JPH08270582A - Oil free two-stage vacuum pump - Google Patents

Abstract

PURPOSE: To reduce the heat generation even in low vacuum viscosity range by communicating the discharge space of a pump on preceding stage to the discharge space of a pump through a bypass passage, and providing a pressure control valve which closes at specified pressure or under on the bypass passage. CONSTITUTION: A lap 8 for a rotary scroll compresses air in cooperation with a lap 4 for a fixed scroll on preceding stage, and discharges compressed air from an aperture 2a. On the other hand, a lap 9 for a rotary scroll on rear stage compresses air in cooperation with a lap 5 for a fixed scroll on the rear stage, and discharges compressed air from a discharge port 3b. In this case, an opening 3d is opened as a bypass to connect the discharge space of the pump part on preceding stage with the discharge space of a pump on the rear stage, and a pressure control valve 25 is provided here. The pressure control valve 25 opens and discharges compressed air to the outside, when the pressure of the compressed gas within the sealed space 3g is higher than the outside atmospheric pressure, so that the interior of the pump on the rear stage may not reach the specified temperature or over.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil-free two-stage vacuum pump having a front-stage pump section and a rear-stage pump section, which are connected in series and driven.

2. Description of the Related Art Conventionally, a technique of vacuuming a container is to put food in a polyvinyl bag and evacuate the air to prevent bacteria floating in the air from adhering to prevent food from spoiling. From ordinary life to low temperature technology such as vacuum car, blood collection tube, thermos, or outer wall of container for storing cooling refrigerant for medical, industrial, or experimental purposes to prevent heat conduction due to air convection. Is widely used. The inside of the closed container is evacuated by connecting a vacuum pump to the suction port of the closed container and sucking out air and other gases by the vacuum pump.

In an exhaust system of low vacuum pressure, one oil rotary pump is housed in one container, but in an exhaust system of high vacuum pressure, an oil diffusion pump and an oil rotary pump are combined. A wet-type vacuum pump device by combination is used. However, this device blows out the vapor of the oil that is heated by the heater and evaporated in the boiler,
The gas diffused by this vapor is compressed, further compressed to atmospheric pressure by an oil rotary pump, and discharged to the outside. According to this wet type exhaust system, there is a problem that the oil adhering to the inside of the device is re-evaporated by the oil vapor and flows back into the vacuum container, and since it is cooled using a cold cap, baffle, trap, etc., the configuration is Becomes complicated,
Gases such as chlorine and fluorine react with oil and the oil deteriorates to increase rotation resistance, which reduces capacity and makes maintenance and inspection more troublesome.

Therefore, a dry type is desired, and an oil-free scroll type has recently been attracting attention as a vacuum pump. The oil-free scroll type vacuum pump
A fixed / orbiting scroll type comprising a fixed scroll and an orbiting scroll having a second wrap that can be fitted to the first wrap planted in the fixed scroll, a drive scroll, and a drive scroll and a drive scroll. There is a drive / driven scroll type including a driven scroll having a second wrap that can be fitted in the first wrap.

In the fixed / orbiting scroll type, the volume of the closed space formed between the two wraps can be changed by revolving the orbiting scroll without rotating it. Therefore, the orbiting scroll is revolved around the center of the wrap of the fixed scroll with a constant radius so that the contact point between the wraps forming the closed space functioning as a compression chamber gradually moves toward the center. The gas taken in from the suction port is taken into the closed space formed by both wraps while wrapping around the winding end of the second wrap, and gradually reduces its volume with the orbiting motion of the orbiting scroll, The pressure is increased while moving toward the outside, and is discharged to the outside when the closed space is electrically connected to the discharge port. In addition, the drive / driven scroll type moves toward the center while gradually reducing the volume of the closed space formed by the drive scroll and the driven scroll, while the pressure is increased and the closed space conducts to the discharge port to the outside. It is what is discharged.

Nowadays, along with the demand for high vacuum, it is desired to shorten the working time for obtaining a desired vacuum pressure.
In a vacuum pump with a low compression ratio, it takes time to evacuate, so a vacuum pump with a high compression ratio is desired. In order to obtain a high compression ratio, it is necessary to increase the number of turns of the spiral scroll, but in that case, the outer shape of the scroll becomes large, and the rotation of the scroll due to the deflection of the shaft at high speed rotation, the fixed scroll and the orbit. There are problems such as generation of noise and heat due to uneven contact with the scroll, deterioration of durability, etc.

[0006]

As a solution to this problem, two vacuum pumps with a small number of scroll turns that do not increase the outer size of the scroll are used, and the suction pipe of the latter pump is connected to the discharge pipe of the former pump. A method of driving both pumps can be considered. However, according to this driving method, in the initial stage of starting when the connected closed container is close to atmospheric pressure, the space formed by the scroll has a high pressure due to the high compression ratio, and there is a problem that high heat is generated,
It is necessary to release this high-pressure compressed gas to the outside. As a technique related to this, when the pressure in the first space between the fixed scroll and the orbiting scroll becomes higher than the pressure in the next second space, the pressure is discharged to the second space via the valve means, and the second space is discharged. A device for discharging the gas to the outside when the space communicates with the discharge port communicating with the outside is disclosed in Japanese Patent Laid-Open No. 62-48979 as a load reduction structure at the time of starting.

This related art is related to a discharge port for discharging compressed gas to the outside of a central portion of a fixed scroll end plate, and
A valve chamber is provided in the vicinity of the discharge port, and when gas is taken in from the end of the scroll by the orbiting scroll, a first communication hole communicating with the valve chamber is opened in a first closed space formed by the orbiting scroll and the fixed scroll. At the same time, in the compression step before discharging the compressed gas to the outside and in the second closed space formed by the fixed scroll and the orbiting scroll when discharging the compressed gas from the discharge port to the outside, the discharge port A second communication hole communicating with the valve chamber, a valve means provided at the opening of the first communication hole in the valve chamber, and the pressure in the first closed space is equal to the pressure in the second closed space. If it is larger, the valve means is opened to discharge the gas in the first closed space into the second closed space.

According to the above technique, two vacuum pumps having a small number of scroll turns that do not increase the outer shape of the scroll are used, and the suction pipe of the latter pump is connected to the discharge pipe of the former pump to drive both pumps. Applying to the method, when the valve means is provided in the preceding pump, when the pressure in the first closed space rises above a predetermined value, the valve means opens the first communication hole to compress the first closed space. The gas can be discharged into the second closed space. However, the second sealed space communicates with the discharge port by the swiveling drive of the orbiting scroll, and the discharge port is connected to the suction end of the subsequent pump. Therefore, all the gas compressed by the front stage pump is sent to the rear stage pump, and as in the front stage pump, the space formed by the fixed scroll and the orbiting scroll has a high pressure and a high heat is still generated. The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object thereof is to provide a vacuum pump that reduces heat generation even in a low-vacuum viscous flow region.

[0009]

SUMMARY OF THE INVENTION The present invention provides an oil-free two-stage vacuum pump which comprises a front-stage pump section and a rear-stage pump section, and which connects these pump sections in series to drive them.
The discharge space of the former-stage pump section is communicated with the discharge space of the latter-stage pump via a bypass passage, and a pressure control valve that is closed below a predetermined pressure is provided on the bypass passage.

Further, it is preferable that the front-stage pump and the rear-stage pump are integrally supported on a common rotary shaft, the rotary shaft is connected to a drive source, and they are rotated by the same rotary drive source. Further, a load sealing container is connected to the suction side of the pre-stage pump, and a control means capable of changing the number of rotations according to the degree of vacuum pressure in the sealing container is provided. The control means controls the rotation of the same rotary drive source. It is preferable to make it possible. Further, it is preferable that the front-stage pump and the rear-stage pump are configured to rotate by separate rotary drive sources.

Further, in a combination of a fixed scroll and an orbiting scroll, it is preferable that a bypass hole is provided on the bottom wall of the fixed scroll to form the bypass passage.
In addition, it is a combination of a driving scroll and a driven scroll, and it is preferable that the discharge passages of both pumps are provided with a bypass pipe to be connected to form the bypass passage. Further, it is provided with a front-stage pump section and a rear-stage pump section which are composed of a fixed scroll and an orbiting scroll, and these pump sections are fitted with separate fixed scroll wraps and orbiting scroll wraps, respectively, and are fixed scrolls of the front stage pump. It is preferable that the compressed air is arranged so as to face the orbiting scroll of the rear stage pump so that compressed air can be supplied to the orbiting scroll of the rear stage pump through a discharge port provided in the fixed scroll of the front stage pump.

Further, it is preferable that the compression ratio of the latter-stage pump is set higher than that of the former-stage pump. It is preferable that the maximum gas pocket volume of the latter-stage pump is smaller than the minimum gas pocket volume of the preceding-stage pump. Further, the height of the scroll wrap of the front stage pump and the rear stage pump from the end plate surface is preferably different from that of the front stage pump and the rear stage pump.

[0013]

Since the present invention is an oil-free two-stage vacuum pump configured by connecting a front-stage pump unit and a rear-stage pump unit in series, a high-speed rotation that occurs when the scroll has a small outer diameter and a large diameter is used. In this case, there are no problems such as rotation blur due to deflection of the shaft, uneven contact between the fixed scroll and the orbiting scroll, noise and heat, or deterioration of durability.

