VEHICLE TRAVEL CONTROL DEVICE

Abstract

Vehicle travel control device comprising: a drive device (20) which drives at least one main drive wheel from the main drive wheel and a subordinate drive wheel of a vehicle (1); a first active stabilizer (60; 50) installed on one side of the main drive wheel; a second active stabilizer (50; 60) installed on one side of the subordinate drive wheel; and a control device (100) which performs a load distribution control when an actual driving force difference between a left side and a right side of the vehicle (1) during acceleration exceeds a threshold value, where a high-µ side is the one from the left side and the right side with a larger actual driving force, and a low-µ side is the other from the left side and the right side, wherein the load distribution control includes a first mode which is performed when a speed (Vx) of the vehicle (1) is less than or equal to a first reference value (Vx_Th1), wherein in the first mode, the control device (100) actuates the first active stabilizer (60; 50) in a direction to raise the high-µ side and actuates the second active stabilizer (50; 60) in a direction to raise the low-µ side, wherein the load distribution control further includes a second mode which is performed when the speed (Vx) is greater than a second reference value (Vx_Th2) which is greater than or equal to the first reference value (Vx_Th1), and wherein in the second mode, the control device (100) actuates the first active stabilizer (60; 50) in a direction to raise the low-µ side and actuates the second active stabilizer (50; 60) in a direction to raise the high-µ side.

Description

BACKGROUNDTechnical field

[0001] The present disclosure relates to vehicle travel control when a driving force difference occurs between left and right wheels during acceleration of a vehicle. Current state of the art

[0002] When braking or accelerating on a μ-split road, a vehicle generates a yaw moment due to a braking force or driving force difference between the left and right wheels. JP 2005-349914 A discloses a technique that detects such a yaw moment and performs rotation control to counteract the detected yaw moment. JP 2010-195089 A discloses a technique that detects a yaw moment generated during braking on a μ-split road and performs rotation control to counteract the detected yaw moment.

[0003] JP 2010-215068 A discloses an active stabilizer for suppressing roll behavior during cornering.

[0004] Furthermore, US 5,517,414 A discloses that an active suspension system connected to each wheel of a motor vehicle is controlled to minimize or reduce wheel slip. In response to the detection of wheel slip, the normal force applied to the slipping wheel is increased and the normal force applied to the wheel laterally opposite the slipping wheel is simultaneously decreased. The changes in the normal force are limited to prevent wheel slip from developing at the laterally opposite wheel. An engine control unit simultaneously reduces engine torque to further reduce wheel slip.

[0005] US 2005 / 0 236 782 A1 discloses a ground contact load control device for a vehicle, comprising front and rear, left and right load supporting devices for respectively supporting the ground contact load of front and rear, left and right wheels; load changing device operating to change the load supported by each of the load supporting devices; vehicle condition detecting device detecting the condition of the vehicle; and control device controlling the operation of the load changing device according to a signal from the vehicle condition detecting device; wherein the load changing device increases or decreases the ground contact load of any one pair of diagonally opposite wheels and the ground contact load of the other pair of diagonally opposite wheels in mutually opposite directions and increases or decreases the ground contact load of diagonally opposite wheels in the same direction.

[0006] Furthermore, US 2008 / 0 283 325 A1 discloses that the driving force of the drive wheels should be increased when a vehicle starts moving when the vehicle is traveling on an uneven road. For this purpose, a road surface for one drive wheel is first determined that has a higher coefficient of friction than the road surface for the other drive wheel. A process for controlling the base load of the drive wheels is performed during a period in which the differential rotations of the drive wheels are limited. The base load of the drive wheel traveling on a road with a high µ value is increased, while the base load of the other drive wheel traveling on a road with a low µ value is reduced. SUMMARY

[0007] According to the technique disclosed in the above-mentioned JP 2005-349914 A, turn control is performed during vehicle acceleration to counteract the yaw moment caused by the driving force difference between the left and right wheels. It is expected that the vehicle behavior will be stabilized by the turn control. However, even if turn control is performed, the driving force is not increased, and thus the acceleration performance is not improved.

[0008] An object of the present disclosure is to provide a technique that can increase acceleration performance when a driving force difference occurs between left and right wheels during acceleration of a vehicle.

[0009] The above object is achieved by the subject matter of claims 1 and 4. Advantageous developments of the invention are the subject matter of the subsequent dependent claims.

[0010] A first disclosure provides a vehicle travel control device.

[0011] The vehicle travel control device includes: a drive device that drives at least one of the main drive wheel and a sub-drive wheel of a vehicle; a first active stabilizer installed on one side of the main drive wheel; a second active stabilizer installed on one side of the subordinate drive wheel; and a control device that performs load distribution control when an actual driving force difference between a left side and a right side of the vehicle during acceleration exceeds a threshold value.

[0012] A high-µ side is the one of the left side and the right side with a larger actual driving force, and a low-µ side is the other of the left side and the right side.

[0013] The load distribution control includes a first mode that is performed when a speed of the vehicle is less than or equal to a first reference value.

[0014] In the first mode, the controller actuates the first active stabilizer in a direction to raise the high-µ side and actuates the second active stabilizer in a direction to raise the low-µ side.

[0015] A second disclosure further includes the following features in addition to the first disclosure.

[0016] The load distribution control further includes a second mode that is performed when the speed is higher than a second reference value that is greater than or equal to the first reference value.

[0017] In the second mode, the controller actuates the first active stabilizer in a direction to raise the low-µ side and actuates the second active stabilizer in a direction to raise the high-µ side.

[0018] A third disclosure further includes the following features in addition to the second disclosure.

[0019] A period of acceleration includes a first period and a second period that is later than the first period.

[0020] In the first period, the speed is less than or equal to the first reference value, and the control device performs the load distribution control in the first mode.

[0021] In the second period, the speed is higher than the second reference value, and the control device performs the load distribution control in the second mode.

[0022] A fourth disclosure further includes the following features in addition to the third disclosure.

[0023] The control device controls the drive device such that a driving force of the drive device becomes smaller in the second period than in the first period.

[0024] A fifth disclosure provides a vehicle travel control device.

[0025] The vehicle travel control device includes: a drive device that drives at least one of the main drive wheel and a sub-drive wheel of a vehicle; a first active stabilizer installed on one side of the main drive wheel; a second active stabilizer installed on one side of the subordinate drive wheel; and a control device that performs load distribution control when an actual driving force difference between a left side and a right side of the vehicle exceeds a threshold value during acceleration.

[0026] A high-µ side is the one of the left side and the right side with a larger actual driving force, and a low-µ side is the other of the left side and the right side.

[0027] When a speed of the vehicle is greater than a reference value, the control device operates the first active stabilizer in a direction to raise the low-µ side and operates the second active stabilizer in a direction to raise the high-µ side.

[0028] A sixth disclosure provides a vehicle travel control device.

[0029] The vehicle travel control device includes: a drive device that drives at least one of the main drive wheel and a sub-drive wheel of a vehicle; a first active stabilizer installed on one side of the main drive wheel; a second active stabilizer installed on one side of the subordinate drive wheel; and a control device that performs load distribution control when an actual driving force difference between a left side and a right side of the vehicle exceeds a threshold value during acceleration.

