JP2011080567A - Power transmission mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a power transmission mechanism to intercept the transmission of rotary power from a worm to a worm wheel in a condition that a large load is applied from an output side on the worm wheel in the power transmission mechanism which performs the transmission of the rotary power by a worm gear. <P>SOLUTION: The power transmission mechanism is configured so that male screws 33A, 33B are formed on both ends of the worm 30 which composes a reduction gear 5 (the power transmission mechanism) and nuts 15A, 15B formed with female screws Aa, Ba capable of threadably engaging with the male screws 33A, 33B are integrally provided on a plug 4A of a body case 10 and an electric motor 4. Axial rotation moving relative to the body case 10 of the worm 30 is remained with stopped state because the engaged rotation reaches a terminate portion of a thread of the male screws 33A(33B) by threadably engaging either of the male screws 33A(33B) with the female screws Aa(Ba) when a load due to resistance from the output side is applied on the worm wheel 41 and thus a predetermined thrust force or larger functions on the worm 30. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power transmission mechanism. Specifically, the present invention relates to a power transmission mechanism that transmits rotational power using a worm gear.

  Conventionally, a worm gear comprising a combination of a worm and a worm wheel is known as a power transmission mechanism. Here, Patent Document 1 below discloses a mechanism for transmitting the rotation output of an electric motor to an output system using the worm gear described above. In this disclosure, the rotational power output from the electric motor is transmitted from the worm to the worm wheel and transmitted to the output system.

JP 2007-202359 A

  However, in the power transmission mechanism using the worm gear as described above, when a large resistance force is applied to the output side and a load is applied, a large load is applied to the worm or electric motor on the driving side with respect to the worm wheel. It is not preferable.

  The present invention has been devised as a solution to the above-described problems, and the problem to be solved by the present invention is that in a power transmission mechanism that transmits rotational power using a worm gear, the worm wheel is greatly affected from the output side. An object of the present invention is to enable transmission of rotational power from the worm to the worm wheel to be interrupted when a load is applied.

In order to solve the above problems, the power transmission mechanism of the present invention takes the following means.
A first invention is a power transmission mechanism that transmits rotational power using a worm gear. The worm gear includes a worm that rotates in response to transmission of rotational power from an electric motor, and a worm wheel that is provided in mesh with the worm and rotates in response to transmission of rotational power from the worm. The worm is supported so as to be axially rotatable with respect to the fixed body. Between the worm and the fixed body, there is provided a screwed structure of a male screw and a female screw which are screwed together with the rotation of the worm shaft. Although this screwing structure is normally in a non-screwing state, the worm wheel is loaded with a resistance from the output side, and a thrust force exceeding a predetermined value acts on the worm so that the worm wheels are screwed together. It has become. Further, a stopper structure is provided between the worm and the fixed body to restrict movement in the direction in which the screwed structure is screwed, and to restrict rotational movement of the worm relative to the fixed body.

  According to the first aspect of the present invention, when a load due to resistance from the output side is applied to the worm wheel and a thrust force exceeding a predetermined value is applied to the worm, the male screw and the female provided between the worm and the fixed body are provided. The screwed structure with the screw is screwed, and the stopper structure restricts the movement in the direction in which the screwed structure is screwed, so that the rotational movement of the worm relative to the fixed body is restricted. Retained. Thus, transmission of rotational power from the worm to the worm wheel can be interrupted when a large load is applied to the worm wheel from the output side.

  Next, according to a second invention, in the first invention described above, the screwing structure has a male screw formed on the worm, and a female screw provided integrally fixed to the fixed body in the rotational direction. It is configured as a combination. And the stopper structure is comprised as a terminal part of the thread of a male screw or a female screw.

  According to the second aspect of the present invention, the screwing structure is configured as a combination of a male screw formed on the worm and a female screw provided on the fixed body, and the stopper structure is a terminal portion of the screw thread on either one side. Therefore, the screwing structure and the stopper structure can each be simply and reasonably configured with a small number of parts. In addition, since the stopper structure can be configured without providing a projection or the like protruding in the radial direction on the worm, the assembling property by inserting the worm in the axial direction with respect to the fixed body is not hindered, and the assembling property is improved. be able to.

