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The two-stroke engine has a small displacement and high output, and therefore saves space when the engine is installed in a vehicle. Thus, the application of two-stroke engines to HEVs is a very effective means of reducing vehicle weight and securing engine space. On the other hand, the unfired element increases in the exhaust gas with a two-stroke engine because the air-fuel mixture is blown through to the exhaust system during the scavenging process inside the cylinder. Moreover, combustion becomes unstable due to the large amount of residual burnt gas in the cylinder. To solve these problems, we propose a two-stroke engine that has intake and exhaust valves that injects fuel directly into the cylinder. We describe the engine shape and the method that can provide high scavenging efficiency and stable combustion in such a two-stroke engine.

The authors developed a gasoline engine that combined direct injection and port fuel injection in order to improve fuel economy for motorcycles. Compared to passenger car engines, motorcycle engines generally have smaller displacement and operate at higher engine speed, so the bore and stroke are generally smaller than those of passenger cars. Therefore, the direct injection spray characteristics optimized for small bore and stroke were selected to reduce fuel adhesion to various parts of the combustion chamber wall. In addition, this engine employed the high tumble intake port that can both strengthen turbulence intensity and suppress the decrease in volumetric efficiency to a lower level. Also, stratification of air-fuel mixture and split injection were employed for reducing catalyst warm-up time and soot. The results showed that excellent fuel economy was achieved without sacrificing engine output performance while meeting emissions regulations.

In recent years, there has been a need to reduce CO2 emissions from internal combustion engines in order to achieve an energy-saving and low-carbon society. Against this backdrop, the authors have focused attention on Homogeneous Charge Compression Ignition (HCCI) combustion that achieves both high efficiency and clean emissions. With HCCI combustion, a premixed mixture of fuel and air is supplied to the cylinder and autoignited by piston compression to drive the engine. Autoignition makes it possible to operate the engine at a high compression ratio, enabling the HCCI combustion system to attain high efficiency. However, HCCI combustion also has some major unresolved issues. Two principal issues that can be cited are ignition timing control for igniting the mixture at the proper time and assurance of suitable combustion conditions following ignition to prevent incomplete combustion and knocking.

During high engine load, adequate engine cooling is necessary to prevent irregularly highly machine temperatures and spark knock that are issues affecting high power from being achieved. However, excessive cooling during low engine load or cooling locations that do not require cooling relatively exacerbates fuel consumption. Therefore, optimization of the engine cooling system is needed to achieve higher performance of motorcycle engines. First of all, in water-cooled engines, conventional water cooling system adjusts the cooling amount via flow channel switching with a thermostat, which is opened in high water temperature. However, with the bypass channel, water may bypass the radiator but still continues to circulate, thereby leading to loss arising from heat transfer from the cylinders.

We developed the motorcycles based on RIDEOLOGY (Ride + Ideology) concept. In the past, the “Ride” was studied by a sensory evaluation with actual driving. However, the recent progress in numerical analysis, there have been developed driving simulators. It allows more quantitative measurement in a sensory evaluation. Therefore, we also developed a riding simulator specialized for motorcycles. In order to develop such riding simulator, there are some technical challenges for motorcycles. First, we need to reproduce roll motion height of motorcycles. Compared to four-wheeled vehicles, motorcycles have a higher center of rotation. Second, we need to reproduce vehicle motion control by rider’s changing body position. A rider controls vehicle’s lean by shifting his center of gravity. Therefore, it is necessary to construct a measurement system of rider’s body position. Third, we need to improve senses of speed and reality.

When an electronically controlled fuel injection device is located at downstream in intake port (hereinafter defined as downstream injection, on the other hand, upstream injection is defined as that fuel injection device is located at upstream in intake port), the possibilities of an improvement in the engine startability, increase in maximum power, and decrease in THC during warming have been reported in visualizations of the intake port. In addition, the amount of wall adhesion decreased with downstream injection in previous paper [1]. In this paper, we examine the influence on the amount of wall adhesion due to the difference in injection position on fuel transport in the intake port during transient operation and the obtained exhaust A/F and the amount of exhaust gas emitted during transient operation are evaluated.

