SPEED LIMITER ATTACHMENT
IMPLEMENT ELECTROHYDRAULIC SYSTEM
The "H" Series Medium Wheel Loader is equipped with a Proportional Priority, Pressure Compensated (3PC) implement electrohydraulic system. The 3PC electrohydraulic system will sense a demand for a flow change and the implement pump will upstroke or destroke in order to provide the demanded flow.
The following components make up the 3PC electrohydraulic system:
- Implement Electronic Control Module (ECM) - Lift and tilt position sensor
- Implement pump
- 3PC electrohydraulic control valve - Lift and tilt cylinders
- Ride control accumulator (optional) - Implement control levers
- Hydraulic tank (hydraulic tank is common to all the hydraulic systems) Hydraulic Tank
Implement Pump
Implement Control
Levers
Tilt Cylinder Lift Cylinder
Electrical Components
Hydraulic System Components
Implement ECM
Ride Control Accumulator
3PC Electrohydraulic Valve Lift Position
Sensor
Tilt Position Sensor
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Implement Electronic Control System
This diagram of the Implement Electronic Control System shows the components which provide input and output signals to the Implement ECM.
The Implement (ECM) receives input signals from the various sensors and switches on the machine, processes the input signals, makes decisions, and provides a corresponding signal voltage to the proportional solenoid valves. The Implement ECM stores information from the calibrations, the machine settings and the operational functions. The Implement ECM monitors diagnostic conditions and reports events to the Cat Monitoring System or to Cat Electronic Technician (ET). Also, the Implement ECM provides a means of calibrating the
electrohydraulic components for optimal operation.
The Implement ECM shares operational data with the other ECMs and the Cat Monitoring System through the Cat Data Link.
Kickout Set Switch Lift / Tilt
CAT Data Link Implement ECM
Input Components Output Components
Engine Start Switch
+ 24 Voltage Fine Modulation Switch
Auxiliary Function HE Solenoid Valve Auxiliary Function RE Solenoid Valve
Autodig Operator Trigger Indicator Autodig Record Mode Indicator Autodig Dig Mode Switch
Autodig Trigger Switch
Auxiliary Continuous Flow Switch
Location Code 4 (Ground) Location Code Enabled (Ground) Autodig Select Mode Switch
Autodig Kickout Set Switch Tilt Lever Sensor Lift Lever Sensor Auxiliary Lever Sensor Hydraulic Lockout Switch
Lift Linkage Position Sensor Tilt Linkage Position Sensor
Lift Head End Pressure Sensor
Lower Solenoid Valve Raise Solenoid Valve
IMPLEMENT ELECTRONIC CONTROL SYSTEM
Caterpillar Monitor System
Fuel Pressure Indicator Autodig Audible Indicator Dump Antidrift Solenoid Valve Lower Antidrift Solenoid Valve Dump Solenoid Valve Tilt Back Solenoid Valve Hydraulic Lockout Valve
Engine start switch: Input to the Implement ECM signaling the ECM to power ON.
Lift linkage position sensor: Sends a PWM signal to the Implement ECM communicating the position of the lift linkage in relation to the loader frame.
Tilt linkage position sensor: Sends a PWM signal to the Implement ECM communicating the position of the tilt linkage in relation to the lift linkage.
Lift lever position sensor: Sends a PWM signal to the Implement ECM communicating the angle of the lift lever position sensor away from the calibrated HOLD position.
Tilt lever position sensor: Sends a PWM signal to the Implement ECM communicating the angle of the tilt lever position sensor away from the calibrated HOLD position.
Auxiliary lever position sensor: Sends a PWM signal to the Implement ECM communicating the angle of the auxiliary function lever position sensor away from the calibrated HOLD
position.
Kickout set switch lift/tilt: Sends an input to the Implement ECM to recognize the desired raise/lower/tilt back kickout position.
Autodig trigger switch: Sends an input signal to the Implement ECM when the operator has pressed the switch to indicate that the loading cycle should begin.
Autodig select mode switch: Sends an input signal to the Implement ECM to signal if autodig should be off or in which mode it should operate (auto, operator trigger or record).
Autodig dig mode switch: Sends an input signal to the Implement ECM to recognize what type of operation is currently desired due to the type of material that is being handled.
Autodig kickout set switch: Sends an input signal to the Implement ECM to set the current position of the lift arms to be the position where autodig stops after a completed autodig cycle.
Lift head end pressure sensor: Measures the pressure of the head end of the lift cylinder to determine operation of autodig.
Fine modulation switch: Sends an input signal to the Implement ECM to reduce the amount of current to the raise solenoid valve.
Hydraulic lockout switch: Sends an input signal to the Implement ECM to not energize the pilot solenoid valve to protect from inadvertent movement of the lift arms.
