KR20200045895A - Drive shaft assay for automobile and its manufacturing method - Google Patents

Abstract

The present invention relates to a drive shaft assay for a vehicle and a manufacturing method thereof and, more particularly, to a shaft and an inner ring. The present invention may include a solid shaft and an inner ring integrally formed with the solid shaft, and a manufacturing method thereof may comprise the steps of: forging a solid shaft to form an inner ring; processing the solid shaft and inner ring; and performing high-frequency heat treatment on the processed solid shaft and inner ring. According to the present invention, the outer diameter of the inner and outer rings is reduced by integrating the shaft and the inner ring, so that the weight of the drive shaft assay can be reduced by 10 to 20%. In addition, the cost of manufacturing and managing parts can be reduced by omitting spline processing and deleting a circlip.

Description

DRIVE SHAFT ASSAY FOR AUTOMOBILE AND ITS MANUFACTURING METHOD}

The present invention relates to a drive shaft assembly for a vehicle and a method for manufacturing the same, and more particularly, to a shaft and an inner ring.

The drive shaft assembly for automobiles transmits the driving force of the engine / transmission to the wheel at a constant speed. 1 is a schematic view of a conventional automobile drive shaft assembly. Referring to Figure 1, the conventional drive shaft assembly for a vehicle shaft 11, inner ring 12, shaft 11 and the inner ring 12 fastening and fixing the circlip 13, a plurality of balls (14) , Outer ring 15, a spline 16 formed on the outside of the shaft 11 and a spline (not shown) formed on the inside of the inner ring 12.

In order to improve the fuel efficiency of automobiles, research and development is currently underway to reduce the weight of a vehicle. When the weight of directly driven parts, such as a drive shaft assembly, is reduced, the effect of improving fuel efficiency is further increased.

As part of this research and development, Patent Document 1 integrates the inner ring by constructing a shaft from a pipe material. Generally, six balls are used in the drive shaft assembly for automobiles. As the number of balls used increases, the diameter of the ball decreases, so that the transmission efficiency of the driving force is increased, and the drive shaft assembly for automobiles can be made lighter. However, Patent Document 1 has three available balls and is limited by the shape of the inner ring and the ball.

Patent Document 2 In addition, the shaft is made of a pipe material to integrate the inner ring. Unlike Patent Document 1, the number of balls that can be used is 3 to 10 balls. However, there is a limit to the height of the inner ring that can be formed according to the pipe thickness. This is because it is technically difficult to form a section that is twice the thickness in one pipe because the pipe has an empty center and warpage occurs. In general, the thickness of the pipe used is 3 to 5 mm and it is technically difficult to form a pipe section having a pipe thickness of 10 mm in the same pipe, so the height of the inner ring hitting portion is limited to less than 5 mm. In addition, when the diameter of the ball is large or the number of balls is large, there are limitations in the design of the shaft and the inner ring.

Japanese Patent Application Publication No. 2014-025486 Japanese Patent Registration No. 5410163

The present invention aims to manufacture a drive shaft assembly formed by integrating a shaft and an inner ring, but not limited to the height or outer diameter of the inner ring.

In order to achieve the above object, the present invention may include a solid shaft and an inner ring integrally formed with the solid shaft.

Preferably, the outer diameter of the inner ring can be up to three times the outer diameter of the solid shaft.

Preferably, it may include up to 14 balls.

Preferably, the inner ring can have a constant depth of cure.

Preferably, the solid shaft and inner ring are 0.45 to 0.60 wt% of carbon (C), 0.2 to 0.6 wt% of chromium (Cr), 0.4 to 0.8 wt% of molybdenum (Mo), and 0.3 to 0.9 wt% of nickel (Ni ), 0.01 to 0.05 wt% of boron (B), 0.15 to 0.35 wt% of silicon (Si), 0.6 to 0.9 wt% of manganese (Mn), and the balance of iron (Fe).

Preferably, more than 0 and less than 0.3wt% copper (Cu) may be further included.

Preferably, it may further include phosphorus (P) greater than 0 and 0.03 wt% or less and sulfur (S) greater than 0 and 0.035 wt% or less.

Preferably, the hardening depth of the inner ring may be 2 to 6 mm.

Meanwhile, the present invention may include a step of forging the solid shaft to form an inner ring, processing the solid shaft and the inner ring, and high-frequency heat treatment of the processed solid shaft and the inner ring.

