2. Operation Explanation

2.Operation Explanation

This valve has P, T and A - D ports. The A - D ports have the same functions and operations, so here we will explain only the A port.

Pressure reduction function <Lever operation 0 - 1.8° range> (Diagram 2) •The pressurized oil fed from the P port is cut off from the A port and T port by the spool (10). •The A port is conducted to the T port by the internal spool (10) circuits and the oil drops to the tank via the T port, so the A port pressure becomes the tank pressure.

Diagram 2

<Lever operation 1.8 - 11 禔 Ñ (Diagram 3) •When the lever (cam (7)) is operated, the spool (10) is pushed downward together with the pusher (11), piston (9), retainer (12), and spring (14). •When the operation angle becomes 1.8°, the P port and the A port are conducted by the (I) section and the A port and T port connection is closed by the (II) section, so the pressure at the A port rises. At this time, force [F] (the A port pressure [P1] × spool surface area a [A]) works on the spool moving it up. •When P1 rises and F becomes larger than the spring (14) load [FS], the spool (10) moves up, the (I) section closes, the (II) section opens, and the A port pressure drops. Through the repetition of this process, the spool (10) is balanced at the position in Diagram 3 and the A port pressure is held at the uniform pressure that just balances the spring (14) load. [FS] = [F] = [P1] × [A] •When the lever is further operated, the spring (14) is deflected by pusher (11), piston (9) and retainer (12), and the spring (14) load [FS] increases. At this time, the spool (10) is balanced at the position in Diagram 3 and pressure is generated at the A port by the spring (14) load.

Diagram 3

<Lever operation 11 - 12.4° range> (Diagram 4) •When the lever operation angle becomes 11°, the spool (10) head section and the piston (9) touch [(III) section], and the spool (10) control is stopped. •Therefore, the (I) section stays open. The (II) section stays closed and the A port pressure becomes the same pressure as the P port pressure. •When the lever is released, the spring (13) force returns the parts to their neutral position.

Damper function •When the lever is pressed in, the damper chamber (IV) hydraulic oil goes through the orifice (V) and is discharged to the T port.

As this time, a damper effect is obtained due to the path resistance of the (V) section. (Diagram 5) •When the lever is returned, the spring (9) is returned by the spring (13) force and the damper chamber (IV) goes into a vacuum state, so the steel ball (30) is lifted up and hydraulic oil is pulled in from the T port, so the spool returns smoothly to the neutral position. (Diagram 6)

Diagram 4

Diagram 5 Diagram 6