JPH0781807B2 - Position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a position detection device suitable for use in various machine tools such as an automatic lathe.

[Outline of Invention]

INDUSTRIAL APPLICABILITY The present invention relates to a position detecting device suitable for use in various machine tools such as an automatic lathe, in which a magnet magnetized at a constant pitch and a plurality of magnetoelectric conversions arranged at a predetermined pitch with respect to the pitch of the magnet. A position detection head that has an element and moves relative to the magnet and that outputs a position signal of two or more phases corresponding to the position on the magnet is provided, and the position signal is counted to determine a predetermined section on the magnet. Is obtained, and this count signal is compared with a desired section designation signal from the outside,
A position signal of a desired phase is selected from the position signals of two or more phases based on the comparison result, and the position of the position detection head with respect to the magnet is detected by this section designation signal and the analog value of the position signal of the desired phase. This makes it possible to detect even minute displacements below the magnetizing pitch so that the so-called dead zone does not occur, and it is possible to perform high-resolution position detection above the resolution determined by the magnetizing pitch. is there.

[Conventional technology]

Generally, as a position detecting device used in various machine tools such as an automatic lathe, a device whose main part is shown in FIG. 8A is used.

In FIG. 8A, (1) shows a magnet in which N poles and S poles are arranged at a constant pitch, and the position detecting magnetic head (2) is arranged at a predetermined interval corresponding to the magnet (1). The position detecting magnetic head can be moved in the directions of arrows a and b.

In the position detecting device having the main part as described above, when the position detecting magnetic head (2) is moved, FIG.
It is possible to obtain the output signal (3) whose absolute value becomes maximum at the position corresponding to the boundary of the magnetized pattern of the magnet (1) as shown in FIG.

Therefore, in the position detecting device of this example, the output signal (3) thus obtained is used for position detection by counting each peak using a predetermined counter (not shown) with a predetermined position as a reference. Head (2) Magnet (1)
The position with respect to can be detected.

[Problems to be solved by the invention]

However, in such a conventional position detecting device, the position of the position detecting magnetic head (2) with respect to the magnet (1) is detected by counting the peak number of the output signal (3) as shown in FIG. 8B. Therefore, the so-called dead zone is present between the peaks of the output signal (3), and the position cannot be detected. Therefore, in order to realize high-resolution position detection in such a conventional position detecting device, the magnetizing pitch must be made very fine, but in this case, in order to obtain a good output signal, the position detecting head ( The gap between 2) and the magnet (1) must be very narrow, and the magnetizing pitch of about 0.1 mm is the limit. For this reason, it is not possible to detect the position with high resolution, and when trying to apply the position servo, there is a disadvantage that the servo is very difficult to apply because the dead zone occurs in a portion below the resolution.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a position detection device capable of obtaining a high resolution equal to or higher than the resolution determined by the magnetizing pitch of the magnet (1).

[Means for solving problems]

The position detecting device according to the present invention is, as shown in FIGS. 1 and 2, arranged with a magnet (1) magnetized at a constant pitch and a predetermined pitch with respect to the pitch of the magnet (1). Position signals of two or more phases corresponding to the position on the magnet (1) and having a plurality of magnetoelectric conversion elements (5) (6) (7) (8) so as to move relative to the magnet (1) And a position detection head (9) for outputting a position signal are provided to count the position signals to obtain a count signal representing a predetermined section on the magnet, and the count signal is compared with a desired section designation signal from the outside. A position signal of a desired phase is selected from the position signals of two or more phases based on the comparison result, and the position of the position detection head with respect to the magnet is detected by this section designation signal and the analog value of the position signal of the desired phase. Also It is.

