FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] RESOLVER AND ELECTRIC POWER STEERING DEVICE EQUIPPED WITH SAME MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. 2 [DESCRIPTION] [Technical Field] [0001] The present disclosure relates to a resolver and an electric power steering device equipped with the same.5 [Background Art] [0002] Patent Document 1 discloses a resolver. The resolver includes a stator and a rotor facing one another in an axial direction. A rotary shaft of a rotating body is attached to the rotor. The resolver detects a rotation angle of the rotating body utilizing10 change in permeance of a gap between the rotor and the stator. [Citation List] [Patent Document] [0003] [Patent Document 1]15 Japanese Unexamined Patent Application, First Publication No. 2007-171131 [Summary of Invention] [PROBLEM TO BE SOLVED BY THE INVENTION] [0004] There may be a case where at least one or both of a rotor and a stator are20 disposed in a manner where at least one or both of the rotor and the stator deviate from original attachment positions. In Patent Document 1, when a stator and/or a rotor is/are disposed in a manner that deviates from the original attachment position, there is a possibility that a state in which the rotor and teeth of the stator do not overlap at all, or a state in which the rotor completely covers the teeth of the stator will continue for a long25 3 time. In such a case, higher-order harmonic waves are superimposed on an output signal used for detecting a rotation angle, and an accuracy of the rotation angle declines. [0005] The present disclosure is made in order to resolve the foregoing problems, and an object thereof is to provide a resolver capable of preventing a decline in the accuracy of5 detecting the rotation angle even when a rotor or a stator are disposed in a manner that deviates from original attachment positions, and an electric power steering device equipped with the same. [MEANS TO SOLVE THE PROBLEM] [0006]10 A resolver according to the present disclosure includes a rotor that is made of a magnetic body and is attached to a shaft of a rotating body, the rotor having a plurality of salient poles disposed in a circumferential direction, a stator which faces the rotor in an axial direction, the stator having an annular core back, a plurality of teeth that are made of a magnetic body and protrude from the core back towards the rotor, and an excitation15 winding and two-phase output windings that are wound around the plurality of teeth, the plurality of teeth being disposed in the circumferential direction, an excitation circuit that is configured to supply an excitation signal to the excitation winding, and an angle computation unit to which output signals from the two-phase output windings are input and which is configured to compute a rotation angle of the rotor based on the output20 signals. Each of the plurality of teeth is formed having line-symmetry with respect to a line connecting a center of the core back and centers of the teeth in the circumferential direction when viewed from the axial direction. An outline of the rotor is expressed by a function Rr(x(θ), y(θ)) defined by the following Equations (1) to (3), where an x axis and a y axis are axes of an orthogonal coordinate system having a center of the shaft set as an25 4 origin, and an angle from a reference axis is θ. [Math. 1] Here, Ri is a minimum distance from the center of the core back to the teeth, Ro is a maximum distance from the center of the core back to the teeth, Nx is the number of5 salient poles, and k1 and k2 are positive numbers. [EFFECTS OF THE INVENTION] [0007] According to the present disclosure, it is possible to provide a resolver capable of preventing a decline in an accuracy of detecting a rotation angle even in a case where a10 rotor or a stator is disposed in a manner that deviates from an original attachment position, and an electric power steering device equipped with the same. [Brief Description of Drawings] [0008] FIG. 1 is a configuration view showing a resolver according to a first15 embodiment. FIG. 2 is a block diagram showing the resolver according to the first embodiment. FIG. 3 is a cross-sectional view taken along a line A-A of FIG. 1, and is a view that shows a resolver main body according to the first embodiment.20 FIG. 4 is a view showing a rotor according to the first embodiment. FIG. 5 is a view showing a stator according to the first embodiment. FIG. 6 is a graph showing a distribution of the number of windings of excitation 5 windings according to the first embodiment. FIG. 7 is a graph showing a distribution of the number of windings of a first output winding and a second output winding according to the first embodiment. FIG. 8 is a graph showing a change of a surface area where the rotor covers teeth of the stator, in a case where the rotor is rotated by one mechanical angle in the resolver5 according to the first embodiment. FIG. 9A is a graph showing a waveform of an output signal obtained from an output winding in the resolver according to the first embodiment. FIG. 9B is a graph showing the waveform of the output signal obtained from the output winding in the resolver according to the first embodiment.10 FIG. 10 is a view showing a case where the stator deviates from an original attachment position in the resolver according to the first embodiment. FIG. 11 is a graph showing the waveform of the output signal obtained from the output winding in a case where the stator deviates from the original attachment position in the resolver according to the first embodiment.15 FIG. 12 is a block diagram showing a resolver according to a second embodiment. FIG. 13 is a view showing a stator according to the second embodiment. FIG. 14 is a graph showing a relationship between a phase difference between an excitation signal of a first system and the excitation signal of a second system, and an20 amount of deviation from 90 degrees of the phase difference between a first output signal of the first system and a second output signal of the first system, in a case where a frequency of the excitation signal of the first system and the frequency of the excitation signal of the second system are the same in the resolver according to the second embodiment.25 6 FIG. 15 is a graph showing a relationship between the phase difference between the excitation signal of the first system and the excitation signal of the second system, and an electrical angle secondary component of an angular error, in a case where the frequency of the excitation signal of the first system and the frequency of the excitation signal of the second system are the same in the resolver according to the second5 embodiment. FIG. 16 is a graph showing an example of waveforms of the excitation signal of the first system and the excitation signal of the second system in a case where the frequency of the excitation signal of the first system and the frequency of the excitation signal of the second system are made to be different in the resolver according to the10 second embodiment. FIG. 17 is a graph showing effects of the excitation signal of the second system on the output signal of the first system in a case where the frequency of the excitation signal of the first system and the frequency of the excitation signal of the second system are made to be different in the resolver according to the second embodiment.15 FIG. 18 is a graph showing the effects of the output signal of the second system on the excitation signal of the first system in a case where the frequency of the excitation signal of the first system and the frequency of the excitation signal of the second system are made to be different in the resolver according to the second embodiment. FIG. 19 is a view showing a stator according to a third embodiment.20 FIG. 20 is a view showing a stator according to a fourth embodiment. FIG. 21 is a side view of a resolver main body according to a fifth embodiment. FIG. 22 is a view showing a first output winding board according to the fifth embodiment. FIG. 23 is a graph showing a distribution of thicknesses of copper wires of first25 7 output windings according to the fifth embodiment. FIG. 24 is a cross-sectional view taken along a line C-C of FIG. 5, and is a view that shows teeth according to a sixth embodiment. FIG. 25 is a view showing teeth according to a seventh embodiment. FIG. 26 is a schematic diagram of an electric power steering device according to5 a ninth embodiment. [Description of Embodiments] [0009] First Embodiment FIG. 1 is a configuration view showing a resolver 100 according to a first10 embodiment. FIG. 2 is a block diagram showing the resolver 100 according to the first embodiment. FIG. 1 shows a state in which the resolver 100 is attached to a shaft 51 that is a rotary shaft of a rotating body of a rotary electric machine 50. An attachment target of the resolver 100 is not limited to the shaft 51 of the rotary electric machine 50. It is15 possible to attach the resolver 100 to a rotary shaft of a rotating body of various devices. [0010] In this description, a direction along a shaft center Os of the shaft 51 (refer to FIG. 3) is referred to as an “axial direction”. In a cross-section perpendicular to the axial direction, a direction intersecting the shaft center Os is referred to as a “radial20 direction”, and a direction revolving around the shaft center Os is referred to as a “circumferential direction”. [0011] The resolver 100 includes a resolver main body 1 that is a sensor, and a control device 2 that controls the resolver main body 1.25 8 [0012] FIG. 3 is a cross-sectional view taken along a line A-A of FIG. 1, and is a view that shows the resolver main body 1 according to the first embodiment. As shown in FIGs. 1 and 3, the resolver main body 1 includes a pair made of a stator 11 and a rotor 12. The stator 11 and the rotor 12 are disposed such as to face one another in the axial5 direction. [0013] The rotor 12 is made of a magnetic body. The rotor 12 is attached to the shaft 51 of the rotary machine 50. The rotor 12 is fixed to the shaft 51 by press-fitting, shrink-fitting, screw fastening, or the like. The rotor 12 is connected to the rotating10 body of the rotary electric machine 50 with the shaft 51 therebetween. The rotor 12 rotates integrally with the rotating body of the rotary electric machine 50. [0014] The rotor 12 has a plurality of salient poles 12a disposed in the circumferential direction. In the first embodiment, a number Nx (here, Nx is a natural number greater15 than or equal to two) of the salient poles 12a is four. The number Nx of the salient poles 12a however is not limited to four. The number Nx of the salient poles 12a is also referred to as an “axial double angle”. [0015] An external shape of the rotor 12 is explained with reference to FIG. 4.20 FIG. 4 is a view of the rotor 12 viewed in the axial direction shown by an x axis and a y axis of an orthogonal coordinate system having the shaft center Os of the shaft 51 set as the origin. As shown in FIG. 4, an angle from a reference axis (for example, a positive direction of the x axis) is θ. At this time, an outline (external shape) of the rotor 12 is expressed by a function Rr(x(θ), y(θ)) defined by the following Equations (1) to (3).25 9 Ri is a minimum distance from a center Ocb of a core back 21 (which is described below) to teeth 22, and Ro is a maximum distance from the center Ocb of the core back 21 to the teeth 22. Nx is the number of the salient poles 12a. In addition, k1 and k2 are positive numbers. [0016]5 [Math. 2] [0017] It is more preferable that the outline of the rotor 12 be formed such that the following Equation (4) is satisfied.10 k1+k2<1 ... (4) [0018] The stator 11 is explained with reference to FIG. 5. The stator 11 includes the core back 21, a plurality of teeth 22, excitation windings 23, first output windings 24, and second output windings 25.15 The core back 21 and the plurality of teeth 22 are made of magnetic bodies. The core back 21 and the plurality of teeth 22 configure an iron core of the stator 11. [0019] The core back 21 has an annular shape about the center Ocb. The plurality of teeth 22 protrude from the core back 21 toward the rotor 12 side.20 The core back 21 and the plurality of teeth 22 may be integrally provided. The core back 21 and the plurality of teeth 22 may be separate bodies. [0020] 10 In the first embodiment, the number Ns (where Ns is a natural number) of the teeth 22 is twelve. However, the number Ns of the teeth 22 is not limited to twelve. Hereinafter, as shown in FIG. 5, the plurality of teeth 22 are also referred to as teeth T1 to T12 moving clockwise. [0021]5 The teeth 22 are disposed with an interval therebetween in the circumferential direction. The plurality of teeth 22 are disposed at equal intervals in the circumferential direction. The teeth 22 have the same shape as one another. Each of teeth 22 is formed into an arc shape having a thickness in the radial direction when viewed from the axial direction. Specifically, when viewed from the10 axial direction, an inner circumferential surface of each of teeth 22 is an arc having the radius Ri with the center Ocb of the core back 21 as the center, and an outer circumferential surface of each of teeth 22 is an arc having the radius Ro (here, Ri