JPS61114125A - Magnetic encoder - Google Patents

Abstract

PURPOSE:To improve resolution by arranging plural magneto-resistance elements so that they are magnetized in turn when a magnetic mark detecting circuit is moved relatively with a magnetic scale, and deciding on its detection output and calculating the position of a magnetic head. CONSTITUTION:A composite bridge circuit 4 consists of magneto-resistance elements 10-19 and reference resistance element 9 and 9'. A position deciding circuit 5 consists of comparing circuits 20-29, AND gates 30-39, FFs 40-49, and a driving circuit 50 for an up/down counter 8. Magnetic marks 2 and 2' are formed by magnetizing the surface of a medium forming the magnetic scale 1 vertically and alternately in the opposite directions at desired pitch lambda. The circuit 4 is fixed and the scale 1 is moved to right and left. When the scale 1 is moved to right by up to 1/10 as large as lambda, three of elements 10-19 are positioned on the marks 2 and 2' invariably in turn. The circuits 20-29 compare the output of the circuit 4 with a reference voltage and outputs the result to display the position of the scale 1 on a position display device 6 accurately. Thus, the resolution is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic encoder capable of detecting angle and position, and particularly to a type of magnetic encoder using a magnetoresistive element.

These magnetic encoders use a magnetic head equipped with a bridge circuit consisting of a magnetoresistive element in order to read magnetic marks provided on a desired magnetic medium.

The magnetic marks are generally provided at regular intervals perpendicularly or parallel to the surface of the medium, and the magnetization directions are alternately opposite.

In the conventionally known bridge circuit, in order to read this magnetic mark, four magnetic units are arranged along the magnetic scale at intervals of 2 or an odd multiple of the interval λ between the magnetic marks. A resistive element is used, so that when the magnetic encoder moves relative to the magnetic scale, one cycle of output is generated each time the magnetic encoder moves through a distance corresponding to one division, that is, the distance λ between the centers of the magnetic marks. A signal is obtained from which an output signal of one or two pulses is obtained.

Therefore, if the interval λ between the magnetic marks is made as small as possible and the magnetic marks are provided at a high density, the resolution of the magnetic scale will increase, but if you try to reduce the interval λ between the magnetic marks, the magnetic force will weaken and the magnetic This makes it difficult to detect marks.
There are limits to how much resolution can be improved with this method.

Therefore, it is convenient if an output signal can be obtained at a high density of 10 pulses to several tens of pulses or more when moving one scale.

In addition, in conventionally known magnetic heads, two sets of bridge circuits are used for the so-called human phase and B phase in order to identify the direction of movement of the magnetic scale. Although identification is possible, the resolution cannot be improved even if the number of magnetoresistive elements used is doubled, so there is a problem that the number of signal pulses obtained is small compared to the large number of magnetoresistive elements used.

The present invention has been made based on the above-mentioned viewpoint, and its object is to provide at least 10
It is an object of the present invention to provide a high-resolution magnetic encoder that can use up to several tens of magnetoresistive elements, or even several hundred in some cases, and can obtain the same number of output pulses as the number of b magnetoresistive elements used.

This object can be easily achieved by employing a composite bridge circuit, which will be explained in detail below with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the magnetic encoder according to the present invention, in particular the arrangement of magnetoresistive elements and their coupling method, and FIGS. 2 and 3 are magnetic 4 is a diagram showing the resistance change of a resistive element, FIG. 4 is a diagram showing the output voltage of an intermediate terminal provided in one electric path constituting the above composite bridge circuit, and FIGS. 5 to 14 are diagrams showing the above composite bridge circuit, respectively. Figures 15 to 24 are pulse waveform diagrams showing the outputs of the 10 AND gates connected to the latter stages of the comparison circuits, respectively. , FIG. 25 is a pulse waveform diagram showing the output of the drive circuit of the amplifier down counter showing the relative position of the bridge circuit and the magnetic scale, and FIG. 26 shows a partially modified embodiment of the magnetic encoder shown in FIG. 1. The partial circuit diagram, FIG. 27, is a front view of a circuit element implementing a composite bridge circuit.

