KR101249341B1 - A drum type washing machine and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A shaft of a drum washing machine and a manufacturing method thereof are provided to fabricate a shaft by multi-stage forging with a pipe material not needing to cut the surface of the shaft, reduce the weight of the shaft for improving performance and productivity of the shaft, and to effectively prevent abrasion of interface between the shaft and a bearing in addition to corrosion of interface between the shaft and a sealing member. CONSTITUTION: A shaft of a drum washing machine comprises an interface with a rotating tank at one end of the shaft; a first serration formed at the outer surface of the interface with a rotating tank; an interface with a sealing member; an interface with a first bearing; a body part; an interface with a second bearing and a driving force delivering part; a second serration formed at the outer surface of the driving force delivering part; and a female screw formed in the center of the end of the driving force delivering part. A manufacturing method of the shaft comprises a forging process(100) of shaping a pipe material by six cold forgings; a partial cutting process(200) for forming an interfaces with the first bearing, the second bearing, and the sealing member; a nitriding process(300) of nitriding the surface of the shaft; a grinding process(400) of grinding the interfaces with the sealing member, the first bearing, and the second bearing; and a filming process(500) of building a film on the surface by homo-treatment. [Reference numerals] (110) First forging; (120) Second forging; (130) Third forging; (140) Fourth forging; (150) Fifth forging; (160) Sixth forging; (200) Cutting and threading; (300) Heat-treating; (400) Grinding; (500) Steam oxidizing; (AA) Pipe material cutting; (BB) Product completion;

Description

Shaft of drum washing machine and its manufacturing method {A DRUM TYPE WASHING MACHINE AND MANUFACTURING METHOD THEREOF}

The present invention relates to a shaft of a drum washing machine and a method of manufacturing the same, which manufactures a shaft through a forging process of pipe materials, thereby reducing material costs and reducing the weight of the shaft, thereby simultaneously improving the performance and productivity of the shaft. The present invention relates to a shaft of a drum washing machine and a method of manufacturing the same.

In general, a drum washing machine is a device that pulls laundry up and then drops it and washes the laundry by the drop, and includes a water tank containing water inside the main body forming the exterior, a rotating tank rotatably installed in the tank, and applying power. It comprises a drive motor for receiving a rotational force and a shaft for transmitting the rotational force of the drive motor to the rotating tub.

One end of the shaft is fixed to the pulley connected to the drive motor and the belt and the other end of the shaft is fixed to the rotating tank through the water tank, whereby the rotating tank is rotated by the rotation operation of the shaft that rotates in accordance with the drive of the drive motor The laundry will be washed.

A pair of bearings are installed on the outer periphery between the rotating tub and the shaft ends connecting the pulleys to facilitate the rotation of the shaft. A rubber sealing member is installed at the outer circumference of the shaft to prevent the washing water from flowing into the bearing receptor to prevent the bearing from being corroded by the washing water.

On the other hand, the shaft is a rod-shaped casting or forging the general structural steel after cutting the surface of the general structural steel, the site where the bearing is installed and the site where the sealing member is installed to cut to suppress cutting and wear It is finished by processing.

However, the shaft of such a conventional drum washing machine, as described above, the cast rod-shaped general structural steel or forged material has a low dimensional accuracy and should be primarily cut to have an approximate shape of the shaft. The weight of the steel is heavier than the shaft forged in multi-stage using hollow pipe material, and its dimensional accuracy is low. In addition, its efficiency is low in terms of productivity.

Korean Patent Publication No. 10-2010-0012642 (2010.02.08) Korean Patent Publication No. 10-1053579 (2011.08.03)

The present invention relates to a shaft of a drum washing machine and a method of manufacturing the same, which manufactures a shaft through a forging process of pipe materials, thereby reducing material costs and reducing the weight of the shaft, thereby simultaneously improving the performance and productivity of the shaft. The present invention relates to a shaft of a drum washing machine and a method of manufacturing the same.

