JP7799545B2 - Headrest support structure - Google Patents

Description

The present invention relates to a headrest support structure.

Patent Document 1 below discloses a locking structure capable of locking and unlocking. This locking structure includes a cylinder, a rod-shaped member inserted into the cylinder, a tapered member fitted into the cylinder so as to be freely movable along the axial direction of the cylinder and having a tapered portion, an elastic body that biases and supports the tapered member in a direction in which the inner diameter of the tapered portion gradually increases, and a locking member. The locking member is housed in the space between the tapered member and the rod-shaped member, and is configured to be pressed against the tapered portion as the rod-shaped member moves in a direction in which the inner diameter of the tapered portion gradually decreases, thereby abutting against the inner wall of the housing space and applying a load to the rod-shaped member. With this configuration, when the rod-shaped member moves in the direction in which the inner diameter of the tapered portion gradually decreases, the locking member engages the lock. Moving the tapered member in the direction in which the inner diameter of the tapered portion gradually decreases against the elastic force of the elastic body releases the load imposed by the locking member, allowing the lock to be easily released.

Japanese Patent Application Laid-Open No. 2008-260446

However, the locking structure of the above-mentioned prior art is applied to an actuator that lifts the rear end of a vehicle's hood, but since it cannot be adjusted continuously, there is room for improvement if it is to be applied to the support part of a headrest.

In consideration of the above, the present invention aims to provide a headrest support structure that allows for easy and continuous adjustment of the headrest's height in the vertical direction of the seat.

The headrest support structure of the present invention described in claim 1 comprises a headrest stay having a leg portion extending downward from inside a headrest main body, a cylindrical member formed in a cylindrical shape and through which the leg portion is inserted, a recess formed in an annular and concave shape along the circumferential direction on one of the inner circumferential surface of the cylindrical member and the outer circumferential surface of the leg portion, a pair of upper and lower tapered portions inclined so as to gradually narrow the opposing gap between them from the open end side of the recess toward the concave bottom side, and a pair of tapered portions disposed within the recess and aligned in the one circumferential direction, which contact both the cylindrical member and the leg portion. and a plurality of balls that hold the leg by frictional force, and further that, when the leg is moved up and down , when one of the balls moves upward relative to the other of the inner peripheral surface of the tubular member and the outer peripheral surface of the leg, the ball is allowed to rotate while its downward relative displacement with respect to the one of the balls is restricted by the lower tapered portion of the pair of upper and lower tapered portions, and when one of the balls moves downward relative to the other of the balls, the ball is allowed to rotate while its upward relative displacement with respect to the one of the balls is restricted by the upper tapered portion of the pair of upper and lower tapered portions .

According to the above configuration, the legs of the headrest stays are inserted into the tubular member. A recess formed in an annular, concave shape along the circumferential direction is provided on one of the inner circumferential surface of the tubular member and the outer circumferential surface of the legs. The headrest support structure of the above configuration also includes a pair of upper and lower tapered portions that are inclined so that the vertical spacing between them gradually narrows from the open end of the recess toward the bottom. The balls arranged in the recess are aligned circumferentially along the one of the recesses and contact both the tubular member and the legs, holding the legs by friction. Furthermore, when the legs are moved up and down , when the one of the legs moves upward relative to the other of the inner circumferential surface of the tubular member and the outer circumferential surface of the legs, the lower of the pair of tapered portions restricts downward relative displacement relative to the one of the pair of tapered portions, allowing rotation. When the one of the legs moves downward relative to the other, the upper of the pair of tapered portions restricts upward relative displacement relative to the one of the pair of tapered portions, allowing rotation. This allows for easy, continuous adjustment of the headrest's vertical height.

The headrest support structure of the present invention described in claim 2 is the same as the headrest support structure described in claim 1, wherein the plurality of balls aligned in one circumferential direction are aligned in a plurality of sets in the axial direction of the leg portion.

With the above configuration, the operating force required for vertical movement of the headrest stay can be easily adjusted by changing the number of balls arranged circumferentially on the inner surface of the cylindrical member and arranged in the axial direction of the leg portion.

The headrest support structure of the present invention described in claim 3 is the configuration described in claim 1 or claim 2 , and is provided with a ring member that is formed in the shape of an endless string, passes through the centers of the plurality of balls lined up in one circumferential direction, has elasticity, and can elastically return to the shape of the assembled state when elastically deformed.

With the above configuration, when placing multiple balls in the recess, the endless string-like ring member makes it easy to place the balls in the appropriate positions within the recess.

The headrest support structure of the present invention described in claim 4 has, in the configuration described in any one of claims 1 to 3 , an upper bush through which the leg is inserted and which is provided on the outer periphery of the tubular member, and a lower bush adjacent to the lower end of the tubular member on the lower side and through which the leg is inserted and which is provided on the lower end side of the upper bush so as to be able to engage and disengage.

With the above configuration, during assembly, the tubular member is first placed inside the upper bush, and then the upper and lower bushes are engaged. The legs of the headrest stay can then be inserted through the upper and lower bushes. Disassembly is also possible by releasing the engagement between the upper and lower bushes.

As described above, the headrest support structure of the present invention has the excellent effect of allowing the height of the headrest in the up-down direction of the seat to be easily and continuously adjusted.

1 is a simplified view showing an upper part of a vehicle seat provided with a headrest support structure according to a first embodiment, as viewed obliquely from above and in front; 2 is a plan cross-sectional view showing a bush and the like cut at a height position along the upper surface of a locking device applied to the headrest support structure of FIG. 1 . 2B is a longitudinal cross-sectional view taken along line 2B-2B of FIG. 2A. 10 is a schematic cross-sectional view for explaining the balance of forces when the headrest is in a stationary state. FIG. 10 is a schematic cross-sectional view showing the force relationship when the headrest stay is raised. FIG. 5 is a schematic cross-sectional view showing the force relationship during a collision. FIG. FIG. 10 is a vertical cross-sectional view showing a headrest support structure according to a second embodiment. FIG. 7 is a vertical cross-sectional view for explaining the assembly of the balls in FIG. 6 . FIG. 10 is a vertical cross-sectional view showing a headrest support structure according to a third embodiment. FIG. 10 is a vertical cross-sectional view showing a headrest support structure according to a fourth embodiment. FIG. 10 is an exploded cross-sectional view showing a part of the headrest support structure of FIG. 9 . FIG. 13 is a bottom view showing the lower end portion of the headrest stay in a modified example of the fourth embodiment, as viewed from below. FIG. 11 is a perspective view showing a headrest support structure according to a fifth embodiment. FIG. 13 is a vertical cross-sectional view showing a headrest support structure according to a sixth embodiment. FIG. 14 is a plan view showing the fastening member of FIG. 13 alone. FIG. 13 is a vertical cross-sectional view showing a modified example of the sixth embodiment. FIG. 13 is a vertical cross-sectional view showing a headrest support structure according to a seventh embodiment. FIG. 17 is an exploded cross-sectional view showing a part of the headrest support structure of FIG. 16 . FIG. 13 is a simplified view showing the upper part of a vehicle seat provided with a headrest support structure according to a ninth embodiment, as viewed obliquely from above and in front. 19 is a schematic horizontal cross-sectional view showing the locking device of FIG. 18 locking the leg portion. FIG. 19B is a schematic horizontal cross-sectional view showing a state in which the operating lever is operated in the unlocking direction from the state of FIG. 19A. FIG. 19C is a schematic horizontal cross-sectional view showing a state in which the operating lever is further operated in the unlocking direction from the state of FIG. 19B and the lock is released. FIG. 19D is a schematic horizontal cross-sectional view showing a state in which the operating lever is operated in a direction opposite to the unlocking direction from the state of FIG. 19C. FIG. FIG. 19E is a schematic horizontal cross-sectional view showing a state in which the operating lever is further operated in the direction opposite to the unlocking direction from the state of FIG. 19D. 19 is a perspective view for explaining an assembly procedure applied to the headrest support structure of FIG. 18. FIG. 20B is a perspective view showing a state in which a holder is welded to the upper frame of FIG. 20A. FIG. FIG. 20C is a perspective view showing a state in which a bush is inserted into the holder of FIG. 20B. 20D is a simplified perspective view showing the state in which the lower part of the locking device is engaged with the bushing of FIG. 20C. FIG.

