Inductive Position Sensors

Abstract

The invention relates to an inductive position sensor, which has a stator element and a receiving system, wherein the stator element has an excitation coil loaded with a periodic alternating voltage, and the signal of the excitation coil is inductively input and coupled into the receiving system; the stator element has a rotor element, and the rotor element affects the strength of the inductive coupling between the excitation coil and the receiving system according to the angular position of the rotor element relative to the stator element. The inductive position sensor has an evaluation circuit, which is used to determine the angular position of the rotor element relative to the stator element from the voltage signal induced into the receiving system. The position sensor has a uniqueness range E, in which the angular position can be uniquely determined, and the receiving system extends over a first angular range, the first angular range is N1=n*E, where n≥1, and the excitation coil extends over a second angular range, the second angular range is N2=m*E, where m≥2, where m and n are positive integers, and m>n.

Description

Technical Field

[0001] The invention relates to an inductive position sensor, in particular an arc sensor, comprising a stator element and a receiving system, wherein the stator element has an excitation coil to which a periodic alternating voltage is applied, wherein a signal of the excitation coil is inductively input-coupled into the receiving system, the position sensor having a rotor element, which influences the strength of the inductive coupling between the excitation coil and the receiving system as a function of the angular position of the rotor element relative to the stator element, and the position sensor having an evaluation circuit for determining the angular position of the rotor element relative to the stator element from a voltage signal induced into the receiving system. Background Art

[0002] Inductive position sensors are used in modern motor vehicles in a wide variety of applications with a large number of boundary conditions. In particular, inductive position sensors are used for locations where the angular position of a rotor is to be detected in order to enable precise control. This is necessary, for example, on steering columns, brake systems or drives for motor vehicles, in particular electric and hybrid vehicles.

[0003] In known inductive position sensors, systems that can detect a certain angular range are usually used. This is sufficient for most fields of use. By limiting the angle detection to a certain range, costs can be saved compared to the angle detection over the entire possible angular range, such as 360° in a fully rotating sensor. These position sensors are known as arc sensors in the prior art. When designing these position sensors, the excitation coil has been designed to be similarly large as the receiving system so as to achieve the smallest possible structural form of the inductive position sensor. This may lead to the disturbing influence of the excitation coil on the voltage signal induced in the receiving system and damage the determination of the angle, especially in the case of arc sensors and linear sensors. If the influence of the excitation coil is to be as small as possible, this means that the excitation coil must be as large as possible relative to the receiving system. When designing the position sensor, it has been attempted to achieve the optimum between minimizing the size of the position sensor and minimizing the influence of the excitation coil on the receiving system in multiple design steps. These design steps increase costs and development work and increase costs. Similarly, it cannot be automatically determined by iterative design steps that the optimal solution has been found. Summary of the invention

[0004] The present invention is based on this.

[0005] The problem underlying the present invention is to improve known position sensors, in particular segment sensors, in such a way that the errors in determining the angle are minimized and at the same time the smallest possible overall size can be achieved.

[0006] According to the invention, the task is solved in that the position sensor has a uniqueness range in which the angular position can be determined uniquely, the receiving system extends over a first angular range, wherein the first angular range is N1=n*E, wherein n≥1, and the excitation coil extends over a second angular range, wherein the second angular range is N2=m*E, wherein m≥2, wherein m and n are positive integers and m>n.

[0007] The unambiguity range is understood to be the range within which the angle can be determined unambiguously by means of the position sensor. The unambiguity range can be between 0° and 360°. Since the position sensor is used at different positions, the unambiguity range that the sensor must detect unambiguously can be very different. However, the unambiguity range is and is predefined by the boundary conditions of the system and can be used as an input variable when designing the position sensor.

[0008] In the inductive position sensor according to the invention, it is possible to minimize the influence of the excitation coil on the voltage signal induced in the receiving system if the angular range over which the excitation coil and the receiving system extend is designed according to the unambiguity range.

[0009] By means of simulations, it can be shown that if the receiving system extends over a first angular range and the excitation coil extends over a second angular range (they are designed as multiples of the unambiguous range), then the error in determining the angle can be minimized. It applies here that the multiple is a positive integer and that the second angular range is greater than the first angular range.

