JP2000145524A - Internal combustion engine with variable turbocharger - Google Patents

Abstract

(57) [Problem] To provide an internal combustion engine equipped with a variable turbocharger capable of rapidly increasing a supercharging pressure even when accelerating from a low load state and obtaining sufficient acceleration performance. SOLUTION: When the shift position is switched to the D range during idling stop (step S4, step S1).
4) In addition to increasing the supercharging pressure by changing the opening of the variable member of the turbocharger to the closed side (step S20) and switching the air-fuel ratio to the second lean air-fuel ratio on the lean side (step S22), While suppressing an increase in engine torque due to an increase in supply pressure, it is possible to increase the boost pressure in advance in a low load state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine (hereinafter, referred to as an engine) having a variable turbocharger capable of changing a supercharging pressure by adjusting an opening degree of a variable member according to an operating state of the engine. It is.

[0002]

2. Related Background Art In recent years, engines equipped with a variable turbocharger have been put into practical use in order to improve torque over the entire range from low speed to high speed. As described in Japanese Utility Model Publication No. 4-33384, for example, this type of variable turbocharger is configured such that the gas inflow speed into a turbine can be changed by a variable member such as a movable vane, and is variable according to the operating state of the engine. By controlling the members, the boost pressure is appropriately adjusted in a wide rotation range to improve the torque. For example, when accelerating from a low load state, such as when starting from an idle stop or accelerating during low-speed traveling, the variable member is controlled to the closed side to increase the supercharging pressure to increase the engine torque. Increase the speed of the vehicle acceleration.

[0003]

In an engine equipped with the above-described variable turbocharger, once the acceleration is started, the supercharging pressure can be appropriately adjusted by controlling the variable members, but the acceleration is started from a low load state. At the moment, the phenomenon that the rise of the boost pressure is delayed occurs. More specifically, since the engine torque is not so required during a low load state such as when the vehicle is idling or running at a low speed, the variable member is controlled to the open side to maintain a substantially supercharged state. When the accelerator is depressed by a person,
The variable member is controlled to be closed to increase the exhaust pressure, and then the boost pressure increases with the turbine speed to increase the volumetric efficiency, and thereafter, the fuel injection amount is controlled in the increasing direction. After that, the engine torque increases. Therefore,
There was a problem that a sufficient acceleration performance could not be obtained immediately after the accelerator operation by the driver.

An object of the present invention is to provide an internal combustion engine equipped with a variable turbocharger capable of rapidly increasing a supercharging pressure even when accelerating from a low load state and obtaining sufficient acceleration performance. is there.

[0005]

In order to achieve the above object, according to the present invention, when the low load state of the internal combustion engine is detected, the opening of the variable member of the variable turbocharger is closed by the supercharging pressure control means. , The supercharging pressure is controlled to the high supercharging pressure side, and the torque of the internal combustion engine is suppressed by the torque suppressing means. When the supercharging pressure is controlled to the high supercharging pressure side, the fuel injection amount is controlled in an increasing direction with an increase in the intake air amount. During traveling, problems such as unintended acceleration occur. Here, since the engine torque is suppressed by the torque suppressing means, it is possible to increase the supercharging pressure in advance under a low load condition while preventing such a problem, and to increase the supercharging pressure during subsequent acceleration. , The engine torque increases immediately just by increasing the fuel injection amount.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a direct injection type engine for directly injecting fuel into a combustion chamber will be described below. In the schematic configuration diagram of FIG. 1, reference numeral 1 denotes an in-cylinder injection gasoline engine for an automobile, in which a combustion chamber 5, an intake system, and the like are designed exclusively for in-cylinder injection. The cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection valve 4 together with an ignition plug 3 for each cylinder, and high-pressure fuel supplied from a fuel pump (not shown) is supplied from the fuel injection valve 4 to the combustion chamber 5. It is designed to be injected directly into the interior. An intake port 6 is formed in the cylinder head 2 in a substantially upright direction, and an intake passage 7 is connected to the intake port 6. The intake air taken in from the intake passage 7 is introduced into the combustion chamber 5 through the intake port 6 with the opening of the intake valve 8,
Fuel is injected from the fuel injection valve 4 into the intake air,
The fuel is burned by the ignition of the spark plug 3.

