JP2000009410A - Position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a miniaturized high-precision position detector. SOLUTION: The position detector 1 is provided with a high frequency-excited coil 5, a core 7 inserted into the coil 5 in such a way that the core 7 can move relatively to the coil 5 in the direction of the center axis of the coil 5, and a detecting means which detects the moved position of the core 7 relatively to the coil 5 based on the impedance of the coil 5 in an enclosure 3. The impedance of the coil 5 changes as the core 7 moves. The length of the core 7 in the moving direction is made longer than the moving amount of the core 7 relative to the coil 5 and the coil length of the coil 5 is also made longer than the moving amount of the core 7 relative to the coil 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a position detecting device for detecting an absolute moving position of a movable part of a machine tool, an industrial robot, or the like.

[0002]

2. Description of the Related Art Conventionally, as a position detecting device for detecting a moving amount and a moving position of a movable portion of a machine tool, an industrial robot, or the like, for example, a differential transformer type position detecting device is known.

FIG. 11 shows a conventional position detecting device using the differential transformer method.

A conventional position detecting device 100 is adjacent to both ends of an exciting coil 101 and a center axis direction of the winding of the exciting coil 101 (hereinafter, the center axis direction of the winding of the coil is referred to as a winding direction). And first and second detection coils 102 and 103 provided.

[0005] First and second detection coils 102 and 103
Is provided adjacent to the end so that the center axis thereof coincides with the exciting coil 101, and its length L in the winding direction is
(Hereinafter, the length in the winding direction of the coil is referred to as the coil length.)
Are the same as the coil length of the exciting coil 101. The excitation coil 101 is driven by, for example,
It is excited by a signal having a frequency of about kh to 3 kh. The first and second detection coils 102 and 103 are
And the magnetic flux generated from the exciting coil 101 induces an electrical output.

In the conventional position detecting device 100, a core 104 made of a round bar-shaped magnetic material, one end in the longitudinal direction is attached to a movable portion 106 of a machine tool or an industrial robot, and the other end of the core 104 is attached to the other end. A spindle 105 to which one end in the longitudinal direction is attached. The core 104 is
The excitation coil 101 and the first detection coil 102 are arranged such that the central axis in the longitudinal direction coincides with the central axis of the excitation coil 101.
And is movably inserted into the second detection coil 103. Since the core 104 is attached to the movable part 106 in which the spindle 105 moves linearly in the X1 direction and the X2 direction, the excitation coil 101, the first detection coil 102, the second Move linearly in the X1 direction and the X2 direction in the detection coil 103 of FIG.

[0007] The conventional position detecting device 1 having the above-described configuration.
At 00, the inductance of each detection coil 102, 103 changes according to the insertion amount of the core 104. for that reason,
In this conventional position detecting device 100, an exciting coil 101
The inductance of each detection coil 102, 103 is detected based on the electrical output excited by the magnetic flux generated from the sensor, and the differential output is obtained, whereby the relative movement position between the core 104 and each detection coil 102, 103 is determined. Can be detected. Therefore, the position detecting device 100 can detect the absolute moving position of the movable portion attached to the core 104 via the spindle 105.

FIG. 12 shows a conventional position detecting device 100.
FIG.

For example, when the core 104 is located at a position where the insertion amount is equal to the first detection coil 102 and the second detection coil 103, the inside of the first detection coil 102 and the second detection coil 103 Have the same amount of magnetic flux. Therefore, the output C1 of the first detection coil 102 and the output C2 of the second detection coil 103 become the same, and the differential output (C2-C1) becomes zero. The state at this time is referred to as an equilibrium state.

When the core 104 moves from the equilibrium state to the first coil 102 side, the output C1 of the first coil 102 increases and the output C2 of the second coil 103 decreases. Therefore, the differential output (C2-C1) decreases.
Also, from this equilibrium state, the core 104 is
When moving to the 03 side, the output C1 of the first coil 102 decreases and the output C2 of the second coil 103 increases. Therefore, the differential output (C2-C1) increases.

As described above, this conventional position detecting device 10
At 0, the output changes linearly according to the movement position of the core 104, so that the movement position of the movable section 106 connected to the core 104 can be detected based on this output.

