JP3945240B2 - Diesel engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a diesel engine.
[0002]
[Prior art]
In general, in a diesel engine, a fuel injection amount is determined based on the accelerator opening and the engine speed, and the generated torque of the engine is controlled by the fuel injection amount. On the other hand, the amount of air taken into the cylinder is determined by the balance with the amount of EGR gas recirculated from the EGR valve. Therefore, in the diesel engine, first, the fuel injection amount is determined, and then the air amount is determined in relation to the EGR control (this is called fuel priority control for convenience of explanation).
[0003]
[Problems to be solved by the invention]
In recent years, diesel aftertreatment technology has been developed, and in order to control regeneration of diesel NOx catalyst and DPF (diesel particulate filter), and to realize a new combustion mode, exhaust gas O 2₂There has been an increasing demand for accurately matching the concentration with the target value.
However, in the conventional fuel priority control, since the air control with a slow response is combined with the fuel control with a fast response, the exhaust O for each combustion is controlled.₂Concentration cannot be controlled or transient exhaust O₂Concentration deviates from the target value and exhaust O₂It was difficult to control the concentration to the target value.
The present invention has been made based on the above circumstances, and its purpose is to exhaust the exhaust gas with high accuracy.₂An object of the present invention is to provide a diesel engine control device capable of controlling the concentration.
[0004]
[Means for Solving the Problems]
  (Means of Claim 1)
  The present invention is based on the operating state of the engine.GoalEGR rate calculating means for calculating the EGR rate, and calculated by this EGR rate calculating meansGoalBased on the EGR control means for controlling the EGR valve provided in the EGR function, the oxygen amount estimation means for estimating the amount of oxygen containing EGR gas sucked into the engine, and the operating state of the engine so that the EGR rate can be obtained. Exhaust gas target exhaust O₂Exhaust O to set concentration₂Concentration setting means and this exhaust O₂Target exhaust O set by concentration setting means₂An injection amount calculating means for calculating the fuel injection amount from the oxygen amount estimated by the oxygen amount estimating means is provided so that the concentration can be obtained.
  Then, the control method of the EGR valve learns the deviation so that the current EGR rate becomes equal to the target EGR rate, and adds the deviation to the operation amount at the time of open control, or the target physical value The feedback control amount gain for converging to is controlled by one of the feedback controls in which the gain is set sufficiently small.
[0005]
  In this configuration, the amount of oxygen (including EGR gas) sucked into the engine is estimated, and the fuel injection amount is determined from the amount of oxygen. Therefore, the responsive fuel control is combined with the slow responsive air control. be able to. As a result, compared with the conventional fuel priority control, the exhaust O₂The density can be accurately controlled to the target value.
  By the way, conventionally, by improving the response of the EGR valve and increasing the response of the new air amount, the target exhaust O ₂ The concentration is controlled. For this reason, it is necessary to set the feedback gain high, and there is a situation where the air amount fluctuates. Therefore, the target exhaust O ₂ When the amount of fuel is controlled so as to have a concentration, the amount of fuel fluctuates due to fluctuations in the amount of air, resulting in a problem that drivability deteriorates. On the other hand, according to the control method of the present invention, the fluctuation of the EGR valve control amount can be suppressed, so that the fluctuation of the fuel amount can be suppressed and good drivability can be obtained.
[0006]
(Means of Claim 2)
In the control device of the diesel engine according to claim 1,
Exhaust gas O in the exhaust path₂O to detect concentration₂Sensor is installed, this O₂Exhaust gas detected by sensor₂Concentration is target exhaust O₂The fuel injection amount calculated by the injection amount calculation means is corrected so as to converge to the concentration.
In this case, an error occurs in the estimated oxygen amount and fuel amount, and the actual exhaust gas O₂Even when the concentration deviates from the target value,₂Exhaust gas detected by sensor₂By correcting the fuel injection amount by feeding back the deviation between the concentration and the target value, the error in the oxygen amount or the fuel amount can be canceled.
[0007]
(Means of claim 3)
In the control device of the diesel engine according to claim 1 or 2,
For a diesel engine having a throttle in the intake path, the throttle opening is set to be larger as the target torque obtained from the accelerator opening and the engine speed is larger.
