Driving force control method and driving force control device

Abstract

When switching from the parking gear to the starting gear, when the accelerator pedal operation amount has reached a level that generates driving force, in order to prevent a sudden start just after the gear switch, the upper limit of the driving force of the driving source is limited to a driving force that is greater than the holding threshold for releasing the vehicle's stopped state and is less than the requested driving force based on the accelerator pedal operation amount.

Description

Technical Field

[0001] The present invention relates to a driving force control method and a driving force control device for a vehicle. Background Art

[0002] A gear switching device is known that has a starting gear that transmits a driving force corresponding to an accelerator pedal operation amount to a driving wheel, and a parking gear that does not transmit a driving force to the driving wheel even if the accelerator pedal is operated. In a vehicle having such a gear switching device, stepping on the accelerator pedal after switching from the parking gear to the starting gear is a normal starting operation. According to this normal starting operation, the driving force also gradually increases in accordance with the gradual increase in the accelerator pedal operation amount after switching to the starting gear, so that the vehicle can start smoothly.

[0003] On the other hand, if the order of the gear switching and the accelerator pedal operation is reversed, even if the accelerator pedal operation amount gradually increases, the driving force will not be transmitted to the drive wheels due to the parking gear. Moreover, if the gear is switched to the starting gear, the driving force corresponding to the operation amount of the accelerator pedal that has been operated will be suddenly transmitted to the drive wheels, and the vehicle may start suddenly.

[0004] In order to suppress a sudden start when the normal start operation as described above is not performed, JP2014-156155A discloses a control for limiting the driving force when the order of the shift switching operation and the accelerator pedal operation is reversed. Summary of the invention

[0005] However, in recent years, there has been an increase in vehicles having a mechanism for maintaining braking force until the driving force transmitted to the drive wheels increases to a predetermined value when the vehicle starts, in order to prevent the vehicle from sliding down when starting on a slope.

[0006] If the control of the above document is applied to a vehicle having such a mechanism to limit the driving force, the driving force will not increase to the prescribed value for releasing the holding of the braking force regardless of whether the starting gear is selected and the accelerator pedal is depressed, which may cause the vehicle to be unable to start. In order to enable the vehicle to start, a strategy of lowering the prescribed value for releasing the holding of the braking force is also considered. However, according to this strategy, when starting on an uphill road, the holding of the braking force can be released, but the vehicle cannot be moved forward by the limited driving force, and the vehicle may move backward.

[0007] Therefore, an object of the present invention is to start the vehicle without performing a sudden start and by releasing the holding of the braking force even when the order of the range switching operation and the accelerator pedal operation is opposite to the normal operation.

[0008] According to a certain embodiment of the present invention, there is provided a driving force control method for a vehicle, the vehicle having: a driving source that generates a driving force for driving the vehicle; a gear switching device that has a starting gear that transmits the driving force from the driving source to the driving wheels according to an accelerator pedal operation, and a parking gear that does not transmit the driving force from the driving source to the driving wheels even if the accelerator pedal is operated; a holding device that maintains the stopped state of the vehicle until the driving force is greater than a holding threshold value at the time of starting, and releases the stopped state if the driving force becomes greater than the holding threshold value; and a control unit that calculates the driver's requested driving force based on the accelerator pedal operation amount. In the driving force control method, when switching from the parking gear to the starting gear, when the accelerator pedal operation amount has reached the magnitude of the generated driving force, the control unit limits the upper limit of the driving force of the driving source to a driving force greater than the holding threshold value and less than the requested driving force. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the vehicle.

[0010] Figure 2 This is a block diagram schematically showing a control system of a vehicle.

[0011] Figure 3 This is a diagram showing an example of a driving force map for forward movement.

[0012] Figure 4 This is a diagram showing an example of a driving force map for reverse travel.

[0013] Figure 5 This is a control block diagram showing the content of the processing executed by the driving force limitation determination unit.

[0014] Figure 6 This is a diagram showing an example of a table for setting the first-level gradient.

[0015] Figure 7 This is a diagram showing an example of a table for setting the second-level gradient.

[0016] Figure 8 This is a first timing chart when starting in an abnormal starting order.

[0017] Fig. 9 This is a second timing chart when starting in an abnormal starting order.

