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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.

A new nitriding technology and material technology have been developed to increase the strength of microalloyed gears. The developed nitriding technology makes it possible to freely select the phase composition of the nitride compound layer by controlling the treatment atmosphere. The treatment environment is controlled to exclude sources of supply of [C], and H2 is applied as the carrier gas. This has made it possible to control the forward reaction that decomposes NH3, helping to enable the stable precipitation of γ′-phase, which offers excellent peeling resistance. A material optimized for the new nitriding technology was also developed. The new material is a low-carbon alloy steel that makes it possible to minimize the difference in hardness between the compound layer and the substrate directly below it, and is resistant to decline in internal hardness due to aging precipitation in the temperature range used in the nitriding treatment.

A new motor has been developed that combines the goals of greater compactness, increased power and a quiet drive. This motor is an interior permanent magnet synchronous motor (IPM motor) that combines an interior permanent magnet rotor and a stator with concentrated windings. In addition, development of the motor focused on the slot combination, the shape of the magnetic circuits and the control method all designed to reduce motor noise and vibration. An 8-pole rotor, 12-slot stator combination was employed, and a gradually enlarged air gap configuration was used in the magnetic circuits. The gradually enlarged air gap brings the centers of the rotor and the stator out of alignment, changing the curvature, and continually changing the amount of air gap as the rotor rotates. The use of the gradually enlarged air gap brings torque degradation to a minimum, and significantly reduces torque fluctuation and iron loss of rotor and stator.

Looking back on steering systems in more than a hundred years that have passed since the introduction of the automobile, it can be seen that original method of controlling cars pulled by animals such as horses was by reins, and early automobiles had a single push-pull bar (tiller steering). That became the steering wheel, and an indirect steering mechanism by rotating up and down caught on. While the steering wheel is the main type of steering system in use today, the team have developed the Twin Lever Steering (TLS) system controlled mainly by bi-articular muscles, making use of advancements in science and technology and bioengineering to develop based on bioengineering considerations as shown in Fig. 1. The objective of that is to establish the ultimate steering operation system for drivers. In the first report, the authors reported on results found by using race-car prototypes as shown in Fig. 2.

A new 6-speed automatic transmission (AT) has been developed with the aim of enhancing fuel economy, raising efficiency, and achieving greater compactness. The unit was built on a parallel-shaft structure similar to the previous Honda AT, which has high torque transmission efficiency. The new AT was given more gear speeds and the ability to handle higher input torque from the engine. On the one hand, bolt structure for shaft tightening was implemented, the forward-reverse shift mechanism was placed on the input shaft and common gear trains are provided. As a result of these and other measures, the total length of the new transmission is 18 mm shorter than the previous model 5-speed AT. A multi-plate lock-up clutch (LC) structure with a separate chamber in the torque converter was also adopted so that the lock-up torque capacity could be increased and the LC control range expanded.

Super-sport motorcycles have shorter wheelbases than other category motorcycles. Due to this, strong braking occasionally causes large pitching motions to occur, including rear-wheel-lift. In order to reduce such pitching motions and achieve an effective braking force, the authors have developed a brake-by-wire system that uses a pressure sensor to detect the braking input pressure and an electric actuator to variably control the hydraulic pressure. This system makes it possible to precisely control the braking force compared with the previous ABS. Large pitching control was performed by the distribution of a front wheel and a rear-wheel braking forces, CBS (Combined Brake System), by using electronic control, and Brake-by-Wire has been suitable for sport riding. As a result, stable braking performance could be obtained without spoiling the handling characteristics of super-sport motorcycles.

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.

This paper discusses a method of predicting the torque distribution on planet gears originating in manufacturing errors, which is necessary for appropriate strength design of the gears in planetary gear sets. First, an expression of relation between manufacturing errors and the torque on the planet gears in a normal n-planet planetary gear set was derived. As a result, an equation expressing the distribution of torque to the planet gears was obtained. Tests were conducted to verify the validity of the equation in the case of a 4-planet planetary gear set. In order to predict the distribution of torque, it was necessary to estimate the stiffness of the planetary gear set that was the subject of the relational expression. These stiffness values were calculated by numerical analysis using a 3D FEM, into which blueprint values and material property values were input.

