Plasma arc welding machine for differential shell

Abstract

The invention relates to the technical field of welding devices, in particular to a differential shell plasma arc welding machine which comprises a supporting seat, a protective cover, a dragging rod, a fixing structure, a positioning structure, a rotating structure, a position adjusting structure, an abutting structure, a welding structure, a dragging table, a main shell, an end cover, a dust suction pipe and a flange. When the main shell is placed on the dragging table, the end cover can be placed on the positioning structure, and the end cover can be accurately positioned through the positioning structure, so that after the end cover is pressed on the main shell by the pressing structure, the position of the end cover can be kept unchanged, and the situation that the position of the end cover and the position of the main shell are greatly deviated during manual placement is avoided; according to the main shell welding device, the quality of a welded finished product is guaranteed, after one of the main shells is welded, the towing rod is rotated by 180 degrees through the position adjusting structure, the positions of the two main shells are exchanged, and therefore the main shells can be fixed and unfixed while welding is conducted, and the welding machining efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of welding devices, and more specifically, to a plasma arc welding machine for a differential housing. Background Art

[0002] As the main frame of the differential, the differential housing provides a stable installation foundation for core components such as internal gears, axle gears, and planetary gears. During production, the differential housing is first formed by stamping a metal sheet with a stamping die to form a half housing, and then two symmetrical half housings are welded to form a main housing. Then, an end cover is welded to one side of the main housing, and a plasma arc welding machine can be selected for welding during the welding process of the end cover.

[0003] However, during the welding process of the end cover and the main housing, most of the time, workers manually place the end cover on the main housing, then press and fix it, and finally perform welding. When manually placing it, due to the lack of precise positioning and relying solely on the operator's naked eye to observe the position of the end cover, it is possible that the position of the end cover deviates significantly, which will have an adverse impact on the quality of the welded finished product. In addition, in order to prevent the main housing from moving during welding, it needs to be fixed. Therefore, after each welding is completed, it takes a certain amount of time to release the fixation of the housing and re-fix the housing, which is not convenient for fixing and releasing the fixation of the housing during welding, thus increasing the welding time and reducing the welding efficiency. Moreover, the harmful fumes generated during welding will directly disperse into the surrounding environment, which is likely to pollute the surrounding environment and result in poor environmental protection during use. Summary of the Invention

[0004] Aiming at the problems in the prior art, the present invention provides a plasma arc welding machine for a differential housing.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a plasma arc welding machine for a differential housing, including a support base, a protective cover is fixedly connected to the support base, a drag bar is rotatably connected to the support base, two drag platforms are rotatably connected to the drag bar, a fixing structure is provided on the drag platform, a positioning structure is provided on the drag platform, a rotating structure is provided on the protective cover, a pressing structure is provided on the protective cover, a welding structure is provided on the protective cover, an adjustment structure is provided on the support base, an end cover is placed on the positioning structure, a main housing is placed on the drag platform, a dust suction pipe is fixedly connected to the protective cover, and one end of the dust suction pipe is fixedly connected to a flange;

[0006] The positioning structure includes a connecting cylinder and a movable rod. The top end of the drag platform is fixedly connected with the connecting cylinder. The movable rod is slidably connected inside the connecting cylinder. A spring is abutted between the movable rod and the connecting cylinder. Four connecting rods are fixedly connected to the movable rod. One end of the four connecting rods is fixedly connected to the same positioning support plate. An end cover is placed on the positioning support plate.

[0007] Specifically, the center of the connecting cylinder and the center of the drag platform are on the same straight line. The two drag platforms are symmetrically distributed about the rotation center of the drag rod.

[0008] Specifically, the fixing structure includes a screw rod and a rotating rod. The screw rod is rotatably connected to the drag platform. Four sliders are slidably connected to the drag platform. A resisting shaft is fixedly connected to the slider. A rotating ring is rotatably connected to the drag platform. Four first guiding grooves are provided on the rotating ring. The bottom end of the resisting shaft extends into the adjacent first guiding groove and is slidably connected with the rotating ring. The four resisting shafts are abutted against the same main housing. A connecting block is fixedly connected to one of the sliders. The connecting block is threadedly connected with the screw rod.

