JP5540761B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine capable of controlling torque by an intake air amount and an ignition timing, and in particular, an internal combustion engine capable of compensating for a decrease in torque due to a retarded ignition timing by increasing the intake air amount. The present invention relates to a control device.

  In the spark ignition type internal combustion engine, the maximum torque can be obtained when the ignition timing is MBT, and the best fuel consumption performance can be obtained. Therefore, basically, it is desirable to set the ignition timing to MBT. However, in some cases, such as when it is desired to warm up the catalyst by increasing the exhaust gas temperature or when knocking is detected, the ignition timing may be set higher than MBT. May be delayed.

  However, retarding the ignition timing has a problem of reducing the torque output from the internal combustion engine. With regard to this problem, in the technique disclosed in Japanese Patent Application Laid-Open No. 2009-068430, when the ignition timing is retarded, the throttle is operated to increase the intake air amount accordingly. That is, a decrease in torque accompanying the retard of the ignition timing is compensated by an increase in the intake air amount.

JP 2009-068430 A

  Since the response sensitivity of the torque with respect to the ignition timing is high, the intake air amount needs to be increased rapidly if it is desired to suppress the decrease in the torque accompanying the retardation of the ignition timing as much as possible. However, the response sensitivity of the intake air amount to the operation of the throttle, that is, the response sensitivity of the torque is not as high as the response sensitivity of the torque to the ignition timing.

  Therefore, what is conventionally proposed is so-called throttle overshoot control. In the overshoot control, the throttle is once overshooted and then converged to a steady target opening. According to this, it is possible to increase the intake air amount rapidly compared to the case where the throttle is opened from the beginning toward the steady opening, and to minimize the decrease in torque due to the retard of the ignition timing. it can.

  However, when the retard of the ignition timing is a retard for preventing knocking, the load increases rapidly by increasing the intake air amount, and the occurrence of knocking may be promoted.

  The present invention has been made in view of the above-described problems. When knocking occurs, the ignition timing is retarded to prevent knocking, and the torque reduction associated with the retarding ignition timing is reduced by increasing the intake air amount. An object of the present invention is to prevent the occurrence of knocking by increasing the intake air amount while compensating.

In order to achieve the above object, a control device for an internal combustion engine of the present invention comprises:
In a control device for an internal combustion engine capable of controlling torque by the amount of intake air and ignition timing,
An ignition timing retarding means for retarding the ignition timing when a predetermined retarding condition is satisfied;
A target air amount setting means for changing the target air amount in conjunction with a change in the ignition timing so as to compensate for a decrease in torque due to the retard of the ignition timing by an increase in the intake air amount;
Means for operating the throttle according to the target air amount, and when the target air amount suddenly increases, the throttle operating means for once overshooting the throttle and then converging to a steady opening corresponding to the target air amount;
When the ignition timing retarded by the ignition timing retarding means is a retard for preventing knocking, overshoot operation prohibiting means for prohibiting the throttle overshoot operation by the throttle operating means;
It is characterized by having.

  According to the control apparatus for an internal combustion engine of the present invention, when the retard of the ignition timing is retarded to prevent knocking, the overshoot operation of the throttle is prohibited. The occurrence of this is prevented. When the ignition timing is retarded for purposes other than knock prevention, it is possible to increase the intake air amount rapidly by operating the throttle overshoot, minimizing the decrease in torque associated with retarding the ignition timing. Can be suppressed.

It is a block diagram which shows the structure of the control apparatus of embodiment of this invention. It is a figure which shows the flow of a series of processes for throttle operation in the control apparatus of embodiment of this invention with a flowchart. It is a figure for demonstrating the effect of the engine control by the control apparatus of embodiment of this invention.

  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 using gasoline as fuel. 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 the throttle and the ignition device, and the control device operates these two actuators to control the torque output by the engine. The operation amount of the throttle by the control device is the throttle opening, and the operation amount of the ignition device is the ignition timing.

  The control device according to the present embodiment acquires a required torque and a required efficiency as a request related to an engine control amount. In a vehicle control system, a power train manager is disposed above the control device, and required torque and required efficiency are input from the power train manager to the control device. The required torque is a torque to be output from the engine, more strictly, a required value of the indicated torque. The efficiency is the ratio of the torque that is actually output to the potential torque that the engine can output, and the required efficiency is the required value. The maximum value of efficiency is 1, and at that time, the potential torque that can be output by the engine is actually output as it is. 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.

