Patent Publication Number: US-2021162890-A1

Title: Seat rotation locking mechanism

Description:
BACKGROUND 
     Technical Field 
     The present invention relates to the technical field of seats, and in particular, to a seat rotation locking mechanism. 
     Related Art 
     Currently, for a rotating seat, there are mainly the following several locking mechanisms: 
     1. The locking mechanism implements locking by inserting a claw-shaped or tooth-shaped member in whole into a corresponding lockhole. There is a fit clearance between a contour of the claw-shaped member or the tooth-shaped member and a contour of the lockhole, which generates noise and shake in a driving process, and this type of technology is mainly represented in “COMMERCIAL VEHICLE SEAT WITH LOCKING PIECE” disclosed in Chinese Patent Authorized Publication No. CN103863151B, “ROTATING DISC FOR CAR SEAT” disclosed in Chinese Patent Application No. CN106427682A, the document disclosed in Korean Application No. KR100799874B1, and “NOVEL ROTATOR MECHANISM OF ROTATING SEAT” disclosed in Chinese Patent Application No. CN102529756A. 
     2. The locking mechanism implements locking by inserting a cylindrical pin into a hole between a fixed disc and a rotating disc from bottom to top. Similarly, there is also a fit clearance between a single hole and a shaft, which generates noise and shake in a driving process. This type of technology is mainly represented in “SEAT ROTATION MECHANISM” disclosed in Chinese Patent Application No. CN104670256A and “ROTATING CAR SEAT” disclosed in Chinese Patent Authorized Publication No. CN206520509U. 
     The locking mechanisms in the prior art both use fitting between metal members, which generates friction-induced noise. 
     In the prior art, when rotating adjustment is performed, a lever needs to be pulled all the time. If the lever is released halfway, a locking member and a rotating plane generate scraping noise. In addition, two cases may occur during the rotating adjustment: One case is that the adjustment is performed by lifting the lever when sitting on a seat. The other case is that the rotating adjustment is performed outside the car, and in this case, it is quite inconvenient to pull the lever all the time. 
     SUMMARY 
     A technical problem to be solved by the present invention is to provide a seat rotation locking mechanism in response to the deficiencies existing in the prior art, and the seat rotation locking mechanism eliminates a fit clearance existing after a rotation mechanism is locked, improves a grade of a product, and improves user experience. In an adjustment process, even if an operator releases an adjustment lever, a locking piece and a fixed disc do not generate scraping noise, and furthermore service life of the product is prolonged since wearing is eliminated. 
     The technical problem to be solved by the present invention may be implemented by the following technical solutions. 
     A seat rotation locking mechanism includes a locking mechanism mounted on a rotating disc in a seat rotation mechanism and at least one lockhole disposed on an outer circumference of a fixed disc in the seat rotation mechanism, where the locking mechanism includes: 
     a lock support fixed on the rotating disc; and 
     at least two lock pins horizontally and moveably configured in the lock support, where a first end of the lock pin is of a truncated-cone-shaped structure; and the first end of the lock pin is inserted into the lockhole, to implement zero-clearance locking by using wedging between the truncated-cone-shaped structure of the first end of the lock pin and the lockhole. 
     In an exemplary embodiment of the present invention, the seat rotation locking mechanism further includes a lock pin return spring sleeved on each lock pin, where when the lock pin return spring is in a locked state, the first end of the lock pin is inserted, under the action of the lock pin return spring, into the lockhole on the outer circumference of the fixed disc to lock the rotating disc. 
     In an exemplary embodiment of the present invention, the seat rotation locking mechanism further includes a release lever hinged to a top surface of the lock support through a release lever rotating shaft, where the release lever includes a release end and an operation end, the release lever is driven by operating the operation end of the release lever to rotate, and the release end of the release lever drives the lock pin to move toward a release direction, so that the first end of the lock pin exits from the lockhole on the outer circumference of the fixed disc to release the rotating disc; and 
     a release lever return spring connected to the release lever and the lock support or the rotating disc, where the release lever return spring drives the release lever to return to the locked state; and during releasing, the release lever return spring accumulates energy. 