[0018] Fig.10 This is the third timing chart when starting in an abnormal starting order. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] Figure 1 It is a schematic configuration diagram of a vehicle C including a vehicle control system 1 according to the present embodiment.

[0021] The vehicle C has an accelerator operation amount sensor 2, a brake operation amount sensor 4, a vehicle speed sensor 6, a shift position sensor 10, and a controller 100 as a control unit. On this basis, the vehicle C also has a brake actuator 14, a brake device 16, a drive motor 20 as a drive source, and wheels W (right front wheel WFR, left front wheel WFL, right rear wheel WRR, left rear wheel WRL).

[0022] The accelerator operation amount sensor 2 is a sensor formed by, for example, a pedal stroke sensor, and detects the operation amount (depression operation amount) of the accelerator pedal 22 by the driver.

[0023] The accelerator pedal 22 is a pedal that the driver of the vehicle C operates with the intention of braking or the intention of accelerating.

[0024] The accelerator operation amount sensor 2 outputs an information signal including the operation amount of the accelerator pedal 22 by the driver (sometimes referred to as “accelerator operation amount signal” in the following description) to the controller 10 .

[0025] The configuration of the accelerator operation amount sensor 2 is not limited to that formed by a pedal stroke sensor, and may be a configuration that detects the opening degree of the accelerator pedal 22 based on the driver's depression operation, for example.

[0026] That is, the accelerator operation amount sensor 2 is a sensor that detects the amount of operation of the accelerator pedal 22 by the driver.

[0027] The brake operation amount sensor 4 is a sensor formed by, for example, a pedal stroke sensor, and detects the operation amount (depression operation amount) of the brake pedal 24 by the driver.

[0028] The brake pedal 24 is a pedal that the driver of the vehicle C operates with the intention of braking.

[0029] The brake operation amount sensor 4 outputs an information signal including the operation amount of the brake pedal 24 by the driver (sometimes referred to as “brake operation amount signal” in the following description) to the controller 100 .

[0030] The brake operation amount sensor 4 has the same structure as the accelerator operation amount sensor 2 and is not limited to a structure using a pedal stroke sensor. For example, it may be a structure that detects the opening of the brake pedal 24 based on the driver's stepping operation.

[0031] That is, the brake operation amount sensor 4 is a sensor that detects the amount of operation of the brake pedal 24 by the driver.

[0032] The vehicle speed sensor 6 is formed of, for example, a resolver that detects the vehicle speed of the vehicle C based on the rotation speed of the drive motor 20 .

[0033] The vehicle speed sensor 6 outputs an information signal including the detected vehicle speed (sometimes referred to as “vehicle speed signal” in the following description) to the controller 100 .

[0034] The shift position sensor 10 detects the current position of the shift handle, shift lever, etc., which changes the gear of the vehicle C. The shift positions include the D gear for forward movement, the R gear for reverse movement, the P gear and the N gear for parking, and the B gear for generating stronger regenerative braking. Among them, the D gear, the R gear, and the B gear are called starting gears, and the P gear and the N gear are called parking gears. When the starting gear is selected, the driving motor 20 generates a driving force corresponding to the accelerator operation amount, and the driving force is transmitted to the right front wheel WFR and the left front wheel WFL as the driving wheels. When the parking gear is selected, the driving motor 20 does not generate a driving force, and therefore the driving force is not transmitted to the driving wheels.

[0035] The shift position sensor 10 outputs an information signal including the detected current position (sometimes referred to as a “shift position signal” in the following description) to the controller 100 .

[0036] The controller 100 controls the braking force and driving force generated by the vehicle C, and is composed of a microcomputer. The microcomputer has, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like.

[0037] The controller 100 performs various processes described below using the various information signals input, and outputs command signals (brake command signals, drive command signals) for controlling the brake actuator 14 and the drive motor 20. The specific structure of the controller 100 will be described below.

[0038] The brake command signal is an information signal including a braking force command value for controlling the braking force generated by the vehicle C.

[0039] The braking force command value includes at least one of a command value for controlling the hydraulic pressure of each brake device 16 , that is, a command value for friction braking torque and a command value for regenerative braking torque generated by the drive motor 20 .

[0040] The controller 100 calculates the braking force command value based on the amount of operation of the accelerator pedal 2 or the amount of depression of the brake pedal 24 by the driver of the vehicle C, the gradient of the traveling road surface, and the like.

