JP2007285386A - Air bearing spindle and control method of air bearing spindle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air bearing spindle and a control method of the air bearing spindle, capable of improving detecting sensitivity of a workpiece. <P>SOLUTION: This air bearing spindle 1 has a housing 9 having hollow parts 6 and 11, a main spindle 5 rotatably arranged in the hollow parts 6 and 11, a thrust plate 7 fixed to the main spindle 5 and having a main surface having a normal in the axial direction, and a sensor 4 detecting information on displacement in the axial direction of the thrust plate 7. The thrust plate 7 is supported by thrust air bearings 21a and 21b to the housing 9, and the main spindle 5 is supported by a radial air bearing 22 to the housing 9. The housing 9 is constituted so as to be capable of independently controlling pressure of gas A1 introduced to the thrust air bearings 21a and 21b and pressure of gas A2 introduced to the radial air bearing 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an air bearing spindle and an air bearing spindle control method, and more particularly to an air bearing spindle in which a main shaft to which a rotary tool is attached is supported by the air bearing and an air bearing spindle control method.

  An air bearing spindle normally has a structure in which a main shaft on which a tool such as a drill is detachably mounted is rotatably held in a hollow housing, and the main shaft is supported in a non-contact manner in a radial direction and a thrust direction by an air bearing. Have. The air bearing spindle is used for drilling a printed circuit board, processing a groove, and the like because it can achieve high-precision rotation with little vibration during rotation.

  When a small-diameter hole is drilled using an air bearing spindle, it is necessary to use a small-diameter tool that matches the diameter of the hole. Therefore, the strength of the tool is reduced, and the tool is easily broken during drilling. For this reason, in order to prevent an overload from being applied to the tool or to detect and predict a breakage of the tool, a technique for detecting a machining reaction force applied to the tool using a sensor has been proposed. Such a technique is disclosed in, for example, Japanese Patent Laid-Open No. 10-47349 (Patent Document 1).

FIG. 16 is a cross-sectional view showing the structure of the hydrostatic bearing spindle described in Patent Document 1. Referring to FIG. 16, main shaft 101 is supported in a non-contact manner with respect to housing 103 by thrust air bearing 110 and radial air bearing 111, and is rotationally driven by motor 104 provided in housing 103. A thrust plate 107 is fixed to the right end of the main shaft 101 in the drawing, and a displacement sensor 105 is provided on the right side of the thrust plate 107 in the drawing. A drill 106 is attached to the left end of the main shaft 101. The housing 103 is provided with an injection hole 108 and passages 102a and 102b communicating with each other. Compressed air is supplied to the thrust bearing gap (the gap between the thrust plate 107 and the housing 103) through the injection hole 108 and the passage 102a, and the radial bearing gap (the gap between the main shaft 101 and the housing 103) through the injection hole 108 and the passage 102b. Is supplied with compressed air. The displacement sensor 105 detects the displacement of the main shaft 101 in the axial direction, thereby detecting the machining reaction force applied to the drill 106.
Japanese Patent Laid-Open No. 10-47349

  However, the conventional air bearing spindle has a problem that the detection sensitivity of the workpiece is poor. The reason for this will be described below.

  When drilling or the like using an air bearing spindle, the tool is rotated at a high speed of about 60,000 to 150,000 revolutions / minute, and the tool is pressed against the workpiece at a high speed. For this reason, a large thrust load is applied to the spindle every time one hole is machined. The thrust air bearing of the air bearing spindle needs to have a high rigidity enough to receive this thrust load. In the conventional air bearing spindle, a passage 102a for supplying compressed air to the thrust bearing gap and a passage 102b for supplying compressed air to the radial bearing gap communicate with each other, and the thrust air bearing and the radial air bearing Both were supplied with the same high pressure compressed air.

  On the other hand, when high-pressure compressed air is supplied to the thrust bearing gap, the axial movement of the main shaft 101 is suppressed by the pressure of the compressed air. Therefore, even if the drill 106 receives a processing reaction force, the main shaft 101 moves. The amount is small. As a result, the conventional air bearing spindle has a problem of poor workpiece detection sensitivity.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an air bearing spindle and a method for controlling the air bearing spindle that can improve the detection sensitivity of a workpiece.

