WEBBING RETRACTOR

Abstract: A webbing retractor (10) in which a retracting shaft (14) for winding up a webbing is urged by a pair of resilient members (26,28) connected in series through a ratchet wheel (24) to cause the webbing to be wound around the retracting shaft, and a pawl (34) is disengageably meshed with the ratchet wheel by a friction spring (42) which is transmitted a rotation of the retracting shaft through a frictional force so that an urging force of one of the resilient members (28) is prevented from transmitting to the retracting shaft (14) during engagement of the pawl (34) with the ratchet wheel (24), wherein a reduced condition of the webbing retracting force is able to be maintained over a wide range.

Description: This invention relates to a webbing retractor comprising a frame, retracting shaft supported in the frame for winding up an occupant restraining webbing, a first resilient member coaxially disposed with the axis of the retracting shaft, a ratchet wheel engaged with an end of the first resilient member, a second resilient member engaged with the ratchet wheel at one end and engaged with the frame at the other end thereof, pawl means engaged with the ratchet wheel so as to prevent an urging force of the second resilient member from being transmitted to the retracting shaft, a frictional rotation means being rotatable to a desired angle under a transmittance of a rotation of the retracting shaft through a frictional force, and enabling the pawl means to be engaged with the ratchet wheel under an intermediate state of rotation, and cam means being rotatable to move the pawl means away from the ratchet wheel when rotated in a webbing retracting direction. A webbing retractor of this kind is disclosed in the Japanese Utility Model Application Laid Open No.60-44856. In a seatbelt device for a vehicle, a webbing retractor for decreasing a winding force is used, the retractor of which has a pair of resilient members provided in series for applying a webbing retracting urging force to a winding shaft. And a connecting portion between the resilient members is held during applying a webbing so that the urging force of one of the resilient members is prevented from transmitting to an occupant. As disclosed in the Japanese Utility Model Application, the retractor device is constructed such that each end of a pair of resilient members connected in series is engaged with a ratchet wheel, and when a webbing is applied to an occupant, a pawl is engaged with the ratchet wheel so that a winding urging force of one of the resilient members is not transmitted to a winding shaft. In this type of webbing retractor, when the winding shaft is rotated in a webbing winding direction after the occupant releases the webbing, the rotating force is transmitted to a cam plate and the cam plate forcedly releases a pawl from the ratchet wheel, and the biasing force of both resilient members is transmitted to the winding shaft and generates a positive winding force in generated. Due to this arrangement, when the rotation of the connecting wheel in a webbing winding direction is transmitted to the cam plate, a state of reducing the winding force is released under a slight winding operation even though the occupant keeps a webbing restraining state. However, in a certain case of pulling-out or winding operation which is normally performed, it is necessary that the state of reducing the winding force is not released. However, the conventional type of cam plate is constructed such that projections are stored in a ring-shaped groove of the connection wheel rotating together with the winding shaft, and when the webbing is to be wound, the cam plate may start to rotate after its maximum one rotation in reference to its relative position with respect to the connection wheel and in addition when the connection wheel is rotated in its maximum one rotation, the cam plate may forcedly move the pawl away from the ratchet wheel. In view of the above-described circumstances, it is an object of the present invention to provide a webbing retractor according to the preamble of Claim 1 in which a reduced condition of the webbing winding force can be maintained for an elongated range in case that the webbing is rotated in its winding direction from the state where the webbing retracting force is reduced. The present invention provides a webbing retractor of a seatbelt device according to the preamble of Claim 1 which is characterized by: a connection wheel is disposed to the retracting shaft and the other end of the first resilient member is engaged with the connection wheel, the cam means has a plurality of projections, and cam driving means are defined by grooves which are formed substantially helically at an outer circumference of the connection wheel for receiving a first projection which is projected from the cam means, whereby a rotation of the connection wheel is transmitted to