JPH0433379Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a fuel-injected internal combustion engine with multiple intake valves.

[Conventional technology]

The leaner the air-fuel mixture supplied to the engine cylinders, the more fuel consumption can be improved.
Therefore, in order to improve the fuel consumption rate, it is desirable to make the air-fuel mixture supplied into the engine cylinder as lean as possible. However, when a lean mixture is used, there is a problem that not only is the ignitability reduced, but even if the mixture is ignited, good combustion cannot be obtained because the flame propagation speed is slow.

In order to solve this problem, the intake passage is extended tangentially to the inner circumferential wall of the combustion chamber, and a fuel injection valve is disposed within the intake passage, so that the intake valve directs the fuel injection from the fuel injection valve. An internal combustion engine is known in which the engine is stopped slightly before the valve closes (Japanese Unexamined Patent Publication No. 148636/1983). In this internal combustion engine, only air is supplied into the combustion chamber during the first half of the intake stroke during partial load operation, and injected fuel is supplied into the combustion chamber during the second half of the intake stroke, so a rich mixture layer is formed at the top of the combustion chamber. A lean air-fuel mixture layer is formed below the combustion chamber, and the inside of the combustion chamber is stratified. the result,
Ignition performance is improved because a rich air-fuel mixture gathers around the spark plug, and swirling flow is generated in the combustion chamber by the airflow flowing in from the intake passage, allowing the ignition flame to spread rapidly into the combustion chamber. I can do it.

By the way, in the case of stratification as described above, if the air-fuel ratio of the stratified gas mixture is kept constant, combustion can be improved by increasing the degree of stratification. For example, if the air-fuel ratio of the entire stratified mixture is 25, the air-fuel ratio of the rich mixture is 20 and the air-fuel ratio of the lean mixture is 30, and the case where the air-fuel ratio of the rich mixture is 15 and the air-fuel ratio of the lean mixture is Considering the case where the air-fuel ratio is 35, better combustion can be obtained in the latter case than in the former case. In other words, the air-fuel ratio of the rich mixture is 20
Even in this case, it is possible to ignite with a spark plug, but the flame from the combustion of a rich mixture is weak, and as a result, it is difficult to achieve good combustion because it takes time to combust a lean mixture. . On the other hand, when the air-fuel ratio of the rich air-fuel mixture is 15, the flame due to combustion of the rich air-fuel mixture is strong. The time required is shorter and better combustion is thus obtained. To obtain such combustion, it is necessary to increase the degree of stratification.

However, in the above-mentioned internal combustion engine, the injected fuel flows into the combustion chamber at a high velocity together with the intake air flow, so the injected fuel tends to spread inside the combustion chamber.Therefore, although stratification occurs, the degree of stratification is not sufficient. be.

In order to solve this problem, a first intake valve, a second intake valve, and a third intake valve are provided, and the first intake passage connected to the combustion chamber through the first intake valve is shaped into a helical shape. a second intake passage connected to the combustion chamber via the second intake valve and a third intake passage connected to the combustion chamber via the third intake valve, each of which opens during high-load operation. The applicant of the present invention has already proposed an internal combustion engine which is provided with an intake control valve and further has a fuel injection valve disposed in a third intake passage downstream of the intake control valve (see Utility Model Application No. 103124/1983). In this internal combustion engine, the intake control valve is kept closed during partial load operation, so when the third intake valve opens during the intake stroke, the pressure in the third intake passage downstream of the intake control valve reaches close to the combustion chamber pressure. drops immediately. As a result, the pressure difference between the pressure in the third intake passage downstream of the intake control valve and the pressure in the combustion chamber is maintained at a relatively small pressure difference, so that the fuel injected into the third intake passage has a slow speed. Flows into the combustion chamber. Therefore, the injected fuel within the combustion chamber does not spread much within the combustion chamber, and thus the degree of stratification can be increased.

