DE102015116545A1 - Magnet unit for a sensor device of a motor vehicle, sensor device with a magnet unit and motor vehicle with a sensor device - Google Patents

Abstract

The invention relates to a magnet unit (10, 20, 30) for a sensor device for connection to a steering shaft, wherein the magnet unit (10, 20, 30) has a sleeve (11, 21, 31) with a sleeve-shaped main body and a rotationally fixed and in tangential direction backlash with the sleeve (11, 21, 31) connected to the magnetic element (12, 22, 32), wherein the sleeve (11, 21, 31) and the magnetic element (12, 22, 32) connected to each other by means of at least one positive connection are, wherein the sleeve (11, 21, 31) and the magnetic element (12, 22, 32) have different thermal expansion coefficients and are designed and connected to each other such that when a change in ambient temperature due to the different thermal expansion coefficients of sleeve (11, 21, 31) and magnetic element (12, 22, 32) leads to a play in the tangential direction in the positive connection, a frictional connection between the Hü lse (11, 21, 31) and the magnetic element (12, 22, 32) is formed and / or reinforced, wherein the frictional forces between the sleeve (11, 21, 31) and magnetic element (12, 22, 32) at least as large are that due to the change in ambient temperature in the positive connection in the tangential direction resulting game is compensated such that the sleeve (11, 21, 31) and the magnetic element (12, 22, 32) continue to be connected without play in the tangential direction ,

Description

The invention relates to a magnet unit for a sensor device for detecting a measured variable characterizing a rotational state of a steering shaft of a motor vehicle, wherein the magnet unit has a sleeve with a bush-shaped main body for connecting the magnet unit to a part of the steering shaft and a magnetic element connected to the sleeve. The invention also relates to a sensor device for detecting a measured variable characterizing a state of rotation of a steering shaft of a motor vehicle and a motor vehicle having such a sensor device.

Generic magnet units are used for example in torque sensor devices for detecting a torque applied to a steering shaft of a motor vehicle and are basically known from the prior art, for example from the EP 0 980 081 B1 , of the EP 1 123 794 A2 , of the US 5,530,344 or the DE 10 2013 006 567 A1 ,

The magnet unit is usually designed to be attached to one of two, opposite in the axial direction parts of the steering shaft, wherein for detecting the state of rotation of the steering shaft on the other shaft part, a sensor unit can be attached to a magnetic stator, which is provided for this purpose to be arranged in the radial direction opposite to the magnetic element of the magnet unit with a small air gap therebetween. By means of the stator, the magnetic flux occurring in the magnetic element, dependent on the rotational state of the shaft magnetic flux for generating a sensor signal from the magnetic element via a flux guide can be passed on to a magnetic sensor, for example to a Hall sensor.

Generic magnet units usually have a magnetic element designed as a permanent magnet and usually a metallic sleeve, via which the magnet unit can be connected to the steering shaft, which is known, the sleeve rotatably, for example by gluing, welding, caulking or by means of a press fit with the steering shaft connect to.

The challenge is on the one hand to ensure a permanent rotationally fixed connection of the magnet unit with the steering shaft, and on the other hand to provide a backlash-free, rotationally fixed connection between the magnetic element and the sleeve.

The magnetic element of generic magnet units usually consists of a plastic filled with magnetic particles and is usually produced by plastic injection molding, wherein the magnetic element can be molded directly onto the sleeve or the sleeve can be encapsulated with the magnetic material.

Due to the generally high degree of filling with the magnetic particles of the plastic, in particular at low temperatures, usually relatively brittle or less elastic. As a result, especially when the magnetic element is molded directly onto the sleeve or when the sleeve is overmolded with the magnetic material, thermally induced shrinkage stresses may occur during cooling of the plastic melt, which can lead to the formation of cracks in the magnetic element. Furthermore, in the case of temperature fluctuations occurring during operation, due to the different coefficients of thermal expansion of sleeve and magnetic element, thermally induced stresses can occur in the magnet unit, which can likewise lead to cracking in the magnetic element.

For this reason, in the aforementioned EP 1 123 794 A2 proposed to attach the magnetic element not directly, but via an intermediate element made of an elastic material to the sleeve. However, this solution is relatively complicated and expensive and requires a certain amount of space.

From the above-mentioned E 0 980 081 B1 it is known to directly overmould the sleeve with the plastic-bonded magnetic material, wherein for receiving thermally induced shrinkage stresses of the plastic is proposed to provide a plurality of circumferentially distributed tabs on the sleeve.

