D8RII-OperacióndeSistemas

8/4/2019 D8RII-OperacindeSistemas

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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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(2) Turbine


(4) Impeller



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(7) Freewheel stator


(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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(2) Turbine


(8) Output shaft

(9) Ring gear

(10) Planetary carrier


(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.

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