JPH0696396A - Vehicle distance warning device - Google Patents

Abstract

PURPOSE:To downshift without spoiling a drive feeling by obtaining a rear-end collision marginal prevention time from the distance to a precedent vehicle and the relative speed and downshifting when the rear-end collision marginal prevention period of time is shorter than a prescribed value. CONSTITUTION:A laser radar unit 1 emits a laser beam 7 at every certain time interval and photodetects the laser beam reflected by the reflector 8a of the precedent vehicle 8. The distance to the precedent vehicle is obtained from the time difference the light emission and reception. The arithmetic part 21 of a control unit 14 calculates the rear-end collision marginal prevention period of time from the vehicle distance, the speed of this vehicle, etc. The rear-end collision marginal prevention period of time is inputted to a comparator 22, which compares it with the previously set prescribed value. The comparator inputs the detection signal of an accelerator opening extent sensor and judges the speed reducing action of the driver on the basis of the input signal. When the speed reducing action is judged and the rear-end collision marginal prevention period of time is less than the prescribed value, an overdrive resetting mechanism 26 sends an overdrive-OFF of downshifting command, etc., to an automatic gear 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-vehicle distance detecting / warning device for detecting an inter-vehicle distance between a vehicle and a front vehicle and issuing an alarm when the distance falls below a certain distance.

[0002]

2. Description of the Related Art The causes of rear-end collisions on highways are
The majority of drivers are drowsy driving and aimless driving.
Under these circumstances, we have developed a vehicle-to-vehicle distance detection / alarm system that detects the vehicle-to-vehicle distance between the vehicle and the front vehicle and alerts the driver when the distance falls below a certain distance. Has been done. The outline of the conventional device is that laser light is emitted forward from the vehicle, and the laser light is reflected by the reflector on the rear surface of the front vehicle. The inter-vehicle distance is calculated from the distance, and when the inter-vehicle distance becomes equal to or less than a predetermined distance, the buzzer in the vehicle interior is sounded.

In the case where the alarm is issued as described above, the driver depresses the brake to decelerate the own vehicle so that the vehicle-to-vehicle distance becomes a predetermined distance or more. For a vehicle equipped with a transmission,
As disclosed in Japanese Unexamined Patent Publication No. 24685, there is proposed a technique of automatically downshifting a transmission of a vehicle to apply engine braking as an aid to a driver's deceleration action. As described in the above publication, this is such that when the difference between the vehicle distance measured last time and the vehicle distance measured this time is a predetermined value or more, the transmission of the own vehicle is downshifted.

[0004]

However, in the device described in the above publication, downshifting is performed due to the difference in the inter-vehicle distance.
There were times when the driver was not very close to the preceding vehicle, that is, when the driver did not feel a sense of crisis, downshifting was performed, which hindered the driving feeling.

[0005]

In order to solve the above-mentioned problems, the present invention is mounted on a vehicle equipped with an automatic transmission, detects the inter-vehicle distance between a front vehicle and a host vehicle, and obtains this inter-vehicle distance in advance. In the inter-vehicle distance warning device that gives an alarm when the distance becomes smaller than a certain safe inter-vehicle distance, a rear-end collision delay time is obtained from the front-rear distance and the relative speed, and when the rear-end collision delay time is less than a predetermined value, deceleration assistance is provided. As a result, the automatic transmission is downshifted.

[0006]

The inter-vehicle distance between the front vehicle and the own vehicle can be obtained, for example, by detecting the time until the laser beam emitted from the own vehicle is reflected by the front vehicle and returns. The relative speed between the front vehicle and the own vehicle is obtained as the speed difference between the front vehicle and the own vehicle.
The rear-end collision delay time is calculated as the time required for a rear-end collision in the current traveling state of the host vehicle, assuming that the traveling state of the preceding vehicle is unchanged. When the rear-end collision delay time is less than or equal to a predetermined value and the driver performs deceleration (throttle OFF, etc.), the control unit receives the overdrive O from the control unit to the automatic transmission.
A shift-down command such as FF is issued.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of an inter-vehicle distance warning device which is the premise of the present invention will be described with reference to FIG. Reference numeral 1 denotes a laser radar unit incorporated in a front bumper of a vehicle or the like, which includes a light emitting portion 2 and a light receiving portion 3 as shown in FIG. The light emitting section 2 is composed of a laser diode drive circuit 4, a laser diode 5, and a light emitting lens 6, and emits a laser beam 7 in a pulse shape at regular time intervals. The light receiving unit 3 includes a light receiving lens 9 that receives the laser beam reflected by the reflector 8a of the front vehicle 8, a photodiode 10, an amplifier 11, a signal processor 12, and the like. An inter-vehicle distance D (= (Δt / 2) × light speed) is obtained by the distance detection circuit 13 from the time difference Δt between the light emission by the light emitting unit 2 and the light reception by the light receiving unit 3. The inter-vehicle distance signal that is the detection value of the laser radar unit 1 is
It is input to the control unit 14 mounted on the vehicle.

