JPS63277885A - Oil-free screw type vacuum pump - Google Patents

Abstract

PURPOSE:To eliminate the leakage of air, by driving a rotor through a rotor shaft in a delivery port side and using grease of vapor pressure lower than the desired vacuum degree to reach serving as the lubricant for a rotor shaft bearing in a suction port side. CONSTITUTION:Both rotors 3, mounting a synchronous gear 7 to each shaft end part in the side of a delivery port 6 and meshing one of the gears with a speed increasing gear 9 mounted to a driving shaft 8, are driven in the delivery side. Grease 10 of vapor pressure lower than the desired vacuum degree to reach is sealed for lubricating a bearing 1 in the side of a suction port 5, and the bearing 1 is provided in a suction flow path 11. Accordingly, the leakage of air from a bearing shaft sealed part in the side of the suction port can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to an oil-free screw type vacuum system that does not inject lubricating oil into the gas suction part, especially for screw type vacuum devices used in vacuum equipment, vacuum packaging, semiconductor manufacturing processes, etc. It concerns pumps.

(Prior Art) An oil-free screw type vacuum pump as shown in FIG. 9 is conventionally known, and includes a pair of male and female screw rotors (hereinafter referred to as rotors) that mesh with each other and are rotatably supported on both sides by bearings 1 and 2. 3 is housed in a rotor chamber in a casing 4, with one side opening to the suction port 5 and the other side opening to the discharge port 6. Further, a synchronizing gear 7 is attached to each shaft end on the suction port 5 side of both rotors 3, and both gears are meshed with each other. It's a combination of.

Then, the rotation of the drive shaft 8 is transmitted to the synchronous gear 7 at increased speed,
The synchronous gear 7 rotates both rotors 3 synchronously in opposite directions without contacting each other, keeping a slight gap between them, and after increasing the pressure of the gas sucked in from the suction port 5, the gas is transferred to the discharge port 6.
It is designed to discharge to.

(Problems to be Solved by the Invention) Generally, the most important value indicating the performance of a vacuum pump is the ultimate vacuum. This ultimate degree of vacuum is the 9th degree above.
In the example shown in the figure, the opening on the side of the suction port 5 is completely closed,
This refers to the degree of vacuum that can ultimately be reached when the vacuum pump is operated.

However, in a vacuum pump with the above configuration, each gear,
The bearing is lubricated with lubricating oil, and while the lubricating oil is accompanied by air, the suction port 5 is in a vacuum state, while the discharge port 6 and the gear chamber 12 are at atmospheric pressure.

For this reason, when the pump is operated, the pressure on the suction port 5 side decreases, and air leaks from the shaft seal 13 on the suction port 5 side as shown by the broken arrow a. There is a tendency for air leakage and return from the discharge port 6 side to the suction port 5 side between the rotor teeth to increase, and as a result, the ultimate degree of vacuum deteriorates. In particular, the suction port 5 is 10-1
When the vacuum state is ~1O-3T orr, atmospheric pressure (7
When air of 60 Torr) leaks in, the pressure is about 10 Torr in the suction state.
Expands to 5-10' times its volume. For this reason, there is a problem in that even if suction is performed on the rotor side, the suction cannot be completed, resulting in a decrease in the ultimate degree of vacuum.

The present invention aims to eliminate air leakage from the shaft seal portion 13 of the two types of air pockets.

(Means for Solving the Problems) In order to solve the above conventional problems, the present invention provides a pair of male and female screw rotors that are rotatably supported through appropriate bearings and mesh with each other, one of which is connected to the suction port. In an oil-free screw type vacuum pump housed in a rotor chamber with the other side open to the discharge port, both rotors are driven by the rotor shaft on the discharge port side, and the lubricant in the rotor shaft bearing on the suction port side is pumped to the desired ultimate vacuum. Formed as a grease with a vapor pressure below

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

1 and 2 show an oil-free screw vacuum pump according to a first embodiment of the present invention.

This vacuum pump has a pair of male and female rotors 3 rotatably supported by bearings 1 and 2 on both sides and meshing with each other in a rotor chamber inside a casing 4, one opening into a suction port 5 and the other opening into a discharge port 6. It is stored in.

However, in this embodiment, a synchronizing gear 7 is attached to each shaft end on the discharge port 6 side of both rotors 3, and both gears are meshed with each other.
The two rotors 3 are meshed with each other to form a discharge side drive. In this way, by providing the part where the driving force is introduced from the outside to the sleeve of the rotor 3, which would cause air leakage, on the discharge port 6 side, there is a structure that completely eliminates the gap leading to the atmosphere in the bearing 1 part on the suction port 5 side. It becomes.

In addition, in this embodiment, the bearing 1 on the side of the suction port 5 is provided with a steam pressure lower than the desired ultimate vacuum for lubrication, for example, when the ultimate vacuum is desired to be 10-3 Torr, a steam pressure lower than this is applied. Grease 10 is sealed and the bearing 1 is provided in the suction passage ll, and the surrounding airflow cools the bearing 1 portion, that is, the grease 10, and the grease I
Efforts are being made to prevent O deterioration.

In this way, as the lubricant for the bearing l on the side of the suction port 5, the grease IO, which can maintain a constant shape in a fixed position for a long time, is used to prevent air leakage.

That is, since it is a liquid, it must be used in a constantly flowing state and must be supplied from the outside, thus eliminating the use of lubricating oil that is likely to be accompanied by air.

The bearing 2, the synchronizing gear 7, and the speed increasing gear 9 on the side of the discharge port 6 are lubricated by, for example, guiding upwards lubricating oil stored in the lower part of the gear chamber 12 by an appropriate method and spraying the lubricating oil. Oil contains air. However, since both the discharge port 6 and the gear chamber 12 are at atmospheric pressure, it is not a problem that the air mixed in the lubricating oil leaks out to the opposite side through the bearing 2.

