JP6209028B2 - Control device for four-wheel drive vehicle - Google Patents

Description

  The present invention relates to a control device for a four-wheel drive vehicle that can freely stop a propeller shaft equipped with an automatic brake control device that adds a yaw moment to the host vehicle for preventing road departure and obstacle avoidance.

  Conventionally, in a four-wheel drive vehicle in which driving force is transmitted from the main drive shaft to the sub drive shaft via a propeller shaft that can be stopped, the vehicle is running from the 2WD state in which the rotation of the propeller shaft is stopped in order to reduce running resistance. When switching to the 4WD state, it is necessary to apply torque to the propeller shaft and first synchronize the rotation with the wheel. Since the rotation synchronous torque to the propeller shaft acts as a braking torque for the drive system, an unpleasant / unnecessary deceleration feeling or shock (front / rear jerk) occurs in the vehicle when the synchronous torque increases. If it is going to suppress generation | occurrence | production of this braking torque, it cannot transfer to a 4WD state from 2WD state quickly, and the trade-off with switching time reduction becomes a big subject. As a technique of such a four-wheel drive vehicle that switches from the 2WD state to the 4WD state, for example, in Japanese Patent Application Laid-Open No. 2010-1000028 (hereinafter referred to as Patent Document 1), the variable part of the drive torque is transmitted to the auxiliary axle of the vehicle. A first clutch for disabling, and a second clutch for disabling a propeller shaft disposed between the first clutch and the second clutch when the first clutch is open The second clutch is closed based on the wheel slip detected in the main axle, and the disabled propeller shaft is accelerated before the second clutch is engaged.

JP 2010-100280 A

  However, as in the four-wheel drive vehicle disclosed in the above-mentioned Patent Document 1, no matter how smooth the rotation of the propeller shaft is realized, the propeller is consumed by running (kinetic) energy of the vehicle and new fuel. The operation of accelerating the rotation of the shaft is still an energy loss that is contrary to the original aim of the stationary mechanism that uses a propeller shaft that can be stopped to improve fuel efficiency. Further, the technology disclosed in Patent Document 1 described above is a technology that suppresses vehicle deceleration accompanying rotation synchronization to a level that does not cause a problem in practice, but after an acceleration operation that requires 4WD and slipping of drive wheels occur. Since rotation synchronization is started as preparation for switching to 4WD, there is also a problem that it is not a drastic solution to the time delay.

  By the way, in recent years, various automatic brake control devices have been developed and put into practical use in vehicles for the purpose of improving safety and reducing the burden on the driver. Is also actively adopted. In the four-wheel drive vehicle that can stop the propeller shaft as described above, the energy required for synchronizing the auxiliary drive shaft and the propeller shaft is diverted from the energy that the automatic brake control device must absorb and consume. If it can be used, it is desirable to effectively use the kinetic energy of the vehicle that must be consumed in some form. Further, in a situation where automatic braking is activated to prevent road departure and obstacle avoidance, there is a high possibility of approaching the limit of tire grip, so switching to the 4WD state in advance is effective for safety. Furthermore, if the operation of the main brake can be relaxed in consideration of the deceleration applied to the vehicle by rotation synchronization, the heat load on the brake can be reduced.

  The present invention has been made in view of the above circumstances. In a four-wheel drive vehicle capable of stopping a propeller shaft equipped with an automatic brake control device that adds a yaw moment to the host vehicle to prevent road departure and obstacle avoidance. The energy required to synchronize the auxiliary drive shaft and propeller shaft is absorbed by the automatic brake control device and diverted and used effectively from the energy that must be consumed, and it is predicted that road departure prevention and obstacle avoidance will occur. In this state, the four-wheeled vehicle can be shifted to the 4WD state in advance to improve safety, improve the yaw response of the vehicle, and further reduce the heat load of the main brake caused by the operation of the automatic brake control device. An object of the present invention is to provide a control device for a driving vehicle.

