Seatbelt retractor

Abstract

A seatbelt retractor capable of variably setting the limited load applied to the seatbelt depending on the emergency state includes a support shaft portion of a spool, which is provided with a second EA mechanism coaxial with the spool. An energy absorbing pin of a third EA mechanism is inserted to be fit in the axial hole of the spool. In the emergency state, the torsion bar is twisted and the energy absorbing pin is pulled out of the spool to absorb energy. At the same time, in the state where the rotation of the second energy absorber support member is locked by the lever, the first energy absorber support member rotates to deform the energy absorbing plate so as to absorb energy. As the second energy absorber support member rotates when the locked rotation is released, the energy absorbing plate is not deformed, and the energy absorption is finished.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.

FIG. 1 is a view showing an example of the seatbelt retractor according to an embodiment with its structure partially omitted.

FIG. 2 is a sectional view taken along line II-II shown in FIG. 1.

FIG. 3 is a partially enlarged view of the seatbelt retractor shown in FIG. 1.

FIG. 4 is a block diagram showing a structure for controlling a second EA mechanism of the seatbelt retractor as the example shown in FIG. 1.

FIGS. 5( a)-5(c) are explanatory views of a third EA mechanism using the energy absorbing pin, wherein FIG. 5(a) is a view showing the state before pull-out of the pin, FIG. 5(b) is a view showing the state where the pin is being pulled out, and FIG. 5(c) is a view showing the state where the pin is fully pulled out.

FIGS. 6( a) to 6(e) are views each showing the EA operation in the seatbelt retractor as the example shown in FIG. 1.

FIG. 7 is a view showing the relationship between the rotation stroke of the spool and the limited load in the seatbelt retractor as the example shown in FIG. 1.

FIG. 8 is a view graphically showing an example of the seatbelt apparatus to which the seatbelt retractor shown in FIG. 1 is applied.

FIG. 9 is a longitudinal sectional view showing an example of a related art seatbelt retractor with a torsion bar.

FIG. 10 is a view graphically showing the other example of the related art seatbelt retractor with the torsion bar.

FIG. 11 is a view showing the property of the FL load of the related art shown in FIG. 10.

DETAILED DESCRIPTION

The seatbelt retractor as disclosed in JP '632 may further include one rotating shaft remote from the rotating shaft of the spool thereabove. The size of the seatbelt retractor is relatively large in the vertical direction. Recently, the seatbelt retractor installed in the vehicle interior has been demanded to be as compact as possible for the purpose of effectively using the vehicle interior space.

Even if the seatbelt retractor may be formed as compact as possible, the limited load applied to the seatbelt is required to be variably set with flexibility depending on the emergency state.

Accordingly, an object of a disclosed embodiment is to provide a seatbelt retractor capable of variably setting the limited load applied to the seatbelt with further flexibility depending on the emergency state while being formed to be further compact, and to provide a seatbelt apparatus which employs the aforementioned seatbelt retractor.

The seatbelt retractor according to a first embodiment is provided with a spool which retracts a seatbelt and a lock unit provided with a locking member that rotates together with the spool upon transmission of a rotation of the spool via a first seatbelt load limiting mechanism in a normal state and the rotation in a seatbelt withdrawal direction is blocked in an emergency state. The first seatbelt load limiting mechanism limits a load applied to the seatbelt when the rotation of the locking member in the seatbelt withdrawal direction is blocked to allow the spool to rotate relative to the locking member in the seatbelt withdrawal direction. The seatbelt retractor further includes a second seatbelt load limiting mechanism coaxially provided with the spool which changes a limited load applied to the seatbelt in the emergency state based on information of the emergency state including an occupant's body size, a seat slide position, a collision speed, the collision at acceleration/deceleration, and a collision type, and a third seatbelt load limiting mechanism provided between the spool and the locking member to limit the load applied to the seatbelt in the emergency state.

In the seatbelt retractor of a second embodiment, when the rotation of the locking member in the seatbelt withdrawal direction is blocked and the spool rotates relative to the locking member in the seatbelt withdrawal direction, the load applied to the seatbelt is limited by the first and the third seatbelt load limiting mechanisms in an initial stage, or the load applied to the seatbelt is limited by the first to the third seatbelt load limiting mechanisms in the initial stage, and further limited only by the first seatbelt load limiting mechanism in at least a last stage.

In the seatbelt retractor of a third embodiment, the first seatbelt load limiting mechanism is formed of a torsion bar disposed between the spool and the locking member.

