Search Results

The need to improve fuel consumption by saving the weights of automobile parts is growing from the viewpoint of global warming mitigation. In the case of a throttle body for controlling the air flow volume into an engine, it is important to achieve a high dimensional accuracy of the valve-bore gap in the state of closed valve. In fact, most throttle bodies are made of precision-machined metal. Therefore, resin throttle bodies are drawing attention as a lightweight alternate. However, in comparison with metal throttle bodies, resin throttle bodies have two potential disadvantages that should be solved prior to productization. The first one is greater air leakage in the state of closed valve, and the second one is smaller heat conduction for unfreezing the valve in a frigid climate. We have developed an electronic resin throttle body that has overcome the above-mentioned disadvantages.

The hole diameter of injection nozzles in diesel engines has become smaller and the nozzle coking could potentially cause injection characteristics and emissions to deteriorate. In this research, engine tests with zinc-added fuels, deposit analyses, laboratory tests and numerical calculations were carried out to clarify the deposit formation mechanisms. In the initial phase of deposit formation, lower zinc carboxylate formed close to the nozzle hole outlet by reactions between zinc in the fuel and lower carboxylic acid in the combustion gas. In the subsequent growth phase, the main component changed to zinc carbonate close to nozzle hole inlet by reactions with CO₂ in the combustion gas. Metal components and combustion gases are essential elements in the composition of these deposits. One way of removing these deposits is to utilize cavitations inside the nozzle holes.

In recent years, the use of acrylic rubber has grown because of improved low temperature performance and heat resistance. Acrylicrubber is now being adopted as a replacementof NBR because it has good oil and heat resistance. One special feature inherent toacrylic rubber is that if it is in contact withmetal, upon heating, it will adhere to the metal. This adhesion would not be a problem with a fixed O-ring; however, in the case of an oilfilter (O/F) gasket which is regularly changed,the rubber which remains due to adhesion couldbe problematic for sealing. In the past, this problem was overcome by utilizing a coating, such as silicone, on the rubber surface, although this adds another step to the rubber process. Therefore, we developed a new method to prevent the adhesion of acrylic rubber by analyzing the mechanism by which the acrylic rubber adheres to a metal surface.

From the view of suppressing the global warming and environmental pollution, responding to the regulation of fuel consumption and exhaust gases along with lengthening the maintenance interval, are becoming more demanded. The development of a high-performance, long-life spark plug has become essential in response to these demands. While improved performance (high ignitability and low required voltage), the discharge part of the spark plug needs to be reduced in size. But, in the past this has been difficult because of the limitations of platinum alloys in terms of wear. Therefore, it has been quite difficult to achieve both smaller discharge parts and longer life. To dramatically improve wear resistance, we researched materials that are both resistant to oxidation and have a high melting point. This research resulted in our development of a new iridium alloy (Iridium-10wt%Rhodium).

This paper presents the oil circulation behavior in a CO2 climate control system operating at low evaporating temperature down to -32°C. The increase of oil circulation ratio (OCR) from 0 to 6 wt.% during steady state conditions degrades the coefficient of performance and cooling capacity by 15% and 8%, respectively. The pressure drop across the heat exchangers increases, especially in the gas cooler. In low temperature CO2 systems some fluctuations of oil and refrigerant flow rates were observed during cyclic operations when the system did not equip the oil separator, but was observed only at high oil charge when the system did equip the oil separator. These instabilities lead to a periodic compressor performance fluctuation, which caused system performance degradations. Therefore, the use of an oil separator is recommended for the low temperature operation if an ordinary metering valve is adopted as an expansion device without any special control strategy.

In gasoline direct injection engines it is important to optimize fuel spray characteristics, which strongly affect stratified combustion process. Spray simulation is anticipated as a tool for optimizing nozzle design, but conventional simulation, which is based on experimental data and/or empirical laws regarding spray boundary condition at the nozzle exit, cannot predict the effect of various nozzle geometries on spray characteristics. In Japan, a fan spray injected from a slit type nozzle has recently been adopted for gasoline direct injection engines. This paper proposes a computational model for the fan spray. The structure of two-phase flow inside the nozzle is numerically analyzed using the volume of fluid (VOF) method in a three-dimensional CFD code based on the nozzle geometry. The results of these analyses are applied to classical linear instability theory to calculate fuel droplet mean diameter after primary breakup.

