JP2009014203A - Intermediate shaft with constant velocity joints connected to both ends - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow intermediate shaft having static strength and torsional fatigue strength greater than a solid one. <P>SOLUTION: The intermediate shaft with constant velocity joints 14, 15 connected to both ends is formed as a hollow shaft 11 where the ratio of the inner diameter to the outer diameter is 0.15-0.8. Induction hardening is applied to the outer peripheral surface of the hollow shaft 11 so that a hardening ratio as a ratio h/t of a hardening depth h from the hardened outer peripheral surface to the thickness t of the hollow shaft is 0.7-0.9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an intermediate shaft in which a constant velocity joint used for a drive shaft of an automobile or the like is connected to both ends.

As shown in FIG. 6 , the drive shaft for a front-wheel drive vehicle is constituted by an intermediate shaft 5 in which constant velocity joints 1 and 2 on the engine side and the wheel side and inner races 3 and 4 of the constant velocity joint are connected to both ends. ing. The constant velocity joint 1 on the engine side is a type capable of moving in the axial direction, and transmits torque by allowing changes in length and angle between the two joints when the suspension is suspended. The constant velocity joint 2 on the wheel side is a large angle type, and mainly enables deflection of the wheel by steering. In order to prevent the intermediate shaft 5 from interfering with the outer races 6 and 7 of the joint during the axial movement and angular displacement of the constant velocity joints 1 and 2, the outer diameters at both ends of the intermediate shaft 5 are limited, Strength and torsional fatigue strength are required.

  Conventionally, in order to ensure static strength and torsional fatigue strength within a limited outer diameter, the intermediate shaft 5 is made solid, and the surface of the shaft is rapidly cooled by heating with a high-frequency coil. In order to improve the static strength, it is effective to increase the quenching rate. However, if the quenching rate is excessively increased, the residual compressive stress on the shaft surface portion is reduced and the torsional fatigue strength is reduced. The quenching rate of the solid shaft is a ratio of the quenching depth from the outer peripheral surface that has been hardened to Hv 400 or more and the radius of the shaft. In order to satisfy the required values of the static strength and torsional fatigue strength, the intermediate shaft 5 has been subjected to surface quenching to a quenching rate of 0.4 to 0.6 by induction quenching.

  In recent years, hollowing of the intermediate shaft has been attempted in order to reduce the weight and increase the rigidity. However, when surface quenching is performed on a hollow shaft having the same diameter as that of the solid shaft at a quenching rate of 0.4 to 0.6, there is a problem that the strength is remarkably reduced as compared with the solid shaft. The quenching rate of the hollow shaft is a ratio of the quenching depth from the outer peripheral surface that is hardened to Hv 400 or more and the thickness of the shaft.

  The present invention has been made in order to eliminate such a conventional problem, and is to make the static strength and torsional fatigue strength of a hollow intermediate shaft more than solid.

In order to solve the above problems, the structural feature of the invention according to claim 1 is that in the intermediate shaft in which constant velocity joints are connected to both ends, the intermediate shaft has a ratio of the inner diameter to the outer diameter of 0.15 to 0.15. By making the hollow shaft of 0.8 and induction hardening the outer peripheral surface of the hollow shaft , the quenching rate which is the ratio of the quenching depth from the outer peripheral surface being quenched and the thickness of the hollow shaft is 0.7 It is set to -0.9 .

The structural feature of the invention according to claim 2 is that the outer circumference of the hollow shaft, wherein the constant velocity joint according to claim 1 is connected to both ends, the hardness is quenched to Hv400 or more by the induction hardening. The quenching rate, which is the ratio between the quenching depth from the surface and the thickness of the hollow shaft, is 0.7 to 0.9 .

The structural feature of the invention according to claim 3 is that in the intermediate shaft in which the constant velocity joint according to claim 2 is connected to both ends, the hollow shaft is made of 0.9 to 2.0% manganese, 0.06 It is formed of carbon steel containing ˜0.2% chromium and 0.0005˜0.005% boron and having a sulfur content reduced to 0.001˜0.005%.

