Main transmission system of heavy machine tool

Abstract

The invention discloses a main transmission system of a heavy machine tool. The invention relates to a variable-speed gear shifting mechanism which comprises a power input part, a power to-be-distributed structure, a variable-speed execution selection structure, a gear shifting driving device and a power output structure, and the gear shifting driving device is provided with a gear sleeve matched with the power to-be-distributed structure and the variable-speed execution selection structure and a linear driving mechanism installed in cooperation with the gear sleeve. The linear driving mechanism is connected with the sliding shaft and can drive the sliding shaft to reciprocate so that the variable speed execution selection structure can be matched with the power to-be-distributed structure and the power output structure to achieve output of different rotating speeds. The rigid tapping device has the advantages that rigid tapping can be achieved, the length of a transmission chain is effectively shortened, the rigid tapping device is easy to manufacture and machine, operation accuracy and reliability are guaranteed, the accuracy of a main transmission system is improved, and noise is greatly reduced.

Description

Technical Field

[0001] The invention relates to a mechanical transmission system, in particular to a main transmission system of a heavy-duty numerically controlled machine tool, and belongs to the technical field of high-end equipment. Background Art

[0002] At present, CNC floor-type milling and boring machines at home and abroad are developing rapidly towards high speed, high precision and reliability. The main transmission system of traditional milling and boring machines is integrated inside the spindle box. The transmission system inside the spindle box indirectly transmits power to the spindle inside the ram through the spline shaft and the auxiliary transmission mechanism, so that the spindle produces the main cutting movement. Taking the floor-type milling and boring machine as an example, the floor-type milling and boring machine is a heavy-duty metal cutting machine tool with a wide range of applications and functions. It has a freely extendable ram, and a milling spindle is installed in the ram. By installing tools or various functional accessories on the end of the milling spindle, it can not only realize heavy cutting of large diameters and large planes, but also process the inner cavities, inner cavity sides, inner cavity holes and large end surface stops of many workpieces; Figure 1 It can be seen that the spindle box is a key component of a floor-standing milling and boring machine. The spindle box assembly is mainly composed of main parts such as the spindle box 01, the main transmission system 02, the slide 03, the auxiliary transmission mechanism 04, the spindle 05 and the spline shaft 06; among them, the main transmission system 02 of the milling and boring machine is integrated into the spindle box 01 and is stationary relative to the spindle box 01; the auxiliary transmission mechanism 04 and the spindle 05 are integrated into the slide 03, and the spline shaft 06 is rigidly connected to the top surface of the slide 03; when the slide 03 moves, the spline shaft 06 and the internal spline at the end of the main transmission system 02 form a spline pair, which can not only realize the axial guiding effect, but also mainly plays the function of transmitting motion and power.

[0003] The existing transmission system can realize the cutting function, but the existence of the spline shaft causes the transmission chain to be too long, and the spline shaft itself is long, and the straightness accuracy of the long-distance spline groove processing is difficult to ensure, resulting in excessive reverse clearance and low accuracy. Rigid tapping cannot be achieved, and the spindle vibrates and makes noise at high speed, which seriously restricts the development of machine tools. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a main transmission system for a heavy-duty machine tool which can effectively shorten the transmission distance and reduce the transmission links, thereby effectively improving the precision and reducing the noise.

[0005] In order to solve the above technical problems, the main transmission system of a heavy machine tool of the present invention includes a power input part driven by a main motor, a power to be distributed structure for preparing power distribution, a speed change execution selection structure that cooperates with the power to be distributed structure and has a sliding shaft, a shift drive device installed in cooperation with the power input part, and a power output structure that cooperates with the speed change execution selection structure to achieve power output. The shift drive device has a gear sleeve that cooperates with the power to be distributed structure and the speed change execution selection structure, and a linear drive mechanism installed in cooperation with the gear sleeve. The linear drive mechanism is connected to the sliding shaft and can drive the sliding shaft to reciprocate, thereby enabling the speed change execution selection structure to cooperate with the power to be distributed structure and the power output structure to achieve different speed outputs.

