Rotating equipment for work

Abstract

To provide a handicraft rotary apparatus which can properly achieve heat generation suppression and foreign matter entering prevention in a seal portion.SOLUTION: An annular inner seal material 81 and an annular outer seal material 82 are arranged so that a space between the inside and the outside is partitioned across an annular gap 100 so as to close a gap between a table 42 and a body 2. A handicraft rotary apparatus includes: a first air supply passage 60 which supplies air to the annular space 100; and a second air supply passage 70 which supplies air to an annular inner gap 101 positioned inside the annular gap 100 across the annular inner seal material 81. The handicraft rotary apparatus further includes a fine differential pressure adjusting mechanism which adjusts so that the annular inner gap 101 has higher air pressure by prescribed fine differential pressure than the annular gap 100.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The disclosed technology relates to machine tools' rotating equipment such as a rotating table that supports an object to be processed. Among them, in particular, it is a technology that achieves both heat generation suppression and foreign matter intrusion prevention at the seal part.

Background Art

[0002] During machining, chips and cutting water scatter around, so this type of rotating equipment rotates in a harsh environment. If foreign matter enters the rotating part, it will cause a failure. Therefore, usually, the rotating part is sealed with a sealing material to prevent foreign matter from entering.

[0003] There is a rotating equipment previously proposed by the inventor in relation to the disclosed technology (Patent Document 1).

[0004] In the rotating equipment of Patent Document 1, a spindle having a circular table is provided, and a pair of annular sealing materials are arranged with a predetermined annular gap therebetween so as to close the gap between the housing that rotatably accommodates the spindle and the table.

[0005] And in the annular gap, air is supplied from a plurality of positions spaced apart from each other in the circumferential direction so that the sealing performance does not locally decrease due to the pressure difference.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By applying the technology of Patent Document 1 to conventional rotating equipment, it has become possible to appropriately achieve both heat generation suppression and foreign matter intrusion prevention at the seal part.

[0008] However, in recent years, there has been a demand for rotating devices that can rotate at a higher speed than before. Therefore, the inventor of the present invention has been conducting research on increasing the rotation speed. During the research process, it has been found that there is room for improvement in the technology of Patent Document 1 in terms of heat generation suppression when the speed is increased.

[0009] Also, in the case of this type of rotating device, even if it is functionally excellent, it is difficult to put it into practical use unless it is inexpensive.

[0010] Therefore, the main object of the disclosed technology is to inexpensively realize a working rotating device that can more appropriately achieve both heat generation suppression and foreign matter intrusion prevention at the seal part and can cope with high speed.

Means for Solving the Problems

[0011] The disclosed technology relates to a working rotating device. The rotating device includes a spindle having a table, a housing that rotatably accommodates the spindle with the table exposed, and a pair of annular seal members including an annular inner seal member and an annular outer seal member that are arranged to partition between the inside and the outside in the radial direction or the axial direction with a predetermined annular gap so as to close the gap between the table and the housing, and a first air supply passage that supplies air to the annular gap.

[0012] And, a second air supply passage that supplies air to an annular inner gap located inside the annular gap with the annular inner seal member therebetween, and a differential pressure adjustment mechanism that adjusts the annular inner gap to have a higher air pressure than the annular gap at a predetermined differential pressure are further provided.

[0013] Preferably, the second air supply passage is formed in a structure in which the pressure loss of the air flowing through the flow path is smaller than that of the first air supply passage, and the differential pressure adjustment mechanism is configured using the structures of the first air supply passage and the second air supply passage.

[0014] Preferably, the differential pressure adjustment mechanism is configured by using a pressure regulating exhaust passage that communicates with the inside of the housing and can adjust the air pressure inside the housing, and is a working rotary device capable of maintaining the inside of the housing higher than the atmospheric pressure by the pressure regulating exhaust passage.

[0015] Preferably, the differential pressure adjustment mechanism is configured by using a decompression exhaust passage that communicates with the inside of the housing and is decompressed by the pressure loss of the flowing air, and is a working rotary device capable of maintaining the inside of the housing higher than the atmospheric pressure by the decompression exhaust passage.

[0016] Preferably, an accommodation chamber for accommodating a motor for rotating the spindle is provided inside the housing, and the second air supply passage supplies air to the annular inner clearance through the accommodation chamber.

