JPH0567769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an intake system for an internal combustion engine equipped with a supercharger that performs supercharging from the end of the intake stroke to the beginning of the compression stroke.

(Background Art) Internal combustion engines employing this type of supercharging system include, for example, Japanese Patent Laid-Open No. 55-69722 or Japanese Patent Laid-open No. 55
There is one as shown in the -139925 publication.

This is an additional supply of compressed air from the supercharger to each cylinder after the end of the normal intake stroke in a 4-cycle engine, and the supercharger only needs to handle the additional supply amount, for example, 150% When trying to obtain a supply rate, it is sufficient to have a discharge capacity of 50%, that is, 1/3 of the total intake air volume. When compared with a system that mechanically discharges and supplies the entire amount of intake air using a Roots blower, etc., it has major advantages such as making the turbocharger smaller and lighter and reducing costs, and it is also widely used. Compared to exhaust turbo superchargers, which have low speeds and are difficult to obtain supercharging effects,
Automotive engines have the advantage of being easier to control output in that the lower the speed, the higher the supercharging efficiency.

By the way, in the supercharging method described in JP-A-55-69722, the intake passage in which a normal intake valve is installed and the supercharging passage in which a supercharger is installed are provided independently. After the intake valve closes near the bottom dead center of the intake stroke, the supercharging valve installed in the supercharging passage is opened to supercharge high-pressure air, and the supercharging valve is closed in the middle of the compression stroke. That's what I do.

However, in such a configuration, the intake valve closes near the bottom dead center even though the intake inertia is large in the high-speed region of the engine, so supercharging due to the intake inertia effect cannot be utilized, and the On the contrary, the output sometimes decreased.

Therefore, in order to improve the intake air filling efficiency in the engine high speed region, the supercharging method described in Japanese Patent Application Laid-Open No. 55-139925 has a main intake port and a supercharging port formed in the combustion chamber. , the opening/closing valve of the supercharging port is opened near the closing of the opening/closing valve of the main intake port, and a communication passage is provided that communicates the main intake passage including the main intake port with the supercharging passage including the supercharging port. On the other hand, a switching valve is provided in the communication passage so that the communication passage is closed when the engine rotation speed is below a set value, and when the engine rotation speed exceeds the set value, the communication passage is opened and the upstream side of the supercharging passage is closed. I have to.

However, in such a configuration, passage resistance increases because intake air is not simultaneously supplied from both the main intake port and the supercharging port even though the engine is in a high-speed region. In addition, the opening/closing valve of the supercharging port, which opens near the closing of the main intake port, has a small lift amount and the opening area of the valve is not sufficient, so the high pressure air from the supercharger or the air using inertial supercharging has a large resistance. As a result, the air does not flow smoothly, and sufficient intake air filling efficiency cannot be obtained, resulting in a decrease in output.

(Object of the Invention) The present invention was made in view of such conventional problems, and is applied to an internal combustion engine having a plurality of intake valves and intake ports for each cylinder. In low-speed regions with small inertia, high-pressure air from the supercharger is smoothly supplied to the combustion chamber without being blown back to the intake port, while in high-speed regions with large intake inertia, it reduces passage resistance.
By making full use of the inertia effect of the intake air to perform supercharging, the internal combustion engine is able to increase charging efficiency as much as possible, maintain high output over the entire operating range, and improve fuel efficiency. The purpose is to provide intake equipment for engines.

(Structure of the Invention) Therefore, the present invention provides an intake system for an internal combustion engine that includes a plurality of intake valves for each cylinder and a plurality of intake ports leading to these intake valves. The closing timing of one intake valve is set to close in the middle of the compression stroke, and the closing timing of the other intake valves is set to close near the bottom dead center of the intake stroke earlier than the closing timing of some of the intake valves. , an on-off valve that is interposed in an intake port leading to some of the intake valves and is controlled to open and close so as to close in a low-speed region of the engine and open in a high-speed region; a supercharger that discharges compressed air; a supercharging passage connecting a discharge port and an intake port downstream of the on-off valve; and a timing control valve that opens the supercharging passage only from near the bottom dead center of the intake stroke to near the closing timing of some of the intake valves. The configuration includes the following.

(Example) Examples of the present invention will be described below.