[Problem that the invention attempts to solve]

However, in this internal combustion engine, if the third intake valve is opened in the latter half of the intake stroke in order to increase the degree of stratification, the injected fuel in the third intake passage will only flow into the combustion chamber at a slow speed. All of the injected fuel cannot flow into the combustion chamber, and the injected fuel that could not flow into the combustion chamber flows into the combustion chamber at the moment when the third intake valve opens in the next intake stroke. However, at the moment when the third intake valve opens, the injected fuel that could not enter in the previous intake stroke flows into the combustion chamber, and this injected fuel collects in the center of the combustion chamber, resulting in a good performance. There is a problem that proper stratification cannot be obtained. On the other hand, in order to supply all the injected fuel into the combustion chamber during the intake stroke,
If the opening timing of the intake valve is advanced, the injected fuel in the third intake passage will be supplied into the combustion chamber from the early stage of the intake stroke, and in this case as well, it will be difficult to obtain good stratification. It's summery. That is, when trying to achieve stratification by closing the intake control valve provided in the third intake passage, good stratification is achieved no matter how the opening timing of the third intake valve is set. cannot be obtained.

The present invention increases the degree of stratification by constantly opening the third intake passage and appropriately determining the opening timing and valve lift of the intake valve. The objective is to provide a valve train system that is as practical as possible.

[Means for solving problems]

According to the present invention, in order to solve the above problems,
The main intake passage includes at least two intake valves consisting of a main intake valve and a sub-intake valve, and at least two intake passages consisting of a main intake passage and a sub-intake passage, and is configured to generate a swirling flow within the combustion chamber. is connected to the combustion chamber via the main intake valve, and the fuel injection valve is arranged in the auxiliary intake passage connected to the combustion chamber via the auxiliary intake valve. In a fuel injection internal combustion engine in which the valve is opened until the beginning of the stroke and the sub-intake valve is opened from near the center of the intake stroke to the beginning of the compression stroke, the engine is equipped with a common camshaft for driving the main intake valve and the sub-intake valve, [Embodiment] The auxiliary intake valve is directly driven by a camshaft, and the main intake valve is driven via a rocker arm. [Example] Referring to FIGS. 4 to 6, 1 is the engine body, 2 is the cylinder block, and 3 is the inside of the cylinder block 2. 4 is a cylinder head fixed on cylinder block 2, 5 is a combustion chamber formed between piston 3 and cylinder head 4, and 6 is placed approximately at the center of the top of combustion chamber 5. Each spark plug is shown. On the inner wall surface of the cylinder head 4, there are three intake valves: a first intake valve 7, a second intake valve 8, which constitutes a main intake valve, and a third intake valve 9, which constitutes a sub-intake valve, and a first exhaust valve. Two exhaust valves consisting of a valve 10 and a second exhaust valve 11 are arranged. The first intake valve 7 and the second intake valve 8 have substantially the same valve diameter, and the third intake valve 9 has a smaller valve diameter than the first intake valve 7 and the second intake valve 8. Furthermore, the third intake valve 9 is arranged between the first intake valve 7 and the second intake valve 8. Inside the cylinder head 4, there are three intake passages consisting of a first intake passage 12, a second intake passage 13, which constitutes a main intake passage, and a third intake passage 14, which constitutes a sub-intake passage, and exhaust valves 10, 11. An exhaust passage 15 connected to the combustion chamber 5 through the exhaust passage 15 is formed.
The first intake passage 12, the second intake passage 13 and the third
The intake passages 14 are separated from each other by a pair of thin partition walls 16 and 17 and extend substantially parallel to each other within the cylinder head 4. The third intake passage 14 is located between the first intake passage 12 and the second intake passage 13;
It has a smaller cross section than the intake passage 13. The first intake passage 12 , the second intake passage 13 , and the third intake passage 14 are connected to the same intake branch pipe 18 and merge with each other inside the intake branch pipe 18 . The first intake passage 12 is connected to the combustion chamber 5 via the first intake valve 7, and the first intake passage 12 is formed in a helical shape to generate a swirling flow within the combustion chamber 5. The second intake passage 13 is connected to the combustion chamber 5 via the second intake valve 8, and is formed as a straight port that extends straight. An intake control valve 1 is provided at the entrance of the second intake passage 13.
9 is arranged, and the valve shaft 20 of the intake control valve 19 is the first
It extends through the intake passage 12, the second intake passage 13, and the third intake passage 14. Third intake passage 14
is connected to the combustion chamber 5 via the third intake valve 9,
This third intake passage 14 is formed as a straight port that extends straight. Third intake passage 14
A fuel injection valve 21 is arranged on the upper wall surface, and fuel is injected from this fuel injection valve 21 toward the back surface of the bulk part of the third intake valve 9.

