DE102015122182A1 - 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) for a sensor device for detecting a measured variable characterizing a rotation state of a steering shaft of a motor vehicle and a sensor device and a motor vehicle having such a magnet unit, wherein the magnet unit (10) has a sleeve (13) and a sleeve (13) ), wherein the sleeve (13) has a sleeve connecting portion (13B) for connection to the magnetic element (12) and a sleeve-shaped sleeve mounting portion (13A) for connecting the magnet unit (10) to the steering shaft , The magnetic element (12) has a magnetic element connecting portion (12B) for connection to the sleeve (13) and a magnet portion (12A), the sleeve (13) in the region of the sleeve connection portion (13B) a plurality of circumferentially distributed and Has spaced apart webs (17) and a plurality of interposed, in the radial direction to the outer edge open recesses (18). The magnetic member connecting portion (12B) has a plurality of circumferentially distributed and spaced apart slots (16) which divide the magnetic member connecting portion (12B) into a plurality of magnetic segments (15), the magnet segments (15) corresponding to the webs (17 ) and recesses (18) in the sleeve connection portion (13 B) are formed, with which they are positively connected to the sleeve (13).

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, the magnet unit having a sleeve for connecting the magnet unit to a first part of the steering shaft and a magnet element connected to the sleeve having a magnetically effective magnet section. 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 in the form of a closed ring magnet and usually a metallic sleeve, via which the magnet unit can be connected to the steering shaft, it being known, the sleeve, for example by gluing, welding, caulking or by means of a Press fit rotatably connected to the steering shaft.

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 encapsulate 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 Magnet element at least in the 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 and a magnetic element connected to the sleeve, wherein the sleeve has a sleeve connection portion for connection to the magnetic element and a sleeve-shaped sleeve mounting portion for connecting the Magnetic unit having a first part of the steering shaft and the magnetic element has a magnetic element connecting portion for connection to the sleeve and a magnetically effective magnetic portion.

In this case, the sleeve in the region of the sleeve connecting portion at least two, at least over a part of the sleeve connecting portion radially outwardly projecting and extending in the axial direction, distributed in the circumferential direction and spaced from each other arranged webs and at least two, in the circumferential direction therebetween , At least over a part of the sleeve-connecting portion in the axial direction extending, in the radial direction to the outer edge open recesses.

According to the invention, the magnetic element has at least two slits extending in the axial direction over at least part of the magnetic element connecting section, distributed in the circumferential direction and spaced from one another, which divide the magnetic element into at least two magnetic segments in the magnetic element connecting section. In this case, the individual magnet segments of the magnetic element connection section each have a geometry corresponding to the webs and / or recesses of the sleeve connection section and are in each case positively connected to the sleeve by means of at least one of the webs and / or by means of one of the recesses of the sleeve connection section , in particular form-fitting in the circumferential direction. In some cases, it may be advantageous if at least one individual magnet segment, preferably all magnet segments, are in each case also connected in a form-fitting manner to the sleeve connection section in the radial direction. In some cases, it may also be advantageous if at least one magnetic element in addition to the positive connection in the circumferential direction in the axial direction is positively connected to the sleeve connection portion.

In an advantageous embodiment of a magnet unit according to the invention, the sleeve and the magnetic element have different thermal expansion coefficients, wherein preferably 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. The sleeve and the magnetic element are preferably designed such that the positive connection between the magnetic element and the sleeve in a reference state at a reference ambient temperature in the tangential direction, i. in the circumferential direction, is free of play.

The reference ambient temperature, at which the positive connection between the magnetic element and the sleeve in the tangential direction is preferably free of play, is preferably in a temperature range of 15 ° C to 30 ° C, in particular between 20 ° C and 25 ° C and is preferably 20 ° C or 23 ° 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 produced by 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, but with a connection to the steering shaft by means of a press fit or a Welding has been found to be particularly advantageous.

Characterized in that the magnetic element in its magnetic element-connecting portion has a plurality, preferably at least two, extending in the axial direction slots which divide the magnetic element connecting portion in the circumferential direction in a plurality of magnetic segments, especially in magnetic units with different thermal expansion coefficients, resulting from temperature fluctuations, thermally induced voltages, in particular in the magnetic element induced voltages are minimized, so that the magnetic segments can expand relatively force and stress-free and / or shrink. The risk of cracking in the magnetic element can thus be significantly reduced.

