A non-contact pneumatic hybrid electric spindle support system

Abstract

A non-contact pneumatic hybrid electric spindle support system, characterized in that: a spindle is provided with a convex cone of the same cross-section, an upper cover plate and a lower cover plate with a concave inner cavity corresponding to the convex cone, a piezoelectric fiber layer is fixed on the bottom surface of the upper cover plate and the lower cover plate respectively, and the upper cover plate and the lower cover plate are provided with evenly distributed air inlet holes on their surfaces. The support system of the present invention couples ultrasonic suspension with gas hydrostatic support, utilizes the inverse piezoelectric effect and the gas hydrostatic effect, performs secondary pressure distribution on the air film in the gap between the spindle and the pressure box, and changes the extrusion state of the air film in the gap by controlling the vibration parameters of the piezoelectric fiber. The present invention changes the structure of the spindle so that the suspension force generated by the air film can be decomposed into a thrust force along the axial direction and a bearing force perpendicular to the axial direction, so that the electric spindle has axial and radial stability during high-speed operation; the spindle support system of the present invention has a large bearing capacity and a high rotation accuracy, and is suitable for ultra-precision machining, aerospace and other precision fields.

Description

Technical Field

[0001] The invention patent relates to an electric spindle rotation support system. Background Art

[0002] In recent years, with the rapid development of industrial modernization, the demand for ultra-precision machine tools and high-speed machine tools has continued to grow, such as diamond lathes used in the defense field to process large optical lenses, ultra-precision grinders used in the electronics industry to process tiny aspheric optical lenses, and high-speed drilling machines used for drilling holes in printed circuit boards. At the same time, ultra-precision machining fields such as aerospace also put forward higher requirements on the performance of machine tools. The support method of the machine tool spindle affects the rotation accuracy of the entire axis system and the machining accuracy of parts. At present, the non-contact electric spindle support method in ultra-precision machining at home and abroad generally adopts air static pressure support, but this support method has poor stability, and air hammer vibration and self-excited vortex will occur, resulting in spindle damage. Therefore, it is necessary to design a new electric spindle support system with good stability and high rotation accuracy.

[0003] The non-contact pneumatic hybrid electric spindle support system of the present invention mixes pneumatic suspension with ultrasonic suspension, does not have electromagnetic radiation, uses piezoelectric fiber and high-pressure gas source as driving devices, generates extrusion film effect through high-frequency vibration of piezoelectric fiber, and generates gas static pressure effect through high-pressure gas source to realize suspension support of the spindle; changes the structure of the spindle to provide axial thrust and radial bearing capacity to the spindle at the same time, and improves the rotation accuracy of the spindle; controls the vibration parameters of high-frequency vibration, changes the extrusion state of input high-pressure gas, forms a controllable suspension force, realizes intelligent monitoring of the suspension state of the electric spindle, and improves the stability of the support system. The new electric spindle support system has large load-bearing capacity, high precision, and good stability. Summary of the invention

[0004] In order to solve the problem that the electric spindle cannot guarantee high rotation accuracy and high stability during operation, the present invention proposes the following technical solution: a non-contact pneumatic hybrid electric spindle support system, characterized in that: a spindle is provided with at least two convex cones of isosceles trapezoidal shapes with the same cross-section. The cross-section of the convex cone on the spindle can also be an isosceles triangle or a circle. An upper cover plate and a lower cover plate are provided with a concave inner cavity corresponding to the isosceles trapezoidal cross-section of the spindle and a flange with screw holes on the side. The cross-section of the concave inner cavity can also be an isosceles triangle or a circle. The piezoelectric fiber layer is respectively fixed on the bottom surface of the concave inner cavity of the upper cover plate and the lower cover plate. Uniformly distributed air inlet holes are provided, which pass through the upper cover plate, the lower cover plate and the piezoelectric fiber layer respectively. The upper cover plate and the lower cover plate are respectively fastened at the two convex cones on the spindle by bolts passing through the screw holes on the flange to form two pressure boxes with the same structure. A gap is provided between the surface of the piezoelectric fiber layer of the upper cover plate and the lower cover plate in the pressure box and the convex cone. The inclination angle α of the convex cone on the main axis is 45°-90°, and the optimal value is 45°. The value range of the gap between the surface of the piezoelectric fiber layer and the convex cone is 50-100 μm, and the optimal value is 50 μm.

