Torque control method and torque control device

Abstract

To suppress shock in a vehicle during gear shifting with a stepped transmission.SOLUTION: There is provided a torque control method for a vehicle that includes: an internal combustion engine 1; a stepped automatic transmission 3; and a controller 10 that executes first torque limitation control to suppress slippage of a fastening element by limiting engine torque through ignition timing retardation when a gear shift operation starts, and second torque limitation control that varies engine torque along a torque profile that restricts torque to a level below target torque by performing ignition timing retardation in synchronization with the vibration cycle in a rotating shaft torsional direction of a power transmission system. In the method, when gear shift is performed during execution of the second torque limitation control, the controller 10 restricts a torque change gradient of the torque profile in the second torque limitation control to a first predetermined torque gradient that suppresses shock due to a sudden increase in a fastening capacity of the fastening element during the gear shift operation at least until the gear shift operation ends in a case where an inertia phase of the gear shift operation is started.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a torque control method and a torque control device for a vehicle. [Background technology]

[0002] When the torque of an internal combustion engine changes, such as when returning from a fuel cut, torsional vibration occurs in the rotating shaft of the power transmission system, and this vibration may cause a shock to the vehicle. Patent Document 1 describes how the torque is gradually increased when returning from a fuel cut, and how a torque profile is adopted in which the time from the start to the end of the gradual increase in torque is an integer multiple of the vibration period in the torsional direction of the rotating shaft of the power transmission system, thereby suppressing the shock to the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-142307 A Summary of the Invention [Problem to be solved by the invention]

[0004] The gear ratio of the transmission is one of the factors that determine the vibration period in the torsional direction of the rotating shaft of the power transmission system, and when the gear ratio changes suddenly due to a gear shift, as in a stepped automatic transmission, the vibration period also changes suddenly. Therefore, if the control described in the above document is executed during a gear shift of a stepped transmission, the torque profile changes suddenly in accordance with the change in the gear ratio. In general, the engagement capacity of the engagement elements of an automatic transmission during a gear shift is controlled to change according to the torque of the internal combustion engine. Therefore, if the torque profile changes suddenly, the engagement capacity also changes suddenly, which may cause a shock.

[0005] In view of the above problems, an object of the present invention is to provide a torque control method capable of suppressing shocks in a vehicle when shifting gears in a stepped transmission. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a torque control method for a vehicle including an internal combustion engine, a stepped automatic transmission connected to the internal combustion engine, having a plurality of friction elements, and performing a gear shift by switching between disengaging elements of the plurality of friction elements and engaging elements, and a controller that executes a first torque limit control for controlling the automatic transmission when a gear shift operation is started, in which an engine torque, which is a torque of the internal combustion engine, is limited by retarding ignition timing to suppress slippage of the engagement elements, and a second torque limit control for controlling when a target torque of the internal combustion engine changes, in which the engine torque is changed in a torque profile that limits the engine torque to be lower than the target torque by retarding ignition timing in accordance with a vibration period in the torsional direction of a rotating shaft of a power transmission system. In this method, when a gear shift is performed during the execution of the second torque limit control, the controller limits the slope of the torque change in the torque profile of the second torque limit control to a first predetermined torque slope that suppresses a shock caused by a sudden increase in the engagement capacity of the engagement elements during the gear shift operation when an inertia phase of the gear shift operation is started, at least until the gear shift operation is completed. Effect of the Invention

[0007] According to the above aspect, it is possible to provide a torque control method capable of suppressing shocks in a vehicle when shifting gears in a stepped transmission. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a drive system of a vehicle. [Diagram 2] FIG. 2 is a comparative example of a timing chart in which the vehicle speed increases as a result of further depression of the accelerator pedal and an upshift is performed. [Diagram 3] FIG. 3 is a comparative example of a timing chart when a downshift is performed. [Figure 4]FIG. 4 is a comparative example of a timing chart when the foot is released from the accelerator pedal during an upshift. [Diagram 5] FIG. 5 is a timing chart when the embodiment of the present invention is executed in the same situation as in FIG. [Figure 6] FIG. 6 is a timing chart when the embodiment of the present invention is executed in the same situation as in FIG. [Figure 7] FIG. 7 is a timing chart when the embodiment of the present invention is executed in the same situation as in FIG. [Figure 8] FIG. 8 shows the first half of a flow chart of control according to an embodiment of the present invention. [Figure 9] FIG. 9 shows the second half of the flow chart of the control according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] FIG. 1 is a schematic configuration diagram of a drive system of a vehicle 100 to which an embodiment of the present invention is applied.

