JP5906048B2 - Vehicle behavior control device - Google Patents

Description

  The present invention relates to a vehicle behavior control device that controls a vehicle behavior by applying a braking force to each wheel independently.

  2. Description of the Related Art In recent years, various vehicle behavior control techniques have been proposed and put into practical use for vehicles in which braking force is independently applied to each wheel to generate a desired yaw moment to improve stability and motion performance. For example, in Japanese Patent Application Laid-Open No. 2007-131251 (hereinafter referred to as Patent Document 1), at the time of rollover prevention control, at the relatively early stage where the absolute value of the actual lateral acceleration is greater than or equal to value Gy1 and less than or equal to value Gy2, Only when the inner front wheel braking force is generated, the inner rear wheel braking force is generated on the rear wheel in the turning direction in addition to the inner front wheel braking force when the value is greater than or equal to Gy2, and the absolute value of the actual lateral acceleration is When the value is Gy3 or more, in addition to the inner rear wheel braking force, an outer wheel braking force is generated on the front wheel outside the turning direction, and a yawing moment in the direction opposite to the turning direction is forcibly generated to suppress an increase in roll angle. A vehicle motion control technology is disclosed.

JP 2007-131251 A

  In general, by detecting the understeer tendency of the vehicle and adding a yaw moment in the vehicle turning direction by the turning inner wheel brake, the rear wheel also has a sufficient slip angle, and it is possible to increase the cornering force of the four wheels to some extent. is there. At this time, in order to avoid a delay in pressurization of the brake control, in order to increase the response of the brake fluid pressure, the rotational speed of the pump motor of the hydraulic unit (H / U) of the brake drive unit is increased, or the H / U When the valve is operated, there is a problem that vibration noise is deteriorated. In particular, in the case of four-wheel pressurization control (which also applies a brake to the turning outer wheel) as disclosed in Patent Document 1 described above, independent control of four-wheel hydraulic pressure increases the operating noise of the H / U valve. End up. That is, in the technique disclosed in Patent Document 1 described above, when braking is first applied to the inner wheel side in the turning direction and further lateral acceleration or the like is increased, the braking force applied to the outer wheel side in the turning direction also increases the deceleration acting on the vehicle body. Thus, the effect of improving the understeer of the vehicle by increasing the ground contact load of the front shaft can be expected. However, the target hydraulic pressure for brake control becomes independent on all four wheels, and in order to suppress vibration noise during control operation, there is a measure in brake hydraulic system hardware (H / U pumps, valves, piping, etc.). This is necessary and causes the problem of reviewing the structure and increasing the cost. Also, for example, in traction control control in a four-wheel drive vehicle, if brake control that suppresses slip of each wheel is executed independently for each wheel, similarly, vibration noise of the hydraulic system becomes a problem, and resonance of the drive system (front and rear There is a risk of vehicle body vibration due to wheel rotation fluctuations in the opposite phase of the shaft.

  The present invention has been made in view of the above circumstances, and reduces the occurrence of vibration noise in a hydraulic system and a drive system when vehicle behavior control is performed using a brake, without requiring special measures or structural changes. An object of the present invention is to provide a vehicle behavior control device that can perform the above-described operation.

One aspect of the vehicle behavior control device according to the present invention includes driving state detection means for detecting a driving state of the vehicle, braking force applied to the left and right front wheels of the vehicle based on the driving state, and right and left front wheels, respectively. Braking force calculating means for calculating the braking force to be applied; the braking force to be applied to the left front wheel and the braking force to be applied to the right front wheel; A brake control unit configured to perform braking control by setting the brake fluid pressure to the same value; and a front / rear driving force distribution control unit capable of variably controlling the driving force distribution between the front and rear shafts. A slip amount between the left and right wheels of the vehicle is calculated based on the driving state of the vehicle, and a braking force applied to the left and right front wheels of the vehicle and a braking force applied to the right and left front wheels respectively based on the slip amount. Calculate The braking force calculation means, if you set the braking force based on the slip amount to brake control by the brake control means, the front-rear driving force distribution control means, a direct connection between the longitudinal axis.

  According to the vehicle behavior control device of the present invention, it is possible to reduce the occurrence of vibration noise in the hydraulic system and the drive system when the vehicle behavior is controlled using a brake, without requiring special measures or structural changes. It becomes possible.