In the seatbelt retractor of a fourth embodiment, the second seatbelt load limiting mechanism includes a first energy absorber support member coaxially provided with the spool so as to be integrally rotatable, a second energy absorber support member coaxially attached to the first energy absorber support member, and an energy absorbing member between the first and the second energy absorber support member.

In the seatbelt retractor of the fifth embodiment, the third seatbelt load limiting mechanism includes an energy absorbing pin slidably inserted into a thin and long axial hole formed in the spool so as to pierce through the locking member such that the load applied to the seatbelt is limited by a load caused by pulling out the energy absorbing pin from the axial hole of the spool when the spool rotates relative to the locking member in the seatbelt withdrawn direction in the emergency state.

A seatbelt apparatus of a sixth embodiment includes at least the seatbelt retractor according to any one of the previous embodiments for retracting the seatbelt, a tongue slidably supported at the seatbelt withdrawn from the seatbelt retractor, and a buckle with which the tongue is detachably engaged. The seatbelt apparatus allows the seatbelt retractor to prevent withdrawal of the seatbelt in the emergency state to restrain an occupant.

The seatbelt retractor and the seatbelt apparatus using the seatbelt retractor are structured to select the limited load applied to the seatbelt in the emergency state based on the information with respect to the emergency state, for example, the preliminarily known information (occupant's weight, seat slide position and the like), the collision forecast information for forecasting the collision, and the information with respect to the seriousness of the collision (for example, collision speed, acceleration/deceleration at the collision, type of the collision). This makes it possible to variably set the limited load applied to the seatbelt upon the vehicle collision with further flexibility in accordance with the emergency information such as the state at the collision, and the occupant's body size. This makes it possible to restrain the occupant upon the collision more effectively and appropriately.

Combining the second seatbelt load limiting mechanism having variable load limiting function with those first and the third seatbelt load limiting mechanisms each having the fixed load limiting function makes it possible to set the limited load applied to the seatbelt in the emergency state such as collision more effectively and appropriately.

With the seatbelt retractor according to the second embodiment, when the rotation of the locking member in the seatbelt withdrawn direction is blocked to allow the spool to rotate relative to the locking member in the seatbelt withdrawal direction, the load applied to the seatbelt is limited by the first and the third seatbelt load limiting mechanisms in the initial stage, or the load applied to the seatbelt is limited by the first to the third seatbelt load limiting mechanisms in the initial stage, and the load is further limited only by the first seatbelt load limiting mechanism at least in the last stage. When the rotation of the locking member in the seatbelt withdrawal direction is blocked to allow the spool to rotate relative to the locking member in the seatbelt withdrawal direction, the load applied to the seatbelt may be largely limited by the first and the third seatbelt load limiting mechanisms or the first to the third seatbelt load limiting mechanisms in the initial stage, and then further limited only by the first seatbelt load limiting mechanism.

The seatbelt apparatus is intended to restrain the occupant to be protected in cooperation with the airbag in the emergency state. So the energy exerted to the occupant in the emergency state (generally referred to as the chest acceleration) is small in the initial stage as it is applied only through the seatbelt. However, as the airbag starts contacting the occupant, the energy of the airbag is added to gradually increase the energy. The second embodiment is structured to limit the load applied to the seatbelt to make the absorption of the energy exerted to the occupant with the arbitrary body size uniform in spite of the additional energy of the airbag operated in the emergency state.

For example, assuming that the body size of the occupant is small, the load applied to the seatbelt in the emergency state is limited by the first and the third seatbelt load limiting mechanisms. Assuming that the body size of the occupant is large, the load applied to the seatbelt is limited by the first to the third seatbelt load limiting mechanisms. Thereby, it is possible to make the absorption of the energy added by the airbag in operation exerted to the occupant with the arbitrary body size uniform. As the load to be limited in the initial stage may be changed depending on the body size of the occupant, the energy absorption in accordance with the body size of the occupant may be effectively performed.

The seatbelt retractor according to the third embodiment includes the second seatbelt load limiting mechanism coaxial with the spool. This makes it possible to make the seatbelt retractor compact in the vertical direction, thus increasing the effective space of the vehicle interior accordingly.

The seatbelt retractor according to the fourth embodiment employs the thin and long energy absorbing pin inserted into the axial hole of the spool as the third seatbelt load limiting mechanism. This makes it possible to make the structure of the third seatbelt load limiting mechanism simple, thus forming the seatbelt retractor further compact.

