Position detector

Abstract

To provide a position detector with which the width of the detector in the direction of movement has been reduced using a single power generation sensor and a plurality of magnetic field generation sources.SOLUTION: A position detector 100 for detecting the position of a moving body 110 that moves linearly and having magnetic field generation sources ME1-ME6 comprises a single power generation sensor 120 and at least one sensor element 130. The power generation sensor includes a magnetic wire that exhibits a giant Barkhausen effect and a coil wound around the magnetic wire, the axial magnetic field of the power generation sensor being an alternating magnetic field that alternates in accordance with the positional relationship between the magnetic field generation sources and the power generation sensor. The power generation sensor outputs a pulse voltage once in one cycle of magnetic field change depending on the direction of the linear movement. The sensor element outputs an identification signal to identify whether the magnetic field change cycle at the time the pulse voltage is outputted is an odd-number cycle or an even-number cycle. The position of the moving body is detected on the basis of the polarity of the pulse voltage and the identification signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a detector for detecting the position of a moving object by using a ferromagnetic element that exhibits the large Barkhausen effect. [Background technology]

[0002] 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 if it is generated, it is very small.

[0003] 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 that there is no chattering. For this reason, this magnetic wire is also used in position detectors in combination 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.

[0004] 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 used as the moving body, and the magnetic field applied to the power generating sensor changes depending on the positional relationship between the magnet (moving body) and the power generating sensor, making it possible to detect the movement of the moving body. However, when a single power generation sensor is used, it is usually not possible to identify the direction of motion of a moving object when the direction of motion changes. As shown in Fig. 1 of Patent Document 1, the direction of motion can be identified by using multiple power generation sensors, but this leads to an increase in the size and cost of the detector. Patent Document 2 describes the use of a single power generation sensor and another sensor element that is not a power generation sensor. The document further describes the use of a single magnet (two poles) and the use of multiple magnets (multiple poles) to improve resolution. Also, Figure 1 of Patent Document 3 is an example of a structure for detection using a single magnet (Figure 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. However, a single magnet cannot detect linear motion. Also, because the power generation sensor and magnet are placed at the center of the rotating shaft, a rotational motion detector with a hollow shaft structure cannot be realized. An example of a structure for detecting linear motion using multiple magnets is shown in Figure 3 of Patent Document 4. In this structure, the power generation sensor is arranged at a right angle to the direction of magnet motion, which makes the detector wider. Examples of the structure of a detector for the rotational motion of a hollow shaft are shown in Figures 1, 2, and 6 of Patent Document 4. In Figures 2 and 6, the power generation sensor is arranged perpendicular to the direction of motion, just like in Figure 3, and in Figure 2 the magnet and power generation sensor face each other on the outer periphery, while in Figure 6 they face each other on the top surface. In Figure 2, the power generating sensor is placed parallel to the rotation axis, which increases the thickness dimension of the detector. In Figure 6, the power generating sensor is placed normal to the rotation axis, which means that the distance between the outer and inner diameters of the detector is restricted by the length of the power generating sensor, meaning that the inner diameter cannot be made large relative to the outer diameter. In Fig. 1, the power generation sensor is placed parallel to the direction of magnet motion (tangential direction of the circumference). With the structure in Fig. 1, the power generation sensor and the pitch between the magnets must match, which creates the problem of limited freedom of design. In addition, it is difficult to realize a hollow shaft detector with a large inner diameter compared to the outer diameter in a structure in which a magnet and a power generation sensor face each other on the outer surface of a rotating body as shown in Figures 1 and 2. The main application of this type of position detector is to use it in combination with another precision position detector and synchronize their outputs to identify the number of cycles of the precision position detector's output and expand the detection range, as in Patent Document 5. Position detectors using power generating sensors have the problem that, in some cases, pulse signals that should be output are not output, and this document describes how current is passed through the coil in the power generating sensor to generate a magnetic field, and the output state is monitored to determine the magnetization direction of the magnetic wire in the power generating sensor, and missing pulse signals are corrected to properly synchronize. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5511748 [Patent Document 2] Patent No. 4712390 [Patent Document 3] U.S. Patent No. 9,528,856 [Patent Document 4] U.S. Patent No. 8,283,914 [Patent Document 5] Patent No. 5730809 Summary of the Invention [Problem to be solved by the invention]

[0006] When detecting a position, using multiple power generating sensors tends to increase the size of the detector itself, while even if a single power generating sensor is used, determining the magnetization direction of the magnetic wire in the power generating sensor may require complicated processing. The present invention aims to provide a position detector that uses a single power generating sensor and multiple magnetic field generating sources to reduce the width of the detector in the direction of movement, and in particular, in the case of a hollow shaft rotation detector, to provide a position detector with high design freedom by maximizing the inner diameter relative to the outer diameter. [Means for solving the problem]

