JPS6311433A - Four wheel drive vehicle with controlling function of front and rear wheel engaging mechanism - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a tight corner braking phenomenon by comparing a reference torque value which is set in accordance with the detected value of a steering angle with a detected torque value and, when said detected torque value is smaller than said reference torque value, controlling a front and rear wheel engaging mechanism to be released. CONSTITUTION:During the operation of a vehicle, a steering angle detected by a steering sensor 1 and a front wheel torque detected by a torque sensor 2 are read into an electronic control device 3 and, first, a reference torque value A corresponding to the detected steering angle is read from a defined memory. Then, the detected front wheel torque is compared with the reference torque value A and, when the front wheel torque is larger than the reference torque value A, it is judged that a tight corner braking phenomenon has occurred, and a hydraulic circuit 4 is controlled to reduce the hydraulic pressure of a center clutch 5 which is a front and rear wheel engaging mechanism, controlling so that the locking of center differential is released. Thereby, the occurrence of a tight corner braking and slippage can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a four-wheel drive system with a function of controlling the front and rear wheel engagement mechanisms to prevent the occurrence of tie I/corner braking phenomenon.
Regarding wheel drive vehicles.

[Conventional technology]

Generally, when driving a car, front-wheel drive has better straight-line stability than rear-wheel drive, but when cornering,
Since you have to use the steering wheel to apply force to the tires that are trying to return, front-wheel drive vehicles tend to be less prone to tipping over. In this respect, rear-wheel drive vehicles are easier to turn, but if the driving force is too strong, they have the disadvantage of causing the vehicle to turn too much. Therefore, it is ideal for driving a car to drive the front and rear wheels with half and half power.
In this respect, four-wheel drive vehicles are extremely superior. By the way, the left and right wheels of a car have different turning radii when cornering, so in order to absorb this effect and perform smooth cornering, the difference in rotation speed between the left and right wheels is absorbed according to the difference in turning radius. It is equipped with a differential mechanism (front differential, rear differential). This difference in turning radius also occurs between the front wheels and the rear wheels, so in a four-wheel drive vehicle,
A mechanism has been proposed that includes a center differential mechanism, which absorbs the difference in rotational speed between the front wheels and the rear wheels in accordance with the difference in turning radius.

However, since this center differential mechanism has the function of distributing the torque between the front wheels and the rear wheels in an equal ratio, the driving force transmission limit is balanced to the value of the lower driving force of the front wheels or the rear wheels. becomes. For example, when one of the front wheels spins, drive energy escapes there,
The driving force of the rear wheels becomes extremely small. 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, the driving force cannot be sufficiently transmitted to the road surface, resulting in phenomena such as front or rear wheels slipping.

In order to prevent such negative effects, conventionally, a locking mechanism has been installed that directly connects the differential between the front and rear wheels without going through a center differential. In this case, the center differential mechanism was manually locked, and during normal driving, which did not require a large amount of driving force, the lock was manually released.

FIG. 5 is a diagram for explaining the driving force transmission mechanism of a full-time four-wheel drive vehicle with a center differential in which the engine is mounted on the front side. In this driving force transmission mechanism, power from the engine is transmitted to a torque converter 31, a main transmission 32, and an auxiliary transmission 33 arranged in an automatic transmission 30, and the output is transmitted to a drive gear 34, and then to a drive gear 34. 34 to the front wheel drive shaft 36 to drive the front wheels. Here, the front differential device 35 is a differential mechanism between the right and left wheels of the front wheels. On the other hand, the rear wheel drive propeller shaft 37 is connected via a bevel gear 38 to a center differential device 39, which is a differential mechanism between the front and rear wheels.
The center differential device 39 is coupled to a rear wheel transmission device 40. Furthermore, a center differential lock clutch 41 is arranged in parallel with the center differential ff39. Therefore, each time the hydraulic circuit 42 controls the engagement state of the clutch 41, the locking of the center differential is controlled.

In general, four-wheel drive vehicles include full-time four-wheel drive vehicles with a center differential as described above, and part-time four-wheel drive vehicles without a center differential. Normally, either the 01 wheel or the rear wheel is driven, and when driving force is required, such as on snowy roads, the remaining wheels are directly connected to the drive shaft via a clutch etc. Switching between driving and driving is performed intermittently.

