Lathe positioning device and lathe

Abstract

The invention relates to the technical field of machining, and discloses a lathe positioning device and a lathe thereof.The lathe positioning device comprises a shell, an expansion piece and a driving unit, the shell comprises a first end and a second end which are arranged in the axial direction of an inner opening of a machined part in a spaced mode, the first end is connected to the lathe, and the second end extends into an inner hole of a to-be-machined part; an annular sliding surface is arranged on the peripheral surface of the second end, and the radial direction of the annular sliding surface is gradually increased from the second end to the first end; the expansion piece comprises an expansion part, the expansion part is arranged on the annular sliding face in a sleeving mode and can move in the axial direction of the inner hole, the expansion part can expand or contract in the radial direction of the annular sliding face under the guidance of the annular sliding face, and the expansion part is used for being supported on the wall face of the inner hole; the driving unit is arranged in the shell and used for driving the expansion part to move in the axial direction of the inner hole, then the expansion part is driven to correspondingly expand or contract in the radial direction so that the inner hole of the to-be-machined part can be supported or retracted, and supporting force can be provided by the shell through the expansion part during supporting.

Description

Lathe positioning device and lathe Technical Field

[0001] This invention relates to the field of machining, specifically to a lathe positioning device. Furthermore, this invention also relates to a lathe including the lathe positioning device. Background Technology

[0002] The form and position tolerances of cylinder parts directly affect product quality, while the manufacturing process and tooling are key factors influencing quality. For cylinder parts with stepped openings, it is crucial to ensure the coaxiality between the stepped holes and the inner and outer diameters. The inner diameter is typically used as the positioning datum during machining. Current technology commonly employs extended internal expansion jaws to support the inner diameter, combined with a center rest for positioning and machining of the stepped holes and outer diameter to control form and position tolerances. However, as the length of the internal expansion jaws increases, their rigidity decreases significantly, leading to reduced positioning accuracy and making it difficult to meet high-precision machining requirements. Summary of the Invention

[0003] This invention provides a lathe positioning device and a lathe thereof to solve the problem of reduced positioning accuracy.

[0004] In a first aspect, the present invention provides a lathe positioning device, comprising: a housing, the housing including a first end and a second end spaced axially along the inner opening of a workpiece, the first end being connected to a lathe, the second end extending into the inner hole of the workpiece, and the outer peripheral surface of the second end being provided with an annular sliding surface, the radial direction of the annular sliding surface gradually increasing from the second end toward the first end; an expansion member, the expansion member including an expansion portion, the expansion portion being sleeved on the annular sliding surface and capable of moving axially along the inner hole, the expansion portion being configured to expand or contract radially along the annular sliding surface under the guidance of the annular sliding surface, the expansion portion being used to support the wall surface of the inner hole; and a driving unit, the driving unit being disposed within the housing and used to drive the expansion member to move axially along the inner hole.

[0005] In this embodiment, the overall support rigidity of the positioning device is primarily borne by the housing itself extending into the inner hole. The expansion member serves only as a support element, with its internal force points acting directly on the highly rigid housing. Therefore, even with the housing extending deep into the workpiece for long-distance support, it provides rigidity far exceeding that of traditional extended internal expansion jaws, fundamentally strengthening the support strength for the inner hole and completely resolving the issues of insufficient rigidity and machining vibration caused by excessive overhang. Simultaneously, this embodiment achieves precise control of expansion and contraction through a drive unit, enabling flexible adjustment of the support position and clamping force, ensuring the stability and reliability of the positioning reference. Therefore, when it is necessary to penetrate deep into the inner hole, the operator can replace the original internal expansion jaws with the lathe positioning device of this embodiment to position and support the workpiece.

[0006] Optionally, the drive unit includes a connecting shaft connected to the housing, the connecting shaft being connected to the expansion member, and the connecting shaft being able to slide relative to the housing along the inner hole axially; wherein, the drive unit also includes a power structure disposed within the housing, and the power structure being disposed at the end of the connecting shaft away from the expansion member, for applying a driving force to the connecting shaft to move along the inner hole axially, so as to drive the connecting shaft to move the expansion member.

