A preloading device for the motorized spindle of a gantry machining center

Abstract

The present invention discloses a preloading device for an electric spindle of a gantry machining center, which includes a pneumatic pressure-regulating preloading mechanism. The pneumatic pressure-regulating preloading mechanism includes an air passage and a pressure-regulating chamber. The air passage can be connected to an external compressed air source. When the electric spindle is under the cutting conditions of low speed and heavy load, the stiffness of the front bearing cannot meet the working conditions requirements. The pneumatic pressure-regulating structure works, and the external compressed air source transports compressed gas into the pressure-regulating chamber through the air passage, thereby generating pressure on the preloading ring, controlling the amount of compressed gas introduced into the pressure-regulating chamber, applying a dynamic load to the front bearing through the preloading ring, and improving the stiffness of the front bearing; when the electric spindle is under the cutting conditions of high-speed rotation, the elastic member and the preloading ring cooperate to apply a flexible variable preloading force to the front bearing, so that the dynamic performance of the electric spindle within the speed range reaches the best state.

Description

Technical Field

[0001] The invention relates to the technical field of electric spindles, in particular to an electric spindle pre-tightening device for a gantry machining center. Background Art

[0002] A gantry machining center refers to a machining center in which the spindle axis is set vertically to the worktable. It is mainly suitable for machining large parts. The spindle is an important component of the gantry machining center. With the rapid development of high-speed machining technology, electric spindles are more and more widely used in the field of CNC machine tools. The electric spindle is a technology that integrates the machine tool spindle and the spindle motor.

[0003] Whether the preload of high-speed electric spindle bearings is reasonable is directly related to the static and dynamic characteristics of the spindle. There are three methods for bearing preload: positioning preload, fixed pressure preload, and pressure-adjusting preload. Under positioning preload, since the axial displacement is limited, and the axial stiffness and radial stiffness increase with the increase of speed, this preload method cannot adapt to high-speed electric spindles. Fixed pressure preload uses an elastic preload device, that is, a suitable spring is used to apply the preload. Its obvious disadvantage is that under low-speed and heavy-load cutting conditions, the deformation of the spring will affect the stiffness of the spindle. Therefore, this preload method also has defects under working conditions with high stiffness requirements. Pressure-adjusting preload mostly uses hydraulic cylinders to apply preload to the bearings. Combined with modern control technology, the preload can be dynamically controlled according to the working conditions such as bearing speed and load. However, the hydraulic control method has a complex structure and high cost, poor precision control, and the preload effect is still not ideal.

[0004] Therefore, how to change the current situation in which the preload structure of the high-speed electric spindle bearing for the gantry machining center cannot simultaneously meet the preload requirements of the electric spindle under high speed and low speed heavy load conditions has become an urgent problem to be solved by technical personnel in this field. Summary of the invention

[0005] The purpose of the present invention is to provide an electric spindle preload device for a gantry machining center to solve the problems existing in the above-mentioned prior art, so that the electric spindle preload device can control the bearing preload force according to specific working conditions such as rotation speed and load, thereby improving the dynamic performance of the electric spindle.

[0006] To achieve the above-mentioned purpose, the present invention provides the following scheme: The present invention provides an electric spindle preload device for a gantry machining center, comprising a spindle shaft core, a motor rotor, a motor stator and an electric spindle housing, wherein the motor rotor is sleeved on the outside of the spindle shaft core, the motor rotor is connected to the spindle shaft core, the motor stator is sleeved on the outside of the motor rotor, the motor rotor is rotatably connected to the motor stator, the two ends of the spindle shaft core are respectively sleeved with a front bearing and a rear bearing, and a pneumatic pressure regulating preload mechanism is arranged at the front bearing;

[0007] The pneumatic pressure-regulating pre-tightening mechanism comprises a bearing end cover and a pre-tightening ring, wherein the pre-tightening ring is sleeved on the outside of the front bearing and abuts against the end face of the front bearing on a side away from the rear bearing, the bearing end cover is sleeved on the outside of the pre-tightening ring, the bearing end cover abuts against the electric spindle housing, an air passage is arranged on the bearing end cover, and the air passage can be connected with an external compressed air source, a gap is provided between the bearing end cover and the end face of the pre-tightening ring on a side away from the front bearing and a pressure-regulating chamber is formed, the air passage is connected with the pressure-regulating chamber, an elastic member is arranged between the bearing end cover and the end face of the pre-tightening ring on a side away from the front bearing, and a sealing element is arranged between the bearing end cover and the pre-tightening ring.