One aspect of the control device for a four-wheel drive vehicle according to the present invention transmits a driving force from one of the front drive shaft and the rear drive shaft to the other auxiliary drive shaft via a power transmission shaft, and A first clutch means is provided between the drive shaft and the power transmission shaft, and the auxiliary drive shaft transmits driving force to the left wheel side and the right wheel side instead of the differential mechanism between the left and right wheels. In a four-wheel drive vehicle provided with a second clutch means that can be freely switched, a front information recognition means that recognizes road information ahead, and a target yaw moment that is applied to the host vehicle based on the forward information from the front information recognition means And an automatic brake control means for operating the automatic brake, and a driving force control means for controlling the engagement and release of the first clutch means and the second clutch means. The first clutch means and the second clutch means If you are a two-wheel drive state in which the opening and latching means, when the automatic braking control means actuate the automatic brake to be added to the target yaw moment to the host vehicle based on the forward information, turning inner wheel side The yaw moment generated when the power transmission shaft and the sub drive shaft are rotationally synchronized based on the clutch torque for fastening the second clutch means and the second clutch means on the turning inner ring side. And yaw moment correcting means for correcting the target yaw moment calculated by the automatic brake control means with the yaw moment.

  According to the control device for a four-wheel drive vehicle according to the present invention, a four-wheel drive vehicle capable of freely stopping a propeller shaft equipped with an automatic brake control device for adding a yaw moment to the host vehicle for preventing road departure and obstacle avoidance. The automatic brake control device absorbs the energy required to synchronize the auxiliary drive shaft and propeller shaft, and diverts and effectively uses the energy that must be consumed. In the predicted state, it is possible to advance to the 4WD state in advance to improve safety, improve the yaw response of the vehicle, and further reduce the heat load of the main brake caused by the operation of the automatic brake control device. Become.

It is explanatory drawing which shows schematic structure of the vehicle by one Embodiment of this invention. It is a functional block diagram of a control unit according to an embodiment of the present invention. 4 is a flowchart of road departure prevention / obstacle avoidance control according to an embodiment of the present invention. It is a flowchart of the target yaw moment correction process by one Embodiment of this invention. It is a flowchart of the clutch release determination process by one Embodiment of this invention. It is explanatory drawing of the positional relationship of the own vehicle with respect to a white line and a roadside obstacle, and the deviation | shift amount with respect to each by one Embodiment of this invention. FIG. 7A is an explanatory diagram of a departure prevention yaw moment set according to a departure amount according to an embodiment of the present invention. FIG. 7A is a first departure prevention yaw moment set according to a departure amount from a white line. FIG. 7B shows an example of the second departure-preventing yaw moment that is set according to the amount of departure from the obstacle.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes an engine disposed in the front part of the vehicle, and the driving force of the engine 1 is transmitted from an automatic transmission device (including a torque converter and the like) 2 behind the engine 1 through a transmission output shaft 2a. It is transmitted to the transfer 3.

  The driving force transmitted to the transfer 3 is input to the rear wheel final reduction gear 7 via the rear drive shaft 4, the propeller shaft 5, and the drive pinion shaft portion 6, while the reduction drive gear 8, the reduction driven gear 9, and the drive It is input to the front wheel final reduction gear 11 via the front drive shaft 10 which is a pinion shaft portion. Here, the automatic transmission 2, the transfer 3, the front wheel final reduction gear 11 and the like are integrally provided in the case 12.

  The driving force input to the rear wheel final reduction gear 7 is configured to be transmitted to the left rear wheel 14rl via the rear wheel left drive shaft 13rl and further to the right rear wheel 14rr via the rear wheel right drive shaft 13rr. .

  The driving force input to the front wheel final reduction gear 11 is transmitted to the left front wheel 14fl via the front wheel left drive shaft 13fl and to the right front wheel 14fr via the front wheel right drive shaft 13fr.

  The transfer 3 is a wet multi-plate clutch (transfer clutch) which is a variable torque transmission capacity clutch formed by alternately overlapping a drive plate 15a provided on the reduction drive gear 8 side and a driven plate 15b provided on the rear drive shaft 4 side. ) 15 and a piston 16 that variably applies the fastening force of the transfer clutch 15.

  The rear wheel final reduction gear 7 does not have a differential mechanism, and a left wheel clutch 17l that can freely transmit and receive driving force is interposed in the rear wheel left drive shaft 13rl, while the rear wheel right A right wheel clutch 17r capable of interrupting transmission / reception of driving force is interposed on the drive shaft 13rr. These left and right wheel clutches 17l and 17r are configured to be executed in synchronization with a known rotational speed when the drive shafts 13rl and 13rr are connected to each other.

