Vehicle drive torque control method
The vehicle drive torque control method addresses resonance and vibration issues by optimizing torque control during transitions, ensuring adequate response and efficient resonance suppression.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2023-12-21
- Publication Date
- 2026-07-07
AI Technical Summary
Existing vehicle drive torque control methods fail to adequately suppress resonance and vibration caused by backlash in gear and spline-fitted sections during transitions between driven and coasting states, leading to inadequate response to driver acceleration requests.
A vehicle drive torque control method that prohibits feedback vibration control during the initial stages of play reduction, calculates an optimal torque rate to suppress resonance, and controls input torque based on this rate, followed by enabling feedback vibration damping control at a predetermined time or upon cancellation of the acceleration request.
This method effectively suppresses resonance and vibration while ensuring a sufficient response to driver acceleration requests, preventing prolonged torque control and enabling quick restoration of resonance suppression.
Smart Images
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Abstract
Description
[Technical Field]
[0001] This invention relates to a method for controlling the drive torque of a vehicle. In particular, this invention relates to an improvement for suppressing vehicle vibration caused by the presence of play (backlash in the meshing parts of gears and spline fitting parts) in the drive force transmission system. [Background technology]
[0002] Generally, in electric vehicles, the output torque from the electric motor used for driving is transmitted to the drive wheels via a drivetrain system that includes multiple gears that mesh with each other. Backlash exists between these meshing gears. When a vehicle transitions from a coasting state to a driven state in response to an acceleration request, the presence of this backlash causes the drivetrain system to temporarily enter a free-running state where the output torque from the electric motor is not transmitted to the drive wheels. After this free-running state, the gears mesh (the play is eliminated), and the resulting collision between the gears can excite drivetrain resonance and vehicle resonance. This excitation of resonance can cause vehicle vibration, worsening the ride comfort. Furthermore, since backlash also exists in the spline-fitted sections of the drivetrain system, the presence of backlash in these spline-fitted sections can similarly cause vehicle vibration.
[0003] In view of this point, Patent Document 1 has been proposed. Patent Document 1 discloses that, during the drive state switching from a driven state to a driven state when the driver switches the prime mover from an unloaded state to a loaded state, the output torque of the prime mover is kept at a predetermined value smaller than the prime mover-required torque corresponding to the driver's operation, thereby reducing the acceleration shock when the rattle is eliminated.
[0004] Furthermore, as a means of suppressing vehicle vibrations caused by the aforementioned backlash, vibration damping control that increases apparent damping by rotational speed F / B (feedback) is also known. [Prior art documents] [Patent Documents]
[0005] [Patent Document 1] Japanese Patent Publication No. 2009-47080 [Overview of the project] [Problems that the invention aims to solve]
[0006] However, in the technology described in Patent Document 1, the period for reducing play (the period during which the output torque of the prime mover is kept low) is set longer than necessary to absorb variations in the amount of play, which resulted in a problem in that the response to the driver's acceleration request could not be obtained sufficiently. Furthermore, when vibration damping control is performed by the rotational speed F / B, the vibration damping torque is calculated for the fluctuation in rotational speed due to coasting during the play reduction period, so the torque during play reduction is reduced, and in this case as well, the response to the driver's acceleration request could not be obtained sufficiently.
[0007] Furthermore, these issues are not limited to electric vehicles; they can also occur in vehicles equipped with internal combustion engines as a power source (conventional vehicles) and vehicles that use both electric motors and internal combustion engines as power sources (hybrid vehicles).