[First embodiment]
A headrest support structure according to a first embodiment of the present invention will be described with reference to Figures 1 to 5. In these figures, the arrow FR indicates the front side of the seat, the arrow UP indicates the upper side of the seat, and the arrow W indicates the width direction of the seat (left-right direction of the seat).

(composition)
1 shows a simplified view of the upper part of a vehicle seat 10 equipped with a headrest support structure 11 according to a first embodiment, viewed from diagonally above the front. The vehicle seat 10 includes a seat cushion (not shown) that supports the buttocks and thighs of a seated occupant, a seat back 12 that supports the back of the seated occupant, and a headrest 20 that supports the head of the seated occupant.

The seat back 12 is configured such that a back pad (not shown), which is a cushioning material, is placed over a back frame 14, which is a skeletal member, and the surface of the back pad is covered with a trim cover 18, which is an upholstery material. The back frame 14 includes a pair of left and right side frames (not shown) extending in the seat back height direction, and a long, pipe-like upper frame 14A connecting the upper ends of the pair of left and right side frames. The upper frame 14A is formed in a horizontally elongated, approximately inverted U-shape when viewed from the front of the seat. A pair of left and right cylindrical holders 16 for connecting headrests 20 are fixed by welding to the front part of the upper frame 14A, which extends in the seat width direction. A cylindrical resin bushing 26 is inserted into the holder 16. The upper end of the bushing 26 is flange-shaped and exposed at the upper end of the seat back 12.

The headrest 20 is configured such that a headrest pad (not shown), which is a cushioning material, is placed on top of the headrest stay 22, which is a framework member, and the surface of the headrest pad is covered with a trim cover 24, which is a skin material. The portion of the headrest pad (not shown) covered by the trim cover 24 constitutes the headrest main body 20A. The headrest stay 22 is formed into a roughly inverted U-shape, for example, by bending a metal pipe, and has legs 22A that extend downward from the inside of the headrest main body 20A. The pair of left and right legs 22A of the headrest stay 22 are inserted into a pair of left and right bushings 26 and are connected to the upper end of the back frame 14 via a pair of left and right holders 16.

The locking device 30 shown in Figure 2A is incorporated within the bushing 26. In this embodiment, the locking device 30 is molded integrally with the bushing 26 during injection molding of the bushing 26. Figure 2A is a plan cross-sectional view of the bushing 26 and other components cut at a height position along the upper surface 32U of the locking device 30, and Figure 2B is a vertical cross-sectional view taken along line 2B-2B in Figure 2A. Note that for convenience, the illustrated range of the leg 22A of the headrest stay 22 in the vertical direction is wider than the illustrated range of the bushing 26 in the vertical direction in Figure 2B.

2A and 2B, the locking device 30 includes a cylindrical member 32. The upper end surface 32U of the cylindrical member 32 forms the upper surface 32U of the locking device 30. The leg portions 22A of the headrest stays 22 are inserted into the cylindrical member 32. The inner peripheral surface 32N of the cylindrical member 32 includes a recess 32X formed in an annular, concave shape along the circumferential direction. As shown in FIG. 2B, the recess 32X includes a pair of upper and lower tapered portions 32B that are inclined so that the vertically opposing distance between them gradually narrows from the open end toward the concave bottom. The tapered portions 32B connect the small diameter portion 32A to the large diameter portion 32C, which has a larger diameter than the small diameter portion 32A, on the inner peripheral surface 32N of the cylindrical member 32. In this embodiment, the large diameter portion 32C extends along the axial direction of the cylindrical member 32 at the axially intermediate portion of the cylindrical member 32.

As shown in FIG. 2A, a plurality of balls 34 are arranged in the recess 32X of the tubular member 32, aligned circumferentially on the inner circumferential surface 32N of the tubular member 32. As shown in FIGS. 2A and 2B, the plurality of balls 34 contact both the tubular member 32 and the leg portion 22A of the headrest stay 22, and hold the leg portion 22A by frictional force. Furthermore, when the leg portion 22A shown in FIG. 2B is moved up and down, the pair of upper and lower tapered portions 32B restricts the relative vertical displacement with respect to the inner circumferential surface 32N of the tubular member 32, allowing the balls 34 to rotate.

As shown in Figure 2A, adjacent balls 34 in the circumferential direction are connected to each other by ball connecting members 36. The ball connecting members 36 are provided to prevent the balls 34 from separating within the tubular member 32, and are attached to the balls 34 in a manner that maintains the balls 34 in a rotatable state.

As shown in FIG. 2B , the balls 34 arranged circumferentially on the inner surface 32N of the tubular member 32 are arranged in multiple sets in the axial direction of the leg portion 22A. For convenience, the balls 34 arranged in the vertically middle portion of the tubular member 32 are omitted from FIG. 2B , and a vertical "..." symbol is added above the omitted portion. However, in reality, multiple sets of balls 34 similar to the upper two sets are arranged in the axial direction of the leg portion 22A at the omitted portion. The number of sets of balls 34 is a factor that contributes to adjusting the operating force required for vertical movement of the headrest stay 22 and is set at the time of design. In this embodiment, a portion of the ball connecting member 36 is interposed between vertically adjacent balls 34 to prevent vertically adjacent balls 34 from interfering with each other. The balls 34 arranged in the uppermost and lowermost rows are in contact with the tapered portion 32B.

