JPH0386628A - Differential controller - Google Patents

Abstract

PURPOSE:To properly restrict the differential movement in a region where the revolution speed difference is large by determining the differential limit torque from the revolution speed difference between the right and left wheels of other wheel and the torque of a transfer clutch and controlling the torque of a clutch for differential limit by the signal corresponding to the torque. CONSTITUTION:A power is transmitted onto other wheels by a transfer clutch 11 according to each traveling condition, and four-wheel drive traveling is performed, and the differential movement of a differential device 14 is restricted with the differential limit torque of a differential limit clutch 17 by the revolution speed difference between the right and left wheels of other wheel. The differential limit torque in this case is corrected according to the power transmission state to other wheels, and the differential limit action can be effectively performed without deteriorating the turning performance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a differential control device for a four-wheel drive vehicle equipped with a transfer clutch, and more specifically, to a differential control device for wheels that transmits power via a transfer clutch. Regarding differential limit $ control.

[Conventional technology]

The applicant has already proposed a number of four-wheel drive vehicles with transfer clutches, and by changing the torque of the transfer clutch under each driving condition and transmitting power to the rear wheels (or front wheels), four-wheel drive driving is possible. It is supposed to be done. In such a four-wheel drive vehicle, a large amount of power is transmitted to the rear wheels (front wheels) on low μ roads where slips are likely to occur, and the rear wheels (front wheels) actively generate driving force as well as the front wheels (rear wheels). , the rear (front) differential device is also provided with a differential control device.

In this type of 4-wheel drive vehicle, limiting the differential of the rear (front) differential when there is little power transmitted to the rear wheels (front wheels) is ineffective and wasteful.
It is necessary to judge the power transmission state of the rear wheels (front wheels) and limit the differential of the rear (front) differential. Further, since the differential limiting torque of the rear (front) differential has a large influence on the behavior of the vehicle, it is desirable to control it appropriately.

Conventionally, regarding this type of differential control device, there is a prior art, for example, disclosed in Japanese Patent Application Laid-Open No. 63-312238, in which a differential control device is used so that the rotational speed difference between the left and right rear wheels becomes a predetermined value determined by the vehicle speed and steering angle. It is shown that uIgi the restriction device.

[Problem to be solved by the invention]

By the way, when the differential limiting device of the above-mentioned prior art is applied to a four-wheel drive vehicle that variably controls the transfer clutch, regardless of the presence or absence of the driving force on the wheel side to which power is transmitted via the transfer clutch, or the magnitude thereof. This limits the differential movement of the wheels, which impairs turning performance and is inefficient.

In addition, as a characteristic of the differential limiting torque with respect to the rotation speed difference,
In the case of a viscous coupling, a chevron-shaped one has problems such as the differential limiting torque being too large in a region where the rotational speed difference is small, and it being difficult to achieve a sufficient differential lock in a region where the rotational speed difference is large.

The present invention has been made in view of the above points, and its object is to effectively limit the differential in a wheel differential device that transmits power via a transfer clutch of a four-wheel drive vehicle having a transfer clutch. The object of the present invention is to provide a differential control device that can perform accurate and optimal control.

[Means to solve the problem]

In order to achieve the above object 1], the differential control device of the present invention has the following features:
Power is always transmitted to one wheel, and power is transmitted to the other wheel via a transfer clutch, with the torque of the transfer clutch being variable, and a differential device between the other wheels is used to limit the differential. In a four-wheel drive vehicle equipped with a clutch, a rotation speed difference calculation means for calculating a rotation speed difference between the left and right wheels of the other wheel, and a difference that determines a differential limiting torque based on the rotation speed difference and the torque of the transfer clutch. Dynamic limit torque setting means and differential ff+1
control means for controlling the torque of the differential limiting clutch with a signal corresponding to the differential limiting clutch, and correcting the differential limiting torque with respect to the rotational speed difference of the differential limiting clutch with an increasing function of the transfer clutch torque. It is something.

[For production]

Based on the above configuration, power is transmitted to the other wheel by the transfer clutch according to each driving condition for four-wheel drive driving, and at this time, the differential of the differential limiting clutch is activated depending on the rotational speed difference between the left and right wheels of the other wheel. 111i Limits the differential movement of the differential device at the 1 limit torque. The differential limiting torque in this case is corrected according to the state of power transmission to the other wheel, thereby effectively limiting the differential without impairing turning performance.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In Fig. 1, the outline of the drive system in front engine/front drive (F F) based four-wheel drive is as follows: l is the engine, 2 is the clutch, 8 is the transmission, and the transmission output shaft 4 A pair of gears 5. It is connected to the front drive shaft 7 via B, and further connected to the front wheels 10L, I via the front differential device 8 and the vehicle 9.
Transmission configured to OH. Further, the transmission output shaft 4 is connected to a rear drive shaft 12 via a transfer clutch 11, and further connected to a propeller shaft 13. Car with rear differential device 14°? Left and right rear wheels 18L, 18 through H5
The transmission is configured in R.

The rear differential device 14 is of a bevel gear type, and a hydraulic clutch 17 for differential limiting is provided in a bypass manner between, for example, a differential case 14a and one side gear 14b of the rear differential device i4.

Next, the hydraulic pressure 1; control system will be described.

The hydraulic control means is an oil pump 20, which is used for n-dynamic shifting when the transmission 3 is a variable transmission, and a line pressure passage 22 whose pressure is regulated by a regulator valve 21 is connected to a clutch. Control valve 23. It communicates with the transfer clutch 11 via an oil passage 24 . In addition, the line pressure oil passage 22 is
Pilot valve 25. An oil passage 27 having an orifice 26 communicates with a duty solenoid valve 28 , so that duty pressure from the duty solenoid valve 28 acts on the control side of the clutch control valve 23 via an oil passage 29 . In this way, by operating the clutch control valve 23 using the duty pressure of the duty solenoid valve 28, the transmission torque Tc of the transfer clutch 11 is variably controlled.

In addition, another set of clutch control valves 2 is installed in the oil passages 22 and 27.
3' and a duty solenoid valve 28' are similarly provided in communication, and an oil passage 24 from the clutch control valve 23'
' is connected to the hydraulic clutch 17 on the rear differential device 14 side. and duty solenoid valve 28
By operating the clutch control valve 23' with the duty pressure ', the differential limiting torque TD of the hydraulic clutch 17 is variably controlled.

Furthermore, we will discuss the electronic control system.

First, let's talk about the transfer clutch control system.
Front and rear wheel rotation speed sensors 3017.30R, 311,.

31R, throttle opening sensor 32. It has a steering angle sensor 33 and the like. The left and right rear wheel rotation speed sensors 30L and 30R have the same rotation speed ωPI1. ωFR is the control unit 40
The front wheel rotation speed calculation means 50 calculates the front wheel rotation speed ωF as the average of both, and similarly the left and right rear wheel rotation speed sensor 31
1. , 31R's left and right rear wheel rotation speed ωR1, ωRR is,
The rotation speed ωR for the rear wheels is calculated by inputting it to the rear wheel rotation speed calculation means 51, and the calculated rotation speeds ωF and ωR for the front and rear wheels are input manually to the heavy speed calculation means 41 and the 1 of both is averaged. The vehicle speed V is calculated, and similarly, the front and rear wheel rotation speed difference calculation means 42 is manually operated to calculate the rotation speed difference Δω1 (-ωF−ωR) between the two. Throttle opening degree θ of sensor 32.

The steering angle ψ of the steering angle sensor 33 is determined by manually inputting the transfer clutch torque calculation means 43 to set the transfer clutch torque Tc according to each driving condition based on the vehicle speed V and the throttle opening θ. In addition, this transfer clutch torque Tc is reduced and compensated by the steering angle ψ, and the rotational speed difference Δω1
An increase compensation iE is applied to the Then, this clutch torque Tc is manually converted into a duty ratio by the control amount setting means 44, and outputted to the duty solenoid valve 28 via the driving means 45.

Regarding the rear differential differential limit ff1l 1m system, the left and right rear wheel rotation speed sensor 311. , 31
R's left and right rear wheel rotational speeds ωR17 and ωRR have a manual left and right rear wheel rotational speed difference calculating means 46, which calculates a rotational speed difference Δω2 by subtracting the two, and this left and right rear wheel rotational speed difference Δ
ω2 is manually applied to the differential limit torque setting lower stage 47. Here, differential limiting torque TD for left and right rear wheel rotational speed difference Δω2
As shown in FIG. 2, the characteristics are set so that the differential limiting torque TD rises smoothly and a sufficiently high differential limiting torque TD is generated. Also,
The signal of the transfer clutch torque Tc is also manually inputted to the differential limiting torque setting means 47, so that the differential limiting torque TD is corrected by the transfer clutch torque Tc. That is, when the transfer clutch torque Tc is small, even if the left and right rear wheel rotational speed difference Δω2 is large, the differential limiting effect by the differential limiting torque TD is small;
The larger the transfer clutch torque Tc, the greater the effect of the differential limiting torque TD, so the differential limiting torque T
D is corrected as an increasing function with respect to transfer clutch torque Tc as shown in FIG. Then, this differential limiting torque TD is converted into a duty ratio D' by the control amount setting means 48, and the duty solenoid valve 28 is
′.

Next, the operation of the four-wheel drive vehicle and the differential control device having such a configuration will be described using the flowchart shown in FIG.

First, the power from the engine 1 is transmitted to the transmission 3 via the clutch 2.
The transmission power is transmitted from the output shaft 4 to the gears 5, 6, . Front drive shaft7. Front differential device 8
．． It is always transmitted to the front wheels 10R, 101 via the axle 9. At this time, each driving condition is set i1 depending on the vehicle speed V and the throttle opening θ, and the transfer clutch torque setting means 43 of the control unit 40 sets the transfer clutch torque Tc according to each condition. and high μ
Under conditions of steady running in a non-slip state (on the road), the transfer clutch torque Tc is set relatively small, and a signal corresponding to the duty ratio is manually applied to the duty solenoid valve 28, and the extraction pressure control system sets a low duty ratio. Pressure is manually applied to the clutch control valve 23 and the transfer clutch 11
By increasing the drain volume, the transfer clutch torque Tc of the transfer clutch 11 is controlled to be small. Then, the power corresponding to the transfer clutch torque Tc is transmitted to the propeller shaft I3 after the transfer clutch 11. Rear differential device 14. The rear wheels 111i1. , 1BI? This results in four-wheel drive driving with torque distribution biased toward the front wheels. In the case of turning, the transfer clutch torque Tc is significantly reduced by the steering angle ψ, and the difference in rotational speed between the front and rear wheels is absorbed by the transfer clutch 11, making it possible to turn smoothly.

On the other hand, when traveling in four-wheel drive, the left and right rear wheel rotation speed sensor 3
The left and right rear wheel rotation speed difference Δω2 between the left and right rear wheel rotation speeds ωR1, ωRR of 1L and 31R is calculated as the left and right rear wheel rotation speed difference calculation means 4.
B is calculated to determine the slip state, and in non-slip, the differential limiting torque TD is set to zero. Then, a duty signal corresponding to this differential limiting torque TD is manually applied to the duty solenoid valve 28, and the clutch control valve 2
3' to the drain side to drain the extraction clutch 17, thereby draining the rear differential device 14.
becomes free and applies a differential action to the n mountain.

By the way, rear wheel 1B+4. When one of the IOHs enters a rough road and slips, and the calculated value of the left and right rear wheel rotational speed difference Δω2 increases, the differential limiting torque setting means 47 sets the differential limiting torque TD according to this left and right rear wheel rotational speed difference Δω2. is set. However, as described above, under conditions where the transfer clutch torque Tc of the transfer clutch 11 is small and the vehicle can be driven with a torque distribution biased toward the front wheels, the differential limiting torque TD is corrected to be small based on the map shown in FIG. ,.

The stability of 16R is ensured.

Next, if the front wheels slip under driving conditions such as starting or accelerating, or on low-μ roads, the weight of the vehicle is transferred to the rear wheels.

Transfer clutch torque T according to road surface friction coefficient μ
c is set to a large value, and the vehicle enters a running state in which the transfer clutch 11 controls the front and rear wheels to be directly coupled. Under such driving conditions, the left and right rear wheels 161. , When a slip occurs in the IBH, the differential limiting torque TD is corrected to increase and a large differential limiting torque TO is generated in the extraction clutch 17. At this time, since the rear wheel transmission torque is large, the differential device 14 is not effective. The differential is limited to provide excellent running performance.

Although the embodiments of the present invention have been described above, the present invention can also be applied to vehicles having other drive systems such as a front engine/rear drive (FR) type.

Furthermore, the transfer clutch and the differential limiting clutch may be clutches that are controlled by other methods instead of using hydraulic pressure.

〔Effect of the invention〕

As described above, according to the present invention, in a differential control device for a four-wheel drive vehicle having a transfer clutch,
Since the differential limiting torque is smoothly set according to the rotational speed difference between the left and right wheels, the differential can be appropriately limited in a region where the rotational speed difference is large.

Further, since the differential limiting torque of the differential device is corrected by an increasing function by the torque of the transfer clutch, the differential can be effectively limited in accordance with the rear wheel power transmission state. In addition, good turning performance can be ensured when the front wheels are unbalanced.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the differential control device of the present invention, Fig. 2 is a characteristic diagram of differential limiting torque with respect to rotational speed difference and transfer clutch torque, and Fig. 3 (a) is a diagram of transfer clutch torque. Flowchart of setting, (b> is a flowchart of differential limiting action. 101, IOR...front wheel, ll...transfer clutch, 14...rear differential device, 17...extraction clutch , 23.23'... Clutch control valve, 28.28'... Duty solenoid valve, 40... Control unit, 43... Transfer clutch torque setting means, 46... Left and right wheel rotation speed difference Calculation means, 47... Differential limit torque setting means, 48... Control 3a amount setting means.

Claims (1)

[Claims] The configuration is such that power is always transmitted to one wheel, and the power is transmitted to the other wheel through a transfer clutch, with the torque of the transfer clutch being variable, and a differential device between the other wheels. In a four-wheel drive vehicle equipped with a differential limiting clutch, a rotation speed difference calculating means calculates a rotation speed difference between the left and right wheels of the other wheel, and a differential transmission is performed based on the rotation speed difference and the torque of the transfer clutch. A differential limiting torque setting means for determining a limiting torque, and a control means for controlling the torque of the differential limiting clutch with a signal corresponding to the differential limiting torque, A differential control device characterized in that dynamic limit torque is corrected by an increasing function of transfer clutch torque.