JP2006112305A - Intake air control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase engine torque by supercharging effect by intake air pulsation while preventing occurrence of knocking. <P>SOLUTION: An intake air passage 2 is provided with an intake air control valve 3 opening and closing in relation to an intake valve 1. Open and close timing of the intake air control valve 3 is controlled to keep pressure in the intake air passage retained in a downstream side of the intake air control valve when both of the intake air control valve 3 and the intake valve 1 open higher than pressure in the intake air passage when the intake air control valve 3 opens and the intake valve 1 closes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an intake air control device that increases the charging efficiency of an engine.

  In the intake passage of the engine, by appropriately setting the intake pipe length between the surge tank disposed on the upstream side and each cylinder, the charging efficiency of the engine is increased by utilizing the intake pulsation generated in the intake passage. be able to. However, since the time until the intake pulsation in the intake passage reflects back to the surge tank and returns to the intake valve as positive pressure depends on the length of the intake passage, the supercharging effect due to the intake pulsation is It can be obtained only when the engine speed is such that the positive pressure is synchronized with the closing timing.

Therefore, an intake control valve that can be opened and closed is provided in the intake passage of each cylinder, and the opening and closing timing of the intake control valve is controlled according to the engine speed, so that the positive pressure of the intake pulsation is taken in a wide range of engine speed. Patent Document 1 discloses a technique that can increase the charging efficiency in synchronization with the closing of the valve.
JP 09-126006 A

  However, since the intake air is adiabatically compressed by the intake pulsation generated in the intake passage, the intake air temperature rises. Therefore, knocking may occur if the supercharging effect is improved by setting the pressure of the intake port to be maximum at the closing timing of the intake valve as in the conventional technique. In addition, if the ignition timing is retarded to avoid knocking due to supercharging, sufficient torque cannot be obtained, and if the ignition timing is excessively retarded, misfire or deterioration of combustibility may occur. There is.

  Further, in the supercharging by the intake control valve, it is structurally difficult to use an intercooler for cooling the heated intake air, unlike the case of using a supercharger or a turbocharger.

  The present invention has been made paying attention to such conventional problems, and provides an intake control device for an engine that can increase engine torque by a supercharging effect by intake pulsation while preventing occurrence of knocking. The purpose is to do.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention is provided in an intake valve (1) for opening and closing a connection between an engine combustion chamber (5) and an intake passage (2), and an intake passage (2) upstream of the intake valve (1). An intake control valve (3) that opens and closes in association with the intake valve (1) every cycle, and opens the intake control valve (3) while the intake valve (1) is open, and the intake valve (1) The intake control valve (3) is closed after the valve is closed and before the intake valve (1) is opened again, and both the intake control valve (3) and the intake valve (1) are closed. An intake control valve for controlling the intake passage pressure held downstream of the intake control valve to be higher than the intake passage pressure when the intake control valve (3) is open and the intake valve (1) is closed. And a control means (S500).

  According to the present invention, since the pressure held in the intake passage is higher than the supercharging pressure of the combustion chamber, the scavenging effect of the residual gas can be preferentially improved over the supercharging effect due to the intake pulsation. Therefore, the generated torque can be increased by the supercharging effect by the intake pulsation while suppressing the occurrence of knocking.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is an overall configuration diagram showing an intake control device for an engine according to the present invention. The engine combustion chamber 5 is defined by a cylinder head 6, a cylinder block 9, and a piston 10. An intake passage 2 that introduces intake air and an exhaust passage 8 that leads exhaust gas are connected to the combustion chamber 5.