[0007] Optionally, the power structure includes a drive sleeve and a rotating component. The drive sleeve is rotatably mounted inside the housing and threadedly fitted onto the connecting shaft. The rotating component is used to apply torque to the drive sleeve, thereby enabling the connecting shaft to move axially.

[0008] Optionally, the rotating component includes at least one drive shaft, which abuts against the drive sleeve radially. The head end of the drive shaft is connected to the drive sleeve via a bevel gear set, and the tail end of the drive shaft extends radially to the outside of the housing and is connected to a power source. The power source is used to apply torque to the drive shaft so as to apply torque to the drive sleeve by driving the drive shaft to rotate.

[0009] Optionally, the bevel gear set includes a first bevel gear and a second bevel gear that mesh with each other. The first bevel gear is fixedly connected to the drive sleeve, and the second bevel gear is fixedly connected to the head end of the drive shaft, so that the first bevel gear is driven by the second bevel gear, thereby applying torque to the drive sleeve.

[0010] Optionally, the end of the connecting shaft away from the expansion member is connected to a first limiting structure. The first limiting structure is configured to abut against the end of the drive sleeve facing the first end when the connecting shaft moves toward the second end to the first extreme position. The end of the connecting shaft facing the expansion member is connected to a second limiting structure. The second limiting structure is configured to abut against the wall of the limiting groove inside the housing near the expansion member when the connecting shaft moves toward the first end to the second extreme position, so as to limit the movement distance of the connecting shaft.

[0011] Optionally, the expansion member abuts against the end of the connecting shaft and is detachably fixed to the connecting shaft by a fastener for easy replacement.

[0012] Optionally, the expansion member includes an expansion end cap, an expansion portion formed in the opening section of the expansion end cap, the inner peripheral surface of the opening section of the expansion end cap abutting against an annular sliding surface, and the opening section is configured to expand outward under the guidance of the annular sliding surface to support the inner hole.

[0013] Optionally, the inner circumferential surface of the opening segment is configured to fit against the annular sliding surface to increase the contact area.

[0014] Secondly, the present invention also provides a lathe, including the lathe positioning device as described above, wherein the lathe chuck and / or the tailstock of the lathe are correspondingly connected to the lathe positioning device to achieve support and positioning of the workpiece. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 is a half-sectional view of the lathe positioning device according to an embodiment of the present invention; Figure 2 is a sectional view AA of Figure 1; Figure 3 is a half-sectional view of the housing according to an embodiment of the present invention; Figure 4 is a sectional view BB of Figure 3; Figure 5 is a half-sectional view of the mounting assembly according to an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached drawings: 1. Housing; 101. First end; 102. Second end; 103. Annular sliding surface; 104. Mounting hole; 105. Weight reduction hole; 106. Axial cavity; 107. Clamping groove; 108. Guide sleeve; 109. Abutment ring plate; 2. Expansion component; 201. Expansion end cap; 2011. Opening section; 3. Connecting shaft; 4. Power structure; 401. Drive sleeve; 402. Drive shaft; 403. First bevel gear; 404. Second bevel gear; 405. First positioning structure; 406. Second limiting structure; 407. Limiting groove; 5. Fixing component; 501. Fixing bolt; 6. Assembly component; 601. Morse taper shank; 602. Annular pressure plate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] If the background section does not describe the shortcomings of the prior art, this section analyzes the shortcomings of the prior art in detail to introduce this solution.

