JP2007177724A - Vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum pump in which tooth sections formed on rotors in a radially outwardly projecting manner do not make contact with a housing even if thermal expansion and contraction of an end face flange and the housing are repeatedly caused. <P>SOLUTION: The vacuum pump compresses and discharges gas sucked into the housing due to rotation of a pair of rotors having the radially outwardly projecting tooth sections. The housing covers both the rotors. The vacuum pump includes the end face flange 7 arranged at an end portion of the housing 4 and formed of a material having a coefficient of thermal expansion larger than that of the housing 4, and restriction means 9, 20 arranged on the housing 4 so as to make contact with the peripheral surface perpendicular to the axis of the end face flange 7. The housing 4 and the end face flange 7 are integrally expanded by the restriction means 9, 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vacuum pump that compresses and discharges gas sucked into a housing that covers both rotors by the rotation of a pair of rotors having teeth protruding outward in the radial direction.

2. Description of the Related Art In semiconductor product manufacturing processes and the like, vacuum pumps that compress and discharge gas sucked into a housing that covers both rotors by rotation of a pair of rotors having teeth that protrude radially outward are widely used. .
An example of this vacuum pump will be described with reference to FIG. As shown in the figure, the vacuum pump 100 includes a housing 103 in which an intake port 101 and an exhaust port 102 connected to an exhaust pipe (not shown) connected to the reaction chamber are formed. In this housing 103, a pair of screw rotors 104, 105 having teeth protruding outward in the radial direction is housed. The pair of screw rotors 104 and 105 are arranged in parallel so as to mesh with each other in a non-contact meshing state with a predetermined clearance (a minute gap).

Between the housing 103 and the screw rotors 104 and 105, bearings 106, 107, 108, and 109 and seal members 110, 111, 112, and 113 for sealing the shaft holes are provided.
An upper end surface flange 117 and a lower end surface flange 118 are attached to the upper end surface and the lower end surface of the housing 103 to seal the end surface of the housing 103.
Furthermore, synchronous gears 114 and 115 that are integrally attached to the screw rotors 104 and 105 are provided, and a driving means 116 such as a motor is provided at one end of the screw rotor 104. This driving means 116 is attached to the upper pump body 120.

Further, the screw rotors 104 and 105 have a predetermined clearance with respect to the inner wall surface 103a of the housing 103, for example, an outer diameter dimension and an axial length separating a gap of 50 microns.
Then, a plurality of spiral working chambers are formed that are partitioned by the meshing portions of the housing 103 and the screw rotors 104 and 105, and the working chambers move in the axial direction of the rotating shaft by the rotation of the screw rotors 104 and 105. It is configured.

In the vacuum pump 100 configured as described above, when the screw rotors 104 and 105 are rotated by the driving means 116 such as a motor, the working chamber partitioned by the meshing portion of the housing 103 and the screw rotors 104 and 105 is inhaled. It moves from the port 101 side to the exhaust port 102 side.
Thereby, the gas (gas) in the working chamber sucked from the suction port 101 is transferred to the exhaust port side, compressed, and exhausted from the vacuum pump 100.

  In this type of vacuum pump, since the gas is compressed as it is transferred from the intake port side to the exhaust port side, compression heat is generated. Therefore, the screw rotors 104 and 105, the housing 103, the upper end surface flange 117, and the lower end surface flange 118 are heated by the generated heat.

  Therefore, when the vacuum pump is continuously operated, the housing 103, the upper end face plate 117, the lower end face plate 118, and the upper pump body 120, due to heat generation of the bearings 106, 107, 108, 109, heat conduction from the housing 103, and the like. The temperature of the lower pump body 121 rises and thermally expands.

However, although the screw rotors 104 and 105 are supported by the upper pump body 120 and the lower pump body 121 via the bearings 106, 107, 108, and 109, the bearings 106, 107, 108, and 109 are prevented from being seized. Cooling grooves (not shown) are provided in the vicinity of the bearings of the upper pump body 120 and the lower pump body 121, thereby cooling the upper pump body 120 and the lower pump body 121.
Therefore, the temperature rise of the upper pump body 120 and the lower pump body 121 is small compared to the temperature rise of the screw rotors 104 and 105.

  As a result, since the screw rotors 104 and 105 expand greatly, the upper pump body 120 and the lower pump body 121 do not change so much, so the gap between the screw rotors 104 and 105 that are paired with each other is narrowed. The contact will eventually occur, and troubles such as seizure and damage may occur.

