JP2005289314A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce loads in a radial direction applied to a worm from a joint body when the worm is eccentric or deflected relative to the shaft line of the output shaft of an electric motor, and preload is applied to an engagement part. <P>SOLUTION: The joint body 2 interlocking and connecting the shaft part 32 of the worm 3 to the output shaft 11 of the electric motor 1 for steering assistance is provided with first and second cruciform transmission pieces 21, 22 crossing each other. The output shaft 11 is provided with first and second engagement grooves 12, 13 mutually engaged with the first and second transmission pieces 21, 22 in a oscillating manner, and the worm 3 is provided with first and second engagement grooves 34, 35 mutually engaged with the first and second transmission pieces 21, 22 in a oscillating manner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus using an electric motor as a generation source of a steering assist force.

  An electric power steering apparatus for a vehicle includes an electric motor for assisting steering and a reduction gear mechanism that transmits a rotational force of the electric motor to a steering means, and the operation of the steering means according to an operation of a steering wheel is controlled by the electric motor. It is configured to assist with the rotation of the vehicle and reduce the labor burden on the driver for steering.

  The reduction gear mechanism includes a drive gear coupled to the output shaft of the electric motor via a joint, and a driven gear meshing with the drive gear and connected to the steering means. As the joint, a serration cylinder that is serrated and fitted to an output shaft and a drive gear is used, and the rotational force of the output shaft is transmitted from the serration cylinder to the drive gear (for example, Patent Document 1). .

  However, in an electric power steering apparatus including a joint composed of a serration cylinder, the drive gear is eccentric or deviated with respect to the axis of the output shaft due to dimensional errors of the serration cylinder, the output shaft and the serration portion of the drive gear. In this case, the backlash amount of the meshing portion increases.

  The driving gear and the driven gear are supported by rolling bearings, and the driving gear and the driven gear are engaged with each other in the direction in which the distance between the rotation centers of the driving gear and the driven gear is shortened. There is also known an electric power steering apparatus configured to apply a preload to a part to reduce a backlash amount of the meshing part to reduce a rattling sound due to backlash during steering (for example, Patent Document 1). .)

  However, when the preload is applied to the meshing portion, the drive gear is deviated with respect to the axis of the output shaft, and the radial gap of the joint portion is increased to allow this declination. Since it is comprised, it becomes easy to generate | occur | produce play in the said joint part.

By the way, as described in Patent Document 2, the elastic body made of rubber having a plurality of transmission pieces on the outer peripheral portion with respect to the eccentricity and deviation of the drive gear due to dimensional errors and the like, as described in Patent Document 2. The above-mentioned problems can be improved by using a joint composed of
JP 2002-211943 A JP 2002-145083 A

  However, in a joint made of an elastic body, when the drive gear is decentered or deviated, and when the drive gear is allowed to deviate, the elastic body bends in the radial direction, and the rotational force of the output shaft Is transmitted from the elastic body to the drive gear, the rigidity of the elastic body needs to be relatively high. However, when the rigidity of the elastic body is increased, the elastic body is difficult to bend in the radial direction, and the elastic restoring force in the radial direction applied from the elastic body to the drive gear is increased, so that the drive gear is decentered and declinated. The load on the rolling bearing that supports the drive gear increases, and the rotational performance of the drive gear decreases. In addition, when preload is applied to the meshing portion and the deflection angle of the drive gear is allowed, the elastic restoring force in the radial direction of the elastic body is applied to the end portion of the drive gear on the electric motor side. Will decrease, and the preload effect will decrease.

  The present invention has been made in view of such circumstances, and a main object thereof is a rolling bearing that supports a drive gear even when the drive gear is decentered or deviated with respect to the axis of the output shaft of the electric motor. The radial force applied to the drive gear from the joint when the drive gear is eccentric or deviated, and when the preload is applied to the meshing portion, can be improved. An object of the present invention is to provide an electric power steering device that can reduce the load in the direction.

