A handheld engine-driven working machine comprises an internal combustion engine with a throttle valve, a throttle adjusting device for adjusting an opening degree of the throttle valve of the internal combustion engine, and a control device provided in the internal combustion engine. The control device is configured to detect a rotational speed and an amount of change in the rotational speed at every at least one rotation of the internal combustion engine. The control device determines that the throttle valve is partially opened when the amount of change in the rotational speed is greater than a predetermined value.

A variety of methods and arrangements for detecting misfire and other engine-related errors are described. In one aspect, a window is assigned to a target firing opportunity for a target working chamber. There is an attempt to fire a target working chamber during the target firing opportunity. A change in an engine parameter (e.g., crankshaft angular acceleration) is measured during the window. A model (e.g., a pressure model) is used to help determine an expected change in the engine parameter during the target firing opportunity. Based on a comparison of the expected change and the measured change in the engine parameter, a determination is made as to whether an engine error (e.g., misfire) has occurred.

In a rough terrain vehicle, at a time of preparing to start movement, in a case that a left paddle switch and a right paddle switch are operated together with an accelerator pedal, an ECU disengages a clutch of an automatic transmission, and causes an output of an engine to increase. On the other hand, at a time of starting movement, in a case that the left paddle switch and the right paddle switch are returned to their initial positions, the ECU engages the clutch and transmits the output of the engine from the engine to vehicle wheels via the automatic transmission, to thereby rapidly start movement of the rough terrain vehicle.

In an alcohol concentration estimation apparatus for an engine, a first crank angular speed (ω1) within a first predetermined interval overlapping with the compression top dead center is calculated, and a first variation amount (Δω1) is calculated by subtracting ω1 from an average engine speed. A second crank angular speed (ω2) within a second predetermined interval overlapping with the combustion bottom dead center is calculated, and a second variation amount (Δω2) is calculated by subtracting ω1 from ω2. In a relationship between air fuel ratio A/F and an indicated mean effective pressure (IMEP)/charging efficiency (ηc) of the engine when the engine is operated with a predetermined fuel injection map indicating a relationship between A/F and IMEP/ηc for each desired alcohol concentration, IMEP/ηc is substituted by Δω2/Δω1 ratio to estimate an alcohol concentration in fuel. The alcohol concentration estimation apparatus eliminates requirement of sensors for detecting an intake air mass.

A drive train abnormality determination device for a straddled vehicle that includes a drive train having a rotator. The drive train abnormality determination device includes an angle signal output unit that periodically outputs an angle signal in accordance with rotation of the rotator, a rotator rotation speed fluctuation physical quantity acquisition unit that acquires a quantity related to a fluctuation in a rotation speed of the rotator, based on the angle signal from the angle signal output unit, a rough road determination unit that determines whether a distribution state or pattern satisfies a predetermined rough road condition, a continuity determination unit that determines whether the rough road condition is continuously satisfied, and a drive train abnormality determination unit that determines, responsive to a determination by the continuity determination unit that the rough road condition is continuously satisfied, that the drive train has an abnormality in its functioning.

A control device of an engine is provided. The engine is operated at a high compression ratio, a geometric compression ratio of the engine being 14:1 or higher. The control device includes a fuel injection controller for controlling a fuel injector of the engine to start a fuel injection in a latter half of a compression stroke within an engine operating range where an engine speed is below a predetermined value and an engine load is above a predetermined value, and an ignition controller for controlling an ignition plug of the engine to retard an ignition timing when a timing for the fuel injection controller to start the fuel injection is on a retarding side of a predetermined timing, the ignition timing being retarded based on a retarding amount of the fuel injection start timing from the predetermined timing.

A vehicle speed control device for an industrial vehicle is configured to control a vehicle speed of the industrial vehicle. The vehicle speed control device includes an operation detector that is configured to detect whether an accelerator pedal is being operated and a controller that is configured to control the vehicle speed of the industrial vehicle by controlling the rotation speed of the engine. The controller is configured to derive a vehicle speed limit value that increases during an operated state of the accelerator pedal and decreases during a non-operated state of the accelerator pedal, and set an upper limit value of the vehicle speed to the derived vehicle speed limit value.

A CPU substitutes a difference between a crank-side speed that is a rotation speed of a crankshaft and a downstream-side speed that is a speed of a portion, opposite from the crankshaft, in a damper into a differential speed. The CPU calculates a torsion angle through a process of integrating the differential speed. The CPU calculates a torsion speed component that is a speed component of the crankshaft due to torsion of the damper based on a process of integrating a value obtained by multiplying the torsion angle by an elastic modulus, and calculates a time that is a variable indicating a speed of the crankshaft, used to determine a misfire, based on the torsion speed component. The CPU subtracts a value obtained by subtracting an output value of the integrating process, applied to a finite response low-pass filter process, from the output value.

A CPU substitutes a difference between a crank-side speed that is a rotation speed of a crankshaft and a downstream-side speed that is a speed of a portion, opposite from the crankshaft, in a damper into a differential speed. The CPU calculates a torsion speed component that is a speed component of the crankshaft due to torsion of the damper based on a physical model of which an input is the differential speed, and calculates a time that is a variable indicating a speed of the crankshaft, used to determine a misfire, based on the torsion speed component. The CPU delays acquisition time of the downstream-side speed used to calculate the differential speed, with respect to acquisition time of the crank-side speed according to the rotation speed of the crankshaft.

A variable spring rate absorber is adjusted to provide the vibration attenuation characteristics needed to match current operating conditions. Control of a variable spring rate absorber determines the desired absorber spring rate for existing conditions based on a number of inputs and predetermined characterization tables. Once the spring rate is calculated, a predetermined map may be used to determine the absorber setting needed to achieve the desired spring rate. A sensor may be used to measure the actual state of the absorber to determine the extent to which the setting must be adjusted to achieve the desired spring rate.