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

Inductive Position Sensor Related Applications

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

[0002] The present invention relates to an inductive position detector.

[0003] Position detectors used to detect rotational position include optical, magnetic, capacitance, resolver, and induction types. Inductive position detectors move a movable part holding a conductor in an AC magnetic field and detect changes in the magnetic field due to the current induced in the conductor. Inductive position detectors are highly environmentally resistant, being less susceptible to dust, dirt, and external magnetic fields. In addition, they are simple in configuration, can be made small and thin, and are relatively inexpensive.

[0004] Inductive position detectors are disclosed in, for example, 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 by a conductor pattern on a printed wiring board, and a conductive target is moved relative to the detection coil. The voltage induced in the detection coil by the AC magnetic field generated by the excitation coil changes depending on the positional relationship between the detection coil and the conductive target. This allows the position of the conductive target to be detected.

[0006] Patent Document 2 discloses a configuration in which a detection coil is formed using a conductor pattern on a printed wiring board, an AC voltage is applied to the detection coil, and a change in inductance of the detection coil is detected when a conductive 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 a conductor pattern on a silicon substrate. The detection principle is the same as that of Patent Documents 1 and 4.

[0008] Japanese Patent Publication No. 61-159101 Japanese Patent Publication No. 5226694 Japanese Patent Publication No. 5300164 Japanese Patent Publication No. 2021-56176 Japanese Patent Publication No. 2000-49014

[0009] In a position detector that detects rotational position, size, resolution, and accuracy are very important performance factors. The number of detection cycles per rotation is called the axial multiplier. One cycle of detection signal is obtained when one conductor target passes through one detection coil. The larger the axial multiplier, the better the resolution and the easier it is to improve accuracy. In order to increase the axial multiplier, it is necessary to increase the number of conductor targets arranged around the circumference of the rotation axis. Therefore, to realize a position detector that is small in size and has high resolution and accuracy, the pitch of the conductor targets must be made finer.

[0010] If the pitch of the conductor target is made finer, the detection coil must also be made smaller accordingly. As the detection coil becomes smaller, the interlinkage magnetic flux decreases, and the detected signal voltage becomes smaller. This reduces the signal-to-noise ratio (S / N ratio), making accurate position detection difficult. Therefore, it is desirable to increase the number of turns in the detection coil as much as possible to ensure sufficient signal voltage.

[0011] When a detection coil is formed using a conductor pattern on a printed circuit board, the signal processing circuit can be configured on the same printed circuit board, resulting in low additional costs.In addition, because the initial cost of manufacturing a printed circuit board is low, it is suitable for high-mix, low-volume production and allows for a high degree of design freedom.

[0012] Examples of creating a detection coil using 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 cases, the detection coil is formed using a spiral conductor pattern. If the number of turns needs to be increased, a multilayer printed wiring board can be used, and spiral conductor patterns formed on multiple wiring layers can be connected via via holes. However, due to constraints such as pattern width, pattern spacing, and via hole diameter, it is difficult to create a small coil with a large number of turns. Increasing the number of wiring layers to increase the number of turns leads to increased costs.

[0013] As in Patent Document 3, by forming a conductor pattern on a silicon substrate using a semiconductor manufacturing process, the pattern width, pattern spacing, and via hole diameter can be made finer than those of a printed wiring board, making it possible to fabricate a very small detection coil. However, the semiconductor manufacturing process requires a large initial cost and has low flexibility, making it unsuitable for high-mix, low-volume production. Furthermore, due to size constraints on silicon substrates, the detection coils must be arranged in a concentrated manner. As a result, detection is limited to a portion of the circumference around the rotation axis. Using multiple elements would enable detection at positions evenly distributed around the circumference, but this is not a practical design due to cost issues.

[0014] Other coil shapes proposed include a detection coil shape in which a figure-eight pattern is intersected to form a loop, as shown in FIG. 15 of Patent Document 1, and a zigzag shape with a vernier effect, as shown in FIG. 2 of Patent Document 4. In both coil shapes, the portion surrounded by the forward and return patterns forms a one-turn coil. While it is possible to increase the number of turns beyond one by multiplexing the forward and return patterns, it is difficult to create a coil with a large number of turns large enough to be placed at a small pitch between conductor targets. Furthermore, to detect rotational position, it is preferable to provide two or more detection coils that output signals with different phases. However, with a figure-eight or zigzag pattern, two detection coils cannot be placed 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 at different radial positions (distance from the axis of rotation) on the same wiring layer. However, two detection coils formed on different wiring layers have different distances from the conductor target. Furthermore, since the conductor target is formed in a sector shape centered on the rotation axis, its circumferential width varies depending on its radial position. As a result, the areas of the portions of the two detection coils located at different radial positions, i.e., the inner diameter detection coil and the outer diameter detection coil, that substantially face the conductor target differ. Therefore, in either case, an imbalance in the detection coil outputs is likely to occur, requiring special signal processing.

[0015] In addition, in the case of the configuration shown in Fig. 2 of Patent Document 4, even within the same phase, plus and minus signals are detected on the outside and inside of the circumference, so a design that balances the offset is required. This makes it difficult to design the pattern shape to obtain the required accuracy.

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

[0017] One embodiment of the present invention provides an inductive position detector that can solve at least one of the above-mentioned problems.

[0018] More specifically, one embodiment of the present invention provides an induction type position detector that has a high degree of freedom in design, is small in size, and has high detection resolution.

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

[0020] 1. An induction type position detector comprising: a stator having a wiring board; a rotor having non-conductive parts arranged opposite the stator and rotating relatively to the stator about a predetermined rotation axis; a plurality of conductive targets of the same shape and size arranged periodically around the circumference about the rotation axis and held by the non-conductive parts of the rotor and moving through a rotational orbit about the rotation axis as the rotor rotates; and a plurality of chip inductors surface-mounted on a main surface of the wiring board of the stator and arranged to face the rotational orbit with different spatial phases relative to the plurality of conductive targets, and each chip inductor constituting a plurality of detection coils that detect changes in magnetic field as the conductive targets pass by.

[0021] As the rotor rotates around its axis of rotation, multiple conductive targets held by non-conductive components of the rotor (typically insulating components, such as an insulating substrate) move through a rotational orbit around the axis of rotation. Chip inductors, each constituting a plurality of detection coils, are arranged on the main surface (mounting surface) of the stator's wiring board, facing the rotational orbits of the conductive targets. The chip inductors detect changes in the magnetic field that accompany the passage of the conductive targets. In other words, they output signals representing the changes in the magnetic field. Because the multiple chip inductors have different spatial phases relative to the multiple conductive targets, they output signals of 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 can be supplied at low cost on the market and have a large number of turns. Therefore, when increasing the number of conductor targets and increasing the number of poles to improve detection resolution, they can be arranged to accommodate a small conductor target period (pitch), preventing the detection signal from becoming too small and avoiding excessive costs. In addition, industrially mass-produced chip inductors have high uniformity in performance. Therefore, a uniform detection signal can be obtained from multiple chip inductors, eliminating the need for complex signal processing.

[0023] Furthermore, unlike a configuration in which multiple detection coils are formed on a silicon substrate using a semiconductor manufacturing process, multiple chip inductors, which are individual elements, can be placed at any position facing the rotational orbit, allowing for greater freedom in placement. Therefore, placement distributed around the entire circumference of the rotational orbit is also possible. This type of full-circumference placement easily accommodates misalignment of the rotating shaft coupled to the rotor. Because the chip inductors are small, full-circumference placement can be achieved even in designs that shorten the conductor target period to increase resolution.

