Backward folding mechanism for seat headrest

Abstract

The invention provides a seat headrest backward folding mechanism which is characterized in that two ends of a headrest main rotating shaft are rotatably mounted on a backrest bottom plate, a headrest rod is fixed on the headrest main rotating shaft, a headrest force storage torsion spring is arranged between the headrest main rotating shaft and the backrest bottom plate, and the headrest force storage torsion spring has torsion for driving the headrest main rotating shaft to rotate backward; the pull rod assembly is hinged to the backrest bottom plate, a reset torsion spring is arranged between the pull rod assembly and the backrest bottom plate, the reset torsion spring has pre-tightening force for driving the pull rod assembly to move upwards, and the cam lock assembly is arranged between the headrest main rotating shaft and the pull rod assembly. The cam lock assembly is in a locking state under the action of the torsion of the headrest force storage torsion spring and the pre-tightening force of the reset torsion spring. The cam lock assembly can be unlocked by pulling the pull rod assembly, so that the rotation constraint on the headrest main rotating shaft is relieved, and the backward folding of the headrest rod is realized. The device has a stable locking function and an automatic resetting function, and is ingenious in structure, convenient to operate and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of automobile seats, and in particular to a backward folding mechanism for a seat headrest. Background Art

[0002] As an important part of the car seat, the seat headrest is designed not only to meet the comfort needs of passengers, but also to ensure the safety of passengers in an emergency. With the rapid development of the automobile industry and the increasing attention of consumers to safety and comfort, the design of the seat headrest is also constantly innovating and improving. Most of the existing car seat headrests can move up and down. When the seat back is adjusted backward, the seat cannot be turned into a bed mode due to the presence of the headrest, and the riding experience is not good. Patent CN118163690A discloses a backward folding electric headrest device, including a driving fixture fixedly mounted on the seat back frame, a driving lifting mechanism rotatably mounted on the driving fixture, a headrest mounting seat hingedly mounted on the driving fixture, and a headrest assembly fixedly mounted on the headrest mounting seat, which can make the headrest fold backward and store, solving the problem of cumbersome operation steps caused by manually pulling out the headrest rod and placing it aside to adjust the front and rear tilt angle of the seat back to lie flat; but the screw motor has the problems of high cost and large weight. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention aims to provide a seat headrest folding mechanism, which adopts an ingenious cam lock structure design to achieve convenient adjustment and stable locking of the headrest, and is light in weight and low in cost.

[0004] In order to achieve the above-mentioned purpose, the present invention proposes a seat headrest backward folding mechanism, comprising a headrest rod and a backrest base plate, and also comprising a headrest main rotating shaft, a cam lock assembly and a pull rod assembly, wherein both ends of the headrest main rotating shaft are rotatably installed on the backrest base plate, the headrest rod is fixed on the headrest main rotating shaft, a headrest force storage torsion spring is provided between the headrest main rotating shaft and the backrest base plate, and the headrest force storage torsion spring has a torsion force driving the headrest main rotating shaft to rotate backward; the pull rod assembly is hinged on the backrest base plate, a return torsion spring is provided between the pull rod assembly and the backrest base plate, and the return torsion spring has a pre-tightening force driving the pull rod assembly to move upward, the cam lock assembly is arranged between the headrest main rotating shaft and the pull rod assembly, and the cam lock assembly is in a locked state under the torsion force of the headrest force storage torsion spring and the pre-tightening force of the return torsion spring; pulling the pull rod assembly can realize the unlocking of the cam lock assembly, thereby releasing the rotation constraint on the headrest main rotating shaft, and then realizing the backward folding of the headrest rod.

[0005] In the above scheme: the cam lock assembly includes a cam plate and a locking plate, the cam plate is fixed on the main rotating shaft of the headrest, the locking plate is hinged to the backrest bottom plate through the first rotating shaft of the locking plate, and the end away from the first rotating shaft of the locking plate is connected to the pull rod assembly, the locking plate and the cam plate are engaged together under the torsion of the headrest storage torsion spring and the preload force of the reset torsion spring; pulling the pull rod assembly can drive the locking plate to rotate around the first rotating shaft of the locking plate, thereby separating the cam plate from the locking plate, so that the cam lock assembly is unlocked. The cam plate and the locking plate cooperate to achieve locking, with a simple structure and ingenious design.

