Induction type position detector

Abstract

The inductive position detector (100) of the present invention comprises: a stator (1) having a wiring board (10); a rotor (2) having a non-conductor part (21) arranged opposite to the stator (1) and rotating relative to the stator (1) about a rotation axis (3a); a conductor pattern (T) held on the non-conductor part (21) and having geometric periodicity in the circumferential direction about the rotation axis (3a), moving along a rotation track about the rotation axis (3a) as the rotor (2) rotates; and a plurality of wafer inductors (L) arranged in a spatially phase-different manner relative to the conductor pattern (T) and facing opposite to the rotation track and surface-mounted on the main surface of the wiring board (10) of the stator (1), and each forming a plurality of detection coils for detecting changes in the magnetic field generated as the conductor pattern (T) passes through.

Description

Technical Field

[0001] [Related Applications]

[0002] This patent application claims priority based on Japanese Patent Application No. 2022-95845 filed on June 14, 2022, and the entire contents are incorporated into this specification by reference.

[0003] The present invention relates to an inductive position detector. Prior Art

[0004] Position sensors used to detect rotational position include optical, magnetic, capacitive, resolver, and inductive sensors. Inductive position sensors move a movable portion holding a conductor within an AC magnetic field and detect changes in the magnetic field caused by the current induced in the conductor. Inductive position sensors are less susceptible to debris, dirt, and external magnetic fields, resulting in excellent environmental resistance. Furthermore, their simple structure allows for miniaturization and thinness, resulting in lower costs.

[0005] Inductive position detectors are disclosed in, for example, Patent Documents 1 to 4 listed below. Patent Documents 1 and 4 disclose a structure in which an excitation coil and a detection coil are formed using a conductor pattern on a printed circuit board. 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 varies according to 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 structure in which a detection coil is formed by a conductor pattern on a printed wiring board, an AC voltage is applied to the detection coil, and a change in the inductance of the detection coil when a conductive target moves relative to the detection coil is detected.

[0007] Patent Document 3 discloses a structure 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. (Prior Technical Literature) (Patent Document)

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 61-159101 Patent Document 2: Japanese Patent No. 5226694 Patent Document 3: Japanese Patent No. 5300164 Patent Document 4: Japanese Patent Application Laid-Open No. 2021-56176 Patent Document 5: Japanese Patent Application Laid-Open No. 2000-49014 Summary of the Invention Problems to be Solved by the Invention

[0009] In a position detector that detects a rotational position, size, resolution, and accuracy are very important performance characteristics. The number of detection cycles per revolution is called the shaft multiple angle. By passing a conductor target through a detection coil, a detection signal for one cycle is obtained. The greater the shaft multiple angle, the higher the resolution, and the easier it is to improve the accuracy. In order to increase the shaft multiple angle, it is necessary to increase the number of conductor targets arranged on the circumference around the rotation axis. Therefore, in order to realize a position detector with high resolution and accuracy in a small size, it is necessary to design the pitch of the conductor targets to be narrow.

[0010] When the pitch of the conductor targets is designed to be narrow, correspondingly, the detection coil must also be reduced. When the detection coil becomes smaller, the linked magnetic flux decreases, and thus the detected signal voltage becomes smaller. As a result, the signal-to-noise ratio (S / N ratio) decreases, and accurate position detection becomes difficult. Therefore, it is preferable to increase the number of turns of the detection coil as much as possible to ensure a sufficiently large signal voltage.

[0011] When forming the detection coil with a conductor pattern on a printed wiring board, a signal processing circuit can be formed on the same printed board, so the additional cost is low. In addition, since the printed wiring board has a low initial cost for production, it is suitable for small-lot production, and a design with a high degree of freedom can be carried out.

[0012] Examples of manufacturing a detection coil with a conductor pattern on a printed wiring board are shown in FIG. 52 of Patent Document 1 and FIG. 9 of Patent Document​

[0013] If a conductor pattern is formed on a silicon substrate using a semiconductor process, as described in Patent Document 3, the pattern width, pattern spacing, and via diameter can be made finer than on a printed wiring board, enabling the production of very small detection coils. However, semiconductor processes incur significant initial costs, coupled with their low degree of flexibility, making them unsuitable for diverse, low-volume production. Furthermore, the size of the silicon substrate is limited, necessitating the compact placement of detection coils. Consequently, detection is performed locally on a circumference around the axis of rotation. Using multiple elements would allow detection at evenly distributed locations around the circumference, but this design is impractical due to cost considerations.

[0014] Regarding coil shapes other than spirals, proposals include detection coils formed by intersecting patterns in a figure-eight pattern, as shown in FIG. 15 of Patent Document 1, and zigzag patterns with a Vernier effect, as shown in FIG. 2 of Patent Document 4. In either case, the portion enclosed by the back-and-forth pattern forms a single turn. Multiplexing the back-and-forth patterns allows for more than one turn, but the narrow spacing between conductors makes it difficult to manufacture coils with a large number of turns. Furthermore, to detect rotational position, it is preferable to provide two or more detection coils that output signals of different phases. However, with figure-eight or zigzag patterns, it is not possible to arrange two detection coils on the same circumference of a single wiring layer. Therefore, the two detection coils must be formed on different wiring layers, or on the same wiring layer, with different radial positions (distances from the axis of rotation). However, the two detection coils formed on different wiring layers have different distances from the conductive target. Furthermore, the conductive target is formed in a sector shape centered on the rotation axis, so its circumferential width varies according to its radial position. Consequently, the areas of the two radially disparate detection coils—the inner and outer detection coils—that actually face the conductive target differ. Consequently, regardless of the design, the output of the detection coils is prone to imbalance, requiring special signal processing.

[0015] Furthermore, the configuration shown in Figure 2 of Patent Document 4 requires an offset balance design because positive and negative detection is performed on the outside and inside of the circle, even when in phase. This makes designing the pattern shape difficult to achieve the necessary accuracy.

[0016] On the other hand, when using a position sensor for electric motor control, the position sensor's rotor is typically mounted on the motor shaft, on the side opposite the output shaft. When the electric motor is assembled into a device utilizing the motor's driving force, radial loads may be applied to the motor shaft. Consequently, the motor shaft may deflect, causing the axis to deviate on the side opposite the output shaft. When only local detection is performed around the rotation axis, as described in Patent Documents 2 and 3, this axis deviation results in a shift in the detection position, adversely affecting motor control.

[0017] One embodiment of the present invention provides an inductive position detector capable of solving at least one of the aforementioned problems.

[0018] More specifically, one embodiment of the present invention provides an inductive position detector that has high design freedom, is compact, and has high detection resolution. The means to solve the problem

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

[0020] 1. An inductive position detector comprising: The stator has a wiring substrate; The rotor comprises a non-conductive part disposed opposite to the stator and configured to rotate relative to the stator about a predetermined rotation axis; a plurality of conductive targets of the same shape and size, which are periodically arranged along a circumference around the rotation axis and retained on the non-conductive part of the rotor, and move along a rotational track around the rotation axis as the rotor rotates; and A plurality of chip inductors are arranged in a manner that their spatial phases are different relative to the plurality of conductive targets and that they face the rotational track. They are surface-mounted on the main surface of the wiring substrate of the stator and each constitutes a plurality of detection coils that detect changes in the magnetic field generated by the passage of the conductive targets.

[0021] As the rotor rotates about its axis of rotation, multiple conductive targets mounted on a non-conductive component (typically an insulator, such as an insulating substrate) on the rotor follow a rotational trajectory around the axis of rotation. Chip inductors, each forming a plurality of detection coils, are arranged on the main surface (mounting surface) of the stator's wiring substrate, facing the rotational trajectory of the conductive targets. The chip inductors detect changes in the magnetic field caused by the passage of the conductive targets, outputting signals representing these changes. The multiple chip inductors have spatially different phases relative to the multiple conductive targets, thus outputting signals with different phases as the rotor rotates. Therefore, by processing the output signals of the multiple chip inductors, the relative rotational position of the rotor with respect to the stator can be detected.

[0022] Chip inductors are compact electronic components that can accommodate a high number of turns and are commercially available at low prices. Therefore, when increasing the number of conductor targets to increase the number of poles and improve detection resolution, configurations corresponding to smaller conductor target periods (pitch between the conductor targets) can be implemented without significantly reducing the detection signal and increasing costs. Furthermore, industrially mass-produced chip inductors offer highly uniform performance. This allows for uniform detection signals from multiple chip inductors, eliminating the need for complex signal processing.

[0023] Furthermore, unlike designs that form multiple detection coils on a silicon substrate using semiconductor processes, multiple chip inductors, each a separate component, can be positioned anywhere relative to the rotating track, offering a high degree of flexibility. This allows for a full-circle arrangement. This full-circle arrangement easily accommodates misalignment of the rotating shaft connected to the rotor. Because chip inductors are compact, they can be placed around the entire circumference of the track, even when reducing the conductor target period to improve resolution.

[0024] As described above, it is possible to provide an inductive position detector that has a high degree of design freedom, is compact, and has a high detection resolution.

[0025] Typically, the plurality of conductor targets are equal to each other along the length of the rotation track. For example, the plurality of conductor targets of the same shape and size are arranged in a rotationally symmetrical manner around the rotation axis.

[0026] The plurality of chip inductors can also be mounted on one main surface, or the same main surface, of the stator's wiring substrate. This allows the distances from the plurality of chip inductors to the conductor target to be uniform, and the outputs from the plurality of chip inductors to be uniform. Typically, the plurality of chip inductors are surface-mounted on the main surface of the wiring substrate that faces the rotor. This allows the chip inductors to be closer to the conductor target, and thus, the output variation of the chip inductors can be increased as the conductor target passes. However, the plurality of chip inductors can also be mounted on the main surface of the wiring substrate that is opposite to the rotor side. In this case, despite the presence of the wiring substrate, the distances from the plurality of chip inductors to the conductor target remain approximately the same.

