AU710603B2

AU710603B2 - Spark ignition two-stroke internal combustion engine having a combustion controller

Info

Publication number: AU710603B2
Application number: AU15165/97A
Authority: AU
Inventors: Shinichi Isomura; Yoshihiro Takada; Yuji Tsushima
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1996-03-08
Filing date: 1997-03-07
Publication date: 1999-09-23
Anticipated expiration: 2017-03-07
Also published as: FR2745848B1; CN1100940C; CN1162693A; FR2745848A1; JPH09242570A; TW311968B; AU1516597A

Description

-1- Spark Ignition Two-Stroke Internal Combustion Engine Having a Combustion Controller Detailed Description of the Invention Technical Field of the Invention This invention relates to a spark ignition two-stroke internal combustion engine with a combustion controller which operates self ignition combustion of fresh in a combustion chamber namely active thermal environment combustion at least during low load operation.

Prior Art In a conventional spark ignition two-stroke internal combustion engine, an exhaust passage and scavenging passage which are opening-and-closing operated by a piston are formed on the inside peripheral surface of a cylinder hole, fresh prei compressed in a crank chamber is supplied from the scavenging passage to a 9 combustion chamber provided on the top of the cylinder hole, burnt gas in the combustion chamber is exhausted from the combustion chamber to the exhaust passage, fresh compressed in the combustion chamber is ignited with aid of the spark plug.

Such conventional spark ignition two-stroke internal combustion engine is disadvantageous in that exhaust gas contains much unburnt hydrocarbon and fuel consumption is high.

To solve the problem, the inventors of this invention had invented an internal combustion engine in which the pressure in a combustion chamber during the closing of an exhaust opening by a piston is appropriately controlled, fresh in the combustion chamber is activated by thermal energy of burnt gas remaining in the combustion chamber, thus fresh in the combustion chamber can be self-ignited at the ignition timing preferable for operation of the internal combustion engine, and a patent (Japanese Patent Laid-open No. Hei 7-71279) was applied.

[N:\LibP00240:BFD

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-2- Problem to the Solved by the Invention In the above-mentioned spark ignition two-stroke internal combustion engine with a combustion controller, for example, under the condition with a small throttle valve opening as in the idling operation, even if an exhaust control valve is throttled to increase the residual amount of burnt gas burnt in the combustion chamber in the abovementioned cycle in order to increase the temperature of the burnt gas and in order to self-ignite the fresh, the temperature of fresh containing residual burnt gas in the combustion chamber does not reach the self-ignition temperature and fresh can fail to be self-ignited because the throttle valve is throttled and fuel supply is reduced correspondingly.

Modification for solving the above-mentioned problem in which the temperature in the combustion chamber around the top dead point is increased by reducing the combustion chamber volume to increase the compression ratio while the stroke volume is maintained unchanged, results in knocking under high load operation, 15 and cannot be used practically.

Means for Solving the Problem and Effects •The present invention relates a spark ignition two-stroke internal combustion engine having a combustion controller in which the passage opening area of the inlet of ooo.oi an exhaust passage or in said exhaust passage is controlled depending on at least the 20 internal combustion engine rotation speed or throttle valve opening by operating an exhaust control valve so that fresh air and/or fuel mixture in a combustion chamber is .*self-ignition burnt during at least low load operation, wherein a combustion chamber volume adjusting means including a rotary valve which has a recess that communicates or not communicates to the combustion chamber through the opening to vary the compression ratio for varying the volume of said combustion chamber depending on operation condition of the internal combustion engine is provided.

Because the present invention is structured as described herein above, the fjl volume of the above-mentioned combustion chamber is reduced to increase the [I:\DAYLIB\LIBP]00240.DOC:BFD:KEH

'L

compression ratio by means of the above-mentioned combustion chamber volume adjusting means during low load operation particularly during idling operation when the throttle valve is throttled to reduce air supply and fuel supply, fresh containing residual burnt gas in the combustion chamber is adiabatically compressed strongly thereby, as the result, the fresh in the combustion chamber is self-ignited and burns in active thermal environment combustion mode to result in suppressed emission of unburnt hydrocarbon and improved fuel consumption.