  An air bearing spindle according to the present invention includes a housing having a hollow portion, a main shaft rotatably disposed in the hollow portion, a thrust member fixed to the main shaft and having a thrust surface having an axial normal line, and a thrust member And a sensor for detecting information on displacement in the axial direction. The thrust member is supported on the housing by a thrust air bearing, and the main shaft is supported on the housing by a radial air bearing. The housing is configured such that the pressure of the gas introduced into the thrust air bearing and the pressure of the gas introduced into the radial air bearing can be controlled independently.

  According to the air bearing spindle of the present invention, when it is desired to increase the detection sensitivity, the main shaft and the thrust member can be easily moved in the axial direction by controlling the pressure of the gas introduced into the thrust air bearing to be low. As a result, when a machining reaction force is applied to the main shaft, the main shaft moves greatly, and the detection sensitivity of the workpiece is improved.

  Preferably, in the air bearing spindle, the housing has a thrust air supply passage communicating with the thrust air bearing from the outside of the housing and a radial air supply passage communicating with the radial air bearing from the outside of the housing. The passage and the radial air supply passage are separated from each other.

  As a result, one pressure gas can be injected into the thrust air bearing through the thrust air supply passage, and another pressure gas can be injected into the radial air bearing through the radial air supply passage. Therefore, the pressure of the gas introduced into the thrust air bearing and the pressure of the gas introduced into the radial air bearing can be controlled independently.

  Preferably, in the air bearing spindle, the thrust member has a first thrust surface and a second thrust surface having an axial normal line, and a pressure of a gas introduced between the first thrust surface and the housing The housing is configured such that the pressure of the gas introduced between the second thrust surface and the housing can be controlled independently. Thereby, the position of the thrust member in the hollow portion can be adjusted to an arbitrary position.

  Preferably, in the air bearing spindle, the thrust air supply passage communicates between the first thrust surface and the housing from the outside of the housing, and between the second thrust surface and the housing from the outside of the housing. The second thrust supply passage is separated from the first thrust supply passage and the second thrust supply passage.

  As a result, a gas having a pressure is injected between the first thrust surface and the housing through the first thrust supply passage, and a pressure between the second thrust surface and the housing is injected through the second thrust supply passage. A gas can be injected. Therefore, the pressure of the gas introduced between the first thrust surface and the housing and the pressure of the gas introduced between the second thrust surface and the housing can be controlled independently.

  Preferably, in the air bearing spindle, the thrust member is fixed to one end of the main shaft, and the sensor is disposed in the housing on the opposite side of the main shaft across the thrust member.

  Thereby, the position of a thrust member leaves | separates from a workpiece. Usually, since the width of the air bearing spindle at the position where the thrust member is arranged becomes large, the space near the work piece can be widened by separating the wide portion from the work piece.

  The air bearing spindle control method of the present invention includes a housing having a hollow portion, a main shaft rotatably disposed in the hollow portion, a thrust member fixed to the main shaft and having a thrust surface having an axial normal line, And a sensor for detecting information on the axial displacement of the thrust member, the thrust member is supported by the thrust air bearing with respect to the housing, and the main shaft is supported by the radial air bearing with respect to the housing. It is a control method of an air bearing spindle. A detection step is provided for detecting the surface of the workpiece based on the displacement of the thrust member in a state where the pressure of the gas introduced into the thrust air bearing is lower than the pressure of the gas introduced into the radial air bearing.

  According to the control method of the air bearing spindle of the present invention, the pressure of the gas introduced into the thrust air bearing in the detection step is lowered, and the main shaft and the thrust member can be easily moved in the axial direction. As a result, the detection sensitivity in the detection process is improved. In addition, since the detection sensitivity in the detection process is improved, the height position of the processed part surface of the workpiece can be accurately measured. For this reason, at the time of processing a groove or the like, it is possible to fast-forward from above the portion to be processed to the very vicinity of the surface by the detection information, and the tact time is improved.

  Preferably, the control method further includes a processing step of processing the workpiece in a state where the pressure of the gas introduced into the thrust air bearing is higher than the pressure in the detection step.