It is explanatory drawing which shows schematic structure of the vehicle carrying the vehicle behavior control apparatus by one Embodiment of this invention. It is a functional block diagram of a control unit according to an embodiment of the present invention. It is composition explanatory drawing of the brake drive part by one Embodiment of this invention. It is a flowchart of the vehicle behavior control program by one Embodiment of this invention. Characteristics of lateral acceleration and steering wheel angle ratio in steady circle turning test when this control is applied to explain the difference between first target yaw moment and second target yaw moment according to an embodiment of the present invention It is explanatory drawing. It is explanatory drawing of the control state which generates the braking force for demonstrating the difference between the 1st target yaw moment and the 2nd target yaw moment by one Embodiment of this invention.

  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.

  Further, the driving force transmitted to the transfer 3 is input to the rear wheel final reduction device 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. Then, it is input to the front wheel final reduction gear 11 via the front drive shaft 10 which is the drive 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 transmitted to the left rear wheel 14rl via the rear wheel left drive shaft 13rl and 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) as a variable torque transmission capacity clutch in which 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 are alternately stacked. ) 15 and a transfer piston 16 that variably applies a fastening force (rear shaft drive torque) of the transfer clutch 15. Therefore, in this vehicle, by controlling the pressing force by the transfer piston 16 and controlling the fastening force of the transfer clutch 15, the torque distribution ratio is variable between the front wheel and the rear wheel, for example, between 100: 0 and 50:50. It is a four-wheel drive vehicle based on a front engine / front drive vehicle base (FF base).

  The pressing force of the transfer piston 16 is given by a transfer clutch drive unit 31b configured by a hydraulic circuit having a plurality of solenoid valves and the like. A control signal (fastening torque between front and rear shafts: transfer clutch torque) for driving the transfer clutch driving unit 31b is output from the front and rear driving force distribution control unit 31a. The front / rear driving force distribution control unit 31a is provided as a front / rear driving force distribution control means, and sets the driving force distribution between the front and rear axes according to parameters such as input torque to the known transfer 3 and vehicle yaw rate, The transfer clutch torque corresponding to the set driving force distribution between the front and rear shafts is output to the transfer clutch drive unit 31b.

  On the other hand, reference numeral 32b denotes a vehicle brake drive unit, and a master cylinder 42 connected to a brake pedal 41 operated by a driver shown in FIG. 3 is connected to the brake drive unit 32b. Then, when the driver operates the brake pedal 41, the master cylinder 42 and the wheel cylinders of the four wheels 14fl, 14fr, 14rl, 14rr (the left front wheel wheel cylinder 17fl, the right front wheel wheel cylinder 17fr, the left rear wheel) through the brake driving unit 32b. The brake pressure is introduced into the wheel cylinder 17rl and the right rear wheel wheel cylinder 17rr), whereby the four wheels are braked.

  The brake driving unit 32b is a hydraulic unit including a pressurizing source, a pressure reducing valve, a pressure increasing valve, and the like. In addition to the brake operation by the driver described above, each wheel cylinder 17fl, With respect to 17fr, 17rl, and 17rr, the brake pressure can be independently introduced.

  Specifically, the brake drive unit 32b is configured as shown in FIG. 3, with the left rear wheel cylinder 17rl on the left rear wheel 14rl, the right rear wheel wheel cylinder 17rr on the right rear wheel 14rr, and the left front wheel 14fl. The left front wheel wheel cylinder 17fl is provided, and the right front wheel wheel cylinder 17fr is provided on the right front wheel 14fr. A brake driving unit 32b for the left front wheel 14fl and the right rear wheel 14rr constitutes a first brake circuit 40a, and a brake driving unit 32b for the left front wheel 14fl and the left rear wheel 14rl constitutes a second brake circuit 40b.

  Each of the wheel cylinders 17fl, 17fr, 17rl, 17rr is connected to a respective outlet valve 42fl, 42fr, 42rl, 42rr and a respective inlet valve 43fl, 43fr, 43rl, 43rr. These valves 42fl, 42fr, 42rl, 42rr, 43fl, 43fr, 43rl, 43rr are electrically operated by the brake control unit 32a.

  These valves 42fl, 42fr, 42rl, 42rr, 43fl, 43fr, 43rl, 43rr are in their operating positions, and the outlet valves 42fl, 42fr, 42rl, 42rr are in the respective brake circuits, and the wheel cylinders 17fl, 17fr, 17rl, and 17rr are communicated with respective pumps 46a and 46b that are driven together by a motor 45 through respective check valves 44a and 44b. In the non-excited basic position, the outlet valves 42fl, 42fr, 42rl, 42rr are blocked from this flow path.

