JP2008190362A - Turbocharger drive control method and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely avoid the worst state such as the extreme deterioration of functions of a turbocharger even if a special traveling state brings about an excessive supercharging pressure state temporarily. <P>SOLUTION: When it is determined that actual charging pressure exceeds a determination threshold A (S204), each of a negative constant used in the calculation of an I term in PID control and a negative constant used in the calculation of a P term is increased by multiplying an increase correction coefficient determined differential pressure between the actual charging pressure and target charging pressure determined according to the operation state of an engine (S206), a delay in a region where the charging pressure exceeds the determination threshold A is reduced as much as possible so as to achieve decompression, and each of the negative constants is returned to an ordinary value when it is lower than a determination threshold B (S212). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turbocharger drive control method and apparatus for use in an internal combustion engine, and more particularly, to an improvement in safety and reliability.

A turbine is provided in an exhaust passage of an internal combustion engine such as a diesel engine, and this is rotated by the flow of exhaust gas to obtain a rotational driving force. A compressor disposed in the intake passage is driven by the rotational driving force to Various turbochargers (superchargers) configured to forcibly send air into an engine have been proposed and put into practical use as effective means for measures against emissions of internal combustion engines.
In recent years, a variable turbocharger that can adjust the turbine efficiency and control the supercharging pressure by using a variable turbine provided with a vane that can change the angle with respect to the flow of exhaust gas has been widely adopted. (See, for example, Patent Document 1).

By the way, in a vehicle, acceleration or deceleration is performed from a normal running state, and the engine rotation may change temporarily. However, in a turbocharger, such a change in engine rotation that can normally occur is observed. In consideration of this, since the operation is controlled, there is no temporary deterioration of the function of the turbocharger even though it may temporarily overspeed.
However, overcharge of the turbocharger may occur due to a failure in the turbocharger system, etc., leading to a decrease in function and the like. Various controls for preventing such a situation have been proposed (see, for example, Patent Document 2). ).

JP 2001-65358 A (page 4-12, FIGS. 1 to 24) Japanese Patent Laid-Open No. 5-10149 (page 2-4, FIGS. 1 to 5)

  However, for example, when the engine speed suddenly increases due to slipping on snowy roads, muddy roads or gravel roads, the conventional turbocharger operation control is suitable engine operating conditions, in other words, However, it was difficult to achieve an appropriate supercharging pressure state, leading to an extreme deterioration in the function of the turbocharger, and it was difficult to say that the responsiveness to a special running state was sufficient.

  The present invention has been made in view of the above circumstances, and even in a temporary running state of excessive supercharging pressure due to a special running state, the worst state such as an extreme deterioration of the turbocharger is surely ensured. A turbocharger drive control method and apparatus that can be avoided are provided.

In order to achieve the above object of the present invention, a turbocharger drive control method according to the present invention comprises:
A turbocharger drive control method in a turbocharger drive control device configured such that a supercharging pressure can be varied,
When performing feedback control based on PID control so that the actual supercharging pressure becomes a target pressure determined according to the operating state of the engine,
When the actual supercharging pressure exceeds a predetermined determination threshold, at least one of the operation constant used for the calculation of the I term and the operation of the P term in the PID control is increased. It will be.
In order to achieve the above object, a turbocharger drive control device according to the present invention includes:
A turbocharger drive control device comprising a turbocharger and a control unit for controlling the operation of the turbocharger, and configured to be able to control a supercharging pressure by the operation control of the turbocharger,
When the control unit performs feedback control of the turbocharger based on PID control so that the actual supercharging pressure input from the outside becomes a target pressure determined according to the operating state of the engine, the actual supercharging pressure Is determined to exceed a predetermined determination threshold, at least one of the operation constant used for the calculation of the I term and the operation of the P term in the PID control is increased. Is.