  As a result, the rigidity of the thrust air bearing is improved, so that when the main shaft receives a large thrust load during machining, such as drilling that requires machining efficiency, the thrust air bearing can receive this thrust load. .

  Preferably, in the above control method, the thrust member has a first thrust surface and a second thrust surface having a normal line in the axial direction. The pressure of the gas introduced between the first thrust surface and the housing and the pressure of the gas introduced between the second thrust surface and the housing are controlled independently. Thereby, the position of the thrust member in the hollow portion can be adjusted to an arbitrary position.

  Preferably, in the above control method, the pressure of the gas introduced between the first thrust surface and the housing and the second thrust surface and the housing so that the axial position of the thrust plate in the hollow portion is always constant. Control the pressure of the gas to be introduced. Thereby, the processing accuracy in the axial direction of the workpiece is improved.

  According to the air bearing spindle and the air bearing spindle control method of the present invention, the detection sensitivity of the workpiece can be improved. Alternatively, high-precision machining can be realized by improving the rigidity of the thrust bearing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a cross-sectional view showing the structure of an air bearing spindle according to Embodiment 1 of the present invention. FIG. 2 is an enlarged cross-sectional view of the vicinity of the thrust plate of FIG. 3 is a sectional view taken along line III-III in FIG. 1, FIG. 4 is a sectional view taken along line IV-IV in FIG. 1, and FIG. 5 is a sectional view taken along line V-V in FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. First, the structure of the air bearing spindle in the present embodiment will be described with reference to FIGS.

  With particular reference to FIG. 1, the air bearing spindle 1 in the present embodiment includes a housing 9, a main shaft 5, a thrust plate 7 as a thrust member, and a sensor 4. The housing 9 has hollow portions 6 and 11. A thrust plate 7 is fixed to the rear end (left side in the figure) of the main shaft 5, and the main shaft 5 and the thrust plate 7 are rotatably arranged in the hollow portions 6 and 11. A sensor 4 is attached to the housing 9 near the thrust plate 7. The thrust plate 7 is supported in the thrust direction by the thrust air bearings 21 a and 21 b with respect to the housing 9, and the main shaft 5 is supported by the radial air bearing 22 in the radial direction with respect to the housing 9. The thrust air bearing 21a is provided on the side opposite to the tool 3 (on the opposite tool side) with the thrust plate 7 therebetween, and the thrust air bearing 21b is provided on the tool 3 side with the thrust plate 7 interposed therebetween. A tool 3 such as an end mill, a grindstone, or a drill is attached to the front end (right side in the figure) of the main shaft 5.

  The housing 9 has a cylindrical shape, and the outer diameter near the rear end is larger than the outer diameter near the front end. The hollow portions 6 and 11 have a shape substantially along the outer shape of the housing 9, and the diameter of the hollow portion 6 near the rear end is larger than the diameter of the hollow portion 11 near the front end. A thrust plate 7 is disposed in the hollow portion 6, and the main shaft 5 is disposed in the hollow portion 11.

  Referring to FIG. 2 in particular, the thrust plate 7 has a disk shape, and has two main surfaces 7a and 7b (thrust surfaces) having normal lines in the axial direction (lateral direction in the figure). The main surface 7 a faces the rear end direction of the air bearing spindle 1 and faces the wall surface 6 a of the hollow portion 6. The main surface 7 b faces the front end direction of the air bearing spindle 1 and faces the wall surface 6 b of the hollow portion 6. A plurality of turbines 16 are provided on the outer peripheral surface of the thrust plate 7.

  A groove or hole 10 leading to the hollow portion 6 is formed at the rear end of the housing 9, and the sensor 4 is disposed in the groove or hole 10. The sensor 4 is disposed in a housing 9 on the side opposite to the tool with a thrust plate 7 therebetween. The sensor 4 is electrically connected to the computer 12 (FIG. 1). The sensor 4 detects information related to the axial displacement of the thrust plate 7. As this sensor, a capacitance type displacement sensor or an eddy current type displacement sensor is used. The sensor 4 converts an analog signal proportional to the amount of movement of the thrust plate into a digital signal and outputs it to the computer 12. The computer 12 calculates and outputs the axial displacement of the thrust plate 7 based on the information from the sensor 4.

