Abstract: A helical gear device includes: first and second helical gear respectively and rotatably disposed about first and third mutually parallel axes; a second helical gear meshing with the first and third helical gears so that a rotary motion is transmitted from the first to the third helical gear through the second, the second helical gear having a center bore; a support shaft disposed coaxially with a second axis parallel to the first, and extending through the center bore with a predetermined amount of radial play between the support shaft and the second helical gear, rotatably supporting the second helical gear. The second and third helical gears have a predetermined radial clearance in their reference meshing state in which their pitch circles contact. The radial clearance is smaller than a radial gap of a backlash between the second and third helical gears in the reference meshing state.

Abstract: A helical gear device includes: first and second helical gear respectively and rotatably disposed about first and third mutually parallel axes; a second helical gear meshing with the first and third helical gears so that a rotary motion is transmitted from the first to the third helical gear through the second, the second helical gear having a center bore; a support shaft disposed coaxially with a second axis parallel to the first, and extending through the center bore with a predetermined amount of radial play between the support shaft and the second helical gear, rotatably supporting the second helical gear. The second and third helical gears have a predetermined radial clearance in their reference meshing state in which their pitch circles contact. The radial clearance is smaller than a radial gap of a backlash between the second and third helical gears in the reference meshing state.

Abstract: A control circuit includes a computing unit, which computes a target oil pressure, a duty output unit, which outputs a drive electric current based on a result of computation of the computing unit, and a dither output unit, which applies a dither signal to a linear solenoid. The dither signal is added to the drive electric current outputted from the duty output unit and is applied to the linear solenoid. The dither output unit always applies the dither signal to the linear solenoid throughout an operation. The dither output unit reduces a pulse height of the dither signal in a dead zone in comparison to a pulse height of the dither signal in a control zone. In this way, even when an axial position of a spool is changed between the control zone and the dead zone, the amplitude of dither of the spool can be made generally constant. Thereby, it is possible to limit a change in an output oil pressure.

Abstract: A control circuit includes a computing unit, which computes a target oil pressure, a duty output unit, which outputs a drive electric current based on a result of computation of the computing unit, and a dither output unit, which applies a dither signal to a linear solenoid. The dither signal is added to the drive electric current outputted from the duty output unit and is applied to the linear solenoid. The dither output unit always applies the dither signal to the linear solenoid throughout an operation. The dither output unit reduces a pulse height of the dither signal in a dead zone in comparison to a pulse height of the dither signal in a control zone. In this way, even when an axial position of a spool is changed between the control zone and the dead zone, the amplitude of dither of the spool can be made generally constant. Thereby, it is possible to limit a change in an output oil pressure.

Abstract: A baffle plate includes a discharge portion that discharges lubricating oil that has dropped onto the baffle plate, to an oil pan. The discharge portion extends to be inclined in a direction in which cylinders are arranged, with respect to a rotation central axis of a crankshaft. The discharge portion includes a guide groove in which an upstream portion in a rotational direction of the crankshaft is located under a counter weight, and a downstream portion in the rotational direction of the crankshaft is located under a crank bearing. The discharge portion includes a discharge hole that is formed in the downstream portion of the guide groove in the rotational direction, and that provides communication between the oil pan and an engine block.

Abstract: A spark plug and cylinder head assembly includes a spark plug and a cylinder head of an engine. The cylinder head has a bore and a surface which faces a combustion chamber of the engine and on which the bore opens. The spark plug is fit in the bore of the cylinder head, and includes a metal shell, an insulator retained in the metal shell, a center electrode secured in the insulator, and a ground electrode facing the center electrode through a spark gap. An end surface of the metal shell has an outer edge and an inner edge, and tapers from the outer edge to the inner edge in a direction toward the inside of an air pocket formed between the metal shell and the insulator. The outer edge of the end surface of the metal shell protrudes from the surface of the cylinder head into the combustion chamber.

Abstract: A baffle plate includes a discharge portion that discharges lubricating oil that has dropped onto the baffle plate, to an oil pan. The discharge portion extends to be inclined in a direction in which cylinders are arranged, with respect to a rotation central axis of a crankshaft. The discharge portion includes a guide groove in which an upstream portion in a rotational direction of the crankshaft is located under a counter weight, and a downstream portion in the rotational direction of the crankshaft is located under a crank bearing. The discharge portion includes a discharge hole that is formed in the downstream portion of the guide groove in the rotational direction, and that provides communication between the oil pan and an engine block.

Abstract: A spark plug and cylinder head assembly includes a spark plug and a cylinder head of an engine. The cylinder head has a bore and a surface which faces a combustion chamber of the engine and on which the bore opens. The spark plug is fit in the bore of the cylinder head, and includes a metal shell, an insulator retained in the metal shell, a center electrode secured in the insulator, and a ground electrode facing the center electrode through a spark gap. An end surface of the metal shell has an outer edge and an inner edge, and tapers from the outer edge to the inner edge in a direction toward the inside of an air pocket formed between the metal shell and the insulator. The outer edge of the end surface of the metal shell protrudes from the surface of the cylinder head into the combustion chamber.

Abstract: In the spark plug, the ground electrode located so as to form a spark discharge gap with the center electrode thereof includes a ground base member fixed to the mounting fitting thereof and an electrode support member connected to the ground base member. The electrode support member has an opposed surface on which a projecting member is mounted so as to face the center electrode across from the spark discharge gap, and a retreating surface continuing the opposed surface and having such a shape as to approach a fore-end of the spark plug with distance from a junction between the projecting member and the opposed surface. The ground electrode further includes an angular portion at each of intersections between its back surface portion on which the electrode support member is provided, and the retreating surface.