In the invention according to claim 1 configured as described above, an intermediate shaft having constant velocity joints connected to both ends is made hollow with a ratio of inner diameter to outer diameter of 0.15 to 0.8, and the hollow shaft is The outer peripheral surface was induction- hardened at a quenching rate of 0.7 to 0.9 . In order to increase the quenching rate, the hollow shaft is heated to the vicinity of the inner peripheral surface in contact with the shaft hole, but the hollow shaft has air in the shaft hole, and this air is heated at the time of heating and from the steel material to the air layer. The hardness is linearly decreased because the heat conductivity is not rapidly cooled in the vicinity of the inner peripheral surface of the hollow shaft. Therefore, by appropriately setting the quenching conditions, the hollow shaft can be surface hardened at a quenching rate of 0.7 to 0.9, and the static strength and torsional fatigue strength can be maintained higher than those of the solid shaft or at the degree of identification. Can be made lighter and more rigid.

In the invention according to claim 2 configured as described above, the ratio between the quenching depth from the outer peripheral surface of the hollow shaft that has been hardened to Hv 400 or more by induction hardening and the thickness of the hollow shaft is set to 0. Since it is 7 to 0.9, the hollow shaft used for the drive shaft of automobiles, etc. is induction-hardened to the required hardness of Hv400 or more by the required depth from the outer peripheral surface, and the static strength and torsional fatigue strength of the hollow shaft are medium It is possible to reduce the weight and increase the rigidity while maintaining the actual shaft or more or the identification degree .

In the invention which concerns on Claim 3 comprised as mentioned above, the said hollow shaft is 0.9-2.0% manganese, 0.06-0.2% chromium, and 0.0005-0.005%. Since it is formed of carbon steel containing boron and sulfur content reduced to 0.001 to 0.005% , the induction hardening stability and hardenability are improved, and the hollow shaft is made 0.7 to 0.9. Thus, a hardened layer with high toughness can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1 , reference numeral 10 denotes a drive shaft for transmitting the rotation of the engine to a wheel. The hollow shaft 11 is an intermediate shaft, and inner races 12 and 13 are spline-fitted on both ends of the hollow shaft 11, respectively. It is composed of constant velocity joints 14 and 15. Both end portions 18 of the hollow shaft 11 are formed to have an outer diameter smaller than that of the central portion 19 so that the hollow shaft 11 does not interfere with the outer races 16 and 17 of the constant velocity joints 14 and 15 when the constant velocity joints 14 and 15 are angularly displaced. Has been. The central portion 19 has an increased outer diameter to increase rigidity. As an example, the hollow shaft 11 is provided with a shaft hole 20 on the axis by striking the outer periphery and shrinking the outer diameter to a predetermined dimension in a state where both ends are restricted so that the pipe material of carbon steel does not extend in the axis direction. It is formed by swaging, and the small-diameter portion 18 at both ends is thicker than the large-diameter portion 19 at the center by the contraction of the outer diameter. The dimensions of the hollow shaft 11 vary depending on the vehicle type, but generally the length is 200 to 650 mm, the outer diameters 16 to 30 mm at both ends 18, the inner diameter 3 to 21 mm, the outer diameter 29 to 39 mm at the central portion, and the inner diameter 20 to 31 mm. The ratio between the inner diameter and the outer diameter of the hollow shaft 11 is 0.15 to 0.8.

  The hollow shaft 11 is formed of carbon steel as described above. An example of the components contained in the carbon steel and the content (% by weight) thereof is as follows: carbon (C) 0.3 to 0.5%, silicon (Si ) 0.01-0.2%, manganese (Mn) 0.9-2.0%, phosphorus (P) 0.001-0.015, sulfur (S) 0.001-0.005%, chromium ( Cr) is 0.06 to 0.20, titanium (Ti) is 0.005 to 0.2%, and boron (B) is 0.0005 to 0.005%. Among these, manganese secures the stability of induction hardening, and chromium and boron improve induction hardening. By reducing the content of sulfur, the toughness of the induction-hardened layer is improved.

  The hollow shaft 11 is quenched by heating the outer peripheral surface of an intermediate product formed of the above-described material and shape with a high-frequency coil and quenching it with a quenching rate of 0.7 to 0.9. In order to increase the quenching rate, the hollow shaft 11 is heated to the vicinity of the inner peripheral surface in contact with the shaft hole 20. However, the hollow shaft 11 has air in the shaft hole 20, and this air is heated at the time of heating. In the vicinity of the inner peripheral surface of the hollow shaft 11, it is not rapidly cooled due to a decrease in the thermal conductivity from the air layer to the air layer. In the case of a solid shaft, the heat of the heated layer is rapidly transferred to the non-heated layer during quenching from the outer peripheral surface and is quenched, so the quenching hardness is increased to the heated depth and in the deeper part In the case of a hollow shaft, the hardness decreases linearly as shown in FIG. 2 because it is not rapidly cooled in the vicinity of the inner peripheral surface as described above. Therefore, the hollow shaft 11 can be surface quenched at a quenching rate of 0.7 to 0.9 by optimizing the quenching conditions. The quenching rate of the hollow shaft 11 is a ratio h / t between the quenching depth h from the outer peripheral surface hardened to a hardness of Hv400 or more and the shaft thickness t. Induction hardening is suitable for optimizing the quenching conditions for quenching the surface of the hollow shaft 11 at a quenching rate of 0.7 to 0.9 because the quenching conditions can be set and controlled accurately.

