CN103286679B - A kind of ultrahigh speed air bearing electric main-shaft - Google Patents

Abstract

The invention discloses an ultra-high-speed air bearing electric spindle, which comprises a casing, a static pressure radial air bearing arranged in the casing, a rotor arranged in the static pressure radial air bearing, a motor shaft connected with the rotor, and the motor shaft The motor rotor connected, the rear thrust bearing and the front thrust bearing arranged at one end of the static pressure radial air bearing, the thrust plate arranged at one end of the rotor and the non-contact gas sealing ring arranged at one end of the motor shaft, the rotor One end is installed and connected with the rear thrust bearing and the front thrust bearing through the thrust plate, and the other end of the rotor is installed and connected with the motor shaft. The invention has high limit speed, low bearing temperature rise and high rotation precision; reduces the weight of the main shaft and improves the dynamic characteristics of the main shaft; solves the cooling problem of small diameter deep hole grinding, and also plays the role of cooling the rotor of the main shaft motor, improving the bearing performance. The support stiffness and the rotation accuracy of the main shaft.

Description

A super high speed air bearing electric spindle

technical field

The invention belongs to the field of high-speed grinding processing equipment, and relates to an ultra-high-speed aerostatic bearing electric spindle.

Background technique

Internal grinding of small-diameter deep holes is one of the problems to be solved urgently in high-speed machining. Ultra-high-speed electric spindle is a necessary equipment for internal grinding of small-diameter deep holes, and its working speed requires more than 100,000 rpm. Traditional ultra-high-speed electric spindles are mostly supported by rolling bearings. Engineering applications show that high-speed operation seriously restricts the life of rolling bearings. First of all, the lubrication of rolling bearings needs to be improved. Traditional grease lubrication cannot achieve the ideal lubrication effect, and oil-air lubrication will be equipped with an additional oil-air lubrication system to increase production costs. Secondly, rolling bearings also show temperature rise and support stiffness changes at high speeds. Small, these will directly affect the rotation accuracy of the spindle. Ultra-high-speed rolling bearings should use small-diameter hybrid ceramic ball bearings, which are expensive and need to be imported. If oil-lubricated or water-lubricated sliding bearings are used, at high speeds, due to the shearing action between the fluids, a large amount of heat will be generated, which will increase the temperature of the fluid, resulting in a decrease in its viscosity, bearing capacity and support stiffness. As the temperature of the fluid rises, the journal and bearing bush will produce temperature deformation, which will lead to changes in the bearing clearance and affect the performance of the bearing.

For the internal grinding process of small diameter deep hole, the supply of grinding coolant is also a big problem. With the external liquid supply method, the coolant cannot reach the grinding area smoothly; while the coolant is passed through the inside of the electric spindle, because the spindle is a slender shaft, the pressurized coolant must be passed in, and a new seal is proposed for the internal seal of the spindle. challenge.

Contents of the invention

Technical problem: In view of the above problems, the present invention provides an ultra-high-speed air bearing electric spindle with high limit speed, low bearing temperature rise and high rotation precision.

Technical solution: An ultra-high-speed air bearing electric spindle of the present invention includes a housing, a static pressure radial air bearing disposed in the housing, a rotor disposed in the static pressure radial air bearing, a motor shaft connected to the rotor, and The motor rotor connected to the motor shaft, the rear thrust bearing and the front thrust bearing arranged at one end of the static pressure radial air bearing, the thrust plate arranged at one end of the rotor and the non-contact gas sealing ring arranged at one end of the motor shaft One end of the rotor is installed and connected with the rear thrust bearing and the front thrust bearing through the thrust plate, and the other end of the rotor is installed and connected with the motor shaft.

In the present invention, the aspect ratio of the rotor is greater than 10.

In the present invention, the rotor is a thin-walled hollow rotor, and the center is provided with a stepped through hole, including a large through hole and a small through hole. Long hollow tube, a central through hole is set in the slender hollow tube, one end of the slender hollow tube is sealed and installed on the transition cone surface between the large hole and the small hole, and the other end is sealed and installed in the motor shaft

In the present invention, the rotor and the motor shaft are interference mounted and connected to form an overall structure. The outside of the motor shaft is a stepped shaft, including three sections of large diameter part, middle diameter part and small diameter part, and the large diameter part is interference mounted in the large through hole of the rotor. inside, and is fixedly connected with the slender hollow tube, the middle diameter part is installed and connected with the motor rotor, and the small diameter part is installed and connected with the gas sealing ring; the center of the motor shaft is provided with a stepped through hole, including the large hole of the motor shaft connected in sequence, the motor shaft Small holes and holes in the motor shaft.

