JPH0961192A - Magnetic detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic detector capable of effectively removing a magnetic field to be externally applied to a magnetic detecting head. SOLUTION: In view of the fact that the noise magnetic field ΦN to be applied to saturable cores 4A, 4B wound with detecting windings of the magnetic detecting head has irregularity in amplitude according to a spatial position, two detecting blocks for constituting one channel, i.e., saturable cores 4A, 4B for constituting two subchannels are aligned in series in the direction of the field ΦN to form the structure that the fields ΦN of the same amplitude are applied to the two subchannels. The detecting windings are wound so as to add to detect the signal magnetic flux ΦS to be applied to the cores 4A, 4B of the subchannels in opposite directions. As a result, the noise voltage induced by the field ΦN is set to zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a saturable core type magnetic detecting device used in a magnetic measuring device having a magnetic flux response type multi-gap head, for example.

[0002]

2. Description of the Related Art As this type of magnetic detection device, a detection device as shown in FIG. 10 has been proposed. This magnetic detection device detects the amount of displacement when the relative position of the magnetic head 2 is changed with respect to the magnetic scale 1.

As shown in the figure, the magnetic head 2 has a pair of two channels CH1 and CH2, and each channel has two detection blocks 3A, 3B or 3C, 3D.
Etc. Details of the structure of the detection blocks 3A and 3B are shown in FIG.

In FIG. 11, the magnetic scale 1 has periodic magnetized sections with alternating polarities, thereby generating a signal magnetic field around the magnetic scale. The detection block CH1a includes detection cores 5A and 5B and a saturable core 4A, and the detection block CH1b includes the detection core 5
It is composed of C and 5D and saturable core 4B.

An excitation winding and a detection winding are wound around the saturable cores 4A and 4B. FIG. 12 shows the saturable cores 4A, 4
The spatial arrangement of B and the sense windings wound on their saturable core are shown. As shown in the figure, saturable core 4
A signal magnetic flux ΦS due to the signal magnetic field from the magnetic scale 1 is added to A and 4B, and the directions thereof are opposite to each other as indicated by the solid arrow in FIG.

When a noise magnetic field from the surroundings is applied to the saturable cores 4A and 4B, the magnetic field is generally considered to be larger than the size of the detection head. Therefore, as shown by the dotted arrow in the figure, A noise magnetic flux ΦN is generated in the same direction. Here, the windings 6A and 6B become stronger in the excitation voltage with respect to the signal magnetic flux ΦS, but are wound so as to cancel each other with respect to the noise magnetic field ΦN, so that the terminals 7a,
A detection signal from which the noise component is removed is obtained at 7b.

[0007]

In the above-described magnetic detection device, the two saturable cores 4A and 4B are placed laterally spatially apart from the direction of the noise magnetic field .PHI.N. There may be cases where the magnitude of the external noise magnetic field applied to 4A and the magnitude of the external noise magnetic field applied to core 4B are different. In such a case, since the magnitude of the noise magnetic field ΦN applied to the saturable core 4A and the magnitude of the noise magnetic field ΦN applied to the saturable core 4B are not the same, the noise component cannot be completely canceled out. Therefore, it is difficult to completely remove the influence of the external magnetic field with this type of magnetic detection device.

Further, as a saturable core, a pair of cores 4A,
Because 4B is arranged to be isolated for a predetermined time,
The number of parts is increasing. An object of the present invention is to overcome the drawbacks of the conventional magnetic detection device and to provide a highly accurate magnetic detection device that has a simple structure and is not affected by an external magnetic field.

[0009]

In order to solve the above problems, according to the present invention, there is provided a magnetic detection device having a magnetic scale for generating a signal magnetic field and a magnetic head of a magnetic flux response type of at least one channel. The magnetic head
It has a saturable core portion formed of two saturable cores that are integrally formed and extend in a direction perpendicular to the moving direction of the magnetic head with respect to the magnetic scale, and two magnetic poles connected to both ends of the saturable core in the extending direction. A saturable core has a signal detection core portion including a core B and a core B having one magnetic pole connected to the center of the saturable core in the extending direction, and the two saturable cores integrally formed by the signal detection core. The vector of the signal magnetic field applied to each of the two becomes opposite to each other, whereby the output voltages of the windings attached to each of the two integrally formed saturable cores are added, and the integrally formed The output voltages due to the noise magnetic fields applied to the two saturable cores cancel each other to provide a magnetic detection device in which the influence of the external magnetic field is removed.

