Double-end spiral screw and vacuum screw pump

Abstract

The invention relates to the technical field of vacuum pumps, in particular to a double-end spiral screw and a vacuum screw pump, the double-end spiral screw comprises a pump body, screws, threads and a sealing ring, the two screws are installed in the pump body, the threads are symmetrically arranged on the screws, the two screws are meshed with each other through the threads, the screws are connected with a motor, spiral grooves are formed in the threads, the thread pitches of the spiral grooves are equal to the thread pitches of the threads, and the sealing ring is arranged in the pump body. A radial compensation assembly is arranged in the spiral groove, a plurality of sealing rings are installed on the outer end face of the thread, the radial compensation assembly is connected with the sealing rings, one ends of the sealing rings are connected with axial compensation assemblies, and the sealing rings are connected with the adjacent sealing rings through the axial compensation assemblies. The radial compensation assembly is used for enabling centripetal force generated when the screw rotates to extend the sealing ring in the radial direction, and the axial compensation assembly is used for enabling the sealing ring to stretch out and draw back in the axial direction when the sealing ring rotates. The outer diameter end face of the sealing ring is in sliding connection with the side wall of the vacuum cavity through the axial compensation assembly and the radial compensation assembly. The vacuum efficiency of the vacuum pump is improved.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum pumps, in particular to a double-headed spiral screw and a vacuum screw pump. Background Art

[0002] A vacuum screw pump is a vacuum pump that belongs to the field of vacuum acquisition equipment. It relies on two screw rotors to rotate synchronously at high speed in opposite directions in the pump casing, so that a constantly changing sealed cavity is formed between the screws and between the screws and the inner wall of the pump casing. The sealed cavity moves from the air inlet to the air outlet, thereby realizing the suction, compression and discharge of the gas. It has the advantages of fast pumping speed, high vacuum degree, smooth operation, low noise, high reliability, and the ability to handle a variety of gases. In addition, since its working chamber does not require lubricating oil, the pollution of oil vapor to the vacuum system is reduced, and a higher ultimate vacuum degree can be achieved.

[0003] A screw vacuum pump comprises a rotor and a casing, wherein the helical teeth on two adjacent rotors mesh with each other. During the operation of the screw vacuum pump, the rotor rotates and compresses the air. During the process, the rotors will generate heat and expand, and then rub against each other. Therefore, a certain rotor movement gap is reserved between the rotors and the rotors, and between the rotors and the pump body at the beginning of the design. However, the reserved gap will allow the gas in the high-pressure area of ​​the vacuum pump to continuously flow back to the low-pressure area, thereby causing the efficiency of the vacuum pump to decrease. A solution to this problem is provided in the prior art. For example, patent application No. CN202322208224.9 provides a screw vacuum pump. The patent provides a solution including a pump body and a rotor that can rotate relative to the pump body, the rotor including a screw and helical teeth arranged on the outer periphery of the screw, and the helical teeth extend spirally around the axis of the rotor. , a spiral groove is provided on the outer edge of the spiral tooth, and the spiral groove extends spirally around the axis of the rotor along the extension direction of the spiral tooth. The screw vacuum pump includes a metal sealing strip, and the metal sealing strip is arranged in the spiral groove. The thermal expansion coefficient of the metal sealing strip is greater than the thermal expansion coefficient of the rotor. During the heating process of the vacuum pump, the metal sealing strip expands faster than the rotor, which can locally compress the rotor movement gap and reduce the reflux of gas from the high-pressure area to the low-pressure area in the vacuum pump, thereby improving the efficiency of the vacuum pump. However, since the temperature generated by the operation of the dry pump is uncontrollable, at too low a temperature, there will be a gap between the metal sealing strip and the pump body, and at too high a temperature, the metal sealing strip will expand and come into contact with the pump body, squeeze it, and wear it. In subsequent use, there will still be a gap between the metal sealing strip and the pump body, which will still reduce the efficiency of the vacuum pump. Summary of the invention

[0004] The object of the present invention is to provide a double-headed helical screw and a vacuum screw pump to solve the problem of a gap between the rotor and the pump body, which causes the gas in the high-pressure area of ​​the vacuum pump to continuously flow back to the low-pressure area, thereby causing the efficiency of the vacuum pump to decrease.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A double-headed helical screw and a vacuum screw pump, comprising a screw, a thread and a sealing ring, wherein the screw is symmetrically provided with threads, the spiral directions of the threads are opposite, a spiral groove is provided on the outer end surface of the thread, the pitch of the spiral groove is equal to the pitch of the thread, a radial compensation component is provided in the spiral groove, a plurality of sealing rings are installed on the outer end surface of the thread, the outer diameter end surface of the sealing ring is slidably connected to the side wall of the vacuum chamber, the radial compensation component is connected to the inner diameter end surface of the sealing ring, an axial compensation component is provided at one end of the sealing ring, the sealing ring is connected to the adjacent sealing ring through the axial compensation component, the radial compensation component is used to extend the sealing ring in the radial direction by the centripetal force when the screw rotates, and the axial compensation component is used to expand and contract the sealing ring in the axial direction when the sealing ring rotates.

