JP3812138B2 - Control device for turbocharged engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine control device including a turbocharger that drives an intake air compressor by an exhaust turbine, and in particular, to improve response delay of the exhaust turbine in preparation for start acceleration or reacceleration at idle stop or deceleration. The present invention relates to a control device for a turbocharged engine that performs control.
[0002]
[Prior art]
As a conventional control device for a turbocharged engine, as disclosed in JP-A-5-280408, at the end of the deceleration state, the target supercharging pressure is corrected to be low, and the corrected target supercharging pressure is corrected. There are some which control the exhaust bypass valve to achieve the above. This is intended to improve combustion (reduction of residual gas) at the time of start acceleration and reacceleration in a two-cycle engine, and set the supercharging pressure at the initial stage of acceleration lower than the normal use condition (first conventional technique). Example).
[0003]
Also, as disclosed in Japanese Patent Laid-Open No. 5-321804, in order to shorten the turbo lag and improve the acceleration response by increasing the exhaust energy at the time of acceleration, a predetermined supercharging is performed at the time of acceleration at which the increase of the supercharging pressure is delayed. There is one in which the exhaust energy given to the turbocharger is increased by controlling the ignition timing to be retarded until the pressure rise state is reached (second conventional example).
[0004]
[Problems to be solved by the invention]
However, in the case of the first conventional example, since the residual gas amount can be controlled to some extent by adapting the opening / closing timing of the intake / exhaust valves in the four-cycle engine, the effect cost by the supercharging pressure control is small. On the other hand, since the supercharging pressure is set low at the end of the deceleration state, there is a problem that the acceleration performance deteriorates due to the turbo lag at the time of reacceleration.
[0005]
In the case of the second conventional example, although the turbo lag can be shortened by increasing the exhaust energy during acceleration, the exhaust pressure is increased by retarding the ignition timing and the boost pressure is raised, so that the output is optimal. There was a problem that the ignition timing could not be used and the generated torque was reduced.
In view of such conventional problems, the present invention is a turbocharger capable of performing good control so as to improve the response delay of the exhaust turbine in preparation for start acceleration or reacceleration at the time of idling stop or deceleration. An object of the present invention is to provide a control device for a machine engine.
[0006]
[Means for Solving the Problems]
Therefore, in the invention according to claim 1, in an engine equipped with a turbocharger for driving the intake compressor by the exhaust gas turbine, as shown in FIG. 1, operating conditions is detected as operating condition that is at least idle stop When detecting the operating condition, the intake air amount is increased by setting the target idle speed in the idle speed feedback control by the intake air quantity control to a relatively high speed , and the air-fuel ratio is made lean. And a control device for the turbocharger-equipped engine.
[0007]
In the invention according to claim 2, in an engine including a turbocharger that drives an intake compressor by an exhaust turbine, as shown in FIG. 1, an operating condition detecting unit that detects at least a deceleration time as an operating condition; wherein upon detection of the operating conditions, as well as increasing the amount of intake air by opening the intake bypass valve for bypassing the intake air compressor intake, provided with control means of the intake air amount and the air-fuel ratio to lean the air-fuel ratio, a, A control device for a turbocharged engine is configured.
[0009]
The invention according to claim 3 is characterized in that the intake air amount and air-fuel ratio control means leans the air-fuel ratio to the surge limit.
The invention according to claim 4 is characterized in that the operating condition detecting means detects that the automatic transmission is in a traveling range as one of operating conditions.
In the invention according to claim 5 , the engine directly injects spark ignition that stratified combustion is performed by injecting fuel directly into the combustion chamber in the compression stroke to form a stratified mixture intensively around the spark plug. It is a type engine.
[0010]
【The invention's effect】
According to the first aspect of the present invention, when the vehicle is idling, the intake air amount is increased and the air-fuel ratio is made lean in preparation for start-up acceleration. On the other hand, the exhaust energy can be increased by increasing the intake air amount to increase the turbine speed, and the response delay of the exhaust turbine during start-up acceleration can be improved, and the transient torque can be improved.
