Roots screw composite vacuum pump

Abstract

The utility model belongs to the technical field of vacuum pumps, and particularly relates to a Roots screw composite vacuum pump. In order to overcome the defects that when an existing Roots screw composite vacuum pump works, compressed gas is accumulated at the joint of a Roots rotor and a screw rotor, so that the temperature rise at the joint is obvious, and the pumping speed ratio of the Roots rotor and the screw rotor is limited due to the temperature rise, the Roots screw composite vacuum pump adopts the following technical scheme that the Roots screw composite vacuum pump comprises a pump body with a pump cavity; the Roots screw composite rotor comprises a Roots rotor and a screw rotor which are axially distributed, the air inlet switching device comprises a Roots air inlet channel and a screw air inlet channel which can be opened and closed respectively; the pump body is provided with a Roots air inlet corresponding to the Roots rotor and a screw air inlet corresponding to the screw rotor, the Roots air inlet is connected with a Roots air inlet channel, the screw air inlet is connected with a screw air inlet channel, and an air outlet is formed in one end, far away from the Roots rotor, of the pump body. The Roots screw composite vacuum pump disclosed by the utility model has the beneficial effect of avoiding or reducing temperature rise.

Description

Technical Field

[0001] This utility model belongs to the field of vacuum pump technology, specifically relating to a Roots screw composite vacuum pump. Background Technology

[0002] The screw-Roots combined vacuum pump mounts Roots vanes and a screw rotor on the same main shaft, offering advantages such as compact structure, high pumping speed, and ease of manufacturing. At the same rotational speed, Roots pumps faster than screw pumps. To improve the overall efficiency of a combined vacuum pump of the same volume, it is desirable to increase the pumping speed ratio between the Roots rotor and the screw rotor.

[0003] However, existing Roots-screw composite vacuum pumps are designed with a relatively small pumping speed ratio (the ratio of the pumping speed of the Roots rotor to that of the screw rotor) (still greater than 1:1). This is because the Roots rotor is directly connected to the first stage of the screw rotor. When the pumping speed difference between the Roots rotor and the screw rotor is large, a large amount of compressed gas will accumulate at the connection point, leading to increased power consumption and temperature in the Roots section (to limit temperature rise, the rotor speed is usually controlled at higher gas pressures). This is analogous to a Roots rotor acting as a multi-lane road and the screw rotor as a single-lane road. When the speed of the multi-lane road is too high (the pumping speed of the Roots rotor is too high), the traffic will be blocked at the entrance of the single-lane road (the first stage of the screw rotor). Roots-screw units can avoid this situation by adjusting the speed of the Roots pump and / or the screw pump. In a Roots-screw composite vacuum pump, since the Roots rotor and the screw rotor are the same composite rotor, and their speeds are the same, the only way to achieve this is by reducing the pumping speed ratio between the Roots rotor and the screw rotor.

[0004] Meanwhile, the operating time of the compound vacuum pump at higher pressures (which will cause a significant temperature rise) is much shorter than that at lower pressures (which will not cause a significant temperature rise). When the pumping speeds of the Roots rotor and the screw rotor are relatively low, the overall pumping speed of the compound vacuum pump of the same volume is low, resulting in lower efficiency. Summary of the Invention

[0005] This invention addresses the problem in existing Roots-screw composite vacuum pumps where compressed gas accumulates at the connection between the Roots rotor and the screw rotor during operation, leading to a significant temperature rise and limiting the pumping speed ratio between the Roots and screw rotors. The invention provides a Roots-screw composite vacuum pump that, by incorporating an intake switching device, avoids or reduces the temperature rise at higher gas pressures, thus extending its service life. The reduced temperature rise allows for a higher pumping speed ratio between the Roots and screw rotors, improving overall efficiency.

[0006] To achieve the above objectives, this utility model adopts the following technical solution: a Roots-screw composite vacuum pump, comprising:

[0007] Pump body, having a pump chamber;

[0008] The Roots-screw composite rotor, located in the pump chamber, consists of an axially distributed Roots rotor and a screw rotor;

[0009] The intake switching device includes two separately openable and closable Roots intake passages and screw intake passages;

[0010] The pump body is equipped with a Roots inlet corresponding to the Roots rotor and a screw inlet corresponding to the screw rotor. The Roots inlet is connected to the Roots intake channel, and the screw inlet is connected to the screw intake channel. An outlet is provided at the end of the pump body away from the Roots rotor.