[0007] It is easy to understand that during the operation of the screw vacuum pump, the threads will heat up and expand, and then rub against each other. Therefore, a certain rotor movement gap will be reserved between the threads and the threads, and between the threads and the pump body at the beginning of the design. However, the reserved gap will allow the gas in the high-pressure area of ​​the vacuum pump to continuously flow back to the low-pressure area, thereby causing the efficiency of the vacuum pump to decrease. Therefore, a spiral groove is opened on the outer diameter end face of the thread, and a radial compensation component is arranged in the groove. When the screw drives the thread to rotate, the compensation component in the spiral groove will rotate to generate centrifugal force to drive the sealing ring to move and extend in the radial direction, and keep the outer diameter end face of the sealing ring in sliding connection with the pump body, thereby reducing the reserved gap between the threads and the threads, and between the threads and the pump body, and avoiding the gas in the high-pressure area of ​​the vacuum pump to continuously flow back to the low-pressure area, thereby improving the vacuum efficiency of the vacuum pump.

[0008] Furthermore, since the centrifugal force mainly acts in the radial direction, when the diameter of the sealing ring increases, since the length of the sealing ring remains unchanged, the sealing ring will shrink in the axial direction, making it impossible for the sealing ring to seal part of the gap between the threads and the threads, and between the threads and the pump body, thereby causing the efficiency of the vacuum pump to decrease. Therefore, an axial compensation component is provided at one end of the sealing ring, and the sealing ring is connected to the adjacent sealing ring through the axial compensation component. When the screw drives the thread to rotate, the axial compensation component will rotate to generate centrifugal force for the sealing ring to expand and contract in the axial direction when the sealing ring rotates, so as to compensate for the shrinkage of the sealing ring, thereby preventing the sealing ring from shrinking in the axial direction, making it impossible for the sealing ring to seal part of the gap between the threads and the threads, and between the threads and the pump body. At the same time, when the sealing ring expands due to heat, it shrinks, thereby preventing the sealing ring from contacting, squeezing, and wearing with the pump body due to expansion, thereby preventing the sealing ring from still having a gap with the pump body during subsequent use, thereby still reducing the efficiency of the vacuum pump, thereby improving the vacuum efficiency of the vacuum pump, and ensuring the vacuum efficiency of the vacuum pump while increasing the service life of the sealing ring.

[0009] Preferably, the radial compensation assembly includes a sliding ring, and a plurality of sliding rings are coaxially slidably installed in the spiral groove. The sliding ring is spirally arranged, and the pitch is equal to that of the sealing ring. The upper end faces of the plurality of sliding rings are connected to the lower end face of the sealing ring.

[0010] When the screw drives the thread to rotate, the centripetal force generated by the rotation drives the sliding ring to slide in the spiral groove and move outward from the axis, thereby driving the sealing ring connected to it to move outward from the axis, so that the sealing ring and the pump body maintain a sliding connection, reducing the gaps reserved between threads and between threads and pump body, and preventing gas in the high-pressure area of ​​the vacuum pump from continuously flowing back to the low-pressure area, thereby improving the vacuum efficiency of the vacuum pump.

[0011] Preferably, the spiral groove includes a first section of the spiral groove and a second section of the spiral groove, the first section of the spiral groove and the second section of the spiral groove are horizontally arranged, the spiral groove close to the air outlet side is the first section of the spiral groove, and a support ring is installed in the second section of the spiral groove, and the support ring is made of memory metal.

[0012] During the operation of the vacuum pump, the air is compressed and a pressure difference will appear on both sides of the sealing ring. At this time, the gas on the side with higher pressure acts on the sliding ring, and the sliding ring will bend toward the side with weaker pressure. Stress concentration occurs at the bending part of the sliding part, which reduces the service life of the sliding ring. Therefore, a support ring is installed in the second section of the screw groove, and the support ring is made of memory metal. The memory metal has shape memory effect, good plasticity and temperature sensitivity. When the screw drives the thread to rotate, the temperature of the thread will rise, thereby driving the support ring to heat up. When the temperature reaches or exceeds this temperature, the crystal structure inside the support ring material will change, and then the external shape of the support ring will change, stretching and recovering to a preset shape. The stretched support ring is connected to the bent side of the sliding ring, thereby providing a supporting force to offset the pressure generated by the gas. The support ring is heated and reshaped, and support is provided to the sliding ring to avoid bending of the sliding ring, which reduces the service life of the sliding ring.