  The intake passage 2 introduces intake air into the combustion chamber 5 via the intake valve 1 provided in the cylinder head 6. For each cylinder, the intake passage 2 is provided with a fuel injection device 17 for injecting fuel, and an intake control valve 3 disposed upstream of the intake passage 2 and capable of blocking the intake passage 2. The intake control valve 3 is opened and closed only once at a predetermined timing for each cycle of the engine in relation to the intake valve 1. While the intake valve 1 is closed, a negative pressure or a positive pressure ( Hereinafter, the pressure is referred to as “intake passage holding pressure”. A surge tank 15 communicating with the intake passage 2 of each cylinder is provided upstream of the intake passage 2. Further, a throttle valve 16 for controlling the intake amount of all cylinders is provided upstream of the surge tank 15. In order to open and close the intake control valve 3 and the throttle valve 16, the intake control valve drive device 22 and the throttle valve drive device 23 are provided, respectively. The exhaust passage 8 leads exhaust from the combustion chamber 5 through an exhaust valve 7 provided in the cylinder head 6.

  A spark plug 12 is provided in the combustion chamber 5 so that the tip faces the combustion chamber 5, and the air-fuel mixture introduced from the intake passage 2 is ignited by the spark plug 12 and burned. The piston 10 is slid downward by the energy generated by the combustion in the combustion chamber 5. The connecting rod 13 connected to the piston 10 and the crank 14 connected to the connecting rod 13 cause the vertical movement of the piston 10 to rotate the crank 14. Converted into movement.

  The ECU 4 determines the ignition timing, the fuel injection amount, the opening degree of the throttle valve 16 and the intake control valve based on the detected values from the accelerator pedal operation amount sensor (APS sensor) 18, the water temperature sensor 19, the crank angle sensor 20, and the knock sensor 21. 3 is controlled. Here, the APS sensor 18 detects the operation amount of the accelerator pedal, the water temperature sensor 19 detects the engine coolant temperature, the crank angle sensor 20 detects the rotation angle of the crank 14, and the knock sensor 21 detects whether knocking has occurred or not. .

  The ECU 4 changes the pressure in the intake passage between the intake valve 1 and the intake control valve 3 by controlling the opening and closing timing of the intake control valve 3 in synchronization with the engine rotation, and the scavenging pressure and supercharging of the combustion chamber 5 are changed. Control the pressure. Control of the intake passage pressure performed by the ECU 4 will be described with reference to FIG. FIG. 2 is a flowchart showing the control of the intake control device for an engine according to the present invention, which is executed for each intake control valve 3 provided in each cylinder. In addition, this control is repeatedly performed every predetermined time (for example, 10 ms).

  In step S100, detection values from the APS sensor 18 and the crank angle sensor 20 are read.

  In step S200, the rotational speed and torque of the engine are calculated based on detection values from each sensor.

  In step S300, the control mode of the intake control valve 3 is searched based on the engine speed and torque. The control mode of the intake control valve 3 is searched with reference to the map shown in FIG.

  FIG. 3 is a map showing the relationship between the rotational speed and torque of the engine and the control mode of the intake control valve 3. This map includes a charging efficiency improvement mode and a normally open mode. The charging efficiency improvement mode is a mode that is selected when it is necessary to improve the charging efficiency of intake air. In this mode, opening / closing control of the intake control valve 3 is performed. The normally open mode is a mode that is selected when it is not necessary to improve the charging efficiency of the intake air. In this mode, the intake control valve 3 is always kept open.

  When the engine speed is high, it is possible to obtain the intake charging effect by the intake pulsation without using the intake control valve 3. In addition, when the required load is low, it is not necessary to improve intake charging efficiency. Therefore, as shown in FIG. 3, the charging efficiency improvement mode is searched when the engine speed is relatively low and the load is high.

  In step S400, it is determined whether or not the intake control valve control mode is the charging efficiency improvement mode. If it is the charging efficiency improvement mode, the process proceeds to step S500, and if it is the normally open mode, the process proceeds to step S600.

  In step S500, the intake control valve 3 is controlled based on the valve opening timing and the valve closing timing stored in the ECU 4. The valve opening timing and the valve closing timing are obtained in advance by experiments or the like.

