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In the automobile industries, weight reduction has been investigated to improve fuel efficiency together with reduction of CO2 emission. In such circumstance, it becomes necessity to make an electric power steering (EPS) more compact and lightweight. In this study, we aimed to have a smaller and lighter EPS gear size by focusing on an impact load caused at steering end. In order to increase the shock absorption energy without increase of stopper bush size, we propose new theory of impact energy absorption by not only spring function but also friction, and a new stopper bush was designed on the basis of the theory. The profile of the new stopper bush is cylinder form with wedge-shaped grooves, and when the new stopper bush is compressed by the end of rack and the gear housing at steering end, it enables to expand the external diameter and produce friction. In this study, we considered the durability in the proposed profile.

This paper will discuss the stress reduction of the worm wheel for an electric power steering (EPS) system. The research discussed in this paper focused on the worm wheel, the EPS component that determines the maximum diameter of the system. If the stress of the worm wheel could be reduced without increasing in size, it would be possible to reduce the size of the worm wheel and EPS system. In order to reduce the stress of the worm wheel, the conventional design method has extended the line-of-action toward outside of the worm wheel to increase the contact ratio of the gears and these method lead to an increase in the outer diameter. In order to address this issue, past research proposes the basic concept to extend line-of-action toward the inside of the worm wheel. And this new meshing theory was named MUB (Meshing Under Base-circle) theory. In this paper, characteristics of meshing of the gear formed by MUB theory are determined in more detail.

This project studied a DC brushless motor for an EPS system that would not cause control performance to decline even when the vehicle was operated with a low steering angle at high vehicle speeds. First, a target for cogging torque was established to ensure that control performance did not decline at high vehicle speed. To set the target, a lane changing simulation using a human-vehicle system model was conducted. A brushless motor structure was designed to achieve this target value, and the magnitude of cogging torque for this design was predicted using FEM analysis. The issues were found when a prototype of this motor was constructed and the knowledge was obtained during the process of analysis were discussed, in addition the design guidelines were proposed to solve these issues. A new prototype brushless motor was constructed on the basis of these design guidelines, and tests showed it to possess suitable cogging torque for an EPS system.

This paper discusses the size reduction and performance enhancement for worm gears of a pinion assist type EPS system. In conjunction with recent trends in vehicles getting larger and tires gaining larger footprints, the EPS motor assist torque has increased considerably. This leads to the issue involving enlargement of the external diameter of the worm gear and the worm wheel gear, which are reduction gears that boost motor torque. In order to address this issue, the authors examined single-threaded worm gears, and fundamental factors that cause the enlargement of the worm gear external diameter from the standpoint of the working of the gear. After the details are explained, a new worm gear that addressed this issue is proposed. This paper describes this worm gear, tooth form shape, and its construction. Moreover, this worm gear was built, installed into an EPS system, and tested.

In this research, we investigate the methods for controlling moment of rotational inertia in the electric power steering (EPS) system. We first look at the effects of moment of rotational inertia on conventional EPS systems. Methods for evaluating those effects and countermeasures for controlling the moment of inertia are proposed. After explaining the evaluation method, we describe a design procedure for filters for controlling the moment of rotational inertia by H∞ control method. We also describe the formation of low-order systems of filters obtained, in addition to control block diagrams using filters in the system and their stabilization. Finally, we have equipped a vehicle with this controlled EPS system. The evaluation results have confirmed that the moment of rotational inertia can be satisfactorily controlled.

In recent years, increasing attention has been paid to a non-throttling technology that is expected to contribute to a reduction in fuel consumption. This paper describes a study on the technology behind the electromagnetic variable valve timing mechanism (electromagnetic valve mechanism). The electromagnetic valve mechanism ensures highly efficient and stable valve opening/closing control. The detailed information and findings will be described in the main body. In addition, the advantages of the mechanism's application to a homogeneous charge compression ignition engine (HCCI engine) will also be described.

A change of vehicle handling characteristics due to increase of lateral acceleration as well as effects of the steering gain adaptation of VGS to that was analyzed by quasi-steady-state analysis to find out a basic strategy for the adaptive gain scheduling in the VGS. A study using a simple fixed base type of simulator showed the upper and lower limit of the appropriate gain of the steering system. A computer simulation study on lane-change response of the driver-vehicle-system gave us a view that there exists a suitable gain setting for the VGS from a view point of driver-vehicle-system stability.

Steering gear ratios in existing automobiles are made almost constant. Therefore, at low speed, the larger steering wheel angle needed increases drivers' physical workload especially in the case of a maneuver with large directional angle change such as parking, and may impair quickness in response necessary for a sudden lane change maneuver such as obstacle avoidance at low speed. On the contrary, at high speed, a relatively small steering angle input can generate comparatively large vehicle lateral acceleration, and this larger overall steering gain may necessitate drivers' more meticulous steering operation which can produce increased mental workload. In addition, for understeer vehicle, steering gain tends to decrease as lateral acceleration increases because of saturation in lateral force of the tire, and this may also reduce maneuverability in directional change, especially during cornering.

The design of engine cylinders must satisfy two conflicting requirements, good cooling performance and ease of manufacture. A cooling system was designed to permit the circulation of engine lubricating oil as a coolant at high speed through grooves provided on the external periphery of the cylinder liner. Testing in an actual operating engine confirmed that this cooling system design not only provides better heat transfer and higher cooling performance but also simplifies the manufacturing of the cylinder since external cooling fins are not required. In this paper, we will discuss the cylinder cooling effect of the new cylinder cooling system, referring mainly to the test results of a single-cylinder motorcycle engine with lubricating oil from the crankcase used as the coolant.

Motorcycles, as an international market product, must satisfy increasingly diverse user needs. These demands lead to various improvements being added and new systems and mechanisms being developed in an effort to arrive at an ideal product concept. Since the two-cycle engine offers particular advantages in combining light weight and compact size with a high output level, attention is focused on this type of engine for use in motorcross bikes and compact sports models. One drawback of the two-cycle engine, however, is that the output characteristic is sharply divided into low-speed and high-speed types. In order to overcome this disadvantage, motorcycle manufacturers are developing exhaust devices which will boost low-speed torque without sacrificing high-speed output. This presentation will describe some of the development and applications concerning exhaust devices already underway at Suzuki.

A new electric power steering (EPS) was developed which uses an electric motor to provide assistance. It is a system combinning the latest in power electronics and high power motor technologies. The development was aimed at enhancing the existing hydraulic power steering's energy efficiency, driver comfort as well as increasing active stability. This paper describies the overall concept of EPS and outlines the components and control strategies using electronics. The EPS was tested on a front wheel drive vehicle weighing 1000kg in front axle load. The results showed a 5.5% improvement in fuel economy. The EPS has also achieved returnability that gives the driver more moderate feelings matching the vehicle in action as well as the active stability control strategy for high speed driving.