[0007] A position detector according to the present invention has a magnetic field generating source and detects the position of a moving body undergoing linear or rotational motion, and includes a single power generating sensor and at least one sensor element. The power generating sensor has a magnetic wire that exhibits the large Barkhausen effect and a coil wound around the magnetic wire, and the magnetic field in the axial direction of the power generating sensor is an alternating magnetic field that alternates over four or more periods within a predetermined detection range depending on the positional relationship between the magnetic field generating source and the power generating sensor. The power generating sensor detects the position of the moving body undergoing linear or rotational motion. Moving Mata is the rotational motion by For one period of magnetic field change Pulse voltage One time output Whether the pulse voltage is positive or negative depends on the direction of the linear motion or the direction of the rotational motion. The sensor element outputs an identification signal for identifying whether the magnetic field change period at the time when the pulse voltage is output is an odd period or an even period. The position of the moving body is detected based on the polarity of the pulse voltage and the identification signal. Effect of the Invention

[0008] According to the present invention, a position detector can be provided in which the width of the detector in the direction of movement is reduced by using a single power generating sensor and multiple magnetic field generating sources, and in particular, in the case of a hollow shaft rotation detector, the inner diameter is maximized relative to the outer diameter, allowing for high design freedom. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a detector according to a first embodiment. [Figure 2A] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2B] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2C] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2D] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2E] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2F] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2G] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2H] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2I] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Figure 2J] 1 is an explanatory diagram showing the state of magnetization of a magnetic wire according to the position of a magnet; [Diagram 3] 1 is an explanatory diagram showing the relationship between the output of a magnetic sensor, the magnetic field in the x-axis direction of a cylindrical magnet, the state of a power generation sensor, and a count value. [Figure 4] 13 is an explanatory diagram showing the relationship between the positive / negative pulse voltage and period identification signal when a previous pulse voltage was generated, the positive / negative pulse voltage and period identification signal when a new pulse voltage was generated, and changes in the count value. FIG. [Diagram 5]FIG. 11 is an explanatory diagram showing a detector and peripheral circuits according to a second embodiment. [Figure 6] 5 is an explanatory diagram showing the state and output of a power generation sensor and the state of a segment counter. FIG. [Figure 7] FIG. 11 is an explanatory diagram showing another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the present invention will be described based on the illustrated embodiment, however, the present invention is not limited to the embodiment described below.

[0011] [First embodiment] A linear motion position detector 100 according to a first embodiment of the present invention is shown in Fig. 1. In this embodiment, four or more periods of magnetic field change are set in a predetermined detection range, and it is identified whether the current period is an even period or an odd period.

[0012] The linear motion position detector 100 includes a moving body 110, a power generation sensor 120, and a magnetic sensor 130 such as an MR sensor. The moving body 110 includes a long plate-like member 111. The longitudinal direction of the plate-like member 111 is parallel to the x-axis, the width direction is parallel to the y-axis, and the thickness direction is parallel to the z-axis. The moving body 110 performs linear motion along the longitudinal direction of the plate-like member 111. Six cylindrical magnets ME1 to ME6 for generating a magnetic field are arranged in order at equal intervals along one longitudinal direction (the left direction in FIG. 1) on the surface of plate-shaped member 111. The axial direction of each of the cylindrical magnets ME1 to ME6 is parallel to the thickness direction of plate-shaped member 111, and the magnets are magnetized so that the upper axial surface is the north pole and the lower axial surface is the south pole.

[0013] On the surface of the plate-shaped member 111, three bar magnets MS1 to MS3 are arranged in order at equal intervals along one longitudinal direction (the left direction in FIG. 1). The bar magnets MS1 to MS3 are arranged parallel to the cylindrical magnets ME1 to ME6. The longitudinal direction of the bar magnets MS1 to MS3 is parallel to the longitudinal direction of the plate-shaped member 111. The bar magnet MS1 is located at approximately the same longitudinal position as the cylindrical magnet ME2 on the plate-shaped member 111, the bar magnet MS2 is located at approximately the same longitudinal position as the cylindrical magnet ME4, and the bar magnet MS3 is located at approximately the same longitudinal position as the cylindrical magnet ME6. All of the bar magnets MS1 to MS3 are magnetized so that the first end face in the width direction (the end face on the far side of the paper in FIG. 1) is the N pole and the second end face in the width direction (the end face on the near side of the paper in FIG. 1) is the S pole.

[0014] The linear motion position detector 100 further includes a stationary body, that is, a printed circuit board 101. On the printed circuit board 101, a power generation sensor 120, a magnetic sensor 130, and a signal processing circuit (not shown) are mounted. The power generation sensor 120 includes a magnetic wire (not shown) and a coil (not shown) wound around the magnetic wire. The axial direction of the power generation sensor 120 is parallel to the longitudinal direction of the plate-like member 111. The position of the power generation sensor 120 is determined so that the cylindrical magnets ME1 to ME6 pass directly below the power generation sensor 120 when the moving body 110 moves linearly.

[0015] As an example, the magnetic wire in the power generation sensor 120 has a soft magnetic portion on the radially inner side and a hard magnetic portion on the radially outer side. When an alternating magnetic field is applied to the magnetic wire, the magnetization direction of the soft magnetic portion and the hard magnetic portion are reversed at a specific magnetic field strength. The magnetic field strength that causes the magnetization direction to be reversed is higher in the hard magnetic portion. When the magnetization directions of the soft magnetic portion and the hard magnetic portion are aligned in one axial direction, and a magnetic field in the opposite direction is applied to reverse the magnetization direction of the soft magnetic portion, the coil in the power generation sensor 120 outputs a pulsed voltage.