  Further, low pressure storage containers 47a and 47b are provided between the outlet valves 42fl, 42fr, 42rl and 42rr of the brake circuits 40a and 40b and the pumps 46a and 46b. The inlet valves 43fl, 43fr, 43rl, 43rr are wheel cylinders 17fl, 17fr, 17rl, 17rr from the master cylinder 42 via the switching valves 48a, 48b to the brake circuits 40a, 40b at the basic positions where they are not excited. Allows unimpeded flow of pressure medium (oil) into the. When the inlet valves 43fl, 43fr, 43rl, 43rr are actuated, the oil flow is cut off.

  Furthermore, control valves 49a and 49b are interposed in the brake circuits 40a and 40b. The control valves 49a and 49b are combined with the switching valves 48a and 48b, and are independent of the operation of the brake pedal 41 by the driver. The brake pressure can be increased. Control of each valve provided in these brake drive parts 32b is performed by the brake control part 32a.

Next, the control unit 30 will be described.
The control unit 30 includes a wheel speed sensor (left front wheel speed sensor 21fl, right front wheel speed sensor 21fr, left rear wheel speed sensor 21rl, right wheel) for each of the wheels 14fl, 14fr, 14rl, 14rr as operating state detection means. From the rear wheel speed sensor 21rr), the steering wheel angle sensor 22, and the lateral acceleration sensor 23, the wheel speed of each wheel (left front wheel speed ωfl, right front wheel speed ωfr, left rear wheel speed ωrl, right rear wheel speed ωrr). ), Steering wheel angle θH, vehicle body lateral acceleration (d ² y / dt ² ), and other signals are input.

Then, the control unit 30 sets the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement based on the vehicle speed V (for example, the average of the four wheel speeds) and the steering wheel angle θH. calculated, the first additional yaw moment to be added to the vehicle based on this target lateral acceleration ^(d 2 y / ^dt 2) actual lateral acceleration as an actual vehicle behavior and t ^(d 2 y / dt ²⁾ Mzt1 is calculated, and the first to be added to the vehicle in addition to the first additional yaw moment Mzt1 based on the target lateral acceleration (d ² y / dt ² ) t and the actual lateral acceleration (d ² y / dt ² ) 2 additional yaw moment Mzt2 is calculated, the braking force applied to the turning inner wheel is calculated as the first braking force FB1 based on the first additional yaw moment Mzt1, and the turning is performed based on the second additional yaw moment Mzt2. Inner wheel and turning outer car Calculating a braking force to be added to the vehicle without changing the braking force difference as a second braking force FB2 between. Further, when the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle is calculated and the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle is larger than a preset value e3, A third braking force FB3 applied to the vehicle is calculated based on the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle. The braking force applied to each wheel based on the first, second and third braking forces FB1, FB2 and FB3 is applied to at least the braking force applied to the left front wheel and the braking force applied to the right front wheel. The brake fluid pressure of the front wheel and the rear wheel on the side of the braking force with the larger power is set to the same value, and is output to the brake control unit 32a. At this time, when the third braking force FB3 is output, a transfer clutch slip prevention control command signal is output to the front / rear driving force distribution control unit 31a to bring the transfer clutch 15 into a substantially directly connected state. Thus, the control unit 30 is configured to have functions as a braking force calculation unit and a braking control unit.

  Therefore, as shown in FIG. 2, the control unit 30 includes a target lateral acceleration calculation unit 30a, a lateral acceleration deviation calculation unit 30b, a target yaw moment calculation unit 30c, first and second braking force calculation units 30d, left and right wheels. An inter-wheel speed difference calculation unit 30e, a left-right wheel speed difference determination unit 30f, a third braking force calculation unit 30g, a braking force calculation unit 30h for each wheel, and a brake fluid pressure calculation unit 30i for each wheel. ing.

The target lateral acceleration calculation unit 30a receives the four-wheel wheel speeds ωfl, ωfr, ωrl, and ωrr from the four-wheel wheel speed sensors 21fl, 21fr, 21rl, and 21rr, and the handle angle sensor 22 receives the handle angle θH. Then, for example, the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement is calculated by the following equation (1), and is output to the lateral acceleration deviation calculating unit 30b.
(D ² y / dt ² ) t = (1 / (1 + A · V ² )) · (V ² / l) · (θH / n) (1)
Here, A is a stability factor, l is a wheel base, and n is a steering gear ratio.

