JP4000923B2 - Inlet throttle valve control device for turbocharged diesel engine for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an intake throttle valve control device for a turbocharged diesel engine for a vehicle, and more particularly to a technique for preventing deterioration of smoke, etc. that occurs immediately after shifting to an acceleration operation due to an insufficient air amount in a cylinder.
[0002]
[Prior art]
In a conventional typical diesel engine, intake throttling is not performed, and the intake air amount (fresh air amount) introduced into the cylinder depends solely on the magnitude of the negative pressure generated by the lowering of the piston. For this reason, the air-fuel ratio (air excess ratio) tends to increase on the low load side where the fuel injection amount is small, and the air-fuel ratio tends to decrease on the high load side where the fuel injection amount is large.
[0003]
On the other hand, in recent years, intake throttles are being adopted due to stricter exhaust gas regulations and requirements for aftertreatment. The intake throttle is achieved by appropriately closing an intake throttle valve (intake throttle valve) provided in the intake passage of the engine.
[0004]
In recent diesel engines, EGR using an EGR device (exhaust gas recirculation device) has become common. The EGR device mainly includes an EGR passage connecting an intake passage and an exhaust passage of the engine, and an EGR valve provided in the EGR passage.
[0005]
The higher the EGR rate (the ratio of the exhaust gas flow rate to the intake air amount (fresh air amount)), the more slowly the combustion in the cylinder becomes, and NOx can be reduced. However, when the engine is turbocharged, the exhaust gas inlet in the intake passage is downstream from the compressor. This is because if it is located upstream, the compressor is corroded by exhaust gas, and the intake air temperature rises and the intake efficiency decreases. For this reason, the difference between the exhaust pressure and the intake pressure is reduced, and the EGR rate cannot be increased. In addition, since the pressure difference is small, there is a limit to the EGR rate control by the EGR valve opening control.
[0006]
Therefore, an intake throttle valve is provided on the upstream side of the exhaust gas inlet of the intake passage, and by performing the intake throttle, a negative pressure is generated on the downstream side of the intake throttle valve, thereby increasing the pressure difference and increasing the EGR rate. be able to. Further, by controlling the intake throttle valve and the EGR valve toward the target EGR rate, the actual EGR rate can be controlled near the target EGR rate.
[0007]
On the other hand, in a diesel engine, the air-fuel ratio (A / F) in the cylinder is generally higher than the theoretical air-fuel ratio (14.3), and air is always excessive with respect to the fuel amount. However, in recent diesel engines, there is an example in which a catalyst is installed in the exhaust passage. In this case, if there is too much excess oxygen, the function as a catalyst may deteriorate, and the oxygen amount in the exhaust gas is adjusted to be small. May be preferred.
[0008]
Accordingly, a means for detecting the intake air amount, for example, an air mass sensor, is provided in the intake passage, and the actual air-fuel ratio is calculated from the detected intake air amount and the actual fuel injection amount, and the actual air-fuel ratio becomes the target. A technique for feedback control of the intake throttle valve has been developed so as to match the air-fuel ratio.
[0009]
In some cases, a desired air-fuel ratio and EGR rate are obtained by controlling the opening of the intake throttle valve and the opening of the EGR valve.
[0010]
[Problems to be solved by the invention]
By the way, when the engine operating state shifts from the steady state to the acceleration operation, the fuel injection amount is immediately increased, and the intake throttle valve is also opened in accordance with this increase, so that the intake air amount is increased. However, since a certain amount of time is required for opening the intake throttle valve, a time lag occurs until the amount of air in the cylinder is actually increased. Therefore, immediately after the shift to the acceleration operation, the inside of the cylinder is short of air for a moment, so that smoke worsens, unburned fuel (HC) is discharged, and CO worsens due to incomplete combustion.