[0041] The drive command signal is an information signal including the drive force generated by the drive motor 20 or the requested drive force for controlling the regenerative braking force. The requested drive force is the drive force requested by the driver of the vehicle C and is calculated by the controller 100 based on the driver's operation amount of the accelerator pedal 2 .

[0042] The brake actuator 14 is a hydraulic control device installed between a master cylinder (not shown) and each brake device 16. In addition, the brake actuator 14 changes the hydraulic pressure of each brake device 16 according to the braking force command value included in the brake command signal received as input from the controller 100. As a result, the brake actuator 14 applies a braking force to each wheel W.

[0043] The brake device 16 generates a pressing force for pressing a brake pad (not shown) constituting a disc brake against a disc rotor (not shown). The disc rotor is a component that rotates integrally with each wheel W and contacts the brake pad to generate friction resistance.

[0044] That is, the brake actuator 14 , the master cylinder, and the brake devices 16 form a friction brake that the vehicle C has.

[0045] In addition, Figure 1 , the brake device 16 configured for the right front wheel WFR is shown as the brake device 16FR, and the brake device 16 configured for the left front wheel WFL is shown as the brake device 16FL. Similarly, Figure 1 In the figure, the brake device 16 arranged for the right rear wheel WRR is shown as the brake device 16RR, and the brake device 16 arranged for the left rear wheel WRL is shown as the brake device 16RL. In addition, in the following description, each brake device 16 may also be shown as described above.

[0046] The controller 100 controls the driving force generated by the driving motor 20 according to the requested driving force included in the driving command signal. In addition, a motor controller for controlling the driving motor 20 may be provided separately, and the motor controller receives the requested driving force from the controller 100 and controls the driving force generated by the driving motor 20. In this case, the motor controller outputs an information signal (sometimes referred to as a "current torque signal" in the following description) including the current driving force (motor torque) generated by the driving motor 20 to the controller 100.

[0047] Furthermore, the controller 100 controls the regenerative torque generated by the driving motor 20 according to the command value of the regenerative braking torque included in the brake command signal.

[0048] The driving motor 20 is configured to generate driving force or regenerative braking force of the vehicle C, and applies the driving force or regenerative braking force to each wheel W via a drive shaft (not shown) or the like.

[0049] The vehicle C of the above structure has a function of maintaining the stopped state of the vehicle until the driving force transmitted from the driving motor 20 to the driving wheels WFL, WFR exceeds the holding threshold, and releasing the stopped state if the driving force exceeds the holding threshold. Specifically, if the brake pedal 24 is stepped on to stop the vehicle C, the hydraulic pressure of the brake device 16 as a holding device is maintained at the value during parking even if the operation amount of the brake pedal 24 becomes zero. Moreover, if the driving force transmitted from the driving motor 20 to the driving wheels WFL, WFR exceeds the holding threshold, the hydraulic pressure of the brake device 16 is released. In addition, the "driving force transmitted from the driving motor 20 to the driving wheels WFL, WFR exceeds the holding threshold" mentioned here is not limited to the case where the driving force actually transmitted exceeds the holding threshold, but also includes the case where the command value of the driving force to the driving motor 20 calculated by the controller 100 exceeds the holding threshold. The holding threshold is, for example, a lower limit torque that enables the vehicle C to start in the traveling direction, and is set according to the slope of the road surface where the vehicle is parked.

[0050] In addition, in the present embodiment, the brake device 16 is used as the holding device, but the present invention is not limited to this. For example, an electric parking brake or an electric parking lock mechanism that operates in the P range may be used as the holding device.

[0051] However, as a sequence for starting the vehicle C from a state where the shift position is in the parking gear, it is normal to switch the shift position to the starting gear and then step on the accelerator pedal 22. The reason is as follows. By switching the shift position from the parking gear to the starting gear, the driving force of the driving motor 20 is transmitted to the driving wheels WFL and WFR. If the accelerator pedal 22 is stepped on in this state, the driving force transmitted to the driving wheels WFL and WFR also gradually increases in accordance with the gradual increase in the amount of stepping on the accelerator pedal 22, so that it will not be a sudden start and can start smoothly.

