Retractor for seat belt

Abstract

To provide a retractor for a seat belt which achieves miniaturization / long service life of a motor concerning clutch operation by enhancing quickness of the clutch operation and at the same time makes it possible to correspond to request of high power / high speed belt winding.SOLUTION: In a clutch mechanism 20, a final gear 10 and an additional gear 11 rotate in opposite directions mutually when a motor 4 rotates by first rotational frequency in a belt winding direction. At this time, a friction ring 50 rotates integrally with the additional gear 11 by connection by friction force which intervenes between the additional gear 11 and the friction ring 50 and moves to an engagement position by pressurizing a pawl 40 and then switches in clutch ON state thereby. The friction ring 50 rotates along with the final gear 10 via the pawl 40 relatively to the additional gear 11 and in a direction opposed to the additional gear 11 because torque caused by rotation of the final gear 10 transmitted to the friction ring 50 via the pawl 40 exceeds the friction force when the motor 4 further rotates in the belt winding direction after the first rotational frequency.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a seat belt retractor. [Background technology]

[0002] Conventionally, a retractor provided in a vehicle seat belt device winds and withdraws a seat belt by rotating a spindle, and in the event of a vehicle collision, the rotation of the spindle is locked by a locking mechanism to prevent the seat belt from being withdrawn.

[0003] A motorized retractor is known that, when a sensor detects a sudden vehicle deceleration state (e.g., when there is a possibility of a collision), rotates a spindle by a motor in the winding direction to wind up a certain amount of the seat belt to lightly restrain the occupant, and when a vehicle collision is detected, activates a pyrotechnic pretensioner to forcibly wind up the seat belt to securely restrain the occupant (see, for example, Patent Documents 1 and 2). It is also known to assist in winding up the seat belt by a motor to eliminate slack when the seat belt is fastened and to improve the storability when the seat belt is removed. In general, the former, lightly winding up the seat belt when a sudden vehicle deceleration state is detected, is called "pre-crash operation," and the latter, auxiliary winding up of the seat belt, is called "comfort operation."

[0004] As disclosed in Patent Documents 1 and 2, in a retractor with a motor, a one-way clutch is interposed in a power transmission mechanism that transmits power from the motor to a spindle. When performing pre-crash and comfort operations, the motor is rotated forward to engage the clutch and retract the seat belt. After performing the pre-crash and comfort operations, the motor is rotated reversely to disengage the clutch, allowing the seat belt to be retracted and withdrawn normally. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-162157 A [Patent Document 2] International Publication No. 2016 / 199525 Summary of the Invention [Problem to be solved by the invention]

[0006] There is a demand for smaller motors in motorized retractors. However, making the motor smaller shortens the motor's lifespan. Also, making the motor smaller reduces the belt winding power, so it is necessary to increase the gear ratio, but increasing the gear ratio delays the timing at which the belt starts to wind up.

[0007] The object of the present invention is to provide a seat belt retractor which improves the speed of clutch operation, reduces the size and extends the life of the motor involved in the clutch operation, and can meet the demands for high power and high speed belt winding. [Means for solving the problem]

