Abstract: A relief device includes a relief housing constituted by a relief inflow portion, a valve passage portion, a recess, and an oil discharge portion having a relief hole; a relief valve having a small-diameter portion between a first large-diameter portion and a second large-diameter portion; and a spring elastically biasing the relief valve toward the relief inflow portion. The recess is formed at a position that is closer to the relief inflow portion side than to the oil discharge portion, the axial length of the recess is larger than the axial length of the first large-diameter portion of the relief valve, and the shortest axial distance between the recess and the relief hole is less than the axial length of the small-diameter portion.

Abstract: A valve control synchronizing apparatus for an internal combustion engine for controlling opening and closing operations of an engine valve includes a synchronizing pin assembly selectively transferring pivoting movement from one or both of first and second adjacent rocker arms to a central rocker arm. The synchronizing pin assembly is received in a bore defined through the central rocker arm and at least partially into each of the first and second rocker arms. The synchronizing pin assembly bridges between the first rocker arm and the central rocker arm to transfer pivoting movement of the first rocker arm to the central rocker arm and bridges between the second rocker arm and the central rocker arm to transfer pivoting movement from the second rocker arm to the central rocker arm.

Abstract: A rocker arm changeover device for an engine includes a major rocker arm to drive intake or exhaust valves. A driven rocker arm is arranged in line with the major rocker arm. A changeover pin is movable within a first pin hole and a second pin hole and to change between engagement and disengagement of the major and driven rocker arms. The first pin hole coaxially matches the second pin hole through rocking motions of the major and driven rocker arms. A first pin is movable within the first and second pin holes between a disengagement position at which the first pin is retracted into the first pin hole and an engagement position at which the first pin protrudes from the major rocker arm. A second pin is movable relative to and coaxially with the first pin within the first pin hole.

Abstract: A relief device includes a relief housing constituted by a relief inflow portion, a valve passage portion, a recess, and an oil discharge portion having a relief hole; a relief valve having a small-diameter portion between a first large-diameter portion and a second large-diameter portion; and a spring elastically biasing the relief valve toward the relief inflow portion. The recess is formed at a position that is closer to the relief inflow portion side than to the oil discharge portion, the axial length of the recess is larger than the axial length of the first large-diameter portion of the relief valve, and the shortest axial distance between the recess and the relief hole is less than the axial length of the small-diameter portion.

Abstract: A valve operation control system for an internal combustion engine in which hydraulic pressure applied to a valve operation mode changing mechanism is controlled by hydraulic pressure control means that is formed from a holder mounted on a cylinder head, a spool valve formed by slidably housing a spool valve body in a valve body, and an electromagnetic open/close valve for controlling hydraulic pressure of a pilot hydraulic chamber, wherein the holder (109) is formed by integrally connecting a housed portion (109a) and a projecting portion (109b) by means of a connection portion (109c), the housed portion (109a) being housed between the cylinder head (22R) and a head cover, the projecting portion (109b) projecting outside the cylinder head (22R) and the head cover and having the electromagnetic open/close valve (113, 114) mounted thereon, a seal face (116) with the head cover is formed on the connection portion (109c), and the valve body (110) is provided so as to be connected to the housed portion (109a) whi

Abstract: A rocker arm changeover device for an engine includes a major rocker arm to drive intake or exhaust valves. A driven rocker arm is arranged in line with the major rocker arm. A changeover pin is movable within a first pin hole and a second pin hole and to change between engagement and disengagement of the major and driven rocker arms. The first pin hole coaxially matches the second pin hole through rocking motions of the major and driven rocker arms. A first pin is movable within the first and second pin holes between a disengagement position at which the first pin is retracted into the first pin hole and an engagement position at which the first pin protrudes from the major rocker arm. A second pin is movable relative to and coaxially with the first pin within the first pin hole.

Abstract: A valve control synchronizing apparatus for an internal combustion engine for controlling opening and closing operations of an engine valve includes a synchronizing pin assembly selectively transferring pivoting movement from one or both of first and second adjacent rocker arms to a central rocker arm. The synchronizing pin assembly is received in a bore defined through the central rocker arm and at least partially into each of the first and second rocker arms. The synchronizing pin assembly bridges between the first rocker arm and the central rocker arm to transfer pivoting movement of the first rocker arm to the central rocker arm and bridges between the second rocker arm and the central rocker arm to transfer pivoting movement from the second rocker arm to the central rocker arm.

Abstract: A valve operation control system for an internal combustion engine in which hydraulic pressure applied to a valve operation mode changing mechanism is controlled by hydraulic pressure control means that is formed from a holder mounted on a cylinder head, a spool valve formed by slidably housing a spool valve body in a valve body, and an electromagnetic open/close valve for controlling hydraulic pressure of a pilot hydraulic chamber, wherein the holder (109) is formed by integrally connecting a housed portion (109a) and a projecting portion (109b) by means of a connection portion (109c), the housed portion (109a) being housed between the cylinder head (22R) and a head cover, the projecting portion (109b) projecting outside the cylinder head (22R) and the head cover and having the electromagnetic open/close valve (113, 114) mounted thereon, a seal face (116) with the head cover is formed on the connection portion (109c), and the valve body (110) is provided so as to be connected to the housed portion (109a) whi