Inductive position detector

Abstract

This inductive position detector (100) includes: a stationary element (1) that has a wiring substrate (10); a rotating element (2) that has a non-conductor component (21) disposed facing the stationary element (1) and rotates relative to the stationary element (1) about a rotation axis (3a); a conductor pattern (T) that is retained by the non-conductor component (21), has a geometric periodicity along the circumferential direction about the rotation axis (3a), and moves along a rotation trajectory about the rotation axis (3a) in association with rotation of the rotating element (2); and a plurality of chip inductors (L) that are surface-mounted on a main surface of the wiring substrate (10) of the stationary element (1) and are disposed so as to face the rotation trajectory while a spatial phase relative to the conductor pattern (T) is varied, the plurality of chip inductors (L) constituting each of a plurality of detection coils that detect any change in a magnetic field associated with passage of the conductor pattern (T).

Description

Related applications

[0001] This application claims priority under Japanese Patent Application No. 2022-95845, filed on 14 June 2022, and the entire contents of this application are incorporated herein by reference. [Technical Field]

[0002] This invention relates to an inductive position detector. [Background technology]

[0003] Various detection methods are used for position detectors that detect rotational position, including optical, magnetic, capacitive, resolver, and inductive types. Inductive position detectors move a movable part holding a conductor in an alternating magnetic field and detect the change in the magnetic field caused by the current induced in the conductor. Inductive position detectors are less susceptible to the effects of dust, dirt, and external magnetic fields, and therefore have excellent environmental resistance. In addition, they have a simple structure, can be miniaturized and thinned, and are relatively inexpensive.

[0004] Inductive position detectors are disclosed, for example, in Patent Documents 1 to 4.

[0005] Patent documents 1 and 4 disclose a configuration in which an excitation coil and a detection coil are formed in a conductor pattern on a printed circuit board, and a conductor target is moved relative to the detection coil. The voltage induced in the detection coil by the alternating magnetic field generated by the excitation coil changes according to the positional relationship between the detection coil and the conductor target. This makes it possible to detect the position of the conductor target.

[0006] Patent Document 2 discloses a configuration in which a detection coil is formed using a conductor pattern on a printed circuit board, an AC voltage is applied to the detection coil, and the change in the inductance of the detection coil is detected when a conductor target moves relative to the detection coil.

[0007] Patent Document 3 discloses a configuration in which an excitation coil and a detection coil are formed by conductor patterns on a silicon substrate. The detection principle is the same as that of Patent Documents 1 and 4.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] In a position detector for detecting a rotational position, size, resolution, and accuracy are very important performance characteristics. The number of detection cycles per rotation is called the shaft angle multiplier. When one conductor target passes through one detection coil, a detection signal for one cycle is obtained. The greater the shaft angle multiplier, the higher the resolution and the easier it is to improve the accuracy. To increase the shaft angle multiplier, it is necessary to increase the number of conductor targets arranged on the circumference around the axis of rotation. Therefore, in order to realize a position detector with a small size, high resolution, and high accuracy, it is necessary to make the pitch of the conductor targets finer.

[0010] When the pitch of the conductor targets is made finer, the detection coil also needs to be made smaller accordingly. When the detection coil becomes smaller, the magnetic flux linkage decreases, so the detected signal voltage becomes smaller. Then, the signal-to-noise ratio (S / N ratio) decreases, making accurate position detection difficult. Therefore, it is desirable to increase the number of turns of the detection coil as much as possible to ensure a sufficient signal voltage.

[0011] When forming a detection coil with a conductor pattern on a printed wiring board, a signal processing circuit can be configured on the same printed board, so the additional cost is low. Also, since the initial cost for manufacturing a printed wiring board is low, it is suitable for multi-variety and small-batch production, and a highly flexible design is possible.

[0012] Examples of making a detection coil with a conductor pattern on a printed wiring board are shown in FIG. 52 of Patent Document 1 and FIG. 9 of Patent Document 2. In both of these, a detection coil is formed with a spiral conductor pattern. When it is desired to increase the number of turns, a multi-layer printed wiring board can be used, and a configuration can be adopted in which spiral conductor patterns formed on a plurality of wiring layers are connected via via holes. However, since there are restrictions such as pattern width, pattern pitch, and via hole diameter, it is difficult to fabricate a small coil with a large number of turns. Increasing the number of wiring layers to increase the number of turns leads to cost increases.

[0013] If a conductor pattern is formed on a silicon substrate using a semiconductor manufacturing process as in Patent Document 3, the pattern width, pattern pitch, via hole diameter, etc. can be made finer than those of a printed wiring board, so a very small detection coil can be fabricated. However, the semiconductor manufacturing process requires a large initial cost, has low flexibility, and is not suitable for multi-variety and small-batch production. Also, since there are size restrictions on the silicon substrate, it is necessary to arrange the detection coils in an aggregated manner. Therefore, detection is performed at a part on the circumference around the rotation axis. If a plurality of elements are used, detection at positions evenly distributed on the circumference is possible, but due to cost issues, it is not a practical design.

[0014] Other coil shapes besides the spiral shape include a detection coil shape where the pattern intersects in a figure-eight shape to form a loop, as shown in FIG. 15 of Patent Document 1, and a zigzag shape with a vernier effect, as shown in Figure 2 of Patent Document 4. In both coil shapes, the portion enclosed by the forward and return patterns forms one turn of the coil. By doubling the forward and return patterns, it is possible to increase the number of turns to more than one, but it is difficult to create a coil with a large number of turns that can be placed at a small pitch between conductor targets. Furthermore, in order to detect the rotational position, it is preferable to provide two or more detection coils that output signals with different phases. However, with the figure-eight or zigzag pattern, it is not possible to place two detection coils on the same circumference of a single wiring layer. Therefore, it is necessary to form two detection coils on different wiring layers, or to create two detection coils on the same wiring layer with different radial positions (distance from the rotation axis). However, two detection coils formed on different wiring layers will have different distances from the conductor target. Furthermore, since the conductive target is formed in a sector shape centered on the axis of rotation, its circumferential width differs depending on its radial position. Therefore, the area of ​​the portion substantially facing the conductive target differs between two detection coils positioned at different radial positions, namely the inner diameter detection coil and the outer diameter detection coil. Consequently, in either case, an imbalance is likely to occur in the output of the detection coils, requiring special signal processing.

[0015] In addition, in the configuration shown in Figure 2 of Patent Document 4, even within the same phase, the positive and negative signals are detected as being on the outside and inside of the circumference, requiring a design that balances the offset. Therefore, designing the pattern shape to obtain the required accuracy is difficult.

[0016] On the other hand, when a position sensor is used to control an electric motor, it is common to attach the rotor of the position sensor to the side of the motor shaft opposite the output shaft. When an electric motor is incorporated into a device that utilizes its driving force, radial loads may be applied to the motor shaft. This can cause the motor shaft to flex, resulting in a misalignment of the axis on the side opposite the output shaft. When detection is performed only on a portion of the circumference around the rotation axis, as in Patent Documents 2 and 3, the misalignment of the axis results in an offset of the detection position, which adversely affects motor control.

[0017] One embodiment of this invention provides an inductive position detector that can solve at least one of the aforementioned problems.

[0018] More specifically, one embodiment of this invention provides an inductive position detector that is compact, has a high degree of design flexibility, and has high detection resolution. [Means for solving the problem]

[0019] One embodiment of this invention provides an inductive position detector having the following features.

[0020] 1. A stator having a wiring board, A rotor having non-conductive components positioned opposite the stator, and rotating relative to the stator about a predetermined axis of rotation, Multiple conductive targets of the same shape and size are periodically arranged along the circumference around the rotation axis and held by the non-conductive component of the rotor, and move along a rotational trajectory around the rotation axis as the rotor rotates, An inductive position detector comprising: a plurality of chip inductors, each constituting a plurality of detection coils, which are surface-mounted on the main surface of the wiring board of the stator, with their spatial phases differing from those of the plurality of conductor targets, and arranged to face the rotational trajectory, and which each constitute a plurality of detection coils for detecting changes in the magnetic field accompanying the passage of the conductor targets.

[0021] As the rotor rotates around its axis, multiple conductive targets held by the rotor's non-conducting components (typically insulating components, such as an insulating substrate) move along a rotational trajectory around the axis. On the main surface (mounting surface) of the stator's wiring board, multiple chip inductors, each constituting a detection coil, are arranged opposite the rotational trajectory of the conductive targets. The chip inductors detect the change in the magnetic field as the conductive targets pass by, that is, they output a signal representing the change in the magnetic field. Since the multiple chip inductors have different spatial phases relative to the multiple conductive targets, they output signals with different phases as the rotor rotates. Therefore, by processing the output signals of the multiple chip inductors, the relative rotational position of the rotor with respect to the stator can be detected.

[0022] Chip inductors are small electrical components that allow for a large number of turns while remaining inexpensive to source from the market. Therefore, when increasing the number of conductor targets to increase the number of poles and thus the detection resolution, it is possible to arrange them to accommodate small conductor target periods (conductor target pitches), preventing the detection signal from becoming too small and without incurring excessive costs. In addition, industrially mass-produced chip inductors have high performance uniformity. As a result, a uniform detection signal can be obtained from multiple chip inductors, eliminating the need for complex signal processing.

[0023] Furthermore, unlike configurations where multiple detection coils are formed on a silicon substrate using a semiconductor manufacturing process, the multiple chip inductors, being individual elements, can be placed at any position opposite the rotational orbit, offering a high degree of freedom in placement. Therefore, it is possible to distribute them around the entire circumference of the rotational orbit. Such a full-circumference arrangement easily accommodates misalignment of the rotational axis coupled to the rotor. Because the chip inductors are small, full-circumference arrangement can be achieved even in designs that shorten the conductor target period to improve resolution.

[0024] In this way, we can provide a guided position detector that offers a high degree of design flexibility, is compact, and has high detection resolution.

[0025] Typically, the multiple conductive targets have equal lengths along the rotational trajectory, for example, multiple conductive targets of the same shape and size are arranged rotationally symmetrically around the axis of rotation.

[0026] The multiple chip inductors may be mounted on one main surface of the stator's wiring board, i.e., on the same main surface. This allows the distance from the multiple chip inductors to the conductor target to be uniform, thus allowing the output from the multiple chip inductors to be uniform. Typically, the multiple chip inductors are surface-mounted on the main surface of the wiring board facing the rotor. This brings the chip inductors closer to the conductor target, allowing for a larger change in the output of the chip inductors as they pass over the conductor target. However, the multiple chip inductors may also be mounted on the main surface of the wiring board opposite to the rotor. In this case as well, although the wiring board is interposed, the distance from the multiple chip inductors to the conductor target will be approximately equal.

