This invention relates to the field of motor vehicle safety systems, more particularly, the present invention relates to the field of collision sensing and protection systems.

Background of the Invention

A conventional protection system for a vehicle includes a bumper mounted on a front and rear ends of the vehicle. The bumper is a shield made of steel, aluminum, rubber, or plastic. The bumper absorbs the shock to prevent or reduce the damage to the vehicle, when a low speed collision occurs. Some bumpers also use energy absorbers or brackets and others make use of foam cushioning materials for shock absorption.

The bumpers are designed to prevent or reduce the physical damage to the front and rear ends of the passenger motor vehicles in case of collisions. The bumpers are designed to protect a hood, a trunk, a grille, a fuel supply system, an exhaust system and cooling systems of the vehicle. Further, the bumpers ensure safety of equipment such as parking lights, headlamps and tail lights of the vehicle, in case of collisions. Furthermore, the bumpers absorb and dissipate most of the energy of the collision, thereby keeping the occupants of the vehicle safe by preventing the shock of the collision from reaching the occupants of the vehicle. More specifically, the bumpers ensure safety to the components and occupants of the vehicles, by using the method of reducing the G loads (Gravitational loads) applied to the components and the occupants by absorbing specific amount of energy during a vehicle collision. In recent times, the bumpers are also being designed to reduce the injury caused to the pedestrians colliding with the vehicle during an accident. To meet the energy absorption needs, numerous cores (foam, metal etc) have been used inside the bumpers. Apart from ensuring the safety, bumpers are also used to detect possibility of a crash as well as severity of the crash. Several types of sensors including force, acceleration, velocity and displacement sensors can be embedded in the bumper for this purpose. Electronic circuitry associated with the sensors send out signals to control units for various safety purposes including airbag deployment inside the vehicle. Different types of crash sensors such as piezoelectric, mechanical, magnetic, acoustic and wire crash sensors have been mounted on the bumpers of the earlier inventions to detect the nature of the crash and the collision status.

For example, United States Patent No. 3830329, issued on August 20, 1974 discloses a sensor with a damper, a piston and a cylinder mounted to the vehicle body or the bumper for absorbing the energy upon a collision. More specifically, the crash sensor has a damper mounted to the vehicle body or bumper for absorbing the energy upon collision. The damper has a cylinder and a piston, which sealingly enclose various gas or liquid for effecting damping. The means for sensing the collision has a coil and a magnet, which are connected to the cylinder and piston of said damper. When the vehicle collides, the crash, attenuated by the damper upon collision, is indicated by means of a voltage produced by the coil and magnet with the strength of the crash indicated by the value of the voltage which is proportional to the speed at which the coil crosses the magnetic flux of the magnet as either the coil or magnet moves. When the strength of the crash that is the voltage exceeds a predetermined value, a safety device such as, for example, ON-OFF operation of an air bag ignition circuit is operated. However, the crash sensor disclosed herein is inefficient, further the crash nature indicating system incorporates an expensive crash sensor.

United States Patent No. 4842301, issued on June 27, 1989 describes an apparatus welded to a unit body structure with an acoustic sensor near the front of each side rail which detects the acoustic vibrations due to metal deformation in a frontal crash. The signals are processed by a filter and an appropriate circuitry generates a crash signal to activate an occupant restraint system.

United States Patent No. 4995639, issued on February 26, 1991 shows a sensor that is operative to determine when and if a crash is severe enough to deploy the passive restraint system (e.g. airbag or seat belt tensioner) of the vehicle. The sensor is responsive to trigger the passive restraint system when the vehicle impact with a barrier causes vehicle elements in the crush zone to deform as far back as the sensor position.

