JP2013029073A - Intake air control device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To combine prevention of oxygen poisoning of an exhaust catalyst with enhancement of combustion stability.SOLUTION: An intake air control device 100 of an engine includes a stop valve 3 which is provided in an intake air path 2 for supplying air to a combustion chamber 5, and which can block the intake air path 2, and a fuel injection valve 18 for supplying the fuel into the combustion chamber 5. The intake air control device 100 of an engine further includes a fuel supply control part 42 that can stop the fuel supply by the fuel injection valve 18 during coasting in which accelerator opening degree is equal to or less than the predetermined value, and a stop valve control part 43 which closes the stop valve 3 when the fuel supply by the fuel injection valve 18 is stopped during the coasting, and opens the stop valve 3 during the valve overlap.

Description

  The present invention relates to an intake air control device that controls intake air of an engine.

  Conventionally, an intake air control device that controls intake air of an engine by adjusting the opening and closing timing of a valve mechanism has been used.

  Patent Document 1 discloses an intake control device including a shut-off valve that can shut off an intake passage between a throttle valve and an intake valve. In this intake control device, the shut-off valve is switched to a closed state while the vehicle is coasting with the accelerator off. As a result, the exhaust gas discharged without being burned when the fuel is cut off when the accelerator is off is suppressed, and oxygen poisoning of the exhaust catalyst is prevented.

JP 2006-112356 A

  However, in the intake control device described in Patent Document 1, when the shutoff valve is in the closed state, the pressure on the intake side is reduced. Since the exhaust pressure becomes higher than the intake pressure, the exhaust gas flows back to the intake side during the valve overlap, and the amount of so-called internal EGR (Exhaust Gas Recirculation) increases. Therefore, when the accelerator is turned on next time and the shut-off valve is switched to the open state, the EGR rate in the combustion chamber increases, and the stability of combustion may be impaired.

  The present invention has been made in view of the above problems, and an object thereof is to achieve both prevention of oxygen poisoning of an exhaust catalyst and improvement of combustion stability.

  An intake control device for an engine according to the present invention includes an on-off valve that is provided in an intake passage that feeds air into a combustion chamber and can shut off the intake passage, and a fuel injection valve that supplies fuel to the combustion chamber. The intake control device includes a fuel supply control unit capable of stopping fuel supply by the fuel injection valve during inertial traveling when the accelerator opening is equal to or less than a predetermined value, and when fuel supply by the fuel injection valve is stopped during inertial traveling. And an on-off valve control section for closing the on-off valve and opening the on-off valve during valve overlap.

  In the present invention, when inertial running is started and the accelerator opening becomes equal to or less than a predetermined value, fuel supply by the fuel injection valve can be stopped. When fuel supply by the fuel injection valve is stopped during coasting, the on-off valve is closed and the on-off valve is opened during valve overlap. Thus, by closing the on-off valve, exhaust exhausted without combustion can be suppressed, and by opening the on-off valve during valve overlap, air can flow from the intake passage to the exhaust passage to scavenge the combustion chamber . Therefore, it is possible to achieve both prevention of oxygen poisoning of the exhaust catalyst and improvement of combustion stability.

1 is a configuration diagram of an intake control device for an engine according to an embodiment of the present invention. FIG. It is a figure which shows operation | movement of an intake control device. It is a figure which shows the change of the valve opening degree, pressure, and flow volume accompanying operation | movement of an intake control device. It is a diagram which shows the relationship between the volume of a combustion chamber, and a pressure.

  Hereinafter, an intake control device 100 for an engine according to an embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of the engine 30 and an intake control device 100 that controls intake air in the engine 30 will be described with reference to FIG.

  The engine 30 includes a combustion chamber 5 defined by the cylinder head 6, the cylinder block 9, and the piston 10, an intake passage 2 that introduces intake air into the combustion chamber 5, and an exhaust passage 8 that leads exhaust from the combustion chamber 5. Is provided. Further, the engine 30 is provided with an ECU (engine control unit) 4 for performing the control.

  The intake passage 2 introduces intake air into the combustion chamber 5 via the intake valve 1 provided in the cylinder head 6. The intake passage 2 has a throttle valve 17 that can adjust the amount of air taken into the combustion chamber 5, an on-off valve 3 that is provided downstream of the throttle valve 17 and can shut off the intake passage 2, and the combustion chamber 5. A fuel injection valve 18 for supplying fuel is provided.

  The throttle valve 17 is provided in the intake passage 2 upstream of the intake valve 1. The throttle valve 17 is provided with a throttle valve driving device 27 for opening and closing and a throttle valve opening sensor 25 for detecting the opening.