[0010] It can be provided that m≥n+1, preferably m=n+1. In order to minimize the error, the second angular range can be any multiple of the unambiguous range, which is greater than the first angular range. However, this is contrary to the desire to achieve a structure that is as compact as possible for the position sensor. Therefore, the following possibility is preferred, namely, the second angular range is a multiple of the unambiguous range, which is exactly 1 greater than the multiple designed for the first angular range. Therefore, when the first angular range coincides with the unambiguous range, the minimum angular range corresponding to these requirements corresponds to this, which corresponds to n=1, and the second angular range corresponds to double the unambiguous range, where m=2.

[0011] If a higher signal strength of the signal coupled into the receiving system is desired, it can be provided that the first angular range is designed with n = 2. In this case, the strength of the inductive coupling between the excitation coil and the receiving system is influenced by the larger area of ​​the rotor element, which increases the influence. The smallest possible second angular range is selected in this case with m = 3.

[0012] It can be provided that the geometric structure of the rotor element can be described by two circular orbits around a center point with different radii, wherein a first radius of a first of the two circular orbits is smaller than a second radius of a second of the two circular orbits, and sections of the outer contour extend alternately and uniformly on the first or second circular orbit, and the ends of the sections are connected to the corresponding adjacent sections on the corresponding other circular orbit via radial connections between the circular orbits.

[0013] The resulting geometry of the rotor element corresponds to the outer contour of the rotor with a certain number of fins and recesses. It can therefore be provided that the segments on the circular path with the second radius each form a fin and the segments on the circular path with the first radius each form a recess. The geometry of the rotor element can determine the unambiguity range of the position sensor. In this case, there is the possibility of determining the unambiguity range E according to the following formula:

[0014] E = 360° / number of blades of the rotor element.

[0015] The number of blades of a rotor element is in many cases a certain size due to other circumstances and is known for the design of the position sensor. The described relationship between the number of blades of a rotor element and the unambiguous range makes it possible to directly determine the unambiguous range when the number of blades is known.

[0016] There is the possibility that the first receiving system has at least two, preferably two or three, first conductor loops. Furthermore, it can be provided that the first conductor loops each form a uniformly repeating loop structure. It can be particularly advantageously provided that the winding direction of the first conductor loops of the uniformly repeating loop structure is changed, wherein a surface is expanded by changing the winding direction. By changing the winding direction, the integral path of the surface periodically expanded by the first conductor loops changes. The magnetic field coupled into the first receiving system by the first rotor element results in a signal voltage amplitude on the conductor loop, which is related to the expression ∫B r dA is proportional, where B r is the magnetic field strength caused by the rotor element in the first conductor loop, and A is the area spanned by the first conductor loop.

[0017] It can be provided that the stator element and the evaluation circuit are arranged on a printed circuit board, wherein the evaluation circuit is arranged within the excitation coil and outside the conductor loop of the receiving system. The described arrangement offers the advantage that the leads of the excitation coil and the receiving system do not cross one another, as would be the case if the evaluation unit were arranged outside the excitation coil. This avoids further influences on the signals coupled into the receiving system. A further advantage can be that unused space on the printed circuit board is utilized, which contributes to a compact design of the inductive position sensor.

[0018] In order to increase the redundancy of the system, it can be provided that a second receiving system and / or a second evaluation circuit is arranged on the printed circuit board. It can be provided that the signal of the excitation coil is inductively coupled into the first and second receiving systems. It is also possible to arrange the second excitation coil on the printed circuit board.

[0019] Up to this point, the problem on which the invention is based and its solution according to the invention have been explained using the example of an arc sensor with a rotor element as an inductive coupling element. However, the problem and the solution are completely analogous for linear displacement sensors. Linear sensors are used in modern motor vehicles where the longitudinal position of the coupling element is to be detected in order to achieve precise control.

[0020] It may be provided that the inductive position sensor, in particular the linear sensor,

[0021] the position sensor comprises a stator element and a receiving system, the stator element comprising an excitation coil to which a periodic alternating voltage is applied, wherein a signal of the excitation coil is inductively coupled into the receiving system,

[0022] the position sensor has a coupling element which influences the strength of the inductive coupling between the excitation coil and the receiving system as a function of the linear position of the coupling element relative to the stator element,

[0023] the position sensor has an evaluation circuit for determining the linear position of the coupling element relative to the stator element from a voltage signal induced into the receiving system,

[0024] It is characterized in that

[0025] the position sensor has an unambiguous range E in which the longitudinal position can be determined unambiguously,

[0026] - the receiving system extends over a first longitudinal extent, wherein the first longitudinal extent is L1=m*E, where n≥1,

[0027] The excitation coil extends over a second longitudinal extent, wherein the second longitudinal extent is L2=m*E, where m≥2,

[0028] Here, m and n are positive integers, and m>n.

