JPS6021580A - Magnetoelectric conversion detector - Google Patents

Abstract

PURPOSE:To enable the emission of output signals having a large S/N ratio by a method wherein the decrease of the resistance value of one of a plurality of magnetic resistors at the time of increase of that of other resistor is contrived by forming an inspected section in saw-tooth form and then making the direction of arrangement of the resistors approximately rectangular to that of movement of the inspected part. CONSTITUTION:A pulse plate 5 has saw teeth 5a of magnetic substance and can rotate in the direction of the arrow. A bias magnet 4 turns the N pole upward, MR1 one of ferromagnetic thin film resistors of the magnetic resistance elements 10 making its current direction coincident with the direction of rotational tangent of the pulse plate 5 thereon, and MR2 the other one making its current direction rectangular to the tangential direction in the same manner. MR1 is arranged outward from the rotary shaft 7 of the plate in the radial direction, and MR2 in a line with MR1 toward the center of the shaft 7. The relation between the center distance from MR1 to MR2 and the height (h) of the tooth is kept approximately at d<h/2, and accordingly the device is so constructed that the tooth sufficiently covers both the resistors MR1 and MR2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the structure of a magnetoelectric conversion detection device when used in a pulse counter or the like.

A magnetoelectric conversion detection device is a device using a magnetoresistive element that detects changes in electrical resistance caused by changes in a magnetic field. Conventionally, as this type of device, one using electromagnetic induction, one using a semiconductor magnetoresistive element, etc. are known. Recently, elements in which a ferromagnetic thin film resistor such as Ni or GO is formed on a glass substrate are also used. In such a ferromagnetic thin film resistor, when the ferromagnetic thin film is magnetized by an external magnetic field, the resistance value changes depending on the angle formed by the direction of magnetization and the current, and the change is such that the direction of magnetization and the direction of current flow upward. When the resistance is maximum, the resistance is minimum when they are perpendicular to each other. Taking advantage of this property, magnetoresistive elements are used in non-contact pulse counters and the like.

Conventionally, non-contact pulse counters mainly use photocouplers, but due to the slow response characteristics of photoelectric elements,
A response signal with a good signal-to-noise ratio cannot be obtained with high-frequency pulses. There is also the problem that if dust adheres to the area around the coupler, it will no longer respond.

Magnetic resistance elements have fast response characteristics, and dust does not change the sensitivity unless it is magnetic dust. Therefore, it has recently attracted attention and is being applied in various fields.

The first example of its application is the configuration of a pulse counter.
It is shown in the figure. Rectangular projections 2a and grooves 2 made of magnetic material on the outer periphery
A bias magnet 4 with an N pole on the other side is placed on the disc-shaped pulse plate 2 having a diameter of 1.
The magnetoresistive element 1 is arranged by folding them together. The magnetoresistive element 1 is two ferromagnetic thin film resistors MR whose current directions intersect at a certain angle.

and Mn2 are lined up in the rotation direction, and the difference in resistance is converted into a voltage by the resistor bridge with the connected resistors R3-R4 and the power supply E, and output from the llj force terminal out. When the pulse plate 2 rotates, the protrusion 2a moves, the direction of the magnetic field relative to the thin film resistors MR, .Mn2 changes, and an output voltage signal appears.

In order to reduce the number of parts in a series of rotating systems including a pulse plate, there is a configuration in which the pulse plate itself has a brake mechanism. A stopper 3 (chain fastening in FIG. 1) is projected and engaged with the groove 2b of the pulse plate 2 to forcibly stop the rotation. In such a brake mechanism, the disc 2
If the groove 2b is rectangular, it will slide and move even after the stopper hits the bottom of the groove. Further, when the stopper hits the top of the protrusion 2a, it bounces back, and it may take several pitches before it engages with the groove 2b, so it does not stop at an accurate position. For this reason, a pulse plate is used in which the grooves on the disk are serrated, and the stamper is stopped by protruding into the serrated grooves. However, when a combination of a pulse plate with sawtooth grooves and a ferromagnetic resistance element was used in a pulse counter, it became clear that sufficient output could not be obtained.

FIG. 2 shows the arrangement of various parts when a pulse plate 5 having sawtooth grooves and a conventional ferromagnetic resistance element 1 are combined. In the figure, the sawtooth 5a of the pulse plate 5 rotates from ('a) to (b) to (b) to (c).