[Action]

According to the present invention, the position signal output from the position detection head (9) is counted to obtain a count signal representing a predetermined section on the magnet (1), and the count signal and a desired external signal are obtained. A section designating signal is compared, and a position signal of a desired phase is selected from the position signals of two or more phases based on the comparison result, and the section designating signal and the analog value of the selected position signal of the desired phase are magnetized. Since the position of the position detection head (9) with respect to (1) is detected, even a minute displacement below the magnetizing pitch can be detected, and high-resolution position detection above the resolution determined by the magnetizing pitch is performed. be able to.

〔Example〕

An embodiment of the position detecting device of the present invention will be described below with reference to FIGS. 1 to 7. In this example, a case where the magnet (1) is fixed and the position detection head (9) is moved to a desired position on the magnet (1) will be described.

In FIG. 1, (1) shows a magnet in which N poles and S poles are arranged at a predetermined pitch P ₁ similar to that shown in the conventional example of FIG. 8, and an arrow a at a predetermined interval with respect to this magnet (1).
And a position detection head (9) adapted to be movable in the directions b and b. In this example, the position detecting head (9) is composed of four magnetoresistive elements (5), (6), (7) and (8) as shown in FIG. In this case, the pitch P ₂ between the magnetoresistive elements is arranged to be a quarter of the magnetizing pitch P ₁ of the magnet (1), and the arrows c and d are set.
The resistance value has a maximum value with respect to the magnetic field in the direction of, and the resistance value has a minimum value with respect to the magnetic fields in the directions of the arrows e and f. Also, one terminal (5a) of the first magnetoresistive element (5)
Is connected to one terminal (6a) of the second magnetoresistive element (6), and the middle point of this connection is connected to the power supply terminal (16) to which a DC voltage is supplied. Also, the other terminal (5b) of the first magnetoresistive element (5) and one terminal (7a) of the third magnetoresistive element (7) are connected, and the midpoint of the connection is connected to one output terminal (17). ). The other terminal (6b) of the second magnetoresistive element (6) is connected to one terminal (8a) of the fourth magnetoresistive element (8), and the midpoint of the connection is connected to the other output terminal (18). ). The other terminal (7b) of the third magnetoresistive element (7) and the other terminal (8b) of the fourth magnetoresistive element (8).
And the middle point of this connection are connected to the ground terminal (19).

In the position detection head (9) configured in this way,
As shown in FIG. 3, by supplying a predetermined DC voltage to the power supply terminal (16) and grounding the ground terminal (19), the position detecting head (9) is moved in the direction of arrow a as shown in FIG. 2A. When it is moved to, the sine wave output signal S _A as shown in FIG. 2B is obtained at one output terminal (17) and the sine wave output signal as shown in FIG. 2 C is obtained at the other output terminal (18). Signal S
_B is obtained.

Therefore, in this example, as shown in FIG. 1, one output terminal (17) of the position detecting head (9) is connected to the input side of one of the offset-adjusted amplifiers (20) and the position detecting head is connected to the output side. connecting the output of one amplifier a sinusoidal signal S _a obtained to one output terminal (9) (17) together with obtaining Zohaba signal S _a (20) on the input side of the amplitude adjustment circuit (21) Then, the sine wave signal S _A whose amplitude is adjusted to a predetermined value is obtained at its output side. Further, the output side of the amplitude adjusting circuit (21) is connected to the respective input sides of the one non-inverting device (22) and the one inverting device (23), and the one non-inverting device (22) and the one inverting device are connected. FIG. 4A and FIG. 4B are respectively provided on the output side of the container (23).
The signal S _A and the signal S are obtained as shown in (3), and the equality signal S _A and the signal S are supplied to the first selection circuit (15), respectively.

Further, the other output terminal (18) of the position detection head (9) is connected to the input side of the other offset-adjusted amplifier (24), and the output side thereof has the other output terminal (18) of the position detection head (9). a sine wave signal S _B obtained) with obtaining the amplified signal S _B to the output side of the other amplifier (24) connected to the input side of the other of the amplitude adjusting circuit (25), a sine wave signal at its output The sine wave signal S _B whose amplitude is adjusted to the same value as S _A is obtained. The output side of the other amplitude adjusting circuit (25) is connected to the respective input sides of the other non-inverting device (26) and the other inverting device (27), and the other non-inverting device (26) and the other of from as obtaining Figure 4 a and signal S _B and S as shown in FIG. 4 B to the output side of the respective inverter (27), further this such signal S _B
And the signal S are supplied to the first selection circuit (15), respectively.