the cam means when the first projection contacts to the longitudinal end portion of the grooves and the cam means is moved under a rotational force of the connection wheel. In the present invention, even though the winding shaft is rotated in a webbing winding direction from a state where the webbing winding force is reduced, the projection of the cam apparatus is guided by the helical groove at the outer circumference of the connection wheel and so the cam apparatus is loosely rotated with the connection wheel, and after the connection wheel, that is, the winding shaft is rotated by several times in a webbing winding direction, the projection of the cam apparatus corresponds to the longitudinal end part of the helical groove, the cam apparatus is rotated together with the connection wheel to cause the pawl to be moved away from the ratchet wheel. With this arrangement, after the winding shaft is rotated by several times in the webbing winding direction from the state where the winding force is reduced, the state where the winding force is reduced is released and then the winding force reduced condition is not uselessly released under a normal action of the occupant during driving the vehicle. The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a sectional view of a first embodiment a webbing retractor according to the present invention is applied; Fig.2 is a sectional view taken along a line II-II of Fig.1; Fig.3 is a sectional view taken along a line III-III of Fig.1; Fig.4 is a sectional view taken along a line IV-IV of Fig.1 Figs.5 and 6 are side views showing operating condition from a state shown in Fig.2, respectively; Fig.7 is a front elevational view showing a cam plate; Fig.8 is a perspective view showing a connection wheel; Fig.9 is a top plan view showing a developed groove shape of a connection wheel; Fig.10 is a perspective view showing a pawl; Figs. 11 to 13 illustrate a second embodiment of a webbing retractor to which the present invention is applied, where Fig. 11 is a sectional view corresponding to Fig. 1 and Fig. 12 is a sectional view corresponding to Fig. 2; Fig. 13 is a perspective view of a pawl corresponding to Fig. 10. DESCRIPTION OF THE PREFERRED EMBODIMENTS In Fig.1 is illustrated a sectional view of a webbing retractor 10 of a first embodiment of the present invention. The webbing retractor 10 is constructed such that a frame 11 is fixed to a chassis by bolts not shown and a retracting shaft 14 is pivotally supported at leg plates 12 and 13 extending from both sides of the frame 11. To the retracting shaft 14 is engaged one end of an occupant restraining webbing 16 and the webbing is wound in a layer form. To the other end of the webbing 16 is fixed a tongue plate which is engaged with a buckle device vertically installed at an opposite side of a seat, thereby the occupant may wear an intermediate part of the webbing 16. A connection wheel 22 is coaxially fixed to the retracting shaft 14 and rotates together with the retracting shaft 14. The connection wheel 22 has a ratchet wheel 24 pivotally supported at a reduced diameter portion 22A axially projected. An outer end of a small spiral spring 26 to an inner circumferential surface of the ratchet wheel 24 is engaged and an inner end of the small spiral spring 26 is engaged with a spring engaging part 22B adjacent to the small diameter portion 22A. To a projected portion 24A of the ratchet wheel 24 is engaged an inner end of a large spiral spring 28 acting as a second resilient member. The large spiral spring 28 has a larger urging force than that of the small spiral spring 26, its outer end is engaged with a cover 30 to be fixed to the leg part 13 and the spring is supported to the frame 11 through the cover 30. Thus, the retracing shaft 14 is constructed such that it may receive a urging force of the small spiral spring 26 and the large spiral spring 28 connected in series through the ratchet wheel 24 and then may be rotated in a winding direction of the webbing 16 (a direction of an arrow head A in Fig.2). As shown in Fig.2, a pawl 34 corresponds with an outer circumference of the ratchet teeth 24B of the ratchet wheel 24. As shown in Fig.10, this pawl 34 has a projected portion 34A pivotally supported in a shaft 38 projected from the cover 30. When a projection 34B projected from the extremity end is engaged with the ratchet teeth 24B, it prevents the ratchet 24 from being rotated in a webbing retracting direction (a clockwise direction in Figs. 5 and 6, a direction of the arrow head A) and further prevents a urging force of the large spiral spring 28 from being transmitted to the retracting shaft 14, transmits only a weak urging force of the small the winding force. Due to the arrangement, a twisted coil spring 38 fixed to an outer circumference of the projected portion 34A has both ends bridged over the cover 30 and the pawl 34 and generates the urging force in such a direction