Rotation angle detection device and rotation angle detection method

Abstract

Rotation angle detection device comprising: a rotor (2) made of a magnetic material; a stator (1) comprising a bias magnetic field generating section (3) and a plurality, namely “a”, of magnetic detection elements (4); and a rotation angle calculation processing unit (20) that is set up, to calculate a rotation angle of the rotor (2) based on detection signals obtained from the plurality of magnetic detection elements (4), wherein a surface of the rotor (2) opposite the stator has convex and concave sections (2a) which change in “x” cycles over a mechanical angle of 360 degrees, where “x” is an integer of 1 or more, and the convex and concave sections (2a) have a shape which changes in a curved manner, the shape enabling each of the plurality of magnetic detection elements (4) to obtain a substantially sinusoidal wave, and wherein the “a” magnetic detection elements (4) of the stator (1) are arranged uniformly spaced along a circumferential direction of the stator over one cycle of the convex and concave sections (2a), such that they face the surface of the rotor (2) opposite the stator (1) with a gap to that surface, and the bias magnetic field generating section (3) extends in the circumferential direction over one cycle of the convex and concave sections, such that it overlaps with the “a” magnetic detection elements (4), wherein “a” is an integer of 2 or more.

Description

Technical field

[0001] The present invention relates to a rotation angle detection device and in particular a rotation angle detection device and a rotation angle detection method which utilize a change in the magnetic field strength. Technical background

[0002] For example, JP 2006-132 978 A discloses a rotation detection device comprising: a rotor provided on a rotating shaft supported by a housing with a bearing, and configured to rotate, the rotation of which is to be detected; a semiconductor chip with a magnetic sensing element configured to sensing a change in a magnetic field in the vicinity of the rotor; and a bias magnet configured to apply a bias magnetic field to the magnetic sensing element, wherein the rotation detection device is configured to detect a rotation mode of the rotor by sensing a change in the magnetic field caused by the bias magnetic field when the rotor rotates, by means of the magnetic sensing element, wherein the bearing and the semiconductor chip are integrally formed with the housing.Furthermore, JP 11-51 695 A and JP 08-21 9709 A disclose a rotation detection device and a rotation detection sensor which exploit a change in magnetic field strength.

[0003] Documents JP 2006-329 888 A, JP 2016-20 819 A, JP 2004-184 115 A and JP 2008-209 340 A, relating to rotation detection devices, are also known from the prior art. Description of the invention: Technical problem

[0004] For example, in the rotation detection device of JP 2006-132 978 A, rectangular protrusions and recesses are formed along an outer circumferential surface of the rotor, and the rotation is detected by sensing, by means of the magnetic sensing element, a change in the magnetic field caused in connection with the bias magnetic field due to these protrusions and recesses.

[0005] An object of the present invention is to provide a rotation angle detection device and the like for the high-precision detection of a rotation angle by forming convex and concave sections on one side of a rotor for which the rotation angle is to be measured, which change in a curved, seamless and periodic manner like a sine wave, and by detecting with a plurality of magnetic detection elements a change in the magnetic field which is caused in connection with a bias magnetic field due to the projections and recesses that change seamlessly and periodically. Solution to the task

[0006] According to one embodiment of the present invention, a rotation angle detection device and the like are provided, comprising: a rotor made of a magnetic material; a stator having a bias magnetic field generation section and a plurality of magnetic detection elements; and a rotation angle calculation processing unit configured to calculate a rotation angle of the rotor based on detection signals obtained from the plurality of magnetic detection elements, wherein a surface of the rotor opposite the stator has convex and concave sections that change in “x” cycles over a mechanical angle of 360 degrees, where “x” is an integer of 1 or more, and the convex and concave sections have a shape that changes in a curved manner, the shape enabling each of the plurality of magnetic detection elements to obtain a substantially sinusoidal wave.and wherein “a” magnetic detection elements of the stator are arranged along a circumferential direction of the stator at equal intervals for one cycle of the convex and concave sections, such that they are opposite the surface of the rotor facing the stator at a distance from that surface, and the bias magnetic field generating section extends in the circumferential direction for one cycle of the convex and concave sections, such that it overlaps with the “a” magnetic detection elements, wherein “a” is an integer greater than or equal to 2. Advantageous effects of the invention

