Dry twin screw vacuum pump

Abstract

This invention relates to a dry twin-screw vacuum pump. A cooling jacket on the outer periphery of the pump casing, a first cooling chamber inside the front cover, and a second cooling chamber inside the rear cover are connected to form a water-cooling channel. An air-cooling device is connected to the pump casing, and the air-cooling pipe of the device passes through the cooling jacket and enters the inner cavity of the pump casing. The first and second screw rotors are conjugately meshed, and the end face profiles of both the first and second screw rotors are formed by connecting six curve segments end-to-end. The advantages of this invention are: through the dual action of water cooling and air cooling, the pump casing, front cover, rear cover, and internal rotor are cooled and cooled, resulting in better cooling and preventing the rotor from being damaged due to thermal expansion, which could affect the pumping performance; by improving the screw rotor profile, lead, and rotor length variation, and through the dual cooling design, the compression ratio can be increased, the pumping speed of the vacuum pump can be improved, and a lower ultimate vacuum can be achieved, thus improving the performance of the screw vacuum pump.

Description

Technical Field

[0001] This invention relates to the field of screw vacuum pump technology, and specifically to a dry twin-screw vacuum pump. Background Technology

[0002] A dry twin-screw vacuum pump is a pumping device that uses a pair of screw rotors to generate suction and exhaust by rotating synchronously and at high speed in opposite directions within a pump casing. The two screws are finely dynamically balanced, supported by bearings, and installed in the pump casing. The pumped medium is captured by the screws, compressed, and then delivered to the exhaust port. There is a certain gap between the screws, and during the compression process, the two screw rotors do not contact each other or the pump housing. Therefore, there is no friction between them during operation, resulting in smooth operation, low noise, and no need for lubricating oil or working fluid in the compression chamber. Dry screw pumps are used for pumping air and other dry, non-corrosive, non-toxic, and non-explosive gases, with lower power consumption.

