Method and apparatus for controlling torque down of vehicle internal combustion engine

Abstract

To enable application of an ignition timing retard of the longest possible amount of time within a range in which thermal deterioration of exhaust purification catalyst can be avoided in response to a torque down requirement from an automatic transmission side.SOLUTION: In an up-shift change of a stepwise automatic transmission, an AT controller outputs a torque down requirement to an engine controller. The engine controller is equipped with a map that allocates torque down continuation-possible times TD with a load on an internal combustion engine and a revolution speed thereof as parameters, and determines a torque down continuation-possible time TD on the basis of the load and revolution speed at the time of input of the torque down requirement. If the torque down continuation-possible time TD elapses before a torque down requirement signal is turned Off, ignition timing retard ends.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to torque reduction control of a vehicle internal combustion engine, which reduces torque by retarding the ignition timing of the internal combustion engine when a stepped automatic transmission connected to the internal combustion engine is shifted or when a continuously variable transmission is shifted in steps. [Background technology]

[0002] It is known that when a stepped automatic transmission connected to an internal combustion engine of a vehicle is shifted or when a continuously variable transmission is shifted in steps, torque is reduced by retarding the ignition timing of the internal combustion engine, mainly to mitigate shift shock.

[0003] Patent Document 1 discloses that executing torque reduction by retarding the ignition timing increases the exhaust gas temperature, adversely affecting the exhaust gas purification catalyst, and that a limit time for retarding the ignition timing is set so as not to affect the exhaust gas purification catalyst. In Patent Document 1, the limit time for retarding the ignition timing is simply set to a fixed time, or the exhaust gas temperature is detected or estimated, and set to a short time when the exhaust gas temperature is high. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-231992 Summary of the Invention [Problem to be solved by the invention]

[0005] If the ignition timing retard duration limit is always set constant, it is necessary to set the ignition timing retard duration limit with a sufficient margin to reliably avoid burnout or thermal degradation of the exhaust purification catalyst, which may result in the ignition timing not being retarded for a sufficient period in response to the demands of the transmission, resulting in worsening gear shift shock. Also, even if the exhaust temperature is taken into consideration, it is not necessarily possible to accurately grasp the thermal impact on the exhaust purification catalyst. [Means for solving the problem]

[0006] 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 during gear shifting of a stepped automatic transmission connected to the internal combustion engine or during step gear shifting of a continuously variable transmission, comprising: A map is created in advance in which a torque down continuation time is allocated using the load and rotation speed of the internal combustion engine as parameters, When a torque reduction request is received from the transmission, the map is referenced to set the torque reduction continuation time, Torque reduction is started and ended in accordance with the torque reduction request, and if the torque reduction continuation allowable time has elapsed before the torque reduction request ends, the torque reduction is ended. [Effects of the Invention]

[0007] According to this invention, an appropriate torque reduction duration is set for the load and rotation speed of the internal combustion engine, so that ignition timing retard is permitted for a sufficiently long period of time within a range that can reliably avoid burnout or thermal degradation of the exhaust purification catalyst, thereby more reliably mitigating gear shift shock. [Brief explanation of the drawings]

[0008] [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] FIG. 2 is an explanatory diagram of a map according to an embodiment. [Figure 3] 10 is a time chart showing an example of a torque reduction request and an ignition timing retard execution period; DETAILED DESCRIPTION OF THE INVENTION

[0009] 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 21 incorporating a lockup clutch and a stepped speed change mechanism 22 including a planetary gear mechanism and multiple friction engagement elements (clutches and / or brakes). The lockup clutch and speed change mechanism 22 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.

