JPH07101258A - Road surface frictional resistance estimating device for vehicle - Google Patents

Abstract

PURPOSE:To enable the estimation of road surface frictional resistance mu also during rectilinear travel without causing large cost increase by estimating the frictional resistance of the travel road surface on the basis of the differential state of differential limiting mechanism, the body speed, and the difference between the rotating speed difference of lateral driving wheels and the reference rotating speed difference. CONSTITUTION:At the time of estimating a road surface frictional resistance mu making use of the relation between the slip factor of a tire and the driving force, a wheel speed difference between lateral driving wheels is computed by a subtracting part 18J on the basis of rotating speed data signals from the lateral wheel speed sensors 19RL, 19RR, and the theoretical rotating speed difference Vo of the driving wheels is computed by a reference rotating speed difference computing means 18F on the basis of the body speed VB computed by an estimated body speed computing part 216 and a steering wheel angle thetaH from a steering angle sensor 20. The difference DELTAV between the wheel speed difference and the reference rotating speed difference is then computed by the subtracting part 18B, and this speed difference DELTAV and the body speed VB are inputted to a road surface frictional resistance estimating part 18D so as to estimate road surface frictional resistance mu by a map also on the basis of the torque moving quantity DELTAT from a control quantity setting part 18C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle road surface frictional resistance estimating device for estimating road surface frictional resistance from a road surface state.

[0002]

2. Description of the Related Art In recent years, a four-wheel steering mechanism has been developed which steers the rear wheels according to the steering angle of the front wheels of an automobile and the vehicle speed. There may be provided a device for detecting the state and estimating the road surface frictional resistance coefficient (road surface frictional resistance).

FIG. 1 shows this road surface frictional resistance estimating device.
This will be described with reference to FIGS. FIG. 14 shows 4 as described above.
1 is a diagram schematically showing an overall configuration of a wheel steering mechanism, and FIG.
In FIG. 4, 25 and 26 are front wheels as steering wheels, and 15,
Reference numeral 16 is a rear wheel, and 105 is a steering handle (hereinafter referred to as a handle). The front wheel steering tie rod 106A arranged so as to connect the front wheels 25 and 26 is provided with a hydraulic cylinder 106 for power steering in addition to a mechanical drive mechanism (not shown) such as a rack and pinion. The hydraulic cylinder 106 is provided with a phase advancing valve 113 for supplying and discharging hydraulic pressure according to the steering state of the handle 105.

Further, a hydraulic cylinder 107 for steering the rear wheels is attached to the tie rod 107A for steering the rear wheels which is arranged so as to connect the rear wheels 15 and 16, and the hydraulic cylinder 107 also has the hydraulic cylinder 107 for steering the rear wheels. Valve 108 is provided. These phase advancing valve 113 and rear wheel steering valve 1
Reference numeral 08 denotes a steering wheel angle θ _H , a vehicle speed V, a hydraulic oil pressure for power steering (hereinafter abbreviated as power steering pressure) P, a rear wheel steering angle (hereinafter, steering angle is abbreviated as steering angle) and L of the alternator 115A by the controller 18. The control is performed based on the terminal output 115 and the like.

For this reason, the controller 18 includes a steering wheel angle sensor 20, a vehicle speed sensor (vehicle speed detecting means) 19, 2.
Power steering pressure sensor 112, rear wheel steering angle sensor 114
Also, the L terminal output 115 of the alternator 115A and the like are connected, and each detection information of these is input to the controller 18. A schematic configuration of steering of the front and rear wheels of the controller 18 will be described. As shown in FIG. 15, the steering wheel angle sensor 20, the wheel speed sensor 19, and the L terminal output 1 of the alternator input as digital signals.
While the rear wheel steering mode is determined based on each information from the steering wheel 15, each information from the power steering pressure sensor 112 input as an analog signal and the steering wheel angle sensor 20,
The road surface frictional resistance estimation unit 18D estimates the road surface state (road surface frictional resistance coefficient μ) based on each information from the vehicle speed sensor 19.

Then, the value of the road surface frictional resistance μ estimated to be the determined rear wheel steering mode, the steering wheel angle sensor 20, the vehicle speed sensor 19 and the rear wheel steering angle sensor 11 described above.
The control amount of each control is set on the basis of each information from 4, and these are digital-to-analog converted and output to the phase advancing valve 113 of the front wheels and the steering valve 108 for the rear wheels.

By the way, the steering wheels 25, 2 of the vehicle during steering
The force acting on 6 is schematically shown in FIG.
As shown in FIG. 17, during steering of the vehicle, a slip angle βf is usually generated between the direction of the tire (front wheel steering angle δf) and the traveling direction of the tire (traveling direction of the vehicle). At this time, the cornering force CF is generated in the tire in a direction orthogonal to the traveling direction of the tire.

This cornering force CF is a frictional force against the ground contact surface of the tire, and as shown in FIG.
The size depends on the friction coefficient μ between the road surface and the tire. Also, the value of the cornering force generated per unit sideslip angle βf (corresponding to the inclination of the graph in FIG. 16)
Varies depending on the value of road friction resistance μ.

Therefore, the road surface frictional resistance estimating unit 18D described above is used.
Then, this side slip angle βf and cornering force CF
Are calculated from the steering angle θ _H of the steering wheel and the hydraulic pressure P of the power steering device 30, respectively, and the road friction resistance μ is estimated from the map shown in FIG. Since the power steering pressure P is proportional to the road surface friction resistance μ and the slip angle βf, it can be expressed as P = K1 · βf · μ (K1 is a constant).

The slip angle βf can be expressed as βf = K3V ² .θ _H / (μ + K ² .V ² ). Note that K2 and K3 are constants.
Then, from the above two equations, P / θ _H = μ · K1 · K3 · V ² / (μ + K2 · V ² )

Therefore, the power steering pressure P and the steering wheel angle θ
By detecting _H and vehicle speed V, the frictional resistance of the road surface μ
Can be estimated. By the way, when the vehicle is in a steady turning state, the frictional resistance μ
Can be estimated, but it may be difficult to estimate in a transient state.

That is, during steering, the phase advancing valve 1
The valve characteristics of No. 13 and the influence of tire inertia, etc.
When the steering wheel operation as shown in 8 (a) is performed,
As shown in FIG. 18B, the power steering pressure P has a phase lead or a phase lag, and in such a case, the above equation cannot be applied. So with this device,
By performing the processing as shown in FIG. 19, the frictional resistance μ of the road surface is stably output.

First, the power steering pressure P is subjected to noise removal by a number H _Z filter as shown in FIG. After this, 2
The next filter is used to remove the phase advance during steering. Then, P / θ _H is calculated from the value obtained by this processing. In addition, the controller 18 is provided with a condition determination unit 18E for removing the influence of the characteristic of the valve 113 of the power steering device and the phase delay, and P / θ
_{After H} is calculated, the condition determination unit 18E estimates the road surface frictional resistance μ only when the following conditions are satisfied.

That is, | θ _H |> 10 °, the handle 10
The road friction resistance μ is estimated when P / θ _H > 0 when 5 is a cut. Then, the road surface frictional resistance estimation unit 18D that maps the relationship between the above-described P / theta _H and the road surface friction mu, road friction resistance mu is estimated P / theta _H and the vehicle speed V as parameters.

Finally, the output value stabilizing means 18 for stabilizing the output value while avoiding the sudden change of the output value.
H is provided, and the limiter is activated so that the change in the output value of the road friction resistance μ per second is within a minute range. Furthermore, the output is further stabilized through the several H _Z filter. To be done.

[0016]

However, such a conventional road surface frictional resistance estimating device requires two high-pressure power steering sensors 112 for detecting the power steering pressure, resulting in an increase in cost. I will end up. Further, since the road surface frictional resistance estimating device as described above estimates the road surface frictional resistance from the power steering pressure, there is a problem that the road surface frictional resistance cannot be estimated in a straight traveling state in which almost no power steering pressure is generated.

The present invention was devised in view of the above problems, and it is possible to estimate the road friction resistance μ even when the vehicle is traveling straight without causing a significant increase in cost. An object is to provide a resistance estimation device.

[0018]

Therefore, the vehicle road surface frictional resistance estimating apparatus according to the present invention as set forth in claim 1 limits the differential state between the left driving wheel and the right driving wheel of the vehicle. A limiting mechanism, a left wheel side rotation speed detecting means and a right wheel side rotation speed detecting means for detecting rotation speeds of the left driving wheel and the right driving wheel, and a steering wheel angle detecting means for detecting a steering wheel angle of the vehicle. At the same time, the vehicle body speed detecting means for detecting the vehicle body speed of the vehicle, and the reference rotational speed difference between the left and right driving wheels based on the vehicle body speed calculated by the vehicle body speed detecting means and the detection information from the steering wheel angle detecting means. And a reference rotational speed difference calculation means for calculating the operating speed of the differential limiting mechanism, the vehicle body speed of the vehicle, the rotational speed difference between the left and right driving wheels, and the reference rotational speed difference between the left and right driving wheels. , The difference between the Road surface frictional resistance estimating means for estimating a frictional resistance is characterized by is provided.

