JP7641871B2 - Rotation Detector - Google Patents

Description

The present invention relates to a rotation detector that detects the rotational motion of a rotating body using a power generation sensor.

A magnetic wire with a large Barkhausen effect (large Barkhausen jump) is known as a Wiegand wire or a pulse wire. This magnetic wire has a core and a skin surrounding the core. One of the core and the skin is a soft layer in which the magnetization direction is reversed even in a weak magnetic field, while the other is a hard layer in which the magnetization direction is not reversed unless a strong magnetic field is applied.
When the hard layer and the soft layer are magnetized in the same direction along the axial direction of the wire, the magnetization direction of the soft layer is reversed when the external magnetic field strength in the opposite direction to the magnetization direction increases and reaches a magnetic field strength at which the magnetization direction of the soft layer is reversed. At this time, the large Barkhausen effect is manifested, and a pulse signal is induced in the coil wound around the magnetic wire. The magnetic field strength at which the magnetization direction of the soft layer is reversed is referred to in this specification as the "operating magnetic field." The magnetic wire and coil are collectively referred to as the power generation sensor.
When the external magnetic field strength is further increased and reaches a magnetic field strength at which the magnetization direction of the hard layers is reversed, the magnetization direction of the hard layers is reversed. The magnetic field strength at which the magnetization direction of the hard layers is reversed is referred to as the "stabilizing magnetic field" in this specification.
In order for the Large Barkhausen effect to occur, it is necessary that the magnetization direction of only the soft layer is reversed, assuming that the magnetization directions of the hard layer and soft layer are the same. Even if the magnetization direction of only the soft layer is reversed when the magnetization directions of the hard layer and soft layer are not the same, no pulse signal is generated, or even if it is generated, it is very small.

The output voltage from this magnetic wire is constant regardless of the speed at which the magnetic field changes, and has hysteresis characteristics with respect to the input magnetic field, meaning there is no chattering. For this reason, this magnetic wire is also used in position detectors and the like when combined with magnets and counter circuits. In addition, the output energy from the magnetic wire can be used to operate peripheral circuits without the need for an external power supply.

When an alternating magnetic field is applied to the power generating sensor, two pulse signals are generated per cycle: one positive pulse signal and one negative pulse signal. The magnet that generates the magnetic field is a rotating body, and the magnetic field applied to the power generating sensor changes depending on the positional relationship between the magnet (rotating body) and the power generating sensor, so that the rotation of the rotating body can be detected.
However, if only one power generation sensor is used, it is not possible to identify the direction of rotation when the direction of rotation of the rotor changes. As shown in Fig. 1 of Patent Document 1, if multiple power generation sensors are used, the direction of rotation can be identified, but this leads to an increase in the size and cost of the detector.
Patent Document 2 describes the use of one power generating sensor and another sensor element that is not a power generating sensor. The document further describes the use of one magnet (two poles) and the use of multiple magnets (multi-pole) to improve resolution.
FIG. 1 of Patent Document 3 shows an example of a structure for detection using one magnet (FIG. 2 of Patent Document 2). A structure in which a two-pole magnet and a power generation sensor face each other is suitable for miniaturization because the diameter can be reduced to the full length of the power generation sensor. FIG. 1 of Patent Document 4 shows an example of a structure for increasing the resolution (FIG. 3 of Patent Document 2). The main use of this type of rotation detector is to detect the number of rotations per revolution. A rotation detector using a power generation sensor has a problem that a pulse signal that should be output is not output in some cases, and a structure with one magnet (two poles) that outputs only two pulses per revolution usually lacks precision and cannot correctly detect the number of rotations.
Patent Document 5 describes a method for determining the magnetization direction of the magnetic wire in a power generation sensor by passing a current through a coil in the power generation sensor to generate a magnetic field and monitoring the output state. The document states that by determining the magnetization direction in this way, it is possible to identify the rotation speed even when a single magnet is used.

Patent No. 5511748 Patent No. 4712390 U.S. Pat. No. 9,528,856 U.S. Pat. No. 8,283,914 Patent No. 5730809

When detecting rotation, using multiple power generating sensors tends to increase the size of the detector itself. On the other hand, even if there is only one power generating sensor, determining the magnetization direction of the magnetic wire inside the power generating sensor can be a complicated process.

Therefore, the present invention aims to provide a rotation detector that is compact by efficiently applying a high-frequency alternating magnetic field to a magnetic wire using one power generation sensor and multiple magnetic field generating sources.

The rotation detector detects the rotational motion of a rotating body using one power generating sensor. The power generating sensor comprises a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire, the magnetic wire is arranged in the radial direction of the rotating body, the rotating body comprises a support made of a soft magnetic material and a plurality of magnetic field generating sources attached to the support at equal intervals in the circumferential direction, each of the plurality of magnetic field generating sources has a pair of N and S poles, the magnetization direction is parallel to the rotation axis direction of the rotating body, the magnetization directions of two adjacent magnetic field generating sources are different, and the outer diameter of the rotation locus of the plurality of magnetic field generating sources is 1/1000th of the diameter of the magnetic wire. The length of the magnetic field source is longer than the length of the wire, and when the magnetic field source is close to the magnetic wire, it faces in the direction of the rotation axis at least a portion of the area from the axial center to the first axial end of the magnetic wire, the attachment surface of the magnetic field source close to the magnetic wire to the support is on the second axial end side of the magnetic wire, and the direction from the attachment surface of the magnetic field source close to the magnetic wire to the support toward the magnetic field source is the same as the direction from the second axial end to the first axial end of the magnetic wire.

The present invention provides a rotation detector that is compact in size by efficiently applying a high-frequency alternating magnetic field to a magnetic wire using multiple magnetic field generating sources.

