1. Field of the Invention
The present invention relates to an air system configured to supply pressure air from a compressed air source to an air-used device through a switching valve and particularly to a dehumidification type air system provided with means for dehumidifying air.
2. Description of the Related Art
In the air system configured to drive the air-used device such as an air cylinder by the pressure air from the compressed air source, a switching valve is connected between the compressed air source and the air-used device, and the air from the compressed air source is supplied to the air-used device through this switching valve.
In this type of air systems, when the switching valve is switched and the air is outputted toward the air-used device, the air adiabatically expands in piping or the air-used device, which lowers its temperature and condenses moisture in the air into a mist. The mist gradually grows by repetition of air feed/discharge and results in harmful effects such as condensation to generate rust in the air-used device or interference with smooth operation of the air-used device due to loss of a lubricant.
Thus, the applicant proposes a dehumidifier device (dehumidification type condensation prevention device) using a polymer permeation membrane so as to dehumidify air outputted from the switching valve by the dehumidifier device and to supply the air in the dry air state to the air cylinder by connecting the dehumidifier device between the switching valve and the air cylinder.
The dehumidifier device is configured to accommodate two sets of hollow fiber membrane module sets side by side formed by arranging a large number of hollow fiber membranes side by side and to incorporate a plurality of three-way valves for controlling a flow-in air flowing into the air cylinder and a flow of flow-out air flowing out of the air cylinder, and the flow-in air outputted from the switching valve is dehumidified while traveling through each hollow fiber membrane in the hollow fiber membrane module set and supplied to the air cylinder as dry air, while the flow-out air flowing out of the cylinder is brought into contact with moisture that permeates through the surface of the hollow fiber membrane by dehumidification of the flow-in air and humidified while communicating through a flow passage formed on the outer side of the hollow fiber membrane and is discharged to the outside through the switching valve.
However, since the dehumidifier device accommodates the hollow fiber membranes inside its housing, the moisture having permeated through the surface of the hollow fiber membrane through dehumidification of the air needs to be forcedly emitted to the outside of the housing by purge air and thus, a flow passage for the purge air should be formed inside the housing or a three-way valve should be provided for controlling the flow of the purge air, by which structure is made complicated to some extent and large-sized as a whole, and that is not suitable for use in connection with a small-sized air cylinder.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2001-300268