JP6040781B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that converts rotation of an electric motor into linear motion of a steered shaft by a ball screw mechanism.

  As the electric power steering device, for example, a device described in Patent Document 1 is known. This system transmits the rotation of the output shaft of the electric motor to the driven pulley via the drive pulley and belt, and converts the rotation of the driven pulley into the axial movement of the rack shaft via the ball nut, ball and ball screw. Yes.

  A driven pulley and a ball nut are rotatably supported on the rack housing via a rolling bearing, and an electric motor is attached to the rack housing so as to be parallel to the rack shaft. The rack housing includes a second housing to which the electric motor is attached and a first housing that fits and supports the rolling bearing, and the first housing and the second housing are connected to each other via bolts. In the first housing and the second housing, a driving pulley and a driven pulley rotate, and an operation space for running the belt is formed.

JP 2012-25246 A

  The electric power steering is assembled by attaching a rolling bearing to the outer periphery of a ball nut screwed to a ball screw, fitting the rolling bearing to the inner periphery of the first housing, hanging a belt on the driven pulley, The second housings are fitted together, and in this state, they are integrally connected by bolts, the drive pulley is hung on the belt, and the electric motor is attached to the second housing. The belt has a land track shape that connects semicircles on both sides with a substantially straight line. This semicircle is larger than the outer diameter of the driven pulley. For this reason, when the first housing and the second housing are fitted to each other, the belt is caught on the second housing, or when the driving pool is hooked on the belt, the driving pulley is caught on the belt, resulting in poor assembly workability. was there. The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric power steering apparatus with improved belt assembly workability.

An electric power steering apparatus that solves the above problems includes a housing, a turning shaft provided in the housing so as to be movable in an axial direction, an electric motor attached to the housing, and rotation of the electric motor. includes a ball screw mechanism for converting the movement in the axial direction of the shaft, and a pulley mechanism for rotating transmitting the rotation of the output shaft of the electric motor to the ball screw mechanism, the ball screw mechanism, ball which is rotatably supported by the housing a nut, a ball screw provided in the steered shaft consists of a ball interposed between the ball nut and the ball screw, the pulley mechanism is mounted et is to the output shaft, a drive pulley having a first diameter the ball nut and integrally mounted, and a driven pulley having a larger second diameter greater than said first diameter, said drive pulley contact The electric power steering apparatus comprising a hanging passed looped belt to fine the driven pulley, the belt, in a state that is not also looped around in any of the drive pulley and the driven pulley, the first diameter having a first arc and second arc having a second diameter with, in the state of not being stretched in driven the drive pulley pawl in place is passed to the pulley, the second arc centers the driven located on the rotation axis of the pulley, the first arc center is characterized in that located on the rotation axis of the drive movement pulley.

The electric power steering apparatus according to claim 2 is characterized in that the belt is made of rubber and has a ring-shaped core wire that can be plastically deformed inside the rubber.

  According to the said structure, the electric power steering apparatus which improved the assembly | attachment workability | operativity of the belt can be provided.

1 is an overall view of an electric power steering apparatus according to an embodiment of the present invention. The A arrow line view of FIG. 1 concerning one Embodiment of this invention. The BB sectional view taken on the line of FIG. 1 concerning one Embodiment of this invention. The electric motor attachment state figure equivalent to FIG. 1 concerning one Embodiment of this invention. The state figure before the fitting of the 1st housing and 2nd housing equivalent to FIG. 1 concerning one Embodiment of this invention. The C arrow line view of FIG. 5 concerning one Embodiment of this invention. The D arrow line view of FIG. 5 concerning one Embodiment of this invention. Sectional drawing of the belt shape formation jig | tool concerning one Embodiment of this invention.

  An embodiment of the present invention will be described with reference to FIGS. 1 is an overall view of the electric power steering apparatus, FIG. 2 is a view taken along arrow A in FIG. 1, FIG. 3 is a sectional view taken along line BB in FIG. 1, and FIG. FIG. 5 is a state diagram before fitting the first housing and the second housing corresponding to FIG. 1, FIG. 6 is a view as viewed from the arrow C in FIG. 5, and FIG. FIG. 8 is a cross-sectional view of the belt shape forming jig.

