DE102012012423A1 - Spindle drive device of parking brake device e.g. electrical actuatable parking device for vehicle, has transmission device that is provided for peripheral transmission of torque to spindle nut in axial portion along axial direction - Google Patents

Abstract

The device has a spindle (15) whose longitudinal axis is extended along axial direction (19) and that is provided with spindle nut. An internal thread is engaged with external thread and transmission device (17) is provided for peripheral transmission of torque to spindle nut in axial portion along axial direction. The spindle nut is supported in thrust bearing (16) and radial bearing (18).

Description

The invention is in the field of mechanical engineering and is particularly advantageous in the automotive industry in the field of parking brakes, z. B. electrically operated parking brakes used.

The invention particularly relates to a spindle drive, by means of which a spindle in the longitudinal direction can be generated by a spindle, which is used for example for tightening or for placing a brake. However, it is also an application in other actuators conceivable in which to be acted upon by a translational movement with a certain force.

Spindle drives are commonly used for vehicle parking brakes. In this case, via a rotary movement of a spindle nut, a longitudinal tension or pressure of the spindle is generated, which acts on a braking device by means of a plunger or a cable. In such facilities, it should be noted that on the one hand a very simple and robust device for generating the axial force must be created, which work independently of temperature changes and other changing environmental conditions, which, for example, a motor vehicle is exposed, reproducible. On the other hand, the forces to be generated are relatively high and the demands on the reproducibility of the forces are also considerable. In this case, the production of such a device is subject to a high cost pressure, so that in the production of a cost-effective construction should be created. In addition, the wear must be low and as predictable as possible.

From the European patent EP 0 988 203 B1 For example, a spindle drive for a parking brake of a vehicle is known, in which the spindle nut can be driven by a motor by means of a gear wheel mounted thereon. The spindle is connected with a pull cable.

From the DE OS 1 00 43 739 A1 a handbrake for a vehicle is known, in which also a spindle for actuating a braking device can be driven in the axial direction.

Likewise shows the German patent DE 199 06 228 B4 a tensioning device for vehicle brakes with a spindle device for the axial movement of a plunger, which actuates the braking device.

From the DE 10 2006 033 569 B4 an axially mounted spindle nut is known, which is drivable and thereby generates an axial movement of a spindle.

From the DE 103 61 127 B4 a spindle device for a parking brake is known in which a spindle nut is driven and in turn generates an axial movement of the spindle, wherein the spindle nut is both axially supported and spring-loaded.

Against the background of the prior art, the present invention seeks to provide a spindle drive that meets the requirements in terms of performance and wear and reproducibility of the forces and is structurally simple as possible.

This object is achieved by the features of claim 1. The invention also relates to a parking brake device with a corresponding spindle drive according to claim 14.

The spindle drive according to the invention for generating a force in an axial direction sees a spindle, whose longitudinal axis extends in the axial direction, and a spindle nut whose internal thread is in engagement with an external thread of the spindle, and a device for the circumferential transmission of a torque to the spindle nut in a first Axial section with respect to the axial direction in front. To solve the problem is also provided that the spindle nut is mounted exclusively in a thrust bearing and a radial bearing.

To drive the spindle nut rotationally, a torque must be transmitted to this. This can be done for example by means of a peripherally acting on the spindle nut friction wheel, a gear or a belt or chain drive, which causes the spindle nut in rotation. Such peripheral drives have the tendency to transmit in addition to a torque and radial forces on the spindle nut. For example, when using gears, a certain compressive force is needed to hold the gears meshing with each other.

Such radial forces on the spindle nut during its rotation are generally undesirable and must be intercepted in the storage of the spindle nut. It has therefore been customary to provide a plurality of bearings for the storage of the spindle nut, in particular a plurality of radial bearings that stabilize the rotational movement of the spindle nut with respect to radially acting forces. In addition, usually a thrust bearing for the spindle nut is provided to allow support in the axial direction and the concomitant development of an axial force on the spindle.

However, the provision of several bearings on the spindle nut requires one hand appropriate design and cost of the bearings and their attachment. On the other hand, this requires space, since the space for the bearings on the spindle nut must be available.

The present invention saves a radial bearing without unduly reducing the stability of the structure. It is thereby used the fact that at the same time strong axial forces are generated when acting on radial forces on the spindle nut, which press the spindle nut in the thrust bearing. At the same time a stabilization of the spindle nut takes place in the axial bearing in the course of a flying storage. Since the radial forces required to transmit torque on the peripheral side of the spindle nut are only a fraction, for example less than 10%, typically as low as about 2% to 4% of the generated axial force, the stabilization generated by the thrust bearing is in the radial direction sufficient. The remaining necessary storage and stabilization of the spindle nut in the radial direction is taken over by the remaining radial bearing.