[0008] The present invention has been made in view of the above, and its objective is to provide a vehicle drive torque control method that can suppress resonance during rattle reduction while obtaining sufficient response to the driver's acceleration request. [Means for solving the problem]
[0009] The solution of the present invention for achieving the above object is premised on a vehicle drive torque control method applied to a drive power transmission system capable of implementing feedback vibration control to suppress drive system resonance when the power transmission elements are tightened. And this vehicle drive torque control method includes a step of prohibiting the feedback vibration control from the start point of the idling period at the initial stage of the start of the tightening, and the input torque from the drive source and the rotational difference (differential rotation) between the drive source and the drive wheels at the time of collision of the power transmission elements due to the tightening, calculating an optimal torque rate that is a torque rate capable of suppressing the drive system resonance, and controlling the input torque to the drive power transmission system according to the optimal torque rate; and a step of ending the control of the input torque to the drive power transmission system according to the optimal torque rate and permitting the feedback vibration control at a predetermined time after starting the control of the input torque to the drive power transmission system according to the optimal torque rate. It is characterized by having these steps.
[0010] Due to this specific matter, at the time of collision of the power transmission elements due to the tightening, the input torque to the drive power transmission system is controlled according to the optimal torque rate capable of suppressing the drive system resonance in a state where the feedback vibration control is not implemented. Therefore, while sufficiently obtaining a response to the driver's acceleration request, it is possible to suppress resonance during the tightening and suppress vehicle vibration.
[0011] Also, between the start point of the idling period and the time of collision of the power transmission elements due to the tightening, the feedback vibration control is prohibited, and the input torque to the drive power transmission system is controlled by a predetermined limit torque rate smaller than the optimal torque rate.
[0012] According to this, it is possible to suppress the rotational difference between the drive source and the drive wheels during the idling period from becoming too large, and effectively suppress the occurrence of vibration caused by the collision of the power transmission elements.
[0013] Furthermore, the predetermined time at which the control of the input torque to the drive force transmission system in accordance with the optimal torque rate ends is, provided that the acceleration request to the vehicle continues, after a predetermined time has elapsed from the time at which the control of the input torque to the drive force transmission system in accordance with the optimal torque rate begins.
[0014] This avoids a situation where the control of the input torque to the drive force transmission system according to the optimal torque rate continues for a long period of time, and makes it possible to quickly restore the drive system resonance suppression operation by feedback vibration damping control.
[0015] Furthermore, if the acceleration request to the vehicle is canceled before the predetermined time has elapsed, the control of the input torque to the drive force transmission system according to the optimal torque rate is terminated at the time the acceleration request is canceled, and the feedback vibration control is permitted.
[0016] According to this, feedback vibration damping control is permitted when the drive system resonance is no longer excited, preventing the control of the input torque to the drive force transmission system according to the optimal torque rate from being prolonged unnecessarily, and allowing the drive system resonance suppression operation by feedback vibration damping control to be restored early. [Effects of the Invention]
[0017] The present invention includes the steps of: prohibiting feedback vibration damping control from the start of the coasting period in the initial stages of rattle reduction; calculating an optimal torque rate that can suppress drive system resonance based on the input torque from the drive source and the rotational difference between the drive source and the drive wheels at the time of collision between power transmission elements due to rattle reduction, and controlling the input torque to the drive force transmission system according to the optimal torque rate; and ending the control of the input torque to the drive force transmission system according to the optimal torque rate at a predetermined time after starting to control the input torque to the drive force transmission system according to this optimal torque rate, and allowing feedback vibration damping control. As a result, resonance during rattle reduction can be suppressed while obtaining sufficient response to the driver's acceleration request, thereby suppressing vehicle vibration. [Brief explanation of the drawing]
[0018] [Figure 1] This figure shows a schematic configuration of the drive system of an electric vehicle according to this embodiment. [Figure 2] This is a block diagram showing a schematic configuration of the drive torque control unit according to an embodiment. [Figure 3] This is a flowchart illustrating the procedure for drive torque control according to the embodiment. [Figure 4] This is a time chart diagram showing the changes in accelerator opening, input torque, drive shaft torque, coasting determination, differential rotation, timer, torque rate, and F / B vibration damping control command when the drive torque control according to the embodiment is implemented. [Figure 5] This is a modified version of Figure 3. [Figure 6] This is a modified version of Figure 4. [Modes for carrying out the invention]
[0019] Hereinafter, embodiments of the present invention will be described based on the drawings. This embodiment describes the case in which the present invention is applied to an electric vehicle.
