JP2006071562A - Angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle sensor with less variation in quality with slant angles of magnetic axes relaxed by arbitrarily together combining magnets even when using magnets whose magnetic axes are aslant. <P>SOLUTION: This angle sensor comprises a hall element 20 disposed at a neutral detection position C opposite to a magnet block 15 attached to a shaft (rotary shaft) 10, and detects the turning angle of the magnet block 15 based on an output of the hall element 20. The magnet block 15 comprises two magnets 15a and 15b unified by directly joining their different magnetic poles to each other. A magnetic body can be put between the magnets 15a and 15b. Though the magnetic axes of the magnets 15a and 15b are aslant respectively, a combined slant angle is eased as the magnet block 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention comprises an angle sensor, in particular, a magnet installed rotatably and a magnetic sensing element fixed at a position affected by the magnetic field from the magnet, and the rotational angle of the magnet is output from the magnetic sensing element. The present invention relates to a non-contact type angle sensor that detects based on the above.

  Conventionally, as an angle sensor, as shown in FIG. 8, a rotation angle (rotation center is P is a rotation angle) of a magnet 51 that is arranged with a magnetism detection element 52 facing a rectangular parallelepiped magnet 51 and attached to a rotation shaft (not shown). ) Is detected based on the output of the magnetic sensing element 52 whose position is fixed.

  The magnetic sensing element 52 is a Hall element or a magnetoresistive element, and is an element that generates an output voltage proportional to the magnitude of the magnetic flux density passing through the element 52 vertically or changes its resistance value. For example, in the case of a Hall element, the output voltage changes in accordance with the change in the circumferential position relative to the magnet 51 from A to E.

  By the way, in the magnet 51 mounted on this type of angle sensor, as shown in FIG. 9, when an inclination angle θ occurs between the central axis L of the magnet 51 and the magnetic axes M of the N and S poles. There is a problem that the linearity of the absolute angle and the detection angle detected by the magnetic detection element 52 is remarkably lowered.

  Here, the cause of the inclination angle θ will be described. Usually, a magnet having a large magnetic force is formed using an anisotropic material. Anisotropy refers to the property of making a large magnetic force by aligning the direction of magnetic domains (magnetizing units) of the magnetic material powder in one direction. As shown in FIG. 10, the anisotropic magnet applies a parallel magnetic field (see arrows) when the material powder 51 ′ is press-molded by the molds 55 and 56, and aligns the magnetic domains in the direction of the magnetic field.

  That is, a parallel magnetic field is applied to the molds 55 and 56, and when magnetic material powder 51 ', which is a magnetic material, is put into the molds 55 and 56 in this state, the parallel magnetic field is concentrated as shown by arrows in FIG. To do. As a result, the direction of the magnetic domain has an inclination with respect to the central axis of the ingot, as the end portion of the press-formed ingot becomes. Thereafter, the ingot is sintered, cut into a magnet 51 having a predetermined size, and further magnetized, as shown in FIG.

  Since the cut magnet 51 is magnetized in the direction of the magnetic domain at the time of molding, the inclination angle θ increases as the magnet 51 is cut from the end of the ingot (see the portion surrounded by a circle in FIG. 11). On the other hand, the magnet 51 cut from the center portion of the ingot has a small inclination angle θ. Conventionally, since these magnets 51 are randomly taken out and mounted, the quality of the mounted angle sensor varies.

  At present, the improvement of the parallel magnetic field at the time of press molding is limited in terms of technology and equipment, and it is not possible to mass-produce only magnets having a small inclination angle θ. Sorting only the magnet with a small inclination angle θ cut from the center portion of the ingot requires labor and cost, and is not practical.

Patent Document 1 discloses an angle sensor in which, in order to improve the linearity of an angle detection output, a magnet is semicircularly fitted into a side groove of a rotating shaft, and a Hall element is opposed to the magnet and fixed in position. Yes. However, even in the case of a semicircular magnet, the problem that the magnetic axis is inclined and the quality varies as described above is not solved.
JP 2000-121309 A

  Therefore, an object of the present invention is to relax the tilt angle of the magnetic axis by any combination even if the magnet has a tilted magnetic axis, and there is little variation in quality, that is, the detectable absolute angle and the linearity of detection. It is to provide an angle sensor that can guarantee

  In order to achieve the above object, the present invention comprises a magnet installed rotatably and a magnetic sensing element fixed at a position affected by the magnetic field from the magnet, and the rotational angle of the magnet is detected by the magnetic sensing. In the angle sensor that detects based on the output of the element, the magnet is configured as a single magnet block by combining a plurality of magnets in the magnetization direction.

