JP2015112978A - Vehicle control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle control method capable of upgrading the capability to accomplish run-through performance by making engine torque control and braking force control to cooperate with each other using a more effective technique in case a vehicle slips.SOLUTION: There are included slip discrimination processing (S104) of determining, based on vehicle information, whether a vehicle slips, automatic transition mode transition processing (S106) of making a transition from an ordinary mode in which a torque is decreased by a first torque decrease quantity in case of slipping, to an automatic transition mode in which the torque is decreased by a second torque decrease quantity which is smaller than the first torque decrease quantity, in case of slipping, and torque control processing (S108) of braking right wheels, the wheel speed of which is larger between left and right wheels, so that a target slip ratio that is a ratio of a difference between left and right wheel speeds to a vehicle speed is attained for allowing the vehicle to escape from the slipping state, in order to distribute torques to the right wheels and to the left wheels via a differential and thus control the torques of the left and right wheels.

Description

  The present invention relates to a vehicle control method in which engine torque control and brake force control are coordinated when a vehicle slips.

  As a method for controlling a vehicle such as an automobile, an electronic stability program, a vehicle attitude control called ESP (registered trademark) for short, is known. ESP includes TCS (Traction Control System) control, and generally controls the driving force of each wheel by coordinating the engine output (torque) with the braking force of each wheel, thereby improving the running stability of the vehicle. Is. Specifically, in TCS control, when wheel over-rotation (slip) occurs and a wheel speed difference occurs between the left and right wheels, the engine torque is reduced and the wheel is braked to reduce the wheel speed difference. .

  Control for reducing the wheel speed difference by applying a brake is also referred to as brake LSD (Limited Slip Differential) control. In the brake LSD control, for example, when a slip occurs due to a difference in friction coefficient μ between the left and right wheels, a brake corresponding to the wheel speed is applied to one of the left and right wheels, which has a higher wheel speed. Torque is distributed from one wheel to the other wheel via a differential mechanism. Here, even if one of the wheels slips on a bad road or a deep snow road, the other wheel is in contact with the road surface having a high friction coefficient μ because the wheel speed is smaller than that of the one wheel. Probability is high. Therefore, if the torque is distributed to the other wheel, the vehicle is more likely to escape from the slip.

  Patent Document 1 describes a driving force control device that suppresses slippage of a drive wheel when the drive wheel slips into mud or deep snow. In this device, the actual slip ratio is calculated from the driving wheel speed and the vehicle body speed, and when the actual slip ratio exceeds a predetermined value, the driving force is reduced, and the control for prohibiting the reduction of the driving force according to the situation of the vehicle is performed. Do.

  In Patent Document 1, when the vehicle state, that is, the accelerator operation amount is equal to or greater than a predetermined value and the vehicle body speed is equal to or less than the predetermined value has elapsed for a predetermined time, control for reducing the driving force is prohibited, thereby reducing the accelerator operation amount. It is said that it can escape from the slip with the corresponding driving force.

JP-A-1-145242

  In the control described in Patent Document 1, when trying to escape from the slip, the accelerator is greatly depressed, so the engine speed is likely to exceed the upper limit (rev limit) of the allowable range, and a large torque is applied at once. Therefore, the load on the drive system of the vehicle increases.

  Furthermore, Patent Document 1 merely prohibits the reduction of the driving force, and reduces the driving force, thereby distributing the torque to the wheels using the brake LSD control to escape from the slip. There is no specific description about. That is, unlike the TCS control, the technique described in Patent Document 1 does not consider coordinating the engine torque control and the brake force control when the vehicle slips. In addition, there is room for improvement in TCS control performed in cooperation between the two.

  In view of such a problem, the present invention provides a vehicle control method capable of improving engine running performance by coordinating engine torque control and brake force control in a more effective manner when the vehicle slips. It is aimed.