In the field of automotive gasoline engines, new products aiming at greater fuel economy and cleaner exhaust gases are under development with the aim of preventing environmental destruction. Severe ignition environments such as lean combustion, stronger charge motion, and large quantities of EGR require ever greater combustion stability. In an effort to meet these requirements, an iridium plug has been developed that achieves high ignitability and long service life through reduction of its diameter, using a highly wear-resistant iridium alloy as the center electrode.(1)(2) Recently, direct injection engines have attracted attention. In stratified combustion, a feature of the direct injection engine, the introduction of rich air-fuel mixtures in the vicinity of the plug ignition region tends to cause carbon fouling. This necessitates plug carbon fouling resistance.

In preparation for compliance with California's SULEV standard and the Euro STAGE-4 standard, which will take effect in 2004 and 2005, respectively, a planar air fuel ratio (A/F) sensor has been developed. By using technology established for the planar oxygen sensor already in practical use, the A/F sensor realizes light-off time of 10 seconds, faster than any conventional A/F sensors. In addition, with its newly developed gas diffusion structure, the planar A/F sensor provides high detection accuracy for a wide A/F range, from rich to lean.

The automotive industry has increasingly been focusing its efforts on vehicle part weight reduction, with the aim of improving fuel efficiency as an environmental protection measure. As part of these efforts, the industry has actively been developing plastic pulleys to replace conventional steel pulleys. Of the various pulleys used in vehicles, the air conditioner (A/C) compressor pulley is exposed to the harshest working environment. We therefore investigated towards development of a plastic pulley for A/C compressor application. Required material properties were first identified on the basis of required product characteristic values. As a result, a phenolic resin material was developed that is superior in heat resistance one of the most important properties among those identified. Using the material, we succeeded in developing an A/C compressor plastic pulley, achieving approximately 50% weight reduction compared to conventional steel pulleys.

To develop injection nozzles and to improve the numerical simulation technology of fuel spray, a measuring technology to analyze the process of disintegration into droplets accurately is required. Performances required by a spray droplets measuring device are: “ability to measure in the combustion condition inside the engine cylinder”, “ability to measure the diameter of spray droplets in high-density fields”, “ability to measure the structure of spray droplets in 3D”, and an improved measuring accuracy of non-spherical droplets. These elements are required in order to analyze the spray droplets structure of gasoline direct injection engines. As a promising method to satisfy these requirements, the laser holography method has been already suggested. However, it has some drawbacks, such as a difficulty in measuring spray droplets in high-density fields and over a long analysis period.

Vehicles have been more required to save energy against the background of the tendency of ecology. As the result of improving efficiency of internal combustion engines and adoption of electric power train, heat loss from engine coolant, which is used to heat the cabin, decreases and consequently additional energy may be consumed to maintain thermal comfort in the passenger compartment in winter. This paper is concerned with the humidity control system that realizes reduction of ventilation heat loss by controlling recirculation rate of the HVAC system by using highly accurate humidity sensor to evaluate risk of fogging on the windshield. As the results of the control, fuel consumption of hybrid vehicles decreases and maximum range of electric vehicles increases.

Cogeneration (also combined heat and power, CHP) systems have become widely used in recent years for reasons such as efficient use of energy resources and CO₂ emissions reduction. As a power source in cogeneration, gas engines are widely used. Large gas engines have a different ignition system from those in medium-sized and small ones. To burn the fuel mixture to the cylinder wall, many large gas engines (2MW or more outputs) with wide cylinder-bore have a pre-chamber. Flame jets from the pre-chamber enable rapid combustion of super lean mixtures throughout the cylinder walls, achieving improved heat efficiency. In contrast, many medium-sized to small gas engines (less than 2 MW outputs) have a general and simple open-chamber, in which a flame kernel produced by the electric spark of a spark plug ignites the mixture in the combustion chamber.

Recently CO₂ emission regulation has become more stringent and higher thermal efficiency of the internal combustion engine is required. Spray-guided gasoline direct injection engine has promising potential for lower fuel consumption. The purpose of this study is to clarify the air-fuel mixture formation requirements and to investigate the spray specification of multi-hole nozzle injector for spray-guided stratified combustion.

