GB2512179A

GB2512179A - Sensing device for detecting an impact with a vehicle

Info

Publication number: GB2512179A
Application number: GB1400628.2A
Authority: GB
Inventors: Dinesh Munjurulima; Mahendra Kurkuri; Parthiv Shah; Bernd Titz
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2014-01-15
Filing date: 2014-01-15
Publication date: 2014-09-24
Also published as: GB201400628D0

Abstract

The invention relates to a sensing device (14, figure 2) for detecting an impact with a vehicle, the sensing device comprising: at least one deformable element 16, wherein at least a portion of the deformable element has a hollow cross-section 18 containing a fluid; and at least one sensor (22) for sensing a pressure change resulting from a deformation of the deformable element due to an impact, wherein the hollow cross-section is variable. The deformable element may comprise an elastic tube which is located between a bumper cross-member (10, figure 1) and a foam element (20, figure 4) transversely across a vehicle. The hollow cross-section may have portions with different diameters D1-D5, where the diameter is increased at locations where the vehicle stiffness is high. In this way a substantially homogenous or uniform pressure signal can be provided at different locations along the deformable element. The sensing device may be used to trigger pedestrian protection devices in the event of an impact.

Description

Sensing Device for Detecting an Impact with a Vehicle The invention relates to a sensing device for detecting an impact with a vehicle according to the preamble of patent claim 1.

Sensing devices for detecting impacts with vehicles are well known from the mass production of passenger vehicles. Such a sensing device comprises at least one deformable element. For example, the deformable element is an elastic tube made of a plastic material, in particular rubber. At least a portion of the deformable element has a hollow cross-section containing a fluid. The fluid is, for example, a gaseous fluid, in particular air.

The sensing device also comprises at least one sensor for sensing a pressure change resulting from a deformation of the deformable element due to an impact. Usually, the deformable element is arranged in front of a cross member of a front bumper of the vehicle in the longitudinal direction of the vehicle. In case of an impact of a pedestrian with the bumper, the deformable element is deformed. This leads to a pressure change, in particular an increase of pressure inside the hollow cross-section. The pressure change can be detected by the sensor. For example, after detecting the pressure change a bonnet of the vehicle is moved upwardly from a first position into a protective position in the vertical direction of the vehicle. Thereby the pedestrian can be caught and supported by the bonnet in order to protect the pedestrian.

ER 1 769 976 Al shows an apparatus for sensing an impact with a vehicle. The apparatus comprises a crushable medium disposed between a vehicle body panel and a rigid frame element extending substantially parallel to said body panel. The apparatus further comprises an air channel in said crushable medium and an airflow sensor responsive to airflow within said air channel. Moreover, the apparatus comprises signal processing means for processing a signal produced by said airflow sensor to detect a body panel impact that displaces air within said air channel.

It is an object of the present invention to provide a sensing device by means of which an impact with a vehicle can be detected very advantageously.

This object is solved by a sensing device having the features of patent claim 1.

Advantageous embodiments with expedient and non-trivial developments of the invention are indicated in the other patent claims.

In order to provide a sensing device of the kind indicated in the preamble of patent claim 1, by means of which an impact with a vehicle can be detected very advantageously, according to the present invention the hollow cross-section of the deformable element is variable. This means the hollow cross-section varies, for example, along the longitudinal direction of the deformable element. In other words, the hollow cross-section of the deformable element has a first portion and at least one second portion abutting the first portion, wherein the second portion is different from the first portion. Thereby, an at least substantially homogeneous pressure change for impacts at different locations of the deformable element at a given impact velocity and energy can be achieved. In other words, the pressure change resulting from an impact at a given impact velocity and energy is at least substantially independent from the location where the impact and the resulting deformation occur.

Thus, the sensor can provide an at least substantially homogeneous or uniform pressure signal for impacts and deformations at different locations along the deformable element.

This helps build a robust pedestrian impact sensing algorithm. Thus, it is possible to distinguish between pressure changes resulting from impacts of pedestrians with the vehicle and pressure changes resulting from impacts of objects other than pedestrians.

Thereby, safety systems such as a movable bonnet and/or a pedestrian airbag can be activated only when the vehicle collides with a pedestrian. This activation can be avoided when the vehicle collides with a small object or an animal.

Further advantages, features and details of the invention derive from the following description of a preferred embodiment as well as from the drawings. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respective indicated combination but also in any other combination or taken alone without leaving the scope of the invention.

