JP4726751B2 - Telescopic device with locking function - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a telescopic device with a locking function, and more particularly to a telescopic device with a locking function that is interposed between two members that perform a separating operation, expands along with the separating operation, and locks in the contracted direction in the expanded state. is there.

  For example, in an automobile seat, a headrest that receives the head of the occupant from the rear is provided above the seat back in order to reduce the occupant's whip hitting obstacle when the automobile collides. However, with a fixed headrest, the seat back tilts backward and the occupant's body rises obliquely backward due to the acceleration of the entire seat and the inertia of the occupant due to the impact at the time of rear-end collision. However, it has been difficult to reliably reduce occupant's whiplash damage due to a large load acting on the neck due to the displacement of the headrest.

  Therefore, the headrest support frame equipped with the headrest is pivotally supported on the seatback frame so that it can pivot back and forth, and a pressure-receiving part that receives the load applied from the front of the seatback is provided below the pivotal part of the headrest support frame. The headrest support frame is rotated by the load applied to the pressure receiving part due to the relative movement backward due to the inertial force of the upper body of the occupant, the headrest is moved forward, and the occupant's head is received from the rear to prevent the whiplash damage. If the occupant's upper body moves forward after the first rear-end collision, the headrest immediately returns to the rear, and if there is a subsequent phenomenon such as recoil or multiple rear-end collision in that state, a whiplash injury In order to reduce this, the headrest support frame is rotated and locked by the locking means, and then returned. There has been proposed a device that can be easily operated to return to a normal use state by preventing movement and providing a release operation means for the locking means (for example, Patent Documents). 1).

  In addition, the load receiving frame and the seat back frame are connected by the upper and lower rotating links to form a parallel link mechanism, and the headrest push-up link on which the headrest is mounted and the upper rotating link are connected to each other, and the load receiving frame is connected. The headrest is slid diagonally forward and upward through the headrest push-up link in conjunction with the rotation of the upper rotation link accompanying the rearward movement of the upper, and only one-way rotation of the upper rotation link is allowed, and in the reverse direction A one-way lock mechanism such as a ratchet gear mechanism for preventing the rotation of the motor and a release means therefor have also been proposed. Further, as a shock absorbing means for urging the load receiving frame forward, there are disclosed one using a spring and a combination of an air damper and a spring that only gradually returns when the load is released (for example, (See Patent Document 2).

Further, in the foot-operated parking brake device, in order to prevent the pedal from suddenly returning to the initial position, an absorber is disposed so as to be contracted by depressing the pedal, and the absorber is connected to the cylinder portion and the piston portion. It has a structure in which the inner surface of the cylinder part is formed into a tapered surface whose diameter increases in the extension direction and a square ring is attached to the outer periphery of the piston part so that the resistance increases as the pedal is depressed deeper. (For example, refer to Patent Document 3).
JP 2000-118280 A Japanese Patent Laid-Open No. 10-6832 JP-A-8-326817

  However, in the configuration disclosed in Patent Document 1, when the headrest support frame rotates forward and the headrest is in a predetermined position, it is locked by the locking means, so that subsequent phenomena such as recoil after a rear-end collision and multiple rear-end collision occur. However, there is a problem that it is necessary to provide a release operation means for returning the headrest to the normal position, and the number of parts increases and the configuration becomes complicated, resulting in high costs. .

  In the configuration disclosed in Patent Document 2, the headrest push-up link on which the headrest is mounted is connected to the upper rotary link that rotates as the load receiving frame moves rearward, and the upper rotary link is unidirectional. A one-way lock mechanism that allows only rotation and prevents rotation in the reverse direction and its release means are provided, so that it can be locked at any position when the headrest moves forward and can effectively prevent whiplash damage and simple Although it can be returned to a normal position by operation, there is a problem that the cost is high because the number of parts is very large and the configuration is complicated.

  Therefore, an expansion / contraction device corresponding to the shock absorber disclosed in Patent Document 3 is extended between the headrest support frame and the seat back frame disclosed in Patent Document 1 when the headrest support frame is rotated forward, and contracted. However, in the telescopic device having a configuration similar to the shock absorber disclosed in Patent Document 3, the locking force against a sudden contraction operation is small and the timing of the locking action is considered. It has been found that there is a problem that the effect is not sufficiently exhibited because of the slowness of the time.

