WO2009035379A1

WO2009035379A1 - A seat belt pretensioner for a motor vehicle

Info

Publication number: WO2009035379A1
Application number: PCT/SE2007/000780
Authority: WO
Inventors: Erik Hjerpe; Dan BRÅSE
Original assignee: Autoliv Development Ab
Priority date: 2007-09-10
Filing date: 2007-09-10
Publication date: 2009-03-19
Also published as: EP2185387A4; EP2185387A1

Abstract

A seat-belt pre-tensioner for a motor vehicle, comprises a piston member 28, 102 displaceable in a chamber 38, 40, 104 under gas pressure from a source of compressed gas or a source of gas generated by a pyrotechnic device applied to said chamber. The piston member is coupled to a seat belt tensioning element. In one arrangement, the piston is a rotary piston in the form of a vane 28 secured to a shaft 30 carrying a crank 50 having at its end a member 54 retaining a loop at one end of a seat belt tensioning cable 56. In another arrangement the piston 102 is movable axially in a cylinder 104 and acts on an eccentrically mounted drum 112 around which a seat belt tensioning cable 130 extends.

Description

Title: A SEAT BELT PRETENSIONER FOR A MOTOR VEHICLE

Description of Invention

THE PRESENT INVENTION relates to a seat belt pretensioner for a motor vehicle.

It is now widely known to provide motor vehicles with a number of different safety devices, most notably inflatable air-bag arrangements and/or seat-belt pre-tensioners. The most common types of such safety devices are arranged to be pyrotechnically operable, that is, the safety arrangements are provided with pyrotechnic charges which are ignited by a squib and which are typically arranged as part of an inflator or gas generator configured to direct a large, rapidly-expanding volume of gas into an operable part of a safety device in order to inflate an air-bag or drive a piston of a safety-belt pre-tensioner arrangement.

Safety devices of the type described briefly above have been provided so as to be pyrotechnically operable in order to ensure that the safety device is operated in an extremely short period of time so as to be properly deployed in the event of an accident situation such as a crash involving a motor vehicle. However, a drawback of such arrangements is that because such safety devices are pyrotechnically operable, they are one-use items which cannot be re-set after actuation for possible subsequent use. This is not generally a problem when the safety device has been actuated in a severe accident situation because it is much more important to prevent injury and possible death to occupants of a motor vehicle than it is to save money and inconvenience in providing a re-settable device, particularly when in such severe impacts, the motor vehicle as a whole is likely to be very severely damaged in any event. However, in low impact accident situations or when it is desirable to actuate (at least partially) a safety-device upon receipt of a signal predictive of a crash (a pre-crash sensor), it is preferable for a safety device to be operable in a manner which can be reversed. For example, if a safety device is installed in order to be primed in advance of an accident situation upon receipt of a predictive pre-crash signal, it is clearly advantageous to be able subsequently to re-set the safety device in the event that the accident was avoided or involved only a very low impact. Re-settable safety devices of this general type have been proposed previously such as, for example, in US2005/0218632A1 which discloses a motor vehicle provided with a central air supply system in order to operate a number of different pneumatically- operated safety devices such as air-bags and seat-belt pre-tensioners.

In the arrangement of US 2005/0218632A1 , after actuation of the restraint devices, regardless of whether or not an impact has occurred and also regardless of the severity of any impact, the restraint devices can be reset to their initial position, without the need for any complicated service or replacement of any component. However, relying solely upon reversible pneumatic safety devices of the type disclosed in US2005/0218632A1 can be disadvantageous because pneumatically-operated safety devices cannot easily be actuated sufficiently quickly in order to provide a proper degree of protection in more severe accident situations occurring at higher speeds. Indeed, it is thought that pre-tensioning of a seat-belt retractor arrangement using only compressed air would necessitate an air supply system able to generate gas pressures of 70 bar or more in order to provide a similar performance to that of a pyrotechnically operable seat-belt pre-tensioner arrangement.

It is an object of the present invention to provide a seat belt pretensioner for a motor vehicle which can be operated in a number of different operating modes.

