JP2020168671A - Main spindle of machine tool - Google Patents

Abstract

To provide a main spindle capable of revealing rigidity equal to an object constituted of only steel while using fiber reinforced plastic.SOLUTION: A main spindle 1 of a hollow and cylindrical machine tool has a part formed by including cylindrical first metal layers Fs1, Rs1 and first fiber reinforced plastic layers Fr, Rr of at least one layer respectively laminated in the radial direction. The first metal layers Fs1, Rs1 in at least its one layer is formed on the outside more than the first fiber reinforced plastic layers Fr, Rr in the radial direction. The first metal layers Fs1, Rs1, in a cross-section orthogonal to the central axis, have a cross-sectional area of 40%-90% to the cross-sectional areas of totaling the first metal layers Fs1, Rs1 and the first fiber reinforced plastic layers Fr, Rr.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spindle of a machine tool, and more particularly to a spindle including a fiber reinforced plastic layer.

In recent years, fiber reinforced plastics (FRP: Fiber-Reinforced Plastics) have been used in various fields such as the interior and exterior of automobiles, railroad vehicles and aircraft, and housing equipment such as unit baths. This fiber reinforced plastic is a composite material whose strength is improved by including fibers such as glass fiber and carbon fiber in the plastic, and it is lightweight while having the same strength as a metal material such as iron. It has the characteristic of being. Therefore, in each of the above-mentioned fields, the replacement of metal materials with fiber reinforced plastics is being promoted.

Further, as a product using such a fiber reinforced plastic, a cylindrical molded product as disclosed in Patent Document 1 below, for example, an industrial roller has been conventionally proposed. This cylindrical molded product is manufactured by laminating several layers of sheet-shaped prepregs, winding the laminate around a core metal, heat-molding the product under pressure, and then removing the core metal. In the past, it was common for the winding angles of the fibers with respect to the longitudinal direction of the cylindrical molded product to be 0 ° and 90 °, but in the cylindrical molded product disclosed in Patent Document 1 below, the fibers are wound. The angle is set to 4 angles of 0 °, 90 °, 40 to 50 ° and -40 ° to -50 °, and by doing so, the cylindrical molded product is made to have high rigidity and little bending. It is said that it can be done.

Japanese Unexamined Patent Publication No. 7-329199

By the way, examples of the product included in the category of the cylindrical molded product include a spindle of a machine tool in addition to the above-mentioned industrial roller. In the field of machine tools, continuous research and improvement are being carried out in order to improve machining accuracy, and in recent years, in order to prevent the machining accuracy from deteriorating due to thermal displacement of the spindle, a coolant is appropriately used. Measures such as cooling the spindle are taken. In particular, from the viewpoint of improving machining efficiency, the speed of spindle rotation is being promoted, and such speeding up tends to increase the amount of heat generated in the spindle device including the spindle, and countermeasures are required. ..

Therefore, the present inventors have come up with the idea that the thermal displacement in the axial direction of the spindle can be reduced by applying the fiber reinforced plastic having a low coefficient of linear expansion to the spindle.

However, fiber reinforced plastic has a problem that it is significantly inferior to steel in terms of rigidity in directions other than the fiber direction, and if the spindle is constructed using only fiber reinforced plastic as a material to replace steel, high processing accuracy is achieved. There is a problem that the rigidity, which is a basic characteristic that the spindle should have in order to obtain the above, is significantly reduced.

The present invention has been made in view of the above circumstances, and has a feature that the coefficient of linear expansion is low and therefore it is difficult to be thermally displaced, but a fiber reinforced plastic having a disadvantageous property that the rigidity is lower than that of steel. It is an object of the present invention to provide a spindle capable of exhibiting the same rigidity as that of a steel-only one while using the above.

The present invention for solving the above problems
It is the spindle of a hollow and cylindrical machine tool.
It has a portion formed by including at least one cylindrical first metal layer and a first fiber reinforced plastic layer laminated in the radial direction.
At least one layer of the first metal layer is formed outside the first fiber reinforced plastic layer in the radial direction.
Further, the first metal layer has a cross section orthogonal to the central axis, which is 40% or more and 90% or less with respect to the total cross-sectional area of the first metal layer and the first fiber reinforced plastic layer. It relates to a spindle of a machine tool characterized by having a cross-sectional area.