[0009] Specifically, the end of the screw rod is fixedly connected with the rotating rod. The rotating rod is perpendicular to the screw rod.

[0010] Specifically, the center of the rotating ring and the center of the drag platform are on the same straight line. The four resisting shafts are circumferentially arrayed about the center of the rotating ring.

[0011] Specifically, the pressing structure includes a second electric push rod and a connecting plate. The second electric push rod is installed at the top end of the protective cover. The bottom end of the second electric push rod is fixedly connected with the connecting plate. The bottom end of the connecting plate is rotatably connected with a pressing plate. The bottom end of the pressing plate is abutted against the top end of one of the end covers.

[0012] Specifically, two sliding columns are fixedly connected to the top end of the connecting plate. Two guiding sleeves are fixedly connected to the protective cover. The sliding column is slidably connected with the adjacent guiding sleeve.

[0013] Specifically, the position adjusting structure includes a connecting seat and a sliding rod. The connecting seat is fixedly connected to the supporting seat. The sliding rod is slidably connected to the connecting seat. A second guiding groove is provided on the sliding rod. The bottom end of the drag rod is fixedly connected with a guiding shaft. The guiding shaft extends into the second guiding groove and is slidably connected with the sliding rod. The first electric push rod is installed on the connecting seat. The extending end of the first electric push rod is fixedly connected with the sliding rod. The included angle between the sliding direction of the sliding rod and the second guiding groove is an acute angle. The position of the guiding shaft deviates from the rotation center of the drag rod.

[0014] Specifically, the rotating structure includes a motor and a gear. A motor is installed on the protective cover. A gear is fixedly connected to the output shaft of the motor. A toothed ring is fixedly connected to the carriage. One of the toothed rings meshes with the gear.

[0015] Specifically, the welding structure includes a connecting sleeve and a sliding shaft. A connecting sleeve is fixedly connected to the protective cover. A sliding shaft is slidably connected inside the connecting sleeve. A welding gun head is fixedly connected to the end of the sliding shaft. A plasma arc welding machine body is installed on the support seat. A third electric push rod is installed on the protective cover. The extending end of the third electric push rod is fixedly connected to the sliding shaft.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) For the plasma arc welding machine for a differential housing of the present invention, when the main housing is placed on the carriage and fixed by the fixing structure, the end cover can be placed on the positioning structure. The positioning structure can accurately position the end cover. Therefore, when the pressing structure presses the end cover against the main housing, the position of the end cover can be ensured to remain unchanged, avoiding the situation where the position deviation between the end cover and the main housing is large during manual placement, thus ensuring the quality of the welded finished product.

[0018] (2) For the plasma arc welding machine for a differential housing of the present invention, when welding one of the main housings and the end cover through the welding structure, the other main housing can be placed on another carriage and fixed by the fixing structure. After one of the main housings is welded, the drag bar is rotated 180 degrees through the position adjustment structure, so that the two main housings are swapped in position. Therefore, the work of fixing and releasing the fixing of the main housing can be realized while welding, thus shortening the welding processing time and improving the welding processing efficiency.

[0019] (3) For the plasma arc welding machine for a differential housing of the present invention, the welding between the main housing and the end cover can be realized through the welding structure. During the welding process, the carriage can be rotated through the rotating structure, so as to realize the all-round welding of the housing and the end cover. And the air inlet pipe of the dust collector can be connected between the flange and the suction pipe. Therefore, the dust generated during the welding process can enter the inside of the suction pipe and finally enter the inside of the dust collector for removal, thus avoiding the dust generated during the welding process from spreading into the surrounding environment and polluting the environment, thereby improving the environmental protection of use. Description of the Drawings

[0020] The present invention will be further described below in conjunction with the drawings and embodiments.

