JPS6277236A - Control device for 4-wheel-drive - Google Patents

Abstract

PURPOSE:To maintain a stable running condition, by memorizing beforehand the point where the torque ratio exceeds a specific value as a value of variable responding to the combination of the accelerator opening and the gear stage number, and locking the center differential unit when the detected value of the variable indicating the actual car condition is smaller than the memorized value. CONSTITUTION:In a memory device 1, coupling points responding to the combination of the accelerator opening theta and the gear stage number x are stored beforehand. The detected value of the accelerator opening theta, and that of the gear stage number x are input to a read out device 3, and the detected value of a variable which indicates the car condition are input to a comparing-and- deciding unit 4. In the unit 4, the detected value of the variable to indicate the car condition and the memory value read out from the memory 1 are compared, and if the detected value is smaller than the other, a differential lock signal is output. Therefore, since the center differential is locked in the condition of a large driving force, a stable and safe running condition can be maintained utilizing the driving force sufficiently.

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 rotational speed differences.

[Conventional technology]

Generally, the left and right wheels of a vehicle have different turning radii when cornering. Therefore, in order to absorb this influence and perform smooth cornering, -M is equipped with a mechanism 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). It is equipped with

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 rotational speed between the front and rear wheels is caused by the difference in turning radius. A mechanism that allows this, that is, 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 given by Fμ2, the front wheel limit traction force, and Fμ2, the rear wheel limit traction force, and for simplicity, considering the case where the torque distribution ratio of the center differential is 1:1, the maximum traction force Fμ is calculated as follows: Wheel drive vehicle: Fμ, = 2XFμm (if Fμ, < Fμm) Four-wheel drive vehicle without center differential or with locked center differential: Fμ, = Fμ, +Fμ.

It can be seen that Fμ,<Fμ2.

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 appears as a phenomenon such as front or rear wheel slipping.

In particular, in drive systems 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 systems with manual transmissions, so the above phenomenon is even more pronounced. However, 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, and by constantly monitoring the vehicle condition and locking the center differential mechanism when the driving force is large, the center differential function is fully utilized and the driving force is increased. The purpose is to provide a four-wheel drive control device that is effectively utilized.

[Means for solving the problem] Therefore, the four-wheel drive control device of the present invention adjusts the rotational speed difference 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 four-wheel drive control device equipped with a center differential that allows for a storage means for storing in advance the values of the variables representing the accelerator opening, the number of gears, and the vehicle state; reading means for reading a stored value of a variable representing a vehicle state from the storage means; successively comparing the detected value of the variable representing the vehicle state obtained by the detecting means with the stored value obtained by the reading means; The device is characterized by comprising a comparison and determination means for disabling the operating mechanism by turning the center differential when the detected value is smaller, and for operating the center differential when the detected value is larger. It is something to do.

[Action and effect of 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 is a diagram showing the configuration of one embodiment of the control system in the control device of the present invention, and FIG. 2 is a diagram showing the power transmission system of a four-wheel drive vehicle with a center differential to which the brake 4n device of the present invention is applied. Third
The figure is a diagram showing a graph at full throttle in a vehicle having a drive system with automatic transmission transmission. In the figure, 1 is a storage means, 2 is a detection means, 3 is a reading means, 4 is a comparison/determination means, 10 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 centerpfrotter 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 transmitted to the torque converter 11, main transmission 12, and auxiliary transmission 13 arranged in the automatic transmission m10, and the output is transmitted to the drive gear 14, the center differential device 19, and then the front differential device 15. The signal is transmitted to the front wheel drive shaft 16 via the front wheel drive shaft 16, and the front wheels are driven. On the other hand, propeller shaft 1 for rear wheel driving force
7 is connected to a center differential device 9 via a bevel gear 18.

In such a power transmission system, the present invention arranges a center differential lock device 21 in parallel with the center differential device 19, and operates the center differential lock device 2z based on a control command signal when the driving force is large. This disables the front/rear wheel differential function by the center differential device 19.