[0008] A seat belt retractor according to one aspect of the present invention includes a spindle that winds up a seat belt, a motor that generates power to rotate the spindle, and a power transmission mechanism that can transmit the power from the motor to the spindle. The power transmission mechanism includes a clutch mechanism that enables the transmission of power from the motor to the spindle when the motor rotates in a belt winding direction. The clutch mechanism includes a first rotating member that rotates together with the spindle, a pawl that is configured to be movable between an engagement position that engages with the first rotating member and a disengagement position that does not engage with the first rotating member, a final gear that holds the pawl and rotates in response to the rotation of the motor, an additional gear that rotates in the opposite direction to the final gear in response to the rotation of the motor, and a friction ring that is configured to be rotatable integrally with and relative to the additional gear. The clutch mechanism is configured such that when the motor rotates a first number of revolutions in the belt winding direction, the final gear and the additional gear rotate in opposite directions to each other, and at this time, due to the coupling caused by the frictional force between the additional gear and the friction ring, the friction ring rotates integrally with the additional gear and presses the pawl to move the pawl from a disengaged position to an engaged position, thereby switching from an OFF state in which the transmission of power from the motor to the spindle is interrupted to an ON state in which the transmission of power from the motor to the spindle is enabled. The clutch mechanism is configured such that when the motor further rotates in the belt winding direction after the first number of revolutions, the rotation of the motor is transmitted to the spindle via the final gear, the pawl, and the first rotating member, causing the spindle to rotate in the belt winding direction, and the torque due to the rotation of the final gear transmitted to the friction ring via the pawl exceeds the frictional force, causing the friction ring to rotate together with the final gear via the pawl relative to the additional gear and in the opposite direction to the additional gear. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram showing a schematic layout of a seat belt retractor according to an embodiment. [Diagram 2] 1 is an exploded perspective view showing a spindle, a motor, and a power transmission mechanism of a seatbelt retractor according to an embodiment of the present invention; [Diagram 3] 7 is a front view showing the pawl, the friction ring, and the gear train of the power transmission mechanism as viewed from the direction of arrow 7(B) in FIG. 2. [Figure 4] FIG. 4 is a perspective view showing a pawl, a friction ring, and a gear train of a power transmission mechanism, taken from a different angle than in FIG. 3. [Diagram 5] FIG. 4 is a perspective view showing an additional gear and a friction ring. [Figure 6] 1 is a diagram showing the clutch mechanism in the clutch-off state, with the direction of rotation of each part of the clutch mechanism when the motor starts to rotate in the belt winding direction added for reference. [Figure 7] 2A and 2B are diagrams showing the clutch mechanism in the clutch-off state, where (A) is a diagram of the final gear side as seen from the arrow 7(A) in Fig. 2, and (B) is a diagram of the final gear side as seen from the arrow 7(B) in Fig. 2. For reference, the direction of rotation of each part of the clutch mechanism when the motor starts to rotate in the belt winding direction is added. [Figure 8] 13 is a diagram showing the clutch mechanism when the motor rotates a first number of revolutions in the belt winding direction and the clutch is switched to an ON state. FIG. [Figure 9] 13 is a diagram showing the clutch mechanism when the motor rotates in the belt winding direction beyond the first rotation speed and the clutch ON state continues. FIG. [Figure 10] 11 is a diagram showing the clutch mechanism at an initial point in time when the motor rotates in the belt withdrawing direction and the clutch is switched from an ON state to an OFF state. FIG. [Figure 11] 13 is a diagram showing the clutch mechanism when the motor further rotates in the belt withdrawing direction and the clutch mechanism is switched to an OFF state. FIG. [Figure 12] FIG. 11 is a diagram showing a schematic flow of torque transmission when the belt is pulled out in a state where a clutch release failure occurs. [Figure 13] 5 is a graph showing a relationship between tension of the belt winding by the motor and time, comparing the seat belt retractor according to the embodiment with a seat belt retractor according to a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings.

[0011] [Retractor Overview] As shown in FIG. 1, the seat belt retractor 1 has a spindle 3 that winds up a seat belt 2, a motor 4 that generates power to rotate the spindle 3, a power transmission mechanism 5 that can transmit the power from the motor 4 to the spindle 3, and a retractor frame 6 that rotatably supports both ends of the spindle 3.

[0012] The motor 4 is disposed below the retractor frame 6. The motor 4 is configured to be rotatable in both forward and reverse directions, and its driving is controlled by an ECU (not shown). Here, the forward rotation is the belt winding direction, and the reverse rotation is the belt unwinding direction.

[0013] The power transmission mechanism 5 has a gear assembly made up of multiple (here, five) gears 7, 8, 9, 10, and 11. Specifically, an output gear 7 is fixed to an output shaft 4a of the motor 4. The output gear 7 meshes with a cluster gear 8, and the cluster gear 8 meshes with a final gear 10 via an idle gear 9. The cluster gear 8 also meshes with an additional gear 11. In other words, the final gear 10 and the additional gear 11 are gear-coupled with the output shaft 4a of the motor 4, and are configured to rotate in opposite directions to each other in response to the rotation of the motor 4.

[0014] The power transmission mechanism 5 also has a clutch mechanism 20 that can allow and block the transmission of power from the motor 4 to the spindle 3. A part of the clutch mechanism 20 is formed by at least some of the gears of a gear assembly. The clutch mechanism 20 is configured as a one-way clutch that allows the transmission of power from the motor 4 to the spindle 3 when the motor 4 rotates in the belt winding direction.

[0015] Specifically, in this retractor 1, when the above-mentioned pre-crash operation and comfort operation are performed, the clutch mechanism 20 is engaged by the rotation of the motor 4 in the belt winding direction, and the rotation of the motor 4 is transmitted to the spindle 3 to wind up the seat belt 2. After the pre-crash operation and comfort operation are performed, the clutch mechanism 20 is released by the rotation of the motor 4 in the belt withdrawing direction. Under normal circumstances, the clutch mechanism 20 is in a released state, in which the power transmission between the motor 4 and the spindle 3 is interrupted, and the seat belt 2 can be withdrawn and wound from the spindle 3.

