JPH04358720A - Intake device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve combustion by increasing the temperature of the air fuel mixture in a cylinder, and thereby reducing loss of a pump so as to improve sufficiently fuel consumption. CONSTITUTION:An intake air amount is controlled by controlling the opening time of an intake control valve 11. The overlap period of an intake/exhaust valve is determined so that previously burned gas in a cylinder chamber 3 can make reverse flow into an intake port 4. In an engine operating range in which an air fuel mixture temperature just before ignition is lowered by closing the intake control valve 11 in an early stage, resulting in deterioration of combustion condition, the intake control valve 11 is set in opening valve condition for a period which is determined beforehand in the first half of overlap period, and the previously burned gas is forced to make reverse flow into the intake branch pipe 8 located upstream of the intake control valve 11 so as to heat intake air. After that, the intake control valve 11 is opened again for the period which is determined beforehand during an intake valve 6 opening period so as to suck heated intake air into the cylinder chamber 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an internal combustion engine.

0002

[Prior Art] Each intake branch pipe connected to each cylinder is provided with an intake control valve that can be opened and closed, and the corresponding intake control valve is operated only for a predetermined period within the period when the intake valve is open. An intake system for an internal combustion engine is known in which the amount of air taken into a cylinder is controlled by opening a valve (see Japanese Patent Laid-Open No. 62-294719).

0003

In this intake system, if the amount of air taken into the cylinder is controlled by controlling the closing timing of the intake control valve,
Since throttling loss due to the throttle valve can be eliminated, pumping loss can be reduced.

However, in an engine operating range where the amount of intake air is relatively small, the intake control valve is closed early, which increases the adiabatic expansion period, which reduces the actual compression period, leading to This results in a problem in that the mixture temperature in the engine decreases and combustion deteriorates. As a result, a problem arises in that fuel efficiency cannot be sufficiently improved by reducing pump loss.

[0005]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, an intake control valve capable of opening and closing the intake passage is provided in the intake passage upstream of the intake valve, and a period during which the intake valve is open is provided. In an internal combustion engine in which the amount of air taken into the cylinder is controlled by opening the intake control valve for a predetermined period of time, the combustion engine is configured to control the amount of air taken into the cylinder by opening the intake control valve for a predetermined period of time. An overlap period in which both the intake valve and the exhaust valve are open is determined, and the intake control valve is opened in advance during the overlap period so that a predetermined amount of burned gas flows backward into the intake passage upstream of the intake control valve. A control means is provided for opening the intake control valve again for a predetermined period of time within the intake valve opening period after opening the valve for a predetermined period of time, thereby sucking air into the cylinder.

[0006]

[Operation] The intake control valve is opened for a predetermined period within the overlap period, and a predetermined amount of burned gas is caused to flow back into the intake passage upstream of the intake control valve. This allows the air in the intake passage to be heated. Then, when the intake control valve is opened again for a predetermined period during the intake valve opening period, the heated air flows into the cylinder and the temperature of the air-fuel mixture within the cylinder can be increased.

[0007]

[Example] Figures 1 and 2 show one of the multi-cylinder gasoline engines.
Showing two cylinders.

Referring to FIGS. 1 and 2, 1 is a cylinder block, 2 is a cylinder head, 3 is a cylinder chamber, and 4 is a cylinder block.
is an intake port, 5 is an exhaust port, 6 is a pair of intake valves, 7
indicate a pair of exhaust valves, respectively. Intake port 4 is an intake branch pipe 8
It is connected to the surge tank 9 via. A fuel injection valve 10 for injecting fuel into the intake port 4 is arranged in the intake branch pipe 8 immediately in front of the intake port 4 . In the intake branch pipe 8 between the surge tank 9 and the fuel injection valve 10, an intake branch pipe 8 is provided.
An intake control valve 11 for opening and closing is arranged. The intake control valve 11 is driven and controlled by an actuator 12 provided below the intake control valve.

FIG. 3 shows a perspective view of the intake control valve 11. Referring to FIG. 3, the intake control valve 11 includes a valve body 11a,
Upper and lower disc-shaped parts 11b and 11c are formed at the upper and lower ends of the valve body 11a, respectively, and a valve shaft 11d extends downward from the lower disc-shaped part 11c and is connected to the actuator 12 (see FIG. 1). It is equipped with

FIG. 4 shows the open position (indicated by a solid line in the figure) and the closed position (indicated by a chain line in the figure) of the valve body 11a of the intake control valve 11. The cross-sectional shape of the valve body 11a is formed to gradually taper from the center toward both ends.

