headrest

Abstract

To provide a front and rear adjustment type vehicular headrest in which a head receiving section moves forward and reduces shock since a distance between the head receiving section and a swung back head becomes shorter in the case of a front collision of a vehicle and a damper function is surely exerted in a collision at a certain set speed or more.SOLUTION: A headrest includes a front and rear position adjustment mechanism 50 which can adjust front and rear positions of a head receiving section 40 by regulating forward and backward movement of a movable side member 30 with respect to a fixed side member 20. The head receiving section 40 is positioned in a rear section in an adjustment section when driving a vehicle and can be used in a state that the front surface is set downward. At the time of a repose when a backrest is leaned, the head receiving section 40 is positioned in the front section in the adjustment section and can be used in a state that the front surface is set upward. As the front and rear position adjustment mechanism 50, a friction brake mechanism which exhibits frictional resistance force in rear movement and front movement is used with respect to the movable side member 30 when the head receiving section 40 is in the adjustment section.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a headrest whose front-rear position can be adjusted.

Background Art

[0002] As a headrest provided on the upper part of a seatback of an automobile or the like, a front-rear adjustable type that can adjust not only the vertical position of the headrest portion that supports the head but also the front-rear position is known. In the front-rear adjustable headrest, it can be positioned at a desired position when moving the headrest portion forward. In this way, by making the headrest front-rear adjustable, during driving, the headrest portion can be positioned so as not to interfere with driving, and when the head shakes due to an impact such as a collision, the head can be received by the headrest portion. Also, when reclining the seatback to relax, the headrest portion can be adjusted to a comfortable position for use as a pillow.

[0003] As front-rear adjustable headrests, various types have been proposed so far, such as step-adjustable types and stepless-adjustable types. For example, in FIG. 1 of Patent Document 1, there is described a stepless-adjustable headrest provided with a front-rear position adjustment mechanism that enables adjustment of the front-rear position of the headrest portion 1 between a rear limit position (rearmost position) where the headrest portion 1 is in a state closest to the rear and a front limit position (frontmost position) where the headrest portion 1 protrudes most forward.

[0004] In the headrest of this document, the section where the headrest portion 1 moves forward from the rearmost position toward the frontmost position is an adjustment section where the front-rear position of the headrest portion 1 can be adjusted, when the headrest portion 1 reaches the frontmost position (front limit position), the movable side member 11 becomes in a released state where it can freely rotate back and forth with respect to the fixed side member 22, when the headrest portion 1 reaches the rearmost position (rear limit position), the backward rotation of the movable side member 11 with respect to the fixed side member 22 is controlled to be in a locked state as described above. In addition, the headrest in the same document is premised for application to the passenger seat or the rear seat, and when in use, the headrest portion 1 is pulled up for use.

[0005] The same document also describes adopting a spring lock mechanism using a coil spring 3 (lock spring) and a drum 223 (lock drum) as the above-described front-back position adjustment mechanism. Even if an attempt is made to move the headrest portion backward within the above adjustment range, since the lock spring 3 strongly clamps the lock drum 223, the headrest portion 1 does not move backward. However, when the head of the occupant hits the headrest portion 1 with a strength equal to or greater than a predetermined level due to a collision of the vehicle or the like, the headrest portion 1 moves backward while the lock spring 3 slips, and the impact can be reduced by the above-described frictional resistance. Thus, by using the lock spring 3 as the front-back position adjustment mechanism, stepless adjustment can be enabled, and a function (damper function) of alleviating the impact during a collision or the like can also be provided.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the headrest of Patent Document 1, no consideration is given to the forward movement of the headrest portion 1 due to inertia, and it is considered that the headrest portion 1 during a collision does not move forward at all or moves forward with almost no resistance. For this reason, the above-described damper function may not be exerted. For example, when the vehicle has a frontal collision while the headrest portion 1 is in the rearmost position (rear limit position), and if the headrest portion 1 does not move forward at all at that time, the headrest portion 1 cannot move further rearward, and the damper function is not exerted. Also, when moving forward with almost no resistance, when the headrest portion 1 reaches the foremost position (front limit position) due to the inertial force, it switches to the unlocked state (a state where the headrest portion 1 can move freely rearward), and the damper function is not exerted. Moreover, during sudden braking or driving on a rough road, there is also a possibility that the headrest portion 1 moves forward due to the inertial force, which may interfere with driving.

