Safety device in vehicle

Abstract

A safety device for a safety device in a vehicle is provided. The safety device (100) comprises: a housing (1) having a first end (2) and a second end (3); a piston (4) adapted to be fitted in the housing (1) and configured to move from a retracted position to an extended position; and a gas generator (15). The piston (4) has a first end forming a pressure surface (6) facing the first end (2) of the housing (1). A gas chamber (8) is formed between the pressure surface (6) of the piston (4) and the inner wall (7) of the housing (1), and the gas generator (15) is located in the gas chamber (8). The housing (1) comprises, at its second end (3), a gas discharge arrangement (20, 20 ', 20' ') which allows the gas generated by the gas generator (15) to be discharged from the gas chamber (8) when the piston (4) is in a fully or substantially fully extended position.

Description

Technical Field

[0001] The present invention relates to a safety device in a vehicle. Background Art

[0002] It is known in the art that actuators are used in safety devices in motor vehicles, these actuators are formed by pistons, which are moved from a retracted position to an extended position by gas generated by a gas generator. One example is the use of a hood lifter to lift the hood or bonnet of a vehicle in order to provide protection for pedestrians hit by the vehicle. It has been observed that if a motor vehicle hits a pedestrian, the bumper of the vehicle will often hit the legs or lower torso of the pedestrian. Therefore, the legs of the pedestrian will usually be pushed in the direction of travel of the vehicle, and the head and upper torso will usually tilt towards the hood and windshield of the vehicle. This tilting movement often causes the head or upper torso of the pedestrian to first contact the hood, and thereafter, if the impact force from the impact is strong enough and the vehicle continues to move forward, it also contacts the windshield. In order to minimize the damage to pedestrians caused by such impacts as described above, motor vehicles are often provided with so-called hood lifting arrangements. These arrangements are usually configured so that the rear part of the hood (i.e., the part closest to the windshield) is lifted by one or more actuators. In the event of a vehicle striking a pedestrian, the hood will generally provide an effective, flexible impact energy absorbing structure. However, if the hood is not raised, there is a higher risk that the hood will deform to the extent that hard, non-flexible parts beneath the hood (e.g., the engine block) come into contact with the hood and an undesirable, rigid impact may result from a collision between the pedestrian and the vehicle. In addition, the raising of the rear portion of the hood will further tilt the surface of the hood and help reduce the speed at which the body moves toward the windshield. In addition, the smaller acute angle between the windshield and the hood will also help to reduce the severity of a person being struck by a vehicle.

[0003] In order to provide effective protection, it is important to perform the lifting quickly. However, it is also necessary to easily maneuver the motor vehicle after an accident, for example to allow it to be driven to the nearest garage or towed in a safe manner if possible. This requires that the hood can be pushed back manually to allow free viewing on the driver's seat. This involves that the force required to push the piston back towards its retracted position should not be too high. For this purpose, gas chambers with exhaust are known, wherein the exhaust holes are arranged in the bottom end of the housing, i.e. opposite to the pressure surface of the piston. However, there is the problem that such exhaust leads to an undesirable leakage flow of the generated gas and thereby places the piston from the retracted position to the extended position more slowly. Therefore, there is a need for an improved actuator, which allows the piston to be placed more forcefully and quickly and easily pushed back when the actuator is actuated. Actuators of this type can also be used in other safety systems of vehicles (such as seat belt pretensioners), and in such applications, it is important to have fast actuation. Summary of the invention

[0004] One object of the present invention is to provide a safety device in a vehicle which allows, in the event of a deployment of the gas generator, to more quickly place the piston from a retracted position into its fully extended position and thus activate the safety device.

[0005] Another object of the invention is to provide a safety device which allows to easily push the piston back towards its retracted position.