[0011]
As a countermeasure, there is a method of increasing the amount of fuel after waiting for the amount of air in the cylinder to increase. However, this deteriorates drivability and makes the driver uncomfortable. In particular, in an engine with a turbocharger, there is a time lag (called a turbo lag) between the increase in fuel and the increase in supercharging pressure until the intake air amount increases, so the increase in intake air tends to be delayed. It is.
[0012]
In order to solve the above problems, in the technique disclosed in Japanese Patent Application Laid-Open No. 62-240436, the acceleration state is detected based on the rate of change of the accelerator operation amount. It is corrected to. As a result, the intake throttle valve is opened larger than usual in the acceleration state, so the amount of intake air introduced into the cylinder is increased.
[0013]
However, even in this technique, the correction of the increase in the opening of the intake throttle valve is started at the same time as the acceleration state is detected. Therefore, the opening is relatively small as in the case where the correction is not performed immediately after the transition to the acceleration operation. The shortage of air volume shortly after the transition to operation cannot be solved.
[0014]
Accordingly, the present invention has been devised in view of the above problems, and an object of the present invention is to prevent an instantaneous air amount shortage immediately after shifting to an acceleration operation, smoke deterioration due to this, and the like.
[0015]
[Means for Solving the Problems]
The present invention is an apparatus for controlling an intake throttle valve provided in an intake passage of a turbocharged diesel engine for a vehicle, and includes a detection means for detecting an operating state of the engine and the vehicle, and a target air condition based on the operating state. Target air-fuel ratio determining means for determining the fuel ratio; actual air-fuel ratio determining means for determining the actual air-fuel ratio based on the operating state; and feedback of the intake throttle valve based on the deviation between the target air-fuel ratio and the actual air-fuel ratio Control means for controlling, determination means for determining whether or not the actual engine operating state is an acceleration pre-stage based on the operation state, and when the determination means determines that the acceleration pre-stage is an acceleration pre-stage, not equal compared with the case where it is determined, and a valve opening degree changing means for changing the side to open the opening degree of the intake throttle valve controlled by said control means, said detecting means, shift Includes a gear position detecting means for detecting a gear position, the acceleration pre-step judging means, when the gear position is equal to or greater than a predetermined stage to provide a stuff judged not to be accelerated advance stage.
The present invention is an apparatus for controlling an intake throttle valve provided in an intake passage of a turbocharged diesel engine for a vehicle, and includes a detection means for detecting an operating state of the engine and the vehicle, and a target air condition based on the operating state. Target air-fuel ratio determining means for determining the fuel ratio; actual air-fuel ratio determining means for determining the actual air-fuel ratio based on the operating state; and feedback of the intake throttle valve based on the deviation between the target air-fuel ratio and the actual air-fuel ratio Control means for controlling, determination means for determining whether or not the actual engine operating state is a pre-acceleration stage based on the operation state, and when the pre-acceleration stage is determined by the determination means, the pre-acceleration stage Compared to a case where it is determined that the opening is not open, the valve opening changing means for changing the opening of the intake throttle valve controlled by the control means to the open side is provided. A gear position detecting means for detecting a gear position; a vehicle speed detecting means for detecting a vehicle speed; and a brake detecting means for detecting the presence / absence of a brake operation, wherein the determining means is configured such that the gear position is not neutral or the vehicle speed is When it is above a predetermined value, when there is no brake operation, and when the gear position is smaller than a predetermined step, it is determined that it is an acceleration pre-step.
[0016]
According to the present invention, since the opening of the intake throttle valve is previously opened from the normal stage during the acceleration pre-stage, the intake throttle valve has already been opened larger than usual at the moment of shifting to the acceleration state, As a result, the delay in opening the intake throttle valve is substantially prevented, and an instantaneous air shortage immediately after acceleration can be prevented.
