Multi-cylinder internal combustion engine

Abstract: OBJECT: To provide an operation control device for an in-cylinder injection type two-cycle engine capable of avoiding the problem of poor combustion state due to lower temperature in operating cylinders caused by lower temperature air flowing from halted cylinders back into the operating cylinders when cylinder halt operation is employed. SOLVING MEANS: An operation control device for an in-cylinder injection type two-cycle engine wherein fuel is supplied by injection with an injection valve (49) to a combustion chamber, ignited with an ignition plug (27), burned, and the burned gas is exhausted to the atmosphere through exhaust passages, characterized in that the device is provided with; an exhaust control valve (71) for variably controlling the cross-sectional area of the exhaust passages and disposed so that the exhaust gas from at least one cylinder is exhausted to the atmosphere after passing through the exhaust control valve (71), and an ECU (50) which serves as cylinder halt control means for halting the operation of at least one cylinder in a specified operation range, and as an exhaust control valve opening control means for making the opening of the exhaust control valve in a cylinder halt operation range smaller than the opening for a non-cylinder halt operation range.

Description: This invention relates to a multi-cylinder internal combustion engine according to the preamble of claim 1. An in-cylinder injection type two-cycle engine has been proposed which operates in the following steps: Fresh mixture is introduced into a crank chamber through an intake passage having a throttle valve, and subjected to a primary compression. While the primarily compressed fresh mixture scavenges the cylinder, fuel is injected at a timing somewhere during the scavenging, exhaust, and compression strokes from the fuel injection valve disposed in the combustion chamber wall, ignited after the compression stroke and burned. The burned gas is exhausted from the combustion chamber prior to the next scavenging stroke. The two-cycle engine has a problem that irregular combustion is likely to occur especially in the low speed, low load operation range because of reasons such as a small amount of fresh mixture for scavenging and resultant low in-cylinder pressure causing reverse flow of burned gas present in the exhaust passage back into the cylinder, diffusion of injected fuel causing decrease in the fuel concentration, and poor flame propagation due to low in-cylinder temperatures. Therefore, the inventors have developed an arrangement for the in-cylinder injection type of two-cycle engine employing an exhaust control valve for variably controlling the cross-sectional area of the exhaust passage, so that the irregular combustion is minimized by maintaining a high pressure at the beginning of compression and a high in-cylinder temperature by reducing the cross-sectional area of the exhaust passage. With the direct fuel injection into combustion chambers, fuel injection valves of a large flow rate are used to inject a necessary amount of fuel within a short period of time, thereby avoiding blow-by and forming satisfactory mixture. On the other hand, there is a limit to the minimum period of time (normally on the order of 1 ms) for a stabilized drive. Therefore, when combustion in the low load operation range is improved, in some cases a required flow rate may be less than the minimum flow rate of the fuel injection valve and a concern arises that the so-called dynamic range is insufficent. From prior art document JP-A-59 170 440 an internal combustion engine is known. Within said engine suction intercept valves are installed in suction passages (a branch pipe from a surge tank) leading to each suction side cylinders of the cylinder number control engine, and exhaust intercept valves are installed in exhaust pipes. And, using a suction pressure sensor or an engine speed sensor installed in the surge tank, fuel feed to these suspended cylinders is intercepted when suction pressure is above the specified value or engine speed is below that, while both intercept valves are fully closed whereby a pumping loss is reduced. It is an objective of the present invention to provide a multi-cylinder internal combustion engine as indicated above having an improved fuel combustion, especially in the low speed and low load operation range. According to the present invention said objective is solved by a multi-cylinder combustion engine according to claim 1. Further advantageous embodiments are laid down in the subclaims. It is known to halt at least one of the cylinders in a specified operation range. As a result, the fuel amount injected from one injection valve per operating cylinder increases. Thus, the problem of insufficient dynamic range is solved. It is also known to control the exhaust control valve opening in the halt cylinder operation range so as to be smaller than the opening outside the halt cylinder operation range, low temperature air in the halted cylinders is prevented from flowing back into the operating cylinders and from lowering temperature in the operating cylinders. According