[0011] The drive system of the vehicle 100 transmits drive torque generated in the internal combustion engine 1 to drive wheels 7 via an engine output shaft 1A, a torque converter 2, an automatic transmission 3, a transmission output shaft 4, a final drive 5, and a drive shaft 6. The final drive 5 includes a final gear in addition to a so-called differential gear.

[0012] The controller 10 controls the operation / stop and torque of the internal combustion engine 1, and the shifting and forward / reverse switching of the automatic transmission 3 based on the detection values ​​of sensors and an inhibitor switch (not shown). The sensors include, for example, a turbine rotating shaft rotation speed sensor that detects the turbine rotation speed of the torque converter 2, an output shaft rotation speed sensor that detects the rotation speed of the transmission output shaft (=vehicle speed), an ATF oil temperature sensor that detects the oil temperature of the automatic transmission 3, an accelerator pedal position sensor that detects the position of the accelerator pedal, etc. The inhibitor switch detects the range position selected by the select operation by the driver.

[0013] The controller 10 is composed of a microcomputer equipped with a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 10 may be composed of a plurality of microcomputers. The controller 10 of this embodiment includes an engine controller 9 that controls the internal combustion engine 1, and an AT controller 8 that controls the automatic transmission 3, and these are connected via a CAN communication line to exchange predetermined signals.

[0014] The automatic transmission 3 is a stepped automatic transmission that includes multiple planetary gear mechanisms and multiple friction elements, some of which function as engagement elements and others as release elements, and achieves multiple gear stages by combining engagement of the friction elements. Note that the specific configuration of the automatic transmission 3 and the engagement combinations for each gear stage can be known (for example, JP 2019-158086 A).

[0015] The AT controller 8 monitors changes in the driving point determined by the vehicle speed and the accelerator opening, and performs gear shift control based on this and a pre-stored gear shift map.

[0016] The engine controller 9 performs various controls of the internal combustion engine 1 alone, as well as torque control through cooperative control with the shift control. For example, when the operating point crosses the upshift line of the shift map, an upshift request is generated in the AT controller 8, and a torque down request is issued from the AT controller 8 to the engine controller 9. This torque down request is for preventing slippage of a release element among the friction elements. The engine controller 9 executes control (also called first torque limit control) to reduce the torque of the internal combustion engine 1 with a torque down amount and gradient according to this torque down request. There are two methods of torque down: slow torque down by intake amount control and fast torque down by ignition timing retard control, and the first torque limit control is fast torque down.

[0017] Furthermore, when there is a change in the target torque of the internal combustion engine 1, for example, when returning from a fuel cut state, the engine controller 9 executes a second torque limiting control that limits the engine torque to a value lower than the target torque determined by the accelerator opening and the vehicle speed. This second torque limiting control is intended to suppress torsional vibration (hereinafter also referred to as torsional vibration) of a rotating shaft of the power transmission system (for example, a rotating shaft of a differential gear, a final gear, etc.). Torsional vibration occurs when the engine torque and the reaction force of the drive system against the engine torque act alternately on the rotating shaft, and causes longitudinal vibration of the vehicle. Specifically, the second torque limiting control changes the engine torque to a torque profile that limits the engine torque to a value lower than the target torque by retarding the ignition timing in accordance with the vibration period of the torsional vibration. This second torque limiting control is also a fast torque down control.

[0018] Incidentally, one of the factors that determines the vibration period of the torsional vibration is the gear ratio of the automatic transmission 3. In other words, if the gear ratio changes, the vibration period also changes. For this reason, if the gear ratio changes suddenly in a short period of time due to a gear shift, as in a stepped automatic transmission, the vibration period also changes suddenly, and accordingly, the torque profile of the second torque limit control also changes suddenly. In general, the engagement capacity of the engagement element of the automatic transmission 3 during a gear shift changes with a gradient according to the torque of the internal combustion engine 1. For this reason, if the torque profile changes suddenly, the engagement capacity also changes suddenly, and there is a risk of a shock occurring due to the sudden engagement. The occurrence of this shock will be described with reference to FIG. 2.

[0019] FIG. 2 is a timing chart showing a case where an upshift is performed as the vehicle speed increases due to further depression of the accelerator pedal.

[0020] When the driver depresses the accelerator pedal further at time t1, increasing the accelerator opening, the target torque (dashed line B in FIG. 2) increases accordingly, but the second torque limit control is executed, so the engine torque is limited and increases according to a gradually increasing torque profile (solid line A in FIG. 2). The torque limit here is performed by retarding the ignition timing as described above.

