CN115200467A - Rotation angle detection device - Google Patents

Abstract

The invention aims to obtain a small and accurate rotation angle detection device. It comprises the following steps: a rotor (2) having a concave-convex portion (21) in which the diameter of the outer peripheral surface (2 fo) changes periodically; and a stator (3) having a bias magnetic field generating unit (31) that faces the rotor (2) with a gap therebetween and generates a magnetic field between the stator and the uneven portion (21), and a plurality of magnetic flux density detecting units (32) that are arranged along the circumferential direction (Dc) on the facing surface (31 fc) and detect the generated magnetic field, wherein a protruding portion (31 p) that protrudes in the radial direction is formed at a portion outside the facing surface (31 fc) in the circumferential direction (Dc) so as to be closer to the rotating shaft (22) than a portion where the magnetic flux density detecting unit (32) located at the end portion is arranged.

Description

Rotation angle detecting device

Technical Field

The present application relates to a rotation angle detection device.

Background

A rotation angle detecting device is known in which a bias magnetic field generating portion extending in a circumferential direction is arranged to face a stator in which a plurality of magnetic flux density detecting portions are arranged in the circumferential direction with respect to an outer circumferential surface of a rotor having a diameter varying in the circumferential direction, and a rotation angle is detected based on a variation in magnetic resistance. In this case, a rotation angle detecting device is disclosed in which the detection accuracy is improved without increasing the weight by defining the circumferential installation range of a magnetic body provided on a bias magnetic field generating unit and the back surface side thereof (for example, see patent document 1).

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2019-109053 (paragraphs 0009 to 0020, FIG. 1 to FIG. 3)

Disclosure of Invention

Technical problem to be solved by the invention

However, in the magnetic sensor described above, disturbance of the magnetic flux density vector occurs at the circumferential end of the bias magnetic field generating unit, and the radial component of the magnetic flux density, which is a signal component, decreases in the magnetic flux density detecting unit at the circumferential end. This causes a problem that the detected values of the magnetic flux densities are unbalanced in the magnetic flux density detection portions at the circumferential end portions and the circumferential center portion, and the angle detection accuracy is deteriorated.

The present application discloses a technique for solving the above-described problems, and an object thereof is to obtain a small and accurate rotation angle detection device.

Means for solving the problems

The rotation angle detection device disclosed in the present application includes: a rotor having a magnetic concave-convex portion whose outer peripheral surface diameter periodically changes and supported rotatably about a rotation axis; and a stator including a bias magnetic field generating portion that faces a part of the outer peripheral surface of the rotor in a circumferential direction with a gap therebetween and generates a magnetic field between the stator and the concave-convex portion, and a plurality of magnetic flux density detecting portions that are arranged along the circumferential direction on a facing surface of the bias magnetic field generating portion facing the rotor and detect the generated magnetic field, wherein a protruding portion that protrudes in a radial direction is formed at a portion of the facing surface that is located outside a portion where the plurality of magnetic flux density detecting portions are arranged in the circumferential direction, so as to be closer to the rotating shaft than a portion where the magnetic flux density detecting portion located at an end portion in the circumferential direction among the plurality of magnetic flux density detecting portions is arranged.

Effects of the invention

According to the rotation angle detecting device disclosed in the present application, by reducing the disturbance of the magnetic flux density vector at the circumferential end portion, the imbalance in the detected values of the magnetic flux density in each magnetic flux density detecting portion can be reduced, and a small and accurate rotation angle detecting device can be obtained.

Drawings

Fig. 1 is a schematic diagram showing the overall configuration of a rotation angle detection device according to embodiment 1.

Fig. 2 is a functional block diagram for explaining the configuration of the rotation angle detection device according to embodiment 1.

Fig. 3A and 3B are partially enlarged schematic views of the rotation angle detecting device according to embodiment 1 with different magnifications.

Fig. 4 is a graph in the form of a bar graph in which the ratios of the second harmonic component to the signal component in the rotation angle detection device according to embodiment 1 and the rotation angle detection device according to the comparative example are compared.

Fig. 5 is a partially enlarged schematic view of a rotation angle detection device according to a modification of embodiment 1.

Fig. 6 is a partially enlarged schematic view of a rotation angle detecting device according to a second comparative example.

Fig. 7 is a graph in the form of a bar graph obtained by comparing the proportions of the second harmonic component with respect to the signal component in the rotation angle detection devices according to the comparative example and the second comparative example.

Fig. 8 is a partially enlarged schematic view of a rotation angle detection device according to a second modification of embodiment 1.

Fig. 9 is a block diagram showing a configuration example of a portion for executing the rotation angle calculation process of the rotation angle detection device according to embodiment 1.

Fig. 10 is a partially enlarged schematic view of the rotation angle detection device according to embodiment 2.

Fig. 11A and 11B are partially enlarged schematic views of the rotation angle detection device according to embodiment 3 and the rotation angle detection device according to the modification thereof, respectively.

Fig. 12 is a graph in the form of a bar graph in which the ratios of the second harmonic component to the signal component in the rotation angle detection device according to embodiment 3 and the rotation angle detection device according to the comparative example are compared.

Fig. 13 is a partially enlarged schematic view of the rotation angle detecting device according to embodiment 4.