As described above, the conventional position detecting device 100
By taking a differential output of the change in inductance of each of the detection coils 102 and 103, it is possible to perform position detection that is resistant to noise and has good linearity.

[0013]

By the way, the conventional position detecting device 100 based on the differential transformer system has a core 104
3 coils with a coil length longer than the same
I needed one. That is, the conventional position detecting device 10
In the case of 0, the total length of the coil lengths of all the coils needs to be at least three times the effective length capable of detecting the moving position. Therefore, in the conventional position detecting device 100, the size of the core 104 in the moving direction is required to be at least about three times the effective length, and it has been difficult to reduce the size of the entire device.

The present invention has been made in view of such circumstances, and has as its object to provide a highly accurate and miniaturized position detecting device.

[0015]

In order to solve the above-mentioned problems, in a position detecting device according to the present invention, a high-frequency-excited coil is provided so as to be relatively movable with respect to the center axis direction of the coil. A core made of a magnetic material inserted therein, and detecting means for detecting a relative movement position between the core and the coil based on the impedance of the coil, wherein a length of the core in a moving direction is equal to the length of the core. The coil is longer than the relative movement amount between the core and the coil, and the coil length of the coil is longer than the relative movement amount between the core and the coil.

In this position detecting device, the impedance of the high-frequency-excited coil, which varies according to the moving position of the core, is detected, and based on the impedance, the moving position of the object attached to the core is detected.

Further, in the position detecting device according to the present invention, a coil made of a magnetic material inserted in the coil and movably mounted relative to the center axis direction of the coil is provided. Detecting means for detecting a relative movement position between the core and the coil based on an impedance of the coil; and a high magnetic permeability material fixed and provided near a tip of the coil in an insertion direction of the core. It is characterized by the following.

In this position detection device, the impedance of the high-frequency-excited coil, which varies according to the movement position of the core, is detected, and the movement position of the object attached to the core is detected based on the impedance. Further, in this position detecting device, the magnetic flux generated from the coil passes through the high magnetic permeability material.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a description will be given of a position detecting apparatus according to a first embodiment of the present invention for detecting a moving position of a movable portion having a linear moving range of 10 mm.

FIG. 1 is a sectional view of a position detecting device according to a first embodiment of the present invention.

The position detecting device 1 detects a moving position of a movable portion 2 which is a linear moving portion of a machine tool or an industrial robot. The movable part 2 moves linearly in the X1 direction or the X2 direction in the figure, for example. The moving amount of the movable part 2 is 10 mm. In the position detecting device 1, the effective length for position detection is 10 mm or more so that the movement of the movable portion 2 can be detected in a range of 10 mm.

The position detecting device 1 includes a cylindrical housing 3 and a coil 5 wound around a bobbin 4 and housed in the housing 3.
And a lid 6 for closing the housing 3.

The housing 3 has, for example, a cylindrical shape with an outer dimension of 8 mm in diameter and 125 mm in the longitudinal direction. The housing 3 has a longitudinal direction parallel to the moving direction of the movable part 2, and one opening 3 a is fixed at a position facing the movable part 2.

The coil 5 has, for example, a diameter of 0.06 mm.
Is wound around the bobbin 4 by one layer. The length of the winding of the coil 5 in the direction of the central axis (coil length) is longer than the movable range of the movable portion 2, that is, the effective length of the device, and is, for example, 25 mm. The coil 5 has a coil diameter of, for example, 4 m.
m. The coil 5 wound around the bobbin 4 has its center axis coincident with the center axis of the cylindrical housing 3.
It is housed inside the housing 3. This coil 5
One of the openings 3b that does not face the movable part 2 of the housing 3 is closed at a predetermined position in the housing 3 by being closed by a bottomed cylindrical lid 6. The coil 5 includes signal lines 5 a and 5 whose both ends of a Cu wire are inserted from the inside of the housing 3 to the outside.
b, and to the drive detection circuit described later via the signal lines 5a and 5b. And coil 5
Are excited at a high frequency by this drive detection circuit.

The position detecting device 1 includes a round bar-shaped core 7 inserted into the coil 5 and a spindle 8 for supporting the core 7.

