| 摘要 |
PURPOSE:To prevent the temperature rise of an operating oil and eliminate an ill effect due to cavitation by providing an opening/closing valve decreasing the opening in response to the temperature rise of the operating oil on a supplementary passage and changing the negative pressure in a cylinder in response to the temperature of the operating oil. CONSTITUTION:When the temperature of an operating oil is increased to a fixed value or higher, the bimetal 49 of an opening/closing valve 50 provided on a pipe 45 supplementing the deficit of the operating oil in an operating oil chamber 8 from a tank 2 during the decompression stroke of a piston 4 is curved to decrease the opening of the valve 50 as shown by a chain line, thereby the supplementary quantity of the operating oil during the descent stroke of the piston 4 is limited, the negative pressure in a cylinder 3 is remarkably increased, the air solved in the operating oil is separated and the deficit of the operating oil is supplemented, the quantity of the operating oil passing through a relief valve 40 during the ascent stroke of the piston 4 is made exremely little, and the temperature rise of the operating oil is suppressed. In addition, the opening of the opening/closing valve 50 is gradually changed in response to the temperature change of the operating oil, thus an ill effect due to cavitation can be eliminated to the utmost. |
