Hood lifter for lifting a hood of a motor vehicle in an accident situation and hood lifter system with various such hood lifters

Abstract

The invention relates to a hood lifter (1) for lifting a hood of a vehicle in an accident situation with a housing (2), a piston rod (3) which is displaceably guided in the housing (2) and is guided out of the housing (2) through an opening (8), a piston (4) connected to the piston rod (3), which is in sealing contact with an inner wall (9) of the housing (2), and a gas generator (5) connected in terms of flow to a pressure chamber (6) of the housing (2), wherein the pressure chamber (6) in the housing (2) is delimited by the piston (4), wherein a stop (7) is provided on a central portion (10) of the piston rod (3), which blocks the piston (4) relative to the piston rod (3) in the direction of an enlargement of the pressure chamber (6) and defines by its arrangement and the arrangement of the piston (4) bearing against it a predetermined volume of the pressure chamber (6).

Description

[0001] Hood lifter for lifting a hood of a motor vehicle in an accident situation and hood lifter system with various such hood lifters

[0002] The present invention relates to a hood lifter and a hood lifter system for lifting a hood of a motor vehicle with the features of the preamble of claim 1 and with the features of the preamble of claim 8.

[0003] In principle, pedestrians are particularly at risk in accidents, since in the event of an accident with a motor vehicle they can in most cases collide unprotected with the body parts, in particular with the hood, and sustain serious injuries.

[0004] Various solutions have been developed to improve pedestrian protection. One solution is to raise the body panel slightly when an accident is sensed, thus creating a distance between the body panel and the adjacent parts of the vehicle. The pedestrian protection now consists of the body part being able to deform over a greater distance when the occupant is hit before it comes into contact with the adjacent stiffer parts, such as the engine or the adjacent body structure. Due to the energy dissipated during this deformation path, the load on the pedestrian can be reduced to such an extent that at least the risk of serious injury is reduced.

[0005] EP 1494895 Bl, for example, discloses a device for lifting a hood, which has a hood lifter with a lifting element that can be acted upon pyrotechnically. The hood is provided with a hinge in the area associated with the windscreen, which enables the edge of the hood associated with the windscreen to be lifted. The lifting element is supported on a fixed, immovable part of the vehicle and rests on the underside of the hood in an area facing the windscreen. When the lifting element is activated, the hood is lifted in the area facing the windscreen and pivots about a pivot point assigned to the front edge of the hood. The pivoting movement when the hood is opened and when it is raised in the event of an accident are therefore directed in opposite directions and have different pivot points. To enable these oppositely directed pivoting movements, the hinge is formed from two pivoting arms that can pivot in relation to each other, which are coupled to each other in normal operation and are decoupled when the lifting element is activated. The lifting element comprises an inflatable element which, when the device is activated by activating a gas generator, is filled with a released gas volume in a short time and thus deployed.

[0006] A device for lifting a hood is known from the publication DE 10 2004037 060 Al, which comprises a hood lifter, referred to there as an actuator, with a cylindrical housing and a piston arranged in the housing and sealed against it. The piston is connected to a piston rod, which is slidably guided in the housing. The piston delimits a pressure chamber provided in the housing, which can be acted upon by a gas flow released by a gas generator when the device is activated. The pressure thus generated in the pressure chamber drives the piston with the piston rod to an extension movement, which is then transferred to the hood so that the hood is raised accordingly.

[0007] The force or the impulse that the hood lifter exerts on the hood depends on the impulse exerted on the piston. Various vehicle manufacturers require for their vehicles of different types that the hood lifter is individually designed for a predetermined impulse to be exerted on the hood, e.g. in order to take into account the different weight of the hoods, different stiffnesses of the hoods, different geometries of the hoods themselves and different geometries of the hoods in the arrangement on the vehicle. This in turn allows the lifting process of the hoods to be designed with regard to optimized restraint and minimized maximum load on the person to be caught.

