 | |
| Illustration 1 | g00693157 |
(1) Propel control lever (2) Rotary selector (automatic speed control) | |
Modulation of the oil flow from the propel pump to the propel motors is controlled by propel control lever (1) and rotary selector (2). Charge oil is used for the hydraulic control functions.
 | |
| Illustration 2 | g00688650 |
(1) Propel control lever (2) Rotary selector (automatic speed control) (3) Propel control block (4) Forward control valve (5) Orifice (6) Check valve (7) Check valve (8) Orifice (9) Automatic speed control block (10) Line (11) Line (12) Line (13) Line (14) Reverse control valve | |
Oil enters automatic speed control block (9) through line (11) from the brake and shift valve. Oil flows through the automatic speed control block into propel control block (3). When propel control lever (1) is in the neutral position, control oil is blocked at forward control valve (4) and at reverse control valve (14). Movement of the propel control lever will allow charge oil to flow through the forward control valve or through the reverse control valve.
The forward and reverse control valves reduce the inlet pressure in line (11). The reduction is proportional to the movement of the propel control lever. Minimum outlet pressure from the control valves is 0 kPa (0 psi). The maximum pressure is 1900 kPa (275 psi).
The outlet oil from the forward and reverse control valves passes through the speed control orifices (5) and (8). Each speed control orifice has one fixed orifice and one adjustable orifice. The adjustable orifices are used in order to balance the pressure output between the forward and the reverse circuits. When the orifices are adjusted properly the forward and reverse speeds are equal.
Oil flows from the automatic speed control block to the servo that is mounted on the propel pump. If the machine is not equipped with the optional automatic speed control, the oil flows directly from the control block to the servo that is mounted on the propel pump.
Note: The automatic speed control is an option.
Oil enters the automatic speed control block through line (11). When the propel control lever is moved, the oil flows through the corresponding forward control valve (4) or through reverse control valve (14). The oil flows to check valve (6) or (7). The pressure side of outlet line (12) or (13) flows through the corresponding check valve. The oil is directed across rotary selector (2) .
Rotary selector (2) in the automatic speed control block controls the pressure of the output oil to the servo on the pump. When the rotary selector is turned clockwise, the oil pressure of the control system will be at a maximum of 1900 kPa (275 psi). When the rotary selector is turned counterclockwise, the oil pressure of the control system is at a minimum of 500 kPa (72 psi). Relief oil from the rotary selector returns to the propel pump case through line (10) .
Output lines (12) and (13) are connected to the servo that is mounted on the propel pump. The oil in these lines controls the piston in the servo. A minimum oil pressure in output lines (12) and (13) produces a minimum inclination of the pump's swashplate. This produces a low pump delivery rate that results in a low travel speed. A higher oil pressure in output lines (12) and (13) will increase the angle of the swashplate. The increased angle of the swashplate increases the pump delivery rate that results in a higher travel speed.