Auxiliary continuous flow switch: Sends an input signal to the Implement ECM keep the auxiliary function output to the solenoid valve at the current that was being commanded at the time of the switch being depressed. This mode can be exited by depressing the switch again or moving the auxiliary lever.
+24 Volts: Unswitched power supplied to the Implement ECM from the battery.
Location code enable (grounded): The location code enable is a grounded input signal to the Implement ECM that enables the location code detection feature to become active. J1-32 pin on the Implement ECM connector is connected.
Location code 4 (grounded): The location code 4 is a grounded input signal that establishes that the ECM is dedicated to the Implement operation. J1-28 pin on the implement ECM connector is connected.
The output components which receive signals from the Implement ECM are:
Hydraulic lockout valve: This ON/OFF solenoid valve is an output from the Implement ECM. This valve opens the flow of pilot oil to the pilot valves.
Raise solenoid valve: This proportional solenoid valve is an output from the Implement ECM.
This solenoid valve sends a proportional amount of pilot oil to the raise end of the lift spool depending on the amount of current applied to the solenoid.
Lower solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the lower end of the lift spool depending on the amount of current applied to the solenoid.
Dump solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the dump end of the tilt spool depending on the amount of current applied to the solenoid.
Tilt back solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the tilt back end of the tilt spool depending on the amount of current applied to the solenoid.
Auxiliary HE solenoid valve: This proportional solenoid valve is an output from the
Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the head end of the auxiliary spool depending on the amount of current applied to the solenoid.
Auxiliary RE solenoid valve: This proportional solenoid valve is an output from the
Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the rod end of the auxiliary spool depending on the amount of current applied to the solenoid.
Lower antidrift solenoid valve: This ON/OFF solenoid valve is a current output from the Implement ECM. The solenoid valve drains oil from the antidrift valve allowing the poppet to unseat and lift cylinder head end oil to flow through the valve.
Implement ECM. The solenoid valve drains oil from the antidrift valve allowing the poppet to unseat and tilt cylinder head end oil to flow through the valve.
Autodig operator trigger mode indicator: This indicator is illuminated when the Implement ECM recognizes that autodig operator trigger mode is activated.
Autodig record mode indicator: This indicator is illuminated when the Implement ECM recognizes that autodig record mode is activated.
Autodig audible indicator: This audible indicator beeps when the Implement ECM
recognizes that a different autodig mode has been activated and to confirm a setting or to warn about failed autodig operations.
Low fuel pressure indicator: This indicator is illuminated when the fuel pressure is reported low from the Engine ECM over CAT datalink. The illumination of indicator is driven by the Implement ECM.
The Implement Electronic Control Module (ECM) is the central component in the transmission electronic control system. The ECM is located at the right side of the cab behind the seat. The rear panel must be removed for access to the ECM. The Implement ECM will be located behind the operator’s seat and have the connectors vertical to each other.
The ECM makes decisions based on switch-type and sensor input signals and memory
information. Input signals to the ECM come from: the operator's station, the machine, and the transmission.
The operator's station input components consist of: the lift/tilt kickout switches, the fine
modulation switch, the hydraulic lockout switch to energize the hydraulic lockout valve, and the autodig feature switches.
The machine input components are: the linkage position sensor, the lever position sensors, and the Caterpillar Monitoring System message center module.
The Implement ECM communicates with other electronic control modules, such as the Caterpillar Monitoring System, the Engine Electronic Control Module (ECM) and the Power Train Electronic Control Module (ECM), through the Cat Data Link.
The implement system uses the A4M1 Electronic Control Module (ECM). To enable the ECM for implement functions, contact (J1-28) is grounded and contact (J1-32) is grounded in order to enable the ECM.
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appropriate circuit which initiates an action. For example, the operator selects to set the lift kickout. The Implement ECM interprets the input signals from the switch, evaluates the current machine operating status, and de-energizes the appropriate solenoid valve when the preset duty cycle of the linkage position sensor is met.
The Implement ECM receives three different types of input signals:
1. Switch input: Provides the signal line to battery, to ground, or to open.
2. PWM input: Provides the signal line with a square wave of a specific frequency and a varying positive duty cycle.
3. Speed signal: Provides the signal line with either a repeating, fixed voltage level pattern signal or a sine wave of varying level and frequency.
The Implement ECM has three types of output drivers:
1. ON/OFF driver: Provides the output device with a signal level of +Battery voltage (ON) or less than one Volt (OFF).
2. PWM solenoid driver: Provides the output device with a square wave of fixed frequency and a varying positive duty cycle.
3. Controlled current output driver: The ECM will energize the solenoid with 1.25 amps for approximately one half second and then decrease the level to 0.8 amps for the
duration of the on time. The initial higher amperage gives the actuator rapid response and the decreased level is sufficient to hold the solenoid in the correct position. An added benefit is an increase in the life of the solenoid.
The Implement ECM controls the lift, tilt, and the auxiliary solenoid valves in the main control valve. The Implement ECM interprets signals from the implement control lever to send current to the appropriate solenoid valves in order to perform one or more of the following options:
Lift, Lower, Tilt Back, and Dump. Also, the Implement ECM triggers the Autodig operator trigger indicator, the Autodig record mode indicator, and the fuel pressure indicator.
The Implement ECM communicates through the CAT Data Link. The CAT Data Link allows high speed proprietary serial communications over a twisted pair of wires. The CAT Data Link allows different systems on the machine to communicate with each other and also with service tools such as Caterpillar Electronic Technician (ET).
The Implement ECM has built-in diagnostic capabilities. As the Implement ECM detects fault conditions in the power train system, it logs the faults in memory and displays them on the Caterpillar Monitoring System.
NOTE: The side panel on the right side of the cab is transparent for viewing purposes.
The upper illustration shows the lift linkage position sensor (1). The lift linkage position sensor is located on the right side of the loader frame. The lower illustration shows the location of the tilt linkage position sensor (2). The lift linkage position sensor is located on the right side of the lift linkage. The tilt linkage position sensor shaft is attached to the tilt lever pin (3) reflecting the rotation of the lift lever compared to the lift linkage.
NOTE: In order to calibrate the lift or tilt linkage position sensors, refer to the Service Manual module "966H and 972H Wheel Loaders Electrohydraulic System,
Troubleshooting, Testing and Adjusting - Position Sensor for the Lift and Tilt Linkage (Electronic Technician) - Calibrate or Position Sensor for the Lift and Tilt Linkage (Operator Monitor) - Calibrate" (Form RENR 8858).
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Implement Control Levers
The tilt control lever (1), the lift control lever (2), and the auxiliary control lever (3) send a Pulse Width Modulated (PWM) signal with the position of the control lever sensor to the Implement ECM. In the HOLD position, the sensor in each lever sends a 50% duty cycle. The movement of each lever in the forward or reverse direction will increase the duty cycle to 90%
or decrease to 10% depending on the direction that the lever is moved. The "H" Series
machines are a self-contained single axis lever equipped with a single sensor and no mechanical or electrical detents. The sensor frequency is 500 Hz.
The self contained single axis lever is equipped with "Soft Detents." With "Soft Detents" the control levers are no longer held in place mechanically. The detents are software controlled within the Implement ECM. When the control lever is moved in either direction into an area of movement with a slight resistance and the lever is released within 1 second, the actuator will continue to move until the software controlled kickout is reached.
During troubleshooting of a control lever or joystick, always move the control lever both fast and slow through lever movement. The duty cycle for the control lever can be viewed through Cat ET.
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The two switches located to the right of the operator’s seat control functions of the implement hydraulic system.
The hydraulic lockout switch (1) sends an input to the Implement ECM to shift the hydraulic lockout solenoid valve to the OPEN position.
The fine modulation switch (2) is an input to the Implement ECM. The fine modulation switch allows the operator to request a lower ramp up current relative to the standard lever curves during control lever movement. In the final one third of the control lever travel, the commanded current is the same as the standard control lever curve.
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Fine Modulation
Fine Modulation allows the operator to reduce the lever sensitivity for better control of the linkage during small movements. The Fine Modulation feature in the "H" Series Wheel Loaders is no longer adjustable as in the "G" Series Wheel Loader.
In the illustration, the vertical coordinates (lift command and tilt command) in each graph show the percentage from minimum to the maximum modulation current directed to the modulating valve on the main control valve.
The fine modulation feature can be turned ON and OFF using the fine modulation switch located on the right side of the armrest.
-100% -50% 10 50% 100%
-100%
100%
0
-50% -10 10 50% 100%
-100%
100%
0
Percentage of Lift Lever Position
TILT LINKAGE MODULATION
Fine Modulation Normal Modulation
Fine Modulation Normal Modulation
Percentage of Lift Lever Position
-10
-100%
Lift CommandTilt Command
The kickout set switch (1) is an input to the Implement ECM.
The kickout set switch is a momentary three-position rocker switch located on the operator panel. The kickout set switch is used to set the kickout positions for the raise and lower
kickout. When the switch is pushed, the Implement ECM records the current position of the lift arm. The Implement ECM uses the recorded position for the raise kickout position or the lower kickout position. If the upper position of the kickout set switch is depressed and the lift arm is above midway, the kickout will be set for raising the lift arm. If the upper position of the kickout set switch is depressed and the lift arm is midway below halfway, the lower kickout will be set. If the lower position of the kickout set switch is depressed, the rotation of the tilt back will be set.
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