  On the other hand, when it is determined in step S400 that the intake control valve control mode is the normally open mode, the process proceeds to step S600, and the intake control valve 3 is controlled to be normally open.

  Next, the contents of the present invention will be described with reference to FIGS. FIG. 4 is a time chart showing control of a conventional intake control valve. FIG. 5 is a time chart showing the control of the intake control device for the engine according to the present invention. 4 and 5, (a) shows the valve lift amount of the intake valve, (b) shows the open / close state of the intake control valve, and (c) shows the pressure (intake passage pressure) on the downstream side of the intake control valve in the intake passage. ) Respectively.

  First, the control of the conventional intake control valve will be described with reference to FIG. The intake control valve 3 is opened and closed only once for each combustion cycle of the engine.

  When the cylinder is in the expansion stroke, the exhaust valve 6 is opened (EVO; (a)), and the residual gas in the combustion chamber 5 is exhausted (BDC) by entering the exhaust stroke. At this time, both the intake control valve 3 and the intake valve 1 are closed (BDC to IVO; (a), (b)), and a positive pressure is maintained in the intake passage 2 (BDC to IVO; (c). )). This positive pressure gradually decreases due to heat transfer to the wall surface of the intake passage 2 and a small amount of leakage from the intake control valve 3 and the intake valve 1, but is sufficiently maintained until the valve overlap time (IVO; c)).

  When the intake valve 1 is opened, the residual gas in the combustion chamber 5 is pushed out of the exhaust valve 6 by the intake passage holding pressure and scavenged (IVO; (a)). When the cylinder enters the intake stroke (TDC) and the exhaust valve closes (EVC), negative pressure is generated in the intake passage 2 by the lowering of the piston 10 (EVC; (c)).

  When the cylinder enters the compression stroke (BDC) and the intake control valve 3 opens (ICVO), the negative pressure generated in the intake passage 2 and the combustion chamber 5 becomes a pressure wave and propagates upstream of the intake passage 2. . The negative pressure wave is reflected by the surge tank 15 to become a positive pressure wave, and returns to the combustion chamber 5 through the intake passage 2 again. The valve opening timing of the intake control valve 3 is controlled so that the timing when the positive pressure wave returns to the vicinity of the intake valve is synchronized with the valve closing timing of the intake valve 1 (IVC; (a), (c)). ICVO; (b)).

  Even after the intake valve is closed, the pressure wave propagates between the surge tank 15 and the intake valve 1, and then the intake control valve 3 is closed when the positive pressure wave returns to the vicinity of the intake valve 1 (ICVC; b), (c)). As a result, the positive pressure when the intake control valve 3 is closed is maintained downstream of the intake control valve 3 in the intake passage 2 (ICVC; (c)). Thereafter, the process proceeds to the combustion stroke again (TDC).

  As a result, the intake passage pressure immediately before closing the intake valve becomes the first maximum value of the positive pressure wave (hereinafter referred to as “positive pressure peak”), and the combustion chamber 5 is supercharged by this pressure, and the intake valve 1 is closed. This supercharging pressure is maintained in the combustion chamber by valve. Further, the intake passage pressure when the intake control valve is closed is held between the intake valve 1 and the intake valve 1 by closing the intake control valve 3, and this intake passage holding pressure is held until the intake valve 1 is opened. Since the positive pressure peak of the intake pulsation generated simultaneously with the opening of the intake control valve 3 is attenuated and becomes a low pressure every time the pulsation is performed, the supercharging pressure becomes higher than the intake passage holding pressure. Thus, the occurrence of knocking becomes a problem because the supercharging effect is relatively higher than the scavenging effect of the residual gas.

  Next, the control of the engine intake control device according to the present invention will be described with reference to FIG. Also in the present invention, the intake control valve 3 is opened and closed only once for each combustion cycle of the engine, but the opening and closing timing of the intake control valve 3 is different from the conventional one. Since the other operation timings of the intake valve 1 and the exhaust valve 7 are the same, the opening / closing timing of the intake control valve 3 will be described here.