The explanation will be given below in order starting from FIG.

In FIG. 1, 1 is a magnetic scale having magnetic marks 2, 2', 3 is a constant voltage power supply, 4 is a composite bridge circuit constituting a magnetic mark detection circuit, and 5 is based on the output signal of the composite bridge circuit 4. Magnetic scale 1 and magnetic mark detection circuit 4
6 is a position indicator consisting of a numeric indicator 7 and an amplifier down power counter 8.

Therefore, in this embodiment, the composite bridge circuit 4 has 10
magnetoresistive elements 10 to 19 (hereinafter, one of them is 11
Indicated by ) and - set of reference resistors 9.9', and the position discrimination circuit 5 is composed of comparison circuits 20 to 29 (
One of them is shown below as 21. ), AND gates 30 to 39 (hereinafter, one of them is indicated by 31), flip-flops 40 to 49 (hereinafter, one of them is indicated by 41).
and a drive circuit 50 for the up/down counter 8,
Furthermore, the drive circuit 50 consists of an OR gate 51, flip-flops 52, 53, 54, 56, an AND gate 57, 58 and a monostable element 58, 59.

The magnetic marks 2.2' are formed by magnetizing the medium forming the magnetic scale 1 perpendicularly to its surface and alternately in opposite directions with a desired pitch λ. Therefore, the center-to-center distance is λ, and north and south poles appear alternately.

In the following description, it is assumed that the magnetic mark detection circuit 4 is fixed and the magnetic scale 1 moves left and right in the figure.

These magnetoresistive elements 10 to 19 are all formed on the surface of an appropriate insulator (not shown) by a known method using an alloy exhibiting a magnetoresistive effect, and are opposed to the magnetic scale 1. The magnetic marks of the magnetic scale 1 are arranged along the trunk on which the magnetic marks are provided, as shown in the figure, at intervals of 1/10 of the pitch λ of the magnetic marks, and when the magnetic scale 1 moves, The magnetoresistive elements 10, 15, 11, 16.
12, 17, 13, 18, 14, and 19 are connected in series, and intermediate terminals a and b are connected to their connection parts.
.

c, d and e are provided.

The resistance values of these magnetoresistive elements 10 to 19 are all the same when the element is located in the middle of the magnetic marks (when it is not magnetized, it is directly above the R1 magnetic mark, and when it is fully magnetized, it is r). Suppose there is.

Here, Tongfeng, R>>r It is.

Therefore, when the magnetic scale 1 moves, for example, to the right in the figure and its relative position with the magnetic mark detection circuit 4 changes, the resistance of these magnetoresistive elements 10 to 19 will vary between the maximum value R and the minimum value r. It will fluctuate periodically.

FIGS. 2 and 3 show how the resistances of these magnetoresistive elements 10 and 15 change.

In these figures, the horizontal axis indicates the moving distance of the magnetic scale l in units of λ, and the vertical axis indicates the resistance value of each magnetoresistive element.

In such a case, the potential of the connecting terminal a between these magnetoresistive elements 10 and 15 will change as shown in FIG.

Therefore, here, ■I”2Vo R/ (R+r) ■2-2 Vo　r/　(R+r) It is.

Since the pinch of the magnetoresistive elements 10 to 19 is λ/10, their resistance changes and the other intermediate terminals b, c,
The voltage changes of d and e can be easily inferred from FIGS. 2 to 4.

On the other hand, the reference resistors 9.9' have the same resistance value, preferably the same R as that of the magnetoresistive element, and are connected in series with each other, and the inter-terminal voltage 2Vo of the constantly constant voltage power supply 3 is connected to the intermediate terminal S. A reference voltage Vo corresponding to -half of the voltage is output.

