JP5244043B2 - Road surface friction coefficient estimation device and vehicle front / rear driving force distribution control device - Google Patents

Description

  The present invention relates to a road surface friction coefficient estimating device and a vehicle front and rear driving force distribution control device that can easily and accurately estimate a road surface friction coefficient and perform vehicle front and rear driving force distribution control.

  Conventionally, in vehicles, various control techniques have been proposed and put into practical use for front-rear driving force distribution control of a four-wheel drive vehicle. Many of these techniques use a road surface friction coefficient for calculation or correction of a necessary control amount, and it is necessary to estimate an accurate road surface friction coefficient in order to reliably execute the control.

For example, in Japanese Patent Laid-Open No. 4-135923 (hereinafter referred to as Patent Document 1), the lateral acceleration Gy1 generated in the vehicle based on the detected rotational speed Vi of the driven inner ring and the rotational speed Vo of the driven outer ring is expressed as follows. Based on the steering angle δ and the detected vehicle speed V, the reference lateral acceleration Gy2 is calculated by the following expression (2), and based on the difference between the lateral acceleration Gy1 and the reference lateral acceleration Gy2. A technique for determining whether the road is a low μ road is disclosed.
Gy1 = (Vo ² −Vi ² ) / 2 · T · g (1)
Gy2 = V ² · δ / L · g (2)
Here, T is a tread, g is a gravitational acceleration, and L is a hole base.

JP-A-4-135923

By the way, the equation (1) disclosed in Patent Document 1 described above is based on the Ackermann geometry shown in FIG. 13A from the relationship between the turning radius R0, the rotation speed Vi of the turning inner ring, and the rotation speed Vo of the turning outer ring. Can also be explained. As shown in FIG. 13B simulating FIG. 13A in the relation of triangles, the relation of the following expression (3) is derived from the similarity law of triangles.
Vi / (R0− (T / 2)) = (Vo−Vi) / T (3)
Solving this equation (3) for the turning radius R0,
R0 = (Vo + Vi) · (T / 2) / (Vo−Vi) (4)
The vehicle speed V is
V = (Vi + Vo) / 2 (5)
The lateral acceleration Ay is
^{Ay = V 2 / R0 ... (} 6)
Therefore, substituting (4) and (5) into (6),
^{Ay = ((Vi + Vo)} 2/4) / ((Vo + Vi) · (T / 2) / (Vo-Vi))
... (7)
Thus, by modifying this equation (7) and replacing Ay with Gy1, the relationship of the above equation (1) is derived. As is clear from this, the use of the above-described equation (1) is based on the above-described equation (3). In order for the rotation speed Vi of the turning inner wheel and the rotation speed Vo of the turning outer wheel to be in the relationship of the turning radius R0 and the above-described equation (3), the turning radius R0, the rotation speed Vi of the turning inner ring, and the rotation speed Vo of the turning outer wheel are The rotation speed Vi of the inner turning wheel and the rotation speed Vo of the outer turning wheel must be the same slip ratio λ. As shown in FIG. 12 (a), when the grounding load is different between the turning inner wheel and the turning outer wheel, the respective driving forces are different even with the same slip ratio λc. As shown in FIG. 12A, the inner and outer wheels have the same slip ratio λ during turning such as when the ground load of the turning inner wheel and the turning outer wheel are different, so that λ = 0 when the driving force does not act. Therefore, the turning inner wheel and the turning outer wheel need to be driven wheels that do not act on the driving force. Therefore, it is difficult to accurately estimate the road surface friction coefficient when the driving force acts on the front and rear wheels as in a four-wheel drive vehicle, and the road surface friction coefficient can be accurately calculated even when the driving force acts. There is a need for a road friction coefficient estimation device that can be estimated. As shown in FIG. 12 (b), even when the same driving force (Fxc in the figure) is applied, the slip ratio λ and the ground contact load are different if the road surface friction coefficient is different. In consideration of all these factors, it is difficult to accurately estimate the road friction coefficient by creating a tire model or the like.