According to the present invention, in addition, under normal operation condition when the throttle valve is opened, particularly under high load low speed operation condition when the engine is apt to knock, the volume of the combustion chamber is increased by means of the above-mentioned combustion chamber volume adjusting means to reduce the compression ratio, and thereby knocking is prevented and operation is performed quietly.

As described hereinbefore, by applying the present invention, the active thermal environment combustion area is expanded while knocking is prevented, fuel consumption is improved, and emission of unburnt hydrocarbon is suppressed.

Preferred Embodiments Embodiments of the present invention shown in Fig. 1 and Fig. 2 will be described hereinafter.

A spark ignition two-stroke internal combustion engine 1 with a combustion controller 1 is to be mounted on a motorcycle not shown in the figures, in the spark ignition two-stroke internal combustion engine 1, a cylinder block 3 and cylinder head 4 are placed one above the other and combined each other solidly above a crank case 2, and the throttle valve opening and internal combustion engine rotation speed have characteristics shown in Z-line charts of Fig. 5 and Fig. 6.

A piston 6 is engaged and inserted slidably in the vertical direction in a cylinder hole 5 formed on the cylinder block 3, the piston 6 and a crank shaft 8 are [N:\LibP]OO240:BFD connected each other by a connecting rod 7, and the crank shaft 8 is rotatably driven as the piston moves up and down.

An intake passage 10 communicating to a crank chamber 9 in the crank case 2 is formed, a carburettor not shown in the figures and reed valve 11 are connected to the intake passage 10 in series, scavenging openings 12 are provided on the peripheral surface of the cylinder hole 5, an exhaust outlet 13 is provided at the position above the scavenging opening 12, the scavenging openings 12 communicate to the crank chamber 9 through a scavenging passage 14, and the exhaust outlet 13 communicates to an exhaust passage A spark plug 17 is provided at the top of a combustion chamber 16 above the cylinder hole 5, fresh mixed with fuel in the carburettor not shown in the figures is inhaled into the crank chamber 9 which is negatively pressurized during up stroke through the reed valve 11 and compressed during down stroke, the compressed fresh is supplied into the combustion chamber 16 from the scavenging passage 14 when the 15 piston 6 goes down and the scavenging openings 12 are opened, burnt gas in the S"combustion chamber 16 is partially excluded from the exhaust outlet 13 into the exhaust passage 15 by the compressed fresh, and the scavenging opening 12 and subsequently the exhaust outlet 13 are closed as the piston 6 moves upward, the mixture in the combustion chamber 16 is compressed as the piston 6 moves upward, and around the

S.

top dead end, the mixture is ignited by the spark plug 17 or self-ignition with aid of thermal energy of residual gas generated in the previous cycle.

A cylindrical recess 18 communicating to the combustion chamber 16 is formed on the cylinder head 4 adjacent to the spark plug, a rotary valve body 19 is rotatably inserted in the cylindrical recess 18, a recess 20 is formed on the rotary valve body 19, the rotary valve body 19 is connected to a movable tab of a solenoid (not shown in the figures) with interposition of a lever not shown in the figures, sensors (not shown in the figures) for detecting the rotation speed of the spark ignition two-stroke internal combustion engine and the opening of a throttle valve not shown in the figures [N:\LibP00240:BFD are provided, a computer for performing following operations in response to reception of these both detected signals, and in the operational area A of Fig. 7 where the rotation speed of the spark ignition two-stroke internal combustion engine 1 is smaller than 5000 and the throttle valve opening is smaller than the above-mentioned solenoid is ON, the recess 20 of the rotary valve body 19 is closed and shielded from the combustion chamber 16 to result in reduced volume of the combustion chamber 16, thus the apparent compression ratio of the combustion chamber 16 is prescribed to be about 8, on the other hand, in the operational area B other than the operational area A in Fig. 7, the above-mentioned solenoid is not ON, the recess 20 of the rotary valve body 19 communicates to the combustion chamber 16 through the opening 21 as shown :0 *in Fig. 1 to result in increased volume of the combustion chamber 16, thus the apparent :compression ratio of the combustion chamber 16 is prescribed to be about 6.

