Seat driving device

A seat 1 has a seat cushion 2 and a seat back 3 and is mounted on a vehicle such as a car. A reclining mechanism 4 capable of adjusting the tilt angle of the seat back 3 is provided between the seat cushion 2 and the seat back 3. The reclining mechanism 4 has a seat driving device 21 provided with an electric motor 22 and a speed reduction mechanism 23. The speed reduction mechanism 23 has a worm shaft 45 connected to a motor shaft 34 of the motor 22 and a worm wheel 47 meshed with a worm 46 of the worm shaft 45. The worm 46 is a multi-thread worm having two or more threads.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a vehicle seat driving device and, more particularly, to an electric seat driving device that performs tilting operation of a seat back.

Related Art Statement

As a vehicle seat such as a car seat, there is known one provided with a seat tilting mechanism that adjusts the reclining angle of a seat back and moves the seat back between a use position and a storage position. Conventionally, such a seat tilting mechanism is generally manually operated; however, in recent years, the number of vehicles mounted with a seat whose tilting operation is electrically performed is increasing mainly in luxurious cars. JP 09-109750 A describes a vehicle seat in which reclining operation of the seat back is electrically performed by an electric motor. In the disclosed technology, the reclining angle of the seat back is adjusted by a seat back adjuster operated by a reclining motor.

In the electric seat as disclosed in JP 09-109750 A, the reclining motor disposed on both sides of the seat is used to change the angle between an upper arm member mounted to the seat back side and a lower arm member mounted to the seat cushion side to change the seat back reclining angle. The reclining motor is mounted with a speed reduction mechanism using a worm and a worm wheel. The body side of the motor is fixed to one of the upper and lower arm members, and the output shaft of the speed reduction mechanism is fixed to the other one of them. When the output shaft is rotated, the angel between the arm members is changed to tilt the seat back.

However, in a conventional electric seat, when an electric motor for drive dose not work due to failure or the like, the seat back is fixed at that position, which may prevent the seat back from being adjusted to a desired position. Particularly, when a failure occurs in a state where the seat back is at the storage position, the seat cannot be returned to the use state, that is, the seat cannot carry an occupant.

In this case, as an emergency operation at the time of a motor failure, a tool or the like may be used to rotate the output shaft of the reclining motor to manually return the seat back to the use state. However, the electric seat is generally mounted with a reverse prevention mechanism, so that the motor side has a structure that does not take the reverse force into account. Therefore, when the shaft directly coupled to the motor is attempted to be rotated, the worm or worm wheel of the speed reduction mechanism part may be damaged. Thus, it is difficult to externally manually return the seat back to the use position, so that seat reclining operation is difficult to perform during abnormality.

Further, when the seat back is to be displaced between the use position and the storage position, if a motor is driven to move the seat back, it takes some time. The movement to the storage position involves less necessity to stop the seat back halfway, and the seat back can be moved in a short time by manual operation. Thus, in the case of the electric seat, temporal stress may be given on a user although the movement work of the seat back itself can be facilitated.

SUMMARY OF THE INVENTION

A seat driving device according to the present invention is provided in a seat having a seat back whose tilt angle can be changed and performs tilting operation of the seat back using an electric motor as a driving source. The seat driving device includes: the electric motor; and a speed reduction mechanism that decelerates rotation of the electric motor and transmits it to the seat back side. The speed reduction mechanism includes a worm shaft connected to a rotary shaft of the electric motor and a worm wheel meshed with a worm formed in the worm shaft and connected to the seat back side. The worm is a multi-thread worm having two or more threads.

In the present invention, the multi-thread worm is used in the speed reduction mechanism of the seat driving device, so that it is possible to speed up the tilting operation of the seat back without changing the motor rotation speed. Thus, performance of the seat can be improved while suppressing motor operation noise. Further, the moving time of the seat back can be shortened, allowing temporal stress on a user to be alleviated. Further, adopting the multi-thread worm facilitates rotation of the worm from the worm wheel side, which in turn facilitates manual reverse operation in emergency. This allows the manual reverse operation to be performed from outside the seat driving device, and hence, the state of the seat back can be manually changed even in emergency. Thus, even when the motor fails to operate, the seat back can still be moved to a desired position. Further, even when a failure occurs in a state where the seat back is at the storage position, the seat can be returned to the use state.

