JP4668563B2 - Vehicle driving force distribution control device - Google Patents

Description

  The present invention relates to a vehicle driving force distribution control device that controls a driving force distribution ratio based on a force acting on driving wheels.

Conventionally, as a technique for controlling a driving force distribution ratio according to a force actually acting on a driving wheel, for example, Patent Document 1 discloses a longitudinal force Fx, a lateral force Fy, and a vertical force Fz of each wheel by various sensors. By detecting and dividing the resultant force of the longitudinal force Fx and the lateral force Fy by the vertical force Fz, the actual frictional force utilization factor of each wheel is obtained, and the frictional force utilization factor is mutually consistent among all the wheels. A technique for controlling the brake pressure of each wheel is disclosed.
Japanese Patent No. 3132190

  However, the above-described technique is a technique that gives priority to efficient use of driving force, and it is difficult to say that stability, responsiveness, and the like are sufficiently considered. Therefore, in particular, if the wheel frictional force utilization rate of each wheel is controlled to the limit when turning, it will be a control that uses the tire grip of the outer wheel greatly, and, for example, lacks stability against disturbances such as sudden changes in the road surface friction coefficient. There are disadvantages such as.

  The present invention has been made in view of the above circumstances, and provides a vehicle driving force distribution control device capable of realizing driving force distribution control excellent in stability and responsiveness while efficiently using tire grips. The purpose is to provide.

The present invention includes a driving force distribution means for transmitting a drive force to one of the drive shaft and the other drive shaft by the driving force distribution ratio is variably set, and force detection means for detecting a force acting on the driving wheels, front and rear The cornering power that can be estimated to actually occur in each wheel is distributed to the linear term in which the amount of change with respect to the side slip angle of the cornering force is linear , at least the detected value of the force acting on the drive wheel, and each drive shaft. When the driving force distribution ratio is expressed by a nonlinear term using the driving force, the driving force distribution ratio to each driving shaft that minimizes the nonlinear term is calculated, and the driving force distribution ratio is calculated by the driving force distribution means. Driving force distribution ratio setting means for setting as a driving force distribution ratio, wherein the driving force distribution ratio setting means sets the driving force distribution ratio to the right wheel drive shaft and the left wheel drive shaft.

  According to the vehicle driving force distribution control device of the present invention, it is possible to realize driving force distribution control excellent in stability and responsiveness while efficiently using tire grips.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings relate to a first embodiment of the present invention, FIG. 1 is a schematic configuration diagram of a driving force distribution control device, FIG. 2 is a skeleton diagram showing a schematic configuration of a front wheel final reduction device, and FIG. 3 is an equivalent of a four-wheeled vehicle. FIG. 4 is an explanatory diagram functionally showing a state motion equation of the vehicle motion model.

  In FIG. 1, reference numeral 1 denotes a vehicle such as an automobile. In this embodiment, the vehicle 1 is a front-wheel drive vehicle, and the driving force of the engine 1 of the vehicle 1 is transmitted to the transmission output shaft 4a through the torque converter 3 and the transmission 4. Further, the driving force transmitted to the transmission output shaft 4 a is transmitted to the drive shaft (front drive shaft) 9 via the reduction gear train 5 and input to the front wheel final reduction device 10. The driving force input to the front wheel final reduction gear 10 is transmitted to the left and right front wheels 12fl and 12fr as driving wheels through the front wheel left and right axle shafts 11fl and 11fr as driving shafts.

  Here, the front wheel final reduction gear 10 is configured to be able to variably control the distribution ratio of the driving force transmitted to the left and right front wheels 12fl, 12fr.

  More specifically, for example, as shown in FIG. 2, the front wheel final reduction gear device 10 includes a differential mechanism portion 20, a gear mechanism portion 21, and a clutch mechanism portion 22.

  The differential mechanism section 20 is configured by, for example, a bevel gear type differential mechanism section (differential device), and a differential gear 25 meshes with a drive pinion 9a of the front drive shaft 9 in a differential case 25 of the differential mechanism section 20. 26 is provided around. A pair of differential pinions 27 are rotatably supported in the differential case 25, and left and right axle shafts 11fl and 11fr are connected to left and right side gears 28l and 28r engaged therewith.

