JPH0530650B2 - - Google Patents

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. 4 in a four-wheel drive vehicle equipped with a center differential to allow for differences in rotational speed.
The present invention relates to a wheel drive control device.

[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 adjusted according to the difference in turning radius. A mechanism that allows this, namely a center differential mechanism, 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 limit traction force is Fμ _f and the rear wheel limit traction force is Fμ _r.For simplicity, consider the case where the torque distribution ratio of the center differential is 1:1. 4-wheel drive vehicle: Fμ ₁ = 2×Fμ _r (if Fμ _f < Fμ _r ) 4-wheel drive vehicle without center differential or with a locked center differential: Fμ ₂ = Fμ _f + Fμ _r , and Fμ ₁ < Fμ It turns out that it is ₂ .

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.
For example, when a large driving force is generated, such as during acceleration, this driving force cannot be sufficiently transmitted to the road surface, resulting in phenomena such as slipping of the front or rear wheels.

In particular, in drive units with automatic transmissions, the torque ratio increases in the torque converter, so the maximum driving force in the low speed range is greater than in drive units with manual transmissions, so the above-mentioned requirements are even greater. Although such a phenomenon is becoming noticeable, a control device for a four-wheel drive with a center differential that can eliminate such adverse effects has not yet been proposed.

The present invention solves the above problems by constantly monitoring the vehicle condition and locking the center differential mechanism when the driving force is large.
It is an object of the present invention to provide a four-wheel drive control device that fully utilizes the function of a center differential and makes effective use of driving force.

[Means for solving problems]

Therefore, the four-wheel drive control device of the present invention is equipped with a four-wheel drive system equipped with a center differential that allows the rotation speed difference between the front wheels and the rear wheels to absorb the difference in turning radius between the front wheels and the rear wheels that occurs during cornering. In a drive control device, a storage means for storing in advance a point at which a torque ratio of a torque converter becomes a specific value or more in correspondence with a combination of an accelerator opening and a number of gears as a value of a variable representing a vehicle state, an accelerator opening; Detection means for actually detecting the values of the variables representing the number of gears and the vehicle state, and a storage value of the variable representing the vehicle state corresponding to the detected values of the accelerator opening degree and the number of gears obtained by the detection means. A readout means for reading out from the storage means successively compares the detected value of the variable representing the vehicle state obtained by the detection means and the stored value obtained by the readout means, and determines that the detected value is better. The present invention is characterized in that it is provided with a comparison and determination means that locks the center differential and disables the operating mechanism when the detected value is smaller, and operates the center differential when the detected value is larger.

[Action and effect of the invention]

The four-wheel drive control device of the present invention operates the center differential in normal conditions to achieve a smooth driving condition, and also quickly detects situations where the driving force is large, such as when the vehicle stalls. Since the center differential is locked, it is possible to maintain stable and safe driving conditions that make full use of 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.
2 is a diagram showing the power transmission system of a four-wheel drive vehicle with a center differential to which the control device of the present invention is applied; FIG. 3 is a diagram showing the power transmission system of a four-wheel drive vehicle with an automatic transmission. FIG. 3 is a diagram showing a graph at full throttle. In the figure, 1 is a storage means, 2 is a detection means, 3 is a reading means, 4 is a comparison/judgment means, 10 is an automatic transmission, 11 is a torque converter, 12 is a main transmission, 13 is an auxiliary transmission, 1
4 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, 2
0 indicates a rear wheel transmission device, and 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 driving force transmission mechanism is as shown in the figure. That is, power from the engine is transmitted to the torque converter 11, main transmission 12, and auxiliary transmission 13 arranged in the automatic transmission 10, and the output thereof is transmitted to the drive gear 1.
4. The signal is transmitted to the front wheel drive shaft 16 via the center differential device 19 and then the front differential device 15, and the front wheels are driven. 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 arranged in parallel with the center differential device 19, and when the driving force is large, the center differential lock device 21 is operated based on a control command signal, and the center differential device 19 is used to differentially drive the front and rear wheels. It disables the function.

Here, how to determine when to lock the center differential will be explained based on Fig. 3. Fig. 3 is a graph at full throttle in a vehicle having a drive unit with an automatic transmission. In a drive system with an automatic transmission, the torque ratio increases in the torque converter, so the driving force increases in a low vehicle speed range. This tendency is particularly noticeable in the lower speed range than the torque converter coupling point indicated by the circle in the figure, so in the present invention, this torque converter coupling point is memorized in advance, and when entering the lower speed range from this point, Since the driving force is large, the center differential is locked.