FIG. 1 is a perspective view of a rotation detector according to a first embodiment. FIG. 2 is a cross-sectional view of the rotation detector according to the first embodiment. FIG. 2 is an explanatory diagram in the form of a cross-sectional view showing the magnetic wire and the rotating body of the first embodiment. FIG. 4 is a magnetic simulation diagram of the first embodiment. 4 is an explanatory diagram showing the positional relationship between a magnetic wire and a rotating body in the first embodiment. FIG. 13 is an explanatory diagram showing the positional relationship between a magnetic wire and a rotating body in a modified example of the first embodiment. FIG. FIG. 11 is another magnetic simulation diagram. FIG. 10 is a perspective view of a support according to a second embodiment; FIG. 11 is a perspective view of a rotation detector according to a second embodiment. FIG. 13 is an explanatory cross-sectional view showing a magnetic wire and a rotating body according to a second embodiment; FIG. 11 is a diagram of a magnetic simulation of the second embodiment. FIG. 11 is a perspective view of a support body based on a modified example of the second embodiment. FIG. 11 is a perspective view of a rotation detector based on a modified example of the second embodiment. FIG. 11 is a perspective view of a rotation detector according to a third embodiment. FIG. 13 is a perspective view of a multi-pole magnetized magnet according to a modified example of the third embodiment. FIG. 13 is a perspective view of a rotation detector based on a fourth embodiment. FIG. 13 is a top view of a rotation detector according to a fourth embodiment. 13 is an explanatory diagram showing a magnetic field applied to a power generation sensor according to a fourth embodiment and an output signal. FIG. 13A and 13B are explanatory diagrams showing a magnetic field applied to a magnetic sensor according to a fourth embodiment and an output signal. 13 is an explanatory diagram showing a combination of detection results of a power generation sensor and a magnetic sensor according to a fourth embodiment. FIG. 13 is an explanatory diagram showing synchronization between a power generation sensor and a magnetic sensor and rotation coordinates of an output signal based on a fourth embodiment. FIG. FIG. 13 is an explanatory diagram showing the count number of an output signal. FIG. 13 is a perspective view of a rotation detector based on a modified example of the fourth embodiment. FIG. 13 is a top view of a rotation detector based on a modified example of the fourth embodiment. 13 is an explanatory diagram showing a magnetic field applied to a power generation sensor and an output signal based on a modified example of the fourth embodiment. FIG. 13A and 13B are explanatory diagrams showing a magnetic field applied to a magnetic sensor and an output signal based on a modified example of the fourth embodiment. 13 is an explanatory diagram showing a combination of detection results of a power generation sensor, a first magnetic sensor, and a second magnetic sensor according to a modified example of the fourth embodiment. FIG. FIG. 13 is a perspective view of a rotation detector based on a fifth embodiment. FIG. 13 is a side view of a rotation detector based on a fifth embodiment.

The present invention will be described below based on the illustrated embodiment. However, the present invention is not limited to the embodiment described below.

[First embodiment]
1A and 1B show a rotation detector 100 according to a first embodiment. The rotation detector 100 includes a rotating body 110 that rotates and one power generation sensor 120.
The rotating body 110 includes a ring-shaped support 111 made of a soft magnetic material and a plurality of magnets 112 that are magnetic field generating sources. The plurality of magnets 112 are fixed to the outer peripheral surface of the support 111 at equal intervals in the circumferential direction. Examples of fixing methods include embedding, fitting, and adhesion. The magnets 112 are magnetized in the axial direction 113 of the rotating body 110 (the vertical direction of the paper surface of FIG. 1B) and have a pair of N and S poles. The magnets 112 have a magnetic pole surface 112a on the axial upper side of the rotating body 110. It is preferable that the magnetic pole surface 112a has no step with the axial upper side surface of the support 111. The plurality of magnets 112 are arranged so that adjacent magnetic pole surfaces 112a have different poles. The rotating body 110 rotates around an axis 113 extending in the vertical direction as a rotation axis.

The power generation sensor 120 has a magnetic wire 121 that exhibits the large Barkhausen phenomenon and a coil 122 wound around the magnetic wire 121. The magnetic wire 121 is arranged in the radial direction of the rotating body 110. The outer diameter of the rotational trajectory of the magnet 112 attached to the rotating body 110 is larger than the magnetic wire length 121L. The magnetic wire 121 has an axial center portion 121a, an axial first end portion 121b, and an axial second end portion 121c. The axial center portion 121a of the magnetic wire 121 is offset in the radial direction of the rotating body 110 with respect to the axis 113. The offset amount is indicated by the symbol OF1. The axial first end portion 121b and the axial second end portion 121c are located radially outside and inside the rotating body 110, respectively. The direction of motion of the magnet 112 accompanying the rotational motion of the rotor 110 is perpendicular to the axial direction of the magnetic wire 121, and the magnetic pole face 112a passes under at least a portion of the region (called the "first region") from the axial center 121a to the axial first end 121b of the magnetic wire 121. At the same time, the support 111 passes under a region (called the "second region") of the magnetic wire 121 adjacent to the radial inside of the first region. As a result, the magnetic field from the magnet 112 is efficiently applied to the region from the axial center 121a to the axial first end 121b of the magnetic wire 121, while a magnetic field greater than the operating magnetic field is not applied to the axial second end 121c of the magnetic wire 121.