[0029] The unambiguity range is understood to be the range within which the longitudinal position can be determined unambiguously by means of the position sensor. The unambiguity range can theoretically be between 0 mm and ∞, but is of course limited by the size of the linear sensor. Since the position sensor is used at different positions, the unambiguity range that the sensor must detect unambiguously can be very different. However, this unambiguity range is and is predefined by the boundary conditions of the system and can be used as an input variable when designing the position sensor.

[0030] In the inductive position sensor according to the invention, it is possible to minimize the influence of the excitation coil on the voltage signal induced in the receiving system if the longitudinal range over which the excitation coil and the receiving system extend is designed according to the unambiguity range.

[0031] Analogously to the simulation results, it is assumed that a minimization of the error in determining the longitudinal position can be achieved if the receiving system extends over a first longitudinal extent and the excitation coil extends over a second longitudinal extent (they are implemented as a multiple of the unambiguous range). It applies here that the multiple is a positive integer and that the second longitudinal extent is greater than the first longitudinal extent.

[0032] It can be provided that m≥n+1, preferably m=n+1. In order to minimize the error, the second longitudinal range can be any multiple of the unambiguous range, which is greater than the first longitudinal range. However, this is contrary to the desire to achieve a structure that is as compact as possible for the position sensor. Therefore, the following possibility is preferred, namely, the second longitudinal range is a multiple of the unambiguous range, which is exactly 1 greater than the multiple designed for the first longitudinal range. Therefore, when the first longitudinal range coincides with the unambiguous range, the minimum longitudinal range corresponding to these requirements corresponds to this, which corresponds to n=1, and the second longitudinal range corresponds to double the unambiguous range, where n=2.

[0033] If a higher signal strength of the signal coupled into the receiving system is desired, it can be provided that the first longitudinal extent is designed with n = 2. In this case, the strength of the inductive coupling between the excitation coil and the receiving system is influenced by the larger area of ​​the coupling element, which increases the influence. The smallest possible second longitudinal extent is selected in this case to be m = 3.

[0034] It can be provided that the coupling element is rectangular or rectangular in shape, for example a metal strip with regularly distributed punched holes. The area of ​​the metal strip that remains filled with material can be called a vernier, similar to the fins in a rotor-shaped coupling element.

[0035] The resulting geometry of the coupling element can be used to determine the unambiguous range of the position sensor. There is the possibility that the unambiguous range E can be determined as the sum of one of the regularly distributed perforations and the cursor.

[0036] There is the possibility that the first receiving system has at least two, preferably two or three first conductor loops. In addition, it can be provided that the first conductor loops each form a uniformly repeated loop structure. It can be particularly advantageously provided that the winding direction of the first conductor loop of the uniformly repeated loop structure is changed, wherein a surface is expanded by changing the winding direction. By changing the winding direction, the integral path of the surface periodically expanded by the first conductor loop changes. The magnetic field coupled into the first receiving system by the first coupling element causes a signal voltage amplitude on the conductor loop, which is proportional to the expression ∫B1dA, where Bl is the magnetic field strength caused by the coupling element in the first conductor loop, and A is the surface expanded by the first conductor loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is explained in more detail below with the aid of the accompanying drawings. Here, it is shown:

[0038] Figure 1 A schematic diagram showing an inductive position sensor;

[0039] Figure 2 A schematic diagram showing a stator element;

[0040] Figure 3 A graphical representation showing the error in determining the angle for different relationships of the receiving system to the excitation coil is shown. DETAILED DESCRIPTION

[0041] The inductive position sensor 1 designed according to the preferred exemplary embodiment of the present invention comprises a printed circuit board 9 on which the stator element 2 is arranged.