  The present invention has been made in view of the above circumstances. Even when a driving force acts, the road surface friction coefficient can be estimated easily and accurately, and the front and rear driving force distribution can be accurately distributed using this road surface friction coefficient. Provided is a road surface friction coefficient estimation device and a vehicle front / rear driving force distribution control device that can be controlled and can easily and accurately set and control the front / rear driving force distribution even when a driving force is applied. The purpose is to do.

  The present invention relates to a wheel speed detecting means for detecting a wheel speed of each wheel, a steering angle detecting means for detecting a steering angle, a vehicle body speed detecting means for detecting a vehicle body speed, and each wheel detected by the wheel speed detecting means. Wheel speed difference calculating means for calculating the wheel speed difference between the turning inner wheel and the turning outer wheel based on the wheel speed of the vehicle, total driving force calculating means for calculating the total driving force generated by the vehicle, and the total driving force Based on the vehicle body speed and the wheel speed difference, the steering angle is estimated by referring to a map of the relationship between the total driving force, the vehicle body speed, the wheel speed difference, and the steering angle that is set in advance. Estimated rudder angle setting means for setting as a rudder angle deviation calculating means for calculating a deviation between the rudder angle detected by the rudder angle detecting means and the estimated rudder angle set by the estimated rudder angle setting means as a rudder angle deviation; Based on the vehicle body speed, the rudder angle, and the rudder angle deviation, Is characterized in that by referring to the map of the relationship between serial steering angle and the steering angle deviation and the road surface friction coefficient and a road friction coefficient setting means for setting a road surface friction coefficient.

  According to the present invention, even when a driving force acts, the road surface friction coefficient can be estimated easily and accurately, and the front and rear driving force distribution control can be accurately performed using the road surface friction coefficient. Even when a driving force acts, it is possible to set and control the front / rear driving force distribution easily and accurately.

It is explanatory drawing which shows schematic structure of the whole vehicle which concerns on 1st Embodiment of this invention. It is a functional block diagram of a control unit concerning a 1st embodiment of the present invention. It is a functional block diagram of the correction gain calculation part which concerns on 1st Embodiment of this invention. It is a flowchart of the front-rear driving force distribution control program according to the first embodiment of the present invention. It is a flowchart of the correction gain calculation process routine which concerns on 1st Embodiment of this invention. It is explanatory drawing of the map of the target differential limiting torque according to the accelerator opening which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows an example of the map of the relationship between the total drive force which concerns on 1st Embodiment of this invention, a vehicle speed, a wheel speed difference, and a steering angle. It is explanatory drawing which shows an example of the map of the relationship between the vehicle speed which concerns on 1st Embodiment of this invention, a steering angle, a steering angle deviation, and a road surface friction coefficient. It is explanatory drawing which shows an example of the map of the relationship between the road surface friction coefficient which concerns on 1st Embodiment of this invention, and correction | amendment gain. It is a functional block diagram of the correction gain calculation part which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows an example of the map of the relationship between the vehicle speed which concerns on 2nd Embodiment of this invention, a steering angle, a steering angle deviation, and a correction gain. It is explanatory drawing which shows the characteristic of the slip ratio and the driving force of a turning inner and outer wheel when the slip ratio and the characteristic of the driving force of the turning inner and outer wheels and the road surface friction coefficient are different. It is explanatory drawing of the relationship of the lateral acceleration by Ackerman geometry.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 9 show a first embodiment of the present invention.

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

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

  The driving force input to the rear wheel final reduction gear 7 is transmitted to the left rear wheel 14rl via the rear wheel left drive shaft 13rl and to the right rear wheel 14rr via the rear wheel right drive shaft 13rr. The driving force input to the front wheel final reduction gear 11 is transmitted to the left front wheel 14fl via the front wheel left drive shaft 13fl and to the right front wheel 14fr via the front wheel right drive shaft 13fr.