[0052] On the other hand, an abnormal operation of switching the shift position from the parking gear to the starting gear after the accelerator pedal 22 is depressed may be performed. In this case, even if the accelerator pedal 22 is depressed when the shift position is in the parking gear, the driving motor 20 does not generate driving force. However, if the driving force limitation described later is not performed, the driving force of the driving motor 20 increases rapidly toward the driving force corresponding to the depression amount of the accelerator pedal 22 at that time when the shift position is just switched to the starting gear, so the vehicle C starts suddenly.

[0053] Therefore, in the case where the normal starting sequence is not performed, the controller 100 notifies the driver of the abnormal starting sequence in order to avoid sudden starting, and limits the upper limit of the driving force generated by the driving motor 20 to a driving force greater than the holding threshold and less than the requested driving force. When limiting the driving force, the controller 100 limits the increase in the driving force per unit time, that is, the increase gradient, to a value less than the maximum increase gradient in the case of the normal starting sequence to start the vehicle, and if the driving force exceeds the threshold described later after starting, the increase gradient is switched to a smaller value. The driving force limitation is described in detail below.

[0054] Figure 2 This is a block diagram schematically showing a control system of a vehicle according to the present embodiment.

[0055] The control system includes a shift position determination unit B1 that determines the current shift position based on the shift operation of the driver. The shift position signal output from the shift position determination unit B1 is input to the instrument panel 30, the required driving force calculation unit B2, and the driving force limitation determination unit B3.

[0056] The instrument panel 30 includes a plurality of measuring instruments such as a speedometer and an output meter, and a display unit, and also includes a shift position display unit that indicates a current shift position. The current shift position is displayed on the shift position display unit.

[0057] In addition to the shift position signal, the required driving force calculation unit B2 also reads the accelerator operation amount signal and the vehicle speed signal, and calculates the required driving force corresponding to the driver's accelerator operation amount based on these signals. Figure 3 , Figure 4 The driving force map shown calculates the required driving force. Figure 3 This is the driving force diagram for the forward gear. Figure 4 The map is a driving force map for the reverse gear position. An arbitrary map is selected according to the shift position signal, and the map is searched using the accelerator operation amount signal and the vehicle speed signal to determine the required driving force.

[0058] The driving force limitation determination unit B3 determines whether to limit the driving force when the normal starting sequence is not performed, and calculates the driving force after the limit, based on the shift position signal, the start state signal, the accelerator operation amount signal, the vehicle speed signal, and the requested driving force. The start state signal refers to a signal indicating whether the vehicle system is started. The contents of the determination and calculation here will be described later.

[0059] The requested driving force calculated by the requested driving force calculation unit B2 and the limited driving force calculated by the driving force limit determination unit B3 are transmitted to the driving motor 20 via the rate limit processing B4, the filter processing B5 and various processing B6. The rate limit processing B4 and the filter processing B5 are processes for weakening the change of the driving force corresponding to the small accelerator operation amount performed unconsciously by the driver. When the driver steps on the accelerator pedal with his foot, the accelerator operation amount sometimes changes slightly even if the driver does not operate it subconsciously. If the driving force is changed in correspondence with the change of this accelerator operation amount, the drivability and comfort deteriorate. Therefore, the change of the driving force is weakened by the rate limit processing B4 and the filter processing B5. In addition, the rate limit processing B4 and the filter processing B5 are well-known processes.

[0060] Various processing B6 limits the driving force based on other conditions. As a condition for limiting the driving force, for example, the battery temperature may exceed a preset threshold value. In addition, various processing B6 is also a well-known process.

[0061] The determination result of the driving force limitation determination unit B3 is also used in the warning request process B7 , the projector request process B8 , the ICC / AD cancellation process B10 , and the ASCD cancellation process B11 .

[0062] The alarm is used to inform the driver that the normal start sequence has not been performed. In the present embodiment, the alarm is sounded to inform the driver. The alarm request process B7 is a process for determining whether to sound the alarm.

[0063] The projection light request processing B8 refers to the processing for determining whether to turn on the projection light. The projection light here refers to a light that is arranged on the instrument panel 30 and turns on when the driving force is limited. If the driving force is limited, the acceleration of the vehicle is lower than the acceleration that should be obtained with the current accelerator operation amount, and the projection light turns on, so that the driver can recognize that the reason for the reduced acceleration is not a vehicle failure. In addition, when the projection light is turned on, the output limitation reason B9 is also displayed on the instrument panel 30.

