1. The variable valve timing system, the VVT
SUMMARY
VVT (Variable Valve Timing) variable valve timing system. The system, the phase of the cam by the engine is equipped with control and adjustment execution system, so that the valve opening, closing time changes with changes in engine speed, to improve the charging efficiency, increased engine power.
Basic profile
variable valve timing engine technology (VVT, Variable Valve Timing) principle is based on the engine operating conditions, adjusting an intake (exhaust) of amount, and the valve opening and closing times, the angle. Entering the amount of air to achieve the best efficient combustion. The advantage is fuel-efficient, liter ratio. The disadvantage is inadequate middle speed torque.
Korean cars VVT is based on the Toyota’s VVT-I and Honda’s VTEC technology from imitation, but the valve timing technology, VVT variable is only compared to Toyota’s VVT-I variable valve technology, the lack of timing technology, so does VVT engine fuel-efficient engine than the average, but keep up with Japanese cars Toyota and Honda fuel-efficient cars.
Before BMW new generation of engines has long been using this technique, the current such as Honda VTEC, i-VTEC, Toyota VVT-i; Nissan CVVT; Mitsubishi MIVEC; Suzuki the VVT; Modern the VVT; Kia CVVT, etc. are also beginning to use. Overall it is actually a technique different names.
VVT – i
VVT Chinese means ldquo; rdquo ;, a variable valve timing since the electronic control unit (ECU) to control, thus starting the Toyota a nice Chinese name called ldquo; intelligent variable valve timing system rdquo ;. The systemControlling the intake valve camshaft, the addition of a small tail ldquo; irdquo ;, is English ldquo; Intakerdquo; (intake) code. These are ldquo; VVT-irdquo; the literal meaning. VVTmdash;. I system is Toyota’s intelligent variable valve timing system abbreviation of the latest Toyota car engine has been widely installed VVTmdash; i system. Toyota VVTmdash; i is a continuously adjustable valve timing system, but can not adjust the valve lift. Its working principle is: when the engine is converted from the low to the high speed, the computer is automatically machine hydraulic pressure to the turbine intake camshaft driving pinion in the gear, so that, under the effect of pressure on small turbine with respect to the gear shell certain angle of rotation, so that the cam shaft rotated forward or backward in the range of 60 degrees, thereby changing the opening timing of the intake valve, the purpose of continuous adjustment of the valve timing.
VVT-i is a device at the intake camshaft timing control valve, when it is optimized by adjusting the valve timing camshaft rotational angle, thereby increasing engine power at all speed range, fuel economy and reduce exhaust emissions.
VVT-i system portion of the valve, controlled by the sensor controller, the ECU and the camshaft hydraulic composition. ECU stores a parameter value optimal valve timing, crankshaft position sensor, an intake manifold air pressure sensor, a throttle position feedback sensor, a water temperature sensor and the camshaft position sensor pooled and compared to the ECU calculates a predetermined parameter value, correction parameter is calculated and issues an instruction to the camshaft timing control hydraulic control valve, the control valve position of the control valve according to ECU sump machine instruction, is to change the hydraulic flow, the advance hysteresis, etc. remain unchanged select command signal sent to the VVT different oil trail -i controller.
VVT-i depends on the system controller? Mounting and divided into two different parts, one is mounted on the exhaust camshaft, referred vane VVT-i, Toyota PREVIA (Great King) install paragraph. The other is mounted on the intake camshaft, referred to as a spiral trough VVT-i, 400, 430, etc. Toyota Lexus limousine mounting section. Some two structure is not the same, but the effect is the same.
sirocco VVT-i is controlled by an intake cam driveBulb and the impeller shaft and coupled to the exhaust camshaft composition, lead or lag-side hydraulic pressure from the oil passage is transmitted to the exhaust camshaft, resulting in the envelope VVT-i controller to drive the rotation of the intake camshaft, continuously changing the intake timing. When the hydraulic pressure applied to the advance side oil chamber when the housing is rotated, in the direction of advance rotation of the intake camshaft; when hydraulic pressure is applied to the rotatable housing-side oil chamber in the hysteresis, the hysteresis along the lateral rotation of the intake camshaft; when the engine is stopped when the camshaft is at a maximum hydraulic pressure control valve hysteresis state.
helical trough VVT-i controller comprises a timing belt drive gear, the intake camshaft movable piston, the piston surface is connected between the rigid internal gear, and an internal gear and the external gear is located there are helical splines, the piston moves axially, will change the phase of the external gear, to produce continuously varying the valve timing of the valve. When oil pressure is applied to the left side of the piston, forces the piston to the right, due to the action of the helical spline on the piston with respect to the intake camshaft will advance to a camshaft timing pulley angle. When oil pressure is applied to the stone side of the piston, forces the piston to the left, it will delay the intake camshaft a certain angle. When obtained over the timing of gas, camshaft timing hydraulic control valve closes oil passages to make equilibrium pressure on both sides of the piston, the piston stops moving.
Now, advanced engine has ldquo; engine control module rdquo; (ECM), the unified management ignition, fuel injection, emission control, fault detection. ECM Toyota VVT-i in the various driving conditions of the engine to automatically search for a corresponding one of the engine rotational speed, intake air amount, the timing and throttle position valve optimum cooling water temperature, and controls the hydraulic control valve camshaft timing, and to sense the actual valve timing of the respective signals by the sensor, then the feedback control is performed, the error compensation system, to achieve optimum valve timing position, which can effectively improve the power and performance of the car, to minimize the fuel consumption and exhaust emissions .