[0030] A high-µ side is the one of the left side and the right side with a larger actual driving force, and a low-µ side is the other of the left side and the right side.

[0031] A driving force of the main drive wheel on the high-µ side and a vertical load thereon are a high-µ side driving force and a high-µ side vertical load, respectively.

[0032] The load distribution control includes a first mode that is performed when the high-µ-side driving force is greater than or equal to the high-µ-side vertical load.

[0033] In the first mode, the controller actuates the first active stabilizer in a direction to raise the high-µ side and actuates the second active stabilizer in a direction to raise the low-µ side.

[0034] A seventh disclosure further has the following features in addition to the sixth disclosure.

[0035] The load distribution control further includes a second mode which is performed when the high-µ-side driving force is smaller than the high-µ-side vertical load.

[0036] In the second mode, the controller actuates the first active stabilizer in a direction to raise the low-µ side and actuates the second active stabilizer in a direction to raise the high-µ side.

[0037] An eighth revelation further has the following features in addition to the seventh revelation.

[0038] A period of acceleration includes a first period and a second period that is later than the first period.

[0039] The control device controls the drive device such that a driving force of the drive device becomes smaller in the second period than in the first period.

[0040] In the first period, the control device performs the load distribution control in the first mode.

[0041] In the second period, the control device performs the load distribution control in the second mode.

[0042] A ninth disclosure further includes the following features in addition to any of the first to eighth disclosures.

[0043] When a lateral acceleration of the vehicle is greater than or equal to a lateral acceleration threshold, the control device multiplies a control amount of each of the first active stabilizer and the second active stabilizer for the load distribution control by a correction gain less than “1”.

[0044] A tenth disclosure further includes the following features in addition to any of the first to ninth disclosures.

[0045] The control device performs the load distribution control such that a roll moment caused by actuation of the first active stabilizer and a roll moment caused by actuation of the second active stabilizer are balanced.

[0046] According to the present disclosure, when the actual driving force difference between the left and right wheels exceeds the threshold value during vehicle acceleration, load distribution control is performed. In the first mode of load distribution control, the first active stabilizer is operated in a high-µ-side lifting direction, and the second active stabilizer is operated in a low-µ-side lifting direction. As a result, the vertical load on the main drive wheel on the high-µ-side is increased, making it possible to efficiently increase the total actual driving force. Accordingly, acceleration performance is improved.

[0047] In the second load distribution control mode, the first active stabilizer is actuated in a direction to raise the low-µ side, and the second active stabilizer is actuated in a direction to raise the high-µ side. As a result, the vertical load on the main drive wheel on the low-µ side is increased, making it possible to increase the total actual driving force. Accordingly, the acceleration performance is improved. Short description of the drawings Fig. 1 is a conceptual diagram for explaining a load distribution controller according to an embodiment of the present disclosure; Fig. 2 is a conceptual diagram for explaining load distribution control according to the embodiment of the present disclosure; Fig. 3 is a conceptual diagram showing two modes of load distribution control according to the embodiment of the present disclosure; Fig. 4 is a conceptual diagram for explaining drive control when an actual driving force difference occurs between left and right wheels during acceleration of a vehicle; Fig. 5 is a conceptual diagram for explaining an effect when the load distribution control according to the present embodiment is performed in a first state; Fig. 6 is a conceptual diagram for explaining an effect when the load distribution control according to the present embodiment is performed in a second state; Fig. 7 is a conceptual diagram illustrating a case of front-wheel drive; Fig. 8 is a diagram showing, in a generalized manner, the load distribution control according to the present embodiment; Fig. 9 is a timing chart for explaining a change between a first mode and a second mode of load distribution control in the embodiment of the present disclosure; Fig. 10 is a block diagram showing a configuration example of a vehicle travel control device according to the embodiment of the present disclosure; Fig. 11 is a block diagram showing a functional configuration of a control device of the vehicle travel control device according to the embodiment of the present disclosure; Fig. 12 is a flowchart showing processing by the control device of the vehicle travel control device according to the embodiment of the present disclosure; Fig. 13 is a flowchart showing in summary form the load distribution control (step S140) according to the embodiment of the present disclosure; Fig. 14 is a time chart showing an example of vehicle travel control according to the embodiment of the present disclosure; and Fig. 15 is a diagram showing an example of a correction gain in the embodiment of the present disclosure. Embodiments

[0048] Embodiments of the present disclosure will be described below with reference to the attached drawings. 1. Overview1-1. Load balancing control

[0049] First, the "load distribution control" will be explained, which serves as a basis for the present embodiment. Here, the load distribution control is intended to actively control a vertical load on each wheel of a vehicle.

[0050] Fig. 1 is a conceptual diagram for explaining the load distribution control according to the present embodiment. The vehicle 1 is provided with a left front wheel 10FL, a right front wheel 10FR, a left rear wheel 10RL, and a right rear wheel 10RR. In the following description, the left front wheel 10FL and the right front wheel 10FR may be collectively referred to as a "front wheel," and the left rear wheel 10RL and the right rear wheel 10RR may be collectively referred to as a "rear wheel." The left front wheel 10FL and the left rear wheel 10RL may be collectively referred to as a "left wheel," and the right front wheel 10FR and the right rear wheel 10RR may be collectively referred to as a "right wheel."

[0051] In the present embodiment, the load distribution control is performed using an active stabilizer. The active stabilizer can actively twist a stabilizer bar using an actuator (electric motor) and can thereby control a roll angle of the vehicle 1. As shown in Fig. As shown in FIG. 1, the vehicle 1 according to the present embodiment is provided with both a front active stabilizer 50 and a rear active stabilizer 60. The front active stabilizer 50 is installed on the front wheel side of the vehicle 1. On the other hand, the rear active stabilizer 60 is installed on the rear wheel side of the vehicle 1.

[0052] CONDITION (A) in Fig. Figure 1 indicates a state before load distribution control is performed. For simplicity, consider a case where a load in CONDITION (A) is equally applied to the left front wheel 10FL, the right front wheel 10FR, the left rear wheel 10RL, and the right rear wheel 10RR. Friction ellipses CFL, CFR, CRL, and CRR with respect to the left front wheel 10FL, the right front wheel 10FR, the left rear wheel 10RL, and the right rear wheel 10RR, respectively, are also conceptually shown.

[0053] CONDITION (B) in Fig. 1 indicates a state during load distribution control. In CONDITION (B), the front active stabilizer 50 is operated in a direction to raise the left front wheel 10FL side and pull down the right front wheel 10FR side. At the same time, the rear active stabilizer 60 is operated in a direction to pull down the left rear wheel 10RL side and lift up the right rear wheel 10RR side. That is, the front active stabilizer 50 and the rear active stabilizer 60 are operated in opposite directions (opposite phases).

[0054] If the actuation directions of the front active stabilizer 50 and the rear active stabilizer 60 are opposite to each other, then a direction of a roll moment caused by the actuation of the front active stabilizer 50 and a direction of a roll moment caused by the actuation of the rear active stabilizer 60 are also opposite to each other. If the roll moment caused by the actuation of the front active stabilizer 50 and the roll moment caused by the actuation of the rear active stabilizer 60 are completely balanced, the roll angle of the vehicle 1 does not change.