Advantages of the Invention

[0017] According to the disclosed technology, although it has a simple structure that can be realized at low cost, heat generation suppression and foreign matter intrusion prevention at the seal part can be more appropriately achieved simultaneously, and it can cope with the high-speed operation of the working rotary device.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the disclosed technology will be described. However, the following description is merely illustrative in nature.

[0020] Unless otherwise specified, the "axial direction" used in the description means the direction in which the rotation axis J extends. Similarly, the "circumferential direction" means the direction of the circumference centered on the rotation axis J, and the "radial direction" means the direction of the radius or diameter centered on the rotation axis J. "Front" means the usage side during operation, and "rear" means the non-usage side during operation.

[0021] <First Embodiment> FIGS. 1 and 2 show an NC circular table 1 (an example of a rotating device) to which the disclosed technology is applied. The NC circular table 1 is generally composed of a housing 2, a box 3, a spindle 4, a motor 5, and the like. The NC circular table 1 is used during operation, and the table 42 on its front surface rotates at high speed.

[0022] That is, a chuck or the like is attached to the table 42 to support a workpiece (object to be processed). In such a state, the spindle 4 is rotationally driven at high speed. While supplying cooling oil or water to the rotating workpiece, machining is performed by pressing a cutting tool or the like against it.

[0023] Especially in recent years, higher rotational speeds than before may be required during operation. Therefore, it is excellent in convenience if it can appropriately cope with such high-speed rotation. The technology disclosed this time is based on such circumstances.

[0024] The housing 2 is composed of a main body portion 21, a front cover portion 22, a rear cover portion 23, and the like. A cylindrical accommodation space penetrating in the front-rear direction is formed in the main body portion 21. The rear cover portion 23 is assembled to the rear side of the main body portion 21 and closes the opening on the rear side of the accommodation space.

[0025] The front cover portion 22 is made of a cylindrical member. The front cover portion 22 is fitted into a circular recess formed on the front side of the main body portion 21. The front cover portion 22 is assembled to the front side of the main body portion 21 so as to cover the front side of the accommodation space of the main body portion 21. Thereby, the front and rear of the accommodation space of the main body portion 21 are blocked, and a substantially sealed accommodation chamber 21a is formed inside the housing 2.

[0026] A circular opening 22a is formed in the front cover portion 22. The center line of the opening 22a and the center line of the accommodation chamber 21a are substantially coincident. An annular bearing 7 is disposed on the front side of the accommodation chamber 21a. The bearing 7 has an outer ring portion 7a and an inner ring portion 7b that rotate freely relative to each other. The bearing 7 is assembled to the housing 2 by sandwiching its outer ring portion 7a between the main body portion 21 and the front cover portion 22.

[0027] The box 3 is made of a box-shaped container and is assembled to one side surface of the housing 2. Various cables and electrical devices used for driving and controlling the NC circular table 1 are disposed inside the box 3. Electric power is supplied to the NC circular table 1 through a cable (not shown) led out from the box 3.

[0028] The spindle 4 of the present embodiment has a shaft 41 and a table 42. The shaft 41 is made of a multi-stage cylindrical member and is accommodated in the accommodation chamber 21a. The shaft 41 has a small-diameter portion 41a and a large-diameter portion 41b having an outer diameter larger than that of the small-diameter portion 41a.

[0029] The table 42 is made of a disk-shaped member having an outer diameter slightly smaller than the inner diameter of the opening 22a and is assembled to the front surface of the shaft 41 (large-diameter portion 41b). By assembling the shaft 41 and the table 42, the inner ring portion 7b of the bearing 7 is sandwiched between the shaft 41 and the table 42. Thereby, the spindle 4 is pivotally supported by the housing 2 via the bearing 7 and is rotatable about the rotation axis J.

[0030] As described above, the table 42 is a part of the spindle 4 where a workpiece is mounted via a chuck or a jig or the like, and the circular front surface of the table 42 is exposed to the front surface of the housing 2 through the opening 22a. Note that the spindle 4 may be configured by combining a plurality of parts as in the present embodiment, or may be integrally configured.

