JP2022190974A - Handicraft rotary apparatus - Google Patents

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

The disclosed technique relates to a rotary machine for machining, such as a rotary table that supports an object to be machined, and in particular, a technique that achieves both suppression of heat generation at a sealing portion and prevention of entry of foreign matter.

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

In relation to the technology disclosed, there is a rotary device previously proposed by the present inventor (Patent Document 1).

In the rotating device of Patent Document 1, a spindle having a circular table is provided, and a pair of annular seal members are provided so as to block a gap between a housing that rotatably accommodates the spindle and the table. They are arranged across an annular gap.

Air is supplied to the annular gap from a plurality of positions spaced apart from each other in the circumferential direction so that the sealing performance is not locally deteriorated due to the pressure difference.

JP 2020-151823 A

By applying the technique disclosed in Patent Document 1 to a conventional rotating device, it has become possible to appropriately achieve both suppression of heat generation at the seal portion and prevention of entry of foreign matter.

However, in recent years, there has been a demand for a rotating device that can rotate at a higher speed than ever before. Therefore, the inventor of the present invention has been studying how to increase the speed of rotation. In the course of the study, it was found that there is room for improvement in the technology of Patent Document 1 in terms of suppressing heat generation when the speed is increased. found.

Moreover, in the case of this type of rotary device, even if it is functionally excellent, it is difficult to put it into practical use if it is not inexpensive.

Therefore, the main purpose of the disclosed technique is to realize a rotary machine for machining at a low cost that can more appropriately achieve both suppression of heat generation at the sealing portion and prevention of entry of foreign matter, and can cope with high speed.

TECHNICAL FIELD The disclosed technology relates to rotating equipment for machining. The rotating device includes a spindle having a table, a housing that rotatably accommodates the spindle with the table exposed, and a predetermined structure that closes a gap between the table and the housing. A pair of annular seal members consisting of an annular inner seal member and an annular outer seal member arranged so as to partition the inside and the outside in the radial direction or the axial direction across an annular gap, and air is supplied to the annular gap. and a first air supply passage for supplying.

A second air supply passage for supplying air to the inner annular gap located inside the annular gap with the inner annular seal material therebetween, and a predetermined gap between the inner annular gap and the annular gap. and a fine differential pressure adjusting mechanism that adjusts the air pressure so that the fine differential pressure of .

Preferably, the second air supply passage is formed to have a structure in which pressure loss of air flowing through the passage is smaller than that of the first air supply passage, and the fine differential pressure adjusting mechanism is configured to operate in the first air supply passage. It is configured using the structures of the air passage and the second air supply passage.

Preferably, the fine differential pressure adjusting mechanism is configured using a pressure regulating exhaust passage that communicates with the interior of the housing and is capable of adjusting the air pressure inside the housing, and the pressure regulating exhaust passage It is a rotary machine for work that can keep the inside of the housing higher than the atmospheric pressure.

Preferably, the fine differential pressure adjusting mechanism is configured using a decompression exhaust passage that communicates with the inside of the housing and decompresses the interior of the housing by the pressure loss of air that flows through the decompression exhaust passage. It is a rotary machine for work that can hold the pressure higher than the atmospheric pressure.

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

According to the disclosed technology, while it is a simple structure that can be realized at a low cost, it is possible to achieve both the suppression of heat generation at the seal portion and the prevention of foreign matter from entering more appropriately, and it is possible to respond to the high speed of rotating equipment for machining. become.

1 is a schematic perspective view showing an NC rotary table (rotating device) of this embodiment; FIG. FIG. 2 is a schematic cross-sectional view along the arrow XX line in FIG. 1; It is a schematic cross-sectional view of an NC rotary table in which an annular seal member is arranged in the radial direction. FIG. 10 is a diagram for explaining the operation of the annular sealing material; It is a schematic sectional drawing of the NC rotary table of other embodiment. It is a schematic sectional drawing of the NC rotary table of other embodiment.

Embodiments of the disclosed technology will be described below. However, the following description is merely exemplary in nature.

