JPH0579359A - Control method for independent throttle valve - Google Patents

Abstract

PURPOSE:To prevent the variations in the sucked air amount of each cylinder and maintain a high level of response, by equipping the system with independent throttle valves provided with respect to suction passages of the air cylinders and with a second throttle valve provided with respect to a common suction passage upstream of the independent throttle valves. CONSTITUTION:The control system is equipped with independent throttle valves 6 to 9 provided to suction passages 1 to 4 of the air cylinders and with a second throttle valve 18 provided to a common passage 19 upstream of the independent throttle valves 6 to 9. During a low-load of the engine, the opening of the independent valves 6 to 9 is set at a degree of opening which does not substantially restrict the sucked air quantity while, on the other hand, the opening of the second throttle valve 18 is so controlled as not to exceed the opening of the independent throttle valve 11. During a middle and high load, the second throttle valve 18 is largely opened to enable controlling the sucked air quantity to each air cylinder in accordance with the opening of the independent throttle valves 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cylinder internal combustion engine having a so-called "independent throttle valve" in which a throttle valve is provided in each intake passage of each cylinder. The present invention relates to a method for controlling the independent throttle valve in such an internal combustion engine.

[0002]

2. Description of the Related Art An internal combustion engine provided with a so-called independent throttle valve, in which a throttle valve is provided for each cylinder of a multi-cylinder internal combustion engine, generally has a high response.
It is suitable for generating high output, but on the other hand, when the independent throttle valve is close to fully closed in the operating state in the low load range including idling, the independent throttle valve composed of the throttle valve for each cylinder Due to a slight difference in the opening area, the intake air amount may vary from cylinder to cylinder, which may cause idle instability or engine vibration due to irregular rotation. Therefore, as shown in FIG. By providing a balance tube across the intake passage of each cylinder, the intake air amount to each cylinder at the time of idling is balanced.

FIG. 3 shows an intake system for a four-cylinder internal combustion engine according to the first prior art. 1, 2, 3, 4 are intake passages leading to respective cylinders of a multi-cylinder internal combustion engine (not shown),
The intake air diverted from the common surge tank 5 is sent to the combustion chamber of each cylinder in the direction of the arrow. Each intake passage 1
To 4 are provided with throttle valves 6, 7, 8 and 9, respectively, which are common throttle shaft 1
It is attached to 0 and is simultaneously opened and closed by means not shown. Reference numeral 12 is a throttle sensor provided to detect the opening degree of the independent throttle valve 11 having such a structure.

In order to cope with the above-mentioned problem of the independent throttle valve 11, in the example of FIG. 3, the balance tube 14 communicating with the throttle valve downstream side portions of the intake passages 1 to 4 by the small holes 13, A bypass passage 16 is provided so as to bridge them, and further has an idle speed control valve (hereinafter, abbreviated as ISC valve) 15 for controlling the intake air amount during idling. In parallel with the above, the upstream side of the surge tank 5 and the above-mentioned balance tube 14 provided on the downstream side of the intake passages 1 to 4 are connected to supply intake air at the time of idling.

A second modification of the prior art shown in FIG.
Japanese Patent Laid-Open No. 61-103523 has been disclosed in the prior art. In this example, the common throttle shaft of the independent throttle valve is made hollow, and this is also fitted to the hollow fixed shaft so that the hollow throttle shaft itself also functions as a balance tube and the overlapping throttle shafts. By constructing a kind of response valve by utilizing the fact that the area of the overlapping portion of the holes provided on each fixed shaft changes in relation to the opening of the independent throttle valve, the opening of the independent throttle valve can be set to a predetermined value. The valve opens only when the load is lower than the specified value, and the intake passage to each cylinder on the downstream side of the independent throttle valve communicates with each other through the balance tube consisting of a hollow throttle shaft, and the intake amount to each cylinder It is designed to balance.