An advantageous embodiment of the invention provides that the first axial section with respect to the axial direction is within a second axial section, which includes the axial extent of the radial bearing, the axial extent of the axial bearing and the region arranged between the two bearings in the axial direction.

The construction according to the invention with only one thrust bearing and only one radial bearing is particularly sufficient for supporting the spindle nut, because the entry of radial forces by the circumferential transmission of torque compared to the developed axial forces is small and takes place in an axial region, either in the region of the thrust bearing , in the region of the radial bearing or in the region lying axially between them, that is to say in total within the second axial section defined in this way. This results in no leverage that could produce an increased force on the bearings, starting from the external radial forces.

A further advantageous embodiment of the invention provides that the spindle nut by the rotation of the spindle moves in the axial direction such that it generates a tensile force. Characterized in that the spindle drive is used to generate a tensile force by means of the spindle, high forces, for example, for a brake application can be generated without a buckling to be feared as in a power transmission by a thrust movement. Due to the axial tensile force, which is transmitted from the spindle nut to the spindle, and the spindle nut is pressed so firmly into the thrust bearing, that in addition to its Axiallagerungsfunktion also exerts a radial bearing function and stabilization against tilting movements of the spindle nut.

According to a suitable embodiment of the invention, the spindle is connected to a pull rope, in particular to a Bowden cable. By means of such a pull rope or wire, the tensile force can be optimally guided by the spindle to a braking device. The force direction is easily deflected due to the flexibility of a rope or a train and accordingly generated forces can be directed in a simple manner to the point where they are needed.

Particularly advantageous is the present invention to design such that the thrust bearing is arranged in the axial direction between the means for the circumferential transmission of torque to the spindle nut and the traction cable.

It can also be advantageously provided that the thrust bearing is a rolling bearing, in particular a ball bearing or a needle bearing. Rolling bearings can absorb very high forces with low friction, are reliable and wear-resistant and can therefore be provided in the embodiment according to the invention in the axial bearing at the location of the expected largest occurring forces. The design of the thrust bearing, for example, with a stable Wälzkörperkäfig, the ability of the bearing can be strengthened to also absorb radial loads and to provide a radial guidance. Also by a conical inclination of the running surfaces of the thrust bearing, a centering of the spindle nut in the thrust bearing can be achieved with an additional radial guidance function.

A further advantageous embodiment of the invention provides that the radial bearing is a sliding bearing. Since the radial bearing must bear significantly lower loads than the thrust bearing, this can be designed inexpensively as a plain bearing, for example, with two opposite plastic sliding surfaces or with a metal surface which faces a plastic surface.

The invention can also advantageously be configured in that the radially inner bearing ring of the sliding bearing is connected to a toothed wheel mounted on the spindle nut, in particular integrally connected thereto. The inner bearing ring may take the form of a pipe socket. Thus, the gear that serves the peripheral drive of the spindle nut can be made particularly easy and inexpensive together with a part of the radial bearing. In addition, this construction ensures that the radial bearing in the axial direction is not far away from the point at which the peripheral drive of the Spindle nut takes place. This minimizes possible leverage when a radial force is applied to the spindle nut. The radial force can be absorbed there by the radial bearing, where it is introduced into the spindle nut.

A further advantageous embodiment of the invention provides that the spindle nut, in particular with one of its end faces or with a flange arranged in an end-side end region, is supported axially on an axially axially sprung support plate. The support plate is supported, for example, by means of a spring, in particular a helical spring or a spiral spring, relative to a housing in the axial direction. In this way, the spindle nut exerts in the course of a developed axial force on the spindle and an increasing compressive force on the support plate and the spring, which is usually used for a force measurement in the course of a displacement measurement on the spring and thus to monitor the developed traction. As a result, the spindle nut moves a bit in the axial direction during loading or force development, so that the means for transmitting torque at the circumference of the spindle nut has to be correspondingly flexible, for example as a gear with a toothed wheel meshing with a toothed wheel mounted on the spindle nut , In this case, the comb area is sufficiently dimensioned by appropriate size dimensions to allow a displacement of one of the gears relative to the other in the axial direction. The two gears can be coupled to each other for example by a straight toothing or by a helical toothing.

A further advantageous embodiment of the invention provides that the thrust bearing between the spindle nut and the support plate is arranged. In this way, the axial force of the spindle nut can be intercepted without significantly more parts move axially or rotationally on the spindle as the spindle nut itself. The support plate and the spring then move only by the compression movement of the spring in the axial direction. This avoids friction losses and additional forces that could create problems with the reproducibility of the developed axial force.