[0008] Against this background, the invention is based on the task of providing a hood lifter and a hood lifter system which enable the impulse to be exerted on the hood by the hood lifter to be adapted as cost-effectively and simply as possible to an impulse predetermined by the vehicle manufacturer. To solve the problem, a hood lifter with the features of claim 1 and a hood lifter system with the features of claim 8 are proposed according to the invention. Further preferred embodiments of the invention can be found in the sub-claims, the figures and the associated description.

[0009] In accordance with the basic idea of the invention, it is proposed that a stop is provided on a central section of the piston rod which blocks the piston relative to the piston rod in the direction of an enlargement of the pressure chamber and defines by its arrangement and the arrangement of the piston resting against it a predetermined volume of the pressure chamber.

[0010] The movement of the piston is limited by the stop provided on the piston rod and thus the volume of the pressure chamber is defined by the arrangement of the stop and the piston in contact with it. This means that the volume of the pressure chamber of the hood lifter can be individually designed by the arrangement of the stop, which in turn means that the impulse force exerted by the hood lifter on the hood can be designed differently using identical housings, piston rods, pistons and gas generators. The smaller the pressure chamber in the initial phase of activation of the gas generator, the higher the impulse exerted on the piston or, conversely, the smaller the impulse in the initial phase, the larger the pressure chamber must be. According to the invention, the size of the pressure chamber can be defined by the positioning of the stop for the piston, whereby identical parts can be used, thereby reducing manufacturing costs.

[0011] It is further proposed that the stop is formed by a securing element that is positively and / or frictionally secured to the piston rod. Circlips or retaining rings, for example, which are either frictionally connected to the piston rod by a clamping connection and / or positively connected to the piston rod, for example by a groove in the piston rod, can be used as retaining elements. The connection between the securing element and the piston rod must be designed in such a way that the pressure force exerted on the piston via the pressure from the pressure chamber is transmitted to the piston rod via the securing element with as little loss as possible. One possible preferred embodiment for the securing element is a ring shaped star lock washer with an outer closed ring and radial inwardly directed sections, which are distanced by gaps.

[0012] The holding force of the securing element relative to the piston rod is preferably dimensioned by the frictional connection and / or the positive connection in such a way that the piston rod passes through the securing element when the securing element comes into contact with an edge of the opening of the housing, overcoming the holding force. The proposed dimensioning of the holding force means that the stroke of the piston rod is not reduced by the arrangement of the piston on the central section, as the piston rod is not blocked in its further movement by the securing element coming into contact with the edge of the opening. The piston and the piston rod thus carry out the first part of the stroke movement together until the piston and the locking element are blocked from further movement by the edge of the opening. The piston rod then passes through the locking element and carries out the further stroke movement on its own, whereby it is driven by the pressure force exerted on the second end or intertia forces acting on the piston rod.

[0013] According to an alternative solution, it is proposed that the stop is formed by a thickening of the piston rod. The thickening can be realized, for example, by plastic local forming of the piston rod, by local material application or by machining of the piston rod.

[0014] It is further proposed that the housing in the area of the edge of the opening has such a deformation resistance that the piston rod passes through the opening with the thickening while expanding the opening. Due to the proposed dimensioning of the housing in the area of the opening or the dimensioning of the stiffness of the piston rod in the area of the thickening, the piston rod can pass through the opening with the thickening while the piston is blocked. This means that the piston and the piston rod perform the first part of the stroke movement together until the piston is blocked from further movement by the edge of the opening. The piston rod then passes through the opening with the thickening and performs the further stroke movement on its own, being driven by the compressive force exerted on the second end.

[0015] It is also proposed that the piston rests against the stop and is additionally fixed to the piston rod against a displacement movement in the direction of a reduction in the pressure chamber. The piston is thus fixed relative to the piston rod both in the direction of a displacement movement with an increase in the pressure chamber and relative to a displacement movement with a reduction in the pressure chamber. The position of the piston is selected in such a way that the pressure chamber has exactly the predetermined volume for the predetermined impulse of the hood lifter at the start of activation.

