JP6729142B2 - Driving force control method and driving force control device - Google Patents

Description

The present invention relates to a driving force control method and a driving force control device.

BACKGROUND ART Conventionally, there is known a vehicle transmission that inputs engine torque via a torque converter and that includes a creep prevention mechanism that prevents a creep phenomenon when an engine idling operation is detected (Patent Document 1). reference). In Patent Document 1, when the brake release of the vehicle is detected, the operation of the creep prevention mechanism is released to prevent the vehicle from moving backward when starting uphill.

Japanese Patent Publication No. 1-51371

In recent years, in vehicles that are driven by the driving force of an electric motor, a traveling mode has been developed in which the vehicle is held in a stopped state simply by turning off the accelerator. In this running mode, the driving force (creep torque) in the power running direction for running the vehicle at a low speed when the accelerator is off is inconvenient and is not normally generated.

However, in a driving scene such as a traffic jam operation or a garage entry operation, the operation of the accelerator is complicated, and it is rather convenient to adjust the vehicle speed by operating the brake while the creep torque is being generated.

The present invention has been made in view of the above problems, and an object thereof is to generate creep torque in a traveling mode in which the vehicle can be stopped and held in a stopped state simply by turning off the accelerator. It is to provide a driving force control method and a driving force control device that improve the convenience of the driver by controlling the.

A method for controlling a driving force of a vehicle according to a first aspect of the present invention is such that when a vehicle is stopped or is traveling at a speed lower than a low speed reference value, an operation is performed from a state in which a brake is operated, a brake threshold When released until, the electric motor generates a driving force for moving the vehicle forward at a low speed.
A method for controlling a driving force of a vehicle according to a second aspect of the present invention is such that an automatic transmission of a vehicle is out of a travel impossible range when the vehicle is stopped or traveling at a speed lower than a low speed reference value. When the vehicle is operated to the travelable range, it causes the electric motor to generate a driving force for moving the vehicle forward at a low speed.

According to the present invention, a driving force that improves the convenience of the driver by controlling the generation of creep torque in a traveling mode in which the vehicle can be stopped and held in a stopped state simply by turning off the accelerator. A control method and a driving force control device can be provided.

FIG. 1 is a block diagram showing a configuration of a hybrid car including a driving force control device according to an embodiment. FIG. 2 is a block diagram showing functional components included in the vehicle controller 14. FIG. 3 is a block diagram showing an algorithm for calculating the driving force of the drive motor 6 according to the accelerator opening in consideration of the road gradient. FIG. 4A is a graph showing the driving force generated by the drive motor 6 when the accelerator is off in order to bring the vehicle to a stop and to keep the vehicle in a stopped state even if the brake is not operated on a flat road (no slope). Is. FIG. 4B is a graph showing the correction amount of the driving force according to the gradient (inclination) required to bring the vehicle to a stop and maintain the stopped state on a road having a gradient. FIG. 4C is a graph showing a state in which the correction amount 41 of FIG. 4B at the time of downhill is added to the driving force of FIG. 4A. FIG. 4D is a graph showing that the acceleration and deceleration applied to the vehicle according to the vehicle speed have the same curve regardless of whether or not there is a gradient. FIG. 5 is a time chart showing an accelerator operation, a vehicle speed, a driving force, and a temporal change of the vehicle G on a flat road and a road having a downward slope. FIG. 6 is a schematic diagram summarizing examples of various traveling conditions for switching between a state without creep torque (without creep) and a state with creep torque (with creep) in the first traveling mode. FIG. 7 is a graph showing the first condition 43, the second condition 44, and the third condition 45 in a two-dimensional orthogonal coordinate system having the vehicle speed on the horizontal axis and the braking force on the vertical axis. FIG. 8 is a time chart showing a time change of each traveling parameter when the third condition 45 is satisfied, that is, when the brake changes from the on state to the off state. FIG. 9 is a time chart showing the change over time of each traveling parameter when the second condition 44 is satisfied, that is, when the automatic transmission of the vehicle is operated from the travel impossible range to the travel possible range. FIG. 10 is a time chart showing a time change of each traveling parameter when the first condition 43 is satisfied, that is, when the first traveling mode is switched to the second traveling mode. FIG. 11 is a graph showing the fourth condition 51, the fifth condition 52, and the sixth condition 53 in a two-dimensional orthogonal coordinate system in which the horizontal axis represents the vehicle speed and the vertical axis represents the driving force by the accelerator. FIG. 12 is a time chart showing a time change of each traveling parameter when the fourth condition 51 is satisfied, that is, when the vehicle speed becomes equal to or higher than the first predetermined value 63. FIG. 13 is a time chart showing the change over time of each traveling parameter when the fifth condition 52 is satisfied, that is, when the vehicle speed becomes equal to or higher than the third predetermined value 64 and the second traveling mode is switched to the first traveling mode. is there. FIG. 14 shows the time of each traveling parameter when the sixth condition 53 is satisfied, that is, when the vehicle speed becomes the second predetermined value 65 or more and the driving force of the vehicle generated by the accelerator operation becomes the predetermined value 66 or more. It is a time chart which shows change. FIG. 15 is a flowchart showing an example of a procedure for determining the correctness of the first condition to the third condition (43 to 45) when the first traveling mode is selected and there is no creep torque. FIG. 16 is a flowchart showing an example of a procedure for determining the correctness of the fourth condition to the sixth condition (51 to 53) in the presence of the creep torque.

Embodiments will be described with reference to the drawings. In the description of the drawings, the same parts are designated by the same reference numerals and the description thereof is omitted.