FIG. 3 shows a second embodiment of the present invention, which is common to the first embodiment in that it is driven on the discharge side and that the bearing on the suction port side is filled with the above-mentioned predetermined grease, and the parts that correspond to each other are the same as the first embodiment. The same reference numerals are given to the same reference numerals, and the explanation thereof will be omitted.

However, unlike the first embodiment, this embodiment is a high-frequency flange motor (a motor that rotates by applying a high-frequency voltage) in which the rotor 3 is arranged vertically and the rotor 16 is directly arranged below without using a gear. ) It has a vertical structure directly connected to the output shaft I8 of the motor casing 17, and the motor casing 19 is also used as a ura tank, and the lower part thereof is formed to store lubricating oil. That is, as shown by the broken line arrow C, the lubricating oil supplied to the bearing 2 of the rotor shaft 16 is guided from between the rotor and stator of the motor 17 and from the hole penetrating the stator to the lower oil reservoir, and 1
7 is also cooled.

Further, the entire device is made smaller by not having any gears interposed between the rotor shaft 16 and the output shaft 18 of the motor 17, and by having the vertical motor casing 19 also used as an oil tank.

In addition, 20.21 in FIG. 3 indicates a water cooling jacket for the pump body and the motor.

FIG. 4 shows a third embodiment of the present invention, which is different from the second embodiment except for the connection part between the rotor shaft 16 and the output shaft 18 of the motor 17 and the support part for the output shaft 18. are substantially the same.

That is, in this third embodiment, one rotor shaft 16 has a shaft-side spline 24 and the output shaft 18 has a boss-side spline 24.
5 and are fitted together so that they can rotate together without restricting movement in the axial direction. Also,
Since the output shaft 18 can be freely separated from the rotor shaft 16 in the axial direction, that is, in the vertical direction, bearings 26 and 27 are independently provided on the motor 17 side to rotatably support the output shaft 18 in a fixed position. It is.

In this manner, the rotor shaft 16 and the output shaft 18 are spline-fitted so that they can be freely separated, thereby facilitating handling during manufacturing, maintenance, and the like.

FIG. 5 shows a fourth embodiment of the present invention, which is substantially the same as the third embodiment except for the orientation of the rotor 3 and motor 17 and the position of the oil tank portion.

That is, in this fourth embodiment, the rotor 3 and the motor 17 are arranged laterally to form a horizontal structure, and an oil tank 30 is provided in the middle between them. This is formed by attaching the casing part of No. 3 and the motor I7.

In each of the above embodiments, the suction port 5 is provided in the suction flow path ll.
Although the embodiment in which the side bearing I is arranged is shown, the present invention is not limited to this, and an embodiment having a different Φ structure will be shown below.

6 and 7 show a fifth embodiment of the present invention, which differs from the first embodiment in that the suction port 5. Suction channel l! Bearing 1 on the suction port 5 side
The bearing 1 is substantially the same except that it is provided separately from the bearing 1 and that the bearing 1 is water-cooled.

That is, in this fifth embodiment, a suction port 5 and a suction passage 11 are formed in the upper part of FIG. 6, which is separated from the bearing 1 by a casing 4, and a water cooling jacket 31 is provided around the bearing I. Provision and bearing 1. This is to cool the grease IO.

In addition, in all of the above embodiments, the replacement of the grease 10 is
Although the cover (not shown) of the casing 4 on the bearing side is removed when the pump is stopped, the present invention is not limited to this.

For example, FIG. 8 shows a sixth embodiment of the present invention that adopts a grease exchange method other than the above. Except for this point, everything else is substantially the same. Therefore, in the vacuum pump according to the sixth embodiment, new grease can be supplied from the grease injection hole 34 and old grease can be discharged from the grease discharge hole 35 without removing the cover of the casing 4 as described above. Moreover, the grease can be replaced at any time.

(Effects of the Invention) As is clear from the above description, according to the present invention, both rotors are driven by the rotor shaft on the discharge port side, and the lubricant in the rotor shaft bearing on the suction port side is applied to the desired ultimate vacuum level. Formed as a lower vapor pressure grease.

For this reason, as confirmed by actual machine tests,
The suction port portion is isolated from the outside, and there is no leakage of air particularly from the bearing shaft sealing portion on the suction port side, resulting in the effect that the ultimate degree of vacuum can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an oil-free screw vacuum pump according to a first embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of the suction port side bearing portion of FIG. 1, FIGS. 3 to 6, FIG. 8 is a sectional view of oil-free screw vacuum pumps according to second to sixth embodiments of the present invention, FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6, and FIG. 9 is a sectional view of a conventional oil-free screw FIG. 2 is a sectional view of a vacuum pump. 1.2...Bearing, 3-...Rotor (screw rotor)
, 5... Suction port, 6... Discharge port, lO... Grease. Patent Applicant: Kobe Steel, Ltd. Agent: Patent Attorney: Aohaku Ao and 2 others Figure 3 Figure 4 Figure 6 Figure 7171

Claims (1)

[Claims] (1) In an oil-free screw type vacuum pump, a pair of male and female screw rotors that mesh with each other and are rotatably supported via appropriate bearings are housed in a rotor chamber with one opening at the suction port and the other opening at the discharge port. An oil-free screw vacuum pump characterized in that the rotor is driven by a rotor shaft on the discharge port side, and the lubricant for the rotor shaft bearing on the suction port side is grease with a vapor pressure lower than the desired ultimate vacuum degree.