JPS6137474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies from a vacuum belonging to the viscous flow region to a vacuum belonging to the molecular region, that is, from around 760 Torr.
This invention relates to a high-vacuum pump configured to continuously perform exhaust action over a wide range up to around 10 ^-6 Torr with a single driving source at atmospheric back pressure.

That is, in a high-vacuum side helical groove molecular pump that pumps air from the outer circumference to the inner circumference along the helical grooves bored in two inner walls facing the rotating disk at a small distance, the helical grooves are formed in multiple stripes. Furthermore, radial flow labyrinth seal grooves are formed on the groove ridges forming the multi-striped spiral grooves, and the distance between the rotating disk and the inner wall facing the rotating disk is set to 0.2 to 1 mm, and , a rotating cylinder integrally constructed with the rotating disk on the double-sided discharge port side of the rotating disk, and facing an inner cylinder surface and an outer cylinder surface with multi-thread grooves bored in the inner wall within the inner wall. By rotating at high speed with an interval of 0.2 to 1 mm, it forms a multi-threaded grooved pump that performs exhaust gas, and a bearing that supports the drive shaft of the rotating disk and rotating cylinder in the integrated structure. A helical groove molecular pump with a multi-start thread groove is arranged by placing it on the atmospheric pressure side of the rotary shaft seal, and the discharge port of the pump is directly connected to the suction port of the low vacuum side vane vacuum pump mechanism. A two-stage series exhaust mechanism of vane pumps is used, and both drive shafts are connected by a suitable transmission force transmission mechanism to operate from a single drive source, and the air is discharged from 760 Torr to 10 ^-6 Torr from the discharge port of the vane pump.
This provides a high vacuum pump that continuously evacuates up to the base.

Incidentally, the history of spiral groove molecular pumps, screw groove molecular pumps, and vane vacuum pumps is old,
Improvements in the grooves of the helical groove molecular pump mechanism and the thread groove molecular pump mechanism, a two-stage configuration as a threaded helical groove molecular pump, improvements in the threaded helical groove molecular pump and the shaft seal of the drive shaft, and furthermore The present invention is the first to propose a two-stage high vacuum pump operated by a single driving source, which is a series arrangement of a threaded helical groove molecular pump and a vane vacuum pump.

We will elaborate on these proposed improvements.

First, the first improvement point will be described. Conventional spiral groove molecular pumps aim for back pressures of 10 ^-1 to 10 ^-2 Torr and suction side of 10 ^-6 to ^{10 -7} Torr.
A high compression ratio of 10 ⁵ or higher was required. Therefore,
As is well known, the gap between the rotating disk and the two opposing inner walls is approximately 0.01mm to 0.03mm.
It was impractical not only in terms of workmanship but also in terms of operational reliability. The present invention first uses this spiral groove molecular pump mechanism as a high-vacuum side pump ^.
The required compression ratio should be kept at about 10 to 100 by operating in the vicinity of 10 ^-6 Torr, and a labyrinth seal groove in the radial flow direction should be bored on the helical groove crest to form two seals facing the rotating disk. The required amount of the gap can be increased to about 0.2 to 1 mm by reducing the amount of gas exhausted back to the suction port through the gap with the inner wall. The above-mentioned gap of about 0.2 to 1 mm is the same or larger than the gap between the rotor and housing of Roots-type vacuum pumps that are currently in practical use, and is sufficient for practical use not only in terms of reliability but also in terms of machining. It is true.

Next, the second improvement point will be described. As mentioned above, the helical groove molecular pump has a compression ratio of 10 to
Since the size is as small as about 100 mm, a screw is inserted into the inner wall of the helical groove molecular pump by attaching a rotating cylinder integral with the rotating disk on the both-side discharge port side of the rotating disk of the helical groove molecular pump. A threaded groove molecular pump is formed by rotating with a gap of about 0.3 ^to 1 mm between the grooved inner cylinder surface and the outer cylinder surface,
The compression ratio of around 100 was compensated for in the region near 10 ^-5 Torr. In order to achieve the compression ratio of 100, the pressure gradient between adjacent thread grooves is reduced by using multiple thread grooves, the back flow of exhaust gas is reduced by the thread groove labyrinth sealing effect, and the cylindrical By increasing the length of the exhaust thread groove by configuring it as a two-stage multi-thread groove molecular pump on the surface and outer cylinder surface,
In contrast to the gap of 0.01 to 0.03 mm that was designed for classical screw groove molecular pumps, it has become possible to achieve a gap of approximately 0.3 to 1 mm. In other words, in combination with the above-mentioned improvement point 1, this multi-thread grooved helical groove molecular pump can now be configured to have a compression ratio of 10 ³ or more as a whole at a practical work level.

Next, the third improvement point will be described. Both conventional helical groove molecular pumps and screw groove molecular pumps have bearings that support the drive shaft placed in the back pressure side vacuum area, and a sealing mechanism such as a gasket is used as a vacuum seal of the drive shaft to the back pressure side vacuum area. Therefore,
Since the bearing lubricant was placed in a vacuum region, not only the durability of the bearing but also the degree of back pressure could not be made very high. However, the leakage was large and the durability was not sufficient. For these reasons, conventional pumps are not practical.
At high speed rotation of 6000 rpm or more, it was impossible to maintain the back pressure side at 10 ^-2 Torr or less.

Therefore, in the present invention, by using a magnetic fluid seal with a leakage rate of 10 ^-8 std cc/sec (He) or less for the vacuum shaft seal of the drive shaft, the leakage amount is dramatically reduced, and the bearing supporting the drive shaft is By configuring the magnetic fluid seal to be on the atmospheric pressure side, the back pressure side vacuum area of the multi-threaded helical groove molecular pump can be maintained at 10 -3 to 10 ^-3 even when rotating at high speeds of 6000 rpm or higher.
It became possible to maintain a vacuum level of 10 ^-4 Torr.