According to the present invention there is provided a seat-belt pre-tensioner for a motor vehicle, comprising a piston member displaceable in a chamber under gas pressure applied to said chamber, said piston member being in sealing relationship with the walls of said chamber and said chamber being provided with respective inlets for connection with a source of compressed gas, with a source of gas generated by a pyrotechnic device, and with an outlet for gas, said piston member being coupled to an element outside said chamber which element is coupled in turn with one part of a vehicle safety belt arrangement, whereby displacement of said member in said chamber by gas pressure applied thereto will cause the seat-belt to be pre-tensioned, with the displacement of said piston member, and thus the pre-tensioning, being greater in a case where the pyrotechnic device is fired than when the source of compressed gas alone is connected with said chamber.

In one embodiment of the invention, said chamber has a cylindrical wall and opposing end walls and said piston member comprises a vane rotatable about the axis of said cylindrical wall between limiting positions defined by a radially extending blocking member within said chamber whereby the sealing member is rotatable through less than 360° within said chamber, said vane being mounted on a shaft extending axially from said chamber through said end walls and carrying an arm or eccentric carrying a pulley or boss around which is extended a cable, belt or other filament connected with one end of the seat- belt, said blocking member extending sealingly between said cylindrical wall and said shaft and between said end walls, and said vane cooperating sealingly with said cylindrical wall and with said end walls.

In another embodiment, said chamber comprises a cylinder and said piston member is movable axially along said cylinder and has a piston rod connected with a drum around which a cable extends in a loop, one end of the cable being fixed and the other end being connected to said one part of said vehicle safety belt arrangement, said drum being rotatable about an eccentric axis whereby axial movement of the piston and piston rod will turn the drum to extend the loop of said cable around the drum and thereby pre-tension the seat-belt.

Embodiments of the invention are described below by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a schematic side view of one form of seat belt pre-tensioner in accordance with the invention, FIGURE 2 is a plan view of the pre-tensioner of Figure 1 ,

FIGURE 3 is a schematic view in section along the line A-A in Figure 1 in one position of the apparatus,

FIGURE 4 is a view similar to Figure 3 but showing another position of the apparatus, FIGURE 5 is a view in section along the line B-B in Figure 2,

FIGURE 6 is a side view of an alternative form of seat belt pre-tensioner in accordance with the invention, and

FIGURES 7A, 7B, 7C and 7D illustrate respective positions of a restraining arrangement used in the apparatus of Figure 6.

Referring to Figures 1 to 5, the seat-belt pre-tensioner illustrated is operable either pneumatically or pyrotechnically and has a first inlet 20 connected, through a pneumatic line, (not shown), to a pressurized gas reservoir, (not shown), via a control valve (not shown) and has a second inlet 22 connected with a pyrotechnic gas generator (not shown) of a kind known per se.

The apparatus of Figures 1 to 5 comprises a prime mover or motor 24 comprising a rotary piston or vane 28 moveable around a cylindrical chamber by pneumatic pressure or pyrotechnic gas pressure. As best illustrated in Figures 3, 4 and 5, the cylindrical chamber is formed in a block 26 and the rotary piston or vane 28 has a radially inner end fixed to or integral with a shaft 30 which extends axially through the chamber and extends sealingly through respective bores through respective end plates at axially opposite axial ends of the block or chamber, which end plates, together with the block 26 define the working chamber for the piston or vane 28. A fixed blocking member 34 within the chamber extends from the peripheral cylindrical wall of the chamber to the shaft 30 which is rotatable but sealed with respect to the member 34. The member 34 and the piston 28 are in sealing engagement with the peripheral wall of the chamber at their radially outer ends and with the inner surfaces of the end plates at the axially extreme edges of the member 34 and piston 28, so that the member 34 and piston or vane 28 together define, within the cylindrical chamber, a first chamber part 38 into which the inlets 20 and 22 open and a second chamber 40 from which an exhaust port 42 normally extends. Figure 3 shows the initial position or normal position of the vane 28 within the chamber.