to the invention, the exhaust passage of the active cylinders is throttled in the cylinder halt operation range, so that it is possible to maintain pressurs and temperature in the cylinders at the beginning of compression and to restrict the occurrence of irregular combustion, due to the flowing back of low temperature air from the halted cylinders into the active cylinders, so that the temperature in the active cylinders is not lowered. According to an embodiment of the invention, the exhaust control valve is provided for part of the cylinders and the cylinder halt control means halts the cylinders not provided with the exhaust control valve. As a result a less number of exhaust control valves suffices. This makes the structure and the halt control simple and reduces the cost. In addition, it is oossible that the exhaust control valve is disposed in the middle of a confluence passage to which independent passages of the cylinders are joined together and that the cylinder halt control means halts the cylinders downstream of the exhaust control valve. Hereinafter the present invention is illustrated and explained by means of a preferred embodiment in conjunction with the accompanying drawings. In the drawings wherein: FIG. 1 is a left side view of an outboard motor employing the two-cycle engine as en embodiment of the invention; FIG. 2 is a cross-sectional plan view of the outboard motor of the above embodiment; FIG. 3 is a cross-sectional rear view of the engine of the above embodiment. FIG. 4 is a block constitution diagram for the operation control device of the above embodiment; FIG. 5 is a cross-sectional plan view of the outboard motor of the above embodiment, for explaining a modification example of the exhaust control valve; FIG. 6 is a cross-sectional rear view of the engine of the above embodiment, for explaining a modification example of the exhaust control valve; FIGs. 7 and 8 are conceptual drawings showing cylinder halt operation range(s) of the above embodiment, FIGs. 9 through 12 are conceptual drawings showing modified location and structure examples of the exhaust control valve of the above embodiment, wherein FIGs. 11(d) and 12(e) are showing examples which do not fall under the teaching of claim 1. FIGs. 1 through 7 illustrate an in-cylinder injection type of two-cycle gasoline engine as an embodiment explaining the invention. FIG. 1 is a side view of an outboard motor employing the engine of the embodiment. FIG. 2 is a cross-sectional plan view of the same engine. FIG. 3 is a cross-sectional rear view of a variant of the same engine. FIG. 4 is a block constitution diagram for the operation control device. FIGs. 5 and 6 are cross-sectional plan and rear views, respectively, of an outboard motor for explaining modification examples of the exhaust control valve. FIG. 7 and 8 are a conceptual drawing for explaining operation halt range. In the drawings are shown an outboard motor 1 employing an embodiment of the invention, supported through a swivel arm 9 and a clamp bracket 8 on the stern 2a of a hull 2 for free, up and down swinging about a support shaft 100. During cruising, the outboard motor 1 is in the vertical attitude with its crankshaft 20 generally vertical. Roughly speaking, the outboard motor 1 comprises a thrusting propeller 3 disposed in a lower case 4 to the top of which is connected an upper case to the top of which is mounted an engine 6 covered with a cop cowl 7. The rotation of the crankshaft 20 of the engine 6 is transmitted co the propeller 3 through an output shaft 6a connected to the crankshaft 20, a vertically extending drive shaft 12, a bevel gear mechanism 10, and a horizontally extending propeller shaft 11. The engine 6 is a water-cooled, V-type, six-cylinder, two-cycle engine roughly comprising, a crankcase 22 including the crankshaft 20, a cylinder body 23 having six cylinders (cylinder bores) 21 forming two banks in a V-shape and connected to the crankcase 22, a cylinder head 24 disposed on the cylinder body 23, six pistons 25 respectively inserted for free sliding in the cylinders 21 and connected through connecting rods 26 to the crankshaft 20. Ignition plugs 27 are screwed into the cylinder head 24. Electrodes of the ignition plugs 27 are disposed to face the insides of combustion chambers surrounded with the cylinder head 24, the cylinders 21 of the cylinder body 23, and the pistons 25. The ignition plugs 27 are energized with an ignition circuit 63 (See FIG. 4.) to produce sparks in the combustion chambers at specified timings. The intake system of the engine 6 is constituted as described below. The crankcase 22 is formed with openings 22b respectively communicating with crank chambers 22a each corresponding to each cylinder 21. Each of the openings 22b is connected through a reed valve 32 to an intake passage 30. A throttle body 33 including a throttle valve 31 is connected to the upstream side of the intake passage 30. The throttle valve 31 is driven to open and close with a throttle actuator 61 (See FIG. 4). The cylinder body 23 is formed with two main scavenging passages 35b and 35c for each cylinder 21, and one opposing scavenging passage 35a for each cylinder 