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| Illustration 1 | g00409340 |
(1) Spline. (2) Hub assembly. (3) Turbine. (4) Converter housing. (5) Impeller. (6) Plate. (7) Disc. (8) Piston for impeller clutch. (9) Clutch housing. (10) Oil passage for impeller clutch. (11) Oil pump drive gear. (12) Oil passage for converter outlet. (13) Carrier. (14) Output yoke. (15) Output shaft. (16) Stator. (17) Carrier. (18) Hub. (19) Adapter. (20) Oil passage for converter inlet. | |
The torque converter has an impeller clutch. The impeller clutch is designed to allow the operator to limit the amount of torque increase in the torque converter. This causes a decrease in wheel slippage and tire wear. This also allows an increase of engine power for the hydraulic implement system. The impeller clutch enables the output torque of the converter to vary.
Spline (1) is a part of converter housing (4). Spline (1) is engaged with the splines on the engine flywheel. These splines turn the converter housing at engine speed. Clutch housing (9) is fastened to the converter housing. Oil pump drive gear (11) is fastened to the clutch housing.
Stator (16) is connected to carrier (13). Carrier (13) is fastened to the cover that is around the torque converter. Carrier (13) and stator (16) do not turn. The carrier helps to support the rotating components of the converter. The carrier also contains the passages that carry oil for the operation of the converter.
Converter housing (4), clutch housing (9) and oil pump drive gear (11) turn as a unit at the speed of the engine. Internal splines in clutch housing (9) turn plates (6) and piston (8). Clutch discs (7) are connected to adapter (19) with splines. Adapter (19) is fastened to impeller (5) with bolts.
Hub assembly (2) is fastened to turbine (3). Splines connect hub assembly (2) to output shaft (15). The output shaft is connected to output yoke (14). The output yoke is fastened to a universal joint and to the drive shaft. The drive shaft connects to the input transfer gears of the transmission with another universal joint.
Oil from the transmission oil pump flows to the transmission oil filters. The oil from the transmission charging section of the transmission oil pump then flows to the priority valve. The oil from the priority valve then flows to the solenoid valve of the converter clutch and the remainder flows to the transmission hydraulic control valve. The oil that is pumped from the torque converter charging pump section of the transmission oil pump flows to the torque converter.
In the transmission hydraulic control valve, the oil flows around the modulating relief valve to the converter inlet ratio valve. Oil from the converter inlet ratio valve flows through a hose into inlet passage (20) in the carrier, and then into the torque converter. The oil then flows through hub (18) into the impeller (5) .
Torque Converter Operation
The oil that is inside of the torque converter flows from impeller (5) to turbine (3), and then to stator (16). The oil from stator (16) then flows to the impeller and to outlet passage (12) in carrier (13) .
The torque converter is operated with pressurized oil. The maximum inlet pressure is controlled by the converter inlet ratio valve. The outlet pressure is controlled by the outlet relief valve and by downstream restrictions.
Oil flows through inlet passage (20) in carrier (13) to hub (18) and impeller (5). The rotation of the impeller gives force to the oil. The impeller sends the oil toward turbine (3). The force of the oil that hits the turbine blades causes the turbine to turn. Turbine (3) turns output shaft (15) .
The oil flows from turbine (3) reversed from the direction that is required for impeller (5). Stator (16) causes the oil to change flow direction into the impeller. Because the stator is held stationary by carrier (17), most of the oil is sent back to the impeller. The remainder of the oil flows through outlet passage (12) to the outlet relief valve.
The oil from the stator adds to the oil from the inlet passage to the impeller.
Impeller Clutch
The impeller clutch is used to change the torque output of the torque converter. The impeller clutch allows the operator to use the left service brake pedal to reduce wheel spin. The impeller clutch also allows the operator to use the left service brake pedal to provide more engine power for the hydraulic system.
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| Illustration 2 | g00123030 |
Right Hydraulic Console (21) Reduced rimpull on/off switch. | |
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| Illustration 3 | g00123031 |
Right Side Console (22) Reduced rimpull selection switch. | |
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| Illustration 4 | g00123032 |
Left Side Front Dash (23) Reduced rimpull indicator lamp. | |
Reduced rimpull on/off switch (21) and reduced rimpull selection switch (22) are used to provide four levels of reduced rimpull. Reduced rimpull is enabled only when the transmission is in first speed forward or first speed reverse.
Reduced rimpull on/off switch (21) is a two-position rocker switch that is located on the implement console. Reduced rimpull selection switch (22) is located on the right hand console. In the MAXIMUM position, the reduced rimpull switch commands maximum rimpull. Maximum rimpull will be provided regardless of the setting of the rimpull selection switch .
Reduced rimpull selection switch (22) works with reduced rimpull on/off switch (21) in order to change the torque output of the torque converter. The power train ECM increases the amount of current to the impeller clutch solenoid valve in order to reduce rimpull. The position of the reduced rimpull selection switch regulates the amount of current that is sent to the impeller clutch solenoid valve.
Reduced rimpull indicator lamp (23) is on when reduced rimpull on/off switch (21) is in the REDUCED position. Also, the transmission must be in first speed forward or first speed reverse. When the transmission is shifted to second speed or to third speed, the reduced rimpull indicator lamp will be off. Reduced rimpull is now disabled.
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| Illustration 5 | g00123046 |
The impeller clutch modulates at each instance of a directional shift. The impeller clutch also absorbs energy during the directional shift. This reduces the amount of energy that is absorbed by the direction clutch, which results in an easier shift.
The oil flow to the impeller clutch is controlled by the impeller clutch solenoid valve. The impeller clutch solenoid valve is positioned on the outer cover. The impeller clutch solenoid valve is activated by the power train ECM.
The following conditions affect the operation of the impeller clutch:
- The position of the left service brake pedal
- Directional shifts and speed shifts
- Engine speed
- Direction of rotation of the torque converter output shaft and torque converter output speed
- Position of the reduced rimpull selection switch
- Position of the reduced rimpull on/off switch
Left Service Brake Pedal
The left service brake pedal controls the amount of brake pressure that is used to apply the service brakes. The left service brake pedal also controls the amount of pressure that actuates the impeller clutch. The impeller clutch is positioned between the engine and the torque converter.
By using the left brake pedal, the operator may divert engine power to the implement hydraulic circuit without putting the transmission in the NEUTRAL position.
As the operator depresses the pedal, the impeller clutch pressure drops quickly to a working pressure.
The pressure is then modulated to a reduced pressure. This sequence occurs during the next ten degrees of pedal travel. Depressing the left pedal past this point applies the service brakes.
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| Illustration 6 | g00107064 |
Typical Torque Converter Impeller Clutch (X) Approximate pedal position in degrees. (Y) Approximate percent of impeller clutch pressure. | |
Range (A) indicates the released position. In this range, the brake pedal does not apply the service brakes.
Range (B) indicates the first two degrees of pedal movement. In this range, the impeller clutch pressure is reduced to the maximum working pressure level. Range (B) is the approximate pressure range that is required to keep the impeller clutch from slipping.
Range (C) indicates the next ten degrees of pedal travel. The impeller clutch pressure is modulated from the maximum working pressure to the minimum impeller clutch pressure.
Range (D) indicates the percent of service brake pressure. Range (E) indicates the impeller clutch pressure.
Engine Speed
When the engine speed drops below 1300 rpm, the power train ECM overrides the setting of the pedal. The power train ECM then reduces the impeller clutch pressure. The impeller clutch pressure is reduced to the impeller clutch hold pressure at 1100 rpm. This improves the response of the machine and the response of the engine when the machine is accelerating from a low idle speed.
Reverse Output Shaft Rotation
When the torque converter output shaft rotates in the opposite direction in excess of 500 rpm, the power train ECM overrides the setting of the pedal. The power train ECM then increases the impeller clutch pressure. This condition could occur if the left brake pedal is used to allow the machine to roll back on a grade with the transmission in a forward gear. This function is used to prevent possible high temperatures in the impeller clutch.
Shift Modulation of the Impeller Clutch
As the operator makes a directional shift of the transmission, the power train ECM overrides the setting of the brake pedal and the impeller clutch pressure is reduced. These functions of the electronic control module help to provide an easier directional shift.
When the power train ECM detects a directional shift, the circuit pressure of the impeller clutch is reduced to a impeller clutch hold pressure. The circuit pressure for the impeller clutch then increases to maximum pressure after the following conditions exist:
- The transmission clutches have fully engaged.
- The left brake pedal is not depressed.
- The engine speed is above 1300 rpm.
The torque converter output speed sensor and the engine speed sensor are used to determine when the transmission clutches have locked up.
Impeller Clutch Solenoid Valve
The impeller clutch solenoid valve is a three-way control valve which modulates pressure proportionally. When the power train ECM increases the amount of current to the solenoid, the impeller clutch pressure is reduced. When the amount of current from the power train ECM is at zero, the impeller clutch pressure is at the maximum.
Operation of the Impeller Clutch
When the impeller clutch solenoid valve is not energized by the power train ECM, oil flows to passage (10) from carrier (13). Oil in passage (10) forces clutch piston (8) against clutch plates (6) and clutch discs (7) .
Clutch piston (8) and clutch plates (6) are connected to clutch housing (9) with splines. Clutch discs (7) are connected to adapter (19) with splines. Adapter (19) is fastened to impeller (5) with bolts. The friction between clutch discs (7) and clutch plates (6) causes the impeller to rotate at the same speed as converter housing (4). This is the maximum torque output in converter drive.
As the amount of current flow to the solenoid is increased, oil pressure to clutch piston (8) is decreased. The friction between the clutch plates and the clutch discs decreases. This causes the impeller to slip. When the impeller slips, less oil is forced to the turbine. With less force on the turbine, there is less torque at the output shaft.
When the amount of current flow to the solenoid is at the maximum, there is minimum oil pressure against clutch piston (8). The clutch plates and the clutch discs now have only a small amount of friction and the impeller forces only a small amount of oil to the turbine. There is a minimum amount of torque at the output shaft.