  The gear mechanism section 21 includes first and second gears 30 and 31 fixed to the front wheel right axle shaft 11fr, third and fourth gears 32 and 33 fixed to the front wheel left axle shaft 11fl, It has the 5th-8th gearwheels 34-37 which respectively mesh | engage with these. In the present embodiment, the second gear 31 is configured with a gear having a diameter larger than that of the first gear 30, and the number of teeth z <b> 2 is set larger than the number of teeth z <b> 1 of the first gear 30. The third gear 32 is configured with a gear having the same diameter as the first gear 30 (number of teeth z3 = z1), and the fourth gear 33 is a gear having the same diameter as the second gear 31 (number of teeth). z4 = z2). The fifth to eighth gears 34 to 37 are arranged on the same rotational axis parallel to the axle shafts 11fl and 11fr. The fifth gear 34 constitutes the first gear train by meshing with the first gear 30. The number of teeth z5 is the gear ratio (z5 / z1) of the first gear train, for example, “1”. .0 ". The sixth gear 35 constitutes the second gear train by meshing with the second gear 31, and the number of teeth z6 is the gear ratio (z6 / z2) of the second gear train, for example. It is set to “0.9”. The seventh gear 36 constitutes the third gear train by meshing with the third gear 32, and the number of teeth z7 is the gear ratio (z7 / z3) of the third gear train, for example. “1.0” is set. The eighth gear 37 constitutes a fourth gear train with the fourth gear 33, and the number of teeth z8 is the gear ratio (z8 / z4) of the fourth gear train, for example. It is set to “0.9”.

  The clutch mechanism 22 includes a first hydraulic multi-plate clutch 38 that fastens and detachably connects the fifth gear 34 and the eighth gear 37, and a sixth gear 35 and a seventh gear 36. And a second hydraulic multi-plate clutch 39 that is detachably fastened. A hydraulic drive control unit 51 (see FIG. 1) is connected to a hydraulic chamber (not shown) of each hydraulic multi-plate clutch 38, 39, and the first hydraulic pressure is supplied by the hydraulic pressure supplied from the hydraulic drive control unit 51. When the multi-plate clutch 38 is engaged, a large amount of driving force is distributed to the left axle shaft 11fl. On the other hand, when the second hydraulic multi-plate clutch 39 is engaged, a large amount of driving force is distributed to the right axle shaft 11fr.

  Here, the hydraulic values for engaging the hydraulic multi-plate clutches 38 and 39 are the driving forces of the left and right front wheels 12fl and 12fr set by a driving force distribution ratio setting unit 50 (to be described later) as driving force distribution ratio setting means. This value is calculated by the hydraulic drive control unit 51 in accordance with the force distribution ratio, and the torque distribution amount (drive force distribution amount) is varied depending on the magnitude of the hydraulic pressure value. That is, the hydraulic drive control unit 51 realizes a function as a driving force distribution unit together with the front wheel final reduction gear 10. In addition, about the structure of this kind of final reduction gear, it is not limited to the structure demonstrated in detail in Unexamined-Japanese-Patent No. 11-263140, for example, and demonstrated in this form.

  As shown in FIG. 1, the driving force distribution ratio setting unit 50 includes force detection sensors 14fl and 14fr as force detecting means for detecting forces acting on the driving wheels (left and right front wheels 12fl and 12fr), and road surface friction coefficient estimation. The part 53 and the front-rear driving force calculation part 54 are connected.

  In this embodiment, the force detection sensors 14fl and 14fr are embedded in the axle housings 13fl and 13fr of the left and right front wheels 12fl and 12fr, and at least lateral forces acting on the wheels 12fl and 12fr (front wheel lateral forces Ffl_y, Ffr_y) and vertical forces (front wheel vertical forces Ffl_z, Ffr_z) are detected based on displacements generated in the axle housings 13fl, 13fr.

  The road surface friction coefficient estimator 53 is composed of, for example, an ABS control unit, and calculates the road surface friction coefficient μ (hereinafter also referred to as road surface μ) by, for example, the estimation method proposed by the present applicant in Japanese Patent Laid-Open No. 8-2274. To do. The road surface friction coefficient estimating unit 53 uses the front wheel steering angle δf, the vehicle speed V, and the actual yaw rate (dφ / dt) input from the steering angle sensor 60, the vehicle speed sensor 61, and the yaw rate sensor 62, and the equation of motion of the lateral movement of the vehicle. Based on the above, the cornering power of the front and rear wheels is extended to a non-linear range, and the road surface μ is estimated from 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 (μ = 1.0). To do. Of course, the estimation method of the road surface μ may be obtained by other methods such as the method disclosed in Japanese Patent Application Laid-Open No. 2000-71968 of the present applicant.