[0016] Furthermore, the position of the magnetic sensor 130 is determined so that the bar magnets MS1 to MS3 pass directly below the magnetic sensor 130 when the moving body 110 makes a linear motion. The magnetic sensing direction of the magnetic sensor 130 is parallel to the width direction of the plate-like member 111.

[0017] Next, the magnetization state of the magnetic wire 121 in the power generation sensor 120 associated with the forward motion of the moving body 110 (movement to the right on the paper surface of FIG. 1) will be described with reference to FIGS. 2A to 2E. Each of the cylindrical magnets ME1 to ME6, which apply a magnetic field to the magnetic wire 121, generates a radial magnetic field from the north pole to the south pole. The cylindrical magnets ME1 to ME6 generate a rightward magnetic field vector when located to the right of the center, and a leftward magnetic field vector when located to the left. Of the cylindrical magnets ME1 to ME6, only the cylindrical magnet ME1 is shown in Figures 2A to 2E. 2A to 2E, "SOFT" indicates a soft magnetic portion, and "HARD" indicates a hard magnetic portion. The arrow next to "SOFT" indicates the magnetization direction of the soft magnetic portion, and the arrow next to "HARD" indicates the magnetization direction of the hard magnetic portion. In these arrows, the black parts indicate that the magnetization state has changed from the previous figure.

[0018] 2A, the soft magnetic portion and the hard magnetic portion of the magnetic wire 121 are magnetized in the same direction (the left direction on the paper in the figure). A cylindrical magnet ME1 approaches the magnetic wire 121 from the left side. The magnetic field from the cylindrical magnet ME1 has a rightward magnetic flux component. 2B, when the magnetic field to the right of the page is strengthened by the approach of the cylindrical magnet ME1, the magnetization direction of the soft magnetic part is reversed from the left to the right of the page. At this time, a positive pulse voltage is output from the power generation sensor 120. As shown in FIG. 2C, when the cylindrical magnet ME1 approaches further and the magnetic field to the right of the page becomes stronger, the magnetization direction of the hard magnetic part is reversed from left to right. As a result, the magnetization directions of the soft magnetic part and the hard magnetic part are aligned. Since the magnetization reversal energy of the hard magnetic part is small, the power generation sensor 120 does not output a voltage, or if it does output a voltage, the level is small. This figure shows that the magnetic wire 121 is set to a state ready to output a negative polarity pulse voltage. FIG. 2D shows the state where the cylindrical magnet ME1 passes under the axial center of the magnetic wire 121. The part of the magnetic wire 121 from the axial center to the right side of the paper remains magnetized to the right side of the paper. In contrast, the part of the magnetic wire 121 from the axial center to the left side of the paper has the magnetization direction reversed to the left side of the paper in both the soft magnetic part and the hard magnetic part. However, as the cylindrical magnet ME1 passes, the magnetization is gradually reversed from the left end of the magnetic wire 121, so no voltage is output from the power generation sensor 120. The output preparation state of the negative polarity pulse voltage shown in FIG. 2C is reset. As shown in FIG. 2E, the cylindrical magnet ME1 passes near the right end of the magnetic wire 121 to the right. The magnetization directions of the soft magnetic part and the hard magnetic part of the magnetic wire 121 are aligned to the left of the paper. This figure shows that the magnetic wire 121 is set to a state in which it is ready to output a positive polarity pulse voltage. In other words, the magnetization state is the same as in FIG. 2A.

[0019] In this manner, a positive pulse voltage is output once each time one cylindrical magnet passes near the power generation sensor 120 due to the forward motion of the moving body 110. As shown in Fig. 1, when the six cylindrical magnets ME1 to ME6 pass near the power generation sensor 120 in order, the state transitions shown in Figs. 2A to 2E are repeated six times.