FIG. 1 shows an example of the embodiment of the seatbelt retractor according to an embodiment having a part of the structure omitted. FIG. 2 is a sectional view taken along line II-II shown in FIG. 1. In the respective explanations of the examples, the same components as those of the previous explanation and the seatbelt retractor 1 as related art shown in FIG. 9 will be designated with the same reference numerals, and explanations thereof, thus will be omitted.

Referring to FIG. 1, likewise the seatbelt retractor 1 as the related art shown in FIG. 9, the seatbelt retractor 1 in the example includes a U-shaped frame 2, a seatbelt 3, a spool 4 which retracts the seatbelt 3, and a torsion bar 7 as a first energy absorbing member of a first EA mechanism. Likewise the seatbelt retractor 1 as the related art shown in FIG. 9, the seatbelt retractor 1 of the example includes a deceleration detection unit 5, a lock unit 6, and a spring member 8 as well as the pretensioner that is the same as the aforementioned pretensioner 11 and a bush that is the same as the aforementioned bush 12 for transmitting the seatbelt retracting torque generated by the pretensioner 11 to the spool 4.

The seatbelt retractor 1 includes a second EA mechanism 41 on the outer circumference of the support shaft portion 4a which protrudes from the end surface of the spool 4 at the side of the locking base 14 coaxially with the spool 4. Referring to FIG. 2, the second EA mechanism 41 includes a strip-like energy absorbing plate 42 as the second energy absorbing member, a ring-like first energy absorber support member 43 which supported by the support shaft portion 4a of the spool 4 rotatably relative thereto and has the ratchet teeth 43a as the inner teeth, and a second energy absorber support member 44 supported by the first energy absorber support member 43 rotatably relative thereto.

The energy absorbing plate 42 is a strip-like plate with predetermined thickness and width, and formed into substantially C-like shape. The energy absorbing plate 42 may be formed into a linear shape. One end of the energy absorbing plate 42, that is, a first support portion 42a is fixedly supported at the first energy absorber support member 43, and the other end slidably supported at the second energy absorber support member 44. A U-shaped portion 42b is formed by bending the energy absorbing plate 42 at the portion around the first support portion 42a.

The second energy absorber support member 44 is formed into a disk-like shape, and has an annular flange 44a on its outer circumference. The first support portion 42a of the energy absorbing plate 42 is fixedly supported at the first energy absorber support member 43, and the portion defined by the U-shaped portion 42b of the energy absorbing plate 42 to the other end abuts against the inner peripheral surface of the flange 44a of the second energy absorber support member 44.

A clutch mechanism 45 is provided between the support shaft portion 4a of the spool 4 and the first energy absorber support member 43 to rotatably connect relative to the respective rotating operations of those members in the belt withdrawal direction. The clutch mechanism 45 includes an annular clutch pawl 46 having a predetermined number of fixing claws 46a engageable with ratchet teeth 43a of the first energy absorber support member 43 at one side. The clutch pawl 46 is slidably supported on the support surface 4b which is curved into a predetermined shape at the support shaft portion 4a.

Referring to FIG. 3, the clutch pawl 46 is provided rotatably with a shear pin 47 which is integrally and coaxially attached to a rotating shaft 13a of the pawl 13 of the lock unit 6. When the pawl 13 rotates to block the rotation of the locking base 14 in the belt withdrawal direction in the emergency state, the clutch pawl 46 is rotated by the rotation of the pawl 13 such that the fixing claw 46a of the clutch pawl 46 is engaged with the ratchet teeth 43a.

When the pawl 13 rotates to be engaged with the inner teeth 19 on the side wall 2b of the frame 2 in the emergency state where the deceleration detection unit 5 is activated, the clutch pawl 46 is rotated associated with the rotation of the pawl 13 such that the fixing claw 46a is engaged with the ratchet teeth 43a of the first energy absorber support member 43 in the belt withdrawal direction to connect the clutch mechanism 45. The connection to the clutch mechanism 45 allows the rotatable connection between the spool 4 and the first energy absorber support member 43 at least in the belt withdrawal direction. When the pawl 13 is engaged with the inner teeth 19 of the frame 2, the rotation of the locking base 14 in the belt withdrawal direction is locked. Meanwhile, the seatbelt 3 is likely to be withdrawn by the inertia of the occupant to keep the spool 4 rotating in the belt withdrawal direction. Relatively large shear load is applied to the shear pin 47 to be ruptured. 100601 When the pawl 13 is engaged with the inner teeth 19 of the frame 2, and the fixing claw 46a of the clutch pawl 46 is engaged with the ratchet teeth 43a in the emergency state, the shear pin 47 is shear ruptured. When the shear rupture occurs in the shear pin 47, the clutch pawl 46 moves relative to the spool 4 toward upstream of its rotation in the belt withdrawal direction while keeping the fixing claw 46a engaged with the ratchet teeth 43a. The clutch pawl 46 is inserted into the portion between the support surface 4b of the support shaft portion 4a of the spool 4 and the first energy absorber support member 43 so as to stop the relative movement to the spool 4. The rotatable connection between the spool 4 and the first energy absorber support member 43 in the belt withdrawal direction may be securely held. Then the rotation of the spool 4 in the belt withdrawal direction is transmitted to the first energy absorber support member 43 via the clutch pawl 46 such that the first energy absorber support member 43 rotates in the belt withdrawal direction as shown by arrow.

