Vacuum pump

Abstract

It is realized to machine a purge duct in the wall between stages of a stator of a vacuum pump having a half-shell configuration. 【Solution means】The present invention relates to a dry vacuum pump (1) provided with at least one purge duct (16) including two channels (17, 18) provided within the thickness of an inter-stage lateral half-wall (9a) of a half-shell (4), each channel (17, 18) opening into the internal space of an intake / exhaust stage (T1 to T6) through respective openings (20, 21) from the front surface (19) of the inter-stage lateral half-wall (9a), and a lateral groove (22) provided in the inter-stage lateral half-wall (9a) at the joint surface (13) of the half-shells (3, 4). The channels (17, 18) are composed of tubular ducts formed between the inclined surface (23) of the lateral groove (22) and the front surface (19).

Description

Technical Field

[0001] The present invention relates to a vacuum pump, and more particularly to a purge duct of the vacuum pump.

Background Art

[0002] A dry vacuum pump has one or more suction and exhaust stages arranged in series, and the gas to be suctioned and exhausted circulates between the suction port and the discharge port. Known vacuum pumps are classified into those with rotating lobes, also called "roots" pumps, and those with claws, also called "claw" pumps. These vacuum pumps are called "dry" because during operation, the rotors rotate without mechanically contacting each other or the stator within the stator, so there is no need to use oil in the suction and exhaust stages.

[0003] Certain vacuum pumps are used in the processes of manufacturing semiconductors, flat screens, solar power generation panels or coatings, particularly in the process of depositing thin films under vacuum known as high aspect ratio processes (HARP), especially in CVD, PECVD, SACVD, ALD, etc. In these processes, usually, an evaporation step of introducing a process gas such as resin vapor or a precursor into a reactor to deposit a thin film and a cleaning step of introducing an active gas such as a corrosive gas species into the reactor to clean the walls of the reactor are performed alternately.

[0004] The gas used in the evaporation step may generate a large amount of by-products in the form of solids (powder, paste, fragments). If a large amount of powder accumulates on the moving parts of the vacuum pump, the pump may stop immediately due to mechanical seizure. Therefore, it is essential to reduce the failure rate of these powder generation processes.

[0005] To prevent overlapping by-products from contaminating the intake and exhaust device, it is known to use a trap in the vacuum line. These traps separate solid by-products from the gas, for example by gravity or centrifugal force, or by condensation or pyrolysis, and accumulate and hold the solid by-products. One problem is that the accumulation of powder in the trap increases the probability of encountering species with different chemical properties. This can cause and promote unwanted chemical reactions such as the polymerization reaction described above. Also, traps at high temperatures of usually 140°C to 170°C provide the activation energy to promote such chemical reactions. Therefore, these traps need to be cleaned regularly.

[0006] Another solution is to adapt the shape of the vacuum pump by design to facilitate the discharge of powder, for example by providing a transfer channel between a wider intake and exhaust stage or between vertical vacuum pumps.

[0007] It is also known to inject a purge fluid such as nitrogen into the vacuum pump to dilute the intake and exhaust gas and promote the discharge of powder. This injection is usually carried out at a plurality of points dispersed along the intake and exhaust stage through an injection nozzle opening into the transfer channel or the discharge port of the intake and exhaust stage.

[0008] However, these injections may prove insufficient if the manufacturing process as described above is highly contaminated and the by-products generated are particularly adhesive. The accumulation of by-products can persist in the meshing area between rotors with very small clearances. In fact, it has been pointed out that in these areas with narrow clearances, powder is drawn in and accumulates, and the compression in these areas further compresses and more firmly adheres these powders.

[0009] Patent Document 1 proposes an apparatus for injecting a purge fluid that enables more efficient purging of a rotor. For this purpose, a purge duct is provided within the thickness of the stator slice and opens into the intake and exhaust stages. By providing it in the stator body in this way, the purge fluid can be heated up to the temperature of the intake and exhaust body before being injected into the stage. Also, by providing a guide groove for the purge fluid on the front surface of the stator slice, the space between the rotors can be cleaned accurately and efficiently. By injecting the purge fluid locally, it can be targeted and injected into these areas, ensuring both the dilution of contaminants and the dispersion by the mechanical action of solid and gaseous by-products that may accumulate on the rotor.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0011] However, this solution is suitable for a vacuum pump having a slice configuration, that is, a vacuum pump in which the stator is constituted by axially coupling a plurality of stator slices, but it is difficult to implement this solution on the wall between the stages of the stator of a vacuum pump having a half-shell configuration. In fact, in a half-shell stator, the wall between the stages is very thin and thinner than the stator of a slice structure, making it difficult to machine the purge duct.

