JP2001107736A - Control device for engine with variabale displacement type turbo supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the convergence ability of supercharged pressure feedback control in an EGR area and improve stability in control in a diesel engine with variable displacement type turbo supercharger. SOLUTION: In a constitution body wherein supercharged pressure is controlled to be an optimum value by feedback controlling the opening of a nozzle vane so that the intake air quantity detected by an air flow meter becomes equal to the target intake air quantity, feedback correction quantity is limited so that the higher the target EGR ratio is, the lesser the feedback gain is corrected, and the intake air quantity does not enter the area where intake air quantity varies to the reduction side by closing the nozzle vane in an EGR area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an engine with a variable displacement turbocharger, and more particularly to a technique for feedback-controlling the supercharging pressure of a variable displacement turbocharger.

[0002]

2. Description of the Related Art Conventionally, as a control method for a supercharged engine, particularly a supercharged diesel engine, there is a control method disclosed in Japanese Patent Application Laid-Open Nos. 6-173752 and 11-13050. Was.

[0003] JP-A-6-173752 discloses that
The supercharging pressure and the exhaust gas recirculation (EG
R) to selectively detect either one of the control negative pressure and
There is disclosed a configuration for controlling the EGR flow rate and the turbo indicator based on the detection result.

Japanese Patent Application Laid-Open No. 11-13050 discloses a diesel engine with a variable displacement turbocharger in which the supercharging pressure is controlled to a target supercharging pressure by opening and closing the nozzle vane. There is disclosed a configuration in which a guard value of the opening / closing command value is set and the guard value is used to limit the opening / closing command value, thereby avoiding the nozzle vane from being closed too much.

[0005]

In the case of a diesel engine having no intake throttle, since the intake air amount and the supercharging pressure have a fixed correlation, a detected value of the intake air amount (instead of the supercharging pressure) is used. By performing feedback control so that the output of the air flow meter matches the target, it is possible to control the supercharging pressure to the target as a result.

Here, if the above-described supercharging pressure control is executed in a region where EGR is not performed (non-EGR region), the correlation between the intake air amount and the supercharging pressure (nozzle vane opening) is maintained. The supercharging pressure can be controlled with high accuracy (FIG. 2B).
EG) to increase the NOx reduction effect of EGR.
If the above-described supercharging pressure control based on the intake air amount is performed in the EGR region in order to satisfy the request to expand the R region and the request to control the supercharging pressure with high accuracy, the following problems occur. Occurs.

For example, in a low-load, low-speed range near idle where the exhaust gas recirculation rate is controlled and the exhaust energy is small, the supercharging pressure hardly changes even when the nozzle vane is closed, but the exhaust pressure is reduced by closing the nozzle vane. Rises,
The differential pressure across the EGR valve increases, the exhaust gas recirculation rate obtained for the same EGR valve opening increases, and the exhaust gas recirculation amount increases, conversely, the intake air amount (new air amount detected by the air flow meter) The phenomenon of reversal, which decreases, occurs (FIG. 2D)
reference).

The above-mentioned reversal phenomenon occurs in the full opening region of the nozzle vane near the above-mentioned idle,
The higher the load / rotation, the lower the opening degree of the nozzle vane shifts, and in the region where the nozzle vane has a predetermined opening degree or more, the smaller the opening degree, the more the intake air amount increases, but if the nozzle vane is reduced to the predetermined opening degree or less. On the other hand, the effect of increasing the exhaust gas recirculation rate due to the increase in exhaust pressure prevails over the effect of increasing the amount of intake air due to supercharging, and a reverse phenomenon occurs in which the amount of intake air decreases (see FIG. 2C).

When the nozzle vanes are feedback-controlled in the opening region where the above-described reversal phenomenon occurs, even if the nozzle vanes are further closed to increase the intake air amount (supercharging pressure), the intake air amount decreases. Therefore, the feedback control does not converge.

Then, based on the detection result of the intake air amount, E
In the case of performing the GR feedback correction, the convergence stability of the EGR feedback control deteriorates because the intake air amount fluctuates without converging the supercharging pressure feedback control.

Further, as described above, in the EGR region, E
The GR control and the supercharging pressure control interact with each other, and the target E
Since there are various combinations of the EGR valve and the nozzle vane opening to maintain the GR rate, the demand for the feedback correction amount may greatly change when shifting from the EGR region to the non-EGR region. Since it takes time for the integrated correction amount accumulated in the region to change to the required amount in the non-EGR region, the controllability of the supercharging pressure is deteriorated until the integrated correction amount changes. Also occurs.