Referring to FIG. 2, the side wall 2b of the frame 2 is provided with an operation control member 48 which controls the EA operation of the second EA mechanism 41, and a drive member 49 which drives the operation control member 48. The operation control member 48 is formed of a lever 50 rotatably supported at the side wall 2b of the frame 2. An engagement protrusion 50a bent at 90° is formed at the tip of the lever 50. The engagement protrusion 50a is normally fit with an engagement recess portion 44b formed in the flange 44a of the second energy absorber support member 44.

The second EA mechanism 41 forms the limited load set unit of embodiments. The drive member 49 includes a gas generator 49a (not shown in FIG. 2: shown in FIG. 4) therein which is activated in the emergency state to generate the reaction gas. The thus generated reaction gas serves to activate the drive member 49 to rotate the lever 50 of the operation control member 48 clockwise as shown in FIG. 2 so as to disengage the engagement protrusion 50a from the engagement recess portion 44b.

Referring to FIG. 4, in the second EA mechanism 41 of the example, operations of the gas generator 49a of the drive member 49 are controlled by a CPU 57 in accordance with the emergency state based on the respective signals output from a seat weight sensor 51, a seat slide position detection sensor 52, an acceleration sensor 53, a front satellite sensor 54, a belt withdrawn amount detection sensor 55, and a buckle switch 56. When the drive member 49 is not activated, and the engagement protrusion 50a of the lever 50 of the operation control member 48 is not disengaged from the engagement recess portion 44b, the load applied to the seatbelt 3 is limited under the control of the second EA mechanism 41. When the engagement protrusion 50a of the lever 50 is disengaged from the engagement recess portion 44b, the load applied to the seatbelt 3 is not limited by the second EA mechanism 41. Accordingly, the load limiting operation performed by the second EA mechanism 41 may be selected between the mode where the load limitation is performed in the emergency state and the mode where the load limitation is not performed.

In the seatbelt retractor 1, the third EA mechanism 63 is provided between the spool 4 and the locking base 14. The third EA mechanism 63 serves as a third energy absorbing member, and includes a thin and long energy absorbing pin 64 extending in the axial direction of the spool 4. The energy absorbing pin 64 is slidably inserted into a thin and long axial hole 4c formed in the position eccentric to the spool 4 to extend in the axial direction, and pierces through the locking base 14. The energy absorbing pin 64 which pierces through the locking base 14 is provided with a flange 64a at one end. The flange 64a is fixed to the locking base 14 to prevent removal of the energy absorbing pin 64 toward the spool 4.

A guide groove 14a for guiding the energy absorbing pin 64 is formed at the position through which the energy absorbing pin 64 pierces in the side surface opposite the spool 4 of the locking base 14. Referring to the chain double-dashed line in FIG. 2, the guide groove 14a is formed like an arc concentric to the locking base 14. The length of the arc-like portion is set such that the energy absorbing pin 64 is completely stored after its energy absorbing operation. In the normal state before the energy absorbing operation is performed by the energy absorbing pin 64, it is kept as the linear shape as shown in FIG. 1.

Referring to FIG. 5(a), in the normal state of the third EA mechanism before pull-out of the pin, the energy absorbing pin 64 is not pulled out from the axial hole 4c of the spool 4, and accordingly kept linearly shaped. In the emergency state, the rotation of the locking base 14 in the seatbelt withdrawal direction is blocked. Then the torsion bar 7 is twisted such that only the spool 4 rotates relative to the locking base 14 in the belt withdrawal direction. At this time, the pull-out of the energy absorbing pin 64 from the axial hole 4c of the spool 4 is started. Referring to FIG. 5(b), the energy absorbing pin 64 is bent at two points A and B at right angles upon the pull-out from the axial hole 4c. The pulled out energy absorbing pin 64b is guided with the guide groove 14a of the locking base 14 so as to be curved into the arc shaped.