<Structure of driving force control device>
A configuration of a hybrid car including a driving force control device according to an embodiment will be described with reference to FIG. The hybrid car of the embodiment includes an engine 1, a generator 4, a battery 5, a drive motor 6, wheels 7 (drive wheels), and a drive motor controller 13 that controls the drive motor 6. The hybrid car is one in which the engine 1 does not drive the wheels 7 but the battery 5 drives the wheels 7. Since the engine 1, the battery 5 and the wheels 7 are connected in series (series connection), they are called series hybrid cars. To be done.

The engine 1 is mechanically connected to the generator 4 via a speed reducer (not shown). The generator 4 is connected to the battery 5 so that power can be transmitted and received. Power transmission/reception is also possible between the battery 5 and the drive motor controller 13, and between the drive motor controller 13 and the drive motor 6. The drive motor 6 is mechanically connected to the axle via a gear 16, and the axle is mechanically connected to the wheels 7.

The driving force of the engine 1 is transmitted to the generator 4, and the generator 4 generates power by the driving force of the engine 1. The battery 5 is charged with the electric power generated by the generator 4. The charging power of the battery 5 is transmitted to the driving motor 6 via the driving motor controller, and the driving motor 6 is driven by the charging power of the battery 5. The driving force of the drive motor 6 is transmitted to the wheels 7 via the gear 16 and the axle. The wheels 7 are rotated by the driving force of the drive motor 6, so that the series hybrid car (hereinafter abbreviated as vehicle) runs.

The vehicle has a mode switch (mode SW) 17 for selectively selecting a plurality of driving modes, a select lever 18 operated by a driver when selecting a range of an automatic transmission, and a brake oil pressure sensor for detecting a braking force. 19, an accelerator position sensor (APS) 20 that detects an accelerator opening, and a vehicle controller 14 that controls the entire hybrid car. The vehicle controller 14 functions as a driving force control device according to the embodiment.

The vehicle controller 14 is electrically connected to each of the mode switch 17, the select lever 18, the brake oil pressure sensor 19, and the accelerator position sensor 20. The vehicle controller 14 receives a signal indicating the selected traveling mode from the mode switch 17, receives a signal indicating the selected range from the select lever 18, and receives a signal indicating the brake hydraulic pressure from the brake hydraulic pressure sensor 19. Then, the signal indicating the accelerator opening is received from the accelerator position sensor 20.

The travel modes selectable by the mode switch 17 include at least the first travel mode and the second travel mode. In the first traveling mode, the vehicle controller 14 causes the drive motor (electric motor) 6 to generate a driving force when the accelerator of the vehicle is not operated, so that the accelerator or the brake of the vehicle is not operated on the road having a slope. Also stops the vehicle and holds it in a stopped state. In the second traveling mode, the vehicle controller 14 does not hold the vehicle in the stopped state unless the brake is operated. The first traveling mode will be described later with reference to FIGS. 3, 4A to 4D, and 5.

Further, the range selectable by the select lever 18 includes, for example, a drive range (D), a reverse range (R), a neutral range (N), and a parking range (P).

The vehicle controller 14 is electrically connected to the drive motor controller 13. The vehicle controller 14 sends a command torque to the drive motor controller 13. The vehicle controller 14 receives from the drive motor controller 13 a signal indicating the motor rotation speed of the drive motor 6 and a signal indicating slope information of the road on which the vehicle travels.

The vehicle controller 14 can be realized by, for example, a general-purpose microcomputer including a CPU (central processing unit), a memory, and an input/output unit. A computer program (driving force control program) for causing the microcomputer to function as the vehicle controller 14 is installed in the microcomputer and executed. As a result, the general-purpose microcomputer functions as the vehicle controller 14. Here, an example in which the vehicle controller 14 is realized by software is shown, but of course, the vehicle controller 14 can be configured by preparing dedicated hardware for executing the following information processing. is there. Further, the plurality of units (23 to 32) included in the vehicle controller 14 may be configured by individual hardware. Further, not only the vehicle controller 14 but also the drive motor controller 13 can be realized as software or dedicated hardware in the same manner. Further, the vehicle controller 14 and the drive motor controller 13 may also serve as an electronic control unit (ECU) used for other control related to the vehicle.

The functional components of the vehicle controller 14 will be described with reference to FIG. The vehicle controller 14 has, as functional components, a selection range determination unit 23, a driving mode determination unit 24, a braking force determination unit 25, a vehicle speed calculation unit 26, a brake speed calculation unit 27, and a creep change calculation unit. 28, a gradient correction amount calculation unit 29, a creep determination unit 30, a creep calculation unit 31, and a driving force calculation unit 32.

The selected range determination unit 23 determines the range selected by the select lever 18. Specifically, it is determined whether the selected range is a drivable range (D range or R range) or a drivable range (N range or P range). The traveling mode determination unit 24 determines the traveling mode selected by the mode switch 17. Specifically, it is determined whether the selected traveling mode is the first traveling mode or the second traveling mode. The braking force determination unit 25 determines whether the braking force detected by the brake oil pressure sensor 19 is equal to or less than a predetermined brake threshold value. If it is less than or equal to the brake threshold, it is determined that the driver's brake operation has been released.

The vehicle speed calculator 26 calculates the traveling speed (vehicle speed) of the vehicle from the signal indicating the motor rotation speed received from the drive motor controller 13. The vehicle speed calculation unit 26 calculates the vehicle speed using a map that shows the correspondence between the motor rotation speed and the vehicle speed stored in the memory of the vehicle controller 14.

