JPS6358101A - Position detector - Google Patents

Abstract

PURPOSE:To reduce malfunctioning by sampling an output voltage of a magnetoresistance effect element (MR element) synchronized with the operation of a magnetized medium when the voltage becomes stable. CONSTITUTION:When a relative position between an MR element 3 and a magnetized medium 1 is at step 0, a drive signal is sent to a driving circuit 11 from a control circuit 10 to move the medium 1 by one step. A sampling pulse is sent to a sampling circuit 7 from the circuit 10, synchronized with this drive signal, to sample a certain fraction of the DC voltage (MR output voltage). Subsequently, the medium 1 is moved by one step again to sample an MR output voltage synchronized with the movement thereof. The signal thus sampled is compared with the value sampled at the preceding step by a comparison circuit 9. When the level difference between these signals is below a specified value, with the judgement that the MR output remains unchanged, the medium 1 is moved by one step again. When it is above the specified value, with the judgement that the MR being changed, the medium 1 will not be moved. Thus, the detection of the position of magnetization is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position detection device using a magnetoresistive element whose resistance value changes depending on an external magnetic field.

[Conventional technology]

A magnetoresistive element (hereinafter abbreviated as ``element'') is a protrusion whose resistance value changes depending on an external magnetic field.Therefore, by detecting a change in the resistance value of the dish element, changes in the external magnetic field can be known. .

Various methods have been devised to detect changes in resistance value, but the simplest method is to connect a resistor and a fixed resistor in series, apply a DC voltage, and then output a DC voltage (hereinafter referred to as MR) from the connection point.
It is possible to detect changes in the resistance value of the plate element based on changes in this DC voltage.

Furthermore, to detect changes in resistance when the magnetic field changes at high speed, such as in a magnetic card reading device, for example, in Japanese Patent Application Laid-Open No. 60-40504, The change in current due to the change in is converted into a change in voltage, amplified, and extracted as a high-frequency signal voltage.

[Problem that the invention seeks to solve]

(2) As an application of detecting external magnetic field changes using an element, there is a position detection device that causes a partially magnetized medium to move linearly or rotationally in a stepped manner, detects a magnetized portion, and stops the movement.

In order to detect a magnetized portion using the first conventional technique described above, it is sufficient to set an appropriate threshold value for the above-mentioned (1) output voltage and determine whether the output voltage exceeds the threshold value. However, (1) the following problems occur due to changes in the resistance of the element due to aging, temperature characteristics, or changes over time.

Above, ■output voltage is based on ■the voltage when no external magnetic field is applied to the element (hereinafter referred to as midpoint voltage), and the voltage change corresponding to the change in resistance due to external magnetic field (hereinafter referred to as displacement voltage). ) to be displaced. However, due to variations in the resistance of each element in the above element, changes in resistance due to placement characteristics and changes over time, the midpoint voltage changes even if the displacement voltage does not change, so the absolute value of the output DC voltage fluctuates. The threshold must be reset.

In addition, the above-mentioned position detection device sends the magnetized medium in a stepwise manner, but the magnetized medium may be affected by a number of factors, such as jumps in the pulses that drive the step motor, a time delay between sending the pulses and the motor moving, and backlash in the mechanism. Immediately after moving the output DC voltage is not stable. For this reason, the above-mentioned 1. When using the second conventional technique, there is a possibility that a change in the output voltage will be detected erroneously.

SUMMARY OF THE INVENTION An object of the present invention is to provide a position detection device with fewer malfunctions in consideration of the above problems.

[Means for solving problems]

The above purpose is to synchronize the output voltage of the dish element with the movement of the magnetized medium, sample it when the NFL output voltage is stable, and use a memory circuit to store the sampled value, and in the next step, This is accomplished by providing comparison means for sampling and comparing with the stored value to detect the relative change in the dish output voltage at each step.