  As shown in FIG. 1, the electric power steering apparatus includes a rack and pinion mechanism 10 that converts rotation of the pinion shaft 13 into movement in the axial direction of the rack shaft 14, an electric motor 30 that assists steering of the steering wheel, and an electric motor 30. And a ball screw mechanism 40 that converts the rotation transmitted by the pulley mechanism 20 into the movement of the rack shaft 14 in the axial direction.

  The rack and pinion mechanism 10 includes a gear housing 11, a rack housing 12 extending in a direction intersecting the gear housing 11, a pinion shaft 13 rotatably supported by the gear housing 11, and an insertion hole 12 c of the rack housing 12. And a rack shaft 14 to be inserted. A pinion gear 13 a is formed on the pinion shaft 13, and a rack gear 14 a is formed on the rack shaft 14. The pinion gear 13a and the rack gear 14a mesh with each other. The rack and pinion mechanism 10 has a function of converting rotation of the pinion shaft 13 into movement of the rack shaft 14 in the axial direction.

  A handle is rotationally connected to one end of the pinion shaft 13 via a steering shaft (not shown). Steering wheels are connected to both ends of the rack shaft 14 via a ball joint (not shown).

  As shown in FIGS. 1 and 3, the pulley mechanism 20 includes a drive pulley 22 attached to the output shaft of the electric motor 30, a driven pulley 23 disposed on the rack shaft 14, and the drive pulley 22 and the driven pulley 23. And a belt 24 stretched over. The pulley mechanism 20 has a function of decelerating the rotation of the electric motor 30 and transmitting it to the ball nut 42. The driven pulley 23 is rotatably supported by the rack housing 12 via a ball nut 42 and a pair of radial bearings 32. A plurality of external teeth are formed on the outer circumferences of the drive pulley 22 and the driven pulley 23, and inner teeth that mesh with the outer teeth are formed on the inner circumference of the belt 24. The pitch circle of the external teeth of the drive pulley 22 is the first diameter with a small diameter, and the pitch circle of the external teeth of the driven pulley 23 is the second diameter with a large diameter.

  The belt 24 has a first arc 24a having a first diameter and a second arc 24b having a second diameter before being hung on the driven pulley 23, and the second arc 24b of the belt 24 is hung on the driven pulley 23. 5 and 6, the center of the second arc 24 b is located on the rotation axis of the driven pulley 23, and the center of the first arc 24 a is located on the rotation axis of the drive pulley 22. The pitch circle of the inner teeth of the first arc 24a has a first diameter, and the pitch circle of the inner teeth of the second arc 24b has a second diameter. The belt 24 is made of rubber, and has a ring-shaped core wire made of a plurality of glass fibers inside the rubber. The core wires (not shown) are arranged at equal intervals in the axial direction of the driven pulley 23.

  Before the belt 24 is hung on the driven pulley 23, it is hung on a belt shape forming jig 70 shown in FIG. The belt shape forming jig 70 includes a small-diameter pulley 71, a large-diameter pulley 72, a small-diameter pulley 71, a connecting plate 73 that connects the large-diameter pulley 72, and an adjustment bolt 74 that attaches one end of the connecting plate 73 to the small-diameter pulley 71. The connecting plate 73 includes a connecting bolt 75 for attaching the other end of the connecting plate 73 to the large-diameter pulley 72. The connecting bolt 75 is inserted into the insertion hole 77 of the connecting plate 73 and screwed into the large diameter pulley 72. The adjustment bolt 74 is inserted into the adjustment hole 76 of the connecting plate 73 and screwed into the small diameter pulley 71. The adjustment hole 76 is formed in a long hole shape. When the adjustment bolt 74 is loosened, the small diameter pulley 71 can be moved closer to and away from the large diameter pulley 72.

  When the small-diameter pulley 71 is brought close to the large-diameter pulley 72 and the adjustment bolt 74 is tightened, the belt 24 can be detached from the large-diameter pulley 72 and the small-diameter pulley 71 and attached, and the small-diameter pulley 71 is separated from the large-diameter pulley 72. When the belt 24 is tensioned, the belt 24 can be formed into a predetermined shape. The first arc 24a and the second arc 24b are formed by the plastic deformation of the rubber and the core wire and storing the shape.

