DE102020214078A1 - Electromechanical wheel brake - Google Patents

Abstract

The invention relates to an electromechanical wheel brake (100) for a motor vehicle with a brake caliper housing (104) and a pressure piston (110) which can be displaced in the brake caliper housing (104) along an application direction (114). The wheel brake (100) has an electric motor drive (106, 108) and a threaded spindle (122) driven by the drive (106, 108), wherein on the threaded spindle (122) a rotatably mounted spindle nut (124) is arranged. The spindle nut (124) is in turn arranged on the pressure piston (110), the threaded spindle (122) being supported in the axial direction counter to the application direction (114) on a roller bearing (126) and the roller bearing (126) being on the brake caliper housing (104) supports. According to the invention, the roller bearing (126) has at least two ring-shaped arrangements (134, 136) of rolling elements (132), with an outer ring-shaped arrangement (136) of rolling elements (132) having a larger diameter than an inner ring-shaped arrangement (134) from rolling elements (132).

Description

The invention relates to an electromechanical wheel brake for a motor vehicle according to the preamble of claim 1.

Electromechanical wheel brakes are known in many variants in the prior art. For example, describes the DE 10 2010 040 426 A1 an electromechanical wheel brake with a brake caliper housing and a pressure piston that can be displaced in the brake caliper housing along an application direction. The wheel brake has a driven threaded spindle and a spindle nut which is arranged on the threaded spindle and is mounted non-rotatably about the longitudinal axis of the threaded spindle. The spindle nut is in turn arranged on the pressure piston, the threaded spindle being supported in the axial direction counter to the application direction on a roller bearing, which in turn is supported on the brake caliper housing.

The threaded spindle is supported by the roller bearing against a force which acts on the threaded spindle in the application direction of the brake as a result of the pressure piston being subjected to a clamping force. Consequently, the entire clamping force of the wheel brake is supported exclusively via the axial bearing, which means that the axial bearing is very important with regard to the service life and efficiency of the wheel brake.

In the case of arrangements known in the prior art, the rolling bearing usually consists of a series of rolling elements which are arranged on a circular path. In particular in the case of rolling elements which have a contact surface extending in the radial direction of the rolling bearing, a speed difference arises between the contact points of the contact surface which are located radially on the inside and the contact points of the contact surface which are located radially on the outside in the axial bearing. However, since the rolling elements rotate at the same rotational frequency in the thrust bearing, the speed difference between the inner and outer contact points causes a slipping movement on the rolling elements, which degrades the efficiency of the thrust bearing.

In contrast, the invention is based on the object of specifying an electromechanical wheel brake which overcomes the disadvantages of the prior art described above and in particular contains an axial bearing with improved efficiency.

This object is achieved with the wheel brake according to claim 1. Advantageous configurations are the subject matter of the dependent claims.

The invention relates to an electromechanical wheel brake for a motor vehicle with a brake caliper housing and a pressure piston that can be displaced in the brake caliper housing along an application direction. The wheel brake has an electric motor drive and a threaded spindle driven by the drive, with a spindle nut mounted non-rotatably about the longitudinal axis of the threaded spindle being arranged on the threaded spindle. The spindle nut is arranged on the pressure piston, and the threaded spindle is supported against the application direction in the axial direction on a roller bearing, the roller bearing being supported on the brake caliper housing. According to the invention it is provided that the roller bearing has at least two ring-shaped arrangements of rolling bodies, with an outer ring-shaped arrangement of rolling bodies having a larger diameter than an inner ring-shaped arrangement of rolling bodies.

The use of a multi-row, in particular a double-row, axial bearing has the advantage that the axially acting force can be supported over a larger area. At the same time, the two ring-shaped arrangements of rolling elements can move independently of one another, so that in particular the peripheral speed of the rolling elements can increase as the distance between the corresponding ring-shaped arrangement and the center of the thrust bearing increases. In this way, friction losses and wear due to slippage of the rolling elements can be avoided, so that efficient and long-lasting operation of the wheel brake can be achieved.