5 and 6, the actuator 12
The structure and operation of Referring to FIG. 5, the actuator 12 includes a rotatable cylindrical magnetic pole 12a connected to a valve shaft 11d (see FIG. 3), and first and second magnetic poles arranged on opposite sides of the cylindrical magnetic pole 12a. 12b,
12c, and third and fourth magnetic poles 1 disposed on opposite sides of the cylindrical magnetic pole 12a and spaced apart by 90 degrees from the first and second magnetic poles 12b and 12c, respectively.
2d and 12e. First, second, third, and fourth magnetic poles 12b, 12c, 1
2d and 12e are magnetized by energizing the coils, and the first magnetic pole 12b is always magnetized to the north pole and the second magnetic pole 12c is always magnetized to the south pole. The cylindrical magnetic pole 12a is S as shown in the figure.
It is magnetized into poles and north poles. When the intake control valve 11 is open, the third magnetic pole 12d is magnetized to the S pole, and the fourth magnetic pole 12e is magnetized to the N pole. As a result, the cylindrical magnetic pole 12
a, the N pole of the cylindrical magnetic pole 12a is the second and third magnetic pole 1
It stands still between 2c and 12d.

On the other hand, when the intake control valve 11 is closed, the third magnetic pole 12d is magnetized to the north pole and the fourth magnetic pole 12e is magnetized to the south pole. As a result, the cylindrical magnetic pole 12a rotates by 90 degrees clockwise in the figure, and comes to rest with the N pole of the cylindrical magnetic pole 12a positioned between the second and fourth magnetic poles 12c and 12e.

Referring again to FIG. 1, the electronic control unit 20 is comprised of a digital computer, which includes a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, and a RAM (Random Access Memory) 23, which are interconnected by a bidirectional bus 21.
It includes a CPU (microprocessor) 24, an input port 25, and an output port 26.

A crank angle sensor 30 that generates an output pulse every time the crankshaft rotates a predetermined crank angle is connected to the input port 25. The engine speed is calculated based on the output pulse of the crank angle sensor 30. Also,
Amount of depression of the accelerator pedal 15 (hereinafter referred to as "accelerator opening degree")
An accelerator pedal sensor 31 is connected to the input port 25 via an AD converter 27. Further, an intake temperature sensor 32 for detecting the intake temperature in the intake branch pipe 8 is connected to the input port 25 via an AD converter 28.

On the other hand, the output port 26 is connected to the actuator 12 via a drive circuit 29.

Next, control of a conventional intake control valve will be explained with reference to FIG. In FIG. 7, the crank angle θ is set to 0 at compression top dead center, and increases toward the right in the figure. The exhaust valve is opened at θEO just before exhaust bottom dead center and closed at θEC just after intake top dead center. The intake valve is opened at θIO just before the intake top dead center, and at θIO after the intake bottom dead center.
The IC will close the valve. Therefore, the overlap period during which both the exhaust valve and the intake valve are open is short. The intake control valve is opened at θ1 before the exhaust valve is opened, and closed at θ2 after the intake valve is opened. θ1 is a fixed value, and θ2 increases as the load increases. Note that θ1 may be varied according to an increase in load. Since air flows into the cylinder only during the period when both the intake valve and the intake control valve are open, the amount of air supplied into the cylinder is controlled by controlling the closing timing θ2 of the intake control valve. Can be done.

[0017] By controlling in this manner, the throttling loss due to the throttle valve can be eliminated, so that the pumping loss can be reduced.

However, in engine operating ranges where the amount of intake air is relatively small, the intake control valve is closed early, which increases the adiabatic expansion period, which reduces the actual compression period, leading to This results in a problem in that the mixture temperature in the engine decreases and combustion deteriorates. As a result, a problem arises in that fuel efficiency cannot be sufficiently improved by reducing pump loss.

