JP2522648Y2 - Two-cycle internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a two-stroke internal combustion engine.

[Conventional technology]

When the combustion pressure rises sharply in an internal combustion engine, combustion noise is generated. Therefore, there is known an internal combustion engine in which when the combustion pressure rises sharply, the ignition timing is delayed to gradually increase the combustion pressure, thereby preventing the generation of combustion noise (see JP-A-59-37272).

[Problems to be solved by the invention]

However, in the two-cycle internal combustion engine, combustion noise peculiar to the two-cycle internal combustion engine is generated. That is, in a two-stroke internal combustion engine, the amount of residual burned gas is large but the temperature of burned gas is low during low engine load operation, and the temperature of burned gas is high but the amount of residual burned gas is low during high engine load operation. . Therefore, under these load conditions, the heat energy of the entire remaining burned gas is relatively small. On the other hand, at the time of engine middle load operation, the amount of residual burned gas is relatively large, and the temperature of the residual burned gas is also relatively high. Therefore, during engine middle load operation, the injected fuel is heated by the residual burned gas and rapidly vaporized, so that when the ignition action is performed, the fuel is rapidly burned, and as a result, the combustion pressure is rapidly increased. Noise will be generated. Such a rapid increase in combustion pressure cannot be prevented even if the ignition timing is delayed.

[Means for solving the problem]

According to the present invention, in a two-stroke internal combustion engine, the vibration of the engine body which occurs when the combustion pressure suddenly rises due to the heating action of the fuel by the residual burned gas during the engine middle load operation, and the frequency at which knocking occurs A vibration detection sensor for detecting vibration at a lower frequency is mounted on the engine body, the engine exhaust passage and the engine air supply passage are connected via an exhaust gas recirculation passage, and vibration is generated in the exhaust gas recirculation passage. An exhaust gas recirculation control valve responsive to the output signal of the detection sensor is provided, and the exhaust gas recirculation control valve is opened when the vibration level of the engine body detected by the vibration detection sensor exceeds a predetermined level. I'm trying to let you know.

[Action]

Recirculating the exhaust gas increases the amount of hot residual burned gas exhausted from the combustion chamber, thereby reducing the overall thermal energy of the burned gas remaining in the combustion chamber.

〔Example〕

FIG. 1 shows an overall view of a two-cycle internal combustion engine. Referring to FIG. 1, 1 is a cylinder block, 2 is a piston reciprocating in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, and 4 is formed between the piston 2 and the cylinder head 3. Combustion chamber, 5 is an air supply valve, 6 is an air supply port, 7 is an exhaust valve, 8 is an exhaust port,
9 denotes air blast valves for injecting fuel together with the compressed air into the combustion chamber 4. As shown in FIG. 2, an ignition plug 24 is disposed at the center of the inner wall surface of the cylinder head 3. The air supply port 6 is connected to the surge tank 11 through the air supply branch 10.
And the surge tank 11 is an engine-driven mechanical turbocharger
12, connected to an air cleaner 15 via an air supply duct 13 and an air flow meter 14. A throttle valve 16 is arranged in the air supply duct 13.

FIG. 3 is an enlarged sectional view of the air blast valve 9. Referring to FIG. 3, a compressed air passage 31 extending straight is formed in the housing 30 of the air blast valve 9, and a nozzle located in the combustion chamber 4 (FIG. 1) is formed at the tip of the compressed air passage 31. A mouth 32 is formed. An on-off valve 33 is disposed in the compressed air passage 31, and a nozzle port is provided at an outer end of the on-off valve 33.
A valve body 34 for controlling the opening and closing of 32 is integrally formed. A compression spring 35 is disposed in the housing 30 coaxially with the on-off valve 33.
The movable core 36 urged toward the on-off valve 33 by the opening and the solenoid 37 for sucking the movable core 36 are arranged.
The inner end of the on-off valve 33 is brought into contact with the end face of the movable core 36 by a compression spring 38, and the spring force of the compression spring 38 is stronger than that of the compression spring 35.
It is closed by 33 valve bodies 34. When the solenoid 37 is energized, the movable core 36 moves in the direction of the on-off valve 33, and as a result, the valve element 34 of the on-off valve 33 opens the nozzle port 32. On the other hand, a compressed air passage 39 that extends obliquely from the compressed air passage 31 is branched from the compressed air passage 31, and the compressed air passage 39 is connected to a compressed air supply port 40. A fuel injection valve 41 is attached to the housing 30, and a nozzle hole 42 of the fuel injection valve 41 is provided.
From there, fuel is injected into the compressed air passage 39.

