JP2011252425A - Controll device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce influences of a degraded state of an air flow meter on a controlled state of an engine speed.SOLUTION: A target torque is divided by a dimensionless quantity to obtain an air quantity control torque, from which a target air quantity is calculated. An estimated air quantity is calculated by using an output of an air flow meter, and an estimated MBT torque and an estimated current torque are each calculated based on the estimated air quantity. An amount of ignition retard to compensate the difference between the estimated MBT torque and the target torque is calculated, and the ignition timing is controlled in accordance with the amount of ignition retard. When the engine speed decreases than a target engine speed during idling, the target torque is increased and the dimensionless quantity is approximated to 1 to maintain the air quantity control torque constant. When the difference between the estimated MBT torque and the estimated current torque is decreased to a reference torque difference, further increase in the dimensionless quantity is restricted. However, when the air flow meter is degraded, the reference torque difference is increased compared to a state with no degradation.

Description

  The present invention relates to a control device for an internal combustion engine that is used in a spark ignition type internal combustion engine having an air flow meter and controls the engine speed during idle operation by controlling the torque based on the air amount and ignition timing.

  During the idling operation of the internal combustion engine, the torque is controlled so that the engine speed becomes the target speed. In the case of a spark ignition type internal combustion engine, air quantity and ignition timing can be used as means for controlling torque. The torque control based on the ignition timing is excellent in responsiveness compared to that based on the air amount. For this reason, when it is desired to quickly suppress a sudden change in the engine speed, torque control based on the ignition timing is effective.

  When performing torque control based on the ignition timing, the initial ignition timing needs to be retarded from MBT. This is to enable not only torque reduction due to retarded ignition timing but also torque increase due to advanced ignition timing. However, as described in, for example, Japanese Patent Application Laid-Open No. 2009-068430, there is a dead zone in the vicinity of MBT where torque sensitivity to changes in ignition timing is low. In this dead zone, the error in ignition timing with respect to torque is large. Therefore, if it is desired to accurately control the torque so that the engine speed becomes the target speed, it is possible to appropriately coordinately control the air amount and the ignition timing while preventing the ignition timing from entering the dead zone. Needed.

JP 2009-068430 A JP 2008-038823 A

  Incidentally, an air flow meter is attached to the internal combustion engine. The output signal of the air flow meter is used in torque control by ignition timing. In torque control based on ignition timing, it is necessary to estimate the current air amount. Although the air amount can be estimated from the throttle opening, the calculation accuracy of the air amount can be increased by using the output signal of the air flow meter as a parameter.

  However, the output characteristics of the air flow meter are not necessarily constant. When the deterioration of the air flow meter advances due to aging, the output characteristics change. In that case, the estimation accuracy of the air amount using the output signal of the air flow meter decreases, and the error between the estimated air amount and the actual air amount increases. The error between the estimated air amount and the actual air amount also affects the control state of the internal combustion engine that is performed using the estimated air amount. As for the ignition timing control, there is a possibility that the ignition timing enters the dead zone or the ignition timing sticks to a guard for preventing the dead zone from entering. In such a case, a desired torque cannot be generated in the internal combustion engine, and there is a possibility that the engine speed during idling cannot be maintained.

  The present invention has been made in view of the above-described problems, and relates to a control device that controls the engine speed during idle operation by controlling the torque based on the air amount and ignition timing. The deterioration state of the air flow meter is a control of the engine speed. The purpose is to reduce the influence on the state.