The spindle is provided with at least one cylindrical first metal layer and a first fiber reinforced plastic layer at least in a part thereof. By forming the spindle from the first metal layer and the first fiber reinforced plastic layer in this way, the high rigidity developed by the first metal layer and the low rigidity developed by the first fiber reinforced plastic layer are exhibited. It can be a spindle with expandability.

Then, by arranging the first metal layer outside the first fiber reinforced plastic layer in the radial direction, the axial rigidity, flexural rigidity, and torsional rigidity of the spindle are comprehensively optimized. Can be.

Further, in the spindle according to the present invention, the first metal layer has a cross section orthogonal to the central axis, with respect to the total cross-sectional area of the first metal layer and the first fiber reinforced plastic layer. It is important to have a cross-sectional area of% or more and 90% or less. When the cross-sectional area of the first metal layer is 40% or more, the main shaft is composed of only the required rigidity required for the axial rigidity, the flexural rigidity, and the torsional rigidity, that is, steel. It is possible to have almost the same rigidity as. On the other hand, by setting the cross-sectional area of the first metal layer to 90% or less, its thermal expansion can be reduced by 10% or more as compared with the case where it is composed of only steel.

As described above, according to the spindle according to the present invention, while having substantially the same rigidity as the spindle composed only of steel, the thermal expansion is reduced by 10% or more as compared with the spindle composed only of steel. be able to. Therefore, according to the spindle according to the present invention, it is possible to realize more accurate machining as compared with the spindle composed of only steel. Further, focusing on the feature that it is difficult to thermally expand, that is, it is difficult to be thermally displaced, in the spindle according to the present invention, the cooling for suppressing the thermal displacement is made low output, or the cooling itself is omitted. It is possible to save labor for cooling.

Further, in the spindle according to the present invention, the first fiber reinforced plastic layer is oriented in one direction in the longitudinal direction of the contained fibers, and ± 45 ° sandwiching the central axis with the central axis as a reference. It is preferable that the fibers are oriented at a set angle within the range of. The fiber orientation angle refers to the angle in the longitudinal direction of the fiber with respect to the central axis when the main axis is viewed from a plane.

By setting the orientation angle of the fibers within the range of ± 45 ° across the central axis of the main axis, the first fiber reinforced plastic layer suppresses thermal expansion in the direction along the central axis and bends. It has the required rigidity for rigidity, torsional rigidity, and rigidity in the direction along the central axis.

Further, the spindle according to the present invention includes the first fiber-reinforced plastic layer having a plurality of layers, and the more the layer arranged on the center side of the first fiber-reinforced plastic layer, the more the orientation of the fiber with respect to the central axis. The angle may be acute. In other words, it is preferable that the outer side of the first fiber reinforced plastic layer has a larger orientation angle of the fiber with respect to the central axis. By doing so, the thermal expansion of the spindle in the radial direction can be suppressed more effectively, and the optimum rigidity required for bending rigidity, torsional rigidity, and rigidity in the direction along the central axis thereof is provided. It is possible to suppress the thermal expansion in the direction along the central axis more effectively. Thus, in the spindle according to the present invention, more preferably, the fibers in the innermost layer of the first fiber reinforced plastic layer are oriented parallel to the central axis thereof, and the fibers in the outermost layer are 45 with respect to the central axis. Oriented to an angle of ° or −45 °.

Further, when the spindle according to the present invention is provided with a tapered hole for mounting a tool, a second metal layer is formed as the innermost layer for forming the tapered hole at the portion having the tapered hole. A second fiber reinforced plastic layer is formed on the outside of the second metal layer so as to be in contact with at least a part thereof, and the first metal layer and the first metal layer are formed on the outside of the second fiber reinforced plastic layer. A first fiber reinforced plastic layer is formed, and at least one layer of the first metal layer is formed on the outside of the first fiber reinforced plastic layer, and the second fiber reinforced plastic layer is formed. The longitudinal direction of the contained fibers may be oriented at an angle of 45 ° or −45 ° with respect to the central axis thereof.

The tool mounted on the tapered hole is held in the tapered hole by a force that pulls it toward the tapered hole along the central axis. Therefore, the tapered hole receives an acting force in the direction of increasing the diameter from the tool by pressing the tool with this pulling force. Therefore, by adopting the above configuration for the portion where the tapered hole is formed, it is possible to prevent the tapered hole from expanding in diameter, whereby the position of the tool in the axial direction is displaced or the tool is tapered. It is possible to prevent the holding force held by the taper from being weakened.