     In an exemplary embodiment of the present invention, at least one outward protruding portion is disposed on the outer circumference of the fixed disc, the lockhole is disposed on each outward protruding portion, each outward protruding portion is transitionally connected to the remaining part of the outer circumference of the fixed disc through an arc-shaped guiding plane, the first end of the lock pin is not in contact with the remaining part of the outer circumference of the fixed disc before entering the arc-shaped guiding plane, and the first end of the lock pin is in contact with the arc-shaped guiding plane after entering the arc-shaped guiding plane. 
     In an exemplary embodiment of the present invention, a kidney-shaped hole is disposed on a top surface of the lock support and a cam rotating along with a release lever rotating shaft is fixed to a shaft end of the release lever rotating shaft on one side of the top surface provided with the kidney-shaped hole, a stop pin avoiding slot and a stop pin limiting slot that are in communication with each other are disposed on the cam and a squeezing shifting plate is disposed axially on the cam, an axis disposition point between the squeezing shifting plate and the cam is located on a first end of the squeezing shifting plate, the first end of the squeezing shifting plate is connected to the lock support through a squeezing shifting plate return spring, and a stop pin is fixed between the first end and a second end of the squeezing shifting plate; a squeezing protrusion is disposed at a position, close to the lockhole, on the outer circumference of the fixed disc; after the release lever is lifted to a release position, the cam rotates to the release position along with the release lever rotating shaft, in this case, the stop pin on the squeezing shifting plate passes through the stop pin limiting slot and the kidney-shaped hole and the stop pin is limited in the stop pin limiting slot and to a position of a first end of the kidney-shaped hole, the release lever is enabled to be at a release position all the time and not return to a locking position even if a hand is released, and the release end of the release lever drives the lock pin to be at the release position all the time, so that a tip of the first end of the lock pin is not in contact with the remaining part of the outer circumference of the fixed disc all the time and not scraped; and when the rotating disc rotates to the locking position, the second end of the squeezing shifting plate is in contact with the squeezing protrusion, the squeezing shifting plate turns over under the action of the squeezing protrusion, to enable the stop pin to pass through the stop pin avoiding slot and the kidney-shaped hole and enable the stop pin to be located in the stop pin avoiding slot and at a position of a second end of the kidney-shaped hole, in this case, the stop pin limiting slot in the cam does not limit the stop pin, the release lever returns to the locking position again under the action of the release lever return spring, and the lock pin is enabled to return to the locking position under the action of the lock pin return spring. 
     In an exemplary embodiment of the present invention, a silencing bushing is disposed in the lockhole, and in the locked state, the first end of the lock pin is inserted into the silencing bushing under the action of the lock pin return spring to lock the rotating disc. 
     In an exemplary embodiment of the present invention, a plastic clip is mounted to a position at which a lockhole is disposed on the fixed disc, a guiding notch corresponding to the lockhole is disposed on the plastic clip, and the first end of the lock pin enters the lockhole through bottom guidance of the guiding notch in the plastic clip. 
     In an exemplary embodiment of the present invention, a silencing cap is sleeved on a tip of the first end of the lock pin, and the silencing cap is in contact with the outer circumference of the fixed disc. 
     In an exemplary embodiment of the present invention, a buffer component is fixed to the release lever, and in the locked state, the release lever is in contact with the lock support through the buffer component, to eliminate noise generated due to a jolt of the release lever in a running process. 
     In an exemplary embodiment of the present invention, the lock support includes a first end surface close to the outer circumference of the fixed disc, a second end surface disposed opposite to the first end surface, and a top surface connecting the first end surface and the second end surface; at least two first lock pin protruding holes are disposed on the first end surface, at least two second lock pin protruding holes are disposed on the second end surface, and the first lock pin protruding holes on the first end surface and the second lock pin protruding holes on the second end surface are in a one-to-one correspondence and coaxial; and a first end and a second end of each lock pin respectively protrude from a corresponding first lock pin protruding hole and a corresponding second lock pin protruding hole. 
     In an exemplary embodiment of the present invention, a releasing plate is fixed to each lock pin, one end of the lock pin return spring is in contact with the releasing plate, and the other end is in contact with the first end surface or the second end surface; in the locked state, the release end of the release lever is not in contact with the releasing plate, in a released state, the release end of the release lever is in contact with the releasing plate and drives the lock pin, through the releasing plate, to move toward the release direction, and when the release lever is located at a middle position, the release end of the release lever is in contact with the releasing plate and drives the lock pin, through the releasing plate, to move toward the release direction. 