  As shown in FIGS. 3 and 8, the distance between the small-diameter pulley 71 and the large-diameter pulley 72 when the belt 24 is formed in a predetermined shape is equal to the distance between the driven pulley 23 and the drive pulley 22. The large-diameter pulley 72 has the same number of external teeth as the driven pulley 23, and the pitch circle of the external teeth of the large-diameter pulley 72 is equal to the pitch circle of the external teeth of the driven pulley 23 and has a second diameter. The large-diameter pulley 72 has the same cross-sectional shape as the driven pulley 23 and is longer in the axial direction than the driven pulley 23 so that the plurality of belts 24 can be hooked simultaneously. The small-diameter pulley 71 has the same number of external teeth as the drive pulley 22, and the pitch circle of the external teeth of the small-diameter pulley 71 is equal to the pitch circle of the external teeth of the drive pulley 22 and has a first diameter. The small-diameter pulley 71 has the same cross-sectional shape as the drive pulley 22 and is longer in the axial direction than the drive pulley 22 so that the plurality of belts 24 can be hooked simultaneously.

  As shown in FIG. 1, the ball screw mechanism 40 includes a ball nut 42 rotatably supported by the rack housing 12 via a pair of radial bearings 32, a ball screw 41 formed on the outer periphery of the rack shaft 14, and a ball nut 42. And a ball 43 inserted between the ball screws 41. The ball 43 moves to the inner peripheral side at one end of the ball nut 42, rolls on the ball screw 41, moves to the outer peripheral side at the other end of the ball nut 42, and passes through a return passage (not shown) to one end of the ball nut 42. It is designed to be returned to the side. The ball screw mechanism 40 has a function of converting the rotation of the electric motor 30 into the movement of the rack shaft 14 in the axial direction.

  The inner rings of the pair of radial bearings 32 are sandwiched between a flange portion of a ball nut 42 (to be described later) and a retaining ring 46 in the axial direction. The outer rings of the pair of radial bearings 32 are fitted to the inner periphery of the first housing 12a described later, and are sandwiched in the axial direction by the stepped portion of the first housing 12a and the end surface of the second housing 12b described later.

  A pair of radial bearings 32 is fitted to the outer periphery of the ball nut 42 and the driven pulley 23 is screwed, and a retaining ring 46 is fitted in an annular groove provided on one side in the axial direction. A flange portion protruding in the outer diameter direction is formed on the other side of the ball nut 42 in the axial direction, and the inner ring of the pair of radial bearings 32 comes into contact with the flange portion to move the driven pulley 23 toward the other side in the axial direction. Movement is restrained. That is, the pair of radial bearings 32 and the driven pulley 23 are restrained by the flange portion and the retaining ring 46 so as to be sandwiched in the axial direction.

  The rack housing 12 is made of a casting formed integrally with the gear housing 11. The rack housing 12 includes a first housing 12 a opposite to the gear housing 11 and a second housing 12 b on the gear housing 11 side, and is connected to each other via bolts 16. An insertion hole 12j through which the bolt 16 is inserted is formed in the first housing 12a, and a screw hole 12f into which the bolt 16 is screwed is formed in the second housing 12b. End surfaces of the first housing 12a and the second housing 12b are in close contact with each other, and a part of the second housing 12b is fitted to the inner periphery of the first housing 12a. A working space 12h is formed inside the first housing 12a and the second housing 12b. The driving pulley 22 and the driven pulley 23 rotate in the working space 12h, and the belt 24 travels.

  The second housing 12b is formed with an insertion hole 12m for inserting the drive pulley 22 from the outside into the working space 12h. The first housing 12a is formed with a peep hole 12k for peeping into the working space 12h from the outside. The insertion hole 12 m and the peep hole 12 k penetrate through the rack shaft 14 in the axial direction. The peep hole 12k is a peep hole when the driving pulley 22 is hung on the belt 24. After the drive pulley 22 is hung on the belt 24, the cap 80 is fitted into the peephole 12k in order to close it.

