JP2000215392A - Magnetic marker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a magnetic marker as much as possible and to prevent a magnet from shaking in a case where the magnet is housed in the case. SOLUTION: The magnetic marker is composed of a magnetic compound material 24 which consists of a sintered magnetic body 20 obtained by integrally sintering magnetic material and a skin part 22 which is molded while the sintered magnetic body is inserted into an internal die cavity and is made from plastic or a plastic magnet covering at least a part of the sintered magnetic body, and magnetic poles are formed at both edges in the height direction of the compound material 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic marker used in a magnetic induction system of a motor vehicle or a magnetic alarm / warning system.

[0002]

2. Description of the Related Art One of the purposes of using a magnetic marker in a magnetic guidance system or the like is to make an automobile run along a prescribed lane (for example, the center of the oblique line on the road surface).
Specifically, as shown in FIG. 1, a magnetic sensor 14 is installed in a central portion 12 of a bottom surface of a vehicle body in an automobile 10,
On the road surface 16 of the road, a magnetic marker 20 for outputting a magnetic signal is installed along the center of the lane, and the magnetic sensor 14 and the magnetic marker 20 cooperate to control the vehicle to run in the center of the lane.

[0003]

As the magnetic marker, several patent applications have already been filed by the present applicant (for example, Japanese Patent Application Nos. 9-266640, 10-255702 and 1).
No. 0-258610) basically comprises a case buried on the road surface and a magnet housed therein. However, the manufacturing cost of the magnetic marker increases due to the necessity of the case, and if there is a gap between the magnet and the case, the magnet rattles in the case.

The present invention has been made in consideration of the above circumstances. First, it is necessary to reduce the manufacturing cost of a magnetic marker as much as possible. Providing a magnetic marker capable of preventing rattling,
It was made for the purpose of.

[0005]

In order to achieve the above object, the present invention provides a magnetic marker used in a magnetic induction system or a magnetic alarm / warning system of an automobile, wherein a magnetic material is integrally sintered. And a skin portion made of a plastic or a plastic magnet covering at least a part of the sintered magnet body in a state where the sintered magnet body is inserted into the cavity in the mold, and both ends in the height direction are formed. It consisted of a magnet composite magnetized on magnetic poles.

According to the present invention, since the magnetic marker is completed only by covering the sintered magnet body with a skin portion made of a plastic magnet or the like, the manufacturing cost of the magnetic marker can be reduced. Further, even when the magnet composite is housed in the case, the skin portion and the case made of a plastic magnet or the like can be finely dimensioned, so that a gap is prevented from being formed between the skin portion and the case.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic marker is used in combination with a magnetic sensor in a magnetic guidance system, an alarm and a warning system of an automobile. The sintered magnet body is formed only of the sintered body, and can be reduced in size because no binder is used. The sintered magnet body may be formed into a predetermined shape during firing, or may be manufactured by cutting a columnar sintered body in a direction perpendicular to the longitudinal direction. As the sintered magnet, a Nd sintered body is preferable.

A plastic or a plastic magnet can be used as the skin. Here, since plastic is a non-magnetic material, when it is used for the skin portion, it is preferable that its thickness is as thin as possible. Further, as the plastic magnet, anisotropic pramag is preferable, and when this is used, the magnetic force of the composite magnet body is improved accordingly. Then, by covering at least a part of the entire surface or a specific surface of the sintered magnet body with a plastic or a plastic magnet as needed, the defect of the sintered magnet body that is easily broken can be solved.