Further, since the discharge space of the front-stage pump section communicates with the discharge space of the rear-stage pump via a bypass passage, and a pressure control valve that is closed below a predetermined pressure is provided on the bypass passage. A closed container to be evacuated is connected to the suction end of the pre-stage pump, and since the atmospheric pressure in the closed container is close to the atmospheric pressure in the initial stage of start-up, the suction gas has already become a high pressure in the compression process of the pre-stage pump,
When the pressure exceeds a predetermined pressure, for example, when the external pressure, which is the pressure in the discharge space of the post-stage pump, becomes higher than the external pressure, the pressure control valve is opened, and the high-pressure compressed gas is not sent to the post-stage pump but compressed by the pre-stage pump. Is discharged to the outside. Therefore, since the compressed gas at atmospheric pressure or higher is not sucked into the rear pump and heat is not generated due to excessive compression in the rear pump section, heat is generated due to high pressure, and the durability of the vacuum pump is reduced or seized. It will not be damaged.

When the front and rear pumps are integrally supported on a common rotary shaft, the rotary shaft is connected to a drive source, and is rotated by the same rotary drive source, one drive source is used. Can drive the vacuum pump by
A compact vacuum pump with a small number of parts is provided. Further, a load sealing container is connected to the suction side of the pre-stage pump, and a control means capable of changing the number of rotations according to the degree of vacuum pressure in the sealing container is provided. The control means controls the rotation of the same rotary drive source. If it is configured as possible,
As the pressure of the loading closed container decreases, the number of revolutions of the front-stage pump and the rear-stage pump is increased to increase the number of discharges of the gas in the closed container, and the processing time can be shortened.

When the front-stage pump and the rear-stage pump are rotated by separate rotary drive sources, the optimum load for the compressed gas due to the compression ratio of the front-stage pump and the load of compressed gas due to the compression ratio of the rear-stage pump is optimal. The rotary drive source can be applied to each pump, and when the compressed gas pressure of the preceding pump exceeds atmospheric pressure in the initial stage of suction of the load closed container, that is, the degree of vacuum in the closed container is low. In the viscous flow region, only the pump in the front stage can be driven and exhausted to the outside via the exhaust valve, and the compressed gas pressure of the front stage pump can be rotationally driven after the compressed gas pressure falls below atmospheric pressure, which is economical. You can drive. Further, in this case, the orbiting scrolls of the front and rear pumps can be driven from both sides of the pump body, and compared with the case where the orbiting scrolls of the front and rear pumps are rotationally driven by the same drive source, The position at which the orbiting scroll of the extending rotary shaft is fixed is shorter than the position of the rotary drive source, and the amount of blurring in rotation due to warping of the shaft is reduced accordingly.

Further, in the case of a combination of a fixed scroll and an orbiting scroll, and when the bypass passage is formed by providing a bypass hole on the bottom wall of the fixed scroll, only the hole is formed in the fixed scroll which is not rotationally driven. The bypass path can be formed with the simple structure. In particular, the fixed scroll of the front stage pump and the orbiting scroll of the rear stage pump are arranged so as to face each other, and compressed air can be supplied to the orbiting scroll of the rear stage pump through a discharge port provided in the fixed scroll of the front stage pump. In this case, the distance between the final closed space formed by the fixed scroll of the front stage pump and the orbiting scroll and the first closed space formed by the fixed scroll of the rear stage pump and the orbiting scroll becomes short, and it is immediately taken into the closed space of the rear stage pump. It is possible to provide an efficient vacuum pump in which the amount of gas remaining between both spaces is small.

Further, in the case of a combination of a driving scroll and a driven scroll, when the discharge spaces of both pumps are provided with a bypass pipe to be connected to form the bypass passage,
By preparing a general-purpose scroll mechanism related to a combination of a driving scroll and a driven scroll, it can be applied to a two-stage vacuum pump and is economical.

Further, when the compression ratio of the latter-stage pump is set to be larger than that of the former-stage pump, the amount of the gas in the closed container for load to be handled can be designed to be large with respect to the former-stage pump having a predetermined volume, and the processing time can be increased. Can be shortened. Further, when the maximum gas pocket volume of the latter-stage pump is configured to be smaller than the minimum gas pocket volume of the former-stage pump, a volume larger than the volume discharged by the former-stage pump is not dealt with, and therefore the maximum stage of the latter-stage pump is the maximum gas pocket. The gas does not expand in the gas pocket, and the compression efficiency in the latter stage does not decrease. Further, when the heights of the scroll wraps of the front-stage pump and the rear-stage pump above the end plate surface are different from those of the front-stage pump and the rear-stage pump, the outer diameter of the scroll is set to a predetermined dimension. Moreover, by setting the wrap height, the gas pocket volume of the scroll mechanism can be easily determined.

[0020]

The present invention will be described in detail below with reference to the embodiments shown in the drawings. However, dimensions, materials, shapes, relative positions, and the like of the components described in this embodiment are not merely intended to limit the scope of the present invention, but are merely illustrative examples, unless otherwise specified. Absent.

FIG. 1 is a constitutional view showing a first embodiment of an oil-free two-stage vacuum pump according to the present invention, FIG. 2 (a) is a sectional view taken along the line AA of FIG. 1, and FIG. BB sectional view, FIG.
1 is a sectional view taken along the line CC of FIG. 1, FIG. 4 is an operation explanatory view of a front stage pump section, FIG. 5 is an operation explanatory view of a rear stage pump, and FIG. 6 is an oil-free two-stage vacuum pump according to the present invention. 8 is a configuration diagram showing a second embodiment, FIG. 7 is a configuration diagram showing a third embodiment of an oil-free two-stage vacuum pump according to the present invention, FIG.
Is the fourth oil-free two-stage vacuum pump according to the present invention.
8 is a configuration diagram showing an embodiment, FIG. 8 (b) is a configuration diagram showing a fourth embodiment of an oil-free two-stage vacuum pump according to the present invention,
9 is a cross-sectional view of the scroll mechanism shown in FIG. 8A on the front side, FIG. 10 is a cross-sectional view of the scroll mechanism on the rear side shown in FIG. 8A, and FIG. FIG. 12 is a block configuration diagram of a control device that drives an oil-free two-stage vacuum pump according to the third embodiment, and FIG. 12 is a block configuration of a control device that drives the oil-free two-stage vacuum pumps according to the fourth and fifth embodiments. It is a figure.

In FIG. 1, an oil-free two-stage vacuum pump main body 1 is provided with two fixed scroll wraps 4 and 5 in a space surrounded by housings 3 and 11 and a pair of fixed scroll wraps 2 facing each other. The orbiting scroll wraps 8 and 9 that are planted in the orbiting scrolls 6 and 7, the rotary drive shaft 28 that rotationally drives these orbiting scrolls, and the fan 22 that is attached to the drive shaft 28 and cools the housing 3. Basically configured.

An opening hole 3a is formed in the center of the inner wall 3e of the housing 3, and a counterbore portion 3f having a diameter larger than that of the opening hole 3a holds a rotary bearing to the right of the opening hole 3a. And a rotary drive shaft 2 connected to a motor (not shown) via a rotary bearing provided in the spot facing portion.
8 is rotatably fitted in the opening 3a. Also,
A plurality of ribs 39 are provided on the outer surface of the housing 3 radially from the central portion toward the outer periphery, and a cover 36 having a plurality of air vent holes 36a is attached to the upper surface of the ribs 39. In FIG. 1, the cooling air that has entered from above flows to the right as indicated by the arrow.

On the surface of the inner wall 3e of the housing 3, a spiral fixed scroll wrap 5 is planted, and the end surface of the wrap 5 has self-lubricating property and elastic force in the thrust direction. The tip seal 23 is fitted.

An opening 3b for discharging compressed gas is provided near the opening 3a, and the opening 3b is provided with the check valve 2.
4 is connected to the discharge port 3c communicating with the outside. The check valve 24 opens when the pressure of the compressed gas in the opening 3b is higher than the atmospheric pressure of the outside, and the opening 3b communicates with the discharge port 3c to discharge the compressed gas to the outside to open the opening 3b.
The internal pressure is closed when the internal pressure is lower than the external atmospheric pressure, and the external gas does not flow back into the opening 3b to give an extra drive load at the time of starting.

Further, in order to maintain airtightness on the inner wall 3e side of the housing 3, an opening 3d is provided between the wall surface 3h standing upright in the peripheral portion and surrounding the inner wall 3e side and the outer peripheral portion of the rear fixed scroll wrap 5. Is opened, and the opening 3d communicates with the discharge port 3c communicating with the outside via the pressure control valve 25. The pressure control valve 25 opens when the pressure of the compressed gas in the closed space 3g between the wall surface 3h and the outer peripheral portion of the rear fixed scroll wrap 5 is higher than the external atmospheric pressure, and the opening 3d opens the discharge port 3c. The compressed gas is discharged to the outside through communication with the closed space, and the closed space is closed when the pressure in the closed space 3g is lower than the atmospheric pressure of the outside. It is controlled not to.