Also, a first constant voltage power supply (28) capable of outputting a DC voltage V _H having a predetermined high level value and a DC voltage having a predetermined low level value
A second constant voltage power supply (29) capable of outputting V _L is provided so that the direct current voltages V _H and V _L are supplied to the first selection circuit (15), respectively.

The output side of the other non-inverting device (26) is connected to the first comparator (1
0) non-inverting input terminal to supply the signal S _B to the non-inverting input terminal and also to the inverting input terminal with a variable resistor (3
0) to supply the average voltage V _B of the signal S _B ,
A digital signal S _C as shown in FIG. 4C is obtained with reference to this average voltage V _B.

The output side of one of the non-inverters (23) is connected to the second comparator (1
1) connected to the non-inverting input terminal so that the signal S _A is supplied to the non-inverting input terminal and the inverting input terminal is supplied with the average voltage V _A of the signal S _A via the variable resistor (31), Based on this average voltage V _A , a digital signal S _D as shown in FIG. 4D is obtained.

Further, the output signal S _C of the first comparator (10) is supplied to the first selection circuit (15) and the first comparator (10)
The output side of is connected to the input side of the clock generator (32), and a clock pulse for counting the S _C signal and an up / down signal for determining whether to count up or down are obtained at this output side. Equivalent clock pulse and up / down signal to one counter (1
2), and one of the counters (12) performs the counter according to the function table shown in FIG. In the function table shown in Fig. 5, "↑" and "↓"
Indicates the rising and falling states of the signal S _C ,
A clock pulse synchronized with this is supplied to the counter (12) as a count signal. "H" and "L" are signal S
_D indicates a high level state, a so-called "1" and a low level state, a so-called "0", and whether the counter (12) counts up or down depends on the rising state and the falling state of the signal S _C. It is determined by the high level state and the low level state of the signal S _D.

That is, as shown in FIG. 5, the one of the counter (12) is rising state of the signal S _C "↑" high level state of the signal S _D in "H" falling state when and signal S _C of the "↓" When the signal S _{D is in} the low level state "L", the signal is counted up. When the signal S _{C is in} the rising state "↑", the signal S _{D is in} the low level state "L" and the signal S _{C is in} the falling state ". ↓ ”
When the signal S _{D is in} the high level state "H", down counting is performed. The diagram showing the count state of this one counter (12) is shown in FIG. 4E. In this case, the count values 0, 1, 2, ... Are respectively on the magnet (1). It represents a predetermined section. Therefore, hereinafter, the sections on the magnet (1) corresponding to the count values 0, 1, 2, ... Are represented as A0, A1, A2 ,.

Further, the output signal S _D of the second comparator (11) is supplied to the first selection circuit (15) and the output side of the second comparator (11) is connected to the input side of the clock generator (32). , A clock pulse for counting the S _D signal and an up / down signal for determining whether to up-count or down-count are obtained at this output side, and the clock pulse and the up-down signal for the other counter (13 6) in the other counter (13)
The counting is performed according to the function table shown in the figure. In the function table shown in FIG. 6, "↑" and "↓" are signals S.
The rising and falling states of _D are shown, and the clock pulse synchronized with this shows the count signal (1
3) Supplied to. Further, “H” and “L” indicate a high level state of the signal S _C , a so-called “1” and a low level state, a so-called “0”, and whether this counter (13) counts up or counts down is It is determined by the high level and low level of the rising state and a falling state and the signal S _C of the signal S _D.