  According to the present invention, the supercharging pressure is a predetermined determination threshold value in a special running state that cannot be dealt with by the normal control so far, such as when the engine rotation suddenly increases due to slipping during running on snow, slack on the road or gravel road In order to reduce the stagnation in the region where the actual supercharging pressure exceeds the predetermined determination threshold as much as possible, among the operation constants used for the I term calculation and the P term calculation in PID control, Since at least one of them is increased, even if the supercharging pressure exceeds a predetermined judgment threshold, unlike the conventional case, the supercharging pressure is quickly reduced to an appropriate level, and the supercharger Thus, it is possible to reliably avoid such a situation that causes a decrease in the function, and to achieve turbocharger drive control excellent in responsiveness, reliability, and the like.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 6.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
Initially, the structural example of the turbocharger drive control apparatus in embodiment of this invention is demonstrated, referring FIG.

In the embodiment of the present invention, the turbocharger 1 is a so-called variable turbocharger, and although not shown, a variable turbine (not shown) having a vane (not shown) whose angle with respect to the flow of exhaust gas can be adjusted. And a compressor (not shown) that is rotationally driven by the rotational driving force of the variable turbine and pumps intake air.
The vane (not shown) is provided with a negative pressure turbo actuator (indicated as “T-ACT” in FIG. 1) 2 so that the angle with respect to the flow of the exhaust gas can be adjusted.

  Exhaust gas from an engine 3 as an internal combustion engine typified by a diesel engine is exhausted through a turbocharger 1, while intake air is taken in through an intake manifold (“IN-MANI” in FIG. 1). And 4).

On the other hand, a negative pressure tank 6 is provided for introducing negative pressure to the turbo actuator 2 and an electromagnetic vacuum adjusting valve (in FIG. 1) is used to control the amount of negative pressure introduced from the negative pressure tank 6 to the turbo actuator 2. Is indicated as “EVRV”) 5.
The operation of the electromagnetic vacuum adjusting valve 5 is controlled by an engine control unit (indicated as “ECU” in FIG. 1) 7 (details will be described later).

The engine control unit 7 includes a microcomputer (not shown) having a known and well-known configuration, a storage element (not shown) such as RAM and ROM, and an input / output force interface circuit (not shown). (Not shown) as a main component.
The engine control unit 7 is configured to execute control processing by various software necessary for the operation of the engine 3, and turbocharger drive control described later is executed as one of the control processing. Yes.

The engine control unit 7 includes an output signal from the atmospheric pressure sensor 11, an output signal from the rotation sensor 12 that detects the number of revolutions of the engine 3, and an intake pressure sucked into the intake manifold 4 for the control process described above. An output signal of the intake pressure sensor 13 that detects the above is input.
The engine control unit 7 outputs an intake air compression ratio control signal as an operation control signal to the electromagnetic vacuum adjustment valve 5 by executing software for turbocharger drive control processing, which will be described later, and controls its operation. ing.

  That is, the valve opening degree of the electromagnetic vacuum adjusting valve 5 is controlled by the engine control unit 7, and the amount of negative pressure introduced to the turbo actuator 2 is changed by adjusting the valve opening degree. The change in the amount of negative pressure introduced to the turbo actuator 2 changes the angle of the vane (not shown) with respect to the exhaust gas flow, thereby changing the rotational efficiency of the variable turbine (not shown), and the compressor (see FIG. The compression rate of the intake air by (not shown) can be changed.

FIG. 2 shows a subroutine flowchart showing the procedure of the turbocharger drive control process executed by the engine control unit 7. Hereinafter, the processing contents will be described with reference to FIG.
When the process is started, first, it is determined whether or not the target injection amount Qt exceeds a predetermined threshold value Qth up that requires control of the supercharging pressure (turbo pressure) by the turbocharger 2 (FIG. 2). (See step S102).
The above-mentioned threshold value as a reference for determining whether or not turbocharger drive control is required is dynamically calculated from a predetermined arithmetic expression or map based on the engine speed and gear ratio, for example. It is preferable that it is calculated.

  In the embodiment of the present invention, since the engine control unit 7 controls the operation of the engine 3, the data such as the target fuel injection amount and the gear ratio are the data of the engine control. The result of the software execution process can be diverted. Accordingly, there is no need to calculate the target fuel injection amount in step S102, and no special processing for determining the gear ratio is necessary.

