EP2946174A1

EP2946174A1 - Coil arrangement having two coils

Info

Publication number: EP2946174A1
Application number: EP13814498.5A
Authority: EP
Inventors: Alexander Graf; Florian WEINL; Michael Pantke
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2013-01-18
Filing date: 2013-12-17
Publication date: 2015-11-25
Also published as: CN104903684A; US20150354991A1; DE102013200698A1; WO2014111218A1

Abstract

The invention relates to a coil arrangement, in particular for a position sensor, having a first coil (1) and a second coil (2) which are electrically connected to one another and are arranged in a substantially coaxial manner with respect to one another, wherein the first coil (1) has a winding density that increases in the longitudinal direction (X) of the coil arrangement, whereas the second coil (2) has a winding density which decreases in the longitudinal direction (X) of the coil arrangement. The invention also relates to a position sensor having such a coil arrangement and to a method for producing such a coil arrangement.

Description

Coil arrangement with two coils

The invention relates to a coil arrangement having a first coil and a second coil, which are electrically connected to one another and are arranged substantially coaxially to each other, wherein the first coil has a winding density increasing in the longitudinal direction of the coil arrangement. Furthermore, the invention relates to a position sensor, as well as to a manufacturing method of the coil arrangement.

Different embodiments of non-contact linear position sensors are known. The main representatives use magnetic fields for sensing. These include sensors that use the Hall effect or the law of induction. The latter, in turn, can be divided into two groups according to their mode of action. Common to both is an arrangement of coil and donor element, which must be electrically conductive in the first group and in the second group must be a soft magnetic material.

The first group, eddy current sensors, uses the induction to build up an opposing field in an electrically conductive material which attenuates the excitation field. The encoder element is used to change the degree of damping proportionally to the path. The energy needed to sustain the excitation field can be used as a measure. In this case, the path-giving element (transmitter element) does not enter the coil.

The second group differs from this in that the magnetic field in the coil is directly influenced by the soft-magnetic sensor element. Here, the inductance of the coil is measured, whereby there are different methods. In a submersible coil sensor, position sensing relies on the utilization of the relative permeability of soft magnetic iron and the associated fact that the inductance of a coil is proportional to the relative permeability of the spool core. The coil core is used as an element giving away, which leads to a change in the inductance and thus to a path proportional to the measured variable. For this simple linear coils are used or simple coils in several chambers to influence the sensitivity. Sensors based on the LVDT (Linear Variable Differential Transformer) or PLCD (Permanent Magnetic Linear Contactless Displacement) principle can be described as a differential transformer. In this case, a primary coil and two secondary coils are used, these being arranged along the path to be sensed. The long primary coil sits midway between the short secondary coils at both ends of the sensor. All three coils sit on a soft magnetic rod, which is arranged parallel to the measuring path. With the help of a magnet, which serves as a donor element, the field distribution of the primary to the secondary coils can be influenced.

A disadvantage of these known sensors is that they are constructed very expensive. In contrast, the position sensor described in the document DE 38 01 779 C2 or the coil assembly underlying the sensor is simple and essentially requires only two coaxial coil, with a movable magnetically conductive element inside the coil. In this case, one of the coils has a variable winding density in the longitudinal direction.

It has been found that a position sensor constructed in this way is less suitable for precise applications because it has too low a measuring accuracy.

The object of the invention is therefore to provide a coil arrangement by means of which a high-precision position sensor can be realized. In addition, it is an object of the invention to provide such a sensor, as well as a manufacturing method for such a coil arrangement. The object is achieved by a coil arrangement with the features of claim 1 and by a position sensor having the features of claim 9 and by a manufacturing method having the features of claim 12. Particularly preferred embodiments thereof are the respective dependent claims.

Accordingly, the invention relates to a coil assembly, in particular for a position sensor. The coil arrangement has a first coil and an ne second coil, which are electrically connected to each other and which are arranged substantially coaxially to each other, wherein the first coil has an increasing in the longitudinal direction of the coil assembly winding density. In addition, the second coil has a winding density decreasing in the longitudinal direction of the coil arrangement.

Accordingly, the winding density of the first winding increases in the longitudinal direction of the coil assembly, while at the same time the winding density of the second winding decreases in this longitudinal direction. The winding densities of the coils thus develop in opposite directions along the coil longitudinal direction. As a result, the second coil no longer serves only as a reference coil for the first coil, but now also the inductance of the second coil is dependent on the position of a magnetically conductive donor element when the coil assembly is used in a position sensor with such a donor element. This results in a significant improvement in the measurement resolution of the position sensor or the coil assembly and a high-precision position sensor can be realized by means of this coil arrangement. In this case, the winding density is in particular the number of windings per unit length in the longitudinal direction of the coil arrangement.