The core 7 is made of, for example, SK material. The core 7 may be made of any material as long as it is made of a magnetic material.
iFe or the like may be used. The core 7 may be made of permalloy, which is a high magnetic permeability material, or an amorphous alloy made of Si, Fe, Co, B, or the like. This core 7
It has an elongated shape whose longitudinal length is longer than the effective length of the device, and has, for example, a round bar shape having a diameter of 2 mm and a longitudinal length of 21.5 mm.

The core 7 is inserted into the coil 5 so that its central axis coincides with the central axis of the coil 5. The core 7 is movable in the direction of the center axis of the coil 5. The core 7 has at least the movable amount of the movable portion 2, that is, the effective length of the position detection device around the center position o of the coil 5 in the center axis direction. It is movable within a certain range of 10 mm. One end of the core 7 in the direction facing the movable portion 2 is attached to the spindle 8.

The spindle 8 has a round bar shape, and is inserted into the housing 3 through the opening 3a of the housing 3 to which the lid 6 is not attached. The spindle 8 is slidably supported by the inner wall of the housing 3 and is movable in the longitudinal direction.

The spindle 8 has a core 7 attached to a tip end of the spindle 3 in the direction of insertion into the housing 3 so that the center axis is aligned. One end of the spindle 8 to which the core 7 is not attached is attached to the movable portion 2.

In the position detecting device 1 having the above configuration,
When the movable section 2 moves linearly in the X1 direction or X2 direction in the figure, the spindle 8 also moves linearly in the housing 3 in the X1 direction or X2 direction in the figure with this movement. This allows the core 7 to move with the coil 5
In the direction of the center axis of the coil 5 within the effective length range.

Here, the impedance of the coil 5 changes according to the insertion amount of the core 7. That is, the impedance of the coil 5 changes depending on the relative position with respect to the core 7.

For example, as shown in FIG. 2, let the coil length of the coil 5 be L, and let the length of the coil 5 in the air core portion where the core 7 is not inserted be x. This x indicates the relative movement position between the coil 5 and the core 7. That is, when x = 0, the core 7 is completely inserted into the coil 5, and when x = L, the core 7
Is not inserted at all. Here, core 7
Moves within the coil 5 by a distance x. At this time, the overall impedance Z _all of the coil 5 is the impedance Z _{1 of the} air-core portion (x) where the core 7 is not inserted.
And the impedance Z _{2 of the} centered portion (L−x) into which the core 7 is inserted, and is expressed by the following equation (1).

Z _all = Z ₁ (x) + Z ₂ (L−x) where x ≦ L (1) Thus, the overall impedance Z of the coil 5
_all is a function of the relative movement position x between the coil 5 and the core 7.

Therefore, in the position detecting device 1, since the impedance of the coil 5 changes as the core 7 moves, by detecting the impedance of the coil 5, the position detecting device 1 is connected to the core 7 via the spindle 8. The movable position of the movable part 2 can be detected.

In order to detect such a change in the impedance of the coil 5, the position detecting device 1 includes a drive detecting circuit outside the housing 3. In the position detection device 1, the drive detection circuit excites the coil 5 at a high frequency and detects the impedance of the coil 5 as a DC voltage to detect the moving position of the movable section 2.

FIG. 3 is a circuit diagram of a drive detection circuit provided in the position detection device 1.

The drive detecting circuit 11 provided in the position detecting device 1 includes an oscillating circuit 12, a switching circuit 13 for switching a driving current of the coil 5 based on a pulse signal from the oscillating circuit 12, and detecting an output voltage of the coil 5. A first smoothing circuit 14 for detecting and smoothing the output voltage of a resistor R connected in parallel with the coil 5, a smoothing coil 5 and a resistor R And a differential amplifying circuit 16 for amplifying the difference between the output voltage and the output voltage.

The coil 5 and the resistor R are connected in parallel to the switching circuit 13 as shown in FIG.
One end of the coil 5 is supplied with the power supply voltage Vcc via the resistor r ₁ , and the other end is grounded via the switching circuit 13. The resistor R has one end supplied with the power supply voltage Vcc through a resistor r ₂ of the resistor r ₁ and the same resistance value, the other end is grounded via the switching circuit 13. The coil 5 and the resistor R are connected to resistors r ₁ and r ₂ , respectively.
The detection output is taken out from the connection point with.