[0006] In the above scheme: the cam lock assembly also includes a shell, the cam plate and the locking plate are both arranged inside the shell, the shell is fixed to the backrest bottom plate, the shell is provided with a shaft hole for the main shaft of the headrest to movably pass through, the front end of the locking plate is hinged to the shell through the first shaft of the locking plate, the rear end is upwardly provided with a groove that bites with the protrusion provided on the cam plate, and the rear end is also movably sleeved with a second shaft of the locking plate extending left and right, the two ends of the shell are provided with a first guide groove for the second shaft of the locking plate to pass outward, and the second shaft of the locking plate is limited in the first guide groove; when the locking plate flips downward around the first shaft of the locking plate, the second shaft of the locking plate can slide along the first guide groove.

[0007] The cam lock assembly realizes the locking and unlocking functions of the main shaft of the headrest through the ingenious combination of the cam plate, the locking plate and the housing. The overall structural design is exquisite, the various components are closely matched, and the backrest space is effectively utilized. Under the torsion of the headrest storage torsion spring and the preload of the reset torsion spring, the cam plate and the locking plate bite together to ensure the stability of the main shaft of the headrest in the locked state. The second shaft of the locking plate is designed through the first guide groove, so that the locking plate can move smoothly during the unlocking process and maintain good guidance. This design enhances the adaptability and reliability of the mechanism and ensures stable operation under various conditions of use.

[0008] In the above scheme: the pull rod assembly includes a U-shaped pull rod, a ball pull rod and a main pull rod, the second rotating shaft of the locking plate is fixed between the two ends of the U-shaped pull rod, the upper end of the ball pull rod is fixed to the bottom end of the U-shaped pull rod, the lower end of the ball pull rod is a ball head end, and the ball head end is clamped on the left end of the main pull rod; a reset torsion spring rotating shaft, a torsion spring limiting shaft and a pull rod limiting bolt are fixed on the backrest bottom plate; the middle part of the main pull rod is hinged to the backrest bottom plate through the reset torsion spring rotating shaft, and is prevented from falling off by the pull rod fixing bolt; the reset torsion spring is sleeved on the reset torsion spring rotating shaft, one end of which is clamped on the main pull rod, and the other end is abutted on the torsion spring limiting shaft; the right end of the main pull rod is provided with a second guide groove for the pull rod limiting bolt to pass through, and the pull rod limiting bolt is limited in the second guide groove; when the main pull rod rotates around the reset torsion spring rotating shaft, the pull rod limiting bolt can slide along the second guide groove. The pull rod assembly realizes the unlocking function of the cam lock assembly through the clever combination of the U-shaped pull rod, the ball pull rod and the main pull rod, and integrates the driving mechanism of the reset torsion spring. This design makes the entire mechanism more compact and reduces space occupation. The user only needs to pull the main pull rod to drive the U-shaped pull rod and the ball pull rod to move, thereby rotating the second rotating shaft of the locking plate to unlock the cam lock assembly. This process is easy to operate and highly user-friendly.

[0009] In the above scheme: the right end of the main pull rod is equipped with a manual drive mechanism and / or an electric drive mechanism, which can drive the main pull rod to flip clockwise, thereby driving the ball pull rod and the U-shaped pull rod to move downward, thereby realizing the separation of the cam plate and the locking plate, so that the cam lock assembly is unlocked. Both manual and electric unlocking can be done independently, and the integrated unlocking of the flashlight and the electric light has good compatibility.

[0010] In the above scheme: the manual drive mechanism includes a pull belt, which is connected to the right end of the main pull rod. Pulling the pull belt upward can drive the main pull rod to flip clockwise, thereby driving the ball pull rod and the U-shaped pull rod to move downward, thereby realizing the separation of the cam plate and the locking plate, so that the cam lock assembly is unlocked. The pull belt has low cost and simple and direct operation, which greatly improves the convenience of unlocking.

