JPS6277233A - Control device for 4-wheel-drive - Google Patents

Abstract

PURPOSE:To maintain a stable running condition, by furnishing a device to lock a center differential provided that the variation rate of the rotations of front wheels or rear wheels comes to be remarkably larger than the variation rate of the accelerator opening. CONSTITUTION:The driving force from an engine is delivered to a torque converter 11, a main transmission 12, and a sub-transmission 13, and the output is transmitted to the front wheels through a front differential unit 15. On the other hand, signals from detectors 1 and 2 are input to an arithmetic unit 3, where the ratio of the variation of rotations of the front wheels or the rear wheels to the variation rate of the accelerator opening is computed, and the resultant value is input to a comparing-and-deciding unit 4. In the unit 4, the present computing value and the computed value an instant ago are compared, and if the present value is larger than the other, a differential lock signal is generated by a signal generator 6, to make the function of a center differential unit ineffective. Therefore, the driving force is utilized sufficiently, and a stable and safe running condition can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive control device, and in particular, the present invention relates to a four-wheel drive control device, and in particular, to absorb the turning radius of the front and rear wheels that occurs during cornering. The present invention relates to a four-wheel drive control device for a four-wheel drive vehicle equipped with a center differential for allowing a difference in rotational speed.

[Conventional technology]

Generally, the left and right wheels of a vehicle have different turning radii when cornering. Therefore, in order to absorb this effect and perform smooth cornering, a mechanism is generally provided that allows the difference in rotation speed between the left and right wheels according to the difference in turning radius, that is, a differential mechanism (front differential, rear differential). There is.

On the other hand, this phenomenon, that is, the difference in turning radius, also occurs between the front and rear wheels, so in a four-wheel drive vehicle,
A mechanism has been proposed that allows a difference in rotational speed between the front and rear wheels depending on the difference in turning radius, that is, a center differential mechanism.

[Problem that the invention seeks to solve]

However, since this center differential has the function of distributing torque between the front and rear wheels in an equal ratio, the driving force transmission limit will be balanced to the lower value of the driving force of the front or rear wheels. . In other words, the maximum traction force Fμ is calculated as follows: When the front wheel's limit traction force is Fμ2 and the rear wheel's limit traction force is Fμ, for the sake of simplicity, consider the case where the torque distribution ratio of the center differential is l:1. Wheel drive vehicle: Fμ+ = 2XF#, (where Fμ, <Fμ.

) A four-wheel drive vehicle without a center differential or with a locked center differential: Fμ2=Fμ, +Fμ, and it can be seen that Fμ+ <FAlt.

For this reason, a four-wheel drive vehicle with a center differential may have inferior transmitted driving force when the road surface friction coefficient is low, compared to a four-wheel drive vehicle without a center differential.

This means that when a large driving force is generated, for example during acceleration, this driving force cannot be sufficiently transmitted to the road surface.
This may occur as a phenomenon such as slipping of the front or rear wheels, but the 4-wheel drive system with a center differential can eliminate such negative effects.
Wheel drive controls have not yet been proposed.

The present invention solves the above-mentioned problems by reliably detecting the point in time when an adverse effect is caused by the center differential mechanism, and when this is detected, locking the center differential mechanism to ensure that the center differential function is fully functional. It is an object of the present invention to provide a four-wheel drive control device that allows the four-wheel drive to exhibit its full potential and does not cause a decrease in driving force.

[Means for solving problems]

To this end, the four-wheel drive control device of the present invention is equipped with a center differential that absorbs the difference in rotational speed between the front wheels and the rear wheels so as to absorb the difference in turning radius between the front wheels and the rear wheels that occurs during cornering. In a wheel drive control device, the accelerator opening degree and the rotational speed of the front and rear wheels are detected, and the rate of change in the rotational speed of the front and rear wheels is compared with the rate of change in the accelerator opening degree. The present invention is characterized by having a mechanism that locks the center differential and disables the operating mechanism under the condition that the rate of change in the rotational speed becomes significantly larger than the rate of change in the accelerator opening.

