JP5594265B2 - Engine intake control device - Google Patents

Description

  The present invention relates to an intake control device for an engine provided with an intake control valve that generates intake pressure pulsation.

  In an internal combustion engine (hereinafter also referred to as an engine), it is effective to increase the compression ratio in order to improve the fuel consumption of the engine alone. However, when the compression ratio is increased, knocking occurs in a high load range. In order to avoid this knocking, for example, it is necessary to delay the intake valve closing timing by, for example, adopting a late closing cam, and to reduce the actual actual compression ratio in the high load range.

However, if the actual compression ratio is reduced by delaying the closing timing of the intake valve, intake air blows back from the cylinder to the intake port side, which makes it impossible to secure the amount of fresh air in the cylinder, and the volume The efficiency is lowered, and the output torque of the engine is lowered as compared with the normal closing timing of the intake valve.
As a method for improving the output torque drop, for example, Patent Document 1 discloses an intake control valve (also called an impulse valve) that can block the intake passage in an intake passage such as an intake manifold between the intake valve and the surge tank of each cylinder. And a technique for improving the charging efficiency of the engine by generating pressure pulsation in the intake passage for each cylinder by controlling the opening and closing of the intake control valve at an appropriate timing during the intake stroke. . In this technology, the intake control valve is always open when supercharging is not required, such as when the engine is under low load, and intake control is performed when supercharging is required, such as when the engine is under high load. A filling efficiency improvement mode is executed to increase the filling efficiency by controlling the opening and closing of the valve.

  Further, in Patent Document 1, in the first cycle in which the normally open mode is shifted to the charging efficiency improvement mode during acceleration or the like, the charging efficiency of the engine is increased by the supercharging effect, but the scavenging effect of the residual gas is obtained. Because there is not, the temperature of the air-fuel mixture becomes high, a high load and high temperature state occurs, and there is a concern of the occurrence of temporary knocking, and a technique to avoid the possibility of knocking during this mode transition period is also proposed Has been.

  In the charging efficiency improvement mode, this technology opens the intake control valve in the middle of the intake stroke, closes the intake control valve at the end of the intake stroke, and sets the valve closing timing to the time when the pressure oscillation becomes the maximum pressure. Although a large supercharging effect can be obtained, the closing timing of the intake control valve is slightly delayed compared to the normal opening / closing timing in the charging efficiency improvement mode in the first cycle that has shifted from the normally open mode to the charging efficiency improvement mode. In fact, the supercharging pressure in the cylinder is made lower than the target supercharging pressure in the steady state to suppress an increase in load and avoid the occurrence of knocking.

Japanese Patent No. 4396253

  However, the inventors' research has revealed that, in the filling efficiency improvement mode, if the volume efficiency is improved to the maximum by the impulse valve, knocking can occur even in the mode transition period. As a result of repeated studies on the phenomenon of occurrence of such knocking, the inventors of the present application have determined that the cause of knocking is that the compression top dead center temperature becomes excessively high.

That is, in order to improve the volumetric efficiency, if the impulse reaction (pressure fluctuation) is strengthened by delaying the opening timing of the impulse valve, the pressure pulsation becomes stronger and the filling efficiency can be improved. However, if the filling efficiency is increased too much, the compression top dead center temperature becomes excessively large, and it is considered that knocking occurs due to this.
In this respect, the technique of Patent Document 1 also suppresses the occurrence of knocking, but there is a limit to narrowing the closing timing of the impulse valve as in the technique of Patent Document 1, and the occurrence of knocking by this method is limited. It is difficult to suppress this.

  The present invention has been devised in view of such problems, and improves the volumetric efficiency of the engine by an intake control valve (impulse valve) and increases the engine output, while suppressing the occurrence of knocking that easily occurs. An object of the present invention is to provide an intake control device for an engine that can be used.

An intake control device for an engine according to the present invention has an intake control valve capable of blocking the intake passage in an intake passage for each cylinder upstream of the intake valve, and changes the operation state of the intake control valve according to the operating state of the engine. In the intake control device for an engine having an intake control valve control means for controlling, the intake control valve control means implements a control valve non-operation mode in which the intake control valve is always opened in a low load operation region of the engine. In the high-load operation region of the engine, a control valve action mode for opening the intake control valve within a period from the start of the intake stroke to the vicinity of the end of the intake stroke to generate intake pressure pulsation is performed. during the implementation of the control valve action mode, the first peak value and the ing opening timing pressure difference caused by the intake air pressure pulsation is most increased volumetric efficiency maximized Do Ri said engine Opening rows that have a well advanced and allowed the advance opening timing by the intake control valve, the engine, the volumetric efficiency retard side of the and will be advanced open timing of the intake control valve engine It has a characteristic of transitioning so as to have a second peak value lower than the first peak value, and the advance angle release timing is an opening timing for giving the second peak value or a timing in the vicinity thereof. It is characterized by that.