From the DE 10 2013 006 567 A1 Furthermore, a magnetic element is known in which the sleeve and the magnetic element are first produced separately and then connected to one another in a form-fitting manner. For this purpose, the sleeve has a bush-shaped main body and a plurality of lugs projecting from the main body in the axial direction, which are provided for connection to the magnetic element, wherein the magnetic element corresponding to the axially projecting tabs of the sleeve has correspondingly arranged and formed recesses, in which the tabs for connecting sleeve and magnetic element can be introduced by heating the magnetic element, wherein the sleeve and the magnetic element are formed such that the tabs after cooling of the magnetic element firmly seated in the recesses, so that the sleeve and the magnetic element at least in a tangential direction rotation and play are connected to each other.

It is an object of the invention to provide an alternative magnet unit, preferably a particularly easy to manufacture magnet unit, in particular a magnet unit with which the risk of cracking in the magnetic element due to thermal stresses can be reduced, but at the same time a play-free, rotationally fixed connection in the tangential direction are ensured can.

This object is achieved by a magnet unit, by a sensor device and by a motor vehicle with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures and are explained in more detail below.

A magnet unit according to the invention for a sensor device for detecting a measured variable characterizing a rotation state of a steering shaft of a motor vehicle has a sleeve with a bush-shaped main body for connecting the magnet unit to a part of the steering shaft and a magnetic element connected to the sleeve. In this case, the sleeve and the magnetic element are connected to each other by means of at least one positive connection, wherein the sleeve and the magnetic element have different thermal expansion coefficients. The sleeve and the magnetic element are designed such that the positive connection is free of play in a reference state at a reference ambient temperature in the tangential direction.

According to the invention, the sleeve and the magnetic element are designed and connected to one another in such a way that, starting from the reference ambient temperature with a change in the ambient temperature resulting in a play in the tangential connection due to the different thermal expansion coefficients of sleeve and magnetic element, a frictional connection arises between the sleeve and the magnetic element and / or is reinforced. The frictional forces between sleeve and magnetic element are at least so great that the resulting due to the change in ambient temperature in the positive connection in the tangential direction game is compensated such that in at least one predefined temperature range around the reference ambient temperature around and / or adjacent to the sleeve and the magnetic element continue to remain connected to each other in a tangential direction without play.

In other words, that means that the magnet unit according to the invention is configured and configured, in particular the sleeve and the magnetic element, that a resulting in a change in ambient temperature due to the different thermal expansion coefficients in the tangential direction in the positive connection by increasing frictional forces between the sleeve and Magnetic element, which are preferably also due to the different thermal expansion coefficients and / or amplified, is compensated such that a relative movement between the sleeve and the magnetic element is avoided and thus in at least one predefined temperature range in a tangential direction play-free, rotationally fixed connection between the magnetic element and Sleeve is maintained.

The reference ambient temperature at which the positive connection between the magnetic element and the sleeve is free of play in the tangential direction is preferably in a temperature range of 15 ° C to 30 ° C, in particular between 20 ° C and 25 ° C and 20 ° C or 23 is preferably ° C.

The magnetic element of a magnet unit according to the invention preferably contains a plastic filled with magnetic particles and / or consists thereof, wherein the magnetic element is preferably produced in a plastic injection molding process. Particularly preferably, the magnetic element has been produced by injection molding on the sleeve and / or by encapsulation of the sleeve and in this way has been connected to the sleeve.

The sleeve of a magnet unit according to the invention preferably contains metal and / or is made of metal, wherein the sleeve is preferably made by deep drawing and subsequent punching. Preferably, the sleeve is designed such that it can be fixed by means of a press fit on a part of the steering shaft or can be welded to the part of the steering shaft. Alternatively, the sleeve can also be caulked or glued to the part of the steering shaft, wherein, however, a connection with the steering shaft by means of a press fit or a welded connection has been found to be particularly advantageous.

Preferably, the sleeve and the magnetic element are connected to each other not only by means of a single positive connection, but more preferably, the magnet unit has a plurality of circumferentially distributed, in particular distributed uniformly distributed in the circumferential direction, form-fitting connections between the sleeve and magnetic element.

At least one positive connection is preferably formed by a recess and a projection corresponding to the recess formed in the recess engages, wherein preferably the sleeve has at least one recess and the magnetic element engages at least one projection corresponding to the recess of the sleeve in the recess of the sleeve. Preferably, the sleeve has in the circumferential direction a plurality of, in particular evenly distributed recesses arranged on the magnet element and corresponding to many corresponding to the recesses in the sleeve and formed projections, wherein preferably in each case a projection of the magnetic element engages in an associated recess in the sleeve and the magnetic element positively connects with the sleeve.