The brake speed calculator 27 calculates the amount of change in the braking force per unit time, that is, the brake change speed. The brake change speed includes, for example, the speed at which the brake pedal is depressed and the speed at which the brake operation is released.

The creep change calculation unit 28 uses the brake change speed calculated by the brake speed calculation unit 27, in particular, the magnitude of the speed at which the brake operation is released, to drive the drive motor to move the vehicle forward at low speed (creep torque). Calculate the speed to generate. The speed at which the creep torque is generated is calculated using the map that shows the correspondence relationship between the brake change speed and the speed at which the creep torque is generated, which is stored in the memory inside the vehicle controller 14. As shown in the map, the speed at which the creep torque is generated changes according to the speed at which the brake operation is released. The faster the brake is released, the faster the creep torque is generated. The creep torque is a driving force generated by the drive motor 6 in a vehicle driven by the drive motor 6 by simulating a creep phenomenon that occurs in a vehicle driven by an engine. It is a driving force for advancing at a low speed of about 8 km or less).

The gradient correction amount calculation unit 29 calculates a correction value for correcting the deviation of the driving force due to the gradient of the road from the signal indicating the gradient information received from the drive motor controller 13. The correction value is calculated using a map showing the correspondence between the gradient information stored in the memory in the vehicle controller 14 and the correction value. The correction of the driving force deviation due to the road gradient will be described later with reference to FIGS. 3, 4A to 4D, and 5.

The memory in the vehicle controller 14 stores a map showing the relationship between the magnitude of creep torque and the vehicle speed, and a map showing the relationship between the vehicle speed and the driving force of the drive motor 6 for each accelerator opening.

The creep determination unit 30 determines the generation and cancellation of creep torque based on the success or failure of various running conditions described later. In the first traveling mode in which the vehicle can be held in a stopped state simply by turning off the accelerator, the driving force (creep torque) in the power running direction for causing the vehicle to travel at a low speed when the accelerator is off is inconvenient and usually occurs. Do not let However, in a driving scene such as a traffic jam operation or a garage entry operation, the operation of the accelerator is complicated, and it is rather convenient to adjust the vehicle speed by operating the brake while the creep torque is being generated. Therefore, the creep determination unit 30 estimates the driver's intention based on whether or not various traveling conditions such as traveling mode switching, shift change, brake operation, and vehicle speed are satisfied, and controls on/off of the creep torque. Details of the operation of the creep determination unit 30 will be described later with reference to FIGS.

When the creep determination unit 30 determines that the creep torque is generated, the creep calculation unit 31 calculates the magnitude of the creep torque. The creep calculation unit 31 calculates the magnitude of the creep torque generated by the drive motor 6 according to the speed at which the creep torque is calculated calculated by the creep change calculation unit 28 and a map showing the relationship between the magnitude of the creep torque and the vehicle speed. To do.

The driving force calculation unit 32 calculates the magnitude of the driving force of the drive motor 6 based on the accelerator opening and the gradient information. The driving force calculation unit 32 calculates the magnitude of the driving force based on a map showing the relationship between the accelerator opening and the vehicle speed and the driving force and a correction value for correcting the deviation of the driving force due to the gradient. When the first traveling mode is selected, the driving force calculation unit 32 causes the drive motor 6 to stop the vehicle and keep the vehicle stopped even if the accelerator or the brake is not operated on a road having a slope. Calculate the driving force to be generated. Details of the driving force calculation unit 32 when the first traveling mode is selected will be described later with reference to FIGS. 3, 4A to 4D, and 5.

The vehicle controller 14 calculates the command torque from the total driving force obtained by adding the creep torque calculated by the creep calculating unit 31 to the driving force calculated by the driving force calculating unit 32, and transmits the command torque to the drive motor controller 13.

<Driving force control considering the gradient>
Next, the control operation of the driving force calculation unit 32 when the first traveling mode is selected by the mode switch 17 will be described with reference to FIGS. 3, 4A to 4D, and 5.

FIG. 3 shows an algorithm for calculating the driving force of the drive motor 6 according to the accelerator opening in consideration of the road gradient. Normally, the vehicle controller 14 sends a command torque to the drive motor controller 13 so that the drive motor 6 generates an appropriate drive force according to the accelerator opening and the vehicle speed without considering the road gradient. .. In the embodiment, a method will be described in which the drive motor controller 13 estimates the gradient of the road and the drive motor 6 outputs an appropriate driving force in consideration of the gradient of the road.

The drive motor controller 13 applies to the drive motor 6 the current and voltage required for the drive motor 6 to generate the command torque received from the vehicle controller 14. The drive motor controller 13 receives a signal indicating the motor rotation speed from the drive motor 6.

The drive motor controller 13 estimates the actual torque that the drive motor 6 may actually generate from the current and voltage applied to the drive motor 6. The drive motor controller 13 obtains the magnitude of the road gradient (tilt angle) in the traveling direction of the vehicle from the actual torque and the change amount of the motor rotation speed. As shown in FIG. 3, a map indicating the relationship between the actual torque and the amount of change in the motor rotation speed is stored in advance in the memory in the drive motor controller 13 for each gradient size.

