JP2005279098A - Fiber-reinforced resin shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the bending strength of a lightweight golf club shaft. <P>SOLUTION: The region with a head side distal end 11 of the golf club shaft 10 made of a layered body of fiber-reinforced prepregs 21-25 as a head side end and with the position apart from the head side end by 400-700 mm as a grip side end is a distal end reinforced region S, and a straight layer B with the reinforced fiber F23 oriented at the angle from 0 to 10° in the axial direction of the shaft is disposed on the outside of a bias layer A with reinforced fibers F21 and F22 oriented at an angle from 25 to 65° in the axial direction of the shaft. In a border straight layer (a distal end border straight layer B1) circumscribed to the bias layer A, at least the percentage content of resin in a region disposed in the distal end reinforced region S is higher than that in the bias layer A. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fiber reinforced resin shaft, and is particularly preferably used as a golf club shaft made of a prepreg laminate, and is intended to improve the bending strength on the head mounting side.

  In recent years, in golf club shafts, in order to improve the hitting speed and stability, the weight is concentrated on the head, and the shaft tends to be lighter. Therefore, the material of the shaft is mainly fiber reinforced resin such as carbon prepreg which is lightweight and has appropriate flexibility. However, the weight reduction of the shaft causes a decrease in strength. In particular, the head-side tip has a small diameter and a large impact force is applied at the time of hitting the ball, so that the shaft may be broken due to insufficient strength.

In addition, a shaft made of a laminate of conventional fiber reinforced resin materials is usually wound with a straight layer in which reinforcing fibers are arranged substantially parallel to the shaft axis outside the bias layer in which the reinforcing fibers are inclined with respect to the shaft axis. Therefore, the bending strength is improved.
The bias layer has a relatively high resin content because it is difficult to mold if the resin content is low, while the straight layer has a low resin content to reduce the weight of the shaft.
However, the shaft tip where shaft bending is most likely to occur is often determined to have a constant outer diameter according to the head neck diameter. If it increases, it becomes necessary to make the straight layer thinner accordingly, resulting in a decrease in strength, and shaft breakage tends to occur at the boundary between the bias layer and the straight layer.
Accordingly, various proposals have been made to improve the strength of the shaft on the head end side.

For example, in Japanese Patent Application Laid-Open No. 10-15129 (Patent Document 1), the bending strength at the head tip side of the shaft and the bending rigidity at the shaft tip are regulated within a certain range, thereby preventing the bending of the shaft tip while preventing the bending rigidity. It has been proposed to optimize.
In JP-A-2002-282398 (Patent Document 2), a bias layer is laminated on the inner peripheral side and a straight layer is laminated on the outer peripheral side to produce a shaft, and 0 ° compressive strength δ and in-plane shear strength of the bias layer are produced. It has been proposed to increase the torsional strength of the shaft by defining SI and the tensile elastic modulus E of the reinforcing fiber of the bias layer.

However, as described above, shaft breakage often occurs at the boundary between the bias layer and the straight layer as described above. Therefore, it is necessary to increase the strength at the boundary portion. The configuration of Document 2 is not a sufficient measure for preventing breakage that tends to occur at the boundary.
Japanese Patent Laid-Open No. 10-15129 JP 2002-282398 A

  The present invention has been made in view of the above problems, and in particular, has a high bending strength and a light weight capable of preventing breakage that easily occurs at the boundary between the bias layer and the straight layer at the tip of the shaft, and is particularly suitable as a golf club shaft. It is an object to provide a fiber-reinforced resin shaft to be used.

In order to solve the above-mentioned problems, the present invention provides a fiber-reinforced resin shaft made of a prepreg laminate in which reinforcing fibers are impregnated with a resin.
A bias layer in which reinforcing fibers are oriented at an angle of 25 ° to 65 ° with respect to the axial direction of the shaft, and a straight layer in which reinforcing fibers are oriented at an angle of 0 ° to 10 ° with respect to the axial direction of the shaft And
In the straight layer that circumscribes or / and inscribes the bias layer, the resin content of the bias layer in the region where the straight layer is circumscribed to a position that is at least 400 mm and 700 mm away from at least one end. Further, the present invention provides a fiber-reinforced resin shaft characterized in that the resin content of the circumscribed straight layer is increased.

