JPH07164902A - Front wheel drive control device for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To smoothly regulate the operation of a set-up gear mechanism by providing a means which regulates the operation of he set-up gear mechanism when a speed exceeds a predetermined level and continuous operational regulation of the set-up gear mechanism until the turning of a vehicle is completed after starting the control. CONSTITUTION:A front axle revolution sensor and a rear axle revolution sensor are provided in the vicinity of a speed change gear in a set-up gear mechanism so as to read a number of revolutions of each revolution unit and input the data to a control unit. Further a vehicle speed sensor is provided to read a vehicle speed and a steering angle sensor is provided to read the steering angle of front wheels. When speed increase regulation control is carried out with a steering angle of front wheels more than the specified value and a vehicle speed exceeding specified level, the speed increase regulation control is continued, until the turning of the vehicle is completed even if a speed is reduced below the specified level. Therefore even if a speed changes while the vehicle turns sharply, the set-up gear mechanism does not work continuously so that the turning of the vehicle may be performed very smoothly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front wheel drive control system for a four-wheel drive vehicle, and more particularly to a front wheel drive control system for a four-wheel drive vehicle provided with a front wheel speed increasing mechanism.

[0002]

2. Description of the Related Art In a four-wheel drive vehicle, two front wheels and two rear wheels are driven so as to have substantially the same peripheral speed when going straight. If the vehicle is turned in this state, the turning performance will be poor.Therefore, when turning the vehicle, the front wheels are stopped and only the rear wheels are driven to improve the turning performance. There is known a front wheel speed-increasing four-wheel drive system at the time of turning in which the vehicle is driven at a higher speed than the rear wheels to reduce the turning speed.

The front wheel speed-increasing four-wheel drive system during turning is as follows:
The steering angle of the wheels is detected to detect the turning of the vehicle, and the speed increasing mechanism provided in the front wheel drive system is automatically operated to increase the peripheral speed of the front wheels to about twice that of the rear wheels. Make a turn. Further, when the vehicle is turned at a high speed while traveling on a general road or the like, the vehicle suddenly turns when the speed increasing mechanism is operated, which is dangerous, so when the transmission is shifted to the high speed position, Means are provided for restricting the speed increasing mechanism from operating.

[0004]

As described above, the conventional front wheel speed-increasing four-wheel drive system at the time of turning is provided with the restricting means so that the speed increasing mechanism does not operate when turning at a high speed. However, since the restricting means works when the transmission is at the high speed position, for example, in order to reduce fuel consumption and noise in low load work, the transmission is set at the high speed position and the throttle is adjusted to adjust the vehicle speed. If you drive like this,
There is a drawback in that the speed increasing mechanism does not operate due to the operation of the regulating means, and the turning performance is not good.

In order to prevent this, the operation of the speed increasing mechanism may be regulated depending on the vehicle speed. However, if the vehicle speed fluctuates during turning of the vehicle, the speed increasing mechanism operates intermittently and the driving is stopped. The problem that it is not done smoothly occurs. Therefore, in a four-wheel drive vehicle equipped with a speed increasing mechanism, there arises a technical problem to be solved in order to smoothly regulate the operation of the speed increasing mechanism, and the present invention solves this problem. The purpose is to do.

[0006]

The present invention has been proposed in order to achieve the above object, and is a four-wheel drive equipped with a speed-up mechanism for driving the front wheels faster than the rear wheels when the vehicle turns. In the vehicle, while providing means for detecting the vehicle speed,
A means for restricting the operation of the speed increasing mechanism at a constant vehicle speed or more is provided, and after the control by the restricting means is started, the operation restriction of the speed increasing mechanism is continued until the end of turning of the vehicle. A front wheel drive control device for a drive vehicle is provided.