In particular, a change in the winding density is caused by an increase or decrease in the radial number of winding layers. Thus, the fill factor of the coils in the longitudinal direction of the coil assembly remains constant, whereby a constant good measurement resolution of the position sensor or the coil assembly is effected in the longitudinal direction. The coils are each wound in particular orthocyclic, which also a particularly good filling factor can be achieved. In addition, the coils particularly preferably have an opposite sense of winding. They thus build up a mutually influencing magnetic field when electrical current is applied.

The distribution of the electrical voltage within the coil arrangement during electrical energization of the same is dependent on the ohmic and inductive portion of the coils. A coil-associated, magnetically conductive donor element thereby significantly influences the inductance of the individual coils, wherein this influence is dependent on the position of the gerber element due to the changing winding density along the coil longitudinal direction. Thus it can be concluded by an evaluation of the voltage difference between the two coils of the coil assembly to the position of the donor element with respect to the coil assembly.

In a preferred embodiment, the winding density of the first coil in the longitudinal direction of the coil arrangement increases substantially as the winding density of the second coil decreases. Thus, although changing the winding density of each coil, the total winding density remains constant. The coil assembly can thereby be made extremely compact, with a constant in the longitudinal direction Au ßendurchmesser.

In a further preferred embodiment, the winding density of the first and second coil changes linearly. The linear change may in this case only be present within a longitudinal section of the coil arrangement in the longitudinal direction or extend over the entire length of the coil arrangement in the longitudinal direction. In the case of a linear change in the winding density, the inductance depends essentially linearly on the position of a magnetically conductive transmitter element with respect to the coil arrangement, whereby the inductance of the coil arrangement can then be used to close the position of the transmitter element with respect to the coil arrangement in a particularly simple manner.

In a further preferred embodiment, the winding density of the first and second coil changes in sections by leaps and bounds. In other words, the coil arrangement has at least two longitudinal sections in the coil longitudinal direction, which have different winding densities at the directly adjoining sides. As a result, the inductance of the coil arrangement changes abruptly when a magnetically conductive donor element is moved relative to the coil arrangement from one of the longitudinal sections into the other of the longitudinal sections. This sudden change in the inductance is very clearly detected, whereby the position of the donor element when passing the density change, ie the transition between the longitudinal sections, very clearly and accurately determined is. Thus, in particular one or more reference points along the coil longitudinal direction can be marked by one or more transitions between two directly consecutive longitudinal sections, having different winding densities. In addition, several or a plurality of longitudinal sections may be provided with mutually different winding densities, which cause an incremental change in the winding density in the coil longitudinal direction. As a result, the position of the magnetically conductive donor element with respect to the coil arrangement is clearly recognizable incrementally. The more such lengths are present, the more accurate the position of the donor element in the longitudinal direction can then be determined incrementally.

In a further preferred embodiment, the winding density of the first and second coil changes in a first longitudinal section of the coil arrangement, wherein this change is in particular linear. In a second longitudinal section directly adjoining the first section, the winding density of the first and second coils is constant. And in a third section immediately adjacent to the second section, the winding density of the first and second coils changes, and this change is also particularly linear. This results in a high measuring sensitivity and easy evaluability of the coil arrangement in the first and third longitudinal section, while a relatively low measuring sensitivity is effected in the second longitudinal section. In particular, this is a section of length within which no accurate measurement is required. Such a design of the coil arrangement can also be used to linearize the sensor characteristic curve when using the coil arrangement in a position sensor.

In a further preferred embodiment, the two coils are electrically connected in series directly one behind the other, with a Meßabgriff between the coils. Thus, the structure of the coil assembly is particularly simple. The coils in this case form a voltage divider.

In an alternative further preferred embodiment, the two coils are each electrically connected in series with a comparison resistor, wherein each of the coils forms a branch of a Wheatstone measuring bridge circuit together with the comparison resistor connected in series. In this case, a measuring tap is provided between each of the coils and the comparison resistor connected in series with the coil. The two coils are thus electrically connected in parallel with each other, wherein each of the coils is electrically connected in series with the respective comparison resistor. As a result, a particularly accurate evaluation of the position of the coil arrangement associated magnetically conductive donor element is possible.