[0031] The motor 5 has a rotor 51 and a stator 52, and is housed in the housing chamber 21a. The rotor 51 is formed of an annular member and is fixed to the small-diameter portion 41a. The stator 52 is formed of an annular member larger than the rotor 51, and is fixed to the main body portion 21 in a state of being opposed to the rotor 51 in the radial direction with a slight gap therebetween.

[0032] By supplying a predetermined control current to the stator 52, a rotating magnetic field is formed between the stator 52 and the rotor 51. As a result, the spindle 4 is directly driven and rotates at a predetermined high speed (for example, the peripheral speed at the outer circumference of the rotor 51 is 10 m / s or more) (so-called direct drive type).

[0033] Note that the higher the rotational speed of the spindle, the more heat is generated by the motor during driving of the motor. Therefore, when proceeding with increasing the rotational speed, it is also important to deal with the heat generation of the motor.

[0034] (Sealing of the gap) There is a gap between the table 42 which is a rotating body and the housing 2 which is a non-rotating body. In the case of the NC circular table 1, since its front surface is exposed to chips and cutting fluid, it is necessary to prevent the intrusion of these foreign matters into the housing chamber 21a through the gap.

[0035] If it is sealed with an oil seal or a face seal having a high contact pressure, the intrusion of foreign matters can be effectively prevented. However, since the contact pressure is high, there is a problem that heat is easily generated due to friction at the contact portion. At high speeds of rotation, the amount of heat generation becomes excessive, leading to deformation and deterioration of the sealing material. There is also a possibility that the spindle 4 and the table 42 thermally expand and the machining accuracy deteriorates. The tendency becomes more prominent as the rotational speed increases.

[0036] On the one hand, if a low-contact-pressure sealing material (for example, an oil seal without a spring, a V-ring, etc.) is used for sealing, since the contact pressure is low, heat generation at the contact part can be reduced. However, accordingly, the sealing performance deteriorates, making it easier for foreign matters to enter. That is, it is impossible to achieve both heat generation suppression and prevention of foreign matter intrusion.

[0037] Therefore, the inventor has previously made intensive efforts to utilize a low-contact-pressure sealing material and air pressure so that both heat generation suppression and prevention of foreign matter intrusion can be achieved (see Patent Document 1). This NC circular table 1 is premised on this idea.

[0038] (Annular Sealing Material) A pair of annular sealing materials 8, 8 (also referred to as an annular inner sealing material 81 and an annular outer sealing material 82) in the present embodiment are arranged to partition between the inside and the outside in the axial direction with a predetermined annular gap 100 therebetween so as to close the gap between the table 42 and the housing 2. Each annular sealing material 8 is press-fitted into a stepped portion 30 formed on the inner peripheral edge of the opening 22a of the front lid portion 22.

[0039] All of these annular sealing materials 8 are low-contact-pressure sealing materials (for example, an oil seal without a spring). Each annular sealing material 8 has an elastically deformable lip 8a and an annular base portion 8b attached to the stepped portion 30.

[0040] Each lip 8a is inclined. Each annular sealing material 8 is arranged such that the inner diameter of the lip 8a becomes smaller toward the outside of the gap. Each annular sealing material 8 is arranged in the gap between the table 42 and the housing 2. The tip portion of the lip 8a is in contact with the outer peripheral surface of the table 42. Note that, in order to increase the contact pressure of each lip 8a, for example, an oil seal without a spring may be changed to an oil seal with a spring.

[0041] (First Air Supply Passage) A first air supply passage 60 that communicates with the annular gap 100 and supplies air to the annular gap 100 is formed in the housing 2.

[0042] As shown in FIG. 2, the first air supply passage 60 of the present embodiment is composed of one main passage 60a, one annular space 60b, a plurality of communication passages 60c, and the like.

[0043] The main passage 60a is composed of a thin hole formed in the housing 2 and is formed in a shape that bends in an L shape in the main body portion 21. The upstream end of the main passage 60a opens to the outer surface of the main body portion 21, and the downstream end of the main passage 60a opens to the joint surface of the main body portion 21 with the front lid portion 22.

[0044] A first throttle valve 9 capable of adjusting the flow rate of the flowing air is attached to the upstream end of the main passage 60a. An air supply pipe 11 connected to an air supply source (not shown) such as a compressor is connected to the first throttle valve 9. Thereby, during operation, air is introduced into the main passage 60a at a predetermined flow rate through the air supply pipe 11 and the first throttle valve 9. The main passage 60a communicates with the annular space 60b.