Further, in the housing 3, there is further provided a rear orbiting scroll end plate 7 in which a spiral orbiting rear orbiting scroll wrap 9 having a substantially same shape as the rear fixed scroll wrap 5 is planted. The wraps 5 and 9 are provided so that they are fitted together with a 180 degree offset. According to a preferred embodiment, the maximum fixed gas pocket volume formed by the rear fixed scroll wrap 5 and the rear orbiting scroll wrap 9 is 56.6 cc, and the minimum gas pocket volume is 19.1 c.
c, the volume ratio (maximum volume / minimum volume = compression ratio) is 2.96
Is set to

A cylindrical portion 7b is provided in the center of the end plate 7, an opening hole 7a is formed in the center of the end plate 7, and a rotary bearing is held to the left of the opening hole 7a. A counterbore portion 7f having a diameter larger than that of the opening hole 7a is provided, and a tip having a shaft center eccentric from a rotation center of a rotary drive shaft 28 connected to a motor (not shown) through a rotary bearing provided in the counterbore portion. The shaft portion 28a is rotatably fitted. In addition, a plurality of pins 7c for fitting and positioning with the positioning holes of the end plate 6 of the former stage orbiting scroll, which will be described later, project from the tip end surface of the cylindrical portion 7b, and a plurality of screw holes for fixing the former stage orbiting scroll are cut. It is set up.

A tip seal 23 having self-lubricating properties and elastic force in the thrust direction is fitted on the end surface of the rear fixed scroll wrap 9 provided on the end plate 7. Then, as described above, the wraps 5 and 9 of each scroll are self-lubricating seal members composed of the tip seal 23 in the groove portions which are recessed in the end faces which come into contact with the scrolls on the other side. To achieve slidability without lubrication, and to maintain airtightness with the outside in a closed space formed by the rear fixed scroll wrap 5 and the rear orbiting scroll wrap 9. .

Further, a revolution mechanism having a pin crank whose one end is connected to the housing 2 of the former stage pump, which will be described later, is provided on the outer peripheral portion of the surface of the latter stage orbiting scroll end plate 7 opposite to the surface on which the wrap is planted. The connecting portion to which 37 is connected is 120
It is provided (3 places) at positions deviated at intervals of °.
Therefore, the end plate 7 of the orbiting scroll moves up and down as shown in FIG. 1 by the rotation of the rotary drive shaft 28, and the end plate 7 of the orbiting scroll is prevented from rotating on its own axis. However, it is configured to be able to revolve around the center of the wrap 5 of the fixed scroll with a constant radius.

The housing 2 is fixed to the housing 3 with screws or the like with the packing 38 interposed therebetween. An opening 2a is formed in the center of the inner wall 2e of the housing 2, and
The cylindrical portion 7b of the rear orbiting scroll end plate 7 is fitted into the opening 2a so as to be rotatable and slidable. Further, a suction opening 2b is formed in the outer peripheral portion of the housing 2 so as to be connected to a closed container (not shown) to suck the gas in the closed container, and the inner wall 2e of the housing 2 has a surface for a scroll-shaped front-stage fixed scroll. The wrap 4 is planted, and a tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted to the end surface of the wrap 4.

In the housing 2, there is further provided a front orbiting scroll end plate 6 in which a spiral orbiting front orbiting scroll wrap 8 of substantially the same shape as that of the front fixed scroll wrap 4 is planted. The wraps 4 and 8 are provided so that they are fitted together with a 180 degree offset. According to a preferred embodiment, the maximum gas pocket volume Vmax formed by the front fixed scroll wrap 4 and the front orbiting scroll wrap 8 is 189.7 cc, the minimum gas pocket volume Vmin is 82.7 cc, and the volume ratio (maximum volume / Minimum volume = compression ratio) is set to 2.29. A cylindrical portion 6b is provided in the center of the end plate 6 in the direction in which the wrap 8 is planted, and an end plate near the cylindrical portion 6b is provided with a pin 7c provided on the cylindrical portion 7b of the subsequent orbiting scroll. A positioning hole 6c to be fitted and a stop hole are provided alongside the positioning hole,
This front orbiting scroll is configured so that it can be fixed integrally with the rear orbiting scroll by means of a screw 27 from the stop hole.

Further, a tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted on the end surface of the front fixed scroll wrap 8 provided on the end plate 6. As described above, the wraps 4 and 8 of the respective scrolls are self-lubricating seal members composed of the tip seal 23 in the groove portions which are recessed in the end faces which contact the other side scrolls. And is configured to be slidable without lubrication, and to maintain airtightness with the outside in a closed space formed by the front fixed scroll wrap 4 and the front orbiting scroll wrap 8. . Further, the housing 11 is fixed to the housing 2 with the packing 38 interposed therebetween.

FIG. 11 is a block diagram of a control device for driving a vacuum pump provided with a scroll mechanism relating to a combination of a fixed scroll and an orbiting scroll.
The suction end of the vacuum pump main body 1 is connected to the suction port of the closed container 35, and the vacuum pump main body 1 is driven by a motor 32, and the motor 32 is wired and connected so that its rotation is controlled by an electric controller 34. The electric control device 34 includes a measuring unit that measures the gas pressure in the closed container 35, and the rotation speed of the motor 32 can be controlled by the measurement value of the measuring unit. Also, (b) is
The suction end of the vacuum pump body 10 is connected to the suction port of the closed container 35. The vacuum pump body 10 is driven by a motor 33 for a front scroll mechanism and a motor 32 for a rear scroll mechanism. The electric control device 34 is connected by wiring so as to be rotationally controlled by the electric control device 34, and the electric control device 34 is provided with a measuring means for measuring the gas pressure in the closed container 35. The number of rotations is controllable.

Next, the operation of this embodiment will be described. As shown in FIG. 11 (a), the suction opening 2 b of the vacuum pump body 1 is connected to the suction end of the closed container 35 by piping, and the rotary drive shaft 28 of the vacuum pump body 1 is connected to the electric control device 34. When the motor 32 is driven by the electric control device 34 after being connected to the motor 32, the front stage orbiting scroll end plate 6 and the rear stage orbiting scroll end plate 7 start to rotate.

Due to the rotation of the rotary drive shaft 28, the bearing portion 7b of the rear orbiting scroll end plate 7 having a rotary shaft that is eccentric to the rotary drive shaft 28 has its outer periphery as shown in FIG. 2 (a). While slidingly contacting the edge of the opening 2a opened in the housing 2, the inside of the opening 2a is vertically moved to move the revolving mechanism 3
The end plate 7 of the orbiting scroll revolves in the counterclockwise direction around the center of the wrap 4 of the fixed scroll with a certain radius while being prevented from rotating on its own axis.

Therefore, the front orbiting scroll wrap 8 makes an orbital movement counterclockwise in FIG. 2 (a) while slidingly contacting the wall surface of the front fixed scroll wrap 4, and the wrap 8 is rotated.
The tip 8a of the is regulated by the rounded wall surface 2h extending to the end of the wrap 4 at the center of the housing 2, and swirls along the rounded surface to discharge the compressed gas from the opening 2a. On the other hand, the rear orbiting scroll wrap 9 integrated with the bearing portion 7b makes an orbital motion in the counterclockwise direction in FIG. 2B while slidingly contacting the wall surface of the rear fixed scroll wrap 5, and the tip 9a of the wrap 9 is a housing. 3 is regulated by a rounded wall surface 3h extending to the end portion of the wrap 5, and swivels along the rounded surface to discharge port 3b.
Discharge compressed gas from

Next, the operation of this embodiment will be described in detail.
When the suction opening 2b and the airtight container 35 are connected by a pipe, a space 2g in the housing 2 constituting the pre-stage pump
(FIG. 4) is filled with gas having the same pressure as in the closed container 35. When the former orbiting scroll rotates, the gas in the space 2g is the maximum gas formed by the fixed scroll wrap 4 on the outer side and the orbiting scroll wrap 8 on the inner side as shown in FIGS. 4 (a) and 4 (d). The pocket Tmax and the maximum gas pocket Smax formed by the orbiting scroll wrap 8 on the outer side and the fixed scroll wrap 4 on the inner side are taken in.

These maximum gas pockets Tmax and S
The gas taken into max is the orbiting scroll wrap 8
Is rotated, the Tmax is compressed as a minimum gas pocket Tmin as shown in (b), and further rotated as shown in (c).
The compressed gas is discharged to the discharge opening 2a from the opening of the space. Further, Smax is compressed as the minimum gas pocket Smin as shown in (c),
Further, the orbiting scroll is further rotated to open the gap between the tip portion 4a at the center of the wrap 4 and the inner wall of the orbiting scroll 8 as shown in (d), whereby the compressed gas is discharged to the discharge opening 2a. To be done.

The compressed gas discharged from the opening 2a flows from the central portion of the rear scroll end plate 7 toward the space 3g of the housing 3 provided in the outer peripheral portion and fills the back surface of the end plate 7 and the space 3g. To do. Airtight container 3 during initial drive
5 is the same pressure as the atmospheric pressure, and the gas taken into the front scroll due to it becomes about twice the atmospheric pressure and fills the space 3 g. Pressure control valve 25 provided in opening 3d provided in communication with discharge passage 3c communicating with the outside
Since the space 3g is higher than the atmospheric pressure, the space is opened and the compressed gas is discharged to the outside.