[0008] Preferably, the airway is an L-shaped airway.

[0009] Preferably, a positioning groove is provided on the preload ring, and the elastic member is arranged in the positioning groove and abuts against the bearing end cover.

[0010] Preferably, the number of the positioning grooves and the number of the elastic members are both multiple and one-to-one corresponding, and the multiple positioning grooves are evenly distributed around the circumference.

[0011] Preferably, the elastic member is a spring.

[0012] Preferably, the electric spindle preload device for the gantry machining center further comprises an auxiliary bearing, wherein the auxiliary bearing is arranged on a side of the front bearing away from the rear bearing, and the auxiliary bearing is arranged between the spindle shaft core and the bearing end cover.

[0013] Preferably, a positioning sleeve is arranged between the auxiliary bearing and the front bearing.

[0014] Preferably, the pneumatic pressure-regulating pre-tightening mechanism also includes an auxiliary positioning ring, which is sleeved on the outside of the positioning sleeve, and the bearing end cover and the pre-tightening ring are respectively abutted against the auxiliary positioning ring, and sealing elements are arranged between the bearing end cover and the auxiliary positioning ring and between the pre-tightening ring and the auxiliary positioning ring.

[0015] Compared with the prior art, the present invention has achieved the following technical effects: the electric spindle preload device for a gantry machining center of the present invention comprises a spindle shaft core, a motor rotor, a motor stator and an electric spindle housing, the motor rotor is sleeved on the outside of the spindle shaft core, the motor rotor is connected to the spindle shaft core, the motor stator is sleeved on the outside of the motor rotor, the motor rotor and the motor stator are rotatably connected, the two ends of the spindle shaft core are respectively sleeved with a front bearing and a rear bearing, a pneumatic pressure regulating preload mechanism is arranged at the front bearing; the pneumatic pressure regulating preload mechanism comprises a bearing end cover and a preload mechanism Ring, the preload ring is sleeved on the outside of the front bearing and abuts against the end face of the front bearing on one side away from the rear bearing, the bearing end cover is sleeved on the outside of the preload ring, the bearing end cover abuts against the electric spindle housing, an air channel is arranged on the bearing end cover, the air channel can be connected with an external compressed air source, a gap is provided between the bearing end cover and the end face of the preload ring on one side away from the front bearing and a pressure regulating chamber is formed, the air channel is connected with the pressure regulating chamber, an elastic part is arranged between the bearing end cover and the end face of the preload ring on one side away from the front bearing, and a sealing element is arranged between the bearing end cover and the preload ring. The electric spindle preload device for a gantry machining center of the present invention is provided with a pneumatic pressure-adjusting preload mechanism. When the electric spindle is in a low-speed and heavy-load cutting condition, the stiffness of the front bearing cannot meet the working condition requirement, and the pneumatic pressure-adjusting preload structure works. An external compressed gas source delivers compressed gas to the pressure-adjusting chamber through an airway, thereby generating pressure on the preload ring, controlling the amount of compressed gas entering the pressure-adjusting chamber, applying a dynamic load to the front bearing through the preload ring, and improving the stiffness of the front bearing. When the electric spindle is in a high-speed rotating cutting condition, the elastic member and the preload ring cooperate to apply a flexible and variable preload force to the front bearing, so that the dynamic performance of the electric spindle within the speed range reaches the best state. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 It is a schematic cross-sectional structure diagram of the electric spindle pre-tightening device for a gantry machining center of the present invention;

[0018] Figure 2 for Figure 1 A magnified schematic diagram of the structure in the middle;

[0019] Among them, 1 is the main shaft core, 2 is the motor rotor, 3 is the motor stator, 4 is the electric spindle housing, 5 is the front bearing, 6 is the rear bearing, 7 is the bearing end cover, 8 is the preload ring, 9 is the airway, 10 is the pressure regulating chamber, 11 is the elastic part, 12 is the auxiliary bearing, 13 is the positioning sleeve, and 14 is the auxiliary positioning ring. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The purpose of the present invention is to provide an electric spindle preload device for a gantry machining center to solve the problems existing in the above-mentioned prior art, so that the electric spindle preload device can control the bearing preload force according to specific working conditions such as rotation speed and load, thereby improving the dynamic performance of the electric spindle.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Please refer to Figure 1-2 ,in, Figure 1 It is a schematic cross-sectional structure diagram of the electric spindle preload device for a gantry machining center of the present invention, Figure 2 for Figure 1 A magnified schematic diagram of the middle part of the structure.