Of course, alternatively, the magnetic element may have one or more recesses and the sleeve one or more corresponding to the recess formed in the magnetic element projections which engage in the recesses of the magnetic element.

The sleeve and the magnetic element can of course already be connected in the reference state in addition to the positive connection by means of a frictional connection. This means that the magnet unit can, of course, be configured in such a way that frictional forces between the sleeve and the magnet element are already active in the reference state. It is only important that the magnet unit is configured and designed in such a way that at least in a predefined temperature range around the reference temperature and / or adjoining it, a play arising as a result of a change in the ambient temperature in the tangential direction in the positive connection is compensated by increasing frictional forces , wherein the magnet unit is preferably configured and designed so that over a total operating temperature range in a tangential direction backlash-free, rotationally fixed connection between the sleeve and the magnetic element can be maintained.

In an advantageous embodiment of a magnet unit according to the invention, the thermal length and / or volume expansion coefficient of the magnetic element is greater than the thermal length and / or volume expansion coefficient of the sleeve, wherein preferably the magnetic element is arranged at least partially concentric with the sleeve, in particular outside the sleeve around. Preferably, the magnetic element is annular disc-shaped or bush-shaped and in particular arranged at least in a region of the sleeve to the sleeve-shaped sleeve on the outside.

Such an embodiment of the magnet unit, in particular a configuration in which the magnetic element is arranged outside as a component with the larger coefficient of thermal expansion, is particularly advantageous to reduce the risk of cracking in the magnetic element, since in this way a largely unhindered, thermally induced expansion of the magnetic element and a uniform shrinkage can be made possible, whereby thermally induced voltages can be reduced or evenly distributed in the magnetic element.

In a particularly advantageous embodiment of a magnet unit according to the invention, the magnet unit is configured and designed such that the frictional forces are created and / or amplified by a shrinkage of the magnetic element as a result of a lowering of the ambient temperature, in particular if the ambient temperature is lowered starting from the reference ambient temperature. That is, a magnet unit according to the invention is preferably designed and designed so that the resulting due to the change in ambient temperature clearance in tangential direction in the positive connection between the magnetic element and sleeve is compensated by frictional forces arising as a result of shrinkage between the sleeve and magnetic element and / or be strengthened.

As a result, a play-free, rotationally fixed connection between the magnetic element and the sleeve can be ensured even in a temperature range below the reference ambient temperature and that the resulting due to the shrinkage of an introduced into a recess of the sleeve projection of the magnetic element game can be compensated in the positive connection between the magnetic element and sleeve and a Relative movement between the magnetic element and sleeve can be avoided.

The magnet unit is preferably configured and designed such that over the entire operating temperature range a play-free, non-rotatable connection between sleeve and magnetic element can be maintained in the tangential direction, wherein preferably at least in a temperature range between 0 ° C and the reference ambient temperature, preferably in a temperature range between - 10 ° C and the reference ambient temperature, in particular between -20 ° C and the reference ambient temperature, more preferably in a temperature range between -40 ° C and the reference ambient temperature, the frictional forces caused by the shrinkage of the magnetic element as a result of lowering the ambient temperature and / or amplified be that in the tangential direction play-free, rotatable connection between the magnetic element and sleeve can be maintained.

In an advantageous embodiment of a magnet unit according to the invention, the magnet unit is designed and constructed such that, at an ambient temperature above the reference ambient temperature, a part of the forces usually acting on the magnet unit in operation in the tangential direction during operation, preferably all of the forces usually acting on the magnet unit in the tangential direction during operation Forces can be transmitted via the positive connection between the sleeve and the magnetic element of the sleeve on the magnetic element and / or the magnetic element on the sleeve.

It can thereby be achieved that all forces can be transmitted alone via the positive connection, so that even without the presence of a frictional connection between the sleeve and magnetic element a backlash-free, rotationally fixed connection can be provided, which is designed for transmitting the forces occurring. In other words, that the magnet unit, in particular the positive connection between sleeve and magnetic element, is designed and designed so that at an ambient temperature above the reference ambient temperature no additional force or frictional connection is required to the forces usually occurring during operation to transfer between sleeve and magnetic element, in particular without damaging the magnet unit.

The fact that in a magnet unit according to the invention the backlash-free connection between sleeve and magnetic element is ensured at low temperatures via a frictional connection and at high temperatures over at least one positive connection between the sleeve and magnetic element, allows a particularly advantageous, geometric design of the magnet unit, in particular of the magnetic element, by means of which in particular critical thermal stresses can be reduced, can even be largely avoided in some special cases, whereby the risk of cracking can be significantly reduced.

In an advantageous embodiment of a magnet unit according to the invention, the sleeve has a radially outwardly extending flange, wherein in the flange preferably at least one recess is provided and wherein the magnetic element has at least one corresponding to the recess in the flange of the sleeve formed projection in engages the recess of the sleeve and forms a positive connection with the recess of the sleeve. In a particularly preferred embodiment, the flange of the sleeve in this case has a plurality of circumferentially distributed, in particular evenly distributed recesses arranged on the magnet element and corresponding to a plurality of corresponding to the recesses in the sleeve and trained, each engaging in the recesses in the sleeve projections.

In an advantageous embodiment, at least one recess in the sleeve is an encircling closed recess, preferably a circular opening, in particular a bore, wherein the bores can be formed as a through-hole bore and / or as a blind hole.

If the sleeve has a flange, preferably at least one recess is arranged in the flange, in particular in the flange plane. If, on the other hand, the sleeve has no flange, then preferably at least one recess is arranged in the sleeve-shaped main body of the sleeve.

In a further advantageous embodiment of a magnet unit according to the invention, at least one projection which engages in a recess, designed as a pin and / or rivet, wherein, if the projection is formed as a rivet, the rivet web preferably transformed after insertion into the recess of the sleeve has been that the sleeve and the magnetic element are connected by means of a riveted joint. In this case, the associated recess is preferably formed as a through hole. Furthermore, in this case, the sleeve and the magnetic element are preferably first prepared separately and then joined together, wherein the projection of the magnetic element is introduced into the recess of the sleeve and when the projection is formed as a rivet, the rivet is correspondingly formed and made the rivet connection becomes.

In an alternative manufacturing method of an alternative magnet unit according to the invention, however, the sleeve can also be encapsulated with the magnetic element material, so that at least one recesses is filled with material, at least one projection is formed and at least one positive connection between sleeve and magnetic element is formed.

For this purpose, it has been found to be particularly advantageous if the flange has at least one recess open to the outer edge of the flange, in particular a notch-shaped recess, and the magnetic element at least one corresponding corresponding to the recess projection which engages in the recess. Preferably, the projection extends in the radial direction, in particular in the radial and tangential direction, so that the Magnetic element and the flange of the sleeve are positively connected to each other in the tangential direction, wherein the flange more preferably distributed in the circumferential direction arranged, in particular evenly distributed arranged to the outer edge of the flange out recesses or notches and the magnetic element according to a plurality, correspondingly arranged and formed projections, which engage respectively in the recesses.

In a further advantageous embodiment of a magnet unit according to the invention, at least one recess arranged in the flange of the sleeve and open towards the outer edge of the flange has a flat area in the notch base and preferably at least one transitional area laterally in the tangential direction and in particular one on each side Flank, wherein preferably at least one transition region has a rounded contour, in particular a rounded with a radius of at least 0.5 mm contour. As a result, occurring notch stresses can be reduced and the component load can be reduced.

In a further advantageous embodiment of a magnet unit according to the invention, at least one flank of at least one notch-shaped recess, preferably both flanks, has at least one flank pitch of 50 ° with respect to the notch base, preferably of 60 °, in particular of approximately 70 ° to 80 °.

It has been found that, by increasing the ambient temperature starting from the reference ambient temperature, it is possible to achieve a particularly good clamping of the projection in the recess in the tangential direction without the protrusion being forced out of the recess in the radial direction and / or the magnetic element is damaged. The resulting thermal stresses in the magnetic element can be easily compensated by a sufficient wall thickness in the tangential direction, so that in a simple manner, a magnet unit with a rotationally fixed, play-free connection between the sleeve and magnetic element without intermediate elements can be provided and without There is an increased risk of cracking in the magnetic element, even with changing ambient temperatures.

The geometry of the sleeve and of the magnetic element, in particular the geometry of the recesses, is preferably designed such that a good compromise of sufficient connection strength and a low notch effect is achieved.