Information such as the vehicle speed, the steering wheel angle, and the turn signal of the vehicle is also input to the control unit 14. A block diagram of sensors for that purpose is shown in FIG. As shown in this figure, an inter-vehicle distance sensor 15 including the above-described distance detection circuit 13, a vehicle speed sensor 16 for detecting the vehicle speed of the host vehicle, an accelerator opening sensor 17, a shift position detector 1
8, a stop lamp switch 19, a turn signal switch 20, and the like, and signals from these sensors 16 and the like are input to the control unit 14. Specifically, signals from the stop lamp switch 19, the turn signal switch 20, the inter-vehicle distance sensor 15, the vehicle speed sensor 16 and the like are input to the calculation unit 21 of the control unit 14, and the accelerator opening sensor 17 and the shift position detector 18 are provided. The detection signal of is input to the comparator 22.

The computing unit 21 calculates whether or not an alarm should be issued, and the rear-end collision delay time, based on the input signals from the sensors 15, 16 and the like. That is, as described above, the distance between the own vehicle and the front vehicle 8 (inter-vehicle distance D (m))
Is obtained by the inter-vehicle distance sensor 15, and the own vehicle speed Vf
(M / s) is detected by the vehicle speed sensor 16 and
The speed Va (m / s) is calculated from the change in the inter-vehicle distance D per minute time. On the other hand, the time until the driver determines that the driver is dangerous and depresses the brake pedal, that is, the free running time Td (s), the time when the driver determines that the driver is dangerous, that is, the determination time Tx (s) and the deceleration of the vehicle. α ₁ (m / s
² ) and the deceleration α ₂ (m / s ² ) of the front vehicle are stored in advance in the memory of the control unit 14. Deceleration α
Values for ₁ and α ₂ are stored assuming that the brakes are fully braked, and normally α ₁ = α ₂ .

The braking distance L ₁ of the front vehicle 8 is determined by the front vehicle speed V
From a and deceleration α _2, it can be obtained by L ₁ = Va ² / 2α ₂ . The free-running distance L ₂ of the vehicle is determined by the speed Vf of the vehicle and the free-running time T.
From d and the judgment time Tx, L ₂ = (Td + Tx) Vf can be obtained. The braking distance L ₃ of the own vehicle is obtained by L ₃ = Vf ² / 2α ₁ from the own vehicle speed Vf and the deceleration α ₁ .

Therefore, as a condition for generating an alarm, the sum of the front vehicle braking distance L ₁ and the inter-vehicle distance D is the automatic braking distance L ₃
And when it becomes smaller than the sum of the vehicle free running distance L ₂ . That is, Va ² / 2α ₂ + D <Vf ² / 2α ₁ + (Td + Tx) Vf Therefore, D <(Td + Tx) Vf + (Vf ² / 2α ₁ −
When Va ² / 2α ₂ ) = Ds (safe inter-vehicle distance), it is judged that the alarm is to be issued.

In this embodiment, the above calculation is not performed each time, and an alarm is issued based on the relationship between the vehicle speed Vf and the relative speed (speed difference between the preceding vehicle and the vehicle) dv as shown in FIG. The generation distance is obtained as a map 23 and is read. The result read from the map 23 is input to the alarm generator 24. The alarm generator 24 uses the alarm lamp 2
4a, alarm / alarm 24b, inter-vehicle distance display panel 24c
Etc.

The alarm is issued in two stages. For example, when D <Ds as described above, the primary alarm is given, and when D <TdVf + (Vf ² / 2α ₁ −Va ² / 2α ₂ ) = Ds ₁ is closer, the secondary alarm is given. In the primary alarm, the alarm lamp 24a is turned on and the alarm sound is emitted only once. In the case of the secondary alarm, the alarm lamp 24a
Blink and make the alarm beep intermittently.

Further, the rear-end collision delay time t is the time required for a rear-end collision to take place in the current traveling state of the own vehicle, assuming that the traveling state of the front vehicle 8 is unchanged. Relative velocity). This collision delay time t
Is input to the comparator 22 and compared with a preset predetermined value (threshold value). FIG. 5 shows threshold values. As described above, the detection signal of the accelerator opening sensor 17 is input to the comparator 22, and the driver's deceleration action is determined based on this signal. If it is determined that the vehicle is decelerating and the rear-end collision delay time has exceeded the threshold value, a shift command is issued to the controller 25 of the automatic transmission in order to shift down and apply engine braking as an aid to the decelerating activity. Is issued. FIG. 1 shows the overdrive release mechanism 26.

Next, a concrete example of control by the apparatus of the above embodiment will be described with reference to the flow charts of FIGS. First, an initial value is set (step (1)). That is, the free running time Td, the judgment time Tx, the decelerations α ₁ , α _2, etc. are set.

Next, the detection information is taken in from each sensor. For example, the vehicle speed Vf is detected from the vehicle speed sensor 16 (step (2)). Next, the inter-vehicle distance sensor 1
The inter-vehicle distance D between the own vehicle and the preceding vehicle 8 is obtained from step 5 (step (3)).