Infinitely variable transmission (IVT) is one of the methods used to extend the ratio coverage. In this paper, a dynamic behavior analysis technology was developed for an IVT utilizing a half-toroidal variator as the shifting device. The traction coefficient of traction fluid used for the half-toroidal IVT varies greatly according to contact surface slip rate, contact pressure and fluid temperature. This paper used measurement values from a four-roller machine to identify the coefficient, and then applied it to the dynamic behavior analysis. Use of the identified traction coefficient enabled power transmission characteristic predictions of a half-toroidal variator. To reproduce the elastic deformation in actual operation, the research used the Finite Element Method (FEM) for modeling. This model was also used to visualize the frictional state of traction surfaces during operation.

In recent years, the contribution of tires on vehicle fuel economy has been garnering attention. Up until now, rolling resistance coefficient (RRC) has been the standard way of measuring the amount of impact the tire has on fuel economy. We devised a new method for evaluating the impact of tires on fuel economy that incorporates the concept of tire “driving transmission efficiency” (hereinafter referred to as “driving stiffness”). In doing so, we have clarified the technology direction for contributing to the improvement of fuel economy while maintaining vehicle maneuverability by reducing RRC and improving tire driving stiffness.

Honda’s purpose is to realize the joy and freedom of mobility and a sustainable society in which people can enjoy life. As such, three series of environmental vehicles-FCVs, BEVs, and PHEVs-have been developed so that users in communities around the world can select the ones best suited to their local energy circumstances and individual lifestyles. This paper discusses a structure that enhances both the motive power performance and quietness of a newly developed FCV/BEV traction motor. To enhance motive power performance, the research focused on the stator lamination technique. As for methods of affixing the stator’s layers, the practice with previous models has been adhesion lamination, using electric steel sheets that come pre-made with adhesive layers. Having adhesive layers, however, lowers the ratio (space factor) of steel sheet layers. The new motor uses electric steel sheets without an adhesive layer in order to enhance motive power performance.

The moment of inertia of the crankshaft cannot be ignored when analyzing the dynamics of a motorcycle. In this research, the tire friction force (calculated by drag and tire side force) was used as an index of the drive performance. The ratio of roll rate and steering torque (here after referred to as a roll rate gain) was used as an index of the cornering performance, and it was analyzed as the influence of the moment of inertia of a crankshaft on the drive performance as well as cornering performance. As a result, the influence on drive performance and cornering performance by the moment of inertia has been found.

The four-wheel controlling antilock brake system is considered as an effective safety device because of its capability to help a driver to maintain vehicle stability and steerability during panic braking even on a slippery road surface. This report deal with a simplified control technique which simultaneously controls right and left wheels on each front or rear axle. Both front wheels are controlled in response to a signal from the front wheel with the least slip, while both rear wheels are controlled in response to a signal from the rear wheel that has the greatest slip. A series of tests proved that this technique ensures vehicle steering ability even during panic braking. On a gravel and other rough roads, this system provided shorter stopping distance compared to other four-wheel antilock systems. It has been generally assumed that stopping distance extension on such roads is only one disadvantage of the four-wheel antilock brake system.

This paper discusses the desired steer angle characteristics of rear wheels in the new concept of four wheel steering system in which the rear wheels are controlled as a function of the steering wheel angle in a manner that the rear wheels are steered in the same direction as the front wheels when the steering wheel angle is kept within a small range while the rear wheels are steered in the opposite direction to the front in the case the steering wheel angle is steered over a larger range. This paper also indicates the basic principle of the four wheel steering system and lists items for consideration in determining the function, and then presents a variety of effects the new steering system produces on operating performances based upon a series of proving ground tests.