[0016] In the following description, the engaged state of the clutch mechanism 20, i.e., the ON state that enables the transmission of power from the motor 4 to the spindle 3, may be referred to as "clutch ON." Also, the released state of the clutch mechanism 20, i.e., the OFF state in which the transmission of power from the motor 4 to the spindle 3 is interrupted, may be referred to as "clutch OFF."

[0017] In addition to the above configuration, the retractor 1 has a known configuration. For example, the retractor 1 has a winding spring device 13 that biases the spindle 3 in the winding direction of the seat belt 2, a locking mechanism 14 that locks the unwinding operation of the seat belt 2 in response to acceleration detected by an acceleration sensor (not shown), and a pretensioner 15 that generates another power to rotate the spindle 3. A torsion bar (not shown) that constitutes an energy absorbing mechanism is provided inside the spindle 3, and one end side of the torsion bar is connected to the spindle 3, and the other end side of the torsion bar is connected to a tread head (not shown) to which a force from the pretensioner 15 is input. The pretensioner 15 is activated when a vehicle collision is detected. In the pretensioner 15, for example, a ball (not shown) is strongly pushed out by gas generated by igniting a gunpowder, and the ball moves along a groove of a pinion (not shown), causing the pinion to rotate. The rotation of the pinion is transmitted to the tread head, the torsion bar, and the spindle 3 via the lock mechanism 14, and the seat belt 2 is forcibly wound up.

[0018] A lower cover 16 and an upper cover 17, which are case members, are attached to the left side surface of the retractor frame 6. A winding spring device 13 is attached to the left side surface of the upper cover 17. A power transmission mechanism 5 is housed in the space between the lower cover 16 and the upper cover 17. For example, referring to FIG. 2, with regard to the gear assembly of the power transmission mechanism 5, the output gear 7 and the final gear 10 are rotatably housed in the lower cover 16, and the additional gear 11 is rotatably housed in the upper cover 17. In addition, a cluster gear 8 and an idle gear 9 are rotatably housed in the lower cover 16 and are rotatably supported by the lower cover 16. Note that FIG. 1 is a schematic diagram, and therefore the housed positions of these gears are different.

[0019] [Outline of clutch mechanism] The clutch mechanism 20 has a clutch housing 30 (first rotating member), a pawl 40, and a friction ring 50. The clutch mechanism 20 also utilizes gears of a gear assembly, and here has the above-mentioned output gear 7, cluster gear 8, idle gear 9, final gear 10, and additional gear 11. In the clutch mechanism 20, the clutch housing 30, the friction ring 50, the final gear 10, and the additional gear 11 are coaxially arranged. The clutch housing 30 is coupled to the spindle 3. The pawl 40 and the friction ring 50 are attached to the final gear 10 by a clutch cover 31.

[0020] To turn the clutch ON, the motor 4 is rotated in the belt winding direction, as will be described later in detail. Then, as shown by the white arrow 100, the final gear 10 rotates via the output gear 7, the cluster gear 8, and the idle gear 9, and the additional gear 11 rotates in the opposite direction to the final gear 10 via the output gear 7 and the cluster gear 8, and the pawl 40 moves to a position where it engages with the clutch housing 30. This turns the clutch ON. After that, the rotation of the final gear 10 transmitted from the motor 4 rotates the clutch housing 30 via the pawl 40, which rotates the spindle 3 in the belt winding direction. At this time, the friction ring 50 rotates together with the final gear 10 via the pawl 40, and rotates relatively to the additional gear 11 in the opposite direction.

[0021] To turn the clutch OFF, the motor 4 is rotated in the belt withdrawing direction. Then, as shown by the black arrow 200, the final gear 10 rotates via the output gear 7, cluster gear 8, and idler gear 9, and the additional gear 11 rotates in the opposite direction to the final gear 10 via the output gear 7 and cluster gear 8, and the pawl 40 moves to a position where it does not engage with the clutch housing 30. This turns the clutch OFF. As a result, the spindle 3 moves away from the gears 7, 8, 9, 10, and 11 of the gear assembly, and the seat belt 2 can be withdrawn and retracted.

[0022] [Details of the clutch mechanism configuration] Next, each component of the clutch mechanism 20 will be described with reference to FIGS.

[0023] 2, the clutch housing 30 is coupled to the spindle 3 so as to rotate together with the spindle 3. The clutch housing 30 has, on the inner peripheral surface of the outer cylindrical wall, internal teeth 32 (engaged portion) with which the pawl 40 can be engaged and disengaged.