Means for Solving the Problems

[0012] One object of the present invention is to propose a vacuum pump that solves at least one of the above-mentioned drawbacks.

[0013] For this purpose, the present invention relates to a dry vacuum pump, - To form at least two intake and exhaust stages arranged in series and axially separated from each other by respective inter-stage lateral walls, a stator including at least a first half-shell and a second half-shell that are complementary and coupled to each other, - A dry vacuum pump including two shafts for a rotor designed to rotate within the intake and exhaust stages and extending axially, The dry vacuum pump includes at least one purge duct, and the purge duct - Two channels provided within the thickness of the inter-stage lateral half-wall of the half-shell, - At the joint surface of the half-shell, a lateral groove provided in the inter-stage lateral half-wall, Each channel opens from the front surface of the inter-stage lateral half-wall into the internal space of the intake and exhaust stage through respective orifices, The two channels are formed by a tubular duct formed between the inclined surface of the lateral groove and the front surface, which is characterized in that.

[0014] The purge duct opening from the front surface facing the rotor into the intake and exhaust stage is continuously injected by the rotation of the rotor, and in particular in the important area between the rotors, it cleans the outer shape of the rotor. In practice, this injection can be localized in the meshing area between the outer shapes of the rotor with a decreasing volume.

[0015] The lateral groove provided in the inter-stage lateral half-wall provides access for a tool for forming the channel by drilling. The reason why diagonal drilling of the inter-stage lateral half-wall is possible is that the lateral groove has an inclined surface, whereby an orifice opening to the front surface under the joint surface can be formed despite the thinness of the inter-stage lateral wall.

[0016] The vacuum pump can also have one or more of the following-described features, individually or in combination.

[0017] For example, the lateral groove has a V-shaped longitudinal cross-section.

[0018] The surface of the stepped lateral half-wall of the other half-shell on the joint surface can be made into a flat surface.

[0019] For example, the purge duct is provided in the stepped lateral half-wall and includes a common duct that opens at the center of the lateral groove.

[0020] The orifices can be provided on a circle defined by the movement of the radial ends of the respective rotors.

[0021] The orifices can be provided at a distance of 5 mm to 15 mm from the joint surface in a direction perpendicular to the longitudinal direction and the lateral direction.

[0022] For example, the length of the channel is 6 mm to 14 mm, for example 10 mm.

[0023] For example, the diameter of the channel is 1 mm to 3 mm, for example 2 mm.

[0024] For example, the channel opens from the front surface of the stepped lateral half-wall of the half-shell that supports the outlet of the intake and exhaust stage.

[0025] The vacuum pump can have more than two intake and exhaust stages. In this case, the half-shell can have a plurality of stepped lateral half-walls. The purge duct can be provided in each stepped lateral half-wall.

[0026] For example, the joint surface passes through the rotation axis of the shaft of the rotor.

[0027] Further advantages and features of the present invention will become apparent by reading the following description and the accompanying drawings of specific but non-limiting embodiments of the present invention.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11a

Figure 11b

Figure 11c

Figure 11d

DETAILED DESCRIPTION OF THE INVENTION

[0029] In these diagrams, the same elements are denoted by the same reference numerals.

[0030] The following embodiments are illustrative. Although one or more embodiments are referred to in this specification, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to one embodiment. The individual features of different embodiments can also be combined or replaced to provide other embodiments.

[0031] A rough vacuum pump is a positive displacement vacuum pump designed to suck, transfer, and discharge gases that are exhausted at pressures above atmospheric pressure. The rotors of the rough vacuum pump include a Roots rotor and a claw rotor. The rotors are supported by two shafts that are rotationally driven by the motor of the rough vacuum pump. The rough vacuum pump is also designed to be started at atmospheric pressure.

[0032] A Roots vacuum pump (also called a blower, Roots compressor, or booster) is a positive displacement vacuum pump designed to use two Roots rotors to suck, transfer, and discharge the gases to be exhausted. The Roots vacuum pump is arranged in series with the rough vacuum pump upstream of the rough vacuum pump. The rotors are supported by two shafts that are rotationally driven by the motor of the Roots vacuum pump.

[0033] An "upstream" component is a component that is located in front of other components with respect to the flow direction of the gases to be exhausted. In contrast, a "downstream" component is a component that is located behind other components with respect to the flow direction of the gases to be exhausted.

[0034] The arrow F in FIG. 1 indicates the flow direction of the gases to be exhausted.

[0035] The axial direction L is the longitudinal direction of the vacuum pump and is the direction in which the rotor shaft extends. The transverse direction T is a direction perpendicular to the axial direction L, and the transverse plane (T, V) is a plane perpendicular to the longitudinal plane (L, T).

[0036] The present invention is applicable to any type of dry vacuum pump including two or more suction and exhaust stages, for example, those including two to ten suction and exhaust stages. This vacuum pump can be a low-vacuum pump including a plurality of suction and exhaust stages and designed to discharge the sucked and exhausted gas at atmospheric pressure. When in use, it can be connected in series with the low-vacuum pump and connected upstream of the low-vacuum pump, and can be a Roots vacuum pump or compressor having two or three suction and exhaust stages, the discharge pressure of which is the discharge pressure obtained by the low-vacuum pump.

[0037] FIG. 1 shows such a vacuum pump 1.

[0038] The vacuum pump 1 includes a stator 2 including at least a first half shell 3 and a second half shell 4 that are complementarily joined. The stator 2 can also include a first end piece 5 and a second end piece 6 joined to the axial ends of the half shells 3, 4.

[0039] The half shells 3, 4 of the stator 2 form at least two suction and exhaust stages T1 to T6 arranged in series between the suction port 7 and the discharge port 8 of the vacuum pump 1, for example, forming two to ten (six in the illustrated example) suction and exhaust stages. The suction and exhaust stages T1 to T6 are axially separated from each other by the respective inter-stage lateral walls 9 of the half shells 3, 4.

[0040] The vacuum pump 1 also includes two shafts of a rotor 10 designed to rotate in the suction and exhaust stages T1 to T6, and the rotor 10 drives the gas sucked and exhausted between the suction port 7 and the discharge port 8 (FIG. 1).

[0041] The rotor has, for example, lobes having the same outer shape, for example, a "Roots" rotor having two or more (three in FIG. 10) lobes, or a "claw" rotor, or a rotor based on another similar principle for a positive displacement vacuum pump. The shaft supporting the rotor is driven by a motor M arranged, for example, beside the discharge stage T6 at the axial end of the vacuum pump 1.

[0042] Each intake and exhaust stage houses two mating rotors 10, and each intake and exhaust stage is provided with an inlet and an outlet respectively. When the shafts of the rotors 10 rotate in opposite directions around their respective axes of rotation, the gas sucked in from the inlet is confined within the space formed by the rotor 10 and the stator 2, and is driven by the rotor 10 towards the next stage.

[0043] The successive intake and exhaust stages T1 - T6 are successively connected in series by respective transfer channels 12 that connect the outlet of the preceding intake and exhaust stage to the inlet of the subsequent intake and exhaust stage. For example, there are two transfer channels 12 for connecting the outlet of an intake and exhaust stage to the inlet of the next intake and exhaust stage, and the transfer channels 12 are arranged on both sides of the intake and exhaust stage. In the half shell 4 of FIG. 2, the openings of the transfer half channels 12 can be seen. This is the half shell 4 where the outlets of the intake and exhaust stages T1 - T6 are provided, and here it is called the second half shell.

[0044] The inlet of the first intake and exhaust stage T1 communicates with the suction port 7. The outlet of the last intake and exhaust stage T6 communicates with the discharge port 8. The duct 11 connecting the outlet of the last intake and exhaust stage T6 to the discharge port 8 of the vacuum pump 1 is formed, for example, within the body of the lower half shell 4 of the intake and exhaust stages T1 - T6.