According to a second aspect of the present invention, there is provided a vehicle road surface frictional resistance estimating apparatus, wherein a left drive wheel and a right drive wheel which constitute either one of the front and rear drive wheels of a four-wheel drive vehicle. A differential limiting mechanism that limits the differential state between
A left wheel side rotation speed detecting means and a right wheel side rotation speed detecting means for detecting the rotation speeds of the left drive wheel and the right drive wheel on the side provided with the differential limiting mechanism of the vehicle; and the differential limiting mechanism of the vehicle. Left wheel side rotation speed detection means and right wheel side rotation speed detection means for detecting the rotation speeds of the left drive wheel and the right drive wheel that are not provided, and the left wheel side rotation that is provided with the differential limiting mechanism Detection information from the speed detection means and the right wheel side rotation speed detection means, and detection from the left wheel side rotation speed detection means and the right wheel side rotation speed detection means on the side not provided with the differential limiting mechanism A calculation means is provided for calculating the amount of change in the slip ratio difference of the drive wheels of the vehicle based on the information and the operating state of the differential limiting mechanism, and the average of the amount of change in the slip ratio difference for each fixed cycle. Value and the maximum of the amount of change in the slip ratio difference for each fixed cycle It is characterized in that it is configured to estimate the frictional resistance of the road surface on which traveling of the vehicle and the difference between the minimum value, and a.

According to a third aspect of the present invention, there is provided a vehicle road surface frictional resistance estimating device according to the first or second aspect of the invention, wherein the differential limiting mechanism is a left wheel drive shaft of the vehicle. A drive force transmission control mechanism capable of adjusting the drive force of the left and right wheels by exchanging the drive force with the right wheel drive shaft is provided. A speed change mechanism connected to one drive shaft side and capable of changing and outputting the rotational speed of the one drive shaft side at a constant speed change ratio; and the other drive shaft side of the left and right drive shafts. And a transmission capacity variable control type torque transmission mechanism which is interposed between the transmission mechanism and the output side and is capable of transmitting driving force between the left and right drive shafts when engaged. Is characterized by.

According to a fourth aspect of the present invention, there is provided a vehicle road surface frictional resistance estimating apparatus according to the first or second aspect of the invention, wherein the differential limiting mechanism includes a left wheel drive shaft of the vehicle. The driving force input from the input unit, which receives the driving force from the engine between the right wheel driving shaft and the left and right driving shafts, is allowed while allowing the differential between the left and right driving shafts. The drive force transmission control mechanism includes a differential mechanism transmitting to each drive shaft and a drive force transmission control mechanism capable of controlling the transmission state of the drive force to adjust the drive force distribution to the left and right wheels. A transmission mechanism connected to the drive shaft side and capable of changing and outputting the rotation speed of the drive shaft side at a constant gear ratio; and a transmission mechanism between the output portion side of the transmission mechanism and the input portion side. Is mounted and capable of transmitting driving force between the drive shaft side and the input portion side when engaged. It is characterized in that it is composed of a variable control type torque transmission mechanism.

According to a fifth aspect of the present invention, there is provided a road surface frictional resistance estimating device for a vehicle according to the first or second aspect of the invention, wherein the differential limiting mechanism is a left wheel drive shaft of the vehicle. The driving force input from the input unit, which receives the driving force from the engine between the right wheel driving shaft and the left and right driving shafts, is allowed while allowing the differential between the left and right driving shafts. The drive force transmission control mechanism includes a differential mechanism transmitting to each drive shaft and a drive force transmission control mechanism capable of controlling the transmission state of the drive force to adjust the drive force distribution to the left and right wheels. A transmission mechanism that is connected to the input portion side and can output the rotational speed of the input portion side at a constant gear ratio and is interposed between an output portion side of the transmission mechanism and the drive shaft side. The transmission capacity that can transmit the driving force between the drive shaft side and the input part side when engaged. It is characterized in that it is composed of a control equation torque transmission mechanism.

Further, the road surface frictional resistance estimating apparatus for a vehicle according to a sixth aspect of the present invention is the one in which the vehicle is in a predetermined driving state in addition to the configuration according to any one of the first to fifth aspects. Is configured to update the estimation of the frictional resistance of the road surface only.

[0024]

In the vehicle road surface frictional resistance estimating apparatus according to the present invention described above, the rotational speeds of the left and right driving wheels are detected by the left wheel side rotational speed detecting means and the right wheel side rotational speed detecting means. Then, the wheel speed difference between the left and right drive wheels is calculated based on these pieces of information, and the vehicle speed is estimated by the vehicle speed detecting means.

Further, the steering angle of the vehicle is detected by the steering wheel angle detecting means, and the reference rotational speed difference between the left and right wheels is calculated from the steering wheel angle information and the above-mentioned vehicle speed. Then, the road surface frictional resistance is estimated from the reference rotational speed difference, the wheel speed difference between the left and right driving wheels, and the differential state of the differential limiting mechanism. In the vehicle road surface frictional resistance estimating device according to the second aspect of the present invention, the left and right wheel rotational speed detecting means and the right wheel side rotational speed detecting means on the side provided with the differential limiting mechanism are connected to the left and right drive wheels. Each rotation speed of is detected,
The rotation speeds of the left and right wheels are detected by the left wheel side rotation speed detection means and the right wheel side rotation speed detection means that are not provided with the differential limiting mechanism.

Further, the calculating means calculates the amount of change in the slip ratio difference between the left and right driving wheels based on these pieces of information and the operating state of the differential limiting mechanism. Further, the difference between the average value and the maximum value and the minimum value of the change amount of the slip ratio difference between the driving wheels for each constant cycle is calculated. Then, the road surface frictional resistance is estimated from the relationship between the average value of the change amount of the slip ratio difference for each constant period and the difference between the maximum value and the minimum value of the change amount of the slip ratio difference for each constant period.

In the vehicle road surface frictional resistance estimating device according to the third aspect of the present invention, the driving force transmission control mechanism causes the driving force to be transmitted between the left wheel rotating shaft side and the right wheel rotating shaft side of the vehicle. Transfers are made. That is, the rotation speed of one of the left and right rotary shafts is changed by the speed change mechanism,
There is a speed difference between the output side of this speed change mechanism and the other rotary shaft side of the left and right rotary shafts, and the left and right rotary shafts are rotated by engaging the variable transmission capacity control type torque transmission mechanism. The driving force is exchanged between the shafts. That is, when the transmission capacity variable control type torque transmission mechanism is engaged, the driving force is transmitted from the high speed side to the low speed side of the other rotary shaft side of the left and right rotary shafts and the output side of the transmission mechanism. As a result, the driving force decreases on the rotating shaft on the high speed side, and the driving force increases on the rotating shaft on the low speed side in response to the decrease in the driving force. As a result, the driving force of the left and right drive wheels is positively distributed at an arbitrary ratio, which makes it possible to estimate the road friction resistance μ even when traveling straight.

Further, in the vehicle road surface frictional resistance estimating device according to the fourth aspect of the present invention, the driving force of the input shaft is transmitted to each of the left wheel driving shaft and the right wheel driving shaft via the differential mechanism. However, at this time, the distribution state of the driving force output to the left and right driving shafts is adjusted by the driving force transmission control mechanism. In other words, in the drive force transmission control mechanism, the speed change mechanism causes the member on the drive shaft side to change speed at a constant speed change ratio, and a speed difference occurs between the output side and the input side of the speed change mechanism, and the transmission is performed. By engaging the variable capacity control type torque transmission mechanism, the driving force is transmitted between the drive shaft side and the input section side. That is, when the transmission capacity variable control type torque transmission mechanism is engaged, the driving force is transmitted from the high speed side of the output side and the input side of the speed change mechanism to the low speed side, and the drive shaft on the high speed side drives. The force decreases, and the drive force increases on the drive shaft on the low speed side in response to the decrease in the drive force. As a result, the left and right driving force distribution is adjusted.

Further, in the vehicle road surface frictional resistance estimating device according to the fifth aspect of the present invention, the driving force of the input shaft is transmitted to each of the left wheel driving shaft and the right wheel driving shaft via the differential mechanism. However, at this time, the distribution state of the driving force output to the left and right driving shafts is adjusted by the driving force transmission control mechanism. That is, in the driving force transmission control mechanism, the speed change mechanism shifts the member on the input side at a constant speed change ratio, and a speed difference is generated between the output side of the speed change mechanism and the drive shaft side. By engaging the variable capacity control type torque transmission mechanism, the driving force is transmitted between the drive shaft side and the input section side. That is, when the transmission capacity variable control type torque transmission mechanism is engaged, the drive force is transmitted from the high speed side to the low speed side of the output side of the speed change mechanism and the drive shaft side, and the drive shaft is driven at the high speed side. The force decreases, and the drive force increases on the drive shaft on the low speed side in response to the decrease in the drive force. As a result, the left and right driving force distribution is adjusted.

Further, in the vehicle road surface frictional resistance estimating device according to the sixth aspect of the present invention, the estimation of the road surface frictional resistance is updated when the driving state of the vehicle is predetermined.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle road surface frictional resistance estimating apparatus as a first embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic block diagram showing the functional configuration of the control system, FIG. 2 is a schematic configuration diagram showing a drive system of a vehicle equipped with the present device, and FIG. 3 is a diagram showing the drive force distribution device shown in FIG. FIG. 4 is a schematic configuration diagram showing another example of the driving force distribution device, FIG. 5 is a control block diagram showing a part of the control system, and FIG. 6 shows its principle. FIG. 7 is a graph for explaining the relationship between the tire slip ratio and the amount of torque movement between the left and right driving wheels, FIG. 7 is a flowchart for explaining the action, and FIG. 8 is a difference provided to the vehicle together with the present device. 9A and 9B are schematic cross-sectional views showing an example of the dynamic control device, and FIGS. 9A and 9B are cross-sectional views taken along the line AA in FIG. 8.