[0008] Here, let's specifically consider the inertial force acting on the headrest shown in FIG. 8. When calculating the inertial force generated in the headrest portion of the headrest due to a frontal collision of the vehicle and the load applied to the headrest portion due to the backward swing of the head, the following Conditions 1 to 8 were used. [Condition 1] Weight of the headrest: 1.0 kg [Condition 2] Head load: 6.5 kg (assuming 1 / 10 of the standard weight of an adult male, 65 kg, as the head load) [Condition 3] Collision time (time from the start of the collision to the stop): 0.15 seconds [Condition 4] Vehicle speed: 10 km / h, 25 km / h, 60 km / h [Condition 5] Distance L1 from the rotation center of the headrest portion to the center of gravity position: 40 mm [Condition 6] Angle θ1: 5.5° [Condition 7] Distance L3 from the rotation center of the headrest portion to the head contact position: 75 mm [Condition 8] Angle θ2: 55°

[0009] Under the above conditions 1 to 8, the results of calculating the load (referred to as F2) that moves the headrest forward by the inertial force generated and the load (referred to as F5) that moves the headrest backward when the swung-back head comes into contact are shown in Table 1 below. Both loads F2 and F5 in Table 1 were calculated at the center of gravity position of the headrest. (References: Mechanical Engineering Dictionary (Japan Society of Mechanical Engineers), Traffic Data Collection 5th Edition (Takashi Makino, Tachibana Shobo))

Table 1

[0010] In the case of a headrest with a front-back adjustment function, it is desirable that it does not unlock even during a collision at 60 km / h. Also, during sudden braking at 20 km / h (stopping time of about 0.81 seconds) or when driving on rough roads, it is desirable that the headrest does not move forward. Furthermore, in a collision at a speed of 10 km / h or more, it is desirable that the headrest moves forward within a range where it does not reach the foremost position (front limit position) and approaches the head, reducing the impact caused by the head swinging back. In addition, during a collision at 25 km / h or more, it is desirable that a damper function is exerted on the head that comes into contact with the headrest due to the swinging back.

[0011] For reference, when calculating the inertial force that attempts to move the headrest contact portion forward at the center of gravity during sudden braking at 20 km / h for the headrest also shown in Fig. 8 under the above conditions 1 to 8, it is 6.9 N. (Reference: Dictionary of Mechanical Engineering (The Japan Society of Mechanical Engineers), Traffic Data Collection 5th Edition (Takashi Makino, Tachibana Shobo)) As shown in Table 1 above, since the load F2 (the load that causes the headrest contact portion to move forward due to the inertial force generated at the center of gravity of the headrest contact portion during a collision) at 10 km / h is 18.4 N, in order for the headrest contact portion to move forward during a collision at 10 km / h or higher, it is preferable to set the resistance to forward movement at the center of gravity of the headrest contact portion to this value (18.4 N). In practice, since the weight and center of gravity of the headrest contact portion are changed depending on the specifications of the headrest, it is preferably set to 10 to 30 N with a margin. From the above calculation results, it can be seen that if the resistance to forward movement is set within this range, the headrest contact portion will not move forward even during sudden braking at 20 km / h. Also, considering the need to exert a damper function during a collision at 25 km / h or higher, since the load F5 (the load that moves the headrest contact portion backward when the shaken-back head comes into contact (calculated at the center of gravity)) in Table 1 above is 323.6 N, it is preferably set to a value smaller than that (specifically, 300 N or less).

[0012] The present invention has been made to solve the above problems, and in a headrest for a vehicle with front-back adjustment, it can be used in all seats including the driver's seat, and during normal driving including sudden braking and driving on rough roads, the headrest contact portion does not move. When the vehicle collides frontally, it moves forward within a range where the headrest contact portion does not reach the foremost position, reducing the impact by approaching the shaken-back head, and in a collision when the vehicle speed is at a certain set speed or higher, the above damper function is surely exerted.

Means for Solving the Problems

[0013] The above problems are a stay for attaching to the upper part of the seat backrest, A fixed-side member fixed to the stay, A movable-side member attached to the fixed-side member so as to be movable back and forth, A headrest portion fixed to the movable-side member, By restricting the back-and-forth movement of the movable-side member with respect to the fixed-side member, a front-back position adjusting mechanism that enables adjustment of the front-back position of the headrest portion in an adjustment section between a rearmost position where the headrest portion is in the most rearward position and a foremost position where the headrest portion protrudes most forward, A front stopper provided at the foremost position, A rear stopper provided at the rearmost position A vehicle headrest comprising: During vehicle operation, the headrest portion can be used with its front face facing downward in a rear section within the adjustment section, When resting with the backrest reclined, the headrest portion can be used with its front face facing upward in a front section within the adjustment section, and As the front-back position adjusting mechanism, a friction brake mechanism that not only exhibits a frictional resistance force for rearward movement but also exhibits a frictional resistance force for forward movement with respect to the movable-side member when the headrest portion is within the adjustment section is used A headrest characterized by this is solved by providing.

[0014] In this way, by using a friction brake mechanism as the front-back position adjusting mechanism and causing a frictional resistance force for forward movement to be exhibited, during sudden braking or driving on a rough road, the headrest portion does not move forward, so that the headrest portion does not interfere with driving. Also, when the vehicle is in a frontal collision, the headrest portion can be moved forward within a range that does not reach the foremost position to reduce the impact by bringing it closer to the head that is swung back. Furthermore, during a collision when the vehicle speed is above a certain set speed, it is also possible to exhibit the above-described damper function.

[0015] In the headrest of the present invention, the friction brake mechanism (front-back position adjusting mechanism) is not limited in its specific configuration as long as it exhibits the above-described operations.

[0016] For example, a friction brake mechanism includes a coil-shaped lock spring having one end fixed to a fixed-side member and the other end being a free end, and a lock drum fixed to a movable-side member for externally or internally fitting the lock spring and is configured to lock the free end of the lock spring to restrict movement or use two lock springs with different locking directions when the head receiving portion is in the adjustment section, so as to generate the frictional resistance to forward movement described above. This can be achieved. Hereinafter, this friction brake mechanism may be referred to as a "spring lock type friction brake mechanism".

[0017] In a spring lock type friction brake mechanism, when locking the free end of the locking spring to restrict movement, usually only one locking spring is used. In this case, the locking spring cannot rotate in the direction of tightening the locking drum (in the headrest of the first embodiment described later, it is the rearward movement direction), and can rotate in the direction of loosening the locking spring (in the headrest of the first embodiment described later, it is the forward movement direction). When the locking spring loosens, while the free end of the locking spring is displaced in that direction, by restricting the movement of the free end, a resistance force against rotation in the loosening direction, that is, a resistance force (clamping force) against forward movement is generated. Thereby, at the time of a frontal collision of the vehicle, the headrest (the headrest in the adjustment section) receiving the inertial force can be moved forward within a range that does not reach the most forward position. When the headrest moves forward, the distance to the head that is swung back can be reduced, and the impact can be reduced. Also, at the time of a collision at a certain set speed or higher, the above-described damper function can be more preferably exhibited. Further, even during sudden braking or driving on a rough road, the headrest does not move forward, and the headrest does not hinder driving. When locking the free end of the locking spring to restrict movement, usually, by operating the free end of the locking spring in the relaxation direction or the tightening direction, a lock release state in which the movable member can freely move back and forth with respect to the fixed-side member and a locked state in which the back-and-forth movement of the movable member is controlled with respect to the fixed-side member are provided with a lock switching mechanism for switching between them.

[0018] On the other hand, in a spring lock type friction brake mechanism, even when using two locking springs with different locking directions, since a frictional resistance force for rearward movement is manifested by one of the locking springs and a frictional resistance force for forward movement is manifested by the other locking spring, the same effects as those described in the previous paragraph can be obtained.

[0019] Also, the friction brake mechanism a fixed-side lock member fixed to the fixed-side member, while being fixed to the movable member, a movable-side lock member attached in a state of being movable left and right with respect to the fixed-side member, a biasing member that biases the movable-side locking member in a direction to press against the fixed-side locking member, and it is provided with, by making the movable-side locking member be pressed against the fixed-side locking member, a frictional resistance force for forward movement is to be generated. This is also possible. In the following, this friction braking mechanism may be referred to as a "shoe brake type friction braking mechanism".

[0020] In the shoe brake type friction braking mechanism, although the headrest support portion does not have a structure that switches to an unlocked state at the foremost position, as a front-rear position adjustment mechanism, by using the above-described friction braking mechanism, the headrest support portion that receives an inertial force during a frontal collision is moved forward within a range that does not reach the foremost position, and the distance from the head that swings back is made closer to reduce the impact, and, at the time of a collision of a certain set Fast degree or more, the above-described damper function can be sufficiently exerted. Also, during hard braking or driving on a rough road, since the headrest support portion does not move forward, it is also possible to prevent the headrest support portion from interfering with driving.

[0021] In the headrest of the present invention, the support mode of the headrest support portion with respect to the stay is not particularly limited either.

[0022] For example, the front-rear position adjustment mechanism is configured to pivot the headrest support portion back and forth about one fulcrum, the fulcrum is positioned above the headrest support portion, and a gripping portion for adjusting the front-rear position is provided at the lower portion of the headrest support portion This is possible. In the following, the headrest having this structure may be referred to as a "one-fulcrum type headrest". In the one-fulcrum type headrest, the operating force when pivoting the headrest support portion forward to adjust the position can be reduced by the principle of a lever. For this reason, the position adjustment of the headrest support portion can be easily performed by hand.

[0023] Also, assume that the front - rear position adjustment mechanism uses a four - link mechanism, and by making the lengths of the opposing links in the four - link different, the front surface of the headrest when in the rear section faces downward, and the front surface of the headrest when in the front section faces upward. This is also possible. In the following, the headrest with this structure may be referred to as a "four - link type headrest".