The load which has been limited by the pull-out resistance of the energy absorbing pin 64 from the axial hole 4c, the deformation of the energy absorbing pin 64 through bending, and the deformation of the energy absorbing pin 64 through curving is applied to the seatbelt as the limited load as shown in FIG. 5. Although the load gradually increases, it is kept constant in the process of the pull-out of the energy absorbing pin 64 by the predetermined amount as shown in FIG. 5(b). In the aforementioned state, the limited load becomes the value obtained by adding the torsional deformation load of the torsion bar 7 to the pull-out load of the energy absorbing pin 64.

Referring to FIG. 5(c), when the energy absorbing pin 64 is fully pulled out, the pull-out load thereof disappears, and the torsional deformation load of the torsion bar 7 only exists. The load limiting operation is fixed to be always performed by the third EA mechanism 63 in the emergency state.

The operation of the thus structured seatbelt retractor 1 will be described.

Referring to FIG. 6(a), in the initial state where the seatbelt retractor 1 is not operated, the fixing claw 46a of the clutch pawl 46 is not engaged with the ratchet teeth 43a, and the clutch mechanism 45 is in Off state. Accordingly, the spool 4 is disconnected from the first energy absorber support member 43 with respect to the rotating operation. The drive member 49 is not operated, and the engagement protrusion 50a of the lever 50 of the operation control member 48 is fit with the engagement recess portion 44b of the second energy absorber support member 44. The second energy absorber support member 44 is disabled to rotate.

In the emergency state as described above, the seatbelt retracting torque generated by the pretensioner 11 rotates the spool 4 in the belt retracting direction (clockwise in the drawing) as shown FIG. 6(b) to retract the seatbelt 3 by a predetermined amount so as to fixedly restrain the occupant. As the spool 4 and the locking base 14 are rotated in the belt withdrawal direction by the occupant's inertia, the pawl 13 rotates to block the rotation of the locking base 14 in the belt withdrawal direction. The torsion bar 7 is torsionally deformed likewise the related art such that the energy of the torsion bar 7 is absorbed. At the same time, the clutch pawl 46 rotates to bring its fixing claw 46a into engagement with the ratchet teeth 43a as shown in FIG. 6(b). That is, the clutch mechanism 45 is brought into On state such that the spool 4 is disconnected from the first energy absorber support member 43 with respect to the rotating operation in the belt withdrawal direction. In this case, the drive member 49 is not activated, and the second energy absorber support member 44 is kept disabled to rotate.

Accompanied with the rotation of the spool 4 in the belt withdrawal direction by the occupant's inertia, the rotation of the spool 4 is transmitted to the first energy absorber support member 43 via the clutch mechanism 45. Referring to FIG. 6(c), the first energy absorber support member 43 also rotates in the belt withdrawal direction (counterclockwise in FIG. 6(c)). The first support portion 42a of the energy absorbing plate 42 also rotates in the same direction together with the rotation of the first energy absorber support member 43. The energy absorbing plate 42 is deformed while its U-shaped portion 42b gradually moving toward the other end portion. The second EA mechanism 41 thus absorbs the energy. Further, the energy absorbing pin 64 of the third EA mechanism 63 is deformed through bending at right angles, and further deformed into the arc-shape through curving. The third EA mechanism 63 thus absorbs the energy. In this way, the energy is effectively absorbed through the aforementioned operations of the torsion bar 7, the second EA mechanism 41, and the third EA mechanism 63. The limited load applied to the seatbelt 3 at this time becomes the value obtained by summing the torsional deformation load of the torsion bar 7, the deformation load of the energy absorbing plate 42, and the pull-out load of the energy absorbing pin 64 as shown by α in FIG. 7. The limited load applied to the seatbelt 3 becomes larger initially by the torsion bar 7, and the second and the third EA mechanisms 41 and 63, respectively.

Referring to FIG. 5(c), when the energy absorbing pin 64 is fully pulled out, the energy absorption performed by the third EA mechanism 63 is finished. The load becomes the value obtained by summing the torsional deformation load of the torsion bar 7 and the deformation load of the energy absorbing plate 42 as shown by β in FIG. 7. More energy is absorbed by the torsion bar 7 and the second EA mechanism 41 so as to change the limited load applied to the seatbelt 3.

Based on the output signals from the respective sensors 51, 52, 53, 54, 55 and the buckle switch 56, the CPU 37 recognizes the current state as the emergency. When it is determined that the energy absorption performed by the second EA mechanism 41 is no longer required, the CPU 37 activates the gas generator 49a of the drive member 49. Referring to FIG. 6(d), the gas generator 49a generates the reaction gas which drives the drive member 49 to rotate the lever 50 of the operation control member 48 clockwise. As the engagement protrusion 50a of the lever 50 is disengaged from the engagement recess portion 44, the second energy absorber support member 44 becomes rotatable.