Fig. 14A and 14B are partially enlarged schematic views of the rotation angle detection device according to embodiment 5 and the rotation angle detection device according to the modification thereof, respectively.

Fig. 15 is a partially enlarged schematic view of a rotation angle detecting device according to a second modification of embodiment 5.

Detailed Description

Embodiment 1.

Fig. 1 to 4 are diagrams for explaining the configuration and operation of the rotation angle detection device according to embodiment 1, fig. 1 is a schematic diagram showing the connection of signals between a cross-sectional shape indicating the positional relationship between a rotor and a stator in a plane direction perpendicular to an axial direction and a rotation angle calculation processing unit as the entire configuration of the rotation angle detection device, and fig. 2 is a functional block diagram showing the connection between the stator and the angle calculation unit. Next, fig. 3 is an enlarged schematic view of the vicinity of a portion where the rotor and the stator of the rotation angle detecting device in fig. 1 face each other (fig. 3A), and an enlarged schematic view of the circumferential end portion of the stator enlarged again (fig. 3B). Fig. 4 is a bar graph in which the ratios of the second harmonic component to the signal component of 3 magnetic flux density detection units are compared with respect to the signal component in the center magnetic flux density detection unit in the rotation angle detection device according to example 1 and comparative example (comparative example 1) for explaining the effects of the rotation angle detection device according to embodiment 1.

Hereinafter, the basic configuration of the rotation angle detection device and the calculation of the rotation angle will be described with reference to the drawings before describing the characteristic configuration of the present application. The rotation angle detection device 1 is directly connected to, for example, a shaft of a rotating electrical machine, detects a rotation angle, a rotation speed, or the like of the rotating electrical machine, and is used for rotation control, measurement, or the like. As shown in fig. 1, the rotation angle detection device 1 according to embodiment 1 includes a rotor 2 that rotates about a rotation shaft 22 as a mechanical structure, and a stator 3 disposed to face an outer peripheral surface 2fo of the rotor 2. As a configuration for performing the calculation process, an angle calculation unit 5 is provided, and the angle calculation unit 5 processes signals output from each of the plurality of magnetic flux density detection units 32 of the stator 3 to calculate the rotation angle.

The rotor 2 has a cylindrical rotating shaft 22, and a concave-convex portion 21 provided radially outside the rotating shaft 22. The concave-convex portion 21 is formed of a magnetic material, and is formed so that the distance from the center X2 of the rotation shaft 22 changes periodically and smoothly to 0. The following is shown in fig. 1: the concave-convex portion 21 has 24 concave-convex portions, and the concave-convex portions periodically change 24 times while the rotor 2 rotates about the rotation shaft 22 for 1 rotation.

The stator 3 is provided on the radially outer side of the rotor 2 so as to face a part of the concave-convex portion 21 (outer circumferential surface 2 fo) in the circumferential direction Dc, and includes 1 bias magnetic field generating portion 31 and a plurality of magnetic flux density detecting portions 32 extending in the circumferential direction Dc. The bias magnetic field generating unit 31 is provided so as to overlap the radially outer side of the magnetic flux density detecting unit 32 and extend in the circumferential direction Dc. The magnetic flux density detection unit 32 is disposed in a plurality of arcs at equal intervals at equal distances from the center X2 of the rotating shaft 22 so as to face the concave-convex portion 21 with a gap. In fig. 1 and 2, the angle calculation unit 5 and the stator 3 are shown separately, but the angle calculation unit 5 may be provided in the stator 3.

The plurality of magnetic flux density detection portions 32 convert the magnetic flux density, which varies substantially in a sine wave form according to the change in the flux guide due to the change in the gap between the bias magnetic field generation portion 31 and the concave-convex portion 21, into an electric signal, and output the electric signal. The figure shows the following: the 3 magnetic flux density detection units 32 are arranged at intervals of 1/3 cycle (120 °) of each unevenness of the uneven portion 21.

In this case, the 3 magnetic flux density detection units 32 output signals a, B, and C, which are 3 substantially sinusoidal signals whose phases are shifted every 1/3 cycle. The angle calculation unit 5 performs two-phase conversion on the plurality of outputs obtained by the magnetic flux density detection unit 32, and calculates the rotation angle by calculating an arctangent function. For example, in the case of the above-described configuration, it is possible to perform two-phase conversion on the output signals of the magnetic flux density detection section 32, i.e., the signal a, the signal B, and the signal C, using equation (1), and calculate the rotation angle θ of the rotor 2 using the arctangent function of equation (2).

[ mathematical formula 1]

When the number of the magnetic flux density detection units 32 is 3, harmonic components having a frequency of 3 times are mounted on the signal components S of the signals a, B, and C, and cancel each other out and are removed at the time of two-phase conversion, so that the final angle calculation result is not affected. Therefore, robustness against the third harmonic component can be provided.

The characteristic structure and operation of the present application will be described based on the above basic structure. As shown in fig. 3A and 3B, protruding portions 31p are provided at both ends (circumferential ends) in the circumferential direction Dc of the bias magnetic field generating portion 31, and the protruding portions 31p protrude such that the opposing surface 31fc facing the rotor 2 is closer to the center X2 of the rotating shaft 22 than the portion where the magnetic flux density detecting portion 32 is disposed.