[0007] According to the embodiments of the present invention, it is possible to provide a rotation angle detection device and the like for highly precise detection of a rotation angle by means of the plurality of magnetic detection elements detecting a change in a magnetic field which is caused in connection with the bias magnetic field due to the convex and concave sections formed on the rotor side and which change in a curved manner, seamlessly and periodically like a sine wave. Brief description of the drawings Fig. Figure 1 is a schematic sectional view of a detection unit of a rotary angle detection device according to an embodiment of the present invention. Fig. 2A and Fig. Figure 2B shows enlarged cross-sectional views of a main part of the detection unit. Fig. 1. Fig. Figure 3 is a configuration diagram of a rotation angle calculation unit of the rotation angle detection device according to an embodiment of the present invention. Fig. Figure 4 is a diagram illustrating an example of a function block diagram of a rotation angle calculation processing unit. Fig. 3. Fig. Figure 5 is a diagram illustrating an example of a hardware design for the rotation angle calculation processing unit. Fig. 3. Fig. Figure 6 is a schematic sectional view of yet another example of the detection unit of the rotation angle detection device according to the present invention. Fig. Figure 7 is a schematic sectional view of yet another example of the detection unit of the rotation angle detection device according to the present invention. Fig. Figure 8 is a schematic sectional view of yet another example of the detection unit of the rotation angle detection device according to the present invention. Description of embodiments

[0008] A rotary angle detection device and the like, according to each embodiment of the present invention, will now be described with reference to the drawings. In each embodiment, identical or corresponding parts are designated by the same reference numerals, and a repetitive description of these parts is omitted. First embodiment

[0009] Fig. Figure 1 is a schematic sectional view of a detection unit of the rotation angle detection device according to an embodiment of the present invention. A stator 1, comprising a magnetic material 5, a bias magnetic field generation section 3, and a plurality of magnetic detection elements 4, is arranged on a portion of the outer circumference of the rotor 2, whose rotation angle is to be detected. Convex and concave sections 2a are formed on a surface of the rotor 2 opposite the stator, for example, an outer circumferential surface of the rotor 2. The convex and concave sections 2a have a shape that changes in a curved manner, enabling each of the magnetic detection elements 4 to generate a substantially sinusoidal wave. Fig. 1 is x equal to 12, which means that twelve convex and concave sections 2a are formed, and therefore, when the rotor 2 has rotated by a mechanical angle of 360 degrees, i.e., once, waveforms from each of the magnetic detection elements 4 are obtained, corresponding to twelve cycles. Fig. For example, three magnetic detection elements 4 are formed for each cycle of the convex and concave sections 2a. Furthermore, for one cycle of the convex and concave sections 2a, three magnetic field detection elements 4 are arranged at substantially equal intervals, and therefore signals with a phase difference of 120 degrees are output by the three magnetic detection elements 4 if it is assumed that one cycle of the convex and concave sections 2a is 360 degrees.

[0010] It is only required that the convex and concave sections 2a “x” have cycles for the mechanical angle of 360 degrees, and that “x” represents an integer of 1 or more.

[0011] Fig. 2A and Fig. Figures 2B are enlarged cross-sectional views of a main part of the detection unit. Fig. 1. In Fig. Figure 2A shows a case where a = 3, i.e., three magnetic detection elements 4 are arranged. Fig. Figure 2B shows a case where a = 2, i.e., two magnetic detection elements 4 are arranged. A structure with an inner rotor, in which the rotor 2 is arranged internally, is used, and therefore the magnetic detection elements 4 are arranged on an inner circumference of the bias magnetic field generation section 3. Furthermore, magnetic material 5 is arranged on an outer circumference of the bias magnetic field generation section 3 and on its outer surfaces in the circumferential direction to increase the magnetic flux that is to be detected by the magnetic detection elements 4.

[0012] It is only required that “a” magnetic detection sections 4 are arranged for one cycle of the convex and concave sections 2a, and that “a” is an integer of 2 or more.

