Sealing mechanism of vacuum pump

Abstract

The invention belongs to the technical field of positive displacement vacuum pumps, and particularly relates to a sealing mechanism of a vacuum pump, which comprises a labyrinth seal and a piston ring seal, the left and right sides of the labyrinth seal and the piston ring seal in the axial direction are respectively provided with an oil cavity and a pump cavity; the radial inner and outer sides of the labyrinth seal and the piston ring seal are respectively provided with a rotor shaft in a pump cavity and an oil tank side sealing plate in an oil cavity; the labyrinth seal comprises a labyrinth seal moving ring and a labyrinth seal static ring, the labyrinth seal moving ring is arranged on the rotor shaft in a sleeving mode and is in linkage with the rotor shaft, and the labyrinth seal static ring is arranged on the labyrinth seal moving ring in a sleeving mode and is fixedly connected with the oil tank side sealing plate; the piston ring seal comprises at least one piston ring; a piston groove is formed in the rotor shaft; or the rotor shaft is sleeved with a piston shaft sleeve, and a piston groove is formed in the outer surface of the piston shaft sleeve; the piston ring is accommodated in the piston groove. Non-contact sealing is completely adopted, the problems of friction heat generation, friction abrasion and the like of a contact lip seal are avoided, the use power consumption of the pump body is reduced, and the quality inspection cost and the manufacturing cost are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of positive displacement vacuum pumps, and particularly relates to a sealing mechanism of a vacuum pump. Background Art

[0002] In semiconductor and photovoltaic manufacturing, dry vacuum pumps are one of the core equipment, which are used in processes such as wafer processing, coating, and etching. Their oil-free characteristics can avoid oil vapor pollution of the ultra-clean environment and ensure the product yield.

[0003] According to the different structures of the rotors, vacuum pumps are often classified into categories such as roots pumps, claw pumps, and screw pumps. During use, a vacuum pump usually rotates the motor-driven shaft and the rotor inside the stator. The stator includes an air inlet and an air outlet. During rotation, gas and impurities are inhaled from the air inlet and discharged from the air outlet after being compressed by the rotor. The rotor and the stator can be respectively composed of a single-stage and a multi-stage series structure.

[0004] The pump shaft is equipped with transmission and support components such as gears and bearings, thus introducing a gear chamber and an oil chamber structure; to prevent impurities and gas inhaled in the pump chamber from contaminating the lubricating oil, and the lubricating oil in the gear chamber and the oil chamber from flowing into the pump chamber, the pump introduces a sealing system to ensure the normal operation of the pump. The traditional sealing system widely uses a combined structure of an "eight"-shaped contact lip seal and nitrogen purge assistance. Under the rotation of the rotating shaft, this "eight"-shaped lip seal can well reverse pump the lubricating oil and process gas on both sides to their respective regions in the initial stage of use; however, as the lip piece wears due to friction, the performance of this seal gradually decreases. Secondly, the lip seal has problems of contact heating and increased pump body power consumption, and in severe cases, it will cause mechanical failures of the pump itself. Finally, the design and processing of the lip seal are complex, and it is difficult to control the product quality, resulting in a relatively high use cost. Summary of the Invention

[0005] In order to solve the above problems existing in the traditional contact lip seal, the purpose of the present invention is to provide a sealing mechanism of a vacuum pump. This sealing mechanism maximally prohibits two-way leakage through non-contact sealing and ensures the stability, reliability, and economy of use.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] The present invention includes a labyrinth seal and a piston ring seal, wherein the left and right sides of the labyrinth seal and the piston ring seal are respectively the oil chamber and the pump chamber, and the inner and outer sides of the labyrinth seal and the piston ring seal are respectively the rotor shaft in the pump chamber and the oil tank side sealing plate in the oil chamber in the radial direction; the labyrinth seal includes a labyrinth seal dynamic ring and a labyrinth seal static ring, the labyrinth seal dynamic ring is sleeved on the rotor shaft and linked to the rotor shaft, the labyrinth seal static ring is sleeved on the labyrinth seal dynamic ring and fixedly connected to the oil tank side sealing plate; the piston ring seal includes at least one piston ring, and a piston groove is provided on the rotor shaft; or a piston sleeve is sleeved on the rotor shaft, and a piston groove is provided on the outer surface of the piston sleeve; the piston ring is accommodated in the piston groove.