Japanese Patent Application Laid-Open No. 11-13050 discloses a nozzle vane opening / closing command value, that is, a nozzle vane opening control region which is controlled by a gate value corresponding to the rotation speed in order to avoid the nozzle vane from being closed too much. Restrict,
This is for setting the opening degree region in which the supercharging pressure is increased by closing the nozzle vane as the control range, and is effective when controlling the detection value of the supercharging pressure as a target. But,
If the supercharging pressure is controlled by feedback controlling the opening of the nozzle vanes so that the intake air amount (new air amount) matches the target, the increase in exhaust gas recirculation rate due to the increase in exhaust pressure will have an effect. However, since the intake air amount (new air amount) changes with a characteristic different from the change characteristic of the supercharging pressure, there is a problem that the convergence of the feedback control cannot be suppressed from being deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. In an engine in which the supercharging pressure is controlled by performing feedback control of a variable displacement turbocharger so that the intake air amount matches a target, the EGR is reduced. It is an object of the present invention to prevent the feedback control of the supercharger from being performed in the reverse rotation phenomenon region in a region where the supercharger feedback control is performed simultaneously, and to improve the convergence of the supercharger feedback control.

In addition, when shifting from the region where EGR is performed simultaneously to the non-EGR region, the amount of correction can be changed with good response to the required correction amount. It is an object of the present invention to be able to quickly control the amount (supercharging pressure) to a target.

[0015]

According to the present invention, the variable displacement type turbocharger is feedback-controlled so that the intake air amount of the engine matches the target intake air amount. In the engine configured to control the amount of exhaust gas recirculation in accordance with the operating conditions of the above, the feedback correction amount of the variable displacement turbocharger is limited in an operation region where exhaust gas recirculation is performed.

According to this configuration, the amount of feedback correction is limited so as not to enter the control region where the reverse phenomenon occurs. For example, in the case of controlling the supercharging pressure by controlling the opening degree of the nozzle vane, from the region where the intake air amount increases and changes by closing the opening degree of the nozzle vane, the suction is reversed by closing the opening degree of the nozzle vane. Entry into a region where the amount of air decreases and increases (reverse phenomenon region) is prevented by limiting the feedback correction amount so as not to exceed a limit value.

According to a second aspect of the present invention, the feedback control of the variable displacement turbocharger is performed including at least a proportional control and an integral control. And the final feedback correction amount obtained from the feedback correction amount by each control operation is limited.

According to this configuration, the final feedback correction amount is limited before entering the reversal phenomenon region, and
The integral correction amount in which the control deviation is accumulated is also individually limited.

According to a third aspect of the present invention, the feedback correction amount is limited to a narrower range in an operation region where the exhaust gas recirculation rate is higher. According to such a configuration, the reversal phenomenon of the change in the intake air amount is likely to occur (the reversal phenomenon occurs from the high opening side of the nozzle vane). The amount of feedback correction is limited to a narrow range (a narrow range on the high opening side of the nozzle vane).

According to a fourth aspect of the present invention, there is provided an engine with a variable displacement turbocharger configured to feedback-control the variable displacement turbocharger so that the intake air amount of the engine matches the target intake air amount. In the control device, when a change direction of an intake air amount predicted by control of the variable displacement turbocharger is different from an actual change direction of the intake air amount, feedback of the variable displacement turbocharger is performed. The control is stopped.

According to this configuration, for example, when the intake air amount shows a decreasing change during the control of the variable displacement turbocharger in order to increase and change the intake air amount toward the target, it is determined that the intake air amount decreases. It is determined that the above region is the reverse rotation region, the feedback control is stopped, and the feedback correction amount is clamped at that time.

According to a fifth aspect of the present invention, the variable displacement type turbocharger is feedback-controlled so that the intake air amount of the engine matches the target intake air amount, and the exhaust gas is exhausted in accordance with the operating conditions of the engine. In a control device for an engine with a variable displacement turbocharger configured to control the recirculation amount, the gain of the feedback control of the variable displacement turbocharger is set to decrease as the exhaust gas recirculation rate increases. .

According to this configuration, in a region where the recirculation rate of the change in the intake air amount is liable to occur and the exhaust gas recirculation rate is high (low load / low speed range of the diesel engine), the supercharger control is performed before the reversal phenomenon occurs. The response of the change in the amount of intake air to the air becomes dull, which causes an overshoot in the feedback correction.

[0024]

According to the first aspect of the invention, when the supercharger is controlled to increase the intake air amount, it is possible to avoid feedback control in a reverse rotation phenomenon region in which the intake air amount decreases. Thus, the feedback control of the supercharger can be made to converge, and the EGR is performed in accordance with the intake air amount.
If the amount feedback control is performed, EG
There is an effect that the feedback control of R can be stabilized and the controllability of the engine can be improved.

