Patent Application
20230150470
This application claims priority to German Priority Application No. 102021129963.2, filed Nov. 17, 2021, the disclosure of which is incorporated herein by reference in its entirety.
The disclosure relates to a spindle drive for an actuator assembly of a vehicle brake, in particular for an electromechanically actuated brake, and to an actuator assembly with a spindle drive and to a method for producing a spindle drive.
Two friction linings can be applied to a brake rotor by an actuating carriage in order to actuate an electromechanical vehicle brake. For this purpose, the actuating carriage contacts the back plate of a brake lining.
However, an application force may occur only locally in the region of the contact surface between the actuating carriage and the back plate of the brake lining.
The disclosure discusses an arrangement to achieve a qualitatively uniform distribution of the application force between a brake lining and the brake rotor.
As discussed herein, a spindle drive for a vehicle brake, with a spindle and a spindle nut mounted on the spindle, forms an actuating carriage that can be displaced between a retracted and an extended position in order to place a brake lining against a brake rotor. The spindle nut has a pressure-distributing element at an end of the spindle nut which is dose to the brake lining, and a contact surface of the pressure-distributing element which faces away from the spindle is continuously or discontinuously annular.
By virtue of a continuously or discontinuously annular contact surface, the application force when the brake lining is applied to the brake rotor is transmitted to a brake lining less punctually than in the case of a round circular surface. This is caused by the fact that the contact surface is shifted away from a centre of the brake lining by the annular shape. The application force is thus distributed particularly uniformly over the whole or almost the whole surface of the brake lining, as a result of which a braking procedure can be particularly effective. In addition, the brake lining becomes worn uniformly, as a result of which consistent braking behaviour is ensured in the long term.
In particular, a distribution of pressure between the friction lining and the brake disc as occurs in the case of hydraulic dual-piston brake calipers can be generated by the spindle drive according to the disclosure.
The annular contact surface can be continuously or discontinuously circular, oval or elliptical when viewed from the front. As a result, the shape of the annular contact surface can be adapted to the size of the brake disc and to a desired pressure distribution.
According to an exemplary arrangement, the pressure-distributing element has a frustoconical projecting collar which ends at the contact surface and widens out from an axial end of the spindle nut to the brake lining. The circumference of the contact surface is consequently greater than the circumference of the spindle nut, as a result of which the application force is distributed over as large as possible an area with at the same time a compact structure of the spindle drive. In particular, the pressure-distributing element has the same diameter as the spindle nut at its end connected to the spindle nut.
Starting from the axial end of the spindle nut, the cross-section of the collar preferably merges from a circular cross-section into an oval or elliptical cross-section. As a result, if it is produced separately from the spindle nut, the pressure-distributing element can be connected simply to the spindle nut, When the pressure-distributing element and the spindle nut are manufactured integrally, such a design is likewise advantageous for manufacturing reasons because there is a gradual transition from the spindle nut to the pressure-distributing element.
The contact surface can have at least one depression, viewed in a side view. In the region of the depression, the pressure-generating element is not in contact with the back plate of the brake lining even when the brake lining is applied such that a discontinuously annular contact surface results by virtue of the depression. The distribution of the application force can consequently be influenced in a more targeted fashion.
In the case of an oval or elliptical contact surface, the depression is arranged in particular in the region of the co-vertices. As a result, the pressure-distributing element is in contact with the back plate of the brake lining in the region of the vertices. The contact surface is consequently on average shifted as far away from a centre of the brake lining as is advantageous with respect to the distribution of the application force.