[0027] Alternatively, multiple chip inductors may be surface-mounted on one main surface of the wiring board and on the other main surface of the wiring board. By mounting chip inductors on both sides of the wiring board, the number of chip inductors can be increased, for example, by doubling the number of chip inductors. The more chip inductors there are, the greater the total number of turns, and therefore the greater the output. Also, the more chip inductors there are, the more the variations between chip inductors are averaged out, so the detection accuracy can be improved. Since the distance from multiple chip inductors to the conductor target is the same on both the main surface of the wiring board, the output of multiple chip inductors placed on each main surface can be made uniform, and complex signal processing is not required.

[0028] 2. The conductor targets are arranged along the rotational trajectory at a predetermined conductor target period, The inductive position detector according to item 1, wherein the chip inductor has a coil width of 25% to 75% of the period of the conductor target along the rotational trajectory.

[0029] In this configuration, the coil width along the rotational trajectory of the chip inductor is 25% to 75% (25% to 75%) of the conductor target period. This allows the chip inductor to output a good detection signal that changes as it passes over the conductor target. By using industrially produced small chip inductors, even if the number of conductor targets is increased to improve detection resolution and the conductor target period is shortened accordingly, a position detector for detecting rotational position can be constructed using a chip inductor with a coil width of 25% to 75% of the conductor target period. While a coil width of approximately 50% of the conductor target period is preferable for the chip inductor, good detection is possible within the range of 25% to 75%. Therefore, it is easy to select an applicable chip inductor from the standardized chip inductors available on the market. However, a coil width of 50% of the conductor target period is not necessarily an ideal condition. Optimal design conditions depend on factors such as the axial angle of the position detector, size, and rotor / stator gap.

[0030] 3. The conductor targets are arranged along the rotational trajectory at a predetermined conductor target period. The inductive position detector according to claim 1 or 2, wherein the plurality of chip inductors constitute a first phase group, a second phase group, a third phase group, and a fourth phase group, each including at least one first phase chip inductor, at least one second phase chip inductor, at least one third phase chip inductor, and at least one fourth phase chip inductor, arranged with a phase difference of one-quarter of a period with respect to the conductor target period.

[0031] The first-phase, second-phase, third-phase, and fourth-phase chip inductors have spatial phase differences of 90 degrees relative to the conductor target, allowing for the acquisition of detection signals to accurately determine the rotational position of the rotor.

[0032] Multiple chip inductors may or may not be arranged at equal intervals along the rotational path. Furthermore, multiple chip inductors may be arranged along the entire circumference of the rotational path, or there may be regions along the rotational path where chip inductors are arranged and regions where chip inductors are not.

[0033] 4.4N chip inductors (where N is a natural number) are arranged at equal intervals along the entire circumference of the rotational trajectory. An inductive position detector according to any one of terms 1 to 3, wherein the number of conductive targets Y (where Y is a natural number) is expressed as Y = 4NM ± N (where M is a natural number).

[0034] In this configuration, 4N chip inductors are arranged at equal intervals along the entire circumference of the circular orbit, while the number Y of conductor targets arranged at equal intervals along the circular orbit satisfies Y = 4NM ± N. Then, the 4N chip inductors can be classified into four groups (each group consisting of N chip inductors) whose spatial phase with respect to the conductor targets differs by 90 degrees. That is, they are classified into a first-phase group containing N first-phase chip inductors, a second-phase group containing N second-phase chip inductors, a third-phase group containing N third-phase chip inductors, and a fourth-phase group containing N fourth-phase chip inductors. Therefore, detection signals with a phase difference of 90 degrees can be obtained from the first-phase group, second-phase group, third-phase group, and fourth-phase group.

[0035] 5. A first set of the plurality of conductor targets and the plurality of chip inductors, whose rotational orbit is a first rotational orbit, and a second set of the plurality of conductor targets and the plurality of chip inductors, whose rotational orbit is a second rotational orbit different from the first rotational orbit, are provided sharing the stator and the rotor. An inductive position detector according to any one of items 1 to 4, wherein the number Y1 (where Y1 is a natural number) of the first set of multiple conductive targets and the number Y2 (where Y2 is a natural number) of the second set of multiple conductive targets are different from each other.

[0036] This configuration allows for the creation of a multi-track inductive position detector having a first rotational orbit and a second rotational orbit. By having a different number of conductive targets Y1 in the first set corresponding to the first rotational orbit and a different number of conductive targets Y2 in the second set corresponding to the second rotational orbit, rotational positions over a wide range of rotation angles can be distinguished and detected.

[0037] 6. The inductive position detector according to item 5, wherein the number Y1 of the first set of plurality of conductive targets and the number Y2 of the second set of plurality of conductive targets are relatively prime.

[0038] This configuration allows for the detection of distinct rotational positions over an even wider range of rotation angles. More specifically, it enables absolute detection, which distinguishes and detects rotational positions within a 360-degree rotation range.

[0039] 7. The inductive position detector according to item 5 or 6, further comprising an excitation coil provided on the wiring board of the stator and shared for inducing voltage in the first set of the plurality of chip inductors and the second set of the plurality of chip inductors.

[0040] This configuration simplifies the design because a common excitation coil can be used to excite the first and second sets of chip inductors.

[0041] 8. The inductive position detector according to item 7, wherein the excitation coil comprises an annular first excitation coil that encloses the first set of the plurality of chip inductors and the second set of the plurality of chip inductors when viewed along the axis of rotation, and an annular second excitation coil arranged around the axis of rotation so as to be enclosed by the first set of the plurality of chip inductors and the second set of the plurality of chip inductors when viewed along the axis of rotation.

[0042] This configuration allows the first and second sets of chip inductors to be sufficiently excited by the two excitation coils, one inside and one outside, thus enabling the acquisition of a large detection signal.

[0043] 9. The inductive position detector according to any one of claims 1 to 8, wherein each conductive target includes a conductive solid pattern or an annular coil conductive pattern formed on the non-conductive component, and the plurality of conductive targets are insulated from one another.

[0044] Typically, the plurality of conductive targets have equal lengths along the rotational trajectory, for example, a plurality of identically shaped and sized conductive targets arranged rotationally symmetrically around the axis of rotation. More typically, there is a gap between adjacent conductive targets along the rotational trajectory. This gap may be equal to the length of the conductive targets along the rotational trajectory.

[0045] 10. The inductive position detector according to any one of claims 1 to 8, wherein the plurality of conductive targets are connected to each other to form an annular coil conductor pattern around the entire circumference.

[0046] Thus, in one embodiment, a plurality of individual conductor targets, separated and arranged at equal intervals along the circumference around the axis of rotation, are held by a non-conductor component of the rotor, forming a periodic (geometrically periodic) conductor pattern. In another embodiment, a periodic (geometrically periodic) conductor pattern is formed such that an annular coil conductor pattern extending around the entire circumference of the axis of rotation constitutes a plurality of interconnected conductor targets.

[0047] Therefore, a conductor target refers to a conductor representing one period of a periodic (geometrically periodic) conductor pattern formed along the circumference around the axis of rotation. In one embodiment, this conductor is an individual conductor pattern, and in another embodiment, it is part of a continuous conductor pattern.

[0048] 11. The inductive position detector according to any one of items 1 to 10, wherein the chip inductor is a multilayer chip inductor having a pair of connecting electrodes at both ends.

[0049] By using multilayer chip inductors, it is possible to construct small detection coils with a large number of turns. This allows for a shorter period for the conductor targets to increase the number of conductor targets and improve detection resolution, which in turn limits the size of the chip inductor, while still enabling the acquisition of a detection signal of the required size from the chip inductor. In addition, it facilitates the design of a full-circumference arrangement where multiple chip inductors are placed around the entire circumference of the rotating orbit.

[0050] 12. An inductive position detector according to any one of claims 1 to 11, further comprising an excitation coil provided on the wiring board of the stator, formed in an annular shape enclosing the plurality of chip inductors when viewed along the axis of rotation, and generating a magnetic field for inducing a voltage in the plurality of chip inductors.

[0051] This configuration allows an AC voltage to be induced in the chip inductor by applying an AC voltage to the excitation coil. When a conductive target passes near the chip inductor, the eddy currents induced in the conductive target by the magnetic field from the excitation coil cancel out the magnetic field of the excitation coil. As a result, the voltage induced in the chip inductor fluctuates. In this way, the chip inductor outputs a detection signal that fluctuates in response to the passage of the conductive target.

[0052] 13. The inductive position detector according to any one of claims 1 to 12, wherein the plurality of chip inductors are connected to form an AC bridge circuit having a pair of AC voltage application terminals and a pair of signal detection terminals.

[0053] In this configuration, when an AC voltage is applied to the AC voltage application terminal of an AC bridge circuit in which chip inductors are bridged, a detection signal representing the change in impedance of the chip inductor appears at the signal detection terminal of the AC bridge circuit. Since most of the impedance of a chip inductor is inductance, the detection signal from the AC bridge circuit can be considered to represent a change in the inductance of the chip inductor. On the other hand, since the inductance of the chip inductor changes depending on its position relative to the conductor target, the change in inductance can be detected by the detection signal from the AC bridge circuit, and thereby the position of the conductor target can be detected. In other words, the rotational position of the rotor holding the conductor target with non-conductor components can be detected.

[0054] The above-mentioned, or further, objectives, features, and effects of the present invention will be made clearer by the following description of embodiments with reference to the accompanying drawings. [Brief explanation of the drawing]

[0055] [Figure 1] Figure 1 is an exploded perspective view illustrating the configuration of an inductive position detector according to a first embodiment of the present invention. [Figure 2] Figure 2 is a side view of the inductive position detector shown in Figure 1. [Figure 3] Figure 3 is a plan view showing the relative arrangement of the rotor's conductor target and the chip inductor placed on the stator. [Figure 4] Figure 4 is an electrical circuit diagram showing the equivalent circuit of the stator. [Figure 5] Figures 5A, 5B, and 5C are waveform diagrams showing examples of AC voltages generated by an excitation source and detection signals with a 90-degree phase difference. [Figure 6] Figure 6 is an exploded perspective view of an inductive position detector according to a second embodiment of the present invention. [Figure 7] Figure 7 is a plan view showing the relative arrangement of the rotor's conductor target and the chip inductor placed on the stator. [Figure 8] Figure 8 is an electrical circuit diagram showing the equivalent circuit of the stator. [Figure 9] Figure 9 is an exploded perspective view showing the configuration of an inductive position detector according to a third embodiment of the present invention. [Figure 10] Figure 10 is an electrical circuit diagram showing the equivalent circuit of the stator of the inductive position detector shown in Figure 9. [Figure 11] Figure 11 is an exploded perspective view illustrating the configuration of an inductive position detector according to a fourth embodiment of the present invention. [Figure 12] Figure 12 is a plan view showing the positional relationship between the rotor's conductor target and the chip inductor placed on the stator. [Figure 13] Figure 13 is an electrical circuit diagram showing the equivalent circuit of the stator. [Figure 14A] Figure 14A is a plan view showing an example configuration comprising a conductor target formed from a coil-shaped conductor pattern. [Figure 14B] Figure 14B is a plan view showing another configuration example that includes a conductor target formed with a coiled conductor pattern. [Figure 15] Figures 15A to 15E show examples of various conductive targets. [Figure 16] Figures 16A to 16D show examples of conductor target divisions in a continuous annular coil conductor pattern around its entire circumference. [Modes for carrying out the invention]

[0056] Hereinafter, embodiments of this invention will be described in detail with reference to the accompanying drawings.