[0020] In the machining of cylinder-type parts, the blank is typically first pre-machined to form the inner hole structure, and the inner hole diameter is used as the positioning datum for subsequent machining. Based on this datum, the stepped holes, outer diameter, and end faces of the part are then precision-machined to ensure coaxiality and positional accuracy between the machined surfaces. Current processes commonly employ extended internal expansion jaws to support the inner hole, achieving stable internal support positioning during machining and avoiding eccentricity or deformation caused by unstable clamping. Simultaneously, when machining the outer diameters and stepped holes at both ends of the part, a center rest is usually used for auxiliary positioning to reduce vibration and deflection of the workpiece under cutting forces.

[0021] However, in the initial machining stage, the workpiece end has high rigidity, and the internal expansion jaws only need to extend a short distance to meet the positioning requirements. But as machining progresses, the stepped hole is gradually cut, the workpiece end wall thickness decreases, and the rigidity decreases. If the original support depth is still used, the datum may become unstable. Therefore, it is often necessary to extend the internal expansion jaws to a deeper position to establish a new support surface in the thicker inner hole section or as close as possible to the outer circle or end face being machined, ensuring stable datum transfer. However, this method will cause the length of the internal expansion jaws to increase continuously, resulting in a decrease in its rigidity. The workpiece is prone to slight wobble under the action of cutting forces, which in turn causes coaxiality deviation between holes, making it difficult to meet the requirements of high-precision machining.

[0022] To address the aforementioned issues, referring to Figures 1 and 2, this embodiment provides a lathe positioning device, which includes a housing 1, an expansion member 2, and a drive unit disposed inside the housing 1. The housing 1 has a first end 101 and a second end 102 axially spaced along the inner opening of the workpiece. The first end 101 is connected to the lathe, while the second end 102 is used to extend into the inner hole of the workpiece.

[0023] An annular sliding surface 103 is provided on the outer circumferential surface of the second end 102 of the housing 1. Referring to Figure 1, the annular sliding surface 103 extends obliquely from the second end 102 toward the first end 101 and away from the second end 102, thereby causing the diameter of the annular sliding surface 103 to gradually increase from the second end 102 toward the first end 101. The expansion portion of the expansion member 2 is fitted onto this annular sliding surface 103. During operation, the drive unit drives the expansion member 2 to move axially: when the expansion portion slides on the annular sliding surface 103 in the direction of increasing diameter, it is forced to expand radially, thereby tightly abutting and clamping the inner hole wall; conversely, when it slides in the direction of decreasing diameter, it automatically contracts and releases the clamping.

[0024] Therefore, in this embodiment, the overall support rigidity of the positioning device is mainly borne by the housing 1 extending into the inner hole, while the expansion member 2 serves only as a support element, with its internal force points directly acting on the highly rigid housing 1. Thus, even with the housing 1 providing long-distance support deep inside the workpiece, it still offers rigidity far exceeding that of traditional extended internal expansion jaws, fundamentally strengthening the support strength for the inner hole and completely solving the problems of insufficient rigidity and machining vibration caused by excessive overhang. Simultaneously, this embodiment achieves precise control of expansion and contraction through a drive unit, enabling flexible adjustment of the support position and clamping force, ensuring the stability and reliability of the positioning reference. Therefore, when it is necessary to penetrate deep into the inner hole, the operator can replace the original internal expansion jaws with the lathe positioning device of this embodiment to position and support the workpiece.

[0025] In one embodiment, referring to FIG1, the drive unit includes a connecting shaft 3 slidably connected within the housing 1, the connecting shaft 3 being connected to the expansion member 2. Thus, when the connecting shaft 3 moves axially relative to the housing 1 along the inner hole, it can cause the expansion portion of the expansion member 2 to expand or contract accordingly.

[0026] Referring to Figure 3, an axially extending cavity 106 is formed within the housing 1, penetrating the housing 1 and sequentially comprising a first cavity and a second cavity with different diameters. The diameter of the first cavity near the first end 101 of the housing 1 is smaller than that of the second cavity near the second end 102 of the housing 1. Correspondingly, the connecting shaft 3 has a first section and a second section respectively adapted to the first and second cavities, allowing the first section of the connecting shaft 3 to extend axially from the second cavity into the first cavity, thereby achieving a sliding installation of the connecting shaft 3 within the housing 1.