[0013] Preferably, the sealing ring is located in a semicircular radial projection of the screw, and the axial compensation assembly includes a pin, which is connected to one end of the sealing ring, the torsion angle of the pin is the same as that of the sealing ring, the upper end surface of the pin is flush with the upper end surface of the sealing ring, and the lower end surface of the pin is lower than the second section of the screw groove, and the other end of the sealing ring is provided with a mating groove, and the mating groove is slidably mated with the pin.

[0014] When the screw drives the thread to rotate, the centripetal force generated by the rotation drives the sliding ring to slide in the spiral groove and move outward from the axis, thereby pushing the sealing ring to move outward from the axis. At this time, the radial projection size of the sealing ring increases. During the process, some pins of adjacent sealing rings slide and separate in the matching groove. Since the upper end face of the pin is flush with the upper end face of the sealing ring and the lower end face of the pin is lower than the second section of the screw groove, when the pin is separated from the matching groove, the sliding connection between the pin and the pump body can still be maintained to maintain air tightness and avoid axial contraction of the sealing ring, which makes it impossible for the sealing ring to seal some gaps between the threads and the threads and the pump body, thereby improving the vacuum efficiency of the vacuum pump.

[0015] Preferably, the radial cross-sectional depth of the first section of the screw groove is greater than the radial cross-sectional depth of the second section of the screw groove, the sliding ring comprises a sliding section and a supporting section, the sliding section is connected to the sealing ring through the supporting section, the sliding section and the supporting section are slidably installed in the first section of the screw groove, the sliding section is located on the side of the supporting section and close to one side of the second section of the screw groove, and the horizontal plane projections of the second section of the screw groove and the sliding section are located within the horizontal projection plane of the support ring.

[0016] Since the sealing ring is semicircular and the sliding ring is slidably connected to the spiral groove, when the screw drives the thread to rotate rapidly, the sliding ring will be separated from the spiral groove under the action of centrifugal force. At this time, a gap appears between the lower end face of the sliding ring and the outer diameter end face of the thread, which may seriously cause damage to the sealing ring and the sliding ring. Therefore, the horizontal plane projections of the second section of the screw groove and the sliding section are located within the horizontal projection plane of the support ring, and the sliding section is designed to be located on the side of the support section close to the second section of the screw groove. When the screw drives the thread to rotate rapidly, the sliding ring and the sealing ring move outward in the radial direction under the action of centrifugal force, and when the upper end face of the sliding part contacts the lower end face of the support ring, the support ring prevents the sliding ring from moving outward. By setting the position of the support ring, when the upper end face of the sliding part contacts the lower end face of the support ring, the position of the sliding ring is restricted to prevent the sliding ring from being separated from the spiral groove.

[0017] Furthermore, through the design of the first section of the screw groove and the second section of the screw groove, the fault tolerance rate during the production process can be improved. The shape of the two-stage trapezoidal groove has certain geometric characteristics, which is convenient for processing and production. At the same time, the setting of the support ring position ensures that the position of the sliding ring is restricted while facilitating the installation of the sliding ring.

[0018] Preferably, a heat dissipation groove is opened in the support section, the heat dissipation groove is vertically arranged, the size between the heat dissipation groove and the side wall of the support section is larger than the size of the heat dissipation groove, the cross-section of the heat dissipation groove is I-shaped, and the inner side wall of the heat dissipation groove is symmetrically and evenly distributed with multiple bosses, the bosses are arranged vertically, and a self-slip coating is provided on the end surface of the boss, and the self-slip coating is made of copper alloy.

[0019] When the screw drives the thread to rotate, the temperature of the thread will rise during the air compression process, and the temperature of the thread will be transmitted to the sliding ring. The sliding ring will heat up and expand, and will be squeezed with the spiral groove and cannot slide. The sliding ring cannot drive the sealing ring to connect with the inner wall of the vacuum chamber, and the gap still exists, which leads to a decrease in the efficiency of the vacuum pump. The cross-section of the heat groove is I-shaped, and the design of the heat dissipation groove improves the heat dissipation effect of the sliding ring. At the same time, when the sliding ring runs for a long time, the side wall of the heat dissipation groove expands inward, and the space of the heat dissipation groove can compensate for the expansion deformation of the side wall of the heat dissipation groove, thereby avoiding squeezing of the sliding ring and the spiral groove. Furthermore, when the sliding ring heats up and expands, the relative bosses on the inner wall of the heat groove come into contact, and the heat dissipation groove is layered into multiple chambers. The support of the sliding ring is improved by the contact of the bosses. At the same time, the heat dissipation of the sliding ring can still be maintained by layering multiple chambers.

[0020] A vacuum screw pump for the above-mentioned double-headed spiral screw comprises a frame, a pump body and a motor, wherein the pump body and the motor are mounted on the frame, an air inlet chamber and a vacuum chamber are arranged in the pump body, the air inlet chamber and the vacuum chamber are communicated, the air inlet chamber is connected to an air inlet, the vacuum chamber is communicated to an air outlet, two screws are rotatably connected inside the pump body, the two screws are meshed with each other through threads, and one end of the two screws is connected to an output end of the motor.