[0024] As shown in Figs. 2 to 4 and 6, the pawl 40 has an engagement claw 41 (engagement portion) that can be engaged with and disengaged from the internal teeth 32 of the clutch housing 30. The pawl 40 has an elongated shape, for example, a U-shape, when viewed from the front, and has the engagement claw 41 in a direction that protrudes perpendicularly from this elongated shape. The pawl 40 also has an engagement groove 42 in the middle in the longitudinal direction. A pressing portion 53 of a friction ring 50 is inserted into the engagement groove 42. Although one pawl 40 may be used, two (plural) are provided here. The two pawls 40 are arranged to face each other with the rotation axis of the spindle 3 in between.

[0025] Moreover, the pawl 40 is held by the final gear 10 and rotates together with the final gear 10. Specifically, one end of the pawl 40 is housed in a pawl slide groove 62 of the final gear 10, and the engagement claw 41 on the other end extends outside the pawl slide groove 62. The pawl 40 is configured to be movable with respect to the clutch housing 30 between an engagement position (radial outer position; see FIG. 8) where the engagement claw 41 engages with the internal teeth 32 and a non-engagement position (radial inner position; see FIGS. 7(B) and 11) where the engagement claw 41 does not engage with the internal teeth 32.

[0026] As shown in Fig. 5, the friction ring 50 has an annular portion 51, a plurality of contact pieces 52 (contact portions) protruding from the annular portion 51 toward the additional gear 11, and a plurality (two in this example) of pressing portions 53 protruding radially outward from the annular portion 51. The plurality of contact pieces 52 extend to the inner circumference of the annular portion 51 at equal intervals in the circumferential direction of the annular portion 51. The inner surface of the contact piece 52 is in pressing contact with the outer circumferential surface of the connecting portion 72 of the additional gear 11, and is thereby connected to the connecting portion 72 by frictional force. The two pressing portions 53 are disposed so as to face each other across the rotation axis of the friction ring 50, and are inserted into the engagement grooves 42 of each pawl 40, respectively (see Figs. 3, 4 and 6).

[0027] The pressing portion 53 is configured to be movable within the engagement groove 42 in the rotational direction of the friction ring 50 (see FIG. 7). The pressing portion 53 presses the inner wall of the engagement groove 42, thereby urging the pawl 40 to move to or remain at the engagement position or non-engagement position. Specifically, when the pressing portion 53 presses the inner wall on one side (the engagement claw 41 side) of the engagement groove 42 in the rotational direction (see FIGS. 8 and 9), the pawl 40 is urged to move toward the engagement position or to remain at the engagement position. When the pressing portion 53 presses the inner wall on the other side (the opposite side to the engagement claw 41) of the engagement groove 42 in the rotational direction (see FIGS. 10 and 11), the pawl 40 is urged to move toward the non-engagement position or to remain at the non-engagement position.

[0028] As shown in Figs. 3, 4 and 6, the final gear 10 is configured as a ring-shaped gear having teeth formed on its outer circumferential surface, and has an inner cylindrical wall 61. The outer circumferential surface of the inner cylindrical wall 61 faces the internal teeth 32 of the clutch housing 30. The inner circumferential surface of the inner cylindrical wall 61 faces the outer circumferential surface of the contact piece 52 of the friction ring 50 (or a coupling portion 72 of the additional gear 11 described later). A pawl slide groove 62 that slidably holds the pawl 40 is formed on a top surface that connects the outer circumferential surface and the inner circumferential surface of the inner cylindrical wall 61. A cam portion 63 for guiding the movement of the pawl 40 is formed on the top surface of the inner cylindrical wall 61. The pawl slide groove 62 and the cam portion 63 are located on one side and the other side of the pressing portion 53 of the friction ring 50, respectively, in the rotational direction. Further, a plurality (two) of pawl slide grooves 62 and cam portions 63 are formed corresponding to the number (two) of pawls 40.

[0029] 3, 4 and 6, the cluster gear 8 has a first gear portion 81 and a second gear portion 82 that is coaxial with the first gear portion 81 and has a smaller diameter than the first gear portion 81. The first gear portion 81 is interposed between the output gear 7 and the additional gear 11 and meshes with both the output gear 7 and the additional gear 11. The second gear portion 82 meshes with the idle gear 9, and the idle gear 9 meshes with the final gear 10. In other words, the idle gear 9 is interposed between the second gear portion 82 and the final gear 10 and meshes with both the second gear portion 82 and the final gear 10.

[0030] 3, 4 and 6, the additional gear 11 is disposed coaxially with the final gear 10. One axial end of the spindle 3 is inserted through the center of the additional gear 11 and the final gear 10, and the one end of the spindle 3 is connected to a spring device 13 (see: FIGS. 1 and 6).