On the other hand, at the time of initial drive, not only the space 3g but also the gas pockets formed by the fixed scroll wraps 5 and the orbiting scroll wraps 9 are filled with the gas at the same pressure as the atmospheric pressure in the latter stage scroll mechanism. ing.
This is because there is a slight gap between each fixed scroll wrap and the orbiting scroll wrap where the wall surface is in sliding contact, there is gas leakage, and the gas leakage can be ignored during driving, but it is left at atmospheric pressure for a long time. This is because the gas that enters through the above-mentioned gap causes the pressure to be almost the same as the atmospheric pressure.

Therefore, the rear scroll mechanism takes in a gas at almost atmospheric pressure at the time of initial drive, and the gas discharged by the front scroll mechanism and the gas existing in the space 3g are mixed until the pressure falls below the atmospheric pressure. It takes in atmospheric pressure gas and compresses it. Therefore, the shape and dimensions of the rear scroll mechanism are such that the tip seal 2 fitted in the wrap end face is
3 temperature characteristics, orbiting scroll rotation speed, maximum gas uptake volume by orbiting scroll, compression ratio, fan 2
2 is designed in consideration of the cooling performance, the time until the gas pressure in the space 3g falls below the atmospheric pressure, and the latter scroll mechanism is operated within that range.

When the second stage orbiting scroll is rotated, as shown in FIG.
As shown in (a) and (d), the gas in the space 3g has a maximum gas pocket Wma formed by the fixed scroll wrap 5 on the outer side and the orbiting scroll wrap 9 on the inner side.
x, and the maximum gas pocket X formed by the orbiting scroll wrap 9 on the outside and the fixed scroll wrap 5 on the inside
Captured as max.

These maximum gas pockets Wmax and X
The gas taken into max is the orbiting scroll wrap 9
Rotation causes Xmax to be compressed as the minimum gas pocket Xmin as shown in (b), and further rotates as shown in (c) to the tip portion 9a of the wrap 9 and the central wall surface of the fixed scroll wrap 5. By opening the gap with 3j, the compressed gas is discharged from there to the discharge opening 3b. Further, Wmax is compressed as the minimum gas pocket Wmin as shown in (d), and further rotated (a).
By opening between the rounded portion 3i of the central portion of the wrap 5 and the tip end portion 9a of the orbiting scroll 9 as shown in FIG.
From there, the compressed gas is discharged to the discharge opening 3b.

As the evacuation of the closed container 35 progresses and the pressure inside the container decreases, the gas intake amount decreases. By detecting this pressure decrease, the electric control unit 34 operates to increase the rotation speed of the motor 32 and compensate for the decrease in the gas suction amount. The capacity of the closed container, the performance of the vacuum pump, and the like may be input into the electric control device 34 in advance, and the motor rotation speed may be controlled after a predetermined time has elapsed.

As described above, the rear scroll can compress a gas at about atmospheric pressure and discharge it to the outside. Even if a compressed gas at atmospheric pressure or higher is supplied by the front scroll mechanism, the pressure control valve can be used. Since it is configured so that it can be bypassed and discharged to the outside, the latter stage scroll mechanism does not take in and compress gas at a higher pressure, and the high temperature generated by it reduces the durability or damage of the scroll mechanism. There is nothing to do.

FIG. 6 is a block diagram showing a second embodiment of the oil-free two-stage vacuum pump according to the present invention. In the figure, an oil-free two-stage vacuum pump main body 10 includes two fixed scroll wraps 14 and 15 and two swiveling rotators provided opposite to them in a space surrounded by housings 13 and 20. Orbiting scroll wraps 18 and 19 planted in the scroll end plates 16 and 17, and rotary drive shafts 29 and 30 for rotationally driving these orbiting scrolls.
And the housing 1 attached to the drive shafts 29, 30
It is basically configured by a fan 22 that cools the units 3 and 20.

An opening hole 13a is formed in the center of the inner wall 13e of the housing 13, and the opening hole 13a is formed.
The opening hole 13a for holding the rotary bearing is provided on the right side of "a".
A counterbore 13f having a larger diameter is provided, and a rotary drive shaft 29 connected to a motor (not shown) via a rotary bearing provided in the counterbore is rotatably fitted in the opening hole 13a. Further, on the outer surface of the housing 13, a plurality of ribs 41 are provided radially from the central portion toward the outer periphery,
A cover 36 having a plurality of air vent holes 36a is attached to the upper surface of the rib 41 so that the cooling air that has entered from above in FIG. 1 flows to the right as shown by the arrow by the rotation of the fan 22. Has been done.

On the surface of the inner wall 13e of the housing 13, a spiral fixed scroll wrap 15 for rear-stage scroll is planted, and the end surface of the wrap 15 has self-lubricating property and elastic force in the thrust direction. The tip seal 23 is fitted.

An opening 13b for discharging compressed gas is formed near the opening 13a, and the opening 13b is connected to a discharge port 13c communicating with the outside through a check valve 24. The check valve 24 opens when the pressure of the compressed gas in the opening 13b is higher than the external atmospheric pressure, and the check valve 24 opens.
3b communicates with the discharge port 13c and discharges the compressed gas to the outside, and closes when the pressure inside the opening 13b is lower than the atmospheric pressure of the outside, and the outside gas flows back into the opening 13b to cause an excess when starting. It is configured so that no driving load is applied.

Further, in order to maintain the airtightness on the inner wall 13e side of the housing 13, an opening 13d is provided between a wall surface 13h standing up in the peripheral portion and surrounding the inner wall 13e side and the outer peripheral portion of the rear fixed scroll wrap 15. Is opened, and the opening 13
d communicates with the discharge port 13c communicating with the outside through the pressure control valve 25. This pressure control valve 25 is attached to the wall 1
When the pressure of the compressed gas in the closed space 13g between the 3h and the outer periphery of the rear fixed scroll wrap 15 is higher than the external atmospheric pressure, the opening 13d communicates with the discharge port 13c and the compressed gas is exposed to the outside. It discharges and closes when the pressure in the closed space 13g is lower than the external atmospheric pressure, and the second-stage pump takes in compressed gas of high pressure and controls so that the temperature inside the second-stage pump does not rise to a temperature higher than a predetermined value. .

In the housing 13, there is further provided a rear orbiting scroll end plate 17 in which a spiral orbiting rear orbiting scroll wrap 19 having substantially the same shape as the rear fixed scroll wrap 15 is planted. The laps 15 and 19 are provided with 180 degrees offset from each other and fitted together. According to a preferred embodiment, the maximum fixed gas pocket volume formed by the rear fixed scroll wrap 15 and the rear orbiting scroll wrap 19 is 56.6 cc, the minimum gas pocket volume is 19.1 cc, and the volume ratio (maximum volume / minimum volume = Compression ratio) is set to 2.96. A cylindrical portion 17b is provided at the center of the end plate 17, and an opening hole 17a is formed at the center of the end plate 17. The opening hole 17a is provided on the left side of the opening hole 17a for holding the rotary bearing. A large-diameter counterbore portion 17f is provided, and a tip shaft portion 29a having a shaft center eccentric from the rotation center of a rotary drive shaft 29 connected to a motor (not shown) via a rotary bearing provided in the counterbore portion is provided. It is rotatably fitted.

Further, a tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted on the end face of the rear fixed scroll wrap 19 provided on the end plate 17. Then, as described above, the wraps 15 and 19 of the scrolls are self-lubricating seal members composed of tip seals 23 in the groove portions which are recessed in the end faces which come into contact with the scrolls on the other side. And is slidable without lubrication, and the airtightness with the outside in the closed space formed by the rear fixed scroll wrap 15 and the rear orbiting scroll wrap 19 is maintained. .

A revolution mechanism 47, one end of which is connected to the housing 12 of the former stage pump, which will be described later, is connected to the outer peripheral portion of the surface of the latter stage orbiting scroll end plate 17 opposite to the surface on which the wrap is planted. The connecting portions are provided at three positions which are offset at 120 ° intervals. Therefore, the end plate 17 of the orbiting scroll moves up and down as shown in FIG. 6 by the rotation of the rotary drive shaft 29, and the end plate 17 of the orbiting scroll is prevented from rotating about its own axis. However, it is configured to be able to revolve around the center of the wrap 15 of the fixed scroll with a constant radius.

The housing 12 is fixed to the housing 13 with screws or the like with the packing 38 interposed therebetween. A suction opening 12b is formed in the outer peripheral portion of the housing 12 so as to be connected to a closed container (not shown) for sucking gas in the closed container, and an inner wall 12e of the housing 12 has a spiral wrap for a front fixed scroll. 14 is implanted, and a tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted on the end surface of the wrap 14. The wrap 14 is provided at the center of the housing 12 on the planting side of the wrap 14.
A recess 12f having a depth smaller than that of the inner wall 12e is provided, and an opening hole 12a for supplying compressed gas to the subsequent scroll mechanism is formed near the recess 12f. In addition, a base of a revolving mechanism 37, one end of which is connected to the rear orbiting scroll end plate 17, is provided on the outer peripheral portion of the housing 12 at positions displaced by 120 ° (three places).