Then referring to FIG. 6(e), the second energy absorber support member 44 rotates in the belt withdrawal direction together with the spool 4 and the first energy absorber support member 43. The U-shaped portion 42b stops moving toward the other end side such that the energy absorbing plate 42 is not deformed. The second EA mechanism 41 finishes the energy absorption, and the torsional deformation load of the torsion bar 7 only exists as the limited load as shown by γ in FIG. 7. In this way, more energy is absorbed only by the torsion bar 7 to further change the limited load applied to the seatbelt 3. When the energy absorption performed by the second EA mechanism 41 is required, the seatbelt retractor 1 is structured to set the limited load in three stages.

Based on the output signals from the respective sensors 51, 52, 53, 54, 55 and the buckle switch 56, the CPU 37 recognizes the current state as emergency. When it is determined that the energy absorption performed by the second EA mechanism in the initial stage is not required, the CPU 37 activates the gas generator 49a of the drive member 49. This allows the second energy absorber support member 44 to be rotatable such that the energy absorbing plate 42 is not deformed as described above. The second EA mechanism 41, thus, does not perform the energy absorption. At this time, the limited load becomes the value obtained by summing the torsional deformation load of the torsion bar 7, and the pull-out load of the energy absorbing pin 64 of the third EA mechanism 63.

Referring to FIG. 5(c), when the energy absorbing pin 64 is fully pulled out, the energy absorption performed by the third EA mechanism 63 is finished. The load of the torsion bar 7 only exists as the limited load applied to the seatbelt 3 in the last stage. In this way, more energy is absorbed only by the torsion bar 7 to further change the limited load applied to the seatbelt 3. When the energy absorption performed by the second EA mechanism 41 is not required, the seatbelt retractor 1 is structured to set the limited load in two stages.

The seatbelt retractor 1 is structured to change the limited load applied to the seatbelt 3 in the emergency state by the second EA mechanism 41 which allows the limited load to be variable based on the emergency state information, that is, the preliminarily known information (for example, occupant's weight and the seat slide position), the collision forecast information which forecasts the collision, and the collision seriousness information (collision speed, acceleration/deceleration upon collision, collision type). The limited load applied to the seatbelt 3 may be variably set with further flexibility depending on the emergency state and the emergency information such as the occupant's body size. This makes it possible to effectively and appropriately restrain the occupant in the emergency state.

Combining the second EA mechanism 41 where the limited load is variably set with the first EA mechanism and the third EA mechanism 63 where the limited load is fixed makes it possible to set the limited load applied to the seatbelt in the emergency state effectively. Accordingly, the occupant may be restrained further effectively and appropriately.

When the rotation of the locking base 14 in the seatbelt withdrawal direction is blocked, and the spool 4 rotates relative to the locking base 14 in the seatbelt withdrawal direction, the load applied to the seatbelt 3 is limited by the torsion bar 7 and the third EA mechanism 63 in the initial state, or the load is limited by the torsion bar 7 and the second and the third seatbelt load limiting mechanisms 41 and 63 in the initial stage, and further limited only by the torsion bar 7 in the last stage. When the rotation of the locking base 14 in the seatbelt withdrawal direction is blocked, and the spool 4 rotates relative to the locking base 14 in the seatbelt withdrawal direction, the load applied to the seatbelt 3 may be largely limited by the torsion bar 7 and the third EA mechanism 63 in the initial stage, or largely limited by the torsion bar 7 and the second and the third seatbelt load limiting mechanisms 41, 63 in the initial stage, and further limited only by the torsion bar 7 in the last stage.

Conventionally, the energy applied to the occupant in the emergency state (normally referred to as the chest acceleration) is small as it is transmitted only through the seatbelt 3. When the airbag starts contacting the occupant, the energy of the airbag is added to the aforementioned energy to become gradually large, failing to perform the uniform energy absorption. The effective load limitation performed by the EA mechanisms as described above limits the load applied to the seatbelt 3 even if the energy of the airbag activated in the emergency state is added. This allows the energy absorption to be made uniform irrespective of the body size of the occupant, resulting in the effective energy absorption.

As the second EA mechanism 41 is provided coaxially with the spool 4, the seatbelt retractor 1 may be made compact in the vertical direction. This makes it possible to increase the effective space of the vehicle interior.