  After completion of the intake stroke (BDC), the valve opening timing of the intake control valve 3 is controlled so that the positive pressure peak of the intake pulsation occurs after the intake valve 1 is closed. After the intake control valve 3 is opened (ICVO; (b)), the intake passage pressure rapidly increases and the intake valve 1 is closed before reaching the positive pressure peak (ICVO to IVC; (a), (c). )). Thereafter, the intake control valve 3 is controlled to be closed in synchronism with the time when the positive pressure peak is reached (ICVC; (b), (c)).

  Thus, the intake passage pressure when the intake valve is closed is held in the combustion chamber by the closing of the intake valve 1 to become a boost pressure, and the intake passage pressure when the intake control valve is closed becomes the intake passage holding pressure. Since the intake passage pressure when the intake control valve is closed is the maximum positive pressure in the formed intake pulsation, the intake passage pressure when the intake control valve is closed is higher than the intake passage pressure when the intake valve is closed. That is, the intake passage holding pressure is higher than the supercharging pressure. Therefore, during the valve overlap period after opening the intake valve, knocking is prevented by sufficiently lowering the temperature of the combustion chamber 5 while scavenging the residual gas inside the combustion chamber 5 more reliably by the high intake passage holding pressure. Generation can be suppressed and engine torque can be increased by moderate supercharging.

  The operation will be described by summarizing the above control. Note that reference numerals corresponding to the flowchart of FIG. 2 and crank angles corresponding to the time chart of FIG. 5 are shown in parentheses.

  In the intake control apparatus for an engine in the present embodiment, the charging efficiency improvement mode is selected at a relatively low rotational speed and a high load based on the rotational speed and torque of the engine (S200, S300). When the charging efficiency improvement mode is selected, the closing timing of the intake valve 1 is reached before the first positive pressure peak of the intake passage pressure formed in the intake port, and then a positive pressure peak is generated after a predetermined time. Next, the opening timing of the intake control valve 3 is controlled (S500; ICVO). Further, the closing timing of the intake control valve 3 is controlled so that the closing timing of the intake control valve 3 is synchronized with the first positive pressure peak of the intake port (S500; ICVC). If not in the charging efficiency improvement mode, the intake control valve is held open (S600).

  As described above, in the present embodiment, the opening timing of the intake control valve 3 is controlled so that the positive pressure peak of the intake pulsation by the intake control valve 3 occurs after the intake valve 1 is closed. Scavenging pressure) can be made higher than the supercharging pressure. Therefore, it is possible to suppress the temperature rise of the air-fuel mixture due to the scavenging effect of the residual gas and improve the charging efficiency, and to increase the engine output while suppressing the occurrence of knocking due to supercharging.

  Further, since the intake control valve 3 is controlled to close at the positive pressure peak of the intake pulsation, the intake passage holding pressure can be set to the maximum pressure of the intake pulsation, and can be surely set higher than the supercharging pressure. it can. Therefore, the engine output can be increased while suppressing the occurrence of knocking due to supercharging with higher accuracy.

(Second Embodiment)
In this embodiment, in addition to the control of the first embodiment, the opening / closing timing of the intake control valve 3 is controlled so as to change according to the rotational speed of the engine. In addition, since it is the same as that of 1st Embodiment except control of the opening / closing timing of the intake control valve 3, description is abbreviate | omitted suitably.

  First, control performed by the ECU 4 in the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing the control of the second embodiment of the intake control apparatus for an engine according to the present invention. Steps S100 to S400, S500, and S600 are the same as those in FIG. 2 showing the control of the first embodiment, and thus the same reference numerals are given.

  In step S450, the opening timing and closing timing of the intake control valve 3 are searched. The opening timing and closing timing of the intake control valve 3 are searched with reference to the table of FIG.

