JP5249281B2 - Magnetic position detector - Google Patents

Description

  The present invention relates to a magnetic position detection device using a magnetoresistive effect element, and more particularly to a magnetic position detection device suitable for use in a magnetic scale, a rotary encoder, or the like.

  Conventionally, as a magnetic position detecting device, as shown in FIG. 6 (A), there are four magnetic position detection devices at the same position with respect to the magnetic pole arrangement direction of the magnetic member 1 in which N poles and S poles are alternately magnetized. A device in which spin valve magnetoresistive elements (SV-GMR1 to SV-GMR4) are arranged is known (see Patent Document 1 below). Of the four spin-valve magnetoresistive elements (SV-GMR1 to SV-GMR4), a pair of two (SV-GMR1 and SV-GMR2) are arranged with the pinned layer magnetization direction shifted by 90 °, and the rest Two pairs (SV-GMR3 and SV-GMR4) are arranged with the pinned layer magnetization direction shifted by 180 ° with respect to the two pairs. The SV-GMR1 to SV-GMR4 are connected as shown in FIG. 6B, and the two-phase output signals Vout1 whose phases are shifted from each other by 90 ° with the relative movement of the magnetic member 1 in the magnetic pole arrangement direction. , Vout2 is obtained. Further, as shown in FIG. 7A, there are two spin-valve magnetoresistive elements (SV-GMR1 and SV-GMR2), and resistors R3 and R4 are connected as shown in FIG. 7B. As a result, two-phase output signals Vout1 and Vout2 whose phases are shifted from each other by 90 ° are obtained (see Patent Document 1 below).

JP 2006-23179 A

  In Patent Document 1, in order to generate a rotating magnetic field (magnetic field) in the spin-valve magnetoresistive element with relative movement of the magnetic member in the magnetic pole arrangement direction, the N pole and the S pole are alternately arranged over the entire length. Those arranged at a pitch are used as magnetic members. That is, all the magnetic poles have the same length in the magnetic pole arrangement direction. In this case, by shortening the length of the magnetic pole in the magnetic pole arrangement direction (example: 14 mm → 10 mm), the total length of the magnetic member can be shortened (example: in the case of quadrupole magnetization, 56 mm → 40 mm). However, in this case, there is a problem that not only the entire length of the magnetic member but also the detection range (sensing range), that is, the total length of the magnetic member excluding the magnetic poles at both ends is similarly shortened (for example, 28 mm → 20 mm).

  The present invention has been made in view of such a situation, and its purpose is to reduce the cost of the magnetic member without reducing the detection range. It is to provide a detection device.

One embodiment of the present invention is a magnetic position detection device. This magnetic position detector
A magnetic member in which N poles and S poles are alternately arranged;
A pair or a plurality of pairs of spin valve magnetoresistive effect elements present at positions facing the magnetic pole array surface of the magnetic member,
It said magnetic member has a length related to the magnetic pole arrangement direction of the magnetic poles of both ends of the magnetic pole arrangement direction, rather shorter than the length in the magnetic pole arrangement direction of the magnetic poles other than the two ends,
When the length of the magnetic poles at both ends in the magnetic pole arrangement direction is P1, and the length of the magnetic poles other than the both ends in the magnetic pole arrangement direction is P2, P2 / P1 ≦ 2 .

The P1 and the P2 may be P2 / P1 ≦ 7/5.

Pole array surface of the front Symbol magnetic member may is flat or curved.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  According to the present invention, since the length of the magnetic poles at both ends of the magnetic pole arrangement direction in the magnetic member is shorter than the length of the magnetic poles other than the both ends in the magnetic pole arrangement direction, Compared to the case where the length in the magnetic pole arrangement direction is as long as the length of the magnetic poles other than the both ends in the magnetic pole arrangement direction, the magnetic member is made smaller (shorter) without narrowing the detection range as the magnetic position device. This makes it possible to reduce costs.

