Design Improvement of ZJ-400 Roots Vacuum Pump

Analysis of the causes of the phenomenon Rotor biting 1) Insufficient gap in the rotor fit, or large misalignment in the shape of the rotor, resulting in uneven clearance between the two rotors. 2) Large amount of external dust enters, dirt accumulates, causing the lumen to swell. 3) The cavity is not assembled during assembly. Washing, plane scraping gear off 1) Design assembly press mounting stroke is too small, resulting in a low amount of interference 2) The gear cone on the rotor is not well matched, the fitting surface is less than 80% 3) Vibration is too large , make it loose 4) tooth surface roughness, precision can not meet the requirements of the pattern, produce a periodic impact at high speed, high working temperature (near 100 ° c) 1) using the involute line is different from the original machine, The interference between the top of the tooth and the bottom of the tooth is severer than that of the original machine, resulting in greater pressure increase, which is the source of heat. 2) The rotor is unbalanced, causing the bearing temperature to rise. 3) The bearing lubrication condition is poor and the vibration is great. 1) The bearing accuracy is not enough. ) Inadequate assembly, resulting in insufficient deformation air volume 1) Large inaccuracy in rotor involute process 2) Large gaps and increased gas return flow rate 1 Problems in Roots vacuum pumps Analysis of Nissan suction tank trucks Duplication of powders in steel pipelines When As a vehicle for transporting powdered lime and sand coke, a certain steel company is used as a common car, which makes the Roots vacuum pump in a state of constant load for a long time, and the Roots vacuum pump that attracts the tanker is in the pipeline. Table 1 Roots vacuum pump problem analysis The strainer strainer and the powder bag filter work under full sealing conditions, so the suction pressure it bears is far greater than that under normal working conditions. This is not considered when designing the original machine, and it is also the main cause of failure of the pump in field use. Secondly, there are problems such as the shrinkage and loosening of the rotor blank and the slightly poor fitting surface of the gear and rotor.

After field investigation and analysis, the main problems are shown in Table 1.

2 Improvement measures 2.1 Improvement of the rotor profile The original rotor profile and coordinate dimensions are shown in Table 2 and Table A in the figure refers to the common reference axis at both ends of the rotor.

The improved rotor profile and coordinate dimensions are shown in Table 3. The improved rotor profile is smoother and wider than the original rotor profile. According to the thermodynamic point of view, the improved profile line heat does not accumulate easily and the heat source is not easily formed. smooth. The improvement items are shown in Table 3.

Table 2 Original Involute Rotor Theoretical Line Coordinates Size Hao Yinpan sin In / (° Cartesian Coordinates Involute Extremity Open Angle 8) 2.2 Roots pump line calculation 2 pitch d 6mm, tool angle a Table 4 Improvements Before and after the relevant parameters of the improvement project improvement before the improvement of the base circle diameter dbmm maximum tooth thickness Smax/mm pitch circle engagement angle a/(°) tooth root arc R tooth top arc ruler 2/md top width Smm correction shift distance mmm 2.2 .1 Correction shift distance >1mm. Correction factor: 2.2.2 Indexing spur tooth thickness S 1) Arc tooth thickness: S=xm 2) Arc tooth thickness half-width 3) Indexing sprocket thickness:: - 2.2.3 pitch circle The tooth thickness S 2.2.4 is calculated at a radius of 100mm and the tooth thickness S1 (W§=94.278mm2.2.5 The length of the common normal of a single tooth is equal to the tooth thickness of the base circle 2.3. This improves the balance accuracy. The unbalance allowed for the original design rotor is 29.4X10-4Nm. In order to reduce the vibration during operation and the temperature rise of the rotor, the precision of the inspection dynamic balance is improved, and the unbalance is allowed to be within 12.74X10-4Nm. To this end, a high-precision balancing machine is added after the process test and implementation. , Vibration and working temperature are reduced.

2.4 to solve the gear does not fall off measures 2. 4.1 to change the original cone taper 130 to 150 in the process to ensure that the rotor cone surface and gear cone grinding after grinding and processing, so that the joint surface reached 85%. After the process test, the strength of the gear and rotor is improved. Static fit Taper connection size is: shaft diameter d 2.4.2 set transmission power is 60kW (QT702), and the index of each parameter is indicated by 1 (the same below). Containment parts: gears, bore diameter 62mm. The material is steel (42CMo). The index of each parameter is denoted by 2 (the same below). Elastic Modulus E1=(1.43~1.57)X105MPa Take E1 2.4.5 Minimum Actual Interference Amount Middle Hole and Axis Roughness Ra0.8m Corresponding to Rz1 =RZ2=3.2 "m Reinforced Mating Strength Decrease First-order Roughness Take 2.4.6 Minimum press stroke 2.4.7 Maximum calculated interference amount Select fit tolerance: Hole ¢ 38+9 Axis Y38=: 2.4.8 Maximum actual interference 2.4.9 Maximum press stroke 2.4.10 Maximum calculation The stress intensity at the time of interference is V2 7=289.41MPa QT702 according to the rotor material 2) Gear hole: a2 = 463.54MPa: Assembled with temperature difference method/=0.14 If oil pressure method/=42CM steel according to gear material, 2= 931.0 (MPa 上二2.4.4 The minimum calculated interference (effective interference) are allowed values.

2.4.12 Surface Ultimate Pressure Strength Without Plastic Deformation Rotor Shaft:: T1 = §2 Gear Hole: Milk =§2 2.4.13 Differential Temperature Assembly 3 Improved Design Results Analysis The minimum interference amount calculated based on 60 kW power is 12.26 um ( Theory) The minimum actual amount of interference is 27.3mils m, the press stroke is 1.37mm, the maximum interference is 92Mm (theoretical), the maximum actual interference is 107b 1, and the maximum press stroke is 4.6mm. When the maximum amount of interference, its tensile strength, compressive strength are lower than the yield strength, so the above calculations meet the requirements. The total map can be pressed to install the journey to 4 +0 +5 requirements.

This calculation uses hot pressure (the original use of hydraulic pressure), and increases the amount of interference nearly doubled, so the modified taper 130 is 150 more reliable bond strength.

The gear processing rolling and shaving processes are rolling and grinding processes, which reduce the radial runout, improve the tooth surface quality and precision, and reduce the periodic impact.

In order to reduce the operating temperature in addition to the above-mentioned profile line can reduce the temperature, improve the bearing accuracy, change the ordinary bearing to a higher precision bearing, improve the high temperature performance of bearing grease, using Nissan high-temperature grease instead of domestic high-speed grease, improve the dynamic balance Accuracy and the like also improve the operating temperature. The degree of highness has also improved slightly, and the air volume has also increased. Practice has proved that the actual use effect is basically consistent with the above theoretical analysis.

2) The working atmosphere of the Roots vacuum pump is to work under severe conditions such as high speed, high temperature, high load, and long-time continuous operation. In order to further improve durability and reliability, it is recommended to redesign or reselect the entire pump. In addition, better ways to improve the cleanliness of the working medium should also be sought, such as the use of a more reliable strainer, strict regulation of filter time, and maintenance of the pump cavity to improve the use of Roots vacuum pumps. life.

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