Unless otherwise specified, the "axial direction" used in the description means the direction in which the rotation axis J extends. Similarly, "circumferential" means a circumferential direction about the axis J of rotation, and "radial" means a radial or diameter direction about the axis J of rotation. "Front" means the side used during machining, and "rear" means the side not used during machining.

<First embodiment>
1 and 2 show an NC rotary table 1 (an example of rotating equipment) to which the disclosed technique is applied. The NC rotary table 1 is roughly composed of a housing 2, a box 3, a spindle 4, a motor 5 and the like. The NC rotary table 1 is used during machining, and the front table 42 rotates at high speed.

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

Especially in recent years, there are cases where higher speed rotation than before is required during machining. Therefore, if it is possible to appropriately cope with such high-speed rotation, it will be very convenient. The technique disclosed this time is based on such circumstances.

The housing 2 is composed of a body portion 21, a front lid portion 22, a rear lid portion 23, and the like. A cylindrical accommodation space is formed in the body portion 21 so as to penetrate therethrough in the front-rear direction. The rear lid portion 23 is attached to the rear side of the main body portion 21 and closes the rear opening of the accommodation space.

The front lid portion 22 is made of a cylindrical member. The front lid portion 22 is fitted into a circular concave portion formed on the front side of the main body portion 21 . The front lid portion 22 is attached to the front side of the body portion 21 so as to cover the front side of the accommodation space of the body portion 21 . As a result, the front and rear sides of the housing space of the body portion 21 are closed, and a substantially sealed housing chamber 21 a is formed inside the housing 2 .

A circular opening 22a is formed in the front lid portion 22 . The centerline of the opening 22a and the centerline of the storage chamber 21a substantially match. An annular bearing 7 is arranged in front of the accommodation chamber 21a. The bearing 7 has an outer ring portion 7a and an inner ring portion 7b that freely rotate relative to each other. The bearing 7 is assembled to the housing 2 by sandwiching the outer ring portion 7 a between the main body portion 21 and the front lid portion 22 .

The box 3 is a box-shaped container and is attached to one side surface of the housing 2 . Inside the box 3, various cables and electric devices used for driving and controlling the NC rotary table 1 are arranged. Power is supplied to the NC rotary table 1 through a cable (not shown) leading out from the box 3 .

The spindle 4 of this embodiment has a shaft 41 and a table 42 . The shaft 41 is made of a multi-stage cylindrical member and is housed in the housing 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.

The table 42 is a disk-shaped member having an outer diameter slightly smaller than the inner diameter of the opening 22a, and is attached 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 7 b of the bearing 7 is sandwiched between the shaft 41 and the table 42 . Thereby, the spindle 4 is supported by the housing 2 via the bearing 7, and is rotatable around the rotation axis J. As shown in FIG.

As described above, the table 42 is a portion of the spindle 4 to which a workpiece is mounted via a chuck or a jig, and the circular front surface of the table 42 is exposed to the front surface of the housing 2 through the opening 22a. ing. The spindle 4 may be configured by combining a plurality of parts as in the present embodiment, or may be configured integrally.

The motor 5 has a rotor 51 and a stator 52 and is housed in the housing chamber 21a. The rotor 51 is made of an annular member and fixed to the small diameter portion 41a. The stator 52 is made of an annular member larger than the rotor 51 and is fixed to the main body 21 so as to face the rotor 51 with a small gap in the radial direction.

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

It should be noted that the faster the rotational speed of the spindle, the greater the amount of heat generated by the motor when it is driven. Therefore, when increasing the rotational speed, it is important to deal with the heat generated by the motor.

(Gap seal)
There is a gap between the table 42, which is a rotating body, and the housing 2, which is a non-rotating body. Since the front surface of the NC rotary table 1 is exposed to chips and cutting water, it is necessary to prevent these foreign substances from entering the storage chamber 21a through the gap.