For a comparable function of magnetically effective magnetic portion of a magnet unit according to the invention with the known from the prior art, circumferentially closed ring magnet, the magnet portion is either also formed sleeve-shaped or annular, i. closed in the circumferential direction, or designed so that it acts like a sleeve or annular shaped magnetic portion or as a conventional, known from the prior art ring magnet.

Preferably, the magnet section and / or the magnetic element connection section are arranged concentrically with the sleeve attachment section and / or the sleeve connection section. Particularly preferably, the entire magnetic element is arranged concentrically to the entire sleeve.

In a further advantageous embodiment of a magnet unit according to the invention, the sleeve has a radially outwardly extending flange, wherein the flange preferably forms the sleeve connection portion. That In other words, in this case, the flange has at least two webs which project radially outward and extend in the axial direction over at least part of the sleeve connection section, are distributed in the circumferential direction and spaced apart, and / or at least two, at least Having over a part of the sleeve connecting portion extending in the axial direction, distributed in the circumferential direction and spaced from each other, in the radial direction to the outer edge open recesses.

The magnetic element connection section, in particular the magnet segments, preferably extend in the axial direction, i. in particular perpendicular to the flange.

By attaching a flange in the region of the sleeve mounting portion, in particular, when the flange extends in the radial direction outward, the magnetic element can be sprayed on the sleeve mounting portion in a simple manner, in particular without it to space conflicts in the interior of the magnet unit comes in which there is a steering shaft in a functional use state of the magnet unit. In particular, a magnet unit can be realized by the flange in a particularly simple manner, in which the magnetic element has a larger inner diameter than the sleeve.

Preferably, therefore, a smallest inner diameter of the sleeve in the region of the sleeve connecting portion is smaller than a smallest inner diameter of the magnetic element in the region of the magnetic element connecting portion. Particularly preferably, the magnet unit is designed such that the magnet segments are arranged in the radial direction on the outside of the sleeve connection section, in particular in such a way that at least one outer surface of at least one magnet segment at least partially defines an outer contour of the magnet unit.

In a further advantageous embodiment of a magnet unit according to the invention, the slots extend in the magnetic element in the axial direction at least over the magnetic element connecting portion, so that at least the magnetic element connecting portion is divided in the circumferential direction in at least two individual, spaced-apart, tab-like magnet segments. In this case, the individual magnet segments are preferably connected in a form-fitting manner to the sleeve connection section both in the circumferential direction and in the radial direction, if necessary also in the axial direction.

In a further advantageous embodiment of a magnet unit according to the invention, the slots extend in the axial direction over the entire magnetic element and are in particular designed such that the entire magnetic element is divided in the circumferential direction in at least two individual, spaced-apart magnetic segments.

In a further advantageous embodiment of a magnet unit according to the invention, the slots extend, at least in the region of the magnetic element connecting portion, in the radial direction over an entire thickness of the magnetic element. That is, the slots are in this case in the radial direction through and extending in the radial direction from an inner side of the magnetic member connection portion to an outer side. As a result, thermally induced stresses can be reduced particularly well, especially in the circumferential direction, because with such slots in particular the extent in the circumferential direction is little or not at all, depending on the width of the slots, hindered.

In a further advantageous embodiment of a magnet unit according to the invention, preferably when the slots extend in the axial direction only over a part of the magnetic element, in particular only via the magnetic element connecting portion, and the magnetic element thereby by injection molding on the sleeve and / or by encapsulation of the sleeve has been prepared and has been connected in this way with the sleeve, the position of at least one injection point of the magnetic element, in particular of all injection points of the magnetic element, each chosen such that in a lying in the axial extension of a slot area no weld line is formed.

An injection point in the sense of the invention is understood to be the point at which the plastic melt is introduced into the tool that gives shape to the magnetic element during the production of the magnetic element in the plastic injection molding process.