     In an exemplary embodiment of the present invention, at least two releasing shifting forks are disposed at the release end of the release lever, each releasing shifting fork corresponds to one lock pin, in the locked state, the releasing shifting fork is not in contact with the releasing plate, in the released state, the releasing shifting fork is in contact with the releasing plate and drives the lock pin, through the releasing plate, to move toward the release direction, and when the release lever is located at the middle position, the releasing shifting fork is in contact with the releasing plate and drives the lock pin, through the releasing plate, to move toward the release direction. 
     In an exemplary embodiment of the present invention, two blocking points are disposed on the outer circumference of the fixed disc, and the two blocking points are arranged at 180° and fit in with the seat rotation locking mechanism, to limit a rotation angle of the rotating disc to 0 to 180° through the seat rotation locking mechanism. 
     Since the foregoing technical solutions are used, compared with the prior art, the present invention has the following advantages: 
     (1) Locking in a Y direction is implemented by using two independent lock pins. 
     (2) Friction-induced noise is eliminated through fit between truncated cones at the first ends of the two lock pins and the silencing bushing. 
     (3) Zero clearance is implemented by using a wedging principle of the truncated cones at the first ends of the two lock pins. 
     (4) In a rotating adjustment process, the release lever may be released, and scraping does not occur between the lock pin and the outer circumference of the rotating disc. 
     (5) Two blocking points arranged at 180° are disposed on the fixed disc, and during rotating adjustment, the rotation may be from the front to the rear, and then from the rear to the front only according to one direction, thereby avoiding unlimited rotation to twist off a wire bundle of a seat. 
     (6) A buffer component is disposed between the release lever and the lock support, to eliminate noise generated due to a jolt of the release lever in a running process. 
     The present invention eliminates a fit clearance existing after a rotation mechanism is locked, improves a grade of a product, and improves user experience. In an adjustment process, even if an operator releases an adjustment lever, a locking piece and a fixed disc do not generate scraping noise, and service life of the product is prolonged since wearing is eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a three-dimensional schematic diagram of assembling between a locking mechanism and a seat rotation mechanism according to Embodiment 1 of the present invention. 
         FIG. 2  is a schematic bottom view of the assembling between the locking mechanism and the seat rotation mechanism according to Embodiment 1 of the present invention. 
         FIG. 3  is a schematic exploded view of the locking mechanism and the seat rotation mechanism according to Embodiment 1 of the present invention. 
         FIG. 4  is a schematic diagram of assembling between a plastic clip and the seat rotation mechanism according to Embodiment 1 of the present invention. 
         FIG. 5  is a schematic structural diagram of the seat rotation mechanism according to Embodiment 1 of the present invention. 
         FIG. 6  is a schematic sectional view of the assembling between the locking mechanism and the seat rotation mechanism according to Embodiment 1 of the present invention. 
         FIG. 7  is a schematic exploded view of the locking mechanism according to Embodiment 1 of the present invention. 
         FIG. 8  is a schematic structural diagram of the locking mechanism viewed from one direction according to Embodiment 1 of the present invention. 
         FIG. 9  is a schematic structural diagram of the locking mechanism viewed from another direction according to Embodiment 1 of the present invention. 
         FIG. 10  is a schematic diagram of a state that a lock pin in the locking mechanism enters an arc-shaped guiding plane according to Embodiment 1 of the present invention. 
         FIG. 11  is a schematic diagram of a state that a lock pin in the locking mechanism is inserted into a lockhole according to Embodiment 1 of the present invention. 
         FIG. 12  is a schematic diagram of a state that another lock pin in the locking mechanism is aligned with a lockhole according to Embodiment 1 of the present invention. 
         FIG. 13  is a schematic diagram of a state that two lock pins in the locking mechanism are inserted into a lockhole according to Embodiment 1 of the present invention. 
         FIG. 14  is a schematic diagram of assembling between a silencing bushing and a seat rotation mechanism according to Embodiment 2 of the present invention. 
         FIG. 15  is a schematic diagram of a state that two lock pins in a locking mechanism are inserted into the silencing bushing according to Embodiment 2 of the present invention. 
         FIG. 16  is a schematic diagram of a state that after the two lock pins in the locking mechanism exit from the silencing bushing and rotate by an angle, tips of first ends of the two lock pins are not in contact with an outer circumference of a fixed disc according to Embodiment 2 of the present invention. 
