JPH07110576B2 - Torque distribution control device for four-wheel drive vehicle - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque distribution control device for a four-wheel drive vehicle that allows a drive torque distribution of front and rear wheels to be arbitrarily controlled in a full-time four-wheel drive vehicle to enable traveling with emphasis on operability or stability. .

[Prior art]

Regarding the distribution of front / rear wheel drive torque in a full-time four-wheel drive vehicle, a hydraulic clutch is provided in the middle of the drive system for the front / rear wheels as disclosed in Japanese Patent Laid-Open No. 56-43031, for example. There was one that controlled the clutch torque.
This is based on the information from the vehicle speed sensor, and at the time of high speed, the stability is more emphasized and the driving force distribution is closer to that of the front wheel drive (FF). On the other hand, at the time of low speed, the maneuverability (turning) is emphasized and the rear wheel drive is used. The driving force distribution is close to (FR).

[Problems to be Solved by the Invention]

By the way, in the configuration of the above-mentioned prior art, the drive torque distribution was controlled by the traveling state based on the information from the vehicle speed sensor, but the traveling road surface condition is not always uniform, and the riding personnel and 4 depending on loading capacity
The difficulty of spinning each wheel is not even.
That is, a wheel located at a low road friction coefficient μ or a wheel having a small vertical load easily spins, and it is not always possible to appropriately deal with the information obtained by the vehicle speed sensor. INDUSTRIAL APPLICABILITY The present invention ensures stability at high speeds and turning performance at low speeds without causing an overall torque loss, and under various conditions such as loading conditions, passengers, and uneven road friction coefficient. The purpose is to be able to keep the wheel spin to a minimum.

[Means for solving problems]

To achieve the above object, the torque distribution control device for a four-wheel drive vehicle according to the present invention stores a vehicle speed sensor and a road surface friction coefficient detection device, and a drive force distribution corresponding to the vehicle speed and the road surface friction coefficient as a map in advance. A device is provided, and based on the vehicle speed signal from the vehicle speed sensor and the road surface friction signal from the road surface friction coefficient detection device, a predetermined drive force distribution is retrieved from the storage device by map search and the drive force distribution is read out. The driving force distribution to the front wheels and the rear wheels is controlled according to the distribution.

[Action]

Based on the above configuration, a predetermined driving force distribution is read from the storage device by a map search by a signal from the vehicle speed sensor, a signal from the road surface friction coefficient detection device, or a signal that the driver judges and manually inputs. The drive force distribution to the front and rear wheels is optimally controlled according to the read drive force distribution.

