JPH06159273A - Vacuum pump - Google Patents

Abstract

PURPOSE:To prevent interference and to enhance the vacuum function by setting at least one of axial gaps between the outer surface of a rotor and the inner surface of a housing, which face an intake port and a discharge port, so that the outer side thereof is larger than the inner side of as viewed radially of the rotor. CONSTITUTION:When intake and discharge side rotors 2, 3 are rotated relative to each other in a housing 20, gas is sucked through an intake port 25, and is then discharged from the discharge port 26 after being compressed between the body parts 4, 5 of both rotors 2, 3 and the housing 20. In this case, the axial gap delta1, for example, between the outer surface 2g of the intake side rotor 2 which faces the intake port 25, and the inner surface 20g of the housing 20 which faces the outer surface 2g, is set so that the outside thereof is larger than the inside thereof as viewed radially of the intake side rotor 2. Accordingly, a height difference part 30 is formed on the inner surface 20g of the housing 20, and the height difference part 30 is located radially outer than that of the outer peripheral surface 4 of the body part 4 of the intake side rotor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump for compressing and discharging gas sucked into a housing covering both rotors by rotating a pair of rotors having tooth portions projecting radially outward from a main body. Regarding

[0002]

2. Description of the Related Art An intake side rotor, an exhaust side rotor, and a housing that covers both rotors are provided. Each rotor has a main body having an outer peripheral surface along the circumferential direction, and a radial direction outward from the main body. An intake port and an exhaust port, which have a protruding tooth portion and are located radially inward of the outer peripheral surface of the main body portion along the circumferential direction of the main body portion, are formed in the housing by the rotation of both rotors from the intake port. 2. Description of the Related Art A vacuum pump that compresses a gas sucked therein and discharges it from an exhaust port has been conventionally used.

In order to improve the vacuum performance of such a vacuum pump, an axial gap between the outer surface of the rotor and the inner surface of the housing, a gap between the outer peripheral surfaces of the main bodies of both rotors, and a tooth portion. It is necessary to reduce the gap between the inside and the outside of the housing.

[0004]

However, the housing and the rotor shaft are thermally deformed by the heat generated by the compression of the gas. In addition, there are assembly errors and processing errors of parts. These gaps are required to prevent interference between the rotors or the rotor and the housing due to such thermal deformation or error. Further, the gap required for the error can be reduced by improving the processing accuracy and the assembly accuracy, but the processing cost and the man-hour increase. Also, the gap required for thermal deformation cannot be eliminated.

In particular, it has been necessary to make the axial clearance between the outer surface of the rotor and the inner surface of the housing larger than the other clearances. That is, the rotor axially moves due to the thermal deformation of the rotor shaft, but the thermal deformation of the rotor itself is small. Therefore, the axial movement amount of the outer surface of the rotor is substantially equal between the radially inner side and the outer side. . On the other hand, the housing has a small amount of thermal deformation on the outside that is in contact with the outside air and a large amount of thermal deformation on the inside, so that the housing does not undergo uniform thermal deformation and thus distortion. Therefore, the axial gap between the inner side surface of the housing and the outer side surface of the rotor varies with the temperature change, and the variation amount is larger on the radially outer side than on the radially inner side of the rotor. Further, due to an error in assembling the rotor with respect to the rotor shaft, the outer surface of the rotor and the inner surface of the housing are relatively inclined.
Therefore, the axial clearance between the inner surface of the housing and the outer surface of the rotor fluctuates depending on the assembly error of the rotor with respect to the rotor shaft, and the fluctuation amount is more radially outward than the radially inner side of the rotor. Is bigger.

That is, the axial clearance between the outer surface of the rotor and the inner surface of the housing fluctuates according to temperature and assembly error, and the fluctuation amount becomes maximum at the radial outer end of the rotor, that is, the tip of the tooth portion. . Therefore, the axial gap between the outer surface of the rotor and the inner surface of the housing is set to be larger than the maximum fluctuation amount, thereby preventing interference between the rotor and the housing.

However, such a large axial clearance between the outer surface of the rotor and the inner surface of the housing hinders improved vacuum performance. In particular, when reducing the diameter of the rotor shaft or the thickness of the rotor to reduce the size and weight of the pump, the relative inclination between the outer surface of the rotor and the inner surface of the housing tends to become large due to assembly errors. The influence of the directional gap on the vacuum performance increases.