The drawings show in: Fig. 1 a schematic perspective view of a cross member of a passenger vehicle's front bumper; Fig. 2 a schematic perspective view of a deformable element of a sensing device for detecting an impact with the passenger vehicle, wherein at least a portion of the deformable element has a hollow cross-section containing a fluid; Fig. 3 a schematic perspective view of a bumper panel of the front bumper, the deformable element being arranged behind the bumper panel in the longitudinal direction of the vehicle; Fig. 4 partially a schematic and perspective sectional view of the cross member, wherein a foam element of the front bumper is arranged in front of the cross member in the longitudinal direction of the vehicle; Fig. 5 a schematic sectional view of the deformable element; and Fig. 6 a schematic sectional view of a tool for manufacturing the deformable element.

In the figures the same elements or elements having the same function are designated with the same reference sign.

Fig. 1 shows a cross member 10 for a front bumper of a passenger vehicle. In its mounting orientation in which the cross member is mounted on the body of the vehicle the cross member 10 extends at least substantially in the transverse direction of the vehicle.

For example, the cross member 10 extends at least substantially over the whole width of the passenger vehicle.

The front bumper also comprises a bumper panel 12 shown in Fig. 3. In its mounting orientation the bumper panel 12 is arranged in front of the cross member 10 so that the cross member 10 is covered by the bumper panel 12 in the longitudinal direction of the vehicle towards the front.

The passenger vehicle comprises a sensing device 14 shown in Fig. 2. The sensing device 14 serves for detecting an impact of a pedestrian with the passenger vehicle. For this purpose, the sensing device 14 comprises a deformable element in the form of an elastic tube 16 made of rubber. Thus, the tube 16 is elastically deformable. As can be seen in Fig. 5, the tube 16 has a hollow cross-section 16 which extends over the whole length of the tube 16. Thus, the tube is designed is an elastic hollow profile. With respect to the mounting orientation of the tube 16, the length of the tube 16 corresponds with the transverse direction of the vehicle. The hollow cross-section 18 contains a gaseous fluid in the form of air.

As can be seen in Fig. 4, the front bumper also comprises a foam element 20. The foam element 20 is attached to the cross member 10 and arranged in front of the cross member 10 between the cross member 10 and the bumper panel 12 with respect to the respective mounting orientation. The foam element 20 is used as an energy absorber. In case of an impact of a pedestrian with the front bumper, the bumper panel 12 and the foam element 20 are deformed. Thereby, impact energy is transformed into deformation energy especially by means of the foam element 20. Such an impact of a pedestrian with the front bumper can be simulated using a pole 21 shown in Fig. 3.

Furthermore, the sensing device 14 also comprises sensors 22 being arranged at respective ends of the tube 16. The sensors 22 are pressure sensors by means of which a pressure change inside the hollow cross-section 18 resulting from a deformation of the tube 16 due to an impact can be detected. As can be seen in Fig. 4, the tube 16 is arranged between the foam element 20 and the cross member 10 in the longitudinal direction of the vehicle. In case of an impact of a pedestrian with the front bumper, the tube 16 is also deformed. Due to this deformation the pressure inside the hollow cross-section 18 increases which can be detected by at least one of the sensors 22.

For example, the sensors 22 are connected to a control unit of the passenger vehicle, the control unit not being shown in the figures. When the sensors 22 detect an increase of pressure inside the hollow cross-section 18 due to an impact, the sensors 22 provide at least one signal characterizing the increase of pressure. The control unit is designed to receive the signal. Moreover, the control unit is connected to a safety system such as a movable bonnet and/or a pedestrian airbag of the passenger vehicle. When the control unit receives the signal, the control unit activates the safety system in order to protect the pedestrian colliding with the passenger vehicle.

For example, by activating the bonnet, the bonnet is moved upwardly from a neutral position into a protective position in the vertical direction of the vehicle by means of at least one actuator. The bonnet being in the protective position can catch and support the pedestrian, thereby protecting the pedestrian from colliding with components being arranged beneath the bonnet.

For example, by activating the pedestrian airbag, the pedestrian airbag is deployed.

Thereby, the pedestrian can be caught, supported and protected from hitting the bonnet directly by means of the airbag. Since the tube 16 extends at least over a major portion of the width of the passenger vehicle, impacts of pedestrians at different locations of the front bumper can be detected.

It is desirable to avoid erroneous activations of the safety systems so that the safety systems are activated only when an impact of a pedestrian with the front bumper occurs.

For example, in case of an impact of a small stationary object with the front bumper the activation of the safety systems is to be avoided since such an activation would be useless.