Further, in the above-mentioned magnetic detection device, a plurality of sets of the core A and the core B are provided with a spacer interposed therebetween, and the core A is arranged at both ends in the width direction of the saturable core. There is provided a magnetic detection device having a portion.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows an embodiment of a magnetic detection device according to the present invention. To simplify the explanation, only the detection head of the channel CH1 is shown in the figure, but in reality, {n + (1 /
4)} λ (n is an integer) and another channel CH
Two detection heads are arranged.

Comparing FIG. 3 and FIG. 10, two sub-channels C which form one channel, for example CH1.
It will be noted that the sequences of H1a and CH1b (ie the two detection blocks) are different. In FIG. 10, the detection blocks 3A and 3B represented by the sub-channels CH1a and CH1b are arranged one behind the other in the longitudinal direction of the magnetic scale 1, but in FIG.
The detection blocks represented by 1a and CH1b are arranged in a direction perpendicular to the longitudinal direction of the magnetic scale 1.

The saturable cores 4A and 4B are theoretically considered as two parts, but they are integrally formed. FIG.
Is a detailed description of the saturable core and winding,
FIG. 5 shows only the detection windings 6A and 6B. Winding 6A and winding 6B are arranged so that the induced voltages due to the signal magnetic flux ΦS applied to winding 6A and the magnetic flux ΦS applied to winding 6B due to the magnetization of the scale are added to each other.
Is connected. Therefore, the sum of the voltages induced in the windings 6A and 6B appears between the terminals 7a and 7b.

On the other hand, as shown in the figure, the noise magnetic field ΦN is uniformly applied in the longitudinal direction of the saturable cores 4A and 4B, so that the voltage induced in the winding 6A by the noise magnetic field ΦN and the winding 6B. The induced voltages cancel each other out, and no noise voltage appears between the terminals 7a and 7b.

FIG. 1 is an exploded perspective view showing a core of a magnetic circuit portion of an example of the detection head of the present invention. Detection core 5
As shown in FIG. 2, A has magnetic poles 1 and 2 at both ends, and a hole into which the rod-shaped magnetic scale 1 is inserted is provided at the center of the magnetic path connecting these magnetic poles. Further, as shown in FIG. 2, the detection core 5B is composed of one magnetic pole and a hole into which the rod-shaped magnetic scale 1 is inserted.

As shown by the arrows in FIG. 1, the two magnetic poles of the detection core 5A are connected to the longitudinal ends of the saturable cores 4A and 4B, and the magnetic pole of the detection core 5B is the longitudinal direction of the saturable cores 4A and 4B. Arranged to connect in the center. With this arrangement, as shown in the figure, as the channel CH1, for example, the magnetic core 1 of the detection core 5A exits and the saturable core 4A
A magnetic path is formed by a path that enters the outer end of the saturable core 4A, exits from the inner end of the saturable core 4A (that is, the central portion of the two saturable cores integrally formed), and enters the magnetic pole of the detection core 5B.

At this time, as a channel CH1b, a magnetic path that exits from the magnetic pole 2 of the detection core 5A, enters the outer end of the saturable core 4B, and exits from the inner end of the saturable core 4B and enters the magnetic pole of the detection core 5B. It is formed. As will be described later, the detection cores 5A and 5B are integrally assembled and configured to move relative to the magnetic scale. Therefore, the direction of the magnetic field depends on the magnetization on the scale as described above. The direction is opposite to the above-mentioned direction. Incidentally, the detection cores 5A and 5B
Are arranged apart from each other by {n + (1/2)} λ (n is an integer).

As shown by the dotted arrow in FIG. 1, the noise magnetic field Φ
Since N is evenly applied in the longitudinal direction of the saturable cores 4A and 4B, as described above with reference to FIG.
When the detection winding is wound around 4B to detect the signal magnetic flux ΦS, the noise voltage induced in the detection winding by this noise magnetic field ΦN becomes zero.

Next, a second embodiment of the magnetic detector of the present invention will be described. The magnetic core exploded view of the magnetic detection device shown in FIG. 6 is basically the same as the magnetic core exploded view shown in FIG. The difference from the case of FIG. 1 is that the magnetic scale has a flat plate shape,
A does not have a through hole of a rod-shaped scale, the detection core 5B has no through hole, and the bottom surface of the detection core 5B has an arm portion having the same width as that of the flat plate scale.