  An electric power steering device according to a first aspect of the present invention includes a drive gear that is interlocked and connected to an output shaft of an electric motor by a joint, and a driven gear that meshes with the drive gear and is connected to a steering means. In the electric power steering apparatus configured to assist steering, the joint includes first and second transmission pieces that intersect each other, and the output shaft can swing with the first and second transmission pieces. First and second engaging grooves that engage with the first and second transmission pieces so as to be swingable with respect to each other. It is characterized by having.

  In the first invention, when the first and second transmission pieces of the joint are formed in a substantially cross shape, for example, when the drive gear is eccentric with respect to the axis of the output shaft of the electric motor, the drive It is possible to move the gear eccentrically in the direction in which the transmission pieces intersect. Further, when the drive gear is deviated with respect to the axis of the output shaft, the drive gear can be swung between the output shaft and the joint or between the drive gear and the joint. The load in the radial direction applied to the bearing can be reduced, the load on the bearing supporting the drive gear can be reduced, and the rotation of the drive gear can be improved. Moreover, even when it is comprised so that a preload may be applied to a meshing part, the load of the radial direction added to a drive gear from a joint can be reduced, and the fall of a preload effect can be reduced.

  An electric power steering apparatus according to a second aspect of the present invention is a drive gear that is interlocked and connected to an output shaft of an electric motor by a joint, a driven gear that meshes with the drive gear and is connected to steering means, and rotation of the drive gear and the driven gear In the electric power steering apparatus, which includes an elastic pressure means for elastically oppressing the non-electric motor side of the drive gear in a direction in which the distance between the centers is shortened, the joints intersect each other. The first and second transmission pieces, the output shaft has first and second engagement grooves that are slidably engaged with the first and second transmission pieces, The drive gear includes first and second engaging grooves that are slidably engaged with the first and second transmission pieces.

  In the second invention, when the drive gear swings and deviates by the elastic means, the first and second engagement grooves of the output shaft and the first and second transmission pieces, or The first and second engagement grooves of the drive gear and the first and second transmission pieces swing with each other. Therefore, the radial load applied to the drive gear from the joint can be reduced, and the decrease in the preload effect can be reduced. In addition, when the first and second transmission pieces of the joint are formed in a substantially cross shape, for example, when the drive gear is eccentric with respect to the axis of the output shaft of the electric motor, the drive piece is connected to the transmission piece. It is possible to move eccentrically in the intersecting direction. Further, when the drive gear is deviated with respect to the axis of the output shaft, the drive gear can be swung between the output shaft and the joint or between the drive gear and the joint. The load in the radial direction applied to the can be reduced.

  An electric power steering apparatus according to a third aspect of the present invention includes an engagement surface of the first engagement groove and the first transmission piece of the output shaft, and a second engagement groove and a second transmission piece of the drive gear. The engagement surface is curved, and the engagement surface of the second engagement groove and the second transmission piece of the output shaft, and the engagement of the first engagement groove and the first transmission piece of the drive gear. The mating surface is flat.

  In the third aspect of the invention, the drive gear can be swung by the curved engagement groove and the curved engagement surface of the transmission piece, and the flat engagement groove and the transmission piece are flat. With the engagement surface, the rotational force of the output shaft can be transmitted from the joint to the drive gear, and the transmission rigidity of the rotational force can be increased. Therefore, it is possible to use a joint made of a flexible material such as rubber having a lower rigidity than that of the metal material, and the cost can be reduced.

  The electric power steering apparatus according to a fourth aspect of the present invention is characterized in that the joint has flexibility.

  In the fourth invention, when the drive gear swings, the transmission piece of the joint can be bent in a direction inclined with respect to the axis of the output shaft. Therefore, the radial length of each transmission piece is relatively long. This can increase the rigidity of the joint.

  According to the first aspect of the present invention, when the drive gear is eccentric or deviated with respect to the axis of the output shaft, the radial load applied to the drive gear from the joint can be reduced, so that the drive gear is supported. The load on the bearing to be reduced can be reduced, and the rotation of the drive gear can be improved.