Furthermore, the fourth improvement point will be described. As is well known from the pumping principle, the pumping speed of both conventional spiral groove molecular pumps and thread groove molecular pumps is significantly lower than that of diffusion pumps and axial flow molecular pumps, and from this point of view, they are difficult to put into practical use. This was a major reason for his disappearance. In other words, as is well known, the exhaust speed is proportional to the cross-sectional area of the groove and the circumferential speed of the rotating disk and rotating cylinder, but unlike conventional pumps, the back pressure is high and a high compression ratio is required. Helical groove molecular pumps, screw groove molecular pumps,
With pumps each having a single unit configuration, it is difficult to increase the depth of the grooves or the number of grooves, and therefore it is not possible to increase the pumping speed.

In the present invention, the back pressure is increased to 10 ^-3 Torr or more,
By lowering the required compression ratio in the molecular pump section from the conventional 10 ⁵ to 10 ³ , and by arranging a spiral groove molecular pump and a screw groove molecular pump in series, the required compression ratio for each molecular pump was lowered. It became possible to secure the required compression ratio even by increasing the depth and number of grooves and increasing the pumping speed.

Finally, the fifth improvement point will be described. The helical groove molecular pump with multi-thread grooves described above for Improvements 1, 2, 3, and 4 is, in principle, a pump that operates in the molecular region of the gas passing through the screw grooves and the helical grooves, respectively. An auxiliary pump is required to keep the pressure side in the molecular stream. Conventional spiral groove molecular pumps and screw groove molecular pumps use vane vacuum pumps that have a separate drive source and are configured separately to maintain vacuum in the molecular flow area on the back pressure side. The entire exhaust system was constructed by arranging the pumps. That is, the system to be evacuated is first evacuated to the molecular region by a vane vacuum pump, and then a spiral groove molecular pump or a screw groove molecular pump is operated to ensure a high vacuum, but it is not possible to drive both at the same time. In other words, conventional spiral groove molecular pumps and thread groove molecular pumps have a high compression ratio of 10 ⁵ or more.
Due to the back pressure maintenance condition of the 10 ^-2 Torr stand, it is not possible to make the depth of the spiral groove or thread groove large in view of the mean free path of the molecules of the gas to be pumped out, especially in the vicinity of the discharge port side of each pump. The depth of the groove was approximately 1 mm. Therefore, in a trench of this depth,
When operating continuously at around 0.5 to 10 Torr, the heat generated by the compression work becomes so large that it cannot be ignored, and the gap between the rotating disk or rotating cylinder and the inner wall surface where they face each other is as small as 0.01 to 0.03 mm, as mentioned above. Due to this, there was a risk of contact accidents due to thermal expansion, and it was necessary to constantly pay attention to the degree of vacuum on the back pressure side. Furthermore, with a high compression ratio of 10 ⁵ or more and a back pressure of 10 ^-2 Torr, the depth of the groove, or in other words the cross-sectional area of the groove, can be increased over the entire length of the helical groove or screw groove. Therefore, it goes without saying that the pumping speed mentioned in Improvement Point 4 cannot be increased, and the vane vacuum pump suction port can be connected directly to the discharge port side of these spiral groove molecular pumps or thread groove molecular pumps to increase the pumping speed continuously from atmospheric pressure. Generally speaking, when two-stage series pumping is performed, in the case of a viscous flow region, the spiral groove molecular pump and thread groove molecular pump act as pumping resistance against the vane vacuum pump, working to reduce the pumping speed of the vane vacuum pump. Bypass piping was installed so that only a vane vacuum pump could be used to pump out the viscous basin.

Therefore, the present invention has a compression ratio of about 10 ³ and a compression ratio of about 10 ^-3.
Since the helical groove molecular pump with multi-thread grooves is operated at a high speed of 6000 rpm or more under the back pressure condition of ~10 ^-4 Torr level, the depth of the helical groove and the thread groove is determined by the mean free path of the molecules of the gas to be pumped. 0.5 to 10 Torr
It is possible to design the helical groove to be large enough to cause heat generation due to compression work to be ignored even during continuous operation in the vicinity, and the groove depth (in other words, the cross-sectional area of the groove) can be designed to be large over the entire length of the helical groove and thread groove. 4. The thread grooves are formed in multiple threads, and the gap between the rotating part of the multi-thread grooved spiral groove molecular pump and the inner wall facing it is large, and this gap acts as an exhaust path under viscous flow. Focusing on the fact that this design allows the vane vacuum pump to be designed as a pre-stage pump without reducing the pumping speed in the viscous region, we installed a vane vacuum pump directly at the discharge port of this multi-thread grooved helical groove molecular pump. It is proposed that the suction ports can be connected and simultaneously driven by a single drive source to form a two-stage pump that can continuously exhaust air from atmospheric pressure.

