JPH0532258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive control device. 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 the rotational speed of rear wheels.

[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, vehicles are generally equipped with a mechanism that allows the difference in rotation speed between the left and right wheels depending on the difference in turning radius, that is, a differential mechanism (front differential, rear differential). ing.

On the other hand, this phenomenon, that is, the difference in turning radius, also occurs between the front wheels and the rear wheels, so in a four-wheel drive vehicle, the difference in rotation speed between the front and rear wheels is allowed according to the difference in turning radius. In order to do so, the front differential,
In addition to the rear differential, a vehicle equipped with a front and rear wheel operating mechanism called a center differential has been proposed.

[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 by assuming that the front wheel's traction limit is Fμ _f and the rear wheel's limit traction force is Fμ _r.For simplicity, let's consider a case where the torque distribution ratio of the center differential is 1:1. Wheel drive vehicle: Fμ ₁ = 2 × Fμ _r (if Fμ _f < Fμ _r ) Four-wheel drive vehicle without center differential or with a locked center differential: Fμ ₂ = Fμ _f + Fμ _r , and Fμ ₁ < Fμ ₂ I understand that there is something.

For this reason, a four-wheel drive vehicle with a center differential may be inferior to a four-wheel drive vehicle without a center differential in the driving force transmitted to the road surface when the road surface friction coefficient is low. This means that when a large driving force is generated by the engine, for example during acceleration, this driving force cannot be sufficiently transmitted to the road surface, resulting in slipping. A four-wheel drive control system with a center differential that can eliminate this problem has not yet been proposed.

The present invention solves the above problems by reliably detecting the point in time when a vehicle slips, and when this is detected, locking the center differential mechanism and disabling the function of the center differential. The object of the present invention is to provide a four-wheel drive control device that allows the center differential to fully function at all times, makes full use of the engine driving force, and enables safe and stable driving.

[Means for solving problems]

Therefore, in the four-wheel drive control device of the present invention, when the vehicle slips, the vehicle speed does not increase even if the accelerator opening is increased, and therefore the acceleration cannot be obtained to correspond to the increase in the accelerator opening. Focusing on this, we have developed a mechanism that detects the accelerator opening and vehicle acceleration and locks the center differential to disable its activation function when the acceleration becomes significantly smaller than the rate of change in the accelerator opening. It is characterized by:

[Action and effect of invention]

The four-wheel drive control device of the present invention detects the accelerator opening and the rotational speed of the front and rear wheels, compares the rate of change in the accelerator opening with the acceleration, and compares the rate of change in the accelerator opening with the acceleration. The system is equipped with a mechanism that locks the center differential and disables the operating mechanism when the amount of slip becomes significantly small. Under normal conditions, the center differential is activated to achieve smooth driving conditions, and in the event of a slip, it is disabled. Since the system quickly detects and locks the center differential, it is possible to realize stable and safe driving conditions that fully utilize the driving force.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 shows one of the control systems in the control device of the present invention.
A diagram showing the configuration of an embodiment, FIG. 2 is a diagram for explaining the flow of processing by the control mechanism of the present invention, and FIG. 3 is a power transmission system of a four-wheel drive vehicle with a center differential to which the control mechanism of the present invention is applied. 4 is a diagram showing a time chart of various variables when no slip occurs, and FIG. 5 is a diagram showing a time chart of various variables when a slip occurs. In the figure, 1
is an accelerator opening detection section, 2 is an acceleration detection section, 3 is a calculation section, 4 is a comparison/judgment section, 5 is a storage section, 6 is a signal generation section, 7 is a reset section, 10 is an automatic transmission,
11 is a torque converter, 12 is a main transmission, 13
is an auxiliary transmission, 14 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, 21 indicates a center differential lock device.

Generally, in a four-wheel drive vehicle with a center differential,
If the engine is mounted on the front side, the third
The driving force transmission mechanism is as shown in the figure. That is, the power from the engine is transferred to the torque converter 11 disposed within the automatic transmission 10, the main transmission 12,
The output is transmitted to 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, thereby driving the front wheels. On the other hand, the propeller shaft 17 for rear wheel driving force is connected to a center differential device 19 via a bevel gear 18 .

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

Next, we will explain the concept of slip detection, which forms the basis of the present invention, in the fourth section, which shows temporal changes in various variables.
This will be explained based on the diagram and FIG.

First, Figure 4 is a time chart when no slip occurs, where θ is the accelerator opening, V is the vehicle speed, Δθ is the rate of change in θ, and a is the acceleration of the vehicle (i.e., the rate of change in V). , a/Δθ represents the ratio between a and Δθ. As shown in Fig. 4, when slip does not occur, as the accelerator opening θ increases, a commensurate acceleration a is obtained, so the value of a/Δθ remains constant. be.

On the other hand, Fig. 5 shows a time chart of various variables similar to Fig. 4 when a slip occurs, but when a slip occurs, the vehicle acceleration V does not increase, so the acceleration a also decreases. Therefore, the value of a/Δθ will also drop sharply as shown in the part A in the same figure, so if this dropping state is detected, it is possible to immediately detect the occurrence of a slip. It is.
Note that when a slip occurs, the value of acceleration a also decreases, but the reason why a slip is not determined based on a change in a is when the upward curve of the vehicle's speed V becomes gradual even if a slip does not occur. teeth,
This is because, for example, a may decrease as shown in the portion B in FIG. 4, and therefore a decrease in acceleration a does not necessarily correspond to a slip state.

