JPH02221887A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To obtain a high resolution type magnetic sensor by adding a simple slit shield plate to a conventional magnetic sensor. CONSTITUTION:An exciting coil 13, detection coils 14 and 14', a shield plate 15, magnetic markers 11 and 11', and slit shield plates 16 and 16' are provided. Part of magnetic flux produced by the coil 13 is terminated by the shield plate 15 provided on both sides for the markers 11 and 12 of the magnetic sensor and never appears on the reverse surface. The magnetic flux appears outside a sensor housing only through a slit opening part to magnetize the markers 11 and 11' provided on the reverse surface. When the width of the slit is reduced, the intensity of a magnetic field becomes weak, but an area which is magnetized nearly corresponds to the slit width, so a sensor detection voltage determined by the quantity of integration of the magnetic marker surface (area which is magnetized) varies greatly with deviation in the sensor position of unit length. Therefore, the resolution when the pattern array of the magnetic markers arranged in a cord shape is improved as compared with when a magnetic sensor having no slit is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic sensor used for detecting the position of an automatic guided vehicle or the like.

[Conventional technology]

In recent years, magnetic induction methods using ferrite or amorphous tape as magnetic markers have attracted attention, and have been put into practical use as golf carts and F-motor cart systems.

Furthermore, an office cart system with a lattice-shaped guideway is being developed for practical use, so that it can be applied in offices as well. Automated guided vehicles (
AGVs) run while identifying their relative positions by counting the number of grid points they pass.
Because there are sensitivity variations in the magnetic markers laid as guideways, grid points may not be regarded as such at one time and may be overlooked, resulting in an incorrect count value as the cumulative number of grid points.

In order to eliminate the drawbacks of such relative position sensing methods, the number b
The absolute position of the AGV is recognized by arranging magnetic markers that extend in a direction perpendicular to the direction of travel of the AGV as a coded pattern at various locations on the lattice guideway.
A possible method is to perform position correction.

[Problem to be solved by the invention]

In this case, if the magnetic sensor used to guide the AGV along the lattice guide path can be shared as is,
Very cost-effective. However, as shown in FIG. 4(a), the conventional magnetic sensor is constructed in such a way that the shield plate 15 surrounds the excitation coil 13 and the detection coil 14, 14' with the magnetic marker surface completely open. To give an example in which it was not possible to resolve and detect a marker pattern that was narrower than the width of the aperture, as shown in the sensor output waveform in FIG. 4(b), Using a magnetic sensor with a height of 5 aa, it has not been possible to identify patterns with a width of 31 or less as a magnetic marker pattern.

This causes a problem in having multiple bits of information in a narrow area. Normally, the spacing between lattice guideways is 30C!
l. Although the width of the guideway is 5G, it is necessary to have about 8 bits of information in the gap of 24a1.

It is necessary to be able to identify markers with a width of 2I, but this level of resolution cannot currently be achieved.

It is an object of the present invention to provide a magnetic sensor that eliminates such conventional drawbacks.

[Means to solve the problem]

In order to achieve the above objects, the present invention provides a method in which a magnetic field is formed by excitation in an alternating current manner using an excitation coil, and a change in the magnetic field of a magnetic marker is detected by a detection coil, or a method in which a magnetic field formed by a magnetic marker is detected. In a magnetic sensor that detects using a detection coil, there is a shield plate configured to surround the excitation coil or detection coil except for the surface facing the magnetic marker, and a slit-shaped slit extending in the longitudinal direction of the magnetic marker on the side facing the magnetic marker. and a slit shield plate forming an opening.

In addition, in the magnetic sensor of the present invention, in an AC excitation type magnetic sensor or a magnetic sensor of a type in which a detection coil detects a magnetic field formed by a magnetic marker, the magnetic sensor is disposed facing the magnetic marker and movable in the longitudinal direction of the magnetic marker. The magnetic marker is equipped with a slit shield plate, a motor for driving the slit shield plate, and a transmission mechanism that transmits the rotational force of the motor to the slit shield plate to move and displace the magnetic marker in a direction perpendicular to the longitudinal direction of the magnetic marker. .

