Patent Application
20080079254
Hereinafter, an embodiment of the present invention will be described with reference to drawings.
The one side of the webbing 2 is wound up by the seat belt retractor 3 such that the webbing 2 is allowed to be withdrawn, the other side end of the webbing 2 is pivotally connected to a vehicle body B by the anchor 7, and the middle portion of the webbing 2 is inserted through the deflection fitting 6. The wearing of the webbing 2 to the occupant M is achieved by pulling the tongue 4 slidably disposed on the webbing 2 to withdraw the webbing 2 from the seat belt retractor 3 and latching the tongue 4 with the buckle device 5, thereby obtaining a state capable of restraining the occupant M by the webbing 2.
The main mechanical element of the seat belt apparatus 1 is the seat belt retractor 3.
The seat belt retractor 3 comprises a spool housing 11, a spring housing 12, and a mechanism housing 13. In the spool housing 11, a spool 14 as winding device for winding and unwinding the webbing according to its rotation is accommodated. The spool 14 is biased in a webbing winding direction by a return spring (not shown) accommodated in the spring housing 12. The spool 14, the return spring, and peripheral elements around them may be conventionally well known ones. Therefore, the description about them will be omitted.
The reduction mechanism 16 includes a first gear 21, a second gear 22, and a ring cam 23 and is adapted to reduce the revolution of the spool 14 at a predetermined reduction ratio to take the rotation as the rotation of the ring cam 23.
The first gear 21 is a pinion gear in which the number of teeth is Z1 and the pinion gear is directly connected to a rotary shaft 24 of the spool 14. Specifically, the first gear 21 is fitted onto the rotary shaft 24 so that the first gear 21 rotates at the same revolution, i.e. a reduction ratio of 1, as the rotary shaft 24.
The second gear 22 comprises a large-diameter gear portion 25 in which the number of teeth is Z2 larger than the number of teeth Z1 and a small-diameter gear portion 26 in which the number of teeth is Z3 smaller than the number of teeth Z2. The large-diameter gear portion 25 is meshed with the first gear 21 so that the second gear 22 rotates at a reduction ratio of Z1/Z2 relative to the gear 21 according to the rotation of the first gear 21.
The ring cam 23 is formed in a ring-like shape and is provided with an internal gear portion 27, formed in the inner periphery thereof, in which the number of teeth is Z4 larger than the number of teeth Z3, and the internal gear portion 27 is also provided with a cam 31 which is composed of a convex portion 28 and a concave portion 29 formed in the outer periphery thereof. The internal gear portion 27 is meshed with the small-diameter gear portion 26 of the second gear 22 so that the ring cam 23 rotates at a reduction ratio of Z3/Z4 relative to the second gear 22 according to the rotation of the second gear 22.
The winding state detection mechanism 17 detects the winding state of the webbing 2 onto the spool 14. Here, in this embodiment, the detection of the winding state is carried out to determine the wearing of the webbing. That is, whether or not the necessary amount of the webbing 2 for the wearing of the webbing is unwound is determined by detecting the winding state of the webbing 2 onto the spool 14.
The winding state detection mechanism 17 is composed of a combination of the reduction mechanism 16 with a signal output device 32. The signal output device 32 includes an actuator 33 (unwound amount detection device) and a limit switch 34. The actuator 33 has a contact end 35 at one end side and a pivot end 36 at the other end side and is allowed to elastically pivot about the pivot end 36 in a state that the contact end 35 is pressed against the cam portion 31 of the ring cam 23. The actuator 33 functions to transmit a cam action by the cam portion 31 of the ring cam 23 to the limit switch 34. More specifically, the actuator 33 in its initial state, as will be described later, is in contact with the limit switch 34 because the contact end 35 is pressed against the convex portion 28 of the cam portion 31 of the ring cam 23. As the ring cam 23 rotates for a predetermined amount from this state, the contact end 35 is pressed against the concave portion 29 of the cam portion 31, whereby the actuator 33 is spaced apart from the limit switch 34. Accordingly, the limit switch 34 carries out its switching action, that is, the limit switch 34 outputs a winding state detection signal to the outside through a signal transmitting wiring 37.
The ALR mechanism 18 is a mechanical element for locking the webbing 2 from being unwound, i. e. locking the spool 14 from rotating, after the webbing 2 is unwound by a predetermined amount and is composed of a combination of the reduction mechanism 16 with a locking device 41. The locking device 41 includes a lock plate 42 and a lock lever 43. The lock plate 42 is formed in a disc shape and is assembled to the ring cam 23 allowing rotations relative to the ring cam 23 within a predetermined range. That is, the lock plate 42 is assembled to the ring cam 23 in such a manner that the lock plate 42 rotates together with the ring cam 23 in a state that the ring cam 23 rotates over the range allowing the relative rotations. The lock plate 42 is provided with a cam portion 44 formed in its outer periphery. By the rotations of the lock plate 42 according to the rotations of the ring cam 23, the cam portion 44 provides a cam action to the lock lever 43.