Here, in the embodiment of the present invention, a so-called hysteresis is provided as a threshold for determining whether or not the target injection amount requires control of the supercharging pressure from the viewpoint of ensuring operational stability. The value Qth up is the upper threshold value.
When it is determined in step S102 that the target injection amount Qt exceeds the threshold value Qth up (in the case of YES), the process proceeds to the processing of step S104 described below, while the target injection amount Qt is the threshold value. If it is determined that Qth up is not exceeded (in the case of NO), the process proceeds to step S106 described later.

In step S104, the turbo pressure control output is calculated.
In other words, the magnitude of the control signal for the electromagnetic vacuum adjusting valve 5 is calculated.
In the embodiment of the present invention, when the process proceeds to step S104 in response to the determination in step S102 that the target injection amount Qt has exceeded the threshold value Qth up, the turbo pressure control output On the other hand, feedback control and feedforward control by PID control are performed.

In the embodiment of the present invention, as shown in FIG. 4 as an example, a region where turbo pressure control is performed only by feedforward control using the engine speed and the target injection amount as parameters (see the hatched portion in FIG. 4). ) And an area to be controlled by using both feedback control and feedforward control.
As described above, when the feedforward control only is used, when the feedforward control and the feedback control are used in combination, and when the engine speed and the target injection amount are used as parameters, two control modes are used in the low load region. As the air pressure becomes unstable, the supercharging pressure correlated with the engine exhaust pressure also becomes unstable. For this reason, it is necessary to avoid feedback control based on an unstable supercharging pressure.

When turbo pressure control is performed by using both feedback control and feedforward control, the P term, I term, and D term obtained by PID control are added to the turbo pressure control output determined by feedforward control. The calculation result is the turbo pressure control output in step S104.
On the other hand, in step S106, the turbo pressure control output is a value determined by feedforward control.

After execution of the process in step S104 or step S106, the process proceeds to the process in step S108, and the turbo pressure control output limiting process is executed.
That is, first, from the viewpoint of ensuring stable engine operation and the like, a predetermined arithmetic expression or map set in advance based on the engine speed, the fuel injection amount, and the total fuel consumption from the start of the engine start. Thus, an upper limit value and a lower limit value for limiting the turbo pressure control output are calculated.

Next, output restriction is executed as described below by comparing the turbo pressure control output calculated in the previous step S104 or step S106 with these upper limit values or lower limit values.
That is, when the turbo pressure control output calculated in the previous step S104 or step S106 is smaller than the above lower limit value, the final turbo pressure control output is set to the lower limit value.

When the turbo pressure control output calculated in the previous step S104 or step S106 is larger than the above upper limit value, the final turbo pressure control output is set to the upper limit value.
If the turbo pressure control output calculated in the previous step S104 or step S106 is in a range smaller than the above upper limit value and larger than the above lower limit value, the calculated turbo pressure control is performed. The output is supposed to be the final output.

  In the embodiment of the present invention, the operation of the electromagnetic vacuum adjustment valve 5 is controlled by PWM control, i.e., so-called duty ratio control that changes the width of the pulse signal with respect to the repetition period. The valve opening state of the electromagnetic vacuum adjusting valve 5 is variable. Therefore, the turbo pressure control output for the electromagnetic vacuum adjusting valve 5 is a so-called duty output.

  After the execution of step S108 as described above, the process once returns to the main routine (not shown), the operation of the electromagnetic vacuum adjustment valve 5 is controlled by the turbo pressure control output determined in step S108, and the turbocharger 1 performs supercharging. The pressure is set according to the operation.

FIG. 3 is a subroutine flowchart showing a procedure of calculation constant setting processing in the PID control used for the feedback control described above, and the contents thereof will be described below with reference to FIG.
When the process is started by the engine control unit 7, the determination threshold A is calculated (see step S202 in FIG. 3). Here, the determination threshold A is whether or not the supercharging pressure is greater than the required level, that is, in the embodiment of the present invention, it is in a special running state as described later, and PID control is performed. This is a criterion for determining whether or not the operation constants are required to be switched.
In the embodiment of the present invention, as the calculation method of the determination threshold A, a desired method can be selected from two calculation methods. That is, the calculation method is selected, for example, by selecting one of the flags defined for calculation method selection as “1” or not, and before starting the process, the engine control unit 7 It is preferable to input flag data.