  In the angle sensor according to the present invention, since the magnet is configured as a single magnet block by combining a plurality of magnets in the magnetization direction, the inclination angle of the magnetic axis as the magnet block is relaxed even if the magnetic axis is inclined. (Details will be described in detail in the embodiment) As a result, the variation in the tilt angle of the magnetic axis becomes smaller than that in the case of mounting a single magnet, and the variation in quality becomes smaller. That is, the absolute angle that can be detected and the linearity of detection are improved.

  In the angle sensor according to the present invention, the magnet block may be one obtained by directly joining a plurality of magnets, or may be one in which a magnetic body is sandwiched between magnets. The former can obtain the same magnetic field strength if the size of the magnet block is the same as that of a conventional magnet. In the latter, since the sandwiched magnetic body does not tilt in the direction of the magnetic axis, the tilt angle of the magnetic axis as a block can be more relaxed than in the former case. Moreover, when combining three or more magnets, it is also possible to combine direct bonding and magnetic material sandwiching.

  According to the present invention, since the magnet is configured as a single magnet block by combining a plurality of magnets in the magnetizing direction, quality variations using a magnet with a tilted magnetic axis manufactured by the same manufacturing method as the conventional method are not required. A small angle sensor can be obtained.

  Embodiments of an angle sensor according to the present invention will be described below with reference to the accompanying drawings.

(Refer 1st Example and FIGS. 1-4)
As shown in FIGS. 1 and 2, the angle sensor 1A according to the first embodiment of the present invention includes a magnet block 15 composed of two magnets 15a and 15b on an arrow a and a shaft 10 that is rotatable in the opposite direction. The Hall element 20 that is a magnetic detection element is arranged at a fixed position at the neutral detection position C so as to be fixed and opposed to the magnet block 15. The rotation center of the shaft 10 and the center of the magnet block 15 are coincident with each other as indicated by reference numeral P1.

  More specifically, as shown in FIGS. 3 and 4, the magnet block 15 is attached to the shaft 10 that is attached to the tip of the shaft 11 via the attachment 12, and is held by the holder 13. 14 is a cover, 17 is a bearing, 18 is a spring member, and 19 is an O-ring. On the other hand, the Hall element 20 is attached to a substrate 21, and the substrate 21 includes a socket 22.

  In the angle sensor 1A, the shaft 10 and the magnet block 15 and the like rotate integrally based on the rotation of the shaft 11, and the Hall element 20 detects a change in the magnetic field that changes according to the rotation angle of the magnet block 15, The rotation angle is detected based on the output of the element 20.

  Here, the magnet block 15 will be described. The magnet block 15 is formed by directly joining magnets 15a and 15b having the same rectangular parallelepiped shape and having different polarities, and no adhesive is required for joining.

  However, when mounting on the shaft 10, the magnets 15 a and 15 b are fitted into a predetermined frame (not shown) in a state where the magnets 15 a and 15 b are directly joined so that the position of the magnets 15 a and 15 b does not shift. It is preferable to fix the resin by pouring an epoxy resin into it.

  In this way, if the magnets 15a and 15b are directly joined without an adhesive, the magnetic field strength is not reduced by the adhesive, and the magnetic field equivalent to that of one magnet of the same size as the magnet block 15 is obtained. You can gain strength.

  Each magnet 15a, 15b is manufactured by being cut individually from a press-molded ingot as described with reference to FIGS. In this case, an inclination angle θ of 0 to ± 4 ° is inevitably generated. A case where the magnetic axis M is inclined to the right in FIG. 9 with respect to the central axis L is defined as +, and a case where the magnetic axis M is inclined to the left is defined as −.

  By the way, when the two magnets 15a and 15b are combined, as shown in FIG. 2, the inclination angle of the combined magnetic axis Mc of the magnetic axis Ma of the magnet 15a and the magnetic axis Mb of the magnet 15b is set to each of the magnetic axes Ma and Mb. It becomes smaller than the inclination angle with the larger absolute value of. For example, when a magnet block is formed by combining a magnet having an inclination angle θ of −4 ° and a magnet having an inclination angle θ of + 1 °, the absolute angle deviation or linearity detected by the Hall element 20 is such that the inclination angle θ is + 1 °. Although it is lower than that of the magnet, the tilt angle θ is improved as compared with the magnet having −4 °, and the tilt angle θ when viewed as a magnet block is relaxed as a result. Therefore, the detection absolute angle and the detection linearity as an angle sensor are improved as a whole, and quality variations are reduced.

