The disclosure of Japanese Patent Application No. 2001-11842 filed on Jan. 19, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a reclining device. More specifically, the invention relates to the fitting of a seat back and a seat cushion.
2. Description of Related Art
A reclining device of a certain type is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-253063. This reclining device is designed such that a cam body presses a plurality of slide pawls each having outer teeth on the front end side against an annular ratchet having inner teeth on the inner periphery side so that the slide pawls are brought into mesh with the ratchet and locked with respect thereto. Further, the operation of pressing the slide pawls against the ratchet is canceled by applying an arbitrary operational force to the cam body so that the slide pawls are retreated from the ratchet and brought out of mesh therewith.
The reclining device of this type is designed to prevent the ratchet from rotating relative to a holder when the slide pawls are locked with respect to the ratchet and to allow the ratchet to rotate relative to the holder when the slide pawls are unlocked from the ratchet. The reclining device of this type is disposed between a rear end portion of a seat cushion and a lower end portion of a seat back, thus constituting a vehicular reclining seat. For example, the reclining device of this type is designed such that the seat back is longitudinally tiltably supported with respect to the seat cushion by mounting the ratchet on the lower end side of the seat back and the holder on the rear end side of the seat cushion.
It is to be noted herein that the reclining device of this type confronts the following problem. If a great circumferential turning force is applied to the seat back constituting the reclining seat, the ratchet is also exposed to a great circumferential turning force, which acts on the slide pawls as radial and tangential components in the circumferential direction. The slide pawls are displaced both radially inwardly and circumferentially. As a result, the slide pawls may be brought out of mesh with the ratchet. Thus, the reclining device of this type requires that the slide pawls securely mesh with the ratchet when the slide pawls are locked with respect to the ratchet.
However, the reclining device according to the related art as disclosed in the aforementioned patent publication is designed to bear each of the slide pawls only at a single point, namely, at the center of a rear end portion thereof. Hence, if a great circumferential turning force is applied to the slide pawls from the ratchet, each of the slide pawls sways circumferentially upon its bearing portion for the cam body and becomes quite unstable although it is still maintained in mesh with the ratchet. Then, the slide pawls may be retreated from the ratchet, disengaged therefrom, and unlocked therefrom.
The invention thus improves the reclining device of the above-mentioned type such that the slide pawls are stably maintained in mesh with the ratchet and cannot be disengaged therefrom easily even if a great circumferential turning force is applied to the slide pawls from the ratchet. To achieve this object, the reclining device of the invention adopts a construction capable of securely maintaining the slide pawls in mesh with the ratchet, taking into account the configuration of the slide pawls and the manner in which the cam body bears the slide pawls.
A reclining device according to one exemplary aspect of the invention comprises a plurality of pawls, an annular ratchet, a cam body, and a holder. Each of the pawls has outer teeth formed on the front end side, first and second leg portions formed at opposed end portions, and a bearing portion formed between the first and second leg portions. The first and second leg portions extend toward the rear end side. The annular ratchet has inner teeth formed on the inner periphery side. The cam body comes into abutment at least on the bearing portion of each of the pawls and possibly on the leg portions and the bearing portion of each of the pawls. The cam body presses the pawls toward the ratchet so that the pawls are brought into mesh with the ratchet and locked with respect thereto and stops pressing the pawls so that the pawls are retreated from the ratchet and unlocked therefrom. The holder holds each of the pawls such that the pawl can move toward and away from the inner teeth of the ratchet, and rotates concentrically with respect to the ratchet. The cam body, which operates by an arbitrary operational force, releases the pressing force applied to the slide pawls and brings them out of mesh with the ratchet. The reclining device is designed to prevent the ratchet from rotating relative to the holder when the slide pawls are in mesh with the ratchet and to allow the ratchet to rotate relative to the holder when the slide pawls are out of mesh with the ratchet.