[0022]
Preferably, the detection means includes engine rotation speed detection means for detecting an engine rotation speed and accelerator opening detection means for detecting an accelerator opening, and the intake throttle valve control device includes the engine rotation speed and the engine rotation speed. A target fuel injection amount determining means for determining a target fuel injection amount based on an accelerator opening, wherein the target air-fuel ratio determining means is based on a predetermined map based on the engine speed and the target fuel injection amount; The target air-fuel ratio is determined, and the map includes a first map used when not in the acceleration pre-stage and a second map used when in the acceleration pre-stage, and the second map is the first map The value of the target air-fuel ratio in the predetermined region is set higher than that of the one map, and the valve opening degree change means determines whether or not the determination by the determination means is an acceleration pre-stage. Therefore, by switching between the first map and the second map and switching to the second map at the pre-acceleration stage, the intake throttle valve is opened in the predetermined region compared to when not at the pre-acceleration stage. Change the degree to the open side.
[0023]
Preferably, the predetermined region is a region where the engine speed is low and the target fuel injection amount is small.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[0025]
FIG. 1 shows the entire engine according to the present embodiment. This engine is a turbocharged diesel engine for a vehicle, and in the case of this embodiment, is a multi-cylinder common rail direct injection diesel engine.
[0026]
An engine main body 1 includes a cylinder 2, a cylinder head 3, a piston 4, an intake port 5, an exhaust port 6, an intake valve 7, an exhaust valve 8, an injector 9, and the like. A combustion chamber 10 is formed in the cylinder 2, and fuel is directly injected from the injector 9 into the combustion chamber 10. A cavity 11 is formed at the top of the piston 4, and the cavity 11 forms a part of the combustion chamber 10. The injector 9 is positioned substantially coaxially with the cylinder 2 and injects fuel radially from a plurality of injection holes simultaneously. The intake port 5 forms part of the intake passage 12, and the exhaust port 6 forms part of the exhaust passage 13.
[0027]
The engine is provided with a turbocharger (turbocharger) 14. The turbocharger 14 includes a turbine 15 provided in the exhaust passage 13 and a compressor 16 connected coaxially thereto. The turbocharger 14 rotationally drives the turbine 15 by using exhaust energy, and thereby rotationally drives the compressor 16. The intake air in the intake passage 12 is supercharged. Means for detecting the intake air amount (fresh air amount), for example, an air mass sensor 17 is provided upstream of the compressor 16, and an intercooler 18 for cooling the intake air is provided downstream of the compressor 16. The turbocharger may be a variable capacity type having a movable vane or the like at the turbine inlet, for example.
[0028]
The engine further includes an EGR device 19. The EGR device 19 includes an EGR passage 20 that connects the intake passage 12 and the exhaust passage 13, and an EGR valve 21 provided in the EGR passage 20 to adjust the EGR amount. The intake passage 12 is provided with an intake throttle valve 23 for restricting the amount of intake air passing through the intake passage 12 by restricting the passage area. The intake throttle valve 23 is located in the intake passage 12 on the upstream side of the connection position between the EGR passage 20 and the intake passage 12.
[0029]
The EGR valve 21 and the intake throttle valve 23 include actuators for operating the respective valve bodies. The actuator of the present embodiment is an electrical one. For the EGR valve 21, for example, an electromagnetic solenoid, and for the intake throttle valve 23, for example, a step. A motor is used. However, the type of actuator is not particularly limited, and may be a negative pressure actuator, for example.
[0030]
The injector 9 is connected to the common rail 24, and high-pressure fuel (20 to 200 MPa) corresponding to the injection pressure stored or accumulated in the common rail 24 is constantly supplied to the injector 9. Fuel pumping to the common rail 24 is performed by a high-pressure supply pump pump 25.
[0031]
This engine is provided with detection means for detecting an actual driving state of the engine or the vehicle. As shown in the figure, the detection means includes an engine rotation sensor, an accelerator opening sensor, a gear position sensor, a brake pedal sensor, a vehicle speed sensor, and a common rail pressure sensor 30. These sensors are connected to an electronic control unit (hereinafter referred to as ECU) 26, and the ECU 26 grasps the actual driving state based on the output signals of these sensors.
