JPS63313321A - Magnetic drum - Google Patents

Abstract

PURPOSE:To simplify stages for production and magnetization and to provide an improvement in finishing accuracy, uniformization of magnetic characteristics and improvement in yield by printing the paste of a magnetic material on the outside peripheral face of a drum by a screen printing method to form the magnetic drum, then subjecting the drum to magnetization. CONSTITUTION:The magnetic drum is formed by printing the paste of the magnetic material by the screen printing method for a curved surface on the outside peripheral drum face of the cylindrical drum 1 consisting of a nonmagnetic metallic material or thermoplastic resin. The magnetic drum for magnetic recording is obtd. by magnetizing this magnetic drum. The nonmagnetic material such as stainless steel or the thermoplastic resin such as acrylonitrile/butadiene/styrene copolymer, polycarbonate or polystyrene or the resin prepd. by dispersing glass fibers in the thermoplastic resin is used as the material of the drum. The paste of the magnetic material is prepd. by dispersing the magnetic material in a vehicle material for printing. This paste is printed on the outside peripheral face of the drum in the printing patterns based on a Gray code.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention is applicable to FA such as NC machine tools and industrial pots.
Of the various rotary encoders used to determine the rotational speed, angle, and position of related equipment, it relates to magnetic rotary encoders, and also relates to incremental types that do not display absolute points from a functional standpoint. The present invention relates to an absolute type that displays an absolute point based on iE based on the zero point, and its purpose is to provide an absolute type magnetic drum for magnetic recording. Normally, on an actual magnetic absolute type rotary encoder, as shown in FIG. The generated magnetic data is read out. As shown in FIG. 9, this magnetoresistive element 14 has the property that the electrical resistance of the element decreases in accordance with the external magnetic field strength, and when the external magnetic field strength reaches about 850 oe, the resistance change saturates. Utilizing the characteristics of this magnetoresistive element, the recording data on each magnetic track of the magnetic drum 7 can be adjusted.
The basic structure and function of the absolute type of magnetic rotary encoder is to use an electric circuit to determine whether the drum shaft is blank or not, and output an electric signal coded as an electric signal that matches the absolute zero or first position of the drum shaft. be.

``Conventional technology'' Currently, most of the conventional absolute type rotary encoders are optical types, and magnetic types are almost never put into practical use. As shown in Fig. 10, the magnetic drum used in the encoder is made by attaching a fate-based or rare earth-based resin magnet plate 16 to a predetermined number of magnetic poles in a predetermined position to match the encoder output code. Alternatively, as shown in FIG. 11, after bonding ferrite-based or rare earth-based resin magnet plates 17 together with a bonding agent or a hot plate 6, each magnetic track 15 is Attempts have been made to attach a predetermined number of magnetic poles at predetermined positions in order to match the encoder output code, and to use it as a magnetic drum 13 for magnetic recording.

``Problems to be Solved by the Invention'' The conventional method described above, in which the magnets shown in FIG. It is difficult to unify the absolute positions in the circumferential direction and on the front and back sides with high accuracy, and the method of turning 6 magnets after bonding and integrating as shown in FIG.
It is impossible to magnetize 5 to 6 magnetic poles at one time if the magnetic recording data of each track is large. , the results are disappointing.

In both cases, the manufacturing process of the magnetic drum and the machining process become complicated, resulting in a decrease in the yield of the magnetic drum.

"Means for Solving the Problems" The present invention aims to simplify the manufacturing and magnetic process of magnetic drums, which are the problems of the prior art, and to improve finishing accuracy and make magnetic properties uniform. The aim is to improve yields by

FIG. 1 is an illustration of the present invention. The magnetic drum 1 has an encoder output code 1, which will be described later, printed on the outer peripheral surface 2 of the drum using a magnetic material paste using a curved surface screen printing method.
The magnetic material layer 3 is printed on the entire circumference in accordance with the gray code, and the dot portions are printed, and the drum material is left on the surface as it is except for the dot portions. Here, the drum 1 is a cut and polished product made of aluminum, stainless steel, non-magnetic metal material, or 7-acrylonitrile butadiene styrene copolymer, polycarbonate, polystyrene, polyethylene terephthalate, polybutylene terephthalate, acrylonitrile styrene copolymer. It is a polished product made by injection molding of a thermoplastic resin such as a combination of resins or a thermoplastic resin with glass fibers dispersed therein. Here, the drum shaft 4 corresponds to a rotating and sliding part as a rotary encoder, and is therefore cut and polished from a metal material with good wear resistance and corrosion resistance, such as bearing steel, and is integrated with the drum 1.

Figure 1 also shows that the drum material is non-resistant due to the magnetization process described later! Since it is a bamboo material, it is not magnetized and only the magnetic material layer 3 of the dot part is Wm at a predetermined magnetization distance λ between the N and S poles, which is why the magnetic absolute type This is because it can be used for the purpose of a magnetic recording magnetic drum for a rotary encoder.

Next, the manufacturing method up to the magnetic drum 1 shown in FIG. 1, which is an embodiment of the present invention, will be explained in detail below.