According to the second aspect of the present invention, the feedback control in the reverse rotation phenomenon region in the EGR region is avoided, and the accumulation of the integral correction amount is prevented from being excessively accumulated. There is an effect that control responsiveness of the intake air amount at the time of transfer can be ensured.

According to the third aspect of the present invention, it is possible to change the limit range of the feedback correction amount according to the change of the control region where the reverse rotation phenomenon occurs, and it is possible to control the supercharger while converging the feedback control. In addition to the effect that the range can be secured to the maximum, there is an effect that the control of the exhaust gas recirculation amount (including the amount of surplus oxygen in the gas = the amount of fresh air) can be realized with high priority given to the EGR control.

According to the fourth aspect of the present invention, the occurrence of the reverse rotation phenomenon is determined and the feedback control is stopped.
Even if the region where the reversal phenomenon occurs changes due to various variation factors, there is an effect that the feedback control in the region where the reversal phenomenon occurs can be reliably avoided.

According to the fifth aspect of the present invention, in the EGR region where the change of the intake air amount in accordance with the supercharger control becomes slow,
It is possible to prevent the feedback correction amount from overshooting, and to achieve the control of the exhaust gas recirculation amount with high accuracy by giving priority to the EGR control.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a diesel engine provided with a variable capacity turbocharger.

In FIG. 1, a diesel engine 1
Is provided with a variable capacity turbocharger 4 including a turbine unit 4A interposed in the exhaust passage 2 and a compressor unit 4B interposed in the intake passage 3.

The variable capacity turbocharger 4 is provided with a nozzle vane (not shown) for variably narrowing the turbine inlet area of the turbine section 4A, and controlling the opening degree of the nozzle vane by an actuator 5 to control the turbine inlet area. The aperture amount can be controlled.

The actuator 5 is constituted by a diaphragm type negative pressure actuator, and a vacuum pump 6
Generated by the reservoir tank 8 via the one-way valve 7
The duty ratio of the negative pressure accumulated in the intake passage 3 is reduced by the atmospheric pressure from the air cleaner 9 mounted on the intake passage 3, and the duty control valve 10 controls the duty ratio to control the negative pressure supplied to the actuator 5. .

Here, when the control duty value of the duty control valve 10 is increased, the introduction rate of the atmospheric pressure is reduced, and the negative pressure supplied to the actuator 5 is increased, so that the nozzle vane is closed more. The turbine inlet area is further reduced, and the flow velocity of the exhaust gas flowing into the turbine section 4A increases. When the control duty value is reduced, the introduction rate of the atmospheric pressure is increased conversely, and the actuator 5
When the negative pressure supplied to the nozzle is reduced, the nozzle vane is opened more, the turbine inlet area is further increased, and the exhaust flow velocity flowing into the turbine section 4A is reduced.

Reference numeral "11" denotes the compressor 4
3 shows an intercooler for cooling the supercharged intake air at B.
Further, the exhaust passage 2 upstream of the turbine section 4A and the intake passage 3 downstream of the intercooler 11 are
And a part of the exhaust gas is returned to the intake passage 3 via the EGR passage 12.
An EGR valve 13 is provided in the middle of the EGR passage 12, and the degree of opening of the EGR valve 13 is controlled almost continuously from a fully closed position to a fully opened position by an actuator (not shown) constituted by a step motor or the like.

The duty control valve 10, the EGR valve 13, and a fuel injection pump (not shown) are controlled by a control unit 14 including a microcomputer.

The control unit 14 includes an accelerator opening signal APS from an accelerator opening sensor 15, a rotation signal from a rotation sensor 16, an atmospheric pressure signal Pa from an atmospheric pressure sensor 17, and a cooling water temperature from a water temperature sensor 18. A signal Tw, an intake air amount signal Q from an air flow meter 19 provided on the upstream side of the compressor unit 4B and the like are input,
Based on these, the fuel injection amount / injection timing and the exhaust gas recirculation amount are controlled, and the intake air amount (supercharging pressure) of the diesel engine 1 is controlled by controlling the opening degree of the nozzle vanes.

In the control of the exhaust gas recirculation amount, FIG.
As shown in (A), the exhaust gas recirculation is stopped in the region near the full load, but in the other EGR regions, the target exhaust gas recirculation rate (target EGR rate) is set higher as the load becomes lower and the engine speed decreases. The target EGR rate is feedback corrected according to the intake air amount (new air amount) detected by the air flow meter 19, and the feedback corrected target EGR is corrected.
The opening of the EGR valve 13 is controlled according to the rate.