as the projection 34B of the pawl 34 to be engaged with the spring engaging portion 22B. In order to control an engaged condition between the pawl 34 and the connection wheel 22 and a releasing of both of them, there are provided a friction spring 42 acting as a frictional rotating apparatus and a cam plate 44 acting as the cam apparatus. As shown in Fig.3, the friction spring 42 is constructed such that a pair of intermediate portions 42A are contacted with the outer circumference of a cylindrical portion 46 of the connection wheel 22 to receive the rotation of the connection wheel 22 through a frictional force. A substantial U-shaped arm 42B is projected from one end of the intermediate portion 42A and is corresponded with the pole 34. The arm 42B is inserted into a groove or a concave portion 4B formed near the extremity end of the pawl 34. As shown in Figs.5 and 6, the groove 48 enables the arm 42B to be rotated up to its abutting position against side walls 48A and 48B. That is, the arm 42B is abutted against the side wall 48A under a rotation of the retracting shaft 14 in a direction of webbing winding operation. The arm 42B is abutted against the side wall 48B under its rotation in a webbing pulling-out direction and a rotation of the friction spring 42 is restricted so as to generate a sliding movement between the intermediate portion 42A of the friction spring and the cylindrical portion 46. Under a condition in which the arm 42B is abutted against the side wall 48A, the extremity end of the arm 42B corresponds with the bottom wall 48C of the groove 48 and in turn under a condition in which tte arm 42B is abutted against the side wall 48B, the arm corresponds with the bottom wall 48D so as to prevent the pawl 34 from being engaged with the ratchet wheel 24. However, under a condition in which the arm 42B is corresponded with the bottom wall 48D, the pawl 34 may be rotated in a clockwise direction as view in Fig.5 only an amount slightly more than that of a condition in which the arm 42B is corresponded with the bottom wall 48C and a depth of the groove 48 is different for each of the bottom walls 48C and 48D in such a manner as the projection 34B reaches near an outer circumference of the ratchet wheel 24. As shown in Fig.10, a recess 48E is formed between the bottom wall 48C and the bottom wall 48D, and the friction spring 42 can be inserted into the recess 48E as shown in Fig .6. In this case, since the arm 42B does not restrict the rotation of the pawl 34, the pawl 34 has its projection 34B which can be engaged with the ratchet teeth 48B. The bottom wall 48C and the bottom wall 48D are formed with chamfers 48F and 48G at the end portion n of the 48E. In the pawl 34, a guide rib 52 projected from the cover 30 and extended in a longitudinal direction around an axis of the shaft 30 corresponds with the opposite surface of the groove 48 so as to prevent any looseness of the pawl 34. In the friction spring 42, an end portion opposite to the arm 42B of the intermediate portion 42A is an arm 42C projected in a redial direction of the cylindrical portion 46 so as to hold it when its fixing operation is performed. In turn, the cam plate 44 is of a hollow ring shape as shown in Fig. 7 and its side surface is, as shown in Fig. 1, arranged between the friction spring 42 and a flange portion 22C of the connection wheel 22, its inner circumference is supported at an outer circumference of a large diameter cylinder 46 between the cylindrical portion 46 and a flange portion 22C so as to enable a relative rotation with the connection wheel 22. The cam plate 44 is formed with a recess 44A which extends over approximately 1/3 of its inner circumference and further formed with a force receiving arm 54 which is integrally projected into the recess 44A. This force receiving arm 54 has its base end connected to one end of the recess 44A and is extended in an arc form along the recess 44A. Its extremity end is a projection 54A which is bent in axial direction and is inserted into a groove 56 formed at an outer circumference of the large diameter cylinder 46A. As shown in Figs.8 and 0, this groove 56 is formed at an outer circumference of the connection wheel 22, has a first groove 56A and a second groove 56B of which axes are arranged within an axial perpendicular plate of the connection wheel 22, the first groove 56A and one end of the second groove 56B communicated with a slant groove 56C inclined in respect to an axial perpendicular plane of the connection wheel 22, thereby it forms a helical groove of about two turns. In the preferred embodiment, although the first groove 56A and the second groove 56B have a slant groove 56C to form a substantial helical groove, it may also be available that it is a helical groove such as a thread in which the first groove and the second groove are inclined in respect to the perpendicular plane of the cam plate. Although each of the end