308C CR Excavator Hydraulic System – Travel Motor



Illustration 1 g00757110

Travel Motor

(1) Counterbalance valve

(2) Drain port

(3) Port

(4) Pilot port (automatic travel speed change)

(5) Port

(6) Cover

(7) Piston

(8) Passage

(9) Timing plate

(10) Passage

(11) Piston

(12) Spring

(13) Barrel

(14) Retainer plate

(15) Shoe

(16) Swashplate

(17) Shaft

(18) Hub

(19) Passage

(20) Spring

(22) Piston

(23) Separator plate

(24) Friction plate

(25) Needle roller

(26) Guide

(27) Piston

(28) Spring

(29) Check valve

(30) Check valve

(31) Plug

(32) Spring

(33) Retainer

(34) Spool

(35) Travel motor

(36) Displacement change valve

(37) Shuttle valve

The travel motor can be divided into the following four groups:

  • The rotary group consists of the following components: barrel (13), shaft (17), piston (11), shoe (15), retainer plate (14), spring (12), needle roller (25) and guide (26) .

  • The parking brake group consists of the following components: piston (22), orifice (21), friction plates (24), separator plates (23) and spring (20) .

  • The counterbalance valve consists of the following components: spool (34), springs (32), retainer (33), plug (31), check valve (29) and check valve (30) .

  • The displacement change valve consists of the following components: spring (28), piston (27), displacement change valve (36) and shuttle valve (37) .

The flow of the pump oil depends on the direction of travel. Pump oil flows into the travel motor through port (3) or port (5). Pump oil is forced out of the travel motor through port (5) or (3) .

The case drain oil that has leaked returns to the tank through the drain port (2) of cover (6) .

Supply oil from the left pump flows into left travel motor (35) through port (3) during forward travel. The oil from port (3) flows through check valve (29) and passage (19) in cover (6). The oil then flows through passage (8) of timing plate (9). The oil then flows through passage (10) of the barrel and the oil forces pistons (11) to move to the right.




Illustration 2 g00757035

Motor passages (side view from cover)

(A) Bottom center

(B) Inlet side (high pressure)

(C) Outlet side (low pressure)

(D) Top center

(8) Passage (timing plate)

(10) Passage (barrel)

(39) Passage (timing plate)

Shoe (15) is coupled to the piston. Shoe (15) and the piston slide on the surface of swashplate (16) from the top center to the bottom center. Shoe (15) and the piston rotate with barrel (13). The pistons force oil out of the outlet side of the motor passage. The oil flows through passage (10) and passage (39) of timing plate (9). The oil then flows through port (5). The barrel turns counterclockwise. Shaft (17) is splined to barrel (13). The shaft and barrel rotate counterclockwise for forward travel.

In reverse travel, port (5) functions as an oil return port. Port (3) functions as a supply port. The left travel motor rotates clockwise.

When the right travel motor is supplied right pump oil through port (5), the right travel motor turns clockwise for forward travel. Right pump oil through port (3) turns the motor counterclockwise for reverse travel.