Method and apparatus for controlling the starting of an internal combustion engine in a vehicle.

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

Technical Field

[0001] The present invention relates to start assist control during vehicle start-up involving the engagement operation of a clutch in a vehicle equipped with a clutch between an internal combustion engine and a transmission, and more particularly to a technique for preventing the engine from surging (a rapid increase in rotational speed) when the clutch is disengaged during start assist control.

Background Art

[0002] When starting a vehicle equipped with a manual transmission, after the driver depresses the clutch pedal and selects a gear, the driver then releases the clutch pedal to a semi-engaged state with clutch slip, so that torque transmission is started. At the time of such vehicle start-up, in order to prevent the rotational speed of the internal combustion engine (engine rotational speed) from excessively decreasing and causing the engine to stop, a technique (so-called start assist control) for controlling the output of the internal combustion engine so that the engine rotational speed approaches a target engine rotational speed higher than the idle rotational speed during the clutch engagement operation is known.

[0003] In such start assist control, for example, when the driver does not shift from the semi-engaged state to the fully engaged state but instead depresses the clutch pedal to disengage the clutch, even if the accelerator pedal is not depressed, the throttle valve opening is large, so engine surging occurs.

[0004] In order to suppress engine surging when the clutch is disengaged during start assist control as described above, Patent Document 1 discloses performing torque-down control by retardation of the ignition timing when an overshoot of the rotational speed is detected.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In Patent Document 1, torque reduction control by retarding the ignition timing terminates when the amount of rotational speed overshoot falls below a threshold, and the retarded ignition timing changes to the advanced side. In other words, it advances to the original ignition timing (e.g., the basic ignition timing) corresponding to the operating conditions at that time.

[0007] However, when the ignition timing is advanced in this way, the torque of the internal combustion engine immediately increases, which can cause the engine to rev up again. [Means for solving the problem]

[0008] This invention relates to a vehicle internal combustion engine starting control method in which the output of the internal combustion engine is transmitted to the transmission via a clutch, and starting assist control is performed to maintain the engine speed at a target starting engine speed higher than the idle speed when the clutch is engaged during starting, and torque reduction control is performed by retarding the ignition timing when the clutch is released during this starting assist control, The advance of the ignition timing at the end of the above torque reduction control is limited by a predetermined upper limit of change. death, Here, the above upper limit rate of change is set such that the rate of change toward the advance side decreases as the intake air volume at the end of the torque reduction increases. [Effects of the Invention]

[0009] According to this invention, by limiting the rate of change in the ignition timing advance at the end of torque reduction control, the torque changes gradually, and a sudden surge in acceleration is suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating the system configuration of one embodiment of this invention. [Figure 2] A flowchart illustrating the process flow of the engine over-revving prevention control. [Figure 3]A time chart showing the changes in parameters when the vehicle starts. [Figure 4] Functional block diagram of the engine over-revving prevention control system. [Figure 5] A functional block diagram showing a second embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, an embodiment of this invention will be described in detail with reference to the drawings.

[0012] Figure 1 is a schematic diagram illustrating the system configuration of one embodiment. In this embodiment, a manual transmission 2 is connected to an internal combustion engine 1, and a clutch 3 is interposed between the output shaft of the internal combustion engine 1 and the input shaft of the transmission 2. The output shaft of the transmission 2 is connected to a drive wheel (not shown) via a final reduction mechanism or the like. A neutral switch 5 is provided on the shift lever 4 for selecting the gear of the transmission 2 or on the transmission 2 body side, which outputs a predetermined signal (neutral signal) when the neutral position is selected.

[0013] The internal combustion engine 1 is a spark-ignition engine, also known as a gasoline engine, and provides output corresponding to the opening degree of the electronically controlled throttle valve 6. In one example, it is equipped with a turbocharger, and a compressor 20, driven by an exhaust turbine (not shown), is located upstream of the throttle valve 6. The engine rotational speed is detected by the crank angle sensor 8. The vehicle speed, or vehicle speed, is detected by the vehicle speed sensor 7. The vehicle speed sensor 7 may be of any type that detects vehicle speed directly or indirectly.

[0014] The output of the internal combustion engine 1 is controlled by the engine control unit 11 via the fuel injector 21 and ignition device 22. The amount the accelerator pedal 12 of the vehicle is pressed, i.e., the accelerator opening, is detected by the accelerator opening sensor 13. This accelerator opening sensor 13 also functions as an idle switch by determining that the detected opening is in an idle state. The brake pedal 14 is equipped with a brake switch 15 that detects the pressing of the brake pedal 14, i.e., brake operation. The clutch pedal 16 for operating the clutch 3 is equipped with a first clutch switch 17 that detects when the clutch pedal 16 is pressed even slightly, and a second clutch switch 18 that detects when the clutch pedal 16 is pressed sufficiently until the clutch 3 is no longer transmitting torque. Therefore, when the driver fully depresses the clutch pedal 16 to shift gears using the manual transmission 2, both the first clutch switch 17 and the second clutch switch 18 are turned on. When the clutch pedal 16 is depressed to an intermediate position, in a so-called half-clutch state, the first clutch switch 17 is turned on and the second clutch switch 18 is turned off.

[0015] The detection signals from the neutral switch 5, vehicle speed sensor 7, crank angle sensor 8, accelerator pedal opening sensor 13, brake switch 15, and first and second clutch switches 17 and 18 are input to the engine control unit 11. When the vehicle starts moving, the engine control unit 11 corrects the output of the internal combustion engine via the throttle valve 6 as a so-called starting assist control, bringing the engine speed closer to the target engine speed for starting. In addition to the above, the engine control unit 11 receives detection signals from numerous other sensors for integrated control of the internal combustion engine 1, but these are not shown in the diagram.

[0016] Figure 3 is a time chart showing changes in various parameters when the vehicle starts. In order from the upper part of the figure, (a) the operation position of the clutch pedal 16, (b) the engine rotation speed, (c) the engine torque, (d) the intake air amount of the internal combustion engine 1, and (e) the ignition timing are shown respectively. In the column of (b) the engine rotation speed, the characteristic line b1 is the target engine rotation speed for starting during the start assist control, the characteristic line b2 is the actual engine rotation speed, and further the characteristic line b3 indicates the rotation speed on the output side of the clutch 3 (that is, the input shaft rotation speed of the transmission 2).

[0017] Until time t1, the vehicle is stopped, the transmission 2 is in an appropriate gear suitable for starting, the clutch 3 is in the released state, and the actual engine rotation speed b2 is at the target idle rotation speed. As shown in the (a) column, at time t1, the operation of the driver returning the clutch pedal 16 starts, and at time t2, a so-called half-clutch state is reached. The half-clutch state continues until time t3.

[0018] The start assist control starts with the operation of the clutch 3 at time t1. That is, as shown in the (b) column, the target engine rotation speed b1 for starting is given, and the engine rotation speed is feedback-controlled via the throttle valve 6 so that the actual engine rotation speed b2 follows the target engine rotation speed b1 for starting. The target engine rotation speed b1 for starting is set higher than the target idle rotation speed for smooth starting. By this start assist control, for example, even if the driver does not step on the accelerator pedal 12, the opening degree of the throttle valve 6 increases and the stall of the internal combustion engine 1 is avoided. During the time t2 - t3, by continuing the half-clutch state, the rotation speed b3 on the output side of the clutch 3 gradually increases. This rotation speed b3 on the output side of the clutch 3 basically corresponds to the change in the vehicle speed at the start.

[0019] Normally, at time t3 when the engagement of clutch 3 is completed, as indicated by broken line a1 in column (a), the driver returns the clutch pedal 16, and clutch 3 shifts to the fully engaged state. However, rarely, as indicated by solid line a2 in column (a), clutch 3 may be released at time t3 when the start assist control is being performed.

[0020] When clutch 3 is released during the start assist control in which the opening degree of throttle valve 6 is relatively large in this way, the rotational speed of internal combustion engine 1 tends to surge. However, engine control unit 11 immediately performs torque down control by retarding the ignition timing of ignition device 22 based on the detection of the surge. That is, as shown in column (e), the ignition timing is gradually retarded step by step from the basic ignition timing determined from the engine rotational speed and load to suppress torque. Thereby, the surge of internal combustion engine 1 accompanying the release of clutch 3 is suppressed. Note that the retardation of the ignition timing is performed by adding a retard amount for torque down in the calculation of the ignition timing.

[0021] This torque down control for suppressing the surge ends at time t5 on the condition that the amount of surge of the rotational speed (for example, the difference between the actual engine rotational speed b2 and the target idle rotational speed) is within a predetermined value as will be described later. Along with the end of this torque down control, the ignition timing that has been forcibly retarded until then advances to the basic ignition timing. That is, the retard amount for torque down described above returns to 0. At this time, in the above embodiment, the change rate of the ignition timing advance is limited by a predetermined upper limit change rate so that the ignition timing does not advance rapidly. Therefore, as shown between times t5 and t6 in column (e), the ignition timing gradually changes toward the advancing side. The change rate toward the advancing side at this time is smaller than the change rate toward the retarding side between times t3 and t4. That is, the retardation of the ignition timing for suppressing the surge is performed promptly, and the ignition timing advance at the end of the torque down control is performed gradually.

[0022] If the ignition timing is advanced rapidly, as shown by the dashed line e1 in column (e), the torque will rise with the advance of the ignition timing, especially before the intake air volume has decreased sufficiently (see the dashed line c1 in column (c)). This will cause the actual engine speed b2 to rev up again, as shown by the dashed line b21. In the above embodiment, this re-revving is prevented by limiting the rate of change of the ignition timing advance.

[0023] Figure 2 is a flowchart showing the processing flow of the above-described engine rev-up prevention control performed in the engine control unit 11. This process is repeatedly performed in the engine control unit 11. In step 1, it is determined whether or not the start assist control is currently being performed. If the start assist control is not currently being performed, the process proceeds to step 2, where it is determined whether or not 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, where the operation of the engine rev-up prevention control is prohibited, that is, the torque reduction control due to ignition timing is prohibited. Note that the start assist control is performed based on the operation of the clutch pedal 16, etc., as described above, by other routines not shown in the figure.

[0024] If the start assist control is being performed in Step 1, proceed to Step 4 to determine whether the vehicle speed is within the predetermined speed. If the vehicle has started moving and has already exceeded the predetermined speed, proceed to Step 3 to disable the anti-revving control.

[0025] If the vehicle speed is within the predetermined range in step 4, step 5 determines whether clutch 3 is in the disengaged state. If YES, proceed to step 6. If clutch 3 is in the engaged state or remains in the partially engaged state, proceed to step 3 and disable the anti-revving control. In step 6, determine whether the amount of revving up (for example, the difference between the actual engine speed and the target idle speed) is greater than or equal to a predetermined value. If YES, proceed to step 7. If the amount of revving up is less than the predetermined value, proceed to step 3 and disable the anti-revving control.

[0026] In step 7, the torque reduction coefficient required to suppress engine over-revving is calculated by referring to a map in which values ​​are assigned to parameters such as the amount of engine over-revving (for example, the difference between the actual engine speed b2 and the target idle speed). Then, in step 8, based on this torque reduction coefficient, engine over-revving prevention control, i.e., torque reduction control, is performed by retarding the ignition timing. The amount of timing retardation for torque reduction described above is determined based on the torque reduction coefficient.

[0027] In the next step, step 9, it is determined whether the amount of rotational speed increase due to torque reduction control, i.e., ignition timing retardation, falls within a predetermined value. The ignition timing retardation state is continued until it falls within the 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 set as appropriate in each case.

[0028] If it is determined in step 9 that the amount of engine revving up is within a predetermined value, the process proceeds to step 10, where the ignition timing is advanced while limiting the rate of change by a predetermined upper limit, and then returned to the basic ignition timing. In other words, the amount of retardation for torque reduction is set to 0. Then, in step 11, the series of engine revving prevention control is terminated.

[0029] Figure 4 is a functional block diagram of the engine over-revving prevention control unit 100 included in the engine control unit 11. The functions shown in this block diagram are realized by software or hardware executed by the engine control unit 11.

[0030] As shown in Figure 4, the engine revving prevention control unit 100 includes a starting assist operation state determination unit 101, an elapsed time determination unit 102, a vehicle speed determination unit 103, a clutch release state determination unit 104, an engine revving amount determination unit 105, a torque reduction coefficient calculation unit 106, and a change rate limit command unit 107.

[0031] The start assist operation status determination unit 101 determines whether start assist control is in progress. The elapsed time determination unit 102 determines whether a predetermined time has elapsed since the end of start assist control. The 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 a released state. The rev-up amount determination unit 105 determines the amount of rev-up in rotational speed. The torque down coefficient calculation unit 106 calculates the torque down coefficient necessary to suppress rev-up. The change rate limit command unit 107 outputs a predetermined upper limit change rate when advancing the ignition timing, which has been retarded for torque reduction, at the end of torque reduction, thereby limiting the change rate of ignition timing advance.