In addition, in the idling stop control, in order to increase the intake air amount, the target idle rotation speed of the idle rotation speed feedback control is set to a relatively high rotation speed, and idling up is performed effectively, so that the intake air volume is effectively Can be increased.
[0011]
According to the second aspect of the present invention, in preparation for re-acceleration at the time of deceleration, the intake air amount is increased and the air-fuel ratio is made lean, so that the deterioration of the fuel consumption is suppressed to the minimum by making the air-fuel ratio lean. The exhaust energy can be increased by increasing the intake air amount to increase the turbine speed, and the response delay of the exhaust turbine during re-acceleration can be improved, and the transient torque can be improved.
In addition, during the deceleration control, the intake air amount can be effectively increased by reducing the intake resistance by opening the intake bypass valve for the intake compressor in order to increase the intake air amount.
[0013]
According to the third aspect of the present invention, the deterioration of fuel consumption can be minimized by reducing the air-fuel ratio to the surge limit.
According to the invention according to claim 4 , there is an intention of starting acceleration or reacceleration by detecting that the automatic transmission is in the traveling range as one of the operating conditions of the idle stop control or the deceleration control. Can be accurately controlled.
[0014]
According to the invention which concerns on Claim 5 , leaning of an air fuel ratio can be made more possible by applying to the direct injection spark ignition type engine which performs stratified combustion.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 2 is an engine system diagram showing an embodiment. First, this will be described.
A combustion chamber of each cylinder of an engine (internal combustion engine) 1 mounted on a vehicle has an air flow meter 2 for detecting an intake air amount Qa, an intake compressor 4 of a turbocharger 3, an intercooler 5, Air is sucked through the electric throttle valve 6 and the intake manifold 7. Further, a bypass passage 8 for bypassing the intake compressor 4 is provided, and an intake bypass valve 9 is interposed therein.
[0016]
An electromagnetic fuel injection valve (injector) 10 is provided so that fuel (gasoline) is directly injected into the combustion chamber of each cylinder.
The fuel injection valve 10 is energized to open a solenoid valve by an injection pulse signal output in an intake stroke or a compression stroke in synchronization with engine rotation from the engine control unit 20 and injects fuel adjusted to a predetermined pressure. It is supposed to be. In the case of intake stroke injection, the injected fuel diffuses into the combustion chamber to form a homogeneous mixture, and in the case of compression stroke injection, a stratified mixture is intensively formed around the spark plug, It is ignited by a spark plug and burns (homogeneous combustion or stratified combustion).
[0017]
Exhaust gas from the engine 1 is discharged through an exhaust manifold 11, an exhaust turbine 12 of the turbocharger 3, and an exhaust purification catalyst 13. Further, a bypass passage 14 for bypassing the exhaust turbine 12 is provided, and an exhaust bypass valve 15 is interposed therein.
An automatic transmission 16 is connected to the output side (crankshaft side) of the engine 1.
[0018]
The engine control unit 20 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors, and performs arithmetic processing based on the signals. The operation of the electric throttle valve 6, the fuel injection valve 10, the intake bypass valve 9, the exhaust bypass valve 15 and the like is controlled.
[0019]
As the various sensors, in addition to the air flow meter 2, a crank angle sensor 21 capable of detecting the engine speed Ne by detecting the crankshaft or camshaft rotation of the engine 1, and a water temperature for detecting the cooling water temperature Tw of the engine 1. A sensor 22, an accelerator sensor 23 (including an idle switch that is turned on when the accelerator opening = 0), and a vehicle speed VSP are detected from the rotation of the output shaft of the automatic transmission 16. A vehicle speed sensor 24, a shift range sensor (switch) 25 for detecting a shift range (D range, N range, etc.) of the automatic transmission 16, a brake switch 26 for detecting depression of a brake pedal, and the like are provided.
