JPH11115719A - Power distribution control device for four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stability of traveling at the time of cornering by efficiently and sufficiently controlling braking force in a four-wheel drive vehicle loaded with a braking force control device. SOLUTION: A braking force control device 40 calculates the differential value of a target yaw rate, the differential value of a predicted yaw rate of traveling on a low μ road, and deviation between both differential values, and also calculates deviation between the actual yaw rate and a target yaw rate, calculates target braking force based on these values, and applies the target braking force to a selected wheel so as to control the braking force. Each control parameter and existence of execution of braking force control are inputted to a power distribution control device 70, and controls a hydraulic multiple disc plate clutch 21 is controlled based on each signal so as to control the distribution of a torque. Here, when the braking force is applied to the selected wheel, by braking force control, the power distribution control device 70 is so arranged that it sets the crimping force of the hydraulic multiple disc plate clutch 21 to a weak predetermined value, thereby each wheel can be freely rotated, and the braking control in conformity with the target by the braking force control device 40 can be sufficiently performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power distribution control device for a four-wheel drive vehicle capable of controlling the braking force to improve the stability of the vehicle by applying a braking force to appropriate wheels when cornering the vehicle.

[0002]

2. Description of the Related Art In recent years, a braking force control device for improving vehicle stability by applying a braking force to an appropriate wheel during cornering has been developed due to the relationship between forces acting on the vehicle at the time of cornering of the vehicle and the like, and has been put into practical use. Is starting to be.

[0003] As such a braking force control device, for example, Japanese Patent Laid-Open Publication No. Hei 2-70561 discloses a braking force control device that performs control based on a rotational motion about a vertical axis passing through the center of gravity of a vehicle, that is, a yaw rate which is an angular velocity of yawing. A power control is shown. In this technique, a target yaw rate is compared with an actual yaw rate (actual yaw rate) to determine whether the vehicle motion state is understeer or oversteer with respect to the target yaw rate, so that the actual yaw rate matches the target yaw rate. In the case of an understeering tendency, a braking force is applied to the inner wheels to correct the same, and in the case of an oversteering tendency, the braking force is corrected to the outer wheels to correct the running stability of the vehicle.

On the other hand, in a four-wheel drive vehicle, the differential between the front wheel side and the rear wheel side is appropriately restricted in order to effectively utilize the driving force from the engine and realize stable and excellent running performance. Various techniques relating to a power distribution control device capable of controlling the distribution of the driving force between the front wheel side and the rear wheel side while maintaining the same have been proposed.

[0005] As the power distribution control device, there is generally known a power distribution control device for controlling the engagement of a variable driving force distribution clutch (transfer clutch) by a center differential device or the like used in a full-time four-wheel drive vehicle.

[0006]

By the way, the above-described braking force control device is applied to a four-wheel drive vehicle having the above-described power distribution control device, and each wheel is individually controlled to improve vehicle stability. When power is applied, if the transfer clutch is strong, the wheels are in a mechanically connected state, and the wheels cannot rotate freely, and the desired braking force is applied. Becomes difficult.

[0007] The present invention has been made in view of the above circumstances, and in mounting a braking force control device on a four-wheel drive vehicle,
It is an object of the present invention to provide a power distribution control device for a four-wheel drive vehicle capable of sufficiently performing the braking force control and improving running stability at the time of cornering of the vehicle.

[0008]

According to a first aspect of the present invention, there is provided a power distribution control apparatus for a four-wheel drive vehicle which calculates a braking force for controlling a vehicle behavior from a motion state of the vehicle. A power distribution control device for a four-wheel drive vehicle mounted on a vehicle having braking force control means for selecting and applying braking control to the wheels to which the braking force is applied, and variably controlling the distribution of driving force between the front wheel side and the rear wheel side. When the braking force is applied to the wheels by the braking force control means, the driving force transmitted to the front wheel side or the rear wheel side is controlled to a value smaller than usual and the driving force is distributed.

According to a first aspect of the present invention, there is provided a power distribution control device for a four-wheel drive vehicle, wherein braking force control means calculates a braking force for controlling a vehicle behavior from a motion state of the vehicle and applies a wheel to which the braking force is added. Select and control braking. Then, when the braking force is applied to the wheels by the braking force control means, the driving force transmitted to the front wheel side or the rear wheel side is controlled to a value smaller than usual,
The driving force distribution control is performed so that the desired braking force can be obtained.

According to a second aspect of the present invention, there is provided a power distribution control apparatus for a four-wheel drive vehicle, wherein a braking force for controlling a vehicle behavior is calculated from a motion state of the vehicle to select a wheel to which the braking force is applied. A power distribution control device for a four-wheel drive vehicle mounted on a vehicle having braking force control means for performing braking control and variably controlling the distribution of driving force between the front wheel side and the rear wheel side. When the braking force is applied, the distribution of the driving force between the front wheel side and the rear wheel side is controlled using the load distribution of the vehicle weight applied to the front wheel side and the rear wheel side as a target value.

According to a second aspect of the present invention, there is provided a power distribution control device for a four-wheel drive vehicle, wherein a braking force controlling means calculates a braking force for controlling a vehicle behavior from a motion state of the vehicle and applies a wheel to which the braking force is added. Select and control braking. When the braking force is applied to the wheels by the braking force control means, the driving force distribution between the front wheel side and the rear wheel side is determined by setting the load distribution of the vehicle weight applied to the front wheel side and the rear wheel side to a target value. To control.
In other words, a differential limiting force that exhibits sufficient traction performance and steering stability as a four-wheel drive vehicle is set, and controllability with braking force control and four-wheel drive performance are optimally maintained.

Further, in the power distribution control apparatus for a four-wheel drive vehicle according to the present invention, a braking force for controlling a vehicle behavior is calculated from a motion state of the vehicle to select a wheel to which the braking force is applied. A power distribution control device for a four-wheel drive vehicle mounted on a vehicle having braking force control means for performing braking control and variably controlling the distribution of driving force between the front wheel side and the rear wheel side. When a braking force is applied, at least one of the driving force distribution on the front wheel side and the rear wheel side is changed and set in accordance with an increase or decrease in the turning performance of the braking control by the braking force control means.

According to a third aspect of the present invention, there is provided a power distribution control device for a four-wheel drive vehicle, wherein a braking force controlling means calculates a braking force for controlling a vehicle behavior from a motion state of the vehicle and applies a wheel to which the braking force is added. Select and control braking. Then, when the braking force is applied to the wheels by the braking force control means, at least one of the driving force on the front wheel side and the rear wheel side in accordance with an increase or decrease in the turning performance of the braking control by the braking force control means. By changing and setting the distribution, the effect of increasing or decreasing the turning performance of the braking control by the braking force control means can be efficiently obtained.

According to a fourth aspect of the present invention, there is provided a power distribution control apparatus for a four-wheel drive vehicle according to the third aspect, wherein the braking force control means controls the wheels. When the braking force control means increases the turning performance when applying power, the driving force distribution on the rear wheel side is changed and set in an increasing direction, and the braking force control means increases the turning performance. In such a case, the turning property is efficiently increased.

According to a fifth aspect of the present invention, there is provided a power distribution control device for a four-wheel drive vehicle according to the fourth aspect of the present invention. When the braking force control means increases the turning performance when adding power, the braking force control is performed by changing and setting the preset value to increase the rear wheel driving force distribution. When the means increases the turning property, the turning property is efficiently increased.

According to a sixth aspect of the present invention, there is provided a power distribution control device for a four-wheel drive vehicle according to the fourth aspect of the present invention, wherein the braking force control means controls the wheels. If the braking force control means increases the turning performance when adding power, the driving force distribution on the rear wheel side is changed and set in a direction to increase according to the deviation between the target yaw rate and the actual yaw rate. In this way, when the braking force control means increases the turning performance, the turning performance is efficiently increased.

According to a seventh aspect of the present invention, there is provided a power distribution control apparatus for a four-wheel drive vehicle according to the third or fourth aspect of the present invention, wherein the braking force control means is provided. When the braking force control means reduces the turning performance when applying the braking force to the wheels, the driving force distribution on the front wheel side is changed and set in an increasing direction. In the case where is decreased, the turning property is efficiently reduced.

In the power distribution control apparatus for a four-wheel drive vehicle according to the present invention, the braking force control means controls the wheels. When the braking force control means reduces the turning performance when adding power, the braking force control means is changed to a preset value for increasing the front wheel side driving force distribution and set. In the case where decreases the turning property, the turning property is efficiently reduced.

Further, according to a ninth aspect of the present invention, there is provided a power distribution control apparatus for a four-wheel drive vehicle according to the seventh aspect of the present invention, wherein the braking force control means controls the wheels. When the braking force control means reduces the turning performance when adding power, the front wheel side driving force distribution is changed and set to increase in accordance with the deviation between the target yaw rate and the actual yaw rate. Then, when the braking force control means reduces the turning performance, the turning performance is efficiently reduced.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 8 show a first embodiment of the present invention.
FIG. 1 is an explanatory view showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device is applied, FIG. 2 is an explanatory view of an operation of a vehicle by braking force control, and FIG. 3 is an example of braking force control FIG. 4 is an explanatory diagram of the differential limiting force control, and FIG.
Is an explanatory diagram showing an example of the characteristic of the differential limiting torque, FIG. 6 is a flowchart of the braking force control, FIG. 7 is a flowchart continued from FIG. 6, and FIG. 8 is a flowchart of the power distribution control. The vehicle according to the first embodiment of the present invention will be described by taking a four-wheel drive vehicle having a compound planetary gear type center differential and an automatic transmission as an example.

In FIG. 1, reference numeral 1 denotes an engine disposed at the front part of the vehicle.
An automatic transmission (including a torque converter and the like) 2 behind the engine 1 to a transmission output shaft 2a
Is transmitted to the center differential device 3 through
While being input from the center differential device 3 to a rear wheel final reduction gear 7 via a rear drive shaft 4, a propeller shaft 5, and a drive pinion shaft 6, a transfer drive gear 8, a transfer driven gear 9,
It is configured to be input to the front wheel final reduction gear 11 via a front drive shaft 10 serving as a drive pinion shaft portion. Here, the automatic transmission 2, the center differential 3, the front wheel final reduction gear 11, and the like are integrally provided in a 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
The signal 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 above-mentioned center differential device 3
Has a first sun gear 15 having a large diameter formed on the transmission output shaft 2a on the input side, and the first sun gear 15 meshes with a first pinion 16 having a small diameter to form a first sun gear.
Gear train is formed.

The rear drive shaft 4 for outputting power to the rear wheels is formed with a second sun gear 17 having a small diameter, and the second sun gear 17 is connected to the second pinion 1 having a large diameter.
8 and a second gear train is formed.

The first pinion 16 and the second pinion 18 are formed integrally with a pinion member 19,
A plurality (for example, three) of the pinion members 19 are rotatably supported on a fixed shaft provided on the carrier 20.

The transfer drive gear 8 is connected to the front end of the carrier 20, so that output to the front wheels is performed.

The transmission output shaft 2a is rotatably inserted into the carrier 20 from the front, and the rear drive shaft 4 is rotatably inserted from the rear. The sun gear 15 and the second sun gear 17 are stored. The first pinions 16 of the plurality of pinion members 19 correspond to the first pinions.
The second pinion 18 is meshed with the second sun gear 17.

Thus, the first sun gear 1 on the input side
5 through the first and second pinions 16 and 18 and the second sun gear 17 to one output side and the other through the carrier 20 of the first and second pinions 16 and 18. And a composite planetary gear without a ring gear.

