A bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump

Abstract

The invention discloses a bearing cavity sealing structure for limiting the self-rotation of a Roots vacuum pump, comprising an end cover, a bearing seat and a rotating shaft, wherein the bearing seat is fixed to the outside of the end cover, a bearing cavity is arranged inside the bearing seat, the outer end of the rotating shaft passes through the end cover and is arranged in the bearing cavity through a bearing, a sealing seat is also arranged in the bearing cavity, a packing seat installation cavity is arranged in the sealing seat, a packing seat is arranged in the packing seat installation cavity, a packing surrounding and tightly hugging the outside of the rotating shaft is arranged in the packing seat, an oil inlet passage is arranged on the upper part of the bearing seat, an oil discharge passage is arranged on the lower part of the bearing seat, an oil inlet through hole communicating with the oil inlet passage is arranged on the top of the sealing seat and the packing seat, and an oil discharge through hole communicating with the oil discharge passage is arranged on the bottom of the sealing seat and the packing seat. The invention can limit the self-rotation of the Roots vacuum pump caused by the pressure difference between the suction and exhaust ports when it is not started, avoid causing a stall fault of the frequency converter, and will not limit the rotation of the Roots vacuum pump under full speed operation to cause a high current.

Description

Technical Field

[0001] The invention relates to the technical field of Roots vacuum pumps, and in particular to a bearing cavity sealing structure for limiting the self-rotation of a Roots vacuum pump. Background Art

[0002] Roots refers to a variable displacement mechanical rotary pump that has two blade-shaped rotors rotating synchronously in opposite directions, with a small gap between the rotors and between the rotors and the inner wall of the pump casing, but they do not touch each other. Since Roots vacuum pumps are generally only suitable for operation within a certain pressure difference range, if the pressure difference is too large, the operating load will be very large, exceeding the allowable power of the motor. Therefore, in practical applications, Roots vacuum pumps are not allowed to be directly discharged into the atmosphere, and it is often necessary to equip a vacuum pump of other types in front for vacuum pre-pumping to achieve the traction effect, such as liquid ring pumps, rotary vane pumps, sliding valve pumps, screw pumps, etc. When these vacuum pumps draw the pressure in the entire system (vacuum chamber) to a lower level, the Roots vacuum pump is started. At this time, the Roots vacuum pump can achieve the functions of speed increase and pressure increase (increasing vacuum) on this basis without the occurrence of overcurrent.

[0003] However, for vacuum environments with large system containers and high air leakage, it is often difficult (or takes a very long time) for the vacuum pump used for pre-evacuation to reach a high vacuum by itself, that is, the pressure value at which the Roots vacuum pump can start. Therefore, the Roots vacuum pump is often required to intervene in operation in advance, but in order to avoid overcurrent in the Roots vacuum pump, a frequency converter is required in this application. By giving the Roots vacuum pump a lower speed at a higher pressure, the speed of the Roots vacuum pump is gradually increased as the pressure in the system (container) gradually decreases, thereby achieving constant power operation, which can not only achieve the intervention operation of the Roots vacuum pump at a higher pressure, but also avoid motor overload and shutdown protection during operation.

[0004] Although the use of frequency converter can start and operate Roots vacuum pumps at higher pressures, there is also a very serious hidden danger. That is, when the system is large (such as vacuum refining furnaces VD in the metallurgical industry, and RH furnaces with large air leakage), the Roots vacuum pump is very likely to rotate due to a certain pressure difference between the suction port and the exhaust port (especially under processes with large leakage rate and load). Spinning is inevitable, and as the pressure at the suction port of the Roots vacuum pump gradually decreases, the speed of spinning sometimes accelerates. This is because the reduction in air resistance (including the resistance of the pump itself) exceeds the pressure difference value (power value), and the speed of the pump's spin will reach between 5-10% of its maximum allowable speed.