[0016] It is further proposed that the piston is annular with a central opening and that the piston rod extends through the central opening into the pressure chamber. Due to the proposed design of the piston and the extension of the piston rod into the pressure chamber, the piston can be arranged in any position of the central section of the piston rod. The piston rod extends into the pressure chamber and reduces the pressure chamber in accordance with its volume extending into the pressure chamber, whereby the piston rod forms an additional force application surface with its free end face facing the gas generator, which supplements the surface of the annular piston and supports the forcing of the stroke movement.

[0017] Furthermore, to solve the problem, a hood lifter system with different hood lifters for lifting one hood each from different vehicles in an accident situation is proposed, in which the housings, the gas generators and the pistons of the different hood lifters each are geometrically identical, and the piston rods of the different hood lifters have an identical length and an identical cross-section and are arranged in an identical arrangement in the housings of the different hood lifters, and a stop is provided on a central section of the respective piston rod, which limits the movement of the respective piston relative to the piston rod in the direction of an enlargement of the pressure chamber, wherein the stops of the various hood lifters are arranged individually differently and define by their arrangement and the arrangement of the piston respectively abutting against them a predetermined volume of the pressure chambers with.

[0018] The proposed hood lifter system is characterized by a cost-effective solution with regard to the realization of different impulses to be exerted on the different hoods of the vehicles, whereby the different impulses are achieved solely by the different dimensioning of the pressure chambers, which in turn are defined solely by the positioning of the stops for the pistons and the position of the pistons defined thereby at the beginning of the activation of the hood lifters. This means that the hood lifters can be designed cost-effectively using otherwise identical parts to achieve the different impulses to be exerted on the hoods.

[0019] The invention is explained below by means of preferred embodiments with reference to the attached figures. It shows

[0020] Fig. 1 various hood lifters of a hood lifter system with pressure chambers of different volumes; and

[0021] Fig. 2 a hood lifter according to a first embodiment with different positions of the piston during activation; and

[0022] Fig. 3 a hood lifter according to a second embodiment with different positions of the piston during activation.

[0023] Figure 1 shows various hood lifters 1 of a hood lifter system according to the invention. The hood lifters 1 each have identical housings 2, piston rods 3, pistons 4 and gas generators 5. The housings 2 are each formed by thin-walled cylindrical tubular housings with a circular cross-section cavity and have an opening 8 on their first end faces, while a gas generator 5 is fixed to each of their second end faces, e.g. by a crimp connection.

[0024] A piston rod 3 with a piston 4 is arranged in each of the housings 2, whereby the piston rods 3 have an identical geometry and are arranged in an identical arrangement. The piston rods 3 each extend outwards with a first end through the openings 8 of the housings 2, while the other second end faces the gas generator 5 held in the housing 2.

[0025] In their attachment positions, the hood lifters 1 are supported by the second ends of the housings 2 on the vehicle structure not to be lifted, while the first ends of the piston rods 3 are in a force-transmitting connection with the hood of the vehicle to be lifted.

[0026] The pistons 4 are ring-shaped with a central opening 11 and are each mounted on a central section 10 of the piston rods 3 at different distances from the gas generators 5 and the second ends of the piston rods 3. The radial outer sides of the pistons 4 lie tightly against the inner walls 9 of the housing 2 and may have additional sealing lips or sealing edges on their radial outer sides for this purpose. In addition, the pistons 4 each form a sealing connection with the piston rods 3, so that they close off a pressure chamber 6, which has a different volume depending on the positioning of the pistons 4 in relation to the piston rods 3.

[0027] Stops 7 are provided on each of the piston rods 3, which are arranged in such a way that the pistons 4 are each fixed in the direction of displacement in the direction of the first ends of the piston rods 3, i.e. in the direction of displacement of an enlargement of the pressure chambers 6 relative to the piston rods 3. The stops 7 can be formed by a separate securing element, such as a spring washer or a retaining ring, which are positively and / or frictionally secured to the piston rods 3. Alternatively, the stops 7 can also be formed by localized thickening, such as plastic deformation of the piston rods 3, or by an additive application of material to the piston rods 3. Furthermore, the pistons 4 are also preferably fixed in the direction of displacement in the direction of the second ends of the piston rods 3, i.e. in the direction of the gas generators 5, so that the pressure chambers 6 cannot be reduced by an unintentional displacement of the pistons 4. This means that the volumes of the pressure chambers 6 and thus the impulses of the hood lifters 1 are individually defined by the position of the pistons 4 on the piston rods 3.