[Effect]

By timing the sampling when the disk output voltage is stable, malfunctions caused by noise immediately after the magnetized medium moves can be eliminated, and by detecting relative changes in the output voltage at each step, fluctuations in the midpoint voltage can be avoided. It is possible to eliminate malfunctions due to

〔Example〕

Hereinafter, details of the present invention will be explained using figures. Figure 1 shows
FIG. 1 is a configuration diagram of a first embodiment of the present invention.

Reference numeral 1 denotes a substance (hereinafter referred to as a magnetized medium) that is magnetized at a predetermined position, and is moved in a stepwise manner by a drive mechanism 2 . 3 is a dish element, 4 is a fixed resistor, and 5 is a DC power supply, which applies a DC voltage to the series connection circuit of the magnetoresistive element 3 and the fixed resistor 4. 6 is a connection point of the series connection circuit, from which a DC voltage C, which is obtained by dividing the DC voltage by the MR element 3 and the fixed resistor 4, is applied.

output voltage). 7 is a sampling circuit that samples the DC voltage obtained by dividing the voltage;
8 is a storage circuit for storing the values sampled by the sampling circuit 7; 9 is a storage circuit for storing the sampled values and 1;
A comparator circuit 10 compares the value sampled before the step and stored in the memory circuit 9. Reference numeral 10 is a control circuit that controls the sampling circuit and the drive circuit described below in accordance with the output of the comparator circuit 9. be. 11 is a circuit that drives the drive mechanism 2 mentioned above.

In the configuration shown in FIG. 1, the magnetized medium 1 is working against the fixed dish element 3, but conversely, the element 3 is working against the fixed magnetized medium 1. Of course it's fine even if it is. In short, it is sufficient if the structure allows both to move relative to each other.

FIG. 2 shows a waveform diagram of the relative position between the magnetized medium 1 and the seed element 3 and the dish output voltage. However, the parts indicated by 1° 3 to 5 in the figure are the same as those explained in FIG. The figure shows the relative relationship between the (1) element 3 and the magnetized medium 1 when the number of steps is 00. Thereafter, the magnetized medium 1 is assumed to move stepwise in the direction of the arrow by one step at a predetermined time interval. The bottom row is
It shows the output voltage at each step. Note that the resistance RMR of the element becomes l'r when a magnetic field is applied from the outside.
MR (BMu > RMR) and thick (assumed to be). However, it does not necessarily have to be this way
But that's fine.

In this case, the voltage change described below is simply reversed, and a decrease in voltage may be detected.

First, consider the state of 0 steps. Voltage E of DC power supply 5
, the resistance of the fixed resistor 4 is assumed to be a bird. At this time, since no magnetic field is applied to the plate element 3, the resistance is &R. Therefore, the output voltage is ERMR/(几wx+R,,). Let this be vL. When the magnetized medium 1 is sequentially fed in the direction of the arrow, up to the 7th step, the external eye field is not applied to the (1) element 3, so the dish output voltage is VX as in the 0th step.

However, in the eighth step, (1) a magnetic field is applied to element 3, so the resistance of the silent element becomes FLtu (H, MR)l'js
u+). Therefore, the German output voltage at this time is gRL
p/(R'MR+R1), and if this is V■, then Vn>Vz. In the ninth step (2), no magnetic field is applied to the child 3, so the output voltage (2) decreases again.

Next, an operation will be described in which the magnetized portion of the magnetized medium 1 is detected using this output voltage and is stopped when the magnetized portion just reaches the raccoon element 3.

Assume now that the relative position of element 3 and the magnetized medium is at step 0 in FIG. Here, a signal is sent from the control circuit 10 to the drive circuit 11 to move the magnetized medium one step. In synchronization with the drive signal at this time, a sampling pulse is sent from the control circuit 10 to the sampling circuit 7, and the output voltage is sampled. The sampled signal is stored in the memory circuit 8.
to be memorized.

Subsequently, the loading and unloading medium is moved one step again, and in synchronization with this, (1) the output voltage is sampled. A comparison circuit 9 compares this sampled signal with the value sampled and stored in the previous step. As a result of the comparison, if the level difference between the two signals is below a predetermined level, it is determined that the output has not changed, and after inputting the signal sampled this time to the storage circuit, the magnetized medium 1 is set to 1 again. Move step by step and follow the process described above.