[0064] ICC / AD cancellation processing B10 refers to the processing of canceling the intelligent cruise control (ICC) and automatic driving (AD) of driving while maintaining the inter-vehicle distance to the preceding vehicle corresponding to the vehicle speed, using the vehicle speed set by the driver as the upper limit. That is, in this embodiment, the driving force is limited when a normal starting operation is not performed, but the above operation is not accepted even if the operation of setting ICC and AD is performed during the period of limiting the driving force. A signal to cancel the above operation is input to the advanced driving assistance system (ADAS) 110.

[0065] The ASCD canceling process B11 is a process for canceling the vehicle speed control of the automatic speed control device (ASCD) that controls the vehicle speed when ICC and AD are executed. This process is accompanied by canceling ICC and AD.

[0066] Next, the processing of the driving force limitation determination unit B3 will be described.

[0067] Figure 5 2 is a control block diagram showing the content of the processing executed by the driving force limitation determination unit B3.

[0068] The alarm request judgment unit B31 judges whether there is an alarm request based on the start-up state signal, the shift position signal, the vehicle speed signal and the accelerator operation amount signal. Specifically, when all the conditions of being in the start-up state, the shift position is the parking gear, the vehicle is parked, and the accelerator pedal is stepped on are met, it is judged that there is an alarm request, and if it is judged that there is an alarm request, the alarm request flag is started. In addition, it is judged whether the vehicle is parked based on the vehicle speed signal. At this time, if the absolute value of the vehicle speed is less than or equal to the specified value (for example, 4km / h), it is judged that the vehicle is parked. In addition, "stepping on the accelerator pedal" means stepping on it to the extent that the driving motor 20 generates driving force, for example, it means that the opening of the accelerator pedal is greater than or equal to 1 / 8 relative to full opening.

[0069] If the alarm request flag is turned on, it is determined that an alarm is issued by the alarm request process B7. In other words, if any of the above conditions is not met, no alarm is issued.

[0070] When it is determined that there is an alarm request, a signal to limit the driving force is input from the alarm request determination unit B31 to the flag setting unit B35.

[0071] The flag setting unit B35 activates the driving force restriction request flag unless a signal to release the restriction on the driving force is input from the restriction release determination unit B32 described later. If the driving force restriction request flag is activated, the projection lamp is turned on, the ICC and AD are canceled, and a cancellation signal is input to the ASCD through the above-mentioned projection lamp request processing B8, ICC / AD cancellation processing B10 and ASCD cancellation processing B11.

[0072] The restriction release judgment unit B32 judges whether to release the restriction of the driving force based on the judgment result of the alarm request judgment unit B31, the requested driving force before restriction, the driving force after restriction, the shift position signal and the driving force restriction request flag. Specifically, if the alarm request flag is released and the state in which the driving force after restriction is greater than or equal to the requested driving force before restriction continues for a predetermined time, the restriction of the driving force is released. In addition, the requested driving force before restriction refers to the driving force after restriction. Figure 2 The driving force after limitation refers to the last calculated value of the driving force limited by the control described later.

[0073] The increasing gradient switching unit B33 switches between the first level gradient as the increasing gradient at the start and the second level gradient as the increasing gradient switched from the first level gradient after the start. Specifically, if the driving force exceeds the switching threshold, the gradient is switched from the first level gradient to the second level gradient. The switching threshold is set to a driving force that does not become a sudden start even if the holding device 16 is released. For example, the driving force is appropriately set to a level that the vehicle does not slide down on an uphill road based on the weight of the vehicle. In addition, the gradient of the uphill road envisioned here is set to about 5 to 10%, for example.

[0074] The input vehicle speed switching unit B34 converts the vehicle speed signal input to the first-level gradient table and the second-level gradient table described later from a negative value to a positive value in the case of the R gear. This is because it is sufficient to prepare one first-level gradient table and one second-level gradient table respectively. In addition, if two types of first-level gradient tables and second-level gradient tables are prepared for forward movement and reverse movement respectively, the input vehicle speed switching unit B34 is not required.

[0075] Regarding the first level gradient table B36, for example Figure 6 As shown, the horizontal axis is vehicle speed [km / h], and the vertical axis is increasing gradient [Nm / 10ms]. When the vehicle speed is greater than or equal to -V1 [km / h], the increasing gradient is roughly constant at Trq1. If it is less than -V1 [km / h], the smaller the vehicle speed, the greater the increasing gradient.