On the other hand, the supercharging pressure control for feedback-controlling the opening degree of the nozzle vanes of the variable capacity turbocharger 4 according to the intake air amount is performed according to a control block diagram shown in FIG.

In the block diagram of FIG. 3, a target air amount setting unit 101 sets a target intake air amount based on an engine speed (rpm) and a fuel injection amount (engine load).

On the other hand, the actual intake air amount (new air amount) is detected by the intake air amount detection unit 102 based on the detection output from the air flow meter 19. Here, it is preferable to smooth the detection result of the air flow meter 19.

The difference between the target intake air amount and the actual intake air amount is calculated as a control deviation, and a feedback correction amount is set by PI control (proportional P / integral I control) based on the control deviation. By correcting the basic control duty value of the duty control valve 10 with the feedback correction amount, the opening degree of the nozzle vane is feedback controlled so as to reach the target intake air amount.

In the feedback control, a differential control may be added, and a feedback operation may be performed by PID control. The control deviation is given to the proportional operation unit 103 and the integral operation unit 104, respectively, and the proportional correction amount and the integral correction amount are calculated respectively.

The proportional correction amount and the integral correction amount are multiplied by a correction coefficient set according to the target EGR rate in the gain correction section 105, and the feedback gain is corrected by multiplying the correction coefficient. ing. The gain correction unit 105 controls the non-EG where the target EGR rate is 0%.
By setting 1 as a correction coefficient in the R region, no substantial correction is performed, but as the target EGR rate increases, the correction coefficient is set to a value smaller than 1, and the proportional correction amount,
The integral correction amount is reduced and the feedback gain is reduced.

This is because, in the EGR region, the change in the intake air amount with respect to the change in the opening degree of the nozzle vane becomes slow due to the increase in the EGR rate due to the increase in the exhaust pressure by reducing the opening degree of the nozzle vane (see FIG. 2). This is because if feedback correction is performed with a gain equivalent to that in the EGR region, overshoot occurs.

Further, with respect to the integral correction amount after the gain correction by the correction coefficient, the engine speed (rp
Based on m) and the fuel injection amount, the upper and lower limit values set by the upper and lower limit setting units 106 and 107 are respectively limited. That is, when the integral correction amount exceeds the upper limit value, the integral correction amount is reset to the upper limit value, and when the integral correction amount falls below the lower limit value, the integral correction amount is reset to the lower limit value.

Further, the engine speed (rpm) and the fuel speed are compared with the feedback correction amount obtained by adding the integral correction amount after being restricted by the upper and lower limit values and the proportional correction amount without restriction. Based on the injection amount, the upper and lower limits set by the upper limit setting unit 108 and the lower limit setting unit 109 are restricted. That is, when the feedback correction amount exceeds the upper limit value, the feedback correction amount is reset to the upper limit value, and when the feedback correction amount falls below the lower limit value, the feedback correction amount is reset to the lower limit value.

The limitation on the feedback correction amount obtained by adding the integral correction amount and the proportional correction amount is feedback corrected to a reverse rotation phenomenon range estimated based on the engine speed (rpm) and the fuel injection amount. In the low rotation and low load region where the EGR rate is high and the reverse phenomenon occurs from a region where the opening of the nozzle vane is relatively high, the maximum throttle amount (minimum opening) of the nozzle vane is reduced. The upper limit value to be limited is set lower, and the controllable range is limited to a narrower range on the fully open side.
In the vicinity of idle, the reverse phenomenon occurs in the full opening range of the nozzle vane (see FIG. 2). Therefore, by setting the upper limit value and the lower limit value to 0%, the open control without feedback correction is performed. Is equivalent.

On the other hand, the limit on the integral correction amount is E
While the integral correction amount accumulated under the influence of the EGR in the GR region is increased or decreased to an appropriate level when shifting to the non-EGR region, the control is performed so as to prevent the controllability of the supercharging pressure from deteriorating. That is, the feedback correction amount is limited to a narrower range than the limited range.

The feedback correction amount obtained by adding the integral correction amount and the proportional correction amount is subjected to a clamping process based on a result of determination as to whether or not the reverse phenomenon has occurred after the above-described limiting process.

