Analysis of adjusting the rotor clearance of screw compressor

The contact line of the twin-screw compressor is a space curve formed when the two rotor tooth faces are in contact with each other when the male and female rotors of the compressor are engaged.

In actual compressors, the theoretical contact line evolves into the actual gap band due to the inter-tooth gap. Since the points on the contact line are engaged at the moment on the female and male screw faces, the screw teeth are The interdental gap along the contact line on the surface is the smallest. The most critical component in a screw compressor is a pair of intermeshing screw rotors, the intersection of which is perpendicular to the rotor axis, referred to as a screw rotor profile. Since the rotor profile forms a tooth surface of the rotor by spiral motion, the rotor profile is also referred to as an end profile or a rotor profile. The female and male rotor profiles of the screw compressor are designed to meet the conjugate engagement law, ie the common normal line passing through the line contact point must pass through the node, regardless of the position.

In fact, the tooth surface of the screw compressor is mainly used for compressing gas, and a cavity formed by the grooves and the convex teeth of the two screws of the female and the yin are engaged with each other, and the female and male rotors are not in contact with each other. The power transmission is done by synchronizing gears. In addition to satisfying the conjugate condition and facilitating the machining, the screw rotor tooth shape must have good axial and lateral airtightness and a large volume and a large exhaust port. Therefore, the rotor profile of a screw compressor usually consists of a series of curves, such as points, straight lines, cycloids, arcs, ellipses and parabolas. The design of the screw compressor, the most important is the design of the rotor profile, rotor type. The line basically determines the performance of the screw compressor.

2 screw meshing gap adjustment method

The screw mounting clearance ratio of the screw compressor is controlled by the synchronizing gear. The main and driven gears of the synchronous gear are respectively the male rotor, and the female rotor has the same pitch circle; since the driving gear and the male rotor are not adjustable after installation, they can be regarded as an integral gear; Both the ring and the backlash ring are sleeved on the hub. When the hub and the female rotor are mounted and positioned, the two ring gears are still adjustable relative to the hub and the female rotor.

For its specific gear pair, when the center distance is constant, the gear pair meshing backlash is determined by the characteristics of the gear itself. For the same reason, for the screwing of the male and female rotors of a screw compressor, the total meshing clearance of the screw should also be a certain value in case of neglecting the slight influence of the sliding bearing clearance on the center distance. When the screw clearance is adjusted during the maintenance process, the female rotor is kept stationary, and the driven gear ring is finely adjusted. The essence is to change the circumferential installation angle between the driven gear ring of the synchronous gear and the female screw rotor to make the yin The initial phase angle of the male screw mesh changes slightly, and the redistribution of the chasing gap and the non-chasing gap on the screw rotor node is realized.

According to the theoretical analysis and the actual maintenance experience, to adjust the screw installation clearance ratio to the specified range, the adjustment method of the driven ring gear is as follows:

(1) Loosen the fastening bolts and positioning pins between the driven gear ring and the hub to make it flexible and movable.

(2) Check the total clearance of the tooth surface with a dial gauge or feeler gauge, and make the male and female rotors close contact by the disc drive, and accurately measure the total clearance of the female and male rotors.

(3) Calculate the value of the chasing surface gap #a with the desired gap ratio and the total gap, and then clamp the feeler that is equal or close to the value of the chasing surface gap #a by the cranking in the negative engaging surface of the male rotor. . When adjusting, use a copper rod to hit the screw on the synchronizing gear until the feeler gauge is pressed.

(4) The driven gear ring is turned to the position just engaged with the driving gear. Note that the gear backlash must be completely vacant on the side participating in the meshing teeth, and the fastening bolt between the driven gear ring and the hub must be tightened.

(5) Pull out the feeler gauge between the male and female rotors. The gap at this time is the engagement gap between the female and the tooth surface of the male rotor. However, for the sake of safety, it is necessary to check the teeth one by one with a feeler while checking the rotor. The meshing gap of each part.

The female and male rotors of the styrene screw compressor have a large total meshing clearance, so the adjustable range of the mounting clearance ratio is large. In general, the screw installation clearance ratio should be controlled at 08~12. In fact, when the compressor is running at high speed, due to the torsional deformation of the shaft and the wear of the gear tooth surface, the chasing clearance tends to shrink, and the non-chasing clearance tends to increase. Big. In order to ensure long-term reliable operation of the compressor, the clearance of the chasing surface is adjusted to a little larger during the inspection and assembly, and the non-chasing clearance is adjusted to be smaller, so that the ratio of the chasing clearance to the non-chasing clearance falls between 1.0 and 1.2. To be reasonable.

3 Conclusion

The adjustment of the tooth gap of the screw compressor is the most important step in the whole overhaul. It is directly related to whether the compressor can operate normally. It is a meticulous and difficult task, and sometimes it needs to be adjusted repeatedly to meet the requirements. The method given in this paper changes the traditional way of thinking, adopting reverse thinking, pre-determining the initial phase of the rotor, then adjusting the driven gear ring to tightly mesh with the active teeth and fixing with fastening bolts. Under normal circumstances, this method can directly obtain a satisfactory screw mounting clearance ratio, reduce the time for repeatedly measuring the gap and adjusting the driven ring gear, and effectively shorten the maintenance period. Moreover, the application of the above method in the screw installation process of the styrene compressor in 2009 has achieved twice the result with half the effort, which saves the assembly time and ensures the accuracy of the screw installation. At the same time, it has accumulated valuable practical experience for the future maintenance and installation technology. .

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