JPS6338101A - Iron detecting device - Google Patents

Abstract

PURPOSE:To detect a magnetic body such as an iron piece and to generate a larger output voltage by obtaining a DC voltage which varies linearly when the iron piece moves on the detection surface of a detection head. CONSTITUTION:A saturable coil 3 is brought into contact with the bottom surface of a container 1 in parallel to the detection surface 2. A permanent magnet 4 is magnetized in the thickness direction and superposed on the coil 3. The winding of the coil 3 is connected to a magnetic detecting circuit through a relay terminal 5. In the magnetic detecting circuit, the coil 3 consists of a saturable core 6 and winding parts L1 and L2 in mutually opposite directions and the winding parts L1 and L2 and two resistances Rs and Rs constitute four sides of a bridge; when a magnetic field is applied in the lengthwise direction of the coil 3, an output voltage is developed between terminals 7 and 8. Then, a detection head which has the coil 3 parallel to the detection surface 2 and the magnet 4 magnetized at right angles to the detection surface 2 is used and the magnetic detecting circuit detect variation of magnet magnetic flux applied to the coil 3 when the iron piece approaches the detection surface 2. Further, the magnetic detecting circuit generates a positive and a negative output voltage according to the position relation between the coil 3 and magnet 4 when the iron piece moves on the detection surface 4.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an iron detection device that accurately detects a specific position of a moving or rotating object in a machine tool or industrial machine without contact. .

[Summary of the invention]

In the present invention, an iron piece is embedded in a moving (or rotating) body, a detection head consisting of a saturable coil and a magnet is placed opposite to the iron piece, and when the iron piece moves across the detection surface of this head, a direct current that changes linearly changes. By obtaining a voltage, the position can be detected continuously over a certain period of time.

[Conventional technology and its problems]

Conventionally, as a device for detecting the origin of a scale device or a fixed point of a moving table in a non-contact manner and with high precision, a combination of a magnet piece and a highly sensitive magnetic sensor that detects the magnetic field generated by this magnet piece has been used. has been done.

This magnetic sensor uses a saturable coil.

This conventional device detects the position of the magnet piece and requires the magnet piece to be attached, which has the drawback of limiting its use.

In addition, there are other devices that use a magnetic sensor that combines a hole y, a quadruple element, or a ventilation resistance element with a permanent magnet to detect a magnetic body such as an iron piece. However, these 11 self-air detectors have the disadvantage of low sensitivity (the distance between the sensor and the object to be detected must be very small, and high precision cannot be obtained).

[Means for solving problems]

The present invention uses a detection head having a saturable coil parallel to the detection surface and a permanent magnet magnetized in the direction of the image point on the detection surface, and the magnet magnetic flux is applied to the saturable coil when an iron piece approaches the detection surface. A magnetic detection circuit detects changes in the magnetic field.

[Effect]

Due to the positional relationship between the saturable coil and the permanent magnet, the magnetic sensing circuit produces positive and negative output voltages as the piece of iron moves across the sensing surface.

〔Example〕

FIG. 1 is a sectional view showing the basic structure of an iron detection head used in the present invention. 2 in the same figure, tl) is a non-magnetic container, (2) is its detection plane, (3) is a saturable coil, (
4) indicates a permanent magnet, and (5) indicates a relay terminal. Container (1)
For example, a non-magnetic stainless steel plate with a thickness of 0.2 milJ is molded into a cylindrical shape with an outer diameter of 10 mm.

The saturable coil (3) is, for example, a permalloy thin plate with a thickness of 0.1 mm, a width of 3 mm, and a length of 5 mm, with a pair of windings in opposite directions (the number of turns is 100). Face (2
), and the permanent magnet (4) has a thickness of, for example, 1.6 milJ and an outer diameter of 8.
It is a disc-shaped plastic magnet of millimeter thickness, magnetized in the Z-axis direction, and is stacked on top of the saturable coil (3).

In this example, the magnetic field strength measured at the outer detection surface (2) of the container (1) was 160 Gauss. The winding of the saturable coil (3) is connected to the magnetic detection circuit of FIG. 2 via a cable via a relay terminal (5).

FIG. 2 is a diagram showing an example of a bridge type magnetic detection circuit used in combination with a detection head. In the same figure, O20
is, for example, a 50 KHz high frequency pulse oscillator, in which case the pulse polarity is constant and the pulse width is 1 μs. R3
is a series resistance, Dl and D2 are diodes'', r1 and r
2 is the output resistance, C1, C2 and C3 are the capacitances, (force and (
8) indicates the output terminal. The saturable coil (3) has permalloy saturable core (6) and windings Ll, L in opposite directions.
The winding L1*R2 and the two resistors R8 and R8 constitute the four sides of the bridge. When a magnetic field is applied in the longitudinal (X-axis) direction of the saturable coil (3), the output terminal (7),
(Produces an output voltage at 81. In the magnetic detection circuit described above, the output is linear up to a range of ±50 Gauss in the magnetic field in the X-axis direction, producing a voltage of ±6 volts, and saturates at ±100 Gauss to approximately 10 volts.) A saturable coil (3
), when the magnetic field is applied in the Y-axis or Z-axis direction perpendicular to the X-axis, almost no output is produced.