[Effect]

By adopting the configuration described in the above means, a part of the magnetic flux generated by the excitation coil terminates in the shield plate provided on the side facing the magnetic marker of the magnetic sensor, and does not exit to the bottom surface. Magnetic flux appears outside the sensor housing only through the opening and magnetizes the magnetic marker provided on the bottom surface.

In this case, since the slit is elongated in the longitudinal direction of the magnetic marker, only the elongated magnetic flux contributes to magnetization.

Although the magnetic field strength decreases by narrowing the slit width,
Since the magnetized area roughly corresponds to its slit width, the sensor detection voltage, which is determined by the integral amount of the magnetic marker surface (magnetized area), changes greatly with respect to the deviation of the sensor position of unit length. . Therefore, the resolution when detecting a pattern array of magnetic markers laid out in a cord shape is improved compared to the case where a magnetic sensor having a structure without slits is used.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1(a) is a diagram showing the configuration of a magnetic sensor and a configuration of a magnetic marker according to a first embodiment of the present invention, and FIG. 1(b) is a diagram showing a change in position of the sensor output voltage. Further, FIG. 2(a) shows how a narrow magnetic marker is monitored using the magnetic sensor of the present invention, and FIG. 2(b) shows a positional change in the sensor output voltage at that time. The same numbers as in FIG. 4 indicate the same components.

In the first embodiment of the invention, the excitation coil 13. A magnetic sensor is constructed by providing a slit shield plate 16.16' for shielding on the side facing the detection coil 14, 14', a shield plate 15 provided to surround these, and a surface of the magnetic marker 11, 11', etc. ing. Therefore, the slit is formed between both slit shield plates 16, 16' and is opened in an elongated manner in the same direction as the longitudinal direction of the encoded magnetic marker pattern. In other words, an AG equipped with a magnetic sensor
Since the traveling direction of the V and the longitudinal direction of the encoded magnetic marker pattern are perpendicular to each other, the longitudinal direction of this slit is also perpendicular to the traveling direction of the AGV.

When a magnetic sensor having such a configuration is used and the sensor is run along a pattern row of magnetic markers 11, 11', magnetic flux is generated outside only from the thin slit, and the magnetic marker is magnetized in the shape of a slit.

In this case, since the detection coils 14 and 14' detect the magnetic field distribution corresponding to the integral amount of the magnetized portion, the rate of change dV per unit deviation length of the detection voltage v0 obtained by the magnetic sensor of the present invention is / dS is the slit width.

Let the unit deviation length be ΔX.

It is considered that it is approximately proportional to dV6/dz=Δx/s. This means that by adopting a configuration with a narrow slit width, the sensitivity to positional deviation of the sensor output voltage can be improved as shown in FIG. 1(b). In Figure 1(b), the width of the magnetic marker is 2.
It shows the position change of the sensor output voltage when the magnetic sensor is set to 5cn, and the width of the magnetic sensor is 6al and the length is 121. height 50m
, the structure of the gap (slit width) S = 2 am of the slit shield plate 16.16' is sufficient for the magnetic marker 11.11'
It is possible to identify the presence or absence of Also for the magnetic marker 12.12' of width 2 (!l) shown in Fig. 2(a),
Figure 2 (b) due to a slight reduction in the magnetic field wrapping around the surrounding area.
Although the response to the gap between the magnetic markers 12 and 12' is large as shown in , it can be identified as code information. These characteristics are high-resolution sensing characteristics that could not be obtained with conventional magnetic sensors having a structure without slits. These sensor output signals are compared with a predetermined threshold voltage level in a signal processing section that processes the sensor output signals, and are converted into code signals of 11' and ``01.

These characteristics were similarly obtained using not only ferrite but also amorphous tape as a magnetic marker. Of course, a permanent magnet type magnetic marker may also be used, and similarly high-resolution characteristics can be obtained. In this case, a magnetic sensor that does not use an excitation coil is used.