Under a weld line, in particular under a dynamic weld line, a confluence of mass flows of the plastic melt in the plastic injection molding process is understood in the context of the invention. Since a weld line generally represents a weak point in a component, the weld lines should not be arranged in a highly loaded area, which is achieved in the above-described embodiment of a magnet unit according to the invention characterized in that the position of the injection points is selected such that in the axial extension of the Slits lying areas no tie line formed.

In an alternative, but also advantageous embodiment of a magnet unit according to the invention, preferably when the slots extend in the axial direction over the entire magnetic element and the magnetic element has been produced by injection molding on the sleeve and / or by molding the sleeve and in this way with the Sleeve has been connected, the location of at least one injection point of the magnetic element, preferably of all injection points of the magnetic element, each chosen such that if the magnetic element would be formed as a circumferentially closed magnetic element and would have no slots, in the manufacture of the magnetic element at least one dynamic Bindenaht in the area of a slot would arise. That in other words, that in this embodiment, the slots according to the invention are particularly preferably introduced where would arise in a corresponding, closed in the circumferential direction magnetic element in the production of tie lines. In particular, the formation of weld lines can be avoided in this way.

In a further advantageous embodiment of a magnet unit according to the invention, the magnet unit is designed such that at least one of the slots is arranged in the magnetic element in the circumferential direction in the region of one of the webs of the sleeve.

In a further advantageous embodiment of a magnet unit according to the invention fills in at least one operating state, preferably in the reference state, at least one magnetic segment in the region of the sleeve connection portion at least over part of the length of the sleeve connection portion in the axial direction located between two webs of the sleeve recess in Circumferential direction completely off and lies with its two side surfaces in the circumferential direction of a respective side surface of the two webs. As a result, a positive connection in the tangential direction between the magnetic element and the sleeve can be realized in a particularly simple manner.

In a further advantageous embodiment of a magnet unit according to the invention a maximum outer diameter of the magnetic element in the region of the magnetic element connecting portion is less than or equal to a maximum outer diameter of the sleeve in the region of the sleeve connecting portion. That the magnet segments extend in the circumferential direction only over the region which lies between the webs of the sleeve connecting portion or fill only the intermediate recesses in the circumferential direction, but do not extend in the circumferential direction over the outer surfaces of the webs. Preferably, the side surfaces of the webs extend in the radial direction and have no undercuts, protrusions or the like. As a result, the magnet segments located between the webs of the sleeve can expand in the radial direction almost unhindered.

In an alternative, but also advantageous embodiment of a magnet unit according to the invention, the magnet unit is designed such that at least one of the slots is arranged in the magnetic element in the circumferential direction in the region of one of the recesses of the sleeve and not in the region of one of the webs.

In a further advantageous, alternative embodiment of an inventive Magnet unit is at least one of the magnet segments of the magnetic element in the radial direction with its inner surface on an outer surface of at least one web of the sleeve and in the circumferential direction on the two side surfaces of this web. That is, at least one magnet segment encloses the web quasi from the outside and extends laterally into the recesses, instead of being arranged directly between two webs in the recess.

In a further advantageous embodiment of a magnet unit according to the invention at least one slot width of a slot between two magnetic segments in the circumferential direction is at least so large that in a provided for the magnet unit, defined operating temperature range a maximum occurring in the circumferential direction, thermally induced length and / or volume expansion not to produce a compression stress in the circumferential direction in the magnetic element connecting portion, in particular not to a reduction of the slot width of the slots to zero.

In a further advantageous embodiment of a magnet unit according to the invention, the magnet unit is designed such that an inner surface of at least one magnet segment in at least one operating state, preferably in the reference state, to an opposite outer surface of the sleeve connection portion, which is located between two webs within a recess, spaced is arranged in the radial direction. That The magnet segments of the magnetic element preferably do not extend to the head of the webs to the foot of the webs, but fill in the radial direction only a part of the recess, in particular an outer part. In other words, this means that preferably the inner surface of the magnet segment in at least one operating state, preferably in the reference state, does not bear against the bottom of the recess, but has a spacing therefrom. In particular, this embodiment allows unimpeded, thermally induced expansion and / or shrinkage in the radial direction inwards.

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

An inventive motor vehicle with a sensor device has a sensor device according to the invention with a magnet unit according to the invention.