  Therefore, in the four-wheel drive vehicle of the present embodiment, when the transfer clutch 15 and the left and right wheel clutches 17l and 17r are all released, the propeller shaft 5 is stopped, and the front wheel left drive shaft 13fl and the front wheel right drive shaft 13fr constitutes the main drive shaft, the rear wheel left drive shaft 13rl and the rear wheel right drive shaft 13rr constitute the auxiliary drive shaft, the propeller shaft 5 is provided as the power transmission shaft, and the transfer clutch 15 is the first clutch means. The left and right wheel clutches 17l and 17r are provided as second clutch means. Then, by controlling the transfer clutch 15 with the pressing force of the piston 16, a rotational torque is applied to the propeller shaft 5 to control the rotation synchronization between the propeller shaft 5 and the main drive shaft, and the vehicle is driven back and forth. Force distribution control is performed. Also, by engaging the left wheel side wheel clutch 17l from the released state, the energy for synchronously rotating the propeller shaft 5 acts as a left wheel side deceleration (braking) force, and similarly, the right wheel side wheel clutch 17r is released. By fastening from the state, energy for synchronously rotating the propeller shaft 5 acts as a deceleration (braking) force on the right wheel side.

  Here, the pressing force of the piston 16 is given by a transfer clutch drive unit 31trc configured by a hydraulic circuit having a plurality of solenoid valves and the like. A control signal (transfer clutch torque) for driving the transfer clutch drive unit 31trc is output from the control unit 30 described later. The left and right wheel clutches 17l and 17r are actuated by left and right wheel clutch drive units 31wcl and 31wcr each formed of a hydraulic circuit having a plurality of solenoid valves and the like. Control signals for driving the left and right wheel clutch drive units 31wcl and 31wcr are output from the control unit 30 described later.

  On the other hand, reference numeral 32 denotes a brake drive unit of the vehicle. A master cylinder connected to a brake pedal (not shown) operated by a driver is connected to the brake drive unit 32, and the driver operates the brake pedal. (Depressed), the master cylinder causes the wheel cylinders of the four wheels 14fl, 14fr, 14rl, 14rr (the left front wheel cylinder 18fl, the right front wheel wheel cylinder 18fr, the left rear wheel wheel cylinder 18rl, the right rear wheel) through the brake drive unit 32. The brake pressure is introduced into the wheel cylinder 18rr), and thereby the four wheels are braked and braked.

  The brake drive unit 32 is a hydraulic unit including a pressurizing source, a pressure reducing valve, a pressure increasing valve, and the like. For each wheel cylinder 18fl, 18fr, 18rl, 18rr according to an input signal from the control unit 30 or the like, The brake pressure can be introduced independently of each other.

  The control unit 30 includes a front recognition device 21, wheel speed sensors for each wheel 14fl, 14fr, 14rl, 14rr (a left front wheel speed sensor 22fl, a right front wheel speed sensor 22fr, a left rear wheel speed sensor 22rl, a right rear wheel). A wheel speed sensor 22rr), a propeller shaft rotational speed sensor 23, and other steering angle sensor, yaw rate sensor, engine control unit (ECU), transmission control unit (TCU), etc. (not shown) are connected, and three-dimensional object data ahead of the host vehicle is connected. And forward information (details will be described later), wheel speed of each wheel 14fl, 14fr, 14rl, 14rr (left front wheel speed ωfl, right front wheel speed ωfr, left rear wheel speed ωrl, right rear wheel) Speed ωrr), propeller shaft rotational speed ωd, steering angle, yaw rate, engine speed, intake air volume, transmission gear Ratio and the like are input. In the present embodiment, the average rotational speed of the left front wheel speed ωfl and the right front wheel speed ωfr is adopted as the rotational speed ωm of the main drive shaft, and the left rear wheel speed ωrl as the rotational speed ωs of the auxiliary drive shaft. The average rotational speed of the right rear wheel speed ωrr (the wheel speed of the turning inner wheel when the vehicle is turning) is adopted.

  Here, the front recognition device 21 is configured to recognize road information ahead based on, for example, an image captured by the stereo camera 21a. The stereo camera 21a is composed of a set of (left and right) CCD cameras using a solid-state imaging device such as a charge coupled device (CCD) as a stereo optical system. These left and right CCD cameras are each mounted at a certain interval in front of the ceiling in the vehicle interior, take a stereo image of an object outside the vehicle from different viewpoints, and input image data to the front recognition device 21.