  In order to solve the above problems, a typical configuration of the vehicle control method according to the present invention is to apply a brake corresponding to the wheel speed to one of the left and right wheels having a large wheel speed when the vehicle slips. In a vehicle control method for distributing torque from one wheel to the other wheel via a differential mechanism, a slip determination process for determining whether or not the vehicle is slipping based on vehicle information, and a vehicle slipping When the determination is made, the automatic mode shifts from the normal mode in which the torque is reduced by a predetermined first torque down amount at the time of slip to the automatic transition mode in which the torque is reduced by a second torque down amount smaller than the first torque down amount at the time of slip. Transition mode transition processing and the ratio of the difference between the left and right wheel speeds with respect to the vehicle speed, and a predetermined slip rate for the vehicle to escape from the slip. So that, characterized in that it comprises a torque control process for controlling the torque of the left and right wheels by braking the one wheel.

  According to the above configuration, when it is determined that a slip has occurred in the vehicle, the traveling mode of the vehicle automatically shifts from the normal mode to the automatic transition mode. Here, in the automatic transition mode, the torque is reduced by a second torque down amount that is smaller than the first torque down amount in the normal mode, so the total amount of engine torque is larger than when slip occurs in the normal mode. . If the wheel that idles during a slip is one wheel, the wheel speed will naturally be greater than that of the other wheel, but even if compared to the wheel speed of one wheel when dealing with slip in normal mode. , Absolutely bigger. This is because the total amount of torque is larger in the automatic transition mode than in the normal mode. Therefore, in the automatic transition mode, the braking force that is determined according to the wheel speed of one wheel and applied to one wheel is larger than that in the normal mode.

  Since the torque is distributed to the left and right wheels via a differential mechanism, when a large braking force is applied to one wheel with a high wheel speed, torque is applied from one wheel to the other wheel with a low wheel speed. Sorted. This utilizes the brake LSD control. Since the brake LSD control is performed in the automatic transition mode, the slip ratio suitable for the vehicle to escape from the slip is more easily achieved in the automatic transition mode in which the braking force is increased than in the normal mode. This is because the total amount of torque is larger in the automatic transition mode, so that a more diverse amount of torque can be distributed to the other wheel, and the possibility of reaching a desired slip ratio that cannot be reached under the normal mode is increased. . Alternatively, the desired slip rate can be reached more quickly than in the normal mode. As described above, in the present invention, by automatically shifting to the above-described automatic transition mode at the time of a slip, the running performance is improved as compared with the case of dealing with the slip in the normal mode.

  The braking applied to one of the wheels in the torque control process described above may be performed with a predetermined braking force determined according to a predetermined slip ratio and vehicle speed. As a result, when shifting from the normal mode to the automatic transition mode, in addition to controlling the torque so as to achieve the slip ratio corresponding to the vehicle speed in the torque control process, the braking force is also controlled so as to obtain a predetermined braking force. The Therefore, the vehicle can more easily achieve the slip rate for escaping from the slip, and the running performance can be further improved.

  The vehicle control method described above further includes a lock mode transition process for shifting to the lock mode by manual operation. In the lock mode, the torque is reduced by a third torque down amount that is smaller than the second torque down amount at the time of slip, It is preferable to apply a braking force larger than the braking force applied to one of the wheels in the normal mode during a slip. Thereby, when the vehicle cannot escape from the slip even in the automatic transition mode, the travel mode can be switched to the lock mode by operating a switch or the like. In the lock mode, the amount of torque reduction is smaller and the braking force is larger than in the automatic transition mode. For this reason, in the lock mode, the effect of the brake LSD control is higher than in the automatic transition mode, and more torque is distributed from one wheel to the other wheel having a lower wheel speed, so that the running performance can be further improved.

  The vehicle information includes the left and right wheel speed difference and the duration after the wheel speed difference has occurred. In the slip determination process, the left and right wheel speed difference and the duration are each greater than or equal to a predetermined threshold. It may be determined that slip has occurred. By setting the threshold value in this way, it is possible to reliably determine that traveling is difficult in the normal mode, and to automatically shift from the normal mode to the automatic transition mode. Therefore, the driver does not need to be aware of the road surface condition, and the burden on the driver can be reduced.

