A fast tool servo system based on worm gear mechanism adjusting stiffness

Abstract

This invention relates to the field of fast-tool servo system technology, and discloses a fast-tool servo system based on a worm gear mechanism for adjusting stiffness. The fast-tool structure includes a cutting tool, with compliant supports connected to its left and right sides via front and rear leaf springs, respectively. The stiffness adjustment structure includes a long worm and front and rear baffles correspondingly located on the side of the compliant support away from the leaf springs. The front and rear worm gears are correspondingly arranged with the baffles and mesh with the long worm. One end of a drive shaft engages with the worm gear, and the other end passes through the fast-tool structure and the baffles. The drive shaft is threaded with the baffles using a single-threaded connection and with the compliant support using a double-threaded connection. The transmission ratios of the front and rear worm gear mechanisms are different. Rotating the long worm allows the drive shaft to finely adjust the stiffness of the fast-tool structure through the lead difference between the single-thread and double-threaded connections. This invention uses the lead difference between the single-thread and double-threaded connections and different spiral directions to symmetrically finely adjust the outward stretching or inward contraction of the compliant mechanism, resulting in high stiffness adjustment accuracy.

Description

Technical Field

[0001] This invention relates to the field of fast tool servo system technology, and in particular to a fast tool servo system based on a worm gear mechanism for adjusting stiffness. Background Technology

[0002] In the actual operation of a high-speed tool servo system with fixed stiffness, its output stroke and natural frequency characteristics are mutually exclusive. A longer stroke allows the mechanism to process larger components, increasing the system's machining range. However, a higher natural frequency means a higher machining frequency response, which improves machining efficiency and workpiece surface finish. Long stroke and high natural frequency are mutually exclusive; for a given input force, a larger stroke results in lower stiffness and consequently, a lower natural frequency. Adjustable stiffness is crucial for improving the flexibility of a high-speed tool servo system's operating environment. In a high-speed tool servo system, changing the geometry of the elastic material can adjust the overall stiffness, thus diversifying the system's application scenarios and meeting different machining conditions.

[0003] Existing fast-tool servo systems often use cam and gear transmission structures for stiffness adjustment. This method has two drawbacks: firstly, the small transmission ratio causes the stiffness adjustment to be too fast, and the leaf spring deforms significantly when the cam or gear rotates once, resulting in low accuracy of stiffness adjustment; secondly, the existing transmission structure has a weaker self-locking capability under heavier loads, resulting in poor self-locking performance under heavy loads. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a fast-tool servo system based on a worm gear mechanism for stiffness adjustment. This system utilizes a worm gear mechanism for stiffness adjustment. The worm gear mechanism has a large transmission ratio, thus minimizing the strain on the leaf spring per revolution of the worm. Furthermore, the difference in lead between single-start and double-start threads, along with different helix directions, allows for symmetrical fine-tuning of the compliant mechanism's outward or inward contraction, resulting in high stiffness adjustment accuracy. In addition, the worm gear mechanism possesses self-locking properties, and its self-locking capability increases with the load.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A fast tool servo system based on a worm gear mechanism for adjusting stiffness includes:

[0007] The fast-cutting structure includes a cutting tool, with the left and right sides of the cutting tool connected to compliant supports via front and rear leaf springs, respectively.

[0008] The stiffness adjustment structure includes a long worm gear and front and rear baffles corresponding to the side of the compliant support away from the leaf spring. The front and rear worm gears are correspondingly positioned with the baffles and mesh with the long worm gear. One end of the drive shaft engages with the worm gear, and the other end passes through the quick-cutting structure and the baffles. The drive shaft has a single-threaded engagement with the baffles and a double-threaded engagement with the compliant support. The transmission ratios of the front and rear worm gears are different. After rotating the long worm gear, the rotation angles of the two drive shafts are different. The difference in lead between the single-threaded and double-threaded drives of the drive shafts stretches or compresses the leaf spring, thereby achieving fine-tuning of the quick-cutting structure's stiffness.

[0009] As a further implementation, the front leaf spring and the rear leaf spring are symmetrically arranged about the cutter, and the front worm gear, the front baffle, the front leaf spring are symmetrically arranged with the rear worm gear, the rear baffle, and the rear leaf spring.