[0005] In the present invention, at least two isosceles trapezoidal convex cones with the same cross-section are provided in the axial direction of the main shaft, and the upper cover plate and the lower cover plate with flanges with screw holes on the side are provided with a concave inner cavity corresponding to the isosceles trapezoidal cross-section of the main shaft, so that the present invention can still have a supporting effect when the main shaft is stationary. Since the isosceles trapezoidal convex cones with the same cross-section are provided on the main shaft of the present invention, the suspension force generated by the high-frequency vibration of the piezoelectric fiber is decomposed into an axial thrust along the main shaft axis direction and a radial bearing force perpendicular to the main shaft axis direction, so that the main shaft remains stable during high-speed rotation. Since multiple air inlet holes are provided on the surface of the upper cover plate and the lower cover plate, air hammer instability is likely to occur when high-pressure gas is introduced, causing the main shaft to vibrate violently. The present invention couples ultrasonic suspension with gas static pressure suspension, performs secondary pressure distribution on the introduced gas, and makes the convex cone on the main shaft in the electric spindle support system and the air film in the gap between the piezoelectric fiber layer on the bottom surface of the upper cover plate and the lower cover plate uniform, and at the same time, by controlling the high-frequency vibration parameters, a controllable suspension force and stress distribution state are formed. The electric spindle support system of the present invention changes the suspension force supporting the electric spindle by changing the extrusion state of the air film in the gap, thereby realizing intelligent monitoring of the suspension state of the electric spindle. The non-contact pneumatic hybrid electric spindle support system overcomes the shortcomings of ultrasonic suspension and pneumatic suspension, reduces the air hammer phenomenon, and improves the stability and rotation accuracy of the support system.

[0006] A non-contact pneumatic hybrid electric spindle support system adopts the above technical solution, utilizing the inverse piezoelectric effect and the gas static pressure effect, by changing the structure of the spindle, and simultaneously changing the gas extrusion state in the gap between the piezoelectric fiber layer flowing from the air inlet into the spindle and the upper cover plate and the bottom surface of the lower cover plate, so that each end face of the convex cone arranged on the spindle has a stable suspension force, and realizes stable support for the entire spindle in the axial and radial directions. The electric spindle support system of the present invention has good working stability, can adjust the suspension force on the electric spindle by controlling the vibration parameters of the piezoelectric fiber layer, so that the suspension state of the electric spindle can be monitored in real time, has a large load-bearing capacity, a simple structure and is easy to process, and is suitable for ultra-precision processing, aerospace and other precision fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A three-dimensional diagram of a non-contact pneumatic hybrid electric spindle support system.

[0008] Figure 2 for Figure 1 main view.

[0009] Figure 3 for Figure 2 Top view of the .

[0010] Figure 4 for Figure 2 Left view of .

[0011] Figure 5 A three-dimensional diagram of the main axis.

[0012] Figure 6 for Figure 5 main view.

[0013] Figure 7 for Figure 3 AA section view.

[0014] Figure 8 for Figure 7 A magnified view of part I.

[0015] In the figure: 1, upper cover plate, 2, lower cover plate, 3, main shaft, 4, convex cone, 5, concave inner cavity, 6, bolt, 7, flange, 8, piezoelectric fiber layer, 9, air inlet, 10, gap. DETAILED DESCRIPTION