[0021] Specifically, the air inlet and the air outlet are trapezoidal, the small-diameter ends of the air inlet and the air outlet point to the air inlet cavity and the vacuum cavity respectively, a guide plate is provided at the connection between the air inlet cavity and the vacuum cavity, and a plurality of air vents are horizontally provided on the guide plate.

[0022] It is easy to understand that when the motor is started, the motor rotates, thereby driving the two screws connected to it to rotate, and then driving the thread to rotate. At this time, the front end profile of the thread is about to be connected with the pump body to form an inter-tooth volume. During the process, the gas enters the air inlet from the air inlet to the air inlet chamber. As the thread rotates, the gas in the inter-tooth volume moves forward under the action of the thread. At this time, the gas in the air inlet chamber follows the inter-tooth volume to the vacuum chamber. Finally, when the inter-tooth volume is connected to the exhaust port, the gas in the inter-tooth volume can be discharged from the outlet. At this time, the air pressure at the air inlet is in a low pressure state, and the air pressure at the air outlet will stabilize at a state slightly higher than a standard atmospheric pressure.

[0023] The internal structure of the double-screw vacuum pump is complex. For example, the shape change of the threaded cavity, the size and shape mutation of the air inlet and exhaust port, etc., may lead to sudden changes in the direction and speed of gas flow. With the rapid rotation of the screw, the gas flows at high speed in the vacuum cavity. At this time, the interaction between the gas molecules becomes disordered, forming turbulence. Turbulence will lead to the intensification of the disordered movement of the gas molecules, making the flow path of the gas in the pump body complicated and irregular, causing gas reflux and vortex, resulting in the gas not being smoothly transported, resulting in a decrease in the vacuum efficiency of the vacuum pump. Therefore, the air inlet and outlet are set to be trapezoidal, and the diameter ends point to the air inlet cavity and the vacuum cavity respectively. The trapezoidal design of the air inlet makes the gas enter the pump body. Gradually accelerate to reduce speed mutations, thereby reducing the generation of turbulence in the air intake section. The design of the air outlet allows the exhausted gas to gradually diffuse, reduce the exhaust speed, and reduce the generation of turbulence. At the same time, a guide plate is provided at the connection between the air intake chamber and the vacuum chamber. The guide plate can guide the gas to flow in an orderly manner, prevent the gases from colliding with each other and mixing disorderly, and reduce the generation of turbulence. The design of the air inlet and air outlet and the guide plate can prevent the gases from colliding with each other and mixing disorderly, reduce the generation of turbulence, and avoid gas backflow, vortex and other phenomena, which result in the gas not being smoothly transported and the vacuum efficiency of the vacuum pump being reduced. The above design further reduces the generation of turbulence and avoids the disordered movement and collision of gas molecules, thereby reducing the generation of noise.

[0024] Preferably, the sealing ring includes a connecting part and a compensating part, the lower end surface of the connecting part is connected to the supporting section, the connecting part is connected to the compensating part on the side close to the air outlet, the upper end surface of the compensating part is slidably connected to the side wall of the vacuum chamber, and the horizontal projection of the compensating part is located outside the horizontal projection of the supporting section.

[0025] During the operation of the vacuum pump, the pressure on the side of the sealing ring close to the air outlet is greater than that on the other side. At this time, the pressure of the gas acts on the sealing ring. At the same time, since the support ring cannot follow the sealing ring for compensatory support, the sealing ring will bend, which will shorten the vertical dimension of the sealing ring, resulting in a gap between the upper end face of the sealing ring and the inner wall of the vacuum chamber, thereby reducing the efficiency of the vacuum pump. Therefore, a compensation part is connected to the side of the connecting part close to the air outlet, and the horizontal projection of the compensation part is outside the horizontal projection of the support section. When the sealing ring bends, the compensation part compensates for the shortened vertical dimension of the sealing ring. The gap is compensated by the compensation part to avoid the generation of the gap and ensure the vacuum efficiency of the vacuum pump.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention adopts the design of the sealing ring, the sliding ring, the latch and the matching groove. The sliding ring matches in the spiral groove, and the centrifugal force generated by the rotation is used to drive the sealing ring to compensate for the radial size. At the same time, the latch and the matching groove match to compensate for the partial gap generated by the axial contraction of the sealing ring, so that the outer diameter end face of the sealing ring maintains a sliding connection with the side wall of the vacuum chamber, thereby improving the vacuum efficiency of the vacuum pump.

[0028] 2. The present invention adopts the design of the support ring, the sliding block and the sealing ring. When the gas pressure acts on the side wall of the sliding ring, the support ring expands due to heat to support the sliding ring, thereby preventing the sliding ring from bending and thus reducing the service life of the sliding ring. At the same time, when the gas pressure acts on the sealing ring, the compensation part compensates for the gap between the upper end face of the sealing ring and the inner wall of the vacuum chamber, thereby avoiding the generation of a gap and ensuring the vacuum efficiency of the vacuum pump.