By providing the protruding portion 31p at the circumferential end portion, a region in which a circumferential component, which is a disturbance component of the magnetic flux density, exists around the bias magnetic field generating portion 31 is limited to the circumferential end portion, and therefore, the bias magnetic field generating portion 31 can generate a uniform magnetic flux density over a wide range in the circumferential direction Dc. As a result, since the influence of the disturbance component of the magnetic flux density on the magnetic flux density detection portions 32 located at the circumferential end portions is reduced, the imbalance between the amplitudes of the signal component S of the output signal of each magnetic flux density detection portion 32 and the harmonic component is reduced, and the angle detection accuracy can be improved.

The effect of this is described with reference to fig. 4, which is a result of comparing the characteristics of example 1 in which the protrusion 31p described in fig. 3A is provided at the circumferential end of the bias magnetic field generating unit 31 with those of comparative example 1 (not shown) in which the bias magnetic field generating unit does not have a protrusion. In fig. 4, the horizontal axis represents the position of the magnetic flux density detection unit that outputs the output signal, and the vertical axis represents the ratio of the second harmonic component Hs having a frequency 2 times the frequency of the signal component S of each magnetic flux density detection unit. When the number of the magnetic flux density detection units is 3, the signal a and the signal C are output signals of the magnetic flux density detection units located at the end portions in the circumferential direction, the signal B is an output signal of the magnetic flux density detection unit located at the center in the circumferential direction, and a difference value with the signal B as a reference is shown.

As shown in fig. 4, the second harmonic component (difference from the signal B) is generated in both the signal a and the signal C regardless of the presence or absence of the projection 31p, but in the case of example 1, 1.4% which is 0.5% lower than 1.9% of comparative example 1, and the difference value is also reduced by 26% with respect to comparative example 1. That is, the presence of the protruding portion 31p at the circumferential end of the bias magnetic field generating portion 31 reduces the imbalance in the output signals of the respective magnetic flux density detecting portions 32.

Here, the protrusion amount will be explained. The following example is illustrated in FIG. 3B: the projection amount Hp of the projection 31p from the facing surface 31fc is set to be larger than the height of the facing surface 32fc of the magnetic flux density detection unit 32 facing the rotor 2 and to be equal to or larger than the thickness of the magnetic flux density detection unit 32. By setting the projection amount Hp as described above, the magnetic flux density detection unit 32 is located in a region where the magnetic flux density component parallel to the projection direction generated by the projection portion 31p is sufficiently larger than the magnetic flux density component perpendicular to the projection direction.

Thereby, the circumferential component (disturbance component) of the magnetic flux density in the magnetic flux density detection portion 32 is reduced, and the radial component (signal component) of the magnetic flux density is increased. As a result, the second harmonic component Hs becomes smaller with respect to the signal component S, and therefore the angle error can be further reduced. In addition, since the signal component S itself becomes large, the noise resistance is further improved.

In addition, the effect of reducing the imbalance of the output signal is not limited to the following case: the projection amount Hp of the projection 31p from the facing surface 31fc is larger than the height of the facing surface 32fc of the magnetic flux density detection unit 32 facing the rotor 2, and Δ H represents a positive value. Basically, even if the projecting portion 31p is slightly smaller than the portion of the opposing surface 31fc of the bias magnetic field generating portion 31 where the magnetic flux density detecting portions 32 are disposed at both ends, it is sufficient to approach the center X2.

However, when Δ H is a negative value and the projection amount Hp of the projection 31p is set to a value smaller than the thickness of the magnetic flux density detection unit 32, it is preferable to set the projection larger than the projection that can be generated by the machining accuracy. Specifically, the projection amount Hp is preferably set to a value exceeding the machining accuracy deviation when the surface of the facing surface 31fc is machined into a circular arc. This makes it possible to obtain the rotation angle detection device 1 with stable reduction effect and high reliability without variation in imbalance of output signals between products.

That is, if the projection amount Hp is positive, the minimum effect can be obtained in reducing the imbalance of the output signals of the magnetic flux density in each magnetic flux density detection unit 32. However, if considering the reliability as a product, it is preferable to set the protrusion amount Hp at least exceeding the processing accuracy and having a significant difference. As a more preferable mode, the protruding portion 31p may be provided so as to be closer to the center X2 (protrude toward the center X2) than at least the opposing surfaces 32fc of the magnetic flux density detection portions 32 at both ends toward the rotor 2.

The influence on the detection accuracy is not particularly limited, and the protrusion amount Hp is increased. However, since it is necessary to prevent interference with the rotor 2, it is necessary to suppress the interference to such an extent that the interference does not contact the outer peripheral surface 2fo of the rotor 2. Specifically, in consideration of the machining accuracy and tolerance of the rotor 2 and the bias magnetic field generating unit 31, the positioning accuracy between the rotor 2 and the stator 3, and the like, it is necessary to set a value that ensures a clearance with the outer peripheral surface 2fo of the rotor 2 as the upper limit of the projection amount Hp.

The projection amount Hp of the projection 31p in each of the embodiments described later is set in this manner, and the effect of reducing the imbalance of the output signal of each magnetic flux density detection unit 32 obtained by setting the projection 31p is more remarkable.