  1 to 6, in the air bearing spindle 1, the pressure of the gas A1 introduced (supplied) into the thrust air bearings 21a and 21b and the pressure of the gas A2 introduced into the radial air bearing 22 are independent. The housing 9 is configured to be controllable. That is, the housing 9 has a thrust air supply passage 15 that leads from the outside of the housing 9 to the bearing clearances of the thrust air bearings 21 a and 21 b, and a radial air supply passage 13 that leads from the outside of the housing 9 to the bearing clearance of the radial air bearing 22. And have.

  The thrust air supply passage 15 is configured by passages 15a to 15g. A passage 15a extends from the outer diameter surface near the rear end of the housing 9 toward the inner diameter, and communicates with the passage 15c. The passage 15c is annular as viewed in FIG. 3, and communicates with, for example, four passages 15d provided at equal intervals in the circumferential direction. Each of the passages 15d extends in the front end direction along the axis, and reaches the space between the main surface 7a of the thrust plate 7 and the wall surface 6a of the hollow portion 6 (bearing gap of the thrust air bearing 21a). Further, the passage 15 b branches from the passage 15 a at a right angle on the way from the outer diameter surface near the rear end of the housing 9 toward the inner diameter. The passage 15b extends in the front end direction along the axis and communicates with the passage 15e. The passage 15e is bent at a right angle from the passage 15b and extends toward the inner diameter, and communicates with the passage 15f. The passage 15f is annular as viewed in FIG. 4, and communicates with, for example, four passages 15g provided at equal intervals in the circumferential direction. Each of the passages 15g extends in the rear end direction along the axis, and reaches the space between the main surface 7b of the thrust plate 7 and the wall surface 6b of the hollow portion 6 (bearing gap of the thrust air bearing 21b).

  The radial air supply passage 13 is constituted by passages 13a to 13f. A passage 13a extends from the rear end surface of the housing 9 along the axis toward the front end. The passage 13a is bent at a right angle near the hollow portion 6 in the front end direction, extends toward the inner diameter, and communicates with the passage 13b. The passage 13b is annular as viewed in FIG. 5, and communicates with, for example, four passages 13c provided at equal intervals in the circumferential direction. Each of the passages 13c extends toward the inner diameter and reaches a space between the outer peripheral surface 5a of the main shaft 5 and the wall surface 11a of the hollow portion 11 (bearing gap of the radial air bearing 22). Further, a passage 13d is branched at each of the four communicating portions of the passage 13b and the passage 13c. Each of the four passages 13d bends at a right angle from the passage 13a, extends in the front end direction along the axis, and communicates with the passage 13e. The passage 13e is annular as seen in FIG. 6, and communicates with, for example, four passages 13f provided at equal intervals in the circumferential direction. Each of the passages 13f extends toward the inner diameter and reaches the bearing gap of the radial air bearing 22.

  Thus, the thrust air supply passage 15 and the radial air supply passage 13 are separated from each other without communicating with each other until they reach the hollow portions 6 and 11 from the outside of the housing 9.

  Referring particularly to FIG. 1, the housing 9 is further provided with passages 17 a and 17 b (dotted lines in the figure) reaching the hollow portion 6 from the outside of the housing 9. The thrust plate 7 and the main shaft 5 are rotated by blowing the gas A3 having a high flow velocity to the turbine 16 of the thrust plate 7 through the passage 17a. The gases A1 to A3 introduced into the housing 9 are released to the outside as gas B mainly through the passage 17b.

Next, a method for controlling the air bearing spindle 1 in the present embodiment will be described.
First, referring to FIGS. 1, 2 and 7, for example, the air bearing spindle 1 is attached to a Z table (not shown), and the workpiece 25 is fixed on the XY table (not shown). Then, the position of the workpiece 25 is adjusted with the XY table so that the machining position of the workpiece 25 comes directly under the tool 3. Next, the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b is made lower than the pressure of the gas A2 introduced into the radial air bearing 22. Thereby, the pressures P1 and P3 of the thrust air bearings 21a and 21b become smaller than the pressure P2 of the radial air bearing 22. In this state, the air bearing spindle 1 is lowered by operating the Z table. When the air bearing spindle 1 is lowered, the rotation of the tool 3 is stopped.