The advantageous embodiments presented with respect to the magnet unit and their advantages also apply correspondingly to a 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 advantageous embodiments with reference to the accompanying drawings, wherein components having the same function in favor of a simpler understanding the same reference numerals, even if they differ in their structural design.

Show it:

1a a known from the prior art magnet unit in a sectional view,

1b in the 1a illustrated, known from the prior art magnet unit in perspective view,

2a A first embodiment of a magnet unit according to the invention in a perspective view,

2 B in a sectional view of a possible embodiment of the positive connections in a radial section through the sleeve connecting portion in the region of the webs in 2a illustrated, inventive magnet unit,

2c Another possible embodiment of the positive connections between the magnetic element and the sleeve of in 2a illustrated embodiment of a magnet unit according to the invention, also in a radial section through the sleeve connecting portion in the region of the webs,

3a A second embodiment of a magnet unit according to the invention, also in perspective view,

3b an associated radial section through the sleeve connecting portion of the magnet unit 3a .

4a a third embodiment of a magnet unit according to the invention, also in a perspective view and

4b an associated radial section through the magnet unit according to the invention 4a , also in the area of the sleeve connection section.

1a shows a sectional view of a known from the prior art magnet unit 1 for a sensor device for detecting a measurement variable which characterizes a rotational state of a steering shaft of a motor vehicle (not illustrated here), wherein the magnet unit 1 a sleeve 3 as well as one with the sleeve 3 connected magnetic element 2 having.

The sleeve 3 has a sleeve attachment portion 3A for connecting the magnet unit 1 with a first part of the steering shaft, not shown here, and a sleeve connecting portion 3B over which the sleeve 3 with the magnetic element 2 connected is. The sleeve attachment section 3A is sleeve-shaped or tubular and has at its, the magnetic element 2 facing the end in a radially outwardly extending flange, which in this case the sleeve connecting portion 3B forms. The sleeve 3 is made of metal, in particular by punching, and designed such that it can be fixed by means of a press fit on the steering shaft.

The magnetic element 2 correspondingly has a magnetic element connecting portion 2 B on and a magnetically effective magnetic section 2A by which later in a functional use state of the magnet unit 1 a sensor signal can be generated. The magnetic element 2 consists of a, filled with magnetic particles plastic and has been produced in a plastic injection molding process, wherein the magnetic element 2 while the sleeve, in particular to the sleeve connecting portion 3B has been molded and in this way with the sleeve 3 has been connected.

As based on 1a It can be seen, are the sleeve 3 and the magnetic element 2 both in the axial direction, ie parallel to a rotation axis L extending direction, as well as positively connected to each other in the radial direction. In addition, a non-rotatable connection between the sleeve connecting portion 3B and the magnetic member connection portion 2 B to reach, the flange of the sleeve 3 Furthermore, not shown here, alternately arranged recesses and webs, in which engages the magnetic element correspondingly similar to a toothing.

The sleeve 3 and the magnetic element 2 have due to the different materials from which they are made, different thermal expansion coefficients, wherein the thermal length and volume expansion coefficient of the magnetic element 2 greater than the thermal length and volume expansion coefficient of the sleeve 3 ,

Due to the different length and volume expansion coefficients of sleeve 3 and magnetic element 2 may occur during operation temperature fluctuations on the one hand to thermally induced voltages in the magnet unit 1 come, especially in the magnetic element 2 , which leads to cracking in the magnetic element 2 being able to lead. One weak point is the in 1b clearly recognizable, dynamic weld line 4 which, in the longitudinal direction of the magnet unit 1 , ie in the axial direction, over the entire width of the magnetic element 2 runs.

Further, depending on the configuration of the positive connection, there is the risk that the positive connection loosens, so that possibly no rotationally fixed connection more in the circumferential direction between the magnetic element 2 and the sleeve 3 consists.

2a shows a first embodiment of a magnet unit according to the invention 10 , which is basically similar to the previously described, known from the prior art magnet unit 1 and also a sleeve 13 with a sleeve attachment portion 13A and a sleeve connecting portion 13B as well as one with the sleeve 13 positively connected magnetic element 12 with a magnetically effective magnet section 12A and a magnetic member connection portion 12B having.