  The fuel injection valve 18 is provided in the intake passage 2 upstream of the intake valve 1 and downstream of the throttle valve 17. The fuel injection valve 18 supplies fuel to the combustion chamber 5 through the intake passage 2. The fuel injection valve 18 is provided for each cylinder.

  The on-off valve 3 is provided in the intake passage 2 upstream of the fuel injection valve 18 and downstream of the throttle valve 17. The on-off valve 3 is opened and closed in synchronization with the intake valve 1. The on-off valve 3 completely shuts off the intake passage 2 when closed. In order to open and close the on-off valve 3, an on-off valve driving device 26 is provided. The on-off valve 3 and the on-off valve driving device 26 are provided for each cylinder.

  A spark plug 12 is provided in the combustion chamber 5 so that the tip faces the combustion chamber 5. The air-fuel mixture introduced from the intake passage 2 is ignited by the spark plug 12 and burned.

  The piston 10 slides downward by the energy generated by the combustion in the combustion chamber 5. The vertical movement of the piston 10 is converted into the rotational movement of the crank 14 by the connecting rod 13 connected to the piston 10 and the crank 14 connected to the connecting rod 13.

  The exhaust passage 8 leads exhaust from the combustion chamber 5 through an exhaust valve 7 provided in the cylinder head 6. An exhaust catalyst 28 for purifying harmful components in the exhaust is provided in the exhaust passage 8 downstream of the exhaust valve 7.

  An external EGR passage 31 is provided between the exhaust passage 8 and the intake passage 2 to recirculate part of the exhaust as EGR gas from the exhaust passage 8 to the intake passage 2 through the outside of the combustion chamber 5. One end of the external EGR passage 31 is connected to the exhaust passage 8 downstream of the exhaust valve 7 and upstream of the exhaust catalyst 28, and the other end is connected to the intake passage 2 downstream of the throttle valve 17 and upstream of the on-off valve 3. . The external EGR passage 31 is provided with an EGR cooler 32 that cools the EGR gas and an EGR valve 33 that adjusts the amount of EGR gas recirculated to the intake passage 2.

  The ECU 4 controls the engine 30 and controls the intake control device 100. The ECU 4 includes a microcomputer having a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and I / O interface (input / output interface).

  Detection signals from the accelerator fully closed switch 19, the clutch switch 20, the vehicle speed sensor 21, the transmission neutral switch 22, the crank angle sensor 24, and the throttle valve opening sensor 25 are transmitted to the ECU 4. The ECU 4 controls the spark plug 12, the fuel injection valve 18, the throttle valve 17, the on-off valve 3, and the EGR valve 33 based on the transmitted signal.

  Here, the accelerator full close switch 19 detects that the operation amount of the accelerator pedal is zero. The clutch switch 20 detects that a clutch (not shown) is in an engaged state. The vehicle speed sensor 21 detects the speed of the vehicle. The transmission neutral switch 22 detects that the transmission (not shown) is neutral. The crank angle sensor 24 detects the rotation angle of the crank 14. The throttle valve opening sensor 25 detects the opening of the throttle valve 17.

  The ECU 4 includes a throttle control unit 41 that controls the opening degree of the throttle valve 17, a fuel supply control unit 42 that controls the fuel injection amount by the fuel injection valve 18, and an on-off valve control unit 43 that controls the on-off valve 3 to open and close. Have.

  The fuel supply control unit 42 can stop the fuel supply by the fuel injection valve 18 during the inertia traveling. The fuel supply control unit 42 stops fuel injection by the fuel injection valve 18 when a predetermined condition is satisfied. The predetermined condition is that the engine speed is not less than a predetermined value (for example, 1000 rpm or more), the vehicle speed is not less than a predetermined value (for example, 10 km / h or more), and the transmission is not neutral. The fuel supply control unit 42 stops the fuel supply by the fuel injection valve 18 when all these conditions are satisfied.

  The on-off valve control unit 43 closes the on-off valve 3 and opens the on-off valve 3 during valve overlap when the fuel supply by the fuel injection valve 18 is stopped during coasting. The throttle control unit 41 controls the throttle valve 17 to be fully closed during this inertia traveling.