[0005] When the rotation speed of the Roots vacuum pump exceeds 3-4% of its maximum allowable speed, the Roots vacuum pump can no longer be started by the frequency converter. This is because after the frequency converter receives the start command, it must accelerate from 1 Hz to the specified maximum Hz number (although there is a flying start command in the frequency converter, if the Roots vacuum pump is not equipped with a speed detector and does not know the actual speed during the rotation, this function cannot be realized). However, at this time, the rotation speed of the Roots vacuum pump is far more than the 5Hz output of the frequency converter, and the front and rear pressure difference power is still maintained. At this time, the actual action of the frequency converter is to first slow down the Roots vacuum pump and give it a reverse traction force to ensure that its speed matches its current frequency. As a result, the frequency converter has a stall fault, and the frequency converter traction force is far from matching the power of the Roots vacuum pump's rotation, so it also causes current overload, resulting in the inability to start the Roots vacuum pump normally. Even if reset is used, it is difficult to solve this problem. Unless the inlet valve of the Roots vacuum pump is closed to eliminate the power of self-rotation (pressure difference between front and rear, self-rotation stops), and then the speed of the Roots vacuum pump is increased to the corresponding value through the frequency converter, and then the valve is opened, which is similar to the mechanism of the automobile gearbox. However, in actual application, not all processes allow the valve to be closed and then opened, and this operation requires a good understanding of the vacuum process to operate effectively, otherwise it is easy to cause serious malfunctions.

[0006] Therefore, under certain specific vacuum conditions, a new structure is needed to limit the self-rotation of the Roots vacuum pump caused by the pressure difference between the suction and exhaust ports when it is not started, so as to avoid causing the inverter stall failure, and not limit the rotation of the Roots vacuum pump at full speed to cause high current. Summary of the invention

[0007] In view of the defects in the prior art, the present invention provides a bearing cavity sealing structure for limiting the self-rotation of a Roots vacuum pump, so that the self-rotation of the Roots vacuum pump caused by the pressure difference between the suction and exhaust ports when the Roots vacuum pump is not started can be limited, thereby avoiding causing a stall failure of the inverter, and will not limit the rotation of the Roots vacuum pump at full speed to cause high current.

[0008] The present invention provides a bearing cavity sealing structure for limiting the self-rotation of a Roots vacuum pump, comprising an end cover, a bearing seat and a rotating shaft, wherein the bearing seat is fixed to the outside of the end cover, a bearing cavity is arranged inside the bearing seat, the outer end of the rotating shaft passes through the end cover and is arranged in the bearing cavity through a bearing, a sealing seat is also arranged in the bearing cavity, a stuffing seat installation cavity is arranged in the sealing seat, a stuffing seat is arranged in the stuffing seat installation cavity, a packing surrounding and hugging the outside of the rotating shaft is arranged in the stuffing seat, an oil inlet channel for introducing lubricating oil into the bearing cavity is arranged on the upper part of the bearing seat, an oil discharge channel for discharging lubricating oil in the bearing cavity is arranged on the lower part of the bearing seat, an oil inlet through hole communicating with the oil inlet channel is arranged on the top of the sealing seat and the stuffing seat, and an oil discharge through hole communicating with the oil discharge channel is arranged on the bottom of the sealing seat and the stuffing seat.

[0009] Furthermore, a skeleton oil seal installation cavity is provided in the sealing seat on the inner side of the packing seat installation cavity, and a skeleton oil seal surrounding the outside of the rotating shaft is installed in the skeleton oil seal installation cavity.

[0010] Further, the diameter of the packing seat installation cavity is greater than the diameter of the skeleton oil seal installation cavity, so that the skeleton oil seal and the packing seat can be respectively installed into the skeleton oil seal installation cavity and the packing seat installation cavity from the outer end of the packing seat installation cavity in sequence, and the inner end of the packing seat is provided with a first inner stop ring that abuts against the packing;

[0011] A bearing seat mounting groove is provided on the outside of the end cover, and the bearing seat is inserted into the bearing seat mounting groove. A connecting ring is provided on the outer end of the bearing seat, and the connecting ring is fixed to the end cover by bolts. A second inner stop ring is provided in the bearing cavity of the bearing seat, and the sealing seat is pressed against the bottom of the bearing seat mounting groove through the second inner stop ring. The packing seat is pressed against the step formed between the packing seat mounting cavity and the skeleton oil seal mounting cavity through the second inner stop ring, and the packing is pressed against the first inner stop ring through the second inner stop ring.