The wheel brake can in particular be a floating caliper brake, so that when the wheel brake is applied, ie a movement of the pressure piston in the direction of a brake disc, a friction lining arranged on the pressure piston is first brought into contact with the brake disc. If the pressure piston is then further subjected to a force in the application direction, a second friction lining is brought into contact with the brake disc by moving the floating caliper part against the application direction, so that the brake disc is clamped between the friction linings and a braking torque can consequently be applied.

According to a preferred embodiment, it is further provided that an axial bearing disk is arranged on the threaded spindle, the threaded spindle being supported on the roller bearing in the axial direction via the axial bearing disk.

The axial bearing disk is preferably arranged concentrically with the threaded spindle. In particular, the axial bearing washer can be secured against rotation of the axial bearing washer relative to the threaded spindle via a form fit on the threaded spindle. The use of such a thrust bearing disk makes it possible, for example, to use a material for the thrust bearing disk and therefore for power transmission to the thrust bearing that differs from the material of the threaded spindle. Furthermore, in particular the specific design of the axial bearing washer can be better adapted to the requirements of an optimized power transmission to the axial bearing than would be the case with a direct power transmission from the threaded spindle to the axial bearing.

According to a further embodiment, the efficiency of the wheel brake can also be improved in that the rolling bodies of the inner ring-shaped arrangement have a smaller or larger diameter in the application direction than the rolling bodies of the outer ring-shaped arrangement. The diameter of the rolling elements in the inner ring-shaped arrangement is preferably smaller than that of the rolling elements in the outer ring-shaped arrangement.

In this case, when the forces to be supported in the axial direction of the threaded spindle are low, the threaded spindle or, according to a corresponding configuration, the axial bearing disk is in contact only with an annular arrangement of rolling bodies. Consequently, the friction of the roller bearing is reduced when the forces to be supported are low. With an increase in the force to be supported in the axial direction, an increasing deformation of the contact surfaces between the threaded spindle and the rolling elements or the axial bearing disk and the rolling elements can occur. This deformation preferably ends only when the contact surfaces between the threaded spindle and the rolling elements or the axial bearing disk and the rolling elements rest on all annular arrangements of rolling elements. In this way, high clamping forces are supported from a certain threshold by several rows of rolling elements, so that the force to be supported can be absorbed by a larger number of rolling elements, or the load rating of the bearing increases.

According to a particularly preferred embodiment, it is also provided that the roller bearing is a needle bearing.

If the roller bearing is designed as a needle bearing, according to a further preferred embodiment, it is also provided that the roller bodies of the needle bearing are barrel-shaped in their cross section perpendicular to the application direction. A “barrel shape” is to be understood as meaning a cylinder-like shape in which the transitions between the top surface of the cylinder shape and the lateral surface of the cylinder shape are rounded.

A barrel shape of the rolling elements has the advantage that even if the contact surface between the threaded spindle and the rolling elements tilts relative to the plane of movement of the rolling elements, a sufficiently large contact area remains between the rolling elements and the threaded spindle or the axial bearing disk, so that reliable and low-wear power transmission is possible.

At the same time, the contact area between the rolling elements and the threaded spindle or the axial bearing disk is not too large, even in operation with a low clamping force to be supported, so that no unnecessarily large friction losses arise. Ideally, the barrel shape is adapted in such a way that there is always a comparably large contact area between the rolling elements and the threaded spindle or the axial bearing disk for every clamping force that occurs and therefore every corresponding tilting of the contact surface.

The assembly of the axial bearing in the wheel brake or in the brake caliper housing is simplified according to a further embodiment in that the axial bearing is arranged in a bearing pot, the bearing pot being arranged on the brake caliper housing.

According to a further embodiment, it is also provided that the rolling elements of the outer ring-shaped arrangement and the rolling elements of the inner ring-shaped arrangement are each arranged in a rolling element cage which is designed to keep the rolling elements equidistant along the respective ring-shaped arrangement, the rolling element cage of the inner annular assembly can rotate independently of the roller retainer of the outer annular assembly about the axis of rotation of the roller bearing. Thus, different circumferential speeds can be established for the ring-shaped arrangements of rolling elements, which correspond to the position of the arrangements in the radial direction of the rolling bearing, which avoids slippage of the rolling elements and consequently inefficient operation of the friction brake.