Sealing with a high contact pressure oil seal or face seal can effectively prevent the intrusion of foreign matter, but the high contact pressure causes the problem that heat is likely to be generated due to friction at the contact portion. At high speed rotation, the amount of heat generated becomes excessive, causing deformation and deterioration of the sealing material. There is also a possibility that the spindle 4 and the table 42 will thermally expand, degrading the machining accuracy. This tendency becomes more pronounced as the rotation speed increases.

On the other hand, if sealing is performed with a low contact pressure sealing material (for example, an oil seal without a spring or a V ring), heat generation at the contact portion can be reduced because the contact pressure is low. However, since the sealing performance is lowered by that amount, it becomes easier for foreign matter to enter. That is, it is not possible to achieve both suppression of heat generation and prevention of entry of foreign matter.

Therefore, the present inventors have previously devised ways to achieve both heat generation suppression and foreign matter intrusion prevention by using a sealing material with a low contact pressure and air pressure (see Patent Document 1). This NC rotary table 1 is premised on such ingenuity.

(Annular seal material)
A pair of annular seal members 8, 8 (also referred to as an annular inner seal member 81 and an annular outer seal member 82) in this embodiment are arranged axially in a predetermined direction so as to close the gap between the table 42 and the housing 2. are arranged so as to separate the inside and the outside with an annular gap 100 between them. Each annular seal member 8 is press-fitted into a stepped portion 30 formed on the inner peripheral edge of the opening 22 a of the front lid portion 22 .

These annular seal members 8 are all low contact pressure seal members (for example, springless oil seals). Each annular seal member 8 has an elastically deformable lip 8 a and an annular base portion 8 b mounted on the stepped portion 30 .

Each lip 8a is slanted. Each annular seal member 8 is arranged so that the inner diameter of the lip 8a becomes smaller toward the outside of the gap. Each annular seal member 8 is arranged in a gap between the table 42 and the housing 2 . A tip portion of the lip 8 a is in contact with the outer peripheral surface of the table 42 . Incidentally, in order to increase the contact pressure of each lip 8a, for example, it is possible to replace the non-spring with the spring.

(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 .

As shown in FIG. 2, the first air supply passage 60 of this embodiment includes one main passage 60a, one annular space 60b, a plurality of communication passages 60c, and the like.

The main passage 60a is a narrow hole formed in the housing 2 and formed in a shape bent in the main body 21 in an L shape. The upstream end of the main passage 60 a opens to the outer surface of the main passage 21 , and the downstream end of the main passage 60 a opens to the joint surface of the main passage 21 with the front lid portion 22 .

A first throttle valve 9 capable of adjusting the flow rate of 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 . As a result, 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 during machining. The main passage 60a communicates with the annular space 60b.

The annular space 60 b is 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 of the rear surface of the front lid portion 22, and an annular space 60b is formed by assembling the front lid portion 22 to the main body portion 21. As shown in FIG. Packings 12 are mounted on both sides of the annular space 60b to ensure airtightness.

Each communication passage 60 c is formed in the front lid portion 22 . Each communication passage 60c is a narrow hole and is formed in a shape bent 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. The annular space 60b and the annular gap 100 communicate with each other through the plurality of communication passages 60c.

Therefore, after the flow rate of the air introduced from the air supply pipe 11 is adjusted by the first throttle valve 9, the air passes through the main passage 60a, the annular space 60b, and the plurality of communication passages 60c to the annular gap 100. supplied. At this time, the generation of a local air pressure difference at a specific portion in the circumferential direction of the annular gap 100 is suppressed, so that the entire circumference can be sealed in a well-balanced manner.

(Second air supply passage)
A second air supply passage 70 is formed in the housing 2 to supply air through the accommodation chamber 21 a to a gap (annular inner gap 101 ) located inside the annular gap 100 . The inner annular gap 101 is a gap positioned inside the annular gap 100 with the inner annular seal member 81 interposed therebetween. In other words, the annular inner gap 100 and the annular inner gap 101 are partitioned inside and out by the annular inner seal material 81 .