[0010] In one embodiment, the internal combustion engine 1 is a four-stroke, spark-ignition internal combustion engine, or so-called gasoline engine. An exhaust passage 25 of the internal combustion engine 1 is provided with an upstream catalyst 26 and a downstream catalyst 27, each of which is, for example, a three-way catalyst, as exhaust purification catalysts. The upstream catalyst 26 is disposed upstream of the exhaust passage 25, for example, at the outlet of an exhaust manifold 25a, and the downstream catalyst 27 is disposed, for example, under the floor of the vehicle. The exhaust passage 25 is finally opened to the outside via a silencer 28, which is disposed further downstream of the downstream catalyst 27.

[0011] The internal combustion engine 1 is controlled by an engine controller 6. The AT controller 5 and engine controller 6 are connected to each other via an in-vehicle network 7 (e.g., CAN communication) and transmit and receive necessary signals. 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, and an air-fuel ratio sensor 15 for detecting the exhaust air-fuel ratio, are input to the engine controller 6 directly or via other controllers. Based on these detection signals, the engine controller 6 optimally controls the amount and timing of fuel injection by the fuel injection valve, the ignition timing by the spark plug, the opening of the throttle valve, and the like.

[0012] Here, when the transmission mechanism 22 is shifting, 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 achieve a smooth shift (so-called 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 optimal ignition timing at that time. Typically, the torque reduction request is output during a period corresponding to the inertia phase of an upshift. However, the present invention can also be applied to cases where a torque reduction request is output during other shifts. 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 the optimum period for the shift.

[0013] Retarding the ignition timing causes an increase in exhaust gas temperature. Therefore, in response to a torque-down request from the AT controller 5, the engine controller 6 sets a torque-down continuation time to protect the exhaust gas purification catalyst (specifically, the upstream catalyst 26) from burnout and thermal degradation, and limits the period during which torque-down, i.e., ignition timing retard, is performed by this torque-down continuation time. In other words, ignition timing retardation initiated in response to a torque-down request ends when the set torque-down continuation time has elapsed. Of course, if the torque-down request from the AT controller 5 ends before the torque-down continuation time has elapsed, torque-down, i.e., ignition timing retardation, ends at that point.

[0014] The engine controller 6 is provided with a map 31 created in advance to determine the allowable torque-down duration. This map 31 allocates the allowable torque-down duration corresponding to the load and rotation speed of the internal combustion engine 1 as parameters. When a torque-down request is input from the AT controller 5, the engine controller 6 refers to the map 31 based on the load and rotation speed at that time, determines the allowable torque-down duration, and sets the value in the timer.

[0015] FIG. 2 is an explanatory diagram illustrating the configuration of the map 31. In the map 31, optimal torque-down durations TD1, TD2, TD3, etc. are assigned to combinations of engine speeds N1, N2, N3, etc., which are parameters shown on the vertical axis, and loads ITAC1, ITAC2, ITAC3, etc., which are parameters shown on the horizontal axis. Here, the cylinder charging efficiency ITAC is used as the load. Other indices may be used as the load indicator. The torque-down durations TD in the map 31 are set to be as long as possible within the range in which ignition timing retardation does not cause burnout or thermal degradation of the upstream catalyst 26 at each operating point determined by the engine speed N and the load ITAC. Each value of the torque-down duration TD can be obtained, for example, by an appropriate simulation.

[0016] The torque-down duration TD assigned to map 31 has the characteristic that the larger the load ITAC, the shorter the torque-down duration TD becomes, and the higher the engine speed N, the shorter the torque-down duration TD becomes. The engine speed N decreases toward the top of FIG. 2 (i.e., N1 is the smallest), and the load ITAC decreases toward the left of FIG. 2 (i.e., ITAC1 is the smallest). Therefore, the torque-down duration TD is set to be longest at the low-speed, low-load operating point shown in the upper left of FIG. 2, and shortest at the high-speed, high-load operating point shown in the lower right of FIG. 2. This is because the higher the load ITAC, the higher the exhaust temperature, and the higher the engine speed N, the more cycles per unit time there are, making it easier for the upstream catalyst 26 to rise in temperature. Note that arrows A1, A2, and A3 superimposed on map 31 in FIG. 2 each schematically indicate the direction in which the torque-down duration TD becomes relatively shorter.

[0017] 3 is a time chart showing an example of operation of one embodiment, and shows, from top to bottom, (a) ON / OFF of the torque down request signal input from the AT controller 5 to the engine controller 6, (b) the rotation speed N of the internal combustion engine 1, (c) the load ITAC of the internal combustion engine 1, and (d) operation / non-operation of the ignition timing retard. Note that this time chart is a diagram created for the purpose of explaining the operation, and does not necessarily show accurate characteristics.

[0018] As described above, when the AT controller 5 executes an upshift of the automatic transmission 2, the AT controller 5 outputs a torque-down request to the engine controller 6 during the inertia phase, which is the latter half of the shift period (e.g., at time t1). In response to this torque-down request, torque-down, i.e., ignition timing retardation, is initiated substantially simultaneously, and the torque of the internal combustion engine 1 decreases with good responsiveness. The torque-down request remains ON until an appropriate end timing (e.g., at time t2) determined by the type of shift, etc., but when the torque-down continuation allowable time TD has elapsed since the torque-down start, the ignition timing retard ends at this point (e.g., at time t3). The torque-down continuation allowable time TD is determined by the rotation speed N and load ITAC of the internal combustion engine 1 when the engine controller 6 receives the torque-down request (e.g., at time t1).

[0019] By limiting the period during which ignition timing retard is performed during a gear shift using the torque-down duration TD, it is possible to reliably prevent burnout or thermal degradation of the upstream catalyst 26, which is subject to a high thermal load. Furthermore, the torque-down duration TD, which is determined by referring to map 31 based on the engine speed N and load ITAC of the internal combustion engine 1, is set as long as possible within a range that avoids burnout or thermal degradation of the upstream catalyst 26. Therefore, compared to when the duration is set to a fixed value regardless of the load or engine speed, a longer ignition timing retard is possible, thereby more fully mitigating gear shift shock. Furthermore, because the torque-down duration TD is set simply by referring to map 31, no additional sensors or devices are required, and control is extremely simple.

[0020] In the example of FIG. 3, the torque-down continuation time TD elapses before the torque-down request signal is turned OFF for each of the four torque-down requests. However, if the torque-down request signal is turned OFF before the torque-down continuation time TD elapses, the ignition timing retard ends at that point.

[0021] 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. [Explanation of symbols]

[0022] 1...Internal combustion engine 2...Automatic transmission 5...AT controller 6...Engine controller 22...Transmission mechanism 26...Upstream catalyst

Claims

1. 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 stepped automatic transmission connected to the internal combustion engine is shifted or when a continuously variable transmission is shifted in a stepwise manner, comprising: A map is created in advance in which a torque down continuation time is allocated using the load and rotation speed of the internal combustion engine as parameters, When a torque reduction request is received from the transmission, the map is referenced to set the torque reduction continuation time, The torque down is started and ended in accordance with the torque down request, and the torque down is ended when the torque down continuation allowable time has elapsed before the torque down request ends. A torque reduction control method for a vehicle internal combustion engine.

2. The map has a characteristic that the greater the load, the shorter the torque down continuation time, and the higher the rotation speed, the shorter the torque down continuation time.

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

3. A torque reduction control device for a vehicle internal combustion engine that reduces torque by retarding ignition timing of the internal combustion engine when a stepped automatic transmission connected to the internal combustion engine is shifted or when a continuously variable transmission is shifted in steps, a map in which a torque reduction continuation time is allocated using the load and rotation speed of the internal combustion engine as parameters, When a torque-down request is made from the transmission side, the torque-down continuation allowable time is set by referring to this map, and the torque-down is started and ended in accordance with the torque-down request, and when the torque-down continuation allowable time has elapsed before the torque-down request ends, the torque-down is ended. A torque reduction control device for a vehicle internal combustion engine.

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