  The transfer 3 is a wet multi-plate clutch (transfer clutch) as a variable torque transmission capacity clutch in which a drive plate 15a provided on the reduction drive gear 8 side and a driven plate 15b provided on the rear drive shaft 4 side are alternately stacked. ) 15 and a transfer piston 16 that variably applies a fastening force (differential limit torque) of the transfer clutch 15. Therefore, this vehicle controls the pressing force by the transfer piston 16 and controls the differential limiting torque of the transfer clutch 15, so that the torque distribution ratio is between the front wheel and the rear wheel, for example, between 100: 0 and 50:50. It is a four-wheel drive vehicle with a front engine / front drive vehicle base (FF base) that can be changed by the vehicle.

  The pressing force of the transfer piston 16 is given by a transfer clutch driving unit 40 configured by a hydraulic circuit having a plurality of solenoid valves and the like. A control signal (transfer clutch torque Ttrf) for driving the transfer clutch drive unit 40 is output from the control unit 30.

  The control unit 30 is provided as a control means, and mainly includes a correction gain calculation unit 31 and a driving force distribution calculation unit 32 as shown in FIG. The control unit 30 also includes a four-wheel wheel speed sensor 21fl, 21fr, 21rl, 21rr as a wheel speed detecting means for detecting the four-wheel wheel speeds ωfl, ωfr, ωrl, ωrr, and a rudder for detecting the steering angle δ. A steering angle sensor 22 as an angle detection means, an accelerator opening sensor 23 for detecting an accelerator opening θACC, an engine control unit 24 for executing various controls related to the engine 1, and various controls related to the automatic transmission 2 A transmission control unit 25 is connected, and the four-wheel wheel speeds ωfl, ωfr, ωrl, and ωrr are supplied to the correction gain calculation unit 31 and the driving force distribution calculation unit 32 to the steering angle δ, the engine output torque Teg, the engine speed Ne, The turbine rotation speed Nt and the main transmission gear ratio i of the torque converter are input to the correction gain calculation unit 31 and the accelerator opening θACC is input to the driving force distribution calculation unit 32.

  Then, as will be described later, the correction gain calculation unit 31 is based on these input signals ωfl, ωfr, ωrl, ωrr, δ, Teg, Ne, Nt, i, and the vehicle speed V, wheels of the turning inner wheel and the turning outer wheel. The speed difference ΔV and the total driving force Fx generated by the vehicle are calculated. Based on the total driving force Fx, the vehicle speed V, and the wheel speed difference ΔV, the preset total driving force Fx, the vehicle speed V, and the wheel The steering angle is set as the estimated steering angle δe with reference to the map of the relationship between the speed difference ΔV and the steering angle (estimated steering angle), and the deviation between the steering angle δ detected by the steering angle sensor 22 and the estimated steering angle δe is calculated. A map of the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the road surface friction coefficient μ set in advance based on the vehicle speed V, the steering angle δ, and the steering angle deviation Δδ. To set the road surface friction coefficient μ, and based on the road surface friction coefficient μ, set the correction gain G that is the correction value for the front-rear driving force distribution. .

  Further, the driving force distribution calculating unit 32 is provided as a front / rear driving force distribution calculating means, and is set in advance as shown in FIG. 6, for example, based on the input signals ωfl, ωfr, ωrl, ωrr, and θACC described above. The target differential limiting torque is set based on the map of the target differential limiting torque corresponding to the vehicle speed and the accelerator opening. The target differential limiting torque is corrected by multiplying it by the correction gain G calculated by the correction gain calculation unit 31 described above to calculate a control signal (transfer clutch torque Ttrf) and output it to the transfer clutch drive unit 40. And control.