  Next, referring to FIGS. 1, 2, and 8, when the air bearing spindle 1 is lowered by the height h <b> 1, the tool 3 comes into contact with the surface of the workpiece 25, and the machining reaction force from the workpiece 25 is reached. F joins tool 3. Since the pressures P1 and P3 of the thrust air bearings 21a and 21b are small, the thrust plate 7 is immediately displaced along the axis in the rear end direction when the processing reaction force F is received. The displacement of the thrust plate 7 is detected by the sensor 4 and output to the computer. As a result, the surface of the workpiece 25 is detected (detection process).

  Next, referring to FIG. 1, FIG. 2 and FIG. 9, for example, in the case where a workpiece is subjected to machining that generates a large thrust load by cutting at high speed, such as drilling, thrust air The pressure of the gas A1 introduced into the bearings 21a and 21b is set higher than the pressure in the detection step. Thereby, the pressures P1 and P3 of the thrust air bearings 21a and 21b become larger than the pressures in the detection process. In this state, the air bearing spindle 1 is further lowered by a desired machining depth d1 while rotating the tool 3, and a hole having a depth d1 is machined in the workpiece 25 (machining process). Since the pressures P1 and P3 of the thrust air bearings 21a and 21b during the machining process are larger than the pressures P1 and P3 during the detection process, the rigidity of the thrust air bearings 21a and 21b is improved and large during drilling. Even if the processing reaction force F is generated, the displacement of the thrust plate 7 is suppressed. In this hole drilling, if the accuracy of the through hole and the hole depth is not strict, the step of detecting the surface of the workpiece 25 may be omitted or the number of times may be reduced.

  1, 2, and 10, a thrust load is generated so much that a fine groove of a soft material is processed with high accuracy using, for example, a small-diameter end mill or a small-diameter shaft grindstone. When the workpiece is subjected to such processing, it is not necessary to increase the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b. In this case, with the pressures P1 and P3 of the thrust air bearings 21a and 21b kept low, the tool is first approached to a height very close to the surface to be detected as detected above, and then the spindle 5 is moved at a low speed. After the hole having the required depth d2 is machined by a low-speed cutting feed while rotating at a low speed, the air bearing spindle 1 is relatively moved in the horizontal direction (lateral direction in FIG. Process the workpiece.

  The control method of the air bearing spindle 1 in the present embodiment includes a housing 9 having hollow portions 6 and 11, a main shaft 5 rotatably disposed in the hollow portions 6 and 11, and fixed to the main shaft 5 in the axial direction. A thrust plate 7 having main surfaces 7 a and 7 b having normal lines and a sensor 4 for detecting information on the axial displacement of the thrust plate 7 are provided. The thrust plate 7 is a thrust air bearing 21 a with respect to the housing 9. The main shaft 5 is supported by a radial air bearing 22 with respect to the housing 9 and is controlled by the air bearing spindle 1. Detection for detecting the surface of the workpiece 25 based on the displacement of the thrust plate 7 in a state where the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b is lower than the pressure of the gas A2 introduced into the radial air bearing 22. It has a process.

  According to the air bearing spindle 1 and the control method thereof in the present embodiment, the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b is lowered in the detection step, so that the main shaft 5 and the thrust plate 7 are moved in the axial direction. Becomes easier. As a result, when the processing reaction force F is applied to the main shaft 5, the main shaft 5 moves greatly, and the detection sensitivity of the workpiece 25 is improved. Moreover, since the force which the tool 3 applies to the surface of the workpiece 25 in a detection process is small, damage to the surface of the workpiece 25 can be suppressed.

  In addition, since the detection sensitivity in the detection process is improved, the detection speed of the surface of the workpiece 25 is increased, and the processing tact time is improved. That is, conventionally, since the detection speed of the surface of the workpiece 25 is slow, the air bearing spindle 1 is moved by a height h0 (<h1) in order to prevent the tool 3 from being damaged and the surface of the workpiece 25 from being damaged. After the lowering, the air bearing spindle 1 is lowered at a low speed so that the tool 3 is brought into contact with the surface of the workpiece 25 so that a large working reaction force F is not generated. In contrast, in the control method according to the present embodiment, the detection sensitivity of the workpiece 25 is high. Therefore, even if the tool 3 is brought into contact with the surface of the workpiece 25 at a high speed, the tool 3 is damaged or the workpiece 25 The surface of the workpiece 25 can be detected before the processing reaction force F that causes damage to the surface of the workpiece is detected, and the lowering of the air bearing spindle 1 can be stopped.

  The housing 9 has a thrust air supply passage 15 that communicates with the thrust air bearings 21a and 21b from the outside of the housing 9, and a radial air supply passage 13 that communicates with the radial air bearing 22 from the outside of the housing 9. Since the supply air passage 15 and the radial supply passage 13 are separated from each other, the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b and the pressure of the gas A2 introduced into the radial air bearing 22 are independent. Can be controlled.

  The thrust plate 7 is fixed to the rear end of the main shaft 5 and the sensor 4 is disposed in the housing 9 on the opposite side of the main shaft 5 with the thrust plate 7 interposed therebetween. A large space can be taken.

  Further, a processing step for processing the workpiece 25 is further provided in a state in which the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b is higher than the pressure in the detection step. Thereby, since the rigidity of the thrust air bearings 21a and 21b is improved, when the main shaft 5 receives a large thrust load, for example, when drilling or the like, the thrust air bearings 21a and 21b receive this thrust load. Can do.

  Further, a processing step for processing the workpiece 25 is further provided in a state where the pressure of the gas A1 introduced into the thrust air bearings 21a and 21b is higher than the pressure in the detection step. Thereby, since the rigidity of the thrust air bearing is improved, when the main shaft 5 receives a large thrust load, for example, when drilling or the like, this thrust load can be received by the thrust air bearings 21a and 21b.

  The shapes of the passages 13a to 13f and 15a to 15g in the present embodiment are merely examples, and the thrust supply passage only needs to communicate with the thrust air bearing from the outside of the housing, and the radial supply passage from the outside of the housing. It only has to communicate with the radial air bearing.

(Embodiment 2)
FIG. 11 is a cross-sectional view showing the structure of the air bearing spindle in the second embodiment of the present invention. 12 is a cross-sectional view taken along line XII-XII in FIG. 11, and FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG.

  11 to 13, the air bearing spindle in the present embodiment is different from the air bearing spindle of the first embodiment in the shape of the thrust air supply passage formed in the housing. In the present embodiment, the housing 9 is configured such that the pressure of the gas A1 introduced into the thrust air bearing 21a and the pressure of the gas A4 introduced into the thrust air bearing 21b can be controlled independently. That is, the thrust air supply passage 15 includes passages 15a, 15c and 15d (first thrust air supply passages) and passages 15e to 15g (second thrust air supply passages) which are separated from each other. Yes. A passage 15a extends from the outer diameter surface near the rear end of the housing 9 toward the inner diameter, and communicates with the passage 15c. The passage 15c is annular as viewed in FIG. 13, and communicates with, for example, four passages 15d provided at equal intervals in the circumferential direction. Each of the passages 15d extends in the front end direction along the axis, and is formed in a space between the main surface 7a (first thrust surface) of the thrust plate 7 and the wall surface 6a of the hollow portion 6 (bearing gap of the thrust air bearing 21a). Has reached. A passage 15e extends from the front end side toward the inner diameter than the passage 15a near the rear end of the housing 9, and communicates with the passage 15f. The passage 15f is annular as viewed in FIG. 14, and communicates with, for example, four passages 15g provided at equal intervals in the circumferential direction. Each of the passages 15g extends in the rear end direction along the axis, and a space between the main surface 7b (second thrust surface) of the thrust plate 7 and the wall surface 6b of the hollow portion 6 (bearing gap of the thrust air bearing 21b). Has reached.

  Thus, the passages 15a, 15c, and 15d constitute a passage that leads from the outside of the housing 9 to the bearing gap of the thrust air bearing 21a, and the passages 15e to 15g pass from the outside of the housing 9 to the bearing gap of the thrust air bearing 21b. It constitutes a passage that leads to. The passages 15 a, 15 c and 15 d and the passages 15 e to 15 g are separated from each other without communicating with each other until reaching the hollow portion 6 from the outside of the housing 9.

