JP2022187941A - Position detector - Google Patents

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

The present invention relates to a detector that detects the position of a moving object using ferromagnetic elements exhibiting a large Barkhausen effect.

Magnetic wires with the large Barkhausen effect (large Barkhausen jump) are known as Wiegand wires or pulse wires. This magnetic wire has a core and a skin that surrounds the core. One of the core and skin is a soft (soft magnetic) layer in which the magnetization direction can be reversed even with a weak magnetic field, and the other of the core and skin is a hard (hard magnetic) layer that does not reverse the magnetization direction unless a strong magnetic field is applied. layer.
When the hard and soft layers are magnetized in the same direction along the axial direction of the wire, the external magnetic field strength in the direction opposite to the magnetization direction increases until it reaches a magnetic field strength that reverses the magnetization direction of the soft layer. Then, the magnetization direction of the soft layer is reversed. At this time, the large Barkhausen effect appears, 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 reverses is referred to herein as the "operating field". Also, the magnetic wire and the coil are collectively called a power generation sensor.
When the above-mentioned external magnetic field strength further increases and reaches the magnetic field strength at which the magnetization direction of the hard layer is reversed, the magnetization direction of the hard layer is reversed. The magnetic field intensity at which the magnetization direction of the hard layer is reversed is referred to herein as the "stabilizing magnetic field".
In order for the large Barkhausen effect to occur, it is necessary that the magnetization direction of only the soft layer is reversed on the premise that the magnetization directions of the hard layer and the soft layer are the same. Even if the magnetization directions of the hard layer and the soft layer do not match, even if the magnetization direction of only the soft layer is reversed, no pulse signal is generated or, if generated, the pulse signal is very small.

The output voltage from this magnetic wire is constant regardless of the changing speed of the magnetic field, and has a hysteresis characteristic with respect to the input magnetic field, so that there is no chattering. Therefore, this magnetic wire is also used for a position detector etc. in combination with a magnet and a counter circuit. In addition, the output energy of the magnetic wire can be used to operate peripheral circuits without supplying external power.

When an alternating magnetic field is applied to the power generation sensor, a total of two pulse signals, one positive pulse signal and one negative pulse signal, are generated for one cycle. The motion of the moving body can be detected by using the magnet as the magnetic field generating source as the moving body and changing the magnetic field applied to the power generation sensor according to the positional relationship between the magnet, which is the moving body, and the power generation sensor. .
However, using only a single power generation sensor normally fails to identify the direction of motion when the direction of motion of the moving body changes. As can be seen in FIG. 1 of US Pat. No. 5,700,000, multiple power generation sensors can be used to identify the direction of motion, but increase 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 (multipole) to improve the resolution.
Further, FIG. 1 of Patent Document 3 can be cited as a structural example of detection by a single magnet (FIG. 2 of Patent Document 2). The structure in which the two-pole magnet and the power generation sensor face each other is suitable for miniaturization because the diameter can be reduced to the entire length of the power generation sensor. However, a single magnet cannot detect linear motion. In addition, since the power generation sensor and the magnet are arranged at the center of the rotation shaft, it is not possible to realize a rotary motion detector with a hollow shaft structure.
FIG. 3 of Patent Literature 4 is an example of a structure for detecting linear motion using a plurality of magnets. In this structure, the power generation sensor is arranged in a direction perpendicular to the motion direction of the magnet, so the width of the detector is increased.
Figs. 1, 2, and 6 of Patent Document 4 are cited as structural examples of a detector for rotational motion of a hollow shaft. In FIGS. 2 and 6, the power generation sensors are arranged perpendicular to the direction of movement, as in FIG.
In FIG. 2, the power generation sensor is arranged in the direction parallel to the rotation axis, so the dimension in the thickness direction of the detector is large, and in FIG. There is a problem that the distance between the outer diameter and the inner diameter of is restricted by the length of the power generation sensor, and the inner diameter cannot be increased with respect to the outer diameter.
In FIG. 1, the power generation sensors are arranged parallel to the motion direction of the magnet (direction tangential to the circumference). In the case of the structure of FIG. 1, it is necessary to match the pitch between the power generation sensor and the magnet, and there is a problem that the degree of freedom in design is small.
In addition, it is difficult to realize a detector with a hollow shaft having a larger inner diameter than the outer diameter in the structure in which the magnet and the power generation sensor face each other on the outer peripheral surface of the rotating body as shown in FIGS.
The main application of this type of position detector is to use it in combination with another precision position detector as in Patent Document 5, and by synchronizing the outputs of each other, identify the periodicity of the output of the precision position detector. However, the detection range may be extended. A position detector using a power generation sensor has a problem that the pulse signal that should be output is not output in some cases. It is described that the magnetization direction of the magnetic wire in the power generation sensor is determined by monitoring, and correct synchronization is performed by correcting missing pulse signals.