[0032]
The engine rotation speed (or rotation speed (rpm)) is detected by the engine rotation sensor, the accelerator opening or the accelerator operation amount is detected by the accelerator opening sensor, the gear position of the transmission is detected by the gear position sensor, and the brake pedal The sensor detects the operating state of the brake by the driver, the vehicle speed sensor detects the vehicle speed, and the common rail pressure sensor 30 detects the common rail fuel pressure (common rail pressure).
[0033]
The ECU 26 controls a metering valve (not shown) for adjusting the fuel pumping amount from the injector 9, the EGR valve 21, the intake throttle valve 23, and the high-pressure supply pump 25 based on the detected operating state.
[0034]
Incidentally, the ECU 26 performs feedback control of the intake throttle valve 23 based on the deviation between the target air-fuel ratio (target A / F) and the actual air-fuel ratio (actual A / F). The target air-fuel ratio is determined in accordance with predetermined target A / F maps 1 and 2 as shown in FIG.
[0035]
As will become clear later, the two target A / F maps are prepared whether the current or actual engine operating state is in the pre-acceleration stage, in other words, the possibility of engine acceleration in the future. This is because the map is switched depending on whether or not the engine is in a high operating state, thereby switching the target air-fuel ratio.
[0036]
The target A / F map 1 is a basic map that is used when the operating state is not the pre-acceleration stage (this is referred to as a normal state). As shown in the figure, the target A / F map 1 has a constant target air-fuel ratio B1 (for example, B1 = 22). ) Is preset. On the other hand, the target A / F map 2 is a map used when the operating state is the pre-acceleration stage. As shown in the figure, the target A / F map 2 is an operation in which the engine speed Ne is low and the target fuel injection amount Qbase is low. A target air-fuel ratio B2 (for example, B2 = 35) higher than the normal value B1 is set in the region, and a normal value B1 is set in the other operation regions.
[0037]
Hereinafter, the control method of the intake throttle valve in this engine will be described based on the flowchart of FIG. This control flow is executed by the ECU 26.
[0038]
First, in step 101, the ECU 26 reads the values of the current engine speed Ne, the accelerator opening Acc, the intake air amount M, the gear position Gr, and the vehicle speed V, respectively.
[0039]
Next, in step 102, the target fuel injection amount Qbase is determined. This determination is made according to a target fuel injection amount calculation map as shown in the figure based on the values of the engine speed Ne and the accelerator opening Acc.
[0040]
Thereafter, in steps 103 to 105, it is determined whether or not the current engine operating state is the pre-acceleration stage.
[0041]
In step 103, it is determined whether or not the gear position Gr is N (neutral) and the vehicle speed V is smaller than a predetermined value V1 (for example, 20 km / h). If yes (Y), it is determined that the acceleration pre-stage is not reached, and the routine proceeds to step 109 where the target air-fuel ratio is determined according to the target A / F map 1. If no (N), the process proceeds to step 104.
[0042]
In step 104, it is determined whether or not there is a brake operation by the driver based on the output signal of the brake pedal sensor. In the case of yes (Y), it is determined that it is not the pre-acceleration stage, and the process proceeds to step 109 and the target air-fuel ratio is determined according to the target A / F map 1 as described above. If no (N), the process proceeds to step 105.
[0043]
In step 105, it is determined whether or not the gear position Gr is greater than or equal to a predetermined stage (in this embodiment, the third speed (3rd)). In the case of yes (Y), it is determined that it is not the pre-acceleration stage, and the process proceeds to step 109 and the target air-fuel ratio is determined according to the target A / F map 1 as described above. If no (N), the process proceeds to step 106.
[0044]
As described above, when all of the steps 103 to 105 are NO (N), that is, when it is determined that the state is not in the pre-acceleration stage, or when it is not determined that it is not the pre-acceleration stage, the pre-acceleration stage In step 106, the target air-fuel ratio is determined according to the target A / F map 2.