The lateral acceleration deviation calculator 30b receives the actual lateral acceleration (d ² y / dt ² ) from the lateral acceleration sensor 23, and receives the target lateral acceleration (d ² y / dt ² ) t from the target lateral acceleration calculator 30a. Is done. Then, the lateral acceleration deviation Δ (d ² y / dt ² ) is calculated by the following equation (2) and output to the target yaw moment calculating unit 30c.
Δ (d ² y / dt ² ) = (d ² y / dt ² ) − (d ² y / dt ² ) t (2)
The target yaw moment calculating unit 30c receives the steering wheel angle θH from the steering wheel angle sensor 22, and receives the lateral acceleration deviation Δ (d ² y / dt ² ) from the lateral acceleration deviation calculating unit 30b.

Then, the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is larger than a preset first lateral acceleration deviation threshold e 1 (| Δ (d ² y / dt ² ) |> e1) When the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs and the vehicle is in an understeer condition, a yaw moment in the turning direction is added to the vehicle. This additional yaw moment is calculated as the first additional yaw moment Mzt1, for example, by the following equation (3).
Mzt1 = GMZ1 · Δ (d ² y / dt ² ) (3)
Here, GMZ1 is a yaw moment gain set in advance by experiments and calculations.

  If it is determined that the above condition is not satisfied and it is not necessary to add a yaw moment in the turning direction to the vehicle, the first additional yaw moment Mzt1 is set to zero.

Further, the target yaw moment calculating unit 30c calculates the second additional yaw moment Mzt2 to be added to the vehicle in addition to the first additional yaw moment Mzt1 as follows. That is, the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is larger than a preset second lateral acceleration deviation threshold e 2 (> e 1) (| Δ (d ² y / dt). ² ) |> e2) and when the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs and the vehicle is in an understeer condition, the first additional yaw moment It is determined that it is necessary to add a yaw moment in the turning direction to the vehicle in addition to Mzt1, and this additional yaw moment is calculated as a second additional yaw moment Mzt2 by, for example, the following equation (4).
Mzt2 = GMZ2 · Δ (d ² y / dt ² ) (4)
Here, GMZ2 is a yaw moment gain set in advance through experiments and calculations.

  If the above condition is not satisfied and it can be determined that it is not necessary to add a yaw moment in the turning direction to the vehicle in addition to the first additional yaw moment Mzt1, the second additional yaw moment Mzt2 is set to 0. Set to.

  Here, details of the calculated first additional yaw moment Mzt1 and second additional yaw moment Mzt2 will be described later.

  Thus, the first additional yaw moment Mzt1 and the second additional yaw moment Mzt2 calculated by the target yaw moment calculation unit 30c are output to the first and second braking force calculation units 30d.

The first and second braking force calculation units 30d receive the first additional yaw moment Mzt1 and the second additional yaw moment Mzt2 from the target yaw moment calculation unit 30c. Then, for example, the braking force applied to the turning inner wheel is calculated as the first braking force FB1 by the following equation (5). For example, the turning inner wheel and the turning outer wheel are calculated by the following equation (6). The braking force applied to the vehicle without changing the braking force difference between and is calculated as the second braking force FB2.
FB1 = | Mzt1 | / (w / 2) (5)
Here, w is a tread.

FB2 = GFb · | Mzt2 | (6)
Here, GFb is a conversion gain (predetermined value) to the braking force. The first braking force FB1 and the second braking force FB2 calculated in this way are output to the braking force calculation unit 30h for each wheel.

Here, the difference between the first braking force FB1 and the second braking force FB2 will be described with reference to FIG.
The characteristic explanatory diagram of the lateral acceleration and the steering wheel angle ratio in the steady circle turning test of FIG. 5 shows the lateral acceleration (d ² y / dt ² ): lateral when the vehicle turns along a circle with a predetermined constant radius. Axis to handle angle ratio (= handle angle θH / handle angle θH0 at extremely low speed): An example of the characteristics of the vertical axis, and a line L0 indicated by a broken line in FIG. 5 is a reference steer characteristic line. A line translated from the reference steer characteristic line L0 by the first lateral acceleration deviation threshold e1 with respect to the horizontal axis in the direction in which the lateral acceleration (d ² y / dt ² ) decreases becomes L1, the second The line translated by the lateral acceleration deviation threshold e2 is L2.

In a normal vehicle, as the vehicle speed V increases and the lateral acceleration (d ² y / dt ² ) increases, a predetermined constant value is obtained unless the steering wheel angle θH is cut off from the steering wheel angle θH0 at an extremely low speed. The steering wheel angle ratio tends to increase because it becomes difficult to turn along a circle with a radius of.

That is, in the general vehicle characteristics, as shown by the broken line Nsu0, when the lateral acceleration (d ² y / dt ² ) increases, the tire cornering force is deviated from the reference steering characteristic line due to the nonlinearity of the tire cornering force, and the lateral acceleration (d ² y / dt ² ), a characteristic with a larger handle angle ratio is drawn.