[0076] The increase gradient Trq1 [Nm / 10ms] here is a value at which the driving force quickly increases to the switching threshold, and is set to about 15 Nm / 10ms, for example.

[0077] When the vehicle speed is less than -V1 [km / h], the smaller the vehicle speed, the greater the increase in gradient is to prevent the vehicle from sliding down. That is, the vehicle speed such as -V1 [km / h] is a sliding threshold for determining whether sliding down occurs. And if sliding down occurs, the driving force is increased rapidly to stop the sliding down.

[0078] The sliding threshold value -V1 [km / h] may be any value that can be used to detect that the vehicle is moving in the direction opposite to the traveling direction, and may be, for example, about -0.5 [km / h].

[0079] Regarding the second level gradient table B37, for example Figure 7 As shown, the horizontal axis is the vehicle speed [km / h], and the vertical axis is the increase gradient [Nm / 10ms]. When the vehicle speed is greater than or equal to -V1 [km / h] and less than or equal to V2 [km / h], the higher the vehicle speed, the smaller the increase gradient. If the vehicle speed is greater than V2 [km / h], the increase gradient is zero. In addition, if the vehicle speed is less than -V1 [km / h], the smaller the vehicle speed, the larger the increase gradient. The reason why the smaller the vehicle speed, the larger the increase gradient when the vehicle speed is less than -V1 [km / h] is based on the same reason as the first-level gradient.

[0080] The increase gradient when the vehicle speed is greater than or equal to -V1 [km / h] is set to a level smaller than the first level gradient and such that the driver does not feel the sudden start. For example, if the comparison is made when the vehicle speed is 0 [km / h], the increase gradient Trq2 [Nm / 10ms] in the second gradient table is set to be smaller than the increase gradient Trq1 in the first gradient table, for example, 1 [Nm / 10ms].

[0081] The vehicle speed V2 [km / h] is appropriately set according to the magnitude of Trq2 [Nm / 10ms], etc. If the vehicle speed exceeds V2 [km / h], the increase gradient becomes zero, so when the vehicle speed exceeds V [km / h] during the driving force limitation, the maximum driving force achieved is lower than the requested driving force.

[0082] The increase gradient setting unit B38 sets the increase gradient based on the value selected by the increase gradient switching unit B33 in the first level gradient or the second level gradient and the information on whether the driving force limit request flag is activated by the flag setting unit B35. Specifically, when the driving force limit request flag is activated, the first level gradient or the second level gradient is set to the increase gradient, and when the driving force limit request flag is not activated, the driving force is not limited. When no restriction is made, it becomes an increase gradient corresponding to the specification of the driving source (this is called "maximum increase gradient").

[0083] Below, refer to Figures 8 to 10 The execution of the above control is described with reference to the timing diagram.

[0084] Figure 8 This is a timing chart showing a basic pattern when starting in an abnormal starting order.

[0085] As shown in the figure, at a timing T1 during parking with the accelerator pedal 22 turned off, the brake pedal 24 turned on, and the shift position set to the starting gear, the driver switches the shift position to the parking gear, and at a timing T2 thereafter, the driver turns off the brake pedal 24. Even if the driver turns off the brake pedal 24, the brake is kept on by the holding device.

[0086] In the above state, if the driver steps on the accelerator pedal 22 at timing T3, all the conditions for starting the alarm request flag are met. As a result, an alarm sound is sounded and the projection lamp is lit. In addition, the alarm sound is emitted in a pulsed manner as shown in the figure.

[0087] If the driver switches the shift position to the starting gear at timing T4 despite the alarm sound, the alarm sound stops and the driving force of the driving motor 20 starts to increase at the first step gradient.

[0088] If the driving force exceeds the switching threshold at timing T5, the increase gradient switches from the first level gradient to the second level gradient. Furthermore, if the driving force exceeds the holding threshold at timing T6, the holding device switches from the holding state to the release state, and the brake state switches from on to off.

[0089] After the vehicle speed reaches the above-mentioned V2 [km / h] at timing T7, the increase gradient becomes zero, so the limited driving force becomes constant.

[0090] Fig. 9 This is a timing diagram for starting in an abnormal starting order on a steep uphill road. Figure 8 The same, therefore the description is omitted.