[0045] The annular space 60b is composed of an annular space extending in the circumferential direction and is provided in the housing 2 so as to surround the spindle 4. Specifically, a recess is formed in the outer peripheral edge portion of the rear surface of the front lid portion 22, and the annular space 60b is formed by assembling the front lid portion 22 to the main body portion 21. Packings 12 for ensuring airtightness are attached to both sides of the annular space 60b.

[0046] Each communication passage 60c is formed in the front lid portion 22. Each communication passage 60c is composed of a thin hole and is formed in a shape that bends in a substantially L shape. Each communication passage 60c is formed at a plurality of locations spaced apart from each other in the circumferential direction. Through these plurality of communication passages 60c, the annular space 60b and the annular gap 100 communicate with each other.

[0047] Therefore, the air introduced from the air supply pipe 11 is supplied to the annular gap 100 through each of the main passage 60a, the annular space 60b, and the plurality of communication passages 60c after the flow rate is adjusted by the first throttle valve 9. At this time, since the generation of a local air pressure difference is suppressed at a specific location in the circumferential direction of the annular gap 100, it is possible to seal evenly over the entire circumference.

[0048] (Second air supply passage) A second air supply passage 70 for supplying air to the gap (annular inner gap 101) located inside the annular gap 100 is formed in the housing 2 through the accommodation chamber 21a. The annular inner gap 101 is a gap located inside the annular gap 100 with the annular inner sealing material 81 therebetween. In other words, the annular gap 100 and the annular inner gap 101 are partitioned inside and outside by the annular inner sealing material 81.

[0049] As shown in FIG. 2, the second air supply passage 70 of the present embodiment is composed of one vertical hole formed in the housing 2. Specifically, the second air supply passage 70 is formed by cutting the main body portion 21 so as to penetrate the accommodation chamber 21a. The upstream end of the second air supply passage 70 opens to the outer surface of the main body portion 21, and the downstream end of the second air supply passage 70 opens to the inner surface of the main body portion 21.

[0050] A second throttle valve 10 similar to the first air supply passage 60 is attached to the upstream end of the second air supply passage 70. The second throttle valve 10 is also connected to the air supply pipe 11. Thereby, during operation, air is introduced into the accommodation chamber 21a at a predetermined flow rate through the air supply pipe 11, the second throttle valve 10, and the second air supply passage 70.

[0051] The accommodation chamber 21a communicates with the annular inner gap 101 through the gap of the bearing 7. Therefore, the air introduced from the air supply pipe 11 into the accommodation chamber 21a also flows into the annular inner gap 101.

[0052] (Pressure regulating exhaust passage, decompression exhaust passage) The housing 2 is provided with an exhaust passage 90 that communicates the accommodation chamber 21a with the environment outside the housing 2. In this embodiment, an exhaust passage 90 penetrating the plate surface is formed in the rear lid portion 23. Note that the exhaust passage 90 may be formed in the main body portion 21 or the front lid portion 22. The exhaust passage 90 may be any passage capable of exhausting the air inside the housing 2.

[0053] A pressure regulating valve 91 is provided at the downstream end of the exhaust passage 90, that is, on the outer surface side of the rear lid portion 23. When the air pressure in the accommodation chamber 21a reaches a predetermined pressure (a pressure higher than the atmospheric pressure) set, the pressure regulating valve 91 automatically exhausts the air. Thereby, the exhaust passage 90 of this embodiment is configured to be able to adjust the air pressure in the accommodation chamber 21a (pressure regulating exhaust passage 90A).

[0054] With this pressure regulating exhaust passage 90A, the inside of the housing 2 including the accommodation chamber 21a can be maintained at a pressure equal to or higher than the atmospheric pressure. Therefore, by supplying air from the second air supply passage 70, the inside of the housing 2 can be maintained at an air pressure higher than the atmospheric pressure.

[0055] Instead of the pressure regulating exhaust passage 90A, a decompression exhaust passage 90B may be provided. The decompression exhaust passage 90B is an exhaust passage 90 having a structure with a large pressure loss of the air flowing through the flow path. For example, the decompression exhaust passage 90B can be formed by increasing the distance of the exhaust passage 90, narrowing the flow path by reducing the flow path cross-section of a part or all of the exhaust passage 90, or bending the flow path.