[0016] Figure 1 It is a non-contact pneumatic hybrid electric spindle support system. Figure 8It is its detailed internal structure. The entire support system includes an upper cover plate 1, a lower cover plate 2, a main shaft 3, and a piezoelectric fiber layer 8. The support system is provided with a main shaft 3 containing at least two isosceles trapezoidal convex cones 4 with the same cross-section. The upper cover plate 1 and the lower cover plate 2 are provided with a concave inner cavity 5 corresponding to the isosceles trapezoidal cross-section on the main shaft 3 and a flange 7 with screw holes on the side. A piezoelectric fiber layer 8 is provided and fixed on the bottom surface of the concave inner cavity 5 of the upper cover plate 1 and the lower cover plate 2 respectively. Uniformly distributed air inlet holes 9 are provided, which pass through the upper cover plate 1 and the lower cover plate 2 and the piezoelectric fiber layer 8 respectively. The upper cover plate 1 and the lower cover plate 2 are respectively fastened at the two convex cones 4 on the main shaft 3 by bolts 6 passing through the screw holes on the flange 7 to form two pressure boxes with the same structure. A gap 10 is provided between the convex cone 4 and the piezoelectric fiber layer 8 of the upper cover plate 1 and the lower cover plate 2. At least two pressure boxes are fixedly placed on the same horizontal plane.

[0017] In the present invention, since at least two convex terraces 4 are provided in the axial direction of the spindle 3, and a very small gap 10 is provided between the concave inner cavity 5 in the upper cover plate and the lower cover plate of the pressure box and the convex terrace 4 on the spindle 3, the electric spindle support system of the present invention still has a supporting function when the spindle 3 is stationary; by providing at least two convex terraces 4 on the spindle 3, the direction of the suspension force generated by the piezoelectric fiber layer 8 on the spindle 3 during high-frequency vibration is changed, so that the suspension force generated by the piezoelectric fiber layer 8 is decomposed into an axial thrust along the axial direction of the spindle 3 and a thrust perpendicular to the spindle. The radial bearing capacity in the axial direction of the shaft 3 enables the main shaft 3 to maintain axial and radial stability during high-speed rotation. At this time, the axial thrust applied to the main shaft 3 is the horizontal component of the suspension force generated by the piezoelectric fiber layer 8 at the inclined surface of the concave inner cavity 5 of the upper cover plate 1 and the lower cover plate 2 of the pressure box, and the radial bearing capacity is the combined force of the vertical component of the suspension force generated by the piezoelectric fiber layer 8 at the inclined surface of the concave inner cavity 5 of the upper cover plate 1 and the lower cover plate 2 of the pressure box and the suspension force generated by the piezoelectric fiber layer 8 at the horizontal surface of the concave inner cavity 5 of the upper cover plate 1 and the lower cover plate 2 of the pressure box. The inclination angle α of the convex truncated cone 4 on the main shaft 3 in the electric spindle support system of the present invention can be any angle between 45°-90°. The axial thrust generated at this time is larger than the axial thrust generated by the truncated cone with an inclination angle of 0°-45°. When the inclination angle α of the truncated cone is 45°, the radial support force and the axial support force generated by the main shaft support system reach the maximum value at the same time, so that the bearing capacity of the electric spindle support system reaches the maximum.

[0018] When the electric spindle support system is working, high-pressure gas is introduced into the air inlet holes 9 arranged on the surfaces of the upper cover plate 1 and the lower cover plate 2, and an AC voltage is input into the piezoelectric fiber layer 8 at the same time. At this time, the high-pressure gas introduced into the air inlet holes 9 will act together with the extruded air film generated by the high-frequency vibration of the piezoelectric fiber layer 8 in the gap 10 between the convex cone 4 on the spindle 3 and the bottom surface of the concave inner cavity 5 in the upper cover plate 1 and the lower cover plate 2, thereby realizing the coupling of ultrasonic suspension and pneumatic suspension. After coupling, the electric spindle support system can perform secondary pressure distribution on the air film in the gap 10, so that the air film in the gap 10 between the convex cone 4 on the spindle and the bottom surface of the concave inner cavity 5 in the upper cover plate 1 and the lower cover plate 2 in the electric spindle support system can be homogenized. When the main shaft 3 in the support system deviates to one side, the gap 10 becomes smaller, so that the suspension force generated by the piezoelectric fiber layer 8 on this side becomes larger, and the suspension force generated by the piezoelectric fiber layer 8 on the other side becomes smaller due to the increase in the gap 10. The main shaft 3 is pulled back to the center of the support system under the combined action of the suspension forces on both sides, forming a controllable suspension force and stress distribution state. By changing the vibration parameters of the high-frequency vibration of the piezoelectric fiber layer 8 and simultaneously changing the extrusion state of the air film in the gap 10, the suspension force on the electric main shaft is changed, thereby improving the stability of the entire main shaft support system.

