JP2017030708A - Vehicle collision detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle collision detecting apparatus capable of accurately detecting occurrence of collision to a vehicle.SOLUTION: A plurality of piezo films 31C, 31R, 31L are attached onto a bumper cover of a vehicle in an aligned manner in vehicle width direction. Voltage detecting circuits 32 comprising a thermistor are connected to the piezo films 31C, 31R, 31L respectively. When collision to the bumper cover occurs, the bumper cover is deformed so that the piezo films 31C, 31R, 31L generate piezo film voltage Vpz. The voltage detecting circuit 32 adjusts generated piezo film voltage Vpz based on temperature T of the bumper cover to generate detection voltage Vout. A collision determining part 64 determines occurrence of collision on the bumper cover when the detection voltage Vout generated by the voltage detecting circuit 32 is larger than a predetermined voltage threshold Vth.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicle collision detection device that detects a collision of a pedestrian or the like with a vehicle.

  There has been a conventional technology related to a vehicle collision detection device that provides a shock absorber behind the bumper cover, disposes a detection tube between the shock absorber and the cross member, and detects a pedestrian collision with the front end of the vehicle ( For example, see Patent Document 1). The collision detection device according to the related art is intended to enable detection of a collision with respect to a wide area in the bumper cover. In this prior art, when a pressure exceeding a threshold value is generated in a detection tube that extends long in the vehicle width direction, it is detected that a pedestrian has collided with the bumper cover.

Special table 2014-505629 gazette

However, in the above-described conventional collision detection device for a vehicle, since the collision with the front end of the vehicle is detected via the buffer, there is a problem that the occurrence of the collision in the vehicle cannot be detected with high accuracy. there were. That is, when a collision occurs in the bumper cover at the front end of the vehicle, the impact due to the collision is attenuated while propagating to the buffer. For this reason, for example, when the impact due to the collision is small, the detection tube disposed behind the buffer cannot accurately detect the pressure increase due to the impact due to the collision.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle collision detection device that can accurately detect the occurrence of a collision with a vehicle.

  In order to solve the above-described problem, the invention of the vehicle collision detection device according to claim 1 is attached to a bumper cover provided at a front portion of the vehicle and generates an output voltage corresponding to the deformation amount of the bumper cover. A collision-voltage conversion element, and a collision determination unit that detects, based on an output voltage formed by the displacement-voltage conversion element, that a collision that requires the operation of a protective device that protects a collision object has occurred on the bumper cover. A collision determination adjustment unit that changes the detection sensitivity of the collision occurrence by the collision determination unit based on the temperature of the bumper cover.

According to this configuration, the displacement-voltage conversion element that generates the output voltage corresponding to the deformation amount of the bumper cover is provided. Then, the collision determination unit detects that a collision has occurred in the bumper cover based on the output voltage formed by the displacement-voltage conversion element. Accordingly, it is possible to accurately detect that a collision with the front portion of the vehicle has occurred based on the output voltage of the displacement-voltage conversion element that directly affects the deformation amount of the bumper cover.
Also, the bumper cover is usually made of a synthetic resin material, and even if the same impact is applied by collision, the amount of deformation is known to decrease at low temperatures compared to high temperatures due to the nature of the material. . On the other hand, in the said structure, the collision determination adjustment part which changes the detection sensitivity of the collision occurrence by a collision determination part based on the temperature of a bumper cover is provided. Therefore, even when the deformation amount of the bumper cover is affected by the temperature, the collision detection adjustment unit changes the detection sensitivity of the collision occurrence, so that the collision occurrence can be accurately detected.
The vehicle collision detection apparatus according to the present invention is intended not only for pedestrian collisions but also for all collision detections for vehicles.