As shown in FIG. 1, an air blast air passage 17 is branched from an air supply duct 13 between an air flow meter 14 and a throttle valve 16, and the air blast air passage 17 is an engine-driven vane pump 18 and a compressed air passage. It is connected to the compressed air distribution chamber 20 via 19. The compressed air distribution chamber 20 is connected to a compressed air supply port 40 of an air blast valve 9 provided for each cylinder. In the compressed air passage 19, a pressure regulating valve 21 for maintaining the compressed air pressure in the compressed air distribution chamber 20 at a predetermined constant pressure is arranged, and excess compressed air is supplied through a compressed air return passage 22. It is returned into the duct 13. Therefore, the compressed air passages 31, 39 of the air blast valve 9 are filled with compressed air of a constant pressure.

FIG. 4 shows the opening period of the supply valve 5 and the exhaust valve 7, the period of fuel injection from the fuel injection valve 41, and the opening period of the valve body 34 of the on-off valve 33, that is, the opening period of the air blast valve 9. . 4th
As shown in the drawing, in the embodiment shown in FIG. 1, the exhaust valve 7 opens before the air supply valve 5 and closes first. Also, the fourth
Before the valve element 34 of the on-off valve 33 opens as shown in the figure,
That is, the fuel is injected from the fuel injection valve 41 into the compressed air in the compressed air passage 39 before the air blast valve 9 opens. Next, when the air blast valve 9 is opened, the injected fuel is injected into the combustion chamber 4 from the nozzle port 32 together with the compressed air.
On the other hand, as shown in FIG. 1, a mask wall 23 is formed on the inner wall surface of the cylinder head 3 so as to cover the opening of the air supply valve 5 on the exhaust valve 7 side during the full opening period of the air supply valve 5. Therefore, when the air supply valve 5 is opened, fresh air is supplied from the air supply port 6 into the combustion chamber 4 through the opening of the air supply valve 5 opposite to the exhaust valve 7. As a result, fresh air flows along the peripheral wall surface of the combustion chamber 4 as shown by the arrow S, and thus good loop scavenging is performed.

On the other hand, as shown in FIG.
Is connected to a three-way catalytic converter 51 via an exhaust manifold 50, and the three-way catalytic converter 51 is connected to an exhaust pipe 56 via an exhaust pipe 52, a sub-muffler 53, an exhaust pipe 54, and a main muffler 55. The outlet of the exhaust pipe 56 is open to the atmosphere. An oxygen concentration detector 57 is installed in the exhaust pipe 52 downstream of the three-way catalytic converter 51.
The fuel injection from the fuel injection valve 41 is controlled based on the output signal of 57. An exhaust gas recirculation (hereinafter referred to as EGR) passage 58 is branched from the exhaust pipe 56, and the EGR passage 58 is connected to the inside of the air supply duct 13 between the throttle valve 16 and the mechanical supercharger 12. In the EGR passage 58, an EGR control valve 59 whose duty is controlled by an output signal of the electronic control unit 60 is arranged. The opening area of the EGR control valve 59 increases as the duty ratio increases, that is, as the generation time ratio of the pulse supplied to the EGR control valve 59 increases.

