Seat belt retractor

Abstract

To provide a seat belt retractor which can perform fine adjustment of EA load easily.SOLUTION: A seat belt retractor 1 comprises a tubular spool 4 which winds up a seat belt 3 and includes an inner hole, a locking base 14 which is disposed coaxially with the spool 4, a torsion bar 7 which is inserted through in the inner hole of the spool 4 and of which one end side is connected to the spool 4 so as to make it impossible to rotate and other end side is connected to the locking base 14 so as to make it impossible to rotate and which twists and deforms at the time of EA and an EA load adjustment pin 20 which penetrates the locking base 14 and of which one end part comes into contact with end surface of an axial direction of the spool 4 and which includes on other end side a flange part 20a which is engaged with the locking base 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seat belt retractor used in vehicles such as automobiles, and more particularly to a seat belt retractor equipped with an energy absorption (EA) mechanism that has a torsion bar built into the spool to absorb energy acting on an occupant. [Background technology]

[0002] A known seat belt retractor has a torsion bar inserted into a spool, one end of which can be fixed to the spool, and the other end of which can be hooked to the frame of the seat belt retractor. In an emergency, such as a vehicle collision, a locking mechanism prevents the spool from rotating in the belt-withdrawing direction. When a force is then applied to the spool in the seat belt-withdrawing direction, the torsion bar twists, causing the spool to gradually rotate and the seat belt to be gradually withdrawn. As a result, part of the kinetic energy applied to the occupant's body is absorbed (EA) by the twisting of the torsion bar, thereby mitigating the impact.

[0003] Patent document 1 describes another EA mechanism that operates when the seat belt is pulled out due to the inertia of the occupant in the aforementioned emergency, namely a seat belt retractor in which a wire fixed to a spool (winding drum) is arranged in a curved path formed in a locking base (plate body).

[0004] In the seat belt retractor described in Patent Document 1, when the seat belt is withdrawn in an emergency, the spool rotates relative to the locked locking base in the seat belt withdrawing direction, causing the wire to be squeezed out of the curved path, generating sliding resistance between the wire and the curved path, as well as bending resistance due to the wire itself. The torsional deformation of the torsion bar and the sliding resistance and bending resistance of the wire absorb the kinetic energy of the occupant when the seat belt is withdrawn.

[0005] However, the seat belt retractor described in Patent Document 1 has a limited range of kinetic energy absorption effectiveness depending on the wire length. Also, in order to withstand the load of the wire being pulled out, the locking base, which forms a curved path, requires a certain level of strength and durability depending on the material and shape, which increases costs. Furthermore, because it is a mechanism that deforms the wire, it is difficult to fine-tune the EA load. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-161001 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a seat belt retractor that allows easy fine adjustment of the EA load. [Means for solving the problem]

[0008] The seat belt retractor of the present invention comprises a cylindrical spool having an inner hole for winding up a seat belt, a locking base arranged coaxially with the spool, a torsion bar inserted into the inner hole of the spool, one end of which is non-rotatably connected to the spool and the other end of which is non-rotatably connected to the locking base, and which is twisted and deformed during EA, and an EA load adjustment pin which passes through the locking base, one end of which contacts the axial end face of the spool, and the other end of which has a flange portion which is engaged with the locking base.

[0009] In one aspect of the present invention, the EA load adjustment pin is bent midway in the length direction.

[0010] In one aspect of the present invention, a portion of the EA load adjustment pin from the flange portion to the bent portion is parallel to the torsion bar.

[0011] In one aspect of the present invention, the EA load adjustment pin has a linear shape.

[0012] In one aspect of the present invention, the vehicle seat further includes a pretensioner that rotates the locking base in the seat belt retracting direction. [Effects of the Invention]

[0013] According to the present invention, the EA load can be easily finely adjusted by changing the material, shape, length, etc. of the EA load adjustment pin. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic cross-sectional view of a seat belt retractor according to an embodiment. [Figure 2] 2A and 2B are schematic diagrams of the seat belt retractor before and after the spool is assembled. [Figure 3] FIG. 10 is a diagram illustrating an EA load. [Figure 4] 1 is a graph showing an EA load curve. [Figure 5] FIG. 10 is a schematic diagram of a modified seat belt retractor. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment will be described with reference to the drawings.

[0016] Fig. 1 is a longitudinal cross-sectional view showing an example of a seat belt retractor of the present invention. As shown in Fig. 1, the seat belt retractor 1 includes a U-shaped frame 2, a spool 4 rotatably supported between both side walls 2a, 2b of the U-shaped frame 2 and winding up a seat belt 3, a deceleration sensing means 5 that senses and activates a large vehicle deceleration that occurs in an emergency, a locking means 6 that is activated by the deceleration sensing means 5 to prevent rotation of at least the spool 4 in the belt-withdrawing direction, a torsion bar 7 that passes through the center of the spool 4 with loose axial clearance and rotationally connects the spool 4 and the locking means 6, a spring means 8 that constantly urges the spool 4 in the belt-winding direction by the spring force of a spiral spring, a pretensioner 11 that is activated in an emergency to generate a belt-winding torque, and a paddle wheel 12 that transmits the seat belt winding torque of the pretensioner 11 to the spool 4.