[0056] In FIG. 2, an example of such a decompression exhaust passage 90B is shown by a two-dot chain line. This decompression exhaust passage 90B is formed as an elongated and bent flow path in the main body portion 21. By providing such a decompression exhaust passage 90B, by supplying air from the second air supply passage 70, the inside of the housing 2 can be dynamically maintained at an air pressure higher than the atmospheric pressure.

[0057] And in both the pressure regulating exhaust passage 90A and the decompression exhaust passage 90B, the air pressure inside the housing 2 can be adjusted by adjusting the air flow rate with the second throttle valve 10. In both the pressure regulating exhaust passage 90A and the decompression exhaust passage 90B, it can be implemented with extremely simple modifications from the existing structure, so it is inexpensive.

[0058] (Radial Arrangement of Annular Sealing Material) The pair of annular sealing materials 8, 8 may be arranged so as to partition between the inside and the outside with an annular gap 100 therebetween in the radial direction, rather than in the axial direction.

[0059] Fig. 3 shows an NC circular table (NC circular table 1') in which the pair of annular sealing materials 8, 8 are arranged in this way. Note that the basic structure is the same as that of the NC circular table 1 shown in Fig. 2.

[0060] In this NC circular table 1', the table 42 has a flange portion 42a that protrudes in front of the front cover portion 22. Thereby, the front surface of the table 42 of this NC circular table 1' is larger than that of the above-described NC circular table 1, and its size can be freely designed.

[0061] In the gap between the flange portion 42a and the front surface of the front cover portion 22, the pair of annular sealing materials 8, 8 are arranged so as to partition between the inside and the outside with an annular gap 100 therebetween in the radial direction. For these annular sealing materials 8, for example, V-rings can be used.

[0062] The V-ring is also a low-contact-pressure sealing material similar to an oil seal without a spring. That is, each annular sealing material 8 (V-ring) has an elastically deformable lip 8a and an annular base portion 8b. Each lip 8a is inclined, and each annular sealing material 8 is formed such that the inner diameter of the tip portion of each lip 8a is larger than the inner diameter of the root portion of each lip 8a.

[0063] The base portion 8b is mounted on a cylindrical receiving surface formed on the rear surface of the flange portion 42a. Thereby, the tip portion of the lip 8a is in contact with the front surface of the front cover portion 22.

[0064] The downstream end of each communication passage 60c is bent and extends forward. The bent end is connected to the rear surface of the annular gap 100.

[0065] (Differential pressure adjustment mechanism) These NC circular tables 1, 1' are provided with a differential pressure adjustment mechanism that adjusts the annular inner gap 101 to have a higher air pressure than the annular gap 100 at a predetermined differential pressure.

[0066] In the present embodiment, the differential pressure adjustment mechanism is configured using the first air supply passage 60 and the second air supply passage 70. That is, as described above, the first air supply passage 60 is long and formed of a flow path with a large air resistance. In contrast, the second air supply passage 70 is shorter than the first air supply passage 60 and is formed of a flow path with a small air resistance. Therefore, the second air supply passage 70 has a smaller pressure loss of the air flowing through the flow path than the first air supply passage 60.

[0067] Thereby, the second air supply passage 70 can dynamically adjust the air pressure higher than the first air supply passage 60. As a result, it becomes possible to easily generate a predetermined differential pressure between the annular gap 100 and the annular inner gap 101. Since an existing structure is utilized and the new structure is also simple, it can be implemented at low cost. Therefore, it is preferable to configure the differential pressure adjustment mechanism using the structures of the first air supply passage 60 and the second air supply passage 70.

[0068] The differential pressure referred to here depends on the type and performance of the annular sealing material 8, but for example, it is preferably 0.05 MPa or less. More preferably, it is 0.01 MPa or less. In the case of using a general annular sealing material 8, appropriate effects can be obtained within this range.