United States Patent No. 5206469, issued on April 27, 1993 disclose a crash sensor that includes a magnet, a sensing mass attractable by the magnet and a sleeve restricting the movement of the sensing mass in one direction, a pair of strips that make a closed circuit by contact with the sensing mass having moved in one direction and a body fitted with the magnet and housing the sensing mass, the sleeve and the contacts; the crash sensor further comprising a magnetic shield made of a ferromagnetic material and covering the magnet and the body. The magnetic shield forms a closed-type magnetic field by covering the magnet and the body and forms an appropriate magnetic loop in the vicinity of the sensing mass, so that the crash sensor also acts as a magnetic shield to protect itself from being influenced by outside ferromagnetic bodies and makes effective use of the magnetic force of the magnet. The above pair of strips is fitted in the same direction vertically on the inner wall of the body, whereby they do not project out in the axial direction so that the crash sensor can be of a reduced whole length, as well as of smaller outside diameter than conventional crash sensor with its contacts positioned facing each other.

Similarly, United States Patent No. 5335749 issued on August 9, 1994 describes a crash detection sensor arranged in a door of a vehicle with a supporting member which has sufficient strength to maintain the sensor's state under normal conditions, but under shocks larger than a predetermined level, a first electrode and a second electrode are brought into contact, thereby allowing the lateral impact to be detected at the door.

United States Patent No. 5389751 issued on February 14, 1995 mentions a vehicle crash detecting sensor. The vehicle crash detecting sensor is having a pivoted sensing mass which rotates, in response to vehicle deceleration occurring in a crash of a vehicle, from an at-rest position through a second position of rotation at which time airbag deployment is enabled and then the mass is intentionally rotated through to a third (long dwell) position at a rotational angle much larger in magnitude and in the same direction as that of the second position. The sensing mass is spring biased to always bias the mass during rotation to the at-rest position regardless of the dwell angle of the mass during rotation. By appropriate configuration of the inner wall of the housing to which the other end of the spring, typically an elastic, a spring, is attached, the part of the spring which touches the wall can be controlled and thereby ensuring that the direction of the torque is always the same,- that is, towards the at-rest position.

United States Patent No. 5777225 issued on July 7, 1998 discloses a crash sensor that facilitates inflation of the airbags. The crash sensor includes an accelerometer, a calculation device, a comparator, a trigger circuit, a physical quantity calculation device, and an adjusting device. The accelerometer develops an acceleration signal and the calculation device calculates a first value corresponding to a magnitude of deceleration based on the acceleration signal. The comparator compares the first value and the trigger circuit actuates a protective device, such as an air bag upon receiving the trigger signal from the trigger circuit. The physical quantity calculation device calculates a magnitude of physical quantities in a wave defined by acceleration signals during an initial stage of a crash. The adjusting device adjusts at least one of the first value corresponding to the magnitude of deceleration and the threshold value used by the comparator on a basis of the magnitude of physical quantities.

United States Patent No. 6206129 issued on March 27, 2001 describes a crush detecting device with an electrically conducting tube having an electrically conducting rod concentrically positioned inside the tube. The electrically conducting tube is deformed during a vehicle crash by a force greater than a predetermined magnitude which causes the tube to contact the rod in response to the crush of a vehicle. The crush sensor is mounted at the rear boundary of the Crush Sensor Zone of the vehicle for frontal and rear impacts and in the door or other appropriate side position for side. The sensor is used to sense crashes for the deployment of automobile passive restraint systems such as airbags.

United States Patent Application No. 20040129479 issued on July 8, 2004 discloses a methodology to detect the different collision states. The methodology makes use of the front vehicle structural section, a tension member, the left and right tensile force sensors and a collision state identifying section for this purpose.