[0011] This utility model discloses a Roots-screw composite vacuum pump. Based on existing Roots-screw composite vacuum pumps, it adds a screw inlet and an inlet switching device (existing Roots-screw composite vacuum pumps have a Roots inlet). Therefore, when the gas pressure in the evacuated container is high, all or most of the gas enters the screw rotor directly through the screw inlet channel and screw inlet of the inlet switching device without passing through the Roots rotor. The Roots rotor does not compress the gas, or at least has little chance of doing so, thus preventing or reducing gas accumulation. When the gas pressure in the evacuated container is low, all or most of the gas enters the Roots rotor (and then passes through the screw rotor) through the Roots inlet channel and Roots inlet of the inlet switching device. At this time, due to the low gas pressure, even if gas accumulates, the impact is minimal. Furthermore, both the Roots rotor and the screw rotor can function, resulting in a high pumping speed for the entire composite vacuum pump. At higher gas pressures (low vacuum), the Roots pump compresses little or no gas, thus avoiding significant temperature rise and extending its service life. The pumping speed ratio can be increased to achieve higher overall pumping speeds for the same volume of a compound vacuum pump at lower gas pressures (medium to high vacuum). The pumping speed ratio of the Roots rotor to the screw rotor is the ratio of the Roots rotor's pumping speed to the screw rotor's pumping speed.

[0012] As an improvement, the Roots-screw composite vacuum pump also includes a vacuum gauge and a controller, which controls the opening and closing of the Roots inlet passage and / or the screw inlet passage based on the vacuum level obtained from the vacuum gauge.

[0013] As an improvement, when the vacuum level obtained by the vacuum gauge is greater than a first threshold, the screw intake channel of the intake switching device opens and the Roots intake channel closes; or, both the screw intake channel and the Roots intake channel of the intake switching device are opened, with the intake volume of the screw intake channel being much greater than that of the Roots intake channel; and / or,

[0014] When the vacuum level obtained by the vacuum gauge is less than the second threshold, the screw intake channel of the intake switching device is closed and the Roots intake channel is opened; or, both the screw intake channel and the Roots intake channel of the intake switching device are opened, and the intake volume of the screw intake channel is much smaller than that of the Roots intake channel.

[0015] As an improvement, the intake switching device includes a first valve for opening and closing the Roots intake passage and a second valve for opening and closing the screw intake passage, both of which are electromagnetic butterfly valves; or...

[0016] The intake switching device includes a common valve for opening and closing the Roots intake passage and the screw intake passage. The common valve is a solenoid valve, which ensures that only one of the Roots intake passage and the screw intake passage is open at any given time.

[0017] As an improvement, the Roots-screw composite vacuum pump also includes a controller and solenoid valves for opening and closing the Roots inlet passage and the screw inlet passage. The controller controls the solenoid valves of the Roots inlet passage and / or the screw inlet passage according to the working time.

[0018] As an improvement, the Roots-screw composite vacuum pump also includes manual valves for opening and closing the Roots inlet passage and the screw inlet passage.

[0019] As an improvement, the intake switching device includes a main intake port, a Roots intake passage, and a screw intake passage, all of which are connected to the main intake port.

[0020] As an improvement, the intake switching device is detachably connected to the Roots intake port; the intake switching device is detachably connected to the screw intake port.

[0021] As an improvement, the Roots inlet is located on the upper surface of the pump body, and the screw inlet is located on the side of the pump body. The outlet is located on the side and / or bottom surface of the pump body.

[0022] As an improvement, the pumping speed ratio between the Roots rotor and the screw rotor is greater than 4:1.

[0023] The beneficial effects of this Roots-screw composite vacuum pump are as follows: Based on the existing Roots-screw composite vacuum pump, a screw inlet and an inlet switching device are added. When the gas pressure in the evacuated container is high, all or most of the gas directly enters the screw rotor through the screw inlet channel of the inlet switching device, with the Roots rotor participating little or no, thus preventing or reducing gas accumulation and increasing the pumping speed ratio between the Roots rotor and the screw rotor. When the gas pressure in the evacuated container is low, all or most of the gas enters the Roots rotor (and then the screw rotor) through the Roots inlet channel of the inlet switching device. At this time, due to the low gas pressure, even if gas accumulates, the impact is minimal, and both the Roots rotor and the screw rotor can function effectively. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the Roots-screw composite vacuum pump according to Embodiment 1 of this utility model (only the relevant structure is shown).