[0013] Furthermore, the magnetic material 5 only needs to be provided according to the requirements of a magnetic path configuration. In some cases, depending on the magnetic path configuration, the magnetic flux from a magnet does not reach the rotor but returns to the magnetic material 5. Therefore, whether or not to provide the magnetic material 5 depends on the design of the magnetic circuit. However, by providing the magnetic material 5, it can act as a shield against the influence of an externally applied magnetic field, such as a magnetic field from a motor coil. Therefore, the magnetic material 5 can readily be provided as a shielding material, provided that its magnetic configuration is suitable.

[0014] Fig. Figure 3 is an embodiment diagram of a rotation angle calculation unit of the rotation angle detection device according to an embodiment of the present invention. The detection signal from each of the magnetic detection elements 4 is subjected to an A / D conversion in an A / D conversion unit 10, and then the resulting signal is input to a rotation angle calculation processing unit 20. In the rotation angle calculation processing unit 20, a rotation angle calculation is performed based on the detection signals, and the calculated rotation angle is displayed, for example, on a display unit 30.

[0015] Fig. Figure 4 is a diagram illustrating an example of a function block diagram of the rotation angle calculation processing unit. Fig. 3. A signal conversion module 24 removes a DC displacement component, which is a DC component of a magnetic field generated by a bias magnetic field. In this case, the DC displacement is subjected to waveform averaging processing to calculate a DC displacement quantity, and this DC displacement quantity is subtracted from each phase signal to remove the DC displacement. For example, in a case of three-phase signals, a DC displacement component can be obtained by dividing the sum of the phase signals by 3, and the DC displacement component can be subtracted from each phase signal. As another example, a DC displacement component can be calculated based on a maximum value (Max) or a minimum value (Min) of a waveform amplitude.An a-phase / two-phase conversion module 21, which serves as a phase signal conversion module, converts the signals according to “a” phases from the “a” magnetic detection elements 4 into two-phase signals containing a sine wave and a cosine wave.

[0016] An example of signal conversion in a case of a = 3, i.e., three-phase signals A, B, and C, represented in expression (1), is described below. This conversion yields α and β signals that differ in phase by 90 degrees, and the signals can therefore be converted into a sine wave and a cosine wave. Furthermore, in expression (1) below, the angles are set to 0, 120, and 240 degrees; however, if the phases of the original waveforms differ, it is desirable that the angles in expression (1) be set to the same phases as those of the original waveforms. [αβ]=[cos 0cos(120)cos(240)sin 0sin(120)sin(240)][ABC]=[1−12−12032−32][ABC]

[0017] A rotation angle calculation module 22 calculates an arctangent of the two-phase signals containing the sine and cosine waves to calculate a rotation angle. For example, the arctangent can be calculated based on expression (2) below. This follows the general concept of trigonometric functions. θ=tan−1sin θcos θ

[0018] The aforementioned method, in which the sum of the phase signals is obtained and a value obtained by dividing the sum by the number of phases is subtracted from each phase signal, can be implemented as a separate step in addition to the removal of a DC displacement component. Performing this step separately eliminates electrical and magnetic noise that would otherwise be introduced into each sensor simultaneously. This reduces the influence of an external factor, thereby minimizing angular error. As a result, a particularly robust sensor can be obtained. A display processing module 23 shows the obtained rotation angle on the display unit 30.

[0019] Fig. Figure 5 is a diagram illustrating an example of a hardware configuration of the rotation angle calculation processing unit. Fig. 3. The rotation angle calculation processing unit 20 is, for example, designed as a computer. The detection signals from the “a” magnetic detection elements 4, corresponding to the “a” phases, which have undergone digital conversion, are input to the rotation angle calculation processing unit 20 via an interface (I / F) 26. Programs corresponding to the respective function blocks, which are stored in a memory 28, are stored in a memory 28. Fig. Figure 4 shows the data used for the calculation, and the predefined data is stored for this purpose. A processor performs a rotation angle calculation on the detection signals input via the interface (IF), according to the programs and data stored in memory 28. The calculated rotation angle is then output via interface (I / F) 26 and displayed on the display unit 30. Fig. 3 displayed.