[0020]
Here, in the present invention, the engine control unit 20 performs control so as to improve the response delay of the exhaust turbine in preparation for start acceleration or reacceleration at the time of idling stop or deceleration in addition to normal control. The contents of each control will be described with reference to flowcharts separately for the control at the time of stopping and the control at the time of deceleration.
FIG. 3 is a flowchart of the idle stop control.
[0021]
In step 1 (denoted as S1 in the figure, the same applies hereinafter), it is determined whether or not the engine warm-up condition (water temperature Tw is equal to or greater than a predetermined value) based on a signal from the water temperature sensor.
In step 2, it is determined whether the idle switch is ON, that is, whether the accelerator opening APO = 0.
In step 3, it is determined whether or not the vehicle speed VSP = 0 based on the signal from the vehicle speed sensor.
[0022]
In step 4, it is determined whether or not the automatic transmission is a travel range represented by the D range, based on a signal from the shift range sensor.
As a result of these determinations, it is determined that all the conditions are YES, that is, when the engine is warmed up and the idle switch is ON, the vehicle speed VSP = 0, and the travel range, the operation conditions are when the vehicle is idling. Accordingly, the steps 1 to 4 correspond to the operating condition detection means. In addition to the conditions in steps 1 to 4, the brake switch may be turned on.
[0023]
On the other hand, if any one of them is NO, the operation condition is not satisfied and the process is terminated.
In step 5, the target idle speed is set to a predetermined value higher than normal for idling up (intake air amount increase).
In step 6, the actual idle speed is detected based on the signal from the crank angle sensor.
[0024]
In step 7, the absolute value of the deviation between the target idle speed and the actual idle speed is compared with a predetermined value A to determine whether or not the absolute value of the deviation is equal to or less than the predetermined value A.
When the absolute value of the deviation is larger than the predetermined value A, the routine proceeds to step 8 where the actual idle speed and the target idle speed are compared, and if the actual idle speed is smaller, the electric throttle valve at step 9 Is increased by a small amount. However, if the actual idle speed becomes larger, the opening degree TVO of the electric throttle valve is decreased by a small amount in step 10. After that, the process returns to Step 6.
[0025]
Such control is repeated, and the opening degree TVO of the electric throttle valve is increased to increase the intake air amount in response to the idle-up setting (intake air amount increase setting) of the target idle speed. As a result, when the actual idle speed reaches the vicinity of the target idle speed, the determination at step 7 proceeds to step 11.
In step 11, the fuel injection amount is set to a lean setting for stratified combustion and fixed.
[0026]
In step 12, the target surge level is set near the surge limit. Although there are various ways of capturing the surge level, for example, it is only necessary to calculate the fluctuation amount (rotational fluctuation amount) of the engine speed during a predetermined time. In this case, the target rotational fluctuation amount can be used as the target surge level. Set as large as possible.
In step 13, an actual surge level (for example, an actual rotation fluctuation amount) is detected.
[0027]
In step 14, the absolute value of the deviation between the target surge level and the actual surge level is compared with a predetermined value B to determine whether or not the absolute value of the deviation is equal to or less than the predetermined value B.
If the absolute value of the deviation is larger than the predetermined value B, the process proceeds to step 15 where the actual surge level is compared with the target surge level. If the actual surge level is smaller, in step 16, the electric throttle valve is opened. The TVO is increased by a small amount, the intake air amount is increased, and the air-fuel ratio is made lean. However, if the actual surge level becomes larger, in step 17, the opening degree TVO of the electric throttle valve is decreased by a small amount, the intake air amount is decreased, and the air-fuel ratio is enriched. After that, the process returns to step 13.
[0028]
By repeating such control, the opening degree TVO of the electric throttle valve is increased corresponding to the surge limit setting of the target surge level, the intake air amount is increased to the surge limit, and the air-fuel ratio is set to A / F = 50. Lean up to ~ 70. As a result, when the actual surge level reaches the vicinity of the target surge level, the process is terminated in the determination in step 14. Accordingly, steps 5 to 17 correspond to intake air amount and air-fuel ratio control means.