In a further preferred embodiment, a magnetically conductive housing is provided, for example made of a ferromagnetic material, within which the coils are arranged, for magnetically influencing the magnetic flux within the coil arrangement. As a result, a transformer effect within the coil assembly is enhanced by the magnetic influence of the housing (increased magnetic flux within the coil assembly) and therefore increases the sensitivity of the coil assembly when used in a position sensor.

The position sensor according to the invention has a coil arrangement according to the invention as described above, as well as a magnetically conductive transmitter element, which is arranged to be movable along the longitudinal direction of the coil arrangement as a position sensor. The transmitter element can thus be arranged either movably in an interior of the coil arrangement along the coil longitudinal direction, in particular coaxially to the coil arrangement, or alternatively movably arranged around an exterior of the coil arrangement along the coil longitudinal direction, in particular coaxially with the coil arrangement, thus enclosing the coil arrangement in an annular manner.

By appropriate electrical energization of at least one of the coils of the coil assembly and a magnetic force can be generated on the donor element in the longitudinal direction of the coil assembly, whereby the position sensor can also be used as an actuator and thus can be referred to as such alternative. This force can be tapped on the encoder element and can be manipulated of devices, such as switching elements of a vehicle transmission or valves, are used. The generated force can be increased and influenced by providing a magnet yoke. In particular, the shape of the magnetic yoke can be such that the position sensor forms a so-called proportional magnet.

In a preferred embodiment of the position sensor, the coil arrangement is designed in the longitudinal direction at least circular segment-shaped, wherein the encoder element is at least circular segment-shaped movable as angular position encoder along the longitudinal direction of the coil assembly, so that the position sensor forms an angular position sensor. Alternatively, the coil assembly is straight in the longitudinal direction, wherein the encoder element is linearly movable as a linear position encoder along the longitudinal direction of the coil assembly, so that the position sensor forms a linear position sensor.

To detect the position of the encoder element, the coil arrangement is particularly preferably first energized with one or more voltage jumps. Subsequently, the step response of the coil arrangement (current and / or voltage curve) is evaluated and finally determines the position of the encoder element. The step response of the coil arrangement is dependent on the position of the encoder element, since this affects the inductance of both coils. Since, in the embodiment of the coil arrangement according to the invention, both coils have a winding density which varies in opposite directions, the step response changes particularly strongly as a function of the position of the transmitter element, as a result of which the position of the transmitter element with respect to the coil arrangement can be evaluated particularly accurately.

As a particularly preferred method for controlling the position sensor or detecting the position of the donor element in the position sensor, the method disclosed in DE DE 1 0200501 8012 A1 and DE 102008043340 A1 and DE 1 0201 1 083007 A1 have proved the Applicant. The manufacturing method according to the invention for the above-mentioned coil arrangement according to the invention is characterized by a first manufacturing step, in which the first radially inner coil is wound, and by a second manufacturing step, in which the second, radially outer coil is wound, and by a third manufacturing step, wherein the first coil is electrically connected to the second coil. The manufacturing steps are preferably carried out in this time staggering. This production method results in a particularly simple and cost-effective production of the coil arrangement. In the second production step, the winding of the second coil preferably takes place in such a way that the mutually opposite ends of the winding layers of the first and second coils lie directly against one another. Thus, voids in the coil assembly are avoided and the fill factor of the entire coil assembly is optimized.

In the following the invention will be explained in more detail with reference to figures, from which further preferred embodiments of the invention can be removed. Shown schematically in each case:

Fig. 1, a first preferred embodiment of the coil assembly;

Fig. 2, a second preferred embodiment of the coil assembly;

Fig. 3, a third preferred embodiment of the coil assembly;

Fig. 4, a preferred embodiment of the coil assembly with a

Casing;

FIG. 5 shows a first preferred electrical connection of the coil arrangement; FIG.

Fig. 6, a second preferred electrical interconnection of the coil assembly;

Fig. 7a-c, preferred driving method of the coil assembly;

Fig. 8a-c, preferred manufacturing steps for producing a coil assembly.

