| 摘要 |
PURPOSE:To reduce the size of a hydraulic motor by exerting the brake force of a mechanical brake device on a hydraulic motor when a direction switching valve is returned to a neutral position and utilizing the mechanical brake device as a dynamic brake in a short time only during the stop of a construction machine. CONSTITUTION:A crawler vehicle is formed such that a hydraulic motor 3 with a mechanical brake device 4 is located in pressure oil feed and discharge circuits 3a and 3b connected to a direction switching valve 5 through a counter balance valve 1. An oil pressure chamber 4b of the mechanical brake device 4 is connected to a tank 9 when the counter balance is located in a neutral position. In this case, when the direction switching valve 5 is returned to a neutron position 51a, the counter balance valve 1 is returned to a neutral position in delay by a time decided from the relation between the press force of a spring 1j, the volume of a pilot chamber 1h, and the opening area of a throttle 1f1. During the return of the counter balance valve, pressure oil in a pressure chamber 4b is exerted as a brake action on a hydraulic motor 3 since pressure oil in a feed discharge passage 5b produces a tank pressure and simultaneously approximately a tank pressure. |