By the way, full-time type 4 with center differential like this
In a wheel drive vehicle, the steering angle of the steered wheels has no relation to the lock control of the center differential, so for example, if the center differential is locked when driving on a rough road, then after getting out of the rough road,
If you return to a normal road with a large coefficient of friction and attempt to turn at a large steering angle without releasing the center differential lock,
The rotational speed of the front wheels cannot become higher than the rotational speed of the rear wheels, and negative torque is generated on the front wheels, resulting in a tight corner braking phenomenon.

Therefore, a four-wheel drive vehicle has been proposed in which the center differential mechanism is unlocked when the steering angle is greater than a predetermined value and the center differential mechanism is locked. -206228).

[Problem that the invention seeks to solve]

However, with the method of unlocking the center differential mechanism when the steering angle exceeds a predetermined value, if the steering wheel is turned more than a predetermined angle on a snowy road, for example, the center differential mechanism will always become free and the center differential mechanism will slip. The problem arises that it becomes easier.

The present invention is intended to solve the above-mentioned problems, and provides a four-wheel drive vehicle with a control function for front and rear wheel engagement mechanisms that can prevent the occurrence of tight corner braking and also prevent the occurrence of slipping. The purpose is to

[Means for solving problems]

To this end, the four-wheel drive vehicle with the control function of the front and rear wheel engagement mechanisms of the present invention limits the differential between the front wheels and the rear wheels from direct coupling to slip areas by controlling the degree of engagement of the front and rear wheel engagement mechanisms. It is a four-wheel drive vehicle that can be controlled until release, and includes a front wheel torque detection means, a steering angle detection means, and a reference torque value set corresponding to each steering angle stored in an internal memory. comprising an electronic control means for reading a reference torque value and comparing it with a detected torque value and outputting a control signal according to the comparison result; and a drive means for driving the front and rear wheel engagement mechanisms controlled by the electronic control means, The driving means is characterized in that it is controlled by the electronic control means so as to drive the front and rear wheel engagement mechanisms in a direction that releases engagement when the detected torque value is smaller than the reference torque value.

[Action and effect]

A four-wheel drive vehicle with a front and rear wheel engagement mechanism control function according to the present invention includes:
Detects front wheel torque and steering angle in a four-wheel drive vehicle that can control the differential limit between the front wheels and rear wheels from direct connection to release through a slip region by controlling the degree of engagement of the front and rear wheel engagement mechanisms. The reference torque value corresponding to the detected steering angle is read out from the reference torque values set corresponding to each steering angle stored in the built-in memory, and compared with the detected torque value, and the detected torque value is smaller than the reference I-lux value. At this time, by controlling the engagement of the front and rear wheel engagement mechanisms in the direction of disengagement, the occurrence of the tight corner break-tongue phenomenon is prevented, and
It is possible to prevent the occurrence of slip, and by setting the reference torque value set corresponding to each steering angle to be large when the steering angle is large and small when the steering angle is small, the steering angle is large. By controlling the engagement of the front and rear wheel engagement mechanisms to disengage early, it is possible to reduce the shock associated with disengagement, and also to prevent engine braking when the steering angle is small from being misjudged as tight corner braking. Things will disappear.

〔Example〕

Examples will be described below with reference to the drawings.

Fig. 1 shows the overall configuration of a control system for a full-time four-wheel drive vehicle with a center differential according to the present invention, and Fig. 2 shows a center differential lock release curve with the horizontal axis as the steering angle and the vertical axis as the front wheel torque. Figure 3 is a diagram in which the release curve in Figure 2 is converted into data to be stored in the memory of the electronic control unit;
The figure is a flowchart for explaining the control flow. In the figure, 1 is a steering sensor, 2 is a front wheel torque sensor, 3 is an electronic control device, 4 is a hydraulic circuit, and 5 is a center clutch consisting of a friction engagement element. In the figure, a steering sensor 1 is attached to a steering wheel, a torque sensor 2 is attached to a front wheel, and the steering angle and front wheel torque detected by each sensor are input to an electronic control device 3. The electronic control device 3
Each torque value data on the center differential lock release curve corresponding to the steering angle shown in the figure is recorded in the built-in memory. The center clutch 5 can control the differential limit between the front wheels and the rear wheels from direct connection to release through a slip region by controlling the degree of engagement thereof.

