WO2010116883A1 - Intermediate shaft for drive shaft - Google Patents

Abstract

Disclosed is an intermediate shaft for a drive shaft wherein the bending rigidity is enhanced while reducing the weight by providing an FRP layer (120) on the outer circumference of a steel hollow shaft (102). The steel hollow shaft (102) consists of the intermediate portion (104) and the coupling portions (106) on the opposite sides of the intermediate portion (104), and the steel hollow shaft is hollow over the entire length and the FRP layer (120) is provided on the outer circumference of the intermediate portion (104). More specifically, there are several modes of fitting FRP formed in the shape of a pipe to the outer circumference of the hollow shaft (102), wrapping a bundle of carbon fibers impregnated with resin around the outer circumference of the hollow shaft (102), and wrapping CFRP formed in the shape of a sheet around the outer circumference of the hollow shaft (102).

Description

Drive shaft intermediate shaft

The present invention relates to an intermediate shaft for a drive shaft of an automobile.

The drive shaft of an automobile is composed of an intermediate shaft and a constant velocity universal joint attached to both ends thereof. The drive shaft is incorporated in the drive system of the automobile to transmit rotational force between rotational axes existing on non-linear lines. For example, in the case of a front wheel drive vehicle, it plays a role of transmitting power by being interposed between an engine and a front wheel. Conventionally, a solid steel shaft has been widely used as this intermediate shaft. Recently, however, while demand for improved fuel efficiency and quietness is required, drive shafts using solid shafts made of steel are often heavy, and due to their low rigidity, fuel efficiency is often improved. There is a demand for increased rigidity for the purpose of weight reduction and vibration reduction. Therefore, hollow shafts are beginning to be adopted instead of solid shafts (Patent Documents 1 and 2).

In Patent Document 1, it is proposed to achieve improvement in vibration characteristics by making the intermediate shaft hollow. Referring to FIG. 1, a drive system of a four-wheel drive automobile is schematically shown in FIG. 1, and a front engine 1 is provided with a transmission 2 and a front shaft differential 3, and a drive shaft 5 at the front. The front wheel 4 is driven through the The driving torque for the rear wheel 6 is branched from the front shaft differential 3 and transmitted to the rear shaft differential 8 through the propeller shaft 7. The rear axle differential 8 drives the rear wheel 6 via a rear drive shaft 9.

FIG. 2 shows an example of an intermediate shaft used for the front and rear drive shafts 5 and 9. The intermediate shaft S is made of steel and is hollow throughout its entire length. The intermediate shaft S is composed of a central portion and ends located on both sides of the central portion and smaller in diameter than the central portion, and the symbol L represents the length of the central portion. A serration (or spline, hereinafter the same) shaft is formed at each end and is connected in torque transmission with a serration hole of an inner joint member (not shown).

FIG. 3 is an example of a drive shaft using a hollow intermediate shaft. The drive shaft includes an intermediate shaft S, a fixed constant velocity joint J1 attached to one end of the intermediate shaft S, and a sliding constant velocity joint J2 attached to the other end of the intermediate shaft S And consists of.

The fixed type constant velocity universal joint J1 is a type that allows only angular displacement between the driving shaft and the driven shaft, and comprises an outer ring 11, an inner ring 12, a plurality of balls 13, and a cage 14, and the inner ring 12 and an intermediate The shaft S (motor shaft) is connected so as to transmit torque, and the outer ring 11 and the wheel hub (driven shaft) of the drive wheel are connected so as to transmit torque.

The sliding type constant velocity universal joint J2 is a type that allows not only angular displacement but also axial displacement (plunging) between the driving shaft and the driven shaft, and here, a tripod type is exemplified. The tripod type constant velocity universal joint J2 includes an outer ring 21, a tripod 22, and a roller 23. The outer ring 21 is connected to the output shaft (driving shaft) of the differential so as to be able to transmit torque, and the tripod 22 is connected to the intermediate shaft S It is connected with the shaft so as to be able to transmit torque.