FIG. 1 shows an internal combustion engine 2 equipped with an exhaust turbocharger 1 to which the present invention is applied.

In the figure, an intake compressor 4 of an exhaust turbo supercharger 1 is installed in an intake passage 3 of an internal combustion engine 2, and an exhaust turbine 6 installed in an exhaust passage 5 is rotated by exhaust pressure. The coaxial compressor 4 is rotationally driven to forcefully feed (supercharge) intake air to the internal combustion engine 2. An exhaust bypass valve 8 is interposed in the exhaust bypass passage 7 that bypasses the exhaust turbine 6, and the exhaust bypass valve 8 is a diaphragm operated by the differential pressure between the boost pressure and the atmospheric pressure between the compressor 4 of the intake passage 3 and the intake throttle valve 9. type actuator 10
is used to control opening and closing of the exhaust bypass valve 8.
As a result, the amount of exhaust gas bypassed to the exhaust bypass passage 7 without rotating the exhaust turbine 6 is controlled according to the supercharging pressure, thereby preventing the supercharging pressure from becoming excessive. In the figure, 11 is a relief valve that prevents the intake air pressure downstream of the intake throttle valve 9 from exceeding a predetermined value, 12 is an air flow meter, and 13 is a fuel injection valve.

As shown in FIGS. 2 and 3, such a supercharged internal combustion engine has two intake valves 20A, 20B, a first and a second, and two exhaust valves 21A, 21 in a combustion chamber 19.
B is provided.

The first and second intake valves 20A, 20B and exhaust valves 21A, 21B are opened and closed by cams 22 and 23, respectively, which are brought into contact with each other. Here, as shown in FIG. 5, the first cam 22A for the first intake valve 20A greatly delays the closing timing of the intake valve 20A (for example, near the middle of the compression stroke from 50° to 80° after bottom dead center). , second cam 2 for the second intake valve 20B
As shown in FIG. 4, the intake valve 2B has a cam shape that causes the intake valve 20B to close at an earlier timing than the above, near the bottom dead center (eg, 0° to 30°). In addition, the intake valves 20A, 2 determine the amount of overlap with the exhaust valves.
The opening timing of 0B is the first cam 22A and the second cam 2.
2B are approximately equal, for example, about 0° to 10° before top dead center. At this time, the opening timings of the exhaust valves 21A and 21B are, for example, 40° to 50° before bottom dead center, and the closing timings are the same, 10° to 20° after top dead center.
The amount of overlap between A and 20B is set to be as small as possible.

As shown in FIGS. 2 and 3, the intake passage 3 has first and second intake ports 3A and 3B that communicate independently with these intake valves 20A and 20B, respectively, and the exhaust passage 5 has an It has exhaust ports 5A and 5B that independently communicate with the valves 21A and 21B, respectively.
A butterfly-type on-off valve 24 is interposed in the first intake port 3A connected to the first intake valve 20A.

In the case of a multi-cylinder engine, the shaft 2 of the on-off valve 24
A lever 25 is pivotally attached to one end of the shaft 24A, and an output rod 26a of a diaphragm actuator 26 is fixed to the tip of the lever 25. The diaphragm actuator 26 is connected to the output rod 2.
A pressure working chamber 26c partitioned on one side by a diaphragm 26b to which the diaphragm 6a is fixed is connected to the supercharging pressure introduction pipe 26.
A return spring 26e is interposed in an atmospheric pressure chamber 26d which is connected to the intake passage 3 downstream of the compressor 4 via f and is partitioned on the other side. When the supercharging pressure from the compressor 4 reaches a pressure near the intercept point where it rapidly increases with respect to the engine rotational speed, the output rod 26a expands while compressing the return spring 26e, and through the rotation of the lever 25, each cylinder The on-off valve 24 is rotated from closed to open.

Further, a vane type air pump 27 is provided as a supercharger for supercharging according to the present invention, and the air pump 2
7 and the intake port 3 downstream of the on-off valve 24.
A is connected to the supercharging passage 29 through a rotary timing control valve 28. The air pump 27 is adapted to be driven in conjunction with a cam pulley. A relief valve 31 is provided in a bypass passage 30 connecting the suction port and discharge port of the air pump 27. The relief valve 31 opens when the supercharging pressure from the air pump 27 exceeds a predetermined value, and maintains the supercharging pressure below a certain value by circulating the supercharging air to the suction port side. .