The third EA mechanism 63 employs the thin and long energy absorbing pin 64 to be inserted into the axial hole 4c of the spool 4. The structure of the third EA mechanism 63, thus, may become simple and the seatbelt retractor 1 may further become compact.

The aforementioned seatbelt retractor 1 is applicable to the one employed in the conventional seatbelt apparatus. The seatbelt apparatus 62, for example as shown in FIG. 8, to which the aforementioned seatbelt retractor 1 is applied includes the seatbelt retractor 1 fixed to the vehicle body, the seatbelt 3 withdrawn from the seatbelt retractor 1, having a belt anchor 3a at the tip fixed to the floor of the vehicle body or the vehicle seat 58, a guide anchor 59 for guiding the seatbelt 3 withdrawn from the seatbelt retractor 1 to the shoulder of the occupant, a tongue 60 slidably supported at the seatbelt 3 which has been guided with the guide anchor 59, and the buckle 61 fixed to the floor of the vehicle body or the vehicle seat, and allows the tongue 60 to be detachably inserted to be engaged therewith.

In the aforementioned example, the gas generator 49a is employed as the drive member 49 for rotating the lever 50 of the operation control member 48. Embodiments are not limited to the one as described above. The lever 50 may be rotated by any other unit as the drive member 49, for example, the electromagnetic force derived from the solenoid. In the aforementioned case, the solenoid may be driven and controlled by the CPU 57 in the same way as the aforementioned example.

In the aforementioned example, the energy absorbing pin 64 is used as the third EA mechanism 63. In this case, the pull-out of the energy absorbing pin 64 limits the load applied to the seatbelt 3. The EA mechanism having the energy absorbing plate like the second EA mechanism 41 having the energy absorbing plate 42 may be employed as the third EA mechanism 63. In the aforementioned case, the length of the energy absorbing plate may be made longer than that of the energy absorbing pin 64 (the length of the energy absorbing pin 64 is required to be shorter than that of the spool 4 in the axial direction). This makes it possible to increase the rotation stroke of the spool 4 for which the limited load by the energy absorbing plate is set. However, it is preferable to use the energy absorbing pin 64 as the third EA mechanism 64 in order to simplify and reduce the size of the structure of the seatbelt retractor including the respective EA mechanisms.

The seatbelt retractor is used in the seatbelt apparatus installed in the vehicle, such as an automobile, for limiting the load applied to the seatbelt in the emergency state, such as a collision, to prevent withdrawal of the seatbelt while absorbing and alleviating the energy exerted to the occupant.

Japan Priority Application 2006-165619, filed Jun. 15, 2006 including the specification, drawings, claims and abstract, is incorporated herein by reference in its entirety.

Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.

Claims

1. A seatbelt retractor, comprising: a spool which retracts a seatbelt;a lock unit provided with a locking member that rotates together with the spool upon transmission of a rotation of the spool via a first seatbelt load limiting mechanism in a normal state and the rotation in a seatbelt withdrawal direction is blocked in an emergency state, the first seatbelt load limiting mechanism limiting a load applied to the seatbelt when the rotation of the locking member in the seatbelt withdrawal direction is blocked to allow the spool to rotate relative to the locking member in the seatbelt withdrawal direction;a second seatbelt load limiting mechanism coaxial with the spool which changes a limited load applied to the seatbelt in the emergency state based on information about the emergency state including at least one of an occupant's body size, a seat slide position, vehicle speed at the time of the collision speed, acceleration/deceleration at the time of the collision, or a collision type; anda third seatbelt load limiting mechanism provided between the spool and the locking member to limit the load applied to the seatbelt in the emergency state.

2. The seatbelt retractor according to claim 1, wherein when the rotation of the locking member in the seatbelt withdrawal direction is blocked and the spool rotates relative to the locking member in the seatbelt withdrawal direction, the load applied to the seatbelt is limited by the first and the third seatbelt load limiting mechanisms in an initial stage, or the load applied to the seatbelt is limited by the first to the third seatbelt load limiting mechanisms in the initial stage, and further limited only by the first seatbelt load limiting mechanism in at least a last stage.

3. The seatbelt retractor according to claim 1, wherein the first seatbelt load limiting mechanism includes a torsion bar disposed between the spool and the locking member.

4. The seatbelt retractor according to claim 1, wherein the second seatbelt load limiting mechanism includes a first energy absorber support member coaxial with the spool so as to be integrally rotatable, a second energy absorber support member coaxially attached to the first energy absorber support member, and an energy absorbing member between the first and the second energy absorber support members.