According to an exemplary arrangement, the contact surface runs at an angle to a friction surface of the brake lining, in particular wherein two regions of the contact surface which are situated circumferentially opposite each other have opposite inclinations. The regions of the contact surface which are situated opposite each other are preferably inclined towards the centre. In particular, the contact surface is roof-shaped when viewed from the side. The elasticity of the pressure-distributing element is compensated by a contact surface inclined to the friction surface or by a region of the contact surface with an opposite inclination. As a result, when the pressure-distributing element is forced towards the back plate of a brake lining in order to apply the brake lining to a brake rotor, the inclined regions are deformed elastically by the resulting pressure in such a way that the contact surface is oriented parallel to the brake lining or the angle at which the contact surface runs parallel to the brake lining is reduced. The contact surface thus runs in an unstressed state at an angle to the friction surface of the brake lining.
The pressure-distributing element is preferably made from metal and press-fitted or welded to the spindle nut. The pressure-generating element can also merge integrally into the spindle nut. In the case of two-part manufacture, the pressure-distributing element has a cylindrical centring extension which sits in a recess of the spindle nut.
The spindle drive is preferably supported on an axial bearing in the brake caliper via the spindle, wherein the contact surface of the axial bearing with the spindle is a conical surface. As a result, the axial bearing is bevelled at its contact surface with the spindle. By virtue of the bevel, the axial bearing can absorb not only axial forces but also a certain amount of transverse force.
The spindle drive is preferably a ball screw. In a ball screw, balls transmit the force between the spindle and the spindle nut. By virtue of the rolling movement of the balls, friction and wear are reduced in a ball screw.
According to an exemplary arrangement, at least one cut-out, which leads to a thread of the spindle and which forms a mounting opening for the balls of the spindle drive, is present in a circumferential wall of the spindle nut. Simple mounting of the balls is consequently possible even in the case of a spindle nut which is closed on one side.
The disclosure also discusses an actuator assembly for a vehicle brake, with a brake lining, a brake rotor and a spindle drive. The pressure-distributing element is arranged at an end of the spindle nut which faces the brake lining and the contact surface of the pressure-distributing element is in contact with a back plate of the brake lining in an extended position of the spindle nut and applies the brake lining to the brake rotor. As has already been described in connection with the spindle drive according to the disclosure, the application force is consequently distributed particularly uniformly over the whole or almost the whole surface of the brake lining.
According to a method, in a first step, balls are inserted into a thread of the spindle, and in a following step the pressure-distributing element is fastened to the spindle nut. In particular, the pressure-distributing element is press-fitted onto the spindle nut and is secured against rotation by a knurled joint or is welded. The balls can be mounted as in a conventional ball screw by the pressure-distributing element being fastened to the spindle nut after the balls have been inserted into the thread. To be precise, the balls can be mounted in the threads and ball returns of the spindle nut by a cylindrical rod being pushed gradually into the latter. The balls are secured against falling out by the cylindrical rod in the spindle nut. The spindle is then twisted into the spindle nut at one end of the latter and the cylindrical rod is thus pushed out of the nut at the other end.
According to a further method, the pressure-distributing element is manufactured as a single piece with the spindle nut, wherein at least one cut-out, which leads to a thread of the spindle, is present in a circumferential wall of the spindle nut, and wherein the balls of the spindle drive are blown into the thread by compressed air through the cut-out. In this case, the advantage is obtained that the pressure-generating element does not need to be fastened subsequently to the spindle.
The balls are arranged, for example, in a mounting tube which is plugged into the cut-out and to which compressed air is applied in order to blow the balls into the thread.
Further advantages and features of the disclosure emerge from the following description and from the attached drawings to which reference is made. In the drawings:
The actuator assembly 10 comprises a control assembly 12 which can be mounted as a separate subunit, and a drive assembly 14 which can be mounted as a separate subunit (see
The control assembly 12 and the drive assembly 14 are arranged in a common housing 16.
The housing 16 comprises an essentially sleeve-shaped housing base part 18 and a housing cover 20 by which the housing base part 18 is tightly closed in the mounted state.
In the exemplary arrangement illustrated, the housing cover 20 is also essentially shell-shaped.
Both the housing base part 18 and the housing cover 20 are produced from plastic material. The housing 16 as a whole is thus made from plastic material.