[0069] The differential pressure adjustment mechanism is also preferably configured using the above-described pressure adjustment exhaust passage 90A or the decompression exhaust passage 90B. That is, by providing these specific exhaust passages 90, it becomes possible to adjust the air pressure inside the housing 2, including the accommodation chamber 21a and the annular inner gap 101, to a predetermined pressure greater than the atmospheric pressure. Since the structure is also simple, it can be implemented at low cost. Therefore, the differential pressure adjustment mechanism is preferably configured using these specific exhaust passages 90.

[0070] Note that the differential pressure adjustment mechanism can also be configured by individually controlling the air pressures supplied to each of the annular gap 100 and the annular inner gap 101 without using the specific structures of the first air supply passage 60 and the second air supply passage 70, and / or the specific exhaust passage 90.

[0071] However, in that case, it is necessary to provide a control device and a solenoid valve capable of controlling the air flow rate. Therefore, the number of parts and the implementation cost also increase. On the other hand, according to the differential pressure adjustment mechanism of the present embodiment, the number of parts and the implementation cost are small, and it can be realized at low cost. Also, once the air pressure is adjusted to an appropriate state, as long as the pressure of the air supply source is stable, the possibility of a large change in the air pressure is low. Therefore, it can function in a practically necessary and sufficient state.

[0072] (Operation of the annular sealing material) Regarding the operation of the annular sealing material 8, a form in which a pair of annular sealing materials 81, 82 are arranged in the radial direction will be described as an example. Note that the operation is the same even in a form arranged in the axial direction.

[0073] First, the operation of the annular sealing material when air is supplied only from the first air supply passage 60 (the same form as the conventional one) will be described. The operation of the annular sealing materials 81, 82 is schematically shown in the upper diagram (z) of FIG. 4.

[0074] As shown by the arrows, each annular sealing material 81, 82 is in contact with the housing 2 with a predetermined pressing force F. Then, as shown by the dashed arrows, when air is supplied to the annular gap 100 through the first air supply passage 60, each annular sealing material 81, 82 is pressurized.

[0075] Thereby, as shown by the arrow, an air pressure P1 acts on the annular outer seal member 82 in a direction of pushing up the lip 8a (a direction of opening the annular gap 100) against the pressing force F. As shown by the arrow, an air pressure P1 acts on the annular inner seal member 81 in a direction of pressing the lip 8a together with the pressing force F (a direction of closing the annular gap 100).

[0076] Therefore, even when the contact pressure of the annular seal members 81 and 82 is low and some gaps may be generated, the air supply to the annular gap 100 can ensure the sealing performance. Further, when the air pressure becomes equal to or higher than a certain level, the annular outer seal member 82 is pushed up and air blows out, so that the intrusion of foreign matters can be further prevented. Therefore, the intrusion of foreign matters from the gap between the table 42 and the front cover portion 22 (housing 2) can be stably prevented.

[0077] Since the contact pressure of each of the annular seal members 81 and 82 may be low, the heat generation at the contact portion can be effectively reduced. Therefore, the heat generation can also be suppressed. The power consumption can be reduced, the deterioration of the seal member can be suppressed, and the durability can be improved.

[0078] However, in this case, it has been found that there is room for improvement in terms of heat generation suppression when the rotational speed is increased. That is, since the air pressure P1 in the annular gap 100 acts on the annular inner seal member 81 in a direction of pressing the lip 8a together with the pressing force F, when the air pressure P1 in the annular gap 100 increases, the contact pressure of the tip portion of the lip 8a with respect to the front cover portion 22 also increases accordingly.

[0079] Since the annular seal members 81 and 82 are seal members with low contact pressure, at normal rotational speeds, even if the air pressure in the annular gap 100 increases somewhat, the amount of heat generated by friction is small. Therefore, due to the balance with heat dissipation, there was no risk that heat generation would become a problem. However, it has been found that when the rotational speed is further increased, heat is generated even at such an air pressure, and suppression of such heat generation becomes necessary.

[0080] In particular, it has been found that the necessity becomes higher when the annular sealing members 81 and 82 are arranged in the radial direction. That is, when the annular sealing members 81 and 82 are arranged in the radial direction, the lips 8a of the respective annular sealing members 8 during rotation are likely to open due to the action of centrifugal force. And the annular outer sealing member 82 located on the outer side in the radial direction is more likely to open than the annular inner sealing member 81 located on the inner side in the radial direction.