[0029]
FIG. 4 is a time chart of the idle stop control.
In this way, when idling in the D range, in preparation for start-up acceleration, the target idle speed of the idle speed feedback control is set to a relatively high speed, and idling up is performed, thereby reducing the intake air amount. While increasing the fuel injection amount, the intake air amount is increased up to the surge limit, and the air-fuel ratio is made lean. Therefore, while making the air-fuel ratio lean to minimize deterioration of fuel consumption, the exhaust energy can be increased by increasing the intake air amount and the turbine speed can be increased, and the response delay of the exhaust turbine during start acceleration can be reduced. It is possible to improve the transient torque.
[0030]
FIG. 5 shows the effect of increasing the turbine speed by idling up in the idling stop control. The exhaust energy is increased by increasing the intake air amount by idling up and increasing the intake air amount by leaning the air-fuel ratio. This indicates that the turbine speed can be increased. In addition, although the fuel efficiency deteriorates due to idle-up, it is shown that the deterioration of the fuel efficiency can be suppressed to a minimum by reducing the air-fuel ratio to the surge limit.
[0031]
FIG. 6 shows an image of transient torque improvement by the idling stop control, and vehicle G indicates that the start acceleration performance is improved by the increase of the turbine rotational speed.
FIG. 7 is a flowchart of the deceleration control.
In step 21, it is determined based on a signal from the water temperature sensor whether or not the engine has been warmed up (water temperature Tw is equal to or greater than a predetermined value).
[0032]
In step 22, it is determined whether the idle switch is ON, that is, whether the accelerator opening APO = 0.
In step 23, a vehicle speed change amount ΔVSP is calculated based on a signal from the vehicle speed sensor, and it is determined whether or not the vehicle speed change amount ΔVSP <0.
In step 24, based on the signal from the shift range sensor, it is determined whether or not the automatic transmission is in a travel range represented by the D range.
[0033]
As a result of these determinations, all are YES, that is, when the engine is warmed up under the condition after engine warm-up, the vehicle speed change amount ΔVSP <0, and the traveling range, it is determined that the operating condition is during deceleration, and the process proceeds to step 25. . Accordingly, the steps 21 to 24 correspond to the operating condition detection means.
On the other hand, if any one of them is NO, the operation condition is not satisfied and the process is terminated.
[0034]
In step 25, the intake bypass valve is opened to bypass intake air to the intake compressor. As a result, the intake resistance can be reduced and the intake air amount can be increased.
In step 26, the exhaust bypass valve is closed to prevent the exhaust from bypassing the exhaust turbine.
[0035]
In step 27, it is determined whether or not the fuel is being cut.
If the fuel is being cut, the routine proceeds to step 28, where the electric throttle valve is controlled to be fully opened, the intake air amount is increased, and the processing is terminated.
If the fuel is not being cut, the process proceeds to step 29.
In step 29, the fuel injection amount is set to a lean setting for stratified combustion and fixed.
[0036]
In step 30, the target surge level (for example, the target rotation fluctuation amount) is set near the surge limit.
In step 31, an actual surge level (for example, an actual rotation fluctuation amount) is detected.
In step 32, the absolute value of the deviation between the target surge level and the actual surge level is compared with a predetermined value B to determine whether or not the absolute value of the deviation is equal to or less than the predetermined value B.
[0037]
If the absolute value of the deviation is larger than the predetermined value B, the process proceeds to step 33, where the actual surge level is compared with the target surge level. If the actual surge level is smaller, in step 34, the electric throttle valve is opened. The TVO is increased by a small amount, the intake air amount is increased, and the air-fuel ratio is made lean. However, if the actual surge level becomes larger, in step 35, the opening degree TVO of the electric throttle valve is decreased by a small amount, the intake air amount is decreased, and the air-fuel ratio is enriched. After that, the process returns to step 31.