[0028] The hood lifter 1 on the left in the illustration has the largest pressure chamber 6 and the hood lifter 1 on the right in the illustration has the smallest pressure chamber 6. Conversely, this results in the smallest impulse for the hood lifter 1 on the left in the illustration and the largest impulse for the hood lifter 1 on the right in the illustration on the hood of the vehicle to be lifted at the start of the activation of the hood lifter 1.

[0029] It can be seen here that the hood lifters 1 each have identical parts and are only designed for a specific predetermined impulse due to the position of the pistons 4 in relation to the piston rods 3, i.e. the size of the pressure chambers 6.

[0030] Figure 2 shows a hood lifter 1 according to a first embodiment. In the hood lifter 1, the stop 7 is formed by a securing element against which the piston 4 rests on the side of the pressure chamber 6. Illustration a) shows the hood lifter 1 before activation, while illustrations b) to d) show the hood lifter 1 during activation of the gas generator 5 with various positions of the piston 4 and the piston rod 3.

[0031] If the gas generator 5 of the hood lifter 1 is activated in the position shown in illustration a), it suddenly releases a large volume of gas, which enters the pressure chamber 6. This builds up pressure in the pressure chamber 6, which drives the piston 4 together with the piston rod 3 to perform an extension movement. This position of piston 4 can be seen in illustration b). The hood of the vehicle connected to the first end of the piston rod 3 is lifted and the pedestrian is caught before the impact in accordance with the function of the hood lifter 1 described at the beginning. The impulse exerted on the hood at the start of this movement is defined by the volume of the pressure chamber 6 in the illustration a).

[0032] The piston 4 is then extended together with the piston rod 3 until the piston rod 3 comes into contact with the stop 7 in this case with the securing element on the inside edge of the opening 8 of the housing 2, as can be seen in the illustration c) of Figure 2. Due to the contact of the stop 7 with the edge of the opening 8, the piston 4 resting against the stop 7 is also blocked against any further extension movement.

[0033] The securing element is preferably f rictiona I ly engaged and / or positively engaged with respect to the piston rod 3 with a predetermined retaining force, so that the piston rod 3 is extended further into the position of illustration d) of Figure 2 due to the pressure exerted continuously on the end face of the second end of the piston rod 3 by the pressure chamber 6, overcoming the retaining force. In doing so, the piston rod 3 is extended through the securing element. This means that the piston rod 3 is used over its maximum length to extend the lifting movement and to lift the lever.

[0034] Figure 3 shows a second embodiment example of a hood lifter 1, which differs from the first embodiment example in that the stop 7 is realized here by a local thickening of the piston rod 3.

[0035] So that the stroke of the piston rod 3 is not reduced by the arrangement of the piston 4 in the central section 10, the edge of the opening 8 comprises such a form resistance that the stop 7 formed by the thickening that the piston rod 3 can pass through the opening 8 with the stop 7, as can be seen in representations c) and d) of Figure 3. List of reference symbols

[0036] 1 Hood lifter

[0037] 2 Housing

[0038] 3 Piston rod

[0039] 4 Piston

[0040] 5 Gas generator

[0041] 6 Pressure chamber

[0042] 7 Stop

[0043] 8 Opening

[0044] 9 Inner wall

[0045] 10 Center section

[0046] 11 Opening

Claims

Claims:

1. Hood lifter (1) for lifting a hood of a vehicle in an accident situation with-a housing (2),-a piston rod (3) which is displaceably guided in the housing (2) and is guided out of the housing (2) through an opening (8),-a piston (4) connected to the piston rod (3), which is in sealing contact with an inner wall (9) of the housing (2), and-a gas generator (5) connected in terms of flow to a pressure chamber (6) of the housing (2), wherein the pressure chamber (6) in the housing (2) is delimited by the piston (4), characterized in that-a stop (7) is provided on a central portion (10) of the piston rod (3), which blocks the piston (4) relative to the piston rod (3) in the direction of an enlargement of the pressure chamber (6) and defines by its arrangement and the arrangement of the piston (4) bearing against it a predetermined volume of the pressure chamber (6).