【Example】

Embodiments of the present invention will be described below with reference to the drawings. First
The figure is a skeleton diagram showing the structure of a transmission system of a four-wheel drive vehicle with a center differential. In the figure, 1 is an engine, 2 is a transmission, 3 is a front wheel, 4 is a rear wheel, 5 is a front diff, 6 is a rear diff, Reference numeral 7 is a center differential, 8 is a gear fixed to the output shaft of the transmission 2, and 9 is a gear provided in the case of the center differential 7, which meshes with the gear 8. 10 is a torque distribution device, 11 is a bypass shaft 10 of the torque distribution device 10.
a hydraulic clutch provided on a, 12 is a gear fixed to the front wheel drive shaft 7a of the center differential 7, 13 is a gear fixed to one end of the bypass shaft 10a, and has the same diameter to mesh with the gear 12, and 14 is A large-diameter gear provided on the drum side of the hydraulic clutch 11 and a small-diameter gear 15 fixed to the rear wheel side drive shaft 7b of the detent differential 7 meshes with the gear 14. Reference numeral 18 is a hydraulic unit that supplies a predetermined hydraulic pressure to the hydraulic clutch 11, 19 is a handle, 20 is a torque distribution control device including a microcomputer, 21 is an output torque sensor, 22 is a vehicle speed sensor provided on the front wheels 3, and 23 is It is a road friction coefficient detection device. Further, in FIG. 2 showing the configuration of the torque distribution control device 20, reference numeral 30 denotes a storage device, which is an optimum torque distribution corresponding to the vehicle speed V and the road surface friction coefficient μ, that is, the front wheel driving force distribution value R _F is in the form of a map. Is stored in advance. Reference numeral 31 denotes a driving force distribution determining means, which is based on signals from the vehicle speed sensor 22 and the road surface friction coefficient detecting device 23, and is stored in the storage device 30 from a map as shown in FIG. Driving force distribution value R _F
Read out. Reference numeral 32 denotes a clutch hydraulic pressure calculating means, which is a clutch for generating a predetermined clutch torque Tc in the hydraulic clutch 11 based on the read front wheel driving force distribution value R _F and the driving torque T detected by the output torque sensor 21. A hydraulic pressure command value is calculated, a command is given to the hydraulic unit 18, and the commanded clutch hydraulic pressure Pc is applied to the hydraulic clutch 11. Next, the operation of the torque distribution device 10 will be described. The drive torque T output from the transmission 2 is transmitted to the center differential 7 via the gears 8 and 9, where the drive force T is distributed into substantially equal parts and the front wheel drive shaft 7a and the rear wheel drive shaft 7b are distributed. And be transmitted to. Here, when the hydraulic clutch 11 is off, the front wheels 3 and the rear wheels 4 are respectively (T / 2).
It is driven by the drive torques T _F and T _R of. This hydraulic clutch 11
The hub 11a rotates at the same speed as the front-wheel-side drive shaft 7a via the gears 12 and 13 having the same diameter and the bypass shaft 10a, and the drum 11b has a gear ratio K between the gear 15 having a small diameter and the gear 14 having a large diameter. Since the rotation is in deceleration, when the hydraulic pressure Pc is gradually applied from the hydraulic unit 18, a clutch torque Tc corresponding to the hydraulic pressure is generated, and the clutch torque Tc is applied to the low speed rotation side drum 11b, and the rear wheel side drive shaft the driving force T _R to 7b (T / 2 + K · Tc) , and the
On the other hand, the driving force T _F applied to the front wheel side drive shaft 7a becomes (T / 2−Tc), the driving force of the front wheels 3 decreases according to the hydraulic pressure applied to the hydraulic clutch 11, and the driving force of the rear wheels 4 decreases. Increase. Conventionally, this torque distribution control has been performed only by the information from the vehicle speed sensor 22, but since the friction coefficient μ changes variously on an actual road surface, control only by the vehicle speed information has not been sufficient yet. For example, if the driving force distribution is close to that of the rear wheel drive (FR) at low speed on a snowy road, the turning performance will be too good, making it difficult to control. Also, when accelerating from a low speed, a large driving force will not be sufficiently transmitted to the road surface. The merit as a wheel drive was not fully exerted. Therefore, as shown in FIG. 3, increase the front wheel drive force distribution R _F as the vehicle speed increases, the driving force distribution value R _F such as to reduce the R _F The larger the road surface friction coefficient μ is, the form of a map In storage device 30
Stored in. Then, the torque distribution control device 20 reads out the corresponding front wheel driving force distribution value R _F from the map 30 by the driving force distribution determining means 31 based on the input signals from the vehicle speed sensor 22 and the road surface friction coefficient detecting device 23. Next, in the clutch hydraulic pressure calculation means 32, the read front wheel drive force distribution value is read.
The clutch torque Tc is obtained by R _F , that is, T _F / (T _F + T _R ) = (T / 2−Tc) / T, and the driving force T from the transmission 2 detected by the output torque sensor 21.
The clutch hydraulic pressure corresponding to this Tc is instructed to the hydraulic unit 18, the corresponding hydraulic pressure Pc is applied to the hydraulic clutch 11 to generate the clutch torque Tc, and the drive torque to the front wheel side drive shaft 7a is generated.
Let T _F correspond to R _F (T / 2−Tc), and drive torque T _R to the rear wheel side drive shaft 7b be corresponding to R _F (T / 2 + K · Tc). In this way, it is possible to suppress the sensitive turning ability even on a slippery road surface. In the above embodiment, the road surface friction coefficient detecting device 23
Although the front wheel driving force distribution value R _F is obtained using the signal from the above, the driver may visually determine the road surface μ and manually input it. The present invention is not limited to the torque distribution device as in the embodiment.

【The invention's effect】

As described above, according to the present invention, the center differential device is provided with the torque distribution device bypassed, and the optimum torque distribution value is determined based on the signal from the vehicle speed sensor and the signal from the road surface friction coefficient detection device. Since the map is searched, the front wheel drive force can be slightly increased on slippery roads while maintaining stability at high speeds and turning performance at low speeds without causing overall torque loss. It is possible to obtain the effect that stable turning can be performed while suppressing the turning ability, and sufficient acceleration can be obtained.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing the configuration of a four-wheel drive vehicle with a center differential of the present invention, FIG. 2 is a block diagram showing the configuration of a torque distribution control device of the present invention, and a torque distribution diagram of the torque distribution device, and a third diagram. The figure is a driving force distribution value map. 2 ... transmission, 3 ... front wheel, 4 ... rear wheel,
7 ... Center differential, 8 and 9 are gears, 10 ... Torque distribution device, 11 ... Hydraulic clutch, 12-15 ... Gear, 20 ... Torque distribution control device, 22 ... Vehicle speed sensor, 23 ... Road surface Friction coefficient detector.

Claims (1)

[Claims] 1. In a four-wheel drive vehicle in which the driving force distribution between the front and rear wheels is variable, a vehicle speed sensor for generating a vehicle speed signal, a road surface friction coefficient detecting device for generating a road surface friction signal, and a vehicle speed and a road surface friction coefficient. A storage device for storing corresponding driving force distribution values in the form of a map in advance is provided, and based on the vehicle speed signal and the road surface friction signal, the driving force distribution value of the predetermined map is read out, and A torque distribution control device for a four-wheel drive vehicle, characterized in that the driving force distribution between the front and rear wheels is controlled in accordance with the above.