The front / rear driving force calculation unit 54 is constituted by, for example, an engine control unit, and calculates, for example, the engine driving force Fe as the front / rear driving force (driver required driving force) Fx. In other words, the engine rotational speed Ne, the turbine rotational speed N1, and the throttle opening θth are input from the engine rotational speed sensor 63, the turbine rotational speed sensor 64, and the throttle opening sensor 65 to the front / rear driving force calculation unit 54. The current transmission gear ratio rg is input from the transmission control unit 66, and the engine driving force Fe is calculated based on these based on the equation (1).
Fe = (Tt · rf) / Rw (1)
Here, rf is the final gear ratio, and Rw is the tire effective radius. Further, Tt is the torque after the transmission gear, and is obtained by the equation (2) where Te is the engine torque, tconv is the torque converter ratio of the torque converter, and η is the power transmission efficiency.
Tt = Te · rg · tconv · η (2)
At this time, the engine torque Te is obtained from a map set in advance based on the engine speed Ne and the throttle opening θth, and the torque converter ratio tconv is determined in advance based on the speed ratio rv (= Nt / Ne) of the torque converter. It is obtained from the set map.

By the way, in the vehicle motion model of FIG. 3, the equation of motion relating to the translational motion in the lateral direction of the vehicle is Ff, Fr for the cornering force (one wheel) of the front and rear wheels, M for the vehicle body mass, and (d ² y / dt ² As
M · (d ² y / dt ² ) = 2 · Ff + 2 · Fr (3)
Given in.

On the other hand, the equation of motion related to the rotational movement around the center of gravity is expressed as follows: the distance from the center of gravity to the front and rear wheel axes is lf, rr, the yaw moment of inertia of the vehicle body is Iz, and the yaw angular acceleration is (d ² φ / dt ² ).
Iz · (d ² φ / dt ² ) = 2 · Ff · lf-2 · Fr · lr (4)
Indicated by

Further, when the vehicle slip angle is β and the vehicle slip angular velocity is (dβ / dt), the lateral acceleration (d ² y / dt ² ) is
(D ² y / dt ² ) = V · ((dβ / dt) + (dφ / dt)) (5)
It is represented by

The average cornering forces Ff_y and Fr_y of the front and rear wheels are as follows. The equivalent cornering powers of the front and rear wheels are Kf and Kr, and the side slip angles of the front and rear wheels are βf and βr.
^{Ff_y = Kf · βf- (Kf 2} · βf 2) / (4 · Ff_yMAX) ... (6)
Fr_y = Kr · βr− (Kr ² · βr ² ) / (4 · Fr_yMAX) (7)
It is represented by

At this time, the actual front and rear wheel cornering powers Kf_a and Kr_a are expressed by the following equations.
Kf_a = (∂Ff_y / ∂βf) = Kf- (Kf 2 · | βf |) / (2 · Ff_yMAX) ... (8)
Kr_a = (∂Fr_y / ∂βr) = Kr- (Kr 2 · | βr |) / (2 · Fr_yMAX) ... (9)
Here, if the average longitudinal force of the front and rear wheels is Ff_x, Fr_x, and the average vertical force of the front and rear wheels is Ff_z, Fr_z,
Ff_yMAX = (μ ² · Ff_z ² −Ff_x ² ) ^1/2 (10)
Fr_yMAX = (μ ² · Fr_z ² −Fr_x ² ) ^1/2 (11)
Further, the side slip angles βf and βr of the front and rear wheels can be simplified as follows with the front wheel rudder angle as δf.
βf = β + lf · (dφ / dt) / V−δf (12)
βr = β + lr · (dφ / dt) / V (13)
Summarizing the above equation of motion, a state equation of motion for obtaining the vehicle body slip angle β and yaw rate (dφ / dt) with the steering angle δf as input is obtained as follows.

a11 = 2 · (kf_a + kr_a) / (M · V) (15)
a12 = 1 + 2 · (lf · kf_a−lr · kr_a) / (M · V ² ) (16)
a21 = 2 · (lf · kf_a−lr · kr_a) / (Iz · V) (17)
a22 = 2 · (lf ² · kf_a−lr ² · kr_a) / (Iz · V) (18)
b1 = 2 · kf_a / (MV) (19)
b2 = 2 · lf · kf_a / Iz (20)
These relationships are functionally represented in FIG.