[0006]

Since the internal combustion engine having the independent throttle valve 11 shown in FIG. 3 is provided with the balance tube 14, the intake air is relatively evenly distributed to each cylinder even at the time of idling. The irregular rotation at a low load due to the variation is unlikely to occur, but if the passage diameter of the balance tube 14 is increased, the good response is reduced and the independent throttle valve 1
There is no point in providing 1, and conversely, if the passage diameter of the balance tube 14 is reduced, the balancing action is weakened, and the rotation at low load becomes unstable.
There is a problem that it is difficult to balance the cylinders sufficiently while maintaining high response.

In the second prior art disclosed in Japanese Utility Model Laid-Open No. 61-103523, the throttle shaft is used as a balance tube, and it is not necessary to provide the balance tube outside the intake passage. Although it has the above advantage, the problem similar to that of the first prior art shown in FIG. 3 remains, and the passage diameter of the balance tube is restricted by the diameter of the throttle shaft, so that it cannot be made too large. Therefore, the effect of balancing the intake air amount distributed to each cylinder may become insufficient at the time of idling and the like, which has not yet been a sufficient countermeasure.

[0008]

A method of controlling an independent throttle valve according to the present invention is provided in an independent throttle valve provided for each intake passage of each cylinder and a common intake passage upstream of the independent throttle valve. In a multi-cylinder internal combustion engine including a second throttle valve, the opening of the independent throttle valve is set to such an extent that it does not substantially reduce the amount of intake air to each cylinder when the engine has a low load. By setting the opening degree and controlling the opening degree of the second throttle valve within a range that does not exceed the opening degree of the independent throttle valve, the intake air amount to each cylinder mainly depends on the opening degree of the second throttle valve. Is controlled, and when the engine is in a medium or high load, the opening of the second throttle valve substantially controls the intake air amount to each cylinder. The opening degree of the independent throttle valve is controlled so that the opening degree of the independent throttle valve is controlled within a range not exceeding the opening degree of the second throttle valve. The feature is that the amount of intake air to the cylinder can be controlled.

[0009]

When the engine is under a low load, the independent throttle valve is opened to the extent that the intake air amount to each cylinder of the engine is not substantially throttled, and the opening of the second throttle valve is set to the opening of the independent throttle valve. Since the control is performed within the range that does not exceed the limit, the intake air amount is controlled mainly by the opening degree of the second throttle valve, and the pressure difference in the independent throttle valve is reduced by the pressure difference caused by the second throttle valve. Therefore, even if there is a slight difference between the opening areas of the constituent throttle valves corresponding to the individual cylinders of the independent throttle valve, it does not cause a large variation in the intake air amount to each cylinder.
The engine operates stably.

Further, when the engine is under high load in the middle of the engine, the second throttle valve is opened to the extent that the intake air amount to each cylinder of the engine is not substantially throttled, and the opening of the independent throttle valve is set to the second throttle. Since the control is performed within the range that does not exceed the valve opening, the intake air amount is mainly controlled by the opening of the independent throttle valve, and the characteristics of the internal combustion engine equipped with the independent throttle valve are fully exerted, and the response High output of high.

[0011]

FIG. 1 shows a first embodiment of an intake system for a four-cylinder internal combustion engine that implements the control method of the present invention. Substantially the same parts as in the prior art intake system shown in FIG. 3 are given the same reference numerals. That is, 1, 2, 3, 4
Is an intake passage for each cylinder, 5 is a surge tank, 6, 7,
8 and 9 are throttle valves provided for each cylinder, 11
Is an independent throttle valve that collectively refers to those throttle valves, 13 is a small hole, 14 is a balance tube, 15 is an ISC valve, and 16 is a bypass passage. In this example, the intake passages 1, 2, 3, 4 are The throttle valves 6, 7, 8, 9 and the balance tube 14 are branched on the downstream side of the small holes 13 and are connected to two intake valves 17 provided for each cylinder.