  In the control according to the present embodiment, when the state after the point P1 deviated by the first lateral acceleration deviation threshold e1 from the reference steering characteristic line L0, the braking force of FBfi and FBri is generated on the turning inner front and rear wheels. One additional yaw moment Mzt1 is added to prevent an understeer tendency of the vehicle. As a result, the characteristics of the vehicle are improved to characteristics close to the line L1 as indicated by Nsu1.

  Even if the vehicle characteristic is improved to Nsu1, if the state after the point P2 deviated from the reference steering characteristic line L0 by the second lateral acceleration deviation threshold e2 is reached, the braking force FBfi of the turning inner front and rear wheels, In addition to FBri, braking force is generated on the four wheels without changing the braking force difference between the turning inner wheel and the turning outer wheel, and the second additional yaw moment Mzt2 is added to prevent the vehicle from understeering. Is done. Thereby, the characteristic of the vehicle is improved to a characteristic approaching the line L2 as indicated by Nsu2.

The wheel speed difference calculation unit 30e between the left and right wheels receives the four wheel speeds ωfl, ωfr, ωrl, ωrr from the four wheel speed sensors 21fl, 21fr, 21rl, 21rr. Then, for example, the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle is calculated and output to the wheel speed difference determining unit 30f between the left and right wheels by the following equation (7).
Δω = max (ωfi, ωri) −max (ωfo, ωro) (7)
Where ωfi is the wheel speed of the front wheel inside the turn, ωri is the wheel speed of the rear wheel inside the turn, ωfo is the wheel speed of the front wheel outside the turn, ωro is the wheel speed of the rear rear wheel, and max (ωfi, ωri) is The larger value of ωfi and ωri, max (ωfo, ωro) is the larger value of ωfo and ωro. The wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle is output to the wheel speed difference determining unit 30f between the left and right wheels.

  The wheel speed difference determination unit 30f between the left and right wheels receives the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle from the wheel speed difference calculation unit 30e between the left and right wheels. Then, an absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle is compared with a preset value e3, and an absolute value | Δω | Is greater than e3 (when | Δω |> e3), a transfer clutch slip prevention control command signal is output to the front / rear driving force distribution control unit 31a to bring the transfer clutch 15 into a substantially directly coupled state. Further, the wheel speed difference determination unit 30f between the left and right wheels is a third braking force calculation unit that compares the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle with a preset value e3. Output to 30 g.

The third braking force calculation unit 30g compares the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle from the wheel speed difference determination unit 30f between the left and right wheels with a preset value e3, and The wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle is input. When the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle is larger than e3 (when | Δω |> e3), for example, the slip correction value is calculated by the following equation (8). Δωd is calculated.
Δωd = Δω−e3 · (Δω / | Δω |) (8)
If | Δω |> e3 is not satisfied, the slip correction value Δωd is set to zero.

The wheel speed difference determining unit 30f between the left and right wheels is based on the calculated (set) slip correction value Δωd, for example, between the left and right wheels (between the turning inner wheel and the turning outer wheel) by the following equation (9). The braking force for correcting the generated slip (the sum of the braking forces applied to the front and rear wheels on the inside of the turn) is calculated as the third braking force FB3 and is output to the braking force calculation unit 30h for each wheel.
FB3 = GFd · Δωd (9)
Here, GFd is a conversion gain (predetermined value) to the braking force set in advance.

The braking force calculation unit 30h for each wheel receives the first braking force FB1 and the second braking force FB2 from the first and second braking force calculation units 30d, and receives the third braking force calculation unit 30g from the third braking force calculation unit 30g. A braking force FB3 is input. For example, the braking force of the turning outer wheel (braking force FBfo of the turning outer front wheel, braking force FBro of the turning outer rear wheel), the braking force of the turning inner wheel (turning inner front wheel) according to the following equations (10) and (11): Braking force FBfi and braking inner rear wheel braking force FBri) are calculated and output to the brake fluid pressure calculation unit 30i for each wheel.
FBfo = FBro = FB2 / 2 + max (-FB3, 0) (10)
FBfi = FBri = FB1 + FB2 / 2 + max (FB3, 0) (11)
Here, max (-FB3, 0) is a larger value of -FB3 and 0, and max (FB3, 0) is a larger value of FB3 and 0.

