JP2023183436A - Vehicular internal combustion engine start-timing control method and apparatus - Google Patents

Abstract

To prevent re-racing of engine by gradually advancing ignition timing when ending torque reduction in performing the torque reduction by delaying ignition timing for suppressing the racing when a clutch is released during start assist control.SOLUTION: In a vehicle provided with a manual transmission, when a clutch is semi-engaged between time t2-t3 at vehicle start, start assist control is executed to maintain an engine revolution speed at a start target engine revolution speed b1. When the clutch is released during the start assist control, the engine is caused to race, and therefore an ignition timing delay is executed (time t3-t5). For preventing re-racing in delaying ignition timing at ending torque reduction, a change rate of delaying is limited to an upper limit change rate (time t5-t6).SELECTED DRAWING: Figure 3

Description

The present invention relates to start assist control when starting a vehicle that involves a clutch engagement operation in a vehicle equipped with a clutch between an internal combustion engine and a transmission. Related to technology to prevent engine over-rev (rapid increase in rotational speed).

When starting a vehicle equipped with a manual transmission, the driver depresses the clutch pedal to select one of the gears, and then returns the clutch pedal to create an engaged state with slipping of the clutch, a so-called half-clutch state. , torque transfer is initiated. When starting such a vehicle, the engine rotation speed is set to idle while the clutch is engaged, so that the rotation speed of the internal combustion engine (engine rotation speed) does not drop excessively and cause the internal combustion engine to stop. A technique (so-called start assist control) for controlling the output of an internal combustion engine so as to approach a target engine rotation speed higher than the engine speed is known.

In this type of start assist control, for example, if the driver does not shift from a half-clutch state to a fully engaged state, but instead depresses the clutch pedal and releases the clutch, even if the driver does not move from the accelerator pedal to the fully engaged state. Even if there is, the internal combustion engine will rev up because the throttle valve opening is large.

In order to suppress the revving of the internal combustion engine when the clutch is released during start assist control, Patent Document 1 discloses that when an overshoot in the rotational speed is detected, the torque is reduced by retarding the ignition timing. Control is disclosed.

Japanese Patent Application Publication No. 2004-52584

In Patent Document 1, the torque down control by retarding the ignition timing ends when the overshoot amount of the rotational speed becomes equal to or less than a threshold value, and the retarded ignition timing changes to the advanced side. In other words, the ignition timing is advanced to the original ignition timing (for example, basic ignition timing) corresponding to the operating conditions at that time.

However, when the ignition timing is advanced in this manner, the torque of the internal combustion engine immediately increases, which may cause the internal combustion engine to rev up again.

This invention transmits the output of the internal combustion engine to the transmission via the clutch, and performs start assist control to maintain the engine speed at a target engine speed for starting, which is higher than the idle speed when the clutch is engaged for starting. In a method for controlling the start of an internal combustion engine for a vehicle, the method also includes performing torque down control by retarding the ignition timing in response to clutch release during the start assist control.
The advance of the ignition timing at the end of the torque down control is limited to a predetermined upper limit rate of change.

According to the present invention, by limiting the rate of change in the advance angle of the ignition timing at the end of the torque down control, the torque gradually changes, and re-revving is suppressed.

FIG. 1 is a configuration explanatory diagram showing a system configuration of an embodiment of the present invention. 5 is a flowchart showing the flow of the overflow prevention control process. 5 is a time chart showing changes in parameters when the vehicle starts. Functional block diagram of overboiling prevention control. FIG. 3 is a functional block diagram showing a second embodiment.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a configuration explanatory diagram showing an outline of the system configuration of one embodiment. In the vehicle of one embodiment, a manual transmission 2 is connected to an internal combustion engine 1, and a clutch 3 is interposed between an output shaft of the internal combustion engine 1 and an input shaft of the transmission 2. The output shaft of the transmission 2 is connected to drive wheels (not shown) via a final reduction mechanism or the like. A neutral switch 5 that outputs a predetermined signal (neutral signal) when a neutral position is selected is provided on the shift lever 4 for selecting a gear of the transmission 2 or on the transmission 2 main body side.

The internal combustion engine 1 is a spark ignition engine, so-called a gasoline engine, and can obtain an output according to the opening degree of an electronically controlled throttle valve 6. Further, in one example, a compressor 20 including a turbocharger and driven by an exhaust turbine (not shown) is disposed upstream of the throttle valve 6 . The engine rotation speed is detected by a crank angle sensor 8. The speed of the vehicle, that is, the vehicle speed, is detected by a vehicle speed sensor 7. Note that the vehicle speed sensor 7 may be of any type that directly or indirectly detects the vehicle speed.