An embodiment of the present invention will be described below based on the accompanying drawings. First, the configuration of the high vacuum side stage spiral groove molecular pump will be explained. 1 is the right housing of the high vacuum side spiral groove molecular pump, and 2 is the left housing of the same spiral groove molecular pump. The right housing 1 and the left housing 2 are fixed together with a tightening bolt 9 via an O-ring 10. 3 is a suction port formed between the right housing 1 and the left housing 2;
It communicates with an exhaust system (not shown). The left housing 2 has an intermediate housing 4 connected to the suction port 7 of the low vacuum side vane vacuum pump.
A discharge hole 5 communicating through a through hole 6 is bored. A rotary disk 12 is housed in an evacuation chamber 11 formed by fitting the right housing 1 to the left housing 2 with an O-ring 10 and a tightening bolt 9. A rotating cylinder 13 that is integrated with the rotating disk 12 protrudes from both sides of the rotating disk 12 on the center side. Shaft sealing of the drive shaft 14 of the rotating cylinder 13 to the evacuation chamber 11 is performed by magnetic fluid seals 15 and 16 fitted into the right housing 1 and the left housing 2, respectively. Further, the drive shaft 14 has a bearing 1 fitted in the right housing 1 and the left housing 2 on the atmospheric pressure side with respect to the magnetic fluid seals 15 and 16.
7, 18. One of the bearings 1
Reference numeral 8 designates two ball bearings or angular ball bearings to which a preload is applied so that not only the radial load of the drive shaft 14 but also the position in the thrust direction can be fixed. Reference numeral 19 denotes an oil seal for sealing lubricating oil for the one bearing 18. The other bearing 17 is a grease-sealed ball bearing.

Further, the drive shaft 14 is provided with a through hole 20 and a cooling hole 21, respectively. In other words, the through hole 2
0 is bored at the center of the drive shaft 14 so as to communicate with the evacuation chambers 11 on both sides of the rotating cylinder 13,
Also, the cooling hole 21 is connected to the light housing 1 of the drive shaft 14.
Perforated at the side end. A cooling water jet nozzle 22 formed in the light housing 1 is disposed within the cooling hole 21 . 23 is a gear formed on the opposite end of the drive shaft 14 from the cooling hole 21. The depth of the cooling hole 21 is the same as that of the magnetic fluid seal 1.
It is good to go up to the vicinity where 6 is placed. Furthermore, the outer circumferential surface 25 and inner circumferential surface 26 of the rotating cylinder 13 are both coated with tetrafluoride resin (trade name: Teflon).

Next, the rotating disk 12 contained in the evacuation chamber 11 is attached to the inner wall 27 of the light housing 1.
and the inner wall 28 of the left housing 2.
They are placed facing each other with a gap of 0.2 to 1 mm. These inner walls 27 and 28 have spiral grooves 2 that rotate in opposite directions.
9 and 30 are the objects from the suction port 3 to the rotating disk 1.
The groove depth is gradually decreased toward the center of the groove. These spiral grooves 29,3
0 communicates with intermediate exhaust chambers 31 and 32 formed in the inner walls 27 and 28. These intermediate exhaust chambers 3
1 and 32 are formed on the inner walls 27 and 28, respectively, facing the intersection of the rotating cylinder 13 and the rotating disk 12.

By the way, when the rotating disk 12 rotates, the gas in the molecular region within the evacuation chamber 11 is dragged by the rotating disk 12 and exhausted from the outer circumference to the inner circumference in the spiral grooves 29 and 30. The pumping principle is the same as that of the conventional spiral groove molecular pump, but the present invention has the following configuration in this respect.

As shown in FIG. 3 as an example, the spiral groove 29 is formed in four strips 29', 29'', 29. The spiral groove groups 29, 29', 29'', 29
The groove dividing wall 3 on the inner wall 27 is bored with
3, 33', 33'', 33, radial labyrinth seal grooves 34, 34', 34'', 34 are spirally closed with respect to the suction port 3 side and opened with respect to the intermediate exhaust chamber 31. configured.

In addition, in FIG. 3, as an embodiment of the present invention, four spiral groove groups 29, 29', 29'', 29
Formation example and four radial labyrinth seal grooves 3
4, 34', 34'', and 34 examples are shown, but other numbers of spiral groove groups and labyrinth seal groove groups may be formed.Also, in FIG. As an example, an example in which the cross-sectional shape is triangular has been shown, but other shapes such as a trapezoidal groove, a rectangular groove, or a serrated groove may also be used.Furthermore,
In FIG. 3, the inner wall 27 of the light housing 1
Although the inner wall 2 of the left housing 2
8, it is obvious that the helical groove group 30 and the radial labyrinth seal groove group 75 are formed in the same manner on mirror surfaces, without the need of illustration.

On the other hand, in the evacuation chamber 11, a rotating cylinder 13 protrudes from both sides of the rotating disk 12 on the center side.
are the inner cylindrical surfaces 35 and 36 and the outer cylindrical surfaces 37 and 38 formed on the inner wall 27 of the right housing 1 and the inner wall 28 of the left housing 2, respectively, and 0.5
They are placed opposite each other with a gap of ~1 mm,
The inner cylinder surfaces 35 and 36 have thread grooves 39 and 40,
Further, thread grooves 43 and 44 are formed in the outer cylindrical surfaces 37 and 38, respectively, as follows. In other words, the thread grooves 39 and 40 are formed on the inner cylindrical surfaces 35 and 36 in opposite directions from the intermediate exhaust chambers 31 and 32, and in the inner walls 27 and 28, respectively. and second intermediate exhaust chambers 41, 42 formed so as to communicate the outer cylinder surfaces 37, 38.
It will be drilled towards. Moreover, the screw grooves 43, 44
are bored on the outer cylindrical surfaces 37, 38 in opposite directions from the second intermediate exhaust chambers 41, 42 toward the back pressure side exhaust chamber 45 of the vacuum exhaust chamber 11 communicating with the discharge hole 5. Ru.