[0031] As shown in FIG. 5, the additional gear 11 has a gear portion 71 formed on its outer circumferential surface and a coupling portion 72 formed coaxially with the gear portion 71. The gear portion 71 meshes with the first gear portion 81 of the cluster gear 8, and receives a rotational force from the motor 4 (see FIG. 6). The coupling portion 72 is cylindrical. The coupling portion 72 protrudes from an end face of a ring member constituting the gear portion 71 toward the final gear 10, and faces the inner circumferential surface of the inner cylindrical wall 61 of the final gear 10 (see FIG. 4). The contact piece 52 of the friction ring 50 is in pressing contact with the outer circumferential surface of the coupling portion 72. As a result, the friction ring 50 is coupled to the additional gear 11 by frictional force.

[0032] Here, the friction ring 50 is configured to be rotatable integrally with and relatively to the additional gear 11. Specifically, the friction ring 50 is configured to be rotatable integrally with the additional gear 11 by the friction force interposed between the additional gear 11 and the friction ring 50. On the other hand, when a torque that rotates the friction ring 50 acts on the friction ring 50 exceeding the friction force, the friction ring 50 is configured to rotate relatively to the additional gear 11. In other words, the friction ring 50 rotates with respect to the additional gear 11 while sliding the contact piece 52 on the coupling portion 72 of the additional gear 11.

[0033] [Clutch mechanism operation] The specific operation of the clutch mechanism 20 will be described with reference to FIGS.

[0034] [1. Clutch OFF (initial position)] 7 shows the clutch mechanism 20 in the clutch-off state. The motor 4 is stopped (not driven). In the clutch-off state, the pawl 40 is located at the deepest part of the pawl sliding groove 62, and is in a disengaged position where it is not engaged with the clutch housing 30. In the clutch mechanism 20, only the clutch housing 30 which rotates integrally with the spindle 3 is rotatable. Therefore, in the retractor 1, the seat belt 2 can be normally wound and unwound without being affected by the motor 4 or the gear assembly (gears 7 to 11).

[0035] [2. Switching the clutch to ON] In the clutch-off state shown in FIG. 7, when the motor 4 starts to rotate in the belt winding direction, each of the gears 7 to 11 starts to rotate in the direction of the arrow 300. At this time, the final gear 10 and the additional gear 11 rotate in opposite directions. In addition, the pawl 40 held by the final gear 10 rotates together with the final gear 10. At the same time, the friction ring 50 coupled to the additional gear 11 by frictional force rotates integrally with the additional gear 11. Please also refer to FIG. 6 for this series of rotation directions.

[0036] Then, when the motor 4 rotates a predetermined number of rotations (first number of rotations) in the belt winding direction, as shown in Fig. 8, the pressing portion 53 of the friction ring 50 comes into contact with the inner wall of the engagement groove 42 of the pawl 40 on the engagement claw 41 side, and presses the pawl 40 so as to push it out of the pawl sliding groove 62, moving the pawl 40 to the engagement position. The movement of the pawl 40 to the engagement position is guided by the cam portion 63 of the final gear 10. When the pawl 40 moves to the engagement position, the engagement claw 41 engages with the internal teeth 32 of the clutch housing 30. This switches the clutch ON.

[0037] As shown in Fig. 8, when the final gear 10 rotates clockwise by a predetermined angle α1 from the clutch-off state, and the additional gear 11 rotates counterclockwise by a predetermined angle β1 from the clutch-off state, the clutch is switched to the clutch-on state. α1<β1.

[0038] In this embodiment, the clutch mechanism 20 has the additional gear 11, which speeds up the switching to clutch ON. In other words, the additional gear 11 rotates in the opposite direction to the final gear 10, which allows the pawl 40 to be quickly moved from the non-engaged position to the engaged position. This is because the speed at which the pawl 40 moves to the engaged position can be calculated approximately as the sum of the rotation speed of the final gear 10 and the rotation speed of the additional gear 11. Since the clutch mechanism 20 switches to clutch ON at high speed, the time from the start of the motor 4 to the start of belt winding is shortened.

[0039] Furthermore, in this embodiment, the number of rotations (first number of rotations) of the motor 4 required to switch the clutch ON can be reduced. This is because the predetermined angle α1 of the final gear 10 for clutch ON becomes smaller as the additional gear 11 rotates in the opposite direction to the final gear 10. Since the number of rotations of the motor for clutch ON can be reduced, the durability of the motor 4 can be improved. This leads to the motor 4 being made more compact.