In the seat driving device, the speed reduction mechanism may further include an output member connected to the worm wheel and coupled to the seat back side. The seat driving device may be configured to be attached with a manually operable member with which the output member can be operated from outside the device so as to allow the warm shaft to be rotated from outside the device using the manually operable member when the electric motor fails to operate. The lead angle of the worm may be in a range of 14° to 33°.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. An object of the present embodiment is to provide a seat driving device capable of manually performing angle adjustment operation of a seat back without damaging a motor even at failure. Another object of the present embodiment is to quickly move the seat back to the storage position to alleviate temporal stress on a user.

FIG. 1is an explanatory view illustrating the configuration of a vehicle seat using a seat driving device according to the embodiment of the present invention. As illustrated inFIG. 1, a seat1is constituted of a seat cushion2and a seat back3and is mounted on a vehicle such as a car. A reclining mechanism4is provided between the seat cushion2and the seat back3. In the seat1, the reclining mechanism4that can appropriately adjust the tilt angle of the seat back3has a seat driving device21using an electric motor. That is, the seat1is an electric seat.

A lower rail5and an upper rail6are provided in a pair at the left and right sides of the seat cushion2. The lower rail5is fixed to the floor of the vehicle, and upper rail6is mounted so as to be movable with respect to the lower rail5. The seat back3has a substantially U-like shape seat back frame11. The lower end side of the frame11is connected to the upper rail6of the seat cushion2through the reclining mechanism4. The reclining mechanism4has an upper arm12and a lower arm13mutually turnably connected to each other. The upper arm12is mounted to the lower end portion of the frame11. The lower arm13is mounted to the rear end portion of the upper arm12. The left and right reclining mechanisms4are connected by a connecting rod14. The left and right reclining mechanisms4operate in sync with each other during reclining.

A recliner15using a differential transmission mechanism (taumel mechanism) is interposed between the upper arm12and the lower arm13. The recliner15has a turning plate16fixed to the upper arm12side and a fixed plate17fixed to the lower arm13side. A sliding locking member (not illustrated) connected to the connecting rod14is provided between the turning plate16and the fixed plate17. The sliding locking member can transition between a lock state and a lock release state to thereby change the connection state between the turning plate16and the fixed plate17. When the connecting rod14is rotated by the seat driving device21in a state where the sliding locking member is put in the lock release state, the turning plate16is turned. As a result, the upper arm12is turned with respect to the lower arm13, whereby the seat back3is reclined.

The seat driving device21is provided in the reclining mechanism4as a driving source for reclining operation.FIG. 2is a perspective view of the seat driving device21according to the embodiment of the present invention, andFIG. 3is an explanatory view illustrating the internal configuration of the seat driving device21. As illustrated inFIGS. 2 and 3, the seat driving device21is constituted as so-called a motor unit with speed reducer and has an electric motor22and a speed reduction mechanism part23which are integrally formed. In the seat1, when the motor22is actuated by operating a reclining switch (not illustrated), the tilt angle of the seat back3is changed, whereby the seat back3is displaced between a flat position X and a storage position Y (seeFIG. 1).

The motor22is a motor with brush and has a bottomed cylindrical motor housing24and an armature25rotatably supported in the housing24. The housing24is fitted such that an opening part24athereof faces the speed reduction mechanism part23. An outer flange part24bis formed in the periphery of the opening part24aof the housing24so as to be bent. A bolt hole26is formed in the outer flange part24b. A bolt27is inserted through the bolt hole26and fastened to the speed reduction mechanism part23, whereby the motor22and the speed reduction mechanism part23are integrated.

A plurality of magnets28are attached to an inner peripheral surface24cof the housing24by an adhesive or the like. At the bottom of the housing24, a protruding part29is formed so as to protrude axially outward. A sliding bearing31is fitted and fixed to the inside of the protruding part29. A thrust plate32is provided at the bottom of the protruding part29. The thrust plate32receives a thrust load from a motor shaft34through a steel ball33.