In the conventional diesel engine, after the fuel amount is determined, the throttle opening is determined by the balance between the supercharging pressure and the EGR gas pressure so that the fresh air amount that requires the fuel amount can pass.
[0008]
Therefore, even if the accelerator opening is increased and the injection amount is increased, the throttle opening is not necessarily increased. For example, in the case of an engine with a supercharger, there is a case of accelerator increase → fuel increase → supercharging pressure increase → throttle closing (determined by balance with EGR gas pressure). However, in the present system that determines the fuel injection amount from the oxygen amount sucked into the engine, the flow increases from accelerator to air to fuel to fuel to boost pressure. Therefore, it is necessary to first increase the amount of air. . Therefore, if the throttle opening is set to be increased in accordance with the increase in the target torque, when the accelerator opening is increased, the air is increased and acceleration is obtained.
[0009]
(Means of claim 4)
In the control apparatus of the diesel engine as described in any one of Claims 1-3,
For a diesel engine equipped with a turbocharger with a variable pressure control mechanism that varies the turbo efficiency by a variable throttle mechanism, etc., the larger the target torque required from the accelerator opening and the engine speed, the larger the target boost pressure. The variable pressure control mechanism of the supercharger is feedback-controlled so as to approach the target supercharging pressure.
[0010]
In the case of an engine including a supercharger with a variable pressure control mechanism, the air amount can be increased without increasing the fuel amount by increasing the supercharging pressure. Therefore, if the target boost pressure is set so as to increase as the target torque increases, acceleration is obtained by increasing the accelerator, boosting the boost pressure, increasing the air, and increasing the fuel.
[0013]
  (Claims5Means)
  Claims 1 to4In the control device for any diesel engine described in
  If the actual torque is too low for the target torque obtained from the accelerator opening and the engine speed, the target exhaust O₂Set the concentration to the richer side than normal.
[0014]
For example, even if the accelerator opening is suddenly opened as in sudden acceleration, there is a delay until the actual air enters the cylinder, so the amount of air in the cylinder only increases gradually. For this reason, if only the fuel amount corresponding to this air amount is injected, the fuel amount does not increase according to the accelerator work, and the feeling of acceleration is insufficient. Therefore, when the actual torque is too low relative to the target torque, the target exhaust O₂If the concentration is moved to the rich side, the fuel injection amount increases with respect to the air amount, so that an acceleration feeling can be obtained and deterioration of drivability can be prevented.
[0015]
  (Claims6Means)
  Claims 1 to5In the control device for any diesel engine described in
  When the actual torque is too low for the target torque obtained from the accelerator opening and the engine speed,In a diesel engine that controls the EGR valve to the closed side or has a throttle in the intake path,Control the throttle to the open side orIn a diesel engine having a turbocharger with a variable pressure control mechanism that varies turbo efficiency by a variable throttle mechanism, etc.At least one of the control to the effective side is executed.
[0016]
  Claim5As described above, even if the accelerator opening is suddenly opened during rapid acceleration, the fuel amount does not increase according to the accelerator work, and the feeling of acceleration is insufficient. Therefore, when the actual torque is too low with respect to the target torque, it is sucked into the engine by controlling the throttle to the open side, controlling the EGR valve to the closed side, or controlling the supercharger to the effective side. The amount of fresh air can be increased. As a result, a feeling of acceleration can be obtained, and deterioration of drivability can be prevented.
[0017]
  (Claims7Means)
  Claims 1 to6In the control device for any diesel engine described in
  The control for determining the fuel injection amount from the oxygen amount described in claim 1 is called air priority control, and after the fuel injection amount is obtained from the operating state of the engine, the control for determining the oxygen amount sucked into the engine When we call priority control,
  When the engine is started or idling, the air priority control is switched to the fuel priority control.
[0018]
When starting the engine, the exhaust gas O₂Since startability is more important than adjusting the concentration to the target value, it is necessary to inject a sufficient amount of fuel for quickly starting the engine. Therefore, when starting the engine, it is better to execute fuel priority control in order to improve startability.
When idling (during idling), exhaust gas O₂Since the variation in concentration is relatively small, it is less necessary to make air priority control, and the fuel priority control can directly control the torque, so that it can be said that the rotational speed controllability during idling is better. For this reason, it is better to execute fuel priority control during idling.