In contrast to the known from the prior art magnet unit 1 has the magnet unit according to the invention 10 but a magnetic element 12 which, according to the invention, in particular to avoid cracking of the magnetic element 12 in structurally weak areas, several, in this case four, extend in the axial direction over the entire width of the magnetic element 12 extending, distributed in the circumferential direction and spaced apart slots 16 which has the magnetic element 12 in several magnet segments 15 subdivide, in this case into four magnet segments 15 ,

2 B shows a sectional view of a possible embodiment of the positive connections between the magnetic element 12 and the sleeve 13 in a radial section through the sleeve connecting portion 13B the in 2a illustrated, inventive magnet unit 10 , by which the embodiment of the sleeve 13 , in particular the Sleeve connecting portion 13B , easy to recognize.

2c showed a further possible embodiment of the positive connections between the magnetic element 12 and the sleeve 13 of in 2a illustrated embodiment of a magnet unit according to the invention 10 , also in a radial section through the sleeve connecting portion 13B ,

The sleeve 13 In this case, in each case in both possible embodiments, at least in the area of the sleeve connection section 13B four, at least over part of the sleeve connection section 13B extending in the axial direction, distributed in the circumferential direction and spaced from each other arranged webs 17 and four, circumferentially therebetween, also at least over part of the sleeve connection portion 13B extending in the axial direction, in the radial direction to the outer edge of the sleeve 13 open recesses 18 onto. 2 B and 2c , The interaction of the magnet segments 15 with the jetties 17 as well as the recesses 18 is doing in the 2 B and 2c clearly visible.

In both cases, the magnet segments 15 According to the invention in each case form-fitting manner with the sleeve connecting portion 13B connected, wherein in these two embodiments, the magnetic segments 15 each the recesses 18 in the sleeve connection section 13B completely fill and on the one hand with their side surfaces on the adjacent webs 17 abutment as well as with their inner surfaces at the bottom of the recesses 18 , In the area of the bridges 17 are the magnet segments 15 each by one over the entire length of the magnetic element 12 extending slot 16 spaced in the circumferential direction, wherein in the in 2 B shown possible embodiment, a width B of the slots 16 corresponds to a width of a web foot. At the in 2 B illustrated embodiment corresponds to the width of the slots 16 each part of the width of the bridge 17 ,

Through the slots 16 , which extends in the radial direction over the entire thickness of the magnetic element 12 extend, wherein the width B of the slots 16 is sized so that the individual magnet segments 12 not touch under the influence of temperature and thus do not hinder their expansion, the formation of compressive stresses in the tangential direction, ie in the circumferential direction, due to a thermal expansion of the magnetic element 12 be avoided.

In 2 B the webs have an undercut and the magnet segments 15 a corresponding projection, whereby additionally a radial positive connection between the magnet segments 15 and the jetties 17 can be achieved, so that a detachment of the magnet segments in the radial outward direction can be avoided in any case, while in the in 2c illustrated, possible embodiment of the positive connections, the webs 17 have no such undercut. Here, the positive connection in the radial direction by the in the webs 17 achieved existing holes, which are not specified, but during encapsulation of the sleeve connection portion 13B be filled with magnetic material such that pins arise which cause the radial positive locking.

In addition, the magnet segments form 15 in these embodiments, in the axial direction in each case a positive connection with the webs 17 , so that also a detachment of the magnetic element 12 can be prevented in the axial direction. With the in the 2a to 2 B shown and described with reference to this, exemplary embodiments of the positive connections of the individual magnet segments 15 with the sleeve connection section 13B can thus, especially in temperature fluctuations, both the detachment in the circumferential direction and the detachment in the axial and radial directions are avoided.

The magnetically acting magnet section 12A the magnet unit according to the invention 10 Although not completely formed circumferentially closed, but behaves in our magnetic properties we almost a closed magnetic section, so that the slots 16 do not lead to a significant, functional disadvantage, but have the positive effect that when temperature changes significantly less thermally induced stresses in the magnetic element 12 be induced.