The top view of the vehicle with which the pedestrian protection system by Embodiment 1 of this invention was attached. II-II sectional view of FIG. Block diagram showing the configuration of the pedestrian protection system A circuit diagram showing a state in which a piezo film is connected to the voltage detection circuit shown in FIG. A graph showing the relationship between the impact load applied to the bumper cover and the amount of deformation of the bumper cover A graph showing the relationship between the amount of deformation of the bumper cover and the piezoelectric film voltage A graph showing the relationship between impact load and piezo film voltage A graph showing the relationship between temperature and thermistor resistance A graph showing the relationship between the collision load and the voltage detected by the voltage detection circuit The figure which showed the control flowchart of a pedestrian protection system The block diagram which showed the structure of the pedestrian protection system by Embodiment 2. The figure showing the graph which showed the deformation amount of the bumper cover by Embodiment 2, and the relationship between the piezo film voltage

<Configuration of Embodiment 1>
A pedestrian protection system 1 (corresponding to a vehicle collision detection device) according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 10. In each of the drawings, the direction indication indicates the direction with respect to the vehicle VE. For example, the indication “front” indicates that the direction of the arrow corresponds to the front of the vehicle VE. Although the following description focuses on pedestrian collisions with the vehicle VE, the vehicle collision detection device according to the present invention targets not only pedestrian collisions but all collision detections with the vehicle VE.

(Overall configuration of pedestrian protection system)
As shown in FIG. 1, a front bumper 21 (corresponding to a front portion of the vehicle) is attached to the front end portion of the vehicle VE. The front bumper 21 extends in the left-right direction and includes a bumper cover 22 and a bumper absorber 23. The bumper cover 22 is formed of a synthetic resin material, and forms a design surface in the front portion of the vehicle VE. The bumper absorber 23 is provided behind the bumper cover 22 as a shock absorber when a collision occurs in the front portion of the vehicle VE. The bumper absorber 23 is made of a foamed resin such as foamed polypropylene, for example.
The bumper absorber 23 is attached to the front surface 24a of the bumper reinforcement 24 at the rear end surface 23a. The bumper reinforcement 24 is a strength member having a hollow interior made of a metal material such as an aluminum alloy, and extends in the left-right direction. The bumper reinforcement 24 is fixed to front ends of a pair of left and right side members 25R and 25L extending in the front-rear direction. The body unit 2 is formed by the front bumper 21, the bumper reinforcement 24, and the side members 25R and 25L described above.

  As shown in FIGS. 1 and 2, a central piezo film 31 </ b> C, a right piezo film 31 </ b> R, and a left piezo film 31 </ b> L are attached to the back surface 22 a located behind the bumper cover 22 with an adhesive or the like. Hereinafter, the central piezo film 31C, the right piezo film 31R, and the left piezo film 31L are collectively referred to as piezo films 31C, 31R, and 31L (corresponding to displacement-voltage conversion elements). The piezo films 31C, 31R, and 31L are each formed into a thin film from a piezoelectric polymer film such as polyvinylidene fluoride (PVDF), polypeptide, polylactic acid, polymethylglutamate, and polybenzylglutamate. Piezofilms are known per se, and are disclosed in, for example, published patent publications JP-A-2004-96980, JP-A-2007-212436, JP-A-2013-29368, etc. Omitted. A piezoelectric ceramic such as lead zirconate titanate (PZT) may be attached to the bumper cover 22 in place of the piezo films 31C, 31R, 31L. The plurality of piezo films 31C, 31R, 31L are arranged on the bumper cover 22 (corresponding to the bumper cover) so as to be aligned in the vehicle width direction. The central piezo film 31 </ b> C is attached to the substantially central portion of the bumper cover 22 in the vehicle width direction. The right piezo film 31R and the left piezo film 31L are attached to the right end portion and the left end portion of the bumper cover 22 in the vehicle width direction, respectively.

  The piezo films 31C, 31R, 31L have a pair of electrodes 31b1, 31b2 (shown in FIG. 4) with the piezo element 31a interposed therebetween. When the bumper cover 22 is deformed, tensile or compressive stress is applied to the piezo films 31C, 31R, and 31L, and an output voltage (hereinafter referred to as piezo film voltage) corresponding to the deformation amount Q of the bumper cover 22 is applied between the electrodes 31b1 and 31b2. Vpz) is generated. Further, as shown in FIG. 1, on the back surface 22a of the bumper cover 22, three voltage detection circuits 32 (corresponding to a collision determination adjusting unit and a voltage adjusting unit) connected to the piezo films 31C, 31R, and 31L, respectively. ) Is attached. All three voltage detection circuits 32 have the same configuration. Each voltage detection circuit 32 includes a thermistor 32a described later. Only the thermistor 32a may be attached to the bumper cover 22, and the remaining part of the voltage detection circuit 32 excluding the thermistor 32a may be formed in the pedestrian protection ECU 6 described later. Details of the voltage detection circuit 32 will be described later. The deformation amount detection unit 3 is formed by the piezo films 31C, 31R, 31L and the voltage detection circuit 32.