[0057] Figure 1 is an exploded perspective view illustrating the configuration of an inductive position detector 100 according to the first embodiment of this invention. Figure 2 is a side view of the inductive position detector 100 as seen in the direction of arrow 101 in Figure 1.

[0058] The inductive position detector 100 includes a stator 1 and a rotor 2 that rotates relative to the stator 1 around a rotation axis 3a, and is configured to output a detection signal representing the relative rotational position of the rotor 2 with respect to the stator 1 around the rotation axis 3a. The rotor 2 is coupled to the rotation axis 3 (see Figure 2) of the object to be detected and rotates together with the rotation axis 3 around the rotation axis 3a. The stator 1 has a printed circuit board 10 (printed wiring board), which is a wiring board. The rotor 2 is composed of another printed circuit board 20 that is placed at a predetermined distance 4 (for example, 0.1 mm to 1 mm) from the printed circuit board 10.

[0059] The printed circuit board 10 of the stator 1 includes an insulating substrate 11 and a conductor pattern (e.g., a copper foil pattern) formed on at least one of the main surfaces 10a and 10b. The printed circuit board 10 may also be a multilayer printed circuit board having multiple stacked wiring layers (e.g., four wiring layers), in which case the wiring layers not exposed on the main surfaces 10a and 10b may have a conductor pattern.

[0060] Similarly, the printed circuit board 20 of the rotor 2 has an insulating substrate 21 which is a non-conductive component, and a plurality of conductor targets T which consist of a conductor pattern (e.g., a copper foil pattern) formed on one of the main surfaces 20a, 20b and thereby held by the insulating substrate 21. In this embodiment, the conductor targets T are formed on the main surface 20a opposite to the stator 1, but they may also be formed on the other main surface 20b facing the stator 1. Furthermore, when the printed circuit board 20 is a multilayer printed circuit board, the conductor targets T may be formed on internal wiring layers other than the main surfaces 20a, 20b. It is preferable that the conductor targets T be formed on the same wiring layer (including the main surface) of the printed circuit board 20. In order to shorten the distance to the chip inductors L1, L2, L3, L4 described later, it is preferable that the conductor targets T be formed on a wiring layer as close as possible to the stator 1 (e.g., the main surface 20b).

[0061] In Figures 1 and 2, the conductor target T is indicated by diagonal lines for clarity. The same applies to other drawings described later.

[0062] Figure 3 is a plan view of the insulating substrate 21 as seen through to the rotation axis 3a, showing the relative arrangement of the conductor target T and the chip inductors L1, L2, L3, and L4 (hereinafter collectively referred to as "chip inductors L") placed on the stator 1.

[0063] The conductor targets T are periodically arranged along the circumference around the rotation axis 3a and held on one main surface of the insulating substrate 21. As a result, the multiple conductor targets T form a conductor pattern with geometric periodicity along the circumferential direction around the rotation axis 3a. One conductor target T represents one period of this conductor pattern. The multiple conductor targets T move along the rotational orbit O (circumferential orbit) around the rotation axis 3a as the rotation of the rotation axis 3, and therefore the rotation of the rotor 2, progresses.

[0064] In this embodiment, multiple conductor targets T are arranged at equal intervals with a predetermined period (pitch) λ (hereinafter referred to as "conductor target period λ") around the entire circumference of the rotation axis 3a. In this embodiment, each conductor target T is a solid conductor pattern formed on one main surface of the insulating substrate 21, and the multiple conductor targets T are separated in the circumferential direction and insulated from each other. That is, each conductor target T is composed of individual conductor patterns (solid conductor patterns). The multiple conductor targets T have equal lengths (widths) along the rotation trajectory O. More specifically, in this embodiment, the multiple conductor targets T are composed of conductor patterns of the same shape and size and are arranged rotationally symmetrically around the rotation axis 3a. Even more specifically, each conductor target T is configured in a sector shape (more precisely, a sector with the inner diameter portion cut off) centered on the rotation axis 3a. In this illustrated example, the spacing along the rotational trajectory O between adjacent conductor targets T, i.e., the length of the non-conductor portion 23 along the rotational trajectory O, is equal to the length (width) of the conductor target T along the rotational trajectory O, but this is just one example. The length (width) of the conductor target T along the rotational trajectory O depends on the design of the inductive position detector 100, and for example, it may be optimal to be around 70% of the conductor target period λ.

[0065] Multiple chip inductors L are surface-mounted on one main surface 10a of the printed circuit board 10 that constitutes the stator 1. In this embodiment, the multiple chip inductors L are mounted on the main surface 10a facing the rotor 2, but they may also be mounted on the other main surface 10b opposite to the rotor 2. The multiple chip inductors L are arranged to face the rotational trajectory O of the conductor targets T, with different spatial phases relative to the conductor targets T. Thus, the multiple chip inductors L each constitute multiple detection coils that detect changes in the magnetic field as the conductor targets T pass by. The multiple chip inductors L are surface-mounted on the same main surface 10a of the printed circuit board 10, and therefore the distance from the rotor 2 (more specifically the distance from the conductor targets T) is substantially equal.

[0066] Multiple chip inductors L are typically industrially mass-produced and of the same specifications. Each chip inductor L has a coil width W along a rotating orbit O that is 25% to 75% (25% to 75%) of the conductor target period λ. While a coil width W of approximately 50% of the conductor target period λ is preferable, good detection is possible within the range of 25% to 75%. Therefore, it is sufficient to select a standardized chip inductor available on the market that has a coil width in the range of 25% to 75% of the conductor target period λ.

[0067] A multilayer chip inductor having a pair of connecting electrodes 31, 32 (see Figure 1) at both ends can be used for the chip inductor L. An example of a multilayer chip inductor is described, for example, in Patent Document 5. By using a multilayer chip inductor, a small detection coil with a large number of turns can be constructed. As a result, even if the conductor target period λ is shortened in order to increase the number of conductor targets T and improve the detection resolution, a detection signal of the required size can be obtained from the chip inductor L.

[0068] The chip inductor L typically has a rectangular parallelepiped shape with the longitudinal direction being the direction in which the connecting electrodes 31 and 32 face each other. When the chip inductor L is surface-mounted on the printed circuit board 10 with the coil central axis direction (direction of the winding's central axis) set perpendicular to the main surface 10a of the printed circuit board 10, its length in the short direction is substantially equal to the coil width W of the built-in coil. In this embodiment, the chip inductor L is mounted on the printed circuit board 10 with its longitudinal direction aligned with the radial direction of the rotational orbit O, but its longitudinal direction does not necessarily need to be aligned with the radial direction of the rotational orbit O.

[0069] In this embodiment, multiple chip inductors L are arranged at equal intervals along the rotational trajectory O, around the entire circumference of the rotational axis 3a. In this embodiment, four chip inductors L are arranged at 90-degree angular intervals on the circumference around the rotational axis 3a. These chip inductors L are the first-phase chip inductor L1 (first-phase group), the second-phase chip inductor L2 (second-phase group), the third-phase chip inductor L3 (third-phase group), and the fourth-phase chip inductor L4 (fourth-phase group), arranged with a phase difference of one-quarter of a conductor target period λ.

[0070] In this embodiment, five conductor targets T are arranged on a circle around the rotation axis 3a with a conductor target period λ of 72 degrees, and this conductor target period λ corresponds to one period of the electrical angle, i.e., 360 degrees. The four chip inductors L are arranged with a period p (pitch) of 90 degrees (hereinafter referred to as "chip inductor period p"), ​​so the difference between the conductor target period λ and the chip inductor period p is 18 (=90-72) degrees. 18 (=72 / 4) degrees corresponds to one-quarter of the conductor target period λ (72 degrees).

[0071] Therefore, two chip inductors L positioned at a 90-degree mechanical angle will have a phase difference of 90 degrees electrically, i.e., one-quarter of the conductor target period λ. Specifically, the second-phase chip inductor L2 has a 90-degree phase difference with respect to the first-phase chip inductor L1. Similarly, the third-phase chip inductor L3 has a 90-degree phase difference with respect to the second-phase chip inductor L2, and the fourth-phase chip inductor L4 has a 90-degree phase difference with respect to the third-phase chip inductor L3. Therefore, the third-phase chip inductor L3 has a 180-degree phase difference with respect to the first-phase chip inductor L1, and these are out of phase with respect to each other. Similarly, the fourth-phase chip inductor L4 has a 180-degree phase difference with respect to the second-phase chip inductor L2, and these are out of phase with respect to each other.

[0072] Each chip inductor L is surface-mounted on the printed circuit board 10 with its coil center axis parallel to the rotation axis 3a. Therefore, when the magnetic field in the direction of the coil center axis, i.e., parallel to the rotation axis 3a, changes, the chip inductor L generates an induced voltage corresponding to that change in the magnetic field.

[0073] An excitation coil 12 is provided on the printed circuit board 10 that constitutes the stator 1. In a plan view along the rotation axis 3a (see Figure 2), the excitation coil 12 is formed in an annular shape that encloses a plurality of chip inductors L. That is, the direction of the coil center axis of the excitation coil 12 is parallel to the rotation axis 3a. In this embodiment, in the same plan view, the excitation coil 12 is formed in an annular shape that encloses a plurality of conductor targets T. In this embodiment, in the same plan view, the excitation coil 12 is substantially annular. Specifically, the excitation coil 12 is a pattern coil composed of spiral-shaped conductor patterns formed on the printed circuit board 10, and the entire structure is annular (annular in this embodiment). The printed circuit board 10 may be, for example, a laminated printed circuit board with multiple wiring layers stacked on top of each other. In this case, a pattern coil may be formed on each of the multiple wiring layers (for example, four layers) with a spiral-shaped conductor pattern, and these pattern coils may be connected by vias connecting the wiring layers to form the excitation coil 12.

[0074] An excitation source 5 that generates an AC voltage is connected to the lead-out portions 12a and 12b of the excitation coil 12. When an AC voltage is applied to the excitation coil 12 from the excitation source 5, the excitation coil 12 generates a high-frequency magnetic field that reverses direction at the frequency of the AC voltage along a direction parallel to the rotation axis 3a. This high-frequency magnetic field links with the chip inductor L, causing an induced electromotive force to be generated in the chip inductor L.