  According to the intermediate shaft in which the constant velocity joint according to the present invention is connected to both ends, the outer diameters of the both end portions 18 of the hollow shaft 11 are static in the both end portions 11 as compared with the conventional solid one having the same diameter. The strength and torsional fatigue strength are equal to or higher than the identification level. In FIG. 3, the horizontal axis shows the quenching rate, and the vertical axis shows the torsional fatigue strength of both ends of the solid and hollow shafts having the same diameter. It is above the required value in the range of 4 to 0.6, but decreases with increasing quenching rate and below the required value at 0.6 or higher. On the other hand, the torsional fatigue strength of the hollow shaft 11 indicated by a black circle is higher in a mountain shape than the required value when the quenching rate is in the range of 0.7 to 0.9. FIG. 4 shows the residual compressive stress of a conventional solid shaft surface hardened at a quenching rate of 0.5 and a hollow shaft according to the present invention surface hardened at a quenching rate of 0.8. The hollow shaft is a solid shaft. The residual compressive stress is increased by 18%.

  FIG. 5 shows the static strength of a solid and hollow shaft with a quenching rate of 0.5 and an end portion of the same diameter of the hollow shaft 11 with a quenching rate of 0.8. If the same 0.5 as the solid shaft is used, the static strength will be reduced by about 10%. Become strength.

  Thus, the intermediate shaft in which the constant velocity joint according to the present invention is connected to both ends has the same outer diameter as that of the conventional solid shaft, and the ratio of the inner diameter to the outer diameter is 0.15 to 0.8. The hollow shaft 11 is reduced in weight, and the surface of the hollow shaft 11 is quenched at a quenching rate of 0.7 to 0.9 so that the static strength and the torsional fatigue strength are equal to or higher than those of a solid one, and Since the outer diameter of the central portion 19 is increased to increase the rigidity, the rotation of the engine can be reliably and efficiently transmitted to the wheels with good responsiveness.

It is a front view of the intermediate shaft with which the constant velocity joint which concerns on this invention was connected with both ends. It is a figure which shows the hardness change between the outer peripheral surface of a hollow shaft, and an inner peripheral surface. It is a graph which shows the relationship between a hardening rate and torsional fatigue strength. It is a graph which shows the residual compressive stress of the conventional solid shaft and the hollow shaft which concerns on this invention. It is a graph which shows the relationship between a hardening rate and static strength. It is a figure which shows the intermediate shaft with which the conventional constant velocity joint was connected with both ends.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Drive shaft, 11 ... Hollow shaft (intermediate shaft), 14, 15 ... Constant velocity joint, 18 ... Both ends, 19 ... Center part, 21 ... Shaft hole.

Claims (3)

In the intermediate shaft in which the constant velocity joint is connected to both ends, the intermediate shaft is a hollow shaft having a ratio of the inner diameter to the outer diameter of 0.15 to 0.8, and the outer peripheral surface of the hollow shaft is induction-quenched, An intermediate in which constant velocity joints are connected to both ends , wherein the quenching rate, which is the ratio of the quenching depth from the quenched outer peripheral surface and the thickness of the hollow shaft, is 0.7 to 0.9 shaft. The quenching rate, which is the ratio of the quenching depth from the outer peripheral surface of the hollow shaft that has been hardened to Hv400 or higher by induction hardening and the wall thickness of the hollow shaft, is 0.7 to 0.9. An intermediate shaft in which the constant velocity joint according to claim 1 is connected to both ends. The hollow shaft contains 0.9 to 2.0% manganese, 0.06 to 0.2% chromium and 0.0005 to 0.005% boron, and has a sulfur content of 0.001 to 0. The intermediate shaft having the constant velocity joint according to claim 1 connected to both ends, formed of carbon steel reduced to 0.005% .

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