1A and 1B, when 20 magnets 112 are provided at equal intervals along the outer periphery of the ring-shaped support 111, 10 positive pulse signals and 10 negative pulse signals are induced in the coil 122 per one forward rotation of the rotor 110. Also, 10 positive pulse signals and 10 negative pulse signals are induced per one reverse rotation of the rotor 110.
This rotation detector 100 is a hollow type rotation detector with a rotor 110. The magnet 112 is located on the outer periphery of the rotor 110, and the power generation sensor 120 faces the outer periphery of the rotor 110 in the direction of the rotation axis. Therefore, the amount of radial outward protrusion of the power generation sensor 120 based on the outer diameter of the rotor 110 is small, and the outer diameter of the entire detector is kept to a necessary minimum, resulting in a small size. In addition, the power generation sensor can be placed horizontally on a substrate (not shown) on which electronic components constituting the detection circuit are mounted, providing high mounting stability.

The positional relationship between the magnetic wire 121 and the rotor 110 will be described in more detail.
2A , when the rotating body 110 rotates, the pole faces 112a of the magnets 112 that generate a magnetic field pass under the first region of the magnetic wire 121. The support 111 passes under the second region of the magnetic wire 121.
2B shows the results of a magnetic simulation using the support 111, the magnet 112, and the magnetic wire 121. The support 111 is soft magnetic, and due to its magnetic collecting effect and shielding effect, a magnetic field is applied intensively to the first axial end 121b side of the magnetic wire 121 facing the magnet 112. When a magnetic field is locally applied to the first axial end 121b, a reversal magnetic field propagates in the magnetic wire 121 from the first axial end 121b to the second axial end 121c, and a single magnetic domain is formed throughout the entire magnetic wire.

Next, referring to FIG. 2C, an additional effect will be described when the distance between the support 111 and the second axial end 121c is smaller than the distance between the magnet 112 and the second axial end 121c. The magnet mounting surface 111b of the support 111 is below the region from the axial center 121a to the first axial end 121b of the magnetic wire 121. In addition, the support surface 111c of the support 111, which is radially opposed to the magnet mounting surface 111b, is below the region from the axial center 121a to the second axial end 121c of the magnetic wire 121.

The direction from the mounting surface 111b of the magnetic field generating source 112 to the support 111 toward the magnetic field generating source is the radially outward direction. In addition, the direction from the second axial end 121c of the magnetic wire 121 toward the first axial end 121b is also the radially outward direction.

At this time, the magnetic wire 121, the magnet 112, and the support 111 made of a soft magnetic material form a magnetic circuit as shown by the arrow in FIG. 2C. Therefore, a stabilizing magnetic field is applied to the magnetic wire over a wider range than the conventional method of applying a magnetic field to both ends of the magnetic wire, and in the same way as applying a magnetic field to the entire magnetic wire. As a result, a single magnetic domain is formed throughout the entire magnetic wire, and a high-output pulse signal is obtained.

In contrast, FIG. 3 shows the results of a magnetic simulation using a non-magnetic support 191 instead of the soft magnetic support 111, a magnet 112, and a magnetic wire 121. Unlike FIG. 2B, a magnetic field is applied to the axial center portion 121a and the second end portion 121c in addition to the axial first end portion 121b. This makes it difficult to form a single magnetic domain across the entire magnetic wire.

Also, as shown in FIG. 2D, the radial dimension of the support 111 may be increased radially inward so that the radial position of the support surface 111c and the second axial end 121c of the magnetic wire 121 are substantially the same. In this case, the magnetic resistance of the magnetic circuit becomes smaller, the applied magnetic field propagates more easily throughout the wire, and the output of the pulse signal is further increased.

[Second embodiment]
4A and 4B show a rotation detector 200 according to a second embodiment. The same elements as those in FIGS. 1A and 1B are denoted by the same reference numerals, and detailed description thereof will be omitted.
The rotation detector 200 has a rotating body 210 that rotates. The rotating body 210 has one ring-shaped support 211 made of a soft magnetic material. The support 211 has a flange 211a that protrudes radially outward from the lower end in the rotation axis direction over the entire outer circumference. A plurality of magnets 112 are fixed to the outer circumferential surface of the support 211 and the upper surface of the flange 211a at equal intervals in the circumferential direction. Due to the back yoke effect (described later) of the flange 211a, the allowable range of the gap H in the rotation axis direction between the power generation sensor 120 and the magnetic pole surface 2112a is wider than that of the first embodiment. In other words, the degree of freedom in design is increased, resulting in a more preferable state.

Figure 4C shows the positional relationship between the support 211, the magnet 112, and the magnetic wire 121. Figure 4D shows the results of a magnetic simulation using the support 211, the magnet 112, and the magnetic wire 121. The flange 211a is attached to the magnetic pole surface 112b opposite the magnetic pole surface 112a of the magnet 112. Therefore, it can be seen that the magnetic pole boundary line of the magnet 112 shifts from the symbol 112c (dotted line) to the symbol 112d (solid line) toward the flange 211a side due to the magnetic collection effect of the flange 211a, that is, the back yoke function of the flange. Due to the effect of such a back yoke, the leakage magnetic field from the magnetic pole surface 112a is increased compared to the leakage magnetic field from the support 111 without the flange. Therefore, the allowable range of the gap H between the power generation sensor 120 and the magnetic pole surface 112a is expanded, the degree of freedom in selecting the size and material of the magnet is increased, and the stability of the installation is also improved.

[Modification of the second embodiment]
5A and 5B show a rotation detector 200-1 according to a modified example of the second embodiment. The rotor 210-1 has one ring-shaped support 211-1 made of a soft magnetic material. This support 211-1 has a flange 211-1a that protrudes radially inward from the lower end in the rotation axis direction over the entire inner circumference. A plurality of magnets 112 are fixed at equal intervals in the circumferential direction to the inner peripheral surface of the support 211-1 and the upper surface of the flange 211-1a. The outer diameter of the rotation locus of the magnet 112 attached to the support 211-1 is larger than the magnetic wire length 121L.