The two liter DOHC-VTEC engine developed for the Honda S2000 produces 179kW (240HP, which is 120HP per liter). It is the highest output power among all naturally aspirated two liter engines ever mass-produced. It also achieves an exhaust emission level within National LEV standards. The new engine utilizes a redesigned VTEC cylinder head, in which MIM (metal injection molding) rocker arms are used. The new cylinder block with a ladder frame structure for its lower part, a newly developed camshaft drive chain and gear system and a metal honeycomb catalyst with an air pump start-up system are also utilized.

While there has been an empirical rule telling suspension designers that a slight rearward inclination of the wheel travel locus could improve ride harshness performance, there has not been any quantitative proof on it, to the extent of authors' knowledge. The authors planned to analyze the phenomenon by quantitatively measuring the force transmission via suspension, to find out that the amplitude of longitudinal force transmission to the sprung mass changes significantly depending on the above inclination angle. Further investigation has lead to a conclusion that the force transmission from ground to tire has a sharp directivity. And that the relationship between this direction and the direction of wheel travel is a dominant factor, which decides the magnitude of longitudinal force transmission to the sprung mass. In order to make use of the finding, the optimal wheel center locus inclination in side view has been studied, to minimize the longitudinal force transmission.

Combined Brake System for small motorcycles has been developed. In small motorcycles, some models have a hydraulic disc brake both in the front and rear wheels but many of them have a hydraulic disc front brake and a mechanical drum rear brake. Accordingly, it was necessary to develop a new system to link the hydraulic system with the mechanical system to allow an application of Combined Brake System to these models. In this paper, a CBS having a new configuration is described where a disc brake and a drum brake are linked in a simple lever structure of an input force distributor, and an inhibitor spring at the foot pedal. With this mechanism equipped, the distribution of brake forces is controlled. When a large input force is applied, a large proportion of brake force is applied to the front brake to obtain adequate deceleration. When a mild input force is applied, which is frequently operated, the brake force proportion is large in the rear compared to the front.

The tires are one of the most important parts of the vehicle chassis, as they significantly influence aspects such as vehicle's directional stability, braking performance, ride comfort, NVH, and fuel consumption. The tires are also a part whose size affects the vehicle's essential specifications such as wheelbase and track width. The size of the tires should therefore be determined in the initial stage of vehicle development, taking into account whether the size allows the vehicle to achieve the targeted overall performance. In estimations of vehicle performance, computer simulation plays more of an important role, and simulated tire models are designed to reproduce the measured tire characteristics of existing tires. But to estimate the chassis performance with various tire sizes or with tires of uncommon sizes, the prevailing modeling approach, “individual models for individual tires,” would not function well because of limited ability to expand tire models to unfamiliar sizes.

Honda announced an independent right and left rear toe control system (first generation) in 2013 and presented it as the world's first. As stated in a previous paper, “Independent Left and Right Rear Toe Control System,” with this system Honda has achieved a balance between an enjoyable driving experience in which handling is performed at the driver's will (“INOMAMA” handling) and stable driving performance.(1) This first generation is optimally designed to the vehicle specifications such as suspension axial force and steering gear ratio of the vehicle to which the system is applied. For more widespread application of independent rear toe control technology, a next generation system (second generation) has been developed, which achieves both cost reduction and flexible system performance which can be adapted to a variety of vehicles. The system development began by setting the required target performance with consideration for adaptation to various car models.

An analytic technology able to rapidly and accurately predict oil flows and churning torque in a transmission has been developed. The new method uses the finite difference method for analysis; with regard to wall boundaries it reproduces the shapes of physical objects by imparting boundary information to cells. This has made it a simple matter to treat the rotation and meshing of the gears, which form oil flows, and has also reduced the calculation cost. Tests of single-phase and multi-phase flows and churning torque were conducted in order to verify the accuracy of the new method. Calculation results for the flow velocity fields produced by rotating bodies, the trajectory of oil, and the behavior of the surface of the fluid displayed a good correlation with test results. Considering air entrainment in the oil, the ability of the method to reproduce these phenomena at high speeds of rotation was also increased.