On the other hand, if the level difference between the two signals is above a predetermined level, it is determined that the dish output has changed, and this state is maintained, and the magnetized medium is not moved. This completes the detection of the magnetized position. The reason why we set 5 to require a difference of at least a certain level when making a judgment is to prevent the output voltage from fluctuating due to noise, etc., and to avoid erroneously detecting fluctuations due to this noise. If the predetermined level is set above the noise level, malfunctions due to noise will not occur ('.

In addition, in the above explanation, as shown in Figure 2, the output voltage is 1
As soon as the step is sent, the voltage is stabilized at either V■ or vL. However, in reality, as shown in FIG. 14, immediately after the step motor is moved, the output voltage may not be stable due to jumps in pulses for driving the motor, backlash in the mechanism, delay in motor response, etc. ■ Correct position detection cannot be performed if the output voltage is sampled during this unstable period. Therefore, if the time from when the motor is started until the output voltage becomes stable is t, sampling must be performed after t seconds or more have elapsed since the motor was started. This can be achieved by providing an appropriate time difference between the signals sent to the drive circuit 11 and the sampling circuit 7 in the control circuit 10. This also applies to all embodiments described below. The time t is determined by the backlash of the cam mechanism, disturbance, etc. In a normal magnetic disk device, the time is about several tens to several hundred ns.

An example in which the above embodiment is applied to a magnetic head feeding mechanism of a magnetic disk device will be described below. FIG. 3 is a perspective view showing a schematic configuration of the head feeding mechanism. In the same figure, 6
Reference numeral 4 denotes a magnetic disk, which is placed on a . 71 is a sensor (MR element) fixed to the chassis 73.

On the other hand, the magnetic head 62 is fixed to the tip of the helad carriage 61 and is in contact with the magnetic disk 64.

The head carriage 61 is guided by a guide shaft 78 and slides. The height and position of the guide shaft 78 are determined by attaching a presser plate 75 to height pins 65 fixed to both ends thereof and the chassis 73 with screws 76 . Therefore,
The magnetic head 62 can move in the direction of arrow 79.

The cam 66 has a rotation hole 69 concentrically with the disc motor 63.
It is rotatably attached to the underside of the disk motor 63, and is configured as shown in FIG.

A gear 70 is provided on the outer periphery of the cam 66 and meshes with a pinion gear 77 of a pulse motor 82 .

A pin 65 fixed to the head carriage 61 is in contact with the cam surface 68 with appropriate pressure.

The cam surface 68 is configured such that the rotation direction increases as the cam surface 68 rotates in the direction of the arrow 80. Therefore, the rotation of the cam 66 in the direction of arrow 80 moves the magnetic head 62 in the direction of arrow 79 (from the inner periphery of the magnetic disk 64 to the outer periphery).

The magnetized ring 67 made of a magnetic material is press-fitted inside the outer circumferential wall 81 of the cam 66, so that when the cam 66 rotates around the rotation hole 69, the magnetized ring 67 also rotates together. It has become. The magnetized link 67 corresponds to the magnetized medium 1 in FIG.

Here, the reduction ratio of the rotational speed from the pulse motor 82 to the cam 66 is set to 1:10, and the magnetic head 62 moves a distance of one track in 10 steps of the pulse motor 82. Normally, if the accuracy of the cam is sufficient, the magnetic head 62 can be sent one track at a time by sending the pulse motor 82 10 steps each time, but due to errors in the cam surface 68, the magnetic head 62 may shift by several steps. It may not be sent accurately onto the track.

Therefore, the present invention is used to accurately move the magnetic head 62 onto the track.

FIG. 5 is a diagram showing the relative positional relationship between the magnetized ring 67 and the sensor 71.

Magnetized portions and non-magnetized portions are alternately formed in the magnetized ring 67, and the magnetized portions correspond to stopping positions on the cam surface 68.

