JPH08296445A - Intake control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Object] To provide an intake control device for an internal combustion engine, which improves the volumetric efficiency of the intake system at low speed and high load. In an intake control device for an internal combustion engine, in which an intake time control valve 13 is arranged in an engine intake passage communicating with a combustion chamber 4 via an intake valve 5, an opening / closing time of the intake time control valve is controlled according to an engine speed. Intake time control valve drive means 12 for
The intake time control valve drive means 12 holds the closing timing of the intake time control valve 13 at BDC when the engine speed is high load rotation below a predetermined value, and the intake time control valve is increased as the engine speed increases. When the opening timing of 13 is shortened to the TDC side, the closing timing of the intake time control valve 13 is delayed from BDC as the engine speed rises and the intake time And a control unit 20 for controlling the opening timing of the control valve 13 to be advanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake control device for an internal combustion engine, and more particularly to an intake control device for an internal combustion engine which improves volumetric efficiency by a dynamic pulsation effect of an intake system.

[0002]

2. Description of the Related Art Various techniques for improving volumetric efficiency have been researched and developed in order to improve the output of an internal combustion engine (hereinafter referred to as an engine). First, a technical background on volume efficiency will be briefly described below. The volumetric efficiency is obtained by dividing the volume of fresh intake air at the pressure and temperature at the inlet of the intake system by the total stroke volume, and represents the suction capacity of the engine. Volumetric efficiency is affected by stationary and dynamic factors. Steady factors include intake port temperature and pressure, wall temperature, intake air resistance, excess air ratio, and opening / closing timing of intake and exhaust valves, and dynamic factors include intake and exhaust pipe internal There are pressure oscillations, intake interference between cylinders in a multi-cylinder engine, and the like.

The dynamic factor is a factor due to pressure oscillation of the intake system and exhaust system due to intermittent intake and exhaust, and when the pressure oscillation directly affects the intake process of the generated cycle. The inertia effect is called the pulsation (resonance) effect when the pressure oscillation affects the intake process of the next cycle when the rotation speed is high or the intake pipe is long.

In a multi-cylinder engine, it is necessary to consider a plurality of intake pressure fluctuations. The following three points can be raised as the main points. [1] The pressure oscillation in the intake port is composed of a short cycle component determined by the intake pipe configuration from the intake valve to the surge tank and a long cycle component determined by the intake pipe configuration upstream of the surge tank. [2] The short cycle component improves the volumetric efficiency of the engine at high speed, and the long cycle component improves the volumetric efficiency of low speed. [3] The improvement of the volumetric efficiency at low speed is caused by the superposition of the long period components generated by the cylinders.

Next, the dynamic effect of the intake system in the conventional 6-cylinder engine will be described. An air cleaner is provided with an independent intake passage for each cylinder, one end of which is independently connected to each cylinder and the other end of which merges in a surge tank, and a common intake passage of which one end is connected to the surge tank and the other end is connected to an air cleaner. There is an engine having an independent intake structure that sucks the outside air through the engine. In this configuration, since the number of intakes per unit time increases as the number of cylinders increases, the longer period component is smoothed and the long period component effect disappears as the number of cylinders increases, that is, 6 cylinders compared with 4 cylinders. . Therefore, in this configuration, only the short period component at high speed is obtained as the volumetric efficiency.

As another intake configuration according to the prior art, six cylinders have two intake groups 1, 2, 3, 6, 2, 4 which are not adjacent to each other and have two intake strokes which do not overlap, that is, 1, 2, and 3. It is divided into a first group and a second group of 4, 5, and 6, one end is independently connected to each cylinder of each group, and the other end is independent for each cylinder that joins and is connected to a common intake passage for each group. There is a two-part intake structure in which the intake passage and the end portion of the intake passage common to each group are joined and connected to an air cleaner to suck the outside air. According to this configuration, the long cycle component is not canceled by the interference between the cylinders, so that the volume cycle has a long cycle component effect at a low speed and a short cycle component effect at a high speed.