  According to the second aspect of the present invention, the radial load applied to the drive gear from the joint can be reduced, and the reduction in the preload effect can be reduced.

  According to the third invention, since the transmission rigidity of the joint can be increased by the flat engagement groove and the flat engagement surface of the transmission piece, the material having flexibility such as rubber having lower rigidity than the metal material. The joint consisting of can be used, and the cost can be reduced.

  According to the fourth invention, since the transmission piece of the joint can be bent in a direction inclined with respect to the axis of the output shaft, the radial length of each transmission piece can be made relatively long, and the rigidity of the joint can be increased. Can be increased.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
1 is an enlarged cross-sectional view of a reduction gear mechanism portion showing the configuration of an electric power steering device according to the present invention, FIG. 2 is a cross-sectional view showing the overall configuration of the electric power steering device, and FIG. FIG. 4 is an enlarged side view of the main part.

  The electric power steering apparatus includes an electric motor 1 for assisting steering, a worm 3 as a driving gear that is interlockedly connected to an output shaft 11 of the electric motor 1 via a joint 2, and a driven gear that meshes with the worm 3. A reduction gear mechanism A having a worm wheel 4 and a steering means 5 having a rotating shaft (described later) supporting the worm wheel 4 and connected to the worm wheel 4 are provided.

  The steering means 5 has one end connected to a steering wheel B for steering, a first steering shaft 51 having a cylindrical portion 51a at the other end, and the first steering shaft 51 inserted into the cylindrical portion 51a. The torsion bar 52 is connected to the cylinder portion 51 a of the steering shaft 51 and twisted by the action of the steering torque applied to the steering wheel B, and is connected to the other end of the torsion bar 52 as a rotating shaft connected to the worm wheel 4. The second steering shaft 53 is connected to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint and an intermediate shaft.

  The worm 3 of the reduction gear mechanism A includes a metal shaft member having a tooth portion 31 at the center and shaft portions 32 and 33 at both ends, and one shaft portion 32 is supported by a support member 7 via a rolling bearing 6. The other shaft portion 33 is housed and supported by the support member 7 via the bearing member 8 while being interlocked and connected to the output shaft 11 while being housed and supported in a freely rotatable manner. The shaft portion 32 is press-fitted into the inner ring of the rolling bearing 6. The rolling bearing 6 is an ordinary deep groove ball bearing.

  The worm wheel 4 has teeth on the outer periphery, a fitting hole in the center, and is fitted and fixed in the middle of the second steering shaft 53.

  The support member 7 accommodates the worm 3, the first accommodating portion 7 a that rotatably supports the shaft portions 32, 33 of the worm 3 via the rolling bearing 6 and the bearing member 8, and the worm wheel 4. It has the 2nd accommodating part 7b which supported this worm wheel 4 via the 2nd steering shaft 53 and the two rolling bearings 9 and 10 fitted to this 2nd steering shaft 53. As shown in FIG.

  The first accommodating portion 7a is elongated in the axial direction of the worm 3, and at one end in the longitudinal direction, a support hole 71 for supporting the rolling bearing 6 by loose fitting, a stepped portion 72 connected to the support hole 71, and A screw hole 73 and a motor mounting portion 74 are provided, and a screw ring 20 that contacts the outer ring of the rolling bearing 6 and fixes the outer ring to the stepped portion 72 is screwed into the screw hole 73. . Further, the electric motor 1 is attached to the motor attachment portion 74 with a plurality of bolts.

  The output shaft 11 of the electric motor 1 and the shaft portion 32 of the worm 3 include a substantially cruciform joint 2 and substantially cruciform first and second engagement grooves 12 provided on the output shaft 11 and the shaft portion 32. 13, 34, and 35 are linked together.

  The joint body 2 is made of an elastic material having flexibility such as synthetic rubber and synthetic resin, and has first and second transmission pieces 21 and 22 that intersect perpendicularly to each other and extend in the radial direction.