[0025] Figure 2 This is an exploded view of the structure of the Roots-screw composite vacuum pump according to Embodiment 1 of this utility model.

[0026] Figure 3 This is a schematic diagram of the pump body of the Roots screw composite vacuum pump according to Embodiment 1 of this utility model.

[0027] Figure 4 This is a schematic diagram of the air inlet switching device of the Roots screw composite vacuum pump according to Embodiment 1 of this utility model.

[0028] Figure 5 This is a structural block diagram of the Roots screw composite vacuum pump according to Embodiment 1 of this utility model.

[0029] Figure 6 This is a structural block diagram of the Roots screw composite vacuum pump according to Embodiment 2 of this utility model.

[0030] In the diagram, 1 is the pump body; 11 is the pump chamber; 12 is the Roots inlet; 13 is the screw inlet; and 14 is the outlet.

[0031] 2. Roots-screw composite rotor; 21. Roots rotor; 22. Screw rotor;

[0032] 3. Intake switching device; 31. Main intake port; 32. Roots intake passage; 33. Screw intake passage; 34. First valve; 35. Second valve. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be explained and described below. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0034] See Figures 1 to 6 The Roots screw composite vacuum pump of this utility model embodiment includes:

[0035] Pump body, having a pump chamber;

[0036] The Roots-screw composite rotor, located in the pump chamber, consists of an axially distributed Roots rotor and a screw rotor;

[0037] The intake switching device includes two separately openable and closable Roots intake passages and screw intake passages;

[0038] The pump body is equipped with a Roots inlet corresponding to the Roots rotor and a screw inlet corresponding to the screw rotor. The Roots inlet is connected to the Roots intake channel, and the screw inlet is connected to the screw intake channel. An outlet is provided at the end of the pump body away from the Roots rotor.

[0039] This utility model discloses a Roots-screw composite vacuum pump. Based on existing Roots-screw composite vacuum pumps, it adds a screw inlet and an inlet switching device. When the pressure in the evacuated container is high, all or most of the gas enters the screw rotor directly through the screw inlet channel of the inlet switching device, minimizing or preventing gas accumulation. When the pressure in the evacuated container is low, all or most of the gas enters the Roots rotor (and then the screw rotor) through the Roots inlet channel of the inlet switching device. At this time, due to the lower pressure, even if gas accumulates, the impact is minimal, and both the Roots rotor and the screw rotor can function effectively. By adding the inlet switching device without changing the pumping speed ratio of the Roots rotor and the screw rotor, temperature rise can be avoided or reduced, and service life can be extended (however, the overall efficiency may decrease slightly).

[0040] Example 1

[0041] See Figures 1 to 5 The Roots screw composite vacuum pump of this utility model embodiment includes:

[0042] Pump body 1, having pump chamber 11;

[0043] The Roots-screw composite rotor 2 is located in the pump chamber 11 and includes an axially distributed Roots rotor 21 and screw rotor 22;

[0044] The intake switching device 3 includes two Roots intake passages 32 and a screw intake passage 33 that can be opened and closed separately;

[0045] The pump body 1 is provided with a Roots inlet 12 corresponding to the Roots rotor 21 and a screw inlet 13 corresponding to the screw rotor 22. The Roots inlet 12 is connected to the Roots inlet channel 32, and the screw inlet 13 is connected to the screw inlet channel 33. The pump body 1 is provided with an outlet 14 at the end away from the Roots rotor 21.

[0046] In this embodiment, the Roots intake passage 32 includes a Roots connecting flange connected to the Roots intake port 12, and the screw intake passage 33 includes a screw connecting flange connected to the screw intake port 13.

[0047] In this embodiment, the Roots-screw composite vacuum pump also includes a vacuum gauge and a controller. The controller controls the opening and closing of the Roots inlet channel 32 and / or the screw inlet channel 33 based on the vacuum level obtained from the vacuum gauge.