The above two intake configurations are invariant regardless of the engine speed, and therefore the natural frequency of the intake system is constant regardless of the engine speed. On the other hand, the pressure vibration of the air in the intake system caused by the reciprocating motion of the piston of the engine is amplified when the cycle changes according to the engine speed and is synchronized with the natural frequency of the intake system, and therefore the volumetric efficiency of the engine, and hence the intake efficiency. Improve. However, in the two intake configurations described above,
The engine speed that is synchronized with the natural frequency of the intake system is limited to one. Therefore, a variable intake configuration has been considered in which the equivalent intake pipe length is switched according to the engine speed. An example of this variable intake structure is an intake control device for a multi-cylinder internal combustion engine (see Japanese Utility Model Laid-Open No. 59-148425). This device is provided with a communication hole that communicates between the common intake passages of the two groups and a control valve that opens and closes the communication hole in the above-described two-split intake structure, closes at low speed and high speed, opens at medium speed, and opens and closes the control valve. By doing so, it is possible to switch between two intake system configurations having different natural frequencies, and the intake efficiency is improved over the entire engine speed range. In this way, the variable intake system is switched to an intake system having a different natural frequency according to the engine speed to improve intake efficiency over the entire engine speed range.

Another example of the variable intake structure is Japanese Patent Laid-Open No. 62-
There is an intake control device for a multi-cylinder engine disclosed in Japanese Patent No. 82228. This intake control device is provided with an intake port that opens and closes in synchronization with the rotation of the engine, and is provided in the intake passage upstream of the intake port, and the intake passage is provided at least after the opening timing of the intake port at low speed and high load. A control valve that opens after intake top dead center and delays the intake start timing, and an intake negative pressure wave that is provided on the upstream side of the control valve and that is downstream of the control valve when the control valve is open. An inversion unit for reversing is provided, and the effect of pushing the intake air into the combustion chamber is measured at the end of the intake stroke, and a high charging efficiency of the intake air is secured by this pushing effect to improve the output of the engine.

[0009]

However, the above-mentioned intake control device of Japanese Utility Model Laid-Open No. 59-148425 is intended to improve the volumetric efficiency by closing the control valve in the low speed and high load region to increase the intake pipe length. However, the pulsation generated in the intake pipe is still small even when synchronized with the natural frequency of the intake system,
There is a problem that the volumetric efficiency is insufficient and the torque becomes insufficient.

Further, in the intake control device of Japanese Patent Laid-Open No. 62-82228, the normal intake valve is 5 to 20 ° before the piston top dead center (TDC) in the cylinder of the engine (360 times for one reciprocation of the piston).
However, this device closes the control valve that shuts off the intake air immediately after the intake valve closes, while it closes at 30 to 50 ° after piston bottom dead center (BDC), which allows for the delay of air inflow. It is set to close, and the intake air amount is determined by the volume in the cylinder when the intake valve is closed. It is sufficient and there is a problem that the torque becomes insufficient.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems and to provide an intake control device for an internal combustion engine which improves the volumetric efficiency at low speed and high load.

[0012]

The intake control device for an internal combustion engine according to the present invention, which achieves the above object, has an intake time control valve arranged in an engine intake passage communicating with a combustion chamber via an intake valve. In the control device, the intake time control valve drive means for controlling the opening and closing time of the intake time control valve according to the engine speed, and the intake time control valve drive means, when the engine speed is high load rotation of less than a predetermined value, The closing timing of the intake time control valve is held at BDC, and the opening time of the intake time control valve is advanced to TDC side with the increase of the engine speed, thereby delaying the delay time.
When the engine speed is equal to or higher than a predetermined value, the control means delays the closing timing of the intake time control valve from BDC as the engine speed rises, and controls the opening time of the intake time control valve to be advanced. It is characterized by having.