[0020] -Outline configuration of the drivetrain of an electric vehicle- Before explaining the drive torque control method, we will first describe the general configuration of the drivetrain of the electric vehicle in which this drive torque control method is implemented.
[0021] Figure 1 is a schematic diagram of the drive system 1 of the electric vehicle according to this embodiment. Note that the configuration of the drive system 1 of the electric vehicle is not limited to that shown in Figure 1. As shown in Figure 1, the drive system 1 of the electric vehicle according to this embodiment is equipped with an electric motor 2 as a drive source. That is, the drive wheels 3 of the electric vehicle (only one of the drive wheels is shown in Figure 1) rotate by receiving rotational driving force (output torque) from the electric motor 2. The electric motor 2 is, for example, a three-phase AC motor.
[0022] More specifically, the drive system 1 further comprises a battery (DC power source) 4, a PCU (Power Control Unit) 5, and a drive force transmission system 6. The battery 4 stores power supplied from outside the vehicle. The PCU 5 includes a power converter (inverter) equipped with multiple switching elements (not shown). When the vehicle is driven by the rotational force from the electric motor 2, the PCU 5 converts the DC power from the battery 4 into AC power by appropriately switching each of the switching elements on and off and supplies it to the electric motor 2.
[0023] The power transmission system 6 includes multiple power transmission elements to transmit rotational driving force from the electric motor 2 to the drive wheels 3. These multiple power transmission elements include the components of the reduction system 60 (drive gear 61, driven gear 62, counter shaft 63, drive gear 64, and differential device 65) and the drive shaft 66 (only one of the drive shafts is shown in Figure 1). More specifically, the drive gear 61, which meshes with the driven gear 62, is fixed to the output shaft 21 of the electric motor 2. The driven gear 62 is fixed to one end of the counter shaft 63, and the drive gear 64 is fixed to the other end. The drive gear 64 meshes with the ring gear 65a of the differential device 65. The differential device 65 is connected to one end of the drive shaft 66, and the drive wheels 3 are connected to the other end.
[0024] In the drive force transmission system 6, multiple power transmission elements mesh with each other via gear sections or spline sections (not shown). Therefore, backlash exists between each power transmission element. In this way, the electric motor 2 is able to transmit rotational driving force to the drive wheels 3 via multiple power transmission elements with backlash.
[0025] The drive system 1 further includes a control device 7 that controls the electric motor 2 and the PCU 5. The control device 7 includes an electronic control unit (ECU) having a processor 71 and a memory 72. The memory 72 stores a program for controlling the operation of the drive system 1. The processor 71 reads the program from the memory 72 and executes it. The control device 7 may be configured using multiple ECUs.
[0026] The control device 7 acquires sensor signals from various sensors for controlling the operation of the drive system 1. These various sensors include a wheel speed sensor 81, a motor angular velocity sensor 82, and an accelerator position sensor 83. The wheel speed sensor 81 measures the angular velocity ω of the drive wheel 3. w It outputs a signal corresponding to the following. The motor angular velocity sensor 82 measures the angular velocity ω of the electric motor 2. mIt outputs a signal corresponding to the amount the vehicle's accelerator pedal is pressed (accelerator opening).
[0027] -Configuration for drive torque control- Next, we will describe the configuration for implementing the drive torque control, which is a feature of this embodiment.
[0028] As mentioned above, conventional techniques for suppressing vehicle vibrations caused by the excitation of drive system resonance and vehicle resonance due to collisions between gears during the resetting of the drive force transmission system from a driven state to a driven state have involved maintaining the output torque of the prime mover at a small predetermined value or increasing the apparent damping by changing the rotational speed F / B during the state change from the driven state to the driven state of the drive force transmission system. However, these conventional techniques had the problem that a sufficient response to the driver's acceleration request could not be obtained. In view of this, this embodiment is designed to suppress resonance during the resetting of the drive system while obtaining a sufficient response to the driver's acceleration request.
