JPH02230963A - Combustion control device for two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To ignite and burn a mixture immediately after an engine is started by repeating the cycle in which fuel is fed but not ignited and the cycle in which fuel is fed and ignited for predetermined cycles when the engine is operated with a low load. CONSTITUTION:When an engine is operated with a low load, first the fuel and compressed air are injected through an air blast valve 30 and a fuel injection valve 36, then the ignition by an ignition plug 10 is stopped, the mixture is once compressed in a cylinder 1, it is strongly mixed with the high- temperature remaining burnt gas, gasification is accelerated by the temperature rise due to a compression action, the time before ignition is extended, thus the mixture is set to the state to be easily ignited and burned. The fuel and compressed air are again injected through the air blast valve 30 and fuel injection valve 36 in the next cycle and ignited by the ignition plug 10. The mixture can be ignited and burned immediately after the engine is started even when the engine is operated with a low load.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a combustion control device for a two-stroke internal combustion engine.

[Conventional technology]

In a cinnulated two-stroke internal combustion engine, once the air-fuel mixture in the combustion chamber is ignited by the spark plug, especially during idling, a large amount of burnt gas remains in the combustion chamber. It cannot be ignited, or even if it is ignited, it will be incompletely burned. The scavenging action is then repeated several times, and when a large amount of fresh air is present in the combustion chamber, the air-fuel mixture is ignited again by the spark plug. When such irregular combustion occurs, torque fluctuations during idling become large, making idling unstable.

Therefore, it is determined whether or not a large amount of fresh air is present in the combustion chamber based on the output signal of an oxygen concentration detector installed in the exhaust passage. A two-stroke internal combustion engine is known that uses a spark plug to ignite the air-fuel mixture when the output signal level of a concentration detector exceeds a predetermined level (Japanese Patent Laid-Open No. 60-230562). (see official bulletin). In this two-stroke internal combustion engine, the ignition action by the ignition plug is performed once every several cycles.

[Problem to be solved by the invention]

However, the oxygen concentration detector does not operate unless the temperature rises to a certain degree, and therefore, in the above-mentioned two-stroke internal combustion engine, there is a problem in that ignition control using the spark plug cannot be performed for some time after the engine is started. Furthermore, as described above, when judged from the oxygen concentration in the exhaust passage, the intervals at which the ignition action is performed by the ignition plug vary, and therefore there is a problem that torque fluctuations still occur.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a two-stroke internal combustion engine in which the air-fuel mixture is ignited and combusted by a spark plug, and there is a cycle in which fuel is supplied but not ignited during low-load engine operation, and a cycle in which fuel is supplied but not ignited. The ignition cycle and the ignition cycle are repeated every predetermined cycle.

[For production]

It is known in advance how many cycles the ignition must be performed to ignite the air-fuel mixture. Therefore, by repeating the ignition action every predetermined cycle, no torque fluctuation occurs, and moreover, the ignition action can be performed every predetermined cycle immediately after the engine is started.

〔Example〕

FIG. 4 shows an overall diagram of a two-stroke internal combustion engine.

In the embodiment shown in FIG. 4, the two-stroke internal combustion engine has the first cylinder #1, the second cylinder #2, the third cylinder #3, and the fourth cylinder #4.
It consists of a 6-cylinder internal combustion engine with the 5th cylinder #5 and the 6th cylinder #6. Each of these cylinders has a similar structure, and their structures are briefly shown in FIGS. 1 to 3.

Referring to FIGS. 1 to 3, 1 is a cylinder block, 2 is a piston that reciprocates within the cylinder block 1, and 3 is a cylinder block.
is the cylinder head fixed on the cylinder block 1,
4 indicates a combustion chamber formed between the inner wall surface 3a of the cylinder head 3 and the top surface of the piston 2, respectively. A groove 5 is formed on the inner wall surface 3a of the cylinder head, and a pair of intake valves 6 are formed on the inner wall surface portion 3b of the cylinder head forming the bottom wall surface of the groove 5.
is placed. On the other hand, the cylinder head inner wall surface portion 3C excluding the groove 5 is substantially flat, and a pair of exhaust valves 7 are arranged on this cylinder head inner wall surface portion 3C. Cylinder head inner wall surface portion 3b and cylinder head inner wall surface portion 3C
are connected to each other via the peripheral wall 8 of the groove 5. This concave groove peripheral wall 8 includes a pair of mask walls 8a extending in an arc shape along the peripheral edge of the air supply valve 6, a fresh air guide wall 8b located between the air supply valves 6, and a peripheral edge of the cylinder head inner wall surface 3a. and a pair of fresh air guide walls 8C located between the air supply valves 6. Each mask wall 8a extends toward the combustion chamber 4 below the intake valve 6 at the maximum lift position shown by the broken line in FIG. The opening between the valve seats 9 is closed by the mask wall 8a throughout the opening period of the air supply valve 6. Further, the pair of fresh air guide walls 8C are located on substantially the same plane, and furthermore, the fresh air guide walls 8b and 8c extend substantially parallel to the line connecting the centers of both air supply valves 6.