[0020] With further reference to Fig. The rotor 2 is made of a magnetic material. The stator 1 has a bias magnetic field generation section 3 and a plurality of magnetic detection elements 4, each configured to detect a magnetic density. The bias magnetic field generation section 3 is, for example, made of a permanent magnet. The magnetic detection element 4 is made of an electromagnetic conversion element, such as a Hall effect sensor. Furthermore, the rotation angle of the rotor 2 is calculated by the rotation angle calculation processing unit 20 based on the detection signals detected by the magnetic detection elements 4.

[0021] The amount of magnetic flux from the bias magnetic field generation section 3 to the side of the rotor 2 varies depending on the distance of a gap between the bias magnetic field generation section 3 and the surface of the convex and concave sections 2a of the rotor 2. A change in the magnetic field, caused by the projections and recesses of the convex and concave sections 2a, which change seamlessly and periodically, is detected by the magnetic detection elements 4. Therefore, the detection signal received by each of the magnetic detection elements 4 changes depending on the shape of the convex and concave projections 2a and consequently changes depending on the rotational angular position of the rotor.Furthermore, the change in the shape of the convex and concave sections 2a results in sinusoidal wave signals with different phases in this case. The detection signals obtained from two magnetic detection elements 4, separated by 1 / 4 of a cycle of the convex and concave sections (i.e., by 90 degrees), exhibit a sine wave and a cosine wave relationship. Then, by calculating the arctangent of these detection signals with a sine wave and a cosine wave relationship, the rotational angular position of the rotor 2 is obtained.

[0022] On the surface of the rotor 2 facing the stator, convex and concave sections 2a are formed, which change in “x” cycles over the mechanical angle of 360 degrees, where the symbol “x” represents an integer of 1 or more. This means that on the surface of the rotor 2 facing the stator, it is only necessary that the convex and concave sections 2a, in which projections and recesses are formed relative to each other in one or more cycles during a rotation of the rotor 2, are formed. Fig. 1 and Fig. 2A and Fig. 2B represents the convex and concave sections 2a in the case of x = 12, i.e., with twelve cycles of protrusions and recesses. The convex and concave sections 2a have a shape that changes in a curved manner, which allows each of the magnetic detection elements 4 to obtain an essentially sine wave or a sine wave. Therefore, the convex and concave sections 2a, for example, have the shape of an essentially sine wave or a sine wave. There are “a” magnetic detection elements 4 of the stator 1 arranged along a circumferential direction of the stator at equal intervals for one cycle of convex and concave sections, such that they face the surface of the rotor 2 opposite the stator with a gap from this surface. In Fig. 1 and Fig. 2A, where a = 3, means that three magnetic detection elements 4 are arranged. The bias magnetic field generating section 3 extends circumferentially for one cycle of the convex and concave sections 2a, such that it overlaps with the magnetic detection elements 4. The bias magnetic field generating section 3 is also arranged so that it faces the surface of the rotor 2 opposite the stator, with a gap between this surface and the rotor. The symbol "a" represents an integer greater than or equal to 2.

[0023] If a is, for example, 2, meaning that two magnetic detection elements 4 are arranged as in Fig. As shown in Figure 2B, the magnetic detection elements 4 are arranged at a distance of essentially one-fourth or one-fifth of a cycle of the convex and concave sections. In this case, processing by the a-phase / two-phase conversion module 21 of the rotation angle calculation processing unit 20 is not required. The rotation angle calculation module 22 calculates an arctangent of the two-phase signals containing the sine and cosine waves detected by the magnetic detection elements 4 to calculate a rotation angle.