Advantages of the Invention

[0024] As described above, according to the present invention, in a front - rear adjustable vehicle headrest, it can be used in all seats including the driver's seat. During normal driving including sudden braking or driving on rough roads, the headrest does not move. When the vehicle has a frontal collision, the headrest moves forward within a range where it does not reach the most forward position, reducing the distance from the head that is swung back and thus reducing the impact. Also, in a collision when the vehicle speed is above a certain set speed, the above - mentioned damper function can be reliably exerted.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0026] Embodiments of the headrest of the present invention will be described more specifically with reference to the drawings. Hereinafter, the headrest of the present invention will be described by taking a total of four embodiments from the first embodiment to the fourth embodiment as examples. However, these embodiments are merely preferred embodiments, and the technical scope of the present invention is not limited to these embodiments. The headrest of the present invention can be appropriately modified within a range that does not impair the gist of the invention.

[0027] 1. Headrest of the First Embodiment First, the headrest of the first embodiment will be described. FIG. 1 is a cross-sectional view showing the headrest of the first embodiment cut along a plane perpendicular to the left-right direction. FIG. 2 is a front view of the headrest of the first embodiment as seen from the front. In FIG. 2, the internal mechanisms (such as the fixed-side member 20, the movable-side member 30, and the front-rear position adjustment mechanism 50, which will be described later) of the headrest portion 40 are schematically shown by thick broken lines. As shown in FIG. 1, the headrest of the first embodiment includes a stay 10, a fixed-side member 20, a movable-side member 30, a headrest portion 40, and a front-rear position adjustment mechanism 50.

[0028] As shown in FIG. 2, the stay 10 is for attaching to the upper part of the seat backrest 300. The stay 10 is formed by bending a metal pipe into a reverse "U" shape when viewed from the front or by welding. Among the pair of left and right struts of the stay 10, one strut is provided with recesses in multiple stages, and by selecting the recess for locking a hook (not shown) provided on the backrest 300 side, the height of the stay 10 (the vertical position of the headrest 40) can be adjusted. The fixed side member 20 is fixed to the upper part of the stay 10 in a non-movable state as shown in FIG. 1.

[0029] On the other hand, the movable side member 30 is attached to the fixed side member 20 in a state where it can move back and forth. The headrest 40 supports the head of the occupant. The headrest 40 is fixed to the movable side member 30 in a non-movable state. In other words, the headrest 40 can move back and forth integrally with the movable side member 30 with respect to the fixed side member 20. In the headrest of the first embodiment, the headrest 40 (movable side member 30) rotates back and forth about one fulcrum (point P1 in FIG. 1), and the fulcrum P1 is located at the upper part of the headrest 40. Therefore, the headrest of the first embodiment corresponds to the above-mentioned "one-fulcrum type headrest". The angle adjustment range θ (FIG. 1) of the headrest 40 is preferably about 10 to 30°, and about 20° is optimal. In the rearmost position, the backward rotation is restricted by the rear stopper α2 due to the contact between the movable side member 30 and the stay 10, and in the foremost position, the forward rotation is restricted by the front stopper α1 due to the contact between the movable side member 30 and the fixed side member 20. In this case, the lower end of the headrest 40 can move back and forth by about 50 mm. The lower part of the headrest 40 can be used as a part (grip part 41) to be gripped when adjusting the front and rear positions. Thereby, as will be described later, using the principle of a lever, the headrest 40 can be rotated back and forth with a small operating force.

[0030] The front-rear position adjustment mechanism 50 is configured to adjust the front-rear position of the headrest portion 40 steplessly within the range between the rearmost position (solid line portion in FIG. 1) and the foremost position (dashed-dotted line portion in FIG. 1) (adjustment range) by restricting the front-rear rotation of the movable side member 30 with respect to the fixed side member 20. Thereby, during driving of the vehicle, as shown in FIG. 3(a), by positioning the headrest portion 40 at the rear position (rear section in the adjustment range), the front surface of the headrest portion 40 can be oriented downward. For this reason, the headrest portion 40 can be adjusted to an optimal position both when the backrest 300 is raised and the vehicle is being driven (during driving) and when the backrest 300 is reclined and the user is at rest (at rest).

[0031] This will be described in more detail. FIG. 3 is a side view of a seat equipped with the headrest of the first embodiment, and is a diagram for explaining the states of the headrest portion 40 and the backrest 300 during driving (FIG. 3(a)) and at rest (FIG. 3(b)). FIG. 3(a) shows the movement of the head during a collision (the head when moving forward due to inertial force and the head when being swung back), as well as the headrest portion 40 when it moves forward during a collision. During driving, as shown in FIG. 3(a), the backrest 300 is raised and the headrest portion 40 is set in the rear section of the adjustment range (the section where the front surface of the headrest portion 40 faces downward). Thereby, while positioning the headrest portion 40 at a position that does not interfere with driving, when an impact such as a collision occurs, the headrest portion 40 moves forward within a range where it does not reach the foremost position, so that the headrest portion 40 approaches the swung-back head and can receive the back of the head. On the other hand, at rest, as shown in FIG. 3(b), the backrest 300 is reclined and the headrest portion 40 is set in the front section of the adjustment range (the section where the front surface of the headrest portion 40 faces upward). Thereby, the headrest portion 40 can be positioned at an optimal position (a position that contacts the lower side of the back of the head) for use as a pillow. The front surface of the headrest portion 40 (the surface that contacts the head) is a smooth surface with a small curvature, and the head can be safely placed thereon without a sense of danger at any position within its adjustment range.

[0032] As the front-back position adjustment mechanism 50, a friction brake mechanism is used that not only exhibits frictional resistance to rearward movement but also frictional resistance to forward movement with respect to the movable-side member 30 when the headrest portion 40 is in the adjustment range. As already described, there are a "spring lock type" and a "shoe brake type" for the friction brake mechanism 50. The friction brake mechanism 50 in the headrest of the first embodiment is of the spring lock type. FIG. 4 is a cross-sectional view extracting the periphery of the friction brake mechanism 50 in the headrest of the first embodiment, showing a cross-section cut by a plane perpendicular to the left-right direction.

[0033] As shown in FIG. 4, the friction brake mechanism 50 is composed of a coil-shaped lock spring 51, a lock drum 52, and a lock switching mechanism 53. The lock drum 52 is a cylindrical member fixed in a non-movable state with respect to the movable-side member 30, and is pivotally supported with respect to the fixed-side member 20 in a state where it can rotate about a fulcrum P1. The lock spring 51 is externally fitted to the lock drum 52 in a tightened state.

[0034] As shown in FIG. 4, one end side of the lock spring 51 is a fixed end 51a fixed to the fixed-side member 20 (fixed by a free-end holding member 70 fixed to the fixed-side member 20 in the headrest of the first embodiment), and the other end side is a free end 51b not fixed to the fixed-side member 20. An acting portion 51c and an extension portion 51d extending ahead of the acting portion 51c are provided on the free end 51b side of the lock spring 51. When setting the frictional resistance when the headrest portion 40 in the adjustment range tries to rotate rearward to around 300 N (the value at the center-of-gravity position of the headrest portion 40 shown in FIG. 8), the lock spring 51 has a wire diameter of about 3.5 mm, a number of turns of about 3.5 to 5 turns, and an inner diameter that is about 4 to 6% smaller than the outer diameter of the lock drum 52.

[0035] The lock switching mechanism 53 switches between an unlocked state in which the movable member 30 can freely pivot back and forth with respect to the fixed member 20 and a locked state in which the back-and-forth rotation of the movable member 30 with respect to the fixed member 20 is controlled by operating the acting portion 51c at the free end 51b of the lock spring 51 in the relaxation direction or the tightening direction. This lock switching mechanism 53 is composed of an unlocking cam 53a, a lock return cam 53b, and a free end locking portion 53c. The unlocking cam 53a and the lock return cam 53b are provided at a portion protruding in an outer flange shape at one end of the lock drum 52. The free end locking portion 53c is a groove-shaped portion provided in the above-described free end holding member 70.

[0036] The operation of the lock switching mechanism 53 will be described. FIG. 5 is a diagram for explaining the operation of the lock switching mechanism 53 in the headrest of the first embodiment. In FIG. 5, for the sake of illustration, only the acting portion 51c (free end 51b) of the lock spring 51, the lock drum 52, and the free end holding member 70 are shown. When the headrest portion 40 is in the rearmost position (the position of the solid line in FIG. 1) and when it is in the adjustment section rotated forward from the rearmost position, the lock switching mechanism 53 is in the state shown in FIG. 5(a), and the headrest portion 40 is in a non-rotatable state (a state in which the lock spring 51 tightens the lock drum 52) with respect to backward rotation. On the other hand, with respect to forward rotation, it becomes a rotatable state (a state in which the lock spring 51 loosens with respect to the lock drum 52).

[0037] When the headrest portion 40 is further rotated forward from the state shown in FIG. 5(a), as shown in FIG. 5(b), the unlocking cam 53a of the lock drum 52 abuts on the acting portion 51c (free end 51b) of the lock spring 51, and the acting portion 51c (free end 51b) of the lock spring 51 moves along the inclination of the unlocking cam 53a while being pushed in the relaxation direction, and is locked to the free end locking portion 53c as shown in FIG. 5(c). Thereby, it switches to a state in which both forward and backward rotation of the headrest portion 40 are possible (unlocked state).

[0038] On one hand, starting from the foremost position shown in FIG. 5(c), the headrest 40 is rotated rearward. When the headrest 40 approaches the rearmost position, as shown in FIG. 5(d), the lock return cam 53b abuts against the acting portion 51c (free end 51b) of the lock spring 51. The acting portion 51c (free end 51b) of the lock spring 51 moves along the inclination of the lock return cam 53b and disengages from the free end locking portion 53c, and returns to the initial position (the same position as in FIG. 5(a)) by its own spring force (FIG. 5(e)). That is, it switches back to the locked state again. Even if an attempt is made to further rotate the headrest 40 rearward from the rearmost position shown in FIG. 5(a), or to further rotate the headrest 40 forward from the foremost position shown in FIG. 5(c), it cannot be rotated any further by the rear stopper α2 or the front stopper α1, respectively.

[0039] Figure By providing the resistance shape 71 as shown in FIG. 5(a) on the free end holding member 70, the lock switching operation force for switching to the unlocked state can be increased. Although the detailed content will be described later, this can prevent unlocking due to inertial force even in a severe collision accident occurring during driving at 60 km / h or more, etc., and enable the damper function to be reliably exerted.

[0040] As described above, in the headrest of the first embodiment, even when the headrest portion 40 is in the adjustment section, the headrest portion 40 can rotate forward. In this regard, as shown in Fig. 4(a), on the free end 51b side of the lock spring 51, an extension portion 51d extending from the acting portion 51c (the portion of the free end 51b where the unlocking cam 53a and the lock return cam 53b abut or are locked to the free end locking portion 53c) is provided, and this extension portion 51d is locked to the fixed side member 20. When the headrest portion 40 is rotated forward, the lock drum 52 rotates in a direction to loosen the lock spring 51 (clockwise in Fig. 4(a)). At this time, the free end 51b of the lock spring 51 is displaced in that direction, and by locking the free end 51b to restrict its movement, a frictional resistance force (locking force for forward movement), that is, a resistance force (clamping force) against forward movement, is generated in the direction in which the lock spring 51 loosens. Further, the extension portion 51d may be locked to the fixed side member 20 in a state where it is elastically displaced in the direction of tightening the lock drum 52. In this case, the adhesion of the lock spring 51 to the lock drum 52 is improved, and not only the locking force for forward rotation is manifested, but also the locking force for backward rotation increases. Thus, by locking the free end 51b of the lock spring, a frictional resistance force (locking force for forward rotation) is manifested between the lock spring 51 and the lock drum 52 even when the headrest portion 40 in the adjustment section is rotated forward. Note that as a method of locking the extension portion 51d of the lock spring 51, not only a method of directly locking to the fixed member 20, but also a method of locking the extension portion 51d using a compression spring 90 (applying a load in the direction of tightening the lock drum 52) as shown in Fig. 4(b) can be adopted. The compression spring 90 may be of any form (such as a coil spring or a leaf spring) as long as it can apply the above load to the extension portion 51d.

[0041] However, the locking force when the headrest 40 in the adjustment section attempts to rotate forward is smaller than the locking force when the headrest 40 in the adjustment section attempts to rotate backward. Specifically, using the headrest shown in FIG. 8 for explanation, the locking force for backward movement (the value at the center of gravity position of the headrest 40 shown in FIG. 8. The same applies hereinafter) is about 300 N, while the locking force for forward movement is about 20 N. Here, the calculation is performed using Conditions 1 to 8 described in the column of "Problems to be Solved by the Invention". As the operating force for moving the headrest 40 forward, in addition to the above-mentioned locking force for forward movement, there is a lock switching operating force for switching to the unlocked state at the most forward position. This is the force required to displace the lock spring 51 in the loosening direction and lock it to the free end locking portion 53c. In the lock spring 51 having the wire diameter, number of turns, etc. described above, it is about 80 N at the center of gravity position of the headrest 40. When the resistance force due to the above-described resistance shape 71 (FIG. 5(a)) is added thereto, it becomes about 110 N, and the operating force required to move the headrest 40 forward is 20 N + 110 N = 130 N. However, this is the operating force when operating at the center of gravity position shown in FIG. 8. Actually, the grip portion 41 in FIG. 8 is gripped with both hands for operation. Since the distance L1: distance L2 in FIG. 8 is approximately 1:2.5, based on the lever principle, the operating force becomes about 52 N, and the headrest 40 can be easily operated.

[0042] As described above, in the headrest of this example, the operating force (lock release operating force) required for the forward movement of the headrest 40 is 130 N at the center of gravity position. From Table 1 above, the load for the forward movement of the headrest 40 due to the inertial force in the case of a frontal collision at 60 km / h is 110.6 N. Therefore, even in the case of a frontal collision at 60 km / h, the lock will not be released, and the damper function will be surely exhibited.

[0043] As described above, when the vehicle undergoes a frontal collision, the headrest 40 can be moved forward within a range where it does not reach the most forward position, reducing the impact by bringing it closer to the head that swings back. In addition, in a collision at a certain set speed or higher, the above-described damper function can be fully exerted. Also, even during sudden braking or driving on rough roads, the headrest 40 does not move and does not interfere with driving, so it can be used for all seats including the driver's seat. Furthermore, since the front surface of the headrest 40 (the surface that contacts the head) is a smooth surface with a small curvature, the head can be safely rested on the headrest 40 without a sense of danger at any position within the adjustment range.

[0044] 2. Headrest of the Second Embodiment Next, the headrest of the second embodiment will be described. However, regarding the headrest of the second embodiment, the description will be mainly focused on the configurations that are different from the headrest of the first embodiment. The configurations not specifically mentioned in the headrest of the second embodiment are substantially the same as those of the headrest of the first embodiment.

[0045] In the headrest of the first embodiment, only one locking spring 51 was used, whereas in the headrest of the second embodiment, two locking springs with different locking directions are used. By externally fitting or internally fitting these two locking springs to the lock drum 51 in a tightened state, frictional resistance forces are generated not only in the rearward direction but also in the forward direction. As a result, the same effects as those of the first embodiment can be obtained.

[0046] 3. Headrest of the Third Embodiment Next, the headrest of the third embodiment will be described. However, regarding the headrest of the third embodiment, the description will be mainly focused on the configurations that are different from the headrests of the first and second embodiments. The configurations not specifically mentioned in the headrest of the third embodiment are substantially the same as those of the headrests of the first and second embodiments. FIG. 6 is a cross-sectional view showing the periphery of the friction brake mechanism 50 in the headrest of the third embodiment, cut along a plane including the rotation center line L.

[0047] In the headrests of the above-described first and second embodiments, a spring lock type friction brake mechanism was used as the front-rear position adjustment mechanism 50, whereas in the headrest of the third embodiment, a shoe brake type friction brake mechanism is used. Specifically, the front-rear position adjustment mechanism 50 (friction brake mechanism) is composed of a lock drum 52, a fixed-side shoe 56 (fixed-side locking member), a movable-side shoe 57 (movable-side locking member), a biasing member 58, a drum cover 59, a headed shaft 60, and a nut 61.

[0048] The lock drum 52 is fixed to the movable-side member 30 by welding or the like. The headed shaft 60 and the drum cover 59 are fixed to each other by a nut 61, and among them, the drum cover 59 is fixed to the fixed-side member 20. The fixed-side shoe 56 is fixed to the head of the headed shaft 60. The movable-side shoe 57 is fixed to the movable-side member 30 so as not to move, while it is attached to the fixed-side member 20 and the headed bolt 60 fixed thereto in a state where it can move left and right (moveable along the headed shaft 60). The biasing member 58 is a coil spring externally inserted into the shaft 60 and is in a compressed state between the bottom of the lock drum 52 and the drum cover 59. Therefore, the biasing member 58 biases the movable-side shoe 57 in a direction to press it against the fixed-side shoe 56.

[0049] By configuring as described above, the movable side shoe 57 is always pressed against the fixed side shoe 56, and when the headrest part 40 (Fig. 1) is rotated forward or backward, frictional resistance due to the contact between the movable side shoe 56 and the fixed side shoe 57 is generated. The magnitude of the frictional resistance is substantially equal in the case of forward rotation and the case of backward rotation. As described above, in the case of the headrest shown in Fig. 8, the locking force for forward movement and backward movement (the value at the center of gravity position of the headrest part 40 shown in Fig. 8) is preferably about 20 N. In this case, in order to supplement the locking force for backward movement, the angle adjustment range θ (Fig. 1) of the headrest part 40 is set to about 30° (moves back and forth about 70 mm at the lower end part of the headrest part 40), and it is more preferable to be able to sufficiently absorb the impact to the rear. The frictional resistance when rotating the headrest part 40 can also be adjusted by changing the roughness of the contact surfaces of the movable side shoe 56 and the fixed side shoe 57, the biasing force of the biasing member 58, etc.

[0050] 4. Headrest of the Fourth Embodiment Finally, the headrest of the fourth embodiment will be described. However, regarding the headrest of the fourth embodiment, mainly, the description will be focused on the configurations different from the headrests of the first to third embodiments. The configurations not particularly mentioned in the headrest of the fourth embodiment are substantially the same as those of the headrests of the first, second, and third embodiments. Fig. 7 is a side view showing the mechanism part in the headrest of the fourth embodiment. Fig. 7(a) shows the state when the headrest part 40 is in the rearmost position, and Fig. 7(b) shows the state when the headrest part 40 is in the foremost position.

[0051] All of the headrests from the first to the third embodiments described above were of the single pivot type in which the headrest portion 40 pivoted back and forth about one pivot point P1 (FIG. 1). In contrast, the headrest of the fourth embodiment is of the four-link type. Specifically, as shown in FIG. 7, the front-back position adjustment mechanism 50 uses a four-link mechanism (the front link 80 and the rear link 81, as well as the upper link 82 and the lower link 83).

[0052] The upper link 82 is configured such that the fixed-side member 20 serves its role, and the lower link 83 is configured such that the movable-side member 30 serves its role. The upper ends of the front link 80 and the rear link 81 are connected to the upper link 82 (fixed-side member 20) in a rotatable state. Also, the lower ends of the front link 80 and the rear link 81 are connected to the lower link 83 (movable-side member 20) in a rotatable state. By adopting the four-link mechanism, the entire headrest portion 40 can also be projected forward.

[0053] In addition, in the headrest of the fourth embodiment, the front link 80 is made shorter than the rear link 81. As a result, when the headrest portion 40 is in the rear section, as shown in FIG. 7(a), the front surface of the headrest portion 40 faces downward, and when the headrest portion 40 is in the front section, as shown in FIG. 7(b), the front surface of the headrest portion 40 faces upward. In other words, it is possible to change the tilt angle of the headrest portion 40. Thereby, in addition to projecting the entire headrest portion 40 forward, the degree of freedom in adjusting the position of the headrest portion 40 is increased. Also in the headrest of the fourth embodiment, the angle adjustment range θ of the headrest portion 40 is preferably 10 to 30°, and optimally around 20°. In the four-link type headrest, the angle adjustment range θ is defined by the sum θ1 + θ2 of the rear angle adjustment range θ1 (FIG. 7(a)) and the front angle adjustment range θ2.

Explanation of Reference Numerals

[0054] 10 Stay 20 Fixed-side member 21 Cylindrical wall part 22 Regulation wall part 30 Movable side member 40 Head receiving part 41 Gripping part 50 Friction brake mechanism (front - rear position adjustment mechanism) 51 Lock spring 51a Fixed end 51b Free end 51c Acting part 51d Extension part 52 Lock drum 53 Lock switching mechanism 53a Lock release cam 53b Lock return cam 53c Free end locking part 56 Fixed side shoe (fixed side lock member) 57 Movable side shoe (movable side lock member) 58 Biasing member 59 Drum cover 60 Shaft with head 61 Nut 70 Free end holding member 71 Resistance shape 80 Front link 81 Rear link 82 Upper link 83 Lower link 90 Compression spring α1 Front stopper α2 Rear stopper

Claims

1. A stay for attaching to the upper part of the seat backrest, A fixed-side member fixed to the stay, A movable-side member attached to the fixed-side member so as to be movable back and forth, A headrest fixed to the movable-side member, A front-back position adjustment mechanism that regulates the back-and-forth movement of the movable-side member with respect to the fixed-side member, and enables adjustment of the front-back position of the headrest within an adjustment range from the rearmost position where the headrest is in the most rearward position to the foremost position where the headrest protrudes most forward, A front stopper provided at the foremost position, A rear stopper provided at the rearmost position A vehicle headrest comprising: During vehicle operation, the headrest can be used with its front surface facing downward in a rear section within the adjustment range. When the backrest is reclined for rest, the headrest can be used with its front surface facing upward in a front section within the adjustment range, and As the front-back position adjustment mechanism, A coiled lock spring having one end fixed to the fixed-side member and the other end being a free end, with an acting portion and an extension portion extending beyond the acting portion provided at the free end side, A lock drum fixed to the movable-side member for externally fitting or internally fitting the lock spring, A lock switching mechanism having a free-end holding member provided with a free-end locking portion, which switches to an unlocked state where the movable-side member can rotate back and forth with respect to the fixed-side member by operating the acting portion of the lock spring in the relaxation direction and locking it to the free-end locking portion when the headrest reaches the foremost position, and switches to a locked state where the back-and-forth rotation of the movable-side member with respect to the fixed-side member is controlled by operating the acting portion of the lock spring in the tightening direction and disengaging it from the free-end locking portion when the headrest reaches the rearmost position is provided, By making the extension portion of the lock spring elastically displaced in the direction of tightening the lock drum, even when the headrest is within the adjustment range, the extension portion of the lock spring restricts the movement of the free end of the lock spring, thereby using a friction brake mechanism that exhibits not only the frictional resistance against backward movement but also the frictional resistance against forward movement with respect to the movable-side member when the headrest is within the adjustment range. The frictional resistance against forward movement is set to be 10 to 30 N at the center of gravity position of the headrest. A resistance shape for increasing the force required for the acting portion of the locking spring to engage with the free end locking portion when switching from the locked state to the unlocked state is provided on the free end holding member A headrest characterized by this.

2. The front-rear position adjustment mechanism is configured to pivot the headrest portion back and forth about one fulcrum, The fulcrum is located above the headrest portion, The gripping portion for adjusting the front-rear position is provided at the lower portion of the headrest portion The headrest according to claim 1.

3. The front-rear position adjustment mechanism uses a four-link mechanism, Due to the different lengths of the opposing links in the four links, the front surface of the headrest portion when in the rear section is downward, and the front surface of the headrest portion when in the front section is upward The headrest according to claim 1.

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