5. The seatbelt retractor according to claim 1, wherein the third seatbelt load limiting mechanism includes an energy absorbing pin slidably inserted into an axial hole formed in the spool so as to pierce through the locking member such that the load applied to the seatbelt is limited by a load caused by pulling out the energy absorbing pin from the axial hole of the spool when the spool rotates relative to the locking member in the seatbelt withdrawn direction in the emergency state.

6. A seatbelt apparatus, comprising: a seatbelt;a seatbelt retractor for retracting the seatbelt;a tongue slidably supported at the seatbelt and withdrawn from the seatbelt retractor; anda buckle with which the tongue is detachably engaged, wherein the seatbelt apparatus allows the seatbelt retractor to prevent withdrawal of the seatbelt in the emergency state to restrain an occupant, andwherein the seatbelt retractor includes: a spool which retracts the seatbelt;a lock unit provided with a locking member that rotates together with the spool upon transmission of a rotation of the spool via a first seatbelt load limiting mechanism in a normal state and the rotation in a seatbelt withdrawal direction is blocked in an emergency state, the first seatbelt load limiting mechanism limiting a load applied to the seatbelt when the rotation of the locking member in the seatbelt withdrawal direction is blocked to allow the spool to rotate relative to the locking member in the seatbelt withdrawal direction;a second seatbelt load limiting mechanism coaxial with the spool which changes a limited load applied to the seatbelt in the emergency state based on information about the emergency state including at least one of an occupant's body size, a seat slide position, vehicle speed at the time of the collision speed, acceleration/deceleration at the time of the collision, or a collision type; anda third seatbelt load limiting mechanism provided between the spool and the locking member to limit the load applied to the seatbelt in the emergency state.

7. The seatbelt apparatus according to claim 6, wherein when the rotation of the locking member in the seatbelt withdrawal direction is blocked and the spool rotates relative to the locking member in the seatbelt withdrawal direction, the load applied to the seatbelt is limited by the first and the third seatbelt load limiting mechanisms in an initial stage, or the load applied to the seatbelt is limited by the first to the third seatbelt load limiting mechanisms in the initial stage, and further limited only by the first seatbelt load limiting mechanism in at least a last stage.

8. The seatbelt apparatus according to claim 6, wherein the first seatbelt load limiting mechanism includes a torsion bar disposed between the spool and the locking member.

9. The seatbelt apparatus according to claim 6, wherein the second seatbelt load limiting mechanism includes a first energy absorber support member coaxial with the spool so as to be integrally rotatable, a second energy absorber support member coaxially attached to the first energy absorber support member, and an energy absorbing member between the first and the second energy absorber support members.

10. The seatbelt apparatus according to claim 6, wherein the third seatbelt load limiting mechanism includes an energy absorbing pin slidably inserted into an axial hole formed in the spool so as to pierce through the locking member such that the load applied to the seatbelt is limited by a load caused by pulling out the energy absorbing pin from the axial hole of the spool when the spool rotates relative to the locking member in the seatbelt withdrawn direction in the emergency state.

11. A seatbelt apparatus, comprising: a seatbelt;a seatbelt retractor for retracting the seatbelt, the seatbelt retractor includes: a spool which retracts the seatbelt;a lock unit provided with a locking member that rotates together with the spool upon transmission of a rotation of the spool via a first seatbelt load limiting mechanism in a normal state and the rotation in a seatbelt withdrawal direction is blocked in an emergency state, the first seatbelt load limiting mechanism limiting a load applied to the seatbelt when the rotation of the locking member in the seatbelt withdrawal direction is blocked to allow the spool to rotate relative to the locking member in the seatbelt withdrawal direction;a second seatbelt load limiting mechanism coaxial with the spool which changes a limited load applied to the seatbelt in the emergency state based on information of the emergency state including an occupant's body size, a seat slide position, a collision speed, acceleration/deceleration at the time of the collision, and a collision type; anda third seatbelt load limiting mechanism provided between the spool and the locking member to limit the load applied to the seatbelt in the emergency state,wherein the seatbelt apparatus is configured to variably set a limited load applied to the seatbelt upon a vehicle collision in accordance with emergency information including at least one of occupant's weight, seat slide position, collision speed, acceleration/deceleration at the collision, and type of collision.

12. The seatbelt apparatus of claim 11, further comprising an operation control member and a drive member to control the second seatbelt load limiting mechanism.

13. The seatbelt apparatus of claim 12, wherein the operation control member includes a lever with an engagement protrusion configured to be releasably positioned in an engagement recess portion of a second energy absorber support member.