AMR angle sensor, design method of AMR angle sensor, and production method of AMR angle sensor

Abstract

The design method of the AMR angle sensor of the present invention utilizes an AMR (anisotropic magnetoresistance) element including one or more arc patterns to detect angles, and the design method of the AMR angle sensor includes: a first step of determining the component of the nth harmonic of the fundamental wave of the angle period T of the output signal to be removed from the output signal of the AMR angle sensor (where n is an odd number greater than 3); and a second step of determining the angle of (where m is a natural number). As a result, the angle detection accuracy of the AMR angle sensor becomes good. The central angle of the arc pattern can also be determined as an angle within the range of 57° to 66°.

Description

Technical Field

[0001] The present invention relates to an AMR (Anisotropic Magneto-Resistor) angle sensor for detecting angles using an AMR element, a design method for the AMR angle sensor, and a production method for the AMR angle sensor. Background Art

[0002] An angle sensor that detects an angle using an anisotropic magnetoresistance (AMR) element (hereinafter also referred to as an AMR angle sensor) is known (Non-Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Laid-Open No. 11-148841 Summary of the invention

[0006] Problems to be solved by the invention

[0007] AMR angle sensors have the following problem: even when the saturation magnetic field strength of the angle detection object is applied, the signal waveform of the output signal is distorted and deviates from the ideal signal waveform, and the angle detection accuracy deteriorates. The reason is that the magnetization direction of the AMR element using shape magnetic anisotropy does not completely match the direction of the magnetic field of the angle detection object and deviates. The deviation causes the output signal to contain harmonic components, which is the main reason for the deterioration of angle detection accuracy.

[0008] An object of the present invention is to improve the angle detection accuracy of an AMR angle sensor.

[0009] Technical means of solving problems

[0010] The AMR angle sensor of the present invention is an AMR angle sensor that outputs an output signal of a fundamental wave including an angular period T=180°, comprising: a substrate; and an AMR (anisotropic magnetoresistance) element formed on the substrate, comprising one or more circular arc patterns, wherein the central angle φ of the circular arc pattern is an angle within the range of (T / n)*m-3°≦φ≦(T / n)*m+6° (wherein m is a natural number and n is an odd number greater than 3).

[0011] The design method of the AMR angle sensor of the present invention is a design method of an AMR angle sensor that uses an AMR (anisotropic magnetoresistance) element including one or more circular arc patterns to detect angles, including: a first step of determining the component of the nth harmonic of the fundamental wave of the output signal with an angular period T=180° (where n is an odd number greater than 3) to be removed from the output signal of the AMR angle sensor; and a second step of determining the center angle φ of the circular arc pattern to be an angle of (T / n)*m-3°≦φ≦(T / n)*m+6° (where m is a natural number).

[0012] The design method of the AMR angle sensor of the present invention is a design method of an AMR angle sensor that uses an AMR (anisotropic magnetoresistive) element including one or more arc patterns to detect angles, including: a process of determining the central angle φ of the arc pattern to be an angle within the range of 57° to 66°.

[0013] The method for producing an AMR angle sensor of the present invention comprises: a process of producing an AMR angle sensor designed by any one of the two design methods.

[0014] Effects of the Invention

[0015] According to the present invention, the angle detection accuracy of the AMR angle sensor is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [ Figure 1 ] Figure 1 The diagram shows an AMR element and a terminal formation pattern and a circuit configuration of an AMR angle sensor designed by a design method according to an embodiment of the present invention.

[0017] [ Figure 2 ] Figure 2 This is an enlarged plan view of the AMR element.

[0018] [ Figure 3 ] Figure 3 yes Figure 2 AA cross-section diagram.

[0019] [ Figure 4 ] Figure 4 This is a graph showing changes in the resistance value of the arc pattern of the linear portion and in the regions A and B of the arc pattern according to the rotation angle of the magnet.

[0020] [ Figure 5 ] Figure 5 This is a graph showing the relationship between the true rotation angle of the magnet and the angle detection error.

[0021] [ Figure 6 ] Figure 6This is a graph showing the maximum value of the angle detection error of each sample having different center angles.

[0022] [ Figure 7 ] Figure 7 This is a graph showing the results of FFT analysis of the output signal from the AMR angle sensor.

[0023] [ Figure 8 ] Figure 8 This is a diagram showing a graph of the relationship between the comprehensive angle detection maximum error and the anisotropic magnetic field intensity.

[0024] [ Fig. 9 ] Fig. 9 is a flow chart of a production method of an AMR angle sensor.

[0025] [ Fig.10 ] Fig.10 It is a partial plan view of an AMR element according to a modified example.

[0026] [ Fig.11 ] Fig.11 This is a graph showing the relationship between the true rotation angle of the magnet and the angle detection error.

[0027] [ Fig.12 ] Fig.12 : is a graph showing the relationship between the true rotation angle of the magnet and the angle detection error in the modified example. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present invention and modifications thereof will be described with reference to the drawings.