[0020] Next, the magnetization state of the magnetic wire 121 in the power generation sensor 120 associated with the backward movement of the moving body 110 (movement to the left in the plane of FIG. 1) will be described with reference to FIG. 2F to 2J. Of the cylindrical magnets ME1 to ME6, only the cylindrical magnet ME6 is shown in FIG. First, as shown in Fig. 2F, the soft magnetic portion and the hard magnetic portion of the magnetic wire 121 are magnetized in the same direction (toward the right in the figure). A cylindrical magnet ME6 approaches the magnetic wire 121 from the right side of the figure. The magnetic field from the cylindrical magnet ME6 has a magnetic flux component in the left direction. 2G, when the magnetic field to the left of the drawing increases due to the approach of the cylindrical magnet ME6, the magnetization direction of the soft magnetic portion is reversed from the right to the left of the drawing. At this time, a negative pulse voltage is output from the power generation sensor 120. As shown in FIG. 2H, when the cylindrical magnet ME6 approaches further and the magnetic field to the left of the page becomes stronger, the magnetization direction of the hard magnetic portion reverses from right to left. As a result, the magnetization directions of the soft magnetic portion and the hard magnetic portion become aligned. Because the energy required for magnetization reversal of the hard magnetic portion is small, no voltage is output from the power generation sensor 120, or even if a voltage is output, the level is small. This figure shows that the magnetic wire 121 is set to a state in which it is ready to output a positive polarity pulse voltage. FIG. 2I shows the state where the cylindrical magnet ME6 passes under the axial center of the magnetic wire 121. The portion of the magnetic wire 121 from the axial center to the left of the paper remains magnetized to the left of the paper. In contrast, the portion of the magnetic wire 121 from the axial center to the right of the paper reverses its magnetization direction to the right of the paper in both the soft magnetic portion and the hard magnetic portion. However, as the cylindrical magnet ME6 passes, the magnetization gradually reverses from the right end of the magnetic wire 121, so no voltage is output from the power generation sensor 120. The output preparation state of the positive polarity pulse voltage shown in FIG. 2H is reset. As shown in FIG. 2J, the cylindrical magnet ME6 passes near the left end of the magnetic wire 121 to the left. The magnetization directions of the soft magnetic part and the hard magnetic part of the magnetic wire 121 are aligned to the right of the paper. This figure shows that the magnetic wire 121 is set to a state ready for output of a negative polarity pulse voltage. In other words, the magnetization state is the same as that of FIG. 2F.

[0021] In this manner, due to the backward movement of the moving body 110, a negative pulse voltage is output once each time one cylindrical magnet passes near the power generation sensor 120. As shown in Fig. 1, when the six cylindrical magnets ME6 to ME1 pass near the power generation sensor 120 in order, the state transitions shown in Figs. 2F to 2J are repeated six times.

[0022] In this way, the magnetic field in the axial direction of the power generation sensor 120 is an alternating magnetic field that alternates over six periods within a predetermined detection range depending on the positional relationship between the cylindrical magnets ME1 to ME6 and the power generation sensor 120. The predetermined detection range is the entire length of the plate-shaped member 111 in the longitudinal direction.

[0023] Next, the relationship between the output of the magnetic sensor 130, the magnetic field in the x-axis direction of the cylindrical magnet (the longitudinal direction of the plate-like member 111), the state of the power generation sensor 120, and the count value will be described with reference to Fig. 3. The magnetic sensor 130 detects the magnetic field strength in the magnetic sensing direction, but does not detect the polarity of the magnetic field. Its magnetic field detection sensitivity is higher than that of a typical Hall element, and a high-resistance element can reduce power consumption to about 1 / 10. 1, the magnetic sensing direction of magnetic sensor 130 is the y-axis direction (the width direction of plate-like member 111), and bar magnets MS1-MS3 are magnetized in the y-axis direction. Magnetic sensor 130 outputs an identification output of 1 when any of the bar magnets is positioned so as to face the bottom surface of magnetic sensor 130, and outputs an identification output of 0 otherwise. The lengths of the bar magnets MS1 to MS3 are set so as to cover the left and right pulse voltage generation points of the cylindrical magnets ME2, ME4, and ME6 (from the positive pulse voltage generation point T_P to the negative pulse voltage generation point T_N). In addition, in FIG. 3, T_P0 and T_P1 are respectively the outputs 0 and 1 of the magnetic sensor 130 added after the positive pulse voltage generation point T_P. The arrows are colored differently for identification. The same applies to T_N, which represents the negative pulse voltage generation point.

[0024] As described with reference to Figures 2A-2E and Figures 2F-2J, a positive pulse voltage is obtained each time a cylindrical magnet passes during forward motion, and a negative pulse voltage is obtained during backward motion. When a positive pulse voltage is obtained, the position count value is counted up, and when a negative pulse voltage is obtained, the position count value is counted down. However, when the direction of motion is reversed, the expected pulse voltage may not be output or an excessive pulse voltage may be output depending on the reversed position, which requires the count value to be corrected. The method of correcting the count value will be described with reference to Fig. 3. The black circles in the figure indicate points at which the pulse voltage is ready to be output (positions at which the stabilizing magnetic field is reached). As an example, consider the state immediately after forward motion, when the count value is incremented to "1," "2," and "3" as each of the cylindrical magnets ME1 to ME3 approaches, and then a positive pulse voltage P1 is generated by the magnetic field generated by the cylindrical magnet ME4, and the count value is incremented to "4." The following four patterns of pulse voltages may be generated next.

[0025] Pattern 1: T_P1 → T_P0 (code CA1 in the figure) If the forward motion continues, it passes through S_P (output preparation state of positive polarity pulse voltage) of cylindrical magnet ME4, and enters the output preparation state of positive polarity pulse voltage. After that, cylindrical magnet ME5 approaches, and positive polarity pulse voltage T_P0 is generated. In this case, the counter value is corrected by counting up by 1 (+1).