[0081] The faster the rotational speed, the greater the influence. Therefore, when the rotational speed is increased, there is a risk that the annular outer sealing member 82 will open too much. In order to prevent the annular outer sealing member 82 from opening too much, it is necessary to increase the pressing force F of the annular sealing members 81 and 82 more than before. Then, the contact pressure of the annular inner sealing member 81 increases.

[0082] Therefore, in the NC circular tables 1 and 1' of the present embodiment, the second air supply passage 70 is provided to pressurize the annular inner gap 101 with air pressure, and a differential pressure adjustment mechanism is provided so that the air pressure in the annular inner gap 101 is higher than that in the annular gap 100 at a predetermined differential pressure.

[0083] Specifically, in addition to the supply of air to the annular gap 100 through the first air supply passage 60 shown in the upper diagram (z) of FIG. 4, as shown by the broken line in the lower diagram (a) of FIG. 4, air is supplied to the annular inner gap 101 through the second air supply passage 70. Thereby, the annular inner sealing member 81 is pressurized, but the annular outer sealing member 82 is not pressurized.

[0084] As shown by the arrow, an air pressure P2 acts on the annular inner sealing member 81 in the direction of pushing up its lip 8a. As a result, the lip 8a of the annular inner sealing member 81 is pressed by the combined force of the pressing force F of the annular inner sealing member 81 and the air pressure P1 in the annular gap 100, and is in a state of being pushed up by the air pressure P2 in the annular inner gap 101.

[0085] That is, the differential force obtained by subtracting the pushing-up force from the pressing force becomes the actual contact pressure of the lip 8a (F + P1 - P2). And since the air pressure P2 in the annular inner clearance 101 is adjusted to be higher than the air pressure P1 in the annular clearance 100 by a predetermined differential pressure by the differential pressure adjustment mechanism (P2 > P1), the pressing force F of the lip 8a itself of the annular inner sealing material 81 can be reduced.

[0086] And as shown in Fig. 4 (b) of the lower figure, when the air pressure in the annular clearance 100 becomes higher than the pressing force (P1 > F), the lip 8a of the annular outer sealing material 82 opens. Thereby, the air in the annular clearance 100 is discharged to the outside.

[0087] At this time, it is preferable to set the air pressure P1 in the annular clearance 100 and the air pressure P2 in the annular inner clearance 101 so that the lip 8a of the annular inner sealing material 81 does not open. Specifically, it is set so that the air pressure P2 in the annular inner clearance 101 is smaller than the force (F + P1) pressing the lip 8a of the annular inner sealing material 81 (F + P1 > P2).

[0088] Note that also at this time, the air pressure P2 in the annular inner clearance 101 is held higher than the air pressure P1 in the annular clearance 100 by a predetermined differential pressure (P2 > P1). By doing so, when the lip 8a of the annular outer sealing material 82 opens, the lip 8a of the annular inner sealing material 81 can be prevented from opening, so that the sealing performance can be surely ensured.

[0089] When the air is discharged, the air pressure P1 in the annular clearance 100 may decrease. In that case, since the air pressure P2 in the annular inner clearance 101 becomes larger than the force (F + P1) pressing the lip 8a of the annular inner sealing material 81, as shown in Fig. 4 (c) of the lower figure, the lip 8a of the annular inner sealing material 81 opens. Thereby, the air in the annular inner clearance 101 is replenished to the annular clearance 100. The air pressure P1 in the annular clearance 100 returns to an appropriate state.

[0090] Thus, according to the NC circular table 1, 1' to which the disclosed technology is applied, the contact pressure of the annular inner sealing material 81 can be effectively reduced. As a result, even when the rotation speed is increased, heat generation at the sealing portion of the lip 8a can be suppressed. Wear of the lip 8a can be suppressed. Along with the suppression of contact resistance, power consumption can also be reduced.

[0091] Since air flows into the sealing portion from both the inside and outside of the annular inner sealing material 81, the lip 8a can be effectively cooled. Even if the air pressure in the annular gap 100 decreases due to the release of air, it can be quickly replenished.

[0092] If air is supplied to the annular inner gap 101 through the accommodation chamber 21a, the bearing 7 and the motor 5 can also be cooled. Heat generation of the motor 5 can also be suppressed. High-temperature air accumulated inside the housing 2 can be discharged.

[0093] <Other Embodiments> In the NC circular tables 1, 1' of the above-described embodiments, the case where the second air supply passage 70 is formed in the main body portion 21 of the housing 2 has been described. However, the second air supply passage 70 can be appropriately changed according to the specifications.

[0094] Such NC circular tables (NC circular table 1A and NC circular table 1B) are exemplified. Note that these NC circular tables 1A and 1B also have the same basic structure as the above-described NC circular tables 1, 1'. Therefore, different configurations will be described, and the same reference numerals will be used for the same configurations and the description thereof will be omitted.

[0095] The NC circular table 1A is shown in FIG. 5. In this NC circular table 1A, similar to the first air supply passage 60, the second air supply passage 70 is constituted by one second main passage 201, one second annular space 202, a plurality of second communication passages 203, and the like.

[0096] These passages 201, 202, 203 are formed in both the main body portion 21 and the front cover portion 22. Thereby, it is configured to bypass the accommodation chamber 21a and supply air to the vicinity of the annular inner gap 101.

[0097] The NC circular table 1B is shown in Fig. 6. In this NC circular table 1B, the second air supply passage 70 is formed by branching from the first air supply passage 60.

[0098] Specifically, as shown enlarged in Fig. 6, at the downstream end of each communication passage 60c of the first air supply passage 60, a branch flow path 210 branched in two directions toward both the annular gap 100 and the annular inner gap 101 is formed. And the second air supply passage 70 is constituted by the branch flow path 210 leading to the annular inner gap 101.

[0099] In this case, in order to flow air while appropriately distributing it to both the annular gap 100 and the annular inner gap 101, it is preferable to provide a throttle port 211 with a reduced flow path cross-section at each of the inflow sites to the annular gap 100 and the annular inner gap 101.

[0100] Note that the disclosed technology is not limited to the above-described embodiments, and includes various other configurations.

[0101] For example, as the annular sealing material, a sealing material with a low contact pressure is preferable, but a sealing material with a normal contact pressure may also be used. By adjusting the air pressure of the first air supply passage and the second air supply passage, the actual contact pressure of each annular sealing material can be adjusted.

Explanation of Reference Numerals

[0102] 1, 1’, 1A, 1B NC circular table (rotating device) 2 Housing 60 First air supply passage 70 Second air supply passage 81 Annular inner sealing material 82 Annular outer sealing material 100 Annular gap 101 Annular inner gap

Claims

1. A rotary device for work, a spindle having a table, a housing that rotatably accommodates the spindle with the table exposed, a pair of annular seal materials including an annular inner seal material and an annular outer seal material, which are arranged to partition between the inside and the outside in the radial direction or the axial direction with a predetermined annular gap so as to close the gap between the table and the housing, a first air supply passage for supplying air to the annular gap, comprising, a second air supply passage for supplying air to an annular inner gap located inside the annular gap with the annular inner seal material therebetween, a differential pressure adjustment mechanism for adjusting the annular gap such that the air pressure in the annular inner gap is higher than that in the annular gap at a predetermined differential pressure of 0.05 MPa or less, further comprising, a rotary device for work, wherein the differential pressure adjustment mechanism is configured using a specific structure of the first air supply passage and the second air supply passage, in which the pressure loss of the air flowing through the second air supply passage is smaller than that of the air flowing through the first air supply passage.

2. In the rotary device for work according to Claim 1, the differential pressure adjustment mechanism is configured using a pressure regulating exhaust passage that communicates with the inside of the housing and can adjust the air pressure inside the housing, a rotary device for work that can maintain the inside of the housing higher than atmospheric pressure by the pressure regulating exhaust passage.

3. In the rotary device for work according to Claim 1 or Claim 2, the differential pressure adjustment mechanism is configured using a decompression exhaust passage that communicates with the inside of the housing and is decompressed by the pressure loss of the flowing air, a rotary device for work that can maintain the inside of the housing higher than atmospheric pressure by the decompression exhaust passage.

4. In the rotary device for work according to Claim 2 or Claim 3, a housing chamber is provided inside the housing for accommodating a motor for rotating the spindle, a rotary device for work, wherein the second air supply passage supplies air to the annular inner gap through the housing chamber.

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