The arrangements of the ports 20, 22 and 42 are such that, as viewed in Figure 3, the vane 28 is always further clockwise than the inlets 20 and 22 whilst the exhaust port 42 remains further clockwise than the vane 28, and thus within the chamber 40, during displacement of the vane 28 under pressure in chamber part 38, until close to the end of that displacement at which point the vane 28 passes the exhaust port 42 allowing the gases in the chamber part 38 to escape. Referring to Figures 1 and 2, the upper end of the shaft 30 carries a radially extending arm 50 from the radially outer end of which extends upwardly a shaft 52 on which a pulley 54 is rotatably mounted.

In the arrangement shown the motor block is fixed in a bracket 45, fixed to the body of the vehicle, for example to the floor of the vehicle. The bracket 45 is U- shaped, providing a lower horizontal limb extending below the motor 24 and having a vertical bore receiving a lower end of shaft 30. The bracket 45 has an upper horizontal limb extending over the arm 50 and pulley 54 and having an arcuate slot 56 through which the upper end of the shaft 52 extends and the edges of which help to support the shaft 52 during the movement of the lever 50 and vane 28 described and the consequent movement of the lever 50.

In an emergency situation, the valve in the pneumatic line connected with port 20 will first be opened as a result of a predictive crash sensor being triggered, causing pressurized air or other gas to enter the chamber 38 and begin to move the vane 28 clockwise in Figures 3 and 4. If the emergency situation develops into an actual crash, the pyrotechnic gas pressure generator connected with the inlet 22 will be triggered, driving the vane 28 further clockwise towards and through the position illustrated in Figure 4 until finally the vane 28 passes the exhaust port 42, allowing the gas from chamber 38 to escape, before the vane 28 is prevented from further movement by the element 28.

A cable loop 56 is extended around the pulley 54 and extends from the pulley 54 under a guide member or pulley 58 to the lower end of a seat-belt fitting 60, which may, for example, carry at its upper end a seat belt buckle adapted to receive a complementary portion of a buckle part through which an associated seat belt runs in known fashion. The guide member or pulley 58 is mounted in a bracket 59 fixed to the body of the vehicle, for example to the floor of the vehicle. The clockwise movement of the vane 28 and the shaft 30, arm 50 and pulley 54 (clockwise as viewed in Figure 2), as described above, in an emergency situation draws the cable loop 56 further away from the guide member 58, thus drawing the seat belt buckle towards the pulley 58, and thereby tensioning the associated seat-belt.

Referring to Figures 6 and 7A to 7D, a variant pre-tensioner is shown which is operated by a conventional piston and cylinder unit 100 comprising a single acting piston 102 displaceable axially within a cylinder 104 in response to pressurised gas supplied to an inlet 20 connected, via a pneumatic line incorporating a sensor-operable valve with a pressurised gas reservoir (not shown) containing, for example, compressed air. The cylinder 104 is likewise connected via an inlet 22 with a pyrotechnic gas generator (not shown). The inlets 20, 22 connect with one end of the cylinder, the piston 102 normally being disposed adjacent that one end and being displaceable towards the opposite end by gas pressure supplied via inlet 20 or 22. A piston rod 106 extends from the piston 102 through said other end of the cylinder and carries at its outer end a bearing member 108 which receives rotatably a journal pin 110 extending from one side of a drum 112. Said one end of the cylinder is closed by a cap 114 having an apertured lug by means of which the cylinder is pivotally mounted on a pin 120 carried by a bracket 122 bolted to the bodywork of the vehicle, for example to the floor of the vehicle. The drum 112 is rotatable in the bracket 122 around the axis of a shaft 124 which is eccentrically located with respect to the drum 112, the axis of shaft 124 thus extending parallel with the central axis of the drum 112 but being displaced radially from that axis. The drum 112 has a peripheral groove, indicated in broken lines in Figure 6, which serves to guide a cable 130 which is secured at one end at 132 to the bracket 122 and which extends under the drum 112 and runs partially around the drum through an arc of approximately 90° when it extends upwardly to a seat buckle 140. The groove around the drum serves to guide the cable 130 but additional means, not shown, may be provided to ensure that the cable 130, in normal use, remains in the groove. The buckle 140 or the upper part of the cable is biased upwardly by means not shown, so that the cable 130 is drawn tightly against the drum.

