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Operacin de SistemasD8R Series II Track-Type Tractor Power Train
General Information
References
Reference: Specifications, RENR3674, "D8R Series II Track-Type Tractor
Power Train"
Reference: Testing and Adjusting, RENR3676, "D8R Series II Track-Type
Tractor Power Train"
Reference: Disassembly and Assembly, RENR3677, "D8R Series II Track-Type
Tractor Power Train"
Note: If the information in the above service modules does not match the
information in this service module, then compare the printing date on each
service module. Use the information that is printed in the service module with
the latest date.
Primary Power Train Components
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Power Train Components
(1) Final drive
(2) Steering differential and brake on the left side of the machine
(3) Engine
(4) Torque divider
(5) Tracks
(6) Main drive shaft
(7) Planetary gears and brake on the right side of the machine
(8 and 11) Axles
(9) Planetary transmission (Power shift)
(10) Bevel and transfer gear
Transfer of Mechanical Power
Engine (3) is the source of the mechanical power. Power flows from engine (3)
to tracks (5) through the power train: torque divider (4), main drive shaft (6),
power shift transmission (9), bevel and transfer gears (10), inner axles (8),
steering differential and brake (2), planetary gears and brake (7), outer axles
(11) and final drives (1).
Engine (3) transfers power from the engine flywheel to torque divider (4).
Torque divider (4) transfers power through the planetary gears and through the
torque converter turbine to drive shaft (6). Torque divider (4) includes a
planetary gear set and a torque converter turbine. The planetary gears are a
mechanical connection and the torque converter turbine is a hydraulic
connection.
Main drive shaft (6) transfers power to planetary transmission (9). Planetary
transmission (9) has three gears in the FORWARD position and three gears in
the REVERSE position.
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The speed clutches and the direction clutches are electronically controlled. The
clutches engage in order to transfer power. The power output from planetary
transmission (9) turns bevel and transfer gears (10).
Bevel and transfer gears (10) turn inner axle shaft (8). Inner axle shaft (8)transfers power to the steering differential and brake (2). Inner axle shaft (8)
also transfers power to the planetary gears and brake (7).
The steering differential is used to steer the machine. The brakes are used to
stop the machine. The steering differential and brake (2) works with the
planetary gears and brake (7) in order to send power through the two outer axle
shafts (11) to final drives (1).
Final drives (1) use two planetary gear sets for double speed reduction. The
planetary gears increase the torque in each stage. The sprockets on the final
drives transfer mechanical power to tracks (5) that move the machine.
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Power Train Hydraulic System
Schematic of power train hydraulic system
(1) Priority valve
(2) Wire harness for the electronic control module
(3) Torque converter inlet relief valve
(4) Oil filter for brakes and for transmission controls
(5) Modulating valves and the main relief valve (transmission)
(6) Brake control valve
(7D) Steering differential and brake on the left side of the machine
(7E) Planetary gears and brake on the right side of the machine
(8) Passage for the lubrication of the transmission and the bevel gear
(9) Oil cooler
(10) Torque converter outlet relief valve
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(11) Torque converter
(12) Power train oil pump
(13) Pump drive
(14) Passages to the steering differential, planetary gears and brake lubrication
(15) Oil filter for the torque converter
(16) Check valve
(A) Transmission and controls section
(B) Torque converter and lubrication section
(C) Transmission and torque converter scavenge section
The power train hydraulic system uses pump (12). The pump consists of three
sections.
Oil pump (12) is mounted on the implement hydraulic pump. The shafts of the
two pumps are connected by splines. The pump is driven from the engine by
gears in the flywheel housing. The bevel gear case is the sump for the power
train hydraulic system.
Transmission and Controls Section
Section (A) of pump (12) draws oil from the bevel gear case. This pump section
supplies the high pressure circuit. The oil flows through oil filter (4). Next, the oil
flows to the modulating valves, main relief valve (5), and brake control valve (6).
The main relief valve is located in the manifold on the top of the transmission.
The main relief valve controls the pressure in the circuit.
The oil that flows past the main relief valve provides part of the lubrication and
cooling for the transmission and bevel gear. The primary use of oil from section
(A) is for control of the transmission clutches and of the brakes.
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Torque Converter and Lubrication Section
Section (B) sends oil from the bevel gear case through oil filter (15) to priority
valve (1). This pump section supplies the low pressure circuit. The priority valve
sends a portion of the oil to torque converter (11). The rest of the oil is used tolubricate the brakes and the transmission.
The oil from torque converter (11) exits through outlet relief valve (10). Next, the
oil is routed to oil cooler (9). Then, the oil flows back to priority valve (1). At the
priority valve, the oil combines with the oil that bypassed torque converter (11) .