[0027] Alternatively, multiple chip inductors may be mounted on one main surface of a wiring substrate, and multiple chip inductors may be mounted on the other main surface of the wiring substrate. By mounting chip inductors on both sides of the wiring substrate, the number of chip inductors can be increased, for example, doubling the number of chip inductors. The greater the number of chip inductors, the greater the number of turns overall, thereby increasing output. Furthermore, the greater the number of chip inductors, the more evenly distributed the variations between chip inductors, thereby improving detection accuracy. The distances from the multiple chip inductors to the conductor target are equal on both the one and other main surfaces of the wiring substrate. Therefore, the outputs of the multiple chip inductors arranged on each main surface can be normalized, eliminating the need for complex signal processing.

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

[0029] In this configuration, the chip inductor's coil width along the rotating track is between 25% and 75% (between 25% and 75%) of the target conductor period. This allows the chip inductor to output a high-quality detection signal that changes with the passage of the target conductor. By using industrially produced, compact chip inductors, the number of target conductors can be increased to improve detection resolution. Even if the target conductor period is shortened accordingly, a position detector for detecting rotational position can still be constructed using a chip inductor with a coil width of 25% to 75% of the target conductor period. While the chip inductor's coil width is preferably approximately 50% of the target conductor period, good detection is possible within the 25% to 75% range. This makes it easy to select a suitable chip inductor from commercially available standard products. However, a chip inductor coil width of 50% of the target conductor period is not necessarily ideal. The optimal design conditions depend on factors such as the position detector's axis angle multiplier, size, and rotor / stator gap.

[0030] 3. The inductive position detector according to item 1 or 2, wherein the conductive targets are arranged along the rotating track at a predetermined conductive target period; The aforementioned multiple chip inductors are composed of: a first phase group, a second phase group, a third phase group and a fourth phase group, each of which contains 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, each of which is configured with a phase difference of 1 / 4 of the target period of the aforementioned conductor.

[0031] The 1st phase chip inductor, the 2nd phase chip inductor, the 3rd phase chip inductor and the 4th phase chip inductor have spatial phases that differ by 90 degrees relative to the conductor target. Therefore, detection signals for correctly detecting the rotation position of the rotor can be obtained from these chip inductors.

[0032] The plurality of chip inductors may be arranged at equal or unequal intervals along the rotating track. Furthermore, the plurality of chip inductors may be arranged over the entire circumference of the rotating track, or there may be areas along the rotating track where chip inductors are arranged and areas where chip inductors are not arranged.

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

[0034] According to this configuration, 4N chip inductors are arranged at equal intervals throughout the entire circumference of the circular track. Meanwhile, the number Y of conductor targets arranged at equal intervals along the circular track satisfies Y = 4NM ± N. Consequently, the 4N chip inductors can be divided into four groups (each consisting of N chip inductors) each with a 90-degree phase difference relative to the spatial phase of the conductor targets. Specifically, the groups are divided into a first phase group consisting of N first-phase chip inductors, a second phase group consisting of N second-phase chip inductors, a third phase group consisting of N third-phase chip inductors, and a fourth phase group consisting of N fourth-phase chip inductors. Consequently, detection signals with 90-degree phase differences can be obtained from the first, second, third, and fourth phase groups.

[0035] 5. The inductive position sensor according to any one of items 1 to 4, comprising a first group of the plurality of conductive targets and the plurality of chip inductors having a first rotation track as the rotation track, and a second group of the plurality of conductive targets and the plurality of chip inductors having a second rotation track different from the first rotation track as the rotation track, wherein the first group and the second group share the stator and the rotor; The number Y1 (Y1 is a natural number) of the plurality of conductor targets in the first group is different from the number Y2 (Y2 is a natural number) of the plurality of conductor targets in the second group.

[0036] This configuration enables a multi-track inductive position detector with a first rotation track and a second rotation track. By differentiating the number Y1 of the first set of conductive targets corresponding to the first rotation track from the number Y2 of the second set of conductive targets corresponding to the second rotation track, it is possible to distinguish and detect rotational positions over a wide range of rotational angles.

[0037] 6. The inductive position detector as described in item 5, wherein the number Y1 of the plurality of conductor targets in the first group and the number Y2 of the plurality of conductor targets in the second group are coprime. This configuration enables detection of rotational positions within a wider range of rotation angles. More specifically, absolute detection is possible, whereby rotational positions within a single rotation (360 degrees) can be detected.

[0038] 7. The inductive position detector as described in item 5 or 6 further comprises an excitation coil which is provided on the aforementioned wiring substrate of the aforementioned stator and is shared for inducing voltage in the aforementioned plurality of chip inductors of the aforementioned first group and the aforementioned plurality of chip inductors of the aforementioned second group. According to this configuration, a common exciting coil can be used for exciting the first and second groups of chip inductors, thereby simplifying the configuration.

[0039] 8. An inductive position detector as described in item 7, wherein the excitation coil comprises: a first annular excitation coil which, when viewed along the rotation axis, encloses the first group of the plurality of chip inductors and the second group of the plurality of chip inductors; and a second annular excitation coil which, when viewed along the rotation axis, is arranged around the rotation axis in a manner enclosed by the first group of the plurality of chip inductors and the second group of the plurality of chip inductors. According to this structure, the two inner and outer excitation coils can fully excite the first and second groups of chip inductors, thereby obtaining a large detection signal.

[0040] 9. An inductive position detector as described in any one of items 1 to 8, wherein each conductive target includes a conductive filling pattern or a ring-shaped coil conductive pattern formed on the aforementioned non-conductive part, and the aforementioned multiple conductive targets are insulated from each other. Typically, the plurality of conductor targets have equal lengths along the rotational track. For example, the plurality of conductor targets of the same shape and size are arranged rotationally symmetrically about the rotation axis. More typically, adjacent conductor targets are spaced apart along the rotational track. This spacing may also be equal to the length of the conductor targets along the rotational track.

[0041] 10. The inductive position detector according to any one of items 1 to 8, wherein the plurality of conductor targets are connected to each other to form a ring-shaped coil conductor pattern extending over the entire circumference.

[0042] As described above, in one embodiment, a plurality of individual conductor targets spaced at equal intervals along the circumference around the rotation axis are retained by a non-conductive component of the rotor, forming a periodic (geometrically periodic) conductor pattern. Furthermore, in another embodiment, a circular coil conductor pattern extending along the entire circumference around the rotation axis is formed by connecting a plurality of conductor targets to form a periodic (geometrically periodic) conductor pattern. Therefore, the so-called conductor target refers to a conductor that is part of a period of a periodic (geometrically periodic) conductor pattern formed along a circumference around the rotation axis. In one embodiment, the conductor is an individual conductor pattern, and in another embodiment, it is part of a continuous conductor pattern.

[0043] 11. The inductive position detector according to any one of items 1 to 10, wherein the chip inductor is a multilayer chip inductor having a pair of connecting electrodes at both ends. The use of multilayer chip inductors enables the construction of compact detection coils with a high number of turns. This allows the necessary detection signal to be obtained from the chip inductor, even if the chip inductor size is limited by the shortened conductor target period caused by increasing the number of conductor targets to improve detection resolution. Furthermore, designs with multiple chip inductors arranged around the entire circumference of the rotating track are easily implemented.

[0044] 12. The inductive position detector as described in any one of items 1 to 11 further includes an excitation coil, which is arranged on the aforementioned wiring substrate of the aforementioned stator and, when viewed along the aforementioned rotation axis, is formed into a ring that surrounds the aforementioned multiple chip inductors and generates a magnetic field for inducing voltage in the aforementioned multiple chip inductors.

[0045] With this configuration, applying an AC voltage to the excitation coil induces an AC voltage in the chip inductor. In this state, when a conductive object passes near the chip inductor, the eddy current induced in the conductive object by the magnetic field from the excitation coil cancels 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 object.

[0046] 13. An inductive position detector as described in any one of items 1 to 12, wherein the plurality of chip inductors are connected in a manner to form an AC bridge circuit having a pair of AC voltage application terminals and a pair of signal detection terminals.

[0047] In this configuration, when an AC voltage is applied to the AC voltage application terminals of an AC bridge circuit formed by connecting chip inductors in a bridge configuration, a detection signal indicating a change in the impedance of the chip inductor appears at the signal detection terminals of the AC bridge circuit. Since the vast majority of the impedance of the chip inductor is inductance, the detection signal series of the AC bridge circuit can also be regarded as indicating a change in the inductance of the chip inductor. On the other hand, the inductance of the chip inductor changes in accordance with the positional relationship with the conductor target. Therefore, by means of the detection signal from the AC bridge circuit, a change in inductance can be detected, and thereby, the position of the conductor target can be detected. That is, it is possible to detect the rotational position of the rotor in which the conductor target is held by non-conductor parts.

[0048] The above or other objects, features, and effects of the present invention will become apparent from the description of the embodiments described below with reference to the accompanying drawings. Effects of the Invention Brief Explanation of the Drawings

[0049] FIG. 1 is an exploded perspective view for explaining the configuration of an inductive position detector according to a first embodiment of the present invention. FIG. 2 is a side view of the inductive position detector of FIG. 1. FIG. 3 is a top view showing the relative arrangement of the conductor target of the rotor and the chip inductors arranged in the stator. FIG. 4 is an electronic circuit diagram showing the equivalent circuit of the stator. FIGS. 5A to 5C are waveform diagrams showing examples of an AC voltage generated by an excitation source and a detection signal with a 90-degree phase difference. FIG. 6 is an exploded perspective view of an inductive position detector according to a second embodiment of the present invention. FIG. 7 is a top view showing the relative arrangement of the conductor target of the rotor and the chip inductors arranged in the stator. FIG. 8 is an electronic circuit diagram showing the equivalent circuit of the stator. FIG. 9 is an exploded perspective view showing the configuration of an inductive position detector according to a third embodiment of the present invention. FIG. 10 is an electronic circuit diagram showing the equivalent circuit of the stator of the inductive position detector of FIG. 9. FIG. 11 is an exploded perspective view for explaining the configuration of an inductive position detector according to a fourth embodiment of the present invention. FIG. 12 is a top view showing the positional relationship between the conductor target of the rotor and the chip inductors arranged in the stator. FIG. 13 is an electronic circuit diagram showing the equivalent circuit of the stator. FIG14A is a plan view showing an example of a structure including a conductor target formed with a coil-shaped conductor pattern. FIG. 14B is a plan view showing another configuration example including a conductor target formed with a coil-shaped conductor pattern. 15A to 15E show various examples of conductive targets. 16A to 16D show examples of how conductor targets are differentiated in a continuous annular coil conductor pattern extending all around. Implementation Method

[0050] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0051] Fig. 1 is an exploded perspective view for explaining the structure of an inductive position detector 100 according to a first embodiment of the present invention. Fig. 2 is a side view of the inductive position detector 100 as viewed in the direction of arrow 101 in Fig. 1 .