  During the valve overlap, the on-off valve control unit 43 starts to open the on-off valve 3 at a timing such that the pressure in the intake passage 2 downstream from the on-off valve 3 becomes substantially maximum when the intake valve 1 starts to open. A certain amount of time is required from when the on-off valve 3 is opened until the pressure in the intake passage 2 downstream of the on-off valve 3 rises to a substantially maximum value. Therefore, the on-off valve control unit 43 opens the on-off valve 3 at an earlier timing than the intake valve 1 starts to open. Thereby, the pressure of the intake passage 2 downstream of the on-off valve 3 can be increased by the time the intake valve 1 starts to open.

  Further, the on-off valve control unit 43 closes the on-off valve 3 at such a timing that it closes before the exhaust valve 7 closes.

  Next, the operation of the intake control device 100 will be described with reference to FIGS.

  State (a) to state (g) shown in FIG. 2 show intake control by the intake control device 100 when the fuel supply by the fuel injection valve 18 is stopped during coasting. The density of dots in the state (a) to the state (g) in FIG. 2 indicates the level of pressure. (A) to (g) in FIGS. 3 and 4 correspond to the states (a) to (g) in FIG.

  The state (a) shown in FIG. 2 is a state when the valve overlap period ends. In the state (a), the intake valve 1 is opened, the exhaust valve 7 is closed, and the on-off valve 3 is closed. As shown in FIG. 3, in the state (a), the pressure in the intake passage 2 downstream of the on-off valve 3, the pressure in the combustion chamber 5, and the pressure in the exhaust passage 8 are equal. From this state, the piston 10 descends and shifts to the state (b).

  The state (b) shown in FIG. 2 is the first half of the intake stroke in which the intake valve 1 is opened, the exhaust valve 7 is closed, and the piston 10 is lowered. Even in the state (b), the on-off valve 3 remains closed. In the state (b), the intake passage 2 and the combustion chamber 5 downstream of the on-off valve 3 are closed by the on-off valve 3 and the exhaust valve 7. Therefore, as shown in FIG. 3, the pressure in the intake passage 2 downstream of the on-off valve 3 and the combustion chamber 5 decreases as the piston 10 descends.

  The state (c) shown in FIG. 2 is the second half of the intake stroke following the state (b). As shown in FIG. 3, in the state (c), the pressure in the intake passage 2 and the combustion chamber 5 downstream of the on-off valve 3 is further lowered by the lowering of the piston 10.

  As shown in FIG. 4, in the intake stroke from the state (a) to the state (c), since the on-off valve 3 is closed, no fresh air is introduced into the combustion chamber 5, and the adiabatic expansion is almost adiabatic. ing.

  The state (d) shown in FIG. 2 is a state in which the intake valve 1 is closed after the piston 10 reaches the intake bottom dead center and the pressure in the combustion chamber 5 has dropped. When the intake valve 1 is closed, the intake passage 2 downstream of the on-off valve 3 is closed by the on-off valve 3 and the intake valve 1. Therefore, as shown in FIG. 3, the intake passage 2 downstream of the on-off valve 3 remains constant at a negative pressure.

  The state (e) shown in FIG. 2 is a compression process in which the intake valve 1 and the exhaust valve 7 are closed and the piston 10 is raised. As shown in FIG. 3, in the state (e), the piston 10 rises while the intake valve 1 and the exhaust valve 7 are closed and the combustion chamber 5 is closed, so that the pressure in the combustion chamber 5 rises.

  At this time, the pressure in the intake passage 2 downstream of the on-off valve 3 is constant because the intake valve 1 is closed. Similarly, the pressure in the exhaust passage 8 is constant because the exhaust valve 7 is closed.

  As shown in FIG. 4, in the compression process from the state (d) to the state (e), the inside of the combustion chamber 5 is almost adiabatically compressed, so that the pressure rises almost in inverse proportion to the decrease in volume. From the state (e), the state proceeds to the state (f) through an expansion stroke in which the piston 10 descends.

  The state (f) shown in FIG. 2 is a state in which, after the piston 10 descends in the expansion stroke, the piston 10 passes the expansion bottom dead center and shifts to the exhaust process. As shown in FIG. 3, in the state (f), when the pressure of the combustion chamber 5 that is in communication with the exhaust valve 7 being opened is compared with the pressure of the exhaust passage 8, the exhaust passage 8 is higher. Also at this time, the pressure in the intake passage 2 downstream of the on-off valve 3 is constant because the intake valve 1 is closed.

  As shown in FIG. 3, in the exhaust process in the state (f), when the exhaust valve 7 is opened, the EGR gas flows backward from the exhaust passage 8 at a substantially atmospheric pressure into the negative pressure combustion chamber 5. Thereafter, exhaust gas flows from the combustion chamber 5 to the exhaust passage 8 due to the rise of the piston 10, and the pressure in the combustion chamber 5 and the exhaust passage 8 at this time is constant. Therefore, as shown in FIG. 4, in the combustion chamber 5, the pressure rises to the atmospheric pressure and becomes constant, and only the volume decreases.