  In view of the above-described conventional problems, the present invention is capable of smoothly performing an extension operation and exhibiting a large locking force against an abrupt contraction operation in an extended state and easily contracting to an original position. It aims at providing a telescopic device with a function.

The telescopic device with a locking function of the present invention is a telescopic device with a locking function that locks in the contracted direction in an extended state, and has a stepped inner surface whose inner diameter increases stepwise in the extending direction. And a piston portion provided on the outer periphery with a stopper portion that follows and contacts the stepped inner surface of the cylinder portion, and the stopper portion reciprocates on the stepped inner surface during the expansion and contraction operation .

  According to this configuration, the piston part moves in the cylinder part with less resistance in the extending direction and operates smoothly. However, if the piston part is rapidly contracted, the stopper part on the outer periphery of the piston part is stepped on the stepped inner surface of the cylinder part. By engaging with the part, the resistance to the contraction operation becomes very large, a large locking force is exerted against the contraction operation, and when the piston part is pushed slowly with a required load, the stopper part is stepped. By overcoming the step on the inner surface relatively easily, it can be easily contracted to the original position.

  In addition, if a return mechanism is provided in the vicinity of the extension limit so that the stopper part is not in contact with the stepped inner surface, the return mechanism operates by moving the piston part to the vicinity of the extension limit, and the stopper part does not work. Therefore, it can be easily returned to the original position and the operability is improved.

  According to the telescopic device with a locking function of the present invention, the piston portion moves in the cylinder portion with less resistance in the extending direction and operates smoothly. However, if the piston portion is rapidly contracted, the stopper portion on the outer periphery of the piston portion is Engaging with the stepped inner surface of the part makes the resistance to the contraction operation very large, exerts a large locking force against the contraction operation, and slowly pushes the piston part with the required load. Then, the stopper portion can easily contract to the original position by overcoming the step portion of the stepped inner surface relatively easily.

  Hereinafter, each embodiment of the telescopic device with a locking function of the present invention will be described with reference to FIGS.

(First embodiment)
First, an automotive seat to which the extension device with a locking function according to the first embodiment of the present invention is applied will be described with reference to FIGS.

  In FIG. 1, reference numeral 1 denotes a seat back of a vehicle seat, which is attached to a seat cushion (not shown) so as to be reclining. Reference numeral 2 denotes a seat back frame having a substantially inverted U-shape as a whole front surface constituting a skeletal structure surrounding the left and right sides and the upper side of the seat back 1. The seat back frame 2 is configured by integrating an upper pipe 3 obtained by bending a pipe material into a substantially inverted U shape and a lower frame plate 4 made of sheet metal on both lower sides. The pivot brackets 5 each having a substantially U-shape in plan view are fitted and arranged on both sides at an appropriate distance below the upper end of the upper pipe 3, and the tips thereof are fixed to the upper pipe 3 by welding. . Both pivot brackets 5 are formed with shaft holes (not shown) facing each other, and a nut (not shown) fixed to the back surface thereof, and the screw portion at the tip of the pivot shaft 6 is used as a nut. It is configured to be fastened and planted. A stopper piece 7 is erected on both pivot support brackets 5.

  Reference numeral 8 denotes a headrest disposed on the upper portion of the seat back 1, and a pair of stays 9 extend downward from both sides of the lower portion. Reference numeral 10 denotes a headrest support frame that supports the headrest 8, and is constituted by a pipe frame 11 bent in a substantially inverted U shape. The pipe frame 11 has a width that fits between the pivot brackets 5 and 5 and is disposed so that its upper side is located in the vicinity of the lower portion of the upper pipe 3. The pivot shaft 6 is pivotally supported so as to be pivotable forward and backward.

  A support cylinder portion 12 is fixed to the upper side of the pipe frame 11 so that the stay 9 can be inserted / removed and fixed at an arbitrary position, and the headrest 8 can be supported to be adjustable in height. A pressure receiving member 13 is installed between the lower ends of the pipe frame 11. The pressure receiving member 13 is composed of a horizontally long plate material formed into a shape having irregularities extending in the width direction at the upper and lower portions so as to have rigidity capable of receiving a load applied from the front side of the seat back 1. .