[Action and effect of invention]

The four-wheel drive control device of the present invention detects the accelerator opening and the rotation speed of the front and rear wheels, and compares the rate of change in the rotation speed of the front and rear wheels with the rate of change in the accelerator opening, The center differential is equipped with a mechanism that locks the center differential and disables the operating mechanism when the rate of change in the rotation speed of the front or rear wheels becomes significantly larger than the rate of change in the accelerator opening. In addition, in the event of abnormal conditions such as slippage, the system quickly detects such conditions and locks the center differential, ensuring stable and safe driving by making full use of the driving force. It is possible to maintain a good running condition.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of the control system in the control device of the present invention, FIG. 2 is a diagram for explaining the flow of processing by the control device of the present invention, and FIG. 3 is the control device of the present invention. A diagram showing the power transmission system of a commonly used 4-wheel drive vehicle with a center differential, Part 4 shows a time chart of various variables when no slip occurs, and Figure 5 shows a diagram of various variables when slip occurs. It is a figure which shows a time chart. In the figure, 1
is the accelerator opening detection part, 2 is the front/rear wheel rotation speed detection part, 3
is an arithmetic unit, 4 is a comparison/judgment unit, 5 is a storage unit, 6 is a signal generation unit, 7 is a reset unit, lo is an automatic transmission, 11 is a torque converter, 12 is a main transmission, 13 is an auxiliary transmission, 14
1 is a drive gear, 15 is a front differential device, 16 is a front wheel drive shaft, 17 is a propeller shaft for rear wheel driving force, 18 is a bevel gear, 19 is a center differential device, 20 is a rear wheel transmission device, 2
1 indicates a center differential lock device.

Generally, in a four-wheel drive vehicle with a center differential, when the engine is mounted on the front side, the driving force transmission mechanism is as shown in FIG. That is, power from the engine is transferred to the torque converter 11 disposed within the automatic transmission 10.
, the main transmission 12, and the auxiliary transmission 13, and the output thereof is transmitted to the front wheel drive shaft 16 via the drive gear 14, the center differential device 19, and then the front differential device 15,
The front wheels are driven. On the other hand, the rear wheel driving force propeller shaft 17 is connected to a center differential device 19 via a bevel gear 18 .

In such a power transmission system, the present invention arranges a center differential device 21 in parallel with the center differential device 19, and operates the center differential device 21 based on a control command signal when slip occurrence is detected. This disables the front/rear wheel differential function by the center differential device 19.

Next, the concept of slip detection, which forms the basis of the present invention, will be explained based on FIGS. 4 and 5, which show temporal changes in various variables.

First, Figure 4 is a time chart when no slip occurs, where θ is the accelerator opening, V, , V,
is the rotation speed of the front and rear wheels, Δθ is the rate of change of θ, Δ■1, Δ■
, is V, the rate of change of V, Δ■1, r/Δθ is Δ■7,
It represents the ratio between Δv7 and Δθ. Note that ■, and vl are not necessarily the same value due to the operation of the center differential, but they change in the same way, so they are drawn together here as a diagram showing their trends.

As shown in Part 4, when no slip occurs even if the accelerator opening degree θ increases, the rotation speeds V, , V, of the front and rear wheels also increase correspondingly, so ΔVt, ,
It can be seen that the ratio of /Δθ is a constant value.

On the other hand, Fig. 5 shows a time chart of various variables similar to Fig. 4 when slipping occurs, but when slipping occurs, the wheels spin at high speed, so the rotation speed (2) increases rapidly, and along with this, its temporal changes, Δvf and ΔvP, also rapidly increase. Therefore, ΔVT1. The ratio of /Δθ will also increase as shown in Figure 5A, so if this rising state is monitored,
It is possible to reliably detect the point at which a slip occurs.

Furthermore, even if no slip occurs, Δ■1 and ΔVr will increase as the wheel rotational speed V and Vl increase, so an increase in Δvf and ΔV does not necessarily mean a slip condition. do not.

Therefore, instead of increasing Δvt, Δ■, ΔV,1,/Δ
It is easy to detect the point at which a slip occurs based on the increase in θ.

Next, one embodiment of the control system in the control device of the present invention will be described with reference to FIG. 1. The front and rear wheel rotation speed detection sections 2 detect the respective rotation speeds of the front and rear wheels.

The detection signals from each detection unit 1.2 are input to the calculation unit 3, where the ratio of the rate of change of the front and rear wheel rotation speed to the rate of change of the accelerator opening at that point in time (Fig. 4, 5
In the figure, ΔV, . On the other hand, the storage unit 5 stores similar calculated values a short time ago, and the values are used for the comparison and calculation.
The calculated value is inputted to the determination unit 4, and the calculated value at the present time is compared with the calculated value a short time ago. If the current calculated value is larger, it is determined that Δ■2 and r/Δθ are increasing in FIG. The recent section 7 also resets the value in the storage section 5 to a new value at this time.