United States Patent No.US6832145 issued on December 14, 2004 discloses a Pedestrian collision protection system and collision site detecting apparatus for use in vehicle. The pedestrian collision protection system in the form of a line sensor, includes a first and a second conductive line fixedly secured onto a front surface or rear surface of the vehicle to extend in lateral directions of the vehicle and placed to be separated from each other by a predetermined spacing in longitudinal directions of the vehicle, with at least one of the conductive lines being elastically deformed at a position of a collision against a body to be restorable to make an electrical connection with the other conductive line. The apparatus simultaneously detects a collision against a pedestrian and the position of the collision on the basis of a current flowing in the conductive lines or a voltage drop therein. The Pedestrian collision protection system disclosed herein incorporates a complex mode for collision sensing. United States Patent Application No. 20060017295 issued on January 26, 2006 describes a method for sensing impact between a vehicle and a pedestrian using an optical fiber array that runs along the bumper. During a crash, the fibers are distorted, thereby modulating the light which is received by a signal processor to generate an output.

United States Patent No. 7036621 issued on May 2, 2006 describes a pedestrian collision system. The pedestrian collision system works to distinguish between impacts with pedestrians and other sorts of impacts using a combination of a collision duration for which a sensor continues to sense a physical impact arising from collision with an object and a time- sequential change in locations of collisions of the vehicle with objects.

United States Patent No. 7104354 issued on September 12, 2006 describes a vehicle collision state detecting device. The vehicle collision state detecting device is configured to provide an extremely effective collision protection by identifying a wide range of collision states. The vehicle collision state detecting device basically comprises a front vehicle structural section, a tension member, left and right tensile force sensors and a collision state identifying section. The front vehicle structural section has a predetermined collision collapsing characteristic. The tension member has a prescribed initial tensile force extending in a width-wise direction of the front vehicle structural section. The tensile force sensors measure left and right tensile forces of the tension member. The tension member and the tensile force sensors form a collision sensing device in one possible embodiment. The collision state identifying section identifies a collision state of the vehicle; At least one passenger restraining device is activated differently depending on the detected collision state identified by the collision state identifying section.

United States Patent Application No. 20060241834 issued on October 26,

2006 describes a piezoelectric sensor that does a wavelet analysis and compares the output from the piezoelectric sensor to reference values which are stored in the vehicle to determine if the vehicle has crashed or not.

United States Patent No. 7131512 issued on November 7, 2006 discloses a device with a crash box having a rod and magnets which are arranged in a frame to detect a collision. More specifically, a low-rigid portion and the crash box are arranged ahead of a high-rigid portion in a front portion of the frame. The front end of a rod is fixed to a bumper. The rod is inserted into a magnetic detector disposed on the high-rigid portion. In the rod, a number of magnets are aligned in the longitudinal direction of the rod such that their N poles and S poles are alternatively arranged. As a vehicle collides, the crash box is first deformed so that the rod moves backward, whereby a collision can be detected before large acceleration is generated.

United States Patent Application No. 20070046044 issued on March 1, 2007 discloses an apparatus which detects an impact load and a control unit determines the object which had collided with the bumper. More specifically, the collision object discrimination apparatus for a vehicle has a bumper absorber, a bumper reinforcement member, a support member, a load detection unit and a control unit for discriminating a sort of object colliding with a bumper based on a load detected by the load detection unit. The load detection unit has a first end and a second end opposite to each other. The first end is connected to the bumper reinforcement member and the second end is connected to the support member. Further, the load detection unit is disposed such that at least a part of the load detection unit is located inside of the bumper reinforcement member.

United States Patent No. 7364222 issued on April 29, 2008 describes a collision sensor system that uses a wire that runs longitudinally on the bumper. The deformation of the wire is sensed by the circuitry to determine whether the vehicle is experiencing a crash.

Further, a large number of prior art disclosed bumpers designed to absorb certain amount of energy and thereby reduce the impact of a collision to the passengers and also reduce the level of damage caused to the vehicle. Different types of bumper support structures have also been used in the earlier inventions.

For example, United States Patent No. 5732801, issued on March 31, 1998 describes a replaceable energy absorbing bumper support structure that has hollow indented cylinders for initiating an indented buckling pattern during the crush of the cylinder.