[0024] In this way, it is possible to provide an induction type position detector that has a high degree of freedom in design, is small in size, and has high detection resolution.

[0025] Typically, the plurality of conductor targets have the same length along the rotation orbit, and for example, the plurality of conductor targets of the same shape and size are arranged rotationally symmetrically around the rotation axis.

[0026] The multiple chip inductors may be mounted on one main surface, i.e., the same main surface, of the wiring board of the stator. This allows the distances from the multiple chip inductors to the conductor target to be uniform, thereby 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 allows the chip inductors to be closer to the conductor target, thereby allowing the output change of the chip inductors to be larger as the conductor target passes. However, the multiple chip inductors may also be mounted on the main surface of the wiring board opposite the rotor. Even in this case, although a wiring board is interposed, the distances from the multiple chip inductors to the conductor target are approximately equal.

[0027] Alternatively, multiple chip inductors may be surface-mounted on one main surface of the wiring board, and multiple chip inductors may be surface-mounted 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, twice as many chip inductors can be mounted. The greater the number of chip inductors, the greater the total number of turns, and therefore the greater the output. Furthermore, the greater the number of chip inductors, the more the variations between the chip inductors are averaged, thereby improving detection accuracy. Since the distances from the multiple chip inductors to the conductor target are equal on both the one main surface and the other main surface of the wiring board, the outputs of the multiple chip inductors arranged on each main surface can be uniform, eliminating the need for complex signal processing.

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

[0029] In this configuration, the coil width of the chip inductor along the rotational orbit 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 the conductor target passes. By using small, industrially produced chip inductors, the number of conductor targets can be increased to improve detection resolution, and even if 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. The coil width of the chip inductor is preferably approximately 50% of the conductor target period, but good detection is possible within the range of 25% to 75%. Therefore, it is easy to select an applicable chip inductor from standardized chip inductors available on the market. However, having a chip inductor coil width of 50% of the conductor target period does not necessarily result in ideal conditions. The optimal design conditions depend on factors such as the shaft angle multiplier, size, and rotor-stator gap of the position detector.

[0030] 3. The inductive position detector according to item 1 or 2, wherein the conductor targets are arranged at a predetermined conductor target period along the rotational orbit, and 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, which are arranged with a phase difference of a quarter period with respect to the conductor target period.

[0031] The first phase chip inductor, the second phase chip inductor, the third phase chip inductor, and the fourth phase chip inductor have spatial phases that differ by 90 degrees relative to the conductor target, and therefore a detection signal can be obtained from them to accurately detect the rotational position of the rotor.

[0032] The plurality of chip inductors may or may not be arranged at equal intervals along the rotational path. Also, the plurality of chip inductors may be arranged over 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 arranged.

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

[0034] With this configuration, 4N chip inductors are arranged at equal intervals around 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. The 4N chip inductors can then be classified into four groups (each group consisting of N chip inductors) whose spatial phases with respect to the conductor targets differ by 90 degrees. That is, the 4N chip inductors are classified into a first-phase group including N first-phase chip inductors, a second-phase group including N second-phase chip inductors, a third-phase group including N third-phase chip inductors, and a fourth-phase group including N fourth-phase chip inductors. Therefore, detection signals with phases differing by 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 having a first rotation orbit as the rotation orbit, and a second set of the plurality of conductor targets and the plurality of chip inductors having a second rotation orbit different from the first rotation orbit as the rotation orbit, are provided to share the stator and the rotor, and the number Y of the plurality of conductor targets in the first set １ (Y １ is a natural number), and the number Y of the plurality of conductor targets in the second set ２ (Y ２ 5. The induction type position detector according to any one of items 1 to 4, wherein the values ​​of the signal and the signal are different from each other.

[0036] With this configuration, an inductive position detector having a multi-track configuration with a first rotational orbit and a second rotational orbit can be configured. The number Y of the first set of conductive targets corresponding to the first rotational orbit is １ and the number Y of the second set of conductor targets corresponding to the second rotation orbit. ２ Since the rotation angle is different from the rotation angle of the rotational axis, the rotation angle can be detected in a wide range.

[0037] 6. The number Y of the plurality of conductor targets in the first set １ and the number Y of the plurality of conductor targets in the second set. ２ Item 6. The inductive position detector according to item 5, wherein and are relatively prime.

[0038] This configuration allows for the rotational position to be detected distinctly over a wider range of rotation angles, more specifically, absolute detection is possible, which allows for the rotational position to be detected distinctly over a range of one rotation (360 degrees).

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

[0040] This configuration allows a common excitation coil to be used to excite the first and second sets of chip inductors, thereby simplifying the configuration.

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

[0042] With this configuration, the first and second sets of chip inductors can be sufficiently excited by the two inner and outer excitation coils, making it possible to obtain 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 a circular coil conductive pattern formed on the non-conductive component, and the plurality of conductive targets are insulated from one another.

[0044] Typically, the multiple conductor targets have the same length along the rotational orbit, and for example, multiple conductor targets of the same shape and size are arranged rotationally symmetrically around the rotation axis. More typically, adjacent conductor targets are spaced apart along the rotational orbit. The spacing may be equal to the length of the conductor targets along the rotational orbit.

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

[0046] Thus, in one embodiment, a plurality of individual conductive targets spaced apart at equal intervals around the axis of rotation are carried by a non-conductive rotor component to form a periodic (geometrically periodic) conductor pattern, and in another embodiment, a full-circumferential annular coil conductor pattern around the axis of rotation forms a periodic (geometrically periodic) conductor pattern comprising a plurality of interconnected conductive targets.

[0047] Thus, a conductor target refers to one period of a periodic (geometrically periodic) conductor pattern formed around the circumference of a rotation axis, which in some embodiments is an individual conductor pattern and in other embodiments 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 connection electrodes on both ends.

[0049] By using a multilayer chip inductor, it is possible to construct a small detection coil with a large number of turns. This allows for a detection signal of the required magnitude to be obtained from the chip inductor even if the conductor target period is shortened to increase the number of conductor targets and improve detection resolution, which limits the size of the chip inductor accordingly. In addition, it is easy to realize a design with a full-circumference arrangement in which multiple chip inductors are arranged around the entire circumference of the rotational orbit.

[0050] 12. The induction-type position detector according to any one of items 1 to 11, further including an excitation coil that is provided on the wiring board of the stator, that is formed in a ring shape that encloses the plurality of chip inductors when viewed along the axis of rotation, and that generates a magnetic field for inducing a voltage in the plurality of chip inductors.

[0051] With this configuration, an AC voltage can be induced in the chip inductor by applying an AC voltage to the excitation coil. When a conductive target passes near the chip inductor in this state, eddy currents induced in the conductive target by the magnetic field from the excitation coil cancel the magnetic field of the excitation coil. This causes the voltage induced in the chip inductor to fluctuate. Thus, the chip inductor outputs a detection signal that fluctuates in response to the passage of the conductive target.

[0052] 13. The induction type position detector according to any one of items 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 the AC bridge circuit in which the chip inductors are bridge-connected, 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 the chip inductor is inductance, the detection signal of the AC bridge circuit can be considered to represent the change in inductance of the chip inductor. Meanwhile, since the inductance of the chip inductor changes depending on its position relative to the conductive target, the change in inductance can be detected by the detection signal from the AC bridge circuit, thereby detecting the position of the conductive target. In other words, the rotational position of the rotor, which holds the conductive target with a non-conductive component, can be detected.