The output of internal combustion engine 1 is controlled by engine control unit 11 via fuel injection device 21 and ignition device 22 . The amount of depression of the accelerator pedal 12 of the vehicle, that is, the accelerator opening degree, is detected by the accelerator opening sensor 13 . This accelerator opening sensor 13 also functions as a so-called idle switch by determining that the detected opening is in the idle state. The brake pedal 14 is provided with a brake switch 15 that detects depression of the brake pedal 14, that is, a brake operation. The clutch pedal 16 for operating the clutch 3 includes a first clutch switch 17 that detects when the clutch pedal 16 is depressed even slightly, and a first clutch switch 17 that detects when the clutch pedal 16 is depressed even slightly, and a first clutch switch 17 that detects when the clutch pedal 16 is depressed sufficiently until the clutch 3 is in a state where no torque is transmitted. A second clutch switch 18 is provided to detect when the clutch is turned on. Therefore, when the driver fully depresses the clutch pedal 16 to operate the manual transmission 2, both the first clutch switch 17 and the second clutch switch 18 are turned on, and the driver depresses the clutch pedal 16 to the intermediate position. When the clutch is in a so-called half-clutch state, the first clutch switch 17 is on and the second clutch switch 18 is off.

Detection signals from the neutral switch 5, vehicle speed sensor 7, crank angle sensor 8, accelerator pedal opening sensor 13, brake switch 15, first and second clutch switches 17, 18, etc. are input to the engine control unit 11. When the vehicle is started, the engine control unit 11 corrects the output of the internal combustion engine via the throttle valve 6 as a so-called start assist control based on these detection signals to bring the engine rotational speed closer to the target engine rotational speed for starting. Note that detection signals from a large number of sensors other than those described above are input to the engine control unit 11 for integrated control of the internal combustion engine 1, but these are not shown.

FIG. 3 is a time chart showing changes in various parameters when the vehicle starts. From the top of the diagram, (a) clutch pedal 16 operation position, (b) engine rotation speed, (c) engine torque, (d) intake air amount of internal combustion engine 1, and (e) ignition timing are shown, respectively. . (b) In the engine rotation speed column, characteristic line b1 is the target engine rotation speed for starting during start assist control, characteristic line b2 is the actual engine rotation speed, and characteristic line b3 is the rotation speed on the output side of clutch 3. (that is, the input shaft rotational speed of the transmission 2).

Until time t1, the vehicle is stopped, the transmission 2 is in an appropriate gear position suitable for starting, the clutch 3 is in a released state, and the actual engine rotational speed b2 is at the target idle rotational speed. As shown in column (a), at time t1, the driver begins to return the clutch pedal 16, and at time t2, the clutch enters a so-called half-clutch state. The half-clutch state continues until time t3.

Start assist control starts with the operation of clutch 3 at time t1. That is, as shown in column (b), a target engine rotation speed b1 for starting is given, and the engine rotation speed is adjusted via the throttle valve 6 so that the actual engine rotation speed b2 follows the target engine rotation speed b1 for starting. Feedback controlled. The starting target engine rotational speed b1 is set higher than the target idle rotational speed for smooth starting. With this start assist control, for example, the opening degree of the throttle valve 6 is increased even without the driver's depression of the accelerator pedal 12, and stalling of the internal combustion engine 1 is avoided. By continuing the half-clutch state from time t2 to t3, the rotational speed b3 on the output side of the clutch 3 gradually increases. This rotational speed b3 on the output side of the clutch 3 basically corresponds to a change in vehicle speed at the time of starting.

Normally, at time t3 when engagement of the clutch 3 is completed, the driver returns the clutch pedal 16 as shown by the broken line a1 in column (a), and the clutch 3 shifts to a fully engaged state. However, in rare cases, as shown by the solid line a2 in column (a), the clutch 3 may be released at time t3 while the start assist control is being performed.

If the clutch 3 is released during the start assist control in which the opening degree of the throttle valve 6 is relatively large in this way, the rotational speed of the internal combustion engine 1 is about to increase, but the engine control unit 11 Based on the detection of racing, torque reduction control is immediately performed by retarding the ignition timing of the ignition device 22. That is, as shown in column (e), the ignition timing is retarded in steps from the basic ignition timing determined from the engine speed and load to suppress the torque. As a result, the engine 1 is prevented from revving up due to the release of the clutch 3. Note that the ignition timing is retarded by adding a retard amount for torque reduction to the calculation of the ignition timing.