The compound planetary gear type center differential device 3 comprises the first and second sun gears 15 and 17 and a plurality of the first and second pinions 1 arranged around the sun gears 15 and 17.
The differential function is provided by appropriately setting the number of teeth 6 and 18.

Further, the first and second sun gears 15, 1
The reference torque distribution is set to a desired distribution (for example, unequal torque distribution with rear wheel biased) by appropriately setting the meshing pitch radius between the first and second pinions 16 and 18 and the first and second pinions 16 and 18.
It is possible to be.

Further, the center differential device 3 is configured such that the first and second sun gears 15 and 17 and the first and second pinions 16 and 18 are, for example, helical gears, and the first gear train The friction torque generated at both ends of the pinion member 19 by remaining the thrust load without canceling the thrust load by changing the torsion angle of the second gear train and the first and second pinions 16, 18 And the surface of the fixed shaft provided on the carrier 20 is engaged so that the combined force of separation and tangential load acts on the surface to generate a friction torque so that a differential limiting torque proportional to the input torque can be obtained. Thus, the differential limiting function can be obtained by the center differential device 3 itself.

The two output members of the center differential device 3, namely, the carrier 20 and the second output member
A hydraulic multi-plate clutch 21 as a variable driving force distribution clutch controlled by a power distribution control device 70 is formed between the sun gear 17 and the sun gear 17.

In the hydraulic multi-plate clutch 21, a plurality of driven plates 21a are provided on the rear drive shaft 4 side integral with the second sun gear 17, and a plurality of drive plates 21b are alternately stacked on the carrier 20 side. Is provided. The power distribution control device 70 is controlled by a piston, a pressing plate, and the like disposed on the case 12 side.
Is operated by being pressed by the hydraulic pressure of a hydraulic chamber (above, not shown in relation to the pressing parts of the hydraulic multi-plate clutch 21) connected to the hydraulic device controlled by.

Therefore, when the hydraulic multi-plate clutch 21 is released, the torque distribution by the center differential device 3 is output as it is, but when the hydraulic multi-plate clutch 21 is completely pressed, the torque distribution is stopped. , And becomes a directly connected state.

The pressing force (engaging force) of the hydraulic multi-plate clutch 21 is controlled by the power distribution control device 70. For example, if the reference torque distribution is 35:65 before and after the rear wheel is biased, the front and rear 35:65 A torque distribution control (power distribution control) is performed between torque distributions obtained in the front-rear direct connection state, for example, 50:50.

Reference numeral 25 denotes a brake drive unit of the vehicle.
The brake drive unit 25 includes a master cylinder 2 connected to a brake pedal 26 operated by a driver.
7 is connected, and the driver operates the brake pedal 2
6 is operated by the master cylinder 27, through the brake drive unit 25, and the four wheels 14fl, 14fr, 1
4rl, 14rr wheel cylinders (front left wheel cylinder 28fl, front right wheel cylinder 28fr, rear left wheel cylinder 28rl, rear right wheel cylinder 28
A brake pressure is introduced to rr), whereby the four wheels are braked and braked.

The brake drive unit 25 is a hydraulic unit provided with a pressurizing source, a pressure reducing valve, a pressure increasing valve, and the like. Each of the wheel cylinders 28fl and 28f is operated in accordance with an input signal.
r, 28rl, and 28rr are formed so as to be capable of independently introducing a brake pressure.

Each of the wheels 14fl, 14fr, 14rl, 14
rr is such that each wheel speed is detected by a wheel speed sensor (left front wheel speed sensor 29fl, right front wheel speed sensor 29fr, left rear wheel speed sensor 29rl, right rear wheel speed sensor 29rr). Also, on the steering wheel of the vehicle,
A steering wheel angle sensor 30 for detecting a rotation angle of the steering wheel is provided.

The vehicle is provided with a yaw rate sensor 31, and the wheel speed sensors 29fl, 29fr, 29rl,
29rr, the steering wheel angle sensor 30 and the yaw rate sensor 31 are connected to a braking force control device 40, and the braking force control device 40
A braking force control means for calculating a braking force for setting the running posture of the vehicle to a target posture from the motion state of the vehicle, selecting a wheel to which the braking force is applied, and performing braking control. Make up.

In the braking force control device 40, FIGS.
The braking force control is performed according to the flowchart shown in FIG. The braking force control program is executed, for example, every predetermined time (for example, 10 ms) while the vehicle is running.

When the program starts, in step (hereinafter abbreviated as S) 101, the steering wheel angle θ, the wheel speed sensors 29fl, 29fr,
The wheel speeds ω1, ω2, ω3, ω4 and the actual yaw rate γ from the yaw rate sensor 31 are read from 29rl and 29rr, respectively, and S1
Go to 02.

In S102, the steering angle θ is divided by the steering gear ratio N to calculate the actual steering angle δf (= θ / N), and the signals of the wheel speeds ω1, ω2, ω3, ω4 are set in advance. The vehicle speed V is calculated by using a formula that has been set (for example, by calculating an average value).

Next, in S103, the target yaw rate steady-state gain Gγδf (0) is calculated by the following equation (1), and the predicted yaw rate steady-state gain Gγδf (0) LOW is calculated by the following equation (3). Is calculated.

The target yaw rate steady-state gain Gγδf
(0) is the value of the yaw rate with respect to the actual steering angle δf at the time of steady circular turning of the vehicle. Assuming that the wheelbase is L and the stability factor determined by the specifications of the vehicle is A0, the target yaw rate steady gain Gγδf (0) is It is calculated by the following equation. Gγδf (0) = 1 / (1 + A0 · V ² ) · V / L (1) Further, the stability factor A0 is represented by m, the vehicle mass, the distance between the front shaft and the center of gravity Lf, and the distance between the rear shaft and the center of gravity. Is Lr, the front equivalent cornering power is CPf, and the rear equivalent cornering power is CPr. A0 = {- m · (Lf · CPf -Lr · CPr)} / (2 · L 2 · CPf · CPr) ... (2) the prediction yaw rate constant gain G.gamma..delta.f (0) LOW is
If the stability factor on low μ road running determined by the specifications of the vehicle is A0LOW, which is the value of the yaw rate with respect to the actual steering angle δf at the time of steady circular turning of the vehicle predicted on low μ road running,
The predicted yaw rate steady-state gain Gγδf (0) LOW is calculated by the following equation. Gγδf (0) LOW = 1 / (1 + A0LOW · V ² ) · V / L (3) The low μ road stability factor A0LOW is low μ
When the front equivalent cornering power on a road is CPfLOW and the rear equivalent cornering power on a low μ road is CPrLOW, the following equation is obtained. A0LOW = {- m · (Lf · CPfLOW-Lr · CPrLOW)} / (2 · L 2 · CPfLOW · CPrLOW) ... (4) In addition, the processing proceeds to S104, and the actual steering angle delta] f, the target yaw rate constant was calculated Based on the gain Gγδf (0), the target yaw rate γ ′ is calculated in consideration of the response delay of the vehicle, and based on the actual steering angle δf and the calculated predicted yaw rate steady-state gain Gγδf (0) LOW, The predicted yaw rate γ′LOW on the low μ road is calculated in consideration of the response delay.

The above-mentioned target yaw rate γ ′ is calculated as follows: γ ′ = 1 / (1 + T · s) · Gγδf (0) · δf (5), where T is the time constant and s is the Laplace operator. The above equation (5) is an equation in which the response delay of the vehicle expressed by the secondary system is approximated to that of the primary system, and T is a time constant, for example, obtained by the following equation. T = (m · Lf · V) / (2 · L · CPr) (6) The calculation of the predicted yaw rate γ′LOW on the low μ road is performed by setting the time constant to TLOW, and γ′LOW = 1 / (1 + TLOW s) · Gγδf (0) LOW · δf (7) The above equation (7) is an equation in which the response delay of the vehicle expressed by the secondary system is approximated to the primary system, and the time constant T
LOW is obtained, for example, by the following equation. TLOW = m · Lf · V / (2 · L · CPrLOW) (8) Then, when the process proceeds to S105, the differential value (target yaw rate differential value) Sγ ′ of the target yaw rate γ ′ and the predicted yaw rate γ′LOW Differential value (predicted yaw rate differential value) S
γ'LOW is calculated, and the process proceeds to S106.

In step S106, the deviation dΔγ (= Sγ′LOW−Sγ ′) between the target yaw rate differential value Sγ ′ and the predicted yaw rate differential value Sγ′LOW, and the yaw rate deviation Δ
γ (= γ−γ ′) is calculated.

Thereafter, the flow advances to S107, and the following (9),
From the equation (10), the first target hydraulic pressures BF1f, BF1r
(First front wheel target hydraulic pressure BF1f, first rear wheel target hydraulic pressure B
F1r) is calculated, and the following (11), (1)
From the equation (2), the second target hydraulic pressures BF2f and BF2r (the second front wheel target hydraulic pressure BF2f, the second rear wheel target hydraulic pressure BF2
r) is calculated.

The first target hydraulic pressures BF1f, BF1r
Is calculated in consideration of the vehicle specifications based on the yaw rate differential deviation dΔγ. BF1f = G1 · | dΔγ | · Iz / (df / 2) (9) BF1r = G1 · G2 · | dΔγ | Iz / (dr / 2) (10) where G1 (for example, 0.05) and G2 (for example, 0.15) are gains, Iz is the yaw moment of inertia of the vehicle, df is the front tread, and dr is Shows the rear tread. In the above equation (9), G1 is a first large gain, and dΔγ · Iz / (df / 2) indicates a portion as a theoretical braking force of the first front wheel. In the above equation (10), G1 · G2 is the first small gain, and dΔγ · Iz / (dr / 2) indicates a portion as the theoretical braking force of the first rear wheel. This is to prevent the rear wheels from skidding and losing stability due to the braking force of the rear wheels, especially on low μ roads, or
When the braking force is applied to the rear wheel, the first rear wheel target hydraulic pressure BF1r is calculated based on the theory of the first rear wheel in order to prevent the turning moment from feeling strong and unstable against the driver's intention. The braking force is multiplied by the first small gain to obtain a smaller value.

As described above, the yaw rate differential deviation dΔγ
Target hydraulic pressures BF1f, BF1r calculated based on
Is a value virtually obtained when traveling on a low μ road. Here, the low μ road running conditions were imagined by the low μ road.
This is because braking force control is required as the vehicle travels on the road. Each constant on the low μ road used in each of the above equations is obtained in advance by experimental data using a vehicle model or a well-known theoretical calculation.

The second target hydraulic pressures BF2f, BF2
2r, taking into account the vehicle specifications, is calculated on the basis of the motion state and the yaw rate deviation of the vehicle, BF2f = G3 · (ΔA · 4 · L 2 · CPf · CPr · V) / {(CPf + CPr) / df} · | γ | ... ( 11) BF2r = G3 · G4 · (ΔA · 4 · L 2 · CPf · CPr · V) / {(CPf + CPr) / dr} · | γ | ... (12) here, G3 (eg, 8.0) and G4 (eg,
0.15) indicates a gain, and ΔA is as follows: ΔA = {δf / (Gγδf (0) · δf + Δγ) −1 / Gγδf (0)} / (LV) (13) Note that Δγ in the above equation (13) may be corrected in consideration of the side slip angle β which is an angle between the traveling direction of the vehicle and the front-back direction.