[0029] 3. The present invention adopts the design of the heat dissipation groove and the boss. The space of the heat dissipation groove compensates for the expansion deformation of the side wall of the heat dissipation groove, thereby avoiding the extrusion of the sliding ring and the spiral groove. At the same time, when the inner wall of the heat dissipation groove is deformed, the relative boss contacts, and the support of the sliding ring is improved through the contact of the boss. At the same time, the heat dissipation of the sliding ring can still be maintained by layering multiple empty chambers of the heat dissipation groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the installation of the double-headed spiral screw and the vacuum screw pump thereof of the present invention;

[0031] Figure 2 It is an axial cross-sectional view of the double-headed helical screw and the vacuum screw pump thereof of the present invention;

[0032] Figure 3 It is a cross-sectional view of the double-headed helical screw and the vacuum screw pump thereof of the present invention;

[0033] Figure 4 for Figure 3 Sectional view of AA in the middle;

[0034] Figure 5 for Figure 3 A partial enlarged view of the sealing ring and radial compensation assembly when the thread at B is not rotated;

[0035] Figure 6 for Figure 5 A partial enlarged view of the sealing ring and radial compensation assembly when the middle thread rotates;

[0036] Figure 7 It is a partial enlarged schematic diagram of the screw and thread;

[0037] Figure 8 is a schematic diagram of the assembly of adjacent sealing rings;

[0038] Fig. 9for Figure 8 Cross-sectional view of CC.

[0039] In the figure: 1. frame; 2. motor; 3. pump body; 31. air inlet chamber; 32. vacuum chamber; 33. air inlet; 34. air outlet; 35. guide plate; 351. air vent; 4. screw; 5. thread; 51. spiral groove; 52. first section of screw groove; 53. second section of screw groove; 6. sealing ring; 61. latch; 62. matching groove; 63. connecting part; 64. compensation part; 7. sliding ring; 71. sliding section; 72. supporting section; 721. heat dissipation groove; 722. boss; 723. self-lubricating coating; 8. supporting ring. DETAILED DESCRIPTION

[0040] See also Figures 1 to 9 The present invention provides a double-headed spiral screw and a vacuum screw pump, and the technical scheme is as follows:

[0041] A double-headed helical screw comprises a screw 4, a thread 5 and a sealing ring 6. The screw 4 is symmetrically provided with threads 5, the spiral directions of the threads 5 are opposite, a spiral groove 51 is provided on the outer end surface of the thread 5, the pitch of the spiral groove 51 is equal to the pitch of the thread 5, a radial compensation component is provided in the spiral groove 51, a plurality of sealing rings 6 are installed on the outer end surface of the thread 5, the outer diameter end surface of the sealing ring 6 is slidably connected to the side wall of the vacuum chamber 32, the radial compensation component is connected to the inner diameter end surface of the sealing ring 6, an axial compensation component is provided at one end of the sealing ring 6, the sealing ring 6 is connected to the adjacent sealing ring 6 through the axial compensation component, the radial compensation component is used to extend the sealing ring 6 in the radial direction by the centripetal force when the screw 4 rotates, and the axial compensation component is used to retract and retract the sealing ring 6 in the axial direction when the sealing ring 6 rotates.

[0042] See also Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 and Fig. 9The radial compensation component includes a sliding ring 7. A plurality of sliding rings 7 are coaxially slidably installed in the spiral groove 51. The sliding ring 7 is spirally arranged, and the pitch is equal to that of the sealing ring 6. The upper end faces of the plurality of sliding rings 7 are connected to the lower end faces of the sealing ring 6. The sealing ring 6 is located in a semicircular shape in the radial projection of the screw 4. The axial compensation component includes a latch 61. The latch 61 is connected to one end of the sealing ring 6. The torsion angle of the latch 61 is the same as that of the sealing ring 6. The upper end face of the latch 61 is flush with the upper end face of the sealing ring 6. The lower end face of the latch 61 is lower than the second section of the screw groove 53. The other end of the sealing ring 6 is provided with a matching groove 62, which is slidably matched with the latch 61. The sealing ring 6 includes a connecting portion 63 and a compensating portion 64. The lower end surface of the connecting portion 63 is connected to the supporting section 72. The connecting portion 63 is connected to the side of the air outlet 34 with the compensating portion 64. The upper end surface of the compensating portion 64 is slidably connected to the side wall of the vacuum chamber 32. The horizontal projection of the compensating portion 64 is located outside the horizontal projection of the supporting section 72. The spiral groove 51 includes a first section spiral groove 52 and a second section spiral groove 53. The first section spiral groove 52 and the second section spiral groove 53 are connected to the compensating portion 64. The spiral groove 51 is arranged horizontally, and the spiral groove 51 near the air outlet 34 is the first section spiral groove 52. The second section spiral groove 53 is installed with a support ring 8, and the support ring 8 is made of memory metal. The radial section depth of the first section spiral groove 52 is greater than the radial section depth of the second section spiral groove 53. The sliding ring 7 includes a sliding section 71 and a support section 72. The sliding section 71 is connected to the sealing ring 6 through the support section 72. The sliding section 71 and the support section 72 are slidably installed in the first section spiral groove 52. The sliding section 71 is located on the side of the support section 72 and is close to the second section. On one side of the screw groove 53, the horizontal plane projections of the second section of the screw groove 53 and the sliding section 71 are located within the horizontal projection plane of the support ring 8. A heat dissipation groove 721 is provided in the support section 72. The heat dissipation groove 721 is vertically arranged. The dimension between the heat dissipation groove 721 and the side wall of the support section 72 is larger than the dimension of the heat dissipation groove 721. The cross-section of the heat dissipation groove 721 is I-shaped. A plurality of bosses 722 are symmetrically and evenly distributed on the inner side wall of the heat dissipation groove 721. The bosses 722 are vertically arranged. A self-slip coating 723 is provided on the end surface of the boss 722. The self-slip coating 723 is made of copper alloy.