Meanwhile, the lower end of the leg 22A of the headrest stay 22 is positioned lower than the lower ends of the locking device 30 and bushing 26. A small protrusion 22A1 is formed at a specific circumferential position on the lower end of the leg 22A of the headrest stay 22, protruding slightly radially outward compared to other positions. The small protrusion 22A1 is an element that prevents the leg 22A of the headrest stay 22 from coming out of the locking device 30. The small protrusion 22A1 is set to a degree that allows the headrest 20 to be removed from the locking device 30 when the user pulls up the headrest 20 with a certain amount of force. When assembling the headrest stay 22 to the locking device 30 and bushing 26, a corresponding pushing force is required for the small protrusion 22A1 to pass through the ball 34, but the required pushing force (insertion force) decreases after the small protrusion 22A1 passes through the ball 34.

In order to reduce the effect of heat on the operating force, the headrest stay 22, tubular member 32, and ball 34 are made of steel, as an example.

(Supplementary explanation regarding basic principles)
Next, a supplementary explanation of the basic principle will be provided with reference to Figures 3 to 5. Figures 3 to 5 are schematic diagrams for explaining the basic principle, and for convenience, the same components as those described in the first embodiment are designated by the same reference numerals. In Figures 3 and 4, the dashed-dotted line CL indicates the central axis of the leg portion 22A of the headrest stay 22.

First, the balance of forces when the headrest 20 is in a stationary state will be explained with reference to Figure 3.

3, the mass of the ball 34 is denoted by m _b , the mass of the entire headrest 20 including the headrest stay 22 is denoted by m _s , and the acceleration due to gravity is denoted by g. Furthermore, the maximum static friction force at the contact portion between the ball 34 and the large diameter portion 32C of the tubular member 32 is denoted by f _w , and the maximum static friction force at the contact portion between the ball 34 and the leg portion 22A of the headrest stay 22 is denoted by f _s . Furthermore, the normal force acting on the ball 34 by the large diameter portion 32C of the tubular member 32 is denoted by N _w , and the normal force acting on the ball 34 by the leg portion 22A of the headrest stay 22 is denoted by N _s .

From the equation for the balance of the ball 34, the following (Equation 1) and (Equation 2) are established.
(m _b + m _s )g=f _w +f _s ... (Formula 1)
_Ns = _Nw ... (Formula 2)

Furthermore, if the static friction coefficient at the contact portion between the ball 34 and the large diameter portion 32C of the tubular member 32 is _μw , and the static friction coefficient at the contact portion between the ball 34 and the leg portion 22A of the headrest stay 22 is _μs , the following (Equation 3) and (Equation 4) are established from the friction relational equations.
f _s = μ _s N _s ... (Formula 3)
f _w = μ _w N _w ... (Formula 4)

From the above (Equation 1) to (Equation 4), the following (Equation 5) is established.
(m _b + m _s ) g = (μ _s + μ _w ) N _s (Formula 5)
When _Ns is calculated from the above (Equation 5), the following (Equation 6) is obtained.
N _s = ((m _b + m _s )/(μ _s + μ _w ))g... (Formula 6)
The above (Equation 6) indicates the condition under which the ball 34 does not fall.

Furthermore, from the equation for balance of the headrest stay 22, the following (Equation 7) is established.
f _s = m _s g... (Formula 7)

From the above (Equation 3) and (Equation 7), the following (Equation 8) is established.
μ _s N _s = m _s g... (Formula 8)
When _Ns is calculated from the above (Equation 8), the following (Equation 9) is obtained.
N _s = (m _s / μ _s ) g... (Formula 9)
The above (Equation 9) indicates the condition under which the headrest stay 22 does not fall. By satisfying this condition, the headrest 20 will stay in place without falling even if an occupant adjusting the height of the headrest 20 shown in FIG. 1 moves away from the headrest 20.

Next, the case where the headrest stay 22 is raised (during normal use) will be described with reference to Figure 4. Note that in Figure 4, for ease of viewing, the angle of inclination of the tapered portion 32B is shown differently from that shown in Figure 3.

4, the normal force acting on the ball 34 by the upper tapered portion 32B of the cylindrical member 32 is designated as _NT . The kinetic friction force at the contact portion between the ball 34 and the large diameter portion 32C of the cylindrical member 32 is designated as _f'w , and the kinetic friction force at the contact portion between the ball 34 and the upper tapered portion 32B of the cylindrical member 32 is designated as _f'T . The other symbols are the same as in FIG. 3.

Here, if the coefficient of dynamic friction at the contact point between the ball 34 and the large diameter portion 32C of the cylindrical member 32 shown in Figure 4 is _μ'w , and the coefficient of dynamic friction at the contact point between the ball 34 and the upper tapered portion 32B of the cylindrical member 32 is _μ'T , then _μs >_μ'T + _μ'w , and if the radius of the ball 34 is r, the following (Equation 10) holds.
f _s r >(f' _T + f' _w ) r... (Formula 10)
That is, when a force F (operating force by the occupant) of a predetermined magnitude or more is applied to lift the headrest stay 22 during normal use, the ball 34 rotates in the direction of arrow R.

Next, we will explain the force relationships during a collision with reference to Figure 5.

5, the maximum static friction force at the contact portion between the ball 34 and the upper tapered portion 32B of the cylindrical member 32 is designated as _fT . The other symbols are the same as those in FIG.

Here, if the inclination angle of the upper tapered portion 32B with respect to the vertical direction in FIG. 5 is θ, the following (Equation 11) is established.
f _s cos θ + f _T > m _b g cos θ (Formula 11)

In other words, during a collision, the leg portion 22A of the headrest stay 22 attempts to rise in a short time, and while the coefficient of friction between the tubular member 32 and the ball 34 remains the static coefficient of friction, the ball 34 attempts to rise up the upper tapered portion 32B, and the so-called wedge effect prevents the leg portion 22A from rising.

(Actions and Effects)
Next, the operation and effects of this embodiment will be described.

As shown in Figures 2A and 2B, the legs 22A of the headrest stays 22 are inserted into the tubular member 32. The inner surface 32N of the tubular member 32 is provided with a recess 32X formed in an annular, concave shape along its circumferential direction. The recess 32X has a pair of upper and lower tapered portions 32B that gradually narrow the vertically opposing distance from the open end toward the bottom. Multiple balls 34 arranged within the recess 32X are aligned circumferentially around the inner surface 32N of the tubular member 32 and contact both the tubular member 32 and the legs 22A of the headrest stays 22. They hold the legs 22A by frictional force, and when the legs 22A are moved up and down, the pair of upper and lower tapered portions 32B restrict their relative vertical displacement with respect to the inner surface 32N of the tubular member 32, allowing them to rotate. This allows for easy, continuous adjustment of the vertical height of the headrest 20 shown in Figure 1.

In addition, in this embodiment, as shown in FIG. 2B, multiple balls 34 are arranged in multiple sets in the axial direction of the leg portion 22A, and are aligned circumferentially on the inner circumferential surface 32N of the tubular member 32. By changing the number of balls 34 aligned circumferentially on the inner circumferential surface 32N of the tubular member 32 arranged in the axial direction of the leg portion 22A, the operating force required for the up and down movement of the headrest stay 22 can be easily adjusted.