A first modification example.

In the above examples, examples are shown in which the protruding portion is provided at the circumferential end portion. In the first modification and the following comparative example 2, the arrangement position of the protruding portion is examined. In the first modification, an example in which a protrusion is provided further inward than a circumferential end will be described. Fig. 5 is a diagram for explaining the configuration of the rotation angle detecting device according to the first modification, and is an enlarged schematic diagram corresponding to fig. 3A in the vicinity of a portion where the rotor and the stator of the rotation angle detecting device face each other.

In the rotation angle detecting device 1 according to the first modification example, as shown in fig. 5, the protruding portions 31p are provided in the vicinity of the circumferential end portions, that is, between the magnetic flux density detecting portions 32 at both ends and the circumferential end portions. Even if the protrusion 31p is not located at the circumferential end of the bias magnetic field generating unit 31, the same effect as that obtained when it is provided at the circumferential end can be obtained as long as it is located in the vicinity of the circumferential end (further outside the magnetic flux density detecting unit 32 at both ends).

Comparative example 2.

As comparative example 2, an example in which the protrusion portion is provided at the portion where the magnetic flux density detection portion is provided, that is, on the root portion side of the magnetic flux density detection portion is shown. Fig. 6 is a diagram for explaining the configuration of the rotation angle detecting device according to comparative example 2, and is an enlarged schematic diagram corresponding to fig. 3A in the vicinity of a portion where the rotor and the stator of the rotation angle detecting device face each other. Fig. 7 is a bar graph showing the ratios of the second harmonic component to the signal component of 3 magnetic flux density detection units, with reference to the signal of the central magnetic flux density detection unit, in the rotation angle detection devices of comparative examples 1 and 2. In addition, among the members of comparative example 2, members having a different structure from that of example 1, which is a comparative target, are denoted by "R" at the end of the reference numeral.

In the rotation angle detecting device according to comparative example 2, as shown in fig. 6, the protruding portion 31pR is provided at the root portion of the magnetic flux density detecting portion 32. As shown in fig. 7, in comparative example 2 in which the projection 31pR is provided at the position of the magnetic flux density detection unit 32, the difference value Hs/S between the signal a and the signal C increases by 0.6% instead by providing the projection 31pR, and the imbalance of the output signals of the magnetic flux density detection units 32 increases.

As described above, in order to reduce the imbalance in the output signal of the magnetic flux density detection unit 32, it is necessary to dispose at least the protruding portion 31p further outside in the circumferential direction Dc of the magnetic flux density detection unit 32. Thus, by setting the arrangement position and the projecting amount Hp, even if the bias magnetic field generating unit 31 is downsized in the circumferential direction, the magnetic flux density distribution becomes uniform over a wide range in the circumferential direction, so that the imbalance of the output signals of the respective magnetic flux density detecting units 32 can be reduced, and the deterioration of the angle detection accuracy can be suppressed.

Therefore, for example, a particularly significant effect can be exhibited in a structure disclosed in japanese patent laid-open No. 2020-176853 in which the magnetic flux density generating portion is arranged in a range smaller than a half period with respect to the concave-convex portion and is miniaturized.

In addition, embodiment 1 shows the following example: the portion where the protruding portion 31p is formed is thicker than the radial thickness of the bias magnetic field generating portion 31 at the position where the magnetic flux density detecting portion 32 is disposed. In the structure in which the thickness is increased at the circumferential end portion or the vicinity thereof, the following effects are obtained in addition to the effect obtained by approaching the center X2: the amplitude of the output waveform of the magnetic flux density detection unit 32 located at both ends of the circumferential direction Dc is increased, and the noise resistance is improved.

A second modification.

In the above example, the stator is constituted by the bias magnetic field generating unit and the magnetic flux density detecting unit. In the second modification, an example in which a magnetic body is provided at an outer side (rear side) in the radial direction of the bias magnetic field generating unit will be described. Fig. 8 is a diagram for explaining the configuration of the rotation angle detecting device according to the second modification, and is an enlarged schematic diagram corresponding to fig. 3A in the vicinity of a portion where the rotor and the stator of the rotation angle detecting device face each other.

As shown in fig. 8, the rotation angle detecting device 1 according to the second modification includes a magnetic body 33 so as to surround a radially outer side from one end side to the other end side in the circumferential direction of the bias magnetic field generating unit 31. As a result, a magnetic path is formed through which the magnetic flux generated from the bias magnetic field generating unit 31 passes, and the amplitude of the output waveform obtained by the magnetic flux density detecting unit 32 increases, thereby improving noise resistance.

The bias magnetic field generating unit 31 may be a plastic magnet obtained by injection molding magnetic particles together with a thermoplastic resin. This ensures the strength of the member even in a thin shape. Further, the bias magnetic field generating unit 31 having a relatively complicated surface shape provided with surface irregularities and the like can be easily molded, and can be preferably used as a material constituting the bias magnetic field generating unit 31 used in the rotation angle detecting device 1 of the present application.