[0029] Figure 2 is a block diagram illustrating the schematic configuration of the drive torque control unit 7A configured by the program. As shown in Figure 2, the drive torque control unit 7A includes a backlash removal completion determination unit 73, an optimal torque rate command unit 74, and an F / B vibration damping control command determination unit 75 as functional units realized by the program.
[0030] The information input to the drive torque control unit 7A includes a coasting detection flag, estimated engine torque (estimated output torque of electric motor 2), engine speed (rotational speed of electric motor 2), and wheel speed (rotational speed of drive wheel 3). The coasting detection flag, estimated engine torque, engine speed, and wheel speed will be explained below.
[0031] The idle speed determination flag is input to the rattle reduction completion determination unit 73 and the F / B vibration damping control command determination unit 75, respectively.
[0032] This coasting detection flag provides different signals depending on whether the drivetrain 6 is coasting (a state in which the output torque from the electric motor 2 is not transmitted to the drive wheels 3) or in the gear-reduced state (a state in which the gears mesh and the gear-reduced gears are engaged) when the vehicle transitions from a driven state to a driven state. Specifically, the coasting detection flag is "1" in the coasting state and "0" in the gear-reduced state. One example of a method for distinguishing between the coasting state and the gear-reduced state is to consider that in the gear-reduced state, fluctuations in rotational speed relative to torque occur due to the twisting of each rotating body associated with power transmission. For example, if the value of the "product of the moment of inertia and the derivative of the angular velocity of rotation" remains constant, it is determined to be in the coasting state. Subsequently, if this value begins to fluctuate, it is determined to be in the gear-reduced state. However, the means for distinguishing between the coasting state and the gear-reduced state are not limited to this.
[0033] The estimated torque of the prime mover is input to the optimal torque rate command unit 74.
[0034] This prime mover torque can be calculated based on state variables such as current and voltage supplied to the electric motor 2. However, the method for estimating this prime mover torque is not limited to this method.
[0035] The prime mover speed is the rotational speed of the output shaft 21 of the electric motor 2, and the angular velocity ω detected by the motor angular velocity sensor 82. m That is the case.
[0036] The wheel rotation speed is the rotation speed of the drive shaft 66, and the angular velocity ω detected by the wheel speed sensor 81. w That is the case.
[0037] These engine rotation speeds and wheel rotation speeds are input to the deviation calculator 76, and the difference (difference rotation) information is input to the optimal torque rate command unit 74.
[0038] The following describes the processing in the rattle reduction completion determination unit 73, the optimal torque rate command unit 74, and the F / B vibration damping control command determination unit 75, respectively.
[0039] The play reduction completion determination unit 73, in response to the input idle judgment flag, provides information to the optimal torque rate command unit 74 indicating that play reduction has been completed (play reduction completion information indicating that the idle judgment flag has changed from "1" to "0") when play reduction is completed. In this embodiment, "the time when play reduction is completed" may be defined as the time when all backlash in the meshing parts (including spline fitting parts) of the multiple gears has been reduced (play reduction time), or it may be defined as the time when some of the backlash has been reduced.
[0040] The optimal torque rate command unit 74 calculates an optimal torque rate that can suppress drive system resonance, based on the input information on the estimated torque of the prime mover and the information on the difference in rotations between the prime mover rotation speed and the wheel rotation speed. This torque rate is the amount of increase in the input torque per unit time (input torque to the drive force transmission system 6: output torque of the electric motor 2).
[0041] Equation (1) below gives the torsional resonance frequency ω in the drive force transmission system 6. n This is the equation in which drive shaft torque vibration becomes "0". Equation (1) contains the torque rate (optimal torque rate) dT required to make drive shaft torque vibration "0". ramp The following section is included.