[0017] The locking means 6 is provided with a locking base 14 that is rotatable integrally with the first torque transmission portion 17 of the torsion bar 7 and that holds the pawl 13 so that it can swing, and is also provided with a lock gear that normally rotates integrally with the torsion bar 7 and stops in an emergency upon activation of the deceleration sensing means 5, generating a relative rotation difference with the torsion bar 7 and engaging the pawl 13 with internal teeth 19 on the side wall 2b of the frame 2, thereby preventing rotation of the locking base 14 in the seat belt withdrawal direction. The locking base 14 is formed with a cylindrical male threaded shaft portion 15, and a nut-shaped stopper member 16 that rotates integrally with the spool 4 is screwed onto the male threaded shaft portion 15.

[0018] A first torque transmission part 17 is formed at one end of the torsion bar 7, and engages with the locking base 14 so as not to rotate relative to the locking base 14. The other end of the torsion bar 7 is formed with a second torque transmission part 18, and engages with the spool 4 so as not to rotate relative to the locking base 14.

[0019] The spool 4 is constantly biased in the seat belt retracting direction by the spring force of the spring means 8 via the torsion bar 7 and the second torque transmission portion 18 of the torsion bar 7.

[0020] A hexagonal portion serving as a non-circular portion is provided on the outer periphery of the locking base 14. The paddle wheel 12 and bearing plate 30 are engaged with this hexagonal portion, and the paddle wheel 12 and bearing plate 30 are attached to the locking base 14 so as to be unable to rotate in the circumferential direction. The bearing plate 30 is disposed between the paddle wheel 12 and the end face of the spool 4 in the cylindrical axis direction. A guide groove 31 that guides the energy absorption pin 20, which will be described later, is formed on the side surface of the bearing plate 30 facing the spool 4. This guide groove 31 circles around the locking base 14.

[0021] When the pretensioner is activated, a power transmission member made of synthetic resin or the like is supplied to the outer periphery of the paddle wheel 12, causing the paddle wheel 12 to rotate, which in turn rotates the locking base 14. This rotation is transmitted to the spool 4 via the torsion bar 7, causing the spool 4 to retract the seat belt 3 by a predetermined amount.

[0022] When the seat belt is not fastened, the seat belt 3 is fully wound up by the biasing force of the spring means 8. When the seat belt 3 is withdrawn at a normal speed to fasten it, the spool 4 rotates in the seat belt withdrawing direction, and the seat belt 3 is smoothly withdrawn. After a tongue (not shown) slidably provided on the seat belt 3 is inserted and locked into a buckle (not shown) fixed to the vehicle body, the excess seat belt 3 is wound up around the spool 4 by the biasing force of the spring means 8, and the seat belt 3 fits snugly enough to the occupant without causing any feeling of pressure.

[0023] In an emergency, the seatbelt winding torque from the pretensioner 11 is transmitted to the spool 4, and the spool 4 winds the seatbelt 3 by a predetermined amount, removing the slack.

[0024] As the retraction of the seat belt 3 progresses and the slack in the seat belt 3 is removed, the retraction of the seat belt by the spool 4 stops.

[0025] Thereafter, a force in the seat belt withdrawing direction applied from the seat belt 3 to the spool 4 causes the spool 4 to begin to rotate in the seat belt withdrawing direction while twisting the torsion bar 7 (EA operation). The locking base 14, which is connected to the spool 4 via the torsion bar 7, is prevented from rotating in the seat belt withdrawing direction by the pressure holding action of the pretensioner 11. As a result, the spool 4 rotates while twisting the torsion bar 7 (EA rotation), and the seat belt is withdrawn. The torsional deformation of the torsion bar 7 absorbs the kinetic energy of the occupant's forward movement.

[0026] As the spool 4 rotates relative to the locking base 14, the stopper member 16, which rotates integrally with the spool 4, rotates relative to the male screw shaft portion 15 with which it is threaded, and moves toward the base end of the locking base 14. When the stopper member 16 abuts against the step portion on the base end side of the male screw shaft portion 15, further rotation of the stopper member 16 is prevented, and therefore rotation of the spool 4 is also prevented, and twisting of the torsion bar 7 stops.