In a further advantageous embodiment of a magnet unit according to the invention a wall thickness of the magnetic element in the radial direction, preferably over the entire circumference of the magnetic element, at least so great that the risk of damage to the magnetic element, in particular by cracking due to occurring during operation temperature loads and consequently resulting, thermally induced voltages, is reduced.

A sensor device according to the invention for detecting a measured variable characterizing a rotation state of a steering shaft of a motor vehicle is characterized in that the sensor device has a previously described magnet unit according to the invention.

A motor vehicle according to the invention with a sensor device is characterized in that it has a prescribed sensor device according to the invention.

The advantageous embodiments presented with respect to the magnet unit and their advantages also apply correspondingly to the sensor device according to the invention and to a motor vehicle according to the invention.

Further features of the invention will become apparent from the claims, the figures and the description of the figures. All the features and feature combinations mentioned above in the description as well as the following features and feature combinations mentioned in the description of the figures and / or shown alone in the figures can be used not only in the respectively indicated combination but also in other combinations or alone.

The invention will now be described with reference to several preferred embodiments and with reference to the accompanying drawings.

Show it:

1 a first embodiment of a magnet unit according to the invention in a sectional view in longitudinal section,

2 A second embodiment of a magnet unit according to the invention in a sectional view, also in longitudinal section,

3a A third embodiment of a magnet unit according to the invention, also in longitudinal section,

3b the magnet unit according to the invention 3a in cross section,

3c the sleeve of the magnet unit according to the invention from the 3a and 3b as an individual part in perspective,

3d the sleeve from the 3a . 3b and 3c in side view and

3e a section of the sleeve 3d in an enlarged view.

This in 1 illustrated, first embodiment of a magnet unit according to the invention 10 has a metallic sleeve 11 with a bush-shaped body and a concentric to the sleeve 11 outside of the sleeve 11 molded magnetic element made of plastic filled with magnetic particles 12 on, wherein the magnet unit for attachment to a part of a not shown here, about an axis of rotation 13 rotatable steering shaft is provided as part of a sensor device.

The sleeve 11 has several circumferentially introduced into the sleeve, circumferentially closed trained recesses 14 in the form of holes or blind holes 14 on, which are distributed uniformly in the circumferential direction over the sleeve.

The magnetic element 12 has in each case a plurality of correspondingly arranged and corresponding to the recesses 14 the sleeve 11 trained protrusions 15 on, which in each case in the blind holes 14 the sleeve 11 engage and thereby the magnetic element 12 with the sleeve 11 connect positively.

The sleeve 11 and the magnetic element 12 , which have different thermal expansion coefficients, wherein the thermal expansion coefficient of the magnetic element 12 larger than the sleeve 11 , Are designed such that the positive connections, which through the projections 15 with the recesses 14 are formed in a reference state at a reference ambient temperature of 20 ° C in the tangential direction r free of play.

The magnet unit according to the invention 10 is further configured such that when the ambient temperature is lowered from the reference ambient temperature and the magnetic element 12 As a result, shrinks and thus due to the larger thermal expansion coefficient, the projections 15 shrink more than the recesses 14 and thereby a game in the tangential direction in the positive connections is created by the shrinkage of the magnetic element 12 the frictional forces between sleeve 11 and magnetic element 12 be strengthened outside of the positive connections in such a way, in particular in the area of the bush-shaped base body 11 in that the play resulting in the positive connections is compensated, so that the sleeve 11 and the magnetic element 12 continue to remain connected in a tangential direction without play.

In particular, the magnetic element 12 and the sleeve 11 coordinated so that the resulting frictional thermal shrinkage due to the shrinkage between sleeve 11 and magnetic element 12 are at least so large that in the positive connection in the tangential direction resulting play is at least compensated such that a relative movement between the sleeve 11 and the magnetic element 12 is avoided in the tangential direction during operation.

If, however, the ambient temperature is increased, in particular starting from the reference ambient temperature, the frictional force between the sleeve decreases 11 and the magnetic element 12 from, as the magnetic element 12 in the radial direction expands more strongly to the outside than the metallic sleeve 11 due to the significantly larger thermal expansion coefficient of the magnetic element 12 opposite to the thermal expansion coefficient of the sleeve 11 , The projections 15 of the magnetic element 12 also expand stronger than the recesses 14 in the sleeve 11 so that the projections 15 in the recesses 14 be braced, thereby continuing a backlash-free connection between sleeve 11 and magnetic element 12 is maintained and thus even with a warming or increasing the ambient temperature, a rotationally fixed backlash-free connection between the sleeve 11 and magnetic element 12 is ensured.