1 is a schematic perspective view of a magnetic position detection device according to an embodiment of the present invention. Explanatory drawing of the magnetic field simulation result at the time of making magnetic pole length other than the both ends of a magnetic member constant, and changing the magnetic pole length of both ends (the 1). Explanatory drawing of the magnetic field simulation result at the time of making magnetic pole length other than the both ends of a magnetic member constant, and changing the magnetic pole length of both ends (the 2). The error graph which shows the relationship between the position in a detection range, and a position error at the time of changing the magnetic pole length of both ends with constant magnetic pole lengths other than the both ends of a magnetic member. The characteristic view which shows the maximum value of the position error in the detection range shown in FIG. 4 in each case of the magnetic pole length of the both ends of a magnetic member. (A) is a schematic block diagram (No. 1) of the magnetic position detection apparatus of patent document 1, (B) is a circuit diagram which shows the connection relation of the spin valve type | mold magnetoresistive effect element in the magnetic position detection apparatus. (A) is a schematic block diagram (No. 2) of the magnetic position detection apparatus of patent document 1, (B) is a circuit diagram which shows the connection relation of the spin valve type | mold magnetoresistive effect element in the magnetic position detection apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  FIG. 1 is a schematic perspective view of a magnetic position detection apparatus 100 according to an embodiment of the present invention. The magnetic position detection device 100 includes a magnetic member 101 and a magnetic sensor 102. The magnetic member 101 has N poles and S poles alternately arranged on the magnetic pole array surface 101a, and here, the magnetic member 101 is quadrupole magnetized. Further, the length P1 of the magnetic poles at both ends in the magnetic pole arrangement direction (the magnetic pole length P1 at both ends) is longer than the length P2 of the magnetic poles other than the both ends in the magnetic pole arrangement direction (the magnetic pole length P2 other than both ends). Also short. Details of the relationship between P1 and P2 will be described later. In the magnetic sensor 102, one or two pairs of spin valve magnetoresistive elements are arranged at positions facing the magnetic pole array surface 101 a of the magnetic member 101. For this, the conventional technique shown in FIGS. 6A and 6B or FIGS. 7A and 7B can be applied.

  2 and 3 are explanatory diagrams of magnetic field simulation results when the magnetic pole length P2 other than both ends of the magnetic member 101 is constant (P2 = 14 mm) and the magnetic pole length P1 at both ends is changed. A) shows P1 = 14 mm, (B) shows P1 = 12 mm, (C) shows P1 = 10 mm, and (D) shows a case where P1 = 8 mm. FIG. 3 (A) shows P1 = 6 mm, (B) Represents P1 = 4 mm, (C) represents P1 = 2 mm, and (D) represents P1 = 0 mm (bipolar magnetization). The simulation range is 14 mm from left to right (magnetic pole arrangement direction) from the boundary between the two magnetic poles in the center, and the magnetic field calculation results at a position 5 mm vertically away from the magnetic pole arrangement surface 101a are expressed as vectors at 0.5 mm intervals. . From these figures, it can be seen that when the magnetic pole length P1 at both ends is reduced to 4 mm or less, the angular deviation of the magnetic field is large at both ends of the detection range (in this type of magnetic member, the magnetic field is not on the boundary between the N pole and the S pole. (It is required to be parallel to the magnetic pole array surface).

  FIG. 4 is an error graph showing the relationship between the position in the detection range and the position error when the magnetic pole length P2 other than both ends of the magnetic member 101 is constant (P2 = 14 mm) and the magnetic pole length P1 at both ends is changed. It is. The magnetic pole length P1 at both ends was set to P1 = 14 mm, 12 mm, 10 mm, 8 mm, 6 mm, 4 mm, 2 mm, and 0 mm as in FIGS. This figure corresponds to the conversion of the angular deviation of the magnetic field at each position within the detection range in the simulation of FIGS. 2 and 3 into a position error. From this figure, it can be seen that if the magnetic pole length P1 at both ends of the magnetic member 101 is 6 mm or more, the position error is generally within about 1 mm.