Unlike the embodiment in which the flange portion is on the outer circumferential surface, the first axial end 121b and the second axial end 121c are located on the radial inner side and outer side of the rotor 210-1, respectively. Due to the rotational motion of the rotor 210-1, the direction of motion of the magnet 112 is perpendicular to the axial direction of the magnetic wire 121, and the magnetic pole surface 112a passes under at least a part of the region (referred to as the "first region") from the axial center 121a to the first end 121b of the magnetic wire. At the same time, the support 211-1 passes under the region (referred to as the "second region") of the magnetic wire 121 adjacent to the radial outer side of the first region. As a result, the magnetic field from the magnet 112 is efficiently applied to the region from the axial center 121a to the axial first end 121b of the magnetic wire 121, while a magnetic field greater than the operating magnetic field is not applied to the axial second end 121c side of the magnetic wire 121.
The rotation detector of this example is a hollow type like the fourth and fifth embodiments, but the positional relationship between the magnet 112 and the support is different, making this structure advantageous when it is desired to have a large radial dimension of the hollow portion.

The direction from the mounting surface 211-1b of the magnetic field generating source 112 to the main body of the support 211-1 toward the magnetic field generating source is the radially inward direction. In addition, the direction from the second axial end 121c of the magnetic wire 121 to the first axial end 121b is also the radially inward direction.

In Figures 2A and 4C, the multiple magnets 112, which are the magnetic field generating sources of the multiple N-S pole pairs, are also arranged on the rear and front sides of the paper. The magnetic field is applied to the first axial end 121b of the magnetic wire 121 due to the magnetic collecting effect of the supports 111 and 211, which also reduces the effect of magnetic interference generated between adjacent magnets on the magnetic wire 121. Therefore, it is possible to bring adjacent magnetic field generating sources closer to each other and increase the pole density of the magnets. In other words, the rotation detector can be made smaller.

[Third embodiment]
As shown in Fig. 6, the rotor 310 of the rotation detector 300 has a ring-shaped support 311 with a flange protruding radially outward from the axial lower end, and a plurality of magnets 112 fixed to the outer circumferential surface at equal intervals in the circumferential direction. A shaft 314 of a device that controls rotation is attached to the axis 113 of the rotor 310. In this way, the rotor 310 can be a shaft type. The material of the shaft 314 may be a non-magnetic material or a magnetic material. While a magnetic field is applied to one axial end of the magnetic wire 121, it is not necessary to apply a magnetic field of equal strength to both axial ends of the magnetic wire or the entire magnetic wire, so such a shaft type structure is also possible and has a high degree of freedom.

As shown in Figure 7, magnet 112-1, which is a ring-shaped hard magnetic material magnetized with multiple poles, can also be used as multiple magnetic field generating sources. When the axial upper and lower surfaces of the ring-shaped hard magnetic material that is the material for magnet 112-1 are simultaneously magnetized using a magnetizing yoke with an area equivalent to a specified magnetization pitch λ, it is magnetized in the direction of axis 113, and magnetic poles appear on the upper and lower surfaces of the hard magnetic material, creating magnet 112-1. One magnet 112-1 magnetized with multiple poles in this way can be fixed to support 111, 211, 211-1 or disk-shaped support 311.

[Fourth embodiment]
8A and 8B show a rotation detector 400 having a multi-rotation detection function based on the fourth embodiment. The detector 400 includes a rotating body 410 and one power generation sensor 120. The rotating body 410 is made of a soft magnetic material and has a support 411 in the shape of a substantially square plate with a flange on the outer circumferential surface, and four magnets 112 that serve as a magnetic field generation source. The four magnets 112 are arranged at equal intervals in the circumferential direction on the four sides of the support 411. A shaft 414 is attached to the axis 113 of the rotating body 410. The magnets 112 are magnetized in the direction of the axis 113, have a pair of N and S poles, and the magnetization directions of two adjacent magnets 112 are different. Although a magnet with an arc-shaped outer circumferential surface is shown, it is also possible to use magnets with a C-shape, a rectangular parallelepiped shape, or the like.

The power generation sensor 120 has a magnetic wire 121 that exhibits the large Barkhausen phenomenon, and a coil 122 wound around the magnetic wire 121. The magnetic wire 121 is located in the radial direction of the rotor 411 and further intersects with the axis 113. The outer diameter of the rotational trajectory of the magnet 112 attached to the rotor 411 is larger than the length of the magnetic wire 121.
Due to the rotational motion of the rotor 410, the magnetic pole surface 112a of the magnet 112 passes under at least a portion of the region (referred to as the "first region") from the axial center 121a to the first axial end 121b of the magnetic wire 121. The support 411 and the shaft 414 pass under a region (referred to as the "second region") of the magnetic wire 121 adjacent to the radial inside of the first region. In addition, although the magnetic wire 121 intersects with the axis 113, the magnetic pole surface 112a of the magnet 112 does not pass under the region from the axial center 121a to the second axial end 121c of the magnetic wire 121.

With the above-described structure, when the rotating body 410 rotates once, two periods of a uniform alternating magnetic field are applied to the region between the axial center portion 121 a and the axial first end portion 121 b of the magnetic wire 121 .
In the case of four magnetic field generating sources, this structure allows the outer diameter of the rotor to be the smallest. In the case of six magnetic field generating sources, the magnetic pole of a magnet close to the second end 121c and the magnetic pole of another magnet radially opposite to the magnet close to the first end 121b can be of different polarity. In this case, even if the outer diameter of the rotor is further reduced so that the magnet 112 passes under the second end 121c, a uniform alternating magnetic field can be applied.

