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Heat Treatment by Induction
Published in Valery Rudnev, Don Loveless, Raymond L. Cook, Handbook of Induction Heating, 2017
Valery Rudnev, Don Loveless, Raymond L. Cook
Camshafts are used in engines controlling the timing and the speed of the opening and closing of the intake and exhaust valves. A camshaft consists of several sets of bearings and cam lobes that are irregular and eccentrically shaped components. As an example, Figure 4.205a shows typical camshafts used in automobiles and truck engines. The number of cam lobes, their size, profile, positioning, and orientation are dependent on the camshaft type and engine specifics (Figure 4.205b). Figure 4.206 illustrates common terms associated with the functionality of a typical camshaft lobe.
Engine systems
Published in Tom Denton, Automobile Mechanical and Electrical Systems, 2018
The camshaft, on most modern engines, is mounted in bearings formed into the cylinder head via an in-line boring process (Fig. 2.97). The camshaft is forged from steel or cast iron and the bearings and cam surfaces are a smooth, machined finish. The camshaft has cam lobes for each valve and to ensure the correct sequence of valve timing, the camshaft is timed and synchronized with the crankshaft position.
Experimental analysis of the volumetric and thermal efficiency performance of a novel direct piezo-acting CVVT mechanism
Published in International Journal of Green Energy, 2023
A. Sürmen, M.I Karamangil, A Avcı, B. Dirim, F. Işıklı, M. Tekin, N. Türköz
Variable valve timing (VVT) can be applied using various techniques. It is possible to find the valve systems with and without a cam. One of the methods applied to valve systems with a cam is to rotate the cam for a certain phase shift. In other words, it is to advance or retard the opening and closing times of the cam by rigid rotation of the camshaft in the relevant direction without changing the amount of valve lift and the time it remains open (Moriya et al. (1996); Schäfer and Balko (2007)). Another application for the system with cams is to divide the entire speed band of the engine into two or three, and gradually use one of the three adjacent cams with different profiles for each speed range. In this method, also benefited from changing the valve lift. This method has been used under trade names such as Honda VTEC, Nissan Neo VVL, BMW Valvetronic, Mitsubishi Mivec (Fukuo et al. 1997; Hatano et al. 1993; Maekawa, Ohsawa, and Akasaka 1989). In these studies, 13%, 21%, and 18% power increases were obtained, respectively, using the aforementioned mechanisms.
Operational feasibility of a spark ignition engine which is subjected to VTEC management strategy
Published in Australian Journal of Mechanical Engineering, 2020
Lucky Anetor, Edward E. Osakue
Research and practical engine operations have shown that various variable valve lift and timing (VVT) technologies can improve idle speed stability, low speed stability, emissions, power and fuel economy of the engine. In view of this, a lot of automobile manufacturers have started incorporating this technology into their products. Some of the automobile companies that have commercialised and incorporated the variable valve lift and timing technology in various forms are Toyota (i-VTEC), BMW (Vanos), Ford (VCT), Delphi (VCP), Nissan (CVVT), Hyundai (VVT) and Kia (CVVT). The mechanics of these variable valve lift and timing systems is based on camshaft phase modulation which adjusts the valve timing by changing the relative phase of the cam shaft and crankshaft. It is worth mentioning that this method of implementing the variable valve lift and timing can only adjust the valve timing over a certain/restricted range of angles. However, when compared with the traditional valve-cam systems, it does improve engine emissions and performance significantly.