The oscillation circuit 12 has, for example, a frequency of 1 MHz.
z, a pulse signal having a pulse width of 200 ns is generated. The switching circuit 13 switches the current flowing through the coil 5 and the resistor R connected in parallel based on the pulse signal. As a result, the coil 5 is excited by the high-frequency pulse current.

The driving of the coil 5 by the oscillation circuit 12 is not limited to a pulse signal, and may be, for example, a sine wave signal. However, by driving with a pulse signal, the circuit can be made inexpensive, and by changing the duty ratio, the impedance characteristics can be improved while suppressing power consumption.

The linearity of the impedance characteristic of the coil 5 is improved by increasing the frequency of the driving signal. Further, the response speed of the coil 5 is increased by increasing the frequency of the driving signal. Therefore, the driving of the coil 5 by the oscillation circuit 12 may be a high-frequency signal that provides good impedance characteristics and has a high response speed.
It can be driven by a signal of about 10 kHz to 10 MHz. Also, depending on the characteristics of the coil 5, for example,
Good characteristics can be obtained with a signal of about 50 kHz to 1 MHz.

The first smoothing circuit 14 includes a coil 5 and a resistor r.
The voltage at the connection point with ₁ is detected and smoothed. The second smoothing circuit 15 smoothes detects the voltage of the connection point between the resistor R and the resistor r _2.

The differential amplifier circuit 16 includes a first smoothing circuit 14
The differential voltage between the output voltage of the coil 5 smoothed by the above and the output voltage of the resistor R smoothed by the second smoothing circuit 15 is detected, and a signal obtained by amplifying the differential voltage is generated. This signal is output as a position signal of the movable section 2.

As described above, the drive detection circuit 11 can excite the coil 5 with a high-frequency pulse current. Further, the drive detection circuit 11 can convert the impedance of the coil 5 into a voltage value and output this value as a position signal of the movable section 2.

FIG. 4 shows an output characteristic diagram of the drive detection circuit 11 with respect to the position of the movable section 2 (Position). FIG. 5 shows a linearity error (Error) of the output with respect to the position of the movable section 2.

As shown in FIG. 4, in the position detecting device 1, the voltage fluctuates linearly within a range of about 0.63 volts to 0.20 volts within an effective length of 10 mm, which is a moving range of the movable part 2. You can get the output. Further, as shown in FIG. 5, in the position detecting device 1, the linearity error can be reduced to 0.5% or less within an effective length of 10 mm, which is a moving range of the movable portion 2.

As described above, the position detecting device 1 according to the first embodiment of the present invention can detect the moving position of the movable section 2 with high accuracy. Further, in the position detection device 1, since the position detection is performed using the coil 5 excited by the high frequency by the drive detection circuit 11, the position detection can be performed using only one coil and the position can be detected with respect to the coil length. The effective length can be lengthened. Therefore, in the position detection device 1, the size of the entire device can be reduced, and the circuit scale can be reduced.

Further, since the position detecting device 1 detects the impedance of the coil 5 which has been excited at a high frequency, it is excellent in responsiveness and the number of windings of the coil 5 can be reduced.

Next, a description will be given of a position detecting device according to a second embodiment of the present invention for detecting the moving position of a movable portion having a linear moving range of 10 mm. In describing the position detecting device according to the second embodiment, the first
The same components as those of the position detection device 1 according to the embodiment are denoted by the same reference numerals in the drawings, and detailed description thereof will be omitted.

FIG. 6 is a sectional view of a position detecting device according to a second embodiment of the present invention.

The position detecting device 20 according to the second embodiment
In order to detect the position of the movable part 2 within a range of 10 mm, the effective length of the movable part 2 is 10 m.
m or more.

The position detecting device 20 includes a cylindrical housing 3 and
A coil 22 wound around a bobbin 21 and housed in the housing 3, a lid 6 for closing the housing 3, and a permalloy 23, which is a high magnetic permeability material, provided inside the coil 22. ing.