The rotation detector 400 further includes a magnetic sensor 440. The magnetic sensor 440 is disposed at a position where it can determine the magnetic field from the magnetic field generation source when the power generation sensor 120 outputs a pulse signal.
When one of the four magnets 112 (called the "first magnet") passes near the magnetic wire 121, a stabilizing magnetic field is applied to the magnetic wire 112. Then, when a second magnet adjacent to the first magnet approaches, an operating magnetic field in the opposite direction to the stabilizing magnetic field is applied to the magnetic wire 112, and the power generation sensor 120 outputs a pulse signal.
The magnetic sensor 440 is disposed at a predetermined angle with respect to the axial direction of the magnetic wire, as shown in Fig. 8B. The predetermined angle is approximately 45 degrees. Alternatively, the predetermined angle may be approximately 135 degrees, approximately 225 degrees, or approximately 315 degrees.

[Explanation of multi-rotation function]
Next, we will explain detectors with multi-revolution detection capabilities. An absolute angle detector within one revolution is used for accurate position detection when the power is turned on. A generator sensor is used for rough detection in units of one revolution when the power is turned off. A generator sensor outputs a total of two pulses, one positive and one negative, for one cycle of the alternating magnetic field, but it is not possible to distinguish between forward and reverse rotation with only these pulses. Therefore, the following method has traditionally been used.
1) A method of increasing the number of power generation sensors to obtain a phase difference signal 2) A method of adding another detection means The former requires multiple power generation sensors, while the latter can be achieved with one power generation sensor and an additional sensor element, as described in Patent Document 2.

When using a single power generation sensor, the stabilizing magnetic field and operating magnetic field must be applied to the magnetic wire in a specific order to obtain a pulse signal of sufficient level. If the rotating body rotates in the forward direction and the operating magnetic field is applied to the magnetic wire and a pulse signal is output, and then the rotating body reverses immediately after, the above order is not followed and one pulse signal required for rotation detection is missed. In that case, the error will exceed ±180° and the correct amount of rotation cannot be detected.

Until now, it has been difficult to achieve both a multi-period alternating magnetic field and a compact detector. However, as shown in Figures 8A and 8B, the number of magnetic field generating sources can be increased to four, so that two periods of the alternating magnetic field are applied to the magnetic wire per rotation. In other words, a detector with multi-rotation detection capability can be obtained that is compact, low-cost, and produces a stable pulse signal output. The form is described in detail below.

[Method for determining rotation speed and direction]
In Fig. 8B, clockwise rotation of the rotor 410 is defined as forward rotation, and counterclockwise rotation is defined as reverse rotation. Fig. 9A shows the magnetic field Ha applied to the power generation sensor 120 during rotation. Furthermore, the positive pulse signal generated in the power generation sensor 120 during forward rotation is indicated by the symbol P, the stabilizing magnetic field that is the premise for the output of signal P is indicated by the symbol Ps, the negative pulse signal is indicated by the symbol N, and the stabilizing magnetic field that is the premise for the output of signal N is indicated by the symbol Ns. The stabilizing magnetic field is ±H2, and the operating magnetic field is ±H1. The output during reverse rotation is indicated by the same symbols as during forward rotation, but the output is indicated by white paint during forward rotation and black paint during reverse rotation.
The magnetic field applied from the permanent magnet 112 to the power generation sensor 120 is an alternating magnetic field with two cycles per rotation. Therefore, the power generation sensor 120 outputs a positive/negative (P, N) signal twice per forward rotation, and outputs a positive/negative (P, N) signal twice per reverse rotation, just like in the case of forward rotation.

In FIG. 9B, the magnetic field Hb applied to the magnetic sensor 440 is shown by a dashed line. As described above, the magnetic sensor 440 is disposed so as to form approximately 45 degrees with the first axial end 121b with respect to the rotating shaft 113. Therefore, the alternating magnetic field Hb is shifted in phase by 45 degrees from the alternating magnetic field Ha shown in FIG. 9A. As the magnetic sensor 440, for example, a magnetic sensor capable of distinguishing between N and S poles (positive and negative in the figure) such as a Hall element or a magnetoresistance effect element (SV-GMR, TMR) can be used. In this case, when the power generation sensor 120 outputs two positive P signals and two negative N signals, the magnetic sensor 440 outputs a signal that detects a negative magnetic field. This is shown by white and black triangles in the figure. Also, when the power generation sensor 120 outputs two positive N signals and two negative P signals, the magnetic sensor 440 outputs a signal that detects a positive magnetic field. This is shown by white and black rectangles in the figure.
FIG. 9C shows a combination of the output signal of the power generation sensor 120 and the detection signal of the magnetic sensor 440.

The rotation coordinates are shown in FIG. 9D. After the positive pulse signal P is output, the rotor 410 rotates right as indicated by the symbol R, and the rotation angle until the next signal N' is detected is +90 degrees. On the other hand, if the rotor 410 rotates left as indicated by the symbol L immediately after the positive pulse signal P is output, the next signal is expected to be signal N. However, since the stabilizing magnetic field Ns has not been passed through, the signal N is not output, or even if it is output, it is very small and difficult to evaluate. Therefore, the rotation angle until the next left rotation signal P' that can be evaluated is output is about -(90 degrees + α). In this way, even if a rotational movement occurs in which a stabilizing magnetic field is not applied in both the forward and reverse directions, no overlapping ranges of the same signal are generated. In addition, the range of positions that can be determined is less than 360 degrees, and the number of rotations of the rotor 410 can be accurately detected.