[0008] Wherein: the labyrinth seal dynamic ring, the labyrinth seal static ring and the piston sleeve are respectively provided with sealing grooves, and O-rings are placed in the sealing grooves; the O-rings placed in the sealing grooves on the labyrinth seal dynamic ring are used to achieve sealing between the labyrinth seal dynamic ring and the rotor shaft, the O-rings placed in the sealing grooves on the labyrinth seal static ring are used to achieve sealing between the oil tank side sealing plate and the labyrinth seal static ring, and the O-rings placed in the sealing grooves on the piston sleeve are used to achieve sealing between the piston sleeve and the rotor shaft.

[0009] An inert gas inlet channel is provided on a side of the oil tank side sealing plate close to the pump chamber. One end of the inert gas inlet channel extends to the piston ring, and the other end of the inert gas inlet channel is connected to an inert gas source through a pipeline.

[0010] The pipelines are respectively provided with a throttling device and a one-way valve which can only allow air to enter the inert gas inlet channel.

[0011] An air pressure balance channel is provided on the side of the oil tank side sealing plate close to the pump chamber, and a filter is provided on the air pressure balance channel. One end of the air pressure balance channel is connected to the inside of the pump chamber, and the other end of the air pressure balance channel extends to the piston ring.

[0012] The piston sleeve and the oil tank side sealing plate are both provided with throttling grooves.

[0013] The oil chamber includes an oil tank, an oil tank side sealing plate, an oil flinging plate, a pressure cover and a bearing. The oil tank is fixedly connected to one side of the oil tank side sealing plate. The oil flinging plate, the pressure cover and the bearing are all located in the space surrounded by the oil tank and the oil tank side sealing plate. The rotor shaft is rotatably connected to one side of the oil tank side sealing plate through the bearing. The pressure cover is located on one side of the bearing. The labyrinth seal and the piston ring seal are located on the other side of the bearing. The pressure cover is sleeved on the rotor shaft and fixedly connected to one side of the oil tank side sealing plate. The oil flinging plate is installed on the rotor shaft and linked to the rotor shaft.

[0014] One side of the gland, bearing and side sealing plate of the oil tank forms a cavity, and an elastic element for fixing the bearing and damping is arranged in the cavity. During the rotation of the rotor shaft, the oil slinger introduces the lubricating oil in the oil cavity into the cavity to lubricate the bearing.

[0015] The pump cavity includes a stator, a rotor shaft and a side sealing plate of the oil tank. The stator is fixedly connected to the other side of the side sealing plate of the oil tank. A locking nut or locking screw is arranged at the end of the rotor shaft to fix the components on the rotor shaft.

[0016] The advantages and positive effects of the present invention are as follows:

[0017] 1. All non-contact seals are adopted in the present invention, avoiding problems such as heat generation and wear caused by friction of contact lip seals, reducing the power consumption of the pump body, and reducing the quality inspection cost and manufacturing cost.

[0018] 2. The present invention introduces a process gas-assisted piston ring seal, and this structure can further reduce the seal cost on the basis of ensuring the seal effectiveness.

[0019] 3. The present invention can provide a variety of sealing strategies according to different working conditions. For example, if it is necessary to further reduce the power consumption of the pump body, the number of piston rings can be reduced and throttle grooves can be set. Description of the Drawings

[0020] Figure 1 It is a structural sectional view of the inert gas-assisted seal in the Roots vacuum pump of the present invention;

[0021] Figure 2 It is a structural sectional view of the process gas-assisted seal of the present invention;

[0022] Figure 3 It is a structural sectional view of the present invention;

[0023] Figure 4 It is a structural sectional view of the present invention after adding throttle grooves;