[0054] The above and other objects, features and advantages of the present invention will become apparent from the following description of the embodiments with reference to the accompanying drawings.

[0055] FIG. 1 is an exploded perspective view illustrating the configuration of an induction-type position detector according to a first embodiment of the present invention. FIG. 2 is a side view of the induction-type position detector of FIG. 1. FIG. 3 is a plan view illustrating the relative arrangement of a conductor target of a rotor and a chip inductor arranged on a stator. FIG. 4 is an electrical circuit diagram illustrating an equivalent circuit of a stator. FIGS. 5A, 5B, and 5C are waveform diagrams illustrating examples of AC voltages generated by an excitation source and detection signals 90 degrees out of phase. FIG. 6 is an exploded perspective view of an induction-type position detector according to a second embodiment of the present invention. FIG. 7 is a plan view illustrating the relative arrangement of a conductor target of a rotor and a chip inductor arranged on a stator. FIG. 8 is an electrical circuit diagram illustrating an equivalent circuit of a stator. FIG. 9 is an exploded perspective view illustrating the configuration of an induction-type position detector according to a third embodiment of the present invention. FIG. 10 is an electrical circuit diagram illustrating the equivalent circuit of a stator of the induction-type position detector of FIG. 9. FIG. 11 is an exploded perspective view illustrating the configuration of an induction-type position detector according to a fourth embodiment of the present invention. FIG. 12 is a plan view illustrating the positional relationship between a conductor target of a rotor and a chip inductor arranged on a stator. Fig. 13 is an electrical circuit diagram showing an equivalent circuit of a stator. Fig. 14A is a plan view showing an example configuration including a conductor target formed with a coil-shaped conductor pattern. Fig. 14B is a plan view showing another example configuration including a conductor target formed with a coil-shaped conductor pattern. Figs. 15A to 15E show examples of various conductor targets. Figs. 16A to 16D show examples of conductor target sections in an annular coil conductor pattern that is continuous around the entire circumference.

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

[0057] Fig. 1 is an exploded perspective view for explaining the configuration of an induction-type position detector 100 according to a first embodiment of the present invention. Fig. 2 is a side view of the induction-type position detector 100 as seen in the direction of an arrow 101 in Fig. 1.

[0058] The induction type position detector 100 includes a stator 1 and a rotor 2 that rotates relative to the stator 1 about a rotation axis 3a, and is configured to output a detection signal that indicates the relative rotation position of the rotor 2 about the rotation axis 3a with respect to the stator 1. The rotor 2 is coupled to a rotating shaft 3 (see FIG. 2) whose rotational position is to be detected, and rotates together with the rotating shaft 3 about the rotation axis 3a. The stator 1 has a printed circuit board 10 (printed wiring board) that is a wiring board. The rotor 2 is composed of another printed circuit board 20 that is arranged 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 10 a and 10 b. The printed circuit board 10 may be a multilayer printed circuit board having multiple stacked wiring layers (e.g., four wiring layers), in which case the conductor pattern may be in a wiring layer that is not exposed on the main surfaces 10 a and 10 b.

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

[0061] 1 and 2, the conductor target T is hatched for clarity, as is the case in other drawings described later.

[0062] Figure 3 is a plan view seen through the insulating substrate 21 and along 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") arranged 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 that has geometric periodicity along the circumferential direction around the rotation axis 3a. The conductors for one period of this conductor pattern constitute one conductor target T. The multiple conductor targets T move through a rotational orbit O (circumferential orbit) around the rotation axis 3a as the rotation shaft 3, and therefore the rotor 2, rotates.

[0064] In this embodiment, the multiple conductor targets T are arranged at equal intervals at a predetermined period (pitch) λ (hereinafter referred to as the "conductor target period λ") around the entire circumference of the rotation axis 3a. In this embodiment, each conductor target T is a conductor solid pattern formed on one main surface of the insulating substrate 21, and the multiple conductor targets T are separated circumferentially and insulated from each other. That is, each conductor target T is composed of an individual conductor pattern (conductor solid pattern). The multiple conductor targets T have the same length (width) along the rotation orbit 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 arranged in a sector shape (more precisely, a sector shape with the inner diameter portion cut out) centered on the rotation axis 3a. In this illustrated example, the interval between adjacent conductive targets T along the rotational orbit O, i.e., the length of the non-conductor portion 23 along the rotational orbit O, is equal to the length (width) of the conductive target T along the rotational orbit O, but this is just an example. The length (width) of the conductive target T along the rotational orbit O depends on the design of the inductive position detector 100, and may be optimally about 70% of the conductive target period λ, for example.

[0065] A plurality of chip inductors L are surface-mounted on one main surface 10a of a printed circuit board 10 that constitutes the stator 1. In this embodiment, the plurality of chip inductors L are mounted on the main surface 10a that faces the rotor 2, but they may also be mounted on the other main surface 10b opposite the rotor 2. The plurality of chip inductors L are arranged so as to face the rotational orbit O of the plurality of conductor targets T with different spatial phases relative to the plurality of conductor targets T. As a result, the plurality of chip inductors L each constitute a plurality of detection coils that detect changes in the magnetic field that accompany the passage of the conductor targets T. The plurality of chip inductors L are surface-mounted on the same main surface 10a of the printed circuit board 10, and therefore the distances from the rotor 2 (more specifically, the distances from the conductor targets T) are substantially equal.

[0066] The multiple chip inductors L are typically mass-produced industrially to the same specifications. Each chip inductor L has a coil width W along the rotation orbit O that is 25% to 75% (25% to 75%) of the conductor target period λ. This coil width W is preferably approximately 50% of the conductor target period λ, but good detection is possible if it is in 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 connection electrodes 31, 32 (see FIG. 1) at both ends can be used as the chip inductor L. An example of a multilayer chip inductor is described in, for example, Patent Document 5. By using a multilayer chip inductor, a small detection coil with a large number of turns can be configured. As a result, even if the conductor target period λ is shortened to increase the number of conductor targets T and improve detection resolution, a detection signal of the required magnitude can be obtained from the chip inductor L.

[0068] The chip inductor L typically has a rectangular parallelepiped shape with its longitudinal direction being the direction in which the connection electrodes 31, 32 face each other. When the chip inductor L is surface-mounted on the printed circuit board 10 with its central axis direction (the direction of the central axis of the winding) set perpendicular to the main surface 10a of the printed circuit board 10, its short-side length 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 need to be aligned with the radial direction of the rotational orbit O.

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

[0070] In this embodiment, five conductor targets T are arranged on a circumference around the rotation axis 3a at a conductor target period λ of 72 degrees, which corresponds to one period of electrical angle, i.e., 360 degrees. The four chip inductors L are arranged at a period p (pitch) of 90 degrees (hereinafter referred to as the "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-fourth of the conductor target period λ (72 degrees).

[0071] Therefore, two chip inductors L positioned at a 90-degree mechanical angle have a phase difference of 90 degrees electrical angle, i.e., a 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 opposite in phase 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 opposite in phase to each other.

