JPH0551046B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an engine intake system.

(Prior art) Regarding the intake system of the engine, Utility Model No. 56-74819
As described in the publication, the length of the passage upstream of the surge tank (resonance chamber) leading to the intake side of each cylinder is changed according to the engine operating condition using a passage length variable section, thereby reducing the inertial effect of the intake air. The idea of effectively utilizing energy for supercharging is generally known.

By the way, if there is a surge tank between the intake side of each cylinder and the upstream open end of the variable passage length section, this surge tank can be used as it is to reverse the intake pressure wave in the high speed range of the engine. It is possible to obtain an intake inertia supercharging effect, but in the low engine speed range, even if you change the passage length on the upstream side of the surge tank, the intake pressure wave in the surge tank will attenuate, causing the passage length to decrease. The intake inertia effect cannot be fully utilized by varying the height.

(Purpose of the Invention) The present invention takes the idea of making the volume of the surge tank variable, and utilizes the reversal of intake air downstream of the surge tank in the high rotation range, and at the same time utilizes the passage on the upstream side of the surge tank in the low rotation range. The aim is to minimize the attenuation of intake pressure waves within the surge tank when the pump is used for intake inertia supercharging.

(Structure of the Invention) In the present invention, the intake port of each cylinder communicates with the surge tank, and upstream of the surge tank there is a passage section whose length can be changed to guide intake air to the surge tank, and the engine operating state In an engine intake system in which the passage length of the passage portion is changed according to the passage length to perform inertial supercharging of intake air between an intake port and the passage portion, the change means for changing the substantial volume of the surge tank; , a control means for controlling this changing means to reduce the substantial volume of the surge tank on the side where the engine speed is low, and when the passage section on the upstream side of the surge tank is used for intake inertia supercharging, the inside of the surge tank is This is to reduce the attenuation of the intake pressure wave.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In the engine intake system shown in FIGS. 1 and 2, 1 is a four-cylinder engine main body, and an intake port 3 of each cylinder 2 and a surge tank 4 communicate with each other through a tank downstream passage 5. 4 and a resonance chamber 6 upstream thereof communicate through a tank upstream passage 8 in which a throttle valve 7 is interposed. This tank upstream passage 8 branches into a short passage 9 with a short passage length and a long passage 10 with a long passage length on the upstream side of the throttle valve 7, and is connected to the resonance chamber 6. An opening/closing valve 11 is interposed in the passageway 9 to open and close the passage.

The surge tank 4 is provided with a volume change valve 12 that can change the substantial volume of the tank by always ensuring communication between the tank downstream passage 5 and the tank upstream passage 8. That is, this volume change valve 12 is supported with respect to the surge tank 4 so that the openings of the tank downstream passage 5 and the tank upstream passage 8 face on one side of the valve rotation axis, and the peripheral edge of the valve body faces the inner surface of the surge tank 4. a closed position in which the surge tank total volume is divided into two by coming into contact with the surge tank, thereby reducing the volume of the surge tank in which both the passages 9 and 10 communicate with each other;
The valve body is configured to rotate between an open position where the peripheral edge of the valve body is separated from the inner surface of the surge tank 4 and the entire volume of the surge tank is communicated with both the passages 9 and 10.

Actuators 13 and 14 are attached to the opening/closing valve 11 and the volume change valve 12, respectively, for rotating the valves.
Control means 16 receives a signal from an engine rotation speed sensor 15 that detects the engine rotation speed and outputs an operation control signal to both actuators 13 and 14.
is connected. In FIGS. 1 and 2, 17 is an exhaust port connected to the exhaust passage 18, 19 is an intake valve that opens and closes the intake port 3, 20 is an exhaust valve that opens and closes the exhaust port 17, and 21 is an exhaust port connected to the cylinder 2. It is a fitted piston.

Next, regarding the operation of the on-off valve 11 and the volume change valve 12, in other words, the control means 16
The operation of this will be explained.

First, the control means 16 sends a signal to the actuator 13 of the opening/closing valve 11, which closes when the engine speed is lower than the low engine speed Nl and opens when the engine speed is higher, as shown in FIGS. 3a and 3b.
A signal is output to the actuator 14 of the volume change valve 12, which closes when the engine speed is lower than the high engine speed Nh and opens when the engine speed is higher than the high engine speed Nh.

The engine speeds Nl and Nh are determined as follows. That is, looking at the dynamic effect of the propagation of intake pressure waves, when the on-off valve 11 is closed, the negative pressure waves generated by the downward movement of the piston 21 flow from the intake port 3 to the tank downstream passage 5, the surge tank 4, and the tank top. It passes through the long path 10 of the flow path 8, reverses itself with the opening of the long path 10 at the resonance chamber 6 as an open end, and returns to the intake port 3 as a positive pressure wave. Therefore, the pressure in front of the intake valve 19 is a composite pressure of a negative pressure wave and a positive pressure wave, and if the intake valve is closed at a timing when the pressure in front of the intake valve and the cylinder pressure match, the intake air filling efficiency becomes high, and the engine Maximum torque can be obtained in terms of output. The torque characteristics when this long path 10 is used are shown by the dashed-dotted line in FIG. 3e. On the other hand, when the on-off valve 11 is open, the intake pressure wave propagates through the short path 9 and is reversed at the opening position of the resonance chamber 6, so that the propagation distance is shorter than in the case of the long path 10. In other words, the period in which the positive pressure wave returns to the intake port becomes shorter (the frequency becomes higher), and the engine speed at which maximum torque is obtained is lower than when using the long passage 10, as shown by the short dashed line in Figure 3e. It shifts to the high rotation side. Therefore, the engine speed Nl at which the on-off valve 11 is switched between open and close is the engine speed Nl at which the torque is higher when the short passage 9 is used than when the long passage 10 is used (the dashed line and the short (the intersection of the dashed lines).

