JPS61218720A - Intake device of engine with supercharger - Google Patents

Abstract

PURPOSE:To prevent an output from decreasing in the time before and after an opening and closing valve is switched, by actuating a supercharge pressure regulating valve to an increasing side of the supercharge pressure in the time before and after the valve, which opens and closes an intake passage for use in high speed operation, is operated, in the case of an engine with a supercharger having intake systems for use in high and low speed operation. CONSTITUTION:An intake passage 17 for use in high speed operation branches from intake passages 12a-d for use in low speed operation, communicating with the first volume chamber 13, and communicates with the second volume chamber 14, and an engine, providing the intake passage 17 for use in high speed operation in every cylinder, arranges in a branch part of the passage 17 an opening and closing valve 19 opened in high speed operation. A control unit 37 opens the opening and closing valve 19 by operating an actuator 20 when the engine is in high speed operation. The control unit 37, outputting a signal of an actuator 31 in the period a little time before the operating period of the actuator 20, closes a waste gate valve 30 of a supercharger 22, and the engine, temporarily increasing the supercharge pressure, compensates a decrease of an output based on a pipe line characteristic in the opening and closing switching period of the opening and closing valve.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in an intake system for a supercharged engine that improves output through the dynamic effect of intake air.

(Prior art) Conventionally, in the intake system of an engine equipped with a supercharger,
Utilizing the fact that the pressure wave that occurs with the start of intake is reflected at the open end of the intake passage to the atmosphere or the volume chamber and returned toward the intake port, the reflected wave causes the intake air to flow just before the intake valve closes. so that it reaches the boat and increases the intake pressure,
J: Increasing the filling efficiency of intake air through the so-called inertia effect of intake air:
There's something I've done. When trying to use power improvement technology that utilizes the dynamic effects of intake air, if the intake path is constant, the oscillation cycle of the pressure waves generated in the intake passage and the intake valve opening/closing cycle will not match, resulting in inertia. The effect is only enhanced in a specific speed range.

For this reason, as seen in Japanese Patent Application Laid-Open No. 56-105621, the length of the intake passage is changed depending on the rotation speed of the supercharged engine, for example, the intake passage for each cylinder is branched at the upstream part. The upstream ends of these passages are opened to the intake volume chamber, etc., and an on-off valve is provided in the short passage, and by opening this on-off valve at high speeds, the intake passage can be opened. A radial intake device has also been proposed in which the effective length is shortened, thereby increasing the inertia effect of intake air in both the low speed range and the high speed range.

In order to obtain the dynamic effect of the intake air over a wide range as described above, an intake switching mechanism such as an on-off valve that selects the intake path according to the engine speed is installed to switch the intake path. . However, a torque valley is formed before and after the operation of the intake switching mechanism, making it impossible to obtain smooth torque characteristics from a low speed range to a high speed range.

That is, for example, in a state where the intake passage is long and the on-off valve is closed, as the engine speed increases in the low speed range, the torque curve will exceed the peak value when the intake passage length and engine speed match. After it gradually decreases, the on-off valve opens, and in the high speed range as well, the intake passage length and engine speed match the increase in engine speed, which gradually increases until the peak value is reached. It gradually declines after passing this value.

Therefore, between the peak value when the on-off valve is closed and the peak value when the on-off valve is open, there is a valley between the torque curves on both sides, and a breathing phenomenon occurs in the torque characteristics, which causes a problem during switching operation. It has problems with torque and shock.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention provides an intake air switching mechanism for increasing the intake air filling efficiency by utilizing the dynamic effect of intake air and expanding the above-mentioned dynamic effect from a low speed range to a high speed range. It is an object of the present invention to provide an intake system for a supercharged engine that eliminates torque shock during switching operation.

(Structure of the Invention) The intake device of the present invention includes boost pressure control means, and in order to match the dynamic effect of intake air in response to changes in engine speed, a plurality of paths are arranged according to the engine speed. The present invention is characterized in that it is provided with an intake switching mechanism that selects the desired intake air, and a switching control means that operates the supercharging pressure control means so that the supercharging pressure increases when the intake switching mechanism is activated.

(Effects of the Invention) According to the present invention, by operating the intake air switching mechanism, the dynamic effect of the intake air is effectively utilized over a wide range of engine speeds, high charging efficiency is obtained from low speed range to high speed range, and output performance is improved. It is possible to improve this.

Furthermore, in response to the torque valley that occurs when the intake switching mechanism switches, the supercharging pressure control means controls the boost pressure to be high during the switching operation.
The charging efficiency increases due to the increase in boost pressure, which acts to fill the torque gap, eliminates torque shock during switching operation, and provides smooth 1 to 1 torque characteristics from low speed range to high speed range. .

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional front view of an engine equipped with an intake system of this embodiment, and FIG. 2 is a schematic plan view.

The engine of this embodiment is a four-cylinder four-cycle engine, and an engine body 1 consisting of a cylinder block 2 and a cylinder head 3 has four cylinders 4a to 4d formed therein. A combustion chamber 6 is formed above the piston 5 in each of the cylinders 4a to 4d, and an intake boat 7 and an exhaust boat 8 open into the combustion chamber 6.
．． 8 is equipped with an intake valve 9 and an exhaust valve 10 which are opened and closed at predetermined timing by a valve operating mechanism 11.