[0006] These and other objects that will be apparent from the following summary and description are achieved by a safety device in a vehicle, the safety device comprising: a housing having a first end and a second end; a piston adapted to fit in the housing and configured to move from a retracted position to an extended position; and a gas generator, wherein

[0007] The piston has a first end forming a pressure surface facing the first end of the housing;

[0008] A gas chamber is formed between a pressure surface of the piston and an inner wall of the housing, and a gas generator is fluidly connected to the gas chamber; and wherein

[0009] The housing comprises a gas exhaust arrangement at a second end thereof, which allows gas generated by the gas generator to be exhausted from the gas chamber when the piston is in a fully or substantially fully extended position.

[0010] Thus, a safety device is provided in which substantially all the gas produced by the gas generator when it is deployed will be used to force the piston to its extended position. The gas is allowed to be discharged only when the piston has reached its extended position. The present solution enables the piston to be placed in its fully extended position more quickly and more forcefully than the prior art solution in which the exhaust hole is arranged in the gas chamber in the bottom end of the housing opposite to the pressure surface of the piston, with a leakage gas flow already from the start of the deployment of the gas generator. In practice, the faster placement will protect the object earlier, whether it is a pedestrian who is hit or a seat belt that should be pulled. In the case where the safety device is a seat belt pretensioner, it enables a person to be connected in the vehicle seat more quickly, which in turn limits the forward movement of the vehicle body. By means of the present invention, when the piston has been placed in its fully or substantially fully extended position, the gas produced by the gas generator is allowed to escape from the gas chamber via the gas discharge arrangement, and only in this position will the pressure in the gas chamber be allowed to decrease to the same as the ambient pressure. Therefore, when pushing back the piston after actuation, there is no positive gas pressure that must be overcome.

[0011] The gas discharge arrangement may comprise a through opening in the side wall of the housing. The number of openings may be one, or two or more. The more openings there are, the faster the gas discharge. In case of more than one opening, the openings may be mutually displaced in the axial extension of the housing. In addition, the openings may have different sizes.

[0012] The opening or openings are arranged in a region adjacent to the upper end of the housing, whereby a free passage for the generated gas is only formed when the piston has been axially displaced to such an extent that the piston has reached its fully or substantially fully extended position.

[0013] The through opening may be provided with a seal (such as a check valve or a membrane) configured to be broken by the gas pressure generated by the gas generator. By providing the opening with a seal, moisture or dust is prevented from entering the interior of the safety device over time during ordinary use of the vehicle.

[0014] The gas exhaust arrangement may comprise an axially extending and radially outwardly projecting recess configured to allow gas generated by the gas generator to axially bypass the piston when the piston is in said fully or substantially fully extended position.

[0015] By forming the gas discharge arrangement as a radially outwardly protruding recess, the bypass passage is only formed when the piston has been axially displaced to such an extent that the piston has reached its fully or substantially fully extended position.

[0016] The piston may comprise a circumferential sealing ring which is axially arranged flush with the recess when the piston is in the fully or substantially fully extended position. Thus, the volume near the sealing ring is added to the volume of the recess, thereby increasing the volume of the bypass channel.

[0017] The recess may have an axial extension which exceeds an axial extension of the sealing ring.

[0018] In one embodiment, the recess may have a circumferential extension. In alternative embodiments, the recess may have a discontinuous circumferential extension or be formed as one or more discrete recesses.

[0019] The safety device may be a hood lifter in a vehicle.

[0020] The safety device may be a seat belt pretensioner in the vehicle.

[0021] The safety device may be a seat structure reinforcement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be described in detail with reference to the schematic drawings.

[0023] Figure 1a A schematic cross-section of an embodiment of a safety device during deployment of its gas generator is disclosed.

[0024] Figure 1b The piston is disclosed as being moved to its fully extended position. Figure 1a safety device.

[0025] Figure 2 A schematic cross section of a safety device according to the invention is disclosed, wherein a gas outlet arrangement is formed as a through-opening.

[0026] Figure 3 A schematic cross section of a safety device according to the invention is disclosed, wherein a gas discharge arrangement is formed as a recess in a housing.

[0027] Figure 4 A schematic cross section of a safety device according to the invention is disclosed, wherein a gas discharge arrangement is formed as a combination of a through opening and a recess.