It is an object of the present invention to provide a vacuum pump which can solve the above problems of the prior art.

[0009]

SUMMARY OF THE INVENTION The present invention comprises an intake side rotor, an exhaust side rotor, and a housing that covers both rotors, and each rotor has a main body portion having an outer peripheral surface along the circumferential direction, and The housing has a tooth portion that projects radially outward from the main body portion, and the housing is provided with an intake port and an exhaust port that are located radially inward of the outer circumferential surface of the main body portion along the circumferential direction. In a vacuum pump that compresses the gas sucked into the housing from the intake port by the rotation of the rotor and discharges it from the exhaust port, the outer surface of the rotor facing at least one of the intake port and the exhaust port and the inner surface of the housing. A step is formed on at least one of the outer surface of the rotor and the inner surface of the housing so that the axial gap between them is set larger on the outer side in the radial direction than on the inner side in the radial direction. Is the circumference of the body It relates outer peripheral surface in the radial direction along the direction in which located in the same position or radially outward.

[0010]

Since the intake port and the exhaust port formed in the housing are located radially inward of the outer peripheral surface of the main body portion along the circumferential direction, the axial gap between the intake port and the exhaust port is The vacuum performance is greatly affected by the area radially inward of the body, and the area radially outward of the body and the axial gap on the opposite side of the intake and exhaust ports affect vacuum performance. Doesn't have much impact.

Therefore, the axial gap facing at least one of the intake port and the exhaust port is formed by the step formed at the same position in the circumferential direction of the main body as the circumferential direction or at the same position in the radial direction or at the radial outside. By setting the outer side in the radial direction to be larger than the inner side in the radial direction, it is possible to prevent interference between the rotor and the housing due to temperature or an assembly error, and improve the performance of the vacuum pump.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

The four-stage dry vacuum pump 1 shown in FIG.
It includes four sets of intake side rotors 2, four sets of exhaust side rotors 3, and a housing 20 that covers these rotors 2 and 3.

As shown in FIGS. 1 and 3, each of the rotors 2 and 3 has a body portion 4 and 5 having outer circumferential surfaces 4a and 5a along the circumferential direction, and radially outward from the body portions 4 and 5. Claw-shaped tooth portions 6 and 7 projecting in the direction of a tooth, and parts of the body portions 4 and 5 adjacent to the tooth portions 6 and 7 are cutout portions 4b and 5b. One rotor shaft 8, 9 is press-fitted into each intake side rotor 2 and each exhaust side rotor 3. Both ends of each rotor shaft 8, 9 are supported by a housing 20 via bearings 10, 11, 12. Each rotor shaft 8, 9
Gears 13 and 14 meshing with each other are attached to one end of the rotor shaft. The rotor shafts 8 and 9 are rotationally driven by a drive unit (not shown) via the gears 13 and 14.

The housing 20 supports the one end of the rotor shafts 8 and 9 and the first member 20a on the rightmost side in FIG.
And a second member 20b adjacent to the first member 20a,
The third member 20c adjacent to the second member 20b, the fourth member 20d adjacent to the third member 20c, and the fourth member 20c
And a fifth member 20e adjacent to the member 20d, and each member 20a, 20b, 20c, 20d, 20e is a bolt 21.
Are connected by. In the second member 20b, a partition wall 20b 'is formed between the intake / exhaust rotors 2 and 3 on the rightmost side in the drawing and the intake / exhaust rotors 2 and 3 which are second from the right, and the third partition wall 20b' is formed.
The member 20c has a second intake / exhaust rotor 2 from the right in the drawing,
A partition wall 20c 'is formed between the third intake air exhaust rotor 2 and the third intake air exhaust rotor 2 from the right, and the fourth intake member 20d is provided on the fourth member 20d of the partition wall 20d. A partition wall 20d 'is formed between the intake and exhaust rotors 2 and 3. Further, the first member 20a and the fifth member 20e are connected to the rotor shaft 8,
Covers 22 and 23 for covering the shaft end of 9 are attached.