[0029] The method for producing an anisotropic magnetoresistive angle sensor (hereinafter also referred to as an AMR angle sensor) of this embodiment includes a step of designing the AMR angle sensor, that is, a design method of the AMR angle sensor, and a step of producing the AMR angle sensor designed by the design method.

[0030] Figure 1 1 shows an AMR angle sensor 10 designed and manufactured by this embodiment. The AMR angle sensor 10 is configured to detect the relative rotation angle of a magnet M arranged opposite to the sensor 10 relative to the sensor 10. The magnet M and the AMR angle sensor 10 are respectively mounted on two components that rotate relative to each other, for example, one component is a base, and the other component is a detection object of the rotation angle that rotates relative to the base. By detecting the rotation angle of the magnet M, the rotation angle of the detection object is detected.

[0031] The AMR angle sensor 10 includes a substrate 20, first anisotropic magnetoresistive (AMR) elements 31 to 34, second anisotropic magnetoresistive (AMR) elements 41 to 44, first connecting terminals 51 to 58, and second connecting terminals 61 to 64.

[0032] The substrate 20 includes, for example, a silicon substrate or a glass substrate. The AMR elements 31 to 34 and the AMR elements 41 to 44 are integrally formed into a film with the terminals 51 to 58 and the terminals 61 to 64 from the same material. As an example of a material, an alloy having a ferromagnetic metal as a main component can be cited, for example, a NiFe alloy can be cited. As an example of a NiFe alloy, there is a Permalloy of Ni: 83%, Fe: 17% having both low hysteresis and low magnetostriction properties. As another example, Permalloys of other ratios can also be used.

[0033] Elements 31 to 34 and elements 41 to 44 are of the same shape but in different directions. Figure 2 The shape is described below. The element 31 is formed into a meander shape. The meander-shaped element 31 includes a plurality of linear portions 31A parallel to each other, and a plurality of return portions 31B connecting the plurality of linear portions 31A in series. Each return portion 31B connects one end (e.g., Figure 2 the lower end) or the other end (e.g. Figure 2 Each linear portion 31A is formed into a circular arc pattern with a central angle φ. Hereinafter, each linear portion of AMR elements 31 to 34 and AMR elements 41 to 44 is sometimes referred to as linear portion 31A to linear portion 34A and linear portion 41A to linear portion 44A, respectively, and each folded portion is sometimes referred to as folded portion 31B to 34B and folded portion 41B to 44B, respectively.

[0034] like Figure 3 As shown, the substrate 20 on which the element 31 and the like are formed includes a substrate body 21 and an insulating film 22 (eg, a silicon oxide film) formed on the substrate body 21. The element 31 and the like are formed on the surface of the insulating film 22.

[0035] like Figure 1As shown, the orientation of element 32 is the orientation obtained by rotating element 31 by 90°, the orientation of element 33 is the orientation obtained by rotating element 31 by 180°, and the orientation of element 34 is the orientation obtained by rotating element 31 by 270°. Similarly, elements 42 to 44 are also formed in the orientation obtained by rotating element 41 by 90° in sequence. Elements 31 to 34 are arranged on a first circumference with the rotation center C of magnet M as the center, and elements 41 to 44 are arranged on a second circumference inside the first circumference with the rotation center C as the center. The overall orientation of elements 41 to 44 is the orientation obtained by rotating the overall orientation of elements 31 to 34 by 45° with the rotation center C as the center.

[0036] Both ends of the elements 31 to 34 are connected to the terminals 51 to 58, respectively. The elements 31 to 34 are connected in full bridge via the terminals 51 to 58. The terminals 51 and 58 are connected to the power supply line Vcc, and the terminals 54 and 55 are connected to the ground. The terminals 52 and 53 are connected to the output terminal OUT1, and the terminals 56 and 57 are connected to the output terminal OUT2. The potential V representing the output terminal OUT1 is OUT1 The potential V of the output terminal OUT2 OUT2 The difference (V OUT1 -V OUT2 ) is input into the control circuit 90 as the first bridge output.

[0037] Both ends of the elements 41 to 44 are connected to any of the terminals 61 to 64, and the elements 41 to 44 are connected in a full bridge via the terminals 61 to 64. The terminal 61 is connected to the power supply line +V, and the terminal 63 is connected to the ground. The terminal 62 is connected to the output terminal OUT3, and the terminal 64 is connected to the output terminal OUT4. The potential V representing the output terminal OUT3 is OUT3 With output terminal OUT4 V OUT4 The potential difference (V OUT3 -V OUT4 ) is input into the control circuit 90 as the second bridge output.