[0091] If the holding device is released at timing T6, the vehicle speed increases in the negative direction. That is, the vehicle starts to slide down. This kind of slide may also occur when the road surface gradient is greater than the gradient assumed when setting the holding threshold.

[0092] Furthermore, when the vehicle speed reaches the above-mentioned -V1 [km / h] at timing T7, the increase gradient of the driving force increases. As a result, the vehicle speed turns to increase and becomes a positive value at timing T8 and thereafter. That is, the vehicle can start.

[0093] Fig.10 This is a timing chart for the case where the vehicle is started in an abnormal starting order and the depression amount of the accelerator pedal 22 is reduced during the execution of the driving force limitation. Figure 8The same, therefore the description is omitted.

[0094] At timing T7 when the driving force increases at the second step gradient, the amount of depression of the accelerator pedal 22 begins to decrease, and the requested driving force before limitation also begins to decrease. Furthermore, if the requested driving force before limitation is lower than the driving force after limitation at timing T8, the limitation of the driving force is terminated, and the requested driving force is used as the driving force of the driving motor 20. At this time, the projection lamp is turned off.

[0095] In addition, Fig.10 In the embodiment, the restriction of the driving force is released at the timing T8 when the requested driving force before the restriction is lower than the driving force after the restriction, and the projection lamp is turned off. However, in order to avoid erroneous judgments based on noise, etc., as described in the description of the restriction release judgment unit B32, it is preferred to release the restriction after the state in which the driving force after the restriction is greater than or equal to the requested driving force before the restriction continues for a predetermined time.

[0096] In addition, Figure 8 In the case of limiting the driving force, the peak value is reached when the driving force after limitation is lower than the requested driving force before limitation. However, in actual driving, there is a chance that the accelerator pedal 22 is disconnected after starting. Fig.10 In the same manner as in the case of , the restriction on the driving force is released.

[0097] As described above, in the present embodiment, a driving force control method for a vehicle is provided, the vehicle having: a driving motor 20 that generates a driving force for driving the vehicle; a gear switching device 8 that has a starting gear in which the driving force is transmitted from the driving motor 20 to the driving wheels WFR and WFL according to an accelerator pedal operation, and a parking gear in which the driving force is not transmitted from the driving motor 20 to the driving wheels WFR and WFL even if the accelerator pedal 22 is operated; a holding device 16 that holds the stopped state of the vehicle until the driving force transmitted from the driving motor 20 to the driving wheels WFR and WFL exceeds a holding threshold value at the time of starting, and releases the stopped state if the driving force exceeds the holding threshold value; and a controller 100 that calculates the driver's requested driving force based on the accelerator pedal operation amount. When switching from the parking gear to the starting gear, when the accelerator pedal operation amount reaches a magnitude that generates the driving force, the controller 100 limits the upper limit of the driving force of the driving motor 20 to a driving force that is greater than the holding threshold value and less than the requested driving force.

[0098] Thus, even when the vehicle is started in an abnormal starting sequence, the vehicle does not start suddenly, and the holding device 16 can be released reliably to start the vehicle.

[0099] In the present embodiment, when limiting the upper limit of the driving force, the controller 100 limits the increase amount of the driving force per unit time, i.e., the increase gradient, to the second level gradient (first gradient) of the maximum increase gradient when the accelerator pedal operation amount reaches the magnitude of the driving force generated after switching from the parking gear to the starting gear. Thus, in the case of starting in an abnormal starting order, it is possible to more reliably prevent a sudden start.

[0100] In this embodiment, when limiting the upper limit of the driving force, until the driving force reaches the switching threshold (gradient change threshold) less than the holding threshold after switching to the starting gear, the controller 100 limits the increase gradient to the first-level gradient (second gradient) greater than the second-level gradient and less than the maximum increase gradient. If the driving force reaches the switching threshold, it is limited to the second-level gradient. In this way, the time until the holding threshold is reached can be shortened. In addition, the switching threshold is less than the holding threshold, so the vehicle does not start during the period when the driving force increases with the first-level gradient. That is, it does not start suddenly.

[0101] In this embodiment, when the vehicle slides down (backwards) after switching to the starting gear, the controller 100 makes the increase gradient greater than the second level gradient. Thus, even when starting in an abnormal starting order on an uphill road, the vehicle can be prevented from sliding down.