[0045] The axial dimensions (and thus the displacement volume) of the rotors and the intake and exhaust chambers are, for example, the same as or reduced by the intake and exhaust stages. The intake and exhaust stage T1 is arranged on the suction port 7 side and houses a rotor having the largest axial dimension and the largest displacement volume.

[0046] These vacuum pumps are called "dry" because during operation, the rotors rotate without mechanically contacting each other or the stator 2 inside the stator 2, so there is no need to use oil in the intake and exhaust stages.

[0047] The half shells 3 and 4 are joined at the joint surface 13. The intake and exhaust stages T1 to T6, the intermediate lateral wall 9 between stages, and the transfer channel 12 are partly formed in the first half shell 3 and partly formed in the second half shell 4. In other words, more specifically, the intermediate lateral wall 9 between stages is formed by joining two intermediate lateral half walls 9a and 9b.

[0048] The joint surface 13 passes through, for example, the longitudinal intermediate plane of the dry vacuum pump 1 including the rotation axis I-I of the shaft of the rotor 10. Seal grooves 14 for accommodating a seal gasket (not shown) can be provided in the half shells 3 and 4 of the joint surface 13.

[0049] The first ends of the half shells 3 and 4 are closed by the first end piece 5, and the second ends of the half shells 3 and 4 are closed by the second end piece 6. Naturally, holes 15 are provided in the intermediate lateral wall 9 between the half shells 3 and 4 separating the intake and exhaust stages T1 to T6 and in the end pieces 5 and 6 for passing the shaft of the rotor 10.

[0050] The vacuum pump 1 further includes at least one purge duct 16 designed to inject a purge gas such as nitrogen.

[0051] The purge duct 16 includes two channels 17 and 18 provided within the thickness of the intermediate lateral half wall 9a of the half shell 4 (FIG. 2).

[0052] Each channel 17 and 18 opens into the internal space of the intake and exhaust stages T1 to T6 (FIGS. 3 and 4) partly delimited by the intermediate lateral half wall 9a through respective orifices 20 and 21 from the front face 19 of the intermediate lateral half wall 9a.

[0053] The front face 19 of the intermediate lateral half wall 9a disposed between the intake and exhaust stages N and N + 1 separates the intake and exhaust stage N. In other words, the channels are oriented to open in a direction opposite to the direction of the flow of the gas being intake and exhausted.

[0054] These orifices 20, 21 are advantageously provided on a circle C defined by the movement of the radial ends of the respective rotor 10 (FIG. 4), the center of the circle C being the rotation axis I-I of the rotor 10. The orifices 20, 21 are provided, for example, at a distance d of 5 mm to 15 mm from the joint surface 13 in a direction (V) perpendicular to the longitudinal direction (L) and the transverse direction (T). This distance d is related to the shape of the rotor 10 and is adapted such that the injection of the purge gas flows out at the discharge ports in the meshing region of the rotor 10.

[0055] As shown more clearly in FIGS. 5 and 6, the purge duct 16 includes a transverse groove 22 provided in the stepped transverse half-wall 9a at the joint surface 13 of the half-shells 3, 4.

[0056] The surface of the stepped transverse half-wall 9b of the other half-shell 3 at the joint surface 13 can be made flat.

[0057] The channels 17, 18 are formed by a (linear) tubular duct formed between the inclined surface 23 of the transverse groove 22 and the front surface 19 (FIGS. 6 and 7). This inclined surface 23 is inclined, for example, at an angle of 30° to 60°, for example 45°, with respect to the longitudinal plane (L, T) of the joint surface 13 separating the half-shells 3, 4 over the entire transverse groove 22.

[0058] The transverse groove 22 has, for example, a V-shaped longitudinal cross-section, one side of the "V" forming the inclined surface 23 on the side of the intake and exhaust stage where the channels 17, 18 open (FIGS. 6 and 7). This V-shape is easy to machine.

