Lead screw motor transmission structure based on taper fit and axial pre-tightening locking

Abstract

The invention discloses a lead screw motor transmission structure based on taper fit and axial pre-tightening locking. The lead screw motor transmission structure comprises a motor shaft, a lead screw and a lead screw nut. A mounting inclined surface at the lower section of the screw rod is matched with a counter bore of a motor shaft in a taper manner to realize gapless radial positioning; and the lower end is axially pre-tightened and locked through an internal expansion type shaft sleeve structure. According to the internal expansion type shaft sleeve, a double fixing mode of a steel ball-trapezoid protrusion structure is utilized, a pre-tightening force is applied to the bolt, so that the whole structure generates an axial tensioning force, and meanwhile, a thread gap can be effectively eliminated. The structure solves the problem of looseness of traditional transmission under the scenes of small and medium axial loads and high vibration frequency, is suitable for the precision fields of industrial robots, semiconductor equipment, automobile part machining and the like, and has the characteristics of high rigidity and long service life.

Description

Technical Field

[0001] This article relates to a screw motor transmission structure based on taper fit and axial pre-tightening and locking. Background Art

[0002] Existing screw motor transmission structures mostly use a positioning key connection method to achieve axial connection, but in some special application scenarios, the traditional connection and fixing method cannot meet the requirements of high-precision axial positioning.

[0003] Traditional connection methods present significant drawbacks, particularly when faced with frequent up-and-down motion. On the one hand, conventional positioning keys are unable to withstand frequent axial impact forces over extended periods of time, and are prone to loosening and wear during prolonged vibrations, leading to unstable axial support and, in turn, affecting the accuracy of the object's motion. On the other hand, internal threaded connections are susceptible to relative slippage and loosening between the threads under dynamic, jolting loads, failing to provide reliable axial fixation. This not only reduces transmission accuracy but can also pose safety risks.

[0004] Therefore, there is an urgent need for a screw motor transmission structure that can provide stable and reliable axial support to meet the needs of high-precision and high-reliability axial vertical motion. Summary of the Invention

[0005] The purpose of the present invention is to provide a screw motor transmission structure based on taper fit and axial pre-tightening and locking, which can effectively reduce the amount of deformation during use by setting pre-load. The specific structure is as follows: A screw motor transmission structure based on taper fitting and axial pre-tightening and locking includes a motor shaft and a screw that bears vertical axial force. The upper part of the screw is sleeved with a screw nut, and the lower part of the screw is a mounting inclined surface with a diameter gradually decreasing from top to bottom. The upper end of the motor shaft is provided with a countersunk hole matching the mounting inclined surface, and the lower end of the screw is connected to the motor shaft through a connecting structure with axial pre-tightening and locking function.

[0006] In order to improve the connection strength and stability between the screw rod and the motor shaft, the connection structure includes a spring washer and a bolt. The bolt passes through the bottom through hole of the motor shaft and is screwed into the threaded hole at the bottom of the screw rod through a threaded connection. The spring washer is arranged at the head step of the bolt.

[0007] In addition, in order to further improve the connection strength, an axial pre-tightening and locking force is applied to the axial connection structure by controlling the taper and setting the pre-pressure. The connection structure includes an internal expansion sleeve and a bolt. The bolt passes through the bottom through hole of the motor shaft and is screwed into the threaded hole at the bottom of the screw rod by a threaded connection. The internal expansion sleeve is arranged between the bolt and the screw rod. The internal expansion sleeve includes an upper sleeve, a lower sleeve, a limit groove and a steel ball. A through hole is provided inside the motor shaft, the top of the through hole is connected to the countersunk hole, and a step hole is provided at the connection between the through hole and the countersunk hole, wherein the diameter of the step hole is smaller than the minimum diameter of the countersunk hole; The upper surface of the upper sleeve abuts against the lower surface of the step hole, the lower end of the upper sleeve is provided with a plurality of upper trapezoidal protrusions, the lower surface of the lower sleeve abuts against the head step of the bolt, the upper section of the lower sleeve is provided with a lower trapezoidal protrusion matching the upper trapezoidal protrusion, the surface of the lower trapezoidal protrusion is provided with an oblique limiting groove, and a plurality of steel balls are embedded in the limiting groove. When the bolt is pre-tightened, the upper sleeve and the lower sleeve move toward each other, the steel balls are squeezed, and the overall connection is forced to generate axial pre-tightening force.

[0008] The steel ball-trapezoidal protrusion structure of the internal expansion sleeve can increase the overall internal preload force. Under bumpy working conditions, the preload force can be adaptively adjusted through the rolling of the steel balls to avoid stress concentration in the rigid connection.

