JP2855453B2 - Road surface friction coefficient alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention determines a change in frictional force between a road surface and a tire by a simple method, and notifies the driver of the change. The present invention relates to a road friction coefficient warning device that calls attention and avoids danger.

(Prior Art) In a conventional general vehicle, a driver grasps the state of a road surface by visual observation and steering feeling, and judges from experience whether or not the vehicle is slippery. For this reason, even when the road surface is slippery, the driver often applies sudden brakes or turns the steering wheel, slipping, and causing an accident.

Also, to prevent accidents caused by such misjudgments,
It is also conceivable to adopt an anti-lock brake system or the like to prevent slippage after the fact. However, antilock brake systems and the like are expensive and difficult to adopt in all vehicles.

An object of the present invention is to provide an inexpensive road surface friction coefficient alarm device that can notify a driver in advance whether or not a road surface is in a slippery state.

(Means for Solving the Problems) The present invention relates to a vehicle speed sensor that detects a vehicle speed and outputs a vehicle speed signal, an acceleration sensor that detects acceleration in a traveling direction of the vehicle and outputs an acceleration signal, and a steering angle of a front wheel. And a steering angle sensor that detects the actual steering torque and outputs an actual steering torque signal; and a vehicle speed sensor, an acceleration sensor, a steering angle sensor, and a steering torque sensor. It is provided with a controller that is connected and outputs a friction coefficient signal according to each input signal, and an output unit that displays a friction coefficient according to the input friction coefficient signal. The controller derives a standard steering torque from a pre-registered torque table in accordance with the input vehicle speed signal and steering angle signal, compares the standard steering torque with the actual torque signal, and calculates a friction coefficient signal. decide. Further, when the acceleration signal from the acceleration sensor is equal to or larger than the set value, the calculation of the friction coefficient is passed.

(Operation of the Present Invention) In the device of the present invention configured as described above, when the friction coefficient between the road surface and the tire changes during running, the actual steering torque also changes according to the friction coefficient. This actual steering torque is detected by a steering torque sensor and sent to the controller as an actual steering torque signal. The controller compares the standard steering torque drawn from the torque table with the actual steering torque in accordance with the running conditions to determine a friction coefficient signal. This friction coefficient signal is output to the output unit. In accordance with the friction coefficient signal, the output unit displays the friction coefficient or issues an alarm notifying that the friction coefficient has decreased.

However, when the acceleration of the vehicle is equal to or higher than the set value, in other words, when a large acceleration occurs in the traveling direction of the vehicle such as sudden braking or sudden starting, the calculation of the friction coefficient is passed, but for the following reason. is there. That is, when the acceleration is equal to or more than the set value, the installation load of the front wheels greatly changes. Therefore, for example, even if all the conditions other than the acceleration are the same, the steering torque changes. Under such special conditions, standard torque table values registered in advance cannot be used. Therefore, when the acceleration is equal to or more than the set value, the calculation of the friction coefficient is passed.

(Effect of the Present Invention) In the device of the present invention, the output unit displays the friction coefficient or issues an alarm informing that the friction coefficient has decreased according to the friction coefficient signal sent from the controller. Can now know the road conditions in advance. For this reason, when the road surface is slippery, the driver will be careful and sudden braking,
Slip accidents due to sudden steering can now be prevented.

Further, when a large acceleration occurs in the traveling direction of the vehicle, the calculation of the friction coefficient is not performed, so that there is no fear that an erroneous alarm is output from the output unit.

Further, since this device is less expensive than an anti-lock brake, it can be easily adopted in a modest vehicle.

(Embodiment of the Present Invention) In the device of the first embodiment of the present invention shown in FIGS. 1 to 6, the device of the present invention is mounted on a vehicle provided with a manual steering device.

That is, the pinion 3 is connected to the tip of the steering input shaft 2 connected to the steering wheel 1, and the pinion 3 is engaged with the rack 4. Both sides of the rack 4 are connected to knuckle arms 7 of wheels 6 via side rods 5. The rack 4 is covered with a gear case 8.
The location where the pinion 3 and the rack 4 are engaged
Covered by gear box 9.

A torque sensor 10 is provided near the gear box 9. The torque sensor 10 is connected to the controller 11. The torque sensor 10 uses the detected actual steering torque as an actual steering torque signal Ts by the controller.
Output to 11.

A steering angle sensor 12 is provided near the steering input shaft 2. The steering angle sensor 12 is connected to the controller 11. Then, the steering angle sensor 12 outputs the detected steering angle to the controller 11 as a steering angle signal θs.

Further, in the device of this embodiment, a vehicle speed sensor 13 for detecting the speed of the vehicle and an acceleration sensor 14 for detecting the acceleration in the traveling direction of the vehicle are provided. This vehicle speed sensor 13
And the acceleration sensor 14 are connected to the controller 11.
The vehicle speed sensor 13 outputs the detected vehicle speed to the controller 11 as a vehicle speed signal V. Further, the acceleration sensor 14 outputs the detected acceleration to the controller 11 as an acceleration signal.

Inside this controller 11 is a microphone processor
18 and the friction coefficient signal μt
And an average friction coefficient signal t is calculated. The microprocessor 18 has a torque table value storage unit 18a that stores in advance a standard steering torque Ts' using the steering angle θs and the vehicle speed v as parameters as a torque table value, and the input vehicle speed signal V and acceleration signal X. A standard steering torque reading section 18b for reading the standard steering torque Ts' from the torque table value storage section 18a. The ratio of the standard steering torque Ts' to the actual torque signal Ts is calculated by a torque signal comparison unit 18c provided in the microprocessor 18. Then, the friction coefficient signal μt is defined as Ts / Ts ′, which is the ratio between the two.

The torque signal comparator 18c includes the acceleration sensor 1
The acceleration signal processing circuit 17 for processing the acceleration signal from the fourth is connected. When the acceleration in the traveling direction of the vehicle output from the acceleration signal processing circuit 17 is equal to or greater than the set value, the calculation of the friction coefficient signal μt is not performed. The time when the acceleration is equal to or higher than the set value can be assumed at the time of sudden braking or sudden start.

The reason why the calculation is not performed when the acceleration of the vehicle is equal to or higher than the set value is as follows. That is, when the acceleration is equal to or greater than the set value, the ground contact load of the front wheels greatly changes. Therefore, even if all the conditions other than the acceleration are the same, the steering torque changes. Under such special conditions, standard torque table values registered in advance cannot be used. Therefore, when the acceleration is equal to or more than the set value, the calculation of the friction coefficient is passed.

Except when the acceleration is equal to or greater than the set value as described above, the friction coefficient signal μt is obtained. The signal obtained by repeating this several times is averaged by the average value calculation unit 18d to obtain the average friction coefficient signal t. . The reason for calculating the average value is to reduce the influence of noise and disturbance.

The average friction coefficient signal t calculated by the average value calculator 18d is input to the output determiner 18e. The output determining unit 18e that has received the average friction coefficient signal t generates the acceleration sensor 1
According to the acceleration signal from 4, it is determined whether or not to output the average friction coefficient signal t. This is because it is meaningless to output the average friction coefficient signal t at the time of sudden braking or sudden start, and there is a risk that the judgment of the driver may be mistaken.

The controller 11 is connected to a bar graph display device 15 as an output unit of the present invention. That is, the bar graph display device 15 is connected to the output determination unit via the D / A converter 22 and the bar graph display unit 23 provided in the controller 11.
Connected to 18c.

The table values stored in the torque table value storage section 18a are determined as follows.

In general, it is known that the relationship between the friction coefficient signal μt and the vehicle speed signal v and the front wheel steering angle signal θs is a three-dimensional graph on a constant steering torque curved surface TR as shown in FIG. . FIG. 2 shows the steering torque Ts with respect to the vehicle speed v and the steering angle θs when the friction coefficient is constant.
Shows the relationship. Now, assuming that the vehicle speed is v1 and the steering angle is θs1, the steering torque surface TR corresponding to the coordinates (v1, θs1) is obtained.
The height T's1 at the upper point is the standard steering torque.

In FIG. 2, except when the steering angle θs is almost zero, the steering torque Ts rapidly decreases as the vehicle speed v increases, and thereafter increases again. The reason why the steering torque Ts sharply decreases at first is because the frictional force changes from static friction to dynamic friction. After that, the steering torque Ts
Increases because the self-aligning torque that balances the centrifugal force of the vehicle increases. Therefore, when the steering angle is almost zero as described above, this centrifugal force does not occur, and the steering torque does not increase.

The steering torque Ts in FIG. 2 is different from the steering torque Ts in FIG. 3 and FIG.
It changes as shown in the figure. That is, FIG.
= 0 and shows the relationship between the steering angle θs and the steering torque Ts when the friction coefficients μ1 to μ3 are used as parameters. FIG. 4 shows the relationship when the friction coefficients μ1 to μ3 are used as the parameters when the steering angle θs = 0 This shows the relationship between the vehicle speed v and the steering torque Ts.

In the device of the present invention, the standard steering torque on the steering torque curved surface TR is stored in the torque table value storage unit 18a in advance as a standard torque table value. The ratio between the standard steering torque and the actual steering torque actually input from the steering wheel 1 is calculated as the friction coefficient μt between the tire and the road surface.
And let the driver know.

That is, when the actual steering torque is larger than the standard steering torque, the friction coefficient is high. Conversely, when the standard steering torque is larger than the actual steering torque, the friction coefficient is low.

Now, when the switch is turned on and the device is started in step (0), in step (1), the acceleration sensor 14
The longitudinal acceleration X of the vehicle detected by the
Microprocessor through the acceleration signal processing circuit 17
Enter in 18.

In step (2), the torque signal comparing unit 18c in the microprocessor 18 checks whether the absolute value of the longitudinal acceleration of the vehicle exceeds a predetermined constant C1. If not, the process proceeds to the next step. However, if it exceeds C1, the process returns to step (1) and the calculation of the friction coefficient μt is passed. This is because if the acceleration in the front-rear direction of the vehicle is caused by brake or accelerator operation, the ground contact load on the front wheels will change, and the standard steering torque value will also change. That's why. If the friction coefficient μt cannot be measured accurately, the friction coefficient μ
Since the calculation of t is passed, there is no need to inform the driver of the erroneous road surface condition.