Preferably, the coil subjected to high-frequency heat treatment may include a curved portion facing the chisel portion of the inner ring along the inner circumferential surface and a protrusion facing the bottom of the inner ring.

Preferably, the range of the frequency may be a frequency index (Frequency Index, FI) ± 5kHz.

The present invention can manufacture a drive shaft assembly that is formed by integrating a shaft and an inner ring, but is not limited to the height or outer diameter of the inner ring.

The present invention has the advantage that the heat treatment properties, durability and economics can be secured by optimizing the alloy component.

The present invention can optimize heat treatment conditions and prevent heat treatment defects.

1 is a schematic view of a conventional automobile drive shaft assembly.
2 is a schematic view of the present invention drive shaft assembly.
3 is a photograph of a shaft and an inner ring formed according to an embodiment of the present invention. 3 (a) shows a solid shaft, and FIGS. 3 (b) to 3 (d) show inner rings having an outer diameter of about 2.1 times, about 2.6 times, and about 3.0 times the outer diameter of the solid shaft shown in Fig. 3 (a). .
Figure 4 shows the solid shaft 21, the inner ring 22 and the ball 24 according to an embodiment of the present invention.
5 is a flow chart showing a method of manufacturing a drive shaft assembly for a vehicle according to the present invention.
6 shows the shape of the coil used for high-frequency heat treatment.
7 (a) and 7 (b) are schematic diagrams showing a desired depth of hardening of the teeth and teeth.
8 (a) and 8 (b) are schematic diagrams showing the depth of hardening below the remarks in Table 7.
9 (a) and 9 (b) are schematic diagrams showing the cure depth exceeded in the remarks of Table 7.

Hereinafter, the present invention will be described in detail. However, the present invention is not limited or limited by the exemplary embodiments, and the objects and effects of the present invention can be naturally understood or more apparent by the following description, and the objects and effects of the present invention are described only by the following description. It is not limited. In addition, in the description of the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

2 is a schematic view of the present invention drive shaft assembly. Referring to FIG. 2, the present invention may include a solid shaft 21 and an inner ring 22 formed integrally with the solid shaft 21. In the present invention, since the solid shaft 21 and the inner ring 22 are integrally formed, a circlip for fastening and fixing the shaft and the inner ring, as well as an inner spline formed on a conventional inner ring and an outer spline formed on a conventional shaft are not required. .

Further, even if the outer diameter of the solid shaft 21 is the same as the outer diameter of the conventional shaft 11, as the outer diameters of the inner ring 22 and the outer ring 25 are reduced, the weight of the drive shaft assembly for automobiles is reduced. According to an embodiment of the present invention, the outer diameter of the inner ring can be reduced from 42 mm to 30 mm, and the outer diameter of the outer ring can be reduced from 86 mm to 74 mm, and the total weight of the inner ring and outer ring can be reduced from 1670 g to 1439 g (saving 231 g). Since two inner and outer rings are used for the drive shaft assembly, a total of 462 g can be reduced.

3 is a photograph of a shaft and an inner ring formed according to an embodiment of the present invention. More specifically, FIG. 3 (a) shows a solid shaft, and FIGS. 3 (b) to 3 (d) show an outer diameter of about 2.1 times, about 2.6 times, and about 3.0 times the outer diameter of the solid shaft shown in Fig. 3 (a). It represents the inner ring having a. Figure 4 shows the solid shaft 21, the inner ring 22 and the ball 24 according to an embodiment of the present invention.

Table 1 shows the maximum number of balls and the ratio of the outer diameter that can be used according to the outer diameter (C) of the inner ring when the outer diameter (A) of the solid shaft is 30 mm and the diameter of the ball is 10 mm. Table 2 shows the maximum number of balls and the ratio of the outer diameter that can be used according to the outer diameter (C) of the inner ring when the outer diameter (A) of the solid shaft is 30 mm and the diameter of the ball is 15 mm.