As described above, the headrest support structure 11 of this embodiment has the excellent effect of allowing the height of the headrest in the up-down direction of the seat to be easily and continuously adjusted.

Second Embodiment
Next, a headrest support structure according to a second embodiment of the present invention will be described with reference to Figures 6 and 7. Figure 6 shows a vertical cross-sectional view of a headrest support structure 40 according to the second embodiment, and Figure 7 shows a vertical cross-sectional view for explaining the assembly of a ball 46. Note that in Figure 6, only the outline of the leg portion 22A of the headrest stay 22 is shown by a two-dot chain line for convenience. Furthermore, since the headrest stay 22 of the second embodiment has the same configuration as the headrest stay 22 of the first embodiment (see Figures 1 to 2B), the same reference numerals are used and description thereof will be omitted.

As shown in FIG. 6, the headrest support structure 40 includes a first bushing 42 made of resin as a cylindrical member. In this embodiment, the first bushing 42 is made of resin as an example, but it may also be made of steel. The leg portion 22A of the headrest stay 22 is inserted into the first bushing 42. A brim-shaped flange portion 42F that protrudes radially outward is formed at the upper end of the first bushing 42. A locking portion 42K is also formed at the lower portion of the first bushing 42. A cylindrical second bushing 44 made of steel is positioned on the outer periphery of the first bushing 42, between the flange portion 42F and the locking portion 42K.

The inner circumferential surface 42N of the first bushing 42 is provided with a recess 42X formed in an annular, concave shape along the circumferential direction. The recess 42X has a pair of upper and lower tapered portions 42B that are inclined so that the vertical spacing between them gradually narrows from the open end side toward the concave bottom side. The tapered portions 42B connect the small diameter portion 42A and the large diameter portion 42C, which has a larger diameter than the small diameter portion 42A, on the inner circumferential surface 42N of the first bushing 42. In this embodiment, the large diameter portion 42C is formed in a linear shape that forms a circle in a plan view, and the recess 42X is formed in a horizontal V-shape in a vertical cross section. Two recesses 42X are formed at a distance from each other in the vertical middle of the first bushing 42.

A plurality of balls 46 are arranged in the recesses 42X on the inner circumferential surface 42N of the first bushing 42, aligned circumferentially about the inner circumferential surface 42N of the first bushing 42. While Figures 6 and 7 illustrate two balls 46 in each recess 42X for ease of illustration, in reality, a large number of balls 46 are arranged in a circumferential alignment in each recess 42X. The balls 46 contact both the first bushing 42 and the leg portion 22A of the headrest stay 22, holding the leg portion 22A by frictional force. Furthermore, when the leg portion 22A is moved up or down, the pair of upper and lower tapered portions 42B restricts vertical displacement relative to the inner circumferential surface 42N of the first bushing 42, allowing the leg portion 22A to rotate.

In addition, in this embodiment, an endless string-like ring member 48 is provided that passes through the centers of multiple balls 46 arranged circumferentially on the inner surface 42N of the first bushing 42. During manufacturing, both ends of the string-like member that passes through the centers of the multiple balls 46 are joined to form the annular ring member 48. The ring member 48 is elastic and can elastically return to its assembled shape when elastically deformed. The balls 46 and ring member 48 form a bracelet-like ball module 49. When placing the ball module 49 composed of the balls 46 and ring member 48 in the recess 42X of the first bushing 42, the ball module 49 shown in FIG. 7 is inserted from the outside to the inside of the first bushing 42 while deforming the ring member 48, and is finally placed as shown in FIG. 6.

In addition, in this embodiment, multiple balls 46 are arranged in the circumferential direction on the inner surface 42N of the first bushing 42, and multiple sets (for example, two sets) are arranged in the axial direction of the leg portion 22A.

The configuration of the second embodiment described above also achieves substantially the same effects and advantages as the first embodiment described above. Furthermore, in the second embodiment, when placing multiple balls 46 within the recess 42X, the endless string-like ring member 48 makes it easy to position the multiple balls 46 in the appropriate positions within the recess 42X.

[Third embodiment]
Next, a headrest support structure according to a third embodiment of the present invention will be described with reference to Fig. 8, with reference to Fig. 1. Fig. 8 shows a vertical cross-sectional view of a headrest support structure 50 according to the third embodiment.

As shown in Figure 8, the headrest support structure 50 has a headrest stay 52 with a leg 52A extending downward from inside the headrest main body 20A (see Figure 1). The outer peripheral surface 52G of the leg 52A of the headrest stay 52 is provided with a recess 52X formed in an annular, concave shape along the circumferential direction of the outer peripheral surface 52G of the leg 52A. The recess 52X has a pair of upper and lower tapered portions 52T that are inclined so that the gap between them gradually narrows from the open end side toward the concave bottom side. The recess 52X is formed in a horizontal V-shape in a vertical cross section, and three recesses 52X are formed in total, for example, spaced apart from each other in the vertical direction.

The headrest support structure 50 also includes a first bushing 54, which is a cylindrical member through which the leg 52A of the headrest stay 52 is inserted. A flange 54F, which is shaped like a brim and protrudes radially outward, is formed at the upper end of the first bushing 54. A locking portion 54K is also formed at the lower part of the first bushing 54. A cylindrical second bushing 55 made of steel is positioned on the outer periphery of the first bushing 54, between the flange 54F and the locking portion 54K.

A plurality of balls 56 are arranged in the recess 52X of the headrest stay 52, aligned circumferentially on the outer peripheral surface 52G of the leg 52A of the headrest stay 52. The balls 56 contact both the first bushing 54 and the leg 52A of the headrest stay 52, and hold the leg 52A by frictional force. Furthermore, when the leg 52A is moved up or down, the pair of upper and lower tapered portions 52T restricts vertical displacement relative to the outer peripheral surface 52G of the headrest stay 52, allowing it to rotate.

In addition, in this embodiment, an endless string-like ring member 58 is provided that passes through the centers of multiple balls 56 arranged in the circumferential direction on the outer peripheral surface 52G of the leg portion 52A of the headrest stay 52. The ring member 58 is elastic and can elastically return to its assembled shape if it is elastically deformed.

In addition, in this embodiment, multiple balls 56 are arranged in the circumferential direction on the outer peripheral surface 52G of the leg portion 52A of the headrest stay 52, and multiple sets (three sets, for example) are arranged in the axial direction of the leg portion 22A.

The configuration of the third embodiment described above also achieves substantially the same effects and advantages as the second embodiment described above. Furthermore, by changing the number of recesses 52X in which multiple balls 56 are arranged, the operating force required to move the headrest stay 52 up and down can be adjusted.

