# US 4,397,272 A · Two stroke engine having exhaust timing control valve means

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- Number: US 4,397,272 A
- Document ID: US4397272A
- Status: Granted
- Kind: A
- Application number: 06/314,970
- Filed: 1981-10-26
- Granted: 1983-08-09
- Earliest claimed: 1980-10-30
- Assignees: Yamaha Hatsudoki Kabushiki Kaisha
- Inventors: Shigenori Omote
- Web page: https://patentgrep.com/patent/US4397272A

## CPC

- F02D 13/0284: {Variable control of exhaust valves only}
- F01L 7/12: specially for two-stroke engines (F01L7/04 takes precedence)
- F02B 77/04: Cleaning of, preventing corrosion or erosion in, or preventing unwanted deposits in, combustion engines
- F02N 19/004: {Aiding engine start by using decompression means or variable valve actuation}
- F02B 61/02: for driving cycles
- F02B 2075/025: {two}
- Y02T 10/12: Improving ICE efficiencies
- F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W)
- F01L: CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G)
- F02N: STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A two stroke engine having an exhaust port formed in the cylinder wall. At the upper portion of the exhaust port, there is provided a rotary type exhaust timing control valve which is adapted to be rotatably actuated to control the exhaust timing in accordance with the engine speed. The control valve is interconnected with the engine starting mechanism so that the control valve is forcedly driven by the starting mechanism to thereby eliminate valve seizure.

## Claims

### Claim 1

A two-stroke engine comprising cylinder means, piston means which is received in said cylinder means for reciprocating movement, said cylinder means having exhaust port means adapted to be closed by said piston means, exhaust port timing control rotary valve means provided in said exhaust port means at upper portion thereof, said valve means being movable between a projected position wherein it is projected into the exhaust port means to thereby cover the upper portion of the exhaust port means and a retracted position wherein it is retracted from the exhaust port means, valve actuating means for actuating the valve means between said projected and retracted positions in accordance with engine speed, engine starting means for cranking said engine for starting the same, said valve means being connected with said engine starting means so that the valve means is actuated during engine starting operation to thereby eliminate valve seizure.

### Claim 2 (depends on 1)

A two-stroke engine in accordance with claim 1 in which said valve actuating means is a centrifugal governor means including rotor shaft means rotated by engine crankshaft means, guide plate means secured to said rotor shaft means to rotate therewith, slidable plate means provided on said rotor shaft means so that it rotates with but axially slidable with respect to said rotor shaft means, biasing means for urging said slidable plate means toward said guide plate means, centrifugal weight means disposed between said guide and slidable plate means so as to be displaced radially outwardly under centrifugal force produced therein to thereby force said slidable plate means axially against the biasing means, and means for converting an axial movement of the slidable plate means into a rotation of the rotary valve means.

### Claim 3 (depends on 2)

A two-stroke engine in accordance with claim 2 in which said engine starting means is an engine starting rotatable shaft which is adapted to be rotated by an external force, means being provided for transmitting a rotating movement of the starting shaft into an axial movement of the slidable plate means to thereby rotate the valve means.

### Claim 4 (depends on 2)

A two-stroke engine in accordance with claim 2 in which said engine starting means is an engine starting rotatable shaft which is adapted to be rotated by an external force, said starting shaft means has cam means and cam follower means is provided to produce axial movements of said slidable plate means in response to a rotation of the starting shaft means.