  Knock detection means for detecting knocking of the engine is provided, and the intake control valve control means opens the intake control valve at the advance opening timing when the knock detection of the engine is detected by the knock detection means. If the engine knocking is not detected by the knocking detecting means, it is preferable that the intake control valve is opened at an opening timing at which the pressure difference caused by the intake pressure pulsation is maximized.

  Alternatively, the high-load operation region is divided into a first high-load operation region on the high-load side where knocking can occur and a second high-load operation region on the low-load side where knocking is difficult to occur, The intake control valve control means opens the intake control valve at the advance opening timing in the first high load operation region of the engine, and the intake pressure in the second high load operation region of the engine. It is also preferable to open the intake control valve at the opening timing at which the pressure difference caused by pulsation is maximized.

It is preferable that the advance angle release timing is a timing advanced from the maximum lift timing of the intake valve .

  It is preferable that the closing timing of the intake control valve in the control valve action mode is a bottom dead center of the intake stroke or a timing slightly delayed from the bottom dead center.

  According to the engine intake control device of the present invention, the intake control valve control means implements the control valve non-operation mode in which the intake control valve is normally opened in the low load operation region of the engine. The engine operates without being affected, but in the high-load operation region of the engine, the control that opens the intake control valve and generates the intake pressure pulsation only during the period from the start of the intake stroke to the end of the intake stroke. Since the valve action mode is implemented, intake pressure pulsation can be used to increase engine charging efficiency and therefore volumetric efficiency.

In the control valve action mode, when the volumetric efficiency is increased by using the intake pressure pulsation, the temperature in the cylinder before ignition rises accordingly, and knocking is likely to occur due to this, but the intake stroke starts. in later time, the opening of the intake control valve in the first peak value and advance opening timing is advanced from Na Ru opening timing of the pressure difference is increased most volumetric efficiency maximized Do Ri engine caused by the intake pressure pulsation Therefore, the pressure difference caused by the intake pressure pulsation is alleviated, the temperature rise in the cylinder before ignition is suppressed, and the occurrence of knocking can be suppressed. Further, even if the intake control valve is opened at such an advance angle opening timing, the effect of improving the volumetric efficiency due to the intake pressure pulsation can be sufficiently obtained.
In other words, the engine has a characteristic that when the opening timing of the intake control valve is advanced, the volume efficiency of the engine changes so as to have a second peak value lower than the first peak value on the retard side. Since the advance angle release timing is set to the release timing that gives the second peak value or a timing in the vicinity thereof, the effect of suppressing the occurrence of knocking and the effect of improving the volumetric efficiency due to the intake pressure pulsation can be obtained more reliably. be able to.

  When engine knocking is detected by the knocking detection means, the intake control valve is opened at the advance opening timing, and when engine knocking is not detected, the intake air is discharged at the opening timing at which the pressure difference caused by the intake pressure pulsation is maximized. If the control valve is opened, it is possible to further obtain the effect of improving the volume efficiency due to the intake pressure pulsation while suppressing the occurrence of knocking.

  Further, the high load operation region is divided into a first high load operation region on the high load side where knocking may occur and a second high load operation region on the low load side where knocking is unlikely to occur. In the first high load operation region, the intake control valve is opened at the advance opening timing, and in the second high load operation region, the intake control valve is opened at the release timing at which the pressure difference caused by the intake pressure pulsation is maximized. However, the volumetric efficiency can be further improved by the intake pressure pulsation while suppressing the occurrence of knocking without relying on the knocking sensor.

If the advance angle opening timing is set to a timing advanced from the maximum lift timing of the intake valve, it is possible to obtain an effect of improving volumetric efficiency due to intake pressure pulsation while reliably suppressing the occurrence of knocking .

  If the closing timing of the intake control valve in the control valve operation mode is set to the bottom dead center of the intake stroke or slightly delayed from the bottom dead center, the volume efficiency due to the intake pressure pulsation is suppressed while suppressing the occurrence of knocking. An improvement effect can be obtained.

