Brake device for a motor vehicle

Abstract

A brake device for a motor vehicle has a spreader unit (7) which, starting from a neutral position, is designed to produce a service brake in one drive direction and to produce self-locking of a function of a parking brake in the other drive direction. To this end, the spreader unit (7) has a nut / spindle unit (18) which selectively interacts with an axial bearing (25) or a frictional clutch device (27). As a result, the brake device is of particularly simple construction.

Description

[0001] Description

[0002] Braking device for a motor vehicle

[0003] The invention relates to a braking device for a motor vehicle with a braking element for generating a frictional engagement with a rotating component and with an actuator which can be driven in two directions of movement and moves the braking element relative to the rotating component, and with a spreading unit of the actuator.

[0004] Such braking devices are used in drum brakes operating according to the Simplex, Duplex, Duo Duplex or similar systems and in floating calipers, and are well known in practice. However, in addition to the function of a service brake, motor vehicles also require the function of a parking brake. In the service brake function, the spreading unit is intended to create the frictional connection between the braking element and the rotating component as quickly as possible when the actuator is energized and to release the frictional connection as quickly as possible when the actuator is de-energized. In the parking brake function, however, the frictional connection must be maintained even when the actuator is de-energized. Therefore, two actuators with respective spreading units are usually used for each function. However, this makes the braking device very complex in terms of construction.

[0005] The invention is based on the problem of developing a braking device of the type mentioned at the outset in such a way that it is of particularly simple construction and enables the function of the service brake and the parking brake.

[0006] This problem is solved according to the invention in that the spreading unit, starting from a neutral position, is designed to generate a service brake in one drive direction of the actuator and to generate a self-locking function of a parking brake in the other drive direction of the actuator. This design utilizes different drive directions in order to generate, in the respective end position of the drive direction, either a smooth-running service brake with a self-locking function or a self-locking function for the function of a parking brake. The self-locking can generate a force-locking or form-locking connection between the components that support the braking forces. Thanks to the invention, only a single actuator with a single spreading unit is required for both functions of the braking device. The braking device is therefore particularly simple in design.

[0007] According to another advantageous development of the invention, the generation of different functions of the braking device is particularly simple in terms of construction if a driven nut-Z-spindle unit with a nut screwed onto a spindle is supported in one drive direction of the actuator via an axial bearing on a first non-rotatable expanding pressure piece and in the other drive direction of the actuator via a force-locking or form-locking coupling device on a second non-rotatable expanding pressure piece. Due to this design, the driven nut-Z-spindle unit with the two non-rotatable pressure pieces is operatively connected either to the axial bearing or to the coupling device. If the nut-Z-spindle unit is supported via the axial bearing, a particularly smooth power transmission between the nut-Z-spindle unit and the expanding pressure pieces is enabled.

[0008] According to another advantageous development of the invention, the design of the braking device is further simplified if one of the components of the spindle or the nut can be moved selectively against the axial bearing or against the clutch device, depending on the drive direction. This design allows the force flow to be easily routed via the axial bearing in one function of the service brake and via the clutch device in the other function of the parking brake.

[0009] The nut-Z-spindle unit could, for example, be axially guided in a housing. However, according to another advantageous development of the invention, the braking device is particularly compact if the expansion pressure pieces are connected to a component of the nut-Z-spindle unit in an axially displaceable and non-rotatable manner. This makes the braking device particularly compact.

[0010] According to another advantageous development of the invention, when functioning as a parking brake, the braking element can be held in its position without additional energy expenditure if the clutch device has a friction pair arranged on the nut / Z-spindle unit and on one of the expansion pressure pieces. This design enables the clutch device to generate self-locking through frictional engagement.

[0011] According to another advantageous development of the invention, a large surface area of ​​the friction pairing can be easily achieved if the friction pairing is arranged between the nut and the second expansion pressure piece.

[0012] According to another advantageous development of the invention, the braking device is capable of supporting high forces in the function of the parking brake if the friction pairing is designed as a chamfer inclined to the axis of rotation of the nut.

[0013] According to another advantageous development of the invention, a uniform introduction of force into the axial bearing can be easily ensured if a support disk is arranged between the nut and the first expansion pressure piece.

[0014] According to another advantageous development of the invention, the spindle is supported selectively on one or the other of the expansion pressure pieces, depending on the drive direction, if the spindle has support surfaces opposite each of the expansion pressure pieces. This also makes the braking device particularly simple in design. The braking device can be driven in both functions with particularly low friction and play if the nut-Z-spindle unit is designed as a ball screw drive.

[0015] According to another advantageous development of the invention, it contributes to a further reduction in the dimensions of the braking device if the nut is rotatably mounted in a housing and has an external toothing for connection to a driven gear.