Referring to FIG. 5, the intake branch pipe 18 is connected to a common surge tank 22, and the surge tank 22 is connected to an air cleaner (not shown) via an intake duct 23 and an air flow meter 24. A throttle valve 25 connected to an accelerator pedal (not shown) is disposed within the intake duct 23, and a throttle switch 27 is connected to a valve shaft 26 of the throttle valve 25. This throttle switch 27
is turned on when the throttle valve 25 is almost fully opened, for example, if the throttle opening is 90 degrees when fully opened, the throttle valve 25 is turned on when the throttle opening exceeds 80 degrees. On the other hand, an arm 28 is fixed to the valve shaft 20 of the intake control valve 19, and the tip of the arm 28 is connected to a diaphragm 31 of a negative pressure actuator 30 via a control rod 29. The negative pressure actuator 30 includes a negative pressure chamber 32 and an atmospheric pressure chamber 33 separated by a diaphragm 31.
A compression spring 34 for pressing the diaphragm is arranged inside. The negative pressure chamber 32 is connected to a negative pressure tank 36 via an electromagnetic switching valve 35 that can communicate with the atmosphere. The negative pressure tank 36 is connected to the surge tank 2 from the negative pressure tank 36.
The negative pressure tank 36 is connected to the inside of the surge tank 22 via a check valve 37 that allows flow only into the inside of the surge tank 22, so that the negative pressure inside the negative pressure tank 36 is maintained at the maximum negative pressure generated inside the surge tank 22. Ru. On the other hand, engine body 1
A distributor 38 is attached to the rotor 38, and a rotor 39 of the distributor 38 is driven by the engine at half the rotational speed of the crankshaft. The rotor 39 has a pair of disks 40,
41 is fixed, and a pair of crank angle sensors 4 are mounted facing the toothed outer peripheral surfaces of these disks 40 and 41.
2,43 are arranged. The crank angle sensor 42 is a sensor that determines, for example, whether or not the No. 1 cylinder is at the intake top dead center, and generates an output pulse when the No. 1 cylinder is at the intake top dead center. On the other hand, the crank angle sensor 43, for example,
Generates an output pulse every time it rotates. Therefore, the crank angle of each cylinder can be calculated from the output pulses of the crank angle sensors 42 and 43, and the engine speed can be calculated from the output pulses of the crank angle sensor 43. These crank angle sensors 42, 43 are connected to an electronic control unit 50.

The electronic control unit 50 consists of a digital computer and includes ROM (read only memory) 52, which are interconnected by a bidirectional buzzer 51.
It includes a RAM (random access memory) 53, a CPU (microprocessor) 54, an input port 55, and an output port 56. air flow meter 2
4 generates an output voltage proportional to the amount of intake air, and this air flow meter 24 is connected to an input port 55 via an AD converter 57. Furthermore, a throttle switch 27 and crank angle sensors 42 and 43 are connected to the input port 55. On the other hand, the output port 56 is connected to the fuel injection valve 21 and the electromagnetic switching valve 35 via corresponding drive circuits 58 and 59, respectively.

The internal combustion engine according to the present invention stratifies the air-fuel mixture in the combustion chamber 5 during partial load operation to operate using a lean air-fuel mixture with an average air-fuel ratio of 25 to 30. In order to obtain this, the air-fuel mixture in the combustion chamber 5 is made uniform and the average air-fuel ratio is made small. In order to increase the degree of stratification during partial load operation, the third
It is necessary to appropriately set the opening timing of the intake valve 9, the valve lift, and the injection completion timing of the fuel injection valve 21. First, the basic operation of the internal combustion engine according to the present invention will be explained, and then the third intake valve 9 will be set. The valve opening timing, valve lift, valve operating mechanism of each intake valve, and injection completion timing of the fuel injection valve 21 will be explained.