         FIG. 17  is a schematic structural diagram of the locking mechanism according to Embodiment 2 of the present invention. 
         FIG. 18  is a three-dimensional schematic diagram of assembling between the locking mechanism and the seat rotation mechanism according to Embodiment 2 of the present invention. 
         FIG. 19  is a schematic diagram of the locking mechanism in a locked state according to Embodiment 2 of the present invention. 
         FIG. 20  is a schematic diagram of the locking mechanism in a released state according to Embodiment 2 of the present invention. 
         FIG. 21  is a schematic diagram of the locking mechanism returning to the locked state again according to Embodiment 2 of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following describes the present invention in detail with reference to the accompanying drawings and specific implementations. 
     Embodiment 1 
     Referring to  FIG. 1  to  FIG. 9 , a seat rotation locking mechanism is shown, including a locking mechanism  200 , where the locking mechanism  200  is mounted on a rotating disc  110  in a seat rotation mechanism  100  to rotate along with the rotating disc  110 . Two lockholes  121   a  are uniformly disposed on an outer circumference  121  of a fixed disc  120  in the seat rotation mechanism  100 , and a central angle between the two lockholes  121   a  is 180°. Each lockhole  121   a  is a kidney-shaped lockhole, to accommodate two lock pins at the same time. 
     The locking mechanism  200  includes a lock support  210 , two lock pins  220  and  230 , two lock pin return springs  240  and  250 , a release lever  260 , and a release lever return spring  270 . 
     The lock support  210  includes a first end surface  211  close to the outer circumference  121  of the fixed disc  120 , a second end surface  212  disposed opposite to the first end surface  211 , and a top surface  213  connecting the first end surface  211  and the second end surface  212 . 
     Two through holes  213   a  are disposed at one end, close to the center of the seat rotation mechanism  100 , of the top surface  213 , two bolts  111  are fixed to the rotating disc  110  at the same time, and nuts  112  are tightened after the two bolts  111  passes through the two through holes  213   a , to fixedly mount the locking mechanism  200  to the rotating disc  110 . 
     Two first lock pin protruding holes  211   a  and  211   b  are disposed on the first end surface  211  of the lock support  210 , and two second lock pin protruding holes  212   a  and  212   b  are disposed on the second end surface  212  of the lock support  210 . The first lock pin protruding hole  211   a  on the first end surface  211  and the second lock pin protruding hole  212   a  on the second end surface  212  are coaxial, and the first lock pin protruding hole  211   b  on the first end surface  211  and the second lock pin protruding hole  212   b  on the second end surface  212  are coaxial. A first end  221  and a second end  222  of one lock pin  220  respectively protrude from the corresponding first lock pin protruding hole  211   a  and the corresponding second lock pin protruding hole  212   a , and a first end  231  and a second end  232  of the other lock pin  230  respectively protrude from the corresponding first lock pin protruding hole  211   b  and the corresponding second lock pin protruding hole  212   b . Each of the first ends  221  and  231  of the two lock pins  220  and  230  is of a truncated-cone-shaped structure. 
     Releasing plates  223  and  233  are respectively fixed to the two lock pins  220  and  230 , and the two lock pin return springs  240  and  250  are respectively sleeved on the two lock pins  220  and  230 . If the two lock pin return springs  240  and  250  are tension springs (as shown in  FIG. 10  and  FIG. 11 ), two ends of the two lock pin return springs  240  and  250  are respectively in contact with the releasing plates  223  and  233 , and the other two ends of the two lock pin return springs  240  and  250  are both in contact with the first end surface  211  of the lock support  210 . If the two lock pin return springs  240  and  250  are compression springs, two ends of the two lock pin return springs  240  and  250  are respectively in contact with the releasing plates  223  and  233 , and the other two ends of the two lock pin return springs  240  and  250  are both in contact with the second end surface  212  of the lock support  210  (as shown in  FIG. 13 ). In a locked state, the first ends of the two lock pins  220  and  230  are inserted, under the action of the two lock pin return springs  240  and  250 , into the lockhole  121   a  on the outer circumference  121  of the fixed disc  120  to lock the rotating disc  110 . 
