JP5704874B2 - Fuel cut control method for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel cut control method for an internal combustion engine that stops the supply of fuel to the internal combustion engine during a deceleration operation of a vehicle equipped with the internal combustion engine and then restarts the supply of fuel.

  Conventionally, in an internal combustion engine mounted on a vehicle such as an automobile, in order to improve fuel efficiency and protect the catalyst and prevent deterioration of the exhaust gas quality, during throttle traveling with the throttle valve fully closed, It is known to perform a fuel cut to stop the fuel supply, and then to perform a fuel cut return to restart the fuel supply when the operating state changes and a predetermined operating condition is satisfied Yes. For example, the device disclosed in Patent Document 1 detects an instantaneous value of the engine speed of an internal combustion engine, calculates a smooth value of the engine speed from the detected instantaneous value, calculates a deviation of the instantaneous value from the smooth value, Accordingly, the basic fuel return speed is corrected to set the fuel return speed.

  By the way, in an internal combustion engine, with time, for example, oil containing oil may accumulate around the throttle valve, and a secular change such as a substantial passage diameter may occur. Due to the aging of the internal combustion engine, the condition of the internal combustion engine at that time, or individual differences among the engines, the engine speed may be delayed until the target idle speed is reached at the time of fuel cut return, so-called return delay may occur. . During this return delay, a so-called undershoot may occur in which the engine speed falls below the target idle speed. If such an undershoot occurs, the engine speed becomes unstable during that time, and if it increases, the internal combustion engine may stop.

  This can occur even in the case described in Patent Document 1. That is, in the thing of patent document 1, since fuel cut return control is performed based on the fuel return rotation speed correct | amended according to deviation as mentioned above, it presupposes that fuel cut return control can be stabilized. ing. However, since this is not a correction of the fuel return rotational speed that takes into account conditions such as aging that differ for each internal combustion engine, the undershoot occurs in the engine rotational speed depending on the state of the internal combustion engine, and the rotation of the internal combustion engine becomes unstable. There is a possibility.

Japanese Patent Laid-Open No. 5-321719

  Therefore, the present invention pays attention to the above points, and when the fuel supply is resumed after temporarily stopping the fuel supply, the engine speed becomes lower than the target idle speed and the operation state of the internal combustion engine becomes unstable. The purpose is to suppress the situation.

That is, the fuel cut control method for an internal combustion engine according to the present invention stops the fuel supply when the internal combustion engine decelerates and restarts the fuel supply when the engine speed decreases to the fuel cut return speed. This cut control method detects the engine speed after resuming fuel supply, and when the detected engine speed falls below the target idling engine speed after resuming fuel supply, the detected engine speed and fuel Measure the speed difference from the target idle speed after resumption of supply, and set the next fuel cut return speed to be higher than the current fuel cut return speed as the measured speed difference is larger. Fuel cut return control for resuming fuel supply in a vehicle in which an automatic transmission having a lockup mechanism is mounted on a torque converter and the lockup mechanism is not operating And executes, as the vehicle speed at that time is high, that to weight the correction values between the upper rotational speed difference is apparently larger as in this fuel cut return rotational speed and the next fuel cut return rotational speed Features.

  According to such a configuration, the next fuel cut return rotational speed is set to the current fuel cut return rotational speed according to the rotational speed difference between the engine rotational speed after restarting the fuel supply and the idle target rotational speed after the restart. Set higher than the rotation speed. As a result, even if the rotational speed difference becomes large due to the current condition or aging of the internal combustion engine, when the next fuel cut return control is executed, the fuel cut return rotational speed is high, so the rotational speed difference Can be suppressed. Therefore, it becomes possible to prevent the operating state of the internal combustion engine including the stop of the internal combustion engine from becoming unstable.

In order to improve fuel efficiency by delaying the timing to restart the fuel supply, if the measured speed difference is less than the specified value, the fuel cut return speed will be reduced to the next fuel cut return speed. What sets a rotation speed is preferable. Further, in a vehicle where an air conditioner exists as a load of the internal combustion engine, the current fuel cut return is performed depending on whether the air conditioner is operating or not when the fuel cut return control is executed. The correction value between the rotation speed and the next fuel cut return rotation speed can be made different.