As a structural feature of the intake system in the multi-cylinder internal combustion engine that implements the method of the present invention, the intake system of FIG. 1 is provided with a second throttle valve 18 in the intake passage 19 upstream of the surge tank 5. .. Further, the inlet 20 of the bypass passage 16 is opened to the wall surface of the intake passage 19 further upstream than the second throttle valve 18.

The method of the present invention is also characterized by the opening / closing control in which the second throttle valve 18 and the independent throttle valve 11 are associated with each other. An example thereof is shown in FIG. 2 as a chart. In the case of an automobile, related control of these two valves is possible by interposing a mechanical link mechanism or a cam mechanism between the accelerator pedal operated by the driver and the valves 11 and 18. It is also possible to use an electromagnetic or hydraulic actuator that opens or closes one or both of these valves in a predetermined mode in response to the depressed position of the accelerator pedal. In such a case, it goes without saying that a control device using a microprocessor, which is a conventional means, can be added.

In FIG. 2, the horizontal axis indicates the amount of depression (stroke) of the accelerator pedal, and the vertical axis indicates the independent throttle valve 11.
3 shows an example of setting the relationship between the opening and closing of the second throttle valve 18 and the opening and closing of these two throttle valves. The "idle and off idle range" that combines the low air volume range (off idle range or low load range) when the accelerator pedal, which is the origin of the horizontal axis, is not pressed and when the accelerator pedal is slightly depressed 2 is shown as an area A in FIG. 2, and in this range, the opening degree of the independent throttle valve 11 shown by a solid line maintains a small opening degree a, but is shown by a broken line. The opening degree of the second throttle valve 18 is a small opening degree b at the time of idling as the accelerator pedal is depressed (the leakage amount of the second throttle valve 18 and the idling directly sucked through the bypass passage 16 and the balance tube 14). Depending on the intake air amount for use, the second throttle valve 18 may have the minute opening b even when the second throttle valve 18 is substantially fully closed. Gradually it has been increased linearly from).

In the example of FIG. 2, the state of the point c (where the range from the idle state to that point) is reached by increasing the opening of the second throttle valve 18 to reach substantially the same as the opening of the independent throttle valve 11. In the region B (medium to high load region) subsequent to the region A), the opening degree of the second throttle valve 18 rapidly increases as the accelerator pedal depression amount increases, and the throttle valve 18 is fully opened at the point d. Is set to reach. On the contrary, the independent throttle valve 11 is set so that its opening gradually increases in accordance with the amount of depression of the accelerator pedal to reach full opening at the point e. The intake amount is determined by the throttle valve 11.

That is, the two throttle valves 11 and 1
If the opening degree characteristics related to each other are set for No. 8, in the area A, the second throttle valve 1 having a small opening degree at that time is set.
8 becomes dominant, and conversely, in the region B, the independent throttle valve 11 having a small opening at that time becomes dominant. Therefore, the total intake amount of the entire engine changes along the line b-c-e in FIG. 2 which connects the predominant throttle valve openings in each of the regions A and B. The amount changes substantially linearly according to the amount of depression of the accelerator pedal, and torque shock does not occur even at the point c.

As described above, in the "idle and off-idle region", which is the region A of FIG. 2, the opening area of the independent throttle valve 11 is made larger than the opening area of the second throttle valve 18, so that area is set. Dominant second
The opening area of the throttle valve 18 determines the intake amount of the entire engine, but since the second throttle valve 18 is provided on the upstream side of the surge tank 5, the negative pressure in the surge tank 5 is in the area A. Becomes relatively large, and the differential pressure across the second throttle valve 18 increases accordingly, so the differential pressure across the independent throttle valve 11 provided in series with it decreases. As a result, even if there is a slight difference in the opening area between the throttle valves 6 to 9 of each cylinder constituting the independent throttle valve 11, there is no large variation in the intake air amount between the cylinders. Therefore, even if the engine is provided with an independent throttle valve, the operating state is stable under idling or low load without increasing the passage diameter of the balance tube 14.

