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| Illustration 1 | g00981016 |
Retarder Air System and Retarder Hydraulic System (1) Retarder hydraulic control valve (2) Torque Converter (3) Line from transmission hydraulic controls (4) Hand air valve for retarder (5) Line to transmission oil tank (6) Transmission oil cooler (7) Engine transfer gear housing and retarder housing (8) Air inlet from hand air valve (9) Opening to transmission lubrication (10) Opening from torque converter (11) Chamber from oil cooler (12) Opening to retarder (13) Chamber to transmission oil cooler (14) Opening from retarder | |
In addition to the service brakes, the hydraulic retarder provides assistance in order to slow the machine. The retarder and engine transfer gears are located in the same housing (7). Retarder hydraulic control valve (1) is fastened to the retarder housing and engine transfer gear housing (7). Pressure air from hand air valve (4) activates retarder hydraulic control valve (1).
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| Illustration 2 | g00703855 |
Operator Compartment (4) Hand air valve for retarder | |
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| Illustration 3 | g00981118 |
Retarder hydraulic control valve (1) (8) Air inlet from hand air valve (9) Opening to transmission lubrication (10) Opening from torque converter (11) Chamber from oil cooler (12) Opening to retarder (13) Chamber to transmission oil cooler (14) Opening from retarder (15) Valve body (16) Plunger (17) Cover (18) Cover (19) Diaphragm (20) Valve spool (21) Spring (22) Stop (23) Spring (24) Slug | |
When hand air valve (4) is moved toward the operator, pressure air flows from valve (4) to retarder hydraulic control valve (1). The pressure air moves valve spool (20) to the right. The movement of valve spool (20) provides a path between opening (12) and opening (10). Oil flows through opening (12) to the retarder.
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| Illustration 4 | g00981120 |
Hydraulic Retarder (7) Retarder and engine transfer gear housing (25) Stator (26) Rotor (27) Gear (28) Gear | |
As the retarder fills, the turning rotor (26) causes an increase in the oil pressure inside the retarder. Inlet oil and outlet oil for the retarder will flow through orifices into valve spool (20). The average of the inlet oil pressure and the outlet pressure in the spring bore plus the force of the spring will work against the pressure air on the left end of valve spool (20). When the force of the pressure oil plus the spring force becomes larger than the force of the pressure air, valve spool (20) moves to the left. This movement causes a restriction to the flow of oil from opening (10) to opening (12). The pressure of the oil in the retarder decreases.
A decrease in the speed of rotor (26) causes a decrease in oil pressure inside the retarder. This drop in oil pressure will cause a decrease in the oil pressure in the spring bore of valve spool (20). When the oil pressure decreases in the spring bore of valve spool (20), the air pressure on the left end of valve spool (20) will move the spool to the right. More oil will flow from opening (10) to opening (12). The oil will then flow into the retarder and the pressure will increase inside the retarder.
An increase in the speed of rotor (26) will cause an increase in the oil pressure inside the retarder. This increase in the oil pressure will cause valve spool (20) to move to the left.
Valve spool (20) is constantly moving in order to make adjustments to the retarder inlet pressure for compensation of the changing rotor speeds. This constant movement of the valve spool is necessary in order to maintain the amount of braking force in the retarder at the level that is set by hand air valve (8) .
The operation of the retarder is similar to the operation of a torque converter. Rotor (26) is connected to gear (27). Stator (25) is fastened to the retarder and the engine transfer gear housing (7). Stator (25) does not turn. The rotor turns inside the retarder housing. The rotor throws oil against the stationary vanes of the stator. When the rotor throws the oil against the stationary stator, a resistance to the flow of oil is created.
The resistance to the flow of oil causes a resistance to the drive shaft. The resistance will slow down the machine. When the pressure increases inside the retarder, more resistance is applied to the drive shaft.
After the oil flows through the retarder, the oil flows back to retarder hydraulic control valve (1). The oil will flow into opening (14) to chamber (13). From chamber (13), the oil flows to transmission oil cooler (6) in order to be cooled. From the transmission oil cooler, the oil flows to retarder hydraulic control valve (1). The oil then flows through chamber (11) to opening (9). The oil then flows from opening (9) to the transmission for lubrication.
When the retarder is not active, the oil from the torque converter will divide. When the oil divides, the oil will flow into retarder hydraulic control valve (1). Some of the oil opens plunger (16) and flows around spool (20) to the retarder. This oil is for the lubrication of the inside components of the retarder. After the oil flows through the retarder, the oil will flow back to retarder hydraulic control valve (1). The oil flows through opening (14) around the right end of valve spool (20). The oil flows from the right end of valve spool (20) to an opening in cover (17). The oil then flows to the transmission oil tank. The remainder of the oil flows from opening (10) to chamber (13). The oil then flows from chamber (13) to transmission oil cooler (6) in order to cool the oil. From the transmission oil cooler, the oil flows through a return line back to retarder hydraulic control valve (1). The oil flows through chamber (11) to opening (9). The oil then flows from opening (9) to the transmission for lubrication.
When hand air valve (4) is moved away from the operator, pressure air to opening (8) is blocked. With no air pressure on the left end of valve spool (20), the pressure oil in the spring bore of spring (23) and the force of spring (23) will move the valve spool to the left against cover (18). The movement of valve spool (20) closes inlet opening (10) to opening (12). Inlet oil to the retarder is blocked. Rotor (26) pushes the oil out of the retarder to retarder hydraulic control valve (1). The oil flows through opening (14) around valve spool (20) to an opening in cover (17). The oil then flows through an oil line to the transmission hydraulic tank.
The position of hand air valve (4) control the amount of pressure air to retarder hydraulic control valve (1). The flow of pressure air will control the pressure of oil inside the retarder. An increase in pressure air to retarder hydraulic control valve (1) will cause a higher pressure of the oil inside the retarder. The higher oil pressure will increase the braking force of the retarder.