In step (3), the steering angle signal θs detected by the steering angle sensor 12 is input to the microprocessor 18 via the steering angle signal processing circuit 19 of the controller 11.

In step (4), the vehicle speed signal V detected by the vehicle speed sensor 13 is input to the microprocessor 18 via the vehicle speed signal processing circuit 20 of the controller 11.

In step (5), the actual torque signal Ts detected by the torque sensor 10 is input to the microprocessor 18 via the torque signal processing circuit 21 of the controller 11.

In step (6), a standard steering torque reading unit 18b in the microprocessor 18 stores a standard torque table previously registered in the torque table value storage unit 18a in accordance with the input steering angle signal θs and the vehicle speed signal V. The standard steering torque Ts' is derived from the value. The standard torque table value takes, for example, a value like the steering torque curved surface TR in FIG.

In step (7), the friction coefficient μt is calculated from the standard steering torque Ts ′ and the actual steering torque Ts in the torque signal comparison unit 18c. For example, a calculation like the following expression (1) is performed.

μt = (Ts / Ts ′) (1) In step (8), the average value calculating unit 18d averages the data of the past n times of the friction coefficient μt to obtain an average friction coefficient signal t. This is to reduce the influence of noise and disturbance.

In step (9), the average friction coefficient signal t is transmitted from the microprocessor 18 via the D / A converter 22 and the bar graph display unit 23 connected to the microprocessor 18,
Output to the bar graph display device 15. Then, returning to step (1), the same loop is repeated to calculate the average friction coefficient signal t.

The bar graph display device 15 displays the level of the average friction coefficient t using a bar graph according to the average friction coefficient signal t.

The driver sees the coefficient of friction shown on the bar graph display device 15 and knows in advance that the road surface is in a slippery state, so that it is possible to prevent a slip accident due to sudden braking or sudden steering.

In the device of the second embodiment shown in FIG. 7, the device of the present invention is applied to an electric power steering device. Here, reference numeral 25 in the figure denotes a motor connected to the controller 11, which is configured to power assist the steering force in response to a command from the controller 11. For this reason, the standard torque table value is set lower than in the case of the first embodiment. Other configurations are the same as those of the first embodiment.

In the device of the third embodiment shown in FIG. 8, the device of the present invention is applied to a hydraulic power steering device. Here, in the figure, reference numeral 26 denotes a pump, 27 denotes an actuator operated by pressure oil from the pump, and 28 denotes a tank.
Also in the device of the third embodiment, the power of the steering force is assisted by the operation of the actuator. Therefore, the standard torque table value is set lower than that of the first embodiment. Other configurations are the same as those of the first embodiment.

In the devices of the first to third embodiments, a bar graph display device 16 is used as the output unit 15. Instead of the bar graph display device 16, a buzzer, a lamp, or the like is provided.
When the average friction coefficient signal μt falls below a certain value,
An alarm may be issued.

[Brief description of the drawings]

1 to 6 show an apparatus according to a first embodiment of the present invention.
FIG. 1 is a diagram showing an overall configuration, FIG. 2 is a diagram showing a steering torque curved surface, FIG. 3 is a diagram showing a relationship between a steering torque and a turning angle when the speed is constant, and FIG. FIG. 4 is a diagram showing the relationship between the vehicle speed and the steering torque when the turning angle is fixed,
FIG. 5 is a block diagram showing a configuration inside the controller,
FIG. 6 is a flowchart showing the procedure of the operation, FIG. 7 is a diagram showing the overall configuration of the device of the second embodiment, and FIG. 8 is a diagram showing the overall configuration of the device of the third embodiment. It is. 10: Torque sensor, 11: Controller, 12: Steering angle sensor, 13: Vehicle speed sensor, 15: Output unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-213852 (JP, A) JP-A-62-255284 (JP, A) JP-A-64-112131 (JP, A) JP-A 62-255 257043 (JP, A) JP-A-1-257242 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60T 17/22 B60T 8/00 G01N 19/02

Claims (1)

(57) [Claims] A vehicle speed sensor for detecting a vehicle speed and outputting a vehicle speed signal; an acceleration sensor for detecting acceleration in a traveling direction of the vehicle to output an acceleration signal; and detecting a steering angle of a front wheel to generate a steering angle signal. A steering angle sensor for outputting, a steering torque sensor for detecting an actual steering torque and outputting an actual steering torque signal, and connecting to these vehicle speed sensor, acceleration sensor, steering angle sensor and steering torque sensor, and inputting each signal. A controller that outputs a coefficient of friction signal, and an output unit that displays the coefficient of friction according to the input coefficient of friction signal, wherein the controller registers in advance according to the input vehicle speed signal and steering angle signal. The standard steering torque is extracted from the obtained torque table, and the standard steering torque is compared with the actual torque signal to determine the friction coefficient signal, while the acceleration Acceleration signal from the difference, when the set value or more, the road surface friction coefficient alarm device was configured to pass the calculation of the friction coefficient.