Two-stage screw compressor

Abstract

A two-stage screw compressor of the invention includes a low pressure stage casing provided with a low pressure stage compression mechanism, a discharge casing provided on a discharge side of the low pressure stage casing, a high pressure stage casing provided with a high pressure stage compression mechanism, and intermediate stage casings for connecting the discharge casing and the high pressure stage casing, and accommodating an electric motor. In such a two-stage screw compressor, a cavity is formed on a discharge casing side in the slide valve so as to enlarge the capacity of a discharge space formed in the discharge casing. Thereby, internal resonance occurring in the discharge casing is prevented.

Description

technical field [0001] The present invention relates to a two-stage screw compressor for use in screw refrigerators and the like. Background technique [0002] The noise spectrum generated by the screw compressor is known as follows: the product of the number of teeth of the convex rotor and the rotation frequency is the fundamental frequency, and the fundamental frequency and its high harmonic components become obvious peaks. As a method of reducing this noise, there are measures such as attaching a sound-absorbing material to the casing, making the casing double-structured to improve sound insulation performance, or adding ribs to the casing to increase the rigidity of the casing. In a single-stage single-screw compressor, as disclosed in Patent Document 1, in order to reduce noise, a resonance space is provided inside the slide valve, and the resonance space communicates with the compression space to reduce noise. [0003] Patent Document 1: Japanese Patent Laid-Open No....

AI Technical Summary

Problems solved by technology

However, in the case of attaching a sound-absorbing material to the casing in the above-mentioned method, it is necessary to cover the entire casting casing with the sound-absorbing material, which is often difficult for a screw compressor having a complicated casting shape.

In addition, there are problems such as making the shell double-structured or adding ribs, which complicates the shape of the casting and increases the weight of the casting

[0005] In addition, any of the prior arts described above, including a low-pressure stage side casing having a low-pressure stage compression mechanism part, a discharge casing provided on the discharge side of the low-pressure stage side casing, a high-pressure stage side casing having a high-pressure stage compression mechanism part, and connecting In the two-stage screw compressor in which the discharge casing and the high-pressure stage side casing house the middle stage casing of the electric motor, the increase in noise due to internal resonance in the discharge casing is not considered.

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