What is not apparent from the above figures, this is the magnet unit 10 is further configured such that all injection points for the individual magnet segments 15 are chosen in their position such that when the magnetic element 12 would be formed as a circumferentially closed magnetic element and no slots 16 would have the tie lines in the area of the slots would arise. In other words, that in 2a illustrated inventive magnet unit 10 is configured such that the magnetic element 12 has no weld lines and accordingly no structurally weak areas.

The basis of 2a described inventive design of a magnet unit 10 for a sensor device for detecting a measured variable characterizing a rotation state of a steering shaft of a motor vehicle is suitable in particular for magnet units in which the difference between the outer diameter of the magnetic element 12 and the inner diameter of the sleeve 13 is relatively low or must be, ie where the outer diameter of the magnetic element 12 not much larger than the inner diameter of the sleeve 13 is or has to be.

3a shows a second embodiment of a magnet unit according to the invention 20 , wherein for the sake of simplicity elements having the same effect have the same reference numerals as in FIGS 2a to 2c , In contrast to the previously described magnet unit according to the invention 10 has this magnet unit according to the invention 20 only slots 16 on, which in the axial direction only via the magnetic element connecting portion 12B extend, but not along the entire magnetic element 12 as in the previously described embodiment.

Another difference is that like based on 3b can be clearly seen, this magnet unit according to the invention 20 not just four bars 17 but eight circumferentially distributed webs 17 and accordingly eight, between the bars 17 trained recesses 18 available. As in the previously described embodiments, the magnetic element connecting portion are also here 12B and the sleeve connection portion 13B over the footbridges 17 and the recesses 18 and the magnet segments 15 positively connected with each other. The magnet segments 15 fill in this case, the recesses 18 completely in the circumferential direction, at least in a reference state at a reference temperature, which in this case is 20 ° C. The slots 16 are in this case in the area of the bridges 17 where the width B of the slots 16 while the width of the webs 17 in the circumferential direction corresponds.

However, in this case, the magnet segments extend 15 not to the bottom of the recesses 18 approach, ie the inner surfaces of the magnetic elements 15 are not at the between the side surfaces of the recesses 18 arranged, circumferentially extending outer surfaces of the sleeve connection portion 13B but at a distance therefrom with a gap 19 between.

Furthermore, in this exemplary embodiment, a magnet unit according to the invention extends 20 the magnet segments 15 not in the circumferential direction over the webs 17 but are only within the recesses 18 ,

Furthermore, the side surfaces of the webs run 17 exactly in the radial direction, causing the magnet segments 15 As a result, it can freely expand in the radial direction, both radially outwards and inwards due to the gaps 19 between the inner surfaces of the magnet segments 15 and the sleeve connecting portion 13B , Because of the magnet segments 15 also not in the circumferential direction over the webs 17 Beyond, an unobstructed shrinkage of the magnetic segments 15 in the radial direction allows inward. Consequently, the generation of thermally induced voltages in the magnetic element 12 be significantly reduced or in some cases even completely avoided.

The basis of the 3a and 3b described embodiment of a magnet unit according to the invention 30 is particularly suitable for magnet units with a larger difference between the outer diameter of the magnet portion and the inner diameter of the sleeve, just as the basis of the 4a and 4b described below embodiment.

4a shows a third embodiment of a magnet unit according to the invention 30 , wherein in this embodiment, the slots 16 over the entire width of the magnetic member connection portion 12B extend as well as in the axial direction in addition to a portion of the magnet portion 12A , Here are the slots 16 but not in the area of the bridges 17 as in the previous embodiment, but are each in the region of the recesses 18 arranged, based on the circumferential direction. Therefore, the magnet segments fill up 15 the recesses 18 not completely in the circumferential direction, s. 4b ,

As with the basis of the 3a and 3b described, magnetic unit according to the invention 20 are the magnet segments 15 also in this embodiment of a magnet unit according to the invention 30 in the radial direction with their inner surfaces also not on the outer surfaces of the recesses 18 on or on, but are to each of these with a distance 19 or a gap 19 spaced to allow unimpeded radially inward expansion and unimpeded shrinkage of the magnetic element, respectively 12 in this area. On the other hand are the magnet segments 15 for a positive connection with the sleeve 13 , in particular for a positive connection in the tangential direction, on the outer surfaces of the webs 17 at and in the circumferential direction in each case on the two side surfaces of the associated web 17 ,

The slit width B of the slits 16 between two magnet segments 15 is chosen in this case in the circumferential direction at least so large that in one for the magnet unit 30 provided, defined operating temperature range a maximum occurring in the circumferential direction, thermally induced length and / or volume expansion not to generate a compressive stress in the circumferential direction in the magnetic element connecting portion 12B leads, in particular not to a reduction of the slot width B to zero.