1 is a system configuration diagram of an engine including an intake air control device according to an embodiment of the present invention. It is a map which shows allocation of the control mode of the intake control valve by the intake control device concerning one embodiment of the present invention. It is a figure explaining the effect by the intake control valve (impulse valve) of the intake control device concerning one embodiment of the present invention. It is a figure which shows the improvement characteristic of the volumetric efficiency by the valve opening timing (valve opening angle) of an intake control valve (impulse valve). It is a figure which shows the fluctuation characteristic of the cylinder pressure according to the valve opening timing (valve opening angle) of an intake control valve (impulse valve). It is a figure which shows the characteristic of the cylinder temperature before ignition by the valve opening timing (valve opening angle) of an intake control valve (impulse valve). It is a figure which shows the fluctuation characteristic of the in-cylinder temperature according to the valve opening timing (valve opening angle) of an intake control valve (impulse valve). It is a figure which shows the characteristic of the cylinder residual EGR amount by the valve opening timing (valve opening angle) of an intake control valve (impulse valve). It is a figure which shows the characteristic of the pre-chamber internal pressure by the valve opening timing (valve opening angle) of an intake control valve (impulse valve). It is a figure which shows the opening-and-closing timing of the intake control valve (impulse valve) concerning an Example, and the fluctuation | variation of the cylinder pressure corresponding to this.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.
1 to 10 show an intake control device according to the present embodiment and an engine (internal combustion engine) including the intake control device, which will be described based on these drawings. Although the present embodiment shows an example in which the present apparatus is applied to a four-cycle gasoline engine, the present invention can be applied not only to a gasoline engine but also to a diesel engine or the like.

[Configuration of intake control device and engine]
FIG. 1 is a system configuration diagram of an engine including an intake air control device according to an embodiment. As shown in FIG. 1, the engine 2 is connected via a plurality of cylinders (cylinders) 4 provided in the cylinder block 2 </ b> A, pistons 6 that slide in the cylinders 4, pistons 6, and connecting rods 8. The crankshaft 10 is provided. Each cylinder 4 includes a combustion chamber 12 defined by a piston 6 on the lower side and a cylinder head 2B on the upper side, and an intake passage 14 and an exhaust passage 16 are connected to the combustion chamber 12. A spark plug 18 is disposed on the upper surface of the central portion of the combustion chamber 12.

  The intake passage 14 is configured by connecting an intake pipe 22, an intake manifold 24, and an intake port 26 from the upstream side, and the intake port 26 is connected to the combustion chamber 12. A surge tank 28 is provided at the upstream end of the intake manifold 24 between the intake pipe 22 and the intake manifold 24. At the downstream end of the intake pipe 22 upstream of the surge tank 28, a butterfly valve type throttle valve 30 capable of arbitrarily adjusting the intake passage area is provided. The throttle valve 30 is a so-called electronically controlled throttle valve whose opening degree is controlled by a throttle valve driving device such as a motor. A fuel injection valve 20 is disposed in the intake port 26, and an amount of fuel corresponding to the engine load, that is, the intake air amount is injected.

  The exhaust passage 16 is configured by connecting an exhaust port 32, an exhaust manifold 34, and an exhaust pipe 36 from the upstream side, and the exhaust port 32 is connected to the combustion chamber 12. The exhaust pipe 36 is provided with an exhaust purification catalyst 38. An intake valve 40 comprising a poppet valve is provided at the opening of the intake port 26 to the combustion chamber 12, and an exhaust valve 42 comprising a poppet valve is provided at the opening to the combustion chamber 12 of the exhaust port 32. Has been.

  The intake valve 40 and the exhaust valve 42 are driven to open and close in synchronization with the rotation of the crankshaft 10 by a valve mechanism (not shown). The intake valve 40 opens slightly before the intake top dead center of the piston 6 and closes slightly after the intake bottom dead center. The exhaust valve 42 is also opened slightly before the exhaust bottom dead center of the piston 6 and is closed slightly after the exhaust top dead center. A valve overlap period in which the exhaust valve 42 and the intake valve 40 are simultaneously opened is provided.

  The intake manifold 24 of each cylinder is provided with an intake control valve 50 that can block the intake passage 14 in the intake manifold 24. The intake control valve 50 can be opened and closed with good responsiveness at any time in one cycle by the intake control valve driving device 52, and is constituted by, for example, a flap valve or a butterfly valve type valve that is opened and closed by an electromagnet. The arrangement position of the intake control valve 50 is set so that the intake pipe length is optimal for obtaining the inertia supercharging effect.

  The intake control valve 50 is also referred to as an impulse valve because it uses the pressure pulsation to improve the efficiency of filling the combustion chamber 12 with air and improve the volumetric efficiency of the engine 2. Although details will be described later, during high load operation where the output of the engine 2 is required, the impulse valve 50 is opened only during the period from the start of the intake stroke of the cylinder to the end of the intake stroke, and the intake pressure pulsation Is generated. A portion of the intake passage 14 from the impulse valve 50 to the opening of the intake port 26 closed by the intake valve 40 to the combustion chamber 12 is referred to as a pre-chamber (sub chamber) 54.

  An engine ECU (Engine Electronic Control Unit) 60 for controlling the opening / closing of the impulse valve 50, the opening degree of the throttle valve 30, the fuel injection amount from the fuel injection valve 20, the ignition timing of the spark plug 18, and the like is provided. Yes. The engine ECU is an electronic control unit configured as an LSI device or a built-in electronic device in which a known microprocessor, ROM, RAM, and the like are integrated.

