Search Results

The technology to estimate engine load using the amplitude of crankshaft angular velocity variation during a cycle, which is referred to as “Δω (delta omega)”, in a four-stroke single-cylinder gasoline engine has been established in our former studies. This study was aimed to apply this technology to the spark advance control system for small motorcycles. The cyclic variation of the Δω signal, which affects engine load detection accuracy, was a crucial issue when developing the system. To solve this issue, filtering functions that can cope with various running conditions were incorporated into the computation process that estimates engine loads from Δω signals. In addition, the system made it possible to classify engine load into two levels without a throttle sensor currently used. We have thus successfully developed the new spark advance system that is controlled in accordance with the engine speed and load.

This paper describes a vision-based vehicle detection system for a blind spot warning function. This detection system has been designed to provide ample performance as a driving safety support system, while streamlining the image processing algorithm so that it can be processed using the computational power of an existing ECU. The procedure used by the system to detect a vehicle in a blind spot is as follows. The system consists of four functional components: obstacle detection, velocity estimation, vertical edge detection, and final classification. In obstacle detection, a predicted image is generated under the assumption that the road surface is a perfectly flat plane, and then an object is detected based on a histogram that is created by comparing the predicted image and an actually observed image. The velocity of the object is estimated by tracking the histogram over time, assuming that both the object and the host vehicle are traveling in the same direction.

We have successfully developed a system to estimate Indicated Mean Effective Pressure (hereafter "IMEP") by detecting the crankshaft angular velocity variation during one cycle of a four-stroke single-cylinder gasoline engine. The system has been commercially applied to the spark-ignition timing control system for small-displacement motorcycle engines. The determined amplitude of crankshaft angular velocity variation during one cycle is defined as "delta omega (Δω)." The relationship between Δω and IMEP has been experimentally examined using engine unit bench tests and actual motorcycles. From the experimental results, it was confirmed that Δω represents IMEP. This paper discusses the experimental study on the estimation of IMEP using crankshaft angular velocity variation.

Aiming for improving fuel economy of vehicles, a new two-stroke gasoline engine utilizing stratified-charge auto-ignition has been designed and tested. The engine concept was to switch the combustion mode according to the engine operating load and speed, i.e., homogeneous-charge spark-ignition for the high-load range, homogeneous-charge auto-ignition for the mid- to low-load range, stratified-charge auto-ignition for the low-load low-speed range, and stratified-charge spark-ignition for idling. Using this engine concept, an experimental two-stroke engine was successfully operated free of irregular combustion throughout the range of operating loads. For small motorcycle applications, a great improvement in fuel economy and exhaust emissions was estimated from the experimental data.

The auto-ignition attracts researchers as an ultimate combustion method that could simultaneously reduce fuel consumption and NOx emissions. The authors have studied auto-ignition combustion in the two-stroke gasoline engines aiming at vehicle engine applications. However, our attempts were in an impasse with the onset of irregular combustion in the lower speed and the extremely lower load range. As a solution for this problem, this paper proposes a new auto-ignition concept, i.e. Stratified Charge Auto-Ignition (SCAI), which focuses on the thermal distribution and mixture formation in the combustion chamber. Visualization of the direct injection spray formation was conducted first, and then a combustion chamber design was determined by using a CFD simulation, so as to form a mixture at the hottest spot in the combustion chamber.

This study presents the possibility of realizing better thermal efficiency in a spark-ignition engine with over-expansion cycle. The test engine with the displacement volume of 649cc was used together with four kinds of expansion ratios (geometric compression ratio) from 10 to 25, and four sets of intake valve closure timings from 0 to 110 ° C.A. ABDC. In previous studies, the indicated thermal efficiency reached 48% However, there was a problem that the maximum output was reduced to almost half compared with the conventional engine, since the effective displacement volume was decreased with decreasing the substantial compression ratio (εc). As a method of solving this problem, supercharging was applied by using compressed air supplied from an external compressor.

From the environmental conscious point of view, subjects of conventional two-stroke engines will be irregular combustion and new mixture shortcut. Concerning for the irregular combustion, our previous papers has however proven that timing controlled auto-ignition, namely Activated Radical (AR) Combustion, was an effective solution. Meanwhile for the new mixture shortcut, no solution is mentioned in those papers. This time, a low pressure pneumatic direct fuel injection engine has been experimented. This engine is however intended to perform homogeneous combustion, the A R Combustion solves irregular combustion effectively in the light load range. Fuel is pneumatically injected into the cylinder by using accumulated in-cylinder gas pressure, after the scavenging process performed by the air only. A mechanically driven rotary type injector is installed in the cylinder wall.

Variable-valve-actuation mechanism is considered to be one of the most suitable solutions to realize the compatibility between higher power output and performances in the practical speed range. A new variable-valve-actuation mechanism named “Shuttle Cam” was designed and studied. In this mechanism which was applied to a conventional motorcycle engine with rocker arms and gear-train-driven valve system, the cam gears move along the idler gear. And cam shafts simultaneously slide along the rocker-arm slipper surfaces which are concentric with the idler gear. Consequently valve lift varies continuously in accordance with the alteration in the rocker-arm lever ratio and the cam phasing changes simultaneously in accordance with the cam gear rotation. Result of the experiments has confirmed that the mechanism functions accurately even at high speeds up to 10,000 rpm and some improvements were achieved in power output, fuel consumption, idling quality, and exhaust-noise level.

The centrifugal-weight-type V-belt automatic transmission is widely used for the light engines of scooters and agricultural machines, etc. for being compact, efficient and comparatively cheap. The operating section of this centrifugal weight, which contains the metal weight coated with thermoplastic resins in its movable pulley, is lubricated with grease to provide stability and life (reliability) for its operation. However, the grease filling work not only requires a substantial number of man-hours but also various seal parts to prevent, during running, the grease from being splashed about by the centrifugal force and dust particles from intruding. To overcome these restrictions, research has been conducted on how to free the centrifugal weight from the grease by experimenting with various self-lubricant resin compositions as the coating materials for this metal weight.