In the figures, identical or at least functionally identical components are provided with the same reference numerals. 1, 2 and 3 each show a coil arrangement with a first coil 1 and a second coil 2 in a longitudinal section along the coil longitudinal direction X. A lower half of the coils 1, 2 is not shown for the sake of clarity. The coil longitudinal direction X preferably simultaneously forms an axis of symmetry of the coil arrangement. The coils 1, 2 thus form a common hollow cylinder around the coil longitudinal direction X. The first coil 1 forms a radially inner coil, while the second coil 2 forms a radially externa ßere coil. The coils 1, 2 are thus arranged substantially coaxially to the coil longitudinal direction X into each other. In the second coil 2, the individual windings of the coil 2 are shown by way of example. They are orthogonal to the plane of the figures. As shown, the windings of the coils 1, 2 are preferably arranged orthocyclically with respect to one another in order to maximize the fill factor of the coils 1, 2. It can also be seen that the coils 1, 2 consist of several radial layers of windings. The steps for preferred manufacture of the coil assembly are shown in Figures 8a-c and the associated description.

A coil 1, 2 associated magnetic conducting element is indicated by the reference numeral 3. The encoder element 3 is designed to be movable along the coil longitudinal direction X. Since it is designed to be magnetically conductive, it influences the inductance of the two coils 1, 2. For this purpose, the tanning element 3 is made, for example, of soft or other ferromagnetic material. Together with the coil arrangement thus results in a position sensor, by means of which a position of the encoder element 3 with respect to the coil assembly, in particular a position along the coil longitudinal direction X, can be determined. In the case shown, the transmitter element 3 is arranged in an inner space of the coils 1, 2 substantially coaxially with these. Alternatively, it may be arranged annularly around an outer surface of the coils 1, 2 substantially coaxially therewith.

The first coil 1 has an increasing coil in the longitudinal direction X winding density (seen from left to right). In contrast, the second coil 2 has a winding density decreasing in the coil longitudinal direction X in this coil longitudinal direction X (seen from left to right). Here, the number of windings per unit length in the coil longitudinal direction X is to be understood as the winding density. hen. Thus, the winding densities of the coils 1, 2 change in opposite directions along the coil longitudinal axis X. In a preferred embodiment, a winding density (windings per coil volume) related to the coil volume can therefore remain constant in the coil longitudinal direction X, which can be seen from the windings of the second coil 2 shown by way of example. In addition, in a further preferred embodiment, the overall winding density of the coil arrangement - ie both coils 1, 2 together - (windings per unit length in the coil longitudinal direction X) remain constant by the coils 1, 2 are wound so that the winding density of the first coil 1 in the coil longitudinal direction X increases as the winding density of the second coil 2 decreases.

In the case of the embodiment according to FIG. 1, the winding density of the first and second coils 1, 2 changes linearly in the coil longitudinal direction X. Thus, the inductance of the first and second coils 1, 2 changes substantially in proportion to the position of the transmitter element 3 along the Coil longitudinal direction X. This allows a simple evaluation of the position. The first coil 1 in this case has a substantially conical outer surface, while the second coil 2 has a substantially conical inner surface, which bears directly against the conical outer surface of the second coil 2.

In the case of the embodiment according to FIG. 2, the winding density of the first and second coils 1, 2 changes abruptly. The coils 1, 2 each have different longitudinal sections 4 (in FIG. 2 in each case a total of 4 longitudinal sections), within which the winding density in the coil longitudinal direction X remains constant. Each longitudinal section 4 has a different winding density compared to the directly adjacent longitudinal section 4. If the transmitter element 3 passes through a transition Ü from one longitudinal section to a directly adjoining another longitudinal section 4, the inductance of the coils 1, 2 suddenly changes, which is easily and clearly ascertainable. Thus, it can be very robust to determine at which transition Ü of the longitudinal sections 4, the donor element 3 is currently. In order to effect a finer recognition of the position of the donor element 3, a plurality of longitudinal sections 4 and thus transitions Ü are provided. A sudden change in the winding density in the coil longitudinal direction X can also serve to represent reference points. For example, in the embodiment of the coil arrangement according to Fig. 1, a sudden change in the winding density in the axial center of the coils 1, 2 may be provided to mark a center position of the donor element 3 and to make the achievement of this center position easily detectable. This means that defined end positions or other defined reference positions can be created as desired.