[0010] As a further implementation, the front baffle includes a second front baffle and a third front baffle located outside the compliant support, with the first front baffle and the third front baffle located on both sides of the front worm gear. The rear baffle includes a second rear baffle and a third rear baffle located outside the compliant support, with the first rear baffle and the third rear baffle located on both sides of the rear worm gear. The compliant supports on both sides of the cutter are provided with two sets, one in the front and one in the rear, and the two sets of compliant supports are either fixedly connected or independent of each other.

[0011] As a further implementation, the drive shaft extends to the outside of the front and rear baffles and is provided with anti-loosening nuts.

[0012] As a further implementation, the transmission ratio of the front worm gear mechanism is greater than the transmission ratio of the rear worm gear mechanism.

[0013] As a further implementation, the threads of the drive shaft and the compliant supports on both sides of the tool have opposite directions of rotation to achieve symmetrical adjustment of stiffness while keeping the tool position unchanged.

[0014] As a further implementation, the front and rear worm gears rotate in opposite directions.

[0015] As a further implementation, the two drive shafts mentioned above are connected to the corresponding worm gears via splines.

[0016] As a further implementation, the long worm is supported at both ends by worm supports, and angle discs are provided on the periphery of the worm on the worm supports.

[0017] As a further implementation, the long worm is inclined and is machined into two sections using a stepped shaft for meshing with the front and rear worm wheels.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. This invention employs a worm gear mechanism for stiffness adjustment. The worm gear mechanism has a large transmission ratio, therefore the stretching of the leaf spring per revolution of the worm is relatively small. Furthermore, the outward or inward contraction of the compliant mechanism is symmetrically fine-tuned by using the lead difference between single-start and double-start threads and different helix directions, resulting in high stiffness adjustment accuracy. In addition, the worm gear has self-locking properties, and its self-locking capability increases with the load.

[0020] 2. The worm gear and the transmission shaft of the present invention are connected in the form of a spline. This connection method not only realizes the axial movement of the transmission shaft when the stiffness is adjusted, but also ensures the normal meshing of the worm gear and worm while satisfying the requirement of adjustable stiffness.

[0021] 3. Because the front and rear worm gears rotate in different directions, the axial force can be eliminated during the meshing of the two worm gears and worms, making the entire stiffness adjustment mechanism work more smoothly.

[0022] 4. The drive shaft of the present invention has opposite thread directions to the compliant supports on both sides of the tool, so as to achieve symmetrical adjustment of stiffness. The internal compliant modules of the first compliant support and the second compliant support are close to or far from each other, which can ensure that the tool position remains unchanged when the stiffness is adjusted.

[0023] 5. The present invention is provided with an anti-loosening nut and an angle plate. The angle plate facilitates obtaining the rotation angle of the worm gear, and the anti-loosening nut facilitates fixing the position of the transmission shaft after stiffness adjustment, thereby fixing the stiffness. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is an isometric view of a fast-tool servo system based on a worm gear mechanism for adjusting stiffness, according to an embodiment of the present invention.

[0026] Figure 2 This is a front view of the fast tool servo system based on the worm gear mechanism for adjusting stiffness according to an embodiment of the present invention;

[0027] Figure 3 This is a top view of the fast tool servo system based on the worm gear mechanism for adjusting stiffness according to an embodiment of the present invention.

[0028] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0029] The components are: 1. First front baffle, 2. Front worm gear, 3. Third front baffle, 4. Front leaf spring, 5. Cutting tool, 6. Second compliant support, 7. Second front baffle, 8. Second rear baffle, 9. Motor, 10. Motor mount, 11. Rear leaf spring, 12. First compliant support, 13. Third rear baffle, 14. Worm support, 15. Angle plate, 16. Long worm, 17. Rear worm gear, 18. First rear baffle, 19. Anti-loosening nut, 20. Rear drive shaft, 21. Front drive shaft. Detailed Implementation

[0030] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] Example 1

[0032] In a typical embodiment of the present invention, reference is made to Figures 1-3 As shown, a fast-tool servo system based on a worm gear mechanism for adjusting stiffness includes a fast-tool structure and a stiffness adjustment structure. The fast-tool structure includes a tool 5, with a compliant support connected to its left and right sides via a front leaf spring 4 and a rear leaf spring 11, respectively. The stiffness adjustment structure includes a long worm 16 and front and rear baffles correspondingly located on the side of the compliant support away from the leaf springs. A front worm gear 2 and a rear worm gear 17 are correspondingly positioned with the baffles and mesh with the long worm 16. One end of a drive shaft engages with the worm gear, and the other end passes through the fast-tool structure and the baffles. The drive shaft has a single-threaded engagement with the baffles and a double-threaded engagement with the compliant support. Due to the different transmission ratios of the front and rear worm gears, the rotation angles of the front drive shaft 21 and the rear drive shaft 20 differ after rotating the long worm. The stiffness of the fast-tool structure is then finely adjusted by the lead difference between the single-threaded and double-threaded drives of the drive shaft.

[0033] like Figure 1 As shown, the fast-cutting structure of this embodiment includes a cutter 5, with a motor 9 connected to the end of the cutter 5. The motor 9 is supported by a motor mount 10. The two sides of the cutter 5 are connected to compliant supports via leaf springs. The leaf springs are divided into a front leaf spring 4 and a rear leaf spring 11. The left side of the cutter is connected to a first compliant support 12 via the front leaf spring 4 and the rear leaf spring 11, and the right side is connected to a second compliant support 6 via the front leaf spring 4 and the rear leaf spring 11. The front leaf spring 4 and the rear leaf spring 11 are symmetrically arranged about the cutter.

[0034] In this embodiment, the compliant supports on both sides of the cutter 5 are provided with two sets, one in the front and one in the back. That is, the first compliant support 12 and the second compliant support 6 both include two sets of internal compliant modules. The two sets of compliant supports are fixedly connected by an I-shaped bracket. The internal compliant modules of the first compliant support 12 and the second compliant support 6 can move closer or further away from each other, so as to realize the extension and retraction of the leaf spring and thus realize the adjustment of stiffness.

[0035] In a preferred example, the two sets of internal compliant modules in the first compliant support 12 and the second compliant support 6 are independent of each other, and the front leaf spring 4 and the rear leaf spring 11 extend and retract independently, so that the front and rear leaf springs can be adjusted in opposite directions, and the stiffness of the flexible leaf spring can be precisely adjusted by using the stiffness adjustment difference.

[0036] like Figure 1 As shown, the stiffness adjustment structure is located on the left side of the quick-cutting structure, and the compliant support is provided with a front baffle and a rear baffle on the side away from the leaf spring. The front baffle includes a first front baffle 1, a second front baffle 7, and a third front baffle 3, and the rear baffle includes a first rear baffle 18, a second rear baffle 8, and a third rear baffle 13.

[0037] The fast-tool structure includes a front worm gear 2 and a rear worm gear 17. The bottom of the front worm gear 2 and the rear worm gear 17 are engaged with a long worm 16. The long worm 16 is inclined and is made of a stepped shaft with two worm sections for meshing with the front worm gear 2 and the rear worm gear 17. The front and rear ends of the long worm 16 are supported by worm support 14. The long worm 16 is rotatably engaged with the worm support 14 through bearings.

[0038] The third front baffle 3 and the third rear baffle 13 are located between the worm gear and the first compliant support 12. The second front baffle 7 and the second rear baffle 8 are located on the right side of the second compliant support 6. The first front baffle 1 and the first rear baffle 18 are located on the left side of the worm gear. The worm gear is located between the first front baffle 1 and the first rear baffle 18 and the third front baffle 3 and the third rear baffle 13.

[0039] The front worm gear 2 and the rear worm gear 17 are correspondingly arranged with the front and rear baffles and mesh with the long worm 16. One end of the drive shaft engages with the worm gear, and the other end passes through the quick-cutting structure and the baffle. Figure 1 As shown, the drive shaft has two sets: the front baffle, the front worm gear 2, the front end of the compliant support, and the front drive shaft are in a straight line; the rear baffle, the rear worm gear 17, the rear end of the compliant support, and the rear drive shaft are in a straight line. The movement of the drive shaft and the leaf spring do not interfere with each other.

