KR101134422B1 - Moving part for automatic transmission and method for surface treatment thereof - Google Patents

Abstract

According to an aspect of the present invention, there is provided a method for treating a surface of a driving component for an automatic transmission, wherein a shot ball having a diameter of 0.2 to 0.7 mm is sprayed on a surface of the driving component by a gas nozzle to perform first shot peening; And a second shot peening by spraying a shot ball having a diameter of 0.01 to 0.1 mm on the surface of the first shot peened metal material by a gas nozzle. Since the surface treatment method has an optimized compressive stress on the surface part of the driving part, the fatigue life and the oral resistance can be improved, and the life of the transmission part can be improved, the strength of the part can be increased, and the design of the part can be reduced. It is possible to increase fuel economy through cost reduction and transmission weight reduction.

Automatic Transmission, Shot Peening, Compression Stress, Gas Nozzle

Description

MOVING PART FOR AUTOMATIC TRANSMISSION AND METHOD FOR SURFACE TREATMENT THEREOF}

The present invention relates to a drive component for an automatic transmission and a surface treatment method thereof. More specifically, the present invention relates to a drive part for an automatic transmission to which an optimized compressive stress is applied to a surface part by applying a stepping pin by varying the size of the shotball, and a surface treatment method thereof.

The automatic transmission converts the driving force generated by the automobile engine to the proper vehicle speed by using various planetary gears and shafts. Therefore, the drive parts of the transmission should have sufficient durability against the driving force generated in the engine, and wear, breakage, etc. should not occur. In order to achieve this purpose, each drive part is manufactured by a high strength material and a special heat treatment. In particular, recently, in order to achieve the goals of fuel efficiency improvement and exhaust gas reduction, the size of parts is small while the durability is increasing.

In particular, since the gears and shafts of the automatic transmission transmit the power of the engine, excessive contact and bending stresses are repeatedly received at the surface portion, which may cause fatigue damage of the contact portion and breakage of gear teeth or shafts. In order to prevent such damage, the shot peening treatment is used for the purpose of improving the durability by forming a compressive stress on the surface of the heat treated product.

The shot peening method applied to driving parts such as gears and shafts is classified into micro shot peening, hard short peening, shot peening by impeller, etc. according to the size of shot ball and injection method. The distribution of compressive residual stresses to be formed has a maximum stress value at a constant depth as shown in FIG. 1. As described above, the conventional shot peening method has a high residual stress value at a constant depth at a surface while having a high residual stress at a surface portion. It is impossible to have.

The technical structure described above is a background technique for assisting the understanding of the present invention, and does not mean the prior art widely known in the technical field to which the present invention belongs.

The present invention has been made in order to improve the above problems, by applying the stepping pins by varying the size of the shotball to have an optimized compressive stress on the surface portion to improve the fatigue life and oral resistance to improve the life of the transmission parts In addition, the present invention provides a driving component for an automatic transmission and a method of treating the surface thereof, which can increase the fuel consumption by reducing the cost and reducing the transmission weight by increasing the strength of the component and reducing the design of the component. There is a purpose.

One aspect of the present invention to achieve the above object provides a new method for treating the surface of the drive component for automatic transmission. The method comprises: first shot peening by spraying a shot ball having a diameter of 0.2 to 0.7 mm with a gas nozzle on a surface of a drive part; And a second shot peening by spraying a shot ball having a diameter of 0.01 to 0.1 mm on the surface of the first shot peened metal material by a gas nozzle.

In an embodiment, the first shot peening is characterized in that the shot ball is sprayed at a speed of 20 to 150 m / sec.

In addition, the second shot peening is characterized in that for spraying the shotball at a speed of 150 to 500 m / sec.

In an embodiment, the driving part may use a heat treated at 150 to 1000 ℃.

Another aspect of the invention relates to a drive part for an automatic transmission processed by the above method. The drive component for the automatic transmission has a maximum residual compressive stress at a depth of 1 to 20 µm from a surface of 1.3 to 2.0 GPa and a maximum residual compressive stress at a depth of 50 to 100 µm from a surface of 1.0 to 1.5 GPa. It is done.

The surface treatment method of the drive component for an automatic transmission according to the present invention has an effect that can have a high residual stress value even at a certain depth on the surface by having an optimized compressive stress on the surface portion of the drive component.

In addition, the drive parts for the automatic transmission processed by the above method can improve the fatigue life and the oral resistance to improve the life of the parts, as well as to increase the strength, and to reduce the design cost can be reduced, transmission weight There is an effect of increasing fuel economy through reduction.

According to an aspect of the present invention, there is provided a method for treating a surface of a driving component for an automatic transmission, wherein a shot ball having a diameter of 0.2 to 0.7 mm is sprayed on a surface of the driving component by a gas nozzle to perform first shot peening; And a second shot peening by spraying a shot ball having a diameter of 0.01 to 0.1 mm on the surface of the first shot peened metal material by a gas nozzle.

In an embodiment, the driving part may use a heat treated at 150 to 1000 ℃.

Although the shot peening method used in the present invention is not particularly limited, it is preferable to apply the injection method by the gas nozzle.

The first shot peening process is sprayed using a shot ball having a diameter of 0.2 to 0.7 mm. In the above range, it may have a better compressive residual stress on the surface. Preferably a shot ball of 0.3 to 0.5 mm in size is used.