[0040] [3. Clutch continues to be ON] 9, when the motor 4 rotates in the belt winding direction beyond a predetermined number of rotations (first number of rotations) from the clutch ON state, the rotation of the final gear 10 transmitted from the motor 4 rotates the clutch housing 30 via the pawl 40, thereby rotating the spindle 3 in the belt winding direction. That is, with the pawl 40 engaged with the clutch housing 30, the clutch housing 30 rotates integrally with the rotation of the final gear 10, which rotates the spindle 3 and winds up the seat belt 2.

[0041] At this time, the friction ring 50 slides against the additional gear 11 as shown in the rotation direction of the arrow 400, and rotates together with the pawl 40, the final gear 10, the clutch housing 30, and the spindle 3. That is, when the motor 4 rotates further from the clutch ON state, the final gear 10 rotates further in the direction of the arrow 300, and the torque due to the rotation is transmitted to the friction ring 50 via the pawl 40 and the pressing portion 53, and exceeds the above-mentioned friction force (i.e., the friction force interposed between the additional gear 11 and the friction ring 50). As a result, the friction ring 50 rotates together with the final gear 10 via the pawl 40 relative to the additional gear 11 and in the opposite direction to the additional gear 11.

[0042] [4. Switching to clutch OFF] Switching the clutch OFF basically involves the opposite movement (rotation direction) to switching the clutch ON. When the motor 4 is rotated in the belt withdrawing direction to switch the clutch OFF from the clutch ON state, the final gear 10 and the additional gear 11 rotate in opposite directions to each other, as shown in FIG. 10. In addition, the pawl 40 held by the final gear 10 rotates together with the final gear 10. At the same time, the friction ring 50 coupled to the additional gear 11 by frictional force rotates integrally with the additional gear 11. Note that this series of rotations is opposite to that in the case of switching the clutch ON.

[0043] Then, when the motor 4 rotates a predetermined number of rotations (second number of rotations) in the belt withdrawing direction, the pressing portion 53 of the friction ring 50 comes into contact with the inner wall of the engagement groove 42 of the pawl 40 on the opposite side to the engagement claw 41, as shown in Fig. 10. When the motor 4 rotates further, the pressing portion 53 of the friction ring 50 presses the pawl 40 into the pawl sliding groove 62, moving the pawl 40 to the disengagement position, as shown in Fig. 11. When the pawl 40 moves to the disengagement position, the engagement claw 41 moves away from the internal teeth 32 of the clutch housing 30. This switches the clutch to OFF.

[0044] In the process of clutch OFF, the final gear 10 rotates counterclockwise by a predetermined angle α2 from the clutch ON state to the state shown in Fig. 10, and rotates counterclockwise by a predetermined angle α3 from the clutch ON state to the state shown in Fig. 11. Meanwhile, the additional gear 11 rotates clockwise by a predetermined angle β2 from the clutch ON state to the state shown in Fig. 10, and rotates clockwise by a predetermined angle β3 from the clutch ON state to the state shown in Fig. 11. α2<β2 and α3<β3.

[0045] As with the clutch ON state, it will be understood that the provision of additional gear 11 in clutch mechanism 20 speeds up clutch OFF switching. Similarly, it will be understood that the number of rotations of motor 4 required for clutch OFF switching can be reduced, thereby improving the durability and miniaturization of motor 4.

[0046] [5. If the belt is pulled out while the clutch is not releasing properly] Fig. 12 shows a schematic diagram of the flow of torque transmission (reference numeral 500) in the case where clutch release failure occurs during switching in "4." above and the seat belt 2 is withdrawn in that state. In this case, when the seat belt 2 is withdrawn, the final gear 10 rotates together with the spindle 3 via the clutch housing 30 and the pawl 40 as the spindle 3 rotates in the withdrawal direction. The rotation direction of the final gear 10 is the same as the rotation direction of the final gear 10 shown in Fig. 10.

[0047] When the final gear 10 rotates, the rotational torque is transmitted to the additional gear 11 via the idle gear 9 and the cluster gear 8. This causes the additional gear 11 to rotate. In this case, the rotation direction of the additional gear 11 is the clutch release direction (the rotation direction of the additional gear 11 and the friction ring 50 shown in FIG. 10) as described above, so the pressing portion 53 of the friction ring 50 presses the pawl 40 to move it to the disengagement position, switching the clutch to OFF. Therefore, even if the energy absorption operation by the torsion bar is started by the withdrawal of the seat belt 2 in a clutch release failure (clutch ON) state, the clutch mechanism 20 switches to clutch OFF, so that the energy absorption performance of the torsion bar is not affected.