United States Patent No. 6082792, issued on July 4, 2000 discloses an energy absorbing bumper having corrugated members and longitudinally extending adjacent members with ribs. More specifically, the energy absorbing bumper includes an elongated energy absorber comprising forwardly projecting corrugated members and an adjacent members which extend in a longitudinally direction with a plurality of ribs extending in a direction transverse to the longitudinal direction for joining the corrugated member to the adjacent member comprised of an elastomeric material whereby said longitudinal members create hollow sections which are adapted for controlled collapse upon impact for absorbing energy. The plurality of ribs is additionally adapted for controlling the collapse of said hollow sections and stretch upon impact for additional energy absorption.

United States Patent No. 6406079, issued on June 18, 2002 discloses an automobile bumper core comprising a surface wall, rear wall and a pair of side walls, wherein the core is embedded inside the bumper face. The automobile bumper core disclosed herein provides greater impact absorbing qualities from impact forces. The core (3) comprises a surface wall (8) and an opposing rear wall (9), with a pair of opposing side walls (7). In one embodiment there are a plurality of ribs (10) and a plurality of hollow portions (6) between the surface wall (8) and the rear wall (9). The bumper core is intended to lie disposed inside the bumper fascia (2) and the resulting bumper is attached to the automobile.

United States Patent No. 6561301 issued on May 13, 2003 disclose a collision discriminating apparatus that uses a complex collision detection sequence and algorithm. More specifically, the discriminating apparatus for vehicles include a collision detection device mounted on a part of the vehicle to detect the deformed amount of a collided portion deformed by collision of a collision object against the vehicle, and a collision object presuming device for presuming what object collided against the vehicle on the basis of the deformed amount of the collided portion detected, and the vehicle speed when the vehicle collided. United States Published Patent Application No. US20030215285 issued on November 20, 2003 disclose collision detection, energy absorption method and mounting configuration that are complex and costly. More specifically, a crash cushion disclosed herein includes a frame that forms at least two bays arranged one behind another in an anticipated impact direction. The frame includes at least three transverse frames and side frames extending between adjacent transverse frames. Each of the side frames is outwardly bowed and includes first and second side frame elements coupled to the respective transverse frames, and a hinge coupled between the first and second side frame elements. At least one energy absorbing element is disposed in one of the bays, and at least first and second restraints are coupled to the side frames to resist movement of the hinges at an early stage in an impact event. The crash cushion is partially collapsed automatically as the crash cushion is raised from a horizontal to a vertical position, and then extended automatically to its operational position as the crash cushion is lowered from the vertical to the horizontal position. The energy absorbing elements can include tapered frusto-conical sheet metal elements that are stacked with the smaller ends facing first and second opposed sides of the energy absorbing element.

Crush tube assemblies have been disclosed in United States Patent No. 6715593, issued on April 6, 2004 where a concentric arrangement of convoluted tubes is used to absorb the impact energy.

United States Patent No. 6877785 issued on April 12, 2005 discloses a bumper with a beam and energy absorbers which include tubular structural columns extending from a front wall to a rear beam wall. United States Patent No. 7073831 issued on July 11, 2006 describes a tubular bumper beam with a crush cone, ridged horizontal channels and recesses acting as additional energy absorbers.

All the above mentioned disclosures disclose collision sensor and protection systems that employ costly sensors and energy absorbing and dissipating means that make the systems costly to implement. Therefore, there is felt a need for a collision sensing and protection system which can be designed and built using inexpensive mechanical elements, implement a predetermined crushing pattern, can reliably detect both low and high speed collisions, compute the severity of collisions and accordingly trigger a occupant safety system such as deployment of an air bag.

OBJECTS OF THE INVENTION

An object of the present invention to provide a collision sensing and protection system that can be designed and built using inexpensive mechanical elements.

Another object of the present invention to provide a collision sensing and protection system that can detect both low and high speed collisions.

Yet another object of the present invention to provide a collision sensing and protection system which can compute severity of collisions.