In the rotation angle detection device 1 disclosed in embodiment 1 and the following embodiments, the angle calculation unit 5 can be expressed as hardware 500 including a processor 501 and a storage device 502, as shown in fig. 9, for example. The storage device 502 includes, although not shown, a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. In addition, an auxiliary storage device such as a hard disk may be provided instead of the flash memory. The processor 501 executes a program input from the storage 502. In this case, the program is input from the auxiliary storage device to the processor 501 via the volatile storage device. The processor 501 may output data such as the operation result to a volatile storage device of the storage device 502, or may store the data in an auxiliary storage device via the volatile storage device.

Embodiment 2.

In embodiment 1, an example is shown in which a protrusion protruding in a protruding manner from the other part is provided at the circumferential end of the bias magnetic field generating portion, but the present invention is not limited to this. In embodiment 2, the following example is explained: the protruding portion is formed by making the opposing surface have a curvature larger than that of an arc having a radius equal to a distance from the center. Fig. 10 is a diagram for explaining the configuration of the rotation angle detecting device according to embodiment 2, and is an enlarged schematic diagram corresponding to fig. 3A used in the explanation of embodiment 1, in the vicinity of a portion where the rotor and the stator of the rotation angle detecting device face each other. Note that in embodiment 2 and the following embodiments, differences from embodiment 1, related embodiments, and the like will be mainly described, and descriptions of the same parts will be omitted as appropriate. Fig. 1, fig. 2, fig. 4, and the like used in embodiment 1 are also cited.

In the rotation angle detecting device 1 according to embodiment 2, as shown in fig. 10, the cross-sectional shapes perpendicular to the rotation axis of the opposite surface 31fc of the bias magnetic field generating unit 31 facing the rotor 2 and the opposite surface (back surface 31 fo) are arcs having different curvatures, that is, portions of cylindrical surfaces. Then, by setting the curvature of the opposing surface 31fc larger than a circle having a radius equal to the distance from the center X2, the protruding portions 31p protruding from the opposing surfaces 32fc of the magnetic flux density detection portion 32 at both ends in the circumferential direction Dc are formed.

Thus, since the circumferential end portion has a portion (the protruding portion 31 p) closer to the center X2 than the opposing surface 32fc, the effect of reducing the imbalance of the output signals of the magnetic flux density detection units 32 can be obtained as in embodiment 1. Further, the projecting portion 31p is formed by making the curvature of the opposing surface 31fc large, and therefore, there is no need to provide a local projecting structure in the bias magnetic field generating portion 31, and productivity and member strength are improved.

Further, by making the curvature of the back surface 31fo smaller than the curvature of the opposite surface 31fc, the radial thickness can be made thicker from the center toward the end in the circumferential direction Dc. Therefore, the following effects can be achieved: the amplitude of the output waveform of the magnetic flux density detection unit 32 located at both ends of the circumferential direction Dc is increased, and the noise resistance is improved.

Embodiment 3.

In embodiments 1 and 2, an example in which a total of 2 projecting portions are formed only at both circumferential ends or in the vicinity thereof has been described. In embodiment 3, an example in which a protruding portion is provided at a portion between both end portions and each magnetic flux density detection portion will be described. Fig. 11A and 11B are enlarged schematic views of the vicinity of a portion where the rotor and the stator face each other in the rotation angle detection device according to embodiment 3 and the modification thereof, respectively, and corresponding to fig. 3A used in the description of embodiment 1. Fig. 12 is a bar graph in which the ratios of the second harmonic component to the signal component of 3 magnetic flux density detection units are compared with each other with reference to the signal of the central magnetic flux density detection unit in the rotation angle detection devices of example 2 and comparative example 1 for explaining the effects of the rotation angle detection device according to embodiment 3.

In the rotation angle detecting device 1 according to embodiment 3, as shown in fig. 11A, the portion where the magnetic flux density detecting portion 32 is disposed is formed as a recess by forming irregularities in the circumferential direction Dc on the facing surface 31fc of the bias magnetic field generating portion 31 facing the rotor 2. The portion of the bias magnetic field generating unit 31 where the magnetic flux density detecting unit 32 is disposed is a concave portion, and the section between them and the portions at both ends that are convex portions are the protruding portions 31p.

When the protruding portions 31p are formed also in the portions between the magnetic flux density detection portions 32, the protruding portions 31p are provided at both ends in the circumferential direction Dc as in embodiment 1, and therefore, the effect of reducing the imbalance in the output signals of the respective magnetic flux density detection portions 32 can be obtained as in embodiment 1. Since the protruding portion 31p is formed between the adjacent bias magnetic field generating portions 31, the amplitude of the output waveform of each magnetic flux density detecting portion 32 increases, and the noise resistance improves. The protrusion 31p is located in the vicinity of all the magnetic flux density detection portions 32 in the circumferential direction Dc (a portion closer to the adjacent magnetic flux density detection portion), and therefore the magnetic flux density distribution around each magnetic flux density detection portion 32 is equal. As a result, the imbalance in the output signals of the magnetic flux density detection units 32 can be further reduced, and the angle detection accuracy can be improved.