[0024] If a > 2, for example, three magnetic detection elements 4 are arranged as in Fig. As shown in Figure 2A, the magnetic detection elements 4 are each arranged at a position of 360 / (x×a) degrees in the circumferential direction. In this case, the a-phase / two-phase conversion module 21 of the rotation angle calculation processing unit 20 performs processing to convert the detection signals corresponding to “a” phases into two-phase signals, which are separated from each other by a quarter of a cycle of the convex and concave sections 2a. In the case of a = 3, as in Fig. 1 and Fig. 2A and Fig. As shown in Figure 2B, the detection signals are processed to convert three-phase detection signals into two-phase detection signals. The rotation angle calculation module 22 then calculates an arctangent of the two-phase signals, which contain sine and cosine wave signals obtained by the a-phase / two-phase conversion module 21, to calculate a rotation angle.

[0025] Furthermore, on the outer circumferential side of the bias magnetic field generating section 3, or outer sides thereof in the circumferential direction, the magnetic material 5 is arranged such that it faces the surface of the rotor 2 opposite the stator with a gap from that surface, in order to increase the amount of magnetic flux to be detected by the magnetic detection elements 3. This magnetic material 5 can be arranged on the outer circumferential side of the bias magnetic field generating section 3 as indicated by reference numeral 6a in Fig. 2A and Fig. 2B. Furthermore, as indicated by references 5b and 5c from Fig. 2A and Fig. As indicated in Figure 2B, the magnetic materials 5 can be arranged such that they extend circumferentially from the end sections of the bias magnetic field generating section 3 to the outer sides of this section. The magnetic material 5 can be arranged circumferentially at only one end side of the bias magnetic field generating section 3, or it can be arranged circumferentially at both end sides of the bias magnetic field generating section 3.

[0026] A portion of the magnetic material 5, extending circumferentially from the end section of the bias magnetic field generation section 3 to the outer surface of this section, is adjusted to have a length greater than or equal to half the circumferential length of the bias magnetic field generation section 3. This makes it possible to efficiently increase the amount of magnetic flux to be detected by the magnetic detection elements 4.

[0027] The embodiment described above describes a configuration in which the rotor 2 is arranged internally and the stator 1 is arranged externally. However, the present invention is not limited to this configuration and can also be applied to a configuration in which the stator 1 is arranged internally and the rotor 2 is arranged externally. Furthermore, the present invention is not limited to the embodiments described above.

[0028] Fig. 6, Fig. 7 to Fig. Figure 8 are each a schematic sectional view of another embodiment of the detection unit of the rotation angle detection device according to the present invention.

[0029] Fig. Figure 6 shows an embodiment in which two stators 1 are arranged, each comprising a bias magnet generation section 3, a plurality of magnet detection elements 4, and the magnetic material 5. In the present invention, a plurality of stators 1 can be arranged. In this case, for example, the rotation angle calculation module 22 of the rotation angle calculation processing unit 20 calculates a rotation angle for each of the stators 1, and an average value of the calculated rotation angles is determined as the final rotation angle.

[0030] Fig. Figure 7 is a representation of an embodiment of a structure with an external rotor, in which the rotor 2 is arranged externally. In each of the examples described above, the case of the structure with an internal rotor, in which the rotor 2 is arranged internally, was described. However, the present invention is also applicable to a structure with an external rotor, in which the rotor 2 is arranged externally.

[0031] Fig.Figure 8 shows an embodiment in which the rotor 2 has x = 6, i.e., six convex and concave sections 2a for a mechanical angle of 360 degrees, and the stator 1 has a = 5, i.e., five magnetic detection elements 4 for one cycle of the convex and concave sections 2a of the rotor 2. In the present invention, the rotor 2 only needs to have the convex and concave sections 2a corresponding to "x" cycles for the mechanical angle of 360 degrees, where "x" is an integer greater than or equal to 1. Furthermore, the stator 1 only needs to have "a" magnetic detection elements 4 for one cycle of the convex and concave sections 2a of the rotor 2, where "a" is an integer greater than or equal to 2. Industrial applicability

[0032] The rotation angle detection device and the rotation angle detection method according to the present invention are applicable to the detection of a rotation angle of a rotating element in various fields. List of reference symbols 1 Stator 2 Rotor 2a convex and concave sections 3 Bias magnetic field generation section 4 magnetic detection elements 5 magnetic material 10 A / D conversion unit 20 Rotation angle calculation processing unit 21 a-Phase / Two-Phase Conversion Module 22 Rotation angle calculation module 23 Display processing module 24 Signal conversion module 26 Interface (I / F) 27 processor 28 storage 30 display units