[0016] The invention permits numerous embodiments. To further clarify its basic principle, one of them is shown in the drawing and is described below. This shows in

[0017] Fig.1 schematically shows a braking device designed as a drum brake,

[0018] Fig.2 perspective view of a housing with a spreading unit from Figure 1,

[0019] Fig.3 the spreading unit from Figure 2 with cut-open housing,

[0020] Fig.4 a longitudinal section through the housing and the spreading unit from Figure 2 in a neutral position,

[0021] Fig.5 the spreading unit shown in Figure 4 in a service brake position,

[0022] Fig.6 the spreading unit shown in Figure 4 in a parking brake position.

[0023] Figure 1 schematically shows a braking device of a motor vehicle designed as a drum brake with a rotatably mounted brake drum 1. The brake drum 1 encloses two braking elements 2, 3 designed as brake shoes with friction linings 4, 5. The brake shoes can be moved against the brake drum 1 by an actuator 6 with a spreading unit 7 in order to generate a frictional torque. In the illustrated embodiment, tension springs 8, 9 pre-tension the brake shoes against the spreading device 7 and thus enable them to move back from the brake drum 1. The actuator 6 has an electric motor 10 that can be driven in both directions of rotation and a housing 11 with the spreading unit 7 arranged therein. Two spreading pressure pieces 12, 13 of the spreading unit 7 protrude from the housing 11 and are supported on the brake shoes. The brake shoes secure the spreading pressure pieces 12, 13 in a non-rotatable position.A gear 14 driven by the electric motor 10 penetrates the housing 11 and drives a drive pinion 15 of the spreading unit 7 selectively in one direction of rotation or the other. In the illustrated embodiment, the housing 11 is mounted in a floating manner on a support plate 16.

[0024] Figure 2 shows a perspective view of the housing 11 of the spreading unit 7 with a mounting flange 17 for connection to the electric motor 10 and the support plate 16 from Figure 1. The drive pinion 15 is accessible via the mounting flange 17.

[0025] Figure 3 shows a perspective view of the expansion unit 7 from Figure 2 with a cut-away housing 11. A nut-Z-spindle unit 18 designed as a ball screw drive is arranged in the housing 11. A nut 20 screwed onto a spindle 19 is mounted in the housing 11 and has an external toothing 21 of the drive pinion 15 on its outer surface. The spindle 19 is arranged radially inside the nut 20 and is connected to it via rotating balls 22. The expansion pressure pieces 12, 13 are guided non-rotatably and axially displaceably on the spindle 19 via keys 23, 24. An axial bearing 25 with a support disk 26 is arranged between a first pressure piece 12 and the nut-Z-spindle unit 18. A coupling device 27 is arranged between a second pressure piece 13 and the nut-Z-spindle unit 18.The axial bearing 25 enables particularly low-friction rotation of the first expansion pressure piece 12 relative to the adjacent component of the nut-Z-spindle unit 18. The coupling device 27 generates a force or form fit between the second expansion pressure piece 13 and the opposite component of the nut-Z-spindle unit 18 in the direction of rotation upon contact. The bearing of the nut 20 in the housing 11 has radial cylindrical roller bearings 28 and enables at least limited axial displacement of the nut-Z-spindle unit 18 in the housing 11, so that the maximum travel of the expansion unit 7 can be covered.

[0026] Figure 4 shows a longitudinal section through the housing 11 and the spreading unit 7 in a neutral position. This position corresponds to an operating position in which the braking elements 2, 3 are away from the brake drum 1. The neutral position Fig.4 is de-energized if the braking device is designed as a Duo Servo drum brake, in which a counter bearing to the friction linings 4, 5 keeps the friction linings 4, 5 at a distance. Otherwise this neutral position in the Si version is an intermediate position in which, for example, the pad springs compress the spreading unit 7 or this position is overrun when changing from, for example, the service brake to the parking brake. This position is overrun when de-energized because the braking device must be designed to be de-energized and open when the service brake is applied.