The gains G3 and G4 are equal to the gain G1.
, G2 are set for the same reason as in (1) above.
In equation (1), G3 is the second large gain,
The other part shows the part as the theoretical braking force of the second front wheel. In the above equation (12), G3 · G4
Represents a second small gain, and the other portion represents a portion as a theoretical braking force of the second rear wheel. That is,
The magnitudes of the braking force applied to the rear wheels are also suppressed by the above equations (11) and (12). For this reason, the braking force of the rear wheels is suppressed finely by setting the gains G1 to G4, thereby realizing the natural behavior of the vehicle and improving the running stability.

At S108, the first target hydraulic pressures BF1f, BF1r and the second target hydraulic pressure BF1r
2f and BF2r are added to calculate final target braking forces (final target hydraulic pressures) BFf and BFr. BFf = BF1f + BF2f (14) BFr = BF1r + BF2r (15) That is, the braking force control device 40 predicts that the traveling condition when performing control is traveling on a low μ road, and compensates for the control delay. To improve tracking and response. Here, the differential calculation used for compensation does not use the actual yaw rate signal,
Since the correction is performed using the value of the vehicle model set in advance, it is possible to perform the compensation with a sufficient size and high accuracy.

In the following, S109 to S119 are steps for discriminating the braking wheels in the braking force control device 40. The signs of the actual yaw rate γ and the target yaw rate γ 'are both + for the left turning direction of the vehicle and + for the right turning direction. First, in S109, it is determined whether or not the actual yaw rate γ is larger than ε (a positive number close to substantially zero obtained in advance by experiment or calculation), that is, whether or not the vehicle is in a leftward turning state to some extent. Is determined, and when the actual yaw rate γ is equal to or smaller than ε,
Proceeding to S110, it is determined whether or not the actual yaw rate γ is smaller than -ε, that is, whether or not the vehicle is in a rightward turning state that is somewhat large.

In the above-mentioned S110, the range of the actual yaw rate γ (ε ≧ γ
.Gtoreq .-. Epsilon.), The motion state is a substantially linear motion state.
Proceeding to 119, no braking wheel is selected and no braking is performed. That is, in the case of straight traveling in FIG. 2, the rear wheel braking selection flag Fvr indicating whether or not the braking control of the rear wheel is selected is cleared (Fvr ← 0).

If it is determined in step S109 that γ> ε and that the vehicle is turning to the left in a relatively large state, the process proceeds to step S111, where ε is determined.
Assuming that .DELTA..gamma. Is a positive number close to approximately 0 obtained in advance by experiments or calculations, it is determined whether or not the yaw rate deviation .DELTA..gamma. Is close to 0 when | .DELTA..gamma..ltoreq..epsilon..DELTA..gamma.

In step S111, | Δγ | ≦ εΔ
γ, and if it is determined that the vehicle is substantially in neutral steer, S11
In other cases (understeer tendency or oversteer tendency), the flow proceeds to S112.

The step S112 is a step of judging whether the vehicle is understeer or oversteer.
It is determined whether <−εΔγ or Δγ> εΔγ, and Δγ <
If the sign of the yaw rate deviation Δγ is negative and different from the sign of the actual yaw rate γ, the target yaw rate γ ′
Is determined to be an understeer tendency, the process proceeds to S113, Δγ> εΔγ, and the sign of the yaw rate deviation Δγ is
If the sign is the same as the sign of the actual yaw rate γ, it is determined that the target yaw rate γ ′ has an oversteer tendency, and S114
Proceed to.

In step S113, in the case 1 of FIG. 2, the left rear wheel 14rl is selected as a braking wheel to be braked by the rear wheel final target hydraulic pressure BFr determined in step S108 (left rear wheel fluid). The pressure BRL = BFr), and the rear wheel braking selection flag Fvr is set (Fvr ← 1).

In step S114, in the case 2 of FIG. 2, the right front wheel 14fr is selected as a braking wheel to be braked by the front wheel final target hydraulic pressure BFf obtained in S108 (right front wheel hydraulic pressure). BFR = BFf), the rear wheel braking selection flag Fvr is cleared (Fvr ← 0).

On the other hand, if it is determined in step S110 that γ <−ε and that the vehicle is turning right to some extent, the process proceeds to step S115.
The yaw rate deviation Δγ is close to 0 when | Δγ | ≦ εΔγ, and it is determined whether or not the vehicle is substantially in neutral steer.

Then, in step S115, | Δγ | ≦ εΔ
γ, and if it is determined that the vehicle is substantially in neutral steer, S11
In other cases (understeer tendency or oversteer tendency), the flow proceeds to S116.

This step S116 is a step of determining whether the vehicle is understeer or oversteer.
> ΕΔγ or Δγ <−εΔγ, and Δγ>
If it is εΔγ and the sign of the yaw rate deviation Δγ is different from the sign of the actual yaw rate γ, it is determined that the target yaw rate γ ′ has an understeer tendency, and the flow proceeds to S117.
If Δγ <−εΔγ and the sign of the yaw rate deviation Δγ is the same negative as the sign of the actual yaw rate γ, it is determined that the target yaw rate γ ′ has an oversteer tendency, and the flow proceeds to S118.

Proceeding to S117, in case 4 of FIG. 2, the right rear wheel 14rr is selected as a braking wheel to be braked by the rear wheel final target hydraulic pressure BFr determined in S108 (right rear wheel fluid). The pressure BRR = BFr), and the rear wheel braking selection flag Fvr is set (Fvr ← 1).

In step S118, in the case 3 of FIG. 2, the left front wheel 14fl is selected as a braking wheel to be braked with the front target final hydraulic pressure BFf obtained in step S108 (left front wheel hydraulic pressure). BFL = BFf), the rear wheel braking selection flag Fvr is cleared (Fvr ← 0).

Further, when the process proceeds from S110, S111 or S115 to S119, in case 5 of FIG. 2, no braking wheel is selected and no braking is performed, and the rear wheel braking selection flag Fvr is cleared. (Fv
r ← 0).

That is, in S109 to S119 described above,
In the range of the actual yaw rate γ and the yaw rate deviation Δγ other than when the vehicle is traveling substantially straight and in the state of approximately neutral steer, when increasing the turning performance of the vehicle in an understeer state where the signs of the actual yaw rate γ and the yaw rate deviation Δγ are different. Selects the inner rear wheel as the braking wheel, and selects the outer front wheel as the braking wheel when reducing the turning performance of the vehicle when the actual yaw rate γ and the sign of the yaw rate deviation Δγ are the same oversteer. I have.

Then, the above-mentioned S113 or S117
If the process with the tendency to understeer (the selection of the braking wheel and the setting of the hydraulic pressure) is performed, the process proceeds to S120, and the process proceeds to S1.
If the processing in the oversteer tendency (selection of the braking wheel and setting of the hydraulic pressure) is performed in S14 or S118, S1
Then, the process proceeds to S122 from S119.

At S113 or S117, the process for the understeer tendency (selection of the brake wheels and setting of the hydraulic pressure) is performed. At S120, the understeer state passage flag FUS is set (FUS ← 1), and S126 is performed. Proceed to.

The understeer state passage flag FUS
Is a flag indicating that the vehicle has been operated with an understeer tendency, and is cleared when a threshold setting timer or a neutral steer tendency is changed from an oversteer tendency (F).
US ← 0).

In step S114 or S118,
After performing the process (selection of the braking wheel and setting the hydraulic pressure) in the oversteer tendency and proceeding to S121, it is determined whether or not the understeer state passage flag FUS is set (FUS = 1), and the understeer state is determined. If the passage flag FUS is set and it is determined that the vehicle has been understeering, the process proceeds to S123. If the understeer passage flag FUS is cleared, the process jumps to S126. In general, the vehicle goes through an understeer tendency before the vehicle enters the oversteer tendency. Therefore, when the vehicle shifts from the understeer tendency to the oversteer tendency, the understeer state passage flag FUS is set, and the above S121 is set. With this, the process proceeds to S123. However, the understeer state passage flag FUS
Is cleared by the threshold setting timer,
If the oversteer tendency is not caused by the understeer tendency for some reason, the process jumps to S126 without performing the steps S123 to S125.

In the above S121, it is determined that FUS = 1 and S1
23, the timer start flag FTR is cleared (F
TR = 0) is determined. The timer start flag FTR is a flag that is set (FTR ← 1) when the threshold setting timer is started, and is cleared (FTR ← 0) when the threshold setting timer stops.

At S123, the timer start flag F
If it is determined that TR is cleared (FTR = 0) and the threshold setting timer is stopped, the process proceeds to S124 to start the threshold setting timer, and the threshold setting timer is started and the timer start flag F
TR is set, the flow proceeds to S125, and a second threshold value εΔS (a positive number obtained in advance by experiment or calculation and a value equal to or greater than the above εΔγ) is set as the determination threshold value εΔ, and the flow proceeds to S126.

If it is determined in step S123 that the timer start flag FTR is set (FTR = 1) and the threshold setting timer is operating, the process jumps to step S126.

In steps S120 and S121, the FUS
= 0, FTR = 1 in the determination in S123, and when the process proceeds from any of S125 to S126, the yaw rate deviation Δγ is compared with the determination threshold εΔ (comparison of absolute values), and the yaw rate deviation Δγ is set in the control region. In some cases (| Δγ |> ε
Δ) proceeds to S127, in which a signal is output from the braking force control device 40 to the brake driving unit 25, and a braking force control execution flag Fv indicating execution of braking force control.
s is set (Fvs ← 1). That is, S1
26, the braking force control execution flag Fvs is set for each of the following, and after passing from S113 to S120, the brake driving unit 25 applies hydraulic pressure to the wheel cylinder 28rl. A braking force corresponding to BRL = BFr is generated,
After the step S120 from the step S117, the brake drive unit 25 generates a braking force corresponding to the hydraulic pressure BRR = BFr on the wheel cylinder 28rr, and
After S121 from S14, the brake drive unit 25 applies the hydraulic pressure BFR =
When a braking force corresponding to BFf is generated, and after passing from S118 to S121, the brake driving unit 25 generates a braking force corresponding to the hydraulic pressure BFL = BFf on the wheel cylinder 28fl.

On the other hand, in S126, the yaw rate deviation Δγ
Is in the non-control region (| Δγ | ≦ εΔ), S12
Proceed to 8.

When the process proceeds from S119 to S122, the straight traveling / steady running state flag FNS indicating that the vehicle is in a substantially straight traveling state or a substantially neutral steer state is set (FNS ← 1), and the process proceeds to S128.

Then, the above S122 or S12
When the process proceeds from S6 to S128, the braking signal is not output, and the braking force control execution flag Fvs is cleared (Fv
s ← 0), the set hydraulic pressure is also cleared.

Thereafter, when the flow proceeds to S129, it is determined whether or not the timer start flag FTR is set (whether or not the threshold setting timer is operating).

If the timer start flag FTR is cleared in S129 and the threshold setting timer is not operating, the flow advances to S135 to clear the straight / steady running state flag FNS, exit from the program, and start the timer. If the flag FTR is set and the threshold setting timer is running, the process proceeds to S130, and it is determined whether a predetermined time has elapsed.

If it is determined in step S130 that the predetermined time has elapsed, the process proceeds to step S132, where the understeer state passage flag FUS is cleared. In step S133, a first threshold value εΔM is determined as a determination threshold value εΔ. , The second threshold value .epsilon..DELTA.S is set), the threshold setting timer is stopped in S134, the timer start flag FTR is cleared, and the straight traveling / steady running state flag FNS is cleared in S135. Through.