For ease of understanding, a method for determining the rotation direction of the rotating body 410 will be described using two consecutive signals as an example.
The determination is performed by a signal processing circuit (not shown) including a memory. This signal processing circuit has an identification function, a reference function, and a calculation function. First, the signal processing circuit uses the identification function to identify the signal from the power generation sensor 120 as one of the four types P, P', N, and N'. Next, the signal processing circuit uses the reference function to write the previous (previous state) history signal stored in the initial state when counting the number of rotations and the direction of rotation begins, and the signal (new state) associated with the subsequent rotation, in sequence, into the memory. The signal processing circuit searches two consecutive signals, past and present, stored in the memory in four types of pre-set coded tables, and returns the matching count value. An example of this table is shown in FIG. 9E. The signal processing circuit searches every time a signal is input, and sequentially adds or subtracts the resulting count value using the calculation function. The added or subtracted value represents the number of rotations and the direction of rotation at that time. By setting a reference position between signals N and P and using a table such as that shown in FIG. 9E, the rotation direction and number of rotations of the rotating body 410 can be counted accurately.

[Method for synchronizing the position within one rotation and the number of rotations]
When the rotation detector is used for multiple rotations of a motor, the number of rotations is detected by the method described above with reference to FIG. 9E during a power outage of the motor drive system. When the motor drive system is started, the signals P, P', N, and N' are present at two locations each in one rotation, so that a choice between two regions is required and the number of rotations cannot be determined. Therefore, it is necessary to determine the displacement angle from the reference position of the rotation counter. Therefore, by attaching an external one-rotation absolute type position sensor, it is possible to determine which region the motor is located in and to determine the number of rotations.

[Modification of the fourth embodiment]
As shown in Figures 10A and 10B, as a modification of the fourth embodiment, a hollow type can also provide a multiple rotation function. The rotation detector 400-1 includes a rotor 410-1, one power generation sensor 120, and two magnetic sensors 440 and 441. The rotor 410-1 is made of a soft magnetic material and includes a ring-shaped support 411-1 with a flange on its outer circumferential surface, and four magnets 112 fixed to the outer circumferential surface of the support 411-1 at equal intervals in the circumferential direction. The power generation sensor 120 includes a magnetic wire 121 and a coil 122.

In the fourth embodiment described above, one magnetic sensor 440 located approximately 45° away from the magnetic wire 121 in the circumferential direction can cover four signals each for forward and reverse rotation of the power generation sensor 120, a total of eight signals. This is because the magnetic field generating sources arranged at equal intervals in the circumferential direction are relatively close to each other, and a magnetic field sufficient to be detected by just one magnetic sensor 440 in both forward and reverse rotation is applied to the magnetic sensor 440. However, when four magnets are provided in a hollow type such as the first or second embodiment, there are cases where the magnets are not close to each other. Such cases are described below.

10A, the power generation sensor 120 outputs a pulse signal when one of the four magnets 112 passes near the magnetic wire 121, and then the next magnet approaches, causing the reverse magnetic field to gradually strengthen and the operating magnetic field to be applied. There are eight rotational positions of the rotor 410-1 when a pulse signal is output: rotational positions where the power generation sensor 120 outputs a positive pulse signal P and a negative pulse signal N during forward rotation, and positions where the power generation sensor 120 outputs a positive pulse signal P and a negative pulse signal N during reverse rotation.
The first magnetic sensor 440 and the second magnetic sensor 441 are arranged so as to detect the magnetic field of the magnetic field generating source in correspondence with these eight locations. The magnetic sensors are arranged with a phase shift of -20 degrees and +20 degrees so that the first magnetic sensor 440 can detect the magnetic field during normal rotation and the second magnetic sensor 441 can detect the magnetic field during reverse rotation. As shown in FIG. 10B, the first magnetic sensor 440 is arranged at a position slightly away from another magnet adjacent to the first magnet in the clockwise direction when one magnet 112 (referred to as the first magnet) is directly under the magnetic wire 121, in the counterclockwise direction, and the second magnetic sensor 441 is arranged at a position slightly away from the first magnet in the clockwise direction. The arrangement of the first magnetic sensor and the second magnetic sensor may be appropriately determined according to the material, size, etc. of the magnet.
In Fig. 10B, clockwise rotation of the rotor 410 is defined as forward rotation, and counterclockwise rotation is defined as reverse rotation. The first magnetic sensor 440 is responsible for identifying the signal of the power generation sensor 120 during forward rotation, and the second magnetic sensor 441 is responsible for identifying the signal of the power generation sensor 120 during reverse rotation. If the 3 o'clock direction in Fig. 10B is defined as 0 degrees, the power generation sensor 120 is at 0 degrees, the first magnetic sensor 440 is at +70 degrees, and the second magnetic sensor 441 is at +20 degrees. The magnetic wire is at the 0 degree position, and both magnetic sensors are disposed in the region from 0 degrees to 90 degrees, but they may be disposed in any of the other three regions (the region from 90 degrees to 180 degrees, the region from 180 degrees to 270 degrees, and the region from 270 degrees to 360 degrees).

In FIG. 11A, the magnetic field Ha applied to the power generation sensor 120 when the rotor 410-1 rotates is shown by a dotted line. In the figure, the positive pulse signal generated in the power generation sensor 120 during forward rotation is indicated by the symbol P, the stabilizing magnetic field that is the premise for the output of the signal P is indicated by the symbol Ps, the negative pulse signal is indicated by the symbol N, and the stabilizing magnetic field that is the premise for the output of the signal N is indicated by the symbol Ns. The stabilizing magnetic field is ±H2, the operating magnetic field is ±H1, and the output during reverse rotation is indicated by the same symbol as during forward rotation, but forward rotation is indicated by white and reverse rotation is indicated by black. The magnetic field applied from the magnet 112 to the power generation sensor 120 is an alternating magnetic field with two periods per rotation. Therefore, the power generation sensor 120 outputs positive and negative (P, N) signals twice each in one forward rotation, and also outputs positive and negative (P, N) signals twice each in one reverse rotation, just like during forward rotation.

11B, the magnetic field Hb applied to the first magnetic sensor 440 is indicated by a two-dot chain line, and the magnetic field Hc applied to the second magnetic sensor 441 is indicated by a one-dot chain line. As described above, the first magnetic sensor 440 and the second magnetic sensor 441 are disposed at a distance in the circumferential direction from the power generation sensor 120. Therefore, the alternating magnetic fields Hb and Hc are out of phase with the alternating magnetic field Ha shown in FIG. 11A.
The magnetic sensors 440 and 441 may be magnetic sensors capable of distinguishing between north and south poles (plus and minus in the figure), such as Hall elements and magnetoresistance effect elements (SV-GMR, TMR).
When the power generation sensor 120 outputs two positive P signals, the first magnetic sensor 440 outputs a negative magnetic field detection signal (white triangle in the figure). When the power generation sensor 120 outputs two positive N signals, the first magnetic sensor 440 outputs a positive magnetic field detection signal (white square in the figure).
When the power generation sensor 120 outputs two inverted P signals, the second magnetic sensor 441 outputs a detection signal of a positive magnetic field (black square in the figure). When the power generation sensor 120 outputs two inverted N signals, the second magnetic sensor 441 outputs a detection signal of a negative magnetic field (black triangle in the figure).
By combining the detection signals of the first magnetic sensor 440 and the second magnetic sensor 441 with the output signal of the power generation sensor 120, four types of signals, P, P', N, and N', are identified as shown in Fig. 11C. By operating these four types of signals according to the above-mentioned [method of determining the number of rotations and the direction of rotation] and [method of synchronizing the position within one rotation with the number of rotations], this detector 400-1 can be used for multiple rotations of a motor.

Other Circuit Examples
The rotation detector of each embodiment uses a power generation sensor equipped with a magnetic wire. Therefore, the output signal due to the large Barkhausen effect is an electromotive force as is already known, and can be used as a power source. That is, by adding a function to process the output of the power generation sensor with a rectifier and a capacitor, the rotation detector of the first to fourth embodiments can be used, for example, as a meter (for flow rate, water, air volume, gas). In such applications where synchronization of the rotation angle within one rotation is not required, it is not necessary to use a power source or a battery. Furthermore, it is possible to transmit data wirelessly using the power generated by the power generation sensor. In the rotation detector of the fourth embodiment, the power generation sensor supplies power to the circuit and the magnetic sensor, making it possible to apply the detector to a battery-less motor multi-rotation position detector.

[Fifth embodiment]
In the fourth embodiment and the modified example of the fourth embodiment, the power generation sensor, the magnetic sensor, and the above circuits can be mounted on the same board. Figures 12A and 12B show a rotation detector 400-2 according to the fifth embodiment. The power generation sensor 120 is housed in a package 123 and fixed with resin or the like. Two terminals 124a and 124b connected to the coil 122 are provided at both ends of the package, and both terminals are mounted on the surface 500a of the board 500. The magnetic sensor 440, which is 45° away from the first axial end 121b of the magnetic wire 121 in the clockwise direction, is mounted on the same board surface 500a. Furthermore, a signal processing circuit 600 including a memory is mounted on the same board surface 500a. A connector 700 is also mounted to extract signals from the board. Furthermore, if the board 500 is a double-sided board, these circuits can also be mounted on the opposite board surface 500b. Also, another detection medium (not shown) can be provided on the surface of the rotating body 410 facing the substrate surface 500b, and a one-revolution absolute type position sensor (not shown) for detecting the medium can be mounted on the substrate surface 500b. In this way, the structure of the present invention has the advantage that electronic components required for the rotation detector can be mounted on the same substrate.

[Action and Effect]
The functions and effects of the embodiments described above will now be explained again.
When the magnetic field source approaches the power generating sensor, a magnetic field is applied to the first axial end of the magnetic wire in the power generating sensor, but the second axial end is not applied with a magnetic field because it does not face the magnetic field source. This causes simultaneous reversal of the magnetic domains from the first axial end to the second axial end, so no magnetic induction yoke is required, and a single magnetic domain is formed throughout the magnetic wire in the same way as in the case of applying a magnetic field to both ends of the magnetic wire. This allows a high-output pulse signal to be obtained from the power generating sensor.

The axial dimension of the portion of the magnetic wire facing the magnetic field source is less than half the length of the magnetic wire, and the relatively large magnets required in methods of applying a magnetic field to the entire length of the magnetic wire are not necessary in embodiments of the present invention. In addition, by appropriately determining the material of the magnet, the magnet can be made thin enough to apply a stabilizing magnetic field. By providing a flange on the support, the magnetic field source can be attached to two surfaces: the surface of the flange and the outer circumferential surface of the support that contacts the flange. This widens the adjustment range of the axial gap between the magnetic field source and the magnetic wire, improving the stability of the attachment and providing durability, resulting in stable output.

The magnetic field is applied to one side of the axial end of the magnetic wire, and the soft magnetic material portion collects magnetic force at the axial end where the magnetic field is not applied. This reduces the effect on the magnetic wire of magnetic interference between adjacent magnetic field sources of different polarities. This allows multiple magnetic field sources to be placed close together. It is possible to increase the pole density (number of poles per circumferential length of the rotor) of the magnetic field sources, and shorten the circumference of the rotor. In other words, the overall structure of the detector becomes smaller.