One more object of the present invention is to provide a collision sensing and protection system which can implement a predetermined crushing pattern. Still another object of the present invention is to provide a collision sensing and protection system that ensures occupant safety.

Another object of the present invention is to provide a collision sensing and protection system that is reliable and accurate.

Yet another object of the present invention is to provide a collision sensing and protection system that simultaneously achieves energy absorption and collision detection.

Another object of the present invention is to provide a collision sensing and protection system that may be modified to suit different class of vehicles by altering the number of crush tubes or pattern of mounting or altering the size of the crush tubes.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a passive collision sensing and safety system for an automobile. The collision sensing and safety system for an automobile includes a bumper element fitted to at least a front end of the automobile. The bumper element includes a front face and a rear face. The front face of the bumper element includes a first frangible elongate element fixed thereto. The rear face of the bumper element includes a second frangible elongate element fixed thereto. The collision sensing and safety system for an automobile further includes a first electrical circuit and a second electrical circuit. The first electrical circuit is adapted to co-operate with the first frangible elongate element and sense breakage of the first frangible elongate element due to a collision. Similarly, the second electrical circuit is adapted to co-operate with the second frangible elongate element and sense breakage of the second frangible elongate element due to the collision. The collision sensing and safety system for an automobile also includes an Electronic Control Unit (ECU) and atleast one occupant safety device. The Electronic Control Unit (ECU) co-operates with the first electrical circuit and the second electrical circuit to determine severity of the collision based on time-delay between breakage of the first and second frangible elongate elements. The deployment of the occupant safety device is triggered by the ECU based on severity of the collision and other variables.

Typically, the front face and the rear face of the bumper element defines a hollow core there-between, the hollow bumper element is adapted to absorb energy of collision by getting deformed.

Alternatively, the bumper element is configured by joining a pair of C- sections.

Preferably, the core of the hollow bumper element includes a plurality of hollow crush tubes angularly extending between the interior surfaces of the front face and the rear face of the bumper element.

Typically, atleast one of the plurality of hollow crush tubes is perpendicularly extending between the interior surfaces of the front face and the rear face of the bumper element. Preferably, the hollow crush tubes are of round, square, rectangular or any other cross-section.

Additionally, the hollow crush tubes are of mild steel or aluminum.

Typically, each of the plurality of hollow crush tubes includes atleast one notch provided along a length thereof to initiate a pre-determined crushing pattern.

Furthermore, the first elongate element and the second elongate element are rods made of electrically conducting material.

Preferably, the first elongate element and the second elongate element are rods made of copper, brass or aluminum.

Additionally, the first elongate element and the second elongate element are provided with notches to pre-define point of failure-initiation thereon.

Preferably, the first elongate element and the second elongate element are respectively connected end-to-end to the front face and the rear face of the bumper element.

Typically, the first elongate element is supported along the front face of the bumper element, at regular intervals by a plurality of clamps.

Also typically, the second elongate element is supported along the rear face of the bumper element, at regular intervals by a plurality of clamps. Preferably, the clamps are made of insulated material, typically nylon.

Specifically, the notches provided on the first elongate element and the second elongate element are of U type or V type and are designed to ensure breaking thereof at correct levels of stress.

Typically, the front face and the rear face of the bumper element are made of a material stiffer than the material used to form the plurality of crush tubes.

Typically, the front face and the rear face of the bumper element are of aluminum or steel or a fiber reinforced plastic.

Particularly, the triggering of the first electrical circuit is based on breakage of the first frangible elongate element.

Also, the triggering of the second electrical circuit is based on breakage of the second frangible elongate element.

Typically, the occupant safety device is an airbag.

Typically, the ECU determines the severity of the collision based on an input from a vehicle speed sensor and also from the input provided in conjunction with other sensor systems such as accelerometer and bumper sensor rod system.