[0019] In the electric spindle support system of the present invention, the radius gap of the static pressure gas support is generally 1 / 1000-1 / 5000 of the diameter of the spindle 3. For supporting the electric spindle, the radius gap 10 is often a larger value. If the pressure in the gap 10 is small, the spindle 3 is no longer in a suspended state, and the spindle 3 has obvious contact with its supporting components, generating vibration noise, and causing instability of the system. In severe cases, the spindle will be stuck and ground.

[0020] In summary, a non-contact pneumatic hybrid electric spindle support system of the present invention realizes simultaneous radial support and axial thrust of the spindle by changing the structure of the spindle and utilizing piezoelectric drive and gas hydrostatic suspension. At the same time, after the coupling of gas hydrostatic suspension and ultrasonic suspension, the air film in the gap can be subjected to secondary pressure distribution, so that the air film in the gap between the spindle and the piezoelectric fiber layer on the concave inner bottom surface of the upper cover plate and the lower cover plate of the pressure box in the electric spindle support system is homogenized. By changing the vibration parameters of the high-frequency extrusion of the piezoelectric fiber layer, the extrusion state of the air film is changed to form a controllable suspension force, and at the same time, the air hammer vibration phenomenon of the support system can be weakened, thereby improving the working stability of the electric spindle. The electric spindle support system of the present invention has good working stability, high precision, large load-bearing capacity, and simple structure, and is suitable for ultra-precision machining, aerospace and other precision operation fields.

Claims

1. A non-contact pneumatic hybrid electric spindle support system, characterized in that: include: A main axis (3) is provided with at least two convex cones (4) of isosceles trapezoidal cross-section; an upper cover plate (1) and a lower cover plate (2) are provided with a concave inner cavity (5) corresponding to the isosceles trapezoidal cross-section of the convex cone (4) and a flange (7) with screw holes on the side; a piezoelectric fiber layer (8) is respectively fixed on the bottom surface of the concave inner cavity (5) of the upper cover plate (1) and the lower cover plate (2); the shape of the piezoelectric fiber layer (8) corresponds to the outer contour of the convex cone (4); and a concave inner cavity (5) corresponding to the isosceles trapezoidal cross-section of the convex cone (4) is provided. The air inlet holes (9) of the cloth respectively pass through the upper cover plate (1), the lower cover plate (2) and the piezoelectric fiber layer (8); the upper cover plate (1) and the lower cover plate (2) are respectively fastened at two convex cones (4) on the main shaft (3) by bolts (6) passing through the screw holes on the flange (7) to form two pressure boxes with the same structure; a gap (10) is provided between the surface of the piezoelectric fiber layer (8) of the upper cover plate (1) and the lower cover plate (2) in the pressure box and the convex cones (4); The inclination angle α of the convex cone (4) on the main shaft (3) is 45°-90°; A gap (10) having a value ranging from 50 to 100 μm is provided between the surface of the piezoelectric fiber layer (8) of the upper cover plate (1) and the lower cover plate (2) in the pressure box and the convex truncated cone (4).

2. A non-contact pneumatic hybrid electric spindle support system according to claim 1, characterized in that: The optimal value of the inclination angle α of the convex cone (4) on the main shaft (3) is 45°.

3. The non-contact pneumatic hybrid electric spindle support system according to claim 1, characterized in that: The optimum value of the gap (10) between the surface of the piezoelectric fiber layer (8) of the upper cover plate (1) and the lower cover plate (2) in the pressure box and the convex truncated cone (4) is 50 μm.

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