In the housing 12, there is further provided a front orbiting scroll end plate 16 in which a spiral orbiting front orbiting scroll wrap 18 having a substantially same shape as that of the front fixed scroll wrap 14 is planted. The wraps 14 and 18 are provided with 180 degrees offset from each other and fitted together. The front orbiting scroll end plate 16 is connected to the other end of a revolving mechanism 47, one end of which is connected to the rear orbiting scroll end plate 17 (three places) at positions deviated at 120 ° intervals on the outer peripheral portion thereof. A cylindrical portion 16b is provided at the center of the end plate 16 toward the direction in which the wrap 18 is planted, and the tip of the cylindrical portion contacts the wall surface of the recess 12f of the housing 12 via the tip seal 23 to drive rotation. The shaft 30 is rotatably provided on the eccentric tip portion 30a. According to a preferred embodiment, the maximum gas pocket volume Vmax formed by the front fixed scroll wrap 4 and the front orbiting scroll wrap 8 is 189.7 cc, the minimum gas pocket volume Vmin is 82.7 cc, and the volume ratio (maximum volume / Minimum volume = compression ratio) is set to 2.29.

A tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted on the end surface of the front fixed scroll wrap 18 provided on the end plate 16. Then, as described above, the wraps 14 and 18 of each scroll are self-lubricating seal members composed of the tip seal 23 in the groove formed in the end face which is in contact with the scroll on the other side. And is configured to be slidable without lubrication and to maintain airtightness with the outside in a closed space formed by the front fixed scroll wrap 14 and the front orbiting scroll wrap 18. .

The housing 20 is fixed to the housing 12 with the packing 38 sandwiched therebetween. Housing 2
An opening hole 20a is opened in the center of the inner wall 20e of 0, and a counterbore portion 20f having a diameter larger than that of the opening hole 20a for holding a rotary bearing is provided on the left side of the opening hole 20a. A rotary drive shaft 30 connected to a motor (not shown) through a rotary bearing provided in the spot facing portion is rotatably fitted in the opening hole 30a. Further, a plurality of ribs 40 are provided on the outer surface of the housing 20 radially from the central portion toward the outer periphery, and a cover 36 having a plurality of air vent holes 36 a is attached to the upper surface of the rib 40 to attach the fan 36 to the fan 22. As shown in the arrow, the cooling air entering from above in FIG. 6 flows to the left as a result of rotation.

Next, the operation of the second embodiment thus constructed will be described with reference to FIGS. 6 and 11 (b). Figure 11
In (b), the electric control unit 34 rotates the motor 33 to drive the front scroll mechanism. In FIG. 6, a gas having a pressure substantially equal to the atmospheric pressure is sucked into the suction opening 12b of the housing 12, and the pre-stage scroll mechanism takes in the gas and compresses the compressed gas into the space 13g of the housing 13 from the discharge opening 12a. To release. Since the released gas has a pressure higher than the atmospheric pressure at the time of initial driving, the pressure control valve 25 discharges the compressed gas to the outside.

The electric control unit 34 causes the motor 32 to rotate after a lapse of time calculated in consideration of the volume of the closed container 35, the working volume of the preceding orbiting scroll, the rotation speed, and the like. Around that time, around that time, a space of 13g
The pressure of the compressed gas of the previous scroll discharged to below is lower than the atmospheric pressure, and the pressure control valve 25 is closed. After that, the compressed gas discharged by the front scroll mechanism is compressed by the rear scroll mechanism and discharged to the outside through the discharge opening 13b. As the pressure in the closed container 35 decreases due to the suction of the vacuum pump, the electric control device 34 controls the motors 33, 3 and 3.
Increase the rotation speed of 2. This compensates for the decrease in the amount of gas exhausted in the closed container and shortens the processing time.

FIG. 7 is a block diagram showing a third embodiment of the oil-free two-stage vacuum pump according to the present invention. In the figure, an oil-free two-stage vacuum pump main body 100 is provided in a space surrounded by housings 102 and 103.
Individual fixed scroll wraps 104, 105, orbiting scroll wraps 108, 107 planted in an orbiting scroll end plate 106 provided opposite thereto, and a rotary drive shaft 31 for rotationally driving the orbiting scroll. And housings 103, 102 attached to the drive shaft 31.
It is basically configured by a fan 22 that cools.

An opening hole 103a is formed in the center of the inner wall 103e of the housing 103, and a counterbored portion 103f having a diameter larger than that of the opening hole 103a holds a rotary bearing to the right of the opening hole 103a. Is provided, and a rotary drive shaft 31 connected to a motor (not shown) via a rotary bearing provided in the spot facing portion is rotatably fitted in the opening hole 103a. Further, on the outer surface of the housing 103, a plurality of ribs 4 are radially provided from the central portion toward the outer periphery.
2 is provided, a cover 36 having a plurality of air vent holes 36a is attached to the upper surface of the rib 42, and the cooling air that has entered from above in FIG. It is designed to flow to.

Further, the inner wall 103 of the housing 103
On the surface of e, a spiral-shaped wrap 10 for the latter-stage fixed scroll
5, the tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted to the end surface of the wrap 105. An opening 103b for discharging compressed gas is provided near the opening 103a, and the opening 103b is connected to a discharge port 103c communicating with the outside via a check valve 24. This check valve 24
Is opened when the pressure of the compressed gas in the opening 103b is higher than the external atmospheric pressure, and the opening 103b is opened in the discharge port 103c.
The compressed gas is discharged to the outside by communicating with the air and closes when the pressure in the opening 103b is lower than the atmospheric pressure of the outside, and the external gas does not flow back into the opening 13b to give an extra drive load at the time of starting. Is configured.

Further, in order to maintain the airtightness on the inner wall 103e side of the housing 103, an opening 103d is provided between a wall surface 103h standing upright on the peripheral portion and surrounding the inner wall 103e side and the outer peripheral portion of the rear fixed scroll wrap 105. Was established,
The opening 103d communicates with the discharge port 103c communicating with the outside via the pressure control valve 25. The pressure control valve 25 opens when the pressure of the compressed gas in the sealed space 103g between the wall surface 103h and the outer periphery of the rear fixed scroll wrap 105 is higher than the external atmospheric pressure.
03d communicates with the discharge port 103c to discharge the compressed gas to the outside, and closes when the pressure in the closed space 103g is lower than the atmospheric pressure of the outside, and the post-stage pump takes in the high-pressure compressed gas and the inside of the post-stage pump is predetermined. The temperature is controlled so that the temperature does not exceed the value.

The housing 102 is fixed to the housing 103 with screws or the like with the packing 38 interposed therebetween. A suction opening 102b is formed on the outer peripheral portion of the housing 102 to connect with a closed container (not shown) to suck gas in the closed container. The inner wall 102e of the housing 102 has a spiral wrap for a front fixed scroll. 104 is implanted, and a tip seal 23 having self-lubricating property and elastic force in the thrust direction is fitted on the end surface of the wrap 104.

An opening hole 102a is formed in the center of the inner wall 102e of the housing 102, and a counterbore 102f having a diameter larger than that of the opening hole 102a holds a rotary bearing to the left of the opening hole 102a. Is provided, and a rotary drive shaft 31 connected to a motor (not shown) via a rotary bearing provided in the spot facing portion is rotatably fitted in the opening hole 102a. Further, on the outer surface of the housing 102, a plurality of ribs 4 are formed radially from the central portion toward the outer periphery.
3 is provided, a cover 36 having a plurality of air vent holes 36a is attached to the upper surface of the rib 43, and the cooling air that has entered from above in FIG. It is designed to flow to.

A discharge opening 102a for the compressed gas is provided near the center of the inner surface of the housing 102, and the compressed gas is supplied to the subsequent scroll through the discharge passage 102c. Further, the base of the revolving mechanism 37 having one end connected to the orbiting scroll end plate 106 is provided at positions (3 places) which are offset at 120 ° intervals on the outer peripheral portion of the housing 102. A swirl scroll end plate 106, in which a swirl-shaped spiral scroll wrap 108 having substantially the same shape as that of the fixed scroll scroll 104 is planted, is further provided in the housing 102.
It is installed by shifting the 8 members by 180 degrees.
According to a preferred embodiment, the maximum gas pocket volume Vmax formed by the front fixed scroll wrap 4 and the front orbiting scroll wrap 8 is 189.7 cc, the minimum gas pocket volume Vmin is 82.7 cc, and the volume ratio (maximum volume / Minimum volume = compression ratio) is set to 2.29.

Further, on the mirror surface 106g of the end plate 106 of the orbiting scroll, a spiral wrap 107 for the subsequent orbiting scroll which has substantially the same shape as the wrap 105 for the latter fixed scroll is provided. They are installed by shifting their companions by 180 degrees. According to a preferred embodiment, this latter fixed scroll wrap 1
5 and the rear orbiting scroll wrap 19 have a maximum gas pocket volume of 56.6 cc, a minimum gas pocket volume of 19.1 cc, and a volume ratio (maximum volume / minimum volume = compression ratio) of 2.96. There is.