In order to achieve the above object, a control device for an internal combustion engine of the present invention comprises:
In a control device that is used in an internal combustion engine having an air flow meter and controls the engine speed during idle operation by controlling the torque based on the air amount and ignition timing,
An air amount control torque setting means for dividing the target torque by a dimensionless amount of 1 or less and setting the calculated value as the air amount control torque;
Target air amount calculation means for calculating a target air amount for realizing the air amount control torque under MBT;
An air amount control means for controlling the air amount according to the target air amount;
Estimated air amount calculating means for calculating a current air amount (hereinafter, estimated air amount) using an output value of the air flow meter;
Estimated MBT torque calculating means for calculating torque generated by the internal combustion engine when the ignition timing is set to MBT (hereinafter, estimated MBT torque) based on the estimated air amount;
An ignition retard amount calculating means for calculating an ignition retard amount for compensating a difference between the estimated MBT torque and the target torque;
Ignition timing control means for controlling the ignition timing according to the ignition retard amount;
Estimated current torque calculating means for calculating torque generated by the internal combustion engine under the current ignition timing (hereinafter, estimated current torque) based on the estimated air amount;
Means for setting the target torque, and when the engine speed is lower than the target speed during idle operation, the target torque setting means for increasing the target torque so as to recover the engine speed;
The non-dimensional amount is a means for setting the non-dimensional amount, and when the target torque is increased as the engine speed decreases during idle operation, the non-dimensional amount is made close to 1 as the target torque increases. Dimensionless amount setting means;
Limiting means for limiting further increase in the dimensionless amount when the difference between the estimated MBT torque and the estimated current torque is reduced to a reference torque difference as the dimensionless amount approaches 1.
Deterioration determining means for determining a deterioration state of the air flow meter;
Means for setting the reference torque difference, and when the air flow meter is deteriorated, a reference torque difference setting means for taking the reference torque difference larger than when the air flow meter is not deteriorated;
It is characterized by having.

  According to the control apparatus for an internal combustion engine of the present invention, when the engine speed decreases during idling, the target torque is increased so as to recover the engine speed, and the air amount control In order to keep the torque constant, the dimensionless amount is made close to 1 as the target torque increases. Meanwhile, since the estimated MBT torque is kept constant, the ignition retardation amount for compensating for the difference between the estimated MBT torque and the target torque is reduced as the target torque increases. That is, the torque is increased by the advance of the ignition timing.

  Then, when the difference between the estimated MBT torque and the estimated current torque is reduced to the reference torque difference, further increase in the dimensionless amount is limited. Thereby, the air amount control torque is increased as the target torque is increased. On the other hand, since the estimated MBT torque is increased in accordance with the increase of the target torque, the ignition retard amount is kept constant. That is, after the difference between the estimated MBT torque and the estimated current torque is reduced to the reference torque difference, the torque is increased by the air amount.

  By the cooperative control of the air amount and the ignition timing as described above, even if the engine speed during the idling operation is reduced, it can be quickly returned to the target speed. Further, since the torque can be switched from the torque increase due to the ignition timing to the torque increase due to the air amount on the way, it is possible to prevent the ignition timing from being advanced to the dead zone.

  However, when the air flow meter is deteriorated, the air flow meter outputs a value larger than the actual mass flow rate of air. For this reason, the actual air amount is smaller than when the air flow meter is not deteriorated, while the retard amount of the ignition timing is reduced so as to suppress the decrease in the engine speed due to the lack of air amount. Yes. For this reason, if switching from torque control based on the ignition timing to torque control based on the air amount is performed in the same manner as when the air flow meter is not deteriorated, the ignition timing may be advanced to the dead zone.

  In this regard, according to the present invention, when the air flow meter is deteriorated, it becomes a determination criterion for switching from torque control based on the ignition timing to torque control based on the air amount, compared to a case where the air flow meter is not deteriorated. A large reference torque difference is taken. This makes it possible to switch to torque control based on the air amount before the ignition timing is advanced to the dead zone regardless of the deterioration state of the air flow meter. Therefore, according to the present invention, the influence of the deterioration state of the air flow meter on the control state of the engine speed can be reduced.

It is a block diagram which shows the structure of the control apparatus of the internal combustion engine of embodiment of this invention. It is a figure for demonstrating the content of the engine speed control at the time of idle driving | running | working by embodiment of this invention, and its control result. It is a figure for demonstrating the content of the engine speed control at the time of idle driving | running | working by embodiment of this invention, and its control result.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 3.

  An internal combustion engine (hereinafter referred to as an engine) to be controlled in an embodiment of the present invention is a spark ignition type four-cycle reciprocating engine. The control device controls the operation of the engine by operating an actuator provided in the engine. The actuator that can be operated by the control device includes an ignition device, a throttle, a fuel injection device, a variable valve timing mechanism, an EGR device, and the like. However, in the present embodiment, the control device operates a throttle and an ignition device, and the control device operates these two actuators to control the torque output by the engine.