[0043] See also Figures 1 to 9 A vacuum screw pump for the above-mentioned double-headed spiral screw comprises a frame 1, a pump body 3 and a motor 2. The pump body 3 and the motor 2 are mounted on the frame 1. An air inlet chamber 31 and a vacuum chamber 32 are arranged in the pump body 3. The air inlet chamber 31 and the vacuum chamber 32 are communicated. The air inlet chamber 31 is connected to an air inlet 33. The vacuum chamber 32 is communicated to an air outlet 34. Two screws 4 are rotatably connected inside the pump body 3. The two screws 4 are meshed with each other through threads 5. One end of the two screws 4 is connected to the output end of the motor 2. The pump body 3 is characterized in that the air inlet 33 and the air outlet 34 are trapezoidal, and the small-diameter ends of the air inlet 33 and the air outlet 34 point to the air inlet chamber 31 and the vacuum chamber 32 respectively. A guide plate 35 is arranged at the connection between the air inlet chamber 31 and the vacuum chamber 32, and a plurality of air vents 351 are horizontally arranged on the guide plate 35.

[0044] Working principle: when the motor 2 is started, the motor 2 rotates and drives the two screws 4 installed horizontally in the vacuum chamber 32 in the pump body 3 to rotate, and then drives the thread 5 to rotate. At this time, the gas enters the air inlet 33 and comes to the air inlet chamber 31. Due to the trapezoidal design of the air inlet 33, the gas gradually accelerates in the process of entering the pump body 3, reducing the sudden change in speed, thereby reducing the generation of turbulence in the air inlet section. At this time, the gas in the air inlet chamber 31 flows to the vacuum chamber 32, and a guide plate 35 is provided at the connection between the air inlet chamber 31 and the vacuum chamber 32. The guide plate 35 is provided with an air inlet hole. The guide plate 35 and the air vent 351 can guide the gas to flow in an orderly manner to prevent mutual collision and disordered mixing of the gases, further reduce the generation of turbulence, and the gas in the vacuum chamber 32 As the thread 5 rotates, it reaches the front end where the thread 5 is connected to the pump body 3 to form an inter-tooth volume and move forward. During the process, when the thread 5 rotates, the centripetal force generated by the rotation drives the sliding ring 7 to slide in the spiral groove 51 and move outward from the axis, thereby driving the supporting section 72 on the sliding ring 7 to push the sealing ring 6 to move outward from the axis, thereby maintaining a sliding connection between the sealing ring 6 and the side wall of the vacuum chamber 32, reducing the gaps reserved between the threads 5 and the threads 5, and between the threads 5 and the pump body 3. Since the sealing ring 6 is semicircular and the sliding ring 7 is slidingly connected to the first section of the screw groove 52, when the screw 4 drives the thread 5 to rotate rapidly, the sliding ring 7 will be separated from the spiral groove 51 under the action of centrifugal force. At this time, there is a gap between the lower end face of the sliding ring 7 and the outer diameter end face of the thread 5. The gap will seriously cause damage to the sealing ring 6 and the sliding ring 7. Therefore, the horizontal plane projection of the second-section screw groove 53 and the sliding section 71 is set in the horizontal projection plane of the support ring 8, and the position of the sliding section 71 is designed to be close to the side of the support section 72 close to the second-section screw groove 53. When the screw rod 4 drives the thread 5 to rotate rapidly, the sliding ring 7 and the sealing ring 6 move outward in the radial direction under the action of centrifugal force. When the upper end surface of the sliding part contacts the lower end surface of the support ring 8, the support ring 8 prevents the sliding ring 7 from moving outward to prevent the sliding ring 7 from detaching from the spiral groove 51. At this time, the radial projection size of the sealing ring 6 increases. During the process, some pins 61 of the adjacent sealing rings 6 slide and separate in the matching groove 62, which fills the partial gap caused by the contraction in the axial direction. At the same time, during the rotation of the sealing ring 6, the gas is compressed and heated. When the sealing ring 6 is heated and expanded, the pin 61 slides in the matching groove 62 to shrink, so as to prevent the expansion of the sealing ring 6 from contacting, squeezing and wearing the pump body 3. At the same time, since the upper end surface of the pin 61 is flush with the upper end surface of the sealing ring 6 and the lower end surface of the pin 61 is lower than the second section of the screw groove 53, when the pin 61 is separated from the matching groove 62, the sliding connection between the pin 61 and the inner wall of the vacuum chamber 32 can still be maintained to maintain air tightness, thereby improving the vacuum efficiency of the vacuum pump. Finally, when the inter-tooth volume is connected to the exhaust port, the gas in the inter-tooth volume can be discharged from the outlet 34. At this time, the air pressure at the air inlet 33 is in a low pressure state, and the air pressure at the outlet 34 will be stabilized at a state slightly higher than a standard atmospheric pressure.