[0052] The inductive position detector 100 includes a stator 1 and a rotor 2 that rotates relative to the stator 1 about a rotation axis 3a. The detector is configured to output a detection signal indicating the relative rotational position of the rotor 2 relative to the stator 1 about the rotation axis 3a. The rotor 2 is coupled to a rotating shaft 3 (see Figure 2), the target of rotational position detection, and rotates along with the shaft 3 about the rotation axis 3a. The stator 1 includes a printed circuit board 10 (printed wiring board), which serves as a wiring substrate. The rotor 2 is configured with another printed circuit board 20, spaced apart from the printed circuit board 10 by a predetermined gap 4 (e.g., 0.1 mm to 1 mm).

[0053] The printed circuit board 10 of the stator 1 includes an insulating substrate 11 and a conductive pattern (e.g., a copper foil pattern) formed on at least one of the main surfaces 10a, 10b. The printed circuit board 10 may also be a multilayer printed circuit board having a plurality of stacked wiring layers (e.g., four wiring layers). In this case, the conductive pattern may be included in the wiring layers not exposed on the main surfaces 10a, 10b.

[0054] Similarly, the printed circuit board 20 of the rotor 2 comprises an insulating substrate 21, which is a non-conductive component, and a plurality of conductive targets T, each consisting of a conductive pattern (e.g., a copper foil pattern) formed on one of the main surfaces 20a and 20b and thereby retained on the insulating substrate 21. In this embodiment, the conductive targets T are formed on the main surface 20a opposite the stator 1 side, but they can also be formed on the other main surface 20b facing the stator 1. Furthermore, when the printed circuit board 20 is constructed as a multilayer printed circuit board, the conductive targets T can also be formed on an internal wiring layer other than the main surfaces 20a and 20b. The conductive targets T are preferably formed on the same wiring layer (including the main surface) of the printed circuit board 20. To minimize the distance from the chip inductors L1 to L4 described later, the conductive targets T are preferably formed on a wiring layer as close to the stator 1 as possible (e.g., the main surface 20b).

[0055] 1 and 2 , for clarity, the conductor target T is shaded. This also applies to the other figures described below.

[0056] 3 is a top view taken through the insulating substrate 21 and viewed along the rotation axis 3 a , showing the relative arrangement of the conductive target T and the chip inductors L1 to L4 (hereinafter collectively referred to as “chip inductors L”) arranged on the stator 1 .

[0057] Conductor targets T are periodically arranged along a circumference around the rotation axis 3a and are held on one main surface of the insulating substrate 21. Thus, the plurality of conductor targets T form a conductor pattern having geometric periodicity along the circumferential direction around the rotation axis 3a. Each conductor in this conductor pattern is a single conductor target T. The plurality of conductor targets T move along a rotation orbit O (a circular orbit) around the rotation axis 3a as the rotating shaft 3, and therefore the rotor 2, rotates.

[0058] In this embodiment, a plurality of conductor targets T are arranged at equal intervals with a predetermined period (pitch) λ (hereinafter referred to as the "conductor target period λ") throughout the entire circumference of the rotation axis 3a. In this embodiment, each conductor target T is a conductor-filled pattern formed on one main surface of the insulating substrate 21. The plurality of conductor targets T are separated and insulated from each other along the circumferential direction. In other words, each conductor target T is formed by a separate conductor pattern (conductor-filled pattern). The plurality of conductor targets T have the same length (width) along the rotation track O. More specifically, in this embodiment, the plurality of conductor targets T are formed by conductor patterns of the same shape and size, and are arranged rotationally symmetrically about the rotation axis 3a. More specifically, each conductor target T is formed into a sector shape (more accurately, a sector shape with the inner diameter portion cut off) centered on the rotation axis 3a. In the illustrated example, the spacing between adjacent conductive targets T along the rotation track O, i.e., the length of the non-conductive portion 23 along the rotation track O, is equal to the length (width) of the conductive targets T along the rotation track O. However, this is merely an example. The length (width) of the conductive targets T along the rotation track O depends on the design of the inductive position sensor 100. For example, approximately 70% of the conductive target period λ may be optimal.

[0059] A plurality of chip inductors L are surface-mounted on one main surface 10a of the printed circuit board 10 that constitutes the stator 1. In this embodiment, the chip inductors L are mounted on the main surface 10a facing the rotor 2, but they can also be mounted on the other main surface 10b opposite the rotor 2. The chip inductors L are arranged so that their spatial phases relative to the plurality of conductive targets T differ and they face the rotational orbit O of the conductive targets T. Thus, the chip inductors L each constitute a plurality of detection coils that detect changes in the magnetic field caused by the passage of the conductive targets T. Because the chip inductors L are surface-mounted on the same main surface 10a of the printed circuit board 10, their spacing from the rotor 2 (more specifically, the spacing from the conductive targets T) is substantially equal.

[0060] Typically, the plurality of chip inductors L are mass-produced, industrially manufactured chip inductors of the same specifications. Each chip inductor L has a coil width W along the rotating track O that is between 25% and 75% (between 25% and 75%) of the target conductor period λ. While this coil width W is preferably approximately 50% of the target conductor period λ, a range of 25% to 75% allows for good testing. Therefore, it is sufficient to select commercially available standard chip inductors with a coil width within the range of 25% to 75% of the target conductor period λ.

[0061] The chip inductor L is a multilayer chip inductor with a pair of connecting electrodes 31 and 32 (see Figure 1) at both ends. Examples of multilayer chip inductors are described in Patent Document 5. Using a multilayer chip inductor enables the construction of a compact detection coil with a high number of turns. This allows the chip inductor L to generate a detection signal of the necessary magnitude even when the target conductor period λ is shortened by increasing the number of target conductors T to improve detection resolution.

[0062] Typically, the chip inductor L has a rectangular parallelepiped shape with its long side oriented in the direction in which the connection electrodes 31 and 32 face each other. Furthermore, when surface-mounted on the printed circuit board 10 with the coil's central axis (the direction of the winding's central axis) perpendicular to the main surface 10a of the printed circuit board 10, the length of its short side 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 long side aligned with the radial direction of the rotating track O. However, this long side does not necessarily need to align with the radial direction of the rotating track O.

[0063] In this embodiment, a plurality of chip inductors L are arranged at equal intervals along the entire circumference of the rotation axis 3a along the rotation track O. In this embodiment, four chip inductors L are arranged at 90-degree intervals around the circumference of 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), each arranged with a phase difference of one-quarter of the target conductor period λ.

[0064] In this embodiment, five conductor targets T are arranged around the rotation axis 3a with a conductor target period λ of 72 degrees. This conductor target period λ corresponds to one electrical angle period, or 360 degrees. Four chip inductors L are arranged with a 90-degree period p (pitch) (hereinafter referred to as the "chip inductor period p"). Therefore, the difference between the conductor target period λ and the chip inductor period p is 18 (=90-72) degrees. 18 (=72 / 4) degrees corresponds to one-quarter of the conductor target period λ (72 degrees).

[0065] Therefore, the two chip inductors L, positioned at a 90-degree mechanical angle, have a phase difference of 90 degrees electrical angle, or one-quarter of the target conductor period λ. Specifically, the second-phase chip inductor L2 has a 90-degree phase difference with the first-phase chip inductor L1. Similarly, the third-phase chip inductor L3 has a 90-degree phase difference with the second-phase chip inductor L2, and the fourth-phase chip inductor L4 has a 90-degree phase difference with the third-phase chip inductor L3. Therefore, the third-phase chip inductor L3 has a 180-degree phase difference with the first-phase chip inductor L1, and the two are in opposite phases. Similarly, the fourth-phase chip inductor L4 has a 180-degree phase difference with the second-phase chip inductor L2, and the two are in opposite phases.

[0066] Each chip inductor L is surface-mounted on a printed circuit board 10 with its coil center axis oriented parallel to the rotation axis 3a. Therefore, when a magnetic field changes in the direction parallel to the coil center axis, i.e., the rotation axis 3a, the chip inductor L generates an induced voltage corresponding to the change in the magnetic field.

[0067] An excitation coil 12 is provided on the printed circuit board 10 that constitutes the stator 1. The excitation coil 12 is formed into a ring shape, enclosing a plurality of chip inductors L, when viewed from above along the rotation axis 3a (see FIG3 ). That is, the center axis of the excitation coil 12 is parallel to the rotation axis 3a. In this embodiment, the excitation coil 12 is formed into a ring shape, enclosing a plurality of conductor targets T, when viewed from above. In this embodiment, the excitation coil 12 is generally annular in shape, when viewed from above. Specifically, the excitation coil 12 is a pattern coil formed from a spiral conductor pattern formed on the printed circuit board 10, and is formed into an annular shape (in this embodiment, an annular shape) as a whole. The printed circuit board 10 may be, for example, a multilayer printed circuit board having a plurality of wiring layers stacked on top of each other. In this case, pattern coils may be formed with spiral conductor patterns on a plurality of wiring layers (eg, four layers), and these pattern coils may be connected via through holes connecting the wiring layers to form the excitation coil 12 .

[0068] The excitation coil 12's lead portions 12a and 12b are connected to an excitation source 5 generating an AC voltage. When the AC voltage is applied to the excitation coil 12 from the excitation source 5, the excitation coil 12 generates a high-frequency magnetic field parallel to the rotation axis 3a, inverted at the frequency of the AC voltage. This high-frequency magnetic field is linked to the chip inductor L by the magnetic field of the excitation coil 12, generating an induced electromotive force in the chip inductor L.