[0055] Fig. Figure 2 conceptually illustrates a change in the vertical load on the rear wheels (10RL, 10RR) caused by load distribution control. Here, consider a case where the roll moment caused by the operation of the front active stabilizer 50 and the roll moment caused by the operation of the rear active stabilizer 60 are completely balanced, and the roll angle thus does not change.

[0056] In CONDITION (A) before performing load distribution control, a sprung mass load W is applied to each of the left rear wheel 10RL and the right rear wheel 10RR. The rear active stabilizer 60 is not actuated, and the rear active stabilizer 60 does not apply any force to the vehicle body. A suspension is compressed according to the load W, and a reaction force FA is generated in the +Z (upward) direction. That is, the load W and the reaction force FA are balanced.

[0057] In CONDITION (B) during load distribution control, the rear active stabilizer 60 applies a force FB in one direction (i.e., +Z direction) to lift the vehicle body on the right rear wheel 10RR side. However, since the roll angle has not changed, the counterforce FA has not changed since CONDITION (A). As a result, a force "FA + FB" acts on the vehicle body in the +Z direction on the right rear wheel 10RR side. The load that balances the force "FA + FB" is "W + ΔW." That is, the load is increased by the amount of the force FB compared to CONDITION (A).

[0058] The increase ΔW in the load is due to the fact that the front active stabilizer 50 applies the force in a direction of diagonally lifting the side of the left front wheel 10FL. That is, the force that lifts the side of the left front wheel 10FL acts in a direction of pulling down the side of the right rear wheel 10RR, which is reflected in the increase ΔW in the load. In other words, due to the balance between the forces that diagonally lift the side of the left front wheel 10FL and the side of the right rear wheel 10RR, the load is increased while the roll angle remains unchanged.

[0059] Similarly, in CONDITION (B), during load distribution control, the rear active stabilizer 60 applies a force FB in one direction (i.e., -Z direction) to pull down the vehicle body on the left rear wheel 10RL side. However, since the roll angle has not changed, the counterforce FA has also not changed since CONDITION (A). As a result, a force "FA - FB" acts on the vehicle body in the +Z direction on the left rear wheel 10RL side. The load that balances the force "FA - FB" is "W - ΔW." That is, the load is reduced by the amount of the force FB compared to CONDITION (A).

[0060] The reduction ΔW of the load is due to the fact that the front active stabilizer 50 applies the force in a direction of diagonally pulling down the side of the right front wheel 10FR. That is, the force that diagonally pulls down the side of the right front wheel 10FR acts in a direction of pulling up the side of the left rear wheel 10RL, which results in the reduction ΔW of the load. In other words, due to the balance between the forces that diagonally pull down the side of the right front wheel 10FR and the side of the left rear wheel 10RL, the load is reduced while the roll angle remains unchanged.

[0061] As described above, according to the Fig. 1 and Fig. 2, the vertical loads on the right rear wheel 10RR and the left front wheel 10FL increase, while the vertical loads on the left rear wheel 10RL and the right front wheel 10FR decrease. Thus, as shown in CONDITION (B) in Fig. 1, the respective friction ellipses CRR and CFL of the right rear wheel 10RR and the left front wheel 10FL expand, while the respective friction ellipses CRL and CFR of the left rear wheel 10RL and the right front wheel 10FR shrink. If the operating directions of the front active stabilizer 50 and the rear active stabilizer 60 are set to the Fig. 1 and Fig. 2, then the increase and decrease of the vertical load are reversed accordingly. Therefore, as a mode of load distribution control, two modes are possible: the "RR increase mode" and the "RL increase mode" as shown in Fig. 3 shown.

[0062] The RR increase mode is the same as in Fig. 1 and Fig. 2. That is, the front active stabilizer 50 is operated in a direction of raising the left front wheel 10FL side and pulling down the right front wheel 10FR side. At the same time, the rear active stabilizer 60 is operated in a direction of pulling down the left rear wheel 10RL side and raising the right rear wheel 10RR side. As a result, the vertical loads on the right rear wheel 10RR and the left front wheel 10FL increase, while the vertical loads on the left rear wheel 10RL and the right front wheel 10FR decrease.

[0063] The RL increase mode is the one in Fig. 1 and Fig. 2. That is, the front active stabilizer 50 is operated in a direction of pulling down the left front wheel 10FL side and raising the right front wheel 10FR side. At the same time, the rear active stabilizer 60 is operated in a direction of raising the left rear wheel 10RL side and pulling down the right rear wheel 10RR side. As a result, the vertical loads on the right rear wheel 10RR and the left front wheel 10FL decrease, while the vertical loads on the left rear wheel 10RL and the right front wheel 10FR increase.

[0064] It should be noted that in load distribution control, it is not essential that the roll moment caused by the operation of the front active stabilizer 50 and the roll moment caused by the operation of the rear active stabilizer 60 be completely balanced. Even if the two roll moments are not balanced, the vertical load will increase to some extent. It is important that the front active stabilizer 50 and the rear active stabilizer 60 be operated in opposite directions (opposite phases). Nevertheless, when the two roll moments are completely balanced, the roll angle does not change, which is preferable in terms of stabilizing the vehicle's behavior and reducing a driver's sense of unease. 1-2. Application to drive control

[0065] The load distribution control described above is applied to a drive control when accelerating the vehicle 1. Specifically, the load distribution control is used when an actual drive force difference occurs between the left and right wheels.

[0066] Fig. Figure 4 is a conceptual diagram for explaining traction control when an actual driving force difference occurs between the left and right wheels during acceleration of vehicle 1. Vehicle 1 is accelerating on a μ-split road. On the μ-split road, a static friction coefficient (μ) is different between the left wheel side and the right wheel side. In the Fig. In the example shown in Figure 4, the left wheel side is a low-μ side, and the right wheel side is a high-μ side. In the following description, the left front wheel 10FL and the left rear wheel 10RL may each be referred to as a "low-μ side wheel," and the right front wheel 10FR and the right rear wheel 10RR may each be referred to as a "high-μ side wheel."

[0067] Fig. Figure 4 shows an example of a rear-wheel drive (RWD) system. When a conventional differential gear is used, a driving force T generated by an engine is equally distributed between the left rear wheel 10RL and the right rear wheel 10RR. That is, a driving force T / 2 is applied to the low-µ-side wheel 10RL and the high-µ-side wheel 10RR, respectively. In this case, slippage of the low-µ-side wheel 10RL may occur.

[0068] To suppress the slip of the low-μ-side wheel 10RL, "traction control (TRC)" is performed. The traction control reduces the driving force T and applies a braking force B to the low-μ-side wheel 10RL to suppress the slip of the low-μ-side wheel 10RL. As a result, the actual driving force of the low-μ-side wheel 10RL becomes "T / 2 - B." A total actual driving force, which is a sum of the actual driving force of the high-μ-side wheel 10RR and the actual driving force of the low-μ-side wheel 10RL, becomes "T - B."

[0069] According to the present embodiment, the above-described load distribution control is used to increase the total actual driving force (T - B). Specifically, according to the present embodiment, the RR increase mode and the RL increase mode, in Fig. 3, appropriately used depending on a state of the drive control. A state in which the RR increase mode is preferred will hereinafter be referred to as a "first state SA." On the other hand, a state in which the RL increase mode is preferred will hereinafter be referred to as a "second state SB."