Since the flow path is configured as described above, when the rotating cylinder 13 rotates, the intermediate exhaust chamber 3
The gas in the molecular region at 1 and 32 moves into the rotating cylinder 13
first, the inside of the thread grooves 39, 40 formed on the inner cylinder surfaces 35, 36 is exhausted toward the second intermediate exhaust chambers 41, 42, and further the second intermediate exhaust chambers 41, 42 are exhausted. 42 is similarly dragged by the rotating cylinder 13 and exhausted toward the back pressure side exhaust chamber 45 through the thread grooves 43 and 44 formed on the outer cylinder surfaces 37 and 38. Although the evacuation principle is the same as that of the conventional thread groove molecular pump, in the present invention, these thread grooves are formed in multiple lines as described above.

In addition, in FIG. 1, as an embodiment of the present invention, thread grooves 39, 40, 43, 4 are bored in the inner cylinder surfaces 35, 36 and the outer cylinder surfaces 37, 38, respectively.
4 is shown with a constant depth, but the thread grooves 39, 40 formed on the inner cylinder surfaces 35, 36 are provided in the second intermediate exhaust chambers 41, 42, and in the outer cylinder surfaces 37, 38. The thread grooves 43 and 44 formed on the top may be formed so that the depth of each thread groove becomes shallower toward the back pressure side exhaust chamber 45.

As described above, a helical groove molecular pump that exhausts air from the outer circumference to the inner circumference along the helical grooves 29 and 30 bored in the two inner walls 27 and 28 facing the rotating disk 12 at an interval of 0.3 to 0.5 mm is created. The spiral grooves 29, 30 are multi-striped, and radial labyrinth seal grooves (eg, three
4, 34', 34'', 34), and furthermore, a rotating cylinder 13 integrally constructed with the rotating disk 12 is provided on the inner wall 27, Within 28, the inner wall 27,
Outer cylinder surface 37, 3 with multiple thread grooves drilled in 28
8 and the inner cylindrical surfaces 35 and 36 with an interval of 0.2 to 1 mm and rotated at high speed to form a multi-thread groove pump that exhausts air. The pump is configured as a high vacuum side stage.

Next, the configuration of the low vacuum side stage vane vacuum pump will be explained. An oil case 45 is fixed to the left housing 2 with a gasket 80 and a bolt 81. 46 is the oil case 45
This is an oil reservoir formed by the left housing 2 and the left housing 2. 48 is a vane vacuum pump cylinder,
As shown in FIG. 4, it has a discharge port 47. This outlet 47 is under atmospheric back pressure. Further, the vane vacuum pump cylinder 48 has the above-mentioned suction port 7. 49 is a side cover plate of the vane vacuum pump cylinder 48. Inside the oil reservoir 46 is a vane vacuum pump cylinder 48.
A side cover plate 49 and the intermediate housing 4 described above are fixed to the left housing 2 by bolts 50.
As shown in FIG. 4, a rotor 51 is provided on the inner surface of the vane vacuum pump cylinder 48 so as to be eccentric and in contact with the inner surface of the vane vacuum pump cylinder 48 with a small gap. A sliding blade 52 is attached to the rotor 51 so as to be slidable in the centrifugal direction. 53 is a drive shaft of the vane vacuum pump, and 54 is a key for fitting the rotor 51 to the drive shaft 53 of the vane vacuum pump.

This vane vacuum pump mechanism has the same configuration as the conventional Goede type vane vacuum pump.
As the rotor 51 rotates in the direction of the arrow in FIG.
The exhaust space 55 formed between the sliding blade 52 and
It performs an evacuation action by being swept by the pump, and is arranged as a low-vacuum side vane vacuum pump in this high-vacuum pump.

Next, in the space 56 bored in the intermediate housing 4, a gear 23 formed on the left housing 2 side end of the drive shaft 14 of the multi-thread grooved helical groove molecular pump, The drive shaft 53 of the vane vacuum pump is meshed with a gear 57 formed at the end of the high vacuum side multi-threaded spiral groove molecular pump side, thereby transmitting driving force from the drive shaft 53 of the vane vacuum pump. A speed change mechanism for transmitting information to the drive shaft 14 of the helical groove molecular pump with threaded grooves is constructed.

In the intermediate housing 4, 58 is a cooling water passage, 59 and 60 are O-rings for preventing leakage of cooling water in the cooling water passage 58, and 6
1 is an O-ring for sealing the exhaust space 55 of the vane vacuum pump against atmospheric pressure, and 62 is a lubricating oil supply port to the space 56.

Reference numeral 63 denotes a rotary shaft seal for the bearing 17, on which a mechanical seal is arranged, and performs shaft sealing of the cooling water supplied from the cooling water jetting nozzle 22 to the cooling hole 21.

Furthermore, 64 is an O-ring that performs vacuum sealing against atmospheric pressure between the through hole 6 of the intermediate housing 4 and the connecting portion of the discharge hole 5 of the multi-thread grooved spiral groove molecular pump.

In addition, 65 is an O-ring for sealing the exhaust space 55 against atmospheric pressure, 66 and 67 are bearings that support the drive shaft 53 of the vane vacuum pump with the side cover plate 49 and intermediate housing 4; Numerals 68, 69, and 70 are oil seals for the drive shaft 53 of the vane vacuum pump, and 71 is an atmospheric exhaust port of the oil case 45.

Next, in one embodiment of the present invention, a single-stage vane vacuum pump was used as an example of the low-vacuum side vane vacuum pump mechanism, but it is equally possible to implement this with a two-stage vane vacuum pump structure. It is obvious that there is no need to illustrate this. Further, in one embodiment of the present invention, a first transmission transmission mechanism between the drive shaft 14 of the high-vacuum side multi-thread grooved helical groove molecular pump and the drive shaft 53 of the low-vacuum side vane vacuum pump is provided. As shown in the figure, the explanation has been given using an example of a gear transmission transmission mechanism. It is also possible to configure a belt transmission transmission mechanism that transmits driving force to a pulley 74 fitted and fixed to the drive shaft 53 of the vane vacuum pump via the drive shaft 53 of the vane vacuum pump. Furthermore,
In one embodiment of the present invention, the magnetic fluid seals 15 and 16 are used as the rotary shaft seals of the drive shaft 14, but oil seals, mechanical seals, etc. may also be used.