[0069] Although not shown in the figure, a conductor pattern (more specifically, a copper foil pattern) for connecting the chip inductor L to constitute a detection circuit is formed on the printed circuit board 10 of the stator 1 .

[0070] Figure 4 shows the equivalent circuit of stator 1. The first-phase chip inductor L1 generates an A-phase detection signal, while the third-phase chip inductor L3 generates an / A-phase detection signal, which is the opposite phase of the A-phase detection signal. Thus, the first-phase chip inductor L1 and the third-phase chip inductor L3 are connected at the same polarity (differential connection) to form an A-phase detection circuit 6 that outputs the differential signal between them 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. Furthermore, the fourth-phase chip inductor L4 generates a / B-phase detection signal, which is the opposite phase of the B-phase detection signal. Thus, the second-phase chip inductor L2 and the fourth-phase chip inductor L4 are connected at the same polarity (differential connection) to form a B-phase detection circuit 7 that outputs the differential signal between them as a detection signal VB.

[0071] As previously mentioned, when an AC voltage (A sin ωt, where A is a constant representing amplitude, ω represents angular frequency, and t represents time) is applied to the excitation coil 12 from the excitation source 5, detection signals VA and VB are generated from the A-phase detection circuit 6 and the B-phase detection circuit 7, respectively, in response to changes in the interlinkage flux 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 conductive 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 conductive target T and the chip inductor L face each other, the voltage induced in the chip inductor L decreases. By utilizing this phenomenon, the signal processing circuit 8 appropriately processes the detection signals VA and VB, thereby obtaining rotational position information.

[0072] For the voltage induced in chip inductor L, let the fixed value be C and the variable value be V. The phase is considered positive when the conductor target T moves in the clockwise direction (CW), with chip inductor L1 in Figure 3 as the reference. Thus, at a rotation angle θ, the voltages VL1 to VL4 induced in each of chip inductors L1 to L4 are as follows. Here, K represents the amplitude of the induced AC voltage. VL1=Ksinωt.{C+V.sin(θ+0)}=Ksinωt.(C+V.sinθ)…(1) VL2=Ksinωt.{C+V.sin(θ+90)}=Ksinωt.(C+V.cosθ)…(2) VL3=Ksinωt.{C+V.sin(θ+180)}=Ksinωt.(CV.sinθ)…(3) VL4=Ksinωt.{C+V.sin(θ+270)}=Ksinωt.(CV.cosθ)…(4)

[0073] The chip inductors L1 and L3, and the chip inductors L2 and L4 are differentially connected, so the detection signals VA and VB are as follows. VA=VL1-VL3=Ksinωt.(C+V.sinθ)-Ksinωt.(CV.sinθ)=2V.Ksinωt.sinθ…(5) VB=VL2-VL4=Ksinωt(C+V.cosθ)-Ksinωt(CV.cosθ)=2V.Ksinωt.cosθ…(6)

[0074] Figure 5A shows an example waveform of the AC voltage generated by the excitation source 5, while Figures 5B and 5C show example waveforms of the detection signals VA and VB. As described above, the detection signals VA and VB output by the detection circuits 6 and 7 are high-frequency signals whose amplitudes are modulated according to the changes in the induced voltage generated by the rotation of the rotor 2. The chip inductors L1 and L3 that constitute the A-phase detection circuit 6 and the chip inductors L2 and L4 that constitute the B-phase detection circuit 7 are arranged on the stator 1 at 90-degree intervals. Therefore, the detection signals VA and VB are signals with a 90-degree phase difference. The detection signals VA and VB are demodulated by the signal processing circuit 8 and subjected to arctangent calculation to determine the rotation angle θ of the rotor 2.

[0075] FIG6 is an exploded perspective view of an inductive position sensor 200 according to a second embodiment of the present invention. FIG7 is a top view of the inductive position sensor 200, viewed along the rotation axis 3a. The top view shows the arrangement of the conductive target T and the chip inductor L, seen through the insulating substrate 21 of the rotor 2. FIG8 is an equivalent circuit diagram showing the electrical configuration of the stator 1. In the above figures, corresponding components shown in FIG1 through FIG4 are denoted by the same reference numerals.

[0076] In this embodiment, the number of conductor targets T and the number of chip inductors L are both 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. Examining the spatial phases of the conductor targets T reveals that the chip inductors L, spaced 180 degrees apart around the rotation axis 3a, are in equal phase. That is, the plurality of chip inductors L can be classified into: a first phase group G1 (A phase) consisting of a pair of first phase chip inductors L1(1) and L1(2) facing each other with the rotation axis 3a interposed therebetween; a second phase group G2 (B phase) consisting of another pair of second phase chip inductors L2(1) and L2(2) facing each other with the rotation axis 3a interposed therebetween; a third phase group G3 ( / A phase) consisting of yet another pair of third phase chip inductors L3(1) and L3(2) facing each other with the rotation axis 3a interposed therebetween; and a fourth phase group G4 ( / B phase) consisting of yet another pair of fourth phase chip inductors L4(1) and L4(2) facing each other with the rotation axis 3a interposed therebetween. In addition, the first phase chip inductor L1(1), L1(2), the second phase chip inductor L2(1), L2(2), the third phase chip inductor L3(1), L3(2) and the fourth phase chip inductor L4(1), L4(2) are spatially spaced around the rotation axis 3a with a phase difference of 1 / 4 of the target conductor period λ.

[0077] Here, a pair of first-phase chip inductors L1(1), L1(2) and a pair of third-phase chip inductors L3(1), L3(2) are connected in series and differentially 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 connected in series and differentially to form a B-phase detection circuit 7. The A-phase detection circuit 6 and the B-phase detection circuit 7 output amplitude-modulated detection signals VA and VB with a phase difference of 90 degrees, similarly to the first embodiment. However, the conductor target period λ, which is equivalent to 360 degrees in electrical angle, is equivalent to 36 (=360 / 10) degrees in mechanical angle. Therefore, compared with the first embodiment, the rotation position can be detected with twice the resolution. Although not shown in the figure, a conductor pattern (more specifically, a copper foil pattern) for connecting the chip inductor L to form the detection circuits 6 and 7 is formed on the printed circuit board 10 of the stator 1 .

[0078] For the voltage induced in the chip inductor L, let the fixed amount be C and the variable amount be V. The phase is positive when the conductor target T moves in the clockwise direction CW, with the chip inductor L1(1) as the reference. Thus, at the rotation angle θ, the voltages VL1(1) to VL4(1) and VL1(2) to VL4(2) induced in each chip inductor L1(1) to L4(1) and L1(2) to L4(2) are as follows. Here, K represents the amplitude of the induced AC voltage. VL1(1)=Ksinωt.{C+V.sin(θ+0)}=Ksinωt.(C+V.sinθ)…(7) VL2(1)=Ksinωt.{C+V.sin(θ+90)}=Ksinωt.(C+V.cosθ)…(8) VL3(1)=Ksinωt.{C+V.sin(θ+180)}=Ksinωt.(CV.sinθ)…(9) VL4(1)=Ksinωt.{C+V.sin(θ+270)}=Ksinωt.(CV.cosθ)…(10) VL1(2)=Ksinωt.{C+V.sin(θ+0)}=Ksinωt.(C+V.sinθ)…(11) VL2(2)=Ksinωt.{C+V.sin(θ+90)}=Ksinωt.(C+V.cosθ)…(12) VL3(2)=Ksinωt.{C+V.sin(θ+180)}=Ksinωt.(CV.sinθ)…(13) VL4(2)=Ksinωt.{C+V.sin(θ+270)}=Ksinωt.(CV.cosθ)…(14)

[0079] The chip inductors L1(1), L1(2) and L3(1), L3(2), and the chip inductors L2(1), L2(2) and L4(1), L4(2) are differentially connected in series, so the detection signals VA and VB are as follows. VA=VL1(1)+VL1(2)-VL3(1)-VL3(2)=2Ksinωt.(C+V.sinθ)-2Ksinωt.(CV.sinθ)=4V.Ksinωt.sinθ…(15) VB=VL2(1)+VL2(2)-VL4(1)-VL4(2) =2Ksinωt(C+V.cosθ)-2Ksinωt(CV.cosθ)=4V.Ksinωt.cosθ…(16)

[0080] As described above, in the second embodiment, by increasing the number of chip inductors L, fluctuations in the detection signals VA and VB can be significantly detected, thereby improving the signal-to-noise ratio (S / N ratio). Furthermore, the chip inductors L, positioned 180 degrees apart in mechanical angle and facing each other, detect signals with the same phase. This reduces the effects 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 on the detection signal, thereby improving detection accuracy.

[0081] Consider the configuration conditions of the chip inductors L used to form two detection circuits 6 and 7 when Y (Y is a natural number) conductor targets T are configured on the rotor 2 and 4N (N is a natural number) chip inductors L are configured at equal intervals on the stator 1. The two detection circuits 6 and 7 generate detection signals VA and VB with a phase difference of 90 degrees in electrical angle.

[0082] The relationship between the conductor target period λ and the chip inductor period p when there is a phase difference of λ / 4 (one-fourth of the conductor target period λ) is expressed as the following equation (17): where M is a natural number. p=λ(M±1 / 4)…(17) The conductor target period λ and the chip inductor period p are respectively expressed by the following equations (18) and (19) using the circumference Cl of the rotating track O through which the conductor target T passes. λ=Cl / Y…(18) p=Cl / 4N…(19) Substituting equations (18) and (19) into equation (7) yields the following equation (20). Therefore, as long as there is a combination of natural numbers Y, N, and M that satisfies the relationship in equation (20), detection circuits 6 and 7 can detect detection signals having a phase difference of 90 degrees in electrical angle. Y=4NM±N…(20)

[0083] The first embodiment corresponds to the case where N = 1, M = 1, and Y = 5. The second embodiment corresponds to the case where N = 2, M = 1, and Y = 10. As described above, according to the first and second embodiments, a plurality of chip inductors L can be used to construct two detection circuits 6 and 7 that generate two detection signals VA and VB that differ in phase by 90 degrees. Furthermore, based on these detection signals VA and VB, the rotational position of the rotor 2, that is, the rotational position (rotation angle) of the rotating shaft 3, can be detected.