[0019]
  (Claims8Means)
  Claims 1 to7In the control device for any diesel engine described in
  The control for determining the fuel injection amount from the oxygen amount described in claim 1 is called air priority control, and after the fuel injection amount is obtained from the operating state of the engine, the control for determining the oxygen amount sucked into the engine When called priority control, when an abnormality occurs in the functions of the intake system and the EGR system necessary for estimating the amount of oxygen taken into the engine, the air priority control is switched to the fuel priority control.
[0020]
When an abnormality occurs in the intake system and the EGR system, for example, if an abnormality occurs in the throttle, EGR valve, air flow meter, etc., the amount of oxygen sucked into the engine cannot be accurately estimated. The amount can vary widely. On the other hand, if the fuel priority control is the same as that of the conventional diesel engine, the fuel injection amount can be obtained from the engine speed and the accelerator opening. The amount does not vary greatly, which is desirable in terms of safety.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing a diesel engine control system.
First, the overall configuration of the system will be described with reference to FIG.
This system is applied to a diesel engine (hereinafter abbreviated as engine 1) having an EGR function (described below) for returning a part of exhaust gas to intake air.
[0022]
The engine 1 employs a common rail type injection system that injects high-pressure fuel accumulated in a common rail (not shown) from an injector 2 attached to a cylinder head of the engine 1 into the combustion chamber 1a.
The EGR function includes an EGR passage 5 that communicates the intake pipe 3 and the exhaust pipe 4, and an EGR valve 6 that adjusts an exhaust gas amount (EGR amount) that recirculates through the EGR passage 5.
[0023]
The intake pipe 3 is provided with an air flow meter 7 and a compressor 8A of a variable turbo 8 upstream from a connection point with the EGR passage 5, and a throttle 9 (diesel throttle) is provided downstream of the compressor 8A. Further, an intake pressure sensor 10 for detecting the intake pressure in the intake pipe 3 and an intake air temperature sensor 11 for detecting the temperature of the intake air are attached downstream of the throttle 9.
The exhaust pipe 4 is provided with an exhaust turbine 8B of the variable turbo 8 downstream from the connection point with the EGR passage 5, and on the downstream side of the exhaust turbine 8B, the exhaust gas O₂O to detect concentration₂A sensor 12 is attached.
[0024]
The air flow meter 7, the intake pressure sensor 10, the intake air temperature sensor 11, and the O₂Each information of the air system detected by the sensor 12 is output to an electronic control device (hereinafter referred to as ECU 13) that controls the operation of the system.
In addition to the above sensors, this system includes a rotation angle sensor 14 that outputs a signal in synchronization with the rotation angle of the engine 1, a water temperature sensor 15 that detects the cooling water temperature of the engine 1, and a depression of an accelerator pedal 16. An accelerator opening sensor 17 or the like for detecting the accelerator opening from the amount is provided, and various pieces of detected information are output to the ECU 13.
[0025]
Next, the control procedure of this system by the ECU 13 will be described below.
First, the overall control flow will be described using the base routine shown in FIG.
When the program starts, the processing of Step 100 is executed after initialization of the program (not shown) is completed.
Step 100... Detects the operating state of the engine 1. Here, sensor information such as the engine speed NE, the accelerator opening, and the coolant temperature is taken in, and it is detected what operating state the engine 1 is currently in.
[0026]
Step 200 ... It is determined whether or not the engine 1 is at the time of starting. For this determination, information such as the number of engine times fetched in Step 100 or a starter signal is used. If it is determined that the engine is starting (YES), the process proceeds to Step 700. If it is determined that the engine is not starting (NO), the process proceeds to Step 300.
Step 300 ... It is determined whether or not the engine 1 is in an idle state. This determination uses information such as the accelerator opening, the idle switch, the vehicle speed, the gear position, and the like. If it is determined that the engine is in the idle state (YES), the process proceeds to Step 700. If it is determined that the engine is not in the idle state (NO), the process proceeds to Step 400.
[0027]
Step 400 ... Detect failure of sensors and actuators of intake system and EGR system. Specifically, abnormalities such as throttle 9, EGR valve 6, air flow meter 7, intake pressure sensor 10 and intake air temperature sensor 11 are output signals from each sensor, electrical circuit connection status (open or short), system operation It is detected by checking. Step500 ... Judge the presence or absence of abnormality from the information captured in Step400. If it is determined that there is an abnormality (YES), the process proceeds to Step 700. If it is determined that there is no abnormality (NO), the process proceeds to Step 600.
