Exhaust control valve system for parallel multi-cylinder two-cycle engine

Claim 2

A multi-cylinder, two-cycle, crankcase compression internal combustion engine having a cylinder block assembly defining a pair of adjacent cylinder bores having their axes lying in a common plane, a crankcase member positioned at one end of said cylinder block, scavenge port means comprising at least one scavenge passage extending from said crankcase to the respective cylinder bore, an exhaust port for each cylinder bore for discharging exhaust gases from the respective cylinder bore to the atmosphere, each of said exhaust ports being disposed so that a line passing from the respective cylinder bore axis through the center of the exhaust port is disposed in non-perpendicular relationship to the said common plane and at an acute angle measured in the same direction to a perpendicular plane containing the respective cylinder bore axis, a pivoted exhaust control valve for controlling the effective area and timing of opening of each of said exhaust ports, and a common control valve shaft supported for rotation by said cylinder block about an axis parallel to the common plane and operatively connected to each of said exhaust control valves.

Claim 3

An engine as set forth in claim 1 wherein the connection between the control valve shaft and the exhaust control valves permit some axial movement therebetween while maintaining the angular relationship.

Claim 4

An engine as set forth in claim 2 wherein the axial movement is provided by a tongue and groove connection between the exhaust control valves and the control valve shaft.

Claim 5

An engine as set forth in claim 1 wherein the exhaust control valves have a configuration that permits the exhaust port to be fully opened when the exhaust control valves are in one position and partially obstructed when the exhaust control valves are in their idle position, said exhaust control valves being configured so that the effective exhaust port opening is symmetric in at least one operative position other than the full throttle position of the exhaust control valves.

Claim 6

An engine as set forth in claim 4 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 7

An engine as set forth in claim 4 wherein the effective exhaust port opening is symmetric at mid-range performance.

Claim 8

An engine as set forth in claim 6 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 9

An engine as set forth in claim 4 wherein the effective exhaust port opening is symmetric at the idle condition.

Claim 10

An engine as set forth in claim 8 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 11

An engine as set forth in claim 9 wherein a spark plug is positioned in the cylinder bore and is offset toward the greater effective area of the exhaust port relative to the cylinder bore axis.

Claim 12

An engine as set forth in claim 6 wherein a spark plug is positioned in the cylinder bore and is offset toward the greater effective area of the exhaust port relative to the cylinder bore axis.

Claim 13

An engine as set forth in claim 1 wherein the lower surface of the exhaust control valve is curved in plan view and the upper surface of the exhaust port is curved in plan view.

Claim 14

An engine as set forth in claim 12 wherein the exhaust control valves have a configuration that permits the exhaust port to be fully opened when the exhaust control valves are in one position and partially obstructed when the exhaust control valves are in their idle position, said exhaust control valves being configured so that the effective exhaust port opening is symmetric in at least one operative position other than the full throttle position of the exhaust control valves.

Claim 15

An engine as set forth in claim 13 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 16

An engine as set forth in claim 13 wherein the effective exhaust port opening is symmetric at mid-range performance.

Claim 17

An engine as set forth in claim 15 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 18

An engine as set forth in claim 13 wherein the effective exhaust port opening is symmetric at the idle condition.

Claim 19

An engine as set forth in claim 17 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 20

A multi-cylinder, two-cycle, crankcase compression internal combustion engine having a cylinder bock assembly defining a pair of adjacent cylinder bores having their axes lying in a common plane, a crankcase member positioned at one end of said cylinder block, scavenge port means comprising at least one scavenge passage extending from said crankcase to the respective cylinder bore, an exhaust port for each cylinder bore for discharging exhaust gases from the respective cylinder bore to the atmosphere, each of said exhaust ports being disposed so that a line passing from said cylinder bore axis through the center of the exhaust port is disposed in nonperpendicular relationship to the said common plane and at an acute angle measured in the same direction to a perpendicular plane containing the respective cylinder bore axis, a pivoted exhaust control valve for controlling the effective area and timing of opening of each of said exhaust ports, said exhaust control valves being pivotally supported for movement relative to the exhaust port so as to assume a non-symmetric effective area for said exhaust port in at least some operative positions of said exhaust control valves, said exhaust control valves being configured so that the effective exhaust port opening is symmetric in at least one obstructing position of said exhaust valves.

Claim 21

A multi-cylinder, two-cycle, crankcase compression internal combustion engine having a cylinder bock assembly defining a pair of adjacent cylinder bores having their axes lying in a common plane, a crankcase member positioned at one end of said cylinder block, scavenge port means comprising at least one scavenge passage extending from said crankcase to the respective cylinder bore, an exhaust port for each cylinder bore for discharging exhaust gases from the respective cylinder bore to the atmosphere, each of said exhaust ports being disposed so that a line passing from said cylinder bore axis through the center of the exhaust port is disposed in nonperpendicular relationship to the said common plane and at an acute angle measured in the same direction to a perpendicular plane containing the respective cylinder bore axis, a pivoted exhaust control valve for controlling the effective area and timing of opening of each of said exhaust ports, said exhaust control valves being pivotally supported for movement relative to the exhaust port so as to assume a non-symmetric effective area for said exhaust port in at least some operative positions of said exhaust control valves, said exhaust control valves being configured so that the effective exhaust port opening is symmetric in at least one obstructing position of said exhaust valves.

Claim 22

An engine as set forth in claim 19 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 23

An engine as set forth in claim 19 wherein the effective exhaust port opening is symmetric at mid-range performance.

Claim 24

An engine as set forth in claim 21 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 25

An engine as set forth in claim 21 wherein a spark plug is positioned in the cylinder bore and is offset toward the greater effective area of the exhaust port relative to the cylinder bore axis.

Claim 26

An engine as set forth in claim 19 wherein the lower surface of the exhaust control valve is curved in plan view and the upper surface of the exhaust port is curved.

Claim 27

An engine as set forth in claim 19 wherein the effective exhaust port opening is symmetric at the idle condition.

Claim 28

An engine as set forth in claim 25 wherein the effective exhaust port opening is symmetric at the full throttle position of the exhaust control valves in addition to at least one operative position other than the full throttle position.

Claim 29

An engine as set forth in claim 25 wherein the lower surface of the exhaust control valve is curved in plan view and the upper surface of the exhaust port is curved in plan view.

Claim 30

An engine as set forth in claim 27 wherein a spark plug is positioned in the cylinder bore and is offset toward the greater effective area of the exhaust port relative to the cylinder bore axis.