JPH0690046B2 - Displacement detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a displacement detection device, and more particularly, to a magnetic detection element (hereinafter referred to as bridge magnetic detection) in which a magnetoresistive effect element (MR element) is connected to a bridge circuit. Element) and a magnetic scale in cooperation with a displacement detection device that detects relative displacement between the bridge magnetic detection element and the magnetic scale from a detection signal derived from the magnetic detection element.

[Background of the Invention] Recently, a displacement detection device employing a displacement sensor is often used when measuring displacement. The displacement sensor detects the amount of displacement and a signal by detecting the amount of displacement so that the magnetic flux density, the amount of light, or the like changes with the movement of the displacement sensor. And a sensing element for deriving

In the displacement detection device, a linear displacement sensor is used to measure the displacement, and a rotary displacement sensor is used to measure the displacement of the rotating body. For example, in a detection unit that employs a linear type and a magnetic displacement sensor as the detection signal generation function unit, the detection signal generation in which magnets or magnetized portions of S polarity and N polarity of the same width are alternately arranged is arranged. The magnetic scale as a member for use is fixed to the moving body. Then, a signal corresponding to the movement of the magnetic scale is derived from the magnetic detection element arranged near the magnetic scale.

However, in the displacement sensor adopting such a light receiving and emitting element of the conventional example, when strong light from the outside is incident, adverse effects are caused, and dust or the like is attached to the light receiving element. It has the inconvenience that the detection capability decreases over time.

[Object of the Invention] The present invention has been made in order to overcome the above-mentioned inconvenience, and a magnetic scale in which magnetization forming portions of S polarity and N polarity having the same width (2 / 3l) are alternately arranged. , A bridge magnetic sensing element separated by a width (l) for deriving a sine wave signal and a cosine wave signal as detection signals by bridge calculation (ratio) corresponding to a relative displacement of 4/3 l of the magnetic scale. Displacement for deriving the relative displacement by a pair of detectors or a sine wave signal and a cosine wave signal derived from detection signal deriving means in which a plurality of the detectors are arranged to derive a signal having a larger value. It is composed of a detection signal forming part, which has a relatively simple structure and does not require a contact member when detecting displacement, so that it does not cause wear of the member and is relatively advantageous for disturbances such as light and vibration. Acting on Aims to decrease over time sensing capabilities provide effectively prevent possible displacement detecting device.

[Means for Achieving the Object] In order to achieve the above object, the present invention provides a displacement for deriving a relative displacement between a magnetic scale and a magnetic sensing element based on a signal detected from the magnetic sensing element. In the detection device, a magnetic scale in which magnetization forming portions of S polarity and N polarity of the same width [(2/3) l] are alternately arranged, a bridge circuit including a plurality of magnetoresistive effect elements, and a pair of polarities. The magnetic sensor includes first and second magnetic sensing elements composed of different bias bodies, and the first and second magnetic sensing elements are spaced apart by a width (1), and the magnetic scale (4/3 ) A detector for deriving a sine wave signal and a cosine wave signal respectively corresponding to a relative displacement of l, and a signal corresponding to the relative displacement from a sine wave signal and a cosine wave signal derived from the detector. Displacement detection signal forming unit to derive , Are provided.

Further, according to the present invention, a magnetic scale in which magnetization forming portions of S polarity and N polarity having the same width [(2/3) l] are alternately arranged, a bridge circuit including a plurality of magnetoresistive effect elements, and a pair of magnetic resistance effect elements. The magnetic scale includes: first and second magnetic sensing elements made of biasing bodies having different polarities, the first and second magnetic sensing elements are spaced apart by a width (l), and the magnetic scale (4 / 3) Detecting signal deriving means in which a set of multiple detectors for deriving a sine wave signal and a cosine wave signal respectively corresponding to a relative displacement of 1 are arranged, and the detecting signal deriving means. A displacement detection signal forming unit for deriving a signal corresponding to the relative displacement from a sine wave signal and a cosine wave signal.

[Embodiment] Next, a preferred embodiment of the displacement detection device according to the present invention will be given and described in detail below with reference to the accompanying drawings.

FIG. 1 shows a displacement detecting device employing a bridge magnetism detecting element and a magnetic scale according to the first embodiment. The displacement detection device includes a magnetic head 12 fixed to a fixed frame or the like (not shown), and a magnetic scale 16 attached to a moving body 14, and a detection signal supplied from the magnetic head 12.
The signal processing section 20 forms S ₁ and S ₂ into predetermined pulse train signals S ₅ and S ₆ and outputs them to output terminals T ₁ and T ₂ .