Each intake boat 7 of each of the cylinders 4a to 4d is communicated with independent intake passages 12a to 12d for each cylinder, which are independent from each other. The upstream ends of these independent intake passages 12a to 12d are connected to the first volume chamber 13 having a certain capacity, and these independent intake passages 128 to 128 are connected to the middle of each of the independent intake passages 12a to 12d. A second volume chamber 14 is connected to communicate the two volumes 12d with each other. by this,
Long and short 2 connecting each cylinder 4a to 4d and volume chamber 13.14
It forms two intake paths.

In this embodiment, in order to configure the intake system compactly, a tank 15 installed in the intake system is divided by a partition wall 16, thereby dividing the tank 15 into a first volume chamber 13 and a second volume chamber 14. A communication hole 17 branched from a midway point of each independent intake passage 12a to 12d is opened at the lower end of the second volume connecting hole 14, and each independent intake passage 12a to 12d is opened on the upstream side of this communication hole 17. It is curved so that its upstream end opens to the side of the first volume chamber 13 . The upstream curved portions of each of the independent intake passages 12a to 12d are integrally formed using the wall of the second volume to 14 of the tank 15.

The communication hole 17 between the second volume chamber 14 and each independent intake passage 12a to 12d is provided with an on-off valve 19 for switching the intake path.
(intake switching mechanism) is provided respectively. Each of the on-off valves 19 is integrally connected to a rotating shaft 19a, and a first actuator 20 (not shown in FIG. 2) of a switching control means 21 is connected to an end of the rotating shaft 19a. Things work together to open and close. Basically, this opening/closing valve is controlled to be closed in a low speed range where the engine speed is less than a set value in a high load range, and opened in a high speed range where the engine speed is higher than the set value.

Further, an upstream intake air introduction passage 26 is connected to one end of the first volume chamber 13.
A throttle valve 27 is disposed at the throttle valve 27, the upstream end of which is connected to the blower 22a of the turbocharger 22, and connected to an air cleaner via an air flow meter (not shown) or the like. An exhaust manifold 23 communicating with the exhaust boat 8 is connected to the turbine 22b of the turbocharger 22,
The blower 22a is driven to rotate through the turbine 22b by introducing exhaust gas.

Further, the turbocharger 20 has a boost pressure control means 24.
(not shown in FIG. 2) is installed, and this supercharging pressure control means 24 is composed of a waste gate valve 30 that opens and closes the exhaust bypass passage 23a, and a second actuator 31 that operates this waste gate valve 30. ing. A fuel injection valve 29 connected to the fuel passage 28 is disposed near the downstream end of each of the independent intake passages 12a to 12d.

A control signal from an engine control unit 37 (ECU) is output to the first actuator 20 that operates the on-off valve 19 in the switching control means 21, and its operation is controlled in accordance with the engine speed. Further, a control signal from the engine control unit 37 is also output to the second actuator 31 of the boost pressure control means 24 to control its operation, and the boost pressure is adjusted to the set pressure. Detection signals of the engine rotation speed and supercharging pressure (intake pressure) from a rotation speed sensor 38 and a pressure sensor 39 are input to the engine control unit 37 .

The opening/closing of the on-off valve 19 by the switching control means 21 is performed at a set value of the engine rotation speed, the on-off valve 19 is closed in a low speed range below this set value, and the on-off valve 19 is closed in a high speed range above the set value. It opens. Furthermore, when the lift amount of the wastegate valve 30 is reduced, the exhaust bypass amount is reduced and the supercharging pressure increases, and the lift is adjusted and controlled so that the supercharging pressure becomes a predetermined value. It is something that This supercharging pressure control basically regulates the upper limit of the supercharging pressure to a constant value, but in the vicinity of the switching operation range of the on-off valve 19, the supercharging pressure is controlled to increase. . Note that the opening/closing operation of the on-off valve 19 according to the engine speed as described above may be performed at least during high loads where output is required, and the on-off valve 19 may be opened and closed at low loads regardless of the engine speed. It may be kept in the open state or in the open state.

In the device of the above embodiment, when the engine speed is in a low speed range below the set value, the on-off valve 19 is closed and the communication between each independent intake passage 12a to 12d and the second volume chamber 14 is cut off. , each of the cylinders 4a to 4d is connected to the first volume chamber 13 via a relatively long passage extending over the entire length of each independent intake passage 12a to 12d.

Therefore, pressure waves generated during the intake stroke of each cylinder 4a to 4d pass through each independent intake passage 128 to 12d to the first volume chamber 13.
The pressure is propagated to the first volume 13 and reflected to each cylinder 4a to 4d, causing intake pressure vibration in each independent intake passage 12a to 12d. For this reason, each cylinder 4a to 4d and the first volume chamber 1
The pressure acting on each cylinder 4a to 4d is low in the rotational speed range in which the cycle of the intake system's unique movement occurring in the independent intake passages 12a to 12d between the cylinders 3 and 3 matches the intake valve opening/closing cycle. It is increased at the end of the intake stroke, improving charging efficiency.