The brake fluid pressure calculation unit 30i for each wheel receives the braking forces FBfo, FBro, FBfi, and FBri for each wheel from the braking force calculation unit 30h for each wheel. And, for example, according to the following equations (12) and (13), the brake fluid pressure of each wheel (turning outer front wheel brake fluid pressure PBfo, turning inner front wheel brake fluid pressure PBfi, turning outer rear wheel brake fluid pressure PBro, turning inner The rear wheel brake hydraulic pressure PBri) is calculated and output to the brake control unit 32a.
PBfo = PBro = FBfo · CB = FBro · CB (12)
PBfi = PBri = FBfi · CB = FBri · CB (13)
Here, CB is a constant determined by brake specifications (wheel cylinder diameter, etc.).

As is apparent from the above equations (10) and (11), in this embodiment, as shown in FIG. 6, first, the absolute value | Δ (d ² y / dt ² ) | When the first lateral acceleration deviation threshold e1 or more is reached and the first additional yaw moment Mzt1 is applied, braking forces of FBfi and FBri are generated on the turning inner front and rear wheels (the state of Cv1 in FIG. 5). ).

Thereafter, when the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation becomes equal to or greater than the second lateral acceleration deviation threshold value e2, the second additional yaw moment Mzt2 is added. In addition to the braking forces FBfi and FBri of the inner front and rear wheels, a braking force is generated on the four wheels without changing the braking force difference between the turning inner wheel and the turning outer wheel (state Cv2 in FIG. 5).

  At this time, the braking force FB3 for preventing the wheel from slipping is in a state where no braking force is applied, a state where the braking force is applied only to the front and rear wheels inside the turn, and a braking force is applied to all the wheels. In any of the states that have been set, it is added according to the slip state of the vehicle. When the braking force FB3 for preventing the slip of the wheel is applied, the transfer clutch 15 is brought into a substantially directly connected state, and the differential rotation between the front and rear shafts is suppressed to surely prevent the slip. ing.

  Then, as shown in the above formulas (10) to (13), the braking force applied to the left front wheel and the braking force applied to the right front wheel and the braking force on the side of the larger braking force on the front wheel and rear wheel The brake fluid pressure is set to the same value (that is, PBfi = PBri or PBfo = PBro) (in this embodiment, the braking force applied to the left front and rear wheels and the right front and rear The brake fluid pressure on the front and rear wheels on the side of the smaller braking force applied to the wheel is also set to the same value). For this reason, in the brake drive part 32b comprised with a hydraulic unit as shown in FIG. 3, the pressure | voltage rise valve by the side of a high pressure wheel can be made into an open state, and the discharge pressure of the motor 45 can be controlled only by motor rotation speed. Therefore, it is possible to suppress the deterioration of vibration noise due to the operation of each valve of the brake drive unit 32b, drive system vibration, and the like.

Next, the vehicle behavior control program executed by the control unit 30 will be described with reference to the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) S101, necessary parameters such as four-wheel wheel speeds ωfl, ωfr, ωrl, ωrr, steering wheel angle θH, vehicle body lateral acceleration (d ² y / dt ² ), etc. Read the signal.

Next, the process proceeds to S102, where the target lateral acceleration calculation unit 30a calculates the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement, for example, by the above-described equation (1). To do.

Next, the process proceeds to S103, where the lateral acceleration deviation calculating unit 30b calculates the lateral acceleration deviation Δ (d ² y / dt ² ) by the above-described equation (2).

Next, the process proceeds to S104, where the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is larger than the preset first lateral acceleration deviation threshold e1 in the target yaw moment calculation unit 30c. (| Δ (d ² y / dt ² ) |> e1) and the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs, and the vehicle has an understeer tendency Therefore, it is determined that it is necessary to add a yaw moment in the turning direction to the vehicle, and this additional yaw moment is calculated as the first additional yaw moment Mzt1 by, for example, the above-described equation (3). If it is determined that the above condition is not satisfied and it is not necessary to add a yaw moment in the turning direction to the vehicle, the first additional yaw moment Mzt1 is set to zero.

Next, the process proceeds to S105, where the absolute value | Δ (d ² y / dt ² ) | of the lateral acceleration deviation is preset by the target yaw moment calculating unit 30c, and the second lateral acceleration deviation threshold e2 (> e1). Is larger than (| Δ (d ² y / dt ² ) |> e2), and the lateral acceleration deviation Δ (d ² y / dt ² ) and the steering wheel angle θH have different signs, the vehicle tends to be understeered. In the case of the condition, it is determined that it is necessary to add a yaw moment in the turning direction to the vehicle in addition to the first additional yaw moment Mzt1, and this additional yaw moment is set as the second additional yaw moment Mzt2, for example The calculation is performed according to the above equation (4). If the above condition is not satisfied and it can be determined that it is not necessary to add a yaw moment in the turning direction to the vehicle in addition to the first additional yaw moment Mzt1, the second additional yaw moment Mzt2 is set to 0. Set to.