That is, as shown in FIG. 6, the other counter (13) rising state of the signal S _D "↑" high level of signal S _C at "H" falling state when and signal S _D of the "↓" When the signal S _{C is in} the low level state “L”, the counting is performed, and when the signal S _{D is in} the rising state “↑”, the signal S _{C is in} the low level state “L” and the signal S _{D is in} the falling state “ ↓ ”
When the signal S _{C is in} the high level state "H", down counting is performed. And, the diagram showing the count state of the other counter (13) is the diagram shown in FIG. 4F. In this case, the count values 0, 1, 2, ... Are respectively on the magnet (1). Not as it represents a predetermined section. So,
The sections on the magnet (1) corresponding to the count values 0, 1, 2, ... Are represented as B0, B1, B2 ,.

The output sides of the one counter (12) and the other counter (13) are connected to the input side of the second selection circuit (33),
In the second selection circuit (33), either one of the counters (12) or the output side of the other counter (13) corresponding to the section designation signal input to the section designation signal input terminal (34) is output. Then, the output of one or the other counter (12) or (13) is selected.

The section designation signal from the outside supplied to the section designation signal input terminal (34) is a signal designating the section to be detected on the magnet (1), and in this example, either the counter (12) or (13) is selected. It includes a counter specifying signal and a section specifying value X.

The count signal obtained at the output side of the second selection circuit (33) and the section designation value X of the section designation signal from the section designation signal input terminal (34) are input to the input side of the third comparator (14), respectively. The count signal supplied to the output side of the second selection circuit (33) is compared with the section designating signal, and when the count value Y and the section designating value X match, as shown in FIG. 4G. The signal S _G is supplied to the first selection circuit (15), and when the count value Y is larger than the section designation value X, the signal S _H as shown in FIG. 4H is supplied to the first selection circuit (15). If the count Y is smaller than the designated section value X, the signal S _I as shown in FIG. 4I is supplied to the first selection circuit (15). Further, the section designation signal counter designation signal is supplied to the first selection circuit (15).

Further, in the first selection circuit (15), in response to the input signals S _C , S _D , S _G , S _H , S _I and the section designation signal, the position signal S _A according to the function table shown in FIG. , S, S _B , S, the high level DC voltage V _H or the low level DC voltage _VL are selected and output. In the function table shown in FIG. 7, "H" represents a high level state of a signal and "L" represents a low level state.

The output side of the first selection circuit (15) is connected to the fourth comparator (3
The variable DC voltage power supply (36) is connected to the non-inverting input terminal and the output side of the fourth comparator (35) is connected to the position detecting head (9) by arrows a and b. It is connected to a servomotor (37) that can move in the direction of. In this case, when a positive voltage is supplied to the servo motor (37), the servo motor (37) moves the position detection head (9) to the arrow a side, and when a negative voltage is supplied, the position detection head (9). (9) is moved to the arrow b side.

Next, the operation of the position detecting device configured as described above will be described. In this example, first the A4
The section is designated as the designated section, and the voltage of the power source (36) for designating the position within the section is set to V _M as shown in FIG.
The case where points are specified will be described.

When the M point in the A4 section is designated in this way, the second selection circuit (33) selects the output signal S _E of one counter (12) by the counter designation signal of the section designation signal, and this signal S _E
Is supplied to the third comparator (14).

Then, in this case, assuming that the position detection head (9) is located within the A1 section, since X> Y, the third comparator (14) outputs the signal S _I to the first selection circuit (15). Supply to
The first selection circuit (15) selects the second constant voltage power source (29) based on the function table of FIG. 7 in response to the signal S _I, and outputs from the second constant voltage power source (29). The low level DC voltage V _L is supplied to the inverting input terminal of the fourth comparator (35).

In this case, since the non-inverting input terminal of the fourth comparator (35) a DC voltage _{V M (V M> V L} ) is supplied, a voltage difference _{(V M -V L) (>} 0) is The error signal is supplied to the servo motor (37), and the servo motor (37) rotates so as to move the position detection head (9) to the arrow a side.