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

Using a plurality of power generation sensors for position detection tends to increase the size of the detector itself. On the other hand, even with a single power generation sensor, determining the magnetization direction of the magnetic wire in the power generation sensor can be a complex process.
In the present invention, a single power generation sensor and a plurality of magnetic field generation sources are used to reduce the width of the detector in the direction of movement. is maximized and the degree of design freedom is high.

A position detector for detecting the position of a linearly or rotationally moving body having a magnetic field generating source according to the present invention includes a single power generation sensor and at least one sensor element. The power generation sensor includes a magnetic wire that exhibits a large Barkhausen effect, and a coil wound around the magnetic wire. It is an alternating magnetic field that alternates over four cycles or more within a predetermined detection range according to the positional relationship. The power generation sensor outputs a pulse voltage of positive polarity or negative polarity depending on the direction of the linear motion or the direction of the rotational motion once per magnetic field change period. The sensor element outputs an identification signal that identifies whether the 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 object is detected based on the polarity of the pulse voltage and the identification signal.

According to the present invention, a single power generation sensor and a plurality of magnetic field generation sources are used to reduce the width of the detector in the direction of movement. On the other hand, it is possible to provide a position detector with a maximized inner diameter and a high degree of design freedom.

1 is a perspective view of a detector according to a first embodiment; FIG. FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the state of magnetization of the magnetic wire according to the position of the magnet; FIG. 4 is an explanatory diagram showing the relationship between the output of the magnetic sensor, the x-axis direction magnetic field of the cylindrical magnet, the state of the power generation sensor, and the count value; FIG. 10 is an explanatory diagram showing the relationship between the positive/negative of the pulse voltage and the period identification signal at the time of previous pulse voltage generation, the positive/negative of the new pulse voltage and the period identification signal, and changes in the count value; FIG. 6 is an explanatory diagram showing a detector and peripheral circuits according to a second embodiment; FIG. 4 is an explanatory diagram showing the state and output of a power generation sensor and the state of a segment counter; It is an explanatory view showing other embodiments.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the illustrated embodiments. However, the present invention is not limited by the embodiments described below.

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

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 has an elongated plate-like member 111 . The plate member 111 has a longitudinal direction parallel to the x-axis, a width direction parallel to the y-axis, and a thickness direction parallel to the z-axis. The moving body 110 performs linear motion along the longitudinal direction of the plate member 111 .
On the surface of the plate-like member 111, six cylindrical magnets ME1 to ME6 for magnetic field generation are arranged in order along one longitudinal direction (the left direction of the paper surface of FIG. 1) at regular intervals. Each of the cylindrical magnets ME1 to ME6 has its axial direction parallel to the thickness direction of the plate-shaped member 111, and is magnetized so that its upper surface in the axial direction is the north pole and the lower surface in the axial direction is the south pole.

Further, three bar magnets MS1 to MS3 are arranged in sequence on the surface of the plate-like member 111 at equal intervals along one longitudinal direction (the left direction of the paper surface of FIG. 1). Bar magnets MS1-MS3 are arranged parallel to cylindrical magnets ME1-ME6. The longitudinal direction of bar magnets MS1 to MS3 is parallel to the longitudinal direction of plate member 111. FIG. The longitudinal position of the bar magnet MS1 is substantially the same as that of the cylindrical magnet ME2 in the plate member 111, the longitudinal position of the bar magnet MS2 is substantially the same as that of the cylindrical magnet ME4, and the bar magnet MS3 is substantially the same as the cylindrical magnet ME6. The longitudinal positions are substantially the same. Each of the bar magnets MS1 to MS3 is arranged so that the first widthwise end surface (the end surface on the far side of the paper surface of FIG. 1) is the N pole and the second widthwise end surface (the end surface on the front side of the paper surface of FIG. 1) is the S pole. magnetized.

The linear motion position detector 100 further includes a printed circuit board 101 that is a stationary body. A power generation sensor 120 , a magnetic sensor 130 and a signal processing circuit (not shown) are mounted on the printed circuit board 101 .
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 member 111 . The power generation sensor 120 is positioned so that the cylindrical magnets ME1 to ME6 pass directly below the power generation sensor 120 when the moving body 110 performs linear motion.