Here, in the equation (14), it is known that the term a11 contributes to the convergence property of the vehicle slip angle. As the term changes linearly, the stability of the vehicle is improved and the responsiveness is improved. Is in line with the driver's feeling. Left front wheel longitudinal force Ffl_x, right front wheel longitudinal force Ffr_x, left rear wheel longitudinal force Frl_x, right rear wheel longitudinal force Frr_x, left front wheel vertical force Ffl_z, right front wheel vertical force Ffr_z, left rear wheel vertical force Frl_z, the right rear wheel vertical force is Frr_z, and the terms a11 shown in the equation (15) are expanded by the cornering power kfl_a, kfr_a, krl_a, krr_a of each wheel using the equations (8) to (11).
a11 = (kfl_a + kfr_a + krl_a + krr_a) / (MV)
= (1 / (M ・ V)) ・ [2 ・ (Kf + Kr)
− (1/2) · [Kf ² / (μfl ² · Ffl_z ² −Ffl_x ² ) ^1/2
+ Kf ² / (μfr ² · Ffr_z ² −Ffr_x ² ) ^1/2 ] · | βf |
− (1/2) · [Kr ² / (μrl ² · Frl_z ² −Frl_x ² ) ^1/2
+ (Kr ² / (μrr ² · Frr_z ² −Frr_x ² ) ^1/2 ) · | βr |] (21)
Here, when the front and rear wheel side slip angles βf and βr are sufficiently small, Kf · | βf | = | Ffl_y | = | Ffr_y | (where Ffl_y is the left front wheel lateral force and Ffr_y is the right front wheel lateral force), Kr · | βr | = | Frl_y | = | Frr_y | (where Frl_y is the left rear wheel lateral force and Frr_y is the right rear wheel lateral force).
a11 = 1 / (M · V)) · [2 · (Kf + Kr)
− (1/2) · [Kf · | Ffl_y | / (μfl ² · Ffl_z ² −Ffl_x ² ) ^1/2
+ Kf · | Ffr_y | / (μfr ² · Ffr_z ² −Ffr_x ² ) ^1/2 ]
− (1/2) · [Kr · | Frl_y | / (μrl ² · Frl_z ² −Frl_x ² ) ^1/2
+ Kr · | Frr_y | / (μrr ² · Frr_z ² −Frr_x ² ) ^1/2 ]] (22)
It becomes.

Here, the front / rear driving force distribution ratio is a (where 0 ≦ a ≦ 1), the right and left front wheel driving force distribution ratio is b (where 0 ≦ b ≦ 1), and the right and left rear wheel driving force distribution ratio is c (where 0 ≦ c ≦ 1), and the driving force of each of the wheels 12fl, 12fr, 12rl, 12rr is expressed as Ffl_x, Ffr_x, Frl_x, Frr_x by the driver required driving force Fx,
Ffl_x = a · b · Fx (23)
Ffr_x = a. (1-b) .Fx (24)
Frl_x = (1-a) · c · Fx (25)
Frl_x = (1-a). (1-c) .Fx (26)
And substituting these into equation (22),
a11 = (1 / (M · V)) · [2 · (Kf + Kr)
− (1/2) · [Kf · | Ffl_y | / (μfl ² · Ffl_z ² −a ² · b ² · Fx ² ) ^1/2
+ Kf · | Ffr_y | / (μfr ² · Ffr_z ² -a ² · (1-b) ² · Fx ² ) ^1/2 ]
− (1/2) · [Kr · | Frl_y | / (μrl ² · Frl_z ² − (1-a) ² · c ² · Fx ² ) ^1/2
+ Kr · | Frr_y | / (μrr ² · Frr_z ^2- (1-a) ² (1-c) ² · Fx ² ) ^1/2 ]] (27)
It becomes. In the equation (27), the elements in [] consist of cornering powers Kf_a and Kr_a of the front and rear wheels.
2 · Ff_x = a · Fx (28)
2 · Fr_x = (1-a) · Fx (29)
If the elements of the front and rear wheel cornering powers Kf_a and Kr_a are extracted from the equation (27),
Kf_a
= Kf− (Kf · | Ffl_y |) / (4 · (μfl ² · Ffl_z ² −a ² · b ² · Fx ² ) ^1/2 )
-(Kf · | Ffr_y |) / (4 · (μfr ² · Ffr_z ² -a ² · (1-b) ² · Fx ² ) ^1/2 )
= Kf− (Kf · | Ffl_y |) / (4 · (μfl ² · Ffl_z ² −4 · b ² · Ff_x ² ) ^1/2 )
− (Kf · | Ffr_y |) / (4 · (μfr ² · Ffr_z ² −4 · (1-b) ² · Ff_x ² ) ^1/2 ) (30)
Kr_a
= Kr− (Kr · | Frl_y |) / (4 · (μrl ² · Frl_z ² − (1-a) ² · c ² · Fx ² ) ^1/2 )
-(Kr · | Frr_y |) / (4 · (μrr ² · Frr_z ^2- (1-a) ² · (1-c) ² · Fx ² ) ^1/2 )
= Kr− (Kr · | Frl_y |) / (4 · (μrl ² · Frl_z ² −4 · c ² · Fr_x ² ) ^1/2 )
− (Kr · | Frr_y |) / (4 · (μrr ² · Frr_z ² -4 · (1-c) ² · F_x ² ) ^1/2 ) (31)
It becomes.