  Since the other configuration is the same as that of the air bearing spindle of the first embodiment shown in FIGS. 1 to 6, the same members are denoted by the same reference numerals, and the description thereof will not be repeated.

  According to the air bearing spindle 1 of the present embodiment, the position of the thrust plate 7 in the hollow portion 6 can be adjusted to an arbitrary position by independently controlling the pressures of the gases A1 and A4. 14 is an enlarged cross-sectional view of the vicinity of the thrust plate of FIG. Referring to FIG. 14, when the pressure of gas A1 is higher than the pressure of gas A4, pressure P1 of thrust air bearing 21a becomes higher than pressure P3 of thrust air bearing 21b, and thrust plate 7 moves in the front end direction. . Conversely, when the pressure of the gas A1 is made lower than the pressure of the gas A4, the pressure P1 of the thrust air bearing 21a becomes lower than the pressure P3 of the thrust air bearing 21b, and the thrust plate 7 moves toward the rear end. By utilizing this phenomenon, the position of the thrust plate 7 in the hollow portion 6 can be adjusted to an arbitrary position.

  Further, according to the air bearing spindle 1 of the present embodiment, the thrust plate 7 can always be arranged at a constant axial position during processing and during non-processing. Referring to FIGS. 14 and 15, for example, when machining a hole having a depth d <b> 1 in the workpiece 25, the tool 3 receives a machining reaction force F from the workpiece 25. The tool 3 may be displaced in response to the processing reaction force F. Δx1: Axial width of the bearing gap of the thrust air bearing 21a, Δx2: Axial width of the bearing gap of the thrust air bearing 21b, and a position where the displacement Δx = Δx2−Δx1 = 0 is assumed as a reference position. When the thrust plate 7 is displaced by Δx (Δx> 0) in response to the processing reaction force F, the depth of the hole that is actually drilled in the workpiece 25 becomes (d1−Δx), which is shifted by Δx from the desired depth. Occurs. Accordingly, when the displacement Δx of the thrust plate 7 is detected by the sensor 4 at the time of machining, the pressure P1 of the thrust air bearing 21a is made higher than the pressure P3 of the thrust air bearing 21b, so that the machining reaction force F is reversed. A force can be generated to keep the displacement Δx of the thrust plate 7 at zero. As a result, a hole having a desired depth can be accurately processed, and the groove can be processed with high accuracy by moving the tool 3 in the horizontal plane in this state.

  The shapes of 15a and 15c to 15g in the present embodiment are examples, and the thrust supply passage may include a first thrust supply passage and a second thrust supply passage that are separated from each other. That's fine.

  In the first and second embodiments, the thrust plate 7 is fixed to the rear end of the main shaft 5, but the fixing position of the thrust member is arbitrary, and may be fixed to the central portion of the main shaft, for example. The position of the sensor is also arbitrary, and it may be arranged at a position where information on the axial displacement of the thrust member can be detected.

  The embodiment disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments but by the scope of claims, and is intended to include all modifications and variations within the scope and meaning equivalent to the scope of claims.

  The present invention is particularly suitable for an air bearing spindle used for machining a groove using an end mill, a grindstone, or the like and a method for controlling the air bearing spindle.

It is sectional drawing which shows the structure of the air bearing spindle in Embodiment 1 of this invention. It is an expanded sectional view of the thrust plate vicinity of FIG. It is sectional drawing which follows the III-III line of FIG. It is sectional drawing which follows the IV-IV line of FIG. It is sectional drawing which follows the VV line of FIG. It is sectional drawing which follows the VI-VI line of FIG. It is a schematic diagram which shows the 1st process of a workpiece | work using the air bearing spindle in Embodiment 1 of this invention. It is a schematic diagram which shows the 2nd process of a workpiece | work using the air bearing spindle in Embodiment 1 of this invention. It is a schematic diagram which shows the 3rd process of a workpiece | work using the air bearing spindle in Embodiment 1 of this invention. It is a schematic diagram which shows the modification of the 3rd process of the process of the workpiece using the air bearing spindle in Embodiment 1 of this invention. It is sectional drawing which shows the structure of the air bearing spindle in Embodiment 2 of this invention. It is sectional drawing which follows the XII-XII line | wire of FIG. It is sectional drawing which follows the XIII-XIII line | wire of FIG. It is an expanded sectional view of the thrust plate vicinity of FIG. It is a schematic diagram which shows a mode that a tool is displaced in response to a processing reaction force from a workpiece during processing. It is sectional drawing which shows the structure of the hydrostatic bearing spindle described in Patent Document 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Air bearing spindle, 3 Tool, 4 Sensor, 5,101 Main shaft, 5a Main shaft outer peripheral surface, 6,11 Hollow part, 6a, 6b, 11a Hollow part wall surface, 7,107 Thrust plate, 7a, 7b Thrust plate main surface, 9, 103 housing, 10 groove, 12 computer, 13 radial air supply passage, 13a-13f, 15a-15g, 17a, 17b, 102a, 102b passage, 15 thrust air supply passage, 16 turbine, 21a, 21b, 110 Thrust air bearing, 22,111 radial air bearing, 25 workpiece, 104 motor, 105 displacement sensor, 106 drill, 108 injection hole, A1-A4, B gas, F processing reaction force, P1-P3 pressure.

Claims (9)

A housing having a hollow portion;
A main shaft rotatably disposed in the hollow portion;
A thrust member fixed to the main shaft and having a thrust surface having an axial normal;
A sensor for detecting information on the axial displacement of the thrust member,
The thrust member is supported by a thrust air bearing with respect to the housing, and the main shaft is supported by a radial air bearing with respect to the housing;
The air bearing spindle according to claim 1, wherein the housing is configured such that the pressure of the gas introduced into the thrust air bearing and the pressure of the gas introduced into the radial air bearing can be independently controlled.   The housing includes a thrust air supply passage that communicates with the thrust air bearing from the outside of the housing, and a radial air supply passage that communicates with the radial air bearing from the outside of the housing, and the thrust air supply passage and the radial air passage The air bearing spindle according to claim 1, wherein the air supply passage is separated from each other.   The thrust member has a first thrust surface and a second thrust surface having an axial normal line, a pressure of a gas introduced between the first thrust surface and the housing, the second thrust surface, The air bearing spindle according to claim 1 or 2, wherein the housing is configured such that a pressure of a gas introduced between the housings can be independently controlled.   The thrust air supply passage communicates from the outside of the housing to the first thrust surface and the housing, and from the outside of the housing to the second thrust surface and the housing. 4. The air bearing spindle according to claim 3, further comprising a second thrust air supply passage, wherein the first thrust air supply passage and the second thrust air supply passage are separated from each other. .   The thrust member is fixed to one end of the main shaft, and the sensor is disposed in the housing on the opposite side of the main shaft across the thrust member. An air bearing spindle according to any one of the above. A housing having a hollow portion, a main shaft rotatably disposed in the hollow portion, a thrust member having a thrust surface fixed to the main shaft and having an axial normal line, and axial displacement of the thrust member And a sensor for detecting information, wherein the thrust member is supported by a thrust air bearing with respect to the housing, and the spindle is supported by a radial air bearing with respect to the housing. Because
A detection step of detecting the surface of the workpiece based on the displacement of the thrust member in a state where the pressure of the gas introduced into the thrust air bearing is lower than the pressure of the gas introduced into the radial air bearing; A method for controlling an air bearing spindle.   The air according to claim 6, further comprising a processing step of processing the workpiece in a state in which a pressure of a gas introduced into the thrust air bearing is higher than a pressure in the detection step. Control method of bearing spindle. The thrust member has a first thrust surface and a second thrust surface having an axial normal,
The pressure of the gas introduced between the first thrust surface and the housing and the pressure of the gas introduced between the second thrust surface and the housing are independently controlled. Or a method of controlling an air bearing spindle according to 7;   Gas pressure introduced between the first thrust surface and the housing and introduction between the second thrust surface and the housing so that the axial position of the thrust plate in the hollow portion is always constant. 9. The method of controlling an air bearing spindle according to claim 8, wherein the pressure of the gas to be controlled is controlled.

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