As shown in FIG. 2 , the second air supply passage 70 of this embodiment is composed of one vertical hole formed in the housing 2 . Specifically, the second air supply passage 70 is formed by cutting the body portion 21 so as to penetrate the housing chamber 21 a , and the upstream end of the second air supply passage 70 extends from 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 21 .

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 . A second throttle valve 10 is also connected to the air supply pipe 11 . As a result, air is introduced into the housing 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 during work.

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

(Pressure adjustment exhaust passage, decompression exhaust passage)
The housing 2 is provided with an exhaust passage 90 that communicates the housing chamber 21 a with the environment outside the housing 2 . In this embodiment, the rear lid portion 23 is formed with an exhaust passage 90 passing through the plate surface thereof. In addition, 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 that can exhaust the air inside the housing 2 .

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

The pressure regulating exhaust passage 90A allows the interior of the housing 2, including the housing chamber 21a, to be maintained at a pressure 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.

A decompression exhaust passage 90B may be provided instead of the pressure regulation exhaust passage 90A. The decompression exhaust passage 90B is an exhaust passage 90 having a structure in which the pressure loss of air flowing through the flow path is large. For example, the reduced pressure exhaust passage 90B is formed by lengthening the distance of the exhaust passage 90, narrowing the flow passage by reducing the cross section of part or all of the exhaust passage 90, or bending the flow passage. can do.

FIG. 2 shows an example of such a decompression exhaust passage 90B with a chain double-dashed line. The decompression exhaust passage 90B is formed in the body portion 21 as an elongated curved passage. By providing such a decompression exhaust passage 90B and 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.

In both cases of the pressure regulating exhaust passage 90A and the pressure reducing exhaust passage 90B, the air pressure inside the housing 2 can be adjusted by adjusting the flow rate of the air with the second throttle valve 10 . Both the pressure regulating exhaust passage 90A and the pressure reducing exhaust passage 90B can be implemented with extremely simple modifications from the existing structure, and are inexpensive.

(Arrangement of annular seal material in radial direction)
The pair of annular seal members 8, 8 may be arranged radially rather than axially so as to separate the inside and the outside with an annular gap 100 therebetween.

FIG. 3 shows an NC rotary table (NC rotary table 1') in which a pair of annular sealing members 8, 8 are arranged in such a manner. The basic structure is the same as that of the NC rotary table 1 shown in FIG.

In this NC rotary table 1 ′, the table 42 has a flange portion 42 a projecting forward of the front lid portion 22 . Thereby, the front surface of the table 42 of this NC rotary table 1' is larger than that of the NC rotary table 1 described above, and its size can be freely designed.

In the gap between the flange portion 42a and the front surface of the front cover portion 22, a pair of annular seal members 8, 8 are arranged radially across an annular gap 100 so as to partition the inside and the outside. there is V-rings, for example, can be used for these annular seal members 8 .

V-rings, like springless oil seals, are also low contact pressure seals. That is, each annular seal member 8 (V ring) has an elastically deformable lip 8a and an annular base portion 8b. Each lip 8a is inclined, and each annular seal member 8 is formed so that the inner diameter of the tip portion is larger than the inner diameter of the root portion of each lip 8a.

The base portion 8b is attached to a cylindrical receiving surface formed on the rear surface of the flange portion 42a. As a result, the tip portion of the lip 8a is in contact with the front surface of the front cover portion 22. As shown in FIG.

The downstream end of each communication passage 60c is bent and extends forward. Its bent end is connected to the rear face of the annular gap 100 .

(Micro differential pressure adjustment mechanism)
These NC rotary tables 1 and 1' are provided with a fine differential pressure adjusting mechanism for adjusting the air pressure in the inner annular gap 101 to be higher than that in the annular gap 100 by a predetermined fine differential pressure. It is

In this embodiment, the first air supply passage 60 and the second air supply passage 70 are used to configure a fine differential pressure adjustment mechanism. That is, the first air supply passage 60 is formed as a flow path that is long and has high air resistance, as described above. On the other hand, the second air supply passage 70 is shorter than the first air supply passage 60 and formed as a flow path with low air resistance. Therefore, the pressure loss of the air flowing through the second air supply passage 70 is smaller than that of the first air supply passage 60 .