In this way, by making the straight layer circumscribed or / and inscribed in contact with the bias layer have a high resin content, it is possible to improve the toughness of the straight layer and increase the bending strength, thereby preventing the occurrence of damage such as cracks. And the growth of cracks from damaged parts can be suppressed.
And usually, since the straight layer has a smaller number of turns than the bias layer, the straight layer in contact with the bias layer among the straight layers, in particular, only the straight layer circumscribing the bias layer has a high resin content, Weight increase can be suppressed.
Furthermore, since cracks and breaks are most likely to occur at the end where the bias layer and the straight layer are in contact, increasing the resin content of the straight layer up to a position at least 400 to 700 mm away from the end. By limiting the region in which the resin content is increased to a minimum, the occurrence of cracks from the end can be effectively suppressed while suppressing an increase in weight.
The position separated from the end by a distance of 400 to 700 mm is preferably about 500 mm, and the resin content of the straight layer is set higher than the resin content of the bias layer in the range of 500 mm from the tip. It is effective in preventing breakage and cracks.

  In the cross section of the shaft in which the resin content of the straight layer is increased, the thickness of the bias layer is not more than half of the total thickness, preferably about one third. Thereby, the thickness of the straight layer effective for improving the bending strength can be increased, and shaft breakage can be effectively prevented.

  Where the straight layer is laminated in contact with the bias layer, the bias layer and the straight layer are often laminated on the end of the shaft, particularly when the shaft is tapered in the axial direction on the small diameter end side. It is not limited to the case. That is, even when a straight layer is laminated on the bias layer in the intermediate region of the shaft, the above configuration prevents the occurrence of folds and cracks that are likely to occur on the end side of the boundary portion between the bias layer and the straight layer. Can do.

The straight layer circumscribing the bias layer has an elastic modulus of the reinforcing fiber of 5 t / cm ² or more and 20 t / cm ² or less, and
It is preferable that the resin content rate of the circumscribed straight layer is 1.2 times or more and 2.3 times or less with respect to the resin content rate of the bias layer in a portion where the straight layer is circumscribed.

  In this way, by increasing the elastic modulus of the reinforcing fiber of the straight layer circumscribing the bias layer (hereinafter, the straight layer is referred to as the boundary straight layer) within the above range, the rigidity of the shaft tip is increased. Therefore, when the shaft is used as a golf club shaft, it is possible to improve the hit feeling and launch conditions. Moreover, the occurrence and growth of shaft damage can be suppressed by setting the resin content within the above range to a high content. Therefore, it is possible to achieve both good hitting feeling and high bending strength in a balanced manner.

Wherein the elastic modulus of the reinforcing fibers of the boundary straight layer is within the above range, while reinforcing strengthening by straight layer is lowered less than 5t / cm ^2, greater than 20t / cm ² when hitting feel the rigidity becomes too large This is due to the worsening.
In addition, the resin content of the boundary straight layer is within the above range with respect to the resin content of the bias layer. If the resin content is less than 1.2 times, toughness and bending strength can be improved to the expected level. If the ratio exceeds 2.3 times, the weight increases and the outer diameter of the shaft is regulated, the resin content of the bias layer must be reduced, and the effect of arranging the bias layer cannot be expected. Due to

The lower limit of the elastic modulus of the reinforcing fiber of the straight layer other than the boundary straight layer is 5 t / cm ² or more, preferably 20 t / cm ² or more, and the upper limit is 100 t / cm ² or less, preferably 40 t / cm ² or less. is there.
The lower limit is set to 5 t / cm ² or more because if the elastic modulus is too low, the shaft rigidity becomes low, it becomes difficult to swing, and the strength becomes low. The upper limit is set to 100 t / cm ² or less because the rigidity of the shaft is increased, the swing is difficult, and the strength is also decreased.
In order to further increase the bending strength, it is preferable to lower the elastic modulus of the reinforcing fiber as it goes to the outer layer, regardless of the straight layer and the bias layer, except for the boundary straight layer in which the reinforcing fiber has a particularly low elastic modulus. .