Next, the relative speed dv is calculated (step (4)), and the warning inter-vehicle distance Ds is calculated or read from the map 23 (step (5)).

Next, the current inter-vehicle distance D obtained in step (3) is compared with the warning inter-vehicle distance Ds calculated in step (5) (step (6)). When it is determined No, that is, when it is determined that the inter-vehicle distance D is larger than the warning inter-vehicle distance Ds, it is not necessary to issue a warning and the process returns to step (2).

If it is determined Yes in step (6), that is, if it is determined that the inter-vehicle distance D is less than or equal to the warning inter-vehicle distance Ds, then it is determined whether there is an alarm stop condition (step ( 7)). The alarm stop condition is, for example, when the stop lamp switch is ON and the turn signal switch is ON. When the stop lamp switch is ON, the vehicle is in the stop preparation state, so that the alarm is not issued even when the distance from the front vehicle 8 is equal to or less than the warning inter-vehicle distance. Also, when the turn signal switch is ON, the driver is gazing ahead because the vehicle is making a turn, and moreover, other than the preceding vehicle, such as the guardrail, is detected, so an alarm is issued to prevent false alarms. Try not to occur.

If there is no alarm stop condition, the alarm lamp 2
4a is turned on, an alarm alarm 24b is sounded, and the inter-vehicle distance display panel 24c displays the inter-vehicle distance. The inter-vehicle distance is always displayed.

Next, a deceleration control determination is made (step (9)). In this process, as shown in FIG. 7, the rear-end collision delay time t is first calculated (step (10)), and then the rear-end collision delay time t is released from overdrive (hereinafter referred to as “OD OF”).
It is judged whether or not it is smaller than a threshold value of "F") (step (11)). In the case of No, that is, when the rear-end collision delay time t is larger than the threshold value, OD OFF is not performed because there is time margin.

When it is judged Yes in step (11), that is, when the rear-end collision delay time t is smaller than the threshold value, it is then judged whether or not the accelerator opening is smaller than 5% (step (12)). )). If it is not small, OD OFF is not performed because the driver does not slow down.

If it is determined in step (12) that the accelerator opening is smaller than 5%, it is determined that there is a deceleration action because the driver is returning his foot from the accelerator pedal. Then, in that case, it is then determined whether or not the current shift stage of the automatic transmission is OD (step (14)). Naturally ODO unless it is an overdrive stage
FF cannot be done.

In the case of an overdrive stage, OD
By turning OFF (step (14)) and applying the engine brake, deceleration is assisted. Since the driver intends to decelerate, the driver does not feel uncomfortable.

Although the above embodiment is applied to the overdrive stage, it can be similarly applied to other shift stages. Further, the driver's deceleration action may be confirmed by means other than throttle-off.

[0026]

In the inter-vehicle distance warning device according to the present invention, the degree of danger of the driver is judged based on the rear-end collision delay time, and the downshift when the feeling of crisis is small is eliminated, so that the driver's feeling is improved. Can be improved. Further, when the rear-end collision delay time becomes equal to or less than the running value and the driver intends to decelerate, the downshift is performed, so that the deceleration can be assisted.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an inter-vehicle distance warning device to which the present invention is applied.

FIG. 2 is an explanatory diagram of a laser radar unit.

FIG. 3 is a block diagram showing an outline of a control unit.

FIG. 4 is an inter-vehicle distance warning map for obtaining an alarm generation distance from a vehicle speed and a relative speed.

FIG. 5 is a diagram showing a threshold of a rear-end collision delay time.

FIG. 6 is a flowchart showing the control content of one embodiment.

FIG. 7 is a subroutine in FIG.

[Explanation of symbols]

 1 Laser Radar Unit 7 Laser Beam 8 Front Vehicle 14 Control Unit 15 Inter-Vehicle Distance Sensor 16 Vehicle Speed Sensor 17 Accelerator Position Sensor 23 Inter-Vehicle Distance Warning Map 24 Alarm Generator 25 Automatic Transmission Controller 26 Overdrive Release Mechanism

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[Procedure amendment]

[Submission date] January 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Therefore, as a condition for generating an alarm, the sum of the front vehicle braking distance L ₁ and the inter-vehicle distance D is the own vehicle braking distance L ₃
And when it becomes smaller than the sum of the vehicle free running distance L ₂ . That is, Va ² / 2α ₂ + D <Vf ² / 2α ₁ + (Td + Tx) Vf Therefore, D <(Td + Tx) Vf + (Vf ² / 2α ₁ −
When Va ² / 2α ₂ ) = Ds (safe inter-vehicle distance), it is judged that the alarm is to be issued.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (1)

[Claims] 1. A vehicle equipped with an automatic transmission,
An inter-vehicle distance warning device that detects the inter-vehicle distance between the preceding vehicle and the host vehicle and issues an alarm when this inter-vehicle distance becomes smaller than the previously determined safe inter-vehicle distance, based on the inter-vehicle distance and the relative speed. An inter-vehicle distance warning device characterized in that a grace time is obtained, and when the rear-end collision grace time is equal to or less than a predetermined value, the automatic transmission is downshifted to assist deceleration.