[0027] The shell 1 can have any suitable shape, preferably a cylindrical structure.

[0028] In this embodiment, the lathe positioning device further includes a power structure 4. The power structure 4 is disposed inside the housing 1 and connected to the end of the connecting shaft 3 away from the expansion member 2. It is used to apply an axial driving force to the connecting shaft 3 so that the operator can control the direction of movement of the connecting shaft 3 through the power structure 4, thereby controlling the expansion and contraction of the expansion member 2.

[0029] The power structure 4 can take any suitable form. Referring to an embodiment shown in Figure 2, the power structure 4 may include a drive sleeve 401 and a rotating member. The drive sleeve 401 is rotatably mounted inside the housing 1 and threaded onto the connecting shaft 3; the rotating member is used to apply torque to the drive sleeve 401. It is understood that when the drive sleeve 401 is driven to rotate by the rotating member, the drive sleeve 401 generates a corresponding torque on the connecting shaft 3. At this time, the friction between the connecting shaft 3 and the axial cavity 106 of the housing 1, and between the expansion portion of the expansion member 2 and the annular sliding surface 103, restricts the synchronous rotation of the connecting shaft 3 with the drive sleeve 401. Thus, by utilizing the threaded action between the two, the rotational motion of the drive sleeve 401 is converted into the axial movement of the connecting shaft 3, thereby driving the expansion member 2 to produce corresponding expansion or contraction.

[0030] To limit the movement distance of the connecting shaft 3 in the axial cavity 106 of the housing 1, this embodiment provides limiting structures at both ends of the connecting shaft 3: a first limiting structure is provided at the end away from the expansion member 2 (i.e., the first segment), and a second limiting structure 406 is provided at the end facing the expansion member 2.

[0031] The first limiting structure is used to abut against the end of the drive sleeve 401 facing the first end 101 of the housing 1 when the connecting shaft 3 moves towards the second end 102 of the housing 1 to the first extreme position, thereby preventing the connecting shaft 3 from moving further. Specifically, the power structure 4 also includes a limiting block, which is fixed to the end face of the first end 101 of the connecting shaft 3 by bolts and located in the first cavity of the housing 1. The diameter of the limiting block is larger than the diameter of the first section of the connecting shaft 3. Therefore, when the connecting shaft 3 moves to the first extreme position, the limiting block will abut against the end of the drive sleeve 401, thereby restricting the further movement of the connecting shaft 3 towards the second end 102 of the housing 1, thus forming the aforementioned first limiting structure.

[0032] Referring to Figure 1, the limiting block is fitted with a guide sleeve 108, which can slide axially along the inner cavity of the guide sleeve 108. The guide sleeve 108 abuts against the inner wall of the first cavity, and its end facing the expansion member 2 abuts against the end face of the drive sleeve 401 facing the first end 101 of the housing 1. Simultaneously, an abutment ring plate 109 is bolted to the end of the first end 101 of the housing 1. The end face of the abutment ring plate 109 abuts against the end face of the guide sleeve 108 facing the first end 101 of the housing 1, thereby fixing the guide sleeve 108 inside the housing 1 through cooperation with the drive sleeve 401. It is understood that the outer peripheral surface of the limiting block abuts against the inner wall surface of the guide sleeve 108, creating friction that restricts the rotation of the limiting block and further enhances the restriction on the rotation of the connecting shaft 3.

[0033] The aforementioned second limiting structure 406 is used to abut against the wall of the limiting groove 407 on the side of the housing 1 near the expansion member 2 when the connecting shaft 3 moves toward the first end 101 of the housing 1 to the second extreme position, thereby limiting further movement of the connecting shaft 3. Specifically, the second section of the connecting shaft 3 includes a first part and a second part whose diameter increases sequentially in the direction toward the expansion member 2. Correspondingly, the second cavity of the axial through cavity 106 also forms a matching structure, that is, it has two parts with different diameters on the side near the expansion member 2, and an annular limiting groove 407 is formed at the transition. Referring to Figure 1, when the connecting shaft 3 moves to the second extreme position, the second part of its second section abuts against the wall of the annular limiting groove 407 on the side of the first end 101 of the housing 1, thereby limiting the connecting shaft 3.