In the intake passage 7, an air flow sensor (AFS) 9 for detecting an intake air amount Af, a compressor 11 of a variable turbocharger 10 for supercharging the intake air, and cooling of the intake air whose temperature has risen due to supercharging by the compressor 11 are cooled. An intercooler 12 and a throttle valve 14 that is opened and closed by a step motor 13 to adjust the amount of intake air is provided. An exhaust port 15 is formed in the cylinder head 2 in a substantially horizontal direction, and an exhaust passage 16 is connected to the exhaust port 15. The exhaust gas after combustion is discharged to the exhaust port 15 and the exhaust passage 1 with the opening of the exhaust valve 17.
It is discharged into the atmosphere via 6. The exhaust passage 16 includes a turbine 18 of the turbocharger 10 which is coaxially coupled with the compressor 11 and is rotationally driven by exhaust gas.
Further, a catalyst and a muffler (not shown) are provided.

In the turbine 18 of the turbocharger 10, a number of vanes 19 are arranged so as to surround a turbine rotor 18a.
The degree of opening is simultaneously changed by the vane adjustment actuator 21 via the connection state of the vane 19 and the rod 20 (not shown), and as a result, the flow rate of the exhaust gas introduced into the turbine rotor 18a is adjusted.

An input / output device (not shown), storage devices (ROM, RAM, BURAM, etc.) for storing control programs and control maps, and a central processing unit (C)
An ECU (engine control unit) 31 including a PU (Public Input Unit), a timer counter, and the like is provided, and performs overall control of the engine 1. On the input side of the ECU 31, in addition to the air flow sensor 9, an accelerator sensor 32 for detecting an accelerator operation amount Acc by the driver, a crank angle sensor 33 for outputting a crank angle signal at every predetermined crank angle, and the turbocharger 10. A supercharging pressure sensor 34 for detecting a supercharging pressure Pb, a shift position sensor 35 for detecting a shift position (P, N, D, etc.) of an automatic transmission (not shown) selected by a driver, an output side of the automatic transmission Switches such as a vehicle speed sensor 36 for detecting a vehicle speed V, and an operating device, such as an air conditioner, that applies a mechanical or electrical load to the engine 1 with operation.
To SWn are connected.

The output side of the ECU 31 is connected to the spark plug 3, the fuel injection valve 4, and the vane adjusting actuator 21, and is connected to an ETV-CU (electronic throttle valve control unit) 37.
The -CU 37 is connected to the step motor 13 of the throttle valve 14 described above. The ECU 31 determines an ignition timing, a fuel injection mode (as will be described later, a stroke of performing fuel injection) based on detection information from each sensor,
The fuel injection time and the like are determined to control the drive of the ignition plug 3 and the fuel injection valve 4, and the vane opening of the turbocharger 10 is determined to control the drive of the vane adjustment actuator 21. Further, the ECU 31 determines the throttle opening θTH and outputs it to the ETV-3CU 37, and the ETV-CU 37 controls the drive of the stepping motor 13 based on the information.

Next, a description will be given of the vane opening control of the variable turbocharger 10 executed by the ECU 31 in the in-cylinder injection type engine 1 configured as described above. The outline of the injection control will be described. The in-cylinder injection engine 1 can arbitrarily perform fuel injection even in a stroke other than the normal intake stroke due to the operation principle of directly injecting fuel into the combustion chamber 5. For example, by performing fuel injection in the compression stroke, , After forming an air-fuel mixture around the stoichiometric (stoichiometric air-fuel ratio) around the spark plug 3,
Combustion (stratified combustion) at an extremely lean air-fuel ratio of about 40 as a whole is enabled. During normal operation, the accelerator operation amount Acc detected by the accelerator sensor 32
Average effective pressure Pe obtained from the above, etc., crank angle sensor 2
Engine speed Ne obtained from the crank angle signal of No. 3,
The fuel injection mode and the target air-fuel ratio are determined based on various information such as the intake air amount Af detected by the air flow sensor 9. For example, in a low-load / low-rotation region where both the target average effective pressure Pe and the engine rotation speed Ne are low, the compression stroke injection mode is selected and the target air-fuel ratio on the lean side is set for the purpose of reducing fuel consumption and emission.
Then, the fuel injection valve 4 is controlled by a fuel injection control routine (not shown) based on the fuel injection time determined from the target air-fuel ratio, and fuel injection is performed in the compression stroke.