FIG. 7 shows the opening periods and valve lifts of the first intake valve 7, the second intake valve 8, and the third intake valve 9. 7th
In the figure, the vertical axis L shows the valve lift, and the horizontal axis θ shows the crank angle. First intake valve 7 and second intake valve 8
The opening periods of the first intake valve 7 and the second intake valve 8 are almost the same, and the opening periods of the first intake valve 7 and the second intake valve 8 are shown by curve A in FIG. As can be seen from curve A, the first intake valve 7 and the second intake valve 8 that make up the main intake valve open a little before the top dead center (TDC) of the intake stroke, and close to the bottom dead center (BDC) of the intake stroke. The valve closes at the beginning of the compression stroke, which is a little beyond . On the other hand, the opening period of the third intake valve 9 constituting the auxiliary intake valve is shown by curve B in FIG. As can be seen from curve B, the third intake valve 9 opens approximately at the center of the intake stroke, and closes simultaneously with the first intake valve 7 and the second intake valve 8. Note that the opening timing of the third intake valve 9 needs to be set approximately at the center of the intake stroke, but there is some degree of freedom in the closing timing of the third intake valve 9. It is also possible to close the intake valve 7 and the second intake valve 8 a little before they close,
It is also possible to close the first intake valve 7 and the second intake valve 8 a little after they are closed. Fuel injection valve 21
The injection timing will be explained in detail later, but generally speaking, fuel injection is completed before the third intake valve 9 closes so that all the injected fuel is supplied into the combustion chamber 5. The intake control valve 19 is fully closed during partial load operation, and fully opened during high load operation.

Next, a valve operating mechanism for controlling the opening and closing of the first intake valve 7, the second intake valve 8, and the third intake valve 9 will be described with reference to FIGS. 1 to 3. Referring to FIG. 1, a common camshaft 60 is provided for each intake valve 7, 8, 9, and this camshaft 6
0 has three cams integrally formed: a cam 60a for the first intake valve 7, a cam 60b for the second intake valve 8, and a cam 60c for the third intake valve 9. Referring to FIG. 2, the third valve constituting the auxiliary intake valve
The intake valve 9 is directly driven by a camshaft 60 via a cap 61 which is slidably inserted into the cylinder head 4. On the other hand, referring to FIG. 3, a rocker arm 62 is disposed on the first intake valve 7 constituting the main intake valve. One end 62a of the rocker arm 62 is swingably supported on the cylinder head 4, and the other end 62b of the rocker arm 62 engages with the top of the first intake valve 7.
Also, the middle part of the rocker arm 62 is a cam 60a.
The first intake valve 7 is therefore driven by the camshaft 60 via the rocker arm 62. Note that a Rocker arm 6 having almost the same shape as the Rocker arm 62 is also used for the second intake valve 8.
3 (FIG. 1), so that the second intake valve 8 is also driven by the camshaft 60 via the rocker arm 63. In this way, each cam 60a, 60
Even if the cam heights relative to the reference circles b and 60c are equal, the valve lifts of the first intake valve 7 and the second intake valve 8 will be larger than the valve lift of the third intake valve 9 (FIG. 7). As described later, the third intake passage 14
A rich mixture is supplied from the combustion chamber 5, but by reducing the valve lift of the third intake valve 9, diffusion of the rich mixture supplied into the combustion chamber 5 is prevented, thereby increasing the degree of stratification. I can do it. Further, the first intake valve 7 and the second intake valve 8 are connected to the rocker arm 62,
63, it is possible to increase the valve lift of the first intake valve 7 and the second intake valve 8, thereby increasing the filling efficiency during high engine load operation. Further, by using both the direct drive method using the camshaft 60 and the indirect drive method using the rocker arms 62 and 63, the first intake valve 7 is not arranged in a straight line by one camshaft 60, The second intake valve 8 and the third intake valve 9 can be driven simultaneously, and the valve operating mechanism can thus be simplified accordingly.