[0011] In the above scheme: the electric drive mechanism includes a cable motor, a cable, a cable fixing bracket and a push rod. The push rod is arranged horizontally below the main pull rod, and its top surface contacts the bottom surface of the main pull rod. The middle part of the push rod is hinged to the backrest bottom plate through the push rod rotating shaft. The cable fixing bracket is fixed to the backrest bottom plate. The cable is fixed to the cable fixing bracket through a protective tube. The upper end of the cable is connected to the left end of the push rod, and the lower end of the cable is connected to the cable motor. The cable motor can drive the cable to pull down, and the cable pulling down can drive the push rod to push the main pull rod to flip clockwise, thereby driving the ball pull rod and the U-shaped pull rod to move down, and then realize the separation of the cam plate and the locking plate, so that the cam lock assembly is unlocked. Through the ingenious combination of the cable motor, the cable, the cable fixing bracket and the push rod, the electric unlocking of the cam lock assembly is realized, and the electric drive mechanism structure has the characteristics of compact structure, high efficiency, stability and reliability.

[0012] In the above scheme: the headrest rod is fixed to the main shaft of the headrest through the headrest sleeve, the headrest force storage torsion spring is sleeved on the main shaft of the headrest, one end of which is plugged into the headrest sleeve, and the other end of which is hooked on the backrest bottom plate. The headrest force storage torsion spring is in a compressed energy storage state due to installation, and the cam piece on it generates a pre-tightening torque T1 due to the compression and energy storage of the force storage torsion spring.

[0013] In the above scheme: the left end of the main pull rod is provided with a ball head slot for the ball head end of the ball pull rod to be inserted into, and the back thereof is also provided with a cavity for accommodating a reset torsion spring and a torsion spring slot for the corresponding end of the reset torsion spring to be inserted into. The reset torsion spring is in a compressed energy storage state due to installation, so the main pull rod will always have a tendency to rotate clockwise around the reset torsion spring shaft, thereby pushing up the ball pull rod and having an upward movement tendency, that is, generating a preload force F2.

[0014] In the above scheme: the protrusion of the cam piece and the groove of the locking piece are engaged with each other to form two front and rear tangent points, and the locking piece is hinged with the shell to form a rotation point; when the headrest is abused backward, the normal direction of the tangent line at the tangent point on the rear side is located below the line between the tangent point and the rotation point, and there is an angle between the two; when the headrest is abused forward, the normal direction of the tangent line at the tangent point on the front side is located above the line between the tangent point and the rotation point, and there is an angle between the two; so that the protrusion of the cam piece cannot escape from the groove of the locking piece. It is ensured that the cam piece cannot escape from the locking piece when the headrest is abused forward and backward, that is, the unique bite principle design is adopted, so that after the headrest is locked, it can meet the headrest strength requirements during vehicle collision, and far exceeds the standard strength value.

[0015] The beneficial effects of the present invention are:

[0016] 1. The headrest rod is connected to the backrest base plate through the main shaft of the headrest, and the headrest force storage torsion spring is cleverly used to provide the driving force for the main shaft of the headrest to rotate backward. This design simplifies the power source for the folding of the headrest. At the same time, the hinged design between the pull rod assembly and the backrest base plate, as well as the introduction of the reset torsion spring, facilitates the unlocking operation of the mechanism and ensures the natural reset of the pull rod assembly when not subject to external force. 2. The cam lock assembly realizes the rotation locking of the main shaft of the headrest through the torsion of the headrest force storage torsion spring and the preload of the reset torsion spring, ensuring that the headrest will not accidentally fold under normal use, thereby ensuring the safety and stability of the seat. 3. In actual operation, the user only needs to simply pull the pull rod assembly to unlock the cam lock assembly, thereby releasing the rotation constraint on the main shaft of the headrest. This operation is simple and quick, greatly improving the user experience. At the same time, the backward folding function of the headrest rod also provides passengers with a more spacious space; and when the headrest is not needed, the headrest can be folded backward and stored to facilitate the seat to realize the bed mode. 4. The clever cam lock structure design allows the headrest to have a large folding angle (the folding angle is greater than 90°) and can still be locked, which is completely different from the traditional screw motor driven folding method, reducing the weight and cost of the headrest folding mechanism and improving the competitiveness of the seat product. In short, the present invention has a stable locking function and automatic reset function, and has a clever structure, convenient operation, and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 It is a schematic diagram of the assembly of the present invention on a backrest assembly.