Inner ring outer diameter
(C, mm) ball
Maximum number

40 6 1.3 50 7 1.7 60 9 2.0 70 11 2.3 80 12 2.7 90 14 3.0

Inner ring outer diameter
(C, mm) ball
Maximum number

40 4 1.3 50 5 1.7 60 6 2.0 70 7 2.3 80 8 2.7 90 9 3.0

3 and 4, Table 1 and Table 2, the present invention is formed by forging the solid shaft 21 to form the inner ring 22, the outer diameter (C) of the inner ring is up to 3 of the solid shaft outer diameter (A) Can be doubled. The outer diameter (C) of the inner ring can exceed three times the outer diameter (A) of the solid shaft, but it is not a suitable shape for use as a drive shaft assembly for automobiles, and the weight of the drive shaft assembly increases, so the outer diameter of the inner ring. (C) is preferably a maximum of three times the outer diameter (A) of the solid shaft.

As the outer diameter (C) of the inner ring increases, the maximum number of balls that can be used increases. For example, when the outer diameter (C) of the inner ring is three times the outer diameter (A) of the solid shaft, that is, when the outer diameter (C) of the inner ring is 90 mm and the outer diameter (A) of the solid shaft is 30 mm, up to 14 balls of 10 mm in diameter Can be used.

According to the present invention, the inner ring 22 may have a constant curing depth. The hardening depth of the inner ring 22 defined in this specification refers to a value obtained by averaging the hardening depth of the chisel portion 221 and the hardening depth of the tooth portion 222. As will be described later in detail, it is preferable that the inner ring has a curing depth of 2 to 6 mm in order to uniformly cure the tooth shape and improve dimensional accuracy.

Material C Cr Mo Ni B Si Mn Cu P S shaft
(Conventional) 0.35
~ 0.41 0.3
Max - - 0.05
Max 0.15
~ 0.35 0.6
~ 0.9 0.3
Max 0.030
Max 0.035
Max Inner ring (conventional) 0.17
~ 0.23 0.8
~ 1.3 0.1
~ 0.4 0.3
Max - 0.15
~ 0.35 0.5
~ 0.9 0.3
Max 0.030
Max 0.035
Max The present invention 0.45
~ 0.60 0.2
~ 0.6 0.4
~ 0.8 0.3
~ 0.9 0.01
~ 0.05 0.15
~ 0.35 0.6
~ 0.9 0.3
Max 0.03
Max 0.035
Max

Table 3 is a table summarizing the composition of the conventional shaft, inner ring and the present invention. Referring to Table 3, the inventors of the solid shaft 21 and the inner ring 22, 0.45 ~ 0.60wt% carbon (C), 0.2 ~ 0.6wt% chromium (Cr), 0.4 ~ 0.8wt% molybdenum (Mo ), 0.3 to 0.9 wt% nickel (Ni), 0.01 to 0.05 wt% boron (B), 0.15 to 0.35 wt% silicon (Si), 0.6 to 0.9 wt% manganese (Mn), and the balance iron (Fe).

The inventors solid shaft 21 and the inner ring 22 may further include 0.3 wt% or less copper (Cu), 0.03 wt% or less phosphorus (P), and 0.035 wt% or less sulfur (S).

When comparing the composition of the conventional shaft, the inner ring, and the present invention, the amount of carbon added in the present invention is greater than the amount of carbon added in the conventional shaft and the inner ring, and the amount of chromium added in the present invention overlaps in some range with the amount of chromium added selectively in the conventional shaft. Less than the amount of chromium added in the inner ring.

Molybdenum and nickel not added to the conventional shaft are added to the solid shaft of the present invention, and the amount of molybdenum and nickel added to the present invention is higher than that of the conventional inner ring. Boron, which is not added to the conventional inner ring, is added to the inner ring of the present invention, and boron is essentially added to the inner ring and shaft of the present invention, unlike that of the conventional shaft. Hereinafter, the amount of each component added to the present invention will be described in detail.

(1) 0.45 ~ 0.60wt% carbon (C)

Carbon is added to increase the strength of the material. When adding less than 0.45wt% carbon, the desired strength cannot be obtained, and when more than 0.60wt% carbon is added, it is preferable to add 0.45 to 0.60wt% carbon because processing and moldability are disadvantageous.

(2) 0.2 ~ 0.6wt% chromium (Cr)

Chromium is added to increase the strength of the material. When adding less than 0.2wt% of chromium, the desired strength cannot be obtained. When adding more than 0.6wt% of chromium, toughness decreases, so it is preferable to add 0.2 to 0.6wt% of chromium.