  Next, proceeding to S106, the wheel speed difference calculation unit 30e between the left and right wheels calculates the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle, for example, by the above-described equation (7).

  Next, in S107, the wheel speed difference determining unit 30f between the left and right wheels compares the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle with a preset value e3. As a result of this comparison, when the absolute value | Δω | of the vehicle wheel speed difference (slip amount) between the left and right wheels of the vehicle is larger than e3 (when | Δω |> e3), the transfer clutch is transferred to the front-rear driving force distribution control unit 31a. A slip prevention control command signal is output to bring the transfer clutch 15 into a substantially directly connected state, and the process proceeds to S109. If | Δω | ≦ e3, the process directly proceeds to S109.

  When the process proceeds from S107 or S108 to S109, the first and second braking force calculation units 30d use the braking force applied to the turning inner wheel as the first braking force FB1 by the above-described equation (5), for example. calculate.

  Thereafter, the process proceeds to S110, and the first and second braking force calculation units 30d add to the vehicle without changing the braking force difference between the turning inner wheel and the turning outer wheel by, for example, the above-described equation (6). The braking force is calculated as the second braking force FB2.

  Next, in S111, when the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle is larger than e3 by the third braking force calculation unit 30g (when | Δω |> e3). For example, the slip correction value Δωd is calculated by the above equation (8). If | Δω |> e3 is not satisfied, the slip correction value Δωd is set to zero.

  Then, based on the slip correction value Δωd calculated (set) by the wheel speed difference determining unit 30f between the left and right wheels, for example, according to the above equation (9), the distance between the left and right wheels (between the turning inner wheel and the turning outer wheel). ) Is corrected as the third braking force FB3.

  Next, proceeding to S112, the braking force calculation unit 30h for each wheel uses the above-described equations (10) and (11) to determine the braking force of the turning outer wheel (braking force FBfo of the turning outer front wheel, braking force of the turning outer rear wheel). FBro), braking force of the turning inner wheel (braking force FBfi of the turning inner front wheel, braking force FBri of the turning inner rear wheel) is calculated.

  Next, the process proceeds to S113, where the brake fluid pressure calculation unit 30i of each wheel calculates the brake fluid pressure of each wheel (the turning outer front wheel brake fluid pressure PBfo, the turning inner front wheel brake fluid) according to the above equations (12) and (13). The pressure PBfi, the turning outer rear wheel brake fluid pressure PBro, and the turning inner rear wheel brake fluid pressure PBri) are calculated and output to the brake control unit 32a to exit the program.

Thus, according to the embodiment of the present invention, the target lateral acceleration (d ² y / dt ² ) t as the vehicle behavior that is the target of the vehicle lateral movement is calculated based on the vehicle speed V and the steering wheel angle θH, Based on the target lateral acceleration (d ² y / dt ² ) t and the actual lateral acceleration (d ² y / dt ² ), first and second additional yaw moments Mzt1 and Mzt2 to be added to the vehicle are calculated. First and second braking forces FB1 and FB2 are calculated based on the first and second additional yaw moments Mzt1 and Mzt2. Further, when the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle is calculated and the absolute value | Δω | of the wheel speed difference (slip amount) between the left and right wheels of the vehicle is larger than a preset value e3, A third braking force FB3 applied to the vehicle is calculated based on the wheel speed difference (slip amount) Δω between the left and right wheels of the vehicle. The braking force applied to each wheel based on the first, second and third braking forces FB1, FB2 and FB3 is applied to at least the braking force applied to the left front wheel and the braking force applied to the right front wheel. The brake fluid pressure of the front wheel and the rear wheel on the side of the braking force with the larger power is set to the same value, and is output to the brake control unit 32a. At this time, when the third braking force FB3 is output, the transfer clutch 15 is brought into a substantially directly connected state. For this reason, in the brake drive part 32b comprised with a hydraulic unit as shown in FIG. 3, the pressure | voltage rise valve by the side of a high pressure wheel can be made into an open state, and the discharge pressure of the motor 45 can be controlled only by motor rotation speed. Therefore, it is possible to suppress the deterioration of the vibration noise due to the operation of each valve of the brake drive unit 32b, the vibration of the drive system, etc., and to control the vehicle behavior using the brake without requiring any special measures or structural changes. It is possible to reduce the occurrence of vibration noise in the hydraulic system and drive system.