The actuator assembly 10 furthermore comprises a brake caliper 15 in which a gap 17 is formed for a brake rotor 19, i.e. a brake disc. The housing 16 is pushed partially onto the brake caliper 15 with its end close to the brake caliper 15.
The drive assembly 14 comprises a support assembly 22 which has a plate-like frame part 24, as can be seen particularly well in
A first fastening interface 26, at which an electric motor 28 is fastened in the exemplary arrangement illustrated, is provided on the plate-like frame part 24.
To be more precise, the electric motor 28 is connected captively to the frame part 24 via the first fastening interface 26. The frame part 24 absorbs the forces of the electric motor 28 and holds the latter.
The electric motor 28 fastened to the frame part 24 such that is centred with respect to a centre axis 34 of the first fastening interface 26.
In addition, an anti-rotation device 36 is provided in the form of an anti-rotation depression which is designed to prevent the electric motor 28 from rotating relative to the frame part 24.
An output gear wheel 40 is arranged on an output shaft 38 of the electric motor 28, as shown in
Furthermore, a journal 42, on which in the exemplary arrangement illustrated a gear wheel 44 is mounted which meshes with the output gear wheel 40, is provided on the frame part 24.
Moreover, a receiving space 46 for a planetary gear stage 48 is provided on the frame part 24.
A centre axis 50 of the receiving space 46 is here arranged essentially parallel to the centre axis 34 of the first fastening interface 26.
A reinforcing part 52 is moreover fastened on the frame part 24 in such a way that it spans the end of the receiving space 46 axially with respect to the centre axis 50.
In the exemplary arrangement illustrated, the reinforcing part 52 is essentially cross-shaped.
In addition, a bearing point 54 for a gear wheel 56 arranged coaxially with respect to the planetary gear stage is provided on the reinforcing part 52.
The gear wheel 56 meshes with the gear wheel 44.
A gear train 58 is consequently formed by the gear wheel 44 and the gear wheel 56, the output gear wheel 40 acting as its input member.
The gear wheel 56 is moreover formed integrally with a sun gear 60 (see
The planetary gear stage 48 moreover comprises a ring gear 62 which runs essentially along an inner circumference of the receiving space 46 (see
In the exemplary arrangement illustrated, a total of three planetary gears 64 are provided drivingly between the sun gear 60 and the ring gear 62, as can be seen in
The planet carrier 66 here represents an output element of the planetary gear stage 48.
The gear train 58 and the planetary gear stage 48 are also referred to together as a gear unit 67.
The frame part 24 furthermore has a second fastening interface 68 which is designed for fastening a guide part 70, held therein, for a spindle drive 72.
In the exemplary arrangement, the guide part 70 is a bearing sleeve which is held in the brake caliper 15. For example, the bearing sleeve is press-fitted in the brake caliper or is welded to the latter.
A centre axis of the second fastening interface 68 here coincides with the centre axis 50 of the receiving space 46 and for this reason is provided with the same reference numeral.
The second fastening interface 68 has an anti-rotation geometry 74, for example a splined shaft geometry, which runs circumferentially around the centre axis 50.
A complementary anti-rotation geometry 82 is provided at that end of the guide part 70 which is to be coupled to the second fastening interface 68 such that the guide part 70 can be pushed along the centre axis 50 into the anti-rotation geometry 74 of the second fastening interface 68 and held there non-rotatably in a form-fitting fashion. The anti-rotation geometry is likewise a splined shaft geometry.
The spindle drive 72 is accommodated inside the guide part 70.
It comprises a spindle 84 which is configured in the present case as a ball screw.
The spindle 84 is here connected non-rotatably to the planet carrier 66 via the toothed section 86.
The spindle drive 72 can thus be driven by the electric motor 28. In detail, the electric motor 28 is coupled to the spindle drive 72 drivingly via the gear train 58 and the planetary gear stage 48.