According to a further embodiment, the efficiency of the wheel brake can also be improved in that the threaded spindle forms a ball screw drive with the spindle nut.

• 1 perspektivische Darstellungen einer beispielhaften Radbremse,
• 2 eine Schnittansicht eines Teilbereichs einer beispielhaften Radbremse,
• 3 eine schematische Darstellung eines beispielhaften zweireihigen Nadellagers,
• 4 eine schematische Darstellung der in der Radbremse nach 2 wirkenden Kräfte und
• 5 eine schematische Darstellung der in dem zweireihigen Nadellager der 3 wirkenden Kräfte.

Preferred configurations of the invention are explained in more detail below with reference to the drawings. show:

• 1 perspective representations of an exemplary wheel brake,
• 2 a sectional view of a portion of an exemplary wheel brake,
• 3 a schematic representation of an exemplary double-row needle bearing,
• 4 a schematic representation of in the wheel brake 2 acting forces and
• 5 a schematic representation of the in the double row needle bearing 3 acting forces.

In the following, features that are similar or identical to one another are marked with the same reference symbols.

the 1 shows two perspective views of an exemplary wheel brake 100. This is an electromechanically actuated floating caliper brake, with a fixed brake caliper bracket 102 and a brake caliper housing 104 that is movably mounted in the brake caliper bracket 102. The wheel brake also has an electric motor 106, which, via a gear 108, connected to a rotation-translation gear in brake caliper housing 104, which converts a drive shaft rotation driven by electric motor 106 into a translation of a pressure piston 110, which is mounted in brake caliper housing 104 to be displaceable along a clamping direction 114. A first friction lining 112 is arranged on the pressure piston 110 and is first brought into contact with a brake disc 116 when the pressure piston is displaced in the application direction 114 .

When pressure piston 110 is further subjected to a force in application direction 114, a second friction lining 118 is then displaced counter to application direction 114, i.e. in the direction of brake disc 116, until second friction lining 118 also rests on brake disc 116. If pressure piston 110 continues to be subjected to a force in application direction 114 from this point onwards by appropriate actuation of electric motor 106, friction linings 112 and 118 are pressed onto brake disk 116 with a corresponding clamping force and thus produce a braking torque that delays the rotation of brake disk 116 . The clamping force acting on the brake disc 116 must be supported essentially by the mounting of the pressure piston 110 in the brake caliper housing 104 and the rotation-translation gear driving the pressure piston 110 .

For this is in the 2 shown in a schematic sectional view of how the pressure piston 110 is guided within the caliper housing 104 and how the pressure piston 110 is supported on the rotation-translation gear. The rotation-translation gear 120 is formed by a threaded spindle 122 and a spindle nut 124 arranged on the threaded spindle. The threaded spindle 122 is connected via the transmission 108 to a drive shaft of the electric motor 106 in such a way that the threaded spindle 122 can be subjected to a torque about its longitudinal axis L by appropriate activation of the electric motor 106 .

The spindle nut 124 is arranged in the pressure piston 110 and secured against rotation about the longitudinal axis L of the threaded spindle 122 by the pressure piston 110 or the attachment in the pressure piston 110 . Consequently, a rotation of threaded spindle 122 about its longitudinal axis L leads to a translation of spindle nut 124 and thus of pressure piston 110 along threaded spindle 122 and thus in or counter to application direction 114 of wheel brake 100. Threaded spindle 122 preferably forms a low-friction relationship with spindle nut 124 ball screw off.

The rotation-translation gear 120 described accordingly converts a torque acting on the threaded spindle 122 into a force acting on the spindle nut 124 and thus the pressure piston 110 along the threaded spindle 122. This force is supported in the illustrated embodiment of the wheel brake 100 by that around the threaded spindle 122 an axial bearing 126 is arranged in a bearing pot 128 on which the threaded spindle 122 is supported in the axial direction. The axial bearing 126 is in the form of a needle bearing, with an axial bearing disk 130 being arranged on the threaded spindle 122 in order to transmit the force from the threaded spindle 122 to the axial bearing 126 . The axial bearing disk 130 is preferably connected to the threaded spindle 122 in a form-fitting manner.

