938G Series II Wheel Loader and IT38G Series II Integrated Toolcarrier Hydraulic System Ride Control System Caterpillar


Ride Control System
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938G Series II Wheel Loader and IT38G Series II <BR>Integrated Toolcarrier Hydraulic System [RENR6077]
HYDRAULIC SYSTEM
LINES GP-RIDE CONTROL
938G Series II Wheel Loader and IT38G Series II Integrated Toolcarrier Hydraulic System Ride Control Accumulator - Test and Charge
938G Series II Wheel Loader and IT38G Series II Integrated Toolcarrier Hydraulic System Ride Control System
1.1. OFF Position
2.1. MANUAL Position
3.1. AUTO Position



Illustration 1g00947744

Hydraulic Schematic of the Ride Control System

HOLD Position

(1) Ride control accumulator

(2) Ride control system

(3) Solenoid valve 1

(4) Check valves

(5) Lift cylinders

(6) Implement pump

(7) Selector and pressure control valve

(8) Stem (lift)

(9) Check valve

(10) Orifice

(11) Diverter valve

(12) Spring

(13) Solenoid valve 2

(14) Hydraulic oil tank

(15) Pilot shutoff valve

(16) Pilot valve

(17) Lever (lift)

The optional ride control system provides a means for dampening the bucket forces which produce a pitching motion as the machine travels over rough terrain. The precharge of nitrogen gas in ride control accumulator (1) provides the cushion.




Illustration 2g00934300

Location of the Ride Control Switch

(18) Ride control switch.

The ride control system is initiated by ride control switch (18). Ride control switch (18) is a three-position switch that is located in the control panel on the right side of the cab.

The ride control system is made up of the following components: ride control accumulator (1), solenoid valve (3), lift cylinders (5), diverter valve (11) and solenoid valve (13).




Illustration 3g00937254

Location of the Ride Control Valve

(9) Check valve. (10) Orifice. (11) Diverter valve.

Diverter valve (11) is installed inside the loader frame on the left side of the machine. Diverter valve (11) is installed in order to balance the pressure between the head end of lift cylinders (5) and ride control accumulator (1). When the ride control system is off, this eliminates the lift arms from dropping when the ride control switch is placed in the ON position. Also, this eliminates the lift arms from dropping when the ride control switch is placed in the AUTO position and the machine is traveling at least 9.6 km/h (6 mph).




Illustration 4g00948477

Diverter Valve (Sectional View)

(10) Orifice. (12) Spring.

The oil pressure from ride control accumulator (1) travels through orifice (10). Then, the oil pressure acts against the bottom of diverter valve (11). The oil pressure from the head end of lift cylinders (5) acts against the top of diverter valve (11). When the pressure is equal, diverter valve (11) is in balance.




Illustration 5g00948514

Diverter Valve (Sectional View)

(10) Orifice. (12) Spring.

If the oil pressure in ride control accumulator (1) is greater than the oil pressure in the head end of lift cylinders (5), diverter valve (11) shifts upward. Oil in ride control accumulator (1) flows to hydraulic oil tank (14) until the pressure in ride control accumulator (1) is equal to the pressure of the head end of lift cylinders (5). At this time, the pressure spool will shift to the CENTER position and the flow of oil through the diverter valve will be blocked.




Illustration 6g00948545

Diverter Valve (Sectional View)

(10) Orifice. (12) Spring.

If the oil pressure in the head end of lift cylinders (5) is greater than the oil pressure in the ride control accumulator (1), diverter valve (11) shifts downward. The oil pressure in the head end of lift cylinders (5) keeps diverter valve (11) shifted downward. If an implement control lever is actuated and the implement pump causes high implement pump pressure, the oil from the implement pump will force open check valve (9). Then, the high pressure oil will flow through diverter valve (11) into ride control accumulator (1). Check valve (9) prevents oil flow from ride control accumulator (1) to implement pump (6) .

This allows oil from implement pump (6) to flow through check valve (9) and into ride control accumulator (1). The implement pump will increase the pressure in ride control accumulator (1). Implement pump (6) can charge ride control accumulator (1) to a pressure that is equal to the main relief valve pressure setting.

Note: An implement control lever must be activated in order to cause the pump output pressure that is necessary to charge the accumulator.

OFF Position

When the ride control switch is in the OFF position, the ride control switch is midway between the ON and AUTO positions. Solenoid valve 1 (3) and solenoid valve (13) are in the BLOCKED position. In this position, the flow of oil between the head end of lift cylinders (5) and the ride control accumulator (1) is blocked. The flow of oil between the rod end of the lift cylinders (5) and the tank line is also blocked.




Illustration 7g00937373

Electrical Diagram of the Ride Control System in the OFF Position

(3) Solenoid valve 1. (13) Solenoid valve 2. (18) Ride control switch. (19) Power train ECM. (20) Transmission output speed sensor (leading). (21) Transmission output speed sensor (lagging).

When the ride control switch is in the OFF position, current travels from contact 21 (G766-GN) on the power train ECM to contact 3 on the ride control switch. At the same time, current travels from contact 22 (G767-WH) on the power train ECM to contact 4 on the ride control switch. Contact 2 and contact 5 on the ride control switch allows current to travel through wire 962-OR to contacts 15, 16 on the power train ECM.

MANUAL Position

When the ride control switch is moved to the MANUAL position, current flows to solenoid valve 1 (3) and solenoid valve 2 (13). Solenoid valve 1 (3) and solenoid valve 2 (13) are energized. The solenoid valves will be in the OPEN position. Oil will flow between the head end of lift cylinders (5) and ride control accumulator (1). There will be a cushion as the machine travels over rough terrain. The precharge of nitrogen gas in ride control accumulator (1) supplies the cushion. The oil in the rod end of lift cylinders (5) can flow to hydraulic oil tank (14).




Illustration 8g00937563

Electrical Diagram of the Ride Control System in the MANUAL Position

(3) Solenoid valve 1. (13) Solenoid valve 2. (18) Ride control switch. (19) Power train ECM. (20) Transmission output speed sensor (leading). (21) Transmission output speed sensor (lagging).

When the ride control switch is in the MANUAL position, current will travel from contact 22 (G766-GN) on the power train ECM to contact 4 on the ride control switch. At the same time, the current will be interrupted between contact 21 (G767-WH) on the power train ECM and contact 3 on the ride control switch. Contact 2 and contact 5 are connected in series through wire 962-OR to contacts 15, 16 on the power train ECM.

AUTO Position

When the ride control switch is placed in the Auto mode, the operation of the ride control system is initiated by power train ECM (19) .

In the Auto Mode, the machine must be traveling at a ground speed of at least 9.6 km/h (6 mph). Power train ECM (19) receives an input from the transmission output speed sensors. Power train ECM (19) uses the inputs from the transmission output speed sensors (20, 21) in order to calculate the ground speed. When power train ECM (19) registers a ground speed of at least 9.6 km/h (6 mph), an output signal is sent to solenoid valve 1 (3) and solenoid valve 2 (13). Solenoid valve 1 (3) and solenoid valve 2 (13) will be energized. The solenoid valves will stay energized, if the machine is traveling at a ground speed of at least 9.6 km/h (6 mph). When the ride control system is in Auto mode, the components of the ride control system work in the same manner as if the machine is in the Manual mode and traveling at a ground speed of at least 9.6 km/h (6 mph). When the ground speed goes below 9.6 km/h (6 mph), the ride control system will shut off. The ground speed that activates the ride control system in the AUTO position can be changed through AVSpare Electronic Technician.




Illustration 9g00937578

Electrical Diagram of the Ride Control System in the AUTO Position

(3) Solenoid valve 1. (13) Solenoid valve 2. (18) Ride control switch. (19) Power train ECM. (20) Transmission output speed sensor (leading). (21) Transmission output speed sensor (lagging).

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