[0048] In this embodiment, when the vacuum level obtained by the vacuum gauge is greater than the first threshold, the screw intake channel 33 of the intake switching device 3 is opened, and the roots intake channel 32 is closed. Alternatively, both the screw intake channel 33 and the roots intake channel 32 of the intake switching device 3 are opened, and the intake volume of the screw intake channel 33 is much greater than the intake volume of the roots intake channel 32. Typically, at the beginning of vacuuming, the vacuum level in the container being evacuated is greater than the first threshold.

[0049] In this embodiment, when the vacuum level obtained by the vacuum gauge is less than the second threshold, the screw intake channel 33 of the intake switching device 3 is closed and the Roots intake channel 32 is opened. Alternatively, both the screw intake channel 33 and the Roots intake channel 32 of the intake switching device 3 are opened, and the intake volume of the screw intake channel 33 is much smaller than the intake volume of the Roots intake channel 32.

[0050] In this embodiment, the intake switching device 3 includes a first valve 34 for opening and closing the Roots intake passage 32 and a second valve 35 for opening and closing the screw intake passage 33. Both the first valve 34 and the second valve 35 are electromagnetic butterfly valves.

[0051] In other embodiments, the Roots-screw composite vacuum pump includes a controller and solenoid valves for opening and closing the Roots inlet passage 32 and the screw inlet passage 33. The controller controls the solenoid valves of the Roots inlet passage 32 and / or the screw inlet passage 33 according to the operating time.

[0052] In other embodiments, the Roots-screw composite vacuum pump also includes a manual valve for opening and closing the Roots inlet passage 32 and the screw inlet passage 33.

[0053] In this embodiment, the air intake switching device 3 includes a main air intake 31, a Roots air intake channel 32 and a screw air intake channel 33, all of which are connected to the main air intake 31.

[0054] In this embodiment, the intake switching device 3 is detachably connected to the Roots intake port 12; the intake switching device 3 is detachably connected to the screw intake port 13, thereby facilitating transportation, storage and cleaning.

[0055] In this embodiment, the Roots inlet 12 is located on the upper surface of the pump body 1, and the screw inlet 13 is located on the side of the pump body 1.

[0056] In this embodiment, the pumping speed ratio of the Roots rotor 21 to the screw rotor 22 is greater than 4:1. In the prior art, the pumping speed ratio of the Roots rotor 21 to the screw rotor 22 is generally 1:1 to 4:1. Changing the pumping speed ratio can be achieved by adjusting the axial length of the Roots rotor 21 and / or the pitch of the screw rotor 22. Increasing the pumping speed ratio of the Roots rotor 21 to the screw rotor 22 can increase the overall pumping speed of the compound vacuum pump by 2 to 3 times.

[0057] In this embodiment, when the composite vacuum pump starts working, the pressure of the container being evacuated is relatively high. The gas in the container being evacuated enters the screw rotor 22 directly through the screw inlet 13. At this time, since the Roots rotor 22 is not working at all or almost not working, gas accumulation is reduced or eliminated, temperature rise is avoided or reduced, and service life is extended. Although only the screw rotor 22 works at higher pressures, the efficiency is lower than that of existing composite vacuum pumps without a gas switching device 3 at higher pressures. However, the working duration at higher pressures (from kPa to atmospheric pressure) is shorter, while the working duration at lower pressures (below kPa) is much longer. At this time, the pumping speed ratio of the Roots rotor 21 and the screw rotor 22 is greater, resulting in a higher overall pumping speed and higher efficiency for the composite vacuum pump. Therefore, the overall efficiency of the composite vacuum pump in this embodiment is higher throughout the entire vacuuming process.

[0058] The beneficial effects of the Roots-screw composite vacuum pump of Embodiment 1 of this utility model are as follows: Based on the existing Roots-screw composite vacuum pump, a screw inlet 13 and an inlet switching device 3 are added. When the gas pressure in the evacuated container is high, all or most of the gas directly enters the screw rotor 22 through the screw inlet channel 33 of the inlet switching device 3, with the Roots rotor 21 participating little or no, thus preventing or reducing gas accumulation, avoiding or reducing temperature rise, and extending service life. It also increases the pumping speed ratio between the Roots rotor 21 and the screw rotor 22. When the gas pressure in the evacuated container is low, all or most of the gas enters the Roots rotor 21 (and then passes through the screw rotor 22) through the Roots inlet channel 32 of the inlet switching device 3. At this time, due to the low gas pressure, even if gas accumulates, the impact is minimal, and both the Roots rotor 21 and the screw rotor 22 can function. Increasing the pumping speed ratio between the Roots rotor 21 and the screw rotor 22 results in a higher overall pumping speed for the same volume of composite vacuum pump, improving efficiency.