Magnetizations of N, S, N, S ... Are recorded in the longitudinal direction of the flat magnetic scale. Therefore, the detection cores 5A and 5B are aligned so as to be aligned with the magnetizations. And 5B are {n + (1/2)} λ (n is an integer)
Only placed apart. When the saturable cores 4A, 4B and the detection cores 5A, 5B are assembled to form a detection block, the magnetic path formed by the magnetic scale is such that the magnetic poles at both ends of the U-shaped detection core 5A lead to the saturable core 4A, 4B
Of the saturable core passing through both ends in the longitudinal direction of the
Two magnetic loops leading to the letter-shaped detection core 5B.

Also in this case, since the noise magnetic field ΦN applied to the saturable cores 4A and 4B is evenly applied in the longitudinal direction of the saturable cores 4A and 4B, the strength of the magnetic field applied to the saturable core 4A and the magnetic field applied to the saturable core 4B. Have the same strength and the same magnetic field direction. Since the detection windings wound around these saturable cores are wound so as to generate induced voltages in opposite directions, the detection voltage due to the noise magnetic field ΦN becomes zero.

The above is a description of a pair of detection blocks constituting the magnetic detection head, but an actual head may be composed of a multi-gap head in which a plurality of pairs of detection blocks are aggregated. Many.

FIG. 6 shows a pair of detection block configurations. In order to form a multi-gap head configuration, the detection cores 5A, 5 are arranged in the longitudinal direction of the magnetic scale 1.
B, 5A, 5B ... 5B, 5A and the repetitive detection cores are arranged side by side and separated from each other for a predetermined period. The interval between the detection cores 5A and 5B is the same as that of the pair of detection blocks {n + (1/2)}.
is λ (n is an integer). Detection cores 5A and 5A or 5B
And 5B are separated by nλ (n = 1, 2, 3, ...).

Next, referring to FIGS. 8 and 9, a concrete configuration example of the multi-gap head will be described. FIG.
8A and 8B show the detection cores A and B, and FIG. 8C shows the saturable core. Both of the detection cores 5A and 5 in FIGS.
B, corresponding to saturable cores 4A and 4B.

In this detection core, the length corresponding to the width direction of the magnetic scale is 11 mm, the length of each of the two magnetic poles of the U-shaped core is 1.2 mm, and the length of the magnetic pole of the T-shaped core in the width direction. Length 2.6mm, height 6mm, core thickness 1.2
mm. The saturable core has a thickness of 0.05 mm.
All materials are made of Permalloy C.

In FIG. 8, the dimensions of the core are not accurately illustrated due to the space limitations. Further, in order to grasp the actual size and shape of the magnetic detection head, dimensions are entered as a reference, but the present invention is not limited to these dimensions.

FIG. 9 shows a side view of the saturable core in the width direction when a multi-gap head is constructed using the detection core and the saturable core shown in FIG. As shown in the figure, the core A (U-shaped core) and the core B (T-shaped core) are the core A,
Spacers, cores B, and spacers are arranged in this order, and the last ends is core A. The distance between core A and core B is (1/2) λ
(That is, the value when n = 0 in the above expression {n + (1/2)} λ), and the interval between the core A and the core A is set to λ (that is, the value when n = 1 in the above expression nλ). Has been done.

Since both ends of the saturable core are straddled by the two magnetic poles of the detection core A, the detection core A serves to magnetically bypass the saturable core. In this case, the magnetic resistance value of the detection core A is almost determined by the thinnest part having a width of 0.5 mm and a length of 5.6 mm as shown in FIG. Then, the cross-sectional area is 0.5 × 0.2 = 0.
1 mm ² .

On the other hand, the magnetic resistance value of the saturable core is 0.5 mm in width and 3 mm in length as shown in FIG. 8 (c).
Is determined by the thinnest part of. Then the cross-sectional area is 0.5 ×
It is 0.05 × 2 = 0.05 mm ² . 2 saturable cores
Since three saturable cores are connected in series (integrally formed), 3 + 3 = 6 mm, which is the above detection core A
The length is about the same as the thin portion of 5.6 mm.

