Abstract: A reciprocating engine with a variable compression ratio mechanism is disclosed. A lubrication system of the engine is improved by controlling an oil pressure according to a compression ratio setting. The lubrication system includes various combinations of control valves and oil passages. The oil relief passage is opened at a high compression ratio setting applied to a low engine load range and is otherwise closed at a low compression ratio setting applied to a high engine load range.

Abstract: A combustion control system for a spark-ignition internal combustion engine includes a variable piston stroke characteristic mechanism changing a compression ratio of the engine, sensors detecting engine operating conditions, i.e., engine speed and engine load, and at least one of a variable lift and working-angle control mechanism simultaneously continuously changing an intake-valve lift and an intake-valve working angle and a variable phase control mechanism changing an angular phase at a central angle corresponding to a maximum valve lift point of the intake valve. Also provided is a control unit that controls the variable piston stroke characteristic mechanism, and at least one of the variable lift and working-angle control mechanism and the variable phase control mechanism, depending on the engine operating conditions.

Abstract: A link mechanism usable for a variable compression ratio mechanism of an internal combustion engine includes first and second links pivotally connected by a pin inserted through cylindrical first and second pin boss portions of the first and second links. Each of the first and second pin boss portions includes a circumferentially extending first narrow section, and a circumferentially extending first wide section having an axial wall thickness greater than the axial wall thickness of the first narrow section. The wide sections of the first and second pin boss portions are overlapped in an region extending in the axial direction of the pin.

Abstract: A control system for an internal combustion engine is provided. The engine includes a compression ratio control mechanism and an ignition timing control system. The control system comprises an engine control for controlling the compression ratio control mechanism and the ignition timing control system so that when the engine is cold, the ignition timing is retarded largely from an MBT point and the compression ratio is set higher than that obtained when the engine is cold and operated at corresponding engine rpm and engine load. A method for controlling such an internal combustion engine is also provided.

Abstract: In a piston actuation system of a V-type internal combustion engine with two cylinder banks having at least one pair of cylinders, a piston pin, an upper link, a lower link, and a control link are mechanically linked to each other for each cylinder bank. When changing a compression ratio of the engine, ends of the control links of the two cylinder banks are moved in synchronism. The lower links of the two cylinder banks are coaxially rotatably fitted on the outer periphery of the same crankpin whose axis is eccentric to the axis of the crankshaft.

Abstract: A swing cam to actuate engine valves is rotatably disposed about a drive shaft. A first eccentric cam is tightly disposed on the drive shaft. A ring-link is rotatably disposed on the first eccentric cam. A second eccentric cam is tightly disposed on a control shaft which rotates to a given angular position in accordance with an operation condition of an associated internal combustion engine. A rocker arm is rotatably disposed on the second eccentric cam. A rod-link extends between the rocker arm and the swing cam. A first connecting pin pivotally connects a first arm portion of the rocker arm with the ring-link. A second connecting pin pivotally connects a second arm portion of the rocker arm with an end of the rod-link. A third connecting pin pivotally connects the other end of the rod-link with the swing cam. The first connecting pin is fixed to either one of the first arm portion of the rocker arm and the ring-link.

Abstract: In a variable compression ratio mechanism for an internal combustion engine employing an upper link, a lower link, and a control link, the lower link includes a crankpin bearing portion into which a crankpin is fitted, a first connecting-pin bearing portion into which a first connecting pin for the upper link is fitted, and a second connecting-pin bearing portion into which a second connecting pin for the control link is fitted. A central connecting portion is provided to connect an axial central portion of at least one of the first and second connecting-pin bearing portions to an axial central portion of the crankpin bearing portion. The central connecting portion has an axial length L1 shorter than each of an axial length L2 of the crankpin bearing portion, an axial length L3 of the first connecting-pin bearing portion, and an axial length L4 of the second connecting-pin bearing portion.