Abstract: A small-sized spark plug is provided which ensures the stability in the location of production of sparks between center and ground electrodes. The center and ground electrodes have joined thereon cylindrical members such as noble metal chips which are opposed to each other through a spark gap. The cylindrical members are so oriented to have longitudinal center lines extend parallel in misalignment with each other. This orientation results in shorter and longer intervals between end surfaces of the cylindrical members. The sparks are concentrated between portions of edges of cylindrical members located apart the shorter interval, thereby resulting in the stability in the location of production of the sparks.

Abstract: A combustion chamber pressure sensor for an internal combustion engine includes an elongated pressure transmitting member having one end exposed to the interior of an engine cylinder and the opposite end contacting a pressure sensing element which generates a pressure measurement signal, the pressure transmitting member and pressure sensing element being contained within an elongated housing. A damping body formed of a viscoelastic material is disposed on an outer or inner circumferential surface of the housing, for reducing an amount of engine vibration that is transmitted to the pressure sensing element and thereby reducing noise in the pressure measurement signal.

Abstract: A combustion chamber pressure sensor for an internal combustion engine includes an elongated pressure transmitting member having one end exposed to the interior of an engine cylinder and the opposite end contacting a pressure sensing element which generates a pressure measurement signal, the pressure transmitting member and pressure sensing element being contained within an elongated housing. A damping body formed of a viscoelastic material is disposed on an outer or inner circumferential surface of the housing, for reducing an amount of engine vibration that is transmitted to the pressure sensing element and thereby reducing noise in the pressure measurement signal.

Abstract: A small-sized spark plug is provided which ensures the stability in the location of production of sparks between center and ground electrodes. The center and ground electrodes have joined thereon cylindrical members such as noble metal chips which are opposed to each other through a spark gap. The cylindrical members are so oriented to have longitudinal center lines extend parallel in misalignment with each other. This orientation results in shorter and longer intervals between end surfaces of the cylindrical members. The sparks are concentrated between portions of edges of cylindrical members located apart the shorter interval, thereby resulting in the stability in the location of production of the sparks.

Abstract: At least one of a center electrode tip and a ground electrode tip is made of an iridium alloy. A discharge gap, formed between the center electrode tip and the ground electrode tip, is less than 1.1 mm. And, cross sections of the center electrode tip and the ground electrode tip are equal to or smaller than 0.95 mm2 in a spherical region where a distance from a midpoint of the discharge gap is within 0.6 mm.

Abstract: A combustion condition detecting device detects combustion ions between opposing electrodes in a combustion chamber by ion current flowing between the electrodes in response to a.c. current voltage applied between the electrodes. A low pass filter for eliminating current components having high order frequencies of the a.c. voltage is disposed in a primary side of the transformer so that a waveform of the a.c. voltage approximates a sine wave. Thus, detection accuracy of the combustion ions is prevented from being affected by variation of capacitive current included in the current flowing between the electrodes, wherein the variation of the capacitive current is caused by distortion of the waveform of the a.c. voltage.

Abstract: An ignition system has an ignition circuit and an ion current detecting circuit. The ignition circuit has an ignition coil that has relatively low inductance of about less than 10 henries (H) because it is used in conjunction with a separate energy accumulating coil, and a driving circuit for a multi-spark ignition sequence. The ion current detecting circuit detects a second harmonic component of engine knock. The components of the system are designed so that the resonance frequency of an ion current path substantially coincides with the second harmonic frequency component, so that the Q-value of the ion current path is greater than 1. As a result, it is possible to improve knock detecting accuracy.

Abstract: At least one of a center electrode tip and a ground electrode tip is made of an iridium alloy. A discharge gap, formed between the center electrode tip and the ground electrode tip, is less than 1.1 mm. And, cross sections of the center electrode tip and the ground electrode tip are equal to or smaller than 0.95 mm2 in a spherical region where a distance from a midpoint of the discharge gap is within 0.6 mm.

Abstract: At least one of a center electrode tip and a ground electrode tip is made of an iridium alloy. A discharge gap, formed between the center electrode tip and the ground electrode tip, is less than 1.1 mm. And, cross sections of the center electrode tip and the ground electrode tip are equal to or smaller than 0.95 mm2 in a spherical region where a distance from a midpoint of the discharge gap is within 0.6 mm.

Abstract: In an engine ignition unit, a transistor and a current detecting resistor are connected to primary and secondary windings of an ignition coil, respectively. The current detecting resistor is used for detecting a current flowing between the opposing electrodes of spark plug. At an ignition by the spark plug, high-frequency square wave signals are generated by an oscillator after an ignition signal is cut off. The square wave signals turn on and off the transistor. By this operation, a battery voltage is intermittently applied to the primary winding and an ion current is measured. A frequency of the square wave signals is set close to a resonant frequency of an ion current path including the spark plug, the secondary winding of the ignition coil and the current detecting resistor.

Abstract: A battery, an energy charge inductance, and a first transistor are connected in series in an ignition system. A primary winding and a second switching device are connected in series between the ground and a point between the energy charge inductance and the first switching device. A drive circuit switches periodically on and off the first switching device and the second switching device during multispark duration of the spark plug such that each switching device has a different switching status from each other. After the multispark duration, the drive circuit switches periodically on and off the second transistor with a short switching interval. The switching interval is set such that a relatively low voltage that almost causes a spark is impressed to the spark plug. An ion current detection is implemented by using this voltage as a power source.