An element 71 is provided at a fixed position near the magnetized ring 67. Rotate the cam 66, ■Element 71.11
.

If the magnetized part comes to the position, the output DC voltage of the head changes, so it is detected using the method described above and the pulse motor 82
If the rotation of the magnetic head 62 is stopped, the magnetic head 62 will be placed exactly on the track.
can be sent.

A second embodiment of the invention is shown in FIG. In the figure, 1 to 6.
10 and 11 are the same as described in FIG.

12 to 14 are switches whose opening and closing are controlled by the control circuit 10.

15 is a capacitor 16, 17 is a resistor, 18 is a diode, and 19 is a comparator. 8W and 125W 213 correspond to the sampling circuit of the first embodiment, and the capacitor 15 similarly corresponds to the comparison circuit 9, and the part consisting of the memory circuit 8, the resistor 15.17, the diode 18, and the comparator 19 corresponds to the comparison circuit 9.

Note that the output of the comparator 19 is at a high level V when the + side voltage of the input is higher than the one side voltage. When H1 is low, the level V is low. L
shall be.

The operation of this embodiment will be explained below. Resistance 16.1
It is assumed that the input impedances of 7 and comparator 19 are sufficiently large. As an initial state, the relative position of the element +12°6 and the magnetized medium 1 is at the 0th step shown in FIG. 2, and the capacitor 15 has the aforementioned t pressure VL.
(= ERMR/ (R, 10 RMR) is charged, and the output voltage of the comparator 19 is at a low level, V.L
(However, VoL<vL). SW1~SW,
Assume that all are open. From this state, the magnetized medium 1 becomes 1
When the step moves, SW, 13.5W synchronizes with this.
314 closes. At this time, one side terminal of the comparator 19 has
The voltage VL stored in the capacitor 15 is added, and +
The side terminals have a dish output voltage vMR and a comparator output voltage V. A voltage obtained by dividing the difference between L by resistors 16 and 17 is applied. That is, if this voltage is Vin, then Vin - (V
MRVoJRa/(R2+1'%). If we are now in the state of the first step in FIG. 2, VMR is VL, so Vin is equal to the one-side terminal voltage Vin(
” becomes lower than VJ. Therefore, the comparator output remains V.L. When the comparison is completed, 5W213.SW, 14
Open SW, 12, close it, charge the capacitor 15 with the German output voltage VMR, and then open SW, 12.

Next, the magnetized medium 1 is fed one step and the above-described operation is performed.

This process is repeated as shown in Figure 2.

In the eighth step, (1) the output voltage becomes vH. At this time, the + limiting voltage V theory of the comparator 19 becomes Vin+= (VHVoL) & / (& 10R,), but with respect to the one side voltage Viπ of the comparator 19, Vlfl >
If the values of R216 and R317 are determined so that Vln, the output of the comparator 19 will be at a high level V. It becomes H. When the control circuit 1° detects that the output of the comparator 19 becomes voH, it stops driving the magnetized medium 1.

That is, as in the first embodiment, position detection is performed by detecting a state in which a sampled value differs from a value sampled one step before by a predetermined level or more. The above-mentioned predetermined level is determined by the values of resistor 1 (t16 and R117).

This embodiment has the advantage of being inexpensive and easy to implement since no expensive parts are used.

A third embodiment of the invention is shown in FIG. 1 to 6.1 in the figure
0.11.16 to 19 are the same as shown in FIG. 20 is an A/D converter, 21 is a memory IJ-RAM,
22 and 23 are D/A converters. Above A/D converter 2
0, memory 21, and D/A converters 22 and 23 are driven by:
It is controlled by a control circuit 10. This embodiment replaces the switches 12 to 14 and capacitor 15 of the second embodiment with an A/D converter 20, memory 21, and D/A converters 22 and 23, and the basic operation is the same. be. In the second embodiment, a capacitor was used to store the raccoon output voltage of one step before, but in this embodiment, it is written and stored in the memory 21 after A/D conversion. After one step, this is read out and D/A converted (compared with the current output voltage by the comparator 19.Other operations are the same as those explained in the second embodiment.In addition, in this embodiment, the current step Although the MR output voltage is first A/D converted and then D/A converted and inputted to the comparator 19, it is of course possible to input it directly to the comparator 19 with the configuration shown in FIG. I don't mind.