[0038] The potential differences, that is, the voltage values ​​represented by the first bridge output and the second bridge output vary according to the relative rotation angle of the magnet M with respect to the AMR angle sensor 10. Figure 1When the magnet M is rotated counterclockwise by one revolution from the state of , the first bridge output becomes a sine wave electrical signal, and the second bridge output becomes a cosine wave electrical signal. The angular period T of the sine wave and the cosine wave (the period of the sine wave and the cosine wave expressed in angle when the horizontal axis is an angle) is 180°. Based on the voltage values ​​Vsin and Vcos respectively represented by the input first bridge output and the second bridge output, the control circuit 90 calculates the relative rotation angle α of the magnet M relative to the AMR angle sensor 10, that is, the relative rotation angle α of the detection object, by the following formula (1) using arctan2.

[0039] [Number 1]

[0040]

[0041] In this type of AMR angle sensor 10, there is a situation where the signal waveforms of the output signals of the first bridge output and the second bridge output, i.e., the sine wave and the cosine wave, are distorted, and the signal waveforms of the output signals deviate from the ideal signal waveforms. In the case, the voltage value Vsin and the voltage value Vcos deviate from the values ​​on the ideal sine wave or cosine wave, and the calculated rotation angle α, i.e., the detection angle α in the sensor 10 deviates from the true rotation angle. That is, a detection error occurs. The reason is that the magnetization directions of the elements 31 to 34 and 41 to 44 that utilize shape magnetic anisotropy do not completely match the direction of the magnetic field of the magnet M and deviate. The deviation causes the output signals of the first bridge output and the second bridge output to include harmonic components, and the signal waveforms of the first bridge output and the second bridge output are distorted, and there is an error in the rotation angle α.

[0042] As a method of reducing the error, it is considered to reduce the harmonic component. Specifically, the inventors of the present application have found that the center angle φ of the arc pattern of each linear portion such as the linear portion 31A can be set to an angle obtained by 180° / n. n is an odd number greater than 3, which is the order of the harmonic to be reduced, that is, a multiple of the frequency of the fundamental wave. For example, in the case where the third harmonic is to be reduced, n=3, and 60° is used as the center angle φ. Below, the theory of reducing the harmonic component is first explained. In addition, the first bridge output is considered here, but it can be considered that the second bridge output and the relative rotation angle α calculated (detected) using the AMR angle sensor 10 are also the same.

[0043] First, if constant terms and harmonic components are also considered, the resistance values ​​R31 to R34 of the AMR elements 31 to 34, in which the linear portions 31A to 34A are set to be straight lines, are expressed by the following equations (2) and (3), and the first bridge output (voltage value) V is expressed by the following equation (4). In addition, n in equations (2) to (4) is an integer greater than 0. θ is the rotation angle of the magnet M (i.e., the external magnetic field) as the detection object of the angle. r n is a constant representing the amplitude of the harmonic component obtained by multiplying the frequency of the fundamental wave by n.

[0044] [Number 2]

[0045]

[0046] In this case, the molecular formula of the formula (4) becomes the following formula (5).

[0047] [Number 3]

[0048]

[0049] Furthermore, as n becomes larger (higher order harmonics), the harmonic component becomes smaller, so the denominator of equation (5) can be transformed as in the following equation (6).

[0050] [Number 4]

[0051]

[0052] According to (5) and (6), the above equation (4) is finally expressed by the following equation (7). Therefore, it can be seen that the influence of the even-numbered (n=2, 4, 6, ...) harmonic components on the first bridge output V can be ignored.

[0053] [Number 5]

[0054]

[0055] Next, consider the case where linear portions 31A to 34A are bent into an arc shape. Let the central angle of the arc be φ. In this case, the resistance values ​​R31 to R34 of AMR elements 31 to 34 are respectively expressed by the following equations (8) and (9).

[0056] [Number 6]

[0057]

[0058] Based on the above equations (8) and (9), the first bridge output V is expressed by the following equation (10).

[0059] [Number 7]

[0060]

[0061] The terms r1, r3, r5, etc. of the formula (10) correspond to the fundamental wave, the third harmonic, the fifth harmonic, etc., respectively. If the coefficients of each term are generalized, they become [sin(2nθ+2nφ)-sin(2nθ)] (n is an odd number), and the coefficients become a composite function of sine waves with the same frequency and amplitude. Therefore, the coefficients of each term r1, r3, r5, etc. can be expressed by a single sine wave. In order to reduce the measurement error, the harmonic component of the first bridge output V must be reduced, but by setting φ=180° / n according to the formula (10), 2nφ=360° can be set in the coefficient [sin(2nθ+2nφ)-sin(2nθ)]. As a result, the coefficient can be set to sin(2nθ)-sin(2nθ)=0. For example, in the case of reducing the third harmonic component, if n=3 (i.e., if the center angle φ of the linear portion 31A, etc. is set to 60°), the coefficient can be set to 0, thereby deleting the term r3 corresponding to the third harmonic in the equation (10). As a result, the third harmonic component is reduced. As described above, the nth harmonic component to be reduced (e.g., a harmonic component that becomes a large component) is selected, the center angle φ is determined according to φ=180° / n, and the AMR element is formed using the linear portion of the arc pattern having the determined center angle φ, thereby reducing the target nth harmonic component.