[0048] [Comparison of tension between embodiment and comparative example] Fig. 13 is a graph showing the relationship between tension and time when the motor 4 winds up the belt. The time on the horizontal axis indicates the time during which the clutch is switched from OFF to ON and the clutch remains ON (the time elapsed from when the motor 4 starts to rotate in the belt winding direction). The tension on the vertical axis indicates the tension acting on the seat belt 2 due to the belt winding by the motor 4. The retractor according to the comparative example does not have the additional gear 11. In the retractor according to the comparative example, the friction ring 50 is coupled by friction to a stationary component (e.g., the lower cover 16) rather than to the additional gear 11.

[0049] 13, the retractor 1 according to the embodiment builds up tension faster than the retractor according to the comparative example. This is because, as described above, the clutch mechanism 20 has the additional gear 11, which speeds up the switching to clutch ON.

[0050] As described above, the seatbelt retractor 1 according to this embodiment can improve the speed of each operation of engaging and disengaging the clutch mechanism 20. Therefore, the motor 4 involved in the clutch operation can be made smaller and have a longer life, and the demand for high-power, high-speed belt winding can be met.

[0051] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The elements of the embodiment, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified, and may be modified as appropriate.

[0052] <Additional Considerations Regarding Various Implementations> [Embodiment 1] A spindle for winding up the seat belt; A motor that generates power to rotate the spindle; a power transmission mechanism capable of transmitting power from the motor to the spindle, the power transmission mechanism includes a clutch mechanism that enables transmission of power from the motor to the spindle when the motor rotates in a belt winding direction; The clutch mechanism includes: A first rotating member that rotates with the spindle; a pawl configured to be movable between an engagement position where it engages with the first rotating member and a disengagement position where it does not engage with the first rotating member; a final gear that holds the pawl and rotates in response to rotation of the motor; an additional gear that rotates in a direction opposite to that of the final gear in response to rotation of the motor; a friction ring configured to be rotatable integrally with and relatively to the additional gear; The clutch mechanism includes: When the motor rotates a first number of revolutions in the belt winding direction, the final gear and the additional gear rotate in opposite directions to each other, and at this time, due to a coupling caused by a frictional force between the additional gear and the friction ring, the friction ring rotates integrally with the additional gear and presses the pawl to move the pawl from the disengaged position to the engaged position, thereby switching from an OFF state in which the transmission of power from the motor to the spindle is interrupted to an ON state in which the transmission of power from the motor to the spindle is enabled, When the motor further rotates in the belt winding direction after the first number of rotations, The rotation of the motor is transmitted to the spindle via the final gear, the pawl, and the first rotating member, so that the spindle rotates in the belt winding direction, a torque caused by the rotation of the final gear transmitted to the friction ring via the pawl exceeds the friction force, and the friction ring is configured to rotate together with the final gear via the pawl relative to the additional gear and in an opposite direction to the additional gear.

[0053] [Embodiment 2] When the motor rotates in a belt withdrawing direction opposite to the belt winding direction, the clutch mechanism A seat belt retractor according to embodiment 1, wherein the final gear and the additional gear rotate in opposite directions to each other, and at this time, due to the frictional force connection, the friction ring rotates integrally with the additional gear, pressing the pawl to move the pawl from the engaged position to the disengaged position, thereby switching from the ON state to the OFF state.

[0054] [Embodiment 3] 3. A seat belt retractor according to claim 1 or 2, wherein the additional gear is arranged coaxially with the final gear.

[0055] [Embodiment 4] The additional gear is a gear portion formed on an outer circumferential surface thereof and receiving a rotational force from the motor; A seat belt retractor according to any one of embodiments 1 to 3, further comprising: a coupling portion formed coaxially with the gear portion and coupled to the friction ring by frictional force.

[0056] [Embodiment 5] A seat belt retractor according to embodiment 4, wherein the coupling portion is cylindrical.

[0057] [Embodiment 6] A seat belt retractor according to embodiment 4 or 5, wherein the coupling portion protrudes toward the final gear.

[0058] [Embodiment 7] The friction ring is An annular portion; a contact portion that protrudes from the annular portion toward the additional gear and is coupled to the coupling portion by frictional force; A seat belt retractor according to any one of embodiments 4 to 6, further comprising a pressing portion protruding radially outward from the annular portion and configured to be capable of pressing the pawl.

[0059] [Embodiment 8] A seat belt retractor as described in embodiment 3, wherein one axial end of the spindle is inserted through the center of each of the additional gear and the final gear.