[0042]
number
[0043]
number
[0044] This optimal torque rate dT ramp is calculated at the timing when information indicating that the backlash has ended (backlash end information) is received as information input from the backlash end determination unit 73. Then, the optimal torque rate command unit 74 outputs the information of this optimal torque rate dT ramp to the PCU 5 and also outputs it to the F / B vibration control command determination unit 75. Thereby, the PCU 5 reflects the optimal torque rate dT ramp as the command information of the input torque (output torque of the electric motor 2) to the driving force transmission system 6 (increases the torque according to the optimal torque rate dT ramp ).
[0045] Also, the optimal torque rate command unit 74 incorporates a timer that starts counting from the time when the information of the optimal torque rate dT ramp is output to the PCU 5. This timer expires, for example, at "resonance frequency of the driving force transmission system 6 / 2" seconds. When this timer expires, the optimal torque rate command unit 74 outputs a timeout signal to the PCU 5 and the F / B vibration control command determination unit 75. Note that this timer does not necessarily have to be incorporated in the optimal torque rate command unit 74, and it is sufficient that a timeout signal is transmitted to the F / B vibration control command determination unit 75 after a predetermined time has elapsed from the time when the information of the optimal torque rate dT ramp is output to the PCU 5.
[0046] Furthermore, the F / B vibration damping control command determination unit 75 is a functional unit for implementing F / B vibration damping control to suppress drivetrain resonance when the vehicle transitions from a driven state to a driven state. This F / B vibration damping control is a control that adjusts the output torque of the electric motor 2 to suppress vehicle vibration while detecting the vehicle vibration. The F / B vibration damping control command determination unit 75 is capable of receiving a coasting judgment flag and information from the optimal torque rate command unit 74. Specifically, when the coasting judgment flag of "1" is input to the F / B vibration damping control command determination unit 75, it outputs a flag to prohibit F / B vibration damping control (F / B vibration damping control command flag "0"). Also, when the F / B vibration damping control command determination unit 75 receives a timer time-up signal as information from the F / B vibration damping control command determination unit 75, it outputs a flag to permit F / B vibration damping control (F / B vibration damping control command flag "1"). Furthermore, if the F / B vibration damping control command determination unit 75 outputs the F / B vibration damping control command flag "0", the torque rate of the electric motor 2 is set to a predetermined relatively low torque rate (limiting torque rate). This limiting torque rate is the optimal torque rate dT ramp A value smaller than this is predetermined by experiments or simulations.
[0047] -Drive Torque Control- Next, we will describe the drive torque control by the drive torque control unit 7A configured as described above. Figure 3 is a flowchart of the drive torque control procedure according to this embodiment. This flowchart is performed under the condition that the vehicle is in motion.
[0048] First, in step ST1, it is determined whether the coasting judgment flag has changed from "0" to "1" because the drive force transmission system 6 entered a coasting state due to the vehicle transitioning from a driven state to a driven state. If the coasting judgment flag has not changed and the result in step ST1 is NO, the process returns as is.
[0049] If the coasting detection flag changes from "0" to "1" and a YES determination is made in step ST1, the process moves to step ST2, where the information of this coasting detection flag "1" is input to the F / B vibration damping control command determination unit 75, thereby prohibiting F / B vibration damping control. In other words, F / B vibration damping control control is prohibited when the F / B vibration damping control command determination unit 75 outputs the F / B vibration damping control command flag "0".
[0050] Next, in step ST3, the torque rate of the electric motor 2 is set to a predetermined, relatively low torque rate (limiting torque rate).
[0051] Next, the process moves to step ST4, where it is determined whether the coasting judgment flag has changed from "1" to "0" due to the reduced play between the gears. As long as the coasting judgment flag remains at "1", the torque rate is maintained at the limited torque rate.
[0052] If the coasting detection flag changes from "1" to "0" and a YES determination is made in step ST4, the process moves to step ST5, where state quantity information such as the difference in rotational speed between the prime mover speed and the wheel rotational speed and the estimated prime mover torque (input torque) is acquired (latched), and in step ST6, this information is input to the optimal torque rate command unit 74, thereby setting the optimal torque rate dT ramp The calculation is performed.