[0084] Chip inductors L are compact electronic components that can accommodate a high number of turns and are commercially available at low prices. Therefore, when increasing the number of conductor targets T to increase the number of poles and improve detection resolution, a configuration corresponding to a smaller conductor target period λ can be used, preventing excessive reduction in detection signals and minimizing costs. Furthermore, by mounting multiple chip inductors L on one principal surface 10a of the printed circuit board 10 of the stator 1, specifically the same principal surface, the distance to the conductor targets T can be made uniform. Furthermore, the performance of industrially mass-produced chip inductors L is highly uniform. Consequently, uniform detection signals can be obtained from multiple chip inductors L, eliminating the need for complex signal processing.

[0085] In the first and second embodiments, a plurality of chip inductors L are mounted on the main surface 10a of the printed circuit board 10, which faces the rotor 2. Therefore, the insulating substrate 11 of the printed circuit board 10 on the stator 1 side is not interposed between the plurality of chip inductors L and the conductive target T. This arrangement minimizes the distance between the plurality of chip inductors L and the conductive target T, allowing signals with significantly fluctuating amplitudes as the conductive target T passes through to be extracted from each chip inductor L.

[0086] Furthermore, unlike configurations in which multiple detection coils are formed on a silicon substrate using semiconductor processes, the multiple chip inductors L, each a separate element, can be positioned at any location relative to the rotating track O, providing a high degree of placement flexibility. Therefore, as described in the first and second embodiments, they can be distributed over the entire circumference of the rotating track O. This full-circumference arrangement easily accommodates deviations in the axial center of the rotating shaft 3 coupled to the rotor 2. Specifically, when the rotating shaft 3 is the end of the motor shaft of an electric motor on the opposite side of the output shaft, even if the axial center of the rotating shaft 3 deviates due to radial loads acting on the motor shaft, deviations in the detection position can be avoided through simple signal processing.

[0087] In particular, using a multilayer chip inductor as the chip inductor L allows for a compact design with fewer windings. Therefore, even when a design reduces the target conductor period λ to improve resolution, the chip inductor L can be positioned along the entire circumference of the rotating track O.

[0088] In the first and second embodiments, the conductor targets T are arranged at a predetermined conductor target period λ along the rotation track O. Furthermore, the chip inductor L has a coil width W along the rotation track O that is 25% to 75% (between 25% and 75%) of the conductor target period λ.

[0089] 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. When the number of conductor targets T on the rotor 2 is increased compared to the second embodiment, the ratio of the coil width W of the chip inductor L to the conductor target period λ increases. As long as this ratio is within approximately 75%, a signal waveform sufficient for accurate rotational position detection can be obtained. Even if the number of conductor targets T is increased to improve detection resolution by using industrially produced small chip inductors L, and the conductor target period λ is shortened accordingly, a compact rotational position detector can still be constructed using chip inductors L with a coil width W of 25% to 75% of the conductor target period λ.

[0090] Furthermore, chip inductors L with a coil width W within the range of 25% to 75% of the target conductor period λ can perform well. This makes it easy to select a suitable chip inductor from commercially available standard chip inductors.

[0091] In the first and second embodiments, the plurality of chip inductors L arranged on the stator 1 constitute a first phase group, a second phase group, a third phase group, and a fourth phase group. The first phase group, the second phase group, the third phase group, and the fourth phase group respectively include 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, each of which is arranged with a phase difference of one-quarter of the conductor target period λ. The 1st phase chip inductor L1 (chip inductor of the 1st phase group), the 2nd phase chip inductor L2 (chip inductor of the 2nd phase group), the 3rd phase chip inductor L3 (chip inductor of the 3rd phase group) and the 4th phase chip inductor L4 (chip inductor of the 4th phase group) have spatial phases that differ by 90 degrees relative to the conductor target T. Therefore, detection signals for correctly detecting the rotation position of the rotor 2 can be obtained from these chip inductors.

[0092] In particular, in the first and second embodiments, the first-phase chip inductor L1 and the third-phase chip inductor L3, each with a spatial phase difference of 180 degrees, are differentially connected to form detection circuit 6. Similarly, the second-phase chip inductor L2 and the fourth-phase chip inductor L4, each with a spatial phase difference of 180 degrees, are differentially connected to form detection circuit 7. This allows detection circuits 6 and 7 to generate large-amplitude detection signals VA and VB with a 90-degree phase difference. Furthermore, the differential connection eliminates noise components common to multiple chip inductors L due to external disturbances, resulting in detection signals VA and VB accurately representing the position of the conductive target T. External disturbances include factors such as the external magnetic field and variations in the distance between the stator 1 and rotor 2 (manufacturing variation).

[0093] In the second embodiment, a plurality of chip inductors L1, L2, L3, L4, L1, L2, L3, and L4 are provided for the first, second, third, and fourth phases, respectively. Chip inductors L of the same phase are connected in series. This allows detection signals VA and VB with large amplitudes to be obtained, improving the signal-to-noise ratio.

[0094] As described above, by arranging Y conductor targets T and 4N chip inductors L that satisfy equation (20) at equal intervals throughout the entire circumference of the rotation axis 3a, the 4N chip inductors L can be divided into four phase groups (each phase group consisting of N chip inductors L) each having a spatial phase difference of 90 degrees relative to the conductor target T. Specifically, the four phase groups are divided into a first phase group G1 consisting of N first-phase chip inductors L1, a second phase group G2 consisting of N second-phase chip inductors L2, a third phase group G3 consisting of N third-phase chip inductors L3, and a fourth phase group G4 consisting of N fourth-phase chip inductors L4. In addition, the chip inductors L1 and L3 of the first phase group G1 and the third phase group G3 are differentially connected, and the chip inductors L2 and L4 of the second phase group G2 and the fourth phase group G4 are differentially connected, thereby forming detection circuits 6 and 7 that output detection signals VA and VB with phases different by 90 degrees.

[0095] FIG9 is an exploded perspective view showing the structure of an inductive position detector 300 according to a third embodiment of the present invention. FIG10 is an electronic circuit diagram showing an equivalent circuit on the stator 1 side. In FIG9 and FIG10 , corresponding components of the second embodiment are denoted by the same reference numerals. Compared to the second embodiment, this embodiment is different in that the stator 1 does not include an exciting coil.

[0096] A plurality of chip inductors L are connected in a bridge configuration to form an AC bridge circuit. More specifically, they constitute an A-phase AC bridge circuit 60 and a B-phase AC bridge circuit 70. That is, although not shown, a conductor pattern (more specifically, a copper foil pattern) is formed on the printed circuit board 10 of the stator 1 for connecting the chip inductors L to form the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70.

[0097] The A-phase AC bridge circuit 60 is constructed by bridge-connecting the first-phase chip inductors L1(1) and L1(2) and the third-phase chip inductors L3(1) and L3(2) having a phase difference of 180 degrees with respect 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 of the first-phase chip inductor L1(1) and the third-phase chip inductor L3(2) is set as the first A-phase AC voltage application terminal 61, and the connection point of the third-phase chip inductor L3(1) and the first-phase chip inductor L1(2) is set as the second A-phase AC voltage application terminal 62. The midpoint between the 1st phase chip inductor L1(1) and the 3rd phase chip inductor L3(1) is set as the 1st A phase signal detection terminal 63, and the midpoint between the 3rd phase chip inductor L3(2) and the 1st phase chip inductor L1(2) is set as the 2nd A phase signal detection terminal 64.

[0098] The B-phase AC bridge circuit 70 is constructed by bridge-connecting the second-phase chip inductors L2(1) and L2(2) and the fourth-phase chip inductors L4(1) and L4(2) having a phase difference of 180 degrees with respect 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 sides of the B-phase AC bridge circuit 70. The connection point of the second-phase chip inductor L2(1) and the fourth-phase chip inductor L4(2) is set as the first B-phase AC voltage application terminal 71, and the connection point of the fourth-phase chip inductor L4(1) and the second-phase chip inductor L2(2) is set as the second B-phase AC voltage application terminal 72. The midpoint between the 2nd phase chip inductor L2(1) and the 4th phase chip inductor L4(1) is set as the 1B phase signal detection terminal 73, and the midpoint between the 4th phase chip inductor L4(2) and the 2nd phase chip inductor L2(2) is set as the 2B phase signal detection terminal 74.

[0099] AC voltage is applied from the excitation source 5 to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70. The excitation source 5 includes a first excitation source 51 that generates a first AC voltage (A sin ωt) and a second excitation source 52 that generates a second AC voltage (-A sin ωt) of opposite phase to the first AC voltage. The first A-phase AC voltage application terminal 61 is connected to the first excitation source 51 to apply the first AC voltage (A sin ωt). The second A-phase AC voltage application terminal 61 is connected to the second excitation source 52 to apply the second AC voltage (-A sin ωt). The first B-phase AC voltage application terminal 71 is connected to the first excitation source 51 to apply the first AC voltage (A sin ωt). The second B-phase AC voltage application terminal 72 is connected to the second excitation source 52 to apply the second AC voltage (-A sin ωt). Furthermore, a voltage appearing between the 1A phase signal detection terminal 63 and the 2A phase signal detection terminal 64 is detected as a detection signal VA. Furthermore, a voltage appearing between the 1B phase signal detection terminal 73 and the 2B phase signal detection terminal 74 is detected as a detection signal VB.

[0100] 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. However, it is also possible to apply AC voltages to the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70 from separate excitation sources 5.

[0101] When the conductive target T and the chip inductor L face each other, the magnetic flux of the chip inductor L is shielded by the conductive target T, reducing the inductance of the chip inductor L. Taking advantage of this, in this embodiment, the rotation angle is detected based on the change in inductance of the chip inductor L caused by the rotation of the rotor 2, without using an excitation coil.