[0027] S1 to S4 denote gaps between the nut-Z-spindle unit 18 and the adjacent components of the expansion pressure pieces 12, 13, the axial bearing 25, or the coupling device 27. The spindle 19 has support surfaces 29, 30 opposite each of the expansion pressure pieces 12, 13. The nut 20 has a support surface 31 opposite the support disc 26 and a friction pair 32 forming the coupling device 27 opposite the second expansion pressure piece 13. The friction pair 32 is designed as a chamfer inclined to the axis of rotation. It can be seen that the gaps S1 to S4 of the nut-Z-spindle unit 18 are open to all adjacent components in the neutral position shown. If the nut 20 is driven starting from the position shown in Figure 4, the spindle 19 is driven via the balls 22 of the nut-Z-spindle unit 18 designed as a ball screw drive.The spindle 19 is displaced axially relative to the expansion pressure pieces 12, 13 via the keys 23, 24, whereby the expansion pressure pieces 12, 13 are held non-rotatably by the braking elements 2, 3 from Figure 1. In one direction of rotation of the nut 20, the spindle 19 comes with one of the support surfaces 30 against the first pressure piece 12 and the nut 20 with its support surface 31 against the support disk 26 of the axial bearing 25, as shown in Figure 5. The gaps S4 and S3 are thereby closed and the expansion pressure pieces 12, 13 are spread in order to move the braking elements 2, 3 shown in Figure 1 against the brake drum 1. For clarity, the force flow through the expansion unit 7 is marked as a freehand line in the drawing.Since the force flow is guided through the axial bearing 25 and past the clutch device 27, the spreading is particularly low-friction, so that the force flow ceases as soon as the electric motor 10 is de-energized. When the electric motor 10 is de-energized, the spreading unit 7 moves independently into the neutral position shown in Figure 4 due to the force of the tension springs 8, 9 shown in Figure 1, thereby releasing the braking device. Thus, the position of the actuator 6 shown in Figure 5 indicates the function of a service brake of the braking device.

[0028] If, starting from the position in Figure 4, the nut 20 is driven in the other direction of rotation, the nut 20 moves against the coupling device 19 and thus against the first expansion pressure piece 12, as shown in Figure 6. The spindle 19 is supported with one of its support surfaces 29 on the first expansion pressure piece 13. As a result, the gaps S1 and S2 are closed and a force flow indicated in the drawing can be transmitted through the expansion pressure pieces 12, 13 and the nut-Z-spindle unit 18. The force flow leads through the coupling device 27 and past the axial bearing 25 and is indicated in Figure 6 as a freehand line. However, the coupling device 27 creates a self-locking effect through friction of the friction pair 32, which holds the components in the position shown even when the electric motor 10 is de-energized.In order to move the spreading unit 7 from the position shown in Figure 6 back to the neutral position shown in Figure 4, it must be actively driven by the electric motor 10 to release the friction torque of the friction pair 32 of the clutch device 27. Figure 6 thus indicates the function of a parking brake of the braking device. Due to the illustrated guidance of the force flow through the components arranged within the housing 11, the external toothing 21 and the drive pinion 15 are not subjected to holding forces when functioning as a parking brake.

[0029] In an embodiment not shown, the expansion unit 7 can have an axial bearing at the gap marked S3. Furthermore, the

[0030] In an embodiment not shown, the spreading unit 7 may have a coupling device at the gap marked S1.

Claims

Patent claims 1. Braking device for a motor vehicle with a brake element (2, 3) for generating a frictional connection with a rotating component and with an actuator (6) which can be driven in two directions of movement and which moves the brake element (2, 3) relative to the rotating component, and with a spreading unit (7) of the actuator (6), characterized in that the spreading unit (7) is designed, starting from a neutral position, in one drive direction of the actuator (6) to generate a service brake and in the other drive direction of the actuator (6) to generate a self-locking function of a parking brake.

2. Braking device according to claim 1, characterized in that a driven nut-Z spindle unit (18) with a nut (20) screwed onto a spindle (19) is supported in one drive direction of the actuator (6) via an axial bearing (25) on a first non-rotatable expanding pressure piece (12) and in the other drive direction of the actuator (6) via a force- or form-locking coupling device (27) on a second non-rotatable expanding pressure piece (13).

3. Braking device according to claim 2, characterized in that one of the components of the spindle (19) or the nut (20) is selectively movable against the axial bearing (25) or against the coupling device (27), depending on the direction of drive.

4. Braking device according to claim 2 or 3, characterized in that the expanding pressure pieces (12, 13) are axially displaceable and non-rotatable connected to a component of the nut-Z spindle unit (18).

5. Braking device according to one of claims 2 to 4, characterized by the fact that the coupling device (27) has a friction pair (32) arranged on the mother Z-spindle unit (18) and on one of the spreading pressure pieces (13).

6. Braking device according to claim 5, characterized in that the friction pairing (32) is arranged between the nut (20) and the second expanding pressure piece (13).

7. Braking device according to claim 5 or 6, characterized in that the friction pairing (32) is designed as a chamfer inclined to the axis of rotation of the nut (20).

8. Braking device according to at least one of claims 2 to 7, characterized in that a support disc (26) is arranged between the nut (20) and the first expanding pressure piece (12).

9. Braking device according to at least one of claims 2 to 8, characterized in that the spindle (19) has support surfaces (29, 30) opposite each of the spreading pressure pieces (12, 13).

10. Braking device according to at least one of claims 1 to 9, characterized in that the nut-Z spindle unit (18) is designed as a ball screw drive.

11. Braking device according to at least one of claims 1 to 10, characterized in that the nut (20) is rotatably mounted in a housing (11) and has an external toothing (21) for connection with a driven gear (14).

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