In the above configuration, the operation is as follows.

(A) When the gas flow from the evacuated system to the helical groove molecular pump mechanism with multiple thread grooves on the high vacuum side stage is in the molecular flow region; that is, the helical grooves 29, 30,
The mean free path of the gas flowing through each of the thread grooves 39, 40, 43, 44 is
The case where the depth is greater than 0, 39, 40, 43, and 44 will be explained.

When the drive shaft 53 of the low-vacuum side vane vacuum pump is energized by an appropriate external drive source, the gear 57 formed on the drive shaft 53 of the vane vacuum pump and the high-vacuum side multi-threaded helical groove molecule The driving force is transmitted to the drive shaft 14 of the high vacuum side multi-threaded helical groove molecular pump through the gear 23 formed on the drive shaft 14 of the pump. In this case, the rotation speed of the drive shaft 14 of the high-vacuum side multi-threaded helical groove molecular pump is 6000 rpm or more, and the drive shaft 53 of the low-vacuum side vane vacuum pump is operated at around 2000 rpm, so the above-mentioned This power transmission is accompanied by an increase in speed. A rotating disk 12 that is integrated with the drive shaft 14 of the high-vacuum side-stage multi-threaded helical groove molecular pump has two inner walls 27 facing the rotating disk 12 with a gap of about 0.2 to 1 mm, As described above, when the drive shaft 53 of the vane vacuum pump is urged to rotate at high speed through the power transmission mechanism in the same direction as the spiral grooves 29 and 30 formed in the The gas that entered through 3 is dragged by the rotating disk 12 and enters the spiral groove 2.
9 and 30 are compressed and exhausted toward intermediate exhaust chambers 31 and 32. As shown in FIG. 3, in this embodiment, the spiral grooves 29, 30 and the radial labyrinth seal grooves 34, 75 are each formed in four grooves (3
0 and 75 are omitted because they are mirror symmetrical in FIG. 3), and it goes without saying that each strip has the same effect. Note that the exhaust efficiency by the spiral grooves 29 and 30 is increased by reducing backflow leakage in the radial flow direction by the radial labyrinth seal grooves 34 and 75, and the radial labyrinth seal groove 3
4, 75 themselves also have the function of supplementary exhausting of backflow leakage gas dragged by the rotating disk 12 toward the intermediate exhaust chambers 31, 32.

Next, the rotating cylinder 13, which is integrated with the rotating disk 12, is rotated along the threaded grooves 39 and 40 formed in the inner cylinder surfaces 35 and 36 facing the rotating cylinder 13 with a gap of about 0.2 to 1 mm. When it rotates, the gas compressed and exhausted into the intermediate exhaust chambers 31 and 32 is dragged by the rotating cylinder 13 and flows through the thread grooves 39 and 40 into the second
The gas is compressed and exhausted to intermediate exhaust chambers 41 and 42. Furthermore,
Thread grooves 4 bored in outer cylinder surfaces 37 and 38 facing the rotating cylinder 13 with a gap of about 0.3 to 1 mm.
3 and 44 as well, they are similarly dragged by the rotating cylinder 13 and compressed and exhausted from the second intermediate exhaust chambers 41 and 42 to the back pressure side exhaust chamber 45, respectively. Furthermore, the back pressure side exhaust chamber 45 communicates with the discharge port 5 of the high vacuum side multi-thread grooved spiral groove molecular pump through the through hole 20, so that the compressed and exhausted gas is It reaches the discharge port 5.

On the other hand, in vane vacuum pumps, as is well known, it is inevitable that some oil vapor will flow back into the system to be evacuated, but according to the present invention, this backflow oil vapor can be Mouth 6
and the thread groove 3 via the back pressure side exhaust chamber 45 of the multi-thread grooved helical groove molecular pump, the thread grooves 43 and 44, and further the second intermediate exhaust chambers 41 and 42.
9 and 40, but the backflow is prevented by the labyrinth seal effect of the multi-thread groove and the multi-thread groove molecular pump effect, and the air is again compressed and evacuated to the suction port 7 of the low-vacuum side vane vacuum pump. Ru. In particular, this backflow oil vapor is mainly composed of hydrocarbon compounds with 4 to 5 or more carbon atoms, which have a larger molecular weight than air or water, so the molecular pump has a characteristic that the heavier the molecule, the higher the compression ratio. , this evacuation action is carried out effectively and a clean vacuum is achieved. still,
Since the rotating cylinder 13 is coated with a non-adhesive tetrafluoride resin, oil creeping to the rotating disk 12 due to adhesion of oil vapor is prevented, and a clean vacuum is always generated.