As a specific calculation method of the determination threshold A in the embodiment of the present invention, one method is a method using the upper limit value of the turbo pressure at high altitude. Here, a specific value of the upper limit value should be selected based on experiments and simulation results according to the size of the vehicle, that is, the engine displacement.
Another method is a method using a map for obtaining a preset determination threshold A using the engine speed and atmospheric pressure as parameters.

The upper limit value and map of the turbo pressure at these high altitudes are stored in advance in an appropriate storage area of the engine control unit 7, and are appropriately selected and used as described above.
In this way, the maximum allowable value of the supercharging pressure can be changed in design by configuring the calculation method of the determination threshold value as a criterion for determining whether or not the supercharging pressure exceeds an allowable level. This makes it possible to easily cope with such cases, and it becomes a highly versatile device.

  Next, it is determined whether or not the actual pressure (actual boost pressure) of the boost pressure detected by the intake pressure sensor 13 exceeds the determination threshold A obtained in step S202 (see step S204 in FIG. 3). When it is determined that the actual supercharging pressure exceeds the determination threshold A (in the case of YES), for example, the engine rotation rapidly increases due to slippage during running on snow, slack on the road, or traveling on a gravel road. In this state, it is determined that the vehicle is in a special traveling state in which PID control during normal traveling is insufficient, and the process proceeds to step S206 described below. On the other hand, when it is determined that the actual supercharging pressure does not exceed the determination threshold A (in the case of NO), the series of processing is unnecessary and the processing is terminated.

In step S206, the calculation constants in the PID control, particularly the negative constants of the I term and the P term are increased so as to obtain an appropriate supercharging pressure even in the special traveling state as described above. It will be.
Here, the negative constant is an arithmetic constant used for the calculation of the I term and the P term in the PID control when the actual supercharging pressure is higher than the target pressure, and is different for each of the I term and the P term. Are pre-selected.
The normal value of this negative (Negative) constant, for example, is not enough to handle special driving conditions where the engine speed rises sharply due to slipping on snowy roads, muddy roads, or gravel roads. This is set assuming that acceleration and deceleration are temporarily performed in the running state.

Therefore, in step S206, a negative increase constant corresponding to the above special traveling state is multiplied by a predetermined increase correction coefficient, and the multiplication result is used for PID control. Become.
The predetermined increase correction coefficient is obtained using a map set in advance so as to be determined using the differential pressure between the actual supercharging pressure and the target pressure as an argument. This map is stored as appropriate in the engine control unit 7. It is stored in the area and used.

Here, from what viewpoint the increase correction coefficient should be selected will be described with reference to FIGS.
First, referring to the explanatory diagrams for explaining the change in the supercharging pressure in the embodiment of the present invention and the change in the supercharging pressure in the conventional apparatus shown in FIG. 5, the change in the supercharging pressure and the selection of the increase correction coefficient are described. Will be described.
In FIG. 5, the horizontal direction on the paper surface represents the passage of time, and the vertical direction on the paper surface represents the magnitude of the supercharging pressure.
This figure shows the change in supercharging pressure when a special driving condition occurs, such as when the engine speed has risen sharply due to slipping during driving on snow, slack on the road, or driving on a gravel road, as described above. Thus, both the supercharging pressure in the embodiment of the present invention and the supercharging pressure in the conventional apparatus show almost the same rising change at the starting point of the increase (see the solid characteristic line in FIG. 5).

  However, in the conventional apparatus, due to the occurrence of the special traveling state as described above, after the supercharging pressure exceeds the determination threshold A, the time during which the turbocharge pressure stagnates in the region exceeding the determination threshold A is relatively long ( (See the dotted characteristic line in FIG. 5). This is set assuming that the negative constant of the I term and the negative constant of the P term in the conventional PID control are accelerated or decelerated during, for example, a normal running state. Therefore, in the special traveling state as described above, the supercharging pressure state more than necessary is continued, which may result in hindering proper engine operation.