[0062] Taking the AMR element 31 and the reduction of the third harmonic component as an example, refer to Figure 4 The mechanism for reducing the nth harmonic component is explained. The third harmonic is a sine wave signal with an angular period of 60°. If the linear portion 31A of the AMR element 31 is divided into six regions A to F with a central angle of 10°, the resistance changes in regions A and D, regions B and E, and regions C and F, which have an angle difference of 30° of half a period, when the magnet M rotates one circle, are in opposite phases with the same amplitude and the same frequency ( Figure 4 The right side of the graph shows the resistance change related to area A and area D). Therefore, if the center angle φ = 60°, the third harmonics in all areas cancel each other out, and the third harmonic component can be reduced. This situation can be considered to be the same for the fifth harmonic, seventh harmonic, etc. (of course, the center angle φ becomes 36°, 25.7°, etc.).

[0063] In addition, the reason why "2n" in the above formulas (2) to (10) is set to "2" is that the angular period T of the fundamental wave of the output signal of the first bridge output is 180°, that is, the frequency is doubled, relative to the 360° cycle of the magnet M. Based on this, it can be considered that the central angle φ of the arc pattern = 180° / n = T / n.

[0064] The inventors of the present application prepared a plurality of AMR angle sensors 10 (other elements such as materials are set to be the same) in which only the center angle φ of the linear portions 31A to 34A and the linear portions 41A to 44A of the AMR elements 31 to 34 and the AMR elements 41 to 44 are different as samples. The center angle φ of each sample prepared is 9°, 26°, 44°, 57°, 60°, 72°, and 96°. Then, the inventors of the present application evaluated the angle detection error of each sample. Here, the magnet M is rotated to 0° to 100° with respect to each sample, and the rotation angle α represented by the output signal output by the AMR angle sensor 10, that is, the rotation angle α calculated by the control circuit 90, is obtained for each sample. The difference between the obtained rotation angle α and the true rotation angle of the magnet M at this time is set as the angle detection error, and the change in the angle detection error when the magnet M is rotated is shown in Figure 5 In addition, the Figure 5 The maximum value of the angle detection error is shown in the figure Figure 6 The true rotation angle is the same as the mechanical angle detection error described below, and is set to the detection value when the mechanical angle of the magnet M is detected by a detector such as an optical encoder. Figure 5 and Figure 6 As shown in FIG. 1 , it can be seen that the angle detection error is the lowest when the center angle φ is 60°. Furthermore, for each sample when the center angle φ is set to 44°, 57°, 60°, and 72°, the output signal of the AMR angle sensor 10 when the magnet M is rotated to 0° to 100° is analyzed by Fast Fourier Transform (FFT), and the obtained results are shown in FIG. Figure 7 .according to Figure 7 It can be seen that the third harmonic reduction degree is the largest when the center angle φ=60°.

[0065] As a second method for reducing the error, it is also possible to reduce the anisotropic magnetic field strength Hk of the AMR angle sensor 10. The anisotropic magnetic field strength Hk is the magnetic field strength at which the magnetization in the hard axis direction reaches saturation. The reduction in the anisotropic magnetic field strength Hk means that the unsaturated region relative to the external magnetic field becomes narrower, and the magnetic moments of the elements 31 to 34 and the elements 41 to 44 become easier to match the magnetization direction of the magnet M. Therefore, if the anisotropic magnetic field strength Hk is reduced, the waveform distortion of the first bridge output and the second bridge output can be suppressed.

[0066] If t is set to the film thickness of the elements 31 to 34 and the elements 41 to 44 (see Figure 3 ), set w to the same line width (refer to Figure 2. In particular, the line width of each linear portion such as the linear portion 31A, Ms is set to the same saturation magnetization (A / m), and Hk0 is set to the same material anisotropy, then the anisotropic magnetic field intensity Hk is expressed by the following formula (2).

[0067] Hk=(t / w)·Ms+Hk0···(11)

[0068] According to the formula (11), in order to reduce the anisotropic magnetic field intensity Hk, it is necessary to make the film thickness t of the element 31 and the like thinner and increase the line width w. However, as the film thickness t becomes thinner, defects are more likely to occur in the element 31 and the like, and the resistance value between the elements is more likely to deviate. Moreover, if the line width w is thicker, the sensor size becomes larger. The AMR angle sensor 10 may also be a structure that calculates the anisotropic magnetic field intensity Hk using a formula other than the formula (11). However, the anisotropic magnetic field intensity Hk is proportional to the film thickness of the AMR element and inversely proportional to the line width of the AMR element.

[0069] The inventors of the present application used the same material to make a plurality of AMR angle sensors 10 as samples, with only the film thickness t and line width w of the element 31 being different, and the other shapes of the element 31 being the same. Then, the inventors of the present application evaluated the mechanical angle detection error of each sample, the hysteresis of the output of each sample, and the comprehensive maximum angle detection error based on these. The material of the element 31 of each sample is the same, so the saturation magnetization Ms and the material anisotropy Hk0 are the same in each sample. Therefore, according to the formula (2), the anisotropic magnetic field intensity Hk can be changed by changing the film thickness t and the line width w.