  Next, a third invention is the above-described first or second invention, wherein at least one of the worm and the screwing structure is elastically supported by the elastic body with respect to the fixed body, and the worm has a predetermined thrust or more. A resistance force due to the elastic force of the elastic body is applied to the operation of the screwing structure when the force is applied.

  According to the third aspect of the invention, a resistance force due to the elastic force of the elastic body is applied to the operation in which the screwing structure is screwed when a predetermined thrust force is applied to the worm. Thus, it is possible to apply a locking force for restricting the rotational movement of the worm shaft without the stopper structure.

It is the schematic of the vehicle seat provided with the gear reducer of Example 1. FIG. It is a disassembled perspective view of a gear reducer. It is a partial sectional view showing the internal structure in the assembly state of a gear reducer. It is the IV section enlarged view of FIG. It is a principal part enlarged view showing the state in which the thrust force more than predetermined was applied to the worm at the time of forward rotation and screwed together. It is the principal part enlarged view showing the state which applied the thrust more than predetermined to the worm at the time of reverse rotation, and screwed together. It is a principal part enlarged view of the gear reducer of Example 2. FIG. It is a principal part enlarged view showing the state in which the thrust force more than predetermined was applied to the worm at the time of forward rotation and screwed together. It is the principal part enlarged view showing the state which applied the thrust more than predetermined to the worm at the time of reverse rotation, and screwed together.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing.

  First, the configuration of the power transmission mechanism according to the first embodiment will be described with reference to FIGS. As shown in FIG. 1, the power transmission mechanism of the present embodiment is provided in a vehicle seat, and the rotational output of an electric motor 4 provided for adjusting the backrest angle of the seat back 1 is reclining on each side. The gear reducer 5 is configured to decelerate and output to the devices 3 and 3. Here, the above-described seat back 1 has lower end portions on both sides of the skeleton frame 1A connected to rear end portions on both sides of the skeleton frame 2A of the seat cushion 2 via electric reclining devices 3 and 3, respectively. The reclining devices 3 and 3 on each side are driven by receiving the transmission of the rotational driving force of the electric motor 4 and the backrest angle is adjusted.

  Here, each of the reclining devices 3 and 3 described above is normally in a state of being prevented from rotating, and is held in a state in which the backrest angle of the seat back 1 is fixed. Each reclining device 3, 3 has a rod 3 </ b> R inserted through the center of the reclining device 3, and is rotated on one side or the other side in accordance with the rotational drive of the electric motor 4. The seat back 1 is operated to raise and lower the backrest angle.

  Specifically, the above-described rod 3R is connected to a gear reducer 5 connected to the electric motor 4, and receives a transmission of rotational power decelerated from the electric motor 4 via the gear reducer 5 to rotate the shaft. It has come to be. Here, the gear reduction device 5 described above is attached to a bracket 1 </ b> Aa coupled to the skeleton frame 1 </ b> A of the seat back 1, and the electric motor 4 is connected to the gear reduction device 5.

  The rod 3R is inserted in the axial direction across the reclining devices 3 and 3 and the gear reducer 5 on each side described above, and is provided in a state in which these are connected in a state where power can be transmitted to each other. Yes. Specifically, the rod 3R described above is provided so as to be inserted into the reinforcing pipe 1Ab spanned between the skeleton frames 1A of the seat back 1, so that the reinforcing pipe 1Ab does not receive an external load such as a backrest load. It is provided in a protected state.

  Hereinafter, the configuration of the above-described gear reducer 5 will be described in detail with reference to FIGS. Here, as shown in FIG. 2, the gear reducer 5 includes a resin-made main body case 10 and a lid case 20, a metal worm 30, a resin-made first gear 40, and a second gear 60. And a metal support shaft 50. The gear reduction device 5 described above is configured by assembling each gear component and shaft component inside a housing case configured by assembling the main body case 10 and the lid case 20. Here, the main body case 10 corresponds to the fixed body of the present invention.

  As shown in FIG. 3, the electric motor 4 is attached to the upper portion of the main body case 10, and the rotation output of the electric motor 4 is transmitted from the worm 30 to the first gear 40 and the second gear. 60 is transmitted in order to be decelerated and output to the rod 3R. Note that the basic configuration of the electric motor 4 described above is a well-known one disclosed in a document such as Japanese Patent Application Laid-Open No. 2008-86110, and detailed description thereof will be omitted.

  Hereinafter, the structure of each part of the above-described gear reducer 5 will be described in detail. First, the main body case 10 will be described. As shown in FIG. 2, the main body case 10 includes a first housing recess 11 in which the first gear 40 is set, a second housing recess 12 in which the second gear 60 is set, and the above-described electric power. The pedestal portion 13 on which the motor 4 is set and the screw tightening portions 14 to be screwed to the lid case 20 are configured. The first housing recess 11 is a cylinder having an outer diameter that is slightly larger than the outer diameter of the worm wheel portion 41 so that a worm wheel portion 41 of the first gear 40 described later can be received inside the recess. It is formed in a concave shape of the mold. A first shaft hole 11A is formed at the center of the first housing recess 11 to receive one end of a support shaft 50, which will be described later, and to support the end rotatably. Here, the worm wheel portion 41 corresponds to the worm wheel of the present invention.

  Then, on the side surface of the first housing recess 11, an insertion port 13 </ b> A formed so as to penetrate straight through the center of the base portion 13 in the illustrated height direction is exposed in the first housing recess 11. An opening window 11B is formed. Further, the second receiving recess 12 is formed at a stepped level with respect to the first receiving recess 11 described above, and receives a spur gear portion 64 of the second gear 60 described later in the recess. As shown in the figure, it is formed in a cylindrical concave shape having an outer diameter slightly larger than the outer diameter of the spur gear portion 64. Then, in the central portion of the second housing recess 12 described above, a second shaft that receives the shaft portion 61 that protrudes from the central portion of the second gear 60 and supports the coaxial portion 61 so as to be axially rotatable. A hole 12A is formed.

  Then, on the inner surface facing the second gear 60 of the second accommodating recess 12 described above, an arc convex portion 12B protruding in an arc shape in the axial direction from the same surface is formed. The arc convex portion 12B is formed in an arc shape drawn around the rotation center of the second gear 60, and the plate surface of the second gear 60 is brought into full contact with the main body case 10. Instead, the second gear 60 is supported so as to be smoothly rotated with respect to the main body case 10 by making contact only with the region where the arc-shaped convex portion 12B is formed.

  Next, the lid case 20 will be described. The lid case 20 is formed on an inner surface facing the first housing recess 11 of the main body case 10 described above, and a first support portion 21A protruding in an arc shape in the axial direction, and the first support portion. The first shaft hole 21B formed at the center of the region surrounded by the portion 21A and the inner surface facing the second housing recess 12 of the main body case 10 are cylindrical in the axial direction. The second support portion 22 </ b> A that protrudes and the screw tightening portion 24 that is screwed together with the screw tightening portion 14.

  The above-mentioned first support portion 21A receives the spur gear portion 42 of the first gear 40 in the axial direction, applies the outer peripheral surface of the spur gear portion 42 by the inner peripheral surface, and the spur gear portion 42 It is a functional part that supports it so that it is not misaligned. Further, the first shaft hole 21B is a functional part that receives the other end portion of the support shaft 50 described above and supports the end portion so as to be capable of rotating the shaft. Further, the second support portion 22A is a functional portion that receives the shaft portion 62 formed to protrude from the center portion of the second gear 60 in the cylinder, and supports the coaxial portion 62 so as to be axially rotatable. .

  The above-described second support portion 22A is formed so that the inside of the cylinder penetrates in the axial direction, and a rod 3R that is integrally connected to a second gear 60 described later is provided in the inside of the cylinder in the axial direction. It is designed to be inserted. Next, the configuration of the worm 30 will be described. The worm 30 is composed of a metal round bar-like member, and spiral teeth 31 are cut on the outer peripheral portion in the central region in the longitudinal direction. The worm 30 is inserted into the insertion port 13A formed through the pedestal 13 of the main body case 10 described above, so that the spirally cut teeth 31 formed in the central region thereof are It is in a state of being exposed in the ten open windows 11 </ b> B and is assembled to the main body case 10.

  A flexible wire 34 that is directly connected to the rotation output shaft of the electric motor 4 is inserted into the upper end portion of the shaft of the worm 30 and attached to the worm 30 in an integral state in the rotation direction. Here, the flexible wire 34 is formed by winding a thin steel material in the shape of a square bar, and both ends connected to the worm 30 and the electric motor 4 are tightly wound, and the center thereof is formed. The part is softly wound so that it can swing.

  Even if the rotation output shaft of the electric motor 4 is assembled at a position displaced to some extent with respect to the central axis of the worm 30 by the flexible wire 34, the rotation output from the electric motor 4 is caused by the swing motion of the flexible wire 34. Can be satisfactorily transmitted to the worm 30. Next, the configuration of the first gear 40 will be described. The first gear 40 includes a worm wheel portion 41 that meshes with the worm 30 and receives rotational power from the worm 30, and a spur gear portion 42 that rotates integrally with the worm wheel portion 41. And are formed side by side in the axial direction so as to rotate integrally around each other.

  In the first gear 40, the above-described round bar-shaped support shaft 50 is inserted into a shaft hole 43 formed through the center of the first gear 40, and one end and the other end of the support shaft 50 are respectively described above. By being inserted into the first shaft hole 11 </ b> A of the main body case 10 and the first shaft hole 21 </ b> B of the lid case 20 and supported so as to be rotatable about the shaft, the main body case 10 and the lid case 20 can be pivoted. It can be assembled in a supported state. Specifically, in the first gear 40, the worm wheel 41 is set in the first housing recess 11 with respect to the main body case 10, and the teeth 41 </ b> A enter the opening window 11 </ b> B and the worm 30. The teeth 31 are engaged with each other and assembled.

  The first gear 40 is set in a state where the spur gear portion 42 is inserted into the space surrounded by the first support portion 21A with respect to the lid case 20, and the outer periphery of the teeth 42A is set. The surface is assembled in a state of being supported from the outer peripheral side by the inner peripheral surface of the first support portion 21A. Next, the configuration of the second gear 60 will be described. The second gear 60 includes a spur gear portion 64 that meshes with the spur gear portion 42 of the first gear 40 described above and receives transmission of rotational power from the spur gear portion 42.

  The second gear 60 has a shaft portion 61 inserted into the second shaft hole 12A of the main body case 10 and supported so as to be rotatable in the center, and a second support portion 22A of the lid case 20. A shaft portion 62 that is inserted into the shaft and supported so as to be rotatable is formed so as to protrude in a cylindrical shape on one side and the other side in the axial direction. In the above-described second gear 60, the above-described one-side shaft portion 61 and the other-side shaft portion 62 are connected to the second shaft hole 12A of the main body case 10 and the second support portion 22A of the lid case 20. By being inserted and supported so as to be rotatable about the shaft, the main body case 10 and the lid case 20 are assembled so as to be supported so as to be rotatable about the shaft.

  Specifically, the second gear 60 is set in the second housing recess 12 of the main body case 10 by the above-described assembly, and the teeth 64 </ b> A of the spur gear portion 64 thereof are the spur gear portion 42 of the first gear 40. The teeth 42A are engaged and assembled. Here, a shaft hole 65 through which the rod 3 </ b> R serving as the output shaft is inserted is formed in the center portion of the second gear 60 so as to penetrate in the axial direction.

  The inner peripheral surface of the shaft hole 65 and the outer peripheral surface of the rod 3R have serrated grooves that fit into each other. By inserting the rod 3R into the shaft hole 65, the serrated shape of each other is reduced. Accordingly, the rod 3R is assembled to the second gear 60 in an integrated state in the rotational direction. Therefore, by the above assembly, the worm 30, the first gear 40, the second gear 60, and the rod 3R are assembled in a state where they are engaged with each other so as to be able to transmit power.

  As a result, the gear reducer 5 uses the rotational power output from the electric motor 4 as the difference in the number of teeth between the worm 30 and the worm wheel portion 41, the spur gear portion 42 of the first gear 40, and the second gear. Due to the difference in the number of teeth with the spur gear portion 64 of the gear 60, the gear is reduced to a reduction ratio corresponding to each difference in the number of teeth and output to the rod 3R. Incidentally, as shown in FIG. 4, a large load is applied to the worm wheel portion 41 from the output side at the attachment portion of the worm 30 to the main body case 10, and the power from the worm 30 to the worm wheel portion 41 is applied. A limiter mechanism that prevents rotational movement of the electric motor 4 from the worm 30 to the worm wheel portion 41 by preventing the worm 30 from rotating and rotating relative to the body case 10 when a certain resistance is applied to the transmission. Is provided.

  Specifically, the above-described limiter mechanism is configured such that the worm 30 rotating on the shaft by receiving the rotational driving force of the above-described electric motor 4 has a lower side or upper side of the worm wheel portion 41 shown in the drawing by a resistance action on the output side. When a thrust force of a certain level or more, which is pushed along with the rotational movement of the shaft, is applied, the male screw 33A formed at the lower end of the worm 30 is inserted into the insertion port 13A of the main body case 10 as shown in FIG. Or a male screw 33B formed at the upper end of the worm 30 as shown in FIG. 6 is fixed in the insertion portion 4A of the electric motor 4. It is configured to prevent axial movement of the worm 30 in each direction accompanying rotation of the electric motor 4 by being screwed into the female screw Ba of the installed nut 15B. Here, the insertion part 4A of the electric motor 4 corresponds to the fixed body of the present invention.

  Hereinafter, the screwed structure between the worm 30 and the nuts 15A and 15B will be described in more detail. Here, as shown in FIG. 4, the worm 30 is configured so that the upper and lower portions of the shaft formed in a round bar shape are respectively inserted into bushes 16 </ b> A and 16 </ b> B provided in the body case 10. 16A and 16B are provided so as to be capable of rotating the shaft. The lower bushing 16A described above is set in a state where the worm 30 is inserted and set in the insertion port 13A before the worm 30 is inserted in the insertion port 13A of the main body case 10, and is projected in a flange shape. Is provided on the step portion 13B in the insertion port 13A of the main body case 10.

  The upper bushing 16B is inserted into the insertion port 13A after the worm 30 is inserted into the insertion port 13A of the main body case 10 and set, and the head of the shape protruding in the flange shape is It is set and provided on the step portion 13C in the insertion port 13A of the case 10. The upper bushing 16A has a difference between the stepped portion 13C of the body case 10 and the electric motor 4 by the insertion portion 4A of the electric motor 4 inserted into the insertion port 13A after the assembly of the bushing 16A. It is assembled in a state of being sandwiched in the axial direction by the insertion portion 4A.

  Here, seat surface portions 32A and 32B each having a shape in which the outer peripheral portion protrudes into a flange shape are formed at the upper and lower portions of the region where the teeth 31 of the worm 30 are formed. Cylindrical rubbers 17A and 17B and ring-shaped washers 18A and 18B are respectively inserted and attached to the upper and lower round bar-shaped portions of the worm 30 shaft. These rubbers 17A and 17B and washers 18A and 18B are provided between the respective seating surface portions 32A and 32B and the heads of the respective bushes 16A and 16B. Here, the rubbers 17A and 17B correspond to the elastic body of the present invention.

  Thereby, the above-described worm 30 is elastically supported in both directions in the axial direction with respect to the main body case 10 by the elastic force of the rubbers 17A and 17B. Here, the washers 18A and 18B are formed of a resin material, and function as seats of contact portions between the rubbers 17A and 17B and the seat surface portions 32A and 32B of the worm 30. As shown in FIG. 4, the lower end portion of the insertion hole 13 </ b> A of the main body case 10 into which the lower end portion of the worm 30 is inserted and the electric motor 4 into which the upper end portion of the worm 30 is inserted. Nuts 15A and 15B having female screws Aa and Ba formed at the center are integrally fixed to the upper end of the insertion portion 4A, respectively.

  These nuts 15 </ b> A and 15 </ b> B are formed in a square shape (polygonal shape) so as not to rotate with respect to the main body case 10 or the electric motor 4, and are inserted into the main body case 10 or the electric motor 4. 4A is provided in a state of being integrally joined to each other by insert molding. As shown in FIG. 4, these nuts 15 </ b> A and 15 </ b> B are arranged so as to be spaced apart from each other in the axial direction with respect to the upper end portion and the lower end portion of the worm 30 that are always elastically supported in the axial direction described above. Has been.

  As a result, the worm 30 is always engaged with the nuts 15A and 15B without being screwed into the nuts 15A and 15B on each side, even if the worm 30 rotates by receiving the rotational power from the electric motor 4 and rotating the shaft. It is supposed to run idle. However, as shown in FIG. 5, when the worm 30 is pushed with axial rotation to the lower side of the worm wheel portion 41 by the thrust force received by the resistance action on the output side, the lower side While crushing the rubber 17A, the male screw 33A formed at the lower end of the rubber 17A is screwed into the female screw Aa of the lower nut 15A so as to be integrally connected to the nut 15A in the axial direction.

  The worm 30 is in a state in which the above-described male screw 33A at the lower end is screwed and rotated to the female screw Aa of the nut 15A up to the end position of the screw thread, thereby preventing the screwed rotation with respect to the nut 15A. Become. As a result, the worm 30 is prevented from rotating and rotating relative to the main body case 10, and power transmission from the worm 30 to the worm wheel portion 41 is prevented. As a result, the rotational power of the electric motor 4 is not transmitted to the worm wheel part 41 receiving a large load from the output side, so that an unreasonable load is applied to the power transmission part such as the worm wheel part 41 or the worm 30. It can be avoided. The screwed state of the worm 30 with respect to the nut 15A is released by rotating the worm 30 in the direction opposite to that described above by driving the electric motor 4 in the opposite direction.

  Similarly, as shown in FIG. 6, when the electric motor 4 rotates in the direction opposite to the above, the worm 30 is driven by the thrust force received by the resistance action on the output side thereof. 41, when the upper rubber 17B is crushed, the male screw 33B formed at the upper end is screwed into the female screw Ba of the upper nut 15B. Thus, the nut 15B is integrally connected in the axial direction.

  The worm 30 is in a state in which the above-described male screw 33B at the upper end portion is screwed and rotated to the female screw Ba of the nut 15B to the end position of the screw thread, thereby preventing the screwing rotation with respect to the nut 15B. Become. As a result, the worm 30 is prevented from rotating and rotating relative to the main body case 10, and power transmission from the worm 30 to the worm wheel portion 41 is prevented. As a result, the rotational power of the electric motor 4 is not transmitted to the worm wheel part 41 receiving a large load from the output side, so that an unreasonable load is applied to the power transmission part such as the worm wheel part 41 or the worm 30. It can be avoided. The screwed state of the worm 30 with respect to the nut 15A is released by rotating the worm 30 in the direction opposite to that described above by driving the electric motor 4 in the opposite direction.