[0019] Figure 2 It is a schematic diagram of the structure of the invention.

[0020] Figure 3 It is a schematic diagram of the explosion of the invention.

[0021] Figure 4 It is a structural schematic diagram of the tie rod assembly.

[0022] Figure 5 This is a schematic diagram of the tie rod assembly from another angle.

[0023] Figure 6 It is the assembly diagram of the main rotating shaft of the headrest.

[0024] Figure 7 It is a schematic diagram of the connection between the cam lock assembly and the pull rod assembly.

[0025] Figure 8 This is the schematic diagram of the manual unlocking of the headrest.

[0026] Fig. 9 This is the schematic diagram of the electric unlocking of the headrest.

[0027] Fig.10 This is the schematic diagram of the headrest lifting and lowering lock.

[0028] Fig.11 It is the force analysis diagram of the cam lock assembly. DETAILED DESCRIPTION

[0029] like Figure 1 As shown in FIG. 11 , a seat headrest folding mechanism is shown, wherein the headrest folding mechanism A is assembled on a backrest assembly 1 of a car seat, and is mainly composed of a headrest rod 2, a backrest base plate 3, a headrest main shaft 4, a cam lock assembly B and a pull rod assembly C.

[0030] Both ends of the headrest main shaft 4 are rotatably mounted on the backrest base plate 3, the headrest rod 2 is fixed on the headrest main shaft 4, and a headrest force storage torsion spring 7 is provided between the headrest main shaft 4 and the backrest base plate 3. The headrest force storage torsion spring 7 has a torque that drives the headrest main shaft 4 to rotate backward.

[0031] The pull rod assembly C is hinged on the backrest base plate 3, and a return torsion spring 8 is provided between the pull rod assembly C and the backrest base plate 3. The return torsion spring 8 has a preload force to drive the pull rod assembly C to move upward. The cam lock assembly B is arranged between the headrest main shaft 4 and the pull rod assembly C, and the cam lock assembly B is in a locked state under the torsion of the headrest storage torsion spring 7 and the preload force of the return torsion spring 8.

[0032] Pulling the pull rod assembly C can unlock the cam lock assembly B, thereby releasing the rotation constraint on the headrest main shaft 4, and then realizing the backward folding of the headrest rod 2. In addition, in order to prevent the headrest from folding too fast, the headrest backward folding mechanism is equipped with a damping mechanism.

[0033] The cam lock assembly B includes a cam plate 9, a locking plate 10 and a housing 11. The cam plate 9 and the locking plate 10 are both arranged inside the housing 11. The two are engaged together under the torsion of the headrest force storage torsion spring 7 and the preload force of the reset torsion spring 8. The housing 11 is fixed to the backrest bottom plate 3. The housing 11 is provided with a shaft hole for the headrest main shaft 4 to movably pass through. The cam plate 9 is fixed to the headrest main shaft 4. The front end of the locking plate 10 is hinged to the housing 11 through the first rotating shaft 12 of the locking plate, the rear end is provided with a groove upwardly engaged with the protrusion provided on the cam plate 9, and the rear end is also movably sleeved with the second rotating shaft 13 of the locking plate extending left and right. The two ends of the housing 11 are provided with a first guide groove 14 for the second rotating shaft 13 of the locking plate to pass outward, and the second rotating shaft 13 of the locking plate is limited in the first guide groove 14; when the locking plate 10 turns downward around the first rotating shaft 12 of the locking plate, the second rotating shaft 13 of the locking plate can slide along the first guide groove 14.