This reference resistor 9.9' is preferably one that does not have magnetoresistive properties, but it can be the same as the magnetoresistive element 10, etc., if it is shielded from the magnetic influence of a magnetic scale, etc. can also be used.

The comparison circuits 20 to 29 compare the potentials V of the output terminals a, b, c, d and e of the magnetic mark detection circuit 4 with
A comparison is made with the reference voltage (2) at the intermediate terminal S of the reference resistor 9.9'.

The five comparison circuits 20 to 24 satisfy ■−■o≧Vs (however, Vs = const, >
Q), the output pulse indicating state 1 is transmitted, and the remaining five comparison circuits 25 to 29 are configured to transmit output pulses indicating state 1 when V-VO5-Vs. In the end, output pulses as shown in FIGS. 5 to 14 are obtained from the comparison circuits 20 to 29.

In this embodiment, when the magnetic scale 1 moves to the right by one-tenth of λ from the state shown in FIG. Since the comparator circuits 20 to 29 are configured to be placed on the magnetic marks 2.2' in rotation at all times, the width of the output pulses of the comparator circuits 20 to 29 is 10 of λ.
It becomes 3/3.

The AND gates 30 to 39 are the comparison circuits 20 to 2.
The number of the magnetoresistive element located at the exact center of one magnetic mark, for example 2 or 2', is input by inputting the output of the adjacent one of 9 (comparison circuits 20 and 29 are adjacent to each other). 11.

The actions of these AND gates 30 to 39 will be readily understood from the positions and shapes of the output pulses of the comparison circuits 20 to 29 shown in FIGS. 5 to 14. The outputs of these AND gates 30-39 are shown in FIGS. 15-25.

(lO) Now, if one magnetoresistive element 11 is located exactly at the center of one magnetic mark, the outputs of the comparator circuit 21 corresponding to this magnetoresistive element 11 and the comparison circuits on both sides thereof become the shape 61, and the other Since the output of the comparison circuit is in the state 0, among the AND gates 30 to 39 connected at the subsequent stage, the AND gates 1 and 31 whose inputs are the outputs of the comparison circuit 21 and the comparison circuits on both sides thereof are connected. Only the output is in state 1, and all the outputs of the other AND gates are in state 0.

As a result, the flip-flop 41 corresponding to the AND gate 31 enters the seso-i state, and the number i is displayed on the number display 7 correspondingly.

These flip-flops 40 to 49 are provided to stabilize the display on the numeric display 7 by eliminating the effects of transient errors in the outputs of the comparison circuits 20 to 29 and the AND gates 30 to 39 that may occur when the magnetic scale 1 moves. It is something.

That is, in a transition state where the moving distance of the magnetic scale 1 is odd and is not an integral multiple of 1/10 of λ, the comparator circuits 20 to 2
There are cases where only two of the 9 outputs have the state 1.

At that time, the outputs of AND gates 30 to 39 are all in the state 0, but the flip-flop 41 is
Antogame-1/3j adjacent to 31 (However, J-1±
Set to 1. ) until the output reaches state 1, it remains in the 7-node state and keeps the display on the number display 7 at 1.

Therefore, when the output of Antogame]・3j becomes state 1,
At the same time, the output of the same 31 returns to state O, so the flip-flop 41 is set and at the same time the same 4j is set to the state O.
・The display on the numeric display 7 changes to j.

On the other hand, the outputs of these flip-flops 40 to 49 are supplied to a drive circuit 50 of the up/down counter 8.

This drive circuit 50 detects the moving direction of the magnetic scale 1, and when the display on the numeric display 7 changes from 9 to O, it supplies one pulse to the addition input terminal of the up/down counter 8, and vice versa. When the value changes from 9 to 9, one pulse is supplied to the subtraction input terminal, and the outputs of the flip-flops 42 to 48 are used as reset inputs of the flip-flops 52, 53, 54, and 56 via the OR gate 51. Ru.