In the case of the embodiment according to FIG. 3, the coils 1, 2 each have three longitudinal sections 4a, 4b, 4c, wherein the winding density in the first and third longitudinal section 4a, 4c changes linearly, while it remains constant in the second longitudinal section 4b. At the transition Ü between the longitudinal sections 4a, 4b, 4c, the winding density is the same in each case. Thus, the winding density at the transition Ü does not change abruptly in the case shown. However, it can also be provided here that the winding density at one or more of the transitions Ü changes abruptly. Since the winding density in the second longitudinal section 4b is constant, the inductance barely changes when the transmitter element 3 is moved within the second longitudinal section 4b; the detection of the position of the transmitter element 3 in this longitudinal section 4b is correspondingly more difficult. Thus, by targeted distribution of lengths with constant winding density and lengths with varying winding density areas generated within which the detection of the position of the donor element 3 is very accurate and areas are generated within which the detection of the position of the donor element 3 is less accurate. In addition, a linearization of the sensor characteristic is possible. This means that the inductance of the coil arrangement of the position sensor is linearly dependent on the position of the transmitter element 3 with respect to the coil arrangement along the coil longitudinal direction X.

The coil arrangement according to FIG. 4 has a coil housing 5 which is magnetically conductive. As a result, the magnetic flux in the interior of the coil arrangement in the region of the encoder element 3 is significantly improved. The

Accuracy of the coil arrangement for detecting the position of the encoder element 3 is thereby significantly increased. The coils 1, 2 in Fig. 4 correspond to those from Fig. 1. However, the housing 5 can of course be used in any type of coil arrangement according to the invention, as for example in the embodiments of FIG. 2 or 3. The housing 5 can also be designed specifically as a magnetic yoke. Thus, a force generated by the magnetic field of the coils 1, 2 force can be amplified or caused on the donor element 3, when the coil assembly is electrically energized accordingly. The position sensor formed from the coil assembly and the encoder element 3 can then serve as an actuator by the magnetic force acting on the donor element 3 is used for actuating a device, such as a valve or a Fahrzeuggetriebeschalt- element.

5 and 6 each show a preferably electrically switched versions of the coil arrangement and the position sensor. In the embodiment according to FIG. 5, the two coils 1, 2 are connected electrically in series directly one behind the other, wherein a measuring tap 6, that is to say an electrical measuring connection, is provided between the coils. The series-connected coils 1, 2 are in this case connected between two electrical potentials, in detail a voltage source Ub and a ground or ground Gnd. One of the coils 1, 2 is thus located between the measuring tap 6 and the voltage source Ub and the other of the coils 1, 2 is located between the measuring tap 6 and the ground or ground Gnd. An electric current flowing through the coils 1, 2 is indicated by i. The coil arrangement forms a voltage divider through the series connection. Accordingly, the total voltage between Ub and Gnd divides on the coils 1, 2, depending on the electrical resistance of the coils. When the coils 1, 2 are energized with a voltage jump or with an alternating voltage, it is in turn dependent on the inductance of the respective coil 1, 2, which on the other hand depends on the position of the encoder element 3 with respect to the coil arrangement. Thus, the position of the transmitter element 3 can be determined on the basis of the voltage potential at the measuring tap 6.

In the embodiment according to FIG. 6, the coils 1, 2 are each connected electrically in series with a comparison resistor 7. One or both of the comparison resistors 7 can have a variable electrical resistance (ohmic resistance) have, for example, these are potentiometers. The series circuits of comparison resistor 7 and coil 1, 2 are connected in parallel to each other between two electrical potentials, in detail a voltage source Ub and a ground or ground Gnd. Thus, each series circuit of comparison resistor 7 and coil 1, 2 form a separate branch of a so-called Wheatstone measuring bridge circuit, wherein in each case a Meßabgriff 6 between each of the coils 1, 2 and the series resistance comparison 7 is provided. As a result, the total electric current i flowing through the coil arrangement divides onto the two branches. Within each branch, a voltage divider is formed by the respective coil 1, 2 and the comparison resistor 7. Thus, similar to the embodiment according to FIG. 5, a specific voltage potential is formed at each measuring tap 6 as a function of the inductance of the coil 1, 2. The resulting voltage potential between the two Meßabgriffen 6 is denoted by dU. Based on dU then the position of the donor element 3 can be determined with respect to the coil assembly.

If one or both of the comparison resistances 7 have a changeable electrical resistance, this resistance can be adjusted such that dU essentially assumes the value zero (= no voltage potential between the measuring taps 6) and then the position of the encoder element 3 based on the set value of the resistance be determined with respect to the coil arrangement. If appropriate, then several voltage jumps occur in order to set dU successively closer to the value zero for each voltage jump.

