JPH038971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a rear-end collision prevention warning device that is installed and used in a motor vehicle.

BACKGROUND OF THE INVENTION In general, the brake lights of automobiles illuminate to indicate that braking is in progress, regardless of whether the vehicle is braking suddenly or slowly. Therefore, since the brake lights are lit for both hard braking and slow braking, it is difficult to distinguish between hard braking and slow braking just by looking at the brake light display.

In particular, when a preceding vehicle that was traveling relatively far away on a highway suddenly stops, it is difficult to determine whether the following vehicle has stopped or not. In such situations, it is only when the vehicle approaches that the driver notices that the vehicle is stopped, but by then it is too late and rear-end collisions occur.

As a way to prevent rear-end collisions, a special indicator such as a rotating light is installed at the rear of the vehicle, and when the vehicle suddenly stops, the driver goes around to the rear of the vehicle and turns on the specially installed indicator. Methods are being considered, such as displaying to following vehicles that the vehicle has stopped, or placing triangular ornaments made of reflectors behind the vehicle.

However, if the vehicle has simply stopped suddenly, the driver can take such measures, but it is difficult to take such measures if the vehicle suddenly stops due to some kind of accident.

Furthermore, it is dangerous to turn the vehicle toward the rear when a following vehicle is approaching.

"Prior art" For these reasons, the applicant has proposed the
We proposed a rear-end collision prevention warning device as disclosed in "Publication No. 40918".

The rear-end collision prevention warning system proposed earlier detects the deceleration of the vehicle using an analog acceleration sensor, integrates the detection signal, and when the integrated value exceeds a predetermined value, it is regarded as sudden braking and activates the warning system. It is structured as follows.

"Problems to be Solved by the Invention" The rear-end collision prevention warning device proposed above is configured to detect the deceleration of a vehicle using an acceleration sensor. It is difficult to create an analog-type acceleration sensor with uniform detection sensitivity. For this reason, there is a drawback that variations occur between products.

In other words, the rear-end collision prevention warning system should rarely be activated because it has a large effect on other vehicles.
For this reason, if there is variation in the detection sensitivity of the sensor with respect to the setting value for activation, there is a drawback that some products may activate in situations other than true sudden braking.

In order to eliminate such inconveniences, it is required to produce acceleration sensors with uniform detection sensitivities, but this increases the cost.

An object of the present invention is to provide a rear-end collision prevention warning device that has uniform detection sensitivity and can be manufactured at low cost.

"Means for Solving the Problem" This invention includes a means for generating a number of pulses proportional to the vehicle speed and counting the pulses in units of time to measure the vehicle speed at each instant, and a memory for storing the measured vehicle speed. a vehicle type changeover switch that sets a time difference between vehicle speed values for calculating vehicle speed deceleration for each vehicle type and selects a time difference corresponding to the vehicle type;
determining means for subtracting the vehicle speed value after the time difference from the vehicle speed value stored in the storage means before the time difference selected by the vehicle type changeover switch, and determining whether or not the deceleration of the vehicle speed is equal to or greater than a predetermined value; A rear-end collision prevention warning device is constituted by an indicator that displays the sudden braking to the following vehicle based on the determination output when the determination means determines that the deceleration is equal to or higher than a predetermined value.

In this configuration, by switching the vehicle type changeover switch, the time difference corresponding to the vehicle type is selected and set. The storage means sequentially stores vehicle speed values within a certain period of time measured by the vehicle speed measurement means. Among these vehicle speed values, the vehicle speed value after the set time difference is subtracted from the vehicle speed value before the set time difference to calculate each instantaneous deceleration. The calculated deceleration is compared with a preset value, and when the deceleration exceeds the set value, sudden braking is determined.
Activate the display.

As described above, according to the present invention, since the vehicle speed is measured using a number of pulses proportional to the vehicle speed, the vehicle speed can be measured with high accuracy. For example, since the vehicle speed is measured by counting the number of rotations of the propeller shaft, the measured vehicle speed does not vary greatly depending on the vehicle. Therefore, vehicle speed data with less variation can be obtained.

Furthermore, since it is sufficient to attach the rotation detector to the propeller shaft or the like, the vehicle speed detection sensor can be manufactured at low cost.

Therefore, according to the present invention, a rear-end collision prevention warning device with little variation during operation can be provided at a low cost.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In the figure, 1 indicates a vehicle speed sensor. The vehicle speed sensor 1 may be a magnetic rotation detector or an optical rotation detector configured by a magnet attached to a rotating body and a magnetic sensor provided along the rotating surface of the magnet. . A rotation detector is attached to, for example, a propeller shaft of an automobile, and generates a number of pulses PS proportional to the rotation speed of the propeller shaft.