     The release lever  260  includes an operation end  261  and a release end  262 , an operation lever sleeve  263  is mounted on the operation end  261 , and two releasing shifting forks  262   a  and  262   b  extending downward may be disposed at the release end  262 . A rectangular hole  213   b  is disposed on the top surface  213  of the lock support  210 , and the two releasing shifting forks  262   a  and  262   b  extending downward of the release end  262  pass through the rectangular hole  213   b  and are respectively forked onto the two lock pins  220  and  230 . 
     The release end  262  of the release lever  260  is hinged to the top surface  213  of the lock support  210  through a release lever rotating shaft  264 . The release lever return spring  270  may be a torsion spring or a tension spring. If the release lever return spring is a torsion spring, the torsion spring is wound around the release lever rotating shaft  264 , one end of the torsion spring acts on the release lever  260 , and the other end acts on the top surface  213  of the lock support  210 . In this embodiment, the release lever return spring  270  is a tension spring, one end of which is hooked to the release lever  260 , and the other end of which is hooked to the lock support  210 . In the locked state, the release lever return spring  270  may enable the release lever  260  to be at a locking position all the time. During releasing, the two releasing shifting forks  262   a  and  262   b  at the release end  262  of the release lever  260  drives, through the releasing plates  223  and  233 , the two lock pins  220  and  230  to move toward a release direction, so that the first ends  221  and  231  of the two lock pins  220  and  230  exit from the lockhole  121   a  on the outer circumference  121  of the fixed disc  120  to release the rotating disc  110 ; and the release lever return spring  270  accumulates energy. 
     To well insert the first ends of the two lock pins  220  and  230  into the lockhole  121   a  on the outer circumference  121  of the fixed disc  120 , in this embodiment, a plastic clip  280  is mounted, by using two screws  281 , to a position at which the lockhole  121   a  is disposed on the fixed disc  120 , and a guiding notch  282  corresponding to the lockhole  121   a  is disposed on the plastic clip  280 . The first ends  221  and  231  of the two lock pins  220  and  230  enter the lockhole  121   a  through bottom guidance of the guiding notch  282  in the plastic clip  280 . 
     In this embodiment, a releasing process is that the operation end  261  of the release lever  260  is lifted up by using a hand, so that the release lever  260  rotates around the release lever rotating shaft  264 ; and the two releasing shifting forks  262   a  and  262   b  of the release end  262  of the release lever  260  drives, through the releasing plates  223  and  233 , the two lock pins  220  and  230  to move toward the release direction, so that the first ends  221  and  231  of the two lock pins  220  and  230  exit from the lockhole  121   a  on the outer circumference  121  of the fixed disc  120  to release the rotating disc  110 . 
     In addition, to eliminate noise generated due to a jolt of the release lever  260  in a running process, a buffer component  290  is fixed to the release lever  260 . In the locked state, the release lever  260  is in contact with the lock support  210  through the buffer component  290 , and the noise generated due to the jolt of the release lever  260  in the running process may be eliminated by fitting in with the release lever return spring  270 . 
     To alleviate noise generated due to scraping between tips of the first ends  221  and  231  of the two lock pins  220  and  230  and the outer circumference  121  of the fixed disc  120  in a rotation process, two methods may be used in this embodiment to solve the problem: One method is that a silencing cap (not shown) is sleeved on the tips of the first ends  221  and  231  of the two lock pins  220  and  230 , and the silencing cap is in contact with the outer circumference  121  of the fixed disc  120 . The other method is that two outward protruding portions  121   b  distributed at 180° are disposed on the outer circumference  121  of the fixed disc  120 , each lockhole  121   a  is disposed on each outward protruding portion  121   b , and each outward protruding portion  121   b  is transitionally connected to the remaining part of the outer circumference  121  of the fixed disc  120  through arc-shaped guiding planes  121   c  and  121   d . Before entering the arc-shaped guiding planes  121   c  and  121   d , the first ends  221  and  231  of the two lock pins  220  and  230  are not in contact with the remaining part of the outer circumference  121  of the fixed disc  120 , and the first ends  221  and  231  of the two lock pins  220  and  230  are in contact with the arc-shaped guiding planes  121   c  and  121   d  only after entering the arc-shaped guiding planes  121   c  and  121   d . In this way, lengths of the tips of the first ends  221  and  231  of the two lock pins  220  and  230  that are in contact with the outer circumference  121  of the fixed disc  120  are reduced, thereby effectively reducing noise generated due to scraping. 