FIG. 2 shows the flow of processing in this control system, which will be explained in detail as follows.

■ Detects the accelerator opening θ and the rotation speeds V, , V, of the front and rear wheels.

■ Rate of change Δθ of θ and rate of change ΔV2 of V, , V,
Calculate Δv, . This calculation can be performed using a differentiating circuit or by counting the amount of change in each of θ, V, , V, during a minute time Δt.

■ Determine whether Δθ is O.

(2) When Δθ is O, that is, when the accelerator opening θ is not changing, the brake/open signal of the center differential device is maintained unchanged. That is, when Δθ is O,
As seen in the changes B and C of Δθ in Fig. 5,
This is because the state of slip occurrence (part C) or non-slip occurrence (part B) continues.

■ If Δθ is not O, ')Ct=Δvr/Δθ,X
Calculate the values of 1=ΔV and /Δθ, respectively.

At this time, due to the inertia of the vehicle, the change in θ and V,
A slight time lag occurs between the changes in ,V, but this can be dealt with in the design by using a time delay element commensurate with this.

■ Determine whether Δθ is positive or not.

■ Here, when Δθ is positive, the minute time Δ stored in the storage unit is divided into the extraction unit value XtO1X1° and the current value xt
,

■ If Δθ is negative in the above (■), and the differential lock signal has been issued until then, this means that the accelerator opening degree θ is decreasing and the slip condition is resolved, as shown in Figure 5. Release the differential lock signal. In addition, if the differential lock signal is not issued, it is impossible for a new slip condition to occur due to a decrease in the accelerator opening θ, so the status quo is maintained (i.e., the center differential is activated). .

■ When neither Xf > Xfo nor Xr > , since it is a slip type aF, the signal related to the center differential will remain as it is.

[Phase] Finally, reset the contents of the memory section to new ones.

■ Repeat steps from ■ to [phase] above.

As is clear from the above explanation, according to the present invention, an abnormal condition such as the occurrence of a slip is quickly detected and the center differential is locked, thereby maintaining a stable and safe driving condition that fully utilizes the driving force. can. Further, by providing a sensor for detecting the accelerator opening degree and the rotational speed of the front and rear wheels, and an electronic arithmetic and control unit, it can be realized with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of one embodiment of the control system in the control device of the present invention, FIG. 2 is a diagram for explaining the flow of processing by the control device of the present invention, and FIG. 3 is the control device of the present invention. Fig. 4 shows a time chart of various variables when no slip occurs, and Fig. 5 shows a time chart of various variables when slip occurs. It is a figure which shows a time chart. DESCRIPTION OF SYMBOLS 1... Accelerator opening detection section, 2... Front/rear wheel rotation speed detection section, 3... Calculation section, 4... Comparison/judgment section, 5.
...Storage section, 6.. Signal generation section, 7.. Reset section, 1o.. Automatic transmission, 11.. Torque converter, 12.. Main transmission, 13.. Sub-transmission. , 14...
・Drive gear, 15...Front differential device, 16...
Front wheel driving force, 17... Propeller shaft for rear wheel driving force, 18... Bevel gear, 19... Center differential device, 2
0... Rear wheel transmission device, 21... Center differential lock device.

Claims (2)

[Claims] (1) In a four-wheel drive control system equipped with a center differential that allows a difference in rotation speed between the front and rear wheels to absorb the difference in turning radius between the front and rear wheels that occurs during cornering, the accelerator is The rate of change in the rotation speed of the front and rear wheels is compared with the rate of change in the accelerator opening, and the rate of change in the rotation speed of the front or rear wheels is detected when the accelerator is opened. A four-wheel drive control device comprising a mechanism for locking a center differential and disabling an operating mechanism under the condition that the rate of change is significantly greater than the rate of change in the degree of rotation. (2) Comparison of the rate of change in the rotational speed of the front and rear wheels and the rate of change in the accelerator opening is performed by calculating the ratio between the rate of change in the rotational speed and the rate of change in the accelerator opening, and then calculating the ratio between the rate of change in the rotational speed and the rate of change in the accelerator opening, and then calculating the ratio of the rate of change in the rotational speed and the rate of change in the accelerator opening. 4. The four-wheel drive control device according to claim 1, wherein the control is performed by comparing with a previously calculated value.