  As is clear from the equations (30) and (31), in the front-wheel drive vehicle having the front-rear driving force distribution ratio a = 1, the front-wheel driving force distribution ratio that minimizes the nonlinear term of the front-wheel cornering power Kf_a is set. Thus, the nonlinear term a11 in the equation (14) can be minimized.

Considering this point, in the driving force distribution ratio setting unit 50, the non-linear term of the front wheel cornering power Kf_a expressed by the linear term and the non-linear term, that is, the non-linear term of Equation (30) =
(Kf · | Ffl_y |) / (4 · (μfl ² · Ffl_z ² -4 · b ² · Ff_x ² ) ^1/2 )
+ (Kf · | Ffr_y |) / (4 · (μfr ² · Ffr_z ² -4 · (1-b) ² · Ff_x ² ) ^1/2 ) (32)
Is calculated, and the control of the distribution ratio when transmitting the driving force 2 · Ff_x (a · Fx) from the front wheel final reduction gear 10 to the left and right axle shafts 11fl and 11fr of the front wheels is calculated. Set as a value.

  Specifically, the driving force distribution ratio setting unit 50 substitutes the front wheel lateral force Ffl_y and the front wheel vertical force Ffl_z detected by the force detection sensor 14fl for Ffl_y and Ffl_z in the equation (32), and the force detection sensor 14fr. The front wheel lateral force Ffr_y and the front wheel vertical force Ffr_z detected in step (2) are substituted into Ffr_y and Ffr_z in the equation (32). Further, assuming that the road surface μ acting on each wheel is equal, the road surface μ estimated by the road surface friction coefficient estimating unit 53 is substituted into μfl and μfr in the equation (32), and calculated by the front / rear driving force calculating unit 54. The driven driving force Fx is substituted into Ff_x (= Fx / 2) in the equation (32).

  Then, the driving force distribution ratio setting unit 50 sequentially substitutes, for example, b = 0.0, 0.1,..., 0.9, 1.0 into b in the equation (32), so that the front wheel cornering is performed. A driving force distribution ratio b that minimizes the nonlinear term of the power Kf_a is obtained.

  According to such a configuration, by setting the driving force distribution ratio that minimizes the nonlinear term of the cornering power that is estimated to actually occur in the wheel, the tire grip is efficiently utilized and the disturbance is prevented. A driving force distribution ratio with excellent stability can be set.

  In addition, since the change in cornering power generated on the wheels is brought closer to a linear change by driving force distribution control, the responsiveness can be improved, and even if the tire approaches the non-linear region, it can be operated with an image close to that in the normal region. it can.

  In addition, since the lateral force and vertical force of the drive wheels directly obtained from the force detection sensor are used for the estimation of cornering power, it is possible to realize accurate drive force distribution control according to actual vehicle behavior.

  Next, FIG. 5 relates to a second embodiment of the present invention, and FIG. 5 is a schematic configuration diagram of the driving force distribution control device. Here, in this embodiment, a case where the driving force distribution ratio setting unit 50 sets the driving force distribution ratio c between the left and right rear wheels will be described. In addition, about the structure similar to the above-mentioned 1st form, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 5, in this embodiment, the driving force by the engine 2 is transmitted to the transmission output shaft 4a via the torque converter 3 and the transmission 4. Further, the driving force transmitted to the transmission output shaft 4 a is transmitted to the drive pinion shaft 17 via the propeller shaft 16 and input to the rear wheel final reduction gear 18. The driving force input to the rear wheel final reduction gear 18 passes through the rear wheel left and right axle shafts 11rl and 11rr as drive shafts and the left and right rear wheels 12rl. 12rr.

  Here, the rear wheel final reduction gear 18 is configured to be able to variably control the distribution ratio of the driving force transmitted to the left and right rear wheels 12rl, 12rr. Specifically, the rear wheel final reduction gear 18 has substantially the same configuration as the front wheel final reduction gear 10 shown in FIG. 2 of the first embodiment described above, for example. In this case, in the rear wheel final reduction gear 18, the drive pinion shaft 17 corresponds to the front drive shaft 9 shown in FIG. 2, and the rear wheel left and right axle shafts 11rl and 11rr are the front wheel left and right axle shafts 11fl and 11fr shown in FIG. It corresponds to.

  Here, in the rear wheel final reduction gear 18, the hydraulic pressure values for engaging the hydraulic multi-plate clutches 38 and 39 are the driving force distribution ratios of the left and right rear wheels 12 rl and 12 rr set by the driving force distribution ratio setting unit 50. Is a value calculated by the hydraulic drive control unit 51, and the distribution amount of the driving force is changed depending on the hydraulic value. That is, the hydraulic drive control unit 51 realizes a function as a driving force distribution means together with the rear wheel final reduction gear 18.

