JPS6259136A - Road surface state detecting apparatus - Google Patents

Abstract

PURPOSE:To improve the safety in traveling by judging that a road surface tends to easily generate slip trouble such as on a frozen road when the max. value of the intensity of the reflected wave is smaller than a set value by using a plurality of reflected wave receiving means and automatically performing the switching from two-wheel drive to four-wheel drive. CONSTITUTION:When a vehicle is under traveling, supersonic waves are transmitted in a certain cycle a road surface W from a supersonic wave transmitter 5 by the operation of a controller 3, and the supersonic waves reflected by the road surface W are received by the receiving apparatuses 11a and 11b through the wave receiving devices 9a and 9b. In the controller 3, the max. value of the reflected waves which each receiving apparatus 11a, 11b receives is compared with the high and low set values, and when the max. value is larger than the high set value, it is judged that the road surface is a smooth concrete-paved road, and two-wheel drive state is generated. When the max. value is smaller than the low set value, it is judged that the road surface is a snow road or frozen road, and a 2W/4W-drive switching apparatus 19 is switched from two-wheel drive to four-wheel drive by an operating device 27.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention transmits a detection wave from a vehicle to the road surface on which it is traveling, detects the road surface condition based on the intensity of the reflected wave, and switches between two-wheel drive and four-wheel drive. Intercepts the road condition detection device.

[Technical background of the invention and its problems] Conventionally, in a four-wheel drive vehicle, when entering a slippery road surface such as a snowy road, the system automatically switches from two-wheel drive (2WD) to four-wheel drive (4WD). As a road surface condition detection device for switching, one described in Japanese Patent Application Laid-Open No. 58-65922 is known. This conventional device detects a slip state based on the rotational difference between the drive wheel and other wheels, and automatically switches from two-wheel drive to four-wheel drive.

Such a conventional road surface condition detection device has a structure that detects actual slippage of the drive wheels and switches to four-wheel drive. However, when cornering, it is already too late to switch after the vehicle slips, and the vehicle may enter a spin state, impairing driving stability. It was wanted.

Therefore, the applicant used ultrasonic waves in Japanese Patent Application No. 59-130985 and Japanese Patent Application No. 59-151700,
We proposed a road condition detection device that determines that the road surface is likely to slip when the average intensity of reflected waves from the road surface falls below a set value, and automatically switches from two-wheel drive to four-wheel drive.

[Object of the Invention] This invention relates to a further improvement of the above-mentioned prior application, and in particular, it is possible to reliably discriminate between a paved road with a rough surface and an icy road, which have similar characteristics in terms of reflected wave intensity, and to improve the two-wheel drive-4. It is an object of the present invention to provide a road surface condition detection device that can perform accurate switching of wheel drive.

[Configuration 1 of the Invention] The present invention includes a transmitting means for transmitting a detection wave toward a road surface, a plurality of receiving means provided at different positions for receiving reflected waves from the road surface, and a detection wave reflected by each of the receiving means. A road surface condition detection device comprising a comparison means for determining the maximum value of wave intensity, and a control means for switching the shaft from two-wheel drive to four-wheel drive when the maximum value of the reflected wave intensity from the comparison means is less than a set value. The gist is:

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be explained in detail based on the drawings. 1st
As shown in the figure, the road surface condition detection device 1 includes an ultrasonic transmitter 5 controlled by a control device 3, and a transmitter 7 that transmits ultrasonic waves from the ultrasonic transmitter 5 toward the road surface W as transmitting means. We are prepared as follows. There are also a plurality of receivers 9a and 9b that receive reflected waves from the road surface W, and ultrasonic receivers 118 and 11b that amplify the reflected waves from these receivers 9a and 9b and output reflected wave intensity voltages. is provided as a receiving means. The receivers 9a and 9b are installed at different positions on the vehicle (for example, installed at the back of the bumper 10 to 20 CI apart). Further, in this embodiment, two pieces are attached, but three or more pieces may be attached.

The control device 3 controls the ultrasonic transmitter 5 to continuously transmit ultrasonic waves from the transmitter 7 toward the road surface W at regular intervals. In addition, the intensity of the reflected waves received by the ultrasonic receiving devices 11a and 11b through the receivers 9a and 9b is input, and the maximum value of the reflected wave intensity is compared, and if the maximum value of the reflected wave intensity is lower than the set value. Determine whether the

In FIG. 1, the two-wheel drive/four-wheel drive switching mechanism of the vehicle includes an engine 13, a transf? Mission 1 with built-in
5. The front wheel 17 is connected to the front export output side of the transformer 77 via a front wheel differential (not shown), and the switching device 19 is provided on the transfer rear wheel output side, and the propeller shaft 21 and the rear It has a hanging ring 25 connected via a wheel differential 23.

The 1i71 conversion device 19 connects and disconnects the transfer 1 and the propeller shaft 21 by, for example, moving the sleeve back and forth, and transmits power to the front wheels 17 only (two-wheel drive) and the rear wheels 25 at the same time. It is configured such that it can be selectively switched to four-wheel drive in which transmission is performed. The switching device 19 is provided with an actuating device 27 that can switch the switching device 19 to the four-wheel drive side by electromagnetically moving the sleeve of the switching device 19, for example. The control device 3 is connected to this actuating device 27 via a drive circuit 29.
A switching signal from the control device 3 allows switching between two-wheel drive and four-wheel drive.