  The present invention is configured as described above, and when the next fuel cut return control is executed even if the rotational speed difference becomes large due to the condition or aging of the internal combustion engine at the time, the fuel cut return rotation is executed. Since the number is high, the occurrence of a rotational speed difference can be suppressed. Therefore, it is possible to prevent the operating state of the internal combustion engine including the stop of the internal combustion engine from becoming unstable.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic structure explanatory drawing of the engine of embodiment of this invention. The flowchart which shows the control procedure of the embodiment. Action | operation explanatory drawing of the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  An engine 100 schematically showing the structure of one cylinder in FIG. 1 is for an automobile, and an intake system 1 is provided with a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown). A bypass passage 3 that bypasses the valve 2 is provided, and a flow rate control valve 4 for controlling the idle speed is interposed in the bypass passage 3. The intake system 1 is further provided with a fuel injection valve 5, and the fuel injection valve 5 and the flow rate control valve 4 are controlled by an electronic control device 6. As the engine itself, those widely known in this field can be used.

  The electronic control device 6 is mainly configured by a microcomputer system including a central processing unit 7, a storage device 8, an input interface 9, and an output interface 11. The input interface 9 includes an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure in the surge tank 12, a rotation speed signal b output from a rotation speed sensor 14 for detecting the engine speed NE, The vehicle speed signal c output from the vehicle speed sensor 15 for detecting the vehicle speed, the IDL signal d output from the idle switch 16 for detecting the open / closed state of the throttle valve 2, and the coolant temperature of the engine 100 as the temperature of the engine 100 A water temperature signal e or the like output from the water temperature sensor 17 is detected. From the output interface 11, a drive signal f corresponding to the calculated fuel injection time is supplied to the fuel injection valve 5, and a control signal g based on the calculated duty ratio is supplied to the flow rate control valve 4. Each is output.

  The electronic control unit 6 determines the opening time of the fuel injection valve 5 by using the intake pressure signal a output from the intake pressure sensor 13 and the rotation speed signal b output from the rotation speed sensor 14 as main information. A program for controlling the fuel injection valve 5 to inject fuel corresponding to the load from the fuel injection valve 5 into the intake system 1 is stored. A fuel cut control program for executing a fuel cut to stop fuel supply in response to the establishment of a predetermined condition such as when the engine speed is equal to or higher than a predetermined speed when the throttle valve 2 is fully closed; In addition, a fuel cut return control program to be executed in an operation state in which the engine speed is equal to or lower than the fuel cut return speed during the fuel cut control is stored.

  The fuel cut return control program of this embodiment is repeatedly executed every predetermined time after the fuel cut return, and detects the engine speed after restarting the fuel supply, and the detected engine speed is the fuel supply restart. Measure the difference in speed between the detected engine speed and the target idling speed after resuming fuel supply when the engine speed falls below the target idling speed. This is a configuration in which the next fuel cut return rotational speed is set higher than the number. In this embodiment, when the measured rotational speed difference is less than a predetermined value, the next fuel cut return rotational speed is set lower than the current fuel cut return rotational speed. The initial value of the fuel cut return rotational speed is stored in the storage device 8 of the electronic control unit 6.

  Below, the control procedure is shown in FIG. 2, and the entire fuel cut return control program will be described. The following description mainly relates to an operation state in which the engine speed is equal to or lower than the fuel cut return speed. Note that the set next fuel cut return rotational speed is stored in the storage device 8 of the electronic control unit 6 and is stored in the storage device 8 every time the fuel cut return rotational speed is set. The return rotational speed is updated (learned).

  First, in step S1, the engine speed is detected based on the speed signal b output from the speed sensor 14. In step S2, it is determined whether or not the detected engine speed is equal to or less than the target idle speed. If it is determined in step S2 that the engine speed exceeds the target idle speed ID, this control program is terminated and the process returns to the main routine.