In order to solve this problem, Patent Document 1 discloses that the upper pump body 120, the lower pump body 121, the upper end surface flange 117, and the lower end surface flange 118 have a larger thermal expansion coefficient than the housing 103 and the screw rotors 104 and 105. It has been proposed to form using materials.
That is, since the thermal expansion coefficients of the materials of the pump bodies 120 and 121 and the upper end surface flange 117 and the lower end surface flange 118 are larger than those of the screw rotors 104 and 105 and the housing 103 covering the rotor, the upper pump body 120 and the lower pump. Even if the temperature rise of the body 121, the upper end surface flange 117, and the lower end surface flange 118 is smaller than the temperature increase of the screw rotors 104 and 105 and the housing 103, the body 121 expands greatly.
Therefore, since the upper pump body 120, the lower pump body 121, and the screw rotors 104 and 105 are thermally expanded in a well-balanced manner, the screw rotors 104 and 105 can avoid contact with each other.
Japanese Utility Model Publication No.7-17979

Incidentally, the upper end surface flange 117 and the lower end surface flange 118 are attached by fixing means such as bolts in order to seal the end surface of the housing 103. Therefore, even if it is the upper end surface flange 117, the lower end surface flange 118, and the housing 103 which have different thermal expansion coefficients, they both expand and contract as a unit.
That is, even if the upper end flange 117, the lower end surface flange 118, and the housing 103 are repeatedly expanded and contracted, their positional relationship does not deviate.

However, actually, as shown in FIG. 10, the positional relationship among the upper end surface flange 117, the lower end surface flange 118 and the housing 103 may be shifted.
That is, when the operation of the vacuum pump is started from the initial state shown in FIG. 10 (a) and the upper end surface flange 117, the lower end surface flange 118, and the housing 103 are heated to high temperatures due to compression heat, as shown in FIG. 10 (b). The upper end surface flange 117, the lower end surface flange 118, and the housing 103 are expanded.
At this time, the thermal expansion coefficients of the upper end surface flange 117 and the lower end surface flange 118 are large and the thermal expansion coefficient of the housing 103 is small, and the bolt through holes formed in the upper end surface flange 117, the lower end surface flange 118, and the housing 103. Since there is a dimensional tolerance of, for example, about 0.5 mm between the diameter of the bolt and the diameter of the bolt, the positional relationship between the two is displaced.

When the operation of the vacuum pump is completed and the upper end surface flange 117, the lower end surface flange 118, and the housing 103 are cooled, the upper end surface flange 117, the lower end surface flange 118, and the housing 103 contract in a shifted state. Sometimes.
Although the cause of this positional relationship shift has not yet been elucidated, it is presumed that it may be due to the influence of frictional forces or the like between the upper end surface flange 117, the lower end surface flange 118, and the housing 103.

  In either case, the upper end flange 117, the lower end surface flange 118, and the housing 103 contract with the positional relationship shifted, and the positional shift increases as the expansion and contraction are repeated. As shown in FIG. 10C, the screw rotors 104 and 105 accommodated in the housing 103 may come into contact with the housing 103 and cannot be used as a vacuum pump.

  In order to solve this problem, the dimensional tolerances between the diameters of the bolt through holes formed in the upper end flange 117, the lower end flange 118, and the housing 103 and the diameter of the bolts are set to the screw rotors 104 and 105 and the housing 103. It is speculated that it can be eliminated if the gap is less than or equal to the inner wall surface 103a (for example, several tens of microns to several hundreds of microns). However, it is practically difficult to make the dimensional tolerance equal to or less than the gap.

  The present invention has been made to solve the above technical problem, and even if the end face flange and the housing repeat thermal expansion and contraction, the radially protruding tooth portion formed on the rotor is formed on the housing. The object is to provide a vacuum pump that is free from contact.

  The present invention has been made to achieve the above object, and a vacuum pump according to the present invention is sucked into a housing covering both rotors by the rotation of a pair of rotors having tooth portions protruding radially outward. A vacuum pump that compresses and discharges a gas to be discharged, and is provided at an end portion of the housing, and is provided at an end surface flange formed of a material having a thermal expansion coefficient larger than the thermal expansion coefficient of the housing; And restricting means in contact with the circumferential surface of the end surface flange in the direction perpendicular to the rotor axis. The housing and the end surface flange are integrally expanded in the direction perpendicular to the rotor axis by the restricting means.