[0026] Pattern 2: T_P1 → T_N0 (code CA2 in the figure) Between S_N of the cylindrical magnet ME4 (ready to output a negative pulse voltage) and T_P0 of the cylindrical magnet ME5, the direction of motion shifts to the backward direction. After that, it passes S_N of the cylindrical magnet ME4 and becomes ready to output a negative pulse voltage. Then, the cylindrical magnet ME3 approaches and a negative pulse voltage T_N0 is generated. In this case, the counter value is corrected by counting down by 1 (-1).

[0027] Pattern 3: T_P1 → T_N1 (code CA3 in the figure) Before the state becomes ready to output a negative polarity pulse voltage (S_N), the direction of motion changes to backward, and cylindrical magnet ME3 approaches. Although it reaches the output position for a negative polarity pulse voltage T_N0, the negative polarity pulse voltage is not output. It passes through the reset state (RESET) and the state ready to output a negative polarity pulse voltage (S_N), and then becomes ready to output a negative polarity pulse voltage. Cylindrical magnet ME2 approaches, and a negative polarity pulse voltage T_N1 is generated. In this case, the counter value is corrected to count down by 2 (−2).

[0028] Pattern 4: T_P1 → T_P1 (code CA4 in the figure) Before reaching the state (S_N) where the cylindrical magnet ME4 is ready to output a negative pulse voltage, the direction of motion changes to retreat, and the cylindrical magnet ME3 approaches. Although it reaches the output position of the negative pulse voltage T_N0, the negative pulse voltage is not output. It continues to retreat, and between the state (S_P) where the cylindrical magnet ME3 is ready to output a positive pulse voltage and T_N1 of the cylindrical magnet ME2, the direction of motion reverses again and it moves forward. It passes S_P of the cylindrical magnet ME3, enters a state where it is ready to output a positive pulse voltage, the cylindrical magnet ME4 approaches again, and a positive pulse voltage T_P1 is generated. In this case, the counter value is not corrected (+0) because the position is the same after all.

[0029] Similarly, FIG. 4 shows the relationship between the positive / negative sign and period discrimination signal of the previous pulse voltage generation, the positive / negative sign and period discrimination signal of the new pulse voltage, and the correction amount of the count value.

[0030] According to this embodiment, the magnetic wire 121 is arranged parallel to the direction of motion of the moving body 110. When a magnetic field is applied locally to one of the longitudinal ends of the magnetic wire 121 depending on the position of the moving body 110, a reversal magnetic field propagates from one of the longitudinal ends to the other, and a single magnetic domain is formed throughout the magnetic wire (FIGS. 2C, 2E, 2H, and 2J). Through the formation of such a single magnetic domain, the magnetic wire can exhibit the large Barkhausen effect. Furthermore, since the magnetic wire 121 is arranged parallel to the direction of movement of the moving body 110 (x-axis direction in Figure 1), the dimensions of the detector in the direction perpendicular to the direction of movement can be made smaller than when the magnetic wire is arranged in a direction perpendicular to the direction of movement of the moving body (y-axis direction in Figure 1).

[0031] [Second embodiment] Fig. 5 shows a precision multi-rotation absolute angle detection system including a rotational position detector 200 according to this embodiment. This is an application of the linear motion position detector 100 shown in Fig. 1 to rotation detection. Combining the rotational position detector 200 with a precision absolute angle detector 310 configures a precision multi-rotation absolute angle detection system that can retain position information even when the power is cut off. The precision multi-rotation absolute angle detection system can also be called a position detector system.

[0032] The rotational position detector 200 includes a rotating body 210. The rotating body 210 includes a ring-shaped member 211, and rotates about an axis 211a passing through the center of the ring-shaped member 211. Four cylindrical magnets ME10 to ME13 for generating a magnetic field are arranged in order on the outer circumferential edge of the surface of the ring-shaped member 211 at equal intervals along one circumferential direction (counterclockwise CCW in FIG. 5) and at equal distances from the rotation axis. Each of the four cylindrical magnets ME10 to ME13 has an axial direction parallel to the rotation axis, and is magnetized so that the axial upper surface is the N pole and the axial lower surface is the S pole.

[0033] Furthermore, in the ring-shaped member 211, a bar magnet MS11 is disposed between the cylindrical magnet ME10 and the rotation shaft 211a, and a bar magnet MS12 is disposed between the cylindrical magnet ME12 and the rotation shaft 211a. The bar magnets MS11 and MS12 are curved along the inner peripheral edge of the ring-shaped member 211, and are equal in distance to the rotation shaft 211a. The bar magnets MS11 and MS12 are magnets for periodic identification. Bar magnet MS11 is disposed so that its longitudinal direction intersects with a line passing through rotation axis 211a and the center of cylindrical magnet ME10. The bar magnet MS12 is disposed so that its longitudinal direction intersects with a straight line passing through the rotation axis 211a and the center of the cylindrical magnet ME12. The magnetization direction of both the bar magnets MS11 and MS12 is parallel to the rotation axis 211a. The bar magnets MS11 and MS12 have the same polarity on one side in the direction of the rotation axis. For example, the bar magnets MS11 and MS12 both have N poles on the front side of the paper in FIG. 5.