[0075] Although not shown in the diagram, the printed circuit board 10 of the stator 1 has a conductive pattern (more specifically, a copper foil pattern) formed thereon for connecting a chip inductor L to form a detection circuit.

[0076] Figure 4 shows the equivalent circuit of stator 1. The first-phase chip inductor L1 generates an A-phase detection signal, and the third-phase chip inductor L3 generates an A-phase detection signal with the opposite phase. Therefore, the same polarity terminals of the first-phase chip inductor L1 and the third-phase chip inductor L3 are connected (differential connection) to form an A-phase detection circuit 6 that outputs their differential signals as a detection signal VA. The second-phase chip inductor L2 generates a B-phase detection signal that is 90 degrees out of phase with respect to the A-phase detection signal. The fourth-phase chip inductor L4 generates an A-phase detection signal with the opposite phase to the B-phase detection signal. Therefore, the same polarity terminals of the second-phase chip inductor L2 and the fourth-phase chip inductor L4 are connected (differential connection) to form a B-phase detection circuit 7 that outputs their differential signals as a detection signal VB.

[0077] As described above, when an AC voltage (Asinωt, where A is a constant representing amplitude, ω is angular frequency, and t is time) is applied from the excitation source 5 to the excitation coil 12, detection signals VA and VB are generated from the A-phase detection circuit 6 and the B-phase detection circuit 7, respectively, in accordance with the change in the flux linkage between the high-frequency magnetic field generated by the excitation coil 12 and the chip inductor L. The high-frequency magnetic field generated by the excitation coil 12 induces eddy currents in the conductor target T. These eddy currents generate a magnetic field in the opposite direction to the magnetic field generated by the excitation coil 12. Therefore, when the conductor target T faces the chip inductor L, the voltage induced in the chip inductor L decreases. By utilizing this phenomenon and appropriately processing the detection signals VA and VB with the signal processing circuit 8, rotational position information can be obtained.

[0078] Let C be the fixed component and V be the variable component of the voltage induced in the chip inductor L. The phase is defined as positive when the conductor target T moves clockwise (CW), with chip inductor L1 in Figure 3 as the reference. Then, the voltages V induced in each chip inductor L1, L2, L3, L4 at the rotation angle θ are... L1 ,V L2 ,V L3 ,V L4 The following applies, where K represents the amplitude of the induced AC voltage. VL1 =Ksinωt·{C + V·sin(θ + 0)} = Ksinωt·(C + V·sinθ) …(1) V L2 =Ksinωt·{C + V·sin(θ + 90)} = Ksinωt·(C + V·cosθ) …(2) V L3 =Ksinωt·{C + V·sin(θ + 180)} = Ksinωt·(C - V·sinθ) …(3) V L4 =Ksinωt·{C + V·sin(θ + 270)} = Ksinωt·(C - V·cosθ) …(4)

[0079] Since the chip inductors L1 and L3, and the chip inductors L2, L4 are differentially connected respectively, the detection signals VA, VB are as follows. VA = V L1 -V L3 =Ksinωt·(C + V·sinθ) - Ksinωt·(C - V·sinθ) =2V·Ksinωt·sinθ …(5) VB = V L2 -V L4 =Ksinωt(C + V·cosθ) - Ksinωt(C - V·cosθ) =2V·Ksinωt·cosθ …(6)

[0080] Fig. 5A shows an example of the waveform of the AC voltage generated by the excitation source 5, and Figs. 5B and 5C show examples of the waveforms of the detection signals VA, VB. Thus, the detection signals VA, VB output by the detection circuits 6, 7 are signals in which a high-frequency signal is amplitude-modulated based on the change in the induced voltage caused by the rotation of the rotor 2. Since the chip inductors L1, L3 constituting the A-phase detection circuit 6 and the chip inductors L2, L4 constituting the B-phase detection circuit 7 are arranged on the stator 1 at an interval of 90 degrees, the detection signals VA, VB are signals having a phase difference of 90 degrees from each other. Therefore, by demodulating the detection signals VA, VB with the signal processing circuit 8 and performing an arctangent calculation, the rotation angle θ of the rotor 2 can be obtained.

[0081] Figure 6 is an exploded perspective view of the inductive position detector 200 according to the second embodiment of this invention. Figure 7 is a plan view of the inductive position detector 200 as seen along the rotation axis 3a, showing the relationship between the arrangement of the conductor target T and the chip inductor L by looking through the insulating substrate 21 of the rotor 2. Furthermore, Figure 8 is an equivalent circuit diagram showing the electrical configuration of the stator 1. In these drawings, the corresponding parts shown in Figures 1 to 4 above are indicated by the same reference numerals.

[0082] In this embodiment, the number of conductor targets T and the number of chip inductors L are doubled compared to the first embodiment. In other words, the conductor target period λ (36 degrees) and the chip inductor period p (45 degrees) are each half of those in the first embodiment. When the spatial phase with respect to the conductor targets T is examined, it can be seen that the phases of the chip inductors L, which are 180 degrees apart around the rotation axis 3a, are equivalent. In other words, the multiple chip inductors L can be classified into a first-phase group G1 (A-phase) consisting of a pair of first-phase chip inductors L1(1) and L1(2) facing each other across the rotation axis 3a, a second-phase group G2 (B-phase) consisting of another pair of second-phase chip inductors L2(1) and L2(2) facing each other across the rotation axis 3a, a third-phase group G3 (A-phase) consisting of yet another pair of third-phase chip inductors L3(1) and L3(2) facing each other across the rotation axis 3a, and a fourth-phase group G4 (B-phase) consisting of yet another pair of fourth-phase chip inductors L4(1) and L4(2) facing each other across the rotation axis 3a. Furthermore, the first-phase chip inductors L1(1), L1(2), the second-phase chip inductors L2(1), L2(2), the third-phase chip inductors L3(1), L3(2), and the fourth-phase chip inductors L4(1), L4(2) are spatially phase-shifted around the rotation axis 3a by one-quarter of the conductor target period λ.

[0083] Therefore, a pair of first-phase chip inductors L1(1), L1(2) and a pair of third-phase chip inductors L3(1), L3(2) are differentially connected in series to form an A-phase detection circuit 6, and a pair of second-phase chip inductors L2(1), L2(2) and a pair of fourth-phase chip inductors L4(1), L4(2) are differentially connected in series to form a B-phase detection circuit 7. The A-phase detection circuit 6 and the B-phase detection circuit 7 output amplitude-modulated detection signals VA and VB that are 90 degrees out of phase, similar to the first embodiment. However, since the conductor target period λ, which corresponds to 360 degrees in electrical angle, corresponds to 36 (=360 / 10) degrees in mechanical angle, the rotational position can be detected with twice the resolution compared to the first embodiment.

[0084] Although not shown in the diagram, the printed circuit board 10 of the stator 1 has a conductive pattern (more specifically, a copper foil pattern) formed thereon for connecting a chip inductor L to form detection circuits 6 and 7.

[0085] Let C be the fixed component and V be the variable component of the voltage induced in the chip inductor L. The phase is defined as positive when the conductor target T moves clockwise (CW), with chip inductor L1(1) as the reference. Then, the voltage V induced in each chip inductor L1(1), L2(1), L3(1), L4(1), L1(2), L2(2), L3(2), L4(2) at the rotation angle θ is... L1(1) ,V L2(1) ,V L3(1) ,V L4(1) ,V L1(2) ,V L2(2) ,V L3(2) ,V L4(2) The following applies, where K represents the amplitude of the induced AC voltage. V L1(1) =Ksinωt·{C+V·sin(θ+0)}=Ksinωt·(C+V·sinθ) …(7) V L2(1) =Ksinωt·{C+V·sin(θ+90)}=Ksinωt·(C+V·cosθ) …(8) V L3(1)=Xinωt·{C+V·sin(θ+180)}=Ksinωt·(CV·sinθ) …(9) V L4(1) =Ksinωt·{C+V·sin(θ+270)}=Ksinωt·(CV·cosθ)…(10) V L1(2) =Xinωt·{C+V·sin(θ+0)}=Ksinωt·(C+V·sinθ) …(11) V L2(2) =Ksinωt·{C+V·sin(θ+90)}=Ksinωt·(C+V·cosθ) …(12) V L3(2) =Ksinωt·{C+V·sin(θ+180)}=Ksinωt·(CV·sinθ)…(13) V L4(2) =Ksinωt·{C+V·sin(θ+270)}=Ksinωt·(CV·cosθ)…(14)

[0086] L1(1), L1(2), L3(1), L3(2), L2(1), L2(1) 2) L4(1),L4(2) WA, VB, VA, VB, WA, VB, and WA. VA=V L1(1) +V L1(2) -V L3(1) -V L3(2) =2Ksinωt·(C+V·sinθ)-2Ksinωt·(CV·sinθ) =4V·Ksinωt·sinθ …(15) VB=V L2(1) +V L2(2) -V L4(1) -V L4(2) =2Ksinωt(C+V·cosθ)-2Ksinωt(CV·cosθ) =4V·Ksinωt·cosθ …(16)

[0087] Thus, in the second embodiment, by increasing the number of chip inductors L, fluctuations in the detection signals VA and VB can be detected more significantly, thereby improving the signal-to-noise ratio (S / N ratio). Furthermore, chip inductors L positioned opposite each other at a mechanical angle of 180 degrees detect signals in phase. This reduces the influence of errors such as the eccentricity of the stator 1 relative to the rotation axis 3 and the inclination of the rotor 2 relative to the stator plane on the detection signal, thereby improving detection accuracy.

[0088] When Y conductive targets T (where Y is a natural number) are placed on rotor 2 and 4N chip inductors L (where N is a natural number) are placed at equal intervals on stator 1, we consider the arrangement conditions for the chip inductors L to construct two detection circuits 6 and 7 that generate detection signals VA and VB with a phase difference of 90 degrees in electrical angle.

[0089] The relationship between the conductor target period λ and the chip inductor period p when they have a phase difference of λ / 4 (one-quarter of the conductor target period λ) is given by equation (17) below, where M is a natural number. p = λ(M ± 1 / 4) …(17)

[0090] The conductor target period λ and the chip inductor period p are expressed by equations (18) and (19), respectively, using the circumference Cl of the rotating orbit O through which the conductor target T passes. λ = Cl / Y …(18) p = Cl / 4N …(19)

[0091] Substituting equations (18) and (19) into equation (7) and rearranging it, we obtain equation (20). Therefore, if there is a combination of natural numbers Y, N, and M that satisfies the relationship in equation (20), then detection signals with a phase difference of 90 degrees in electrical angle can be detected from detection circuits 6 and 7. Y = 4 NM ± N …(20)

[0092] The first embodiment corresponds to the case where N=1, M=1, and Y=5. The second embodiment corresponds to the case where N=2, M=1, and Y=10.

