JPS6283620A - Magnetic scale - Google Patents

Abstract

PURPOSE:To obtain a magnetic scale with high S/N and a high reliability by constituting the magnetic scale by the base of the austenite steel of a ferromagnetic material containing over 10% martensite texture produced by a cold working induced transformation and a scale with a nonmagnetic austenite texture produced by a local melting processing. CONSTITUTION:A stainless steel which contains Ni, Cr, Mn, Mo and N and wherein the quantity DELTANi of Ni as mentioned in the accompanying expression is -7-2 is used and martensite texture produced by a cold working induced transformation shall be above 10vol%. When the degree of working is increased, the quantity of martensite transformation is increased to decreased a saturation flux density, which is suitable for a scale. This quasi-austenite steel has a ferromagnetism through a cold working and, when a solution heat treatment is applied thereto after held at about 1,100 deg.C and quickly cooled, completely transformed to an austenite texture to be nonmagnetic. The combination of a ferromagnetic base body 1 and a nonmagnetic scale 2 increases S/N; the magnetic scale has a low cost because its material is a general austenite stainless steel; has a base material with a strength increased by cold working and notches are unnecessary because the scale is made by melting processing, which increases a mechanical strength.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic scale used for measuring displacement amounts, displacement speeds, etc. The present invention relates to a magnetic scale suitable for forming and measuring various displacement quantities thereof.

[Prior art and its odes]

The magnetic scale is made by forming a scale part (7) on the surface of a base material such as a metal material, and forming a regular array of linear or band-shaped magnetically altered parts having different magnetic properties, and placing a magnetic sensor close to and facing the surface of the scale part (7).
By reading the scale with a magnetic sensor, the relative displacement between the base and the magnetic sensor is measured.

The reading sensitivity of the scale increases as the difference in magnetic properties between the altered part and the non-altered part increases.In general, the maximum sensitivity (for example, peak-to-peak It is said that 700 mV) can be obtained.

However, 7? When trying to form an r scale,
Since surface smoothness is required, the void method described above cannot be applied.

In JP-A No. 57-16309, a high-energy beam is irradiated onto the surface of a metal material! - A method is shown in which a scale is created by locally heat-treating and magnetically altering the properties. Although this method is simple, the difference in emotional characteristics between the base material portion (substrate portion) and the heat-treated portion is generally small, and an expensive detection device is required. The disadvantage is that the reliability of detection is low.

As a countermeasure to this, examples have been shown of applying very expensive magnetic materials such as 25% Fe and 75% Nx gold alloys, but these are not only expensive but also have poor strength and wear resistance. In addition to having many restrictions in terms of use, it is difficult to perfect the magnetic properties.

In other words, it has already been mentioned that theoretically the maximum magnetic output can be obtained in the air gap groove, but in other words, the air gap groove means a non-magnetic material, and in short, it is a combination of a ferromagnetic material and a non-magnetic material. shows that it is the best as a magnetic scale. However, in the above publication, Fe, Ni
In the case of alloys, both the base material (base part) and the heat-treated part are ferromagnetic, and the scale is simply formed by the difference in magnetic permeability between them, so it is not necessarily an ideal combination. be.

Also, as shown in Japanese Patent Application Laid-Open No. 58-7517,
N1 and P? by chemical plating on the surface of metal materials. A thin film (0.2 to 0.3 N thick) of the main component is formed as a base, and the thin film of this base is partially heated with electricity or heated with a particle beam such as a laser, and the thin film is electromagnetic. There is a known method in which altered parts are formed at predetermined intervals.

However, if a plated thin film containing N1 and P as the main components is heat-treated to form an altered part, the reading sensitivity of the scale is relatively low, so the S/N is low.
The disadvantage is that the ratio is poor, and in order to increase sensitivity the thin film must be made considerably thicker, which poses an economical problem.

Furthermore, if the surface of the magnetic scale is required to have wear resistance, it is necessary to apply a wear coating such as chrome plating to the surface, which has the drawback of complicating the processing process.

Furthermore, there is a risk that damage such as cracks may occur in the heat-treated plated thin film. 'The present invention solves all of the problems in the conventional techniques and provides a magnetic scale with a high S/N ratio, excellent workability and economic efficiency, and also high mechanical strength including wear resistance. It is.

[Means for solving problems]

The magnetic scale of the present invention has a base made of ferromagnetic austenite (N4) containing 10% or more of martensitic structure due to cold work-induced transformation, and the scale portion has a non-magnetic austenitic structure due to local melting treatment.

[Action and effect]

Some austenitic steels undergo solution heat treatment to form a completely austenitic structure and exhibit non-magnetism, but subsequent cold working causes strain-induced transformation to form a martensitic structure and become ferromagnetic. . This type of copper is called a metastable austenitic steel, which is made ferromagnetic through cold working and then subjected to solution heat treatment again to become a completely austenitic structure and become non-magnetic.