[0028] Figure 5 A schematic cross section of an embodiment of a safety device during exhaustion of gas by using a gas exhaust system according to the invention is disclosed.

[0029] Figure 6 The action of pushing back the piston after actuation is schematically disclosed. DETAILED DESCRIPTION

[0030] Turning now to Figure 1, there is disclosed a schematic cross-section of one embodiment of a safety device 100. The safety device 100 is disclosed with its piston in a fully retracted position.

[0031] The safety device 100 comprises a housing 1 in the form of a hollow cylinder having a first end 2 and a second end 3. The housing 1 may be formed of a deep drawn metal material. The first end 2 is a closed end. The housing 1 contains a piston 4. The piston 4 is disclosed as having a portion 5 extending from the housing 1 via the second end 3 of the housing 1. It should be understood that the piston 4 maintaining the functionality of the present invention may also be of a type in which the piston 4 is completely contained in the housing 1 when the piston 4 is in its fully retracted position.

[0032] The piston 4 is assembled in the housing 1. The piston 4 can be axially moved from a retracted position to a fully or substantially fully extended position in the housing 1. The retracted position is the default position of the piston 4. The piston 4 has a pressure surface 6 facing the first end 2 of the housing 1. The pressure surface 6 generally has an outer cross-sectional area and an outer cross-sectional geometry that substantially corresponds to the inner cross-sectional area and the inner cross-sectional geometry of the housing 1. Thereby, the inner wall 7 of the housing 1 together with the pressure surface 6 of the piston 4 define a gas chamber 8. The volume of the gas chamber 8 can vary depending on the instantaneous axial position of the piston 4 in the housing 1. When the piston 4 is in its fully retracted position, the gas chamber 8 has its minimum volume, and when the piston 4 is in its fully extended position, the gas chamber has its maximum volume.

[0033] The envelope surface 9 of the piston 4 supports a sealing ring 10 which sealingly abuts an axial portion of the inner wall 7 of the housing 1. The sealing ring 10 is received in a circumferential groove 11 in the envelope surface 9 of the piston 4.

[0034] An end portion 12 of the housing 1 adjacent to the second end 3 of the housing 1 comprises a neck portion 13 having a locally reduced cross-sectional area. An edge portion 14 of the piston 4 opposite the pressure surface 6 is configured to abut against said end portion 12 when the piston is placed in its fully extended position, see Figure 1b Thereby, a physical stop is formed which prevents the piston 4 from falling out of the housing 1 .

[0035] The safety device 100 further comprises a gas generator 15. The gas generator 15 is located in the gas chamber 8. In the disclosed embodiment, the gas generator 15 is disclosed as being received in an axially extending groove 16 of the piston 4 and is therefore supported by the piston 4. In an alternative (not illustrated), the gas generator 15 may be arranged adjacent to the first end 2 of the housing 1. Therefore, the gas generator 15 does not have to be supported by the piston 4. Regardless of the position of the gas generator 15, the gas chamber 8 is defined by the inner wall 7 of the housing 1, the pressure surface 6 of the piston 4 and the gas generator 15.

[0036] The gas generator 15 is directly or indirectly connected to a schematically disclosed power connector 17. In the disclosed embodiment, the power connector 17 is arranged outside the housing 1 and supported by the portion 5 of the piston 4 extending from the housing 1. In this embodiment, the power connector 17 is designed to communicate with and power the gas generator 15 via a wire arrangement 18, which extends along the axial extension of the piston 4 and therefore extends within the housing 1.

[0037] On the contrary, in the case where the gas generator 15 should be arranged adjacent to the first end 2 of the shell 1, the power connector 17 can be arranged on the first end 2 of the shell 1 and connected to the gas generator 15 via an opening in the first end 2 of the shell 1 and power the gas generator.