[0093] Thus, according to the first and second embodiments, two detection circuits 6 and 7 can be configured using multiple chip inductors L to generate two detection signals VA and VB with a 90-degree phase difference. Based on these detection signals VA and VB, the rotational position of the rotor 2, i.e., the rotational position (rotation angle) of the rotation axis 3, can be detected.

[0094] Chip inductors L are small electrical components that can have a large number of turns and are readily available at low cost in the market. Therefore, when increasing the number of poles by increasing the number of conductor targets T to improve detection resolution, it is possible to arrange them to correspond to a small conductor target period λ, without the detection signal becoming too small or requiring excessive costs. In addition, by mounting multiple chip inductors L on one main surface 10a of the printed circuit board 10 of the stator 1, i.e., on the same main surface, the distance to the conductor targets T can be made uniform. Furthermore, the performance of industrially mass-produced chip inductors L is highly uniform. Therefore, a uniform detection signal can be obtained from multiple chip inductors L, eliminating the need for complex signal processing.

[0095] In the first and second embodiments, multiple chip inductors L are surface-mounted on the main surface 10a of the printed circuit board 10 facing the rotor 2, so that the insulating substrate 11 of the printed circuit board 10 on the stator 1 side is not interposed between the multiple chip inductors L and the conductor target T. As a result, the distance between the multiple chip inductors L and the conductor target T is short, so that signals with large amplitude fluctuations can be extracted from each chip inductor L as they pass over the conductor target T.

[0096] Furthermore, unlike configurations in which multiple detection coils are formed on a silicon substrate using a semiconductor manufacturing process, the multiple chip inductors L, which are individual elements, can be placed at any position facing the rotational orbit O, thus offering a high degree of freedom in placement. Therefore, as in the first and second embodiments, it is also possible to arrange them so that they are distributed around the entire circumference of the rotational orbit O. Such a full-circumference arrangement makes it easy to accommodate misalignment of the rotational shaft 3 coupled to the rotor 2. Specifically, if the rotational shaft 3 is the end of the motor shaft of an electric motor that is not on the output shaft side, even if the axis of the rotational shaft 3 is misaligned due to radial load on the motor shaft, the offset of the detection position can be avoided with simple signal processing.

[0097] In particular, by using a multilayer chip inductor as the chip inductor L, the chip inductor L can be made small and have many windings. Therefore, even when designing to increase resolution by reducing the conductor target period λ, the chip inductor L can be arranged along the entire circumference of the rotational orbit O.

[0098] Furthermore, in the first and second embodiments, the conductor target T is positioned along the rotating orbit O with a predetermined conductor target period λ. The chip inductor L has a coil width W along the rotating orbit O that is 25% to 75% (25% or more and 75% or less) of the conductor target period λ.

[0099] More specifically, in the first embodiment, the coil width W of the chip inductor L is approximately 25% of the conductor target period λ. In the second embodiment, the coil width W of the chip inductor L is approximately 50% of the conductor target period λ. If the number of conductor targets T on the rotor 2 is increased compared to the second embodiment, the ratio of the coil width W of the chip inductor L to the conductor target period λ increases, and if this ratio is up to approximately 75%, a waveform signal that can accurately detect the rotational position can be obtained. By using industrially produced small chip inductors L, even if the number of conductor targets T is increased to improve detection resolution and the conductor target period λ is shortened accordingly, a small rotational position detector can be constructed using chip inductors L with a coil width W of 25% to 75% of the conductor target period λ.

[0100] Furthermore, good detection is possible if the coil width W of the chip inductor L is within the range of 25% to 75% of the conductor target period λ. Therefore, it is easy to select an applicable chip inductor from the standardized chip inductors available on the market.

[0101] In the first and second embodiments, the multiple chip inductors L arranged on the stator 1 constitute a first phase group, a second phase group, a third phase group, and a fourth phase group, each including at least one first phase chip inductor L1, at least one second phase chip inductor L2, at least one third phase chip inductor L3, and at least one fourth phase chip inductor L4, which are arranged with a phase difference of one-quarter of a period with respect to the conductor target period λ. Since the first phase chip inductor L1 (chip inductor of the first phase group), the second phase chip inductor L2 (chip inductor of the second phase group), the third phase chip inductor L3 (chip inductor of the third phase group), and the fourth phase chip inductor L4 (chip inductor of the fourth phase group) have spatial phase differences of 90 degrees with respect to the conductor target T, a detection signal for accurately detecting the rotational position of the rotor 2 can be obtained from them.

[0102] In particular, in the first and second embodiments, a detection circuit 6 is configured by differentially connecting a first-phase chip inductor L1 and a third-phase chip inductor L3, which have a spatial phase difference of 180 degrees, and similarly, a detection circuit 7 is configured by differentially connecting a second-phase chip inductor L2 and a fourth-phase chip inductor L4, which also have a spatial phase difference of 180 degrees. As a result, detection signals VA and VB with large amplitudes and a 90-degree phase difference are obtained from the two detection circuits 6 and 7. Moreover, since noise components that appear in common in multiple chip inductors L due to disturbances are removed by the differential connection, the detection signals VA and VB accurately represent the position of the conductor target T. Disturbances include external magnetic fields and variations in the distance between the stator 1 and rotor 2 (manufacturing variations).

[0103] In the second embodiment, multiple first-phase chip inductors L1, second-phase chip inductors L2, third-phase chip inductors L3, and fourth-phase chip inductors L4 are provided, and chip inductors L of the same phase are connected in series. This makes it possible to obtain detection signals VA and VB with large amplitudes, and improve the signal-to-noise ratio.

[0104] As described above, by arranging Y conductor targets T and 4N chip inductors L that satisfy equation (20) at equal intervals around the entire circumference of the rotation axis 3a, the 4N chip inductors L can be classified into four phase groups (each phase group consists of N chip inductors L) whose spatial phase with respect to the conductor target T differs by 90 degrees. Specifically, they are classified into a first phase group G1 containing N first phase chip inductors L1, a second phase group G2 containing N second phase chip inductors L2, a third phase group G3 containing N third phase chip inductors L3, and a fourth phase group G4 containing N fourth phase chip inductors L4. Then, by differentially connecting the chip inductors L1 and L3 of the first phase group G1 and the third phase group G3, and differentially connecting the chip inductors L2 and L4 of the second phase group G2 and the fourth phase group G4, detection circuits 6 and 7 that output detection signals VA and VB with a phase difference of 90 degrees can be constructed.

[0105] Figure 9 is an exploded perspective view showing the configuration of an inductive position detector 300 according to a third embodiment of the present invention. Figure 10 is an electrical circuit diagram showing the equivalent circuit on the stator 1 side. In Figures 9 and 10, the corresponding parts of the second embodiment described above are indicated by the same reference numerals.

[0106] This embodiment differs from the second embodiment in that the stator 1 is not equipped with an excitation coil.

[0107] Multiple chip inductors L are bridge-connected to form an AC bridge circuit. More specifically, an A-phase AC bridge circuit 60 and a B-phase AC bridge circuit 70 are configured. That is, although not shown in the diagram, the printed circuit board 10 of the stator 1 has conductor patterns (more specifically, copper foil patterns) formed on it for connecting the chip inductors L to form the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70.

[0108] The A-phase AC bridge circuit 60 is constructed by bridging the first-phase chip inductors L1(1) and L1(2) with the third-phase chip inductors L3(1) and L3(2), which have a phase difference of 180 degrees relative to them. The first-phase chip inductors L1(1) and L1(2) are arranged on opposite sides of the A-phase AC bridge circuit 60, respectively, and the third-phase chip inductors L3(1) and L3(2) are arranged on the other opposite sides of the A-phase AC bridge circuit 60, respectively. The connection point between the first-phase chip inductor L1(1) and the third-phase chip inductor L3(2) is the first A-phase AC voltage application terminal 61, and the connection point between the third-phase chip inductor L3(1) and the first-phase chip inductor L1(2) is the second A-phase AC voltage application terminal 62. The midpoint between the first phase chip inductor L1(1) and the third phase chip inductor L3(1) is the first A phase signal detection terminal 63, and the midpoint between the third phase chip inductor L3(2) and the first phase chip inductor L1(2) is the second A phase signal detection terminal 64.

[0109] The B-phase AC bridge circuit 70 is constructed by bridging the second-phase chip inductors L2(1) and L2(2) with the fourth-phase chip inductors L4(1) and L4(2), which have a phase difference of 180 degrees relative to them. The second-phase chip inductors L2(1) and L2(2) are arranged on opposite sides of the B-phase AC bridge circuit 70, respectively, and the fourth-phase chip inductors L4(1) and L4(2) are arranged on the other opposite sides of the B-phase AC bridge circuit 70, respectively. The connection point between the second-phase chip inductor L2(1) and the fourth-phase chip inductor L4(2) is the first B-phase AC voltage application terminal 71, and the connection point between the fourth-phase chip inductor L4(1) and the second-phase chip inductor L2(2) is the second B-phase AC voltage application terminal 72. The midpoint between the second-phase chip inductor L2(1) and the fourth-phase chip inductor L4(1) is the first B-phase signal detection terminal 73, and the midpoint between the fourth-phase chip inductor L4(2) and the second-phase chip inductor L2(2) is the second B-phase signal detection terminal 74.

[0110] AC voltages are applied from the excitation source 5 to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70. The excitation source 5 includes a first excitation source 51 that generates a first AC voltage (Asinωt) and a second excitation source 52 that generates a second AC voltage (-Asinωt) which has the phase inverted from the first AC voltage. The first A-phase AC voltage application terminal 61 is connected to the first excitation source 51 and the first AC voltage (Asinωt) is applied. The second A-phase AC voltage application terminal 62 The first B-phase AC voltage application terminal 71 is connected to the first excitation source 51 and the first AC voltage (Asinωt) is applied to it. The second B-phase AC voltage application terminal 72 is connected to the second excitation source 52 and the second AC voltage (-Asinωt) is applied to it. The voltage appearing between the first A-phase signal detection terminal 63 and the second A-phase signal detection terminal 64 is detected as the detection signal VA. The voltage appearing between the first B-phase signal detection terminal 73 and the second B-phase signal detection terminal 74 is detected as the detection signal VB.

[0111] In this embodiment, AC voltage is applied to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70 from a common excitation source 5, but it is also acceptable to configure the system so that AC voltage is applied to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70 from individual excitation sources 5.

[0112] When a conductor target T faces a chip inductor L, the magnetic flux of the chip inductor L is blocked by the conductor target T, and the inductance of the chip inductor L decreases. This property is utilized in this embodiment; instead of using an excitation coil, the rotation angle is detected from the change in inductance of the chip inductor L caused by the rotation of the rotor 2.