Figure 3 shows the resistance value (solid line) of the thin film resistor MR and Mn2 when the sawtooth is in each position shown in Figures 2 (a) to (C).
The change in the resistance value (shown by the dotted line) is shown in (a), and the output voltage of the output OUT at that time is shown in (b).

In FIG. 2, the magnetic field of the bias magnet 4 is generated toward the front side, and while repelling, it curves toward the immediate vicinity of the sawtooth 5a, which is a magnetic material, or the sawtooth 5b following it. At this time, if the current direction (horizontal direction) of the composite resistor MR matches the direction component of the magnetic field, the resistance 1ifj of the thin film resistor MR increases. The same phenomenon occurs with the thin film resistor MR2 (the current direction is the vertical direction). When the sawtooth 5a is in the position (a), the resistance value of the thin film resistor MR is slightly decreased (see FIG. 3(a)-(a)). At the same <, (a), the resistance value of the thin film resistor MR2 is increasing. The sawtooth 5a is (b)
At the position , the resistance values of the thin film resistors MR and φMR2 both reach their maximum value at a position slightly shifted from each other (see C (b)). At the position (C), the resistance value of the thin film resistor MHI is an intermediate value, and the resistance value of the thin film resistor MR2 is approximately the minimum value (see (C)).

In response to the resistance changing in this manner, the output voltage from the bridge circuit constructed thereby has a waveform shown in FIG. 3(b). With the output shown in this waveform, a sufficiently satisfactory output S/N ratio cannot be obtained for all usage conditions.

This is because the period deviation of the resistance change of the thin film resistors MR and Mn2 is not optimal, and the characteristics of the resistance change are not fully utilized. .

The greater the SN ratio of the output signal of any sensor, including a pulse counter, the easier it will be to perform subsequent processing in amplification, etc., and the inclusion of noise will also be removed.

The present invention was made in view of this situation, and an object of the present invention is to provide a magnetoelectric conversion detection device that can output an output signal with an extremely high signal-to-noise ratio.

In order to achieve this purpose, the present invention provides a magnetoresistive element in which a plurality of magnetoresistive elements whose resistance value changes when the direction of an external magnetic field changes with respect to the current direction are arranged in a manner that changes the current direction. In a magnetoelectric conversion detection device that detects a test object made of a movable magnetic material that changes the direction of the external magnetic field,
The test part's shape is made into a silver tooth shape, and the direction in which the plurality of magnetic resistances are arranged is substantially perpendicular to the moving direction of the test part, so that the resistance value of one of the plurality of magnetic resistances is increased. This magnetoelectric conversion detection device is characterized in that it is configured such that the resistance value of the other side decreases when the other side decreases.

Examples of the present invention will be described in detail below.

FIG. 4 shows a magnetoelectric conversion detection device to which the present invention is applied.

The pulse plate 5 has saw teeth 5a made of magnetic material, and can be rotated in the direction of the arrow. The sawtooth shape has a short side on the forward side of the pulse plate and a long side on the rear side. The bias magnet 4 has its north pole facing upward, and the magnetic resistance element 10 is superimposed thereon.

Two ferromagnetic thin film resistors of the magnetoresistive element 10 are arranged. One of them, MHI, has a current direction that coincides with the tangential direction of rotation of the pulse plate 5, and the other, MB2, has a current direction that is also perpendicular to the tangential direction. The former MR is the rotation axis 7 of the pulse plate 5
The latter MR2 is arranged radially outward from the center of the support 7, and the former MR is arranged side by side near the center of the support 7. Therefore, Re
The resistors MR1 and MB2 are arranged substantially in the short side direction of the sawtooth 5a.

Each electrical connection forms a bridge circuit with resistors R3φR4 and is connected to power supply E, as in the previous example.

In particular, in this example, the center distance f between the magnetic resistors MR1 and MB2 is
The relationship between In, d and sawtooth height h is roughly expressed as d<h/2
The structure is such that the sawtooth sufficiently covers both magnetic resistors MR and MB2.