[0021] When the clutch capacity torque of the engagement element reaches a predetermined value at time t2, the inertia phase starts and the first torque limit control is executed. That is, a torque reduction request is generated in the AT controller 8, and the torque reduction request is sent from the AT controller 8 to the engine controller 9 (dotted line D in FIG. 2).

[0022] Since the torsional vibration period changes depending on the gear ratio, when the gear ratio begins to change at time t3 during the inertia phase, the torque profile of the second torque limit control becomes larger in gradient of torque increase with the progress of the upshift (area i in Figure 2).

[0023] Between time t3 when the gear ratio starts to change and time t4 when the upshift ends, the actual engine torque changes according to the second torque limit control as shown by the two-dot chain line C in Figure 2. However, the clutch capacity torque of the engagement element changes according to the torque profile of the first torque limit control, so it increases rapidly as the upshift progresses (region iii in Figure 2). This sudden change in the clutch capacity torque of the engagement element causes a sudden change in the longitudinal acceleration of the vehicle, generating a shock (region ii in Figure 2).

[0024] There are other situations in which shocks occur when shifting gears.

[0025] FIG. 3 is a timing chart in which the second torque limit control is started at time t1, a torque reduction request is issued from the AT controller 8 at time t2, and a downshift is performed from time t3 to time t4.

[0026] From time t1 to time t4, the torque profile (solid line A in FIG. 3) by the second torque limit control is controlled so as not to exceed the post-limit upper limit torque (dotted line D in FIG. 3). Note that the two-dot chain line C in FIG. 3 represents the actual engine torque due to the torque reduction by the first torque limit control.

[0027] When the shift is completed at time t4, the engine torque increases to the target engine torque (dashed line B in FIG. 3) corresponding to the accelerator opening (area iv in FIG. 3). At this time, if the engine torque increases suddenly, a shock will occur.

[0028] FIG. 4 is a timing chart showing a case in which the second torque limit control is initiated at time t1 as the accelerator opening increases, a torque reduction request is issued from the AT controller 8 at time t2, and a downshift is initiated, but the accelerator is released midway through the shift, and the downshift ends at subsequent time t4.

[0029] When the second torque limit control is started at time t1, the engine torque (solid line A in FIG. 4) is controlled so as not to exceed the post-limitation upper limit torque (dotted line D in FIG. 4). When the accelerator is released, the target torque (dashed line B in FIG. 4) decreases, and the engine torque also decreases accordingly. Then, when the torque reduction request from the AT controller 8 disappears at time t3, the torque increases as shown by the thick arrow in the figure, and then decreases along the post-limitation upper limit torque toward the target torque (area v in FIG. 4). This sudden change in engine torque at time t3 causes a shock.

[0030] Therefore, in this embodiment, in order to suppress the above shock, the engine torque is controlled as described below.

[0031] FIG. 5 is a timing chart in the case where the control according to this embodiment is executed in a situation similar to that in FIG.

[0032] In this embodiment, when a torque down request is generated from the AT controller 8 at time t2, the second torque limit control is stopped, and the gradient of the torque change is limited to a first predetermined gradient during the period from time t2 to time t4 when the torque down request is generated from the AT controller 8. The first predetermined gradient is a magnitude capable of suppressing a shock caused by a sudden increase in the engagement capacity of the engagement element during a gear shift operation, and is determined according to the final target torque and the gear ratio determined according to the accelerator opening. The specific magnitude of the first predetermined torque gradient is ultimately set by adaptation for each vehicle model to which this embodiment is applied, but the first predetermined torque gradient tends to be larger as the final target torque is larger and smaller as the final gear ratio is larger. In the adaptation work, a driving test or the like is performed with a provisional adaptation value set based on this tendency, and it is verified whether a shock actually occurs and whether the magnitude of the shock is within the acceptable range for the occupant, and the final adaptation value is set.

[0033] In this way, by limiting the slope of the torque change in the torque profile by the second torque limit control while a torque down request is being issued from the AT controller 8, the slope of the change in the clutch capacity torque of the engagement element between time t3 and time t4 becomes smaller than that in Figure 2. As a result, a sudden change in the longitudinal acceleration of the vehicle during that period is suppressed, thereby suppressing shock.

[0034] FIG. 6 is a timing chart in the case where the control according to this embodiment is executed in a situation similar to that in FIG.