[0040] The two ends of the drive shaft extend to the outside of the first front baffle 1, the first rear baffle 18, the second front baffle 7, and the second rear baffle 8, and are fitted with anti-loosening nuts 19. The drive shaft can be fixed by setting the anti-loosening nuts 19, so as to achieve the fixation after stiffness adjustment.

[0041] like Figure 3 As shown, in this embodiment, the drive shaft and the baffle are fitted with a single-threaded connection, and the drive shaft and the compliant support are fitted with a double-threaded connection. The drive shaft and the worm gear are connected by a spline. Rotating the long worm 16 drives the front worm gear 2 and the rear worm gear 17 to rotate, so that the rigidity of the fast tool structure can be finely adjusted by the lead difference between the single-threaded and double-threaded connections.

[0042] In this embodiment, the worm gear is connected to both the front drive shaft 21 and the rear drive shaft 20 by a spline. This connection method enables the axial movement of the drive shaft during stiffness adjustment to meet the requirements of adjustable stiffness while ensuring normal meshing of the worm gear and worm.

[0043] An angle disk 15 is provided around the worm on the worm support 14. The angle disk 15 is circular and has an angle indicator. By setting the angle disk 15, the rotation angle of the long worm 16 can be obtained, which is convenient for subsequent calculation of the stiffness to be adjusted.

[0044] like Figure 1 As shown, the transmission ratio of the front worm gear mechanism is different from that of the rear worm gear mechanism; the transmission ratio of the front worm gear mechanism is greater than that of the rear worm gear mechanism. Furthermore, the front and rear worm wheels have opposite directions of rotation: the front worm wheel is right-handed, and the rear worm wheel is left-handed. Because the front worm wheel 2 and the rear worm wheel 17 have different directions of rotation, axial force can be eliminated during the meshing process of the two worm wheels, resulting in smoother operation of the entire stiffness adjustment mechanism.

[0045] The drive shaft on the front worm gear 2 is connected to the first front baffle 1 and the third front baffle 7 by a right-hand single-threaded connection, to the front end of the first compliant support 12 by a right-hand double-threaded connection, to the front end of the second compliant support by a left-hand double-threaded connection, and to the second front baffle 7 by a left-hand single-threaded connection.

[0046] The drive shaft on the rear worm gear 17 is engaged with the first rear baffle 18 and the third rear baffle 13 by a left-hand single-threaded connection, with the rear end of the first compliant support 12 by a left-hand double-threaded connection, with the front end of the second compliant support 6 by a right-hand double-threaded connection, and with the second rear baffle 8 by a right-hand single-threaded connection.

[0047] In this embodiment, the drive shaft and the compliant supports on both sides of the tool have opposite thread directions to achieve symmetrical adjustment of stiffness. The internal compliant modules of the first compliant support 12 and the second compliant support 6 are close to or far from each other, which can ensure that the tool position remains unchanged when the stiffness is adjusted.

[0048] In special cases, when the front and rear flexible supports in each set of flexible supports are independent, the front leaf spring 4 and the rear leaf spring 11 can be stretched in opposite directions by setting the thread direction, and the stiffness of the flexible leaf spring can be precisely adjusted by using the stiffness adjustment difference.

[0049] The stiffness adjustment is achieved by rotating a long worm gear to drive the double worm wheels. Since the baffles fixing the drive shaft at both ends have single-start threads, while the compliant mechanism has double-start threads, and the threads of the drive shaft and the compliant supports on both sides of the tool have opposite directions of rotation, the compliant mechanism is symmetrically fine-tuned to extend outwards or contract inwards by using the lead difference between the single-start and double-start threads and the different directions of rotation. Because the geometry of the leaf spring changes, the stiffness of the system becomes adjustable.

[0050] When the stiffness of both the front and rear worm gear mechanisms is adjusted simultaneously, a more precise stiffness adjustment is achieved by using the difference in stiffness between the two worm gear mechanisms and the tension leaf spring. After stiffness adjustment, the stiffness is fixed by using the anti-loosening nut 19 on the outside of the baffle.

[0051] Compared to a single worm gear mechanism, when adjusting the stiffness of two worm gears with different helix directions, modules, and numbers of teeth, the effect on the compliance of the leaf spring differs: a worm gear combination with a larger transmission ratio has a smaller effect on adjusting the leaf spring stiffness, while a combination with a smaller transmission ratio has a larger effect. Worm gear mechanisms also possess self-locking properties. The self-locking condition of a worm gear is that the helix angle of the worm is less than the equivalent friction angle between the meshing teeth of the worm and worm gear. Furthermore, the greater the load, the stronger its self-locking capability.

[0052] Compared to other transmission mechanisms such as cams and gears, the gear meshing in the worm gear mechanism adopts a gradual engagement and disengagement method, thus avoiding impact and vibration during the transmission process, and has the characteristics of smooth transmission and low noise.

[0053] The worm gear mechanism has a large transmission ratio, and the extension of the leaf spring by one revolution of the worm is relatively small. Furthermore, by using the lead difference between single-start and double-start threads, as well as different helix directions, the compliant mechanism can be symmetrically and finely adjusted to extend outwards or contract inwards, resulting in high stiffness adjustment precision. The worm gear mechanism can also achieve bidirectional adjustment of the stiffness of the compliant mechanism. During stiffness adjustment, the axial extension and contraction of the leaf spring is calculated by using the worm's rotation angle, transmission ratio, and lead difference, thus approximating the stiffness adjustment amount and allowing for a more accurate calculation of the overall stiffness.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fast-tool servo system based on a worm gear mechanism for adjusting stiffness, characterized in that, include: The fast-cutting structure includes a cutting tool, with the left side of the cutting tool connected to a first compliant support via a front leaf spring and a rear leaf spring, and the right side of the cutting tool connected to a second compliant support via a front leaf spring and a rear leaf spring. The stiffness adjustment structure includes a long worm gear and a front baffle and a rear baffle corresponding to the side of the compliant support away from the leaf spring. The front baffle includes a first front baffle, a second front baffle, and a third front baffle, and the rear baffle includes a first rear baffle, a second rear baffle, and a third rear baffle. The front and rear worm gears are correspondingly arranged with the baffles and mesh with the long worm. One end of the drive shaft engages with the worm gear, and the other end passes through the quick-cutting structure and the baffles. The third front baffle and the third rear baffle are located between the worm gear and the first compliant support. The second front baffle and the second rear baffle are located to the right of the second compliant support. The first front baffle and the first rear baffle are located to the left of the worm gear. The worm gear is located between the first front baffle, the first rear baffle, the third front baffle, and the third rear baffle. The drive shaft is threaded with the baffles with a single thread and with the compliant support with a double thread. The transmission ratios of the front and rear worm gears are different. After rotating the long worm, the rotation angles of the front and rear drive shafts are different. The stiffness of the quick-cutting structure is then finely adjusted by the lead difference between the single-thread and double-thread threads of the drive shaft. The threads of the drive shaft that engage with the compliant supports on both sides of the tool have opposite directions of rotation to achieve symmetrical adjustment of stiffness while keeping the tool position unchanged.

2. The fast tool servo system based on worm gear mechanism for adjusting stiffness according to claim 1, characterized in that, The front and rear leaf springs are symmetrically arranged about the cutter, and the front worm gear and front baffle are symmetrically arranged with respect to the rear worm gear and rear baffle.

3. The fast tool servo system based on worm gear mechanism for adjusting stiffness according to claim 1, characterized in that, The drive shaft extends to the outside of the front and rear baffles and is equipped with anti-loosening nuts.

4. A fast tool servo system based on a worm gear mechanism for adjusting stiffness according to claim 1, characterized in that, The transmission ratio of the front worm gear is greater than that of the rear worm gear.

5. A fast tool servo system based on a worm gear mechanism for adjusting stiffness according to claim 1, characterized in that, The front and rear worm gears rotate in opposite directions.

6. A fast tool servo system based on a worm gear mechanism for adjusting stiffness according to claim 1, characterized in that, The two drive shafts mentioned above are connected to the corresponding worm gears via splines.

7. A fast tool servo system based on a worm gear mechanism for adjusting stiffness according to claim 1, characterized in that, The long worm is supported at both ends by worm supports, and angle discs are provided on the periphery of the worm on the worm supports.

8. A fast tool servo system based on a worm gear mechanism for adjusting stiffness according to claim 7, characterized in that, The long worm is inclined and is made of a stepped shaft with two sections for meshing with the front and rear worm wheels.

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