2. Hood lifter (1) according to claim 1, characterized in that-the stop (7) is formed by a securing element fixed on the piston rod (3) in a form-fitting and / or frictionally engaged manner.

3. Hood lifter (1) according to claim 2, characterized in that-the retaining force of the securing element relative to the piston rod (3) is dimensioned by the frictional connection and / or the positive connection such that the piston rod (3) passes through the securing element, overcoming the retaining force, when the securing element bears against an edge of the opening (8) of the housing (2).

4. Hood lifter (1) according to claim 1, characterized in that -the stop (7) is formed by a thickening of the piston rod (3).

5. Hood lifter (1) according to claim 4, characterized in that-the housing (2) has such a deformation resistance in the region of the edge of the opening (8) that the piston rod (3) passes through the opening (8) with the thickening while widening the opening (8).

6. Hood lifter (1) according to one of claims 1 to 5, characterized in that-the piston (4) rests against the stop (7) and is additionally fixed on the piston rod (3) with respect to a displacement movement in the direction of a reduction in the pressure chamber (6).

7. Hood lifter (1) according to one of claims 1 to 6, characterized in that-the piston (4) is annular with a central opening (11), and the piston rod (3) extends through the central opening (11) into the pressure chamber (6).

8. Hood lifter system with different hood lifters (1) for lifting a hood of different vehicles in an accident situation, wherein the hood lifters (1) each comprise-a housing (2),-a piston rod (3) guided displaceably in the housing (2) and guided out of the housing (2) through an opening (8),-a piston (4) connected to the piston rod (3), which is in sealing contact with an inner wall (9) of the housing (2), and-a gas generator (5) connected in terms of flow to a pressure chamber (6) of the housing (2), wherein the pressure chamber (6) in the housing (2) is delimitied by the piston (4), characterized in that-the housings (2), the gas generators (5) and the pistons (4) of the various hood lifters (1) each are geometrically identical, and the piston rods (3) of the various hood lifters (1) have an identical length and an identical cross-section and are arranged in an identical arrangement in the housings (2) of the various hood lifters (1), and-a stop (7) is provided on a central section (10) of the respective piston rod (3), which limits the movement of the respective piston (4) relative to the piston rod (3) in the direction of an enlargement of the pressure chamber (6), wherein-the stops (7) of the various hood lifters (1) are arranged individually differently and define by their arrangement and the arrangement of the piston (4) resting against them a predetermined volume of the pressure chambers (6).

9. Hood lifter system according to claim 8, characterized in that-the stops (7) are each formed by a securing element fixed on the piston rod (3) in a formfitting and / or frictionally manner.

10. Hood lifter system according to claim 9, characterized in that-the retaining force of the securing elements relative to the piston rods (3) is dimensioned by the frictional connection and / or the form-fitting connection such that the piston rods (3) pass through the securing elements while overcoming the retaining force when the securing elements come into contact with an edge of the openings (8) of the housing (2).

11. Hood lifter system according to claim 8, characterized in that-the stops (7) are each formed by a thickening of the piston rods (3).

12. Hood lifter system according to claim 11, characterized in that-the housings (2) have such a deformation resistance in the region of the edges of the openings (8) that the piston rods (3) pass through the openings (8) with the thickenings.

13. Hood lifter system according to one of claims 8 to 12, characterized in that-the pistons (4) of the various hood lifters (1) are additionally fixed to the piston rod (3) with respect to a displacement movement in the direction of a reduction in the pressure chamber (6).

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