While executing the above fuel injection control, the ECU
31 executes the vane opening degree control routine shown in FIG. 2 at a predetermined control interval. First, detection information from each sensor is input in step S2, and it is determined in step S4 whether the vehicle is stopped during idling. For example, this determination is based on the accelerator operation amount Acc detected by the accelerator sensor 32.
The operation is performed based on the vehicle speed V detected by the vehicle speed sensor 36. When both the accelerator operation amount Acc and the vehicle speed V are 0, it is determined that the vehicle is idling. When the determination of NO (No) is made in step S2, the process proceeds to step S6, and the vane opening of the turbocharger 10 is controlled according to the operating state of the engine 1.

More specifically, the target average effective pressure Pe
The target boost pressure is set according to a preset map based on the engine speed Ne and the engine speed Ne, and the vane adjustment actuator is set so that the actual boost pressure detected by the boost pressure sensor 34 becomes the target boost pressure. Drive control of 21 is performed to adjust the vane opening. Turbocharger 10 according to vane opening
When the supercharging pressure of the engine 1 increases or decreases, the operating state of the engine 1 changes. Therefore, an appropriate fuel injection mode and a target air-fuel ratio are set on the fuel injection control routine side, and the fuel injection amount is controlled.

On the other hand, when it is determined that the vehicle is idling and stopped (YES) in step S4, it is determined in step S8 whether the lean prohibition condition is satisfied based on the ON / OFF state of the switches SW1 to SWn of the operating device. Is determined. As described later, in the present embodiment, the lean operation in which the target air-fuel ratio is set to the lean side during the idling operation is performed, but when the engine load increases, for example, when the air conditioner is operating, the lean operation cannot be continued. Then, it is determined that the lean prohibition condition is satisfied. If the determination in step S8 is YES, in step S10, the vane adjusting actuator 21 is drive-controlled to hold the vane 19 in the fully open state, and in step S12, the stoichiometric (14.7) is set as the target air-fuel ratio.

Therefore, by fully opening the vane in step S10, the flow velocity of the exhaust gas introduced into the turbine rotor 18a is reduced, and the turbine speed does not rise sufficiently during idling operation due to the small absolute amount of the exhaust gas. As in the conventional example, the turbocharger 10 is maintained in a substantially supercharged state during the idling operation. Also, in response to the setting of the target air-fuel ratio in step S12, the actual air-fuel ratio is controlled to stoichiometric in the fuel injection control routine, and the engine torque against the increase in the load on the operating equipment is secured. For example, the intake stroke injection mode is selected as the fuel injection mode at this time, and the fuel injection is performed in the intake stroke.

If the lean prohibition condition is not satisfied and the determination in step S8 is NO, step S14 is reached.
Then, the current shift position detected by the shift position sensor 35 is determined. For example, P (parking) or N
If a shift position, such as (neutral), which is likely to continue stopping, is determined, step S1
Then, the routine proceeds to step S6, where the vane 19 is held in the fully open state as in step S10, the first lean air-fuel ratio is set as the target air-fuel ratio in step S18, and the routine ends.

That is, in this case, since it is not necessary to cope with an increase in the load as in the case of the operation of the operating device, the lean operation is executed in the compression stroke injection mode by the fuel injection control routine, thereby reducing fuel consumption. The turbocharger 10 is maintained in a substantially non-supercharged state as described above. On the other hand, when it is determined in step S14 that the shift position is likely to start the vehicle, such as D (drive), the vane adjustment actuator 21 is drive-controlled in step S20 to drive the vane 19. The preset idle opening vane opening is maintained, and in step S22, a second lean air-fuel ratio leaner than the first lean air-fuel ratio is set as a target air-fuel ratio, and the routine ends.

As the idle standby vane opening, an opening close to the vane minimum opening applied at the time of rapid acceleration requiring high supercharging pressure is set. Further, the second lean air-fuel ratio is set to an air-fuel ratio capable of maintaining almost the same idle rotation speed as in the case of no supercharging, based on the supercharging pressure at this time. That is, as is well known, the idling rotational speed is affected by the fuel injection amount, and the idling rotational speed increases as the fuel injection amount increases. Then, it is expected that the fuel injection amount will inevitably increase and the idle rotation speed will increase. Accordingly, in order to suppress the substantial fuel injection amount to the same extent and maintain an appropriate idle speed, the air-fuel ratio leaner than the first lean air-fuel ratio is set as the second lean air-fuel ratio. It is. In this embodiment, the second lean air-fuel ratio is set to 40, which is a value near the lean limit of the engine 1 (the most operable lean-air air-fuel ratio), and the first lean air-fuel ratio is slightly increased. 35 is set.