In this study on the motorcycle engine, we investigated the geometry of the newly developed intake port with an objective of improving the fuel consumption and the torque in practical range. Herein we present the results obtained. We believe that an effective measure for achieving the stated objective is to improve the combustion speed and combustion stability. To realize that, it is necessary to increase the turbulence during combustion and improve the homogeneity of air-fuel mixture. To investigate the feasible shape of the port, the CFD simulation (including fuel spray analysis) was performed and a geometry that improved the turbulent kinetic energy and mixture homogeneity at the time of ignition was selected. For confirming the combustion improvement effect achieved by tumble strengthening, an engine test was conducted with the same amount of intake air as that used in.

Owing to the recent developments in sensors with reduced size and weight, it is now possible to install sensors on a body of a motorcycle to monitor its behavior during running. The analysis of maneuverability and stability has been performed based on the data resulted from measurements by these sensors. The tire forces and moments is an important measurement item in maneuverability and stability studies. However, the tire forces and moments is difficult to measure directly, therefore, it is a common practice to measure the force and the moment acting on the center of the wheel. The measuring device is called a wheel forces and moments sensor, and it is widely used for cars. The development of a wheel forces and moments sensor for motorcycles has difficulty particular to motorcycles. First, motorcycles run with their bodies largely banked, which restricts positioning the sensors.

This paper describes an engine mount system that achieves reduced vibration on an industrial type utility vehicle. First the vibration level and direction of the inline three cylinder engine installed in the vehicle was analyzed and based on these results a mount layout that leads to a reduced level of vibration felt by the passengers was developed. Next, this was applied on an actual vehicle and spring characteristics were designed for each mount. The actual spring constants were set such that when considering the engine to be a rigid body, the resonance frequency thereof occurs at an engine speed lower than idle and in addition were set to ensure component strength relative to driving forces and inertial forces that act while the utility vehicle is being driven. Lastly, achievement of significant vibration reduction was confirmed on an actual vehicle showing that this engine mount system is effective at reducing vibration.

1 In the development of motorcycle engines, a strong feeling of power, an element of being fun to ride has continued strong demand. However, demand to meet environmental performance, a conflicting element, has increased dramatically in recent years and a breakthrough technology that achieves both environmental performance and a feeling of power is in demand. Here, the newly developed engine has greatly enhanced feeling of power while clearing stringent environmental restrictions through use of a centrifugal type supercharger. However, there were several problems that had to be resolved with regards to application of a supercharger to a motorcycle engine. In applying a supercharger to a motorcycle, a major problem is the best way to keep the engine size from increasing in size. The engine, which is the heaviest parts on a motorcycle greatly affects motorcycle maneuverability so it must be compact and the mass concentrated.

Engine sound is one of the most important factors when selecting a motorcycle from various models. Therefore, it is necessary to create an appealing sound in the rider's ears in addition to complying with noise regulations. In this paper, how we control intake sound is described through the study of a sports-type motorcycle with an inline 4 cylinder engine. To control intake sound, both intake pressure pulsations generated by the engine and acoustic transfer characteristics of the intake system are important. It is shown by unsteady-state one-dimensional computational fluid dynamics analysis that specifications of the exhaust system affect intake pressure pulsations across the valve overlap period. Therefore, to emphasize high order components of the engine revolutions in the intake sound, for example, modifying the layout of the exhaust muffler is effective.

In the expansion of composite material application, it is one of the most important subjects in assembly of aircraft structure how drilling of composite/metal stack should be processed in an efficient way. This paper will show the result of development of a drill bit for CFRP/Aluminum-alloy stack by Kawasaki Heavy Industries (KHI) and Sumitomo Electric Hardmetal (SEH). In order to improve workability and economic performance, the drill bit which enables drilling CFRP/Al-alloy stack: at 1 shot; from both directions; without air blow and coolant (just usual vacuuming); was required. A best mix drill bit which has smooth multi angles edge and pointed finishing edge was produced as a result of some trials. Developed drill bit achieved required performance and contributed to large cost reduction, labor hour saving, production speed increase and work environment improvement.

The purpose of this paper is to propose a control method to reduce acceleration shock in motorcycles. Reducing the acceleration shock is very important in improving driveability of motorcycles. Motorcycles equipped with manual transmission have some backlashes in the transmission, with large backlash especially in dog clutch portions. We have figured out that one of the main causes of the acceleration shock is the collision of the dogs at high relative angular velocity during acceleration. Also, our data analysis has revealed that there is a correlation between a peak value of the longitudinal body acceleration and the relative angular velocity at the moment of the dog collision. A simulation was undertaken to verify this phenomenon, and its results have made it clear that we need to decrease the relative angular velocity at the moment of the dog collision so as to reduce the acceleration shock.