  The processing of the image from the stereo camera 21a in the front recognition device 21 is performed as follows, for example. First, a process for obtaining distance information from a corresponding positional shift amount is performed on a pair of stereo images in the traveling direction environment of the host vehicle captured by the CCD camera of the stereo camera 21a, and a three-dimensional distance distribution is obtained. Generate a distance image to represent.

  Based on this data, it is compared with well-known grouping processing and pre-stored three-dimensional road shape data, side wall data, three-dimensional object data, etc., and white line data, front obstacle data (existing along the road) 3d object data such as guardrails, side walls such as curbs, fixed obstacles such as utility poles, four-wheeled vehicles, two-wheeled vehicles, and pedestrians). The white line data and forward obstacle data extracted in this way are assigned different numbers for each type of data.

  Then, the front recognition device 21 memorizes the positions of the white line and the front obstacle on the predetermined two-dimensional coordinates centered on the camera position of the host vehicle determined in advance, and stores them in the control unit 30. Output.

  Further, as shown in FIG. 6, the front recognition device 21 calculates the angle formed by the white line and the current traveling direction of the host vehicle (the straight traveling direction centered on the camera position) as the intersection angle α, The distance from the center of the host vehicle to the white line (distance in the vertical direction to the white line) yL0, and the distance from the current vehicle center to the obstacle (distance in a direction parallel to the vertical direction to the white line) ys0 Calculate and output to the control unit 30. Thus, the stereo camera 21a and the forward recognition device 21 are provided as forward information recognition means. In the present embodiment, the example in which the stereo camera 21a is used as the forward information recognition unit has been described. However, the present invention is not limited to this, and for example, a monocular camera, a radar, a laser, or a combination thereof may be used. good.

  Then, the control unit 30 is based on each input signal described above, and is a target to be added to the host vehicle for preventing a lane departure based on forward information such as a white line and a front obstacle, and for avoiding an obstacle. The yaw moment Mzt0 is calculated to activate the automatic brake. When this automatic brake is operated, the wheel clutch (17l or 17r) on the turning inner wheel side is fastened, and the propeller shaft 5 and the auxiliary drive shaft are connected based on the clutch torque Tw for fastening the wheel clutch on the turning inner wheel side. Yaw moment ΔMz generated by the rotation synchronization of the two is calculated, the target yaw moment Mzt0 is corrected with the yaw moment ΔMz to calculate the final target yaw moment Mzt, and the brake corresponding to the final target yaw moment Mzt is calculated. The hydraulic pressure (inner front wheel brake hydraulic pressure Pbf, inner rear wheel brake hydraulic pressure Pbr) is calculated and output to the brake drive unit 32. Further, when not in the 4WD state and when a predetermined time has elapsed after passing through the white line portion or the front obstacle that is the subject of automatic braking, all the clutches 15, 17l, 17r are opened.

  Therefore, as shown in FIG. 2, the control unit 30 mainly includes a four-wheel drive control unit 30a, an out-of-road departure prevention / obstacle avoidance control unit 30b, a target yaw moment correction processing unit 30c, and a clutch release determination unit 30d. It is configured.

  The four-wheel drive control unit 30a receives the wheel speeds ωfl, ωfr, ωrl, and ωrr of each wheel from the four-wheel wheel speed sensors 22fl, 22fr, 22rl, and 22rr, and receives the steering angle from a steering angle sensor (not shown). The yaw rate is input from the yaw rate sensor, the engine speed and the intake air amount are input from the ECU, the transmission gear ratio is input from the TCU, and the wheel clutch (17l, 17r), a signal related to an instruction to release all the clutches 15, 17l, and 17r is input from the clutch release determination unit 30d.

  Then, the four-wheel drive control unit 30a calculates, for example, a yaw moment that suppresses an understeer tendency of the vehicle as a target yaw moment as a normal four-wheel drive control, and average wheel speeds ((ωfl + ωfr) of the left and right wheels of the front axle / 2) exceeds the wheel speed of the turning outer wheel on the rear axle, when the above-mentioned target yaw moment is applied to the vehicle, the wheel clutch on the outer turning wheel side of the rear axle is fastened and the turning inner wheel side And the fastening force of the transfer clutch 15 is controlled based on the target yaw moment.