  An electric motor 30 is attached to the second housing 12b via a bolt 15. The second housing 12b is formed with an insertion hole 12d through which the bolt 15 is inserted, and the electric motor 30 is formed with a screw hole (not shown) into which the bolt 15 is screwed. The insertion hole 12d is formed in a long hole shape that extends in a direction approaching and separating from the rack shaft 14, and the tension of the belt 24 can be adjusted by moving the bolt 15 within the range of the long hole.

  As shown in FIG. 3, the 1st spacer 44 and the 2nd spacer 45 are arrange | positioned at the axial direction both sides of a pair of radial bearing 32, and these are fitted by the inner periphery of the 1st housing 12a. The first spacer 44, the pair of radial bearings 32, and the second spacer 45 are sandwiched in the axial direction by the stepped portion of the first housing 12a and the end surface of the second housing 12b. A disc spring (not shown) is inserted between the first spacer 44 and the pair of radial bearings 32, and a disc spring (not shown) is inserted between the pair of radial bearings 32 and the second spacer 45.

  Next, the assembly operation will be described based on the above-described configuration.

  As a preparation, the belt 24 is formed in a predetermined shape. This work procedure will be described. As shown in FIG. 8, the adjustment bolt 74 is loosened, the small-diameter pulley 71 is brought close to the large-diameter pulley 72, the plurality of belts 24 are hung on the large-diameter pulley 72, and the small-diameter pulley 71 is separated from the large-diameter pulley 72. The belt 24 is also hung on the small-diameter pulley 71, and the adjustment bolt 74 is completely tightened with some tension applied to the plurality of belts 24 at the same time. In this state, it is left until plastic deformation.

  Before the assembly is started, the adjustment bolt 74 is loosened, the small-diameter pulley 71 is brought close to the large-diameter pulley 72, and the belt 24 can be removed at any time while the adjustment bolt 74 is tightened.

  A pinion shaft 13 is assembled to the gear housing 11, and a ball nut 42 is screwed to the rack shaft 14 via a ball 43. A pair of radial bearings 32 is fitted to the ball nut 42, and the driven pulley 23 is screwed together. In order to prevent the driven pulley 23 from loosening, a retaining ring 46 is fitted in the annular groove of the ball nut 42.

  A pair of radial bearings 32 assembled with the ball nut 42, the rack shaft 14, the driven pulley 23, and the like are fitted to the inner periphery of the first housing 12a. Before the pair of radial bearings 32 is fitted to the first housing 12a, the first spacer 44 is fitted to the first housing 12a, and after the pair of radial bearings 32 is fitted to the first housing 12a, the first The second spacer 45 is fitted into the housing 12a.

  The belt 24 is removed from the belt shape forming jig 70 and the second pulley 24 b of the belt 24 is hung on the driven pulley 23. The rack shaft 14 assembled with the ball nut 42, the pair of radial bearings 32, the driven pulley 23 and the like is inserted into the insertion hole 12c of the second housing 12b, and the rack gear 14a is engaged with the pinion gear 13a (FIGS. 5 and 6). .

  A part of the second housing 12b is fitted to the inner periphery of the first housing 12a, the end surface of the first housing 12a and the end surface of the second housing 12b are brought into close contact with each other, the first spacer 44, the pair of radial bearings 32, and the first The first housing 12a and the second housing 12b are connected by the bolt 16 in a state where the two spacers 45 are sandwiched in the axial direction by the step portion of the first housing 12a and the end surface of the second housing 12b.

  When a part of the second housing 12b is fitted to the inner periphery of the first housing 12a, the belt 24 is located on the inner periphery side of the second housing 12b, and therefore the second housing 12b may interfere with the belt 24. Absent.

  The drive pulley 22 is attached in advance to the output shaft of the electric motor 30, and the drive pulley 22 integral with the electric motor 30 is inserted into the working space 12 h from the insertion hole 12 m and the drive pulley 22 is hung on the belt 24. At this time, the operator looks into the working space 12h from the peep hole 12k and confirms that the drive pulley 22 has entered the inner peripheral side of the belt 24 (FIG. 4).