[0007]

The vehicle speed is constantly measured by the vehicle speed detecting means, and the restricting means controls the speed increasing mechanism so that the speed increasing mechanism does not operate above a certain vehicle speed, thereby preventing a sudden turning motion during high speed turning. Then, after the control of the restricting means is started, even if the vehicle speed is reduced, the operation restriction of the speed increasing mechanism is continued until the end of turning of the vehicle, and the speed increasing mechanism is caused by the fluctuation of the vehicle speed in the low speed range. Prevents the part from operating intermittently.

[0008]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of a transmission system and a control system of a four-wheel drive vehicle such as a tractor. Power of an engine is transmitted to a rear wheel via a main clutch and a transmission. In addition, the power is branched during transmission to the rear wheels, and the power is transmitted to the front wheels via the speed increasing mechanism. Although illustration is omitted, the speed increasing mechanism section is provided with a direct coupling clutch and a speed increasing clutch, and one of the clutches is turned on by a command from the control section.
For example, if the direct coupling clutch is on, the driving force of the rear wheels is transmitted to the front wheels as it is, and normal four-wheel drive is performed. Is transmitted to the front wheels, and the front wheels become four-wheel drive in which the speed is increased from the rear wheels. If both clutches are off, the neutral state is achieved, and the driving force of the rear wheels is not transmitted to the front wheels, and only the rear wheels are driven.

Thus, a front shaft rotation sensor and a rear shaft rotation sensor are provided in the vicinity of the transmission gears in the speed increasing mechanism unit, and the rotation speeds of the respective rotation units are read and input to the control unit. In addition, a vehicle speed detection sensor is provided to read the actual speed or theoretical speed of the vehicle (hereinafter referred to as "vehicle speed"),
A steering angle sensor is provided to read the steering angle of the front wheels. It should be noted that the rotation of the front axle and the rear axle may be read and the vehicle speed may be calculated from the detected value. Furthermore, a mode selector switch is provided near the operation panel in the driver's seat so that each mode such as a normal four-wheel drive traveling mode and a working mode with a front wheel speed-up function can be selected by the mode selector switch. The mode of is displayed.

Next, the front wheel drive control method of the present invention will be described with reference to the flow chart of FIG. First, the steering angle of the front wheels is read by the steering angle sensor, and it is determined whether the steering angle is equal to or greater than a predetermined steering angle α (step 101). When the four-wheel drive vehicle is traveling straight ahead or in a gentle turn, the steering angle of the front wheels is smaller than α, so if the speed increase regulation flag to be described later is on, clear it (step 102), and step 1
The process proceeds to the forward speed increase regulation control of 03 to 107.

Here, in step 103, it is determined whether or not the front and rear wheels are synchronized, and when the peripheral speeds of the front and rear wheels are different, the slip state of the rear wheels is confirmed (step 10).
4). When the rear wheels are slipping, 4WD is set for four-wheel drive (step 107), and when the rear wheels are not slipping, it is determined whether or not the vehicle is in a straight traveling state (step 105). If the vehicle is in a straight traveling state, 4WD is set as described above (step 105 → 107), and if the vehicle is in a gentle turn, 2W is used to drive only the rear wheels.
D is set (step 106) to improve the turning performance of the vehicle. If the front and rear wheels are in synchronization at step 103, the process jumps to step 106, and only the rear wheel 2W
It becomes D setting. After setting 2WD or 4WD,
The process proceeds to step 108, and when the control is continued, the process returns to step 101.

On the other hand, when the four-wheel drive vehicle makes a sharp turn at the steering angle α or more at step 101, the routine proceeds to step 109, where it is judged if the speed increase regulation flag is on. When the speed increase restriction flag is off, the routine proceeds to step 110, where the vehicle speed sensor reads the vehicle speed to determine whether the vehicle speed is equal to or higher than a predetermined speed V. When the vehicle speed is lower than the predetermined speed V, the front wheel speed is set so that the speed increasing mechanism is operated (step 112), and the peripheral speed of the front wheel when making a sharp turn is about double that of the rear wheel. Increase the speed to a certain degree to reduce the turning speed of the vehicle.

