Home
Articles
Forum
Toyota Valvematic system

Eugenio,77
mail@toyota-club.net

© Toyota-Club.Net
Nov 2012


In addition to ZR engines review, "Valvematic" (VM) - continuous variable valve lifting system - is described below.



Valvematic allows to control the amount of intake valve lift in the range 0.9..10.9 mm. Accordingly, the valve opening duration varies at range 106..260° (crank angle).



VM management is inextricably related to the control of variable valve timing (VVT-i) and electronically controlled throttle (ETCS-i).

Effect

The differences of conventional and VM engines are shown at the indicator diagram (for idle and under 30% load).



In contrast to a conventional engine, the throttle valve substantially continuously maintained in the fully open position during VM operation, and the mixture dosing is performed by varying valve lift.

At the beginning of the intake stroke, in VM engine the pressure in the intake manifold is close to barometric, so pumping losses are reduced on the piston down stroke.
After the desired amount of the mixture received in the cylinder, the intake valve closes. As the piston continues to move down, pumping losses increase even in VM engine due to vacuum in the cylinder.
Although to the end of the piston stroke vacuum in the cylinders of both engines is equal, but in VM engine the admission was performed more effective.

ValvematicVVT
Timing: Changes continuouslyTiming: Changes continuously
Valve lift: Changes continuouslyValve lift: Unchanged
Advantages: Precise control of the timing and lifting in accordance with driving conditions, that allows to reach the same output at less consumption. Advantages: Valve timing control to improve efficiency or to increase output, in accordance with driving conditions.



Operation

Condition-FunctionEffect
Starting / Stalling - The operating crank angle of the intake valve is 200°
- The intake valves close soon after BDC, reducing the overlap to increase compression
- Improved starting performance
Idle (fast) - The operating crank angle of the intake valve is 250°
- The valve lift is enlarged to increase the overlap, increasing internal EGR
- Reduced NOx and HC emissions
Engine warming up (except fast idle) - The operating crank angle of the intake valve is 240°
- Increased efficiency at the intake stroke
- Increased power output
- Reduced fuel consumption
Engine warmed up (low to medium load) - The operating crank angle of the intake valve is 106-245°
- Cooperation of VVT and ETCS
- Valve lift is varied to close early and reduce pumping losses
- Exhaust valves timing also is varied
- Reduced fuel consumption
Engine warmed up (high load) - The operating crank angle of the intake valve is 230-260°
- Cooperation of VVT and ETCS
- Valve lift is varied to close lately and increase cylinder admission
- Exhaust valves timing also is varied
- Increased power output
- Reduced fuel consumption
- Reduced exhaust gas temperature

Design


Timing drive. 1 - VVT actuator (exhaust), 2 - VVT actuator (intake), 3 - exhaust camshaft, 4 - intake camshaft, 5 - Valvematic controller, 6 - rocker, 7 - lash adjuster, 8 - valve, 9 - intake valve, 10 - exhaust valve, 11 - chain dumper, 12 - tensioner slipper, 13 - hydraulic tensioner.

Valvematic controller
- The controller (actuator) consists of the driver (EDU), electric motor and conversion mechanism.
- Brushless motor - three-phased, uses neodymium magnets.
- The driver - controls the motor operation, sets the target and determines the actual rotor position, using the angle sensor (detects rotor rotation angle) and position sensor (detects the number of rotor revolutions).


1 - Valvematic controller, 2 - oil outlet, 3 - oil inlet, 4 - position sensor, 5 - driver, 6 - motor, 7 - stator, 8 - rotor, 9 - bearing, 10 - conversion mechanism.

- The conversion mechanism (planetary gear) converts the rotation of the rotor into linear movement of the control rod. The mechanism is lubricated with engine oil.
- Ring gear (straight cut teeth) connected to the case, the sun gears are mounted on the control rod, the planet carrier are in engagement with the left-handed thread of the case and right-hand threads of the rod. Number of teeth: ring gear - 50, pinion gears - 10, sun gear - 31. Screw thread: ring gear - 5 lead left-hand, pinion gear - 1 lead left-hand, sun gear - 4 lead right-hand.
- The electric motor rotates the case with ring gears, which in turn, rotate pinion gears. The sun gears and the rod are moved axially, allow to control the valve lift.


1 - pinion gear 1, 2 - carrier, 3 - case, 4 - carrier screw, 5 - ring gear 1, 6 - ring gear 2, 7 - sun gear 1, 8 - sung gerar 2, 9 - control rod.

Variable Valve Lifting mechanism
- Continuous variable valve lift actuator consists of control rod, slider, roller arm, oscillation arms, damper.



- The control rod transmits linear movement from the controller to slider. Slider have oblique-spur teeth are meshing with the teeth of the roller and oscillation arms, and determines the relative position of these arms.


Roller arm is in contact with the intake camshaft cam, its movement is transmitted via the slider to oscillation arms, which push the rockers to open the intake valves. The damper constantly presses the roller arm to track a cam profile.


1 - control rod, 2 - rocker shaft, 3 - oscillation arm, 4 - roller arm, 5 - slider, 6 - damper, 7 - intake camshaft, 8 - rocker, 9 - intake valve, 10 - lash adjuster.

Reduced valve lift Increased valve lift


Toyota engines review


Более 2000 руководств
по ремонту и техническому обслуживанию
автомобилей различных марок
 








Рейтинг@Mail.ru