The key of the present invention is that the main shaft is supported by air static pressure bearings with a large length-to-diameter ratio (up to 10 or more), four static pressure air bearings are used in the radial direction, and a set of closed static pressure thrust bearings are used in the axial direction; the main shaft is hollow Thin-walled structure, with thin-walled and slender pipes inside, used to feed coolant. This structure can effectively reduce the mass and moment of inertia of the spindle, and the static pressure air bearing can provide sufficient support stiffness at high speed, so the electric spindle has a high critical speed, which meets the technical requirements of internal grinding of small diameter deep holes.

Beneficial effect: compared with the prior art, the present invention has the following advantages:

The invention is supported by a static pressure air bearing with a large length-to-diameter ratio, with high limit speed, low temperature rise of the bearing and high rotation precision; the main shaft adopts a hollow structure, which reduces the weight of the main shaft and improves the dynamic characteristics of the main shaft; the middle hole of the main shaft is used to supply grinding coolant technology, which solves the cooling problem of small diameter deep hole grinding, and also plays the role of cooling the rotor of the spindle motor, which improves the support stiffness of the bearing and the rotation accuracy of the spindle; in order to prevent the leakage of the coolant, the coolant supply end adopts non-contact gas Sealing technology.

Compared with the traditional rolling bearing electrical spindle or fluid lubricated bearing, the present invention has the same features as: it is driven by a built-in motor and cooled by cooling water jacket circulation. The difference is that compared with traditional rolling bearings and fluid-lubricated sliding bearings, air bearings with large aspect ratios have greater radial stiffness. As the speed increases, the dynamic pressure effect increases, thereby improving the bearing stiffness. The spindle adopts a hollow structure, which greatly increases the critical speed of the spindle; the use of the middle hole to supply grinding coolant can further reduce the temperature rise of the spindle motor; the efficient non-contact gas seal does not affect the power consumption and rotation accuracy of the spindle.

Description of drawings

Fig. 1 is a schematic structural view of the ultra-high-speed air-bearing electric spindle of the present invention.

Fig. 2 is a structural schematic diagram of the ultra-high-speed air bearing electric spindle of the present invention.

Figure 3 is a schematic diagram of the rotor structure.

Figure 4 is a schematic diagram of the structure of the motor shaft.

Fig. 5 is a schematic diagram of the structure of the static pressure radial air bearing.

In the figure, there are: shell 1, motor cooling water inlet 101, first compressed air inlet 105, second compressed air inlet 104, third compressed air inlet 103, fourth compressed air inlet 102, the first One intake ring 201, the second intake ring 202, the third intake ring 203, the fourth intake ring 204, the intake channel 106, the static pressure bearing intake hole 107, the first air outlet hole 108, and the second air outlet hole 109. The third air outlet 110, the coolant inlet 1101, the first external air outlet 205, the second external air outlet 206, the third external air outlet 207, the exhaust channel 113, the first air outlet 111, the second exhaust Hole 112, non-contact gas-tight compressed air inlet hole 114, rotor 20, large through hole 2002, small through hole 2001, slender hollow tube 18, central through hole 1801, motor shaft 17, large hole 1702, middle hole 1701 , small hole 1703, static pressure radial air bearing 2, first inner air outlet groove 208, second inner air outlet groove 209, third inner air outlet groove 210, first communication hole 211, second communication hole 212, third communication hole 213, thrust bearing air intake hole 215, small hole restrictor 214, rear thrust bearing 3, throttle hole 301, rear thrust bearing air intake slot 302, front thrust bearing 4, front thrust bearing air intake slot 401, front thrust bearing throttle hole 402, end cover 5, end cover air inlet 501, cooling water jacket 6, motor stator 7, motor rotor 8, cooling water overflow sleeve 9, water inlet pipe 11, water outlet pipe 13, gas Sealing ring 14, thrust plate 19, adjustment ring 16, main shaft rear end cover 12, grinding wheel connecting rod 21,