In this way, by using the magnetic sensor of the present invention,
It becomes possible to significantly improve the resolution of sensing the magnetic marker pattern compared to the conventional method.

As a result, by simply installing a magnetic sensor, which is a conventional magnetic sensor with a slit shield plate such as an IQ plate, on the AGV, a code pattern containing approximately 8 bits of information can be laid on the grid guideway and detected. You will be able to do this. Since the cost increase due to the addition of this slit shield plate is small, it is possible to use a magnetic sensor that costs almost the same as a conventional product.

(Embodiment 2) FIG. 3 is a diagram showing the configuration of a magnetic sensor according to a second embodiment of the present invention. In this figure, the same numbers as in other figures indicate the same components. Shield plate 2
6 and 26' along the external lower surface of the magnetic sensor. In addition, the magnetic sensor has a shield plate 15.
Underneath the slit shield plates 26, 26', support plates 17°17', 18, 18 are placed so that they fit properly.
' are provided at the lower edge of the magnetic sensor. These support plates 17
．． The gaps 17' and 18.18' are set to be the same as the slit spacing in FIG. In addition, as the material for these support plates, non-metallic materials such as acrylic plates are desirable;
It is not necessarily limited to this, and may be made of metal as long as it is small.

When a magnetic sensor with such a configuration is installed and an AGV is run, the motors 19 and 19' are activated only when the AGV detects a digitally coded magnetic marker pattern.
A slit shield plate 26.2 is placed on the bottom surface of the rotated sensor.
Move and set 6'. After detecting the code pattern of the magnetic marker in this state, the motors 19, 19' are turned on again.
By rotating the slit shield plate 2 in the opposite direction, the slit shield plate 2
6. Remove 26'. By doing so, the effect obtained (high resolution) is the same as in the first embodiment, but one magnetic sensor can be used for both guidance and coat pattern detection.

〔Effect of the invention〕

As explained in detail above, according to the present invention, by simply adding a simple slit shield plate to a conventional magnetic sensor,
A high-resolution magnetic sensor can be realized. Further, it is possible to easily realize the common use of the magnetic sensor for guiding the AGV and for detecting the code signal, and it is possible to reduce the cost of the AGV system.

[Brief explanation of the drawing]

FIG. 1(a) is a diagram showing the configuration of a magnetic sensor according to the first embodiment of the present invention, FIG. 1(b) is a sensor output waveform diagram, and FIG.
Figure (a) shows the change in position of the sensor output voltage;
b) is a sensor output waveform diagram, FIG. 3 is a diagram showing the configuration of a magnetic sensor according to a second embodiment of the present invention, FIG. 4(a) is a diagram showing the configuration of a conventional magnetic sensor, and FIG. b) is a sensor output waveform diagram. 11.11', 12.12'...Magnetic marker 13.
...Exciting coil 14.14'...Detection coil
15... Shield plate 16.16', 26.26'.
...Slit shield plate 17.17', 18,18'
...Support plate 19.19'...Motor 20.2
0'...Rotating friction body

Claims (2)

[Claims] (1) A method in which a magnetic field is formed by excitation in an alternating current manner using an excitation coil, and a detection coil detects changes in the magnetic field of a magnetic marker, or a method in which a detection coil detects the magnetic field formed by a magnetic marker. In the sensor, there is a shield plate configured to surround the excitation coil or detection coil except for the surface facing the magnetic marker, and a slit shield that forms a slit-shaped opening extending in the longitudinal direction of the magnetic marker on the side facing the magnetic marker. A magnetic sensor comprising a plate. (2) In an AC excitation type magnetic sensor or a magnetic sensor that uses a detection coil to detect the magnetic field formed by a magnetic marker, a slit shield plate is provided facing the magnetic marker and movable in the longitudinal direction of the magnetic marker. A magnetic sensor comprising: a motor for driving the slit shield plate; and a transmission mechanism that transmits the rotational force of the motor to the slit shield plate to move and displace the magnetic marker in a direction perpendicular to the longitudinal direction of the magnetic marker.