Next, the gas that has been compressed and exhausted to the discharge port 5 of the high-vacuum side multi-thread grooved spiral groove molecular pump is
The air is sucked in from the low vacuum side vane vacuum pump suction port 7 through the through hole 6 of the intermediate housing 4, and the vane vacuum pump cylinder 48 and rotor 51 are evacuated, similar to the exhaust action of conventional vane vacuum pumps. The space between the chambers 55 is swept by the sliding blades 52, and the air is exhausted to the atmosphere through the exhaust port 47 and the atmosphere exhaust hole 71. In addition, as a vacuum shaft seal against the atmospheric pressure of the drive shaft 14 of the high-vacuum side stage multi-threaded helical groove molecular pump, the leakage amount is 10 ^-8 std.
Magnetic fluid seals 15 and 16 below cc/sec (He)
The back pressure side exhaust chamber 45 can maintain the vacuum level close to the ultimate vacuum of the vane vacuum pump even during rotation. That is, if the vane vacuum pump has a single-stage configuration, a value of 10 ^-1 to 10 ^-2 Torr is maintained, and if it has a two-stage configuration, a value of 10 ^-3 to 10 ^-4 Torr is maintained.

Next, a cooling water jet nozzle 22 formed in the light housing 1 supplies cooling water from the outside to the drive shaft 1.
4, the frictional heat generated by the magnetic fluid seals 15 and 16 and the rotating disk 1
2 and the rotating cylinder 13 to remove some of the compression heat of the gas.

Further, the cooling water passage 58 formed in the intermediate housing 4 is supplied with cooling water from the outside, and contributes to cooling the intermediate housing 4 and the left housing 2 as well as the vane vacuum pump cylinder 48 and the like. This functions to make it advantageous for the vane vacuum pump to rotate at high speed and achieve high vacuum.

As described above, we have described the operation of a two-stage pump in a molecular flow area, in which a multi-threaded spiral groove molecular pump is arranged in series in the high vacuum side stage and a vane vacuum pump in series in the low vacuum side stage. Let's elaborate a little on the characteristics of the pump.

(1) About compression work in a helical groove molecular pump with multiple threads; Now, at the suction port 3 of the helical groove molecular pump with multiple threads, gas with a suction pressure P ₁ is flowing through the spiral grooves 29, 3.
0, is sequentially compressed along the thread grooves 39, 40, 43, and 44, and is compressed to P2 at the discharge hole ₅ and discharged. At this time, the compression work of the intake gas is P ₁ → P ₂
corresponds to the work W when subjected to adiabatic compression, It is. Here, K is the ratio of specific heat, V ₁ is the suction pressure P ₁
is the volume of gas when . Since the Honda thread grooved helical groove molecular pump mechanism is designed with a depth of approximately 10 mm or more for the screw grooves 29, 30 and the spiral grooves 39, 40, 43, and 44, the mean free path (N ₂ , O2 _, etc.), the back pressure side exhaust chamber 45 is
It begins to be held on a 10 ^-3 Torr platform and acts as a molecular pump. In other words, at low vacuum levels of 10 ^-2 Torr or less, the molecular pump hardly operates and therefore runs in idling mode, so it goes without saying that heat generation can be ignored. When operating as a molecular pump, P ₁ takes a high vacuum value of 10 ^-3 Torr or higher, so in equation (a) above, W becomes an extremely small value, and a pump with extremely high pumping efficiency is constructed. be done. Incidentally, the heat generation is also extremely small, and this was detailed in the fifth improvement point.

(2) Regarding the pumping speed of a helical groove molecular pump with multiple thread grooves; As is well known, the pumping speed _S0 of a single thread groove and spiral groove molecular pump is as follows, if leakage from the gap is not considered. It is expressed by the formula.

S ₀ =bhu/2...(b) Here, b is the spiral groove or thread groove 29, 30,
39, 40, 43, 44, h is the depth of the spiral groove or screw groove 29, 30, 39, 40, 43, 44, and u is the circumferential speed of the rotating disk 12 or rotating cylinder 13. In the present helical groove molecular pump with multi-thread thread grooves, b, h, and u can all be increased in the above equation (b) by the means described in the sections 1, 2, 3, and 4 improvements. By increasing the number of threads and increasing the number of threads, the pumping speed, which was previously thought to be impractical, has been reduced to a practical level of 100/sec.
It has become possible to design more than this.

In addition, the exhaust characteristics of the low-vacuum side-stage vane vacuum pump at this time will be added below. Generally, in a helical groove molecule with a high vacuum side multi-thread groove,
Let P ₁ and V ₁ be the pressure and volumetric flow rate at the suction port 3,
If P ₂ and V ₂ are the pressure and volumetric flow rate at the discharge port 5, the mass of the exhausted gas is equal at the suction port 3 and the discharge port 5, so the following relationship holds true.

P ₂ /P ₁ =V ₁ /V ₂ ...(c) P ₂ /P ₁ is the compression ratio of this pump, and as mentioned above, 10
Since a value of ³ units can be secured, V ₁ /V ₂ is also 10 ³ units, and the volumetric flow rate V ₂ at the discharge port 5 also takes an extremely small value compared to the volumetric flow rate V ₁ at the suction port 3. For example, if P ₂ /P ₁ =1000, then V ₂ =V ₁ /1000. Therefore, in this case, assuming that V ₁ =6000/min, the pumping speed of the vane vacuum pump is theoretically good if V ₂ =6/min or more. In reality, vane vacuum pumps in a two-stage series arrangement are usually arranged at a rate of 100/min or more. This does not interfere with the pumping action of the multi-thread grooved helical groove molecular pump.

(3) Regarding the ultimate vacuum level of a helical groove molecular pump with multiple thread grooves; The ultimate vacuum level r ₀ of the thread grooves 39, 40, 43, 44 and the spiral groove molecular pump is as follows, without considering leakage from the gaps: As is well known, it is expressed by the following equation.

r ₀ = exp [θ/hLu] ...(d) Here, θ is a constant related to gas friction, and h is the spiral or thread groove 29, 30, 39, 40, 43,
44 depth, L is a spiral or thread groove 29, 30,
39, 40, 43, and 44, and u is the circumferential speed of the rotating disk 12 or the rotating cylinder 13. Since the gap is large in the helical groove molecular pump with Honda thread groove, the above formula (d) cannot be applied as is, but the first,
By taking the measures described in sections 2, 3, and 4 for improvements, the back pressure can be reduced to 10 ^-6 Torr at a level of 10 ^-3 Torr.
The ultimate vacuum level of the table is possible.