[0070] Fig. Figure 5 is a conceptual diagram for explaining an effect when the load distribution control (specifically, the RR increase mode) is performed in the first state SA. The friction ellipses CRR and CRL with respect to the high-µ-side wheel 10RR and the low-µ-side wheel 10RL are shown in Fig. 5 is also shown conceptually. In this example, the static friction coefficients on the high-µ side and the low-µ side are 1.0 and 0.1, respectively.

[0071] First, consider a comparative example in which load distribution control is not performed. The vertical loads Fz on the low-μ-side wheel 10RL and the high-μ-side wheel 10RR are equal, for example, 5600 N. The driving force T is 11200 N, and thus, the driving force T / 2 = 5600 N is applied to the high-μ-side wheel 10RR and the low-μ-side wheel 10RL, respectively. Regarding the high-μ-side wheel 10RR, the driving force T / 2 is equal to the vertical load Fz. That is, the driving force T is set large enough to prevent slippage of the high-μ-side wheel 10RR. On the other hand, the braking force B = 5040 N is applied to the low-μ-side wheel 10RL to suppress slippage. As a result, the actual drive force of the low-µ-side wheel 10RL is 560 N (= 5600 N - 5040 N). Therefore, the total actual drive force is 6160 N (= 5600 N + 560 N).

[0072] Next, consider a case where load sharing control is performed. In the case of the first state SA, load sharing control is performed in the “RR increase mode” from the two Fig. 3. As a result, the vertical load Fz on the high-μ-side wheel 10RR is increased by, for example, 1000 N to 6600 N, and the vertical load Fz on the low-μ-side wheel 10RL is decreased by 1000 N to 4600 N. In this case, it is possible to increase the driving force T / 2 of the high-μ-side wheel 10RR to 6600 N. In other words, it is possible to increase the driving force T to 13200 N. The low-μ-side wheel 10RL is supplied with the driving force T / 2 = 6600 N, and the braking force B = 6140 N is applied thereto to suppress slippage. As a result, the actual driving force of the low-μ-side wheel 10RL is 460 N (= 6600 N - 6140 N). Therefore, the total actual driving force is 7060 N (= 6600 N + 460 N). This means that the total actual driving force increases by approximately 14.6% compared to the comparative example in which load distribution control is not implemented.

[0073] In view of the above, it is preferable to perform the load distribution control in the RR increase mode when the driving force T / 2 of the high-μ-side wheel 10RR is greater than or equal to the vertical load Fz. As a result, the vertical load Fz on the high-μ-side wheel 10RR is increased, which makes it possible to efficiently increase the total actual driving force.

[0074] However, if, as in Fig. 5, the driving force T is increased, then the braking force B necessary for suppressing the slip of the low-μ-side wheel 10RL is also increased. It is undesirable that a state in which the strong braking force B is applied continues for a long time during acceleration of the vehicle 1. In order to reduce the braking force B to some extent, it is necessary to also reduce the driving force T. Such a state in which the driving force T (i.e., the braking force B) is reduced is the second state SB. In the second state SB, the load distribution control is preferably performed in the RL increase mode rather than in the RR increase mode.

[0075] Fig. Fig. 6 is a conceptual diagram for explaining an effect when the load distribution control (specifically, the RL increase mode) is performed in the second state SB. A Fig. 5 shown case is omitted where appropriate.

[0076] First, consider a comparison example in which the load distribution control is not implemented. The driving force T is smaller than that in the Fig. 5 and is, for example, 9000 N. The driving force T / 2 = 4500 N is supplied to the high-µ-side wheel 10RR and the low-µ-side wheel 10RL, respectively. With respect to the high-µ-side wheel 10RR, the driving force T / 2 is smaller than the vertical load Fz (5600 N). The actual driving force of the low-µ-side wheel 10RL is 560 N (= 4500 N - 3940 N), which is the same as that in the first state SA. Note that the braking force B required to suppress slippage is 3940 N, which is smaller than that in the first state SA. The total actual driving force is 5060 N (= 4500 N + 560 N).

[0077] Next, consider a case where load sharing control is performed. In the case of the second state SB, load sharing control is performed in the “RL increase mode” from the two Fig. 3. As a result, the vertical load Fz on the high-μ-side wheel 10RR is reduced by 1000 N to 4600 N, for example, and the vertical load Fz on the low-μ-side wheel 10RL is increased by 1000 N to 6600 N. In this case, it is possible to increase the actual driving force of the low-μ-side wheel 10RL to 660 N. That is, the braking force B required to suppress slippage is further reduced to 3840 N. As a result, the actual driving force of the low-μ-side wheel 10RL is 660 N (= 4500 N - 3840 N). Thus, the total actual driving force is 5160 N (= 4500 N + 660 N). This means that the total actual driving force increases by about 2% compared to the comparative example in which the load distribution control is not performed.

[0078] In view of the above, it is preferable to perform the load distribution control in the RL increase mode when the driving force T / 2 of the high-μ-side wheel 10RR is smaller than the vertical load Fz. As a result, the vertical load Fz on the low-μ-side wheel 10RL is increased, making it possible to increase the actual driving force of the low-μ-side wheel 10RL and thus increase the total actual driving force. In this case, it is not necessary to increase the driving force T. By reducing the braking force B, it is possible to increase the actual driving force of the low-μ-side wheel 10RL.

[0079] The case of rear-wheel drive is in Fig. 4 to 6. The load distribution control according to the present embodiment is also applicable to front-wheel drive (FWD) as in Fig. 7 and four-wheel drive (4WD). In the case of front-wheel drive, in the first state SA, not the RR increase mode but the RL increase mode is selected to increase the vertical load Fz on the high-µ side wheel 10FR. On the other hand, in the second state SB, not the RL increase mode but the RR increase mode is selected to increase the vertical load Fz of the low-µ side wheel 10FL. That is, the mode to be selected in the case of front-wheel drive is opposite to the mode to be selected in the case of rear-wheel drive.

[0080] Fig. 8 is a diagram showing the load distribution control according to the present embodiment in a generalized manner. A "main drive wheel" is one of the front wheel (10FL, 10FR) and the rear wheel (10RL, 10RR) that is primarily driven. A "subordinate drive wheel" is the other of the front wheel (10FL, 10FR) and the rear wheel (10RL, 10RR). In the case of front-wheel drive, the main drive wheel is the front wheel, and the subordinate drive wheel is the rear wheel. In the case of rear-wheel drive, the main drive wheel is the rear wheel, and the subordinate drive wheel is the front wheel. In the case of four-wheel drive, the main drive wheel is the one of the front wheel and the rear wheel to which more drive power is distributed, and the subordinate drive wheel is the other of the front wheel and the rear wheel.

[0081] A "first active stabilizer" is one of the front active stabilizer 50 and the rear active stabilizer 60 installed on the main drive wheel side. A "second active stabilizer" is one of the front active stabilizer 50 and the rear active stabilizer 60 installed on the subordinate drive wheel side. In the case of front-wheel drive, the first active stabilizer is the front active stabilizer 50, and the second active stabilizer is the rear active stabilizer 60. In the case of rear-wheel drive, the first active stabilizer is the rear active stabilizer 60, and the second active stabilizer is the front active stabilizer 50.