[0024] Wherein: 1 is the oil tank, 2 is the side sealing plate of the oil tank, 2a is the inert gas inlet channel, 2b is the air pressure balance channel, 3 is the stator, 4 is the rotor shaft, 5 is the oil slinger, 6 is the socket head cap screw, 7 is the gland, 8 is the bearing, 9 is the O-ring, 10 is the dynamic ring of the labyrinth seal, 11 is the static ring of the labyrinth seal, 12 is the piston shaft sleeve, 13 is the piston ring, 14 is the cavity, 15a is the pipeline A, 15b is the pipeline B, 16 is the throttling device, 17 is the check valve, 18 is the inert gas source, 19 is the throttle groove, 20 is the filter, 111 is the oil cavity, 222 is the sealing mechanism, 333 is the pump cavity. Detailed Embodiments

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but it shall not be used as a basis for limiting the present invention. Unless otherwise specified, the terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention pertains. It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure.

[0026] The present invention is applicable to positive displacement vacuum pumps and their related bi-directional rotary sealing mechanisms. As Figure 1 , Figure 3 shown, the present invention includes a labyrinth seal and a piston ring seal. On the left and right sides in the axial direction of the labyrinth seal and the piston ring seal are respectively an oil chamber 111 and a pump chamber 333. On the inner and outer sides in the radial direction of the labyrinth seal and the piston ring seal are respectively a rotor shaft 4 in the pump chamber 333 and a tank side seal plate 2 in the oil chamber 111. The labyrinth seal includes a labyrinth seal moving ring 10 and a labyrinth seal stationary ring 11. The labyrinth seal moving ring 10 is sleeved on the rotor shaft 4 and is linked with the rotor shaft 4. The labyrinth seal stationary ring 11 is sleeved on the labyrinth seal moving ring 10 and is fixedly connected to the tank side seal plate 2. The piston ring seal includes at least one piston ring 13. A piston groove is provided on the rotor shaft 4; alternatively, a piston shaft sleeve 12 is sleeved on the rotor shaft 4, and a piston groove is provided on the outer surface of the piston shaft sleeve 12. The piston ring 13 is accommodated in the piston groove.

[0027] The oil chamber 111 of this embodiment includes a fuel tank 1, a tank side seal plate 2, an oil slinger 5, an internal hexagonal screw 6, a gland 7, a bearing 8, and an O-ring 9. One side of the fuel tank 1 is fixedly connected to the tank side seal plate 2. The oil slinger 5, the gland 7, and the bearing 8 are all located in the space enclosed by the fuel tank 1 and the tank side seal plate 2. The rotor shaft 4 is rotatably connected to one side of the tank side seal plate 2 through the bearing 8. The gland 7 is located on one side of the bearing 8, and the labyrinth seal and the piston ring seal are located on the other side of the bearing 8; the gland 7 is sleeved on the rotor shaft 4, and the internal hexagonal screw 6 passes through the through hole on the gland 7 to fix the gland 7 on one side of the tank side seal plate 2. The oil slinger 5 is installed on the rotor shaft 4 and is linked with the rotor shaft 4. One side of the gland 7, the bearing 8, and the tank side seal plate 2 form a cavity 14, and an elastic element for fixing the bearing 8 and damping is provided in the cavity 14; the elastic element of this embodiment can be a spring, and the two ends of the spring respectively abut against the end faces of the gland 7 and the bearing 8. When there is an axial force causing the rotor shaft 4 to axially move, the spring can well fix the bearing 8 and play a role in damping feedback. Lubricating oil is installed at the bottom of the oil chamber 111, and the oil slinger 5 introduces the lubricating oil into the cavity 14 in a splashing manner during the rotation with the rotor shaft 4 to form lubrication for the bearing 8.

[0028] The stator 3, the rotor shaft 4 and the oil tank side seal plate 2 together form a pump chamber 333 for inhaling and discharging process gas. The stator 3 is fixedly connected to the other side of the oil tank side seal plate 2. The end of the rotor shaft 4 is provided with a locking nut or a locking screw for fixing the components (such as the bearing 8, the labyrinth seal, the piston ring seal, etc.) on the rotor shaft 4, so as to ensure the common rotation of the entire shafting.