  As shown in the figure, the driving force distribution ratio setting unit 50 is connected to force detection sensors 14rl and 14rr as force detecting means for detecting forces acting on the driving wheels (left and right rear wheels 12rl and 12rr). In this embodiment, the force detection sensors 14rl and 14rr are embedded in the axle housings 13rl and 13rr of the left and right rear wheels 12rl and 12rr, and at least a lateral force acting on each of the wheels 12rl and 12rr (front wheel lateral force Frl_y). , Frr_y) and vertical forces (front wheel vertical forces Frl_z, Frr_z) are detected based on the amount of displacement generated in the axle housings 13rl, 13rr.

  As is clear from the expressions (30) and (31) shown in the first embodiment, in the rear wheel drive vehicle with the front / rear driving force distribution ratio a = 0, the nonlinear term of the rear wheel cornering power Kr_a is minimized. By setting the rear wheel driving force distribution ratio as follows, the nonlinear term of a11 in the equation (14) can be minimized.

Considering this point, in the driving force distribution ratio setting unit 50, the non-linear term of the rear wheel cornering power Kr_a expressed by the linear term and the non-linear term, that is, the non-linear term of Equation (31) =
(Kr · | Frl_y |) / (4 · (μrl ² · Frl_z ² -4 · c ² · Fr_x ² ) ^1/2 )
+ (Kf · | Frr_y |) / (4 · (μrr ² · Frr_z ² -4 · (1-c) ² · Fr_x ² ) ^1/2 ) (33)
Is calculated from the rear wheel final reduction gear 18 to the left and right axle shafts 11 rl and 11 rr of the rear wheels. It is set as the control value of the distribution ratio when

  Specifically, the driving force distribution ratio setting unit 50 substitutes the front wheel lateral force Frl_y and the front wheel vertical force Frl_z detected by the force detection sensor 14rl into Frl_y and Frl_z in the equation (33), and the force detection sensor 14rr. The front wheel lateral force Frr_y and the front wheel vertical force Frr_z detected in step (3) are substituted into Frr_y and Frr_z in the equation (33). Further, assuming that the road surface μ acting on each wheel is equal, the road surface μ estimated by the road surface friction coefficient estimating unit 53 is substituted into μrl and μrr in the equation (33), and calculated by the front / rear driving force calculating unit 54. The driven driving force Fx is substituted into Ff_x (= Fx / 2) in the equation (33).

  Then, the driving force distribution ratio setting unit 50 sequentially substitutes, for example, c = 0.0, 0.1, 0.2,..., 0.9, 1.0 into c in the equation (33). Thus, the driving force distribution ratio c that minimizes the nonlinear term of the front wheel cornering power Kr_a is obtained.

  According to such a configuration, it is possible to achieve substantially the same effect as that of the first embodiment described above with respect to the driving force distribution control of the rear wheels.

  Next, FIG. 6 relates to a third embodiment of the present invention, and FIG. 6 is a schematic configuration diagram of the driving force distribution control device. In this embodiment, a case where the driving force distribution ratio setting unit 50 sets the driving force distribution ratio a between the front and rear wheels will be described. In addition, about the structure similar to the above-mentioned 1st, 2nd form, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 6, in this embodiment, the driving force from the engine 2 is transmitted from the transmission output shaft 4 a to the center differential device 19 via the torque converter 3 and the transmission 4. Further, the driving force transmitted to the center differential device 19 is input to the rear wheel final reduction device 18 via the rear drive shaft 15, the propeller shaft 16, and the drive pinion shaft 17, while the front wheel via the front drive shaft 9. It is configured to be transmitted to the final reduction gear 10.

  Here, the center differential device 19 is configured to variably control the distribution ratio of the driving force transmitted to the front drive shaft 9 and the rear drive shaft 15 as drive shafts. Specifically, the center differential device 19 has substantially the same configuration as the front wheel final reduction device 10 shown in FIG. 2 of the first embodiment described above, for example. In this case, in the center differential device 19, the transmission output shaft 4a corresponds to the front drive shaft 9 shown in FIG. 2, the front drive shaft 9 corresponds to the front wheel right axle shaft 11fr shown in FIG. Corresponds to the front wheel left axle shaft 11fl shown in FIG.

  Here, in the center differential device 19, the hydraulic pressure value for engaging the hydraulic multi-plate clutches 38 and 39 is hydraulic drive control according to the driving force distribution ratio of the front and rear wheels set by the driving force distribution ratio setting unit 50. This value is calculated by the unit 51, and the amount of distribution of the driving force is changed depending on the hydraulic value. That is, the hydraulic drive control unit 51 realizes a function as a driving force distribution means together with the center differential device 19.