  Further, the four-wheel drive control unit 30a stops the propeller shaft 5 and performs the above-described four-wheel drive control in the 2WD traveling state from the target yaw moment correction processing unit 30c to the wheel clutch (171, When either of the 17r engagement signals is input, the corresponding wheel clutch (either 17l or 17r) is engaged.

  Furthermore, when the four-wheel drive control unit 30a is not in the four-wheel drive control state and the release instruction of all the clutches 15, 17l, and 17r is input from the clutch release determination unit 30d, all the clutches 15 and 17l. , 17r are opened.

  In addition to the signals (engaged / released) to each of the clutches 15, 17l, 17r, the four-wheel drive control unit 30a determines the operation state of the four-wheel drive control as a target yaw moment correction processing unit 30c, a clutch release determination unit. 30d, and the target yaw moment correction process is performed on the wheel clutch engagement torque Tw related to the engagement of the wheel clutch (either 17l or 17r) on the turning inner wheel, which is executed in accordance with the instruction from the target yaw moment correction processing unit 30c. To the unit 30c. Thus, the four-wheel drive control unit 30a is provided as a driving force control means.

  The out-of-road departure prevention / obstacle avoidance control unit 30b receives forward information from the front recognition device 21 such as white lines and front obstacles (specifically, white line and front obstacle coordinate position information, intersection angle α, current The distance yL0 from the center of the host vehicle to the white line, the distance ys0 from the center of the host vehicle to the obstacle is input, and the wheel speeds ωfl of the respective wheels from the four-wheel wheel speed sensors 22fl, 22fr, 22rl, 22rr, ωfr, ωrl, and ωrr are input, and the yaw moment ΔMz generated when the propeller shaft 5 and the sub drive shaft are synchronized in rotation is appropriately input from the target yaw moment correction processing unit 30c. Then, for example, according to the flowchart shown in FIG. 3, road departure prevention / obstacle avoidance control is executed, and the brake fluid pressure (inner front wheel brake fluid pressure Pbf, inner rear wheel brake fluid) corresponding to the yaw moment applied to the host vehicle. Pressure Pbr) is calculated and output to the brake drive unit 32.

  In addition, the operating state of out-of-road departure prevention / obstacle avoidance control is output to the target yaw moment correction processing unit 30c, and when out-of-road departure prevention / obstruction avoidance control is operated, forward information (white line) The part number and the obstacle number) are output to the clutch release determination unit 30d.

The out-of-road departure prevention / obstacle avoidance control executed by the out-of-road departure prevention / obstacle avoidance control unit 30b will be described.
First, in step (hereinafter abbreviated as “S”) 101, for example, a foreseeable distance Lx corresponding to the vehicle speed V (for example, the average of the wheel speeds of four wheels) is calculated by the following equation (1).
Lx = V · t (1)
Here, t is a preset preview time. That is, the foreseeing distance is a distance to a position where the host vehicle is estimated to exist after the foreseeing time t, as shown in FIG. The foreseeing distance Lx is not limited to the distance calculated by the above equation (1).

Next, the process proceeds to S102, and the deviation amount yL from the white line of the vehicle at the foreseeing distance Lx is calculated by the following equation (2), for example (see FIG. 6).
yL = Lx · sin (α) −yL0 (2)
Next, the process proceeds to S103, and the deviation amount yS with respect to the obstacle of the own vehicle at the foreseeing distance Lx is calculated by the following equation (3), for example (see FIG. 6).
yS = Lx · sin (α) −ys0 (3)
Next, the process proceeds to S104, where the deviation yL from the white line, the crossing angle α, and the first deviation prevention yaw moment MzL, as shown in FIG. The first deviation prevention yaw moment MzL is set with reference to the map. Note that the reference position in FIG. 7A is a preset position, for example, a position that is a certain distance away from the white line toward the center of the road, or an end (inside the road center) of the white line. The first departure prevention yaw moment MzL is not limited to that set from the map shown in FIG. 7A, and may be calculated from a preset calculation formula or the like.

  As can be seen from FIG. 7A, the first departure-preventing yaw moment MzL increases as the crossing angle α increases, that is, as the urgency level is determined to be higher as the crossing angle α increases. Set to a large value. The first deviation prevention yaw moment MzL is set to a larger value as the deviation amount yL from the white line is larger.