The wall thickness of the magnetic element 12 is chosen at least so large in the radial direction that damage to the magnetic element due to thermally induced voltages is avoided.

2 shows a second embodiment of a magnet unit according to the invention 20 which also has a sleeve 21 and a magnetic element 22 and wherein the sleeve 21 also a bush-shaped body 21b and for non-rotatable connection with a about an axis of rotation 23 rotatable, here also not shown steering shaft is formed.

In this case, the sleeve points 21 , which is also made of metal, unlike that in 1 illustrated embodiment in addition to the bush-shaped base body 21b one radially outwardly extending flange 21a in which distributed in the circumferential direction a plurality of circular openings 24 are formed, wherein the openings 24 in this case as hole drilled holes 24 are formed with a bore axis extending in the axial direction, ie with a parallel to the axis of rotation 23 extending bore axis.

The magnetic element 22 is also concentric with the sleeve 21 arranged, however, is located in this embodiment, the magnetic element 22 not like in 1 over its entire axial length in the radial direction outside of the sleeve 21 but only in the area of the projections 25 which are in the recesses 24 engage and passed through them.

In contrast to that on the basis of 1 described embodiment of a magnet unit according to the invention 10 is at the in 2 shown magnet unit 20 the magnetic element 22 not by molding the sleeve 21 been made, but separately. That is, the sleeve 21 and the magnetic element 22 were first produced independently and then joined together by the projections 25 of the magnetic element 22 , which in this case rivets 25 form, in the recesses 24 the sleeve 21 have been introduced. Then the rivets were 25 reshaped so that fixed rivet connections between sleeve 21 and magnetic element 22 have been trained.

This magnet unit 20 allows for temperature changes an almost unhindered expansion of the magnetic element 22 or an almost unhindered shrinkage of the magnetic element 22 without the play in tangential direction between the sleeve 21 and the magnetic element 22 arises, causing thermal stresses in the magnetic element 22 can be largely avoided and thus the risk of cracking in the magnetic element 22 can be reduced.

3a shows in longitudinal section a third embodiment of a magnet unit according to the invention 30 which likewise has a metallic sleeve formed as a stamped part 31 and a non-rotatably connected to this magnetic element 32 made of plastic filled with magnetic particles, wherein the magnetic element 32 in this case, directly to the sleeve 31 has been injected.

This sleeve 31 also has a radially outwardly extending flange 31a and a socket-shaped body 31b for non-rotatable connection with one about an axis of rotation 33 rotatable, also not shown here, part of a steering shaft.

As based on the 3b . 3c and 3d can be seen, the flange extends 31a in the radial direction perpendicular to the outside of the bush-shaped base body 31b away and has outwardly open, uniformly distributed in the circumferential direction U, notch-shaped recesses 34 on, wherein in this embodiment twelve recesses 34 are provided.

As based on 3b can be seen, the magnetic element has 32 each also distributed uniformly distributed circumferentially and corresponding to the recesses 34 trained protrusions 35 on, each with a projection 35 in a recess 34 engages and the magnetic element 32 with the sleeve 31 positively connects.

The recesses 34 each have a flat Kerbgrund 34a and each have a laterally adjoining transition region 34b on two flanks 34c , please refer 3e , The width b of the flat Kerbgrunds is in this embodiment in about 2 mm, the radius in the transition region about 0.6 mm and an edge slope α about 70 ° at a notch depth of about 1 mm, an Inn endurchmesser the sleeve of about 21 mm and an outer diameter of about 27 mm.

Due to the rounded contour in the transitional areas or the intended radius of 0.6 mm, both in the sleeve 31 as well as in the magnetic element 32 Notch stresses are reduced.

The 3a and 3b show the magnet unit according to the invention 30 while in a reference state at reference ambient temperature of 20 ° C, at which the from the projections 35 and recesses 34 formed positive connections in the tangential direction U are free of play.

The magnetic element 32 owns as in the previously described magnet units 10 and 20 also a larger thermal expansion coefficient than the sleeve 31 , so that when the temperature is lowered, the magnetic element 32 on the flange 31a the sleeve 31 shrinks and the frictional forces between the flange 31a and the magnetic element 32 be strengthened, so that also, if as a result of lowering of temperature the projections 35 shrink more than the recesses 34 , in a tangential direction U play-free rotationally fixed connection can be ensured.