  On the other hand, when it is determined that the engine speed is equal to or less than the target idle speed ID, in step S3, the speed difference (undershoot amount) between the engine speed and the target idle speed ID is measured. In step S4, it is determined whether or not the measured rotational speed difference is maximized. The rotational speed difference is caused by a time delay until the control is reflected in the engine speed even though the fuel cut return control is started, and increases with the passage of time until the control is reflected. , Which becomes smaller from the time when the control is reflected. If it is determined that the rotational speed difference is not the maximum, step S3 is executed.

  If it is determined in step S4 that the rotational speed difference is maximum, it is determined whether or not the rotational speed difference determined in step S5, that is, the maximum value of the rotational speed difference exceeds a predetermined value. This predetermined value is for determining whether the next fuel cut return rotational speed is higher or lower than the current fuel cut return rotational speed in accordance with the rotational speed difference.

  If it is determined in step S5 that the maximum value of the rotational speed difference has exceeded a predetermined value, the next fuel cut return rotational speed is set higher than the current fuel cut return rotational speed corresponding to the maximum value of the rotational speed difference in step S6. Set. On the other hand, if it is determined that the maximum value of the rotational speed difference is equal to or smaller than the predetermined value, the next fuel cut return rotational speed is set lower than the current fuel cut return rotational speed corresponding to the maximum value of the rotational speed difference in step S7. Set.

  The next fuel cut return rotational speed is set by adding or subtracting a correction value to the current fuel cut return rotational speed. For example, the correction value is set to 30% of the rotational speed difference. Accordingly, the higher the maximum value of the rotational speed difference exceeds the judgment value, the higher the next fuel cut return rotational speed is set. Conversely, the smaller the maximum value of the rotational speed difference is below the judgment value, the lower the next fuel cut recovery speed. The rotational speed is set low.

  In such a configuration, the fuel supply is stopped by the fuel cut control program when the throttle valve 2 is fully closed and the vehicle starts to decelerate and the engine speed is equal to or higher than the fuel cut speed. Thereafter, when the engine speed becomes equal to or lower than the fuel cut return speed, the fuel cut return control is executed to control the intake air amount so that the engine speed becomes substantially the target idle speed ID.

  At this time, as shown in FIG. 3 (b), after the engine speed becomes equal to or lower than the fuel cut return speed (referred to as FC return speed in the figure), the engine speed returns due to the condition of the engine 100 or aging. If a delay occurs and the engine speed decreases and falls below the target idle speed, Steps S3 and S4 are repeatedly executed. Then, depending on whether the maximum value of the rotational speed difference is larger or smaller than the predetermined value, a correction value corresponding to the maximum value of the rotational speed difference is set, and the current fuel is determined based on the obtained correction value. The next fuel cut return rotational speed is set by correcting the cut return rotational speed (step S5 and step S6, or step S7).

  Thereafter, when the fuel cut control is executed and the fuel cut return control is executed when the fuel cut return condition is satisfied, the next fuel cut return rotational speed described above becomes the fuel cut return condition. In this case, as shown in FIG. 3A, the fuel cut return rotational speed is set higher than the previous time, so that the fuel cut return control is executed earlier than the previous time.

  In this way, the fuel cut return speed is increased when the speed difference is large, based on the transition state of the engine speed after the fuel cut return, and the next fuel cut return timing is advanced to shorten the fuel cut. Return control is performed. As a result, the fuel cut return speed is set higher and the fuel cut return timing is advanced to prevent the engine speed from falling below the normal return time even if the engine speed drops from the normal return time due to the return delay. be able to.

  On the other hand, when the rotational speed difference is small, step S7 is executed and the fuel cut return rotational speed is set lower than the previous time, so the next fuel cut control is performed and the fuel supply is stopped. The time will be longer. For this reason, a reduction in fuel consumption can be suppressed.

  In this embodiment, a correction value is set when setting the fuel cut return rotation speed, and the next fuel cut return rotation speed is set by adding the correction value to the current fuel cut return rotation speed. Since it is set to 30% of the maximum value of the number difference, it is possible to suppress a rapid increase in the set fuel cut return rotational speed. Therefore, it is possible to reduce the possibility that engine rotation causes hunting.

  As for the correction value of the fuel cut return rotational speed, the correction value obtained in the same manner is used for the correction value in addition to adopting the ratio calculated with respect to the maximum value of the rotational speed difference. The correction value may be used as a correction value for the next fuel cut return rotational speed. The annealing process itself may be known in this field. For example, the correction value after the previous annealing process and the correction value before the annealing process obtained as a ratio to the maximum value of the current rotational speed difference are calculated. The total value of the value obtained by dividing the difference by the set annealing constant and the correction value before the annealing process may be the annealing value.

  By smoothing the correction value in this way, it is possible to suppress a rapid change in the set fuel cut return rotational speed.

  In the case where an air conditioner (hereinafter referred to as an air conditioner) is provided as an engine load, this embodiment may be applied only when the air conditioner is not operating (when not operating). On the other hand, when the air conditioner is in operation (during operation), the engine speed is the target even if there is a return delay at the time of fuel cut return because the fuel cut return speed is set higher. There is almost no lower than the idling speed. Therefore, this embodiment may not be applied when not in operation.

  However, when giving priority to the safety at the time of fuel cut return, regardless of the operating state of the air conditioner, if it is detected that the engine speed after the fuel cut return is below the target idle speed at that time, It is preferable to set the next fuel cut return rotational speed according to this embodiment. In this case, since the initial value of the fuel cut return rotational speed is different between when the air conditioner is not operating and when the air conditioner is operating, the correction value is set to a different value between when the air conditioner is not operating and when the air conditioner is operating. It may be a thing.

Further, when the vehicle is equipped with an automatic transmission having a lockup mechanism in the torque converter, the fuel cut return control is executed when the lockup mechanism is not operating, that is, when the lockup is not being performed. Is what is executed. In this case, for example, the correction value may be used by weighting according to the vehicle speed. That is, the engine is rotated by receiving reverse torque from the wheels from the torque converter in accordance with the vehicle speed. Therefore, the reverse torque increases as the vehicle speed increases, so the maximum value of the actual rotational speed difference becomes smaller (undershoot is less likely to occur). If the actual maximum value is the same, the higher the vehicle speed, the apparent The correction value is weighted so as to increase the upper maximum value.

  In addition, this invention is not limited to the said embodiment.

  In the above embodiment, the configuration in which the intake air amount during the idling operation is adjusted by controlling the opening degree of the flow control valve 4 provided in the bypass passage 3 that bypasses the throttle valve 2 has been described. A so-called electronic throttle operated by an electromagnetic actuator such as a motor may be used, and the bypass passage 3 and the flow rate control valve 4 may not be used.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, there is an example applied to an engine of a type that is mounted on a vehicle such as an automobile and mainly supplies fuel by injecting it into an intake port or a cylinder.

2 ... Throttle valve 3 ... Bypass passage 4 ... Flow control valve 6 ... Electronic control device 14 ... Rotation speed sensor

Claims (2)

A fuel cut control method for an internal combustion engine that stops fuel supply when the internal combustion engine decelerates and resumes fuel supply when the engine speed decreases to the fuel cut return speed,
Detects engine speed after resuming fuel supply,
When the detected engine speed is lower than the target idle speed after resumption of fuel supply, the difference between the detected engine speed and the target idle speed after resumption of fuel supply is measured,
The larger the measured rotational speed difference is, the higher the current fuel cut return rotational speed is set, and the next fuel cut return rotational speed is set.
In a vehicle in which an automatic transmission having a lockup mechanism is mounted on a torque converter, fuel cut return control for restarting fuel supply in a situation where the lockup mechanism is not operating,
The fuel cut control of the internal combustion engine weights the correction value between the current fuel cut return rotational speed and the next fuel cut return rotational speed so that the higher the vehicle speed at that time, the larger the rotational speed difference becomes apparently Method. In a vehicle in which an air conditioner exists as a load of the internal combustion engine, the current fuel cut return rotational speed depends on whether the air conditioner is operating or not when the fuel cut return control is executed. 2. The fuel cut control method for an internal combustion engine according to claim 1, wherein a correction value between the engine speed and a next fuel cut return rotational speed is made different.

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