In order to prevent the leakage of lubricating grease and the entry of foreign matter, it is common to use bellows-like boots 15, 25. The fixed type constant velocity universal joint J1 may be referred to as an outboard joint, and the sliding type constant velocity universal joint J2 may be referred to as an inboard joint, from the positional relationship in a state mounted on a vehicle. The details of the constant velocity universal joint are already well known, and since they are not directly related to the subject matter of the present invention, they are omitted here.

Unexamined-Japanese-Patent No. 5-263819 JP 2001-208037 A

The effect of weight reduction by adopting a hollow shaft instead of a solid shaft is small, and a lighter drive shaft has been required. For example, the required strength can not be obtained by thinning the central portion for weight reduction. If the outer diameter of the central portion is increased to secure torsional rigidity and the thickness is secured, the desired light weight effect can not be obtained. In addition, since it is necessary to provide a groove (boot groove) for attaching the boot to the intermediate shaft in the minimum shaft diameter portion, there is a limit in increasing the axial length of the central portion for weight reduction.

An object of the present invention is to further reduce the weight of a drive shaft while securing its strength.

The present invention solves the problem by replacing the outer peripheral portion of the hollow shaft with a fiber reinforced resin (hereinafter referred to as FRP). That is, according to one aspect of the present invention, the drive shaft intermediate shaft is an intermediate shaft in a drive shaft including the intermediate shaft and constant velocity universal joints attached to both ends, and the intermediate shaft is An intermediate portion and connection portions on both sides of the intermediate portion, and having a hollow hollow shaft over the entire length, and an FRP layer provided on the outer periphery of the intermediate portion.

A specific embodiment of the FRP layer is, for example, one in which FRP molded in a pipe shape is fitted to the outer periphery of the middle portion of the hollow shaft, a bundle of carbon fibers impregnated with resin is used as the hollow shaft. What was wound around the outer periphery of the said intermediate part, and what wound the carbon fiber reinforced resin (CFRP) shape | molded in the sheet form around the outer periphery of the said intermediate part of the said hollow shaft is mentioned.

When forming an FRP layer by fitting an FRP molded into a pipe shape to the outer periphery of the middle portion of the hollow shaft, a length for fitting the molding length of the FRP molded into a pipe shape to the middle portion of the hollow shaft It may be an integral multiple of 2 or more of L. If an FRP pipe having a length that is an integral multiple of 2 or more of the fitting length L with the middle portion of the hollow shaft is formed and cut into the fitting length L for use, a plurality of pipes can be obtained Since FRP pipes can be formed at one time, the number of steps can be reduced.

Also, an adhesive may be used to bond the FRP which has been formed into a pipe shape and the middle portion of the hollow shaft. In this case, for example, an epoxy adhesive or a urethane adhesive can be used.

A bundle of carbon fibers impregnated with resin is wound around the outer periphery of the middle portion of the hollow shaft, or a carbon fiber reinforced resin (CFRP) formed in a sheet shape is wound around the outer periphery of the middle portion of the hollow shaft to form an FRP layer In this case, the angle of the carbon fiber with respect to the axis of the hollow shaft may be 45 °. Carbon fibers are anisotropic in strength and differ in strength depending on the winding method. Basically, for twisting, wind in the 45 ° direction. Since the failure mode of the intermediate shaft is twisting, it is expected to strengthen against twisting by winding in the direction of 45 ° with respect to the axis. In addition, bending stiffness is enhanced by making the angle of the carbon fiber smaller than 45 ° with respect to the axis of the hollow shaft, and the tension is further strengthened, so bending stiffness can be selected by selecting a winding angle of 0 to 45 ° if necessary. Tensile rigidity can be improved.

In addition, the angle of the carbon fiber with respect to the axis of the hollow shaft may be any angle larger than 0 and 45 ° or less, and two or more types of angles may be combined.

In order to prevent rotation of the hollow shaft and the FRP layer, the contour of the outer peripheral surface of the intermediate portion of the hollow shaft may be polygonal, or an axial groove may be provided on the outer peripheral surface of the intermediate portion of the hollow shaft.

The use of an adhesive, the outline of the outer peripheral surface of the intermediate portion of the hollow shaft is polygonal, and the axial groove is provided on the outer peripheral surface of the intermediate portion of the hollow shaft can be used alone or in combination. Can also be implemented.