  The engine ECU 60 includes accelerator opening information from an accelerator position sensor 62 that detects an operation amount (accelerator opening) of an accelerator pedal, crank angle information from a crank angle sensor 64 that detects a crank angle of the crankshaft 10, and knocking. Signals such as detection information of a knock sensor (knocking detection means) 66 that detects vibration of the cylinder block 2B due to air and intake air amount information from an air flow sensor (not shown) are input, and the engine is based on the input information. The ECU 60 controls each part. The knocking detection means is not limited to the knock sensor 66 as long as it is an object that detects knocking.

  That is, the engine ECU 60 controls the opening of the throttle valve 30 based on the accelerator opening information, controls the fuel injection amount from the fuel injection valve 20 based on the intake air amount information, and is calculated based on the crank angle information. The ignition timing is controlled based on the engine speed Ne and the engine load calculated based on the accelerator opening information (here, the average effective pressure Pe is used). In addition, when knocking detection information is input from the knock sensor 66 during operation in the control valve non-operation mode described later, the ignition timing is retarded. For the impulse valve 50, the engine ECU 60 controls the opening and closing by setting a control mode based on the engine speed Ne and the engine load Pe. In this case, the engine ECU 60 functions as intake control valve control means (impulse valve control means).

[Control of intake control valve (impulse valve 50)]
Here, the opening / closing control of the impulse valve 50, which is a feature of the present apparatus, will be described.
FIG. 2 is a map showing assignment of control modes of the impulse valve 50. As shown in FIG. 2, the engine speed Ne is low or low in the engine operation range defined by the engine speed Ne and the engine load Pe. A region where the engine load Pe is high due to rotation (low rotation high load region) is a control valve action mode (filling efficiency improvement mode) in which the impulse valve 50 is operated to improve the charging efficiency, and the other region is the impulse valve 50. A control valve non-operation mode (normally open mode) in which the valve is always open and does not particularly act is set.

In the control valve action mode (filling efficiency improvement mode), the impulse valve 50 is opened only during the period from the start of the intake stroke to the vicinity of the end of the intake stroke, and the impulse valve 50 is closed during the other periods. The charging efficiency of the engine is improved to cope with a high engine load (load demand) Pe.
Here, the principle of improving the charging efficiency of the engine by the impulse valve 50 will be described.

  FIG. 3 shows the case where the impulse valve 50 is opened from the crank angle A1 (120 degrees after the intake top dead center) to the crank angle A2 (immediately after the intake bottom dead center) and in the cylinder (in the cylinder and in the cylinder 4). The fluctuation of each pressure in the chamber 54 with respect to the change in the crank angle is compared with the in-cylinder pressure of the base (when there is no impulse valve 50, this corresponds to the control valve non-operation mode in which the impulse valve 50 is normally opened). FIG.

  As shown by the one-dot chain line in FIG. 3, when the impulse valve 50 is closed, the pressure in the pre-chamber 54 is substantially maintained in the pre-chamber 54 in the exhaust stroke, while in the cylinder 4 The pressure decreases with the exhaust, and becomes lower than that in the prechamber 54. In the valve overlap period, since the intake valve 40 is opened, a flow from the pre-chamber 54 into the cylinder 4 occurs, and the pressure increases until the pressure in the cylinder 4 becomes the same as that in the pre-chamber 54. As the exhaust valve 42 is closed and the piston 6 is lowered, negative pressure is generated in the cylinder 4 and the pre-chamber 54, and the pressure in the cylinder and the pressure in the pre-chamber 54 are gradually reduced (see section a).

  When the impulse valve 50 is opened from the crank angle A1 during the intake stroke, the intake air flows into the cylinder at a high speed due to the pressure difference between the upstream and downstream of the impulse valve 50 (see section b). When the negative pressure wave generated at this time is reflected by the upstream surge tank 28 and transmitted to the cylinder 4 as a positive pressure wave, the impulse valve 50 is closed. Thereby, the amount of intake air into the cylinder 4 is increased, the charging efficiency is improved, and the volumetric efficiency is improved. Further, the positive pressure confined in the pre-chamber 54 (see section c) can suppress the exhaust blowback from the cylinder 4 into the pre-chamber 54 during the valve overlap period of the next cycle as described above. .

  The improvement in volumetric efficiency by such an impulse valve 50 is to fix the valve closing angle (crank angle and valve closing timing of the impulse valve 50) and to open the valve opening angle (open the impulse valve 50). When the crank angle and the valve opening timing are changed, as shown in FIG. 4, the volume efficiency improvement effect varies depending on the valve opening angle, but the volume efficiency improvement effect can be obtained at any valve opening angle in the intake stroke. Note that the difference in volumetric efficiency due to the valve opening angle is considered to be due to the degree of confinement of the reflected wave from the surge tank 28 in the cylinder, as shown in FIG.