A fourth embodiment of the invention is shown in FIG. 1~6°11,
20.21 are the same as those already explained. 24.1
5° is the microcomputer, 25 is the drive circuit 11. A control function for controlling the A/D converter 20 and an arithmetic function 26 are both performed by microcomputer software. The operation of this embodiment is essentially the same as the previously described embodiments. In synchronization with the movement of the magnetized medium 1, (1) the output voltage is taken into the microcomputer through the A/D converter 20; Store this value in RAM1
It is compared with the value before the step, and if the difference is greater than a predetermined value, the drive is stopped. Comparisons are performed using calculations.

A fifth embodiment of the invention is shown in FIG. 3 to 6 in the figure are the same as those already described. 27-32 are resistances, 33
．． 34 is a capacitor, 35.56 is a transistor, 37
is a diode, 38 is a comparator, 39 is an input terminal, 40
is the output terminal. The circuit shown in the figure consists of a triangular wave generating circuit and a comparing circuit for the triangular wave and the ripple output. First, the triangular wave generation circuit will be explained.

Now, when the voltage Vt of the input terminal 39 is at a low level, the diode D
, 37 are off, the base voltage of the transistor Q36 is the power supply voltage V. It becomes the voltage divided by Le to the resistor. The emitter voltage is the base voltage, 16.

The base-emitter voltage VB of transistor Q and 36 is
Adding E means pregnancy. Let this be vtl. Next, the voltage Vt at the input terminal 39 becomes high level, and the diode 37
When turned on, the capacitor C234 is charged until the emitter voltage of the transistor Q becomes the sum of the input voltage of the transistor 69 minus the forward voltage of the diode 37 and the VBB of the transistor Q (referred to as VtIN). When the input terminal is set to low level again, transistor Q2 is turned on and discharged through resistor R032, and the emitter voltage becomes vtb.
become. In this way, by sequentially switching the voltage Vt of the input terminal 39 from low level to high level, the transistor Q! A triangular wave can be obtained from 36 emitters.

FIG. 11 shows a timing chart of the circuit of this embodiment. A driving pulse that drives the magnetized medium 1 one step at a time from the upper stage. The second stage is a pulse synchronized with the above pulse, which connects terminal 39.
pulse applied to. The third stage is the transistor Q, and the emitter voltage of 36 forms a triangular wave as shown in the figure from the above explanation. Also, ① output voltage is shown superimposed on this waveform. The output of the comparator 38 at the bottom is a high level when the output voltage is higher than the triangular wave, and a low level when it is lower, resulting in a waveform as shown in the figure.

If we calculate the time from when the triangular wave rises until the comparator output becomes low level for each step, for example, ■ it is longer when the output voltage is high (t,) than when it is low (tl+j3). It should be clear from the figure. Therefore, if this time is counted by some method, it is possible to determine whether the voltage is high or low. For example, the output of the comparator 38 is taken into the microcontroller,
Count the time until the same output voltage drops to a low level. The counted value is stored in the RAM in the microcomputer and compared with the counted value in the next step to determine whether the voltage is at a high level or a low level. That is, in this embodiment, a type of A/D conversion is performed in which voltage is converted into pulse width and pulse length is counted. In this embodiment, since an expensive A/D converter is not used, the cost can be reduced.

In the first to fifth embodiments described above, cases were explained in which a two-terminal type MR element was used. However, the above embodiment is not necessarily limited to a two-terminal type receiving element, and the same effect can be obtained even if a three-terminal type (1) element consisting of two plate elements is used.