The shaft has a tapered shape in which the diameter of the other end is enlarged from one end, and is provided with a tip reinforcing region in which the straight layer circumscribing the bias layer is disposed on one end side of the small diameter,
The resin content of the straight layer disposed in the tip reinforcing region is 30 wt% or more and 45 wt% or less, and the resin content of the bias layer to which the straight layer is circumscribed is 20 wt% or more and 25 wt% or less. preferable.

As described above, when the shaft has a tapered shape whose diameter increases from one end side to the other end side like a golf club shaft, the tip reinforcing region in which the boundary straight layer circumscribing the bias layer is arranged on the small diameter end side Is preferably provided.
In the boundary straight layer locally disposed in the tip reinforcing region, the resin content is preferably 30% by weight or more and 45% by weight or less, and the resin content of the bias layer disposed in the tip reinforcing region is included. The rate is preferably 20% by weight or more and 25% by weight or less.

The resin content of the tip boundary straight layer is 30% by weight or more and 45% by weight or less because if it is less than 30% by weight, the effect of improving the bending strength cannot be sufficiently obtained, and if it exceeds 45% by weight, the weight increases. Due to the inability to control. More preferably, it is 35 wt% or more and 45 wt% or less.
The reason why the resin content of the bias layer is 20% by weight or more and 25% by weight or less is that, if it is less than 20% by weight, in the production method by the sheet winding method, the adhesion between the sheets is lowered and the workability is inferior. If it exceeds 25% by weight, it results in an increase in weight.

The resin content of the straight layer other than the boundary straight layer in the tip reinforcing region has a lower limit of 15% by weight or more, preferably 20% by weight or more, and an upper limit of 40% by weight or less, more preferably 30% by weight or less. Is preferred.
This is because if the amount is less than 15% by weight, the strength of the shaft decreases, and if it exceeds 40% by weight, the weight increases.

  And it is preferable that the resin content rate of the boundary straight layer of the said tip reinforcement area | region is made higher than the resin content rate of any other straight layer arrange | positioned in this tip reinforcement area | region. Thus, by increasing the resin content of only the specific part, the weight increase of the shaft can be minimized.

When the shaft is a tubular golf club shaft, a tip reinforcing region including the straight layer that circumscribes the bias layer from the head side tip is provided, and the resin content of the straight layer in the tip reinforcing region is The straight layer is higher than the resin content of the bias layer circumscribed.
As described above, in the golf club shaft, the strength is insufficient at the tip on the head mounting side and the shaft is likely to be broken. Therefore, a straight layer is externally connected to the bias layer at the tip on the head mounting side, Providing a tip reinforcing region in which the resin content is higher than the resin content of the bias layer makes it possible to suppress or prevent the shaft from being bent or cracked at the tip of the head mounting side.

In the golf club shaft, an inner diameter enlarged portion whose diameter is greatly increased with respect to the inner diameter on the head side is provided at a position separated by 50 mm or more and 400 mm or less from the head side tip, and the tip reinforcing region includes the inner diameter enlarged portion. It is preferable to use the area.
When increasing the wall thickness in order to increase the strength of the small diameter tip on the head mounting side of the shaft, the outer diameter of the shaft is specified, so the inner diameter is decreased to increase the wall thickness, and an inner diameter enlarged portion is provided. . The inner diameter enlarged portion changes its strength because the inner diameter taper changes. Since stress concentration is likely to occur at locations where the strength changes, disposing the boundary straight layer having a high resin content at the inner diameter enlarged portion compensates for insufficient strength of the inner diameter enlarged portion and effectively increases the bending strength. be able to. In addition, the impact at the time of hitting can be reduced, and the hit feeling can be made soft.

The resin content of the straight layer disposed in the region including the inner diameter enlarged portion is preferably higher on the grip side than on the head side.
Further, in order to achieve both the damage prevention due to the inner diameter change and the damage prevention between the bias layer and the straight layer, the minimum resin content of the resin content of the tip boundary straight layer should be 35% by weight or more. preferable.

As described above, according to the fiber-reinforced resin shaft according to the present invention, it is possible to effectively prevent the shaft from being bent or cracked easily from the end of the laminated region at the position where the straight layer is in contact with the bias layer.
In particular, in the case of a golf club shaft, it is possible to effectively prevent bending of the shaft by increasing the bending strength of the tip end portion of the shaft on the head mounting side where breakage is likely to occur while maintaining the lightness of the shaft.
Further, by lowering the elastic modulus of the reinforcing fiber of the boundary straight layer circumscribing the bi-hus layer, it is possible to suppress the increase in rigidity only at the tip portion and to improve the feel of hitting and the conditions for launching.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIGS. 1 to 3 show a golf club shaft 10 according to a first embodiment of the present invention, and the shaft 10 is formed of a long tapered tubular body made of a laminate of fiber reinforced prepregs 21 to 26. A head 13 is attached to the head end 11 on the small diameter side, and a grip 14 is attached to the rear end 12 on the grip side on the large diameter side. The total length of the shaft 10 is 800 mm to 1300 mm, and in this embodiment is 1200 mm.

As shown in FIG. 2, the inner diameter of the shaft 10 is provided with a first taper changing point 15 at a position within a range of 50 mm to 400 mm from the head-side tip 11, in this embodiment, at a position of 200 mm. The second taper changing point 16 is provided at a position 20 mm to 150 mm apart from the point 15 on the grip side, in this embodiment at a position 50 mm apart. A region sandwiched between the first taper changing point 15 and the second taper changing point 16 is defined as an inner diameter enlarged portion 17 having an inner diameter taper larger than that of the other regions. A region including the inner diameter enlarged portion 17 is a tip reinforcing region S.
The inner diameter of the region on the head side with respect to the inner diameter enlarged portion 17 is 4 mm to 6 mm, the thickness is 2 mm to 3 mm, and the inner diameter of the region on the grip side with respect to the inner diameter enlarged portion 17 is 6.5 mm to 8 mm. Is 0.5 mm to 2 mm.

  As shown in FIG. 3, the shaft 10 is formed by winding a prepreg in which reinforcing fibers are aligned and impregnated with resin around a mandrel 20 by a sheet winding method, and then winding a polypropylene tape (not shown). The shaft 10 is manufactured by heating and pressing in an oven to cure the resin and integrally molding it, and pulling out the mandrel 20 to manufacture the shaft 10. The shaft surface is polished and then cut at both ends and painted.

  The prepreg constituting the shaft 10 includes prepregs 22 and 23 that form the prepreg 21 and the bias layer A, and prepregs 24 to 26 that form the straight layer B. The prepreg 24 circumscribes the prepreg 23 in the tip reinforcing region S. Thus, the prepregs 21, 22, 23, 24, 25, and 26 are laminated in this order from the inner layer side.

The prepregs 21 to 26 are all impregnated with reinforcing fibers F21, F22, F23, F24, F25, and F26 made of carbon fiber with an epoxy resin, and the thickness is 0.01 mm to 0.3 mm, preferably 0.05 mm to Within the range of 0.15 mm. Further, the prepreg basis weight is in the range of ^{5g / m 2 ~500g / m 2} , carbon fiber basis weight is in the range of ^{5g / m 2 ~300g / m 2} , bending at 0 degrees to the fiber direction strength I have used within the scope of ^{100kgf / mm 2 ~200kgf / mm 2} .
In addition, glass fiber and boron fiber may be used for the reinforcing fiber, and thermosetting resin other than epoxy resin may be used for the resin.

