JPH0725458Y2 - Inner race of constant velocity joint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to an inner race of a telescopic type constant velocity joint (ball joint) which is generally used for automobiles, particularly front-wheel drive vehicles.

<< Prior Art >> This kind of joint is composed of an outer race and an inner race each having a ball groove, a plurality of balls (usually 6 balls), and a ball holding cage. Ball groove 2 as shown in FIG.
A chamfered portion 4 is provided between the outer surface 3 and the outer spherical surface 3. If the 4th
As shown in the figure, if the corners where the surface of the ball groove 2 and the outer spherical surface 3 intersect (the portions 8 that require chamfering) are not chamfered,
When torque is applied, a "chip" occurs in the portion 8 that requires chamfering.

The formation of the chamfered portion for preventing the occurrence of this "chip" is performed during forging. In addition to high strength, this type of constant velocity joint requires high precision, so the inner race is forged (chamfered) → machined → gas carburized and tempered → outer spherical surface / ball groove polishing It has been manufactured through.

By the way, as shown in FIG. 5 and FIG. 6 (enlarged view of XI part of FIG. 5), the outer layer of the inner race 1a produced by the gas carburizing and quenching treatment is usually a carburized irregular layer 6 (incomplete quenching). Layer) is present from the surface 9 to a depth of about 20 μm. Since this carburized abnormal layer 6 has a lower hardness and a lower strength than the normal carburized hardened layer 5, the carburized abnormal layer 6 produced in the carburizing and tempering step is finally produced in the production of the inner race 1a. It is removed in the outer spherical surface / ball groove polishing process.

However, the chamfered part 4 of the inner race 1a that does not contact the ball
It was thought that it was not necessary to remove the abnormal carburizing layer 6 generated in
The inner race 1a which has left the carburized abnormal layer 6 has been used.

<Problems to be solved by the invention> The constant velocity joint assembled using such an inner race 1a has a chamfered portion 4 of the inner race 1a when subjected to a high torque load by a high-power engine developed in the future. There is a problem that is missing. As a result of investigating the cause, when a high torque is applied to the constant velocity joint, the ball has a greater tendency to ride on the chamfered portion 4 of the inner race 1a and wear the chamfered portion 4, and also the chamfered portion 4 and the ball. It was found that this is because stress concentrates on the corner ridge portion 7 at the boundary of the groove 2.

The present invention has been made for the purpose of solving the above problems, and a problem to be solved is to provide an inner race which is not damaged even when subjected to a high torque load and which enhances the durability of a constant velocity joint. .

<< Means for Solving the Problem >> The inner race of the constant velocity joint manufactured by the carburizing and quenching treatment of the present invention for solving the above problem has an abnormal carburizing at the chamfered portion between the outer spherical surface and the ball groove. There is no layer, and the chamfered portion and each surface of the ball groove are connected by an R surface (a part of a curved surface drawing a circle having a radius R).

To prevent the carburized abnormal layer from being formed in the chamfered portion of the inner race produced by carburizing and quenching treatment, remove the carburized abnormal layer by an appropriate method after normal gas carburizing and quenching, or remove the carburized abnormal layer. A carburizing and quenching treatment method such as vacuum carburizing or plasma carburizing that does not occur may be adopted.

The above-mentioned "each surface of the chamfered portion and the ball groove is connected by the R surface" means that the chamfered portion at the boundary between the chamfered portion and the ball groove is scraped into a rounded shape. means.

In order to make such a state, the corner ridge is forged from the beginning with the R surface, or the ridge after the forging is polished by a polishing method (polishing with an abrasive, electrolytic polishing, chemical polishing, etc.) or surface. The R surface may be finished by a cutting method (turning, milling, grinding, etc.). It goes without saying that these surface processing means may be appropriately used together in the continuous manufacturing process of the inner race. In addition, in the case of a product manufactured through a normal gas carburizing and quenching treatment, it is convenient to finally remove the carburized abnormal layer and cut off the corner ridges into a rounded shape at the same time.

<Operation> The inner race configured as described above is used by being assembled into a constant velocity joint because the chamfered surface is made of a normal carburized hardened layer like the outer spherical surface and the surface of the ball groove. When the ball is hit, even if the ball rides on the chamfered portion of the inner race due to a high torque load, it is less likely to wear.

In addition, since the corner ridges that have been intensively stressed by such balls no longer exist, stress concentration is relieved and the inner race is less likely to be damaged.

Such inner races greatly improve the durability of constant velocity joints.

<Examples> The present invention will be described more specifically with reference to Examples along with Comparative Examples.

