JPH02167602A - Spindle of machine tool - Google Patents

Abstract

PURPOSE:To accomplish the reduction of weight and linear expansion of a spindle of a machine tool which can not be accomplished only by metal materials, by excluding metal materials used for the spindle as much as possible while using carbon fiber reinforced plastic materials. CONSTITUTION:A spindle 1 body of a machine tool like a horizontal boring machine is constituted of hollow cylindrical structures 10a,10b made of carbon fiber reinforced plastic material(CFRP) and wound with different winding angles. When the winding angle of the CFRP is properly selected, the absolute value of coefficient of longitudinal of linear expansion can be restrained to 0.5 X10<-6> deg.C<-1>. One of winding angles of carbon fiber or aramid fiber is within the range of 0 deg.+ or -15 deg. and the other within the range of + or -(40-50) deg.. An end 11 of the spindle into which the shunk portion of a tool is inserted is made of steel materials. A hollow cylindrical member 13 made of steel material is glued integrally to the inner surface of a hollow cylinder interposing member 12. The spindle 1 having these members incorporated is formed on the outer surface with a corting layer 18 of hard metal or ceramics.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to the main shaft of machine tools, and in particular eliminates metal materials as much as possible as materials used. This relates to the main spindle of a machine tool, which uses a previously used material to reduce weight and linear expansion, which cannot be achieved with metal materials alone.

(Prior Art) Steel or alloy steel, which is heavy, is generally used as the main shaft material in conventional machine tools such as machining centers, boring machines, and milling machines.

This is because steel or alloy steel has a high modulus of elasticity, and the surface can be hardened, making it suitable for economical aspects including processing.

By the way, the coefficient of linear expansion of steel is 11~16X10-'°C
For example, if there is a temperature change of 10 °C on a 2 m long main shaft, the
A dimensional change of m will occur. For example, when cutting a flat surface with a boring machine, if the temperature of the spindle increases by 10"C between the start and end of cutting, this is 0.3
This means that a difference in depth of cut of about nvn is generated, which is a serious problem in producing highly accurate workpieces. In addition, since steel has a high specific gravity, the weight of the spindle is also inevitably large, which causes large deformation due to centrifugal force during high-speed rotation, making the dimensions of the workpiece unstable, and low vibration damping properties, making it unsuitable for high-speed rotation. Appropriate. Furthermore, if the weight of the main shaft is large, it will take time to start up to high speed rotation, and it is also necessary to secure the power for this purpose.

On the other hand, fiber-reinforced composite materials such as carbon fiber-reinforced plastic material (CCFRP) have been well known as materials that are lightweight and have excellent rigidity, and have been used in many fields. However, the fields in which this type of material is used are limited, and are mainly used in consumer parts, aircraft-related parts, etc., and are extremely rarely used as structural materials for machines. As a rare example, JP-A-61-194197
There is a roller proposed in Japanese Utility Model Application Publication No. 63-69812. This was developed in search of characteristics not found in conventional metal rollers, and was made possible by focusing on the fact that the above-mentioned composite materials, especially CFRP, are extremely lightweight and highly rigid materials. However, this type of roller has a double-sided structure and is often used in paper machines, printing machines, synthetic resin film manufacturing machines, etc., and it is important to minimize the deflection of the center part when conveying paper, film, etc. The main focus is on ensuring followability during sudden stops and gear changes, and it cannot be said that the structure is structurally sufficient to withstand use under harsh mechanical conditions. Therefore, although the techniques proposed in the above-mentioned publications have achieved some success in the construction of roller structures, they are not suitable for use in mechanical parts such as machine tools, which are operated under harsh conditions. It is impossible to apply it directly to the main shaft of a machine.

The main shaft of a machine tool is the part that receives the most load from all directions when machining hard and brittle materials such as metal materials and ceramics by cutting or grinding, and because it has a cantilevered structure, As mentioned above, steel or alloy steel materials are naturally used as materials that are heavy but have high elasticity and rigidity, and whose surfaces are easily hardened. At present, it is difficult to put into practical use the use of materials with low hardness and wear resistance, such as fiber-reinforced plastic materials, which are known to have such characteristics.

