JP2017136635A - Power transmission system shaft for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide a hollow power transmission system shaft.SOLUTION: A constant-thickness steel tube 6 being a raw material is arranged inside an outer die 7 being a metallic mold having an inner surface shape 7a of the same shape as an external shape of a power transmission system shaft 1 while the tube 6 is separated from an inner surface of the metallic mold 7. Then the steel tube 6 is subjected to die forging in which the steel tube 6 is axially compressed between a pair of metallic molds which have base parts 8-1 and 8-2 capable of pressing respective both axial end surfaces 6-1 and 6-2 of the steel tube 6 in the axial direction of the steel tube 6 and core metal parts 9-1 and 9-2 having an outer surface shape of the same shape as an inner surface shape of both axial end parts 1-1 and 1-2 of the power transmission system shaft 1. Thereby a hollow power transmission system shaft 1 for an automobile having, toward an axial center portion from both axial end portions, thickness increase parts 3-1 and 3-2 thickest in the thickness, bulging parts 4-1 and 4-2 and a central part 5 is manufactured.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power transmission shaft for an automobile.

  Currently, there is a demand for weight reduction of automobiles from the viewpoint of protecting the global environment. For example, the reduction of the plate thickness by increasing the tension of the steel plate constituting the vehicle body and the weight reduction of various automobile-mounted components are being strongly promoted. For this reason, the manufacturing cost of automobiles tends to increase, and further cost reduction of various automobile-mounted parts is required.

  For example, in a power transmission system shaft that is connected to the left and right drive shafts to prevent torque steer, it has already been put into practical use to reduce the weight by hollowing out a conventional solid part.

  Such a hollow shaft often has a shape in which an outer diameter and an inner diameter change in the axial direction, and has been manufactured by the manufacturing methods listed below.

(A) Manufacturing method using friction welding This is a method in which the axial central portion and both axial end portions of a shaft having a shape whose outer diameter and inner diameter change in the axial direction are separately manufactured, and these are joined by friction welding. . The central part in the axial direction is manufactured by cutting a steel pipe, and both end parts in the axial direction are manufactured by cutting a forged product.

(B) Manufacturing method using rotary swaging This is a method of manufacturing both ends of a steel pipe having a constant axial thickness by reducing the thickness, reducing the diameter, and increasing the thickness by rotary swaging. Patent Document 1 discloses an invention for producing a hollow shaft by this method.

JP 2011-121068 A

  According to the manufacturing method using friction welding, it is possible to reduce the weight of the shaft because the axial central portion of the product can be thinned, but the axial central portion and both axial end portions are joined. Since it is necessary, an increase in manufacturing cost is inevitable. In addition, it is necessary to strictly control the quality of the joint, and the manufacturing cost increases from this aspect.

  In addition, the equipment for carrying out the manufacturing method using rotary swaging is very expensive, and the processing time by this manufacturing method is inevitably long, so the manufacturing cost increases.

  As described above, in the conventional technique, it has been difficult to inexpensively manufacture a hollow shaft such as a power transmission shaft.

  An object of the present invention is to provide a hollow power transmission system shaft.

  As a result of intensive studies in order to solve the above problems, the inventors have made a steel pipe with a constant thickness as a material inside an outer mold having the same inner shape as that of the product to be manufactured. And a base part capable of pressing both end faces in the axial direction of the steel pipe in the axial direction of the steel pipe, and an outer face shape provided on the base part and having the same shape as the inner face of the both end parts in the axial direction of the steel pipe It has been found that a hollow power transmission system shaft can be manufactured at low cost by compressing a steel pipe in the axial direction between a pair of molds having a core metal part, and further studies have been made to complete the present invention.

The present invention includes a thickened portion having the thickest wall thickness from both axial end portions to a central portion in the axial direction, a bulge portion having a larger outer diameter and a thinner wall thickness than the thickened portion, A hollow power transmission system shaft for an automobile having a central portion having a smaller outer diameter than the bulging portion,
The thickness of the thickened portion and the bulging portion is a hollow power transmission system shaft for an automobile that is larger than the hardness of the central portion.

  According to the present invention, a hollow power transmission system shaft can be provided at low cost.