[0059] Example 2

[0060] See Figure 6 In this embodiment, the intake switching device 3 includes a shared valve for opening and closing the Roots intake passage 32 and the screw intake passage 33. The shared valve is a solenoid valve, ensuring that only one of the Roots intake passage 32 and the screw intake passage 33 is open at any given time. Using a shared valve reduces the number of valves while ensuring that at least one intake passage remains unobstructed. Specific structures for switching between the two passages using the same shared valve can be found in existing technologies.

[0061] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A Roots-screw composite vacuum pump, characterized in that: include: Pump body (1), having pump chamber (11); The Roots-screw composite rotor (2) is located in the pump chamber (11) and includes an axially distributed Roots rotor (21) and screw rotor (22); The intake switching device (3) includes two Roots intake passages (32) and a screw intake passage (33) that can be opened and closed separately; The pump body (1) is provided with a Roots inlet (12) corresponding to the Roots rotor (21) and a screw inlet (13) corresponding to the screw rotor (22). The Roots inlet (12) is connected to the Roots inlet channel (32), and the screw inlet (13) is connected to the screw inlet channel (33). The pump body (1) is provided with an outlet (14) at the end away from the Roots rotor (21).

2. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The Roots-screw composite vacuum pump also includes a vacuum gauge and a controller. The controller controls the opening and closing of the Roots inlet channel (32) and / or the screw inlet channel (33) based on the vacuum level obtained from the vacuum gauge.

3. The Roots-screw composite vacuum pump according to claim 2, characterized in that: When the vacuum level obtained by the vacuum gauge is greater than the first threshold, the screw intake channel (33) of the intake switching device (3) is opened and the Roots intake channel (32) is closed; or, both the screw intake channel (33) and the Roots intake channel (32) of the intake switching device (3) are opened, and the intake volume of the screw intake channel (33) is much greater than the intake volume of the Roots intake channel (32); and / or, When the vacuum level obtained by the vacuum gauge is less than the second threshold, the screw intake channel (33) of the intake switching device (3) is closed and the Roots intake channel (32) is opened. Alternatively, both the screw intake channel (33) and the Roots intake channel (32) of the intake switching device (3) are opened, and the intake volume of the screw intake channel (33) is much smaller than that of the Roots intake channel (32).

4. The Roots-screw composite vacuum pump according to claim 2, characterized in that: The intake switching device (3) includes a first valve (34) for opening and closing the Roots intake passage (32) and a second valve (35) for opening and closing the screw intake passage (33), wherein both the first valve (34) and the second valve (35) are electromagnetic butterfly valves; or, The intake switching device (3) includes a common valve for opening and closing the Roots intake passage (32) and the screw intake passage (33). The common valve is a solenoid valve, which ensures that only one of the Roots intake passage (32) and the screw intake passage (33) is open.

5. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The Roots-screw composite vacuum pump also includes a controller and solenoid valves for opening and closing the Roots inlet passage (32) and the screw inlet passage (33). The controller controls the solenoid valves of the Roots inlet passage (32) and / or the screw inlet passage (33) according to the working time.

6. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The Roots-screw composite vacuum pump also includes manual valves for opening and closing the Roots inlet passage (32) and the screw inlet passage (33).

7. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The intake switching device (3) includes a main intake port (31), a Roots intake passage (32) and a screw intake passage (33), all of which are connected to the main intake port (31).

8. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The intake switching device (3) is detachably connected to the Roots intake port (12); the intake switching device (3) is detachably connected to the screw intake port (13).

9. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The Roots inlet (12) is located on the upper surface of the pump body (1), and the screw inlet (13) is located on the side of the pump body (1).

10. The Roots-screw composite vacuum pump according to claim 1, characterized in that: The pumping speed ratio of the Roots rotor (21) and the screw rotor (22) is greater than 4:1.

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