Honda's Torque Converter: How it Works - 2003 Honda Rincon

Jul. 01, 2002 By ORC STAFF
Honda's innovative Rincon™ boasts the only true automotive-style automatic transmission in the entire ATV world. The use of a torque converter makes this possible, and the Rincon's torque converter is truly a unique piece of engineering. Many items distinguish the Rincon's torque converter from automotive-style torque converters, but two innovations stand out: An ingenious one-way lock-up clutch mechanism, and another system Honda calls "creep control." Honda's Innovative Creep Control System
A torque converter transmits torque even when a vehicle is idling, causing some amount of forward motion, or "creep" to occur. In the case of an automobile, creep can add a measure of smoothness when the vehicle begins to move, but it also requires the operator to keep a foot on the brake when the vehicle is stopped in gear.
To allow the Rincon to idle in gear without moving forward, Honda's new creep control system detects the idling of the vehicle while it is stationary, and disengages a hydraulic clutch mechanism within the transmission in order to cut creep. In addition, an ECU computes the necessary hydraulic pressure according to throttle position and engine speed in order to engage the clutch gradually. The result: the ability to idle in gear without creep, while maintaining the smooth engagement of power off-idle that torque converters deliver.
One-way to Engine Braking
Another shortcoming of traditional torque-converters is a lack of engine braking. Because of their power transmission efficiencies, torque converters can only provide a small amount of engine braking, which is not a desirable trait in an ATV. To counter this, Honda engineers designed the Rincon's torque converter with a built-in one-way lock-up clutch--the first time in the world that this construction has been employed.
The problem of engine braking has been overcome in some four-wheel drive vehicles with a hydraulically controlled lock-up clutch. However, such systems are immensely complex, large and heavy, and not at all suitable for an ATV. Honda's solution was to incorporate a one-way clutch mechanism for engine braking that transmits power to the crankshaft instead of the torque converter during deceleration. As a result, the Rincon features the same kind of direct engine braking feel as that of ATVs with conventional transmissions. Torque Converter Basics
Though it features several innovations that cater specifically to ATV application, the Rincon's torque converter operates in principle much like other torque converters: In the most basic sense, it serves to link the engine to the automatic transmission much like a manual clutch connects an engine to a manual gearbox. Both systems are used to drive a vehicle, and they also come into play when the vehicle stops.
With a manual transmission, manual actuation of the clutch serves to temporarily disengage the engine from the transmission when coming to a stop. In similar fashion, a torque converter performs this very important connect/disconnect function between the engine and the transmission, but automatically, as needed. Moreover, with a torque converter and automatic transmission, the rider need only operate one control, the brake, when stopping the vehicle. A torque converter can accomplish this because it is a fluid coupling, rather than a solid coupling. At low engine speeds, the torque converter can slip internally, which allows the engine to spin independently of the transmission. As a result, the engine of the stopped vehicle is allowed to run at an idle while the transmission is in gear. When it's time to roll, the rider simply opens the throttle to increase engine speed, and the torque converter then transfers power to the transmission to make the vehicle move. How is this accomplished? Picture in your mind a pair of electric fans facing each other. Turn on one fan, and the blowing air creates enough force to spin the blades of the second fan-power is transferred. In a similar fashion, a torque converter incorporates a driven impeller to pump a fluid that drives the turbine portion of the torque converter. The driven turbine, in turn, then powers the transmission. In the Rincon, the engine output shaft drives the torque converter's impeller, which uses fins to pump fluid-in this case, engine oil. As this fluid drives the vanes of the torque converter's turbine, the spinning turbine then powers the automatic transmission to propel the vehicle. The Rincon's automatic transmission employs three hydraulic clutches and an electronic control unit (ECU) that automatically selects one of three forward gears (or reverse if reverse is engaged). The ECU monitors throttle opening, vehicle speed, engine speed, gear selector position (if engaged), brake application and engine oil temperature, and processes this information to select the correct drive gear for the appropriate conditions.

The other key component within a torque converter is the stator, which redirects fluid flow within the torque converter to create torque multiplication. This occurs when the engine is spinning much faster than the transmission, i.e. when the rider quickly opens the throttle from a standing start--just the time that more pulling power is needed!
The automotive world has been graced with torque converters and automatic transmissions for decades. But it took the creative minds at Honda to adapt this proven technology for the ATV market and apply these innovative solutions on a whole new, smaller scale. At Honda, elegance in engineering takes on many forms, but it's always for the same goal: Customer satisfaction.
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Griffin Recovery Equipment, Inc.
P.O. Box 26454
Honolulu, HI 96825
Telephone (808) 226-7744
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