As the ambient temperature increases, the magnetic element expands 32 stronger than the sleeve due to the larger thermal expansion coefficient 31 , especially as the flange 31a the sleeve 31 , so that the frictional forces between sleeve 31 and magnetic element 32 . in particular along the outer edge of the flange 31a , lose weight. The magnetic element 32 However, it also widens in the tangential direction U, so that the projections 35 increased on the flanks 34c the recesses 34 in the flange 31a the sleeve 31 support, whereby a play-free in the tangential direction rotatable connection between the sleeve 31 and the magnetic element 32 preserved. As a result, even with an increase in the ambient temperature, a relative movement between the sleeve 31 and the magnetic element 32 be prevented. The slope α of the flanks 34c is preferably as large as possible, but as small as necessary in order to reduce occurring notch stresses to the extent that in particular a thermally induced cracking or due to thermally induced stress resulting cracking is avoided.

Especially with in the 3a to 3e illustrated embodiment of a magnet unit according to the invention 30 can be critical, thermally induced voltages in the magnetic element 32 be avoided as far as possible.

To the risk of cracking in the magnetic element 32 to further reduce since thermally induced stresses can not be completely ruled out, the sleeve has 32 in the radial direction, a corresponding minimum wall thickness of about 3 to 4 mm.

Of course, a variety of constructive modifications to the illustrated embodiments possible without departing from the content of the claims.

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 0980081 B1 [0002]
• EP 1123794 A2 [0002, 0008]
• US 5530344 [0002]
• DE 102013006567 A1 [0002, 0010]

Claims (13)