  When the drive pulley 22 is hung on the belt 24, the center of the first arc 24a is positioned at the rotation center of the drive pulley 22 to be mounted, and the diameter (first diameter) of the pitch circle of the inner teeth of the first arc 24a is Since it is equal to the diameter (first diameter) of the pitch circle of the outer teeth of the drive pulley, the drive pulley 22 can be easily hung on the belt 24 without interfering with the belt 24.

  The bolt 15 is inserted into the insertion hole 12 d and screwed into the electric motor 30. While the bolt 15 is not completely tightened, the drive pulley 22 and the electric motor 30 are moved along the insertion hole 12d in a direction away from the driven pulley 23, and a force is applied in the direction away from the driven pulley 23. When a force is applied in the direction of separating, the belt 24 is tensioned. When the predetermined tension is reached, the bolt 15 is completely tightened while maintaining the force applied in the separating direction. The cap 80 is fitted into the peep hole 12k to complete the assembly (FIGS. 1 and 2).

  Next, the operation of the electric power steering apparatus assembled in this way will be described.

  When the handle is operated, the pinion shaft 13 rotates, and the rotation of the pinion shaft 13 is converted into the movement of the rack shaft 14 in the axial direction by the rack and pinion mechanism 10. A handle torque applied to the pinion shaft 13 is sensed by a sensor (not shown), and a drive current corresponding to the handle torque is applied to the electric motor 30.

  The rotation of the output shaft of the electric motor 30 is transmitted to the ball nut 42 via the drive pulley 22, the belt 24 and the driven pulley 23. The rotation of the ball nut 42 is converted into movement in the axial direction of the rack shaft 14 by the ball screw mechanism 40. Thus, power assist corresponding to the handle torque is applied to the rack shaft 14.

  The present invention is not limited to these embodiments, and can of course be implemented in various modes without departing from the gist of the present invention.

  In the above-described embodiment, the pitch circle of the first arc 24 a of the belt 24 has the same first diameter as the pitch circle of the drive pulley 22 when the belt 24 is removed from the belt shape forming jig 70. As another embodiment, the pitch circle of the first arc 24 a of the belt 24 may be slightly larger than the pitch circle of the drive pulley 22.

  In the embodiment described above, when the belt 24 is removed from the belt shape forming jig 70, the pitch circle of the second arc 24b of the belt 24 has the same second diameter as the pitch circle of the driven pulley 23. As another embodiment, the pitch circle of the second arc 24 b of the belt 24 may be slightly larger than the pitch circle of the driven pulley 23.

12: rack housing (housing), 14: rack shaft (steering shaft), 20: pulley mechanism, 22: drive pulley, 23: driven pulley, 24: belt, 24a: first arc, 24b: second arc, 30 : Electric motor, 40: Ball screw mechanism, 41: Ball screw, 42: Ball nut, 43: Ball, 60: Ball bearing (rolling bearing)

Claims (2)

A housing, a steered shaft provided in the housing so as to be movable in the axial direction, an electric motor attached to the housing, and a ball screw mechanism for converting the rotation of the electric motor into the axial movement of the steered shaft When, a pulley mechanism for rotating transmitting the rotation of the output shaft of the electric motor to the ball screw mechanism, the ball screw mechanism comprises a ball nut rotatably supported in said housing, a ball screw provided in the steering shaft consists of a ball interposed between the ball nut and the ball screw, the pulley mechanism is mounted et is to the output shaft, a drive pulley having a first diameter, integrally mounted with said ball nut, a driven pulley having a larger second diameter greater than the first diameter, Toka belt looped around the ring to the drive pulley and the driven pulley Comprising an electric power steering apparatus, the belt is in a state that is not also looped around in any of the drive pulley and the driven pulley, the second having a first arc and said second diameter with said first diameter It has an arc, in the state where the driven pulley multiplied only be passed not passed over to the drive pulley, the second circular arc center is located on the rotation axis of the driven pulley, of the first arc central electric power steering device for being located on the rotation axis of the drive movement pulley.

The electric power steering apparatus according to claim 1, wherein the belt is made of rubber and has a ring-shaped core wire that can be plastically deformed inside the rubber.

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