  As described above, the housing and the end surface flange are integrally expanded by the restricting means, so that the positional relationship between the end surface flange and the housing is not shifted, and even if the end surface flange and the housing are repeatedly expanded and contracted, they are formed on the rotor. The tooth portion protruding radially outward does not contact the housing.

Here, the restricting means is a restricting plate in contact with a rotor shaft perpendicular direction peripheral surface of the housing and an end surface flange of the rotor shaft perpendicular direction, and the restricting plate is fixed to the housing by a fixing means. Is desirable.
Preferably, the restricting means is a protrusion protruding in the axial direction of the housing, and a circumferential surface of the protrusion in a direction perpendicular to the rotor axis is in contact with a circumferential surface of the end flange in the direction perpendicular to the rotor axis. As described above, the restricting means may be provided integrally with the housing.

  The fixing means includes a through hole for inserting a bolt formed in the restriction plate and a screw hole formed in the housing, and the bolt is screwed into the screw hole from a direction perpendicular to the rotor axis. Therefore, it is desirable to fix the restriction plate to the housing. Thus, since the bolt can be screwed from the direction perpendicular to the rotor axis, the workability is good and the restriction plate can be easily attached.

Furthermore, since the cross section of the restriction plate is formed in an L-shape and is formed by the restriction plate protrusion, a shim ring is interposed in the space, and the restriction plate is circumferentially disposed in the direction perpendicular to the rotor axis of the housing via the shim ring. It is desirable that the protruding portion of the regulating plate is in contact with the circumferential surface of the end surface flange in the direction perpendicular to the rotor axis without being in pressure contact.
In this way, the restriction plate contacts the rotor shaft perpendicular direction circumferential surface of the housing via the shim ring, and the projecting portion of the restriction plate contacts the rotor shaft perpendicular direction circumferential surface of the end surface flange without being in pressure contact. The housing and the end flange can be in a state where no compressive force or tensile force is applied.

  ADVANTAGE OF THE INVENTION According to this invention, even if an end surface flange and a housing repeat thermal expansion and contraction, the tooth | gear part which protrudes to the radial direction outward formed in the rotor can obtain the perfect vacuum pump which contacts a housing. .

  An embodiment of the present invention will be described with reference to FIGS. 1 is a schematic sectional view of one embodiment, FIG. 2 is a plan view of a vacuum pump according to the embodiment shown in FIG. 1, and FIG. 3 is an upper portion of the vacuum pump according to the embodiment shown in FIG. 4 is a top right side view of the vacuum pump according to the embodiment shown in FIG. 1, FIG. 5 is a bottom view of the vacuum pump according to the embodiment shown in FIG. 1, and FIG. 1 is a bottom right side view of the vacuum pump according to the embodiment shown in FIG. 1, FIG. 7 is a bottom left side view of the vacuum pump according to the embodiment shown in FIG. 1, and FIG. It is a principal part enlarged view of a form.

  As shown in FIG. 1, the vacuum pump 1 includes a housing 4 having an intake port 2 and an exhaust port 3 connected to an exhaust pipe connected to a reaction chamber, similarly to a conventional vacuum pump. A pair of screw rotors 5 and 6 are accommodated in the housing 4 in parallel so as to mesh with each other in a non-contact meshing state with a predetermined clearance (a minute gap).

  Further, an upper end flange 7 and a lower end flange 8 are attached to the upper and lower ends of the housing 4 to seal the inside of the vacuum pump in which the pair of screw rotors 5 and 6 are accommodated. The housing 4 is made of a material having a smaller coefficient of thermal expansion than the upper end surface flange 7 and the lower end surface flange 8.

  Although not shown, a bearing and a seal member for sealing the shaft hole are provided between the housing 4 and the pair of screw rotors 5 and 6 as in the case of a conventional vacuum pump. Further, although not shown, a synchronous gear integrally attached to the screw rotors 5 and 6 is provided, and one end of the screw rotor 5 is provided with driving means such as a motor.

  The pair of screw rotors 5 and 6 have a predetermined clearance with respect to the inner wall surface 4 a of the housing 4, for example, an outer diameter and an axial length that separate a gap of several tens to several hundreds of microns. . A plurality of spiral working chambers are formed which are partitioned by the meshing portions of the housing 4 and the pair of screw rotors 5 and 6, and the working chambers move in the axial direction of the rotating shaft by the rotation of the screw rotors 5 and 6. Is configured to do.