In order to keep the danger of erroneous activations of the safety systems particularly low and detect an impact of a pedestrian with the front bumper at different locations of the front bumper precisely and reliably, the hollow cross-section 18 is variable. As can be seen in Fig. 5, the hollow cross-section 18 varies along the longitudinal direction of the tube 16, i.e. along the width of the passenger vehicle.

The hollow cross-section 18 has five consecutive portions 24a-e. The second portion 24b abuts the first portion 24a in the longitudinal direction of the tube 16, i.e. in the transverse direction of the vehicle. The third portion 24c abuts the second portion 24b in the longitudinal direction of the tube 16. The fourth portion 24d abuts the third portion 24c in the longitudinal direction of the tube 16. And the fifth portion 24e abuts the fourth portion 24d in the longitudinal direction of the tube 16. The portions 24a-e each have an inner circumference in the form of a circle. Moreover, the portions 24a-e each have an inner diameter Dl -5. The first diameter Dl, the third diameter D3 and the fifth diameter D5 are equal. As can be seen in Fig. 5, the second diameter D2 is larger than the diameters Dl and D3-D5. Moreover, the fourth diameter D4 is larger than the diameters Dl, D3 and D5 but smaller than the second diameter D2.

By varying the inner diameter of the hollow cross-section 18, the hollow cross-section 18 can be adapted to the vehicle stiffness. In other words, the respective inner diameter D2 and D4 of the portions 24b and 24d of the tube 16 is increased to a respective desired value in comparison with the diameters Dl, D3 and D5 so that the inner diameter of the tube 16 is increased at locations where the vehicle stiffness is high in comparison with other locations corresponding with the portions 24a, 24c and 24d where the vehicle stiffness is low. Thus, the resulting compression of the air inside the tube 16 is uniform when impacts occur at different locations. This means the compression of air inside the tube 16 is at least substantially independent from the location at which the impact of the pedestrian with the front bumper occurs.

Thereby, an at least substantially homogeneous pressure increase can be measured by the sensors 22 for different impact locations. Hence, the sensors 22 can provide an at least substantially homogenous or uniform signal no matter where an impact of an object or a pedestrian with the front bumper occurs. Thus, impacts of pedestrians can be distinguished from impacts of objects other than pedestrians at almost any location of the front bumper at least.

Fig. 6 illustrates the manufacturing of the tube 16 having the different diameters D1-5. For example, in a first step, the tube 16 is provided with a uniform hollow cross-section 19 having the diameter Dl which is equal to the diameters D3 and D5. In a second step, the tube 16 having the uniform hollow cross-section 19 is inserted into a rigid die 26 of a tool.

In a third step, a hot fluid in the form of hot air is conveyed into the uniform hollow cross-section 19. The hot air is illustrated by directional arrows 28 in Fig. 6. By means of the hot air, the tube 16 is heated so that the tube 16 can be formed. Moreover, the tube 16 is blown up by means of the hot air so that the tube 16 is moved in contact with the die 26.

Thereby, the large diameters D2 and D4 of the portions 24b and 24d are manufactured so that the uniform hollow cross-section 19 is transformed into the non-uniform, variable hollow cross-section 18.

List of reference signs cross member 12 bumper panel 14 sensing device 16 tube 18 hollow cross-section 19 hollow cross-section foam element 21 pole 22 sensor 24a-e portion 26 die 28 directional arrows D1-5 diameter

Claims

Claims A sensing device (14) for detecting an impact with a vehicle, the sensing device (14) comprising: -at least one deformable element (16), wherein at least a portion of the deformable element (16) has a hollow cross-section (18) containing a fluid, and -at least one sensor (22) for sensing a pressure change resulting from a deformation of the deformable element (16) due to an impact, characterized in that the hollow cross-section (18) is variable.
2. The sensing device (14) according to claim 1, characterized in that the hollow cross-section (18) is variable along the longitudinal direction of the deformable element (16).
3. The sensing device (14) according to any one of claims 1 or 2, characterized in that the hollow cross-section (18) has a first portion (24a) with a first diameter (Dl) and at least one second portion (24b) abutting the first portion (24a), the second portion (24b) having a second diameter (D2) being different from the first diameter (Dl).
4. The sensing device (14) according to any one of the preceding claims, characterized in that the deformable element (16) is designed as a deformable tube (16).
5. A vehicle, in particular a passenger vehicle, comprising at least one sensing device (14) according to any one of the preceding claims.