If it is determined in S130 that the predetermined time has not elapsed, the routine proceeds to S131, in which it is determined whether or not the straight traveling / steady running state flag FNS is set (FNS = 1).

Then, the straight / steady running state flag F
If NS has been cleared (FNS = 0), the program exits. If it has been set, the process proceeds to S132, the understeer state passage flag FUS is cleared, and a first threshold εΔM is set as a determination threshold εΔ in S133. And S13
In step 4, the threshold setting timer is stopped, the timer start flag FTR is cleared, and in step S135, the straight traveling / steady running state flag FNS is cleared and the program exits.

In other words, even before the threshold setting timer expires, if the vehicle is in the straight traveling / steady running state, the first threshold εΔM is set as the judgment threshold εΔ.

The result of the braking force control execution flag Fvs set by the braking force control device 40 is output to the power distribution control device 70.

FIG. 3 shows an example of the above-described control (particularly regarding the threshold value) of the braking force control device 40. This figure shows that t0
FIG. 3A shows a change in the target yaw rate γ 'and the actual yaw rate γ, and FIG. 3B shows a change in the yaw rate deviation Δγ. FIG. 3 (c) shows the setting of the straight / steady running state flag FNS in the control, FIG. 3 (d) shows the setting of the timer start flag FTR in the control, and FIG. 3 (e) shows the understeer state in the control. FIG. 3F shows the setting of the passage flag FUS, and FIG. 3F shows ON-OFF of the braking signal output. Here, since only the braking force control will be described, it is assumed that there is no influence by other control.

After t1, the actual yaw rate γ also increases following the gradually increasing target yaw rate γ ′, but the difference between the actual yaw rate γ and the target yaw rate γ ′ gradually increases, and the target yaw rate γ ′ from the actual yaw rate γ ′ increases. Difference,
That is, the yaw rate deviation Δγ is an absolute value | Δ in the negative direction.
γ | increases.

The absolute value | Δγ | of the yaw rate deviation Δγ is
From t2, the absolute value of the threshold value .epsilon..DELTA..DELTA..gamma. that determines the state of the substantially neutral steer becomes larger than the value .epsilon..epsilon..gamma., and the target yaw rate .gamma. 'tends to understeer. The straight traveling / steady running state flag FNS which has been set until t2 is cleared from t2. Further, a first threshold value εΔM is set as the determination threshold value εΔ (the range indicated by oblique lines in FIG. 3B) in the non-control area, and the yaw rate deviation Δ
The braking signal is not output until the absolute value | Δγ | of γ reaches t3, which is greater than the determination threshold εΔ.

Then, after t3, the yaw rate deviation Δ
Until the absolute value | Δγ | of γ reaches t4, which is smaller than the determination threshold value εΔ, the braking signal is output. The output of this braking signal is γ> ε (positive sign, left turn), Δ
γ <−εΔγ (negative sign, understeer tendency), which is the case of FIG. 2 (Case 1). In this case 1, the braking force is applied to the left rear wheel 4rl, the moment indicated by the arrow is added, and the drift is corrected. Eliminate the out. In this state, even if the left rear wheel 4rl tends to lock due to excessive braking on the left rear wheel 4rl and the lateral force is lost, the vehicle is in the oversteer direction, and the original control is performed. The yaw rate can be generated in the same direction (arrow direction) as the rule.

The actual yaw rate γ approaches the target yaw rate γ ', and during the period from t4 to t5, although the vehicle tends to understeer, the absolute value | Δγ | of the yaw rate deviation Δγ is smaller than the determination threshold value εΔ and becomes a non-control region. , No braking signal is output. During the period from t5 to t6, the absolute value | Δγ | of the yaw rate deviation Δγ becomes smaller than the threshold value εΔγ, and the vehicle enters a substantially neutral steer state.
The steady running state flag FNS is set.

When the absolute value | Δγ | of the yaw rate deviation Δγ increases in the + direction and elapses after t6 and the target yaw rate γ ′ tends to oversteer, the straight-line
The steady running state flag FNS is cleared, the timer start flag FTR is set, the threshold setting timer is operated,
In addition, a second threshold εΔS having an absolute value smaller than the first threshold εΔM is set as the determination threshold εΔ.

Thereafter, until t7, the yaw rate deviation Δγ
Is the absolute value | εΔ of the determination threshold εΔ.
| Because of the following values, no braking signal is output,
After t7, a braking signal is output. The output of this braking signal is γ> ε (positive sign, left turn), Δγ> εΔγ
(Positive sign, oversteer tendency) in the case (case 2) of FIG. 2, in which case the right front wheel 4fr
The braking force is applied to the, and the moment shown by the arrow is added to correct it, thereby eliminating spin. In this state, even when the right front wheel 4fr exerts excessive braking on the right front wheel 4fr and the right front wheel 4fr shows a tendency to lock, and the lateral force is lost, the vehicle is in the understeer direction, and is in the same direction as the original control law (arrow). direction)
Of yaw rate can be generated.

Then, from t8, the absolute value | Δγ | of the yaw rate deviation Δγ is smaller than the determination threshold value εΔ and becomes an uncontrolled area, and before the threshold setting timer times out, the absolute value | Δγ |
From which the vehicle enters a substantially neutral steer state.

Therefore, at t9, the straight traveling / steady running state flag FNS is set, the understeer state passing flag FUS is cleared, the threshold setting timer is stopped, and the timer start flag FTR is cleared. Also,
A first threshold εΔM is set as the determination threshold εΔ.

Thereafter, between t10 and t11, the absolute value | Δγ | of the yaw rate deviation Δγ is again changed from the threshold value ε
It becomes larger than Δγ, the straight traveling / steady running state flag FNS is cleared, the vehicle tends to understeer with respect to the target yaw rate γ ′, and the understeer state passage flag FUS is set.

Then, from t11, the yaw rate deviation Δγ
Is smaller than the threshold value εΔγ, and the vehicle is in a substantially neutral steer state (the straight traveling / steady running state flag FNS is also set), and the actual yaw rate γ has substantially the same value as the target yaw rate γ ′. Here, the understeer state passage flag FUS remains set, but in general, before the vehicle tends to oversteer,
This is not a problem because the vehicle is going understeer.

After t8, since the absolute value | Δγ | of the yaw rate deviation Δγ is smaller than the determination threshold value εΔ and is in the non-control region, no braking signal is output.

That is, the output determination unit 25 sets the time when the oversteer tendency is changed from the understeer tendency to the set time or when the control based on the oversteer tendency is terminated even if the set time has not elapsed. Since the second threshold value εΔS having an absolute value smaller than the first threshold value εΔM is set as the determination threshold value εΔ until the end of the control with the oversteering tendency,
The start of the control when the tendency to oversteer after the tendency to understeer becomes quicker (as shown by the two-dot chain line in FIG. 3, in the ordinary control that does not depend on the threshold, the tendency to oversteer after the tendency to understeer) Is started at time t7 '). Therefore, the actual yaw rate γ
The difference between the target yaw rate γ 'and the target yaw rate γ' does not increase after the tendency to oversteer, and the actual yaw rate can quickly converge to the target yaw rate γ '. It is possible to perform control. When shifting from the understeer tendency to the oversteer tendency, the non-control area is set large in the understeer tendency in which the braking force is controlled by the rear wheels, and the non-control area is set small in the oversteer tendency in which the braking force is controlled by the front wheels. Therefore, the braking force control by the rear wheels is suppressed. Further, the determination threshold ε
As Δ, the return from the second threshold value εΔS to the first threshold value εΔM is reliably performed by detecting the end of the control due to the timer and the oversteer tendency. Further, since the value of the braking force applied to the rear wheel is also a suppressed value, it is possible to prevent the rear wheel from skidding and losing stability due to the braking force of the rear wheel particularly on a low μ road or the like, It is also possible to prevent the turning moment from feeling strong and unstable against the driver's intention. Also, the turning direction of the vehicle is determined based on the actual yaw rate γ, and it is determined whether the running state is understeer or oversteer with respect to the target yaw rate γ ′ based on the actual yaw rate γ and the yaw rate deviation Δγ. By selecting the most appropriate wheel to be braked inside, drift-out and spin can be reliably prevented. That is,
Prevents increasing the spin by applying braking force to the rear wheels despite the tendency to spin, or increasing the drift-out by applying braking force to the front wheels despite the tendency to drift out it can. Further, even during counter-steering, it is possible to prevent a braking force from being applied to the wheels in the direction of increasing the spin.

On the other hand, reference numeral 50 denotes a transmission control device.
Controls such as lock-up control and line pressure control are performed. In the first embodiment of the present invention, the gear ratio i is output from the transmission control device 50 to the power distribution control device 70. ing.

Reference numeral 60 denotes an engine control unit.
2 performs fuel injection control, ignition timing control, air-fuel ratio control, supercharging pressure control, throttle opening control, and the like. In the first embodiment of the present invention, the engine control device 60 sends the throttle opening θth Is output to the power distribution control device 70.

The power distribution control device 70 determines the wheel speeds ω1, ω2, ω3, ω4 from the wheel speed sensors 29fl, 29fr, 29rl, 29rr, and the braking force control execution flag Fvs from the braking force control device 40. The gear ratio i is input from the transmission control device 50, and the throttle opening θth is input from the engine control device 60. Based on these signals, the hydraulic multiple disc clutch 21 is
, The torque distribution control (power distribution control) of the vehicle between 35:65 before and after 35:65, for example, 50:50, as described above.

Specifically, when the braking force control device 40 applies a braking force to a specific wheel, the braking force control device 40 applies a weak predetermined value CFT.
1 (the value set in advance by experiments, calculations, etc.) is set to the pressing force (fastening force) of the hydraulic multi-plate clutch 21, and the braking force control device 40 applies a force to a specific wheel. When the braking force is not applied, for example, the differential limiting torque by the hydraulic multi-plate clutch 21 is set in advance in a table map of the duty ratio using the throttle opening θth and the speed V as parameters as shown in FIG. Aside
Basically, a map value is searched for and controlled from the running state. In this case (when no braking force is applied to a specific wheel by the braking force control device 40), the torque distribution control includes normal control, start control, steering control, slip control, and the like, as shown in FIG. Be executed.

Mainly, in the above-described normal control, the table map is used for the normal control, and a total of five surfaces are provided at each of the first to fourth speeds and the reverse speeds, and the throttle opening θth is different between the low opening and the high vehicle speed regions. The dynamic limiting torque is controlled to a lower value to improve turning performance and fuel efficiency.

In the start control described above, in order to ensure easy and smooth start performance on a low μ road, when the vehicle speed is 0 km / h and the vehicle is determined to be in a straight running state, the throttle opening θth
The differential limiting torque is controlled to a value proportional to.

In the turning control, the front and rear wheel rotation ratio NR / NF (NR: rear wheel rotation speed, NF: front wheel rotation speed) is improved in the set vehicle speed range with respect to the normal control in order to improve the steering feeling in the low vehicle speed range. ) Is performed to reduce the differential limiting torque.

In the above-described slip control, in order to secure the maximum driving force and improve running stability, when the rear wheel or the front wheel slips over a set value, the differential limiting torque is controlled to a higher value than the normal control. doing.

The control of the power distribution control device 70 will be described with reference to the flowchart shown in FIG. This control program is executed, for example, at predetermined time intervals while the vehicle is traveling. First, in S201, the result of the braking force control execution flag Fvs is read from the braking force control device 40, and the process proceeds to S202, where the execution of the braking force control is performed. The flag Fvs is set (←
1) It is determined whether it has been cleared or cleared (← 0).