The electronic control unit 60 is composed of a digital computer, and a ROM (read only memory) 62, a RAM (random access memory) 63, a CPU (microprocessor) 64, and an input port 65 interconnected by a bidirectional bus 61.
And an output port 66. A vibration detection sensor 67 for detecting vibration of the engine body is attached to the cylinder head 3, and this vibration detection sensor 67 generates an output voltage proportional to the vibration level of the engine body. Vibration detection sensor 67 is an amplifier
The output terminal of the amplifier 68 is connected to the input terminal of the amplifier 68, and the output terminal of the amplifier 68 is passed through a first band-pass filter 69 and a second band-pass filter 70 that pass only voltage fluctuations of different frequencies. Circuit 71 and second peak hold circuit
Connected to 72. These peak hold circuits 71 and 72 hold the maximum voltage of the voltage input to each of the peak hold circuits 71 and 72. The output terminal of each peak hold circuit 71, 72 is connected to the input port 65 via the corresponding AD converter 73, 74. Further, the input port 65 includes a top dead center detection sensor 75 that generates an output pulse indicating that the piston 2 is at the top dead center, and a crank angle sensor 76 that generates an output pulse every time the crankshaft rotates 15 degrees, for example. Connected. Therefore, the current crank angle can be calculated from the output signal of the top dead center detection sensor 75 and the output pulse of the crank angle sensor 76. The output port 66 is connected on the one hand to the EGR control valve 59 via a drive circuit 77 and on the other hand to the spark plug 24 via a drive circuit 78 and an igniter 79. The output port 66 is connected to each of the peak hold circuits 71 and 72 to reset the peak hold circuits 71 and 72.

By the way, as described above, in the two-stroke internal combustion engine, the heat energy of the entire remaining burned gas becomes the largest during the middle load operation of the engine, so that the combustion pressure may suddenly increase at this time. That is, when the vaporization of the injected fuel is not so rapid, the combustion pressure P in the combustion chamber 4 rises relatively slowly as shown by the broken line L in FIG. 5, but when the injected fuel is rapidly vaporized, FIG. As shown by the solid line M, the combustion pressure P in the combustion chamber 4 sharply increases. When such a rapid increase in the combustion pressure occurs, the rate of increase dP / dθ of the combustion pressure P with respect to the crank angle θ is approximately 0.2 MPa / deg.
(2 kg / deg), it has been found that intense combustion noise occurs.

Further, when the air-fuel mixture is ignited by the spark plug 24 in the two-cycle internal combustion engine, the pressure around the spark plug 24 first increases. As a result, the air-fuel mixture at the periphery of the combustion chamber 4 is compressed and self-ignites, causing knocking. When such knocking occurs, the combustion pressure P sharply increases as indicated by M in FIG. 5, and combustion noise is generated.

By the way, when the combustion pressure suddenly rises due to the heating of the residual burned gas during the medium load operation of the engine, the engine body oscillates at a frequency of about 1 KHz, whereas when knocking occurs, the engine body oscillates at a frequency of about 7 KHz. . This is shown in FIG. In FIG. 6, the horizontal axis represents the frequency of vibration (KHz), and the vertical axis represents the vibration level when a rapid pressure rise or knocking occurs due to rapid vaporization of the injected fuel and the vibration level when these do not occur. Ratio to (dB)
Is shown. From Fig. 6, when the pressure rises rapidly due to the rapid vaporization of the injected fuel during the engine medium load operation, it is almost 1 kHz.
It can be seen that the vibration level increases in the vicinity, and when knocking occurs, the vibration level increases in the vicinity of approximately 7 KHz.