On the other hand, in the embodiment of the present invention, the negative constant of the I term and the negative constant of the P term in the PID control in the normal control state are increased as described above. When the difference is small, the supercharging pressure is rapidly reduced unlike the conventional case (see the characteristic line of the solid line in FIG. 5).
However, when the negative constant of the I term and the negative constant of the P term are increased, when the difference between the actual supercharging pressure and the target pressure is reduced, the supercharging pressure is suddenly reduced. The pressure is also significantly lower (see the characteristic line of the one-dot chain line in FIG. 5 and the double-headed arrow marked with α).

Therefore, in the embodiment of the present invention, the magnitude of increase in the negative constant of the I term and the negative constant of the P term is changed by the differential pressure between the actual supercharging pressure and the target pressure, and the supercharging pressure is determined by the determination threshold A. The pressure is appropriately reduced to the target pressure or the vicinity thereof without excessively reducing the pressure when the pressure falls below the range.
Specifically, as shown in FIG. 6, when the differential pressure between the actual supercharging pressure and the target pressure exceeds a predetermined value, the increase correction coefficient is increased in accordance with the magnitude of the differential pressure. On the other hand, when the differential pressure is lower than the predetermined value K, the increase correction coefficient is “1”, that is, the negative constant of the I term and the negative constant of the P term are the same as in the normal control. It has become so. Such an increase correction coefficient is switched by storing a map of the characteristics shown in FIG. 6 or a calculation formula stored in a predetermined storage area of the engine control unit 7 and using it. It has come to be.
FIG. 6 shows an example of the change in the negative constant of the P term, but the change in the negative constant of the I term is basically the same.
Further, the numerical values shown in FIG. 6 are merely examples, and the present invention is not limited to this, and appropriate values should be selected depending on the scale of the vehicle and the like.

  As a result, in the embodiment of the present invention, after the supercharging pressure falls below the determination threshold A, unlike the conventional case, the supercharging pressure does not drop significantly below the target pressure, and changes with a slight degree of undershoot. (See the characteristic line of the solid line in FIG. 5).

After the negative constants of the I term and the P term are increased as described above, the threshold determination B is calculated (see step S208 in FIG. 3).
In the embodiment of the present invention, from the viewpoint of ensuring the stability of the operation, etc., after the supercharging pressure exceeds the determination threshold A, the hysteresis decreases to determine whether or not the determination threshold A is exceeded. The determination threshold B is a determination value (threshold for determination of pressure reduction) for that purpose. The determination threshold B is calculated and set as a relative value with respect to the determination threshold A by a predetermined arithmetic expression, and a value smaller than the determination threshold A by a predetermined value is set. It has become.

After the determination threshold B is calculated, it is determined whether or not the actual supercharging pressure is below the determination threshold B (see step S210 in FIG. 3).
When it is determined that the actual supercharging pressure has not yet fallen below the determination threshold B (in the case of NO), the process returns to the previous step S202 and the series of processes is repeated.
On the other hand, when it is determined in step S210 that the actual boost pressure is lower than the determination threshold B (in the case of YES), the negative constants of the I term and the P term are returned to normal values. Returning to the subroutine shown in FIG. 2, which is the main routine for the subroutine shown in FIG.

It is a block diagram which shows the structural example of the turbocharger drive control apparatus in embodiment of this invention. 2 is a subroutine flowchart showing a procedure of turbocharger drive control processing executed in an engine control unit of the turbocharger drive control device shown in FIG. 1. FIG. 3 is a subroutine flowchart showing a procedure of PID control calculation constant setting processing executed in the turbocharger drive control processing shown in FIG. 2. FIG. It is the schematic diagram which showed typically the proper use of feedback control and feedforward control in embodiment of this invention. Explanatory drawing explaining the change of the supercharging pressure in embodiment of this invention in relation to the negative constant of P term of PID control. It is a characteristic diagram explaining the example of a change to the differential pressure of the increase correction coefficient multiplied by the negative constant of P term of PID control in an embodiment of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Turbocharger 2 ... Turbo actuator 3 ... Engine 5 ... Electromagnetic vacuum adjustment valve 7 ... Engine control unit

Claims (11)