When the braking force control execution flag Fvs is set (← 1) in S202, the braking force control device 40 applies a braking force to a specific wheel.
Proceeding to S203, a weak predetermined value CFT1 is set as the engagement force of the hydraulic multiple disc clutch (transfer clutch) 21, and the process proceeds to S204 to perform transfer clutch control.

On the other hand, when the braking force control execution flag Fvs is cleared (← 0) in S202, it means that the braking force control device 40 has not applied braking force to a specific wheel. To the respective wheel speeds ω1, ω from the wheel speed sensors 29fl, 29fr, 29rl, 29rr.
2, ω3, ω4, the gear ratio i from the transmission control device 50, and the throttle opening θth from the engine control device 60 are read.

Then, the program proceeds to S206, in which the wheel speeds ω1, ω
The rear wheel speed NR, the front wheel speed NF, the front / rear wheel speed ratio NR / NF, and the vehicle speed V are calculated from 2, ω3, ω4, and the routine proceeds to S207, where the table map corresponding to the gear ratio i is set to the throttle opening θth and Based on the search using the speed V, the front-rear wheel rotation ratio NR / NF and the vehicle speed V are set as the engaging force of the transfer clutch 21 by normal control, starting control, turning control, slip control, and the like, and the process proceeds to S204. Control the transfer clutch.

That is, according to the first embodiment of the present invention, when the braking force control device 40 applies a braking force to a specific wheel, the pressing force of the hydraulic multiple disc clutch 21 is set to a weak predetermined value CFT1. Since the (fastening force) is set, the rotation of each wheel becomes free, and the braking control according to the target by the braking force control device 40 is sufficiently performed to improve the running stability at the time of cornering or the like of the vehicle. be able to.

Next, FIGS. 9 to 11 show a second embodiment of the present invention.
FIG. 9 is an explanatory diagram showing the overall schematic configuration of a four-wheel drive vehicle to which the power distribution control device is applied, FIG. 10 is an explanatory diagram showing the relationship between the rotational speed ratio and the torque ratio of the torque converter, and FIG. It is a flowchart of a control. In the second embodiment of the present invention, when the braking force control device applies the braking force to a specific wheel by the braking force control, the engagement force of the transfer clutch is not a weak constant value, but the front wheel side and the rear wheel side. In this case, the distribution of the driving force is controlled with the target load distribution being the load distribution applied to the front wheels and the rear wheels with respect to the total weight of the vehicle. The distribution of the contact load differs between when the vehicle is stopped or when traveling at a constant speed, and when the vehicle starts or decelerates.

For this reason, the vehicle is provided with a longitudinal acceleration sensor 81 for detecting the longitudinal acceleration Gx used as one parameter for calculating the distribution of the contact load between the front wheels and the rear wheels. Output to the device 80. The power distribution control device 80 receives the wheel speeds ω1, ω2, ω3, ω4 from the wheel speed sensors 29fl, 29fr, 29rl, 29rr.

Further, the power distribution control device 80 includes:
From the braking force control device 40, the braking force control execution flag Fv
As a result, the turbine speed Nt and the gear ratio i are input from the transmission control device 50, and the engine speed Ne, the engine output torque Te, and the throttle opening θth are input from the engine control device 60, and the signals are transmitted via the hydraulic circuit based on these signals. Pressure force (fastening force) of the hydraulic multi-plate clutch 21
, And torque distribution control (power distribution control) of the vehicle is performed.

In the power distribution control device 80 according to the second embodiment of the present invention, when no braking force is applied to a specific wheel by the braking force control device 40, the first embodiment of the present invention is performed.
Although the power distribution control described in the embodiment is performed, when the braking force control device 40 applies the braking force to a specific wheel, the driving force distribution between the front wheel side and the rear wheel side is set to the calculated ground contact load distribution. It is controlled as a value.

The control by the power distribution control device 80 will be described with reference to the flowchart shown in FIG. This control program is executed, for example, at predetermined time intervals while the vehicle is traveling. First, in step S301, the result of the braking force control execution flag Fvs is read from the braking force control device 40, and the process proceeds to step S302 to execute the braking force control execution. Flag Fvs is set (← 1)
It is determined whether the data has been cleared or cleared (← 0).

If the braking force control execution flag Fvs is set (← 1) in S302, it means that the braking force control device 40 applies a braking force to a specific wheel.
Proceeding to S303, the engine control device 60 sends the engine speed Ne and engine output torque Te, the transmission control device 50 gives the turbine speed Nt, the gear ratio i,
The longitudinal acceleration Gx is read from the longitudinal acceleration sensor 81.

Then, the program proceeds to S304, in which the engine speed Ne is determined.
And a rotational speed ratio e (= Nt / Ne) of the torque converter (torque converter) from the turbine speed Nt and the turbine rotational speed Nt, for example, as shown in FIG. The torque ratio t of the torque converter is set with reference to the map.

Next, the routine proceeds to S305, where the center differential input torque Ti is calculated based on the following equation (16).
Is calculated based on the following equation (17).
Is calculated. Ti = Te · t · i (16) Dw = (Mf−M · Gx · HI / WB) / (M · g) (17) Here, in the above equation (17), Mf is a front wheel at rest. load,
M is the vehicle mass, HI is the height of the center of gravity, WB is the wheel base, and g is the gravitational acceleration.

Then, the process proceeds to S306, where the transfer torque T is set so that the drive torque distribution ratio Dt becomes as follows.
t is determined and the transfer clutch engagement force is calculated and set. Here, the torque distribution ratio of the center differential device 3 is set as Dt0 (fixed value), so that Dt = (Ti ・ Dt0 + Tt) / Ti. That is, since Tt = (Dt−Dt0) · Ti (18), the drive torque distribution ratio Dt in the above equation (18) is made equal to the ground load distribution Dw of the front and rear shafts (Dt = Dw), and 18) Calculate the equation. Then, the process proceeds to S307, where the transfer clutch control is performed with the set value.

On the other hand, when the braking force control execution flag Fvs is cleared (← 0) in S302, it means that the braking force control device 40 has not applied braking force to a specific wheel. To the respective wheel speeds ω1, ω from the wheel speed sensors 29fl, 29fr, 29rl, 29rr.
2, ω3, ω4, the gear ratio i from the transmission control device 50, and the throttle opening θth from the engine control device 60 are read.

Next, the routine proceeds to S309, where the wheel speeds ω1, ω
The rear wheel rotation speed NR, the front wheel rotation speed NF, the front and rear wheel rotation ratio NR / NF, and the vehicle speed V are calculated from 2, ω3, ω4, and the routine proceeds to S310, where the table map corresponding to the gear ratio i is set to the throttle opening θth and On the basis of the search by the speed V, the engaging force of the transfer clutch 21 is set by the normal control, the starting control, the turning control, the slip control, and the like with the front and rear wheel rotation ratio NR / NF and the vehicle speed V, and the process proceeds to S307. Control the transfer clutch.

That is, according to the second embodiment of the present invention, when the braking force control device 40 applies a braking force to a specific wheel by the braking force control, the driving force distribution between the front wheel side and the rear wheel side is performed. Controlling the ground load distribution as the target value, and the differential limiting force is set to the minimum necessary differential limiting force that exhibits sufficient traction performance and steering stability as a four-wheel drive vehicle,
Braking force control device 40 while ensuring the performance of four-wheel drive
, The braking force control by the control is fully exerted, and both controllability improvements can be optimized.

Next, FIGS. 12 and 13 show a third embodiment of the present invention, and FIG.
FIG. 13 is an explanatory diagram showing a schematic configuration of the entire wheel drive vehicle, and FIG. 13 is a flowchart of power distribution control. In the third embodiment of the present invention, the braking force control means controls the wheels by using a four-wheel drive vehicle whose torque distribution ratio is closer to that of the rear wheels and whose characteristics when the transfer clutch is released are close to those of an FR vehicle. When the braking force control means increases the turning performance when applying power, the engagement force of the transfer clutch is set to a predetermined value to change the driving force distribution ratio on the rear wheel side while increasing the braking force. When the control means reduces the turning performance, the engagement force of the transfer clutch is set in the same manner as in the second embodiment of the present invention, and the braking force control and the differential limiting control are kept optimal.

Therefore, the power distribution control device 90 includes the longitudinal acceleration sensor 8 as in the second embodiment of the present invention.
1 to longitudinal acceleration Gx, wheel speed sensors 29fl, 29f
Wheel speeds ω1, ω2, ω3, ω4 are input from r, 29rl, and 29rr.

Further, the power distribution control device 90 includes, in addition to the result of the braking force control execution flag Fvs from the braking force control device 40, the result of the rear wheel braking selection flag Fvr described in the first embodiment of the present invention. Is input from the transmission control device 50, the turbine speed Nt, the gear ratio i,
The engine speed Ne, the engine output torque Te, and the throttle opening θth are input from the engine control device 60, and based on these signals, the pressing force (fastening force) of the hydraulic multi-plate clutch 21 is controlled via a hydraulic circuit, Vehicle torque distribution control (power distribution control) is performed.

The control by the power distribution control device 90 will be described with reference to the flowchart shown in FIG. This control program is executed, for example, every predetermined time while the vehicle is running. First, in S401, the result of the braking force control execution flag Fvs from the braking force control device 40 and the rear wheel braking selection flag Fvr
Is read, and the routine proceeds to S402, where it is determined whether the braking force control execution flag Fvs is set (← 1) or cleared (← 0).

When the braking force control execution flag Fvs is set (← 1) in S402, the braking force control device 40 applies a braking force to a specific wheel.
Further, the process proceeds to S403, and it is determined whether the rear wheel braking selection flag Fvr is set (← 1) or cleared (← 0).

In the above S403, the rear wheel braking selection flag Fvr
Is set (← 1), the vehicle tends to understeer, and the braking force control device 40 performs control in a direction to increase the turning performance, and the process proceeds to S404.
A weak predetermined value CFT2 is set as the engagement force of the hydraulic multiple disc clutch (transfer clutch) 21 so that the driving force distribution ratio on the rear wheel side is increased. Then, the process proceeds to S405 to perform transfer clutch control.

When the rear wheel braking selection flag Fvr is cleared (← 0) in S403, the vehicle tends to oversteer, and the braking force control device 40 controls in a direction to decrease the turning performance. Then, the process proceeds to S406, where the engine control device 60 sends the engine speed Ne, the engine output torque Te, and the transmission control device 5
From 0, the turbine rotational speed Nt, the gear ratio i, and the longitudinal acceleration Gx from the longitudinal acceleration sensor 81 are read.

Hereinafter, S3 in the second embodiment of the present invention will be described.
04, S305, and S306, the process proceeds to S407, the rotational speed ratio e of the torque converter is calculated from the engine speed Ne and the turbine speed Nt, the torque ratio t of the torque converter is set, and the process proceeds to S408. ), The center differential input torque Ti is calculated as
7) Calculate the load distribution Dw of the front-rear axis based on the equation
409, the transfer torque Tt is set so that the drive torque distribution ratio Dt becomes equal to the ground load distribution Dw of the front-rear shaft.
Is determined and the transfer clutch engagement force is calculated and set. Then, the process proceeds to S405, where the transfer clutch control is performed using the set value.