  In the vehicle control method described above, an escape determination process that determines whether the escape is successful or not is determined based on whether or not a state in which the difference between the left and right wheel speeds is less than a predetermined threshold has continued for a predetermined time after the torque control process, and the success of the escape is determined. Then, it is preferable to further include a normal mode return process for returning from the automatic transition mode to the normal mode. Thus, after the transition from the normal mode to the automatic transition mode, the automatic transition mode is continued until the vehicle escapes from the slip, and when it is determined that the escape from the slip is successful, the normal mode can be restored. Therefore, since the transition from the automatic transition mode to the normal mode does not occur frequently, an increase in vibration associated with the switching of the travel mode does not occur frequently, and it is possible to suppress a sense of incongruity in operation for the driver.

  According to the present invention, it is possible to provide a vehicle control method that can improve engine running performance by coordinating engine torque control and brake force control in a more effective manner when the vehicle slips.

1 is a diagram schematically illustrating a vehicle to which a vehicle control device that executes a vehicle control method according to an embodiment is applied. It is a block diagram which shows the function of the vehicle control apparatus of FIG. It is a figure which shows the driving mode table of FIG. It is a flowchart which shows the process of the vehicle control method in this embodiment. It is a figure which shows the slip ratio table and brake force table of FIG. It is a figure which compares the slip ratio with respect to the vehicle speed in each driving mode, and a braking force.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  FIG. 1 is a diagram schematically illustrating a vehicle 102 to which a vehicle control device 100 that executes a vehicle control method according to the present embodiment is applied. FIG. 2 is a block diagram illustrating functions of the vehicle control device 100 of FIG. In FIG. 1, only the vehicle control unit 104 and the wheel speed sensor 106 included in the vehicle control device 100 are shown, and other configurations are illustrated in FIG.

  A vehicle control apparatus 100 is mounted on the vehicle 102 as shown in FIG. The vehicle control device 100 is installed in the vicinity of an engine room on the front side of the vehicle and executes a vehicle attitude control called ESP (Electronic Stability Program), a wheel speed sensor 106 that detects a wheel speed of each wheel, Have The ESP includes TCS (Traction Control System) control, which is performed by coordinating engine torque control and brake force control of each wheel to improve the running stability of the vehicle. The vehicle 102 is premised on four-wheel drive, but is not limited thereto, and may be front-wheel drive or rear-wheel drive as long as engine torque control and brake force control are performed in cooperation.

  As shown in FIG. 2, the vehicle control unit 104 includes a slip determination unit 108, a travel mode instruction unit 110, and a brake force control unit 112. The slip determination unit 108 determines whether or not the vehicle 102 is slipping based on the vehicle information. The vehicle information here includes the left and right wheel speed difference detected by the wheel speed sensor 106 of the vehicle information output unit 114 and the duration time measured by the timer 116 after the wheel speed difference has occurred.

  The travel mode instruction unit 110 reads the travel mode table 120 (see FIG. 3) stored in the storage unit 118 according to the determination result of the slip determination unit 108, and sends it to the brake force control unit 112 and the engine torque control unit 122. Instruct to switch the driving mode. The travel mode instruction unit 110 outputs, for example, the vehicle speed detected by the vehicle speed sensor 124 of the vehicle information output unit 114 to the brake force control unit 112 and the engine torque control unit 122 in addition to the travel mode switching instruction. .

  The engine torque control unit 122 reads the slip rate table 126 (see FIG. 5A) in the storage unit 118, adjusts the throttle opening of the engine 128 based on this, and reduces the torque according to the travel mode. Reduce the torque by the amount. The brake force control unit 112 reads the brake force table 130 (see FIG. 5B) of the storage unit 118, adjusts the brake hydraulic pressure of the brake system 132 based on this, etc., and thereby the left and right wheels 134a, 134b. Controls the braking force applied to the vehicle. This brake force control is in accordance with brake LSD control for reducing the wheel speed difference between the left and right wheels 134a and 134b.