  A tension spring 14 is interposed between the lower ends of both sides of the pressure receiving member 13 at the lower part of the headrest support frame 10 and the front edge of the lower frame plate 4 of the seat back frame 2, and a load exceeding a certain level does not act on the pressure receiving member 13. The pressure receiving member 13 is configured not to rotate backward. Further, in a state where the pressure receiving member 13 is urged forward by the tension spring 14, the support cylinder portion 12 is engaged with the front end of the upper side of the upper pipe 3 of the seat back frame 2, whereby the headrest support frame 10 is in a normal state. The rotational position is restricted. Further, the rotation limit position of the headrest support frame 10 when the pressure receiving member 13 is rotated rearward is restricted by the pipe frame 11 being engaged with the stopper piece 7.

  An expansion / contraction device 15 with a locking function is interposed between the seat back frame 2 and the headrest support frame 10 so that the pressure receiving member 13 extends when the headrest support frame 10 rotates when receiving a load from the front. It is disguised. Specifically, the receiving groove 16a at the tip of the mounting bracket 16 projecting inward from the rear edge of the lower frame plate 4 of the seat back frame 2, and the mounting bracket projecting downward from the lower edges of both side portions of the pressure receiving member 13 The engagement grooves 15 a and 15 b formed at both ends of the locking device 15 with the locking function are fitted into the receiving groove 17 a at the tip of the 17 to be coupled and fixed. A pair of elastic support members 18 (specifically, formed by forming a wire rod made of spring steel into a wave shape) 18 are vertically spaced apart from each other at the lower part of the seat back frame 2. Both ends thereof are locked to locking pieces 19 formed by cutting and raising the lower frame plate 4.

  As shown in FIG. 2, the telescopic device 15 with a locking function is composed of a cylinder part 20 and a piston part 21. The cylinder portion 20 is configured by a cylindrical body whose one end is closed and the other end is opened, and an attachment boss 22 is projected from one end, and an engagement groove 15 a is formed between the attachment boss 22 and the cylinder portion 20. ing. An orifice 24 is formed in an axial core portion at one end of the cylinder portion 20 to communicate the internal cylinder space 23 with the external space. A stepped inner surface 25 whose inner diameter increases stepwise toward the extending direction of the telescopic device 15 with a locking function, that is, toward the other end side, is formed in the central portion of the inner peripheral surface of the cylinder portion 20 in the axial direction. Yes. Specifically, for the stepped inner surface 25, for example, it is appropriate that the width of the step portion is several mm, the number of steps is 3 to 8, and the step is about 0.1 to 0.2 mm. Further, both sides of the stepped inner surface 25 are formed with tapered surfaces 26a and 26b whose diameters are increased in the extending direction of the telescopic device 15 with a locking function. Instead of the tapered surfaces 26a and 26b, a straight cylindrical surface may be formed.

  The piston portion 21 includes a piston main body portion 27 at one end having a stopper portion 30 on the outer periphery that slides in contact with the inner peripheral surface of the cylinder portion 20, and a cross-section extending from the piston main body portion 27 toward the other end. The shaft portion 28 is provided with a mounting boss portion 29 provided at the other end. The shaft portion 28 is in a state where the piston main body portion 27 is located at the far end portion of the cylinder space 23 and the mounting boss portion 29 is provided. The length is set to protrude from the other end of the cylinder portion 20, and an engagement groove 15 b is formed in the intermediate portion of the outer peripheral surface of the mounting boss portion 29.

  The stopper portion 30 is configured by mounting an elastic ring 33 such as a C ring 32 and an O ring in an annular groove 31 formed on the outer peripheral surface of the piston main body portion 27. The C-ring 32 has a substantially rectangular cross-sectional shape, and an inclined surface 32a is formed on the other end side with the outer peripheral side facing the other end. The elastic ring 33 is disposed so as to contact the inclined surface 32a. The diameter of the arrangement part of the elastic ring 33 is formed slightly smaller. Thereby, the C-ring 32 is displaced to the other end side in the annular groove 31 by sliding resistance during the contracting operation of the expansion / contraction device 15 with the locking function in which the piston main body portion 27 slides toward one end of the cylinder portion 20. Thus, the inclined surface 32 a is pushed by the elastic ring 33 and the C ring 32 is urged to expand its diameter, so that the C ring 32 is pressed against the inner peripheral surface of the cylinder portion 20.