[0045] When the gas reaches the front end thread 5 and is connected with the pump body 3 to form an inter-tooth volume, the gas pressure on the side close to the outlet 34 is greater than the pressure on the side close to the inlet 33. The pressure of the body acts on the sliding ring 7, and the sliding ring 7 will bend, resulting in a reduction in the service life of the sliding ring 7. Therefore, a support ring 8 is installed in the second section of the screw groove 53 on the side away from the outlet 34. The support ring 8 is made of memory metal. The memory metal has a shape memory effect, good plasticity, and temperature sensitivity. When the screw 4 drives the thread 5 to rotate, the temperature of the thread 5 will rise, thereby driving the support ring 8 to heat up. When the temperature reaches or exceeds this temperature, the crystal structure inside the support ring 8 material will change, thereby supporting The outer shape of the ring 8 changes and returns to a preset shape, thereby providing support for the sliding ring 7. At the same time, since the support ring 8 cannot follow the sealing ring 6 for compensatory support, the sealing ring 6 will bend, causing the size of the sealing ring 6 in the vertical direction to be shortened, resulting in a gap between the upper end face of the sealing ring 6 and the inner wall of the vacuum chamber 32. Therefore, a connecting portion 63 and a compensating portion 64 are provided on the sealing ring 6. The lower end face of the connecting portion 63 is connected to the supporting end, and the compensating portion 64 is connected to the side of the connecting portion 63 close to the air outlet 34, and the horizontal projection of the compensating portion 64 is located outside the horizontal projection of the supporting section 72. When the sealing ring 6 bends, the compensating portion 64 compensates for the shortened size of the sealing ring 6 in the vertical direction.

[0046] When the screw rod 4 drives the thread 5 to rotate, the temperature of the thread 5 will rise during the air compression process, and the temperature of the thread 5 will be transmitted to the sliding ring 7, the sliding ring 7 will heat up and expand, and will be squeezed with the spiral groove 51 and unable to slide. The sliding ring 7 cannot drive the sealing ring 6 to connect with the inner wall of the vacuum chamber 32, and the gap is still there. The design of the heat dissipation groove 721 with an I-shaped cross section of the heat groove improves the heat dissipation effect of the sliding ring 7. At the same time, when the sliding ring 7 is running for a long time, the side wall of the heat dissipation groove 721 expands and deforms inwardly, and the expansion deformation of the side wall of the heat dissipation groove 721 can be measured through the space of the heat dissipation groove 721. To compensate for the situation, the sliding ring 7 and the spiral groove 51 are prevented from being squeezed. Furthermore, when the sliding ring 7 heats up and expands, the relative bosses 722 on the inner wall of the heat groove come into contact, and the heat dissipation groove 721 is layered with a plurality of empty chambers. The support of the sliding ring 7 is improved by the contact of the boss 722. At the same time, the heat dissipation groove 721 is layered with a plurality of empty chambers, and the heat dissipation of the sliding ring 7 can still be maintained. A self-lubricating coating 723 is provided on the boss 722. The self-lubricating coating 723 is made of copper alloy, has good self-lubricity and wear resistance, can reduce the wear of the boss 722 during use, and thus ensure the heat dissipation of the sliding ring 7.

[0047] A specific embodiment of the present invention is described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above described embodiment. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments without departing from the principles and ideas of the present invention should still fall within the scope of protection of the present invention.