On the other hand, when the braking force control execution flag Fvs is cleared (← 0) in S402, it means that the braking force is not applied to a specific wheel by the braking force control device 40, and S410 To the respective wheel speeds ω1, ω from the wheel speed sensors 29fl, 29fr, 29rl, 29rr.
2, ω3, ω4, the gear ratio i from the transmission control device 50, and the throttle opening θth from the engine control device 60 are read.

Next, the routine proceeds to S411, where the wheel speeds ω1, ω
The rear wheel rotational speed NR, the front wheel rotational speed NF, the front and rear wheel rotational ratio NR / NF, and the vehicle speed V are calculated from 2, ω3, ω4, and the routine proceeds to S412, where the table map corresponding to the gear ratio i is represented by the throttle opening θth and On the basis of the search using the speed V, the fastening force of the transfer clutch 21 is set by the normal control, the start control, the turning control, the slip control, and the like based on the front and rear wheel rotation ratio NR / NF and the vehicle speed V, and the process proceeds to S405. Control the transfer clutch.

That is, if the engaging force of the transfer clutch is weakened during the braking force control operation, the driving force of the rear wheel increases, and the lateral driving force of the rear wheel decreases due to the increase of the driving force, and the spin force decreases. The tendency becomes stronger and the vehicle becomes unstable.

Particularly, when there is a strong tendency to oversteer,
In the case where this is solved by the braking force control, if the transfer clutch is weakened, the tendency of oversteer is increased, and the effect of the braking force control cannot be sufficiently obtained.

For this reason, in the braking force control, when the vehicle is turning in the direction of improving the turning performance (when the vehicle tends to understeer),
Although the transfer clutch engagement force is reduced, when the braking force control is controlled in a direction that reduces the turning performance (stable direction) (when the vehicle tends to oversteer), the reduction of the transfer clutch engagement force is prohibited. is there.

By performing such control, according to the third embodiment of the present invention, the effect of increasing or decreasing the turning performance of the braking force control means can be efficiently obtained.

Next, FIGS. 14 and 15 show a fourth embodiment of the present invention, and FIG. 14 shows a fourth embodiment to which the power distribution control device is applied.
FIG. 15 is an explanatory diagram showing an overall schematic configuration of a wheel drive vehicle, and FIG. 15 is a flowchart of power distribution control. In the fourth embodiment of the present invention, the torque distribution ratio between the front wheels and the rear wheels is 100: 0.
For example, when the transfer clutch is disengaged and the transfer clutch is disengaged, the characteristics when the transfer clutch is disengaged are taken as an example of a four-wheel drive vehicle of an FF vehicle. In the case where the means increases the turning performance, the engagement force of the transfer clutch is set in the same manner as in the second embodiment of the present invention to keep the braking force control and the differential limiting control optimal, while the braking force control means To reduce the turning performance, the engagement force of the transfer clutch is set to a predetermined value, and the driving force distribution ratio on the front wheel side is increased.

For this reason, in FIG. 14, in the wet multi-plate clutch 101 as a transfer clutch, a plurality of driven plates 101a are provided on the rear drive shaft 4 side, and a plurality of drive plates 101b are alternately stacked on the transfer drive gear 8 side. It is provided. The power distribution control device 100 performs a crimping (fastening) operation via a hydraulic circuit (not shown) so that the torque distribution ratio between the front wheels and the rear wheels can be varied from 100: 0 to, for example, 50:50.

In the power distribution control device 100, the longitudinal acceleration Gx and the wheel speed sensors 29fl, 29fr, 2
Wheel speeds ω1, ω2, ω3, ω4 are input from 9rl and 29rr.

Further, the power distribution control device 100 includes:
The result of the braking force control execution flag Fvs and the result of the rear wheel braking selection flag Fvr are input from the braking force control device 40, and the turbine speed N
t, gear ratio i, engine speed Ne from the engine control unit 60, engine output torque Te, throttle opening θth
Is input, and based on these signals, the pressing force (engaging force) of the wet-type multi-plate clutch 101 is controlled via a hydraulic circuit, and torque distribution control (power distribution control) of the vehicle is performed.

The control by the power distribution control device 100 is as follows.
This will be described with reference to the flowchart shown in FIG. This control program is executed, for example, every predetermined time while the vehicle is running. First, in step S501, the braking force control execution flag Fvs and the rear wheel braking selection flag Fvr are output from the braking force control device 40.
The program proceeds to S502, in which it is determined whether the braking force control execution flag Fvs is set (← 1) or cleared (← 0).

When the braking force control execution flag Fvs is set (← 1) in S502, the braking force control device 40 applies a braking force to a specific wheel.
The process further proceeds to S503, and it is determined whether the rear wheel braking selection flag Fvr is set (← 1) or cleared (← 0).

In step S503, the rear wheel braking selection flag Fvr is set.
Is cleared (← 0), the vehicle is in an oversteer tendency, and the braking force control device 40 controls the vehicle in a direction to decrease the turning performance, and the process proceeds to S504.
A weak predetermined value CFT3 is set as the engagement force of the wet multi-plate clutch (transfer clutch) 101 so that the driving force distribution ratio on the front wheel side is increased. Then, the process proceeds to S505 to perform transfer clutch control.

When the rear wheel braking selection flag Fvr is set (← 1) in S503, the vehicle tends to understeer, and the braking force control device 40 controls in a direction to increase the turning performance. Yes, the process proceeds to S506, where the engine control device 60 sends the engine speed Ne, the engine output torque Te, and the transmission control device 5
From 0, the turbine rotational speed Nt, the gear ratio i, and the longitudinal acceleration Gx from the longitudinal acceleration sensor 81 are read.

Hereinafter, S3 according to the second embodiment of the present invention will be described.
04, S305, and S306, the process proceeds to S507, the rotational speed ratio e of the torque converter is calculated from the engine speed Ne and the turbine speed Nt, the torque ratio t of the torque converter is set, and the process proceeds to S508. ), The center differential input torque Ti is calculated as
7) Calculate the load distribution Dw of the front-rear axis based on the equation
Proceeding to step 509, the transfer torque Tt is set such that the drive torque distribution ratio Dt is equal to the ground load distribution Dw of the front-rear shaft.
Is determined and the transfer clutch engagement force is calculated and set. Then, the process proceeds to S505, where the transfer clutch control is performed with the set value.

On the other hand, if the braking force control execution flag Fvs is cleared (← 0) in S502, it means that the braking force is not applied to a specific wheel by the braking force control device 40, and S510 To the respective wheel speeds ω1, ω from the wheel speed sensors 29fl, 29fr, 29rl, 29rr.
2, ω3, ω4, the gear ratio i from the transmission control device 50, and the throttle opening θth from the engine control device 60 are read.

Next, the program proceeds to S511, in which the wheel speeds ω1, ω
The rear wheel rotation speed NR, the front wheel rotation speed NF, the front and rear wheel rotation ratio NR / NF, and the vehicle speed V are calculated from 2,3, ω4, and the process proceeds to S512. Based on the search using the speed V, the transfer clutch 101 is controlled by the normal control, the start control, the turning control, the slip control, etc., based on the front / rear wheel rotation ratio NR / NF and the vehicle speed V.
And the process proceeds to S505 to perform the transfer clutch control.

That is, if the turning force of the transfer clutch is reduced while the turning performance is further enhanced during the braking force control operation, the driving force of the front wheels increases, and the vehicle tends to understeer.

For this reason, in the braking force control, when the vehicle is turning in the direction of improving the turning performance (understeer tendency),
A direction in which braking force control reduces turning performance, although a decrease in transfer clutch engagement force is prohibited (stable direction)
(When oversteering tends to occur)
The transfer clutch engagement force is reduced.

By performing such control, according to the fourth embodiment of the present invention, the effect of increasing or decreasing the turning performance of the braking force control means can be efficiently obtained.

The third embodiment of the present invention relates to a four-wheel drive vehicle having a rear-wheel drive base without a center differential device, and the fourth embodiment of the present invention relates to a four-wheel drive vehicle having a front wheel drive base without a center differential device. Each can be adapted to driving vehicles.

Next, FIGS. 16 and 17 show a fifth embodiment of the present invention. FIG.
FIG. 17 is an explanatory diagram showing a schematic configuration of the entire wheel drive vehicle, and FIG. 17 is a flowchart of power distribution control. In the fifth embodiment of the present invention, the characteristics of the four-wheel drive vehicle of the automatic transmission described in the third embodiment described above (when the torque distribution ratio is closer to the rear wheels and the transfer clutch is released, are close to those of the FR vehicle. For example, in the case of a four-wheel drive vehicle, the calculation of the setting of the transfer clutch engagement force in the power distribution control device is changed, and when the braking force control means increases the turning performance, the drive force distribution on the rear wheel side is changed. In the case where the braking force control means reduces the turning performance while changing and setting the preset value to be increased, the setting is changed to the preset value which increases the driving force distribution on the front wheel side. Thus, the braking force control and the differential limit control are kept optimal.

That is, as shown in FIG. 16, the power distribution control device 110 according to the fifth embodiment includes the wheel speed sensors (front left wheel speed sensor 29fl, front right wheel speed sensor 29fr, rear left wheel speed sensor 29rl). , Right rear wheel speed sensor 29rr) is connected, and the respective wheel speeds ω1, ω2, ω3, ω4 are input, and the steering wheel angle sensor 30, the yaw rate sensor 31
Is connected, and the steering angle θ and the actual yaw rate γ are input.

From the braking force control device 40, in addition to the result of the braking force control execution flag Fvs and the result of the rear wheel braking selection flag Fvr, the calculated yaw rate deviation Δγ
(= Γ−γ ′) is also input.

From the transmission control device 50, in addition to the turbine speed Nt and the gear ratio i, the range position Lposi (particularly, P (parking), N (neutral),
1st speed) is input, and from the engine control device 60,
The engine speed Ne, the engine output torque Te, and the throttle opening θth are input.

Further, the present vehicle is provided with a method disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 8-2274 by the present applicant, that is, based on the equation of motion of the lateral motion of the vehicle using the vehicle speed V, the steering wheel angle θ, and the yaw rate γ. The cornering power of the front and rear wheels is extended to the nonlinear region and estimated, and the road surface friction coefficient μ is determined based on the road surface condition based on the ratio of the estimated cornering power of the front and rear wheels to the equivalent cornering power of the front and rear wheels on a high μ road. A road friction coefficient estimating unit 113 to be estimated is provided, and the road friction coefficient μ estimated by the road friction coefficient estimating unit 113 is input to the power distribution control device 110.

Then, the power distribution control device 110
Based on each of the input signals, a basic clutch engagement force F to be described later is used.
Otb is calculated, and the transfer clutch engagement force is changed to the basic clutch engagement force FOtb (when no braking force is applied to a specific wheel) according to the operation state of the braking force control device 40,
A preset low engaging force FOCL (when the vehicle is understeer and the braking force control device 40 is controlled to increase the turning performance), and a preset high engaging force FOCH (vehicle (In the case where the braking force control device 40 performs control in a direction to reduce the turning performance), and the transfer clutch control is performed.

The calculation of the basic clutch engagement force FOtb will be described. First, an increase correction torque (steer control correction torque) FA1, which is set in accordance with the center differential input torque Ti, a throttle opening degree θth, and an actual yaw rate γ with respect to the base clutch torque VTDout0 which is made to respond to the road surface friction coefficient μ. And the correction torque TADy for adding / decreasing according to the yaw rate deviation Δγ, and the lateral acceleration correction torque VTDg for decreasing / correcting according to the estimated lateral acceleration. The control output torque VTDout is calculated.