Thereby, the air pressure of the second air supply passage 70 can be dynamically adjusted higher than that of the first air supply passage 60 . As a result, it is possible to easily generate a predetermined minute differential pressure between the annular gap 100 and the annular inner gap 101 . In addition to using the existing structure, the new structure is also simple, so it can be implemented at low cost. Therefore, it is preferable to use the structure of the first air supply passage 60 and the second air supply passage 70 to configure the fine differential pressure adjusting mechanism.

It should be noted that although the slight differential pressure referred to here depends on the type and performance of the annular seal member 8, it is preferably 0.05 MPa or less, for example. 0.01 MPa or less is more preferable. Appropriate effects can be obtained within this range if a general annular seal member 8 is used.

The fine differential pressure adjusting mechanism is also preferably configured using the pressure adjusting exhaust passage 90A or the pressure reducing exhaust passage 90B described above. 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 higher than the atmospheric pressure. Since the structure is also simple, it can be implemented at low cost. Therefore, it is preferable to configure the fine differential pressure adjusting mechanism using these specific exhaust passages 90 .

It should be noted that the fine differential pressure adjustment mechanism can be achieved 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. It is also possible to configure by individually controlling the air pressure supplied to each of.

However, in that case, it is necessary to provide a control device, an electromagnetic valve capable of controlling the air flow rate, or the like. Therefore, the number of parts and implementation costs are also increased. On the other hand, according to the fine differential pressure adjusting mechanism of the present embodiment, the number of parts and implementation cost are small, and it can be realized at low cost. Also, once the air pressure is adjusted to an appropriate state, it is unlikely that the air pressure will change significantly as long as the pressure of the air supply source is stable. Therefore, it can be made to function in a practically necessary and sufficient state.

(Operation of annular seal material)
The operation of the annular seal member 8 will be described with an example in which a pair of annular seal members 81 and 82 are arranged in the radial direction. It should be noted that the operation is the same even in the form arranged in the axial direction.

First, the operation of the annular seal member when air is supplied only from the first air supply passage 60 (the same form as in the conventional art) will be described. The upper diagram (z) of FIG. 4 schematically shows the operation of the annular seal members 81 and 82 .

As indicated by arrows, each of the annular seal members 81 and 82 is in contact with the housing 2 with a predetermined pressing force F. As shown in FIG. When air is supplied to the annular gap 100 through the first air supply passage 60 as indicated by the dashed arrows, the annular seal members 81 and 82 are pressurized.

As a result, the air pressure P1 acts on the annular outer seal member 82 in the direction of pushing up the lip 8a (in the direction of opening the annular gap 100) against the pressing force F, as indicated by the arrow. As indicated by an arrow, the annular inner seal member 81 is acted upon with a pressing force F and an air pressure P1 in the direction of pressing the lip 8a (the direction of closing the annular gap 100).

Therefore, even if the contact pressure between the annular seal members 81 and 82 is low and a slight gap may occur, air is supplied to the annular gap 100 to ensure sealing performance. Furthermore, when the air pressure exceeds a certain level, the annular outer seal member 82 is pushed up and the air blows out, so that the intrusion of foreign matter can be further prevented. Therefore, foreign matter can be stably prevented from entering through the gap between the table 42 and the front lid portion 22 (the housing 2).

Since the contact pressure between the annular seal members 81 and 82 may be low, heat generation at the contact portions can be effectively reduced. Therefore, heat generation can also be suppressed. Power consumption can be reduced, deterioration of the sealing material can be suppressed, and durability is improved.

However, in this case, it has been found that there is room for improvement in terms of heat generation suppression if the rotation speed is increased. That is, since the air pressure P1 in the annular gap 100 acts on the annular inner seal member 81 in the direction of pressing the lip 8a along with the pressing force F, when the air pressure P1 in the annular gap 100 increases, the front The contact pressure of the tip portion of the lip 8a against the lid portion 22 also increases.