The operation of the road surface condition detection device having the above configuration will be explained based on FIGS. 2 to 4. Due to the action of the control device 3, the ultrasonic transmitter 5 transmits a constant cycle (for example, 10 m5ec) to the road surface W.
) transmits ultrasonic waves, receivers 9a, 9b, and receiver 11
Constantly monitor the intensity of reflected waves from a and 11b - Steps 31 to 33 The output voltage of the transmitted ultrasonic wave and the received input voltage at this time have a relationship as shown in FIG. For the ultrasonic voltage T11 shown in FIG. 2(a), reflected wave intensity voltages H2 and H3 shown in FIG. 2(b) and (C) are obtained.

Then, the control device 3 controls the received reflected wave intensities H2 and H3.
Compare the high setting value 11C1 for day 2 which is the maximum value.
(3V), compared to the low setting value HC2 (1,5V)? ,Q
- Steps 34 to 39° In the case of Fig. 2 (b), the received reflected wave intensity H2 becomes 83, which is higher than the high setting voltage 1''C1.In this case, the road surface is a smooth concrete paved road. It is determined that the two-wheel drive (2WD) counter is increased by +1 step 38, 39°. Conversely, the maximum value of the received reflected wave strength is the low setting value HC2 (1, 5
V), it is determined that the road surface is a snowy or frozen road, and the 4WD (4WD) counter is incremented by +1 - Step 36.37.
9 is a step 40 which is repeated until the number of ultrasound transmissions reaches a predetermined value, for example 128 times. When the 4WD counter is equal to or higher than a predetermined count value,
2WD-4WD switching signal is given, 2WD to 4W
Switch to D - Step 41.42 If there is no 4WD switching, then it is determined whether the count value of the 2WD counter is greater than or equal to a predetermined value, and if the count value of the 2WD counter is greater than or equal to the predetermined number of times, the 4WD-2WD A switching signal is given and switching to 2WD is executed - step 43
゜44゜In this way, the control device 3 does not provide a four-wheel drive signal when the maximum value of the received wave intensity falls below the setting 1aHc2 just once, but instead
The system monitors the maximum input value of the reflected wave intensity, counts the number of times it falls below the set value H02 within a certain period of time, and when the total value exceeds the specified number of times, the road surface becomes slippery like a snowy road. The reason why it is determined that the vehicle is in an easy state and outputs a four-wheel drive signal to the drive circuit 29 to operate the actuating device @27 is as follows. In other words, as shown in Figure 3,
The installation location of the receiver 9 is changed with respect to the transmitter 7 which is in a fixed position, and the reflection is applied to a smooth concrete pavement, a pavement with a rough surface, another pavement B with a rough surface, and an icy road. Looking at changes in wave intensity, the reflected wave intensity on smooth concrete pavement is almost constant and high, and can be easily distinguished from frozen roads. However, in the case of paved roads A and B with rough surfaces, the reflected wave intensity was sometimes lower than that of frozen roads. Therefore, if a road is judged to be a slippery road such as an icy road just because the reflected wave intensity has fallen below the set value (1c), it will incorrectly detect a paved road with a rough surface and an icy road. Become.

Therefore, we focused on the fact that the variation in reflected wave intensity is extremely large on rough paved roads compared to frozen roads.
The number of times the value falls below the set value HC at regular intervals is used as a criterion for discriminating between the two. If the road falls below the set value HC more than a certain number of times, it is determined that the road is frozen, and the set value H is
If the number of times below C is less than a predetermined number of times, it is determined that the road is a paved road with a rough surface, and a distinction is made between a frozen road and a paved road with a rough surface.

If the 4WD or 2WD switching signal is not given within the predetermined number of transmissions, the 2WD and 4WD counters are reset and the determination flow is re-executed in step 45.In addition, in the above embodiment, the high setting value HC+, Low set value HC
2 is used to determine the road surface condition, but this setting value is 1.
It is also possible to determine that the road is frozen when it exceeds the set value HC and falls below the good road. In addition, in the above embodiment, the configuration is such that the switch to four-wheel drive is executed when the number of times the value falls below the set value exceeds a predetermined number of times,
Although an attempt is made to obtain a more accurate drive form depending on the road surface condition, the present invention is not limited to this embodiment. The road surface condition may be determined by just one comparison.

[Effects of the Invention] This invention uses a plurality of reflected wave receiving means, and when the maximum value of the reflected wave intensity is below a set value, it is determined that the road surface is prone to slipping, such as an icy road, and the system changes from two-wheel drive to four-wheel drive. Because the system automatically switches to Because it is hard, it is possible to distinguish it from a road surface that shows a relatively uniform reflected wave intensity, and it is possible to accurately distinguish
It has the advantage of being able to switch between wheel drive and four-wheel drive.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of an embodiment of the present invention, Fig. 2 is a timing chart showing the characteristics of the ultrasonic output voltage and reflected wave voltage of the above embodiment, and Fig. 3 is a transmitter and a receiver. FIG. 4 is a graph showing the change in reflected wave intensity depending on the distance from the object, and FIG. 4 is a flowchart explaining the operation of the above embodiment. 3... Control device 5... Ultrasonic transmitter 7... Transmitter 9a, 9b... Receiver 11a, 11b...
Ultrasonic receiving device 19... Switching device 27... Actuating device 29... Drive circuit Patent applicant Nissan Motor Co., Ltd. Figure 3

Claims (2)

[Claims] (1) A transmitting means that sends a detected wave toward the road surface, a plurality of receiving means installed at different positions that receive reflected waves from the road surface, and a maximum value of the reflected wave intensity by each of the receiving means. A road surface condition detection device comprising a comparison means for determining the intensity, and a control means for switching the shaft from two-wheel drive to four-wheel drive when the maximum value of the reflected wave intensity from the comparison means is less than a set value. (2) The control means is characterized in that it counts the number of times the reflected wave intensity falls below a set value at regular intervals, and switches from two-wheel drive to four-wheel drive when this number of times exceeds the set number. A road surface condition detection device according to claim 1.