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VVT variable valve timing system
Source:hailongvvt                Time:2018-06-06

What does the VVT variable valve timing system mean? The following is a detailed introduction of the VVT variable valve timing system.

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Outlines

VVT (Variable Valve Timing) variable valve timing system. The system is equipped with the control and execution system to adjust the phase of the engine cam, so that the valve opening and closing time changes with the change of the engine speed, in order to improve the inflating efficiency and increase the engine power.

basic introduction

Engine variable valve timing technology (VVT, Variable Valve Timing) principle is based on the operation of the engine, adjust the volume of intake (exhaust), and the valve opening time, angle. It is the volume of air that comes into the best place, and the efficiency of progress is extinguished. The advantage is oil saving and higher ratio of the liter. The defect is the lack of speed and torque in the middle section.

The VVT of the Korean car is based on the VTEC technology simulation of the VVT-I and Honda (model pictures) of TOYOTA in Japan, but compared to TOYOTA's VVT-I variable timing valve technology, VVT is only a variable valve technology and short timing technology, so the VVT engine does have to save fuel than the usual engine, but TOYOTA and Honda cars can't keep up with Japanese brand cars.

BMW has already used this technology in the previous generation of engines, such as Honda (car picture) VTEC, i-VTEC, TOYOTA's VVT-i; Nissan (car picture) CVVT; MITSUBISHI (car picture) MIVEC; SUZUKI (car picture) VVT; modern (car picture) VVT; KIA (model picture) CVVT and so on. It is also beginning to use. Generally speaking, it is a technology with different names.

VVT--i

VVT means "variable valve timing" in Chinese, because of the use of electronic control unit (ECU) control, that is why TOYOTA has a difficult Chinese title called "intelligent variable valve timing system".  The system controls the intake camshaft and has a small tail "I", which is the code of the English "Intake" (intake). These are the literal meanings of "VVT-i". The VVT - I. system is the English abbreviation of the Toyota Corporation's intelligent variable valve timing system, and the most new TOYOTA car engine has been universally equipped with the VVT - I system. TOYOTA VVT I system can continue to adjust valve timing, but can not adjust valve lift. Its principle is that when the engine is converted from low speed to high speed, the computer automatically drives the oil pressure to the intake camshaft to drive the small turbine in the gear, so that under pressure, the small turbine rotates a certain angle about the gear shell, so that the camshaft is rotated forward or backward outside the range of 60 degrees. Thereby changing the time when the intake valve opens, reaching the purpose of continuing the conditioning valve timing.

VVT-i is a kind of installation that controls the intake camshaft valve timing. It stops optimizing after adjusting the camshaft angle distribution, thus improving the engine's power and fuel economy in all speed range and reducing exhaust emission.

The VVT-i system consists of sensors, ECU and camshaft hydraulic control valves, controllers and so on. ECU stored the optimum valve timing parameter values. The reaction information such as the crankshaft position sensor, the air pressure sensor, the throttle position sensor, the water temperature sensor and the camshaft status sensor were gathered to ECU and calculated with the predetermined parameter value, and the correction parameters were calculated and the instructions were recovered to control the camshaft. In the hydraulic control valve, the control valve controls the position of the oil slot valve according to the ECU instruction, that is, the change of the hydraulic flow and the selection of the signal instructions, such as the early, the lag, and the retention, to the different oil channels of the VVT-i controller.

The VVT-i system is divided into two different parts of the controller, one is the device on the exhaust camshaft, called the blade VVT-i, and the TOYOTA PREVIA (reking) device. The other is installed on the intake camshaft, called spiral groove VVT-i, TOYOTA Lexus 400, 430 and other primary car device. The two structures are somewhat different, but their effects are not different.

The vane VVT-i controller consists of a tube that drives the intake camshaft and an impeller coupled with the exhaust camshaft. The oil pressure from the early or lag side oil channels is transferred to the exhaust camshaft, causing the VVT-i controller to rotate to drive the intake camshaft, which continues to change the intake timing. When the oil pressure is applied to the early side oil chamber, the intake camshaft is rotated along the early direction; when the oil pressure is applied to the case of the lag side oil chamber, the intake camshaft is rotated along the lag direction; when the engine is discontinued, the camshaft hydraulic control valve is in the largest lagging state.

The spiral groove VVT-i controller includes the gear driven by the timing belt, the inner gear with the rigid connection with the intake camshaft, and a movable piston between the inner and outer gears. The piston has a spiral spline on the surface. The piston moves along the axis and changes the phase of the inner and outer gear so that the valve timing is formed. Continue the change. When the oil pressure is applied to the left side of the piston, the piston is moved to the right. The intake camshaft will have a certain angle about the camshaft timing pulley due to the function of the spiral spline on the piston. When the oil pressure is applied to the stone side of the piston, forcing the piston to move left, the intake camshaft will be delayed at some angle. When the ideal timing of valve timing is achieved, the camshaft timing hydraulic control valve will close the oil passage, so that the pressure on both sides of the piston is balanced, and the piston stops moving.

Nowadays, advanced engines have "engine control module" (ECM), unified ignition, fuel radiation, emission control, defect detection and so on. The ECM of TOYOTA (model picture) VVT-i engine automatically searches for an optimal valve timing corresponding to the engine speed, intake, throttle position and cooling water temperature in various driving conditions, and controls the camshaft timing hydraulic control valve, and perceives the practical valve timing through the signals of each sensor, and then holds it again. The system can effectively improve the power and performance of the car, and increase the fuel consumption and exhaust emissions as much as possible.

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