The timing control valve 28 is 1/1 of the camshaft.
A valve hole 28a is provided in a valve body 28A that rotates at a rotation speed of 2.
is provided so that, as shown in FIG. 4, the valve hole 28a is open only from near the bottom dead center of the intake stroke when the second intake valve 20B closes to near the compression stroke where the first intake valve 20A closes. is set to .

Next, the operation of this embodiment will be explained.

When the engine rotational speed is in a low speed region of 1600 rpm or less, the boost pressure downstream of the compressor 4 is small, so the output rod 26a of the actuator 26 is retracted to the shortest length by the biasing force of the return spring 26e, and in this state. The on-off valve 24 is fully closed.

Therefore, the intake air first passes through the second intake valve 20B.
The combustion chamber 1 is opened only through the second intake port 3B from the vicinity of the top dead center of the intake stroke to the vicinity of the bottom dead center of the intake stroke.
9 , and a large swirl is formed in the combustion chamber 19 . Next, the timing control valve 28 opens from the intake bottom dead center, and the high pressure air discharged from the air pump 27 passes through the supercharging passage 29 and flows into the combustion chamber 1 from the first intake port 3A downstream of the on-off valve 24.
Supercharged to 9. In this case, as shown in Figure 5,
When the second intake valve 20B closes, the first intake valve 20A still has a considerable amount of lift (about 4 mm, which is half of the maximum lift if the maximum lift is 8 mm), and the high-pressure air for supercharging does not encounter much resistance. Fills quickly. Furthermore, since the second intake valve 20B is closed almost simultaneously with the start of supercharging from the air pump 27,
It is possible to prevent supercharged air from blowing back into the second intake port 3B.

In this way, since the exhaust energy is small in the low speed region, the boost pressure of the exhaust turbo supercharger is small, but after sufficiently introducing intake air with small inertia to the vicinity of the bottom dead center of the intake stroke,
7 performs supercharging until the middle of the compression stroke, which can more than compensate for the lack of supercharging in the exhaust turbo supercharger, resulting in high charging efficiency and a significant increase in output. .

Further, the first intake valve 20A is the exhaust valve 21A, 21
B is set to open with a slight overlap before closing, and during this time the high pressure air trapped in the first intake port 3A expands to the exhaust pressure and remains in the combustion chamber 19. It is possible to effectively scavenge the existing combustion gases, and from this aspect as well, it is possible to increase the filling efficiency of fresh air and contribute to an increase in output. In a normal engine, the volume of the first intake port 3A is slightly larger than the top volume at the top dead center of the piston.
If fresh air of about 2 atmospheres is maintained in A, most of the combustion gas will be scavenged. Incidentally, the internal volume of the combustion chamber 19 at compression top dead center is, for example, 500 x (8-1) ≒ 71.4 in the case of a 4-cylinder engine with a displacement of 2000 c.c. and a compression ratio of 8.
cc, and even if the combustion gas remaining in this area is only scavenged, the filling efficiency of fresh air is (500 + 71.4) /
500×100=114, which is an improvement of about 14%.

On the other hand, when the engine speed increases and exceeds 1600 rpm and the supercharging pressure of the exhaust turbo supercharger reaches approximately 200 mmHg or more, the output rod 26a starts an extension stroke and the lever 25 rotates counterclockwise in FIG. The on-off valves 24 of each cylinder connected to this via the shaft 24a rotate in the same direction and begin to open.
When the boost pressure reaches about 300mmHg, it will be fully opened and the first
Open the intake port 3A.

In this way, when the first intake port 3A opens in the high speed region, the first intake port 3A
Since intake air is supplied from both the intake port 3B and the second intake port 3B, which is always open, passage resistance is reduced, and the compression stroke starts from near the bottom dead center of the intake stroke when only the first intake valve 20A is open. Towards the middle, the supercharging pressure of the exhaust turbo supercharger increases due to high speed rotation, and due to the increase in inertia, supercharging using the inertia effect can be performed well, so the supercharging pressure is increased from the air pump 27. It exceeds the boost pressure and can maximize intake air filling efficiency.
In addition, the two intake valves 20A and 20B are cooled by the intake air flow, and the flame propagation distance from the spark plug is the same, so hot spots are less likely to form and the tendency for knocking to occur is reduced. On the other hand, since supercharging using the inertia effect does not receive any external work, it does not lead to an increase in intake air temperature and does not increase the tendency for knocking to occur. Therefore, in the high-speed range, it is possible to suppress the occurrence of knocking, increase the intake air filling efficiency as much as possible, improve the output, and prevent deterioration of fuel efficiency.