Comparative Example 1 A carbon steel for machine structure was forged to produce a coarse inner race body of a constant velocity joint. After coining it to correct the dimensional deviation of the outer spherical surface and ball groove, put it in a heating furnace and heat it for about 2 hours at 900-930 ℃ while feeding carburizing gas (gas carburizing and quenching), then around 130 ℃ And tempered for about 4 hours.

When the carburized abnormal layer on the outer spherical surface and ball groove of the heat-treated product thus obtained is removed by polishing, the inner race 1a similar to the conventional product having the carburized abnormal layer 6 only on the chamfered portion 4 as shown in FIG. Was manufactured.

Comparative Example 2 In Comparative Example 1, the outer spherical surface 3 and the ball groove 2 were polished, but here, as shown in FIG. 3, the chamfered portion 4 was also polished by the grindstone 10 to a depth of 100 μm, and as shown in FIG. The inner race 1b having no abnormal carburizing layer 6 on the chamfered portion 4 was manufactured. A CBN metal bond was used for the grindstone 10, and the grindstone was ground at a peripheral speed of 500 m / sec by controlling NC 3 axes (see X, Y, and Z in FIG. 3).

Comparative Example 3 The inner surface without the abnormal carburizing layer 6 in the chamfered portion 4 as shown in FIG. 2 was carried out in the same manner as in Comparative Example 1 except that the heat treatment (gas carburizing quenching and tempering) in Comparative Example 1 was changed to vacuum carburizing quenching treatment. Race 1b manufactured.

In this example, since the abnormal carburizing layer 6 does not occur, the work of removing the abnormal carburizing layer performed in Reference Example 1 is naturally omitted. The vacuum carburizing and quenching process is performed with the furnace pressure: 200 Torr, CH ₄ amount: 0.1
%, Gas treatment temperature: 1040 ° C., quenching temperature: 880 ° C.

Example Ball groove 2 of the inner race of Comparative Example 3 (see FIG. 2)
The chamfered portion 7 at the boundary between the chamfered portion 4 and the chamfered portion 4 is treated with a chemical polishing liquid containing hydrofluoric acid + hydrogen peroxide as a main component, and the chamfered portion 4 and the ball groove 2 as shown in FIG. There is no corner part 7 between
An inner race 1 was manufactured in which those 2 and 4 surfaces were connected by an R surface. The surface layer is made of the carburized hardened layer 5, and there is no abnormal carburized layer on the surface.

Test Example Each CVJ assembly (constant velocity joint) made by using the inner races of Comparative Examples 1 to 3 and Example, respectively.
assembly) was attached to a Rebro joint tester, durability (durability time) was compared under the same high load condition, and the final damage state was investigated. The results are shown in FIG.

From the figure, the CVJ assembly using the one without the abnormal carburizing layer in the chamfered portion of the inner race (Comparative Examples 1 and 2) has twice as much durability as that of the conventional product (Comparative Example 1). Further, it can be seen that the one using the inner race of the embodiment, in which the corner ridge portion at the boundary between the chamfered portion and the ball groove is cut off into a rounded shape, has durability more than 5 times that of the conventional product. Then, in the CVJ assembly using the inner race of the example, it was confirmed that flaking, which is the original damage form of rolling parts, determines the life.

<Effects of the invention> As described above, the inner race of the constant velocity joint of the present invention has a high carburizing abnormal layer existing in the chamfered portion between the outer spherical surface and the ball groove. Even if the chamfered portion rubs against the ball at the time of torque load, the chamfered portion will not be worn, and since the chamfered portion 7 at the boundary between the chamfered portion and the ball groove is eliminated, stress concentration from the ball is relieved. , Never chip.

Therefore, the inner race of the present invention has the effect of significantly improving the durability of the constant velocity joint.

[Brief description of drawings]

FIG. 1 is a sectional view of an inner race of a constant velocity joint according to an embodiment of the present invention, FIG. 2 is a sectional view of an essential portion of an abrasive product obtained in the manufacturing process of the inner race, and FIG. 3 is a polishing method. FIG. 4 is a view showing a portion of the inner race that needs chamfering, FIG. 5 is a sectional view of a main portion of a conventional inner race, and FIG. 6 is an enlarged view of a portion XI of FIG. FIG. 7 is a sectional view showing the durability test results of the constant velocity joint using the inner race according to the present invention in comparison with that of the conventional product. In the figure: 1 ... inner race, 2 ... ball groove, 3 ... outer spherical surface, 4 ... chamfered portion, 5 ... abnormal carburized layer, 6 ... carburized hardened layer, 7 ...

Claims (1)

[Scope of utility model registration request] 1. A carburizing and quenching treatment characterized in that there is no abnormal carburizing layer in the chamfered portion between the outer spherical surface and the ball groove, and the chamfered portion and each surface of the ball groove are connected by an R surface. Inner race of constant velocity joint manufactured by.