Additionally, the ECU is adapted to receive inputs from a seat belt sensor regarding the seat belt being in a buckled or an un-buckled configuration. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The collision sensing and protection system will now be described with reference to the accompanying drawing, in which:

Figure 1 illustrates the block diagram of the collision sensing and protection system in accordance with the present invention;

Figure 2(a) illustrates different views of the bumper element along with an arrangement of a front notched rod secured to a front face of the bumper element;

Figure 2(b) illustrates different views of the bumper element along with an arrangement of a rear notched rod secured to a rear face of the bumper element;

Figure 3 illustrates various structural elements of the bumper element in accordance with the present invention;

Figure 4 illustrates an exploded view of the bumper element in accordance with the present invention;

Figure 5 (a) illustrates different views of crush-tubes of a bumper element in accordance with another embodiment of the present invention, wherein the crush tubes of the bumper element are surrounded by a reinforcement material; Figure 5(b) illustrates a view of crushed crush-tubes of the bumper element of Figure 5 (a), wherein the crushed crush-tubes are surrounded by a reinforcement material;

Figure 6(a) illustrates a single crush-tube of the plurality of crush tubes, the crushed crush-tube and the associated load-displacement curve in accordance with the present invention;

Figure 6(b) illustrates the finite element analysis result of a single tube crushing along with the load-displacement curve in accordance with the present invention;

Figure 6(c) illustrates several deformed crush-tubes and the associated load- displacement curve in accordance with the present invention; and

Figure 7 illustrates the functional block diagram illustrating the method followed to detect and compute the severity of the collision by the Electronic Control Unit (ECU) in accordance with the present invention.

Detailed Description of the Accompanying Drawings

The drawings and the description thereto are merely illustrative of a collision sensing and protection system and only exemplify the system of the invention and in no way limit the scope thereof. In accordance with the present invention, a combination of a pair of frangible elongate elements in form of notched sensor rods, a plurality of crush tubes, a bumper element and associated circuits acting as passive sensors work together to determine whether the vehicle is experiencing a low speed crash or a high speed crash. The bumper core consists of crush tubes which act as energy absorbing materials. An electronic control unit (ECU) receives signals from the associated circuits acting as passive sensors and depending upon the signals received, the ECU decides whether to deploy an airbag or not.

Referring to the accompanying drawings, Figure 1 illustrates the block diagram of the collision sensing and protection system, indicated by the reference numeral 10. The main components of the system are a first frangible elongate element also called a front sensor rod 11, a second frangible elongate element also called a back sensor rod 12, a vehicle speed sensor 13, a seat belt sensor 14, an electronic control unit (ECU) 15 and a protection device 16. As is clear from the block diagram, inputs from the front sensor rod 11, back sensor rod 12, the vehicle speed sensor 13, and the seat belt sensor 14 are processed by the electronic control unit (ECU) 15 and the electronic control unit 15 controls the triggering of the protection device 16, based on outcome of the processing done at the electronic control unit (ECU) 15.

The front sensor rod 11 and the back sensor rod 12 are electrically active and are notched. The front sensor rod 11 and the back sensor rod 12 are made of copper, brass, aluminum or any other good electrical conducting material. The front sensor rod 11 is mounted on the bumper front plate and the back sensor rod 12 is mounted on the bumper back plate, the front sensor rod 11 and the back sensor rod 12 run along a length of the bumper element. The core of the bumper between the front and the back plates include a plurality of crush tubes made up of mild steel or aluminum or any other suitable material. These crush tubes are designed to absorb a specific amount of energy. The vehicle speed sensor 13 scans the speed of the vehicle continuously and feeds this crucial data to ECU 15. The seat belt sensor 14 is mounted on the buckle of the seat belt of the vehicle. The seat belt sensor

14 is turned on, when the vehicle is started. If the seat belt is not buckled properly within a preset period of time, the electronic control unit (ECU) 15 raises an alarm or a light signal. The protection device 16 is typically an air bag.