The results of comparing the characteristics of example 2 (fig. 11A) in which the protrusion 31p is also provided between the adjacent magnetic flux density detection units 32 and comparative example 1 in which the bias magnetic flux generating unit used in the description of fig. 4 does not have a protrusion will be described with reference to fig. 12. As shown in fig. 12, the second harmonic component (difference from the signal B) is generated in both the signal a and the signal C regardless of the presence or absence of the projection 31p, but in the case of example 2, 1.6% which is 0.3% lower than 1.9% of comparative example 1, and the difference value is reduced by 16% with respect to comparative example 1. That is, when the protruding portions 31p are provided at adjacent portions, the protruding portions 31p are present at or near the circumferential end portions of the bias magnetic field generating portion 31, and thus the imbalance in the output signals of the respective magnetic flux density detecting portions 32 is also reduced.

A modified example.

Fig. 12 illustrates the effect of the rotation angle detecting device 1 according to example 2 in which the surface of the bias magnetic field generating unit facing the rotor is formed with the recesses and projections in a rectangular shape in the circumferential direction. In this modification, as shown in fig. 11B, the opposing surface 31fc has curved irregularities formed in the circumferential direction Dc. In this case, similarly to the rectangular irregularities described in fig. 11A, the effect of reducing the imbalance of the output signals of the respective magnetic flux density detection portions 32 and the effect of further reducing the imbalance of the output signals of the respective magnetic flux density detection portions 32 and improving the angle detection accuracy can be obtained.

Embodiment 4.

The following examples are explained in the above embodiments: in the bias magnetic field generating portion, the radial thickness of the portion where the protruding portion is formed becomes thicker according to the protrusion. The following examples are explained in embodiment 4 and the following embodiments: a collapsed portion is provided on the back surface side to compensate for thickness variation accompanying the projection of the opposite surface side. Fig. 13 is a diagram for explaining the configuration of the rotation angle detecting device according to embodiment 4, and is an enlarged schematic diagram corresponding to fig. 3A used in the explanation of embodiment 1, in the vicinity of a portion where the rotor and the stator of the rotation angle detecting device face each other.

In the rotation angle detecting device 1 according to embodiment 4, as shown in fig. 13, a depressed portion 31d closer to the center X2 than the portion where the magnetic flux density detecting portion 32 is disposed is formed on the back surface 31fo of the bias magnetic field generating portion 31 in accordance with the formation of the protruding portion 31p on the opposing surface 31 fc. The collapsed portion 31d may be set to a collapsed amount of depth to the same extent as the projecting amount Hp of the projecting portion 31p on the opposing face 31fc to compensate for the increase in volume (thickness) of the bias magnetic field generating portion 31 due to the provision of the projecting portion 31p. For example, it may be arranged so that the thickness in the radial direction of the bias magnetic field generating portion 31 in the region where the protruding portion 31p and the collapsed portion 31d are provided is the same as or equal to that in the other region.

Since the rotation angle detecting device 1 in embodiment 4 has the protruding portion 31p at the circumferential end of the bias magnetic field generating portion 31, the effect of reducing the imbalance of the output signals of the respective magnetic flux density detecting portions 32 can be obtained, as in embodiment 1. Further, by providing the recessed portion 31d having a recessed amount corresponding to the protruding amount of the protruding portion 31p on the back surface 31fo side, resources can be more effectively utilized without increasing the volume of the bias magnetic field generating portion 31.

Embodiment 5.

The following example is explained in the above embodiment 4: the depressed portion is formed on the back surface in accordance with the arrangement of the protruding portion as exemplified in embodiment 1, but the present invention is not limited thereto. In embodiment 5, the following example is explained: the collapsed portions are also formed corresponding to the protruding portions disposed between the adjacent magnetic flux density detection portions as exemplified in embodiment 3.

Fig. 14A and 14B are enlarged schematic views of the vicinity of a portion where the rotor and the stator face each other in the rotation angle detecting device according to embodiment 5 and the modification thereof, respectively, and correspond to fig. 3A used in the description of embodiment 1. Fig. 15 is an enlarged schematic view of fig. 3A used in the description of embodiment 1, in the vicinity of a portion where the rotor and the stator face each other in the rotation angle detecting device according to the second modification of embodiment 5.

In the rotation angle detecting device 1 according to embodiment 5, as shown in fig. 14A, the protrusion 31p is disposed between the adjacent magnetic flux density detecting portions 32 and is formed at 3 or more positions on the opposing surface 31fc facing the rotor 2, in the same manner as in fig. 11A of embodiment 3, except for both end portions. Then, on the back surface 31fo, depressed portions 31d are formed closer to the center X2 than the arrangement portion of the magnetic flux density detection portion 32, corresponding to 3 or more protruding portions 31p, respectively.

The depressed portions 31d corresponding to the projecting portions 31p of 3 or more positions may be set to a depth approximately equal to the projecting amount Hp of the projecting portion 31p of the facing surface 31fc so as to compensate for an increase in volume (thickness) of the bias magnetic field generating portion 31 due to the provision of the projecting portions 31p.

Since the rotation angle detecting device according to embodiment 5 has the protruding portion 31p at or near the circumferential end of the bias magnetic field generating portion 31, the effect of reducing the imbalance in the output signals of the respective magnetic flux density detecting portions 32 can be obtained, as in embodiment 1. Since the protrusion 31p is also provided between the adjacent magnetic flux density detection units 32, the amplitude of the output waveform of each magnetic flux density detection unit 32 is increased and the noise resistance is improved, as in embodiment 3. Then, since the collapsed portion 31d is provided to compensate for the increase in thickness caused by the protruding portion 31p, the same effect as that of embodiment 3 can be obtained without increasing the volume of the bias magnetic field generating portion 31, as in embodiment 4.