For example, on a flat road (no gradient), the relationship between the actual torque and the amount of change in the motor rotation speed is uniquely determined. That is, the amount of change in the motor rotation speed can be estimated from the actual torque. On the uphill slope, the amount of change in the motor speed becomes smaller than on a flat road even if the actual torque is the same. The amount of change is small. In this way, the relationship between the actual torque and the change amount of the motor rotation speed changes according to the magnitude of the gradient. By referring to the map, the drive motor controller 13 can determine the magnitude of the road gradient in the traveling direction of the vehicle from the actual torque and the amount of change in the motor rotation speed. The magnitude of the gradient is transmitted to the vehicle controller 14 as gradient information.

On the other hand, the vehicle controller 14 (vehicle speed calculation unit 26) calculates the vehicle speed from the motor rotation speed. Then, the driving force of the drive motor 6 is calculated from the vehicle speed and the accelerator opening detected by the APS 20. At this time, the vehicle controller 14 calculates the driving force using a map showing the correspondence between the vehicle speed and the driving force for each accelerator opening. However, this driving force is a value on a flat road, and the slope of the road is not taken into consideration. Therefore, the vehicle controller 14 (gradient correction amount calculation unit 29) calculates the correction amount of the driving force from the gradient information, the driving force calculation unit 32 corrects the driving force using the correction amount, and the corrected driving force. Is transmitted to the drive motor controller 13 as a command torque. As a result, the deviation of the driving force due to the gradient of the road can be corrected, and the same acceleration/deceleration control of the vehicle as on a flat road can be realized.

Next, with reference to FIGS. 4A to 4D, a method of calculating a driving force for stopping the vehicle and keeping the vehicle in the stopped state even if the accelerator or the brake is not operated on a road having a slope will be described. To do.

First, consider a scene on a flat road (no slope). When the accelerator is off, as shown in FIG. 4A, the drive motor 6 is caused to generate a drive force determined by the vehicle speed. As a result, the vehicle can be stopped and the vehicle can be held in a stopped state even if the brake is not operated. The drive force shown in FIG. 4A is a drive force in the direction opposite to the rotation direction of the drive motor 6 (drive force in the regeneration direction), and if the vehicle speed is a positive value (forward) in the graph of FIG. Is a negative value. If the vehicle speed has a negative value (reverse), the driving force has a positive value. Then, when the vehicle speed is zero, the driving force of the drive motor 6 also becomes almost zero. However, when the vehicle speed is zero, a weak driving force for maintaining balance with the frictional force of the vehicle axle system may be generated.

Next, consider a road scene with a slope. When the vehicle speed is zero and the driving force is zero, the vehicle slides down the road and cannot hold the stopped state. Therefore, as shown in FIGS. 4B and 4C, the driving force in FIG. 4A is corrected by the driving force correction amount 41 according to the gradient (inclination). As a result, on a road having a slope, the vehicle can be stopped and the vehicle can be held in a stopped state even if the accelerator or the brake is not operated. Specifically, by generating a driving force in the power running direction on the uphill without the accelerator operation, or by generating a driving force in the regenerative (braking) direction on the downhill without the brake operation. It is possible to prevent the vehicle from sliding down.

As shown in FIG. 4B, the correction amount of the driving force changes according to the gradient (inclination). The correction amount increases as the gradient increases. The example of FIG. 4C shows the correction of the driving force on a road with a downward slope. The correction amount 41 of the driving force according to the gradient is subtracted from the curve (flat) of the driving force on the flat road. Therefore, when the vehicle speed is zero, the driving force has a negative value (the driving force in the backward direction). In FIG. 4C, in the case of an uphill slope, if the slopes are the same, the same correction amount 41 may be added. Therefore, when the vehicle speed is zero, the driving force has a positive value (driving force in the forward direction).

As shown in FIG. 4D, by correcting the driving force according to the gradient, the acceleration and deceleration of the vehicle (hereinafter referred to as “vehicle G”) become the same curve regardless of the presence or absence of the gradient.

FIG. 5 is a time chart showing an accelerator operation, a vehicle speed, a driving force, and a temporal change of the vehicle G on a flat road and a road having a downward slope. The solid line shows the case where the driving force is not corrected on a flat road, the broken line shows the case where the driving force is not corrected on the downward slope, and the alternate long and short dash line shows the case where the driving force is corrected on the downward slope.

The accelerator operation from the on state to the off state is common in all cases. The driving force is the same when the driving force is not corrected on a flat road and when the driving force is not corrected on a downward slope.

When the driving force is corrected in the downward slope, the driving motor 6 is corrected even if the driving force shown in FIG. 4C is corrected to generate a larger driving force in the regenerative direction and the vehicle speed becomes zero. Negative (backward) driving force is generated. As a result, the vehicle speed does not become zero when the driving force is not corrected on the downhill, but the vehicle speed can be maintained at zero when the driving force is corrected on the downhill. Further, when the driving force is corrected on the downhill slope, the same vehicle G as when the driving force is not corrected on the flat road can be realized.

As described above, the driving force generated by the drive motor according to the gradient (inclination) is calculated when the accelerator is operated (when the accelerator is on) and when the accelerator is not operated (when the accelerator is off). to correct. As a result, the vehicle speed and the vehicle G can be controlled in the same manner as on a flat road, regardless of the presence or absence of a gradient (inclination) and its size. In particular, when the first traveling mode is selected, the vehicle can be held in a stopped state on a road having a slope even if the brake of the vehicle is not operated.

<Detailed operation of creep determination unit 30>
Next, an algorithm for the creep determination unit 30 to determine generation and cancellation of creep torque will be described.

FIG. 6 shows an example of combinations of various traveling conditions for switching between the state without creep torque (without creep) and the state with creep torque (with creep) in the first traveling mode. In the first traveling mode, creep torque is not normally generated.