In recent years, even motorcycles impose demands for engine power controls that are more flexible and precise. The Electronic Throttle Control (ETC) system is one of the methods that addresses this need. However, the most important issue facing the installation of the ETC system on the motorcycle is handling failures. To avoid this problem, we developed an ETC system for motorcycles that can properly effect engine power control in case of a failure. This ETC system contains in duplicate the major components to detect failures and switch to a failure mode properly. To effect control that is optimally suited to the type of failure, this system switches between three types of failure modes. These failure modes are designed to minimize risks in case of a failure and maximize the operational capability while the rider is on the way to have the motorcycle repaired.

Motorcycle configurations, such as CG (center of gravity) location, have come to be fixed to the current ones by trial and error since motorcycle was born. Generally motorcycles' ratio of CG height to wheelbase is relatively higher than four-wheel cars'. We have analyzed the optimal motorcycle CG location with relatively simple formulas, which we have derived to calculate the maximum acceleration with three performance limitations and calculate the maximum speed and the shortest time to run through a course. The results show that the calculated speed is significantly close to actual sport motorcycle's and that the optimal CG locations for various courses are bounded in a certain limited area which is near actual sport motorcycle's.

The aim of this study was to clarify the feasibility of applying ion current measurement to detect knock and misfire in lean-burn gas engines. The practical applicability was evaluated by conducting a basic test on a small engine and a test on a large engine. The tests were conducted by advancing the ignition timing to cause knocking, and an evaluation was carried out by comparing the knocking intensity detected by ion current signals and by cylinder pressure signals. By increasing the application voltage and including an amplifier circuit, the weak ion current signals were detected, which indicates that it should be possible to use ion current measurement to detect knock and misfire in lean-burn gas engines.

It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions.

Hydraulic fluid (HF) specifications for mobile construction equipment called JCMAS HK and HKB have been established by the Fuels and Lubricants Committee of Japan Construction Mechanization Association (JCMA). The specifications are designated by two viscosity categories of single grade and multigrade. Each category has ISO viscosity grade (VG) 32 and 46. The JCMAS HK oils are recommended for use in hydraulic systems designed at pressure up to 34.3MPa(5000psi) and to heat hydraulic fluid up to 100 °C. These oils also provide wear control, friction performance, oxidation and rust protection, seal swell control and filterability performance. Two piston pump test procedures were developed to evaluate lubricating performance of these oils under high pressure conditions. The JACMAS HKB oils are classified as environmentally friendly oils due to the additional requirement for biodegradability.

In line with the increase in the output of motorcycle engines, there has been an increase in incidents of the seizure between shift fork and gear because of the increased thrust force. We designed a test method that uses actual shift forks to simulate actual sliding conditions, then used that test method to evaluate the feature of the shift fork sliding and the different shift fork surface treatments. The shift fork slid against the gear not as surface contact but as tilted contact. We selected the candidates from the view that the surface treatment of the shift fork contact surface to give it higher seizure resistance when in tilted contact is required. We evaluated chromium nitride thin film, diamond-like carbon thin film, molybdenum sprayed coating, and sulphonitriding, and molybdenum sprayed coating exhibited the highest seizure resistance. The conformability plays a significant role in the sliding between the shift fork and the gear.

Motorcycle engines are required to have high output levels but low exhaust gas emission levels. Measuring the combustion condition proves useful for understanding the engine's operating condition. We developed a compact, high-performance combustion analyzer for measuring the combustion condition of motorcycle engines. This newly developed combustion analyzer is capable of analyzing the indicated mean effective pressure at each engine cycle at the engine speeds exceeding 10,000 rpm required of a high-performance motorcycle engine. Its compact size makes it easily applicable for onboard use, allowing measurement in any operating condition, including circuit travel, which has never been possible with conventional combustion analyzers. We used this new combustion analyzer to measure combustion condition not only on a chassis dynamo but also during circuit travel, when the motorcycle and engine are subjected to much harsher operating conditions.