  In other words, the left and right wheels 134a and 134b are distributed with the torque that has been reduced according to the travel mode by the engine torque control unit 122 via the differential 136 that is a differential mechanism. As an example, when a large braking force is applied to one wheel with a high wheel speed (for example, the right wheel 134a), torque is distributed from the right wheel 134a to the other wheel with a low wheel speed (for example, the left wheel 134b). Note that the travel mode is not only automatically switched by the travel mode instruction unit 110 according to the determination result of the slip determination unit 108, but may also be switched as appropriate by a manual operation using the switch 138.

  FIG. 3 is a diagram showing the travel mode table 120 of FIG. A plurality of travel modes are set for the vehicle 102 as shown in the figure. These travel modes are distinguished by how much torque is reduced when the vehicle 102 slips, and how much braking force is applied to the wheels.

  The normal mode is a reference mode and is also called an AUTO mode. In the normal mode, when the vehicle 102 slips, the torque is reduced by a predetermined first torque reduction amount (“normal” in the figure), and a predetermined braking force (“normal” in the figure) is applied to the wheels. The snow mode is a preferable mode when traveling on a road surface with a low coefficient of friction μ, and the torque reduction amount when the vehicle 102 slips is the largest among the travel modes (“large” in the figure), and the braking force is normal. It is smaller than the mode ("Small" in the figure). The sport mode is a preferable mode when driving on a dry road. In the sport mode, the torque is reduced by a second torque down amount ("small" in the figure) smaller than the first torque down amount in the normal mode, and the braking force is larger than in the normal mode ("medium" in the figure). ).

  The lock mode is a mode that places emphasis on running performance, and is used when the driving force of each wheel cannot be sufficiently obtained when traveling on bad roads such as a mogul road or a deep snow road with many undulations. The lock mode reduces the torque by a third torque down amount (“minimum” in the figure) smaller than the second torque down amount when the vehicle 102 slips, and the braking force is the largest in the traveling mode (in the figure, “ maximum"). The third torque reduction amount is the smallest in the traveling mode. Note that the braking force in the lock mode is more than double the braking force in the normal mode. These four travel modes can be appropriately selected by manual operation using the switch 138 of the vehicle control device 100.

  Unlike the four travel modes, the automatic transition mode is a mode that automatically transitions when the vehicle 102 slips when a mode other than the lock mode is selected (described later). In the automatic transition mode, when the vehicle 102 slips, the torque is reduced by the second torque down amount ("small" in the figure) as in the sport mode, and the brake force is the second largest after the lock mode ("large" in the figure). .

  Next, a vehicle control method when a slip occurs in the vehicle 102 traveling on a rough road in the normal mode will be described. FIG. 4 is a flowchart showing processing of the vehicle control method in the present embodiment. FIG. 5 is a diagram showing the slip ratio table 126 and the brake force table 130 of FIG.

  First, when the vehicle 102 is traveling in the normal mode (step S100), if a difference occurs between the left and right wheel speeds (step S102), the slip determination unit 108 determines whether or not to regard it as a slip (step S104). , Slip determination processing). In the slip determination process, if the difference between the left and right wheel speeds detected by the wheel speed sensor 106 is about 3.0 km / h or more, and the timer 116 measures that the wheel speed difference has continued for 500 ms or more, Is determined to occur (Yes). If the difference between the left and right wheel speeds and the duration time are less than the respective threshold values, the slip determination unit 108 does not regard the slip (No) and returns to step S102 again.