  According to the above configuration, in the normal state before the rear-end collision, as shown in FIG. 1, the pressure receiving member 13 at the lower part of the headrest support frame 10 is biased forward by the tension spring 14. The upper support cylinder 12 is engaged with the upper end of the seat back frame 2 and is stationary.

  Next, when the automobile is collided, the seat is pushed impactively forward, and the upper body of the occupant moves rearward due to the reaction, and a large load acts rearward on the front surface of the seat back 1. Then, the pressure receiving member 13 is strongly pressed rearward, and the lower part of the headrest support frame 10 rotates rearward around the pivot shaft 6 against the urging force of the tension spring 14, and the upper part of the headrest support frame 10 is The support cylinder part 12 rotates forward, and the headrest 8 moves forward. Thus, the head of the occupant can be reliably received by the headrest 8, and the neck of the occupant can be protected to effectively reduce the whiplash injury.

  Further, as the pressure receiving member 13 moves rearward, the telescopic device 15 with a locking function extends. At this time, the stepped inner surface 25 of the cylinder portion 20 of the expansion device 15 with the locking function and the tapered surfaces 26a, 26b on both sides thereof are formed so that the diameter increases in the extending direction of the expansion device 15 with the locking function. Therefore, the piston portion 21 is smoothly extended only by the small sliding resistance and the air resistance when the air passes through the orifice 24 formed at one end of the cylinder portion 20. The head of the occupant can be reliably received by the headrest 8 without the movement amount of the movement being reduced or the movement timing being delayed.

  Thereafter, when a backward load no longer acts on the pressure receiving member 13, the pressure receiving member 13 moves forward by the urging force of the tension spring 14, and in conjunction with this, the telescopic device 15 with a locking function contracts. However, when the telescopic device 15 with the locking function is contracted, the C ring 32 in the stopper portion 30 of the piston portion 21 is strongly pressed against the stepped inner surface 25 of the cylinder portion 20 as described above, so that the C ring 32. Engages with the step portion of the stepped inner surface 25, and as a result, a large lock load is generated against a sudden contraction operation, and the forward movement of the pressure receiving member 13 and the accompanying rearward movement of the headrest 8 are prevented by the large load. . Thus, when the headrest 8 is moved forward, the headrest support frame 10 is locked by the telescopic device 15 with the locking function, and the head of the occupant can be reliably received by the headrest 8.

  After that, when the impact load is continuously applied to the headrest 8, or after that, the impact load is applied again, and a load greater than the braking force due to the engagement between the first step portion of the stepped inner surface 25 and the C ring 32 is applied. The C-ring 32 gets over the stepped portion, and immediately after the stepping over, the braking load once becomes extremely small, but the C-ring 32 immediately engages with the next stepped portion of the stepped inner surface 25, which is large against a sudden contraction operation. A lock load will be generated, and thereafter, a large lock load will act on each step portion in turn and be locked. Thus, as shown in FIG. 3, each time the C-ring 32 is engaged with each step of the stepped inner surface 25, the forward movement is locked with a relatively large lock load (400 to 800 N in the example of FIG. 3). In the meantime, the impact energy acting on the headrest 8 is absorbed, and the lashing injury of the occupant can be effectively reduced.