When the magnet composite is used as it is (without a case), the magnet composite becomes a magnetic marker, and a combination of the magnet composite and a non-magnetic case sometimes becomes a magnetic marker. In the latter case, the composite magnet body may be housed in a separately prepared case after fabrication, or the sintered magnet may be placed in a case made of a non-magnetic material with a gap kept between them, and a plastic may be placed in the gap. A magnet material or the like may be supplied.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> This embodiment 1 is a magnetic marker using a magnet composite as it is. In consideration of the property of the sintered magnet that the shape is distorted in the firing process even when the weight is controlled to be constant during firing, in this embodiment, as shown in FIG. 2, a cylindrical sintered magnet (sintered magnet body) After firing, the entire surface (cylindrical surface and upper and lower surfaces) was covered with a skin portion 22 made of plastic or a plastic magnet. The skin portion 22 was formed on the surface of the sintered magnet 20 by placing the sintered magnet 20 with a gap kept in the cavity of the mold and supplying plastic or a plastic magnet to the gap.

The magnet composite 24 is magnetized so that its upper and lower ends become magnetic poles, and is buried in a road surface as it is. According to this embodiment, the composite magnet body 24 can be used as it is as a magnetic marker, and a case is unnecessary. Therefore, the structure is simple, the number of parts is small, and the manufacturing cost can be reduced.

Next, in order to examine the relationship between the characteristics of the sintered magnet 20 and the characteristics of the skin portion, ie, the plastic magnet 22, the weight of the sintered magnet 20 and the volume of the magnet composite 24 are kept constant, With the performance of the plastic magnet 22 changed, a vertical magnetic field was measured at a point about 250 mm above the magnet composite 24. In this case, the sintered magnet 20
Has a cylindrical shape with a diameter of 36 mm and a height of 28 mm, and the plastic magnet 22 has a cylindrical shape with a diameter of 40 mm and a height of 30 mm. Therefore, the ratio of the diameter to the height of the magnet composite 24 is about 1.3.

The results are shown in Table 1. As can be seen from Table 1, when the weight of the sintered magnet 20 is constant, a higher magnetic field is obtained as the magnetic properties of the plastic magnet 22 are higher, and the magnetic marker 24 has excellent magnetic properties.

According to another experiment conducted by the inventor,
When the magnet composite 24 is housed in a case made of a non-magnetic material, as long as the configuration (shape, size, weight, magnetic characteristics, etc.) of the magnet composite is the same, even if the shape of the case is different,
The strength of the magnetic force obtained is almost the same. More specifically, as shown in FIG. 3A, a magnet composite 24 having the same configuration is formed of a case 3 having a bottomed cylindrical portion with a flange and a hexagonal plate portion.
2, and a case made of a bottomed hexagonal cylinder as shown in FIG. 3C when housed in a case 34 consisting of a bottomed cylinder and a hexagonal plate as shown in FIG. 36
When the magnetic force was measured, the size was the same.

<Embodiment 2> In this embodiment, a sintered magnet manufactured by cutting and firing a columnar sintered body is used, and a composite magnet body is housed in a case to form a magnetic marker. is there. When a sintered magnet is manufactured by cutting a columnar fired body,
In the firing step, the weight of the sintered magnet is not stable because the shape of the sintered body is distorted. In consideration of this, in the present embodiment, FIG.
As shown in (a) and (b), only the outer peripheral surface of the four flat quadrant disc-shaped sintered magnets 40 is
And magnetized so that the upper end and the lower end in the height direction become magnetic poles, to produce a magnet composite 44. Then, the magnet composite 44 was housed in a magnet housing space 50 of a case 48 made of a non-magnetic material, and the bottom cover 52 was joined by screws, welding, or the like. At the center of the case, a special nut 54 is
It is fixed at 6.

In order to confirm the magnetic effect of the magnetic marker 55, an experiment was conducted while the size of the magnet storage space 50 of the case 48 was fixed and the properties of the sintered magnet 40 and the plastic magnet 42 were changed. The magnetic flux was measured at a point 250 mm above the magnet composite 44. Table 2 shows the measurement results. It should be noted that there is a maximum value and a minimum value in the weight of the sintered magnet 40 because, as described above, when the block-shaped sintered magnet is cut, even if it is manufactured with the same components and processes, the width dimension Is different.

