Torque-down control method and device for internal combustion engine for vehicle

Abstract

To solve the problem of a supercharged internal combustion engine that when an accessor pedal is operated into a fully closed state during up-shift gear change of an automatic transmission, a target torque-down amount TD2 is excessively calculated under an influence of remaining boost pressure, resulting in generation of unnecessary secondary torque-down.SOLUTION: An AT transmission torque calculation part 23 normally finds AT transmission torque Te3 as an intermediate value between driver request torque Te1 corresponding to an accelerator pedal opening and estimated torque Te2 based upon charging efficiency, and outputs it to an AT request torque calculation part 25. If an accelerator pedal is fully closed during up-shift gear change, a torque signal changeover flag FL1 is turned ON, and the AT transmission torque calculation part 23 supplies a value of the estimated torque Te2 as the AT transmission torque Te3 to an AT controller 5. Consequently, AT request torque Te4 becomes larger, and no secondary torque-down is generated.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to torque reduction control for a vehicle internal combustion engine, which reduces torque by retarding the ignition timing of the internal combustion engine when a gear change in a stepped automatic transmission connected to a supercharged internal combustion engine or an upshift by step shifting in a continuously variable transmission. [Background technology]

[0002] When upshifting by shifting gears in a stepped automatic transmission connected to a vehicle's internal combustion engine or by step shifting in a continuously variable transmission, it is known to reduce torque by retarding the ignition timing of the internal combustion engine, as described in Patent Document 1, mainly to mitigate shift shock.

[0003] The amount or degree of ignition timing retard is basically determined by comparing the target torque during the torque reduction request with the estimated torque that should be output at a reference ignition timing (e.g., MBT point), as described in Patent Document 1. In other words, the smaller the target torque is compared to the estimated torque at the MBT point, the greater the required amount of torque reduction, i.e., the amount or degree of ignition timing retard. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-316632 Summary of the Invention [Problem to be solved by the invention]

[0005] An upshift in an automatic transmission is performed, for example, when the vehicle speed increases while the vehicle is slowly accelerating on a flat road. Therefore, the accelerator pedal is generally held at a certain intermediate position. A so-called change of mind may occur when the driver releases the accelerator pedal, i.e., fully closes it, before the shift process is completed (in other words, during the period when ignition timing retardation is permitted). In such a case, in an internal combustion engine equipped with a supercharger, the decrease in boost pressure is delayed even though the throttle valve opening area is reduced as the accelerator pedal is closed.

[0006] Therefore, the estimated torque value at the MBT point, which is the basis for calculating the amount of torque reduction, increases by the amount of boost pressure remaining in the intake system.If the target torque after torque reduction were simply determined without taking the remaining boost pressure into account, the deviation between the target torque and the estimated torque at the MBT point would become large, resulting in a secondary torque reduction (ignition timing retard) that is unrelated to the gear shift process.

[0007] Depending on the timing of when the accelerator pedal is fully closed, a secondary torque reduction unrelated to the above-mentioned gear shift process may occur after the torque reduction associated with the gear shift has ended, causing large temporary fluctuations in the torque input to the transmission. For example, such torque fluctuations can cause front-to-rear vibrations in the vehicle. [Means for solving the problem]

[0008] The present invention provides a torque reduction control method for a vehicle internal combustion engine, which reduces torque by retarding ignition timing of the internal combustion engine when a gear change of a stepped automatic transmission connected to the internal combustion engine or an upshift by step shift of a continuously variable transmission connected to the internal combustion engine having a supercharger, comprising: Calculates the driver's requested torque according to the accelerator pedal opening, A charging efficiency of the internal combustion engine is obtained, and an estimated torque to be output under a reference ignition timing is calculated based on the charging efficiency. calculating an AT transmission torque as a torque value excluding the torque reduction due to the ignition timing retard and the torque reduction due to the throttle opening correction based on the driver requested torque and the estimated torque; The required torque reduction amount necessary for inertia absorption is determined, and the AT required torque is calculated from this required torque reduction amount and the AT transmission torque. determining a target torque reduction amount by retarding the ignition timing based on a comparison between the estimated torque and the AT required torque; A torque reduction control method for a vehicle internal combustion engine, comprising: When the accelerator pedal is closed during an upshift, the value of the AT transmission torque used to calculate the AT required torque is switched to the value of the estimated torque.