Magnetic unit ( 10 . 20 . 30 ) for a sensor device for detecting a measured variable characterizing a state of rotation of a steering shaft of a motor vehicle, - wherein the magnet unit ( 10 . 20 . 30 ) a sleeve ( 11 . 21 . 31 ) with a bush-shaped basic body ( 11 . 21b . 31b ) for connecting the magnet unit ( 10 . 20 . 30 ) with a part of the steering shaft and one with the sleeve ( 11 . 21 . 31 ) connected magnetic element ( 12 . 22 . 32 ), - the sleeve ( 11 . 21 . 31 ) and the magnetic element ( 12 . 22 . 32 ) are connected to each other by means of at least one positive connection, - wherein the sleeve ( 11 . 21 . 31 ) and the magnetic element ( 12 . 22 . 32 ) have different thermal expansion coefficients, - wherein the sleeve ( 11 . 21 . 31 ) and the magnetic element ( 12 . 22 . 32 ) are designed such that the positive connection in a reference state at a reference ambient temperature in the tangential direction (U) is free of play, - wherein the sleeve ( 11 . 21 . 31 ) and the magnetic element ( 12 . 22 . 32 ) are configured and connected to one another in such a way that, starting from the reference ambient temperature with a change in the ambient temperature, due to the different thermal expansion coefficients of sleeve ( 11 . 21 . 31 ) and magnetic element ( 12 . 22 . 32 ) leads to a play in the tangential direction (U) in the positive connection, a frictional connection between the sleeve ( 11 . 21 . 31 ) and the magnetic element ( 12 . 22 . 32 ) is created and / or amplified, - wherein the frictional forces between sleeve ( 11 . 21 . 31 ) and magnetic element ( 12 . 22 . 32 ) are at least so great that the resulting due to the change in ambient temperature in the positive connection in the tangential direction game is compensated such that in at least one predefined temperature range around the reference ambient temperature around and / or adjacent to the sleeve ( 11 . 21 . 31 ) and the magnetic element ( 12 . 22 . 32 ) remain connected in the tangential direction (U) without play. Magnetic unit ( 10 . 20 . 30 ) according to claim 1, characterized in that the thermal length and / or volume expansion coefficient of the magnetic elements ( 12 . 22 . 32 ) is greater than the thermal length and / or volume expansion coefficient of the sleeve ( 11 . 21 . 31 ), wherein preferably the magnetic element ( 12 . 22 . 32 ) at least partially concentric with the sleeve ( 11 . 21 . 31 ) is arranged, in particular outside the sleeve ( 11 . 21 . 31 ) around. Magnetic unit ( 10 . 20 . 30 ) according to claim 1 or 2, characterized in that the magnet unit ( 10 . 20 . 30 ) is designed and designed such that the frictional forces due to a shrinkage of the magnetic element ( 12 . 22 . 32 ) as a result of a lowering of the ambient temperature, in particular at a lowering of the ambient temperature, starting from the reference ambient temperature, arise and / or amplified. Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that the magnet unit ( 10 . 20 . 30 ) is designed and constructed in such a way that, at an ambient temperature above the reference ambient temperature, a part of the one which is usually connected to the magnet unit during operation ( 10 . 20 . 30 ) acting in tangential direction (U) forces, preferably all of the in operation usually on the magnet unit ( 10 . 20 . 30 ) acting in tangential direction forces, via the positive connection between the sleeve ( 11 . 21 . 31 ) and magnetic element ( 12 . 22 . 32 ) of the sleeve ( 11 . 21 . 31 ) on the magnetic element ( 12 . 22 . 32 ) and / or the magnetic element ( 12 . 22 . 32 ) on the sleeve ( 11 . 21 . 31 ) are transferable. Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that the sleeve ( 11 . 21 . 31 ) a radially outwardly extending flange ( 21a . 31a ), wherein the flange ( 21a . 31a ) preferably at least one recess ( 24 . 34 ), and wherein the magnetic element ( 12 . 22 . 32 ) at least one, corresponding to the recess in the flange ( 21a . 31a ) of the sleeve ( 11 . 21 . 31 ) trained advantage ( 25 . 35 ), which in the recess ( 24 . 34 ) of the sleeve ( 11 . 21 . 31 ) engages and with the recess ( 24 . 34 ) of the sleeve ( 11 . 21 . 31 ) forms a positive connection. Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that the recesses ( 14 . 24 ) in the sleeve ( 11 . 21 ) circumferentially closed recesses ( 14 . 24 ), preferably circular openings ( 14 . 24 ), in particular holes ( 14 . 24 ). Magnetic unit ( 20 ) according to claim 6, characterized in that at least one projection ( 25 ) of the magnetic element ( 22 ), which is in a recess ( 24 ) engages, as a pin and / or rivet web ( 25 ), wherein when the projection ( 25 ) is designed as Nietsteg, the Nietsteg ( 25 ) has preferably been converted after insertion into the recess such that the sleeve ( 21 ) and the magnetic element ( 20 ) are interconnected by means of a riveted joint. Magnetic unit ( 30 ) according to at least one of claims 1 to 5, characterized in that the flange ( 31a ) at least one for outer edge of the flange ( 31a ) recess ( 34 ), in particular a notch-shaped recess ( 34 ), and the magnetic element ( 32 ) at least one corresponding to the recess ( 34 ) trained advantage ( 35 ), which in the recess ( 34 ) engages, so that the magnetic element ( 32 ) and the flange ( 31a ) of the sleeve ( 31 ) in the tangential direction (U) are positively connected to each other, wherein the projection ( 35 ) extends preferably in the radial direction, in particular in the radial and tangential direction, and wherein the flange ( 31a ) preferably in the circumferential direction (U) arranged distributed, in particular evenly distributed, to the outer edge of the flange ( 31a ) open recesses ( 34 ) and the magnetic element ( 32 ) preferably according to a plurality of correspondingly arranged and formed projections ( 35 ), which in the recesses ( 34 ) in the flange ( 31a ) of the sleeve ( 31 ) intervene. Magnetic unit ( 30 ) According to claim 8, characterized in that at least one (in the flange 31a ) of the sleeve ( 31 ) and to the outer edge of the flange ( 31a ) recess ( 34 ) in the notch bottom a flat area ( 34a ) and preferably at least one laterally adjacent thereto in the tangential direction transition region ( 34b ) and in particular one flank each on each side ( 34c ), wherein preferably at least one transition region ( 34b ) has a rounded contour, in particular a rounded with a radius of at least 0.5 mm contour. Magnetic unit ( 30 ) according to claim 8 or 9, characterized in that at least one flank ( 34c ) at least one notch-shaped recess, preferably both flanks ( 34c ), at least one edge slope (α) of 50 ° relative to the notch base, preferably of 60 °, in particular of about 70 ° to 80 °. Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that a wall thickness of the magnetic element ( 12 . 22 . 32 ) in the radial direction, preferably over the entire circumference of the magnetic element ( 12 . 22 . 32 ), at least so great that the risk of damage to the magnetic element ( 12 . 22 . 32 ), in particular by cracking due to occurring during operation temperature loads and consequently resulting thermal stresses is reduced. Sensor means for detecting a characterizing a state of rotation of a steering shaft of a motor vehicle measured variable, characterized in that the sensor device (a magnet unit 10 . 20 . 30 ) according to one of claims 1 to 11. Motor vehicle with a sensor device, characterized in that the sensor device is designed according to claim 12.

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