The orbiting scroll end plate 106 is connected to one end of a pin crank mechanism 37 whose base portion is connected to the housing 102 (three places) at positions offset at 120 ° intervals on the outer peripheral portion thereof. A cylindrical portion 106b is provided at the center of the end plate 106 in the direction of planting the wrap 108, and the tip of the cylindrical portion contacts the mirror surface 102e of the housing 102 via the tip seal 23, thereby rotating the rotary drive shaft. It is rotatably provided on the eccentric tip portion 31 a of the member 31. Cylindrical part 1 provided at the center of this end plate 106
An opening hole 106a is formed in the center of 06b, and a counterbore portion 106f having a diameter larger than that of the opening hole 106a for holding a rotary bearing is provided on the left side of the aperture hole 106a. An eccentric portion 31a having a shaft center eccentric from the rotation center of a rotary drive shaft 31 connected to a motor (not shown) via a rotary bearing provided in the above is rotatably fitted.

Next, the operation of the thus constructed third embodiment will be described with reference to FIGS. 7 and 11A. Figure 11
In (a), the electric control unit 34 rotates the motor 32 to drive the orbiting scroll end plate 106. In FIG. 7, gas having a pressure substantially equal to atmospheric pressure is sucked into the suction opening 102b of the housing 102, and the orbiting wrap 108 and the fixed wrap 104 of the preceding scroll mechanism take in the gas, compress it, and discharge it from the discharge opening 102a. Housing 1
The compressed gas is discharged into the space 103g of 03.

At the time of initial drive, the pressure in the closed container 35 is the same as the atmospheric pressure, and the gas taken into the front scroll due to the atmospheric pressure is about twice the atmospheric pressure and fills the space 103g. A pressure control valve 25 provided in an opening 103d provided in communication with a discharge passage 103c communicating with the outside.
Since the space 103g is higher than the atmospheric pressure, it opens and discharges the compressed gas to the outside.

On the other hand, at the time of initial drive, not only the space 103g but also the gas pockets formed by the fixed scroll wraps 105 and the orbiting scroll wraps 107 are filled with the gas at the same pressure as the atmospheric pressure in the latter stage scroll mechanism. ing. Therefore, the rear scroll mechanism takes in gas at almost atmospheric pressure at the time of initial driving, mixes the gas discharged by the front scroll mechanism with the gas existing in the space 103g, and maintains the atmospheric pressure until the pressure falls below atmospheric pressure. The gas is taken in and compressed, and the compressed gas is discharged through the discharge opening 103b.
Is discharged.

As the evacuation of the closed container 35 progresses and the pressure inside the container decreases, the amount of gas sucked in decreases. By detecting this pressure decrease, the electric control unit 34 operates to increase the rotation speed of the motor 32 and compensate for the decrease in the gas suction amount. The capacity of the closed container, the performance of the vacuum pump, and the like may be input to the electric control device 34 in advance, and the motor rotation speed may be controlled after a predetermined time has elapsed.

FIG. 8 is a constitutional view showing a fourth embodiment of the oil-free two-stage vacuum pump according to the present invention, which uses a driving scroll and a driven scroll. In the figure, the oil-free two-stage vacuum pump main body 200 has a front-stage vacuum pump main body 200A and a rear-stage vacuum pump main body 200B connected to both ends of a rotary drive shaft 53 of a motor 50, and the discharge opening of the rear-stage vacuum pump 200B is reversed. The front stage vacuum pump 200 is connected to the discharge passage 57 communicating with the outside by a stop valve 124.
A pressure control valve 12 that connects the discharge opening of A and the suction opening of the rear vacuum pump 200B with a pipe 56 and opens when the pressure inside the pipe 56 becomes a predetermined pressure or more and exhausts it to the outside.
5 is arranged to bypass the discharge passage.

Next, details of the front stage vacuum pump main body 200A and the rear stage vacuum pump main body 200B will be described. FIG.
It is sectional drawing which shows the detail of the front | former stage vacuum pump main body 200A. In the figure, the housings 60A and 60B are integrally formed with a mounting member (not shown) with a dust housing 61 formed in the shape of a doughnut interposed therebetween. The motor 50 is provided at the center of the outer wall 60Ad of the housing 60A.
The inner wall 60A into which the rotary drive shaft 53A is rotatably fitted
The opening 60Ac communicating with b is opened, and the housing 6
An opening 60Bc communicating with the inner wall 60Bb is formed in the center of the outer wall 60Bd of 0B into which the tip end shaft of a mounting seat 67 described later is rotatably fitted.

The mounting seat 66 is formed in a mushroom shape, and a communication hole for fitting the drive shaft 53A toward the upper surface of the stem is opened, and the mounting portion 66 has three mounting portions 66 radially.
While having b, three opening holes 66a through which cooling air flows are formed in the stem portion outside the mounting portion. A rotary bearing is fitted to the outer periphery of the stem portion of the mounting seat 66, and the outer periphery of the rotary bearing has the hole 6 of the housing 60A.
The mounting seat 66 is rotatably arranged in the housing 60A while being fixed to the drive shaft 53A. Further, on the outer surface of the housing 60A, a plurality of opening holes 60Ag for sucking air for cooling the drive scroll 62 are provided.
And a plurality of opening holes 60Ai for discharging the air are provided.

The drive scroll 62 is basically provided on the back surface of a disk-shaped scroll blade and has a plurality of fan blades 62a radially provided from the central portion to the outer peripheral portion.
And a spiral wrap 63. On the back surface of the drive scroll 62, three fan blades are erected radially at intervals of 120 °, and the attachment seat 66b is provided on the thick portion above the fan blade 62c by the attachment portion 66b.
6 is attached. Also, a wrap 63 is planted in the drive scroll 62, and 1 is provided on the outer peripheral portion of the drive scroll.
Three pairs of revolution mechanisms 68 are provided at three locations in the circumferential direction at intervals of 20 °.

A driven scroll 64 is provided in which a wrap 65 having a lap wall facing the wrap 63 is planted via a revolution mechanism 68. This driven scroll 64
Is provided with a cylindrical portion 64b on the surface opposite to the wrap, and an opening hole 64a for discharging compressed gas reaching the tip end surface of the cylindrical portion 64 from the surface on which the wrap is planted to the outside at the center of rotation. Has been established. On the back surface of the driven scroll 64, three fan blades are erected radially at intervals of 120 °, and a mounting seat 67 is attached to the thick portion above the fan blade 64a by an attachment portion 67b.
Further, a packing 69 is sandwiched between the tip end surface of the cylindrical portion 64b and the mounting seat 67 to maintain airtightness.

The mounting seat 67 is formed in a mushroom shape.
In order to discharge the compressed gas discharged from the opening 64a of the driven scroll to the outside, a communication hole 67c is opened with the stem portion facing the upper surface of the umbrella, and the umbrella portion has three mounting portions 67b radially. In the stem portion outside the mounting portion, three opening holes 67a through which cooling air flows are formed. A rotary bearing is fitted to the outer periphery of the stem portion of the mounting seat 67, the outer periphery of the rotary bearing is fixed to the hole 60Ba of the housing 60B, and the tip portion of the stem portion projects into a cylindrical shape to form the opening hole of the housing 60B. It is rotatably fitted in 60Bc. The mounting seat 67 is rotatably arranged in the housing 60B with the driven scroll 64 fixed.

Further, on the outer surface of the housing 60B, a plurality of opening holes 6 for sucking air for cooling the driven scroll 64 are provided.
A plurality of opening holes 60Bi for releasing 0Bg and the air are provided. According to a preferred embodiment, the maximum gas pocket volume Vmax formed by the front drive scroll wrap 63 and the front drive scroll wrap 65 is:
189.7 cc, minimum gas pocket volume Vmin is 8
2.7 cc, and the volume ratio (maximum volume / minimum volume = compression ratio) is set to 2.29.

FIG. 10 is a sectional view showing the details of the latter-stage vacuum pump body 200B. The same symbols are used for the same members as in FIG. In the figure, housings 60A and 60B
Is a dust housing 6 formed in the shape of a donut in the middle
It is integrally formed with a mounting member (not shown) sandwiching 1. An opening 60Ac communicating with the inner wall 60Ab, into which the rotary drive shaft 53B of the motor 50 is rotatably fitted, is opened at the center of the outer wall 60Ad of the housing 60A, and will be described later at the center of the outer wall 60Bd of the housing 60B. An opening 60Bc communicating with the inner wall 60Bb into which the tip end shaft of the mounting seat 67 is rotatably fitted is provided.

The mounting seat 66 is formed in a mushroom shape, and a communication hole for fitting the stem portion toward the upper surface of the umbrella to the drive shaft 53B is opened, and three mounting portions 66 are radially arranged on the umbrella portion.
While having b, three opening holes 66a through which cooling air flows are formed in the stem portion outside the mounting portion. A rotary bearing is fitted on the outer periphery of the stem portion of the mounting seat 66, and the outer periphery of the rotary bearing is provided with the hole 60A of the housing 60A.
The mounting seat 66 is rotatably disposed in the housing 60A while being fixed to the drive shaft 53B. Further, on the outer surface of the housing 60A, a plurality of opening holes 60Ag for sucking air for cooling the drive scroll 62 and a plurality of opening holes 60Ai for discharging the air are formed.