  In the case of the conventional lock mechanism described in Patent Document 1, as shown by a one-dot chain line in FIG. 3, only once with a large lock load (900 N or more in the example of FIG. 3) at a predetermined stroke position. Will be locked. In this conventional lock mechanism, when the pressure receiving member moves to a predetermined position on the rear side, the headrest is firmly locked, so that a large head receiving effect is exhibited at the time of rear-end collision and subsequent subsequent phenomenon. The effect is not exhibited at the time of impact impact that does not move to the predetermined position. On the other hand, in the present embodiment, when the pressure receiving member moves rearward according to the degree of impact at the time of the rear-end collision, the lock acts in the vicinity of the position, so that the head receiving effect can be obtained during the subsequent subsequent phenomenon. This can effectively reduce occupant whiplash in any rear-end collision. Further, when the one disclosed in Patent Document 3 is applied as the expansion / contraction device 15 with a locking function, and the inner peripheral surface of the cylinder portion 20 is configured with a tapered inner surface 36 as shown in FIG. As shown in FIG. 4 (b), the braking force gradually increases with the contraction operation of the expansion / contraction device 15 with the locking function, and the lock state is merely entered immediately before the contraction operation ends. In addition, since the lock load is small (in the example of FIG. 4, about 140 N at the maximum), the effect of reducing the lashing injury of the occupant is hardly obtained, and the case where the stepped inner surface 25 is provided as in the present embodiment. There are significant differences in effectiveness.

  As described above, after receiving the head of the occupant during the rear-end collision, the headrest 8 does not move greatly or return after that. When the vehicle moves backward, when it receives multiple impacts due to multiple rear-end collisions, or when it collides with a previous obstacle due to rear-end collision and overlaps with the reaction after the rear-end collision, Even in the case of overlapping, the head can be received by the headrest 8 locked at the front position before the head of the occupant largely moves rearward, and the whiplash injury can be prevented.

  Thereafter, in order to return the headrest 8 to the normal state, the step of the stepped inner surface 25 of the cylinder portion 20 has a small height by pushing the headrest 8 slowly backward with a predetermined load or more. Since the C-ring 32 is not strongly pressed against the stepped inner surface 25 by the compression reaction force of the elastic ring 33, the C-ring 32 of the piston portion 21 can easily get over the stepped portion, and the telescopic device with a locking function. 15 can be easily contracted, and the headrest 8 can be returned to the original state. Thus, it is not necessary to provide locking means and locking release means having complicated configurations, the number of parts does not increase, and the normal use state can be restored with an inexpensive configuration and simple operation.

(Second Embodiment)
Next, 2nd Embodiment of the expansion-contraction apparatus with a locking function of this invention is described with reference to FIGS. In the following description of the embodiment, the same components as those in the preceding embodiment are denoted by the same reference numerals, description thereof is omitted, and differences are mainly described.

  In the first embodiment, when the piston portion 21 is returned to the initial contracted position, the C ring 32 of the stopper portion 30 engages with the step portion of the stepped inner surface 25 of the cylinder portion 20, so that it is overcome. There is a problem that it is necessary to load a certain amount of load and the operability at the time of return is not so good. Therefore, in the present embodiment, as shown in FIG. 5, an end cylindrical body 41 having a reverse tapered inner surface 42 whose diameter increases toward the one end side of the cylinder portion 20 at the extended end portion of the cylinder portion 20 is screwed. 43, the stopper portion 30 on the outer periphery of the piston main body 27 in the piston portion 21 is formed in a tapered annular groove 44 formed with a tapered surface whose diameter decreases toward the one end side. Similarly, a wedge-shaped C-ring 45 having a wedge-shaped cross section formed on a tapered surface whose diameter decreases toward the one end side is provided. The width of the tapered annular groove 44 is larger than the width of the wedge-shaped C-ring 45, and the wedge-shaped C-ring 45 is positioned on one side surface of the tapered annular groove 44, and the outer periphery of the wedge-shaped C-ring 45 is The inner peripheral surface is configured to be loosely fitted to one end portion having the smallest diameter.

  According to this configuration, when the telescopic device 15 with the locking function slowly expands and contracts by slowly moving the headrest 8 back and forth on a daily basis, and when the rear-end collision occurs, the pressure receiving member 13 is impacted and pushed backward. Accordingly, when the telescopic device 15 with a locking function rapidly extends, the wedge-shaped C-ring 45 is connected to one end of the tapered annular groove 44 in the stopper portion 30 as shown in FIGS. 6 (a) and 6 (b). Since the state located on the side surface is maintained, the wedge-shaped C-ring 45 does not engage with the step portion of the stepped inner surface 25, and the piston portion 21 can freely move in and out of the cylinder portion 20. The expansion / contraction operation of the expansion / contraction device 15 with the locking function is smoothly performed without resistance.