The combined oil flows from priority valve (1) in order to lubricate the
transmission and brakes. Then, the oil drains to the bevel gear case. A small
portion of the oil is diverted from the torque converter inlet in order to lubricate
the drive gears and bearings.
Priority valve (1) routes oil from section (B) of pump (12) to torque converter
(11). Signals from the electronic control module (ECM) to the priority valve can
divert oil from section (B) through check valve (16). The oil flow from section (B)
adds to the flow from section (A). Oil pressure increases until a minimum
pressure is achieved for controlling the transmission and brakes (7).
Torque converter inlet relief valve (3) is located in priority valve (1). Torque
converter inlet relief valve (3) limits the maximum oil pressure to torque
converter (11).
Scavenge Section
Section (C) removes oil from torque converter (11) and from the transmission.
The oil is returned to the bevel gear case. The oil is drawn through screens at
torque converter (11) and at the transmission.
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Electronic Control System Components
Schematic for the power train electronic control
(1) Parking brake switch
(2) Tiller for the differential steering
(3) Cat data link
(4) Electronic control module (ECM)
(5) CMS (monitoring system)
(6) Connector
(7) Connector
(8) Service tool
(9) Steering differential and brake on the left side of the machine
(10) Planetary gears and brake on the right side of the machine
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(11) Brake control valve
(12) Transmission modulating valves and the main relief valve
(13) Priority valve
(14) Brake pedal
(A) Output speed of the torque converter
(B) Intermediate speed of the transmission
(C) Output speed of the transmission
(D) Engine speed
(E) Oil temperature
Reference: Refer to Service Manual, SENR8367, "Power Train Electronic
Control System" for system operation, testing and adjusting procedures.
The electronic control system for the power train performs two main functions:
Shifting of the transmission Braking
The electronic control system for the power train also performs the following
functions:
Parking brake function Neutral start Warning function Backup alarm
Shifting of the Transmission
The electronic control system for the power train performs the shifting of the
transmission. Electronic control module (4) responds to the request for shifting.
ECM (4) controls the electrical current of the modulating valves for the
transmission. The current to the valve solenoids controls the oil pressure that
engages the transmission clutches.
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The electronic control system for the clutch pressure controls the transmission
clutch engagement.
Electronic Clutch Pressure Control (ECPC)
The ECPC is used with the power train electronic control system. Electronic
control module (4) selects the transmission clutches that will be engaged. The
clutch pressure is modulated electronically. Solenoid valves control the
modulation of the clutch pressure. Electronic control module (4) uses signals
from the transmission speed, the engine speed and the power train oil
temperature. These signals are used to control the smooth engagement of the
clutches.
Each transmission clutch has a corresponding solenoid valve. Electronic control
module (4) uses the transmission valves to modulate the oil pressure to each
transmission clutch. The solenoid valves operate in a proportional manner.
Electronic control module (4) modulates the current of the solenoids.
Modulating the solenoid valves controls the power train oil flow to the
transmission clutches. First, the operator requests a transmission shift.
Electronic control module (4) selects the appropriate transmission clutches for
engaging. The ECM also controls the rate of the modulation of the clutch
pressure.
Braking
Braking is controlled by the electronic control system for the power train. The
brakes are applied with springs. The brakes are released hydraulically.
Service brake pedal (14) and parking brake switch (2) inform ECM (4) of the
requests for braking. The ECM removes the current from the solenoid valve on
brake control valve (11). When braking is not requested, the solenoid valve
receives current. The valve opens and the brakes are hydraulically released.
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Torque Divider
SMCS - 3113; 3114
Ver imagen
Illustration 1g00759083
(1) Flywheel
(2) Turbine
(3) Torque converter housing
(4) Impeller
(5) Case
(6) Yoke
(7) Freewheel stator
(8) Output shaft
(9) Ring gear
(10) Planetary carrier
(11) Planetary gears
(12) Sun gear
The torque divider connects the engine to the planetary transmission. The connection is
both a hydraulic connection and a mechanical connection. The hydraulic connection is
through a torque converter. The mechanical connection is through a planetary gear set.
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The torque converter uses oil from the torque converter charging pump section to
multiply the torque to the transmission. When the machine works against a low load, the
torque multiplication is low. When the machine works against a high load, the torque
multiplication is higher. A higher torque can then be sent to the transmission during
high load conditions.
The planetary gear set also multiplies the torque from the engine by making an increasein the mechanical advantage. The torque multiplication also makes an increase as the
load on the machine becomes higher.
During no-load conditions, neither the torque converter nor the planetary gear set can
multiply the torque from the engine.
The torque converter housing (3) and sun gear (12) are installed onto engine flywheel
(1). The torque divider case is installed on the engine flywheel housing. Output shaft (8)
is connected to yoke (6). Yoke (6) is connected to the planetary transmission through a
drive shaft.
The planetary gear set is composed of the following parts: sun gear (12), planetarycarrier (10), planetary gears (11), and ring gear (9). Sun gear (12) is connected to theflywheel by splines. Planetary carrier (10) is connected to output shaft (8) by splines.
Planetary gears (11) are held by planetary carrier (10). Planetary gears (11) are engagedby sun gear (12) and by ring gear (9) .
The torque converter is composed of the following parts: housing (3), impeller (4),
turbine (2), and stator (7). Housing (3) is connected to flywheel (1) by splines. Impeller
(4) is connected to housing (3). Turbine (2) is connected to ring gear (9) by splines.
Stator (7) is connected to carrier (14) .
Torque Converter Operation
Ver imagen
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Illustration 2g00759091
(2) Turbine
(3) Torque converter housing
(4) Impeller
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(7) Freewheel stator
(11) Planetary gears
(13) Outlet passage
(14) Carrier
(15) Inlet passage
(A-A) End view of freewheel stator (7)
Oil for the operation of the torque converter flows through inlet passage (15) in carrier
(14) to impeller (4). The rotation of the impeller drives the oil. The impeller sends theoil around the inside of housing (3) to turbine (2) .
The force of the oil on the blades of the turbine turns the turbine. The turbine drives the
planetary gears (11) around ring gear (9). The torque that is given to the turbine by the
force of the oil cannot be a greater force than the torque output of the engine to the
impeller.
As the oil flows from the turbine, the oil moves in a direction that is opposite from the
rotation of impeller (4). Stator (7) changes the direction of the oil. As the stator isconnected to carrier (14), most of the oil flows from the stator through outlet passage
(13) to the oil cooler.
The force of the oil from the stator can now add to the torque output from the engine tothe impeller. The extra force can give an increase to the torque output of the engine to
the turbine. A larger difference between the speeds of the impeller and of the turbine
translates to a larger amount of force of the oil from the stator.
The load on the machine changes the speed of the turbine. A greater load translates to a
larger difference in the speeds between the impeller and the turbine. The different loads
on the machine control the amount of torque multiplication that is added by the force of
the oil from the stator.
Freewheel Stator
Freewheel stator (7) reduces the load from the torque converter on the engine during
some low load conditions. These conditions are roading, reverse cycles, and downhill
runs, when the engine is operating at speed. The freewheel stator releases the torque
converter from carrier (14), and the engine speed matches the machine speed without
driving the torque converter. Increases in the load cause the freewheel clutch to engage,and the torque converter resumes normal operation.
Torque Divider Operation
Ver imagen
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Illustration 3g00759092
(2) Turbine
(3) Torque converter housing
(8) Output shaft
(9) Ring gear
(10) Planetary carrier
(11) Planetary gears
(12) Sun gear
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The torque converter is driven by the engine through housing (3). The planetary gear set
is driven by the engine through sun gear (12). These connections allow the torque
output of the engine to go in two separate directions.
Because of the larger radius of ring gear (9), most of the torque is sent by the torque
converter through the ring gear to planetary gears (11). The remainder of the torque is
sent by sun gear (12) to planetary gears (11). If planetary carrier (10) has no resistanceto rotation, then the following components turn at the same speed: sun gear (12),
planetary gears (11), planetary carrier (10) and ring gear (9) .
The torque from the converter and from the planetary gear set is now through the
planetary carrier to output shaft (8) and the planetary transmission. Neither the torque
converter nor the planetary gear set can multiply the torque from the engine when both
these components turn at the same speed.
When the machine has a load, planetary carrier (10) has a resistance to rotation. Since
sun gear (12) is turning at the rpm of the engine, the resistance to rotation turns
planetary gears (11). This rotation is the reverse of the rotation of ring gear (9). The
speed of the ring gear decreases.
Since turbine (2) is connected to the ring gear, a decrease in speed will cause the torque
converter to multiply the torque from housing (3). The torque multiplication is sent toplanetary carrier (10) and the output shaft.
If the resistance to rotation of planetary carrier (10) increases, the speed of the ring gear
will decrease more. The slower speed will allow the torque multiplication through both
the torque converter and the sun gear to become higher.
If the resistance to rotation of the planetary carrier increases enough, the ring gear stops.
During some very high load conditions, the rotation of the planetary carrier and the
output shaft also stop. The stopped output shaft turns the ring gear slowly in the
opposite direction. The torque multiplication of the torque converter and the sun gear is
at the maximum.
Torque Divider Lubrication
Oil for the lubrication of the torque divider bearings and for the planetary gear set
comes from the supply that is used for the operation of the torque converter. Thebearings constantly run in oil. Bearings and gears in the planetary gear set and the pilot
bearing get lubrication through passages in the output shaft.