[0003] Currently, to effectively control pump body temperature and prevent deformation from affecting pumping performance, a water cooling system is installed on the casing of the screw vacuum pump. Typically, a cooling jacket is installed on the outer wall of the pump casing to achieve cooling water injection and circulation for heat dissipation. In existing technologies, cooling water is usually injected directly into the internal channel of the cooling jacket through external pipelines. For example, Chinese patent CN202422351161.7 discloses a high-temperature single-suction twin-screw pump, which has a water-cooling chamber on the outside of the pump casing, with an inlet and an outlet. The water-cooling chamber cools the pump casing, but the pump casing also has a front end cover and a rear end cover at both ends. The end support and mounting structure of the screw rotor are located inside the front end cover and the rear end cover, making it impossible to simultaneously cool the interior of the front end cover and the rear end cover. Chinese patent CN201821096708.1 also discloses a turbofan-cooled screw pump, which uses both air cooling and water cooling, but it uses a different cooling method. Both the air duct and cooling water channel are located within the cooling jacket of the pump casing. This only cools the pump casing and cannot directly introduce cold air into the internal cavity of the pump casing to cool the rotor, thus reducing the cooling effect. Furthermore, some systems use a turbofan impeller mounted within an air-cooling connection frame, cooling the pump casing only through an internally installed turbofan impeller. Air cooling in these systems requires a separate turbofan impeller component. Other systems rely on air blowing onto the pump casing to control temperature rise. Additionally, the screw rotor is the most critical pumping component in a screw vacuum pump, directly determining the pump's performance and lifespan. The end face profile design of the screw rotor is the most critical technology in the entire screw pump design, directly affecting the ultimate vacuum and pumping rate. Improving the profile of existing screw rotors can increase the compression ratio and vacuum acquisition efficiency, thereby increasing the pumping rate while maintaining a lower ultimate vacuum. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dry twin-screw vacuum pump that can solve the problems of existing technologies, such as cooling the pump housing through a water-cooling chamber but not being able to cool the front and rear end covers at both ends simultaneously, water cooling and air cooling only cooling the pump housing, not being able to introduce cold air into the internal cavity of the pump housing to directly cool the rotor, weakened cooling effect, requiring an additional drive component, a turbofan impeller, and the need to modify the profile of the screw rotor to increase the compression ratio and pumping speed.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: a dry twin-screw vacuum pump, comprising a pump housing, a front end cover and a rear end cover disposed at both ends of the pump housing, and a pair of screw rotors installed inside the pump housing. A motor for driving the screw rotors to rotate is disposed on one side of the front end cover, and a gearbox is disposed between the motor and the front end cover. The pair of screw rotors includes a first screw rotor and a second screw rotor. The first screw rotor is driven to rotate by the motor, and the first screw rotor drives the second screw rotor to rotate through a gear structure disposed in the gearbox. The pump housing is characterized in that: a cooling jacket is disposed on the outer periphery of the pump housing, a first cooling chamber is disposed inside the front end cover, and a second cooling chamber is disposed inside the rear end cover. The cooling jacket, the first cooling chamber, and the second cooling chamber are connected to form a water-cooling channel. The inlet of the water-cooling channel is connected to an inlet pipe, and the outlet of the water-cooling channel is connected to an outlet pipe. The inlet pipe and the outlet pipe are respectively connected to a coolant storage tank. A water pump and a plate heat exchanger are installed on the inlet pipe. The pump housing, the front end cover, and the rear end cover are cooled by water cooling through the circulation of coolant entering the water-cooling channel. An air inlet is provided at the top of the end of the pump housing away from the motor, and an exhaust outlet is provided at the bottom side of the front cover; The pump housing is connected to an air-cooling device. The air-cooling pipe of the air-cooling device passes through the cooling jacket and enters the inner cavity of the pump housing. The air-cooling pipe is connected to an air filter. When the pressure at the air inlet is <300mbar, cooling air is automatically drawn into the inner cavity of the pump housing through the air filter and the air-cooling pipe to cool the screw rotor. The first screw rotor and the second screw rotor are conjugate meshing with each other, and the end face profiles of the first screw rotor and the second screw rotor are formed by connecting the beginning and end of six curves in sequence: tooth tip arc A1A2, curve A2A3, curve A3A4, curve A4A5, tooth root arc A5A6, and epicycloid A6A1. The curves A2A3 and A3A4 transition smoothly, and the curves A3A4 and A4A5 transition smoothly. The length variation curve of the first screw rotor is as follows: Segment 1: L1(φ)=15.495597307*φ, 0≤φ≤2.7925256709; Section 2: L1(φ)=22.5326230526*φ^2-110.3502593065*φ+175.7138925837, 2.7925256709≤φ≤3.4906596363; Section 3: L1(φ)=46.9571762728*φ-98.8394653494, 3.4906596363≤φ≤9.0757109781; Section 4: L1(φ)=-22.5326230526*φ^2+455.9563250793*φ-1954.8184977698, 9.0757109781≤φ≤9.7738449435; Section 5: L1(φ)=15.495597307*φ+197.6789306989, 9.7738449435≤φ≤25.1327412287; The lead variation curve of the first screw rotor is as follows: Segment 1: T1(φ)=97.3617093253, 0≤φ≤2.7925256709; Section 2: T1(φ)=283.1532921929*φ-693.3511279183, 2.7925256709≤φ≤3.4906596363; Section 3: T1(φ)=295.0406400241, 3.4906596363≤φ≤9.0757109781; Section 4: T1(φ)=-283.1532921929*φ+2864.8580824538, 9.0757109781≤φ≤9.7738449435; Section 5: T1(φ)=97.3617093253, 9.7738449435≤φ≤25.1327412287; The φ above represents the rotation angle of the first screw rotor.

[0006] Furthermore, the tooth profile of the first screw rotor is formed by sequentially connecting the tooth root surface, the helical tooth surface, the tooth tip surface, and the transition tooth surface. The helical lead of the first screw rotor gradually increases from the exhaust end to the intake end with the helical expansion angle, and the increasing trend is a discontinuous linear increase. The increase at the intake end is greater than the increase at the exhaust end, and the helical lead at the intake end is more than twice that at the intake end. The axial width of the helical tooth surface gradually increases from the exhaust end to the intake end, and the axial width of the helical tooth surface at the intake end is more than three times the axial width of the helical tooth surface at the intake end. The width of the tooth tip gradually increases from the exhaust end to the intake end, and the width of the tooth tip at the intake end is more than three times the width of the tooth tip at the intake end.