In FIG. 5, each curve of A _{1 to} A ₁₂ shows the characteristic of pressure change in each cylinder when the valve opening angle of the impulse valve 50 is changed, and the valve opening angle A ₁ is approximately 20 after intake top dead center. and in degrees, opening angle a ₂ is the intake top dead center Koryaku 30 degrees since, a _{3, a 4,} a valve opening angle delayed by 10 degrees substantially in ... and the crank angle, the valve opening angle a ₁₂ is the intake top dead center Koryaku 130 degrees. The valve closing angle of the impulse valve 50 is fixed at the crank angle A2 (immediately after the intake bottom dead center).

If the impulse valve 50 is closed, according to the piston 6 exhaust valve 42 is closed down, negative pressure is generated in the cylinder 4 and the pre-chamber 54, cylinder pressure is decreased gradually, the opening angle A ₁ , A ₂ , when the valve opening angle is fast, intake air flows into the cylinder 4 at a stage where the pressure in the cylinder does not decrease so much, and therefore, at a stage where the pressure difference between the upstream and downstream of the impulse valve 50 does not increase. . In this case, since the intake pulsation is not so strong, the negative pressure wave generated at this time is also relatively weak, and the cylinder pressure oscillates with a rise and fall after the rise, and then the inside of the cylinder with the rise of the piston 6 The pressure also rises. As the valve opening angle is made slower, the pressure difference between the upstream and downstream of the impulse valve 50 when the impulse valve 50 is opened increases, the intake pulsation increases, the cylinder pressure increases greatly, and then decreases. As the piston 6 rises, it rises again.

In any of the valve opening angles A _{1 to} A ₁₂ , the intake valve 40 is made to be more than the case where the impulse valve 50 is not provided (this corresponds to the base and the control valve non-operation mode in which the impulse valve 50 is normally opened). The in-cylinder pressure after closing (the in-cylinder pressure corresponds to volumetric efficiency) increases, and the in-cylinder pressure after closing the intake valve 40 tends to increase as the valve opening angle is delayed.

However, at the valve opening angles A ₆ , A ₇ , A ₈ (about 70 to 90 degrees), the cylinder pressure after closing the intake valve 40 is lower than the valve opening angles A _{1 to} A ₅ earlier than that. It has become. This is presumably because the intake valve 40 is closed when the cylinder pressure is lowered by the intake pulsation. On the other hand, at the relatively fast valve opening angles A _{1 to} A ₅ , after the pressure in the cylinder has decreased due to the intake pulsation, the intake valve 40 closes when the pressure rises again. It is thought that the cylinder pressure increases.

This tendency is also shown in FIG. That is, as shown in FIG. 4, the amount of increase in volumetric efficiency varies depending on the valve opening angles A _{1 to} A ₁₂ of the impulse valve 50, and the volumetric efficiency is the most in the vicinity of the relatively slow valve opening angles A _{9 to} A _12. There is a first peak that rises, and there is a second peak whose volumetric efficiency rises second in the vicinity of the relatively fast valve opening angles A _{1 to} A ₅ .
On the other hand, as the volume efficiency is improved by the impulse valve 50, the in-cylinder temperature before ignition rises, so that knocking is likely to occur. FIG. 6 shows the in-cylinder temperature before ignition according to the opening angle of the impulse valve 50. As shown in FIG. 6, the in-cylinder temperature tends to increase as the opening angle of the impulse valve 50 is delayed. Yes, under conditions where the volumetric efficiency improvement is the largest, such as a valve opening angle of 120 degrees or 130 degrees, the in-cylinder temperature before ignition rises by several tens of degrees Celsius compared to those without the impulse valve 50, and knocking is very likely to occur. .

On the other hand, when the valve opening angle of the impulse valve 50 is made small (opening the valve early), the generation of negative pressure is suppressed, and the temperature rise due to the pressure difference when the impulse valve 50 is opened and closed is reduced.
In addition, since the impulse valve 50 is closed during the exhaust stroke, the inside of the pre-chamber 54 can be maintained at a high pressure, and the exhaust air blowback to the intake side during the valve overlap can be avoided. As a result, the internal EGR (= residual EGR gas) can be reduced, whereby the temperature rise due to the EGR gas can be prevented and the temperature in the cylinder 4 at the intake top dead center can be lowered.

FIG. 7 is a diagram showing changes in the cylinder 4 temperature according to the crank angle for the valve opening angles A _{1 to} A ₁₂ (A _{1 to} A ₁₂ are the same as those in FIG. 5) of the impulse valve 50.
The temperature at the intake top dead center can be classified into a group d having a high temperature, a group e having a medium temperature, and a group f having a low temperature.
Group d is the case without the impulse valve 50 and the valve opening angles A ₆ , A ₇ , A ₈ (about 70 ° to 90 °), and these are all the cylinder pressures after the intake valve 40 is closed. Is relatively low. This is presumably because, during the exhaust stroke, the pressure in the intake port 26 or the pre-chamber 54 is low, so that the exhaust during the valve overlap is blown back to the intake side and the temperature in the cylinder 4 increases.

