Key Technical Characteristics of the VVT System
The ultimate goal of the VVT system is to achieve real-time adjustment and control of camshaft timing. Like other control systems, the most critical technical features are as follows:
(1) Response speed: that is, the adjustment speed of the VVT system, which can adjust the angle at which the camshaft rotates per unit time. Among them, the structural parameters of the phaser itself have the greatest influence on the index, and can be measured by introducing a torque-to-pressure ratio parameter, which is only related to the phaser structure. In addition, the installation position of the OCV in the oil passage also has a large influence on the response speed of the VVT system.
(2) Control accuracy: that is, the degree of conformity between the actual phase angle of the VVT system and the target angle set by the ECU. In the VVT system functional test, it is usually characterized by a follow-up curve.
(3) Control stability: that is, the VVT system will interfere with the system when the external conditions change (such as engine oil pressure, temperature, etc.). Besides, whether the closed-loop control system can work stably is generally measured by the amount of adjustment angle fluctuation at a certain control position.
In short, the above three indicators are closely related to the phaser, the structure as well as performance of the OCV itself, the system installation method, and the control algorithm.
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