The coil 22 has, for example, a diameter of 0.06 m.
It is formed by winding m layers of Cu wire around the bobbin 21 by one layer. The coil length of the coil 22 is longer than the movable range of the movable portion 2, that is, the effective length of the device, and is shorter than the coil length of the coil 5 of the first embodiment, for example, 20 mm. Has become. The coil diameter of the coil 22 is, for example, 4 mm. The coil 22 wound around the bobbin 21 is housed inside the housing 3 such that the center axis thereof coincides with the center axis of the cylindrical housing 3. The coil 22 is fixed at a predetermined position in the housing 3 by closing one opening 3 b not facing the movable portion 2 of the housing 3 with a bottomed cylindrical lid 6. The coil 22 includes signal lines 5a and 5b having both ends of a Cu wire inserted from the inside of the housing 3 to the outside.
And to the drive detection circuit 11 via the signal lines 5a and 5b. The drive detection circuit 11 excites the coil 22 at a high frequency and detects the impedance as a DC voltage.

The coil 22 has a high magnetic permeability material at an end near the opening 3 b of one of the casings 3 not facing the movable portion 2, that is, near an end in the insertion direction of the core 7. Is fixedly provided. Permalloy 23 has a diameter of 2 mm and a height of 3 m, for example.
m.

Here, when the coil 22 is not provided with the permalloy 23, the magnetic flux generated by the excited coil 22 is diffused at the coil end as shown in FIG. 7A. On the other hand, when the permalloy 23 is provided in the coil 22, the magnetic flux of the excited coil 22 becomes an ideal parallel state at the coil end as shown in FIG. 7B. That is, by providing the permalloy 23 at the end of the coil 22, the magnetic flux passing through the inside of the coil 22 is focused on the permalloy 23. for that reason,
In the coil 22, the linearity of the change in impedance with respect to the change in the amount of magnetic flux is improved.

The position where the permalloy 23 is provided is near the front end of the core 7 in the insertion direction, as shown in FIG.
The position shown in (b) is not limited to the position where the whole is completely inserted inside the coil 22. For example, as shown in FIG. 8A, a part of the permalloy 23 may protrude outside the coil 22 and may be provided at a position where a part is inserted inside. Further, as shown in FIG.
May be provided adjacent to the outside of the coil 22. Further, as shown in FIG. 8C, the permalloy 23 may be provided outside the end of the coil 22.

In the position detecting device 20, instead of the permalloy 23, for example, a high magnetic permeability material such as Fe, Co, Si, or B may be provided on the coil 22.

Further, the position detecting device 20 includes the coil 2
A core 24 having a round bar shape inserted into the core 2 and the spindle 8 supporting the core 24 are provided.

The material and the like of the core 24 are the same as those of the core 7 of the first embodiment, but the length in the longitudinal direction is
It is shorter than 16.5 mm and has a round bar shape.

In the position detecting device 20 having the above-described configuration, when the movable portion 2 moves linearly in the X1 direction or the X2 direction in the drawing, the spindle 8 also moves in the X1 direction or the inside of the housing 3 with this movement. It moves linearly in the X2 direction. As a result, the core 24 linearly moves within the effective length of the coil 22 in the direction of the center axis of the coil 22 as the movable portion 2 moves.

FIG. 9 shows an output characteristic diagram of the drive detection circuit 11 with respect to the position (Position) of the movable section 2, and FIG.
The linearity error (Error) of the output with respect to the position of the movable part 2 is shown.

As shown in FIG. 9, this position detecting device 20
Then, within an effective length of 10 mm, which is a moving range of the movable part 2,
An output in which the voltage fluctuates linearly in the range of about 1.00 volt to 0.48 volt can be obtained. Further, as shown in FIG. 10, in the position detecting device 1, the linearity error can be reduced to 0.5% or less within the effective length of 10 mm, which is the moving range of the movable portion 2.

As described above, the position detecting device 20 according to the second embodiment of the present invention can detect the moving position of the movable section 2 with high accuracy. Also, the position detecting device 20
Then, the coil 2 excited by the drive detection circuit 11 at a high frequency
2, the position can be detected using only one coil, and the effective length of the position that can be detected with respect to the coil length can be made longer. for that reason,
In the position detection device 20, the size of the entire device can be reduced, and the circuit scale can be reduced.