[Fourth embodiment]
Next, a headrest support structure according to a fourth embodiment of the present invention will be described with reference to Figures 9 and 10. Figure 9 shows a vertical cross-sectional view of a headrest support structure 60 according to the fourth embodiment. Figure 10 shows an exploded cross-sectional view of a portion of the headrest support structure 60. The configuration of the fourth embodiment shown in Figures 9 and 10 is substantially similar to that of the first embodiment, except for the points described below. Therefore, components substantially similar to those of the first embodiment are designated by the same reference numerals, and their description will be omitted.

As shown in Figure 9, the leg portion 62A of the headrest stay 62 differs from the headrest stay 22 of the first embodiment shown in Figures 1 to 2B in that the notch 62A1 shown in Figure 9 is formed instead of the small protrusion 22A1 on the leg portion 22A of the headrest stay 22 of the first embodiment shown in Figure 2B etc., but in other respects it has the same configuration as the headrest stay 22 of the first embodiment. The notch 62A1 shown in Figure 9 is intended to prevent the leg portion 62A of the headrest stay 62 from coming loose in the event of a collision (impact). This point will be discussed later.

The headrest support structure 60 includes a locking device 30 similar to the locking device 30 in the first embodiment (see Figures 2A and 2B). A resin upper bushing 64 is provided on the outer periphery of the cylindrical member 32 of the locking device 30. The upper bushing 64 is generally cylindrical, and the leg portion 62A of the headrest stay 62 is inserted through it. A thick, annular stopper portion 64S is formed at the upper end of the upper bushing 64.

A locking member 66 is provided on the stopper portion 64S. The locking member 66 is generally plate-shaped and has a push knob 66A on part of the upper part of the stopper portion 64S. The push knob 66A can be pushed in a direction toward the axis of the upper bush 64 against the biasing force of a return spring (not shown). The locking member 66 also has a through hole 66H through which the leg portion 62A of the headrest stay 62 passes in plan view, and is equipped with a locking portion 66B that forms part of the periphery of the through hole 66H and can come into contact with and separate from the leg portion 62A of the headrest stay 62.

As a result, if the leg portion 62A of the headrest stay 62 is about to come loose upward from the upper bushing 64, the locking portion 66B fits into the notch 62A1 on the lower end of the leg portion 62A, preventing it from coming loose.

A cylindrical body portion 64A is formed continuously below the intermediate portion between the inner and outer circumferential ends of the stopper portion 64S. A crushed rib 64R is formed on the lower surface of the stopper portion 64S, near the inner circumferential end, protruding toward the upper surface 32U of the cylindrical member 32 and contacting the upper surface 32U of the cylindrical member 32. The crushed rib 64R is used to absorb dimensional variations. A recessed engagement recess 68 that opens toward the axial center of the upper bushing 64 is formed at the lower end of the body portion 64A.

Meanwhile, a lower bushing 70 is provided adjacent to the lower end 32Z of the tubular member 32 of the locking device 30, below the lower end 32Z. The lower bushing 70 is generally cylindrical, and the leg portion 62A of the headrest stay 62 is inserted through it. A locking portion 70K is formed at the bottom of the lower bushing 70. A crushed rib 70R is formed at the top of the lower bushing 70, protruding toward the lower end 32Z of the tubular member 32 and contacting the lower end 32Z of the tubular member 32. The crushed rib 70R is used to absorb dimensional variations.

A locking member 72 is provided at the top of the lower bushing 70, radially outward of the crushing rib 70R, with a protruding engagement claw 72A that can engage and disengage with the engagement recess 68 of the upper bushing 64. The locking member 72 is L-shaped overall and includes a first arm 72B that extends downward from the upper portion where the engagement claw 72A is formed, and a second arm 72C that extends radially outward from the lower end of the first arm 72B. The locking member 72 is biased radially outward from the lower bushing 70 by a return spring (not shown). Under normal conditions, the terminal end 72C1 of the second arm 72C protrudes from the outer peripheral surface of the lower bushing 70 and can be pressed toward the axis of the lower bushing 70 (see arrow 72P) against the biasing force of the return spring (not shown).

When the terminal portion 72C1 of the second piece 72C of the locking member 72 is not pressed, the engagement claw 72A engages with the engagement recess 68 of the upper bushing 64. When the terminal portion 72C1 of the second piece 72C of the locking member 72 is pressed, the engagement claw 72A disengages from the engagement recess 68 of the upper bushing 64. As a result, the lower bushing 70 is capable of engaging and disengaging with the lower end of the upper bushing 64.

Now, we will explain how to assemble the headrest support structure 60 shown in Figure 9. First, the locking device 30 is inserted from below into the upper bushing 64 shown in Figure 10 (see arrow S1). Next, the lower bushing 70 is brought closer to the upper bushing 64 and locking device 30 from below (see arrow S2) so that the engagement claw 72A of the lower bushing 70 engages with the engagement recess 68 of the upper bushing 64. Finally, as shown in Figure 9, the leg 62A of the headrest stay 62 is inserted from above so that it passes through the axes of the upper bushing 64, locking device 30, and lower bushing 70, thereby obtaining the headrest support structure 60 shown in Figure 11.

The configuration of the fourth embodiment described above also achieves the same effects and advantages as the first embodiment. Furthermore, in this fourth embodiment, when the locking member 72 provided on the lower bushing 70 is pressed, the engagement (lock) between the engagement claw 72A of the locking member 72 and the engagement recess 68 of the upper bushing 64 is released, allowing the locking device 30, upper bushing 64, and lower bushing 70 to be easily disassembled.

[Modification of the Fourth Embodiment]
Next, a modified example of the fourth embodiment will be described with reference to Fig. 11. Fig. 11 shows a bottom view of the lower end side of the leg portion 74A of the headrest stay 74 in the modified example of the fourth embodiment, as viewed from below. The headrest stay 74 has the same configuration as the headrest stay 62 shown in Fig. 9, except for the points described below.

In the configuration of the fourth embodiment described above, a notch 62A1 is formed on the lower end of the leg 62A of the headrest stay 62 to prevent the leg 62A from coming loose during a collision (impact). However, instead of this notch 62A1, a pin mounting portion 74A1 as shown in FIG. 11 may be provided, and a pin 75 may be attached to this pin mounting portion 74A1. As an example, the pin 75 is bent into a generally hat shape when viewed from the bottom in FIG. 11. In this modification of the fourth embodiment, when the headrest stay 74 is pulled up by more than a predetermined amount during a collision, the pin 75 hits the bottom side of the lower bush 70 (see FIG. 9), stopping the leg 74A from moving upward. This prevents the leg 74A of the headrest stay 74 from coming loose.

Fifth Embodiment
Next, a headrest support structure according to a fifth embodiment of the present invention will be described with reference to Fig. 12. Fig. 12 shows a perspective view of a headrest support structure 76 according to the fifth embodiment. In Fig. 12, components that are substantially the same as those in the first embodiment are designated by the same reference numerals.

As shown in Figure 12, in the fifth embodiment, the locking device 30 is positioned in substantially the same position as the holder 16 (see Figure 1) in the first embodiment and is directly joined to the upper frame 14A of the back frame 14, and the leg portion 22A of the headrest stay 22 is inserted into this locking device 30. This fifth embodiment also achieves substantially the same functions and effects as the first embodiment described above.

Sixth Embodiment
Next , a headrest support structure according to a sixth embodiment will be described with reference to Figures 13 and 14, with reference to Figure 1. Note that the sixth embodiment is not an embodiment of the present invention but a reference example. Figure 13 shows a vertical cross-sectional view of a headrest support structure 80 according to the sixth embodiment.

The headrest stay 62 shown in Figure 13 has the same configuration as the headrest stay 62 in the fourth embodiment (see Figure 9). The leg portion 62A is inserted into a cylindrical resin bushing 82 and is connected to the upper end of the back frame 14 via a pair of left and right holders 16 shown in Figure 1.

A thick, annular stopper portion 82S is formed at the upper end of the bushing 82 shown in Figure 13. The stopper portion 82S is also provided with a locking member 66 similar to the locking member 66 in the fourth embodiment (see Figure 9). A cylindrical first body portion 82A is formed continuously below the intermediate portion between the inner and outer circumferential ends of the stopper portion 82S, and a cylindrical second body portion 82C with a smaller diameter than the first body portion 82A is formed below the first body portion 82A. The lower end of the first body portion 82A and the upper end of the second body portion 82C are connected by a connecting portion 82B. A locking portion 82K is formed at the lower end of the second body portion 82C.

A locking device 84 serving as a locking mechanism is incorporated into the inner periphery of the first body portion 82A inside the upper inside of the bushing 82. In this embodiment, the locking device 84 is, for example, integrally molded with the bushing 82 during injection molding of the bushing 82. The locking device 84 includes a tubular member 86 made of steel. The leg portion 62A of the headrest stay 62 is inserted into the tubular member 86. A restricting protrusion 86A serving as a restricting portion that protrudes radially inward around the entire circumference is formed at the upper end of the tubular member 86, for example.

A steel fastening member 88 is housed within the tubular member 86. Figure 14 shows a plan view of the fastening member 88 alone. As shown in Figures 13 and 14, the fastening member 88 is C-shaped in plan view and follows the outer periphery of the leg portion 62A of the headrest stay 62, and uses its restoring force to fasten the leg portion 62A from the outer periphery.

As a supplemental explanation, the inner diameter of the fastening member 88 shown in Figure 14 before assembly is set to be smaller than the outer diameter of the leg portion 62A of the headrest stay 62 shown in Figure 13. When the leg portion 62A of the headrest stay 62 is inserted inside the fastening member 88, the fastening member 88 deforms within its elastic range and fastens the leg portion 62A of the headrest stay 62.

As shown in Figure 13, multiple fastening members 88 are provided, aligned in the axial direction of the leg portion 62A. A stopper 89 serving as a restricting portion is located adjacent to the lower side of the lowest fastening member 88. The stopper 89 is fixed to the fastening member 88 and, together with the restricting protrusion 86A described above, restricts the up and down movement of the fastening member 88. The locking device 84, which includes the tubular member 86, fastening members 88, and stopper 89, is configured to allow the leg portion 62A to move up and down while maintaining the shape of the fastening member 88.

In the present embodiment described above, the clamping member 88 clamps the leg portion 62A from the outer periphery with its restoring force, while its vertical movement is restricted by the restricting protrusion 86A and stopper 89. This generates a frictional force between the leg portion 62A and the clamping member 88, holding the leg portion 62A in place. Furthermore, when a force is applied to move the leg portion 62A of the headrest stay 62 up or down to adjust the height of the headrest 20 (see FIG. 1), the locking device 84 restricts the vertical movement of the clamping member 88 with the restricting protrusion 86A and stopper 89, while allowing the leg portion 62A to move up or down while maintaining the shape of the clamping member 88. Therefore, with a simple configuration, it is possible to continuously adjust the height of the headrest 20 (see FIG. 1) in the seat vertical direction.

Furthermore, according to this embodiment, multiple fastening members 88 are provided so as to be aligned in the axial direction of the leg portion 62A of the headrest stay 62. Here, by changing the number of fastening members 88, it is possible to change the friction load between the leg portion 62A of the headrest stay 62 and the locking device 84 side, making it possible to easily adjust the operating force required for vertical movement of the headrest stay 62.

[Modification of the Sixth Embodiment]
Next, a modified example of the sixth embodiment will be described with reference to Fig. 15. Note that the modified example of the sixth embodiment is not an embodiment of the present invention but a reference example. Fig. 15 shows a vertical cross-sectional view of a headrest support structure 80A according to a modified example of the sixth embodiment. The headrest support structure 80A according to the modified example shown in Fig. 15 has the same configuration as the sixth embodiment, except for the points described below.

As shown in FIG. 15, the headrest support structure 80A includes a bushing 83 in place of the bushing 82 (see FIG. 13) of the sixth embodiment. The bushing 83 has the same configuration as the bushing 82 of the sixth embodiment, except that a stopper portion 83S is provided instead of the stopper portion 82S (see FIG. 13) of the bushing 82 of the sixth embodiment. Therefore, for convenience, the same components of the bushing 83 as those of the bushing 82 of the sixth embodiment are denoted by the same reference numerals and will not be described again. The stopper portion 83S is formed in a thick, annular shape, and its outer and inner diameters are the same as those of the stopper portion 82S (see FIG. 13) of the sixth embodiment, but no component equivalent to the locking member 66 (see FIG. 13) of the sixth embodiment is provided. The connection position of the first body portion 82A to the stopper portion 83S is the same as the connection position of the first body portion 82A to the stopper portion 82S in the sixth embodiment (see Figure 13 for both).

In addition, in the configuration of the sixth embodiment described above, as shown in FIG. 13, a notch 62A1 is formed on the lower end side of the leg portion 62A of the headrest stay 62 to prevent the leg portion 62A from coming off during a collision (impact). However, in a modified version of the sixth embodiment, a stopper 63X shown in FIG. 15 is provided in place of the notch 62A1. The stopper 63X can be joined to the lower end side of the leg portion 63A by bolting, welding, or the like, for example, after the headrest stay 63 is assembled. The stopper 63X includes a large-diameter portion 63X1 having a diameter larger than the general portion 63A1 of the leg portion 63A, and an inclined step portion 63X2 whose diameter gradually decreases from the upper end of the large-diameter portion 63X1 to the same diameter as the general portion 63A1 of the leg portion 63A. In this modification of the sixth embodiment, if the headrest stay 63 is raised by more than a predetermined amount during a collision or other event, the stopper 63X hits the bottom of the bush 82, stopping the leg 63A from rising, thereby preventing the leg 63A of the headrest stay 63 from coming loose.

Seventh Embodiment
Next , a headrest support structure according to a seventh embodiment will be described with reference to Figures 16 and 17. Note that the seventh embodiment is not an embodiment of the present invention but a reference example. Figure 16 shows a vertical cross-sectional view of a headrest support structure 90 according to the seventh embodiment, and Figure 17 shows an exploded cross-sectional view of a portion of the headrest support structure 90.

As shown in FIG. 16, the headrest support structure 90 according to the seventh embodiment has a configuration in which the locking device 30 in the headrest support structure 60 according to the fourth embodiment shown in FIG. 9 is replaced with the locking device 84 in the headrest support structure 80 according to the sixth embodiment shown in FIG. 13. Therefore, in the seventh embodiment, components that are substantially similar to those in the fourth embodiment and those in the sixth embodiment are given the same reference numerals and descriptions thereof are omitted. Note that in the seventh embodiment, the locking device 84 is the same size and is located in the same position as the locking device 30 in the fourth embodiment shown in FIG. 9.

Now, we will explain how to assemble the headrest support structure 90 shown in Figure 16. First, the locking device 84 is inserted from below into the upper bushing 64 shown in Figure 17 (see arrow S3). Next, the lower bushing 70 is brought closer to the upper bushing 64 and locking device 84 from below (see arrow S4) so that the engagement claw 72A of the lower bushing 70 engages with the engagement recess 68 of the upper bushing 64. Finally, as shown in Figure 16, the leg 62A of the headrest stay 62 is inserted from above so that it passes through the axial centers of the upper bushing 64, locking device 84, and lower bushing 70, thereby obtaining the headrest support structure 60 shown in Figure 16.

The configuration of the seventh embodiment described above provides the same functions and effects as the sixth embodiment, and also allows the locking device 84, upper bushing 64, and lower bushing 70 to be easily disassembled.

Eighth Embodiment
Although not shown , an eighth embodiment may employ a configuration in which the locking device 84 of the sixth embodiment shown in Fig. 13 is directly joined to the upper frame 14A (see Fig. 12) instead of the locking device 30 of the fifth embodiment shown in Fig. 12. Note that the eighth embodiment is not an embodiment of the present invention but a reference example.

Ninth Embodiment
Next , a headrest support structure according to a ninth embodiment will be described with reference to Figures 18 to 20D. Note that the ninth embodiment is not an embodiment of the present invention but a reference example. In the ninth embodiment, components that are substantially the same as those in the first embodiment are designated by the same reference numerals and descriptions thereof will be omitted.

Figure 18 shows a simplified view of the upper part of a vehicle seat 98 equipped with a headrest support structure 100 according to the ninth embodiment, viewed from diagonally above the front. Of the pair of legs 22A of the headrest stay 22 shown in Figure 18, one leg 22A (22AL) can be locked and unlocked, while the other leg 22A (22AR) can move freely up and down. Hereinafter, for convenience, one leg 22A (22AL) will be simply abbreviated as leg 22AL, and the other leg 22A (22AR) will be simply abbreviated as leg 22AR.

A cylindrical metal holder 102 is fixed by welding to the front portion of the seat widthwise extending portion 14A1 of the upper frame 14A, corresponding to the non-lockable leg 22AR. A cylindrical resin bushing 104 is inserted into the holder 102. The leg 22AR is then inserted into the bushing 104.

Meanwhile, a cylindrical metal holder 106, whose upper end is positioned lower than the holder 102, is fixed by welding to the front portion of the seat widthwise extending portion 14A1 of the upper frame 14A, corresponding to the lockable leg portion 22AL. A cylindrical resin bushing 108 is inserted into the holder 106. A locking device 110 serving as a locking mechanism is provided above the holder 106 and bushing 108. Note that components of the locking device 110 have been omitted from Figure 18 where appropriate.

The locking device 110 is equipped with an operating lever 112 as an operating member through which the leg 22AL passes and which is rotatable around the axis of the leg 22AL. The locking device 110 is configured to unlock the leg 22AL when the operating lever 112 is rotated in one direction (see arrow R1), and to lock the leg 22AL when the operating lever 112 is rotated in the other direction (see arrow R2).

Next, the specific configuration of the locking device 110 will be described with reference to Figures 19A to 19E.

Figure 19A shows a schematic horizontal cross-sectional view of the locking device 110 locking the leg 22AL. Note that the leg 22AL is actually formed in a hollow cylindrical shape, but for ease of viewing, in Figure 19A it is hatched to represent a solid cylindrical body (the same applies to Figures 19B to 19E).

As shown in FIG. 19A, the locking device 110 includes a spring member 114 as a tightening member, having a portion 114B that is annular in plan view along the outer periphery of the leg portion 22AL. The spring member 114 is wound around the outer periphery of the leg portion 22AL, with one end serving as a fixed end 114A that is engaged and fixed to the engaging portion 112B of the operating lever 112, and the other end serving as a free end 114C, which urges the leg portion 22AL into a locked state by tightening it from the outer periphery with its restoring force. Note that the engaging portion 112B is, as an example, a portion formed integrally with the operating lever 112, and rotates integrally with the operating lever 112 when the operating lever 112 rotates.

The locking device 110 also includes a switching mechanism 116, which has a release block (also known as a "piece") 117 and a cam member 118.

The release block 117 is positioned near the free end 114C of the spring member 114 and is rotatably supported on a shaft 112C that is parallel to the leg portion 22AL. As an example, the shaft 112C is formed integrally with the operating lever 112. A predetermined amount of frictional resistance exists between the release block 117 and the shaft 112C, preventing the release block 117 from rotating inadvertently. The release block 117 has a longitudinal shape in plan view, with the shaft 112C passing through its central region. Furthermore, the lower portion of the release block 117 facing the free end 114C of the spring member 114 in the state shown in Figure 19A, and the portion diagonally opposite it (upper right in the figure) are arc-shaped.

The cam member 118 is fixed to the bushing 108 via a plate 119 shown in FIG. 18. As a result, the cam member 118 shown in FIG. 19A is configured not to rotate even when the operating lever 112 is rotated. The cam member 118 comprises a disk portion 118A that is circular in plan view, and an unlocking cam portion 118B and a re-locking cam portion 118C that protrude from the outer periphery of the disk portion 118A in plan view. The unlocking cam portion 118B is formed in a roughly fan shape and is a component that deforms the spring member 114 via the release block 117 to release the lock. The re-locking cam portion 118C is also formed in a roughly fan shape and is a component that executes re-locking by the spring member 114 via the release block 117. The outer peripheral arc portion 118B1 of the unlocking cam portion 118B in a plan view and the outer peripheral arc portion 118C1 of the re-locking cam portion 118C in a plan view are positioned closer to the axis of the leg portion 22AL than the shaft 112C.

Here, we will explain how to unlock and re-lock using the locking device 110.

Figure 19B shows a schematic horizontal cross-sectional view of the state in which the operating lever 112 has been operated in the unlocking direction (one direction (see arrow R1)) from the state shown in Figure 19A. In this state, the release block 117 is in contact with the side wall surface 118B2 of the unlocking cam portion 118B and is about to rotate clockwise in the figure. When the operating lever 112 is further operated in the unlocking direction from the state shown in Figure 19B, the release block 117 rotates approximately 90° as shown in Figure 19C, pushing the free end 114C of the spring member 114, causing the spring member 114 to expand slightly in diameter, thereby achieving an unlocked state. At this point, the occupant can move the headrest stay 22 up and down.

19C), the state shown in FIG. 19D is reached. In this state, the release block 117 maintains its longitudinal direction aligned with the circumferential direction of the leg 22AL, maintaining the unlocked state. From the state shown in FIG. 19D, the state shown in FIG. 19E is reached. In this state, the release block 117 contacts the side wall surface 118C2 of the re-lock cam portion 118C and attempts to rotate counterclockwise in the figure. From the state shown in FIG. 19E, the state shown in FIG. 19A is reached. In this state, the release block 117 no longer presses against the free end 114C of the spring member 114, so the spring member 114 tightens the leg 22AL from the outer periphery, restoring the lock state. Incidentally, even if a load of 500 N is applied in this state in the height retention test required by headrest regulations, the frictional force of the spring member 114 prevents the headrest 20 from moving up or down.

As described above, the switching mechanism 116 presses the free end 114C of the spring member 114 as shown in FIG. 19C in response to the rotation of the operating lever 112 in one direction (see arrow R1), thereby expanding the diameter of the spring member 114 and releasing the locked state, and releases the pressure on the free end 114C of the spring member 114 as shown in FIG. 19A in response to the rotation of the operating lever 112 in the other direction (see arrow R2), thereby causing the spring member 114 to elastically return to the locked state. The locking device 110 is configured to allow the leg portion 22AL of the headrest stay 22 to move up and down by changing the shape of the spring member 114.

Next, an example of assembling the locking device 110 will be outlined using Figures 20A to 20D. As shown in Figure 20A, the seat width direction extending portion 14A1 of the upper frame 14A has a crushed portion 14X for attaching the holder 106 (see Figure 20B).

First, the holder 106 shown in FIG. 20B is welded to the crushed portion 14X of the upper frame 14A shown in FIG. 20A. Next, as shown in FIG. 20C, the bushing 108 is inserted into the holder 106, causing the multiple engagement claws 108A of the bushing 108 to protrude upward from the holder 106. Next, as shown in FIG. 20D, a predetermined portion (an engaged portion with a hole) of the lower plate 119 of the locking device 110 is engaged with the engagement claws 108A provided on the upper part of the bushing 108. Note that for clarity, the internal components of the locking device 110 are not shown in FIG. 20D. The plate 119 has a hole 119H formed therein through which the leg 22AL (see FIG. 18) of the headrest stay 22 is inserted. After the step shown in Figure 20D, the back pad (not shown), the trim cover 18 shown in Figure 18, and the operating lever 112 are installed, completing the assembly of the locking device 110.

The ninth embodiment described above also allows for easy and continuous adjustment of the height of the headrest 20 in the up-down direction of the seat.

[Supplementary explanation of the embodiment]
1 to 10, multiple sets of the circumferentially aligned balls 34, 46, 56 are provided aligned in the axial direction of the leg portions 22A, 52A of the headrest stays 22, 52, but a configuration in which only one set of circumferentially aligned balls is provided may also be employed. Also, in the sixth and seventh embodiments shown in Figures 13 to 17, multiple fastening members 88 are provided aligned in the axial direction of the leg portions 62A of the headrest stays 62, but a configuration in which only one fastening member is provided may also be employed.

The above embodiment and the various modifications described above can be implemented in appropriate combinations.

The above describes one example of the present invention, but the present invention is not limited to the above, and it goes without saying that various modifications and variations are possible within the scope of the present invention.

REFERENCE SIGNS LIST 11 Headrest support structure 20A Headrest main body 22 Headrest stay 22A Leg 32 Cylindrical member 32B Tapered portion 32N Inner peripheral surface of cylindrical member 32X Recess 32Z Lower end portion of cylindrical member 34 Ball 40 Headrest support structure 42 First bush (cylindrical member)
42B Tapered portion 42N Inner peripheral surface of first bush (inner peripheral surface of cylindrical member)
42X: Recess 46: Ball 48: Ring member 50: Headrest support structure 52: Headrest stay 52A: Leg 52G: Outer circumferential surface of leg 52T: Tapered portion 52X: Recess 54: First bush (cylindrical member)
56 Ball 58 Ring member 60 Headrest support portion structure 62 Headrest stay 62A Leg portion 63 Headrest stay 63A Leg portion 64 Upper bush 70 Lower bush 74 Headrest stay 74A Leg portion 76 Headrest support portion structure 80 Headrest support portion structure 80A Headrest support portion structure 84 Locking device (locking mechanism)
86 Cylindrical member 86A Restricting protrusion (restricting portion)
88 Fastening member 89 Stopper (regulating portion)
90 Headrest support structure 100 Headrest support structure 110 Locking device (locking mechanism)
112 operating lever (operating member)
114 Spring member (fastening member)
114A Fixed end 114B Annular portion in plan view 114C Free end 116 Switching mechanism

Claims (4)

a headrest stay including a leg portion extending downward from inside the headrest body;
a cylindrical member formed in a cylindrical shape and through which the leg portion is inserted;
a recess formed in an annular and concave shape along a circumferential direction on one of an inner circumferential surface of the cylindrical member and an outer circumferential surface of the leg portion;
a pair of upper and lower tapered portions inclined so as to gradually narrow the gap between the upper and lower opposing portions from the opening end side of the recessed portion toward the recessed bottom side;
a plurality of balls arranged in the recess and aligned in the circumferential direction of one of the balls, which are in contact with both the cylindrical member and the leg portion and hold the leg portion by frictional force, and when the leg portion is moved up and down, when one of the balls moves upward relative to the other of the inner peripheral surface of the cylindrical member and the outer peripheral surface of the leg portion, the balls are rotatable while their downward relative displacement with respect to the one of the balls is restricted by the lower tapered portion of the pair of upper and lower tapered portions, and when one of the balls moves downward relative to the other of the balls, the balls are rotatable while their upward relative displacement with respect to the one of the balls is restricted by the upper tapered portion of the pair of upper and lower tapered portions ;
A headrest support structure having the following features. The headrest support structure of claim 1, wherein the plurality of balls aligned in one circumferential direction are arranged in multiple sets aligned in the axial direction of the leg portion. 3. The headrest support structure according to claim 1, further comprising a ring member formed in an endless string shape that passes through the centers of the plurality of balls arranged in one circumferential direction, the ring member having elasticity and capable of elastically returning to the assembled shape when elastically deformed. an upper bushing into which the leg portion is inserted and which is provided on the outer circumferential side of the cylindrical member;
a lower bushing adjacent to the lower end of the tubular member on the lower side, through which the leg portion is inserted, and provided on the lower end side of the upper bushing in an engageable and disengageable manner;
The headrest support structure according to any one of claims 1 to 3 , comprising: