Intake system by the air cleaner, the air flow meter, intake air pressure sensor, the throttle body, the additional air valve, the idle speed control valve, the resonant cavity, the power
chamber, the intake manifold, etc.. During engine operation, the driver through the accelerator pedal to manipulate the degree of opening of the throttle valve, in order to change the intake air
quantity, the control operation of the engine. The dust and other impurities was filtered out, the air entering the engine through the air cleaner through the air flow meter along the throttle
channel to enter the power chamber, and then allocated to each cylinder via an intake manifold; car idling operation of the engine is cold, the portion additional parts of air through the air
valve or bypass the throttle idle control valve into the cylinder.
Classification of contemporary automotive intake system variable intake system. Variable intake system mainly consists of VVT (variable valve timing), CVVT (continuously variable valve timing), VVT-i (variable timing electronic), i-VTEC (electronic variable valve lift) these four species. Application models four main variable intake system application models are:
Beijing Hyundai Elantra: VVT (variable valve timing)
Dongfeng Yueda Kia Cerato: CVVT (continuously variable valve timing)
Toyota cars, such as the Corolla, Corolla VVT-i (electronic variable timing)
Honda cars, for example, Accord, CRV, Civic i-VTEC (electronic variable valve lift)
Variable Valve Technology
Variable valve technology, from the category points, including variable valve timing and variable valve stroke two categories.
Let me first explain the the ordinary engine valve train, and we all know valve driven by the engine crankshaft via camshaft the valve valve timing depends on the corner of the camshaft. When the engine is running, we need to get more fresh air into the combustion chamber, so that the exhaust gas discharge combustion chamber, the best solution is to make the intake valve opened prematurely, the exhaust valve postponed Close. Thus, between the intake stroke and the exhaust stroke, occurs simultaneously open the case of the intake valve and exhaust valve, the overlap between this intake and exhaust valves is known as valve superimposed angle. In an ordinary engine, the intake valve and the exhaust valve opening and closing time is fixed, valve superimposition angle is also fixed, is obtained according to the test valve timing during engine operation is can not be changed. However, the level of the engine speed, the intake and exhaust flow and the combustion process within the cylinder is influential. High speed, the intake air flow rate is high, the inertial energy, and therefore the intake valve earlier opened and later closed so that the fresh gas is smoothly charged into the cylinder as much as possible the number of mixed gas or air. Whereas in the intake flow at lower engine speeds, low-speed, inertial energy flow is also small, if the intake valve open prematurely, since the piston is upstream exhaust, it is easy to fresh air out of the cylinder, so that the intake instead The less unstable engine work. Therefore, without any kind of fixed valve superimposed angle setting allows the engine at high and low speed can be the perfect output If no variable valve timing technology, the engine can only be based on the needs of its matching models, select optimal fixed the valve superimposed angle. For example, the engine of the car generally use of a smaller valve superimposed angle in order to facilitate the high speed when the power output. Ordinary civilian car superimposed moderate valve angle, both high-speed and low-speed is the power output, but will lose a lot of power at low speed and high speed. Variable valve timing technology, through technical means, valve the superposition angle variable to solve this contradiction.
The early 1990s, Japan's Honda introduced a valve timing can be changed, and can change the law of motion of the valve variable valve timing - lift control mechanism, is the world's first simultaneous control of valve opening and closing The two different situations such as the time and lift valve control system. Is now familiar VTEC bodies: Average engine valves per cylinder group only is driven by a set of cams, VTEC system of the engine there is in low-speed and high-speed using two sets of different valve driving cam, and through automatic electronic control system manipulation, the conversion automatically. VTEC system, to ensure that the requirements of low-speed and high-speed different with the gas phase and into the gas engine, the engine power, economy and low emissions are to achieve a unified and excellent state in terms of the operation of any rate. It should be noted that, while engine with variable valve timing technology to obtain these benefits, does not have any negative impact, in other words, is not put forward higher requirements for the engine work intensity.
Of VTEC design seems like two different camshaft, one for low speed, and one for high speed, but VTEC engine difference is that the thus two different camshaft design in a camshaft on.
Honda engine intake camshaft, in addition to the original control two valves cam (main cam and the second cam) and a pair of rocker (main rocker and sub-rocker), also increased in the middle of a high the cam and the corresponding rocker arm (intermediate rocker) inside the three rocker is provided with movement of the smaller piston by the hydraulic control.
Low engine speed, the smaller piston in its original position, the three rocker separation, the main cam and the sub-cam, respectively, to promote the main rocker arm and the sub-rocker arm, to control two of the intake valve opening and closing, the less the amount of valve lift, like an ordinary case engine.
Although the intermediate cam promoting intermediate rocker without its control, but has been separated due to the rocker arm between the other two rocker arms, and so it will not affect the state of the valve opening and closing. Engine to achieve a set of high-speed, computer instruction solenoid valve to start the hydraulic system, to promote the rocker within small piston, so that of three rocker locks into one, driven together by the middle cam c than the other, because the middle cam cam are higher, the lift, the intake valve open time, lift is also increases. When the engine speed is reduced to a set low speed, a hydraulic pressure within the rocker arm is also decreased, and the piston is returned in the return spring under the action in situ, the three rocker arms separately.
Entire VTEC system is controlled by the electronic engine control unit (ECU), the ECU receives the engine sensors (including speed, intake pressure, speed, temperature, etc.) the parameters and processing, and outputs a corresponding control signal, through a solenoid valve to adjust the rocker piston hydraulic system, so that at different rotation speed, the engine operating conditions affecting the degree of opening of the intake valve is controlled by a different cam and time.
Honda's VTEC engine technology has been around for a decade or so, the facts also prove that this design is reliable. It can improve the performance of the engine at various speeds, whether it is the low speed fuel economy and running smoothly or high speed under acceleration. It can be said that in the electronic control the valve mechanism instead of the traditional cam mechanism before Honda's VTEC technology at present can be said is a good method.