As mentioned above, the intake control valve 19 is fully opened during partial load operation. Therefore, even if the first intake valve 7 and the second intake valve 8 are opened and the intake stroke is started, the intake air is not supplied into the combustion chamber 5 from the second intake passage 13, and the intake air is not supplied into the combustion chamber 5 from the second intake passage 13. 1 is supplied into the combustion chamber 5 only through the intake passage 12. As described above, since the first intake passage 12 is formed in a helical shape, the air flows into the combustion chamber 5 while swirling, thereby generating a strong swirling flow within the combustion chamber 5. When the piston 3 descends by about half a stroke, the third intake valve 9 opens, and the fuel injected from the fuel injection valve 21 causes the third intake passage 1 to be opened.
The air-fuel mixture formed in the combustion chamber 4 flows into the combustion chamber 5 via the third intake valve 9. Initially, when the third intake valve 9 opens, the lift of the third intake valve 9 is small, so the amount of air-fuel mixture flowing into the combustion chamber 5 is also small, and this air-fuel mixture mixes with the air inside the combustion chamber 5. A lean mixture is formed near the top of the combustion chamber 5. At this time, only air exists near the top surface of the piston 3. Next, when the piston 3 further descends, the valve lift of the third intake valve 9 increases, and the rich air-fuel mixture flowing into the combustion chamber 5 from the third intake passage 14 gradually increases. In the second half of the intake stroke, the valve lift of the first intake valve 7 gradually becomes smaller, so the amount of intake air flowing into the combustion chamber 5 from the first intake passage 12 decreases. In order to increase the valve lift, the third intake passage 1
4, the amount of air-fuel mixture flowing into the combustion chamber 5 increases. At this time, since the valve lift of the third intake valve 9 is relatively small, the air-fuel mixture is prevented from diffusing downward into the combustion chamber 5, and thus the air-fuel mixture is collected at the top of the combustion chamber 5. The air-fuel mixture formed at the top of the combustion chamber 5 gradually becomes richer. First intake valve 7
This tendency becomes even stronger as the valve approaches the closing time, and when the first intake valve 7 and the third intake valve 9 close, a rich mixture gathers at the top of the combustion chamber 5, and the concentration of the mixture decreases. It gradually becomes thinner toward the piston 3, and there is only air on the top surface of the piston 3. Next, when the compression stroke starts, the air on the top surface of the piston 3 mixes with the surrounding lean mixture to form a lean mixture. Therefore, at the end of the compression stroke, a rich mixture gathers at the top of the combustion chamber 5, and the piston 3 Lean mixture gathers near the top surface. In this way, the air-fuel mixture in the combustion chamber 5 becomes stratified. Since the rich mixture gathers at the top of the combustion chamber 5, the ignition plug 6
A rich air-fuel mixture gathers around the air-fuel mixture, so the air-fuel mixture is easily ignited. At this time, since a swirling flow is generated within the combustion chamber 5, the ignition flame rapidly spreads within the combustion chamber 5.

As mentioned above, in order to obtain good combustion in the case of stratification, it is necessary to increase the degree of stratification, and for this purpose, the opening timing of the third intake valve 9, the valve lift, and the completion of injection of the fuel injection valve 21 are important. The timing must be determined appropriately. That is, if the opening timing of the third intake valve 9 is advanced, the air-fuel mixture is supplied into the combustion chamber 5 from the beginning of the intake stroke, so that the degree of stratification becomes smaller. On the other hand, if the opening timing of the third intake valve 9 is delayed, all the injected fuel cannot flow into the combustion chamber 5 while the third intake valve 9 is open, and the fuel that cannot flow into the combustion chamber 5 is transferred to the third intake passage. It stays in the combustion chamber 14 and flows into the combustion chamber 5 at once when the third intake valve 9 opens in the next intake stroke. However, if the fuel accumulated in this way flows into the combustion chamber 5 at once immediately after opening the third intake valve 9, a rich air-fuel mixture is formed in the combustion chamber 5 in the middle of the intake stroke, so that the degree of stratification is no longer high. cannot be increased. According to experiments conducted by the inventor of the present invention, it has been found that the degree of stratification can be maximized by setting the opening timing of the third intake valve 9 to approximately the center of the intake stroke. The opening timing of the intake valve 9 is set approximately at the center of the intake stroke.