It can be seen from Table 2 that in sample 1, even if the sintered magnet 40 is manufactured in the same process, variation in the weight of the sintered magnet leads to variation in the magnetic characteristics of the magnetic marker 55 (about 10%). Is caused). On the other hand, in the samples 4 and 5, the magnetic characteristics of the magnetic marker 55 are stable even if the weight of the sintered magnet 40, that is, the weight ratio between the sintered magnet 40 and the plastic magnet 42 is different. This is considered to be because the magnetic properties of the sintered magnet 40 and the plastic magnet 42 in the sample 1 are significantly different from each other, whereas the magnetic properties of the samples 4 and 5 are the same. Thus, the sintered magnet 40 and the magnet composite 44
It was found that the closer the characteristics of the sintered magnet 40 and the plastic magnet 42 were, the more stable the performance of the magnetic marker 55 was irrespective of the weight variation of the magnetic marker 55.

In this embodiment, the sintered magnet 40 and the case 48
Since it is made by integral molding of the plastic magnet 42 with the plastic magnet 42, it can be housed without any gap between them, so that there is no fear that the composite magnet body 44 will rattle in the case 48. Further, the composite magnet body 44 is placed in the space 50 of the case 48.
The space of the magnet composite 44 in the case 48 can be improved by filling the case
It is reinforced by the composite magnet body 44 itself.

<Embodiment 3> In this embodiment, a metal case is used as a mold when molding a plastic magnet. Specifically, as shown in FIGS. 5 and 6 (a) to (d), one sintered magnet block is divided into two to form two cylindrical sintered magnets 60 having a diameter of 44 mm and a height of 20 mm. Make two. This sintered magnet 60 is 46 mm in inner diameter and 25 mm in height.
In the space 68 of the bottomed cylindrical case 66. Then, an annular gap 70 is formed between the outer peripheral surface of the sintered magnet 60 and the inner peripheral surface of the case 68.

Next, as shown in FIG. 6B, the resin material of the plastic magnet 74 is supplied from the molding gate 76 to the gap 70.
Then, injection molding is performed on the upper surface of the sintered magnet to be integrated, and then a cap 78 is attached to the case 68 as shown in FIG. In this way, a magnet composite magnetized on the upper and lower magnetic poles, that is, the magnetic marker 80 is completed. In this magnet composite, the ratio of diameter to height is about 1.8. Note that FIG.
Instead of the method (b), as shown in FIG. 6 (c), a plastic magnet 74 may be compression molded by a punch 79 and integrated with the gap 70 and the upper surface of the sintered magnet.

According to the magnet composite 80 of this embodiment, the metal case 66 serves as a mold for forming the plastic magnet 74. Therefore, it is not necessary to prepare a dedicated mold, and the step of assembling the magnet composite 80 and the case 66 can be omitted, so that the manufacturing cost of the magnetic marker can be reduced accordingly. In addition, plastic magnet 6
Since there is no gap between the case 0 and the case 68, high filling of the magnet can be achieved and the magnet performance is enhanced, and the case 68 itself is reinforced by the magnet composite 74.

Table 3 shows a specific example of the magnet composite 74 manufactured according to this embodiment.

Example 4 This example was performed to find the limit of the ratio of the diameter of the plastic magnet to the diameter of the magnet composite. Generally, in order to obtain a compact and high-performance magnetic marker, a sintered magnet and a plastic magnet having high magnetic properties may be combined. As a magnet currently used, a combination of an Nd sintered magnet and an anisotropic plastic magnet is excellent. The larger the ratio of the volume of the sintered magnet to the volume of the magnet composite, in other words, the smaller the ratio of the volume of the plastic magnet, the better the magnetic performance of the magnet composite. However, if the proportion of the plastic magnet is extremely small, its manufacture is difficult or impossible.