  Next, the process proceeds to S105, and a map of the deviation amount yS and the second deviation prevention yaw moment MzS with respect to the obstacle as shown in FIG. Thus, the second deviation preventing yaw moment MzS is set. Note that the reference position in FIG. 7B is a preset position, for example, a position away from the obstacle end by a certain distance toward the center of the road. Further, the second departure prevention yaw moment MzS is not limited to the one set from the map shown in FIG. 7B, and may be calculated from a preset calculation formula or the like.

  As can be seen from FIG. 7B, the second departure prevention yaw moment MzS is set to a larger value as the departure amount yS with respect to the obstacle is larger.

Next, proceeding to S106, the target yaw moment Mzt0 is calculated from the first deviation preventing yaw moment MzL set in S104 and the second deviation preventing yaw moment MzS set in S105, for example, by the following equation (4). .
Mzt0 = MzL + MzS (4)

Next, the process proceeds to S107, and when the yaw moment ΔMz generated when the propeller shaft 5 and the sub drive shaft are rotationally synchronized is input from the target yaw moment correction processing unit 30c, the final target yaw moment Mzt is set as follows. On the other hand, when the yaw moment ΔMz is not inputted, the target yaw moment Mzt0 is corrected by setting the target yaw moment Mzt0 as the final target yaw moment Mzt as it is.
Mzt = Mzt0−ΔMz (5)
Next, proceeding to S108, the braking forces Bf and Br applied to the front and rear wheels on the turning inner wheel side are calculated by, for example, the following equations (6) and (7).
Bf = min (Kbr · Mzt · Cy, ΔBf_max) (6)
Br = Kbr · Mzt−Bf (7)
Here, min in the equation (6) is a function for selecting the smaller of Kbr · Mzt · Cy and ΔBf_max. Kbr is a conversion coefficient of the yaw moment into the braking force, and Cy is a front shaft load factor of the yaw moment that is set in advance through experiments, calculations, and the like. ΔBf_max is a maximum value of the braking force difference between the left and right front axle wheels calculated in advance.
Then, the process proceeds to S109, where the brake hydraulic pressures Pbf and Pbr of the front and rear wheels on the turning inner wheel side are calculated by the following equations (8) and (9), output to the brake drive unit 32, and the program exits.
Pbf = Cbf · Bf (8)
Pbr = Cbr · Br (9)
Here, Cbf and Cbr are constants determined by brake specifications.

  Thus, the off-road departure prevention / obstacle avoidance control unit 30b is provided as an automatic brake control means.

  The target yaw moment correction processing unit 30c receives the wheel speeds ωfl, ωfr, ωrl, ωrr of the respective wheels from the four-wheel wheel speed sensors 22fl, 22fr, 22rl, 22rr, and the propeller shaft rotational speed ωd from the propeller shaft rotational speed sensor 23. Is input from the four-wheel drive control unit 30a to the operation state of the four-wheel drive control, and the wheel clutch (either 17l or 17r) on the turning inner wheel side executed to prevent white line deviation prevention and obstacle avoidance The wheel clutch engagement torque Tw related to the engagement is input, and the operation state of the road departure prevention / obstacle avoidance control unit 30b is input from the road departure prevention / obstacle avoidance control unit 30b. Then, for example, according to the flowchart shown in FIG. 4, the target yaw moment correction process is executed, and the engagement instruction signal for the wheel clutch (either 17l or 17r) on the turning inner wheel side is output to the four-wheel drive control unit 30a. The yaw moment ΔMz generated by the rotation synchronization of the propeller shaft 5 and the sub drive shaft is appropriately output to the out-of-road departure prevention / obstacle avoidance control unit 30b.

  The target yaw moment correction process performed by the target yaw moment correction processing unit 30c will be described with reference to the flowchart of FIG.

  First, in S201, the four-wheel drive control unit 30a determines whether or not the 4WD operation is in progress. If the 4WD operation is in progress, the routine is exited, and if the 4WD operation is not in progress, the process proceeds to S202.

  In S202, it is determined whether or not the automatic braking for road departure prevention / obstacle avoidance control unit 30b has been activated by the road departure prevention / obstacle avoidance control unit 30b. When the automatic brake is activated, the process proceeds to S203, and a signal for engaging the wheel clutch (either 17l or 17r) on the turning inner wheel side is output to the four-wheel drive control unit 30a, and the corresponding wheel clutch is engaged. Let Whether the turning inner wheel is the left wheel side or the right wheel side is determined by the road departure prevention / obstacle avoidance control unit 30b based on the forward information input to the road departure prevention / obstacle avoidance control unit 30b. .