Next, as described above, if the injected fuel stays in the third intake passage 14, good stratification cannot be obtained and the acceleration response also deteriorates, so all the injected fuel is combusted during the intake stroke. It is necessary to flow into the chamber 5. In this case, if the fuel is injected too early, fuel will remain in the third intake passage 14,
Since this stagnant fuel flows into the combustion chamber 5 when the third intake valve 9 is opened, the degree of stratification becomes small. That is, it is necessary to delay the fuel injection timing as much as possible. However, according to experiments conducted by the present inventor, the injected fuel reaches the inner wall surface of the third intake passage 14 or the back surface of the third intake valve 9 by approximately the intake bottom dead center (BDC) shown by the chain line C in FIG. It has been found that all the injected fuel can be supplied into the combustion chamber 5 if the combustion chamber 5 is reached. For example, it takes a certain amount of time for the fuel injected from the fuel injection valve 21 to reach the back surface of the third intake valve 9, and this time is almost constant, but when this time is converted into a crank angle, the engine rotation speed It will change accordingly. That is, the crank angle at which the injected fuel reaches the rear surface of the bulk portion of the third intake valve 9 increases as the engine speed increases. Therefore, in order for the last injected fuel to reach the rear surface of the bulk part of the third intake valve 9 near the intake bottom dead center, the injection completion timing of the fuel injection valve 21 must be advanced according to the increase in engine speed. Must be.
Further, the time taken for the injected fuel to reach the back surface of the bulk portion of the third intake valve 9 also changes depending on the flow velocity of the intake air flowing inside the third intake passage 14. That is,
As the engine speed increases, the flow velocity of the intake air flowing through the third intake passage 14 increases, and therefore, from the viewpoint of the flow velocity of the intake air, it is necessary to delay the injection completion timing as the engine speed increases. .

The optimum fuel injection completion timing in consideration of the flow velocity of intake air is shown by curve D in FIG. In addition, in FIG. 7, the vertical axis N shows the engine speed, and the horizontal axis θ shows the crank angle. As can be seen from the curve D, the injection completion time represented by the crank angle θ is generally advanced as the engine speed N increases. However, when the engine speed N increases, the third intake passage 1
Since the flow velocity of the intake air flowing through the engine 4 becomes faster, the amount of change in the injection completion timing with respect to an increase in the engine speed N becomes smaller. When fuel injection is completed at the crank angle shown by curve D in FIG. 7, the last injected fuel reaches the back surface of the bulk part of the third intake valve 9 near the intake bottom dead center, regardless of the engine speed N. In this way, all the fuel is supplied into the combustion chamber 5 while the third intake valve 9 is open, and a large amount of air-fuel mixture is supplied into the combustion chamber 5 at the end of the intake stroke, so that the degree of stratification is reduced. can be increased. In FIG. 7, τ ₀ indicates the control time from the injection completion time to the intake bottom dead center, and τ indicates the fuel injection period.

On the other hand, during high engine load operation, the intake control valve 19 is fully opened and the amount of injected fuel is increased by a predetermined ratio. When the intake control valve 19 is fully opened, in addition to the intake air supplied from the first intake passage 12, the second intake passage 13, which has a small flow resistance, is
Since intake air is also supplied from the fuel tank, the filling efficiency is increased. Further, at this time, the injection completion timing is set slightly before the first intake valve 7 and the second intake valve 8 open, as shown by the chain line E in FIG. τ' in FIG. 7 indicates the fuel injection period at this time. If the injection completion timing is advanced in this way, the injected fuel will remain in the third intake passage 14 as described above, and this injected fuel will be supplied into the combustion chamber 5 when the third intake valve 9 is opened, resulting in stratification. The degree of Further, the fuel accumulated in the third intake passage 14 is sucked out into the first intake passage 12 and the second intake passage 13 by the intake air flow flowing through the first intake passage 12 and the second intake passage 13. The air-fuel mixture is also supplied into the combustion chamber 5 from the first intake passage 12 and the second intake passage 13. Therefore, during high-load operation, the degree of stratification is extremely weakened and a nearly uniform air-fuel mixture is formed in the combustion chamber 5, so even if the amount of injected fuel is increased by a certain percentage, the spark plug 6
The area around the area will not be extremely dense. Therefore, good ignitability can be ensured, and high output can be obtained by increasing the amount of injected fuel.

Next, referring to the flowcharts shown in FIGS. 8 and 9, the fuel injection valve 21 and the intake control valve 1 will be explained.
9 will be explained.