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

[0073] An excitation coil 12 is provided on a printed circuit board 10 constituting the stator 1. In a plan view (see FIG. 2 ) taken along the rotation axis 3 a, the excitation coil 12 is formed in an annular shape with a plurality of chip inductors L facing inward. That is, the coil central axis direction of the excitation coil 12 is parallel to the rotation axis 3 a. In this embodiment, the excitation coil 12 is formed in an annular shape with a plurality of conductor targets T facing inward in the same plan view. In this embodiment, the excitation coil 12 is substantially annular in the same plan view. Specifically, the excitation coil 12 is a pattern coil formed of a spiral conductor pattern formed on the printed circuit board 10, and is formed in an annular shape as a whole (annular in this embodiment). The printed circuit board 10 may be, for example, a laminated printed circuit board in which a plurality of wiring layers are stacked. In this case, the excitation coil 12 may be formed by forming a pattern coil with a spiral conductor pattern on each of a plurality of wiring layers (e.g., four layers), and connecting these pattern coils with vias that connect the wiring layers.

[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 from the excitation source 5 to the excitation coil 12, 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 is interlinked with the chip inductor L, and an induced electromotive force is generated in the chip inductor L.

[0075] Although not shown, a conductor pattern (more specifically, a copper foil pattern) for connecting the chip inductor L to configure a detection circuit is formed on the printed circuit board 10 of the stator 1 .

[0076] FIG. 4 shows an equivalent circuit of the 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 of opposite phase. The same-polarity ends of the first-phase chip inductor L1 and the third-phase chip inductor L3 are connected (differentially connected) to form an A-phase detection circuit 6 that outputs the differential signal 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 the A-phase detection signal. The fourth-phase chip inductor L4 generates a / B-phase detection signal of opposite phase to the B-phase detection signal. The same-polarity ends of the second-phase chip inductor L2 and the fourth-phase chip inductor L4 are connected (differentially connected) to form a B-phase detection circuit 7 that outputs the differential signal as a detection signal VB.

[0077] As described above, when an AC voltage (A sinωt, 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 changes in the magnetic 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. Utilizing this phenomenon, rotational position information can be obtained by appropriately processing the detection signals VA and VB using the signal processing circuit 8.

[0078] The voltage induced in the chip inductor L is represented by a fixed component C and a variable component V. The phase is positive when the conductor target T moves in the clockwise direction CW, and the chip inductor L1 in FIG. 3 is used as the reference. Then, the voltage V induced in each of the chip inductors L1, L2, L3, and L4 at the rotation angle θ is Ｌ１ , V Ｌ２ , V Ｌ３ , V Ｌ４ where K represents the amplitude of the induced AC voltage. Ｌ１ =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・(CV・sinθ)…(3) V Ｌ４ =Ksinωt・{C+V・sin(θ+270)}=Ksinωt・(CV・cosθ)…(4)

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

[0080] 5A shows an example of the waveform of the AC voltage generated by the excitation source 5, and FIGS. 5B and 5C show example waveforms of the detection signals VA and VB. Thus, the detection signals VA and VB output by the detection circuits 6 and 7 are signals in which a high-frequency signal is amplitude-modulated based on changes in the induced voltage caused by the rotation of the rotor 2. Because the chip inductors L1 and L3 that make up the A-phase detection circuit 6 and the chip inductors L2 and L4 that make up the B-phase detection circuit 7 are arranged on the stator 1 at 90-degree intervals, the detection signals VA and VB are signals with a 90-degree phase difference from each other. Therefore, the detection signals VA and VB are demodulated by the signal processing circuit 8, and the rotation angle θ of the rotor 2 can be determined by performing an arctangent calculation.

[0081] Fig. 6 is an exploded perspective view of an induction-type position detector 200 according to a second embodiment of the present invention. Fig. 7 is a plan view of the induction-type position detector 200 as seen along the rotation axis 3a, showing the relative positions of the conductor targets T and the chip inductors L as seen through the insulating substrate 21 of the rotor 2. Fig. 8 is an equivalent circuit diagram showing the electrical configuration of the stator 1. In these drawings, parts corresponding to those shown in Figs. 1 to 4 are designated by the same reference numerals.

[0082] In this embodiment, the number of conductor targets T and the number of chip inductors L are each 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 examining the spatial phase relative to the conductor targets T, it is found that the phases of the chip inductors L spaced 180 degrees apart around the rotation axis 3a are equivalent. That is, 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), 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), 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), 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), L4(2) facing each other across the rotation axis 3a. The first-phase chip inductors L1(1), L1(2), second-phase chip inductors L2(1), L2(2), third-phase chip inductors L3(1), L3(2), and fourth-phase chip inductors L4(1), L4(2) are spatially phase shifted around the rotation axis 3a by one-fourth 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. As in the first embodiment, 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 with each other. However, the conductor target period λ, which corresponds to 360 degrees in electrical angle, corresponds to 36 (= 360 / 10) degrees in mechanical angle, so that the rotational position can be detected with twice the resolution compared to the first embodiment.

[0084] Although not shown, a conductor pattern (more specifically, a copper foil pattern) for connecting the chip inductor L to configure the detection circuits 6 and 7 is formed on the printed circuit board 10 of the stator 1 .

[0085] Regarding the voltage induced in the chip inductor L, the fixed component is C and the variable component is V. The phase is positive when the conductor target T moves in the clockwise direction CW, and the chip inductor L1(1) is used 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), and 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) where K represents the amplitude of the induced AC voltage. 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) =Ksinωt・{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) =Ksinωt・{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] Since chip inductors L1(1), L1(2), L3(1), L3(2), and chip inductors L2(1), L2(2), L4(1), L4(2) are differentially connected in series, respectively, the detection signals VA and VB are as follows: 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] As described above, in the second embodiment, the increased number of chip inductors L allows greater fluctuations in the detection signals VA and VB to be detected, improving the signal-to-noise ratio (S / N ratio). Furthermore, the chip inductors L, which are positioned opposite each other and separated by 180 mechanical degrees, detect in-phase signals. This reduces the effect on the detection signals of errors such as eccentricity of the stator 1 relative to the rotating shaft 3 and tilt of the rotor 2 relative to the stator plane, improving detection accuracy.

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

[0089] When the conductor target period λ and the chip inductor period p have a phase difference of λ / 4 (one-fourth of the conductor target period λ), the relational expression is given by the following expression (17), where M is a natural number: p=λ(M±¼) (17)

[0090] The conductor target period λ and the chip inductor period p are expressed by the following equations (18) and (19), respectively, using the circumferential length Cl of the rotational 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 yields the following equation (20). Therefore, if there is a combination of natural numbers Y, N, and M that satisfy the relationship in equation (20), it is possible to detect detection signals having a phase difference of 90 electrical degrees from the detection circuits 6 and 7. Y=4NM±N (20)

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

[0093] As described above, according to the first and second embodiments, two detection circuits 6 and 7 that generate two detection signals VA and VB that are 90 degrees out of phase with each other can be configured using a plurality of chip inductors L. Then, based on these detection signals VA and VB, the rotational position of the rotor 2, i.e., the rotational position (rotation angle) of the rotating shaft 3, can be detected.

[0094] The chip inductor L is an electrical component that can be procured at a low price on the market despite its small size, allowing for a large number of turns. Therefore, when increasing the number of conductor targets T to increase the number of poles and improve detection resolution, it is possible to arrange the chip inductors L in accordance with a small conductor target period λ, preventing the detection signal from becoming too small and requiring excessive costs. Additionally, by mounting multiple chip inductors L on one main surface 10a of the printed circuit board 10 of the stator 1, i.e., the same main surface, the distances 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. This results in an arrangement where the distance between the multiple chip inductors L and the conductor target T is short, so that a signal whose amplitude fluctuates greatly as the conductor target T passes can be extracted from each chip inductor L.

