JPH09172770A - Eddy current decelerator rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eddy current decelerator rotor which exhibits both a high braking torque and durability. SOLUTION: The rotor cylindrical part 3 of a rotor is made of steel whose chemical composition is 0.75-12wt.% of Cr and 0.3-2.5wt.% of Mo+(W/2) containing at least one among Mo and W. A surface treatment layer made of copper or copper alloy is applied to the surface of the rotor cylindrical part 3 on the side facing a permanent magnet 5. Or, the rotor cylindrical part 3 of the rotor is made of steel whose chemical composition is 0.04-0.3wt.% of C, not more than 1wt.% of Si, 0.3-1wt.% of Mn, not more than 0.03wt.% of P, not more than 0.03wt.% of S, not more than 0.5wt.% of Ni, 0.75-12wt.% of Cr, 0.3-2.5wt.% of Mo+(W/2) containing at least one among Mo and W, not more than 0.1wt.% of Nb, not more than 0.3wt.% of V and remainders of Fe and unavoidable impurities. A surface treatment layer made of copper or copper alloy is applied to the surface of the rotor cylindrical part on the side facing the permanent magnet 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for an eddy current type speed reducer used in large automobiles such as trucks and buses.

[0002]

2. Description of the Related Art In addition to a foot brake, which is a main brake, and an exhaust brake, which is an auxiliary brake, a braking device for a large-sized automobile performs stable deceleration when descending a long hill and prevents burnout of the foot brake. An eddy current type speed reducer is used for this purpose.

FIG. 1 is a vertical sectional view showing an example of an eddy current type speed reducer using a permanent magnet (Japanese Patent Laid-Open No. 1-2340).
No. 43, No. 1-234045, No. 1
-298948). In this device, the rotor 1 is integrally joined to the rotor arm 2 and the rotor cylindrical portion 3. The rotor 1 attached to one end of the rotating shaft 10 has a rotor arm 2 and a rotor cylindrical portion 3 which are members of the rotor as the rotating shaft 10 rotates.
It rotates together with the above. A magnet support ring 6 around the permanent magnet 5 is screwed to a piston rod 8 and is slidably reciprocated along a plurality of guide rods 11 by driving a cylinder 9. By operating the cylinder 9 to move the magnet support ring 6 forward and backward, the magnetic pole surface of the permanent magnet 5 becomes
The rotor cylinder portion 3 is reciprocated from a position magnetically opposed to the rotor cylindrical portion 3 via a pole piece 7 (braking on state) to a magnetically deviating position (braking off state).

At a position where the magnetic pole surface of the permanent magnet is magnetically entirely opposed to the rotor (in a braking-on state), the rotor cylindrical portion 3 moves across the magnetic flux generated from the permanent magnet to cause an eddy current on the surface of the rotor cylindrical portion. Flows. A braking torque is generated by the interaction between the eddy current and the magnetic flux. The cylindrical portion is heated by Joule heat accompanying the generation of eddy current when the braking is turned on, and is air-cooled by the cooling fin 4 when the braking is turned off. For this reason, the rotor cylindrical portion 3 is subjected to a remarkable thermal cycle due to repeated on / off control of braking. Hereinafter, the material of the rotor cylindrical portion 3 may be referred to as “rotor material”.

In recent years, the number of large-sized automobiles equipped with an eddy current type speed reducer has been increasing. In particular, the reduction gears are being installed on trucks and trailers, which have a heavier load than before. For this reason, the required braking performance for the eddy current type speed reducer tends to become more sophisticated, and depending on the vehicle model, a braking torque of 70 to 100 kg · m may be required.

There are the following three methods for increasing the braking force of the eddy current type speed reducer.

One is a method of increasing the number of permanent magnets or increasing the size. In this case, the weight of the device increases and the size of the device itself increases, which is disadvantageous as a device mounted on a vehicle in which the loading space and total weight are limited. Further, the cost required for the permanent magnet per device increases, which is also disadvantageous in terms of cost.

The second method is to reduce the electric resistance of the rotor material as much as possible. Conventionally, cast steel has been used as a rotor material of an eddy current type speed reducer, but in recent years, a rotor material made of steel containing Ni, Mo, Nb, V, and B that has been subjected to quenching and tempering after hot forging and its production. A method has been proposed (Japanese Patent Application No. 6-204313).
The main purpose of the proposal is to improve the braking performance of the eddy current type speed reducer by reducing the electrical resistance of the rotor material, but also to improve the static high temperature strength and to improve the heat generated by repeated on / off control. It also considers suppressing deformation. According to the proposal, an element such as Cr, which has an effect of improving high temperature strength but greatly increases electric resistance, is excluded. The proposed example shows that a braking torque of 38-44 kg.m is obtained.

However, even if an attempt is made to obtain a higher braking torque, there is a limit in reducing the electric resistance only for the rotor material. When the braking torque is high, durability against thermal deformation is particularly important, but addition of alloying elements is unavoidable in order to improve durability, and electrical resistance cannot be reduced by adding alloying elements. Therefore, it is impossible to significantly improve the braking torque by improving only the rotor material.

The third method is to provide a metal layer made of a material having a small electric resistance on the surface of the rotor facing the magnet (Japanese Patent Laid-Open Nos. 63-274359 and 64-3).
No. 0450). In these inventions, a metal layer made of a material having a low electric resistance is provided on the rotor surface to increase the eddy current generated in the rotor and improve the braking torque. However, no reference is made to the rotor material itself. In these inventions, as the material of the metal layer,
Copper, copper alloys or aluminum are mentioned. In the above-mentioned Japanese Patent Laid-Open No. 63-274359, an example is presented in which the braking torque is increased from about 0.9 kg · m to about 2.2 kg · m by providing the rotor with a copper layer having a thickness of 1 mm. ing.

However, it is not necessary to take measures against thermal deformation of the rotor material in a range where the braking torque is small, but when the braking torque becomes large, eddy currents concentrate on the surface-treated layer having a small electric resistance, and the surface-treated layer and its The temperature of the rotor material in the vicinity becomes extremely high. Therefore, when the braking torque is large and the maximum temperature of the rotor exceeds 600 ° C., the thermal deformation of the rotor becomes large and the durability deteriorates. Further, since the braking torque is increased, the fracture toughness is also required to be excellent.

[0012]

The temperature rise in the case where the surface treatment layer having a small electric resistance is provided is larger than that in the case where only the rotor material is used (when there is no surface treatment layer) because a high density eddy current flows. . Therefore, the problem of thermal deformation in the case of providing the surface treatment layer is the above-mentioned high-strength rotor material (Japanese Patent Application No.
(No. 204313 publication) cannot be solved by the improvement.

An object of the present invention is to provide a rotor for an eddy current type speed reducer which has a high braking torque by applying a surface treatment layer, has less thermal deformation, and at the same time has excellent fracture toughness and excellent durability. To aim.

[0014]

[Means for Solving the Problems] The inventors conducted an electromagnetic field analysis by the finite element method for the eddy current type speed reducer of FIG. 1 (analysis method: Masato Enokizono, Naofumi Sato, Too Sakamoto, Kenji Araki). , Proc. Of the 3rd Electromagnetic Force Dynamics Symposium (The Japan Society of Mechanical Engineers, The Institute of Electrical Engineers of Japan: 1991) p.480-485
), The effect of the electric resistance of the material of the rotor cylindrical portion on the braking torque with and without the surface treatment layer made of copper having a low electric resistance was clarified.

FIG. 2 is a drawing showing the influence of the rotational speed of the rotor on the braking torque when the thickness of the copper layer on the surface is changed, which is obtained by electromagnetic field analysis.

FIG. 3 is a diagram showing the relationship between the electric resistance of the rotor material and the maximum braking torque with and without the surface treatment layer made of copper, which is obtained by electromagnetic field analysis.

These figures are obtained as a result of the electromagnetic field analysis by the above finite element method.

The analysis was performed under the following conditions.

Common: Inner diameter of rotor cylinder is 380 m
m, wall thickness 20 mm, axial length 80 mm, copper electrical resistance 1.67 μΩcm, copper relative permeability 1 FIG. 2: Rotor material electrical resistance 20 μΩcm, rotor material relative permeability 1000 FIG. 3: Rotor material ratio Permeability 1000 As shown in these figures, the braking torque when the surface treatment layer having a small electric resistance is provided is significantly improved as compared with the case where the surface treatment layer is not provided. Further, as shown in FIG. 2, when the thickness of the surface treatment layer is changed between 0.1 and 0.5 mm, the relationship between the rotation speed and the braking torque changes, but the maximum value of the braking torque does not change. Few. Therefore, the thickness of the surface treatment layer may be set so that a desired braking torque curve can be obtained. That is, the thickness of the surface treatment layer may be determined depending on at which rotation speed the braking torque is maximized.

As shown in FIG. 3, the effect of the electric resistance of the rotor material on the braking torque is smaller than the improvement effect of the surface treatment layer. Further, when the surface treatment layer is provided, the braking torque tends to increase a little as the electric resistance of the rotor material increases, which is the reverse of the case where the surface treatment layer is not provided. This is because when the surface treatment layer is provided, the eddy current is limited to the surface treatment layer, and more eddy current flows in the surface treatment layer than when the electric resistance of the rotor material is small.

Therefore, as the rotor material, it is not necessary to select a material that lowers the electromagnetic characteristics, especially the electric resistance, unlike the conventional rotor, and the thermal deformation of the entire rotor is suppressed, so that the rotor material has excellent high temperature strength. Just select the material.

Further, the inventors conducted a durability test using a rotor provided with a surface treatment layer having a low electric resistance by using various materials for the rotor cylindrical portion, and investigated thermal deformation. As a result, it was confirmed that the amount of thermal deformation of the rotor when used under the condition where the maximum temperature exceeds 600 ° C. is correlated with the creep strength of the rotor material near the maximum operating temperature.

That is, in order to suppress thermal deformation of the entire rotor, a material having a high creep strength may be used for the cylindrical portion of the rotor. It is even better if the material satisfies the conditions and is excellent in high temperature static tensile strength. Since the eddy current flows only in the surface-treated layer having a low electric resistance, the rotor material can be given priority only to the creep strength in order to suppress thermal deformation. Therefore, in the rotor material,
Conventionally, elements such as Cr, the content of which has been suppressed for the reason of deteriorating electromagnetic characteristics (especially electric resistance), can be positively utilized.

Here, the gist of the present invention is a rotor having a rotor cylindrical portion made of the following materials, which is provided with the following surface treatment layer.

(1) An eddy current type speed reducer characterized in that the rotor cylindrical portion is steel having the following chemical composition and has a surface treatment layer made of copper or copper alloy on the surface side facing the permanent magnet. Rotor (referred to as [Invention 1]).

In weight%, Cr: 0.75 to 12% and one or two of Mo and W are Mo (%) + (W
(%) / 2) steel containing 0.3 to 2.5%.

(2) The eddy current type speed reducer characterized in that the rotor cylindrical portion is steel having the following chemical composition, and has a surface treatment layer made of copper or copper alloy on the surface side facing the permanent magnet. Rotor (referred to as [Invention 2]).

% By weight, C: 0.04 to 0.3%,
Si: 1% or less, Mn: 0.3 to 1%, P: 0.03%
Below, S: 0.03% or less, Ni: 0.5% or less, C
r: 0.75 to 12%, one or two kinds of Mo and W in Mo (%) + (W (%) / 2) 0.3 to 2.5
%, Nb: 0.1% or less, V: 0.3% or less, B: 0.
006% or less and solAl: 0.005-0.1%
Containing the balance iron and inevitable impurities.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why the above rotor is used in the present invention will be described below.

1. Surface Treatment Layer The surface treatment layer is provided on the surface of the rotor cylindrical portion facing the permanent magnet, that is, on the inner surface of the rotor cylindrical portion. The material of the surface treatment layer is preferably a material having low electric resistance.

As a typical example thereof, JP-A-63-2743
As exemplified in Japanese Patent Publication No. 59, there are copper or copper alloy or aluminum. Among them, aluminum has a low melting point, so it can be used when the braking torque is small and the maximum temperature of the rotor is low, but the braking torque is large,
It cannot be used when the maximum temperature exceeds 600 ° C. Therefore, in the present invention, the material of the surface treatment layer having a low electric resistance is limited to copper and copper alloy having a relatively high melting point and high temperature strength.

Copper having a purity of ordinary tough pitch copper, deoxidized copper or the like may be used. Even in the case of phosphorous deoxidized copper, the usual P concentration may be 0.02% or less. Usually, as will be described later, since the surface treatment layer is provided by plating, the impurities are relatively low. A copper alloy having a low electric resistance, for example, chromium copper containing 0.5 to 1.2% of Cr may be used. However, when a copper alloy is used unlike copper, it is unavoidable that the electric resistance increases, so that it is limited to the case where strength at high temperature is particularly required.

The thickness of the surface treatment layer is 0.05 to 1.00.
It is desirable to be in the range of mm.

This is because if it is less than 0.05 mm, a sufficient eddy current does not flow, and if it exceeds 1.00 mm, the rotation speed at which the maximum braking torque is generated decreases, and a high braking torque is generated at the rotation speed of the object to be braked. This is because copper and copper alloys are non-magnetic and the amount of magnetic flux entering the rotor cylindrical portion is reduced and the maximum braking torque is also reduced. It is desirable that the thickness be determined within the above range in consideration of the rotation speed that is frequently used according to the type of the truck mounted based on FIG.

The surface treatment layer is usually applied by plating. The plating treatment may be performed by a usual method. The cylinder having the surface-treated layer can also be manufactured by a steel tube having copper or copper alloy welded or internally clad, and this method is particularly suitable for mass production.

2. Material of Rotor Cylindrical Section 1) Component Composition of Rotor Cylindrical Section Material The reason why the chemical composition of the material forming the rotor cylindrical section provided with the surface treatment layer is limited will be described. Less than,
“%” Means “% by weight”.

Cr: 0.75 to 12% Cr is the most important element that determines the heat resistance of steel such as high temperature strength, creep strength and oxidation resistance. Cr is 0.7
If it is less than 5%, sufficient high temperature strength and creep strength cannot be obtained. Moreover, even if it exceeds 12%, the effect of improving strength is saturated,
The amount of Cr is 0.75 because it is economically disadvantageous, workability deteriorates, fracture toughness decreases, and it becomes difficult to form a surface treatment layer by plating.
12%. Conventionally, it was not used for reducing the electric resistance, but in the present invention, it can be used because the above-mentioned surface treatment layer is provided. Rather, a high-density eddy current is generated in the surface-treated layer, which causes large thermal deformation, and therefore, it is actively used to prevent it.

Mo (%) + (W (%) / 2): 0.3 to 2.5% Mo has the effect of improving the toughness, high temperature strength and creep strength of steel. Further, W has an action of improving the high temperature strength and the creep strength of steel like Mo, but M
To obtain the same effect as o, the amount of Mo is required to be twice the amount. In the present invention, either or both of Mo and W are added in order to secure high temperature strength and creep strength of the rotor. If the amount of Mo (%) + (W (%) / 2) is less than 0.3%, the creep strength required for the rotor cannot be secured. On the other hand, if it exceeds 2.5%, the effect of improving the high temperature strength and creep strength is saturated, which is economically disadvantageous and the fracture toughness decreases, so Mo (%) + (W (%)
The amount of / 2) is 0.3 to 2.5%.

In the present invention, Cr, Mo and W must be contained in the above amounts. This is because if the above amount is not contained, it is not possible to secure a 1000-hour creep strength of 5 kgf / mm ² or more at 650 ° C., which will be described later. [Invention 1] is a rotor material having C within the above range.
As long as r, Mo and W are contained, other chemical components and their contents are not limited. However, it is limited to those that fall into the category of steel.

The rotor cylinder material of [Invention 2] has a chemical composition specified as a desirable embodiment of the above [Invention 1]. This contains the following chemical components in addition to the above-mentioned Cr, Mo and W in the following range.

C: 0.04 to 0.3% C is the most basic element that determines the strength, but if the content is less than 0.04%, the creep strength level required for the rotor material is secured. I can't. On the other hand, if the content exceeds 0.3%, the effect of improving the creep strength is saturated, and there are disadvantages such as a decrease in weldability and a decrease in fracture toughness, so the content is made 0.04 to 0.3%. .

Si: 1% or less Si acts as a deoxidizing agent for steel and also has an effect of improving hardenability. Although it is used as a deoxidizing agent for steel, it may not be contained in steel as a constituent element. When added for improving the hardenability, Si is not preferably contained in a large amount from the viewpoint of the toughness of the grain boundary and the matrix phase, and if it exceeds 1%, the fracture toughness is lowered. Therefore, the Si content is 1% or less.

Mn: 0.3 to 1% Mn acts as a deoxidizing agent for steel and a fixing agent for sulfur, and also has an effect of improving hardenability and strength by solid solution strengthening. If the Mn content is less than 0.3%, the effect of increasing the strength cannot be sufficiently obtained. However, when the Mn content increases and exceeds 1%, the strength improving effect is saturated. Therefore, the Mn content is 0.3 to 1%.

P: 0.03% or less P is an element effective in increasing the strength of steel by solid solution strengthening, but if its content exceeds 0.03%, hot forgeability deteriorates. Therefore, the upper limit of P is set to 0.03%. P may be substantially zero.

S: 0.03% or less S forms sulfides such as MnS to deteriorate the fracture toughness and fatigue properties, and the electrical resistance increases with an increase in the S content. 0.03% or less.
The smaller the S, the better.

Ni: 0.5% or less Ni need not be added positively. Ni has the effect of increasing the strength of steel by quenching and solid solution strengthening, but if the content thereof exceeds 0.5%, the effect of improving strength is saturated. Further, Ni has almost no effect of improving creep strength.

Therefore, the Ni content is 0.5% or less.

Nb: 0.1% or less Nb may not be added. However, Nb has an effect of improving the high temperature strength and the creep strength in addition to the effect of refining the crystal grains of steel, so Nb is added as necessary for adjusting the creep strength. When adding it, 0.
Desirably, it is not less than 01%. Below 0.01%,
This is because no clear effect can be obtained. But 0.1%
If it is contained in excess of 0.1%, the toughness will be reduced.
% Or less.

V: 0.3% or less V may not be added. However, V has the effect of improving the high temperature strength and creep strength of steel by the precipitation strengthening of vanadium carbide, so V is added as necessary to adjust the creep strength. When adding, 0.
It is preferably set to 02% or more. Below 0.02%,
This is because a clear increase in creep strength cannot be obtained. However, if the content exceeds 0.3%, the effect of improving the creep strength is saturated and the toughness decreases, so that
3% or less.

B: 0.006% or less B may not be added. However, B has an effect of ensuring high temperature strength and creep strength by improving the hardenability with a very small amount and dispersing and stabilizing carbides.
Add as needed. If added, 0.0005
% Is desirable. This is because if it is less than 0.0005%, a clear effect cannot be obtained. However, 0.006
%, The effect of improving the creep strength is saturated and the toughness is lowered, so the content is made 0.006% or less.

SolAl: 0.005 to 0.1% N increases the creep strength because N in a solid solution state precipitates on dislocations and hinders the movement of dislocations.
In the present invention, considering the toughness, Al is added and N is fixed as AlN, so such an effect of improving creep strength by N cannot be obtained. Therefore, N is usually contained in the range of 0.001 to 0.02%, and Al is the amount necessary to fix the N as AlN, that is, s.
It is 0.005-0.1% as olAl. The amounts of N and solAl are in the range contained in ordinary electric furnace steel and converter steel.

The balance other than the above components is Fe and inevitable impurities.

2) Creep Strength of Rotor Material In the present invention, the improvement of the braking torque is ensured by the surface treatment layer having a small electric resistance, and the thermal deformation of the entire rotor is suppressed by the creep strength of the rotor material itself. Therefore, it is necessary for the rotor material to have high creep strength near the maximum operating temperature of the eddy current type speed reducer of the present invention. The reason why the 1000 hour creep strength of the rotor material at 650 ° C. is 5 kgf / mm ² or more is 1000
When the time creep strength is less than 5 kgf / mm ² ,
Thermal deformation increases with repeated braking on / off,
This is because durability cannot be ensured.

The steel having the above-mentioned composition range has the above-mentioned creep strength even after being subjected to usual hot rolling or hot forging. However, the following heat treatments 1 to 3 may be further performed.

Quenching and tempering Normalizing (normalizing) or normalizing / tempering Annealing (annealing) or annealing / tempering

[0056]

EXAMPLES Next, the effects of the present invention will be described more specifically by way of examples.

Table 1 is a list showing the chemical composition of the rotor material used for the implementation. The invention examples 1 to 11 are all
It is included in [Invention 2] which is a preferable embodiment of [Invention 1]. Comparative Examples 1-5 and Conventional Examples 1-3
Both are chemical compositions outside the scope of the present invention. Steel having the chemical composition shown in the same table was melted, heated to 1250 ° C. and hot forged to a final thickness of 40 mm, and then the following heat treatment was performed to obtain a test material.

Conventional Examples 1 to 3: Quenching and tempering (900 ° C
Inventive Examples 6 to 8 and Comparative Examples 4 and 5: Annealing / tempering (1000 ° C. × 15 min furnace cooling + 700 ° C. × 30 m)
in cooling) Other examples: Annealing / tempering (950 ℃ × 15m)
In furnace cooling + 700 ° C. × 30 min cooling) Here, the conventional examples 1 to 3 are the same as the steel of the invention of Japanese Patent Application No. 6-204313. These conventional examples 1 to 3
Is also a comparative material to the rotor material that constitutes the rotor of the present invention.

[0059]

[Table 1]

Table 2 shows the electric resistance ρ at room temperature, the fracture toughness value, the yield stress (0.2% proof stress) at 650 ° C., the tensile strength and the creep rupture test at 650 ° C. for each of the steels in Table 1. The measured creep strength is 1000 hr. As shown in the table, the rotor materials of Examples 1 to 11 of the present invention included in [Invention 2], which is a preferred embodiment of [Invention 1], are lower in static high temperature strength than conventional examples. However, all the creep strengths are superior to the conventional example. Further, the fracture toughness values of the rotor materials of Examples 1 to 11 of the present invention are equal to or higher than those of conventional materials, and are excellent values of 200 kgf / mm ^1.5 or more.

[0061]

[Table 2]

Comparative Examples 1 to 3 are Mo and W (that is,
Since the content of Mo + (W / 2)) or Cr is small,
Low high temperature strength and creep strength. Further, Comparative Example 4 contains Cr in a larger amount and Comparative Example 5 contains Mo + (W / 2) in a larger amount than the composition range of the rotor material of the present invention, but the high temperature strength and creep strength are higher than those of the present invention example. Not necessarily improved. That is, excessive Cr or Mo +
The inclusion of (W / 2) does not improve the creep strength, but rather lowers the fracture toughness value.

Next, the eddy current type speed reducer rotor shown in FIG. 1 was produced using each of the test materials shown in Table 1. An eddy current type speed reducer to which this was applied was installed in the middle of the propeller shaft at the rear of the transmission of a heavy-duty truck to measure braking torque and to carry out repeated braking tests to investigate durability. The eddy current type speed reducer used for this measurement was for a 10-ton vehicle, and the inner diameter of the rotor cylindrical portion was about 380 mm, the wall thickness was about 20 mm, and the axial length was about 80 mm. A surface treatment layer made of copper was provided on the inner surface of the rotor cylinder by plating. The plating treatment is carried out in a copper cyanide bath (main plating bath composition: copper cyanide 60 g / l, potassium cyanide 115 g / l), the bath temperature is 55 ° C., the pH is 10.2 and the current density is 1.5 A / dm. ² Thickness of plating layer is 0.2
mm. Further, for comparison, in Conventional Examples 1 to 3, the braking torque was measured even under the condition that the surface treatment layer was not provided.

In measuring the braking torque, first, the rotational speed of the propeller shaft (the shaft to which 10 in FIG. 1 is connected) is gradually increased until the rotational speed is 1000 rp.
The braking torque was measured at m and 2000 rpm. Further, in the repeated braking test, the rotational speed of the propeller shaft was kept constant at 2000 rpm, and the rotor was repeatedly subjected to braking and non-braking to repeatedly change the temperature.
The braking on time was 120 seconds and the braking off time was 180 seconds. The maximum temperature of the inner surface of the rotor at this time was about 600 ° C. when the surface treatment layer was not provided, while it reached nearly 700 ° C. when the surface treatment layer was provided.

The braking and non-braking were repeated 1000 cycles, and the thermal deformation amount of the rotor cylindrical portion after the test was measured. When measuring the amount of thermal deformation, the inner diameter of the rotor cylindrical portion was measured at the central portion in the axial direction, and the amount of enlargement of the inner diameter (average value at eight circumferential positions) was taken as the amount of thermal deformation.

Table 3 shows the above test results. Conventional example 1
Regarding No. 3, comparing the case where the surface treatment layer made of copper is provided and the case where it is not provided, the braking torque is larger when the surface treatment layer is provided, but the amount of thermal deformation of the rotor is also larger and durability is improved. From the point of view, the conventional example is inappropriate.

On the other hand, in the example of the present invention, the braking torque is larger than that of the conventional example having no surface treatment layer. Further, comparing the heat deformation amounts of the conventional example and the present invention example, the heat deformation amount of the present invention example is smaller, and particularly in the present invention examples 1 to 10, as shown in Table 2, the toughness of the rotor material itself is high. Therefore, it can be seen that the durability is excellent.

Further, in the case of Comparative Examples 1 to 3, the amount of thermal deformation is much larger than that of the examples of the present invention.

[0069]

[Table 3]

[0070]

According to the present invention, the braking torque can be improved as compared with the conventional rotor for an eddy current type speed reducer, the thermal deformation during repeated use can be suppressed, and at the same time, the fracture toughness value is high, so that the durability is improved. improves. This rotor is industrially inexpensive and can be mass-produced, and has an extremely useful effect industrially.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of an eddy current type speed reducer using a permanent magnet.

FIG. 2 is a drawing showing the influence of the rotational speed of the rotor on the braking torque when the thickness of the copper layer on the surface is changed, which is obtained by electromagnetic field analysis.

FIG. 3 is a drawing showing the relationship between the electric resistance of the rotor material and the maximum braking torque with and without the surface treatment layer made of copper, which is obtained by electromagnetic field analysis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Rotor arm, 3 ... Rotor cylindrical part, 4 ... Cooling fin, 5 ... Permanent magnet, 6 ... Magnet support ring, 7 ... Pole piece, 8 ... Piston rod, 9 ... Cylinder, 10 ... Rotation axis, 11 ... Guide rod

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akiyoshi Ishida 5-1-1109 Shimaya, Konohana-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. Kansai Works Steel Works (72) Inventor Shozo Suehiro Osaka Prefecture Sumitomo Metal Industries, Ltd. 4-53-3 Kitahama, Chuo-ku, Osaka

Claims (2)

[Claims] 1. An eddy current type speed reducer characterized in that the rotor cylindrical portion is made of steel having the following chemical composition, and has a surface treatment layer made of copper or copper alloy on the surface side facing the permanent magnet. rotor. Cr: 0.75 to 12% and Mo and W in wt%
Steel containing 0.3 to 2.5% of Mo (%) + (W (%) / 2). 2. An eddy current type speed reducer characterized in that the rotor cylindrical portion is steel having the following chemical composition and has a surface treatment layer made of copper or copper alloy on the surface side facing the permanent magnet. rotor. % By weight, C: 0.04 to 0.3%, Si: 1% or less, Mn: 0.3 to 1%, P: 0.03% or less, S:
0.03% or less, Ni: 0.5% or less, Cr: 0.75
~ 12%, 1 or 2 kinds of Mo and W are Mo (%)
+ (W (%) / 2) 0.3 to 2.5%, Nb: 0.
1% or less, V: 0.3% or less, B: 0.006% or less and solAl: 0.005-0.1%, with the balance being iron and unavoidable impurities.