Group e is a case of relatively fast valve opening angles A _{1 to} A ₅ , and as described above, the pressure in the cylinder after closing the intake valve 40 becomes relatively high as described above, and in the exhaust stroke, Since the pressure in the pre-chamber 54 is kept relatively high, it is considered that the exhaust of the exhaust during the valve overlap to the intake side is suppressed and the temperature in the cylinder 4 is suppressed.
The group f is a case of the slow valve opening angles A _{9 to} A ₁₂ , and as described above, the pressure in the cylinder after closing the intake valve 40 becomes significantly high as described above, and the pre-chamber 54 is in the exhaust stroke. Since the internal pressure is kept high, it is considered that the blowback of the exhaust gas to the intake side during the valve overlap is reliably suppressed and the temperature in the cylinder 4 is largely suppressed.

On the other hand, looking at each temperature behavior after the valve opening of the impulse valve 50, the temperature rise after the valve opening becomes steeper as the temperature at the intake top dead center is lower, and the end of the compression stroke (crank angle after 300 degrees) As a result, it can be seen that the temperature in the cylinder 4 at) is highest in the group f, then in the group d, and lowest in the group e.
8 is a diagram showing a characteristic of internal EGR (=) with respect to the valve opening angle of the impulse valve 50, and FIG. 9 is a diagram showing a characteristic of pressure in the pre-chamber 54 with respect to the valve opening angle of the impulse valve 50. Also from the figure, since the pressure in the pre-chamber 54 is secured to some extent in the group e, the residual EGR gas amount is small, and in the group d, the pressure in the pre-chamber 54 is low, so the residual EGR gas amount is large, and the group f It can be seen that the pressure in the pre-chamber 54 is extremely high and the amount of residual EGR gas is very low.

Here, the temperature behavior in the cylinder 4 in the intake stroke in accordance with the impulse valve opening angle will be considered.
First, at the start of the intake stroke, as the pressure in the cylinder 4 and the pre-chamber 54 is increased due to valve overlap, the exhaust gas is scavenged and the internal EGR decreases, so the temperature in the cylinder 4 decreases.

When the impulse valve 50 is not used, the pressure is almost atmospheric pressure during the opening period of the intake valve 40. Thereafter, as the piston 6 descends and fresh air enters, the high temperature residue remaining in the cylinder 4 remains. The EGR gas is diluted and the temperature in the cylinder 4 is lowered. The transition of this temperature (in-cylinder temperature T) is the volume ratio between the amount of fresh air (new volume V2) and the amount of residual EGR (volume V1 of residual EGR), the temperature T1 of residual EGR, and the new temperature T2. It can be simulated by the following formula.
T = V1 / V2 × T1 + (1−V1 / V2) × T2
On the other hand, when the impulse valve 50 is used, since the impulse valve 50 is closed at the beginning of the intake stroke, the polytropy (≈ adiabatic) changes in the closed system, and the product of the in-cylinder temperature T and the in-cylinder volume V is constant. (TV = const). Accordingly, the in-cylinder temperature T decreases due to the increase in the in-cylinder volume V (= adiabatic expansion) accompanying the lowering of the piston 6. In the initial stage of expansion, the decrease rate of the in-cylinder temperature T is smaller than when the impulse valve 50 is not used, but as the expansion proceeds, the decrease in the in-cylinder temperature T becomes larger than when the impulse valve 50 is not used.

  However, if the negative pressure is increased while the impulse valve 50 is closed and the impulse valve 50 is opened with a pressure difference before and after (upstream and downstream) of the impulse valve 50, the outer diameter of the valve body portion of the intake valve 40 is increased. Correspondingly, the flow path area is reduced, so that a loss occurs, resulting in an irreversible adiabatic change. Therefore, even when the pressure before and after (upstream / downstream) of the impulse valve 50 becomes equal and the transition of the fresh air amount stops, the temperature in the cylinder remains before the impulse valve 50 (the intake manifold 24 upstream of the impulse valve 50, etc.) ) And the temperature before the impulse valve 50 is lower than the temperature when the valve is closed. For this reason, when the impulse valve 50 is used, it is considered that the temperature rises according to the pressure difference than when the impulse valve 50 is not used (= no pressure difference is provided).