21. to make connection between each crank chamber 22a and each cylinder 21. The scavenging ports 35 of the scavenging passages 35a, 35b, and 35c are open to the inside of the cylinder 21. Fuel injection valves 49, one for each cylinder 21, are provided in the side wall of the cylinder body 23. Each fuel injection valve 49 is connected to a fuel supply rail (not shown) with its end portion having a pressure adjustment valve. High pressure fuel is supplied through a fuel pump to the fuel supply rail. The high pressure fuel is injection-supplied into the cylinder 21 while an injection nozzle is open as a valve piece is moved by a solenoid coil 62 (See FIG. 4.) built in the fuel injection nozzle 49. The exhaust system of the engine 6 is constituted as described below. The cylinder body 23 is formed with an exhaust branch passage (independent passage) 42 connected to an exhaust port 41 opening to each cylinder 21. For each bank of cylinders, the exhaust branch passages 42 are joined to one exhaust confluence passage 40 running vertically generally parallel to the crankshaft 20. The lower end exhaust opening 6b of each of the exhaust confluence passages 40 is open to the underside of the cylinder body 23. An exhaust guide 13 is connected to the underside of the cylinder body 23. The exhaust guide 13 is formed with paired exhaust holes 13a, 13a connecting to the lower end exhaust openings 6b, and connected to exhaust pipes 14 respectively extending from the exhaust holes 13a downward. To the exhaust guide 13 is connected a muffler 16 surrounding the exhaust pipe 14 and forming an exhaust expansion chamber. The lower end of the muffler 16 is open to the water inside the lower case 4. In this way an exhaust passage for exhausting exhaust gas from the cylinders is constituted. An exhaust pressure sensor 55 is disposed in the muffler 16 to detect pressure (back pressure) in the exhaust passage. The exhaust pressure sensor 55 is disposed to pass through from outside the upper case 5 into the muffler 16. A detecting portion of the sensor 55 is located near the downstream opening of the exhaust pipe 14. According to the variant of the embodiment as shown in FIG. 3, an exhaust control valve 70 of a butterfly type is disposed in every independent passage 42 at a position just after the exhaust port 41. The exhaust control valves 70 comprise six valve plates 71 respectively disposed in the independent passages 42, with three valve plates 71 secured to one valve shaft 72 for each of two banks of six cylinders. The valve shafts 72 are disposed in a straight line at right angles to the cylinder axis. Each of the valve plates 71 is formed with a communication hole 71a to serve as a leak passage for the exhaust gas when the valve is fully closed. The opening area of the communication hole 71a is set to minimize the difference in the exhaust gas discharge resistance among the cylinders due to their locations and cooling conditions. The upper ends of the valve shafts 72 are interconnected through a connection mechanism 73 comprising pulleys 73a, 73b, and a link 73c, and driven with a drive motor 75 through the pulley 73a and a cable 74. The confluence passages 40 is covered with a removable cover member 40a extending between the cylinder banks in the crankshaft direction. Onto the cover member 40a are attached the motor 75 and other components for driving the exhaust control valve. Once the cover member 40a is removed, the valve plates 71 face the outside and accessible for easy attachment co and removal from the valve shaft 72. FIGs. 5 and 6 show another form of the exhaust control valves with a valve shaft 82 for each cylinder 21 according to the present invention. In this case, each exhaust control valve 80 comprises a valve plate 81 disposed just after each exhaust port 41 and secured to the valve shaft 82 disposed generally parallel to the cylinder axis with one end of the valve shaft 82 projecting outward. The valve shaft 82 is driven for rotation with a drive motor (not shown) through a pulley 83 secured to the projecting end of the valve shaft 82 and a cable (not shown). If the exhaust control valves 80 are respectively provided with drive motors, the openings of the exhaust control valves 80 may be respectively controlled. FIG. 4 shows an ECU 50 for controlling the operation of the engine 6. Signals representing the operating state of the engine 6 are sent from various sensors to the ECU 50. Such signals include for example: an engine revolution signal REV from a revolution sensor 51, an accelerator opening (for example accelerator pedal travel) signal ACC from an accelerator opening sensor 52, an engine cooling water temperature signal TW from a water temperature sensor 53, a crank angle (piston position) signal CA from a crank angle sensor 54, an in-exhaust pipe pressure (back pressure) signal PE from the exhaust pressure sensor 55, a crank chamber pressure signal from a crank chamber pressure sensor 56, an ambient pressure signal from an ambient pressure sensor 57, and an ambient temperature signal from an ambient temperature sensor 58. The ECU 50 performs various calculations using various signals coming from the above-described