The bearing pot 128 is in turn supported on the brake caliper housing 104 , which is indicated here only schematically, counter to the application direction 114 .

In the 2 an enlarged partial section is also shown, which essentially shows the bearing of the threaded spindle 122 via the axial bearing disk 130 on the axial bearing 126. It can be clearly seen that the axial bearing 126 has two rows of needle-shaped or cylindrical rolling bodies 132 . The following will now refer to the 3 the specific structure of the thrust bearing 126 is explained.

The 3 a) a plan view of the thrust bearing 126, while the 3 b) a side sectional view of the thrust bearing 126 in the rota tion level of the rolling elements 132 shows. Like in the 3 a) As can be seen clearly, the thrust bearing has two ring-shaped arrangements 134 and 136 of rolling elements 132 . The rolling elements 132 of an inner ring-shaped arrangement 134 run on a circular path with a smaller diameter than the rolling elements 132 of an outer ring-shaped arrangement 136.

Since the rotational frequency of both assemblies 134 and 136 is the same during active operation of wheel brake 100, different track speeds and therefore different rolling speeds of rolling elements 132 occur depending on the distance between rolling elements 132 and central axis 138 of axial bearing 126. By dividing the rolling elements into two independent arrangements 134 and 136, slippage of the rolling elements 132 due to these different rolling speeds is reduced, since the rolling elements 132 can roll at the speed appropriate for their distance from the central axis L of the rolling-element bearing 126. The rolling elements 132 of the outer arrangement 136 are arranged in a first rolling element cage which can move independently of a second rolling element cage in which the rolling elements 132 of the inner arrangement 134 are arranged.

the 3 b) shows again the two-row arrangement of the rolling elements 132 in a lateral sectional view. It is also clear that the rolling elements 132 of the inner ring-shaped arrangement 134 have a smaller diameter in the clamping direction 114, i.e. along the axis of rotation L, than the rolling elements 132 of the outer ring-shaped arrangement 136. In addition, the rolling elements 132 of the inner arrangement 134 and the outer Arrangement 136 each have a barrel shape. This means that the rolling bodies 132 deviate from a cylindrical shape in terms of their geometry to the extent that the transitions from the lateral lateral surfaces 138 to the cover surfaces 140 are rounded. Depending on the configuration, this rounding can also be designed in such a way that the lateral surfaces 138 are slightly curved outwards, that is to say have an outwardly directed camber.

The effect of this geometric design of the rolling elements 132 is described below with reference to the 4 and 5 described. The 4 essentially again the view of 2 , but with an outline of the forces acting during operation of the wheel brake 100. This assumes an operating state in which electric motor 106 of wheel brake 100 is energized in such a way that a torque acts on threaded spindle 122, which torque is converted by rotation-translation gear 120 into a force 142 in application direction 114, which is applied to the Plunger 110 acts. A friction lining 112 arranged on the pressure piston 110 is then pressed onto a brake disc 116 with precisely this force 142 , which is also referred to as the clamping force.

The application force 142 acting in the process must also be supported at the same time against the application direction 114 by a corresponding force 144 . This force initially acts essentially on the threaded spindle 122 and is transmitted to the axial bearing 126 via the axial bearing disk 130 . Within the axial bearing 126, the majority of the force 144 to be supported is then transmitted 146 through the rolling elements 132 of the outer arrangement 136 to the bearing cup 128 and thus to the brake caliper housing 104, while only a smaller part 148 of the force 144 to be supported is transmitted through the rolling elements 132 of the inner Arrangement 134 is supported. The reason for this is in particular from the view of 5 clear.