The lock lever 43 has a pivot portion 45, a cam action receiving portion 46, and an engaging portion 47 and is allowed to pivot about the pivot portion 45. The lock lever 43 is biased by a spring (not shown) in such a manner so as to press the cam action receiving portion 46 against the cam portion 44 of the lock plate 42. When the cam action receiving portion 46 receives the cam action from the cam portion 44 of the lock plate 42, the engaging portion 47 is engaged with a lock gear (not shown). By the engagement of the engaging portion 47 with the lock gear, the spool 14 is locked from rotating so as to lock the webbing 2 from being unwound. Such mechanism may be a known mechanism disclosed in Japanese Unexamined Patent Application Publication No 2003-191822, for example.
Hereinafter, the actions of the winding state detection mechanism 17 and the ALR mechanism 18 will be described. First, the action of the winding state detection mechanism 17 will be described. In the initial state where the webbing 2 is fully wound onto the spool 14 before the occupant wears the seat belt, the ring cam 23 is in a state that the concave portion 29 of the cam portion 31 is placed at a position apart from the contact end 35 of the actuator 33 by a certain distance and the actuator 33 is in a state that the contact end 35 is pressed against the convex portion 28 of the cam portion 31 of the ring cam 23. As the webbing 2 is withdrawn from this state, the spool 14 rotates in the counter-clockwise direction in
Here, the reduction ratio Rc of the ring cam 23 relative to the spool 14 is set such that the ring cam 23 does not rotate for a full one circle even when the webbing 2 is withdrawn by the predetermined amount, specifically, the webbing 2 is withdrawn by a necessary amount of the webbing for the occupant to wear the webbing in the predetermined state. In this embodiment, for example, the reduction ratio Ra is set to be about 0.325, the reduction ratio Rb is set to be about 0.185, and the reduction ratio Rc is set to be about 0.06.
As the withdrawal of the webbing 2 accompanying the rotation of the ring cam 23 is conducted for the aforementioned predetermined amount, the contact end 35 of the actuator 33 pressing the convex portion 28 is brought to press the concave portion 29. As a result, the actuator 33 is spaced apart from the switching contact of the limit switch 34 as mentioned above, whereby the limit switch 34 outputs a winding state detection signal. In this manner, the detection of the winding state is carried out.
On the other hand, as the webbing 2 is wound up when the contact end 35 of the actuator 33 presses the concave portion 29, the spool 14 through the ring cam 23 rotates in directions opposite to the aforementioned directions, respectively. Accordingly, the contact end 35 of the actuator 33 pressing the concave portion 29 is brought to press the convex portion 28 again. In this state, the winding state is not detected.
Now, the action of the ALR mechanism 18 will be described. In the aforementioned initial state, the engaging portion 47 of the lock lever 43 is not engaged with the aforementioned lock gear. As the webbing 2 is withdrawn by the predetermined amount accompanying the rotation of the spool 14 through the ring cam 23 as mentioned above from the initial state, the lock lever 43 receives the cam action from the cam portion 44 of the lock plate 42 so as to engage the engaging portion 47 with the aforementioned lock gear, thereby locking the spool 14 from rotating.
On the other hand, as the webbing 2 is wound when the spool 14 is locked from rotating as mentioned above, the spool 14 through the ring cam 23 rotates in the directions opposite to the aforementioned directions, respectively. Accordingly, the engaging portion 47 is disengaged from the aforementioned lock gear, thereby cancelling the locking of the rotation of the spool 14.
In the seat belt retractor 3 as mentioned above, the detection of the winding state of the webbing 2 is conducted by the winding state detection mechanism 17 based on the rotation amount of the spool 14, thereby achieving high accuracy detection. The reduction mechanism 16 as the main mechanical element of the winding state detection mechanism 17 is composed of only three components, i.e. the first and second gears 21, 22 and the ring cam 23, thereby achieving reduction in the number of parts and low cost structure. Further, the reduction mechanism 16 is shared also for the ALR mechanism 18, thereby achieving significant reduction in the number of parts as the whole seat belt retractor 3 and thus achieving further low cost structure.
When the aforementioned function by the ALR mechanism 18, i.e. the function of locking the webbing 2 from being unwound after the webbing 2 is unwound by the predetermined amount, is not required, the lock lever 43 may be omitted so that the first gear 21, the second gear 22, and the ring cam 23 are used as only components for the winding state detection mechanism 17, for example. Since, also in this case, the winding state detection mechanism 17 is composed of only three components, i.e. the first and second gears 21, 22, and the ring cam 23, this case also provides the effect of reduction in the number of parts and thus achieves low cost structure.
Though the present invention has been described with reference to one of embodiments, the present invention is not limited thereto and can be carried out in various forms without departing from the scope of the invention.
The disclosure of Japanese Patent Application No. 2006-271982 filed on Oct. 3, 2006 is incorporated as a reference.
While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-271982 | Oct 2006 | JP | national |