[0034] The cam lock assembly B realizes the locking and unlocking functions of the main shaft 4 of the headrest through the ingenious combination of the cam plate 9, the locking plate 10 and the shell 11. The overall structural design is exquisite, the various components are closely matched, and the backrest space is effectively utilized. Under the torsion of the headrest storage torsion spring 7 and the preload force of the reset torsion spring 8, the cam plate 9 and the locking plate 10 bite together to ensure the stability of the main shaft 4 of the headrest in the locked state. The second shaft 13 of the locking plate is designed through the first guide groove 14, so that the locking plate 11 can move smoothly during the unlocking process and maintain good guidance. This design enhances the adaptability and reliability of the mechanism and ensures stable operation under various conditions of use.

[0035] The tie rod assembly C includes a U-shaped tie rod 15, a ball tie rod 16 and a main tie rod 17. The second rotating shaft 13 of the locking plate is fixed between the two ends of the U-shaped tie rod 15, the upper end of the ball tie rod 16 is fixed to the bottom end of the U-shaped tie rod 15, and the lower end of the ball tie rod 16 is a ball head end, which is clamped to the left end of the main tie rod 17. A reset torsion spring rotating shaft 18, a torsion spring limiting shaft 19 and a tie rod limiting bolt 20 are fixed to the backrest base plate 3. The middle part of the main tie rod 17 is hinged to the backrest base plate 3 through the reset torsion spring rotating shaft 18, and is prevented from falling off by the tie rod fixing bolt 21. The reset torsion spring 8 is mounted on the reset torsion spring rotating shaft 18, one end of which is clamped to the main tie rod 17, and the other end is abutted against the torsion spring limiting shaft 19. The right end of the main pull rod 17 is provided with a second guide groove 22 for the pull rod limiting bolt 20 to pass through, and the pull rod limiting bolt 20 is limited in the second guide groove 22; when the main pull rod 17 rotates around the reset torsion spring shaft 18, the pull rod limiting bolt 20 can slide along the second guide groove 22.

[0036] The rod assembly C realizes the unlocking function of the cam lock assembly C through the ingenious combination of the U-shaped rod 15, the ball rod 16 and the main rod 17, and integrates the driving mechanism of the reset torsion spring 8. This design makes the entire mechanism more compact and reduces the space occupied. The user only needs to pull the main rod 17 to drive the U-shaped rod 15 and the ball rod 16 to move, thereby rotating the second rotating shaft 13 of the locking plate to unlock the cam lock assembly B. This process is easy to operate and user-friendly.

[0037] The right end of the main pull rod 17 is equipped with a manual drive mechanism and / or an electric drive mechanism, which can drive the main pull rod 17 to flip clockwise, thereby driving the ball pull rod 16 and the U-shaped pull rod 15 to move downward, thereby separating the cam plate 9 from the locking plate 10, so that the cam lock assembly B is unlocked. Both manual and electric unlocking can be done independently, and the integrated unlocking of the flashlight and the electric light has good compatibility.

[0038] Preferably, the manual drive mechanism includes a pull strap 23, which is connected to the right end of the main pull rod 17. Pulling the pull strap 23 upward can drive the main pull rod 17 to flip clockwise, thereby driving the ball pull rod 16 and the U-shaped pull rod 15 to move downward, thereby separating the cam plate 9 from the locking plate 10, so that the cam lock assembly B is unlocked. The pull strap 23 is low in cost and the operation method is simple and direct, which greatly improves the convenience of unlocking.