In the embodiment of the present invention, the target lateral acceleration (d ² y / dt ² ) t is used as the target vehicle behavior of the vehicle lateral motion, using the target target lateral acceleration (d ² y / dt ² ) t. The first additional yaw moment Mzt1 and the second additional yaw moment Mzt2 are calculated based on the actual lateral acceleration (d ² y / dt ² ). For example, the following equation (14) Thus, the target yaw rate γt is calculated, and based on the target yaw rate γt and the actual yaw rate γ (detected value from the yaw rate sensor), the yaw rate deviation Δγ is obtained to obtain the first additional yaw moment Mzt1 and the second additional yaw moment. Mzt2 may be calculated.
γt = (1 / (1 + A · V ² )) · (V / l) · (θH / n) (14)
Further, in the embodiment of the present invention, the first additional yaw moment Mzt1 is generated by applying the first braking force FB1 to the turning inner wheel. This is an example in which the braking force is set to 0. In addition, the first additional yaw moment is provided by providing a predetermined braking force difference between the braking force applied to the turning inner wheel and the braking force applied to the turning outer wheel. The same applies to the control for generating Mzt1.

  Furthermore, in the embodiment of the present invention, the first, second, and third braking forces FB1, FB2, and FB3 are calculated, and based on these first, second, and third braking forces FB1, FB2, and FB3. The braking force applied to each wheel is obtained. However, the present invention is not limited to this. For example, one of the first, second, and third braking forces FB1, FB2, FB3, or any two Needless to say, the present invention can also be applied to the case where the braking force applied to each wheel is obtained based on one braking force.

DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Transfer 14fl, 14fr, 14rl, 14rr Wheel 15 Transfer clutch 17fl, 17fr, 17rl, 17rr Wheel cylinder 21fl, 21fr, 21rl, 21rr Wheel speed sensor (operation state detection means)
22 Handle angle sensor (driving condition detection means)
23 Lateral acceleration sensor (driving state detection means)
30 Control unit (braking force calculation means, braking control means)
30a Target lateral acceleration calculating unit 30b Lateral acceleration deviation calculating unit 30c Target yaw moment calculating unit 30d First and second braking force calculating units 30e Left and right wheel speed difference calculating unit 30f Left and right wheel speed difference determining unit 30g Third Braking force calculation unit 30h Brake force calculation unit 30i Brake fluid pressure calculation unit 31a Front / rear driving force distribution control unit 31b Transfer clutch drive unit 32a Brake control unit 32b Brake drive unit

Claims (3)

Driving state detection means for detecting the driving state of the vehicle;
Braking force calculating means for calculating the braking force applied to the left and right front and rear wheels of the vehicle and the braking force applied to the right and left front and rear wheels, respectively, based on the driving state;
Brake control is performed by setting the brake fluid pressure of the front wheel and the rear wheel on the side of the larger braking force applied to the left front and rear wheels and the braking force applied to the right front and rear wheels to the same value. Braking control means ;
Front and rear driving force distribution control means capable of variably controlling the driving force distribution between the front and rear axes;
The braking force calculation means calculates a slip amount between the left and right wheels of the vehicle based on at least the driving state of the vehicle, and applies the braking force applied to the left and right wheels on the left side of the vehicle based on the slip amount and the right side of the vehicle. When the braking force to be applied to the front and rear wheels is set, and the braking force calculation means sets the braking force based on the slip amount and performs braking control by the braking control means, the longitudinal driving force distribution control means Is a vehicle behavior control device characterized in that the front and rear shafts are directly connected .   The braking force calculation means calculates a vehicle behavior that is a target of the vehicle lateral movement based on at least the driving state of the vehicle, detects an actual vehicle behavior of the vehicle lateral movement, Calculating a yaw moment to be added to the vehicle based on the vehicle behavior to be performed and the actual vehicle behavior of the vehicle lateral movement, and applying the braking force to the left and right front and rear wheels of the vehicle based on the additional yaw moment and the above 2. The vehicle behavior control device according to claim 1, wherein a braking force applied to each of the right and left front wheels is calculated. The braking control means equalizes the brake fluid pressure of the front wheel and the rear wheel on the side of the larger braking force applied to the left front wheel and the braking force applied to the right front wheel respectively. 2. The brake drive unit configured by a hydraulic unit that controls the discharge pressure of the motor only by the motor rotational speed is set and the booster valve on the high-pressure wheel side is opened, and braking control is performed. Item 3. The vehicle behavior control device according to Item 2.

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