On the other hand, when the vehicle speed read in step 110 is equal to or higher than the predetermined speed V, the speed increase restriction flag is turned on (step 111), and the above-described step 10 is executed.
The process proceeds to the forward speed increasing regulation control of 3 to 107. Also, when the speed increase regulation flag is ON in step 109, the routine jumps to step 103 to execute the forward speed increase regulation control.

That is, when the steering angle of the front wheels is equal to or greater than α, the vehicle speed is equal to or greater than the predetermined speed V and the speed increase restriction control is executed, the speed increase restriction flag is ON, and therefore the vehicle speed is increased. Even when is lower than the predetermined speed V, the speed increase regulation control is continued until the end of turning of the vehicle. Therefore, even if the vehicle speed fluctuates during a sharp turn of the vehicle, the speed increasing mechanism does not intermittently operate, and the turning of the vehicle becomes extremely smooth.

FIG. 3 shows the operation panel 11 of the driver's seat, to which various instruments are attached. A mode selector switch 12 is provided near the operation panel 11, and a monitor 13 for displaying the driving states of the front and rear wheels is provided. FIG. 4 is an enlarged view of the mode changeover switch 12, which allows the traveling modes of the four-wheel drive vehicle to be freely changed as follows. A normal drive mode is provided at the center position of the switch position, a work mode having a front wheel speed increasing function is provided at the right position of the drive mode, and a four wheel drive mode is always locked at the left position of the drive mode in a four-wheel drive state. To provide.
Since the most frequently used traveling mode is arranged at the center of the switch position, the operability of the switch is improved, and mistakes in operating the switch can be prevented to ensure safety.

FIG. 5 is an enlarged view of the monitor 13. The front and rear wheel lamps 14 and 15 are turned on to display the driving states of the front and rear wheels. When the vehicle is in the two-wheel drive state with only the rear wheels, the front wheel lamp 14 is turned off and the rear wheel lamp 15 is turned on. In the four-wheel drive state, both the front wheel lamp 14 and the rear wheel lamp 15 are turned on. When the rear wheels are braked during four-wheel drive, the braking force of the rear wheels also acts on the front wheels that do not have a brake.
At this time, the front wheel lamp 14 is in a blinking state. Furthermore,
In the front wheel speed-up state, the front wheel lamp 14 lights up in a different color (for example, red) different from that during four-wheel drive.

Thus, the running condition of the vehicle can be recognized by the operator in real time, and the operator can perform an appropriate driving operation. Here, the peripheral speeds of the front wheels and the rear wheels are measured by the front axle rotation sensor and the rear axle rotation sensor described above, and based on the peripheral speed ratio of the front and rear wheels, two-wheel drive of only the rear wheels, four-wheel drive, and front wheel acceleration are performed. When the drive control is performed so as to automatically set any of the four-wheel drive, when the vehicle is in an ultra-low speed region, the rotation speed of the front and rear shafts cannot be measured by the rotation sensor, and the front wheel drive control becomes uncontrollable. Therefore, in the ultra-low speed range where the peripheral speeds of the front and rear wheels cannot be detected, the four wheels are locked in consideration of safety.
However, for example, in a narrow place such as a warehouse, when performing a turning-back operation in an ultra-low speed range, there is a problem that turning performance deteriorates in a normal four-wheel drive state.

FIGS. 6 and 7 are flowcharts of the front wheel drive control taking into consideration the case where the peripheral speeds of the front and rear wheels cannot be detected. FIG. 6 shows the case where the front wheel speed increasing mode is manually set by the changeover switch. The front wheel acceleration control shown in FIG. 7 is performed, and when the changeover switch is set to a mode other than the front wheel acceleration mode, the front wheel drive control shown in FIG. 7 is performed. First, the front wheel speed increase control routine will be described with reference to FIG. First, the steering angle of the front wheels is read by the steering angle sensor, and it is determined whether the steering angle is equal to or greater than a predetermined steering angle α (step 201). When the steering angle of the front wheels is smaller than α, the routine proceeds to step 202, where it is determined whether or not the vehicle speed can be detected. When the vehicle speed can be detected, steps 103 to 107 described in FIG.
The same control as the front wheel speed increase restriction control in step 203 to 207 is performed, and 2WD setting (step 206) or 4WD setting (step 207) is performed. Further, when the vehicle speed is in the ultra-low speed range, the vehicle speed cannot be detected as described above, and therefore 4WD is set in consideration of safety (step 202 → 207).