[0035] In this embodiment, after the time t4 when the shift operation is completed, the engine torque limit is released and the torque change slope until the torque matches the target torque is limited to a second predetermined torque slope (region iv in FIG. 6). This makes it possible to suppress shock caused by a sudden increase in engine torque. As with the first predetermined torque slope, the specific magnitude of the second predetermined torque slope is ultimately set according to suitability for each vehicle model to which this embodiment is applied.

[0036] FIG. 7 is a timing chart in the case where the control according to this embodiment is executed in a situation similar to that in FIG.

[0037] In this embodiment, after the time t3 when the shift operation is completed, the gradient of the torque change until the engine torque coincides with the upper limit torque is limited to a second predetermined torque gradient (region v in FIG. 6). The second predetermined torque gradient here is sufficient as long as it is not a gradient in the direction in which the engine torque increases and is not a gradient in which the engine torque decreases rapidly, and is set to zero, for example, as shown in the figure.

[0038] The above-mentioned control routine according to the present embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 shows the first half of a flowchart illustrating the control routine according to the present embodiment executed by the controller 10, and Fig. 9 shows the second half of the same flowchart.

[0039] In step S100, it is determined whether or not a gear shift has started, and if it has started, the process proceeds to step S110, and if it has not started, the determination is repeated. Note that in this step, not only is a gear shift request generated, but also a determination is made as to whether or not the automatic transmission 3 has started a gear shift operation.

[0040] In step S110, it is determined whether or not the second torque limit control is being executed. If it is being executed, the process proceeds to step S120, and if it is not being executed, the process proceeds to step S160.

[0041] In step S120, the torque required by the driver (also referred to as driver required torque) and the gear ratio are obtained. The driver required torque can be calculated based on the accelerator opening. The gear ratio can be calculated based on a gear shift map.

[0042] In step S130, it is determined whether or not a restriction is required on the slope of the torque change. If it is required, the process proceeds to step S140, and if it is not required, the process proceeds to step S150.

[0043] In step S140, the slope of the torque change is limited to the first predetermined torque slope described above. Note that in this step, additional torque down requests (for example, torque down for shock countermeasures in a non-shifting state) other than the torque down request from the AT controller 8 are prohibited.

[0044] In step S150, it is determined whether the second torque limit control has ended, and if it has ended, the process proceeds to step S160, and if it has not ended, the determination is repeated. In other words, the determination in this step is whether the engine torque due to the second torque limit control has reached the upper limit torque.

[0045] In step S160, it is determined whether the shift has been completed (i.e., whether the torque down request from the AT controller 8 has disappeared or not), and if it has been completed, the process proceeds to step S170, and if it has not been completed, the determination is repeated. Note that in this step, it is determined whether the actual shift operation (inertia phase) has been completed.

[0046] In step S170, the prohibition of additional torque down that was started in step S140 is lifted.

[0047] In step S180, it is determined whether or not a torque reduction request other than that from the AT controller 8 is being executed. If a torque reduction request is being executed, the current routine is terminated. If a torque reduction request is not being executed, the process proceeds to step S190.

[0048] In step S190, the same process as in step S120 is performed.

[0049] In step S200, the slope of the torque change is limited to a second predetermined torque slope.

[0050] In step S210, it is determined whether the torque of the torque profile with the limited slope coincides with the target torque or whether the torque down is complete, and if at least one of the above is true, the routine ends, otherwise the determination is repeated. Note that "torque down is complete" in this step means that the torque of the torque profile with the limited slope has reached the upper limit torque.

[0051] As described above, in this embodiment, there is provided a torque control method for a vehicle including an internal combustion engine 1, a stepped automatic transmission 3 connected to the internal combustion engine 1, having a plurality of friction elements, and performing gear changes by switching between releasing elements of the plurality of friction elements and engaging elements of the engaging elements, and a controller 10 that performs the following control when shifting gears in the automatic transmission 3: a first torque limiting control that suppresses slippage of the engaging elements by limiting the engine torque, which is the torque of the internal combustion engine 1, by retarding the ignition timing when the gear shift operation is started, and a second torque limiting control that controls when the target torque of the internal combustion engine 1 changes, by retarding the ignition timing in accordance with the vibration period in the torsional direction of the rotating shaft of the power transmission system, thereby changing the engine torque with a torque profile that is limited to be lower than the target torque. In this method, when a gear shift is performed while the second torque limit control is being executed, the controller 10 limits the slope of the torque change in the torque profile of the second torque limit control to a first predetermined torque slope that suppresses shock caused by a sudden increase in the engagement capacity of the engagement element during the gear shift operation, once the inertia phase of the gear shift operation starts, at least until the gear shift operation ends. This suppresses a sudden change in the engagement capacity torque of the engagement element that changes according to the torque profile of the second torque limit control, and thus suppresses shock to the vehicle.