[0102] The change in the inductance of the chip inductors L1(1) to L4(1) and L1(2) to L4(2) can be expressed as follows, assuming that the fixed amount is LC and the change amount is LV. 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)

[0103] Therefore, the output signals from the A-phase AC bridge circuit 60 and the B-phase AC bridge circuit 70, that is, the detection signals VA and VB, are respectively expressed as follows: (29) and (30) where k is a constant representing the amplitude. VA={L1(2) / (L1(2)+L3(2))-L3(1) / (L1(1)+L3(1))}.(2ksinωt-ksinωt) =LV / LC.ksinωt.sinθ…(29) VB={L2(2) / (L2(2)+L4(2))-L4(1) / (L2(1)+L4(1))}.(2ksinωt-ksinωt)=LV / LC.ksinωt.cosθ…(30)

[0104] AC bridge circuits 60 and 70 detect changes in the impedance of chip inductor L caused by changes in its positional relationship with conductive target T. The impedance of chip inductor L includes a small DC resistance component in addition to its inductance. However, this inductance component dominates, making the DC resistance component essentially negligible. Therefore, AC bridge circuits 60 and 70 can detect changes in the inductance of chip inductor L caused by changes in its positional relationship with conductive target T.

[0105] The detection signals VA and VB expressed by equations (29) and (30) vary in accordance with the rotational position of the conductor target T and have a phase shift of 90 degrees. Comparing equations (29) and (30) with equations (5) and (6) above shows that the detection signals VA and VB have waveforms similar to those shown in Figures 5B and 5C, respectively, corresponding to the rotational position of the conductor target T. Therefore, similar to the first and second embodiments described above, the rotational position of the rotor 2 can be detected. Thus, a position detector capable of detecting the position of the rotor 2 can be constructed, even though it does not include an excitation coil.

[0106] FIG11 is an exploded perspective view illustrating the structure of an inductive position sensor 400 according to a fourth embodiment of the present invention. FIG12 is a top view of the inductive position sensor 400, viewed along the rotation axis 3 a, showing the positional relationship between the conductive target T and the chip inductor L, viewed through the insulating substrate 21 of the rotor 2. In the above figures, corresponding components in the first and second embodiments are designated by the same reference numerals.

[0107] This position detector 400 has a multi-track configuration with a plurality of rotational tracks O1 and O2 (see Figure 12) around the rotation axis 3a, and detects the rotational position on each of the rotational tracks O1 and O2. Specifically, this embodiment of the position detector 400 has a two-track configuration with a first rotational track O1 and a second rotational track O2 concentrically arranged around the rotation axis 3a. The first rotational track O1 is arranged inside the second rotational track O2, forming a circumference with a smaller diameter than the second rotational track O2. On one main surface 20a of the printed circuit board 20 of the rotor 2 (the main surface opposite the stator 1 side in this embodiment), a plurality of conductive targets T1 are arranged at equal intervals along the entire circumference of the first rotational track O1, and a plurality of conductive targets T2 are arranged at equal intervals along the entire circumference of the second rotational track O2. On a main surface 10a of the printed circuit board 10 of the stator 1 (in this embodiment, the main surface facing the rotor 2), a plurality of chip inductors L1 are arranged at equal intervals along a first rotation orbit O1 throughout the entire circumference, and a plurality of chip inductors L2 are arranged at equal intervals along a second rotation orbit O2 throughout the entire circumference.

[0108] The plurality of chip inductors L1 arranged along the first rotation track O1 can be classified into, based on their spatial phases around the rotation axis 3a relative to the conductor target T1, a first phase group (A phase) consisting of the first phase chip inductors L11(1) and L11(2); a second phase group (B phase) consisting of the second phase chip inductors L12(1) and L12(2); a third phase group ( / A phase) consisting of the third phase chip inductors L13(1) and L13(2); and a fourth phase group ( / B phase) consisting of the fourth phase chip inductors L14(1) and L14(2). In addition, the first phase chip inductors L11(1) and L11(2), the second phase chip inductors L12(1) and L12(2), the third phase chip inductors L13(1) and L13(2), and the fourth phase chip inductors L14(1) and L14(2) have a spatial phase difference around the rotation axis 3a of 1 / 4 of the target conductor period λ.

[0109] Similarly, the plurality of chip inductors L2 arranged along the second rotation track O2 can be classified into, based on their spatial phases around the rotation axis 3a relative to the conductor target T2, a first phase group (A phase) consisting of the first phase chip inductors L21(1), L21(2), and L21(3); a second phase group (B phase) consisting of the second phase chip inductors L22(1), L22(2), and L22(3); a third phase group ( / A phase) consisting of the third phase chip inductors L23(1), L23(2), and L23(3); and a fourth phase group ( / B phase) consisting of the fourth phase chip inductors L24(1), L24(2), and L24(3). In addition, the first phase chip inductors L21(1), L21(2), L21(3), the second phase chip inductors L22(1), L22(2), L22(3), the third phase chip inductors L23(1), L23(2), L23(3) and the fourth phase chip inductors L24(1), L24(2), L24(3) have a spatial phase difference around the rotation axis 3a of 1 / 4 of the target conductor period λ.

[0110] The plurality of conductive targets T1 and the plurality of chip inductors L1 arranged along the first rotating track O1 form a first group S1, facing each other. Similarly, the plurality of conductive targets T2 and the plurality of chip inductors L2 arranged along the second rotating track O2 form a second group S2, facing each other. The first and second groups S1 and S2 share a rotor 2 and a stator 1.

[0111] The number Y1 of the plurality of conductor targets T1 in the first group S1 and the number Y2 of the conductor targets T2 in the second group S2 are different. The number Y1 of the conductor targets T1 in the first group S1 and the number 4N1 of the chip inductors L1 satisfy the aforementioned equation (20), and therefore satisfy the following equation (31). Similarly, the number Y2 of the conductor targets T2 in the second group S2 and the number 4N2 of the chip inductors L2 satisfy the aforementioned equation (20), and therefore satisfy the following equation (32). Y1=4N1M1±N1 (Y1, N1, M1 are natural numbers)…(31) Y2=4N2M2±N2 (Y2, N2, M2 are natural numbers)…(32)

[0112] The examples shown in FIG. 11 and FIG. 12 correspond to the case where Y1=14, N1=2, M1=2, Y2=15, N2=3, and M2=1. By making the number Y1 of the plurality of conductive targets T1 in the first set S1 different from the number Y2 of the conductive targets T2 in the second set S2, it is possible to distinguish and detect rotational positions over a wide range of rotational angles. In particular, if the number Y1 of the plurality of conductive targets T1 in the first set S1 and the number Y2 of the conductive targets T2 in the second set S2 are coprime, single-turn absolute detection is possible, distinguishing and detecting rotational positions within a single turn (360 degrees).

[0113] In this example, the plurality of chip inductors L1 constituting the first group S1 and the plurality of chip inductors L2 constituting the second group S2 are chip inductors of the same specifications and have the same shape and size when viewed from above along the rotation axis 3a.

[0114] In the illustrated example, each chip inductor L is arranged with its longitudinal direction aligned with the rotation radius around the rotation axis 3a. Typically, the longitudinal direction of the chip inductor L is the direction in which the pair of connecting electrodes 31 and 32 face each other. In the illustrated example, the ratio of the coil width W1 of chip inductor L1 to the pitch (conductor target period λ1) of the plurality of conductor targets T1 constituting the first group S1 is approximately 25%. On the other hand, the ratio of the coil width W2 of chip inductor L2 to the pitch (conductor target period λ2) of the plurality of conductor targets T2 constituting the second group S2 is 50%. This is, of course, merely an example. The arrangement of these components can be determined by designing the conductor targets T1 and T2 and selecting the chip inductors L1 and L2 so that the ratio of the coil widths W1 and W2 to the conductor target periods λ1 and λ2 in each of the first and second groups S1 and S2 is between 25% and 75%.

[0115] The first group S1 and the second group S2 do not need to use chip inductors of the same specifications. The multiple chip inductors L1 of the first group S1 can also use the same specifications, and the multiple chip inductors L2 of the second group S2 can use different same specifications.

[0116] The printed circuit board 10 of the stator 1 is provided with a common excitation coil 12 for inducing voltage in the plurality of chip inductors L1 of the first group S1 and the plurality of chip inductors L2 of the second group S2. In this embodiment, the excitation coil 12 includes a first excitation coil 121 and a second excitation coil 122. These excitation coils are formed from a conductor pattern formed on the printed circuit board 10. The first excitation coil 121 is formed in a ring shape (in the illustrated example, a circular ring shape) surrounding the plurality of chip inductors L1 of the first group S1 and the plurality of chip inductors L2 of the second group S2, as viewed from above along the rotation axis 3a. On the other hand, the second excitation coil 122 is formed in a ring shape (in the illustrated example, a circular ring shape) around the rotation axis 3a, so as to be surrounded by the plurality of conductor targets T1 of the first set S1 and the plurality of conductor targets T2 of the second set S2, when viewed from above along the rotation axis 3a. Specifically, the first excitation coil 121 is positioned on the outer periphery of the plurality of chip inductors L1 and L2 of the first set S1 and the second set S2, while the second excitation coil 122 is positioned on the inner periphery thereof.

[0117] The first excitation coil 121 is formed in an annular shape, for example, by forming a spiral wiring pattern along a circumference around the rotation axis 3a. If the printed circuit board 10 is a multilayer printed circuit board having multiple wiring layers, the spiral wiring patterns formed on the multiple wiring layers can be connected via vias to form the first excitation coil 121. The same applies to the second excitation coil 122.

[0118] The first excitation coil 121 and the second excitation coil 122 are connected via a wiring pattern (not shown) within the printed circuit board 10 so that current flows in opposite circumferential directions around the rotation axis 3a when viewed from above. Therefore, when current is applied to the first excitation coil 121 and the second excitation coil 122, magnetic fields in the same direction are generated in the region between them, i.e., in the region where the plurality of chip inductors L1 and L2 of the first and second groups S1 and S2 are located. In other words, the first excitation coil 121 and the second excitation coil 122 are configured so that the magnetic fields in the region between them are constructive.