The magnetic wire in the power generation sensor 120 has, for example, a soft magnetic portion radially inward and a hard magnetic portion radially outward. When an alternating magnetic field is applied to the magnetic wire, the soft magnetic portion and the hard magnetic portion each reverse the magnetization direction at a specific magnetic field strength. The magnetic field intensity that causes the magnetization direction to reverse is higher in the hard magnetic portion. In a state where the magnetization directions of the soft magnetic portion and the hard magnetic portion are aligned in one axial direction, when a magnetic field in the opposite direction is applied and the magnetization direction of the soft magnetic portion is reversed, the coil in the power generation sensor 120 generates a pulse voltage. to output

Further, 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 performs linear motion. The magnetic sensing direction of the magnetic sensor 130 is parallel to the width direction of the plate member 111 .

Next, referring to FIGS. 2A to 2E, the magnetization state of the magnetic wire 121 in the power generation sensor 120 accompanying the forward motion of the moving body 110 (the rightward motion on the page of FIG. 1) will be described.
Cylindrical magnets ME1 to ME6 that apply a magnetic field to the magnetic wire 121 all generate radial magnetic fields from the N pole to the S pole. Cylindrical magnets ME1-ME6 generate rightward magnetic field vectors at positions to the right of the center, and leftward magnetic field vectors at positions to the left of the center. Of the cylindrical magnets ME1-ME6, only the cylindrical magnet ME1 is shown in FIGS. 2A-2E.
Also, in FIGS. 2A-2E, "SOFT" denotes a soft magnetic portion and "HARD" denotes a hard magnetic portion. The arrow adjacent to "SOFT" represents the magnetization direction of the soft magnetic portion, and the arrow adjacent to "HARD" represents the magnetization direction of the hard magnetic portion. In these arrows, the blackened parts indicate that the magnetization state has changed from the previous figure.

First, as shown in FIG. 2A, the soft magnetic portion and the hard magnetic portion of the magnetic wire 121 are magnetized in the same direction (to the left of the drawing). A cylindrical magnet ME1 approaches the magnetic wire 121 from the left side. The magnetic field from cylindrical magnet ME1 has a rightward magnetic flux component.
As shown in FIG. 2B, when the magnetic field in the right direction on the page is strengthened by the approach of the cylindrical magnet ME1, the magnetization direction of the soft magnetic portion is reversed from the left direction on the page to the right direction on the page. At this time, the power generation sensor 120 outputs a positive pulse voltage.
As shown in FIG. 2C, when the cylindrical magnet ME1 approaches further and the magnetic field in the right direction on the paper surface is further strengthened, the magnetization direction of the hard magnetic portion is reversed from the left direction to the right direction. As a result, the magnetization directions of the soft magnetic portion and the hard magnetic portion are aligned. Since the magnetization reversal energy of the hard magnetic portion is small, no voltage is output from the power generation sensor 120, or if it is output, the level is low. The figure shows that the magnetic wire 121 is set in a state of preparation for outputting a negative pulse voltage.
FIG. 2D shows a state in which the cylindrical magnet ME1 passes below the axially central portion of the magnetic wire 121 . The portion of the magnetic wire 121 on the right side of the paper surface from the central portion in the axial direction remains magnetized in the right direction on the paper surface. On the other hand, the magnetization directions of both the soft magnetic portion and the hard magnetic portion are reversed in the left direction of the paper in the left portion of the magnetic wire 121 from the center in the axial direction of the paper. However, since magnetization is gradually reversed from the left end of the magnetic wire 121 as the cylindrical magnet ME1 passes, the power generation sensor 120 does not output a voltage. The output preparation state of the negative pulse voltage shown in FIG. 2C is reset.
As shown in FIG. 2E, cylindrical magnet ME1 passes rightward near the right end of magnetic wire 121 . The magnetization directions of the soft magnetic portion and the hard magnetic portion of the magnetic wire 121 are aligned in the left direction of the paper. The figure shows that the magnetic wire 121 is set to a positive pulse voltage output ready state. That is, the magnetization state is the same as in FIG. 2A.