  As shown in the figure, the driving force distribution ratio setting unit 50 includes force detection sensors 14fl, 14fr as force detecting means for detecting forces acting on the driving wheels (the left and right front wheels 12fl, 12fr and the left and right rear wheels 12rl, 12rr). 14rl and 14rr are connected.

In the present embodiment, the driving force distribution ratio a of the front and rear wheels that minimizes the nonlinear term in the equations (30) and (31) is obtained assuming that the driving force distribution ratio b = c = 1/2. That is, the nonlinear term of the four-wheel cornering power Kfr_a (= Kf_a + Kr_a) expressed by a linear term and a nonlinear term is
The front wheel average lateral force is Ff_y (= (Ffl_y + Ffr_y) / 2),
The rear wheel average lateral force is Fr_y (= (Frl_y + Frr_y) / 2),
The front wheel average vertical force is Ff_z (= (Ffl_z + Ffr_z) / 2),
If the rear wheel average vertical force is Fr_z (= (Frl_z + Frr_z) / 2),
= Nonlinear term (Kf · | Ffl_y |) / (4 · (μfl 2 · Ffl_z 2 -a 2 · Fx 2/4) 1/2)
+ (Kf · | Ffr_y |) / (4 · (μfr 2 · Ffr_z 2 -a 2 · Fx 2/4) 1/2)
+ (Kr · | Frl_y |) / (4 · (μrl 2 · Frl_z 2 - (1-a) 2 · Fx 2/4) 1/2)
+ (Kr · | Frr_y |) / (4 · (μrr 2 · Frr_z 2 - (1-a) 2 · Fx 2/4) 1/2)

≒ Kf · | Ff_y | / ( 2 · (μf 2 · Ff_z 2 -a 2 · Fx 2/4) 1/2)
+ Kr · | Fr_y | / ( 2 · (μr 2 · Fr_z 2 - (1-a) 2 · Fx 2/4) 1/2) ... (34)

However, Ffl_y ≒ Ffr_y ≒ Ff_y, Frl_y ≒ Frr_y ≒ Fr_y
Ffl_z ≒ Ffr_z ≒ Ff_z, Frl_z ≒ Frr_z ≒ Fr_z
It can be expressed as. The driving force distribution ratio setting unit 50 calculates a driving force distribution ratio a that minimizes the equation (34) by processing substantially similar to that in the first and second embodiments described above, and calculates the driving force Fx as the driving force Fx. It is set as a control value of the distribution ratio when transmitting from the center differential device 19 to the front drive shaft 9 and the rear drive shaft 15.

  Further, the driving force distribution ratio setting unit 50 uses the front wheel driving force Ff_x and the rear wheel driving force Fr_x based on the set driving force distribution ratio a, respectively, and the front wheel left / right driving force distribution ratio b and the rear wheel left / right driving force. It is possible to set the distribution ratio c. Specifically, in the first and second embodiments, the distribution ratio is set to 1 or 0, but these values are calculated and set as nonlinear values of the front wheel cornering power Kf_a or the rear wheel cornering power Kr_a. This is done by calculating the driving force distribution ratio that minimizes the term.

  According to such a form, substantially the same effects as those of the first form described above can be achieved with respect to the drive force distribution control of all four wheels including the drive force distribution control to the front and rear wheels. The nonlinear terms used when determining the driving force distribution do not use the values of the tire lateral forces Ffl_y, Ffr_y, Frl_y, and Frr_y, but before and after being obtained from equations (12) and (13) as follows: A formula using wheel tire slip angles βf and βr may be used.

Nonlinear term = (Kf ² · | βf |) / (4 · (μfl ² · Ffl_z ² -4 · b ² · Ff_x ² ) ^1/2 )
+ (Kf ² · | βf |) / (4 · (μfr ² · Ffr_z ² -4 · (1-b) ² · Ff_x ² ) ^1/2 ) (32 ')
Nonlinear term = (Kr ² · | βr |) / (4 · (μrl ² · Frl_z ² -4 · c ² · Fr_x ² ) ^1/2 )
+ (Kr ² · | βr |) / (4 · (μrr ² · Frr_z ² -4 · (1-c) ² · Fr_x ² ) ^1/2 ) (33 ')
Nonlinear term ^{= Kf 2 · | βf | /} (2 · (μf 2 · Ff_z 2 -a 2 · Fx 2/4) 1/2)
^{+ Kr 2 · | βr | /} (2 · (μr 2 · Fr_z 2 - (1-a) 2 · Fx 2/4) 1/2) ... (34 ')
Needless to say, each expression indicating the cornering power in terms of a linear term and a non-linear term, its deformation, approximation, and the like are not limited to those shown in the above embodiments.