The first to fourth members 20a, 20b, 20
c and 20d, the intake port 25 located radially inward of the outer peripheral surface 4a of the main body 4 of the intake side rotor 2 along the circumferential direction.
Are formed, and the second to fifth members 20b, 20c, 20 thereof are formed.
At d and 20e, the exhaust port 26 located radially inward of the outer peripheral surface 5a of the main body 5 of the exhaust side rotor 3 along the circumferential direction.
Are formed. The intake port 25 formed in the first member 20a is connected to the intake air intake passage 2 formed in the first member 20a.
7 and the exhaust port 2 formed in the fifth member 20e thereof
6 communicates with the exhaust gas discharge passage 28 formed in the fifth member 20e. In addition, the intake port 25 formed in the second member 20b
And the exhaust port 26 communicate with each other through a communication passage (not shown), and the intake port 25 and the exhaust port 26 formed in the third member 20c communicate with each other through a communication passage (not shown) and the fourth member 20d. The formed intake port 25 and exhaust port 26 communicate with each other through a communication passage (not shown).

As a result, as the intake side rotor 2 and the exhaust side rotor 3 rotate, the gas introduced from the intake introduction passage 27 is first introduced from the intake port 25 on the rightmost side in FIG. Is introduced into the housing 20 through the cutout portion 4b, and compressed between the main body portions 4 and 5 of the intake and exhaust rotors 2 and 3 and the inner and outer circumferences of the housing 20, and extends through the cutout portion 5b of the exhaust side rotor 3 to the far right in the figure. Is discharged from the exhaust port 26. Next, the gas is the second intake port 2 from the right in the figure.
5 through the notch 4b of the intake side rotor 2 to the housing 2
0, and compressed in the same way. After this is repeated, the gas is discharged from the leftmost exhaust port 26 in the figure through the exhaust discharge path 28.

As shown in (1) of FIG. 4, between the outer side surface 2g of each intake side rotor 2 facing the intake port 25 and the inner side surface 20g of the housing 20 facing the outer side surface 2g. The axial clearance δ1 is set larger on the radially outer side of the rotor 2 than on the radially inner side. Due to this setting, a step 30 is formed on the inner side surface 20g of the housing 20, and the step 30 is located radially outward of the outer peripheral surface 4a of the main body 4 of the intake side rotor 2.

Further, the axial gap δ2 between the outer side surface 3h of each exhaust side rotor 3 facing the exhaust port 26 and the inner side surface 20h of the housing 20 facing the outer side surface 3h.
Is set larger on the radially outer side of the rotor 3 than on the radially inner side. Due to this setting, a step 31 is formed on the inner side surface 20h of the housing 20, and the step 31 is located radially outward of the outer peripheral surface 5a of the main body 5 of the exhaust side rotor 3.

When the internal temperature of the housing 20 rises by operating the vacuum pump 1, the rotor shafts 8,
9 is expanded in the axial direction by thermal deformation, whereby the rotors 2 and 3 move in the axial direction. In the above embodiment, the bearings 10 and 11 supporting the rotor shafts 8 and 9 in the fifth member 20e of the housing 20 are used as a reference, and the rotor shafts 8 and 9 are
Extends to the right in the figure. At this time, since the thermal deformation of each of the rotors 2 and 3 is small, the outer surface 2 of each of the rotors 2 and 3 is small.
The axial movement amounts of g, 2h, 3g, and 3h are substantially equal on the radially inner side and the outer side. On the other hand, the housing 20
Since the thermal deformation is small on the outer side in contact with the outside air and the thermal deformation is large on the inner side, it does not undergo uniform thermal deformation and causes distortion.
Therefore, the amount of axial movement of the inner side surfaces 20g and 20h of the housing 20 due to thermal deformation is small on the outer side and large on the inner side. As a result, the axial gaps δ1, δ2 between the inner side surfaces 20g, 20h of the housing 20 and the outer side surfaces 2g, 2h, 3g, 3h of the rotors 2, 3 before the temperature rise shown in (1) of FIG. δ3 and δ4 are as shown in FIG.
(2), the amount of fluctuation is greater on the radially outer side of each rotor 2, 3 than on the radially inner side. In addition, due to an assembly error of the rotors 2 and 3 with respect to the rotor shafts 8 and 9, as shown in (1) and (2) of FIG.
The outer side surfaces 2g, 2h, 3g, 3h of 3 relatively incline.
Therefore, the axial gaps δ1, δ2, δ3, δ4 are
It fluctuates according to the assembly error of the rotors 2 and 3 with respect to the rotor shafts 8 and 9, and the fluctuation amount is larger on the outer side than on the radially inner side of the rotors 2 and 3. As a result, the axial gaps δ1, δ2, δ3, δ4 fluctuate according to the temperature and the assembly error, and the fluctuation amount becomes maximum at the radial outer ends of the rotors 2, 3, that is, the tips of the tooth portions 6, 7.