[0029] The sealing mechanism 222 composed of the O-ring 9, the labyrinth seal moving ring 10, the labyrinth seal static ring 11, the piston shaft sleeve 12, the piston ring 13 and the oil tank side seal plate 2 seals the lubricating oil in the oil chamber 111, the process gas and impurities in the pump chamber 333. In this embodiment, the labyrinth seal moving ring 10, the labyrinth seal static ring 11 and the piston shaft sleeve 12 are respectively provided with sealing grooves, and the O-ring 9 is accommodated in the sealing grooves. The number of the O-rings 9 can be multiple, and the design structure of the sealing grooves can be various, as long as it can achieve the function of static sealing. As a static sealing element, the O-ring 9 in this embodiment is arranged in three places. The O-ring 9 accommodated in the sealing groove on the labyrinth seal moving ring 10 is used to realize the seal between the labyrinth seal moving ring 10 and the rotor shaft 4. The O-ring 9 accommodated in the sealing groove on the labyrinth seal static ring 11 is used to realize the seal between the oil tank side seal plate 2 and the labyrinth seal static ring 11. The O-ring 9 accommodated in the sealing groove on the piston shaft sleeve 12 is used to realize the seal between the piston shaft sleeve 12 and the rotor shaft 4, so as to ensure that the lubricating oil cannot leak into the pump chamber 333 through other channels, and the process substances in the pump chamber 333 cannot leak into the oil chamber 111. When the lubricating oil in the bearing 8 is thrown to the sealing mechanism 222 as the inner ring rotates, due to the centrifugal force of the high-speed rotating labyrinth seal moving ring 10, most of the lubricating oil is blocked here, and these lubricating oils with nowhere to go can only be forced back into the bearing 8 to continue lubricating the bearing 8. The labyrinth seal composed of the labyrinth seal moving ring 10 and the labyrinth seal static ring 11 is a non-contact seal. Its principle is that a small gap (the gap can be 0.15 - 0.25 mm) is set between the labyrinth seal moving ring 10 and the labyrinth seal static ring 11 in the axial and radial concave-convex combinations, so as to form a good throttling effect. The high-speed rotation of the labyrinth seal moving ring 10 will disrupt the flow of the fluid and further prevent the passage of the lubricating oil.

[0030] On one side of the fuel tank side seal plate 2 close to the pump chamber 333 in this embodiment, an inert gas inlet channel 2a is provided. One end of the inert gas inlet channel 2a extends to the piston ring 13, and the other end of the inert gas inlet channel 2a is connected to an inert gas source 18 through a pipeline, so that inert gas (such as N2) enters the piston ring 13 through the inert gas inlet channel 2a. A throttling device 16 and a one-way valve 17 that can only intake gas into the inert gas inlet channel 2a are respectively provided on the pipeline. The specific structure is that the inert gas inlet channel 2a is connected to the throttling device 16 (the throttling device 16 in this embodiment can be a throttle valve) through pipeline A15a, then connected to the one-way valve 17 through pipeline B15b, and finally connected to the inert gas source 18 through pipeline C15c. The one-way valve 17 only allows inert gas to pass through positively from the inert gas source 18, thus preventing gas backflow.

[0031] There is a non-constant pressure gradient between the oil chamber 111 and the pump chamber 333. When the vacuum pump is in an idle state, both the oil chamber 111 and the pump chamber 333 are in a high vacuum state and have the same pressure at this time; when process gas is released from the processing chamber, the pressure in the pump chamber 333 will increase, thus generating a pressure gradient from the pump chamber 333 to the oil chamber 111, and this pressure gradient causes the process gas and impurities to enter the oil chamber 111; under the pumping of the vacuum pump, when the pump chamber 333 is in a high vacuum state, a pressure gradient from the oil chamber 111 to the pump chamber 333 is generated at this time, and this pressure gradient causes lubricating oil to enter the pump chamber 333.

[0032] It is set that the pressure of the inert gas source 18 is greater than the pressures in the above two states, so as to ensure that the inert gas inlet channel 2a is under positive pressure in any state, and the throttling device 16 can accurately control the amount of inert gas used. When it is not necessary to maintain a relatively high positive pressure (such as above 100 mbar), the throttling device 16 allows a small flow rate (such as 0.4 SLM) of inert gas to flow out. When process gas is suddenly released into the pump chamber 333, after a short delay of about one second, a large flow rate (such as 40 SLM) of gas flows out through the throttling device 16, thus ensuring a positive pressure gradient.