Specifically, the prepreg 21 has an orientation angle of 0 °, an elastic modulus of 30 t / mm ² , and a resin content of 25% by weight.
The prepregs 22 and 23 have a length that extends over the entire length of the shaft, and a width that is wound twice at the head-side tip 11. The reinforcing fiber F22 has an orientation angle of −45 ° with respect to the shaft axis, and the reinforcing fiber F23 has an orientation angle of + 45 ° with respect to the shaft axis, both of which have an elastic modulus of 30 t / mm ² . In both prepregs 22 and 23, the resin content is uniformly 25% by weight. These prepregs 22 and 23 are wound around the mandrel 20 in an overlapped state.

The prepreg 24 forms a tip boundary straight layer B1 as a shape arranged in the tip reinforcing region S.
Specifically, as shown in FIG. 3, the width is a width that is wound once at the head-side tip 11, and the length is a substantially trapezoidal shape in which the long side is 700 mm and the short side is 500 mm. The reinforcing fiber F24 has an orientation angle of 0 ° with respect to the shaft axis and an elastic modulus of 5 t / mm ² . The resin content is uniformly 35% by weight.

The prepreg 25 has a length that extends over the entire length of the shaft and a width that is wound twice at the head-side tip 11 to form the outer layer-side straight layer B2. The reinforcing fiber F25 has an orientation angle of 0 ° with respect to the shaft axis and an elastic modulus of 24 t / mm ² . The resin content is uniformly 25% by weight.

The prepreg 26 has a shape that is disposed at the head-side tip of the shaft 10.
Specifically, as shown in FIG. 3, the width is a width that is wound three times at the head-side tip 11, and the length is a right triangle having a long side of 400 mm and a short side of 0 mm. The reinforcing fiber F26 has an orientation angle of 0 ° with respect to the shaft axis, and an elastic modulus of 24 t / mm ² . The resin content is uniformly 25% by weight.

In the golf club shaft 10 having the above-described configuration, the resin content of the tip boundary straight layer B1 and the inner straight layer B0 arranged in the tip reinforcing region S of the shaft 10 is such that the other bias layers A and the outer straight layer B2 have a resin content. The shaft 10 that is higher than both and is 1.4 times the resin content of the bias layer A and is within the range of 1.2 times to 2.3 times, so that the shaft 10 is susceptible to strong impact. The bending strength can be increased by effectively preventing breakage of the tip portion of the metal layer, particularly damage at the boundary between the bias layer A and the straight layer B, which has been easy to occur conventionally.
Further, since the tip boundary straight layer B1 is also disposed in the region of the inner diameter enlarged portion 17, the insufficient strength of the inner diameter enlarged portion 17 can be compensated, and the bending strength can be increased from this point.
Further, the elastic modulus of the reinforcing fibers of the tip boundary straight layer B1 are the low elastic modulus in the range of ^{5t / cm 2 ~20t / cm 2} , that the extreme rigidity increases at the tip portion of the shaft 10 It is possible to suppress and make the hit feeling and the condition of launching favorable by appropriate bending.
Furthermore, since the straight layer having a high resin content is the front end boundary straight layer B1 wound around only the front end of the shaft 10, the weight increase can be minimized and the light weight can be maintained.

  4 and 5 show a shaft 10 'according to the second embodiment of the present invention. The length of the prepreg 24' constituting the boundary straight layer B1 'is the length over the entire length of the shaft, and the resin content of the prepreg 24' is shown. Is higher at the portion that hits the tip reinforcing region S and lower at the portion that hits the grip side than the tip reinforcing region.

Specifically, in the prepreg 24 ′, the resin content of the tip portion 24 a ′ within the range of 350 mm from the head-side tip 11 is 30 wt%, and the resin content of the other portion 24 b ′ is 25 wt%. Further, the elastic modulus of the reinforcing fiber F23 is uniformly 24 t / cm ² .

Further, as shown in FIG. 5, the inner diameter of the shaft 10 is provided with a first taper changing point 15 ′ at a position 200 mm from the head-side tip 11, and a position separated from the first taper changing point 15 ′ by 150 mm toward the grip side. Is provided with a second taper changing point 16 '. A region sandwiched between the first taper changing point 15 ′ and the second taper changing point 16 ′ is an inner diameter enlarged portion 17 ′ having a larger inner diameter taper than the other regions, and the second taper changing point from the head-side tip 11. A region including the inner diameter enlarged portion 17 ′ up to 16 ′ is defined as a tip reinforcing region S.
The inner diameter of the region closer to the head than the inner diameter enlarged portion 17 ′ is 4 mm to 6 mm, the thickness is 2 mm to 3 mm, and the inner diameter of the region closer to the grip than the inner diameter enlarged portion 17 ′ is 6.5 mm to 8 mm. The wall thickness is 0.5 mm to 2 mm.
In other respects, the configuration is the same as that of the first embodiment, so that the same reference numerals are given and description thereof is omitted.

  Also in the present embodiment, among the prepregs 23 ′ constituting the boundary straight layer B1 circumscribing the bias layer A, the resin content rate is changed only by the tip portion 23a ′ arranged in the tip portion reinforcing region S of the shaft 10. The bias layer A and the straight layer B2 on the outer layer side are higher than the bias layer A and 1.2 times the resin content of the bias layer A. Accordingly, it is possible to prevent the occurrence and growth of damage at the boundary between the bias layer A and the straight layer B, while suppressing the increase in weight, and to compensate for the insufficient strength of the inner diameter enlarged portion 17 ′ and increase the shaft strength. .

  In addition, this invention is not limited to the said embodiment. In particular, in the first embodiment, the prepreg 24 that forms the tip boundary straight layer B1 gradually increases the resin content from the head side toward the grip side, and the minimum resin content is the bias layer A. However, in this case, the strength of the inner diameter enlarged portion 17 can be improved more effectively.

(Example)
In order to confirm the above, Examples 1 to 3 and Comparative Examples 1 to 3 of the golf club shaft of the present invention will be described in detail.

  As shown in Table 1 below, the prepreg 21 that forms the inner straight layer BO of the golf club shaft, the prepregs 22 and 23 that form the bias layer A, the prepreg 24 that forms the boundary straight layer B1, and the outer straight layer B2 are formed. Examples 1 to 3 and comparative examples 1 to 3 having different elastic modulus and resin content of the reinforcing fibers of the prepregs 25 and 26 to be manufactured were prepared, the bending fracture strength was measured, and the feeling was obtained by an actual hit test. The launch angle was also examined, and the results are shown in Table 2. The head combined with the shaft was made of Ti, the volume was 400 cc, the weight was 200 g, the grip (Dunlop original grip) was 50 g, and the club count was # 1.

  All of Examples 1 to 3 and Comparative Examples 1 to 3 were produced by the sheet winding method, and the constituent materials of the prepregs 21 to 26 and the laminated configuration of the prepregs 21 to 26 were the same as those in the first embodiment. That is, any of the prepregs 21 to 26 is impregnated with an epoxy resin using carbon fiber as a reinforcing fiber, and the prepreg 21 with an orientation angle of 0 ° of the reinforcing fiber F21 is wound from the inner layer side to form a straight layer BO, which is reinforced. The bias layers A are formed by winding the prepregs 22 and 23 having the orientation angles of the fibers F22 and F23 of −45 ° and + 45 °, and the prepreg 24 having the orientation angle of the reinforcing fibers F24 of 0 ° is formed on the outer periphery thereof. The front end boundary straight layer B1 was wound around the outer periphery, and the outer layer-side straight layer B2 was formed around the outer periphery by winding the prepregs 25 and 26 having the orientation angles of the reinforcing fibers F25 and F26 of 0 °.

(Example 1)
The elastic modulus and resin content of the reinforcing fibers of the prepregs 21 to 26 were the same as those in the first embodiment. That is, the prepreg 21 of the straight layer BO and the prepregs 22 and 23 of the bias layer A have a reinforcing fiber elastic modulus of 30 t / mm ² and a uniform resin content of 25% by weight, and the prepreg 24 of the tip boundary straight layer B1. The reinforcing fiber elastic modulus is 5 t / mm ² and the resin content is uniformly 35% by weight. The prepregs 25 and 26 of the outer layer side straight layer B2 have a reinforcing fiber elastic modulus of 24 t / mm ² and a uniform resin content. 25% by weight. Thereby, the resin content of the tip boundary straight layer B1 was 1.4 times the resin content of the bias layer A.

(Example 2)
The resin content of the tip boundary straight layer B1 is reduced to 30% by weight, the reinforcing fiber elastic modulus is increased to 24 t / mm ^{2 than in} Example 1, and the others are the same as in Example 1. Therefore, the resin content of the tip boundary straight layer B1 is 1.2 times the resin content of the bias layer A.

(Example 3)
The resin content of the tip boundary straight layer B1 was higher than that of Example 1 to be 57.5% by weight, the reinforcing fiber elastic modulus was increased to 24 t / mm ² , and the others were the same as those of Example 1. Therefore, the resin content of the tip boundary straight layer B1 is 2.3 times that of the bias layer A.

(Comparative Example 1)
While increasing the resin content of the bias layer A as compared with Example 1, the resin content of the tip boundary straight layer B1 was decreased to the same 30% by weight. Others were the same as those in Example 1.

(Comparative Example 2)
The resin content of the tip boundary straight layer B1 was lowered to 20% by weight from that of Example 1, and 0.8 times the resin content of the bias layer A. The reinforcing fiber elastic modulus of the tip boundary straight layer B1 was increased to 30 t / mm ² . Others were the same as Example 1.

(Comparative Example 3)
The resin content of the tip boundary straight layer B1 was further increased to 67.5% by weight than in Example 3, and 2.5 times the resin content of the bias layer A. Others were the same as Example 3.

(Measurement of 3 point bending fracture strength)
The three-point bending fracture strength is a fracture strength determined by the Product Safety Association. As shown in FIG. 6, the shaft 10 was supported at three points, a load F was applied from above, and a load value (peak value) when the shaft 10 was broken was measured (n = 5). The measurement point was 90 mm (T point) from the head-side tip 11 of the shaft 10 and the span of the support point 31 was 150 mm.

(Actual test)
The Ti head was mounted, and 10 testers hit 20 balls for each shaft. The hit feeling was evaluated from a maximum of 5 points (the higher the score, the better the hit feeling), and the launch angle was also measured. Table 1 shows the average value for the hit feeling. The average handicap of these 10 testers was 9, and the average age was 48 years old.

  As can be confirmed from Tables 1 and 2, it was found that Examples 1 to 3 all had high bending fracture strength, good feel in the actual hit test, and good launch angle. This is because, in all of Examples 1 to 3, the resin content of the tip boundary straight layer B1 was higher than the resin content of the bias layer A, and was in the range of 1.2 times to 2.3 times. The toughness of the tip boundary straight layer B1 is increased, and the occurrence and growth of damage between the straight layer and the bias layer can be suppressed, and the reinforcing fiber elastic modulus of the tip boundary straight layer B1 is low. This is because the increase in rigidity of the shaft tip can be suppressed.

  Moreover, when Examples 1-3 were compared, it turned out that bending strength is also improving as Example 2 and Example 3 in which the resin content rate of front-end | tip part boundary straight layer B1 becomes higher.

  On the other hand, Comparative Examples 1 and 2 had low bending fracture strength. This is because in Comparative Examples 1 and 2, the resin content of the tip boundary straight layer B1 was less than or equal to the resin content of the bias layer A. Moreover, it turned out that all of Comparative Examples 1-3 have a bad hit feeling in an actual hit test, and a launch angle is not good. This is because in Comparative Example 1, the return of the head deteriorated due to the high resin content of A. In Comparative Example 2, the reinforcing fiber elastic modulus of the tip boundary straight layer B1 is high, and the rigidity of the shaft tip is increased too much. In Comparative Example 3, the resin content of B1 is too high, and the feeling of elasticity Due to the disappearance of

  The fiber-reinforced resin shaft of the present invention is most preferably used as a golf club shaft, but is also preferably used as a shaft for fishing rods.

1 is a schematic view of a golf club shaft according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part in the axial direction of the golf club shaft shown in FIG. 1. 2 shows a laminated structure of a mandrel and a fiber reinforced prepreg used in the golf club shaft shown in FIG. It is sectional drawing of the axial direction of the golf club shaft which concerns on 2nd embodiment of this invention. 5 shows a laminated structure of a mandrel and a fiber reinforced prepreg used for the golf club shaft shown in FIG. It is a figure which shows the measuring method of bending fracture strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Shaft 11 Head side front end 12 Grip side rear end 17, 17 'Inner diameter enlarged part 21-25, 23' Fiber reinforced prepreg A Bias layer B Straight layer B1 Tip part boundary straight layer B1 'Boundary straight layer B2 Outer layer side straight layer S Tip reinforcement area

Claims (6)

In a fiber reinforced resin shaft made of a laminate of prepregs in which reinforcing fibers are impregnated with resin,
A bias layer in which reinforcing fibers are oriented at an angle of 25 ° to 65 ° with respect to the axial direction of the shaft, and a straight layer in which reinforcing fibers are oriented at an angle of 0 ° to 10 ° with respect to the axial direction of the shaft And
In the straight layer circumscribed or / and inscribed in the bias layer, the resin content of the bias layer in the region where the straight layer is circumscribed to a position that is separated from at least one end by a distance of 400 mm to 700 mm. The fiber-reinforced resin shaft is characterized in that the resin content of the straight layer circumscribing is increased. The straight layer circumscribing the bias layer has an elastic modulus of the reinforcing fiber of 5 t / cm ² or more and 20 t / cm ² or less, and
2. The fiber reinforcement according to claim 1, wherein the resin content of the straight layer that circumscribes the straight layer is 1.2 times or more and 2.3 times or less of the resin content of the bias layer at a portion where the straight layer is circumscribed. Plastic shaft. The shaft has a tapered shape in which the diameter of the other end is enlarged from one end, and is provided with a tip reinforcing region in which the straight layer circumscribing the bias layer is disposed on one end side of the small diameter,
The straight layer disposed in the tip reinforcing region has a resin content of 30 wt% or more and 45 wt% or less, and the bias layer to which the straight layer is circumscribed has a resin content of 20 wt% or more and 25 wt% or less, and
The fiber content of the fiber reinforced resin according to claim 1 or 2, wherein the resin content of the straight layer circumscribing the bias layer is made higher than the resin content of another straight layer disposed in the tip reinforcing region. shaft.   The shaft is formed of a tubular golf club shaft, provided with a tip reinforcing region provided with the straight layer that circumscribes the bias layer from the tip on the head side, and the resin content of the straight layer in the tip reinforcing region is determined by the straight The fiber-reinforced resin shaft according to any one of claims 1 to 3, wherein the resin content of the bias layer to which the layer is circumscribed is higher than the resin content.   An inner diameter enlarged portion having a diameter that greatly increases with respect to the inner diameter on the head side is provided at a position separated from the head-side tip by a distance of 50 mm or more and 400 mm or less, and the tip reinforcing region is a region including the inner diameter enlarged portion. Item 5. A fiber-reinforced resin shaft according to Item 4.   The fiber-reinforced resin shaft according to claim 5, wherein the resin content of the straight layer disposed in the region including the inner diameter enlarged portion is higher on the grip side than on the head side.

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