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

Next, the magnetization state of the magnetic wire 121 in the power generation sensor 120 accompanying the backward movement of the moving body 110 (movement leftward on the page of FIG. 1) will be described with reference to FIGS. 2F to 2J. Of the cylindrical magnets ME1-ME6, only the cylindrical magnet ME6 is shown in FIGS. 2F-2J.
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 (to the right of the drawing). A cylindrical magnet ME6 approaches the magnetic wire 121 from the right side of the paper. The magnetic field from cylindrical magnet ME6 has a leftward magnetic flux component.
As shown in FIG. 2G, when the magnetic field in the left direction of the paper surface is strengthened by the approach of the cylindrical magnet ME6, the magnetization direction of the soft magnetic portion is reversed from the right direction in the paper surface to the left direction in the paper surface. At this time, the power generation sensor 120 outputs a negative pulse voltage.
As shown in FIG. 2H, when the cylindrical magnet ME6 approaches further and the magnetic field in the left direction of the paper surface becomes stronger, the magnetization direction of the hard magnetic portion is reversed from the right direction to the left direction. As a result, the magnetization directions of the soft magnetic portion and the hard magnetic portion are aligned. Since the magnetization reversal energy of the hard magnetic portion is small, no voltage is output from the power generation sensor 120, or if it is output, the level is low. The figure shows that the magnetic wire 121 is set to a positive pulse voltage output ready state.
FIG. 2I shows a state in which the cylindrical magnet ME6 passes below the axially central portion of the magnetic wire 121 . A portion of the magnetic wire 121 on the left side of the paper surface from the central portion in the axial direction remains magnetized in the left direction on the paper surface. On the other hand, in the portion of the magnetic wire 121 on the right side of the paper surface from the center in the axial direction, the magnetization directions of both the soft magnetic portion and the hard magnetic portion are reversed to the right side of the paper surface. However, since magnetization is gradually reversed from the right end of the magnetic wire 121 as the cylindrical magnet ME6 passes, the power generation sensor 120 does not output a voltage. The positive pulse voltage output readiness state shown in FIG. 2H is reset.
As shown in FIG. 2J, cylindrical magnet ME6 passes leftward near the left end of magnetic wire 121 . The magnetization directions of the soft magnetic portion and the hard magnetic portion of the magnetic wire 121 are aligned in the right direction of the paper surface. The figure shows that the magnetic wire 121 is set in a state of preparation for outputting a negative pulse voltage. That is, the magnetization state is the same as in FIG. 2F.

In this way, due to the backward motion of the moving body 110, a negative pulse voltage is output once each time one cylindrical magnet passes near the power generation sensor 120. FIG. As shown in FIG. 1, when the six cylindrical magnets ME6 to ME1 sequentially pass near the power generation sensor 120, the state transitions shown in FIGS. 2F to 2J are repeated six times.

Thus, depending on the positional relationship between cylindrical magnets ME1 to ME6 and power generation sensor 120, the magnetic field in the axial direction of power generation sensor 120 is an alternating magnetic field that alternates over six cycles within a predetermined detection range. The predetermined detection range is the total length of the plate member 111 in the longitudinal direction.

Next, referring to FIG. 3, the relationship between the output of the magnetic sensor 130, the magnetic field of the cylindrical magnet in the x-axis direction (longitudinal direction of the plate member 111), the state of the power generation sensor 120, and the count value. explain. The magnetic sensor 130 detects the magnetic field strength in the magnetosensitive direction, but does not detect the polarity of the magnetic field. The magnetic field detection sensitivity is higher than that of a general Hall element, and the power consumption can be suppressed to about 1/10 of the high resistance one.
As described with reference to FIG. 1, the magnetically sensitive direction of the magnetic sensor 130 is the y-axis direction (the width direction of the plate member 111), and the bar magnets MS1 to MS3 are magnetized in the y-axis direction. The magnetic sensor 130 outputs an identification output 1 when any bar magnet is positioned so as to face the bottom surface of the magnetic sensor 130, and outputs an identification output 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). It is In FIG. 3, T_P0 and T_P1 are obtained by adding outputs 0 and 1 of the magnetic sensor 130 after the positive pulse voltage generation point T_P, respectively. The color of the arrow is changed for identification. The same applies to T_N representing the negative pulse voltage generation point.

As described with reference to FIGS. 2A-2E and 2F-2J, forward motion results in a positive pulse voltage for each pass of the cylindrical magnet, while backward motion results in a negative pulse voltage. A pulsed voltage is obtained. The position count value is counted up when a positive pulse voltage is obtained, and the position count value is counted down when a negative pulse voltage is obtained.
However, when the motion direction is reversed, depending on the position of the reversal, the expected pulse voltage may not be output, or an extra pulse voltage may be output. Therefore, it is necessary to correct the count value.
A method of correcting the count value will be described with reference to FIG. The black circles in the figure represent the points where the pulse voltage is ready to be output (positions where the stabilization magnetic field is reached).
As an example, a forward motion is performed, and the count value is counted up to "1", "2", "3" by the approach of each of the cylindrical magnets ME1 to ME3, and then the magnetic field generated by the cylindrical magnet ME4 causes the positive electrode to move forward. Consider the state immediately after the positive pulse voltage P1 is generated and the count value is counted up to "4". The pulse voltages that may occur next are the following four patterns.

Pattern 1: T_P1→T_P0 (symbol CA1 in the figure)
When the forward motion continues, it passes S_P (positive pulse voltage output ready state) of the cylindrical magnet ME4 and enters a positive pulse voltage output ready state. After that, the cylindrical magnet ME5 approaches and a positive pulse voltage T_P0 is generated.
In this case, the counter value is corrected by counting up (+1) by one.

Pattern 2: T_P1→T_N0 (symbol CA2 in the figure)
Between S_N of cylindrical magnet ME4 (state of preparation for outputting negative pulse voltage) and T_P0 of cylindrical magnet ME5, the direction of movement is reversed. After that, it passes S_N of the cylindrical magnet ME4 and becomes ready to output a negative pulse voltage. Subsequently, 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).

Pattern 3: T_P1→T_N1 (symbol CA3 in the figure)
Before entering the output preparation state (S_N) of the negative pulse voltage, the direction of movement is reversed, and the cylindrical magnet ME3 approaches. Although the output position of the negative pulse voltage T_N0 is reached, the negative pulse voltage is not output. After passing through the reset state (RESET) and the negative pulse voltage output preparation state (S_N), the negative pulse voltage output preparation state is entered. Cylindrical magnet ME2 approaches and negative pulse voltage T_N1 is generated.
In this case, the counter value is corrected by counting down by 2 (-2).

Pattern 4: T_P1→T_P1 (symbol CA4 in the figure)
Before reaching the output ready state (S_N) of the negative pulse voltage of cylindrical magnet ME4, the movement direction turns backward and cylindrical magnet ME3 approaches. Although the output position of the negative pulse voltage T_N0 is reached, the negative pulse voltage is not output. Further retreat continues, and the direction of motion is reversed again between the positive pulse voltage output ready state (S_P) of cylindrical magnet ME3 and T_N1 of cylindrical magnet ME2 to move forward. After passing through S_P of the cylindrical magnet ME3, the positive pulse voltage is ready to be output, the cylindrical magnet ME4 approaches again, and the positive pulse voltage T_P1 is generated.
At this time, the counter value is not corrected (+0). This is because the positions are the same after all.

Similarly, FIG. 4 shows the relationship between the positive/negative and cycle identification signals of the pulse voltage when the previous pulse voltage was generated, the positive/negative and cycle identification signals of the new pulse voltage, and the correction amount of the count value.

According to this embodiment, the magnetic wires 121 are arranged parallel to the motion direction of the moving body 110 . Then, when a magnetic field is locally applied to one of the longitudinal ends of the magnetic wire 121 according to the position of the moving body 110, the reversing magnetic field propagates from one of the longitudinal ends to the other. A single magnetic domain is formed throughout (FIGS. 2C, 2E, 2H, 2J). A magnetic wire can exhibit the large Barkhausen effect through the formation of such a single magnetic domain.
In addition, since the magnetic wire 121 is arranged parallel to the movement direction of the moving body 110 (x-axis direction in FIG. 1), the magnetic wire is arranged in a direction perpendicular to the movement direction of the moving body (y-axis direction in FIG. 1). The dimensions of the detector in the direction perpendicular to the direction of motion can be reduced compared to when the detector is used.

[Second embodiment]
FIG. 5 shows a precision multi-rotation absolute angle detection system comprising a rotational position detector 200 according to this embodiment. This is obtained by applying the linear motion position detector 100 shown in FIG. 1 to rotation detection. Combining the rotational position detector 200 with the precision absolute angle detector 310 constitutes a precision multi-rotation absolute angle detection system capable of retaining position information even when power is cut off. A precision multi-turn absolute angle sensing system may also be referred to as a position sensing system.

The rotational position detector 200 has 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 as a rotation axis. On the outer peripheral edge of the surface of the ring-shaped member 211, four magnets for generating a magnetic field are provided at equal intervals along one circumferential direction (counterclockwise CCW in FIG. 5) and at positions equidistant from the rotation axis. Cylindrical magnets ME10 to ME13 are arranged in order. Each of the four cylindrical magnets ME10 to ME13 has its axial direction parallel to the rotation axis, and is magnetized so that its upper surface in the axial direction is the north pole and the lower surface in the axial direction is the south pole.

Further, in the ring-shaped member 211, a bar magnet MS11 is arranged between the cylindrical magnet ME10 and the rotating shaft 211a, and a bar magnet MS12 is arranged between the cylindrical magnet ME12 and the rotating shaft 211a. The bar magnets MS11 and MS12 have a curved shape along the inner peripheral edge of the ring-shaped member 211, and are equidistant from the rotation axis 211a. Bar magnets MS11 and MS12 are magnets for period identification.
Bar magnet MS11 is arranged such that its longitudinal direction intersects a straight line passing through rotation axis 211a and the center of cylindrical magnet ME10.
The bar magnet MS12 is arranged such that its longitudinal direction intersects a straight line passing through the rotation axis 211a and the center of the cylindrical magnet ME12.
Both the bar magnets MS11 and MS12 have magnetization directions parallel to the rotating shaft 211a. In addition, the bar magnets MS11 and MS12 have the same polarity in one direction of the rotation axis. For example, both bar magnets MS11 and MS12 have their north poles on the front side of the paper surface of FIG.

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 orthogonal to a straight line connecting a point 211b on the outer circumference of the ring-shaped member 211 and the rotating shaft 211a, and is tangential to the point 211b (or a point on the circular orbit drawn by the cylindrical magnet). tangent line passing through).
Power generation sensor 220 is positioned so that cylindrical magnets ME10 to ME13 pass below power generation sensor 220 when rotor 210 rotates.

The magnetic sensor 230 is arranged so as to generally face the power generation sensor 220 with the rotating shaft 211a interposed therebetween. The magnetic sensor 230 is positioned such that the bar magnets MS11 and MS12 pass below the magnetic sensor 230 when the rotating body 210 rotates. As an example, the magnetosensitive direction of the magnetic sensor 230 is parallel to the rotating shaft 211a. The magnetic sensor 230 outputs 1 when the bar magnet MS11 or MS12 is positioned below the magnetic sensor 230, and outputs 0 otherwise.

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

The system further includes a precision absolute angle sensor 310 , a power supply circuit 610 , an arithmetic section 620 and a non-volatile memory 630 . Power supply circuit 610 receives power from an external power supply, and supplies power to precision absolute angle sensor 310 , computing unit 620 , and nonvolatile 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 degrees to the computing section 620 . The calculation unit 620 exchanges multi-rotation count data of the rotor 210 with the non-volatile memory 630, and exchanges multi-rotation precision angle data with the outside.

Precision absolute angle sensor 310 is a so-called one-turn absolute encoder. As an example, the precision absolute angle sensor 310 has a detection period of displacement corresponding to an even multiple of four or more periods of the magnetic field change in the rotational position detector 200, and detects the displacement with an absolute value of four bits or more in the detection period. To detect.
The rotational position detector 200 can be called a first position detector, and the precision absolute angle sensor 310 can be called a second position detector.

The system further comprises a full-wave rectified 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 the full-wave rectification voltage adjustment section 410 and the first signal evaluation circuit 411 .
The magnetic sensor 230 is connected to the second signal evaluation circuit 412 .
The full-wave rectified voltage adjustment unit 410 receives the pulse power generated in the coil 222 and supplies power to the first signal evaluation circuit 411, the second signal evaluation circuit 412, the counter logic circuit 510, and the nonvolatile memory 630. offer.
First signal evaluation circuit 411 evaluates the pulse signal received from coil 222 and outputs the evaluation result to 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 .
Counter logic circuit 510 exchanges data with non-volatile memory 630 .

The principle of operation is basically the same as that of the direct acting mechanism shown in FIG. FIG. 6 shows that the state and output of the power generation sensor shown in FIG. 3 are changed to the rotation system and the state of the segment counter is added. The segment counter is composed of 4 segments of "0" to "3", and hysteresis causes different points of switching between clockwise rotation (CW rotation) and counterclockwise rotation (CCW rotation). The inner circle CR1 indicates the segment counter for clockwise rotation, and the outer circle CR2 indicates the state of the segment counter for counterclockwise rotation.
The counter performs 4 counts for one rotation, and continues to count 4, 5, 6, . . . even when one rotation is exceeded.
In principle, it is possible to count the number of rotations infinitely, but the number of rotations must be limited due to the configuration of the processing circuit. As an example, if the maximum value of the count value is 16 bits and 65536, rotation angles up to 16384 rotations can be measured.

When synthesizing the angle information of 0 to 360° from the precision absolute angle sensor 310 and the count value of the power generation sensor 220, the count value is used only to identify the shaft rotation number n. The shaft rotation speed n is obtained by the following equation.
n=INT ((90a−θ _abs +180)/360) (1)
However, a is a count value and θ _abs is a detection value of the precision absolute angle sensor 310 . “INT( )” is a function that returns the largest integer that does not exceed its argument.