The shaft of the drum washing machine for achieving the object of the present invention is one end of the rotating tub connecting portion 51 is connected to the rotating tub, the driving force transmission unit 56, the rotating tub connecting portion 51 provided at the other end to receive the driving force of the driving motor. In the shaft (50) of the drum washing machine provided with a body portion 54 provided between the driving force transmission unit 56 and the drive motor to rotate the rotating tub, the shaft 50 is a pipe It is characterized by having a hollow cross section by forming the required shape of the shaft by the cold forging process of a multi-stage material.

In addition, the cold forging process for each step of the multi-stage is characterized in that the required shape is inserted by pressing a pair of molds to the outside of the pipe by inserting the corresponding mandrel for each step in the inner diameter of the pipe material.

In addition, the cold forging of the multi-stage is the driving force transmission unit 56, the second bearing contact portion 55, the body portion 54, the first bearing contact portion 53 and the sealing member contact portion 52, the rotary nail connecting portion 51 And a first serration 51a, a driving force transmission unit 56, and a second serration 56a.

In addition, after the multi-step cold forging, the partial cutting to cut the first and second bearing contact parts 53 and 55 and the sealing member contact part 52 of the shaft 50, and the end center of the driving force transmission part 56, respectively. Drill and tap processing to form the female thread 57, nitriding treatment on the surface of the shaft 50, grinding finishing on the sealing member contacting portion 52 and the first and second bearing contacting portions 53 and 55; It is characterized by forming a film 10a by surface treatment of the homo treatment.

Shaft manufacturing method of the drum washing machine according to the present invention, one end of the rotating tub connecting portion 51 is connected to the rotating tub, the driving force transmission unit 56, the rotating tub connecting portion 51 and the driving force provided at the other end to receive the driving force of the driving motor. It is provided with a body portion 54 provided between the transmission portion 56 to rotate the rotating tub when the drive motor is driven, the bearing portion for supporting the outer circumference of the body portion on the outer circumference of the body portion of the driving force transmission portion In order to manufacture the shaft of the drum washing machine is provided with a bearing receptor for the installation, a sealing member is installed on the outer circumference of the body between the bearing receptor and the rotating tubular connection to block the wash water from flowing into the bearing receptor. It is characterized in that it comprises a forging step having a hollow cross-section by forming the required shaft shape by the cold forging of the pipe-shaped material in multiple stages It shall be.

In addition, the cold forging process for each step of the multi-stage is characterized in that the required shape is inserted by pressing a pair of molds to the outside of the pipe by inserting the corresponding mandrel for each step in the inner diameter of the pipe material.

In addition, the cold forging process of the multi-stage is made of a total of five forging process, the driving force transmission unit 56 is formed in the first forging step, the second bearing contact portion 55 is formed in the second forging step, and the third In the forging step, the trunk portion 54 is formed, and in the fourth forging step, the first bearing contact part 53 and the sealing member contact part 52 are formed, and in the fifth forging step, the rotating tub connecting part 51 and the first age are formed. The formation 51a is formed, and in the sixth forging step, the driving force transmission unit 56 and the second serration 56a are formed in the order of being formed.

In addition, after the cold forging of the multi-stage, the first and second bearing contact parts 53 and 55 and the sealing member contact part 52 of the shaft 50 are internally screwed to the end of the cutting and driving force transmission part 56. 57) a partial cutting step of drilling and tapping to form a part, a nitriding treatment step on the surface of the shaft 50, and a grinding finishing step on the sealing member contact part 52 and the bearing contact surfaces 53 and 55; And it is characterized in that it further comprises the step of forming a coating (10a) by the surface treatment of the homo treatment.

Thus, the shaft of the drum washing machine according to the present invention forms the overall appearance through the forging molding obtained in the forging processing step, and the part requiring fine finishing, such as the bearing contact surface in contact with the bearing and the sealing member contact in contact with the sealing member. Only the cutting process is performed through the cutting step, the surface of the forged moldings after the partial cutting step is formed as a whole through at least one heat treatment of nitriding treatment or homo treatment in the heat treatment step.

Therefore, according to the shaft of the drum washing machine according to the present invention and the manufacturing method thereof, there is no need to cut the entire shaft surface, and the inconvenience of manufacturing and coupling a separate bush to the sealing member contact portion which is in contact with the sealing member occurs. By not doing so, the productivity of the shaft can be further improved.