Since both the detection core A and the saturable core are made of permalloy C and the cross-sectional area is half, the detection core A is approximately the same as the saturable core according to the law that the magnetic resistance value is inversely proportional to the cross-sectional area. It has a magnetic resistance value of half the size. This means that when the noise magnetic field ΦN is applied, the noise magnetic field ΦN flows through the detection core A and the saturable core at a ratio of 2: 1 and the influence of the noise magnetic field ΦN on the saturable core is reduced. means.

As shown in FIG. 9, the assembly in which the detection core A and the detection core B are arranged with a spacer interposed therebetween is assembled so as to form a magnetic circuit by connecting to the saturable core at both ends or in the center, respectively. . In the case of the figure, a 6-gap multi-gap configuration is shown, in which 4 detection cores A are connected in parallel.

Therefore, the value of the magnetic resistance forming the bypass is 1/4 of the case where there is one detection core A. Therefore, the noise magnetic field ΦN from the outside, which bypasses the detection core A, is increased, which also reduces the influence of the external noise magnetic field ΦN. Since the external magnetic field often enters from the outside of the detection core, the effect of noise removal can be enhanced by disposing the detection core A having a bypass function on the outer side.

Even in the case of this multi-gap structure,
The excitation winding and the detection winding are wound around the saturable core to detect the reading voltage of the magnetic scale, and the noise magnetic field ΦN entering from the outside is canceled so that it does not appear in the output. It is as follows.

[0034]

Since the magnetic detection device of the present invention is formed by integrating two saturable cores, the amount of the external magnetic field that passes through is approximately the same, and the influence of the external magnetic field is reduced. The U-shaped core A is magnetically bypassed with respect to the saturable core, and since the external magnetic field does not pass through the saturable core portion and bypasses the core A portion, the influence of the external magnetic field is further reduced. . There are only two types of detection cores, A and B, and the saturable core is integrally formed, so that the configuration is simple.
Therefore, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is an exploded view of essential parts in an embodiment of a magnetic detection head of the present invention.

FIG. 2 is a schematic diagram of a detection core in one embodiment of the magnetic detection head of the present invention.

FIG. 3 is a perspective view of an embodiment of a magnetic detection device of the present invention.

FIG. 4 is an explanatory diagram showing a saturable core used in the magnetic detection head of the present invention, and an excitation winding and a detection winding wound around the saturable core.

FIG. 5 is an explanatory diagram showing a magnetic field applied to a saturable core used in the magnetic detection head of the present invention and a detection winding.

FIG. 6 is an exploded view of a main part in another embodiment of the magnetic detection device of the invention.

7 is a schematic diagram showing the shape of a detection core in the apparatus of FIG.

FIG. 8 is a schematic diagram showing the shapes of a detection core and a saturable core used in the multi-gap head of the present invention.

FIG. 9 is a schematic view showing the structure of a multi-gap head of the present invention.

FIG. 10 is a perspective view showing an overview of a conventional magnetic detection device.

FIG. 11 is an exploded view of a magnetic core portion of a conventional magnetic detection device.

FIG. 12 is an explanatory diagram showing a configuration of a saturable core and a winding state used in a conventional magnetic detection device.

[Explanation of Codes] 1 Magnetic scale 4A, 4B Saturable core 5A Detection core A 5B Detection core B

Claims (2)

[Claims] 1. A magnetic detection device having a magnetic scale for generating a signal magnetic field and a magnetic head of a magnetic flux response type of at least one channel, wherein the magnetic head extends in a direction perpendicular to a moving direction of the magnetic head with respect to the magnetic scale. And a saturable core portion composed of two saturable cores integrally formed, a core A having two magnetic poles connected to both ends in the extending direction of the saturable core, and a center in the extending direction of the saturable core. The signal detecting core portion is composed of a core B having one magnetic pole to be connected, and the vector of the signal magnetic field applied to each of the two saturable cores integrally formed by the signal detecting core is in opposite directions. Thus, the output voltages of the windings mounted on each of the two integrally formed saturable cores are added and applied to the two integrally formed saturable cores. The magnetic detection device is characterized in that the output voltages due to the noise magnetic field cancel each other out so that the influence of external noise is removed. 2. The magnetic detection device according to claim 1, wherein a plurality of sets of the core A and the core B are provided with a spacer interposed, and the core A is arranged at both ends in the width direction of the saturable core. A magnetic detection device, comprising: