Method and device for controlling the torque of an internal combustion engine

Abstract

Depending on various situations, the second starting-time target torque T #2, which is the final target torque, may approach the driver requested torque TR immediately after the start of the control, and the starting-time torque suppression control may end.SOLUTION: In the starting-time torque suppression control, the first starting-time target torque T #1 is set with respect to the driver request torque TR corresponding to the accelerator opening APO so as to reduce the shock of the vehicle caused by the inversion of the transmission torque immediately after the starting. A second starting time target torque T #2 is set by adding a limit of minimum torque Tmin determined by a maximum retard quantity to the first starting time target torque T #1, and ignition timing retard is performed so as to realize this. When the first start-time target torque T #1, not the second start-time target torque T #2, approaches the driver request torque TR, the start-time torque suppression control is ended.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a torque suppression control at start-up that suppresses the torque of an internal combustion engine by retarding ignition timing in order to reduce shock caused by a reversal of torque transmitted between a vehicle drivetrain and an internal combustion engine when the vehicle starts moving. [Background technology]

[0002] It is known that when a driver depresses the accelerator pedal to start a vehicle, a relatively large shock occurs in the vehicle due to a reversal in the direction of torque transmitted between the vehicle drivetrain and the internal combustion engine.

[0003] For this reason, as described in Patent Document 1, torque suppression control at start-up is generally performed, which limits the actual torque to a value lower than the required torque indicated by the accelerator pedal position. In Patent Document 1, torque is limited by correcting the throttle valve position, but a more responsive torque suppression method is ignition timing retardation. By retarding the ignition timing to achieve a target torque that is set to suppress the shock caused by the reversal of the transmission torque described above, torque can be limited with good responsiveness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-124857 Summary of the Invention [Problem to be solved by the invention]

[0005] The torque suppression control during start-up as described above can generally be released, or terminated, when the target torque during torque suppression approaches the required torque corresponding to the accelerator pedal position. When torque suppression is performed by retarding the ignition timing, the target torque is limited by the maximum possible retard amount. In other words, the target torque cannot be set to a value smaller than the minimum torque determined by the maximum retard amount.

[0006] Therefore, depending on the transient driving conditions at the time of starting, the target torque limited by the maximum retard amount may become a relatively large value immediately after starting, i.e., immediately after the torque suppression control starts, and may approach the required torque at that time. As a result, the torque suppression control may end earlier than the period required to reduce the shock caused by the reversal of the transmission torque. [Means for solving the problem]

[0007] The present invention provides a torque control method for an internal combustion engine for performing start-up torque suppression control for suppressing the torque of the internal combustion engine by retarding ignition timing in order to reduce shock caused by a reversal of torque transmitted between a vehicle drivetrain and the internal combustion engine when the throttle valve opening of the internal combustion engine changes from an idle position to a non-idle position and the vehicle starts, comprising: Sets the driver's requested torque based on the accelerator opening. setting a first target torque at start-up suitable for reducing the shock based on the driver requested torque; The minimum torque corresponding to the maximum allowable retard amount of the ignition timing retard is calculated. setting a second target torque at the time of starting by adding a limit based on the minimum torque to the first target torque; During the start-up torque suppression control, the ignition timing is retarded so that the actual torque is in line with the second start-up target torque, and the first target torque is compared with the driver requested torque, and when the first target torque approaches the driver requested torque, the start-up torque suppression control is terminated.

[0008] In other words, the second target torque for starting, which is limited by the minimum torque determined from the maximum retard amount, is used as the target torque for controlling the actual torque via ignition timing retard, while the first target torque for starting, which does not take into account the minimum torque based on the maximum retard amount, is used as the target torque for determining the end of the starting torque suppression control. Therefore, even if the minimum torque based on the maximum retard amount is relatively large, the starting torque suppression control will not end prematurely. [Effects of the Invention]

[0009] According to this invention, it is possible to reliably avoid the phenomenon in which torque suppression control is terminated earlier than the period required to reduce the shock associated with the reversal of the transmission torque due to transient operating conditions at the time of starting, and it is possible to reliably suppress torque at the time of starting by using ignition timing retard. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating the configuration of a drive system of a vehicle according to an embodiment of the present invention; [Figure 2] 4 is a time chart of torque suppression control at the time of starting in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of a drivetrain of a vehicle equipped with an internal combustion engine 1 to which torque control according to one embodiment is applied. The embodiment is a rear-wheel drive vehicle. A transmission 2 is connected to the internal combustion engine 1, and the output of the transmission 2 drives drive wheels 4 via a final drive unit 3. In this embodiment, the transmission 2 is a stepped automatic transmission. Although not shown in detail, the automatic transmission 2 is composed of a torque converter with a lock-up clutch and a stepped transmission mechanism including a planetary gear mechanism and multiple friction engagement elements (clutches and / or brakes). The lock-up clutch and transmission mechanism of the automatic transmission 2 are controlled by an automatic transmission controller 5. For example, when a selector (not shown) selects the automatic shift range (so-called D range), an appropriate gear is selected based on a predetermined shift map using mainly accelerator pedal depression and vehicle speed as parameters, and gears are automatically shifted. A vehicle speed signal and an accelerator pedal depression signal are input to the automatic transmission controller 5 directly or indirectly via another controller.

[0012] The internal combustion engine 1 is a four-stroke, spark-ignition internal combustion engine, commonly known as a gasoline engine. The internal combustion engine 1 is controlled by an engine controller 6. The AT controller 5 and the engine controller 6 are connected to each other via an on-board network 7 (e.g., CAN communication) and transmit and receive necessary signals. The engine controller 6 receives detection signals directly or via other controllers from sensors such as a crank angle sensor 11 for detecting the engine speed, an air flow meter 12 for detecting the intake air amount corresponding to the load, a water temperature sensor 13 for detecting the coolant temperature, an accelerator position sensor 14 for detecting the accelerator pedal position (depression amount) operated by the driver, an idle switch 15 for detecting whether the throttle valve is at the idle position, and an air-fuel ratio sensor 16 for detecting the exhaust air-fuel ratio. Based on these detection signals, the engine controller 6 optimally controls the fuel injection amount and injection timing of the fuel injection valve, the ignition timing of the spark plug, the throttle valve opening, and the like.

[0013] Here, when the vehicle starts, that is, when the throttle valve opening changes from the idle position to the non-idle position and the vehicle starts, the engine controller 6 executes start-up torque suppression control that suppresses the torque of the internal combustion engine 1 by retarding the ignition timing in order to reduce vehicle shock caused by a reversal in the direction of the torque transmitted between the internal combustion engine 1 and the vehicle drivetrain including the transmission 2. In other words, when the driver depresses the accelerator pedal to start the vehicle, torque suppression is performed by retarding the ignition timing so that the actual torque is temporarily lower at the time of the reversal of the transmitted torque than the required torque indicated by the accelerator opening.

[0014] Next, specific examples of the torque suppression control at start-up will be described with reference to the time chart in Figure 2. The time chart in Figure 2 shows the torque suppression control at start-up when the accelerator pedal is not depressed and the vehicle is stationary until time t0, and the driver depresses the accelerator pedal at time t0, causing the vehicle to start. Column (a) at the top of the chart shows the accelerator opening APO. As shown in the figure, the accelerator opening is 0 until time t0, increases from time t0, and reaches a constant opening at time t1. The accelerator opening at this time is relatively small, resulting in what is known as slow acceleration.

[0015] The next column (b) is PAJState, which indicates the progress of the start-up torque suppression control, and is shown in five stages from the initial stage 1 to stage 5. As will be described later, the start-up torque suppression control ends when a predetermined time has elapsed since the system reached stage 5. The start-up torque suppression control starts when the idle switch 15 is turned off.