Also, the integration into the precision angle θ _com over multiple rotations is given by the following equation.
θ _com =θ _abs +360n (2)
where θ _com is the integrated angle detection value and n is the shaft rotation speed.

From equation (1), it can be seen that if the difference between the angle 90a obtained from the count value a and the detection value θ _abs of the precision absolute angle sensor 310 has an error of less than 180°, the shaft rotation speed n can be obtained correctly.
In FIG. 6, consider immediately after the pulse voltage T_P0 of the cylindrical magnet ME0 is counted as 0 in the clockwise rotation. The range of movement without outputting the next pulse voltage is up to T_P1 of the cylindrical magnet ME1 (arrow AR11) when the clockwise rotation is continued, and T_N0 of the cylindrical magnet ME2 when the rotation is reversed to the counterclockwise direction. (arrow AR12). In either case, the next pulse voltage is output before rotating 180 degrees or more.
Next, consider immediately after the counterclockwise rotation is counted as 0 by the pulse voltage T_N0 of the cylindrical magnet ME0. The range of movement without outputting the next pulse voltage is up to T_N1 of the cylindrical magnet ME3 (arrow AR21) when the counterclockwise rotation is continued, and T_P0 of the cylindrical magnet ME2 when the clockwise rotation is reversed. (Arrow AR22). In either case, the next pulse voltage is output before rotating 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 to the output of the next pulse voltage is less than ±180°. Therefore, it is possible to synthesize the angle information of the precision absolute angle sensor 310 and the multi-rotation count value of the power generation sensor 220 without correcting the count value.
Therefore, it is not necessary to determine the magnetization direction described in Patent Document 5 each time the external power supply is turned on. There is no need to correct the count value.

According to this embodiment, a magnetic wire 221 is placed parallel to a tangent line passing through point 211b (FIG. 5). When a magnetic field is locally applied to one of the longitudinal ends of the magnetic wire 221 in accordance with the rotational position of the rotating body 210, the reversal magnetic field propagates from one of the longitudinal ends to the other. A single magnetic domain is formed throughout the wire. A magnetic wire can exhibit the large Barkhausen effect through the formation of such a single magnetic domain.
Moreover, according to this embodiment, the difference between the outer diameter and the inner diameter of the rotating body (the width of the ring) can be reduced compared to the case where the magnetic wires are arranged in the radial direction of the rotating body. That is, a large radial dimension of the hollow portion 212 can be ensured without changing the outer diameter of the ring-shaped member 211 .

[Other embodiments]
FIG. 7(a) again shows the cylindrical magnet ME1.
FIG. 7(b) shows a magnetic field generating source ME1a in which two magnets MG11 and MG12 are arranged so that the same poles face each other. The cylindrical magnet ME1 can be replaced by the magnetic field source ME1a. Similar substitutions can be made for other cylindrical magnets and bar magnets.
As shown in FIG. 7C, a yoke YK is arranged on the upper surface of the plate-like magnet MG21. Three protrusions YK1 to YK3 are provided on the upper surface of the yoke YK. Projections YK1 to YK3 are magnetic field sources ME1b to ME3b, respectively. That is, the cylindrical magnets ME1-ME3 can be replaced with the magnetic field sources ME1b-ME3b. The number of protrusions can be changed. A bar magnet can likewise be constituted by a projection of the yoke.

Other examples of cycle identification are described below.
In the above-described embodiment, a long bar magnet is used as the identification magnet so that the pulse voltage generation points at both ends of the power generation sensor can be covered with one MR element (magnetic sensor).
However, it is also possible to use relatively small (short) magnets and cover two pulse voltage generation points with two MR sensors.
Alternatively, by using a small (short) magnet and combining a magnetic sensor with a yoke to collect a wide range of magnetic field, it is possible to cover two pulse voltage generating points with one MR element.
In order to explain the function, the magnetic field generating magnet (ME) and the identification magnet (MS) are separated. Identification is also possible by changing the shape and strength of magnetic force between magnets and even-numbered magnets.
The identification means is not limited to magnetism, and various detection means such as mechanical contact switches, capacitance, and electromagnetic induction can be used.

Other examples of detection positions of the power generation sensor, magnetic sensor, and absolute detector will be described below.
Since the embodiment of the present invention counts the pulse voltage once per cycle after distinguishing between odd and even cycles, deceleration and movement direction conversion are performed via the transmission mechanism. is also established.
The installation and detection positions of the power generation sensor, the magnetic field generation source, the period identification sensor, and the absolute detector described above are examples, and the present invention is not limited to these.