[0007] Furthermore, the front cover has a through hole on the lower side near the pump housing that communicates with the exhaust port and the inner cavity of the pump housing respectively; the front cover also has a first connecting hole on the upper side near the pump housing, which communicates with the first cooling cavity inside the front cover; the water inlet of the water cooling channel is located on the lower side of the first cooling cavity away from the exhaust port. The top of the rear end cover has a protrusion, the interior of which is connected to the second cooling chamber inside the rear end cover. The side of the rear end cover near the pump housing has a second connecting hole, which is connected to the interior of the protrusion. The outlet of the water cooling channel is located below one side of the second cooling chamber. The cooling jacket of the pump housing is connected to the first connecting hole and the second connecting hole on both sides, respectively, so as to realize the connection between the cooling jacket, the first cooling chamber and the second cooling chamber.

[0008] Furthermore, the top and bottom of the pump housing are respectively provided with an upper rectangular opening and a lower rectangular opening, both of which are connected to the interior of the cooling jacket, and a cover plate is installed on the top of the upper rectangular opening and the bottom of the lower rectangular opening respectively. The pump housing has a vertical reinforcing plate inside the cooling jacket, which divides the cooling jacket into a left jacket and a right jacket. A flow hole is provided at the bottom of the reinforcing plate to connect the left jacket and the right jacket.

[0009] Furthermore, the air-cooling device includes two inverted U-shaped air-cooling pipes, which are arranged side by side and interconnected. After being connected, they are connected to an air filter through a connecting pipe. The penetration points of the two air-cooling pipes and the cooling jacket are staggered vertically, and the penetration points of the two air-cooling pipes are both located below the middle of the pump housing.

[0010] Furthermore, one end of both the first and second screw rotors is mounted inside the front cover via a support ring and a bearing. A sealing gas system is installed on the front cover. The sealing gas system includes a gas delivery pipe. The inlet end of the gas delivery pipe is connected to a gas supply device, and the outlet end of the gas delivery pipe is connected to two connection holes on the top of the front cover. The bottom of the two connection holes is connected to the outer peripheral space of the first and second screw rotors via connection channels. Nitrogen gas reaches the outer periphery of the ends of the first and second screw rotors through the connection holes and connection channels to achieve gas sealing. A pressure gauge, a flow meter, a pressure regulating valve, and a flow regulator are installed on the gas delivery pipe. The nitrogen supplied by the gas supply device is either dry nitrogen or air, with a gas temperature of 0-60°C, a gas pressure ≤13 bar, and a gas flow rate of 30 L / min.

[0011] The advantages of this invention are as follows: By setting the cooling jacket of the pump housing, the first cooling chamber in the front cover, and the second cooling chamber in the rear cover as interconnected water-cooling channels, the coolant circulates into the water-cooling channels to simultaneously cool the pump housing, the front cover, and the rear cover. Furthermore, the coolant is cooled by heat exchange through a plate heat exchanger, ensuring the cooling effect of the coolant. Simultaneously, an air-cooling device is installed on the pump housing. The air-cooling pipe of the air-cooling device passes through the cooling jacket and enters the inner cavity of the pump housing. When the inlet pressure is low, air filtered by the air filter is automatically drawn into the inner cavity of the pump housing through the air-cooling pipe to cool the screw rotor, achieving self-cooling. The air-cooling pipeline also plays a role in balancing pressure. Through the dual action of water cooling and air cooling, the pump housing, the front cover, the rear cover, and the internal rotor are cooled, resulting in better cooling and preventing the rotor from being damaged due to thermal expansion, which could affect the pumping performance. Moreover, the air cooling is a self-cooling structure design, eliminating the need for additional drive components. By improving the screw rotor profile, modifying the lead and rotor length variations, and implementing a dual cooling design, the compression ratio can be increased, the volume of gas propelled by the screw per revolution can be increased, the vacuum efficiency can be improved, the pumping speed of the vacuum pump can be increased, and a lower ultimate vacuum can be achieved, thus enhancing the performance of the screw vacuum pump. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the overall structure of the dry twin-screw vacuum pump of the present invention; Figure 2 This is a partial structural schematic diagram of the dry twin-screw vacuum pump of the present invention; Figure 3 This is a cross-sectional view of the pump housing of the dry twin-screw vacuum pump of the present invention; Figure 4 This is a schematic diagram of the front end cover of the dry twin-screw vacuum pump of the present invention; Figure 5 This is a cross-sectional view of the front cover of the dry twin-screw vacuum pump of the present invention; Figure 6 This is a cross-sectional view of the rear end cover of the dry twin-screw vacuum pump of the present invention; Figure 7 This is a top view of the pump housing, front cover, and rear cover of the dry twin-screw vacuum pump of the present invention. Figure 8 for Figure 7 AA section view; Figure 9 This is a side view of the dry twin-screw vacuum pump of the present invention; Figure 10 for Figure 9 BB cross-sectional view; Figure 11 and Figure 12 This is a cross-sectional view of the dry twin-screw vacuum pump of the present invention; Figure 13 This is a profile of the first screw rotor end face of the dry twin-screw vacuum pump of the present invention; Figure 14 This is a schematic diagram of the structure of the first screw rotor of the dry twin-screw vacuum pump of the present invention; Figure 15 This is a cross-sectional view of the inner reinforcing plate of the cooling jacket of the dry twin-screw vacuum pump of the present invention; Figure 16 This is a schematic diagram of the screw rotor installation structure of the dry twin-screw vacuum pump of the present invention; Figure 17 This is a graph showing the length variation of the first screw rotor of the dry twin-screw vacuum pump of the present invention. Figure 18 This is a graph showing the lead variation of the first screw rotor of the dry twin-screw vacuum pump of the present invention. Figure 19 This is a pumping speed test diagram of the dry twin-screw vacuum pump of the present invention. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments will enable those skilled in the art to more fully understand this invention, but do not limit the invention to the scope of the described embodiments.