  As shown in FIG. 3, the correction gain calculator 31 includes a vehicle speed calculator 31a, a wheel speed difference calculator 31b, a transmission output torque calculator 31c, a total driving force calculator 31d, an estimated steering angle setting unit 31e, and a steering angle deviation. The calculation unit 31f mainly includes a road surface friction coefficient estimation unit 31g and a correction gain setting unit 31h.

  The vehicle speed calculation unit 31a receives the four-wheel wheel speeds ωfl, ωfr, ωrl, and ωrr from the four-wheel wheel speed sensors 21fl, 21fr, 21rl, and 21rr. For example, the vehicle speed V (= (ωrl + ωrr) / 2) is calculated by calculating the average of the wheel speeds of the left and right rear wheels, and is output to the estimated rudder angle setting unit 31e and the road surface friction coefficient estimating unit 31g. Thus, the vehicle speed calculation unit 31a is provided as vehicle body speed detection means.

  The wheel speed difference calculation unit 31b receives the four-wheel wheel speeds ωfl, ωfr, ωrl, and ωrr from the four-wheel wheel speed sensors 21fl, 21fr, 21rl, and 21rr. Then, for example, the absolute value of the wheel speed difference between the left and right rear wheels is calculated as the wheel speed difference ΔV (= | ωrl−ωrr |) and output to the estimated steering angle setting unit 31e. Thus, the wheel speed difference calculation unit 31b is provided as a wheel speed difference calculation unit.

The transmission output torque calculation unit 31c receives the engine output torque Teg and the engine speed Ne from the engine control unit 24, and receives the turbine speed Nt of the torque converter and the main transmission gear ratio i from the transmission control unit 25. Then, for example, the transmission output torque Ttm is calculated by the following equation (8) and output to the total driving force calculation unit 31d.
Ttm = Teg · t · i (8)
Here, t is a torque ratio of the torque converter, and is obtained by referring to a preset map of the rotational speed ratio e (= Nt / Ne) of the torque converter and the torque ratio of the torque converter.

The total driving force calculation unit 31d receives the transmission output torque Ttm from the transmission output torque calculation unit 31c. Then, the total driving force Fx is calculated by the following equation (9) and output to the estimated steering angle setting unit 31e.
Fx = Ttm · if · η / Rt (9)
Here, if is the final gear ratio, η is the transmission efficiency, and Rt is the tire radius. Thus, the total driving force calculation unit 31d is provided as a total driving force calculation unit. It is assumed that the driving force Fxl on the left wheel side and the driving force Fxr on the right wheel side are equal (that is, Fxl = Fxr = Fx / 2).

  The estimated rudder angle setting unit 31e receives the vehicle speed V from the vehicle speed calculation unit 31a, the wheel speed difference ΔV from the wheel speed difference calculation unit 31b, and the total driving force Fx from the total driving force calculation unit 31d. Then, for example, refer to a map of the relationship between the total driving force Fx, the vehicle speed V, the wheel speed difference ΔV, and the steering angle (estimated steering angle) δe that has been set in advance through experiments, calculations, etc., as shown in FIG. Then, the estimated steering angle δe is set and output to the steering angle deviation calculating unit 31f. As shown in FIG. 7, a map of the relationship between the total driving force Fx, the vehicle speed V, the wheel speed difference ΔV, and the steering angle (estimated steering angle) δe shows that the total driving force Fx and the wheel speed difference ΔV are constant. The estimated steering angle δe is set to be lower as the vehicle speed V is higher. When the total driving force Fx and the vehicle speed V are constant, the estimated steering angle δe is set larger as the wheel speed difference ΔV increases. It is a characteristic. Thus, the estimated rudder angle setting part 31e is provided as an estimated rudder angle setting means.