Therefore, the flip-flops 52.53.54.56 are
Any one of flip-flops 42 to 48 is
In the reset state, while the number display 7 is displaying 2 to 8, the reset input is always present.

However, the magnetic scale 1 continues to move to the right in the figure,
When the magnetoresistive element 19 comes to be located at the center of one magnetic mark, the flip-flop 49 enters the cent state and the number display 7 shows 9.

Although the cent output of this flip-flop 49 cannot pass through the AND gate 57, it inverts the flip-flop 52 to the set state, so the magnetic scale 1 subsequently moves to the right, and the magnetoresistive element 10 becomes one. When the center of the magnetic mark is reached (the state shown in FIG. 1) and the flip-flop 40 is inverted to the cent state, its cent output passes through the AND gate 56, inverting the flip-flop 54 and changing to the cent state. Make it.

The set output of this flip-flop 53 triggers the monostable element 5 to generate an output pulse to be sent to the addition input terminal 8a of the up/down counter 8.

When the magnetic scale I continues to move in the same direction and the flip-flop 41 is set, and the display on the numeric display 7 becomes 1, the output is sent to the flip-flops 52 and 54 via the OR gate 51. Reset.

Conversely, when the magnetic scale 1 moves to the left in the figure and the display on the numeric display 7 changes from 0 to 9, the effect will be obvious.

When the display becomes O, the set output of flip-flop 40 now sets flip-flop 53, which then allows the cent output when flip-flop 49 is set to pass through AND gate 57. The flip-flop 7 block 55 is inverted to the set state, and the monostable element 59 generates an output pulse to be sent to the subtraction input terminal 8b of the A-knob down counter 8.

Therefore, according to the present invention, the position of the magnetic scale 1 can be accurately measured at all times without using the A and B two-phase detection circuits as in the conventionally known ones.

Furthermore, as mentioned above, in the present invention, the pinch of the magnetoresistive element can be reduced regardless of the width of the magnetic mark,
Therefore, even if the pinch of the magnetic mark is made coarse, the resolution can be improved by arranging the magnetoresistive elements at a high density. Since each magnetoresistive element can be strongly magnetized by generating magnetic flux, it is less affected by external magnetic fields.

In the above embodiment, ten magnetoresistive elements are used, and it is assumed that R (3111) magnetoresistive elements are always placed on top of the magnetic mark and are magnetized.

However, the number of magnetoresistive elements and the number of magnetoresistive elements to be magnetized are not limited to 10 or 3, and the former can generally be about 5 to 20, and depending on the case, about 50 to 100. Regarding the latter, it is generally recommended that about one-third of the magnetoresistive elements used be configured so that they are always magnetized by the magnetic marks; It can be freely set within the range of the number of magnetoresistive elements.

When the number of magnetized magnetoresistive elements is large, the state of only a few magnetoresistive elements within a certain range near the boundary line between magnetized and unmagnetized Obtaining to determine the position of the magnetic scale.

In addition, in the above embodiment, the number of magnetoresistive elements magnetized by the magnetic mark is constant, but depending on the accuracy of the magnetic scale and the number of magnetoresistive elements used, the movement of the magnetic scale may vary. The number of magnetoresistive elements magnetized may vary significantly depending on the However, even in such a case, accurate measurements can be made by using the circuit shown in FIG. 26, which will be described next.

In this case, the width and pitch λ of the magnetic marks are not strictly constant (, if these errors cannot be ignored compared to the value of λ/10, one reference position, that is, the actual value of magnetic scale 1) When the position of is equal to the value expressed by (M+m/10) λ, where M and m are integers, in other words, the position of the magnetoresistive element 10, which is the reference for the position of the magnetic mark detection circuit 4, is The number of magnetoresistive elements actually magnetized by the magnetic mark varies in the range of 2 to 4 when it coincides with one of the positions of the points dividing the space between adjacent magnetic marks 2.2' into 10. shall be taken as a thing.

Circuits 30', 31', 32', 33' in FIG.
. . , 39' are arithmetic circuits to be used in place of the AND gates 30 to 39 shown in FIG. 1, respectively.