Therefore, a pair of bandpass filters 69 and 70 are provided as shown in FIG. 1 to detect a rapid pressure rise and knocking due to rapid vaporization of these combustion injections using one vibration detection sensor 67. . That is, the first bandpass filter 69 is a filter that passes only voltage fluctuations having a frequency of about 1 KHz. Therefore, when a rapid pressure rise occurs due to rapid vaporization of the injected fuel, the output voltage of the vibration detection sensor 67 accompanying the rapid pressure increase is generated. The fluctuation is input to the one peak hold circuit 71. The first peak hold circuit 71 outputs the maximum value of the input voltage. Therefore, a rapid pressure rise due to rapid vaporization of the injected fuel can be detected from the output voltage of the first peak hold circuit 71. On the other hand, the second bandpass filter 70 is a filter that passes only voltage fluctuations having a frequency of about 7 KHz. Therefore, when knocking occurs, the output voltage fluctuations of the vibration detection sensor 67 are input to the second peak hold circuit 72. Is done. The second peak hold circuit 72 outputs the maximum value of the input voltage, and therefore, the occurrence of knocking can be detected from the output voltage of the second peak hold circuit 72.

By the way, the sudden rise of the combustion pressure caused by the heating action of the high-temperature residual burned gas during the middle load operation of the engine and the knocking due to the self-ignition of the unburned gas around the combustion chamber 4 are completely different phenomena. Is different.

Therefore, in the embodiment according to the present invention, when the combustion pressure suddenly rises due to the heating action of the high-temperature residual burned gas, the EGR control valve 59 is opened to suppress the rapid rise of the combustion pressure. That is, in FIG. 1, the pressure in the exhaust pipe 56 is substantially atmospheric pressure, and the pressure in the air supply duct 13 downstream of the throttle valve 16 is negative. Therefore, when the EGR control valve 59 is opened, the EGR gas is supplied into the air supply duct 13 through the EGR passage 58, and thus the EGR gas is supplied from the air supply port 6 into the combustion chamber 4 in addition to the fresh air. Is done. Therefore, the amount of the high-temperature burned gas discharged into the exhaust port 8 increases by the amount of the EGR gas supplied from the air supply port 6. As a result, the amount of high-temperature burned gas remaining in the combustion chamber 4 decreases, and the total heat energy of the remaining burned gas decreases, so that the injected fuel is not rapidly vaporized. Is prevented from rising rapidly. Further, the temperature of the exhaust gas in the exhaust pipe 56 is considerably low. Therefore, by supplying such low-temperature EGR gas into the combustion chamber 4 together with fresh air, it is possible to further prevent a rapid rise in the combustion pressure.

On the other hand, in the embodiment according to the present invention, when knocking occurs, the ignition timing is delayed. If the ignition timing is delayed, the occurrence of knocking is suppressed because the combustion pressure decreases.

That is, as shown in FIG. 7 (A), the injected fuel is rapidly vaporized and the combustion pressure P sharply rises. As a result, the vibration level of the engine body increases, and the output voltage of the first peak hold circuit 71 increases. V ₁ is the duty ratio DT is made to increase exceeds the set value V _10. As a result, a sharp increase in the combustion pressure due to an increase in the supply amount of the EGR gas is suppressed. on the other hand,
As shown in FIG. 7 (B), knocking occurs and the combustion pressure P
Rapidly it rises, so that output voltage V ₂ is the ignition timing exceeds the set value V ₂₀ of the second peak hold circuit 72 engine body vibration level increases θ is retarded. As a result, occurrence of knocking is suppressed.

Next, a control routine of the EGR control valve and the ignition timing will be described with reference to FIGS. 8 and 9 while referring to a time chart shown in FIG. This routine is executed at a crank angle at a time after the top dead center as shown in FIG.

Referring to FIGS. 8 and 9, the first step is
In 80 the output voltage V ₁ of the first peak hold circuit 71 is greater or not than the set value V ₁₀ is determined. V _1> if V ₁₀ constant value which is predetermined on the duty ratio DT proceeds to step 81 alpha is added. Next, at step 82, it is determined whether or not the duty ratio DT has exceeded 1.0 (100%). If DT> 1.0, the routine proceeds to step 83, where the duty ratio DT is set to 1.0. Next, at step 84, the EGR control valve 59
Is controlled in accordance with the duty ratio DT. That is, as the duty ratio DT increases, the opening area of the EGR control valve 59 increases.