[0024] The present invention provides an electric spindle pre-tightening device for a gantry machining center, comprising a spindle core 1, a motor rotor 2, a motor stator 3 and an electric spindle housing 4, wherein the motor rotor 2 is sleeved on the outside of the spindle core 1, the motor rotor 2 is connected to the spindle core 1, the motor stator 3 is sleeved on the outside of the motor rotor 2, the motor rotor 2 is rotatably connected to the motor stator 3, a front bearing 5 and a rear bearing 6 are respectively sleeved on both ends of the spindle core 1, and a pneumatic pressure regulating pre-tightening mechanism is arranged at the front bearing 5. The pneumatic pressure-regulating preload mechanism comprises a bearing end cover 7 and a preload ring 8. The preload ring 8 is sleeved on the outside of the front bearing 5 and abuts against the end face of the front bearing 5 on the side away from the rear bearing 6. The bearing end cover 7 is sleeved on the outside of the preload ring 8. The bearing end cover 7 abuts against the electric spindle housing 4. An air passage 9 is arranged on the bearing end cover 7. The air passage 9 can be connected with an external compressed air source. There is a gap between the bearing end cover 7 and the end face of the preload ring 8 on the side away from the front bearing 5 and a pressure-regulating chamber 10 is formed. The air passage 9 is connected with the pressure-regulating chamber 10. An elastic member 11 is arranged between the bearing end cover 7 and the end face of the preload ring 8 on the side away from the front bearing 5. A sealing element is arranged between the bearing end cover 7 and the preload ring 8.

[0025] The electric spindle preload device for a gantry machining center of the present invention is provided with a pneumatic pressure-adjusting preload mechanism. When the electric spindle is in a low-speed and heavy-load cutting condition, the stiffness of the front bearing 5 cannot meet the working condition requirements, and the pneumatic pressure-adjusting preload structure works. An external compressed air source delivers compressed gas to the pressure-adjusting chamber 10 through the airway 9, thereby generating pressure on the preload ring 8, controlling the amount of compressed gas entering the pressure-adjusting chamber 10, and applying a dynamic load to the front bearing 5 through the preload ring 8, thereby improving the stiffness and structural stability of the front bearing 5; when the electric spindle is in a high-speed rotating cutting condition, the elastic member 11 and the preload ring 8 cooperate to apply a flexible and variable preload force to the front bearing 5, so that the dynamic performance of the electric spindle within the speed range reaches the optimal state, thereby improving the machining accuracy.

[0026] In this specific embodiment, the air passage 9 is an L-shaped air passage, and the portion of the L-shaped air passage communicating with the pressure regulating chamber 10 is parallel to the axis of the preload ring 8, so as to reduce the impact of the compressed gas on the preload ring as much as possible.

[0027] Specifically, a positioning groove is provided on the preload ring 8, and the elastic member 11 is arranged in the positioning groove and abuts against the bearing end cover 7. The positioning groove serves to position the elastic member 11 for installation, prevents the elastic member 11 from shifting, and reduces the difficulty of disassembly and assembly.

[0028] In order to improve the uniformity of the pneumatic pressure regulating pre-tightening mechanism pre-tightening the front bearing 5, the number of the positioning grooves and the elastic member 11 are both multiple and one-to-one corresponding, and the multiple positioning grooves are evenly distributed in the circumferential direction.

[0029] In this specific embodiment, the elastic member 11 is a spring, which is low-cost and easy to install.

[0030] More specifically, the electric spindle preload device for the gantry machining center also includes an auxiliary bearing 12. The auxiliary bearing 12 is arranged on the side of the front bearing 5 away from the rear bearing 6. The auxiliary bearing 12 is arranged between the spindle core 1 and the bearing end cover 7. The bearing end cover 7 is abutted against the outer ring of the auxiliary bearing 12. The auxiliary bearing 12 also plays the role of auxiliary supporting the bearing end cover 7.