portions opposite to the first groove 56A and the slant groove 56C of the second groove 56B is applied as a wall 56D and a wall 56E, a part of the wall 56D is a slant surface 56F in which a groove depth of the first groove 56A is gradually decreased. Due to this arrangement, although the force receiving arm projection 54A of the cam plate 44 entering into the groove 56 is moved in a direction of an arrow head B as shown in Fig.9 when the webbing is pulled out, the arm projection may ride over this wall 56D at the end portion of the first groove 56A in a direction of an arrow head D and enter again into the slant groove 56C. The wall 56D is made lower than the large diameter cylinder 46A to enable the force receiving arm projection 54A to be guided positively in a direction of the arrow head D. The force receiving arm 54 can be resiliently deformed in a radial direction of Fig.7, i.e. such a direction as away from the center axis and in a direction in parallel with the axial center (a direction perpendicular to the sheet of Fig.7), the force receiving projection 54A is moved toward the first groove 56A and the second groove 56B through the slant groove 56C and can ride over the wall 56D in a direction of the arrow head D in Fig.9 The arrow head B in Fig.9 indicates the moving direction of the force receiving arm projection 54A when the webbing is pulled out and an arrow head C indicates the moving webbing is retracted. Four projections 22D shown in Fig.8 are used for connecting with the retracting shaft 14 of the connection wheel 22. The outer circumferential part of the cam plate 44 has a substantial triangle cam projection 44B at a portion thereof. The cam projection 44B has a vertical wall 44C and a slant wall 44D to cause the pawl 34 to be moved away from the ratchet wheel 24 in response to the projection 34B of the pawl 34 when the pawl 34 is rotated in a clockwise direction while being engaged with the ratchet wheel 24 as shown in Fig.5. Then, the action of the preferred embodiment of the present invention will be described. Fig.4 shows a state of the fully wound and stored condition of the webbing 18 in case that the occupant may not wear the webbing 16 . Under this condition, the arm 42B corresponds to the bottom wall 48C and causes the pole 34 to be moved away from the ratchet wheel 24. The cam plate 44 is not placed at a specified location. In order for the occupant to pull out the webbing 16 in a direction opposite to the direction of the arrow head A, the retracting shaft 14 and the connection wheel 22 are rotated in a counterclockwise direction of Fig.4, so that the friction spring 42 is rotated in a counterclockwise direction while its intermediate portion 42A receives a friction force from the cylindrical portion 46. Due to this fact, the extremity end of the arm 42B corresponds to the recess 48E of the pawl 34. Thus, the pawl 34 has a projection 34B contacted with the ratchet wheel 24 though a urging force of the twisted coil spring 38. However, as the webbing 16 continuously receives a tensile force, the projection 34B of the pawl 34 is pushed up over the slant surface 24D of the racthet wheel 24, resulting in that the friction spring 42 receiving a rotational force of the counterclockwise direction in Fig.4 shows that its arm 42B is moved toward the bottom wall 48D and then as shown in Fig.5, the pawl 34 is kept at a state where it is spaced apart from the racthet wheel 24. In addition, as the webbing 16 is pulled out further, the friction spring 42 has its intermediate portion 42A rotated in respect to the cylindrical portion 46 and the friction spring 42 is topped while the arm 42B is being abutted against the side wall 48B. The cam plate 44 receives the frictional force in a counterclockwise direction of the connection wheel 22, is rotated with a low rotational force in a counterclockwise direction, and the vertical wall 44C is abutted against the projection 34B of the pawl and stopped. Due to this arrangement, as the webbing is pulled out, the force receiving cam projection 54A of the cam plate continues to perform a relative movement within the groove of the connection wheel, i.e. the first groove 56A in the directions of arrow heads B and D in Fig.9. After the occupant pulls out the webbing 16 sufficiently, as the tongue plate not shown in the drawing is enaged with the buckle device to wear the webbing 16, a surplus amount of pulling-out webbing until it is closely contacted with the occupant is wound by the urging forces of the small spiral spring 26 and the large spiral spring 28. Due to this fact, the retracting shaft 14 and the connection wheel 22 are rotated in a clockwise direction of Fig.5 by about one turn. Accordingly, the friction spring 42 accepting this rotation through frictional force between it and the cylinder 46 shows that the arm 42B corresponds to the recess 48E of the pole 34 and as shown in Fig.6 the pawl 34 is rotated