  The control device of the present embodiment uses torque and efficiency as engine control amounts. Strictly speaking, the torque here means the indicated torque. The efficiency in this specification is a dimensionless quantity with a value of 1 or less, and means the ratio of the torque that is actually output to the potential torque that the engine can output. When the efficiency is smaller than 1, the torque that is actually output is smaller than the potential torque that can be output by the engine, and the margin is mainly output as heat and output from the engine.

  The block diagram of FIG. 1 shows the configuration of the control device 2 of the present embodiment. The control device 2 includes a target torque setting unit 12, a target efficiency setting unit 14, an air amount control torque calculation unit 16, a target air amount calculation unit 18, a throttle opening calculation unit 20, and an estimated air amount calculation according to the functions that the control device 2 has. Divided into a unit 22, an estimated MBT torque calculation unit 24, an ignition timing control efficiency calculation unit 26, an ignition timing calculation unit 28, an estimated current torque calculation unit 30, an efficiency guard control unit 32, an efficiency guard 34, and an AFM deterioration determination unit 36. Can do. However, these elements 12-36 are specially expressed only in the elements related to the cooperative control of the air amount and the ignition timing by the operation of the throttle 4 and the ignition device 6 among the various functional elements of the control device 2. It is a thing. Therefore, FIG. 1 does not mean that the control device 2 is composed of only these elements. Each element may be configured by dedicated hardware, or the hardware may be shared and virtually configured by software. Hereinafter, the structure of the control apparatus 2 is demonstrated centering on the function of each element 12-36.

  The target torque setting unit 12 sets a torque target, which is a control amount of the engine, according to an engine operating condition and an operating state. During idle operation, the target torque setting unit 12 adjusts the target torque by feedback control so that the engine speed becomes the target speed. When the engine speed falls below the target speed, the target torque is increased so as to recover the engine speed.

  The target efficiency setting unit 14 sets an efficiency target, which is also the engine control amount, according to the engine operating conditions and operating conditions. During idle operation, the target efficiency setting unit 14 calculates the ratio of the target torque to the allowable maximum torque as the target efficiency. Therefore, when the engine speed decreases during idling, the target efficiency is brought close to 1 as the target torque is increased.

  The target torque and target efficiency are input to the air amount control torque calculator 16. The air amount control torque calculator 16 calculates the air amount control torque by dividing the target torque by the target efficiency. Since the target efficiency is set to a value smaller than 1 during idle operation, the air amount control torque is raised above the target torque. Note that the target efficiency that has passed through the efficiency guard 34 described later is input to the air amount control torque calculator 16.

  The air amount control torque is input to the target air amount calculation unit 18. The target air amount calculation unit 18 converts the air amount control torque into the target air amount using the air amount map. The amount of air here means the amount of air sucked into the cylinder (a non-dimensional filling efficiency or load factor can be used instead). The air amount map is a map in which the torque and the air amount are associated with various engine state amounts including the engine speed and the air-fuel ratio as keys on the assumption that the ignition timing is MBT. For the search of the air amount map, the actual value or target value of the engine state amount is used.

  The target air amount is input to the throttle opening calculation unit 20. The throttle opening calculation unit 20 converts the target air amount into the throttle opening using an inverse air model. The reverse air model includes a reverse model of a throttle model, a reverse model of an intake pipe model, and a reverse model of an intake valve model. Since the air model is a physical model that models the response characteristic of the air amount to the operation of the throttle 4, the throttle opening necessary for achieving the target air amount can be calculated backward by using the inverse model.

  The control device 2 operates the throttle 4 according to the throttle opening calculated by the throttle opening calculation unit 20.

  In parallel with the above processing, the control device 2 calculates the estimated air amount based on the actual throttle opening by the estimated air amount calculation unit 22. The estimated air amount is an air amount estimated to be realized by operating the throttle 4 by the control device 2. The estimated air amount calculation unit 22 converts the throttle opening into an air amount using an air model. The air model includes a throttle model, an intake pipe model, and an intake valve model. The air model and the inverse air model share the same model calculation formula. However, the air model used by the estimated air amount calculation unit 22 has a function not found in the reverse air model. The function is a function for correcting the flow coefficient of the throttle model according to the output value of the air flow meter (AFM) 8. The flow coefficient is corrected so that the throttle passage air amount calculated by the throttle model matches the throttle passage air amount calculated from the output value of the air flow meter 8. Because of this function, the output value of the air flow meter 8 is sequentially input to the estimated air amount calculation unit 22.