Example) Ball screw drive 1
This is the case where the ball screw is driven by a motor.
A disc is provided on the motor shaft and two magnetic field generating magnets are provided. The power generation sensor outputs two pulses per rotation.
The strength of the magnetic force of the two magnetic field generating magnets is different, and the magnetic field strength is measured by the MR sensor. Two magnets are identified.
Provide an absolute linear scale on the ball screw. The detection cycle is twice the lead pitch of the ball screw.

Example) Ball screw drive 2
A disk is provided on the motor shaft, and one magnetic field generating magnet is provided. The power generation sensor outputs one pulse per revolution.
An MR sensor is mounted on the moving part of the ball screw. Magnets for period identification are installed on the fixed portion at an interval twice the lead pitch.
Provide an absolute linear scale on the ball screw. The detection period is four times the lead pitch of the ball screw.

The following notes are disclosed with respect to the embodiments described so far.
[Appendix 1]
A position detector that has a magnetic field generation source and detects the position of a moving body that moves linearly or rotationally,
a single power generation sensor;
at least one sensor element;
The power generation sensor has 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 cycles or more within a predetermined detection range according to the positional relationship between the magnetic field source and the power generation sensor,
The power generation sensor outputs a pulse voltage of positive polarity or negative polarity depending on the direction of the linear motion or the direction of the rotational motion once per magnetic field change cycle,
The sensor element outputs an identification signal that identifies 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 object 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 generation source passes through the vicinity of 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 line passing through a contact point on the circular orbit drawn by the magnetic field generation source due to the rotational motion,
The magnetic field generating source generates a radial magnetic field from a central portion of the magnetic field generating source,
When there are a plurality of the magnetic field generating sources, all the magnetic field generating sources generate magnetic fields in the same direction.
The position detection device of appendix 1.
[Appendix 3]
3. The position detector according to appendix 2, wherein the plurality of magnetic field sources are configured by either a plurality of magnets or a combination of a single magnet and a magnetic field induction yoke having a plurality of projections.
[Appendix 4]
4. A position detector according to any one of the appendices 1 to 3, wherein the sensor element is a magnetoresistive element.
[Appendix 5]
The position detector according to any one of Appendices 1 to 4 is provided as a first position detector, and a second position detector operated by an external power supply and detecting the position of the moving body is provided,
the first detector operates without the external power supply;
The second position detector has a detection period that is an even multiple of four periods or more of the magnetic field change period of the first position detector, and detects the displacement as an absolute value in the detection period. ,
By integrating the detected value of the first position detector and the detected value of the second position detector when the external power supply is supplied, the resolution is higher than that of the first position detector, and the position detection is performed with a detection range wider than the detection cycle of the second position detector;
Position detector system.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes are possible based on the technical idea of the present invention.

100, 200 detectors 110, 210 moving bodies 120, 220 power generation sensors 121, 221 magnetic wires 222 coils 130, 230 magnetic sensors

Claims (5)

A position detector that has a magnetic field generation source and detects the position of a moving body that moves linearly or rotationally,
a single power generation sensor;
at least one sensor element;
The power generation sensor has 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 cycles or more within a predetermined detection range according to the positional relationship between the magnetic field source and the power generation sensor,
The power generation sensor outputs a pulse voltage of positive polarity or negative polarity depending on the direction of the linear motion or the direction of the rotational motion once per magnetic field change cycle,
The sensor element outputs an identification signal that identifies 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 object is detected based on the polarity of the pulse voltage and the identification signal;
Position detector. As the moving body moves, the magnetic field generation source passes through the vicinity of 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 line passing through a contact point on the circular orbit drawn by the magnetic field generation source due to the rotational motion,
The magnetic field generating source generates a radial magnetic field from a central portion of the magnetic field generating source,
When there are a plurality of the magnetic field generating sources, all the magnetic field generating sources generate magnetic fields in the same direction.
The position detection device according to claim 1. 3. The position detector according to claim 2, wherein the plurality of magnetic field sources are composed of a plurality of magnets or a combination of a single magnet and a magnetic field induction yoke having a plurality of projections. A position detector according to any one of claims 1 to 3, wherein the sensor element is a magnetoresistive element. Equipped with the position detector according to any one of claims 1 to 4 as a first position detector, and a second position detector operated by an external power supply and detecting the position of the moving body,
the first detector operates without the external power supply;
The second position detector has a detection period that is an even multiple of four periods or more of the magnetic field change period of the first position detector, and detects the displacement as an absolute value in the detection period. ,
By integrating the detected value of the first position detector and the detected value of the second position detector when the external power supply is supplied, the resolution is higher than that of the first position detector, and the position detection is performed with a detection range wider than the detection cycle of the second position detector;
Position detector system.

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