[0009] When the bolt is pre-tightened, the force acting on it gradually reduces the distance between the upper and lower sleeves until the steel balls are squeezed. At this point, because the upper end of the internal expansion sleeve abuts the lower surface of the stepped hole, the upper end of the internal expansion sleeve is effectively limited by the motor shaft. Under the action of the relative force, the internal expansion sleeve can only exert a downward force on the bolt, further tightening the screw rod and thus closing the thread gap between the bolt and the screw rod. This allows the overall installation structure to maintain good connection stability and withstand a certain amount of axial load, while also preventing the generation of gaps after repeated reciprocating motions, which can lead to a decrease in transmission accuracy.

[0010] The installation method under this structure is as follows: Installation method: 1. Install the screw rod and the motor shaft through a taper fit and obtain a tight interference fit connection by press fitting.

[0011] 2. Embed the steel ball into the limiting groove of the lower sleeve, and insert the assembled internal expansion sleeve into the bottom through hole of the screw rod so that the upper surface of the upper sleeve abuts against the lower surface of the step hole, and the lower surface of the lower sleeve abuts against the step of the bolt head.

[0012] 3. Use a torque wrench to pre-tighten the bolts. The upper and lower sleeves move relative to each other by 0.1mm. The steel balls roll along the limit grooves and squeeze the lower sleeve, causing it to produce a slight radial expansion (about 0.05mm) and axial tension.

[0013] In order to further enhance the elastic compensation capability of the internal expansion sleeve, the bevel angles of the upper trapezoidal protrusion and the lower trapezoidal protrusion are 10°-30°, and the oblique angle of the limiting groove matches the bevel angle of the trapezoidal protrusion.

[0014] To monitor and output the number of motor shaft revolutions and direction in real time, an encoder is connected to the bottom of the motor shaft. This encoder effectively captures and controls the number of motor revolutions, thereby controlling the vertical movement distance, speed, and frequency of the lead screw nut.

[0015] In order to further control the movement of the steel ball, the cross-sectional shape of the limiting groove is arc-shaped or V-shaped, and the fitting clearance between the steel ball and the limiting groove is ≤0.005mm.

[0016] At the same time, the outer surface of the mounting bevel is provided with symmetrical flattened portions, and the countersunk hole is provided with a slotted groove that matches the flattened portions. This arrangement can effectively enhance the transmission of radial force between the motor shaft and the screw rod, and increase the amount of transmittable force.

[0017] In order to improve the installation stability of the motor shaft and the screw rod and perform axial positioning through the inclined surface, the taper of the installation inclined surface is 1:10-1:20, and the fitting clearance between the countersunk hole and the installation inclined surface is ≤0.01mm. Beneficial effects

[0018] Through the taper fit (mounting bevel and countersunk hole), gapless radial positioning can be achieved, avoiding the clearance problem caused by the traditional key connection method. At the same time, in order to further solve the thread clearance problem caused by the threaded connection, the axial pre-tightening locking structure (spring washer or internal expansion sleeve) provides continuous axial pressure to suppress loosening caused by vibration, thereby achieving double axial reinforcement.

[0019] At the same time, in low-frequency, high-precision vibration scenarios, due to the existence of continuous axial preload, the energy brought by the vibration can be absorbed and released through the slight deformation of the spring gasket or the friction movement of the steel ball, avoiding the problem of sudden stress change and accumulation at the purely rigid connection, thereby improving the service life of the overall lead screw motor and maintaining high-precision equipment capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a screw motor transmission structure based on taper fit and axial pre-tightening and locking; Figure 2 This is a schematic diagram after the screw rod and motor shaft are installed; Figure 3 It is a schematic diagram of the screw rod; Figure 4 This is a cross-sectional view after the screw rod and motor shaft are installed; Figure 5 yes Figure 4 A partial enlarged view of the middle circled part; Figure 6 This is a schematic diagram of the installation location of the screw rod and the motor shaft; Figure 7 This is a schematic diagram of the assembly of the upper and lower sleeves of the internal expansion sleeve; Figure 8 This is an assembly diagram showing the internal expansion sleeve after it is horizontally expanded; In the figure, 1. screw nut 2. screw 3. motor shaft 4. internal expansion sleeve 41. upper sleeve 42. lower sleeve 43. limit groove 44. steel ball 5. bolt 6. mounting bevel. DETAILED DESCRIPTION

[0021] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Example 1

[0022] like Figure 1-8 As shown, a screw motor transmission structure based on taper fit and axial pre-tightening and locking includes a screw 2, a motor shaft 3, an internal expansion sleeve 4 and a bolt 5.

[0023] The mounting bevel 6 (taper 1:10) of the lower section of the screw rod 2 forms an interference fit with the countersunk hole of the motor shaft 3, and the flat part is embedded in the slotted groove to achieve circumferential positioning, which can effectively transmit radial force.