In addition, according to the shaft of the drum washing machine according to the present invention and a method for manufacturing the same, the coating formed through the heat treatment step to improve the corrosion resistance and wear resistance of the shaft at the same time to prevent corrosion of the shaft in contact with the bearing as well as contact with the bearings It is also possible to effectively prevent the wear of the shaft of the site to be improved in the performance of the shaft can be improved than before.

1 is a cross-sectional view showing the overall structure of a drum washing machine employing a shaft according to the prior art.
Figure 2 is an enlarged cross-sectional view showing the shaft side in the drum washing machine employing the shaft of Figure 1
3 is a process flowchart showing a manufacturing process sequence of the shaft of the present invention.
Figures 4a and 4b is a cross-sectional view and a flow chart showing the machining site for each forging process of the present invention
5 is a cross-sectional view and a cutaway view showing a state in which the shaft is partially cut in the present invention;
6 is a process flowchart showing the heat treatment process of the present invention sequentially
7 is a process flowchart showing the homo treatment process of the present invention sequentially

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows the overall structure of a drum washing machine employing a shaft according to the prior art. FIG. 2 shows an enlarged view of the shaft side in FIG. 1.

As shown in Figure 1 and 2, the drum washing machine employing the shaft 10 according to the prior art is for the fresh water of the wash water is a cylindrical tub (2) installed in the main body (1), and the tank (2) It is rotatably installed in the inside, and is provided with the rotating cylinder 3 of the cylindrical shape in which the several through-hole 3a was formed. An inlet 4 is formed at the front of the water tank 2, the rotating tub 3, and the main body 1 so as to communicate laundry to the inside of the rotating tub 3, and the opening 4 is openable. The door 5 is installed.

A water supply and detergent input device 6 for supplying washing water and detergent to the inside of the water tank 2 is installed at an upper portion of the water tank 2, and a driving motor for rotating the rotating tank 3 at the lower portion of the water tank 2 ( 7) and a drainage device 8 for draining the wash water. In addition, the inside of the rotating tub (3) protrudes from the inner surface of the rotating tub (3) in the form of a mountain so that when the rotating tub (3) rotates to lift and drop the laundry and washing water, the front and rear longitudinal direction of the rotating tub (3) A plurality of lifters 3b extending in length are provided.

The drive motor 7 is connected to a pulley 9 installed at the rear of the water tank 2 through a belt 7a, and the shaft 10 is connected between the pulley 9 and the rotating tank 3. By the driving force of the drive motor 7 so that the rotating tub (3) can be rotated.

That is, the shaft 10 transmits the driving force of the other end connected to the pulley (9) to receive the driving force of the rotating tub connecting portion 11 provided at one end to be connected to the rotating tub (3) and the driving motor (7). It is configured to include a portion 12, the body portion 13 formed between the rotary tub connecting portion 11 and the driving force transmission portion (12).

The double rotary tubular connector 11 is coupled to the center of the radial spider 3c coupled to the rear side of the rotary tub 3 by passing through the rear of the tank 2, and the driving force transmission unit 12 is threaded to the pulley 9 Helical portion 12a of the end that is screwed into the screw hole 9a of the screw), and a polygonal cross section formed in a polygonal cross section in the pulley 9 in front of the screw hole 9a. It is composed of a polygonal shaft portion (12b) to be smoothly transmitted to the shaft 10 by being coupled to the pulley (9). Of course, unlike the present embodiment, the shaft 10 may also be directly connected to the driving motor 7, in which case the driving motor 7 is located at the rear side of the water tank 2, and the driving force of the shaft 10 is different. The transmission unit 12 may be fixed directly to the rotor (not shown) of the drive motor 7.