[0045]
As shown in the figure, the target A / F maps 1 and 2 are parameters of the engine speed Ne and the target fuel injection amount Qbase. Therefore, when the target air-fuel ratio is determined in steps 106 and 109, the value of the current engine speed Ne read in step 101 and the target fuel injection amount Qbase determined in step 102 are set as target A. The value of the target air-fuel ratio is determined in comparison with the / F maps 1 and 2.
[0046]
If the target air-fuel ratio value is determined in this way, the routine proceeds to step 107, where the calculation based on the intake air amount (M / cyl) per cylinder based on the intake air amount M and the target fuel injection amount Qbase is performed. The actual air-fuel ratio (actual A / F) as a result is determined.
[0047]
Thereafter, the routine proceeds to step 108, where the intake throttle valve is feedback-controlled based on the deviation between the target air-fuel ratio and the actual air-fuel ratio. As a result, the intake throttle valve is controlled so that the actual air-fuel ratio approaches the target air-fuel ratio.
[0048]
Thus, according to the above control, the target A / F map 2 is selected when the operating state is the pre-acceleration stage, and in this target A / F map 2, the engine speed Ne is low and the target fuel injection amount is selected. In the region where Q is on the small amount side (this corresponds to the case where the engine is on the low rotation / low load side), the target air-fuel ratio is a value B2 higher than the normal value B1, so the operating state is in the pre-acceleration stage. In some cases and in the above range, the opening of the intake throttle valve is controlled in advance to the opening side from the normal state, and the actual air-fuel ratio is also controlled to a value B2 higher than the normal value B1. As a result, the intake throttle valve is already opened larger than the normal state at the moment of shifting to the acceleration operation, the time delay of the opening operation of the intake throttle valve is eliminated, and even if the fuel is increased immediately after shifting to the acceleration operation, It is possible to prevent air shortage in the cylinder for a moment. Therefore, it is possible to prevent instantaneous smoke deterioration immediately after the transition to acceleration operation, unburned fuel (HC) emission, and CO deterioration.
[0049]
In particular, in an engine with a turbocharger as in the present embodiment, there is a turbo lag in combination with a delay in operation of the intake throttle valve at the time of transition to acceleration operation. This solves that problem. Therefore, the above control is particularly effective for the turbocharged engine.
[0050]
On the other hand, when the operating state is not in the pre-acceleration stage or not in the above range, the intake throttle valve is controlled as usual, so that the effect of the intake throttle described above is normal in the operating range where turbo lag and exhaust gas deterioration do not become a problem. Can be enjoyed.
[0051]
Various other embodiments of the present invention are conceivable. For example, in the above embodiment, when the operating state is the pre-acceleration stage, the map is switched to the map (map 2) in which the high target air-fuel ratio is set. Instead, when the operating state is the pre-acceleration stage It is also possible to obtain a higher target air-fuel ratio by adding a predetermined correction amount to the value of the basic map (map 1). Specifically, an opening-side correction amount ΔB is added to the target air-fuel ratio value B1 of map 1 to obtain a new target air-fuel ratio value.
[0052]
Further, in this embodiment, as understood from the target A / F map 2, the intake throttle valve opening degree is set only in the engine operation region where the engine speed Ne is the low speed side and the target fuel injection amount Q is the small side. Although the engine operating area is changed to the opening side, the engine operation area can be appropriately changed according to circumstances, and can be, for example, the entire area.
[0053]
In addition to the above, there are various methods for determining whether or not it is the pre-acceleration stage. In the above-described embodiment, steps 103 and 104 can be omitted.
[0054]
【The invention's effect】
In short, according to the present invention, an excellent effect is exhibited that it is possible to prevent an instantaneous air amount shortage immediately after shifting to an acceleration operation and a smoke deterioration caused by this.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating an engine according to an embodiment.
