The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 08, 2002
Filed:
Sep. 28, 2000
Hiroshi Ohta, Shimizu, JP;
Masakazu Aoki, Shimizu, JP;
Hiroyuki Matsuda, Yaizu, JP;
Hitoshi Nishimura, Shimizu, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
In a capacity control method for an oil-free screw compressor, when an air consumption is larger than a set amount, a rotation frequency of a motor using an inverter to drive the compressor is set to be variable. When the air consumption is a set air amount or less, the inverter is controlled in such a manner that the rotation frequency of the motor is kept at a constant value. In this state, when an operation gas pressure of the compressor reaches an upper-limit value, an air release valve is opened to discharge the operation gas to the atmosphere. Additionally, the rotation frequency of the motor is lowered to a lower-limit value. Re-compression in the compressor can be prevented, and a compressor drive torque is lowered.