[0009] When the accelerator pedal is pressed during an upshift, the estimated torque based on the charging efficiency is affected by the residual boost pressure in the intake system. By switching to the estimated torque value as the AT transmission torque value used to calculate the AT required torque, the AT required torque also takes into account the influence of the residual boost pressure in the intake system. In other words, the AT required torque becomes larger than the driver required torque based on the accelerator pedal opening, and the target torque reduction amount based on the comparison between the estimated torque and the AT required torque becomes smaller (for example, to 0). In other words, the occurrence of a secondary torque reduction due to the influence of the residual boost pressure is avoided. [Effects of the Invention]

[0010] According to this invention, in an internal combustion engine having a supercharger, when the accelerator pedal is closed during an upshift in which torque is reduced by retarding the ignition timing, the occurrence of a secondary torque reduction due to the influence of the supercharging pressure remaining in the intake system is avoided, and torque fluctuations and vehicle vibrations caused by this secondary torque reduction can be prevented. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating the configuration of a drive system of a vehicle according to an embodiment; [Figure 2] FIG. 4 is a functional block diagram relating to a calculation process of a torque reduction amount. [Figure 3] 6 is a time chart showing the operation of an embodiment when the accelerator pedal is fully closed during an upshift. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows the configuration of a drivetrain for a vehicle according to the embodiment. This embodiment is a rear-wheel drive vehicle. A transmission 2 is connected to an internal combustion engine 1, and the output of the transmission 2 drives drive wheels 4 via a final drive unit 3. The transmission 2 is a stepped automatic transmission. Although not shown in detail, the automatic transmission 2 includes a torque converter 2A incorporating a lockup clutch and a stepped speed change mechanism 2B including a planetary gear mechanism and multiple friction engagement elements (clutches and / or brakes). The lockup clutch and speed change mechanism 2B 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 (the so-called D range), an appropriate gear is selected based on a predetermined shift map, with accelerator pedal position and vehicle speed as parameters, and gears are automatically changed. A vehicle speed signal VSP and an accelerator pedal position signal APO are input to the automatic transmission controller 5 directly or indirectly via another controller.

[0013] In one embodiment, the internal combustion engine 1 is a four-stroke spark-ignition internal combustion engine, or so-called gasoline engine, equipped with a turbocharger (not shown) as a supercharger. 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 exchange necessary signals. The engine controller 6 receives, directly or via other controllers, detection signals from various sensors, such as a crank angle sensor 11 for detecting the engine speed, an air flow meter 12 for detecting the intake air amount, a water temperature sensor 13 for detecting the coolant temperature, an accelerator pedal position sensor 14 for detecting the accelerator pedal position operated by the driver and outputting the above-mentioned position signal APO, an air-fuel ratio sensor 15 for detecting the exhaust air-fuel ratio, and a supercharging pressure sensor 16 for detecting the supercharging pressure. 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, the supercharging pressure (in other words, the wastegate valve opening), and the like.

[0014] During an upshift of the transmission mechanism 2B (a shift from a low gear to a high gear, such as "3rd gear to 4th gear"), the AT controller 5 requests the engine controller 6 to temporarily reduce the torque of the internal combustion engine 1 in order to mitigate shift shock and ensure a smooth shift (i.e., a gear change). In response to this torque reduction request from the AT controller 5, the engine controller 6 executes ignition timing retard, which corrects the ignition timing from the reference ignition timing at that time (e.g., MBT point). Typically, the torque reduction request is output during a period corresponding to the inertia phase of the upshift. The period during which the torque reduction request is output varies depending on the nature of the upshift (from which gear to which gear) and other conditions, and is controlled by the AT controller 5 to achieve an optimum period for the shift.

[0015] The torque reduction amount is ultimately calculated by the engine controller 6 so as to realize the requested torque (torque to be input to the transmission 2) that the AT controller 5 outputs to the engine controller 6.

[0016] In addition to torque reduction by retarding the ignition timing, throttle valve opening correction may be performed for various purposes as a slow torque reduction with low response, but the present invention is concerned with torque reduction by retarding the ignition timing.

[0017] 2 is a functional block diagram showing the exchange of signals between the AT controller 5 and the engine controller 6 for calculating the torque reduction amount. An opening signal APO from an accelerator pedal opening sensor 14, which indicates the opening of the accelerator pedal operated by the driver, is input to a driver requested torque calculation unit 21 in the engine controller 6. The driver requested torque calculation unit 21 calculates a driver requested torque Te1 based on the opening signal APO. Simply put, the greater the accelerator pedal opening, the greater the driver requested torque Te1.