Therefore, in this embodiment, an overlap period (
determine the period during which both the intake valve and exhaust valve are open,
In the engine operating region (hereinafter referred to as the "combustion deterioration region") where the air-fuel mixture temperature immediately before ignition decreases and combustion worsens because the intake control valve is closed early, the intake control valve is With the valve open, burned gas flows backward into the intake branch pipe upstream of the intake control valve to heat the intake air, and then during the intake valve open period, the intake control valve is opened to direct the heated intake air into the cylinder. I try to make him inhale.

FIG. 8 shows the combustion deterioration region (region I) based on the engine speed Ne and the accelerator opening θA (indicating the engine load). Since combustion becomes stable as the engine speed Ne increases, the load belonging to region I becomes smaller as the engine speed increases. In FIG. 8, region II above region I is a region where good combustion can be obtained without a drop in air-fuel mixture temperature just before ignition.

FIG. 9 shows the opening/closing timing of the intake and exhaust valves and the control of the intake control valve in this embodiment. The opening/closing timing of the exhaust valve is the same as the conventional one, and the valve opens at θEO and closes at θEC. The opening timing of the intake valve is advanced compared to the conventional one, and the valve is opened at θIO after the exhaust bottom dead center and near the exhaust bottom dead center. The closing timing of the intake valve is the same as in the conventional case, and the intake valve is closed at θIO. Therefore, the overlap period becomes longer than in the conventional case. Therefore, during the overlap period, the burned gas in the cylinder flows back to the intake port.

[0022] When the engine operating state is in region I of Fig. 8,
The intake control valve is controlled as in region I of FIG. That is, the intake control valve is opened at θ3 before the exhaust valve is opened, and closed at θ4 within the overlap period. θ3 is a fixed value, and may be set after the exhaust valve is opened as long as it is before the intake valve is opened. When the intake valve is opened at θIO, the burnt gas in the cylinder chamber 3 flows into the intake branch pipe 8 upstream of the intake control valve 11, and the air in the intake branch pipe 8 is heated. This heating is controlled by controlling θ4 so that the intake temperature detected by the intake temperature sensor 32 becomes the target intake temperature. That is, if θ4 is made faster, the amount of burned gas flowing back into the intake branch pipe is reduced, and the amount of heating of the air is reduced, and if θ4 is made slower, the amount of heating of the air is increased.

FIG. 10 shows the target intake air temperature based on the engine speed Ne and the accelerator opening θA. The target intake temperature is
This is the intake temperature for achieving the minimum fuel consumption in each engine operating state. The target intake temperature decreases as the engine speed Ne and the accelerator opening θA increase.

The reason why the burnt gas is caused to flow back into the intake branch pipe in the first half of the overlap period, as shown in FIG. 9, is to heat the air with a small amount of burnt gas. That is, since the temperature of the burnt gas is higher in the first half of the overlap period than in the second half, the air can be heated with a small amount of burnt gas, making it easier to control the amount of fresh air.

Next, the intake control valve is opened again at θ5 near the intake top dead center, and closed at θ6 before the intake valve closes. As a result, air heated to the target intake temperature flows into the cylinder chamber 3. Therefore, even in region I, good combustion can be obtained without the temperature of the air-fuel mixture immediately before ignition decreasing. As a result, a sufficient effect of reducing pump loss can be obtained and fuel consumption can be reduced. Further, since the burnt gas is caused to flow backward, NOx can be reduced by internal EGR.

The amount of intake air is controlled by controlling θ5 and θ6. At this time, a large amount of intake air is allowed to flow in by the amount of backflow of the burnt gas. θ5 is varied, for example, within a range of 10° before the intake top dead center and 30° after the intake top dead center.

FIG. 11 shows θ5 based on the engine speed Ne and the accelerator opening θA. θ5 is slowed down as the engine speed Ne and accelerator opening θA decrease. Therefore, when the load is low, θ5 is delayed and θ6 is also delayed, so that the drop in the intake air temperature sucked into the cylinder chamber 3 can be reduced. In addition, θ5
And the decrease in pump loss reduction effect by slowing down θ6 is negligible.

FIG. 12 shows θ6 based on the engine speed Ne and the accelerator opening θA. θ6 is accelerated as the engine speed Ne and accelerator opening θA decrease.

When the engine operating state is in region II of FIG. 8, the intake control valve is controlled as in region II of FIG. That is, the intake control valve is opened at θ7 within the overlap period and closed at θ8 immediately after the intake valve is closed. Region II has a high load, so it is necessary to suck in as much air as possible. θ8 is a fixed value, and θ7
is controlled as follows.