Further, in the medium-high load region in the range B in FIG. 2, the opening area of the second throttle valve 18 is set to be larger than the opening area of the independent throttle valve 11, so this area is set. Then, the influence of the second throttle valve 18 becomes small, the pressure in the surge tank 5 becomes close to the atmospheric pressure as in the usual case, and the opening area of the independent throttle valve 11 which is dominant in that region is the engine. It will determine the total intake volume. Even if there is a slight difference in the opening area between the throttle valves 6 to 9 for each cylinder at a small opening degree, in the region B where the opening area becomes large, the difference is almost equal to the opening area size. Since it does not cause a problem, the intake air amount does not vary among the cylinders. Therefore, it is not necessary to increase the passage diameter of the balance tube 14, and the balance at the time of low load is not adversely affected, the good response characteristic of the internal combustion engine provided with the independent throttle valve 11 is sufficiently exhibited, and a high output is obtained. Can be generated.

Next, if the independent throttle valve 11 and the second throttle valve 18 provided in the internal combustion engine for carrying out the method of the present invention are used, the evaporated fuel is adsorbed from the charcoal canister which adsorbs the evaporated fuel generated from the fuel tank. A second embodiment of an intake system for a four-cylinder internal combustion engine, which is equipped with a purge pipe for that purpose, is shown in FIG. Portions substantially the same as those in FIGS. 1 and 3 are designated by the same reference numerals and the description thereof will be omitted.

In an internal combustion engine for an automobile or the like, vaporized fuel generated from a fuel tank or the like is temporarily adsorbed to a charcoal canister, and when the engine is in a medium or high load operating state, air is evacuated through the canister. By sucking into the intake passage, so-called "purging" is performed to desorb the evaporated fuel adsorbed in the canister, and the capacity of the adsorbent such as activated carbon particles inside the canister is regenerated. If the charcoal canister is to be purged even when the intake amount is small and the load is low, such as when the internal combustion engine is idle, the throttle valve is fully closed during idling, so there is no negative pressure on the upstream side, so purging The port must be located downstream of the throttle valve,
Since the downstream side has a considerably high negative pressure at idle when the throttle valve is fully closed, a large amount of evaporated fuel will be purged as it is, and too much evaporated fuel will be purged with respect to the intake air amount. Therefore, there is a possibility that the air-fuel ratio becomes too rich and the operating state becomes unstable, or the emission becomes worse. Therefore, it is common to stop purging the canister during low loads, such as in the "idle and off idle regions."

However, the capacity of the canister tends to be small due to the necessity of miniaturizing the canister, and the evaporated fuel from the fuel tank may increase even during idling or the like depending on the operating condition. If it exceeds the adsorption capacity, it may be released into the atmosphere.
It is desirable to perform purging not only when the load is medium or high, but also when the load is low. Therefore, in the past, a vacuum switching valve (VSV for short) was installed in the middle of the purge pipe connecting the canister and the intake passage, and this valve was opened at a time when there was relatively no problem even during low load operation, and adsorption to the canister. The evaporated fuel thus drawn is sucked by the negative pressure of intake air of the engine and is purged to the downstream side of the throttle valve. In this method, the time when purging can be performed in the low load operation is limited, and it is necessary to provide a control valve such as VSV, which is not a desirable solution.

As shown in FIG. 4, in an internal combustion engine having the independent throttle valve 11 and the second throttle valve 18 for carrying out the method of the present invention, the pipe 22 of the charcoal canister 21 has the fuel tank as in the conventional engine. It is connected to and receives the evaporated fuel and adsorbs it to the activated carbon particles inside. To purge adsorbed fuel vapor in a timely manner 1
One purge pipe 23 is connected to the surge tank 5, and the other purge pipe 24 branches to form the throttle valve 6 of each cylinder that constitutes the independent throttle valve 11.
9 to 9 in the vicinity of the valve closed positions are opened on the wall surfaces of the intake passages 1 to 4. In addition, 25 in FIG. 4 is a canister 2.
1 shows the atmospheric opening.