[0070] The mechanical angle detection error is the absolute value of the difference between the detection value when the mechanical angle of the magnet M is detected by a detector such as an optical encoder and the angle α calculated by the control circuit 90. Here, the absolute value of the difference at each of a plurality of rotational positions of the magnet M is obtained.

[0071] Magnetic hysteresis is the difference between the angle α calculated by the control circuit 90 when the magnet M is rotated in a first rotation direction to a predetermined rotation position and the angle α calculated by the control circuit 90 when the magnet M is rotated in a second rotation direction opposite to the first rotation direction to the predetermined rotation position. Here, the difference at each of the plurality of rotation positions of the magnet M is obtained.

[0072] The comprehensive angle detection maximum error is the square root of the sum of the squares of the maximum value of the mechanical angle detection error and the maximum value of the hysteresis.

[0073] Table 1 shows the relationship among the film thickness t, line width w, anisotropic magnetic field intensity Hk, the maximum value of mechanical angle detection error, the maximum value of hysteresis, and the comprehensive maximum angle detection error for each sample.

[0074] [Table 1]

[0075]

[0076] As can be seen from Table 1, there is a correlation between the anisotropic magnetic field intensity Hk, the mechanical angle detection error, the hysteresis, and the comprehensive angle detection maximum error based on these. Figure 8 The table 1 is shown in the table 1. Figure 8 It can be seen that in order to obtain a comprehensive angle detection error of 0.1° or less, which can be considered as good angle detection accuracy, Hk can be set to 30 Oe or less (refer to Figure 8 dashed straight line).

[0077] Based on the above, refer to Fig. 9 , the production method of the AMR angle sensor 10 is described. Fig. 9 As shown, in the method for producing the AMR angle sensor 10 of the present embodiment, first, a method for designing the AMR angle sensor 10 is performed.

[0078] In the design method of the AMR angle sensor 10, the material of the substrate 20 is first determined, and the materials of the elements 31 to 34 and the elements 41 to 44, the terminals 51 to 58, and the terminals 61 to 64 are determined (step S11). By determining the materials of the elements 31 and the terminals 51, the saturation magnetization Ms and the material anisotropy Hk0 of the above formula (2) are determined. Therefore, the anisotropic magnetic field intensity Hk can be adjusted by the film thickness t and the line width w.

[0079] Then, the nth harmonic to be removed from the output signal of the AMR angle sensor 10 (the signal indicating the relative rotation angle α), i.e., the order n (where n is an odd number greater than 3) of the harmonic to be removed is determined (step S12). For example, when the influence of the third harmonic is large, n=3 is set. Then, the center angle φ of the shape (i.e., a circular arc pattern) of the linear portion 31A to the linear portion 34A and the linear portion 41A to the linear portion 44A is determined by T / n (where T=180°) (step S13). When n=3, the center angle φ becomes 60°.

[0080] Then, other patterns of elements 31 to 34 and elements 41 to 44 (the number of linear portions 31A to 34A and linear portions 41A to 44A, the pattern shapes of folded portions 31B to 34B and 41B to 44B), and the patterns of terminals 51 to 58 and terminals 61 to 64 are determined (step S14).

[0081] Through steps S12 to S14, the basic shapes of elements 31 to 34, elements 41 to 44, terminals 51 to 58, and terminals 61 to 64 are determined. Then, the anisotropic magnetic field intensity Hk is adjusted by adjusting the film thickness t and line width w of elements 31 to 34 and elements 41 to 44. Specifically, the film thickness t and line width w are determined within the range of the anisotropic magnetic field intensity Hk with 30 Oe as the upper limit value (step S15). In particular, the film thickness t and line width w are determined in consideration of defects caused by the film thickness t and sensor size caused by the line width w.

[0082] Through the above steps S11 to S15, the AMR angle sensor 10 is designed. Then, the designed AMR angle sensor 10 is produced, for example, mass-produced, by a known production method (step S16). For example, an insulating film is formed on the surface of the silicon substrate 20, and the element 31 and the terminal 51 are formed by sputtering. Then, the element 31 and the terminal 51 can be covered with a protective film.

[0083] According to the present embodiment, the output signal output by the AMR angle sensor 10 includes a fundamental wave (sine wave or cosine wave) with an angle period of T = 180° and harmonics of the fundamental wave when the detection object of the rotation angle (more specifically, the magnet M installed on the detection object of the rotation angle) rotates. The harmonics generate angle detection errors. In the present embodiment, based on the order n of the harmonics to be reduced, the center angle φ of the arc pattern constituting the linear portion 31A to the linear portion 34A and the linear portion 41A to the linear portion 44A is determined by φ = T / n = 180° / n. By the center angle φ, the nth harmonic is reduced, so the angle detection error is reduced.