FIG. 2 shows a drum 1 made of the above-mentioned non-magnetic metal material or thermoplastic resin which has been cut or molded and polished, in which the roundness, coaxiality, and drum diameter of the drum outer circumferential surface 2 and the drum shaft 4 are , high accuracy is required.

FIG. 3 shows a printing pattern in which a magnetic material paste is printed on the entire circumference of the drum outer peripheral surface 2 shown in FIG. 2 by a curved surface screen printing method. This printing pattern determines the output code of the rotary encoder of the magnetic absolute tie 1, and the accuracy of the printing pattern is considered to be the most important.
- The output code of the tally encoder is a Gray code, and the print pattern is designed as follows to obtain this Gray code output.

For convenience of explanation below, it is assumed that a magnetic absolute type rotary encoder with 360 resolution is designed. In Figure 4, a) represents 360 resolution as a decimal number from O to 359, and b) represents a as a decimal number from 76 to 435.
) is shown shifted. To express this b) in binary, 9 bits (R upper bit B8
to the least significant bit B. up to 9 bits) data.

Next, the binary representation of C) (B8, B7, B6, B5, B
4, B3, B2, B4, Bo) 08=88 G・=8・■Bi+1 Go=80■B1 ■ indicates exclusive OR.

As shown in d), the gray code (G8, G7, G6, G5, G4, G3) is 9-bit data.
, G2, G4, Go) are found. FIG. 3 shows a print pattern of the "1" portion of this Gray code data.

The feature of this pattern is that as the data changes sequentially,
Unlike binary numbers and binary coded decimal codes, only one bit always changes from "0" to "1" or from "1" to rOJ, and multiple bits never change at the same time. This means that reading errors can be prevented when reading magnetically recorded data on the magnetic drum, and the use of this output code in the print pattern is an important aspect of the present invention.

As shown in Fig. 5, the printing pattern shown in Fig. 3 is applied to the curved screen printing silk plate 5, the above-mentioned drum 1 is set, the magnetic material paste 6''C is applied, and the squeegee 8 is fixed, and the drum 1 is rotated. It is also the most important matter of the present invention to synchronize the distance and the moving distance of the silk plate 5 to print the mg material layer of the printing pattern 7 or J3 on the drum outer peripheral surface 2.

Here, the length calculated by the drum diameter and the print pattern size (third size) are made equal to each other, and the bit width of each gray code bit of the print pattern 7 (Wl in FIG. 3) is It is natural that the track width (W2 in FIG. 1) formed on the magnetic drum is equal to each other, but the absolute dimension of the track width W2 is determined in advance in step 81.

On the other hand, the magnetic material paste 6 has the chemical formula Ba as a tan material.
Ferrite particles/powders with a magnetobrambite crystal morphology represented by O"6Fe2 G3 or SrO'6Fe203 are used in cellulose acetate, vinyl acetate-vinyl chloride copolymer, epoxy, acrylic, nitrile butadiene styrene copolymer or It is obtained by adding it to a urethane-based printing vehicle agent together with a solvent and mixing it uniformly to prepare it in advance.

What is important here is the addition of ferrite particles/powder, which determines the magnetic properties of the printed magnetic drum.
．． From 5 to 10 (8 and τ are added as appropriate. Each) 1
Lie 1 - The particle size distribution of the particles/powder must also be selected in accordance with the roughness of the screen printing mesh used. Furthermore, the strong flexure of the printed magnetic material layer 3 and the tram 1 must be taken into account when selecting the vehicle material and solvent for printing, taking into account the environment in which the magnetic drum is used.

The final process is to magnetize the printed drum so that τ, magnetism + AE is applied over the entire circumference of the drum according to the gray code printing pattern. FIG. 6 shows the state of magnetic processing according to the present invention, in which the magnetizing yoke 9 is fixed, the printed drum 1 is rotated at a constant speed, and the coil 10 wound around the magnetizing yoke 9 is rotated at a constant speed. DC current I
The current direction is instantaneously and alternately changed depending on the rotational speed of the drum 1 and the required number of magnetized N poles and S poles, and a magnetic field 12 is generated from the magnetizing yoke tip 11 to perform magnetization processing. It is.

"Function" The feature of the present invention is that the conventional method has 1
Instead of magnetizing each track one by one, all magnetic tracks corresponding to all bits of the Gray code are rotated and magnetized all at once. As a result, the magnetic material layer 3 in the dot part is magnetized, and the surface outside the dot part is made of non-magnetic material, so even if a magnetic field 12 is generated from the magnetizing yoke tip 11, it will not be magnetized and will not be magnetized. It is possible to easily obtain magnetic recording based on the Gray code. This means that the present invention has the advantage of shortening the magnetization process and simplifying the magnetization technique. In addition, as shown in FIG. 11 of the conventional method, the method of performing ira one track at a time has a large effect on the inter-track relative positional accuracy of the magnetizing yoke 19 to the drum 15 and the magnetic recording accuracy of the magnetic drum 13, but the present invention In this case, as long as the yoke is machined to ensure the linearity and etchability of the magnetizing yoke tip 11 in the track width direction as shown in Fig. 6, magnetic recording compatible with the target gray code can be performed on all tracks. Another advantage is that magnetic characteristics are formed on the outer peripheral portion 2 of the magnetic drum with high accuracy and uniformity over the entire circumference.