[0042] Furthermore, the inductive position sensor 1 comprises a rotor element 5. The rotor element 5 is arranged rotatably relative to a printed circuit board 9. Sections on the outer radius of the rotor element 5 can be seen. These can be assumed to be wings 7. Sections on the inner radius of the rotor element 5 can be assumed to be gaps 8. Here, the wings 7 and the gaps 8 each define a uniqueness range E of the position sensor 1. The uniqueness range E is understood to be the range within which an angle can be determined uniquely with the aid of the position sensor 1. The uniqueness range of the position sensor can be calculated according to the following formula:

[0043] E=360° / number of blades of the rotor element 5 .

[0044] Figure 2 Show Figure 1 . The stator element including the excitation coil 3 and the receiving system 4 is arranged on the side of the printed circuit board 9 facing the rotor element 5. The printed circuit board 9 is adapted to the shape of the stator element 2 in terms of its actual shape. The receiving system 4 includes two first conductor loops 4a, 4b. The first conductor loops 4a, 4b form a periodically repeated loop structure, which expands a surface by changing the winding direction.

[0045] The inductive position sensor 1 has an oscillating circuit (not shown individually here) which generates a periodic AC voltage signal during operation of the inductive position sensor 1, by which the first excitation coil 3 is supplied. The rotor element 5 influences the strength of the inductive coupling between the excitation coil 3 and the receiving system 4 during its rotation.

[0046] By influencing the strength of the inductive coupling between the excitation coil 3 and the receiving system 4 as a function of its angular position relative to the stator element 2, the angle between the rotor element 5 and the receiving system 4 can be determined. This angle is becoming increasingly important for many applications, especially in motor vehicles. In order to be able to determine the angle within the unambiguous range E of the sensor, the excitation coil 3 and the receiving system 4 must extend at least over this angular range of the sensor 1. The excitation coil 3 influences the signal coupled into the receiving system 4 via the end region of the excitation coil 3. This influence is undesirable because errors in the determination of the angle can occur as a result. Figure 2 The possibility of optimizing the design of the relationship between the excitation coil 3 and the receiving system 4 and minimizing the errors is shown. For this purpose, it is possible that both the excitation coil 3 and the receiving system 4 are larger than the unambiguous range E by an integer multiple. For the receiving system 4, it is also applicable that the multiple can be 1, whereby the receiving system 4 is as large as the unambiguous range E. Furthermore, it is a prerequisite that the excitation coil 3 must always be larger than the receiving system 4. In the present case, the angular range over which the receiving system 4 extends corresponds to the unambiguous range E, and the angular range over which the excitation coil 3 extends is twice the unambiguous range E.

[0047] The inductive position sensor 1 further comprises an evaluation circuit 6 for determining the angular position of the rotor element 5 relative to the stator element 2 from the signal coupled into the receiving system 4. The evaluation circuit 6 is arranged within the excitation coil 3 and outside the conductor loops 4a, 4b of the receiving system 4. This arrangement offers the advantage that unused space on the printed circuit board 9 can be optimally utilized. If the evaluation circuit 6 is located outside the excitation coil 3, the required dimensions of the printed circuit board 9 are larger, which increases the costs of the printed circuit board.

[0048] Figure 3 A graphical representation of the error to be expected for different sizes of the excitation coil 3 in determining the angle by the influence of the excitation coil 3 on the signal coupled into the receiving system 4 is shown. Here, the error of the inductive position sensor is plotted in percentage relative to the determined angle of the sensor. In this case, the receiving system 4 is as large as the unambiguity range E of the sensor. The illustration shows a simulation of the expected error. It can be seen that the error is minimal for integer values ​​m. The graph shows the minimum values ​​for m=2 and m=3. A continuation of the graph is possible, which shows the minimum values ​​for all integers m. From the graph, it can be seen that the error in determining the angle, which error is caused by the influence of the excitation coil 3 on the signal coupled into the receiving system 4, can be minimized by designing the excitation coil 3 and the receiving system 4 relative to the unambiguity range E of the sensor. A very particular advantage of this mathematical relationship is the fact that, given the known unambiguity range E of the sensor determined by the geometry of the rotor element 5, the design of the excitation coil 3 and the receiving system 4 can be carried out immediately. This can reduce the development effort and ensure an optimized result.