The invention can also advantageously be configured in that the means for the circumferential transmission of a torque is axially in a range in which the thread of the spindle nut with the spindle is force-transmitting manner engaged. As a result, it is achieved, for example, that the spindle nut is also guided to some extent in the region in which radial forces act on it, in addition to the guide in the radial bearing and in the axial bearing on the spindle and by its inherent stability.

A further advantageous embodiment of the invention provides that the means for the circumferential transmission of torque has a coaxially mounted on the spindle nut first gear. In this case, it is also advantageous, for example, provided that a second gear which can be driven by means of a motor and in particular a gear is provided which engages circumferentially with the first gearwheel. In this way, a device for torque transmission is provided, which is particularly flexible with respect to a relative movement of the parts, for example, the two gears, in the axial direction. By the gearbox, a sufficient reduction of the movement of the motor can be achieved to develop the required forces. The spindle nut is driven by the device in both directions and thus suitable for driving the spindle in both orientations of the axial direction.

Alternatively, the first gear, for example, by means of a chain can be driven, which is driven by a further gear of the device for the circumferential transmission of torque. If the length of the chain and the distance between the gears / sprockets chosen sufficiently large, so also allows such a device relative movement of the elements in the axial direction.

Except for a spindle drive, the invention also relates to a parking brake device, in particular for a vehicle with a corresponding spindle drive for a spindle, which is connected to a brake.

Embodiments of the invention will be explained in more detail with reference to a drawing. Show:

1 schematically a brake system that acts on a vehicle wheel,

2 in a longitudinal section an inventive embodiment of the spindle drive,

3 a three-dimensional view of a spindle drive for a parking brake,

4 a special embodiment of the spindle nut, and

5 a variant of the drive for the spindle nut.

1 shows a spindle drive 1 in a housing 2 is arranged and with its operation in a by the arrow 3 indicated direction (axial direction) one in the 1 not shown separately spindle can be moved. To the casing 2 closes a Bowden cable 4 to whose soul 5 with a braking device 6 connected in the two brake levers 7 . 8th opposite a brake disc 9 are drivable. By exerting a pull on the soul 5 of the Bowden cable 4 become two operating levers 7a . 8a the braking device 6 in the direction of the arrows 10 . 11 moved towards each other, so that the corresponding brake lever 7 . 8th also be moved towards each other and the brake disc 9 pinch between them. The brake disc 9 is exemplary and schematic on a shaft 12 attached, on the other hand, an impeller 13 is attached. By exerting a tensile force on the Bowden cable 4 through the spindle drive 1 can thus the wheel 13 be slowed down. The device shown schematically here can be used for example as a parking brake for a motor vehicle.

In 2 the internal structure of the spindle drive is shown in a longitudinal section. It is a spindle nut 14 shown, which has an internal thread with the external thread of the spindle 15 is engaged. The spindle nut 14 is at its upper end in the figure in a thrust bearing 16 stored, which is designed as a rolling bearing, in particular as a ball bearing or needle roller bearings. The thrust bearing 16 For example, may have straight, flat bearing surfaces or conical bearing surfaces to ensure the best possible radial guidance in addition to the axial bearing. Even a stable bearing cage can support this.

The spindle nut 14 carries at the periphery of a first gear 17 , the circumference with a in 2 not shown second gear meshes, so that the first gear 17 and thus the rotatably connected thereto spindle nut 14 are driven in rotation. The first gear 17 has an integrally connected with this hollow cylindrical neck 18 on, extending in the axial direction - indicated by the arrow 19 - Of the one sprocket bearing part of the gear 17 extends away, and which forms the radially inner bearing ring of a radial bearing, which is designed as a sliding bearing. The sliding bearing comprises the hollow cylinder 18 as the first, inner bearing ring and as an outer bearing ring an end-side part of a tube 20 which part directly axially the gear 17 is adjacent. The pipe socket 18 thus slides like a sleeve on the inner wall of the tube 20 and thus stores the spindle nut 14 radial.

The first gear 17 and the pipe socket 18 can consist of a suitable material, usually a metal, for example steel, brass or a brass alloy. It can also be in the pipe 20 In the region of the radial bearing thus formed a plastic storage are introduced, which forms the outer ring of the radial bearing. The area where the pipe 20 with the pipe socket 18 interacts with is 21 and is referred to as a radial bearing. The radial bearing 21 is in the embodiment shown here at the end of the spindle nut 14 intended.