As will be described later, the torque down control for suppressing engine speed rise is performed on the condition that the amount of speed rise (for example, the difference between the actual engine speed b2 and the target idle speed) is within a predetermined value. It ends at t5. Upon completion of this torque down control, the ignition timing, which had been forcibly retarded up to that point, is advanced to the basic ignition timing. In other words, the amount of retardation for reducing the torque described above returns to zero. At this time, in the embodiment described above, the rate of change in the ignition timing advance is limited to a predetermined upper limit rate of change so that the ignition timing does not advance rapidly. Therefore, as shown in column (e) between time t5 and time t6, the ignition timing gradually changes to the advanced side. The rate of change toward the advance angle side at this time is smaller than the rate of change toward the retard side between time t3 and time t4. In other words, the ignition timing is quickly retarded to suppress engine racing, and the ignition timing is gradually advanced at the end of the torque down control.

If the ignition timing is advanced rapidly as shown by the broken line e1 in column (e), the torque will rise as the ignition timing is advanced, especially when the intake air amount has not decreased sufficiently ((c) (See dashed line c1 in the column) As a result, the actual engine speed b2 rises again as shown by the dashed line b21. In the embodiment described above, by limiting the rate of change in the ignition timing advance angle, the engine revs up again are prevented.

FIG. 2 is a flowchart showing the flow of the above-described engine racing prevention control process executed in the engine control unit 11. This process is repeatedly executed in the engine control unit 11. In step 1, it is determined whether or not the start assist control is being executed. If the start assist control is not being executed, the process proceeds to step 2, where it is determined whether a predetermined time has elapsed since the end of the start assist control. If the predetermined time has already elapsed, the process proceeds to step 3, and the operation of the engine racing prevention control is prohibited, that is, the torque reduction control based on the ignition timing is prohibited. Note that the start assist control is executed based on the operation of the clutch pedal 16, etc., as described above, by another routine (not shown).

If the start assist control is being executed in step 1, the process proceeds to step 4, where it is determined whether the vehicle speed is within a predetermined vehicle speed. If the vehicle has started and has already exceeded the predetermined vehicle speed, the process proceeds to step 3 and the operation of the engine speed prevention control is prohibited.

If the vehicle speed is within the predetermined speed in step 4, it is determined in step 5 whether the clutch 3 is in a released state, and if YES, the process proceeds to step 6. If the clutch 3 is in the engaged state or remains in the half-clutch state, the process proceeds to step 3, and the operation of the engine racing prevention control is prohibited. In step 6, it is determined whether the amount of increase in rotational speed (for example, the difference between the actual engine rotational speed and the target idle rotational speed) is greater than or equal to a predetermined value, and if YES, the process proceeds to step 7. If the amount of racing is smaller than the predetermined value, the process proceeds to step 3, and the operation of the racing prevention control is prohibited.

In step 7, a torque down coefficient necessary for suppressing engine speed is calculated with reference to a map in which values are assigned using the amount of engine speed (for example, the difference between the actual engine speed b2 and the target idle speed) as a parameter. Based on this torque down coefficient, in step 8, engine racing prevention control by retarding the ignition timing, that is, torque down control is executed. The above-mentioned retardation amount for torque down is determined based on the torque down coefficient.

In the next step 9, it is determined whether the amount of increase in rotational speed has become within a predetermined value due to torque down control, that is, ignition timing retardation. The retarded state of the ignition timing continues until it falls within a predetermined value. Note that the "predetermined value" in step 6 and the "predetermined value" in step 9 are not necessarily the same value, but are each set as appropriate.

If it is determined in step 9 that the amount of engine speed is within the predetermined value, the process proceeds to step 10, in which the ignition timing is changed to the advanced side while limiting the rate of change by a predetermined upper limit rate of change, and the ignition timing is adjusted to the basic ignition timing. return. In other words, the amount of retardation for torque reduction is set to zero. Then, in step 11, a series of overspeed prevention control is completed.

FIG. 4 is a functional block diagram of the engine racing prevention control section 100 included in the engine control unit 11. Note that the functions shown in this block diagram are realized by software or hardware executed by the engine control unit 11.

As shown in FIG. 4, the engine racing prevention control unit 100 includes a start assist operating state determining unit 101, an elapsed time determining unit 102, a vehicle speed determining unit 103, a clutch release state determining unit 104, and an engine racing amount determining unit. 105, a torque down coefficient calculation section 106, and a rate of change limit command section 107.