[0013]

In the intake control device for an internal combustion engine according to the present invention, the closing timing of the intake time control valve is held at BDC when the engine speed is lower than a predetermined value and the intake time is increased as the engine speed increases. By controlling the intake time control valve drive means so as to advance the delay time to the TDC side by opening the control valve, the pressure vibration synchronized with the natural frequency of the intake system is obtained according to the change of the engine speed. Are amplified and the volume efficiency is improved. Further, when the engine speed is equal to or higher than a predetermined value, the closing timing of the intake time control valve is delayed from BDC as the engine speed rises, and the opening time of the intake time control valve is controlled to be advanced. Insufficient intake effect due to insufficient amount can be avoided, and intake efficiency improves.

[0014]

1 is a configuration diagram showing an intake system and an exhaust system of a 6-cylinder engine 1 adopted in an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing a cross-sectional configuration of an intake system of the engine shown in FIG. The cylinder head 3a is provided with combustion chambers 4, intake valves 5 and exhaust valves 7 for 6 cylinders, and pistons 2 for 6 cylinders are enclosed in a cylinder block 3b. From the fuel injection valve 14 to the intake port 6, the engine 1
Fuel is injected in each combustion cycle. The intake air is also the air cleaner 11, the intake duct 10, the surge tank 9a, the intake passages 8a to 8c, or the air cleaner 1 in this order.
1, intake duct 10, surge tank 9b, intake passage 8d
Each cylinder 1 of the engine 1 via the intake port 6 as a mixture with the injected fuel when the intake valve 5 is open.
a to 1f. The six cylinders 1a to 1f are divided into two groups in which the intake orders 1, 5, 3, 6, 2, 4 are not adjacent to each other and the intake strokes do not overlap. That is, the first group 1a to 1c having the intake order of 1, 2, 3 and the second group 1d to 1f having the intake order of 4, 5, 6 are divided into the intake passages 8a to 8c and the surge tank 9a. Corresponds to the second group and the intake passages 8d-8d
f and surge tank 9b correspond. In addition, the intake duct 1
A throttle valve 31 is provided inside 0, and the opening degree of the throttle valve 31 is controlled according to the depression amount of an accelerator pedal (not shown) and detected by a throttle sensor 32.

The intake time control valves 13a to 13f are provided in the intake passages 8a to 8f, respectively, and have a function of changing the supply timing of intake air to the cylinders 1a to 1f. Details will be described later with reference to FIGS. The intake switching valve 18 is an on-off valve that closes the surge tank 9a of the first group and the surge tank 9b of the second group at low speed and high load, and opens them at low speed and low load or at high speed to communicate with each other. This is to improve the volumetric efficiency by switching to an intake system with a different natural frequency.

The exhaust system of the engine 1 is also divided into two groups like the intake system. Each exhaust pipe connected to each exhaust valve 7 is connected to a common exhaust pipe for each group, and a catalytic converter 19 is provided in each group's common exhaust pipe to purify exhaust gas. Further, these common exhaust pipes are further connected to an exhaust duct, and a catalytic converter 19 is also provided in the exhaust duct.

The electronic control unit 20 comprises a digital computer and comprises a ROM 22, a RAM 23, a CPU 24, an input port 25 and an output port 26 which are connected to each other via a bidirectional bus 21. The electronic control unit 20 controls the fuel injection amount of the engine 1, the fuel injection timing, the ignition timing,
The throttle opening and the like are controlled, and the intake control described later according to the present invention is executed.

The electronic control unit 20 includes a load sensor 15,
Input data is obtained from the crank angle sensor 16 and the air flow meter 17. The load sensor 15 is the throttle sensor 32.
The analog voltage output from the A / D converter 29 is input to the input port 25. Crank angle sensor 1
6 is an input port 25 for a pulse signal for each predetermined crank angle
Enter directly into. The air flow meter 17 inputs an analog voltage proportional to the intake air amount into the input port 25 via the A / D converter 30.