First, the magnetic head 12 will be described. In the magnetic head 12, bridge magnetism detecting elements 22 and 24 are arranged so as to be separated from each other by a predetermined width (1). The bridge magnetic sensing element 22 is a second
As shown in FIGS. (A) and (b), well-known magnetoresistive effect elements (MR elements) 26a, 26b and 26c, 26d are connected as a bridge circuit, and N for identifying the polarity of an external magnetic field is connected.
The polarity bias magnet 26e and the S polarity bias magnet 26f are engaged and attached. Here, a predetermined voltage, for example, + 15V is applied to the connection portions 27b and 27d which are one terminal portion of the bridge circuit. Then, with the rotation of the external magnetic field, that is, the change of the S polarity and the N polarity due to the movement of the magnetic scale 16, the magnetoresistive effect elements 26a, 26b and 26 are
The connection where the resistance values of c and 26d are changed, so that the corresponding signal becomes the other terminal of the bridge circuit.
Derived from 27a and 27c. The bridge magnetism sensing element 24 is similarly constructed.

The signals derived from the connection parts 27a and 27c are derived as detection signals S ₁ and S ₂ formed into sine wave signals and cosine wave signals.

Next, the magnetic scale 16 arranged in parallel and facing the vicinity of the magnetic head 12 is the bridge magnetic sensing element.
With magnetized portions of S-polarity Sa to Sn and N-polarity Na to Nn which are spaced apart by a width 2 / 3l for a given width (l) of 22 and 24, eg magnets are arranged alternately ing.

Furthermore, the signal processing unit 20 detects the detection signal S ₁ derived from the bridge magnetism detecting elements 22 and 24, respectively, in the relative displacement between the bridge magnetism detecting elements 22 and 24 and the magnetic scale 16.
And S ₂ are supplied to the differential amplifiers 28 and 30, and the amplified signals S ₃ and S ₄ amplified here are supplied to the phase division circuit 32. A predetermined voltage, for example, + 15v is applied to the differential amplifiers 28 and 30 from a power source (not shown), and is connected to the connecting portions 27b and 27d of the bridge magnetism detecting element 22. . The bridge magnetism detecting element 24 is similarly connected. Furthermore, the pulse train signal from the phase division circuit 32
Output terminals T ₁ and T _{2 from} which S ₅ and S ₆ are derived are provided.

The operation of the first embodiment configured as above will be described.

3A and 3B, the correspondence between the movement of the magnetic scale 16 in the direction Vi of the arrow and the bridge magnetism detecting elements 22 and 24, and the detection signals S ₁ and S ₂ derived from the bridge magnetism detecting elements 22 and 24 by this. Shows the output waveform of.

Here, the bridge magnetic sensing elements 22 and 24 in the diagrams (a) to (e) of FIG. 3A are moved by the magnetic scale 16 to detect the sine wave and cosine wave detection signals S ₁ shown in FIG. 3B.
And derive S ₂ . The points (a) to (e) in FIG. 3B correspond to the signal transition points of the detection signals S ₁ and S ₂ derived in the diagrams (a) to (e) of FIG. 3A. The detection signals S ₁ and S ₂ are supplied to differential amplifiers 28 and 30 and then amplified amplified sine and cosine signals.
It is supplied to the phase division circuit 32 as S ₃ and S ₄ . Here, the amplified signals S ₃ and S ₄ are divided at predetermined phase points, and are formed into pulse train signals S ₅ and S ₆ , after which they are counted on a time axis using a counter or the like not shown, The displacement of the magnetic scale 16 is detected.

In the first embodiment configured and operated as described above, the detection signals S ₁ and S ₂ are derived from the bridge magnetic detection elements 22 and 24 as the magnetic scale 16 moves in the arrow direction Vi or Vo. It In this case, the bridge magnetism detecting elements 22 and 24 are the magnetoresistive effect elements (MR elements) 26, respectively.
a, 26b and 26c, 26d are connected as a bridge circuit and are sensitive to magnetism when the magnetic scale 16 moves in the direction of arrow Vi or Vo, and the corresponding detection signals S ₁ and S ₂ are known. It is derived by the bridge calculation (ratio).
Therefore, in the movement of the magnetic scale 16 in the direction of arrow Vi or Vo, the accuracy is improved without merely deriving a signal corresponding to the magnetism of the moving point, and against disturbance. Works in an advantageous manner.

Next, a second embodiment will be described. The purpose of this example is to derive the output signals S ₂₁ and S ₂₂ of, for example, twice the level of the detection signals S ₁ and S _{2 of the first} embodiment.

FIG. 4 is a block diagram showing the second embodiment, and FIGS. 5 (a) to 5 (e) are signal waveform diagrams used for explaining the operation of the displacement detecting device shown in FIG.