The armature25has the motor shaft (rotary shaft)34, an armature core35externally inserted and fixed to the shaft34, and a commutator36disposed on the speed reduction mechanism part23side relative to the armature core35. One end portion (the left end side inFIG. 3) of the shaft34is rotatably supported to the housing24by the sliding bearing31provided in the housing24. The other end portion (the right end portion inFIG. 3, i.e., speed reduction mechanism part23side end portion) of the shaft34is rotatably supported to the housing24by a sliding bearing37. The sliding bearing37is mounted to a brush holder38press-fitted and fixed to the housing24.

The armature core35is a member obtained by laminating magnetic materials such as electromagnetic steel sheets and is disposed at a position corresponding to the magnets28. A winding (not illustrated) is wound around the armature core35, and the terminal portion of the winding is connected to the commutator36. The commutator36is a substantially columnar member and is disposed on the other end side of the armature25. A plurality of plate-like segments39are arranged side by side on the outer peripheral surface of the commutator36. The segments39are connected with the terminal portion of the winding. The commutator36is in sliding contact with a brush41housed in the brush holder38. The brush41is electrically connected to an external power supply (not illustrated), whereby current is supplied to the winding through the brush41and commutator36.

The speed reduction mechanism part23has a box-shaped gear case42having one opening surface and a gear cover43that closes the opening of the gear case42. The gear cover43is fastened and fixed to the gear case42by a tapping screw44. A worm shaft45to which power of the motor22is transmitted, a worm wheel47to be meshed with a worm46of the worm shaft45, and an output wheel (output member)48to be meshed with the worm wheel47are housed in a space closed by the gear case42and the gear cover43. In the speed reduction mechanism part23, two-step speed reduction is performed by a combination of the worm46and the worm wheel47and that of the worm wheel47and the output wheel48, thereby ensuring a large reduction ratio with a small space. In the seat1, a multi-thread worm having two or more threads is used (two threads in the present embodiment) as the worm46.

The worm shaft45is disposed coaxially with the shaft34and is connected to the other end side of the shaft34through a joint member49so as not to be relatively rotated. The worm shaft45is rotatably supported to the gear case42by two sliding bearings51and52provided in the gear case42. The worm wheel47to be meshed with the worm shaft45has a large-diameter resinous gear47aand a small-diameter gear47bmade of a metal sintered body insert-molded in the large-diameter gear47a. The large-diameter gear47aand the small-diameter gear47bare disposed concentrically with each other. The large-diameter gear47ais meshed with the worm shaft45. The small-diameter gear47bis meshed with an output gear48aof the output wheel48. The worm wheel47is axially supported by a worm wheel shaft53. The worm wheel shaft53is rotatably supported by bearing parts (not illustrated) formed respectively in the gear case42and gear cover43.

The output wheel48is a substantially disk-shaped member made of a metal sintered body and has the output gear48aat the outer periphery thereof. An output take-out part48bthat outputs a rotation torque to an external device is formed in substantially the center of the output wheel48. The output take-out part48bis a hole that penetrates the output wheel48in the thickness direction thereof. The connecting rod14connecting the left and right reclining mechanisms4is inserted through the output take-out part48b. An engaging part48cis formed at the inner peripheral surface of the output take-out part48balong the peripheral direction. The engaging part48cis engaged with a concave part (not illustrated) formed in the connecting rod14. This restricts relative rotation between the connecting rod14and the output take-out part48b, allowing a rotation torque to be output to the connecting rod14.

The gear case42is a member made of, e.g., resin and is formed by injection molding or the like. The gear case42has a motor mounting part54and a gear housing part55. The motor mounting part54is formed on the motor22side (left side inFIG. 3) of the gear case42. The gear housing part55is formed on the side opposite to the motor22with respect to the motor mounting part54. The motor mounting part54has an opening at its motor22side. The opening of the motor mounting part54and the gear housing part55communicate with each other through a through hole (not illustrated) through which the shaft34is inserted. The motor22is mounted to the gear case42by inserting the shaft34into the through hole from the opening side of the gear case42and then fixing the housing24to the motor mounting part54using the bolt27. A power-feeding connector56is assembled to the motor mounting part54. Power is supplied from the connector56to the motor22through the brush holder38.

A mounting hole57for fixing the seat driving device21to the vehicle is formed between the motor mounting part54and the gear housing part55. A bolt (not illustrated) is inserted through the mounting hole57, whereby the seat driving device21is mounted to the reclining mechanism4. In the seat1, the seat driving device21is fixed to the lower arm13side. When the motor22is actuated, the connecting rod14fixed to the upper arm12side is turned. As a result, the upper arm12is turned with respect to the lower arm13. This changes an angle between the arm13and the arm12to tilt the seat back3.

The gear cover43is formed into a substantially flat plate shape and closes the opening of the gear case42. That is, the gear cover43functions as a cover that covers the gear housing part55. The gear cover43has a worm wheel cover part58covering the worm wheel47and an output wheel cover part59covering the output wheel48. A bearing part (not illustrated) that rotatably supports the worm wheel shaft53is formed on the inner side of substantially the center of the cover part58. An output take-out hole61is formed at substantially the center of the cover part59. The connecting rod14is inserted through the output take-out hole61. A manually operable wrench (manually operable member)62for emergency use can be attached to the end portion of the connecting rod14. When the motor22is not actuated due to a failure or some other reason, a tilt state of the seat back3can be adjusted by externally directly rotating the connecting rod14.

In the seat driving device21, when a user operates the reclining switch, the motor22is actuated, and rotation of the shaft34is transmitted from the worm shaft45to the worm46, worm wheel47, and output wheel48. Then, the connecting rod14mounted to the output wheel48is turned to change the angle between the lower arm13and the upper arm12. As a result, the seat back3is displaced between the flat position X and the storage position Y. During the displacement of the seat back3between the positions X and Y, the rotation speed of the worm wheel47can be increased without changing a conventional motor specification since the multi-thread worm is used as the worm46in the seat driving device21, which in turn increases the motion of the seat back3. When the operation speed of the seat back3is not changed, the motor rotation speed can be reduced, which correspondingly can reduce the size of the motor, allowing miniaturization of the entire seat driving device21.

FIG. 4is a table illustrating the relationship between the number of threads of the worm46and seat back operation. As illustrated inFIG. 4, when the number of threads is increased, the rotation speed of the worm wheel47is increased in proportion thereto. That is, using the multi-thread worm can increase the operation speed of the seat back3without need of increasing the motor rotation speed. Thus, by using the seat driving device21according to the present invention, it is possible to improve the performance of the electric seat while suppressing motor operation noise. As a result, the moving time of the seat back3can be shortened, allowing temporal stress on the user to be alleviated.

Further, when the number of threads of the worm46is increased, a lead angle θ of the worm is also increased. A smaller lead angle may make it difficult to perform reverse rotation from the worm wheel47side. Therefore, in a conventional electric seat, manual reverse operation in emergency is difficult to perform as described above. On the other hand, in the seat driving device21according to the present invention, adopting the multi-thread worm as the worm46facilitates rotation of the worm46even when reverse rotation from the worm wheel47side is performed. As illustrated inFIG. 4, in a case where a two-thread worm is adopted, reversibility of armature25is reduced to half of that of a one-thread worm. Thus, even when an excessive reverse input is given to the worm wheel47, the worm shaft45is reversely rotated.

This allows reverse operation to be performed by the manually operable wrench62, whereby the state of the seat back3can be manually changed even in emergency. Thus, even when an electric motor for drive does not operate due to a failure or the like, the seat back3can be moved to a desired position. Further, even when a failure occurs in a state where the seat back is at the storage position, the seat can be returned to the use state, so that a problem that the seat cannot carry an occupant does not occur.

The present invention is not limited to the above embodiment and may be variously modified without departing from the spirit of the invention.

For example, in the above embodiment, a two-thread worm is used as the worm46; however, the number of threads is not limited to two, and a multi-thread worm having three or more threads can be used. However, in a worm having an excessively large number of threads, a tooth module size is reduced, and manufacturing man-hours are increased. Thus, it is preferable to use a worm having two to five threads (lead angle of about 14° to 33°). Further, in the above embodiment, the left and right upper arms12are connected by the connecting rod14and are subjected to synchronous control; alternatively, however, the seat driving devices21may be disposed to the left and right of the seat, respectively, and subjected to synchronous control so as to operate the upper arms12.

When the seat back3is to be tilted, the operation speed of the seat back3may be changed between rearward tilting operation (reclining operation) on the flat position X side and frontward tilting operation (storage operation) on the storage position Y side. That is, by changing the rotation speed of the motor22according to the switch operation, it is possible to perform the reclining operation comparatively slowly and perform the storage operation quickly.