[0018] Changes in the accelerator pedal opening degree also affect the charging efficiency of the internal combustion engine 1. The estimated torque calculation unit 22 in the engine controller 6 determines the charging efficiency at that time using the boost pressure detected by the boost pressure sensor 16, the throttle valve opening, the intake air amount, the engine rotation speed, and other parameters, and calculates the estimated torque Te2 that will be output at the reference ignition timing based on this charging efficiency. Any method for calculating the charging efficiency may be used. The torque generated by combustion is basically correlated with the charging efficiency.

[0019] The driver request torque Te1 and the estimated torque Te2 are input to an AT transmission torque calculation unit 23 in the engine controller 6. Based on the driver request torque Te1 and the estimated torque Te2, the AT transmission torque calculation unit 23 calculates an AT transmission torque Te3 as an intermediate torque value between the two values, and outputs the calculated value to the AT controller 5. The AT transmission torque Te3 is generated as a torque value excluding torque reduction due to ignition timing retardation and torque reduction due to throttle valve opening correction. In other words, the estimated torque Te2, which indicates the torque generated under the reference ignition timing, does not include torque reduction due to ignition timing retardation. However, if torque reduction due to throttle valve opening correction is performed for some purpose, this will affect the charging efficiency, which in turn will affect the estimated torque Te2. To suppress this effect, the estimated torque Te2 is corrected using the value of the driver request torque Te1 to obtain the AT transmission torque Te3. For example, in a simple manner, the AT transmission torque Te3 is generated as an intermediate value between the value of the estimated torque Te2 and the value of the driver request torque Te1.

[0020] The AT transmission torque Te3 output from the engine controller 6 is input to an AT required torque calculation unit 25 in the AT controller 5. Furthermore, an inertia absorption torque down calculation unit 26 in the AT controller 5 calculates a required torque down amount TD1 required for inertia absorption during an upshift. The required torque down amount TD1 changes from moment to moment during the shift process, so the inertia absorption torque down calculation unit 26 calculates the required torque down amount TD1 required at that time based on the mode of the upshift and the progress of the shift, and outputs this to the AT required torque calculation unit 25. The AT required torque calculation unit 25 calculates an AT required torque Te4 from the AT transmission torque Te3 and the required torque down amount TD1 provided by the engine controller 6. For example, the AT required torque Te4 can be obtained by subtracting the required torque down amount TD1 from the AT transmission torque Te3. This AT required torque Te4 is output from the AT controller 5 to the engine controller 6. That is, the AT required torque Te4 indicates a torque value that is desirable on the transmission 2 side during the shift period.

[0021] The AT required torque Te4 is input to a target torque reduction amount calculation unit 28 in the engine controller 6. Preferably, the AT required torque Te4 is filtered to suppress sudden changes before being input to the target torque reduction amount calculation unit 28. The target torque reduction amount calculation unit 28 also receives the estimated torque Te2 based on the above-mentioned charging efficiency. The target torque reduction amount calculation unit 28 calculates a target torque reduction amount TD2 from the estimated torque Te2 and the AT required torque Te4. For example, the target torque reduction amount TD2 is obtained by subtracting the AT required torque Te4 from the estimated torque Te2. The ignition timing retard amount for the ignition device of the internal combustion engine 1 is determined based on this target torque reduction amount TD2. For example, the target torque reduction amount TD2 is converted into the ignition timing retard amount using a map.

[0022] In the present invention, when the accelerator pedal opening becomes 0 (i.e., fully closed) during a period (torque down request period) during an upshift gear change in which torque down is permitted, a torque signal switch flag output unit 30 outputs a torque signal switch command (i.e., the torque signal switch flag FL1 is turned ON) to the AT transmission torque calculation unit 23. Based on this torque signal switch command, the AT transmission torque calculation unit 23 switches the AT transmission torque Te3 from an intermediate value between the estimated torque Te2 and the driver request torque Te1 to the value of the estimated torque Te2, and outputs this AT transmission torque Te3 to the AT request torque calculation unit 25 in the AT controller 5. In other words, the AT transmission torque Te3 is generated as a value substantially equal to the estimated torque Te2. Note that, during switching, appropriate processing is added so that the AT transmission torque Te3 changes gradually to avoid a sudden change in value. The torque signal switch flag FL1 turns OFF, for example, when the torque down request period for gear change ends. Alternatively, it turns OFF after a predetermined time has passed since it was turned ON. When the torque signal switching flag FL1 is turned OFF, the AT transmission torque calculation unit 23 returns to its initial state and generates the AT transmission torque Te3 as an intermediate value between the estimated torque Te2 and the driver request torque Te1 based on the both.