In the above-mentioned spark ignition two-stroke internal combustion engine 1, S" while the recess 20 of the rotary valve body 19 communicates to the combustion 15 chamber 16 through the opening 21 to prescribe the apparent compression ratio to about 6, the active thermal environment combustion area X is in a range shown in Fig. 5, and while the recess 20 of the rotary valve body 19 is shielded from the combustion S chamber 16 to prescribe the apparent compression ratio to about 8, the thermal environment combustion area Y is expanded as shown in Fig. 6.

Further, in operational condition of the spark ignition two-stroke internal combustion engine 1, when the ignition switch is cut-off, the exhaust control valve 24 is opened upward or the above-mentioned solenoid is turned off, the apparent compression ratio is prescribed to be 6 or the throttle valve is throttled to an opening smaller than the idle throttle opening of Further, a valve containing recess 22 is formed above the exhaust passage and the base of an exhaust control valve 24 is supported swingably in the vertical direction by a shaft 23 inserted through the cylinder block 3 in parallel to the crank shaft 8 in the downstream of the valve containing recess 22.

IN:\LibP00O240:BFD Further, a flat slotted hole 25 is formed along the flat plane of the exhaust control valve 24 at the tip of the exhaust control valve 24, rotors 26 are inserted rotatably around the shaft in parallel to the crank shaft 8 in both sides of the abovementioned exhaust passage 15, and both ends of a connecting shaft 27 inserted in the flat slotted hole 25 of the exhaust control valve 24 is eccentrically inserted in integration to the above-mentioned both rotors 26.

The rotors 26 are connected to a governor not shown in the figures which detects rotation speed of the crank shaft for operation, while the rotation speed of the crank shaft is low, the exhaust control valve 24 swings downward as shown in Fig. 2, on the other hand, while the rotation speed of the crank shaft is high, the rotors 26 rotate in the counter clockwise direction and the exhaust control valve 24 swings upward as shown in Fig. 1 (instead of rotation control of the rotors 26 using the governor, the rotation of the rotors 26 may be controlled by an exhaust control servo *°oao motor which is controlled by a control signal of a CPU for calculation based on a prescribed control map in response to reception of input signals such as rotation speed of the crank shaft, throttle opening, and suction pressure).

The embodiment shown in Fig. 1 and Fig. 2 is structured as described *OoOO° hereinbefore, operations described hereinafter are therefore performed.

In detail, because the engine is under no-load condition at the starting, the throttle valve not shown in the figures is opened, and though the engine rotation speed increases along Z-curve of Fig. 5 and Fig. 6 as the opening increases, the opening of the throttle valve is smaller than 8% and the engine rotation speed is lower than 5000, the recess 20 of the rotary valve body 19 is shielded from the combustion chamber 16, and the exhaust control valve 24 swings downward, thus the apparent compression ratio is switched to 8 because of reduction of the volume of the combustion chamber 16, the chocking starting timing of the exhaust outlet 13 during the up stroke of the piston is advanced, the opening starting timing of the exhaust outlet 13 during the down stroke of the piston is advanced, and such operations result in the condition that fresh is heated [N:\LibP00240:BFD -7sufficiently to a high temperature due to the adiabatic compression with high compression ratio even if the temperature of the combustion chamber is low, consequently, the active thermal environment combustion is promoted, emission of unburnt hydrocarbon is suppressed, and combustion is improved.

Under the normal operation condition while the throttle valve not shown in the figures is opened with the opening of larger than high load operation, or high speed operation condition exceeding engine rotation speed of 5000, the exhaust control valve 24 swings upward as shown in Fig. 1, the recess 20 of the rotary valve body 19 communicates to the combustion chamber 16 through the opening 21, and the volume of the combustion chamber 16 is expanded, as the result, the choking starting timing of the exhaust outlet 13 during up stroke of the piston 6 is delayed and the opening starting timing of the exhaust outlet 13 during the down stroke of the piston 6 is advanced, thus large quantity of gas is exchanged smoothly without knocking and output power is increased quietly.

