows a more compact electromechanical brake to be realized despite the higher braking force. To leave the level of the higher braking force unchanged, it is possible, as an alternative, either to use larger balls, which reduces the reduction with respect to the motor. Correspondingly, a much larger electric motor would have to be used, which would increase the cost of such an electromechanical brake. The device according to the invention composed of two ball screw mechanisms leaves the gear ratio unchanged so that the cost of the electric motor remains the same.The invention thus allows a more economical manufacture of the electromechanical brake although the braking force it provides is greater.

[0014] According to a preferred development of the invention, the spindle nut acts on the brake actuator by a rotationally decoupled bearing. The two ball screw mechanisms rotate not only the spindle, but also the spindle nut. The spindle nut, however, is part of the spindle transmission unit which transmits the braking force to the brake actuator. This arrangement of a corresponding bearing which decouples the rotational movement of the spindle nut prevents decoupling between the brake actuator and the brake lining. The brake lining is thus integral with the brake actuator.

[0015] According to another preferred development of the invention, the bearing is a plain bearing. A plain bearing has the advantage of being economical to manufacture. In addition, such a plain bearing is compact, which allows for the construction of an electromechanical brake with small dimensions. In addition, the plain bearing does not require much maintenance; it is easy to install and is not very sensitive to vibrations and noise. Thus, the plain bearing increases user comfort.

[0016] Preferably, the bearing is a needle bearing and advantageously an axial needle bearing, of low height. In addition, a needle bearing allows greater forces to be transmitted. A needle bearing also has a lower friction torque at low rotational speeds. Compared to plain bearings, the needle bearing wears less.

[0017] According to an advantageous development, the spindle transmission unit acts on a hydraulic piston to generate the brake pressure for the brake actuator. The braking force can thus be transmitted via the hydraulic fluid of the brake. As a result, the brake actuator does not act directly on the brake lining. The hydraulic transmission of the brake force provides an alternative to a purely mechanical transmission of the force.

[0018] Advantageously, the balls of the second ball mechanism are larger than the balls of the first ball screw mechanism. Larger balls have the advantage of resisting a higher force due to their larger bearing surface than those of small balls. The large balls of the second ball screw mechanism make it possible to introduce a reaction force opposite to the braking force, directly into the caliper housing. The spindle transmission unit can thus be designed for lower loads, which makes them less bulky.

[0019] According to a further development, the first ball screw mechanism has a ball return in the spindle. By means of a ball return, the balls are transported through a return channel to the axially opposite end of the ball screw mechanism. This allows for a greater actuating stroke. The realization of the return in the spindle does not result in additional bulk so that this ball return is space-saving.

[0020] The invention also applies to a vehicle equipped with such an electromechanical brake. This vehicle has the advantages and properties developed above. Brief description of the drawings

[0021] The present invention will be described below in more detail with the aid of embodiments of electromechanical brakes according to the invention shown in the attached drawings in which:

[0022] [Fig. 1] perspective view of an exemplary embodiment of an electromechanical brake,

[0023] [Fig.2] sectional view of an exemplary embodiment of a drive unit of spindle according to the invention,

[0024] [Fig.3] sectional view of another exemplary embodiment of a drive unit of spindle according to the invention.

[0025] DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0026] [Fig. 1] is a perspective view of an electromechanical brake 10 according to an exemplary embodiment of the invention. The electromechanical brake 10 comprises an electric motor 14 housed in a brake caliper housing 18. The electric motor 14 drives the transmission unit 30 formed of a screw 22 and a worm wheel 26. The worm wheel 26 drives a spindle 34 of a spindle drive unit 38 not shown in this figure, so as to move the brake actuator 42 (see [Fig. 2]) which comprises a thrust plate 46 in this exemplary embodiment, to move it axially for braking.

[0027] [Fig. 2] is a sectional view of the spindle drive unit 38 according to one embodiment of the invention. The spindle drive unit 38 comprises the spindle 34 driven by the worm wheel 26 and an axially adjustable nut 50. In the exemplary embodiment shown, the nut 50 acts via a bearing 54 on the brake actuator 42. The brake actuator 42 here comprises the thrust plate 46 provided with a brake lining 58. The bearing 54 of this exemplary embodiment is not detailed because it may be a plain bearing or a needle bearing.

[0028] A first ball screw mechanism 66 formed by a large number of balls 62 is provided between the spindle 34 and the nut 50; the spindle 34 and the nut 50 are rotatably mounted relative to each other by this mechanism. In addition, a second ball screw mechanism 74 having a large number of balls 70 is provided between the spindle nut 50 and the brake caliper housing 18; the nut 50 is rotatably mounted relative to the brake caliper housing 18 by this ball mechanism. The two ball screw mechanisms 66, 74 amplify the received braking force, without having to lengthen the spindle drive unit 38. In the exemplary embodiment shown, the balls 70 of the second ball screw mechanism 74 are larger than the screws 62 of the first ball screw mechanism 66. This increases the braking force that the brake caliper housing 18 must receive, which makes the spindle transmission unit 38 compact.

[0029] [Fig. 3] is a sectional view of a spindle drive unit 38 of another exemplary embodiment of the invention. This example differs from the spindle drive unit 38 shown in [Fig. 2] by a ball return 78 in the spindle 34 which guides the balls 62 at the axial end opposite that of the first ball screw mechanism 66.

[0030] NOMENCLATURE OF THE MAIN ELEMENTS

[0031] 10 Electromechanical brake

[0032]

[0033]

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[0040]

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[0044]

[0045]

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[0047]

[0048] 14 Electric motor 18 Brake caliper housing 20 Screw 26 Worm wheel 30 Transmission unit 34 Spindle 38 Spindle drive unit 42 Brake actuator 46 Pressure plate 50 Nut 54 Bearing 58 Brake lining 62 Ball of the first ball screw mechanism 66 First ball screw mechanism 70 Ball of the second ball screw mechanism 74 Second ball screw mechanism 78 Ball return

Claims

Claims

1. Electromechanical brake (10) for a motor vehicle comprising an electric motor (14) mounted in a brake caliper housing (18), a transmission unit (30) coupled to a spindle (34) of a spindle drive unit (38) is driven by the electric motor (14) to axially move the brake actuator (42) to generate the braking force, brake characterized in that a spindle nut (50) of the spindle drive unit (38) and the spindle (34) are rotatably mounted relative to each other by a first ball screw mechanism (66), a second ball screw mechanism (74) being provided between the spindle nut (50) and the brake caliper housing (18), the spindle nut (50) being rotatably mounted by this ball mechanism relative to the brake caliper housing (18).

2. Electromechanical brake (10) according to claim 1, characterized in that the spindle nut (50) acts on the brake actuator (42) by a bearing (54) decoupled from the rotational movement.

3. Electromechanical brake (10) according to claim 2, characterized in that the bearing (54) is a plain bearing.

4. Electromechanical brake (10) according to claim 2, characterized in that the bearing (54) is a needle bearing.

5. Electromechanical brake (10) according to one of the preceding claims, characterized in that the spindle drive unit (38) acts on a hydraulic piston to generate the brake force applied to the brake actuator (42).

6. Electromechanical brake (10) according to one of the preceding claims, characterized in that the balls (70) of the second ball screw mechanism (74) are larger than the balls (62) of the first ball screw mechanism (66).

7. Electromechanical brake (10) according to one of the preceding claims, characterized in that the first ball screw mechanism (66) has a ball return (78) provided in the spindle (34).

8. Vehicle comprising an electromechanical brake (10) according to one of the re- previous claims.

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