[0024] The internal expansion sleeve 4 consists of an upper sleeve 41 and a lower sleeve 42, which transform and transmit force through trapezoidal projections and steel balls 44. When the bolt 5 is pre-tightened, the upper and lower sleeves move toward each other, and the steel balls 44 roll along the spiral limiting grooves 43, causing the internal expansion sleeve to move vertically.

[0025] The bolt pre-tightening force is converted into axial tensioning force and radial expansion force through the action of the steel ball 44 and the inclined surface of the trapezoidal protrusion, while eliminating the thread gap and the cone surface gap.

[0026] Installation method: 1. Install the screw rod 2 and the motor shaft 3 through taper fit, and obtain a tight interference fit connection by press fitting.

[0027] 2. Place the upper sleeve 41, steel ball 44, and lower sleeve 42 into the through hole of the motor shaft 3 in sequence, ensuring that the upper surface fits the lower surface of the stepped hole.

[0028] 3. The assembled internal expansion sleeve 4 is inserted into the lower surface of the stepped hole of the screw rod 2 so that the lower surface of the lower sleeve 42 abuts against the step of the head of the bolt 5.

[0029] 4. Use a torque wrench to pre-tighten the bolt 5. The upper and lower sleeves move relative to each other by 0.3 mm. The steel ball 44 rolls along the limiting groove 43 and squeezes the lower sleeve 42, causing it to generate a slight radial expansion (expansion of about 0.05 mm) and axial tension. Example 2

[0030] A screw motor transmission structure based on taper fit and axial pre-tightening and locking, wherein an internal expansion sleeve is replaced with a spring washer, while the rest remains unchanged.

[0031] This device eliminates both thread and taper clearances through a dual-fixation method using axial preload and mounting bevels. This allows the device to withstand axial periodic load shocks and is suitable for high-precision control of axial vertical motion with a certain horizontal load.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A screw motor transmission structure based on taper fit and axial pre-tightening and locking, characterized in that: It includes a motor shaft and a screw rod that bear vertical axial force. The upper part of the screw rod is provided with a screw nut, and the lower part of the screw rod is a mounting inclined surface with a diameter gradually decreasing from top to bottom. The upper end of the motor shaft is provided with a countersunk hole matching the mounting inclined surface. At the same time, the lower end of the screw rod is connected to the motor shaft through a connecting structure with an axial pre-tightening and locking function.

2. A screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 1, characterized in that The connection structure includes a spring washer and a bolt. The bolt passes through the bottom through hole of the motor shaft and is screwed into the threaded hole at the bottom of the screw rod through a threaded connection. The spring washer is arranged at the head step of the bolt.

3. The screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 1 is characterized in that The connection structure includes an internal expansion sleeve and a bolt. The bolt passes through the bottom through hole of the motor shaft and is screwed into the threaded hole at the bottom of the screw rod by means of a threaded connection. The internal expansion sleeve is arranged between the bolt and the screw rod. The internal expansion sleeve includes an upper sleeve, a lower sleeve, a limit groove and a steel ball. A through hole is provided inside the motor shaft, the top of the through hole is connected to the countersunk hole, and a step hole is provided at the connection between the through hole and the countersunk hole, wherein the diameter of the step hole is smaller than the minimum diameter of the countersunk hole; The upper surface of the upper sleeve abuts against the lower surface of the step hole, the lower end of the upper sleeve is provided with a plurality of upper trapezoidal protrusions, the lower surface of the lower sleeve abuts against the head step of the bolt, the upper section of the lower sleeve is provided with a lower trapezoidal protrusion matching the upper trapezoidal protrusion, the surface of the lower trapezoidal protrusion is provided with an oblique limiting groove, and a plurality of steel balls are embedded in the limiting groove. When the bolt is pre-tightened, the upper sleeve and the lower sleeve move toward each other, the steel balls are squeezed, and the overall connection is forced to generate axial pre-tightening force.

4. The screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 3 is characterized in that The bevel angles of the upper trapezoidal protrusion and the lower trapezoidal protrusion are 10°-30°, and the oblique angle of the limiting groove matches the bevel angle of the trapezoidal protrusion.

5. A screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 2 or 3, characterized in that ,The bottom of the motor shaft is connected to the encoder.

6. The screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 3 is characterized in that The cross-sectional shape of the limiting groove is arc-shaped or V-shaped, and the fitting clearance between the steel ball and the limiting groove is ≤0.005mm.

7. The screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 3 is characterized in that The outer surface of the mounting bevel is provided with a symmetrical flat position, and the countersunk hole is provided with a straight groove matching the flat position.

8. The screw motor transmission structure based on taper fit and axial pre-tightening and locking according to claim 3 is characterized in that The taper of the mounting bevel is 1:10-1:20, and the fitting clearance between the countersunk hole and the mounting bevel is ≤0.01mm.

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