In the configuration as described in -1-, when the two magnetic resistances MR and MB2 on the element surface are oriented to a magnetic field in the same direction, when the resistance value of one magnetic resistance MR increases, the other magnetic resistance increases. The magnetic resistance MR2 will decrease. 2 on the element surface
A phase in which the two sensing parts are simultaneously covered with sawtooth patterns and a phase in which they are simultaneously exposed to a uniform magnetic field appear repeatedly. Therefore, a phase in which the resistance values of the two sensing parts MR and MB2 are both intermediate values and equal, and a phase in which the resistance values of the sensing parts MR and MB2 have a large difference appear repeatedly, so that position detection with a good S/N ratio is not possible. It becomes possible.

Actual changes in output will be explained according to the drawings. Figure 5 (a) shows the magnetic resistance MR, value (
2 shows the change in the magnetic resistance MR2 resistance (shown by a solid line) and the magnetic resistance MR2 resistance value (shown by a dotted line). Similarly, (b) shows the change in output voltage.

When the sawtooth 5a is in the position shown in FIG. 4(a),
The resistance values of both magnetic resistors MR and MB2 are equal at intermediate values (see FIG. 5(a)-(a)). When the sawtooth 5a comes to the position (b), the current direction of the magnetic resistor MR and the direction of the magnetic field therein become substantially perpendicular, so that its resistance value becomes minimum. At this position, the current direction of the magnetic resistor MR2 and the direction of the magnetic field therein become substantially parallel, and the resistance value becomes maximum (see (b)). The sawtooth 5a further rotates, and the changes in the resistance values of the magnetic resistors MR and MB2 become equal at an intermediate value almost simultaneously. After passing that position, at the position (c), the direction of the current in the magnetic resistor MR and the direction of the magnetic field at this time are almost in the same direction, so the resistance value reaches a maximum. At this time, the resistance value of the magnetic resistor MR2 decreases slightly (see (C)).

According to this series of resistance changes, the output voltage changes as shown in ff15 (
b), resulting in a waveform with a higher SN ratio than the conventional arrangement.

Although the pulse plate is a rotating body in the above embodiment, it may be a unidirectionally moving body. Even if the center-to-center pressure #d of the two magnetic resistors MR and MB2 is larger than half of the sawtooth height h (d
> h/2), the amplitude of the resistance change of the magnetic resistor MR2 becomes slightly smaller, but it can be implemented. A configuration in which the sawtooth 5a of a magnetic material is magnetized may also be used.

FIG. 6 is an example in which the magnetoelectric conversion detection device of the present invention is applied to detecting the position of an automatic aperture of a camera lens. 11 is the aperture unit of the lens, 12 is the aperture blade, 13 is the aperture signal lever, 14 is the automatic aperture lever, and 15 is the automatic aperture lever 1.
The aperture lever that operates No. 4 is shown.

A driving member, ie, a driving lever 16, is provided for driving the signal lever 15 of this aperture. The drive lever 16 has slots 16 a e 16 a' in the center, and these slots are slidably engaged with the pins 17 and 17', respectively, so that the drive lever 16 can be slid up and down. . A spring 18 is attached to one end of the drive lever 16 to bias it upward. The drive lever 16 has an aperture drive part 1.6b that engages with the aperture signal lever 13 to control the aperture in a part, a locking part 16c in the center side part, and a charge part 16d in the lower end.
, and a rack 16e is formed along one side thereof. The drive lever 16 is engaged with the engaging W portion 16c.
A locking l/bar 19 for locking is rotatably supported by a shaft 20. Engagement II: The lever 19 is held in a position where the drive lever 16 is locked by the spring 21. 2
Reference numeral 2 designates a release button, which has a locking and operating portion 22a that contacts the lever 19 of the locking lever 11 and rotates it against the force of the spring 21. Further, a photometry switch 23 is arranged on the side of the release button 22.
A photometric switch operating section 22b for operating the photometric switch 23 is provided. Reference numeral 24 indicates a charge lever that charges the drive lever 16 in conjunction with a winding member (not shown). A speed regulating mechanism is connected to the drive lever 16 and is driven to increase the speed synchronously. This speed regulating mechanism is connected to the rack 1 of the drive lever 16.
6e, the last gear of which is connected to a rotating pulse plate 26. The rotating pulse plate 26 has a serrated outer peripheral portion. Also, the pulse plate 26
On the back side (or front side) of the 6-pulse plate 26, which also serves as the stop wheel of the automatic aperture button/key mechanism, there is a magnetic resistance element 28 formed integrally with a magnet 27 for generating a bias magnetic field. It is arranged.