The electronic control unit 20 includes drive circuits 27, 2
The intake time control valve drive means (actuator) 12 and the intake switching valve 18 are driven and controlled by the control unit 8 respectively. The actuator 12 is energized by the drive circuit 27 of the electronic control unit 20 and swings 90 ° when the energizing polarity is switched to open and close the intake time control valves 13a to 13f at high speed. The intake switching valve 18 is opened and closed by a drive circuit 28.

FIG. 3 is a diagram showing the intake valve opening area and intake port pressure that change as the piston moves at low speed, and FIG. 4 shows the intake valve opening area that changes as the piston moves at medium speed. It is a figure which shows and an intake port pressure. In these figures, the horizontal axis indicates the piston position indicated by the crank angle, the lower row indicates the time, the vertical axis indicates the intake valve opening area, and the lower row indicates the intake port pressure. First, FIG.
The operation of intake control at low speed according to the present invention will be described by using the piston reciprocating motion of the cylinder 1a as a representative.

The piston 2 reciprocates in the intake stroke.
When opening and closing the intake valve 5 is mechanically determined,
The intake valve 5 has a piston 2 in front of TDC (shown by a broken line).
Time t at ~ 20 °₀Start opening at (shown by the chain double-dashed line)
Therefore, a time t of 30 to 50 ° after BDC (shown by a broken line)
_FiveClose (shown by the chain double-dashed line). Time t₀From time t_Five
During that time, the lift amount of the intake valve 5 rises and falls, and the intake
The opening area of the air valve 5 changes like a mountain as shown. Intake valve
5 is time t₀When the intake time control valve 13a starts to open
Since it is closed, the time t when the piston 2 comes to TDC₁
(Indicated by a broken line) to intake port 6 and intake time control valve 13
Negative pressure is generated between a and. Time t₂Intake time control
When the valve 13a is opened, fresh air is supplied to the air cleaner 11 and the intake duct.
10, the surge tank 9a, the intake passage 8a
Suddenly flowing into the intake port 6, the negative pressure gradually goes to 0.
Time t₃Switch to positive pressure. Piston 2 comes to BDC
Time t _FourAfter closing the intake time control valve 13a,
Since there is no inflow, the positive pressure gradually goes to zero. The figure
Time t indicated by middle T₂To t_FourThe time until is peculiar to the intake system
It is a cycle and is constant regardless of the rotation speed of the engine 1.

Next, referring to FIG. 4, the action of intake control at the medium speed according to the present invention will be described by using the piston reciprocating motion in the cylinder 1a as a representative. Like the low speed, the intake valve 5 starts to open at time t ₀ when the piston 2 is in the TDC the front 5 to 20 ° (indicated by a two-dot chain line), the time t ₅ the BDC after 30 to 50 °
(Closed by a chain double-dashed line), the opening area of the intake valve 5 changes like the illustrated peak from time t ₀ to time t ₅ .
When the intake valve 5 starts to open at time t ₀ , the intake time control valve 13
Since a is still closed, a negative pressure is generated between the intake port 6 and the intake time control valve 13a from the time t ₁ (shown by the broken line) when the piston 2 comes to TDC. When the intake time control valve 13a is opened at time t ₂ (shown by a chain line), fresh air rapidly flows into the intake port 6 via the air cleaner 11, the intake duct 10, the surge tank 9a, and the intake passage 8a. The negative pressure gradually goes to 0 and switches to a positive pressure at time t ₃ . Time t when piston 2 passes BDC (shown by a broken line)
_{After the} intake time control valve 13a is closed at ₄ (indicated by the one-dot chain line), the inflow of fresh air is stopped and the positive pressure gradually goes to zero. The time from time t ₂ to t ₄ indicated by T in the figure is the same as in FIG. 3 and is constant.