[0033] such as Figure 2As shown, in the case where no inert gas is introduced, in this embodiment, a pneumatic balance passage 2b is provided on one side of the fuel tank side seal plate 2 close to the pump chamber 333. A filter 20 is provided on the pneumatic balance passage 2b. One end of the pneumatic balance passage 2b is communicated with the inside of the pump chamber 333, and the other end of the pneumatic balance passage 2b extends to the piston ring 13. The filter 20 first functions to filter impurities, harmful molecules, and lubricating oil in the process gas. Secondly, by providing two one-way passages (from the filter 20 to the piston ring 13 and from the filter 20 to the inside of the pump chamber 333), whether it is the pressure gradient from the pump chamber 333 to the oil chamber 111 or the pressure gradient from the oil chamber 111 to the pump chamber 333, the gas on the high-pressure side can be introduced into the low-pressure side, thereby achieving pressure balance and preventing contamination under a negative pressure gradient.

[0034] As Figure 3 shown, three piston grooves are provided on the piston shaft sleeve 12 of this embodiment, and a corresponding number of piston rings 13 are installed in the piston grooves. The piston rings 13 can be rectangular rings with openings (not limited to rectangular rings), and the openings are flat openings (not limited to parallel openings); in order to ensure the same thermal expansion amount, the material of the piston rings 13 is the same as that of the rotor shaft 4, such as cast iron material. The gap between the piston rings 13 and the piston grooves is very small (the gap can be 0.1 mm), and this gap is much smaller than the concave-convex gap between the labyrinth seal dynamic ring 10 and the labyrinth seal static ring 11. This gap design maximizes the throttling effect, and even if lubricating oil passes through the labyrinth seal, it will be sealed, throttled, and blocked by the piston rings 13. Similarly, when harmful substances in the pump chamber 333 want to flow to the oil chamber 111, most of them are intercepted by the first ring sealed by the piston rings 13, for example, 90% of the amount, and the remaining exhaust gas is completely blocked by the second ring with a gas assistance function.

[0035] As Figure 4 shown, although the piston ring 13 seal is classified as a non-contact seal, in fact, it is not equivalent to the labyrinth seal. Under the rotational disturbance or thermal expansion of the rotor shaft 4, there is a certain contact friction behavior, which causes frictional power consumption. In order to further reduce the pump body power consumption, the number of piston rings 13 can be reduced and set as a labyrinth seal. The present invention gives a corresponding case where throttling grooves 19 are respectively provided on the fuel tank side seal plate 2 and the piston shaft sleeve 12. The structure of the throttling grooves 19 can be various, such as comb-shaped, spiral-shaped, labyrinth-shaped, etc.; correspondingly, the number of piston rings 13 becomes two. When the exhaust gas in the pump chamber 333 wants to pass through, its flow state is interrupted by the throttling grooves 19, losing its forward direction and kinetic energy.

[0036] The fuel tank side seal plate 2 of this embodiment can have various design structures. For example, it can be designed as a U-shaped structure with a middle cutout for heat dissipation considerations, or a sealed cavity structure with an internal cutout for enhancing the sealing function, etc., as long as it can cooperate with the sealing member to achieve the sealing function.

[0037] It should be noted that the above embodiments only illustrate the specific ideas and principles of the present invention. For those skilled in the art of this technology, without departing from the technical principles of this disclosure, there are various forms of its structural design, and these improvements and deformations should also be regarded as the protection scope of this disclosure.

Claims

1. A sealing mechanism for a vacuum pump, characterized in that: It includes a labyrinth seal and a piston ring seal. On the left and right sides in the axial direction of the labyrinth seal and the piston ring seal are an oil chamber (111) and a pump chamber (333) respectively. On the inner and outer sides in the radial direction of the labyrinth seal and the piston ring seal are the rotor shaft (4) in the pump chamber (333) and the tank side seal plate (2) in the oil chamber (111) respectively. The labyrinth seal includes a labyrinth seal moving ring (10) and a labyrinth seal stationary ring (11). The labyrinth seal moving ring (10) is sleeved on the rotor shaft (4) and is linked with the rotor shaft (4). The labyrinth seal stationary ring (11) is sleeved on the labyrinth seal moving ring (10) and is fixedly connected with the tank side seal plate (2). The piston ring seal includes at least one piston ring (13). A piston groove is formed on the rotor shaft (4); or a piston shaft sleeve (12) is sleeved on the rotor shaft (4), and a piston groove is formed on the outer surface of the piston shaft sleeve (12). The piston ring (13) is accommodated in the piston groove.