  Table 1 shown below summarizes the combination probabilities when a magnet block is configured by combining two magnets cut from a magnet ingot. For example, when a magnet having a normal distribution of inclination angles θ in a range of ± 4 ° is used as a population, and two magnets are arbitrarily extracted from these, inclination angles θ having a low existence probability are + 4 ° and −4 °. The probability of extracting and combining the magnets is very low. That is, there is 1.1% of one magnet with an inclination angle θ of ± 4 °, but the probability that these two are combined is 0.0007% (shown as 0.0% in Table 1). And rarely occurs.

  In other words, when two magnets cut from the magnet ingot are combined, the number with a small combined tilt angle is larger than that of the original population, and the number with a large combined tilt angle is extremely small.

(Refer to the second embodiment, FIGS. 5 and 6)
As shown in FIGS. 5 and 6, the angle sensor 1B according to the second embodiment of the present invention basically has the same configuration as that of the angle sensor 1A according to the first embodiment. Are denoted by the same reference numerals as those in FIGS. 1 and 2, and a duplicate description is omitted.

  The second embodiment differs from the first embodiment in that a magnet block 15 is configured by sandwiching a magnetic body 15c between magnets 15a and 15b.

  The magnetic body 15c sandwiched between the magnets 15a and 15b does not tilt the magnetic axis. Therefore, even if the magnets 15a and 15b each have the inclination angle θ on the magnetic axis, the combined inclination angle is further relaxed than in the first embodiment in which the magnets 15a and 15b are directly joined. If the strength of the magnetic field is not a problem, the combined tilt angle is greatly relaxed as the thickness of the magnetic body 15c increases.

(Rotation center of magnet block, see Fig. 7)
In the angle sensor according to the present invention, the rotation center of the magnet block 15 can be set at an arbitrary position with respect to the Hall element 20. In the first and second embodiments, as shown in FIG. 7A, the center P1 of the magnet block 15 is also the center of rotation. Further, as shown in FIG. 7B, the rotation center P3 may be set at a position away from the center P1 of the magnet block 15. As described above, the distance between the center P1 of the magnet block 15 and the Hall element 20 may not be constant according to the rotation of the magnet block 15, but the distance between the rotation center P3 and the Hall element 20 is always constant.

(Other examples)
The angle sensor according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist thereof.

  For example, a magnetoresistive element other than the Hall element may be used as the magnetic sensing element. Of course, the structure of attaching the magnet and the magnetic body to the rotating shaft and the positional relationship with the magnetic sensing element are arbitrary.

  Furthermore, the number of magnets constituting the magnet block is two or more, and the magnet block can be arbitrarily combined so as to form one magnet as a whole block so that the combined inclination angle is relaxed.

It is a perspective view which shows the basic composition of 1st Example of the angle sensor which concerns on this invention. It is a front view which shows the basic composition of the said 1st Example. It is sectional drawing which shows the said 1st Example. It is a disassembled perspective view which shows the said 1st Example. It is a perspective view which shows the basic composition of 2nd Example of the angle sensor which concerns on this invention. It is a front view which shows the basic composition of the said 2nd Example. (A), (B) is explanatory drawing which shows the arrangement | positioning relationship between the magnet block and magnetic detection element in an angle sensor. It is explanatory drawing of the conventional angle sensor. It is explanatory drawing which shows the inclination of the magnetic axis in the conventional angle sensor. It is explanatory drawing which shows the press molding of a magnet ingot. It is explanatory drawing which shows the state which cuts each magnet from a magnet ingot.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A, 1B ... Angle sensor 15 ... Magnet block 15a, 15b ... Magnet 15c ... Magnetic body 20 ... Hall element

Claims (3)

In an angle sensor comprising a magnet installed rotatably and a magnetic sensing element fixed at a position affected by the magnetic field from the magnet, and detecting the rotation angle of the magnet based on the output of the magnetic sensing element,
The magnet is configured as a single magnet block by combining a plurality of magnets in the magnetization direction;
An angle sensor characterized by.   The angle sensor according to claim 1, wherein the magnet block is formed by directly joining a plurality of magnets.   The angle sensor according to claim 1 or 2, wherein the magnet block has a magnetic body sandwiched between magnets.

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