  The first transmission piece 21 has an engagement surface 21a in which a half on one side from the central portion in the axial direction of the rotation center axis is curved in a semicircular shape, and a flat engagement surface 21b having a prismatic shape on the other half. ing. The second transmission piece 22 has a prismatic flat engagement surface 22a on one side half from the axial center of the rotation center axis, and an engagement surface 22b whose other half is curved in a semicircular shape. ing.

  The first and second engaging grooves 12 and 13 of the output shaft 11 and the first and second engaging grooves 34 and 35 of the shaft portion 32 have shapes corresponding to the transmission pieces 21 and 22 of the joint body 2. It has become. That is, the first engagement groove 12 of the output shaft 11 and the second engagement groove 35 of the shaft portion 32 are mutually connected to the curved engagement surfaces 21 a and 22 b of the first and second transmission pieces 21 and 22. The first engagement groove 34 of the shaft portion 32 and the second engagement groove 13 of the output shaft 11 are curved so as to be swingable, and the prisms of the first and second transmission pieces 21 and 22 are formed. It is flat so as to engage with the flat engaging surfaces 21b and 22a of the shape. Further, a slight radial gap is provided between each of the first and second transmission pieces 21 and 22 and each of the engagement grooves 12, 13, 34, and 35 so that the worm 3 is eccentric with respect to the output shaft 11. It is to allow.

  The first and second engagement grooves 12, 13 of the output shaft 11 are provided in the transmission member 14 having a fitting hole 14 a that is externally fitted to the output shaft 11, and the first and second of the shaft portion 32 are provided. The engaging grooves 34 and 35 are provided in the transmission member 36 having a fitting hole 36 a that is externally fitted to the shaft portion 32.

  A receiving hole 75 for receiving the bearing member 8 and a through hole 76 facing the center of the receiving hole 75 are provided at the other end of the first receiving part 7a. A seat 77 is projected.

  The bearing member 8 includes a rolling bearing 81 having an inner ring fitted on the shaft portion 33 and a bearing housing 82 fitted and fixed to the outer ring of the rolling bearing 81. The bearing housing 82 is externally fitted to the rolling bearing 81, and has a bottomed cylindrical portion 82a that is loosely fitted into the receiving hole 75. The bottom of the cylindrical portion 82a is concentrically provided with the cylindrical portion 82a, and has a through hole. The elastic member 30 is formed of a tension coil spring on the shaft portion 82b and the seat 77, and the worm 3 and the distance between the rotation centers of the worm 3 and the worm wheel 4 are provided. It is repressing in the direction that H becomes shorter.

  An elastic cylinder 83 made of an elastic material such as synthetic rubber or synthetic resin is held on the outer peripheral portion of the cylindrical portion 82a. The elastic cylinder 83 is integrally formed by a molding means such as vulcanization molding, but may be held by fitting, bonding or the like.

  The support member 7 includes a torque sensor 40 for detecting a steering torque applied to the steering wheel B based on the relative rotational displacement of the steering shafts 51 and 53 according to the twist of the torsion bar 52. The torque sensor The electric motor 1 is configured to be driven and controlled based on the torque and the like detected by 40.

  In the electric power steering apparatus configured as described above, when the worm 3 and the electric motor 1 are assembled, the worm 3 in which the rolling bearings 6 and the bearing members 8 are respectively fitted on the shaft portions 32 and 33 are attached to the support member 7. 1 is inserted into the accommodating portion 7a, and a transmission member 36 is externally fitted and attached to the shaft portion 32 of the worm 3, and the joint 2 is inserted and supported in the first and second engaging grooves 34 and 35 of the transmission member 36. The electric motor 1 is attached to the motor mounting portion 74 while the first and second engaging grooves 12 and 13 of the transmission member 14 attached to the output shaft 11 by external fitting are engaged with the transmission pieces 21 and 22 of the joint 2. Install.

  In this case, the output shaft 11 and the joint 2 are engaged with the first engagement groove 12 and the curved engagement surface 21a of the first transmission piece 21, and further with the second engagement groove 13 and the second engagement groove 21a. The flat engagement surface 22a of the transmission piece 22 is engaged. In addition, the shaft portion 32 and the joint body 2 are engaged with the first engagement groove 34 and the flat engagement surface 21b of the first transmission piece 21, and further, the second engagement groove 35 and the second transmission surface. The curved engagement surface 22 b of the piece 22 is engaged, and the output shaft 11 and the shaft portion 32 can be interlocked and connected by the joint body 2.

  By this interlocking connection, the output shaft 11 and the joint body 2 can swing between the first engagement groove 12 and the engagement surface 21a, and along the second engagement groove 13 and the engagement surface 22a. Relative movement is possible in the radial direction. Further, the shaft portion 32 and the joint body 2 can swing between the second engagement groove 35 and the engagement surface 22b, and in the radial direction along the first engagement groove 34 and the engagement surface 21b. Relative movement is possible.

  As a result, the worm 3 is deviated with respect to the axis of the output shaft 11 between the first engagement groove 12 and the engagement surface 21a and between the second engagement groove 35 and the engagement surface 22b. The worm 3 can be eccentric with respect to the axis of the output shaft 11 by the second engagement groove 13 and the engagement surface 22a, and the first engagement groove 34 and the engagement surface 21b. Therefore, even when the worm 3 is decentered and deviated with respect to the axis of the output shaft 11, the backlash amount of the meshing portion can be reduced, and the elastic recovery in the radial direction applied from the joint 2 to the worm 3 can be achieved. Power can be reduced. Further, the rotational force of the output shaft 11 can be transmitted to the joint 2 from the first engagement groove 12 and the engagement surface 21a, and the second engagement groove 13 and the engagement surface 22a, and further the second engagement groove. 35 and the engaging surface 22b, and the first engaging groove 34 and the engaging surface 21b can be transmitted to the worm 3.

  After the electric motor 1 is attached as described above, both ends of the elastic member (tensile coil spring) 30 are hooked on the shaft portion 82b and the receiving seat 77 inserted into the through hole 76 of the support member 7, thereby 3 is repressed in a direction that shortens the distance H between the rotation centers, and a preload is applied to the meshing portion.

  FIG. 5 is an explanatory diagram of a state where the worm is deflected. The worm 3 to which the preload is applied swings in the direction in which the distance H between the rotation centers becomes shorter around the position O near the center of the axial direction of the rolling bearing 6 (see FIGS. 1 and 5). In this case, the elastic pressure of the elastic member 30 is applied in the F direction, the preload is applied in the F1 direction, a force in the F2 direction is applied to the joint 2, and a reaction force of the force in the F2 direction is applied to the shaft portion 32. However, the shaft portion 32 of the worm 3 swings between the first engagement groove 12 and the engagement surface 21a or between the second engagement groove 35 and the engagement surface 22b, so that the joint body 2 is radial. Since the force to bend in the direction can be reduced, the radial elastic restoring force applied from the joint 2 to the worm 3 can be reduced. Accordingly, the load on the rolling bearing 6 that supports the worm 3 can be reduced, the worm 3 can be maintained in rotation, and the reduction in the preload applied by the elastic member 30 to the meshing portion can be reduced. It is possible to maintain a state in which the amount of backlash is small. Further, since the joint body 2 has flexibility, when the worm 3 deviates between the first engagement groove 12 and the engagement surface 21a, one end of the second transmission piece 22 is in the second engagement. When the worm 3 is deflected between the joint grooves 13 and 35 and the worm 3 is deviated between the second engagement groove 35 and the engagement surface 22b, one end of the first transmission piece 21 is in the first engagement. The amount of deflection can be increased by bending between the grooves 12 and 34.