On the other hand, when the engine speed is in a high speed range equal to or higher than the set value, the on-off valve 19 opens and each independent intake passage 128
12d and the second volume chamber 14 are communicated through the communication hole 17, and each cylinder 4a to 4d is connected to the second volume chamber 14 through a relatively short passage length of each independent intake passage 12a to 12d. It is connected to a two-volume chamber 14. At this time, intake air is supplied from the first volume chamber 13 through the independent intake passages 12a to 12d, and the intake air is supplied from the independent intake passages 12a to 12d of the other cylinders.
12d through the second volume chamber 14 which communicates with the second volume chamber 14, and is supplied by the independent intake passages 12a to 12d.

In this state, the pressure waves generated during the intake stroke are reflected by the second volume chamber 14, and the length of the passage through which the pressure waves and reflected waves propagate becomes shorter, thereby reducing the intake inertia effect in the high-speed range. At the same time, in this operating range, pressure waves propagated from other cylinders also act effectively, improving charging efficiency.

FIG. 3 shows the relationship between engine speed and torque, where curve A is the fully open line when the on-off valve 19 is closed, and curve B is the fully open line when the on-off valve 19 is open. , the engine rotational speed No. corresponding to the point where both lines A and 8 intersect is the setting [No. The opening/closing valve 19 is closed at a speed lower than the set rotation speed No. and opened at a higher speed, thereby increasing the intake air filling efficiency over the entire rotation range and improving the output.

In FIG. 3, at the intersection of both torque curves A and B in the vicinity of the set rotation speed No., from the peak point a of the curve A on the low rotation side to the peak point of the curve B on the high rotation side, The torque value is lowered, and a substantially triangular valley portion (2) is formed in this portion.

Then, as shown in FIG. 4, the supercharging pressure is adjusted by the supercharging pressure control means 24 to compensate for the valley part (■) of the torque, as shown in FIG. It is intended to raise the That is, the engine control unit 37 monitors the engine speed and determines whether the detected supercharging pressure is high or low with respect to the characteristics shown in FIG. Accordingly, a control signal is output to the boost pressure control means 24 to increase or decrease the lift amount of the waste gate valve 30. Note that the characteristic (2) for increasing the supercharging pressure may be implemented with various characteristics in addition to the above-mentioned chevron shape, but sudden increases and decreases should be avoided.

As shown in the above characteristics, near the switching operation range, the lift amount of the wastegate valve 30 to increase the boost pressure is reduced compared to the constant pressure control characteristics (broken line), as shown in FIG. According to the characteristic (2), the amount of exhaust bypass is decreased and the rotational speed of the blower 22a is increased to increase the supercharging pressure as shown in the characteristic (H).

In addition, although the above-mentioned embodiment shows an example of a turbo supercharger, other superchargers can also be used. Further, supercharging by a supercharger and natural intake may be used together.

In addition to the plurality of intake passages for obtaining the dynamic effect of intake air, in addition to the one in which the length of the intake passage is changed and the communication with the intake passages of other cylinders is switched as in the above embodiment, It is possible to adopt a plurality of intake paths by changing various intake dynamic characteristics such as changing the intake passage area or changing the volume of the intake volume chamber, or a combination structure thereof. A mechanism is installed, and a switching control means switches according to the engine speed. Further, the upstream end of the intake path for obtaining the dynamic effect of intake air communicates with the intake volume chamber or the atmospheric opening.

Furthermore, as the supercharging pressure control means 24, in addition to the waste gate valve 30 for the turbo supercharger 22 as described above, a means for relieving intake air can be used.
In other types of superchargers, supercharging pressure control means corresponding to each type, such as intake air relief and rotational speed control, can be adopted as appropriate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view of an engine equipped with an intake system according to an embodiment of the present invention, FIG. 2 is a schematic plan view thereof, and FIG. A characteristic diagram showing the relationship, Figure 4 is a characteristic diagram showing the control characteristics of supercharging pressure with respect to engine speed, Figure 5 is a characteristic diagram showing the control characteristics of wastegate valve lift amount with respect to engine speed, and Figure 6 FIG. 2 is an explanatory diagram showing the opening/closing operation of the on-off valve with respect to the engine speed. 1...Engine body 4a-4d...
...Cylinder 12a to 12d...Independent intake passage 13
...First volume chamber 14...Second volume chamber 19...Opening/closing valve (intake switching mechanism) 20...
...First actuator 21...Switching control means 22...Turbo supercharger

Claims (1)

[Claims] (1) Equipped with a supercharger and supercharging pressure control means,
In an intake system for a supercharged engine that is provided with a plurality of intake passages that communicate one cylinder with an intake volume chamber or an atmospheric opening, and is provided with an intake switching mechanism that selects the plurality of intake passages according to the engine speed, An intake system for a supercharged engine, comprising a switching control means for operating the supercharging pressure control means so that the supercharging pressure increases when the intake switching mechanism is activated.