FIG. 5 is a diagram showing the control valve opening / closing timing with respect to the engine speed when the engine is operating at low, medium speed and high load. In this figure, the horizontal axis represents the engine speed and the vertical axis represents the piston crank angle. The upper solid line shows the time when the intake time control valve 13 is closed, and the lower solid line shows the time when the intake time control valve 13 is opened. Also, the upper broken line indicates the timing of closing the intake valve 5,
The lower broken line shows the timing of opening the intake valve 5. Since the opening / closing timing of the intake valve 5 is the same as that in FIGS. 3 and 4, description thereof will be omitted. A map of the opening / closing timing of the intake time control valve 13 as shown in [1] to [4] below is created in advance and stored in the ROM 22. The intake time control valves 13a to 13f correspond to the load sensor 1
When it is determined that the load detected from No. 5 is high, the opening / closing control is performed according to the engine speed and the crank angle detected by the crank angle sensor 16 based on this map.

The opening / closing timing of the intake time control valve 13 is controlled as follows according to the engine speed N detected by the crank angle sensor 16. The following engine speeds N ₁ and N
₂ , N ₃ is different in each engine, but is 2000 in the embodiment.
4000 and 5000 rpm. [1] When the engine speed N of the engine 1 is 0 <N <N ₁ , BDC
Closes at, and the larger N is, the sooner it opens after TDC. This is BD
This is because the intake port pressure is maximized at C and opened earlier than BDC by the natural period T of the intake system. As a result, a pulsating (resonance) effect is obtained. [2] When the engine speed N of the engine 1 is N ₁ ≦ N <N ₂ , the larger N is, the sooner it opens after TDC, and the larger N is, the BDC.
Closes late. This is for inhaling the control valve 13 during a time period when the opening area of the control valve 13 is large, and for closing the valve by delaying it by the natural period T of the intake system from the opening timing and maximizing the intake port pressure when the valve is closed. is there. This produces a pulsating effect. The amount of change that advances the opening timing in proportion to the rotation speed N when N ₁ ≦ N <N ₂ is proportional to the rotation speed N rather than the amount of change when 0 <N <N _1. It's less than the delay. [3] When the engine speed N of the engine 1 is N ₂ ≦ N ≦ N ₃ , the larger N is, the sooner it opens after TDC, and the larger N is, the BDC.
Closes late. This is to control the opening timing of the intake time control valve 13 so that the intake port pressure becomes maximum when the intake valve 5 is closed. This produces a pulsating effect. [4] When the engine speed N of the engine 1 is N> N ₃ , it is fully opened. At this time, since the intake switching valve 18 is opened, the pulsating effect due to the natural period shorter than T can be obtained.

FIG. 6 is a diagram showing the relationship between the number of revolutions of the engine and the opening / closing of the switching valve with respect to load. As shown in the figure, the intake switching valve 18 is the engine speed N is low speed (N <N _L) high load closed when the engine rotational speed N is low speed (N <N _L) low load and the engine speed N Open at high speed (N ≧ N _L ). Such a map of the opening / closing timing of the intake switching valve 18 is created in advance and stored in the ROM 22. Based on this map, the intake switching valve 18 is opened / closed according to the load detected by the load sensor 15 and the engine speed detected by the crank angle sensor 16. The engine speed N _L varies depending on the engine, but is in the range of about 4000 to 5000 rpm.

FIG. 7 is a diagram showing the relationship between the engine speed and the engine torque. As shown in the figure, when the engine speed N is low speed (N <N _L ) and high load, the engine is generated at the engine speed N _SL which is synchronized with the natural period of the intake system when the intake switching valve 18 is closed. The torque becomes maximum, and a torque curve as shown by the solid line on the low speed side is obtained. The reason is that when the intake switching valve 18 is closed in the intake system divided into two cylinder groups in which the intake strokes hardly overlap each other as shown in FIG. 1, the negative pressure wave generated in the intake port 6 during intake is a surge tank. Pressure vibration is generated by propagating and reflecting beyond 9a and 9b to the branch portion connected to the intake duct 10. This pressure vibration has a natural period, and the pressure vibration at the intake stroke at the engine speed N _SL and the natural period are synchronized with each other, so that the pressure vibration is amplified and the intake air amount is increased. According to the intake control device of the present invention, the volumetric efficiency is further improved, the torque characteristic shown by the alternate long and short dash line is obtained, and the torque characteristic of the engine is improved.