  FIG. 6 is a perspective view showing another configuration of the joint. In the joint body 2 of this embodiment, one half or the other half of the first and second transmission pieces 21 and 22 from the central portion in the axial direction of the rotation center axis is a prismatic flat engaging surface 21b and 22a. Instead, the surfaces facing the bottom surfaces of the second engagement groove 13 and the first engagement groove 34 are curved surfaces 21c and 22c that are curved toward both ends in the longitudinal direction, and when the worm 3 deviates as described above, The bending of the first and second transmission pieces 21 and 22 may be reduced. In this case, the bottom surfaces of the first engagement groove 34 and the second engagement groove 13 are curved corresponding to the curved surfaces 21c, 22c of the first and second transmission pieces 21, 22. In addition, also in FIG. 6, the joint body 2 has flexibility.

  In the embodiment described above, the flexible joint 2 is used. However, the joint 2 may be inflexible. Further, the transmission pieces 21 and 22 of the joint body 2 are provided with engagement surfaces 21a and 22b that are curved from the central portion in the axial direction of the rotation center axis to one half and the other half and prismatic flat engagement surfaces 21b and 22a. In addition, the transmission pieces 21 and 22 may have a cylindrical shape that is entirely curved.

  Further, in the embodiment described above, the electric power steering apparatus in which the distance H between the rotation centers can be adjusted has been described. However, other electric power steering apparatuses in which the distance H between the rotation centers cannot be adjusted are also described. Good.

  In the embodiment described above, the elastic member 30 made of a tension coil spring is used as the elastic means. However, an elastic member made of a compression coil spring may be used, and the structure of the elastic means and the elastic means. The arrangement position is not particularly limited.

  In the embodiment described above, the reduction gear mechanism A is a worm gear provided with a drive gear that is the worm 3 and a driven gear that is the worm wheel 4, but may be a bevel gear, a hypoid gear, or a helical gear. .

It is an expanded sectional view of the reduction gear mechanism part which shows the structure of the electric power steering apparatus which concerns on this invention. It is sectional drawing which shows the whole structure of an electric power steering device. It is the expansion perspective view by which the principal part was decomposed | disassembled. It is an enlarged side view of the principal part. It is explanatory drawing of the state which deviated the worm. It is a perspective view which shows the other structure of a joint body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 11 Output shaft 12 1st engagement groove 13 2nd engagement groove 14 Transmission member 2 Joint body 21 1st transmission piece 21a, 21b Engagement surface 22 2nd transmission piece 22a, 22b Engagement surface 3 Worm (drive gear)
34 First engaging groove 35 Second engaging groove 36 Transmission member 4 Worm wheel (driven gear)
5 Steering means H Distance between rotation centers 30 Repression means

Claims (4)

  An electric power steering apparatus comprising: a drive gear that is interlocked and connected to an output shaft of an electric motor by a joint; and a driven gear that meshes with the drive gear and that is connected to steering means, and that assists steering by rotation of the electric motor. The joint includes first and second transmission pieces intersecting each other, and the output shaft engages with the first and second transmission pieces in a swingable manner. An electric power steering apparatus having a mating groove, wherein the drive gear has first and second engaging grooves that are slidably engaged with the first and second transmission pieces. .   A drive gear interlocked to the output shaft of the electric motor by a joint, a driven gear meshing with the drive gear and connected to the steering means, and the drive gear in a direction in which the distance between the rotation centers of the drive gear and the driven gear is shortened; In the electric power steering apparatus, the joint includes first and second transmission pieces that intersect with each other. The output shaft has first and second engaging grooves that are slidably engaged with the first and second transmission pieces, and the drive gear has first and second transmission gears. An electric power steering apparatus having first and second engaging grooves that are swingably engaged with each other.   The engagement surface of the first engagement groove and the first transmission piece of the output shaft and the engagement surface of the second engagement groove and the second transmission piece of the drive gear are curved, The engagement surface of the second engagement groove and the second transmission piece of the output shaft and the engagement surface of the first engagement groove and the first transmission piece of the drive gear are flat. 3. The electric power steering apparatus according to 2. The electric power steering apparatus according to any one of claims 1 to 3, wherein the joint has flexibility.

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