[0053] Then, in step ST7, the torque rate of electric motor 2 is calculated to be the optimal torque rate dT. ramp The optimal torque rate dT is set to the optimal torque rate dT as command information for the input torque to the drive force transmission system 6 (output torque of the electric motor 2). ramp This will be reflected. Also, this optimal torque rate dT ramp The timer countdown begins simultaneously with the setting of the timer.
[0054] In step ST8, check if the timer has timed out (optimal torque rate dT rampIt is determined whether or not "resonant frequency of the drive force transmission system 6 / 2" seconds have elapsed since the setting was made. Until the timer expires, the optimal torque rate dT is used as the torque rate of the electric motor 2. ramp The state reflected in this will be maintained.
[0055] If the timer expires and a YES is determined in step ST8, the process moves to step ST9, where the torque rate of the electric motor 2 is set to the acceleration request torque rate, which corresponds to the current accelerator pedal depression (accelerator opening). This acceleration request torque rate is then reflected as the command information for the input torque to the drive force transmission system 6 (output torque of the electric motor 2). In step ST10, the F / B vibration damping control, which had been prohibited until then, is permitted. This returns the system to F / B vibration damping control, and control is implemented to adjust the output torque of the electric motor 2 to suppress vehicle vibrations while detecting them. The above operations are repeated.
[0056] Figure 4 is a time chart showing the changes in accelerator opening, input torque, drive shaft torque, coasting detection (coasting detection flag), differential rotation (difference in rotation between engine speed and wheel speed), timer, torque rate, and F / B vibration damping control command during the implementation of this drive torque control.
[0057] First, when the vehicle is in a driven state, and the accelerator opening increases at timing t0, the torque rate becomes the torque rate dT corresponding to this accelerator opening. initial This is the result.
[0058] Then, at timing t1, when the drive force transmission system 6 enters a coasting state and the coasting judgment flag changes from "0" to "1", the torque rate of the electric motor 2 becomes the limited torque rate dT minThis is set (step ST3 in the flowchart of Figure 3). As a result, the input torque of the drive force transmission system 6 becomes smaller than the required torque corresponding to the accelerator opening (see the dashed line between timing t1 and timing t2 of the input torque in Figure 4) (see the solid line between timing t1 and timing t2 of the input torque in Figure 4). Also, at this point, F / B vibration damping control is disabled (step ST2 in the flowchart of Figure 3).
[0059] Then, at timing t2, when the gears become loose and the coasting detection flag changes from "1" to "0", the torque rate becomes the optimal torque rate dT calculated by the optimal torque rate command unit 74. ramp This setting suppresses resonance during the play-reducing process (step ST7 in the flowchart of Figure 3). Between timing t2 and timing t3, the input torque of the drive force transmission system 6 is smaller than the required torque corresponding to the accelerator opening (see the dashed line between timing t2 and timing t3 of the input torque in Figure 4) (see the solid line between timing t2 and timing t3 of the input torque in Figure 4). Also, the timer count starts at timing t2.
[0060] When the timer expires at timing t3, the torque rate of electric motor 2 changes to the acceleration request torque rate dT corresponding to the current accelerator pedal depression amount. end As this is set (step ST9 in the flowchart of Figure 3), F / B vibration control is permitted (step ST10 in the flowchart of Figure 3).
[0061] -Effects of the embodiment- As described above, this embodiment includes the following steps as a drive torque control method: (1) A step to prohibit F / B vibration damping control from the start of the coasting period in the initial stage of play reduction (step ST2 in Figure 3, timing t1 in Figure 4). (2) An optimal torque rate dT that can suppress drive system resonance based on the input torque from the drive source (electric motor 2) and the rotational difference between the drive source (electric motor 2) and the drive wheel 3 at the time of collision between power transmission elements (gears, etc.) due to play reduction. ramp Calculate the optimal torque rate dT ramp (3) Optimal torque rate dT ramp At a predetermined time after initiating control of the input torque to the drive force transmission system 6, the optimal torque rate dT ramp The control of the input torque to the drive force transmission system 6 in accordance with the above is terminated, and F / B vibration damping control is permitted (steps ST9 and ST10 in Figure 3, timing t3 in Figure 4). This allows for sufficient response to the driver's acceleration request while suppressing resonance during rattle reduction, thereby suppressing vehicle vibration.