[0034] The power generation sensor 220 includes a magnetic wire 221 and a coil 222 wound around the magnetic wire 221. The axial direction of the magnetic wire 221 is perpendicular to a line connecting a point 211b on the outer circumference of the ring-shaped member 211 and the rotation axis 211a, and is arranged parallel to a tangent line passing through the point 211b (or a tangent line passing through a point on the circular orbit described by the cylindrical magnet). The position of the power generation sensor 220 is determined so that the cylindrical magnets ME10 to ME13 pass below the power generation sensor 220 when the rotating body 210 rotates.

[0035] The magnetic sensor 230 is disposed so as to generally face the power generation sensor 220 across the rotation axis 211a. The position of the magnetic sensor 230 is determined so that the bar magnets MS11 and MS12 pass below the magnetic sensor 230 when the rotor 210 rotates. As an example, the magnetic sensing direction of the magnetic sensor 230 is parallel to the rotation axis 211a. The magnetic sensor 230 outputs 1 when the bar magnet MS11 or MS12 is located below the magnetic sensor 230, and outputs 0 otherwise.

[0036] In this way, the magnetic field in the axial direction of the power generation sensor 220 is an alternating magnetic field that alternates over four periods within a predetermined detection range depending on the positional relationship between the cylindrical magnets ME10 to ME13 and the power generation sensor 220. The predetermined detection range is one rotation of the rotor 210.

[0037] This system further includes a precision absolute angle sensor 310, a power supply circuit 610, a calculation unit 620, and a non-volatile memory 630. The power supply circuit 610 receives power from an external power supply and supplies power to the precision absolute angle sensor 310, the calculation unit 620, and the non-volatile memory 630. The precision absolute angle sensor 310 is mechanically connected to the rotating body 210, and sends precision angle data in the range of 0 to 360° to the calculation unit 620. The calculation unit 620 exchanges multiple rotation count data of the rotating body 210 with the non-volatile memory 630, and exchanges multiple rotation precise angle data with the outside.

[0038] The precision absolute angle sensor 310 is a so-called one-revolution absolute encoder. As an example, the precision absolute angle sensor 310 detects a displacement amount equivalent to an even multiple of the magnetic field change period of the rotational position detector 200 that is equal to or greater than four periods as a detection period, and detects the displacement as an absolute value of 4 bits or more during the detection period. The rotational position detector 200 may be referred to as a first position detector, and the precision absolute angle sensor 310 may be referred to as a second position detector.

[0039] The system further includes a full-wave rectifier voltage regulator 410 , a first signal evaluation circuit 411 , a second signal evaluation circuit 412 , and a counter logic circuit 510 . Both ends of the coil 222 in the power generation sensor 220 are connected to a full-wave rectifier voltage regulator 410 and a first signal evaluation circuit 411 . The magnetic sensor 230 is connected to a second signal evaluation circuit 412 . The full-wave rectifier voltage regulator 410 receives the pulse power generated in the coil 222 , and provides power to the first signal evaluation circuit 411 , the second signal evaluation circuit 412 , the counter logic circuit 510 , and the non-volatile memory 630 . The first signal evaluation circuit 411 evaluates the pulse signal received from the coil 222 and outputs the evaluation result to the counter logic circuit 510 . The second signal evaluation circuit 412 evaluates the detection signal received from the magnetic sensor 230 and outputs the evaluation result to the counter logic circuit 510 . The counter logic circuit 510 exchanges data with the non-volatile memory 630 .

[0040] The operating principle is basically the same as the linear motion mechanism shown in Figure 1. Figure 6 shows the state and output of the power generation sensor shown in Figure 3 changed to a rotational system, with the state of the segment counter added. The segment counter is made up of four segments, "0" to "3," and due to hysteresis, the switching points for the counts for clockwise rotation (CW rotation) and counterclockwise rotation (CCW rotation) are different. The inner circle CR1 shows the segment counter for clockwise rotation, and the outer circle CR2 shows the state of the segment counter for counterclockwise rotation. The counter counts 4 for one rotation, and continues counting 4, 5, 6, ... even if it exceeds one rotation. In principle, it is possible to count an infinite number of rotations, but due to the configuration of the processing circuit, it is necessary to make it finite. For example, if the maximum count value is 16 bits, or 65536, it is possible to measure rotation angles up to 16384 rotations.

[0041] When the angle information from 0 to 360° from the precision absolute angle sensor 310 and the count value of the power generation sensor 220 are combined, the count value is used only to identify the shaft rotation speed n. The shaft rotation speed n is calculated by the following formula. n=INT((90a-θ abs +180) / 360) (1) where a is the count value and θ absis the detection value of the precision absolute angle sensor 310. "INT()" is a function that returns the maximum integer not exceeding the argument.

[0042] In addition, the precision angle θ com The integration into is given by the following formula: θ com =θ abs +360n (2) Where θ com is the integrated angle detection value, and n is the shaft rotation speed.