Next, one embodiment of the control system in the control device of the present invention will be described with reference to FIG. 1. As shown in Figure 3, the coupling point of the torque converter differs for each gear stage and accelerator opening, and also differs depending on the accelerator opening (the one in Figure 3 is for full throttle, In other words, the graph is representative when the accelerator opening is ← 100%, and the graph changes depending on the accelerator opening.) Therefore, the storage means 1 stores the combination of the accelerator opening θ and the number of gears x. The coupling points are stored in a matrix in correspondence with the above. When storing these coupling points, the values of variables representing the vehicle state corresponding to each point are stored as the values of variables representing the vehicle state. Here, the variables representing the vehicle state include vehicle speed, transmission input, etc. The rotational speed, transmission output rotational speed, etc. can be used.

To give an example of the stored value in the storage means 1, when "vehicle speed" is selected as the storage target, the stored value representing the coupling point corresponding to 100% accelerator opening and 1st gear stage is as shown in the graph of FIG. As you can read from the figure, it is about 26KM/h.

Furthermore, the control system in the control device of the present invention includes:
Detection means 2 consisting of an accelerator opening detection section, a gear stage number detection section, and a variable detection section representing the vehicle state;
It has a readout means 3 for reading out a stored value from the storage means 1, and a comparison determination means 4 for comparing the stored value and a detected value and outputting a necessary control command signal.

Next, the flow of processing in this control system will be explained step by step.

The detection means 2 detects the accelerator opening θ, the number of gears x, and the values of variables representing the vehicle state. Here, when the storage target in the storage means 1 is "vehicle speed", as a matter of course,
The vehicle speed is detected as the above-mentioned "value of the variable representing the vehicle state" Detected values θ and x of the accelerator opening and the number of gears
is input to the reading means 3, and the detected value of the variable representing the vehicle condition is input to the comparison and determination means 4.

The reading means 3 reads out the stored values corresponding to the above θ and x from the storage means 1.

The read stored value is input to the comparison/judgment means 4.

A comparison/judgment means 4 compares the detected value of the variable representing the vehicle condition with the stored value. Then, if the detected value is smaller than the stored value,
Since the vehicle is in a low speed range and the driving force is large, a deflock signal for locking the center differential is output. Further, if the detected value is larger than the stored value, the center differential is controlled based on a differential lock release signal for releasing the locked state of the center differential.

The center differential is controlled based on the output signal of the comparison control means 4.

In addition, in the above explanation, it has been explained that the decision on when to lock the center differential is made based on the coupling point of the torque converter.
The present invention is not limited to this, but the point is to set in advance a point at which a large driving force that causes an adverse effect due to the center differential is generated, and to store this point in the storage means.

As is clear from the above description, according to the present invention, a state in which the driving force is large is quickly detected and the center differential is locked, so that a stable and safe running state that fully utilizes the driving force can be maintained. Further, by providing a sensor and an electronic arithmetic control unit that detect values representing vehicle conditions such as the accelerator opening, the number of gears, and the vehicle speed, it can be realized with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 shows one of the control systems in the control device of the present invention.
2 is a diagram showing the power transmission system of a four-wheel drive vehicle with a center differential to which the control device of the present invention is applied; FIG. 3 is a diagram showing the power transmission system of a four-wheel drive vehicle with an automatic transmission. FIG. 3 is a diagram showing a graph at full throttle. DESCRIPTION OF SYMBOLS 1...Storage means, 2...Detection means, 3...Reading means, 4...Comparison/judgment means, 10...Automatic transmission, 11...Torque converter, 12...Main transmission, 13...Sub-transmission Machine, 14... Drive gear, 15
...Front differential device, 16...Front wheel drive force, 1
7... Propeller shaft for rear wheel driving force, 18...
Bevel gear, 19... Center differential device, 20... Rear wheel transmission device, 21... Center differential lock device.

Claims (1)

[Scope of 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. a storage means for storing in advance a point at which the torque ratio of the torque converter exceeds a specific value in correspondence with a combination of an accelerator opening degree and a gear position number as a value of a variable representing a vehicle state; an accelerator opening degree, a gear position number, and the vehicle; a detection means for detecting the value of a variable representing the state; a reading means for reading from the storage means a stored value of the variable representing the vehicle state corresponding to the detected values of the accelerator opening degree and the number of gears obtained by the detection means; , successively compares the detected value of the variable representing the vehicle state obtained by the detecting means and the stored value obtained by the reading means, and if the detected value is smaller, the center differential is removed. A control device for a four-wheel drive system, comprising: a comparative determination means for locking and disabling an operating mechanism, and for operating a center differential when the detected value is larger. 2. The four-wheel drive control device according to claim 1, wherein the point at which the torque ratio of the torque converter exceeds a specific value is a coupling point of the torque converter. 3. The variable representing the vehicle state is one of vehicle speed, transmission input rotation speed, or transmission output rotation speed. Wheel drive control device.