in a clockwise direction under a biasing force of the twisted coil spring 38 and then the projection 34B is engaged with the ratchet wheel 24. Due to this arrangement, in the large spiral spring 28, the urging force acting against the connection wheel 22 and the retracting shaft 14 is prohibited and only the small spiral spring 26 may apply a weak retracting force to the retracting shaft 14 to make a reduced tention state. With this operation, a feeling of compression toward the occupant is reduced. When the webbing 16 is pulled out of the retracting shaft 14 under an operation in which the occupant changes his driving attitude, the retracting force retracted state is maintained until the small spiral spring 26 is closely contacted. When the webbing 16 is retracted onto the retracting shaft 14 due to a variation of driving attitude and a breathing of the occupant, the connection wheel 22 is rotated in a clockwise direction as shown in Fig.6. The projection 54A arranged in the groove 56 of the connection wheel 22 does not accept any rotational force by the connection wheel 22 until it is moved in the direction of the arrow head C in Fig.9 and abutted against the wall 56E. Although the projection 54A is different in view of the stopped position of the cam plate 44, the cam projection 44B of the cam plate 44 just after the retracting force is reduced keeps a condition shown in Fig.6. Although it is different from the stopped position of the cam plate, the projection 54A of the force receiving arm 54 is arranged in the first groove 56A, resulting in that the connecting member can be rotated by a minimum amount of two turns and a maximum amount of about three turns until the webbing 16 is retracted around the retracting shaft 44B and the cam projection 44B of the cam plate 44 pushes up the pawl 34. This tension reduced state may not be reduced uselessly under a retracting operation during the time in which the webbing 16 is worn by the occupant. When the occupant releases the restraining webbing 16, the webbing 16 is wound around the retracting shaft 14 under a weak urging force of the small spiral spring 26. Thus, as the winding shows a minimum number of two rotations and a maximum number of about three rotations, the projection 54A of the force receiving arm 54 corresponds to the wall 56E, the slant wall 44D of the cam projection 44B pushes up the projection 34B away from the ratchet wheel 24, so that the ratchet wheel 24 can be rotated and a large urging force of the large spiral spring 28 is added to the retracting shaft 14 and the retracting shaft 14 may wind up the webbing 18 by a strong force to its fully stored condition. In Figs.11 to 13 is illustrated a second embodiment, a modified form of the above-described preferred embodiment and in this retractor deice 10, a winding diameter sensing lever 100 for sensing a winding diameter of the webbing 16 is fixed to the pawl 34. The base end of the diameter sensing lever 100 is fixed to the extremity end of the pawl 34, its intermediate portion passes through the leg plate 13 of the frame 11, and the extremity end is opposite to the outer-most circumferential layer of the webbing 16 wound around the retracting shaft 14. The extremity end of the winding diameter sensing lever 100 is made such that as the winding diameter of the webbing 16 is more than a desired intermediate diameter between the occupant restraining condition and the fully-wound condition, it may abut against the outer-most circumferential layer of the webbing 16 wound in a layered form. Under this condition, the pawl 34 may not oscillate toward its biasing direction under an influence of the twisted coil spring 38. Even in case that th arm 42B of the friction spring 42 is opposite to the recess 48E of the pole 34, the pole 34 may not be engaged with the ratchet wheel 24. Accordingly, even in case that the retracting of the webbing 16 is temporarily stopped in the midway of its retracting operation due to a certain reason after the occupant release the restraining webbing 16 and the retracting of the webbing 16 is started, the retracting urging force of the webbing 16 is not reduced, so that the webbing 16 can be positively retracted up to its fully-wound condition. Also, even in case that the pulling-out of the webbing is stopped after the fully-wound webbing 16 is pulled out slightly, the retracting urging force of the webbing 16 is not reduced, so that the webbing 16 can be positively wound up to its fully-wound or retracted condition. As described above, the present invention is operated such that the projection in the cam apparatus is guided by the helical groove arranged in the connection wheel, so that the present invention has a superior effect that a range of condition of the retracting force reduced is extended and the retracting force reduced condition is not uselessly released during the time when the occupant is restrained by the webbing.