  On the other hand, after the pressure receiving member 13 is impacted and pushed rearward during the rear-end collision, when the piston portion 21 moves forward together with the pressure receiving member 13, that is, toward one end of the cylinder portion 20 with a certain acceleration or more, FIG. As shown in (a) and (b), the wedge-shaped C-ring 45 moves relative to the other end side in the tapered annular groove 44, and as a result, the wedge-shaped C-ring 45 expands on the tapered inner peripheral surface of the tapered annular groove 44. Then, the wedge-shaped C-ring 45 is engaged with the step portion of the stepped inner surface 25, and the contraction operation of the expansion / contraction device 15 with the locking function is blocked and locked in that state. Thereby, a head can be received by the headrest 8 locked at the front position, and a whiplash injury can be prevented.

  Further, when the headrest 8 is returned to the original position after the rear-end collision is released, the headrest 8 is once moved forward slowly slowly against the urging force of the tension spring 14. As shown to (a), (b), if the expansion / contraction apparatus 15 with a locking function is extended to near the maximum extension state, the piston body part 27 of the piston part 21 moves to the end cylinder 41, and the stopper part 30 Is engaged with the reverse tapered inner surface 42, and the wedge-shaped C-ring 45 is engaged with the reverse tapered inner surface 42. When the piston portion 21 is pulled out as shown by the arrow a, the wedge-shaped C-ring 45 is moved as shown by the arrow b. As a result, the wedge-shaped C-ring 45 is reduced in diameter along the inner circumferential surface of the tapered annular groove 44, and the wedge-shaped C-ring 45 is stepped on the stepped inner surface 25. In charge It is set in a state that does not. Accordingly, the headrest 8 is then moved rearward by the urging force of the tension spring 14 and returned to the original position. Therefore, the headrest 8 can be reliably and easily returned to the original position by a simple operation without providing a complicated unlocking means.

(Third embodiment)
Next, 3rd Embodiment of the expansion-contraction apparatus with a locking function of this invention is described with reference to FIGS.

  In the telescopic device 15 with the locking function of the second embodiment, the stopper portion 30 on the outer periphery of the piston main body 27 has a configuration in which a wedge-shaped C-ring 45 is attached to the tapered annular groove 44 and is wedge-shaped during a sudden contraction operation. The C-ring 45 is moved to the other end side of the tapered annular groove 44 by the inertial force so as to expand the diameter and engage with the stepped inner surface 25. However, the wedge-shaped C-ring 45 of the tapered annular groove 44 is engaged only by the inertial force. Since it is necessary to expand the diameter by moving on the taper surface, there may be a case where it does not act reliably when necessary. Therefore, in the present embodiment, as shown in FIGS. 9A and 9B, the wedge-shaped C-ring 45 is formed to have a diameter that is in pressure contact with the stepped inner surface 25 in a natural state, and the diameter of the tapered annular groove 44 is increased. The engaging projection 51 is provided on the inner peripheral portion of one end surface of the wedge-shaped C-ring 45, and the engaging projection 51 is fitted and engaged with the side surface on one end side of the tapered annular groove 44. The engagement groove 52 is formed, and the engagement protrusion 51 is fitted and engaged with the engagement groove 52 so that the wedge-shaped C-ring 45 is held in a reduced diameter state. The outer peripheral surface of the engagement groove 52 is formed as a tapered surface having a diameter slightly larger toward the other end side so that the engagement protrusion 51 can be easily detached.

  According to the expansion / contraction device 15 with the locking function having the above-described configuration, the engagement protrusion 51 is formed in the engagement groove 52 at a position slightly before the contraction limit illustrated in FIG. Even in the engaged state, the wedge-shaped C-ring 45 is engaged with the step portion of the stepped inner surface 25, and as shown in FIG. Further, the engagement protrusion 51 comes out of the engagement groove 52, and the wedge-shaped C-ring 45 comes into contact with the stepped inner surface 25 by its own diameter-enlarging urging force. Thereafter, when the telescopic device 15 with a locking function is extended as indicated by the white arrow 54, the wedge-shaped C-ring 45 is pushed by the side surface on one end side of the tapered annular groove 44 and comes into contact with the stepped inner surface 25. The expansion operation of the expansion / contraction device 15 with the locking function is smoothly performed with almost no resistance.