The pulse PS is input to the microcomputer 2, which constitutes a vehicle speed measuring means, a storage means, a deceleration calculating means, and a determining means.

As is well known, the microcomputer 2 stores a central processing unit 2A and a program for operating the central processing unit 2A in the order of determination.
ROM2B, RAM2C, input port 2D,
It is configured by an output port 2E.

The pulse PS output from the vehicle speed sensor 1 is taken into the central processing unit 2A via the input port 2D. For example, the central processing unit 2A generates pulses for 1 second each.
RAM2 counts the PS and uses the counted value as the vehicle speed value.
Write to C. M ₁ shown in FIGS. 2A and 3A,
Pulse PS measured for 1 second each of M ₂ , M ₃ , M ₄ ...
, which corresponds to each instantaneous vehicle speed value. These vehicle speed values M ₁ , M ₂ , M _{3 .} . . are sequentially taken into the microcomputer 2 and stored in the RAM 2C. For example, the capacity of the vehicle speed storage area of RAM2C is
With 10 addresses, RAM2C can always store the vehicle speed from the current vehicle speed to 10 seconds ago.

The operating speed of the microcomputer 2 is considerably faster than the operating speed of mechanical elements such as the propeller shaft. Therefore, when viewed from the microcomputer 2, the interval between the pulses PS appears to be quite long.

For this reason, microcomputer 2 uses pulse PS
is counted, for example, by an interrupt operation, and is written to RAM2C during steady state when no pulse PS is input, and the vehicle speed value written to RAM2C a predetermined time ago is read out and that vehicle speed value and, for example, the current value Calculation operation to calculate deceleration by subtracting the latest vehicle speed value, and the deceleration calculated by that calculation and the deceleration calculated in advance.
A determination operation can be performed to compare the set value written in the ROM 2B and determine whether or not it is larger than the set value.

For example, if the time △T is 3 seconds and the deceleration is calculated by subtracting the current vehicle speed value from the vehicle speed value measured 3 seconds ago, the vehicle is traveling at a constant speed as shown in Figure 2A. For example, in the state where M ₁ − M ₄ =
0, the deceleration rate maintains the value of 0.

On the other hand, when braking is started as shown after time t ₀ , M ₂ − M ₅ = δ ₁ , M ₃ − M ₆ = δ ₂ , M ₄ −
Deceleration rates δ ₁ , δ ₂ , δ ₃ . . . are obtained as M ₇ = δ _{3 . .} . (Fig. 2B). A braking curve 3 shown in FIG. 2A is a braking characteristic during gentle braking. Therefore, the deceleration δ exhibits a gradual increase and a decrease as shown in FIG. 2B. Therefore, in this case, the deceleration δ is the set value δ _t
will never reach.

On the other hand, as shown by curve 4 in FIG. 3A, when so-called sudden braking is applied to stop the vehicle within a short period of time, the deceleration δ rapidly increases and reaches the set value _δt .
The set value δ _t is written in the ROM 2B in advance, and the central processing unit 2A compares this set value δ _t with the deceleration rate δ. When the deceleration δ exceeds the set value _δt , the central processing unit 2A generates an alarm signal and outputs the alarm signal to the display 6 through the output port 2E. The display 6 is activated by this alarm signal to indicate that sudden braking has been applied. As the display 6, for example, a rotating light or the like can be used. 6A indicates a reset switch for the display 6. In other words, once the display device 6 is activated, it is configured to self-hold by the self-holding circuit. With this configuration, even when the vehicle is stopped and the brake pedal is released, the display 6 continues to operate, and a warning can continue to be given to the rear. When the user escapes from the dangerous situation, the reset switch 6A is operated to stop the operation of the display 6.

On the other hand, input port 2D of microcomputer 2
A vehicle type changeover switch 7 is connected to. By switching this vehicle type changeover switch 7, the time difference ΔT in vehicle speed to be subtracted is changed.

Car types include light cars, regular passenger cars,
They can be classified into medium-sized trucks, large trucks, buses, etc. Since there is a large difference in vehicle weight between these vehicle types, the braking characteristics vary as shown in FIG.

In other words, as shown in curve 11, light vehicles have a short time from the start of braking to stopping. Therefore,
The braking distance is short, and as the vehicle weight increases, the braking distance becomes longer. Curve 1 shown in Figure 4
2 shows the braking characteristics of an ordinary passenger car, curve 13 shows the braking characteristics of a medium-sized truck, and curve 14 shows the braking characteristics of a large truck or bus.