[0014] like Figure 1 As shown, the specific embodiment adopts the following technical solution: a dry twin-screw vacuum pump, including a pump housing 1, a front end cover 2 and a rear end cover 3 provided at both ends of the pump housing 1, and a pair of screw rotors installed inside the pump housing 1. A motor 4 for driving the screw rotors to rotate is provided on one side of the front end cover 2. A gearbox 5 is provided between the motor 4 and the front end cover 2. An air inlet 7 is provided on the top of the end of the pump housing 1 away from the motor 4.

[0015] like Figure 2 As shown, a pair of screw rotors includes a first screw rotor 61 and a second screw rotor 62. The first screw rotor 61 is driven to rotate by a motor 4. The first screw rotor 61 drives the second screw rotor 62 to rotate through a gear structure set in a gearbox 5. The gear structure in the gearbox 5 is a mature and conventional technology, and the specific structure will not be described in detail. An oil mist filter is installed on the gearbox 5, and an exhaust port 8 is provided on the bottom side of the front cover 2.

[0016] like Figure 4 As shown, the front cover 2 has a through hole 22 on the lower side near the pump housing 1, which is connected to the exhaust port 8 and the inner cavity of the pump housing 1 respectively.

[0017] like Figure 3 As shown, a cooling jacket 11 is provided on the outer periphery of the pump housing 1, such as... Figure 5 As shown, the front cover 2 is provided with a first cooling cavity 21, such as Figure 6 As shown, a second cooling chamber 31 is provided inside the rear cover 3, such as... Figure 7 and Figure 8 As shown, the front cover 2 is provided with a first connecting hole 23 on the side near the pump housing 1. The first connecting hole 23 is connected to the first cooling cavity 21 inside the front cover 2, and the cooling jacket 11 is connected to the first cooling cavity 21 through the first connecting hole 23.

[0018] like Figure 15 As shown, a vertical reinforcing plate 110 is provided in the cooling jacket 11 of the pump housing 1. The reinforcing plate 110 divides the cooling jacket into two parts: a left jacket and a right jacket. A flow hole 111 is provided at the bottom of the reinforcing plate 110, which connects the left jacket and the right jacket. The reinforcing plate 110 strengthens the cooling jacket 11 and ensures the overall structural strength of the pump housing 1.