Detailed ways

As shown in Figure 1 is a schematic diagram of an ultra-high-speed air bearing motorized spindle, which mainly includes: housing 1, static pressure radial air bearing 2, a pair of closed static pressure thrust air bearings (rear thrust bearing 3 and front thrust bearing Bearing 4), rotor 20, motor assembly and gas sealing device at the motor end. The rotor 20 is a thin-walled hollow rotor with stepped through-holes in the center, including a large through-hole 2002 and a small through-hole 2001 , and the connection between the large through-hole 2002 and the small through-hole 2001 is a tapered surface. The large through hole 2002 of the rotor 20 is equipped with an elongated hollow tube 18 inside, and the elongated hollow tube 18 is provided with a central through hole 1801 . One end of the elongated hollow tube 18 is installed on the transition cone surface of the large through hole 2002 and the small through hole 2001, and is sealed with a sealing ring, and the other end is installed in the motor shaft 17, and is sealed with a sealing ring. The motor shaft 17 is a stepped shaft, which is divided into three sections: the large diameter part is installed in the large through hole 2002 of the rotor 20, and the slender hollow tube 18 is fixed, the middle diameter part is installed in the motor rotor 8, and the small diameter part is installed Non-contact gas sealing ring 14. The center of the motor shaft 17 is provided with a stepped through hole, including the large motor shaft hole 1702, the motor shaft middle hole 1701 and the motor shaft small hole 1703, and the motor shaft small hole 1703 is used for the transition between the motor shaft large hole 1702 and the motor shaft middle hole 1701. The cooling water overflow cover 9 is installed in the gap in the motor shaft middle hole 1701. The outer side of the rotor 20 is equipped with a static pressure radial air bearing 2, and the static pressure radial air bearing 2 is provided with 8 rows of throttle holes, and is also provided with 4 intake rings, which are respectively the first intake ring 201, the second intake ring 201, and the second intake ring. The intake ring 202, the third intake ring 203 and the fourth intake ring 204, two rows of throttle holes are installed in each intake ring, and the outer wall of the static pressure radial air bearing 2 is provided with The external air outlet grooves adjacent to the intake ring are respectively: the first external air outlet groove 205, the second external air outlet groove 206, and the third external air outlet groove 207, and the inner wall is provided with an internal air outlet groove corresponding to the external air outlet groove, respectively. These are: the first inner air outlet groove 208 , the second inner air outlet groove 209 , and the third inner air outlet groove 210 . Communication holes are provided between the inner and outer air outlet grooves, which are respectively: a first communication hole 211 , a second communication hole 212 and a third communication hole 213 . The front end of the bearing 2 is provided with a thrust bearing inlet hole 215 , and the thrust bearing inlet hole 215 communicates with the inlet ring 201 . A casing 1 is installed outside the static pressure radial air bearing 2 , and a motor cooling water inlet 101 is provided on the casing 1 for passing the external cooling water into the motor cooling water jacket 6 . Housing 1 is provided with four bearing compressed air intake holes, namely: the first compressed air intake hole 105, the second compressed air intake hole 104, the third compressed air intake hole 103 and the fourth compressed air intake hole hole 102, these four compressed air inlet holes are respectively connected with the first intake ring 201, the second intake ring 202, the third intake ring 203 and the fourth intake ring 204 intake ring, while the four compressed air The air intake holes communicate with each other through an air intake channel 106 , and the compressed air is fed in from an external air source through a hydrostatic bearing air intake hole 107 arranged on the housing 1 . The housing 1 is provided with three bearing internal air outlets, which are respectively the first air outlet 108, the second air outlet 109 and the third air outlet 110, and the three air outlets are connected with the first external air outlet groove 205 on the outer wall of the bearing 2 respectively. , the second external air outlet groove 206, and the third external air outlet groove 207 are connected, and the three air outlet holes are connected through the exhaust channel 113 on the shell 1, and the exhaust channel 113 is connected through the first exhaust hole 111 on the shell 1 and the second The second exhaust hole 112 communicates with the outside world and is used to remove the air inside the bearing. The front end of the static pressure radial air bearing 2 is equipped with a pair of closed thrust bearings 3 and 4, the rear thrust bearing 3 is installed inside the static pressure radial air bearing 2, and the rear thrust bearing 3 is provided with a rear thrust bearing The air intake slot 302 and several rear thrust bearing throttle holes 301, the throttle hole 301 communicates with the air intake slot 302, and the air intake slot 302 passes through the thrust bearing air intake hole hole 215 on the static pressure radial air bearing 2 It communicates with the first intake ring 201 on the static pressure radial air bearing 2 . One end of the rear thrust bearing 3 adjacent to the end cover 5 is provided with a thrust plate 19 , and the thrust plate 19 is mounted on the rotor 20 with interference. The front end of the thrust plate 19 is equipped with a front thrust bearing 4, and the front thrust bearing 4 is provided with a front thrust bearing air inlet groove 401 and several front thrust bearing throttle holes 402, and the front thrust bearing air inlet groove 401 It communicates with the throttle hole 402 , and the front thrust bearing air inlet groove 401 communicates with the external air source through the end cover air inlet hole 501 provided on the end cover 5 . The outside of the thrust plate is equipped with an adjusting ring 16 for adjusting the air film gap of the closed thrust bearings 3 and 4. The rear end of the motor shaft 17 is equipped with a non-contact gas sealing device, which feeds compressed air through the non-contact gas sealing compressed air inlet hole 114 on the casing 1 .