In addition, bearings 21 and 22 are installed on the outer circumference of the body portion 13 so as to facilitate the rotational movement of the shaft 10, and the bearings 21 and 22 are formed as bearing bodies integrally with the tank 2. 20 is installed to be embedded inside. The bearings 21 and 22 comprise a pair including a first bearing 21 installed to be close to the rotary tub connecting part 11 and a second bearing 22 installed to be close to the driving force transmission part 12. The bearing contact surfaces 13a and 13b are formed on the outer surface of the trunk portion 13 of the shaft 10 on which the first and second bearings 21 and 22 are supported.

And the outer periphery of the body portion (13) of the shaft (10) between the bearing receptor 20 and the rotary tub connecting portion 11 to prevent the bearing (21, 22) from being corroded by the wash water in the water tank (2) The member 30 is provided. The sealing member 30 is provided in a ring shape of a rubber material, and installed to cover the first bearing 21 inside one end of the bearing receptor 20 so as to block washing water from flowing into the bearing receptor 20. The outer surface of the trunk portion 13 of the shaft 10 on which the sealing member 30 is supported forms a sealing member contact portion 13c to which the sealing member 30 contacts.

On the other hand, in the present embodiment, after cutting the pipe material, the shaft 50 is subjected to six cold forgings in multiple stages to form the shaft 50 taking the shape of the hollow shaft 50, and The first and second bearing contact parts 53 and 55 and the sealing member contact part 52 are machined by cutting and drilled and tapped to form the female thread 57 at the center of the end of the driving force transmission part 56. Thereafter, the surface of the shaft 50 is manufactured through a process of forming the coating film 10a through nitriding treatment, grinding finish processing, and homogeneous treatment, which is manufactured through the manufacturing method of the shaft according to the present embodiment. The shaft 50 has a structure in which the sealing member contact portion 52 has a large improvement in corrosion resistance and abrasion resistance compared to the surface of a general structural steel, and thus has a configuration of a bush which is separately installed at a portion in contact with the sealing member 30 in the conventional shaft. Will be removed, and It is possible to manufacture the shaft 50 without the hassle of having to cut a plurality of times through several times the semi-structural force, so that the productivity of the shaft 10 can be greatly improved.

3 to 5, the shaft 50 according to the present embodiment includes a first serration 51 a formed outside the rotary tub connecting portion 51 and the rotary tub connecting portion from one end and the sealing member contacting portion 52. ), The first bearing contact portion 53, the trunk portion 54, the second bearing contact portion 55, the driving force transmission portion 56, the second serration 56a formed outside the driving force transmission portion, the end of the driving force transmission portion Consists of the formed female thread (57).

The shaft 50 of FIG. 5, which is an embodiment of the present invention, and the shaft 10 shown in FIG. 2, which is a prior art, have some differences in overall shape. Looking at the difference, the shaft 10 shown in FIG. The male screw line 12a is machined in the driving force transmission part 12 to be screwed into the screw hole 9a of the pulley 9, and the polygonal shaft part 12b is fastened in the polygonal hole to transmit the driving force, whereas the shaft of the present embodiment 50 constitutes a second serration 56a in a configuration corresponding to the polygonal shaft portion 12b of the prior art, and in the end portion of the driving force transmission section 56 in a configuration corresponding to the male threaded line 12a of the prior art. It is obvious that the formed female thread 57 is formed and the shape of the pulley coupled to the shaft 50 of the present embodiment is also changed to correspond to the shape of the present embodiment.

The shaft 50 is a forging step (100) for forming a six-stage cold forging process of the pipe material, and the first and second bearing contacts (53, 55) and the sealing member of the shaft (50) Partial cutting step 200 for cutting the contact portion 52, the nitriding treatment step 300 on the surface of the shaft 50, the sealing member contact portion 52 and the first and second bearing contact portion (53, 55) The grinding process step 400 and the step of homogeneous surface treatment to form a coating (10a) is produced through the step 500.

Looking at the processing site for each forging process shown in Figure 4, first of all, in the forging processing step 100, the forging press is inserted into a pipe-shaped material through a forging press, etc., then cold forging pressurized between a pair of molds The course is conducted six times in total. The mandrel is preferably tapered at an angle of 2 to 5/100 in order to facilitate extraction from the pipe-shaped material after each forging process.