However, in the case of free expansion of the gas, that is, when there is no loss during the inflow of the gas, the temperature change of the gas does not occur.
Another reason why the temperature of the gas rises is the influence of the difference in specific heat ratio depending on the gas that is the working fluid. For example, the specific heat ratio of oxygen O ₂ is 1.4, the specific heat ratio of carbon dioxide CO ₂ is 1.29, and the gas in the cylinder when the negative pressure is increased is mainly burnt gas. The burned gas is obtained by replacing oxygen O ₂ in fresh air (air) with carbon dioxide CO _2, so that the specific heat ratio is smaller than that of air and the temperature is less decreased. Since the unburned gas (= air) enters the cylinder 4 after being opened, the temperature rise is considered to be larger than the burned gas.

Therefore, if the valve opening of the impulse valve 50 is delayed to increase the pressure difference across the impulse valve 50 when the impulse valve 50 is opened, that is, if the volumetric efficiency is greatly improved, the in-cylinder temperature before ignition increases. It is thought that it will end up.
Such an increase in the in-cylinder temperature before ignition leads to knocking of the engine 2, so that knock detection information is input to the engine ECU 60 from the knock sensor 66 during operation in the control valve action mode (filling efficiency improvement mode). The engine ECU 60 serving as the intake control valve control means determines the valve opening angle of the impulse valve 50 from the group e (valve opening angles A _{1 to} A ₅ ) in which the volumetric efficiency is the second peak (FIG. 4), that is, The cylinder temperature before ignition is low and a certain volume efficiency improvement effect is obtained, such as approximately 20 degrees to approximately 60 degrees after intake top dead center, and preferably approximately 30 degrees to approximately 50 degrees after intake top dead center. The timing is set so that the volumetric efficiency is not the maximum, but the occurrence of knocking can be suppressed. On the other hand, during operation in the control valve action mode (filling efficiency improvement mode), if knock detection information is not input from the knock sensor 66 to the engine ECU 60, the engine ECU 60 serving as the intake control valve control means opens the impulse valve 50. The above-mentioned group f (valve opening angle A _{8 to} A ₁₂ , that is, approximately 90 degrees to approximately 130 degrees after the intake top dead center, in particular, the intake top dead center, where the volumetric efficiency becomes the first peak (FIG. 4). The timing at which the effect of improving the volumetric efficiency is most obtained is obtained, such as about 110 degrees to about 130 degrees later.

  In other words, when knocking occurs, the engine ECU 60 creates a large negative pressure, which is a normal technique of the impulse valve 50, creates a pressure difference, opens the impulse valve 50, and the generated negative pressure wave causes an upstream surge. Rather than using the half-wave (abdominal to abdominal) of a large amplitude pressure wave that is reflected by the tank and transmitted as a positive pressure wave into the cylinder, the amplitude is small with a relatively small negative pressure. In addition to creating pulsation and controlling the impulse valve to close at the antinode of the second and subsequent waves of pulsation (positive pressure part), to suppress the occurrence of knocking while obtaining a certain volumetric efficiency improvement effect The valve opening timing of the impulse valve 50 is controlled.

[Action and effect]
Since the engine intake control device according to the embodiment of the present invention is configured as described above, the engine ECU (intake control valve control means) 60 controls the engine 2 in the medium / low rotation / high load operation region. The valve action mode (filling efficiency improvement mode) is implemented, the valve opening of the impulse valve 50 is controlled and the intake pressure pulsation is used to increase the charging efficiency of the engine 2 and increase the volumetric efficiency, thus making engine output easier It can be increased and the load demand of the engine can be sufficiently and promptly met.

On the other hand, if the engine 2 is not in the middle / low rotation / high load operation region, the control valve non-operation mode (normally open mode) is executed and the impulse valve 50 is always opened, and therefore, it is affected by the impulse valve 50. Therefore, intake air can be sent into the cylinder 4 with normal characteristics, and the engine 2 operates.
In the control valve action mode, when the volumetric efficiency is increased by using the intake pressure pulsation, the temperature in the cylinder before ignition rises accordingly, and knocking is likely to occur due to this. If knocking occurs based on the information of No. 66, the opening timing of the impulse valve 50 is determined from the opening timing of the impulse valve 50 at which the pressure difference caused by the intake pressure pulsation becomes maximum, as shown by two types of thick broken lines in FIG. In particular, the opening timing of the impulse valve 50 is set to the above-mentioned group e (opening angles A _{1 to} A ₅ , that is, about 20 after the intake top dead center, where the volumetric efficiency becomes the second peak (FIG. 4). Timing at which the pre-ignition in-cylinder temperature is low and a certain volumetric efficiency improvement effect is obtained, such as approximately 60 degrees to approximately 60 degrees, and preferably approximately 30 degrees to approximately 50 degrees after intake top dead center. Since A01 and A02 are set, occurrence of knocking can be suppressed while obtaining a certain volumetric efficiency improvement effect.