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, and as shown here, In a drive system with an automatic transmission, the torque ratio increases in the torque converter, so the driving force increases in the low vehicle speed range. This tendency is particularly noticeable in the lower speed range than the torque converter coupling point indicated by O in the figure, so in the present invention, this torque converter coupling point is memorized in advance, and when the low speed range is entered from this point. When this happens, the center differential is locked because the driving force is large.

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 compression point of the torque converter differs depending on the number of gears and the degree of accelerator opening, and also differs depending on the degree of accelerator opening. Opening degree -100
%, and the graph changes depending on the accelerator opening degree). Therefore, the storage means 1 stores information in a matrix format corresponding to the combination of the accelerator opening degree θ and the number of gears X. The cambling point is stored in the cambling point. When remembering this coupling point,
It is stored as the value of a variable representing the vehicle state corresponding to each point, but here, the vehicle speed, transmission input rotation speed, transmission output rotation speed, etc. can be used as the variable representing the vehicle condition. can.

To give an example of the stored value in the storage means I, when "vehicle speed" is selected as the storage target, the stored value representing the coupling point corresponding to 100% accelerator opening and 1st variable speed is as shown in the graph of FIG. Approximately 26KM/ as read from
h.

Further, the control system in the control device of the present invention includes a detection means 2 comprising an accelerator opening degree detection section, a gear stage number detection section, and a variable detection section representing the vehicle state; and a reading means 3 for reading out stored values from the storage means 1. , and comparison/judgment means 4 that compares the stored value and the detected value and outputs a necessary control command signal.

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

■ The detection means 2 detects the accelerator opening θ, the number of gears
and the values of variables representing the vehicle state. Here, when the storage target in the storage means 1 is "vehicle speed", it goes without saying that the "value of the variable representing the vehicle state"
The detected values θ and X of the accelerator opening degree and the number of gears for detecting the vehicle speed are inputted to the readout means 3, and the detected values of variables representing the vehicle condition are inputted to the comparison determination means 4.

(2) 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.

(2) The comparison/judgment means 4 compares the detected value of the variable representing the vehicle condition with the stored value. If the detected value is smaller than the stored value, this means that the vehicle is in a low speed range and the driving force is large, so a differential lock 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 defroster signal release signal for releasing the locked state of the center differential.

(2) Control the center differential based on the output signal of the comparison control means 4.

In the above explanation, it has been explained that the point at which the center differential is locked is determined based on the coupling point of the torque converter, but the present invention is not limited to this. What is necessary is to set in advance a point at which such a large driving force is generated, and to store this point in the storage means.

As is clear from the above description, according to the present invention, since a state in which the driving force is large is quickly detected and the center differential is locked, it is possible to maintain a stable and safe running state that makes full use of the driving force. In addition, the accelerator opening and the number of gears,
It can be realized with a simple configuration by including a sensor that detects a value representing a vehicle state such as a vehicle speed, and an electronic arithmetic and control unit.

[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 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, and FIG. The figure is a diagram showing a graph at full throttle in a vehicle having a drive device with an automatic transmission. ■...Storage means, 2...Detection means, 3...Reading means, 4...Comparison/judgment means, 10...Automatic transmission, 1
1... 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 (3)

[Claims] (1) In a four-wheel drive control device equipped with a center differential that allows the 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,
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 condition; an accelerator opening degree, a gear position number, and the vehicle condition; a detection means for detecting the value of a variable representing the vehicle condition; 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;
The detected value of the variable representing the vehicle state obtained by the detecting means is successively compared with the stored value obtained by the reading means, and if the detected value is smaller, the center differential is locked and the operating mechanism is activated. A control device for a four-wheel drive system, comprising: a comparison determination means for disabling the detection value, and for operating a center differential when the detected value is larger. (2) The point at which the torque ratio of the torque converter exceeds a specific value is a coupling point of the torque converter.
Wheel drive control device. (3) The four-wheel vehicle according to claim 1 or 2, wherein the variable representing the vehicle state is one of vehicle speed, transmission input rotation speed, or transmission output rotation speed. Drive control device.