In the present invention, this metastable austenitic steel, which has been made ferromagnetic by cold working, is used as the base of the V'i scale, and a part of it is made nonmagnetic by melting treatment to form the scale part. be.

According to the invention, the 0 base is ferromagnetic and the scale part is non-magnetic, that is, an ideal combination of ferromagnetism and non-magnetism, S.
/N ratio is high. ■Low cost because common austenitic stainless steel can be used as the material. ■Cold working to make it ferromagnetic contributes to improving the strength of the base. ■
Since the scale part is formed by processing each part, even though the scale part is non-magnetic, there is no decrease in strength like providing a notch, making it suitable for materials that require mechanical strength such as piston rods. becomes. - When forming the scale part, the temperature can be raised until the material melts in the bath, so temperature control is easy and productivity is good.

[Specific explanation]

In the present invention, the austenitic steel used as the base steel has a completely austenitic structure after heavy-duty heat treatment, and is a metastable austenite steel in which a martensitic structure is generated by deformation-induced transformation by cold working. Specifically, depending on N1 and Cr, υ and Mn
, Stainless steel containing Mo5N is preferably one in which ΔN1, which is determined by the following formula, is greater than -7 and less than 2.

ΔN'1=Ni-4(Cr+1.5M0-20)2/1
゜-0,5Mn-a+(C+N)+IF) (However, weight %) If ΔN1 is less than 17, the austenite structure becomes unstable and the scale part becomes unstable due to slight deformation during use or temperature drop in cold regions. It is inconvenient to use as a magnetic scale because it changes again. On the other hand, in the case of 2 or more, the stability Jy of the austenite structure is high, and the deformation transformation practically does not occur, so that it cannot be used in the present invention.

The reason why the martensitic structure due to cold working and transformation in the base steel is set to 10% (volume %) or more is because if it is less than 10%, ferromagnetization is insufficient and the S/N ratio for reading the scale is insufficient. It is. There is no need to limit the upper limit from a magnetic point of view, but if it exceeds 40%, the material q becomes brittle and cracks are likely to occur during processing, and it is also undesirable for use, so in practice it should be lower than this. It is desirable to do so.

Cold processing is not limited to any type of processing, such as cold rolling, cold drawing, cold extrusion, hot pressing, etc., but
(about 0 to 100 toughness f), straightening is preferable because the processing load is smaller. Generally, as the degree of processing increases, the amount of martensite variation B increases and the saturation magnetic strength decreases, making it suitable for use as a magnetic scale.

For the melting process to form the scale, laser beams, electron beams, or other high-energy beams are irradiated to predetermined positions on the base surface due to positional accuracy, processing time, and prevention of heat-affected zones. preferable.

In this melting process, it is sufficient to melt only the surface layer. In a magnetic scale, since the volume of the base portion is overwhelmingly larger than the scale portion, that is, the melted portion, the melted portion rapidly solidifies and cools and becomes non-magnetic. In addition, this melting process
Since all that is required is melting, strict temperature control is not required, and whether or not it has melted can be determined visually, making the overall processing operation extremely easy.

In addition, the warming heat treatment of Austenai) M is 1000
By heating and holding at a temperature of about 1100° C. and then rapidly cooling, the processed structure is recrystallized, and various precipitates are dissolved in solid solution to adjust the strength, rewardability, magnetic properties, etc.

In addition, deformation-induced transformation is a phenomenon in which a part of the austenite transforms into martensite when cold plastic deformation is applied to the austenite structure at room temperature after solution treatment.

〔Example〕

Chopsticks 1 A hot rolled steel bar having the composition shown in Table 1 is heated to 1050°C.
A piston rod with a diameter of 20 cm was immediately obtained by subjecting it to a warming heat treatment at a temperature of 200 m, followed by cold drawing and straightening, and further surface polishing. Note that the correction was performed by a repeated bending correction method using a 20-rule.

Next, in the direction of the outer peripheral axis of this piston rond, ring band-shaped areas of a constant width at constant intervals (interval 2 eyebrow 1, i7i 1
WIl) was set, and this region was heated to a temperature higher than the melting point of the material using a laser to form a nonmagnetic material.

At this time, the heat treatment conditions were as follows: a carbon dioxide laser with a spot diameter of one head and an output of one laser was used, the processing speed was O-5 m/min, and the melting depth was 0.1 to 0.2 toughness.

The ratio was measured by placing a magnetic sensor close to the surface of the piston rod equipped with the magnetic scale constructed as described above.

FIG. 19 is a partial cross-sectional view of a piston rod provided with an inventive magnetic scale. (1) is a base, <2) is a non-magnetic material, and (3) is a magnetic sensor.

Table 2 shows the characteristics and measurement results of these piston rods.

Table 2 [- As is clear from Table 2, cold drawing with an area reduction of 5X or more significantly increases the tensile strength, making it suitable as a piston rod, and with a magnetic permeability of about 20 or more. It is a magnetic material. In addition, when measuring the area reduction rate of 20.96 or more with a magnetic sensor, it was found that the distance from peak to peak was 600 m.
It was possible to obtain an output signal of V or more. This bond is comparable to that of the above-mentioned air-gap type, and is more than seven times that of the conventional plated thin film type.