An exhaust air fuel ratio sensor (A/F sensor), which is applied to a 1997 model year LEV vehicle was developed. This sensor enables the detection of the exhaust gas air fuel ratio, both lean and rich of stoichiometric. This A/F sensor was developed from a lean mixture sensor, which has a proportional output to the exhaust gas air fuel ratio in the lean region only, by widening the detection range to rich air fuel ratios to 12:1. This sensor is comprised of a zirconia solid electrolyte and a platinum electrode with a ceramic coating used as a diffusion layer. As a result of improvements, it has a effective air fuel ratio range from 12 to 18 as required for LEV vehicles with model based air fuel control systems. It has a fast light off, -- within 20 seconds -- to minimize exhaust hydrocarbon content. Further, it has fast response times, less than 200 msec., to improve air fuel ratio controllability.

The recent progress of electronic control systems in vehicles is remarkable as evidenced by the development of electronic fuel injection systems,(EFI), automatic transmission control systems, and anti-lock brake systems,(ABS). The number of actuators for the systems has been increasing. Consequently, a need has been identified for a reduction in volume and number of the system actuators for control purposes. A composite magnetic material has been developed with the aim of miniaturizing magnetic solenoid valves for actuator applications. A composite magnetic material is such that both ferromagnetic and paramagnetic sections coexist within a single material, and can contribute to optimization of the magnetic circuit of a solenoid valve. This paper describes the development of a composite magnetic material, and its resultant characteristics.

This paper will focus on fuel flow analysis in nozzles, in particular, in the injection hole, a key component of Fuel Injection Equipment(FIE). Optimum controlled flow in the hole improves flow efficiency and atomization. To meet the emission regulations which will be introduced from the end of '90's to the 21st century, Diesel Engines require FIE to produce higher injection pressure which creates better atomization and higher utilization of air. But higher injection pressure results in increased pump driving torque, larger pump size and higher cost. We have studied the improvement in fuel flow characteristics of the nozzle, using an enlarged flow model and the theoretical analysis method. As a result, we have found that the cavitation, which occurs at the inlet of the hole, is affected by the configuration of the sac hole and injection hole. And, furthermore, the cavitation has a direct effect on the contraction and its recovery flow.

For improving DI diesel engine performance, such as lower nitrogen oxidant (NOx), particulate molecular (PM) emission and higher output, etc., atomization of the fuel spray plays an important role. In order to obtain better fuel atomization without increasing the fuel injection pressure, increasing the flow velocity at the injection nozzle spray holes is regarded as an effective way. Through experiments, enlarging the chamfer at the spray hole inlet proved to be the most effective and suitable method for establishing high flow velocity injection nozzles. We have compared the high flow velocity injection nozzles with conventional nozzles in terms of injection characteristics and fuel spray characteristics, and confirmed the improved fuel spray atomization with the high flow velocity injection nozzles. Finally the high flow velocity injection nozzles were tested on a medium duty class, natural aspirated DI diesel engine.

The required fuel spray characteristics, controlled fuel pressure, and injector installation configurations in gasoline direct injection differ among manufacturers. As a result, there are currently a variety of injector types and configurations being proposed by many different component manufacturers. This paper proposes a new injector design that both enables high fuel pressure operation by utilizing a highly efficient electromagnetic valve using a composite magnetic material for the injector actuator, and increases manufacturing productivity while also meeting the requirements of each engine manufacturer by simplifying the construction of the injector.

A new mechanism DL-pulley has been developed to improve the riding quality by avoiding ON/OFF shock caused by turning on/off of the conventional magnetic clutch (MagCl) for the automotive air conditioner (A/C) compressor. DL-pulley was aimed for Dampening compressor torque fluctuation and Limiting torque transfer when the A/C compressor is seized. For its development, high performance sliding material was the key to realize the sliding mechanism of the torque limiting function. Specifically, the friction coefficient of sliding material must be stable in any environment that the automobile is used. This paper describes the development of new structure DL-pulley with sliding mechanism and new sliding material. In the development process, the relationship between stability of friction coefficient and adhesion has been experimentally clarified.

A direct injection spark ignition (DISI) gasoline engine with a new stratified charge combustion concept has been launched on the Japanese domestic market. This new concept consists of two components. First, a thin fan-shaped spray from a slit nozzle enables wide spray dispersion, moderate spray penetration and a fine atomization. Second, a shell-shaped piston cavity allows better mixture formation, however avoiding distinct charge motions (such as tumble or swirl). Simple intake port geometry increases the full load performance. The combustion concept, at the same time allows stratified charge to be used at higher load and at higher engine speeds and improves the homogeneous charge combustion. A new 3L in-line 6 gasoline engine with this combustion concept showed 20% better fuel economy than a 3L port fuel injection (PFI) engine (λ=1 feed back system) under the Japanese 10-15 mode.