  The estimated air amount is used to calculate the estimated MBT torque and the estimated current torque. The estimated MBT torque in this specification is an estimated value of torque obtained when the ignition timing is set to MBT under the estimated air amount. The estimated current torque is an estimated value of torque obtained at the current ignition timing based on the estimated air amount.

  The estimated MBT torque is calculated by the estimated MBT torque calculator 24. The estimated MBT torque calculation unit 24 converts the estimated air amount into the estimated MBT torque using the torque map. The torque map is an inverse map of the air amount map described above, and is a map associated with the air amount, torque, and various engine state amounts as keys on the assumption that the ignition timing is MBT.

  The estimated current torque is calculated by the estimated current torque calculator 30 in parallel with the calculation of the estimated MBT torque by the estimated MBT torque calculator 24. The estimated current torque calculation unit 30 converts the estimated air amount into the estimated current torque using the torque map described above. However, in the search of the torque map by the estimated current torque calculation unit 30, the current ignition timing is used as the ignition timing.

  The estimated MBT torque is input to the ignition timing control efficiency calculation unit 26 together with the target torque. The ignition timing control efficiency calculation unit 26 calculates the ratio of the target torque to the estimated MBT torque as the ignition timing control efficiency. The calculated ignition timing control efficiency is input to the ignition timing calculation unit 28.

  The ignition timing calculation unit 28 calculates MBT based on the engine state quantity such as engine speed, air quantity, air-fuel ratio, and the like, and calculates the retard amount with respect to MBT from the input ignition timing control efficiency. Then, the final ignition timing is calculated by adding the retard amount to MBT. For the calculation of the MBT, for example, an MBT map that associates the MBT with various engine state quantities can be used. For the calculation of the retard amount, for example, a retard amount map that associates the retard amount with the ignition timing control efficiency and various engine state amounts can be used. The actual value or target value of the engine state quantity is used for searching each map.

  According to the retard amount map, the retard amount is increased as the ignition timing control efficiency is smaller than 1, and the retard amount is decreased as the ignition timing control efficiency is closer to 1. However, a lower limit is set for the retard amount. This is because the vicinity of MBT is a dead zone in which the sensitivity of the torque to the change in the ignition timing is low, and the error in the ignition timing with respect to the torque is large. The boundary of the dead band corresponds to the lower limit value of the retardation amount. The ignition timing determined by the MBT and the lower limit value of the retard amount is the advance limit of the ignition timing. Even if the efficiency for controlling the ignition timing further approaches 1, the ignition timing is guarded by this advance limit. Become.

  The control device 2 operates the ignition device 6 according to the ignition timing calculated by the ignition timing calculation unit 28.

  Moreover, the control apparatus 2 calculates the difference between the estimated MBT torque and the estimated current torque in parallel with the above processing. Then, the calculated torque difference is input to the efficiency guard control unit 32. The efficiency guard control unit 32 determines whether or not the difference between the estimated MBT torque and the estimated current torque is larger than the reference torque difference, and controls the above-described efficiency guard 34 according to the determination result.

  The efficiency guard 34 is controlled by the efficiency guard control unit 32 when the engine is idling. When the engine speed decreases during idling, the target torque is increased so as to recover the engine speed, and the target efficiency approaches 1 as the target torque increases. Meanwhile, the difference between the estimated MBT torque and the estimated current torque gradually decreases as the target efficiency approaches 1. The efficiency guard control unit 32 determines whether the difference between the estimated MBT torque and the estimated current torque is greater than the reference torque difference. When the difference between the estimated MBT torque and the estimated current torque is reduced to the reference torque difference, the above-described efficiency guard 34 restricts further increase in the target efficiency.

  The reference torque difference used by the efficiency guard control unit 32 for determination is set corresponding to the lower limit value of the retard amount. Although a specific example will be described later, when the increase in the target efficiency is limited by the efficiency guard 34, the ignition timing is kept constant for some time. The reference torque difference is set so that the retard amount with respect to MBT at that time does not fall below the lower limit. However, such an appropriate reference torque difference value is not constant, and an appropriate reference torque difference value varies depending on conditions.