The other, the radial bearing 21 axially opposite end of the spindle nut 14 is in the thrust bearing 16 stored. This is on the trained as an annular disc support disk 22 supported, which in turn resiliently by a coil spring 23 opposite a housing 24 or a stop disk 25 is supported. The other coil spring 26 serves for example to eliminate mechanical play in the course of the possible movements of the spindle 15 without axial load and is thus used as a biasing spring.

The interaction of the first gear 17 on the spindle nut 14 with a driving this second gear finds in a first axial section 27 of the spindle drive instead. This first axial section 27 can feel when the spring 23 is compressed, in the axial direction 19 depending on the on the spindle 15 slightly shift the acting tensile force, that the spindle nut 14 rotates and the spindle 15 attracts against an external force. A corresponding displacement of the support plate 22 or another, with the spring 23 movable part, such as the spring housing 23a , can by means of a magnetic sensor device 45 be recorded. The detected displacement represents a measure of the developed axial force.

The first axial section 27 lies within a second axial section 28 , on the one hand, the axial extent 29 of the thrust bearing, the axial extent 30 of the radial bearing and the Axialbereich lying between them. This ensures that the circumferential load on the spindle nut can only take place in the area supported by the bearings.

In the area not shown above the drawings of 2 is the spindle 15 with the soul of one on the case 24 attached Bowden cable connected.

3 shows in a three-dimensional view, omitting the housing and the tube 20 the spindle drive with the spindle 15 , the spindle nut 14 , the first gear 17 and the second gear 31 , which is axially parallel to the first gear 17 is stored with this combing. On the shaft is a third, smaller gear 32 fastened, in the context of a gearbox by a on the shaft 33 of the motor 34 stored gear is driven. In addition, in 3 the coil spring 23 as well as the chassis 35 shown for the housing of the spindle drive.

4 shows a spindle in a three-dimensional view 15 with a spindle nut 14a , the material saving a thin-walled tube 36 For example, from a metal, with a profiled in the circumferential direction injection molded body 37 , for example, made of a plastic, is encapsulated. The injection-molded body 37 can, for example, distributed on the circumference webs 38 have, which are aligned in the axial direction of the spindle drive and to a positive connection of the gear 39 with the spindle nut 14a serve. To stabilize the injection-molded body 37 this can also have reinforcing inserts, for example made of steel. The bridges 38 can in the longitudinal direction of the spindle nut 14a up to the thrust bearing 16 range and support themselves there in the axial direction.

The gear 39 points for the positive connection with the webs 38 at its inner circumference 40 a number of grooves 41 for positive reception of the webs 38 on. The gear 39 can thus in the axial direction on the spindle nut 14a pushed and fastened there.

With the use of in 4 shown spindle nut 14a Thus, material can be saved, and also the spindle nut should be made as short as possible. For example, on the thrust bearing 16 opposite axial end of the spindle nut 14a the inner bearing ring of the radial bearing also on the pipe 36 and the footbridges 38 be postponed like the gear 39 , The bearing ring can also in this variant in one piece with the gear 39 be produced coherently. Depending on the number of bars 38 on the circumference of the spindle nut 14a These can form with the outer contour and the sliding surface of the inner bearing ring of the radial bearing.

5 shows a section of a spindle drive in a three-dimensional view, wherein the spindle is not shown, but only the spindle nut 14 with the thrust bearing 16 as well as the gear 39a , The gear 39a is circumferentially not directly driven by a second gear, but by a link chain 42 , the corresponding recesses for the teeth of the first gear 39a and by means of a second gear 43 is drivable. With an axial movement of the spindle nut 14 with the gear 39a in the direction of the arrow 44 in the course of generating an axial force, the second gear 43 remain stationary in the axial direction, as long as the output angle of the link chain 42 not changed too much. Since usually the suspension of the spindle nut by a spring, like this in 2 is shown is very hard, can be expected axial movements of the first gear 39a compensate by an inclination of the link chain 42 ,

Even with a peripheral drive of the first gear 39a or the spindle nut 14 through a link chain 42 , as in 5 shown, a reliable radial bearing of the spindle nut is necessary, by the inventive positioning of the radial bearing and the thrust bearing with respect to the position of the first gear 39a can be guaranteed.