The speed sensor 4 provided in the vehicle VE is attached to a wheel or a transmission (not shown) of the vehicle VE and detects the traveling speed of the vehicle VE.
The cowl airbag device 51 is included in the pedestrian protection device 5 (corresponding to a protection device). When a pedestrian collides with the front bumper 21, the cowl airbag device 51 deploys a bag from the engine hood HE shown in FIG. 1 to the lower part of the front window WF, and protects colliding objects such as a pedestrian colliding.
A pop-up hood 52 is also included in the pedestrian protection device 5. The pop-up hood 52 raises the rear end of the engine hood HE when a pedestrian or the like collides with the front bumper 21. As a result, the engine hood HE serves as a buffer member, preventing a pedestrian from colliding with a rigid member such as an engine, and protecting colliding objects such as a colliding pedestrian.

(Configuration of pedestrian protection ECU)
In the vehicle VE, a pedestrian protection ECU 6 is mounted on a floor tunnel in front of the driver's seat (not shown). The pedestrian protection ECU 6 is a control device formed by an input / output device (not shown), a CPU, a RAM, and the like. As shown in FIG. 1, the voltage detection circuit 32, the speed sensor 4, the cowl airbag device 51, and the pop-up hood 52 described above are connected to the pedestrian protection ECU 6 by communication lines.

As shown in FIG. 3, the pedestrian protection ECU 6 includes a vehicle speed determination unit 61, a collision position detection unit 62, a threshold setting unit 63, a collision determination unit 64, an AND circuit 65, and a protection device driver 66.
The vehicle speed determination unit 61 is connected to the speed sensor 4. The vehicle speed determination unit 61 determines whether the vehicle speed detection value Sdet by the speed sensor 4 is equal to or greater than a predetermined first vehicle speed threshold value Sth1 and equal to or less than a predetermined second vehicle speed threshold value Sth2. The vehicle speed determination unit 61 outputs a high (H) signal when the vehicle speed detection value Sdet is not less than the first vehicle speed threshold value Sth1 and not more than the second vehicle speed threshold value Sth2.
The collision position detection unit 62 is connected to all the voltage detection circuits 32. The collision position detection unit 62 detects the position in the vehicle width direction where the collision has occurred on the bumper cover 22 based on the detection voltage Vout (corresponding to the correction voltage) output from the voltage detection circuit 32. Specifically, the voltage detection circuit 32 that generates the largest detection voltage Vout is selected from the plurality of voltage detection circuits 32. And the position where the piezo films 31C, 31R, 31L connected to the selected voltage detection circuit 32 are arranged is the position in the vehicle width direction where the collision has occurred. A method for forming the detection voltage Vout will be described later.