[0119] FIG13 is an electronic circuit diagram showing an equivalent circuit of the stator 1. FIG13 is an electronic circuit diagram showing an equivalent circuit of the stator 1.

[0120] The plurality of chip inductors L1 of the first group S1 (inner circumference side) arranged along the first rotation track O1 are connected in the same manner as in the second embodiment. That is, a pair of first-phase chip inductors L11 (1), L11 (2) and a pair of third-phase chip inductors L13 (1), L13 (2) are connected in series and differentially to form an A-phase detection circuit 61. Furthermore, a pair of second-phase chip inductors L12 (1), L12 (2) and a pair of fourth-phase chip inductors L14 (1), L14 (2) are connected in series and differentially to form a B-phase detection circuit 71. The A-phase detection circuit 61 and the B-phase detection circuit 71 output amplitude-modulated detection signals VA1 and VB1 with a phase difference of 90 degrees.

[0121] The plurality of chip inductors L2 of the second group S2 (outer peripheral side) arranged along the second rotation track O2 are connected in the same manner. That is, the three first-phase chip inductors L21 (1), L21 (2), L21 (3) and the three third-phase chip inductors L23 (1), L23 (2), L23 (3) are connected in series and differentially to form the A-phase detection circuit 62. In addition, the three second-phase chip inductors L22 (1), L22 (2), L22 (3) and the three fourth-phase chip inductors L24 (1), L24 (2), L24 (3) are connected in series and differentially to form the B-phase detection circuit 72. The A-phase detection circuit 62 and the B-phase detection circuit 72 output amplitude-modulated detection signals VA2 and VB2 with a phase difference of 90 degrees.

[0122] By appropriately processing the detection signals VA1, VB1, VA2, and VB2 using the signal processing circuit 8, information about the rotational position of the rotor 2 can be obtained. As previously mentioned, the number Y1 of the plurality of conductor targets T1 in the first set S1 differs from the number Y2 of the conductor targets T2 in the second set S2. This allows for detection of rotational positions over a wider range of rotational angles than using only the detection signals VA1 and VB1 or only the detection signals VA2 and VB2. In particular, as long as the number Y1 of the plurality of conductor targets T1 in the first set S1 and the number Y2 of the conductor targets T2 in the second set S2 are coprime, single-turn absolute detection can be performed using the detection signals VA1, VB1, VA2, and VB2, enabling detection of rotational positions over a range of one revolution (360 degrees).

[0123] Although not shown in the figure, a conductor pattern (more specifically, a copper foil pattern) for connecting the chip inductor L to form the A-phase detection circuits 61 and 62 and the B-phase detection circuits 71 and 72 is formed on the printed circuit board 10 of the stator 1 .

[0124] Figures 14A and 14B illustrate another embodiment. In the aforementioned embodiment, each conductor target T is formed as a conductor filling pattern (more specifically, a copper foil filling pattern) formed on the insulating substrate 21. However, as shown in Figures 14A and 14B , each conductor target T can also be formed as a coil conductor pattern 80 or 90. In Figures 14A and 14B , corresponding parts shown in Figure 3 are labeled with the same reference numerals.

[0125] In the example of Figure 14A , the multiple individual annular coil conductor patterns 80 that constitute the multiple conductor targets T are separated by gaps along the circumferential direction around the rotation axis 3a, thereby insulating each other. The multiple conductor targets T form a conductor pattern that exhibits geometric periodicity along the circumferential direction around the rotation axis 3a. In Figure 14A , the annular coil conductor pattern 80 of each conductor target T is formed as a linear conductor pattern along the outer circumference (contour) of a sector (more accurately, a sector with the inner diameter portion cut off) centered on the rotation axis 3a. However, as shown by the dotted line, the annular coil conductor pattern 80 can also be formed as a curved conductor pattern (e.g., a circular or elliptical shape). By forming the conductor targets T with such a curved annular coil conductor pattern 80, the output signal waveform can be made close to a sine wave. Furthermore, when the insulating substrate is a multilayer wiring substrate, a plurality of conductor patterns formed on a plurality of conductor layers may be connected to form a coil having a plurality of turns, and the coil having a plurality of turns may be used as each conductor target T.

[0126] In the example of Figure 14B , multiple conductor targets T are connected to form a circular coil conductor pattern 90 extending throughout the entire circumference. This circular coil conductor pattern 90 exhibits geometric periodicity along the circumference around the rotation axis 3a. More specifically, the circular coil conductor pattern 90 repeats a predetermined number of times (five times in the example of Figure 14B ) around the rotation axis 3a, with the conductors of one period constituting a single conductor target T. A single conductor target T is the portion of the circular coil conductor pattern 90 within the angular region obtained by dividing the full angular range (360 degrees) around the rotation axis 3a by the number of periods (five times in the example of Figure 14B ). The angular positions of the divisions by the number of periods can be arbitrarily set.

[0127] In the illustrated example, the annular coil conductor pattern 90 includes an outer diameter linear conductor pattern 91 and a radial linear conductor pattern 92, respectively, along the outer diameter portion and a pair of radial portions (i.e., portions other than the inner diameter portion) of the outer circumference (contour) of a sector (more accurately, a sector with the inner diameter portion cut out) centered on the rotation axis 3a. The annular coil conductor pattern 90 also includes an inner diameter linear conductor pattern 93 that connects adjacent radial linear conductor patterns 92 on the inner diameter side. The outer diameter linear conductor pattern 91 connects a pair of adjacent radial linear conductor patterns 92 on the outer diameter side. One radial linear conductor pattern 92 is connected to the outer diameter end of the adjacent radial linear conductor pattern 92 on one side of the circumference around the rotation axis 3a via the outer diameter linear conductor pattern 91, and is connected to the inner diameter end of the adjacent other radial linear conductor pattern 92 on the inner diameter side via the inner diameter linear conductor pattern 93 on the other side of the circumference. In this example, the outer linear conductor pattern 91 and the inner linear conductor pattern 93 are formed linearly along an arc centered on the rotation axis 3a. Thus, the annular coil conductor pattern 90 is formed as an endless, circumferentially continuous structure consisting of a U-shaped coil portion opening toward the rotation axis 3a and a U-shaped coil portion opening toward the side opposite the rotation axis 3a. In other words, the annular coil conductor pattern 90 is formed in a zigzag wave pattern, zigzagging back and forth between the inner and outer diameters across the rotational track O.

[0128] As shown by the dotted line in FIG14B , the loop-shaped coil conductor pattern 90 can also be a curved pattern. By forming a plurality of conductor targets T with the above-described curved loop-shaped coil conductor pattern 90 , the output signal waveform can be made close to a sine wave.

[0129] The operating principle of the configuration shown in Figures 14A and 14B is the same as that of the previous embodiment. However, while the previous embodiment utilized eddy currents flowing through the conductor-filled pattern forming the conductor target T, the configuration of Figures 14A and 14B flows current through the coil conductor patterns 80 and 90 forming 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 through the coil conductor patterns 80 and 90 in the direction of arrow 86, thereby hindering changes in the magnetic field. The voltage induced in the detection coil formed by the chip inductor L is influenced 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.

[0130] Specifically, in the configuration of Figure 14A , when the detection coil (chip inductor L) faces the area enclosed by the coil conductor pattern 80, the magnetic field of the excitation coil 12 weakens, and the output voltage of the detection coil decreases. The opposing area changes as the rotor 2 rotates, and the output voltage of the detection coil changes accordingly. In the configuration of Figure 14B , when the detection coil (chip inductor L) faces the U-shaped coil portion that opens toward the rotation axis 3a, the magnetic field of the excitation coil 12 weakens. On the other hand, when the detection coil (chip inductor L) faces the U-shaped coil portion that opens away from the rotation axis 3a, the magnetic field of the excitation coil 12 strengthens. Furthermore, the output voltage of the detection coil changes in accordance with the change in the opposing area.

[0131] As described above, the rotational position of rotor 2 can be detected by utilizing changes in the magnetic field caused by the current flowing through coil conductor patterns 80 and 90. By utilizing the current flowing through coil conductor patterns 80 and 90, better detection can be achieved than by utilizing eddy currents flowing through the conductor fill pattern.

[0132] The aforementioned configuration described using FIG. 14A and FIG. 14B is applicable not only to the first embodiment but also to the second, third, and fourth embodiments.

[0133] Figures 15A to 15E illustrate various examples of conductor targets T, showing the arrangement of multiple conductor targets T by expanding a circular rotational track O into a straight line. Figure 15A shows a configuration in which conductor targets T, formed from a plurality of separate conductor fill patterns, are arranged at equal intervals. The configurations shown in Figures 1, 3, 6, 7, 9, 11, and 12 fall into this category. Figure 15B shows a configuration in which conductor targets T, formed from a plurality of separate annular coil conductor patterns, are arranged at equal intervals. The configuration shown in Figure 14A also falls into this category.

[0134] Figure 15C shows an example of a plurality of conductor targets T formed by a circular coil conductor pattern extending all around the circumference. The configuration shown in Figure 14B is an example of this type. In this case, as previously described, each conductor target T is formed by equally dividing the entire circumference of the rotation axis 3a by the number of periods. The division positions are arbitrary, so, for example, each conductor target T can have a variety of shapes corresponding to a single period, as illustrated in Figures 16A to 16D.

[0135] Figure 15D shows an example of a curved loop-shaped coil conductor pattern forming multiple conductor targets T. The configuration shown by the dashed line in Figure 14B belongs to this type of configuration. Conductor targets T represent portions of this cycle. For example, in the configuration of Figure 14B , different loop-shaped coil conductor patterns can also be formed on both sides of the insulating substrate. Figure 15E shows an example of conductor targets T in this case.

[0136] Conductor target T refers to a conductor that is part of a 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 a portion of a continuous conductor pattern in the examples of Figures 15C and 15E .

[0137] Although the embodiments of the present invention have been described above, the present invention can also be implemented in other forms.