  FIG. 1 is a block diagram showing the configuration of the control device 2 of the present embodiment. The control device 2 has an air control target torque calculator 4, a target air amount calculator 6, a target opening calculator 8, a torque efficiency calculator 10, a target ignition timing calculator 12, and a required efficiency upper limit for each function it has. It can be divided into a guard unit 14, a torque efficiency upper limit guard unit 16, and a knock control unit 18. These elements 4, 6, 8, 10, 12, 14, 16, and 18 may each be configured by dedicated hardware, or the hardware is shared and configured virtually by software. But you can.

  First, among the plurality of elements 4, 6, 8, 10, 12, 14, 16, 18 constituting the control device 2, elements 4, 6, 8, 10, 12, 14, 16 related to engine torque control are included. The function of will be described.

  The required torque and the required efficiency acquired by the control device 2 are input to the air control target torque calculator 4. The air control target torque calculator 4 calculates the air control target torque by dividing the required torque by the required efficiency. When the required efficiency is smaller than 1, the air control target torque is raised more than the required torque. This means that the throttle is required to be able to potentially output a torque larger than the required torque.

  However, with respect to the required efficiency, the value that has passed through the required efficiency upper limit guard unit 14 is input to the target torque calculation unit 4 for air control. The required efficiency upper limit guard unit 14 limits the maximum value of the required efficiency input to the air control target torque calculation unit 4 by the upper limit guard efficiency. The value of the upper limit guard efficiency is variable, and the default is set to 1.

  The target torque for air control is input to the target air amount calculation unit 6. The target air amount calculation unit 6 converts the air control target torque into an air amount value using the air amount map. This map is a map in which the torque and the intake air amount are associated with various engine information such as the engine speed as a key on the assumption that the ignition timing is MBT. The target air amount calculation unit 6 calculates the intake air amount necessary for realizing the target torque for air control as the target air amount of the engine.

  The target air amount is input to the target opening calculation unit 8. The target opening calculation unit 8 converts the target air amount into the target opening of the throttle using an air model inverse model (air inverse model). Since the air model is a physical model that models the response of the in-cylinder intake air amount to the throttle operation based on fluid dynamics, etc., the inverse model is used to reversely calculate the throttle opening required to achieve the target air amount. be able to. Further, according to the air inverse model, the response sensitivity of the actual intake air amount with respect to the target air amount can be freely adjusted by appropriately setting the model parameters. The parameter setting of the air inverse model here is variable, and the default setting is such that the throttle overshoots in response to a sudden increase in the target air amount.

  The control device 2 operates the throttle according to the target opening calculated by the target opening calculation unit 8.

  In parallel with the above process, the control device 2 calculates the estimated MBT torque based on the actual throttle opening. The estimated MBT torque is a torque that can be output when the ignition timing is set to MBT based on the current throttle opening, that is, an estimated value of the torque that the engine can potentially output. This estimated MBT torque is input to the torque efficiency calculation unit 10 together with the duplicated required torque. In the torque efficiency calculation unit 10, the ratio of the required torque to the estimated MBT torque is calculated as the torque efficiency. The torque efficiency is an estimated efficiency when the ignition timing is manipulated so as to achieve the required torque under the current throttle opening, and coincides with the required efficiency in a steady state.

  The torque efficiency calculated by the torque efficiency calculation unit 10 is input as the instruction efficiency to the target ignition timing calculation unit 12 after passing through the torque efficiency upper limit guard unit 16. The torque efficiency upper limit guard unit 16 limits the maximum value of the indicated efficiency input to the target ignition timing calculation unit 12 by the upper limit guard efficiency. The value of the upper limit guard efficiency is variable, and the default is set to 1.

  The target ignition timing calculation unit 12 calculates MBT from engine information such as engine speed and air amount, calculates a retard amount with respect to MBT from the input instruction efficiency, and adds them to the target ignition timing. Calculate as In the calculation of the retard amount, if the instruction efficiency is 1, the retard amount is zero. The smaller the instruction efficiency is, the larger the retard amount is.

  The control device 2 operates the ignition device according to the target ignition timing calculated by the target ignition timing calculation unit 12.

  The above is the description of the functions of the elements 4, 6, 8, 10, 12, 14, 16 related to engine torque control. Next, functions of the elements 18, 14, 16, 6 related to engine knock control will be described.

  Knock control unit 18 acquires a signal generated by a knock sensor (not shown), and determines from the signal whether knock has occurred in the engine. When knocking occurs, the knock control unit 18 sets knock efficiency having a value smaller than 1 as the upper limit guard efficiency of the torque efficiency upper limit guard unit 16. As a result, the value of the instruction efficiency input to the target ignition timing calculation unit 12 is limited to a value smaller than 1, and the ignition timing is retarded with respect to MBT. The value of knock efficiency is set to a larger value as the strength (knock level) of the generated knock is higher.