[0059] The lateral grooves 22 provided in the inter-stage lateral half-wall 9a provide access for tools to form the channels 17, 18 by drilling. The reason why the inter-stage lateral half-wall 9a can be obliquely drilled is that the lateral grooves 22 have inclined surfaces 23, thereby enabling the formation of orifices 20, 21 that open to the front surface 19 below the joint surface 13 despite the thinness of the inter-stage lateral wall 9.

[0060] The lengths of the channels 17, 18 between the inclined surface 23 and the front surface 19 are, for example, 6 mm to 14 mm, for example, 10 mm. The diameters of the tubular channels 17, 18 are, for example, 1 mm to 3 mm, for example, 2 mm.

[0061] The channels 17, 18 open, for example, to the front surface 19 of the inter-stage lateral half-wall 9a of the half-shell 4 (referred to here as the second half-shell) that supports the outlets of the intake and exhaust stages T1 to T6. Therefore, the purge gas is injected to the side where the gas pressure is the highest and thus the risk of deposit formation is the highest.

[0062] As more clearly shown in the cross-sectional view of FIG. 8, the purge duct 16 includes, for example, a common duct 24 provided in the inter-stage lateral half-wall 9a and communicating with the lateral groove 22. The common duct 24 opens, for example, at the center of the lateral groove 22.

[0063] In FIG. 8, the common duct 24 is formed by first and second straight ducts 24a, 24b communicating with each other. The first straight duct 24a extends perpendicular to the joint surface 13 and is easily formed by machining from the joint surface 13. The second straight duct 24b extends at a right angle to the outer surface of the half-shell 4 (in this case, a flat surface) and can also be easily formed by machining from the outer surface of the stator 2. Thereby, for example, a common duct 24 with an elbow extending between the lateral groove 22 provided in the joint surface 13 and the outer surface of the stator 2 located on one side of the vacuum pump 1 is provided.

[0064] For example, within the thickness of the last stage intermediate lateral half-wall 9a of the vacuum pump 1, a purge duct 16 is provided in the flow direction of the gas F to be sucked and exhausted, and the channels 17, 18 open into the internal space of the last suction and exhaust stage T6. The last suction and exhaust stage T6 is the suction and exhaust stage with the highest gas pressure.

[0065] According to an exemplary embodiment, the half-shells 3, 4 have a plurality of stage intermediate lateral half-walls 9a (five in the illustrated example), and a purge duct 16 is provided in each stage intermediate lateral half-wall 9a. Therefore, all the common ducts 24 extend within their respective stage intermediate lateral half-walls 9a, for example, in a vertical plane (FIG. 9), and open laterally from the stator 2 through their respective outlet orifices 25 (FIG. 3). These outlet orifices 25 are connected to a source of purge gas by an external distributor (not shown).

[0066] During operation, the purge gas is distributed to the purge ducts 16 of each suction and exhaust stage T1 to T6, first to the common duct 24, then to the lateral groove 22, and then the channels 17 and 18 flow out from the front wall 9 into the internal space of the suction and exhaust stages T1 to T6.

[0067] The rotation of the rotor 10 in the suction and exhaust stage is schematically shown in successive FIGS. 11a to 11d over a total rotation angle of approximately 120°, and FIG. 10 shows these rotors 10 in perspective view in front of the front face 19 of the stage intermediate lateral half-wall 9a provided with the orifices 20, 21.

[0068] It can be seen that while the second orifice 21 is closed by the second rotor 10 between FIGS. 11a and 11b, the purge gas injected through the first orifice 20 flows around the first rotor 10. Therefore, the gas injected into the purge duct 16 mainly flows out through the first opening orifice 20 to the edge of the first rotor 10. Then, as the rotation of the rotor 10 continues (FIG. 11c and then FIG. 11d), the first orifice 20 is closed by the first rotor 10, and the purge gas injected into the purge duct 16 flows around the second rotor 10 through the second orifice 21. Then, the rotor 10 continues to rotate and returns to the angular position that coincides with the initial angular position of FIG. 11a. There is a position between the angular positions shown in FIGS. 11a to 11d where the rotor 10 closes both orifices 20 and 21 simultaneously. The purge gas is pushed out behind the rotor 10, between the rotor 10 and the front surface 19, thereby cleaning the rotor 10.