The threshold setting unit 63 is connected to the collision position detection unit 62. The threshold setting unit 63 sets the voltage threshold Vth according to the position in the vehicle width direction where the collision detected by the collision position detection unit 62 has occurred. Specifically, on the bumper 22, when it is detected that a collision has occurred at the position in the vehicle width direction where the central piezo film 31C is disposed, the voltage threshold value Vth1 is set. On the bumper 22, when it is detected that a collision has occurred at the position in the vehicle width direction where the right piezo film 31R or the left piezo film 31L is disposed, the voltage threshold Vth2 is set. Here, the voltage threshold Vth1 is set to a value larger than the voltage threshold Vth2 (voltage threshold Vth1> voltage threshold Vth2). Hereinafter, the voltage threshold Vth1 and the voltage threshold Vth2 are collectively referred to as the voltage threshold Vth.
The method for setting the voltage threshold Vth described above is merely an example, and the voltage threshold Vth2 when a collision occurs at the end in the vehicle width direction of the bumper cover 22 does not necessarily have to be set to a small value. For example, the voltage threshold Vth may be set according to the design of the bumper cover 22. That is, in the bumper cover 22, when a collision occurs at an uneven part or a part formed by a curved surface, the deformation amount Q tends to be small, so the voltage threshold Vth may be set to a small value. Further, in the bumper cover 22, when a collision occurs on a wide plane portion, the deformation amount Q tends to increase, so the voltage threshold value Vth may be set to a large value.
Further, the voltage threshold Vth may be set according to the rigidity of the bumper cover 22. That is, in the bumper cover 22, when a collision occurs at a portion where a highly rigid structure such as a headlamp exists inside, the deformation amount Q tends to be small, so even if the voltage threshold Vth is set to a small value. Good.

  The collision determination unit 64 is connected to all the voltage detection circuits 32 and the threshold setting unit 63. The collision determination unit 64 compares the detection voltage Vout input from the voltage detection circuit 32 with a predetermined voltage threshold Vth (voltage threshold Vth1 or voltage threshold Vth2) set by the threshold setting unit 63. When the detection voltage Vout is equal to or higher than the voltage threshold Vth (corresponding to a voltage threshold or higher), the collision determination unit 64 detects that a collision requiring the operation of the pedestrian protection device 5 has occurred on the bumper cover 22. Output a signal. The collision determination unit 64 may compare the largest value among the detection voltages Vout output from the plurality of voltage detection circuits 32 with the voltage threshold Vth, or detect the detection voltages output from the plurality of voltage detection circuits 32. The average value of Vout may be compared with the voltage threshold value Vth.

  As described above, since the voltage threshold value Vth is set to a different value depending on the position in the vehicle width direction where the collision has occurred, the collision determination unit 64 determines whether the collision detected by the collision position detection unit 62 has occurred in the vehicle width direction. Depending on the position, the detection sensitivity of the collision occurrence can be changed. For example, a pedestrian may collide with the vicinity of the end of the front bumper 21 in the left-right direction. In this case, the amount of deformation Q generated in the bumper cover 22 may be smaller even when the impact applied to the vehicle VE is the same as compared to when the front bumper 21 collides with the vicinity of the central portion in the left-right direction. Therefore, the voltage threshold Vth2 when a collision occurs at both ends in the vehicle width direction is set smaller than the voltage threshold Vth1 when a collision occurs at the center in the vehicle width direction, and the occurrence of the collision is detected. It is easy. Further, as described above, the voltage threshold value Vth may be set in accordance with the design or rigidity of the bumper cover 22 so that the collision can be accurately detected regardless of the design or rigidity of the bumper cover 22.

A pair of input ends of the AND circuit 65 is connected to the vehicle speed determination unit 61 and the collision determination unit 64. The AND circuit 65 outputs an H signal when the vehicle speed determination unit 61 outputs an H signal and the collision determination unit 64 outputs an H signal.
The protective device driver 66 is connected to the output terminal of the AND circuit 65 and operates the cowl airbag device 51 or the pop-up hood 52 when the H signal is output from the AND circuit 65.

(Configuration and function of voltage detection circuit)
As shown in FIG. 4, each voltage detection circuit 32 includes a thermistor 32 a (corresponding to a variable resistance element) attached to the bumper cover 22. The thermistor 32 a has a thermistor resistance value Rthm (corresponding to a resistance value) that varies depending on the temperature T of the bumper cover 22. One end 32a1 of the thermistor 32a is connected to one electrode 31b1 of the piezo films 31C, 31R, 31L, respectively. The other end portion 32a2 of the thermistor 32a is connected to one end 32b1 of the reference resistor 32b having the detection resistance value Rref. Furthermore, the other electrode 31b2 of the piezo films 31C, 31R, 31L is grounded together with the other end 32b2 of the reference resistor 32b.