  Thereafter, the process proceeds to S204, where a rotational speed difference Δωsd (= ωs · Gf−ωd: Gf is a final gear ratio) between the auxiliary drive shaft and the propeller shaft 5 is calculated.

  Next, the process proceeds to S205, where the absolute value | Δωsd | of the rotational speed difference is compared with a threshold value Sd set in advance by experiment, calculation, etc., and the absolute value | Δωsd | of the rotational speed difference is larger than the threshold value Sd. If (| Δωsd |> Sd), it is determined that the synchronization between the auxiliary drive shaft and the propeller shaft 5 has not been completed, and the process proceeds to S206 to be output from the four-wheel drive control unit 30a as the rotation synchronization torque Tsw. A wheel clutch engagement torque Tw is set (Tsw = Tw).

  Conversely, when the absolute value of the rotational speed difference | Δωsd | is equal to or smaller than the threshold value Sd (when | Δωsd | ≦ Sd), it is determined that the synchronization between the auxiliary drive shaft and the propeller shaft 5 is completed, and the process proceeds to S207. Then, 0 is set as the rotation synchronization torque Tsw (Tsw = 0).

After setting the rotation synchronization torque Tsw in S206 or S207, the process proceeds to S208, and the yaw moment ΔMz due to rotation synchronization is calculated by, for example, the following equation (10) to prevent out-of-road departure prevention / obstacle avoidance control: Output to 30b and exit the program.
ΔMz = (Tsw / Rt) · (d / 2) (10)
Here, Rt is a tire diameter and d is a tread.

  Thus, the target yaw moment correction processing unit 30c is provided as a yaw moment correcting means.

  The clutch release determination unit 30d receives front information such as a white line and a front obstacle from the front recognition device 21, and receives an operation state of four-wheel drive control from the four-wheel drive control unit 30a. The avoidance control unit 30b receives the forward information (white line part, obstacle number) that is the target of activation when the out-of-road departure prevention / obstacle avoidance control is activated. Then, according to the flowchart shown in FIG. 5 to be described later, when the vehicle is not in a four-wheel drive state, the control target for the road departure prevention / obstacle avoidance control unit 30b to operate the automatic braking for road departure prevention / obstacle avoidance When a predetermined time has elapsed after passing (white line part or obstacle), a signal for releasing all the clutches 15, 17l, 17r is output to the four-wheel drive control unit 30a.

  That is, FIG. 5 shows a flowchart of the clutch release determination process executed by the clutch release determination unit 30d. First, in S301, the 4-wheel drive control unit 30a determines whether or not the 4WD is operating, and the 4WD is operating. In this case, the routine is exited as it is, and if the 4WD is not operating, the process proceeds to S302.

  In S302, it is determined whether or not a predetermined time has elapsed after passing the white line part or the obstacle to be controlled by the road departure prevention / obstacle avoidance control unit 30b.

  As a result of the determination, if the predetermined time has not passed after passing through the white line part or the obstacle, the routine is left as it is, and if the predetermined time has passed, the process proceeds to S303 and the automatic braking for the white line part or the obstacle is performed. It is determined that there is no operation, and a signal for releasing all the clutches 15, 17l, 17r is output to the four-wheel drive control unit 30a to exit the program.

  As described above, according to the embodiment of the present invention, the target yaw moment to be added to the host vehicle for preventing the lane departure based on the forward information such as the white line and the front obstacle, and for avoiding the obstacle. Calculate Mzt0 and activate the automatic brake. When this automatic brake is operated, the wheel clutch (17l or 17r) on the turning inner wheel side is fastened, and the propeller shaft 5 and the auxiliary drive shaft are connected based on the clutch torque Tw for fastening the wheel clutch on the turning inner wheel side. Yaw moment ΔMz generated by the rotation synchronization of the two, the target yaw moment Mzt0 is corrected with the yaw moment ΔMz to calculate the final target yaw moment Mzt, and the brake corresponding to the final target yaw moment Mzt is calculated. The hydraulic pressure (inner front wheel brake hydraulic pressure Pbf, inner rear wheel brake hydraulic pressure Pbr) is calculated and output to the brake drive unit 32. Further, when not in the 4WD state and when a predetermined time has elapsed after passing through the white line portion or the front obstacle that is the subject of automatic braking, all the clutches 15, 17l, 17r are opened. For this reason, in a four-wheel drive vehicle capable of stopping a propeller shaft equipped with an automatic brake control device that adds a yaw moment to the host vehicle to prevent road departure and obstacle avoidance, the auxiliary drive shaft and the propeller shaft are synchronized. Sometimes the necessary energy is absorbed by the automatic brake control device and is diverted and used effectively from the energy that must be consumed, and when the vehicle is expected to prevent road departure and avoid obstacles, it will shift to the 4WD state in advance. Thus, safety is improved, the yaw response of the vehicle is improved, and further, the heat load of the main brake generated by the operation of the automatic brake control device can be reduced.