  When it is determined that slip has occurred in the slip determination process, the traveling mode instruction unit 110 outputs an instruction to the engine torque control unit 122 and the brake force control unit 112 to shift from the normal mode to the automatic transition mode. (Step S106, automatic transition mode transition process). Here, in the automatic transition mode transition process, a transition is made to an automatic transition mode in which the torque is reduced by a second torque down amount that is smaller than the first torque down amount in the normal mode. For this reason, the total amount of engine torque is larger than when slip occurs in the normal mode. That is, in the automatic transition mode transition process, a larger slip is allowed by transitioning to the automatic transition mode.

  Subsequently, the engine torque control unit 122 and the brake force control unit 112 cooperate to control the torque of the left and right wheels 134a and 134b (step S108, torque control process). In the torque control process, the wheel speed of the right wheel 134a is increased, for example, to the right wheel 134a so as to obtain a slip ratio corresponding to the vehicle speed based on the slip ratio table 126 of FIG. Accordingly, the torque is distributed from the right wheel 134a to the left wheel 134b via the differential 136.

Here, as shown in FIG. 5A, the slip ratio table 126 is an approximate function obtained based on each point A when the horizontal axis X is the vehicle speed and the vertical axis Y is the slip ratio, as an example. stores power function of ^{1 / X (Y = 9.6X -1.2} ). The slip ratio according to the vehicle speed indicated by the power function is a ratio of the left and right wheel speed difference to the vehicle speed for the vehicle 102 to escape from the slip. Each point A indicates a slip rate corresponding to the vehicle speed when the vehicle 102 actually escapes from the slip. For this reason, the engine torque control unit 122 may appropriately set, for example, an engine control threshold value for adjusting the throttle opening of the engine so as to obtain the slip ratio indicated by the power function corresponding to the vehicle speed. In the sport mode, as in the automatic transition mode, the torque is reduced by the second torque down amount at the time of slip. For this reason, even in the sport mode, an engine control threshold value based on the slip ratio shown in the slip ratio table 126 may be set.

Further, in the torque control process, in order to obtain a slip rate corresponding to the vehicle speed for the vehicle 102 to escape from the slip, for example, the brake applied to the right wheel 134a is based on the brake force table 130 shown in FIG. You may decide. As shown in the figure, the brake force table 130 is an approximate function obtained based on each point B when the horizontal axis X is the vehicle speed and the vertical axis Y is the change rate of the brake force, for example, a power of 1 / X. The function (Y = 66.2X− ^0.8 ) is stored. The change rate of the braking force indicated by the power function is a magnification when the braking force in the normal state is set to “1”, and is the inertia force acting on the vehicle 102 and the driving force (torque) necessary for escape. It is set appropriately from the relationship, and it is shown that a larger braking force is required as the vehicle speed is lower. Each point B indicates the change rate of the braking force at which the slip ratio shown in FIG. 5A is actually obtained. For this reason, the brake force control unit 112 appropriately sets, for example, a brake control threshold value for adjusting the brake hydraulic pressure of the brake system 132 so as to obtain the change rate of the brake force indicated by the power function corresponding to the vehicle speed. Good.

  That is, in the torque control process, the brake LSD control is performed in the automatic transition mode. Here, assuming that the wheel that idles during the slip in the automatic transition mode is the right wheel 134a, the wheel speed is larger than the wheel speed of the left wheel 134b. Further, the wheel speed of the right wheel 134a under the automatic transition mode has a larger total torque amount in the automatic transition mode than in the normal mode. Even if it compares, it becomes absolutely large. Therefore, in the automatic transition mode, the braking force applied to the right wheel 134a determined according to the wheel speed of the right wheel 134a is larger than that in the normal mode.

  Since the total amount of torque is larger in the automatic transition mode than in the normal mode, more various amounts of torque can be distributed to the left wheel 134b, and there is a possibility that a desired slip ratio that cannot be reached under the normal mode can be reached. Rise. Also, the desired transition rate can be reached more quickly in the automatic transition mode than in the normal mode. Therefore, in the torque control process, it is easier to achieve a slip rate suitable for the vehicle 102 to escape from the slip in the automatic transition mode in which the braking force is increased than in the normal mode. Therefore, in the vehicle control method, by automatically shifting to the automatic transition mode at the time of a slip, the running performance can be improved as compared with the case of dealing with the slip in the normal mode. In other words, in the vehicle control method, engine torque control and brake force control are coordinated in a more effective manner when the vehicle slips, thereby improving running performance.