したがって、リファレンス抵抗３２ｂの両端３２ｂ１、３２ｂ２には、下記数式で表した検出電圧Ｖｏｕｔが発生する。

上式から分かるように、検出電圧Ｖｏｕｔは、ピエゾフィルム電圧Ｖｐｚとサーミスタ抵抗値Ｒｔｈｍとの影響を受ける。検出電圧Ｖｏｕｔは、ピエゾフィルム電圧Ｖｐｚが高くなることにより増大し、サーミスタ抵抗値Ｒｔｈｍが大きくなることにより減少する。 When the bumper cover 22 is deformed due to a collision with the front bumper 21, as described above, the piezoelectric film voltage Vpz (corresponding to the output voltage) corresponding to the deformation amount Q of the bumper cover 22 is applied to the piezoelectric films 31C, 31R, and 31L. Occur. The piezo film voltage Vpz is applied to the thermistor 32a, and an output current Iref expressed by the following equation flows through the reference resistor 32b.

Therefore, the detection voltage Vout expressed by the following equation is generated at both ends 32b1 and 32b2 of the reference resistor 32b.

As can be seen from the above equation, the detection voltage Vout is affected by the piezo film voltage Vpz and the thermistor resistance value Rthm. The detection voltage Vout increases as the piezo film voltage Vpz increases, and decreases as the thermistor resistance value Rthm increases.

Here, as shown in FIG. 5, the deformation amount Q (Force-Stroke characteristic) of the bumper cover 22 due to the collision is influenced by the temperature T of the bumper cover 22. Even if the collision load F applied to the bumper cover 22 by the collision is the same, the deformation amount Q of the bumper cover 22 increases as the temperature T rises.
Further, as shown in FIG. 6, the piezo film voltage Vpz with respect to the deformation amount Q of the bumper cover 22 may be considered to have a linear relationship, and as the deformation amount Q of the bumper cover 22 increases, the piezo film The voltage Vpz also increases. The piezo film voltage Vpz itself has temperature characteristics but is negligible.
Therefore, as shown in FIG. 7, the piezo film voltage Vpz with respect to the collision load F is also affected by the temperature T of the bumper cover 22, and even if the collision load F is the same, the piezo film increases as the temperature T increases. The voltage Vpz increases.

On the other hand, as shown in FIG. 8, the thermistor resistance value Rthm increases as the temperature T of the bumper cover 22 increases. Therefore, in the above equation (2), the increase in the piezo film voltage Vpz accompanying the increase in the temperature T of the bumper cover 22 can be offset by the increase in the thermistor resistance value Rthm. On the contrary, the decrease in the piezo film voltage Vpz accompanying the decrease in the temperature T of the bumper cover 22 can be offset by the decrease in the thermistor resistance value Rthm. Therefore, as shown in FIG. 9, fluctuations in the detection voltage Vout due to changes in the temperature T of the bumper cover 22 can be reduced. As described above, the voltage detection circuit 32 corrects the piezo film voltage Vpz based on the temperature T of the bumper cover 22 to form the detection voltage Vout.
That is, the voltage detection circuit 32 can correct the piezo film voltage Vpz based on the temperature T of the bumper cover 22 and change the detection sensitivity of the collision occurrence in the bumper cover 22.

(Control method for pedestrian protection system)
Hereinafter, based on FIG. 10, the control method of the pedestrian protection system 1 by pedestrian protection ECU6 is demonstrated. First, the vehicle speed detection value Sdet of the vehicle VE is input from the speed sensor 4 to the vehicle speed determination unit 61 (step S101). Next, the vehicle speed determination unit 61 determines whether or not the vehicle speed detection value Sdet is greater than or equal to the first vehicle speed threshold Sth1 and less than or equal to the second vehicle speed threshold Sth2 (step S102). When it is determined that the vehicle speed detection value Sdet is less than the first vehicle speed threshold value Sth1 or exceeds the second vehicle speed threshold value Sth2, this control flow ends. When it is determined that the vehicle speed detection value Sdet is equal to or greater than the first vehicle speed threshold Sth1 and equal to or less than the second vehicle speed threshold Sth2, the voltage detection circuit 32 moves toward the collision position detection unit 62 and the collision determination unit 64. The detection voltage Vout is input (step S103).