Further, in the embodiment shown in FIGS. 1 to 4, a pair of fresh air guide walls 8c extend to the bottom wall surface of the cylinder head inner wall surface 3a. That is, the bottom wall surface of the cylinder head inner wall surface 3a has a pair of bottom wall surface portions 3d that protrude into the combustion chamber 4 in a U-shape, and each fresh air guide wall 8C extends from the cylinder head inner wall surface portion 3b to this bottom wall surface. It extends to the wall portion 3d. Therefore, the height of the fresh air guide wall 8c is higher than the height of the mask wall 8a. On the other hand, the mask wall 8a located on the fresh air guide wall 8c side has an extension portion 8d extending to the bottom wall surface portion 3d.
This extension 8d also forms a fresh air guide wall. As can be seen from FIG. 3, this fresh air guide wall 8d is curved and extends to the fresh air guide wall 8c.
The height increases as it approaches the fresh air guide wall 8C.

On the other hand, as shown in FIGS. 1 and 2, a burnt gas guide wall 8e is formed on the opposite side from the fresh air guide wall 8C. This burnt gas guide wall 8e consists of a curved surface extending from the cylinder head inner wall surface portion 3C to the bottom wall surface portion 3d.

As shown in FIG. 2, the ignition plug 10 is arranged on the cylinder head inner wall surface portion 3C so as to be located at the center of the cylinder head inner wall surface 3a. On the other hand, the exhaust valve 7 is not provided with a mask wall that covers the opening between the exhaust valve 7 and the valve seat 11. Therefore, when the exhaust valve 7 is opened, a mask wall is formed between the exhaust valve 7 and the valve seat 11. The entire opening opens into the combustion chamber 4.

In the cylinder head 3, there is an air intake port 1 for the air intake valve 6.
2 is formed, and an exhaust port 13 is formed for the exhaust valve 7. Each air supply port 12 is connected to a surge tank 15 via a corresponding air supply branch pipe 14, as shown in FIG. The surge tank 15 is connected to an air cleaner 20 via an ink cooler 16, an engine-driven mechanical supercharger 17, an air supply duct 18, and an air flow meter 19, and a throttle valve 21 is disposed within the air supply duct 18.

The exhaust ports 13 of the No. 1 cylinder #1, the No. 2 cylinder #2, and the No. 3 cylinder #3 are connected to a common exhaust manifold 22, and the exhaust ports 13 of the No. 4 cylinder #4, the No. 5 cylinder #5, and the No. 6 cylinder #6 are connected to a common exhaust manifold 22. Each exhaust port 13 is connected to a common exhaust manifold 23. Each exhaust manifold 22,23 has a corresponding catalytic converter 2.
4,25.

As shown in FIG. 4, the throttle valve 21 has a throttle sensor 26 for detecting the opening degree of the throttle valve 21.
is attached to the engine body, and a water temperature sensor 27 for detecting the engine cooling water temperature is attached to the engine body.

On the other hand, as shown in FIG. 1, an air blast valve 30 for injecting compressed air and fuel into the combustion chamber 4 is attached to the cylinder head 3. This air blast valve 30
is a compressed air passage 3 with a nozzle nozzle 31 formed at its tip.
2, an on-off valve 33 arranged in the compressed air passage 32 to control the opening and closing of the nozzle 31, an actuator 34 for driving and controlling the on-off valve 33, a compressed air passage 35 branched from the compressed air passage 32, and a compressed air passage 35 branched from the compressed air passage 32; A fuel injection valve 36 for injecting fuel into the air passage 35 is provided. The compressed air passage 35 is connected to an engine-driven air pump 37, so that the compressed air passage 32.35 is constantly filled with compressed air.