[0027] As shown in Figures 1, 2A, and 2B, the seat belt retractor 1 is provided with an EA load adjustment pin 20 (hereinafter referred to as "pin 20"). Figures 2A and 2B are schematic diagrams for explaining the pin 20. The pin 20 penetrates the locking base 14, the paddle wheel 12, and the bearing plate 30 (the bottom surface of the guide groove 31 of the bearing plate 30), and one end 20b contacts the end surface of the spool 4. A flange 20a is formed on the other end of the pin 20, and this flange 20a is engaged with the locking base 14, thereby preventing the pin 20 from slipping out toward the spool 4.

[0028] The portion of the pin 20 that penetrates the locking base 14, the paddle wheel 12, and the bottom surface of the guide groove 31 of the bearing plate 30 is linear and parallel to the axial direction of the spool 4 (torsion bar 7). The pin 20 is bent midway along its length, and the portion from the bent portion to one end 20b is curved along the guide groove 31. The bent portion of the pin 20 is located within the guide groove 31. The bending direction of the pin 20 (the direction of one end 20b as viewed from the bent portion) is the same as the EA rotation direction of the spool 4.

[0029] As shown in Fig. 2A, before the spool 4 is assembled, one end 20b of the pin 20 protrudes from the guide groove 31 of the bearing plate 30. As shown in Fig. 2B, the spool 4 is assembled while bending the pin 20. Due to spring back, one end 20b of the pin 20 is pressed against the end face of the spool 4.

[0030] In the event of an emergency as described above, rotation of the locking base 14 in the seat belt withdrawing direction is prevented, so the torsion bar 7 is twisted and only the spool 4 rotates in the seat belt withdrawing direction relative to the locking base 14. At this time, sliding resistance is generated between the spool 4 and the pin 20, as shown in Figure 3.

[0031] Therefore, the limit load applied to the seat belt 3 is the sum of the torsional deformation load of the torsion bar 7 and the load due to the sliding resistance of the pin 20. Figure 4 shows the EA load curves when the pin 20 is provided and when the pin 20 is omitted. By providing the pin 20, the EA load increases by the amount of the load due to the sliding resistance.

[0032] The pin 20 is made of metal, and the material is not particularly limited, but stainless steel, for example, can be used. The load due to sliding resistance can be changed by changing the material, thickness, cross-sectional shape, protrusion amount P of the pin 20 (see FIG. 2A), length from the bent portion to one end 20b, and contact position of the pin 20 (distance from the spool 4 axis to the contact point), etc. Therefore, the EA load can be easily fine-tuned.

[0033] The pin 20 may be formed into a bent shape during the manufacturing process and then inserted into the insertion holes formed in the locking base 14, the paddle wheel 12, and the bearing plate 30, or a straight pin 20 may be inserted and then bent.

[0034] In the above embodiment, the bending direction of the pin 20 is the same as the EA rotation direction of the spool 4, but it may be the opposite direction. Also, the bending direction of the pin 20 may be the direction from the axis of the spool 4 to the outer periphery, or the direction from the outer periphery to the axis.

[0035] The shape of one end 20b of the pin 20 may be rounded or angular. The surface roughness of the end face of the spool 4 that comes into contact with the pin 20 may be changed.

[0036] The number of pins 20 is not limited to one, but two or more may be provided.

[0037] A straight pin 20' that is not bent midway may be used as shown in Fig. 5. A guide groove that matches the shape of the pin 20' is formed in the bearing plate 30.

[0038] In the above embodiment, a configuration has been described in which the pin 20 that passes through the locking base 14, the paddle wheel 12, and the bearing plate 30 contacts the spool 4, but the pin may also be fixed to the spool 4 side and the tip of the pin may contact the locking base 14.

[0039] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0040] 1 Seat belt retractor 3 Seatbelts 4 spools 5 Deceleration sensing mechanism 6 Locking means 7 Torsion Bar 8 Spring means 12 Paddle Wheel 13 Paul 14 Rocking Base 20,20´ EA Load Adjustment Pin 20a Flange 30 bearing plate

Claims

1. a cylindrical spool having an inner hole for winding up the seat belt; a locking base arranged coaxially with the spool; a torsion bar that is inserted into an inner hole of the spool, has one end non-rotatably connected to the spool, and the other end non-rotatably connected to the locking base, and that is torsionally deformed during EA; an EA load adjustment pin that penetrates the locking base, has one end that contacts an end face of the spool in the axial direction, and has a flange portion on the other end that is engaged with the locking base; A seat belt retractor comprising:

2. 2. The seat belt retractor according to claim 1, wherein the EA load adjusting pin is bent at a midpoint in the length direction.

3. 3. The seat belt retractor according to claim 2, wherein a portion of the EA load adjusting pin from the flange portion to the bent portion is parallel to the torsion bar.

4. 2. The seat belt retractor according to claim 1, wherein the EA load adjustment pin has a linear shape.

5. The seat belt retractor according to claim 1, further comprising a pretensioner that rotates the locking base in a seat belt winding direction.

Images