Claims

Rotation angle detection device comprising: a rotor (2) made of a magnetic material; a stator (1) comprising a bias magnetic field generating section (3) and a plurality, namely “a”, of magnetic detection elements (4); and a rotation angle calculation processing unit (20) configured to calculate a rotation angle of the rotor (2) based on detection signals obtained from the plurality of magnetic detection elements (4), wherein a surface of the rotor (2) opposite the stator has convex and concave sections (2a) that change in “x” cycles over a mechanical angle of 360 degrees, where “x” is an integer of 1 or more, and the convex and concave sections (2a) have a shape that changes in a curved manner, the shape enabling each of the plurality of magnetic detection elements (4) to obtain an substantially sinusoidal wave,and wherein the “a” magnetic detection elements (4) of the stator (1) are arranged at uniform intervals along a circumferential direction of the stator over one cycle of the convex and concave sections (2a), such that they face the surface of the rotor (2) opposite the stator (1) with a gap to that surface, and the bias magnetic field generating section (3) extends in the circumferential direction over one cycle of the convex and concave sections, such that it overlaps with the “a” magnetic detection elements (4), wherein “a” is an integer of 2 or more. Rotation angle detection device according to claim 1, wherein if a=2 and a number of the magnetic detection elements (4) is two, the magnetic detection elements are arranged with a distance of substantially a quarter cycle of a cycle of the convex and concave sections. Rotation angle detection device according to claim 2, wherein the rotation angle calculation processing unit (20) is configured to detect the rotation angle based on two-phase signals detected by the magnetic detection elements (4). Rotation angle detection device according to claim 1, wherein if a > 2 and a number of magnetic detection elements (4) is three or more, the magnetic detection elements are spaced apart by 360 / (x×a) degrees in the circumferential direction. Rotation angle detection device according to claim 4, wherein the rotation angle calculation processing unit (20) is configured to convert α-phase detection signals detected by the plurality of magnetic detection elements (4) into two-phase signals separated by a fourth cycle from a cycle of the convex and concave sections, and to calculate the rotation angle based on the two-phase signals. Rotation angle detection device according to one of claims 1 to 5, wherein the stator (1) contains a magnetic material (5) which is arranged in the circumferential direction outside a circumferential end section of a bias magnetic field generating section (3). Rotation angle detection device according to one of claims 1 to 5, wherein the stator (1) has magnetic materials (5) which are arranged in the circumferential direction outside respective end sections of the bias magnetic field generation section (3). Rotation angle detection device according to claim 6 or 7, wherein a section of the magnetic material (5) extending outwards in the circumferential direction from the end section of the one bias magnetic field generating section (3) has a length equal to or greater than half the length of the one bias magnetic field generating section (3) in the circumferential direction. Rotation angle detection method comprising: arranging, on a rotor (2) made of a magnetic material, a stator (1) having a bias magnetic field generating section (3) and a plurality, namely “a”, of magnetic detection elements (4), with a gap between the stator and the rotor; forming, on a surface of the rotor (2) opposite the stator (1), convex and concave sections (2a) which change in “x” cycles over a mechanical angle of 360 degrees, wherein “x” is an integer of 1 or more, wherein the convex and concave sections (2a) have a shape which changes in a curved manner, the shape enabling each of the plurality of magnetic detection elements (4) to obtain a substantially sinusoidal curve;uniformly spaced arrangement of the “a” magnetic detection elements (4) of the stator (1) along a circumferential direction of the stator over one cycle of the convex and concave sections (2a) such that they face the surface of the rotor (2) opposite the stator with a gap to that surface, wherein one bias magnetic field generating section (3) extends in the circumferential direction over one cycle of the convex and concave sections so that it overlaps with “a” magnetic detection elements (4), where “a” is an integer of 2 or more; and calculating a rotation angle of the rotor (2) based on detection signals obtained from the plurality of magnetic detection elements (4).

Images