[0039] Preferably, the electric drive mechanism includes a cable motor 24, a cable 25, a cable fixing bracket 26 and a push rod 27. The push rod 27 is arranged horizontally below the main pull rod 17, and its top surface contacts the bottom surface of the main pull rod 17. The middle part of the push rod 27 is hinged to the backrest bottom plate 3 through the push rod rotating shaft. The cable fixing bracket 26 is fixed to the backrest bottom plate 3, and the cable 25 is fixed to the cable fixing bracket 26 through a protective tube. The upper end of the cable 25 is connected to the left end of the push rod 24, and the lower end of the cable 24 is connected to the cable motor 27. When the cable motor 27 works, it can drive the cable 25 to pull down, and the cable 25 pulling down can drive the push rod 24 to push the main pull rod 17 to flip clockwise, thereby driving the ball pull rod 16 and the U-shaped pull rod 15 to move downward, thereby realizing the separation of the cam plate 9 and the locking plate 10, so that the cam lock assembly B is unlocked. The cam lock assembly B is electrically unlocked by the ingenious combination of the cable motor 27, the cable 25, the cable fixing bracket 26 and the push rod 25, and the electric drive mechanism structure is compact, efficient, stable and reliable.

[0040] Preferably, the headrest rod 2 is fixed to the headrest main shaft 4 through the headrest sleeve 5, and the headrest force storage torsion spring 7 is sleeved on the headrest main shaft 4, one end of which is plugged into the headrest sleeve 5, and the other end of which is hooked on the backrest bottom plate 3. The headrest force storage torsion spring 7 is in a compressed energy storage state due to installation, and the cam plate 9 on it generates a pre-tightening torque T1 due to the compression and energy storage of the force storage torsion spring. T1 causes the cam plate 9 to generate a positive pressure Fn on the locking plate 10.

[0041] The principle of generating preload torque T1:

[0042] The angle between the two end leads of the free-state headrest force storage torsion spring 7 is 0°. After assembly, one end lead is limited by the mounting hole of the backrest base plate 3, and the other end lead is twisted at a certain angle and limited in the mounting hole of the headrest sleeve 5. The headrest force storage torsion spring 7 is in a compressed energy storage state due to installation; the headrest main shaft is fixedly connected to the headrest sleeve 5 and the cam piece 9, and is rotationally connected to the backrest base plate 3 through the step bolt shaft 6, and the cam piece 9 thereon generates a pre-tightening torque T1 due to the compression energy storage of the headrest force storage torsion spring 7.

[0043] Preferably, the left end of the main pull rod 17 is provided with a ball head slot for the ball head end of the ball pull rod 16 to be inserted into, and the back thereof is also provided with a cavity for accommodating the reset torsion spring 8 and a torsion spring slot for the corresponding end of the reset torsion spring 8 to be inserted into. The reset torsion spring 8 is in a compressed energy storage state due to installation, so the main pull rod 17 will always have a tendency to rotate clockwise around the reset torsion spring shaft 18, thereby pushing up the ball pull rod 16 to have an upward movement tendency, that is, generating a preload force F2.

[0044] The principle of generating preload force F2:

[0045] The angle between the two end leads of the free-state reset torsion spring 8 is 0°. After the assembly is completed, one end lead of the reset torsion spring 8 is twisted clockwise at a certain angle and is limited on the left side of the torsion spring limit axis 19; the other end lead of the reset torsion spring 8 is installed in the torsion spring slot of the pull rod; the reset torsion spring 8 is in a compressed energy storage state due to the installation; the main pull rod 17 will always have a tendency to rotate clockwise around the reset torsion spring rotating shaft 18, so that the lifting ball pull rod 13 has a tendency to move upward, that is, a preload force F2 is generated.

[0046] Preferably, the protrusion of the cam plate 9 and the groove of the locking plate 10 are engaged with each other at two front and rear tangent points P2, and the locking plate 10 is hinged with the housing 11 to form a rotation point P1; when the headrest is abused backward, the normal direction of the tangent line of the tangent point P2 located at the rear side (i.e., the Fn direction at this time) is located below the line between the tangent point P2 and the rotation point P1, and there is an angle a between the two; when the headrest is abused forward, the normal direction of the tangent line of the tangent point P2 located at the front side (i.e., the Fn direction at this time) is located above the line between the tangent point P2 and the rotation point P1, and there is an angle a between the two; so that the protrusion of the cam plate 9 cannot escape from the groove of the locking plate 10. Ensure that the cam plate 9 cannot escape from the locking plate 10 when the headrest is abused forward and backward, that is, adopt a unique bite principle design, so that the headrest can meet the headrest strength requirements during vehicle collision after being locked, and far exceed the standard strength value.

Claims

1. A seat headrest folding mechanism, comprising a headrest rod (2), a backrest base plate (3) and a headrest main shaft (4), wherein both ends of the headrest main shaft (4) are rotatably mounted on the backrest base plate (3), the headrest rod (2) is fixed on the headrest main shaft (4), a headrest force storage torsion spring (7) is provided between the headrest main shaft (4) and the backrest base plate (3), and the headrest force storage torsion spring (7) has a torsion force for driving the headrest main shaft (4) to rotate backward; characterized in that: It also includes a cam lock assembly (B) and a pull rod assembly (C), wherein the pull rod assembly (C) is hinged on the backrest base plate (3), a reset torsion spring (8) is provided between the pull rod assembly (C) and the backrest base plate (3), and the reset torsion spring (8) has a preload force for driving the pull rod assembly (C) to move upward, the cam lock assembly (B) is arranged between the headrest main shaft (4) and the pull rod assembly (C), and the cam lock assembly (B) is in a locked state under the torsion force of the headrest force storage torsion spring (7) and the preload force of the reset torsion spring (8); pulling the pull rod assembly (C) can unlock the cam lock assembly (B), thereby releasing the rotation constraint on the headrest main shaft (4), and further realizing the backward folding of the headrest rod (2).

2. The seat headrest folding mechanism according to claim 1, characterized in that: The cam lock assembly (B) comprises a cam plate (9) and a locking plate (10), wherein the cam plate (9) is fixed on the main rotating shaft (4) of the headrest, and the locking plate (10) is hinged on the backrest base plate (3) through the first rotating shaft (12) of the locking plate, and the end away from the first rotating shaft (12) of the locking plate is connected to the pull rod assembly (C), and the locking plate (10) and the cam plate (9) are engaged together under the action of the torsion of the headrest storage torsion spring (7) and the preload force of the return torsion spring (8); pulling the pull rod assembly (C) can drive the locking plate (10) to rotate around the first rotating shaft (12) of the locking plate, thereby realizing the separation of the cam plate (9) and the locking plate (10), so that the cam lock assembly (B) is unlocked.

3. The seat headrest folding mechanism according to claim 2, characterized in that: The cam lock assembly (B) also includes a shell (11), the cam plate (9) and the locking plate (10) are both arranged inside the shell (11), the shell (11) is fixed on the backrest bottom plate (3), the shell (11) is provided with a shaft hole for the headrest main shaft (4) to movably pass through, the front end of the locking plate (10) is hinged to the shell (11) through the first locking plate shaft (12), the rear end is upwardly provided with a groove to engage with the protrusion provided on the cam plate (9), and the rear end is also movably sleeved with a second locking plate shaft (13) extending left and right, and the two ends of the shell (11) are provided with first guide grooves (14) for the second locking plate shaft (13) to pass outward, and the second locking plate shaft (13) is limited in the first guide groove (14); when the locking plate (10) turns downward around the first locking plate shaft (12), the second locking plate shaft (13) can slide along the first guide groove (14).

4. The seat headrest folding mechanism according to claim 3, characterized in that: The tie rod assembly (C) comprises a U-shaped tie rod (15), a ball tie rod (16) and a main tie rod (17); the second rotating shaft (13) of the locking plate is fixed between the two ends of the U-shaped tie rod (15); the upper end of the ball tie rod (16) is fixed to the lower end of the U-shaped tie rod (15); the lower end of the ball tie rod (16) is a ball head end, which is clamped to the left end of the main tie rod (17); a reset torsion spring rotating shaft (18), a torsion spring limiting shaft (19) and a tie rod limiting bolt (20) are fixed on the backrest bottom plate (3); the middle part of the main tie rod (17) is hinged by the reset torsion spring rotating shaft (18) It is connected to the backrest base plate (3) and is prevented from falling off by a pull rod fixing bolt (21). The reset torsion spring (8) is sleeved on the reset torsion spring rotating shaft (18), one end of which is clamped on the main pull rod (17), and the other end is abutted on the torsion spring limiting shaft (19). The right end of the main pull rod (17) is provided with a second guide groove (22) for the pull rod limiting bolt (20) to pass through, and the pull rod limiting bolt (20) is limited in the second guide groove (22); when the main pull rod (17) rotates around the reset torsion spring rotating shaft (18), the pull rod limiting bolt (20) can slide along the second guide groove (22).

5. The seat headrest folding mechanism according to claim 4, characterized in that: The right end of the main pull rod (17) is equipped with a manual drive mechanism and / or an electric drive mechanism, and the manual drive mechanism or the electric drive mechanism can drive the main pull rod (17) to flip clockwise, thereby driving the ball pull rod (16) and the U-shaped pull rod (15) to move downward, thereby realizing the separation of the cam plate (9) and the locking plate (10), so that the cam lock assembly (B) is unlocked.

6. The seat headrest folding mechanism according to claim 5, characterized in that: The manual drive mechanism includes a drawstring (23), and the drawstring (23) is connected to the right end of the main pull rod (17). Pulling the drawstring (23) upward can drive the main pull rod (17) to flip clockwise, thereby driving the ball pull rod (16) and the U-shaped pull rod (15) to move downward, thereby achieving the separation of the cam plate (9) and the locking plate (10), so that the cam lock assembly (B) is unlocked.

7. The seat headrest folding mechanism according to claim 5, characterized in that: The electric drive mechanism comprises a cable motor (24), a cable (25), a cable fixing bracket (26) and a push rod (27). The push rod (27) is arranged transversely below the main pull rod (17), and its top surface contacts the bottom surface of the main pull rod (17). The middle part of the push rod (27) is hinged to the backrest bottom plate (3) through the push rod rotating shaft. The cable fixing bracket (26) is fixed to the backrest bottom plate (3). The cable (25) is fixed to the cable fixing bracket (26) through a protective tube. 26), the upper end of the cable (25) is connected to the left end of the push rod (24), and the lower end of the cable (24) is connected to the cable motor (27). The operation of the cable motor (27) can drive the cable (25) to pull down, and the downward pulling of the cable (25) can drive the push rod (24) to push the main pull rod (17) to flip clockwise, thereby driving the ball pull rod (16) and the U-shaped pull rod (15) to move downward, thereby realizing the separation of the cam plate (9) and the locking plate (10), so that the cam lock assembly (B) is unlocked.

8. The seat headrest folding mechanism according to claim 1, characterized in that: The headrest rod (2) is fixed to the headrest main rotating shaft (4) through a headrest sleeve (5); the headrest force storage torsion spring (7) is sleeved on the headrest main rotating shaft (4), one end of which is plugged into the headrest sleeve (5) and the other end of which is hooked on the backrest bottom plate (3).

9. The seat headrest folding mechanism according to claim 4, characterized in that: The left end of the main pull rod (17) is provided with a ball head slot for the ball head end of the ball pull rod (16) to be inserted into, and the back thereof is also provided with a cavity for accommodating a reset torsion spring (8) and a torsion spring slot for the corresponding end of the reset torsion spring (8) to be inserted into.

10. The seat headrest folding mechanism according to claim 3, characterized in that: The protrusion of the cam plate (9) and the groove of the locking plate (10) are engaged with each other to form two front and rear tangent points (P2), and the locking plate (10) and the housing (11) are hinged to form a rotation point (P1); when the headrest is abused backward, the normal direction of the tangent of the tangent point (P2) located on the rear side is located below the line between the tangent point (P2) and the rotation point (P1), and there is an angle (a) between the two; when the headrest is abused forward, the normal direction of the tangent of the tangent point (P2) located on the front side is located above the line between the tangent point (P2) and the rotation point (P1), and there is an angle (a) between the two; so that the protrusion of the cam plate (9) cannot escape from the groove of the locking plate (10).

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