FIG. 5 shows the electronic control unit 40. Referring to FIG. 5, the electronic control unit 40 consists of a digital computer, R
It is equipped with an OM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45, and an output port 46.The output voltage of the throttle sensor 26, which is proportional to the opening degree of the throttle valve 21, is The output voltage of the air flow meter 19, which is input to the input port 45 via the AD converter 47 and is proportional to the amount of intake air, is input to the human power port 45 via the AD converter 48. A rotation speed sensor 49 that generates a signal is connected to the human power port 45, and a crank angle sensor 50 that detects, for example, that the No. 1 cylinder #1 is at the top dead center position is connected to the input port 45. The output voltage of the water temperature sensor 27, which is proportional to the water temperature, is supplied to the human-powered boat 45 via the AD converter 51, and the starter switch 52 is connected to the input port 45. On the other hand, the output port 46 is connected to the corresponding drive circuit 53.
The output port 46 is further connected to the fuel injection valve 36 of each air blast valve 30 through a corresponding drive circuit 54. . Further, the output port 46 is connected to each spark plug 10 via a corresponding drive circuit 55.

FIG. 6 shows an example of the opening period of the air supply valve 6 and the exhaust valve 7, as well as an example of the opening period of the fuel injection period and the air blast valve 30. In the example shown in FIG. 6, the exhaust valve 7 opens before the intake valve 6, and the exhaust valve 7 closes before the intake valve 6.

Further, fuel is injected from the fuel injection valve 36 of the air blast valve 30 into the compressed air passage 35 before the bottom dead center BDC. Next, before and after the exhaust valve 7 closes after passing the bottom dead center BDC, the on-off valve 33 is opened, that is, the air blast valve 30 is opened. At this time, the injected fuel is injected from the nozzle tube 31 into the combustion chamber 4 together with compressed air.

As shown in FIG. 7, when the air supply valve 6 opens, the air supply port 1
2, fresh air flows into the combustion chamber 4 from the opening of the air supply valve 6, but since the mask wall 8a is provided to the opening of the air supply valve 6, the fresh air flows from the opening of the air supply valve 6 on the opposite side to the mask wall 8a. It flows into the combustion chamber 4. Next, this fresh air descends along the inner wall surface of the cylinder below the intake valve 6, as shown by arrow S, then advances along the top surface of the piston 2, and then rises along the inner wall surface of the cylinder below the exhaust valve 7. Because of this, strong loop scavenging air can be obtained. Next, fuel is ejected from the air blast valve 30 together with compressed air, and the air-fuel mixture thus formed is ignited by the ignition plug lO. Note that since the fuel injection from the air blast valve 30 is started before and after the exhaust valve 7 closes, this injected fuel does not blow through into the exhaust port 13.

As shown in FIG. 1, in a two-stroke internal combustion engine, fuel injected from the air blast valve 30 comes into contact with high-temperature burnt gas remaining in the combustion chamber 4, thereby promoting vaporization of the fuel. However, during low-load engine operation, combustion chamber 4
The amount of burnt gas remaining in the tank increases, but the temperature of the remaining burnt gas decreases. Therefore, in this case, the injected fuel is not sufficiently vaporized, resulting in a problem of misfire. In order to prevent such misfires, the present invention first injects fuel and compressed air from the air blast valve 30 when the engine is operating at low load, then stops the ignition by the ignition plug 10, and then injects the air again in the next cycle. After injecting fuel and compressed air from the blast valve 30, the ignition plug 10
The ignition is carried out by the following. That is, the injected fuel from the air blast valve 30 is once compressed without being ignited, and in the next cycle, this injected fuel is ignited by the ignition plug 10 together with the fuel injected from the air blast valve 30 again. In this way air blast valve 30
Once the fuel injected from the compressor is compressed without igniting, the fuel is mixed with high-temperature residual burnt gas, promoting vaporization of the fuel, and vaporization is also promoted by the temperature rise caused by the compression action. Furthermore, vaporization is promoted by the longer time until ignition occurs, resulting in a state in which ignition and combustion are extremely easy.

Therefore, in the next cycle, if ignition is performed after fuel is injected from the air blast valve 30, the air-fuel mixture will be reliably ignited and combusted. In addition, it is difficult to ignite 2
In a cycle internal combustion engine, it is also possible to repeatedly compress the fuel injected from the air blast valve 30 without igniting it over a plurality of cycles, and then perform the ignition action using the ignition plug 10.

Note that if the fuel is compressed without ignition, there is a risk that the fuel will blow into the exhaust port 13 due to loop scavenging in the next cycle. However, when the engine is running at a low load, the amount of fresh air flowing into the combustion chamber 4 from the intake port 12 is small, and therefore only a weak loop scavenging air flow occurs, resulting in a considerably small amount of fuel blow-through.

FIG. 8 shows an embodiment in which ignition is basically performed every cycle during low-load engine operation. In addition, in Fig. 8, the ignition order is 1-6-2-4-3-5.
The circle mark in the ignition process in FIG. 8 indicates the time when ignition is performed. As shown in FIG. 8, for example, focusing on cylinders 2, 3, 4, 5, and 6, these cylinders are ignited every cycle. On the other hand, cylinder No. 1 is not ignited for two cycles. In a six-cylinder engine, if the ignition order is set so that every other cylinder is ignited, some cylinders will not ignite during two cycles. The cylinders that are not ignited during these two cycles are shifted one by one according to the ignition order. Furthermore, as shown in Figure 8, fuel is injected even if ignition is not performed, but if ignition is not performed for two cycles, fuel injection is stopped during the first cycle. . However, in this case, the fuel injection for the next cycle may be stopped, or half of the fuel may be injected in each of the two cycles in which ignition is not performed.

Further, in the embodiment shown in FIG. 8, the fuel injection time TAU is different between when ignition is performed and when ignition is not performed. Figure 9 shows the correction coefficient K+ of fuel injection time TAU,
K*, and as these correction coefficients Kr and K2 increase, the fuel injection time TAU becomes longer. The correction coefficient K1 represents a correction coefficient in a cycle in which ignition is performed, and the correction coefficient K2 represents a correction coefficient in a cycle in which ignition is not performed. In Figure 9, the horizontal axis T
W represents the engine cooling water temperature, and it can therefore be seen that the lower the engine cooling water temperature TW, the smaller K1 becomes and the larger K2 becomes. In addition, in the embodiment shown in FIG. 9, K +
+K2=2. Although it is set to 0, the value of K+10K2 can be freely selected.

The lower the engine cooling water temperature TW, the more difficult it is to burn, so the correction coefficient K2 in the cycle where ignition is not performed is increased to increase the amount of fuel whose vaporization is promoted by the compression action. In addition, if the amount of fuel whose vaporization is promoted by the compression action increases, the amount of fuel that blows through in the next cycle will increase, so the higher the engine cooling water temperature TW becomes and the easier it is to burn, the smaller the correction coefficient K2 can be. We are trying to suppress blow-through as much as possible. The injection time TAU in Figure 8 is the engine cooling water temperature T in Figure 9.
W indicates when tw, therefore, the injection time TAU when ignition is performed is the injection time TA when ignition is not performed.
It is longer than U.

Note that the relationship shown in No. 9 is stored in the ROM 42 in advance.

FIG. 10 shows a control routine for an ignition control flag indicating that the engine is in an operating state in which ignition is performed every other cycle. This routine is executed by interrupts at regular intervals.

Referring to FIG. 10, first, in step 60, it is determined whether the starter switch 52 is on. If the starter switch 52 is on, step 64
jumps to and the ignition control flag is set. On the other hand, if the starter switch 52 is not on, the process proceeds to step 61, where the engine rotation speed N is set to a predetermined constant value N based on the output signal of the rotation speed sensor 49. It is determined whether or not it is lower than . When N<N0, the process proceeds to step 62, where it is determined from the output signals of the rotational speed sensor 49 and the air flow meter 19 whether or not the intake air amount Q/engine rotational speed N is smaller than a predetermined constant value of 80. . Q/
When N<Aa, the process proceeds to step 63, where the opening degree θ of the throttle valve 21 is set to a predetermined constant value θ based on the output signal of the throttle sensor 26. It is determined whether or not it is smaller than . When θ<θ0, the process advances to step 64. Therefore, N is No, and Q/N<A. and θ and θ. In other words, when the engine is operating at a low load, the routine proceeds to step 64 and the ignition control flag is set. On the other hand, N>No or Q
/N≧A0 or θ≧θ. In this case, the process advances to step 65 and the ignition control flag is reset.