When at least any one of the following three running conditions (43 to 45) is satisfied in the state where there is no creep torque, the creep determination unit 30 estimates the driver's driving intention and generates the creep torque. In other words, it switches to a state in which there is creep torque.

The first condition 43 is to switch from the first traveling mode to the second traveling mode. In the case of a vehicle equipped with a normal automatic transmission (AT vehicle), creep torque is generated, and therefore the vehicle cannot be held in a stopped state unless the brake is operated. Therefore, when the vehicle is switched to the second traveling mode, it is more convenient for the driver to generate creep torque to assist in starting or traveling, as in a normal AT vehicle. The convenience of the driver is improved in a traveling scene in which traveling and stopping are repeated, such as traffic jam driving or garage parking operation.

The second condition 44 is that the automatic transmission of the vehicle is operated from the non-travelable range to the travelable range when the vehicle is stopped or traveling at a speed lower than the low speed reference value. .. In other words, when traveling at low speed including zero vehicle speed, the range in which travel is impossible (N range, P range) is switched to the range in which travel is possible (D range, R range). In the case of an ordinary AT vehicle, creep torque is generated during low speed traveling including stop. Therefore, when the intention of starting or running can be estimated by shift change during low-speed running including stop, creep torque is generated to assist the starting or running. The convenience of the driver is improved in a traveling scene in which traveling and stopping are repeated, such as traffic jam driving or garage parking operation.

The third condition 45 is that when the vehicle is stopped or traveling at a speed lower than the low speed reference value, the brake operation is released up to the brake threshold from the state where the brake is operated. In other words, the brake changes from the on state to the off state during low speed traveling including zero vehicle speed. Despite the fact that the vehicle can be held in a stopped state without any brake operation, the brake was operated in the low speed range and the operation was released up to the brake threshold, so the driver's intention to start or run can be estimated. .. From the establishment of the third condition 45, for example, it is possible to estimate a traveling scene in which the vehicle speed is adjusted by operating a brake such as a traffic jam or a garage parking operation. Therefore, creep torque is generated to assist starting or running.

FIG. 7 is a graph showing the first condition 43, the second condition 44, and the third condition 45 in a two-dimensional Cartesian coordinate system. The horizontal axis represents the vehicle speed, and the vertical axis represents the braking force by the brake. The fact that the vehicle speed is equal to or lower than the low speed reference value 61 is common to the second condition 44 and the third condition 45, but the first condition 43 indicates the entire vehicle speed range because the vehicle speed does not matter. Further, the third condition 45 includes that the brake operation is released up to the brake threshold 62 or less, but the first condition 43 and the second condition 44 do not matter the brake operation or the braking force.

FIG. 8 shows a change with time of each traveling parameter when the brake changes from the ON state to the OFF state when the third condition 45 is satisfied, that is, when the vehicle travels at low speed including zero vehicle speed. Each travel parameter includes a travel mode, a travel range, a vehicle speed, a braking force (a brake operation amount or a brake oil pressure), a driving force by an accelerator, and a creep torque. The time charts shown in FIG. 9, FIG. 10, and FIGS. 12 to 14 also show the same change over time of each traveling parameter as in FIG.

The traveling mode is the first traveling mode, and no creep torque is generated. The range in which the automatic transmission can travel is selected. The vehicle speed has decreased due to the brake being operated. Since the accelerator is not operated, the driving force by the accelerator is not generated. In this situation, when the vehicle is traveling at a speed lower than the low speed reference value 61 and the operation is released up to the brake threshold 62 from the state where the brake is operated, the creep determination unit 30 causes the drive motor 6 to operate. Generates a driving force (creep torque) that moves the vehicle forward at low speed.

When the third condition is satisfied, the creep change calculation unit 28 changes the speed at which the drive motor 6 generates a driving force (creep torque) for moving the vehicle forward at a low speed in accordance with the speed at which the brake operation is released. Let The solid line in FIG. 8 indicates an example in which the speed at which the brake operation is released and the speed at which the creep torque is generated are slow, and the broken line in FIG. 8 indicates the speed at which the brake operation is released and the creep torque is generated. Here is an example in which the speed of the operation is high. The vehicle speed will also follow both brake and creep speeds. As a result, the fluctuation of the vehicle G when the creep torque is generated can be suppressed.

In the example of FIG. 8, the vehicle is traveling at a speed lower than the low speed reference value 61, but the vehicle speed may be zero or negative under the third condition. In other words, this includes when the vehicle is stopped or moving backward.

FIG. 9 shows a change with time of each travel parameter when the second condition 44 is satisfied, that is, when the automatic transmission of the vehicle is operated from the travel impossible range to the travel possible range. The traveling mode is the first traveling mode, and no creep torque is generated. The brake is not operated and the vehicle speed is zero. No driving force is generated by the accelerator. The automatic transmission is in the non-driving range. Under this circumstance, when the automatic transmission is operated from the travel impossible range to the travel possible range, the creep determination unit 30 causes the drive motor 6 to generate a driving force (creep torque) for moving the vehicle forward at a low speed. As a result, the vehicle starts traveling at a low speed even if the accelerator is not operated.

In the example of FIG. 9, the vehicle speed is zero, but the vehicle speed may be lower than the low speed reference value 61 or a negative speed under the second condition. In other words, this includes when the vehicle is moving forward or backward at low speed.