[0006] The sliding shaft is provided with an external spline and a speed gear set, the speed execution selection structure also includes a transmission gear set arranged outside the sliding shaft and used to cooperate with the speed gear set, the power to be distributed structure has a coaxial gear set that cooperates with the transmission gear set, the power output structure has an internal spline that cooperates with the external spline and can output power through the cooperation between the external spline of the speed execution selection structure and the internal spline of the power output structure.

[0007] The power input part includes shaft I, shaft II and shaft III arranged in parallel at the top, middle and bottom, and shaft I gear installed on shaft I, shaft II gear installed on shaft II and shaft III gear installed on shaft III respectively; the shaft III gear is directly installed on the gear sleeve and the gear sleeve serves as the shaft III; the shaft I gear, shaft II gear and shaft III gear are meshed with each other for power transmission.

[0008] The power distribution structure includes shaft IV and shaft IV gear 1, shaft IV gear 2, and shaft IV gear 3 fixedly installed side by side on shaft IV; the shift drive device is coaxially arranged with the speed change execution selection structure, and one end of the gear sleeve is provided with an end external gear located on one side of the speed change execution selection structure and a No. 1 internal meshing gear; the shaft IV gear 1 is meshed with the end external gear of the gear sleeve.

[0009] The transmission gear set includes a first gear of the V-axis arranged outside the sliding shaft and meshing with the second gear of the IV-axis, and a second gear of the V-axis meshing with the third gear of the IV-axis; the speed gear set includes a first speed gear and a second speed gear, the first speed gear is arranged at the end of the sliding shaft and can selectively mesh with the first gear of the V-axis and the first internal meshing gear of the gear sleeve; the second speed gear is arranged on the rear side of the first speed gear and can mesh with the second gear of the V-axis.

[0010] The power output structure includes the VI shaft, the VII shaft, the VI shaft gear installed on the VI shaft, the VII shaft gear installed on the VII shaft, and the V shaft three gears arranged at the end of the V shaft. The internal spline is arranged in the V shaft three gears and can cooperate with the external spline of the sliding shaft to transmit power; the V shaft three gears, the VI shaft gear and the VII shaft gear are meshed with each other to realize power output.

[0011] The linear drive mechanism includes a cylinder body installed in cooperation with the gear sleeve, a push rod arranged in the gear sleeve and the cylinder body, and a support sleeve for supporting the push rod. The end of the push rod is connected to the head end of the sliding shaft, and the head end of the push rod is connected to a piston rod that can move back and forth in the cylinder body.

[0012] The head end of the piston rod is connected to an extension rod extending out of the cylinder body, the head end of the extension rod is provided with a bumper, and the side of the extension rod is provided with a travel switch that can be triggered by the bumper and is used to detect the meshing position of the sliding shaft.

[0013] The first gear 17, the second gear 18, the third gear 19 of the IV axis and the gear 14, the first gear 20 and the second gear 21 of the V axis are all helical gears, and are meshed with each other.

[0014] The three gears of the V-axis are supported and installed by deep groove ball bearings, and the gears of the VI-axis are supported and installed by angular contact bearings.

[0015] The advantages of the present invention are: (1) During the gear shifting process, the mechanical speed change is driven by the linear drive mechanism to drive the sliding shaft. A speed change gear set that can move back and forth is arranged on the sliding shaft to cooperate with the transmission gear set. The reciprocating movement of the sliding shaft is used to change the meshing position to realize the power distribution, thereby realizing the internal meshing gear sliding shifting transmission. After the mechanical three-speed gear shifting, the main shaft is driven to rotate, so that the main shaft can meet the speed requirement and provide sufficient torque. This structural design directly integrates it on the top surface of the slide and moves with the slide. It is no longer necessary to process a long spline shaft to realize gear shifting. It can not only realize rigid tapping, but also effectively solve the problem that when the end of the traditional main transmission system is connected to the spline shaft, it is necessary to manually adjust the matching clearance to ensure the transmission accuracy. It completely breaks through the traditional external meshing gear sliding shifting transmission method and effectively shortens the length of the transmission chain. It is easy to manufacture and process and ensures the operation accuracy and reliability, thereby improving the accuracy of the main transmission system and greatly reducing the noise.

[0016] (2) The travel switch for detecting the meshing position of the sliding shaft, which can be triggered by the impact block and is arranged on the side of the extension rod, can detect the meshing position of the speed gear of the sliding shaft, that is, the impact block triggers the corresponding travel switch, and only when the meshing position is correct can the main transmission be started to work in the corresponding gear. In addition, the differential pressure shift transmission mode is added to ensure fast switching between the three gears, and the travel switch outputs a signal after mechanical triggering, which is fast and accurate.

[0017] (3) Gear 17, gear 18, gear 19 and gear 14 on axis IV, gear 20 and gear 21 on axis V are all helical gears, and mesh with each other. This causes axial force to the meshing gears, so the corresponding supporting bearings must bear both radial and axial forces. Therefore, deep groove ball bearings with large diameters and large rated static and dynamic loads are selected. This eliminates the need for artificial pre-tightening and clearance adjustment. During operation, the deep groove ball bearings adjust themselves in time according to the changes in the alternating load, thereby increasing the service life of the bearings.

[0018] (4) The VI shaft is the power output end of the main transmission system. Its rotation speed is relatively low, its torque is relatively large, and its axial force is also relatively large. Therefore, the supports at both ends adopt a combination of angular contact bearings and deep groove ball bearings to ensure radial support while also offsetting the axial force of the helical gears of the transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Structural diagram of existing heavy machine tools; Figure 2 It is a schematic diagram of the structure of the main transmission system of a heavy machine tool in use state of the present invention; Figure 3 It is a structural schematic diagram of the main transmission system of the heavy machine tool of the present invention; Figure 4 It is a partial schematic diagram of the coordination state between the speed change execution selection structure and the gear shift driving device in the present invention; Figure 5 It is a partial structural schematic diagram of the gear shift drive device in the present invention. DETAILED DESCRIPTION

[0020] The main transmission system for heavy machine tools of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0021] As shown in the figure, the main transmission system of a heavy machine tool of the present invention includes a power input part 2 driven by a main motor 1, a power to-be-allocated structure 3 for preparing power distribution, a speed change execution selection structure 5 coordinated with the power to-be-allocated structure, a gear shift drive device 6 installed in coordination with the power input part 2, and a power output structure 7 for realizing power output in coordination with the speed change execution selection structure.

[0022] The main power transmission between the power distribution structure 3, the speed change execution selection structure 5 and the power output structure 7 adopts an upper, middle and lower three-axis parallel layout structure, the middle axis is the speed change structure layout, the upper axis is the power selection distribution layout, the lower axis is the power output structure layout, and the rest is the power input. The shift drive device 6 has a gear sleeve 8 that cooperates with the power distribution structure 3 and the speed change execution selection structure 5 and a linear drive mechanism installed in cooperation with the gear sleeve 8. It can be seen from the figure that the speed change execution selection structure 5 includes a sliding shaft 4, an external spline 9 set on the left side of the sliding shaft 4, and a first speed gear 22 and a second speed gear 23 set on the right side of the sliding shaft 4. The speed gear set and the transmission gear set arranged outside the sliding shaft 4 and used to cooperate with the speed gear set; the power distribution structure 3 has a coaxial gear set that cooperates with the transmission gear set, and the coaxial gear set of the power distribution structure 3 includes the IV shaft and the IV shaft fixedly installed side by side and arranged from right to left in sequence. The IV shaft one gear 17, the IV shaft two gear 18, and the IV shaft three gear 19, and the transmission gear set includes the V shaft one gear 20 arranged outside the sliding shaft and always meshing with the IV shaft two gears and the V shaft two gears 21 that always meshes with the IV shaft three gears, wherein it is important to explain that the V shaft one gear 20, the V shaft two gear 21 and the gear sleeve 8 all have There are inner teeth and outer teeth, the shift drive device 6 is coaxially arranged with the speed execution selection structure 5 (that is, the two are on the same axis. In this embodiment, the speed execution selection structure 5 is arranged on the left side of the shift drive device 6), and the left end of the gear sleeve 8 is provided with an end outer gear 14 located on the right side of the speed execution selection structure 4 and a No. 1 internal meshing gear 15 located inside the end outer gear 14. The IV axis-gear 17 and the end outer gear 14 of the gear sleeve are always meshed. The linear drive mechanism is connected to the sliding shaft 4 and can drive the sliding shaft to reciprocate so that the speed execution selection structure 5 and the power distribution structure 3 are shifted and changed, wherein the No. 1 speed gear 22 is arranged The right end of the sliding shaft can mesh with the V-axis first gear 20 or the first internal meshing gear 15 of the gear sleeve, and the second speed gear 23 is arranged on the rear side of the first speed gear 22 and can mesh with the V-axis second gear 21. It can be seen that the sliding shaft 4 is driven to move left and right by the linear drive mechanism, thereby switching between the speed gear set and the transmission gear set in the speed execution selection structure 5 to achieve different speed outputs, and cooperate with the power to be distributed structure 3 to achieve the purpose of shifting and changing gears. The V-axis three gears 24 of the power output structure 7 have an internal spline 13 that cooperates with the external spline 9, and can output power through the cooperation of the external spline of the speed execution selection structure and the internal spline of the power output structure.

[0023] Furthermore, the power input part 2 includes an I-axis, a II-axis and a III-axis arranged in parallel at the top, the middle and the bottom, and an I-axis gear 10 installed on the I-axis, an II-axis gear 11 installed on the II-axis and an III-axis gear 12 installed on the III-axis respectively; the III-axis gear 12 is directly installed on the gear sleeve 8 and the gear sleeve serves as the III-axis; the main motor 1 is connected to the I-axis through a coupling 16, and the I-axis gear 10, the II-axis gear 11 and the III-axis gear 12 are supported by paired support bearings respectively, and the I-axis gear 10, the II-axis gear 11 and the III-axis gear 12 are meshed with each other for power transmission, The I-axis gear 10, the II-axis gear 11 and the III-axis gear 12 are all standard spur gears without axial force, and are characterized by high speed and small torque; the main motor 1 is an AC servo spindle motor, and the II-axis gear is an idler gear. When working, the main motor 1 outputs power to the I-axis through the coupling 16, and then the power is transmitted from the II-axis gear to the III-axis gear 12 of the III-axis. As can be seen from the figure, the III-axis gear 12 and the gear sleeve 8 are coaxial rigidly connected gears, and three-speed gear shifting is performed here. Gears with different speeds and torques are selected according to processing needs, and the internal meshing gear is arranged at the left end of the gear sleeve 8.

[0024] Furthermore, the power output structure 7 includes the VI shaft, the VII shaft, the VI shaft gear 25 installed on the VI shaft, the VII shaft gear 26 installed on the VII shaft, and the V shaft three gears 24 arranged at the end of the V shaft. The internal spline 13 is arranged in the V shaft three gears 24 and can cooperate with the external spline 9 of the sliding shaft 4 for sliding and power transmission; the V shaft three gears 24, the VI shaft gear 25 and the VII shaft gear 26 are meshed with each other to realize power output.

[0025] Furthermore, the linear drive mechanism includes a cylinder body 27 mounted in cooperation with the gear sleeve 8, a push rod 28 capable of reciprocating in the gear sleeve 8 and the cylinder body 27, and a support sleeve 29 for supporting the push rod. As can be seen from the figure, a support bearing 33 is arranged between the left end of the support sleeve 29 and the gear sleeve 8, and a self-aligning ball bearing 34 is arranged between the left end of the push rod 28 and the sliding shaft 4, so as to connect the left end of the push rod 28 with the right end of the sliding shaft 4 (in this embodiment, the left end is defined as the end, then the right end must be the head end), and the push rod 28 is connected to the right end of the sliding shaft 4. The right end of the rod 28 is connected to a piston rod 30 capable of reciprocating in the cylinder body through a threaded connection. Of course, the cylinder body 27 is provided with necessary No. 1 oil port 37, No. 2 oil port 38, stepped hole shoulder 39 and exhaust hole 40; a flange 41 is provided at the right end of the cylinder body, and the flange encapsulates the piston rod 30 in the cylinder body. A No. 3 oil port 42 is provided on the flange. In addition, in order to ensure the smooth and reliable operation, a positioning sleeve 43 is also provided in the cylinder body. The left end of the positioning sleeve 43 contacts the stepped hole shoulder 39 of the cylinder, and its inner hole guides the piston rod 30.

[0026] Furthermore, the right end of the piston rod 30 is connected to an extension rod 31 extending out of the cylinder body through a pin 36, and a collision block 32 is provided at the right end of the extension rod. The piston of the piston rod is located at the left end of the extension rod, and a travel switch 35 (each gear position corresponds to a travel switch, and in this embodiment, there are three travel switches) that can be triggered by the collision block is provided on the side of the extension rod 31 for detecting the engagement position of the sliding shaft. The corresponding travel switch 35 is triggered by the collision block 32, and only when the engagement position is correct can the main transmission be started to work in the corresponding gear.

[0027] Among them, it is necessary to further emphasize that the IV and V axes are the power transmission and speed change parts, and the speed gradually decreases and the torque gradually increases from the III gear → the II gear → the I gear. In this embodiment, the outer teeth of the IV axis gear 17, the second gear 18, the third gear 19 and the gear 14, the V axis gear 10, the second gear 21 are all helical gears, and they are meshed in pairs according to the above arrangement. The VI axis is the output end of the main transmission system, which is characterized by a low speed, a large torque, and a large axial force. Therefore, the V axis gears are supported and installed by large-diameter deep groove ball bearings, and the VI axis gears are supported and installed by angular contact bearings. The combined support of angular contact bearings and deep groove ball bearings is adopted to ensure radial support and offset the axial force of the helical gears of the transmission. In addition, the force transmission layout adopts multi-point support on the same axis to prevent deflection and deformation as much as possible, and the coaxial multiple holes are completed in one processing, with good precision retention; left-handed and right-handed helical gears are reasonably arranged on the same axis of the IV and V axes to effectively offset each other's axial forces. At the same time, large-diameter deep groove ball bearings are selected to resist residual axial forces and ensure high speed.

[0028] The power input part 2, the power to-be-distributed structure 3 for power to be distributed, the speed change execution selection structure 5 coordinated with the power to-be-distributed structure, and the shift drive device 6 coordinated with the power input part 2 in the present invention are installed in an independent transmission system box 02 and the transmission system box is installed on the top surface of the slide 03. At the same time, the power output structure 7 outputs power to the spindle 04, thereby enabling it to move synchronously with the slide, that is, it moves independently relative to the spindle box 01 and is stationary relative to the slide 03. As a separate transmission component, it is completely separated from the technical solution of the traditional milling and boring machine main transmission system 2 integrated inside the spindle box 01, thereby eliminating the influence of the traditional spline shaft, greatly shortening the transmission chain, improving the transmission efficiency and spindle processing accuracy, and realizing rigid tapping.

[0029] In actual operation, the main motor 1 drives the main shaft to rotate after mechanical three-speed gear shifting; the main transmission is electrically steplessly regulated and connected in series with three-speed gear shifting, so that the main shaft meets the speed requirement and provides sufficient torque; the mechanical speed change is achieved by the oil cylinder driving the sliding shaft 4 to change the meshing position. The electrical limit switch detects the meshing position of the sliding gear, that is, the collision block 31 triggers the corresponding travel switch 35, and only when the meshing position is correct can the main transmission be started to work in the corresponding gear. The main shaft transmission system of the present invention transmits the power of the main motor, that is, the speed and torque, to the main shaft through the seven-axis gear mechanism, and the three-speed shifting function meets the power requirements of different processing procedures.

[0030] The working principle of gear shifting is as follows: When the sliding shaft 4 moves to the right end, that is, after the No. 1 speed gear 22 meshes with the No. 1 internal meshing gear 15, the I gear shift is generated, and the power transmission sequence is I axis gear 10 → II axis gear 11 → III axis gear 12 → gear sleeve 8 → sliding shaft 4 → V axis three gear 24 → VI axis gear 25 → VII axis gear 26, thereby realizing the cutting movement of the main shaft 27.

[0031] When the sliding shaft 4 moves to the middle, that is, after the first speed gear 22 is meshed with the internal teeth of the V-axis first gear 20, the Ⅱ gear shift is generated, and the power transmission sequence is the Ⅰ-axis gear 10 → Ⅱ-axis gear 11 → Ⅲ-axis gear 12 → gear sleeve 8 → Ⅳ-axis first gear 17 → Ⅳ-axis second gear 18 → sliding shaft 4 → Ⅴ-axis third gear 24 → Ⅵ-axis gear 25 → Ⅶ-axis gear 26, thereby realizing the spindle cutting movement.

[0032] When the sliding shaft 4 moves to the left end, that is, after the second speed gear 23 meshes with the V-axis second gear 21, the Ⅲ gear shift is generated, and the power transmission order is the I-axis gear 10 → the II-axis gear 11 → the III-axis gear 12 → the gear sleeve 8 → the IV-axis first gear 17 → the IV-axis third gear 19 → the V-axis second gear 21 → the sliding shaft 4 → the V-axis third gear 24 → the VI-axis gear 25 → the VII-axis gear 26, thereby realizing the cutting movement of the main shaft 27.

[0033] The operating principle of its linear drive mechanism is as follows: The push rod 28 is connected to the piston 44 by threads, and the piston 44 and the rod 45 are an integral structure; the left end of the rear end (piston) plug 46 can fit or disengage with the right end of the rod 45, and the rear end (piston) plug 46 is radially slidably connected to the extension rod 31 through a sealing ring.

[0034] In the figure, the piston rod 29 is in the gear III position. When the gear is shifted from gear I to gear III, oil enters the No. 1 oil port 37, and the oil passes through the No. 1 oil port 37 and enters the rod cavity, pushing the left end of the piston 44 to move rightward. The transmission sequence is: piston 44 → rod 45 → pin 36 → extension rod 31 → bumper 32 → right end travel switch 35. At the same time, the push rod 28 pulls the sliding shaft 4 to move accordingly, completing the gear shift and triggering the travel switch to send a signal.

[0035] When shifting from gear III to gear II, oil enters No. 3 oil port 42, and oil returns from No. 1 and No. 2 oil ports. The oil moves to the left through No. 3 oil port 42 and the right end of the rear end (live) plug 46. The transmission sequence is: rear end (live) plug 46→pin 36→rod 45→piston 44→push rod 28→sliding shaft 4, and at the same time drives the extension rod 31 to move to the left, and the left end of the bump block 32 triggers the middle travel switch, completing the gear shift and triggering the travel switch to send a signal.

[0036] When shifting from gear II to gear I, oil enters No. 2 oil port 38, and oil returns from No. 1 and No. 3 oil ports. The oil passes through No. 2 oil port and the right end of piston 44 moves to the left. The transmission sequence is: piston 44→push rod 28→sliding shaft 4. At the same time, piston 44←rod 45←pin 36→extension rod 31→bumper 32→left end travel switch act in sequence. The left end of bumper 32 triggers the left end travel switch, completing the gear shift and triggering the travel switch to send a signal.

[0037] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A main transmission system for a heavy machine tool, characterized in that: The invention comprises a power input part (2) driven by a main motor (1), a power to-be-allocated structure (3) for preparing power to be allocated, a speed change execution selection structure (5) cooperating with the power to-be-allocated structure and having a sliding shaft (4), a gear shift drive device (6) mounted in cooperation with the power input part (2), and a power output structure (7) cooperating with the speed change execution selection structure to achieve power output, wherein the gear shift drive device (6) comprises a gear sleeve (8) cooperating with the power to-be-allocated structure (3) and the speed change execution selection structure (5), and a linear drive mechanism mounted in cooperation with the gear sleeve (8), wherein the linear drive mechanism is connected to the sliding shaft (4) and can drive the sliding shaft to reciprocate, thereby enabling the speed change execution selection structure (5) to cooperate with the power to-be-allocated structure (3) and the power output structure (7) to achieve output at different speeds.

2. The main transmission system for a heavy machine tool according to claim 1, characterized in that: The sliding shaft (4) is provided with an external spline (9) and a speed gear set, the speed execution selection structure (5) further comprises a transmission gear set arranged outside the sliding shaft (4) and used to cooperate with the speed gear set, the power distribution structure (3) has a coaxial gear set that cooperates with the transmission gear set, and the power output structure (7) has an internal spline (9) that cooperates with the external spline and can output power through the cooperation between the external spline of the speed execution selection structure and the internal spline of the power output structure.

3. The main transmission system for heavy machine tools according to claim 2, characterized in that: The power input part (2) comprises an I shaft, a II shaft and a III shaft which are arranged in parallel at the top, the middle and the bottom, and an I shaft gear (10) mounted on the I shaft, an II shaft gear (11) mounted on the II shaft and a III shaft gear (12) mounted on the III shaft respectively; the III shaft gear (12) is directly mounted on the gear sleeve (8) and the gear sleeve serves as the III shaft; the I shaft gear (10), the II shaft gear (11) and the III shaft gear (12) are meshed with each other to transmit power.

4. The main transmission system for a heavy machine tool according to claim 3, characterized in that: The power distribution structure (3) comprises a shaft IV and a shaft IV first gear (17), a shaft IV second gear (18), and a shaft IV third gear (19) fixedly mounted side by side on the shaft IV; the gear shift drive device (6) is coaxially arranged with the speed change execution selection structure (5); one end of the gear sleeve (8) is provided with an end external gear (14) located on one side of the speed change execution selection structure (5) and a first internal meshing gear (15); the shaft IV first gear (17) meshes with the end external gear (14) of the gear sleeve.

5. The main transmission system for a heavy machine tool according to claim 4, characterized in that: The transmission gear set comprises a V-axis first gear (20) arranged outside the sliding shaft and meshing with the IV-axis second gear, and a V-axis second gear (21) meshing with the IV-axis third gear; the speed change gear set comprises a first speed change gear (22) and a second speed change gear (23), wherein the first speed change gear (22) is arranged at the end of the sliding shaft and can selectively mesh with the V-axis first gear (20) and the first internal meshing gear (15) of the gear sleeve; and the second speed change gear (23) is arranged at the rear side of the first speed change gear (22) and can mesh with the V-axis second gear (21).

6. The main transmission system for a heavy machine tool according to claim 5, characterized in that: The power output structure (7) comprises a VI shaft, a VII shaft, a VI shaft gear (25) mounted on the VI shaft, a VII shaft gear (26) mounted on the VII shaft, and a V shaft three gear (24) arranged at the end of the V shaft; the internal spline (9) is arranged in the V shaft three gear (24) and can cooperate with the external spline (7) of the sliding shaft (4) to transmit power; the V shaft three gear (24), the VI shaft gear (25) and the VII shaft gear (26) are meshed with each other to achieve power output.

7. The main transmission system for a heavy machine tool according to claim 6, characterized in that: The linear drive mechanism comprises a cylinder body (27) mounted in cooperation with the gear sleeve (8), a push rod (28) arranged in the gear sleeve (8) and the cylinder body (27), and a support sleeve (29) for supporting the push rod, the end of the push rod (28) being connected to the head end of the sliding shaft (4), and the head end of the push rod (28) being connected to a piston rod (30) capable of reciprocating in the cylinder body.

8. The main transmission system for a heavy machine tool according to claim 7, characterized in that: The head end of the piston rod (30) is connected to an extension rod (13) extending out of the cylinder body, the head end of the extension rod is provided with a bumper (31), and the side of the extension rod (13) is provided with a travel switch (32) that can be triggered by the bumper and is used to detect the meshing position of the sliding shaft.

9. The main transmission system for a heavy machine tool according to claim 8, characterized in that: The first gear 17, the second gear 18, the third gear 19 of the IV axis and the gear 14, the first gear 20 and the second gear 21 of the V axis are all helical gears, and are meshed with each other.

10. The main transmission system for a heavy machine tool according to claim 8, characterized in that: The V-axis three gears (24) are supported and installed via deep groove ball bearings, and the VI-axis gears (25) are supported and installed via angular contact bearings.

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