Although it is very recent, Japanese Patent Laid-Open No. 63-96 reported that a C/C composite, which is a material similar to but different from the fiber-reinforced plastic material mentioned above, was applied to the main shaft of machine tools.
Proposed in No. 311.

However, C/C composites (carbon/carbon composites) themselves have been used for a long time as mechanical parts, nuclear reactor materials, materials for space development, etc.
55.11.1, co-authored by Ohkama and Wood, Kindai Editorial Co., Ltd.), and the present inventors also attempted to apply the same material to the main shaft of machine JR machines in the same way as the technology proposed above, but it was not put into practical use. However, due to the difficulty in developing plastic materials, the development shifted to the use of fiber-reinforced plastic materials.

That is, the C/C composite is obtained by thermally decomposing the fiber-reinforced plastic composite material at high temperature and carbonizing the matrix plastic material.As it is inferior in physical properties as it is, it is further processed to obtain the desired properties. It is for obtaining parts.

Therefore, it is necessary to go through an extremely multi-step processing process to manufacture it, which inevitably increases the cost and makes it expensive.

(Problem to be solved by the invention) The problems to be solved by the present invention are as follows.

(1) Poor dimensional stability caused by the high linear expansion that conventional steel spindles inevitably have. It is also possible to use a metal material other than steel to make the linear expansion coefficient smaller than that of steel, but even the smallest announced Invar alloy has a linear expansion coefficient of 1 to 3 x 10-6°c-1.
Furthermore, Hoko's invar alloy is a difficult-to-cut material, is expensive, and has low hardness, so it is inappropriate to use it as the main material for the spindle.

(2) Since the conventional steel spindle is heavy, there are various problems that arise from this. In other words, the deformation due to centrifugal force during high-speed rotation is large and the vibration damping properties are poor, which has a large effect on machining quality and machining accuracy, and the moment of inertia becomes large, making it difficult and necessary to increase the speed further. Since the power also increases, the amount of heat generated also increases, which competes with the above-mentioned high coefficient of linear expansion and deteriorates processing accuracy.

(3) For example, to obtain a main shaft made of CTC composite,
It requires a large number of steps, which inevitably increases production costs, making it impractical for practical use.

Therefore, an object of the present invention is to reduce the linear expansion of the main shaft and at the same time reduce the weight, taking into consideration ease and economy in manufacturing.

(Means and operations for solving the problem) In order to achieve the above object, the present invention employs the structure as described in the claims, and uses the structure as a means for solving the above problem.

This will be explained in more detail along with its effect as follows.

First, the present inventors developed fiber-reinforced composite materials, which have been difficult to consider in the past in the field of machine tools, as mentioned above.
In particular, carbon fiber reinforced plastic materials (CFR)
Focusing on P), we began investigating the possibility of its practical application as a spindle material.

As mentioned above, CFRP has desirable characteristics as a material for the main shaft in that it can have a low coefficient of thermal expansion and can be lightweight.

However, when looking at the spindle of a boring machine, for example, chips etc. tend to get stuck on the spindle end surface (if the surface hardness is not high, it will be easily damaged, but CFRP
Since the hardness of the resin itself is controlled by the hardness of the matrix resin, it generally has a low hardness and can easily receive the damage described above.

Therefore, in order to put CFRP into practical use as a spindle material for machine tools, it must compensate for the drawbacks of conventional spindles made of the above-mentioned steel materials, and at the same time satisfy all the requirements required for spindles of machine tools. Must be.

In addition, C
Looking at FRP hollow cylindrical structures, if the wrapping angle is selected appropriately, the coefficient of linear expansion in the longitudinal direction can be negative or zero, and at most the absolute value can be 0.5 x 10-6°c.
It has been found that it is possible to suppress the value to -1. Here, carbon fiber is preferable as the fiber of the fiber-reinforced composite material.
Another possibility is aramid fiber.

The above hollow cylindrical structure made of CFRP generally has a linear expansion coefficient shown in Table 1 depending on the winding angle of the fibers, although this varies depending on the type of fibers and resin.

As shown in Table 1, CFRP has a negative coefficient of linear expansion where the winding angle of the fibers is small, and as the winding angle of the fibers increases, the coefficient of linear expansion becomes large and positive. Therefore, by combining these angles or using a certain specific angle, it is theoretically possible to make the coefficient of linear expansion of the hollow cylindrical structure zero or negative.

Table I CFRP Linear Expansion Coefficient The hollow cylindrical structure which is the main component of the main shaft of the present invention is:
By selecting the winding angle of the carbon fiber, the absolute value of the coefficient of linear expansion is lowered to below 0.5×10-'°C''. A temperature change of °C causes only a dimensional change of IXl0-2 mm.

When such a hollow cylindrical structure made of CFRP is combined with metal such as copper material, the coefficient of linear expansion is 5 x 10-6°c.
The coefficient of linear expansion of the main spindle made of conventional steel materials is 11 to 16×10 −6°c −1, which enables cutting with extremely high precision.

Most of the main shaft of the present invention may be substantially made of CFRP, and a part thereof may be made of metal material or ceramics.

Furthermore, it is also possible to partially use fibers other than carbon fibers, such as glass fibers and aramid fibers.

By the way, in most cases, the required performance of the main shaft is not only dimensional stability but also bending rigidity and torsional rigidity, but if only one type of fiber angle is used, the coefficient of linear expansion of the hollow cylindrical structure itself becomes zero. If you choose one, you will not be able to achieve other required performance. However, by combining at least two types of carbon fiber winding angles, many cases can be selected for the method of reducing the coefficient of linear expansion to zero, increasing the degree of freedom in designing other performances. In order to obtain high bending rigidity, the highest value is obtained when the fiber wrapping angle is 0°, so it is preferable to include this configuration. However, when performing filament wind molding, it is extremely difficult to wind at 0°;
It is more practical to wind at an angle of 0 to 15)°.

Since the main shaft performs cutting work while rotating itself or rotating the workpiece, torsional rigidity is also required. When using CFRP to obtain the main axis, the torsional rigidity is maximized when the fiber winding angle is arranged at ±45°, so it is preferable to include ±45° in the laminated structure. .

If we consider the disturbance during molding, it is actually
)°.

Therefore, it is desirable that the main shaft using the hollow cylindrical structure made of CFRP according to the present invention has at least two types of carbon fiber winding angles, and the - direction C+(0-15)'
On the other hand, it is more preferably (40 to 50) 6. These structures may be divided into many layers, or may be grouped together. Also, angles other than these, for example 90'' may be added.

Incidentally, the main spindle of a machine tool is used under extremely severe conditions as described above. In other words, the conditions that must be met for the spindle include, of course, the low thermal expansion mentioned above, but also: ■ high impact resistance, ■ high surface hardness, and ■ mechanical processing applied to the spindle itself. For example, there is no decrease in strength even when

To explain this, for example, with reference to Fig. 3 regarding the main shaft of a horizontal boring machine, the shaded part in the figure is the main shaft 1, and this main shaft 1 is used for interrupted cutting such as milling and machining of the machined surface. Subject to large impact and surface pressure due to thickness variations. In particular, in the fitting part A of the tool drive key 2 and both side surfaces of the key groove part B where the key 3 fixed to the drive gear of the main shaft 1 fits,
This shock and surface pressure will be taken seriously.

In addition, during hollow cutting, the spindle 1 moves in the axial direction within the sleeve 4 while rotating, and protrudes from the sleeve 4 by a predetermined length. I'm obsessed with the club.

Therefore, unless this surface hardness is higher than that of chips, the spindle surface is likely to be scratched, and its life will be shortened accordingly. on the other hand,
The holding force of the tool by the drawbar 5 and collet 6 is 3
ton, and when a tool is attached, the taper surface of the spindle end directly receives this force, and when a tool is not attached, the force acts on the contact surface E with the collet end. Therefore, the taper surface and the collet contact surface E
Therefore, it is necessary to sufficiently withstand high surface pressure.

The tapered surface is also subjected to cutting vibrations. Furthermore, in the hollow part of the main shaft l, there is a counter spring 7 that acts when attaching and detaching the tool.
is accommodated, and the force of this spring is usually 3 to 8 tons.
It's on. Therefore, the main shaft 1 that supports the end surface of the spring 7
The reaction force acts on the end face F of the hollow stepped portion, and a large surface pressure is applied to the end face F of the hollow stepped portion, similar to the above-mentioned taper face and the collet contact face E.

Moreover, as shown in FIGS. 1 and 2, the main shaft 1 is not a simple cylindrical member, but includes, for example, the tapered surface, step, key groove, etc.
Processing is applied to threaded parts, etc., and such processing must not reduce strength. For example, the reaction force of a counter spring of 3 to 8 tons acts on the threaded portion G at the rear end of the spindle when a tool attached to the tip of the spindle is attached or removed, similar to the end surface F of the hollow step, so it is important not to reduce the strength due to thread cutting. Must be avoided together. The use of CFRP as the main shaft of a boring machine is no exception, and all of the above conditions must be met.

Therefore, as a result of various studies, we decided to make the main shaft body from CFRP.
We considered supplementing the drawbacks of CFRP by employing metals, ceramics, etc. in parts where the above conditions cannot be satisfied with CFRP alone.

In terms of thermal expansion and rigidity, as mentioned above, it has been concluded that even if CFRP is used, it can withstand practical use if the winding angle etc. are appropriately selected. However, the above ■~
Regarding the condition (2), it was found at the experimental stage that CFRP alone could not be put into practical use.

That is, since CFRP has low impact resistance, it was decided to use nitrided steel, for example, for the fitting part A and the keyway part B of the tool drive key.

Further, in particular, the main shaft 1 of a boring machine or the like must be able to move in the axial direction, and must also be fixed at an arbitrary position. Therefore, generally, the main shaft 1 is made to move in the axial direction using a keyway or a spline, and is fixed by gripping the outer periphery of the main shaft 1 with a sleeve 4. Therefore, the surface C of the outer periphery of the main shaft gripped by the sleeve needs to have sufficient hardness. When viewed microscopically, the surface of CFRP is a mixture of carbon fiber and resin, and it is difficult to simply express its hardness, but in any case, it is unsuitable for wear to occur as a gripping part for the main shaft. Furthermore, the surface of the spindle 1 is easily scratched by chips and the like, so high hardness is required to prevent this. Therefore, it is necessary to use metal or ceramic to increase the hardness of at least the portion of the spindle 1 that is gripped by the sleeve 4 and the portion where chips get stuck during cutting. There are various ways to do this, for example,
CFR as disclosed in Publication No. 0-162793
Metal coating can be applied to the surface of a hollow cylindrical structure made of P. In particular, hard Cr plating is hard and suitable for this purpose. Instead of metal plating, a thin metal ring may be fitted and fixed by adhesive or shrink fit. Furthermore, hard Cr plating or the like can be applied thereon.

The main shaft obtained by sequentially forming a base treatment layer for thermal spraying, a metal thermal spraying treatment layer, an intermediate plating layer, and an outermost plating layer on the surface of a hollow cylindrical structure made of CFRP from the inner layer is a hollow cylindrical structure made of CFRP. The structure and the metal plating layer are strongly bonded, and this can be said to be a preferable structure.

Here, the above-mentioned base treatment layer for thermal spraying has a thermal conductivity of 0.001 cal -CT11-'-5ec-', for example.
An inorganic filler that is not flat and satisfies λ-S≧0.05 (λ: thermal conductivity, S: surface area expressed in rd/g) at -deg-' or more, or an inorganic filler whose surface has complex irregularities, etc. It is formed by blending a specially shaped metal or inorganic powder with a thermosetting resin, applying it to the surface of a carbon fiber composite material, and thermosetting it. In addition, the material of the metal sprayed layer is C
There are no particular limitations, as long as the surface can be electroplated, such as u, Ni, At, Fe, etc. The material of the intermediate plating layer is selected from the viewpoint of sealing performance and corrosion resistance, and as a result of various experiments for this purpose, (?u or Ni
was found to be particularly effective. Furthermore, the material for the outermost plating layer is appropriately selected depending on the application, but Ni and Cγ are generally employed, and Cr plating is particularly advantageous when surface hardness is required.

In addition, on the surface of the hollow cylindrical structure of CFRP,
Ceramic spraying as disclosed in Japanese Patent No. 98534 can also be applied. Alumiqi 40 Titania (,4
1,03-40T 1ox) and Chromina (Cr20.)
A robust surface can be obtained by using Alternatively, a thin ceramic ring can be fitted and fixed by adhesive.

In this way, the main shaft manufactured from a hollow cylindrical structure whose main material is hardened by treating the surface of CFRP has the above-mentioned characteristics necessary for a gripping part, and at the same time is resistant to scratches caused by chips generated during cutting. This is preferable in terms of protection and obtaining high dimensional accuracy.

In addition, nitrided steel or ceramics are used for parts that are subject to high surface pressure and cutting vibration, such as the tapered surface of the main shaft end, and the contact surface E of the collet end and the end surface of the hollow step part that receive the reaction force of the spring 7 are used. Hard tempered steel or ceramics is used for F and the threaded portion G at the rear end of the spindle.

As mentioned above, in addition to metal plating or ceramic spraying on the spindle surface, metal or ceramics can be applied to each part of the spindle by forming the bottom of each part with metal or ceramics, fitting it into the corresponding part, and bonding it with adhesive. can do.

However, it is important to note here that there is a difference in linear expansion coefficient between metal or ceramic materials and CFRP, so if the difference is large, peeling is likely to occur at the adhesive surface, especially when the adhesive length in the longitudinal direction of the main axis is It is easy to peel off in long parts. Therefore, it is necessary to select a material with a small linear expansion coefficient as the metal or ceramic used in such a part.

In the above explanation, the types of carbon fiber are high strength type,
Either a medium elasticity type or a high elasticity type may be used, but it goes without saying that a main shaft with higher rigidity can be obtained by using high elasticity carbon fiber. Although carbon fibers are mainly explained here, some aramid fibers have a negative coefficient of linear expansion in the fiber direction, and can be used in the same way. There are no particular restrictions on the matrix resin.

In addition to thermosetting resins such as epoxy resins, phenolic resins, and polyester resins, vinyl ester resins and polyimide resins can be used, and thermoplastic resins such as nylon 66, polycarbonate, polyethylene terephthalate, and PEEK can be used.

PEK, PPS, 5PEI, etc. can also be used.

The molding method is also not particularly limited, and both filament wind moldability and sheet wrap methods can be applied.

(Example) Hereinafter, the present invention will be specifically explained by comparing an example and a conventional example.

FIG. 1 shows a main shaft cross section of a width boring machine according to a typical embodiment of the present invention.

In the same figure, 101Z and 10b are the inner and outer layers of a CFRP hollow cylindrical structure in which the carbon fibers forming the main body of the main shaft l according to the present invention have different winding angles.

Reference numeral 11 denotes a main shaft end member having a tapered surface into which the shank portion of the tool is inserted.The main shaft end member 11 is individually manufactured from a steel material, and a small diameter portion formed on a part of the outer peripheral surface is connected to the inner surface of the inner layer 101Z. They fit into and come into contact with the stepped portion formed on the surface and are bonded and integrated.

12 has an outer diameter equal to the inner diameter of the CFRP hollow cylindrical structure.
10 (a hollow cylindrical intervening member having an inner diameter equal to the inner diameter of Z) is fitted into the hollow part of the inner layer 10a so that one end thereof comes into contact with the inner end surface of the main shaft end member 11, and is bonded and integrated with an adhesive.

Reference numeral 13 denotes a hollow cylindrical member made of steel and having a flange at one end, which accommodates the collet and extends to a portion where one end surface of the spring spring comes into contact with the hollow cylindrical interposed member 12.
It is fitted and integrated with the inner surface of the

On the outer peripheral surface of the main shaft rear end side of the CFRP hollow cylindrical structure,
A groove 14 of a predetermined length extending parallel to the axis is formed, and a key groove member 15 is fitted and adhered to the intermediate groove 14 to form a key groove 16. Furthermore, a hollow cylindrical rear end member 17 with a collar and having a keyway 11a is fitted and fixed to the inner surface of the rear end of the CFRP hollow cylindrical structure with an adhesive. The inner diameter of this hollow cylindrical rear end member 17 is set equal to the inner diameter of the inner layer 10 (Z).

A hard metal or ceramic coating layer 18 is formed on the outer surface of the main shaft 1 after these members have been assembled.

Example 1 A hollow cylindrical structure serving as the main body of the main shaft was manufactured using CFRP. The finished dimension of this hollow cylindrical structure is an outer diameter of 11
0 ++++n, length 1590m+, inner diameter 64.7m
It was molded using a filament winding method using mesolateral carbon fiber (Pyrofil@MM-1 manufactured by Mitsubishi Rayon) so as to have a diameter of m. The matrix is an epoxy resin. Inside N1
0a is ±4501, outer layer 10b is each wrapped at a winding angle of ±10°, and each thickness is 18.65mm and 411II11
I made it so that After sufficiently hardening this, cutting and grinding are performed on the necessary parts, and the main shaft end member 11, hollow cylindrical intervening member 12, hollow cylindrical member 13, keyway member 15, and hollow cylinder are cut into each processed part and the necessary parts. The rear end members 17 were fitted and fixed with adhesive. Thereafter, it was finished by machining again, and the outer surface was coated with a conductive coating, and then Cu plating and Cr plating were sequentially performed by electroplating to form a coating layer 18, and further, it was finished by grinding.

Here, SACM645 was used for the main shaft end member 11, Invar alloy was used for the hollow cylindrical intervening member 12, and SCM440 hard tempered steel was used for the hollow cylindrical member 13, the keyway member 15, and the hollow cylindrical rear end member 17. .

In addition, in order to suppress the deviation due to the linear expansion difference between SCM440 high contrast material and CFRP and eliminate the peeling of the adhesive,
A hollow cylindrical intervening member 12 made of Invar alloy, which is a low thermal expansion alloy, is interposed between 10a and a hollow cylindrical member 13 made of SCM440 hard contrast material.

The main shaft (■) obtained in this example according to this example has a total length of 1815 mm.
mm, weight (IP) is 32 kg, bending rigidity (El) is 6
゜4X10"kgf-mm", torsional rigidity <GIp> is 2
．． 93 x 1010 kg, 7-mm'', and it was found that the dimensional change in thermal expansion was only 9μ shrinkage (-9μ) when the temperature increased by 15°C.

Table 2 compares this with a conventional spindle (manufactured by our company) made only of steel.

Table 2 (1) Reducing the weight of the main shaft from 92 kg to 32 kg has the following advantages.

■ Improved spindle control performance by reducing moment of inertia,
Easy to speed up.

The moment of inertia of the spindle according to this embodiment is 25% lower than that of a conventional steel spindle, and the torque required to start the spindle from a stopped state to high-speed rotation in a unit time is also 25% of the steel spindle.

This means that the rise time to high-speed rotation is shortened, making it easier to increase the speed. For example, in tapping, it is possible to repeat forward and reverse rotation at high speed. Also, for example, 3000yJ in the same time,
Since the torque required to accelerate up to m is only 25% of the conventional torque for the spindle according to this embodiment, the amount of work is small and the heat generation is also small. This results in energy savings and reduction in thermal displacement.

■ Improved spindle positioning accuracy.

In machine tools with a spindle feeding mechanism, the weight of the spindle is reduced, which reduces the slip resistance when feeding the spindle.
Therefore, the torsion angle of the drive system of the feeding mechanism is reduced, and positioning accuracy is improved.

(2) According to Table 2, the main shaft according to this embodiment has a lower rigidity than the conventional example, but the above values for both bending rigidity and torsional rigidity are sufficient for practical use.

The values of the conventional example above are based on our product as an example, and are intended for low-speed, high-torque cutting. ), and therefore it can be said that the rigidity is sufficient.

(3) When the temperature increases by 15°C, the main shaft according to this embodiment contracts by 9μ, while the conventional main shaft expands by 250μ.

This particularly affects the machining accuracy in the depth direction of the hole, and generally heat is generated around the spindle during machining. There will be a difference in depth of 250μ in the ninth hole.

On the other hand, the spindle according to this embodiment has an error of 10μ even when viewed simply.
However, if you take into account the elongation of the tool due to the heat generated during cutting, for example, if a tool with a tool length of 300 mm is used and the tool temperature rises by 5°C, the tool will elongate by 15 μ. The total elongation is 15(μ)−
9(μ)=6(μ), which gives a more favorable result.

Example 2 Filament wind molding was performed using the same material so that the hollow cylindrical structure forming the main body of the main shaft had the same shape and dimensions as in Example 1. After this was sufficiently hardened, grinding and cutting were performed, and the same type of steel or alloy material was adhered to the necessary parts in the same manner as in Example 1, and the product was finished by machining again.

After masking the necessary parts, a bond coat was applied and then cured, and Cr2O was plasma sprayed on it, and it was ground to match the dimensions.

The thermal expansion and rigidity of this shaft were almost the same as in Example 1.

Example 3 Filament wind molding was performed using the same material so that the hollow cylindrical structure forming the main body of the main shaft had the same shape and dimensions as in Example i. After this was sufficiently hardened, grinding and cutting were performed, and the same type of steel/alloy material was adhered to the necessary parts in the same manner as in Example 1, and the product was finished by a-machining again.

After masking the necessary parts, a base treatment for thermal spraying is applied to the outer surface, a copper thermal spraying treatment is applied on top of that, and then Cu, plating, and hard Cr plating are sequentially performed by electroplating.
I ground it to size.

The thermal expansion and rigidity of this shaft were almost the same as in Example 1.

(Effects of the Invention) As described above in detail, according to the present invention, the weight of the main shaft of a machine tool can be reduced, and thermal expansion in the axial direction can be reduced, so that machining accuracy is further improved.

Furthermore, this reduction in weight and linear expansion leads to energy savings and increased speed.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the main shaft of a machine tool according to the present invention, FIG. 2 is a cross-sectional view taken along the χ-X line of FIG.
FIG. 3 is a partial vertical sectional view of the main shaft head of the width boring machine. Explanation of the main parts of the figure ■... - Main shaft 10a - Inner layer 10b (of CCFRP) - Outer layer 11, 12.13.15.17.18... - Metal 16 -
keyway

Claims (1)

[Scope of Claims] 1. A main shaft of a machine tool, characterized in that the main body is constituted by a hollow cylindrical structure made of a fiber-reinforced composite material. 2. The spindle according to claim 1, wherein carbon fiber or aramid fiber is used as the fiber. 3. The main shaft according to claim 1 or 2, wherein the hollow cylindrical structure has an absolute value of linear expansion coefficient in the longitudinal direction of 0.5×10^-^6°C^-^1 or less. 4. The spindle according to claim 1 or 2, wherein the winding angle of the fibers is at least two types. 5. At least one of the winding angles of carbon fiber is 0° to ±1
5° and at least one is ±(40-50)
5. The main axis according to claim 4, which is in the range of .degree. 6. The spindle according to any one of claims 1 to 5, wherein metal or ceramic is arranged on a part or all of the outer peripheral surface, inner peripheral surface, or end of the hollow cylindrical structure. 7. The main shaft according to claim 6, wherein the hollow cylindrical structure and the metal or ceramic are fixed by an adhesive. 8. The main shaft according to claim 6, wherein the hollow cylindrical structure and the metal or ceramic are fixed by metal plating or ceramic spraying. 9. The main shaft according to claim 6 or 7, wherein a low thermal expansion metal is interposed between the hollow cylindrical structure and the metal or ceramic.