(3) Molybdenum (Mo) 0.4 ~ 0.8wt%

In the high-frequency heat treatment of the material, molybdenum is added to secure heat treatment property, that is, the curing depth. When adding molybdenum of less than 0.4 wt%, heat treatment properties of the material cannot be ensured, and when adding molybdenum greater than 0.8 wt%, durability is reduced by segregation, so it is preferable to add molybdenum of 0.4 to 0.8 wt%.

(4) 0.3 ~ 0.9wt% nickel (Ni)

Nickel is added to improve durability such as toughness of the material. When adding less than 0.3wt% nickel, the effect of improving toughness cannot be obtained, and when adding more than 0.9wt% nickel, it is preferable to add 0.3 to 0.9wt% nickel because the cost-effectiveness decreases.

(5) Boron (B) of 0.01 ~ 0.05wt%

When high-frequency heat treatment of the material, boron is added to secure heat treatment properties, ie, depth of hardening. When adding boron of less than 0.01wt%, the effect of improving heat treatment cannot be obtained, and when adding boron of more than 0.05wt%, segregation occurs and problems occur, so it is preferable to add boron of 0.01 ~ 0.05wt%. .

(6) Silicon (Si) of 0.15 ~ 0.35wt%

Silicon is added to suppress the formation of harmful carbides. It is preferable to add 0.15 to 0.35wt% of silicon because adding less than 0.15wt% of silicon cannot effectively suppress the generation of harmful carbides and segregation occurs when adding more than 0.35wt% of silicon.

(7) 0.6 ~ 0.9wt% manganese (Mn)

Manganese is added to increase the strength of the material. When adding less than 0.6wt% of manganese, it is impossible to achieve the strength improvement effect of the material, and when adding more than 0.9wt% of manganese, toughness and machinability are lowered, so it is preferable to add 0.6 ~ 0.9wt% of manganese. .

In the present invention, copper, phosphorus and sulfur are added in an amount of 0.3 wt% or less, 0.03 wt% or less, and 0.035 wt% or less, respectively, in order to prevent deterioration in quality due to segregation and inclusion formation.

5 is a flow chart showing a method of manufacturing a drive shaft assembly for a vehicle according to the present invention. Referring to Figure 5, the present invention for forming the inner ring by forging the solid shaft (S101), processing the solid shaft and the inner ring (S102) and heat-treating the processed solid shaft and the inner ring (S103) It can contain.

The conventional shaft was manufactured by processing the raw material of the shaft (including the formation of the outer spline) and then performing high-frequency heat treatment (using a circular coil, 3 ≤ frequency f (kHZ) ≤ 30), and the conventional inner ring forged and processed the raw material (internal spline After the formation of) was prepared by carburizing heat treatment. The reason why the conventional inner ring is subjected to carburizing heat treatment rather than high-frequency heat treatment is because the amount of carbon added to the conventional inner ring is small. This is because it increases. Unlike the conventional carburizing heat treatment of the inner ring to improve the surface hardness of the inner ring, the present invention is contrasted in that it improves the surface hardness by high-frequency heat treatment of the inner ring.

On the other hand, in the present invention, since the solid shaft and the inner ring are integrally formed, when the solid shaft and the inner ring are separately subjected to high-frequency heat treatment, a portion in which heat treatment is overlapped may occur and cracks may occur in the portion. Therefore, it is preferable to heat-treat the solid shaft and the inner ring at once.

6 shows the shape of the coil used for high-frequency heat treatment. Referring to FIG. 6, the inside of the coil 27 includes a curved portion 271 that faces the chisel portion 221 of the inner ring and a protruding portion 272 that faces the bottom portion 222 of the inner ring, and the curved portion 271 and The protrusions 272 may be alternately formed along the inner circumferential surface of the coil.

In the case of using a circular coil in which the curved portion 271 and the protruding portion 272 are not formed during the high-frequency heat treatment of the present invention in which the solid shaft and the inner ring are integrally formed, the abutment portion 221 of the inner ring is adjacent to the circular coil, so that the abutment portion of the inner ring is formed. A sufficient heat treatment can be applied to (221). However, since the toothed portion 222 and the solid shaft of the inner ring are not adjacent to the circular coil compared to the toothed portion 221 of the inner ring, sufficient heat treatment cannot be applied to the toothed portion 222 and the solid shaft of the inner ring. Therefore, when the coil 27 of the present invention is used, it is possible to solve the above-described problem because sufficient heat treatment can be applied to the chisel portion 221 of the inner ring as well as the tooth portion 222 and the solid shaft of the inner ring.

The frequency range that can be used in the high-frequency heat treatment step (S103) of the present invention is a frequency index (FI) ± 5 kHz, and the frequency index refers to Equation 1 below.

[Equation 1]

Gap (mm) means B-A (however, B ≥ A) and Height (mm) means C-B (however, C> B), A is the outer diameter of the solid shaft, B is the inner diameter of the inner ring, and C is It means the outer diameter of the inner ring.

The frequency condition needs to be changed according to the dimensional difference between the outer diameter of the solid shaft, the inner diameter of the inner ring, and the outer diameter. Since the frequency index can be used as a standard for adjusting the heat treatment conditions according to the shape of the solid shaft and inner ring during high frequency heat treatment, the present invention can prevent heat treatment defects through quality pre-management through optimization of high frequency heat treatment conditions.

division A (mm) B (mm) C (mm) Gap Height FI One 30 30 50 0 20 27.1 2 30 30 40 0 10 25.0 3 30 30 90 0 60 32.2 4 30 33 53 3 20 22.3 5 30 33 43 3 10 20.2 6 28 28 48 0 20 27.1 7 28 28 38 0 10 25.0 8 28 33 50 5 17 18.5 9 28 33 40 5 7 16.2

Table 4 is a table summarizing the frequency index according to the outer diameter (A) of the solid shaft, the inner diameter (B) of the inner ring, and the outer diameter (C) of the inner ring. The solid shafts and inner rings of divisions 1 to 9 have the same composition as the chemical components of Example 1, which will be described later. Referring to Category 1 as an example of Table 4, when the outer diameter (A) of the solid shaft is 30 mm, the inner diameter (B) of the inner ring is 30 mm, and the outer diameter (C) of the inner ring is 50 mm, the outer diameter (A) of the solid shaft and The difference between the inner diameter B of the inner ring is 0 (Gap = 0), and the difference between the outer diameter C of the inner ring and the inner diameter B of the inner ring is 20 (Height = 20). Substituting Gap = 0 and Height = 20 into Equation 1, the frequency index becomes 27.1 kHz. Finally, the frequency f used for high-frequency heat treatment is selected from 22.1 ≤ f ≤ 32.1.

Even if the solid shaft and the inner ring are heat-treated collectively, if considering the fact that the outer diameter of the solid shaft is smaller than the outer diameter of the inner ring, even if the high-frequency heat treatment conditions are optimized using the frequency index, the surface hardness is relatively long because the distance from the solid shaft to the coil is relatively long. And the depth of hardening cannot be sufficiently secured. Therefore, it is necessary to reinforce the components that can compensate for this, which has already been described above.

Hereinafter, a specific embodiment of the present invention will be described in detail. However, the examples described below are only for specifically illustrating or describing the present invention, and the present invention is not limited thereto.

division Chemical composition (wt%) C Si Mn Cr Mo Ni B shaft
(Conventional) 0.38 0.2 0.7 - - - - Inner ring (conventional) 0.2 0.25 0.7 1.0 0.2 - - Example 1 0.5 0.25 0.7 0.3 0.6 0.6 0.03 Comparative Example 1 0.42 0.25 0.7 0.3 0.6 0.6 0.03 Comparative Example 2 0.65 0.25 0.7 0.3 0.6 0.6 0.03 Comparative Example 3 0.5 0.25 0.7 0.05 0.6 0.6 0.03 Comparative Example 4 0.5 0.25 0.7 0.8 0.6 0.6 0.03 Comparative Example 5 0.5 0.25 0.7 0.3 0.04 0.6 0.03 Comparative Example 6 0.5 0.25 0.7 0.3 1.0 0.6 0.03 Comparative Example 7 0.5 0.25 0.7 0.3 0.6 0.1 0.03 Comparative Example 8 0.5 0.25 0.7 0.3 0.6 0.6 - Comparative Example 9 0.5 0.25 0.7 0.3 0.6 0.6 0.07

Table 5 is a table summarizing the composition of the conventional shaft and inner ring, and the compositions of Examples and Comparative Examples of the present invention. 0.3 wt% copper, 0.03 wt% phosphorus and 0.035 wt% sulfur were added to each composition.

When comparing the composition of Example 1 and the conventional shaft and inner ring with reference to Table 5, in order to increase the surface hardness, 0.5 wt% of carbon more than 0.38 wt% and 0.2 wt% of the carbon amount of the conventional shaft and inner ring was added to Example 1 Was added. The chromium addition amount of the conventional inner ring was less than 1.0wt%, and 0.3wt% of chromium not added to the conventional shaft was added to Example 1, and the amount of molybdenum added to the conventional inner ring was more than 0.2wt% and 0.6wt% of the conventional inner ring was not added. Molybdenum was added to Example 1. 0.6 wt% nickel and 0.03 wt% boron, which were not added to the conventional shaft and inner ring, were added to Example 1.

Comparative Examples 1 and 2 are comparative examples in which 0.42 wt% of carbon and 0.65 wt% of carbon not included in the carbon addition amount (0.45 to 0.60 wt%) of the present invention are added, and Comparative Examples 3 and 4 are chromium of the present invention This is a comparative example in which 0.05 wt% of chromium and 0.8 wt% of chromium are not included in the addition amount (0.2 to 0.6 wt%).

Comparative Examples 5 and 6 are comparative examples in which 0.04 wt% molybdenum and 1.0 wt% molybdenum are not included in the molybdenum addition amount (0.4 to 0.8 wt%) of the present invention, and Comparative Example 7 is the nickel addition amount ( It is a comparative example in which 0.1 wt% of nickel not included in 0.3 to 0.9 wt%) is added. Comparative Example 8 is a comparative example in which boron was not added, and Comparative Example 9 is a comparative example in which 0.07 wt% of boron was added in excess of the boron addition amount (0.01 to 0.05 wt%) of the present invention.

division shape High frequency conditions A
(mm) B
(mm) C
(mm) Frequency index
(kHz) result
(kHz) shaft
(Conventional) 30 - - 19.1 20 Inner ring
(Conventional) - 35 55 - - Example 1 and Comparative Examples 1 to 9 30 30 50 27.1 27

Table 6 is a table summarizing the frequency index and frequency result values calculated according to the shape of the solid shaft and the inner ring. The inner and outer diameter dimensions of the conventional inner ring were used to calculate the frequency index. Unlike the conventional shaft, the conventional inner ring was subjected to carburizing heat treatment. In Example 1 and Comparative Examples 1 to 9, since the high-frequency conditions are the same, effects according to the composition of the shaft and the inner ring can be compared.

evaluation division Surface hardness
(HV) Hardening depth
(mm) burglar
(MPa) durability
(Number of times) Remark shaft
(Conventional) 680 3 105 510,000 - Inner ring
(Conventional) 770 One Example 1 750 4.0 115 560,000 OK Comparative Example 1 635 2.5 86 380,000 Below surface hardness Comparative Example 2 790 7.1 87 450,000 Hardening depth exceeded Comparative Example 3 715 1.5 98 41 million Less than hardening depth Comparative Example 4 770 6.9 87 470,000 Hardening depth exceeded Comparative Example 5 720 1.8 91 390,000 Less than hardening depth Comparative Example 6 745 8.5 85 460,000 Hardening depth exceeded Comparative Example 7 748 3.9 103 400,000 Lack of durability Comparative Example 8 748 1.8 95 41 million Under hardening depth, lack of strength,
Lack of durability Comparative Example 9 750 4.0 110 490,000 Lack of durability

Table 7 is a table summarizing surface hardness, hardening depth, strength and durability measured after high-frequency heat treatment of the conventional shaft and inner ring, Examples 1 and 9 of the present invention under the high-frequency conditions of Table 6. The desired properties are HV700 or higher, surface hardness of 2 to 6 mm, strength of 100 MPa or higher, and durability of 500,000 or higher.

7 (a) and 7 (b) are schematic diagrams showing a desired depth of hardening of the teeth and teeth. 8 (a) and 8 (b) are schematic diagrams showing the depth of hardening below the remarks in Table 7. 9 (a) and 9 (b) are schematic diagrams showing the cure depth exceeded in the remarks of Table 7.

It is necessary to uniformly cure the tooth-shape between sections to improve the dimensional accuracy, and for this, it is desirable to form a curing depth of 2 to 6 mm on the inner ring. More specifically, the hardening depths of the target tooth and the base are 2-8 mm and 2-4 mm, respectively. When the hardening depth of the tooth base is less than 2mm, the strength required for the drive shaft assembly cannot be met, and when the hardening depth of the chisel is more than 8mm, that is, when the hardening depth of the inner ring is greater than 6mm, dimensional accuracy due to distortion due to overheating Decreases.

Durability evaluation is based on the torsional fatigue test of the drive shaft assembly. The torsional fatigue test is to check the point of failure by repeatedly applying a torsional load to the test equipment and one to the other while the drive shaft assembly is assembled.

Referring to Tables 5 to 7 and FIGS. 7 to 9, Example 1 shows the surface hardness, strength, and strength of the conventional shaft and inner ring, except that the surface hardness of the conventional inner ring subjected to carburization heat treatment is higher than that of Example 1. It can be seen that the durability is excellent.

The surface hardness of Comparative Example 1 was lower than that of Example 1, and the desired surface hardness was lower than HV700 as Comparative Example 1 was added with 0.42 wt% of carbon less than the minimum carbon addition amount of the present invention of 0.45 wt%. . On the other hand, the surface hardness of Comparative Example 2 was higher than that of Example 1 as more than 0.65 wt% of carbon was added to Comparative Example 2, more than the maximum amount of carbon of the present invention was 0.60 wt%, but the hardening depth of the inner ring was Exceeded 6 mm.

In Comparative Example 3, as the chromium of the present invention was added with less than 0.2wt% of chromium and less than 0.05wt% of chromium, the hardening depth of the inner ring was less than 2mm, and in Comparative Example 4, 0.8wt more than the chromium max. The hardening depth of the inner ring exceeded 6 mm as% chromium was added.

In Comparative Example 5, as the molybdenum of 0.04 wt% less than the minimum molybdenum addition amount of the present invention was added, the hardening depth of the inner ring was less than 2 mm, and in Comparative Example 6, the molybdenum maximum addition amount of the present invention was greater than 0.8 wt% 1.0 The hardening depth of the inner ring exceeded 6 mm as wt% molybdenum was added.

In Comparative Example 7, 400,000 times lower than the desired durability of 500,000 times was measured as 0.1 wt% of nickel less than 0.3 wt% of the minimum amount of nickel of the present invention was added. In Comparative Example 8, although the amount of addition of the elements other than boron was the same as in Example 1, as the boron was not added, the hardening depth of the inner ring was less than 2 mm, and the strength was less than 100 MPa and durability was less than 500,000. Comparative Example 9 showed durability of less than 500,000 as more than 0.07 wt% of boron was added than the boron addition amount (0.01 to 0.05 wt%) of the present invention.

division shape High frequency conditions A
(mm) B
(mm) C
(mm) Frequency index
(kHz) result
(kHz) Example 1 30 30 50 27.1 27 Comparative Example 10 20 Comparative Example 11 35 Example 2 30 33 42 20.2 20 Comparative Example 12 10 Comparative Example 13 30 Example 3 28 33 40 16.2 12 Example 4 20 Example 5 30 30 90 32.2 32

division evaluation Remark Surface hardness
(HV) Hardening depth
(mm) burglar
(MPa) durability
(Number of times) Example 1 750 4.0 115 560,000 OK Comparative Example 10 633 3.2 85 430,000 Below surface hardness Comparative Example 11 711 1.5 90 400,000 Less than hardening depth Example 2 751 4.0 113 550,000 OK Comparative Example 12 628 3.0 84 41 million Below surface hardness Comparative Example 13 719 1.7 92 400,000 Less than hardening depth Example 3 748 4.1 114 550,000 OK Example 4 749 4.0 112 540,000 OK Example 5 749 4.1 113 530,000 OK

Table 8 is composed of the same composition as in Example 1, but is a table summarizing the high-frequency conditions according to the shape of the solid shaft and the inner ring, and Table 9 is a table summarizing the surface hardness, hardening depth, strength, and durability after high-frequency heat treatment. . Referring to Table 8 and Table 9, Examples 1 to 5 were subjected to high-frequency heat treatment at 27 kHz, 20 kHz, 12 kHz, 20 kHz, and 32 kHz in the ± 5 kHz range of 27.1 kHz, 20.2 kHz, 16.2 kHz, and 32.2 kHz of each frequency index (FI). The desired surface hardness, hardening depth, strength and durability were obtained.

On the other hand, Comparative Examples 10 and 12 are comparative examples in which high-frequency heat treatment was performed at 20 kHz and 10 kHz outside the -5 kHz range of 27.1 kHz and 20.2 kHz of each frequency index (FI), and the surface hardness was less than HV700. Example 13 is a comparative example in which high-frequency heat treatment was performed at 35 kHz and 30 kHz outside the +5 kHz range of 27.1 kHz and 20.2 kHz of each frequency index (FI), and it can be seen that the hardening depth of the inner ring was less than 2 mm.

Although the present invention has been described in detail through exemplary embodiments above, those skilled in the art to which the present invention pertains understand that various modifications are possible within the limits of the embodiments described above without departing from the scope of the present invention. will be. Therefore, the scope of rights of the present invention should not be limited to the described embodiments, and should be determined not only by the claims to be described later, but also by all modified or modified forms derived from the claims and equivalent concepts.

11: shaft 12: inner ring
13: Circle clip 14: Ball
15: paddle 16: spline
21: shaft 22: inner ring
24: ball 25: paddle
221: Chichibu 222: Chichibu
S101: Forging of the solid shaft and the step of forming the inner ring
S102: Machining step of solid shaft and inner ring
S103: High-frequency heat treatment step of solid shaft and inner ring
271: indentation 272: protrusion
A: Outer diameter of solid shaft
B: inner diameter of inner ring
C: outer diameter of the inner ring

Claims (12)

A drive shaft assembly for a vehicle comprising a solid shaft and an inner ring integrally formed with the solid shaft.
According to claim 1,
The outer diameter of the inner ring is up to three times the outer diameter of the solid shaft drive shaft assembly for a vehicle.
According to claim 2,
A drive shaft assembly for a vehicle, comprising up to 14 balls.
According to claim 1,
The inner ring is a drive shaft assembly for a vehicle, characterized in that it has a constant hardening depth.
The method of claim 1 or 4,
The solid shaft and inner ring are 0.45 to 0.60 wt% of carbon (C), 0.2 to 0.6 wt% of chromium (Cr), 0.4 to 0.8 wt% of molybdenum (Mo), and 0.3 to 0.9 wt% of nickel (Ni), A drive shaft for automobiles characterized by comprising 0.01 to 0.05 wt% of boron (B), 0.15 to 0.35 wt% of silicon (Si), 0.6 to 0.9 wt% of manganese (Mn) and the balance of iron (Fe). Asssay.
The method of claim 5,
Automotive drive shaft assembly further comprising less than 0.3wt% copper (Cu).
The method of claim 5,
A drive shaft assembly for automobiles further comprising 0.03 wt% or less phosphorus (P) and 0.035 wt% or less sulfur (S).
The method of claim 5,
The drive shaft assembly for a vehicle, characterized in that the hardening depth of the inner ring is 2 to 6 mm.
Forging the solid shaft to form an inner ring;
Processing the solid shaft and the inner ring; And
Method of manufacturing a drive shaft assembly for a vehicle comprising a; high-frequency heat treatment of the processed solid shaft and inner ring.
The method of claim 9,
Inside the coil to heat-treat high frequency,
A curved portion facing the chipping portion of the inner ring; And a protruding portion facing the tooth portion of the inner ring.
The method of claim 9,
The range of frequency is frequency index (FI) ± 5kHz,
The frequency index is a method of manufacturing a drive shaft assembly for a vehicle, characterized in that the following equation (1).
[Equation 1]

Gap (mm) = B-A (However, B ≥ A)
height (mm) = C-B (however, C> B)
A: Outer diameter of solid shaft, B: Inner diameter of inner ring, C: Outer diameter of inner ring
The method of claim 9,
The solid shaft and inner ring are 0.45 to 0.60 wt% of carbon (C), 0.2 to 0.6 wt% of chromium (Cr), 0.4 to 0.8 wt% of molybdenum (Mo), and 0.3 to 0.9 wt% of nickel (Ni), A drive shaft for automobiles characterized by comprising 0.01 to 0.05 wt% of boron (B), 0.15 to 0.35 wt% of silicon (Si), 0.6 to 0.9 wt% of manganese (Mn) and the balance of iron (Fe). Method of manufacturing an assembly.

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