FIG. 1 is an explanatory diagram schematically showing the implementation status of the present invention, in which FIG. 1 (a) shows before forging and FIG. 1 (b) shows after forging. FIG. 2 (a) is an explanatory view showing the range of dimensions of a steel pipe of a work material that can be used in the present invention, and FIG. 2 (b) is a dimension of a hollow power transmission system shaft that can be manufactured according to the present invention. It is explanatory drawing which shows the range. FIG. 3 is an explanatory view showing a modification of the pair of molds shown in FIGS. 1 (a) and 1 (b). FIG. 4A is an explanatory view showing the taper angle α when the cored bar portion has a tapered shape, and FIG. 4B shows the state when the molding is completed when the taper angle of the cored bar portion is constant. 4 (c) is an explanatory view showing a state at the time of completion of molding when the taper angle of the cored bar portion changes stepwise, and FIG. 4 (d) is a diagram showing the core. It is explanatory drawing which shows the state at the time of completion of shaping | molding in case the taper angle of a metal part changes continuously. FIG. 5 is an explanatory view showing another modification of the pair of molds shown in FIGS. 1 (a) and 1 (b). FIG. 6 is an explanatory view showing still another modification of the pair of molds shown in FIGS. 1 (a) and 1 (b).

  A hollow power transmission system shaft for an automobile according to the present invention and a method for manufacturing the same will be described with reference to the accompanying drawings.

1. Hollow power transmission shaft 1 for automobiles
FIG. 1 is an explanatory diagram schematically showing the implementation status of the present invention, in which FIG. 1 (a) shows before forging and FIG. 1 (b) shows after forging.

  As shown in FIG.1 (b), the hollow power transmission system shaft 1 for motor vehicles is manufactured in one process by a forge process by this invention.

  The power transmission shaft 1 includes thickening portions 3-1 and 3-2 and a bulging portion 4-1 from both axial end portions 2-1 and 2-2 toward the axial center portion 2-3. 4-2, and a central portion 5.

  The thickening portions 3-1 and 3-2 are the thickest portions among the thickening portions 3-1 and 3-2, the bulging portions 4-1 and 4-2, and the central portion 5. Furthermore, splines are engraved on the outer surfaces of the increased thickness portions 3-1 and 3-2.

  The bulging portions 4-1 and 4-2 are portions having a larger outer diameter and a smaller thickness than the thickening portions 3-1 and 3-2. The outer diameters of the thickened portions 3-1 and 3-2 gradually increase starting from the outer diameter of the thickened portions 3-1 and 3-2, and in the axial direction of the bulging portions 4-1 and 4-2. The maximum value is obtained at a substantially central position, and then gradually decreases toward the central portion 5. Further, the inner diameters of the thickening portions 3-1 and 3-2 gradually increase starting from the outer diameter of the thickening portions 3-1 and 3-2, and the axial direction of the bulging portions 4-1 and 4-2 It becomes the maximum value at the approximate center position, and then gradually decreases toward the center portion 5.

  The central part 5 has a smaller outer diameter than the bulging parts 4-1, 4-2. The thickness of the central portion 5 is substantially constant in the axial direction of the power transmission system shaft 1.

  Since the thickened portions 3-1 and 3-2 are thickened by forging, they are large and uniformly work-hardened. Here, “largely and uniformly” means that the hardness is about 200 to 250 Hv, and the variation in hardness (difference between the maximum hardness and the minimum hardness) is about 50 Hv.

  Further, the bulging portions 4-1 and 4-2 are also work hardened because the diameter is expanded by forging. The degree of work hardening is approximately 200 to 250 Hv, although it depends on the amount of swelling.

  Furthermore, since the diameter of the central portion 5 is also expanded by forging, it is work hardened uniformly. However, the degree of work hardening is small as compared with the thickened portion and the bulging portion, and the hardness is about 190 to 210 Hv, and the variation in hardness (difference between the maximum hardness and the minimum hardness) is about 20 Hv.

  The power transmission system shaft 1 has a power transmission system for automobiles by the work hardening of the thickening portions 3-1 and 3-2, the bulging portions 4-1 and 4-2 and the central portion 5 in this way. The characteristics to torsional strength and torsional fatigue required as the basic performance of the shaft are sufficiently improved.

  For example, the power transmission shaft 1 is made of an S45CB softening material (TS = 550 MPa class), but is not limited thereto. Since the power transmission shaft 1 is increased in thickness and expanded by axial pressing by forging, deformation due to processing is mainly compression deformation and has little tensile deformation. For this reason, the risk of breakage due to the high strength of the material is very low. Therefore, it goes without saying that a low-strength material can be used as compared with the S45CB softening material, but even if a high-strength material is used than the S45CB softening material, it can be molded without breaking.

  In the case of high-strength material than S45CB softened material, the axial load increases in proportion to the increase in strength. However, in the case of S35CB softened material, it is about 350 tons. Even mass production presses can be fully manufactured.

2. Manufacturing Method of Power Transmission System Shaft 1 First, as shown in FIG. 1A, an outer mold 7 having a steel pipe 6 having a constant thickness as a material and an inner surface shape 7a having the same shape as the outer shape of the power transmission system shaft 1. In the inside, it arrange | positions away from the inner surface of the outer type | mold 7. FIG.

  The gap W (mm) between the inner surface of the outer mold 7 and the outer surface of the steel pipe 6 in the radial direction of the steel pipe 6 is t (mm) at an arbitrary position in the axial direction of the steel pipe 6 and the outer diameter is When d (mm), W ≧ 0.2 × (t / d) is desirable because the load during processing can be reduced.

  Although not shown, the outer die 7 is divided into left and right parts in the same manner as a die used for general die forging, and is configured so that a molded product can be taken out. ing.

  Next, both end surfaces 6-1 and 6-2 in the axial direction of the steel pipe 6 are respectively pressed into the base portions 8-1 and 8-2 and the base portions 8-1 and 8-2 that can be pressed in the axial direction of the steel pipe 6. Core bars 9-1 and 9-2 having outer surface shapes 9-1a and 9-2a that are provided and have the same shape as the inner surface shapes 1-1 and 1-2 of both ends in the axial direction of the power transmission system shaft 1; The die forging which compresses the steel pipe 6 in the axial direction is performed between a pair of upper and lower molds (punch with a cored bar) 10-1 and 10-2.

  At the time of this die forging, the thickened portions 3-1 and 3-2 are formed by axial pressing from the bottom surfaces of the molds 10-1 and 10-2 in the portion A in FIG. In part B in FIG. 1B, the steel pipe 6 is not constrained, so that the bulging parts 4-1 and 4-2 are formed by expanding the pipe with almost no increase in wall thickness by pushing the shaft. Furthermore, in C part in FIG.1 (c), since the steel pipe 6 is not restrained, the pipe part is expanded a little by axial pushing, and the center part 5 is formed by thickening in some cases.

  FIG. 2 (a) is an explanatory view showing the range of dimensions of a steel pipe 6 that is a work material that can be used in the present invention, and FIG. 2 (b) is a hollow power transmission system shaft 1 that can be manufactured according to the present invention. It is explanatory drawing which shows the range of the dimension. In addition, each part dimension shown to Fig.2 (a) and FIG.2 (b) is a case where S45CB softening material (TS = 550MPa class) is used as a raw material of the steel pipe 6. FIG.

The power transmission shaft 1 shown in FIG. 2B satisfies the following condition 1 regarding the thickness of each part and the following condition 2 regarding the outer diameter of each part.
Condition 1: t ₁ > t ₂ , t ₃ and 4 mm <t ₁ , t ₂ , t ₃ <15 mm
Condition 2: D ₂ > D ₁ and D ₂ > D ₃ , 20 mm <D ₁ , D ₃ <45 mm and 22 mm <D ₂ <55 mm
Furthermore, it is desirable to satisfy the following condition 3 regarding the axial length L (mm) of the steel pipe 6.
Condition 3: 100 ≦ L ≦ 2000
Thereafter, the molds 10-1 and 10-2 are extracted from the hollow power transmission system shaft 1 formed by die forging, the outer mold 7 is divided into left and right parts, and the power transmission system shaft 1 is extracted. Thus, the hollow power transmission system shaft 1 is manufactured by one-step die forging.

  FIG. 3 is an explanatory view showing a modification of the pair of molds 10-1 and 10-2 shown in FIGS. 1 (a) and 1 (b).

  In order to reduce the drawing load when the molds 10-1 and 10-2 are extracted from the hollow power transmission system shaft 1 formed by die forging, the metal core portion 9- of the molds 10-1 and 10-2 is reduced. As shown in FIG. 3, it is desirable that 1, 9-2 have a tapered shape in which the outer diameter decreases toward the tip.

  In particular, in order to obtain the desired thickness distribution in the thickened portions 3-1 and 3-2 which are the pipe end portions, the outer diameters of the cored bar portions 9-1 and 9-2 are set to the thickened portion 3-1. , 3-2 is desirably changed stepwise or continuously according to the thickness.

  4A is an explanatory diagram showing the taper angle α when the cored bar part 9-1 has a tapered shape, and FIG. 4B shows the case where the taper angle of the cored bar part 9-1 is constant. FIG. 4C is an explanatory view showing a state when molding is completed when the taper angle of the cored bar portion 9-1 changes stepwise. FIG.4 (d) is explanatory drawing which shows the state at the time of completion | finish of shaping | molding in case the taper angle of the metal core part 9-1 changes continuously.

  The taper angle α shown in FIG. 4A is preferably not less than 0.3 ° and not more than 10 °.

  The cored bar part 9-1 shown in FIG. 4B is the same as the cored bar part 9-1 shown in FIGS. 3A and 3B.

  On the other hand, by using the mold 10-1 having the core metal part 9-1 shown in FIG. 4C, the thickness of the manufactured power transmission shaft 1 can be changed stepwise. In the cored bar part 9-1 shown in FIG. 4C, the taper angle α is divided into three stages of A part, B part, and C part. What is necessary is just to combine suitably the taper angle (alpha) of each of A-C part in the range of 0.3 degree or more and 10 degrees or less, respectively.

  Furthermore, the thickness of the power transmission shaft 1 to be manufactured can be continuously changed by using the mold 10-1 having the core metal part 9-1 shown in FIG. The taper angle α may be appropriately changed within a range of 0.3 ° to 10 °.

  Moreover, by having this taper shape, it is also possible to facilitate the alignment of the axes when the molds 10-1 and 10-2 are set on the steel pipe 1.

  FIG. 5 is an explanatory view showing another modification of the pair of molds 10-1 and 10-2 shown in FIGS. 1 (a) and 1 (b).

  In order to reduce the drawing load when the molds 10-1 and 10-2 are extracted from the hollow power transmission system shaft 1 formed by die forging, the metal core portion 9- of the molds 10-1 and 10-2 is reduced. As shown in FIG. 5, reference numerals 1 and 9-2 denote contact portions 8-1a and 8− of the base portions 8-1 and 8-2 with both end surfaces 6-1 and 6-2 in the axial direction of the steel pipe 6. 2a is preferably formed to be inclined toward the outside of the steel pipe 6. Further, by forming the contact portions 8-1a and 8-2a so as to be inclined as described above, it is easy to align the axes when setting the molds 10-1 and 10-2 to the steel pipe 1. Is also possible.

  Furthermore, when the contact portions 8-1a and 8-2a are formed in such an inclination, the contact portions 8-1a and 8-2a are not formed in such an inclination (FIG. ) And FIG. 1 (b)), a force in the tube expansion direction is more applied to the portions formed in the bulging portions 4-1 and 4-2 in the steel pipe 6, and as a result, Since the protruding portions 4-1 and 4-2 can be formed earlier, it is possible to mold with a smaller axial load.

  FIG. 6 is an explanatory view showing still another modification of the pair of molds 10-1 and 10-2 shown in FIGS. 1 (a) and 1 (b).

  As shown in FIG. 6, the cored bar portions 9-1 and 9-2 may have this tapered shape and the contact portions 8-1a and 8-2a may be formed to be inclined. Needless to say.

  Thus, according to the present invention, the hollow power transmission shaft 1 can be manufactured at low cost by one-step die forging.

DESCRIPTION OF SYMBOLS 1 Power transmission system shaft 1-1, 1-2 Both ends 3-1 and 3-2 Thickening part 4-1 and 4-2 Expansion part 5 Center part 6 Steel pipe 6-1 and 6-2 Both end surfaces 7 Out Mold 7a Inner surface shape 8-1, 8-2 Base part 8-1a, 8-2a Contact part 9-1, 9-2 Core part

Claims (1)

From the both axial end portions to the axial central portion, the thickened portion having the largest thickness, the bulging portion having a larger outer diameter than the thickening portion and having a small thickness, and the bulging portion A hollow power transmission system shaft for an automobile having a central portion with a small outer diameter,
A hollow power transmission system shaft for an automobile in which the thickness of the thickened portion and the bulging portion is greater than the hardness of the central portion.

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