  The collision position detection unit 62 detects the position in the vehicle width direction where the collision has occurred on the bumper cover 22 based on the input detection voltage Vout (step S104). The threshold setting unit 63 sets the voltage threshold Vth according to the position in the vehicle width direction where the collision has occurred, detected by the collision position detection unit 62 (step S105). It is determined whether or not the detection voltage Vout input to the collision determination unit 64 is equal to or higher than the voltage threshold Vth set by the threshold setting unit 63 (step S106). When it is determined that the detection voltage Vout is equal to or higher than the voltage threshold Vth, the bumper cover 22 detects that a collision requiring the operation of the pedestrian protection device 5 has occurred (step S107), and the pedestrian protection device 5 is activated (step S108). In step S106, when it is determined that the detected voltage Vout is less than the voltage threshold Vth, the present control flow ends.

<Effect of Embodiment 1>
According to the present embodiment, the piezo films 31C, 31R, and 31L that generate the piezo film voltage Vpz corresponding to the deformation amount Q are attached to the bumper cover 22. The collision determination unit 64 compares the detection voltage Vout formed by correcting the piezo film voltage Vpz by the voltage detection circuit 32 with a predetermined voltage threshold Vth. When the detection voltage Vout is equal to or higher than the voltage threshold Vth, it is detected that a collision has occurred in the bumper cover 22 of the vehicle VE. As a result, the amount of deformation Q of the bumper cover 22 can detect that a collision has occurred in the bumper cover 22 of the vehicle VE, based on the piezo film voltage Vpz of the piezo films 31C, 31R, and 31L that are directly affected. it can. For this reason, it is possible to accurately detect that a collision of the vehicle VE with the front bumper 21 has occurred.
Further, it is only necessary to affix the piezo films 31C, 31R, 31L to the outer peripheral surface of the bumper cover 22, and it is not necessary to arrange the detection tube or the like in the bumper absorber 23 so as to extend in the vehicle width direction. Therefore, the pedestrian protection system 1 can be easily manufactured.

Further, the bumper cover 22 is usually made of a synthetic resin material, and even when the same impact is applied by the collision, the deformation amount Q may be reduced at a lower temperature than at a high temperature due to the nature of the material. . On the other hand, in the present embodiment, a voltage detection circuit 32 is provided as a collision determination adjustment unit that changes the detection sensitivity of the collision occurrence by the collision determination unit 64 based on the temperature T of the bumper cover 22. Therefore, even when the deformation amount Q of the bumper cover 22 is affected by the temperature T, the detection sensitivity of the collision occurrence is changed by the voltage detection circuit 32, so that the occurrence of the collision can be accurately detected. it can.
In the present embodiment, the collision detection adjusting unit corrects the piezo film voltage Vpz generated by the piezo films 31C, 31R, and 31L based on the temperature T of the bumper cover 22, and forms a detection voltage Vout. A circuit 32 is provided. Therefore, determination adjustment logic or the like is not required, and it is possible to accurately detect that a collision has occurred in the bumper cover 22 of the vehicle VE regardless of the variation in the temperature T of the bumper cover 22.
The voltage detection circuit 32 includes a variable resistance element that changes the thermistor resistance value Rthm according to the temperature T of the bumper cover 22, and a piezo film voltage Vpz is applied to the variable resistance element. Thus, the voltage detection circuit 32 cancels the increase in the piezo film voltage Vpz accompanying the increase in the temperature T of the bumper cover 22 by the increase in the thermistor resistance value Rthm. Therefore, it is possible to form the detection voltage Vout with little fluctuation due to temperature without requiring a temperature detection sensor, a resistance detection circuit of a variable resistance element, a temperature correction logic, and the like.
Further, by using the temperature sensitive thermistor 32a as the variable resistance element, the follower with respect to the temperature T of the bumper cover 22 is good, and the piezo film voltage Vpz can be reliably corrected.

