Hydraulic device for stepless transmission

A hydraulic device for a stepless transmission, the hydraulic device comprising:

• an engine-driven main pump and an engine-driven sub-pump;
• a main passage for connecting the main pump to a speed-changing hydraulic pressure circuit and a lubricating-hydraulic pressure circuit;
• a sub-passage for connecting the sub-pump to the lubricating-hydraulic pressure circuit;
• a regulator that opens when the hydraulic pressure of hydraulic oil supplied to the speed-changing hydraulic pressure circuit through the main passages increases, controls the amount of hydraulic oil supplied to the lubricating-hydraulic pressure circuit through the main passage and the sub-passage, and adjusts the hydraulic pressure of hydraulic oil supplied to the speed-changing hydraulic pressure circuit;
• a bypass passage for connecting, to each other, a section of the main passage located upstream of a location where the speed-changing hydraulic pressure circuit is connected and a section of the sub-passage located upstream of the regulator;
• a check valve that is provided in the bypass passage and permits only flow of hydraulic oil in a direction from the sub-passage toward the main passage, wherein the check valve closes when discharge performance of the main pump increases, and supply paths for hydraulic oil discharged from the sub-pump are automatically switched in accordance with the discharge performance of the main pump;
• and
• a switch-over valve provided at a section of the sub-passage located downstream of a location where the bypass passage is connected and located upstream of the regulator, and the switch-over valve is configured to be capable of being switched between a first state, where a section of the sub-passage located upstream of the switch-over valve is brought into communication with a section of the main passage located upstream of a location where the speed-changing hydraulic pressure circuit is connected, and a second state, where the section of the sub-passage located upstream of the switch-over valve is brought into communication with a section of the sub-passage located downstream of the switch-over valve,
• wherein the switch-over valve is switched to the first state before the supply paths for hydraulic oil discharged from the sub-pump are automatically switched in accordance with the discharge performance of the main pump.