2. The sealing mechanism of the vacuum pump according to claim 1, characterized in that: Seal grooves are respectively formed on the labyrinth seal moving ring (10), the labyrinth seal stationary ring (11) and the piston shaft sleeve (12), and O-rings (9) are accommodated in the seal grooves. The O-ring (9) accommodated in the seal groove on the labyrinth seal moving ring (10) is used to achieve the seal between the labyrinth seal moving ring (10) and the rotor shaft (4). The O-ring (9) accommodated in the seal groove on the labyrinth seal stationary ring (11) is used to achieve the seal between the tank side seal plate (2) and the labyrinth seal stationary ring (11). The O-ring (9) accommodated in the seal groove on the piston shaft sleeve (12) is used to achieve the seal between the piston shaft sleeve (12) and the rotor shaft (4).

3. The sealing mechanism of the vacuum pump according to claim 1, characterized in that: An inert gas inlet channel (2a) is formed on one side of the tank side seal plate (2) close to the pump chamber (333). One end of the inert gas inlet channel (2a) extends to the piston ring (13), and the other end of the inert gas inlet channel (2a) is connected with an inert gas source (18) through a pipeline.

4. The sealing mechanism of the vacuum pump according to claim 3, characterized in that: A throttling device (16) and a one-way valve (17) that can only intake gas into the inert gas inlet channel (2a) are respectively arranged on the pipeline.

5. The sealing mechanism of the vacuum pump according to claim 1, wherein: A pressure balance channel (2b) is formed on one side of the tank side seal plate (2) close to the pump chamber (333). A filter (20) is arranged on the pressure balance channel (2b). One end of the pressure balance channel (2b) is communicated with the inside of the pump chamber (333), and the other end of the pressure balance channel (2b) extends to the piston ring (13).

6. The sealing mechanism of the vacuum pump according to claim 1, characterized in that: Throttling grooves (19) are respectively formed on the piston shaft sleeve (12) and the tank side seal plate (2).

7. The sealing mechanism of the vacuum pump according to claim 1, characterized in that: The oil chamber (111) includes an oil tank (1), an oil tank side seal plate (2), an oil slinger (5), a gland (7) and a bearing (8). The oil tank (1) is fixedly connected to one side of the oil tank side seal plate (2). The oil slinger (5), the gland (7) and the bearing (8) are all located in the space enclosed by the oil tank (1) and the oil tank side seal plate (2). The rotor shaft (4) is rotatably connected to one side of the oil tank side seal plate (2) through the bearing (8). The gland (7) is located on one side of the bearing (8), and the labyrinth seal and the piston ring seal are located on the other side of the bearing (8). The gland (7) is sleeved on the rotor shaft (4) and is fixedly connected to one side of the oil tank side seal plate (2). The oil slinger (5) is mounted on the rotor shaft (4) and is linked with the rotor shaft (4).

8. The sealing mechanism of the vacuum pump according to claim 7, characterized in that: One side of the gland (7), the bearing (8) and the oil tank side seal plate (2) forms a cavity (14). An elastic element for fixing the bearing (8) and damping is provided in the cavity (14). During the rotation of the oil slinger (5) with the rotor shaft (4), the lubricating oil in the oil chamber (111) is introduced into the cavity (14) to lubricate the bearing (8).

9. The sealing mechanism of the vacuum pump according to claim 1, wherein: The pump chamber (333) includes a stator (3), a rotor shaft (4) and an oil tank side seal plate (2). The stator (3) is fixedly connected to the other side of the oil tank side seal plate (2). A locking nut or a locking screw is provided at the end of the rotor shaft (4) for fixing the components on the rotor shaft (4).

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