The start assist operating state determining unit 101 determines whether start assist control is being performed. The elapsed time determination unit 102 determines whether a predetermined time has elapsed since the start assist control ended. Vehicle speed determination unit 103 determines whether the vehicle speed is within a predetermined vehicle speed. The clutch release state determination unit 104 determines whether the clutch 3 is in the release state. The speed-up amount determination unit 105 determines the speed-up amount of the rotational speed. The torque down coefficient calculation unit 106 calculates a torque down coefficient necessary for suppressing engine racing. The rate of change limit command unit 107 outputs a predetermined upper limit rate of change when advancing the ignition timing that has been retarded due to torque down at the end of the torque down, and limits the rate of change of the ignition timing advance.

In the above embodiment, the upper limit rate of change is a predetermined constant value, and therefore control is simplified.

Next, a second embodiment of the present invention will be described. In the second embodiment, the upper limit change rate when returning the ignition timing retarded due to torque down to the basic ignition timing at the end of torque down is determined by adjusting the intake air amount according to the intake air amount at the end of torque down. The setting is made so that the larger the value, the smaller the rate of change toward the advance angle side. In other words, the larger the amount of intake air compared to the amount of intake air equivalent to the target idle rotation speed, the more likely it is that revs will occur as the ignition timing advances; If the engine is close to the fuel level, revving is unlikely to occur even if the ignition timing is advanced. Therefore, in the second embodiment, the upper limit change rate is set depending on the intake air amount at the end of torque down.

FIG. 5 is a functional block diagram showing the configuration of the overspeed prevention control section 100 of the second embodiment. Similarly to the first embodiment shown in FIG. 4, the engine racing prevention control unit 100 includes a start assist operating state determining unit 101, an elapsed time determining unit 102, a vehicle speed determining unit 103, and a clutch release state determining unit 104. , a racing amount determination section 105 , a torque down coefficient calculation section 106 , and a rate of change limit command section 107 . It further includes an intake air amount determining section 108. The intake air amount determination unit 108 determines the intake air amount at the end of torque down, which is when the angle is advanced from the retarded state, and sets an upper limit rate of change in accordance with this intake air amount.

Preferably, the advance of the ignition timing is completed after the amount of intake air increased due to the start assist control (see column (d)) returns to the amount of intake air corresponding to the target idle rotation speed after the end of the start assist control. The magnitude of the upper limit rate of change is set in .

According to the second embodiment, the retard amount can be returned to 0 relatively quickly while reliably suppressing the retardation of the engine speed during advance.

Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the present invention is applied to a supercharged engine equipped with a turbocharger, but the present invention can also be applied to a naturally-charged engine. In addition, in the above-mentioned embodiments equipped with a turbocharger, the reduction in the amount of intake air after the end of the start assist control tends to be delayed, so that the engine speed increases again due to the advance of the ignition timing at the end of the torque down, which is more likely to become a problem. .

1... Internal combustion engine 2... Transmission 3... Clutch 6... Throttle valve 11... Engine control unit 11
16...Clutch pedal

Claims (6)

The output of the internal combustion engine is transmitted to the transmission via the clutch, and when the clutch is engaged for starting, start assist control is performed to maintain the engine speed at a target engine speed for starting that is higher than the idle speed. In a start control method for a vehicle internal combustion engine that performs torque reduction control by retarding ignition timing in response to clutch release during start assist control,
A start control method for a vehicle internal combustion engine, which limits the advance of ignition timing at a predetermined upper limit rate of change at the end of the torque down control. The upper limit rate of change is set so that the rate of change of the ignition timing toward the retard side at the end of the torque down control is smaller than the rate of change toward the retard side at the start of the torque down control;
The method for controlling a vehicle internal combustion engine according to claim 1 at the time of starting. The upper limit rate of change is set in accordance with the amount of intake air such that the larger the amount of intake air, the smaller the rate of change toward the advance side.
The method for controlling a vehicle internal combustion engine according to claim 1 at the time of starting. The above-mentioned upper limit rate of change is set so that the advance of the ignition timing is completed after the intake air amount increased due to the start assist control returns to the amount of intake air equivalent to the idle rotation speed after the end of the start assist control. The method for controlling a vehicle internal combustion engine at the time of starting according to claim 3. Internal combustion engines are equipped with a turbocharger,
The method for controlling a vehicle internal combustion engine according to claim 1 at the time of starting. The output of the internal combustion engine is transmitted to the transmission via the clutch, and when the clutch is engaged for starting, start assist control is performed to maintain the engine speed at a target engine speed for starting that is higher than the idle speed. In a start control device for a vehicle internal combustion engine that performs torque reduction control by retarding ignition timing in response to clutch release during start assist control,
A start control device for a vehicle internal combustion engine, which limits the advance of ignition timing at a predetermined upper limit rate of change at the end of the torque down control.

Images