First, the first embodiment will be described. Before describing the road surface frictional resistance estimating device for a vehicle, a drive system of an automobile equipped with the device will be described. As shown in FIG. 2, this vehicle receives the driving force from the engine 1 via a transmission 2 by a center differential 3 composed of planetary gears, and transmits it from the center differential 3 to the front wheel side and the rear wheel side. It is a four-wheel drive vehicle.

In particular, the center differential 3 is provided with a center differential differential limiting mechanism 5 capable of appropriately limiting the differential between the front and rear wheels. The differential limiting mechanism 5 is composed of a hydraulic multi-plate clutch here, and can control the distribution of the driving force to the front and rear wheels while limiting the differential between the front and rear wheels according to the supplied hydraulic pressure. , A device for controlling the distribution of driving force between the front and rear wheels.

In this way, one of the driving forces distributed from the center differential 3 is transmitted to the left and right front wheels 25, 26 through the front differential 4. On the other hand, the other of the driving force distributed from the center differential 3 is transmitted to the rear differential 8 via the propeller shaft 6 and is transmitted to the left and right rear wheels 15 and 16 through the rear differential 8. Reference numeral 7 is a bevel gear mechanism including a drive pinion and a ring gear.

A drive force transmission control mechanism 9A (hereinafter referred to as drive force transmission control mechanism in a broad sense) is composed of a transmission mechanism 10 and a multi-disc clutch mechanism 12 as a transmission displacement variable control type torque transmission mechanism in the rear differential 8. Is designated by 9), and a left / right driving force adjusting device 70 is constituted by the rear differential (differential mechanism) 8 and the driving force transmission control mechanism 9A. Although a bevel gear type is used as the differential mechanism 8 here, the differential mechanism 8 allows the driving force input from the engine to be applied while allowing the differential between the two drive shafts. As long as it can be transmitted to each drive shaft, it goes without saying that another known differential mechanism including a gear mechanism such as a planetary gear type or a roller mechanism can be applied. Further, the multi-plate clutch mechanism 12 is of a hydraulic type, and by adjusting the hydraulic pressure, the distribution of the driving force to the left and right wheels can be controlled.

The hydraulic system of the multi-disc clutch mechanism 12 of the drive force transmission control mechanism 9A is controlled by the control unit 18 together with the hydraulic system of the multi-disc clutch mechanism 5 of the front-rear drive force adjusting device. Has become. That is, the hydraulic system of the multi-plate clutch mechanism 12 and the hydraulic system of the multi-plate clutch mechanism 5 include hydraulic chambers (not shown) attached to the respective clutch mechanisms, an electric pump 24 and an accumulator 23 that form a hydraulic source, And a clutch hydraulic pressure control valve 17 for supplying a required amount to the hydraulic chamber. The opening of the clutch hydraulic pressure control valve 17 is controlled by the control unit 18.

In the control unit 18, the wheel speed sensors 19FL, 19FR, 19RL, 19RR,
The opening of the clutch hydraulic pressure control valve 17 is controlled based on information from the steering wheel angle sensor 20, the yaw rate sensor 21, the acceleration sensor (or acceleration calculation means) 22, and the like. Here, the main part of the left-right driving force adjusting device 70 will be described. As shown in FIG. 3, a rotational driving force (hereinafter referred to as driving force or torque) is provided at the rear end of the propeller shaft 6 and is input. An input shaft 6A, a left wheel rotation shaft (drive shaft for the left rear wheel 15) 13 and a right wheel rotation shaft (drive shaft for the right rear wheel 16) 14 that output the driving force input from the input shaft 6A are provided. A left-right driving force adjusting device 70 is interposed between the left wheel rotating shaft 13, the right wheel rotating shaft 14, and the input shaft 6A.

The driving force transmission control mechanism 9A of the left / right driving force adjusting device 70 is configured as follows, while permitting the differential between the left wheel rotating shaft 13 and the right wheel rotating shaft 14.
The driving force transmitted to the left wheel rotating shaft 13 and the right wheel rotating shaft 14 can be distributed to a required ratio. That is, the transmission mechanism 10 and the multi-disc clutch mechanism 12 are provided between the left wheel rotating shaft 13 and the input shaft 6A and between the right wheel rotating shaft 14 and the input shaft 6A, respectively.
3 or the rotation speed of the right wheel rotation shaft 14 is changed (increased in speed in this example) by the speed change mechanism 10 and transmitted to the hollow shaft 11 as a driving force transmission auxiliary member.

The multi-disc clutch mechanism 12 is interposed between the hollow shaft 11 and a differential case (hereinafter referred to as a differential case) 8A on the input shaft 6A side.
By engaging the multi-plate clutch mechanism 12, the driving force is fed from the member of the differential case 8A and the hollow shaft 11 which is rotating at high speed to the member which is rotating at low speed. It has become. This is because, as a general characteristic of the clutch plates arranged to face each other, torque is transmitted from a higher speed to a lower speed.
In the case of this example, the differential between the left and right rotary shafts 13 and 14 is large, and the rotary shaft 13 or 14 has a predetermined ratio (a ratio corresponding to the reduction ratio of the speed change mechanism 10) or more than that of the differential case 8A. Unless the speed is high, the diff case 8A is on the low speed side, and the hollow shaft 11 is on the high speed side, so that the driving force is fed from the hollow shaft 11 to the differential case 8A.

Therefore, for example, when the multiple disc clutch mechanism 12 between the right wheel rotary shaft 14 and the input shaft 6A is engaged,
The driving force distributed to the right wheel rotating shaft 14 is increased or decreased (mainly decreased in this example) along the route from the input shaft 6A side, and the driving force distributed to the left wheel rotating shaft 13 is decreased or reduced by this amount. Increase (mainly increase in this example). The gear mechanism type speed change mechanism 10 will be described below by taking the case where it is provided on the right wheel rotary shaft 14 as an example.

That is, as shown in FIG. 3, a first sun gear 10A is fixedly attached to the right wheel rotary shaft 14, and the first sun gear 10A has a first planetary gear (planetary pinion) on its outer periphery. It meshes with 10B. The first planetary gear 10B is integrally fixed to the second planetary gear 10D, and is pivotally supported by a carrier 10F that is fixed to the casing (fixed portion) and does not rotate through a pinion shaft 10C provided on the carrier. ing. As a result, the first planetary gear 10
B and the second planetary gear 10D rotate in the same manner about the pinion shaft 10C.

Further, the second planetary gear 10D is
The second sun gear 10E is meshed with the second sun gear 10E pivotally supported by the right wheel rotation shaft 14, and the second sun gear 10E is connected to the clutch plate 12A of the multi-plate clutch mechanism 12 via the hollow shaft 11. The other clutch plate 12B of the multi-plate clutch mechanism 12 is connected to the differential case 8A driven by the input shaft 6A.

In the structure of this embodiment, since the first sun gear 10A is formed to have a diameter larger than that of the second sun gear 10E, the rotation speed of the second sun gear 10E is higher than that of the first sun gear 10A. As a result, the speed change mechanism 10 functions as a speed increasing mechanism. Therefore, the rotational speed of the clutch plate 12A is
When the multiple disc clutch mechanism 12 on the right wheel side, which is larger than 2B, is engaged, a torque corresponding to this engagement state is sent from the right wheel rotating shaft 14 side to the differential case 8A side. It is like this.

On the other hand, the transmission mechanism 10 and the multi-disc clutch mechanism 12 provided for the left wheel rotary shaft 13 are also constructed in the same manner, and drive torque from the input shaft 6A is transferred to the left wheel rotary shaft 13.
If more distribution is desired, the multi-plate clutch mechanism 12 on the right wheel rotating shaft 14 side is appropriately engaged according to the degree of distribution (distribution ratio), and if more distribution is desired for the right wheel rotating shaft 14. , The left wheel rotating shaft 13 according to the distribution ratio
The side multi-plate clutch mechanism 12 is appropriately engaged.

At this time, since the multi-plate clutch mechanism 12 is hydraulically driven, the engagement state of the multi-plate clutch mechanism 12 can be controlled by adjusting the magnitude of hydraulic pressure, and the input shaft 6A to the left wheel rotary shaft 13 or The feed amount of the driving force to the right wheel rotating shaft 14 (that is, the left / right distribution ratio of the driving force) can be adjusted with appropriate accuracy. The left and right multi-plate clutch mechanisms 12 are set so as not to be completely engaged, and when one of the left and right multi-plate clutch mechanisms 12 is completely engaged, the other multi-plate clutch mechanism 12 slips. It is happening.

The speed change mechanism 10 of this embodiment described above is constituted by a so-called double planetary gear mechanism in which two planetary gear mechanisms are connected in series. The speed change mechanism 10 itself receives the input rotation. A mechanism that accelerates or decelerates the speed at a constant speed ratio and outputs the speed may be used. For example, a mechanism using a belt, a chain, or the like may be considered, and the mechanism is not limited to the gear mechanism.

Further, in this embodiment, the speed change mechanism 10 is
The speed increasing mechanism is configured to increase the rotational speed of the left wheel rotating shaft 13 or the right wheel rotating shaft 14 and transmit the rotating speed to the hollow shaft 11.
The driving force transmission control mechanism 9A may be configured with the speed change mechanism 10 as the speed reduction mechanism by reversing the magnitude relationship between B and the second planetary gear 10D.

As another example of the driving force transmission control mechanism 9A, a mechanism shown in FIG. 4 can be considered. In this drive force transmission control mechanism 9A, as shown in FIG. 4, the transmission mechanism 31 and the multiple disc clutch mechanism 42 differ from the above-mentioned mechanism. Here again, the device on the right side will be described.