On the other hand, as the engine speed increases, the intake port 3 and the surge tank 4 in the tank downstream passage 5
The dynamic effect of the propagation of the intake pressure wave between the opening (which becomes the open end that reverses the pressure wave) greatly affects the intake air filling efficiency, that is, the torque. Looking at the dynamic effects when the substantial volume of the surge tank 4 is made small and large by the volume change valve 12, when the substantial volume is small, the surge tank 4 is
The effect of making the opening function as an open end (the efficiency of reversing pressure waves) is small, and the reversal of pressure waves becomes insufficient.On the other hand, when the volume is substantially large, the opening does not function effectively as an open end. , the reversibility of the pressure wave increases. Therefore, the torque characteristics when the actual volume is small and large are shown by the long dashed line and 2 in Fig. 3e, respectively.
As shown by the dotted chain line, the larger the actual volume, the higher the torque at higher engine speeds, while the smaller the actual volume, the lower the engine speed, the higher the torque. becomes higher. Therefore,
The engine speed Nh at which the volume change valve 12 is switched between opening and closing is set to an engine speed (the intersection of the long dashed line and the two-dot chain line) at which the torque is higher when the actual volume is large than when the volume is small. has been done.

Therefore, in the above embodiment, when the engine speed is low, both the open/close valve 11 and the volume change valve 12 are closed, and as shown in FIG. 3c and d, the upstream length of the surge tank is long, and the surge tank is substantially The structure has a small volume. At this time, the function of the surge tank 4 as a passage for propagating the intake pressure waves becomes stronger, and the intake pressure waves are transmitted to the surge tank 4.
is propagated with almost no attenuation, and inertia supercharging is performed with the opening of the long path 10 to the resonance chamber 6 as an open end, and the torque characteristics at this time correspond to the dashed-dotted line in Fig. 3e. Become something.

Next, when the engine speed exceeds Nl, the on-off valve 11 opens, the upstream length of the surge tank 4 is short, and the substantial volume of the surge tank 4 is small. At this time, the intake pressure wave is reversed with the opening of the short passage 9 relative to the resonance chamber 6 as an open end to perform inertial supercharging, and the torque characteristic corresponds to the short broken line in Fig. 3e. Become. Then, as the engine speed increases and the dynamic effect of making the opening of the tank downstream passage 5 relative to the surge tank 4 into an open end increases, the torque characteristic corresponds to the long broken line in FIG. 3e.

Then, when the engine speed exceeds Nh,
Both the on-off valve 11 and the volume change valve 12 are in an open state, resulting in a configuration in which the upstream length of the surge tank is short and the substantial volume of the surge tank is large. At this time, since the substantial volume of the surge tank is large, the dynamic effect of making the opening of the tank downstream passage 5 relative to the surge tank 4 into an open end works effectively, and the torque characteristics are as shown by the two-dot chain line in Fig. 3e. It will be compatible.

As a result, the engine output torque in the embodiment increases as the engine speed increases, as shown by the solid line in FIG.
Inertial supercharging with the opening to the surge tank 4 as the open end, inertia supercharging with the opening of the short passage 9 as the open end, and inertial supercharging with the opening of the tank downstream passage 5 to the surge tank 4 as the open end. Particularly on the low-speed side of the engine where the long passage 10 and short passage 9 are used for inertial supercharging, there is almost no attenuation of pressure waves in the surge tank.

In the embodiment, the substantial volume of the surge tank is changed by opening and closing the valve, but the substantial volume may be changed using other means such as a bellows.

(Effects of the Invention) According to the present invention, when the passage section upstream of the surge tank is used for inertial supercharging of intake air, the substantial volume of the surge tank becomes smaller on the side where the engine speed is lower. Attenuation of the intake pressure wave is suppressed, increasing the inertial supercharging effect and improving engine output.

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention, and FIG. 1 is a schematic diagram of the intake system of an engine showing each cylinder in a plan view, and FIG. 2 is a diagram of the same intake system showing the cylinders in longitudinal section. The schematic configuration diagram, FIG. 3, is a characteristic diagram showing the relationship between the opening and closing of the on-off valve, the opening and closing of the variable volume valve, the upstream length of the surge tank, the substantial volume of the surge tank, and the engine output torque with respect to the engine rotation speed. 1... Engine body, 2... Cylinder, 3... Intake port, 4... Surge tank, 5... Tank downstream passage, 6... Resonance chamber, 8... Tank upstream passage, 9... Short passage. , 10...long passage, 11
...Opening/closing valve, 12...Volume change valve, 15
...Engine speed sensor, 16...Control means.

Claims (1)

[Claims] 1. The intake port of each cylinder communicates with a surge tank, and upstream of this surge tank there is a passage section that guides intake air to the surge tank, the length of which can be changed, and the passage length of the passage section can be changed according to the operating condition of the engine. In an engine intake system that performs inertial supercharging of intake air between an intake port and the passage section by changing the surge tank, the change means changes the substantial volume of the surge tank, and the change means is controlled to change the engine rotational speed. and control means for reducing the substantial volume of the surge tank on the side where the surge tank is lower.