In the first forging step 110 shown in Figure 4a, after inserting the first mandrel 41 in the pipe-shaped material, cold forging to pressurize the pipe-shaped material located between the pair of molds. . The portion formed at this time is the driving force transmission unit 56.

Thereafter, in the second forging step illustrated in FIG. 4B, after the second mandrel 42 is inserted into the pipe material after the first forging step, the cold forging pressurizes the pipe-shaped material located between the pair of molds. Is carried out. The portion formed at this time is the second bearing contact portion 55.

Thereafter, in the third forging step illustrated in FIG. 4C, after the third mandrel 43 is inserted into the pipe material after the second forging step, the cold forging presses the pipe-shaped material positioned between the pair of molds. Is carried out. The portion formed at this time is the trunk portion 54.

Thereafter, in the fourth forging step illustrated in FIG. 4D, after inserting the fourth mandrel 44 into the pipe material after the third forging step, the cold forging pressurizes the pipe-shaped material positioned between the pair of molds. Conduct. The portion formed at this time is the trunk portion 54, the first bearing contact portion 53 and the sealing member contact portion 52.

Thereafter, in the fifth forging step illustrated in FIG. 4E, after the fifth mandrel 45 is inserted into the pipe material after the fourth forging step, the cold forging pressurizes the pipe-shaped material positioned between the pair of molds. Is carried out. At this time, the portion formed is the rotating tubular connector 51 and the first serration (51a).

 Thereafter, in the sixth forging step illustrated in FIG. 4F, after inserting the sixth mandrel 46 into the pipe material after the fifth forging step, cold forging pressurizes the pipe-shaped material positioned between the pair of molds. Is carried out. The portion formed at this time is the driving force transmission unit 56 and the second serration 56a.

Thus, if the shaft is manufactured by cold forging in multiple stages using a pipe-shaped material, the material cost is reduced compared to the conventional solid shaft 50, and when cold forging is performed at room temperature without additional heating, by forging The structure is compact and the overall mechanical properties are excellent, and the dimensional accuracy is very high, it does not need to be cut except for the parts requiring very high precision of the bearing part and the sealing part. Shipping cost to reduce also has a number of advantages.

And as shown in FIG. 5, the partial cutting is completed in the shaft 50. In the partial cutting step 200, the first and second bearing contact parts 53 and 55 and the sealing member contact part 52 are cut and processed. In the shaft 50 to prevent abrasion during operation of the drum washing machine between the first and second bearing contact portions 53 and 55 and the bearings 21 and 22 or between the sealing member contact portion 52 and the sealing member 30. Only the parts that need to be cut are partially cut so that the shaft 50 can be manufactured without excessive cutting. In addition, the partial cutting step 200 is drilled and tapped to form a female screw 57 to the center of the end of the driving force transmission unit 56.

After the partial cutting step 200, the heat treatment step 300 is performed, and this heat treatment step is nitriding treatment. As shown in FIG. 6, the heat treatment step for nitriding the surface of the shaft 50 through the partial cutting step 200 is performed by heating the shaft 50 in a nitriding furnace in a nitrogen gas atmosphere to raise the temperature to about 500 to 520 ° C. In step 310, in this state, the nitriding step 320 for nitriding while heating for 150 to 180 minutes for a long time and the cooling step 330 for cooling the inside of the nitriding furnace to room temperature after the nitriding step 320 are performed. In the nitriding step 320, the generator nitrogen atom is diffused in the shaft 50 so that nitriding proceeds, and the ammonia gas is generated by the thermal decomposition by the catalytic action of the surface of the shaft 50 heated to 500 ° C. or more. 50 is adsorbed on the surface and diffuses therein to form a nitride layer, and the film 10a is formed through the nitride layer.

The thickness of the nitride layer forming the film 10a on the surface of the shaft 50 is approximately 12 to 22 microns, and the nitride layer is porous formed through iron nitride to improve the hardness of the surface of the shaft 50 and to improve wear resistance. In addition to improving the corrosion resistance. Therefore, the shaft 50 manufactured to have the coating 10a can effectively suppress the corrosion of the sealing member contacting portion 52 directly contacting the sealing member 30 due to the washing water without a separate bush. .

In addition, since the surface of the shaft 50 to which the coating film 10a formed of such a nitride layer is applied as a whole is greatly improved compared to the surface of a general structural steel in hardness, the first, 2 bearing contact portion (53, 55) is not feared to wear due to excessive contact with the bearing (21, 22) so that the service life of the shaft 50 can be further extended, this heat treatment step 300 is nitriding Properly designed sizes of tens to hundreds of films 10a can be simultaneously formed on the surface of the shaft 50, which is effective in terms of productivity.

In addition, as a second embodiment of the heat treatment step 300 of the present invention, in the heat treatment step, a homo treatment may be performed instead of the nitriding treatment, and through the homo treatment, the entire surface of the shaft 50 is formed as the film 10a. An oxide film formed of iron tetraoxide is formed.

After the nitriding heat treatment step 300 is polished to improve the surface accuracy of the first and second bearing contact parts 53 and 55 and the sealing member contact part 52 to correct distortion such as may be caused by the heat treatment. .

As shown in FIG. 7, the heat treatment step 500 for the homo treatment includes a pre-cleaning step 510, a homo furnace charging step 520, a homo furnace preheating step 530, a steam input step 540, and cooling. Step 550 is performed through the same process as the post-cleaning step 560 in sequence.

In detail, first, in the pre-cleaning step 510, the shaft 50, which has undergone the partial cutting step 200, is put into the cleaning liquid, and the cleaning liquid is vibrated by an ultrasonic vibrator to clean the surface of the shaft 50 to form the coating film 10a. In the forging processing step 100 or the partial cutting step 200, foreign matters, etc. that are attached to the shaft 50 surface are removed.

And in the homo furnace charging step 520 to seal the homo furnace in a state in which the plurality of shafts 50 passed through the pre-cleaning step 510 inside the homo furnace, the homo furnace preheating step 530 inside the homo furnace This state is maintained for about 30 minutes while the temperature is heated to 350 ± 10 ° C to activate the surface of the inner shaft 50 with a homo.

When the steam input step 540 is in this state, the homo furnace is further heated than the preheating step 530 by the homo furnace so that the internal temperature of the homo furnace is about 550 ± 5 ° C for 15 to 30 minutes. By introducing water vapor, a thin oxide film having a thickness of 2 to 3 microns is formed as a film 10a on the surface of the shaft 50 through ion coupling between the shaft 50 and water vapor, and after the steam injection step 540 is completed, Cooling step 550 is made.

In the cooling step 550, the shaft 50 in which the oxide film is formed is first cooled first to approximately 120 to 150 ° C. in a nitrogen gas atmosphere, and then secondly air-cooled. At this time, the shaft 50 in which the oxide film is formed is nitrogen gas atmosphere. The reason for cooling in is to prevent the adhesion between the oxide film and the inside of the oxide film may be reduced if the oxide film is oxidized before the oxide film is completely dried.

In addition, the homo treatment cleans the shaft 50 in which the cooling step 550 is completed in the same manner as in the pre-cleaning step 510 in the post-cleaning step 560 so that no foreign matter is formed on the surface of the manufactured shaft 50. It is done.

In the case of the film 10a formed of an oxide film through such a homo treatment, it is hard and porous and has a small coefficient of friction. The shaft 10 according to the present invention having such an oxide film as the film 10a is also the sealing. Even when the member contact portion 52 is in direct contact with the sealing member 30 without passing through a separate bush, the member contact portion 52 does not corrode during the use period, and at the same time, the bearing contact surface ( The wear of 53 and 55 can also be effectively suppressed.

In addition, in the present invention, the heat treatment step 500 may undergo a complex heat treatment process of additionally performing a homo treatment after nitriding treatment, unlike the above-described embodiments, and the heat treatment process may be performed after the nitriding treatment process described above. Homo treatment will be performed again. When the homo treatment is performed after the nitriding treatment, a coating film 10a formed of a thin oxide film having a thickness of about 1 to 2 microns is formed on the surface of the nitride layer forming the diffusion layer, and the coating film 10a is formed of an internal nitride. The hardness is doubled through the layer, which is more advantageous than the film formed through the heat treatment process according to the first and second embodiments described above on the hardness surface.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention but to describe the present invention, and the technical scope of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

41 to 46: first to sixth mandrel 50: shaft
51: rotary tub connecting portion 51a: the first serration
52: sealing member contact portion 53: first bearing contact portion
54: body portion 55: second bearing contact portion
56: driving force transmission unit 56a: second serration
57: female thread
21: first bearing 22: second bearing
30: sealing member 100: forging step
200: partial cutting step 300: heat treatment step
400: grinding step 500: homo treatment step

Claims (8)

delete delete One end of the rotating tub connecting portion 51 connected to the rotating tub, the driving portion transmitting portion 56 provided at the other end to receive the driving force of the driving motor, the trunk portion provided between the rotating tub connecting portion 51 and the driving force transmitting portion 56 In the shaft (50) of the drum washing machine provided with 54 to rotate the rotary tub when the drive motor is driven,
The shaft 50 is cold forging of multiple stages of the pipe-shaped material,
The cold forging process of the multi-stage is the driving force transmission unit 56, the second bearing contact portion 55, the body portion 54, the first bearing contact portion 53 and the sealing member contact portion 52, the rotary tub connecting portion 51 and The first serration 51a, the driving force transmission unit 56 and the second serration 56a are formed,
The cold forging process of each stage of the multi-stage drum washing machine, characterized in that for inserting the corresponding mandrel into the inner diameter of the pipe material, press the outer side of the pipe by a pair of molds to form the required shape. . The method of claim 3,
After the multi-stage cold forging, the partial cutting to cut the first and second bearing contact portions 53 and 55 and the sealing member contact portion 52 of the shaft 50, and to the center of the end of the driving force transmission portion 56 Drilling and tapping to form the female thread 57, nitriding on the surface of the shaft 50, grinding of the sealing member contacting portion 52 and the first and second bearing contacting portions 53 and 55; And a surface treatment of the homo treatment to form a coating (10a). delete delete One end of the rotating tub connecting portion 51 connected to the rotating tub, the driving portion transmitting portion 56 provided at the other end to receive the driving force of the driving motor, the trunk portion provided between the rotating tub connecting portion 51 and the driving force transmitting portion 56 (54) is provided to rotate the rotating tub when the drive motor is driven, a bearing receptor for the installation of a bearing for supporting the outer circumference of the body portion is provided on the outer circumference of the body portion of the driving force transmission portion, In order to manufacture the shaft 50 of the drum washing machine is provided with a sealing member on the outer periphery of the body between the bearing receptor and the rotating tub connecting portion to block the wash water from flowing into the bearing receptor,
Cold-forged multi-stage pipe material,
In the first forging step, the driving force transmission unit 56 is formed,
In the second forging step, the second bearing contact portion 55 is formed,
In the third forging step, the trunk portion 54 is formed,
In the fourth forging step, the first bearing contact portion 53 and the sealing member contact portion 52 are formed,
In the fifth forging step, the rotary tub connecting portion 51 and the first serration 51a are formed,
In the six forging step, the driving force transmitting part 56 and the second serration 56a are forged in the order of being formed.
The cold forging process of each stage of the multi-stage drum washing machine, characterized in that for inserting the corresponding mandrel into the inner diameter of the pipe material, press the outer side of the pipe by a pair of molds to form the required shape. Manufacturing method. The method of claim 7, wherein
After the cold forging of the multi-stage
Drilling and drilling to form the female thread (57) to the center of the end of the cutting and driving force transmission portion 56 of the first and second bearing contact portion (53, 55) and the sealing member contact portion (52) of the shaft (50) Part cutting step for tapping,
Nitriding treatment step on the surface of the shaft 50
Grinding step for the sealing member contact portion 52 and the first and second bearing contact portion (53, 55),
The method of manufacturing a shaft of a drum washing machine, characterized by further comprising the step of forming a coating (10a) by the surface treatment of the homo treatment.

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