A modified example.

Fig. 14A illustrates the formation of a collapsed portion corresponding to a protruding portion formed in a rectangular shape in the circumferential direction, in accordance with embodiment 3 (fig. 11A). In this modification, as shown in fig. 14B, a collapsed portion 31d is formed corresponding to the protruding portion 31p formed in a curved shape in the circumferential direction Dc, corresponding to the modification of embodiment 3 (fig. 11B). In this case, the effect of reducing the imbalance of the output signals of the respective magnetic flux density detection portions 32, the effect of further reducing the imbalance of the output signals of the respective magnetic flux density detection portions 32 to improve the angle detection accuracy, and the above-described effect can be achieved without increasing the volume of the bias magnetic field generation portion 31.

A second modification.

The following example is explained in the second modification: the magnetic body described in the second modification of embodiment 1 is arranged for the bias magnetic field generating portion having the depressed portion corresponding to the protruding portion formed in a curved shape in the circumferential direction. In a second modification of embodiment 5, as shown in fig. 15, the magnetic body 33 is disposed so as to extend in the circumferential direction on the back surface 31fo side of the bias magnetic field generating portion 31 in correspondence with the back surface 31fo that changes in a curved shape due to the collapsed portion 31d.

As a result, a magnetic path is formed through which the magnetic flux generated from the bias magnetic field generating unit 31 passes, and the amplitude of the output waveform obtained by the magnetic flux density detecting unit 32 increases, thereby improving noise resistance. In the case of forming the bias magnetic field generating unit 31 in a curved shape with a constant thickness, the bias magnetic field generating unit 31 may be formed by using a bendable magnetic sheet, and the bias magnetic field generating unit 31 may be deformed and attached so as to match the curve of the inner circumferential surface 33fi of the magnetic body 33 formed in advance.

In addition, although various exemplary embodiments and examples are described in the present application, the various features, forms, and functions described in one or more embodiments are not limited to the application to the specific embodiments, and may be applied to the embodiments alone or in various combinations. Thus, it is considered that numerous modifications not illustrated are also included in the technical scope disclosed in the present specification. For example, the present invention includes a case where at least one of the components is modified, added, or omitted, and a case where at least one of the components is extracted and combined with the components of the other embodiments.

As described above, the rotation angle detection device 1 according to the present application includes: a rotor 2 having a magnetic uneven portion 21 in which the diameter of an outer peripheral surface 2fo periodically changes, and supported rotatably about a rotation shaft 22; and a stator 3 having an offset magnetic field generating portion 31 and a plurality of magnetic flux density detecting portions 32, the offset magnetic field generating portion 31 facing a part of the outer circumferential surface 2fo of the rotor 2 in the circumferential direction Dc with a gap therebetween and generating a magnetic field between the concave-convex portion 21, the plurality of magnetic flux density detecting portions 32 being disposed along the circumferential direction Dc on an opposing surface 31fc of the offset magnetic field generating portion 31 facing the rotor 2 and detecting the generated magnetic field, and a protruding portion 31p protruding in the radial direction being formed at a portion of the opposing surface 31fc outside a portion where the plurality of magnetic flux density detecting portions 32 are disposed in the circumferential direction Dc so as to be closer to (the center X2 of) the rotating shaft 22 than a portion where the magnetic flux density detecting portion 32 at an end of the circumferential direction Dc among the plurality of magnetic flux density detecting portions 32 is disposed. As a result, by reducing the disturbance of the magnetic flux density vector at the circumferential end portion, the unevenness in the detection values of the magnetic flux densities in the respective magnetic flux density detection portions 32 can be reduced, and the rotation angle detection device 1 can be made small and accurate.

At this time, if the protruding portion 31p is formed closer to (the center X2 of) the rotating shaft 22 than (the opposing surface 32fc of) the magnetic flux density detection portion 32 located at the end portion, the circumferential component (disturbance component) of the magnetic flux density in the magnetic flux density detection portion 32 decreases, and the radial component (signal component) of the magnetic flux density increases. As a result, the second harmonic component Hs becomes smaller than the signal component S, and thus the angle error can be further reduced. In addition, since the signal component S itself also becomes large, the noise resistance is further improved.

Further, if the portion of the bias magnetic field generating unit 31 where the projecting portion 31p is formed is configured to be thicker in the radial direction than other portions, in addition to the effect obtained by approaching the center X2, the amplitude of the output waveform of the magnetic flux density detecting unit 32 located at both ends in the circumferential direction Dc can be increased, and the noise resistance can be improved.

Alternatively, if the configuration is such that the collapsed collapse portions 31d are formed so as to be closer to the rotating shaft 22 than the portion where the magnetic flux density detection portion 32 located at the end portion is arranged and the portion at the same position in the circumferential direction Dc, at the portion where the protruding portion 31p on the opposing surface 31fc is formed and the portion at the same position in the circumferential direction Dc of the back surface 31fo in the radial direction of the bias magnetic field generation portion 31, an increase in the volume of the bias magnetic field generation portion 31 can be suppressed, and resources can be effectively utilized.