[0113] The change in inductance of the chip inductors L1(1), L2(1), L3(1), L4(1), L1(2), L2(2), L3(2), and L4(2) can be expressed as follows, where LC is the fixed component and LV is the variable component. L1(1):LC + LV·sin(θ+0)= LC + LV·sinθ …(21) L2(1):LC + LV·sin(θ+90)= LC + LV·cosθ …(22) L3(1):LC + LV·sin(θ+180)= LC - LV·sinθ …(23) L4(1):LC + LV·sin(θ+270)= LC - LV·cosθ …(24) L1(2):LC + LV·sin(θ+0)= LC + LV·sinθ …(25) L2(2):LC + LV·sin(θ+90)= LC + LV·cosθ …(26) L3(2):LC + LV·sin(θ+180)= LC - LV·sinθ …(27) L4(2):LC + LV·sin(θ+270)= LC - LV·cosθ …(28)

[0114] Therefore, the output signals from the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70, i.e., the detection signals VA and VB, are given by equations (29) and (30), respectively, where k is a constant representing the amplitude. VA={L1(2) / (L1(2)+L3(2)) - L3(1) / (L1(1)+L3(1))}·(2ksinωt-ksinωt) =LV / LC·ksinωt·sinθ …(29) VB={L2(2) / (L2(2)+L4(2)) - L4(1) / (L2(1)+L4(1))}·(2ksinωt-ksinωt) =LV / LC·ksinωt·cosθ …(30) The AC bridge circuits 60 and 70 detect changes in the impedance of the chip inductor L due to changes in its positional relationship with the conductor target T. The impedance of the chip inductor L includes a small DC resistance component in addition to the inductance component, but since the inductance component is dominant, the DC resistance component can be practically ignored. Therefore, the AC bridge circuits 60 and 70 can detect changes in the inductance of the chip inductor L due to changes in its positional relationship with the conductor target T.

[0115] The detection signals VA and VB, represented by equations (29) and (30), are signals that change according to the rotational position of the conductor target T and have a phase shift of 90 degrees. As is clear from the comparison with equations (5) and (6) above, the detection signals VA and VB will have waveforms similar to those shown in Figures 5B and 5C, respectively, depending on the rotational position of the conductor target T. Therefore, the rotational position of the rotor 2 can be detected, similar to the first and second embodiments described above. Thus, a position detector capable of detecting the position of the rotor 2 can be constructed without an excitation coil.

[0116] Figure 11 is an exploded perspective view illustrating the configuration of an inductive position detector 400 according to a fourth embodiment of the present invention. Figure 12 is a plan view of the inductive position detector 400 as seen along the rotation axis 3a, showing the positional relationship between the conductor target T and the chip inductor L by looking through the insulating substrate 21 of the rotor 2. In these drawings, corresponding parts of the first and second embodiments are denoted by the same reference numerals.

[0117] The position detector 400 has a multi-track configuration in which it has multiple rotational orbits O1 and O2 (see Figure 12) around the rotation axis 3a and detects the rotational position in each rotational orbit O1 and O2. Specifically, the position detector 400 in this embodiment has a two-track configuration in which it has a concentric first rotational orbit O1 and a second rotational orbit O2 around the rotation axis 3a. The first rotational orbit O1 is located inside the second rotational orbit O2 and forms a circumference with a smaller diameter than the second rotational orbit O2. On one main surface 20a of the printed circuit board 20 of the rotor 2 (in this embodiment, the main surface opposite to the stator 1), multiple conductive targets T1 are arranged at equal intervals around the entire circumference along the first rotational orbit O1, and multiple conductive targets T2 are arranged at equal intervals around the entire circumference along the second rotational orbit O2. On one main surface 10a of the printed circuit board 10 of the stator 1 (in this embodiment, the main surface facing the rotor 2), a plurality of chip inductors L1 are arranged at equal intervals around the entire circumference along the first rotational trajectory O1, and a plurality of chip inductors L2 are arranged at equal intervals around the entire circumference along the second rotational trajectory O2.

[0118] Multiple chip inductors L1 arranged along the first rotational orbit O1 can be classified into four groups based on their spatial phase with respect to the conductor target T1: the first phase group (A phase) consisting of the first phase chip inductors L11(1) and L11(2), the second phase group (B phase) consisting of the second phase chip inductors L12(1) and L12(2), the third phase group (A phase) consisting of the third phase chip inductors L13(1) and L13(2), and the fourth phase group (B phase) consisting of the fourth phase chip inductors L14(1) and L14(2). The first phase chip inductors L11(1) and L11(2), the second phase chip inductors L12(1) and L12(2), the third phase chip inductors L13(1) and L13(2), and the fourth phase chip inductors L14(1) and L14(2) are spatially phase-shifted around the rotational axis 3a by one-quarter of the conductor target period λ each.

[0119] Similarly, the multiple chip inductors L2 arranged along the second rotational orbit O2 can be classified into a first-phase group (A-phase) consisting of first-phase chip inductors L21(1), L21(2), L21(3), a second-phase group (B-phase) consisting of second-phase chip inductors L22(1), L22(2), L22(3), a third-phase group (A-phase) consisting of third-phase chip inductors L23(1), L23(2), L23(3), and a fourth-phase group (B-phase) consisting of fourth-phase chip inductors L24(1), L24(2), L24(3). Furthermore, the first-phase chip inductors L21(1), L21(2), L21(3), the second-phase chip inductors L22(1), L22(2), L22(3), the third-phase chip inductors L23(1), L23(2), L23(3), and the fourth-phase chip inductors L24(1), L24(2), L24(3) are spatially phase-shifted around the rotation axis 3a by one-quarter of the conductor target period λ.

[0120] Multiple conductor targets T1 and multiple chip inductors L1 arranged along the first rotational orbit O1 constitute the first set S1, which faces each other. Similarly, multiple conductor targets T2 and multiple chip inductors L2 arranged along the second rotational orbit O2 constitute the second set S2, which faces each other. The first set S1 and the second set S2 share the rotor 2 and the stator 1.

[0121] The number Y1 of multiple conductor targets T1 in the first set S1 and the number Y2 of conductor targets T2 in the second set S2 are different from each other. The number Y1 of conductor targets T1 and the number 4N1 of chip inductors L1 in the first set S1 satisfy equation (20) above, and therefore satisfies equation (31). Similarly, the number Y2 of conductor targets T2 and the number 4N2 of chip inductors L2 in the second set S2 satisfy equation (20) above, and therefore satisfies equation (32). Y1 = 4N1M1 ± N1 (where Y1, N1, and M1 are natural numbers) ... (31) Y2 = 4N2M2 ± N2 (where Y2, N2, and M2 are natural numbers) ... (32)

[0122] The examples shown in Figures 11 and 12 correspond to the case where Y1=14, N1=2, M1=2, Y2=15, N2=3, and M2=1.

[0123] By having different numbers Y1 for the multiple conductor targets T1 in the first set S1 and Y2 for the multiple conductor targets T2 in the second set S2, it becomes possible to distinguish and detect rotational positions over a wide range of rotation angles. In particular, if the number Y1 for the multiple conductor targets T1 in the first set S1 and the number Y2 for the multiple conductor targets T2 in the second set S2 are relatively prime, it becomes possible to perform one-rotation absolute detection, which distinguishes and detects rotational positions within a range of one rotation (360 degrees).

[0124] In this example, the multiple chip inductors L1 constituting the first set S1 and the multiple chip inductors L2 constituting the second set S2 are all chip inductors of the same specifications and are identical in shape and size when viewed in a plan view along the rotation axis 3a.

[0125] In the illustrated example, each chip inductor L is positioned so that its longitudinal direction aligns with the radial direction of rotation around the rotation axis 3a. The longitudinal direction of the chip inductor L is typically the direction in which the pair of connecting electrodes 31 and 32 face each other. In the illustrated example, the ratio of the coil width W1 of the chip inductor L1 to the pitch (conductor target period λ1) of the multiple conductor targets T1 constituting the first set S1 is approximately 25%. On the other hand, the ratio of the coil width W2 of the chip inductor L2 to the pitch (conductor target period λ2) of the multiple conductor targets T2 constituting the second set S2 is 50%. Of course, these are just examples, and in each of the first set S1 and the second set S2, the conductor targets T1 and T2 should be designed and the chip inductors L1 and L2 selected and their arrangement determined so that the ratio of the coil widths W1 and W2 to the conductor target periods λ1 and λ2 is between 25% and 75%.

[0126] It is not necessary to use chip inductors of the same specifications for the first group S1 and the second group S2. Multiple chip inductors L1 in the first group S1 may be of the same specifications, while multiple chip inductors L2 in the second group S2 may be of different but identical specifications.

[0127] The printed circuit board 10 of the stator 1 is provided with an excitation coil 12 that is shared to induce voltage in a plurality of chip inductors L1 of the first set S1 and a plurality of chip inductors L2 of the second set S2. In this embodiment, the excitation coil 12 includes a first excitation coil 121 and a second excitation coil 122. These are made up of conductor patterns formed on the printed circuit board 10. The first excitation coil 121 is configured in an annular shape (circular in the illustrated example) that encloses the plurality of chip inductors L1 of the first set S1 and the plurality of chip inductors L2 of the second set S2 in a plan view along the rotation axis 3a. On the other hand, the second excitation coil 122 is configured in an annular shape (circular in the illustrated example) around the rotation axis 3a so as to be enclosed in the plurality of conductor targets T1 of the first set S1 and the plurality of conductor targets T2 of the second set S2 in a plan view along the rotation axis 3a. In other words, the first excitation coil 121 is positioned on the outer circumference side of the multiple chip inductors L1 and L2 of the first set S1 and the second set S2, while the second excitation coil 122 is positioned on the inner circumference side of them.

[0128] The first excitation coil 121 is configured in an annular shape by forming a spiral wiring pattern along the circumference around the rotation axis 3a. If the printed circuit board 10 is a laminated printed circuit board with multiple wiring layers stacked on top of each other, the first excitation coil 121 may be configured by connecting spiral wiring patterns formed on multiple wiring layers with interlayer vias. The same applies to the second excitation coil 122.

[0129] The first excitation coil 121 and the second excitation coil 122 are connected by wiring patterns (not shown) in the printed circuit board 10 such that, in a plan view along the rotation axis 3a, current flows in opposite circumferential directions around the rotation axis 3a. Therefore, when current is supplied to the first excitation coil 121 and the second excitation coil 122, they form a magnetic field in the same direction in the region between them, i.e., the region where the multiple chip inductors L1 and L2 of the first set S1 and the second set S2 are arranged. In other words, the first excitation coil 121 and the second excitation coil 122 are configured to reinforce each other's magnetic fields in the region between them.

[0130] Figure 13 is an electrical circuit diagram showing the equivalent circuit of stator 1.

[0131] Multiple chip inductors L1 of the first set S1 (inner side) arranged along the first rotational orbit O1 are connected in the same manner as in the second embodiment. Specifically, a pair of first-phase chip inductors L11(1), L11(2) and a pair of third-phase chip inductors L13(1), L13(2) are differentially connected in series to form the A-phase detection circuit 61. A pair of second-phase chip inductors L12(1), L12(2) and a pair of fourth-phase chip inductors L14(1), L14(2) are differentially connected in series to form the B-phase detection circuit 71. The A-phase detection circuit 61 and the B-phase detection circuit 71 output amplitude-modulated detection signals VA1 and VB1 that are 90 degrees out of phase.

[0132] Multiple chip inductors L2 of the second set S2 (outer circumference side), arranged along the second rotational orbit O2, are similarly connected. Specifically, the A-phase detection circuit 62 is formed by differentially connecting three first-phase chip inductors L21(1), L21(2), L21(3) and three third-phase chip inductors L23(1), L23(2), L23(3) in series. The B-phase detection circuit 72 is formed by differentially connecting three second-phase chip inductors L22(1), L22(2), L22(3) and three fourth-phase chip inductors L24(1), L24(2), L24(3) in series. The A-phase detection circuit 62 and the B-phase detection circuit 72 output amplitude-modulated detection signals VA2 and VB2, which are 90 degrees out of phase.

[0133] By appropriately processing the detection signals VA1, VB1, VA2, and VB2 in the signal processing circuit 8, rotational position information of the rotor 2 can be obtained. As mentioned above, because the number Y1 of multiple conductor targets T1 in the first set S1 and the number Y2 of conductor targets T2 in the second set S2 are different from each other, it becomes possible to distinguish and detect rotational positions over a wider range of rotation angles than by using only detection signals VA1, VB1 or only detection signals VA2, VB2. In particular, if the number Y1 of multiple conductor targets T1 in the first set S1 and the number Y2 of conductor targets T2 in the second set S2 are relatively prime, then by using the detection signals VA1, VB1, VA2, and VB2, it becomes possible to perform one-rotation absolute detection, which distinguishes and detects rotational positions within a range of one rotation (360 degrees).

[0134] Although not shown in the diagram, the printed circuit board 10 of the stator 1 has a conductor pattern (more specifically, a copper foil pattern) formed thereon for connecting chip inductors L to form A-phase detection circuits 61, 62 and B-phase detection circuits 71, 72.

[0135] Figures 14A and 14B illustrate yet another embodiment. In the embodiment described above, each conductor target T is composed of a conductor solid pattern (more specifically, a copper foil solid pattern) formed on the insulating substrate 21, but as shown in Figures 14A and 14B, each conductor target T may be composed of coil conductor patterns 80, 90. In Figures 14A and 14B, the corresponding parts shown in Figure 3 are denoted by the same reference numerals.

[0136] In the example shown in Figure 14A, multiple individual annular coil conductor patterns 80, each constituting a plurality of conductor targets T, are separated at intervals in the circumferential direction around the rotation axis 3a, thereby insulating them from one another. The plurality of conductor targets T constitute a conductor pattern with geometric periodicity along the circumferential direction around the rotation axis 3a. In Figure 14A, the annular coil conductor pattern 80 of each conductor target T is composed of a linear conductor pattern along the outer circumference (contour) of a sector (more precisely, a sector with its inner diameter cut off) centered on the rotation axis 3a. However, as shown by dashed lines, the annular coil conductor pattern 80 can also be composed of a curved (e.g., circular or elliptical) conductor pattern. By configuring the conductor targets T with such a curved annular coil conductor pattern 80, the output signal waveform can be made closer to a sine wave. Furthermore, if the insulating substrate is a multilayer wiring board, multiple conductor patterns formed on multiple conductor layers can be connected to form a multi-turn coil, and this multi-turn coil can be used as each conductor target T.

[0137] In the example shown in Figure 14B, multiple conductor targets T are connected to each other to form an annular coil conductor pattern 90 that extends around the entire circumference. This annular coil conductor pattern 90 has geometric periodicity along the circumferential direction around the rotation axis 3a. More specifically, the annular coil conductor pattern 90 has a repeating shape with a predetermined number of periods (5 periods in the example of Figure 14B) around the rotation axis 3a, and one conductor of that period constitutes one conductor target T. One conductor target T is a portion of the annular coil conductor pattern 90 within an angular region obtained by dividing the entire angular range (360 degrees) around the rotation axis 3a into equal parts by the number of periods (5 equal parts in the example of Figure 14B). The angular division positions when dividing by the number of periods can be set arbitrarily.

[0138] In the illustrated example, the annular coil conductor pattern 90 includes an outer diameter linear conductor pattern 91 and a radial linear conductor pattern 92 along the outer diameter portion and a pair of radial portions (i.e., portions other than the inner diameter portion) of the outer circumference (contour) of a sector (more precisely, a sector with the inner diameter portion cut off) centered on the rotation axis 3a, and further includes an inner diameter linear conductor pattern 93 that connects adjacent radial linear conductor patterns 92 on the inner diameter side. The outer diameter linear conductor pattern 91 connects adjacent pairs of radial linear conductor patterns 92 on the outer diameter side. One radial linear conductor pattern 92 is connected on the outer diameter side via the outer diameter linear conductor pattern 91 to the outer diameter end of another radial linear conductor pattern 92 adjacent on one side in the circumferential direction around the rotation axis 3a, and on the inner diameter side via the inner diameter linear conductor pattern 93 to the inner diameter end of yet another radial linear conductor pattern 92 adjacent on the other side in the circumferential direction. In this example, the outer diameter linear conductor pattern 91 and the inner diameter linear conductor pattern 93 are formed linearly along an arc centered on the rotation axis 3a. Thus, the annular coil conductor pattern 90 is configured in an endless manner, with a U-shaped coil portion opening toward the rotation axis 3a and a U-shaped coil portion opening toward the opposite side of the rotation axis 3a continuing in the circumferential direction. In other words, the annular coil conductor pattern 90 is formed in a zigzag wave shape that moves back and forth between the inner diameter side and the outer diameter side across the rotation orbit O.

[0139] As shown by dashed lines in Figure 14B, the annular coil conductor pattern 90 can also be a curved pattern. By configuring multiple conductor targets T with such a curved annular coil conductor pattern 90, the output signal waveform can be made closer to a sine wave.

[0140] The operating principle in the configurations shown in Figures 14A and 14B is the same as in the previously described embodiment. However, while the previously described embodiment utilizes eddy currents flowing through the solid conductor pattern constituting the conductor target T, in the configurations of Figures 14A and 14B, current flows through the coil conductor patterns 80 and 90 constituting the conductor target T. Specifically, when an AC excitation current is applied to the excitation coil 12, as the excitation current increases in the direction of arrow 85, a current flows through the coil conductor patterns 80 and 90 in the direction of arrow 86 to oppose the change in the magnetic field. The voltage induced in the detection coil, which is composed of a chip inductor L, is affected by the magnetic field of the excitation coil 12 on the stator 1 side and the magnetic field of the coil conductor patterns 80 and 90 (conductor target T) on the rotor 2 side.

[0141] Specifically, in the configuration shown in Figure 14A, when the detection coil (chip inductor L) faces the region surrounded by the coil conductor pattern 80, the magnetic field of the excitation coil 12 is weakened, and the output voltage of the detection coil decreases. As the rotation of the rotor 2 changes the facing region, the output voltage of the detection coil changes accordingly. In the configuration shown in Figure 14B, when the detection coil (chip inductor L) faces the U-shaped coil portion that opens toward the rotation axis 3a, the magnetic field of the excitation coil 12 is weakened, while when the detection coil (chip inductor L) faces the U-shaped coil portion that opens toward the opposite side of the rotation axis 3a, the magnetic field of the excitation coil 12 is strengthened. The output voltage of the detection coil then changes according to the change in the facing region.

[0142] In this way, the rotational position of the rotor 2 can be detected using the change in the magnetic field caused by the current flowing through the coil conductor patterns 80 and 90. By utilizing the current flowing through the coil conductor patterns 80 and 90, better detection can be achieved than when using eddy currents flowing through a solid conductor pattern.

[0143] The configuration described above using Figures 14A and 14B is applicable not only to the first embodiment but also to the second, third, and fourth embodiments.

[0144] Figures 15A to 15E show various examples of conductor targets T, illustrating the arrangement of multiple conductor targets T by unfolding the rotating trajectory O along the circumference into a straight line. Figure 15A shows a configuration in which conductor targets T composed of multiple separate solid conductor patterns are arranged at equal intervals, and configurations such as those in Figures 1, 3, 6, 7, 9, 11, and 12 fall into this category. Figure 15B shows a configuration in which conductor targets T composed of multiple separate annular coil conductor patterns are arranged at equal intervals, and configurations such as those in Figure 14A fall into this category.

[0145] Figure 15C shows an example in which an annular coil conductor pattern extending around the entire circumference constitutes multiple conductor patterns T, the configuration of which is shown in Figure 14B. In this case, as mentioned above, each portion obtained by dividing the entire circumference around the rotation axis 3a into equal parts equal to the number of periods is a conductor target T. Since the division positions are arbitrary, for example, each conductor target T can have various shapes corresponding to one period, as illustrated in Figures 16A, 16B, 16C, and 16D.

[0146] Figure 15D shows an example in which a curved annular coil conductor pattern constitutes multiple conductor patterns T, corresponding to the configuration shown by dashed lines in Figure 14B. The conductor target T is the portion corresponding to one cycle. For example, in the configuration of Figure 14B, alternating annular coil conductor patterns can also be formed on both sides of the insulating substrate. An example of the conductor target T in this case is shown in Figure 15. E This will be shown.

[0147] The conductor target T refers to one period of a periodic (geometrically periodic) conductor pattern formed along the circumference (rotational orbit O) around the rotation axis 3a. In the examples of Figures 15A and 15B, this conductor is an individual conductor pattern, while in the examples of Figures 15C to 15E, it is part of a continuous conductor pattern.

[0148] While embodiments of this invention have been described above, this invention can also be implemented in other forms.

[0149] For example, in the above-described embodiment, an example was given in which multiple chip inductors L are arranged around the entire circumference of the rotation axis 3a, but the multiple chip inductors L may be arranged only in a limited angular range around the rotation axis 3a. For example, in the second embodiment shown in Figures 6, 7, and 8, the chip inductors L1(2), L2(2), L3(2), and L4(2) may be omitted.

[0150] Furthermore, while the above-described embodiment showed an example in which multiple chip inductors L are arranged at equal intervals around the entire circumference of the rotation axis 3a, the multiple chip inductors L do not necessarily need to be arranged at equal intervals. For example, in the second embodiment shown in Figures 6, 7, and 8, even if one of the first-phase chip inductors L1(1) and L1(2) is omitted, one of the second-phase chip inductors L2(1) and L2(2) is omitted, one of the third-phase chip inductors L3(1) and L3(2) is omitted, and one of the fourth-phase chip inductors L4(1) and L4(2) is omitted, detection signals VA and VB with a 90-degree phase difference can still be obtained.