FIG. 12 shows a sixth embodiment. In the first embodiment, the detection section consisting of the two-terminal plate element 3 and the fixed resistor 4 is replaced with a three-terminal plate element consisting of two plate elements, a receiving element, and a three-plate element B41. It is. 1.2.5~
11 is the same as already described.

Resistance A and B of the plate element when no magnetic field is applied from each part
Both are the same when RMR1 magnetic field is applied (R'MR(
> RMR) Toru. First, MRA3, MRB
41. If no magnetic field is applied to either connection point 6
■If the output voltage VMR is VM, then VM=ERMR/(RMR+RMR)=,.

becomes. Next, if the plate output voltage VMR when a magnetic field is applied to MR, 3 is VL, ■p = ERMR/ (&R+ R'MR) < V
M yells. ■When a magnetic field is applied to MRn4j, assuming that the output voltage is 7 RMR, VH = ER'MR/(RMR+R'MR) > VM
becomes. That is, when a three-terminal type MR element is used, VL.

Three types of output voltages, VM and VH, can be obtained. FIG. 13 shows the relative positions of the magnetized medium 1 and (1) the elements A6 and B41, and (2) the output voltage at each step.

Seed h from 0th step to 6th step 3. AfL
Since no magnetic field is applied to either B41 or K, the output voltage is VM. In the seventh step, a magnetic field is applied to the MRA 3, so the dish output voltage becomes VL. M in the 8th step
A magnetic field is applied to RB 41, and the dish output voltage becomes VH,
In the ninth step, it becomes a VM again. Using the method already described for this change in output voltage, the state in which the output voltage becomes VH is detected. In the case of a three-terminal type element, a larger voltage difference can be obtained compared to a two-terminal type element. Therefore, when comparing and detecting a voltage difference, a large threshold value can be used, and malfunctions due to noise can be more reliably eliminated.

Although this embodiment has been described by replacing the plate element of the first embodiment with a three-terminal type, it goes without saying that the same can be applied to the second to fifth embodiments.

In addition, in all the embodiments described above, the magnetized medium and MR, f
, we have explained the mechanism in which the relative position changes stepwise, but even in a mechanism in which the relative position changes continuously, the same effect can be obtained by sampling in synchronization with the relative movement of the magnetized medium and plate element. can get.

〔Effect of the invention〕

According to the present invention, since the MR ratio output is sampled in a stable state, there is no possibility of erroneously detecting a change in the output voltage due to noise immediately after the magnetized medium is moved, and the relative MR output for each step is Since the voltage displacement is detected, there is an effect that malfunction does not occur even if the resistance of the MR element changes due to changes over time and the midpoint voltage fluctuates.

[Brief explanation of the drawing]

Figure 1, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10,
FIG. 12 is a block diagram of an embodiment of the present invention, FIGS. 2, 5, and 16 are waveform diagrams showing the relative positions of the dish element and the magnetized medium, and (1) output waveform. FIG. , a timing chart of the fifth embodiment, FIGS. 3 and 4 are perspective views of the head feeding mechanism, and FIG. 14 is a waveform diagram of the output voltage. DESCRIPTION OF SYMBOLS 1... Magnetized medium, 3.41... MR element, 7... Sampling circuit, 8... Memory circuit, 9... Comparison circuit.

Claims (1)

[Claims] a first member configured to generate a magnetic field at a predetermined location;
A first and a second device, at least one of which is a magnetoresistive element.
a detection means comprising a series connection circuit of resistive elements;
and a position moving means for changing the relative position between the predetermined position of the member and the magnetoresistive element of the detection means;
In a position detection device that detects a predetermined position of the first member by a DC voltage at a connection point between a resistive element and a second resistive element; a sampling means for sampling a DC voltage at a connection point between the element and the second resistance element; a storage means for storing the DC voltage value; a DC voltage value sampled at a predetermined sampling timing and stored in the storage means; , comprising comparison means for comparing DC voltage values sampled at the next temporally continuous sampling timing;
A position detection device characterized in that position detection is performed by detecting a position where the difference between the compared two values is equal to or higher than a predetermined level.