On the other hand, if it is determined in step 80 that it is V ₁ V ₁₀ , then in step 85, the duty ratio DT
Is subtracted. Next, at step 86, it is determined whether or not the duty ratio has become negative.
Proceeding to 87, DT is made zero. Next, the routine proceeds to step 84.

When the driving process of the EGR control valve 59 is completed in step 84, the process proceeds to step 88, where the optimum ignition timing θ is calculated based on the intake air amount, the engine speed, and the like. Then step 89
Then, the output voltage V _{2 of} the second peak hold circuit 72 becomes the set value V
_It is determined whether it is greater than ₂₀ . If V ₂ > V ₂₀ , the routine proceeds to step 90, where a predetermined constant value β is added to the retard amount Δθ of the ignition timing. Next, at step 91, it is determined whether or not the retard amount Δθ has exceeded the maximum allowable retard amount MAX. If Δθ> MAX, the routine proceeds to step 92, where the retard amount Δθ
Is set to MAX. Next, the routine proceeds to step 93.

On the other hand, if it is determined in step 89 that it is V ₂ V ₂₀ , then in step 94, a constant value β is subtracted from the retard amount Δθ. Next, at step 95, it is determined whether or not Δθ has become negative. If Δθ <0, the routine proceeds to step 96, where Δθ
Is set to zero. Next, the routine proceeds to step 93.

In step 93, for example, the retard amount Δθ is added to the optimum ignition timing based on the bottom dead center, and the addition result is set as the crank angle θs to be ignited. Next, at step 97, data indicating the crank angle θs is output to the output port 66,
The ignition is performed based on this data. Then step 98
Then, the peak hold circuits 71 and 72 are reset.

[Effect of the invention]

By supplying EGR gas when the combustion pressure rises rapidly due to the heating action of the fuel by the residual burned gas during the engine medium load operation, the combustion pressure is prevented from rising sharply, thus reducing the generation of combustion noise. Can be suppressed.

[Brief description of the drawings]

1 is an overall view of a two-cycle internal combustion engine, FIG. 2 is a bottom view of the inner wall surface of the cylinder head in FIG. 1, FIG. 3 is a side sectional view of an air blast valve, and FIG. FIG. 5 is a diagram showing changes in fuel pressure, FIG. 6 is a diagram showing changes in vibration level, FIG. 7 is a time chart of EGR control valve and ignition timing control, FIG. Figure 9 and Figure 9
4 is a flowchart for controlling an EGR control valve and an ignition timing. 5 ... air supply valve, 7 ... exhaust valve, 12 ... mechanical supercharger, 13
…… air supply duct, 16 …… throttle valve, 56 …… exhaust pipe,
58: EGR passage, 59: EGR control valve.

Continued on the front page (56) References JP-A-57-16252 (JP, A) JP-A-59-37254 (JP, A) JP-A-63-170533 (JP, U) JP-A-57-123946 (JP) , U)

Claims (1)

(57) [Scope of request for utility model registration] In a two-stroke internal combustion engine, vibrations of an engine body that occur when the combustion pressure suddenly rises due to a heating action of fuel by residual burned gas during engine middle load operation. A vibration detection sensor for detecting vibration at a frequency lower than the frequency is mounted on the engine body, and the engine exhaust passage and the engine supply passage are connected via the exhaust gas recirculation passage, and the vibration detection sensor is provided in the exhaust gas recirculation passage. An exhaust gas recirculation control valve responsive to an output signal of the vibration detection sensor is disposed, and the exhaust gas recirculation is performed when the vibration level of the engine body detected by the vibration detection sensor exceeds a predetermined level. A two-stroke internal combustion engine in which a control valve is opened.