Toyota all-wheel drive. DTV AWD

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Eugenio,77
mail@toyota-club.net
© Toyota-Club.Net
Jan 2019


The new Toyota all-wheel drive type - Dynamic Torque Vectoring AWD - was introduced in 2018. The core of this scheme: full-time front-wheel drive, without center and rear differentials, with independent connection of the rear wheels via electromechanical multi-plate clutches mounted on the rear reductor. The main innovation - two dog clutches (cam clutches) that disconnect driveline in the transfer and the rear reductor so the propeller shaft does not rotate during 2WD driving.




Let's see DTV details by example RAV4 AXAA54 (2018), with transfer GF2A and rear reductor* FD15EF.
* originally named "rear differential" by Toyota - but we can't call so the device without traditional planetary differential mechanism


1 - transfer (position switch), 2 - rear reductor (position switch), 3 - revolution sensor, 4 - temperature sensor, 5 - LH coupling, 6 - RH coupling

Rear reductor

The assembly includes: rear angular reductor, shaft, two electromechanical couplings, driveline opening cam clutch.


1 - electromechanical coupling, 2 - clutches and 4WD control solenoid, 3 - rear cam clutch solenoid, 4 - ball bearing, 5 - ring gear

The final gear ratio is less than the transfer gear ratio, so the rotational speed of the components before the coupling is always some higher, which should improve the response at the moments of 4WD connecting (special note for those who makes DIY controls for Toyota ATC couplings).


1 - propeller shaft, 2 - flange, 3 - ring gear, 4 - main clutch, 5 - coupling housing, 6 - sleeve, 7 - shaft, 8 - inner hub, 9 - drive pinion, 10 - drive shaft

Electromechanical multi-plate coupling is mounted on the rear reductor. The outer parts of the main clutch and control clutch are coupled to the front housing, the inner part of the main clutch - to the shaft, the inner part of the control clutch - to the cam. The control clutch - multiple metal plate type, the main clutch - multiple wet plate type.


1 - front housing, 2 - shaft, 3 - inner hub, 4 - piston, 5 - armature, 6 - cam, 7 - solenoid, 8 - control clutch, 9 - main clutch

If the solenoid not energized, the control clutch not engaged, and the drive force not transmitted from the front housing to inner hub and driveshaft.


1 - front housing, 2 - inner hub, 3 - piston, 4 - cam, 5 - 4WD ECU, 6 - 4WD solenoid, 7 - control clutch, 5 - armature, 9 - main clutch

When the control unit energizes the solenoid, the armature is attracted to the control clutch to engage it. This causes the cam to rotate and rotational movement of the cam causes the piston to push and engage the main clutch. The drive force is transmitted from the front housing to the inner hub and then to the drive shaft.


1 - front housing, 2 - inner hub, 3 - piston, 4 - cam, 5 - 4WD ECU, 6 - 4WD solenoid, 7 - control clutch, 8 - armature, 9 - main clutch. a - high amperage, b - low amperage

The amount of transmitted drive force is controlled steplessly by controlling the amperage applied to the solenoid - the higher current amperage means the greater piston stroke.


Low amperage. a - control clutch engagement force (small), b - piston travel


High amperage. a - control clutch engagement force (large), b - piston travel, c - main clutch engagement force (large)

The driveline opening mechanism - cam (dog) clutch, which connects the ring gear to the shaft if necessary. For a smoother switching, the mechanism is supplemented with a synchronizer, which allows equalizing the speeds of rotating components.


1 - drive pinion, 2 - ring gear, 3 - sleeve, 4 - return spring, 5 - shaft, 6 - piston, 7 - holder, 8 - cam 2, 9 - solenoid, 10 - ball, 11 - cam 1. a - synchronizer, b - cam clutch

Operation (connection):
- Current is supplied to the solenoid
- The armature attracted suppressing the rotation of the cam 2
- A rotational difference between the cam 1 and cam 2 is created
- The ball is wedged and pushes the cams apart
- Cam 1 pushes the piston, which moves the sleeve
- The synchronizer equalizes the rotational speeds of the ring gear and the shaft


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - ball, 9 - cam 2, 10 - solenoid, 11 - armature

- Current supply is stopped
- Piston and sleeve are pushed back by return spring
- During return stroke the piston jumps to another notch of holder (so return stroke of the piston and sleeve is more than forward stroke)
- The cam clutch engages
- Ring gear is connected to the shaft via the sleeve


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - ball, 9 - cam 2, 10 - solenoid, 11 - armature


1 - sleeve, 2 - holder, 3 - cam 1. a - disconnected, b - solenoid ON, c - solenoid OFF, d - connected

Operation (disconnection):
- Current is supplied to the solenoid
- The armature attracted suppressing the rotation of the cam 2
- A rotational difference between the cam 2 and cam 1 is created
- The ball is wedged and pushes the cams apart
- Cam 1 pushes the piston, which moves the sleeve
- The cam clutch disengages


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - ball, 9 - cam 2, 10 - solenoid, 11 - armature

- Current supply is stopped
- Piston and sleeve are pushed back by return spring
- During return stroke the piston jumps to next notch of holder (so return stroke of the piston and sleeve is less than forward stroke)
- The clutch remains disengaged, the ring gear is not connected to the shaft via the sleeve


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - ball, 9 - cam 2, 10 - solenoid, 11 - armature


1 - sleeve, 2 - holder, 3 - cam 1. a - connected, b - solenoid ON, c - solenoid OFF, d - disconnected

Transfer

A traditional angular reductor in this scheme is supplemented with the front driveline opening cam clutch.


1 - front differential case, 2 - input shaft, 3 - sleeve, 4 - ring gear, 5 - driven gear, 6 - output shaft, 7 - propeller shaft

The cam (dog) clutch connects the ring gear to the transfer input shaft if necessary.


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - input shaft, 5 - piston, 6 - holder, 7 - cam 2, 8 - solenoid, 9 - ball, 10 - cam 1

Operation (connection):
- Current is supplied to the solenoid
- The armature attracted suppressing the rotation of the cam 2
- A rotational difference between the cam 2 and cam 1 is created
- The ball is wedged and pushes the cams apart
- Cam 1 pushes the piston, which moves the sleeve


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - cam 2, 9 - solenoid, 10 - armature, 11 - ball

- Current supply is stopped
- Piston and sleeve are pushed back by return spring
- During return stroke the piston jumps to another notch of holder (so return stroke of the piston and sleeve is more than forward stroke)
- The cam clutch engages
- Ring gear is connected to the shaft via the sleeve


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - cam 2, 9 - solenoid, 10 - armature, 11 - ball


1 - sleeve, 2 - holder, 3 - cam 1. a - disconnected, b - solenoid ON, c - solenoid OFF, d - connected

Operation (disconnection):
- Current is supplied to the solenoid
- The armature attracted suppressing the rotation of the cam 2
- A rotational difference between the cam 2 and cam 1 is created
- The ball is wedged and pushes the cams apart
- Cam 1 pushes the piston, which moves the sleeve
- The cam clutch disengages


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - cam 2, 9 - solenoid, 10 - armature, 11 - ball

- Current supply is stopped
- Piston and sleeve are pushed back by return spring
- During return stroke the piston jumps to next notch of holder (so return stroke of the piston and sleeve is less than forward stroke)
- The clutch remains disengaged, the ring gear is not connected to the shaft via the sleeve


1 - ring gear, 2 - sleeve, 3 - return spring, 4 - shaft, 5 - piston, 6 - holder, 7 - cam 1, 8 - cam 2, 9 - solenoid, 10 - armature, 11 - ball


1 - sleeve, 2 - holder, 3 - cam 1. a - connected, b - solenoid ON, c - solenoid OFF, d - disconnected


Control

Compared to ATC, the number of elements has increased several times: in the transfer - front cam clutch solenoid and position sensor, in the rear reductor - rear cam clutch solenoid and position sensor, propeller shaft speed sensor, reductor temperature sensor, RH and LH 4WD coupling solenoids.

4WD control unit is separate, located at the rear of vehicle. The system uses the signals from steering wheel position sensor, wheel speed sensors, yaw rate sensor, deceleration sensor; brake pedal and parking brake position, throttle position, crankshaft rotation speed, selected gear signals; data from engine, transmission ABS/VSC control units...

The control system automatically maintains the target value of torque transmitted to the rear wheels, and corrects torque distribution between the rear wheels to improve vehicle stability.
During the steady driving and at cruising speed, the system reduces the torque transmitted to the rear wheels, and after a while turns to 2WD mode and opens the driveline in order to better fuel efficiency.



During sudden takeoff drive force at rear wheels is increased, during low-speed cornering is decreased. During braking 4WD is off for better braking performance.



Receiving data from the vehicle sensors, the system determines the cornering initial moment, compares the current acceleration values with the ideal, and, thanks to the ability to control the torque on the outer and inner rear wheels separately, corrects understeer or oversteer. Interaction between DTV and VSC should allow smooth acceleration even when cornering on conditionally slippery surface.



The combination meter indicator (torque distribution diagram) indicates the torque value supplied to each of the wheels by the number of segments highlighted.



Earlier the driver of Toyota with ATC had the only button for forced 4WD connection, now he obtain three "Multi-Terrain Select" switches Formally, it is some kind of intelligent function of optimal 4WD control for selected road and off-road conditions, really - all the same 4WD forced connection with different speed threshold (in Mud&Sand pseudo-locking is OFF at 40 km/h, in Rock&Dirt - at 25 km/h).



However, the new scheme advantage is obvious - if ATC "lock" mode imitated 4WD with a locked center differential, DTV essentially simulates the 4WD with a locked center and rear differentials (without the need to brake the skid wheel by VSC).

As for market position, DTV does not replace, but only complements ATC/DTC scheme, and so far will be installed to high grades of Toyota models.


Toyota all-wheel drive. Review











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