In the present invention, the fibers contained in the first fiber reinforced plastic layer and the second fiber reinforced plastic layer preferably have a tensile elastic coefficient of 400 GPa or more, and for example, pitch-based carbon fibers and PAN-based fibers. Examples thereof include carbon fibers, boron fibers, alumina fibers, silicon carbide fibers, beryllium fibers and tungsten fibers.

Further, the resin as a matrix constituting the first fiber reinforced plastic layer and the second fiber reinforced plastic layer is a thermosetting resin such as an epoxy resin, a phenol resin, an unsaturated polyester resin, and a polyimide resin, particularly epoxy. A resin can be preferably used, but the resin is not limited to these as long as it has the required strength, and a thermoplastic resin may be used.

Further, the spindle according to the present invention can be manufactured by using a prepreg sheet in which the contained fibers are oriented in one direction, but the manufacturing method is not limited to this.

As described above, the spindle according to the present invention has both high rigidity developed by the first metal layer and low expansion property developed by the first fiber reinforced plastic layer, and also has axial rigidity. The flexural rigidity and the torsional rigidity can be comprehensively optimized. Further, the spindle according to the present invention has substantially the same rigidity as the spindle composed only of steel in terms of axial rigidity, flexural rigidity and torsional rigidity, while its thermal expansion is a spindle composed only of steel. Compared with, it is reduced by 10% or more.

Therefore, according to the spindle according to the present invention, it is possible to realize more accurate machining as compared with the spindle composed of only steel. Further, focusing on the feature that it is difficult to thermally expand, that is, it is difficult to be thermally displaced, in the spindle according to the present invention, it is possible to reduce the output of cooling for suppressing the thermal displacement or omit the cooling. It is possible to save labor for the cooling.

It is sectional drawing which showed the spindle of the machine tool which concerns on one Embodiment of this invention. It is a graph which showed the characteristic of the spindle composed of steel and fiber reinforced plastic. It is explanatory drawing for demonstrating the orientation of the fiber contained in the fiber reinforced plastic. It is sectional drawing which showed the structure of the spindle which concerns on Example 1. FIG. It is sectional drawing which showed the structure of the spindle which concerns on Example 2. FIG. It is explanatory drawing which showed the specifications of the laminate which constitutes the spindle which concerns on Example 1. FIG. It is explanatory drawing which showed the specifications of the laminate which constitutes the spindle which concerns on Example 1. FIG. It is explanatory drawing which showed the specifications of the laminate which comprises the spindle which concerns on Example 2. FIG. It is explanatory drawing which showed the specifications of the laminate which comprises the spindle which concerns on Example 2. FIG. It is explanatory drawing which compared the performance of the spindle which concerns on Example and the spindle which concerns on a comparative example.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The spindle of this example is a spindle provided in a machining center which is a machine tool. As shown in FIG. 1, the spindle 1 is a hollow and cylindrical member, and is composed of a rear portion R rotatably supported by a bearing 10 and a front portion F having a tapered tool holding hole 2. , Another member may be connected to this rear portion R.

The rear portion R includes an outer steel pipe (outer steel pipe) Rs1 made of a steel material, an inner steel pipe (inner steel pipe) Rs2, and a fiber reinforced plastic layer Rr formed between the outer steel pipe Rs1 and the inner steel pipe Rs2. Consists of. The outer steel pipe Rs1 has a structure in which the front end portion Rs1b is formed in a flange shape and the inner diameter of the rear end portion Rs1c is reduced, and the inner steel pipe Rs2 has a front end portion Rs1b and an intermediate portion of the outer steel pipe Rs1. It is coaxially inserted so as to face Rs1a, and the fiber reinforced plastic layer Rr is formed between the front end portion Rs1b and the intermediate portion Rs1a and the inner steel pipe Rs2.

On the other hand, the front portion F is composed of a tapered steel pipe Fs2 and an outer steel pipe Fs1 also made of a steel material, and a fiber reinforced plastic layer Fr formed between the tapered steel pipe Fs2 and the outer steel pipe Fs1. The front end portion Fs2b of the tapered steel pipe Fs2 is formed in a flange shape, and the tapered steel pipe Fs2 is provided with a tapered hole 2 in the central portion. Further, the outer steel pipe Rs1 and the inner steel pipe Rs2, and the tapered steel pipe Fs2 and the outer steel pipe Fs1 are arranged coaxially with each other, and the outer side is provided between the front end portion Fs2b of the tapered steel pipe Fs2 and the front end portion Rs1b of the outer steel pipe Rs1. Steel pipe Fs1 is arranged. Then, the fiber reinforced plastic layer Fr is formed between the tapered portion Fs2a of the tapered steel pipe Fs2 and the outer steel pipe Fs1. Further, the front end portion of the fiber reinforced plastic layer Rr and the rear end portion of the fiber reinforced plastic layer Fr are in a state of being connected to each other.

The outer steel pipes Rs1 and Fs1 and the inner steel pipes Rs2 form the first metal layer, and the tapered portion Fs2a of the tapered steel pipes Fs2 constitutes the second metal layer. Further, the fiber reinforced plastic layer Rr constitutes a first fiber reinforced plastic layer, and the fiber reinforced plastic layer Fr provided on the outside of the tapered portion Fs2a so as to be in contact with at least a part thereof is the second fiber. The reinforced plastic layer is formed, and the fiber reinforced plastic layer Fr outside the reinforced plastic layer constitutes the first fiber reinforced plastic layer.

When the spindle 1 has such a configuration, the outer steel pipes Rs1 and Fs1 and the inner steel pipes Rs2 and the tapered steel pipes Fs2 exhibit high rigidity, and the fiber reinforced plastic layers Fr and Rr exhibit low expandability. As a result, the spindle 1 has both features of high rigidity and low expansion. By arranging the outer steel pipes Rs1 and Fs1 outside the fiber reinforced plastic layers Rr and Fr in the radial direction, the axial rigidity, flexural rigidity and torsional rigidity of the spindle 1 are comprehensively optimized. Can be.

Then, in the main shaft 1 of this example, in the region portion where the cross-sectional area of the cross section orthogonal to the central axis is small, that is, in the rear portion R, the outer steel pipe Rs1 and the inner steel pipe Rs2 (first metal layer) constituting the main shaft 1 are cut off. The area is 40% or more and 90% of the total cross-sectional area, that is, the total cross-sectional area of the outer steel pipe Rs1 and the inner steel pipe Rs2 (first metal layer) and the fiber reinforced plastic layer Rr (first fiber reinforced plastic layer). The thicknesses of the outer steel pipe Rs1, the inner steel pipe Rs2, and the fiber-reinforced plastic layer Rr are set so as to have the following cross-sectional areas.

According to the findings obtained by the present inventors, the fiber reinforced plastic has almost the same performance as the steel material in terms of axial rigidity and flexural rigidity by appropriately setting the orientation of the fibers contained therein. However, the torsional rigidity is inferior to that of steel materials. FIG. 2 shows the volume ratio of steel in a cylindrical composite material composed of steel and fiber reinforced plastic, the tensile modulus related to the axial rigidity and bending rigidity of the composite material, and the shear modulus related to torsional rigidity. The relationship between the coefficient and the linear expansion coefficient related to thermal expansion is shown. ○ is the case where the volume ratio of the layer in which the fibers are oriented along the axis direction and the layer in which the fibers are oriented in the direction orthogonal to the axis is 5: 5 in the fiber reinforced plastic, and ● is the case where the fibers are also oriented along the axis. This is a case where the volume ratio of the layer oriented along the direction and the layer oriented in the direction orthogonal to the axis of the fiber is 6: 4. The cylindrical composite material is a material having a predetermined length in which the steel and the fiber reinforced plastic constituting the composite material each have a uniform cross section along the axial direction. Therefore, the volume ratio of the steel and the fiber reinforced plastic is described above. Is equivalent to the ratio of each cross-sectional area.

As can be seen from FIG. 2, the higher the proportion of fiber reinforced plastic, the lower the coefficient of linear expansion, that is, the lower the coefficient of thermal expansion, and the axial rigidity and flexural rigidity are irrespective of the proportion of fiber reinforced plastic. , It is almost the same as the case of steel only. On the other hand, the torsional rigidity decreases as the proportion of fiber reinforced plastic increases, and when the proportion of steel falls below 40%, the torsional rigidity decreases by about 20% as compared with the case of steel alone.

Therefore, as described above, in the rear portion R whose overall cross-sectional area is smaller than that of the front portion F and which is a neck in strength as compared with the front portion F, the outer steel pipe Rs1 and the inner steel pipe Rs2 (the first) constituting the rear portion R. The cross-sectional area of the outer steel pipe Rs1 and the inner steel pipe Rs2 (first metal layer) is set to 40% or more of the combined cross-sectional area of the fiber-reinforced plastic layer Rr (first fiber-reinforced plastic layer). By doing so, the rigidity in the axial direction and the bending rigidity can be made almost the same as in the case of being composed of only the steel material, and the torsional rigidity can be obtained by about 80%. The torsional rigidity can be almost the same as that of the case where the steel material is used alone. On the other hand, by setting the cross-sectional area of the outer steel pipe Rs1 and the inner steel pipe Rs2 (first metal layer) to 90% or less of the total cross-sectional area, the linear expansion coefficient of the spindle 1, that is, the thermal expansion is composed of only the steel material. It can be reduced by 10% or more, and the thermal displacement of the spindle 1 can be effectively suppressed.

As described above, according to the spindle 1 of this example, the rigidity is almost the same as that of the spindle composed only of steel, while the thermal expansion is reduced by 10% or more as compared with the spindle composed only of steel. be able to. Therefore, according to the spindle 1 of this example, it is possible to realize more accurate machining as compared with the spindle composed of only steel. Further, paying attention to the feature that it is difficult to thermally expand, that is, it is difficult to be thermally displaced, in the spindle 1 of this example, the cooling for suppressing the thermal displacement is made low output, or the cooling itself is omitted. It is possible to save labor for cooling.

In this example, the fibers contained in the fiber-reinforced plastic layers Fr and Rr preferably have a tensile elastic coefficient of 400 GPa or more, and for example, pitch-based carbon fibers, PAN-based carbon fibers, boron fibers, and alumina fibers. , Silicon carbide fiber, beryllium fiber, tungsten fiber and the like can be exemplified.

Further, as the resin as the matrix constituting the fiber-reinforced plastic layers Fr and Rr, a thermosetting resin such as an epoxy resin, a phenol resin, an unsaturated polyester resin, and a polyimide resin, particularly an epoxy resin can be preferably used. It is not limited to those having the required strength, and may be a thermoplastic resin.

Further, the spindle 1 of this example can be manufactured by using a prepreg sheet in which the contained fibers are oriented in one direction. In this example, when the orientation angle of the fiber is referred to, the angle in the longitudinal direction of the fiber with respect to the central axis of the spindle 1 when viewed from a plane is used. FIG. 3A shows an explanatory diagram of the orientation angle. The angle at which the clockwise angle becomes an acute angle with respect to the central axis c is defined as a positive angle (θ), and the counterclockwise angle is an acute angle. Let the angle be a negative angle (−θ). Further, FIG. 3 (b) shows a schematic view of a prepreg in which the fibers are oriented at an angle (θ = 0 °) parallel to the central axis c, and FIG. 3 (c) shows the fibers with the central axis c. A schematic view of the prepreg oriented at an orthogonal angle (θ = 90 °) is shown, and FIG. 3 (d) shows a schematic view of the prepreg oriented so that the fibers intersect the central axis c at θ = 45 °. Is shown.

In the spindle 1 of this example, since the front portion F has a sufficient thickness as compared with the rear portion R, the required torsional rigidity can be secured even if the ratio of the fiber reinforced plastic Fr is increased. Since there is a possibility, if the required torsional rigidity can be secured, it is not always necessary to follow the above configuration, but the cross-sectional area of the outer steel pipe Fs1 and the tapered steel pipe FS2a is set to 40% or more of the total cross-sectional area. There is nothing to prevent you from doing.

Further, in the spindle 1 of this example, it is preferable that the fiber reinforced plastic layers Fr and Rr have a layer in which the contained fibers are oriented within a range of ± 45 ° with the central axis c interposed therebetween. By setting the orientation angle θ of the fibers within a range of ± 45 ° across the central axis c of the main axis 1, the main axis 1 is suppressed from thermal expansion in the direction along the central axis c, and the spindle 1 is said to be the same. The rigidity in the direction along the central axis c, the bending rigidity, and the torsional rigidity are also provided with the required rigidity.

Further, in the main shaft 1 of this example, it is preferable that the more the fiber-reinforced plastic layer Rr is arranged on the central side thereof, the sharper the orientation angle θ of the fiber with respect to the central axis c. In other words, it is preferable that the fiber-reinforced plastic layer Rr arranged on the outer side has a larger orientation angle θ with respect to the central axis c of the fiber. By doing so, the thermal expansion of the spindle in the radial direction can be suppressed more effectively, and the optimum rigidity required for the rigidity, flexural rigidity and torsional rigidity in the direction along the central axis is provided. In addition to being able to do so, thermal expansion in the direction along the central axis c can also be suppressed more effectively. Thus, in the main shaft 1 of this example, more preferably, the fibers in the innermost layer of the fiber reinforced plastic layer Rr are oriented parallel to the central axis thereof, and the fibers in the outermost layer are at 45 ° or − It is oriented so that it has an angle of 45 °.

Further, in the main shaft 1 of this example, in the front portion F provided with the tapered hole 2, the innermost side of the fiber reinforced plastic layer Fr provided on the outside of the tapered portion Fs2a of the tapered steel pipe Fs2 so as to be in contact with at least a part thereof. The layer is preferably oriented so that the fibers contained are at an angle of 45 ° or −45 ° with respect to the central axis c.

The tool mounted on the tapered hole 2 is held in the tapered hole 2 by a force of pulling it toward the tapered hole 2 along the central axis c. Therefore, the taper hole 2 receives an acting force in the direction of increasing the diameter from the tool by pressing the tool with the pulling force. Therefore, the taper hole 2 is formed by orienting the fibers in the innermost layer of the fiber reinforced plastic layer Fr at an angle of 45 ° or −45 ° with respect to the central axis c. It is possible to prevent the diameter of the tool from expanding, thereby preventing the position of the tool in the axial direction from being displaced and the holding force of the tool from being weakened.

Hereinafter, as more specific examples, the spindle 1A according to the first embodiment and the spindle 1B according to the second embodiment will be described.
[Example 1]
The structure of the spindle 1A according to the first embodiment is shown in FIG. 4, and the specifications thereof are shown in FIGS. 6 and 7. The basic structure of the spindle 1A is the same as that of the spindle 1 shown in FIG. 1, and therefore, the same components are designated by the same reference numerals in FIG. The main dimensions of the spindle 1A are as shown in FIG.

The outer steel pipe Rs1, Fs1, inner steel pipe Rs2, and tapered steel pipe Fs2 of the spindle 1A according to the first embodiment are composed of SCM415, the thickness of the intermediate portion Rs1a of the outer steel pipe Rs1 is 2 mm, the thickness of the inner steel pipe Rs2 is 4 mm, and the outer side. The thickness of the steel pipe Fs1 was 2 mm, and the thickness of the tapered portion Fs2a of the tapered steel pipe Fs2 was 2 mm.

Further, the fiber reinforced plastic layer FrA in the front portion F was composed of five layers of Fr1A, Fr2A, Fr3A, Fr4A and Fr5A in order from the outside, and each was formed by heat curing using a prepreg. A thermosetting epoxy resin curable at 180 ° C. was used as the resin to be the matrix. Further, the layer Fr1A is a layer in which the fibers are oriented at θ = 90 °, and the thickness thereof is set to 3 mm. The layer Fr2A is a mixed layer in which the orientation of the fibers is θ = 90 ° and θ = 0 ° in order from the inside, and the thickness thereof is 1 mm. The layer Fr3A is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 45 °, θ = 0 °, and θ = −45 ° in order from the inside, and the thickness thereof is 12.5 mm. The layer Fr4A is a mixed layer in which the orientation of the fibers is θ = 90 ° and θ = 0 ° in order from the inside, and the thickness thereof is 7 mm. The layer Fr5A is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 45 °, θ = 0 °, and θ = −45 ° in order from the inside, and the thickness thereof is 3 mm.

Further, the fiber reinforced plastic layer RrA in the rear portion R was composed of two layers, Rr1A and Rr2A, in this order from the outside, and each was formed by heat curing using a prepreg. A thermosetting epoxy resin curable at 180 ° C. was used as the resin to be the matrix. Further, the layer Rr1A is a mixed layer in which the orientation of the fibers is set to θ = 90 ° and θ = 0 ° in order from the inside, the thickness thereof is 7 mm, and the layer is continuous with the layer Fr4A of the front portion F. is there. The layer Fr2A is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 45 °, θ = 0 °, and θ = −45 ° in order from the inside, and the thickness thereof is 3 mm.

In the front portion F of the main shaft 1A, the cross-sectional area of the tapered portion Fs2a of the tapered steel pipe Fs2 and the outer steel pipe Fs1 is 13% with respect to the total cross-sectional area, and the orientation angle of the fibers in the fiber reinforced plastic layer FrA is 0. The cross-sectional area of the ° layer was 39%, the cross-sectional area of the 45 ° layer was 25%, and the cross-sectional area of the 90 ° layer was 22%. Further, in the rear portion R, the cross-sectional area of the intermediate portion Rs1a of the outer steel pipe Rs1 and the inner steel pipe Rs2 is 42% with respect to the total cross-sectional area, and the layer of the fiber reinforced plastic layer RrA having a fiber orientation angle of 0 ° is cut off. The area was 29%, the cross-sectional area of the 45 ° layer was 6%, and the 90 ° layer was 23%.

For the layer of θ = 90 °, a prepreg using PAN-based carbon fiber (product name: HyEJ17HX1, fiber elastic modulus 230 GPa, manufacturer name: Mitsubishi Chemical Co., Ltd.) was used, and θ = 0 °, ± 45 °. As the fibers oriented to, a prepreg (product name: HyEJ28M80QDHX1, fiber elastic modulus 760 GPa, manufacturer name: Mitsubishi Chemical Co., Ltd.) using pitch-based carbon fibers was used.

[Example 2]
The structure of the spindle 1B according to the second embodiment is shown in FIG. 5, and the specifications thereof are shown in FIGS. 8 and 9. The basic structure of the spindle 1B is the same as that of the spindle 1 shown in FIG. 1, and therefore, in FIG. 5, the same components are designated by the same reference numerals. The main dimensions of the spindle 1B are as shown in FIG.

The outer steel pipes Rs1, Fs1, inner steel pipes Rs2, and tapered steel pipes Fs2 of the spindle 1B according to the second embodiment are composed of SCM415 as in the first embodiment, and the thickness of the intermediate portion Rs1a of the outer steel pipes Rs1 is 2 mm, and the inner steel pipes. The thickness of Rs2 was 4 mm, the thickness of the outer steel pipe Fs1 was 2 mm, and the thickness of the tapered portion Fs2a of the tapered steel pipe Fs2 was 2 mm.

Further, the fiber reinforced plastic layer FrB in the front portion F was composed of four layers of Fr1B, Fr2B, Fr3B and Fr4B in order from the outside, and each was formed by heat curing using a prepreg. A thermosetting epoxy resin curable at 180 ° C. was used as the resin to be the matrix. Further, the layer Fr1B is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 45 °, θ = 0 °, and θ = −45 ° in order from the inside, and the thickness thereof is 4 mm. The layer Fr2B is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 30 °, θ = 0 °, and θ = −30 ° in order from the inside, and the thickness thereof is 12.5 mm. The layer Fr3B is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 45 °, θ = 0 °, and θ = −45 ° in order from the inside, and the thickness thereof is 7 mm. The layer Fr4B is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 30 °, θ = 0 °, and θ = −30 ° in order from the inside, and the thickness thereof is 3 mm.

Further, the fiber reinforced plastic layer RrB in the rear portion R was composed of two layers, Rr1B and Rr2B, in order from the outside, and each was formed by heat curing using a prepreg. A thermosetting epoxy resin curable at 180 ° C. was used as the resin to be the matrix. Further, the layer Rr1B is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 45 °, θ = 0 °, and θ = −45 ° in order from the inside, and the thickness thereof is 7 mm. It is a layer continuous with the layer Fr3B of the front portion F. The layer Fr2B is a mixed layer in which the orientation of the fibers is θ = 0 °, θ = 30 °, θ = 0 °, and θ = −30 ° in order from the inside, and the thickness thereof is 3 mm.

In the front portion F of the main shaft 1B, the cross-sectional area of the tapered portion Fs2a of the tapered steel pipe Fs2 and the outer steel pipe Fs1 is 10% with respect to the total cross-sectional area, and the orientation angle of the fibers in the fiber reinforced plastic layer FrB is 30. The cross-sectional area of the ° layer was 19%, the cross-sectional area of the 0 ° layer was 45%, and the cross-sectional area of the 45 ° layer was 26%. Further, in the rear portion R, the cross-sectional area of the intermediate portion Rs1a and the inner steel pipe Rs2 of the outer steel pipe Rs1 is 40% with respect to the total cross-sectional area, and the layer of the fiber reinforced plastic layer RrB having a fiber orientation angle of 0 ° is cut off. The area was 30%, the cross-sectional area of the 30 ° layer was 8%, and the 45 ° layer was 22%.

For each layer, a prepreg using pitch-based carbon fiber (product name: HyEJ28M80QDHX1, fiber elastic modulus 760 GPa, manufacturer name: Mitsubishi Chemical Corporation) was used.

[Comparison example]
The spindles have the same dimensions as the spindles 1A and 1B shown in FIGS. 4 and 5, and all of them are composed of SCM415.

In the spindle 1A of the first embodiment, the spindle 1B of the second embodiment, and the spindle of the comparative example having the above configuration, the static rigidity in the bending direction, the axial direction, and the torsion direction, the primary natural frequency, the damping ratio, and the temperature of 15 ° C. increase. FIG. 10 shows the results of a partial FEM analysis and the results of a partial actual measurement of each characteristic related to the axial thermal displacement of the front portion F at the time of. As can be seen from this figure, both the spindle 1A of Example 1 and the spindle 1B of Example 2 are superior in axial thermal displacement as compared with the comparative example. Further, the spindle 1B of Example 2 is almost the same as Comparative Example 1 although its static rigidity is slightly inferior, and its natural frequency and damping ratio are superior to those of Comparative Example 1. On the other hand, the spindle 1A of Example 1 is inferior in static rigidity to Comparative Example 1, but has almost the same natural frequency and damping ratio as those of Comparative Example 1.

From the above, as described above, it can be said that the fiber orientation angle θ in the fiber reinforced plastic layers Fr and Rr is preferably within a range of ± 45 ° across the central axis c. Further, as for the fiber reinforced plastic layer Rr, the layer arranged on the center side preferably has an acute angle θ of orientation θ with respect to the central axis c of the fiber, for example, 0 °, and is arranged on the outside. It can be said that it is preferable that the orientation angle θ is a large angle, for example, 45 ° or −45 °.

Although the specific embodiment of the present invention has been described above, the description of the above-described embodiment is exemplary in all respects and is not limiting. Modifications and changes can be made as appropriate for those skilled in the art. The scope of the present invention is indicated by the scope of claims, not by the above-described embodiment. Further, the scope of the present invention includes modifications from the embodiment within the scope of the claims and within the scope of the claims.

1,1A, 1B Main shaft 10 Bearing F Front part Fs1 Outer steel pipe Fs2 Tapered steel pipe Fs2a Tapered part Fs2b Front end part Fr, FrA, FrB Fiber reinforced plastic layer R Rear part Rs1 Outer steel pipe Rs1a Middle part Rs1b Front end part Rs1c Rr, RrA, RrB fiber reinforced plastic layer

Claims (5)

It is the spindle of a hollow and cylindrical machine tool.
It has a portion formed by including at least one cylindrical first metal layer and a first fiber reinforced plastic layer laminated in the radial direction.
At least one layer of the first metal layer is formed outside the first fiber reinforced plastic layer in the radial direction.
Further, the first metal layer has a cross section orthogonal to the central axis, which is 40% or more and 90% or less with respect to the total cross-sectional area of the first metal layer and the first fiber reinforced plastic layer. A spindle of a machine tool characterized by having a cross-sectional area. In the first fiber reinforced plastic layer, the longitudinal direction of the contained fibers is oriented in one direction, and the angle is set within a range of ± 45 ° with the central axis as a reference. The spindle of the machine tool according to claim 1, wherein the spindle is oriented. A plurality of layers of the first fiber reinforced plastic layer are provided, and the layer arranged on the center side of the first fiber reinforced plastic layer has an acute angle of orientation of the fiber with respect to the central axis. The spindle of the machine tool according to claim 2, which is characterized. The fibers in the innermost layer of the first fiber reinforced plastic layer are oriented parallel to the central axis thereof, and the fibers in the outermost layer are oriented at an angle of 45 ° or −45 ° with respect to the central axis. The spindle of the machine tool according to claim 3, characterized in that. In the part having a tapered hole to which the tool is mounted and having the tapered hole
A second metal layer is formed as the innermost layer forming the tapered hole, and a second fiber reinforced plastic layer is formed on the outside of the second metal layer so as to be in contact with at least a part of the second metal layer. The first metal layer and the first fiber reinforced plastic layer are formed on the outside of the fiber reinforced plastic layer of 2, and at least one layer of the first metal layer is formed on the outside of the first fiber reinforced plastic layer. Is formed,
Claims 1 to 4 characterized in that the second fiber-reinforced plastic layer is oriented so that the longitudinal direction of the contained fibers is at an angle of 45 ° or −45 ° with respect to the central axis thereof. Spindle of any of the machine tools listed.

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