Since the annular seals 81 and 82 are low contact pressure seals, 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, there was no possibility that heat generation would become a problem due to the balance with heat dissipation. However, it has been found that if the rotation speed is further increased, heat is generated even with such an air pressure, and it is necessary to suppress the heat generation.

In particular, it has been found that the need for the annular seal members 81 and 82 increases when the annular seal members 81 and 82 are arranged in the radial direction. That is, when the annular seal members 81 and 82 are arranged in the radial direction, the lip 8a of each annular seal member 8 is easily opened by the action of centrifugal force during rotation. The annular outer seal member 82 positioned radially outward is easier to open than the annular inner seal member 81 positioned radially inward.

The faster the rotation speed, the greater the effect. Therefore, if the rotation speed is increased, the annular outer seal member 82 may open too much. In order to prevent the annular outer seal member 82 from opening too much, it becomes necessary to increase the pressing force F of the annular seal members 81 and 82 more than before. As a result, the contact pressure of the annular inner seal material 81 increases.

Therefore, in the NC rotary tables 1 and 1' of the present embodiment, the second air supply passage 70 is provided to pressurize the inner annular gap 101 with air pressure, and a fine differential pressure adjusting mechanism is provided to On the other hand, the annular inner gap 101 is adjusted so that the air pressure is higher with a predetermined minute differential pressure.

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. , air is supplied to the annular inner gap 101 through the second air supply passage 70 . Thereby, the annular inner seal member 81 is pressurized, but the annular outer seal member 82 is not pressurized.

Air pressure P2 acts on the annular inner seal member 81 in the direction of pushing up the lip 8a as indicated by the arrow. As a result, the lip 8a of the annular inner seal member 81 is pressed by the combined force of the pressing force F of the annular inner seal member 81 and the air pressure P1 of the annular clearance 100, and is pushed up by the air pressure P2 of the annular inner clearance 101. become a state.

That is, the difference force obtained by subtracting the pushing force from the pressing force becomes the actual contact pressure of the lip 8a (F+P1-P2). Since the air pressure P2 in the inner annular gap 101 is adjusted to be higher than the air pressure P1 in the annular gap 100 by the fine differential pressure adjusting mechanism by a predetermined fine differential pressure (P2>P1), the annular The pressing force F of the lip 8a itself of the inner seal member 81 can be reduced.

When the air pressure in the annular gap 100 becomes higher than the pressing force (P1>F), the lip 8a of the annular outer seal member 82 opens, as shown in FIG. 4B. As a result, the air in the annular gap 100 is released to the outside.

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

Also at this time, the air pressure P2 in the annular inner gap 101 is maintained higher than the air pressure P1 in the annular gap 100 by a predetermined minute pressure difference (P2>P1). By doing so, the lip 8a of the annular inner seal member 81 can be prevented from opening when the lip 8a of the annular outer seal member 82 opens, so that the sealing performance can be reliably ensured.

Due to the release of air, the air pressure P1 in the annular gap 100 may decrease. In this case, the air pressure P2 in the inner annular gap 101 becomes greater than the force (F+P1) that presses the lip 8a of the inner annular seal member 81, so that as shown in the lower part (c) of FIG. The lip 8a of the inner seal member 81 is opened. Thereby, the air in the annular inner clearance 101 is replenished to the annular clearance 100 . The air pressure P1 in the annular gap 100 returns to a proper state.

Thus, according to the NC rotary tables 1 and 1' to which the disclosed technology is applied, the contact pressure of the annular inner seal member 81 can be effectively reduced. As a result, even when the rotational speed is increased, heat generation at the sealing portion of the lip 8a can be suppressed. Wear of the lip 8a can be suppressed. As the contact resistance is suppressed, power consumption can also be reduced.

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

By supplying air to the annular inner gap 101 through the storage 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.