Abstract: In a rockable-cam equipped reciprocating internal combustion engine, a rockable cam is rotatably fitted on the outer periphery of an intake-valve drive shaft that is rotatable in synchronism with rotation of a crankshaft. The rockable cam oscillates within predetermined limits during rotation of the intake-valve drive shaft so as to directly push an intake-valve lifter. As viewed from an axial direction of the crankshaft, an axis of the intake-valve drive shaft is offset from a centerline of the intake-valve stem in a first direction that is normal to both the cylinder centerline and the crankshaft axis and directed from the cylinder centerline to the intake valve side. The crankshaft axis is also offset from the cylinder centerline in the first direction.

Abstract: A link mechanism of an engine includes: an upper link having a first end connected to a piston pin of a piston; a lower link connected to the upper link via an upper pin having a center, the lower link being connected to a crank pin of a crank shaft; a control shaft extending substantially in parallel with the crank shaft, the control shaft having a rotational center; and a control link including: a first end swingably connected to the control shaft, and a second end connected to the lower link. In a process of the center of the upper pin moving nearer to the axial line of the piston pin, the center of the control pin moves in the upward direction, thus inclining the lower link and allowing the center of the upper pin and the center of the piston pin to move in the downward direction.

Abstract: In an internal combustion engine of variable compression ratio type, a piston control mechanism is employed which comprises a lower link rotatably disposed on a crank pin of a crankshaft of the engine, an upper link having one end pivotally connected to the lower link and the other end pivotally connected to a piston of the engine, a control link having one end pivotally connected to the lower link; and a position changing mechanism which changes a supporting axis about which the other end of the control link turns. When the piston comes up to a top dead center, a compression load is applied to the control link in an axial direction of the control link in accordance with an upward inertial load of the piston.

Abstract: A variable compression ratio mechanism for a reciprocating engine includes upper and lower links linking a piston pin to a crankpin, an eccentric cam equipped control shaft and a control link cooperating with each other to vary the attitude of the upper and lower links. A control-shaft actuator is provided to vary a compression ratio. The actuator includes a reciprocating block slider linked at a front end to the control shaft, and a rotary member being in meshed-engagement with the rear end of the slider by a meshing pair of screw-threaded portions. A hydraulic modulator has a hydraulic pressure chamber facing the rear end face of the slider, so that working-fluid pressure in the pressure chamber forces the slider in the same axial direction as the direction of action of reciprocating load acting on the slider owing to combustion load.

Abstract: A control system for an internal combustion engine is provided which comprises a compression ratio control mechanism and a control unit for controlling the compression ratio control mechanism. The control unit including an acceleration parameter obtaining section for obtaining an acceleration parameter corresponding to a change of an engine speed, an acceleration determining section for determining whether the engine is in a slow or fast acceleration state on the basis of the acceleration parameter, and a control section for controlling at least one of a compression ratio change speed at which the engine compression ratio during engine acceleration is changed and a compression ratio change start time at which a change of the engine compression ratio during engine acceleration is started, on the basis of whether the engine is in a slow or fast acceleration state. A control method is also provided.

Abstract: A swing cam to actuate engine valves is rotatably disposed about a drive shaft. A first eccentric cam is tightly disposed on the drive shaft. A ring-link is rotatably disposed on the first eccentric cam. A second eccentric cam is tightly disposed on a control shaft which rotates to a given angular position in accordance with an operation condition of an associated internal combustion engine. A rocker arm is rotatably disposed on the second eccentric cam. A rod-link extends between the rocker arm and the swing cam. A first connecting pin pivotally connects a first arm portion of the rocker arm with the ring-link. A second connecting pin pivotally connects a second arm portion of the rocker arm with an end of the rod-link. A third connecting pin pivotally connects the other end of the rod-link with the swing cam. The first connecting pin is fixed to either one of the first arm portion of the rocker arm and the ring-link.

Abstract: A paired counterweights of a crankshaft have projected inner surfaces which protrude toward each other defining a given space therebetween. A plurality of links are arranged to convert a reciprocating motion of a piston to a rotational motion of the crankshaft. One of the links is pivotally connected to other links through link connecting portions and swingably disposed on a crank pin of the crankshaft so that upon rotation of the crankshaft, a peripheral portion of the link passes through the given space. At least one of the link connecting portions is placed within an imaginary circle which would be described by a radially innermost part of the projected inner surfaces of the paired counterweights when the paired counterweights turn about an axis of the crank pin.

