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Recently emissions regulations are being strengthened. An air-fuel ratio cylinder imbalance causes emissions to increase due to universal exhaust gas oxygen (UEGO) sensor error or exhaust gas oxygen (EGO) sensor error. Various methods of reducing an air-fuel ratio cylinder imbalance have been developed. It is preferable for a control system to operate over a wide range of conditions. Our target is to expand the operating conditions from idling to high load conditions. Our approach is to use both an UEGO sensor and a crank angle sensor. A two-revolution frequency component calculated from the UEGO sensor output signal and angular acceleration calculated from the crank angle sensor output signal are used to identify the cylinder where the air-fuel ratio error occurs.

A new diagnosis method for an air-fuel ratio cylinder imbalance has been developed. The developed diagnosis method is composed of two parts. The first part detects an occurrence of an air-fuel ratio cylinder imbalance by using a two revolution frequency component of an EGO sensor output signal or an UEGO sensor output signal upstream from a catalyst. The two revolution frequency component is from a cycle where an engine rotates twice. The second part of the diagnosis method detects an increase of emissions by using a low frequency component which is calculated from the output of an EGO sensor downstream from the catalyst. When the two revolution frequency component calculated using the upstream sensor output is larger than a certain level and the low frequency component calculated using the downstream sensor output is shifted to a leaner range, the diagnosis judges that the emissions increase is due to an air-fuel ratio cylinder imbalance.

Emission regulations continue to be strengthened, and it is important to decrease cold start hydrocarbon concentrations in order to meet them, now and in the future. The HC concentration in engine exhaust gas is reduced by controlling the air-fuel ratio to the low HC range and retarding the ignition timing as much as possible until the engine stability reaches a certain deterioration level. Conventionally however, the target air-fuel ratio has been set at a richer range than the low HC range and the target ignition timing has been more advanced than the engine stability limit, in order to stabilize the engine for various disturbances. As a result, the HC concentration has not been minimized. To solve this problem, a new engine control has been developed. This control uses a crank angle sensor to simultaneously control the air-fuel ratio and the ignition timing so that the HC concentration can be minimized.

Emission regulations continue to be strengthened, and it is important to decrease cold start hydrocarbon concentrations in order to meet them, now and in the future. The HC concentration in engine exhaust gas can be reduced by optimizing the air-fuel ratio. However, a conventional air-fuel ratio feedback control does not operate for the first ten seconds after the engine has started because the air-fuel ratio sensor has not yet been activated. In this paper, we report on a study to optimize the air-fuel ratio using a crank angle sensor until the air-fuel ratio sensor has been activated. A difference in fuel properties was used as a typical disturbance factor. The control was applied to both a direct-injection engine (DI) and a port-injection engine (MPI). It was evaluated for two fuel types: one which evaporates easily and one which does not. The experimental results show the air-fuel ratio is optimized for both types of fuel.

In recent years, integrated vehicle control systems have been developed to improve fuel economy and safety. As a result, engine control is shifting to torque-based systems for throttle / fuel / ignition control, to realize an engine torque demand from the system. This paper describes torque-based engine control technologies for SI (Spark Ignition) engine to improve torque control accuracy using a feedback control algorithm and an airflow sensor.

In this study, the possibility of real-time HCCI control in a multi-cylinder gasoline engine was examined. Specifically, we applied a multivariate analysis based on an experimental design of quality engineering, and picked out several engine parameters which influence gasoline HCCI combustion stability. We clarified the characteristics of engine parameters in a gasoline HCCI operation area and propose the control concept: The internal EGR control is applied to multi-cylinder control by using the variable valve system, and air-fuel mixture control is applied to each-cylinder injection control while keeping the mixture homogeneous. Combustion conditions and engine out A/F need to be detected and fed back individually for each cylinder. With the proposed concept, it is possible to construct a real-time HCCI control system in a multi-cylinder gasoline engine.

A new feedback control for an LNT has been developed. This control adapts the rich spike (regeneration) operation in accordance with conditions of the engine and the LNT to realize high precision and robustness. The control consists of three components. First is a reference model composed of an inlet Nox concentration model and an LNT model. Second is a controller for rich spike timing and its duration. The start timing of the rich spike and its duration are determined based on the reference model. Third is a self tuning function. It adapts the parameters of the reference model using an Nox sensor downstream from the LNT. In particular, it can distinguish between deterioration of the LNT and unexpected change (increase or decrease) of Nox concentration in inlet gas in lean operation. To evaluate the performance of the proposed control, two other types of controls (type 1 and type 2) are discussed. Type 1 is a control based on the reference model without a sensor.

This paper describes a combustion stability control using fuel injection control for a gasoline homogeneous charge compression ignition (HCCI) engine. First, using a single-cylinder engine we examined the influence that fuel injection and air/fuel mixture had on HCCI engine auto-ignition and combustion. This was achieved by visualization experiment of in-cylinder air/fuel mixture with fuel injection as a parameter. Next, the effect of the fuel injection control was evaluated by using a 4-cylinder HCCI engine. We proposed the following concept for a gasoline HCCI combustion control: internal-EGR (I-EGR) is applied to either internal EGR control of each-cylinder or a multi-cylinder control scheme using a variable valve event and timing system, and the fuel injection is applied to each cylinder control while keeping the mixture homogeneous.

A high performance catalyzed hydrocarbon (HC) trap, consisting of a Ag-impregnated zeolite and a three-way catalyst (TWC), was developed to achieve the stringent exhaust regulations such as SULEV. To improve the HC retention ability and durability of Ag-zeolite, the effects of wash-coat loading, HCs species, space velocities (SV) etc. on HC desorption profiles upon heating-up were examined in detail. In the present study, a simulated durability test using a cyclic lean-stoichiometric aging, was developed and applied for durability evaluation. An ultraviolet visible near-infrared spectrophotometer (UV-Vis) showed that specific chemical species of Ag were responsible for the delay of HC desorption. After the cyclic aging, the retention effect of Ag was only seen with aromatic compounds. It was revealed that the HC retention effect on aromatic compounds was maintained at high SV values, which was confirmed by actual vehicle tests.

A catalyzed hydrocarbon (HC) trap aiming at the super-ultra low emission vehicle (SULEV) regulation was developed using a metal-impregnated zeolite. To enhance the adsorption and to raise the desorption temperature for a wide range of HC species, the modification of zeolite with certain metals was needed and Ag was found to be the most promising. Using a Ag impregnated zeolite, a three way catalyst was prepared, and its HC purification ability for a model gas simulating cold-start HCs was studied. Its heat resistance was also examined. A vehicle test for a fresh catalyzed HC trap showed that the cold-start HC after the newly developed trap almost reached the SULEV regulation level.

A new catalyzed hydrocarbon (HC) trap control system has been developed to reduce HC emission at cold engine start. The HC trap function changes according to its temperature, so it is important to optimize its temperature profile. To realize the best profile, the engine system was optimized with a thin wall exhaust tube, a thin wall HC trap and a new engine control, which controls ignition timing without engine stability deterioration. In a LA-4 mode test with some trial HC traps, the results showed good performance which met ULEV/SULEV standard.

A new A/F F/B control has been developed composed of two controls using one linear A/F sensor at the confluence point of exhaust gas to meet emission regulations such as the ULEV/SULEV. One control is individual cylinder A/F F/B control using the DFT algorithm with the linear A/F sensor at the confluence point. The other is confluence point A/F F/B control using the Smith Dead Time (SDT) controller. We discuss each A/F control and show results of their respective engine tests. These A/F F/B controls are integrated and, compared with conventional controls, show the good performance in the FTP mode test.