[0021] Figure 1Schematic diagram of the overall structure of a preferred embodiment of a differential housing plasma arc welding machine provided by the present invention;

[0022] Figure 2 Schematic diagram of the connection structure between the carriage and the gear ring of the present invention;

[0023] Figure 3 For Figure 2 Enlarged schematic diagram of part A shown;

[0024] Figure 4 Schematic diagram of the connection structure between the second electric push rod and the protective cover of the present invention;

[0025] Figure 5 For Figure 4 Enlarged schematic diagram of part B shown;

[0026] Figure 6 For Figure 5 Enlarged schematic diagram of part C shown;

[0027] Figure 7 For Figure 5 Enlarged schematic diagram of part D shown.

[0028] In the figure: 1, support base; 2, protective cover; 3, drag bar; 4, fixing structure; 401, screw; 402, rotating rod; 403, connecting block; 404, slider; 405, abutting shaft; 406, rotating ring; 407, first guide groove; 5, positioning structure; 501, connecting cylinder; 502, movable rod; 503, spring; 504, connecting rod; 505, positioning support plate; 6, rotating structure; 601, motor; 602, gear; 603, gear ring; 7, position adjusting structure; 701, connecting seat; 702, sliding rod; 703, second guide groove; 704, guide shaft; 705, first electric push rod; 8, pressing structure; 801, second electric push rod; 802, connecting plate; 803, guide sleeve; 804, sliding column; 805, pressing plate; 9, welding structure; 901, connecting sleeve; 902, sliding shaft; 903, welding gun head; 904, plasma arc welding machine body; 905, third electric push rod; 10, carriage; 11, main housing; 12, end cover; 13, dust suction pipe; 14, flange. Detailed implementation manners

[0029] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with the specific implementation manners.

[0030] Such as Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 AndFigure 7 As shown in the figure, a plasma arc welding machine for a differential housing according to the present invention includes a support base 1, a protective cover 2 is fixedly connected to the support base 1, a drag bar 3 is rotatably connected to the support base 1, two drag platforms 10 are rotatably connected to the drag bar 3, a fixing structure 4 is provided on the drag platform 10, a positioning structure 5 is provided on the drag platform 10, a rotating structure 6 is provided on the protective cover 2, a pressing structure 8 is provided on the protective cover 2, a welding structure 9 is provided on the protective cover 2, an adjusting structure 7 is provided on the support base 1, an end cover 12 is placed on the positioning structure 5, a main housing 11 is placed on the drag platform 10, a dust suction pipe 13 is fixedly connected to the protective cover 2, and one end of the dust suction pipe 13 is fixedly connected to a flange 14;

[0031] As Figure 1 , Figure 4 , Figure 5 and Figure 7As shown in the figure, the positioning structure 5 includes a connecting cylinder 501 and a movable rod 502. The top end of the drag platform 10 is fixedly connected with the connecting cylinder 501. The movable rod 502 is slidably connected inside the connecting cylinder 501. A spring 503 is abutted between the movable rod 502 and the connecting cylinder 501. Four connecting rods 504 are fixedly connected to the movable rod 502. One end of the four connecting rods 504 is fixedly connected with the same positioning support plate 505. An end cover 12 is placed on the positioning support plate 505. The center of the connecting cylinder 501 and the center of the drag platform 10 are on the same straight line. The two drag platforms 10 are symmetrically distributed about the rotation center of the drag rod 3. The pressing structure 8 includes a second electric push rod 801 and a connecting plate 802. The second electric push rod 801 is installed at the top end of the protective cover 2. The bottom end of the second electric push rod 801 is fixedly connected with the connecting plate 802. The bottom end of the connecting plate 802 is rotatably connected with a pressing plate 805. The bottom end of the pressing plate 805 abuts against the top end of one of the end covers 12. Two sliding columns 804 are fixedly connected to the top end of the connecting plate 802. Two guiding sleeves 803 are fixedly connected to the protective cover 2. The sliding columns 804 are slidably connected with the adjacent guiding sleeves 803. That is, when the main housing 11 is placed on the drag platform 10 and positioned and fixed by the four abutting shafts 405, the end cover 12 can be placed on the positioning support plate 505. Since the outer side of the positioning support plate 505 is in a conical structure, the end cover 12 can be accurately positioned after the outer side of the positioning support plate 505 and the inner side of the end cover 12 are fitted. When the end cover 12 is located at the bottom end of the connecting plate 802, the second electric push rod 801 can be started. The elongation of the second electric push rod 801 will drive the connecting plate 802 to move. The connecting plate 802 drives the pressing plate 805 to move towards the end cover 12. When the pressing plate 805 contacts the end cover 12, the movement of the pressing plate 805 will abut against the movement of the positioning support plate 505. During the movement of the positioning support plate 505, the movable rod 502 will slide inside the connecting cylinder 501, and the spring 503 will contract. When the end cover 12 is tightly abutted against the main housing 11, the second electric push rod 801 stops elongating. At this time, the fixation between the end cover 12 and the main housing 11 is realized, avoiding the movement of the end cover 12 during the welding process, and ensuring that the position of the end cover 12 remains unchanged after each fixation. Therefore, it can avoid large deviations in the position during manual placement and have an adverse impact on the quality of the welded finished product, thus effectively ensuring the quality of the welded finished product.