Abstract: A swing cam to actuate engine valves is rotatably disposed about a drive shaft. A first eccentric cam is tightly disposed on the drive shaft. A ring-link is rotatably disposed on the first eccentric cam. A second eccentric cam is tightly disposed on a control shaft which rotates to a given angular position in accordance with an operation condition of an associated internal combustion engine. A rocker arm is rotatably disposed on the second eccentric cam. A rod-link extends between the rocker arm and the swing cam. A first connecting pin pivotally connects a first arm portion of the rocker arm with the ring-link. A second connecting pin pivotally connects a second arm portion of the rocker arm with an end of the rod-link. A third connecting pin pivotally connects the other end of the rod-link with the swing cam. The first connecting pin is fixed to either one of the first arm portion of the rocker arm and the ring-link.

Abstract: A variable compression ratio mechanism for a reciprocating engine includes a connecting rod split into upper and lower connecting rod portions linked to each other through a first connecting pin. A rockable arm is oscillatingly linked at one end to the lower connecting rod portion through a second connecting pin. A control mechanism shifts the center of oscillating motion of the rockable arm to vary a compression ratio of the engine. A piston stroke is set to be greater than two times a crank radius of a crank, irrespective of variations in the compression ratio. A linkage is dimensioned and laid out, so that its crankpin load is less than a crankpin load produced by a linkage that the crankpin is located on a perpendicular line at substantially the midpoint of a line segment between and including the centers of the first and second connecting pins.

Abstract: A control system for an internal combustion engine is provided which comprises a compression ratio control mechanism and a control unit for controlling the compression ratio control mechanism. The control unit including an acceleration parameter obtaining section for obtaining an acceleration parameter corresponding to a change of an engine speed, an acceleration determining section for determining whether the engine is in a slow or fast acceleration state on the basis of the acceleration parameter, and a control section for controlling at least one of a compression ratio change speed at which the engine compression ratio during engine acceleration is changed and a compression ratio change start time at which a change of the engine compression ratio during engine acceleration is started, on the basis of whether the engine is in a slow or fast acceleration state. A control method is also provided.

Abstract: A supercharged internal combustion engine is provided with a double-link type piston crank mechanism connecting between a piston and a crankshaft. The piston crank mechanism causes the piston to move at a speed which is smaller around a top dead center (TDC) and larger around a bottom dead center (BDC) as compared with respective corresponding piston speeds attained by a comparable single-link type piston crank mechanism. The double-link type piston crank mechanism variably controls a compression ratio by varying an angular position of one of links constituting the piston crank mechanism.

Abstract: In a rockable-cam equipped reciprocating internal combustion engine, a rockable cam is rotatably fitted on the outer periphery of an intake-valve drive shaft that is rotatable in synchronism with rotation of a crankshaft. The rockable cam oscillates within predetermined limits during rotation of the intake-valve drive shaft so as to directly push an intake-valve lifter. As viewed from an axial direction of the crankshaft, an axis of the intake-valve drive shaft is offset from a centerline of the intake-valve stem in a first direction that is normal to both the cylinder centerline and the crankshaft axis and directed from the cylinder centerline to the intake valve side. The crankshaft axis is also offset from the cylinder centerline in the first direction.

Abstract: An internal combustion engine is constructed to include a variable compression ratio mechanism. The mechanism has the following structure. An upper link has one end pivotally connected to a piston pin of a piston of the engine. A lower link is pivotally disposed on a crank pin of a crankshaft of the engine and has one part pivotally connected to the other end of the upper link. A control shaft extends substantially in parallel with the crankshaft. A control link has an end pivotally connected to the other part of the lower link. The other end of the control link is connected to the control shaft through an eccentric bearing structure, so that rotation of the control shaft about its axis induces a pivoting of the lower link about the crank pin varying the stroke of the piston.