FIG. 2 is a flowchart showing the contents of intake throttle valve control according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine main body 14 Turbocharger 17 Air mass sensor 23 Intake throttle valve 26 Electronic control unit Gr Transmission gear position V Vehicle speed V1 Predetermined value of vehicle speed Ne Engine rotation speed Acc Accelerator opening Qbase Target fuel injection amount

Claims (4)

A device for controlling an intake throttle valve provided in an intake passage of a turbocharged diesel engine for a vehicle,
Detecting means for detecting the operating state of the engine and the vehicle;
Target air-fuel ratio determining means for determining a target air-fuel ratio based on the operating state;
An actual air-fuel ratio determining means for determining an actual air-fuel ratio based on the operating state;
Control means for feedback controlling the intake throttle valve based on the deviation between the target air-fuel ratio and the actual air-fuel ratio;
Determination means for determining whether or not the actual engine operating state is a pre-acceleration stage based on the operating state;
When it is determined by the determining means that the pre-acceleration stage is reached, the opening degree of the intake throttle valve that is controlled by the control means is changed to the open side compared to the case where it is determined that the pre-acceleration stage is not reached and a change means,
The detection means includes gear position detection means for detecting a gear position of the transmission, and the acceleration preliminary stage determination means determines that the acceleration prior stage is not an acceleration preliminary stage when the gear position is equal to or greater than a predetermined stage. An intake throttle valve control device for a turbocharged diesel engine for vehicles. An apparatus for controlling an intake throttle valve provided in an intake passage of a turbocharged diesel engine for a vehicle,
Detecting means for detecting the operating state of the engine and the vehicle;
Target air-fuel ratio determining means for determining a target air-fuel ratio based on the operating state;
An actual air-fuel ratio determining means for determining an actual air-fuel ratio based on the operating state;
Control means for feedback controlling the intake throttle valve based on the deviation between the target air-fuel ratio and the actual air-fuel ratio;
Determination means for determining whether or not the actual engine operating state is a pre-acceleration stage based on the operating state;
When the determination means determines that it is the pre-acceleration stage, the valve opening degree changes the opening degree of the intake throttle valve controlled by the control means to the open side compared to the case where it is determined that it is not the pre-acceleration stage Change means and
With
The detection means includes gear position detection means for detecting a gear position of the transmission, vehicle speed detection means for detecting a vehicle speed, and brake detection means for detecting presence or absence of a brake operation, and the determination means includes the gear position detection means. Is not neutral, or when the vehicle speed is equal to or higher than a predetermined value, when the brake operation is not performed, and when the gear position is smaller than a predetermined step, it is determined that the vehicle is in a pre-acceleration step. An intake throttle valve control device for a turbocharged diesel engine for vehicles. The detection means includes engine rotation speed detection means for detecting engine rotation speed, and accelerator opening detection means for detecting accelerator opening,
A target fuel injection amount determining means for determining a target fuel injection amount based on the engine speed and the accelerator opening;
The target air-fuel ratio determining means determines the target air-fuel ratio according to a predetermined map based on the engine speed and the target fuel injection amount, and the map is used when the acceleration pre-stage is not in progress. And a second map used in the acceleration pre-stage, the second map has a target air-fuel ratio value in a predetermined region set higher than the first map,
The valve opening changing means switches between the first map and the second map depending on whether or not the determination by the determining means is in the acceleration pre-stage, and in the acceleration pre-stage, the second map is changed to the second map. 3. The intake throttle valve control for a turbocharged diesel engine for a vehicle according to claim 1 or 2 , wherein the opening degree of the intake throttle valve in the predetermined region is changed to an open side by switching, as compared to a case where the acceleration pre-stage is not performed. apparatus. The intake throttle valve control device for a turbocharged diesel engine for a vehicle according to claim 3 , wherein the predetermined region is a region where the engine speed is low and the target fuel injection amount is small .

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