These arithmetic circuits 30-0.31', 32', 33',
. . , 39' have the same configuration, so only 30' is illustrated here. This circuit 3
0' consists of - OR gates 30-1 and three UN gates 1-30-2, 30-3 and 30-4.

The detailed configuration of the other circuits 3 is not shown, but they all include -1 for the OR gate 3, -2 for the three AND gates 3, -3 for 3, and -4 for 3. It consists of

From these AND gate input symbols, AND gate 3
0-2 is 211 of the magnetoresistive elements 10 to 19! It will be immediately understood that it can only take part in determining the relative position of the magnetic scale 1 and the composite bridge circuit 4 when it is not magnetized; otherwise its output is always in state 0.

Similarly, Antoge-130-3 and 30-3 can participate in determining the relative position only when the number of similarly magnetized magnetoresistive elements is 3 and 4, respectively, but in other cases, the output will never be in state 1.

Therefore, it is assumed here that the relative positions of the magnetic scale 1 and the composite bridge circuit 4 are determined according to the outputs of the comparison circuits 20 to 29 as shown in Table 1 on the next page.

In that case, the number of magnetized magnetoresistive elements is 2.3
or 4, respectively, and gate 3 −
-3 to 2, 3, -4 to 3 (k = O~9) determines the relative position of the magnetic scale in place of the above-mentioned comparison circuits 20 to 29.

The actions of the corresponding AND gates are the same as those of the AND gates 30 to 39 explained in FIG.
The relative position is determined according to the rules shown in Table 1 on the next page, and the output of only one corresponding AND gate is in the form fit, and its output pulse passes through the OR gate provided at the subsequent stage as shown in Figure 1. The signal is transmitted to the cent input terminal of one of the flip-flops 40 to 49.

The functions of these flip-flops 40 to 49 and the circuit elements connected to their subsequent stages are as described above, and they prevent the occurrence of transient errors accompanying the movement of the magnetic scale 1, and prevent the movement of the magnetic scale 1. The orientation will be determined and the correct position of the magnetic scale 1 will be displayed on the magnetic scale position indicator 6.

Table 1 According to this circuit, as shown in Table 1 on the previous page, even when the number of output magnetized magnetoresistive elements of comparison circuits 20 to 29 varies, the magnetic scale 1 The position can always be displayed accurately.

Next, an example of a circuit element in which a composite bridge circuit is mounted will be described with reference to FIG. 27.

The figure is a front view of a circuit element, and 100 in the figure is a substrate made of an insulating material such as glass or ceramics, and 10-E
, 11-E, 12-E, 13-L 144.15
-E, 16-[! , 17-E, 18-[! , 19-B
is a magnetoresistive element made of permalloy or other magnetoresistive alloy formed on the surface of the substrate 100 by a thin film forming technique such as vapor deposition or sputtering.

At both ends of these magnetoresistive elements, leads 10-J, 11-J, each made of a copper thin film formed by the same technique as above or by plating, etc., are provided to selectively connect the magnetoresistive elements in series. 12-J, 13-J.

14-J, 15-J, 16-J, 17-J, 1B-
J, 19-J, and leads 10-ν, II-V, made of copper thin film similar to the above, which are connected to the constant voltage power supply 3.
12-ν, 13-ν, 14-v, 15-G, 16-
G, 17-G, 1B-G, 19-G are connected, leads 10-J and 15-J, 11-J and 16-J
, 12-J and 17-J, 13-J and 18-J,
14-J and 19-J are through-holes a and a', respectively, which are provided at one end and have conductive treatment on their inner surfaces.
bIl! : b', c and d', d and d' and e and e/, and through-hole coupling jumps A, B, C, , D and E made of a thin copper film provided on the back surface of the substrate 100. are connected to each other in series through.