In the event of a low impact the front notched sensor rod 11 will be broken and the ECU 15 will sense the breakage. However, the crush tubes inside the bumper and disposed between the front notched sensor rod 11 and the back sensor rod 12, will absorb all the energy and the back sensor rod 12 attached to the bumper back plate will remain intact. In the event of a higher impact collision, the front notched rod 11 will be broken and again the ECU 15 will sense the breakage. But, the crush tubes can only absorb a certain percentage of the energy of the high impact collision and will transfer the remaining energy to the vehicle chassis (crush can), through the bumper back plate 32, the back sensor rod 12, there by breaking the back sensor rod 12. The ECU

15 will sense the breaking of both the front sensor rod 11 and the back sensor rod 12 and then computes the time delay between the two events, i.e. breaking of the front notched sensor rod 11 and breaking of the back sensor rod 12 to determine the severity of the collision (low, high or severe). The front sensor rod 11 and the back sensor rod 12 are connected to the ECU 15 through wires with appropriate electrical connectors.

Referring to Figure 2(a) and Figure 2(b), the bumper element 300 used in the collision sensing and protection system is illustrated. The bumper element 300 includes a front face or front plate 31 and a rear face or rear plate 32. The front face 31 and the rear face 32 of the bumper element 300 defines a hollow core there-between, the hollow bumper element 300 is adapted to absorb energy of collision by getting deformed. More specifically, the bumper element 300 is configured by joining a pair of C- sections. The front notched rod 11 (one attached to the front plate 31 of the bumper, shown in Figure - 2(a)) and the back sensor rod 12 (attached to the back plate 32 of the bumper, shown in Figure— 2(b)) collectively act together to determine whether the vehicle is experiencing a collision or not.

The rods 11 and 12 are supported on the front face 31 and rear face 32 respectively of the bumper element 300. The rods 11 and 12 are supported at regular intervals by means of clamps which keep the rods in position. The rods extend from one extreme end to another extreme end of the bumper element. The clamps are adapted to properly insulate the rods 11 and 12 from the bumper element 300 to avoid shorting. Accordingly, the clamps used for supporting the rods 11 and 12 on the front and rear face of the bumper element are made of an insulating material, typically nylon. Figure 2(a) illustrates one clamp 101 of the plurality of clamps used for supporting the rod 11 on the front face 31 of the bumper element 300. The front sensor rod 11 and the back sensor rod 12 are provided with notches. The notches on the rods 11 and 12 act as stress raisers. Different types of notches (V, U and the like) can be used, after accurate calibration, to ensure the breakage of the sensor rods at the correct level of stress.

Figure 3 illustrates the various structural elements of the bumper element in accordance with the present invention. The bumper front plate and back plate are indicated by reference numerals 31 and 32 respectively. The bumper front plate 31 and the bumper back plate 32 are rigid plates which help in transferring the load to and from the crush tubes 33. The bumper front plate 31 and back plate 32 are relatively stiff members when compared to the crush tubes 33. The bumper front plate 31 and the bumper back plate 32 are made of aluminum or any other light weight material like fiber reinforced plastic (FRP).