[0096] Furthermore, unlike a configuration 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 arranged at any position facing the rotational orbit O, allowing for a high degree of freedom in arrangement. Therefore, as in the first and second embodiments, an arrangement distributed around the entire circumference of the rotational orbit O is also possible. Such an arrangement around the entire circumference is an arrangement that easily accommodates misalignment of the axis of the rotating shaft 3 coupled to the rotor 2. Specifically, if the rotating shaft 3 is at the end of the motor shaft opposite the output shaft of an electric motor, even if the axis of the rotating shaft 3 is misaligned due to a radial load acting on the motor shaft, offset of the detection position can be avoided with simple signal processing.

[0097] In particular, by using a laminated chip inductor as the chip inductor L, the chip inductor L can be configured to be small and have many windings. Therefore, even in a design in which the conductor target period λ is reduced to increase resolution, the chip inductor L can be arranged around the entire circumference of the rotation orbit O.

[0098] In the first and second embodiments, the conductor targets T are arranged at a predetermined conductor target period λ along the rotational orbit O. The chip inductor L has a coil width W along the rotational 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. Furthermore, 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 becomes larger, and as long as this ratio is up to approximately 75%, a signal with a waveform that allows accurate detection of the rotational position can be obtained. By using small, industrially produced chip inductors L, the number of conductor targets T can be increased to increase the detection resolution. Even if the conductor target period λ is shortened accordingly, a small rotational position detector can be configured using chip inductors L with a coil width W that is 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 in the range of 25% to 75% of the conductor target period λ. Therefore, it is easy to select an applicable chip inductor from standardized chip inductors available on the market.

[0101] In the first and second embodiments, the multiple chip inductors L arranged on the stator 1 are configured into 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 a quarter period with respect to the conductor target period λ. The first-phase chip inductor L1 (the chip inductor of the first phase group), the second-phase chip inductor L2 (the chip inductor of the second phase group), the third-phase chip inductor L3 (the chip inductor of the third phase group), and the fourth-phase chip inductor L4 (the chip inductor of the fourth phase group) have spatial phases that differ by 90 degrees with respect to the conductor target T, and therefore a detection signal for accurately detecting the rotational position of the rotor 2 can be obtained from these groups.

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

[0103] In the second embodiment, a plurality of first-phase chip inductors L1, a plurality of second-phase chip inductors L2, a plurality of third-phase chip inductors L3, and a plurality of fourth-phase chip inductors L4 are provided, and chip inductors L of the same phase are connected in series, thereby enabling detection signals VA and VB with large amplitudes to be obtained, and improving the S / N ratio.

[0104] As described above, by arranging Y conductor targets T and 4N chip inductors L that satisfy Equation (20) at equal intervals all around the rotation axis 3a, the 4N chip inductors L can be classified into four phase groups (each phase group consisting of N chip inductors L) whose spatial phases with respect to the conductor target T differ by 90 degrees. That is, the 4N chip inductors L are classified into a first phase group G1 including N first-phase chip inductors L1, a second phase group G2 including N second-phase chip inductors L2, a third phase group G3 including N third-phase chip inductors L3, and a fourth phase group G4 including 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, it is possible to configure the detection circuits 6 and 7 that output detection signals VA and VB that are different in phase by 90 degrees.

[0105] Fig. 9 is an exploded perspective view showing the configuration of an induction-type position detector 300 according to a third embodiment of the present invention. Fig. 10 is an electrical circuit diagram showing an equivalent circuit on the stator 1 side. In Figs. 9 and 10, parts corresponding to those in the second embodiment are designated by the same reference numerals.

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

[0107] The plurality of 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, a conductor pattern (more specifically, a copper foil pattern) for connecting the chip inductors L to configure the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70 is formed on the printed circuit board 10 of the stator 1.

[0108] The A-phase AC bridge circuit 60 is configured by bridging first-phase chip inductors L1(1) and L1(2) with third-phase chip inductors L3(1) and L3(2), which have a phase difference of 180 degrees relative to the first-phase chip inductors L1(1) and L1(2). The first-phase chip inductors L1(1) and L1(2) are respectively arranged on opposite sides of the A-phase AC bridge circuit 60, and the third-phase chip inductors L3(1) and L3(2) are respectively arranged on the other opposite sides of the A-phase AC bridge circuit 60. The connection point between the first-phase chip inductor L1(1) and the third-phase chip inductor L3(2) is a 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 a 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 end 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 end 64.

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

[0110] An AC voltage is applied to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70 from an excitation source 5. The excitation source 5 includes a first excitation source 51 that generates a first AC voltage (A sinωt) and a second excitation source 52 that generates a second AC voltage (-A sinωt) that is out of phase with the first AC voltage. The first A-phase AC voltage application terminal 61 is connected to the first excitation source 51 and receives the first AC voltage (A sinωt). The second A-phase AC voltage application terminal 61 is connected to the second excitation source 52 and receives the second AC voltage (-A sinωt). The first B-phase AC voltage application terminal 71 is connected to the first excitation source 51 and receives the first AC voltage (A sinωt). The second B-phase AC voltage application terminal 72 is connected to the second excitation source 52 and receives the second AC voltage (-A sinωt). The voltage appearing between the first A-phase signal detection terminal 63 and the second A-phase signal detection terminal 64 is detected as a 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 a detection signal VB.

[0111] In this embodiment, an 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 an AC voltage may also be applied to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70 from separate excitation sources 5.

[0112] When the conductor target T faces the chip inductor L, the magnetic flux of the chip inductor L is blocked by the conductor target T, reducing the inductance of the chip inductor L. Taking advantage of this, in this embodiment, an excitation coil is not used, and 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 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 expressed by equations (29) and (30), respectively. Here, k is a constant representing 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 a change in the impedance of the chip inductor L due to a change 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 essentially 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 expressed by equations (29) and (30) are signals that change depending on the rotational position of the conductor target T and are shifted in phase by 90 degrees. As is clear from a comparison of equations (29) and (30) with the above-described equations (5) and (6), the detection signals VA and VB have waveforms similar to the waveforms shown in Figures 5B and 5C, respectively, depending on the rotational position of the conductor target T. Therefore, as in the first and second embodiments described above, the rotational position of the rotor 2 can be detected. Therefore, a position detector that can detect the position of the rotor 2 can be configured without including an excitation coil.

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

[0117] This position detector 400 detects a plurality of rotational orbits O around the rotation axis 3a. １ , O ２ (see FIG. 12 ), and each rotation orbit O １ , O ２ Specifically, the position detector 400 of this embodiment has a first rotation orbit O concentrically arranged around the rotation axis 3a. １ and the second rotational orbit O ２ The first rotation orbit O １ is the second rotation orbit O ２ and the second rotation orbit O ２ The rotor 2 has a circumference having a smaller diameter than the stator 1. The first rotation orbit O is formed on one main surface 20a of the printed circuit board 20 of the rotor 2 (the main surface opposite to the stator 1 in this embodiment). １ A plurality of conductor targets T １ are arranged at equal intervals around the circumference, and the second rotation orbit O ２ A plurality of conductor targets T ２ are arranged at equal intervals around the entire circumference. A first rotation orbit O is formed 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). １ A plurality of chip inductors L １ are arranged at equal intervals around the circumference, and the second rotation orbit O ２ A plurality of chip inductors L ２ are evenly spaced around the circumference.