  On the other hand, when the piston portion 21 tries to move toward one end side of the cylinder portion 20 as indicated by the white arrow 55 in the extended state of the telescopic device 15 with the locking function as shown in FIG. As shown in (a) and (b), the wedge-shaped C-ring 45 is securely engaged with the step portion of the stepped inner surface 25 in the vicinity of the extended position, and the contraction operation of the expansion / contraction device 15 with the locking function is prevented. It is locked in that state. At this time, the wedge-shaped C-ring 45 is pressed with a strong force against the stepped inner surface 25 by being pressed in the diameter-expanding direction by the tapered surface of the tapered annular groove 44, so that reliable locking is performed.

  Furthermore, when the locking state is released and the expansion / contraction device 15 with the locking function is contracted, the expansion / contraction device 15 with the locking function is in the maximum extended state as shown by an arrow 56 as shown in FIG. When extended to the vicinity, the piston main body 27 of the piston portion 21 moves to the end cylinder 41, the stopper portion 30 is fitted to the reverse tapered inner surface 42, and the outer peripheral edge of the other end of the wedge-shaped C ring 45 is the reverse tapered inner surface. 42, the wedge-shaped C-ring 45 is relatively moved toward one end side surface of the tapered annular groove 44 while being reduced in diameter as indicated by an arrow 57, and the engagement protrusion 51 is fitted into the engagement groove 52. As a result, the wedge-shaped C-ring 45 is reduced in diameter and is held in the unlocked state where it does not contact the stepped portion of the stepped inner surface 25. Thereafter, as shown in FIG. 11 (b), the expansion / contraction device 15 with the locking function can be smoothly contracted, and the state shown in FIGS. 9 (a) and 9 (b) is obtained at a position slightly before the contraction limit. Furthermore, the state of FIG. 9C is restored by performing the contraction operation to the contraction limit. The wedge-shaped C-ring 45 may be detached from the engagement groove 52 with a certain acceleration or more.

  In the description of the first to third embodiments, the example in which the expansion / contraction device 15 with the locking function is disposed between the lower portion of the pivot shaft 6 of the headrest support frame 10 and the seat back frame 2 is shown. However, the headrest support frame 10 may be disposed between the upper part of the pivot shaft 6 and the seat back frame 2. Moreover, in the said embodiment, since the orifice 24 is provided in the end of the expansion / contraction apparatus 15 with a locking function, the damper function of the expansion / contraction apparatus 15 with a locking function can be adjusted by adjusting the hole diameter.

(Fourth embodiment)
Next, an automobile hood apparatus having a pop-up function to which the expansion / contraction apparatus with a locking function according to the fourth embodiment of the present invention is applied will be described with reference to FIG.

  In the above embodiment, the example in which the expansion / contraction device with the locking function of the present invention is applied to the headrest support structure in the automobile seat has been shown. However, as shown in FIG. The extension device with a locking function of the present invention is applied to an actuator in a hood device. In FIG. 12 (a), 61 is a hood that covers the upper surface of the engine room 60 of the automobile. The actuator 63 extends as shown by the white arrow 64 at the time of a collision, and the piston rod 65 pushes up the rear end of the hood 61 and moves the hood 61 upward as shown by a solid line with the front end as a fulcrum. And the space between the hood 61 and the device 62 is formed, and when the obstacle 66 collides with the hood 61, the deformation allowance of the hood 61 as shown by the phantom line is secured. It is configured to absorb the impact received. Reference numeral 67 denotes a link mechanism that regulates the lifting amount of the hood 61 to be constant.

  In such a hood device, as shown in FIG. 12 (b), the actuator 63 includes a piston portion 71 that is accommodated in a cylinder portion 70 that is arranged with its axis center vertical, and that is movable up and down. A piston rod 65 is connected to the piston portion 71. An inflator 74 that ejects gas into the cylinder space 73 at the time of collision is disposed at the lower end of the cylinder portion 70, and is configured to push up the piston portion 71 at the time of collision. A stepped inner surface 75 whose diameter increases from the lower portion toward the upper portion is formed on the inner surface of the cylinder portion 70, and a stopper similar to the stopper portion 30 described in the above embodiments is provided on the outer periphery of the piston portion 71. A unit 80 (details omitted) is provided.