Figure 4 illustrates an exploded view of the bumper element 300 in accordance with the present invention. The plurality of crush tubes 33 sandwiched between the bumper front plate 31 and back plate 32 are designed to absorb a specific amount of energy due to the crushing. The hollow crush tubes 33 are angularly extending between the interior surfaces of the front face 31 and the rear face 32 of the bumper element 300. The hollow crush tubes 33 are angularly disposed to take care of collisions occurring at an angle. However, atleast one of the plurality of hollow crush tubes 33 is perpendicularly extending between the interior surfaces of the front face 31 and the rear face 32 of the bumper element 300 to take care of a head on collision. . Also in another configuration the hollow crush tubes 33 are placed inside a reinforcement material 35 which may be foam or any other suitable soft material in order to absorb more energy and offset impact forces, as illustrated in Figure 5(a) and Figure 5(b). The impact of the collision gets transmitted to the bumper back plate 32 only after some energy is absorbed by the crush tubes 33 and some energy by the reinforcement material 35. The crush tubes 33 are welded or glued onto the back plate 32. The crush tubes 33 can be arranged in different forms to satisfy the energy absorption requirement for different vehicles. The crush tubes 33 are typically having square shaped cross-section. But crush tubes 33 having round, rectangular or any other cross-sections can also be used. Typically, the crush tubes 33 are made of aluminum and with a length of 25 mm to 50 mm. The crush tubes 33 can also be made of any other metal. The length of the crush tubes 33 can also be varied based on the bumper shape, size and the like for a given vehicle. To initiate a predetermined crushing pattern, the crush tubes 33 are notched. Notches placed at various locations along the crush tubes 33 determine the failure initiation. During the impact of the vehicle, the bumper core acts as an energy absorber. In the present invention, the core absorbs only enough energy to determine whether the vehicle is experiencing a low speed collision or a high speed collision. The other important parts of the bumper are a tube support plate 34, the bumper front plate 31, the front sensor rod 11 and the back sensor rod 12. The crush tubes 33 are welded or glued to the tube support plate 34 (made of aluminum) and then riveted to the bumper back plate 32. The bumper front plate 31 and the bumper back plate 32 are held in position by a welding process along the periphery of the front and back bumper plates.

Figure 6(a) illustrates the original single crush tube 51 of the plurality of crush tubes 33 and the crushed crush-tube 52 along with load-displacement curve 53. The area under the curve 53 determines the amount of energy absorbed by one crushed tube 52. Figure 6(b) illustrates the finite element analysis results of a single tube crushing 54 along with the load- displacement curve 55. Figure 6(c) illustrates the several deformed tubes 56 and the associated load-displacement curve 57. These experiments are conducted to measure energy absorbed by a single tube as well as by an array of tubes. The arrangement of tubes in the actual bumper is based on finite element analysis.

In accordance with another aspect of the present invention, the ECU is a part of an electronic circuit consisting of the notched rods, wire harness, the ECU and an ignition circuit. The ECU takes the decision regarding whether the vehicle is experiencing a high speed crash or not when both the notched rods mounted on the bumper front and back plates get broken. The ECU will compute the time delay between the breakage of the rods at a given vehicle speed based on the input from the vehicle speed sensor and other decision making parameters. This information is used to trigger an airbag (protection device) by the ignition circuit.

Figure 7 illustrates the functional block diagram that illustrates the method followed to detect and compute the severity of a collision by the ECU. The electrical continuity for the bumper front plate sensor rods and the bumper back plate sensor rods and the vehicle speed are always scanned. Also the seat belt open/close conditions are scanned. During the occurrence of an impact, the electrical continuity for both the bumper plate sensor rods will be disturbed. In case of the impact due to a low speed collision, the crush tubes in the bumper will absorb the energy and the electrical continuity of the back plate sensor rod will not be broken. In case of the impact due to a high speed collision, bumper will experience a complete crush and the electrical continuity of both the front and back bumper plate sensor rods will be broken. The ECU will then compute the time delay between the two continuity breaking events along with the inputs from the vehicle speed sensor and the seat belt sensor and then determine the severity of the impact. Then, the ECU will trigger an airbag (or any protection device) by sending a signal to the ignition circuit depending upon the severity of the impact.

TECHNICAL ADVANCEMENTS

The technical advancements of the present invention include realization of a collision sensing and protection system which can:

• be designed and built using inexpensive mechanical elements;

• capable of detecting both low and high speed collisions;

• capable of computing the severity of collisions;

• implement a predetermined crushing pattern; and

• Energy absorbing crush tubes placed inside the bumper element are surrounded by another high energy reinforcement material such as foam in order to absorb higher impact forces and offset impacts

The numeral values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention and the claims unless there is a statement in the specification to the contrary. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.