[0084] In addition, if Figure 8 As shown in formula (10), the closer the center angle φ is to T / n (where T=180°), the smaller the nth harmonic is, so the center angle φ may not be strictly T / n. Specifically, the center angle φ may be substantially T / n ("substantially" means that it includes angles near T / n in addition to the angle of T / n itself), or may be an angle within the range of T / n±3°, and more preferably within the range of T / n±1°. In addition, according to formula (10), it is considered that the third harmonic is reduced even if the center angle φ is 120°, which is a multiple of 60°. As described above, the center angle φ may be set to (T / n)*m-3°≦φ≦(T / n)*m+3° (where m is a natural number and n is an odd number greater than 3), and more preferably to (T / n)*m-1°≦φ≦(T / n)*m+1° (where m is a natural number and n is an odd number greater than 3).

[0085] Furthermore, according to the present embodiment, the film thickness t and the line width w can be determined within the range of the anisotropic magnetic field strength Hk=30Oe which sets the upper limit value at which the comprehensive angle detection maximum error becomes 0.1°. Therefore, the angle detection error can be suppressed to below 0.1°, and the AMR element 31, etc. can be thickened, or the line width of the AMR element 31, etc. can be thinned.

[0086] (Variation Example)

[0087] Various modifications may be made to the above-described embodiment. Modification examples are listed below.

[0088] (Variant 1)

[0089] The shape of the element 31 and the like is arbitrary. For example, each linear portion 31A may include Fig.10 The wavy pattern shown is formed by connecting a plurality of arc patterns P with a central angle φ in series, rather than a single arc pattern as described above (the same applies to the linear portions 32A to 34A and the linear portions 41A to 44A). Fig.11 As shown, the angle detection error in such linear portion 31A is also reduced. Each linear portion 31A may be a straight line instead of an arc shape. Furthermore, any of the elements 31 to 34 and the elements 41 to 44 may be omitted. The number of elements is arbitrary as long as it is plural.

[0090] (Variant 2)

[0091] The comprehensive angle detection maximum error and the upper limit of the anisotropic magnetic field strength Hk can be set arbitrarily. For example, if the comprehensive angle detection maximum error is less than 0.1° as described above, it is considered that the detection accuracy of the AMR angle sensor is high, so the maximum error can be less than 0.1°, but the maximum error can also be other values. Moreover, the upper limit of the anisotropic magnetic field strength Hk can be determined according to the comprehensive angle detection error. In the past, the correlation between the anisotropic magnetic field strength Hk and the hysteresis and even the comprehensive angle detection error was unknown. The inventors of the present application discovered the correlation, and in the design of the AMR angle sensor, it was found that the film thickness and line width of the AMR element can be determined within the range of the anisotropic magnetic field strength value that makes the comprehensive angle detection maximum error of the AMR angle sensor based on the mechanical angle detection error and the hysteresis value become the required value as the upper limit value. In this way, the comprehensive angle detection error can be suppressed, and the AMR element 31, etc. can be thickened, or the line width of the AMR element 31, etc. can be thinned. In addition, the comprehensive angle detection maximum error can also be replaced by the mechanical angle detection error, etc.

[0092] (Variant 3)

[0093] In the above embodiment, attention is paid to a specific harmonic, but even if the third harmonic is reduced, higher harmonics, especially the fifth harmonic, may adversely affect the angle detection accuracy. The reason is: Figure 7 There are several fifth harmonics in the equation (10), and the term of the fifth harmonic in the equation (10) is not 0. Here, the accuracy of φ=60°, which is closest to better reducing the third harmonic in the center angle φ=(180° / 5)*m for reducing the fifth harmonic, is 72°. Therefore, there is a possibility that the third and fifth harmonics can be efficiently reduced by increasing the center angle φ from 60° to 72°. The inventors of the present application conducted a simulation based on the equation (10). φ is set to 57°, 60° (angle for reducing the third harmonic), 62.5°, 66°, 72° (angle for reducing the fifth harmonic). Moreover, r1, r3, r5, etc. in the equation (10) are calculated based on the results of intensity FFT analysis of the output signal of the prototype of the AMR angle sensor in which the linear portion 31A, etc. is set to a straight line. The simulation results (changes in the angle detection error when the magnet M is rotated to 0°~100°) are shown in Fig.12 .like Fig.12 As shown, the angle detection error is the smallest when the center angle φ = 62.5° (in addition, 66° can also be considered to be within the allowable range). According to this result, the center angle φ can be within the range of 59° to 66° (within the range of ±3.5° based on 62.5 as the optimal angle). Moreover, it is better to be within the range of 61.5° to 63.5° (within the range of ±1° based on 62.5 as the optimal angle). The center angle φ can also be 62.5° itself, or substantially 62.5° ("substantially" means that in addition to 62.5°, it also includes angles near it). Combining the angle range mentioned this time with the angle range mentioned above for reducing specific harmonics, the center angle φ can be specified to be within the range of (T / n)*m-3°≦φ≦(T / n)*m+6° (where m is a natural number and n is an odd number greater than 3), and more preferably within the range of (T / n)*m-1°≦φ≦(T / n)*m+3.5. T is the angular period of the fundamental wave of the output signal of the sensor, which is 180°. The range can be used to determine the nth harmonic that is mainly desired to be removed from the output signal of the AMR angle sensor, and the center angle φ can be determined from the range based on the determined n.

[0094] (Scope of the present invention)

[0095] The present invention has been described above with reference to the embodiments and variations, but the present invention is not limited to the embodiments and variations. For example, the present invention includes various changes to the embodiments and variations that can be understood by those skilled in the art within the scope of the technical concept of the present invention. The various structures listed in the embodiments and variations can be appropriately combined within the scope of non-contradiction.

[0096] (Note)

[0097] The following notes describe various configurations using the above-described embodiment and modification examples as examples. In addition, the configurations of the following notes A and B may be combined with each other.

[0098] (Note A)

[0099] (Note A1)

[0100] An AMR angle sensor, the output of which includes an output signal of a fundamental wave with an angle period of T=180°, the AMR angle sensor comprising:

[0101] substrate; and

[0102] AMR (anisotropic magnetoresistance) element, formed on the substrate, includes more than one arc pattern,

[0103] The central angle φ of the arc pattern is an angle in the range of (T / n)*m-3°≦φ≦(T / n)*m+6° (where m is a natural number and n is an odd number greater than or equal to 3).

[0104] The output signal including the fundamental wave with an angular period of 180° is output from the AMR angle sensor when, for example, a detection target (external magnetic field) whose rotation angle is to be detected by the AMR angle sensor rotates.

[0105] (Note A2)

[0106] An AMR angle sensor as described in Note A1, wherein n=3, m=1.

[0107] (Note A3)

[0108] The AMR angle sensor as described in Note A1 or Note A2, wherein the AMR element comprises: a plurality of linear portions including one or more arc patterns and parallel to each other; and a plurality of folded portions connecting two adjacent linear portions among the plurality of linear portions.

[0109] (Note A4)

[0110] The AMR angle sensor as described in any one of Notes A1 to A3, wherein the plurality of linear portions each include an arc pattern.

[0111] (Note A5)

[0112] The AMR angle sensor as described in any one of Notes A1 to A3, wherein the plurality of linear portions each include a wave-shaped pattern formed by connecting a plurality of arc patterns in series.

[0113] (Note A6)

[0114] The AMR angle sensor as described in any one of Notes A1 to A5, wherein n is determined as a multiple of a harmonic to be removed from an output signal of the AMR angle sensor.

[0115] (Note A7)

[0116] A design method of an AMR angle sensor, which detects an angle using an AMR (anisotropic magnetoresistance) element including more than one arc pattern, the design method of the AMR angle sensor comprising:

[0117] The first step is to determine the nth harmonic component of the fundamental wave of the output signal with an angular period T=180° to be removed from the output signal of the AMR angle sensor (where n is an odd number greater than or equal to 3); and

[0118] In the second step, the central angle φ of the arc pattern is determined to be (T / n)*m-3°≦φ≦(T / n)*m+6° (where m is a natural number).

[0119] The output signal including the fundamental wave of the angle period T is output from the AMR angle sensor when the detection object (external magnetic field) whose rotation angle is to be detected by the AMR angle sensor rotates, for example. The nth harmonic to be removed from the output signal of the AMR angle sensor includes the nth harmonic that is mainly to be removed from the output signal.

[0120] (Note 8)

[0121] A design method of an AMR angle sensor, which detects an angle using an AMR (anisotropic magnetoresistance) element including one or more arc patterns, comprises the following steps:

[0122] The central angle φ of the arc pattern is determined to be within a range of 57° to 66°.

[0123] (Note A9)

[0124] The design method of the AMR angle sensor as described in Note A7 or Note A8 also includes the following step: determining the film thickness and line width of the AMR element within a range where the value of the anisotropic magnetic field strength of the AMR angle sensor becomes a required value as an upper limit value.

[0125] (Note A10)

[0126] A method for producing an AMR angle sensor, comprising the following steps: producing an AMR angle sensor designed by the design method described in any one of Notes A7 to A9.

[0127] In addition, the production method may also include the design method as described in Note A1 or Note A2.

[0128] (Note B)

[0129] (Topic of Note B)

[0130] As a method of reducing waveform distortion of the output of the AMR angle sensor, it is considered to reduce the anisotropic magnetic field strength. The anisotropic magnetic field strength is proportional to the film thickness of the AMR element and inversely proportional to the line width of the AMR element. Therefore, in the case of reducing the anisotropic magnetic field strength, it is ideal to make the film thickness thinner and / or thicker the line width, but if the film thickness becomes too thin, the AMR element is prone to defects, and if the line width is thicker, the size of the sensor becomes larger. The subject of the present invention is to suppress the angle detection error, and to thicken the AMR element and / or thin the line width of the AMR element.