sensors and representing the engine operation state, according to a preset program, and using various control maps stored in a data storage, and outputs various control signals to various actuators. The output signals include for example; a throttle valve opening signal TH to a throttle actuator 61 for driving the throttle valve 31 in opening and closing directions, a fuel injection duration (injection rate) signal FD and fuel injection start timing signal INJ to a solenoid coil 62 for driving a fuel injection valve 49 in opening and closing directions, an ignition signal IGN to an ignition circuit 63 for supplying a high tension current to the ignition plug 27, and an exhaust control valve opening signal EXV to an actuator 64 for driving the exhaust control valve 43 in opening and closing directions. The opening of the throttle valve 31 and the opening of the exhaust control valve 43 are detected with a throttle opening sensor and an exhaust control valve opening sensor (both not shown) and the detected signals are fed back to the ECU 50. Here, the ECU 50 has the following functions. [Cylinder Halt Operation Control Function] FIG. 7 shows cylinder halt operation ranges according to the engine revolution REV and the accelerator opening ACC. with ranges A. B. and C with more number of halted cylinders per rotation of the crankshaft toward the low speed, low load operation. In this engine 6, combustion occurs six times per crankshaft revolution. That is to say, for five crankshaft revolutions (30 combustions), for example in the range A, the cylinder halt occurs three times (one halt per 10 combustions): in the range B, 4.3 times (one halt per seven combustions); and in the range C six times (one halt per five combustions). Specifically, halts and combustions occur as shown below, with the numerals in parentheses denoting the halted cylinders while naked numerals denoting the operated cylinders, [Range A] (1)-2-3-4-5-6-1-2-3-4-(5)-6-1-2-3-4-5-6-1-2-(3)-4-5-6-1-2-3-4-5-6-(1)-2-3-4-5-6 [Range B] (1)-2-3-4-5-6-1-(2)-3-4-5-6-1-2-(3)-4-5-6-1-2-3-(4)-5-6-1-2-3-4-(5)-1-2-3-4-5-(6) [Range C: regular interval halts] (1)-2-3-4-5-(6)-1-2-3-4-(5)-6-1-2-3-(4)-5-6-1-2-(3)-4-5-6-1-(2)-3-4-5-6-(1)-2-3-4-5-(6) [Irregular interval halts] (1)-2-3-4-(5)-6-1-2-3-4-(5)-6-1-2-(3)-4-5-6-1-2-(3)-4-5-6-(1)-2-3-4-5-6-(1)-2-3-4-(5)-6 There are two possible methods for the cylinder halt operation: one is to stop the ignition only to the cylinder to be halted, and the other is to stop both fuel supply and ignition. From the viewpoint of avoiding the deterioration in the exhaust gas composition, stopping the fuel supply is preferable. [Exhaust Control Valve Opening Control Function] In the non-cylinder halt operation range (all cylinder operation range), the opening EXV of the exhaust control valve is controlled to the accelerator-revolution-dependent exhaust control valve opening EXVo set according to the accelerator opening ACC and/or engine revolution REV. In the cylinder halt operation range on the other hand, the exhaust control valve opening EXV is made smaller than the opening in the non-cylinder halt operation range. Since this embodiment is arranged as described above with ranges A. B. and C with more number of halted cylinders per rotation of the crankshaft toward the low speed and low load operation range, when the amount of fuel required for the engine as a whole decreases, the amount of fuel not injected into the halted cylinders is added co the amount of fuel injected into the operating cylinders. That is to say, the amount of fuel per operating cylinder, namely the amount of fuel injected from one injection valve per one combustion increases. As a result, the problem of insufficient dynamic range may be avoided. In the cylinder halt operation ranges A through C, the opening EXV of the exhaust control valve 70 or 80 is controlled to be smaller than the exhaust control valve opening (accelerator-revolution-dependent exhaust control valve opening EXVo) in the non-cylinder halt operation range (all cylinder operation range), namely the passages 42 connecting to the operating cylinders are throttled. As a result, low temperature air from the halted cylinders (with numerals in parentheses) is prevented from flowing back into the operating cylinders (with naked numerals) and lowering the operating cylinder temperature. Also, throttling the exhaust control valves makes it possible to maintain high pressure and temperature in the cylinders at the beginning of compression. As a result. irregular combustion is restricted. Since the halted cylinder is changed in sequence among all the cylinders, the halted cylinder may smoothly resume operation. while avoiding overheat or poor lubrication in specific cylinders. Since the exhaust control valve 70 or 80 is disposed in every independent passage it is possible to change the halted cylinder in sequence as described above and low temperature air from the halted cylinders is prevented from flowing back into the operating cylinders. While the present embodiment employs the three cylinder halt ranges of A. B. and C. only one cylinder halt range may be employed as shown in FIG. 8 with a single pattern of halting