Since there is no need to apply a magnetic field of equal strength to both ends or the entire magnetic wire, there is a high degree of freedom in placement. Both hollow and shaft types can be used as rotation detectors. With hollow types, if you want to make the inner diameter of the rotation detector large, you can place the power generation sensor on the outer circumference, and if you want to make the outer diameter small, you can place the power generation sensor on the inner circumference. In other words, there is a high degree of freedom in design.

In terms of freedom of placement, the magnetic wire can be placed so that it is perpendicular to the axis of rotation of the rotating body. In this case, it becomes a shaft-type rotation detector. This allows for further miniaturization (especially miniaturization of radial dimensions) by applying two or more periods of alternating magnetic field per rotation. In addition, the stability of the signal induced in the coil wound around the magnetic wire can be improved.

Another advantage is that the electronic components required for the rotation detector can be mounted on the same board.

Regarding the embodiments described above, the following supplementary notes are disclosed.
[Appendix 1]
A rotation detector that detects the rotational motion of a rotating body using one power generation sensor,
The power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect and a coil wound around the magnetic wire,
The magnetic wires are arranged in a radial direction of the rotor,
the rotor includes a support made of a soft magnetic material and a plurality of magnetic field generating sources attached to the support at equal intervals in a circumferential direction;
Each of the plurality of magnetic field generation sources has a pair of N and S poles, a magnetization direction is parallel to a rotation axis direction of the rotating body, and the magnetization directions of two adjacent magnetic field generation sources are different,
an outer diameter of a rotation locus of the plurality of magnetic field generating sources is larger than a length of the magnetic wire, and when the magnetic field generating sources approach the magnetic wire, the magnetic field generating sources face in a rotation axis direction at least a part of a region of the magnetic wire from an axial center portion to a first axial end portion;
The attachment surface of the magnetic field generating source to the support body, which is adjacent to the magnetic wire, is on the axial second end side of the magnetic wire.
a direction from a mounting surface of the magnetic field source to the support body adjacent to the magnetic wire toward the magnetic field source is the same as a direction from the second axial end to the first axial end of the magnetic wire;
Rotation detector.
[Appendix 2]
2. The rotation detector of claim 1, wherein the support has a radially protruding flange.
[Appendix 3]
2. The rotation detector of claim 1, wherein the magnetic wire is arranged to intersect with the rotation axis of the rotating body.
[Appendix 4]
2. The rotation detector of claim 1, wherein the multiple magnetic field sources are multiple magnets of the same shape.
[Appendix 5]
2. The rotation detector according to claim 1, wherein the plurality of magnetic field generating sources are a single magnet formed by magnetizing a ring-shaped hard magnetic body with multiple poles.
[Appendix 6]
a magnetic sensor that detects a magnetic field from the magnetic field generation source when a signal is output from the power generation sensor;
a circuit for determining a rotation speed and a rotation direction of the rotating body based on signals output by the power generation sensor and the magnetic sensor.
[Appendix 7]
7. The rotation detector according to claim 6, wherein the power generation sensor, the magnetic sensor, and the circuit are mounted on the same substrate.

Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and various modifications and changes are possible based on the technical concept of the present invention.

100, 200, 200-1, 300, 400, 400-1, 400-2 Rotation detector 110, 210, 210-1, 310, 410, 410-1 Rotating body 111, 211, 211-1, 311, 411, 411-1 Support 112 Magnetic field generating source 120 Power generation sensor 121 Magnetic wire 122 Coil 211a, 211-1a Flange portion 440, 441 Magnetic sensor 500 Substrate 600 Signal processing circuit 700 Connector

Claims (7)

A rotation detector that detects the rotational motion of a rotating body using one power generation sensor,
The power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect and a coil wound around the magnetic wire,
The magnetic wires are arranged in a radial direction of the rotor,
the rotor includes a support made of a soft magnetic material and a plurality of magnetic field generating sources attached to the support at equal intervals in a circumferential direction;
Each of the plurality of magnetic field generation sources has a pair of N and S poles, a magnetization direction is parallel to a rotation axis direction of the rotating body, and the magnetization directions of two adjacent magnetic field generation sources are different,
an outer diameter of a rotation locus of the plurality of magnetic field generating sources is larger than a length of the magnetic wire, and when the magnetic field generating sources approach the magnetic wire, the magnetic field generating sources face in a rotation axis direction at least a part of a region of the magnetic wire from an axial center portion to a first axial end portion;
The attachment surface of the magnetic field source to the support body, which is adjacent to the magnetic wire, is on the second axial end side of the magnetic wire;
a direction from a mounting surface of the magnetic field source to the support body adjacent to the magnetic wire toward the magnetic field source is the same as a direction from the second axial end to the first axial end of the magnetic wire;
Rotation detector. The rotation detector according to claim 1, wherein the support has a flange portion protruding in the radial direction. The rotation detector according to claim 1, wherein the magnetic wire is arranged to intersect with the rotation axis of the rotating body. The rotation detector of claim 1, wherein the multiple magnetic field generating sources are multiple magnets of the same shape. The rotation detector according to claim 1, wherein the multiple magnetic field generating sources are a single magnet made of a ring-shaped hard magnetic material magnetized with multiple poles. a magnetic sensor that detects a magnetic field from the magnetic field generation source when a signal is output from the power generation sensor;
The rotation detector according to claim 1 , further comprising: a circuit for determining a rotation speed and a rotation direction of the rotating body based on signals output by the power generation sensor and the magnetic sensor. The rotation detector according to claim 6, in which the power generation sensor, the magnetic sensor, and the circuit are mounted on the same board.

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