[0019] like Figure 9 and Figure 10 As shown, the top of the rear end cover 3 has a protrusion 32, the interior of which is connected to the second cooling chamber 31 inside the rear end cover 3. The rear end cover 3 has a second connecting hole 33 on the side near the pump housing 1, which is connected to the interior of the protrusion 32. The second cooling chamber 31 is connected to the cooling jacket 11 through the second connecting hole 33. Both sides of the cooling jacket 11 of the pump housing 1 are connected to the first connecting hole 23 and the second connecting hole 33, respectively, thus realizing the connection between the cooling jacket 11, the first cooling chamber 21, and the second cooling chamber 31. The cooling interlayer 11, the first cooling chamber 21, and the second cooling chamber 31 are connected to form a water-cooled channel. The inlet of the water-cooled channel is connected to an inlet pipe 9. The inlet of the water-cooled channel is located on the side of the first cooling chamber 21 of the front end cover 2 away from the exhaust port 8. The outlet of the water-cooled channel is connected to an outlet pipe 10. The outlet of the water-cooled channel is located on the side of the second cooling chamber 31 of the rear end cover 3. The inlet pipe 9 and the outlet pipe 10 are respectively connected to the coolant storage tank 12. The coolant storage tank 12 is installed on the top of the front end cover 2 by a support frame.

[0020] A water pump 13 and a plate heat exchanger 14 are installed on the water inlet pipe 9. The coolant enters the water cooling channel and circulates to achieve water cooling and cooling of the pump housing 1, the front cover 2, and the rear cover 3. The coolant circulates through the water pump 13 and achieves heat exchange and cooling through the plate heat exchanger 14 to ensure the cooling effect.

[0021] like Figure 11As shown, a cooling device is connected to the pump housing 1. The cooling pipe 15 of the cooling device passes through the cooling jacket 11 and enters the inner cavity of the pump housing 1. The cooling pipe 15 is connected to an air filter 16. The air filter 16 is a mature and conventional technology, and its specific structure will not be described in detail. The cooling device includes two inverted U-shaped cooling pipes 15. The two cooling pipes 15 are arranged side by side and connected to each other. After being connected, they are connected to the air filter 16 through a connecting pipe 20. The penetration points of the two cooling pipes 15 and the cooling jacket 11 are staggered vertically, and the penetration points of the two cooling pipes 15 are both located below the middle of the pump housing 1. When the pressure at the air inlet is <300mbar, the cooling air is automatically drawn into the inner cavity of the pump housing 1 through the air filter 16 and the cooling pipe 15 to cool the screw rotor.

[0022] The pump housing 1 has an upper rectangular opening 17 and a lower rectangular opening 18 at the top and bottom, respectively. Both the upper rectangular opening 17 and the lower rectangular opening 18 are connected to the interior of the cooling jacket 11. The top of the upper rectangular opening 17 and the bottom of the lower rectangular opening 18 are respectively equipped with cover plates 19 for easy observation and cleaning.

[0023] like Figure 12 As shown, one end of the first screw rotor 61 and the second screw rotor 62 are both mounted inside the front cover 2 via a support ring 30 and a bearing. A sealing gas system is installed above the front cover 2. The sealing gas system includes a gas supply pipe 24. The inlet end of the gas supply pipe 24 is connected to a gas supply device. A pressure gauge, a flow meter, a pressure regulating valve, and a flow regulator are installed on the gas supply pipe 24. The gas supply device, pressure gauge, flow meter, pressure regulating valve, and flow regulator are conventional existing technologies, and their specific structures will not be described in detail. The exhaust end of the gas supply pipe 24 is connected to two connection holes 25 on the top of the front cover 2. The bottom of the connecting hole 25 is connected to the outer peripheral space of the first screw rotor 61 and the second screw rotor 62 through the connecting channel 26. Nitrogen gas reaches the outer periphery of the ends of the first screw rotor 61 and the second screw rotor 62 through the connecting hole 25 and the connecting channel 26, and finally reaches the inner cavity of the pump housing 1 to achieve gas sealing. The nitrogen gas output by the gas supply device is dry nitrogen gas or air, with a gas temperature of 0-60°, a gas pressure ≤13 bar, and a gas flow rate of 30 L / min. By introducing inert gas to form a dynamic barrier inside the pump, the reliability, efficiency and adaptability of the equipment are improved.

[0024] like Figure 16As shown, the first screw rotor 61 and the second screw rotor 62 are also sealed to the piston ring sealing kit 100 through the lip seal seat 200. The piston ring sealing kit 100 and the lip seal seat 200 are both sleeved on the outer periphery of the end shafts of the first screw rotor 61 and the second screw rotor 62. The first screw rotor 61 and the second screw rotor 62 are both installed through the bearing seat 300. The structural seal is achieved by the combined action of the piston ring sealing kit 100, the lip seal seat 200 and the nitrogen blowing.