[0023] In a preferred embodiment, the torque signal switch flag output unit 30 turns on the torque signal switch flag when all of the following conditions are met: a torque down request period is in progress, the actual gear ratio is equal to or less than a predetermined threshold as the gear change progresses (for example, at the end of the gear change process), and the accelerator pedal opening degree has changed from a state greater than the predetermined threshold to a state less than the threshold during the upshift. The accelerator pedal opening degree threshold is set, for example, to be close to fully closed, but it may also be a slightly larger intermediate opening degree.

[0024] If the accelerator pedal opening APO becomes zero due to a change of mind during a torque-down request period during which torque reduction is permitted during an upshift, the driver requested torque Te1 drops sharply along with the accelerator pedal opening APO. However, the estimated torque Te2 becomes relatively higher than the driver requested torque Te1 due to residual boost pressure in the intake system. In this situation, if the AT transmission torque Te3 is generated as an intermediate value between the driver requested torque Te1 and the estimated torque Te2, even if the requested torque-down amount TD1 calculated by the inertia absorption torque-down calculation unit 26 is zero, the AT transmission torque Te3 will be lower than the estimated torque Te2, resulting in the AT requested torque Te4 being lower than the estimated torque Te2. As a result, the target torque-down amount TD2 output from the target torque-down amount calculation unit 28 is based on the difference between the two. This results in an unnecessary secondary torque-down, which can cause vehicle longitudinal vibration.

[0025] In contrast to this, in the above embodiment, when accelerator pedal opening APO becomes 0 due to a change of mind, AT transmission torque Te3 temporarily becomes the value of estimated torque Te2 and is input to AT required torque calculation section 25. Therefore, for example, if required torque down amount TD1 by inertia absorption torque down calculation section 26 is 0, AT required torque Te4 calculated from AT transmission torque Te3 and required torque down amount TD1 becomes substantially equal to estimated torque Te2, and target torque down amount TD2 output by target torque down amount calculation section 28 becomes substantially 0. This prevents unnecessary secondary torque down from occurring.

[0026] Next, Figure 3 is a time chart showing the operation of one embodiment when the accelerator pedal is fully closed during an upshift. From top to bottom, the chart shows (a) upshift determination, (b) accelerator pedal opening APO, (c) torque signal switch flag FL1, (d) torque, (e) torque reduction request flag FL2, (f) actual gear ratio, and (g) requested torque reduction amount TD1. In the (d) torque column, the actual torque Te0 of the internal combustion engine 1 (torque after torque reduction due to ignition timing retard), the driver requested torque Te1, and the AT transmission torque Te3 are shown superimposed.

[0027] In the illustrated example, a decision (i.e., a request) for an upshift (e.g., from third to fourth gear) is made (i.e., requested) at time t1 based on vehicle operating conditions, and a series of gear shifting processes is initiated. In order to absorb the inertia torque associated with the gear shift, a torque reduction is requested during the period from time t2 to t3. The actual requested torque reduction amount TD1 is not constant during this period, but is calculated to have the characteristics shown in, for example, column (g).

[0028] Here, after the shift starts, the driver closes the accelerator pedal as a so-called change of mind, and at time t4, it is detected that the accelerator pedal opening APO is equal to or less than a predetermined threshold APO#. Also, in the illustrated example, at time t4, the actual gear ratio R is equal to or less than the predetermined threshold R#, as shown in line (e). Therefore, the torque signal switch flag FL1 shown in line (c) is turned ON, and the AT transmission torque Te3 output to the AT controller 5 becomes substantially equal to the estimated torque Te2.

[0029] This avoids the secondary torque reduction caused by the estimated torque Te2 including the influence of the boost pressure remaining in the intake system, as described above. As shown in section (d), the actual torque Te0 is reduced in accordance with the requested torque reduction amount TD1 required by the AT controller 5 to absorb the inertia torque, and then decreases with a slight delay from the reduction in the driver requested torque Te1.

[0030] Column (d) also shows a comparative example. The characteristics shown by the imaginary line Te3' represent the characteristics of the AT transmission torque Te3' when it is generated as an intermediate value between the driver request torque Te1 and the estimated torque Te2 based on the two. This value of the AT transmission torque Te3' is lower than the estimated torque Te2, which is affected by the remaining boost pressure, and therefore a secondary torque reduction occurs. The characteristics shown by the imaginary line Te0' represent the characteristics of the actual torque Te0' when such a secondary torque reduction occurs. This secondary torque reduction results in large torque fluctuations.

[0031] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, an example is given of a gear shift in the stepped automatic transmission 2, but even in the case of a continuously variable transmission, if the transmission is a step-type gear shift (pseudo-step gear shift) in which the gear ratio is fixed in stages, for example, from third gear to fourth gear, the present invention can be similarly applied to the torque reduction request during this step shift.

[0032] In addition, in the above embodiment, torque reduction control is realized by two controllers, the AT controller 5 and the engine controller 6, but the control method of the present invention can also be applied when torque reduction control is performed by a single controller.

[0033] Furthermore, the supercharger is not limited to a turbocharger, but may be a mechanically driven supercharger, an electric supercharger, etc. In the case of a turbocharger, since it continues to rotate due to inertia even when the accelerator pedal opening becomes zero, a delay in the reduction of the supercharging pressure is likely to occur. [Explanation of symbols]

[0034] 1...Internal combustion engine 2...Automatic transmission 5...AT controller 6...Engine controller 21...Driver required torque calculation section 22...Estimated torque calculation section 23...AT transmission torque calculation section 25...AT required torque calculation section 26...Inertia absorption torque down calculation section 28...Target torque reduction amount calculation unit

Claims

1. A torque reduction control method for a vehicle internal combustion engine, which performs torque reduction by retarding ignition timing of the internal combustion engine when shifting a gear of a stepped automatic transmission connected to the internal combustion engine or when upshifting by step shifting of a continuously variable transmission connected to the internal combustion engine, comprising: Calculates the driver's requested torque according to the accelerator pedal opening, A charging efficiency of the internal combustion engine is obtained, and an estimated torque to be output under a reference ignition timing is calculated based on the charging efficiency. calculating an AT transmission torque as a torque value excluding the torque reduction due to the ignition timing retard and the torque reduction due to the throttle opening correction based on the driver requested torque and the estimated torque; A required torque reduction amount necessary for inertia absorption is obtained, and an AT required torque is calculated from this required torque reduction amount and the AT transmission torque. determining a target torque reduction amount to be achieved by retarding the ignition timing based on a comparison between the estimated torque and the AT required torque; A torque reduction control method for a vehicle internal combustion engine, comprising: When the accelerator pedal is closed during an upshift, the value of the AT transmission torque used to calculate the AT required torque is switched to the value of the estimated torque. A torque reduction control method for a vehicle internal combustion engine.

2. When the accelerator pedal opening degree changes from a state greater than a predetermined threshold to a state equal to or less than the threshold during an upshift, the estimated torque value is switched to the value described above.

2. The torque reduction control method for a vehicle internal combustion engine according to claim 1.

3. Switching to the estimated torque value is performed on the condition that the actual gear ratio becomes equal to or less than a predetermined threshold value as the gear shift progresses.

2. The torque reduction control method for a vehicle internal combustion engine according to claim 1.

4. The internal combustion engine is equipped with a turbocharger as a supercharger.

2. The torque reduction control method for a vehicle internal combustion engine according to claim 1.

5. A torque reduction control device for a vehicle internal combustion engine, which reduces torque by retarding ignition timing of the internal combustion engine when a gear change of a stepped automatic transmission connected to the internal combustion engine or an upshift by step shift of a continuously variable transmission connected to the internal combustion engine, comprises: an engine controller that controls the internal combustion engine; an AT controller that controls the gear shift of the stepped automatic transmission or the continuously variable transmission; and the engine controller is configured to calculate a driver requested torque in accordance with an accelerator pedal opening, determine a charging efficiency of the internal combustion engine, calculate an estimated torque to be output at a reference ignition timing based on this charging efficiency, calculate an AT transmission torque as a torque value excluding torque down due to the ignition timing retard and torque down due to throttle opening correction based on the driver requested torque and the estimated torque, and output the AT transmission torque to the AT controller, and further determine a target torque down amount due to ignition timing retard based on a comparison between the AT requested torque input from the AT controller and the estimated torque, the AT controller is configured to determine a required torque reduction amount necessary for inertia absorption, calculate an AT required torque from the required torque reduction amount and the AT transmission torque, and output the AT required torque to the engine controller. A torque reduction control device for a vehicle internal combustion engine, When the accelerator pedal is closed during an upshift, the engine controller switches the AT transmission torque value used for calculating the AT required torque to the estimated torque value and outputs the estimated torque value to the AT controller. A torque reduction control device for a vehicle internal combustion engine.

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