Further, as shown in FIG. 1, restricting plates 9, 10, 11, and 12 that prevent the housing 4, the upper end surface flange 7, and the lower end surface flange 8 from being positioned are provided. The restricting plates 9, 10, 11, 12 are attached to the housing 4 by bolts 20.
As shown in FIGS. 1 to 4, the restriction plates 9 and 10 are attached to the upper portion of the housing 4 by bolts 20 so as to face each other. Here, although the restriction plate 9 is formed in a rectangular plate shape, the restriction plate 10 is formed in a gate shape straddling the intake port 2.

  Similarly, as shown in FIGS. 1 and 5 to 7, the restriction plates 11 and 12 are attached to the lower portion of the housing 4 by bolts 20 so as to face each other. Here, although the restriction plate 12 is formed in a rectangular plate shape, the restriction plate 11 is formed in a gate shape straddling the intake port 3.

  As shown in FIG. 2, the position of the upper end surface flange 7 and the housing 4 is regulated by a reference pin 21 and fixed by a bolt 22. Similarly, as shown in FIG. 5, the lower end flange 8 and the housing 4 are regulated by a reference pin 23 and fixed by a bolt 24.

Furthermore, the mounting structure of the restriction plates 9, 10, 11, 12 will be described with reference to FIG. FIG. 8 is a view showing the restricting plate 9. Since the mounting structure of the other restricting plates 10, 11, and 12 is the same as that of the restricting plate 9, the restricting plate will be described in the following description. 9 will be described as an example.
As shown in FIG. 8, the restriction plate 9 is in contact with the outer peripheral surface of the housing 4 in the direction perpendicular to the rotor axis and the outer peripheral surface of the upper end surface flange 7 in the direction perpendicular to the rotor axis. The bolt 20 for fixing the restriction plate 9 is inserted through the through hole 9a formed in the restriction plate 9 from the direction perpendicular to the rotor axis and screwed into the screw hole 4b formed in the housing 4 from the direction perpendicular to the rotor axis. ing.
Thus, since the bolt 20 can be attached from the direction perpendicular to the rotor axis, workability is good.

The restriction plate 9 has an L-shaped cross section, and the protruding portion 9 b is in contact with the peripheral surface of the end surface flange 7. A shim ring 30 is interposed in the space 9c formed by the protruding portion.
The shim ring 30 is an adjustment member for attaching the restricting plate 9 so that the protruding portion 9b of the restricting plate 9 is in contact with the outer peripheral surface of the end surface flange 7 in a state where the pressing force is zero.

In order to attach the shim ring 30, first, the shim ring 30 having a thickness not less than the depth of the space portion 9 c is disposed in the space portion 9 c, and the restriction plate 9 is attached to the outer peripheral surface of the housing 4 by the bolt 20. Install.
Next, the width dimension of the gap generated between the outer peripheral surface of the end surface flange 7 and the protruding portion 9b from which the restriction plate 9 protrudes is measured.
Then, the width dimension of the gap is subtracted from the thickness dimension of the shim ring 30 to determine the thickness of the shim ring 30 to be actually arranged.

  The shim ring 30 having the thickness dimension determined in this manner is accommodated in the space portion 9 c, and the restriction plate 9 is attached to the outer peripheral surface of the housing 4 by the bolt 20. At this time, when the shim ring 30 is housed in the space 9c without rattling by the bolt 20, the protruding portion 9b of the restricting plate 9 has substantially zero pressure contact force with respect to the circumferential surface of the end flange in the direction perpendicular to the rotor axis. Will be contacted in the state of.

In the vacuum pump configured as described above, when the screw rotors 5 and 6 are rotated by driving means such as a motor, the work chamber partitioned by the meshing portion of the housing 4 and the screw rotors 5 and 6 is formed in the intake port 2. It moves from the side to the exhaust port 3 side.
As a result, the gas (gas) in the working chamber sucked from the intake port 2 is transferred to the exhaust port 3 side and exhausted from the vacuum pump 1.

At this time, the vacuum pump 1 becomes hot due to the compression heat, but the thermal expansion coefficient of the material of the end surface flanges 7 and 8 is larger than that of the material of the housing 4 that covers the screw rotors 5 and 6 and the rotor. Therefore, even if the temperature rise of the upper end face flange 7 and the lower end face flange 8 is smaller than the temperature rise of the screw rotors 5, 6 and the housing 4, the upper end face flange 7 and the lower end face flange 8 expand greatly.
However, the expansion of the end surface flanges 7 and 8 is restricted by the restriction plates 9, 10, 11, and 12, and expands in the direction perpendicular to the rotor axis together with the housing 4. In this expanded state at a high temperature, the upper end surface flange 7 and the lower end surface flange 8 receive a compressive force and the housing 4 receives a tensile force by the restriction plates 9, 10, 11, and 12.