[0031] In addition, a positioning sleeve 13 is provided between the auxiliary bearing 12 and the front bearing 5 to facilitate installation, reduce the labor burden of operators, and improve work efficiency.

[0032] Furthermore, in order to enhance the sealing performance of the pressure regulating chamber 10 and avoid leakage of compressed gas, the pneumatic pressure regulating pre-tightening mechanism also includes an auxiliary positioning ring 14, which is mounted on the outside of the positioning sleeve 13, and the bearing end cover 7 and the pre-tightening ring 8 are respectively abutted against the auxiliary positioning ring 14, and sealing elements are arranged between the bearing end cover 7 and the auxiliary positioning ring 14, and between the pre-tightening ring 8 and the auxiliary positioning ring 14. In this specific embodiment, the sealing element is an O-ring to enhance the sealing performance and improve work efficiency.

[0033] The electric spindle preload device for a gantry machining center of the present invention is provided with a pneumatic pressure-adjusting preload mechanism. When the electric spindle is in a low-speed and heavy-load cutting condition, the stiffness of the front bearing 5 cannot meet the working condition requirements, and the pneumatic pressure-adjusting preload structure works. An external compressed air source delivers compressed gas to the pressure-adjusting chamber 10 through the airway 9, thereby generating pressure on the preload ring 8, controlling the amount of compressed gas entering the pressure-adjusting chamber 10, applying a dynamic load to the front bearing 5 through the preload ring 8, and improving the stiffness of the front bearing 5; when the electric spindle is in a high-speed rotating cutting condition, the elastic member 11 and the preload ring 8 cooperate to apply a flexible and variable preload force to the front bearing 5, so that the dynamic performance of the electric spindle within the speed range reaches the best state.

[0034] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A preload device for an electric spindle used in a gantry machining center. Features: It includes a spindle core, a motor rotor, a motor stator and an electric spindle housing, wherein the motor rotor is sleeved on the outside of the spindle core, the motor rotor is connected to the spindle core, the motor stator is sleeved on the outside of the motor rotor, the motor rotor is rotatably connected to the motor stator, and the two ends of the spindle core are respectively sleeved with a front bearing and a rear bearing, and a pneumatic pressure regulating pre-tightening mechanism is arranged at the front bearing; The pneumatic pressure-regulating pre-tightening mechanism comprises a bearing end cover and a pre-tightening ring, wherein the pre-tightening ring is sleeved on the outside of the front bearing and abuts against the end face of the front bearing on one side away from the rear bearing, the bearing end cover is sleeved on the outside of the pre-tightening ring, the bearing end cover abuts against the housing of the electric spindle, an air passage is arranged on the bearing end cover, the air passage can be connected with an external compressed air source, a gap is provided between the bearing end cover and the end face of the pre-tightening ring on one side away from the front bearing and a pressure-regulating chamber is formed, the air passage is connected with the pressure-regulating chamber, an elastic member is arranged between the bearing end cover and the end face of the pre-tightening ring on one side away from the front bearing, and a sealing element is arranged between the bearing end cover and the pre-tightening ring; The air duct is an L-shaped air duct, and the part of the L-shaped air duct communicating with the pressure regulating chamber is parallel to the axis of the preload ring; a positioning groove is provided on the preload ring, and the elastic member is provided in the positioning groove and abuts against the bearing end cover; the number of the positioning grooves and the elastic member are both multiple and one-to-one corresponding, and the multiple positioning grooves are evenly distributed circumferentially.

2. The electric spindle preload device for a gantry machining center according to claim 1, Features: The elastic member is a spring.

3. The electric spindle preload device for a gantry machining center according to claim 1, Features: It also includes an auxiliary bearing, which is arranged on a side of the front bearing away from the rear bearing, and the auxiliary bearing is arranged between the main shaft core and the bearing end cover.

4. The electric spindle preload device for a gantry machining center according to claim 3, Features: A positioning sleeve is arranged between the auxiliary bearing and the front bearing.

5. The electric spindle preload device for a gantry machining center according to claim 4, Features: The pneumatic pressure-regulating pre-tightening mechanism also includes an auxiliary positioning ring, which is sleeved on the outside of the positioning sleeve. The bearing end cover and the pre-tightening ring are respectively abutted against the auxiliary positioning ring. Sealing elements are arranged between the bearing end cover and the auxiliary positioning ring and between the pre-tightening ring and the auxiliary positioning ring.

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