[0032] Specifically, as Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 7As shown, the fixing structure 4 includes a screw rod 401 and a rotating rod 402. The screw rod 401 is rotatably connected to the carriage 10. Four sliders 404 are slidably connected to the carriage 10. A resisting shaft 405 is fixedly connected to the slider 404. A rotating ring 406 is rotatably connected to the carriage 10. Four first guiding grooves 407 are provided on the rotating ring 406. The bottom end of the resisting shaft 405 extends into the interior of an adjacent first guiding groove 407 and is slidably connected to the rotating ring 406. The four resisting shafts 405 are in contact with the same main housing 11. A connecting block 403 is fixedly connected to one of the sliders 404. The connecting block 403 is threadedly connected to the screw rod 401. The end of the screw rod 401 is fixedly connected to the rotating rod 402. The rotating rod 402 is perpendicular to the screw rod 401. The center of the rotating ring 406 and the center of the carriage 10 are on the same straight line. The four resisting shafts 405 are circumferentially arranged about the center of the rotating ring 406. The position adjusting structure 7 includes a connecting seat 701 and a sliding rod 702. The connecting seat 701 is fixedly connected to the support base 1. The sliding rod 702 is slidably connected to the connecting seat 701. A second guiding groove 703 is provided on the sliding rod 702. The bottom end of the towing rod 3 is fixedly connected to a guiding shaft 704. The guiding shaft 704 extends into the interior of the second guiding groove 703 and is slidably connected to the sliding rod 702. A first electric push rod 705 is installed on the connecting seat 701. The extending end of the first electric push rod 705 is fixedly connected to the sliding rod 702. The included angle between the sliding direction of the sliding rod 702 and the second guiding groove 703 is an acute angle. The position of the guiding shaft 704 is offset from the rotation center of the towing rod 3. That is, when welding one of the main housings 11 and the end cover 12, the other main housing 11 can be placed on the carriage 10. Then, by holding the rotating rod 402 and rotating the screw rod 401, as the screw rod 401 rotates, the connecting block 403 will move axially. The movement of the connecting block 403 will drive one of the sliders 404 to slide on the carriage 10. One of the sliders 404 will drive one of the resisting shafts 405 to move towards the main housing 11. When one of the resisting shafts 405 moves, it will move inside one of the first guiding grooves 407. At this time, the rotating ring 406 will rotate. The rotation of the rotating ring 406 will cause the remaining three first guiding grooves 407 to move synchronously, so that the other three resisting shafts 405 will move towards the main housing 11 at the same time. Continuously rotate the screw rod 401 until the four resisting shafts 405 are in contact with the main housing 11 at the same time. At this time, the positioning and fixing of the main housing 11 are achieved. By positioning and fixing the main housing 11, it can be ensured that its position remains consistent every time it is placed, thus facilitating the subsequent welding of the main housing 11 and the end cover 12. When one of the main housings 11 is welded, the first electric push rod 705 can be started. The contraction of the first electric push rod 705 will drive the sliding rod 702 to slide on the connecting seat 701,During the movement of the sliding rod 702, the guiding shaft 704 will move inside the second guiding groove 703. At this time, the towing rod 3 will rotate. When the towing rod 3 just rotates 180 degrees to make the first electric push rod 705 stop contracting, the positions of the two main shells 11 are swapped. Next, the main shell 11 that has not been welded is welded, and the welded main shell 11 is removed from the towing table 10, so that the fixing and unfixing of the main shell 11 can be realized while welding, thus shortening the welding time and effectively improving the welding efficiency.

[0033] Specifically, as Figure 4 , Figure 5 and Figure 6 shown, the rotating structure 6 includes a motor 601 and a gear 602. The motor 601 is installed on the protective cover 2. A gear 602 is fixedly connected to the output shaft of the motor 601. A toothed ring 603 is fixedly connected to the towing table 10. One of the toothed rings 603 meshes with the gear 602. The welding structure 9 includes a connecting sleeve 901 and a sliding shaft 902. The connecting sleeve 901 is fixedly connected to the protective cover 2. A sliding shaft 902 is slidably connected inside the connecting sleeve 901. A welding gun head 903 is fixedly connected to the end of the sliding shaft 902. A plasma arc welding machine body 904 is installed on the support base 1. A third electric push rod 905 is installed on the protective cover 2. The extending end of the third electric push rod 905 is fixedly connected to the sliding shaft 902, that is: the main shell 11 and the end cover 12 can be welded by the plasma arc welding machine body 904 cooperating with the welding gun head 903. During the welding process, the motor 601 can be started. The output shaft of the motor 601 rotates to drive the gear 602 to rotate. The rotation of the gear 602 will drive the toothed ring 603 to rotate. The rotation of the toothed ring 603 will drive the towing table 10 to rotate. The rotation of the towing table 10 will drive the main shell 11 to rotate, so as to realize the all-round welding of the main shell 11. After the welding is completed, the third electric push rod 905 can be started. The third electric push rod 905 extends to drive the sliding shaft 902 to slide on the connecting sleeve 901. The movement of the sliding shaft 902 drives the welding gun head 903 to move away from the main shell 11, so that a certain distance is maintained between the welding gun head 903 and the main shell 11, avoiding collision between the welding gun head 903 and the welding gun head 903 during the movement of the end cover 12 and causing damage to the welding gun head 903, thus improving the safety of use. And the air inlet pipe of the dust collector can be connected between the flange 14 and the dust suction pipe 13. Therefore, the dust generated during the welding process can enter the inside of the dust suction pipe 13 and finally enter the inside of the dust collector for removal, thus avoiding the dust generated during the welding process from spreading into the surrounding environment and polluting the environment, thus improving the environmental protection of use.

[0034] When the present invention is in use, when welding one of the main housings 11 and the end cap 12, the other main housing 11 can be placed on the drag platform 10, and then the screw 401 is rotated by holding the rotating rod 402. As the screw 401 rotates, the connecting block 403 will move axially thereon. The movement of the connecting block 403 will drive one of the sliders 404 to slide on the drag platform 10. One of the sliders 404 will drive one of the abutting shafts 405 to move towards the main housing 11. When one of the abutting shafts 405 moves, it will move inside one of the first guiding grooves 407. At this time, the rotating ring 406 will rotate. The rotation of the rotating ring 406 will cause the remaining three first guiding grooves 407 to move synchronously, so that the other three abutting shafts 405 move towards the main housing 11 at the same time. Continuously rotate the screw 401 until the four abutting shafts 405 are in contact with the main housing 11 at the same time. At this time, the positioning and fixing of the main housing 11 is achieved. By positioning and fixing the main housing 11, it can be ensured that its position remains consistent every time it is placed, thus facilitating the subsequent welding of the main housing 11 and the end cap 12. When the main housing 11 is placed on the drag platform 10 and positioned and fixed by the four abutting shafts 405, the end cap 12 can be placed on the positioning support plate 505. Since the outer side of the positioning support plate 505 is in a conical structure, when the outer side of the positioning support plate 505 is in contact with the inner side of the end cap 12, the end cap 12 can be accurately positioned. Then, by starting the first electric push rod 705, the contraction of the first electric push rod 705 will drive the sliding rod 702 to slide on the connecting seat 701. During the movement of the sliding rod 702, the guiding shaft 704 will move inside the second guiding groove 703. At this time, the drag rod 3 will rotate. When the drag rod 3 just rotates 180 degrees, the first electric push rod 705 stops contracting. At this time, the positions of the two main housings 11 are swapped. When the end cap 12 is located at the bottom of the connecting plate 802, the second electric push rod 801 can be started. The elongation of the second electric push rod 801 will drive the connecting plate 802 to move. The connecting plate 802 drives the pressing plate 805 to move towards the end cap 12. When the pressing plate 805 comes into contact with the end cap 12, the movement of the pressing plate 805 will abut against the positioning support plate 505 to move. During the movement of the positioning support plate 505, the movable rod 502 will slide inside the connecting cylinder 501, and the spring 503 contracts. When the end cap 12 is tightly abutted against the main housing 11, the second electric push rod 801 stops elongating. At this time, the fixing between the end cap 12 and the main housing 11 is achieved, avoiding the movement of the end cap 12 during the welding process, and ensuring that the position of the end cap 12 remains unchanged after each fixing. Therefore, it can avoid large deviations in position during manual placement, which may have an adverse impact on the quality of the welded finished product, thus effectively ensuring the quality of the welded finished product. Next, the main housing 11 that has not been welded is welded, and the welded main housing 11 is removed from the drag platform 10, so that the fixing and releasing of the main housing 11 can be achieved while welding, thus shortening the welding time and effectively improving the welding efficiency;

[0035] The main housing 11 and the end cap 12 can be welded by the plasma arc welding machine body 904 in cooperation with the welding gun head 903. During the welding process, the motor 601 can be started. The output shaft of the motor 601 rotates to drive the gear 602 to rotate. The rotation of the gear 602 drives the ring gear 603 to rotate. The rotation of the ring gear 603 drives the turntable 10 to rotate. The rotation of the turntable 10 drives the main housing 11 to rotate, so as to realize the all-round welding of the main housing 11. After the welding is completed, the third electric push rod 905 can be started. The third electric push rod 905 extends to drive the sliding shaft 902 to slide on the connecting sleeve 901. The movement of the sliding shaft 902 drives the welding gun head 903 to move away from the main housing 11, so as to keep a certain distance between the welding gun head 903 and the main housing 11, and avoid collision with the welding gun head 903 during the movement of the end cap 12, resulting in damage to the welding gun head 903, thus improving the safety of use. And the air inlet pipe of the dust collector can be connected between the flange 14 and the dust suction pipe 13. Therefore, the dust generated during the welding process can enter the inside of the dust suction pipe 13 and finally enter the inside of the dust collector for removal, so as to avoid the dust generated during the welding process from spreading into the surrounding environment and polluting the environment, thus improving the environmental protection of use.

[0036] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0037] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A plasma arc welding machine for a differential housing, characterized in that, It includes a support base (1), a protective cover (2) is fixedly connected to the support base (1), a towing rod (3) is rotatably connected to the support base (1), two towing platforms (10) are rotatably connected to the towing rod (3), a fixing structure (4) is provided on the towing platform (10), a positioning structure (5) is provided on the towing platform (10), a rotating structure (6) is provided on the protective cover (2), a pressing structure (8) is provided on the protective cover (2), a welding structure (9) is provided on the protective cover (2), an adjusting structure (7) is provided on the support base (1), an end cover (12) is placed on the positioning structure (5), a main housing (11) is placed on the towing platform (10), a dust suction pipe (13) is fixedly connected to the protective cover (2), and a flange (14) is fixedly connected to one end of the dust suction pipe (13). The positioning structure (5) includes a connecting cylinder (501) and a movable rod (502). The top end of the towing platform (10) is fixedly connected with the connecting cylinder (501). The movable rod (502) is slidably connected inside the connecting cylinder (501). A spring (503) is abutted between the movable rod (502) and the connecting cylinder (501). Four connecting rods (504) are fixedly connected to the movable rod (502). One same positioning support plate (505) is fixedly connected to one ends of the four connecting rods (504). The end cover (12) is placed on the positioning support plate (505).

2. The plasma arc welding machine for a differential housing according to claim 1, wherein: The center of the connecting cylinder (501) and the center of the towing platform (10) are on the same straight line. The two towing platforms (10) are symmetrically distributed about the rotation center of the towing rod (3).

3. A plasma arc welding machine for a differential housing according to claim 1, characterized in that: The fixing structure (4) includes a screw rod (401) and a rotating rod (402). The screw rod (401) is rotatably connected to the towing platform (10). Four sliders (404) are slidably connected to the towing platform (10). An abutting shaft (405) is fixedly connected to the slider (404). A rotating ring (406) is rotatably connected to the towing platform (10). Four first guiding grooves (407) are provided on the rotating ring (406). The bottom end of the abutting shaft (405) extends into the adjacent first guiding groove (407) and is slidably connected with the rotating ring (406). The four abutting shafts (405) are abutted against the same main housing (11). A connecting block (403) is fixedly connected to one of the sliders (404). The connecting block (403) is threadedly connected with the screw rod (401).

4. The plasma arc welding machine for a differential housing according to claim 3, wherein: The end of the screw rod (401) is fixedly connected with the rotating rod (402). The rotating rod (402) is perpendicular to the screw rod (401).

5. A plasma arc welding machine for a differential housing according to claim 3, characterized in that: The center of the rotating ring (406) and the center of the towing platform (10) are on the same straight line. The four abutting shafts (405) are circumferentially arrayed about the center of the rotating ring (406).

6. A plasma arc welding machine for a differential housing according to claim 1, characterized in that: The pressing structure (8) includes a second electric push rod (801) and a connecting plate (802). The second electric push rod (801) is installed at the top end of the protective cover (2). The bottom end of the second electric push rod (801) is fixedly connected to the connecting plate (802). The bottom end of the connecting plate (802) is rotatably connected to a pressing plate (805). The bottom end of the pressing plate (805) abuts against the top end of one of the end covers (12).

7. A plasma arc welding machine for a differential housing according to claim 6, characterized in that: Two sliding columns (804) are fixedly connected to the top end of the connecting plate (802). Two guiding sleeves (803) are fixedly connected to the protective cover (2). The sliding columns (804) are slidably connected to the adjacent guiding sleeves (803).

8. A plasma arc welding machine for a differential housing according to claim 1, characterized in that: The position adjusting structure (7) includes a connecting seat (701) and a sliding rod (702). The connecting seat (701) is fixedly connected to the support seat (1). The sliding rod (702) is slidably connected to the connecting seat (701). A second guiding groove (703) is provided on the sliding rod (702). The bottom end of the towing rod (3) is fixedly connected to a guiding shaft (704). The guiding shaft (704) extends into the second guiding groove (703) and is slidably connected to the sliding rod (702). A first electric push rod (705) is installed on the connecting seat (701). The extending end of the first electric push rod (705) is fixedly connected to the sliding rod (702). The included angle between the sliding direction of the sliding rod (702) and the second guiding groove (703) is an acute angle. The position of the guiding shaft (704) deviates from the rotation center of the towing rod (3).

9. A plasma arc welding machine for a differential housing according to claim 1, wherein: The rotating structure (6) includes a motor (601) and a gear (602). The motor (601) is installed on the protective cover (2). The output shaft of the motor (601) is fixedly connected to the gear (602). A toothed ring (603) is fixedly connected to the towing platform (10). One of the toothed rings (603) meshes with the gear (602).

10. A plasma arc welding machine for a differential housing according to claim 1, characterized in that: The welding structure (9) includes a connecting sleeve (901) and a sliding shaft (902). The connecting sleeve (901) is fixedly connected to the protective cover (2). The sliding shaft (902) is slidably connected to the inside of the connecting sleeve (901). The end of the sliding shaft (902) is fixedly connected to a welding gun head (903). A plasma arc welding machine body (904) is installed on the support seat (1). A third electric push rod (905) is installed on the protective cover (2). The extending end of the third electric push rod (905) is fixedly connected to the sliding shaft (902).

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