In this embodiment, the ECU 31 at the time of executing the processing of steps S4, S8 and S20 functions as a supercharging pressure control means.
The ECU 31 at the time of executing the processing of 22 functions as a torque suppressing unit. Next, the execution state of the above-described vane opening control routine will be described by taking as an example a case where the vehicle is switched from the stopped state in the P range or the N range to the D range shown in FIG.

When the shift position of the automatic transmission is maintained at the P range or the N range during idle stop and the operating equipment such as the air conditioner is stopped, the vane 19 is switched to the fully open state by the processing of step S16. At the same time, the lean operation is executed based on the first lean air-fuel ratio by the processing of step S18. As described above, when the vehicle is held in the P range or the N range, it can be estimated that the driver does not intend to start immediately and is likely to continue the stopped state. By fully opening the vane 19 described above, the turbocharger 10 is maintained in a substantially non-supercharged state, so that noise caused by supercharging and unnecessary consumption due to high rotation are prevented, and fuel consumption is reduced by lean operation.

When the shift position is switched to the D range from this state, the vane 19 is moved by the processing of step S20.
Is reduced to the idling standby vane opening degree, and the lean operation is executed based on the second lean air-fuel ratio by the process of step S22. The exhaust pressure increases due to the reduction of the vane opening, and the turbine speed sufficiently increases even in idle operation with a small exhaust gas flow rate, and the supercharging pressure of the turbocharger 10 is increased to a high supercharging pressure comparable during acceleration. To rise.

Further, by applying the second lean air-fuel ratio which is set to be leaner than the first lean air-fuel ratio, the first lean air-fuel ratio can be reduced.
As compared with the case of no supercharging in which the lean air-fuel ratio is applied, the actual fuel injection amount is suppressed to the same extent, and an appropriate idle speed is maintained. The driver confirms the completion of the switch to the D range, switches the foot from the brake pedal to the accelerator pedal, and starts the depressing operation after the switch to the D range and before the vehicle actually starts. Meanwhile, the increase of the supercharging pressure according to the vane opening is completed. Therefore, at the time of starting, the boost pressure has already been sufficiently increased. In FIG. 3, the first lean air-fuel ratio is switched stepwise from the first lean air-fuel ratio to the second lean air-fuel ratio. However, the air-fuel ratio may be continuously changed in accordance with an increase in the supercharging pressure.

When the vehicle starts to be started by the driver's accelerator operation, the opening degree of the vane is controlled to the minimum opening degree by the processing of step S6, and the maximum supercharging pressure obtained by the exhaust gas flow rate at that time is used. The vehicle is accelerated quickly. When the exhaust gas flow rate increases with the engine rotation speed Ne and the supercharging pressure reaches a preset upper limit, an overboost value is set as the vane opening degree thereafter, and an increase in the supercharging pressure is suppressed. On the other hand, the fuel injection at this time is variously controlled according to the acceleration condition. That is, the fuel injection mode and the target air-fuel ratio are set according to the map from the target average effective pressure Pe and the engine rotation speed Ne at that time. For example, in the case of rapid acceleration, the mode is switched to the intake stroke injection mode and the stoichiometric or rich side is set. Is controlled.

As described above, the control of the vane opening and the fuel injection amount after the start of acceleration is not different from that of a normal engine. However, in this embodiment, when the vehicle is stopped before that, the start is performed based on the switching to the D range. When predicted, the boost pressure of the turbocharger 10 is increased in advance by reducing the vane opening. As a result, there is no need to wait for an increase in the supercharging pressure at the time of starting as in the conventional example, and the engine torque can be immediately increased only by increasing the fuel injection amount, and sufficient acceleration performance can be obtained. Moreover, in order to maintain an appropriate idle rotation speed by leaning the air-fuel ratio in accordance with the increase of the supercharging pressure, the above-described problems such as an increase in the idling rotational speed caused by the supercharging pressure control are taken beforehand. Advantages regarding acceleration performance can be obtained.