[0025] The first screw rotor 61 and the second screw rotor 62 are conjugate meshing, such as Figure 13 As shown, the end face profiles of the first screw rotor 61 and the second screw rotor 62 are formed by connecting the first and second ends of six curves in sequence: tooth tip arc A1A2, curve A2A3, curve A3A4, curve A4A5, tooth root arc A5A6, and epicycloid A6A1. Curves A2A3 and A3A4 transition smoothly, and curves A3A4 and A4A5 transition smoothly.

[0026] like Figure 17 As shown, the length variation curve of the first screw rotor 61 is as follows: Segment 1: L1(φ)=15.495597307*φ, 0≤φ≤2.7925256709; Section 2: L1(φ)=22.5326230526*φ^2-110.3502593065*φ+175.7138925837, 2.7925256709≤φ≤3.4906596363; Section 3: L1(φ)=46.9571762728*φ-98.8394653494, 3.4906596363≤φ≤9.0757109781; Section 4: L1(φ)=-22.5326230526*φ^2+455.9563250793*φ-1954.8184977698, 9.0757109781≤φ≤9.7738449435; Section 5: L1(φ)=15.495597307*φ+197.6789306989, 9.7738449435≤φ≤25.1327412287; like Figure 18 As shown, the lead variation curve of the first screw rotor 61 is as follows: Segment 1: T1(φ)=97.3617093253, 0≤φ≤2.7925256709; Section 2: T1(φ)=283.1532921929*φ-693.3511279183, 2.7925256709≤φ≤3.4906596363; Section 3: T1(φ)=295.0406400241, 3.4906596363≤φ≤9.0757109781; Section 4: T1(φ)=-283.1532921929*φ+2864.8580824538, 9.0757109781≤φ≤9.7738449435; Section 5: T1(φ)=97.3617093253, 9.7738449435≤φ≤25.1327412287; The φ above is the rotation angle of the first screw rotor 61. The rotation angle is the angle of twist from a certain point to the starting point, in radians.

[0027] like Figure 14 As shown, the tooth profile of the first screw rotor 61 is formed by sequentially connecting the root tooth surface 611, the helical tooth surface 612, the tooth tip surface 613, and the transition tooth surface 614. The helical leads Ta, Tb, and Tc of the first screw rotor 61 gradually increase from the exhaust end to the intake end with the helical expansion angle, and the increasing trend is a discontinuous linear increase. The increase at the intake end is greater than that at the exhaust end, and the helical lead at the intake end is more than twice that at the intake end. The axial widths La, Lb, and Lc of the helical tooth surface 612 gradually increase from the exhaust end to the intake end, and the axial width of the helical tooth surface 612 at the intake end is more than three times that at the intake end. The widths Ba, Bb, and Bc of the tooth tip surface 613 gradually increase from the exhaust end to the intake end, and the width of the tooth tip surface 613 at the intake end is more than three times that at the intake end.

[0028] Performance Testing: The twin-screw vacuum pump was turned on to perform performance tests on pumping speed and ultimate vacuum. The pumping speed curve is shown in the figure below. Figure 19 As shown in the figure below, the pumping speed performance of the vacuum pump with the self-cooled structure design of this embodiment is compared with that of the vacuum pump in the prior art that controls the temperature rise through additional air cooling.

[0029] As can be seen from the above comparison, the pumping speed of the vacuum pump with the self-cooling structure design of this embodiment is significantly higher than that of the vacuum pump with the gas-cooled pumping speed design in the prior art that controls the temperature rise by introducing cooling gas. The pumping speed of the vacuum pump is significantly improved, and the ultimate vacuum degree of the vacuum pump of this embodiment can be measured to be below 100 Pa. While improving the pumping speed, a lower ultimate vacuum degree can be achieved. The performance of the screw vacuum pump is improved, and it can be applied to fields such as electronic manufacturing and semiconductor processing, which helps to improve product quality and production efficiency.