[0082] In the first state SA, the load distribution control is performed in a "first mode." Specifically, in the first mode, the first active stabilizer is operated in a direction to raise the high-μ side, and the second active stabilizer is operated in a direction to raise the low-μ side to increase the vertical load Fz on the main drive wheel on the high-μ side. In the case of front-wheel drive, the first mode is the one in Fig. 3 shown RL increase mode. In the case of rear-wheel drive, the first mode is the one shown in Fig. 3 and Fig. 5. By performing load distribution control in the first mode, the vertical load Fz on the main drive wheel on the high-µ side is increased, making it possible to efficiently increase the total actual driving force. As a result, the acceleration performance is improved.

[0083] In the second state SB, the load distribution control is performed in a "second mode." Specifically, in the second mode, the first active stabilizer is operated in a direction to raise the low-μ side, and the second active stabilizer is operated in a direction to raise the high-μ side to increase the vertical load Fz on the main drive wheel on the low-μ side. In the case of front-wheel drive, the second mode is the one described in Fig. 3 shown RR increase mode. In the case of rear-wheel drive, the second mode is the one shown in Fig. 3 and Fig. 6. By performing load distribution control in the second mode, the vertical load Fz on the main drive wheel on the low-µ side is increased, making it possible to increase the total actual drive force. As a result, the acceleration performance is improved.

[0084] The load sharing control according to the present embodiment may include only one of the first mode and the second mode. Even in that case, at least the effect of increasing acceleration performance can be obtained. For example, if the load sharing control includes only the first mode, acceleration performance is increased by using the first mode in the first state SA. If the load sharing control includes only the second mode, acceleration performance is increased by using the second mode in the second state SB. 1-3. Switching between first mode and second mode

[0085] According to the present embodiment, as described above, the first mode is selected in the first state SA, and the second mode is selected in the second state SB. A strategy for switching between the first mode and the second mode will be considered below.

[0086] Fig. Figure 9 is a timing chart for explaining the change between the first mode and the second mode of the load distribution control in the present embodiment. An example of a change in the driving force T during traction control is shown in Fig. 9. In addition, Fig. Figure 9 shows a temporal change in vehicle speed Vx (i.e., a speed of vehicle 1). When a driver presses an accelerator pedal, vehicle 1 begins to move and accelerate. The vehicle speed Vx gradually increases. Meanwhile, the driving force T tends to decrease over time.

[0087] Specifically, if slippage of the low-μ-side wheel is detected, the traction control system applies the braking force B to the low-μ-side wheel and reduces the driving force T. However, if the driving force T is reduced too much, sufficient driving force T / 2 is not available at the high-μ-side wheel, and thus, acceleration performance may deteriorate. Therefore, the driving force T is set large enough to prevent slippage of the high-μ-side wheel. For example, assuming that the static friction coefficient on the high-μ-side is 1.0, the driving force T is set to satisfy a condition "T / 2 = vertical load Fz on the high-μ-side wheel 10RR." This condition corresponds to the Fig. 5 shown first state SA.

[0088] In the first state SA, the slip of the low-μ-side wheel is suppressed mainly by applying the braking force B. However, it is undesirable for a state in which a strong braking force B is applied to continue for a long time during acceleration. Therefore, the traction control further reduces the driving force T after the first state SA. As a result, it is possible to reduce the braking force B necessary to suppress the slip of the low-μ-side wheel. This state corresponds to the Fig. 6 shown second state SB.

[0089] The first state SA occurs at a comparatively early stage of an acceleration period of vehicle 1. In contrast, the second state SB occurs at a later stage than the first state SA. For further generalization, a first period PA and a second period PB are considered, which occur in the Fig. 9. The first period PA corresponds to the first state SA. The second period PB is later than the first period PA and corresponds to the second state SB. The driving force T in the second period PB is smaller than the driving force T in the first period PA. The vehicle speed Vx in the second period PB is higher than the vehicle speed Vx in the first period PA.

[0090] For example, one of the simplest methods is to switch between the first mode and the second mode depending on the vehicle speed Vx. More specifically, in the first period PA corresponding to the first state SA, the vehicle speed Vx is less than or equal to a first reference value Vx_Th1. In this case, load sharing control is performed in the first mode. Conversely, in the second period PB corresponding to the second state SB, the vehicle speed Vx is higher than a second reference value Vx_Th2. In this case, load sharing control is performed in the second mode. Note that the second reference value Vx_Th2 is greater than or equal to the first reference value Vx_Th1. The second reference value Vx_Th2 may be equal to the first reference value Vx_Th1.

[0091] Another example is to switch between the first mode and the second mode depending on a relationship between the driving force T and the vertical load Fz. For explanatory purposes, the driving force T / 2 of the main drive gear on the high-µ side and the vertical load Fz thereon are hereinafter referred to as a “high-µ-side driving force” and a “high-µ-side vertical load,” respectively. Furthermore, it is assumed that the static friction coefficient on the high-µ side is 1.0. A state in which the high-µ-side driving force is greater than or equal to the high-µ-side vertical load corresponds to the Fig. 5. Thus, the load distribution control is performed in the first mode. On the other hand, a state in which the high-µ-side driving force is smaller than the high-µ-side vertical load corresponds to the state shown in Fig. 6 shown second state SB. Thus, the load distribution control is performed in the second mode.

[0092] As described above, by switching between the first mode and the second mode depending on the state of the vehicle 1 during acceleration, it is possible to efficiently increase the total actual driving force.

[0093] Hereinafter, a configuration and processing according to the present embodiment will be described in more detail. 2. Configuration example of a vehicle travel control device

[0094] Fig. 10 is a block diagram showing a configuration example of a vehicle travel control device according to the present embodiment. The vehicle travel control device is mounted on the vehicle 1. The vehicle travel control device is provided with a drive device 20, a braking device 30, a turning device 40, a front active stabilizer 50, a rear active stabilizer 60, a sensor group 70, and a control device 100. 2-1. Drive device

[0095] The drive device 20 is a device for driving the vehicle 1. In the case of front-wheel drive, the drive device 20 drives the front wheel, which is the main drive wheel. In the case of rear-wheel drive, the drive device 20 drives the rear wheel, which is the main drive wheel. In the case of four-wheel drive, the drive device 20 drives both the main drive wheel and the sub-drive wheel.

[0096] An example is Fig. 10 shows the case of rear-wheel drive. Specifically, the drive device 20 includes an accelerator pedal 21, an engine 25, a propeller shaft 26, a differential gear 27, and a drive shaft 28. The accelerator pedal 21 is an operating element used by the driver to perform an acceleration operation. A stroke amount of the accelerator pedal 21 is detected by an accelerator pedal sensor (not shown), and the detected information is sent to the control device 100.

[0097] The engine 25 is a driving force generating device for generating the driving force. Instead of the engine 25, an electric motor can be used as the driving force generating device. The engine 25 generates the driving force T in accordance with an instruction from the control device 100. The driving force T is distributed to the left rear wheel 10RL and the right rear wheel 10RR through the propeller shaft 26, the differential gear 27, and the drive shaft 28. 2-2. Braking device

[0098] The brake device 30 is a device for generating braking force. The brake device 30 includes a brake pedal 31, a master cylinder 32, wheel cylinders 33, and a brake actuator 35. The brake pedal 31 is an operating element used by the driver to perform braking. The master cylinder 32 is connected to the wheel cylinders 33 through the brake actuator 35. The wheel cylinder 33 is provided for each of the left front wheel 10FL, the right front wheel 10FR, the left rear wheel 10RL, and the right rear wheel 10RR.