Since the braking characteristics differ for each vehicle model, if the deceleration is calculated while keeping the time difference of the subtracted vehicle speed constant, the magnitude of the deceleration calculated for each vehicle model even though it is sudden braking. The quality will be different. In other words, as the braking characteristics become gentler, the magnitude of the calculated deceleration δ becomes smaller.

It is necessary to eliminate this inconvenience and make it possible to detect when sudden braking is applied in any vehicle type.

Therefore, by changing the vehicle type changeover switch 7, the calculation formula can be changed by changing the time difference ΔT of the vehicle speed to be subtracted while keeping the set value _δt for operating the display 6 constant.

The difference in the arithmetic expression is the difference in how many seconds ago the current vehicle speed value is subtracted from the vehicle speed value. As in the example explained earlier, if we use the formula for calculating deceleration by subtracting the current vehicle speed from the vehicle speed 3 seconds ago as the formula for a regular passenger car, this will allow the vehicle to stop in a short time. A shorter calculation formula can be used for light vehicles that can calculate the deceleration, for example, by subtracting the current vehicle speed value from the vehicle speed value two seconds ago.

Furthermore, in the case of medium-sized trucks and large-sized trucks that take longer to stop than ordinary passenger cars, it is necessary to increase the time difference to increase the detection sensitivity of deceleration. In other words, if it takes a long time to stop, for example in the case of a medium-sized truck, the current vehicle speed value is subtracted from the vehicle speed value 4 seconds ago, for example. Further, in the case of a large truck, the deceleration is calculated by subtracting the current vehicle speed value from the vehicle speed value six seconds ago, for example. This time difference may be determined in proportion to the times t ₁ , t ₂ , t ₃ , and t ₄ required for braking for each vehicle type.

In this way, the deceleration δ corresponds to the difference in braking characteristics.
Detection sensitivity can be adjusted by selecting the time difference between vehicle speed values for calculating , and an appropriate detection sensitivity can be set for any vehicle type.

FIG. 5 shows a flowchart outlining a program for operating the microcomputer 2. As shown in FIG.

"Operations and Effects of the Invention" As explained above, according to the present invention, a number of pulses proportional to the vehicle speed are generated, the pulses are counted, and this counted value is taken in and stored as a vehicle speed value,
Subtract the memorized vehicle speed value with a time difference,
Since the configuration is such that deceleration is determined, there will be no variation in vehicle speed values for each vehicle.

Moreover, since the time difference ΔT between the vehicle speed values to be subtracted is set by the vehicle type changeover switch 7, there will be no variation in deceleration detection sensitivity between vehicles unless the vehicle type changeover switch 7 is changed.

A vehicle speed sensor that generates a pulse in proportion to the rotation of a rotating body such as a propeller shaft does not require adjustment or the like and can be manufactured relatively inexpensively. Microcomputers can also be obtained relatively inexpensively. Therefore, the entire system can be manufactured at low cost, and a rear-end collision prevention warning device with uniform operating points of the indicator 6 indicating sudden braking can be provided at low cost.

Although not specifically mentioned above, one of the conditions for displaying sudden braking is that the vehicle speed at which braking begins is above a certain value, for example 80 km/h to 100 km/h or above. It's okay.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining one embodiment of this invention, FIGS. 2 to 4 are graphs for explaining the operation of this invention, and FIG. 5 is a program for operating a microcomputer. This is a flowchart showing an overview. 1: Vehicle speed sensor, 2: Microcomputer,
2A: Central processing unit, 2B: ROM, 2C:
RAM, 2D: input port, 2E: output port,
6: Display, 7: Vehicle type selection switch.

Claims (1)

[Scope of Claims] 1. A vehicle speed sensor that generates a number of pulses proportional to the vehicle speed; B. Measuring means for counting the number of pulses output from this vehicle speed sensor to obtain a vehicle speed value; C. This vehicle speed measuring means. a storage means for sequentially capturing and storing measured vehicle speed values; D; a vehicle type changeover switch for setting a time difference between the vehicle speed values for calculating the deceleration of the vehicle speed for each vehicle type and selecting a time difference corresponding to the vehicle type; E: determining means for determining whether the deceleration obtained by subtracting the vehicle speed value after the time difference from the vehicle speed value stored in the storage means before the time difference selected by the vehicle type changeover switch is equal to or greater than a predetermined value; F. A rear-end collision prevention warning device comprising: an indicator that displays sudden braking to a following vehicle based on the determination output in a state in which the determination means determines that the deceleration at the time difference is equal to or greater than a predetermined value.