By the way, the estimated steering angle δe is geometrically expressed by the following equation (10), where Wb is a wheel base.
tan (δe) = Wb / R0 (10)
Since R0 = Wb / tan (δe) from the equation (10), the relationship of the following equation (11) can be obtained from the equations (4) and (5).
δe = tan ⁻¹ (Wb / T · (Vo−Vi) / V) (11)
This equation (11) means that the estimated steering angle δe is inversely proportional to the vehicle speed V and proportional to the wheel speed difference ΔV. In addition, as shown in FIG. 12B, in the linear range of the characteristics of the slip ratio λ and the driving force Fx of the turning inner and outer wheels, the slip ratio λ is doubled when the driving force Fx is doubled. And the estimated steering angle δe is also doubled. In FIG. 7, this characteristic is well expressed.

  The steering angle deviation calculation unit 31f receives the steering angle δ from the steering angle sensor 22, and receives the estimated steering angle δe from the estimated steering angle setting unit 31e. Then, a deviation between the steering angle δ and the estimated steering angle δe is calculated as a steering angle deviation Δδ (= | δ−δe |) and output to the road surface friction coefficient estimating unit 31g. Thus, the steering angle deviation calculating unit 31f is provided as a steering angle deviation calculating unit.

  The road surface friction coefficient estimating unit 31g receives the steering angle δ from the steering angle sensor 22, the vehicle speed V from the vehicle speed calculation unit 31a, and the steering angle deviation Δδ from the steering angle deviation calculation unit 31f. Then, for example, referring to a map of the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the road surface friction coefficient μ set in advance by experiment, calculation, etc., as shown in FIG. μ is set and output to the correction gain setting unit 31h. As shown in FIG. 8, a map of the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the road surface friction coefficient μ shows that the road surface increases as the vehicle speed V increases as the steering angle δ and the steering angle deviation Δδ are constant. The friction coefficient μ is set to a low value. When the steering angle δ and the vehicle speed V are constant, the road surface friction coefficient μ is set to be smaller as the steering angle deviation Δδ increases. That is, as shown in FIG. 12B, in the case of a low μ road surface, slip between the tire and the road surface is likely to occur, so that the difference between the left and right wheels tends to be smaller than that of the high μ road surface. When the difference between the left and right wheels is reduced, the estimated steering angle δe estimated from the wheel speed is reduced (close to straight ahead), and the characteristic that the steering angle deviation Δδ is increased is reflected. Further, since this tendency becomes more prominent as the actual steering angle (the steering angle sensor 22 to the steering angle δ) is larger, the map is corrected by the steering angle δ from the steering angle sensor 22. Thus, the road surface friction coefficient estimation unit 31g is provided as a road surface friction coefficient setting unit.

  As described above, in the first embodiment of the present invention, the vehicle speed calculation unit 31a, the wheel speed difference calculation unit 31b, the transmission output torque calculation unit 31c, the total driving force calculation unit 31d, the estimated steering angle setting unit 31e, the steering angle The deviation calculation unit 31f and the road surface friction coefficient estimation unit 31g constitute a road surface friction coefficient estimation device.

  The correction gain setting unit 31h receives the road surface friction coefficient μ from the road surface friction coefficient estimation unit 31g. Then, for example, as shown in FIG. 9, the correction gain G is set with reference to a map of the relationship between the road surface friction coefficient μ and the correction gain G set in advance by experiment, calculation, etc., and the driving force distribution is calculated. To the unit 32. As shown in FIG. 9, the map of the relationship between the road surface friction coefficient μ and the correction gain G is set to a characteristic that the correction cane G becomes lower as the height μ increases. In order to prevent this, the transfer clutch torque Ttrf of the transfer 3 is corrected and set low, and the transfer clutch torque Ttrf of the transfer 3 can be corrected and set high on a low μ road surface. It is possible to travel with adequately secured.

  Next, the front / rear driving force distribution control program executed by the control unit 30 will be described with reference to the flowchart of FIG. First, in step (hereinafter abbreviated as “S”) 101, necessary parameters, that is, four-wheel wheel speeds ωfl, ωfr, ωrl, ωrr, rudder angle δ, engine output torque Teg, engine speed Ne, turbine of the torque converter. The rotational speed Nt, the main transmission gear ratio i, and the accelerator opening θACC are read.