FIG. 1 is a diagram showing one embodiment of the control device of the present invention from the above viewpoint. To explain this, the control system of the control device of the present invention includes an accelerator pedal that detects the accelerator opening degree. Opening degree detection unit 1 and vehicle acceleration detection unit 2 that detects vehicle acceleration
and has. Then, the detection signals from each of the detection units 1 and 2 are input to the calculation unit 3, and the ratio of the acceleration to the rate of change of the accelerator opening at that time (the value of a/Δθ in Figs. 4 and 5) is calculated. calculate,
The value is input to the comparison/judgment section 4. On the other hand, the storage unit 5 stores a similar calculated value from an infinitesimal time ago, and inputs that value to the comparison/judgment unit 4 to compare the current calculated value with the calculated value from an infinitesimal time ago. . If the current calculated value is smaller, it is determined that the slip condition is occurring since a/Δθ has decreased as shown in FIG. 5A, and the signal generator 6 generates a defrock signal. Further, the reset section 7 resets the value in the storage section 5 to a new value.

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

The accelerator opening θ and vehicle acceleration a are detected.
The vehicle acceleration a can be detected not only by a vehicle accelerometer, but also by the rate of change in the rotational speed of the drive wheels with a large load distribution.

Calculate the rate of change Δθ of θ. This calculation can be performed using a differentiating circuit or by counting the rate of change Δθ of θ during a minute time Δt.

Determine whether Δθ is 0 or not.

When Δθ is 0, that is, when the accelerator opening θ is not changing, the control signal for the center differential device is maintained unchanged. In other words, when Δθ is 0, this is because, as shown in C to E in FIG. 5, a state in which no slip occurs (sections C and E) or a state where slip occurs (section D) continues. .

If Δθ is not 0, calculate the value of X=a/Δθ. At this time, a slight time lag occurs between the change in θ and the change in a due to the inertia of the vehicle, but this can be dealt with in the design by using an appropriate time delay element.

Determine whether Δθ is positive or not.

Here, when Δθ is positive, that is, when the accelerator opening θ is increasing, and there is a possibility of slippage, the value X ₀ stored in the memory a minute time Δt seconds ago and the current time the value of
If the current value X is smaller than the current value, it is determined that a slip has occurred, and a defrock signal is generated, since it is in the state A shown in FIG.

In the above, if Δθ is negative, if the defrock signal has been output up to that point, the accelerator opening θ will change as shown in F in FIG.
Since this is the time when the slip condition is eliminated as the differential voltage decreases, the deflock signal is released. Also,
If the defrock signal is not issued, it is impossible for a new slip condition to occur due to a decrease in the accelerator opening θ.
The status quo will be maintained (that is, the center differential will be in operation).

If X<X ₀ does not hold in the above, as shown in G to I in FIG. H), the signals related to the center differential will remain as they are.

Finally, the contents of the storage section are reset to new contents.

Repeat ~ above.

As is clear from the above description, according to the present invention, the center differential is operated in normal conditions to achieve smooth running conditions, and when a slip occurs, it is promptly detected and the center differential is operated in the best possible condition. It is possible to realize stable and safe driving conditions by making full use of the driving force.

[Brief explanation of drawings]

Figure 1 shows one of the control systems in the control mechanism of the present invention.
A diagram showing the configuration of an embodiment, FIG. 2 is a diagram for explaining the flow of processing by the control mechanism of the present invention, and FIG. 3 is a power transmission system of a four-wheel drive vehicle with a center differential to which the control mechanism of the present invention is applied. 4 is a diagram showing a time chart of various variables when no slip occurs, and FIG. 5 is a diagram showing a time chart of various variables when a slip occurs. 1... Accelerator opening detection section, 2... Acceleration detection section,
3... Arithmetic unit, 4... Comparison/judgment unit, 5... Storage unit, 6
...Signal generation section, 7.. Reset section, 10.. Automatic transmission, 11.. Torque converter, 12.. Main transmission,
13... Sub-transmission, 14... Drive gear, 15... Front differential device, 16... Front wheel drive force, 17... Propeller shaft for rear wheel drive force, 18... Bevel gear, 19... Center differential device, 20... Rear wheel transmission device , 21...Center differential lock device.

Claims (1)

[Claims] 1. In a four-wheel drive control device equipped with a center differential that allows a difference in rotational speed between the front and rear wheels to absorb the difference in turning radius between the front and rear wheels that occurs during cornering. , detects the accelerator opening and the acceleration of the vehicle, compares the rate of change in the accelerator opening with the acceleration, and locks the center differential on the condition that the acceleration becomes significantly smaller than the rate of change in the accelerator opening. A four-wheel drive control device characterized by comprising a mechanism for disabling a differential mechanism. 2. The comparison between the rate of change in the accelerator opening and the acceleration of the vehicle is performed by calculating the ratio between the acceleration and the rate of change in the accelerator opening, and comparing it with a pre-stored calculated value a short time ago. A four-wheel drive control device according to claim 1. 3. The four-wheel drive control device according to claim 1 or 2, wherein the acceleration of the vehicle is detected by a vehicle accelerometer. 4. The four-wheel drive system according to claim 1 or 2, wherein the acceleration of the vehicle is detected by detecting the rate of change in the rotational speed of the drive wheels with a large load distribution. Control device.