When the engine speed N is low speed (N <N _L ) low load and the engine speed N is high speed (N ≧ N _L ), it is synchronized with the natural period of the intake system when the intake switching valve 18 is opened. The torque generated by the engine becomes maximum at the engine speed N _SH , and the torque curve shown by the solid line on the high speed side is obtained. This is because when the intake switching valve 18 is open, the surge tanks 9a and 9b communicate with each other to smooth the pressure vibration generated by the intake stroke of each cylinder.
The vibration is generated on the downstream side of a and 9b. Therefore, the natural cycle is shorter than the natural cycle when the intake switching valve 18 is closed, and the torque curve shown by the solid line on the high speed side shown in the figure is obtained.

The reason why the volume efficiency is not improved at low speed and low load is to reduce the pump loss of the engine and improve the fuel consumption. This is because when the intake switching valve 18 is closed, pulsation increases, pump loss increases, and fuel consumption deteriorates. Therefore, the intake switching valve 18 is closed only when high torque at low speed and high load is required.

[0029]

As described above, according to the intake control device of the internal combustion engine of the present invention, the intake efficiency at low speed and high load and at high speed is improved. Further, the intake air flow can be increased at low speed and high load, the air-fuel mixture in the cylinder can be diffused, and combustion can be improved against knocking and the like.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an intake / exhaust system of an engine adopted in an embodiment of the present invention.

FIG. 2 is a diagram showing a cross-sectional configuration of an intake system of the engine shown in FIG. 1 and an electronic control unit.

FIG. 3 is a diagram showing an intake valve opening area and an intake port pressure, which change as the piston moves at a low speed.

FIG. 4 is a diagram showing an intake valve opening area and an intake port pressure that change as the piston moves at a medium speed.

FIG. 5 is a diagram showing a control valve opening / closing timing with respect to an engine speed.

FIG. 6 is a diagram showing a relationship between opening / closing of a switching valve with respect to engine speed and load.

FIG. 7 is a diagram showing a relationship between engine speed and engine torque.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Piston 3a ... Cylinder head 3b ... Cylinder block 4 ... Combustion chamber 5 ... Intake valve 6 ... Intake port 7 ... Exhaust valve 8a-8f ... Intake passage 9a, 9b ... Surge tank 10 ... Intake duct 11 ... Air cleaner 12 Intake time control valve drive means (actuator) 13a to 13f ... Intake time control valve 14 ... Fuel injection valve 15 ... Load sensor 16 ... Crank angle sensor 17 ... Air flow meter 18 ... Intake switching valve 19 ... Catalytic converter 20 ... Electronic control unit

Claims (1)

[Claims] 1. An intake control device for an internal combustion engine, wherein an intake time control valve is arranged in an engine intake passage communicating with a combustion chamber via an intake valve, wherein the opening / closing time of the intake time control valve is controlled according to the engine speed. The intake time control valve drive means and the intake time control valve drive means control the closing timing of the intake time control valve BD when the engine speed is high load rotation below a predetermined value.
C, hold the opening time of the intake time control valve to TDC side as the engine speed increases, and delay the intake time control valve to the TDC side. When the engine speed is equal to or higher than a predetermined value, the intake time control valve increases as the engine speed increases. Control means for delaying the closing timing of the time control valve from BDC and for controlling the opening timing of the intake time control valve to be advanced.
An intake control device for an internal combustion engine, comprising: