JP2009073372A - Transmission ratio variable device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission ratio variable device mitigating a transmission torque applied at the time of locking and preventing displacement in a normal operating range. <P>SOLUTION: The transmission ratio variable device 30 is equipped with a torque limiting ring 80 to limit the transmission of torque between a motor shaft 34A and a lock holder 71. The torque limiting ring 80 is equipped with: a thin cylindrical ring portion 81 coming into frictional contact with an outer circumferential surface 35 of the motor shaft 34A; and a plurality of elastic pieces 82 projecting outward from an outer circumferential surface of the ring portion 81. An inner circumferential surface 71b of the lock holder 71 is provided with: a plurality of grooves 71c; and a plurality of engagement portions 71d each engaging with a front end portion 82a of each elastic piece 82 on the bottom side of each of the plurality of grooves 71c. Each groove 71c is formed such that a root portion 82b of the elastic piece 82 engaging with each engagement portion 71d abuts on the groove 71c in an elastically deformed condition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmission ratio variable device that changes a turning angle of a steered wheel with respect to a steering angle of a steering according to a driving situation.

  Generally, a transmission ratio variable device changes the transmission ratio between an input shaft connected to a steering and an output shaft connected to a steering system such as a steered wheel by rotating the motor, thereby steering the steering. Change the steering angle of the steered wheel with respect to the angle. The transmission ratio variable device includes a lock mechanism, and the lock mechanism includes a lock holder disposed via a torque limit mechanism on a motor shaft connected to an output shaft via a gear mechanism and the like, and an input shaft. And a lock lever that is connected to the input shaft via the housing and rotates together with the input shaft. The lock mechanism engages the lock claw portion of the lock lever with the lock groove of the lock holder, thereby connecting (locking) the input shaft and the output shaft and fixing the transmission ratio.

The torque limit mechanism plays a role of limiting the transmission of torque between the motor shaft and the lock holder. As a technique related to the torque limit mechanism, for example, in an electric steering device shown in Patent Document 1 below. An elastic body is known that is disposed between a bearing that rotatably supports one end of a rotating shaft (motor shaft) of a steering assist motor and a fitting hole of a motor housing. This elastic body urges the motor shaft in the other end direction by elastic deformation of a plurality of protrusions having a semicircular cross section. As a result, the drive gear coupled to the other end of the motor shaft is brought into contact with the driven gear so as to eliminate the gap, thereby preventing backlash without being affected by the dimensional error of the parts such as the drive gear or the assembly accuracy. It disappears well.
JP 2001-163229 A

  By the way, when the engaging claw portion of the lock lever is engaged with the lock groove of the lock holder (hereinafter also referred to as locking), torque in the counter-rotating direction is transmitted from the lock holder to the motor shaft via the torque limit mechanism. Is done. When this transmission torque exceeds the predetermined limit value, in order to prevent damage to the lock holder, the torque limit mechanism is activated and the lock holder is slid in the counter-rotating direction with respect to the motor shaft to alleviate the transmission torque. ing.

  However, for example, when a large impact torque is momentarily generated in the lock holder at the time of locking, even if the transmission torque is less than the predetermined limit value, the torque limit mechanism is activated and the lock holder is moved relative to the motor shaft. It may shift in the counter-rotating direction. As a result, the engagement groove of the lock holder is formed on the motor shaft in spite of the lock in the normal use region (the region where the transmission torque is less than the predetermined limit value) where the torque limit mechanism is not scheduled to limit the torque transmission. On the other hand, the position is shifted in the counter-rotating direction, which causes problems such as a shift in the center position of the steering wheel and an engagement claw portion of the lock lever not smoothly engaging with the engagement groove of the lock holder.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a transmission ratio variable device that can reduce transmission torque at the time of locking and prevent positional deviation in a normal use region. It is to provide.

  In order to achieve the above object, in the transmission ratio variable device according to claim 1, the steering system (14, 16) of the vehicle connecting the steering (12) and the steered wheels (FR, FL). A motor (34) which is provided in the middle and rotates in accordance with the rotation of the input shaft (14) on the steering side, and the motor shaft (34A) of this motor is connected to the output shaft (16) on the steering wheel side Then, a motor that changes the transmission ratio between the input shaft and the output shaft by rotational driving of the motor, and an engagement groove portion (71) of an engaged member (71) disposed on the outer peripheral portion of the motor shaft. A locking mechanism (70) for connecting the input shaft and the output shaft by engaging and locking an engagement piece (76) connected to one of the input shaft and the output shaft to 71a) , The outer peripheral surface (35) of the motor shaft and the front A torque limit mechanism (80, 80a, 80b, 80c) that is disposed between the inner peripheral surface (71b) of the engaged member and limits the transmission of torque between the motor shaft and the engaged member. The torque limit mechanism is a thin-walled cylinder that can be brought into frictional contact with either the outer peripheral surface of the motor shaft or the inner peripheral surface of the engaged member. A ring portion (81, 86); and a plurality of elastic pieces (82, 83, 84, 87) protruding from the ring portion, the outer peripheral surface of the motor shaft or the inner peripheral surface of the engaged member Includes a plurality of grooves (35a, 71c, 77c) and a plurality of fittings that can be respectively fitted to the tip portions (82a, 83a, 84a, 87a) of the elastic piece on the bottom sides of the plurality of grooves. Parts (35b, 71d, 77d) are provided. Technically, the plurality of groove portions are formed such that the base portions (82b, 83b, 84b, 87b) of the elastic pieces respectively fitted to the plurality of fitting portions abut in an elastically deformed state. Features.

  In the first aspect of the invention, the transmission ratio variable device includes a lock mechanism that connects (locks) the outer peripheral surface of the motor shaft of the motor that changes the transmission ratio between the input shaft and the output shaft, and the input shaft and the output shaft. And a torque limit mechanism which is disposed between the inner peripheral surface of the engaged member and restricts transmission of torque between the motor shaft and the engaged member. The torque limit mechanism includes a thin cylindrical ring portion that can be brought into frictional contact with either the outer peripheral surface of the motor shaft or the inner peripheral surface of the engaged member, and a plurality of elastic pieces that protrude from the ring portion. Yes. And on the outer peripheral surface of the motor shaft or the inner peripheral surface of the engaged member, there are a plurality of groove portions and a plurality of fitting portions that can be respectively fitted to the tip end portions of the elastic pieces on the bottom sides of the plurality of groove portions. And are provided. Each groove part is formed so that the base part of the elastic piece fitted to each fitting part abuts in an elastically deformed state.

  The torque limit mechanism is configured so that the ring portion is brought into frictional contact with one of the outer peripheral surface of the motor shaft and the inner peripheral surface of the engaged member, and each elastic piece is fitted to each fitting portion. It is arrange | positioned between to-be-engaged members. For this reason, when the engagement piece is engaged with the engagement groove of the engaged member (hereinafter also referred to as locking), an impact torque is generated in the engaged member, and the impact torque is fitted to each fitting portion. The tip portions of the elastic pieces of the torque limit mechanism to be combined rotate relative to the rotating motor shaft in the counter-rotating direction.

  At this time, the base portion of each elastic piece is elastically deformed until it comes into contact with each groove portion by the transmission torque transmitted through the engaged member. The elastic deformation of the base part alleviates the above-described transmission torque, and the engaged member rotates relative to the motor shaft in the counter-rotating direction. And if the base part of each elastic piece contact | abuts to each groove part and the above-mentioned elastic deformation is suppressed, the relative position of the rotation direction of each said elastic piece and to-be-engaged member will be fixed.

At this time, when the transmission torque relaxed as described above is smaller than the friction torque generated on the frictional contact surface in the ring portion, no slip occurs between the engaged member and the motor shaft. Then, due to the disengagement between the engaged member and the engagement piece, the base portion of each elastic piece that is elastically deformed returns to its original shape. For this reason, the relative rotation between the engaged member and the motor shaft generated at the time of locking is eliminated.
On the other hand, when the transmission torque is larger than the friction torque, a slip occurs between the engaged member and the motor shaft, and relative rotation between the engaged member and the motor shaft is allowed.

As described above, since the transmission torque at the time of locking is relaxed, even if a large impact torque is momentarily generated at the engaged member at the time of locking in the normal use region, the engagement between the engaged member and the motor shaft is avoided. There is no positional deviation in the rotational direction.
Accordingly, it is possible to reduce the transmission torque at the time of locking and to prevent the positional deviation between the engaged member and the motor shaft in the normal use region.

  Further, as in the second aspect of the invention, the ring portion of the torque limit mechanism is formed so as to be in frictional contact with the outer peripheral surface of the motor shaft, and a plurality of elastic pieces protrude outward from the outer peripheral surface of the ring portion. May be formed. At this time, the plurality of groove portions and the plurality of fitting portions are formed on the inner peripheral surface of the engaged member.

  Further, as in the invention described in claim 3, the ring portion of the torque limit mechanism is formed so as to be in frictional contact with the inner peripheral surface of the engaged member, and the plurality of elastic pieces are formed from the inner peripheral surface of the ring portion. It may be formed so as to protrude inward. At this time, the plurality of groove portions and the plurality of fitting portions are formed on the outer peripheral surface of the motor shaft.

  According to a fourth aspect of the present invention, the groove is formed so that the circumferential width gradually increases as the circumferential width approaches the inner peripheral surface of the engaged member. As a result, the base part of each elastic piece that is elastically deformed at the time of locking comes into contact with each groove part so as to be evenly in surface contact with each other, thus preventing stress concentration when each base part comes into contact with each groove part. Can do.

[First Embodiment]
Hereinafter, a variable transmission ratio device according to a first embodiment of the present invention will be described with reference to the drawings for a vehicle control device. FIG. 1 is an explanatory diagram showing a schematic configuration of a vehicle control device 10 to which the transmission ratio variable device 30 according to the first embodiment is applied.
The vehicle control device 10 mainly includes a steering wheel 12, a first steering shaft 14, a second steering shaft 16, a torque sensor 18, a pinion gear 20, a rack shaft 22, a rod 24, a transmission ratio variable device 30, an ECU 90, and the like. ing.

  As shown in FIG. 1, the steering wheel 12 is fixed to the first steering shaft 14, the first steering shaft 14 is connected to the input side of the transmission ratio variable device 30, and the second steering shaft 16 is variable in transmission ratio. It is connected to the output side of the device 30. The torque sensor 18 detects a steering torque and a steering angle from a torsion amount of a torsion bar (not shown) provided in the middle of the second steering shaft 16, and outputs a detection signal corresponding to the steering torque and the steering angle to the ECU 90. .

  The pinion gear 20 at the tip of the second steering shaft 16 meshes with the rack shaft 22, and the rotational motion of the second steering shaft 16 is converted into the linear motion of the rack shaft 22. A rod 24 is connected to both ends of the rack shaft 22, and steering wheels FR and FL are connected to the end of the rod 24 via a knuckle (not shown). Thus, when the second steering shaft 16 rotates, the turning angle of the steered wheels FR, FL can be changed via the rack shaft 22, the rod 24, etc., so that the rotation amount and the rotation direction of the second steering shaft 16 can be changed. The steering wheels FR and FL can be steered according to the above.

FIG. 2 is a cross-sectional view of the transmission ratio variable device 30.
The transmission ratio variable device 30 is a device that changes the steered angle of the steered wheels FR and FL with respect to the steering angle in accordance with the steering situation. The transmission ratio variable device 30 includes a motor 34 that changes a transmission ratio between the first steering shaft 14 and the second steering shaft 16 by rotational driving in housings 52, 54, and 56 that are integrally coupled. A wave gear mechanism 40 as a gear mechanism, a lock mechanism 70 that can connect the first steering shaft 14 and the second steering shaft 16 are provided, and a spiral cable unit 38 is provided outside the housing 52. The lower end 14a of the first steering shaft 14 is connected to a housing 52 on the input side of the transmission ratio variable device 30, so that the housing 52 and the first steering shaft 14 rotate together. On the other hand, the upper end 16 a of the second steering shaft 16 is connected to the output side of the transmission ratio variable device 30.

  The motor 34 is fixed in the housing 54 by the motor housing 46, is connected to the first steering shaft 14 via the housings 52, 54, and rotates together with the first steering shaft 14. The motor housing 46 includes a motor housing body 46a and a motor end plate 46b. A cup-shaped shaft hole 46c is formed at the center of the motor housing body 46a on the second steering shaft 16 side. A motor end plate 46b is fixed on the first steering shaft 14 side of the motor housing body 46a so as to close the opening of the motor housing body 46a.

  A stator 34S is fixed to the inner peripheral surface of the motor housing main body 46a, and a rotor 34R that is rotationally driven by the stator 34S is provided in the stator 34S. A motor shaft 34A is fixed in the rotor 34R so as not to be relatively rotatable, and the motor shaft 34A protrudes from both ends of the rotor 34R in the axial direction. One end 34a of the motor shaft 34A is supported by a ball bearing 48 provided between the motor end plate 46b and the other end 34b of the motor shaft 34A is provided between the shaft hole 46c of the motor housing body 46a. It is supported by a ball bearing 58. Thereby, the motor shaft 34A can rotate coaxially with respect to the motor housing main body 46a and the housings 52, 54, and 56.

  A wave gear mechanism 40 constituted by a harmonic drive (registered trademark) is connected to the other end 34b of the motor shaft 34A. The wave gear mechanism 40 includes a wave generator 64 in which the other end 34b of the motor shaft 34A is fitted and can rotate integrally with the motor shaft 34A. The wave generator 64 includes a cam 64a having a substantially elliptical cross section perpendicular to the axis, and a ball bearing 64b provided on the outer periphery of the cam 64a. The inner ring of the ball bearing 64b is fixed to the outer periphery of the cam 64a, and the outer ring of the ball bearing 64b can be elastically deformed via the ball. An annular flexspline 66 that is elastically deformable integrally with the outer ring of the ball bearing 64b is provided on the outer periphery of the wave generator 64. External teeth 66 a are formed on the outer periphery of the flex spline 66.

  An annular stay circular spline 68 is formed on the motor 34 side in the housing 54. Inner teeth 68a having a greater number of teeth (102) than the number of teeth (100) of outer teeth 66a of the flexspline 66 are formed on the inner periphery of the stay circular spline 68, whereby the stay circular spline 68 meshes with the flexspline 66. ing.

  An annular drive circular spline 69 adjacent to the stay circular spline 68 is rotatably supported on the second steering shaft 16 side in the housing 54 via a bearing metal 54a. On the inner periphery of the drive circular spline 69, the same number (100) of inner teeth 69a as the outer teeth 66a of the flexspline 66 are formed, so that the drive circular spline 69 is also meshed with the flexspline 66.

  A protective plate 67 is provided between the motor housing body 46 a and the wave gear mechanism 40. An upper end 16 a of the second steering shaft 16 is fixed to the drive circular spline 69.

  That is, the housings 52, 54, and 56 are configured to rotate together with the first steering shaft 14, and the rotation of the first steering shaft 14 is 50 by the wave gear mechanism 40 composed of the above-described harmonic drive (registered trademark). / 51 to rotate the second steering shaft 16. On the other hand, as described above, the rotation of the motor 34 is decelerated to (1/50) × (50/51) to rotate the second steering shaft 16. As the second steering shaft 16 is rotated by the motor 34, the turning angles of the left and right steering wheels FR, FL are changed.

FIG. 3 is a cross-sectional view taken along the line 3-3 shown in FIG.
The lock mechanism 70 is a mechanism capable of locking (connecting) the motor shaft 34A to the housing 52. As shown in FIGS. 2 and 3, the lock mechanism 70 transmits torque to the outer periphery of one end 34a of the motor shaft 34A. A lock holder 71 that is disposed via a torque limit ring 80 that is a torque limit mechanism that limits the rotation of the motor shaft 34A and rotates integrally with the motor shaft 34A, and a substantially disc-shaped lock base that is fixed to the motor end plate 46b. 72 and a single lock lever 76 that is pivotally supported via a metal bush 74 around a lock pin 73 parallel to the shaft center with respect to the housing 52 and driven by a solenoid 75. ing.

  A plurality of lock groove portions 71 a are formed on the outer periphery of the lock holder 71, and a single engagement claw portion 76 a that can be engaged with each lock groove portion 71 a is formed at one end of the lock lever 76. Around the lock pin 73, a first torsion coil spring 73 a is provided with one end fixed to the housing 52 and the other end fixed to the anti-lock base 72 side of the lock lever 76. Around the lock pin 73, a second torsion coil spring 73b having one end fixed to the lock base 72 side of the lock lever 76 and the other end fixed to the lock base 72 is provided. The first and second torsion coil springs 73 a and 73 b urge the lock lever 76 so that the engaging claw 76 a of the lock lever 76 is close to the lock holder 71.

  In the lock mechanism 70 configured as described above, when the solenoid 75 is excited, the lock lever 76 swings counterclockwise in FIG. 3, and the engagement claw portion 76 a of the lock lever 76 and the lock groove portion of the lock holder 71. The engagement with 71a is released and an unlocked state is established. When the excitation to the solenoid 75 is stopped, the lock lever 76 swings clockwise by the urging force of the first and second torsion coil springs 73a and 73b, and the engagement claw 76a of the lock lever 76 is locked. The lock 71 is engaged with the lock groove 71a of the holder 71, and the first steering shaft 14 and the motor shaft 34A are locked (connected). Whether the solenoid 75 is excited is controlled by the ECU 90.

4A is a partially enlarged view of the torque limit ring 80 in the unlocked state, and FIG. 4B is a partially enlarged view of the torque limit ring 80 in the locked state.
As shown in FIGS. 3 and 4A, the torque limit ring 80 includes a ring portion 81 formed of a cylindrical steel plate that is an elastic material, and a width direction of the ring portion 81 from the outer peripheral surface of the ring portion 81. And a plurality of elastic pieces 82 projecting outward so as to be in the longitudinal direction.

  The ring portion 81 is formed so as to be in frictional contact with the outer peripheral surface 35 of the motor shaft 34A on the inner peripheral surface thereof. Further, each elastic piece 82 is formed by cutting and raising a part of the ring portion 81 for ease of formation, but each elastic piece 82 is formed by attaching another member to the ring portion 81 by welding or the like. You may do it.

  Further, as shown in FIG. 4A, the inner peripheral surface 71b of the lock holder 71 has a plurality of grooves 71c that are recessed in a direction corresponding to the axial direction of the motor shaft 34A, and the bottoms of these grooves 71c. On the side, a plurality of fitting portions 71d that are recessed in a direction corresponding to the axial direction of the motor shaft 34A are provided in the same manner as the groove portions 71c. Each fitting portion 71d is formed so as to be fitted to the tip end portion 82a of each elastic piece 82. Each groove portion 71c is in such a manner that the base portion 82b of each elastic piece 82 having the tip portion 82a fitted to each fitting portion 71d is in surface contact evenly with the side wall of each groove portion 71c in an elastically deformed state when locked. The width t in the rotational direction is formed so as to gradually increase as it approaches the inner peripheral surface 71 b of the lock holder 71. The corner portion 71e between the inner peripheral surface 71b and each groove portion 71c prevents stress concentration occurring at the root portion 82b when the root portion 82b of each elastic piece 82 comes into contact with each groove portion 71c. It is formed in an R shape.

  The torque limit ring 80 is in frictional contact with the outer peripheral surface 35 of the motor shaft 34A at the inner peripheral surface of the ring portion 81, and is fitted into each fitting portion 71d of the lock holder 71 at the tip portion 82a of each elastic piece 82. By combining, it plays a role of restricting torque transmission in the rotational direction between the motor shaft 34 </ b> A and the lock holder 71. At the time of unlocking, the base portion 82b of each elastic piece 82 is disposed so as not to contact the groove portion 71c of the lock holder 71 (see FIG. 4A).

  The spiral cable unit 38 is provided with a substantially cylindrical casing 38 a that is held by a vehicle body (not shown), and is provided inside the casing 38 a so as to be rotatable relative to the casing 38 a and is fixed to the housing 52 outside the housing 52. And an inner cylinder 38b. A flexible flat cable 38c is provided between the housing 38a and the inner cylinder 38b. The flexible flat cable 38c is formed by insulating and coating a plurality of lead wires. One end of the flexible flat cable 38c is connected to the inner cylinder 38b. It is wound around the inner cylinder 38b and the other end is connected to the casing 38a. The lead wire connected to the flexible flat cable 38c and extending from the inner cylinder 38b is connected to the stator 34S and the like of the motor 34, and the lead wire connected to the flexible flat cable 38c and extended from the housing 38a is not shown in the figure of the vehicle body. The battery and ECU 90 are connected by a connector.

  The ECU 90 is a control device including a motor drive circuit that drives and controls the motor 34, and the steering wheel FR with respect to the steering angle of the steering wheel 12 according to the steering situation such as the steering torque and the steering angle detected by the torque sensor 18. The motor 34 is driven so that the turning angle of the FL is changed. Further, the ECU 90 excites the solenoid 75 of the lock mechanism 70 (unlocked state) to change the turning angle of the steering wheels FR and FL with respect to the steering angle of the steering wheel 12, and steers the steering wheel 12 with respect to the steering angle. When the change of the turning angle of the wheels FR and FL is made constant, the excitation of the solenoid 75 of the lock mechanism 70 is stopped (locked state).

  When the lock mechanism 70 configured as described above is operated to engage the engagement claw portion 76a of the lock lever 76 with the fitting portion 71d of the lock holder 71, that is, at the time of locking, an impact torque is generated in the lock holder 71. . Due to this impact torque, the distal end portion 82a of the elastic piece 82 of the lock holder 71 and the torque limit ring 80 fitted to the fitting portion 71d of the lock holder 71 in the counter-rotating direction with respect to the rotating motor shaft 34A. Relative rotation.

  At this time, since the ring portion 81 of the torque limit ring 80 is in frictional contact with the motor shaft 34A and rotates together with the motor shaft 34A, the root portion 82b of the elastic piece 82 is transmitted via the lock holder 71. It will be elastically deformed until it contacts the groove 71c of the lock holder 71 by torque. The above-described transmission torque is relieved by the elastic deformation of the root portion 82b, and the lock holder 71 rotates relative to the ring portion 81 in the counter-rotating direction. When the base portion 82b of the elastic piece 82 comes into contact with the groove portion 71c and the above-described elastic deformation is suppressed, the relative position in the rotational direction between the ring portion 81 connected to the elastic piece 82 and the lock holder 71 is fixed. The

  At this time, if the transmission torque relaxed as described above is smaller than the friction torque generated on the friction contact surface between the inner peripheral surface of the ring portion 81 and the outer peripheral surface 35 of the motor shaft 34A, the ring portion 81 and No slip occurs between the motor shaft 34A. Then, by releasing the engagement between the lock holder 71 and the lock lever 76, the base portion 82b of the elastic piece 82 that is elastically deformed returns to its original shape. For this reason, the relative rotation between the lock holder 71 and the motor shaft 34A generated at the time of locking is eliminated.

  On the other hand, when the transmission torque is larger than the friction torque, slip occurs between the ring portion 81 and the motor shaft 34A, and relative rotation between the lock holder 71 and the motor shaft 34A is allowed.

Here, the transmission torque T that is relaxed by the torque limit ring 80 and transmitted to the motor shaft 34A when an impact torque is generated in the lock holder 71 during locking will be described with reference to FIG. FIG. 5 is an explanatory diagram showing the relationship between the relative angle θ that is the degree of relative rotation and the transmission torque T between the lock holder 71 and the motor shaft 34A. Incidentally, T ₁ indicated by a solid line in FIG. 5 shows the transmission torque in the case of applying the present invention, T ₂ indicated by wavy lines, shows the transmitted torque of the application of the prior art as a comparative example is there.

  As can be seen from FIG. 5, when the present invention is applied, the transmission torque T gradually increases without increasing rapidly even when the relative angle θ increases as compared with the comparative example. This is because the transmission torque T transmitted to the torque limit ring 80 via the lock holder 71 is relaxed by elastically deforming until the base portion 82b of the elastic piece 82 contacts the groove portion 71c at the time of locking.

When the root portion 82b comes into contact with the groove portion 71c, the elastic deformation of the root portion 82b is suppressed and the transmission torque T is not relaxed, so that the transmission torque T increases rapidly. When the transmission torque T that rapidly increases in this way becomes a torque limit value (hereinafter also referred to as a limit torque _TL ) that can be transmitted by the torque limit ring 80, slip occurs between the ring portion 81 and the motor shaft 34A. Thus, the relative rotation between the lock holder 71 and the motor shaft 34A is allowed, and the transmission torque T is limited to be constant at the limit torque _TL .

On the other hand, the conventional torque limit ring, which is a comparative example, does not include a mechanism that positively relaxes the transmission torque T. Therefore, the transmission torque T increases rapidly to the limit torque _TL due to an increase in the relative angle θ. .

  As described above, the transmission ratio variable device 30 according to the first embodiment has the outer peripheral surface 35 of the motor shaft 34A of the motor 34 that changes the transmission ratio between the first steering shaft 14 and the second steering shaft 16. And the inner peripheral surface 71b of the lock holder 71 of the lock mechanism 70 that connects (locks) the first steering shaft 14 and the second steering shaft 16, and the motor shaft 34A and the lock holder 71 Torque limit ring 80 is provided to limit the transmission of torque between the two. The torque limit ring 80 includes a thin cylindrical ring portion 81 capable of frictional contact with the outer peripheral surface 35 of the motor shaft 34A, and a plurality of elastic pieces 82 projecting outward from the outer peripheral surface of the ring portion 81. . And on the inner peripheral surface 71b of the lock holder 71, there are a plurality of groove portions 71c, and a plurality of fitting portions 71d that can be fitted to the distal end portions 82a of the elastic pieces 82 on the bottom sides of the plurality of groove portions 71c, respectively. , Is provided. Each groove portion 71c is formed such that the base portion 82b of the elastic piece 82 fitted to each fitting portion 71d abuts in an elastically deformed state. The torque limit ring 80 is configured so that the ring portion 81 is brought into frictional contact with the outer peripheral surface 35 of the motor shaft 34A and the elastic pieces 82 are fitted to the fitting portions 71d of the lock holder 71, respectively. 71.

  For this reason, due to the impact torque generated in the lock holder 71 at the time of locking, the tip end portion 82a of the elastic piece 82 fitted to the fitting portion 71d of the lock holder 71 is in contact with the ring portion 81 in frictional contact with the motor shaft 34A. Thus, it rotates relative to the counter-rotating direction. At this time, the base portion 82b of the elastic piece 82 relieves the transmission torque T transmitted through the lock holder 71 due to its elastic deformation. When the base portion 82b of the elastic piece 82 that is elastically deformed returns to its original shape due to the engagement release between the lock holder 71 and the lock lever 76, the lock holder 71 and the motor shaft 34A generated at the time of locking are restored. There will be no relative rotation between them.

Thus, since the transmission torque T at the time of locking is relaxed, a large impact torque is instantaneously generated in the lock holder 71 when locking in the normal use region where the limitation of the transmission torque T by the torque limit ring 80 is not scheduled. Even in this case, there is no positional deviation in the rotational direction between the lock holder 71 and the motor shaft 34A.
Accordingly, it is possible to reduce the transmission torque T at the time of locking and to prevent the positional deviation between the lock holder 71 and the motor shaft 34A in the normal use region.

  Further, in the transmission ratio variable device 30 according to the first embodiment, the groove 71c of the lock holder 71 is formed so as to gradually widen as the width t in the rotation direction approaches the inner peripheral surface 71b of the lock holder 71. Yes. As a result, the base portions 82b of the elastic pieces 82 that are elastically deformed at the time of locking come into contact with the side walls of the respective groove portions 71c so as to be evenly in surface contact with each other. Stress concentration can be prevented.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. 6 (A) and 6 (B) are partially enlarged views showing a main part of the torque limit ring 80a of the transmission ratio variable device 30 according to the second embodiment of the present invention.
The transmission ratio variable device 30 according to the second embodiment includes a torque limit ring 80a shown in FIGS. 6A and 6B instead of the torque limit ring 80 and the lock holder 71 described in the first embodiment. While adopting, the point which employ | adopts the lock holder 77 corresponding to this torque limit ring 80a differs from the transmission ratio variable apparatus which concerns on the said 1st Embodiment. Therefore, substantially the same components as those of the transmission ratio variable device of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The torque limit ring 80a is different from the torque limit ring 80 in that a pair of elastic pieces 83 and 84 corresponding to the elastic piece 82 in the first embodiment is formed to protrude outward from the ring portion 81.

  On the inner periphery of the lock holder 77, groove portions 77c and fitting portions 77d corresponding to the groove portions 71c and the fitting portions 71d of the lock holder 71 are provided. Each fitting portion 77d has both a side surface that does not oppose the pair of elastic pieces 84 in the front end portion 83a of the elastic piece 83 and a side surface that does not oppose the pair of elastic pieces 83 in the front end portion 84a of the elastic piece 84. It is formed to fit. Each groove portion 77c is in a state of elastic deformation when either one of the base portions 83b, 84b of both elastic pieces 83, 84 having both end portions 83a, 84a fitted to each fitting portion 77d is locked. Each of the widths is formed so as to gradually widen toward the inner peripheral surface 77b of the lock holder 77 so as to be in surface contact with the side wall of the lock holder 77 evenly. The corner 77e between the inner peripheral surface 77b and each groove 77c has a base 83b or a base when the root 83b of each elastic piece 83 or the base 84b of each elastic piece 84 abuts each groove 77c. In order to prevent stress concentration occurring in the portion 84b, it is formed in an R shape. In addition, an engagement groove portion similar to the engagement groove portion 71 a of the lock holder 71 is formed on the outer periphery of the lock holder 77.

Since the torque limit ring 80a according to the second embodiment configured as described above relieves the transmission torque T by elastic deformation of both base portions 83b and 84b of the elastic pieces 83 and 84 when locked, each elastic piece Compared with the case of the first embodiment in which only 82 is fitted, the amount of relaxation of the transmission torque T can be increased. Furthermore, the torque limit ring 80a can suppress variation in the amount of relaxation of the transmission torque T in forward and reverse rotation due to its objectivity.
[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. 7 (A) and 7 (B) are partially enlarged views showing a main part of the torque limit ring 80b of the transmission ratio variable device 30 according to the third embodiment of the present invention.
The transmission ratio variable device 30 according to the third embodiment employs a torque limit ring 80b shown in FIGS. 7A and 7B instead of the torque limit ring 80a described in the second embodiment. This is different from the transmission ratio variable device according to the second embodiment. Therefore, substantially the same components as those in the transmission ratio variable device of the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The torque limit ring 80b is different from the torque limit ring 80a in that the torque limit ring 80b is formed such that the tips of both ends 83a and 84a of the elastic pieces 83 and 84 in the second embodiment are connected by a connecting portion 85.

  The torque limit ring 80b according to the third embodiment configured as described above is transmitted torque by elastic deformation of the connecting portion 85 in addition to elastic deformation of both the base portions 83b and 84b of the elastic pieces 83 and 84 when locked. Since T is relaxed, the amount of relaxation of the transmission torque T is further increased and the amount of relaxation of the transmission torque T in forward and reverse rotations as compared with the case of the second embodiment in which only both elastic pieces 83 and 84 are fitted. Variation can be further suppressed.

The present invention is not limited to the above embodiments, and may be embodied as follows. Even in this case, the same operations and effects as those of the above embodiments can be obtained.
(1) In order to adjust the relaxation amount of the transmission torque T at the time of locking, the root portion 82b of each elastic piece 82 in the first embodiment and the roots of both elastic pieces 83 and 84 in the second and third embodiments. You may make it change the elastic force of the parts 83b and 84b.

(2) In order to adjust the relaxation amount of the transmission torque T at the time of locking, the spread angle of the groove 71c in the first embodiment and the groove 77c in the second and third embodiments may be changed.

(3) In the above embodiments, the second steering shaft 16 is connected to the motor shaft 34A via the wave gear mechanism 40 and the like, and the first steering shaft 14 is not connected to the motor shaft 34A. Therefore, when the second steering shaft 16 is not connected to the motor shaft 34A via the wave gear mechanism 40 or the like and the first steering shaft 14 is connected to the motor shaft 34A, the lock mechanism 70 is (2) The lock lever connected to the steering shaft 16 may be engaged with the lock holder connected to the motor shaft 34A to lock the second steering shaft 16 and the motor shaft 34A.

(4) Instead of the torque limit ring 80 described above, a torque limit ring 80c shown in FIGS. 8 and 9 may be employed. FIG. 8 is a cross-sectional view illustrating a modification of the torque limit ring 80c, and FIG. 9 is a partially enlarged view of the torque limit ring 80c of FIG. As shown in FIG. 8, the torque limit ring 80 c includes a ring portion 86 formed so as to be in frictional contact with the inner peripheral surface 71 b of the lock holder 71 and a plurality of elastic pieces 87 protruding inward from the ring portion 86. I have.

  As shown in FIG. 9, the outer peripheral surface 35 of the motor shaft 34 </ b> A has a plurality of groove portions 35 a that are recessed in the axial direction, and in the axial direction on the bottom side of each of the groove portions 35 a, similarly to the groove portions 35 a. A plurality of recessed fitting portions 35b are provided. Each fitting part 35b is formed so as to be fitted to the tip part 87a of each elastic piece 87. Each groove portion 35a is in such a manner that the base portion 87b of each elastic piece 87 having the tip portion 87a fitted to each fitting portion 35b is in surface contact evenly with the side wall of each groove portion 35a in an elastically deformed state when locked. The width t in the rotational direction is formed so as to gradually increase as it approaches the outer peripheral surface 35 of the motor shaft 34A. The corner portion 35c between the outer peripheral surface 35 and each groove portion 35a is formed in order to prevent stress concentration occurring at the root portion 87b when the root portion 87b of each elastic piece 87 is in contact with each groove portion 35a. It is formed into a shape. Further, the plurality of groove portions 71c and the plurality of fitting portions 71d on the inner peripheral surface 71b of the lock holder 71 are eliminated.

  Even if the torque limit ring 80c is configured in this manner, the transmission torque T transmitted to the motor shaft 34A via the lock holder 71 can be reduced as in the above embodiments.

It is explanatory drawing which shows the structure outline | summary of the vehicle control apparatus to which the transmission ratio variable apparatus which concerns on 1st Embodiment of this invention is applied. It is sectional drawing of the transmission ratio variable apparatus of FIG. It is sectional drawing by the cut surface equivalent to the 3-3 line shown in FIG. 4A is a partially enlarged view of the torque limit ring in the unlocked state, and FIG. 4B is a partially enlarged view of the torque limit ring in the locked state. It is explanatory drawing which shows the relationship between a relative angle and transmission torque between a lock holder and a motor shaft. It is a partially expanded view which shows the principal part of the torque limit ring of the transmission ratio variable apparatus which concerns on 2nd Embodiment of this invention. It is a partial enlarged view which shows the principal part of the torque limit ring of the transmission ratio variable apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing explaining the modification of a torque limit ring. FIG. 9 is a partially enlarged view of the torque limit ring of FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Vehicle control apparatus 14 ... 1st steering shaft (input shaft)
16 ... Second steering shaft (output shaft)
DESCRIPTION OF SYMBOLS 30 ... Transmission ratio variable apparatus 34 ... Motor 34A ... Motor shaft 35 ... Outer peripheral surface 35a ... Groove part 35b ... Fitting part 70 ... Lock mechanism 71, 77 ... Lock holder 71a ... Lock groove part (engagement groove part)
71b, 77b ... inner peripheral surfaces 71c, 77c ... groove portions 71d, 77d ... fitting portion 76 ... lock lever 76a ... engagement claw portions 80, 80a, 80b, 80c ... torque limit ring (torque limit mechanism)
81, 86 ... ring portions 82, 83, 84, 87 ... elastic pieces 82a, 83a, 84a, 87a ... tip portions 82b, 83b, 84b, 87b ... root portion 85 ... connecting portion T ... transmission torque _TL ... limit torque θ ... relative angle

Claims (4)

Provided in the middle of the steering system of the vehicle connecting the steering and the steering wheel,
A motor that rotates in accordance with the rotation of the input shaft on the steering side, wherein the motor shaft of the motor is connected to the output shaft on the steering wheel side, and the motor is driven to rotate between the input shaft and the output shaft. A motor that changes the transmission ratio between,
The input shaft is obtained by engaging and locking an engagement piece connected to one of the input shaft and the output shaft in an engagement groove portion of an engaged member disposed on the outer peripheral portion of the motor shaft. And a lock mechanism for connecting the output shaft,
A torque limit mechanism that is disposed between the outer peripheral surface of the motor shaft and the inner peripheral surface of the engaged member, and that limits transmission of torque between the motor shaft and the engaged member;
A transmission ratio variable device comprising:
The torque limit mechanism includes a thin cylindrical ring portion that can be brought into frictional contact with one of an outer peripheral surface of the motor shaft and an inner peripheral surface of the engaged member, and a plurality of elastic pieces that protrude from the ring portion. With
On the outer peripheral surface of the motor shaft or the inner peripheral surface of the engaged member, a plurality of grooves and a plurality of fittings that can be fitted to the tip portions of the elastic pieces on the bottom sides of the plurality of grooves, respectively. Are provided, and
The variable groove ratio transmission device according to claim 1, wherein the plurality of groove portions are formed such that base portions of the elastic pieces respectively fitted to the plurality of fitting portions abut on each other in an elastically deformed state. The ring portion is formed so as to be in frictional contact with the outer peripheral surface of the motor shaft,
The plurality of elastic pieces are formed so as to protrude outward from the outer peripheral surface of the ring portion,
The transmission ratio variable device according to claim 1, wherein the plurality of groove portions and the plurality of fitting portions are formed on an inner peripheral surface of the engaged member. The ring portion is formed so as to be in frictional contact with the inner peripheral surface of the engaged member,
The plurality of elastic pieces are formed so as to protrude inward from the inner peripheral surface of the ring portion,
The transmission ratio variable device according to claim 1, wherein the plurality of groove portions and the plurality of fitting portions are formed on an outer peripheral surface of the motor shaft.   The transmission ratio according to any one of claims 1 to 3, wherein the groove portion is formed so that a width in a circumferential direction gradually increases as it approaches an inner peripheral surface of the engaged member. Variable device.

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