  Furthermore, in each of the embodiments, an example in which driving force is distributed to the left and right driving wheels has been described by taking an FF vehicle (Front engine-Front drive), an FR (Front engine-Rear drive) vehicle, and a 4-wheel drive vehicle as an example. However, the present invention is not limited to these, and even in a four-wheel independent motor vehicle that includes a motor on four wheels and obtains a driving force by controlling each motor, the motor driving force on the left and right wheels, and further the four-wheel motor The present invention can be applied by controlling the driving force based on the driving force distribution calculated by the present invention. In this case, the unit for calculating and controlling the driving force for each wheel corresponds to the vehicle driving force distribution control means.

Schematic configuration diagram of a driving force distribution control device according to the first embodiment of the present invention. Same as above, skeleton diagram showing schematic configuration of front wheel final reduction gear As above, an explanatory diagram showing an equivalent two-wheeled vehicle model of a four-wheeled vehicle Same as above, explanatory diagram functionally showing the state motion equation of the vehicle motion model Schematic configuration diagram of a driving force distribution control device according to the second embodiment of the present invention. Schematic configuration diagram of a driving force distribution control device according to the third embodiment of the present invention.

Explanation of symbols

9 ... Front drive shaft (drive shaft)
10 ... Front wheel final reduction gear (drive force distribution means)
11fl: Front wheel left axle shaft (drive shaft)
11fr: Front wheel right axle shaft (drive shaft)
11rl ... Rear wheel left axle shaft (drive shaft)
11rr: Rear wheel right axle shaft (drive shaft)
12fl ... Left front wheel (drive wheel)
12fr ... Front right wheel (drive wheel)
12rl ... Left rear wheel (drive wheel)
12rr ... Right rear wheel (drive wheel)
14fl: Force detection sensor (force detection means)
14fr: Force detection sensor (force detection means)
14rl: Force detection sensor (force detection means)
14rr ... Force detection sensor (force detection means)
15 ... Rear drive shaft (drive shaft)
18 ... Rear wheel final reduction gear (drive force distribution means)
19 ... Center differential device (drive force distribution means)
50: Driving force distribution ratio setting unit (driving force distribution ratio setting means)
51... Hydraulic drive control unit (drive force distribution means)
Agent Patent Attorney Susumu Ito

Claims (5)

Drive force distribution means for transmitting drive force to one drive shaft and the other drive shaft at a variable drive force distribution ratio;
Force detecting means for detecting the force acting on the drive wheel;
The cornering power that can be estimated to actually occur on the front and rear wheels is distributed to the linear term in which the amount of change with respect to the side slip angle of the cornering force is linear , at least the detected value of the force acting on the drive wheels, and the drive shafts. When the driving force is expressed by a nonlinear term using the driving force, a driving force distribution ratio to each driving shaft that minimizes the nonlinear term is calculated, and the driving force distribution ratio is calculated as the driving force distribution means. Driving force distribution ratio setting means for setting as a driving force distribution ratio of
The driving force distribution control device for a vehicle, wherein the driving force distribution ratio setting means sets a driving force distribution ratio to the right wheel drive shaft and the left wheel drive shaft.   The driving force distribution ratio setting means sets a driving force distribution ratio to the front wheel driving shaft and the rear wheel driving shaft, and based on the driving force distribution, the right wheel driving shaft on at least one side of the front wheel side or the rear wheel side. The drive force distribution control device for a vehicle according to claim 1, wherein a drive force distribution ratio to the left wheel drive shaft is set.   2. The vehicle according to claim 1, wherein the driving force distribution ratio setting means sets a driving force distribution ratio to the right wheel driving shaft and the left wheel driving shaft on the front wheel side based on the driving force to the front wheel driving shaft. Driving force distribution control device.   2. The driving force distribution ratio setting means sets the driving force distribution ratio to the right wheel driving shaft and the left wheel driving shaft on the rear wheel side based on the driving force to the rear wheel driving shaft. Vehicle driving force distribution control device. Force detecting means for detecting the force acting on the drive wheel;
The cornering power that can be estimated to actually occur on the front and rear wheels is generated by a linear term in which the amount of change with respect to the side slip angle of the cornering force is linear , at least the detected value of the force acting on the driving wheel, and each driving wheel. When the driving force distribution ratio is expressed by a nonlinear term using the driving force, the driving force distribution ratio in each driving wheel that minimizes the nonlinear term is calculated, and the right wheel and the left wheel are calculated so as to be the driving force distribution ratio. A driving force distribution control device for a vehicle, wherein the driving force is controlled.

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