[0038] Regardless of the location, the power connector 17 is configured to be connected to a (not illustrated) electronic control unit (ECU) of the vehicle in a manner well known in the art. In the event that the ECU, via the crash sensors and a processor integrated in the ECU, should determine that there is an emergency situation to be responded to, such as a head-on collision with a pedestrian or cyclist, an activation signal is communicated to the igniter of the gas generator 15 which will cause the gas generator to deploy. The gas generator 15 will in turn generate a volume of gas having a pressure that is substantially higher than the ambient pressure. The gas acts on the pressure surface 6 of the piston 4 and forcibly moves the piston 4 in the axial direction from its retracted position to its extended position, see Figure 1b .

[0039] Now go to Figure 2 , a first embodiment of the gas exhaust arrangement 20 of the present invention will be discussed. The gas exhaust arrangement 20 is provided in the second end portion 3 of the housing 1. The general purpose of the gas exhaust arrangement 20 is to allow the gas generated by the gas generator 15 to be exhausted from the gas chamber 8 in the case where the gas generator has been deployed. By exhausting the gas, the gas pressure in the gas chamber 8 will be reduced to a level corresponding to the ambient pressure. The gas exhaust arrangement 20 is arranged in an axial position in the housing 1 such that a free passage for the generated gas is only formed when the piston 4 has been axially displaced to such an extent that the piston 4 has reached its fully or substantially fully extended position.

[0040] exist Figure 2In a first embodiment, the gas exhaust arrangement 20 is disclosed as a through opening 21 arranged in the side wall 7 of the housing 1. The number of through openings 21 can be one or two or more. The more through openings 21 there are, the faster the gas is exhausted. One or more openings 21 are arranged in an area adjacent to the second end 3 of the housing 1, whereby a free passage is only formed for the generated gas when the piston 4 has been axially displaced to such an extent that the piston has reached its fully or substantially fully extended position. In this position, the sealing ring 10 of the piston 4 has at least partially passed through the through opening 21, thereby allowing the gas chamber 8 to communicate with the outside via at least one opening 21. In the disclosed embodiment, the sealing ring 10 has completely passed through the opening 21. Those skilled in the art recognize that when the sealing ring 10 reaches the edge portion 22 of the opening 21, a passage through the opening 21 is formed, and then as the piston 4 moves to Figure 2 In the fully extended position shown, the size of the passage will gradually increase until it corresponds to the full cross-sectional area of ​​the opening 21.

[0041] In the case of two or more openings 21, these openings may be displaced axially and / or circumferentially. The more openings there are, the faster the gas discharge of the gas. In the case of two or more openings, the openings may have different cross-sectional areas.

[0042] The through opening 21 may be provided with a seal 22. The seal 22 is schematically illustrated by a dashed line. The seal may be a check valve or a membrane. In the case of a membrane, the membrane is configured to be ruptured by the gas pressure generated by the gas generator 15. By providing the opening 21 with a seal 22, moisture or dust is prevented from entering the interior of the housing over time during ordinary use of the vehicle.

[0043] Now go to Figure 3 , discloses a second embodiment of a gas exhaust arrangement 20'. The gas exhaust arrangement 20' comprises an axially extending and radially outwardly protruding recess 23. The recess 23 is configured to allow the gas generated by the gas generator 15 to axially bypass the piston 4 only when the piston 4 is in a fully or substantially fully extended position.

[0044] The recess 23 has an extension in the axial direction of the housing 1 , so that the bypass channel 24 is only formed when the piston 4 has been axially displaced into a fully or substantially fully extended position and in which the sealing ring 10 of the piston 4 has at least partially passed through the recess 23 .

[0045] When the piston 4 is in said fully or substantially fully extended position, the circumferential sealing ring 10 of the piston 4 is preferably arranged axially flush with the recess 23. The recess 23 may have an axial extension that exceeds the axial extension of the sealing ring 10.

[0046] The recess 23 is disclosed as a single discrete recess. In an alternative embodiment, the recess may have a circumferential, continuous extension. In an alternative embodiment, the recess may have a discontinuous circumferential extension. In addition, two or more recesses may also be arranged along the axial extension of the housing 1.