[0102] In the present embodiment, when the requested driving force is lower than the restricted driving force, the controller 100 removes the restriction on the upper limit of the driving force. The driving force is restricted in the case of starting in an abnormal starting order, but the restriction on the driving force needs to be removed in order to continue traveling. In this regard, there is indeed a chance that the amount of depression of the accelerator pedal decreases after starting, so according to the present embodiment, the restriction can be removed without complicated operations. In addition, if the requested driving force is greater than the restricted driving force when the restriction is removed, it is possible that the driving force will increase sharply in order to follow the requested driving force. However, according to the present embodiment, the restriction is removed when the requested driving force is lower than the restricted driving force, so there is no worry that the driving force will increase sharply after the restriction is removed.

[0103] In addition, in this embodiment, the case where the driving source is the driving motor 20 is described, but the present invention is also applicable to a vehicle where the driving source is an internal combustion engine and has a transmission device that disconnects or connects the power transmission between the driving source and the driving wheels. In addition, in this embodiment, the structure that can control the braking force using the accelerator pedal 2 is described, but even if the accelerator pedal 2 only controls the driving force, this embodiment can be applied.

[0104] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate a part of application examples of the present invention, and the technical scope of the present invention is not limited to the specific structures of the above embodiments.

Claims

1. A driving force control method for a vehicle, the vehicle having: a driving source that generates a driving force for driving the vehicle; a gear switching device having a starting gear for transmitting the driving force from the driving source to the driving wheels in response to an accelerator pedal operation, and a parking gear for not transmitting the driving force from the driving source to the driving wheels even if the accelerator pedal is operated; a holding device for holding the vehicle in a stopped state until the driving force becomes greater than a holding threshold value at the time of starting, and releasing the stopped state if the driving force becomes greater than the holding threshold value; and A control unit calculates a driver's requested driving force based on an accelerator pedal operation amount, wherein: When the accelerator pedal operation amount reaches a magnitude that generates the driving force when switching from the parking gear to the starting gear is performed, the control unit limits the upper limit of the driving force of the driving source to a driving force that is greater than the holding threshold and less than the requested driving force. When limiting the upper limit of the driving force, the control unit limits the increase in the driving force per unit time, i.e., the increase gradient, to a second gradient greater than the first gradient and less than the maximum increase gradient, until the driving force reaches a gradient change threshold value less than a holding threshold value after switching to the starting gear. If the driving force reaches the gradient change threshold value, it is limited to the first gradient, wherein the maximum increase gradient is the increase gradient when the accelerator pedal operation amount reaches a magnitude that generates the driving force after switching from the parking gear to the starting gear, and the first gradient is less than the maximum increase gradient.

2. The driving force control method according to claim 1, wherein: When the vehicle moves backward after switching to the starting gear, the control unit makes the increase gradient larger than the first gradient.

3. The driving force control method according to claim 1 or 2, wherein: The control unit releases the limitation on the upper limit of the driving force when the requested driving force is lower than the limited driving force.

4. A driving force control device for a vehicle, the vehicle comprising: a driving source that generates a driving force for driving the vehicle; a gear switching device having a starting gear for transmitting the driving force from the driving source to the driving wheels in response to an accelerator pedal operation, and a parking gear for not transmitting the driving force from the driving source to the driving wheels even if the accelerator pedal is operated; a control unit that calculates a driver's requested driving force based on an accelerator pedal operation amount and controls the driving source based on the requested driving force; as well as A holding device that holds the vehicle in a stopped state until the driving force is greater than a holding threshold value when starting, and releases the stopped state if the driving force transmitted from the driving source to the driving force is greater than the holding threshold value, wherein: When the accelerator pedal operation amount reaches a magnitude that generates the driving force when switching from the parking gear to the starting gear is performed, the control unit limits the upper limit of the driving force of the driving source to the driving force that is greater than the holding threshold and less than the requested driving force, When limiting the upper limit of the driving force, the control unit limits the increase in the driving force per unit time, i.e., the increase gradient, to a second gradient greater than the first gradient and less than the maximum increase gradient, until the driving force reaches a gradient change threshold value less than a holding threshold value after switching to the starting gear. If the driving force reaches the gradient change threshold value, it is limited to the first gradient, wherein the maximum increase gradient is the increase gradient when the accelerator pedal operation amount reaches a magnitude that generates the driving force after switching from the parking gear to the starting gear, and the first gradient is less than the maximum increase gradient.

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