  Next, in S102, the correction gain calculation unit 31 calculates a correction gain G, which is a correction value for front-rear driving force distribution, according to a correction gain calculation processing routine described later.

  Next, the process proceeds to S103, where the driving force distribution calculating unit 32 sets a target based on a map of a target differential limiting torque corresponding to the vehicle speed and the accelerator opening that is set in advance as shown in FIG. 6, for example. A differential limiting torque is set, and this target differential limiting torque is corrected by multiplying it by a correction gain G to calculate a control signal (transfer clutch torque Ttrf), which is output to the transfer clutch drive unit 40 to exit the program. .

Next, the correction gain calculation processing routine executed by the correction gain calculation unit 31 will be described with reference to the flowchart of FIG.
First, in S201, the transmission output torque calculation unit 31c calculates the transmission output torque Ttm by the above-described equation (8).

  Next, in S202, the total driving force calculation unit 31d calculates the total driving force Fx by the above-described equation (9).

  Next, it progresses to S203 and the vehicle speed calculation part 31a calculates the vehicle speed V by calculating the average of the wheel speed of a right-and-left rear wheel.

  Next, in S204, the wheel speed difference calculation unit 31b calculates the absolute value of the wheel speed difference between the left and right rear wheels as the wheel speed difference ΔV.

  Next, in S205, the estimated rudder angle setting unit 31e determines the total driving force Fx, the vehicle speed V, the wheel speed difference ΔV, and the rudder angle (estimated rudder) based on the total driving force Fx, the vehicle speed V, and the wheel speed difference ΔV. (Angle) Estimated steering angle δe is set with reference to a map of the relationship with δe (FIG. 7).

  Next, in S206, the steering angle deviation calculation unit 31f calculates a deviation between the steering angle δ and the estimated steering angle δe as a steering angle deviation Δδ.

  Next, proceeding to S207, the road surface friction coefficient estimating unit 31g, based on the vehicle speed V, the steering angle δ, and the steering angle deviation Δδ, the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the road surface friction coefficient μ. The road surface friction coefficient μ is set with reference to the map (FIG. 8).

  In step S208, the correction gain setting unit 31h sets the correction gain G with reference to a map (FIG. 9) of the relationship between the road surface friction coefficient μ and the correction gain G based on the road surface friction coefficient μ, and executes a routine. Exit.

  Thus, according to the first embodiment of the present invention, the vehicle speed V, the wheel speed difference ΔV, and the total driving force Fx generated by the vehicle are calculated, and the total driving force Fx, the vehicle speed V, and the wheel speed difference ΔV are calculated. Based on the above, an estimated steering angle δe is set and detected with reference to a map of the relationship between the preset total driving force Fx, vehicle speed V, wheel speed difference ΔV, and steering angle (estimated steering angle) A deviation between the steering angle δ and the estimated steering angle δe is calculated as a steering angle deviation Δδ. Based on the vehicle speed V, the steering angle δ, and the steering angle deviation Δδ, the vehicle speed V, the steering angle δ, and the steering angle that are set in advance are calculated. A road surface friction coefficient μ is set with reference to a map of the relationship between the deviation Δδ and the road surface friction coefficient μ, and a correction gain G that is a correction value for the front-rear driving force distribution is set based on the road surface friction coefficient μ. Therefore, even when a driving force acts, the road surface friction coefficient μ can be estimated easily and accurately, and the front and rear driving force distribution control can be performed with high accuracy using the road surface friction coefficient μ.

  Next, FIG. 10 and FIG. 11 show a second embodiment of the present invention. In the second embodiment, the correction gain calculation unit 31 calculates the steering angle deviation Δδ and then directly estimates the vehicle speed V and the steering angle δ without estimating the road surface friction coefficient μ as in the first embodiment. Based on the steering angle deviation Δδ, the correction gain G is set with reference to the map of the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the correction gain G. Since the operation is the same as that of the first embodiment described above, the same components are denoted by the same reference numerals and description thereof is omitted.