Although the control in the reverse rotation phenomenon region is avoided by the limitation by the upper and lower limit values, the feedback control is performed by entering the reverse rotation phenomenon region due to the fluctuation of the reverse rotation phenomenon region due to engine variation or environmental conditions. Could be

Therefore, in the clamp processing unit 110, a reverse rotation phenomenon occurs based on the correlation between the change direction of the control duty value finally output to the duty control valve 10 and the intake air amount at that time. Then, when it is determined whether or not the reverse rotation phenomenon has occurred, the feedback correction amount is clamped to the value at that time, and the feedback control is stopped.

In the present embodiment, the increasing change direction of the control duty value is a direction in which the opening degree of the nozzle vane is reduced, and is a condition in which an increasing change in the intake air amount due to an increase in the supercharging pressure is predicted. A case where the intake air amount is decreasing and changing while the control duty value is increasing and changing is determined as a state of occurrence of the reverse rotation phenomenon. Even when it is increasing, it is determined that the reverse phenomenon has occurred.

When the occurrence of the reverse rotation phenomenon is determined, the feedback correction amount is clamped to the value at that time, and the clamp state (feedback stop state) is held until a predetermined release condition is satisfied. Here, feedback control may be resumed using the convergence to the target intake air amount by the EGR valve or the shift to a different operation region as the clamp release condition.

The feedback correction amount that has passed through the clamp processing section 110 is added to a basic control duty value set based on the engine speed (rpm) and the fuel injection amount (engine load), and the result of the addition processing is obtained. The final control duty value is output to the duty control valve 10.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a diesel engine with a variable displacement turbocharger in an embodiment.

FIG. 2 is a diagram showing an exhaust gas recirculation rate characteristic and a correlation between a nozzle vane opening degree and an intake air amount in each embodiment in an embodiment.

FIG. 3 is a control block diagram showing supercharging pressure control in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Exhaust passage 3 ... Intake passage 4 ... Variable capacity turbocharger 12 ... EGR passage 13 ... EGR valve 14 ... Control unit 15 ... Accelerator opening sensor 16 ... Rotation sensor 17 ... Atmospheric pressure sensor 18 ... Water temperature Sensor 19: Air flow meter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/18 F02D 43/00 301N 43/00 301 301R F02M 25/07 550C F02M 25/07 550 550F 550G 550R 570D 570 570J 570P F02B 37/12 301Q F-term (Reference) 3G005 DA02 EA04 EA15 EA16 FA06 GA04 GC05 GD00 GE01 GE02 HA12 JA02 JA39 JA42 JA45 3G062 AA01 AA05 BA00 BA02 BA04 BA05 CA06 EA11 GA04 GA04 GA04 BA08 BA20 DA05 EA11 EB08 EB14 EB15 EC06 FA07 FA13 FA33 3G092 AA02 AA17 AA18 DB03 DC09 DC12 DE18S DG06 DG08 EA02 EA09 EA22 EB02 EB03 EC02 EC03 EC08 FA06 HA01X HA01Z HA05Z HD07X HD09XHE01 NC03 MA03 HA03 NE19 PA01Z PA09Z PA11Z PB03Z PE01Z PE08Z

Claims (5)

[Claims] A variable-capacity turbocharger is feedback-controlled so that an intake air amount of an engine matches a target intake air amount, and an exhaust gas recirculation amount is controlled in accordance with operating conditions of the engine. A control device for an engine with a variable displacement turbocharger, wherein the feedback correction amount of the variable displacement turbocharger is limited in an operating region in which exhaust gas recirculation is performed in the configured engine. 2. The feedback control of the variable displacement turbocharger is performed including at least proportional control and integral control, and only the integral correction amount of the feedback correction amount by each control operation is controlled. 2. The control device for an engine with a variable displacement turbocharger according to claim 1, wherein the control unit limits the final feedback correction amount obtained from the feedback correction amount by each control operation. 3. The control device for a variable displacement turbocharged engine according to claim 1, wherein the feedback correction amount is limited to a narrower range in an operation region where the exhaust gas recirculation rate is higher. 4. A control device for an engine with a variable displacement turbocharger configured to feedback-control a variable displacement turbocharger so that an intake air amount of the engine matches a target intake air amount. When the change direction of the intake air amount predicted by the control of the displacement turbocharger is different from the actual change direction of the intake air amount, the feedback control of the variable displacement turbocharger may be stopped. Characteristic control device for variable displacement turbocharged engine. 5. A variable displacement turbocharger is feedback-controlled so that an intake air amount of the engine matches a target intake air amount, and an exhaust gas recirculation amount is controlled in accordance with operating conditions of the engine. In the configured control device for an engine with a variable displacement turbocharger, wherein the gain of the feedback control of the variable displacement turbocharger is reduced as the exhaust gas recirculation rate increases. Control device for supercharged engine.