[0151] Furthermore, although the above-described embodiment showed an example in which a chip inductor L is surface-mounted on one main surface 10a of the printed circuit board 10 of the stator 1, multiple chip inductors L may be surface-mounted on one main surface 10a of the printed circuit board 10, and multiple chip inductors L may also be surface-mounted on the other main surface 10b of the printed circuit board 10. By mounting chip inductors L on both sides of the printed circuit board 10, the number of chip inductors L can be increased, for example, twice the number of chip inductors L can be mounted on the printed circuit board 10. The more chip inductors L there are, the greater the total number of turns, so the output can be increased. Also, the more chip inductors L there are, the more the variation between chip inductors L is averaged out, so the detection accuracy can be improved. Since the distance from multiple chip inductors L to the conductor target T is equal on each of the one main surface 10a and the other main surface 10b of the printed circuit board 10, the output of multiple chip inductors L arranged on each main surface 10a and 10b can be made uniform. Therefore, complex signal processing is not required.

[0152] In the fourth embodiment described above, a two-track configuration is shown in which two sets of conductor targets and chip inductors are provided along each of the two rotating orbits. However, a configuration in which three or more sets of conductor targets and chip inductors are provided along each of the three or more rotating orbits is also possible.

[0153] In the first, second, and fourth embodiments described above, examples were shown in which the excitation coil is configured in a ring shape, but the excitation coil may also be configured in other ring shapes such as a polygonal ring.

[0154] In the embodiments described above, an example using a multilayer chip inductor was explained, but a wound chip inductor may also be used. However, since multilayer chip inductors can be made smaller, it is advantageous to use a multilayer chip inductor in order to reduce the period of the conductor target (i.e., increase the number of conductor targets) and perform position detection with high resolution. More specifically, even if the width of the rotating orbit of the conductor target is about 2 mm, a position detector can be constructed using a multilayer chip inductor with a width of about 1 mm (preferably arranged around the entire circumference of the rotating orbit).

[0155] Although embodiments of the present invention have been described in detail, these are merely specific examples used to clarify the technical content of the present invention, and the present invention should not be interpreted as being limited to these specific examples. The scope of the present invention is limited only by the appended claims. [Explanation of Symbols]

[0156] 1 Stator 10 Printed circuit boards 12 Excitation coil 2 rotors 20 Printed circuit boards 21 Insulating substrate 23 Non-conducting part 3 rotation axes 3a Rotation axis 31,32 Connecting electrodes 5 Excitation source 51 1st excitation source 52 Second excitation source 6. Phase A detection circuit 7. Phase B detection circuit 61A Phase Detection Circuit 71B Phase Detection Circuit 62A Phase Detection Circuit 72B Phase Detection Circuit 8. Signal Processing Circuit 12 Excitation coil 121 First Excitation Coil 122 Second Excitation Coil 60 A-phase AC bridge circuit 61 First A phase AC voltage applied terminal 62 Second A phase AC voltage applied terminal 63 1st A phase signal detection end 64 2nd A phase signal detection end 70 B-phase AC bridge circuit 71 First B-phase AC voltage application terminal 72 Second B-phase AC voltage application terminal 73 1B phase signal detection end 74 2nd B phase signal detection end 80 Annular coil conductor patterns 90 Annular coil conductor pattern 100 Inductive position detectors 200 Inductive position detectors 300 Inductive position detectors 400 Guided position detectors T Conductor Target O Rotational orbit λ Conductor target period p Chip inductor period L1 Phase 1 Chip Inductor L2 Phase 2 Chip Inductor L3 Third-phase chip inductor L4 Phase 4 Chip Inductor L1(1), L1(2) First-phase chip inductors L2(1), L2(2) Second-phase chip inductor L3(1), L3(2) Third-phase chip inductors L4(1), L4(2) Phase 4 Chip Inductor G1 Phase 1 Group G2 Phase 2 Group G3 Phase 3 Group G4 Phase 4 Group O1 First Rotational Orbit O2 Second Rotational Orbit T1 Conductor Target T2 conductor target L11(1), L11(2) First Phase Chip Inductor L12(1), L12(2) Phase 2 Chip Inductor L13(1), L13(2) Third-phase chip inductors L14(1), L14(2) 4th phase chip inductor L21(1), L21(2), L21(3) Phase 1 Chip Inductor L22(1), L22(2), L22(3) Phase 2 Chip Inductor L23(1), L23(2), L23(3) Third-phase chip inductors L24(1), L24(2), L24(3) Phase 4 Chip Inductor S1 Group 1 S2 2nd group

Claims

1. A stator having a wiring board, A rotor having non-conductive components positioned opposite the stator, and rotating relative to the stator about a predetermined axis of rotation, Multiple conductive targets of the same shape and size are periodically arranged along the circumference around the rotation axis and held by the non-conductive component of the rotor, and move along a rotational trajectory around the rotation axis as the rotor rotates, It includes a plurality of chip inductors, each constituting a plurality of detection coils, which are surface-mounted on the main surface of the wiring board of the stator, arranged to face the rotational trajectory with different spatial phases relative to the plurality of conductor targets, and which detect changes in the magnetic field accompanying the passage of the conductor targets. The conductor targets are arranged along the rotational trajectory at a predetermined conductor target period, An inductive position detector comprising a plurality of chip inductors arranged with a phase difference of one-quarter of a period with respect to the conductor target period, including at least one first-phase chip inductor, at least one second-phase chip inductor, at least one third-phase chip inductor, and at least one fourth-phase chip inductor.

2. The conductor targets are arranged along the rotational trajectory at a predetermined conductor target period, The inductive position detector according to claim 1, wherein the chip inductor has a coil width of 25% to 75% of the period of the conductor target along the rotational trajectory.

3. The 4N chip inductors (where N is a natural number) are arranged at equal intervals along the entire circumference of the rotational trajectory. The inductive position detector according to claim 1, wherein the number of conductive targets Y (where Y is a natural number) is represented by Y = 4NM ± N (where M is a natural number).

4. A stator having a wiring board, A rotor having non-conductive components positioned opposite the stator, and rotating relative to the stator about a predetermined axis of rotation, Multiple conductive targets of the same shape and size are periodically arranged along the circumference around the rotation axis and held by the non-conductive component of the rotor, and move along a rotational trajectory around the rotation axis as the rotor rotates, It includes a plurality of chip inductors, each constituting a plurality of detection coils, which are surface-mounted on the main surface of the wiring board of the stator, arranged to face the rotational trajectory with different spatial phases relative to the plurality of conductor targets, and which detect changes in the magnetic field accompanying the passage of the conductor targets. The 4N chip inductors (where N is a natural number) are arranged at equal intervals along the entire circumference of the rotational trajectory. An inductive position detector in which the number of conductive targets Y (where Y is a natural number) is expressed as Y = 4NM ± N (where M is a natural number).

5. A first set of the plurality of conductor targets and the plurality of chip inductors, whose rotational orbit is a first rotational orbit, and a second set of the plurality of conductor targets and the plurality of chip inductors, whose rotational orbit is a second rotational orbit different from the first rotational orbit, are provided sharing the stator and the rotor. The number Y of the first set of multiple conductor targets １ (Y １ Y is a natural number and the number of the second set of the plurality of conductor targets. ２ (Y ２ An inductive position detector according to claim 1, wherein (a is a natural number) and are different from each other.

6. A stator having a wiring board, A rotor having non-conductive components positioned opposite the stator, and rotating relative to the stator about a predetermined axis of rotation, Multiple conductive targets of the same shape and size are periodically arranged along the circumference around the rotation axis and held by the non-conductive component of the rotor, and move along a rotational trajectory around the rotation axis as the rotor rotates, It includes a plurality of chip inductors, each constituting a plurality of detection coils, which are surface-mounted on the main surface of the wiring board of the stator, arranged to face the rotational trajectory with different spatial phases relative to the plurality of conductor targets, and which detect changes in the magnetic field accompanying the passage of the conductor targets. A first set of the plurality of conductor targets and the plurality of chip inductors, whose rotational orbit is a first rotational orbit, and a second set of the plurality of conductor targets and the plurality of chip inductors, whose rotational orbit is a second rotational orbit different from the first rotational orbit, are provided sharing the stator and the rotor. An inductive position detector in which the number Y1 (where Y1 is a natural number) of the first set of multiple conductive targets and the number Y2 (where Y2 is a natural number) of the second set of multiple conductive targets are different from each other.

7. The number Y of the first set of multiple conductor targets １ And the number Y of the second set of the plurality of conductor targets. ２ The inductive position detector according to claim 5 or 6, wherein and are relatively prime.

8. The inductive position detector according to claim 5 or 6, further comprising an excitation coil provided on the wiring board of the stator and shared for inducing voltage in the first set of the plurality of chip inductors and the second set of the plurality of chip inductors.

9. The inductive position detector according to claim 8, wherein the excitation coil includes an annular first excitation coil that encloses the first set of the plurality of chip inductors and the second set of the plurality of chip inductors when viewed along the axis of rotation, and an annular second excitation coil arranged around the axis of rotation so as to be enclosed by the first set of the plurality of chip inductors and the second set of the plurality of chip inductors when viewed along the axis of rotation.

10. An inductive position detector according to any one of claims 1 to 6, wherein each conductive target includes a conductive solid pattern or an annular coil conductive pattern formed on the non-conductive component, and the plurality of conductive targets are insulated from one another.

11. The induction type position detector according to any one of claims 1 to 6, wherein the plurality of conductive targets are connected to each other to form an annular coil conductor pattern around the entire circumference.

12. The inductive position detector according to any one of claims 1 to 6, wherein the chip inductor is a multilayer chip inductor having a pair of connecting electrodes at both ends.

13. An inductive position detector according to any one of claims 1 to 6, further comprising an excitation coil provided on the wiring board of the stator, formed in an annular shape that encloses the plurality of chip inductors when viewed along the axis of rotation, and generating a magnetic field for inducing voltage in the plurality of chip inductors.

14. The inductive position detector according to any one of claims 1 to 6, wherein the plurality of chip inductors are connected to form an AC bridge circuit having a pair of AC voltage application terminals and a pair of signal detection terminals.

15. A stator having a wiring board, A rotor having non-conductive components positioned opposite the stator, and rotating relative to the stator about a predetermined axis of rotation, Multiple conductive targets of the same shape and size are periodically arranged along the circumference around the rotation axis and held by the non-conductive component of the rotor, and move along a rotational trajectory around the rotation axis as the rotor rotates, It includes a plurality of chip inductors, each constituting a plurality of detection coils, which are surface-mounted on the main surface of the wiring board of the stator, arranged to face the rotational trajectory with different spatial phases relative to the plurality of conductor targets, and which detect changes in the magnetic field accompanying the passage of the conductor targets. An inductive position detector in which the plurality of chip inductors are connected to form an AC bridge circuit having a pair of AC voltage application terminals and a pair of signal detection terminals.

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