[0138] For example, in the aforementioned embodiment, a plurality of chip inductors L are arranged throughout the entire circumference of the rotation axis 3a. However, the plurality of chip inductors L may be arranged within 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) to L4 (2) may be omitted.

[0139] Furthermore, in the aforementioned embodiment, an example is shown in which the plurality of chip inductors L are arranged at equal intervals throughout the entire circumference of the rotation axis 3a. However, the plurality of chip inductors L do not necessarily need to be arranged at equal intervals. For example, in the second embodiment shown in FIG6 to FIG8 , even if one of the first-phase chip inductors L1(1) and L1(2) is omitted, one of the second-phase chip inductors L2(1) and L2(2) is omitted, one of the third-phase chip inductors L3(1) and L3(2) is omitted, and one of the fourth-phase chip inductors L4(1) and L4(2) is omitted, and the plurality of chip inductors are arranged at unequal intervals, detection signals VA and VB having a phase difference of 90 degrees can still be obtained.

[0140] Furthermore, in the aforementioned embodiment, a chip inductor L is surface-mounted on one principal surface 10a of the printed circuit board 10 of the stator 1. However, multiple chip inductors L may be surface-mounted on one principal surface 10a of the printed circuit board 10, and multiple chip inductors L may be surface-mounted on the other principal 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 improving output. Furthermore, the greater the number of chip inductors L, the more evenly distributed the variations among the chip inductors L, thereby improving detection accuracy. Because the distances from the plurality of chip inductors L to the conductive target T are equal on both the one main surface 10a and the other main surface 10b of the printed circuit board 10, the outputs of the plurality of chip inductors L arranged on each main surface 10a or 10b can be normalized. This eliminates the need for complex signal processing.

[0141] In the aforementioned fourth embodiment, a dual-track structure is shown in which two sets of conductor targets and chip inductor groups are respectively arranged along two rotating tracks, but it can also be constructed in which more than three sets of conductor targets and chip inductor groups are respectively arranged along more than three rotating tracks.

[0142] In the aforementioned first, second and fourth embodiments, the exciting coil is configured as a circular ring. However, the exciting coil may be configured as a polygonal ring or other ring shape.

[0143] While the aforementioned embodiments illustrate the use of multilayer chip inductors, wire-wound chip inductors can also be used. However, because multilayer chip inductors can be compact, they are advantageous for reducing the conductor target period (i.e., increasing the number of conductor targets) and achieving high-resolution position detection. More specifically, even if the conductor target's width on the rotational track is approximately 2 mm, a position detector can be constructed using multilayer chip inductors approximately 1 mm wide (preferably arranged throughout the entire circumference of the rotational track).

[0144] The embodiments of the present invention have been described in detail, but these embodiments are merely specific examples used to illustrate the technical content of the present invention. The present invention should not be limited to these specific examples for interpretation. The scope of the present invention is limited only by the scope of the patent application.

[0145] 1: Stator 2: Rotor 3: Rotation axis 3a: Rotation axis 5: Excitation source 6: Phase A detection circuit 61: Phase A detection circuit 62: Phase A detection circuit 7: Phase B detection circuit 71:B phase detection circuit 72:B phase detection circuit 8: Signal processing circuit 10:Printed substrate 10a, 10b: Main surface 11: Insulating substrate 12: Excitation coil 12a, 12b: Lead-out section 20:Printed substrate 20a, 20b: Main surface 21: Insulating substrate 23: Non-conductive part 31,32: Connect electrodes 51: 1st excitation source 52: Second excitation source 60:A phase AC bridge circuit 61: 1A phase AC voltage application terminal 62: 2A phase AC voltage application terminal 63: 1A phase signal detection terminal 64: 2A phase signal detection terminal 70:B phase AC bridge circuit 71: 1B phase AC voltage application terminal 72: 2B phase AC voltage application terminal 73: 1B phase signal detection terminal 74: Phase 2B signal detection terminal 80: Coil conductor pattern 90: Ring coil conductor pattern 91: Outer diameter linear conductor pattern 92: Radius linear conductor pattern 93: Inner diameter linear conductor pattern 100: Inductive position detector 121: 1st excitation coil 122: Second excitation coil 200: Inductive position detector 300: Inductive position detector 400: Inductive position detector λ: conductor target period CW: Clockwise G1: Phase 1 group G2: Phase 2 group G3: Phase 3 Group G4: Phase 4 Group L1: Phase 1 chip inductor L2: 2nd phase chip inductor L3: 3rd phase chip inductor L4: 4th phase chip inductor L1(1), L1(2): Phase 1 chip inductor L2(1), L2(2): Phase 2 chip inductor L3(1), L3(2): 3rd phase chip inductor L4(1), L4(2): 4th phase chip inductor L11(1), L11(2): Phase 1 chip inductor L12(1), L12(2): Phase 2 chip inductor L13(1), L13(2): 3rd phase chip inductor L14(1), L14(2): 4th phase chip inductor L21(1), L21(2), L21(3): Phase 1 chip inductor L22(1), L22(2), L22(3): Phase 2 chip inductor L23(1), L23(2), L23(3): 3rd phase chip inductor L24(1), L24(2), L24(3): 4th phase chip inductor O: Rotating orbit O1: 1st rotation orbit O2: 2nd rotation orbit p: Chip inductor period S1: Group 1 S2: Group 2 T: Conductor Target T1: Conductor Target T2: Conductor Target VA, VA1, VA2: detection signal VB, VB1, VB2: detection signal W, W1, W2: Coil width

Claims

1. An inductive position detector comprising: a stator having a wiring board; a rotor having a non-conductive part disposed opposite to the stator and rotating relative to the stator about a predetermined rotation axis; a plurality of conductive targets of the same shape and size periodically disposed along a circumference about the rotation axis and held on the non-conductive part of the rotor, and moving along a rotation track about the rotation axis as the rotor rotates; and a plurality of chip inductors disposed spatially out of phase with respect to the plurality of conductive targets and opposite to the rotation track, surface-mounted on the main surface of the wiring board of the stator, and each forming a plurality of detection coils for detecting changes in the magnetic field generated as the conductive targets pass by; the conductive targets being disposed along the rotation track at a predetermined conductor target period; The aforementioned plurality of chip inductors includes 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 configured with a phase difference of one-quarter of a period for each of the aforementioned conductor target periods.

2. The inductive position detector as described in claim 1, wherein, The aforementioned conductor target is configured along the aforementioned rotation track with a predetermined conductor target period; the aforementioned wafer inductor has a coil width of 25% to 75% of the aforementioned conductor target period along the aforementioned rotation track.

3. The inductive position detector as described in claim 1, wherein, The aforementioned 4N (N is a natural number) chip inductors are arranged at equal intervals along the entire circumference of the aforementioned rotating track; the number Y (Y is a natural number) of the aforementioned conductor targets is represented by Y=4NM±N (M is a natural number).

4. The inductive position detector as described in claim 1, comprising a first group of a plurality of conductor targets and a plurality of chip inductors with a first rotating track as the aforementioned rotating track, and a second group of a plurality of conductor targets and a plurality of chip inductors with a second rotating track different from the aforementioned first rotating track as the aforementioned rotating track, wherein the first group and the second group share the aforementioned stator and the aforementioned rotor; the number Y1 (Y1 is a natural number) of the plurality of conductor targets in the first group and the number Y2 (Y2 is a natural number) of the plurality of conductor targets in the second group are different from each other.

5. The inductive position detector as described in claim 4, wherein, The number Y1 of the aforementioned complex conductor targets in the first group and the number Y2 of the aforementioned complex conductor targets in the second group are coprime.

6. The inductive position detector as described in claim 4, further comprising an excitation coil disposed on the aforementioned wiring board of the aforementioned stator, and shared for sensing voltages in the aforementioned plurality of chip inductors of the aforementioned first group and the aforementioned plurality of chip inductors of the aforementioned second group.

7. The inductive position detector as described in claim 6, wherein, The aforementioned excitation coil comprises: a first annular excitation coil, which, when viewed along the aforementioned axis of rotation, surrounds the aforementioned plurality of chip inductors of the first group and the aforementioned plurality of chip inductors of the second group; and a second annular excitation coil, which, when viewed along the aforementioned axis of rotation, is arranged around the aforementioned axis of rotation such that it is surrounded by the aforementioned plurality of chip inductors of the first group and the aforementioned plurality of chip inductors of the second group.

8. The inductive position detector as described in claim 1, wherein, Each conductor target includes a conductor-filled pattern or a loop coil conductor pattern formed on the aforementioned non-conductor parts, and the aforementioned plurality of conductor targets are insulated from each other.

9. The inductive position detector as described in claim 1, wherein, The aforementioned plurality of conductor targets are connected to each other to form a loop coil conductor pattern that covers the entire circumference.

10. The inductive position detector as described in any one of claims 1 to 9, wherein, The aforementioned chip inductor is a multilayer chip inductor with a pair of connecting electrodes at both ends.

11. The inductive position detector as described in any one of claims 1 to 9, further comprising an excitation coil disposed on the aforementioned wiring board of the aforementioned stator, which, when viewed along the aforementioned axis of rotation, is formed in a ring surrounding the aforementioned plurality of chip inductors and generates a magnetic field for inducing voltage in the aforementioned plurality of chip inductors.

12. An inductive position detector comprising: a stator having a wiring board; a rotor having a non-conductive part disposed opposite to the stator and rotating relative to the stator about a predetermined rotation axis; a plurality of conductive targets of the same shape and size periodically disposed along a circumference about the rotation axis and held on the non-conductive part of the rotor, and moving along a rotational track about the rotation axis as the rotor rotates; and a plurality of chip inductors disposed spatially out of phase with respect to the plurality of conductive targets and opposite to the rotational track, surface-mounted on the main surface of the wiring board of the stator, and each forming a plurality of detection coils for detecting changes in the magnetic field generated as the conductive targets pass by; wherein, The aforementioned plurality of chip inductors are connected in such a way that they form an AC bridge circuit having a pair of AC voltage application terminals and a pair of signal detection terminals.

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