"Example" Examples of the present invention will be shown below. First, the magnetic material paste is: Printing vehicle agent (ABS medium for screen printing) 1 part Magnetic material (manufactured by Toda Kogyo Co., Ltd. GP-500, Ba-ferrite)
1 part silane cutting agent (Shin-Etsu Chemical (1) KB
N-403> 0.02 to 0.1 part Slow-drying solvent (ethyl acetate) 0, 2 to 0.5 parts of the four substances were mixed and uniformly dispersed using a ball mill to prepare the mixture.

The mesh for curved clean printing is a 150-mesh silk screen, with a drum diameter of 34.33 m/m (development length 108 m/TrL), a magnetic track width of 3.0 m/m corresponding to one gray code bit, and a 360 resolution. A gray code printing pattern was used.

The drum was made of a thermoplastic resin of acrylonitrile butadiene styrene copolymer.

After printing the magnetic material paste on the drum using the above-mentioned silk screen, the printed surface was dried by heating to obtain a coating amount of about 10R9/cm.

For the 6-magnet, a 30-turn copper wire coil is attached to a knife-etched yoke made of pure iron, and a DC pulse current of about 40A is alternately passed through it, so that the magnetized distance between the N and S poles is 1!11150μ7n.
I did it.

FIG. 7 shows chart data obtained by measuring the self-cutting on the drum surface leaking from the magnetic tracks by bringing a Hall element with a magnetically sensitive portion of 70 μm into contact with the magnetic tracks corresponding to the Go and G1 bits in the Gray code. From the chart, the surface magnetic force magnetized to the magnetic material layer is uniformly magnetized with an absolute value of 50 Gauss from the positive peak (N pole) to the negative peak (S pole), and the magnetic drum surface leakage magnetic force on the resin surface is zero. It was determined that.

I. Effects of the Invention From the above, the present invention provides a magnetic rotary encoder absolute type magnetic drum for magnetic recording.
The magnetic properties are uniform, and the magnetoresistive element used as a magnetoelectric transducer facing the magnetic drum has a surface leakage magnetic force strong enough to be magnetized, so that it has high magnetization accuracy and also It can be easily provided during the manufacturing process.

[Brief Description of the Drawings] Fig. 1 is an actual diagram of the present invention, Fig. 2 is a drum shape of the present invention, and Fig. 3 is a printing pattern in which magnetic material paste is printed using a curved screen printing method. shows. Figure 4 shows the output code. Figure 5 shows the printing situation. Figure 6 shows the state of magnetization processing. FIG. 7 shows chart data obtained by measuring the drum surface magnetic force leaking from the magnetic track. Figure 8 shows an example of the use of a magnetic drum for an absolute type rotary encoder. Figure 9 is a characteristic graph of the magnetic field and electric resistance change rate of the magnetoresistive element for magnetoelectric conversion. Figures 10 and 11 are:
A magnetic drum made using conventional manufacturing methods is shown. 1: Magnetic drum 3: Printed/, = magnetic moon layer 5: Silk board 6:! 7: Print pattern 9: Magnetizing yoke 10: Coil 11: Magnetizing yoke tip 12: Magnetic field 14: Wi magnetoresistive element Applicant: Takagaku Seisakusho Co., Ltd. Figure 2 Figure 3 Figure 6 -'g nof1 Figure 8 Isokai (〃us)

Claims (5)

[Claims] (1) A magnetic drum is formed by printing a magnetic material paste, in which a magnetic material is dispersed in a printing vehicle material, on the outer peripheral surface of a cylindrical drum made of a non-magnetic metal material or a thermoplastic resin using a curved screen printing method. Then, a magnetic drum for magnetic recording is obtained by subjecting it to a magnetizing process. (2) As the drum material for the magnetic drum, non-magnetic metal materials such as aluminum and stainless steel, or thermal materials such as acrylanitrile butadiene styrene copolymer, polycarbonate, polystyrene, polyethylene terephthalate, polybutylene terephthalate, and acrylonitrile styrene copolymer are used. The magnetic drum according to claim 1, characterized in that it is made of a plastic resin or a thermoplastic resin in which glass fibers are dispersed. (3) As the magnetic material of the magnetic material paste, the chemical formula BaO.
The magnetic material paste according to claim 1, characterized in that it is ferrite fine particles represented by 6Fe_2O_3 or SrO.6Fe_2O_3. (4) A patent claim characterized in that the magnetic material paste is printed on the outer peripheral surface of a cylindrical drum using a curved screen printing method in a printing pattern based on a gray code, which is one of the numerical encoding methods. The first item in the range of magnetic drums. (5) In item (4) above, the entire magnetic track of the magnetic drum printed with the magnetic material paste, which corresponds to all the bits of the Gray code, is subjected to rotational multi-pole magnetization by one magnetizing yoke. The magnetic drum according to claim 1, characterized in that: