PROBLEM TO BE SOLVED: To simply constitute a structure for performing the descending control of a single-acting cylinder without adding an exclusive device such as a descending pressure compensation valve when ascending and descending a working device by using the single-acting cylinder.SOLUTION: An end part large-diameter part 46 for closing a through-oil passage 35 extending from a cylinder port C up to a tank port T in an ascending position and a neutral position, and opening the through-oil passage 35 extending from the cylinder port C up to the tank port T at a descending position is formed at one end part of a spool 41 of a direction control valve in a slide movement direction, and an end part chamber 30a into which the end part large-diameter part 46 can intrude is formed at a control valve unit, and end part through-oil parts 46a, 46b for permitting the flow-in of a working fluid from the through-oil passage 35, which extends from the cylinder port C up to the tank port T, up to the end part chamber 30a are formed at points over the through-oil passage 35 and the end part chamber 30a from the cylinder port C up to the tank port T out of the end part large-diameter part 46.SELECTED DRAWING: Figure 6COPYRIGHT: (C)2018,JPO&INPIT【課題】単動シリンダを用いて作業装置の駆動昇降を行うにあたり、単動シリンダの下げ制御を、下げ用の圧力補償弁などの専用装置の付加を要さずに構造簡単に構成する。【解決手段】方向制御弁におけるスプール４１のスライド移動方向の一端部に、上昇位置と中立位置ではシリンダポートＣからタンクポートＴへの通油路３５を閉じ、下降位置でシリンダポートＣからタンクポートＴへの通油路３５を開く端部大径部４６が形成され、制御弁ユニットには、端部大径部４６が入り込み可能な端部室３０ａが形成され、端部大径部４６のうち、シリンダポートＣからタンクポートＴへの通油路３５と端部室３０ａとにわたる箇所に、シリンダポートＣからタンクポートＴへの通油路３５から端部室３０ａへの作動油の流入を許す端部通油部４６ａ，４６ｂが形成されている。【選択図】図６