  Next, after the torque control process in step S108, the slip determination unit 108 determines that the escape is successful when the state where the left and right wheel speed difference is less than 3.0 km / h continues for 2500 ms or more (step S110, Escape judgment process). When it is determined that the escape is successful in the escape determination process (Yes), the travel mode instruction unit 110 instructs the engine torque control unit 122 and the brake force control unit 112 to return from the automatic transition mode to the normal mode. Is output (normal mode return processing).

  On the other hand, when it is determined in the escape determination process that the escape has not been successful (No), the travel mode instruction unit 110 determines whether or not a travel mode switching signal is generated due to the manual operation of the switch 138 (step S112). ). When the travel mode switching signal is generated in step S112 (Yes), the travel mode instruction unit 110 outputs an instruction to shift from the automatic transition mode to the lock mode to the engine torque control unit 122 and the brake force control unit 112 ( Step S114, lock mode transition processing).

  In the lock mode, as described above, at the time of slip, the torque is reduced by a third torque down amount that is smaller than the second torque down amount in the automatic transition mode and the sport mode. Further, in the lock mode, the braking force applied to the right wheel 134a during the slip is the largest among the respective travel modes. For this reason, in the lock mode, the effect of the brake LSD control is higher than in the automatic transition mode, and more torque is distributed from the right wheel 134a having a higher wheel speed to the left wheel 134b having a lower wheel speed, so that the running performance can be further improved. . After shifting to the lock mode, the vehicle 102 can escape from the slip (step S116).

  FIG. 6 is a diagram comparing the slip ratio and the braking force with respect to the vehicle speed in each travel mode. A graph C shown in FIG. 6A is obtained by connecting the points A instead of the approximate function obtained based on the points A shown in the slip ratio table 126 of FIG. is there. Graph C shows the slip ratio in the automatic transition mode and the sport mode. Graphs D, E, and F shown in FIG. 6A indicate slip ratios in the normal mode, the lock mode, and the snow mode, respectively, and are graphs obtained by connecting the plotted points.

  When comparing the graphs C, D, E, and F, as an example, when the vehicle speed is about 15 (km / h), the magnitude of the slip rate is “snow mode <normal mode <automatic transition mode = sport mode <lock mode”. " From this, it is clear that the magnitude relationship between the slip ratios corresponds to the amount of torque reduction in each travel mode shown in FIG.

  The graph G shown in FIG. 6B is obtained by connecting the points B instead of the approximate function obtained based on the points B shown in the braking force table 130 of FIG. is there. Graph G shows the braking force in the automatic transition mode. Graphs H, I, J, and K shown in FIG. 6B show the braking force in the sport mode, the normal mode, the lock mode, and the snow mode, respectively, and were obtained by connecting the plotted points. It is a graph.

  Comparing the graphs G, H, I, J and K, the magnitude of the brake force corresponds to the magnitude relationship of the brake force shown in FIG. 3, and “snow mode <normal mode <sport mode <automatic transition mode” <Lock mode>.

  As described above, according to the vehicle control method, when it is determined that slip has occurred in the vehicle 102, the travel mode automatically shifts from the normal mode to the automatic transition mode, and based on the slip ratio table 126 and the brake force table 130. Thus, the torque of the left and right wheels 134a and 134b can be controlled by coordinating the engine torque control and the brake force control in a more effective manner. Therefore, in the vehicle control method, since the automatic transition mode is set, not only the driving performance is improved as compared with the normal mode, but also the driver himself / herself does not need to manually operate the switch 138 to switch the driving mode at the time of slipping. Thus, the burden on the driver can be reduced.

  Further, in the vehicle control method, it is determined based on a predetermined threshold that the vehicle 102 has slipped. Therefore, it is possible to reliably determine that traveling is difficult in the normal mode, and the driver is aware of the road surface condition. This reduces the burden on the driver.

  In the vehicle control method, if the vehicle 102 cannot escape from the slip even in the automatic transition mode, the switch 138 can be manually operated to switch to the lock mode. For this reason, in the vehicle control method, the effect of the brake LSD control is enhanced to improve the running performance, and it is possible to escape from the slip.

  In the vehicle control method, after the transition from the normal mode to the automatic transition mode, the automatic transition mode is continued until the vehicle 102 escapes from the slip, and when it is determined that the escape from the slip is successful, the normal mode is automatically performed. Can be restored. Therefore, since the transition from the automatic transition mode to the normal mode does not occur frequently, an increase in vibration associated with the switching of the travel mode does not occur frequently, and it is possible to suppress a sense of incongruity in operation for the driver.

  Furthermore, in the vehicle control method, the automatic transition mode is different from the lock mode that emphasizes running performance, and the braking force is small, so the impact and load on the drive system can be reduced, and the vibration associated with the brake does not increase and the operation is reduced. A sense of incongruity can be suppressed.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention can be used for a vehicle control method in which engine torque control and brake force control are coordinated when a vehicle slips.

DESCRIPTION OF SYMBOLS 100 ... Vehicle control apparatus, 102 ... Vehicle, 104 ... Vehicle control part, 106 ... Wheel speed sensor, 108 ... Slip determination part, 110 ... Driving mode instruction part, 112 ... Brake force control part, 114 ... Vehicle information output part, 116 ... Timer 118 ... Storage unit 120 ... Running mode table 122 ... Engine torque control unit 124 ... Vehicle speed sensor 126 ... Slip rate table 128 ... Engine 130 ... Brake force table 132 ... Brake system 134a ... Right Wheel, 134b ... Left wheel, 136 ... Differential, 138 ... Switch

Claims (5)

A vehicle control method for applying a brake according to a wheel speed of one of the left and right wheels having a large wheel speed when the vehicle slips, thereby distributing torque from the one wheel to the other wheel via a differential mechanism In
A slip determination process for determining whether the vehicle is slipping based on the vehicle information;
If it is determined that the vehicle is slipping, the torque is reduced by a second torque down amount smaller than the first torque down amount from the normal mode in which the torque is reduced by a predetermined first torque down amount at the time of slipping. Automatic transition mode transition processing to transition to automatic transition mode,
Torque control processing for controlling the torque of the left and right wheels by applying a brake to the one wheel so as to obtain a predetermined slip ratio for the vehicle to escape from slip, which is the ratio of the left and right wheel speed difference to the vehicle speed A vehicle control method comprising:   The vehicle control method according to claim 1, wherein the brake applied to the one wheel in the torque control process is performed with a predetermined braking force determined according to the predetermined slip ratio and the vehicle speed. The vehicle control method further includes a lock mode transition process for shifting to the lock mode by manual operation,
In the lock mode, the torque is reduced by a third torque-down amount that is smaller than the second torque-down amount at the time of slip, and a brake force that is greater than the brake force applied to the one wheel in the normal mode at the time of slip. The vehicle control method according to claim 1, wherein the vehicle control method is applied. The vehicle information includes a wheel speed difference between left and right, and a duration after the wheel speed difference has occurred,
4. The slip determination process according to claim 1, wherein the slip determination process determines that a slip has occurred when a left and right wheel speed difference and a duration time are each equal to or greater than a predetermined threshold value. 5. Vehicle control method. The vehicle control method includes an escape determination process for determining success of an escape depending on whether or not a state in which the difference between the left and right wheel speeds is less than a predetermined threshold continues for a predetermined time after the torque control process;
The vehicle control method according to any one of claims 1 to 4, further comprising a normal mode return process for returning from the automatic transition mode to the normal mode when it is determined that the escape is successful.

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