FIGS. 7a to 7c each show possibilities for electrical energization (activation) of the coil arrangement, for example the electrically interconnected coil arrangement according to FIG. 5 or 6. The ordinate axis plots the electrical voltage U, the time ti is plotted on the abscissa axis.

According to FIG. 7 a, the coil arrangement is electrically energized with a purely positive voltage which has a substantially rectangular chronological progression (positive rectangular oscillation), that is to say with as steep flanks as possible. According to FIG. 7b, the coil arrangement is electrically energized with an alternating voltage. which likewise has a rectangular time profile, and according to FIG. 7c, the coil arrangement is electrically energized with an alternating voltage which has a sinusoidal time profile. Alternatively, for example, a sawtooth-shaped time course of the voltage can be selected. In addition, the voltage can be purely negative or purely positive or have alternating components. By alternating components, the problem of magnetic remanence in the coils 1, 2 attenuated or even eliminated altogether, since in this way the remaining after a voltage pulse in each period T magnetic fields in the coils 1, 2 at least in part by a subsequent, opposite voltage pulse in the subsequent period T be attenuated or extinguished.

The duty cycle of the voltage oscillations, ie the ratio between pulse duration t and period T can be suitably selected. In the case shown, the duty cycle is about 50%, which is only an example.

FIGS. 8a to 8c show preferred production steps for producing a coil arrangement according to the invention. In a first production step (FIG. 8a), the first coil 1 is wound, which forms the radially inner coil of the coil arrangement. In this case, first an innermost layer of the windings is helically wound along the coil longitudinal direction X, for example on a cylindrical carrier element (not shown) which remains in the coil arrangement or is removed after its production. The first six rows of the first winding layer are shown by way of example in cross section in FIG. 8a. Subsequently, the second layer of the windings in the opposite direction to the first layer is helically wound along the coil longitudinal direction X, radially spaced from the first layer. The production of the other winding layers is done analogously, ie each layer is wound in the opposite direction to the directly preceding winding layer helically along the coil longitudinal axis X. In order to achieve the largest possible filling factor of the coils 1, 2, the windings are arranged orthocyclically. Depending on how the winding density is to change in the coil longitudinal direction X (rising sharply, rising linearly, etc.), the winding layers are designed to have different lengths in the coil longitudinal direction X. To produce a linear increase in the winding density, the length l of the winding layers of the first coil 1 decreases continuously, ie each winding layer is shorter by a predetermined amount than the directly preceding winding layer. To produce a plurality of longitudinal sections, each with the same winding densities, the length l of the winding layers decreases abruptly, that is, for example, two or more winding layers are wound directly after one another with an identical winding length and then a third and a fourth winding layer with an identical, but to the first and wound second layer shorter length I, resulting in a transition of the winding density at the shortened end of the third and fourth winding layer.

In the exemplary case shown in Fig. 8a, the winding density of the first coil 1 increases substantially linearly. Thus, the length I of each individual winding layer with respect to the immediately preceding layer is shortened continuously until the desired number of windings or the desired outer diameter is reached.

In a second production step (FIG. 8b), the second coil 2 is wound, which forms the radially outer coil of the coil arrangement. For this purpose, an innermost layer of the windings is also initially helically wound along the coil longitudinal direction X. Subsequently, the second layer is helically wound in the opposite direction along the coil longitudinal direction X, radially spaced from the first layer. The production of the other winding layers is done analogously, ie each layer is wound in the opposite direction to the directly preceding winding layer helically along the coil longitudinal axis X. In order to achieve the largest possible fill factor, the windings are arranged orthocyclically. In contrast to the first coil 1, however, the winding length l of the second coil increases, and preferably to the extent to which the winding length of the first coil 1 decreases. Moreover, the winding of the layers of the second coil 2 preferably takes place in such a way that the mutually assigned turned ends of the winding layers of the first and second coil 1, 2 abut directly against each other. This avoids gaps in the coil assembly and optimizes the fill factor. In order to obtain the most homogeneous possible coil arrangement with a high fill factor, the wires of the coils 1, 2 are basically made as thick as possible.

In a third production step (FIG. 8c), the two finished wound coils 1, 2 are electrically connected to one another. This can, as shown in Fig. 8c, by electrical contacting two adjacent free ends of the wires of the coils 1, 2 take place directly on the coil assembly (by means of the connecting conductor 8) or alternatively such that the free ends of the wires 1, 2 electrically into a directly adjacent or remotely spaced electronics, where they are electrically connected according to the desired interconnection (see Fig. 5 and 6), optionally together with other electrical and / or electronic components.