[0118] First rotation orbit O １ A plurality of chip inductors L arranged along １ is the conductor target T １Based on the spatial phase around the rotation axis 3a with respect to the first phase chip inductor L １ 1(1), L １ The first phase group (A phase) consists of 1(2), and the second phase chip inductor L １ 2(1), L １ 2 (2) The second phase group (B phase) and the third phase chip inductor L １ 3(1), L １ 3(2) consists of the third phase group ( / A phase), the fourth phase chip inductor L １ 4(1), L １ 4(2) can be classified into the fourth phase group ( / B phase). And the first phase chip inductor L １ 1(1), L １ 1(2), Second phase chip inductor L １ 2(1), L １ 2(2), Third-phase chip inductor L １ 3(1), L １ 3(2) and 4th phase chip inductor L １ 4 (1), L １ 4(2) are spatially phase shifted about the axis of rotation 3a by one-fourth of the conductor target period λ.

[0119] Similarly, the second rotational orbit O ２ A plurality of chip inductors L arranged along ２ is the conductor target T ２ Based on the spatial phase around the rotation axis 3a with respect to the first phase chip inductor L ２ 1(1), L ２ 1(2), L ２ The first phase group (A phase) consists of 1(3), and the second phase chip inductor L ２ 2(1), L ２ 2(2), L ２ The second phase group (B phase) consists of 2(3), and the third phase chip inductor L ２ 3(1), L ２ 3(2), L ２ The third phase group ( / A phase) consists of 3(3), and the fourth phase chip inductor L ２ 4(1), L ２ 4(2), L ２4(3) can be classified into the fourth phase group ( / B phase). And the first phase chip inductor L ２ 1(1), L ２ 1(2), L ２ 1(3), Second phase chip inductor L ２ 2(1), L ２ 2(2), L ２ 2(3), Third phase chip inductor L ２ 3(1), L ２ 3(2), L ２ 3(3) and 4th phase chip inductor L ２ 4 (1), L ２ 4(2), L ２ 4(3) are spatially phase shifted around the rotation axis 3a by one-fourth of the conductor target period λ.

[0120] First rotation orbit O １ A plurality of conductor targets T arranged along １ and a plurality of chip inductors L １ The first group S １ Similarly, the second rotational orbit O ２ A plurality of conductor targets T arranged along ２ and a plurality of chip inductors L ２ The second group S ２ The first set S １ and the second group S ２ The rotor 2 and the stator 1 are shared by the two.

[0121] 1st group S １ A plurality of conductor targets T １ The number Y １ And the second group S ２ Conductor target T ２ The number Y ２ are different from each other. １ Conductor target T １ The number Y １ and chip inductor L １ The number 4N １ satisfies the above-mentioned formula (20), and therefore satisfies the following formula (31). ２ Conductor target T２ The number Y ２ and chip inductor L ２ The number 4N ２ satisfies the above-mentioned formula (20), and therefore satisfies the following formula (32). １ = 4N １ M １ ±N １ (Y １ , N １ , M １ is a natural number) ... (31) Y ２ = 4N ２ M ２ ±N ２ (Y ２ , N ２ , M ２ is a natural number) ...(32)

[0122] The examples shown in FIGS. 11 and 12 are １ = 14, N １ = 2, M １ = 2, Y ２ = 15, N ２ = 3, M ２ This corresponds to the case where .times. ...

[0123] 1st group S １ A plurality of conductor targets T １ The number Y １ And the second group S ２ Conductor target T ２ The number Y ２ Since the first set S and the second set S are different from each other, it is possible to distinguish and detect the rotational position in a wide rotational angle range. １ A plurality of conductor targets T １ The number Y １ And the second group S ２ Conductor target T ２ The number Y ２ If and are relatively prime, one-rotation absolute detection is possible, which distinguishes and detects the rotation position within the range of one rotation (360 degrees).

[0124] In this example, the first set S １ A plurality of chip inductors L １ and the second set S ２ A plurality of chip inductors L ２are all chip inductors of the same specifications, and have the same shape and size when viewed in a plan view along the rotation axis 3a.

[0125] In the illustrated example, each chip inductor L is arranged so that its longitudinal direction is along the direction of the radius of rotation about the rotation axis 3a. The longitudinal direction of the chip inductor L is typically the direction in which the pair of connection electrodes 31, 32 face each other. １ A plurality of conductor targets T １ pitch (conductor target period λ １ ) chip inductor L １ Coil width W １ The ratio of the second set S is about 25%. ２ A plurality of conductor targets T ２ Pitch (conductor target period λ ２ ) chip inductor L ２ Coil width W ２ The ratio of the first set S is 50%. １ and the second set S ２ In each of the above, the conductor target period λ １ , λ ２ Coil width W １ , W ２ The ratio of the conductor target T １ , T ２ and a chip inductor L １ , L ２ and determine their placement.

[0126] 1st group S １ and the second set S ２ It is not necessary to use chip inductors of the same specifications for the first set S. １ A plurality of chip inductors L １ The second set S ２ A plurality of chip inductors L ２ may be different but with the same specifications.

[0127] The printed circuit board 10 of the stator 1 has a first set S １ A plurality of chip inductors L １ and the second set S２ A plurality of chip inductors L ２ In this embodiment, the excitation coil 12 includes a first excitation coil 121 and a second excitation coil 122. These are configured by conductor patterns formed on the printed circuit board 10. The first excitation coil 121 is arranged in a plane view along the rotation axis 3a, and is connected to the first set S １ A plurality of chip inductors L １ and the second set S ２ A plurality of chip inductors L ２ On the other hand, the second excitation coil 122 is configured in a ring shape (annular in the illustrated example) that includes the first set S in a plan view along the rotation axis 3 a. １ A plurality of conductor targets T １ and the second set S ２ A plurality of conductor targets T ２ The first excitation coil 121 is configured in a ring shape (annular shape in the illustrated example) around the rotation axis 3a so as to be included in the first set S １ and the second set S ２ A plurality of chip inductors L １ , L ２ The first excitation coil 121 is disposed on the outer periphery side of the first excitation coil 121, and the second excitation coil 122 is disposed on the inner periphery side of the first excitation coil 121.

[0128] The first excitation coil 121 is configured, for example, in a circular 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 in which multiple wiring layers are stacked, the first excitation coil 121 may be configured by connecting spiral wiring patterns formed on the 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 a wiring pattern (not shown) in the printed circuit board 10 so that currents flow in opposite circumferential directions around the rotation axis 3a in a plan view along the rotation axis 3a. Therefore, when the first excitation coil 121 and the second excitation coil 122 are energized, the first excitation coil 121 and the second excitation coil 122 are energized in the region between them, i.e., the first set S １ and the second set S ２ A plurality of chip inductors L １ , L ２ In other words, the first excitation coil 121 and the second excitation coil 122 are configured to mutually strengthen the magnetic fields in the region therebetween.

[0130] FIG. 13 is an electric circuit diagram showing an equivalent circuit of the stator 1.

[0131] First rotation orbit O １ The first set S is arranged along １ (inner circumference side) of a plurality of chip inductors L １ are connected in the same manner as in the second embodiment. That is, the pair of first-phase chip inductors L １ 1(1), L １ 1(2) and a pair of third-phase chip inductors L １ 3(1), L １ 3(2) are differentially connected in series to form the A-phase detection circuit 6 １ The pair of second-phase chip inductors L １ 2(1), L １ 2(2) and a pair of fourth-phase chip inductors L １ 4(1), L １ 4(2) are differentially connected in series to form the B-phase detection circuit 7 １ The A-phase detection circuit 6 is configured as follows. １ and B-phase detection circuit 7 １ is the amplitude modulated detection signal VA that is out of phase by 90 degrees. １ , VB １ Output.