  Therefore, for example, while the seat back 1 (see FIG. 1) is raised or lowered by the rotational driving force of the electric motor 4, a large load accompanying a vehicle collision is input to the seat back 1 and the like. When a large load acting as a resistance is applied to the driving for raising and tilting, an unreasonable load is not applied to each power transmission unit of the gear reducer 5 by the rotational driving force continuously output from the electric motor 4. Thus, transmission of the rotational power of the electric motor 4 can be prevented.

  As described above, according to the configuration of the gear reducer 5 (power transmission mechanism) of the present embodiment, a load serving as a resistance from the output side is applied to the worm wheel portion 41, and a thrust force of a predetermined level or more is applied to the worm 30. When it works, the screwing structure provided between the worm 30 and the main body case 10 (and the insertion part 4A of the electric motor 4) is screwed, and the rotational movement of the worm 30 relative to the main body case 10 is restricted. It is held in a state. Thereby, when a large load is applied to the worm wheel portion 41 from the output side, the power transmission can be interrupted so that the rotational power of the electric motor 4 is not transmitted from the worm 30 to the worm wheel portion 41.

  Further, the above-described screwed structure is configured as a combination of male screws 33A and 33B formed on the worm 30 and female screws Aa and Ba of nuts 15A and 15B integrally provided on the body case 10, and Since the stopper structure that stops the rotation is configured as the end portion of the thread of the male threads 33A and 33B, the screwed structure and the stopper structure can be configured simply and with a small number of parts. it can. Further, since the stopper structure can be configured without providing the worm 30 with a protrusion or the like protruding in the radial direction, the assembling property of inserting the worm 30 into the main body case 10 in the axial direction is not hindered, and the assembling property is not hindered. Can also be improved.

  Further, a resistance force due to the elastic force of the rubbers 17A and 17B is applied to the operation in which the screwed structure is engaged when a thrust force of a predetermined level or more is applied to the worm 30. Thus, it is possible to apply a locking force that restricts the rotational movement of the worm 30 without the stopper structure.

  Then, the structure of the gear reducer 5 (power transmission mechanism) of Example 2 is demonstrated using FIGS. In the present embodiment, portions that are substantially the same in configuration and operation as those of the gear reducer 5 described in the first embodiment are denoted by the same reference numerals and description thereof is omitted, and different portions are provided. Will be described in detail.

  As shown in FIG. 7, the gear reducer 5 of the present embodiment includes nuts 15 </ b> A and 15 </ b> B on the respective sides that are screwed with male screws 33 </ b> A and 33 </ b> B of the worm 30, respectively, into which the main body case 10 and the electric motor 4 are inserted. The part 4A is movable in the axial direction (vertical direction in the figure), and is elastically supported by rubber 19A, 19B provided between the bushes 16A, 16B on each side. . Here, the rubbers 19A and 19B correspond to the elastic body of the present invention. As a result, as shown in FIGS. 8 to 9, the worm 30 is screwed with the nuts 15 </ b> A and 15 </ b> B on each side by a thrust force, so that the nuts 15 </ b> A and 15 </ b> B on each side are accompanied with the shaft rotation of the worm 30. The rubbers 19A and 19B on each side are crushed and drawn toward the end of each side of the worm 30.

  In this manner, the nuts 15A and 15B on the respective sides are elastically supported by the rubbers 19A and 19B, and the screwing structure when the thrust force exceeding a predetermined level is applied to the worm 30 is engaged. In addition to the action of the resistance force due to the elastic force of the rubbers 17A, 17B shown in Example 1, the resistance force due to the elastic force of the rubbers 19A, 19B is also given, so that these rubbers 17A, 17B and The combination of the rubbers 19A and 19B can adjust the locking force that restricts the axial rotation of the worm 30.

  As mentioned above, although embodiment of this invention was described using two Examples, this invention can be implemented with various forms other than the said Example. For example, the power transmission mechanism of the present invention operates a driving device for raising and lowering a vehicle seat to change the installation height with respect to the floor, a driving device for folding the seat back, and an active headrest. It can be applied as a mechanism for transmitting rotational power of various driving devices provided in association with the vehicle seat.

  Further, the power transmission mechanism of the present invention can be applied to various mechanisms that transmit rotational power using a worm gear, in addition to the uses related to the vehicle seat described above. Further, in each of the above embodiments, as a stopper structure that stops the screwing rotation of the male screw and the female screw that are screwed together with the shaft rotation of the worm, a structure that is rotated and stopped by the terminal portion of the male screw is exemplified. A structure in which rotation is stopped by the end portions of the female screws Aa and Ba may be employed. Further, between the worm and the fixed body, a contact portion that receives the movement of the worm in the axial direction with respect to the fixed body by the contact and stops rotation may be set. Moreover, the structure which stops the axial direction movement with respect to the fixed body of a worm | warm by the elastic force by the collapse of an elastic body may be sufficient.

  In addition to rubber, various elastic members such as a spring can be applied as the elastic body. In addition, when the thrust force is applied to the worm, the configuration in which the worm moves in the axial direction with respect to the fixed body against the elastic force of the elastic body is illustrated. However, the worm is applied to the fixed body by the pressing force by the thrust force. On the other hand, it may be configured to move in the axial direction with sliding resistance due to friction.

DESCRIPTION OF SYMBOLS 1 Seat back 1A Frame | frame 1Aa Bracket 1Ab Reinforcement pipe 2 Seat cushion 2A Frame | frame 3 Reclining apparatus 3R Rod 4 Electric motor 4A Insertion part (fixed body)
5 Gear reducer (power transmission mechanism)
10 Body case (fixed body)
DESCRIPTION OF SYMBOLS 11 1st accommodation recessed part 11A 1st shaft hole 11B Opening window 12 2nd accommodation recessed part 12A 2nd shaft hole 12B Arc convex part 13 Base part 13A Insertion port 13B Step part 13C Step part 14 Screw fastening part 15A, 15B Nut Aa, Ba Female thread 16A, 16B Bushing 17A, 17B Rubber (elastic body)
18A, 18B Washer 19A, 19B Rubber (elastic body)
DESCRIPTION OF SYMBOLS 20 Lid case 21A 1st support part 21B 1st shaft hole 22A 2nd support part 24 Screw tightening part 30 Worm 31 Tooth 32A, 32B Seat surface part 33A, 33B Male thread 34 Flexible wire 40 1st gear 41 Warm wheel Part (worm wheel)
41A tooth 42 spur gear part 42A tooth 43 shaft hole 50 support shaft 60 second gear 61 shaft part 62 shaft part 64 spur gear part 64A tooth 65 shaft hole

Claims (3)

In the power transmission mechanism that transmits rotational power by worm gear,
The worm gear is
A worm that rotates by receiving rotational power from an electric motor;
A worm wheel provided in mesh with the worm and rotating in response to transmission of rotational power from the worm,
The worm is supported so as to be rotatable with respect to a fixed body, and a screwed structure of a male screw and a female screw that are screwed together with the rotation of the worm shaft between the worm and the fixed body. The screwed structure is normally in a non-screwed state, but the worm wheel is subjected to a load due to resistance from the output side and a thrust force of a predetermined level or more acts on the worm to screw together. Furthermore, the movement of the screwing structure in the direction in which the screwing structure is screwed between the worm and the fixed body is restricted, and the rotational movement of the worm relative to the fixed body is restricted. A power transmission mechanism characterized in that a stopper structure is provided. The power transmission mechanism according to claim 1,
The screwing structure is configured as a combination of a male screw formed on the worm and a female screw provided integrally fixed to the fixed body in the rotation direction, and the stopper structure is the male screw or the A power transmission mechanism configured as a terminal portion of a female thread. A power transmission mechanism according to claim 1 or claim 2,
An operation in which at least one of the worm or the screwing structure is elastically supported by the elastic body with respect to the fixed body, and the screwing structure is screwed when a thrust force of a predetermined level or more is applied to the worm. A power transmission mechanism characterized in that a resistance force due to the elastic force of the elastic body is applied to the power transmission mechanism.

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