Claims: A webbing retractor comprising a frame (11), retracting shaft (14) supported in the frame (11) for winding up an occupant restraining webbing (16), a first resilient member (26) coaxially disposed with the axis of the retracting shaft (14), a ratchet wheel (24) engaged with an end of the first resilient member (26), a second resilient member (28) engaged with the ratchet wheel (24) at one end and engaged with the frame at the other end thereof, pawl means (34) engaged with the ratchet wheel (24) so as to prevent an urging force of the second resilient member (28) from being transmitted to the retracting shaft (14), a frictional rotation means (42) being rotatable to a desired angle under a transmittance of a rotation of the retracting shaft (14) through a frictional force, and enabling the pawl means (34) to be engaged with the ratchet wheel (24) under an intermediate state of rotation, and cam means (44) being rotatable to move the pawl means away from the ratchet wheel (24) when rotated in a webbing retracting direction, characterized in that a connection wheel (22) is disposed to the retracting shaft (14) and the other end of the first resilient member (26) is engaged with the connection wheel (22), the cam means (44) has a plurality of projections (44B,54A) and cam driving means (56,56E) are defined by grooves (56) which are formed substantially helically at an outer circumference of the connection wheel (22) for receiving a first projection (54A) which is projected from the cam means (44), whereby a rotation of the connection wheel (22) is transmitted to the cam means (44) when the first projection (54A) contacts to the longitudinal end portion (56E) of the grooves (56) and the cam means is moved under a rotational force of the connection wheel (22). A webbing retractor according to Claim 1, characterized in that the pawl means (34) is provided with a restricting means (48) for restricting a rotational angle of the frictional rotating means (42) to the desired angle. A webbing retractor according to Claim 2, characterized in that the frictional rotating means (42) has a rotational transmitting portion (42A) where a rotation of the retracting shaft (14) is transmitted through a frictional force, and an abutting portion (42B) abutted against the pawl means to prevent the pawl means from engaging with the ratchet wheel (24). A webbing retractor according to Claim 3, characterized in that the pawl means (34) is formed with a recess (48) for storing the abutting portion (42B), and the restricting means (48) is comprised of a pair of side walls (48A,48B) forming a portion of the recess (48) abutting against the side surface of the abutting portion (42B) to restrict a rotation of the frictional rotating means (42). A webbing retractor according to Claim 4, characterized in that the recess (48) of the pawl means (34) has bottom wall portions (48C,48D) constituting an engagement preventing means in which an extremity end of the abutting portion of the frictional rotating means (42) is abutted to prevent an engagement between the pawl means (34) and the ratchet wheel (24). A webbing retractor according to Claim 5, characterized in that the bottom wall portion (48C,48D) is formed with a recess portion (48E) one part of which is cut and this cut portion stores the extremity end of the abutting portion (42B) to enable the engagement of the pawl means (34) with the ratchet wheel (24) to be performed. A webbing retractor according to Claim 1, characterized in that the grooves (56) are provided with a plurality of first grooves (56A) formed in planes perpendicular to an axial direction of the connection wheel (22) and a second groove (56B) communicating with the first grooves (56A) and formed at an angle to the perpendicular plane. A webbing retractor according to Claim 1, characterized in that the grooves (56) are composed of grooves (56A,56B,56C) which are inclined with respect to the plane perpendicular to the axial direction of the connection wheel (22). A webbing retractor according to Claim 1, characterized in that the cam means (44) comprises a second projection (44B) projecting from an outer circumference part of an annular plate supported by the connection wheel (22) for disengaging the engagement of the pawl means (34) with the ratchet wheel (24). A webbing retractor according to Claim 1, characterized in that the first projection (54A) is radially projected from an inner circumference part of the annular plate. A webbing retractor according to Claim 1, characterized in that the frictional rotating means (42) is composed of a leaf spring member. A webbing retractor according to Claim 1, characterized by an engagement preventing means (100) is provided to prevent the pawl means (34) from engaging with the ratchet wheel (24) when the amount of winding of the webbing (16) around the retracting shaft (14) exceeds a desired amount. A webbing retractor according to Claim 2, characterized in that the engagement preventing means (100) is comprised of a lever abutting against an outer-most circumferential layer of said webbing (16), one end of which is supported by the pawl means (34) and the other end of which is supported by the webbing (16), wound around the retracting shaft (14).

Inventors: MORI, SHINJI K.K. TOKAI-RIKA-DENKI-SEISAKUSHO
Applicants: KABUSHIKI KAISHA TOKAI RIKA DENKI SEISAKUSHO
Application year: 1988
Main classification: B60R22
IPC codes: F16D43, B60R22