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2 Journal of KONES

2 2016

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The analysis of friction in the bearing of rocker arms

Kubiak P., Siczek K., Siczek K.

Journal of KONES

2016

Vol. 23, No. 2

231--238

Rocker arms are important parts in many valve train systems of combustion engines. They are responsible for translating the profile of the camshaft into motion for opening and closing the inlet and outlet valves. The design, materials and lash adjuster elements for existing rocker arms were discussed. The modified rocker arm bearing was designed for the investigated Benzer 50cc four-stroke engine. The modification for the analysed engine includes the change of bearing for both inlet and outlet rocker arms. The original rocker arm bearing is of the slide type and mates with the axis fixed via the pin to the cylinder head. The modified bearing can be of the needle roller or the slide type and include two bearings mating with the axis, to which the rocker arm is fixed. The aim of the presented study was to obtain the courses of pressure in cylinder against the crankshaft angle, which was needed to calculate the loading force of rocker arm bearing and then friction torque therein. The models of valve train assembly and of the bearing operating under boundary friction were elaborated. Resulted values of the friction torque in rocker arm bearing for different operating conditions of engine were presented in the paper.

Development of a simplified method for measuring engine motoring friction and its application to valve train friction measurement

Nakashima K., Kato T., Goto K., Murakami Y.

Journal of KONES

2016

Vol. 23, No. 2

261--267

We developed a simpler and less expensive method for measuring friction. Our equipment floats the double-end shaft motor by supporting both sides of the motor shaft with bearings, allowing the stator within the motor case to swing on the rotor with the shaft. Two arms were installed in the motor case; one is attached to a load meter; the other to a balance weight. The motor shaft is connected to the engine shaft, and when the engine is operated by the motor, torque is exerted on the stator with the motor case in the direction opposite to the motor shaft rotation, with engine friction acting as the reaction force. Torque is calculated by multiplying the arm length by the load as measured by the load meter in the arm. As an application of our new motoring friction test method, we measured valve train friction. The cylinder head of a single cylinder gasoline engine was clamped on a test bed, and its camshaft was connected to our friction measuring equipment. Utilizing various follower configurations of the rocker arms, we investigated the friction loss between the rocker arms and the cam. We thus clarified the effect of the valve-opening period and the valve lift on friction loss under various camshaft rotation speeds, and understood the lubricating conditions between the rocker arms and the cam.