<Other embodiments>
In the NC rotary tables 1 and 1' of the above-described embodiments, the case where the second air supply passage 70 is formed in the body portion 21 of the housing 2 has been described. However, the second air supply passage 70 can be changed as appropriate according to specifications.

Examples of such NC circular tables (NC circular table 1A and NC circular table 1B) are illustrated. These NC circular tables 1A and 1B also have the same basic structure as the NC circular tables 1 and 1' described above. Therefore, the different configurations will be explained, and the same reference numerals will be used for the same configurations, and the explanation thereof will be omitted.

NC rotary table 1A is shown in FIG. In this NC rotary table 1A, like the first air supply passage 60, the second air supply passage 70 is made up of one second main passage 201, one second annular space 202, a plurality of second communication passages 203, and the like. It is configured.

These passages 201 , 202 , 203 are formed in both the body portion 21 and the front lid portion 22 . As a result, the air is supplied to the vicinity of the annular inner gap 101 bypassing the accommodation chamber 21a.

FIG. 6 shows the NC rotary table 1B. In this NC rotary table 1</b>B, the second air supply passage 70 is configured by branching from the first air supply passage 60 .

Specifically, as shown in an enlarged view in FIG. 6, at the downstream end of each connecting passage 60c of the first air supply passage 60, there is branched in two directions toward both the annular gap 100 and the annular inner gap 101. A branched flow path 210 is formed. A second air supply passage 70 is formed by the branch flow path 210 directed toward the inner annular gap 101 .

In this case, in order to flow air into both the annular gap 100 and the annular inner gap 101 while distributing it in an appropriate state, the passage cross section is made small at each of the inflow portions to the annular gap 100 and the annular inner gap 101. A throttle opening 211 is preferably provided.

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

For example, the annular seal is preferably a low contact pressure seal, but may be a normal contact pressure seal. By adjusting the air pressure in the first air supply passage and the second air supply passage, the actual contact pressure of each annular seal member can be adjusted.

1, 1', 1A, 1B NC rotary table (rotating equipment)
2 Housing 60 First Air Supply Passage 70 Second Air Supply Passage 81 Annular Inner Seal Material 82 Annular Outer Seal Material 100 Annular Gap 101 Annular Inner Gap

Claims (5)

A rotary machine for work,
a spindle having a table;
a housing that rotatably accommodates the spindle with the table exposed;
An annular inner seal member and an annular ring arranged to partition 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 pair of annular seals made of outer seals;
a first air supply passage for supplying air to the annular gap;
with
a second air supply passage for supplying air to the inner annular gap located inside the annular gap with the inner annular seal member therebetween;
a fine differential pressure adjusting mechanism for adjusting the air pressure in the inner annular gap to be higher than the annular gap by a predetermined fine differential pressure;
A rotary machine for work, further comprising: In the rotary machine for work according to claim 1,
The second air supply passage is formed to have a structure in which pressure loss of air flowing through the passage is smaller than that of the first air supply passage,
A rotary machine for work, wherein the fine differential pressure adjusting mechanism is configured using the structures of the first air supply passage and the second air supply passage. In the rotary machine for work according to claim 1 or claim 2,
The fine differential pressure adjusting mechanism is configured using a pressure regulating exhaust passage communicating with the inside of the housing and capable of adjusting the air pressure inside the housing,
A rotary machine for work, wherein the pressure regulating exhaust passage allows the interior of the housing to be maintained at a pressure higher than atmospheric pressure. In the rotary machine for work according to claim 1 or claim 2,
The fine differential pressure adjustment mechanism is configured using a decompression exhaust passage that communicates with the interior of the housing and is decompressed by pressure loss of flowing air,
A rotary machine for work, wherein the decompression exhaust passage allows the inside of the housing to be maintained at a pressure higher than the atmospheric pressure. In the rotary machine for work according to claim 3 or 4,
An accommodation chamber accommodating a motor for rotating the spindle is provided inside the housing,
A rotary machine for work, wherein the second air supply passage supplies air to the annular inner gap through the storage chamber.

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