COMPONENT OPERATION ／

HST Motor

・ＨＤ Controller（1st gear drive ）（UCHIDA ／ Serial No. 4501 ～）

In this case, the hydraulic force due to the pilot pressure [Px] is larger than the force due to the springs (3) and (4). Thus the pilot piston (1) is located at the position shown in the figure to transfer the pressure of the primary side of the control bush [A] to the secondary side of the control bush [B]. In addition, the cut-off valve (12) moves to the position as shown in the figure to transfer the pressure of the secondary side of the control bush [B] to the larger diameter side of the control piston [D], because the hydraulic force of the primary side of the control bush [A] which is applied to the cut-off valve (12) is smaller than the force due to the spring (13). As a result, three forces, “hydraulic force due to the difference in section area between large [D] and small [C] diameters of the control piston (when driving with the 1st gear, the pressure at the primary side of the control bush is approx. 50 % of that for automatic drive)", “Hydraulic force due to the pilot pressure [Px]” , and the sng force due to the spring (4), are applied to the control piston (5), and it is moved to a certain location where these forces are balanced.

※ In the 1st gear drive, the pressure in the primary side of the control bush [A] is approximately 50 % of that in the case of automatic drive.