Claims

1. A double-start helical screw, characterized in that: The invention comprises a screw (4), a thread (5) and a sealing ring (6), wherein the screw (4) is symmetrically provided with threads (5), the threads (5) have opposite spiral directions, a spiral groove (51) is provided on the outer end surface of the thread (5), the pitch of the spiral groove (51) is equal to the pitch of the thread (5), a radial compensation component is provided in the spiral groove (51), a plurality of sealing rings (6) are installed on the outer end surface of the thread (5), the outer diameter end surface of the sealing ring (6) is slidably connected to the side wall of the vacuum chamber (32), the radial compensation component is connected to the inner diameter end surface of the sealing ring (6), an axial compensation component is provided at one end of the sealing ring (6), the sealing ring (6) is connected to the adjacent sealing ring (6) through the axial compensation component, the radial compensation component is used to extend the sealing ring (6) in the radial direction due to the centripetal force when the screw (4) rotates, and the axial compensation component is used to extend and retract the sealing ring (6) in the axial direction when the sealing ring (6) rotates.

2. A double-start helical screw according to claim 1, characterized in that: The radial compensation component comprises a sliding ring (7), a plurality of sliding rings (7) are coaxially slidably installed in the spiral groove (51), the sliding ring (7) is spirally arranged, and the pitch is equal to that of the sealing ring (6), and the upper end surfaces of the plurality of sliding rings (7) are connected to the lower end surface of the sealing ring (6).

3. A double-start helical screw according to claim 2, characterized in that: The spiral groove (51) comprises a first section of the spiral groove (52) and a second section of the spiral groove (53), wherein the first section of the spiral groove (52) and the second section of the spiral groove (53) are arranged horizontally, the spiral groove (51) close to the air outlet (34) is the first section of the spiral groove (52), and a support ring (8) is installed in the second section of the spiral groove (53), wherein the support ring (8) is made of memory metal.

4. A double-start helical screw according to claim 2, characterized in that: The sealing ring (6) is located in a semicircular shape in radial projection of the screw rod (4); the axial compensation component comprises a latch (61); the latch (61) is connected to one end of the sealing ring (6); the torsion angle of the latch (61) is the same as that of the sealing ring (6); the upper end surface of the latch (61) is flush with the upper end surface of the sealing ring (6); the lower end surface of the latch (61) is lower than the second section of the screw groove (53); the other end of the sealing ring (6) is provided with a matching groove (62); the matching groove (62) is slidably matched with the latch (61).

5. A double-start helical screw according to claim 2, characterized in that: The radial cross-sectional depth of the first section of the screw groove (52) is greater than the radial cross-sectional depth of the second section of the screw groove (53); the sliding ring (7) comprises a sliding section (71) and a supporting section (72); the sliding section (71) is connected to the sealing ring (6) via the supporting section (72); the sliding section (71) and the supporting section (72) are slidably installed in the first section of the screw groove (52); the sliding section (71) is located on the side of the supporting section (72) and close to the side of the second section of the screw groove (53); the horizontal plane projection of the second section of the screw groove (53) and the sliding section (71) is located in the horizontal projection plane of the support ring (8).

6. A double-start helical screw according to claim 5, characterized in that: A heat dissipation groove (721) is provided in the support section (72), the heat dissipation groove (721) is arranged vertically, the dimension between the heat dissipation groove (721) and the side wall of the support section (72) is larger than the dimension of the heat dissipation groove (721), the cross section of the heat dissipation groove (721) is in an I-shape, a plurality of bosses (722) are symmetrically and evenly distributed on the inner side wall of the heat dissipation groove (721), the bosses (722) are arranged vertically, and a self-slip coating (723) is provided on the end surface of the boss (722), and the self-slip coating (723) is made of copper alloy.

7. A vacuum screw pump using a double-headed helical screw as described in any one of claims 1 to 6, comprising a frame (1), a pump body (3) and a motor (2), wherein the pump body (3) and the motor (2) are mounted on the frame (1), an air inlet chamber (31) and a vacuum chamber (32) are arranged in the pump body (3), the air inlet chamber (31) and the vacuum chamber (32) are communicated, the air inlet chamber (31) is connected to an air inlet (33), the vacuum chamber (32) is communicated to an air outlet (34), two screws (4) are rotatably connected inside the pump body (3), the two screws (4) are meshed with each other through a thread (5), one end of the two screws (4) is connected to an output end of the motor (2), and is characterized in that: The air inlet (33) and the air outlet (34) are trapezoidal in shape, and the small-diameter ends of the air inlet (33) and the air outlet (34) point to the air inlet cavity (31) and the vacuum cavity (32) respectively. A guide plate (35) is provided at the connection point between the air inlet cavity (31) and the vacuum cavity (32), and a plurality of air holes (351) are horizontally provided on the guide plate (35).

8. A double-start helical screw according to claim 6, characterized in that: The sealing ring (6) comprises a connecting portion (63) and a compensating portion (64); the lower end surface of the connecting portion (63) is connected to the supporting section (72); the compensating portion (64) is connected to the side of the connecting portion (63) close to the air outlet (34); the upper end surface of the compensating portion (64) is slidably connected to the side wall of the vacuum chamber (32); and the horizontal projection of the compensating portion (64) is located outside the horizontal projection of the supporting section (72).

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