A spindle nut 88, which is configured as a piston and forms an actuating carriage for a brake lining, is mounted on the spindle 84.
Rotation of the spindle 84 thus causes the spindle nut 88 to be shifted axially along the centre axis 50.
The spindle nut 88 is here guided along the centre axis 50 directly on a running surface 90, wherein the running surface 90 is formed by an inner side of the guide part 70. The running surface 90 corresponds essentially to a cylindrical surface forming the inner circumference of the guide part 70. In other words, the spindle nut 88 is guided linearly displaceably in the guide part 70.
The guide part 70 is open towards the gap 17 such that the spindle nut 88 can move into the gap 17.
The spindle nut 88 is moreover prevented from rotating relatively about the centre axis 50 by an anti-rotation device 92 which is designed as a slot on the guide part 70. For this purpose, an anti-rotation element 94 which engages in the slot (see
The spindle nut 88 serves to apply a first brake lining 96 of a brake caliper assembly 98 to the brake rotor 19. As a result, the first brake lining 96 can be moved actively onto a brake rotor 19 by the actuator assembly 10.
In detail, the spindle nut 88 is transferred selectively into an extended position, which is associated with the application of the first brake lining 96 to the brake rotor 19, by the electric motor 28 via the gear train 58, the planetary gear stage 48 and the spindle drive 72.
Because of the reaction forces acting inside the actuator assembly 10 and the brake caliper assembly 98, a second brake lining 102 is consequently also applied to the brake rotor 19.
It should be understood that the spindle nut 88 can be moved in the same way by operation of the electric motor 28 into a retracted position which is associated with lifting the first brake lining 96 and the second brake lining 102 off the brake rotor 19.
The spindle drive 72 is supported on an axial bearing 104 in the brake caliper 15 via the spindle 84.
Specifically, in the exemplary arrangement, the axial bearing 104 is supported on a wall 105 which is formed integrally with the guide part 70 and which runs transversely to a direction of movement of the spindle nut 88. In the exemplary arrangement, the wall 105 is a radially inward facing flange.
A contact surface 106, which is in contact with the spindle 84, of the axial bearing 104 is a conical surface. As a result, transverse forces, which occur in particular when the brake lining 96 is applied to the brake rotor 19, can be absorbed by the axial bearing 104 and be absorbed by the brake caliper 15 via the guide part 70.
The axial bearing 104 is a rolling bearing, in particular a needle bearing.
In the present case, the actuator assembly 10 is designed so that it is not self-locking, such that the spindle nut 88 also shifts back automatically into the retracted position by virtue of elasticities inherent in the system when it is no longer actively forced into the extended position by the electric motor 28.
A spindle drive according to a first arrangement will be described below in detail with the aid of
The spindle nut 88 has a pressure-distributing element 108 at an end of the spindle nut 88 which is close to the brake lining 96.
The pressure-distributing element 108 is, for example, made from metal.
In the exemplary arrangement, the pressure-distributing element 108 is manufactured separately from the spindle nut 88 and press-fitted or welded to the spindle nut 88. In this case, the pressure-distributing element 108 preferably has a cylindrical centring extension 110 which sits in a recess 112 of the spindle nut 88 (see
In the case of two-part manufacture, the pressure-distributing element 108 forms a sealing cap for the spindle nut 88.
The pressure-distributing element 108 can also merge into the spindle nut 88 as a single piece. The spindle nut 88 with the integrated pressure-distributing element 108 can be produced in this case as a milled or cast part.
A contact surface 114, facing away from the spindle 84, of the pressure-distributing element 108 is annular (see
In an extended position of the spindle nut 88, the contact surface 114 of the pressure-distributing element 108 is in contact with a back plate 115 (see
In the arrangement according to
The pressure-distributing element 108 has a frustoconical projecting collar 116.