[0052] In this embodiment, even when the limit on the engine torque is released after the shift operation is completed, the slope of the torque change is limited to the second predetermined torque slope that suppresses shock caused by a sudden increase in engine torque, thereby suppressing shock to the vehicle caused by an unintended sudden change in engine torque.

[0053] In this embodiment, the controller 10 sets the first predetermined torque gradient according to the final target torque and the gear ratio, which are determined according to the accelerator opening. The tolerable level of shock to the vehicle changes according to the torque required by the driver. For example, when the required torque is large, such as during full-throttle acceleration, the driver can tolerate a larger shock than when driving at a constant speed. In addition, the driving force of the drive wheels 7 changes depending on the gear ratio. Therefore, by setting the first predetermined torque gradient according to both the target torque and the gear ratio, it is possible to achieve both vehicle shock and acceleration responsiveness.

[0054] In this embodiment, the first predetermined torque gradient is larger as the final target torque is larger. Since the higher the target torque is, the higher the priority of acceleration response is over suppression of shock, the gradient of the torque change is increased to improve acceleration response.

[0055] In this embodiment, the first predetermined torque gradient is smaller as the final gear ratio is larger. Since the driving force for the same engine torque increases as the gear ratio increases, the gradient of the torque change is made smaller to keep the shock of the vehicle within an acceptable range.

[0056] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments. [Explanation of symbols]

[0057] 1 internal combustion engine, 2 torque converter, 3 automatic transmission, 5 final drive, 8 engine controller, 9 AT controller, 10 controller

Claims

1. An internal combustion engine; a stepped automatic transmission connected to the internal combustion engine, having a plurality of friction elements, and performing gear shifting by switching between disengaging elements and engaging elements of the plurality of friction elements; a controller that executes: a first torque limiting control, which is a control when shifting gears of the automatic transmission, and suppresses slippage of the engagement element by limiting engine torque, which is the torque of the internal combustion engine, by retarding ignition timing when a shifting operation is started; and a second torque limiting control, which is a control when a target torque of the internal combustion engine changes, and changes the engine torque with a torque profile that is limited to be lower than the target torque by retarding ignition timing in accordance with a vibration period in the torsional direction of a rotating shaft of a power transmission system; A torque control method for a vehicle comprising: When a gear shift is performed while the second torque limiting control is being executed, the controller limits a slope of the torque change of the torque profile of the second torque limit control to a first predetermined torque slope that suppresses a shock caused by a sudden increase in the friction capacity of the friction element during the gear shift operation, when an inertia phase of the gear shift operation starts, at least until the gear shift operation ends.

2. 2. The torque control method according to claim 1, The torque control method further comprises limiting a slope of the torque change to a second predetermined torque slope that suppresses a shock caused by a sudden increase in the engine torque even when the limit on the engine torque is released after the shift operation is completed.

3. 2. The torque control method according to claim 1, The torque control method, wherein the controller sets the first predetermined torque gradient in accordance with the final target torque and a gear ratio that are determined in accordance with an accelerator opening degree.

4. 4. The torque control method according to claim 3, A torque control method, wherein the first predetermined torque gradient is larger as the final target torque is larger.

5. 4. The torque control method according to claim 3, The torque control method, wherein the first predetermined torque gradient is smaller as the final gear ratio is larger.

6. An internal combustion engine; a stepped automatic transmission connected to the internal combustion engine, having a plurality of friction elements, and performing gear shifting by switching between disengaging elements and engaging elements of the plurality of friction elements; a controller that executes: a first torque limiting control, which is a control when shifting gears of the automatic transmission, and suppresses slippage of the engagement element by limiting engine torque, which is the torque of the internal combustion engine, by retarding ignition timing when a shifting operation is started; and a second torque limiting control, which is a control when a target torque of the internal combustion engine changes, and changes the engine torque with a torque profile that is limited to be lower than the target torque by retarding ignition timing in accordance with a vibration period in the torsional direction of a rotating shaft of a power transmission system; A torque control device for a vehicle comprising: the controller is programmed to limit a slope of torque change in the torque profile of the second torque limit control to a first predetermined torque slope that suppresses a shock caused by a sudden increase in the friction capacity of the friction element during the gear shift operation, when a gear shift is performed while the second torque limit control is being executed, at least until the gear shift operation is completed, once an inertia phase of the gear shift operation is started.

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