Further, according to another aspect of the present invention, the drive shaft intermediate shaft is fitted to the outer periphery of the large diameter portion of the steel member and the hollow steel member including the large diameter portion at the center and the small diameter portions at both ends. It is comprised by the composite body with the CFRP member, and the boot groove is provided in the outer peripheral surface of the said CFRP member.

The CFRP member formed into a pipe shape may be fitted to the large diameter portion of the steel member.

The boot groove of the CFRP member may be formed by machining.

The boot groove of the CFRP member may be formed by pressing.

The steel member and the CFRP member may be fixed by an adhesive.

An adhesive reservoir may be provided on the outer periphery of the large diameter portion of the steel member.

The pipe-like CFRP member and the steel member may be press-fitted and fixed via a locking portion in the rotational direction.

The rotational direction locking portions may be provided at both ends of the steel member.

The rotational direction locking portion may be serration or spline.

The rotational direction locking portion may be a knurled surface.

According to one aspect of the present invention, the outer peripheral portion of the middle portion of the hollow shaft made of steel constituting the intermediate shaft is replaced with a layer made of a fiber reinforced resin which is a lightweight material, that is, an FRP layer. Weight reduction is realized. Therefore, by using the drive shaft intermediate shaft according to the present invention, it is possible to improve the fuel efficiency and the vibration characteristic of the automobile.

According to another aspect of the present invention, a pipe-like CFRP member obtained by molding a drive shaft intermediate shaft with CFRP (carbon fiber reinforced plastic), which is a lightweight high-strength material, and a hollow shaft-like steel member are combined. In this way, further weight reduction of the drive shaft can be achieved without a decrease in strength. Therefore, the reduction of the weight of the drive shaft can contribute to the improvement of the fuel consumption of the vehicle.
Further, by forming a boot groove on the outer periphery of the CFRP member, the axial length of the large diameter portion (central portion) can be made longer. Therefore, the torsional rigidity obtained by the axial length of the large diameter portion (central portion) is improved, which contributes to the improvement of the vibration characteristic of the vehicle on which the drive shaft is mounted.

Diagram of the drive system of a car Half sectional view of the conventional intermediate shaft Longitudinal sectional view of a conventional drive shaft Half-longitudinal sectional view of the intermediate shaft of the embodiment Transverse view of the intermediate shaft of FIG. 4A The enlarged view of part C in FIG. 4A Half-longitudinal cross-sectional view of the intermediate shaft of another embodiment A partial enlarged view of FIG. 5A Transverse view of the intermediate shaft of FIG. 5A Transverse sectional view of intermediate shaft showing modified example A partial enlarged view of FIG. 6B Transverse view of the intermediate shaft of another embodiment Transverse sectional view of intermediate shaft showing modified example A partial enlarged view of FIG. 7B Half-longitudinal cross-sectional view of the intermediate shaft of another embodiment Half-longitudinal cross-sectional view of the intermediate shaft of another embodiment A half sectional view of an intermediate shaft showing another embodiment, in which one side of the center line is cut. A half sectional view showing a state before compounding of the intermediate shaft in FIG. 10 A partial enlarged view of FIG. 10 showing a modified example FIG. 10 is a partially enlarged view of FIG. 10 showing another modification Partially enlarged view of the intermediate shaft partially cut off FIG. 14A is a cross-sectional view of bb Partially enlarged view similar to FIG. 14A partially cut away

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The intermediate shaft is composed of a steel hollow shaft 102 and an FRP layer 120. The hollow shaft 102 will be described first.

As shown in FIGS. 4A and 4B, the hollow shaft 102 is composed of the middle portion 104 and the connection portion 106 smaller in diameter than the middle portion 104 on both sides thereof, and is hollow over the entire length. The hollow shaft 102 has the intermediate portion 104 and the connection portion 106 integrally formed by reducing the diameter of a pipe material larger in diameter than the intermediate portion 104 by cold working. Work hardening is imparted by cold working.

Each connection portion 106 is integrated with the intermediate portion 104 via a tapered portion 108 formed at an end (inner end) on the intermediate portion 104 side. In each connection portion 106, boot attachment grooves 110a and 110b are formed by rolling or the like at a position closer to the intermediate portion 104. This is the part where the small diameter part of the boot is attached. Further, serrations 112 are formed at the tip (outer end) of each connection portion 106 by rolling or the like. A retaining ring groove 114 is formed at the tip (outer end) of the serration 112, and a bulging portion 116 is formed at the end of the serration 112. The portion 118 between the bulging portion 116 and the boot mounting grooves 110a and 110b has the smallest diameter at the connecting portion 106.

In the embodiment shown in FIG. 4A, a layer of fiber reinforced resin, that is, an FRP layer 120 is provided on the outer periphery of the intermediate portion 104 of the above-described steel hollow shaft 102. In other words, the steel material of the outermost layer of the intermediate portion 104 is replaced with FRP. As well known, FRP is a composite material made of a resin reinforced with fibers such as carbon fibers and glass fibers. The fiber reinforcing materials include glass fibers, organic fibers, carbon fibers, metal fibers, inorganic fibers and the like. This embodiment is an example in which the FRP layer 120 formed into a pipe shape is fitted to the outer periphery of the middle portion 104 of the hollow shaft 102.

For bonding the hollow shaft 102 and the FRP layer 120, an adhesive 122 (FIG. 4C) or laser welding 124 (FIG. 5A) can be employed. For example, an epoxy-based or urethane-based adhesive can be used as the adhesive. The adhesive 122 plays a role in strengthening the bonding state of the base material (hollow shaft 102) and the FRP layer 120. If the bonding state between the base material and the FRP layer is poor, only the base material, that is, the intermediate shaft 102 receives torque, and the FRP layer 120 can not share torque, and the purpose of strengthening can not be achieved. FIG. 5A shows an example in which laser welding is performed between the hollow shaft 102 as the base material and the end of the FRP layer 120 at a plurality of places as indicated by reference numeral 124.

As shown in FIG. 5B, in order to improve the adhesion between the base material of the hollow shaft 102 and the FRP layer 120, the outer surface of the hollow shaft 102 may be subjected to a surface treatment 126. The surface treatment here is a kind of roughening, and by increasing the surface area by providing a large number of irregularities on the surface on which the adhesive is interposed, the adhesive strength of the adhesive is enhanced. Shot blast and knurling can be mentioned as a specific example of such base treatment.

In order to prevent strength reduction due to slippage between the hollow shaft 102 and the FRP layer 120, as shown in FIG. 6A, the contour of the outer peripheral surface of the intermediate portion 104 (maximum diameter portion) of the hollow shaft 102 may be polygonal. Good. Although the case of a regular polygon is illustrated in the drawings, the regular polygon need not necessarily be used. As shown in FIG. 7A, a plurality of axial grooves may be provided on the outer peripheral surface of the intermediate portion 104 of the hollow shaft 102. In this case, in addition to the cross-sectional shape similar to serration as illustrated, it may be a spline or a concavo-convex shape similar to a gear.

When the contour of the outer peripheral surface of the intermediate portion 104 is polygonal or axial grooves are provided, stress concentration on the FRP layer 120 is achieved by rounding the ridge as shown in FIGS. 6B, 6C and 7B, 7C. Can be secured to ensure high strength.

As described above, by forming the composite of the hollow shaft 102 made of steel and the FRP layer 120, it is possible to achieve both weight reduction and high strength. Further, as described above, since the middle portion 104 has a larger diameter than the connection portion 106, the middle portion 104 is the largest outer diameter portion of the hollow shaft 102. By replacing the outer periphery of the maximum outer diameter portion with the FRP layer 120, it is possible to maximize the effects of weight reduction and bending rigidity improvement. When specific gravity is compared, specific gravity of CFRP (assumed to be 60% of fiber volume content of resin) is 1.6 relative to specific gravity 7.9 of steel. The strength can not be generally stated because the strength of the carbon fiber is anisotropic, but the specific strength (tensile strength per unit density) is 60MPa for steel, whereas CFRP is 300MPa for the same weight. It will have double tensile strength.