  The state (g) shown in FIG. 2 is a state in which the valve overlap is started by opening the intake valve 1 while the exhaust valve 7 is opened. In the state (g), the intake valve 1 and the exhaust valve 7 are opened, and the on-off valve 3 is opened. As a result, fresh air is introduced from the intake passage 2 and the EGR gas that has accumulated from the combustion chamber 5 to the intake passage 2 is scavenged.

  Therefore, when the accelerator operation is performed next, the intake passage 2 and the combustion chamber 5 are scavenged and the concentration of the EGR gas is reduced, so that stable combustion is possible without misfire.

  As shown in FIG. 3, when the on-off valve 3 begins to open, the pressure in the intake passage 2 downstream of the on-off valve 3 begins to rise, and reaches a substantially maximum value at the timing at which the intake valve 1 begins to open. When the intake valve 1 begins to open, the pressure in the combustion chamber 5 increases. Therefore, as shown in FIG. 4, the combustion chamber 5 is reduced in volume and increased in pressure as the piston 10 rises.

  Thereafter, when the on-off valve 3 starts to close, the flow rate of the introduced fresh air decreases, so the pressure in the intake passage 2 upstream of the on-off valve 3 begins to decrease. Even if the on-off valve 3 starts to close, the pressure in the combustion chamber 5 is constant while the exhaust valve 7 is open. When the exhaust valve 7 is closed, the pressure in the combustion chamber 5 starts to decrease and shifts to the state (a) again.

  Since the opening / closing timing of the opening / closing valve 3 is determined by the rotation angle of the crank 14, when the engine speed increases, the time during which the opening / closing valve 3 is open is shortened. If the on-off valve 3 is open for a short time, the pressure in the intake passage 2 downstream of the on-off valve 3 does not rise sufficiently, and there is a risk that scavenging will not be performed sufficiently during valve overlap.

  Therefore, the opening / closing valve control unit 43 advances the angle as the engine speed increases, and opens the opening / closing valve 3. Thereby, even if the engine speed changes, the time during which the on-off valve 3 is open can be made constant. Therefore, even if the engine speed changes, the scavenging effect of the combustion chamber 5 due to the opening / closing valve 3 being opened is not impaired.

  On the other hand, the opening / closing valve control unit 43 opens the opening / closing valve 3 during the valve overlap when the period during which the accelerator opening is the predetermined opening during inertial traveling is shorter than the set period. When the period of the predetermined opening during inertia traveling is equal to or longer than the set period, the on-off valve 3 is closed without opening.

  The setting period at this time is set based on a time integrated value of the engine speed after the accelerator opening reaches a predetermined opening during inertial traveling. Specifically, during the set period, the amount of EGR gas that has remained after the scavenging of the intake passage 2 and the combustion chamber 5 has been sufficiently reduced, and the exhaust catalyst 28 provided downstream of the exhaust passage 8. Is set to a period during which the oxygen poisoning amount falls within the allowable range.

  Thereby, since the set period is set based on the total flow rate of scavenging, scavenging can be stopped while the oxygen poisoning amount of the exhaust catalyst 28 is within the allowable range. Therefore, scavenging of the intake passage 2 and the combustion chamber 5 can be sufficiently performed, and the exhaust catalyst 28 can be prevented from being poisoned by oxygen due to excessive scavenging.

  Also, during the set period, a part of the exhaust gas is recirculated by the internal EGR as compared with a case where the accelerator opening is a predetermined opening degree during inertia traveling from an operating state in which a part of the exhaust gas is recirculated through the external EGR passage 31. The accelerator opening is set to be shorter when the accelerator opening becomes a predetermined opening during inertia traveling.

  When external EGR is performed through the external EGR passage 31, the EGR gas is recirculated to the combustion chamber 5 through the intake passage 2. On the other hand, when the internal EGR is performed, the EGR gas is recirculated from the exhaust passage 8 to the combustion chamber 5 when the intake valve 1 is closed. Therefore, as compared with the case of the external EGR, the amount of the EGR that stays in the case of the internal EGR is less by the amount that the EGR gas is not recirculated into the intake passage 2. Therefore, even if the set period is set short, it is possible to perform sufficient scavenging and minimize the oxygen poisoning amount of the exhaust catalyst 28.

  After that, when the accelerator is operated and the accelerator opening becomes larger than the predetermined opening during inertial running, the opening / closing valve control unit 43 opens the opening / closing valve 3 during the valve overlap as described above. Once closed, the on-off valve 3 is opened and closed again during the intake stroke in the same cycle.

  Thereby, the air-fuel mixture can be newly introduced into the combustion chamber 5 after scavenging the combustion chamber 5. Therefore, both the scavenging of the combustion chamber 5 and the introduction of fresh air can be achieved, and the combustion can be stabilized.

  The control for reopening the on-off valve 3 during the intake stroke is executed when the rotational speed of the engine 30 is, for example, 3200 rpm or less, which is a rotational speed that is frequently used in the market. When the engine 30 has a higher rotational speed, the on-off valve 3 is always kept open.

  According to the above embodiment, the following effects are obtained.

  When the inertia running is started, the fuel supply by the fuel injection valve 18 is stopped under a predetermined condition. When fuel supply by the fuel injection valve 18 is stopped during coasting, the on-off valve 3 is closed. As a result, exhaust exhausted without being combusted can be suppressed, so that the exhaust catalyst 28 can be prevented from being poisoned by oxygen.

  Moreover, after closing the on-off valve 3, the on-off valve 3 is opened during valve overlap. As a result, air can flow from the intake passage 2 to the exhaust passage 8 to scavenge the inside of the combustion chamber 5, so that the stability of combustion when the accelerator is operated next time can be improved.

  Therefore, it is possible to achieve both prevention of oxygen poisoning of the exhaust catalyst 28 and improvement of combustion stability.

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

  For example, in the above, the case where the fuel injection valve 18 is provided in the intake passage 2 is illustrated. However, the present invention is not limited to this, and a direct injection type in which the fuel injection valve 18 is provided in the cylinder head 6 of the engine 30 may be used.

100 Intake Control Device 1 Intake Valve 2 Intake Passage 3 On-off Valve 4 ECU (Engine Control Unit)
5 Combustion chamber 7 Exhaust valve 8 Exhaust passage 17 Throttle valve 18 Fuel injection valve 28 Exhaust catalyst 30 Engine 31 External EGR passage 41 Throttle control unit 42 Fuel supply control unit 43 Open / close valve control unit

Claims (7)

An on-off valve provided in an intake passage for sending air into the combustion chamber and capable of blocking the intake passage;
A fuel injection valve for supplying fuel to the combustion chamber;
A fuel supply control unit capable of stopping fuel supply by the fuel injection valve during inertial traveling when the accelerator opening is equal to or less than a predetermined value;
An engine intake control device comprising: an open / close valve control unit that closes the open / close valve and opens the open / close valve during valve overlap when fuel supply by the fuel injection valve is stopped during the inertia traveling.   The on-off valve control unit starts opening the on-off valve so that the pressure in the intake passage downstream from the on-off valve becomes substantially maximum when the intake valve starts to open, and before the exhaust valve fully close timing 2. The engine intake control device according to claim 1, wherein the on-off valve is closed so as to be closed.   3. The engine intake control device according to claim 1, wherein the on-off valve control unit opens the on-off valve by advancing as the engine speed increases. 4.   The on-off valve control unit opens the on-off valve during the valve overlap when the period during which the accelerator opening is the predetermined opening is shorter than a set period, and the accelerator opening is the predetermined opening. The engine intake control device according to any one of claims 1 to 3, wherein when the period of the opening is equal to or longer than the set period, the on-off valve is closed without being opened. An exhaust catalyst disposed in the exhaust passage;
During the set period, the intake passage and the combustion chamber are scavenged based on a time integrated value of the engine rotation speed after the accelerator opening reaches the predetermined opening, and oxygen poisoning of the exhaust catalyst The engine intake control device according to claim 4, wherein the intake air control device is set to a period during which the amount is within an allowable range. An external EGR passage that recirculates part of the exhaust gas from the exhaust passage to the intake passage through the outside of the combustion chamber;
The set period is an operation state in which part of the exhaust gas is recirculated by internal EGR compared to a case where the accelerator opening is the predetermined opening degree from an operation state in which part of the exhaust gas is recirculated through the external EGR passage. 6. The intake control device for an engine according to claim 5, wherein the accelerator opening is set shorter when the accelerator opening becomes the predetermined opening.   When the accelerator opening is opened from the predetermined opening, the on-off valve controller opens and closes the on-off valve during the valve overlap, and closes the on-off valve during the intake stroke in the same cycle. The intake control device for an engine according to any one of claims 1 to 6, wherein the intake control device is opened and closed again.