That is, in order to prevent an excessive drift-out of the turning acceleration when traveling on a high μ road, the clutch torque (road friction) is determined according to the road friction coefficient μ by a map or an arithmetic expression set in advance by experiments, calculations, or the like. The smaller the coefficient μ, the smaller the value), and this is used as the base clutch torque VTDout0.

The steering control correction torque FA1 is for preventing a change in steering at the time of acceleration, and is set to a larger value in advance as the center differential input torque Ti increases in a map or the like corresponding to the center differential input torque Ti. It is something to keep.

Tack-in prevention control correction torque FA2
Is used to prevent head-in behavior when the accelerator is off.When the actual yaw rate γ and the front wheel speed are equal to or higher than a predetermined value and the throttle opening θth changes to zero, the front wheel is determined in advance using a map or the like corresponding to the front wheel speed. The value is set to a larger value as the vehicle speed increases.

The yaw rate feedback correction torque VTDy is for preventing understeer or oversteer of the vehicle, and the yaw rate deviation Δγ is previously determined.
Is set to a larger value as the yaw rate deviation Δγ becomes larger in a map or the like corresponding to. Note that a characteristic in which the gain for the yaw rate deviation Δγ differs between understeer and oversteer may be used.

The lateral acceleration correction torque VTDg is for preventing understeer near the limit of turning of the vehicle, and has a smaller value (base clutch torque VTDout0) as the lateral acceleration increases in advance in a map or the like corresponding to the lateral acceleration.
Is set so as to be greatly reduced).

The control output torque VTDout is corrected by the steering wheel angle θ to obtain a steering wheel angle sensitive clutch torque. Specifically, when the front wheel speed is low (for example, 30 km / h or less), the control output torque VTDou is increased with increasing the steering wheel angle θ in order to prevent the tight corner braking phenomenon.
reduce t. Further, when the front wheel speed is, for example, 50 km / h or more and the steering wheel angle θ is near neutral, the control output torque VTDout is set low for the purpose of improving fuel efficiency. The value finally obtained in this manner is used as the basic clutch engagement force FOtb.
That is.

The control by the power distribution control device 110 is as follows.
This will be described with reference to the flowchart shown in FIG. This control program is executed, for example, every predetermined time while the vehicle is running. First, in S601, each input value (each wheel speed ω1, ω2, ω
3, ω4, steering wheel angle θ, actual yaw rate γ, result of braking force control execution flag Fvs, rear wheel braking selection flag Fvr
As a result, the yaw rate deviation Δγ, the turbine speed Nt, the gear ratio i, the range position Lposi, the engine speed Ne, the engine output torque Te, the throttle opening θth, the operation signal of the traction control device 111, and the operation signal of the antilock brake control device 112 Read the operation signal and road friction coefficient μ),
Proceeding to S602, the above-described basic clutch engagement force FOtb is calculated.

Then, the program proceeds to S603, in which it is determined whether the braking force control execution flag Fvs is set (← 1) or cleared (← 0).
When vs is cleared (← 0), it means that there is no braking force applied to a specific wheel by the braking force control device 40, and the process proceeds to S604, in which the engagement force of the transfer clutch is directly applied to the engagement of the basic clutch. Set to force FOtb.

On the other hand, when the braking force control execution flag Fvs is set (← 1) in S603, it means that the braking force control device 40 applies a braking force to a specific wheel, and further proceeds to S605. The rear wheel braking selection flag F
It is determined whether vr is set (← 1) or cleared (← 0).

In step S605, the rear wheel braking selection flag Fvr is set.
Is cleared (← 0), the vehicle is in an oversteer tendency, and the braking force control device 40 performs control in a direction to decrease the turning performance. The process proceeds to S606, and the engagement force of the transfer clutch is set in advance. Set to the set higher fastening force FOCH.

When the rear wheel braking selection flag Fvr is set (← 1) in S605, the vehicle tends to understeer, and the braking force control device 40 controls in a direction to increase the turning performance. , S607, and sets the transfer clutch engagement force to a preset lower engagement force FOCL.

Then, the flow advances to S608, where S604 is used.
The transfer clutch control is performed based on the engagement force of any of the transfer clutches in S606 and S607. When the range position Lposi is in the P range or the N range, the transfer clutch engagement force is set to zero.

As described above, according to the fifth embodiment of the present invention, when the braking force control device increases the turning performance, the transfer clutch engagement force is reduced to a preset lower engagement force FOCL. When set, the driving force distribution on the rear wheel side is increased and the control to increase the turning performance is promoted, and when the braking force control device reduces the turning performance, the transfer clutch engagement force is set in advance. It is set to a higher fastening force FOCH and becomes a direct connection direction to increase stability. Therefore, the effect of increasing or decreasing the turning performance of the braking force control device can be efficiently obtained.

The transfer clutch engagement forces FOCL, FOCH set when the braking force control device is activated.
Is simply a fixed value, so that control can be simplified and responsiveness is good.

Next, FIGS. 18 and 19 show a sixth embodiment of the present invention, and FIG.
FIG. 19 is an explanatory diagram showing a schematic configuration of the entire wheel drive vehicle, and FIG. 19 is a flowchart of power distribution control. According to a sixth embodiment of the present invention, in the fifth embodiment, when the braking force control means increases the turning performance, the power distribution control device lowers the driving force distribution to increase the rear wheel side driving force distribution. When the braking force control means reduces the turning performance while changing and setting the set value FOCL and the basic clutch engagement force FOtb to lower values, the power distribution control device increases the front wheel side driving force distribution. The braking force control and the differential limit control are kept optimal by changing and setting the set value FOCH and the basic clutch engagement force FOtb to higher values as much as possible.

Therefore, as shown in FIG. 18, the power distribution control device 120 according to the sixth embodiment has the same input and output as the power distribution control device 110 according to the fifth embodiment, except for the control. I have.

As shown in FIG. 19, the power distribution control device 120 first reads each input value in S601, calculates the basic clutch engagement force FOtb in S602, and sets the braking force control execution flag Fvs in S603. If it has been cleared (← 0) (if no braking force is applied to a specific wheel by the braking force control device 40), the process proceeds to S604, where the transfer clutch engagement force is directly changed to the basic clutch engagement force FOtb. Set. In addition, S60
At 3, the braking force control execution flag Fvs is set (← 1).
If it is performed (when the braking force control device 40 applies a braking force to a specific wheel), the process further proceeds to S605, and the rear wheel braking selection flag Fvr is set (← 1) or cleared (← 0). ) Is determined. The above is the same as the fifth embodiment.

Thereafter, in step S605, the rear wheel braking selection flag Fvr is cleared (← 0) (when the vehicle has an oversteer tendency and the braking force control device 40 controls in a direction to decrease the turning performance). Proceeds to S701,
The basic clutch engagement force FOtb is compared with a higher set value FOCH. When the basic clutch engagement force FOtb is equal to or higher than the higher set value FOCH (FOtb ≧ FOCH), S7
In step 02, the transfer clutch engagement force is set to the basic clutch engagement force FOtb.

When the basic clutch engagement force FOtb is lower than the higher set value FOCH in S701 (FOtb
In the case of <FOCH), the process proceeds to S703, where the engagement force of the transfer clutch is set to a higher set value FOCH.

That is, according to S701 to S703, when the vehicle is in an oversteer tendency and the braking force control device 40 is controlled to decrease the turning performance, the basic clutch engagement force FOtb and the higher set value FOCH are calculated. A higher value is set as the transfer clutch engagement force.

On the other hand, when the rear wheel braking selection flag Fvr is set (← 1) in S605 (when the vehicle has an understeer tendency and the braking force control device 40 is controlled to increase the turning performance) The routine proceeds to S704, where the basic clutch engagement force FOtb is compared with a lower set value FOCL. If the basic clutch engagement force FOtb is equal to or less than the lower set value FOCL (FOtb ≦ FOCL), the process proceeds to S70.
Proceeding to 5, the engagement force of the transfer clutch is set to the basic clutch engagement force FOtb.

When the basic clutch engagement force FOtb is higher than the lower set value FOCL in S704 (FOtb
> FOCL), the process proceeds to S706, and the engagement force of the transfer clutch is set to a lower set value FOCL.

That is, according to the above S704 to S706, when the vehicle is understeer and the braking force control device 40 is controlled to increase the turning performance, the basic clutch engagement force FOtb and the lower set value FOCL are reduced. A low value is set as the transfer clutch engagement force.

Then, the flow advances to S608, where the above-mentioned S604,
The transfer clutch control is performed based on the engagement force of any one of S702, S703, S705, and S706.

As described above, according to the sixth embodiment of the present invention, in addition to the effect of the fifth embodiment, when the braking force control device increases the turning performance, a lower value is definitely obtained. If the braking force control device reduces the turning performance while prompting the control to increase the turning performance by being appropriately set, it is certain that a higher value will be appropriately set to increase the stability.

Next, FIGS. 20 and 21 show a seventh embodiment of the present invention. FIG.
FIG. 21 is an explanatory diagram showing a schematic configuration of the entire wheel drive vehicle, and FIG. 21 is a flowchart of power distribution control. According to a seventh embodiment of the present invention, when the braking force control means increases the turning performance in the fifth embodiment, the power distribution control device basically increases the rear wheel side driving force distribution. Clutch fastening force FOtb
On the other hand, when the braking force control means reduces the turning performance, the power distribution control device increases and corrects the basic clutch engagement force FOtb so as to increase the driving force distribution on the front wheel side. The differential limiting control is kept optimal.

Therefore, as shown in FIG. 20, the power distribution control device 130 according to the seventh embodiment has the same input and output as the power distribution control device 110 according to the fifth embodiment, except for the control. I have.

As shown in FIG. 21, the control by the power distribution control device 130 first reads each input value in S601, calculates the basic clutch engagement force FOtb in S602, and sets the braking force control execution flag Fvs in S603. If it has been cleared (← 0) (if no braking force is applied to a specific wheel by the braking force control device 40), the process proceeds to S604, where the transfer clutch engagement force is directly changed to the basic clutch engagement force FOtb. Set. In addition, S60
At 3, the braking force control execution flag Fvs is set (← 1).
If it is performed (when the braking force control device 40 applies a braking force to a specific wheel), the process further proceeds to S605, and the rear wheel braking selection flag Fvr is set (← 1) or cleared (← 0). ) Is determined. The above is the same as the fifth embodiment.

Thereafter, in step S605, the rear wheel braking selection flag Fvr is cleared (← 0) (when the vehicle has an oversteer tendency and the braking force control device 40 controls in a direction to decrease the turning performance). Proceeds to S801,
The basic clutch engagement force FOtb is corrected to increase and set as the transfer clutch engagement force.

The increase of the basic clutch engagement force FOtb is corrected, for example, by multiplying the basic clutch engagement force FOtb by a constant larger than 1 (a constant set in advance by experiment, calculation, or the like), or by increasing the basic clutch engagement force FOtb. This is performed by adding a constant set in advance by an experiment, calculation, or the like to the force FOtb.

On the other hand, if the rear wheel braking selection flag Fvr is set (← 1) in S605 (when the vehicle is understeer and the braking force control device 40 is controlled to increase the turning performance) , S802, the basic clutch engagement force FOtb is reduced and corrected and set as the transfer clutch engagement force.