  In this embodiment, the out-of-road departure prevention / obstacle avoidance control unit 30b is described as an example of an apparatus that generates an automatic brake for out-of-road departure prevention and obstruction avoidance control. Instead of outside deviation prevention and obstacle avoidance control), an apparatus that generates an automatic brake for either of them may be used.

1 Engine 2 Automatic transmission 3 Transfer 4 Rear drive shaft 5 Propeller shaft (power transmission shaft)
6 Drive pinion shaft 7 Rear wheel final reduction gear 8 Reduction drive gear 9 Reduction driven gear 10 Front drive shaft 11 Front wheel final reduction gear 13fl, 13fr Front wheel drive shaft (main drive shaft)
13rl, 13rr Rear wheel drive shaft (sub drive shaft)
14fl, 14fr Front wheel 14rl, 14rr Rear wheel 15 Transfer clutch (first clutch means)
17l, 17r wheel clutch (second clutch means)
18fl, 18fr, 18rl, 18rr Wheel cylinder 21 Forward recognition device (forward information recognition means)
21a Stereo camera (forward information recognition means)
22fl, 22fr, 22rl, 22rr Wheel speed sensor 23 Propeller shaft rotation speed sensor 30 Control unit 30a Four-wheel drive control unit (drive force control means)
30b Road departure prevention / obstacle avoidance control unit (automatic brake control means)
30c Target yaw moment correction processing unit (yaw moment correcting means)
30d Clutch disengagement determination unit (driving force control means)
31 trc Transfer clutch drive unit 31 wcl, 31 wcr Wheel clutch drive unit 32 Brake drive unit

Claims (3)

A driving force is transmitted from the main drive shaft of either the front shaft or the rear shaft to the other sub drive shaft via the power transmission shaft, and a first clutch is provided between the main drive shaft and the power transmission shaft. 4 wheel drive in which the auxiliary drive shaft is provided with a second clutch means capable of interrupting transmission of driving force to each of the left and right wheels instead of the differential mechanism between the left and right wheels. In the car,
Forward information recognition means for recognizing road information ahead;
Automatic brake control means for operating the automatic brake by calculating a target yaw moment to be added to the vehicle based on the forward information from the forward information recognition means;
Driving force control means for controlling engagement and release of the first clutch means and the second clutch means;
The driving force control means, if you are a two-wheel drive state in which the opening and the first clutch means and said second clutch means, the target to the host vehicle the automatic brake control means on the basis of the front information When operating the automatic brake to add a yaw moment, the second clutch means on the turning inner wheel side is engaged,
Based on the clutch torque for fastening the second clutch means on the turning inner wheel side, the yaw moment generated by the rotation synchronization of the power transmission shaft and the auxiliary drive shaft is calculated, and the automatic brake control is performed based on the yaw moment. Yaw moment correcting means for correcting the target yaw moment calculated by the means;
A control device for a four-wheel drive vehicle. The driving force control means, said first clutch means is opened, if you are a two-wheel drive state in which engagement of the second clutch means of the turning inner wheel side, and, the automatic brake control means the automatic 2. The four-wheel drive vehicle according to claim 1, wherein when a predetermined time has elapsed after passing through an object for operating a brake, all of the first clutch means and the second clutch means are opened. Control device.   The automatic brake control means operates the automatic brake by calculating a target yaw moment to be added to the own vehicle according to at least one of the deviation from the white line of the own vehicle obtained from the forward information and the deviation from the front obstacle. The control apparatus for a four-wheel drive vehicle according to claim 1 or 2, wherein

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