If knocking of the engine 2 is not detected, as shown by a thin broken line in FIG. 10, the opening timing of the impulse valve 50 is set to the above-described group f (valve opening angle) in which the volume efficiency becomes the first peak (FIG. 4). a ₈ to a _12, that is, the intake top dead center Koryaku 90 degrees to approximately 130 degrees, in particular, as in the preferred) intake top dead center Koryaku 110 degrees to approximately 130 degrees, the maximum pressure difference caused by the intake pressure pulsation Since the opening timing A1 is as follows, the effect of improving the volumetric efficiency due to the intake pressure pulsation can be further obtained.

[Others]
Although the embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and can be appropriately modified and implemented without departing from the gist of the present invention. Is.
For example, in the above-described embodiment, when the knocking occurs based on the information of the knock sensor 66, the opening timing of the impulse valve 50 is advanced, but the present invention is not limited to this. For example, without relying on the knock sensor 66, an operation condition that causes knocking is obtained in advance by a test or the like, and the opening timing of the impulse valve 50 is advanced when the operation conditions obtained from various sensors satisfy the knocking occurrence condition. May be. Or, in the control valve action mode (filling efficiency improvement mode) regardless of the occurrence of knocking, the opening timing of the impulse valve 50 at which the pressure difference caused by the intake pressure pulsation is always the maximum, as in group e above. You may make it advance rather than.

  Further, as shown by a two-dot chain line in FIG. 2, the operation region of the control valve action mode (filling efficiency improvement mode) is set to a first high load operation region a1 on the high load side where knocking may occur, and a low It is divided into a second high load operation region a2 on the load side where knocking is unlikely to occur. In the first high load operation region a1, the impulse valve 50 is opened at the advance opening timing, and the second high load operation region In a2, even if the impulse valve 50 is opened at the opening timing at which the pressure difference caused by the intake pressure pulsation is maximized, the volumetric efficiency due to the intake pressure pulsation is suppressed while suppressing the occurrence of knocking without depending on the knocking sensor 66. An improvement effect can be obtained.

  Of course, the knocking sensor 66 is applied to this technique, and even when the knocking sensor 66 detects the occurrence of knocking even in the second high-load operation region a2, the impulse valve 50 is opened at the advance opening timing. May be.

2 Engine 4 Cylinder
6 piston 10 crankshaft 12 combustion chamber 14 intake passage 16 exhaust passage 18 spark plug 20 fuel injection valve 22 intake pipe 24 intake manifold 26 intake port 28 surge tank 30 throttle valve 40 intake valve 42 exhaust valve 50 impulse valve (intake control valve)
54 Pre-chamber
60 Engine ECU (intake control valve control means)
62 Accelerator position sensor (APS)
64 Crank angle sensor 66 Knock sensor (knocking detection means)

Claims (5)

Intake control valve control means for controlling the operating state of the intake control valve according to the operating state of the engine, as well as having an intake control valve capable of blocking the intake passage in the intake passage for each cylinder upstream of the intake valve In the engine intake control system,
The intake control valve control means includes
In the low load operation region of the engine, a control valve non-operation mode in which the intake control valve is always opened is performed,
In the high-load operation region of the engine, the control valve action mode for opening the intake control valve within a period from the start of the intake stroke to the vicinity of the end of the intake stroke to generate intake pressure pulsation is performed.
Wherein the time of execution of the control valve action mode, the intake pressure pulsation due to the pressure difference is maximized Do Ri said advance was the advance is angularly than the first peak value and name Ru opening timing volumetric efficiency of the engine is most increased opening caused the have the opening of the intake control valve row at the timing,
The engine has a characteristic that, when the opening timing of the intake control valve is advanced, the volume efficiency of the engine changes so as to have a second peak value lower than the first peak value on the retard side. Have
The engine intake control device according to claim 1, wherein the advance angle release timing is an opening timing for giving the second peak value or a timing in the vicinity thereof. A knocking detecting means for detecting knocking of the engine;
The intake control valve control means opens the intake control valve at the advance angle release timing when the knock detection means detects the engine knock, and the knock detection means does not detect the engine knock. The intake control device for an engine according to claim 1, wherein the intake control valve is opened at an opening timing at which a pressure difference caused by the intake pressure pulsation is maximized. The high load operation region is divided into a first high load operation region on the high load side where knocking may occur, and a second high load operation region on the low load side where knocking is unlikely to occur,
The intake control valve control means opens the intake control valve at the advance opening timing in the first high load operation region of the engine, and the intake pressure in the second high load operation region of the engine. The intake control apparatus for an engine according to claim 1, wherein the intake control valve is opened at an opening timing at which a pressure difference caused by pulsation is maximized. The engine intake control device according to any one of claims 1 to 3, wherein the advance angle release timing is a timing advanced from a maximum lift timing of the intake valve . Closing timing of the control valve acting mode by the intake control valve is characterized in that the to timing retarded slightly from the bottom dead center or the bottom dead center of the intake stroke, claim 1-4 The engine intake control device according to claim 1.

Images