     Referring to  FIG. 10 , before the rotating disc  110  rotates to the locking position, the first ends  221  and  231  of the two lock pins  220  and  230  first enter the arc-shaped guiding plane  121   c . In this case, neither of the first ends  221  and  231  of the two lock pins  220  and  230  is aligned with the lockhole  121   a , and the first ends  221  and  231  of the two lock pins  220  and  230  butt against and slide on the arc-shaped guiding plane  121   c  of the outer circumference  121  of the fixed disc  120 . 
     Referring to  FIG. 11 , with continuous rotation of the rotating disc  110 , when the first end  221  of the first lock pin  220  is aligned with the lockhole  121   a , under the action of restoring force of the lock pin return spring  240 , the first end  221  of the first lock pin  220  is ejected and inserted into the lockhole  121   a , and the first end  231  of the second lock pin  230  continues to butt against and slide on the arc-shaped guiding plane  121   c  of the outer circumference  121  of the fixed disc  120 . 
     Referring to  FIG. 12 , with the continuous rotation of the rotating disc  110 , the first end  231  of the second lock pin  230  is also aligned with the lockhole  121   a . In this case, the first end  221  of the first lock pin  220  has come into contact with a hole wall  121   aa  on one side of the lockhole  121   a , and deflects under the action of the hole wall  121   aa  on this side to make room for insertion of the first end  231  of the second lock pin  230  into the lockhole  121   a , and under the action of restoring force of the lock pin return spring  250 , the first end  231  of the second lock pin  230  is ejected and inserted into the lockhole  121   a.    
     Referring to  FIG. 13 , with the continuous rotation of the rotating disc  110 , the first ends  221  and  231  of the two lock pins  220  and  230  are both inserted into the lockhole  121   a  and tilt respectively as shown in  FIG. 13 . The first end  221  of the lock pin  220  forms two contact points a and b with the hole wall  121   aa  of the lockhole  121   a  and a hole wall  211   aa  of the first lock pin protruding hole  211   a  on the first end surface  211  of the lock support  210 , and the second end  222  of the lock pin  220  forms a third contact point c with a hole wall  212   aa  of the second lock pin protruding hole  212   a  on the second end surface  212  of the lock support  210 . Besides, the first end  231  of the lock pin  230  forms two contact points d and e with a hole wall  121   ab  of the lockhole  121   a  and a hole wall  211   ba  of the first lock pin protruding hole  211   b  on the first end surface  211  of the lock support  210 , and the second end  232  of the lock pin  230  forms a third contact point f with a hole wall  213   ba  of the second lock pin protruding hole  213   b  on the second end surface  212  of the lock support  210 . The two lock pins  220  and  230  wedge the fixed disc  120  and the rotating disc  110  together through the six contact points a, b, c, d, e, and f, thereby effectively eliminating a fit clearance existing after the rotation mechanism is locked, improving a grade of a product, and improving user experience. 
     In addition, to prevent the rotating disc  110  from rotating by over 180° to twist off a wire bundle of a seat, in this embodiment, two blocking points  122  and  123  are disposed on the outer circumference  121  of the fixed disc  120 . The two blocking points  122  and  123  are arranged at 180° and fit in with the seat rotation locking mechanism, to limit a rotation angle of the rotating disc  110  to 0 to 180° through the seat rotation locking mechanism. In this way, when the seat rotation mechanism  100  performs rotating adjustment, the rear may only be rotated from the front according to one direction, and then the front is rotated from the rear, thereby avoiding unlimited rotation to twist off the wire bundle of the seat. 
     Embodiment 2 
     To further solve the problem that the tips of the first ends  221  and  231  of the two lock pins  220  and  230  are in contact with the outer circumference  121  of the fixed disc  120  and scraped, in this embodiment, improvements are further performed to Embodiment 1, and the improvements are as follows: Referring to  FIG. 14 , a silencing bushing  124  is disposed in the lockhole  121   a , and in the locked state, the first ends  221  and  231  of the two lock pins  220  and  230  are inserted, under the action of the lock pin return springs  240  and  250 , into the silencing bushing  124  to lock the rotating disc  110 . 