[0012] Furthermore, the outer circumference of the rotating shaft is provided with a first step surface, a second step surface and a third step surface with diameters increasing successively from the outer end to the inner end, and the second inner retaining ring and the sealing seat are arranged outside the third step surface;

[0013] The bearing includes an inner ring and an outer ring arranged coaxially, and a ball arranged between the inner ring and the outer ring. The inner ring is sleeved on the outside of the second step surface. The first step surface is externally threaded with a locking nut that presses the inner ring against the step between the second step surface and the third step surface. The outer ring is adapted to the bearing cavity. The outer end of the bearing seat is also fixed with a bearing cover by bolts that presses the outer ring against the second inner retaining ring.

[0014] Furthermore, an avoidance groove is provided at the outer end of the second inner retaining ring to separate the inner ring of the bearing from the second inner retaining ring.

[0015] Furthermore, an oil inlet groove extending in the front-to-back direction is formed at the top of the bearing cavity, and the oil inlet channel is formed between the oil inlet groove and the outer ring of the bearing and the sealing seat; an oil drain groove extending in the front-to-back direction is formed at the bottom of the bearing cavity, and the oil drain channel is formed between the oil drain groove and the outer ring of the bearing and the sealing seat; an oil inlet port connected to the oil inlet channel is vertically provided at the upper part of the connecting ring, and an oil drain port connected to the oil drain channel is provided at the lower part of the bearing pressure cover.

[0016] Furthermore, a piston ring is provided between the rear portion of the end cover and the outer periphery of the rotating shaft.

[0017] The beneficial effects of the present invention are embodied in:

[0018] The present application uses packing to hold the rotating shaft of the Roots vacuum pump tightly to limit the self-rotation caused by the pressure difference between the suction and exhaust ports of the Roots vacuum pump when it is not started. When the Roots vacuum pump is not started, the lubricating oil in the lubricating oil tank cannot be splashed and lubricated through the gear (non-driving end) or the oil-slinging plate (driving end), so the lubricating oil cannot be brought into the bearing cavity through the oil inlet channel to lubricate the packing. The packing without lubrication will produce a large friction resistance to the rotating shaft, which will automatically limit the self-rotation of the vacuum pump. If the front and rear pressure difference between the suction and exhaust ports of the Roots vacuum pump is very large, the power generated exceeds the friction force of the packing, and the vacuum pump will still be rotated. However, as long as the self-rotation speed of the vacuum pump is less than 4% of its maximum allowable speed, the frequency converter can be started smoothly without stalling failure.

[0019] As the speed of the pump increases, the lubricating oil in the lubricating oil tank is splashed and lubricated through the gear (non-driving end) or the oil slinger (driving end), and sufficient lubricating oil begins to enter the oil inlet channel, and then enters the packing through the oil inlet holes on the top of the sealing seat and the stuffing seat, giving the packing sufficient lubrication. The lubricating oil will penetrate into the contact surface between the rotating shaft and the packing through the internal gap of the packing, playing a lubricating role, thereby reducing the friction between the packing and the rotating shaft, so that there will be no influence of excessive load at high speed. After the lubricating oil fully lubricates the packing, it is discharged from the oil discharge holes at the bottom of the sealing seat and the stuffing seat, and finally flows back to the oil tank through the oil discharge channel.

[0020] Therefore, the present application can limit the rotation of the Roots vacuum pump caused by the pressure difference between the suction and exhaust ports when it is not started, thereby avoiding causing a stall failure of the inverter, and will not limit the rotation of the Roots vacuum pump at full speed to cause a high current. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0022] Figure 1 is a schematic cross-sectional structural diagram of an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the three-dimensional structure of a bearing seat according to an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the three-dimensional structure of the sealing seat according to an embodiment of the present invention;

[0025] Figure 4 is a cross-sectional view of a sealing seat according to an embodiment of the present invention;

[0026] Figure 5 4 is a cross-sectional view of a packing seat according to an embodiment of the present invention.