Therefore, as shown in FIGS. 7A and 7B, a case 82 having a relatively small sectional area and a deep
Case 8 having a relatively small cross-sectional area and shallow as shown in FIG.
4 is prepared (the size of both storage spaces is the same), a case 82 accommodates a magnet composite 86 having a diameter of 40 mm and a height of 30 mm, and a case 84 having a diameter of 70 mm and a height of 9.8 mm. The magnet composite 88 was housed. Both magnet composites 86 and 88 are composed of Nd sintered magnets 92, 94 and anisotropic plastic magnets 91, 93. The Nd sintered magnet is cut into a 30 mm or 9.8 mm height by cutting a fired product. The anisotropic plastic magnet was manufactured by injection molding and covered only the outer peripheral surface of the sintered magnet.

Table 4 shows the results obtained by changing the diameter X of the sintered magnets 92 and 94 accommodated in the cases 82 and 84 and measuring the magnetic flux intensity at that point 250 mm above the magnets.

As can be seen from Samples 1 to 3 or Samples 4 to 6 in Table 4 above, if the size of the magnet storage space in the cases 82 and 84 is constant, the plastic magnets 92 and 94 become the magnet composites 86 and The smaller the volume set in 88, the better the magnetic performance of the magnet composite. Here, based on the magnetic flux of samples 1 and 4, samples 2 and
Looking at the magnetic fluxes of Samples 3 and 5 and 6, in Samples 2 and 5 in which the volume ratio of the plastic magnet to the magnet composite is 20%, about 90% of the magnetic flux in Samples 1 and 4 is obtained. Therefore, this is considered as one limit point. The other limit point can be reduced as much as theoretically, but is considered to be 0.5% due to restrictions in manufacturing the plastic magnet.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a use state of a magnetic marker.

FIG. 2 is a front sectional view showing the first embodiment of the present invention.

FIGS. 3A to 3C are perspective views showing a state in which a sintered magnet body is housed in various cases.

FIG. 4A is a front sectional view showing a second embodiment of the present invention, and FIG. 4B is a plan view (partially broken).

FIG. 5 is a front sectional view showing a third embodiment of the present invention.

FIGS. 6A to 6D are explanatory views showing a manufacturing process of the third embodiment.

FIGS. 7A and 7B are cross-sectional views showing a fourth embodiment of the present invention.

[Explanation of symbols]

20, 40, 60 Sintered magnet body 22, 42, 7
4 Skin portion 24, 44 Magnet composite 48, 66 Case 50, 68 Storage space 24, 55 Magnetic marker

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 1, 1999 (1999.2.1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art One of the purposes of using a magnetic marker in a magnetic guidance system or the like is to make an automobile run along a prescribed lane (for example, the center of the oblique line on the road surface).
Specifically, as shown in FIG. 1, a magnetic sensor 14 is installed in a central portion 12 of a bottom surface of a vehicle body in an automobile 10,
On the road surface 16 of the road, a magnetic marker 18 for outputting a magnetic signal is provided along the center of the lane, and the magnetic sensor 14 and the magnetic marker 18 cooperate to control the vehicle to travel in the center of the lane.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

[Procedure amendment 7]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

[Procedure amendment 8]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroaki Hirano 1 Wanowari, Arao-cho, Tokai-shi, Aichi F-term in Aichi Steel Corporation (reference) 2G005 BA03 5H180 AA01 CC19 CC24 FF17 FF21 GG02 HH19 JJ28 LL09

Claims (3)

[Claims] 1. A magnetic marker used for a magnetic induction system or a magnetic alarm / warning system of an automobile, comprising: a sintered magnet body in which a magnetic material is integrally sintered; It is formed in a state of being inserted into the inner cavity, and is made of a plastic or plastic skin covering at least a part of the sintered magnet body, and a magnet composite having both ends in the height direction as magnetic poles. A magnetic marker, comprising: 2. The magnetic marker according to claim 1, further comprising a case for housing and holding the magnet composite. 3. In the magnet composite, the skin portion is formed by disposing the sintered magnet body in a storage space of the case and filling the gap of the storage space with the plastic or a plastic magnet. The magnetic marker according to claim 2.