Further, when forming a CFRP (carbon fiber reinforced resin) pipe, the winding angle of carbon fiber is set to 45 ° direction. Bending rigidity is improved by combining with a winding angle of 5 to 30 °. The 1 ° direction sheet-like CFRP may be wound around the outer periphery of the intermediate portion 104 of the hollow shaft 102 in advance. Thereby, the bending rigidity can be further improved. Carbon fibers are anisotropic in strength and differ in strength depending on the winding method. Basically, for twisting, wind in the 45 ° direction. Since the failure mode of the intermediate shaft is twisting, it is expected to strengthen against twisting by winding in the direction of 45 ° with respect to the axis. In addition, bending stiffness is enhanced by making the angle of the carbon fiber smaller than 45 ° with respect to the axis of the hollow shaft, and the tension is further strengthened, so bending stiffness can be selected by selecting a winding angle of 0 to 45 ° if necessary. Tensile rigidity can be improved.

The molding length of the FRP pipe is an integral multiple of 2 or more of the fitting length L (FIG. 4) of the middle portion 104 of the hollow shaft 102 to be fitted, so that a plurality of FRP pipes can be made at one time Since molding is possible, the number of steps can be reduced.

Next, in the embodiment shown in FIG. 8, an FRP layer 120 is formed by directly winding a carbon fiber bundle impregnated with a resin or a carbon fiber formed into a sheet shape around a hollow shaft 102 made of steel. is there. In this case, since it is not necessary to form a separate CFRP pipe, the manufacturing efficiency can be improved.

The cross-sectional shape of the hollow shaft 102 made of steel can be the same as that described above with reference to FIGS. 6 and 7. The angle α at which the carbon fibers are wound is preferably 45 ° with respect to the axial direction of the intermediate shaft.

As shown in FIG. 9, bending rigidity can be improved by winding the winding angles β and γ in combination of the directions of 5 to 30 ° and 45 °. When the sheet-like CFRP is wound, a 0 ° direction (axial direction of the intermediate shaft 102) is also possible.

As shown in FIGS. 10 and 11, the intermediate shaft S1 is a composite of a steel member 210 and a CFRP member 220. The steel member 210 is hollow throughout its entire length, and the reference numeral 212 represents a hollow portion. The steel member 210 includes a central large diameter portion 214 and small diameter portions 216 at both ends, and the length of the large diameter portion 214 is indicated by a symbol L1. A serration shaft 218 is provided at the axial end of the small diameter portion 216.

The CFRP member 220 is a CFRP formed into a pipe shape. Here, the method of manufacturing the CFRP member 220 and the details of the material plastic are not particularly limited. For example, as a manufacturing method, a filament winding method, a sheet winding method, a pultrusion process, a rolling method of a prepreg sheet, and the like are known. Further, the type and winding angle of carbon fiber which is a reinforcing fiber are not particularly limited.

The length L1 of the CFRP member 220 is approximately equal to the length L1 of the large diameter portion 214 of the steel member 210 described above. The CFRP member 220 has substantially the same diameter over the entire length, and a boot groove 222 for fitting a boot on the outer periphery of both ends is provided. By forming the boot groove 222 in the CFRP member 220, the small diameter portion 216 of the steel member 210 can be shortened and the large diameter portion 214 can be lengthened accordingly.

Thus, the length L1 of the large diameter portion 214 of the steel member 210 and the length L1 of the CFRP member 220 are set longer than the length L of the large diameter portion of the conventional shaft S shown in FIG. (L1> L). By adopting such a configuration, the shaft S1 is lighter than the conventional shaft S and has high rigidity. That is, (1) Weight reduction can be achieved by thinning the large diameter portion 214 of the steel member 210 and reinforcing it with the CFRP member 220 (replacement of material). (2) By increasing the ratio of the large diameter portion 214 to the entire length of the steel member 210 (L1> L), not only the weight reduction effect is further promoted, but the large diameter portion (central portion) 214 The torsional rigidity obtained by lengthening is improved, which contributes to the improvement of the vibration characteristics of the vehicle equipped with the power transmission shaft.

The compounding in which the steel member 210 and the CFRP member 220 in which the boot groove 222 is formed at both ends of the outer diameter are fitted can be implemented by various methods. As shown in FIG. 12, the steel member 210 and a CFRP member 220 formed in advance in a pipe shape may be joined by an adhesive 224. Further, as shown in FIG. 13, an adhesive reservoir 226 may be provided in order to enhance the adhesion by the adhesive. FIG. 13 shows an example in which the adhesive reservoir 226 is formed by the concave portion formed on the outer periphery of the large diameter portion 214 of the steel member 210. 12 and 13 are somewhat exaggerated with respect to the thickness of the adhesive layer and the depth of the adhesive reservoir 226.

As shown in FIGS. 14A and 14B, in order to increase the bonding strength between the steel member 210 and the CFRP member 220, a rotational direction locking portion 230 may be provided on the outer periphery of the large diameter portion 214 of the steel member 210. Then, by pressing the steel member 210 into the CFRP member 220, the convex portion of the rotation direction locking portion 230 is bitten into the inner peripheral surface of the CFRP member 220 to be integrated. The rotational direction locking portion 230 may be disposed over the entire length of the large diameter portion 214 of the steel member 210, or may be disposed only at both ends as shown in FIG. 14A. The rotational direction locking portion 230 plays the role of interposing between the steel member 210 and the CFRP member 220 to prevent relative rotation, and serrations and splines can be mentioned as a representative example, but other similar shapes Can also be adopted. If the rotational direction locking portion 230 takes the form of serrations or splines, the teeth and grooves extend axially (FIG. 14A) and appear as a series of asperities as shown at 32 in the cross section (FIG. 14B).

A knurled surface can be mentioned as another form of the rotational direction locking portion 230. That is, as shown in FIG. 15, in order to increase the bonding strength between steel member 210 and CFRP member 220, uneven surface 234 is formed on the outer peripheral surface of large diameter portion 214 of steel member 210 by knurling. The convex portion may be made to bite into the inner circumferential surface of the CFRP member 220.

The boot groove 222 of the CFRP member 220 is formed by machining after heat curing of the CFRP member 220, or when heat curing the CFRP member 220, the die is pressed from the outer diameter side toward the axial center by pressing Depending on the situation, it may be baked at the same time.
In the case where serrated, splined or knurled projections and recesses are formed on both ends of the large diameter portion 214 of the steel member 210, the steel member 210 may be formed by a filament winding method or a sheet winding method. A carbon fiber containing a resin or a sheet of a carbon fiber containing a resin may be directly wound, and then the steel member and the CFRP member may be composited by a thermal effect (curing). In this case, the CFRP member is shrunk by heat curing, whereby the inner diameter surface of the CFRP member 220 bites into the concavo-convex portion provided in the steel member 210, thereby being integrated. The boot groove is formed as described above.

The effects of the embodiment described above with reference to FIGS. 10-15 are as follows.

The shaft S1 for power transmission shaft affects the torsional rigidity by forming a CFRP member 220 which is shaped like a pipe by attaching boot grooves at both ends of the outer diameter surface and fitting it to the large diameter portion 214 of the steel member 210. The large diameter portion can be elongated in the axial direction, and high rigidity can be achieved.

By forming the boot groove 222 of the CFRP member 220 by machining, the boot groove 222 can be easily formed into an arbitrary shape (advantage by machining).

By forming the boot groove 222 of the CFRP member 220 by press working, when forming a steady shape, cutting becomes unnecessary, and cost reduction can be achieved.

By fixing the steel member 210 and the CFRP member 220 with the adhesive 224, the bonding strength between the steel member 210 and the CFRP member 220 is increased.

The adhesive reservoir 226 is provided on the outer periphery of the large diameter portion 214 of the steel member 210, so that a slight adhesive layer (see FIG. 13) existing between the steel member 210 and the CFRP member 220 temporarily extends in the radial direction. Even if the equal members are fitted in a biased state and the circumferentially discontinuous bonding state is achieved, the adhesive reservoir portion can be adhesively fixed on the entire circumferential surface regardless of the bias.

By press-fitting the pipe-like CFRP member 220 and the steel member 210 via the rotational direction locking portion, the bonding strength of the steel member 210 and the CFRP member 220 is further increased.

By providing the rotational direction locking portions at both ends of the steel member 210, it is possible to securely fix the most loaded place of the combined portion in a state where the shaft is twisted.

By forming the rotational direction locking portion into a concavo-convex shape by serration or spline or knurling, formability to the steel member 210 by machining becomes easy.

102 hollow shaft 104 intermediate portion 106 connection portion 108 tapered portion 110a, 110b boot mounting groove 112 spline 114 retaining ring groove 116 bulging portion 118 minimum diameter portion 120 FRP layer 122 adhesive 124 laser welding 126 surface treatment S1 intermediate shaft 210 steel member 212 hollow portion 214 large diameter portion 216 small diameter portion 218 serration shaft 220 CFRP member 222 boot groove 224 adhesive 226 adhesive reservoir 230 rotational direction locking portion 232 serration shaft 234 knurled surface

Claims (20)

An intermediate shaft in a drive shaft comprising an intermediate shaft and a constant velocity universal joint attached to both ends, wherein the intermediate shaft comprises an intermediate portion and connection portions on both sides of the intermediate portion, and is hollow over the entire length A drive shaft intermediate shaft having a shaft and a fiber reinforced resin layer provided on the outer periphery of the intermediate portion. An intermediate shaft for a drive shaft according to claim 1, wherein a fiber reinforced resin formed into a pipe shape is fitted on the outer periphery of said intermediate portion of said hollow shaft. 3. An intermediate shaft for a drive shaft according to claim 2, wherein a molding length of the pipe-shaped fiber reinforced resin is a multiple of a required length for fitting to the hollow shaft. 4. An intermediate shaft for a drive shaft according to claim 2, wherein an adhesive is used to join the fiber reinforced resin formed into a pipe shape and the hollow shaft. The drive shaft intermediate shaft according to claim 1, wherein a bundle of carbon fibers impregnated with a resin is wound around the outer periphery of the middle portion of the hollow shaft. The intermediate shaft for a drive shaft according to claim 1, wherein a carbon fiber reinforced resin formed into a sheet shape is wound around an outer periphery of the intermediate portion of the hollow shaft. 7. An intermediate shaft for a drive shaft according to claim 5, wherein the angle of the carbon fiber with respect to the axis of the hollow shaft is 45 degrees. The intermediate shaft for a drive shaft according to claim 5 or 6, wherein the angle of the carbon fiber with respect to the axis of the hollow shaft is any angle larger than 0 and 45 ° or less, and two or more types of angles are combined. The drive shaft intermediate shaft according to any one of claims 1 to 6, wherein a contour of an outer peripheral surface of the intermediate portion of the hollow shaft is a polygon. The drive shaft intermediate shaft according to any one of claims 1 to 7, wherein an axial groove is provided on an outer peripheral surface of the intermediate portion of the hollow shaft. The intermediate shaft is a composite of a hollow steel member consisting of a central large diameter portion and small diameter portions at both ends, and a CFRP member fitted to the outer periphery of the large diameter portion of the steel member. The drive shaft intermediate shaft according to claim 1, wherein a boot groove is provided on the outer peripheral surface. The drive shaft intermediate shaft according to claim 11, wherein the pipe-shaped CFRP member is fitted to the large diameter portion of the steel member. The drive shaft intermediate shaft according to claim 11 or 12, wherein a boot groove of the CFRP member is formed by machining. The drive shaft intermediate shaft according to claim 11 or 12, wherein a boot groove of the CFRP member is formed by pressing. The drive shaft intermediate shaft according to any one of claims 11 to 14, wherein the steel member and the CFRP member are fixed by an adhesive. The intermediate shaft for a drive shaft according to any one of claims 11 to 15, wherein an adhesive reservoir is provided on the outer periphery of the large diameter portion of the steel member. The drive shaft intermediate shaft according to any one of claims 11 to 14, wherein the steel member is press-fitted to the pipe-like CFRP member via the rotational direction locking portion. The drive shaft intermediate shaft according to claim 17, wherein the rotational direction locking portion is provided at both ends of the large diameter portion of the steel member. The drive shaft intermediate shaft according to claim 17 or 18, wherein the rotational direction locking portion is a serration or a spline. The drive shaft intermediate shaft according to claim 17 or 18, wherein the rotational direction locking portion is a knurled surface.

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