[0047] Now go to Figure 4 , a third embodiment is disclosed, in which the gas discharge arrangement 20" comprises a combination of a through opening 21 and a recess 23 extending axially and protruding radially outwardly. The type of the opening 21 and the recess 23 is the same as the type discussed above. The recess 23 is disclosed as being arranged closer to the second end 3 of the housing 1 than the opening 21. When the piston 4 has reached its fully extended position, the gas generated in the gas chamber 8 will be allowed to discharge from the gas chamber in a radial direction via the through opening 21 and in an axial direction via the bypass channel 24 through the recess 23. The combination of the opening 21 and the recess 23 allows a very fast gas discharge.

[0048] Now go to Figure 5 and Figure 6 . Figure 5 A safety device 100 is disclosed which is placed in its fully extended position, wherein the gas chamber 8 is filled with gas and when the piston is in its fully or substantially fully extended position, the gas is exhausted by a gas exhaust arrangement 20, 20', 22" in the second end 3 of the housing 1, which is located directly below the piston. When the internal pressure has been reduced to a level which substantially corresponds to the ambient pressure, the piston 4 can be pushed back into its retracted position, see Figure 6 This is achieved by applying an axial pressure F to the piston 4, thereby pushing it back into the housing. Since the pressure difference between the gas already exhausted to the inside of the housing 1 has been significantly reduced to such an extent, the required pressure is very low and in most cases it can be pushed back manually.

[0049] This is useful, for example, when the safety device is a hood lifter. A hood lifter is typically arranged in the rear of a motor vehicle and in the hood of a motor vehicle adjacent to its windshield. In the event of an accident, the hood lifter is configured to lift the rear end of the hood, thereby protecting the body of, for example, a pedestrian struck by the vehicle. The safety device may be a seat belt pretensioner. The seat belt pretensioner may be configured to apply a tension to the seat belt in the event of an accident, thereby providing early attachment of the seated body. Alternatively, the safety device may be a seat structure reinforcement, which provides a lifting force to the seat structure in the event of an accident.

Claims

1. A safety device in a vehicle, the safety device comprising: A housing (1) having a first end (2) and a second end (3); a piston (4) adapted to be mounted in the housing (1) and configured to move from a retracted position to an extended position; and A gas generator (15), wherein The piston (4) has a first end, which forms a pressure surface (6) facing the first end (2) of the housing (1); A gas chamber (8) is formed between the pressure surface (6) of the piston (4) and the inner wall (7) of the housing (1), and the gas generator (15) is fluidically connected to the gas chamber (8); and wherein The housing (1) comprises a gas exhaust arrangement (20, 20', 20") at its second end (3) which allows gas generated by the gas generator (15) to be exhausted from the gas chamber (8) when the piston (4) is in a fully or substantially fully extended position.

2. Safety device according to claim 1, wherein the gas outlet arrangement (20, 20', 20") comprises a through opening (21) in a side wall of the housing (1).

3. Safety device according to claim 2, wherein the through opening (21) is provided with a seal (22), such as a non-return valve or a membrane configured to be ruptured by the gas pressure generated by the gas generator (15).

4. A safety device according to claim 1, wherein the gas exhaust arrangement (20, 20', 20") comprises an axially extending and radially outwardly projecting recess (23), the recess (23) being configured to allow the gas generated by the gas generator (15) to axially bypass the piston (4) when the piston (4) is in the fully or substantially fully extended position.

5. A safety device according to claim 4, wherein the piston (4) comprises a circumferential sealing ring (10), and wherein when the piston (4) is in the fully or substantially fully extended position, the sealing ring (10) is axially arranged to be flush with the recess (23).

6. Safety device according to claim 4 or 5, wherein the recess (23) has an axial extension which exceeds the axial extension of the sealing ring (10).

7. Safety device according to any one of claims 4 to 6, wherein the recess (23) has a circumferential extension, or wherein the recess (23) has an interrupted circumferential extension.

8. A safety device according to any one of claims 1 to 7, wherein the safety device is a hood lifter in a vehicle.

9. A safety device according to any one of claims 1 to 7, wherein the safety device is a seat belt pretensioner in a vehicle.

10. A safety device according to any one of claims 1 to 7, wherein the safety device is a seat structure reinforcement.

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