When the position detection head (9) enters the A4 section, X =
Since it becomes Y, the third comparator (14) supplies the signal S _G to the first selection circuit (15), and the first selection circuit (15) responds to this signal S _G and the signal S _G shown in FIG. The signal S is selected according to the function table, and the voltage as shown in FIG. 4J is output according to the position within the A4 section, and the output voltage is output to the fourth comparator (3
It will be supplied to the inverting input terminal of 5). Therefore, since the voltage output from the first selection circuit (15) is smaller than V _M until the position detection head (9) reaches the point _M , the error signal always takes a positive voltage value and the servo motor (37) Keeps spinning.

When the position detection head (9) reaches point M, the fourth
Since the voltage supplied to the inverting input terminal of the comparator (35) and the voltage supplied to the non-inverting input terminal are the same and the error voltage is 0 [V], the servo motor (37) stops rotating. , The position detection head (9) stops corresponding to the point M.

Next, the case where the section B4 is designated as the designated section by the section designation signal from the outside and the voltage of the position specifying power supply (36) is set to V _N as shown in FIG. Try.

If you specify an N-point of such a B4 interval, the second selection circuit by the counter designating signal interval designation signal (33) selects the output signal S _F of the other counter (13), the signal S _F It is supplied to the third comparator (14).

Then, in this case, X <Y assuming that the position detection head (9) is located in the section B8, and therefore the third comparator (14) outputs the signal S _H to the first selection circuit (15). In response to this signal S _H , the first selection circuit (15) selects the first constant voltage power supply (28) based on the function table of FIG. 7, and supplies the first constant voltage power supply (28 The high-level DC voltage V _H output from the second comparator (35) is supplied to the inverting input terminal of the fourth comparator (35).

In this case, since the DC voltage V _N (V _N <V _H ) is supplied to the non-inverting input terminal of the fourth comparator (35), the voltage difference (V _N −V _H ) (<0) is generated. The error signal is supplied to the servo motor (37), and the servo motor (37) rotates so as to move the position detection head (9) to the arrow b side.

When the position detection head (9) enters the section B4, X =
Since it becomes Y, the third comparator (14) supplies the signal S _G to the first selection circuit (15), and the first selection circuit (15) responds to the signal S _G and is shown in FIG. The signal S _B is selected in accordance with the function table of No. 4, and the voltage shown in FIG. 4k is output according to the position in the section B4, and the output voltage is output to the fourth comparator (35).
It is supplied to the inverting input terminal of.

Therefore, until the position detection head (9) reaches the N point, the first
Since the voltage output from the selection circuit (15) is larger than V _N , the error signal always takes a negative voltage value and the servomotor (37) continues to rotate.

When the position detection head (9) reaches the N point, the voltage supplied to the inverting input terminal and the voltage supplied to the non-inverting input terminal of the fourth comparator (35) match and the error voltage is Since it becomes 0 [V], the servo motor (37) stops its rotation, and the position detection head (9) stops corresponding to point N.

Thus, according to this embodiment, four magnetoresistive elements (5) are provided.
The position detection head (9) is composed of (6), (7) and (8),
Position signal S _A of the 2-phase from the position detection head (9), to give the S _B, further the position signal S _A, a digital signal S _B S _C, S _D converted and position detecting head (9) is a magnet The signals S _E and S _F indicating the section located with respect to (1) are obtained, and the signals S _E and S _F are compared with the section designation signal to determine the magnet (1)
The position detection head (9) is moved by the servo motor (37) so that the section where the position detection head (9) is positioned and the designated section of the position detection head (9) for the magnet (1) coincide with each other. When the section in which the position detection head (9) is positioned with respect to the magnet (1) and the designated section of the position detection head (9) with respect to the magnet (1) match, the first selection circuit (15) determines a predetermined value. A position signal is selected, the voltage indicated by this position signal is compared with the position designation voltage, and the position detection head (9) is designated by the servo motor (37) so that the voltage indicated by the position signal matches the position designation voltage. It is designed to move to a position.

Further, in this example, the output signal S of the position detection head (9)
_Since the signals S and S obtained by inverting _A and S _B are also used as the position signals, the linear parts of the four-phase position signals having different equal phases are placed on the magnet (1) as shown by the solid line in FIG. 4L. All positions in can be specified.

Therefore, according to the present embodiment, it is possible to detect a minute displacement of the magnet (1) which is equal to or smaller than the magnetizing pitch, a so-called dead zone is not generated, and a high-resolution position detection which is higher than the resolution verified by the magnetizing pitch is performed. There is a benefit of being able to do it. Incidentally, in this example, even if the gap between the magnet (1) and the position detection head (9) is about 0.1 mm to 0.4 mm, it is possible to realize high-resolution position detection of about 10 μm. Moreover, in this example, since the position signal output from the position detection head (9) is used as it is and the position detection is performed by the analog value of this position signal, it is possible to perform high-resolution position detection with a simple structure. There is a benefit of being able to.

Incidentally, in the above-mentioned embodiment, the magnetoresistive elements (5) (6)
Although the cases where (7) and (8) are used have been described, it is also possible to apply other magnetoelectric conversion elements such as a Hall element instead of this, and in this case, it is easy to obtain the same effect as the above. You can understand.

Further, in the above embodiment, four magnetoresistive elements (5)
Although the case where the two-phase position signals S _A and S _B are obtained by using (6), (7), and (8) has been described, instead of this, six or more magnetoresistive elements are used and three-phase or more position positions are obtained. When the signal is obtained, a more linear portion of the position signal can be used, so that there is an advantage that the resolution can be further increased.

Further, in the above embodiment, the case where the magnet (1) is fixed and the position detecting head (9) is moved has been described, but instead of this, the position detecting head (9) is fixed and the magnet (1) is moved. It can be easily understood that it can be moved and the same action and effect as described above can be obtained in this case as well.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

〔The invention's effect〕

According to the present invention, it is possible to detect a minute displacement equal to or less than the magnetizing pitch, so that there is an advantage that it is possible to perform position detection with high resolution equal to or higher than the resolution determined by the magnetizing pitch.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the position detecting device of the present invention,
2 is a diagram used for explaining a position detecting head used in an embodiment of the present invention, FIG. 3 is a diagram showing an equivalent circuit of the position detecting head shown in FIG. 2A, and FIG. A diagram used to explain the example of the figure, FIG. 5 is a diagram showing a function table of one counter, FIG. 6 is a diagram showing a function table of the other counter, and FIG.
FIG. 8 is a diagram showing a function table of the first selection circuit, and FIG. 8 is a diagram used for explaining a conventional position detecting device. (1) is a magnet, (5), (6), (7) and (8) are magnetoresistive elements respectively, (9) is a position detection head, (10)
(11), (14) and (35) are comparators, (12) and (1
3) is a counter, (15) and (33) are selection circuits, (28) and (29) are DC constant voltage power supplies, (32) is a clock generator, (34) is a section designation signal input terminal,
(36) is a variable power source for position designation in the section, and (37) is a servo motor.

Claims (1)

[Claims] 1. A magnet magnetized at a constant pitch,
The magnet has a plurality of magnetoelectric conversion elements arranged at a predetermined pitch with respect to the pitch of the magnet so as to move relative to the magnet, and position signals of two or more phases corresponding to the position on the magnet are provided. A position detecting head for outputting is provided, the position signal is counted, a count signal representing a predetermined section on the magnet is obtained, and the count signal is compared with a desired section designation signal from the outside. Based on the above, the position signal of the desired phase is selected from the position signals of the two or more phases, and the position of the position detection head with respect to the magnet is detected by the section designation signal and the analog value of the position signal of the desired phase. A position detecting device characterized in that