The axial gap δ1 facing each intake port 25 is set to be larger than the maximum fluctuation amount on the radially outer side of the step 30. Further, the axial gap δ1 is smaller than the maximum variation on the radially inner side of the step 30, and even if there is variation due to temperature or error, the intake rotor 2 and the housing 20 do not interfere with each other. The size is set so that it will not occur.

The axial gap δ2 facing each exhaust port 26 is set to be larger than the maximum fluctuation amount on the radially outer side of the step 31. Further, the axial clearance δ2 is smaller than the maximum variation on the radially inner side of the step 31, and even if there is variation due to temperature or error, the exhaust side rotor 3 and the housing 20 do not interfere with each other. The size is set so that it will not occur.

Further, the axial gap δ3 between the outer side surface 2h of each intake side rotor 2 opposite to the intake port 25 and the inner side surface 20h of the housing 20 facing the outer side surface 2h, and each exhaust gas. The axial gap δ4 between the outer side surface 3g of the side rotor 3 opposite to the exhaust port 26 and the inner side surface 20g of the housing 20 facing the outer side surface 3g is set to be larger than its maximum fluctuation amount. There is. (Note that the gaps in the drawings are larger than the actual gaps for convenience of description.)

According to the above construction, the intake port 25 and the exhaust port 26 formed in the housing 20 are located radially inward of the outer peripheral surfaces 4a, 5a of the body portions 4, 5 along the circumferential direction. In the axial gaps δ1 and δ2 between the intake port 25 and the exhaust port 26, the vacuum performance is greatly affected by the portions radially inward of the outer peripheral surfaces 4a and 5a of the body portions 4 and 5. And the outer peripheral surfaces 4a of the body portions 4 and 5,
A portion radially outward of 5a and the axial gaps δ3 and δ4 on the opposite side of the intake port 25 and the exhaust port 26 do not significantly affect the vacuum performance.

Therefore, the step 3 formed radially outward of the outer peripheral surfaces 4a, 5a of the body portions 4, 5 along the circumferential direction.
By setting the axial gaps δ1 and δ2 facing the intake port 25 and the exhaust port 26 by 0 and 31 to be larger on the radially outer side of the rotors 2 and 3 than on the radially inner side, It is possible to prevent interference between the rotors 2 and 3 and the housing 20 due to an assembly error and improve vacuum performance. Further, since the precision of processing and assembling the pump parts can be set low, the cost can be reduced.

The present invention is not limited to the above embodiment. For example, in the above embodiment, both the axial gaps δ1 and δ2 facing the intake port 25 and the exhaust port 26 are set to be larger on the radially outer side than on the radially inner side, but either one of them is set. Only the axial gap may be set larger on the radially outer side than on the radially inner side. Further, the axial gaps δ3, δ4 on the opposite side of the intake port 25 and the exhaust port 26 may be set to be larger on the radially outer side than on the radially inner side. For example, in the structure of the above embodiment, the exhaust side rotor 3 and the housing 20 do not interfere with each other even if the axial gap δ2 facing the exhaust port 26 fluctuates due to thermal deformation. If the assembling accuracy and the component processing accuracy can be improved, it suffices to set only the axial gap δ1 facing the intake port 25 on the radially outer side to be larger than the radially inner side. Further, in the above embodiment, the housing 2
Although the steps 30 and 31 are formed at 0, as shown in FIG.
Steps 3 are formed on the outer surfaces 2g, 2h, 3g, 3h of the rotors 2, 3.
0 ', 31' may be formed or housing 2
0 and the rotors 2 and 3 may be formed. Further, the steps 30, 31, 30 ', 31' may be formed at the same position in the radial direction as the outer peripheral surfaces 4a, 5a of the body portions 4, 5 along the circumferential direction.

Further, in the above structure, the axial extension of the rotor shaft 9 on the exhaust side in the axial direction due to heat increases the axial gap δ2 itself facing the exhaust port 26, which also reduces the vacuum performance. Therefore, as shown in FIG. 7, a part of the housing 20 facing the outer surface 3h of the exhaust side rotor 3 is a movable portion 20a that is movable in the axial direction.
0a of the driving piezoelectric element 40, the measurement sensor 41 of the axial gap δ2 thereof, and the control device 42 connected to the piezoelectric element 40 and the measurement sensor 41 are provided.
By moving the movable portion 20a in the axial direction by the piezoelectric element 40 according to the change of 2, the expansion of the axial gap δ2 due to the thermal deformation of the rotor shaft 9 may be prevented. The rest of the configuration is the same as that of the above-described embodiment, and the same portions are denoted by the same reference numerals. Alternatively, the exhaust side rotor 3 is attached to the rotor shaft 9 so as to be displaceable in the axial direction, and as shown in FIG.
Spiral grooves 50 are formed on both outer side surfaces 3g and 3h of the rotor, and the rotation of the rotor 3 causes the gas to swirl in the axial gaps δ2 and δ4. By axially moving the rotor 3 in balance with the dynamic pressure, it is possible to prevent the axial gap δ2 from expanding due to thermal deformation of the rotor shaft 9. Alternatively, the exhaust side rotor 3 is attached to the rotor shaft 9 so as to be displaceable in the axial direction, static pressure holding grooves are formed on both outer side surfaces 3g, 3h of the exhaust side rotor 3, and the static pressure holding grooves are fixed from the outside of the housing 20. A gas having a pressure is introduced and held, and the rotor 3 is axially moved by the balance between the static pressure in the one axial gap δ2 and the static pressure in the other axial gap δ4, whereby the rotor shaft 9 is thermally deformed. The axial gap δ2 may be prevented from expanding. In order to prevent the gas introduced into the housing 20 for balancing the static pressure from having a great influence on the vacuum performance, the static pressure holding grooves are provided from the leftmost side and the leftmost side in FIG. It is preferable to stop at the second exhaust side rotor 3.

[0028]

According to the vacuum pump of the present invention, the axial gap required for preventing interference is secured between the outer surface of the rotor and the inner surface of the housing, and the vacuum performance is improved. Further, the processing and assembling accuracy can be set low, so that the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a side sectional view of a main part of a vacuum pump according to an embodiment of the present invention.

FIG. 2 is a front sectional view of a vacuum pump according to an embodiment of the present invention.

FIG. 3 is a perspective view for explaining the configuration of a vacuum pump according to an embodiment of the present invention.

FIG. 4 (1) is an explanatory view of the operation of the vacuum pump of the embodiment of the present invention before the temperature is raised, and (2) is an explanatory view of the operation after the temperature is raised.

5 (1) and (2) are views showing the influence of a rotor mounting error on a rotor shaft in a vacuum pump according to an embodiment of the present invention.

FIG. 6 (1) is a side view of a rotor of a modified example of the present invention,
(2) is a front view

FIG. 7 is a partial cross-sectional view of a vacuum pump of a modified example of the present invention.

FIG. 8 is a side view of a rotor of a modified example of the invention.

[Explanation of symbols]

 2 Intake side rotor 2g Outer side surface 3 Exhaust side rotor 3h Outer side surface 4, 5 Main body section 4a, 5a Outer peripheral surface 6, 7 Tooth section 20 Housing 20g, 20h Inner side surface 25 Inlet port 26 Exhaust port 30, 31 Step δ1, δ2 Shaft Direction gap

Claims (1)

[Claims] 1. An intake side rotor, an exhaust side rotor, and a housing that covers both rotors, each rotor having a main body having an outer peripheral surface along the circumferential direction, and a radial direction outward from the main body. An intake port and an exhaust port, which have a protruding tooth portion and are located radially inward of the outer peripheral surface of the main body portion along the circumferential direction of the main body portion, are formed in the housing by the rotation of both rotors from the intake port. In a vacuum pump that compresses the gas sucked into the interior thereof and discharges it from the exhaust opening, the axial gap between the outer surface of the rotor and the inner surface of the housing facing at least one of the intake opening and the exhaust opening is The outer surface of the rotor and the inner surface of the housing are stepped so that they are set larger on the outer side in the radial direction than on the inner side in the radial direction. Along the outer peripheral surface and the radial direction A vacuum pump located at the same position or radially outward.