[0028]
Step 600: Air priority control is executed (the contents of control will be described later).
Step 700 ... Execute fuel priority control. This fuel priority control is a control performed in a conventional diesel engine. Basically, the fuel injection amount is calculated from the required torque of the engine, and the amount of oxygen drawn into the engine on the assumption of the fuel injection amount ( Including EGR gas). This fuel priority control has been conventionally known and will not be described here.
[0029]
When it is determined at Step 200 that the engine is started, that is, when the engine 1 is started, the exhaust gas O is controlled by the air priority control described later.₂Since startability is more important than adjusting the concentration to the target value, it is necessary to inject a sufficient amount of fuel for quickly starting the engine after fully taking in air with the throttle fully open. Therefore, when the engine is started, it is preferable to execute the fuel priority control because the startability of the engine 1 is improved.
[0030]
When it is determined in step 300 above that the engine is idling, that is, when the engine 1 is idling, the exhaust gas O₂Since the variation in concentration is relatively small, it is less necessary to make air priority control, and the fuel priority control can directly control the torque, so that it can be said that the rotational speed controllability during idling is better. For this reason, fuel priority control is executed during idling. In particular, when load fluctuations such as an air conditioner and an alternator occur during idling, the fuel priority control has an advantage that the idling engine speed can be suppressed to a minimum and the blow-up can be minimized.
[0031]
If it is determined in Step 500 that there is an abnormality, that is, if the intake system and EGR sensors, actuators, etc. fail, the amount of oxygen sucked into the engine 1 cannot be accurately estimated. The fuel injection amount may vary greatly. On the other hand, if the fuel priority control is used, the fuel injection amount can be obtained from the engine speed and the accelerator opening as in the conventional case. Therefore, even if an abnormality occurs in the intake system and the EGR system, the fuel injection amount can be obtained. Does not vary greatly, which is desirable in terms of safety over air priority control. Moreover, since it becomes controllable by the function of fail operable, it can prevent that it becomes impossible to drive | work.
[0032]
Next, the air priority control in Step 600 will be described.
FIG. 3 is a flowchart showing a processing procedure of air priority control.
Step 6010 ... Calculate the target torque TTRG. Here, as shown in the map of FIG. 4, the target torque TTRG required for the engine 1 is calculated from the engine speed NE and the accelerator opening. In general, in a diesel engine, the torque and the fuel injection amount have a one-to-one correspondence. Therefore, the target torque TTRG can be considered by replacing the target injection amount QTRG. However, this target injection amount QTRG is merely a temporary injection amount, and in this embodiment, the fuel injection amount is not determined by this.
[0033]
That is, the target injection amount QTRG is merely used as an argument of various maps, as it means the target torque TTRG on the program in the ECU 13. Recently, torque is often handled as torque even in the program in the ECU 13 (referred to as torque demand control or torque base control). Therefore, in this embodiment, the target torque TTRG will be described as it is. To do.
[0034]
Step6020 ... Control the supercharging pressure. Here, as shown in the map of FIG. 5, the target supercharging pressure PbTRG is calculated from the engine speed NE and the target torque TTRG, and the pressure control mechanism of the variable turbo 8 is controlled using the target supercharging pressure PbTRG as a target value. . Note that this processing is skipped for an engine not equipped with the variable turbo 8.
Step 6030 ... The throttle opening (opening of the throttle 9) is set. Here, as shown in the map of FIG. 6, the throttle opening is calculated from the engine speed NE and the target torque TTRG, and the throttle 9 is controlled so that the throttle opening can be obtained.
[0035]
In general, in a gasoline engine, the throttle opening changes according to the accelerator opening, and the characteristic that the air amount changes straightly according to the accelerator operation is adopted. Is desirable. However, in the case of this embodiment, in order to switch to the fuel priority control at the time of engine start or idling, the throttle 9 is set to fully open at start-up and half open to fully open at idling. However, in the present invention, the throttle 9 is not necessarily a necessary requirement.