FIG. 10 shows a time change of each traveling parameter when the first condition 43 is satisfied, that is, when the traveling mode selected by the mode switch 17 is switched from the first traveling mode to the second traveling mode. The range in which the automatic transmission can travel is selected. Since neither the brake nor the accelerator is operated, neither the braking force by the brake nor the driving force by the accelerator is generated. However, since the first traveling mode is selected, the drive motor 6 stops the vehicle and stops the vehicle on the road having the slope as described with reference to FIGS. 4A to 4D and FIG. 5. The driving force for maintaining the state is generated. For this reason, the vehicle speed decreases and is maintained at zero even without the brake operation.

In this situation, when the first traveling mode is switched to the second traveling mode, the driving force calculation unit 32 releases the driving force for keeping the vehicle in the stopped state. Further, the creep determination unit 30 causes the drive motor 6 to generate a driving force (creep torque) for moving the vehicle forward at low speed. As a result, the vehicle starts traveling at a low speed even if the accelerator is not operated.

Next, with reference to FIG. 6, an example of a combination of various traveling conditions for canceling the creep torque once generated will be described.

When at least any one of the following three running conditions (51 to 53) is satisfied in the presence of creep torque, the creep determination unit 30 estimates the driver's deceleration intention or prepares for the driver's deceleration intention. , Release the creep torque. That is, the state is switched to the state where there is no creep torque.

The fourth condition 51 is that the vehicle speed becomes equal to or higher than the first predetermined value. Since creep torque is generated when the first traveling mode is selected, the vehicle cannot be held in a stopped state even if the brake is not operated, which is inconvenient for the driver. Therefore, when the vehicle speed becomes higher than the speed (first predetermined value) at which the creep torque is released in the normal automatic transmission, it is interpreted that the creep torque becomes unnecessary and the creep torque is released. That is, when the vehicle speed becomes equal to or higher than the first predetermined value, it is determined that the creep torque has exceeded the required vehicle speed range. Further, since the first traveling mode is selected, the drive motor 6 generates a driving force for stopping the vehicle and holding the vehicle in the stopped state when the accelerator is not operated. For example, the fourth condition 51 assumes a scene where the vehicle is traveling on a downhill.

The fifth condition 52 is that the vehicle speed becomes equal to or higher than the third predetermined value and the second traveling mode is switched to the first traveling mode. In the first traveling mode, it is convenient for the driver to cancel the creep torque because the vehicle is brought to a stop and kept in a stopped state even if the accelerator or the brake is not operated. The driver cancels the creep torque by interpreting that he/she desires the vehicle to be able to stop without the brake operation, rather than traveling using the creep torque.

In addition, it should be avoided that the behavior of the vehicle becomes unstable by releasing the creep torque in the second traveling mode. For example, when the vehicle is stopped or traveling at a low speed, the stopped state or the low-speed traveling state of the vehicle may be held by the creep torque. It is necessary to prevent the vehicle from slipping down due to the release of the creep torque, because the vehicle is not maintained in the stopped state or the low speed running state. Therefore, even if the second traveling mode is switched to the first traveling mode, the creep torque is not released if the vehicle speed is less than the third predetermined value.

The sixth condition 53 is that the vehicle speed is equal to or higher than a second predetermined value, and the driving force of the vehicle generated by operating the accelerator is equal to or higher than a predetermined value. For example, by depressing the accelerator pedal, the driver's intention to start or accelerate is estimated, and it is interpreted that the creep torque is no longer necessary. Then, the creep torque is released in preparation for the next deceleration or vehicle stop.

Note that, due to the occurrence of twist in the drive shaft system of the vehicle, a deviation may occur between the motor rotation speed and the wheel 7 rotation speed. For example, the wheel 7 may not rotate, but the drive shaft may rotate. In order to confirm that the wheels 7 are rotating, the sixth condition includes that the vehicle speed is equal to or higher than the second predetermined value.

FIG. 11 is a graph showing the fourth condition 51, the fifth condition 52, and the sixth condition 53 in a two-dimensional orthogonal coordinate system. The horizontal axis is the vehicle speed, and the vertical axis is the driving force by the accelerator operation. The fourth condition 51, the fifth condition 52, and the sixth condition 53 all include conditions relating to the vehicle speed, but the vehicle speed threshold values are all different. The first predetermined value 63 under the fourth condition 51 is the speed at which the creep torque is released in a normal automatic transmission. The second predetermined value 65 under the sixth condition 53 is a value that takes the drive shaft system into consideration. The third predetermined value 64 under the fifth condition 52 is a value that considers the traveling speed that the creep torque can hold. The sixth condition 53 includes that the driving force by the accelerator operation is a predetermined value 66 or more, but the fourth condition 51 and the second condition 52 do not matter the driving force by the accelerator operation.

FIG. 12 shows a change with time of each traveling parameter when the fourth condition 51 is satisfied, that is, when the vehicle speed becomes equal to or higher than the first predetermined value 63. The travel mode is the first travel mode, and the travel range of the automatic transmission is selected. Since the accelerator and the brake are not operated, neither the driving force by the accelerator nor the braking force by the brake is generated. Creep torque is generated. Under this circumstance, the creep torque is released when the vehicle speed becomes high and becomes equal to or higher than the first predetermined value 63, for example, by traveling downhill. The fourth condition 51 is only a condition regarding the vehicle speed and does not include conditions regarding other travel parameters.