     Referring to  FIG. 15  and  FIG. 16 , it is set that an insertion amount of the first ends  221  and  231  of the two lock pins  220  and  230  inserted into the silencing bushing  124  is A2, and a size of a surface difference between the outward protruding portion  121   b  on the outer circumference  121  of the fixed disc  120  and the remaining part of the outer circumference  121  of the fixed disc  120  is A1, where A1 is greater than A2 by 2.5 mm to 3 mm. In this way, in a process of the rotating adjustment, even if the release lever  260  is released, there is always a clearance A3 between the tips of the first ends  221  and  231  of the two lock pins  220  and  230  and the remaining part of the outer circumference  121  of the fixed disc  120 , to avoid a case that the tips of the first ends  221  and  231  of the two lock pins  220  and  230  are in contact with the remaining part of the outer circumference  121  of the fixed disc  120  to generate scraping noise, and eliminate an embarrassment that it is inconvenient to lift up the release lever all the time during adjustment outside a car in the prior art. 
     To implement the foregoing function, in the present invention, the following improvements are performed to the locking mechanism  200 : Referring to  FIG. 17  and  FIG. 18 , a kidney-shaped hole  213   e  is disposed on the top surface  213  of the lock support  210  and a cam  300  rotating along with the release lever rotating shaft  264  is fixed to a shaft end of the release lever rotating shaft  264  on one side of the top surface  213  provided with the kidney-shaped hole  213   e , where a stop pin avoiding slot  310  and a stop pin limiting slot  320  that are in communication with each other are disposed on the cam  300  and a squeezing shifting plate  400  is disposed axially on the cam  300 . 
     An axis disposition point  410  between the squeezing shifting plate  400  and the cam  300  is located on a first end  420  of the squeezing shifting plate  400 , the first end  420  of the squeezing shifting plate  400  is connected to the lock support  210  through a squeezing shifting plate return spring  430 , and a stop pin  450  is fixed between the first end  420  and a second end  440  of the squeezing shifting plate  400 . The squeezing shifting plate return spring  430  is a compression spring. 
     In addition, a squeezing protrusion  121   f  is disposed at a position, close to the lockhole  121   a , on the outer circumference  121  of the fixed disc  120 . 
     Referring to  FIG. 19 , in the locked state, the release lever  260  is in the locked state under the action of the release lever return spring  270 , and the two lock pins  220  and  230  are also in the locked state under the action of the two lock pin return springs  240  and  250 . In this case, the cam  300  rotates along with the release lever rotating shaft  264  to the locking position. In this case, under the action of the squeezing shifting plate return spring  430 , the stop pin  450  on the squeezing shifting plate  400  passes through the stop pin avoiding slot  310  and the kidney-shaped hole  213   c  and the stop pin  450  is located in the stop pin avoiding slot  310  and at a position of a second end  213   bb  of the kidney-shaped hole  213   c.    
     Referring to  FIG. 20 , after the release lever  260  is lifted up to the release position, the cam  300  rotates along with the release lever rotating shaft  264  to the release position. In this case, the stop pin  450  on the squeezing shifting plate  400  passes through the stop pin limiting slot  320  and the kidney-shaped hole  213   c  and the stop pin  450  is limited in the stop pin limiting slot  320  and to a position of a first end  213   ba  of the kidney-shaped hole  213   c , the release lever  260  is enabled to be at the release position all the time and not return to the locking position even if a hand is released, and the release end of the release lever  260  drives the two lock pins  220  and  230  to be at the release position all the time, so that the tips of the first ends  221  and  231  of the two lock pins  220  and  230  are not in contact with the remaining part of the outer circumference  121  of the fixed disc  120  all the time and not scraped. 
     Referring to  FIG. 21 , when the rotating disc  110  rotates to the locking position, the second end  440  of the squeezing shifting plate  400  is in contact with the squeezing protrusion  121   c  on the outer circumference  121  of the fixed disc  120 , the squeezing shifting plate  400  turns over counterclockwise under the action of the squeezing protrusion  121   c , to enable the stop pin  450  to pass through the stop pin avoiding slot  310  and the kidney-shaped hole  213   c  again and enable the stop pin  450  to be located in the stop pin avoiding slot  310  and at the position of the second end  213   bb  of the kidney-shaped hole  213   c . In this case, the stop pin limiting slot  320  in the cam  300  does not limit the stop pin  450 , the release lever  260  returns to the locking position again under the action of the release lever return spring  270 , and the two lock pins  220  and  230  are enabled to return to the locking position under the action of the lock pin return springs  240  and  250 .