[0099] The master cylinder 32 supplies brake fluid of a pressure corresponding to a stroke amount of the brake pedal 31 to the brake actuator 35. The brake actuator 35 distributes the brake fluid output from the master cylinder 32 to the wheel cylinders 33. The braking force at each wheel is determined depending on a pressure of the brake fluid supplied to the corresponding wheel cylinder 33.

[0100] The brake actuator 35 is capable of individually adjusting the respective pressure of the brake fluid supplied to the wheel cylinders 33. That is, the brake actuator 35 is capable of individually adjusting the respective braking force of the left front wheel 10FL, the right front wheel 10FR, the left rear wheel 10RL, and the right rear wheel 10RR. The operation of the brake actuator 35 is controlled by the control device 100. That is, the control device 100 is capable of actuating the brake actuator 35 to control the braking force of each wheel. 2-3. Rotating device

[0101] The turning device 40 is a device for turning the front wheel (10FL, 10FR). The turning device 40 includes a steering wheel 41, a steering shaft 42, a pinion 43, a rack 44, and an EPS (electric power steering) device 45.

[0102] The steering wheel 41 is an operating member used by the driver to perform a steering operation. One end of the steering shaft 42 is connected to the steering wheel 41, and the other end is connected to the pinion gear 43. The pinion gear 43 meshes with the rack gear 44. Both ends of the rack gear 44 are connected to the left and right front wheels, respectively. Rotation of the steering wheel 41 is transmitted to the pinion gear 43 through the steering shaft 42. Rotation of the pinion gear 43 is converted into linear movement of the rack gear 44, thereby changing a steering angle of the front wheel.

[0103] The EPS device 45 is a device for generating a turning moment for turning the front wheel. Specifically, the EPS device 45 includes an electric motor. For example, the electric motor is connected to the rack 44 through a conversion mechanism. The conversion mechanism is, for example, a ball screw. When a rotor of the electric motor rotates, the conversion mechanism converts the rotational motion into a linear motion of the rack 44, thereby changing the steering angle of the front wheel. The operation of the EPS device 45 is controlled by the control device 100. That is, the control device 100 is capable of actuating the EPS device 45 to turn the front wheel. 2-4. Active stabilizer

[0104] The front active stabilizer 50 is installed on the front wheel side of the vehicle 1. The front active stabilizer 50 includes stabilizer rods 51 and 52 and a stabilizer actuator 55. The stabilizer rod 51 is connected by a connecting rod to a suspension arm provided for the left front wheel 10FL. The stabilizer rod 52 is connected by a connecting rod to a suspension arm provided for the right front wheel 10FR.

[0105] The stabilizer actuator 55 includes an electric motor. One of the stabilizer bars 51 and 52 is integrally connected to a stator of the electric motor for rotation. The other of the stabilizer bars 51 and 52 is connected to a rotor of the electric motor. By rotating the electric motor, it is possible to rotate the stabilizer bars 51 and 52 in opposite directions. A rotational operation of the electric motor is also controlled by the control device 100. The control device 100 is capable of actively controlling the roll angle of the vehicle 1 by actuating the front active stabilizer 50.

[0106] The rear active stabilizer 60 is installed on the rear wheel side of the vehicle 1. The rear active stabilizer 60 includes stabilizer rods 61 and 62 and a stabilizer actuator 65. The stabilizer rod 61 is connected by a connecting rod to a suspension arm provided for the left rear wheel 10RL. The stabilizer rod 62 is connected by a connecting rod to a suspension arm provided for the right rear wheel 10RR.

[0107] The stabilizer actuator 65 includes an electric motor. One of the stabilizer rods 61 and 62 is integrally connected to a stator of the electric motor for rotation. The other of the stabilizer rods 61 and 62 is connected to a rotor of the electric motor. By rotating the electric motor, it is possible to rotate the stabilizer rods 61 and 62 in opposite directions. A rotational operation of the electric motor is also controlled by the control device 100. The control device 100 is capable of actively controlling the roll angle of the vehicle 1 by actuating the rear active stabilizer 60. 2-5. Sensor group

[0108] The sensor group 70 is provided for detecting a variety of state variables of the vehicle 1. For example, the sensor group 70 includes wheel speed sensors 71, a vehicle speed sensor 72, a yaw rate sensor 73, a longitudinal acceleration sensor 74, and a lateral acceleration sensor 75.

[0109] The wheel speed sensors 71 are provided for the wheels 10FL, 10FR, 10RL, and 10RR, respectively. The wheel speed sensors 71 detect rotational speeds of the wheels 10FL, 10FR, 10RL, and 10RR, respectively, and output detected information indicating the detected rotational speeds to the control device 100.

[0110] The vehicle speed sensor 72 detects the vehicle speed, which is a speed of the vehicle 1. The vehicle speed sensor 72 outputs detected information indicating the detected vehicle speed to the control device 100.

[0111] The yaw rate sensor 73 detects an actual yaw rate of the vehicle 1. The yaw rate sensor 73 outputs detected information indicating the detected actual yaw rate to the control device 100.

[0112] The longitudinal acceleration sensor 74 detects a longitudinal acceleration Gx acting on the vehicle 1. The longitudinal acceleration sensor 74 outputs detected information indicating the detected longitudinal acceleration Gx to the control device 100.

[0113] The lateral acceleration sensor 75 detects a lateral acceleration Gy acting on the vehicle 1. The lateral acceleration sensor 75 outputs detected information indicating the detected lateral acceleration Gy to the control device 100. 2-6. Control device

[0114] The control device 100 is a controller that performs the vehicle travel control according to the present embodiment. Typically, the control device 100 is a microcomputer that includes a processor, a memory, and an input / output interface. The control device 100 is also called an ECU (electronic control unit). The control device 100 receives the detected information from the sensor group 70 and sends instructions to a plurality of actuators and devices (25, 35, 45, 55, 65) through the input / output interface.

[0115] Hereinafter, functions and a processing flow of the control device 100 according to the present embodiment will be described in more detail. 3. Functions and processing sequence of the control device

[0116] Fig. 11 is a block diagram showing a functional configuration of the control device 100 according to the present embodiment. The control device 100 includes, as functional blocks, a drive control unit 110, a condition judgment unit 120, a rotation control unit 130, and a load distribution control unit 140. These functional blocks are implemented by the processor of the control device 100 executing a control program stored in the memory. The control program may be recorded on a computer-readable recording medium.

[0117] Fig. Fig. 12 is a flowchart showing processing by the control device 100 according to the present embodiment. The control device 100 repeatedly executes a Fig. 12 shown processing sequence. 3-1. Step S110 (Drive Control Process)

[0118] The drive control unit 110 performs drive control. Specifically, when the driver steps on the accelerator pedal 21, detected information of a stroke amount of the accelerator pedal 21 is sent to the control device 100. The drive control unit 110 determines the driving force T according to the stroke amount. Then, the drive control unit 110 controls the operation of the engine 25 to achieve the driving force T. The driving force T generated by the engine 25 is equally distributed to the left rear wheel 10RL and the right rear wheel 10RR through the differential gear 27. That is, the driving force T / 2 is applied to each of the left rear wheel 10RL and the right rear wheel 10RR.

[0119] Further, the drive control unit 110 performs traction control (TRC). More specifically, the drive control unit 110 detects a wheel showing a sign of slippage. By a wheel showing a sign of slippage, we mean that a slip amount or a slip ratio of the wheel exceeds a threshold. The drive control unit 110 can calculate a slip amount and a slip ratio of a wheel based on a rotational speed of the wheel and the vehicle speed. The rotational speed of each wheel is detected by the wheel speed sensor 71. The vehicle speed is detected by the vehicle speed sensor 72. Alternatively, the vehicle speed may be calculated from the rotational speed of the wheels. Based on the detected information, the drive control unit 110 can judge whether or not any wheel shows the sign of slippage.

[0120] The wheel exhibiting the indication of slippage is a target wheel, which is a target of the traction control system. Typically, the target wheel is the low-μ-side wheel. To prevent slippage of the target wheel, the drive control unit 110 controls the brake actuator 35 of the brake device 30 to apply the braking force B to the target wheel. Furthermore, the drive control unit 110 reduces the driving force T, if necessary, to prevent slippage of the target wheel.

[0121] If the driving force T is reduced too much, the acceleration performance may deteriorate. Therefore, the drive control unit 110 sets the driving force T in the first state SA (i.e., the first period PA) to be large enough to prevent slippage of the high-µ-side wheel. For example, assuming that the static friction coefficient on the high-µ side is 1.0, the drive control unit 110 sets the driving force T to satisfy a condition of “T / 2 = vertical load Fz on the high-µ-side wheel.” In the second state SB (i.e., the second period PB) after the first state SA, the drive control unit 110 further reduces the driving force T compared to the case of the first state SA.

[0122] If traction control is active (step S110; Yes), processing proceeds to step S120. Otherwise (step S110; No), the current processing cycle ends. 3-2. Step S120 (condition judgment processing)

[0123] The condition judging unit 120 judges whether the actual driving force difference between the left and right wheels exceeds a threshold value Th or not. Fig. 4 to 6, the actual driving force of the high-μ-side wheel 10RR is "T / 2," and the actual driving force of the low-μ-side wheel 10RL is "T / 2 - B." Therefore, the condition judgment unit 120 may calculate the actual driving force difference based on the driving force T and the braking force B. Alternatively, since the actual driving force difference is equivalent to a braking force difference between the high-μ-side wheel 10RR and the low-μ-side wheel 10RL, the condition judgment unit 120 may calculate the braking force difference as the actual driving force difference.

[0124] If the actual driving force difference exceeds the threshold Th (step S120; Yes), then processing proceeds to steps S130 and S140. Otherwise (step S120; No), the current processing cycle ends. 3-3. Step S130 (rotation control processing)

[0125] The actual driving force difference between the left and right wheels causes a yaw moment of the vehicle 1. To stabilize the vehicle, the rotation control unit 130 performs rotation control to counteract such a yaw moment. During rotation control, the rotation control unit 130 uses the EPS device 45 of the rotation device 40 to rotate the front wheel. If the vehicle 1 is further equipped with a device for rotating the rear wheel, the rear wheel can be rotated simultaneously.

[0126] A target steering angle is determined based on the actual driving force difference. For example, the steering control unit 130 includes a steering angle map that defines a relationship between an input parameter and the target steering angle. Examples of the input parameter include (a) the actual driving force difference, (b) a yaw moment expected from the actual driving force difference, and the like. As the value of the input parameter increases, the target steering angle increases accordingly. The steering control unit 130 uses the input parameter and the steering angle map to obtain the target steering angle. The steering control unit 130 then actuates the EPS device 45 to achieve the target steering angle. 3-4. Step S140 (Load distribution control processing)

[0127] The load distribution control unit 140 executes the load distribution control according to the present embodiment to increase the total actual driving force. As described above, there are two types of load distribution control: the first mode and the second mode (see Fig. 3, Fig. 5, Fig. 6, Fig. 8 and Fig. 9). The load distribution control unit 140 uses the first mode and the second mode appropriately depending on the state of the vehicle 1. A condition for selecting the first mode will hereinafter be referred to as a "first mode condition." On the other hand, a condition for selecting the second mode will hereinafter be referred to as a "second mode condition."

[0128] For example, one of the simplest methods is to switch between the first mode and the second mode depending on the vehicle speed Vx (see Fig. 9). In this case, the first mode condition is that "the vehicle speed Vx is less than or equal to the first reference value Vx_Th1." Conversely, the second mode condition is that "the vehicle speed Vx is greater than the second reference value Vx_Th2." The vehicle speed Vx can be obtained from the vehicle speed sensor 72. The second reference value Vx_Th2 is greater than or equal to the first reference value Vx_Th1. The second reference value Vx_Th2 can be equal to the first reference value Vx_Th1.

[0129] Another example is switching between the first mode and the second mode depending on a relation between the high-µ-side driving force T / 2 and the high-µ-side vertical load Fz. More specifically, the first mode condition is that “the high-µ-side driving force T / 2 is greater than or equal to the high-µ-side vertical load Fz” (see Fig. 5). In contrast, the second mode condition is that the “high-µ-side driving force T / 2 is smaller than the high-µ-side vertical load Fz” (see Fig. 6).

[0130] In the case of rear-wheel drive, the high-µ-side vertical load Fz during acceleration is given by the equation "static vertical load Fz0 + load shift amount ΔFz." In the case of front-wheel drive, the high-µ-side vertical load Fz during acceleration is given by the equation "static vertical load Fz0 - load shift amount ΔFz." The static vertical load Fz0 per wheel is precalculated based on the vehicle mass, longitudinal weight distribution, and so on. The load shift amount ΔFz per wheel is given by the following equation (1). [Equation (1)] ΔFz=0.5mGxhl

[0131] Where, m is a mass of the vehicle 1, Gx is the longitudinal acceleration that can be obtained from the longitudinal acceleration sensor 74, h is a center of gravity height of the vehicle, and l is a wheelbase of the vehicle 1.

[0132] Fig. 13 is a flowchart summarizing the load distribution control (step S140) according to the present embodiment. The load distribution control unit 140 judges whether one of the first mode condition and the second mode condition is satisfied (steps S141, S142).

[0133] If the first mode condition is met (step S141; Yes), the load distribution control unit 140 performs load distribution control in the first mode (step S143). Specifically, the load distribution control unit 140 operates the first active stabilizer in a high-µ-side raising direction and operates the second active stabilizer in a low-µ-side raising direction.

[0134] If the second mode condition is met (step S141; No, step S142; Yes), the load distribution control unit 140 performs load distribution control in the second mode (step S144). Specifically, the load distribution control unit 140 operates the first active stabilizer in a low-µ-side raising direction and operates the second active stabilizer in a high-µ-side raising direction.

[0135] If none of the first mode condition and the second mode condition is satisfied (step S141; No, step S142; No), then the load distribution control unit 140 does not perform the load distribution control (step S145).