LIST OF REFERENCE NUMBERS

1

spindle drive

2

Housing of a spindle drive

3

axially

4

Bowden

5

Soul of 4

6

braking means

7

brake lever

7a

actuating lever

8th

brake lever

8a

actuating lever

9

brake disc

10

arrow

11

arrow

12

wave

13

wheel

14

spindle nut

14a

spindle nut

15

spindle

16

thrust

17

first gear

18

pipe socket

19

axially

20

pipe

21

radial bearings

22

support disc

23

support spring

23a

spring housing

24

casing

25

stop disc

26

feather

27

first axial area

28

second axial region

29

axial extension of the thrust bearing

30

axial extension of the radial bearing

31

second gear

32

third gear

33

Shaft of the engine

34

engine

35

chassis

36

Tube of a spindle nut

37

injection moldings

38

web

39

first gear

39a

first gear

40

Inner circumference of the gear

41

Longitudinal groove on the inner circumference of the gear

42

drive chain

43

second gear

44

axially

45

sensor device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• EP 0988203 B1 [0004]
• DE 10043739 A1 [0005]
• DE 19906228 B4 [0006]
• DE 102006033569 B4 [0007]
• DE 10361127 B4 [0008]

Claims (14)

Spindle drive for generating a force in an axial direction ( 3 . 19 . 44 ) with a spindle ( 15 ) whose longitudinal axis in the axial direction ( 3 . 19 . 44 ), and with a spindle nut ( 14 . 14a ) whose internal thread with an external thread of the spindle ( 15 ) and with a device ( 17 . 31 . 39 . 39a . 42 . 43 ) for the circumferential transmission of torque to the spindle nut ( 14 . 14a ) in a first axial section ( 27 ) with respect to the axial direction ( 3 . 19 . 44 ), characterized in that the spindle nut ( 14 . 14a ) exclusively in a thrust bearing ( 16 ) and a radial bearing ( 18 . 21 ) is stored. Spindle drive according to claim 1, characterized in that the first axial section ( 27 ) with respect to the axial direction ( 3 . 19 . 44 ) within a second axial section ( 28 ), the axial extent of the radial bearing ( 18 . 21 ), the axial extent of the thrust bearing ( 16 ) as well as in the axial direction ( 3 . 19 . 44 ) between the two camps ( 16 . 18 . 21 ). Spindle drive according to claim 1 or 2, characterized in that the spindle nut ( 14 . 14a ) by its rotation the spindle ( 15 ) in the axial direction ( 3 . 19 . 44 ) is moved so that it generates a tensile force. Spindle drive according to claim 3, characterized in that the spindle ( 14 . 14a ) with a pull rope ( 4 . 5 ), in particular a Bowden cable is connected. Spindle drive according to claim 4, characterized in that the thrust bearing ( 16 ) in the axial direction ( 3 . 19 . 44 ) between the means for transmitting a torque ( 17 . 31 . 39 . 39a . 42 . 43 ) and the traction cable ( 4 . 5 ) is arranged. Spindle drive according to one of claims 1 to 5, characterized in that the thrust bearing ( 16 ) is a rolling bearing, in particular a ball bearing or a needle bearing. Spindle drive according to one of claims 1 to 6, characterized in that the radial bearing ( 18 . 21 ) is a sliding bearing. Spindle drive according to claim 7, characterized in that the radially inner bearing ring ( 18 ) of the sliding bearing ( 18 . 21 ) with one on the spindle nut ( 14 . 14a ) attached gear ( 17 . 39 . 39a ), in particular integrally connected thereto. Spindle drive according to one of claims 1 to 8, characterized in that the spindle nut ( 14 . 14a ) in particular with one of its end faces or arranged at one of its ends flange axially on an axially sprung support plate ( 22 ) is supported. Spindle drive according to claim 9, characterized in that the thrust bearing ( 16 ) in the axial direction ( 3 . 19 . 44 ) between the spindle nut ( 14 . 14a ) and the support plate ( 22 ) is arranged. Spindle drive according to one of claims 1 to 10, characterized in that the means for the circumferential transmission of a torque ( 17 . 31 . 39 . 39a . 42 . 43 ) axially in a region in which the thread of the spindle nut ( 14 . 14a ) with the spindle ( 15 ) is force-transmitting engaged. Spindle drive according to claim 11, characterized in that the device for the circumferential transmission of a torque ( 17 . 31 . 39 . 39a . 42 . 43 ) coaxially on the spindle nut ( 14 . 14a ) fixed first gear ( 17 . 39 . 39a ) having. Spindle drive according to claim 12, characterized in that the device for the circumferential transmission of a torque ( 17 . 31 . 39 . 39a . 42 . 43 ) by means of a motor ( 34 ) and in particular a transmission ( 32 . 33 ) drivable second gear ( 31 ), which is connected to the first gear ( 17 . 39 ,) is engaged. Parking brake device with a spindle drive according to one of claims 1 to 13.

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