In the displacement detecting device of the second embodiment, the magnetic scale 16 formed in the same manner as in the first embodiment and the magnetic head in which the bridge magnetic detection elements 36a, 36b and 36c, 36d are connected in a width (1) 38 and the detection signals S ₁₁ , S ₁₂ , S ₁₃ , S derived from the bridge magnetic detection elements 36a, 36b and 36c, 36d.
₁₄ and a signal processing unit 40 to which it is supplied. The signal processing unit 40 forms a signal S ₁₅ which is the difference between the detection signal S ₁₂ and the detection signal S ₁₄ as shown in the processing waveform of FIG.
Further, a signal S ₁₆ that is the difference between the detection signal S ₁₁ and the detection signal S ₁₃ is formed, and for example, an output signal S ₂₁ having a level twice that of the detection signals S ₁ and S _{2 of the first} embodiment. , S ₂₂ is derived. As a result, the subsequent signal processing acts advantageously, and the influence on disturbances such as temperature characteristics and / or external magnetic fields, that is, superposed noises is reduced. Further, the bridge magnetic sensing elements 36a, 36b and 36c, 36d are the first
The same magnetoresistive effect element as in the above embodiment is used, and the influence thereof against external disturbance can be further reduced.

[Effects of the Invention] As described above, according to the present invention, a magnetic scale in which S and N magnetization forming portions having the same width (2 / 3l) are alternately arranged, and 4 / 3l of the magnetic scale. A pair of detectors composed of bridge magnetic sensing elements separated by a width (l) for deriving a sine wave signal and a cosine wave signal as detection signals by a ratio corresponding to the relative displacement of minutes, or a signal of a larger value To detect the relative displacement using a sine wave signal and a cosine wave signal derived from the detection signal deriving means provided in multiples. With a simple structure and when detecting displacement, no contact member for detection is required, so that it does not cause wear of the member, acts relatively advantageously on disturbance such as light, vibration, etc. Drop can be effectively prevented Achieve the results.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this embodiment,
It goes without saying that various improvements and design changes can be made without departing from the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a displacement detecting device according to the present invention, and FIGS. 2 (a) and 2 (b) are bridge magnetic sensing elements adopted in the displacement detecting device shown in FIG. 3A and 3B are used to explain the operation of the displacement detection device shown in FIG. 1 and show the correspondence between the magnetic scale and the bridge magnetic sensing element and the derived signal waveform. FIG. 4 is a configuration diagram showing a second embodiment of the displacement detection device according to the present invention, and FIGS. 5 (a) to 5 (e) are operation explanations of the displacement detection device shown in FIG. It is a signal waveform diagram provided. 12 ... Magnetic head, 14 ... Moving body 16 ... Magnetic scale, 20 ... Signal processing unit 22, 24 ... Bridge magnetic sensing element 26a to 26d ... Magnetoresistive effect element (MR element) 26e ... N polarity Bias magnet 26f …… S polarity bias magnet 28,30 …… Differential amplifier, 32 …… Phase division circuit T ₁ , T ₂ …… Output terminals, S ₁ , S ₂ …… Detection signal S ₃ , S ₄ …… Amplified signal S ₅ , S ₆ ... Pulse train signal

Claims (3)

[Claims] 1. A displacement detection device for deriving a relative displacement between a magnetic scale and a magnetic sensing element based on a signal detected from the magnetic sensing element, wherein S polarities of the same width [(2/3) l] are provided. And a magnetic scale in which magnetization forming portions of N polarity are alternately arranged, a bridge circuit of a plurality of magnetoresistive effect elements, and a first and second magnetic sensing element composed of a pair of bias bodies having different polarities, The first and second magnetic sensing elements are arranged so as to be separated by a width (l), and a sine wave signal and a cosine signal are respectively provided corresponding to the relative displacement of the magnetic scale and (4/3) l. A displacement detecting signal forming section for deriving a signal corresponding to the relative displacement from a sine wave signal and a cosine wave signal derived from the detector; Detection device. 2. The displacement detection device according to claim 1, wherein the displacement detection signal forming section includes at least one or more differential amplifiers and a phase division circuit. 3. A displacement detecting device for deriving a relative displacement between a magnetic scale and a magnetic sensing element based on a signal detected from the magnetic sensing element, wherein S polarities of the same width [(2/3) l] And a magnetic scale in which magnetization forming portions of N polarity are alternately arranged, a bridge circuit of a plurality of magnetoresistive effect elements, and a first and second magnetic sensing element composed of a pair of bias bodies having different polarities, The first and second magnetic sensing elements are arranged so as to be separated by a width (l), and a sine wave signal and a cosine signal are respectively provided corresponding to the relative displacement of the magnetic scale and (4/3) l. A set of detectors for deriving a wave signal is arranged in multiples, and a signal corresponding to the relative displacement is derived from a sine wave signal and a cosine wave signal derived from the detection signal deriving means. Displacement detection signal forming unit, Displacement detection device characterized by comprising.