(B) Next, when the gas flow from the evacuated system to the high-vacuum side multi-thread grooved helical groove molecular pump mechanism is in a viscous region; that is, the helical grooves 29, 3
0, the mean free path of the gas flowing through each of the thread grooves 39, 40, 43, and 44 is
A case where the depth is smaller than 9, 30, 39, 40, 43, and 44 will be explained.

When the drive shaft 53 of the low-vacuum side vane vacuum pump is energized by an appropriate external drive source, the gear 57 formed on the drive shaft 53 of the vane vacuum pump and the high-vacuum side multi-threaded helical groove molecule The driving force is transmitted to the drive shaft 14 of the high-vacuum side stage multi-threaded helical groove molecular pump through the gear 23 formed on the drive shaft 14 of the pump, and the rotating disk 12 and rotating cylinder 13 move at high speed. However, in a high-vacuum side stage multi-threaded helical groove molecular pump, the gas flow is a viscous flow, so as is well known, the gas that enters from the pumped system through the suction port 3 is compressed. It is not possible to exhaust the air. In this case, the high-vacuum side multi-threaded helical groove molecular pump has its discharge port 5 connected in series with the suction port 7 of the low-vacuum side vane vacuum pump. It only serves as a gas passage for the compression and exhaust operations of the vacuum pump. That is, as the low-vacuum side vane vacuum pump is driven, the suction port 3 of the high-vacuum side multi-threaded helical groove molecular pump is
The gas to be exhausted passes through the high-vacuum side multi-thread grooved helical groove molecular pump without being compressed, and passes through the through hole 6 of the intermediate housing 4 to the low-vacuum side vane. The air is sucked in through the suction port 7 of the vacuum pump, and the space between the exhaust chambers 55 between the vane vacuum pump cylinder 48 and the rotor 51 is swept by the sliding blades 52, similar to the exhaust action of conventional vane vacuum pumps. Exhaust port 47
and is exhausted to the atmosphere via the atmosphere exhaust port 71.

As described above, in a viscous flow region, we have described the pumping action of a two-stage pump with a multi-threaded helical groove molecular pump arranged in series on the high vacuum side stage and a vane vacuum pump arranged in series on the low vacuum side stage. Let me elaborate a little on the characteristics of this pump.

(1) Regarding compression work in a helical groove molecular pump with multiple threads; In the case of viscous flow, this pump can be considered to have no compression work as mentioned above, so in equation (a) above, P ₂ /P ₁ ≒
1, and W≈0. Therefore, there is no problem of heat generation. Note that some compression work is done in the region between 0.1 and 10 Torr, which is the intermediate region between the molecular region and the viscous region, but as detailed in the fifth improvement point, there is no problem with heat generation. It is possible to suppress the value to a small value, and furthermore, the cooling hole 2
1 also cools the rotating disk 12 and rotating cylinder 13, which are integrated with the drive shaft 14, so there is no problem of heat generation due to compression work.

(2) Regarding exhaust resistance in a helical groove molecular pump with multiple threads and grooves; From now on, if the rotating disk 12 and rotating cylinder 13 of the high vacuum side stage multi-thread and grooved helical groove molecular pump are stopped. Assuming that, the pumping speed at the suction port 7 of the low-vacuum side vane vacuum pump is S ₀ , the effective pumping speed at the suction port 3 of the high-vacuum side multi-threaded spiral groove molecular pump is S ₁ , If the conductance of the high-vacuum side stage multi-threaded helical groove molecular pump as a passage for the gas to be pumped is C ₁ , then 1/S ₁ = 1/C ₁ + 1/S ₀ (E), and the effective exhaust The speed S ₁ will be less than the pumping speed S ₀ of the low vacuum side stage vane vacuum pump. In contrast, in the present invention, first, as mentioned above in the fifth improvement point, grooves with multiple grooves and a large cross-sectional area are designed, and as mentioned in the first and second improvement points, the gap Due to the two points that made it possible to expand the
It has become possible to make the conductance C ₁ in the viscous region so large that it is practically acceptable for the pumping speed S ₀ of the vane vacuum pump. That is, in the above equation (E), C ₁ ≫S ₀ , and S ₁ ≈S ₀ can now be satisfied. Furthermore, according to experiments conducted by the inventor, in the two-stage pump having the present configuration, both the rotary disk 12 and the rotary cylinder 13 of the high-vacuum side stage multi-threaded helical groove molecular pump, the low-vacuum side stage Since it operates at the same time as the vane vacuum pump and rotates at high speed,
It has been confirmed that even in the viscous flow region, some gas transport action is derived along the spiral grooves 29, 30 and thread grooves 39, 40, 43, 44. Therefore, in this case, the high-vacuum side-stage multi-threaded helical groove molecular pump acts as a booster pump for the low-vacuum side-stage vane vacuum pump, and the effective pumping speed S ₁ is equal to the conductance C ₁ It was confirmed that, in addition to increasing , it is possible to design the pump with sufficient margin without substantially impairing the pumping speed S ₀ of the low-vacuum side vane vacuum pump.