[0027] In the attached drawings, 100-end cover; 110-bearing seat mounting groove; 200-bearing seat; 210-bearing cavity; 220-oil inlet channel; 221-oil inlet groove; 230-oil discharge channel; 231-oil discharge groove; 240-connecting ring; 241-oil inlet; 250-second inner retaining ring; 251-avoidance groove; 300-rotating shaft; 310-first step surface; 320-second step surface; 330-third step surface; 4 00-bearing; 410-inner ring; 420-outer ring; 430-ball; 440-locking nut; 450-bearing cover; 451-oil drain port; 500-packing; 600-skeleton oil seal; 700-seal seat; 710-stuffing seat installation cavity; 720-skeleton oil seal installation cavity; 730-stuffing seat; 731-first inner retaining ring; 740-oil inlet hole; 750-oil drain hole; 800-piston ring. DETAILED DESCRIPTION

[0028] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0029] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0030] like Figure 1-Figure 4As shown, an embodiment of the present invention provides a bearing cavity sealing structure for limiting the self-rotation of a Roots vacuum pump, including an end cover 100, a bearing seat 200 and a rotating shaft 300, wherein the bearing seat 200 is fixed to the outside of the end cover 100, a bearing cavity 210 is provided inside the bearing seat 200, and the outer end of the rotating shaft 300 passes through the end cover 100 and is installed in the bearing cavity 210 through a bearing 400.

[0031] A sealing seat 700 is also installed in the bearing cavity 210, and a packing seat installation cavity 710 is provided in the sealing seat 700, and a packing seat 730 is installed in the packing seat installation cavity 710. A packing 500 is installed in the packing seat 730 and surrounds and hugs the outside of the rotating shaft 300. The packing 500 is preferably a metal-wound packing 500. An oil inlet channel 220 for introducing lubricating oil into the bearing cavity 210 is provided at the upper portion of the bearing seat 200, and an oil discharge channel 230 for discharging the lubricating oil in the bearing cavity 210 is provided at the lower portion of the bearing seat 200. An oil inlet through hole 740 communicating with the oil inlet channel 220 is provided at the top of the sealing seat 700 and the packing seat 710, and an oil discharge through hole 750 communicating with the oil discharge channel 230 is provided at the bottom of the sealing seat 700 and the packing seat 710.

[0032] The present application uses the packing 500 to hold the rotating shaft 300 of the Roots vacuum pump tightly to limit the self-rotation caused by the pressure difference between the suction and exhaust ports of the Roots vacuum pump when it is not started. When the Roots vacuum pump is not started, the lubricating oil in the lubricating oil tank cannot be splashed and lubricated by the gear (non-driving end) or the oil-slinging plate (driving end), so the lubricating oil cannot be brought into the bearing cavity 210 through the oil inlet channel 220 and lubricated by the packing 500. The packing 500 without lubrication will generate a large friction resistance to the rotating shaft 300, which will automatically limit the self-rotation of the vacuum pump. If the front and rear pressure difference between the suction and exhaust ports of the Roots vacuum pump is very large, the power generated by it exceeds the friction force of the packing 500, and the vacuum pump will still be rotated. However, as long as the self-rotation speed of the vacuum pump is less than 4% of its maximum allowable speed, the frequency converter can be started smoothly without a stall failure.

[0033] As the speed of the pump increases, the lubricating oil in the lubricating oil tank is splashed and lubricated through the gear (non-driving end) or the oil slinger (driving end), and sufficient lubricating oil begins to enter the oil inlet channel 220, and then enters the packing 500 through the oil inlet hole 740 at the top of the sealing seat 700 and the stuffing seat 730, giving the packing 500 sufficient lubrication. The lubricating oil will penetrate into the contact surface between the rotating shaft 300 and the packing 500 through the internal gap of the packing 500, and play a lubricating role, thereby reducing the friction between the packing 500 and the rotating shaft 300, so that there will be no influence of excessive load at high speed. After the lubricating oil fully lubricates the packing 500, it is discharged from the oil discharge hole 750 at the bottom of the sealing seat 700 and the stuffing seat 730, and finally flows back to the oil tank through the oil discharge channel 230.

[0034] Therefore, the present application can limit the rotation of the Roots vacuum pump caused by the pressure difference between the suction and exhaust ports when it is not started, thereby avoiding causing a stall failure of the inverter, and will not limit the rotation of the Roots vacuum pump at full speed to cause a high current.

[0035] At the same time, when the inverter needs to decelerate the existing vacuum pump, the friction force of the packing 500 can also play a strong restraining role.

[0036] It should be specially explained here that before the Roots vacuum pump is started, the lubricating oil is in a cold environment, the viscosity of the lubricating oil is relatively high, and the penetration of the packing 500 is relatively weak. After the Roots vacuum pump is running at high speed, the heat generated by the friction between the packing 500 and the shaft 300 is not only taken away by the lubricating oil, but also the temperature of the lubricating oil is increased, and its viscosity is reduced, so that it can better penetrate into the packing 500, increase the lubrication of the shaft 300 and the packing 500, and reduce the friction.