  The deterioration state of the air flow meter 8 is one of the conditions that influence the value of the reference torque difference. For this reason, the efficiency guard control unit 32 sets the reference torque difference according to the deterioration state of the air flow meter 8 determined by the AFM deterioration determination unit 36 with the value of the reference torque difference when the air flow meter 8 is not deteriorated as an initial value. Change the value of the difference. Specifically, the efficiency guard control unit 32 changes the value of the reference torque difference to a larger value as the deterioration of the air flow meter 8 progresses.

  When the air flow meter 8 is deteriorated, the air flow meter 8 outputs a value larger than the actual mass flow rate of air. For this reason, when the air flow meter 8 is deteriorated, the influence is exerted on engine control using the air amount, for example, air-fuel ratio feedback control. The AFM deterioration determination unit 36 determines the deterioration state of the air flow meter 8 by a known method. For example, the deterioration state of the air flow meter 8 can be determined from a correction value or a learning value by air-fuel ratio feedback control.

  2 and 3 are diagrams showing the contents of the engine speed control during idling by the control device 2 and the results thereof. Hereinafter, the effect on the engine speed control obtained in the present embodiment will be described with reference to FIGS.

  In the uppermost charts of FIGS. 2 and 3, the temporal change of the engine speed (actual speed) during idling is shown together with the target speed. In the second chart, each time change of the target torque, the air amount control torque, the estimated MBT torque, the estimated current torque, the actual MBT torque, and the actual current torque is shown. The time chart of the target efficiency and the ignition timing control efficiency is shown in the third chart. In the bottom chart, the time change of the ignition timing is shown together with the advance limit of the ignition timing.

  FIG. 2 shows the contents and results of engine speed control performed in a state where the air flow meter 8 is not deteriorated. Here, a case where the engine speed starts to decrease at time t1 is shown. In this case, the target torque is increased in order to suppress the decrease in the engine speed by increasing the torque and to recover the engine speed to the target speed. Further, the target efficiency approaches 1 as the target torque increases.

  The target efficiency is increased so that the air amount control torque obtained by dividing the target torque by the target efficiency is maintained constant. When the air amount control torque is kept constant, the throttle is operated so as to keep the air amount constant. Further, during this time, the estimated MBT torque determined by the air amount (estimated air amount) is also maintained constant, and therefore the ignition timing control efficiency, which is the ratio of the estimated MBT torque and the target torque, corresponds to the increase in the target torque. Will increase. Thereby, the ignition timing is advanced toward MBT.

  Then, when the difference between the estimated MBT torque and the estimated current torque is reduced to the reference torque difference (time t2 in FIG. 2), the efficiency guard 34 limits further increase in the target efficiency. Thereby, after the time t2, the air amount control torque increases as the target torque increases. On the other hand, the estimated MBT torque starts to increase behind the air amount control torque by the amount of response delay of the air amount with respect to the operation of the throttle 4. As the estimated MBT torque increases as the target torque increases, the ignition timing control efficiency, which is the ratio of the estimated MBT torque and the target torque, becomes constant, and the ignition timing is maintained substantially constant. At this time, the ignition timing is advanced close to the advance angle limit, but the ignition timing does not stick to the advance angle limit by setting the reference torque difference as described above.

  As described above, when the engine speed during the idling operation decreases, the control device 2 first increases the torque by the advance of the ignition timing, and then at an appropriate timing determined by the value of the reference torque difference. Switch to torque control by air volume. According to such cooperative control of the air amount and the ignition timing, the engine speed can be quickly returned to the target speed even if the engine speed during idling is reduced.

  On the other hand, FIG. 3 shows the contents and results of engine speed control performed in a state where the air flow meter 8 is deteriorated. When the air flow meter 8 is deteriorated, the actual air amount is smaller than the estimated air amount calculated using the output value of the air flow meter 8. For this reason, the actual MBT torque and the current torque are smaller than the estimated MBT torque and the estimated current torque. On the other hand, as can be seen from the comparison between FIG. 2 and FIG. 3, when the air flow meter 8 is deteriorated, the target efficiency is a larger value so as to suppress the decrease in the engine speed due to the lack of the air amount. Thus, the ignition timing is controlled to the more advanced side. For this reason, the margin to the advance angle limit of the ignition timing is smaller than when the air flow meter 8 is not deteriorated.