The magnetoresistive element is a thin film with a thickness of about 500 mm, for example, 0.5 mm thick.
Provide with a pinch of 10 to 2 μm. It is recommended that its length be approximately equal to or less than the width of the track on which the magnetic mark is provided.

Each lead and jump is not affected by magnetism and is made of a rather thick thin film of gold, silver, or copper that has low resistance.

Further, although this circuit element is not provided with the aforementioned reference resistors 9,9', it is recommended that they be provided integrally with this circuit element.

Since the present invention is constructed like an ironwork, according to the present invention, a large number of magnetoresistive elements can be arranged at high density without being limited by the spacing, width, etc. of magnetic marks, and the resolution can be increased to a desired level. What you gain is what you gain.

It should be noted that the configuration of the present invention is not limited to the embodiments of ironwork, and can of course be modified freely within the scope of the purpose of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the magnetic encoder according to the present invention, in particular the arrangement of magnetoresistive elements and their coupling method, and FIGS. 2 and 3 are magnetic 4 is a diagram showing the resistance change of a resistive element, FIG. 4 is a diagram showing the output voltage of an intermediate terminal provided in one electric path constituting the above composite bridge circuit, and FIGS. 5 to 14 are diagrams showing the above composite bridge circuit, respectively. Figures 15 to 24 are pulse waveform diagrams showing the outputs of the 10 AND gates connected to the latter stage of the comparison circuits, respectively. , FIG. 25 is a pulse waveform diagram showing the output of the up/down counter drive circuit showing the relative position of the bridge circuit and the magnetic scale, and FIG. 26 shows a partially modified embodiment of the magnetic encoder shown in FIG. 1. The partial circuit diagram, FIG. 27, is a front view of a circuit element that implements a composite block circuit. 1----------1 Magnetic scale 2--1 Magnetic mark 3~ =------Constant voltage power supply 4---Composite bridge circuit 5-- ---------1 Magnetic scale position determination circuit 6
−−−−−−−−−−−Magnetic scale position indicator 7−
-------~-111-Numeric display 8--------Up/down counter 9.9'-----Reference resistor 10 to 19-- - Magnetoresistive elements 20 to 29 - - Comparison circuits 100 to -1 - Circuit element substrate patent applicant Inoue Japax Research Institute Agent (
7524) Most" two thick part i I+cc: L, -o to -low low low 0 - low C1xO1+o -6ri>>shi c2 &><36 self 56566
56 ward ward ward ward round country map garden ward garden ward diagram dimension 10 Φ ω ri 0-
To ω! Thief Thief Thief Taste Taste Taste Taste Taste Taste Taste Pulse <<<<<<<<<<<< Power Dogu Ku Ku Kaiming Ku Ku Ku Ku Ku 11') C
D I + ωOo- to one-one-one-hehehehehe

Claims (1)

[Scope of Claims] A magnetic mark detection circuit comprising a plurality of magnetoresistive elements, a power supply circuit that supplies voltage to the magnetic mark detection circuit, and a discrimination circuit that decodes the output signal of the magnetic mark detection circuit. In a magnetic encoder used to read magnetic marks provided on a magnetic scale, a magnetic mark detection circuit detects 2N magnetoresistive elements (N is a positive integer) between adjacent magnetic marks. are spaced apart by 1/2N of the center-to-center distance λ or an integer multiple thereof, and are magnetized by the magnetic marks one time in rotation when the magnetic mark detection circuit moves by λ relative to the magnetic scale. 2N magnetoresistive elements arbitrarily selected from among the above 2N magnetoresistive elements are connected in series with each other, an intermediate terminal is provided at the connection point, and furthermore, the two magnetoresistive elements connected in series are It is equipped with a circuit in which all of the circuits consisting of magnetoresistive elements are connected in parallel with each other, and the discrimination circuit individually compares a constant reference voltage and the voltage output from each of the N intermediate terminals. and an arithmetic circuit that decodes the output signals of the N comparison circuits and transmits a signal indicating the position of the magnetic head. magnetic encoder.