[0049] Reference numerals list

[0050] 1 Inductive position sensor

[0051] 2 Stator elements

[0052] 3 Excitation coil

[0053] 4 Receiving system

[0054] 4a, 4b First conductor loop

[0055] 5 Rotor elements

[0056] 6 Evaluation Units

[0057] 7 Wings

[0058] 8. Gap

[0059] 9. Printed Circuit Board

[0060] E Sensor uniqueness range

Claims

1. An inductive position sensor (1), The position sensor comprises a stator element (2) having an excitation coil (3) to which a periodic alternating voltage is applied and a receiving system (4), wherein: The signal of the excitation coil (3) is inductively input-coupled into the receiving system (4). the position sensor has a rotor element (5) which, depending on the angular position of the rotor element relative to the stator element (2), influences the strength of the inductive coupling between the excitation coil (3) and the receiving system (4), the position sensor has an evaluation circuit (6) for determining the angular position of the rotor element (5) relative to the stator element (2) from the voltage signal induced into the receiving system (4), It is characterized in that the position sensor (1) has an unambiguous range E in which the angular position can be determined unambiguously, The receiving system (4) extends over a first angular range, wherein the first angular range is N1=n*E, where n≥1, The excitation coil (3) extends over a second angular range, wherein the second angular range is N2=m*E, wherein m≥2, Where m and n are positive integers, and m>n, and The uniqueness range E can be determined according to the following formula: E=360° / number of blades of the rotor element (5).

2. The inductive position sensor (1) according to claim 1, characterized in that m≥n+1.

3. The inductive position sensor (1) according to claim 1 or 2, characterized in that: The geometric structure of the rotor element (5) can be described by two circular orbits with different radii around a center point, wherein a first radius of a first of the two circular orbits is smaller than a second radius of a second of the two circular orbits, and segments of the outer contour extend alternately and uniformly on the first circular orbit or the second circular orbit, and the ends of the segments are connected to corresponding adjacent segments on the corresponding other circular orbit via radial connections between the two circular orbits.

4. The inductive position sensor (1) according to claim 3, characterized in that The sections on the circular path with the second radius each form a wing (7), and the sections on the circular path with the first radius each form a recess (8).

5. The inductive position sensor (1) according to claim 1 or 2, characterized in that: The receiving system (4) has at least two first conductor loops (4a, 4b).

6. The inductive position sensor (1) according to claim 5, characterized in that The first conductor loops (4a, 4b) respectively form uniformly repeated loop structures.

7. The inductive position sensor (1) according to claim 6, characterized in that The winding direction of the first conductor loop (4a, 4b) of the uniformly repeated loop structure is changed, wherein a surface is expanded by changing the winding direction.

8. The inductive position sensor (1) according to claim 5, characterized in that The stator element (2) and the evaluation circuit (6) are arranged on a printed circuit board (9), wherein the evaluation circuit (6) is arranged within the excitation coil (3) and outside a first conductor loop (4a, 4b) of the receiving system (4).

9. The inductive position sensor (1) according to claim 1, characterized in that The inductive position sensor (1) is an arc sensor.

10. The inductive position sensor (1) according to claim 2, characterized in that m=n+1.

11. The inductive position sensor (1) according to claim 5, characterized in that The receiving system (4) has two or three first conductor loops (4a, 4b).

12. An inductive position sensor (1), The position sensor comprises a stator element (2) having an excitation coil (3) to which a periodic alternating voltage is applied and a receiving system (4), wherein: The signal of the excitation coil (3) is inductively input-coupled into the receiving system (4). the position sensor has a coupling element which influences the strength of the inductive coupling between the excitation coil (3) and the receiving system (4) as a function of the linear position of the coupling element relative to the stator element (2), the position sensor has an evaluation circuit (6) for determining the linear position of the coupling element relative to the stator element (2) from the voltage signal induced into the receiving system (4), It is characterized in that the position sensor (1) has an unambiguous range E in which the longitudinal position can be determined unambiguously, The receiving system (4) extends over a first longitudinal extent, wherein the first longitudinal extent is L1=n*E, wherein n≥1, The excitation coil (3) extends over a second longitudinal extent, wherein the second longitudinal extent is L2=m*E, wherein m≥2, Wherein, m and n are positive integers, and m>n; The uniqueness range E can be determined according to the following formula: E=360° / number of blades of the rotor element (5).

13. The inductive position sensor (1) according to claim 12, characterized in that The inductive position sensor (1) is a linear sensor.

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