  When knocking occurs, the knock control unit 18 also sets the above knock efficiency to the upper limit guard efficiency of the required efficiency upper limit guard unit 14. As a result, the required efficiency value input to the air control target torque calculation unit 4 is limited to a value smaller than 1, and the air control target torque is raised above the required torque. The amount of increase is equal to the decrease in torque due to the retard of the ignition timing. Therefore, the target air amount calculated by the target air amount calculation unit 6 is increased so as to compensate for the decrease in torque due to the retard of the ignition timing.

  Further, when knocking occurs, the knock control unit 18 requests the target opening degree calculation unit 8 to prohibit the overshoot of the throttle. In response to this prohibition request, the target opening degree calculation unit 8 changes the parameter setting of the air inverse model from the default setting to a setting that does not cause the throttle to overshoot with respect to the sudden increase in the target air amount. Thus, a sudden increase in the intake air amount when the throttle is operated according to the target opening is avoided, and the occurrence of knocking by the sudden increase in the intake air amount is prevented.

  Here, a flow of a series of processes for throttle operation in the control device 2 is summarized in a flowchart as shown in FIG.

  According to the flowchart of FIG. 2, the required torque is acquired in the first step S2, and the required efficiency is acquired in step S4. In the next step S6, the target torque for air control is calculated from the required torque and the required efficiency. In the next step S8, the target air amount is calculated from the air control target torque.

  The processing to be performed next differs depending on whether or not the ignition timing is retarded (knock retard) for preventing knock. If there is no knock retardation, the determination in step S10 is No, and the target opening is calculated from the target air amount as it is in step S14.

  On the other hand, if there is a knock retardation, the determination in step S10 is Yes, and throttle overshoot is prohibited in step S12. Specifically, the parameter setting of the air inverse model is changed to a setting that does not overshoot the throttle with respect to the sudden increase in the target air amount. Then, in the next step S14, the target opening is calculated from the target air amount.

  Finally, the effect on the knock control obtained by the function of the control device 2 of the present embodiment will be described with reference to FIG.

  FIG. 3 shows a comparison between the control result by the control device 2 of the present embodiment and the control result by the conventional control device when knocking occurs. The control results compared in FIG. 3 are changes over time in torque, ignition timing, knock level, intake air amount, and throttle opening. A solid line is a control result by the control apparatus 2 of this Embodiment, and a broken line is a control result by the conventional control apparatus.

  First, as can be seen from the comparison of the throttle opening at the lowest stage, in the conventional control device, the throttle overshoot operation is performed in response to the rapid increase of the target air amount, whereas in the control device 2 of the present embodiment, Such an operation is not performed. Therefore, as can be seen from the comparison of the intake air amount, the conventional control device causes a sudden increase in the intake air amount, whereas in the control device 2 of the present embodiment, the intake air amount can be gradually increased. it can.

  As a result, as can be seen from the comparison of the knock levels, the occurrence of knock is promoted in the conventional control device, whereas the occurrence of knock is not promoted in the control device 2 of the present embodiment. By facilitating the occurrence of knocking, the ignition timing is retarded in the conventional control device, and as a result, there is a possibility that the required torque cannot be realized due to rough torque. On the other hand, according to the control device 2 of the present embodiment, even if a temporary torque drop occurs, it is possible to quickly terminate the knock, and as a result, the required torque can be realized with high satisfaction. Can do.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

2 Control device 4 Air control target torque calculation unit 6 Target air amount calculation unit 8 Target opening calculation unit 10 Torque efficiency calculation unit 12 Target ignition timing calculation unit 14 Required efficiency upper limit guard unit 16 Torque efficiency upper limit guard unit 18 Knock control unit

Claims (1)

In a control device for an internal combustion engine capable of controlling torque by the amount of intake air and ignition timing,
An ignition timing retarding means for retarding the ignition timing when a predetermined retarding condition is satisfied;
A target air amount setting means for changing the target air amount in conjunction with a change in the ignition timing so as to compensate for a decrease in torque due to the retard of the ignition timing by an increase in the intake air amount;
Means for operating the throttle according to the target air amount, and when the target air amount suddenly increases, the throttle operating means for once overshooting the throttle and then converging to a steady opening corresponding to the target air amount;
When the ignition timing retarded by the ignition timing retarding means is a retard for preventing knocking, overshoot operation prohibiting means for prohibiting the throttle overshoot operation by the throttle operating means;
A control device for an internal combustion engine, comprising:

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