[0060] [Embodiment 9] The clutch mechanism includes: an output gear fixed to an output shaft of the motor; a cluster gear including a first gear portion interposed between the output gear and the additional gear and meshing with both the output gear and the additional gear, and a second gear portion formed coaxially with the first gear portion; A seat belt retractor according to any one of embodiments 1 to 8, further comprising an idler gear interposed between the second gear portion of the cluster gear and the final gear and meshing with both the second gear portion and the final gear. [Explanation of symbols]

[0061] 1...seat belt retractor, 2...seat belt, 3...spindle, 4...motor, 4a...output shaft, 5...power transmission mechanism, 6...retractor frame, 7...output gear, 8...cluster gear, 9...idle gear, 10...final gear, 11...additional gear, 13...winding spring device, 14...lock mechanism, 15...pretensioner, 16...lower cover, 17...upper cover, 20...clutch mechanism, 30...clutch housing (first rotating member), 32...internal teeth, 40...pawl, 41...engagement claw, 42...engagement groove, 50...friction ring, 51...annular portion, 52...contact piece, 53...pressing portion, 61...inner cylindrical wall, 62...pawl sliding groove, 63...cam portion, 71...gear portion, 72...coupling portion, 81...first gear portion, 82...second gear portion

Claims

1. A spindle for winding up the seat belt; A motor that generates power to rotate the spindle; a power transmission mechanism capable of transmitting power from the motor to the spindle, the power transmission mechanism includes a clutch mechanism that enables transmission of power from the motor to the spindle when the motor rotates in a belt winding direction; The clutch mechanism includes: a first rotating member that rotates with the spindle; a pawl configured to be movable between an engagement position where it engages with the first rotating member and a disengagement position where it does not engage with the first rotating member; a final gear that holds the pawl and rotates in response to rotation of the motor; an additional gear that rotates in a direction opposite to that of the final gear in response to rotation of the motor; a friction ring configured to be rotatable integrally with and relatively to the additional gear; The clutch mechanism includes: When the motor rotates a first number of revolutions in the belt winding direction, the final gear and the additional gear rotate in opposite directions to each other, and at this time, due to a coupling caused by a frictional force between the additional gear and the friction ring, the friction ring rotates integrally with the additional gear and presses the pawl to move the pawl from the disengaged position to the engaged position, thereby switching from an OFF state in which the transmission of power from the motor to the spindle is interrupted to an ON state in which the transmission of power from the motor to the spindle is enabled, When the motor further rotates in the belt winding direction after the first number of rotations, The rotation of the motor is transmitted to the spindle via the final gear, the pawl, and the first rotating member, so that the spindle rotates in the belt winding direction, a torque caused by the rotation of the final gear transmitted to the friction ring via the pawl exceeds the friction force, and the friction ring is configured to rotate together with the final gear via the pawl relative to the additional gear and in an opposite direction to the additional gear.

2. When the motor rotates in a belt withdrawing direction opposite to the belt winding direction, the clutch mechanism 2. The seat belt retractor according to claim 1, wherein the final gear and the additional gear rotate in opposite directions to each other, and at this time, the friction ring rotates integrally with the additional gear due to the connection by the frictional force, and presses the pawl to move the pawl from the engaged position to the disengaged position, thereby switching from the ON state to the OFF state.

3. 3. The seat belt retractor according to claim 1, wherein the additional gear is disposed coaxially with the final gear.

4. The additional gear is a gear portion formed on an outer circumferential surface thereof and receiving a rotational force from the motor; 4. The seat belt retractor according to claim 3, further comprising: a coupling portion formed coaxially with said gear portion and coupled to said friction ring by frictional force.

5. 5. The seat belt retractor according to claim 4, wherein the coupling portion is cylindrical.

6. 5. The seat belt retractor according to claim 4, wherein the connecting portion projects toward the final gear.

7. The friction ring is An annular portion; a contact portion that protrudes from the annular portion toward the additional gear and is coupled to the coupling portion by frictional force; 5. The seat belt retractor according to claim 4, further comprising: a pressing portion protruding radially outward from the annular portion and configured to be able to press the pawl.

8. 4. The seat belt retractor according to claim 3, wherein one axial end of the spindle is inserted through a center of each of the additional gear and the final gear.

9. The clutch mechanism includes: an output gear fixed to an output shaft of the motor; a cluster gear including a first gear portion interposed between the output gear and the additional gear and meshing with both the output gear and the additional gear, and a second gear portion formed coaxially with the first gear portion; 3. The seat belt retractor according to claim 1, further comprising an idler gear interposed between the second gear portion of the cluster gear and the final gear and meshing with both the second gear portion and the final gear.

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