A three-degree-of-freedom grinding machine tailstock device

Abstract

The invention discloses a tailstock device for a three-degree-of-freedom grinding machine, comprising a spindle sleeve, a center, a ball bearing, a ball bearing sleeve, a bearing positioning sleeve, an axial stator, an axial guide magnetic ring, a bolt, a magnetic bearing mover, a top holding winding, a permanent magnet ring, a spring, a screw sleeve, a deflection winding assembly, a tailstock housing and a screw seat; in the invention, the ball bearing is used as a spindle sleeve supporting component to ensure the continuous rotation of the spindle and the center, and magnetic levitation technology is applied to the tailstock device, and a high-rigidity pure electromagnetic bearing and a high-precision Lorentz bearing are used to respectively control the axial translation and radial two-degree-of-freedom deflection of the tailstock, thereby ensuring the top holding rigidity of the tailstock, realizing high-precision deflection fine-tuning, and improving the machining accuracy of the grinding machine.

Description

Technical Field

[0001] The invention relates to the field of high-precision CNC grinding machine precision machining, in particular to a three-degree-of-freedom grinding machine tailstock device. Background Art

[0002] Grinding, as the final step in precision machining, directly determines the performance of the test piece through its machining quality and accuracy. As a key functional component of a machine tool, the tailstock's holding stiffness and deflection fine-tuning capabilities significantly impact part grinding accuracy. Insufficient holding stiffness can cause part chatter, while excessive stiffness can lead to plastic deformation and reduced machining accuracy. Furthermore, due to assembly errors, the center points of the headstock, workpiece, and tailstock are not aligned horizontally, necessitating deflection fine-tuning based on the workpiece's mounting position. Patent CN107443218A describes a tailstock for a tool grinder that utilizes a purely mechanical structure consisting of an interference fit ball bearing and a compression spring to increase tailstock stiffness. However, ball bearings exhibit rolling friction, and relying solely on threaded support can easily lead to thread slippage, making them unsuitable for applications requiring high stiffness and high load capacity. Patent CN104440535B proposes a tailstock for a cylindrical grinder that incorporates a hydraulic clamping device in addition to a compression spring structure, improving holding stiffness. However, the hydraulic system places high demands on tailstock sealing and requires a dedicated hydraulic oil pump, increasing production costs. In addition to the above analysis, the two grinding machine tailstock structures do not have a deflection fine-tuning function.

[0003] Magnetic bearings offer advantages such as non-contact, low vibration, high precision, and controllability. They are primarily categorized as drag bearings and Lorentz bearings. Drag bearings generate an electromagnetic force proportional to the square of the magnetic flux density, making them suitable for applications requiring high torque and high stiffness. Lorentz bearings generate an Ampere force that is linearly proportional to the magnetic flux density, making them suitable for high-precision deflection control. Based on the demands of high-precision grinding machines and the characteristics of magnetic bearings, the two are combined to achieve precision design of the grinder's tailstock. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and to propose a three-degree-of-freedom grinding machine tailstock device with high holding rigidity, high deflection accuracy and active controllability, which is particularly suitable for precision and ultra-precision grinding machine processing.

[0005] The technical solution of the present invention is: a three-degree-of-freedom grinder tailstock device, including a spindle sleeve, a center, a dense ball bearing, a dense ball bearing sleeve, a bearing positioning sleeve, an axial stator, an axial guide magnetic ring, a bolt, a magnetic bearing mover, a top holding winding, a permanent magnet ring, a spring, a screw sleeve, a deflection winding assembly, a tailstock housing and a screw seat; the spindle sleeve is a hollow structure, with a tapered hole at the left end and a straight hole at the right end; the center is a conical structure, coaxially installed in the tapered hole at the left end of the spindle sleeve; the dense ball bearing is located on the radial outside of the spindle sleeve and on the radial inside of the dense ball bearing sleeve, and there is relative rolling between the spindle sleeve and the dense ball bearing sleeve; the dense ball bearing sleeve is located on the radial outside of the dense ball bearing; the bearing positioning sleeve is located on the radial outside of the dense ball bearing sleeve and has a sealing and positioning function; the axial stator is located at the axial right end of the dense ball bearing, dense ball bearing sleeve and bearing positioning sleeve; the axial guide magnetic ring is embedded in the right end face of the axial stator, and the axial stator is fixed to the right end face of the bearing positioning sleeve by bolts; the magnetic bearing mover It is installed on the radial outer end of the main shaft sleeve by means of a threaded connection, and is located on the axial right side of the axial stator, with an air gap of 0.5mm between it and the axial stator; the top holding winding is embedded in the left end face of the magnetic bearing mover, and is collinear with the center of rotation of the axial guide magnetic ring; the left permanent magnet ring and the right permanent magnet ring are respectively installed in parallel at the radial left and right ends of the magnetic bearing mover; the spring is located at the inner hole on the axial right side of the main shaft sleeve; the screw sleeve is located on the axial right side of the main shaft sleeve and the magnetic bearing mover, and is located on the radial outside of the left permanent magnet ring and the right permanent magnet ring; the deflection winding assembly is located on the radial inside of the screw sleeve, and has an air gap of 0.5mm in the radial direction with the magnetic bearing mover, the left permanent magnet ring and the right permanent magnet ring; the tailstock housing is located on the radial outside of the bearing locating sleeve, the axial stator and the screw sleeve, and its left and right ends are connected to the screw sleeve and the bearing locating sleeve by means of shaft shoulders, bolts and bolts; the screw seat is located at the axial right end of the main shaft sleeve and the spring and the inner hole of the screw sleeve, and is connected to the screw sleeve by means of threads.

[0006] The tailstock device of a three-degree-of-freedom grinding machine has three degrees of freedom in the working state, adopts pure electromagnetic bearings to realize the axial high-rigidity translational holding function of the tailstock, and adopts Lorentz bearings to realize the high-precision radial two-degree-of-freedom deflection fine-tuning function; the magnetic bearing mover is made of magnetic conductive material, and has an annular groove on its left end face for accommodating the holding winding, and has two annular grooves in the radial direction for accommodating the left permanent magnet ring and the right permanent magnet ring; the deflection winding assembly is mainly composed of a deflection magnetic conductive ring, a deflection winding, a magnetic isolation ring, and bolts; the deflection magnetic conductive ring is a ring structure, and the deflection winding is a ring-shaped structure.

[0007] The principle behind this solution is that the tailstock assembly for a three-degree-of-freedom grinding machine, proposed in this invention, achieves high-rigidity axial support and precise fine-tuning in two radial degrees of freedom. The center is assembled within the spindle sleeve, and a screw sleeve is rotated to compress the spring for initial support of the shaft. Based on the workpiece's characteristics, current is applied to the support winding. This, in conjunction with the axial guide ring, forms a pure electromagnetic bearing based on the principle of electromagnetic induction. This drives the spindle sleeve and center in translational motion along the workpiece's axial direction, thereby improving the tailstock's support stiffness. Based on the tailstock's assembly accuracy and the workpiece's length, the radial deflection angle errors in the X and Y directions between the headstock and tailstock are determined. Corresponding currents are applied to two pairs of deflection windings, controlling the spindle sleeve and center and driving precise fine-tuning of the part, compensating for tailstock radial two-degree-of-freedom installation errors. The deflection winding current can also be adjusted multiple times based on machining errors along the part's surface axis. After workpiece machining is completed, the currents in the deflection and support windings are sequentially shut off, and the screw sleeve is rotated in the opposite direction to reduce spring compression, thereby unloading the tailstock's support force.

[0008] The advantages of this invention over existing technologies include: a three-degree-of-freedom tailstock device for a grinding machine, offering high precision and controllability. Compared to the traditional machinist's threaded and spring-loaded support method, the addition of a pure electromagnetic bearing increases support stiffness, reduces the risk of thread stripping, and improves safety. Compared to hydraulic support methods, the magnetic bearing reduces sealing requirements, is compact, and offers low cost. Furthermore, this invention features high-precision deflection fine-tuning, compensating for machine tool installation errors and improving specimen machining accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the technical solution structure of the present invention;

[0010] Figure 2 This is a diagram of the magnetic bearing mover assembly of the technical solution of the present invention;

[0011] Figure 3 This is a diagram of the deflection winding assembly of the technical solution of the present invention;

[0012] Figure 4 This is a diagram of a three-degree-of-freedom magnetic bearing assembly, which is a technical solution of the present invention; DETAILED DESCRIPTION

[0013] like Figure 1The figure shows the structural principle diagram of the technical solution of the present invention, which is a tailstock device of a three-degree-of-freedom grinding machine, characterized in that it consists of a spindle sleeve 1, a top 2, a dense ball bearing 3, a dense ball bearing sleeve 4, a bearing positioning sleeve 5, an axial stator 6, an axial guide magnetic ring 7, a bolt 8, a magnetic bearing mover 9, a top holding winding 10, a permanent magnet ring 11, a spring 12, a screw sleeve 13, a deflection winding assembly 14, a tailstock housing 15 and a screw seat 16; the characterizing feature is that the spindle sleeve 1 is a hollow structure with a tapered hole at the left end and a straight hole at the right end; the top 2 is a conical structure and is coaxially mounted on the spindle sleeve 1 The left end tapered hole of the bead bearing 3 is located on the radial outside of the main shaft sleeve 1 and on the radial inside of the bead bearing sleeve 4, and there is relative rolling between the main shaft sleeve 1 and the bead bearing sleeve 4; the bead bearing sleeve 4 is located on the radial outside of the bead bearing 3; the bearing positioning sleeve 5 is located on the radial outside of the bead bearing sleeve 4 and has a sealing and positioning function; the axial stator 6 is located on the axial right end of the bead bearing 3, the bead bearing sleeve 4 and the bearing positioning sleeve 5; the axial guide magnetic ring 7 is embedded in the right end face of the axial stator 6, and the axial stator 6 is fixed to the right end face of the bearing positioning sleeve 5 by bolts 8A; the magnetic bearing is dynamic The rotor 9 is installed on the radial outer end of the main shaft sleeve 1 by a threaded connection, and is located on the axial right side of the axial stator 6, and there is an air gap of 0.5mm between the axial stator 6; the top holding winding 10 is embedded in the left end face of the magnetic bearing rotor 9, and is collinear with the rotation center of the axial guide magnetic ring 7; the left permanent magnet ring 11A and the right permanent magnet ring 11B are respectively installed in parallel at the radial left and right ends of the magnetic bearing rotor 9; the spring 12 is located at the inner hole on the axial right side of the main shaft sleeve 1; the screw sleeve 13 is located on the axial right side of the main shaft sleeve 1 and the magnetic bearing rotor 9, and is located on the left permanent magnet ring 11A and the right permanent magnet ring The deflection winding assembly 14 is located on the radial inside of the screw sleeve 13, and there is a 0.5mm air gap in the radial direction with the magnetic bearing mover 9, the left permanent magnet ring 11A and the right permanent magnet ring 11B; the tailstock housing 15 is located on the radial outside of the bearing positioning sleeve 5, the axial stator 6 and the screw sleeve 13, and its left and right ends are connected to the screw sleeve 13 and the bearing positioning sleeve 5 by means of shaft shoulders and bolts 8B and bolts 8C; the screw seat 16 is located at the axial right end of the spindle sleeve 1 and the spring 12 and the inner hole of the screw sleeve 13, and is connected to the screw sleeve 13 by a thread.

[0014] like Figure 2The figure shows the structure diagram of the magnetic bearing mover assembly of the technical solution of the present invention. The magnetic bearing mover assembly is mainly composed of a left magnetic bearing mover 9A, a right magnetic bearing mover 9B, a top holding winding 10, a right permanent magnet ring 11A and a left permanent magnet ring 11B. The left magnetic bearing mover 9A and the right magnetic bearing mover 9B are both made of magnetic conductive materials (such as DT4C) and are installed on the radial outer end of the main shaft sleeve 1 by threaded connection. There are two grooves in the radial direction of the left magnetic bearing mover 9A and one groove in the axial direction of the right magnetic bearing mover 9B. The top holding winding 10 is fixed in the axial groove of the right magnetic bearing mover 9B. The left permanent magnet ring 11A and the right permanent magnet ring 11B are both semicircular splicing forms and are installed on the right In the two radial grooves of the magnetic bearing mover 9B, the specific installation sequence of the magnetic bearing mover assembly is as follows: first, wind the top holding winding 10 on the left magnetic bearing mover 9A and remove it after shaping, then use bolts 8D to fix the left magnetic bearing mover 9A and the right magnetic bearing mover 9B together, secondly place the top holding winding 10 in the axial groove of the left magnetic bearing mover 9A and fix it with epoxy resin glue, then respectively adsorb the left permanent magnet ring 11A and the right permanent magnet ring 11B in the two radial grooves of the right magnetic bearing mover 9B by magnetic force, finally, install the magnetic bearing mover 9 composed of the left magnetic bearing mover 9A and the right magnetic bearing mover 9B on the radial outer end of the main shaft sleeve 1 through a threaded connection.

[0015] like Figure 3 The figure shows a deflection winding assembly according to the technical solution of the present invention, which mainly includes a deflection magnetic ring 1401, a deflection winding 1402, a magnetic isolation ring 1403, and bolts 8E. The deflection magnetic ring 1401 has a ring structure, the deflection winding 1402 has a ring-shaped structure, and the magnetic isolation ring 1403 has a structure approximately 1 / 4 of the circumference and is mounted on the deflection magnetic ring 1401 via bolts 8E. The specific assembly sequence of the deflection winding assembly is as follows: first, the magnetic isolation ring 1403 is mounted on the deflection magnetic ring 1401 via bolts 8E. Then, the deflection winding 1402 is wound around the magnetic isolation ring 1403 into a ring-shaped structure and fixed with epoxy resin glue. Finally, the deflection magnetic ring 1401 is fixed to the screw sleeve 13.

[0016] like Figure 4The figure shows a three-degree-of-freedom magnetic bearing assembly diagram of the technical solution of the present invention, which mainly includes an axial guide magnetic ring 7, a bolt 8, a left magnetic bearing mover 9A, a right magnetic bearing mover 9B, a holding winding 10, a left permanent magnet ring 11A, a right permanent magnet ring 11B, a deflection guide magnetic ring 1401, a deflection winding 1402 and a magnetic isolation ring 1403. Based on the high-rigidity holding requirement of the tailstock, an axial translation pure electromagnetic bearing consisting of an axial guide magnetic ring 7, a bolt 8D, a left magnetic bearing mover 9A, a right magnetic bearing mover 9B and a holding winding 10 is designed, wherein the axial guide magnetic ring 7, the left magnetic bearing mover 9A and the right magnetic bearing mover 9B are all made of magnetic conductive materials (such as DT4C), and current is applied to the holding winding 10, which generates a high-rigidity axial holding force Fa based on the electromagnetic induction effect, driving the spindle sleeve 1 and the center 2 to move toward the workpiece, thereby improving the holding stiffness of the tailstock; based on the high-precision deflection requirement, a left magnetic guide magnetic ring is designed. The radial two-degree-of-freedom deflection Lorentz bearing is composed of a bearing mover 9A, a right magnetic bearing mover 9B, a left permanent magnet ring 11A, a right permanent magnet ring 11B, a deflection magnetic ring 1401, a deflection winding 1402, a magnetic isolation ring 1403, and a bolt 8E. The magnetic bearing mover 9A, the right magnetic bearing mover 9B, and the deflection magnetic ring 1401 are made of magnetic conductive material (such as DT4C). The left permanent magnet ring 11A and the right permanent magnet ring 11B are both made of semicircular neodymium iron boron splicing, and the magnetization directions are upper N and lower S and upper S and lower N, respectively. Therefore, the magnetic flux formed in the XOZ plane has the following direction: Figure 4 As shown by the arrows, the current directions of the upper deflection winding 1402A and the lower deflection winding 1402B are both left-out and right-in, so the Lorentz magnetic bearing generates two deflection forces Fr of equal magnitude and opposite directions, thereby realizing the deflection fine-tuning function of the tailstock. The deflection principle of the tailstock in the YOZ plane is the same as the deflection principle in the XOZ plane.

[0017] The contents not described in detail in the specification of the present invention belong to the prior art known to those skilled in the art.

Claims

1. A three-degree-of-freedom grinding machine tailstock device, characterized in that: The invention comprises a spindle sleeve (1), a top (2), a ball bearing (3), a ball bearing sleeve (4), a bearing positioning sleeve (5), an axial stator (6), an axial guide magnetic ring (7), a bolt, a magnetic bearing mover (9), a top holding winding (10), a permanent magnetic ring (11), a spring (12), a screw sleeve (13), a deflection winding assembly (14), a tailstock housing (15) and a screw seat (16); the spindle sleeve (1) is a hollow structure, with a tapered hole at the left end and a straight hole at the right end; the top (2) is a conical structure and is coaxially mounted in the tapered hole at the left end of the spindle sleeve (1); the ball bearing (3) is located at the diameter of the spindle sleeve (1). The axial stator (6) is located at the right end of the axial stator (6), the axial stator (6) is fixed to the right end face of the axial stator (6) by bolts, and the magnetic bearing mover (9) is connected to the right end face of the axial stator (6) by screw thread. The magnetic bearing rotor (9) is mounted on the radial outer end of the main shaft sleeve (1) and is located on the axial right side of the axial stator (6) and has an air gap with the axial stator (6); the top holding winding (10) is embedded in the left end face of the magnetic bearing rotor (9) and is collinear with the rotation center of the axial guide magnetic ring (7); the left permanent magnet ring (11A) and the right permanent magnet ring (11B) are respectively mounted in parallel on the radial left and right ends of the magnetic bearing rotor (9); the spring (12) is located at the inner hole on the axial right side of the main shaft sleeve (1); the screw sleeve (13) is located on the axial right side of the main shaft sleeve (1) and the magnetic bearing rotor (9) and is located on the left permanent magnet ring (11A) and the right permanent magnet ring (11B). B); the deflection winding assembly (14) is located on the radial inner side of the screw sleeve (13), and has an air gap in the radial direction with the magnetic bearing mover (9), the left permanent magnet ring (11A) and the right permanent magnet ring (11B); the tailstock housing (15) is located on the radial outer side of the bearing positioning sleeve (5), the axial stator (6) and the screw sleeve (13), and its left and right ends are connected to the screw sleeve (13) and the bearing positioning sleeve (5) by means of shaft shoulders and bolts; the screw seat (16) is located at the axial right end of the main shaft sleeve (1) and the spring (12) and the inner hole of the screw sleeve (13), and is connected to the screw sleeve (13) by threads.

2. The three-degree-of-freedom grinding machine tailstock device according to claim 1, characterized in that: This device has three degrees of freedom in working state. It adopts pure electromagnetic bearing to realize the high rigidity axial translation holding function of the tailstock and adopts Lorentz bearing to realize the high precision radial two degree of freedom deflection fine adjustment function.

3. The three-degree-of-freedom tailstock device of a grinding machine according to claim 1, characterized in that: The magnetic bearing mover (9) is made of a magnetic conductive material, and has an annular groove on its left end surface for accommodating a top-holding winding (10), and two annular grooves in its radial direction for accommodating a left permanent magnet ring (11A) and a right permanent magnet ring (11B).

4. The three-degree-of-freedom tailstock device for a grinding machine according to claim 1, characterized in that: The deflection winding assembly (14) consists of a deflection magnetic ring (1401), a deflection winding (1402), a magnetic isolation ring (1403), and bolts. The deflection magnetic ring (1401) is a ring-shaped structure, and the deflection winding (1402) is a circular structure.

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