The drive scroll 62 is basically provided on the back surface of a disk-shaped scroll blade, and has a plurality of fan blades 62a radially provided from the central portion to the outer peripheral portion.
And a spiral wrap 63. On the back surface of the drive scroll 62, three fan blades are erected radially at intervals of 120 °, and the mounting portion 66b is used to attach the mounting seat 6 to the thick portion above the fan blade 62a.
6 is attached. Also, a wrap 63 is planted in the drive scroll 62, and 1 is provided on the outer peripheral portion of the drive scroll.
Three pairs of revolution mechanisms 68 are provided at three locations in the circumferential direction at intervals of 20 °.

A driven scroll 64 is provided in which a wrap 65 having a lap wall facing the wrap 63 is planted via a revolution mechanism 68. This driven scroll 64
Is provided with a cylindrical portion 64b on the surface opposite to the wrap, and an opening hole 64a for discharging compressed gas reaching the tip end surface of the cylindrical portion 64 from the surface on which the wrap is planted to the outside at the center of rotation. Has been established. On the back surface of the driven scroll 64, three fan blades are erected radially at intervals of 120 °, and an attachment seat 67 is attached to the thick portion above the fan blade 64c by an attachment portion 67b.
Further, a packing 69 is sandwiched between the tip end surface of the cylindrical portion 64b and the mounting seat 67 to maintain airtightness.

The mounting seat 67 is formed in a mushroom shape,
In order to discharge the compressed gas discharged from the driven scroll opening hole 64a to the outside, a communication hole 67c is opened with the stem portion facing the upper surface of the umbrella, and three attachment portions 6 are radially formed on the umbrella portion.
7b is provided, and three opening holes 67a through which cooling air circulates are formed in the stem portion outside the attachment portion. A rotary bearing is fitted to the outer periphery of the stem portion of the mounting seat 67, and the outer periphery of the rotary bearing has the hole 6 of the housing 60B.
It is fixed to 0Ba, and the tip portion of the stem portion projects in a cylindrical shape and is rotatably fitted in the opening hole 60Bc of the housing 60B. The mounting seat 67 is rotatably arranged in the housing 60B with the driven scroll 64 fixed.

Further, the outer surface of the housing 60B has a plurality of opening holes 6 for drawing in air for cooling the driven scroll 64.
A plurality of opening holes 60Bi for releasing 0Bg and the air are provided. According to a preferred embodiment, the maximum gas pocket volume formed by the rear drive scroll wrap 63 and the rear driven scroll wrap 65 is 56.6c.
c, the minimum gas pocket volume is set to 19.1 cc, and the volume ratio (maximum volume / minimum volume = compression ratio) is set to 2.96.

FIG. 12 is a block diagram of a control device for driving a vacuum pump provided with a scroll mechanism relating to a combination of a driving scroll and a driven scroll.
The suction end of the front stage vacuum pump body 200A is connected to the suction port of the closed container 35 by a pipe 59. The discharge opening of the front stage vacuum pump body 200A and the suction end of the rear stage vacuum pump body 200B are connected to the pipe 56. The discharge opening and the suction end of the latter-stage vacuum pump main body 200B are bypassed by a pipe 57. This front stage vacuum pump body 200A
Is connected to the rotary drive shaft 53A of the motor 50, the latter-stage vacuum pump main body 200B is connected to the rotary drive shaft 53B of the motor 50, and the motor 50 is wired and connected so as to be rotationally controlled by the electric controller 34. Controller 34
Is equipped with a measuring means for measuring the gas pressure in the closed vessel 35, and the rotational speed of the motor 32 can be controlled by the measured value of the measuring means.

Further, in (b), the suction end of the pre-stage vacuum pump main body 300A is connected to the suction port of the closed container 35 by the pipe 59, and the discharge opening of the pre-stage vacuum pump main body 300A and the post-stage vacuum pump main body 300B. Is connected to the pipe 56, and the discharge opening of the latter stage vacuum pump main body 300B and the suction end are bypassed by the pipe 57. The front-stage vacuum pump main body 300A is connected to the rotary drive shaft 54 of the motor 51, and the rear-stage vacuum pump main body 300B is connected to the rotary drive shaft 55 of the motor 52.
1, 52 are wired and connected so that rotation is controlled by an electric control device 34, and the electric control device 34 is provided with a measuring means for measuring the gas pressure in the hermetically sealed container 35. The number of rotations of 32 is controllable.

The operation of the thus constructed fourth embodiment will be described with reference to FIGS. 8 (a), 9, 10 and 12 (a). When the hermetic container 35 is connected to the vacuum pump main body 200A and the motor 50 is rotationally driven by the electric control device 34, the drive scroll 62 is rotated by the rotary drive shaft 53A. This rotational driving force is transmitted to the driven scroll 64 by the revolution mechanism 68, and the driven scroll 64 is driven.
Drive. The compressed gas compressed by the drive and driven scrolls is supplied from the pipe 56 to the suction end 61a of the post-stage vacuum pump 200B through the discharge passage 67c in FIG.

At this time, the inside of the pipe 56 is filled with the gas discharged from the preceding vacuum pump, its pressure is higher than the external atmospheric pressure, and the pressure control valve 125 is opened by the pressure to discharge the compressed gas inside to the outside. When the pressure of the gas in the pipe 56 falls below the atmospheric pressure, the pressure control valve 125 closes.

On the other hand, the rear vacuum pump 200B is driven simultaneously with the rotation of the rotary drive shaft 53B so that the front vacuum pump 200A starts to operate, and the gas compressed by the drive scroll 62 and the driven scroll 64 passes through the discharge passage 67c and is non-returned. The valve 124 is pushed to discharge it to the outside. As the pressure in the closed container 35 decreases, the electric control device 34
Increases the rotation speed of the motor 50 to compensate for the decrease in the gas suction amount.

FIG. 8B is a structural diagram showing a fifth embodiment of the oil-free two-stage vacuum pump according to the present invention, which uses a driving scroll and a driven scroll. The same members as those in the above-described fourth embodiment are designated by the same reference numerals. In the figure, the oil-free two-stage vacuum pump main body 300 is shown in FIG.
To the rotary drive shaft 54 of the motor 52 and the rotary drive shaft 55 of the motor 52.
00B, the discharge opening of the rear vacuum pump 300B is connected to the discharge passage 57 communicating with the outside by the check valve 124, and the discharge opening of the front vacuum pump 300A and the suction opening of the rear vacuum pump 300B are piped. It is connected by 56 and is arranged to bypass the discharge passage by an exhaust valve 125 that opens and exhausts to the outside when the inside of the pipe 56 becomes a predetermined pressure or more.

Here, the pre-stage vacuum pump main body 300A shown by a block has the same configuration as the pre-stage vacuum pump main body 200A shown in FIG. 9, and the post-stage vacuum pump main body 300B is the post-stage vacuum pump main body 300B shown in FIG. 20
0B is the same as that of the fourth embodiment, and the difference from the fourth embodiment is that the fourth embodiment drives the front stage and rear stage vacuum pumps by the same motor, whereas the present embodiment uses different front stage and rear stage vacuum pumps. It is driven by a motor.

Next, the operation of this embodiment will be described with reference to FIGS. 8 (b), 9, 10 and 12 (b). When the airtight container 35 is connected to the vacuum pump main body 300A and the motor 51 is rotationally driven by the electric control device 34, the drive scroll 62 is rotated by the rotary drive shaft 54. The rotational driving force is transmitted to the driven scroll 64 by the revolution mechanism 68, and the driven scroll 64 is driven. The compressed gas compressed by this driving and driven scroll is supplied from the pipe 56 to the subsequent vacuum pump 300B.

At this time, the inside of the pipe 56 is filled with the gas discharged from the preceding vacuum pump, the pressure thereof is higher than the external atmospheric pressure, and the exhaust valve 125 is opened by the pressure to exhaust the compressed gas inside to the outside. This continues until the pressure of the gas in pipe 56 falls below atmospheric pressure.

The electric controller 34 causes the motor 52 to rotate after a lapse of time calculated in consideration of the volume of the closed container 35, the working volume of the front scroll mechanism, the rotation speed, and the like. Around the time, around that time, the pressure of the compressed gas of the preceding scroll mechanism discharged to the pipe 56 is lower than the atmospheric pressure, and the pressure control valve 125 is closed. After that, the compressed gas discharged by the front scroll mechanism is compressed by the rear scroll mechanism, and the check valve 124 is opened to be discharged to the outside.

As the pressure in the closed container 35 decreases due to the suction of the vacuum pump, the electric control unit 34 increases the number of rotations of the motors 51 and 52. This compensates for the decrease in the amount of gas exhausted in the closed container and shortens the processing time.

In both the second embodiment and the fifth embodiment, the start timing of the motor for driving the latter-stage vacuum pump is calculated by taking into consideration the volume of the closed container and the performance of the former-stage vacuum pump. However, the invention is not necessarily limited to this, and a moving piece that operates in conjunction with the opening / closing operation of the pressure control valve, a sensor, or the like may be arranged and detected to drive the latter stage vacuum pump.