the 5 shows two different load states of the thrust bearing 126 in a side sectional view. It acts in the representation of 5 a) only a small force 144 to be supported on the axial bearing disk 130 and thus on the axial bearing 126. Due to the larger diameter of the rolling elements 132 of the outer arrangement 136, the axial bearing disk 130 only rests on the rolling elements 132 of the outer arrangement 136, while between the axial bearing disk 130 and the rolling elements 132 of the inner arrangement 134 remains a gap whose width d is given by the difference in the diameters of the rolling elements 132 . Consequently, in this situation, the entire force 144 is fully supported by a counterforce 146 acting via the rolling elements 132 of the outer arrangement 136 . The rolling bodies 132 of the inner arrangement 134 do not contribute to the overall friction of the rolling bearing 126, so that the friction of the rolling bearing 126 is reduced when the load is low. Rather, when the wheel brake 100 is in operation, the rolling elements 132 of the inner arrangement 134 can run with play and without load in this state.

in the in 5b) The situation shown now acts on the axial bearing disk 130, which is so great that the axial bearing disk 130 is bent in the direction of the inner arrangement 134. From a certain strength of the force 144 to be supported, a part 148 of the force 144 to be supported is therefore also supported by the rolling bodies 132 of the inner arrangement 134, since the load rating of the axial bearing 126 increases situationally from a certain force 144 to be supported. The barrel shape of the rolling elements 132 enables a better support of the axial bearing disk 130 on the axial bearing, since even if the axial bearing disk 130 is not horizontally aligned, there is a correspondingly aligned contact surface with the rolling elements 132 is available. At the same time, the friction of the rolling bodies 132 is reduced by a cambering of the lateral surfaces 138 of the rolling bodies 132 .

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102010040426 A1 [0002]

Claims (8)

Electromechanical wheel brake (100) for a motor vehicle with a brake caliper housing (104) and a pressure piston (110) which can be displaced in the brake caliper housing (104) along an application direction (114), the wheel brake (100) having an electric motor drive (106, 108) and a threaded spindle (122) driven by the drive (106, 108), with a spindle nut (124) mounted non-rotatably about the longitudinal axis (L) of the threaded spindle (122) being arranged on the threaded spindle (122), the spindle nut (124) being is arranged on the pressure piston (110), the threaded spindle (122) being supported in the axial direction counter to the application direction (114) on a roller bearing (126), the roller bearing (126) being supported on the brake caliper housing (104) , characterized in that the rolling bearing (126) comprises at least two annular assemblies (134, 136) of rolling elements (132), an outer annular assembly (136) of rolling elements (132) having a larger diameter, al s an inner annular array (134) of rolling elements (132). Electromechanical wheel brake (100) after claim 1 , characterized in that an axial bearing disk (130) is arranged on the threaded spindle (122), the threaded spindle (122) being supported in the axial direction on the roller bearing (126) via the axial bearing disk (130). Electromechanical wheel brake (100) after claim 1 or 2 , characterized in that the rolling elements (132) of the inner annular arrangement (134) have a smaller or larger diameter in the application direction (114) than the rolling elements (132) of the outer annular arrangement (136). Electromechanical wheel brake (100) according to one of the preceding claims, characterized in that the roller bearing (126) is a needle bearing. Electromechanical wheel brake (100) after claim 4 , characterized in that the rolling elements (132) of the needle bearing are barrel-shaped in their cross section perpendicular to the application direction (114). Electromechanical wheel brake (100) according to one of the preceding claims, characterized in that the axial bearing (126) is arranged in a bearing pot (128), the bearing pot (128) being arranged on the brake caliper housing (104). Electromechanical wheel brake (100) according to one of the preceding claims, characterized in that the rolling elements (132) of the outer annular arrangement (136) and the rolling elements (132) of the inner annular arrangement (134) are each arranged in a rolling element cage which is designed for this purpose is to maintain the rollers (132) equidistant along the respective annular assembly (134, 136) with the roller cage of the inner annular assembly (134) being independent of the roller cage of the outer annular assembly (136) about the axis of rotation (L) of the roller bearing (126) can rotate. Electromechanical wheel brake (100) according to one of the preceding claims, characterized in that the threaded spindle (122) forms a ball screw drive with the spindle nut (124).

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