In the example of FIG. 4, the independent throttle valve 11 and the second throttle valve 11 are operated in the mode shown in FIG. 2, for example.
Since the throttle valve 18 is opened, the pressure of the surge tank 5 close to the atmospheric pressure in an ordinary engine causes the independent throttle valve 11 to open by the opening a in the "idle and off idle range", while the second throttle As a result of the valve 18 being throttled further than that, the pressure in the surge tank 5 leans to a weak negative pressure, and the degree thereof is adjusted by the opening degree of the second throttle valve 18.

Therefore, at this time, the air that has entered from the air port 25 of the charcoal canister 21 is discharged into the canister 21.
Flows through the inside of the adsorbent to desorb the evaporated fuel into a lean mixture, which is sucked into the surge tank 5 through the purge pipe 23 little by little due to a weak negative pressure. Is uniformly diffused in the air, is branched evenly into the intake passages 1 to 4, and is sucked into the combustion chamber from the intake valve 17 of each cylinder for processing. In this case, since the negative pressure of the surge tank 5 is comparatively small, a large amount of evaporated fuel is not purged at one time at the time of idling, and the evaporated fuel does not cause a large change in the air-fuel ratio.

While the second throttle valve 18 is wide open, when the load is high, the inside of the surge tank 5 becomes substantially atmospheric pressure, and the purge of the evaporated fuel through the purge pipe 23 is almost stopped. Since 6 to 9 open relatively large, the flow velocity of the intake air near the purge ports 26 to 29 increases, so the evaporated fuel purged from the canister 21 passes through the purge pipe 24 through the purge ports 26 to 29 and the throttle valve 6 9 to 9 is sucked into the intake passage on the downstream side, and a large amount of evaporated fuel is purged. As described above, by using the method of the present invention, it is possible to perform the purge of the evaporated fuel in the “idle and off-idle regions” without adversely affecting the operating state, and it is necessary to provide a control valve such as VSV. Nor.

[0026]

According to the present invention, while maintaining the high response and high output, which are advantages of the internal combustion engine provided with the independent throttle valve for each cylinder, as it is, the balance between the cylinders which is not compatible with the high response and the high output can be sufficiently achieved. It is also possible to obtain the effect that the rotation under low load does not become unstable.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a first embodiment of an intake system for an internal combustion engine embodying the present invention.

FIG. 2 is a diagram showing a setting example of a valve opening characteristic, which is a feature of the present invention.

FIG. 3 is a conceptual diagram showing an example of a conventional intake device for an internal combustion engine.

FIG. 4 is a conceptual diagram showing a second embodiment of an intake system for an internal combustion engine embodying the present invention.

[Explanation of symbols]

1, 2, 3, 4 ... Intake passage of each cylinder 5 ... Surge tank 6, 7, 8, 9 ... Throttle valve of each cylinder constituting an independent throttle valve 11 ... Independent throttle valve 14 ... Balance tube 16 ... Bypass passage 18 … Second throttle valve 21… Charcoal canister 23,24… Purge piping

Claims (1)

[Claims] 1. A multi-cylinder internal combustion engine comprising an independent throttle valve provided for each intake passage of each cylinder, and a second throttle valve provided in a common intake passage upstream of the independent throttle valve. When the load of the engine is low, the opening of the independent throttle valve is set to such an extent that it does not substantially reduce the amount of intake air to each cylinder, and the opening of the second throttle valve is set. Is controlled within a range that does not exceed the opening degree of the independent throttle valve, so that it is possible to control the intake amount to each cylinder mainly by the opening degree of the second throttle valve. At times, the opening of the second throttle valve is set to such an extent that it does not substantially reduce the intake air amount to each cylinder, and the independent throttle valve By controlling the opening of the lube within a range that does not exceed the opening of the second throttle valve, the amount of intake air to each cylinder can be controlled mainly by the opening of the independent throttle valve. Independent throttle valve control method