  FIG. 3 shows a case where the engine speed starts to decrease at time t3. Also in this case, the target torque is increased in order to suppress the decrease in the engine speed by increasing the torque, and to recover the engine speed to the target speed. Further, the target efficiency approaches 1 as the target torque increases. Then, when the difference between the estimated MBT torque and the estimated current torque is reduced to the reference torque difference (time t4 in FIG. 3), the efficiency guard 34 limits the further increase in the target efficiency. However, the reference torque difference in this case is set to a larger value than that in a state where the air flow meter 8 is not deteriorated. By taking a large reference torque difference, the target efficiency is limited by the efficiency guard 34 at an earlier timing than when the air flow meter 8 is not deteriorated.

  By limiting the target efficiency by the efficiency guard 34 at an earlier timing, the timing for switching from the torque control based on the ignition timing to the torque control based on the air amount can be advanced. This makes it possible to switch to torque control based on the air amount before the ignition timing reaches the advance limit, so that the ignition timing does not stick to the advance limit. That is, it is possible to switch to the torque control based on the air amount while the torque control based on the ignition timing is effective. Therefore, even when the air flow meter 8 is deteriorated, the engine speed can be quickly returned to the target speed by appropriate cooperative control of the air amount and the ignition timing.

  As described above, according to the control device 2 of the present embodiment, the influence of the deterioration state of the air flow meter 8 on the control state of the engine speed during idling can be reduced.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

2 Control device 4 Throttle 6 Ignition device 8 Air flow meter 12 Target torque setting unit 14 Target efficiency setting unit 16 Air amount control torque calculation unit 18 Target air amount calculation unit 20 Throttle opening calculation unit 22 Estimated air amount calculation unit 24 Estimated MBT Torque calculation unit 26 Ignition timing control efficiency calculation unit 28 Ignition timing calculation unit 30 Estimated current torque calculation unit 32 Efficiency guard control unit 34 Efficiency guard 36 AFM deterioration determination unit

Claims (1)

In a control device that is used in an internal combustion engine having an air flow meter and controls the engine speed during idle operation by controlling the torque based on the air amount and ignition timing,
An air amount control torque setting means for dividing the target torque by a dimensionless amount of 1 or less and setting the calculated value as the air amount control torque;
Target air amount calculation means for calculating a target air amount for realizing the air amount control torque under MBT;
An air amount control means for controlling the air amount according to the target air amount;
Estimated air amount calculating means for calculating a current air amount (hereinafter, estimated air amount) using an output value of the air flow meter;
Estimated MBT torque calculating means for calculating torque generated by the internal combustion engine when the ignition timing is set to MBT (hereinafter, estimated MBT torque) based on the estimated air amount;
An ignition retard amount calculating means for calculating an ignition retard amount for compensating a difference between the estimated MBT torque and the target torque;
Ignition timing control means for controlling the ignition timing according to the ignition retard amount;
Estimated current torque calculating means for calculating torque generated by the internal combustion engine under the current ignition timing (hereinafter, estimated current torque) based on the estimated air amount;
Means for setting the target torque, and when the engine speed is lower than the target speed during idle operation, the target torque setting means for increasing the target torque so as to recover the engine speed;
The non-dimensional amount is a means for setting the non-dimensional amount, and when the target torque is increased as the engine speed decreases during idle operation, the non-dimensional amount is made close to 1 as the target torque increases. Dimensionless amount setting means;
Limiting means for limiting further increase in the dimensionless amount when the difference between the estimated MBT torque and the estimated current torque is reduced to a reference torque difference as the dimensionless amount approaches 1.
Deterioration determining means for determining a deterioration state of the air flow meter;
Means for setting the reference torque difference, and when the air flow meter is deteriorated, a reference torque difference setting means for taking the reference torque difference larger than when the air flow meter is not deteriorated;
A control device for an internal combustion engine, comprising:

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