Referring to FIG. 8, first, in step 70, a crank angle sensor 4 indicating the engine speed N is
3 and the output signal of the air flow meter 24 representing the intake air amount Q are taken into the CPU 54, and in step 71, Q/N is calculated. This Q/N represents the amount of air taken into each cylinder per cycle, and therefore, Q/N corresponds to the engine load. Next, in step 72, the basic fuel injection pulse width τ _p is determined from the equation τ _p =K ₁ ·Q/N. Here K ₁ is a constant. Then step 73
Then, it is determined whether or not the throttle switch 27 is on, that is, it is determined whether or not the throttle valve 25 is almost fully open. If the throttle valve 25 is not nearly fully open, the process proceeds to step 74, where the engine speed N is changed to a predetermined speed No., for example.
It is determined whether or not it is greater than 3000r.pm. N
If ≦No, the process advances to step 75 and data for deenergizing the electromagnetic control valve 35 is output to the output port 56. At this time, the negative pressure chamber 32 of the negative pressure actuator 30 is connected to the negative pressure tank 36 via the electromagnetic switching valve 35.
As a result, the diaphragm 31 moves toward the negative pressure chamber 32, and the intake control valve 19 is fully closed. Next, in step 76, the control time τ ₀ from the injection completion time to the intake bottom dead center is calculated. FIG. 10 shows the relationship between the control time τ ₀ and the engine speed N, and the relationship shown in FIG. 10 is stored in advance in the ROM 52 in the form of a function or a data table. Then, in step 77, the increase factor K ₂
Set it to 1.0 and proceed to step 78. In step 78, the fuel injection pulse width τ is calculated from the formula τ=K ₂ ·K ₃ ·τ _p +τ _r . where K ₃ is the correction factor,
τ _r is the invalid injection time. Next, in step 79, the injection start timing θ ₁ of the fuel injection valve 21 is determined as θ ₁ =θ ₀ −(τ
+τ ₀ ). Here, θ ₀ indicates the crank angle at intake bottom dead center. τ indicates the crank angle at which fuel injection is performed, and τ ₀ indicates the control time expressed in crank angle. Therefore, in step 79, the injection start crank angle θ ₁ is calculated with reference to the intake bottom dead center. Next, in step 80, the injection completion crank angle θ ₂ with reference to the intake bottom dead center is calculated from the equation θ ₂ =θ ₀ −τ ₀ . Next, in step 81, the thus calculated injection time crank angle θ ₁ and injection completion crank angle θ ₂ are stored in the RAM 53.

On the other hand, if it is determined in step 73 that the throttle switch 27 is on, or if it is determined in step 74 that N>N ₀ , the process advances to step 82. At step 82, data for energizing the electromagnetic switching valve 35 is output to the output port 56. At this time, the negative pressure chamber 32 of the negative pressure actuator 30 is opened to the atmosphere via the electromagnetic switching valve 35, so the diaphragm 31 moves toward the atmospheric pressure chamber 33, and thus the intake control valve 19 is fully opened at this time. It will be done. Next, in step 83, a constant value G is entered into the control time τ ₀ . This constant value G is determined by the first intake valve 7 and the second intake valve 8 as shown in FIG.
This is the crank angle from the crank angle E just before the valve opens to the intake bottom dead center C. Then step 84
Then, the increase coefficient K ₂ is determined. This increase factor K ₂
is determined by Q/N and N as shown in FIG. 11, and each increase coefficient K _{11 .} . . K _no shown in FIG. 11 is stored in advance in the ROM 52 in the form of a map. This increase coefficient K ₂ is larger than 1.0 and Q/N
and increases as N increases. Next, in step 78, the fuel injection pulse width τ is determined, but since K ₂ is greater than 1.0, the amount of fuel is increased. In addition, in step 80, the injection completion crank angle θ ₂ is determined, and since τ ₀ is a constant value G, the fuel injection completion timing is determined at the crank angle slightly before the first intake valve 7 and the second intake valve 8 open. It will be fixed at

FIG. 9 shows the fuel injection processing routine. This routine is performed by time interrupt. Referring to FIG. 9, first, in step 90, the current crank angle CA is calculated from the output pulses of the crank angle sensors 42, 43. Then step 91
Then, it is determined whether the current crank angle CA is the injection start crank angle θ ₁ stored in the RAM 53, and if the injection start crank angle θ ₁ is the injection start crank angle θ 1, the process advances to step 92 and data to start fuel injection is output. The signal is output to the port 56 and fuel injection from the fuel injection valve 21 is started. On the other hand, if the injection start crank angle θ is not ₁ , the process advances to step 93 and the current crank angle is
It is determined whether CA is the injection completion crank angle θ ₂ , and if the injection completion crank angle θ 2 is the injection completion crank angle θ ₂ , step 94 is performed.
Then, data for stopping fuel injection is output to the output port 56, and fuel injection from the fuel injection valve 21 is stopped.