A turbocharger drive control method in a turbocharger drive control device configured such that a supercharging pressure can be varied,
When performing feedback control based on PID control so that the actual supercharging pressure becomes a target pressure determined according to the operating state of the engine,
When the actual supercharging pressure exceeds a predetermined determination threshold, at least one of an operation constant used for the calculation of the I term and an operation constant used for the calculation of the P term in the PID control is increased. Turbocharger drive control method.   The increase in the calculation constant used for the calculation of the I term in the PID control or the calculation constant used for the calculation of the P term is a target supercharging determined in accordance with the actual supercharging pressure and the engine operating condition. The turbocharger drive control method according to claim 1, wherein the turbocharger drive control method is performed by multiplying by an increase correction coefficient determined in accordance with a pressure difference from the pressure.   The increase correction coefficient is increased as the differential pressure increases when the differential pressure exceeds a predetermined value, and is set to a predetermined constant value when the differential pressure falls below the predetermined value. The turbocharger drive control method according to claim 2.   When the increase correction coefficient is set to a predetermined constant value, the result of multiplication with the operation constant used for the calculation of the I term or the operation constant used for the calculation of the P term is used in a normal control state. The turbocharger drive control method according to claim 3, wherein the turbocharger drive control method matches an operation constant.   When the actual supercharging pressure falls below a depressurization determination threshold value that is smaller than a predetermined determination threshold value by a predetermined value, the respective operation constants used for the calculation of the I term and the P term in PID control are returned to normal values. The turbocharger drive control method according to any one of claims 1 to 4. A turbocharger drive control device comprising a turbocharger and a control unit for controlling the operation of the turbocharger, and configured to be able to control a supercharging pressure by the operation control of the turbocharger,
When the control unit performs feedback control of the turbocharger based on PID control so that the actual supercharging pressure input from the outside becomes a target pressure determined according to the operating state of the engine, the actual supercharging pressure Is determined to exceed a predetermined determination threshold, at least one of the operation constant used for the calculation of the I term and the operation of the P term in the PID control is increased. A turbocharger drive control device characterized by that.   The control unit determines an increase in a calculation constant used for the calculation of the I term in the PID control or a calculation constant used for the calculation of the P term according to the actual supercharging pressure and the engine operating condition. The turbocharger drive control device according to claim 6, wherein the turbocharger drive control device is configured to be multiplied by an increase correction coefficient determined in accordance with a differential pressure with respect to a target supercharging pressure.   When it is determined that the differential pressure exceeds the predetermined value, the control unit increases the increase correction coefficient as the differential pressure increases. On the other hand, when the differential pressure is determined to be lower than the predetermined value, the control unit is predetermined. 8. The turbocharger drive control device according to claim 7, wherein the turbocharger drive control device is configured to have a constant value.   When it is determined that the actual supercharging pressure falls below the pressure-reducing determination threshold value that is smaller than the predetermined determination threshold value by a predetermined value, 9. The turbocharger drive control device according to claim 6, wherein the turbocharger drive control device is configured to return to a value. A turbocharger and a control unit for controlling the operation of the turbocharger, and the turbocharger is controlled by a feedback control based on PID control to control a supercharging pressure under a predetermined condition. A turbocharger drive control program executed by the control unit in a turbocharger drive control device comprising:
Determining whether the actual supercharging pressure exceeds a predetermined determination threshold;
When it is determined that the actual supercharging pressure exceeds a predetermined determination threshold, the actual supercharging pressure and the engine are respectively set to the arithmetic constant used for the calculation of the I term in the PID control and the arithmetic constant used for the calculation of the P term. A step of correcting the calculation constant by multiplying each increase correction coefficient determined according to a differential pressure with a target supercharging pressure determined according to the operation state of
A turbocharger drive control program comprising: Determining whether or not the actual supercharging pressure falls below a threshold for pressure reduction determination that is smaller than a predetermined determination value by a predetermined value;
A step of returning the respective operation constants used for the calculation of the I term and the P term in the PID control to the normal values when it is determined that the actual supercharging pressure is lower than the depressurization determination threshold value that is smaller than the predetermined determination value by a predetermined value. When,
The turbocharger drive control program according to claim 10, comprising:

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