[0036]
This is because, in the engine 1 having the EGR function, the EGR rate is usually set higher as the load is lighter. In this case, even if the throttle 9 is not provided, the air amount (fresh air) is as light as possible ( That is, the smaller the accelerator opening, the smaller, and consequently the same result is obtained. However, it is desirable to install the throttle 9 because the torque controllability is far superior.
[0037]
The throttle 9 may be an electronically controlled throttle such as a DC motor, a step motor, or a torque motor, or may be a mechanical throttle that is mechanically linked to the accelerator pedal 16. However, with a mechanical throttle, since the throttle opening at the time of start and at the time of idling is small, the amount of air is reduced, and there is a possibility that startability and idling stability are inferior. However, considering the cost priority, a mechanical throttle can be selected.
[0038]
Step 6040 (EGR control means): The base opening degree of the EGR valve 6 is set. Here, as shown in the map of FIG. 7, the base opening degree of the EGR valve 6 is calculated from the engine speed NE and the target torque TTRG. In this case, the smaller the target torque TTRG (that is, the light load), the larger the base opening degree of the EGR valve 6 is set, and the EGR amount increases.
Step 6050 (EGR rate calculating means, EGR control means)... Calculation of target EGR rate and EGR learning control. In general, when performing highly accurate EGR control, for example, feedback EGR control using an air flow meter signal is used. However, in this embodiment, open loop control or open loop control combined with learning control is used. Is preferable.
[0039]
This is because in the feedback EGR control, the amount of air entering the cylinder fluctuates with time, so the air priority control (target exhaust O₂This is because, in a system in which the fuel amount is set according to the concentration), the variation in the air amount directly leads to the variation in the fuel amount, resulting in unnecessary torque variation. Therefore, it is desirable to use open loop control that is less likely to cause temporal air fluctuations. Alternatively, feedback control with a sufficiently small gain of the feedback control amount may be used.
[0040]
However, because the EGR amount may deviate even if the opening degree of the EGR valve 6 is determined due to the influence of the manufacturing tolerance of the engine 1, in this embodiment, in combination with learning control instead of mere open loop control. Done.
That is, as shown in the map of FIG. 8, the target EGR rate is calculated from the engine speed NE and the target torque TTRG, the deviation is learned so that the current EGR rate becomes equal to the target EGR rate, and the deviation is opened. The opening degree of the EGR valve 6 is determined by adding to the operation amount at the time of control. The current EGR rate is, for example, estimated from the supercharging pressure (intake pressure) the amount of intake air taken into the cylinder, and the difference between the intake amount and the air amount measured by the air flow meter 7 is used as the EGR amount. It can be calculated and calculated by dividing the EGR amount by the intake air amount sucked into the cylinder.
[0041]
As the EGR valve 6, various types such as a negative pressure type, a step motor type, a linear solenoid type, and a DC motor type can be used. In the case of a negative pressure type valve, the duty ratio is a conduction ratio between the negative pressure passage and the atmospheric pressure passage, and this duty ratio can be used as the base opening degree or learning value of the EGR valve 6. In the case of a step motor type, the number of steps can be used as the value. In the case of the linear solenoid type, the duty ratio and current value can be used as the base opening degree and learning value of the EGR valve 6. Further, in the case of a linear solenoid valve with a lift sensor, the lift amount can be used as the base opening degree or learning value of the EGR valve 6.
[0042]
Step6060… Target exhaust at normal time O₂Set the density. Here, as shown in the map of FIG. 9, the target exhaust O during normal operation is calculated from the engine speed NE and the target torque TTRG.₂Set the density. This target exhaust O₂The concentration is determined from the required values of emission requirements and drivability (hereinafter abbreviated as drivability). In the emission area, target exhaust O₂Concentration is determined in conformity to minimize emissions such as NOx, PM, HC, CO, etc., but exhaust O which places more emphasis on drivability in higher load areas where torque demand is high₂The density is set.
[0043]
Step6070… Transition exhaust O₂Correct the density target value. The purpose is to ensure drivability during acceleration. That is, the target torque TTRG is determined by the engine speed NE and the accelerator opening, and the target exhaust O is determined by the target torque TTRG and the engine speed NE.₂Since the concentration is determined, as shown in FIG. 10, when the accelerator opening is opened, the target exhaust O at the steady state is set.₂The concentration (solid line) corresponds to the movement of the accelerator opening.