Starting from an axial end of the spindle nut 88, the collar 116 widens out towards the brake lining 96 and ends at the contact surface 114. The contact surface 114 consequently has a larger external circumference than the spindle nut 88, in particular an external circumference which is larger by at least 50%.
In the exemplary arrangement, starting from the axial end of the spindle nut 88, the cross-section of the collar 116 merges from a circular cross-section into an oval cross-section.
As can be seen particularly well in
There is a clearance between the collar 116 and an end side of the spindle nut 88 such that a circumferential depression 118 is formed for receiving a seal 120. Such a clearance can be obtained simply by an appropriate dimensioning of the recess 112.
The depression 18 is formed in particular when the pressure-distributing element 108 is attached to the spindle nut 88.
As can be seen in
The discontinuously annular form of the contact surface 114 which has already been mentioned above is obtained by the depressions 122. There is in particular no contact of the pressure-distributing element 108 with the back plate 115 of the brake lining 96 in the region of the depressions 122. The contact surface 114 thus comprises two ring segments 124.
In the case of an oval or elliptical contact surface 114, the depression 122 is arranged in the region of the co-vertices 125. The contact surface 114 is thus in contact with the back plate 115 of the brake lining 96 in the region of the vertices 126.
As can be seen in
Because a pressure-distributing element 108 is provided on the spindle nut 88, improved distribution of the application force in the brake lining is achieved such that the brake lining 96 is deformed as little as possible when acted upon by the spindle nut 88 or the pressure-distributing element 108 and is consequently applied to a large area of a brake disc of the brake rotor 19.
A further spindle drive 72 according to the disclosure, which can likewise be used in the actuator assembly 10 shown in
The same reference numerals are used below for the same structures with the same functions which are known from the above arrangement and reference is made in this respect to the preceding explanations, wherein the differences in the respective arrangements are discussed below in order to prevent repetitions.
In the arrangement of the spindle drive 72 illustrated in
In particular, the contact surface 114 is flat in
The spindle drive 72 illustrated in
The spindle drive 72 illustrated in
The cut-out 130 forms in particular a mounting opening for the balls 134 of the spindle drive 72.
The spindle drive 72 according to
The cut-out 130 enables mounting of the spindle drive 72 when the pressure-distributing element 108 forms a single piece with the spindle nut 88 or when the pressure-distributing element 108 has been connected to the spindle nut 88 before the spindle nut 88 is mounted on the spindle 84.
The balls 134 of the spindle drive 72 can be blown through the cut-out 130 into the thread 132 by compressed air.
The balls 134 are, for example, arranged in a mounting tube 136 which is pushed into the cut-out and to which compressed air is applied in order to blow the balls into the thread. The mounting tube 136 preferably has a curve.
The ball return can be integrated into the spindle nut 88 or into the spindle 84.
For example, a ball return integrated into the spindle 84 is provided with individual ball recirculation functionality. In this case, a cut-out 130 is provided as a mounting opening for each individual ball recirculation.
The cut-outs 130 can be closed with a cover once the mounting is complete.
In a first step the balls 134 can also be inserted into the thread 132 of the spindle 84, and in a subsequent step the pressure-distributing element 108 is fastened to the spindle nut 88, In this case, a rod, which serves as a mounting aid, can be pushed gradually into the spindle nut 88, wherein the balls 134 are mounted in the threads of the spindle nut 88. The balls 134 are secured against falling out during mounting by virtue of being covered by the cylindrical rod. The spindle 84 can then be screwed into the spindle nut 88, wherein the rod is pushed out of the spindle nut 88. Afterwards, the pressure-distributing element 108 can be fastened to the spindle nut 88.
Regardless of whether the pressure-distributing element 108 is fastened to the spindle nut 88 before or after the balls 134 are mounted, the pressure-distributing element 108 can be press-fitted to the spindle nut 88 and secured against rotation by a knurled joint. The pressure-distributing element 108 can also be welded to the spindle nut 88.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021 129963.2 | Nov 2021 | DE | national |
