Mitsuhiro Soejima

Piston ring friction in internal combustion engines

Abstract The tribological phenomena of the sliding surfaces between piston rings and cylinder liners may be among the most complex in internal combustion engines, and could become even more severe with an increase of the engine power. The friction between the piston rings and the cylinder liner significantly contributes to the mechanical power losses of the engine. The calculations of friction force for a piston ring pack are conducted based on hydrodynamic lubrication theory. The oil starvation within the piston ring pack is considered in the calculation of oil-film thickness. The friction characteristics of piston rings are evaluated with the frictional mean effective pressure. The instantaneous friction force of a piston assembly under firing engine conditions is measured by an improved floating liner method in which the cylinder liner is supported by means of hydrostatic bearings. The friction characteristics are made clear by analyses and experiments.

Studies on friction and wear characteristics of cam and follower: influences of soot contamination in engine oil

Abstract In order to clarify the friction and wear mechanism of the contact between cam and follower in the valve train incorporated in an EGR system, an experimental investigation was performed with a cam-follower test rig. A fresh CD-class SAE10W-30 multigrade oil and its deteriorated versions with different contaminants were tested. Changes in friction force and amount of wear were measured during the course of the tests. The influence of the soot in the deteriorated oil was examined by mixing the exhaust gas soot blended with the dispersant, ZnDTP and MoDTC additives. Results are summarized as follows. (1) The friction fluctuated and gradually increased with the lapse of time in case of contaminated oils with the soot. (2) Under the coexistence of ZnDTP and MoDTC, however, the friction gradually decreased in spite of existence of soot. (3) The soot dispersed in the oil increased wear rate and reduced the anti-wear effect of the ZnDTP. (4) The smallest wear rate was observed because the anti-wear effect was maintained owing to the MoDTC.

Improvement of Lubrication for Cam and Follower

In order to improve the lubrication between cam and follower of internal combustion engines, the influences of materials or oil viscosity and additives on the friction and scuffing characteristics have been examined with a test rig by increasing the contact load at a constant revolution speed. Also the effects of oil supply through the oil-hole of the camshaft on the reduction of friction and the prevention of scuffing have been examined. From the experiments the following results were made obvious. Firstly, the effect of the material on the reduction of friction or the prevention of scuffing is dependent upon the combination of cam and follower materials. The follower material of hard sintered metal or silicon nitride ceramics is superior in both effects to chilled cast iron when mating with the cam material of hardened S48C steel cam. Secondly, as the viscosity of base-oil becomes low, the friction increases or decreases depending on oil additives, but the scuffing resistance always becomes small. The o...

Studies on the measuring method of the total friction loss of internal combustion engines

Abstract In the present study a new test method is investigated to measure the total friction loss of engines over the whole range of speed and load. It is based on the idea that the friction loss close to the true one of fired and braked engines can be measured by the run-out method because the temperature mainly influencing the friction loss is almost stable for the short run-out test duration. From the test results and the comparison with those measured by other conventional test methods, the following becomes evident: 1. (1) The total friction mean effective pressure slightly increases as the revolution speed becomes high, but it decreases as either the load or the cooling water temperature becomes high. 2. (2) The total friction mean effective pressure measured by the present method is smaller than that measured by the run-out method, the motoring method or Willans-line method, but it is larger than that measured by the indicated pressure diagram method.

INFLUENCE OF CAM SURFACE FINISH AND ROUGHNESS ON FRICTIONAL POWER LOSS IN VALVE TRAINS WITH ROLLER TAPPETS

In order to reduce the frictional power loss and the wear in the valve train of internal combustion engines, the cam follower mechanism tends to be shifted from the sliding contact to the rolling contact such as a roller follower [1–5]. Design criteria for the valve train with roller tappets have been investigated by making obvious the effect of the cam lobe surface finish and its surface roughness on reduction of the friction loss. In particular the friction loss in the case of a cam lobe finished by shot-peening was compared with that of one finished by grinding. Also the influence of surface roughness on the friction loss was examined.Copyright

On the Load Carrying Capacity of Crosshead-pin Bearing with Eccentric Journal

This paper refers to a new investigation to improve the load carrying capacity of the crossheadpin bearing in a 2-stroke cycle diesel engine. By using a specially equipped journal with a pair of eccentric sections the oscillating bearing can be forced to move up and down just like a piston-pin bearing in a 4-stroke cycle engine. Such a squeeze motion of the oil-film between a journal and a bearing has an ability to increase the oil-film thickness. Then, from the theoretical analyses on effects of various bearing shapes the following features and optimums for design became evident.(1) According to the change of an oscillating direction each sliding face is alternatively unloaded and the oil-pumping ability is generated.(2) In order to keep the oil-film pressure lower than the elastic flow pressure of a bearing metal and make the oil-film thickness as large as possible the next designing points are needed.(i) The ratio of a radial clearance to the radius is about 5 × 10-4 .(ii) The eccentricity between journals is as large as the radial clearance.(iii) The width ratio of a main journal to the whole bearing is about 0.7.