As a result of the above, the gas flow from the high-vacuum side multi-threaded helical groove molecular pump to the high-vacuum side stage multi-threaded helical groove molecular pump can be controlled by two stages in series with the low-vacuum side vane vacuum pump, whether in the case of molecular flow or viscous flow. With this arrangement, it has become possible to realize a two-stage pump that can be simultaneously driven by a single drive source and can effectively exhaust air continuously.

Incidentally, FIG. 6 shows an example of an evacuation speed curve of a vane vacuum pump with an evacuation speed of 200/min. In addition, Fig. 7 shows the design pumping speed of 6000 /
min, design pumping speed of low vacuum side vane vacuum pump
An example of the pumping speed curve of the high vacuum pump of the invention at 200/min is shown.

As described above, according to the present invention, the following effects can be obtained.

1.10 ^-4 Torr with conventional vane vacuum pump alone
It goes without saying that it is impossible to obtain a vacuum higher than 10 -4 Torr, and no pump with a single drive source that can effectively and easily reduce the vacuum to less than 10 ^-4 Torr has yet to be developed. Ta. According to the present invention, a high vacuum pump with a single driving source capable of continuously evacuation over a wide range from 760 Torr to 10 ^-6 Torr level under atmospheric pressure back pressure can be obtained.

2. According to the present invention, both the high-vacuum side stage multi-threaded spiral groove molecular pump and the low-vacuum side stage vane vacuum pump are evacuated by a completely mechanical mechanism.
Unlike oil diffusion pumps and ion pumps, there is no problem with unexpected pressure rises (in extreme cases, atmospheric pressure intrusion), and the exhaust action starts at the same time as the pump is driven, so it is not as difficult as oil diffusion pumps. A high vacuum pump with excellent controllability can be obtained without the need for heating preparation time.

3. According to the present invention, a spiral groove molecular pump with multi-thread grooves is arranged in the high vacuum side stage, so the phenomenon of backflow of oil vapor into the vacuum system, which is observed in conventional vane vacuum pumps and oil diffusion pumps, can be avoided. Therefore, a so-called hydrocarbon-free clean vacuum can be obtained.

4 According to the present invention, the tendency of the pumping speed of the low-vacuum side vane vacuum pump is that, as shown in ^the pumping speed curve illustrated in ^FIG . Although the speed decreases rapidly, a multi-thread grooved spiral groove molecular pump is placed in the high vacuum side stage as a mechanical booster pump, so the speed is lower than 10 ^- ₁ to 10 ^-2 Torr from the middle region to the molecular region of high vacuum. In this region, the pumping speed is greatly improved, and the tendency of the pumping speed curve of the high vacuum pump of the present invention in combination with this is illustrated in FIG. That is, 760 ~ 10 ^-1 ~
In a viscous flow region of 10 ^-2 Torr, the low vacuum side stage vane vacuum pump operates efficiently ^and
In intermediate to molecular basins below 10 ^-2 Torr,
The efficient operation of the high-vacuum side-stage multi-threaded helical groove molecular pump enables the overall
It consists of a high vacuum pump that can continuously pump air from 760 Torr to 10 ^-6 Torr with high efficiency.

5. According to the present invention, the high-vacuum side-stage multi-threaded helical groove molecular pump has a higher pumping speed than conventional helical groove molecular pumps and thread groove molecular pumps, and also reduces the gap between the rotating part and the fixed wall. It also became larger and more reliable, making it a practical molecular pump.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the entire high vacuum pump parallel to the drive shaft at the center of the drive shaft according to an embodiment of the present invention, and FIG. 2 is a height view of one component in FIG. A perspective view of the drive shaft of a helical groove molecular pump with multiple threads and grooves on the vacuum side; FIG. 3 is a light housing of the helical groove molecular pump with multiple threads and grooves on the high vacuum side as a component of FIG. 1; FIG. 4 is a sectional view taken along the arrow A-A' line in FIG. , FIG. 6 is an evacuation speed curve diagram of a general vane vacuum pump, and FIG. 7 is an evacuation speed curve diagram of a high vacuum pump according to the present invention. 5... Discharge port, 7... Suction port, 12... Rotating disk, 13... Rotating cylinder, 14, 53... Drive shaft,
15, 16... Magnetic fluid seal, 17, 18...
Bearing, 27, 28... Inner wall, 29, 30... Spiral groove, 34... Radial flow direction labyrinth seal groove,
35... Inner cylinder surface, 37... Outer cylinder surface.

Claims (1)

[Claims] 1. In a high-vacuum side helical groove molecular pump that exhausts air from the outer circumference to the inner circumference along the helical grooves bored in two inner walls facing the rotating disk at a small distance,
A plurality of the spiral grooves are provided, and labyrinth seal grooves in the radial flow direction are formed on the groove ridges forming the multiple spiral grooves, and an interval between the rotating disk and an inner wall facing the rotating disk is set. 0.2 to 1 mm, and a rotating cylinder integrally constructed with the rotating disk on both sides of the rotating disk on the side of the discharge ports on both sides thereof. By rotating at high speed with an interval of 0.2 to 1 mm relative to the cylindrical surface, a pump with multiple threads and grooves for exhausting air is formed, and the rotating disk and rotating cylinder in the integrated structure are driven. A bearing that supports the shaft is placed on the atmospheric pressure side of the rotary shaft seal to form a multi-thread grooved helical groove molecular pump, and the pump's discharge port is directly connected to the suction port of the low vacuum side vane vacuum pump mechanism. Then, a two-stage series exhaust system consisting of a molecular pump and a vane pump is used, and both drive shafts are connected by a suitable transmission force transmission mechanism to operate from a single drive source, and the air is discharged from 760 Torr to 10 ^-6 from the discharge port of the vane pump. A high vacuum pump that is characterized by continuous evacuation up to the Torr level.