FIG. 13 shows a change with time of each traveling parameter when the fifth condition 52 is satisfied, that is, when the vehicle speed becomes equal to or higher than the third predetermined value 64 and the second traveling mode is switched to the first traveling mode. The range in which the automatic transmission can travel is selected. Since the accelerator and the brake are not operated, neither the driving force by the accelerator nor the braking force by the brake is generated. In this situation, when the second traveling mode is switched to the first traveling mode, the driving force calculation unit 32 causes the driving motor 6 to generate the driving force for keeping the vehicle in the stopped state. Further, the creep determination unit 30 releases the creep torque. As a result, the vehicle can be stopped and held in a stopped state even if the brake is not operated.

FIG. 14 shows the time of each traveling parameter when the sixth condition 53 is satisfied, that is, when the vehicle speed becomes the second predetermined value 65 or more and the driving force of the vehicle generated by the accelerator operation becomes the predetermined value 66 or more. Show changes. The travel mode is the first travel mode, and the travel range of the automatic transmission is selected. Since the brake is not operated, no braking force is generated by the brake. Creep torque is generated. Under this circumstance, the creep torque is released when the vehicle speed becomes equal to or higher than the second predetermined value 65 and the driving force of the vehicle generated by the operation of the accelerator becomes equal to or higher than the predetermined value 66. This makes it possible to prepare for the driver's deceleration intention and stop intention after the accelerator operation. That is, the vehicle can be stopped and held in a stopped state without the operation of the brake.

With reference to FIG. 15, an example of a procedure for determining the success or failure of the first to third conditions (43 to 45) in the state where the first traveling mode is selected and there is no creep torque will be described. FIG. 15 is repeatedly executed under a predetermined cycle when the first traveling mode is selected and there is no creep torque.

In step S01, the traveling mode determination unit 24 detects the traveling mode selected by the mode switch 17, and in step S02 determines whether the detected traveling mode is the first traveling mode. If it is the first traveling mode (YES in S02), the process proceeds to step S03, and the vehicle speed calculation unit 26 detects the vehicle speed. Then, it progresses to step S04. On the other hand, when it is not the first traveling mode (NO in S02), it is determined that the first traveling mode is switched to the second traveling mode (that is, the first condition 43 is satisfied), and the process proceeds to step S09.

In step S04, it is determined whether the vehicle speed is lower than the low speed reference value 61 (including zero). When it is lower than the low speed reference value 61 (YES in S04), the process proceeds to step S05, and when it is equal to or higher than the low speed reference value 61 (NO in S04), the process returns to step S01.

In step S05, the brake speed calculator 27 detects the speed at which the brake operation is released. Then, in step S06, the braking force determination unit 25 determines whether the braking force detected by the brake oil pressure sensor 19 is equal to or less than a predetermined brake threshold value. If it is equal to or less than the brake threshold (YES in S06), it is determined that the third condition 45 is satisfied, and the process proceeds to step S07. On the other hand, if it is not equal to or less than the brake threshold value (NO in S06), the process proceeds to step S08.

In step S07, the creep change calculation unit 28 calculates the speed at which the creep torque is generated from the magnitude of the speed at which the brake operation is released, which is calculated by the brake speed calculation unit 27. Then, it progresses to step S09.

In step S08, it is determined whether or not the travelable range is switched to the travelable range. When the range is changed to the travelable range (YES in S08), it is determined that the second condition 44 is satisfied, and the process proceeds to step S09.

In step S09, the creep determination unit 30 determines the generation of creep torque. Proceeding to step S10, the creep calculator 31 generates the creep torque calculated by the creep change calculator 28, and the creep torque generated by the drive motor 6 in accordance with a map showing the relationship between the magnitude of the creep torque and the vehicle speed. Calculate the size of.

In step S11, the vehicle controller 14 calculates the command torque from the total driving force obtained by adding the creep torque calculated in step S10 to the driving force calculated by the driving force calculation unit 32, and the driving motor controller 13 Send to. In this way, when at least one of the three traveling conditions (43 to 45) is satisfied, the creep determination unit 30 estimates the driver's driving intention and generates creep torque. In other words, it switches to a state in which there is creep torque. As a result, creeping is possible and convenience for the driver is improved. The convenience of the driver is improved in a traveling scene in which traveling and stopping are repeated, such as traffic jam driving or garage parking operation.

With reference to FIG. 16, an example of a procedure for determining the success or failure of the fourth condition to the sixth condition (51 to 53) in the state where the creep torque is present will be described. FIG. 15 is repeatedly executed under a predetermined cycle when the second traveling mode is selected and there is creep torque.

In step S21, the traveling mode determination unit 24 detects the traveling mode selected by the mode switch 17, and in step S22 determines whether the detected traveling mode is the first traveling mode. When the vehicle is in the first traveling mode (YES in S22), the vehicle speed calculation unit 26 detects the vehicle speed in step S23. Then, it progresses to step S24. On the other hand, when it is not the first traveling mode (NO in S22), the process proceeds to step S25.

In step S24, it is determined whether the vehicle speed is equal to or higher than the first predetermined value 63. If it is equal to or greater than the first predetermined value 63 (YES in S24), it is determined that the fourth condition 51 is satisfied, and the process proceeds to step S30. When it is not equal to or more than the first predetermined value 63 (NO in S24), the process proceeds to step S25.

In step S25, it is determined whether the vehicle speed is equal to or higher than the third predetermined value 64. If the third predetermined value is 64 or more (YES in S25), the process proceeds to step S26. If it is not equal to or larger than the third predetermined value 64 (NO in S25), the process proceeds to step S28.

In step S26, the driving mode determination unit 24 detects whether or not the driving mode has been changed. In step S27, the traveling mode determination unit 24 determines whether the second traveling mode has been switched to the first traveling mode. When the traveling mode is changed (YES in S27), it is determined that the fifth condition 52 is satisfied, and the process proceeds to step S30.