In addition, piezoelectric films 31C, 31R, and 31L formed of thin films are used as the displacement-voltage conversion elements. Accordingly, the displacement-voltage conversion element can be easily attached to the bumper cover 22 with an adhesive or the like. Furthermore, since the piezo films 31C, 31R, and 31L have good followability with respect to the deformation of the bumper cover 22, the deformation amount Q of the bumper cover 22 can be accurately detected.
The piezo films 31C, 31R, and 31L are arranged on the bumper cover 22 so that a plurality of the piezo films 31C, 31R, and 31L are arranged in the vehicle width direction. A collision position detection unit 62 that detects the position in the vehicle width direction where the collision has occurred on the bumper cover 22 is provided based on the piezoelectric film voltage Vpz output by the piezoelectric films 31C, 31R, and 31L. In addition, a threshold value setting unit 63 that sets the voltage threshold value Vth according to the position in the vehicle width direction where the collision has occurred, detected by the collision position detection unit 62, is provided. Accordingly, the collision determination unit 64 can change the detection sensitivity of the collision occurrence according to the position in the vehicle width direction where the detected collision has occurred, and can accurately detect the occurrence of the collision in the bumper cover 22. Can do.
Further, the threshold value setting unit 63 sets the voltage threshold value Vth according to the position in the vehicle width direction where the collision has occurred. For this reason, it is possible to easily change the detection sensitivity of the occurrence of a collision according to the collision position without requiring a major hardware change such as a change in the shape of the bumper cover 22.

<Configuration of Embodiment 2>
A pedestrian protection system 1A according to the second embodiment will be described with reference to FIGS. As shown in FIG. 11, in the pedestrian protection system 1A according to the present embodiment, the pedestrian protection ECU 6A does not include the collision position detection unit 62 and the threshold setting unit 63. Therefore, in the present embodiment, the voltage threshold Vth is fixed, and the voltage threshold Vth is not varied according to the position in the vehicle width direction where the collision has occurred.
On the other hand, in the present embodiment, the plurality of piezo films 31C, 31R, and 31L have different piezo film voltages Vpz generated with respect to the deformation amount Q of the bumper cover 22 depending on the mounting position on the bumper cover 22. . As shown in FIG. 12, the piezo film voltage Vpz generated according to the deformation amount Q of the bumper cover 22 is set larger in the right piezo film 31R and the left piezo film 31L than in the central piezo film 31C. Has been.

On the other hand, in the first embodiment described above, the piezo film voltage Vpz with respect to the deformation amount Q of the bumper cover 22 is set to the same value among the plurality of piezo films 31C, 31R, and 31L. In FIG. 12, for the piezoelectric films 31C, 31R, and 31L according to the first embodiment, the piezoelectric film voltage Vpz with respect to the deformation amount Q of the bumper cover 22 is shown by a broken line as a uniform characteristic.
The piezo film voltage Vpz generated in the right piezo film 31R and the left piezo film 31L according to the present embodiment (shown by a solid line in FIG. 12) is larger than the piezo film voltage Vpz generated in the first embodiment. Further, the piezo film voltage Vpz (shown by a solid line in FIG. 12) generated in the central piezo film 31C according to the present embodiment is smaller than the piezo film voltage Vpz generated in the first embodiment. In this embodiment, since the other structure is the same as that of Embodiment 1, further description is abbreviate | omitted.

<Effects of Second Embodiment>
According to this embodiment, the plurality of piezo films 31C, 31R, and 31L have different piezo film voltages Vpz to be generated with respect to the deformation amount Q of the bumper cover 22 depending on the mounting position on the bumper cover 22. Thereby, the collision detection can be accurately performed regardless of the position in the vehicle width direction of the bumper cover 22 where the collision has occurred without providing the collision position detection unit 62 and the threshold setting unit 63.