the cylinders. In that case, the exhaust control valves need not be disposed to correspond to all the cylinders, and the structure is simplified. To carry out the cylinder halt operation of FIG. 8, various forms may be considered depending on the engine types as shown in FIGs. 9 through 12. In any case, the cylinders not provided with the exhaust control valves are to be halted. FIG. 9 shows examples of side-by-side, two-cylinder engines. In FIG. 9(a), the exhaust control valve 90 is disposed to correspond to the cylinder (1) only. In FIG. 9(b) the exhaust control valve 90 is disposed to correspond to the cylinder (2) only. In FIG. 9(a), the cylinder (2) is halted and in FIG. 9(b), the cylinder (1) is halted. This prevents low temperature air from the halted cylinder (2) or (1) from flowing back into the operating cylinder (1) or (2), and high pressure and. temperature are maintained in the cylinders at the beginning of compression. As a result, irregular combustion is restricted. FIG. 10 shows an example of a three-cylinder engine with an exhaust control valve 90 corresponding to cylinders (1) and (2), and with the cylinder (3) halted. This prevents low temperature air from the cylinder (3) from flowing back into the cylinders (1) and (2), and high pressure and temperature are maintained in the cylinders (1) and (2) at the beginning of compression. FIG. 11 shows examples of a four cylinder engines also capable of preventing irregular combustion in the operating cylinders. In FIG. 11(a), an exhaust control valve 90 is disposed to correspond to the left bank of cylinders (2) and (4) while the right bank of cylinders (1) and (3) halted. Alternatively the exhaust control valve 90 may be disposed to correspond the right bank of cylinders (1) and (3). In that case, the left bank of cylinders (2) and (4) are halted. In the example shown in FIG. 11(b), one exhaust control valve 90 is disposed to correspond to the cylinder (1) while the other exhaust control valve (90) to the cylinders (2) and (4), with the cylinder (3) halted. By the way. if the exhaust valves 90. 90 are disposed in positions shown with broken lines, the cylinder (4) is halted. FIG. 11(c) shows an example in which an exhaust control valve 90' comprising two valve plates corresponding to cylinders (1) and (2) and attached to a single valve shaft, with the cylinders (3) and (4) halted. FIG. 11(d) shows an example which does not fall under the teaching of independent claim 1, with a similar exhaust control valve 90' corresponding to all the cylinders, with two cylinders in either bank halted. FIG. 12 shows six-cylinder engines also capable of preventing irregular combustion in the operating cylinders. An exhaust control valve 90' comprising two valve plates corresponding to cylinders (1), (3) and (2), (4) and attached to a single valve shaft, with the cylinders (5) and (6) halted. FIG. 12(b) shows another example with one exhaust control valve 90 disposed to correspond to the right hand bank of cylinders (1), (3) and (5), with the other exhaust control valve 90 disposed co correspond to the cylinder (2) in the left hand bank, and the cylinders (4) and (6) in the left hand bank may be halted. Alternatively, the exhaust control valves 90 may disposed as shown with broken. lines. In that case, the cylinders (3) and (5) in the right hand bank may be halted. FIG. 12(c) shows another example with one exhaust control valve 90 disposed to correspond to the right hand bank of cylinders (1), (3) and the other exhaust control valve 90 disposed to correspond to the cylinder (2), (4) and (6) in the left hand bank. and the cylinder (5) may be halted. Alternatively, the exhaust control valves 90 may disposed as shown with broken lines. In that case. the cylinder (6) may be halted. FIG. 12(d) shows another example with the exhaust control valve 90 disposed on the downstream end of the confluence passage of either left hand cylinder bank as shown with solid lines or right hand cylinder bank as shown with broken lines, with either one of cylinder banks not provided with the exhaust control valves halted. FIG. 12(e) shows another example which does not fall under the teaching of independent claim 1, in which two valve plates attached to a single valve shaft to constitute an exhaust control valve 90' are disposed in the downstream end portions of the confluence passages with cylinders in either one of the banks halted. In any of the arrangements of FIGs. 9 through 12, some of the cylinders are halted in the cylinder halt operation range shown in FIG. 8. Therefore, if the fuel amount for the cylinder halt operation is maintained the same as that for the all cylinder operation, the fuel amount required for one operating cylinder, namely the fuel amount injected from one injection valve for one combustion increases. As a result, the problem of insufficient dynamic range may be avoided. Also, since the exhaust control valve 90 or 90' is disposed in the middle of the confluence passage and the cylinders located downstream of the exhaust control valve are halted, less number of exhaust control valves suffices, structure and halt control are simple, and the production cost is reduced.