Next, to explain the operation, the electronic control bag W4 reads the detected front wheel torque in step (3) of the control flow shown in FIG. 4, and reads the detected steering angle in step (2). In step (2), the torque value A stored in the memory corresponding to the steering angle read in step (2) is read out. In step (■), it is determined whether the front wheel torque is greater than A. N
In the case of O, it is determined that a tie 1~corner braking phenomenon is occurring, and the hydraulic circuit 4 is controlled in step ■.
The oil pressure of the center clutch 5 is lowered and controlled in the direction of releasing the lock of the C center differential. If YES, it is determined that no tight corner braking phenomenon has occurred.

The center differential lock release curve in Figure 2 shows that when the steering angle is large, the reference torque value is increased, and if the torque decreases even slightly, it is determined that negative torque has occurred and the center differential lock is quickly removed. This reduces the shock when releasing the lock. In addition, when the steering angle is small, by reducing the reference torque value, it is determined that tight corner braking has not occurred even if the torque decreases to some extent. I try not to misjudge.

In the above embodiment, a full-time 4-wheel drive vehicle was described, but the 4-wheel drive vehicle with a control function for front and rear wheel engagement mechanisms according to the present invention can also be applied to part-time 4-wheel drive vehicles. . In this case, as the front and rear wheel engagement mechanism, a clutch of a differential limiting mechanism of a center differential is controlled in the former, whereas a clutch that directly connects the front wheels and rear wheels is controlled in the latter. Further, this clutch may be of the T, Ifi type, or any other type as long as it is capable of controlling the differential restriction between the front wheels and the rear wheels from direct coupling to disengagement through a slip region by controlling the degree of engagement.

As described above, according to the present invention, not only the steering angle but also the front wheel torque is used as a criterion for determining the occurrence of tight corner braking. Therefore, when the steering angle is large, tight corner braking may not occur and slipping is likely to occur. The front and rear wheel engagement mechanisms no longer disengage on the road.
Occurrence of slip can be prevented. In addition, since the reference torque value for comparison with the front wheel torque is set small when the steering angle is small and large when the steering angle is large, engine braking at a small steering angle may be mistakenly judged as tight corner braking. When the steering angle is large, the engagement of the front and rear wheel engagement mechanisms is released early, so that the shock associated with the release of engagement can be reduced.

4. Drawing IMT iii f, c Explanation Fig. 1 is a diagram showing the overall configuration of a four-wheel drive vehicle with a control function for front and rear wheel engagement mechanisms according to the present invention, and Fig. 2 shows the steering angle on the horizontal axis and the vertical axis. Diagram showing the center differential lock release curve with front wheel torque, Part 3
The figure is a diagram in which the release curve of Figure 2 is converted into data to be stored in the memory of the electronic control device, and Figure 4 is a diagram showing a flowchart of a four-wheel drive vehicle with a control function for the front and rear wheel engagement mechanism of the present invention. FIG. 5 is an explanatory diagram of a driving force transmission mechanism of a full-time four-wheel drive vehicle with a center differential in which the engine is mounted on the front 1- side.

1... Steering sensor, 2... Torque sensor,
3...Electronic control device, 4...Hydraulic circuit, 5...Center clutch agent Patent attorney Masanobu Hirukawa (2 others) Fig. 1 Steering angle [degrees j

Claims (4)

[Claims] (1) A four-wheel drive vehicle capable of controlling the differential limit between the front wheels and the rear wheels from direct connection to release through a slip region by controlling the degree of engagement of the front and rear wheel engagement mechanisms, the front wheel torque detection means Then, the reference torque value corresponding to the detected steering angle is read out from the reference torque value set corresponding to each steering angle stored in the built-in memory using the steering angle detection means and compared with the detected torque value. comprising an electronic control means that outputs a corresponding control signal, and a drive means that is controlled by the electronic control means and drives the front and rear wheel engagement mechanisms, the drive means comprising:
4 with a control function for the front and rear wheel engagement mechanisms, characterized in that the electronic control means controls the front and rear wheel engagement mechanisms to be driven in a direction to disengage the front and rear wheel engagement mechanisms when the detected torque value is smaller than the reference torque value. wheel drive car. (2) The reference torque value set corresponding to each steering angle is large when the steering angle is large, and small when the steering angle is small, the front and rear wheels according to claim 1. A four-wheel drive vehicle with an engagement mechanism control function. (3) The front and rear wheel engagement mechanism according to claim 1 or 2, wherein the front and rear wheel engagement mechanism is a center clutch that locks a center differential device when fully engaged. A four-wheel drive vehicle with control functions. (4) A four-wheel drive vehicle with a control function for a front and rear wheel engagement mechanism according to claim 1 or 2, wherein the drive means is a hydraulic circuit.