[0131] (Note B1)

[0132] A design method of an AMR angle sensor, which detects angles using a zigzag AMR (anisotropic magnetoresistance) element, the design method of the AMR angle sensor comprising:

[0133] The step of determining a film thickness and a line width of the AMR element is performed within a range where a value of anisotropic magnetic field intensity of the AMR angle sensor at which a maximum error in angle detection of the AMR angle sensor becomes a desired value is set as an upper limit value.

[0134] (Note B2)

[0135] In the method for designing an AMR angle sensor as described in Supplementary Note B1, the angle detection maximum error is a value based on a mechanical angle detection error of the AMR angle sensor and a hysteresis value of an output of the AMR angle sensor.

[0136] (Note B3)

[0137] The design method of the AMR angle sensor as described in Note B1 or Note B2, wherein the required value is 0.1° and the upper limit value is 30 Oe.

[0138] (Note B4)

[0139] The method for designing an AMR angle sensor as described in any one of Notes B1 to B3, wherein the AMR element includes a plurality of linear portions that are parallel to each other and are in an arc shape.

[0140] (Note B5)

[0141] A method for producing an AMR angle sensor, comprising:

[0142] The determination step is a step included in the design method described in any one of Notes B1 to B4; and

[0143] A production process is to produce the AMR angle sensor with the film thickness and the line width determined by the determination process.

[0144] (Note B6)

[0145] An AMR angle sensor detects angles using a meandering AMR (Anisotropic Magneto-Resistance) element, wherein:

[0146] The AMR element has a film thickness and a line width set within a range where the value of the anisotropic magnetic field intensity of the AMR angle sensor at which the maximum angle detection error of the AMR angle sensor becomes a required value is an upper limit value.

[0147] (Effect of Note B)

[0148] According to the above-mentioned supplementary structure, it is possible to suppress the angle detection error and to increase the thickness of the AMR element or to reduce the line width of the AMR element.

[0149] Description of Figure Numbers

[0150] 10: AMR angle sensor

[0151] 20: Substrate

[0152] 31-34: First anisotropic magnetoresistive element

[0153] 41-44: Second anisotropic magnetoresistive element

[0154] 31A: Linear part

[0155] 31B: Return part

[0156] 51-58: First connection terminal

[0157] 61-64: Second connection terminal

[0158] 90: Control circuit

[0159] C: Center of rotation

[0160] M: Magnet

[0161] φ: Center angle

[0162] P: Arc pattern

Claims

1. An AMR angle sensor outputs an output signal containing a fundamental wave with an angle period of T=180°, wherein the AMR angle sensor comprises: substrate; as well as AMR (anisotropic magnetoresistance) element, formed on the substrate, includes more than one arc pattern, The central angle φ of the arc pattern is an angle in the range of (T / n)*m-3°≦φ≦(T / n)*m+6° (where m is a natural number and n is an odd number greater than or equal to 3).

2. The AMR angle sensor according to claim 1, characterized in that: n=3, m=1.

3. The AMR angle sensor according to claim 1, characterized in that: The AMR element includes: a plurality of linear portions including at least one arc pattern and the plurality of linear portions are parallel to each other; and a plurality of return portions connecting two adjacent linear portions among the plurality of linear portions.

4. The AMR angle sensor according to claim 1, characterized in that: The plurality of linear portions each include a circular arc pattern.

5. The AMR angle sensor according to claim 1, characterized in that: The plurality of linear portions respectively include: a wave-shaped pattern formed by connecting a plurality of arc patterns in series.

6. The AMR angle sensor according to claim 1, characterized in that: The n is determined as a multiple of the harmonics to be removed from the output signal of the AMR angle sensor.

7. A method for designing an AMR angle sensor, which uses an AMR (anisotropic magnetoresistance) element including one or more arc patterns to detect an angle, wherein the method for designing an AMR angle sensor is characterized by comprising: The first step is to determine the nth harmonic component of the fundamental wave of the output signal with an angular period T=180° to be removed from the output signal of the AMR angle sensor (where n is an odd number greater than or equal to 3); and In the second step, the central angle φ of the arc pattern is determined to be (T / n)*m-3°≦φ≦(T / n)*m+6° (where m is a natural number).

8. A method for designing an AMR angle sensor, which uses an AMR (anisotropic magnetoresistance) element including one or more arc patterns to detect an angle, wherein the method for designing an AMR angle sensor is characterized by comprising: A step of determining a central angle φ of the arc pattern to be within a range of 57° to 66°.

9. The design method of the AMR angle sensor according to claim 7 or 8, characterized in that: Also includes: The step of determining the film thickness and line width of the AMR element within a range where the value of the anisotropic magnetic field intensity of the AMR angle sensor at which the maximum angle detection error of the AMR angle sensor becomes a required value is set as an upper limit value.

10. A method for producing an AMR angle sensor, characterized in that: include: A process for producing an AMR angle sensor designed by the design method according to claim 7 or 8.

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