[0136] Fig. 14 is a timing chart showing an example of vehicle travel control according to the present embodiment. When the vehicle 1 starts moving, the control device 100 generates a large driving force T. The vehicle 1 accelerates, and the vehicle speed Vx gradually increases. If the low-μ-side wheel shows a sign of slippage, the control device 100 performs traction control (see Fig. 12, step S110; Yes). The control device 100 reduces the driving force T and applies the braking force B to the low-µ-side wheel.

[0137] At a time ts, an actual driving force difference between left and right wheels exceeds the threshold value Th (see Fig. 12, step S120; Yes). In response to this, the control device 100 performs the load distribution control (see Fig. 12, step S140). First, the load distribution control is performed in the first mode (see Fig. 13, step S143). At a time tx, the load distribution control is switched from the first mode to the second mode (see Fig. 13, step S144).

[0138] A control amount of each active stabilizer (50, 60) during the load distribution control is expressed, for example, by the following equation (2). [Equation (2)] Control amount = basic gain g1 × mode gain g2

[0139] The base gain g1 is set to a value greater than 0 when the actual driving force difference between the left and right wheels exceeds the threshold Th. The base gain g1 can be expressed as a function of the actual driving force difference. In this case, the base gain g1 increases with increasing actual driving force difference. The base gain g1 can change gradually, as shown in Fig. 14 shown.

[0140] The mode gain g2 is changed according to the load distribution control mode. For example, the mode gain g2 is +1.0 in the first mode and -1.0 in the second mode. The mode gain g2 can change gradually, as shown in Fig. 14 shown.

[0141] As a modification example, consider a case where the vehicle 1 is cornering. When the vehicle 1 is cornering, the front active stabilizer 50 and the rear active stabilizer 60 must fulfill their primary role, that is, suppress roll variation. To this end, a correction is made to reduce the control amount for load distribution control. Specifically, in the present modification example, the control amount of each active stabilizer (50, 60) is expressed by the following equation (3). [Equation (3)] Control amount = basic gain g1 × mode gain g2 × correction gain g3

[0142] Fig.15 is a diagram showing an example of the correction gain g3. A horizontal axis represents the lateral acceleration Gy, and a vertical axis represents the correction gain g3. The lateral acceleration Gy is obtained from the lateral acceleration sensor 75. When the lateral acceleration Gy is less than a lateral acceleration threshold Gy_Th, the correction gain g3 is 1.0. When the lateral acceleration Gy is greater than or equal to the lateral acceleration threshold Gy_Th, the correction gain g3 is less than 1.0.

[0143] In other words, when the vehicle 1 is cornering and the lateral acceleration Gy becomes greater than or equal to the lateral acceleration threshold Gy_Th, the control device 100 multiplies the control amount by the correction gain g3 of less than 1. In other words, the control device 100 reduces the control amount of the active stabilizer (50, 60) for load distribution control. As a result, priority is given to suppressing the roll variation, which is the primary role of the active stabilizer.

Claims

[1] A vehicle travel control device comprising: a drive device (20) which drives at least one main drive wheel from the main drive wheel and a subordinate drive wheel of a vehicle (1); a first active stabilizer (60; 50) installed on one side of the main drive wheel; a second active stabilizer (50; 60) installed on one side of the subordinate drive wheel; and a control device (100) which performs a load distribution control when an actual driving force difference between a left side and a right side of the vehicle (1) during acceleration exceeds a threshold value, where a high-µ side is the one from the left side and the right side with a larger actual driving force, and a low-µ side is the other from the left side and the right side, wherein the load distribution control includes a first mode which is performed when a speed (Vx) of the vehicle (1) is less than or equal to a first reference value (Vx_Th1), wherein in the first mode, the control device (100) actuates the first active stabilizer (60; 50) in a direction to raise the high-µ side and actuates the second active stabilizer (50; 60) in a direction to raise the low-µ side, wherein the load distribution control further includes a second mode which is performed when the speed (Vx) is greater than a second reference value (Vx_Th2) which is greater than or equal to the first reference value (Vx_Th1), and wherein in the second mode, the control device (100) actuates the first active stabilizer (60; 50) in a direction to raise the low-µ side and actuates the second active stabilizer (50; 60) in a direction to raise the high-µ side. [2] Vehicle travel control device according to claim 1, wherein a period of acceleration includes a first period (PA) and a second period (PB) which is later than the first period (PA), wherein in the first period (PA) the speed (Vx) is less than or equal to the first reference value (Vx_Th1) and the control device (100) performs the load distribution control in the first mode, and wherein in the second period (PB) the speed (Vx) is higher than the second reference value (Vx_Th2) and the control device (100) performs the load distribution control in the second mode. [3] The vehicle travel control device according to claim 2, wherein the control device (100) controls the drive device (20) such that a driving force of the drive device (20) in the second period (PB) becomes smaller than in the first period (PA). [4] A vehicle travel control device comprising: a drive device (20) which drives at least one main drive wheel from the main drive wheel and a subordinate drive wheel of a vehicle (1); a first active stabilizer (60; 50) installed on one side of the main drive wheel; a second active stabilizer (50; 60) installed on one side of the subordinate drive wheel; and a control device (100) which performs a load distribution control when an actual driving force difference between a left side and a right side of the vehicle (1) during acceleration exceeds a threshold value, where a high-µ side is the one of the left side and the right side with a larger actual driving force and a low-µ side is the other of the left side and the right side, where a driving force of the main drive wheel on the high-µ side and a vertical load thereon are a high-µ side driving force and a high-µ side vertical load, respectively, wherein the load distribution control includes a first mode which is performed when the high-µ-side driving force is greater than or equal to the high-µ-side vertical load, wherein in the first mode, the control device (100) actuates the first active stabilizer (60; 50) in a direction to raise the high-µ side and actuates the second active stabilizer (50; 60) in a direction to raise the low-µ side, wherein the load distribution control further includes a second mode performed when the high-µ-side driving force is smaller than the high-µ-side vertical load, and wherein in the second mode, the control device (100) actuates the first active stabilizer (60; 50) in a direction to raise the low-µ side and actuates the second active stabilizer (50; 60) in a direction to raise the high-µ side. [5] Vehicle travel control device according to claim 4, wherein a period of acceleration includes a first period (PA) and a second period (PB) which is later than the first period (PA), wherein the control device (100) controls the drive device (20) such that a driving force of the drive device (20) in the second period (PB) becomes smaller than in the first period (PA), wherein in the first period (PA) the control device (100) performs the load distribution control in the first mode, and wherein in the second period (PB) the control device (100) performs the load distribution control in the second mode. [6] A vehicle travel control device according to any one of claims 1 to 5, wherein, when a lateral acceleration (Gy) of the vehicle (1) is greater than or equal to a lateral acceleration threshold value (Gy_Th), the control device (100) multiplies a control amount of each of the first active stabilizer (60; 50) and the second active stabilizer (50; 60) for the load distribution control by a correction gain (g3) less than 1. [7] The vehicle travel control device according to any one of claims 1 to 6, wherein the control device (100) performs the load distribution control such that a roll moment caused by an operation of the first active stabilizer (60; 50) and a roll moment caused by an operation of the second active stabilizer (50; 60) are balanced.

Images