The basic clutch engagement force FOtb can be reduced by, for example, multiplying the basic clutch engagement force FOtb by a constant smaller than 1 (a constant set in advance through experiments or calculations) or by adjusting the basic clutch engagement force FOtb. This is performed by subtracting (but not less than 0) a constant previously set in an experiment, calculation, or the like from the force FOtb.

Then, the flow advances to S608, where the above-mentioned S604,
The transfer clutch is controlled based on the engagement force of any one of S801 and S802.

As described above, according to the seventh embodiment of the present invention, when the braking force control device increases the turning performance,
Certainly, if a lower value is appropriately set to encourage control to increase turning, and if the braking force control device reduces turning, a higher value is set appropriately to ensure stability. It will be a direction to increase.

Next, FIG. 22 and FIG. 23 show an eighth embodiment of the present invention, and FIG.
FIG. 23 is an explanatory diagram showing a schematic configuration of the entire wheel drive vehicle, and FIG. 23 is a flowchart of power distribution control. The eighth embodiment of the present invention is different from the sixth embodiment in that a higher set value FO is used.
CH and a lower set value FOCL are set according to the yaw rate deviation Δγ.

Therefore, as shown in FIG. 22, the power distribution control device 140 according to the eighth embodiment has the same input and output as the power distribution control device 120 according to the sixth embodiment, except for the control. I have.

As shown in FIG. 23, the power distribution control device 140 first reads each input value in S601, calculates the basic clutch engagement force FOtb in S602, and sets the braking force control execution flag Fvs in S603. If it has been cleared (← 0) (if no braking force is applied to a specific wheel by the braking force control device 40), the process proceeds to S604, where the transfer clutch engagement force is directly changed to the basic clutch engagement force FOtb. Set. In addition, S60
At 3, the braking force control execution flag Fvs is set (← 1).
If it is performed (when the braking force control device 40 applies a braking force to a specific wheel), the process further proceeds to S605, and the rear wheel braking selection flag Fvr is set (← 1) or cleared (← 0). ) Is determined. The above is the same as the fifth embodiment.

Thereafter, in step S605, the rear wheel braking selection flag Fvr is cleared (← 0) (when the vehicle has an oversteer tendency and the braking force control device 40 controls in a direction to decrease the turning performance). Proceeds to S901,
A higher set value FOCH is set according to the yaw rate deviation Δγ, and the process proceeds to S701.

The setting of the higher set value FOCH in S901 is performed, for example, by using a map obtained in advance through experiments, calculations, or the like.
Alternatively, a higher set value FOCH corresponding to the yaw rate deviation Δγ is determined by the equation. As a characteristic of the map or the equation, in order to enhance the control effect, the set value FOCH is set higher as the yaw rate deviation Δγ increases.

[0198] The steps after S701 are the same as those in the sixth embodiment. In S701, the basic clutch engagement force FOtb is compared with the higher set value FOCH, and the basic clutch engagement force FOtb is set to the higher set value FOtb. FOCH or more (F
If Otb ≧ FOCH), the process proceeds to S702, and the engagement force of the transfer clutch is reduced to the basic clutch engagement force FOtb.
Set to.

If the basic clutch engagement force FOtb is lower than the higher set value FOCH in S701 (FOtb
In the case of <FOCH), the process proceeds to S703, where the engagement force of the transfer clutch is set to a higher set value FOCH.

On the other hand, if the rear wheel braking selection flag Fvr is set (← 1) in S605 (when the vehicle has an understeer tendency and the braking force control device 40 is controlled to increase the turning performance) , And proceeds to S902 to set a lower set value FOCL according to the yaw rate deviation Δγ, and proceeds to S704.

The setting of the lower set value FOCL in S902 is performed, for example, by using a map obtained in advance through experiments, calculations, or the like.
Alternatively, the corresponding lower set value FOCL is determined according to the yaw rate deviation Δγ. As a characteristic of the above-mentioned map or the equation, in order to enhance the control effect, the set value FOCL is set lower as the yaw rate deviation Δγ increases.

After S704, the same as in the sixth embodiment, the basic clutch engagement force FOtb is compared with the lower set value FOCL in S704, and the basic clutch engagement force FOtb is set to the lower set value FOtb. FOCL or less (F
If Otb ≦ FOCL), the process proceeds to S705, in which the transfer clutch engagement force is reduced to the basic clutch engagement force FOtb.
Set to.

When the basic clutch engagement force FOtb is higher than the lower set value FOCL in S704 (F
If Otb> FOCL), the process proceeds to S706, in which the engagement force of the transfer clutch is set to the lower set value FOCL.

Then, the flow advances to S608, where the above-mentioned S604,
The transfer clutch control is performed based on the engagement force of any one of S702, S703, S705, and S706.

As described above, according to the eighth embodiment of the present invention, the higher set value FOCH and the lower set value FOCL are set according to the yaw rate deviation Δγ. Thus, more precise control can be performed. Also,
It goes without saying that setting the higher set value FOCH and the lower set value FOCL in accordance with the yaw rate deviation Δγ can be applied to the fifth embodiment. further,
Only one of the higher set value FOCH and the lower set value FOCL may be set according to the yaw rate deviation Δγ.

The braking force control method, the center differential device, the transfer clutch, and the like cited in the embodiments of the present invention may be other methods and forms.

If the parameters used in the above embodiments of the present invention are obtained by another control device, they may be quoted by communication or the like, or directly detected using a sensor. As long as the prediction can be calculated without using the calculated value, the calculated value may be used. On the contrary, the detection value may be directly detected using a sensor instead of the calculated value.

Further, it goes without saying that the basic clutch engagement force FOtb set in the fifth, sixth, seventh and eighth embodiments described above may be a value set by another method. Also,
If the present invention is applied to only one of the turning increase / decrease control in which the braking force control is performed, the effect of the control on the applied side can be improved.

[0209]

As described above, according to the present invention,
When the braking force control device is mounted on the four-wheel drive vehicle, the braking force control is sufficiently performed, and the running stability at the time of cornering or the like of the vehicle can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a first embodiment of the present invention is applied;

FIG. 2 is an explanatory diagram of an operation of the vehicle by braking force control according to the embodiment;

FIG. 3 is a time chart showing an example of braking force control according to the first embodiment;

FIG. 4 is an explanatory diagram of the differential limiting force control according to the first embodiment;

FIG. 5 is an explanatory diagram showing an example of a characteristic of a differential limiting torque according to the first embodiment;

FIG. 6 is a flowchart of braking force control according to the first embodiment;

FIG. 7 is a flowchart subsequent to FIG. 6;

FIG. 8 is a flowchart of power distribution control according to the first embodiment;

FIG. 9 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a second embodiment of the present invention is applied.

FIG. 10 is an explanatory diagram of a relationship between a rotational speed ratio and a torque ratio of the torque converter;

FIG. 11 is a flowchart of power distribution control according to the first embodiment;

FIG. 12 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a third embodiment of the present invention is applied;

FIG. 13 is a flowchart of power distribution control according to the first embodiment;

FIG. 14 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a fourth embodiment of the present invention is applied.

FIG. 15 is a flowchart of power distribution control according to the first embodiment;

FIG. 16 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a fifth embodiment of the present invention is applied.

FIG. 17 is a flowchart of power distribution control according to the first embodiment;

FIG. 18 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a sixth embodiment of the present invention is applied.

FIG. 19 is a flowchart of power distribution control according to the second embodiment;

FIG. 20 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to a seventh embodiment of the present invention is applied.

FIG. 21 is a flowchart of power distribution control according to the first embodiment;

FIG. 22 is an explanatory diagram showing an overall schematic configuration of a four-wheel drive vehicle to which a power distribution control device according to an eighth embodiment of the present invention is applied.

FIG. 23 is a flowchart of power distribution control according to the second embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 2a Transmission output shaft 3 Center differential device 4 Rear drive shaft 10 Front drive shaft 14fr, 14fl Front wheel 14rr, 14rl Rear wheel 21 Hydraulic multi-plate clutch (transfer clutch) 25 Brake drive unit 28fr, 28fl, 28rr, 28rl Wheel cylinder 29fr, 29fl, 29rr, 29rl Wheel speed sensor 30 Handle angle sensor 31 Yaw rate sensor 40 Braking force control device 50 Transmission control device 60 Engine control device 70 Power distribution control device

Claims (9)

[Claims] 1. A vehicle having braking force control means for calculating a braking force for controlling a vehicle behavior from a motion state of the vehicle and selecting a wheel to which the braking force is applied, and controlling the braking, wherein a front wheel side and a rear wheel are provided. In the power distribution control device for a four-wheel drive vehicle that variably controls the distribution of the driving force between the front wheel side and the rear wheel side when the braking force is applied to the wheels by the braking force control means. A power distribution control device for a four-wheel drive vehicle, wherein the driving force is controlled to a value smaller than usual and the driving force is distributed. 2. A vehicle equipped with braking force control means for calculating a braking force for controlling the vehicle behavior from a motion state of the vehicle and selecting a wheel to which the braking force is applied, and controlling the braking, wherein a front wheel side and a rear wheel are provided. A power distribution control device for a four-wheel drive vehicle that variably controls the distribution of driving force between the front wheel side and the rear wheel side when the braking force control means applies a braking force to the wheels. A power distribution control device for a four-wheel drive vehicle, characterized in that the distribution is controlled with a load distribution of the vehicle weight applied to the front wheel side and the rear wheel side as a target value. 3. A vehicle equipped with braking force control means for calculating a braking force for controlling the vehicle behavior from a motion state of the vehicle and selecting a wheel to which the braking force is applied and controlling the braking, wherein a front wheel side and a rear wheel are provided. In a power distribution control device for a four-wheel drive vehicle that variably controls the distribution of driving force with respect to a wheel, a turning characteristic of the braking control by the braking force control means when the braking force is applied to the wheels by the braking force control means. A power distribution control device for a four-wheel drive vehicle, wherein at least one of the front wheel side and the rear wheel side driving force distribution is changed and set in accordance with the increase or decrease of the driving force. 4. When the braking force control means increases the turning performance when the braking force is applied to the wheels by the braking force control means, the driving force distribution on the rear wheel side is changed and set to increase. 4. The power distribution control device for a four-wheel drive vehicle according to claim 3, wherein: 5. When the braking force control means increases the turning performance when the braking force is applied to the wheels by the braking force control means, the driving force distribution on the rear wheel side is increased in advance. 5. The method according to claim 4, wherein the value is changed and set.
A power distribution control device for a four-wheel drive vehicle as described in the above. 6. When the braking force control means increases the turning performance when the braking force is applied to the wheels by the braking force control means, the braking force is increased according to a deviation between a target yaw rate and an actual yaw rate. The power distribution control device for a four-wheel drive vehicle according to claim 4, wherein the distribution of the driving force on the wheel side is changed and set in a direction to increase. 7. When the braking force control means reduces the turning performance when the braking force is applied to the wheels by the braking force control means, the front wheel side driving force distribution is changed and set to increase. The power distribution control device for a four-wheel drive vehicle according to claim 3 or 4, wherein 8. When the braking force control means reduces the turning performance when the braking force is applied to the wheels by the braking force control means, the driving force distribution on the front wheel side is increased in advance. 8. The method according to claim 7, wherein the value is changed and set.
A power distribution control device for a four-wheel drive vehicle as described in the above. 9. The front wheel according to a deviation between a target yaw rate and an actual yaw rate, when the braking force control means reduces the turning performance when the braking force control means applies a braking force to the wheel. The power distribution control device for a four-wheel drive vehicle according to claim 7, wherein the driving force distribution on the side is changed and set in an increasing direction.