FIG. 3 is a diagram showing the disturbance of the magnetic flux generated by the magnet (4) when a piece of iron approaches the detection surface (2) of the detection head shown in FIG. When there is no iron piece, the magnetic flux is symmetrical about the Z-axis, and the magnetic field in the X-axis direction applied to the saturable coil (3) is 0,
The output of the magnetic detection circuit is O.

When the iron piece (7) approaches the position A, the magnetic flux changes to the right as shown, creating a magnetic field in the X-axis direction in the saturable core (6). When the iron piece (7) moves to position B, the magnetic field shifts to the left, producing a magnetic field in the -X direction. Therefore, when the iron piece (7) is moved in the X plow direction near the detection surface (2), the output of the magnetic detection circuit changes.

FIG. 4 is an explanatory diagram showing the positional relationship when moving the iron piece close to the detection surface. The iron piece (7) is a soft iron plate with a length of 10 mm in two directions, a width of 20 mm in the Y direction, and a thickness of 1 mm in the X direction.
When moved in the direction, the output of the magnetic detection circuit becomes as shown in FIG.

The output curve in FIG. 5 shows that the iron piece (7) is at O voltage when it comes to the center, and the output changes almost linearly before and after that, with a slope of 5 volts/1 mm.

When d=0.5 mm, the output will be ±6 volts, and d=2
An output of ±2 volts can be obtained even in millimeters. The drift at the center of the magnetic detection circuit is very small, and it can only reach 5 m with a temperature change of 10°C.
Since it is stable at V or less, the temperature change of 10℃
Position detection is possible with an accuracy of μm.

FIG. 6 shows an output curve of the magnetic detection circuit when a long iron plate is moved in the X direction at a distance of d from the detection surface of the detection head. The dimensions of the iron plate are 30 mm in length in the X direction, and 30 mm in the Y direction.
The direction is 4xOmi+J, and the width in both directions is 1mm. In this case, positive and negative peaks are produced at 93 on the iron plate, and the output becomes O at the center.

Therefore, the iron detection device according to the present invention can detect the edge of an iron piece, but cannot detect an iron plate that spreads evenly.

In the above embodiment, a small and weak magnet was used, but if the magnetic field of the magnet is strengthened, the output of the magnetic detection circuit can be made thicker.Also, even if the size of the magnet is increased, If the interval d is used, it is possible to increase the distance and obtain the same output.

In the explanation so far, the object to be detected has been described as a piece of iron, but it is not limited to iron, and may be ferrite or cast metal as long as it is a magnetic material with low residual magnetism. A subject with large residual magnetism is not preferable because it lowers position detection accuracy.

[Application example]

The iron detection device of the present invention can be used not only for position detection, but also for multi-purpose (
It can be used to non-contact detect whether a screw or nut is in the correct position. For example, when tightening a device that rotates around an axis using a large number of screws at regular intervals, as shown in Figure 7, if the detection head is placed as shown, screws may be missing or not tightened enough. It is easy to detect defects that may occur. Furthermore, since the output from the detection head corresponds to each screw, it can also be applied as an encoder to detect the position of a rotating body.

〔Effect of the invention〕

As explained above, according to the present invention, the following great effects can be obtained.

1) Even if a relatively weak magnet is used, a magnetic material such as an iron piece can be detected and a large output voltage can be generated.

2) Even if the distance between the object and the detection head is increased to 2 mm or more, a large output can still be obtained.

3) Compared to conventional methods that detect the position of magnet pieces, the same accuracy and stability can be obtained, and since magnet pieces are not used and replaced with iron pieces, etc., iron powder does not adhere to them like in the case of magnet pieces. This is very advantageous because it does not reduce the position detection accuracy.

4) It can be used not only for position detection on a straight line (but also for inspecting a large number of screws on a rotating body and detecting the position of a rotating body).

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic structure of the detection head of the present invention;
Figure 2 is a diagram showing an example of a magnetic detection circuit used in combination with the detection head, Figure 3 is an explanatory diagram showing how the magnetic flux changes due to the iron piece in the detection head of Figure 1, and Figure 4 is the detection head and iron piece. Figure 5 is an output curve diagram when an iron plate is moved in the X direction, Figure 6 is an output curve diagram when a long iron plate is used in the X direction, and Figure 7 is an application of the present invention. It is a side view which shows an example.

Claims (1)

[Claims] A saturable coil is placed parallel to the detection plane in a non-magnetic container having a detection plane, and a permanent magnet magnetized in a direction perpendicular to the detection plane is provided above the saturable coil. It comprises a detection head, and a bridge-type magnetic detection circuit in which two sides of a bridge are a pair of windings of the saturable coil wound in opposite directions, and when a piece of iron approaches the detection plane, positive and negative signals are detected. An iron detection device characterized in that it produces an output voltage of