[0034] In one embodiment, the rotating component includes at least one drive shaft 402. The drive shaft 402 is arranged radially along the drive sleeve 401, with its head end connected to the drive sleeve 401 via a bevel gear set, and its tail end extending radially to the outside of the housing 1 and connected to an external power source. The power source applies torque to the drive shaft 402, thereby causing the bevel gear set to mesh through rotation of the drive shaft 402, and thus applying torque to the drive sleeve 401 to control the movement of the connecting shaft 3.

[0035] In this embodiment, the number of drive shafts 402 can be set to three, and they are evenly distributed along the axial direction of the connecting shaft 3, thereby providing multi-point radial support and fixation for the drive sleeve 401. Based on this arrangement, the operator can adjust the depth of the three drive shafts 402 extending into the housing 1 to achieve a stable coaxial installation of the drive sleeve 401 and the housing 1. Referring to Figure 2, of the three drive shafts 402, the two located at the bottom can be selected as power transmission units to achieve effective drive.

[0036] Referring to Figure 4, the housing 1 is provided with three mounting holes 104. These three mounting holes 104 penetrate the side wall of the housing 1 and are equally spaced along the circumference of the connecting shaft 3, so that the drive shaft 402 in this embodiment can pass through the mounting holes 104 one by one and extend into the first cavity of the housing 1 to be connected with the drive shaft 402.

[0037] In another embodiment, the drive sleeve 401 can be rotatably mounted within the housing 1 via bearings. In this structure, the drive sleeve 401 does not require radial support or fixation by the drive shaft 402; simply applying torque through one or more drive shafts 402 is sufficient to rotate the drive sleeve 401, thereby achieving axial drive of the connecting shaft 3. It should be noted that this embodiment requires a redesign of the housing 1 to provide a location for bearing installation, resulting in a more complex internal structure. Therefore, this embodiment preferably utilizes three drive shafts 402 to provide radial support for the drive sleeve 401.

[0038] In one embodiment, the bevel gear set includes a first bevel gear 403 and a second bevel gear 404 that mesh with each other. The first bevel gear 403 is fixedly sleeved on the drive sleeve 401, and the second bevel gear 404 is fixedly mounted on the head end of the drive shaft 402. When the drive shaft 402 rotates, the second bevel gear 404 rotates accordingly and meshes with the first bevel gear 403, thereby transmitting power to the drive sleeve 401. The first bevel gear 403 and the drive sleeve 401, and the second bevel gear 404 and the drive shaft 402, can each be constructed as an integral part to reduce the number of components and improve the stability and reliability of the transmission.

[0039] In one embodiment, referring to FIG1, the expansion member 2 is mounted on the end of the connecting shaft 3 and is detachably connected to the connecting shaft 3 by the fastener 5. When the expansion member 2 wears out during use, the operator can replace it simply by removing the fixing bolt 501, thereby keeping the device in a reliable working condition for a long time.

[0040] The fastener may include a fixing bolt 501.

[0041] In one embodiment, the expansion member 2 may include an expansion end cap 201, the opening section 2011 of which forms an expansion portion, and the inner circumferential surface of the opening section 2011 abuts against the annular sliding surface 103. When the connecting shaft 3 drives the expansion end cap 201 to move axially, the opening section 2011 expands radially outward under the guidance of the annular sliding surface 103, thereby causing the outer circumferential surface of the expansion end cap 201 to fit tightly against the inner hole of the workpiece; when the connecting shaft 3 moves in the opposite direction, the opening section 2011 contracts under the guidance of the sliding surface, and the outer circumferential surface releases contact with the inner hole. Thus, the axial displacement of the connecting shaft 3 is converted into the radial deformation of the expansion end cap 201, realizing the clamping and release of the workpiece. At the same time, when the expansion end cap 201 expands outward, it can form a large-area contact with the inner hole of the workpiece, making the clamping force distribution more uniform, effectively reducing the concentration of local stress, and making it less prone to slippage under the action of cutting force, thereby maintaining the stability of the workpiece position during processing. At the same time, uniform support avoids indentations on the inner hole surface caused by point or line force, which helps maintain the integrity of the workpiece surface.

[0042] To accommodate different workpiece inner hole sizes, the external dimensions of the expansion end cap 201 can be flexibly designed according to the workpiece specifications. In this way, the device can be widely used in various types of cylinder part processing scenarios.

[0043] In this embodiment, the expansion end cap 201 is preferably made of brass, a material with good plasticity and ductility. When the end cap contacts the workpiece surface, the brass can undergo a certain amount of slight deformation under external force to alleviate frictional impact and prevent scratches on the finished surface. Since the expansion end cap 201 is in large-area contact with the inner hole of the workpiece, the unit contact pressure is low, and the workpiece surface can still remain smooth even under large clamping force conditions.

[0044] Furthermore, the inner circumferential surface of the opening section 2011 of the expansion end cap 201 is designed to fit closely with the annular sliding surface 103 over a large area. This allows the guiding force of the annular sliding surface 103 to be applied evenly to the opening section 2011, reducing damage to the sliding surface or end cap caused by excessive localized force. During the reciprocating sliding process of the end cap, the uniform contact also reduces the risk of friction concentration, resulting in smoother wear on the annular sliding surface 103.

[0045] Specifically, the inner circumferential surface of the opening section 2011 of the expansion end cap 201 has a gradually increasing inner diameter along the axial direction of the connecting shaft 3, thereby forming an inclined surface with the same tilt angle as the annular sliding surface 103 of the housing 1. During the process of the connecting shaft 3 driving the expansion end cap 201 to slide axially, the inner circumferential surface of the opening section 2011 can always maintain contact with the annular sliding surface 103.

[0046] On the other hand, this embodiment also provides a lathe that includes the lathe positioning device as described above, and the positioning device can be installed on the chuck and / or tailstock of the lathe respectively.

[0047] Specifically, the first end 101 of the housing 1 of the positioning device has a clamping groove 107, which the lathe chuck can clamp into, thereby stably fixing the positioning device on the chuck. If the positioning device needs to be installed on the tailstock of the lathe, an accessory 6 can be added to the first end 101 of the housing 1 to connect with the tailstock. Referring to Figure 5, the accessory 6 may include a Morse taper shank 601, which is inserted into the tailstock for positioning. During installation, the guide sleeve 108 and the abutment ring plate 109 can be disassembled first, and the end of the Morse taper shank 601 can be abutted against the first end 101 of the housing 1, while partially contacting the end face of the guide sleeve 108 facing the first end 101. Subsequently, an annular pressure plate 602 is fitted onto the end of the Morse taper shank 601, and the annular pressure plate 602 is detachably fixed to the housing 1 by bolts, forming a clamping fixation on the end of the Morse taper shank 601, thereby ensuring that the accessory 6 is stable and reliable.

[0048] In this embodiment, a blind hole extending axially can be provided on the end face of the Morse taper shank 601. This blind hole can be fitted onto the outer circumferential surface of the limiting block in the positioning device to act as a guide sleeve 108. That is, the inner wall of the blind hole applies a frictional force to the limiting block to restrict its rotation, causing the limiting block to slide in a predetermined direction during the movement of the connecting shaft 3. Simultaneously, in this embodiment, the depth of the blind hole can be designed to be equal to the maximum moving distance of the connecting shaft 3 plus the thickness of the limiting block. When the connecting shaft 3 moves to the second limit position, the end face of the limiting block contacts the bottom surface of the blind hole, thereby restricting further movement of the connecting shaft 3 and achieving safe and reliable stroke control.

[0049] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A lathe positioning device, characterized in that, include: A housing (1) includes a first end (101) and a second end (102) spaced axially along the inner opening of the workpiece. The first end (101) is connected to a lathe, and the second end (102) extends into the inner hole of the workpiece. The outer circumferential surface of the second end (102) is provided with an annular sliding surface (103). The radial direction of the annular sliding surface (103) gradually increases from the second end (102) toward the first end (101). An expansion member (2) includes an expansion portion, which is sleeved on the annular sliding surface (103) and can move axially along the inner hole. The expansion portion is configured to expand or contract radially along the annular sliding surface (103) under the guidance of the annular sliding surface (103). The expansion portion is used to support the wall of the inner hole. A driving unit is disposed inside the housing (1) and is used to drive the expansion member (2) to move axially along the inner hole.

2. The lathe positioning device according to claim 1, characterized in that, The drive unit includes a connecting shaft (3) connected to the housing (1), the connecting shaft (3) being connected to the expansion member (2), and the connecting shaft (3) being able to slide relative to the housing (1) along the inner hole axial direction; wherein, the drive unit also includes a power structure (4), the power structure (4) being disposed in the housing (1) and connected to one end of the connecting shaft (3) away from the expansion member (2), for applying a driving force to the connecting shaft (3) to move along the inner hole axial direction.

3. The lathe positioning device according to claim 2, characterized in that, The power structure (4) includes a drive sleeve (401) and a rotating member. The drive sleeve (401) is rotatably installed inside the housing (1) and threadedly sleeved on the connecting shaft (3). The rotating member is used to apply torque to the drive sleeve (401).

4. The lathe positioning device according to claim 3, characterized in that, The rotating component includes at least one drive shaft (402), which abuts against the drive sleeve (401) radially. The head end of the drive shaft (402) is connected to the drive sleeve (401) via a bevel gear set. The tail end of the drive shaft (402) extends radially to the outside of the housing (1) and is connected to a power source. The power source is used to apply torque to the drive shaft (402).

5. The lathe positioning device according to claim 4, characterized in that, The bevel gear set includes a first bevel gear (403) and a second bevel gear (404) that mesh with each other. The first bevel gear (403) is fixedly connected to the drive sleeve (401), and the second bevel gear (404) is fixedly connected to the head end of the drive shaft (402).

6. The lathe positioning device according to claim 3, characterized in that, The connecting shaft (3) is connected to a first limiting structure at one end away from the expansion member (2). The first limiting structure is configured to abut against the end of the drive sleeve (401) facing the first end (101) when the connecting shaft (3) moves toward the second end (102) to the first limit position. The connecting shaft (3) is connected to a second limiting structure (406) at one end facing the expansion member (2). The second limiting structure (406) is configured to abut against the wall of the limiting groove (407) inside the housing (1) near the expansion member (2) when the connecting shaft (3) moves toward the first end (101) to the second limit position.

7. The lathe positioning device according to claim 2, characterized in that, The expansion member (2) abuts against the end of the connecting shaft (3) and is detachably fixed to the connecting shaft (3) by means of the fastener (5).

8. The lathe positioning device according to claim 1, characterized in that, The expansion member (2) includes an expansion end cap (201), the expansion portion being formed in the opening section (2011) of the expansion end cap (201), the inner circumferential surface of the opening section (2011) of the expansion end cap (201) abutting the annular sliding surface (103), and the opening section (2011) being configured to expand outward under the guidance of the annular sliding surface (103).

9. The lathe positioning device according to claim 8, characterized in that, The inner circumferential surface of the opening segment (2011) is configured to fit against the annular sliding surface (103).

10. A lathe, characterized in that, The lathe includes a lathe positioning device as described in any one of claims 1-9, wherein the lathe chuck and / or the lathe tailstock are correspondingly connected to the lathe positioning device.

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