[0016] Column (c) of Figure 2 shows a comparison of several torque characteristics. Characteristic line TR is the driver-requested torque based on accelerator pedal position APO. In the illustrated example, driver-requested torque TR increases in accordance with accelerator pedal position APO until time t1, and remains constant after time t1. Note that although the throttle valve opening is not shown, the throttle valve opening basically has a characteristic that follows the driver-requested torque TR (in other words, accelerator pedal position APO). If necessary, the throttle valve opening may be set by making an appropriate correction to the accelerator pedal position APO.

[0017] Characteristic line T#1 is a first target torque at start-up that is set based on the driver request torque TR as a characteristic suitable for reducing shock when the transmission torque is reversed. As shown in the figure, this first target torque at start-up T#1 is set to a value that is sufficiently low to reduce shock for an appropriate period immediately after start-up, and then gradually approaches the driver request torque TR.

[0018] The characteristic line Tmax shows the characteristics of the maximum torque obtained when the ignition timing is not retarded, that is, when the ignition timing is at the reference ignition timing (effectively the MBT point). In other words, when the accelerator opening APO changes as shown in the figure, the vehicle starts moving, and then slowly accelerates, if torque suppression by ignition timing retardation is not performed, the actual torque will be generated along the characteristics of this maximum torque Tmax.

[0019] The characteristic line Tmin shows the minimum torque characteristic obtained when the ignition timing is retarded by the maximum allowable retard amount. The maximum retard amount is set to the maximum retard amount within the range in which misfires are not caused by the ignition timing retard. Therefore, the minimum torque Tmin is the smallest torque that can be achieved by retarding the ignition timing without causing misfires, and the actual torque cannot be reduced below this by retarding the ignition timing.

[0020] Therefore, in the torque suppression control at the time of starting using the ignition timing retard, the actual torque can be controlled between the maximum torque Tmax and the minimum torque Tmin.

[0021] The characteristic line T#2 is a second target torque at start-up obtained by adding a limit of the minimum torque Tmin to the first target torque at start-up T#1. In other words, if the target torque is smaller than the minimum torque Tmin, there is a concern that misfires may occur due to ignition timing retardation. Therefore, the second target torque at start-up T#2 is a target torque obtained by limiting the lower limit of the first target torque at start-up T#1 by the minimum torque Tmin.

[0022] Ultimately, the torque of the internal combustion engine 1 is controlled using this second target torque T#2 at start-up as the target torque. In other words, the amount of ignition timing retard is controlled to realize the second target torque T#2 at start-up. Because the torque change due to the ignition timing retard is obtained with good responsiveness, the actual torque has characteristics that substantially follow the second target torque T#2 at start-up as shown in the figure.

[0023] In the illustrated example, the first starting target torque T#1 is smaller than the minimum torque Tmin until time t2, so the second starting target torque T#2 has characteristics that are different from the first starting target torque T#1 and are in line with the minimum torque Tmin. After time t2, the first starting target torque T#1 is larger than the minimum torque Tmin, so the second starting target torque T#2 has the same characteristics as the first starting target torque T#1.

[0024] As a result of the actual torque being suppressed in accordance with the second start-up target torque T#2 in this manner, the shock caused by the reversal of the torque transmitted between the vehicle drivetrain and the internal combustion engine 1 is reduced.

[0025] Here, the above-described start torque suppression control is terminated when the first start target torque T#1, not the second start target torque T#2, approaches the driver request torque TR. In other words, the first start target torque T#1, which does not take into account the minimum torque Tmin based on the maximum retard amount, is used as the target torque for determining the termination of the start torque suppression control. Therefore, even if the minimum torque Tmin based on the maximum retard amount is relatively large, the start torque suppression control is not terminated prematurely.

[0026] Specifically, after the start of the torque suppression control, the first target torque T#1 is repeatedly compared with the driver's requested torque TR. The five-stage PAJState shown in section (b) indicates the progress of the torque suppression control, and at time t3 when the difference between the first target torque T#1 and the driver's requested torque TR becomes equal to or smaller than a predetermined value, the PAJState advances from the fourth stage to the fifth stage. Then, when a predetermined time has elapsed since the PAJState advanced to the fifth stage (time t4), the torque suppression control ends.