  5 is a characteristic diagram showing the maximum value of the position error within the detection range shown in FIG. 4 in each case of the magnetic pole length P1 at both ends of the magnetic member 101. In FIG. From this figure, it is understood that the maximum position error is almost constant when the magnetic pole length P1 at both ends of the magnetic member 101 is in the range of 10 mm to 14 mm (P2 / P1 ≦ 7/5). It can also be seen that if P1 is 7 mm or more (P2 / P1 ≦ 2), the maximum position error does not exceed 1 mm. It can also be seen that the maximum position error is about 1 mm when P1 is 6 mm (P2 / P1 = 7/3). On the other hand, if P1 is less than 6 mm, the maximum position error tends to increase rapidly.

  As described above, even if the magnetic pole length P1 at both ends of the magnetic member 101 is shorter than the magnetic pole length P2 other than both ends, by setting the range of P2 / P1 appropriately, equal length multiple pole magnetization (P1 = P2) It can be said that the accuracy comparable to the case can be obtained, or the position error can be sufficiently reduced even if the accuracy is not as high as the case. That is, a stable rotating magnetic field (magnetic field) is generated in the magnetic sensor 102 (element position) with the relative movement of the magnetic member 101 in the magnetic pole arrangement direction, as in the case of equal length multiple pole magnetization (P1 = P2). Can be made.

  According to the present embodiment, the following effects can be achieved.

(1) Since the magnetic member 101 has the magnetic pole length P1 at both ends shorter than the magnetic pole length P2 at both ends, the magnetic member 101 has a magnetic length 101 that is longer than the magnetic pole length P2 at both ends. The overall length can be shortened to reduce the size, and the cost can be reduced accordingly. On the other hand, the detection range is the same as in the same case. That is, the magnetic member can be made smaller (shorter) without reducing the detection range as the magnetic position device, and the cost can be reduced.

(2) Even if the magnetic pole length P1 at both ends of the magnetic member 101 is made shorter than the magnetic pole length P2 at both ends, the position error can be kept sufficiently small, and the accuracy is greatly reduced when miniaturization and cost reduction are achieved. There is nothing.

  The present invention has been described above by taking the embodiment as an example. However, it will be understood by those skilled in the art that various modifications can be made to each component of the embodiment within the scope of the claims. Hereinafter, modifications will be described.

  In the embodiment, the case where the magnetic pole array surface 101a of the magnetic member 101 is a flat surface has been described. However, in the modification, the magnetic pole array surface 101a may be a curved surface such as an arc surface.

  In the embodiment, the case where the magnetic member 101 is quadrupole magnetized has been described. However, in the modification, the magnetic member 101 may be multipolar magnetized with five or more poles. Further, the magnetic member 101 may be a multi-pole magnetized one magnetic body or a combination of a plurality of permanent magnets.

  As the spin valve magnetoresistive element, a tunnel effect magnetoresistive element (SV-TMR) can be used in addition to the spin valve giant magnetoresistive element (SV-GMR).

DESCRIPTION OF SYMBOLS 100 Magnetic type position detection apparatus 101 Magnetic member 102 Magnetic sensor

Claims (3)

A magnetic member in which N poles and S poles are alternately arranged;
A pair or a plurality of pairs of spin valve magnetoresistive effect elements present at positions facing the magnetic pole array surface of the magnetic member,
It said magnetic member has a length related to the magnetic pole arrangement direction of the magnetic poles of both ends of the magnetic pole arrangement direction, rather shorter than the length in the magnetic pole arrangement direction of the magnetic poles other than the two ends,
P2 / P1 ≦ 2, where P1 is the length of the magnetic poles at both ends in the magnetic pole arrangement direction, and P2 is the length of the magnetic poles other than the both ends in the magnetic pole arrangement direction. Detection device. 2. The magnetic position detecting device according to claim 1, wherein the P1 and the P2 satisfy P2 / P1 ≦ 7/5. 3. The magnetic position detecting device according to claim 1, wherein the magnetic pole array surface of the magnetic member is a flat surface or a curved surface.

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