  In this embodiment, at the time of collision, gas is ejected from the inflator 74 into the cylinder part 70 of the actuator 63 to push up the piston part 71, and the hood 61 is shown by a solid line in FIG. 12A through the piston rod 65. Lifted up. After that, even if a downward load acts on the hood 61 due to the weight of the hood 61 or the collision load of the obstacle 66 and the hood 61 tries to descend, the stopper portion 80 of the piston portion 71 is engaged with the step portion of the stepped inner surface 75. By doing so, since the hood 61 is held in a lifted state, it is possible to secure the deformation allowance of the hood 61 and absorb the impact received by the obstacle 66 as described above.

  The expansion / contraction device with a locking function of the present invention operates smoothly in the extending direction, but when attempting to rapidly contract, the stopper portion on the outer periphery of the piston portion engages with the step portion on the stepped inner surface of the cylinder portion. A large locking force is exerted with respect to the contracting operation, and it can be easily contracted to the original position. It is useful for various stretching devices.

It is a perspective view which shows schematic structure of the principal part of the vehicle seat which applied the expansion-contraction apparatus with the latching function of the 1st Embodiment of this invention. The structure of the expansion / contraction apparatus with a locking function in the same embodiment is shown, (a) is a sectional view, (b) is an AA arrow view of (a), (c) is an arrow view of BB of (a). It is operation | movement explanatory drawing of a figure. It is a characteristic view which shows the stroke position and lock load at the time of contraction operation | movement of the expansion / contraction apparatus with the latching function of the embodiment. The expansion / contraction apparatus which has a taper inner surface of a comparative example is shown, (a) is sectional drawing, (b) is a characteristic view which shows the stroke position and lock load at the time of shrinkage | contraction operation | movement. It is sectional drawing which shows the structure of the expansion-contraction apparatus with the latching function of the 2nd Embodiment of this invention. The expansion | extension initial stage state in the expansion-contraction apparatus with the latching function of the embodiment is shown, (a) is sectional drawing, (b) is an expanded sectional view of the principal part. The expansion | extension state in the expansion-contraction apparatus with the latching function of the embodiment is shown, (a) is sectional drawing, (b) is an expanded sectional view of the principal part. The state which extended beyond the predetermined action | operation range in the expansion / contraction apparatus with the latching function of the embodiment is shown, (a) is sectional drawing, (b) is an expanded sectional view of the principal part. The structure of the expansion-contraction apparatus with the latching function of the 3rd Embodiment of this invention is shown, (a) is sectional drawing, (b) is an expanded sectional view of the principal part, (c) is the principal part of the state in a contraction limit. FIG. The state which extended in the expansion-contraction apparatus with the latching function of the embodiment is shown, (a) is sectional drawing, (b) is an expanded sectional view of the principal part. It is explanatory drawing of the return contraction operation | movement in the expansion / contraction apparatus with a locking function of the embodiment, (a) is sectional drawing of the state extended beyond the predetermined action range, (b) is a cross section of the state at the time of return contraction FIG. The hood apparatus for motor vehicles which applied the expansion-contraction apparatus with the latching function of the 4th Embodiment of this invention is shown, (a) is a longitudinal cross-sectional view which shows the whole schematic structure, (b) is sectional drawing of the actuator which is a principal part. It is.

Explanation of symbols

15 Telescopic device with locking function 20, 70 Cylinder part 21, 71 Biston part 25, 75 Stepped inner surface 30, 80 Stopper part 63 Actuator

Claims (2)

An expansion device with a locking function that locks in the contracted direction in an extended state,
A cylinder portion having a stepped inner surface whose inner diameter increases stepwise toward the extending direction;
A piston portion provided on the outer periphery with a stopper portion that follows and contacts the stepped inner surface of the cylinder portion ;
An expansion / contraction device with a locking function , wherein the stopper part reciprocates on the stepped inner surface during the expansion and contraction operation .   2. A telescopic device with a locking function according to claim 1, further comprising a return mechanism for bringing the stopper portion into a non-contact state with the stepped inner surface in the vicinity of the extension limit.