A fuel estimation apparatus includes a combustion characteristic acquisition portion and a mixing ratio estimation portion. The combustion characteristic acquisition portion acquiring a combustion characteristic value indicating a physical amount relating to a combustion of an internal combustion engine acquires the combustion characteristic values of the combustions executed in different combustion conditions. The mixing ratio estimation portion estimates the mixing ratios of various components included in a fuel, based on the combustion characteristic values acquired by the combustion characteristic acquisition portion.

A combustion system controller controls an operation of a combustion system including an internal combustion engine. The combustion system controller includes a mixing ratio acquisition portion and a control portion. The mixing ratio acquisition portion acquires the mixing ratios of various components included in a fuel. The control portion controls the operation of the combustion system based on the mixing ratios acquired by the mixing ratio acquisition portion.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a method and system are provided for displacing a free-piston assembly to achieve a desired engine performance by repeatedly determining position-force trajectories over the course of a propagation path and effecting the displacement of the free-piston assembly based, at least in part, on the position-force trajectory. In a dual-piston assembly free-piston engine, synchronization of the two piston assemblies is provided.

A controller for an internal combustion engine is configured, when the speed of combustion of a fuel in a cylinder changes as the property of the fuel injected from a fuel injection valve changes, to change a combustion limit excess air ratio that is a target value of a fuel injection amount feedforward control according to a first relationship that the combustion limit excess air ratio increases as the speed of combustion of the fuel in the cylinder increases. The controller is also configured, when the speed of combustion of the fuel in the cylinder changes as the property of the fuel injected from the fuel injection valve changes, to change the value of a combustion limit combustion speed parameter that is the target value of a fuel injection amount feedback control according to a second relationship that the speed of combustion of the fuel in the cylinder corresponding to a combustion limit increases as the speed of combustion of the fuel in the cylinder increases.

A control device for an internal combustion engine is provided. The internal combustion engine includes a cylinder, an in-cylinder pressure sensor, a fuel injection valve, and an alcohol concentration sensor. The control device includes an electronic control unit. The electronic control unit is configured to: carry out learning of fuel properties with the fuel injected from the fuel injection valve as a target; calculate a combustion speed parameter, showing a combustion speed, within the cylinder, of the fuel that is a learning target of the fuel properties, on a basis of the in-cylinder pressure; and determine that water is included in the fuel when the capacitance of the fuel detected by the alcohol concentration sensor is larger than a preset first threshold, and when the combustion speed of the fuel within the cylinder is smaller than a preset second threshold.

A control device for an internal combustion engine is provided that can detect the adherence of deposits to a cylinder pressure sensor without subjecting the internal combustion engine to an impact or the like. A control device for an internal combustion engine equipped with a cylinder pressure sensor detects changes in the sensitivity of the cylinder pressure sensor. If the control device detects a decrease in the sensitivity of the cylinder pressure sensor after detecting an increase in the sensitivity of the cylinder pressure sensor, the control device determines that deposits are adhered to the cylinder pressure sensor.

To provide a controller and a control method, for an internal combustion engine, that can detect occurrence of knocking appropriately, even though the frequency distribution of the knock signal is distorted according to the occurrence state of knocking. The controller for the internal combustion engine calculates the background level by processing a low pass filter to the knock signal; and performs a low side frequency increase which makes a low side frequency, which is a cutoff frequency of the low pass filter in the case where the knock signal is smaller than an output value of the low pass filter, higher than a high side frequency, which is a cutoff frequency of the low pass filter in the case where the knock signal is larger than the output value of the low pass filter.

A system and method for assessing the presence or absence of ignition coil degradation for an ignition system that includes two ignition coils for each spark plug. Ignition coil degradation may be determined without having to monitor ignition coils via specialized hardware circuitry. In one example, degradation of one or more ignition coils may be inferred from cylinder the presence or absence of cylinder misfire.

Fuel in a fuel tank is supplied by a low-pressure pump to intake passage injectors mounted on an intake manifold via a low-pressure fuel supply pipe and a low-pressure fuel distribution pipe. A high-pressure pump is provided on the low-pressure fuel supply pipe. The pressure of the fuel is boosted by the high-pressure pump, and then is supplied to in-cylinder injectors via a high-pressure fuel distribution pipe. In an intake passage injection (MPI) mode, excitation of a solenoid is stopped and operation of an electromagnetic spill valve is stopped so as reduce vibration and noise caused by the seating of the electromagnetic spill valve in a valve seat.

A combustion pressure detection device for detecting combustion pressure inside a combustion chamber of an internal combustion engine, the combustion pressure detection device being attachable to a communication hole communicating an inside of a cylinder head configuring the combustion chamber and an outside thereof, the combustion pressure detection device includes: a housing; and an piezoelectric element and the like that are located in the housing and detect the combustion pressure. The housing has an attachment structural part attachable to the communication hole, the attachment structural part has a third outer peripheral surface to which a first seal member is attachable, and a inclined surface to which a second seal member is attachable, and the inclined surface is arranged at a front end side in a direction to the combustion chamber relative to the third outer peripheral surface when the combustion pressure detection device is attached to the communication hole.