In the fourth and fifth embodiments, the front and rear vacuum pumps are combined with the fixed scroll and the orbiting scroll mechanism or the combination of the driving scroll and the driven scroll, respectively. Of course, the former combination may be used for the pump, the latter combination may be used for the latter vacuum pump, and the latter combination may be used for the former pump and the latter combination may be used for the latter pump. .

As described above, the present embodiment is an oil-free two-stage vacuum pump constructed by connecting the front-stage pump section and the rear-stage pump section in series, so that the outer shape of the scroll can be reduced. . As a result, problems such as rotation blurring due to shaft deflection during high-speed rotation, uneven contact between fixed scroll and orbiting scroll, noise and heat, or deterioration of durability, etc. There is no.

Since the discharge space of the front-stage pump section communicates with the discharge space of the rear-stage pump via a bypass path, and a pressure control valve that closes below a predetermined pressure is provided on the bypass path. A closed container to be evacuated is connected to the suction end of the pre-stage pump, and since the atmospheric pressure in the closed container is close to the atmospheric pressure in the initial stage of start-up, the suction gas has already become a high pressure in the compression process of the pre-stage pump,
When the pressure exceeds a predetermined pressure, for example, when the pressure becomes higher than the external pressure which is the pressure in the discharge space of the rear pump, the pressure control valve is opened and the compressed gas by the front pump is discharged to the outside. Therefore, since compressed gas above atmospheric pressure is not sucked into the post-stage pump, heat is not generated due to excessive compression in the post-stage pump section, and heat is generated due to high pressure, reducing the durability of the vacuum pump. Or it will not be burned and damaged.

When the front and rear pumps are integrally supported on a common rotary shaft, and the rotary shaft is connected to a drive source and rotated by the same rotary drive source, one drive source is used. Can drive the vacuum pump by
A compact vacuum pump with a small number of parts is provided. Further, a load sealing container is connected to the suction side of the pre-stage pump, and a control means capable of changing the number of rotations according to the degree of vacuum pressure in the sealing container is provided. The control means controls the rotation of the same rotary drive source. If it is configured as possible,
As the pressure of the loading closed container decreases, the number of revolutions of the front-stage pump and the rear-stage pump is increased to increase the number of discharges of the gas in the closed container, and the processing time can be shortened.

When the front and rear pumps are rotated by separate rotary drive sources, the optimum compression load for the compressed gas due to the compression ratio of the front pump and the compression gas due to the compression ratio of the rear pump is optimal. A rotary drive source can be applied to each pump. Also, in the initial stage of inhalation of the load closed container, when the compressed gas pressure of the preceding pump exceeds the atmospheric pressure, that is, in the viscous flow region where the degree of vacuum in the closed container is low, only the preceding pump is driven. The pressure control valve exhausts the gas to the outside, and after the compressed gas pressure of the front stage pump falls below the atmospheric pressure, the rear stage pump can be rotationally driven, and economical operation can be performed. Further, in this case, the orbiting scrolls of the front and rear pumps can be driven from both sides of the pump main body, and the orbiting scrolls of the front and rear pumps can be driven to rotate by the same drive source, compared to the rotary drive source. The position at which the orbiting scroll of the extending rotary shaft is fixed is shorter than the position of the rotary drive source, and the amount of blurring in rotation due to warping of the shaft is reduced accordingly.

Further, in the case of a combination of a fixed scroll and an orbiting scroll, and when the bypass passage is formed by providing a bypass hole on the bottom wall of the fixed scroll, only the hole is formed in the fixed scroll which is not rotationally driven. The bypass path can be formed with the simple structure. In particular, the fixed scroll of the front stage pump and the orbiting scroll of the rear stage pump are arranged so as to face each other, and compressed air can be supplied to the orbiting scroll of the rear stage pump through a discharge port provided in the fixed scroll of the front stage pump. In this case, the distance between the final sealed space formed by the fixed scroll of the preceding pump and the orbiting scroll and the first sealed space formed by the fixed scroll of the succeeding pump and the orbiting scroll becomes shorter, and it is immediately taken into the sealed space of the latter pump. It is possible to provide an efficient vacuum pump in which the amount of gas remaining between both spaces is small.

[0105]

As described above, the present invention can provide an economical vacuum pump that reduces heat generation even in a low-vacuum viscous flow region.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an oil-free two-stage vacuum pump according to the present invention.

2A is a sectional view taken along the line AA of FIG. 1, and FIG. 2B is a sectional view taken along the line BB of FIG.

3 is a sectional view taken along line CC of FIG.

FIG. 4 is a diagram for explaining the operation of the pre-stage pump unit.

FIG. 5 is an operation explanatory diagram of a rear stage pump.

FIG. 6 is a configuration diagram showing a second embodiment of an oil-free two-stage vacuum pump according to the present invention.

FIG. 7 is a configuration diagram showing a third embodiment of an oil-free two-stage vacuum pump according to the present invention.

8A is a configuration diagram showing a fourth embodiment of an oil-free two-stage vacuum pump according to the present invention, and FIG. 8B is a block diagram of an oil-free two-stage vacuum pump according to the present invention. It is a block diagram which shows 4th Example.

9 is a cross-sectional view of the scroll mechanism shown in FIG. 8A on the front stage side.

10 is a cross-sectional view of the scroll mechanism shown in FIG. 8A on the rear stage side.

FIG. 11 is a block configuration diagram of a control device that drives an oil-free two-stage vacuum pump according to first to third embodiments.

FIG. 12 is a block configuration diagram of a control device that drives an oil-free two-stage vacuum pump according to fourth and fifth embodiments.

[Explanation of symbols]

1, 10, 100, 200, 300 Oil-free two-stage vacuum pump body 2, 12, 102, 3, 13, 103 Housing 4, 14, 104 Front-stage fixed scroll wrap 5, 15, 105 Rear-stage fixed scroll wrap 6 , 16, front orbiting scroll end plate 7, 17 rear orbiting scroll end plate 8, 18 front orbiting scroll wrap 9, 19 rear stage orbiting scroll wrap 11 to 13, 20, 21, 60 housing 22 fan 23 chip seal 24, 124 Check valve 25, 125 Pressure control valve 26 Balance weight 28-31, 53-55 Rotation drive shaft 32, 33, 50-52 Motor 34 Electric control device 35 Sealed container 36 Cover 37, 47, 68 Revolution mechanism 38, 69 Packing 39-43 Rib 56-59 Piping 61 Dust Hauge Grayed 62 driving scroll 63 driven scroll lap 64 driven scroll 65 driven scroll wrap 66 and 67 mounting seat

Claims (10)

[Claims] 1. A front stage pump unit and a rear stage pump unit are provided,
In an oil-free two-stage vacuum pump in which these pump units are connected in series and driven, a discharge space of the preceding-stage pump unit communicates with a discharge space of the following-stage pump via a bypass passage, and a predetermined pressure is applied on the bypass passage. An oil-free two-stage vacuum pump having a pressure control valve that is closed below. 2. The oil according to claim 1, wherein the front-stage pump and the rear-stage pump are integrally supported by a common rotary shaft, the rotary shaft is connected to a drive source, and is rotated by the same rotary drive source. Free 2-stage vacuum pump. 3. A suction means of the pre-stage pump is connected to a closed vessel for load, and a control means is provided which can change the number of rotations according to the degree of vacuum pressure in the closed vessel, and the same rotation drive is performed by the control means. The oil-free two-stage vacuum pump according to claim 2, wherein the source is configured to be rotation-controllable. 4. The oil-free two-stage vacuum pump according to claim 1, wherein the front-stage pump and the rear-stage pump are rotated by separate rotary drive sources. 5. A combination of a fixed scroll and an orbiting scroll, wherein a bypass hole is provided on the bottom wall of the fixed scroll to form the bypass passage, and the oil-free two-stage type. Vacuum pump. 6. The oil-free 2 according to claim 1, which is a combination of a driving scroll and a driven scroll, wherein the discharge passages of both pumps are connected by providing a bypass pipe to form the bypass passage. Stepped vacuum pump. 7. A pre-stage pump unit and a post-stage pump unit each comprising a fixed scroll and an orbiting scroll, wherein these pump units are fitted with separate fixed scroll wraps and orbiting scroll wraps, respectively. The fixed scroll and the orbiting scroll of the rear stage pump are arranged so as to face each other, and compressed air can be supplied to the orbiting scroll of the rear stage pump through a discharge port provided in the fixed scroll of the front stage pump. The oil-free two-stage vacuum pump according to claim 1. 8. The oil-free two-stage vacuum pump according to claim 1, wherein the compression ratio of the latter-stage pump is higher than the compression ratio of the front-stage pump. 9. The oil-free two-stage vacuum pump according to claim 7, wherein the maximum gas pocket volume of the rear stage pump is smaller than the minimum gas pocket volume of the front stage pump. 10. The oil according to claim 7, wherein the height of the scroll wrap of the front-stage pump and the rear-stage pump from the end plate surface is different from that of the front-stage pump and the rear-stage pump. Free 2-stage vacuum pump.