Next, ignition and injection control will be explained with reference to FIG. 8 and FIG. 11. FIG. 11 shows a routine for performing ignition and injection control shown in FIG.
This routine is executed every time the fuel injection valve 36 of each air blast valve 30 reaches a crank angle slightly before the fuel is injected.

Referring to FIG. 11, first, in step 71, the ignition timing is calculated from the engine speed N, intake air amount Q, engine cooling water temperature TW, etc. Next, in step 72, the basic fuel injection time TP is calculated from the engine speed N and the intake air amount Q. Next, in step 73, the engine cooling water temperature TW
The fuel injection time TAU is calculated by multiplying the basic fuel injection time TP by a correction coefficient F determined by the following equation. Next, in step 74, it is determined whether the ignition control flag is set, that is, whether the engine is operating at a low load or the starter switch 52 is turned on. If the ignition control flag is set, the process proceeds to step 75, where it is determined whether the count value N is greater than 6 or not. At this time, since N=O, the process proceeds to step 76, where it is determined whether or not the determination flag is set.

If the determination flag is not set, step 77
Then the judgment flag is set. Then step 7
8, the fuel injection time TAU is corrected by multiplying TAU by a correction coefficient K1 shown in FIG. Next, in step 80, the count value N is incremented by one. Next, in step 79, data for ignition at the ignition timing calculated in step 71 is sent to the output port 46.
Output to. Next, in step 81, data for performing fuel injection for the fuel injection time TAU is output from the output port 46, and the processing routine is completed. Therefore, at this time, fuel is injected from the air blast valve 30 when ignition injection control is to be performed, and then ignition is performed by the ignition plug 10.

Next, when the interrupt routine for the ignition injection control is executed, since the determination flag is set at this time, the process proceeds from step 76 to step 82 and the determination flag is reset. Next, in step 83, the fuel injection time TAU is corrected by multiplying TAU by a correction coefficient K2 shown in FIG. Next, in step 84, the count value N is incremented by 1, and then in step 80, an injection process is performed.

Therefore, no ignition process is performed for this cylinder, that is, no ignition action by the ignition plug 10 is performed. However, since fuel is injected from the air blast valve 30, the injected fuel is compressed.

When the count value N reaches 6 or becomes larger than 6 by repeating these steps, the process proceeds from step 75 to step 85, where the count value N is set to 0, and the processing routine is completed. Therefore, at this time, neither fuel injection nor ignition is performed for the fuel that should be under ignition injection control.

On the other hand, if the ignition control flag is reset, step 74
The process then proceeds to step 86, where the count value N is set to zero.

Next, in step 80, ignition processing is performed, and in step 81, fuel injection processing is performed. Therefore, at this time, fuel injection and ignition are performed every cycle.

〔Effect of the invention〕

Even when the engine is operating at a low load, the air-fuel mixture can be ignited and burned immediately after the engine is started.

[Brief explanation of the drawings] Fig. 1 is a side sectional view of a two-stroke internal combustion engine, Fig. 2 is a view showing the inner wall surface of the cylinder head, and Fig. 3 is an arrow shown in Fig. 1.
Fig. 4 is an overall view of a two-stroke internal combustion engine, Fig. 5 is a circuit diagram of an electronic control unit, and Fig. 6 is a diagram showing opening periods of intake and exhaust valves, etc. , FIG. 7 is a side sectional view of a two-stroke internal combustion engine showing the opening of the intake and exhaust valves, FIG. 8 is a time chart showing ignition and injection control, FIG. 9 is a diagram showing correction coefficients, and FIG. The figure is a flowchart for controlling the ignition control flag, No. 11.
The figure is a flowchart for controlling ignition and injection. 4... Combustion chamber, 6... Air supply valve, 7... Exhaust valve, 10... Ignition plug, 30... Air blast valve, 34... Actuator, 36... Fuel injection valve. v. 1 Figure 3d Figure 2 10...Ignition hydrant construction diagram Figure 7 Figure 10

Claims (1)

[Claims] In a two-stroke internal combustion engine in which the air-fuel mixture is ignited and combusted by a spark plug, a cycle in which fuel is supplied but not ignited during low-load operation of the engine, and a cycle in which fuel is supplied and ignited are set in each predetermined cycle. A combustion control device for a two-stroke internal combustion engine that repeats.