15 In the conventional two-stroke internal combustion engine, around the idle setting point that the throttle opening is throttled to about the active thermal environment combustion is impossible in the two-stroke internal combustion engine *with an apparent compression ratio of 6 and in the area the engine is apt to cause irregular combustion which generates emission containing large quantity of unburnt •eoo hydrocarbon, however, in the embodiment shown in Fig. 1 and Fig. 2, the apparent compression ratio is increased to 8 by closing the rotary valve body 19 as shown in Fig. 2, as the result, the active thermal environment combustion area is expanded from the area shown in Fig. 5 to the area shown in Fig. 6, thus the active thermal environment combustion is possible, fuel consumption is improved, and operational condition is stabilized.

A plurality of rotary valve bodies 19 with different volume of the recess may be provided and opening-and-closing operated selectively in the embodiment [N:\LibP]OO240:BFD

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shown in Fig. 1 and Fig. 2, thereby the apparent compression ratio can be varied stepwise.

The volume of the combustion chamber 16 is varied by rotating the rotary valve body 19 in the embodiment shown in Fig. 1 and Fig. 2, but instead, a recess 28 communicating to the combustion chamber 16 is formed on the cylinder head 4 as shown in Fig. 3 and a shutter valve 30 opening-and-closing operated by a valve opening-and-closing operating means such as a solenoid not shown in the figures is provided on the opening 29 of the recess 28, and in the embodiment shown in Fig. 3, the embodiment shown in Fig. 3 provides the same effect as the embodiment shown in Fig. 1 and Fig. 2.

The combustion controller may be structured as shown in Fig. 4. In detail, a sub-cylinder hole 31 communicating to the cylinder hole 5 is formed on the cylinder head 4, a sub-piston 32 is inserted slidably in the sub-cylinder hole 31, the outer end of *geaa the sub-cylinder hole 31 is closed by a lid 33 to form an oil pressure chamber 34, and by supplying or discharging pressure oil to or from the oil pressure chamber 34, the volume of the sub-chamber 35 of the sub-cylinder 35, namely the volume of the combustion chamber 16, may be varied, this embodiment provides the same effect as the above-mentioned embodiments and also stepless variation of apparent compression ratio.

Brief Description of the Drawings Fig. 1 is a vertical cross-sectional side view of an embodiment of a spark ignition two-stroke internal combustion engine having a combustion controller in accordance with the present invention under the normal operation condition.

Fig. 2 is a vertical cross-sectional side view of the embodiment of Fig. 1 under low load low speed operation condition.

Fig. 3 is a vertical cross-sectional view of a selected portion of another embodiment.

[N:\LibP]OO240:BFD Fig. 4 is a vertical cross-sectional view of a selected portion of yet another embodiment.

Fig. 5 is a characteristic chart for describing the boundary between the active environment combustion area and normal combustion area while the rotary valve is opened under low load and low speed operation condition in the embodiment shown in Fig. 1 and Fig. 2.

Fig. 6 is a characteristic chart for describing the boundary between the active thermal environment combustion area and normal area while the rotary valve is closed in the embodiment shown in Fig. 1 and Fig. 2.

Fig. 7 is a control graph for describing the switching of the rotary valve in the embodiment shown in Fig. 1 and Fig. 2.

Description of Reference Characters :1 SPARK IGNITION TWO-STROKE INTERNAL COMBUSTION ENGINE "2 CRANK CASE 3 CYLINDER BLOCK 4 CYLINDER HEAD CYLINDER HOLE 6 PISTON 7 CONNECTING ROD 8 CRANK SHAFT 9 CRANK CHAMBER INTAKE PASSAGE 11 REED VALVE 12 SCAVENGING OPENING 13 EXHAUST OUTLET 14 SCAVENGING PASSAGE EXHAUST PASSAGE 16 COMBUSTION CHAMBER [N:\LibP]OO240:BFD 17 18..

19..

521 22..

23 24 26 27 28 29 30 15 31 32..

33 34 SPARK PLUG CYLINDRICAL RECESS ROTARY VALVE

RECESS

OPENING

VALVE BODY CONTAINING RECESS

SHAFT

EXHAUST CONTROL VALVE FLAT SLOTTED HOLE

ROTOR

CONNECTING SHAFT

RECESS

OPENING

SHUTTER VALVE

SUB-CYLINDER

SUB-PISTON

LID

OIL PRESSURE CHAMBER

SUB-CHAMBER

9* I 0.*t [N:\LibP]00240:BFD -11- The claims defining the invention are as follows: 1. A spark ignition two-stroke internal combustion engine having a combustion controller in which the passage opening area of the inlet of an exhaust passage or in said exhaust passage is controlled depending on at least the internal combustion engine rotation speed or throttle valve opening by operating an exhaust control valve so that fresh air and/or fuel mixture in a combustion chamber is selfignition burnt during at least low load operation, wherein a combustion chamber volume adjusting means including a rotary valve which has a recess that communicates or not communicates to the combustion chamber through the opening to vary the compression ratio for varying the volume of said combustion chamber depending on operation condition of the internal combustion engine is provided.

2. A spark ignition two-stroke internal combustion engine having a combustion controller in which the passage opening area of the inlet of an exhaust passage or in said exhaust passage is controlled depending on at least the internal 5 combustion engine rotation speed or throttle valve opening by operating an exhaust control valve so that fresh air and/or fuel mixture in a combustion chamber is selfignition burnt during at least low load operation, wherein the self-ignition timing is made adjustable by varying the volume of said combustion chamber depending on ooooo operation condition of the internal combustion engine by a combustion chamber volume 20 adjusting means including a rotary valve which has a recess that communicates or not communicates to the combustion chamber through the opening to vary the compression ratio.

3. A spark ignition two-stroke internal combustion engine having a combustion controller in which the passage opening area of the inlet of an exhaust passage or in said exhaust passage is controlled depending on at least the internal combustion engine rotation speed or throttle valve opening by operating an exhaust control valve so that fresh air and/or fuel mixture in a combustion chamber is selfignition burnt during at least low load operation, wherein, outside the cylinder top of a .:\DAYLB\LIBP]00240.DOC:BFD:KEH [I:\DAYLIB\LIBP] 00240.DOC: BFD: KEH

Claims

12- main combustion chamber, at least one sub-combustion chamber communicating to said main combustion chamber and an opening-and-closing means provided for opening-and- closing operating said main combustion chamber and sub-combustion chamber are provided, and said opening-and-closing means is operated depending on operational condition of the internal combustion engine so that self-ignition timing can be adjusted. 4. The spark ignition two-stroke internal combustion engine as claimed in claim 1 or claim 2, wherein, outside the cylinder top of a main combustion chamber, at least one sub-combustion chamber communicating to said main combustion chamber and opening-and-closing means for opening-and-closing operating said main combustion chamber and sub-combustion chamber are provided. The spark ignition two-stroke internal combustion engine as claimed in claim 3, wherein said opening-and-closing means described in claim 3 comprises at least one rotary valve communicating to the main combustion chamber provided at the cylinder top, and said sub-combustion chamber described in claim 3 comprises the 15 internal space in the rotary valve body of said rotary valve. 6. The spark ignition two-stroke internal combustion engine as claimed in claim 3, wherein said opening-and-closing means described in claim 3 is a poppet valve or shutter valve. 7. A spark ignition two-stroke internal combustion engine substantially as 20 hereinbefore described with reference to the accompanying drawings. Dated 28 July, 1999 Honda Giken Kogyo Kabushiki Kaisha Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [I:\DAYLIB\LIBP]00240.DOC:BFD:KEH Spark Ignition Two-Stroke Internal Combustion Engine Having a Combustion Controller ABSTRACT A spark ignition two-stroke internal combustion engine comprises a combustion controller, which is capable of self-ignition burning of fresh air-fuel mixture in a combustion chamber (16) at least during low load operation by controlling an inlet of an exhaust passage (15) or opening area of a passage in an exhaust passage (15) with the aid of an exhaust control valve dependently on at least the internal combustion engine rotation speed or throttle valve opening. Combustion chamber volume adjusting means (19, 20) are provided for varying the volume of the combustion chamber (16) depending on the operational condition of the internal combustion engine by operating the exhaust control valve (24) so that the fresh air-fuel mixture in the combustion chamber (16) is self-ignition burnt during at least low load operation. o *o* a *a [N:\LIBM]05779:CMS