Regarding the scavenging efficiency, an increase in supercharging pressure makes it possible to obtain scavenging efficiency that is superior to that in the low speed region.

In addition, although this embodiment has been applied to a so-called 4-valve engine, there are other examples of this type of engine, such as the
A system has been put into practical use that aims to create two independent intake ports and provide an on-off valve on one of them to add swirl to the intake air and to prevent residual gas from blowing back into the intake system. When applying the present invention, it is only necessary to provide an air pump as a supercharger and a timing control valve without changing the structure of the engine. The air pump and timing control valve may be driven by a camshaft, crankshaft, or the like.

In addition, since a rotary type timing control valve is used in this embodiment, the maximum opening degree can be larger than that of a lift type type (Japanese Patent Application Laid-Open No. 139925/1982), as shown in Fig. 5, and the amount of supercharging can be reduced. Since it is provided outside the cylinder head, it is not exposed to combustion gas and the sealing mechanism has excellent durability. Furthermore, an air reservoir 32 for accumulating pressure of the air discharged from the air pump 27 may be provided in the middle of the supercharging passage connecting the air pump 27 and the timing control valve 28, as shown by the chain line in FIG.

Furthermore, since this example was applied to an engine equipped with an exhaust turbo supercharger, the boost pressure of the exhaust turbo supercharger that is insufficient in the low speed range is supplemented to improve the output, and the output is smooth over the entire speed range. Although the characteristics can be secured,
It goes without saying that the present invention can also be applied to engines that are not equipped with an exhaust turbocharger, and in this case, the effect of improving output by effectively utilizing inertia supercharging in a high-speed region is high.

(Effects of the Invention) As explained above, according to the present invention, there is a difference in the closing timing between some intake valves and other intake valves among the plurality of intake valves provided for each cylinder, so that the closing timing is delayed. By supplying supercharged air from the turbocharger to the intake port equipped with a side intake valve at the right timing, supercharging can be performed efficiently in the low speed range, resulting in lower output in the low speed range. It is extremely advantageous for improvement. In addition, in high-speed ranges, by reducing passage resistance and effectively performing supercharging using inertia effects, charging efficiency can be further increased and maximum output can be sufficiently ensured, resulting in full power consumption. This allows engine performance such as fuel efficiency and output to be maximized over the operating range.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an internal combustion engine with a supercharger to which an embodiment of the present invention is applied, and Fig. 2 shows the intake and
3 is a sectional view showing the overall configuration of the same embodiment as above; FIG. 4 is a time chart showing the characteristics of various components of the above embodiment; FIG. 5 is a diagram showing the present invention. FIG. 3 is an explanatory diagram showing the supercharging characteristics of the conventional example in comparison with that of the conventional example. 2...Internal combustion engine, 3...Intake passage, 3A, 3B
...Intake port, 20A, 20B...Intake valve, 2
2A, 22B...Cam, 24...Opening/closing valve, 25...
... lever, 26 ... actuator, 27 ... air pump, 28 ... timing control valve.

Claims (1)

[Claims] 1. In an intake system for an internal combustion engine comprising a plurality of intake valves for each cylinder and a plurality of intake ports leading to these intake valves, the closing timing of some of the intake valves is compressed. The closing timing of the other intake valves is set to close near the bottom dead center of the intake stroke earlier than the closing timing of the some intake valves, while the closing timing of the other intake valves is set to close in the middle of the intake stroke. An on-off valve installed in an intake port and controlled to open and close so as to close in a low-speed region of the engine and open in a high-speed region, a supercharger that discharges compressed air, and a discharge port of the supercharger and an intake air downstream of the on-off valve. The intake valve is characterized by being configured by providing a supercharging passage that connects the supercharging passage to the port, and a timing control valve that opens the supercharging passage only from the vicinity of the bottom dead center of the intake stroke to the vicinity of the closing timing of some of the intake valves. intake system for internal combustion engines.