It should be noted that the electrical connection of the coils 1, 2 shown in FIG. 8c results in the series connection of the coils 1, 2 illustrated in FIG. 5 by means of the connecting conductor 8. The connecting conductor 8 is accordingly designed to be electrically contactable to form the measuring tap 6 (indicated by the right-hand arrow), while the remaining ends of the coil wires are each made electrically contactable with an electrical potential (indicated by the two left-hand arrows).

The staggering of the first, second and third production steps is preferred in this order, so preferably the first step, then the second step and finally the third step take place. The illustrated production steps result in a simple and cost-effective production method for the coil arrangement according to the invention. REFERENCE CHARACTERS

1 first coil

2 second coil

3 encoder element

4, 4a-c longitudinal section

5 housing

6 measuring tap

7 comparative resistance

8 connecting conductor dU resulting electric voltage potential

Gnd electrical grounding, ground

i electric current

I length of a winding layer

t pulse duration

T period

ti time

U electrical voltage

Ub electrical voltage source

X Coil longitudinal direction

Claims

claims

1 . Coil arrangement, in particular for a position sensor, having a first coil (1) and a second coil (2), which are electrically connected to each other and are arranged substantially coaxially with each other, wherein the first coil (1) in the longitudinal direction (X) of the coil assembly Has increasing winding density, characterized in that the second coil (2) has a decreasing in the longitudinal direction (X) of the coil assembly winding density.

2. A coil assembly according to claim 1, wherein the winding density of the first coil (1) increases in the longitudinal direction of the coil assembly substantially to the extent that the winding density of the second coil (2) decreases.

3. Coil arrangement according to one of claims 1 or 2, wherein the winding densities of the first and second coil (2) change linearly.

4. coil arrangement according to one of claims 1 to 3, wherein the winding density of the first and second coil (2) change in sections leaps and bounds.

5. Coil arrangement according to one of claims 1 to 4, wherein the winding density of the first and second coil (1, 2) in a first longitudinal section (4a) changes, in particular linear, and in a subsequent to the first longitudinal section (4a) second longitudinal section (4b) is constant, and changes in a subsequent to the second longitudinal section third longitudinal section (4c), in particular linear.

6. coil arrangement according to one of claims 1 to 5, wherein the first and second coil (2) are electrically connected in series directly one behind the other, with a Meßabgriff (6) between the coils (1, 2).

7. Coil arrangement according to one of claims 1 to 5, wherein the first and second coils (1, 2) are each connected in series with a comparison resistor (7), and wherein each of the coils (1, 2) with the series-connected Vergleichswi - the resistor (7) forms a branch of a Wheatstone bridge circuit, and wherein in each case a Meßabgriff (6) between each coil (1, 2) and the series-connected comparison resistor (7) is provided.

8. Coil arrangement according to one of the preceding claims, wherein a magnetically conductive housing (5) is provided, within which the coils (1, 2) are arranged, for the magnetic influence of the magnetic flux within the coil assembly.

9. Position sensor, comprising a coil arrangement (1, 2) according to one of the preceding claims and with a magnetically conductive transmitter element (3), which is arranged along the longitudinal direction (X) of the coil arrangement as a position sensor movable.

10. Position sensor according to claim 9, wherein the coil arrangement (1, 2) in the longitudinal direction (X) is at least circular segment-shaped and the transmitter element (3) along the coil assembly (1, 2) is at least circular segment-shaped movable, as Winkelpositionsgeber, so that the position sensor Angular position sensor forms.

1 1. A position sensor according to claim 9, wherein the coil assembly (1, 2) is straight in the longitudinal direction and the transmitter element is linearly movable along the longitudinal direction of the coil assembly (1, 2) as a linear position sensor so that the position sensor forms a linear position sensor.

12. A manufacturing method for producing a coil assembly according to any one of claims 1 to 8, wherein in a first manufacturing step, the first, radially inner coil (1) is wound, and wherein in a second manufacturing step, the second, radially outer coil (2) is wound, and wherein in a third manufacturing step, the first coil (1) is electrically connected to the second coil (2).

13. The manufacturing method according to claim 1, wherein in the second manufacturing step, the winding of the second coil (2) takes place such that the opposite ends of the winding layers of the first and second coil (1, 2) lie directly against each other.