[0132] Second rotation orbit O ２ A second set S arranged along ２(Outer periphery) of the plurality of chip inductors L ２ The three first-phase chip inductors L ２ 1(1), L ２ 1(2), L ２ 1(3) and three third-phase chip inductors L ２ 3(1), L ２ 3(2), L ２ 3(3) are differentially connected in series to form the A-phase detection circuit 6 ２ The three second-phase chip inductors L ２ 2(1), L ２ 2(2), L ２ 2(3) and three fourth-phase chip inductors L ２ 4(1), L ２ 4(2), L ２ 4(3) are differentially connected in series to form the B-phase detection circuit 7 ２ The A-phase detection circuit 6 is configured as follows. ２ and B-phase detection circuit 7 ２ is the amplitude modulated detection signal VA that is out of phase by 90 degrees. ２ , VB ２ Output.

[0133] Detection signal VA １ , VB １ , V.A. ２ , VB ２ By appropriately processing the signals in the signal processing circuit 8, the rotational position information of the rotor 2 can be obtained. １ A plurality of conductor targets T １ The number Y １ And the second group S ２ Conductor target T ２ The number Y ２ Since the detection signal VA is different from the detection signal VA, １ , VB １ Only, or detection signal VA ２ , VB ２ In particular, it is possible to distinguish and detect the rotational position in a wider range of rotation angles than when only the first set S is used. １ A plurality of conductor targets T １ The number Y １ And the second group S ２Conductor target T ２ The number Y ２ If and are relatively prime, the detection signal VA １ , VB １ , V.A. ２ , VB ２ By using the above, it becomes possible to perform one-rotation absolute detection that distinguishes and detects the rotation position within the range of one rotation (360 degrees).

[0134] Although not shown, a chip inductor L is connected to the printed circuit board 10 of the stator 1, and an A-phase detection circuit 6 １ , 6 ２ and B-phase detection circuit 7 １ , 7 ２ A conductor pattern (more specifically, a copper foil pattern) is formed to form the wiring board.

[0135] 14A and 14B are diagrams illustrating yet another embodiment. In the above-described embodiment, each conductor target T is configured as a conductor solid pattern (more specifically, a copper foil solid pattern) formed on an insulating substrate 21. However, as shown in FIGS. 14A and 14B, each conductor target T may be configured as a coil conductor pattern 80, 90. In FIGS. 14A and 14B, parts corresponding to those shown in FIG. 3 are designated by the same reference numerals.

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

[0137] In the example of Figure 14B, multiple conductor targets T are connected to each other to form an annular coil conductor pattern 90 that spans 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 (five periods in the example of Figure 14B) around the rotation axis 3a, and the conductors for one period constitute one conductor target T. One conductor target T is a portion of the annular coil conductor pattern 90 within an angular region obtained by equally dividing the angular range (360 degrees) of the entire circumference around the rotation axis 3a by the number of periods (five equal divisions in the example of Figure 14B). The angular positions of the divisions when equally dividing by the number of periods can be set arbitrarily.

[0138] In the illustrated example, the annular coil conductor pattern 90 includes an outer radial linear conductor pattern 91 and a radial linear conductor pattern 92 along the outer radial portion and a pair of radial portions (i.e., portions other than the inner radial portion) of the outer periphery (outline) of a sector (more precisely, a sector with the inner radial portion cut out) centered on the rotation axis 3 a, respectively, and further includes an inner radial linear conductor pattern 93 that connects adjacent radial linear conductor patterns 92 at their inner radial sides. The outer radial linear conductor pattern 91 connects adjacent pairs of radial linear conductor patterns 92 at their outer radial sides. One radial linear conductor pattern 92 is connected on its outer radial side via the outer radial linear conductor pattern 91 to the outer radial end of another adjacent radial linear conductor pattern 92 on one circumferential side around the rotation axis 3 a, and is also connected on its inner radial side via the inner radial linear conductor pattern 93 to the inner radial end of yet another adjacent radial linear conductor pattern 92 on the other circumferential side. In this example, the outer radial linear conductor pattern 91 and the inner radial linear conductor pattern 93 are linearly formed along an arc centered on the rotation axis 3 a. Thus, the annular coil conductor pattern 90 is configured endlessly, with a U-shaped coil portion opening toward the rotation axis 3 a and a U-shaped coil portion opening away from the rotation axis 3 a 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 and outer radial sides across the rotation orbit O.

[0139] 14B, the annular coil conductor pattern 90 may be a curved pattern. By configuring multiple conductor targets T with such curved annular coil conductor patterns 90, the output signal waveform can be made closer to a sine wave.

[0140] The operating principle of the configuration shown in Figures 14A and 14B is the same as that of the previously described embodiment. However, while the previously described embodiment utilizes eddy currents flowing in the conductor solid pattern that constitutes the conductor target T, in the configuration shown in Figures 14A and 14B, current flows in the coil conductor patterns 80 and 90 that constitute the conductor target T. Specifically, when an AC excitation current flows through the excitation coil 12, as the excitation current increases in the direction of arrow 85, a current flows in the coil conductor patterns 80 and 90 in the direction of arrow 86 so as to prevent magnetic field changes. The voltage induced in the detection coil formed by the 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 of Fig. 14A, when the detection coil (chip inductor L) faces an area 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 is reduced. As the facing area changes with the rotation of the rotor 2, the output voltage of the detection coil changes accordingly. In the configuration of Fig. 14B, when the detection coil (chip inductor L) faces a U-shaped coil portion that opens toward the rotation axis 3a, the magnetic field of the excitation coil 12 is weakened. On the other hand, when the detection coil (chip inductor L) faces a U-shaped coil portion that opens away from the rotation axis 3a, the magnetic field of the excitation coil 12 is strengthened. The output voltage of the detection coil changes as the facing area changes.

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

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

[0144] 15A to 15E show various examples of conductor targets T, and illustrate the arrangement of multiple conductor targets T by linearly expanding a rotational orbit O along a circumference. Fig. 15A shows a configuration in which conductor targets T made up of multiple separated conductor solid patterns are arranged at equal intervals, and corresponds to the configurations in Figs. 1, 3, 6, 7, 9, 11, 12, etc. Fig. 15B shows a configuration in which conductor targets T made up of multiple separated annular coil conductor patterns are arranged at equal intervals, and corresponds to the configuration in Fig. 14A.

[0145] Fig. 15C shows an example in which a ring-shaped coil conductor pattern covering the entire circumference constitutes a plurality of conductor patterns T, which corresponds to the configuration in Fig. 14B. In this case, as described above, each portion obtained by equally dividing the entire circumference around the rotation axis 3a by the number of periods is a conductor target T. The division position is arbitrary, and therefore, for example, each conductor target T may have various shapes corresponding to one period, as illustrated in Figs. 16A, 16B, 16C, and 16D.

[0146] Fig. 15D shows an example in which multiple conductor patterns T are formed from curved annular coil conductor patterns, and corresponds to the configuration shown by the phantom lines in Fig. 14B. The conductor target T is a portion of one period. For example, in the configuration of Fig. 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 Fig. 15F.

[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. This conductor is an individual conductor pattern in the examples of Figures 15A and 15B, and is part of a continuous conductor pattern in the examples of Figures 15C to 15E.

[0148] Although the embodiment of the present invention has been described above, the present invention can also be embodied in other forms.

