TH220B, TH330B and TH340B Telehandlers Hydraulic System General Information Caterpillar


General Information
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1.1. Main Control Valve Group (Implement)
2.2. Electronic Pilot Valve Group (Implement)
3.1. Machine ECM
4.2. Inputs to the Machine ECM
5.2. Outputs from the Machine ECM
6.2. Interlocks
7.3. Interlock for the Machine Security System
8.1. Electronic Joystick
9.1. Operator Switches
10.1. Piston Pump (Implement and Steering)
11.1. Hydraulic Oil Tank
12.1. Hydraulic Oil Filter
13.1. System Operation
14.1. Load Independent Flow Division (LIFD)
15.2. Condition One
16.2. Condition Two

The hydraulic system includes the following main components:

  • Main Control Valve Group (Implement)

  • Machine ECM

  • Electronic joystick

  • Operator Switches

  • Piston Pump (Implement and Steering)

  • Hydraulic oil tank

  • Hydraulic oil filter

Main Control Valve Group (Implement)




Illustration 1g01009691

(1) Control Valve (Auxiliary)

(2) Control Valve (Coupler Tilt)

(3) Control Valve (BOOM EXTEND/RETRACT)

(4) Boom Control Valve (RAISE/LOWER)

(5) Outlet Manifold

(6) Inlet Manifold

(7) Electronic Pilot Valve

(8) Pilot Shutoff Solenoid

(9) Pilot Valve ECM 1

(10) Pilot Valve ECM 2

The main control valve (implement) contains an outlet manifold (5), an inlet manifold (6) and an Electronic Pilot Valve Group (implement) (7). The inlet manifold contains the following items, the Valve As (Steering priority), the Relief Valve (Load sensing oil), and the Flow Control Valve Group (Dump valve for the load sensing oil). The outlet manifold contains the Relief Valve (Pressure reducing valve) and the Solenoid Valve Group (shutoff for Pilot oil) (8). The Main Control Valve Group (Implement) also includes hydraulic control valve sections for the following functions:

  • Auxiliary circuits (1)

  • Coupler Tilt (2)

  • Boom EXTEND/RETRACT (3)

  • Boom RAISE/LOWER (4)

Electronic Pilot Valve Group (Implement)




Illustration 2g01009705

(7) Electronic Pilot Valve (Implement)

(9) Pilot Valve ECM 2

(10) Pilot Valve ECM 1

Electronic Pilot Valve Group (Implement) (7) contains two Control Manifold Group (Pilot ECMs) and eight proportional pilot solenoids. The electronic pilot valve (implement) uses the eight proportional pilot solenoids in order to control 4 functions. Two functions are controlled by each ECM. Each function requires 2 proportional solenoids.

  • Control Manifold Group (Pilot ECM1) (10) controls the boom RAISE/LOWER and the coupler tilt FORWARD and the coupler tilt BACKWARD. Pilot ECM1 is located on the Electronic Pilot Valve Group (Implement).

  • Control Manifold Group (Pilot ECM2) (9) controls the auxiliary functions and the boom EXTEND/RETRACT. Pilot ECM2 is located on the Electronic Pilot Valve Group (Implement).

The electronic pilot valve electronically controls the amount of pilot pressure that is sent to the control valve sections in order to obtain movement of the functions. The electronic pilot valve is controlled by the machine ECM. The machine ECM controls the pilot pressure by sending a signal to the Pilot ECM. The Pilot ECM sends a signal to the proportional pilot solenoid for that function.

The Pilot ECM is powered by 10 VDC that is supplied by the machine ECM. The Pilot ECM supplies 12 VDC from the battery to the pilot solenoids in order to operate the pilot solenoids. If the 10 VDC is interrupted, the Pilot ECM cannot communicate with the machine ECM and a diagnostic code will be generated. If the current of the 12 VDC that is delivered to the pilot solenoid by the Pilot ECM is not correct, a diagnostic code will be generated.

The Electronic Pilot Valve Group (Implement) is calibrated in ET in order to ensure the proper operation of the control valves.

Machine ECM




Illustration 3g01026709

The machine ECM (24) makes decisions based on the operator inputs, the machine conditions and the parameters that are programmed into the machine ECM in order to provide proper control of the hydraulic system.

The machine ECM communicates to the other components on the machine via the AVS data link (31), the CAN data link (32) and a CAN/ADDRESS data link (30) that is dedicated for the electronic control modules that are on the Electronic Pilot Valve Group (Implement).

CAN/ADDRESS data link (30) is used in order to communicate with the following components:

  • The electronic control modules that are on the Electronic Pilot Valve Group (Implement)

AVS data link (31) is used in order to communicate with the following components:

  • Machine ECM (24)

  • The Diagnostic Connector

  • Engine ECM (34) (if equipped)

  • Product Link ECM (35) (if equipped)

  • Machine Security System ECM (36) (if equipped)

CAN data link (32) is used in order to communicate with the following components:

  • Machine ECM (24)

  • Engine ECM (34) (if equipped)

  • Instrument Cluster (33)

The machine ECM stores the diagnostic codes and the event codes that are generated from the hydraulic system.

Inputs to the Machine ECM

Inputs to the machine ECM include the following components:

  • The joystick (11)

  • The operator switches (15), (17), (20), and (23)

  • The switches for machine condition (26) and (27)

  • Engine and transmission speed sensors (28) and (29)

  • Engine ECM (34) (if equipped)

  • Machine Security System ECM (36) (if equipped)

  • Product Link ECM (35) (if equipped)

Outputs from the Machine ECM

Outputs from the machine ECM include the following components:

  • Pilot ECM 1 (9)

  • Pilot ECM 2 (10)

  • Instrument cluster (33)

  • Relays for quick coupler (21), diverter valve (18) for the auxiliary functions (if equipped) and trailer circuits (13) (if equipped)

  • Engine ECM (34) (if equipped)

  • Machine Security System ECM (36) (if equipped)

  • Product Link ECM (35) (if equipped)

  • Pilot shutoff solenoid (25)

Interlocks

The machine ECM monitors the switches of the Machine condition in order to control the hydraulic system correctly. Switches for machine condition would include the following components:

  • Switch for Critical angle (26)

  • Parking brake switch (27)

  • Engine speed sensors (28)

  • Transmission speed sensors (29)

The machine ECM also receives information regarding the machine condition from other electronic control modules that are equipped on the machine.

If the machine is in a condition that could create a dangerous situation, the machine ECM will limit the movement of the hydraulic implements.

Interlock for the Machine Security System

When the interlock for the machine security system is active, the following functions may be disabled:

  • Boom RAISE/LOWER

  • Boom EXTEND/RETRACT

  • Trailer circuits

  • Transmission

Electronic Joystick




Illustration 4g01009772

(11) Joystick

(37) Thumb Slider

(38) Auxiliary Buttons

(39) Trigger Switch

The joystick (11) is located on the right side of the operator seat. The joystick contains one thumb slider switch (37), two auxiliary buttons (38) and one trigger switch (39) .

The lateral movement of the joystick and the longitudinal movement of the joystick is monitored by two sensors that are mounted in the base of the joystick. These sensors send signals to the machine ECM (24) in order to operate the selected functions. The signals that are sent to the machine ECM are proportional to the distance of the joystick movement.

Thumb slider switch (37) also sends a proportional signal to the machine ECM for the function that is assigned to the thumb switch.

The two auxiliary buttons (38) control the auxiliary functions. The trigger switch (39) is used in order to select the auxiliary circuit, if more than one auxiliary circuit is installed.

The joystick is calibrated in ET in order to ensure the proper input from the joystick to the machine ECM.

The joystick has two modes of operation. Table 1 shows the configurations and the functions that are controlled by the joystick. The configuration of the joystick is selected in ET.

Table 1
Configuration of the Joystick    
    Construction     Bucket    
Joystick forward and backward     Boom RAISE/LOWER     Boom RAISE/LOWER    
Joystick left and right     Boom EXTEND/RETRACT     Coupler Tilt FORWARD and Tilt BACKWARD    
Thumb slider switch     Coupler Tilt FORWARD and Tilt BACKWARD     Boom EXTEND/RETRACT    

Operator Switches

The following switches are located in the cab. These switches provide direct input to the machine ECM in order to control some of the functions of the hydraulic system:

  • Quick coupler switch (17)

  • Continuous flow switch (20)

  • Differential lock switch (23)

The switch for trailer circuits (15) is also located in the cab but the switch for the trailer circuits does not provide direct input to the machine ECM. The control valve (16) for the trailer circuits contains two solenoids. The switch controls the two solenoids directly. The hydraulic system for the trailer circuits is enabled by the machine ECM through the relay for the interlock of the trailer circuits (12) .

Piston Pump (Implement and Steering)

The hydraulic pump is capable of producing a maximum flow of 106 L/min (28 US gpm). The hydraulic pump is a variable displacement axial piston pump. Also, the pump has flow and pressure compensation.

The hydraulic pump supplies pressurized oil for the braking system, the steering system and the implement system.

Pump output only takes place when an implement demands flow. When the demand is low, the pump destrokes and the pump output is reduced. This conserves power that can be used on other systems and increases fuel efficiency.

Hydraulic Oil Tank

The hydraulic oil tank supplies oil for two hydraulic circuits that operate independently.

  • The hydraulic system

  • The transmission system

The hydraulic system contains the implement system, the braking system, the system for the trailer circuits and the steering system.

The transmission system includes the hydraulic oil cooler, the torque converter, and the hydraulic oil filter.

Hydraulic Oil Filter

The filter for the hydraulic system is located in the transmission section. Oil from the hydraulic oil tank passes through the hydraulic oil filter before entering the transmission. The oil is then returned to the hydraulic oil tank.

System Operation




Illustration 5g01009423

Hydraulic pump (42) draws oil from the hydraulic oil tank (41). The pump is a variable displacement piston pump with permanent drive. The output of the pump is controlled by the highest load sensing oil pressure that is present in the hydraulic system.

Pump supply oil flows into the inlet manifold of the Main Control Valve Group (implement). The pump supply oil flows to the steering priority valve and the pressure reducing valve. The pressure reducing valve supplies oil to the pilot system and the braking system.

The steering priority valve gives flow priority to the steering system over the rest of the hydraulic system. When the demands of the steering system have been met, excess oil is then diverted by the priority valve to the Main Control Valve Group (implement) (7). The oil flows into the control valve (16) for the trailer circuits (if equipped).

When the operator selects a function that is controlled by ECM (9) or by ECM (10), a signal is sent to the machine ECM (24) by the joystick. The signal is in the form of a pulse width modulation (PWM). The machine ECM makes decisions based on operator input, machine conditions and the programmed parameters in the machine ECM. The machine ECM then sends a signal to the proper Pilot ECM. The ECM for the pilot valve sends a proportional signal to the pilot solenoid valve of that function. When the solenoid opens, oil moves past the open spool in order to operate the function. Oil is returned to the tank through the control valve.

A load sensing oil relief valve is located in the load sensing oil line. This load sensing oil relief valve limits the pressure of the load sensing oil to the hydraulic pump in order to limit the maximum system pressure.

Load Independent Flow Division (LIFD)

The control valve (implement) on these machines utilizes Load Independent Flow Division (LIFD). The (LIFD) system operates in one of two modes. Oil flow that is demanded from the attached implement determines the mode of operation for the (LIFD) system. The (LIFD) system is similar to the proportional priority pressure compensated system (PPPC). The (PPPC) system is available on other AVSpare products.

Condition One

The flow that is demanded by the Main Control Valve Group (implement) is less than the maximum output of the pump.

In this condition, the flow demand for each implement control valve will be met.

Condition Two

The flow that is demanded by the Main Control Valve Group (implement) is more than the maximum output of the pump.

In this condition, the pressure compensator in each individual valve will restrict the flow proportionally to the flow that is commanded by each valve. This will bring the flow demand in line with the pump output.

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