In addition, since the position detecting device 20 detects the impedance of the coil 22 which has been excited at a high frequency, the response is excellent and the number of windings of the coil 22 can be reduced.

Further, in the position detecting device 20, the magnetic flux in the coil 22 can be made parallel by providing the permalloy 23 fixed to the tip of the coil 22 in the insertion direction of the core 24. The effective length can be made longer than the length.

In the above description of the embodiment of the present invention, the position detecting device in which the core moves in the fixedly arranged coil has been described. However, the impedance of the coil changes according to the relative position between the coil and the core. Therefore, the coil may be moved with respect to the fixedly arranged core, that is, the case may be attached to the movable portion to detect the position.

In describing the embodiment of the present invention, a position detecting device in which the shape of the housing, the core, the coil, and the spindle is cylindrical or round is shown. Without limitation, for example, a rectangular cylindrical housing,
A plate-shaped core, a spindle, a coil wound in a rectangular shape, or the like may be used.

Further, in describing the embodiment of the present invention, the position detecting device for detecting the moving position of the movable portion which moves linearly has been described. However, the present invention is not limited to the linear moving but may be, for example, a center axis. Is an arc-shaped coil,
A core having the same shape as the center axis of the coil may be inserted to detect the rotational position of the movable portion that moves in a circular manner.

[0069]

According to the position detecting device of the present invention, the impedance of the high-frequency excited coil which changes according to the moving position of the core is detected, and based on this impedance, the moving position of the object attached to the core is detected. I do. As a result, in this position detecting device, highly accurate position detection can be performed, and the effective length capable of detecting the position with respect to the coil length can be lengthened, thereby reducing the size of the entire device. be able to. Further, in this position detecting device, the position can be detected by only one coil, and the circuit can be simplified. In addition, since the position detection device detects the impedance of the coil that has been excited at a high frequency, the response is excellent and the number of windings of the coil can be reduced.

Further, in the position detecting device according to the present invention, the high magnetic permeability material fixed near the tip of the coil in the core insertion direction enables the magnetic flux in the coil to be parallelized. , And highly accurate position detection can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a position detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a change in impedance with respect to a relative position between a coil and a core provided in the position detection device.

FIG. 3 is a circuit diagram of a drive detection circuit of the position detection device.

FIG. 4 is an output characteristic diagram of a drive detection circuit of the position detection device with respect to a position of a movable portion.

FIG. 5 is a diagram illustrating a linearity error of an output of a drive detection circuit of the position detection device with respect to a position of a movable portion.

FIG. 6 is a sectional view of a position detecting device according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a state of a magnetic flux in a coil.

FIG. 8 is a diagram for explaining a position of a permalloy provided at an end of the coil.

FIG. 9 is an output characteristic diagram of a drive detection circuit of the position detection device with respect to a position of a movable portion.

FIG. 10 is a diagram illustrating a linearity error of an output of a drive detection circuit of the position detection device with respect to a position of a movable portion.

FIG. 11 is a diagram showing a conventional position detecting device.

FIG. 12 is a diagram showing output characteristics of a conventional position detecting device.

[Explanation of symbols]

1,20 position detecting device, 2 movable part, 3 housing, 4,
21 bobbins, 5,22 coils, 6 lids, 7,24
Core, 8 spindles, 11 drive detection circuit, 23
Permalloy

Claims (2)

[Claims] 1. A high-frequency excited coil, a core made of a magnetic material inserted in the coil so as to be relatively movable with respect to a center axis direction of the coil, and the core based on an impedance of the coil. Detecting means for detecting a relative movement position with respect to the coil, wherein a length of the core in a movement direction is longer than a relative movement amount between the core and the coil, and a coil length of the coil is equal to the core length. A position detecting device characterized by being longer than a relative movement amount with respect to the coil. 2. A high-frequency excited coil, a core made of a magnetic material inserted into the coil so as to be relatively movable in a direction of a center axis of the coil, and the core based on an impedance of the coil. A position detecting device comprising: detecting means for detecting a relative movement position with respect to the coil; and a high-permeability material fixed and provided near a tip portion of the coil in an insertion direction of the core.