[0030] Working principle: When the dry twin-screw vacuum pump is working, gas is drawn into the inner cavity of the pump housing 1 through the air inlet 7 at the top of one end of the pump housing 1. After being compressed, it is delivered to the through hole 22 of the front cover 2 and discharged through the exhaust port 8 at the bottom side of the front cover 2. By setting the cooling jacket 11 of the pump housing 1, the first cooling chamber 21 in the front cover 2, and the second cooling chamber 31 in the rear cover 3 as a connected water-cooling channel, the coolant enters the water-cooling channel to circulate and simultaneously cool the pump housing 1, the front cover 2, and the rear cover 3. The coolant is also cooled by heat exchange through the plate heat exchanger 14 to ensure the cooling effect of the coolant. At the same time, an air-cooling device is installed on the pump housing 1. The air-cooling pipe 15 of the air-cooling device passes through the cooling jacket 11 and enters the inner cavity of the pump housing 1. When the inlet pressure is low, the air passes through the air filter. 16. Filtered air is automatically drawn into the inner cavity of the pump housing 1 through the air-cooling pipe 15 to cool the screw rotor. The air-cooling pipe 15 also plays a role in balancing pressure. Through the dual action of water cooling and air cooling, the pump housing 1, front cover 2, rear cover 3 and the internal rotor are cooled down, resulting in better cooling effect and preventing the rotor from being damaged due to thermal expansion, which would affect the pumping performance. Moreover, the air cooling is self-cooling and does not require additional drive components. By improving the screw rotor profile, the lead and rotor length variation, and the dual cooling design, the compression ratio can be increased, the volume of gas pushed by the screw per revolution can be increased, the vacuum efficiency can be improved, the pumping speed of the vacuum pump can be increased, and a lower ultimate vacuum degree can be achieved, thus improving the performance of the screw vacuum pump.

[0031] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A dry-type twin-screw vacuum pump, comprising a pump housing, a front end cover and a rear end cover arranged at both ends of the pump housing, and a pair of screw rotors installed in the pump housing, wherein a motor for driving the screw rotors to rotate is arranged on one side of the front end cover, a gear box is arranged between the motor and the front end cover, the pair of screw rotors comprises a first screw rotor and a second screw rotor, the first screw rotor is driven to rotate by the motor, and the first screw rotor drives the second screw rotor to rotate through a gear structure arranged in the gear box. The pump housing is provided with a cooling jacket on its outer periphery, the front cover is provided with a first cooling chamber, and the rear cover is provided with a second cooling chamber. The cooling jacket, the first cooling chamber, and the second cooling chamber are connected to form a water-cooling channel. The inlet of the water-cooling channel is connected to an inlet pipe, and the outlet of the water-cooling channel is connected to an outlet pipe. The inlet pipe and the outlet pipe are respectively connected to a coolant storage tank. A water pump and a plate heat exchanger are installed on the inlet pipe. The pump housing, the front cover, and the rear cover are cooled by water cooling through the circulation of coolant in the water-cooling channel. An air inlet is provided at the top of the end of the pump housing away from the motor, and an exhaust outlet is provided at the bottom side of the front cover; The pump housing is connected to an air-cooling device. The air-cooling pipe of the air-cooling device passes through the cooling jacket and enters the inner cavity of the pump housing. The air-cooling pipe is connected to an air filter. When the pressure at the air inlet is <300mbar, cooling air is automatically drawn into the inner cavity of the pump housing through the air filter and the air-cooling pipe to cool the screw rotor. The first screw rotor and the second screw rotor are conjugate meshing with each other, and the end face profiles of the first screw rotor and the second screw rotor are formed by connecting the beginning and end of six curves in sequence: tooth tip arc A1A2, curve A2A3, curve A3A4, curve A4A5, tooth root arc A5A6, and epicycloid A6A1. The curves A2A3 and A3A4 transition smoothly, and the curves A3A4 and A4A5 transition smoothly. The length variation curve of the first screw rotor is as follows: Segment 1: L1(φ)=15.495597307*φ, 0≤φ≤2.7925256709; Section 2: L1(φ)=22.5326230526*φ^2-110.3502593065*φ+175.7138925837, 2.7925256709≤φ≤3.4906596363; Section 3: L1(φ)=46.9571762728*φ-98.8394653494, 3.4906596363≤φ≤9.0757109781; Section 4: L1(φ)=-22.5326230526*φ^2+455.9563250793*φ-1954.8184977698, 9.0757109781≤φ≤9.7738449435; Section 5: L1(φ)=15.495597307*φ+197.6789306989, 9.7738449435≤φ≤25.1327412287; The lead variation curve of the first screw rotor is as follows: Segment 1: T1(φ)=97.3617093253, 0≤φ≤2.7925256709; Section 2: T1(φ)=283.1532921929*φ-693.3511279183, 2.7925256709≤φ≤3.4906596363; Section 3: T1(φ)=295.0406400241, 3.4906596363≤φ≤9.0757109781; Section 4: T1(φ)=-283.1532921929*φ+2864.8580824538, 9.0757109781≤φ≤9.7738449435; Section 5: T1(φ)=97.3617093253, 9.7738449435≤φ≤25.1327412287; The φ above represents the rotation angle of the first screw rotor.