[0062] Furthermore, in this embodiment, F / B vibration damping control is prohibited from the start of the coasting period until the point of collision between power transmission elements (gears, etc.) due to play reduction, and the optimal torque rate dT ramp A predetermined limiting torque rate dT that is smaller than min This controls the input torque to the drive force transmission system 6. This prevents the rotational difference (difference in rotation) between the drive source (electric motor 2) and the drive wheels 3 from becoming too large during the coasting period, and effectively suppresses the generation of vibrations caused by collisions between power transmission elements (gears, etc.).
[0063] Also, the optimal torque rate dT ramp The predetermined time at which the control of the input torque to the drive force transmission system 6 is terminated is determined by the optimal torque rate dT, provided that the acceleration request to the vehicle continues.ramp This is defined as a predetermined time elapsed from the time when control of the input torque to the drive force transmission system 6 is started according to the method. This results in the optimal torque rate dT ramp This avoids a situation where the control of the input torque to the drive force transmission system 6 in accordance with this method continues for a long period of time, and makes it possible to quickly restore the drive system resonance suppression operation by F / B vibration damping control.
[0064] -Variations- Next, a modified example will be described. This modified example adds drive torque control for the case where the accelerator opening is returned to its original position (the accelerator opening becomes smaller) before the timer expires. The configuration of the electric vehicle's drive system 1 and the configuration for drive torque control are the same as those of the embodiment described above, so only the drive torque control will be described here.
[0065] Figure 5 is a flowchart showing the procedure for drive torque control according to this modified example. This flowchart is also performed under the condition that the vehicle is in motion. In Figure 5, the same step numbers are used for operations that are the same as those in Figure 3 of the previously described embodiment, and their explanations are omitted.
[0066] In step ST8, if the timer is still counting and a NO result is obtained, the process proceeds to step ST11. In step ST11, it is determined whether or not an acceleration request to the vehicle is continuing. This determination is made according to the accelerator opening detected by the accelerator position sensor 83. In other words, if the accelerator opening decreases by a predetermined amount, it is determined that the acceleration request to the vehicle has been canceled. This predetermined amount is set appropriately through experimentation or simulation.
[0067] If the request for acceleration to the vehicle continues and the result in step ST11 is YES, the process returns to step ST8. On the other hand, if the request for acceleration to the vehicle is canceled and the result in step ST11 is NO, the process proceeds to step ST9 without waiting for the timer to expire, and the torque rate of the electric motor 2 is set to the requested acceleration torque rate. Other operations are the same as those of the embodiment described above.
[0068] Figure 6 is a diagram equivalent to Figure 4 when drive torque control is implemented in this modified example. Here again, only the parts that differ from Figure 4 of the previously described embodiment will be explained. Also, in Figure 6, the dashed line shows the transition of the timer and torque rate in the previously described embodiment, and the solid line shows the transition in this modified example.
[0069] At timing t2, the coasting detection flag changed from "1" to "0", and the torque rate became the optimal torque rate dT. ramp After being set, at timing t3', if the accelerator opening decreases by a predetermined amount, the torque rate of the electric motor 2 will be set to the acceleration request torque rate dT corresponding to the current accelerator pedal depression amount. end As this is set (step ST9 in the flowchart of Figure 5), F / B vibration damping control is permitted (step ST10 in the flowchart of Figure 5). In other words, without waiting for the timer to expire, the torque rate of the electric motor 2 is set to the acceleration request torque rate dT end This setting will enable F / B vibration control.
[0070] According to this modified version, when the accelerator opening is reduced by a predetermined amount, and the drive system resonance is no longer excited, F / B vibration damping control is permitted, resulting in the optimal torque rate dT ramp This prevents the control of the input torque to the drive force transmission system 6 from being prolonged unnecessarily, and allows for the early recovery of the drive system resonance suppression operation by F / B vibration damping control.