[0044]
However, even if the accelerator opening is suddenly opened as in sudden acceleration, there is a delay until the actual air enters the cylinder, so the amount of oxygen in the cylinder only increases gradually. For this reason, if only the amount of fuel commensurate with this amount of oxygen is injected, the amount of fuel will not increase according to the accelerator work, and the feeling of acceleration will be insufficient. An engine with NA (natural air supply) is allowed to some extent, but an engine with turbo impairs the feeling of acceleration due to the turbo lag.
[0045]
In the fuel priority control performed in the conventional diesel engine, in order to generate the necessary torque, the necessary amount of fuel is injected first, so the acceleration feeling is excellent, but the exhaust O₂Concentration control accuracy is significantly deteriorated. Therefore, in the present embodiment, the target exhaust O at the time of acceleration.₂Move the concentration to the rich side and exhaust O₂Prevents deterioration of drabbilities while managing the concentration with high accuracy. That is, when the acceleration state is detected, the target exhaust O₂Target exhaust O when the concentration is steady₂Correction is made to a richer side than the density (see FIG. 10).
[0046]
The acceleration state can be detected by the change rate of the accelerator opening, the change rate of the target torque TTRG, or the like. Alternatively, it can be determined that there is an acceleration request when the difference between the target torque TTRG (which can be substituted with the target injection amount) and the actual torque (which can be substituted with the current injection amount) is large. When such a determination is made, the target exhaust O₂Target exhaust O when the concentration is steady₂Shift density to the rich side by a certain amount. At this time, it is desirable to change the shift amount according to the strength of the acceleration state. Alternatively, when the acceleration state is detected, the target exhaust gas O that is predetermined on the rich side for a certain period of time is set.₂A method of fixing the concentration and gradually decreasing the degree of richness is also conceivable.
[0047]
Step6080 (Exhaust O₂Concentration setting means) ... Final target exhaust O₂Set the density. In other words, in the steady state, the value set in Step 6060 is the final target exhaust O.₂If the concentration becomes transient, the value corrected in Step 6070 will be the final target exhaust O₂Concentration.
Step 6090 (oxygen amount estimation means, injection amount calculation means): Calculates the final fuel injection amount. Here, the amount of oxygen sucked into the cylinder is estimated from time to time based on information such as an air flow meter signal. For this estimation, calculation is performed using a transfer function that takes into account the transfer delay of the intake system from the installation position of the air flow meter 7 until air enters the cylinder, or the intake system is expressed by a physical model and calculated by this. A method etc. can be adopted.
[0048]
Further, when EGR is being executed, it is necessary to estimate the amount of oxygen sucked into the cylinder in consideration of the amount of oxygen in the EGR gas contained in the gas sucked into the cylinder. Therefore, in this embodiment, the amount of EGR gas contained in the gas sucked into the cylinder and the oxygen concentration of the EGR gas are obtained.
There are a method of calculating the EGR gas amount based on the target EGR rate calculated in Step 6050, and a method of calculating from the physical model considering the gas balance in the in-manifold from the intake pressure signal and the air flow meter signal.
[0049]
The oxygen concentration of the EGR gas takes into account the delay time of the EGR system from the EGR gas from the EGR passage 5 to the intake pipe 3, and the exhaust gas O in the delay time (that is, the time past from the present).₂Use concentration. Exhaust O₂Concentration is O₂Exhaust gas O predicted by the physical model using the output value of the sensor 12 and the command injection amount information₂Past concentration value or target exhaust O₂Use past values of concentration.
The amount of EGR gas and the EGR gas oxygen concentration thus determined (OGR before the delay time)₂The amount of oxygen in the EGR gas is calculated by multiplying the output value of the sensor 12).
[0050]
Further, the amount of fresh air out of the gas sucked into the cylinder is calculated by the air flow meter signal or the like as described above. The oxygen concentration of the fresh air gas can be obtained from the atmospheric composition, and the oxygen amount in the fresh air gas is obtained by the product of this and the amount of the fresh air gas.
Then, by adding the oxygen amount in the EGR gas and the oxygen amount in the fresh air gas, the oxygen amount in the air amount (fresh air amount + EGR gas amount) taken into the cylinder can be obtained.