[0043] From the formula (1), the angle 90a calculated from the count value a and the detection value θ of the precision absolute angle sensor 310 are abs If the error in the difference with is less than 180°, it can be seen that the shaft rotation speed n can be obtained correctly. In Figure 6, consider the moment immediately after the count reaches 0 due to the pulse voltage of T_P0 of cylindrical magnet ME0 during clockwise rotation. The range in which it can move without outputting the next pulse voltage is up to T_P1 of cylindrical magnet ME1 if it continues to rotate clockwise (arrow AR11), and up to T_N0 of cylindrical magnet ME2 if it starts to rotate counterclockwise (arrow AR12). In either case, the next pulse voltage is output before it rotates 180 degrees or more. Next, consider the moment immediately after the count reaches 0 due to the pulse voltage of T_N0 of cylindrical magnet ME0 during counterclockwise rotation. The range in which it can move without outputting the next pulse voltage is up to T_N1 of cylindrical magnet ME3 (arrow AR21) if it continues to rotate counterclockwise, and up to T_P0 of cylindrical magnet ME2 if it starts to rotate clockwise (arrow AR22). In either case, the next pulse voltage is output before it rotates 180 degrees or more. From the above, it can be seen that if the center of the cylindrical magnet ME0 is taken as the reference point for count 0, the rotation angle from that reference point until the next pulse voltage is output is less than ±180°. Therefore, it is possible to combine the angle information of the precision absolute angle sensor 310 and the multiple rotation count value of the power generation sensor 220 without correcting the count value. Therefore, there is no need to perform the magnetization direction discrimination described in Patent Document 5 every time the external power source is turned on. There is also no need to correct the count value.

[0044] According to this embodiment, the magnetic wire 221 is arranged parallel to a tangent line passing through the point 211b (FIG. 5). When a magnetic field is applied locally to one of the longitudinal ends of the magnetic wire 221 according to the rotational position of the rotor 210, a reversal magnetic field propagates from one of the longitudinal ends to the other, and a single magnetic domain is formed throughout the magnetic wire. Through the formation of such a single magnetic domain, the magnetic wire can exhibit the large Barkhausen effect. Furthermore, according to this embodiment, the difference between the outer diameter and the inner diameter of the rotor (the width of the ring) can be made smaller than when the magnetic wire is arranged in the radial direction of the rotor. In other words, the radial dimension of the hollow portion 212 can be made large without changing the outer diameter of the ring-shaped member 211.

[0045] [Other Examples] FIG. 7(a) again shows cylindrical magnet ME1. Figure 7(b) shows a magnetic field source ME1a, which is composed of two magnets MG11 and MG12 arranged with the same poles facing each other. The cylindrical magnet ME1 can be replaced with the magnetic field source ME1a. Similar replacements can be made for other cylindrical magnets and bar magnets. As shown in FIG. 7(c), a yoke YK is disposed on the top surface of a plate-shaped magnet MG21. Three protrusions YK1 to YK3 are provided on the top surface of the yoke YK. The protrusions YK1 to YK3 serve as magnetic field generating sources ME1b to ME3b, respectively. In other words, the cylindrical magnets ME1 to ME3 can be replaced with magnetic field generating sources ME1b to ME3b. The number of protrusions can be changed. A bar magnet can also be formed by the protrusions of the yoke in the same manner.

[0046] Other embodiments for periodicity identification are described below. In the embodiment described above, a long bar magnet is used as the identification magnet, and the pulse voltage generation points at both ends of the power generation sensor can be covered by one MR element (magnetic sensor). However, the present invention is not limited to this, and it is also possible to use a relatively small (short) magnet and cover the two pulse voltage generation points with two MR sensors. Alternatively, it is possible to use a small (short) magnet and combine a yoke with a magnetic sensor to collect a wide range of magnetic fields, thereby covering two pulse voltage generation points with a single MR element. In addition, the magnetic field generating magnet (ME) and the identification magnet (MS) are separated in order to explain their functions, but identification is also possible by using only the magnetic field generating magnet (ME) without using a separate identification magnet, and by changing the shape or magnetic strength of the odd-numbered magnets and the even-numbered magnets. The means of identification is not limited to magnetism, and various detection means such as a mechanical contact switch, electrostatic capacitance, and electromagnetic induction can be used.

[0047] Other examples of the detection positions of the power generation sensor, the magnetic sensor, and the absolute detector will be described below. In the embodiment of the present invention, the pulse voltage is counted once per cycle after distinguishing between odd and even cycles, so it is effective even if deceleration or change in direction of movement is performed via a transmission mechanism. The installation and detection positions of the power generation sensor, magnetic field generation source, period identification sensor, and absolute detector described above are merely examples and are not limiting.

[0048] Example: Ball screw drive 1 This is the case when a ball screw is driven by a motor. A disk is attached to the motor shaft, and two magnets are installed to generate a magnetic field. The power generation sensor outputs two pulses per rotation. The magnetic force strength of the two magnetic field generating magnets is different, and the magnetic field strength is measured by the MR sensor, allowing the two magnets to be identified. An absolute linear scale is provided on the ball screw. The detection cycle is twice the lead pitch of the ball screw.