In this embodiment, the location of the injection points for the magnetic element 12 especially chosen such that in extension of the slots 16 no tie lines are formed in the axial direction, as in the notch bottom of the slots 16 Stress can occur, in particular notch stresses can occur, resulting in damage to the magnetic element 12 can lead in the field of weld lines.

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, 0009]
• EP 1123794 A2 [0002, 0008]
• US 5530344 [0002]
• DE 102013006567 A1 [0002, 0010]

Claims (17)

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 ( 13 ) and one with the sleeve ( 13 ) connected magnetic element ( 12 ), wherein the sleeve ( 13 ) a sleeve connecting portion ( 13B ) for connection to the magnetic element ( 12 ) and a bush-shaped sleeve attachment portion ( 12A ) for connecting the magnet unit ( 10 . 20 . 30 ) with a first part of the steering shaft, - wherein the magnetic element ( 12 ) a magnetic element connecting portion ( 12B ) for connection to the sleeve ( 13 ) and a magnetically effective magnetic section ( 12A ), wherein the sleeve ( 13 ) in the region of the sleeve connecting portion ( 13B ) at least two, at least over a part of the sleeve connection portion ( 13B ) in the radial direction outwardly projecting and extending in the axial direction, distributed in the circumferential direction and spaced from each other arranged webs ( 17 ) and at least two, in the circumferential direction therebetween, at least over a part of the sleeve connection portion (FIG. 13B ) in the axial direction extending, in the radial direction to the outer edge open recesses ( 18 ), characterized in that the magnetic element ( 12 ) At least two, at least over a part of the magnetic element connection portion ( 12B ) extending in the axial direction, distributed in the circumferential direction and spaced from each other slots ( 16 ), which the magnetic element ( 12 ) in the magnetic member connection portion (FIG. 12B ) in at least two magnet segments ( 15 ), wherein the individual magnet segments ( 15 ) of the magnetic member connection portion (FIG. 12B ) one to the webs ( 17 ) and / or recesses ( 18 ) of the sleeve connection section ( 13B ) have correspondingly formed geometry and in each case by means of at least one of the webs ( 17 ) and / or using one of the recesses ( 18 ) of the sleeve connection section ( 13B ) in a form-fitting manner with the sleeve ( 13 ) are connected. Magnetic unit ( 10 . 20 . 30 ) according to one of the preceding claims, characterized in that the sleeve ( 13 ) and the magnetic element ( 12 ) have different thermal expansion coefficients, wherein preferably the thermal length and / or volume expansion coefficient of the magnetic element ( 12 ) is greater than the thermal length and / or volume expansion coefficient of the sleeve ( 13 ), and wherein in particular the sleeve ( 13 ) and the magnetic element ( 12 ) are formed such that the positive connection is free of play in a reference state at a reference ambient temperature in the tangential direction. Magnetic unit ( 10 . 20 . 30 ) according to claim 1 or 2, characterized in that the sleeve ( 13 ) has a radially outwardly extending flange, wherein the flange preferably the sleeve connecting portion ( 13B ). Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that the slots ( 16 ) in the magnetic element ( 12 ) in the axial direction at least over the magnetic element connecting portion ( 12B ) so that at least the magnetic member connection portion (FIG. 12B ) in the circumferential direction in at least two individual, spaced-apart, lug-like magnet segments ( 15 ) is divided. Magnetic unit ( 10 ) according to at least one of the preceding claims, characterized in that the slots ( 16 ) in the axial direction over the entire magnetic element ( 12 ) and in particular are formed such that the entire magnetic element ( 12 ) in the circumferential direction in at least two individual, spaced-apart magnetic segments ( 15 ) is divided. Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that the slots ( 16 ), at least in the region of the magnetic element connection section ( 12B ), in the radial direction over an entire thickness of the magnetic element ( 12 ). Magnetic unit ( 20 . 