[0027] 2, the second start-up target torque T#2, which is the final target torque, is limited by the minimum torque Tmin. Therefore, when the vehicle starts to start and the start-up torque suppression control is initiated, the second start-up target torque T#2 moves away from the first start-up target torque T#1 and increases to the magnitude of the minimum torque Tmin. If the start-up torque suppression control is to be terminated when the second start-up target torque T#2 as the target torque approaches the driver request torque TR, depending on various circumstances, as shown at point P in the figure, the second start-up target torque T#2 may approach the driver request torque TR immediately after the start of the control, thereby terminating the start-up torque suppression control. If the start-up torque suppression control is terminated at point P, the actual torque will be generated according to the characteristics of the maximum torque Tmax, and torque suppression for shock reduction will not be achieved.

[0028] In the above embodiment, the first starting target torque T#1, which does not take into account the minimum torque Tmin, which is different from the final target torque, is used as the target torque for determining the end of starting torque suppression control, so that starting torque suppression control can be reliably continued until this first starting target torque T#1 approaches the driver required torque TR.

[0029] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified in various ways. For example, the configuration of the vehicle drivetrain is not limited to the configuration shown in FIG. 1, and any type of configuration, such as a configuration in which the internal combustion engine is mounted transversely, may be used. Furthermore, the present invention is not limited to slow acceleration when starting a vehicle, and can be similarly applied to relatively sudden starts. [Explanation of symbols]

[0030] 1...Internal combustion engine 2...Gearbox 4...Drive wheels 6...Engine controller 14...Accelerator opening sensor 15...Idle switch

Claims

1. A torque control method for an internal combustion engine for a vehicle, which performs start-up torque suppression control to suppress the torque of the internal combustion engine by retarding ignition timing in order to reduce shock caused by a reversal of torque transmitted between a vehicle drivetrain and the internal combustion engine when a throttle valve opening of the internal combustion engine changes from an idle position to a non-idle position and the vehicle starts, comprising: Sets the driver's requested torque based on the accelerator opening. setting a first target torque at start-up that is suitable for reducing the shock based on the driver requested torque; The minimum torque corresponding to the maximum allowable retard amount of the ignition timing retard is calculated. setting a second target torque at the time of starting by adding a limit based on the minimum torque to the first target torque; During the start-up torque suppression control, ignition timing is retarded so that the actual torque is in line with the second start-up target torque, and the first target torque is compared with the driver request torque, and when the first target torque approaches the driver request torque, the start-up torque suppression control is terminated. A method for controlling torque in an internal combustion engine.

2. The maximum retard amount is set to the largest amount possible within the range where misfires do not occur due to ignition timing retard.

2. The torque control method for an internal combustion engine according to claim 1.

3. When a predetermined time has elapsed since the difference between the first target torque and the driver requested torque becomes equal to or less than a predetermined value, the start-up torque suppression control is terminated.

2. The torque control method for an internal combustion engine according to claim 1.

4. A torque control device for an internal combustion engine performs start-up torque suppression control by retarding ignition timing to suppress torque of the internal combustion engine in order to reduce shock caused by reversal of torque transmitted between a vehicle drivetrain and the internal combustion engine when a throttle valve opening of the internal combustion engine changes from an idle position to a non-idle position and the vehicle starts, This torque control device is Sets the driver's requested torque based on the accelerator opening. setting a first target torque at start-up that is suitable for reducing the shock based on the driver requested torque; The minimum torque corresponding to the maximum allowable retard amount of the ignition timing retard is calculated. setting a second target torque at the time of starting by adding a limit based on the minimum torque to the first target torque; During the start-up torque suppression control, ignition timing is retarded so that the actual torque is in line with the second start-up target torque, and the first target torque is compared with the driver request torque, and when the first target torque approaches the driver request torque, the start-up torque suppression control is terminated. Torque control device for internal combustion engines.

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