  FIG. 7 is a table showing the relationship between the engine speed and the opening timing and closing timing of the intake control valve 3. As shown in FIG. 7, the valve closing timing is constant regardless of the engine rotation speed, and the valve opening timing increases as the engine rotation speed increases in order to synchronize the positive pressure peak of the intake pulsation with the valve closing timing of the intake control valve 3. Advance. A table as shown in FIG. 7 is obtained in advance by experiments or the like and stored in the ECU 4.

  Next, the contents of the control performed in this embodiment will be described with reference to FIGS. FIG. 8 is a time chart showing the control of the second embodiment of the intake control apparatus for an engine according to the present invention, and shows a state where the rotational speed of the engine is higher than that in FIG.

  Since the period of the intake pulsation depends on the speed of sound and the length of the intake passage 2 and is almost constant regardless of the engine speed, FIG. 8 shows the period of the intake pulsation longer than that in FIG. 5 with respect to the crank angle. Will be. If the intake control valve 3 is opened at the same crank angle as in FIG. 5, the intake passage pressure does not sufficiently increase until the intake valve 1 is closed, and the boost pressure decreases accordingly. The higher the speed, the more the opening timing of the intake control valve 3 is advanced (ICVO; (b)). At this time, the intake control valve 3 is opened so that the interval between the closing timing of the intake valve 1 and the generation timing of the first positive pressure peak of the intake pulsation is constant regardless of the rotational speed of the engine. Advance the time.

  As a result, the intake passage holding pressure is constant regardless of the engine speed as shown in FIG. 9, but the boost pressure is higher because the higher the rotation speed, the greater the period of intake pulsation on the crank angle base. Become. That is, in FIG. 8, the inclination of the intake passage pressure after opening the intake control valve becomes smaller as the engine speed increases, so the interval between the intake valve closing time and the first positive pressure peak generation time of intake pulsation is constant. Then, the pressure difference between the intake passage pressure and the supercharging pressure becomes small. Further, since the pressure at the first positive pressure peak of the intake pulsation is constant regardless of the engine rotation speed, the supercharging pressure increases as the engine rotation speed increases.

  Here, the occurrence of knocking becomes a problem particularly when the engine speed is low. At high rotational speeds, the turbulence intensity in the combustion chamber increases as the intake air flow rate increases, and the flame propagation speed increases, and the unburned gas is burned by flame propagation before self-ignition. , Knocking is less likely to occur. That is, when the rotational speed of the engine is relatively high, a larger engine output can be obtained by increasing the supercharging pressure even considering the occurrence of knocking.

  On the other hand, the scavenging effect of residual gas due to the intake passage holding pressure not only suppresses knocking but also improves intake charging efficiency, so it is always high regardless of the engine speed, that is, the intake passage pressure is kept high. There is a need to.

  Therefore, as shown in FIG. 8, as the engine speed increases, the valve opening timing of the intake control valve 3 is advanced to control the boost pressure to be increased while keeping the intake passage pressure constant. The engine output can be increased due to high intake charging efficiency while preventing knocking.

  The operation will be described by summarizing the above control. In addition, the code | symbol corresponding to the flowchart of FIG. 6 was shown in the parenthesis.

  In the engine intake control device in the present embodiment, when the charging efficiency improvement mode is selected, the opening timing and closing timing of the intake control valve 3 are searched (S450). At this time, the valve closing time is constant regardless of the engine speed, and the valve opening time is searched to advance as the engine speed increases. The intake control valve 3 is controlled based on the searched opening / closing timing (S500).

  As described above, in the present embodiment, the valve closing timing of the intake control valve 3 is made constant regardless of the engine rotation speed, and the valve opening timing is controlled to advance as the rotation speed increases. Regardless of this, the engine output can be increased by the larger supercharging effect as the engine speed increases while maintaining the scavenging effect of the residual gas high.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

  In this embodiment, control is performed so that the interval at the crank angle base between the closing timing of the intake valve 1 and the first positive pressure peak generation timing of the intake pulsation is constant regardless of the engine speed. Without being limited thereto, the valve opening timing of the intake control valve 3 may be controlled so that a desired boost pressure is obtained at each engine rotation speed. For example, the higher the engine speed, the higher the supercharging pressure is controlled by shortening the interval on the crank angle base between the closing timing of the intake valve 1 and the generation timing of the first positive pressure peak of the intake pulsation. Obtainable.