[0038]
By repeating such control, the opening degree TVO of the electric throttle valve is increased corresponding to the surge limit setting of the target surge level, the intake air amount is increased to the surge limit, and the air-fuel ratio is set to A / F = 50. Lean up to ~ 70. As a result, when the actual surge level reaches the vicinity of the target surge level, the determination is made at step 32, and the process is terminated. Accordingly, steps 25 to 35 correspond to intake air amount and air-fuel ratio control means.
[0039]
FIG. 8 is a time chart of the deceleration control.
Thus, at the time of deceleration in the D range, in preparation for re-acceleration, by opening the intake bypass valve for the intake compressor, the intake resistance is reduced, the intake air amount is increased, and the fuel injection amount is fixed, The intake air amount is increased to the surge limit, and the air-fuel ratio is made lean. Therefore, while making the air-fuel ratio leaner while minimizing the deterioration of fuel consumption, the exhaust energy can be increased by increasing the amount of intake air and the turbine speed can be increased, and the response delay of the exhaust turbine during re-acceleration can be reduced. It is possible to improve the transient torque.
[0040]
FIG. 9 shows the effect of increasing the turbine speed by opening the intake bypass in the control at the time of deceleration. It is shown that it can be increased to increase the turbine speed.
FIG. 10 shows an image of transient torque improvement by control during deceleration, and vehicle G indicates that the reacceleration performance is improved as the turbine rotational speed is increased.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing a configuration of the present invention. FIG. 2 is a system diagram showing an embodiment of the present invention. FIG. 3 is a flowchart of idle stop control. 5] Diagram showing the effect of increasing the turbine speed by idling up. [Fig. 6] Image of transient torque improvement by idling stop control. [Fig. 7] Deceleration control flowchart [Fig. 8] Deceleration control time chart [Fig. ] Diagram showing the effect of increasing turbine speed due to intake bypass opening [Fig. 10] Image of transient torque improvement by control during deceleration [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 2 Air flow meter 3 Turbocharger 4 Intake compressor 5 Intercooler 6 Electric throttle valve 7 Intake manifold 8 Bypass passage 9 Intake bypass valve 10 Fuel injection valve 11 Exhaust manifold 12 Exhaust turbine 13 Catalyst 14 Bypass passage 15 Exhaust bypass valve 16 Automatic transmission 20 Engine control unit 21 Crank angle sensor 22 Water temperature sensor 23 Acceleration sensor 24 Vehicle speed sensor 25 Shift range sensor 26 Brake switch

Claims (5)

In an engine equipped with a turbocharger that drives an intake compressor by an exhaust turbine,
An operating condition detecting means for detecting at least that the vehicle is in an idle stop as an operating condition;
When the operating condition is detected, the intake air amount is increased by setting the target idle speed in the idle speed feedback control based on the intake air amount control to a relatively high speed , and the air-fuel ratio is made lean. And air-fuel ratio control means;
A control device for a turbocharged engine, characterized by comprising: In an engine equipped with a turbocharger that drives an intake compressor by an exhaust turbine,
An operating condition detecting means for detecting at least that the vehicle is decelerating as an operating condition;
Upon detection of said operating condition, thereby increasing the amount of intake air by opening the intake bypass valve for bypassing the intake air compressor intake, and control means of the intake air amount and the air-fuel ratio to lean the air-fuel ratio,
A control device for a turbocharged engine, characterized by comprising: 3. The control device for an engine with a turbocharger according to claim 1, wherein the intake air amount and air / fuel ratio control means leans the air / fuel ratio to a surge limit. The turbocharger according to any one of claims 1 to 3 , wherein the operating condition detecting means detects that the automatic transmission is in a traveling range as one of the operating conditions. Engine control device. The engine is a direct-injection spark-ignition engine in which stratified combustion is performed by forming a stratified mixture intensively around a spark plug by directly injecting fuel into a combustion chamber in a compression stroke. The control device for the turbocharged engine according to any one of claims 1 to 4 .

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