[0069] In this way, the purge duct 16 that opens from the front surface 9 facing the rotor 10 to the intake and exhaust stages T1 to T6 cleans the outer shape of the rotor 10 by injection ordered by the rotation of the rotor 10, particularly in the important area between the rotors 10. This injection can actually be localized in the meshing area between the outer shapes of the rotor 10 where the volume decreases.

Explanation of Reference Numerals

[0070] 1 Vacuum pump 2 Stator 3 First half shell 4 Second half shell 5 First end piece 6 Second end piece 7 Suction port 8 Discharge port 9 Intermediate stage lateral wall 9a, 9b Intermediate stage lateral half walls 10 Rotor 11 Duct 12 Transfer channel, transfer half channel 13 Joint surface 14 Seal groove 15 holes 16 purge ducts 17, 18 channels 19 front surface 20 first orifice 21 second orifice 22 horizontal groove 23 inclined surface 24 common duct 24a first straight duct 24b second straight duct 25 outlet orifice Rotation axis of I-I shaft M motor T1 to T6 intake and exhaust stages

Claims

1. - A stator (2) comprising at least a first half-shell (3) and a second half-shell (4) which are complementary and coupled to each other in order to form at least two intake and exhaust stages (T1 to T6) arranged in series and axially separated from each other by respective inter-stage lateral walls (9); - A dry vacuum pump (1) comprising two shafts (10) designed to rotate within said intake and exhaust stages (T1 to T6) and extending axially for a rotor (10), wherein said dry vacuum pump (1) comprises at least one purge duct (16), said purge duct (16) comprising: - Two channels (17, 18) provided within the thickness of the inter-stage lateral half-wall (9a) of the half-shell (4); - A lateral groove (22) provided in said inter-stage lateral half-wall (9a) at the joint surface (13) of said half-shells (3, 4); each channel (17, 18) opening into the internal space of said intake and exhaust stages (T1 to T6) from the front face (19) of said inter-stage lateral half-wall (9a) via respective orifices (20, 21); characterized in that said two channels (17, 18) are formed by a tubular duct formed between the inclined surface (23) of said lateral groove (22) and said front face (19).

2. The dry vacuum pump (1) according to claim 1, characterized in that said lateral groove (22) has a V-shaped longitudinal cross-section.

3. The dry vacuum pump (1) according to claim 1 or 2, characterized in that the surface of the inter-stage lateral half-wall (9b) of the other half-shell (3) at said joint surface (13) is a flat surface.

4. The dry vacuum pump (1) according to claim 1 or 2, characterized in that said purge duct (16) comprises a common duct (24) provided in said inter-stage lateral half-wall (9a) and opening at the center of said lateral groove (22).

5. The dry vacuum pump (1) according to claim 1 or 2, characterized in that said orifices (20, 21) are provided on a circle (C) defined by the movement of the radial ends of respective rotors (10).

6. The dry vacuum pump (1) according to claim 1 or 2, wherein the orifices (20, 21) are provided at a distance (d) of 5 mm to 15 mm from the joint surface 13 in a direction (V) perpendicular to the longitudinal direction (L) and the transverse direction (T).

7. The dry vacuum pump (1) according to claim 1 or 2, wherein the length of the channels (17, 18) is 6 mm to 14 mm, for example 10 mm.

8. The dry vacuum pump (1) according to claim 1 or 2, wherein the diameter of the channels (17, 18) is 1 mm to 3 mm, for example 2 mm.

9. The dry vacuum pump (1) according to claim 1 or 2, wherein the channels (17, 18) open from the front surface (19) of the intermediate transverse half-wall (9a) of the half-shell (4) that supports the outlet of the intake and exhaust stages (T1 to T6).

10. The dry vacuum pump (1) according to claim 1 or 2, wherein the half-shells (3, 4) have a plurality of intermediate transverse half-walls (9a), and the purge ducts (16) are provided in each intermediate transverse half-wall (9a).

11. The dry vacuum pump (1) according to claim 1 or 2, wherein the joint surface (13) is passed through by the rotation axis (I-I) of the shaft of the rotor (10).

Images