In step S26, it is determined whether the vehicle speed is equal to or higher than the second predetermined value 65. If the second predetermined value is 65 or more (YES in S28), the process proceeds to step S29. If the second predetermined value is not more than 65 (NO in S28), the process returns to step S21. In step S29, it is determined whether or not the driving force of the vehicle generated by operating the accelerator is a predetermined value 66 or more. When the driving force of the vehicle is equal to or greater than the predetermined value 66 (YES in S29), it is determined that the sixth condition 53 is satisfied, and the process proceeds to step S30. If the driving force of the vehicle is not equal to or greater than the predetermined value 66 (NO in S29), the process returns to step S21.

In step S30, the creep determination unit 30 determines to release the creep torque. In step S31, the driving force calculation unit 32 calculates the magnitude of the driving force of the drive motor 6 based on the accelerator opening and the gradient information.

In step S32, the vehicle controller 14 calculates the command torque from the driving force calculated by the driving force calculation unit 32, and transmits the command torque to the driving motor controller 13. As described above, when at least one of the three traveling conditions (51 to 53) is satisfied, the creep determination unit 30 estimates the driver's deceleration intention or can estimate the driver's deceleration intention, and thus the creep torque is determined. To release. That is, the state is switched to the state where there is no creep torque. As a result, the vehicle can be stopped and the stopped state can be maintained without operating the brake, which improves the convenience of the driver.

Although embodiments of the present invention have been described above, it should not be understood that the discussion and drawings forming a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

Each function shown in each of the above embodiments can be implemented by one or a plurality of processing circuits. The processing circuit includes a programmed processing device such as a processing device including an electrical circuit. Processing devices also include devices such as application specific integrated circuits (ASICs) and conventional circuit components arranged to perform the functions described in the embodiments.

6 Drive motor (electric motor)
14 Vehicle controller (driving force control device)
19 Brake oil pressure sensor (means for detecting braking force by brake operation)
20 Accelerator position sensor (means to detect driving force by accelerator operation)
61 low speed reference value 62 brake threshold 63 first predetermined value 64 third predetermined value 65 second predetermined value 66 predetermined value

Claims (8)

A driving force control method for a vehicle driven by an electric motor, comprising:
On a road having a slope, the electric motor is driven based on the slope so that the vehicle is stopped at the same deceleration as the flat road and is held in a stopped state even if the accelerator or the brake of the vehicle is not operated. Force is corrected, and the corrected driving force is generated in the electric motor,
When the vehicle is stopped or traveling at a speed lower than the low speed reference value, if the operation is released up to the brake threshold value from the state where the brake is operated, the vehicle is set to the electric motor. Generate driving force to move the
A driving force control method comprising: The driving force control method according to claim 1, wherein a speed for generating a driving force for moving the vehicle forward at a low speed is changed according to a speed at which the operation is released. A driving force control method for a vehicle driven by an electric motor, comprising:
On a road having a slope, the electric motor is driven based on the slope so that the vehicle is stopped at the same deceleration as the flat road and is held in a stopped state even if the accelerator or the brake of the vehicle is not operated. Force is corrected, and the corrected driving force is generated in the electric motor,
When the vehicle is stopped or traveling at a speed lower than the low speed reference value, when the automatic transmission of the vehicle is operated from the non-travelable range to the travelable range, Generate a driving force for moving the vehicle forward at a low speed,
A driving force control method comprising: The driving force for causing the electric motor to move the vehicle forward at a low speed is released when the traveling speed of the vehicle exceeds a first predetermined value. The driving force control method described. When the traveling speed of the vehicle is equal to or higher than a second predetermined value and the driving force of the vehicle generated by operating the accelerator is equal to or higher than a predetermined value, the motor causes the motor to drive the vehicle forward at a low speed. The driving force control method according to claim 1, wherein the force is released. From the second traveling mode in which the vehicle is not held in the stopped state unless the traveling speed of the vehicle is equal to or higher than a third predetermined value and the brake is not operated, the accelerator or the brake of the vehicle is operated on a road having a slope. Even if the vehicle is switched to the first traveling mode that causes the electric motor to generate a driving force that causes the electric vehicle to stop at the same deceleration as the flat road and keeps the vehicle in the stopped state, the vehicle generated by the electric motor is driven at a low speed. The driving force control method according to any one of claims 1 to 3, wherein the driving force for advancing by is released. A driving force control device for a vehicle driven by an electric motor,
On a road having a slope, the electric motor is driven based on the slope so that the vehicle is stopped at the same deceleration as the flat road and is held in a stopped state even if the accelerator or the brake of the vehicle is not operated. A first control circuit for correcting the force and generating a corrected driving force in the electric motor;
When the vehicle is stopped or traveling at a speed lower than the low speed reference value, if the operation is released up to the brake threshold value from the state where the brake is operated, the vehicle is set to the electric motor. And a second control circuit for generating a driving force for moving the vehicle forward at a low speed. A driving force control device for a vehicle driven by an electric motor,
On a road having a slope, the electric motor is driven based on the slope so that the vehicle is stopped at the same deceleration as the flat road and is held in a stopped state even if the accelerator or the brake of the vehicle is not operated. A first control circuit for correcting the force and generating a corrected driving force in the electric motor;
When the vehicle is stopped or traveling at a speed lower than the low speed reference value, when the automatic transmission of the vehicle is operated from the non-travelable range to the travelable range, And a third control circuit that generates a driving force for moving the vehicle forward at a low speed.

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