  That is, as shown in FIG. 10, the correction gain calculation unit 31 according to the second embodiment includes a vehicle speed calculation unit 31a, a wheel speed difference calculation unit 31b, a transmission output torque calculation unit 31c, a total driving force calculation unit 31d, and an estimation. It is mainly composed of a rudder angle setting unit 31e, a rudder angle deviation calculating unit 31f, and a correction gain setting unit 31i.

  The correction gain setting unit 31i receives the steering angle δ from the steering angle sensor 22, receives the vehicle speed V from the vehicle speed calculation unit 31a, and receives the steering angle deviation Δδ from the angle deviation calculation unit 31f. Then, for example, referring to a map of the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the correction gain G that has been set in advance by experiment, calculation, etc., as shown in FIG. This is set and output to the driving force distribution calculation unit 32. As shown in FIG. 11, the map of the relationship between the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the correction gain G shows that the correction gain increases as the vehicle speed V increases with the steering angle δ and the steering angle deviation Δδ constant. G is a characteristic that is set to be large, and when the steering angle δ and the vehicle speed V are constant, the correction gain G is set to be large as the steering angle deviation Δδ increases. The map also incorporates the influence of the road surface friction coefficient μ described in. As described above, the correction gain setting unit 31i is provided as a front-rear driving force distribution correction value setting unit.

  As described above, in the second embodiment of the present invention, the vehicle speed V, the wheel speed difference ΔV, the total driving force Fx generated by the vehicle are calculated, and the total driving force Fx, the vehicle speed V, and the wheel speed difference ΔV are calculated. Based on the preset map of the relationship among the total driving force Fx, the vehicle speed V, the wheel speed difference ΔV, and the steering angle (estimated steering angle), the estimated steering angle δe is set, and the detected steering angle A deviation between δ and the estimated steering angle δe is calculated as a steering angle deviation Δδ. Based on the vehicle speed V, the steering angle δ, and the steering angle deviation Δδ, the vehicle speed V, the steering angle δ, the steering angle deviation Δδ, and the correction gain G are calculated. A correction gain G, which is a correction value for the front-rear driving force distribution, is set with reference to the relationship map. For this reason, even when a driving force acts, it is possible to easily set and control the front / rear driving force distribution with high accuracy.

DESCRIPTION OF SYMBOLS 1 Engine 2 Automatic transmission 3 Transfer 14fl, 14fr, 14rl, 14rr Wheel 15 Transfer clutch 21fl, 21fr, 21rl, 21rr Wheel speed sensor (wheel speed detection means)
22 Rudder angle sensor (steering angle detection means)
24 engine control unit 25 transmission control unit 30 control unit (control means)
31 correction gain calculation unit 31a vehicle speed calculation unit (body speed detection means)
31b Wheel speed difference calculation unit (wheel speed difference calculation means)
31c Transmission output torque calculation unit 31d Total driving force calculation unit (total driving force calculation means)
31e Estimated rudder angle setting unit (estimated rudder angle setting means)
31f Rudder angle deviation calculating part (steering angle deviation calculating means)
31g Road surface friction coefficient estimator (road surface friction coefficient setting means)
31h Correction gain setting unit 31i Correction gain setting unit (front-rear driving force distribution correction value setting means)
32 Driving force distribution calculation unit (front and rear driving force distribution calculation means)
40 Transfer clutch drive

Claims (5)