30 ) according to claim 4, characterized in that, preferably when the slots ( 16 ) extend in the axial direction only over a part of the magnetic element, in particular only via the magnetic element connecting portion ( 12B ), and the magnetic element ( 12 ) by injection molding on the sleeve ( 13 ) and / or by overmolding the sleeve ( 13 ) and in this way with the sleeve ( 13 ), the position of at least one injection point of the magnetic element ( 12 ), preferably of all injection points of the magnetic element ( 12 ), each chosen such that in an axial extension of a slot ( 16 ) lying area no weld line is formed. Magnetic unit ( 10 ) according to at least one of the preceding claims, in particular according to claim 5, characterized in that, preferably when the slots ( 16 ) in the axial direction over the entire magnetic element ( 12 ) and the magnetic element ( 12 ) thereby by injection molding on the sleeve ( 13 ) and / or by encapsulation of the sleeve ( 13 ) and in this way with the sleeve ( 13 ), the position of at least one injection point of the magnetic element ( 12 ), preferably of all injection points of the magnetic element ( 12 ), in each case selected such that when the magnetic element ( 12 ) as a circumferentially closed magnetic element ( 12 ) and no slots ( 16 ), in the manufacture of the magnetic element ( 12 ) at least one dynamic weld line in the region of a slot ( 16 ) would arise. Magnetic unit ( 10 . 20 ) according to at least one of the preceding claims, characterized in that the magnet unit ( 10 . 20 . 30 ) is formed such that at least one of the slots ( 16 ) in the magnetic element ( 12 ) in the circumferential direction in the region of one of the webs ( 17 ) of the sleeve ( 13 ) is arranged. Magnetic unit ( 10 . 20 ) according to claim 9, characterized in that in at least one operating state, preferably in the reference state, at least one magnetic segment ( 15 ) in the region of the sleeve connecting portion ( 13B ) over at least part of the length of the sleeve connection portion ( 13B ) in the axial direction one between two webs ( 17 ) of the sleeve ( 13 ) located in the circumferential direction completely fills and with its two side surfaces in the circumferential direction on each side surface of the two webs ( 17 ) is present. Magnetic unit ( 10 . 20 ) according to claim 9 or 10, characterized in that a maximum outer diameter of the magnetic element ( 12 ) in the region of the magnetic element connecting portion ( 12B ) less than or equal to a maximum outer diameter of the sleeve ( 13 ) in the region of the sleeve connecting portion ( 13B ). Magnetic unit ( 30 ) according to at least one of claims 1 to 8, characterized in that the magnet unit ( 10 . 20 . 30 ) is formed such that at least one of the slots ( 16 ) in the magnetic element ( 12 ) in the circumferential direction in the region of one of the recesses ( 18 ) in the sleeve ( 13 ) is arranged. Magnetic unit ( 30 ) according to claim 12, characterized in that at least one of the magnet segments ( 15 ) of the magnetic element ( 12 ) in the radial direction with its inner surface on an outer surface of at least one web ( 17 ) of the sleeve ( 13 ) and in the circumferential direction on the two side surfaces of this web ( 17 ). Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that at least one slot width (B) of a slot ( 16 ) between two magnet segments ( 15 ) in the circumferential direction is at least as large that in one for the magnet unit ( 10 . 20 . 30 ), a defined maximum operating temperature range in the circumferential direction, thermally induced length and / or volume expansion not to generate a compressive stress in the circumferential direction in the magnetic element connecting portion ( 12B ), in particular does not lead to a reduction in the slot width of one of the slots ( 16 ) to zero. Magnetic unit ( 10 . 20 . 30 ) according to at least one of the preceding claims, characterized in that the magnet unit ( 10 . 20 . 30 ) is formed such that an inner surface of at least one magnetic segment ( 15 ) in at least one operating state, preferably in the reference state, to an opposite outer surface of the sleeve connecting portion (FIG. 13B ), which are between two webs ( 17 ) within a recess ( 18 ), spaced in the radial direction. 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 15. Motor vehicle with a sensor device, characterized in that the sensor device is designed according to claim 16.

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