2. The dry twin-screw vacuum pump according to claim 1, characterized in that: The tooth profile of the first screw rotor is formed by connecting the tooth root surface, the helical tooth surface, the tooth tip surface and the transition tooth surface in sequence. The helical lead of the first screw rotor gradually increases from the exhaust end to the intake end with the helical expansion angle, and the increasing trend is a discontinuous linear increase. The increase at the intake end is greater than the increase at the exhaust end, and the helical lead at the intake end is more than twice that at the intake end. The axial width of the helical tooth surface gradually increases from the exhaust end to the intake end, and the axial width of the helical tooth surface at the intake end is more than three times the axial width of the helical tooth surface at the intake end. The width of the tooth tip gradually increases from the exhaust end to the intake end, and the width of the tooth tip at the intake end is more than three times the width of the tooth tip at the intake end.

3. A dry twin-screw vacuum pump according to claim 1, characterized in that: The front cover has a through hole on the side near the pump housing that communicates with the exhaust port and the inner cavity of the pump housing respectively; the front cover also has a first connecting hole on the side near the pump housing that communicates with the first cooling cavity inside the front cover; the water inlet of the water cooling channel is located on the side of the first cooling cavity away from the exhaust port. The top of the rear end cover has a protrusion, the interior of which is connected to the second cooling chamber inside the rear end cover. The side of the rear end cover near the pump housing has a second connecting hole, which is connected to the interior of the protrusion. The outlet of the water cooling channel is located below one side of the second cooling chamber. The cooling jacket of the pump housing is connected to the first connecting hole and the second connecting hole on both sides, respectively, so as to realize the connection between the cooling jacket, the first cooling chamber and the second cooling chamber.

4. A dry twin-screw vacuum pump according to claim 1, characterized in that: The pump housing has an upper rectangular opening and a lower rectangular opening at the top and bottom, respectively. Both the upper and lower rectangular openings are connected to the interior of the cooling jacket, and a cover plate is installed at the top of the upper rectangular opening and the bottom of the lower rectangular opening, respectively. The pump housing has a vertical reinforcing plate inside the cooling jacket, which divides the cooling jacket into a left jacket and a right jacket. A flow hole is provided at the bottom of the reinforcing plate to connect the left jacket and the right jacket.

5. A dry twin-screw vacuum pump according to claim 1, characterized in that: The air-cooling device includes two inverted U-shaped air-cooling pipes, which are arranged side by side and connected to each other. After being connected, they are connected to the air filter through a connecting pipe. The penetration points of the two air-cooling pipes and the cooling jacket are staggered vertically, and the penetration points of the two air-cooling pipes are both located below the middle of the pump housing.

6. A dry twin-screw vacuum pump according to claim 1, characterized in that: One end of each of the first and second screw rotors is mounted inside the front cover via a support ring and a bearing. A sealing gas system is installed on the front cover. The sealing gas system includes a gas delivery pipe. The inlet end of the gas delivery pipe is connected to a gas supply device, and the outlet end of the gas delivery pipe is connected to two connection holes on the top of the front cover. The bottom of the two connection holes is connected to the outer peripheral space of the first and second screw rotors via connection channels. Nitrogen gas reaches the outer periphery of the ends of the first and second screw rotors through the connection holes and connection channels to achieve gas sealing. A pressure gauge, a flow meter, a pressure regulating valve, and a flow regulator are installed on the gas delivery pipe. The nitrogen supplied by the gas supply device is either dry nitrogen or air, with a gas temperature of 0-60°C, a gas pressure ≤13 bar, and a gas flow rate of 30 L / min.

Images