Wheel speed detection means for detecting the wheel speed of each wheel;
Rudder angle detecting means for detecting the rudder angle;
Vehicle speed detection means for detecting the vehicle speed;
Wheel speed difference calculating means for calculating the wheel speed difference between the turning inner wheel and the turning outer wheel based on the wheel speed of each wheel detected by the wheel speed detecting means;
Total driving force calculating means for calculating the total driving force generated by the vehicle;
Based on the total driving force, the vehicle body speed, and the wheel speed difference, the steering wheel is steered with reference to a preset map of the relationship between the total driving force, the vehicle body speed, the wheel speed difference, and the steering angle. Estimated rudder angle setting means for setting the angle as an estimated rudder angle;
Rudder angle deviation calculating means for calculating a deviation between the rudder angle detected by the rudder angle detecting means and the estimated rudder angle set by the estimated rudder angle setting means as a rudder angle deviation;
Based on the vehicle body speed, the rudder angle, and the rudder angle deviation, a road surface friction coefficient is determined with reference to a preset map of the relationship between the vehicle body speed, the rudder angle, the rudder angle deviation, and the road surface friction coefficient. Road surface friction coefficient setting means for setting
A road surface friction coefficient estimating device comprising:   The pre-set map of the relationship between the total driving force, the vehicle body speed, the wheel speed difference, and the steering angle indicates that the vehicle body speed is high when the total driving force and the wheel speed difference are constant. The estimated rudder angle is set to be lower, and the estimated rudder angle is set to be larger as the wheel speed difference is larger under a constant total driving force and the vehicle body speed. The road surface friction coefficient estimating apparatus according to claim 1.   The map of the relationship between the vehicle body speed, the rudder angle, the rudder angle deviation, and the road surface friction coefficient that is set in advance indicates that the higher the vehicle body speed is, the higher the vehicle body speed is. The road surface friction coefficient is set to a low value, and the road surface friction coefficient is set to be smaller as the steering angle deviation is larger under a constant rudder angle and vehicle body speed. The road surface friction coefficient estimating device according to claim 1. In a front-rear driving force distribution control device for a vehicle, comprising control means for calculating front-rear driving force distribution according to the driving state of the vehicle, and controlling the vehicle with front-rear driving force distribution set by the control means,
A road surface friction coefficient estimating device according to any one of claims 1 to 3,
The control means sets a correction value for the front / rear driving force distribution based on the road surface friction coefficient estimated by the road surface friction coefficient estimation device, and corrects and outputs the front / rear driving force distribution with the correction value. A vehicle front / rear driving force distribution control device characterized by the above. Front-rear driving force distribution calculating means for calculating the front-rear driving force distribution of the vehicle according to the driving state of the vehicle;
Wheel speed detection means for detecting the wheel speed of each wheel;
Rudder angle detecting means for detecting the rudder angle;
Vehicle speed detection means for detecting the vehicle speed;
Wheel speed difference calculating means for calculating the wheel speed difference between the turning inner wheel and the turning outer wheel based on the wheel speed of each wheel detected by the wheel speed detecting means;
Total driving force calculating means for calculating the total driving force generated by the vehicle;
Based on the total driving force, the vehicle body speed, and the wheel speed difference, the steering wheel is steered with reference to a preset map of the relationship between the total driving force, the vehicle body speed, the wheel speed difference, and the steering angle. Estimated rudder angle setting means for setting the angle as an estimated rudder angle;
Rudder angle deviation calculating means for calculating a deviation between the rudder angle detected by the rudder angle detecting means and the estimated rudder angle set by the estimated rudder angle setting means as a rudder angle deviation;
Based on the vehicle body speed, the rudder angle, and the rudder angle deviation, refer to a map of the relationship between the vehicle body speed, the rudder angle, the rudder angle deviation, and the correction value for the front-rear driving force distribution set in advance. Front and rear driving force distribution correction value setting means for setting a correction value for front and rear driving force distribution;
Front / rear driving force distribution correcting means for correcting the front / rear driving force distribution of the vehicle set by the front / rear driving force distribution calculating means with the correction value set by the front / rear driving force distribution correction value setting means;
A vehicle front-rear driving force distribution control device comprising:

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