In an emergency situation in which gas under pressure is supplied to the head of the cylinder either from the compressed gas reservoir or from the pyrotechnic device, the piston 102 is propelled along the cylinder 104, extending the piston rod 106 and causing the drum to rotate anticlockwise as viewed in Figure 6, from the position shown in the solid lines to the position indicated in broken lines at 112', thereby extending the length of the cable 130 between the anchoring point 132 and the drum and thus pulling the seat belt buckle 130 downwards to pretension the seat-belt. Referring to Figures 7A to 7D, as well as Figure 6, a ratchet segment 150 fixed to the drum shaft 124 cooperates with a pawl 152 pivotally mounted on the bracket 122. The pawl 152 is spring biased into engagement with the ratchet and operates to ensure that the seat-belt, once pre-tensioned, remains so until the apparatus is re-set manually.

Figure 7A shows positions of the ratchet segment and pawl in a so-called presenter phase in which the seat belt arrangement is placed in readiness for fitting around a seat occupant and securing; Figure 7B shows the position of normal use once the seat belt has been secured around the occupant of the respective seat; Figure 7C shows the position after pre-tensioning by the compressed gas or pneumatic source alone, whilst Figure 7D shows the position after pre-tensioning by the pyrotechnic device. A similar ratchet and pawl arrangement may be provided, for the same purpose, in the apparatus of Figures 1 to 5, the ratchet being secured to the shaft 30 and the pawl being mounted on the bracket 45, for example.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A seat-belt pre-tensioner for a motor vehicle, comprising a piston member (28, 102) displaceable in a chamber (38, 40, 104) under gas pressure applied to said chamber, said piston member being in sealing relationship with the walls of said chamber and said chamber being provided with respective inlets (20, 22) for connection with a source of compressed gas and, with a source of gas generated by a pyrotechnic device, and being provided with an outlet for gas, said piston member (28, 102) being coupled to an element (54, 112) outside said chamber which element is coupled in turn with one part (56, 130) of a vehicle seat belt arrangement, whereby displacement of said piston member in said chamber by gas pressure applied thereto will cause the seat- belt to be pre-tensioned, with the displacement of said piston member, and thus the pre-tensioning, being greater in a case where the pyrotechnic device is fired than when the source of compressed gas alone is connected with said chamber.

2. A pre-tensioner according to claimi wherein said chamber has a cylindrical wall and opposing end walls and said piston member comprises a vane (28) rotatable about the axis of said cylindrical wall between limiting positions defined by a radially extending blocking member (34) within said chamber whereby the vane (28) is rotatable through less than 360^° within said chamber, said vane being mounted on a shaft (30) extending axially from said chamber through said end walls and carrying an arm or eccentric (50) carrying a pulley or boss (54) around which is extended a cable, belt or other filament (56) connected with said one part of the vehicle safety arrangement said blocking member (34) extending sealingly between said cylindrical wall and said shaft (30) and between said end walls, and said vane (28) cooperating sealingly with said cylindrical wall and with said end walls.

3. A seat-belt pre-tensioner according to claim 1 wherein said chamber comprises a cylinder (104) and said piston member (102) is movable axially along said cylinder and has a piston rod (106) connected with a drum (112) around which a cable (130) extends in a loop, one end of the cable (130) being fixed and the other end being connected to said one part of said vehicle safety belt arrangement, said drum (112) being rotatable about an eccentric axis (124) whereby axial movement of the piston and piston rod will turn the drum to extend the loop of said cable (130) around the drum and thereby pretension the seat-belt.

4. A seat belt arrangement according to Claim 3 including a ratchet arrangement operable to maintain the drum in positions to which it is turned by axial movement of the piston, until released manually.

5. A seat belt arrangement according to Claim 2 including a ratchet arrangement operable to maintain said vane and shaft in positions to which they are turned by gas pressure applied to said chamber, until released manually.