[0032] In the above embodiment, the upper limit change rate is a predetermined constant value, and therefore, control is simplified.

[0033] Next, a second embodiment of the present invention will be described. In the second embodiment, the upper limit of the rate of change when returning the ignition timing, which has been retarded for torque reduction, to the basic ignition timing at the end of torque reduction is set according to the amount of intake air at the end of torque reduction, such that the rate of change toward the advance side decreases as the amount of intake air increases. In other words, the larger the amount of intake air compared to the amount of intake air equivalent to the target idle speed, the more likely it is that the engine will rev up when the ignition timing is advanced. Conversely, if the amount of intake air is close to the amount of intake air equivalent to the target idle speed, the less likely it is that the engine will rev up even if the ignition timing is advanced. For this reason, in the second embodiment, the upper limit of the rate of change is set according to the amount of intake air at the end of torque reduction.

[0034] Figure 5 is a functional block diagram showing the configuration of the rev-up prevention control unit 100 of the second embodiment. Similar to the first embodiment shown in Figure 4, the rev-up prevention control unit 100 includes a start assist operation state determination unit 101, an elapsed time determination unit 102, a vehicle speed determination unit 103, a clutch release state determination unit 104, a rev-up amount determination unit 105, a torque down coefficient calculation unit 106, and a change rate limit command unit 107. Furthermore, it includes an intake air amount determination unit 108. The intake air amount determination unit 108 determines the intake air amount at the end of the torque down, when the ignition timing advances from a retarded state, and sets an upper limit change rate according to this intake air amount.

[0035] Preferably, the magnitude of the upper limit change rate is set such that the intake air volume (see column (d)), which increased with the start assist control, returns to the intake air volume equivalent to the target idle speed after the start assist control ends, and then the ignition timing advance is completed.

[0036] According to this second embodiment, the amount of retardation can be returned to 0 relatively quickly while reliably suppressing further acceleration during ignition timing advance.

[0037] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and various modifications are possible. For example, although the above embodiment is applied to a supercharged engine equipped with a turbocharger, the present invention can also be applied to a naturally aspirated engine. In the above embodiment equipped with a turbocharger, the decrease in intake air volume after the end of the starting assist control tends to be delayed, so the re-revving due to the advance of the ignition timing at the end of the torque reduction is more likely to become a problem. [Explanation of Symbols]

[0038] 1…Internal combustion engine 2…Transmission 3...Clutch 6…Throttle valve 11…Engine control unit 11 16... Clutch pedal

Claims

1. In a vehicle internal combustion engine starting control method in which the output of the internal combustion engine is transmitted to the transmission via a clutch, and starting assist control is performed to maintain the engine speed at a target starting engine speed higher than the idle speed when the clutch is engaged during starting, and torque reduction control is performed by retarding the ignition timing when the clutch is released during this starting assist control, The advance angle of the ignition timing at the end of the above torque reduction control is limited to a predetermined upper limit of change rate. Here, the above upper limit rate of change is set such that the rate of change toward the advance side decreases as the intake air volume at the end of the torque reduction increases. A method for controlling the starting of an internal combustion engine in a vehicle.

2. The above upper limit of the change rate is set such that the rate of change towards the ignition timing advance at the end of the torque reduction control is smaller than the rate of change towards the retarded ignition timing at the start of the torque reduction control. A method for controlling the starting of a vehicle internal combustion engine according to claim 1.

3. The starting control method for a vehicle internal combustion engine according to claim 1, wherein the upper limit change rate is set such that the intake air volume, which increased in conjunction with the starting assist control, returns to the intake air volume equivalent to the idle rotation speed after the start assist control is completed, and then the ignition timing advance is completed.

4. The internal combustion engine is equipped with a turbocharger. A method for controlling the starting of a vehicle internal combustion engine according to claim 1.

5. In a vehicle internal combustion engine starting control device, the output of the internal combustion engine is transmitted to the transmission via a clutch, and when the clutch is engaged during starting, starting assist control is performed to maintain the engine speed at a target starting engine speed higher than the idle speed, and torque reduction control is performed by retarding the ignition timing when the clutch is released during this starting assist control, The advance angle of the ignition timing at the end of the above torque reduction control is limited to a predetermined upper limit of change rate. Here, the above upper limit rate of change is set such that the rate of change toward the advance side decreases as the intake air volume at the end of the torque reduction increases. A control device for starting an internal combustion engine in a vehicle.

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