Therefore, as can be seen from the flowchart shown in FIG. 8, when the opening degree of the throttle valve 25 is smaller than the predetermined opening degree and the engine speed is lower than the predetermined rotation speed _N0 , the intake control valve 19 is
is closed, and fuel injection is completed at the time indicated by curve D in FIG. As a result, the degree of stratification increases as described above, and thus good combustion can be obtained. In addition, the third intake valve 9
When the valve is opened, intake air flows through the third intake passage 14, which promotes vaporization of the injected fuel, thus ensuring good ignitability. On the other hand, if the throttle valve 25 is almost fully opened or the engine speed N
When the engine speed is higher than a predetermined rotational speed N ₀ , the intake control valve 19 is fully opened, and fuel injection is completed at a certain time indicated by the chain line E in FIG. As a result, as described above, the degree of stratification is weakened and a substantially uniform air-fuel mixture is formed in the combustion chamber 5. Also, at this time, the amount of fuel is increased and the average air-fuel ratio becomes smaller, but the degree of stratification is weakened, so the air-fuel mixture around the spark plug 6 does not become too rich, thus ensuring good ignition performance. be able to. Further, by reducing the average air-fuel ratio, high output can be obtained.

[Effect of idea]

By using both the direct drive method of the intake valves using the camshaft and the indirect drive method using the rocker arm, it is possible to simultaneously open and close a plurality of intake valves that are not arranged in a straight line with respect to the extending direction of the camshaft. As a result, a plurality of intake valves for each cylinder can be driven by one camshaft, so the structure of the valve operating mechanism can be simplified. Furthermore, by reducing the valve lift of the third intake valve, it is possible to prevent the rich air-fuel mixture flowing into the combustion chamber from the third intake passage from diffusing, thereby increasing the degree of stratification within the combustion chamber. In this way, good combustion can be obtained even when using a lean mixture with an average air-fuel ratio of 25 to 30. Further, since the valve lifts of the first intake valve and the second intake valve can be made larger than in the case where they are directly driven by a camshaft, it is possible to increase the filling efficiency during high-load operation of the engine.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a valve mechanism using a camshaft, Fig. 2 is a side sectional view taken along the - line in Fig. 1, Fig. 3 is a side sectional view taken along the - line in Fig. 1, and Fig. 3 is a side sectional view taken along the - line in Fig. 1. Fig. 4 is a side sectional view of the internal combustion engine, Fig. 5 is a plan sectional view of Fig. 4, Fig. 6 is an overall view of the internal combustion engine, and Fig. 7 is a diagram showing the intake valve opening period and injection completion timing. , FIG. 8 is a flowchart for determining the injection start crank angle and the injection completion crank angle,
Figure 9 is a flowchart for fuel injection processing;
FIG. 10 is a diagram showing the relationship between control time and engine speed, and FIG. 11 is a diagram showing the increase coefficient stored in the ROM. 5... Combustion chamber, 6... Spark plug, 7... First intake valve, 8... Second intake valve, 9... Third intake valve, 12
...First intake passage, 13...Second intake passage, 14
...Third intake passage, 19...Intake control valve, 21...
...Fuel injection valve. 60...camshaft, 60a,
60b, 60c...cam, 62, 63...Rotzker arm.

Claims (1)

[Scope of utility model registration request] At least two consisting of a main intake valve and a sub-intake valve
and at least two intake passages consisting of a main intake passage and a sub-intake passage, and the main intake passage is connected to the combustion chamber via the main intake valve to generate a swirling flow within the combustion chamber. The fuel injection valve is placed in the auxiliary intake passage connected to the combustion chamber via the auxiliary intake valve, and the main intake valve opens from near the top dead center of the intake stroke to the beginning of the compression stroke, and the auxiliary intake valve opens. A fuel injection internal combustion engine that opens from near the center of the intake stroke to the beginning of the compression stroke is equipped with a common camshaft for driving the main intake valve and the sub-intake valve. A fuel injection type internal combustion engine equipped with a plurality of intake valves in which the valve lift of the main intake valve is made larger than the valve lift of the auxiliary intake valve by driving the intake valves by a camshaft via a Rocker arm.