  In the present embodiment, the charging efficiency improvement mode and the normally open mode are switched based on the rotational speed and torque of the engine. However, the present invention is not limited to these. For example, the intake valve 1 is opened in the first half of the intake stroke. A mode that reduces the pump loss while limiting the intake air amount by closing the valve in the middle of the intake stroke may be combined.

1 is an overall configuration diagram of an intake control device for an engine according to the present invention. It is the flowchart which showed control of 1st Embodiment of the intake control apparatus of the engine by this invention. It is the map which showed the control mode of the intake control valve. It is a time chart explaining the prior art. It is the time chart which showed the content of 1st Embodiment of the intake control apparatus of the engine by this invention. It is the flowchart which showed control of 2nd Embodiment of the intake control apparatus of the engine by this invention. It is the table which showed the opening and closing timing of the intake control valve with respect to engine speed. It is the time chart which showed the content of 2nd Embodiment of the intake control apparatus of the engine by this invention. It is the table which showed the relationship between the supercharging pressure with respect to the rotational speed of an engine, and an intake passage holding pressure.

Explanation of symbols

1 Intake valve 2 Intake passage 3 Intake control valve 4 Engine control unit (ECU)
5 Combustion chamber 6 Cylinder head 7 Exhaust valve 8 Exhaust passage 9 Cylinder block 10 Piston 12 Spark plug 13 Connecting rod 14 Crank 15 Surge tank 16 Throttle valve 17 Fuel injection valve 18 Accelerator pedal operation amount sensor (APS sensor)
19 Water temperature sensor 20 Crank angle sensor 21 Knock sensor 22 Intake control valve drive device 23 Throttle valve drive device

Claims (6)

An intake valve that opens and closes the connection between the combustion chamber of the engine and the intake passage;
An intake control valve that is provided in the intake passage upstream of the intake valve and opens and closes in association with the intake valve every operating cycle of the engine;
The intake control valve is opened while the intake valve is open, and the intake control valve is closed after the intake valve is closed and before the intake valve is opened again. The intake passage pressure held downstream of the intake control valve when both the valve and the intake valve are closed is the intake passage when the intake control valve is open and the intake valve is closed. An intake control valve control means for controlling the pressure to be higher than the pressure;
An intake control device for an engine, comprising: The intake control valve control means is configured so that an initial maximum value of an intake pulsation generated in the intake passage by opening the intake control valve is generated downstream of the intake control valve after the intake valve is closed. Control the opening timing of the intake control valve,
The engine intake control device according to claim 1. The intake control valve control means controls the closing timing of the intake control valve so that the intake control valve is closed when the pressure on the downstream side of the intake control valve is the first maximum value of the intake pulsation. ,
The engine intake control device according to claim 2. As the rotational speed of the engine is higher, the intake control valve control means has an intake passage pressure held downstream of the intake control valve when both the intake control valve and the intake valve are closed, and the intake air Controlling the intake control valve so that a difference from the intake passage pressure when the control valve is open and the intake valve is closed is small;
The engine intake control device according to any one of claims 1 to 3, wherein the intake control device for an engine is provided. The intake control valve control means controls the valve closing timing of the intake control valve to be constant regardless of the engine rotation speed, and advances the valve opening timing of the intake control valve as the engine rotation speed increases. ,
The engine intake control device according to claim 4. The intake control valve control means controls the intake control valve so that the interval between the closing timing of the intake valve and the closing timing of the intake control valve becomes shorter as the rotational speed of the engine is higher;
The engine intake control device according to claim 4.

Images