On the other hand, when the steering angle of the front wheels becomes α or more in step 201 and the vehicle makes a sharp turn, step 208
Jump to and set the front wheel speedup so that the speedup mechanism operates. In that case, the peripheral speed of the front wheels can be increased about twice that of the rear wheels to reduce the turning speed of the vehicle. Then, after setting the driving method in steps 206 to 208, the process proceeds to step 209, and when the control is continued, the process returns to step 201.

On the other hand, when the changeover switch is set to a mode other than the front wheel speed increasing mode, the front wheel drive control shown in FIG. 7 is performed. In the figure, first, it is determined whether or not the vehicle speed can be detected (step 301). When the vehicle speed can be detected, the step 30 is performed in the same manner as the control of the steps 203 to 207 in the above-mentioned front wheel speed increase control routine.
2 to 306, and 2WD setting (step 30
5) or 4WD setting (step 306) is performed.

On the other hand, when the vehicle is in the ultra-low speed range and the vehicle speed cannot be detected, the routine proceeds from step 301 to step 307, where the steering angle of the front wheels is read to determine whether the steering angle is equal to or greater than a predetermined steering angle α. To do. When the steering angle of the front wheels is smaller than α, the vehicle is in a straight traveling state or a gentle turning state, and so high turning performance is not required, so the routine proceeds to step 306 and 4WD
It will be set. Further, when the steering angle of the front wheels becomes equal to or greater than α in step 307, the process jumps to step 308 to set the front wheel acceleration. That is, even when the vehicle becomes in the ultra-low speed range and the vehicle speed cannot be detected, the front wheel speed-increasing operation is performed and the turning performance of the vehicle is improved when the switching operation is performed.

The present invention can be modified in various ways without departing from the spirit of the present invention, and it goes without saying that the present invention covers the modifications.

[0023]

The present invention, as described in detail in the above embodiment,
When the vehicle speed exceeds a certain level, the operation of the speed increasing mechanism is restricted,
Prevents sudden turning motion during high-speed turning. After the regulation control is started, the regulation control is continued even if the vehicle speed decreases, so that it is possible to prevent the speed increasing mechanism section from intermittently operating with respect to the variation of the vehicle speed in the low speed range.

Thus, the invention is effective in various kinds of effects such as smooth regulation of operation of front wheel acceleration in a four-wheel drive vehicle and improvement in turning performance and safety.

[Brief description of drawings]

FIG. 1 is a block diagram of a transmission system and a control system of a four-wheel drive vehicle that is an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of a front wheel drive control method.

FIG. 3 is a front view of a driver's seat operation panel.

FIG. 4 is an enlarged view of a mode changeover switch.

FIG. 5 is an enlarged view of a monitor.

FIG. 6 is a flowchart of a front wheel speed-up control routine showing another embodiment of the front wheel drive control method.

FIG. 7 is a flowchart of a front wheel drive control routine showing another embodiment of the front wheel drive control method.

Claims (1)

[Claims] 1. A four-wheel drive vehicle having a speed increasing mechanism for driving a front wheel at a higher speed than a rear wheel when the vehicle is turning, is provided with a means for detecting a vehicle speed, and increases at a certain vehicle speed or more. A four-wheel drive vehicle characterized in that a means for restricting the operation of the speed mechanism portion is provided, and after the control by the restricting means is started, the operation restriction of the speed increasing mechanism portion is continued until the end of turning of the vehicle. Front wheel drive controller.