[0037] In the application of vacuum pumps, packing 500 is generally used in liquid ring pumps to play a sealing role. Therefore, packing 500 is used in the bearing cavity 210 to prevent self-rotation in the initial stage and also plays a good sealing role.

[0038] There are two main reasons why the lubricating oil is sucked into the pump chamber of a Roots vacuum pump: the first reason is that the pressure of the bearing chamber 210 is higher than the pressure of the pump chamber, thereby forming a power difference. When the lubricating oil droplets approach the end cover 100 near the pump chamber side, they are sucked into the pump chamber due to the pressure difference; the second reason (the main reason) is that at the driving end (oil-slinging plate) and the non-driving end (gear) after splash lubrication, these lubricating oils are accumulated in the bearing chamber 210 in large quantities through splashing or other means (because the bearing 400 needs lubrication, it is necessary to ensure that the lubricating oil has a channel to enter the bearing chamber 210) and cannot be discharged in time, then when the oil level of the lubricating oil in the bearing chamber 210 is higher than the gap between the bearing 400 and the end cover 100, the lubricating oil will be continuously sucked into the vacuum pump chamber. At this time, you will see that the lubricating oil in the lubricating oil tanks on both sides is getting less and less, until it is insufficient and splash lubrication occurs, which will inevitably cause oil shortage and insufficient lubrication of the bearing 400, heat and eventually lead to failure and shutdown.

[0039] Therefore, ensuring that the lubricating oil in the bearing cavity 210 is discharged in time after splash lubrication and ensuring that the lubricating oil lubrication passage is unobstructed are the main solutions to ensure that the lubricating oil will not be sucked into the pump cavity.

[0040] The present application forms an oil inlet channel 220 and an oil discharge channel 230 for lubricating oil by machining the upper and lower parts of the bearing seat 200 respectively. After the splashed lubricating oil enters from the oil inlet channel 220, it can fully lubricate the packing 500 and the bearing 400. The lubricating oil after lubrication is then discharged from the oil discharge channel 230 and returned to the lubricating oil tank. In this way, the lubricating oil will not accumulate in the bearing cavity 210. Similarly, it is ensured that after the machine is shut down, the lubricating oil in the packing 500 will gradually flow back to the oil tank through the oil discharge channel 230 and will not remain in the shaft and the packing 500, thereby restoring the friction between the packing 500 and the rotating shaft 300.

[0041] In order to further ensure the sealing effect and prevent the lubricating oil from being sucked into the pump chamber, a skeleton oil seal installation cavity 720 is further provided on the inner side of the packing seat installation cavity 710 in the sealing seat 700. A skeleton oil seal 600 surrounding the outside of the rotating shaft 300 is installed in the skeleton oil seal installation cavity 720. The skeleton oil seal 600 mainly utilizes the sealing property of the rubber meshing shaft to further prevent the lubricating oil in the tank from being sucked into the pump chamber.

[0042] In addition, a piston ring 800 is provided between the rear portion of the end cover 100 and the outer periphery of the rotating shaft 300. In this embodiment, a plurality of piston ring grooves are opened on the outer periphery of the rotating shaft 300 on the side close to the impeller. During installation, the piston ring 800 is installed in the piston ring groove and inserted into the end cover 100. At this time, the piston ring 800 is pressed in the piston ring groove and fits tightly with the end cover 100. During actual operation, the rotating shaft 300 rotates at a high speed, and the piston ring 800 rubs relative to the piston ring groove of the rotating shaft 300, thereby forming a sealing effect to prevent dust and particulate matter drawn into the pump chamber from entering the bearing chamber 210.

[0043] In a preferred embodiment, the diameter of the packing seat mounting cavity 710 is larger than the diameter of the skeleton oil seal mounting cavity 720, so that the skeleton oil seal 600 and the packing seat 730 can be respectively installed from the outer end of the packing seat mounting cavity 710 into the skeleton oil seal mounting cavity 720 and the packing seat mounting cavity 710, and the inner end of the packing seat 730 is provided with a first inner retaining ring 731 that abuts against the packing 500. A bearing seat mounting groove 110 is provided on the outside of the end cover 100, and the bearing seat 200 is inserted into the bearing seat mounting groove 110. A connecting ring 240 is provided on the outer end of the bearing seat 200, and the connecting ring 240 is fixed to the end cover 100 by bolts. A second inner stop ring 250 is provided in the bearing cavity 210 of the bearing seat 200, and the sealing seat 700 is pressed against the bottom of the bearing seat mounting groove 110 through the second inner stop ring 250. The packing seat 730 is pressed against the step formed between the packing seat mounting cavity 710 and the skeleton oil seal mounting cavity 720 through the second inner stop ring 250, and the packing 500 is pressed against the first inner stop ring 731 through the second inner stop ring 250.

[0044] When installing the bearing seat 200, it is necessary to first install the skeleton oil seal 600 and the stuffing seat 730 into the sealing seat 700 in sequence, and cut the packing 500 into 4 groups, each group is staggered and installed in the stuffing seat 730, and then install the sealing seat 700 and the stuffing seat 730 together in the bearing cavity 210 on the inner side of the second inner retaining ring 250, and then install the bearing seat 200 into the bearing seat mounting groove 110 of the end cover 100, and fix the connecting ring 240 on the bearing seat 200 to the end cover 100 by bolts. In the process of tightening the bolts, under the extrusion of the second inner retaining ring 250, the packing 500 inside the stuffing seat 730, which was originally loose, will be compressed and firmly embraced with the rotating shaft 300.

[0045] The outer circumference of the rotating shaft 300 is provided with a first step surface 310, a second step surface 320 and a third step surface 330 with increasing diameters from the outer end to the inner end, and the second inner retaining ring 250 and the sealing seat 700 are arranged outside the third step surface 330. The bearing 400 includes an inner ring 410 and an outer ring 420 arranged coaxially, and a ball 430 arranged between the inner ring 410 and the outer ring 420. The inner ring 410 is sleeved outside the second step surface 320, and the first step surface 310 is externally threaded with a locking nut 440 that presses the inner ring 410 against the step between the second step surface 320 and the third step surface 330. The outer ring 420 is adapted to the bearing cavity 210, and the outer end of the bearing seat 200 is also fixed with a bearing gland 450 that presses the outer ring 420 against the second inner retaining ring 250 by bolts.

[0046] After the bearing seat 200 is installed on the end cover 100 , the bearing 400 is installed into the bearing cavity 210 outside the second retaining ring, and finally the locking nut 440 and the bearing gland 450 are installed to lock the entire bearing 400 in the bearing cavity 210 .

[0047] In order to prevent the inner ring 410 of the bearing 400 from pressing against the second inner retaining ring 250 , an escape groove 251 is provided at the outer end of the second inner retaining ring 250 to separate the inner ring 410 of the bearing 400 from the second inner retaining ring 250 .

[0048] In this embodiment, an oil inlet groove 221 extending in the front-to-back direction is formed at the top of the bearing cavity 210, and an oil inlet channel 220 is formed between the oil inlet groove 221 and the outer ring 420 of the bearing 400 and the sealing seat 700. An oil drain groove 231 extending in the front-to-back direction is formed at the bottom of the bearing cavity 210, and an oil drain channel 230 is formed between the oil drain groove 231 and the outer ring 420 of the bearing 400 and the sealing seat 700. An oil inlet port 241 connected to the oil inlet channel 220 is vertically provided at the upper part of the connecting ring 240, and an oil drain port 451 connected to the oil drain channel 230 is provided at the lower part of the bearing cover 450.

[0049] When the oil-slinging plate or gear drives the lubricating oil to splash, the lubricating oil is brought to the oil inlet 241 and enters the oil inlet channel 220 through the oil inlet 241. After the lubricating oil enters the oil inlet channel 220, it can fully lubricate the packing 500 and the bearing 400. The first inner retaining ring 731 at the inner end of the stuffing seat 730 can effectively ensure that the oil path of the lubricating oil only lubricates the packing 500 and the bearing 400 without contacting the skeleton oil seal 600. The lubricating oil after lubrication is then collected in the oil drain channel 230, and finally discharged through the oil drain port 451 at the lower part of the bearing pressure cover 450 and returned to the lubricating oil tank.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump, comprising an end cover, a bearing seat and a rotating shaft, wherein the bearing seat is fixedly mounted on the outside of the end cover, a bearing cavity is arranged inside the bearing seat, and the outer end of the rotating shaft passes through the end cover and is mounted in the bearing cavity through a bearing, characterized in that: A sealing seat is also installed in the bearing cavity, a packing seat installation cavity is provided in the sealing seat, a packing seat is installed in the packing seat installation cavity, a packing surrounding and hugging the outside of the rotating shaft is installed in the packing seat, an oil inlet passage for introducing lubricating oil into the bearing cavity is provided at the upper part of the bearing seat, an oil discharge passage for discharging lubricating oil in the bearing cavity is provided at the lower part of the bearing seat, an oil inlet through hole communicating with the oil inlet passage is provided at the top of the sealing seat and the packing seat, and an oil discharge through hole communicating with the oil discharge passage is provided at the bottom of the sealing seat and the packing seat; When the Roots vacuum pump is not started, the lubricating oil in the lubricating oil tank cannot be splashed through the gears or oil slinger for lubrication, and thus cannot be brought into the bearing cavity through the oil inlet channel to lubricate the packing. The lack of lubrication in the packing creates a large friction resistance to the rotating shaft, thereby limiting the rotation of the vacuum pump.

2. The bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump according to claim 1, characterized in that: A skeleton oil seal installation cavity is also provided in the sealing seat on the inner side of the packing seat installation cavity, and a skeleton oil seal surrounding the outside of the rotating shaft is installed in the skeleton oil seal installation cavity.

3. The bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump according to claim 2 is characterized in that: The diameter of the packing seat installation cavity is larger than the diameter of the skeleton oil seal installation cavity, so that the skeleton oil seal and the packing seat can be respectively installed into the skeleton oil seal installation cavity and the packing seat installation cavity from the outer end of the packing seat installation cavity in sequence, and the inner end of the packing seat is provided with a first inner stop ring that abuts against the packing; A bearing seat mounting groove is provided on the outside of the end cover, and the bearing seat is inserted into the bearing seat mounting groove. A connecting ring is provided on the outer end of the bearing seat, and the connecting ring is fixed to the end cover by bolts. A second inner stop ring is provided in the bearing cavity of the bearing seat, and the sealing seat is pressed against the bottom of the bearing seat mounting groove through the second inner stop ring. The packing seat is pressed against the step formed between the packing seat mounting cavity and the skeleton oil seal mounting cavity through the second inner stop ring, and the packing is pressed against the first inner stop ring through the second inner stop ring.

4. The bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump according to claim 3 is characterized in that: The outer circumference of the rotating shaft is provided with a first step surface, a second step surface and a third step surface with diameters increasing successively from the outer end to the inner end, and the second inner retaining ring and the sealing seat are arranged outside the third step surface; The bearing includes an inner ring and an outer ring arranged coaxially, and a ball arranged between the inner ring and the outer ring. The inner ring is sleeved on the outside of the second step surface. The first step surface is externally threaded with a locking nut that presses the inner ring against the step between the second step surface and the third step surface. The outer ring is adapted to the bearing cavity. The outer end of the bearing seat is also fixed with a bearing cover by bolts that presses the outer ring against the second inner retaining ring.

5. The bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump according to claim 4 is characterized in that: An escape groove is provided at the outer end of the second inner retaining ring to separate the inner ring of the bearing from the second inner retaining ring.

6. The bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump according to claim 4, characterized in that: An oil inlet groove extending in the front-to-back direction is formed at the top of the bearing cavity, and the oil inlet channel is formed between the oil inlet groove and the outer ring of the bearing and the sealing seat; an oil drain groove extending in the front-to-back direction is formed at the bottom of the bearing cavity, and the oil drain channel is formed between the oil drain groove and the outer ring of the bearing and the sealing seat; an oil inlet port connected to the oil inlet channel is vertically provided at the upper part of the connecting ring, and an oil drain port connected to the oil drain channel is provided at the lower part of the bearing pressure cover.

7. The bearing cavity sealing structure for limiting the rotation of a Roots vacuum pump according to claim 1, characterized in that: A piston ring is arranged between the rear portion of the end cover and the outer periphery of the rotating shaft.

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