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

[0150] Furthermore, in the above-described embodiment, an example was shown in which multiple chip inductors L were arranged at equal intervals around the entire circumference of the rotation axis 3a, but the multiple chip inductors L do not necessarily have 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), one of the second-phase chip inductors L2(1) and L2(2), one of the third-phase chip inductors L3(1) and L3(2), and one of the fourth-phase chip inductors L4(1) and L4(2) were omitted, and the multiple chip inductors were arranged at unequal intervals, detection signals VA and VB that are 90 degrees out of phase with each other can still be obtained.

[0151] In the above embodiment, the chip inductor L is surface-mounted on one main surface 10a of the printed circuit board 10 of the stator 1. However, 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 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 as many chip inductors L can be mounted on the printed circuit board 10. The greater the number of chip inductors L, the greater the total number of turns, thereby increasing output. Furthermore, the greater the number of chip inductors L, the more evenly the variations between the chip inductors L are averaged, thereby improving detection accuracy. Since the distances from the multiple chip inductors L to the conductor target T are equal on both the one main surface 10a and the other main surface 10b of the printed circuit board 10, the output of the multiple chip inductors L arranged on each main surface 10a, 10b can be uniform. Therefore, complex signal processing is not required.

[0152] The above-described fourth embodiment shows a two-track configuration in which two sets of conductor targets and chip inductors are provided along each of two rotational orbits, but a configuration in which three or more sets of conductor targets and chip inductors are provided along each of three or more rotational orbits may also be used.

[0153] In the first, second and fourth embodiments described above, examples have been shown in which the excitation coil is configured in a circular ring shape, but the excitation coil may be configured in another ring shape such as a polygonal ring shape.

[0154] In the above-described embodiment, an example using a multilayer chip inductor was described, but a wire-wound chip inductor may also be used. However, since a multilayer chip inductor can be configured more compactly, it is advantageous to use a multilayer chip inductor in order to perform position detection with high resolution by reducing the conductor target period (i.e., increasing the number of conductor targets). More specifically, even if the width of the conductor target on the rotational orbit is about 2 mm, a position detector can be configured using a multilayer chip inductor with a width of about 1 mm (preferably arranged around the entire circumference of the rotational orbit).

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

[0156] REFERENCE SIGNS LIST 1 stator 10 printed circuit board 12 excitation coil 2 rotor 20 printed circuit board 21 insulating substrate 23 non-conductor portion 3 rotating shaft 3a rotation axis 31, 32 connection electrode 5 excitation source 51 first excitation source 52 second excitation source 6 A-phase detection circuit 7 B-phase detection circuit 6 １ A phase detection circuit 7 １ B phase detection circuit 6 ２ A phase detection circuit 7 ２DESCRIPTION OF SYMBOLS B-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 application terminal 62 Second A-phase AC voltage application terminal 63 First A-phase signal detection terminal 64 Second A-phase signal detection terminal 70 B-phase AC bridge circuit 71 First B-phase AC voltage application terminal 72 Second B-phase AC voltage application terminal 73 First B-phase signal detection terminal 74 Second B-phase signal detection terminal 80 Annular coil conductor pattern 90 Annular coil conductor pattern 100 Inductive position detector 200 Inductive position detector 300 Inductive position detector 400 Inductive position detector T Conductive target O Rotational orbit λ Conductive target period p Chip inductor period L1 First phase chip inductor L2 Second phase chip inductor L3 Third phase chip inductor L4 Fourth phase chip inductor L1(1), L1(2) 1st phase chip inductor L2(1), L2(2) 2nd phase chip inductor L3(1), L3(2) 3rd phase chip inductor L4(1), L4(2) 4th phase chip inductor G1 1st phase group G2 2nd phase group G3 3rd phase group G4 4th phase group O １ First rotation orbit O ２ 2nd rotational orbit T １ Conductor target T ２ Conductor target L １ 1(1), L １ 1(2) First phase chip inductor L １ 2(1), L １ 2(2) Second phase chip inductor L １ 3(1), L １ 3(2) Third-phase chip inductor L １ 4(1), L １ 4(2) 4th phase chip inductor L ２ 1(1), L ２ 1(2), L ２ 1(3) First phase chip inductor L ２ 2(1), L ２ 2(2), L ２ 2(3) Second-phase chip inductor L ２ 3(1), L ２ 3(2), L２ 3(3) Third-phase chip inductor L ２ 4(1), L ２ 4(2), L ２ 4(3) 4th Phase Chip Inductor S １ 1st group S ２ Group 2

Claims

1. a stator having a wiring board; a rotor having a non-conductive part disposed opposite the stator and rotating relative to the stator about a predetermined rotation axis; a plurality of conductive targets of the same shape and size, which are periodically arranged around a circumference of the rotation axis and held by the non-conductive part of the rotor, and which move through a rotational orbit around the rotation axis as the rotor rotates; and a plurality of chip inductors that are surface-mounted on the main surface of the wiring board of the stator and arranged to face the rotation orbit with different spatial phases relative to the plurality of conductor targets, each chip inductor constituting a plurality of detection coils that detect changes in a magnetic field associated with the passage of the conductor targets.

2. The conductor targets are arranged along the rotational orbit at a predetermined conductor target period; 2. The inductive position detector of claim 1, wherein the chip inductor has a coil width along the rotational path that is between 25% and 75% of a period of the conductor target.

3. The conductor targets are arranged along the rotational orbit at a predetermined conductor target period; 2. The inductive position detector of claim 1, wherein the plurality of chip inductors include 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 a quarter period with respect to the conductor target period.

4. 4N pieces (N is a natural number) of the chip inductors are disposed at equal intervals along the entire circumference of the rotational orbit, 2. The inductive position detector according to claim 1, wherein the number Y of the conductor targets (Y is a natural number) is expressed as Y=4NM±N (M is a natural number).

5. a first set of the plurality of conductor targets and the plurality of chip inductors having a first rotation orbit as the rotation orbit, and a second set of the plurality of conductor targets and the plurality of chip inductors having a second rotation orbit different from the first rotation orbit as the rotation orbit, the first set sharing the stator and the rotor; The number Y of the first set of the plurality of conductor targets １ (Y １ is a natural number), and the number Y of the plurality of conductor targets in the second set ２ (Y ２ 2. The inductive position detector according to claim 1, wherein the first and second inputs are different from each other.

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

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

8. 8. The inductive position detector of claim 7, wherein the excitation coil includes: an annular first excitation coil that contains the first set of the chip inductors and the second set of the chip inductors when viewed along the rotation axis; and an annular second excitation coil arranged around the rotation axis so as to be contained by the first set of the chip inductors and the second set of the chip inductors when viewed along the rotation axis.

9. 2. The inductive position detector according to claim 1, wherein each conductive target comprises a conductive solid pattern or a circular coil conductive pattern formed on the non-conductive component, and the plurality of conductive targets are insulated from one another.

10. 2. The inductive position detector according to claim 1, wherein the plurality of conductor targets are connected to each other to form a circular coil conductor pattern extending around the entire circumference.

11. 11. The inductive type position detector according to claim 1, wherein the chip inductor is a multilayer chip inductor having a pair of connection electrodes on both ends.

12. The inductive position detector according to any one of claims 1 to 10, further comprising an excitation coil provided on the wiring board of the stator, formed in a ring shape that encapsulates the plurality of chip inductors when viewed along the axis of rotation, and that generates a magnetic field for inducing a voltage in the plurality of chip inductors.

13. The inductive position detector according to any one of claims 1 to 10, 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.