Compressed air is fed through the non-contact gas-sealed compressed air inlet hole 114, the static pressure bearing inlet hole 107 and the end cover inlet hole 501, the cooling water is fed through the motor cooling water inlet 101, and the cooling liquid inlet 1101 is fed into it. Coolant. The cooling liquid flows through the cooling liquid inlet 1101, the middle hole 1701, the small hole 1703 and the large hole 1702 of the motor shaft step, the central through hole 1801 of the elongated hollow tube 18 and the small through hole 2001 of the rotor 20, and enters the grinding wheel. The inner hole of the post, which eventually enters the machining area. The non-contact gas seal prevents the cooling water from overflowing between the casing 9 and the motor shaft 17 and the leakage cooling liquid enters the motor. The compressed air introduced from the air inlet hole 107 of the static pressure bearing and the air inlet hole 501 of the end cover forms a bearing air film in the gap of the static pressure air bearing. Since the air is extremely low compared to other liquid lubricants, the friction power consumption is low , The temperature rise is small, and due to the dynamic pressure effect of the air bearing when the rotor rotates at high speed, as the rotor speed increases, the support stiffness of the bearing also increases to ensure the stable operation of the electric spindle at high speed.

Claims (3)

1. a ultrahigh speed air bearing electric main-shaft, it is characterized in that, this electro spindle comprises shell (1), be arranged on the static pressure radial air bearing (2) in described shell (1), be arranged on the rotor (20) in described static pressure radial air bearing (2), the motor shaft (17) be connected with described rotor (20), the rotor (8) be connected with described motor shaft (17), be arranged at rear thrust bearing (3) and the front thrust bearing (4) of described static pressure radial air bearing (2) one end, and be arranged on the thrust button (19) of described rotor (20) one end and be arranged on the contactless gas seal ring (14) of described motor shaft (17) one end, rotor (20) one end is installed with rear thrust bearing (3) and front thrust bearing (4) by thrust button (19) and is connected, rotor (20) other end is installed with motor shaft (17) and is connected,

Described rotor (20) is thin wall hollow rotor, center is provided with ladder hole, comprise large through-hole (2002) and small through hole (2001), the junction of described large through-hole (2002) and small through hole (2001) is the conical surface, large through-hole (2002) inside is provided with the integrally-built elongated hollow tube of thin-walled (18), central through hole (1801) is provided with in described elongated hollow tube (18), one end sealing of elongated hollow tube (18) is arranged on the transition conical surface of large through-hole (2002) and small through hole (2001), and other end sealing is arranged in motor shaft (17).

2. ultrahigh speed air bearing electric main-shaft according to claim 1, is characterized in that, the draw ratio of described rotor (20) is greater than 10.

3. ultrahigh speed air bearing electric main-shaft according to claim 1 and 2, it is characterized in that, described rotor (20) is installed with motor shaft (17) interference and is connected, form overall structure, described motor shaft (17) outside is multidiameter, comprise large diameter portion, middle path portion and path part three sections, described large diameter portion interference is arranged in the large through-hole (2002) of rotor (20), and be fixedly connected with elongated hollow tube (18), described middle path portion is installed with rotor (8) and is connected, and described path part is installed with gas seal ring (14) and is connected; Motor shaft (17) center is provided with ladder hole, comprises the motor shaft macropore (1702), motor shaft aperture (1703) and the motor shaft mesopore (1701) that connect successively.