Hydraulic driving device for working machine

A hydraulic driving device for a working machine comprising:

• an engine;
• a variable displacement hydraulic pump driven by being transmitted with power of the engine;
• a single rod double acting cylinder including a rod chamber formed on a rod side of a piston and a bottom chamber formed on a bottom side of a cylinder tube, and driven by being selectively supplied with oil discharged from the variable displacement hydraulic pump to the rod chamber and the bottom chamber;
• a spool valve capable of switching to a first actuating position leading the discharged oil to the rod chamber and leading hydraulic fluid inside the bottom chamber to a hydraulic fluid tank, a second actuating position leading the discharged oil to the bottom chamber and leading hydraulic fluid inside the rod chamber to the hydraulic fluid tank, and a neutral position leading the discharged oil to the hydraulic fluid tank without leading it to the single rod double acting cylinder;
• an exhaust emission control device catching particulate matter in exhaust gas generated by the engine by a filter;
• a clogging detection section detecting clogging of the filter;
• a variable throttle disposed downstream of the spool valve and capable of throttling a flow of oil discharged from the hydraulic pump which passes through the spool valve and is discharged to the hydraulic fluid tank;
• and
• a discharge pressure control section controlling the variable throttle,
• the discharge pressure control section controlling the variable throttle to raise discharge pressure of the variable displacement hydraulic pump so that a load of the engine increases to a degree to which temperature of exhaust gas reaches temperature required for burning particulate matter when a valve position of the spool valve is held at the neutral position and the clogging detection section detects clogging of the filter,
• wherein a prevention section is provided to prevent the flow of oil directed from the rod chamber of the single rod double acting cylinder toward the spool valve when the variable throttle is controlled by the discharge pressure control section so that the load of the engine increases to the degree to which the temperature of the exhaust gas reaches the temperature required for burning the particulate matter.