The speed change mechanism 31 is provided on each of the left and right side portions of the differential case 8A on the input shaft 6A side, and comprises two sets of planetary gear mechanisms in series. The first sun gear 31A, the second sun gear 31E, and the first sun gear 31E. A planetary gear 31B, a second planetary gear 31D, a pinion shaft 31C, and a planetary carrier 31F, and a first sun gear 31A.
The plate portion of is a driving force transmission assisting member 41.

A multi-plate clutch mechanism 42 is provided between the driving force transmission auxiliary member 41 and the right wheel rotary shaft 14. In this multi-disc clutch mechanism 42, a clutch disc 42B on the rotating shaft 14 side and a clutch disc 42B on the driving force transmission assisting member 41 side are alternately superposed, and in accordance with a hydraulic pressure supplied from a hydraulic system (not shown). The engagement state is adjusted.

Therefore, when the multi-disc clutch mechanism 42 is engaged, the multi-disc clutch mechanism 42, the first disc
Sun gear 31A, first planetary gear 31B, second
A transmission path of the driving force is formed through the planetary gear 31D and the second sun gear 31E, to the differential case 8A on the input shaft 6A side. Here, since the first sun gear 31A is formed to have a diameter larger than that of the second sun gear 31E, the rotation speed of the second sun gear 31E is higher than that of the first sun gear 31A, and the speed change mechanism 31 has a driving force. The transmission assisting member 41 serves as a speed reduction mechanism that reduces the speed of the transmission auxiliary member 41 from the input shaft 6A side.

Therefore, the rotation speed of the clutch plate 42A is higher than that of the clutch plate 42B, and the multi-plate clutch mechanism 4
When 2 is engaged, an amount of torque corresponding to the engaged state is sent (returned) from the right wheel rotary shaft 14 side to the input shaft 6A side. On the other hand, the transmission mechanism 31 and the multiple disc clutch mechanism 42 provided on the left wheel rotation shaft 13
Also has a similar configuration, and when more drive torque from the input shaft 6A is to be distributed to the left wheel rotary shaft 13, a multi-disc clutch on the right wheel rotary shaft 14 side is distributed according to the degree of distribution (distribution ratio). The mechanism 42 is appropriately engaged, and the right wheel rotating shaft 1
4 to distribute more, the multi-plate clutch mechanism 42 on the left wheel rotary shaft 13 side is appropriately engaged according to the distribution ratio.

At this time, since the multi-plate clutch mechanism 42 is a hydraulic drive type, the engagement state of the multi-plate clutch mechanism 42 can be controlled by adjusting the magnitude of hydraulic pressure, and the input shaft 6A to the left wheel rotary shaft 13 or The feed amount of the driving force to the right wheel rotating shaft 14 (that is, the left / right distribution ratio of the driving force) can be adjusted with appropriate accuracy. Further, the left and right multi-plate clutch mechanisms 42 are set so as not to be completely engaged with each other, and when one of the left and right multi-plate clutch mechanisms 42 is completely engaged, the other multi-plate clutch mechanism 42 slips. It is happening.

By configuring the driving force transmission control mechanism 9A as described above, the torque distribution is not adjusted by using the energy loss of the brake or the like, but the required amount of one torque is transferred to the other torque distribution. Therefore, a desired torque distribution can be obtained without causing a large torque loss or energy loss.

Also in this transmission mechanism 31, the first
Planetary gear 31B and second planetary gear 31
The speed change mechanism 31 may be configured as a speed-up mechanism by reversing the magnitude relationship of D. By the way, as shown in FIG. 1, the control unit 18 includes a vehicle body speed V of the vehicle.
An estimated vehicle speed calculation unit 216 that estimates and calculates B is provided.

The calculation of the vehicle body speed by the estimated vehicle body speed calculation unit 216 will now be described.
6 is a wheel speed sensor 19FL, 19FL, as shown in FIG.
A wheel speed selection unit 216a that selects the wheel speed data of the second largest value from the bottom (smallest) of the rotation speed data signals detected by FR, 19RL, and 19RR, and is estimated from the selected wheel speed data and the like. It comprises an estimated vehicle speed calculation unit 216c for setting the vehicle speed.

In particular, in the estimated vehicle speed calculation unit 216c, the wheel speed data SVW obtained by applying the filter 216b to the wheel speed data selected by the wheel speed selection unit 216c to remove noise components and the longitudinal acceleration sensor 36 detect the wheel speed data. Based on the longitudinal acceleration data Gx obtained by removing the noise component by applying the longitudinal acceleration to the filter 216d, the vehicle speed after that is estimated from both data SVW and Gx at a certain time point. That is, the wheel speed data S at a certain point
Assuming that VW is V ₂ and longitudinal acceleration data Gx is a, the theoretical vehicle speed VB after time t is VB
= V ₂ + a · t

It should be noted that, from the bottom of the rotation speed data signal, 2 from the bottom.
The second wheel speed data is adopted for each wheel 1.
This is because all of 5, 16, 25 and 26 usually slip to the vortex rotation side in many cases. Therefore, although it is originally preferable to adopt the wheel speed on the lowest rotation side, the second wheel speed from the bottom is adopted in consideration of the reliability of data.

Here, the structure of the road surface frictional resistance estimating device for a vehicle will be described. The present device utilizes the relationship between the slip ratio of the tire and the driving force to determine the road surface frictional resistance μ indicating the slipperiness of the road surface. Estimating means 18 'of the control unit 18 and the wheel speed sensor 1 on the drive wheel side
It comprises 9RL and 19RR and a steering wheel angle sensor 20, and the arithmetic means 18 'can estimate the road surface frictional resistance μ.

Therefore, the slip ratio of the tire will be described first. The slip ratio S (%) is distinguished between the wheel speed V (= VR or VL) when the tire is in a driving state and when the tire is in a braking state. From the vehicle speed VB and the vehicle speed VB, when driving, S = (V-VB) / V (1A) is defined, and when braking, S = (VB-V) / VB ... (1B) is defined.

The relationship between the tire slip ratio S and the driving force (or braking force) T is shown in FIG. As shown in this figure, even if the driving force T is the same, the slip ratio S of the tire varies greatly depending on the magnitude of the road surface frictional resistance μ. That is, when focusing on the linear region portion of this graph, the inclination of this straight line portion (the ratio ΔT / ΔS between the driving force difference ΔT between the left and right wheels and the slip ratio difference ΔS between the left and right wheels = the amount of change in the slip ratio difference) is, for example, Smaller on low μ road, high μ
The larger the road, the bigger it gets. Therefore, the road surface frictional resistance μ can be estimated from the change amount ΔS of the slip ratio and the movement amount ΔT of the driving force.

Therefore, as shown in FIG.
Reference numeral 8'denotes a reference rotational speed difference calculation means 18F, a road surface frictional resistance estimation means (or a road surface frictional resistance estimation part) 18D,
Estimated value storage means 18I, estimated condition determination part 18E, first and second output value stabilization means 18H and 18L, subtraction parts 18B and 18J, and absolute value calculation means 18G are provided, and calculation means is provided. 18 ', wheel speed sensor 19R
Based on the rotation speed data signals RL and RR from L and 19RR, the subtraction unit 18J calculates the wheel speed difference signal dvrd (= RL-RR) between the left and right driving wheels.

The reference rotational speed difference calculating means 18F is
Vehicle speed VB calculated by the estimated vehicle speed calculation unit 216
Based on the steering wheel angle θ _H detected by the steering wheel angle sensor 20, the theoretical rotational speed difference V _O between the drive wheels 15 and 16 is geometrically calculated from the turning state of the vehicle. In the reference rotational speed difference calculating means 18F, for example, a map as shown in the block in FIG. 1 is provided, and the reference rotational speed difference V _O is calculated using the vehicle body speed VB and the steering wheel angle θ _H as parameters. Rotational speed difference signal dvh
It is designed to be output as r.

Then, the subtracting portion 18B causes the wheel speed difference signal dvrd of the left and right driving wheels and the reference rotational speed difference V to be obtained.
_After the difference ΔV (signal ddvr) from _O (signal dvhr) is calculated, absolute value processing is performed by the absolute value calculation means 18G.
The speed difference ΔV and the vehicle body speed VB thus obtained are input to the road surface frictional resistance estimating unit 18D described later. Further, as shown in FIG. 1, a control amount setting unit 18C is connected to the road surface frictional resistance estimation unit 18D, and a signal of the torque movement amount ΔT is input to the road surface frictional resistance estimation unit 18D on the other hand. It has become.

The control amount setting unit 18C determines the torque movement amount ΔT between the left and right driving wheels in accordance with the running state of the vehicle, and the command value of the torque movement amount ΔT output from the control amount setting unit 18C. Accordingly, the hydraulic system of the multi-plate clutch mechanism 12 of the driving force transmission control mechanism 9A is controlled. Then, in the road surface frictional resistance estimation unit 18D, the torque difference command value ΔT, the speed difference ΔV, and the vehicle body speed VB.
The road surface frictional resistance μ is estimated based on and.

Further, as shown in the block in FIG. 1, the road surface frictional resistance estimating section 18D has ΔT and ΔV.
And VB are provided as parameters, and the road surface frictional resistance μ is estimated by this map.
In this map, the horizontal axis is ΔT / ΔV,
The vertical axis represents the road friction resistance μ. Here, this map will be briefly described.

Normally, when the frictional resistance μ of the road surface is low and the road is slippery, a large rotational speed difference (= VL-VR) occurs between the drive wheels even if the torque movement amount ΔT between the drive wheels is small. Further, when the frictional resistance μ of the road surface is high, for example, when the steering angle is large, the torque movement amount ΔT between the drive wheels is large, but the rotational speed difference is small. Also, at a certain torque movement amount ΔT ₁ , if the frictional resistance μ of the road surface is small, the rotational speed difference ΔV is large, and conversely, the frictional resistance μ of the road surface is
Is larger, the rotational speed difference ΔV should be smaller.

Therefore, the smaller ΔT / ΔV is, the smaller the road surface frictional resistance μ is, and the road surface frictional resistance μ can be estimated from the map shown in FIG. Since the value of ΔT / ΔV is influenced by the vehicle speed VB,
With the vehicle body speed VB as a parameter, the road surface frictional resistance μ is estimated using different maps depending on the size of the vehicle body speed VB.

Instead of this map, the road surface frictional resistance estimating unit 18D may estimate the road surface frictional resistance μ by using the linear region portion of the map shown in FIG. This map is for estimating the road surface frictional resistance μ from the relationship between the slip ratio and the driving (or braking) torque. The horizontal axis of the map is the tire slip ratio and the vertical axis is the driving (or braking).
This is the amount of lateral movement of the torque.

That is, when the torque movement amount is ΔT, the larger the slip ratio difference ΔS between the left and right tires, the larger the road surface friction resistance μ.
Is low and the slip ratio difference ΔS is small, the road friction resistance μ
Is high, the ratio ΔT / ΔS between the torque movement amount ΔT and the slip ratio difference ΔS between the left and right tires of the vehicle (= slip ratio SL of the left wheel-slip ratio SR of the right wheel), that is, the slope of the map to the road surface. The value of frictional resistance is estimated.

In FIG. 6, the road surface friction resistance is divided into three stages of high μ, medium μ and low μ, but it may be simply divided into two stages of high μ and low μ. On the contrary, the road surface frictional resistance may be obtained by further subdividing. Further, ΔSh, ΔSm and ΔSl in the figure are the slip ratio differences of the tires on the high μ road, medium μ road and low μ road, respectively.

By the way, the control unit 18 is provided with an estimated value storage means 18I and an estimated condition judging section 18E, and the estimated value storage means 18I estimates the road surface friction resistance μ immediately before the estimation. The value of the road surface frictional resistance μ is stored. Then, the estimation condition determination unit 18
At E, the road surface frictional resistance μ estimated by the road surface frictional resistance estimating unit 18D is output only when the condition of the vehicle satisfies the required condition, and if not, the estimated value storage means 1
The road friction resistance μ estimated previously is output from 8I.

Explaining the estimation condition determining unit 18E, the road friction resistance μ estimated this time is output when all of the following conditions (1) to (4) are satisfied. | Θ _H |> θ ₀ : The steering wheel angle θ _H is larger than a certain threshold θ ₀ . | Θ _H ′ | <θ ₀ ′: The value of the value θ _H ′ (steering wheel angular velocity) obtained by differentiating the steering wheel angle θ _H with time is smaller than the threshold value θ ₀ ′.

| G _Y | <G _Y0 : The magnitude of the lateral acceleration G _Y is smaller than the threshold value G _Y0 . ΔT> ΔT ₀ : The left / right drive wheel torque movement command value ΔT is larger than the threshold value ΔT ₀ . | G _X | <G _X0 : The magnitude of the longitudinal acceleration G _X is the threshold G _X0.
Less than. Further, in the first output value stabilizing means 18H, the fluctuation rate of the estimated road surface frictional resistance μ is, for example, ± per second.
The output value is regulated within 0.2 (limiter processing), and the output value is stabilized by the second output value stabilizing means 18L by, for example, 1 Hz filter processing.

If any of the above conditions (1) to (4) is not satisfied, the road surface friction resistance μ estimated immediately before is output from the estimated value storage means 18I, and all the above conditions (1) to (4) are satisfied. Only, road friction resistance μ
The estimated value is updated and output. Since the vehicle road surface frictional resistance estimating apparatus as the first embodiment of the present invention is configured as described above, the road surface frictional resistance μ is estimated in accordance with the flowchart shown in FIG. 7, for example.

First, in step S1, the controller 18 takes in the wheel speeds VL and VR of the left and right driving wheels 15 and 16, the vehicle body speed VB, the steering wheel angle θ _H, and the torque shift ΔT between the left and right driving wheels. Then, step S2
Then, the reference rotation speed difference calculation means 18F calculates the reference rotation speed difference V _O.

Then, based on this reference rotational speed difference V _O and each value fetched in step S1, ΔV is calculated by the following equation (step S3). ΔV = (VL−VR) −V _{O Based on} this speed difference ΔV and the torque movement ΔT between the left and right driving wheels, the road surface frictional resistance estimating unit 18D determines the road surface frictional resistance μ.
Is estimated (step S4).

Thereafter, in step S5, it is judged whether or not the road surface frictional resistance μ estimated this time satisfies the updating condition. Then, if any one of the update conditions is not satisfied, the process proceeds to step S6, the previous road friction resistance μ estimated immediately before is held, and the road friction resistance μ estimated this time is canceled. It Then, after this, the process proceeds to step S7.

If all the update conditions are satisfied, the process directly proceeds from step S5 to step S7, where limiter processing and filter processing are performed, and then road surface friction resistance μ is output in step S8. As described above, in the present invention, the road surface frictional resistance μ is set to the wheel speed difference VL-V of the drive wheels.
Since it is estimated from R and the torque movement amount ΔT between the driving wheels, the road surface frictional resistance μ can be estimated not only during turning but also during straight traveling.

Further, in the conventional road surface friction resistance μ estimating device, it is necessary to provide a hydraulic sensor or the like of the power steering device in order to estimate the road surface friction resistance μ, but in this device, it is necessary to newly provide a sensor or the like. Therefore, the road surface frictional resistance μ can be estimated with almost no increase in manufacturing cost. Further, by estimating the road surface frictional resistance μ in this way, it is possible to distribute the driving force according to the road surface frictional resistance μ and improve the running performance of the vehicle.

Further, the vehicle road surface frictional resistance estimating apparatus as described above can be applied to a vehicle having a vehicle differential limiting control apparatus as described in detail below.
As shown in FIG. 8, this differential limitation control device is a device that does not have a speed change mechanism like the above-described left-right driving force adjustment device 70, and limits this when a left-right wheel differential occurs. A device adapted to move torque between the left and right wheels. This device will be briefly described below.

As shown in FIG. 8, an input shaft 401 is connected to the rear end of the propeller shaft 6, and the input shaft 40 is connected to the input shaft 401.
1, the drive pinion gear 402 is supported so as to rotate integrally. Further, the input shaft 401 is the bearing 41
It is rotatably supported in the front part of the case 413 via the shaft 2. A crown gear 403 is meshed with the drive pinion gear 402, and a power transmission annular member 404 and a first housing 405 are integrally coupled to the crown gear 403 by a bolt 431.

The rear differential 8 is a planetary gear type differential using a planetary gear mechanism, and the power transmission annular member 404 is formed therein, and a ring gear 407 formed on the inner peripheral surface of the annular member 404. It is composed of a sun gear 408 that is spline-connected to the axle of the left wheel 15, a carrier 409 that is spline-connected to the axle of the right wheel 16, and planetary gears 411a and 411b that are attached to the carrier 409 via shafts 410a and 410b. There is.

A second housing 406 is provided on the right side of the carrier 409, and the second housing 406 has a ring-shaped support member 4 via a bearing 428.
It is supported by 18. And in this rear differential 8,
A differential limiting device 400 is provided so that the differential of the rear differential 8 can be limited.

The differential limiting device 400 includes a multi-disc clutch 414 as a differential limiting mechanism, a driving device 417 for driving the multi-disc clutch, and a rear differential control section (not shown) of a controller for controlling the driving device 417. No)) and. The multi-plate clutch 414 includes an annular member 404.
The clutch disc 41 is provided inside the
The holder portion 415a for supporting the shaft 4a includes shafts 410a, 410
The clutch disc 414a is coupled to the carrier 409 via the b so that the clutch disc 414a rotates integrally with the carrier 409, and the holder part 415b for supporting the other clutch disc 414b is formed on the hollow shaft 416 provided with the sun gear 408. The clutch disc 414b
Is designed to rotate integrally with the sun gear 408.

Further, the driving device 417 is provided with the carrier 40.
9 and the second housing 406. The force direction conversion mechanism 429 and the electromagnetic clutch mechanism 430 for driving the force direction conversion mechanism 429 are provided. In addition,
This rear differential 8 is called an electromagnetically controlled differential because it limits the differential by an electromagnetic clutch mechanism. The force direction conversion mechanism 429 includes a ball 421 interposed between the carrier 409 and the second housing 406, and FIG.
As shown in (a), it comprises a rhombic (or rectangular) chamber 425 for accommodating the ball 421, and the chamber 425 includes a groove 422 formed on the carrier 409 side, the carrier 409, and the second housing 406. And a groove 424 formed in the annular member 423 between them.

The annular member 423 is the carrier 40.
9 and the second housing 406, which is normally free in the rotational direction with respect to these members and rotates integrally with the carrier 409 via the balls 421. When the rotational torque on the housing 406 side (that is, the crown gear 403 or the power transmission annular member 404 side) is received, a differential rotation is generated with respect to the carrier 409, and the force due to this rotational torque is changed in direction to cause the clutch. 414 acts as a pressing force.

The second housing 406 is attached to the annular member 423.
It is the electromagnetic clutch mechanism 430 that exerts the rotational torque on the side, and the electromagnetic clutch mechanism 430 includes a clutch 427 interposed between the annular member 423 and the member 426 on the second housing 406 side. , An electromagnetic clutch drive system including a magnet 419 and a solenoid (EMCD coil) 420 as a differential limiting mechanism control means.

That is, the clutch 427 is disposed inside the second housing 406, and the second housing 4
A magnet 419 is installed on the inner side of 06, while a solenoid 420 capable of attracting the magnet 419 is installed on the outer side of the second housing 406. As a result, when the solenoid 420 operates, the magnet 419 moves to the second position.
The clutch 416 is engaged with the second housing 406 by being attracted to the housing 406 side.

When the clutch 416 comes into engagement, the annular member 423 receives the rotational torque of the second housing 406 side and tries to rotate integrally with the second housing 406 side. At this time, if there is a rotation speed difference (differential rotation) between the second housing 406 side (hence, the sun gear 407 side) and the carrier 409, that is, if there is a rotation speed difference between the left and right wheels, an annular shape is formed. Member 4
23 causes a differential rotation with respect to the carrier 409, and when the annular member 423 differentially rotates with respect to the carrier 409 in this way, as shown in FIG. 9B, the inclination of the ball 421 and the grooves 422, 424. The force in the direction of differential rotation is converted into a force in the direction orthogonal to the direction through the surface, that is, a force parallel to the axial direction of the rear differential and the axial direction of the axle, and this force causes the carrier 409 to move in the axial direction. Driven, shaft 41
The multi-plate clutch 414 is pressed and engaged through 0a, 410b and the holder portion 415a.

The engaging force of the multi-plate clutch 414 as described above corresponds to the difference in the rotational speeds of the left and right wheels and the magnitude of the electromagnetic force generated by the solenoid 420.
By adjusting the current to 0, the engagement force of the multi-plate clutch 414, and thus the differential limiting force, can be controlled.
Then, using such a differential limiting control device, the wheel speed difference and the slip ratio difference between the left and right driving wheels are calculated, and the road surface is determined from these values and the torque movement amount between the left and right driving wheels due to the differential limiting. The frictional resistance μ can be estimated.

In addition, the present apparatus is not limited to the above-described differential limiting control device, but the road surface frictional resistance μ can be estimated as long as it is a differential limiting device capable of appropriately controlling the differential state of the left and right wheels. You can Next, a vehicle road surface frictional resistance estimating apparatus as a second embodiment of the present invention will be described with reference to FIG.
0 is a graph for explaining the principle thereof, which is a graph corresponding to FIG. 6, FIG. 11 is a map showing the tendency of road surface friction resistance, and FIGS. 12 (a) to 12 (c) are all calculation methods of the characteristic values thereof. FIG. 13 is a graph for explaining the above, and FIG. 13 is a flow chart for explaining the operation.

As shown in FIG. 10, on the high μ road (the road friction resistance μ is large) and on the low μ road (the road friction resistance μ is small), even if the torque movement amount of the left and right wheels is the same, The slip rate difference is different. Also in this embodiment, the road surface frictional resistance μ is estimated using this characteristic, and the method of estimating the road surface frictional resistance μ is different from that of the first embodiment. Further, this device is provided in a vehicle together with the left-right driving force adjusting device 70 capable of adjusting the driving force distribution between the left-right driving wheels, as in the first embodiment. Further, this vehicle is also a four-wheel drive vehicle having a center differential and capable of driving front and rear wheels, as in the first embodiment.

In the present apparatus, the subtraction unit 1 in the calculating means 18 '
In 8B, the change amount α of the slip ratio difference between the left and right drive wheels is calculated according to the following equation (2), and the road surface frictional resistance μ is estimated using the change amount α of the slip ratio difference. α = (ΔVr−ΔVf) / (ΔT · VB) (2) where ΔVr is the wheel speed difference (VL) between the left and right driving wheels 15, 16 on the side provided with the left / right driving force adjusting device 70. -V
R), which is calculated based on the wheel speed information detected by the wheel speed sensors 19RL and 19RR. Also, ΔV
f is a wheel speed difference between the left and right driving wheels 25 and 26 on the side where the left and right driving force adjusting device 70 is not provided, and is calculated based on the wheel speed information from the wheel speed sensors 19FL and 19FR (FIG. 2). reference).

The change amount α of the slip ratio difference will be briefly described. The wheel speed difference ΔVr between the left and right drive wheels 15 and 16 includes the wheel speed difference between the inner and outer wheels due to turning, the wheel speed difference due to left and right load movement, and the wheel speed difference due to left and right torque movement. However, in order to know the frictional resistance of the road surface, it suffices to know the wheel speed difference of the drive wheels with respect to the torque movement amount ΔT between the drive wheels.

In the first embodiment, the influence of the wheel speed difference between the inner and outer wheels due to the turning is removed by subtracting the reference rotational speed difference V _O between the driving wheels from the wheel speed difference ΔVr between the left and right driving wheels. The wheel speed difference due to the left and right load movement of the vehicle is included. Therefore, in the present embodiment, turning is performed by subtracting the wheel speed difference ΔVf of the left and right driving wheels (front wheels in this case) 25 and 26 on the side where the left and right driving force adjusting device 70 is not provided from the wheel speed difference ΔVr of the driving wheels. The effect of the difference between the inner and outer wheels and the difference in wheel speed due to the movement of the load on the left and right are removed.

That is, the numerator of the equation (2) is only the left and right wheel speed difference due to the torque movement between the drive wheels. Therefore, the change amount α of the slip ratio difference is
When a torque movement occurs in the vehicle, how much the tire slip ratio difference between the left and right driving wheels (SL-SR) per torque movement
Indicates that it changes.

The torque movement amount ΔT is set to the torque movement amount ΔT in consideration of the response delay until the torque movement is actually completed when the movement torque amount setting unit 18A issues a torque movement command. First-order delay processing is performed. The vehicle body speed VB is the estimated vehicle body speed calculation unit 2 described above.
Calculated at 16. Then, the control unit 18 calculates the average value α _AV of α at constant time intervals and the difference α _PP between the maximum value and the minimum value of α at constant time intervals from the change amount α of the slip ratio difference. And this α
_The road surface frictional resistance μ is estimated from a map as shown in FIG. 11 based on _AV and α _PP .

That is, on a road surface with a relatively large road friction resistance μ (that is, a small value of α) such as asphalt, both α _AV and α _{PP have a} relatively small value, and a road surface with a small μ such as an icy road. Then, these values tend to be large. Therefore, for example, the values of α _AV and α _PP are
The road surface is judged to be a low μ road when it is in the area within the line A in 1 and it is judged to be a medium μ road when it is between the line A and the line B. . Similarly, when it is below the line B, it is determined to be a high μ road.

By the way, as shown in FIGS. 12A to 12C, such values of α _AV and α _PP are, for example, 300 ms.
Is calculated on the basis of the fluctuation of the value of α for 300 ms immediately before that. This is because the change amount α of the slip ratio difference reacts to a small change in the wheel speed differences ΔVr and ΔVf, so that the average value α _AV and the difference α _PP between the maximum value and the minimum value of these are introduced. Thus, the change amount α of the slip ratio difference is stabilized.

Further, the calculating means 18 'of the control unit 18 is provided with an estimating condition judging section 18E. Only when the estimating condition judging section 18E satisfies the required condition, the vehicle condition is satisfied. The road surface frictional resistance μ estimated by the road surface frictional resistance estimating unit 18D is output, and if not, the road surface frictional resistance μ estimated immediately before is output.

The estimation condition determining section 18E will be described. The road surface frictional resistance μ is output when all of the following conditions are satisfied. | Θ _H |> θ ₀ : The steering wheel angle θ _H is larger than a certain threshold θ ₀ . | Θ _H ′ | <θ ₀ ′: The magnitude θ _H ′ of the time derivative (handle angular velocity) of the steering wheel angle θ _H is smaller than the threshold value θ ₀ ′.

ΔT> ΔT ₀ : The left and right drive wheel torque movement command value ΔT is larger than the threshold value ΔT ₀ . | G _X | <G _X0 : The magnitude of the longitudinal acceleration G _X is the threshold G _X0.
Less than. The control unit 18 is also provided with first and second output value stabilizing means 18H and 18L for stabilizing the output road friction resistance μ, as in the first embodiment.

The first output value stabilizing means 18H is a limiter, and regulates, for example, the variation rate of the estimated road friction resistance μ within ± 0.2 per second. The second output value stabilizing means 18L is, for example, a 1 Hz filter. Since the vehicle road surface frictional resistance estimating apparatus according to the second embodiment of the present invention is configured as described above, the road surface frictional resistance μ is estimated according to the flowchart shown in FIG. 13, for example.

First, in step SA1, the value ΔT obtained by filtering the torque movement amount between the left and right drive wheels is calculated, and the change amount α of the slip ratio difference is calculated by the equation (2). Then, in step SA2, it is determined whether or not the torque movement amount ΔT is larger than the predetermined value T _{O, and} if the torque movement amount ΔT is smaller than the predetermined value T _O , the process proceeds to step SA3 and a counter t _{4 of a} timer (not shown) Is reset to 0 and returned. This is because if the torque movement amount ΔT of the left and right wheels is too small, the accuracy of calculation will decrease.

If the torque movement amount ΔT is larger than the predetermined value T _O , the process proceeds to step SA4 and the timer count t ₄ is incremented by one. Then, step SA5
Then, it is judged whether or not the count t ₄ of the timer is 1. The initial value of the count t ₄ of the timer is 0.
Then, when the count t _{4 of} the timer is 1, the process proceeds to step SA6 to set α _sum = α, and then step SA7
Then, α _max = α and α _min = α are set, and the process proceeds to step SA13. Incidentally, alpha is the amount of change in the slip ratio difference, alpha _sum is the accumulated value of alpha, the maximum value of alpha _{ma x} is alpha, the alpha _min is the minimum value of alpha.

In the control cycle after performing the processing of steps SA6 and SA7, the count t ₄ of the timer becomes 2 or more at step SA5 and becomes not 1 so that the routine proceeds to step SA8 and α _sum = α _sum It is calculated as + α, and the process proceeds to step SA9. Then, in step SA9, it is determined whether or not α is larger than α _max. If α is larger, this α is set in step SA10.
Is newly set as α _max and the process proceeds to step SA11.

If α is smaller in step SA9, the process proceeds to step SA11. Then, in step SA11, it is determined whether or not α is smaller than α _min , and when α is smaller, this α is determined in step SA12.
Is newly set as α _min and the process proceeds to step SA13.

If α is larger in step SA11, the process proceeds to step SA13. Then, in step SA13, it is determined whether or not the timer has counted a predetermined number (for example, 30 here). Here, when the count t ₄ of the timer is 30, the routine proceeds to step SA14, where the cumulatively added α _sum is divided by 30 to calculate the average value α _AV of α. Along with this, by subtracting α _min from α _max , the difference α _PP between the maximum value and the minimum value of α is calculated.

Then, after this, in step SA15, the count t ₄ of the timer is reset to 0 and then the process is returned. If the timer count t ₄ is not 30 in step SA13, the process directly returns. As described above, in the present embodiment, the change amount α of the slip ratio difference is introduced as the determination index of the road surface friction resistance μ, and the average value α _AV of the constant amount of the change amount α of the slip ratio difference and the maximum value By estimating the road surface frictional resistance μ using the difference α _PP between the minimum value and the minimum value, the road surface frictional resistance μ can be estimated with higher accuracy.

That is, at the stage of calculating the change amount α of the slip ratio difference, the wheel speed difference ΔVr of the drive wheel on the side where the differential limiting mechanism is provided is changed from the wheel speed difference ΔVr of the drive wheel on the side where the differential limiting mechanism is not provided. Since the wheel speed difference ΔVf is reduced, the influence of the difference between the inner and outer wheels due to the turning and the effect of the wheel speed difference due to the movement of the left and right loads can be eliminated. Therefore, in the estimation condition determination unit 18E, the condition for the lateral acceleration G _Y is eliminated, and the lateral acceleration sensor can be eliminated. And this can reduce the cost.

The device of this embodiment can also be applied to a vehicle equipped with the differential limiting control device as shown in FIG. 8 as in the case of the first embodiment.

[0113]

As described in detail above, according to the vehicle road surface frictional resistance estimating apparatus of the present invention, the differential state between the left drive wheel and the right drive wheel of the vehicle is limited. A differential limiting mechanism, a left wheel side rotational speed detecting means and a right wheel side rotational speed detecting means for detecting rotational speeds of the left driving wheel and the right driving wheel, and a steering wheel angle detecting means for detecting a steering wheel angle of the vehicle. And a reference rotation of the left and right drive wheels based on the vehicle speed detected by the vehicle speed detection means for detecting the vehicle speed of the vehicle, and the detection information from the steering wheel angle detection means. A reference rotational speed difference calculating means for calculating a speed difference is provided, and the operating state of the differential limiting mechanism, the vehicle body speed of the vehicle, the rotational speed difference of the left and right driving wheels, and the reference rotational speed of the left and right driving wheels. The difference between the difference and the road on which the vehicle is traveling The configuration of the road surface frictional resistance estimating means for estimating a frictional resistance is provided, the power steering device is not necessary to provide a hydraulic pressure sensor or the like, it is possible to estimate the road surface frictional resistance without almost increasing the manufacturing cost.

According to the vehicle road surface frictional resistance estimating apparatus of the present invention, the left drive wheel and the right drive wheel that constitute either one of the front and rear drive wheels of the four-wheel drive vehicle. A differential limiting mechanism for limiting the differential state between the driving wheels and a left wheel side rotational speed detecting means for detecting the rotational speeds of the left driving wheel and the right driving wheel on the side provided with the differential limiting mechanism of the vehicle. And right wheel side rotation speed detection means, left wheel side rotation speed detection means and right wheel side rotation speed detection means for detecting the rotation speeds of the left drive wheel and the right drive wheel on the side not provided with the differential limiting mechanism of the vehicle. Means, detection information from the left wheel side rotational speed detecting means on the side provided with the differential limiting mechanism and the right wheel side rotational speed detecting means, and the left wheel on the side not provided with the differential limiting mechanism. From the side rotation speed detection means and the right wheel side rotation speed detection means A calculation means is provided for calculating the amount of change in the slip ratio difference of the drive wheels of the vehicle based on the detection information and the operating state of the differential limiting mechanism. Since the frictional resistance of the road surface on which the vehicle is running is estimated from the average value and the difference between the maximum value and the minimum value of the change amount of the slip ratio difference for each constant cycle, high accuracy is achieved. The road friction resistance can be estimated with.

Further, since the lateral acceleration sensor is not necessary, the cost can be reduced. Further, claim 3
According to the road surface frictional resistance estimating device for a vehicle of the present invention described,
The differential limiting mechanism includes a drive force transmission control mechanism capable of adjusting the drive force of the left and right wheels by transmitting and receiving the drive force between the left wheel drive shaft and the right wheel drive shaft of the vehicle. A force transmission control mechanism connected to one drive shaft side of the left and right drive shafts and capable of shifting and outputting the rotation speed of the one drive shaft side at a constant gear ratio; A transmission capacity that is interposed between the other drive shaft side of the left and right drive shafts and the output portion side of the speed change mechanism, and is capable of transmitting drive force between the left and right drive shafts when engaged. Due to the structure of the vehicle left-right driving force adjusting device including the variable control torque transmission mechanism, the road surface friction resistance can be estimated not only when the vehicle turns but also when the vehicle travels straight.

Further, by estimating the road surface frictional resistance in this way, the driving force can be distributed according to the road surface frictional resistance, and the running performance of the vehicle is improved. According to the vehicle road surface frictional resistance estimating device of the present invention, the differential limiting mechanism applies a driving force from the engine between the left wheel drive shaft and the right wheel drive shaft of the vehicle. An input unit for inputting, a differential mechanism for transmitting the driving force input from the input unit to each of the left and right driving shafts while allowing a differential between the left and right driving shafts, and A driving force transmission control mechanism capable of controlling the transmission state to adjust the distribution of the driving force to the left and right wheels, and the driving force transmission control mechanism is connected to the driving shaft side to rotate the driving shaft side. A speed change mechanism capable of speed-changing and outputting a speed at a constant speed change ratio, and being interposed between an output portion side of the speed change mechanism and the input portion side, the drive shaft side and the input portion when engaged. Since it is composed of a transmission capacity variable control type torque transmission mechanism that can transmit driving force to and from the The torque distribution is adjusted by transferring the required amount of one torque to the other instead of adjusting the torque distribution by using the energy loss of the brakes, etc. The torque distribution can be obtained.

According to the vehicle road surface frictional resistance estimating device of the present invention, the differential limiting mechanism is provided between the left wheel drive shaft and the right wheel drive shaft of the vehicle, and An input unit to which a driving force is input; a differential mechanism that transmits the driving force input from the input unit to each of the left and right driving shafts while allowing a differential between the left and right driving shafts; A drive force transmission control mechanism capable of controlling the transmission state of the drive force to adjust the distribution of the drive force to the left and right wheels, the drive force transmission control mechanism being connected to the input portion side, And a drive mechanism that is capable of changing the rotational speed of one side at a constant gear ratio and outputting the same, and is interposed between an output portion side of the speed change mechanism and the drive shaft side, and is engaged between the drive shaft side and the drive shaft side when engaged. It is composed of a transmission capacity variable control type torque transmission mechanism capable of transmitting driving force to the input side. Therefore, the torque distribution is adjusted by transferring the required amount of one torque to the other instead of adjusting the torque distribution by using the energy loss of the brake or the like, so that a large torque loss or energy loss is not caused. The desired torque distribution can be obtained.

According to the vehicle road surface frictional resistance estimating apparatus of the present invention, the estimation of the frictional resistance of the road surface is updated only when the vehicle is in a predetermined driving state. With this structure, the road friction resistance can be accurately estimated.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an overall configuration of a control system in a vehicle road surface frictional resistance estimating device as a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing a drive system of a vehicle equipped with a vehicle road surface frictional resistance estimating device as a first embodiment of the present invention.

FIG. 3 is a schematic diagram for specifically explaining a vehicle driving force distribution device equipped with a vehicle road surface frictional resistance estimation device as a first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing another example of a vehicle driving force distribution device provided with a vehicle road surface frictional resistance estimation device as a first embodiment of the present invention.

FIG. 5 is a control block diagram showing a part of a control system in the vehicle road surface frictional resistance estimating apparatus as the first embodiment of the present invention.

FIG. 6 is a graph for explaining the principle of the vehicle road surface frictional resistance estimating device as the first embodiment of the present invention, and is a graph showing the relationship between the tire slip ratio and the amount of torque movement between the left and right driving wheels. .

FIG. 7 is a flow chart for explaining the operation of the vehicle road surface frictional resistance estimating apparatus as the first embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view showing an example of a differential control device provided in a vehicle together with a vehicle road surface frictional resistance estimating device as a first embodiment of the present invention.

FIG. 9 is a partial cross-sectional view of a differential control device provided in a vehicle together with a vehicle road surface frictional resistance estimating device as a first embodiment of the present invention, and FIGS. 8
3 is a cross-sectional view taken along the line AA in FIG.

FIG. 10 is a graph for explaining the principle of the vehicle road surface frictional resistance estimating device as the second embodiment of the present invention, and is a graph corresponding to FIG. 6;

FIG. 11 is a graph showing a tendency of road surface frictional resistance in the vehicle road surface frictional resistance estimating apparatus as the second embodiment of the present invention.

FIG. 12 is a road surface friction for a vehicle as a second embodiment of the present invention.
6 is a graph for explaining the operation of the resistance estimation device.
Therefore, (a) is a graph showing the transition of the change amount α of the slip ratio difference.
Rough, (b) shows the change amount α of the slip ratio difference for each constant cycle.
Average value α_AVOf the slip ratio difference,
Difference α between the maximum value and the minimum value of change amount α of each constant cycle _PPof
It is a graph which shows a transition.

FIG. 13 is a flow chart for explaining the operation of the vehicle road surface frictional resistance estimating device as the second embodiment of the present invention.

FIG. 14 is a schematic configuration diagram showing a vehicle having a conventional four-wheel steering mechanism.

FIG. 15 is a schematic block diagram showing a configuration of a conventional four-wheel steering mechanism.

FIG. 16 is a graph showing the relationship between tire slip angle and cornering force.

FIG. 17 is a schematic diagram showing a force acting on the steered wheels when the vehicle turns.

FIG. 18: Steering angle input to steering wheel (steering wheel angle)
Is a graph showing the relationship between the output power steering pressure and
(A) relates to the steering angle, and (b) relates to the power steering pressure.

FIG. 19 is a schematic block diagram showing a conventional road surface frictional resistance estimating device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 engine 2 transmission 3 center differential 4 front differential 5 center differential differential limiting mechanism 6 propeller shaft 6A input shaft 7 bevel gear mechanism 8 rear differential 8A differential case 9, 9A drive force transmission control mechanism as differential limiting mechanism 10, 31 speed change mechanism 10A, 31A First Sun Gear 10B, 31B First Planetary Gear (Planetary Pinion) 10C, 31C Pinion Shaft 10D, 31D Second Planetary Gear (Planetary Pinion) 10E, 31E Second Sun Gear 10F, 31F Carrier 11 Hollow Shaft 12, 42 Multi-disc clutch mechanism as variable transmission capacity control type torque transmission mechanism 12A, 12B, 42A, 42B Clutch plate 13, 14 Drive shaft 17 Clutch hydraulic control valve 18 Control unit 18 ' Computation means 18A Torque movement command value output section 18B, 18J Subtraction section 18C Control amount setting section 18D Road surface friction resistance estimation means (Road surface friction resistance estimation section) 18E Estimation condition determination section 18F Reference rotational speed difference calculation means 18G Absolute value calculation means 18H , 18L Output value stabilizing means 18I Estimated value storage means 19FL, 19FR, 19RL, 19RR Wheel speed sensor as rotation speed detecting means 20 Handle angle sensor 21 Yaw rate sensor 22 Accelerometer 23 Accumulator 24 Electric pump 25, 26 Front wheel 36 Front / rear acceleration Sensor 41 Drive force transmission assisting member 70 Left and right drive force adjusting device 105 Handles 106, 107 Hydraulic cylinders 106A, 107A Tie rod 108 Rear wheel steering valve 112 Power steering sensor 113 Phase advancing valve 114 Rear wheel steering angle sensor 11 Alternator L terminal output 115A Alternator 216 Estimated vehicle speed calculation unit 216a Wheel speed selection unit 216b Filter 216c Estimated vehicle speed calculation unit 216d Filter 400 Differential limiting device 401 Input shaft 402 Drive pinion gear 403 Crown gear 404 Power transmission annular member 405th No. 1 housing 406 No. 2 housing 407 Ring gear 408 Sun gear 409 Carriers 410a, 410b Shafts 411a, 411b Planetary gears 412 Bearings 413 Cases 414 Multi-plate clutches 414a, 414b Clutch discs 415a, 415b Holder part 416 Annular shaft drive 417 Support member 419 Magnet 420 Solenoid 421 Ball 422, 424 Groove 423 Annular member 425 Chamber 427 Clutch 4 8 bearing 429 force direction converting mechanism 430 electromagnetic clutch mechanism 431 volts

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Claims (6)

[Claims] 1. A differential limiting mechanism for limiting a differential state between a left drive wheel and a right drive wheel of a vehicle, and a left wheel side rotational speed detection for detecting rotational speeds of the left drive wheel and the right drive wheel. Means and a right wheel side rotation speed detecting means, and a steering wheel angle detecting means for detecting a steering wheel angle of the vehicle, and a vehicle body speed detecting means for detecting a vehicle body speed of the vehicle, and the vehicle body speed detecting means. A reference rotation speed difference calculating means for calculating a reference rotation speed difference between the left and right drive wheels based on the vehicle speed and the detection information from the steering wheel angle detecting means, and an operating state of the differential limiting mechanism, Road surface frictional resistance estimating means for estimating the frictional resistance of the road surface on which the vehicle is traveling from the vehicle speed of the vehicle and the difference between the rotational speed difference between the left and right driving wheels and the reference rotational speed difference between the left and right driving wheels. Is provided, Two-way road surface friction resistance estimating device. 2. A differential limiting mechanism for limiting a differential state between a left drive wheel and a right drive wheel, which constitutes one of the front and rear drive wheels of a four-wheel drive vehicle, A left wheel side rotation speed detecting means and a right wheel side rotation speed detecting means for detecting the rotation speeds of the left drive wheel and the right drive wheel on the side provided with the vehicle differential limiting mechanism, and the vehicle differential limiting mechanism. Left wheel rotation speed detection means and right wheel rotation speed detection means for detecting the rotation speeds of the left drive wheel and the right drive wheel on the non-loaded side, and the left wheel rotation speed on the side provided with the differential limiting mechanism Detection information from the detection means and the right wheel side rotation speed detection means, and detection information from the left wheel side rotation speed detection means and the right wheel side rotation speed detection means on the side not provided with the differential limiting mechanism And the operating state of the differential limiting mechanism, based on the driving state of the vehicle. A calculation means is provided for calculating the amount of change in the slip ratio difference of the driving wheel, and the average value of the amount of change in the slip ratio difference for each constant cycle and the maximum and minimum values of the amount of change for the slip ratio difference in each constant cycle. A road surface frictional resistance estimating device for a vehicle, which is configured to estimate a frictional resistance of a road surface on which the vehicle is traveling from the difference between 3. A drive force transmission control mechanism capable of adjusting the drive force of the left and right wheels by transmitting and receiving the drive force between the left wheel drive shaft and the right wheel drive shaft of the vehicle by the differential limiting mechanism. The drive force transmission control mechanism is connected to one drive shaft side of the left and right drive shafts, and the rotational speed of the one drive shaft side can be output at a constant gear ratio. It is interposed between the speed change mechanism and the other drive shaft side of the left and right drive shafts and the output side of the speed change mechanism, and when engaging, the driving force is transmitted between the left and right drive shafts. The vehicle road surface frictional resistance estimating device according to claim 1 or 2, comprising a transmission capacity variable control type torque transmission mechanism capable of performing transmission. 4. The differential limiting mechanism is provided between a left wheel drive shaft and a right wheel drive shaft of the vehicle, an input section to which a driving force from an engine is input, and a difference between the left and right drive shafts. And a differential mechanism that transmits the driving force input from the input section to the left and right driving shafts while allowing the movement, and controls the transmission state of the driving force to distribute the driving force to the left and right wheels. An adjustable drive force transmission control mechanism, wherein the drive force transmission control mechanism is connected to the drive shaft side and is capable of changing the rotational speed of the drive shaft side at a constant gear ratio and outputting it. , A transmission capacity variable control which is interposed between the output portion side of the speed change mechanism and the input portion side and can transmit the driving force between the drive shaft side and the input portion side when engaged. 3. A vehicle road according to claim 1 or 2, characterized in that Frictional resistance estimation apparatus. 5. The differential limiting mechanism is provided between a left wheel drive shaft and a right wheel drive shaft of the vehicle, an input section for inputting a driving force from an engine, and a difference between the left and right drive shafts. And a differential mechanism that allows the driving force input from the input section to be transmitted to the left and right driving shafts, and controls the driving force transmission state to adjust the driving force distribution to the left and right wheels. A driving force transmission control mechanism capable of controlling the driving force transmission control mechanism, the driving force transmission control mechanism being coupled to the input portion side, and capable of shifting the rotational speed of the input portion side at a constant gear ratio and outputting the rotational speed. A transmission capacity variable control torque which is interposed between the output portion side of the speed change mechanism and the drive shaft side and can transmit the drive force between the drive shaft side and the input portion side when engaged. 3. A vehicle road surface friction according to claim 1 or 2, characterized by comprising a transmission mechanism. Anti-estimating apparatus. 6. The vehicle according to claim 1, wherein the vehicle is configured to update the estimation of the frictional resistance of the road surface only in a predetermined driving state. Vehicle road friction resistance estimation device.