The description of the embodiment has been completed above, but the embodiments of the present invention are not limited to this embodiment. For example,
In the above embodiment, the boost pressure was increased by reducing the vane opening in advance, assuming the time of starting from idle stop.
If the vehicle is accelerating from a low load state, the vehicle is not limited to idling stop. Therefore, for example, the vane opening control of the present invention can be applied during acceleration from a low-speed running state. That is, in this case, when predetermined conditions such as the vehicle speed V and the engine load are satisfied, it is determined that the vehicle is traveling at a low speed, the vane opening is reduced to increase the supercharging pressure, and the air-fuel ratio is reduced to the lean side. Set to. Since the increase in the fuel injection amount due to the increase in the supercharging pressure is offset by the leaning of the air-fuel ratio, unintended acceleration due to the increase in the engine torque is prevented, and the constant vehicle speed V is maintained. When the stepping operation is performed, the engine torque increases immediately due to the increase in the fuel injection amount, and sufficient acceleration performance can be obtained.

In the above-described embodiment, the increase in the fuel injection amount due to the increase in the supercharging pressure is offset by the lean air-fuel ratio. It suffices if defects such as unintended acceleration during traveling can be suppressed. Therefore, instead of leaning the air-fuel ratio, the ignition timing may be retarded, or the recirculation amount of the EGR device may be increased. Even in this case, the engine torque can be reliably suppressed and the above-described problem can be suppressed. As in the embodiment, the acceleration performance can be improved by increasing the supercharging pressure in advance.

Further, in the above embodiment, when it is presumed that the shift position does not start immediately in the P range or the N range, it is considered that there is no need to increase the supercharging pressure, and the vane 1
9 was held in the fully open state, but it is not always necessary to perform such control. For example, in this case, similarly to the D range,
In order to prepare for acceleration, the vane opening may be reduced to the idle standby vane opening, and the air-fuel ratio may be switched to the second lean air-fuel ratio.

[0028]

As described above, according to the internal combustion engine equipped with the variable turbocharger of the present invention, when the internal combustion engine is in a low load state, the increase in the engine torque is suppressed and the supercharging pressure is reduced. Therefore, the supercharging pressure can be quickly raised at the time of acceleration, and sufficient acceleration performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an internal combustion engine including a variable turbocharger according to an embodiment.

FIG. 2 is a flowchart showing a vane opening control routine executed by an ECU.

FIG. 3 is a time chart showing a control state of a supercharging pressure and an air-fuel ratio when the vehicle starts from a stopped state.

[Explanation of symbols]

 Reference Signs List 1 engine (internal combustion engine) 10 turbocharger 15 turbine 19 vane (variable member) 40 ECU (supercharging pressure control means, torque suppression means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 23/02 F02D 41/02 330D 41/02 330 F02B 37/12 301Q F-term (Reference) 3G005 DA08 EA14 EA16 FA04 FA10 GA04 GB25 GD12 GE09 HA04 HA05 JA02 JB11 3G084 AA04 BA07 BA09 BA13 CA03 CA04 DA05 DA15 EB08 EB12 EC03 FA05 FA06 FA07 FA10 FA38 3G092 AA01 AA06 AA09 AA18 BA01 BA04 BB01 BB06 DB03 EA06 EA06 HA03 EA06 EA01 HE06Z HF03Z HF08Z HF12Z HF13Z HF21Z 3G301 HA01 HA04 HA11 HA16 JA03 KA08 KA12 LA00 LB04 PA01Z PE01Z PE03Z PF01Z PF03Z PF08Z PF11Z

Claims (1)

[Claims] A variable turbocharger for adjusting a supercharging pressure by changing an opening of a variable member provided in a passage for introducing exhaust gas into a turbine; and a variable turbocharger for detecting a low load state of the internal combustion engine. A supercharging pressure control means for controlling the supercharging pressure to a high supercharging pressure side by changing an opening degree of the variable member to a closed side; and a supercharging pressure of the variable turbocharger by the supercharging pressure control means. An internal combustion engine provided with a variable turbocharger, comprising: a torque suppressing means for suppressing the torque of the internal combustion engine when the internal combustion engine is controlled.