When the operation of the vacuum pump is completed and the upper end surface flange 7, the lower end surface flange 8, and the housing 4 are cooled, the compressive force of the upper end surface flange 7 and the lower end surface flange 8 and the tensile force of the housing are gradually weakened. The upper end surface flange 7, the lower end surface flange 8 and the housing 4 contract and return to the initial state.
As described above, the upper end surface flange 7 and the lower end surface flange 8 and the housing 4 are expanded without being separated from each other, so that the positional relationship between the upper end surface flange 7 and the lower end surface flange 8 and the housing 4 is not shifted. The adverse effect that the screw rotors 5 and 6 housed in the housing 4 come into contact with the housing 4 during contraction can be prevented.

  In the above-described embodiment, the case where the regulating plate which is a separate member from the housing is used has been described. However, a protruding portion may be formed so as to protrude in the rotor axial direction of the housing and used as the regulating plate. That is, even if the circumferential surface in the direction perpendicular to the rotor axis of the protrusion formed integrally with the housing is in contact with the circumferential surface in the direction perpendicular to the rotor axis of the end flange, the same effect as in the above embodiment can be obtained. be able to.

  The present invention can be suitably used for a vacuum pump that compresses and discharges gas sucked into a housing covering both rotors by rotation of a pair of rotors having teeth projecting radially outward. The pump can be suitably used, for example, in the electronic component manufacturing field and the semiconductor manufacturing field.

FIG. 1 is a schematic sectional view of an embodiment according to the present invention. FIG. 2 is a plan view of the vacuum pump according to the embodiment shown in FIG. FIG. 3 is an upper left side view of the vacuum pump according to the embodiment shown in FIG. FIG. 4 is an upper right side view of the vacuum pump according to the embodiment shown in FIG. FIG. 5 is a bottom view of the vacuum pump according to the embodiment shown in FIG. 1. 6 is a bottom right side view of the vacuum pump according to the embodiment shown in FIG. 7 is a bottom left side view of the vacuum pump according to the embodiment shown in FIG. FIG. 8 is an enlarged view of a main part of the embodiment shown in FIG. FIG. 9 is a sectional view of a conventional vacuum pump. FIG. 10 is a schematic diagram for explaining the problem of the conventional vacuum pump.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum pump 2 Intake port 3 Exhaust port 4 Housing 5 Screw rotor 6 Screw rotor 7 Upper end surface flange 8 Lower end surface flange 9 Restriction plate 10 Restriction plate 11 Restriction plate 12 Restriction plate 20 Bolt 30 Shim ring

Claims (5)

A vacuum pump that compresses and discharges gas sucked into a housing that covers both rotors by rotation of a pair of rotors having teeth that project radially outward.
An end surface flange provided at an end portion of the housing and formed of a material having a thermal expansion coefficient larger than that of the housing, and a restriction provided on the housing and in contact with a circumferential surface of the end surface flange in a direction perpendicular to the rotor axis Means and
The vacuum pump characterized in that the housing and the end surface flange are integrally expanded in a direction perpendicular to the rotor axis by the regulating means. The restricting means is a restricting plate in contact with the rotor shaft perpendicular direction circumferential surface of the housing and the rotor shaft perpendicular direction circumferential surface of the end surface flange,
The vacuum pump according to claim 1, wherein the restriction plate is fixed to the housing by a fixing means. The restricting means is a protrusion protruding in the rotor axial direction of the housing,
2. The vacuum pump according to claim 1, wherein a circumferential surface of the protrusion in a direction perpendicular to the rotor axis is in contact with a circumferential surface of the end surface flange in the direction perpendicular to the rotor axis. The fixing means includes a through hole for inserting a bolt formed in the restriction plate, and a screw hole formed in the housing.
3. The vacuum pump according to claim 2, wherein the restriction plate is fixed to the housing by screwing the bolt into the screw hole from a direction perpendicular to the rotor axis. A cross section of the restriction plate is formed in an L shape, and a shim ring is interposed in a space formed by the restriction plate protrusion.
The said restricting plate is in contact with the rotor shaft perpendicular direction circumferential surface of the housing through a shim ring, and the protruding portion of the restricting plate is in contact with the rotor shaft perpendicular direction circumferential surface of the end flange in a state where it is not pressed. The vacuum pump according to claim 2 or 4.

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