Further, the cross-sectional shape of the rotating shaft 22 perpendicular to the opposing surface 31fc is a circular arc having a curvature larger than that of a circle having a radius of a distance from the rotating shaft 22 (center X2), and therefore, the protruding portion 31p can be easily formed.

Further, if the protruding portion 31p is configured to be formed also in the intermediate portion between the magnetic flux density detection portions 32 adjacent in the circumferential direction Dc among the plurality of magnetic flux density detection portions 32, the amplitude of the output waveform of each magnetic flux density detection portion 32 increases, and the noise resistance improves.

If the stator 3 is configured to have the magnetic body 33 extending in the circumferential direction Dc and arranged radially outward of the bias magnetic field generating unit 31, a magnetic path through which the magnetic flux generated from the bias magnetic field generating unit 31 passes is formed, and the amplitude of the output waveform obtained by the magnetic flux density detecting unit 32 is increased, thereby improving noise resistance.

If 3 magnetic flux density detection units 32 as the plurality of magnetic flux density detection units 32 are arranged in the circumferential direction Dc, and the angle calculation unit 5 is provided that performs two-phase conversion on the signals from the 3 magnetic flux density detection units 32 and calculates the rotation angle θ of the rotor 2 by using an arctan function, robustness against the third harmonic component can be provided.

In addition, since the above-described effects can be obtained when 3 magnetic flux density detection units 32 are provided, as a more preferable embodiment, an example in which 3 magnetic flux density detection units 32 are provided as a specific example is described, but the number of magnetic flux density detection units 32 may be further increased. If at least 3 or more magnetic flux density detection sections 32 are provided, robustness can be provided for a specific high frequency component. Further, if a plurality of magnetic flux density detection units 32 are provided, the basic effect of the rotation angle detection device 1 disclosed in the present application that the imbalance of the output signals of the respective magnetic flux density detection units 32 can be reduced can be obtained in common.

Description of the reference symbols

1. Rotation angle detecting device

2. Rotor

21. Concave-convex part

22. Rotating shaft

2fo outer peripheral surface

3. Stator

31. Bias magnetic field generating unit

31d collapsed portion

31fc opposite surface

31fo back side

31p projection

32. Magnetic flux density detection unit

32fc opposite surface

33. Magnetic body

33fi inner peripheral surface

5. Angle calculating part

Dc circumferential direction

Hp projection

Center of X2

Theta is rotated by an angle.

Claims (8)

1. A rotation angle detecting device, comprising:

a rotor having a magnetic uneven portion whose outer peripheral surface diameter periodically changes, and supported rotatably about a rotation axis; and

a stator including a bias magnetic field generating portion facing a part of the outer peripheral surface of the rotor in a circumferential direction with a gap therebetween and generating a magnetic field between the stator and the concave-convex portion, and a plurality of magnetic flux density detecting portions arranged along the circumferential direction on a facing surface of the bias magnetic field generating portion facing the rotor and detecting the generated magnetic field,

a projection portion projecting in a radial direction is formed at a portion of the opposing surface that is further outside a portion where the plurality of magnetic flux density detection portions are arranged in the circumferential direction so as to be closer to the rotating shaft than a portion where the magnetic flux density detection portion located at an end portion in the circumferential direction among the plurality of magnetic flux density detection portions is arranged.

2. The rotation angle detecting device according to claim 1,

the protruding portion is formed so as to be closer to the rotating shaft than the magnetic flux density detection portion located at the end portion.

3. The rotation angle detecting device according to claim 1 or 2,

the bias magnetic field generating portion has a portion where the protruding portion is formed, the portion having a thickness in the radial direction being thicker than other portions.

4. The rotation angle detecting device according to claim 1 or 2,

a collapsed portion is formed at a portion of the back surface in the radial direction of the bias magnetic field generating portion where the protruding portion on the opposing surface is formed and a portion at the same position in the circumferential direction so as to be closer to the rotation shaft than a portion where a magnetic flux density detecting portion at the end portion is arranged and a portion at the same position in the circumferential direction.

5. The rotation angle detecting device according to any one of claims 1 to 3,

the cross-sectional shape of the rotating shaft perpendicular to the opposing surface is an arc having a curvature larger than that of a circle having a radius equal to the distance from the rotating shaft.

6. The rotation angle detecting device according to any one of claims 1 to 5,

the protruding portion is also formed at an intermediate portion between the magnetic flux density detection portions adjacent to each other in the circumferential direction among the plurality of magnetic flux density detection portions.

7. The rotation angle detecting device according to any one of claims 1 to 6,

the stator includes a magnetic body extending in the circumferential direction and disposed radially outward of the bias magnetic field generating unit.

8. The rotation angle detecting device according to any one of claims 1 to 7,

3 magnetic flux density detection portions are arranged in the circumferential direction as a plurality of the magnetic flux density detection portions,

the magnetic flux density detection device is provided with an angle calculation unit which performs two-phase conversion on signals from the 3 magnetic flux density detection units and calculates the rotation angle of the rotor by using an arctangent function.

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