<Other embodiments>
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows.
As the displacement-voltage conversion element, an organic actuator may be used in place of the piezo films 31C, 31R, 31L, piezoelectric ceramics and the like.
Further, as a variable resistance element having temperature characteristics, a resistance temperature detector, a linear resistor, or the like may be used instead of the thermistor 32a.
Further, any number of the piezo films 31C, 31R, 31L may be provided on the bumper cover 22, and four or more may be arranged in the vehicle width direction depending on the specification of the vehicle VE.
Further, in order to change the detection sensitivity of the collision occurrence in the bumper cover 22, it is not always necessary to take a method of correcting the piezo film voltage Vpz based on the temperature T of the bumper cover 22 and forming the detection voltage Vout. . For example, a collision in the bumper cover 22 is detected when the piezo film voltage Vpz generated by the piezo films 31C, 31R, and 31L is equal to or higher than the voltage threshold Vth. When the temperature T of the bumper cover 22 is low, the voltage threshold Vth may be made smaller than when the temperature T is high.

  In the drawings, 1, 1A is a pedestrian protection system (vehicle collision detection device), 5 is a pedestrian protection device (protection device), 21 is a front bumper (front part of the vehicle), 22 is a bumper cover, and 31C is a central piezo film. (Displacement-voltage conversion element), 31R is a right piezo film (displacement-voltage conversion element), 31L is a left piezo film (displacement-voltage conversion element), 32 is a voltage detection circuit (collision determination adjustment unit, voltage adjustment unit), 32a is a thermistor (variable resistance element), 62 is a collision position detection unit, 63 is a threshold setting unit, 64 is a collision determination unit, Q is a deformation amount of the bumper cover, Rthm is a thermistor resistance value, T is a temperature of the bumper cover, VE Is a vehicle, Vout is a detection voltage (correction voltage), Vpz is a piezo film voltage (output voltage), Vth1 is a first voltage threshold (voltage threshold), and Vth2 is a second voltage threshold. It shows the voltage threshold).

Claims (7)

A displacement-voltage conversion element (31C) which is attached to a bumper cover (22) provided in a front portion (21) of a vehicle (VE) and generates an output voltage (Vpz) corresponding to the deformation amount (Q) of the bumper cover. , 31R, 31L),
Based on the output voltage formed by the displacement-voltage conversion element, a collision determination unit (64) detects that a collision that requires the bumper cover to activate a protection device (5) that protects a collision object has occurred. )When,
A collision determination adjustment unit (32) that changes the detection sensitivity of the collision occurrence by the collision determination unit based on the temperature (T) of the bumper cover;
A vehicle collision detection device (1). The collision determination adjustment unit
A voltage adjustment unit (32) for correcting the output voltage generated by the displacement-voltage conversion element based on the temperature of the bumper cover;
The collision determination unit
A correction voltage (Vout) formed by correcting the output voltage by the voltage adjusting unit is compared with a predetermined voltage threshold value (Vth). When the correction voltage is equal to or higher than the voltage threshold value, the bumper cover The vehicle collision detection device according to claim 1, wherein the collision detection device detects that a collision has occurred. The voltage regulator is
A variable resistance element (32a) attached to the bumper cover and having a resistance value (Rthm) changed according to the temperature of the bumper cover and applied with the output voltage generated by the displacement-voltage conversion element; The vehicle collision detection device according to claim 2.   4. The vehicle collision detection device according to claim 3, wherein the variable resistance element includes a thermistor (32a).   The vehicle collision detection device according to any one of claims 1 to 4, wherein the displacement-voltage conversion element includes a piezo film (31C, 31R, 31L). The displacement-voltage conversion element is arranged on the bumper cover so that a plurality thereof are arranged in the vehicle width direction,
A collision position detector (62) for detecting a position in the vehicle width direction where a collision has occurred on the bumper cover, based on the output voltage output by the displacement-voltage conversion element;
A threshold value setting unit (63) for setting the voltage threshold value according to the position in the vehicle width direction where the collision occurred, detected by the collision position detection unit;
The vehicle collision detection device according to any one of claims 2 to 4, further comprising: The displacement-voltage conversion element is arranged on the bumper cover so that a plurality thereof are arranged in the vehicle width direction,
A plurality of the displacement-voltage conversion elements are:
The vehicle collision detection device according to any one of claims 1 to 5, wherein the output voltages generated according to the amount of deformation of the bumper cover are different from each other depending on a mounting position on the bumper cover.

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