This means that the combination of ferromagnetic material and non-magnetic material is the most effective for the construction of the magnetic scale, and Japanese Patent Laid-Open No. 58-7517
This shows that the combination of ferromagnetic materials is superior to the combination of ferromagnetic materials disclosed in JP-A-57-16:d09.

Further, from Table 2, when cold straightening is combined, ferromagnetization further progresses, which has the effect of reducing the output difference between reciprocations of the sensor, that is, hysteresis, and is more suitable for magnetic scales.

Furthermore, cold straightening can apply plastic deformation without changing the dimensions of the material, and the processing load is relatively small, so it has the advantage that it can be applied to materials with fairly large diameters.

Please note that in the non-example, heat treatment was performed using a carbon dioxide laser, but the point is to heat a predetermined area to a temperature higher than the melting point of the material.
Local heating is a requirement, and it goes without saying that the same effect can be obtained by other particle beams such as electron beams or electrical heating.

Furthermore, in the non-practical example, an example was shown in which a bar was pulled out, straightened, and scales were given on the surface in a band shape on the circumference, but the same is true for plates and pipes other than bar-shaped materials, but the shape of each material is different. It goes without saying that the same effect can be obtained by selecting rolling or other processing methods depending on the situation. -! , the scale shape can be any shape.

Next, a specific example of a displacement detecting device for a piston rod having a magnetic scale (v) obtained by applying the invention is shown in FIGS. 2 and 3, and the effects achieved by the invention will be explained. explain.

As shown in Figure 2, the hydraulic piston cylinder (21)
is a cylinder (22) and a piston inserted into it (
23) and a constant pinuton rod (11) directly connected to this. This piston rod α1) is formed in the same manner as the embodiment shown in FIG.
2), the pitch is P, the width of the non-altered part α is Q, (Q.

m-). Two magnetic cessors (2A) and (2B) are arranged on the outer circumferential surface of the piston rod α° C. with a constant gap ζ and shifted by δ in the axial direction. The reason for arranging the two sensors in a staggered manner in this manner is to detect the direction of displacement of the piston rod α, and δ is determined to satisfy the following equation (1).

Here, n-0, 1, 2,... Also, the signals SA, SB output from the magnetic sensors (2A) (2B)
is a sinusoidal waveform as shown in Fig. 4(a), and
These signals are processed by the waveform shaping circuit (c) as shown in Figure 3.
has been entered. Here, the waveform-shaped signal SA,
The SB has a rectangular waveform as shown in Fig. 4(b), one of which is directly input to the displacement direction discrimination circuit (e), and the other to the pulse generation circuit (to), where the SB has a rectangular waveform as shown in Fig. 4(c).
) is generated. This pulse signal SAP is converted into a unipolar signal SAP in the displacement direction discrimination circuit (to), and is input to the pulse counting circuit @ together with the displacement direction discrimination signal. The pulse counting circuit S is configured to add or subtract the pulse signal S'AP based on the displacement direction discrimination signal and output the displacement amount X of the piston rod circle.

In the displacement detection device configured in this way, the signals SA and SB output from the magnetic sensors (2A) (2B)
The center of the amplitude of the blade is normally offset by ε from the blade level, as shown in FIG. 4(a). Therefore, the signal SA whose waveform is shaped in the waveform shaping circuit (c) with reference to the zero level has a pitch p as shown in FIG.
are the same, but the valley length q of the rectangular wave with respect to this changes depending on ε. Now, assuming that the amplitude of the signal SA is a, the sill ratio can be expressed by the following equation (21).

In other words, if a is constant, the larger ε is, the more irregular the pulse period of the pulse signal S'AP becomes, as shown in FIG. 4(C). As a result, the detection resolution of the displacement amount X, that is, the detection accuracy deteriorates.

However, according to the non-example, the amplitude a is about 7 times or more compared to the conventional magnetic scale, so (1/p!,
becomes. As a result, the q/I) ratio is significantly improved and the detection accuracy is improved.

[Brief explanation of drawings]

Fig. 1 is a side view showing a partial cross-section of a t-piston rod equipped with a magnetic scale according to the present invention, and Figs. 2 to 4 are explanatory diagrams showing the structure and function of an example of a displacement detecting device having the same rod. In the figure, 1: base, 2: non-magnetic material, 3: magnetic sensor. Applicant: Sumitomo Metal Industries, Ltd. No. 1m No. 2 Fig. 3 Fig. 3-1-1-- Fig. 4 (G)

Claims (1)

[Claims] (1) A magnetic material characterized in that the base is a ferromagnetic austenitic steel containing 10% or more of martensitic structure due to cold work-induced transformation, and the scale portion is a non-magnetic austenitic structure due to local melting treatment. scale.