FIG. 13 shows the relationship between the engine speed Ne and θ7. θ7 is equal to the exhaust valve closing timing θEC until just before the engine speed Ne2, and when the engine speed becomes equal to Ne2, it becomes θX immediately after the intake valve opening timing θIO. As the engine speed increases from Ne2, θ7
is retarded, and when the engine speed is over Ne4, θ7
is again equal to θEC.

FIG. 14 shows the engine speed N shown in FIG.
It shows the change in exhaust port pressure from e1 to Ne4. At engine speed Ne1, the negative pressure wave returns during the overlap period, but the exhaust port pressure becomes positive at the end of the overlap period, so when the intake control valve is opened, the burned gas in the cylinder chamber flows back. Therefore, the intake control valve is opened at θEC at the end of the overlap period (
(See Figure 13). As the engine speed increases, the timing at which the negative pressure wave reaches the exhaust port is delayed, and at the engine speed Ne2, the exhaust port pressure does not reach positive pressure even at the end of the overlap period, but reaches atmospheric pressure at θEC. Therefore, when the engine speed is Ne2, the intake control valve is opened at θX when the exhaust port pressure starts to become negative pressure during the overlap period. In other words, since the intake control valve is opened when the exhaust port pressure is negative during the overlap period, a good scavenging effect can be obtained, and a large amount of air can be sucked into the cylinder chamber. Can be done. Furthermore, as the engine speed increases,
The crank angle at which the exhaust port pressure starts to become negative is delayed (for example, Ne3), and the intake valve opening timing is also delayed accordingly. At engine speed Ne4, the crank angle at which the exhaust port pressure starts to become negative becomes equal to the overlap period end timing θEC, so at this time the intake control valve is adjusted to θ.
Open the valve at EC. Furthermore, as the engine speed increases, the crank angle at which the exhaust port pressure starts to become negative is delayed, but the intake control valve opening timing is kept constant at θEC. Note that Ne2 and Ne4 are determined by exhaust system specifications such as exhaust pipe length.

FIG. 15 shows a routine for calculating θ4, θ5, θ6 and θ7. This routine is executed by an interrupt at every fixed crank angle.

Referring to FIG. 15, first, in step 40, it is determined from the map shown in FIG. 8 whether the engine operating state is in region I or not. If the engine operating state is in region I, the process proceeds to step 41 and the first intake control valve closing timing θ4 is determined from the map shown in FIG.

FIG. 16 shows θ4 based on the engine speed Ne and the accelerator opening θA. θ4 is accelerated as the engine speed Ne and accelerator opening θA increase. This is because combustion becomes more stable as Ne and θA increase, so the amount of backflow of burnt gas can be reduced.

Referring again to FIG. 15, θ4 is corrected by multiplying θ4 by F in step 42. Here, F is a feedback correction coefficient for feedback controlling the intake temperature to the target intake temperature T0. In step 43, the second intake control valve opening timing θ5 is determined based on the relationship shown in FIG. In step 44,
Based on the relationship shown in 2, the second intake control valve closing timing θ6
is required.

On the other hand, when it is determined in step 40 that the engine operating state is in region II, the process proceeds to step 45, where the intake control valve opening timing θ7 is determined based on the relationship shown in FIG.

FIG. 17 shows a routine for calculating the feedback correction coefficient F. This routine is executed by interrupts at regular intervals. The value of the feedback correction coefficient F fluctuates around 1.0.

Referring to FIG. 17, first in step 50, a target intake temperature T0 is determined from the relationship shown in FIG. In step 51, it is determined whether the intake temperature T detected by the intake temperature sensor 32 is equal to or lower than T0+ΔT. Here, ΔT is the allowable range of the target intake temperature T0.

If T>T0 +ΔT, the process proceeds to step 52, where the feedback correction coefficient F is decreased by α. Here, α is a positive value smaller than 1. T≦T0+
In the case of ΔT, the process advances to step 53 and the intake temperature T is T0 −
It is determined whether or not it is greater than or equal to ΔT. If T<T0 −ΔT,
Proceeding to step 54, the feedback correction coefficient F is added by β. Here, β is a positive value smaller than 1 and may be equal to α. If T≧T0 −ΔT, the feedback correction coefficient F is maintained at its current value.

FIG. 18 shows a routine for controlling the intake control valve. This routine is executed by an interrupt at every fixed crank angle.

Referring to FIG. 18, in step 60 it is determined whether the engine operating state is within region I of FIG. When it is determined that the engine operating state is within region I, the routine proceeds to step 61, where it is determined whether the crank angle .theta. is equal to .theta.3. When θ=θ3, the process proceeds to step 62 and the intake control valve is opened. Step 62 is skipped if θ is not equal to θ3. Step 6
3, it is determined whether the crank angle θ is equal to θ4. When θ=θ4, the process proceeds to step 64 and the intake control valve is closed. If θ is not equal to θ4, step 64 is skipped.

In step 65, it is determined whether θ is equal to θ5. When θ=θ5, the process proceeds to step 66 and the intake control valve is opened. If θ is not equal to θ5, step 66 is skipped. Step 67
Then, it is determined whether θ is equal to θ6. θ=θ6
At this time, the process proceeds to step 68 and the intake control valve is closed. If θ is not equal to θ6, step 68 is skipped.

On the other hand, when it is determined in step 60 that the engine operating state is in region II, the process proceeds to step 69, where it is determined whether the crank angle θ is equal to θ7. When θ=θ7, the process proceeds to step 70 and the intake control valve is opened. If θ is not equal to θ7, step 70 is skipped. In step 71, θ is θ8
It is determined whether it is equal to or not. When θ=θ8, the process proceeds to step 72 and the intake control valve is closed. θ is θ
8, step 72 is skipped.

[0044]

Effects of the Invention: Combustion can be improved by raising the temperature of the air-fuel mixture in the cylinder, and thereby fuel efficiency can be sufficiently improved by reducing pump loss.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an internal combustion engine equipped with an intake system of the present invention.

FIG. 2 is a plan cross-sectional view of FIG. 1;

FIG. 3 is a perspective view of the intake control valve.

FIG. 4 is a diagram showing the open and closed positions of the valve body of the intake control valve.

FIG. 5 is a diagram showing the actuator when the intake control valve is opened.

FIG. 6 is a diagram showing the actuator when the intake control valve is closed.

FIG. 7 is a diagram showing conventional control of an intake control valve.

FIG. 8 is a diagram showing a combustion deterioration region (region I).

FIG. 9 is a diagram showing control of the intake control valve according to the embodiment of the present invention.

FIG. 10 is a diagram showing the relationship between engine speed Ne, accelerator opening θA, and target intake temperature T0.

FIG. 11 is a diagram showing the relationship between engine speed Ne, accelerator opening θA, and second intake control valve opening timing θ5.

FIG. 12 is a diagram showing the relationship between engine speed Ne, accelerator opening θA, and second intake control valve closing timing θ6.

[Figure 13] Engine speed Ne and intake control valve opening timing θ7
FIG.

FIG. 14 is a diagram showing changes in exhaust port pressure at various engine speeds.

FIG. 15 is a flowchart for calculating θ4, θ5, θ6, and θ7.

FIG. 16 is a diagram showing the relationship between engine speed Ne, accelerator opening θA, and first intake control valve closing timing θ4.

FIG. 17 is a flowchart for calculating a feedback correction coefficient F.

FIG. 18 is a flowchart for controlling the intake control valve.

[Explanation of symbols]

3...Cylinder chamber 4...Intake port 6...Intake valve 7...Exhaust valve 8...Intake branch pipe 11...Intake control valve

Claims (1)

[Claims] 1. An intake control valve capable of opening and closing the intake passage is provided in the intake passage upstream of the intake valve, and the intake control valve is opened only for a predetermined period within the period in which the intake valve is open. In an internal combustion engine in which the amount of air taken into the cylinder is controlled by
An overlap period in which the intake valve and the exhaust valve are both open is determined so that the burned gas in the cylinder flows back into the intake passage, and a predetermined overlap period is determined in which the intake valve and the exhaust valve are both open. After opening the intake control valve for a predetermined period during the overlap period so that the amount of burned gas flows backward, the intake control valve is opened again for a predetermined period within the intake valve opening period. An intake system for an internal combustion engine that is equipped with a control means that closes a valve to draw air into a cylinder.