[0049] Example: Ball screw drive 2 A disk is attached to the motor shaft, and one magnet is installed to generate a magnetic field. The power generation sensor outputs one pulse per rotation. An MR sensor is installed on the moving part of the ball screw. Magnets for periodic identification are installed on the fixed part at intervals twice the lead pitch. An absolute linear scale is provided on the ball screw. The detection cycle is four times the lead pitch of the ball screw.

[0050] Regarding the embodiments described above, the following supplementary notes are disclosed. [Appendix 1] A position detector having a magnetic field generating source and detecting a position of a moving body performing linear or rotational motion, A single power generation sensor; At least one sensor element; Equipped with The power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect and a coil wound around the magnetic wire, the magnetic field in the axial direction of the power generation sensor is an alternating magnetic field that alternates over four or more periods within a predetermined detection range in accordance with a positional relationship between the magnetic field generation source and the power generation sensor, the power generation sensor outputs a pulse voltage of positive or negative polarity once per one period of magnetic field change depending on the direction of the linear motion or the direction of the rotational motion; the sensor element outputs an identification signal for identifying whether a magnetic field change period at the time when the pulse voltage is output is an odd number period or an even number period; a position of the moving body is detected based on the polarity of the pulse voltage and the identification signal; Position detector. [Appendix 2] As the moving body moves, the magnetic field source passes near the power generation sensor, the axial direction of the power generation sensor is parallel to the direction of the linear motion or parallel to a tangent passing through a certain contact point on a circular orbit described by the magnetic field generation source due to the rotational motion; The magnetic field generating source generates a magnetic field radially from a center portion of the magnetic field generating source, When there are a plurality of magnetic field generating sources, all of the magnetic field generating sources generate magnetic fields in the same direction. 2. The position detection device of claim 1. [Appendix 3] 3. The position detector of claim 2, wherein the multiple magnetic field generating sources are either multiple magnets or a combination of a single magnet and a magnetic field inducing yoke having multiple protrusions. [Appendix 4] 4. The position detector according to claim 1, wherein the sensor element is a magnetoresistive element. [Appendix 5] A first position detector is provided with the position detector according to any one of claims 1 to 4, and a second position detector is provided that is operated by an external power source and detects the position of the moving body; the first detector operates independently of the external power source; the second position detector detects a displacement amount corresponding to an even multiple of an even number of periods, which is equal to or greater than four periods, of a magnetic field change period of the first position detector as a detection period, and detects a displacement in an absolute value during the detection period; When the external power source is supplied, a detection value of the first position detector and a detection value of the second position detector are integrated to perform position detection having a higher resolution than the first position detector and a wider detection range than the detection cycle of the second position detector. Position detector system.

[0051] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made based on the technical concept of the present invention. [Explanation of symbols]

[0052] 100, 200 detector 110, 210 moving body 120, 220 Power generation sensor 121, 221 Magnetic wire 222 Coil 130, 230 Magnetic sensor

Claims

1. A position detector having a magnetic field generating source and detecting a position of a moving body performing linear or rotational motion, A single power generation sensor; At least one sensor element; Equipped with The power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect and a coil wound around the magnetic wire, the magnetic field in the axial direction of the power generation sensor is an alternating magnetic field that alternates over four or more periods within a predetermined detection range depending on the positional relationship between the magnetic field generation source and the power generation sensor, the power generation sensor outputs a pulse voltage once for one period of magnetic field change caused by the linear motion or the rotational motion, and whether the pulse voltage is positive or negative is determined depending on the direction of the linear motion or the direction of the rotational motion; the sensor element outputs an identification signal for identifying whether a magnetic field change period at the time when the pulse voltage is output is an odd number period or an even number period; The position of the moving body is detected based on the polarity of the pulse voltage and the identification signal. Position detector.

2. With the movement of the moving body, at least a part of the magnetic field source passes through the power generation sensor while facing the power generation sensor; the axial direction of the power generation sensor is parallel to the direction of the linear motion or parallel to a tangent passing through a certain contact point on a circular orbit described by the magnetic field generation source due to the rotational motion; The magnetic field generating source generates a magnetic field radially from a center portion of the magnetic field generating source, When there are a plurality of magnetic field generating sources, all of the magnetic field generating sources generate magnetic fields in the same direction. The position detection device according to claim 1.

3. 3. The position detector of claim 2, wherein the plurality of magnetic field generating sources are either a plurality of magnets or a combination of a single magnet and a magnetic field inducing yoke having multiple lobes.

4. The position detector according to any one of claims 1 to 3, wherein the sensor elements are magnetoresistive elements.

5. A position detector according to any one of claims 1 to 4 is provided as a first position detector, and a second position detector is provided which is operated by an external power source and detects the position of the moving body, the first position detector operates without being dependent on the external power source; the second position detector detects a displacement amount corresponding to an even multiple of an even number of periods, which is equal to or greater than four periods, of a magnetic field change period of the first position detector as a detection period, and detects a displacement in an absolute value during the detection period; when the external power source is supplied, a detection value of the first position detector and a detection value of the second position detector are integrated to perform position detection having a higher resolution than the first position detector and a wider detection range than the detection cycle of the second position detector. Position detector system.

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