A stopper 31 that engages with and stops the stop wheel 26, which is a pulse plate, is supported by a shaft 31a, and has a claw portion 31b that engages with the saw teeth of the stop wheel and a cover portion 31C made of a magnetic material. ing. Stopper 3
1 is provided with a spring 30 that always biases it clockwise. An electromagnet 32 is provided at a position facing the cover 31c and attracts the stopper 31. When the electromagnet 32 is de-energized, the spring 30 causes the spring 30 to move the spring 30 toward the shaft 31a.
The stop wheel 26 is rotated clockwise to engage the claw portion 31b with the saw teeth of the stop wheel 26.

2. The magnetoelectric conversion detection device 35 is provided with 41 output circuits 34 consisting of the bridge circuit shown in the previous example and a power supply for receiving a signal output from the magnetoresistive element 28.

FIG. 7 is a block diagram of a control circuit for such an automatic diaphragm device.

In the figure, 53 is an operational amplifier, 54 is a Schmitt trigger circuit, 55 is a pulse counter, 56 is a digital comparator, 57 is a photometric calculation circuit, 32 is an electromagnet shown in FIG. 5, and 35 is a magnetoelectric conversion detection device. . .

In the aperture control circuit, when the release button 22 is pressed, the photometry switch actuator 22b first closes the photometry switch 23, and thereby the photometry calculation circuit 57 is activated. When the release button 22 is further pushed in, its tip 22a comes into contact with the end of the locking lever 19 and locks against the force of the spring 21, rotating the 8-19 clockwise. Since the locking portion 16c and the locking lever 19 are disengaged, the drive lever 16 is moved in one direction along the slot 16ae16a slidingly engaged with the pins 17 and 17' due to the biasing force of the spring 18. . When the drive lever 16 moves upward, the pinion gear train 25 performs speed increasing movement in conjunction with the movement of the rack 16e of the drive lever, thereby rotating the final stage pulse plate 26. At this time, the magnetoresistive element 28 outputs the number of sawtooths of the pulse plate 26 passing over the element surface as a pseudo sine wave voltage from the magnetoelectric conversion detection device 35.

This output value is amplified by an operational amplifier 53 and shaped into a waveform by a Schmitt trigger circuit 54. The pulse waveform is counted as pulses by a pulse counter 55. This count value is input to the digital comparator 56. on the other hand,
The aperture value (
The count value corresponding to the A/V value is also the digital comparator 5.
Enter 6. When these two values become equal, the electromagnet 32 is turned off. Then, the drive lever 16 stops at the position where the desired aperture value is selected.

The output waveform obtained from the magnetoresistive element during these series of operations is different from that of conventionally known magnetoresistive elements.
High signal-to-noise ratio. Therefore, since a waveform with sharp rises and falls is output, erroneous detection due to chattering is small.

This makes it possible to detect positions with high precision. Further, the installation h1 of the electric circuit becomes easier.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional magnetoelectric conversion detection device, Figure 2 is a diagram of a magnetoelectric conversion device using a sawtooth pulse plate, and Figure 3 explains the detection characteristics of the device shown in Figure 2. 4 is a front view of a magnetoelectric conversion detection device to which the present invention is applied, FIG. 5 is a diagram explaining the detection characteristics of the device shown in FIG. 4, and FIG. FIG. 7 is a front view of an embodiment applied to an automatic diaphragm, and a block diagram of its control circuit. 4 is a magnetic material, 5 is a pulse plate, 5a is a sawtooth, 11 is a magnetoresistive element, MR, 6MR2 is a ferromagnetic thin film resistor. 5 Japanese Patent Application Sho GO-21580 (6)

Claims (1)

[Claims] (1) A movable magnetic resistance element that changes the direction of the external magnetic field by arranging a plurality of magnetic resistance elements whose resistance value changes as the direction of the external magnetic field changes with respect to the current direction. In a magnetoelectric conversion detection device that detects a test section made of a magnetic material, the test section has a sawtooth shape, and the direction in which the plurality of magnetic resistors are arranged is substantially perpendicular to the moving direction of the test section. A magneto-electric conversion detection device characterized in that when the resistance value of one of the plurality of magnetic resistances increases, the resistance value of the other one decreases in the direction of the magnetic resistance.