The short ball may be used in various kinds, such as steel ball, stainless steel ball, ceramic ball, high-strength steel ball, preferably using a steel ball.

The gas for the injection may be air or nitrogen gas. Preferably compressed air can be used.

In the specific example, the air pressure during the first shot peening process is 100 to 1000 kPa, preferably 300 to 800 kPa.

In the first shot peening process, the injection speed of the shotball is in the range of 20 to 150 m / sec. The maximum value of the compressive residual stress and the formation depth thereof can be obtained in the above range. Preferably in the range from 50 to 120 m / sec.

In addition, the second shot peening process is sprayed using a shot ball having a diameter of 0.01 to 0.1 mm. In the above range, it may have a better compressive residual stress on the surface. Preferably, a shot ball having a size of 0.03 to 0.08 mm is used.

The type of shotball during the second shot peening process may be the same as or different from that applied in the first shot peening process.

In the specific example, the air pressure during the second shot peening process is 300 to 1200 kPa, preferably 500 to 1000 kPa.

In the second shot peening process, the injection speed of the shotball is in the range of 150 to 500 m / sec. The maximum value of the compressive residual stress and the formation depth thereof can be obtained in the above range. Preferably it is in the range from 200 to 350 m / sec.

The drive parts for automatic transmissions surface-treated in the above manner have a maximum residual compressive stress of 1.3 to 2.0 GPa at a depth of 1 to 20 μm from the surface, and a maximum residual compressive stress at a depth of 50 to 100 μm from the surface of 1.0 to It may have a range of 1.5 GPa. Preferably the maximum residual compressive stress at a depth of 1 to 20 μm from the surface is 1.4 to 2.0 GPa, the maximum residual compressive stress at a depth of 50 to 100 μm from the surface is 1.1 to 1.5 GPa, and 100 to 100 from the surface. The maximum residual compressive stress at a depth of 150 μm may range from 1.0 to 0.6 GPa. Therefore, the distribution of the compressive residual stress formed in the surface portion is superior to the conventional surface treatment method.

The product to which the surface treatment method of the present invention can be applied is not particularly limited, but may be preferably applied to a drive part for an automatic transmission. The drive part for the automatic transmission can be suitably applied to not only a gear and a shaft but also a welded part and a spring steel.

The invention may be better understood by the following examples, which are intended for purposes of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

After the first shot peening by adhering a 0.4 mm diameter shotball to the compressed air nozzle on the heat treated shaft surface, a second shot peening was performed by spraying a 0.05 mm diameter shotball through the compressed air nozzle. For each of the surface treated shafts, the compressive residual stresses were measured at a depth of 0 to 200 μm from the surface, and the measurement results are shown in FIG. 2. In addition, a torsion test (torque: 51.25 kgm, frequency: 5 Hz) was performed on the manufactured shaft, and the number of times until the crack formed and was measured was measured. The test was repeated three times to obtain an average for each number, and the results are shown in Table 1 below.

Comparative Example 1

A shot ball of 0.4 mm diameter was sprayed with an impeller to perform only one shot peening. Compressive residual stress results and torsion test conditions were performed in the same manner as in Example 1.

Comparative Example 2

A shotball with a diameter of 0.05 mm was sprayed with a compressed air nozzle to perform only one shot peening. Compressive residual stress results and torsion test conditions were performed in the same manner as in Example 1.

Example Comparative Example 1 Comparative Example 2 Life Span 2.5 million 250,000 80,000

As shown in Table 1, in the case of the composite shot peening as in Example, the lifespan is increased by more than 30 times compared to Comparative Example 1, it can be seen that 10 times higher than Comparative Example 2. In addition, in the case of residual stress, the embodiment of the composite shot peening can confirm that the compressive residual stress distribution of the surface part is optimized.

Simple modifications and variations of the present invention can be easily made by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

1 is a view schematically showing the residual stress distribution according to the shot peening method.

2 is a graph showing the compressive residual stress distribution according to the depth of the Examples and Comparative Examples.

Claims (5)

First shot peening by spraying a shot ball having a diameter of 0.2 to 0.7 mm with a gas nozzle on a surface of the driving part; And Spraying a shot ball having a diameter of 0.01 to 0.1 mm on a surface of the first shot pinned metal material by a gas nozzle to second shot peening; Including the steps, Drive parts for automatic transmissions having a maximum residual compressive stress of 1.3 to 2.0 GPa at a depth of 1 to 20 μm from the surface and a maximum residual compressive stress at a depth of 50 to 100 μm from the surface of 1.0 to 1.5 GPa Surface treatment method. The method of claim 1, wherein the first shot peening sprays a shot ball at a speed of 20 to 150 m / sec. The method of claim 1, wherein the second shot peening sprays a shot ball at a speed of 150 to 500 m / sec. The method of claim 1, wherein the drive part is heat-treated at 150 to 1000 ° C. Treated by the method of any one of claims 1 to 4, the maximum residual compressive stress at a depth of 1 to 20 μm from the surface is 1.3 to 2.0 GPa, and the maximum residual compressive stress at a depth of 50 to 100 μm from the surface. A drive component for an automatic transmission, characterized in that 1.0 to 1.5 GPa.

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