The cylinder intake oxygen amount thus estimated and the target exhaust gas O set in Step 6080.₂From the concentration, the required fuel amount (F) can be calculated.
[0051]
Step 6100: Command the injector 2 to inject fuel. The fuel injection amount calculated in Step 6090 is converted into the drive pulse width of the injector 2 and the injector 2 is energized, and fuel injection is performed from the injector 2.
If the estimated oxygen amount has an error, or if an error occurs in the fuel amount due to product tolerance of the injector 2, the exhaust O which is the ratio₂Since the concentration has an error, it is desirable to correct the fuel injection amount so that the influence of the error can be canceled. That is, actually O₂O of exhaust gas detected by the sensor 12₂The actual fuel injection amount can be obtained as QBASE + ΔQF / B by feeding back the correction amount ΔQF / B to the fuel injection amount QBASE calculated in Step 6090 so that the concentration approaches the target value.
[0052]
(Effect of this embodiment)
In this system, the amount of oxygen (including EGR gas) sucked into the engine 1 is estimated, and the fuel injection amount is determined from the amount of oxygen. Therefore, fuel control with quick response is performed for air control with slow response. Can be matched. As a result, compared with the conventional fuel priority control, the exhaust O₂The density can be accurately controlled to the target value. Even if the estimated oxygen amount has an error or an error occurs in the fuel amount due to the product tolerance of the injector 2, etc.₂Exhaust gas O detected by the sensor 12₂By correcting the fuel injection amount by feeding back the deviation between the concentration and the target value, errors in the oxygen amount and the fuel amount can be canceled.₂Concentration controllability can be improved.
[0053]
Further, when the actual torque is too low with respect to the target torque (for example, during acceleration), the target exhaust O₂Since the concentration is set to a richer side than the steady-state value, the lack of acceleration can be solved and dribble deterioration can be prevented. Similarly, when the actual torque is too low with respect to the target torque, at least one of controlling the throttle 9 to the open side, controlling the EGR valve 6 to the closed side, and controlling the variable turbo 8 to the effective side is at least By executing one, it is possible to prevent the deterioration of the drivability.
[0054]
In the conventional feedback EGR control, the feedback gain is set high in order to improve the responsiveness of the EGR valve 6, so that there is a situation where the air amount fluctuates. For this reason, in the air priority control in which the fuel amount is determined from the oxygen amount, when the conventional feedback EGR control is performed, the fuel fluctuates due to the fluctuation of the air amount, and the drivability deteriorates. On the other hand, in the present embodiment, by performing open loop control in which temporal air fluctuation is less likely to occur or open loop control with a learning control function, unnecessary torque fluctuation can be prevented and good drivability can be achieved. It is possible to obtain
[0055]
When the engine is started or idle, the air priority control is switched to the fuel priority control. In other words, when the engine is started, the exhaust air O is controlled by air priority control.₂Since startability is more important than adjusting the concentration to the target value, fuel priority control is executed to improve startability. During idling, exhaust gas O₂Because there is relatively little variation in concentration, there is less need for air priority control and fuel priority control can directly control torque, so fuel priority control is executed instead of air priority control. .
[0056]
Further, when an abnormality occurs in the intake system and the EGR system, the air priority control is switched to the fuel priority control. For example, if an abnormality occurs in the throttle 9, the EGR valve 6, the air flow meter 7, etc., the amount of oxygen sucked into the engine 1 cannot be accurately estimated, so that the fuel injection amount determined from the amount of oxygen may vary greatly. . On the other hand, if the fuel priority control is the same as that of the conventional diesel engine, the fuel injection amount can be obtained from the engine speed and the accelerator opening, so that even if an abnormality occurs in the intake system and the EGR system, the fuel injection is performed. The amount does not vary greatly, which is advantageous in terms of safety.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a control system of a diesel engine.
FIG. 2 is a flowchart showing an overall control flow of the system.
FIG. 3 is a flowchart showing a processing procedure for air priority control.
FIG. 4 is a map for calculating a target torque.
FIG. 5 is a map for calculating a target boost pressure.
FIG. 6 is a map for calculating a throttle opening.
FIG. 7 is a map for calculating a base opening degree of an EGR valve.
FIG. 8 is a map for calculating a target EGR rate.
FIG. 9 Target exhaust O at steady state₂It is a map for calculating a density.
[Fig. 10] Accelerator opening and target exhaust O at steady state and transient time₂It is drawing which shows the correlation with a density | concentration.
[Explanation of symbols]
1 Diesel engine
3 Intake pipe (intake route)
4 Exhaust pipe (exhaust path)
6 EGR valve (intake system function)
7 Air flow meter (intake system function)
8 Variable turbo (supercharger with variable pressure control mechanism)
9 Throttle (intake system function)
12 O₂Sensor
13 ECU (control device)

Claims (8)

A control device for a diesel engine having an EGR function of returning a part of exhaust gas to intake air,
EGR rate calculating means for calculating a target EGR rate based on the operating state of the engine;
EGR control means for controlling an EGR valve included in the EGR function so that the target EGR rate calculated by the EGR rate calculation means is obtained;
An oxygen amount estimating means for estimating an oxygen amount including an EGR gas component sucked into the engine;
Exhaust O ₂ concentration setting means for setting a target O ₂ concentration of the exhaust gas based on the operating state of the engine;
As the target exhaust O ₂ concentration set by the exhaust O ₂ concentration setting means to obtain, possess the injection amount calculating means for calculating a fuel injection amount from the amount of oxygen estimated by the oxygen amount estimating means,
The control method of the EGR valve learns the deviation so that the current EGR rate is equal to the target EGR rate, and adds the deviation to the manipulated variable at the time of open control, or the target physical value A control apparatus for a diesel engine, which is performed by any one of feedback control in which a gain of a feedback control amount for converging to the above is set to be sufficiently small . In the control device of the diesel engine according to claim 1,
An O ₂ sensor for detecting the exhaust O ₂ concentration of the exhaust gas is installed in the exhaust path,
A control device for a diesel engine, wherein the fuel injection amount calculated by the injection amount calculation means is corrected so that the exhaust O ₂ concentration detected by the O ₂ sensor converges to the target exhaust O ₂ concentration. . In the control device of the diesel engine according to claim 1 or 2,
A diesel engine control device, wherein a throttle opening is set to be larger as a target torque obtained from at least an accelerator opening and an engine speed is larger than a diesel engine having a throttle in an intake path. In the control apparatus of the diesel engine as described in any one of Claims 1-3,
For a diesel engine equipped with a turbocharger with a variable pressure control mechanism that varies the turbo efficiency by a variable throttle mechanism, etc., the target boost pressure is increased as the target torque required from at least the accelerator opening and the engine speed is larger. The diesel engine control apparatus performs feedback control of the variable pressure control mechanism of the supercharger so as to approach the target supercharging pressure. In the control apparatus of the diesel engine as described in any one of Claims 1-4,
A control apparatus for a diesel engine, characterized in that the target exhaust O ₂ concentration is set to a richer side than the steady state when the actual torque is too low with respect to the target torque obtained from at least the accelerator opening and the engine speed. . In the control apparatus of the diesel engine in any one of Claims 1-5,
If the actual torque is too low with respect to the target torque obtained from at least the accelerator opening and the engine speed , the throttle valve is opened in a diesel engine that controls the EGR valve to the closed side or has a throttle in the intake path. In a diesel engine equipped with a turbocharger with a variable pressure control mechanism that controls the turbo efficiency by a variable throttle mechanism or the like, at least one of the supercharger is controlled to the effective side is executed Diesel engine control device. In the control apparatus of the diesel engine in any one of Claims 1-6,
The control for determining the fuel injection amount from the oxygen amount according to claim 1 is called air priority control, and after obtaining the fuel injection amount from the operating state of the engine, the control for determining the oxygen amount sucked into the engine Is called fuel priority control,
A diesel engine control device that switches from the air priority control to the fuel priority control when the engine is started or idling . In the control apparatus of the diesel engine in any one of Claims 1-7,
The control for determining the fuel injection amount from the oxygen amount according to claim 1 is called air priority control, and after obtaining the fuel injection amount from the operating state of the engine, the control for determining the oxygen amount sucked into the engine Is called fuel priority control,
A control apparatus for a diesel engine , wherein when an abnormality occurs in functions of an intake system and an EGR system necessary for estimating an oxygen amount taken into the engine, the air priority control is switched to the fuel priority control. .

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