Claims: Multi-cylinder internal combustion engine (6) comprising an exhaust system including a respective number of exhaust passages (42) and at least one exhaust control valve (80;90), cylinder halt means for halting the operation of at least one of the engine's cylinders (21) in a specific range of operation of said engine (6), and a control device (50) for controlling the operation of said exhaust control valve (80;90) and said cylinder halt means by reducing the opening degree of said at least one exhaust control valve (80;90) in said specific range of operation compared with the opening degree of said exhaust control valve (80;90) outside said specific range of operation, characterized in that said at least one cylinder (21) the corresponding exhaust passage (42) of which is controlled by said exhaust control valve (80;90) is different from the at least one cylinder (21) being halted by said cylinder halt means. Multi-cylinder internal combustion engine according to claim 1, characterized in that said control device (50) being adapted to variably control the opening degree of said at least one exhaust passage (42), that said exhaust control valve (80;90) being disposed such that the exhaust gas from said at least one cylinder (21) being exhausted to the atmosphere after passing said exhaust control valve (80;90). Multi-cylinder internal combustion engine according to one of the preceding claims 1 or 2, characterized in that said exhaust control valve (90) being provided for a part of said cylinders (21). Multi-cylinder internal combustion engine according to claim 1, characterized in that said exhaust control valve (80;90) being provided for all of said cylinders (21) and that said control device (50) being adapted to control said cylinder halt means according to a predetermined sequence. Multi-cylinder internal combustion engine according to claim 1, characterized in that one exhaust control valve (80) being provided for each of said cylinders (21) within each exhaust passage (42). Multi-cylinder internal combustion engine according to claim 1, characterized in that exhaust passages (42) are joined together to a confluence passage (40), that said exhaust control valve (90) being provided within said confluence passage (40), and that said cylinder or cylinders (21) downstream of said exhaust control valve (90) being haltable. Multi-cylinder internal combustion engine according to at least one of the preceding claims 1 to 6, characterized in that said or each exhaust control valve (80;90) comprising valve plates (81). Multi-cylinder internal combustion engine according to at least one of the preceding claims 1 to 7, characterized in that said or each exhaust control valve (80;90) being adapted to provide a leak passage for exhaust gas when said exhaust control valve or valves (80;90) being fully closed. Multi-cylinder internal combustion engine according to at least one of the preceding claims 1 to 8, characterized in that said internal combustion engine is an in-line engine or a V-type engine (6). Multi-cylinder internal combustion engine according to claim 9 whereas the engine (6) is of the V-type, characterized in that each cylinder line being provided with a valve shaft for simultaneously controlling all of said respective exhaust control valves of one cylinder line. Multi-cylinder internal combustion engine according to claim 9, characterized in that each of said exhaust control valves (80) being provided with a single valve shaft (82). Multi-cylinder internal combustion engine according to at least one of the preceding claims 1 to 11, characterized in that said control device (50) being adapted to control said engine (6) by using signals representing engine operating states according to a preset program, and by using prestored control maps. Multi-cylinder internal combustion engine according to at least one of the preceding claims 1 to 12, characterized in that said cylinder halt means being adapted to interrupt fuel supply and/or ignition. Multi-cylinder internal combustion engine according to claim 13, characterized in that the amount of fuel not injected into the halted cylinders is distributable to said cylinder or cylinders (21) being operated. Multi-cylinder internal combustion engine according to at least one of the preceding claims 1 to 14, characterized in that said internal combustion engine is an in-cylinder injection type two-stroke cycle internal combustion engine (6).

Inventors: OHOKUBO AKIHIKO, YU MOTOYAMA, OHOKUBO, AKIHIKO
Applicants: YAMAHA MOTOR CO LTD, YAMAHA HATSUDOKI KABUSHIKI KAISHA
Application year: 1997
Main classification: F02D17
IPC codes: F02B25, F02D41, F02B75, F02D17, F02D9