[0071] -Other Embodiments- Furthermore, the present invention is not limited to the embodiments and modifications described above, and all modifications and applications covered within the scope of the claims and equivalents thereof are possible.
[0072] For example, the above embodiments and modifications described the case in which the present invention is applied to an electric vehicle. However, the present invention is not limited to this and can also be applied to vehicles equipped with an internal combustion engine as a power source (conventional vehicles) and vehicles that use both an electric motor and an internal combustion engine as power sources (hybrid vehicles).
[0073] Furthermore, in the above embodiments and modifications, each torque rate was switched at each timing, but each torque rate may be changed gradually. This makes it possible to suppress abrupt changes in the torque rate and contribute to further suppression of vehicle vibration.
[0074] Furthermore, in the above embodiment, when there is a continuous acceleration request to the vehicle, the torque rate of the electric motor 2 is set to the optimal torque rate dT ramp From acceleration request torque rate dT end The timing for transitioning to and enabling F / B vibration damping control was set using a timer. The present invention is not limited to this, but determines by other means that a situation has been reached where drive system resonance is not excited, and based on that determination, sets the torque rate of the electric motor 2 to the optimal torque rate dT ramp From acceleration request torque rate dT end You may also enable F / B vibration damping control at the same time as transitioning to this mode. [Industrial applicability]
[0075] The present invention is applicable to a drive torque control method for suppressing drive system resonance when eliminating play between power transmission elements in a vehicle's drive force transmission system. [Explanation of Symbols]
[0076] 1. Drivetrain 2. Electric motor (drive source) 3 drive wheels 6. Power transmission system 61, 64 Drive gear (power transmission element) 62. Driven gear (power transmission element) 65a Ring gear (power transmission element) 7 Control device 73. Completion of rattle removal determination unit 74 Optimal Torque Rate Command Unit 75 F / B vibration damping control command determination unit 81 Wheel speed sensor 82 Motor angular velocity sensor
Claims
1. A method for controlling the drive torque of a vehicle applied to a drive force transmission system that can implement feedback vibration damping control to suppress drive system resonance when play between power transmission elements is reduced, A step of prohibiting the feedback vibration damping control from the start of the coasting period in the initial stages of rattle reduction, The steps include: calculating an optimal torque rate that can suppress the resonance of the drive system based on the input torque from the drive source and the rotational difference between the drive source and the drive wheel at the point of collision between the power transmission elements due to the aforementioned play reduction, and controlling the input torque to the drive force transmission system according to the optimal torque rate; The steps include: at a predetermined time after starting to control the input torque to the drive force transmission system according to the optimal torque rate, ending the control of the input torque to the drive force transmission system according to the optimal torque rate and permitting the feedback vibration control; A method for controlling the drive torque of a vehicle, characterized by having [a certain feature].
2. In the vehicle drive torque control method according to claim 1, A method for controlling the drive torque of a vehicle, characterized in that the feedback vibration damping control is prohibited from the start of the coasting period until the point of collision between the power transmission elements due to the removal of rattle, and the input torque to the drive force transmission system is controlled by a predetermined limiting torque rate smaller than the optimal torque rate.
3. In the vehicle drive torque control method according to claim 1 or 2, A method for controlling the drive torque of a vehicle, characterized in that the predetermined time at which the control of the input torque to the drive force transmission system in accordance with the optimal torque rate is terminated is after a predetermined time has elapsed from the time at which the control of the input torque to the drive force transmission system in accordance with the optimal torque rate is started, provided that an acceleration request to the vehicle continues.
4. In the vehicle drive torque control method according to claim 3, A method for controlling the drive torque of a vehicle, characterized in that, if the acceleration request to the vehicle is canceled before the predetermined time has elapsed, the control of the input torque to the drive force transmission system in accordance with the optimal torque rate is terminated at the time the acceleration request is canceled, and the feedback vibration damping control is permitted.